Effect of Rotor Diameter on the Thermal Stresses of a Turbine Rotor Model
Dávalos, J. O.; García, J. C.; Urquiza, G.; Castro-Gómez, L. L.; Rodríguez, J. A.; De Santiago, O.
2016-04-01
Thermal stresses in a simplified steam turbine rotor model during a cold startup are analyzed using finite element analysis (FEA). In order to validate the numerical model, an experimental array is developed in which a hollow cylinder is heated with hot air in the external surface. At the thick wall of the cylinder, temperature distribution is measured in real time, while at the same time an algorithm computes thermal stresses. Additional computational fluid dynamics (CFD) calculations are made to obtain magnitudes of velocity and pressure in order to compute convective heat transfer coefficient. The experimental results show good agreement with the FEA computations. To evaluate the effect of rotor diameter size, FEA computations with variation in external and internal diameters are performed. Results show that thermal stresses are proportional to rotor diameter size. Also, zones of higher stress concentration are found in the external and internal surfaces of the rotor.
Woodward, Richard P.; Gordon, Eliott B.
1988-01-01
A model high-speed advanced counterrotation propeller, F7/A3, was tested in the NASA Lewis Research Center 9 by 15 foot Anechoic Wind Tunnel at simulated takeoff/approach conditions of 0.2 Mach number. Acoustic measurements were taken with an axially translating microphone probe, and with a polar microphone probe which was fixed to the propeller nacelle and could take both sideline and circumferential acoustic surveys. Aerodynamic measurements were also made to establish propeller operating conditions. The propeller was run at two setting angles (front angle/rear angle) of 36.4/43.5 and 41.1/46.4 degrees, forward rotor tip speeds from 165 to 259 m/sec, rotor spacings from 8.48 to 14.99 cm based on pitch change axis separation, and angles of attack to 16 degrees. The aft rotor diameter was 85 percent of the forward rotor diameter to reduce tip vortex-aft rotor interaction as a major interaction noise source. Results are compared with equal diameter F7/A7 data which was previously obtained under similar operating conditions. The aft rotor-alone tone was 7 dB lower for the reduced diameter aft rotor, due to reduced tip speed at constant rpm. Interaction tone levels for the F7/A3 propeller were higher at minimum row spacing and lower at maximum spacing.
Woodward, Richard P.; Gordon, Eliott B.
1988-01-01
A model high-speed advanced counterrotation propeller, F7/A3, was tested in the NASA Lewis Research Center 9 by 15 foot Anechoic Wind Tunnel at simulated takeoff/approach conditions of 0.2 Mach number. Acoustic measurements were taken with an axially translating microphone probe, and with a polar microphone probe which was fixed to the propeller nacelle and could take both sideline and circumferential acoustic surveys. Aerodynamic measurements were also made to establish propeller operating conditions. The propeller was run at two setting angles (front angle/rear angle) of 36.4/43.5 and 41.1/46.4 degrees, forward rotor tip speeds from 165 to 259 m/sec, rotor spacings from 8.48 to 14.99 cm based on pitch change axis separation, and angles of attack to 16 degrees. The aft rotor diameter was 85 percent of the forward rotor diameter to reduce tip vortex-aft rotor interaction as a major interaction noise source. Results are compared with equal diameter F7/A7 data which was previously obtained under similar operating conditions. The aft rotor-alone tone was 7 dB lower for the reduced diameter aft rotor, due to reduced tip speed at constant rpm. Interaction tone levels for the F7/A3 propeller were higher at minimum row spacing and lower at maximum spacing.
Measurement of Vortex Strength and Core Diameter in the Wake of a Hovering Rotor
Wadcock, Alan J.
1997-01-01
Detailed hot wire measurements have been acquired in the tip vortex of a three-bladed model tilt rotor in hover. Testing was conducted at a rotor tip speed of 752 ft/sec, a Reynolds number (based on blade tip chord) of 1.77 x 10(exp 6), for thrust coefficients up to 0.0160. A figure shows the hot wire mounted above the inverted rotor at the Outside Aerodynamic Rotor Facility (OARF) at NASA Ames Research Center. Strobed shadowgraph flow visualization was used to define the vortex trajectory as an aid in hot wire positioning. Considerable variations in tip vortex structure with time were observed, even from the same blade, under essentially uniform test conditions. The only velocity signatures analyzed were those corresponding to passage of the probe directly through the center of the vortex. These time histories were ensemble averaged after compensating for jitter in the vortex arrival time at the probe, thereby retaining the core structure with minimal smearing. An example of a mean velocity signature, after ensemble averaging, is shown. The mean velocity signature was analyzed under the assumption of constant (unknown) translation speed of the vortex filament past the fixed probe. The translation speed of the vortex is deduced and the vortex strength and core diameter inferred. The results were highly unexpected. The indicated vortex strength is seen to decrease rapidly after first blade passage. In addition, the core radius is seen to decrease with increasing wake age, not increase as might be expected from simple diffusion.
Open Rotor Aeroacoustic Modelling
Envia, Edmane
2012-01-01
Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
Directory of Open Access Journals (Sweden)
Bharat Raj Singh
2011-05-01
Full Text Available This study describes new results of the performance evaluations of an air powered vane type rotary novel air turbine/engine. The mathematical model with different parametric values such as; different rotor to casing diameter (d/D ratios at optimum vane angle of 45º and injection angle of 45º, have been considered and analyzed. The optimum power output is obtained at some typical values of rotor/casing diameter ratios without consumptions of excessive air. The study shows that the optimum power developed under such conditions would be 4.3-5.5 kW (5.84-7.47 HP at linear expansion (without excessive air consumption when d/D ratios are between 0.85 to 0.80 and casing diameter is kept 150 mm, injection pressure as 6 bar (90 psi and speed of rotation as 2500 rpm. This power output is enough to drive any motorbike or light vehicle.
Identification of helicopter rotor dynamic models
Molusis, J. A.; Bar-Shalom, Y.; Warmbrodt, W.
1983-01-01
A recursive, extended Kalman-filter approach is applied to the identifiction of rotor damping levels of representative helicopter dynamic systems. The general formulation of the approach is presented in the context of a typically posed stochastic estimation problem, and the method is analytically applied to determining the damping levels of a coupled rotor-body system. The identified damping covergence characteristics are studied for sensitivity to both constant-coefficient and periodic-coefficient measurement models, process-noise covariance levels, and specified initial estimates of the rotor-system damping. A second application of the method to identifying the plant model for a highly damped, isolated flapping blade with a constant-coefficient state model (hover) and a periodic-coefficient state model (forward flight) is also investigated. The parameter-identification capability is evaluated for the effect of periodicity on the plant model coefficients and the influence of different measurement noise levels.
Directory of Open Access Journals (Sweden)
Bharat Raj Singh,
2010-03-01
Full Text Available This paper deals with new concept of compressed air energy storage system using atmospheric air at ambient temperature as a zero pollution power source for running motorbikes. The proposed motorbike is equipped with an air turbine in place of an internal combustion engine, and transforms the energy of the compressed air into shaft work. The mathematical modeling and performance evaluation of such small capacity compressed air driven vaned type novel air turbine is presented here. The effect of isobaric admission and adiabatic expansion of high pressure air for different rotor to casing diameter ratios with respect to different vane angles (number of vanes have been considered and analyzed. It is found that the shaft work output is optimum for some typical values of rotor to casing diameter ratios at a particular vane angle (i.e. no. of vanes. In this study, when casing diameter is considered 100 mm, and rotor to casing diameter ratios are kept 0.70 to 0.55, the average maximum power is obtained to the order of 4.95 kW (6.6 HP which is sufficient to run motorbikes.
Smart rotor modeling aero-servo-elastic modeling of a smart rotor with adaptive trailing edge flaps
Bergami, Leonardo
2014-01-01
A smart rotor is a wind turbine rotor that, through a combination of sensors, control units and actuators actively reduces the variation of the aerodynamic loads it has to withstand. Smart rotors feature?promising load alleviation potential and might provide the technological breakthrough required by the next generation of large wind turbine rotors.The book presents the aero-servo-elastic model of a smart rotor with Adaptive Trailing Edge Flaps for active load alleviation and provides an insight on the rotor aerodynamic, structural and control modeling. A novel model for the unsteady aerodynam
HARP model rotor test at the DNW. [Hughes Advanced Rotor Program
Dawson, Seth; Jordan, David; Smith, Charles; Ekins, James; Silverthorn, Lou
1989-01-01
Data from a test of a dynamically scaled model of the Hughes Advanced Rotor Program (HARP) bearingless model main rotor and 369K tail rotor are reported. The history of the HARP program and its goals are reviewed, and the main and tail rotor models are described. The test facilities and instrumentation are described, and wind tunnel test data are presented on hover, forward flight performance, and blade-vortex interaction. Performance data, acoustic data, and dynamic data from near field/far field and shear layer studies are presented.
A VORTEX MODEL OF A HELICOPTER ROTOR
Directory of Open Access Journals (Sweden)
Valentin BUTOESCU
2009-06-01
Full Text Available A vortex model of a helicopter rotor is presented. Each blade of the rotor has three degrees of freedom: flapping, lagging and feathering. The motions after each degree of freedom are also known for all blades. The blade is modelled as a thin vortex surface. The wakes are free fluid surfaces. A system of five equations are obtained: the first one is the integral equation of the lifting surface (rotor, the next three describe the wakes motion, and the last one relates the vortex strength on the wakes and the variation of vorticity on the rotor. A numerical solution of this system is presented. To avoid the singularities that can occur due to the complexity of vortex system, a desingularized model of the vortex core was adopted. A Mathcad worksheet containing the method has been written.The original contribution of the work. The calculation method of the motion of the wakes free vortex system, the development of the vortex cores in time and a new method to approximate the aerodynamic influence of remoted wake regions.
Stability of Rotor Systems: A Complex Modelling Approach
DEFF Research Database (Denmark)
Kliem, Wolfhard; Pommer, Christian; Stoustrup, Jakob
1996-01-01
A large class of rotor systems can be modelled by a complex matrix differential equation of secondorder. The angular velocity of the rotor plays the role of a parameter. We apply the Lyapunov matrix equation in a complex setting and prove two new stability results which are compared with the resu......A large class of rotor systems can be modelled by a complex matrix differential equation of secondorder. The angular velocity of the rotor plays the role of a parameter. We apply the Lyapunov matrix equation in a complex setting and prove two new stability results which are compared...
Thermal modeling of a mini rotor-stator system
Dikmen, Emre; Hoogt, van der Peter; Boer, de André; Aarts, Ronald; Jonker, Ben
2009-01-01
In this study the temperature increase and heat dissipation in the air gap of a cylindrical mini rotor stator system has been analyzed. A simple thermal model based on lumped parameter thermal networks has been developed. With this model the temperature dependent air properties for the fluid-rotor i
Modeling of high speed micro rotors in moderate flow confinement
Dikmen, E.; Hoogt, van der P.J.M.; Aarts, R.G.K.M.
2008-01-01
The recent developments in high speed micro rotating machinery lead to the need for multiphysical modeling of the rotor and the surrounding medium. In this study, thermal and flow induced effects on rotor dynamics of geometries with moderate flow confinement are studied. The structure is modeled via
PIV in a model wind turbine rotor wake
DEFF Research Database (Denmark)
Meyer, Knud Erik; Naumov, Igor; Karbadin, Ivan
2013-01-01
Stereoscopic particle image velocimetry (PIV) measurements of the flow in the wake of scale model of a horizontal axis wind turbine is presented Near the rotor, measurements are made in vertical planes intersecting the rotor axis These planes capture flow effect from the tip and root vortices...
Smart Rotor Modeling: Aero-Servo-Elastic Modeling of a Smart Rotor with Adaptive Trailing Edge Flaps
DEFF Research Database (Denmark)
Bergami, Leonardo
This book presents the formulation of an aero-servo-elastic model for a wind turbine rotor equipped with Adaptive Trailing Edge Flaps (ATEF), a smart rotor configuration. As the name suggests, an aero-servo-elastic model consists of three main components: an aerodynamic model, a structural model......, and a control model. The book first presents an engineering type of aerodynamic model that accounts for the dynamic effects of flap deflection. The aerodynamic model is implemented in a Blade Element Momentum framework, and coupled with a multi-body structural model in the aero-servoelastic simulation code HAWC...... the trailing edge flap deflection to actively reduce the fatigue loads on the structure. The performance of the smart rotor configuration and its control algorithms are finally quantified by aero-servo-elastic simulations of the smart rotor turbine operating in a standard turbulent wind field....
Energy Technology Data Exchange (ETDEWEB)
Moroz, E. [Univ. of Texas at El Paso, Dept. of Mechanical and Industrial Engineering, El Paso, TX (United States)
1997-12-31
An experimental investigation into the acoustic noise from a small (7.6 m diameter) teetered rotor wind turbine, set at various yaw angles up to 90 degrees of yaw, was conducted. The results revealed a 1/3 octave spectra which was dominated by a broad peak in the higher frequency range, at all yaw angles investigated. This prompted a theoretical investigation to reveal the mechanisms producing the dominant feature in the experimentally obtained noise spectra and resulted in the development of a wind turbine aerodynamic noise prediction coce, WTNOISE. The location near busy roads and the relatively rough terrain of the wind test site caused difficulties in obtaining useful noise spectral information below 500Hz. However, sufficiently good data was obtained above 500Hz to clearly show a dominant `hump` in the spectrum, centered between 3000 and 4000Hz. Although the local Reynolds number for the blade elements was around 500,000 and one might expect Laminar flow over a significant portion of the blade, the data did not match the noise spectra predicted when Laminar flow was assumed. Given the relatively poor surface quality of the rotor blades and the high turbulence of the test site it was therefore assumed that the boundary layer on the blade may have tripped relatively early and that the turbulent flow setting should be used. This assumption led to a much better correlation between experiment and predictions. The WTNOISE code indicated that the broad peak in the spectrum was most likely caused by trailing edge bluntness noise. Unfortunately time did not allow for modifications to the trailing edge to be investigated. (au)
A Computational Model for Rotor-Fuselage Interactional Aerodynamics
Boyd, D. Douglas, Jr.; Barnwell, Richard W.; Gorton, Susan Althoff
2000-01-01
A novel unsteady rotor-fuselage interactional aerodynamics model has been developed. This model loosely couples a Generalized Dynamic Wake Theory (GDWT) to a thin-layer Navier-Stokes solution procedure. This coupling is achieved using an unsteady pressure jump boundary condition in the Navier-Stokes model. The new unsteady pressure jump boundary condition models each rotor blade as a moving pressure jump which travels around the rotor azimuth and is applied between two adjacent planes in a cylindrical, non-rotating grid. Comparisons are made between measured and predicted time-averaged and time-accurate rotor inflow ratios. Additional comparisons are made between measured and predicted unsteady surface pressures on the top centerline and sides of the fuselage.
Numerical modeling of a rotor misalignment; Modelado numerico del desalineamiento de un rotor
Energy Technology Data Exchange (ETDEWEB)
Leon Pina, Roberto
2009-12-15
In the turbo-machinery area after an unbalancing, the misalignment is the fault that most frequently appears, and this one has been little studied compared to the unbalance. The misalignment appears when the geometric centers of two shafts and/or bearings do not coincide, these differences take place by different factors such as: incorrect installation of the bearings or rotors, thermal effects, or rotor weight, to mention some of them. The of the misalignment diagnosis continues being an area little studied, since the effects it generates are complex and include diverse physical processes reason why it presents/displays similar symptoms to those of other faults; thus, one of the methods that are used to diagnose this fault, is based on analyzing the vibration phantoms but this works only under particular conditions. In order to reproduce the dynamic behavior of a misaligned rotor, in the present work non-linear simplified models of the supports are used, whose objective is to contribute to facilitate future studies of the flow-dynamic behavior of the bearing, helping to identify the type and magnitude of the existing non-linearity in the supports and leaning in the analysis of the vibratory behavior of misaligned rotors observed in the field. [Spanish] En el area de turbomaquinaria despues del desbalance, el desalineamiento es la falla que se presenta con mayor frecuencia, y esta se ha estudiado poco comparada con el desbalance. El desalineamiento se presenta cuando los centros geometricos de dos flechas y/o chumaceras no coinciden, estas diferencias se producen por diferentes factores como: instalacion incorrecta de las chumaceras o rotores, efectos termicos, o el peso del rotor, por mencionar algunos. El diagnostico del desalineamiento sigue siendo una area poco estudiada, ya que los efectos que genera son complejos y abarcan diversos procesos fisicos por lo que presenta sintomas similares a los de otras fallas; asi, uno de los metodos que se utilizan para
Reference Model 2: %22Rev 0%22 Rotor Design.
Energy Technology Data Exchange (ETDEWEB)
Barone, Matthew F.; Berg, Jonathan Charles; Griffith, Daniel
2011-12-01
The preliminary design for a three-bladed cross-flow rotor for a reference marine hydrokinetic turbine is presented. A rotor performance design code is described, along with modifications to the code to allow prediction of blade support strut drag as well as interference between two counter-rotating rotors. The rotor is designed to operate in a reference site corresponding to a riverine environment. Basic rotor performance and rigid-body loads calculations are performed to size the rotor elements and select the operating speed range. The preliminary design is verified with a simple finite element model that provides estimates of bending stresses during operation. A concept for joining the blades and support struts is developed and analyzed with a separate finite element analysis. Rotor mass, production costs, and annual energy capture are estimated in order to allow calculations of system cost-of-energy. Evaluation Only. Created with Aspose.Pdf.Kit. Copyright 2002-2011 Aspose Pty Ltd Evaluation Only. Created with Aspose.Pdf.Kit. Copyright 2002-2011 Aspose Pty Ltd
Rotor scale model tests for power conversion unit of GT-MHR
Energy Technology Data Exchange (ETDEWEB)
Baxi, C.B., E-mail: baxicb1130@hotmail.com [General Atomics, P.O. Box 85608, San Diego, CA 92186-5608 (United States); Telengator, A.; Razvi, J. [General Atomics, P.O. Box 85608, San Diego, CA 92186-5608 (United States)
2012-10-15
The gas turbine modular helium reactor (GT-MHR) combines a modular high-temperature gas-cooled reactor (HTGR) nuclear heat source with a closed Brayton gas-turbine cycle power conversion unit (PCU) for thermal to electric energy conversion. The PCU has a vertical orientation and is supported on electromagnetic bearings (EMB). The rotor scale model (RSM) tests are intended to directly model the control of EMB and rotor dynamic characteristics of the full-scale GT-MHR turbo-machine (TM). The objectives of the RSM tests are to: Bullet Confirm the EMB control system design for the GT-MHR turbo machine over the full-range of operation. Bullet Confirm the redundancy and on-line maintainability features that have been specified for the EMBs. Bullet Provide a benchmark for validation of analytical tools that will be used for independent analyses of the EMB subsystem design. Bullet Provide experience with the installation, operation and maintenance of EMBs supporting multiple rotors with flexible couplings. As with the full-scale TM, the RSM incorporates two rotors that are joined by a flexible coupling. Each of the rotors is supported on one axial and two radial EMBs. Additional devices, similar in concept to radial EMBs, are installed to simulate magnetic and/or mechanical forces representing those that would be seen by the exciter, generator, compressors and turbine. Overall, the lengths of the RSM rotor is about 1/3rd that of the full-scale TM, while the diameters are approximately 1/5th scale. The design and sizing of the rotor is such that the number and values of critical speeds in the RSM are the same as in the full-scale TM. The EMBs are designed such that their response to rotor dynamic forces is representative of the full-scale TM. The fabrication and assembly of the RSM was completed at the end of 2008. All start up adjustments were finished in December 2009. To-date the generator rotor has been supported in the EMBs and rotated up to 1800 rpm. Final tests are
General model and control of an n rotor helicopter
DEFF Research Database (Denmark)
Sidea, Adriana-Gabriela; Brogaard, Rune Yding; Andersen, Nils Axel
2015-01-01
The purpose of this study was to create a dynamic, nonlinear mathematical model ofa multirotor that would be valid for different numbers of rotors. Furthermore, a set of SingleInput Single Output (SISO) controllers were implemented for attitude control. Both model andcontrollers were tested exper...
Modeling of Exterior Rotor Permanent Magnet Machines with Concentrated Windings
Vu Xuan, H.
2012-01-01
In this thesis modeling, analysis, design and measurement of exterior rotor permanent magnet (PM) machines with concentrated windings are dealt with. Special attention is paid to slotting effect. The PM machine is integrated in flywheel and used for small-scale ship application. Analytical model and
Helicopter Rotor Load Prediction Using a Geometrically Exact Beam with Multicomponent Model
DEFF Research Database (Denmark)
Lee, Hyun-Ku; Viswamurthy, S.R.; Park, Sang Chul
2010-01-01
rotor-blade/control-system model was loosely coupled with various inflow and wake models in order to simulate both hover and forward-flight conditions. The resulting rotor blade response and pitch link loads are in good agreement with those predicted byCAMRADII. The present analysis features both model......In this paper, an accurate structural dynamic analysis was developed for a helicopter rotor system including rotor control components, which was coupled to various aerodynamic and wake models in order to predict an aeroelastic response and the loads acting on the rotor. Its blade analysis was based...... on an intrinsic formulation of moving beams implemented in the time domain. The rotor control system was modeled as a combination of rigid and elastic components. A multicomponent analysis was then developed by coupling the beam finite element model with the rotor control system model to obtain a complete rotor-blade/control...
A New Hybrid Model Rotor Flux Observer and Its Application
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A new hybrid model rotor flux observer, based on a new voltage model, is presented. In the first place, the voltage model of an induction machine was constructed by using the modeling method discussed in this paper and then the current model using a flux feedback was adopted in this flux observer. Secondly, the two models were combined via a filter and then the rotor flux observer was established. In the M-T synchronous coordinate, the observer was analyzed theoretically and several important functions were derived. A comparison between the observer and the traditional models was made using Matlab software. The simulation results show that the observer model had a better performance than the traditional model.
Flow diagnostics downstream of a tribladed rotor model
DEFF Research Database (Denmark)
Naumov, I. V.; Rahmanov, V. V.; Okulov, Valery
2012-01-01
This paper presents results of a study of vortex wake structures and measurements of instantaneous 3D velocity fields downstream of a triblade turbine model. Two operation modes of flow around the rotor with different tip speed ratios were tested. Initially the wake structures were visualized and...
2017-01-01
resonance (NMR) Spectral density functions Spin - spin relaxation Molecular dynamics Nuclear Overhauser effect Symmetric top rotor Spin -lattice relaxation...SYMMETRIC TOP ROTOR MODELS AND THE FLEXIBLE SYMMETRIC TOP ROTOR MODEL ECBC-TR-1428 Terry J. Henderson RESEARCH AND TECHNOLOGY DIRECTORATE...Symmetric Top Rotor Models and the Flexible Symmetric Top Rotor Model 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR
Model and Stability Analysis of a Flexible Bladed Rotor
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available This paper presents a fully bladed flexible rotor and outlines the associated stability analysis. From an energetic approach based on the complete energies and potentials for Euler-Bernoulli beams, a system of equations is derived, in the rotational frame, for the rotor. This later one is made of a hollow shaft modelled by an Euler-Bernoulli beam supported by a set of bearings. It is connected to a rigid disk having a rotational inertia. A full set of flexible blades is also modelled by Euler-Bernoulli beams clamped in the disk. The flexural vibrations of the blades as well as those of the shaft are considered. The evolution of the eigenvalues of this rotor, in the corotational frame, is studied. A stability detection method, bringing coalescence and loci separation phenomena to the fore, in case of an asymmetric rotor, is undertaken in order to determine a parametric domain where turbomachinery cannot encounter damage. Finally, extensive parametric studies including the length and the stagger angle of the blades as well as their flexibility are presented in order to obtain robust criteria for stable and unstable areas prediction.
General model and control of an n rotor helicopter
Sidea, A. G.; Yding Brogaard, R.; Andersen, N. A.; Ravn, O.
2014-12-01
The purpose of this study was to create a dynamic, nonlinear mathematical model of a multirotor that would be valid for different numbers of rotors. Furthermore, a set of Single Input Single Output (SISO) controllers were implemented for attitude control. Both model and controllers were tested experimentally on a quadcopter. Using the combined model and controllers, simple system simulation and control is possible, by replacing the physical values for the individual systems.
General model and control of an n rotor helicopter
2015-01-01
The purpose of this study was to create a dynamic, nonlinear mathematical model ofa multirotor that would be valid for different numbers of rotors. Furthermore, a set of SingleInput Single Output (SISO) controllers were implemented for attitude control. Both model andcontrollers were tested experimentally on a quadcopter. Using the combined model andcontrollers, simple system simulation and control is possible, by replacing the physical valuesfor the individual systems.
Directory of Open Access Journals (Sweden)
HIDERALDO L. V. SANTOS
2013-08-01
Full Text Available Usually, electrical machines have a metallic cylinder made up of a compacted stack of thin metal plates (referred as laminated core assembled with an interference fit on the shaft. The laminated structure is required to improve the electrical performance of the machine and, besides adding inertia, also enhances the stiffness of the system. Inadequate characterization of this element may lead to errors when assessing the dynamic behavior of the rotor. The aim of this work was therefore to evaluate three beam models used to represent the laminated core of rotating electrical machines. The following finite element beam models are analyzed: (i an “equivalent diameter model”, (ii an “unbranched model” and (iii a “branched model”. To validate the numerical models, experiments are performed with nine different electrical rotors so that the first non-rotating natural frequencies and corresponding vibration modes in a free-free support condition are obtained experimentally. The models are evaluated by comparing the natural frequencies and corresponding vibration mode shapes obtained experimentally with those obtained numerically. Finally, a critical discussion of the behavior of the beam models studied is presented. The results show that for the majority of the rotors tested, the “branched model” is the most suitable
Application of aeroacoustic models to design of wind turbine rotors
Energy Technology Data Exchange (ETDEWEB)
Fuglsang, P.; Madsen, H.A. [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)
1997-12-31
A design method is presented for wind turbine rotors. The design process is split into overall design of the rotor and detailed design of the blade tip. A numerical optimization tool is used together with a semi-empirical noise prediction code for overall rotor design. The noise prediction code is validated with measurements and good agreement is obtained both on the total noise emission and on the sensitivity to wind speed, tip pitch angle and tip speed. A design study for minimum noise emission for a 300 kW rotor shows that the total sound power level can be reduced by 3 dB(A) without loss in energy production and the energy production can be increased by 2% without increase in the total noise. Detailed CFD calculations are subsequently done to resolve the blade tip flow. The characteristics of the general flow and the tip vortex are found, and the relevant parameters for the aeroacoustic models are derived for a sharp rectangular tip. (au) 16 refs.
Rotor-Flying Manipulator: Modeling, Analysis, and Control
Directory of Open Access Journals (Sweden)
Bin Yang
2014-01-01
Full Text Available Equipping multijoint manipulators on a mobile robot is a typical redesign scheme to make the latter be able to actively influence the surroundings and has been extensively used for many ground robots, underwater robots, and space robotic systems. However, the rotor-flying robot (RFR is difficult to be made such redesign. This is mainly because the motion of the manipulator will bring heavy coupling between itself and the RFR system, which makes the system model highly complicated and the controller design difficult. Thus, in this paper, the modeling, analysis, and control of the combined system, called rotor-flying multijoint manipulator (RF-MJM, are conducted. Firstly, the detailed dynamics model is constructed and analyzed. Subsequently, a full-state feedback linear quadratic regulator (LQR controller is designed through obtaining linearized model near steady state. Finally, simulations are conducted and the results are analyzed to show the basic control performance.
Dynamic Model of Contact Interface between Stator and Rotor
Zhao, Zenghui; Wang, Yuping; Yuan, YiKun; Zhao, Xiangdong
2013-01-01
Based on the equivalent principle, a linear spring contact model was established for the friction layer between stator and rotor. Different contact conditions were described by a distance index δ. Detailed analysis of the nonlinear contact behavior especially the static and dynamic slipping was carried on using a space-time equation. A contact deflection angle was proposed to quantitatively express the influence of friction force on the output performance. A more precision simulation model wa...
Model of the double-rotor induction motor in terms of electromagnetic differential
Directory of Open Access Journals (Sweden)
Adamczyk Dominik
2016-12-01
Full Text Available The paper presents a concept, a construction, a circuit model and experimental results of the double-rotor induction motor. This type of a motor is to be implemented in the concept of the electromagnetic differential. At the same time it should fulfill the function of differential mechanism and the vehicle drive. One of the motor shafts is coupled to the direction changing mechanical transmission. The windings of the external rotor are powered by slip rings and brushes. The inner rotor has the squirrel-cage windings. The circuit model parameters were calculated based on the 7.5 kW real single-rotor induction motor (2p = 4. Experimental verification of the model was based on comparison between the mentioned single-rotor motor and double-rotor model with the outer rotor blocked. The presented results showed relatively good compliance between the model and real motor.
Active Magnetic Bearing Rotor Model Updating Using Resonance and MAC Error
Directory of Open Access Journals (Sweden)
Yuanping Xu
2015-01-01
Full Text Available Modern control techniques can improve the performance and robustness of a rotor active magnetic bearing (AMB system. Since those control methods usually rely on system models, it is important to obtain a precise rotor AMB analytical model. However, the interference fits and shrink effects of rotor AMB cause inaccuracy to the final system model. In this paper, an experiment based model updating method is proposed to improve the accuracy of the finite element (FE model used in a rotor AMB system. Modelling error is minimized by applying a numerical optimization Nelder-Mead simplex algorithm to properly adjust FE model parameters. Both the error resonance frequencies and modal assurance criterion (MAC values are minimized simultaneously to account for the rotor natural frequencies as well as for the mode shapes. Verification of the updated rotor model is performed by comparing the experimental and analytical frequency response. The close agreements demonstrate the effectiveness of the proposed model updating methodology.
Measurement of the Lightweight Rotor Eigenfrequencies and Tuning of its Model Parameters
Directory of Open Access Journals (Sweden)
Luboš SMOLÍK
2013-06-01
Full Text Available The common sizes and weights of rotors, which can be found e.g. in the energy production industry, allow to employ a standard methodology of an experimental modal analysis. However, certain applications with rotors of small weights lead to the usage of alternative measuring methods suitable for the identification of rotor eigenfrequencies. One of these methods, which is characterized by the measuring of noise, is introduced in this paper and the results for a particular rotor is presented. Moreover the tuning of the finite element rotor model on the basis of such measured values is shown.
An Incidence Loss Model for Wave Rotors with Axially Aligned Passages
Paxson, Daniel E.
1998-01-01
A simple mathematical model is described to account for the losses incurred when the flow in the duct (port) of a wave rotor is not aligned with the passages. The model, specifically for wave rotors with axially aligned passages, describes a loss mechanism which is sensitive to incident flow angle and Mach number. Implementation of the model in a one-dimensional CFD based wave rotor simulation is presented. Comparisons with limited experimental results are consistent with the model. Sensitivity studies are presented which highlight the significance of the incidence loss relative to other loss mechanisms in the wave rotor.
Efficient Beam-Type Structural Modeling of Rotor Blades
DEFF Research Database (Denmark)
Couturier, Philippe; Krenk, Steen
2015-01-01
The present paper presents two recently developed numerical formulations which enable accurate representation of the static and dynamic behaviour of wind turbine rotor blades using little modeling and computational effort. The first development consists of an intuitive method to extract fully...... coupled six by six cross-section stiffness matrices with limited meshing effort. Secondly, an equilibrium based beam element accepting directly the stiffness matrices and accounting for large variations in geometry and material along the blade is presented. The novel design tools are illustrated...
Particle-rotor-model calculations in 125I
Indian Academy of Sciences (India)
Hariprakash Sharma; B Sethi; P Banerjee; Ranjana Goswami; R K Bhandari; Jahan Singh
2001-07-01
Recent experimental data on 125I has revealed several interesting structural features. These include the observation of a three quasiparticle band, prolate and oblate deformed bands, signature inversion in the yrast positive-parity band and identiﬁcation of the unfavoured ℎ11/2 band showing very large signature splitting. In the present work, particle-rotor-model calculations have been performed for the ℎ11/2 band, using an axially symmetric deformed Nilsson potential. The calculations reproduce the experimental results well and predict a moderate prolate quadrupole deformation of about 0.2 for the band.
Flap motion of helicopter rotors with novel, dynamic stall model
Directory of Open Access Journals (Sweden)
Han Wei
2016-01-01
Full Text Available In this paper, a nonlinear flapping equation for large inflow angles and flap angles is established by analyzing the aerodynamics of helicopter blade elements. In order to obtain a generalized flap equation, the Snel stall model was first applied to determine the lift coefficient of the helicopter rotor. A simulation experiment for specific airfoils was then conducted to verify the effectiveness of the Snel stall model as it applies to helicopters. Results show that the model requires no extraneous parameters compared to the traditional stall model and is highly accurate and practically applicable. Based on the model, the relationship between the flapping angle and the angle of attack was analyzed, as well as the advance ratio under the dynamic stall state.
Failure Diameter of PBX 9502: Simulations with the SURFplus model
Energy Technology Data Exchange (ETDEWEB)
Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-07-03
SURFplus is a reactive burn model for high explosives aimed at modelling shock initiation and propagation of detonation waves. It utilizes the SURF model for the fast hot-spot reaction plus a slow reaction for the energy released by carbon clustering. A feature of the SURF model is that there is a partially decoupling between burn rate parameters and detonation wave properties. Previously, parameters for PBX 9502 that control shock ini- tiation had been calibrated to Pop plot data (distance-of-run to detonation as a function of shock pressure initiating the detonation). Here burn rate parameters for the high pres- sure regime are adjusted to t the failure diameter and the limiting detonation speed just above the failure diameter. Simulated results are shown for an uncon ned rate stick when the 9502 diameter is slightly above and slightly below the failure diameter. Just above the failure diameter, in the rest frame of the detonation wave, the front is sonic at the PBX/air interface. As a consequence, the lead shock in the neighborhood of the interface is supported by the detonation pressure in the interior of the explosive rather than the reaction immediately behind the front. In the interior, the sonic point occurs near the end of the fast hot-spot reaction. Consequently, the slow carbon clustering reaction can not a ect the failure diameter. Below the failure diameter, the radial extent of the detonation front decreases starting from the PBX/air interface. That is, the failure starts at the PBX boundary and propagates inward to the axis of the rate stick.
An advanced stochastic model for threshold crossing studies of rotor blade vibrations.
Gaonkar, G. H.; Hohenemser, K. H.
1972-01-01
A stochastic model to analyze turbulence-excited rotor blade vibrations, previously described by Gaonkar et al. (1971), is generalized to include nonuniformity of the atmospheric turbulence velocity across the rotor disk in the longitudinal direction. The results of the presented analysis suggest that the nonuniformity of the vertical turbulence over the rotor disk is of little influence on the random blade flapping response, at least as far as longitudinal nonuniformity is concerned.
a Uqp(u2) Rotor Model for Rotational Bands of Superdeformed Nuclei
Barbier, R.; Meyer, J.; Kibler, M.
A nonrigid rotor model is developed from the two-parameter quantum algebra Uqp(u2). (This model presents the Uqp(u2) symmetry and shall be refered to as the qp-rotor model.) A rotational energy formula as well as a qp-deformation of E2 reduced transition probabilities are derived. The qp-rotor model is applied (through fitting procedures) to twenty rotational bands of superdeformed nuclei in the A~130, 150, and 190 mass regions. Systematic comparisons between the qp-rotor model and the q-rotor model of Raychev, Roussev, and Smirnov, on one hand, and a basic three-parameter model, on the other, are performed on energy spectra, on dynamical moments of inertia and on B(E2) values. The physical significance of the deformation parameters q and p is discussed.
Estimating Tree Height-Diameter Models with the Bayesian Method
Directory of Open Access Journals (Sweden)
Xiongqing Zhang
2014-01-01
Full Text Available Six candidate height-diameter models were used to analyze the height-diameter relationships. The common methods for estimating the height-diameter models have taken the classical (frequentist approach based on the frequency interpretation of probability, for example, the nonlinear least squares method (NLS and the maximum likelihood method (ML. The Bayesian method has an exclusive advantage compared with classical method that the parameters to be estimated are regarded as random variables. In this study, the classical and Bayesian methods were used to estimate six height-diameter models, respectively. Both the classical method and Bayesian method showed that the Weibull model was the “best” model using data1. In addition, based on the Weibull model, data2 was used for comparing Bayesian method with informative priors with uninformative priors and classical method. The results showed that the improvement in prediction accuracy with Bayesian method led to narrower confidence bands of predicted value in comparison to that for the classical method, and the credible bands of parameters with informative priors were also narrower than uninformative priors and classical method. The estimated posterior distributions for parameters can be set as new priors in estimating the parameters using data2.
Dynamic Model and Fault Feature Research of Dual-Rotor System with Bearing Pedestal Looseness
Directory of Open Access Journals (Sweden)
Nanfei Wang
2016-01-01
Full Text Available The paper presents a finite element model of dual-rotor system with pedestal looseness stemming from loosened bolts. Dynamic model including bearing pedestal looseness is established based on the dual-rotor test rig. Three-degree-of-freedom (DOF planar rigid motion of loose bearing pedestal is fully considered and collision recovery coefficient is also introduced in the model. Based on the Timoshenko beam elements, using the finite element method, rigid body kinematics, and the Newmark-β algorithm for numerical simulation, dynamic characteristics of the inner and outer rotors and the bearing pedestal plane rigid body motion under bearing pedestal looseness condition are studied. Meanwhile, the looseness experiments under two different speed combinations are carried out, and the experimental results are basically the same. The simulation results are compared with the experimental results, indicating that vibration displacement waveforms of loosened rotor have “clipping” phenomenon. When the bearing pedestal looseness fault occurs, the inner and outer rotors vibration spectrum not only contains the difference and sum frequency of the two rotors’ fundamental frequency but also contains 2X and 3X component of rotor with loosened support, and so forth; low frequency spectrum is more, containing dividing component, and so forth; the rotor displacement spectrums also contain fewer combination frequency components, and so forth; when one side of the inner rotor bearing pedestal is loosened, the inner rotor axis trajectory is drawn into similar-ellipse shape.
Model based methods for rotor position detection of doubly-fed induction generator
DEFF Research Database (Denmark)
Zhu, Rongwu; Chen, Zhe; Zhang, Yunqian;
2014-01-01
Model based strategy to detect the initial position angle of doubly-fed induction generator (DFIG) is proposed in this paper. As the stator windings are open-circuit when the wind speed is below the cut-in speed, the stator flux is determined by both rotor position and currents. Based...... on the characteristic, the initial position angle of the rotor is derived by rotor voltage injection (RVI) method and rotor current close loop injection (RCCLI) method, respectively. Further, the two methods are validated by a scaled-down 7.5kW DFIG setup, and the results clearly show that with the RCCLI, the rotor...... initial position of DFIG can be accurately and fast detected for a DFIG with rated parameters and rotor resistance deviations....
A Coupled Helicopter Rotor/Fuselage Dynamics Model Using Finite Element Multi-body
Directory of Open Access Journals (Sweden)
Cheng Qi-you
2016-01-01
Full Text Available To develop a coupled rotor/flexible fuselage model for vibration reduction studies, the equation of coupled rotor-fuselage is set up based on the theory of multi-body dynamics, and the dynamic analysis model is established with the software MSC.ADMAS and MSC.NASTRAN. The frequencies and vibration acceleration responses of the system are calculated with the model of coupled rotor-fuselage, and the results are compared with those of uncoupled modeling method. Analysis results showed that compared with uncoupled model, the dynamic characteristic obtained by the model of coupled rotor-fuselage are some different. The intrinsic frequency of rotor is increased with the increase of rotational velocities. The results also show that the flying speed has obvious influence on the vibration acceleration responses of the fuselage. The vibration acceleration response in the vertical direction is much higher at the low speed and high speed flight conditions.
Advances in transitional flow modeling applications to helicopter rotors
Sheng, Chunhua
2017-01-01
This book provides a comprehensive description of numerical methods and validation processes for predicting transitional flows based on the Langtry–Menter local correlation-based transition model, integrated with both one-equation Spalart–Allmaras (S–A) and two-equation Shear Stress Transport (SST) turbulence models. A comparative study is presented to combine the respective merits of the two coupling methods in the context of predicting the boundary-layer transition phenomenon from fundamental benchmark flows to realistic helicopter rotors. The book will of interest to industrial practitioners working in aerodynamic design and the analysis of fixed-wing or rotary wing aircraft, while also offering advanced reading material for graduate students in the research areas of Computational Fluid Dynamics (CFD), turbulence modeling and related fields.
Rigid Rotor as a Toy Model for Hodge Theory
Gupta, Saurabh
2009-01-01
We apply the superfield approach to the toy model of a rigid rotor and show the existence of the nilpotent and absolutely anticommuting Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetry transformations, under which, the kinetic term and Lagrangian remain invariant. Furthermore, we also derive the off-shell nilpotent and absolutely anticommuting (anti-) co-BRST symmetry transformations, under which, the gauge-fixing term and Lagrangian remain invariant. The anticommutator of the above nilpotent symmetry transformations leads to the derivation of a bosonic symmetry transformation, under which, the ghost terms and Lagrangian remain invariant. Together, the above transformations (and their corresponding generators) respect an algebra that turns out to be the realization of the algebra obeyed by the de Rham cohomological operators of differential geometry. Thus, our present model is a toy model for the Hodge theory.
Rigid rotor as a toy model for Hodge theory
Gupta, Saurabh; Malik, R. P.
2010-07-01
We apply the superfield approach to the toy model of a rigid rotor and show the existence of the nilpotent and absolutely anticommuting Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST symmetry transformations, under which, the kinetic term and the action remain invariant. Furthermore, we also derive the off-shell nilpotent and absolutely anticommuting (anti-) co-BRST symmetry transformations, under which, the gauge-fixing term and the Lagrangian remain invariant. The anticommutator of the above nilpotent symmetry transformations leads to the derivation of a bosonic symmetry transformation, under which, the ghost terms and the action remain invariant. Together, the above transformations (and their corresponding generators) respect an algebra that turns out to be a physical realization of the algebra obeyed by the de Rham cohomological operators of differential geometry. Thus, our present model is a toy model for the Hodge theory.
Dynamic Model of Contact Interface between Stator and Rotor
Directory of Open Access Journals (Sweden)
ZengHui Zhao
2013-01-01
Full Text Available Based on the equivalent principle, a linear spring contact model was established for the friction layer between stator and rotor. Different contact conditions were described by a distance index δ. Detailed analysis of the nonlinear contact behavior especially the static and dynamic slipping was carried on using a space-time equation. A contact deflection angle was proposed to quantitatively express the influence of friction force on the output performance. A more precision simulation model was established based on the theoretical analysis, and influences of different preload pressures and elastic modulus Em of friction layer on output performance were analyzed. The results showed the simulation results had very good consistency with experimental results, and the model could well reflect the output characteristics of contact interface.
On the flow field around a Savonius rotor
Bergeles, G.; Athanassiadis, N.
A model of a two-bucket Savonius rotor windmill was constructed and tested in a wind tunnel. The flow field around the rotor was examined visually and also quantitatively with the use of a hot wire. The flow visualization revealed an upstream influence on the flow field up to 3 rotor diameters away and a strong downwash downstream. Hot wire measurements showed a large velocity deficit behind the rotor and a quick velocity recovery downstream due to strong mixing; the latter was associated with high levels of turbulence. Energy spectra revealed that all turbulence was concentrated in a single harmonic corresponding to twice the rotational speed of the rotor.
Ice accretion modeling for wind turbine rotor blades
Energy Technology Data Exchange (ETDEWEB)
Chocron, D.; Brahimi, T.; Paraschivoiu, I.; Bombardier, J.A. [Ecole Polytechnique de Montreal (Canada)
1997-12-31
The increasing application of wind energy in northern climates implies operation of wind turbines under severe atmospheric icing conditions. Such conditions are well known in the Scandinavian countries, Canada and most of Eastern European countries. An extensive study to develop a procedure for the prediction of ice accretion on wind turbines rotor blades appears to be essential for the safe and economic operation of wind turbines in these cold regions. The objective of the present paper is to develop a computer code capable of simulating the shape and amount of ice which may accumulate on horizontal axis wind turbine blades when operating in icing conditions. The resulting code is capable to predict and simulate the formation of ice in rime and glaze conditions, calculate the flow field and particle trajectories and to perform thermodynamic analysis. It also gives the possibility of studying the effect of different parameters that influence ice formation such as temperature, liquid water content, droplet diameter and accretion time. The analysis has been conducted on different typical airfoils as well as on NASA/DOE Mod-0 wind turbine. Results showed that ice accretion on wind turbines may reduce the power output by more than 20%.
Optimization model for rotor blades of horizontal axis wind turbines
Institute of Scientific and Technical Information of China (English)
LIU Xiong; CHEN Yan; YE Zhiquan
2007-01-01
This paper presents an optimization model for rotor blades of horizontal axis wind turbines. The model refers to the wind speed distribution function on the specific wind site, with an objective to satisfy the maximum annual energy output. To speed up the search process and guarantee a global optimal result, the extended compact genetic algorithm (ECGA) is used to carry out the search process.Compared with the simple genetic algorithm, ECGA runs much faster and can get more accurate results with a much smaller population size and fewer function evaluations. Using the developed optimization program, blades of a 1.3 MW stall-regulated wind turbine are designed. Compared with the existing blades, the designed blades have obviously better aerodynamic performance.
Development of Motor Model of Rotor Slot Harmonics for Speed Sensorless Control of Induction Motor
Okubo, Tatsuya; Ishida, Muneaki; Doki, Shinji
This paper proposes a novel mathematical dynamic model to represent steady-state and transient-state characteristics of rotor slot harmonics of an induction motor for sensorless control. Although it is well known that the rotor slot harmonics originate from the mechanical structure of the induction motor, a mathematical model that describes the relationship between stator/rotor currents of the induction motor and the slot harmonics has not yet been proposed. Therefore, in this paper, a three-phase model of the induction motor that depicts the rotor slot harmonics is developed by taking into consideration the magnetomotive force harmonics and the change in the magnetic air gap caused by the rotor slots. Moreover, the validity of the proposed model is verified by comparing the experimental results and the calculated values.
Measured Boundary Layer Transition and Rotor Hover Performance at Model Scale
Overmeyer, Austin D.; Martin, Preston B.
2017-01-01
An experiment involving a Mach-scaled, 11:08 f t: diameter rotor was performed in hover during the summer of 2016 at NASA Langley Research Center. The experiment investigated the hover performance as a function of the laminar to turbulent transition state of the boundary layer, including both natural and fixed transition cases. The boundary layer transition locations were measured on both the upper and lower aerodynamic surfaces simultaneously. The measurements were enabled by recent advances in infrared sensor sensitivity and stability. The infrared thermography measurement technique was enhanced by a paintable blade surface heater, as well as a new high-sensitivity long wave infrared camera. The measured transition locations showed extensive amounts, x=c>0:90, of laminar flow on the lower surface at moderate to high thrust (CT=s > 0:068) for the full blade radius. The upper surface showed large amounts, x=c > 0:50, of laminar flow at the blade tip for low thrust (CT=s layer transition models in CFD and rotor design tools. The data is expected to be used as part of the AIAA Rotorcraft SimulationWorking Group
Matrix product states and the nonabelian rotor model
Milsted, Ashley
2015-01-01
We use uniform matrix product states (MPS) to study the (1+1)D $O(2)$ and $O(4)$ rotor models, which are equivalent to the Kogut-Susskind formulation of matter-free nonabelian lattice gauge theory on a "hawaiian earring" graph for $U(1)$ and $SU(2)$, respectively. Applying tangent space methods to obtain ground states and determine the mass gap and the $\\beta$-function, we find excellent agreement with known strong results, locating the BKT transition for $O(2)$ and successfully entering the asymptotic weak-coupling regime for $O(4)$. To obtain a finite local Hilbert space, we truncate in the space of irreducible representations (irreps) of the gauge group, comparing the effects of different cutoff values. We find that higher irreps become important in the crossover and weak-coupling regimes of the nonabelian theory, where entanglement also suddenly increases. This could have important consequences for TNS studies of Yang-Mills on higher dimensional graphs.
Stand diameter distribution modelling and prediction based on Richards function.
Directory of Open Access Journals (Sweden)
Ai-guo Duan
Full Text Available The objective of this study was to introduce application of the Richards equation on modelling and prediction of stand diameter distribution. The long-term repeated measurement data sets, consisted of 309 diameter frequency distributions from Chinese fir (Cunninghamia lanceolata plantations in the southern China, were used. Also, 150 stands were used as fitting data, the other 159 stands were used for testing. Nonlinear regression method (NRM or maximum likelihood estimates method (MLEM were applied to estimate the parameters of models, and the parameter prediction method (PPM and parameter recovery method (PRM were used to predict the diameter distributions of unknown stands. Four main conclusions were obtained: (1 R distribution presented a more accurate simulation than three-parametric Weibull function; (2 the parameters p, q and r of R distribution proved to be its scale, location and shape parameters, and have a deep relationship with stand characteristics, which means the parameters of R distribution have good theoretical interpretation; (3 the ordinate of inflection point of R distribution has significant relativity with its skewness and kurtosis, and the fitted main distribution range for the cumulative diameter distribution of Chinese fir plantations was 0.4∼0.6; (4 the goodness-of-fit test showed diameter distributions of unknown stands can be well estimated by applying R distribution based on PRM or the combination of PPM and PRM under the condition that only quadratic mean DBH or plus stand age are known, and the non-rejection rates were near 80%, which are higher than the 72.33% non-rejection rate of three-parametric Weibull function based on the combination of PPM and PRM.
Stand diameter distribution modelling and prediction based on Richards function.
Duan, Ai-guo; Zhang, Jian-guo; Zhang, Xiong-qing; He, Cai-yun
2013-01-01
The objective of this study was to introduce application of the Richards equation on modelling and prediction of stand diameter distribution. The long-term repeated measurement data sets, consisted of 309 diameter frequency distributions from Chinese fir (Cunninghamia lanceolata) plantations in the southern China, were used. Also, 150 stands were used as fitting data, the other 159 stands were used for testing. Nonlinear regression method (NRM) or maximum likelihood estimates method (MLEM) were applied to estimate the parameters of models, and the parameter prediction method (PPM) and parameter recovery method (PRM) were used to predict the diameter distributions of unknown stands. Four main conclusions were obtained: (1) R distribution presented a more accurate simulation than three-parametric Weibull function; (2) the parameters p, q and r of R distribution proved to be its scale, location and shape parameters, and have a deep relationship with stand characteristics, which means the parameters of R distribution have good theoretical interpretation; (3) the ordinate of inflection point of R distribution has significant relativity with its skewness and kurtosis, and the fitted main distribution range for the cumulative diameter distribution of Chinese fir plantations was 0.4∼0.6; (4) the goodness-of-fit test showed diameter distributions of unknown stands can be well estimated by applying R distribution based on PRM or the combination of PPM and PRM under the condition that only quadratic mean DBH or plus stand age are known, and the non-rejection rates were near 80%, which are higher than the 72.33% non-rejection rate of three-parametric Weibull function based on the combination of PPM and PRM.
Prediction and measurement of low-frequency harmonic noise of a hovering model helicopter rotor
Aggarawal, H. R.; Schmitz, F. H.; Boxwell, D. A.
Far-field acoustic data for a model helicopter rotor have been gathered in a large open-jet, acoustically treated wind tunnel with the rotor operating in hover and out of ground-effect. The four-bladed Boeing 360 model rotor with advanced airfoils, planform, and tip shape was run over a range of conditions typical of today's modern helicopter main rotor. Near in-plane acoustic measurements were compared with two independent implementations of classical linear theory. Measured steady thrust and torque were used together with a free-wake analysis (to predict the thrust and drag distributions along the rotor radius) as input to this first-principles theoretical approach. Good agreement between theory and experiment was shown for both amplitude and phase for measurements made in those positions that minimized distortion of the radiated acoustic signature at low-frequencies.
Quasimodes instability analysis of uncertain asymmetric rotor system based on 3D solid element model
Zuo, Yanfei; Wang, Jianjun; Ma, Weimeng
2017-03-01
Uncertainties are considered in the equation of motion of an asymmetric rotor system. Based on Hill's determinant method, quasimodes stability analysis with uncertain parameters is used to get stochastic boundaries of unstable regions. Firstly, A 3D finite element rotor model was built in rotating frame with four parameterized coefficients, which is assumed as random parameters representing the uncertainties existing in the rotor system. Then the influences of uncertain coefficients on the distribution of the unstable region boundaries are analyzed. The results show that uncertain parameters have various influences on the size, boundary and number of unstable regions. At last, the statistic results of the minimum and maximum spin speeds of unstable regions were got by Monte Carlo simulation. The used method is suitable for real engineering rotor system, because arbitrary configuration of rotors can be modeled by 3D finite element.
An $U_{qp}(u_2)$ Rotor Model for Rotational Bands of Superdeformed Nuclei
Barbier, R.; Meyer, J.; Kibler, M.
1995-01-01
A nonrigid rotor model is developed from the two-parameter quantum algebra $U_{qp}({\\rm u}_2)$. [This model presents the $U_{qp}({\\rm u}_2)$ symmetry and shall be referred to as the qp-rotor model.] A rotational energy formula as well as a qp-deformation of E2 reduced transition probabilities are derived. The qp-rotor model is applied (through fitting procedures) to twenty rotational bands of superdeformed nuclei in the $A \\sim 130$, 150 and 190 mass regions. Systematic comparisons between th...
Elastic multiple-mass model for rotordynamic analysis of flexible electrical rotors
Energy Technology Data Exchange (ETDEWEB)
Werner, U. [Siemens AG, Nuernberg (Germany). Industry, Drive Technologies, Large Drives, Products R and D
2011-12-15
The paper presents an elastic multiple-mass model for rotordynamic analysis of flexible electrical rotors supported in sleeve bearings, considering mechanical unbalances and electromagnetic forces. This model has been especially developed for flexible electrical rotors, which operate near below or near above the first critical bending speed of the rotor. Using this simplified model, a static rotor active part eccentricity can be simulated and the orbital movement of the rotor can be calculated. Additionally, the influence of different balancing concepts - elastic balancing versus rigid balancing - on the shaft vibrations is analyzed. To verify the model, a finite element analysis was performed, which indicates a satisfactory match. On the one hand, the aim of the paper is to derive an elastic multiple-mass model for rotordynamic analysis of flexible electrical rotors for special boundary conditions. On the other hand, the aim is to show the mathematical coherences - based on a simplified model - between the rotordynamics, the oil film characteristics of the sleeve bearings, the elasticity of the rotor structure, the electromagnetics and the balancing concept. (orig.)
Vibratory Loads Data from a Wind-Tunnel Test of Structurally Tailored Model Helicopter Rotors
Yeager, William T., Jr.; Hamouda, M-Nabil H.; Idol, Robert F.; Mirick, Paul H.; Singleton, Jeffrey D.; Wilbur, Matthew L.
1991-01-01
An experimental study was conducted in the Langley Transonic Dynamics Tunnel to investigate the use of a Bell Helicopter Textron (BHT) rotor structural tailoring concept, known as rotor nodalization, in conjunction with advanced blade aerodynamics as well as to evaluate rotor blade aerodynamic design methodologies. A 1/5-size, four-bladed bearingless hub, three sets of Mach-scaled model rotor blades were tested in forward flight from transition up to an advance ratio of 0.35. The data presented pertain only to the evaluation of the structural tailoring concept and consist of fixed-system and rotating system vibratory loads. These data will be useful for evaluating the effects of tailoring blade structural properties on fixed-system vibratory loads, as well as validating analyses used in the design of advanced rotor systems.
Validation of the Actuator Line Model for Simulating Flows past Yawed Wind Turbine Rotors
DEFF Research Database (Denmark)
Shen, Wen Zhong; Zhu, Wei Jun; Yang, Hua
2015-01-01
The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of −2.3˚, wind speeds of 10, 15, 24 m/s and yaw angles of 15......˚, 30˚ and 45˚. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm......, a pitch angle of 3˚, a wind speed of 5 m/s and yaw angles of 10˚ and 30˚. The computed loads are compared to the loads measured from pressure measurement....
Laiho, Antti; Holopainen, Timo P.; Klinge, Paul; Arkkio, Antero
2007-05-01
In this work the effects of the electromechanical interaction on rotordynamics and vibration characteristics of cage rotor electrical machines were considered. An eccentric rotor motion distorts the electromagnetic field in the air-gap between the stator and rotor inducing a total force, the unbalanced magnetic pull, exerted on the rotor. In this paper a low-order parametric model for the unbalanced magnetic pull is coupled with a three-dimensional finite element structural model of the electrical machine. The main contribution of the work is to present a computationally efficient electromechanical model for vibration analysis of cage rotor machines. In this model, the interaction between the mechanical and electromagnetic systems is distributed over the air gap of the machine. This enables the inclusion of rotor and stator deflections into the analysis and, thus, yields more realistic prediction for the effects of electromechanical interaction. The model was tested by implementing it for two electrical machines with nominal speeds close to one of the rotor bending critical speeds. Rated machine data was used in order to predict the effects of the electromechanical interaction on vibration characteristics of the example machines.
Ugarte, Juan P; Orozco-Duque, Andrés; Tobón, Catalina; Kremen, Vaclav; Novak, Daniel; Saiz, Javier; Oesterlein, Tobias; Schmitt, Clauss; Luik, Armin; Bustamante, John
2014-01-01
There is evidence that rotors could be drivers that maintain atrial fibrillation. Complex fractionated atrial electrograms have been located in rotor tip areas. However, the concept of electrogram fractionation, defined using time intervals, is still controversial as a tool for locating target sites for ablation. We hypothesize that the fractionation phenomenon is better described using non-linear dynamic measures, such as approximate entropy, and that this tool could be used for locating the rotor tip. The aim of this work has been to determine the relationship between approximate entropy and fractionated electrograms, and to develop a new tool for rotor mapping based on fractionation levels. Two episodes of chronic atrial fibrillation were simulated in a 3D human atrial model, in which rotors were observed. Dynamic approximate entropy maps were calculated using unipolar electrogram signals generated over the whole surface of the 3D atrial model. In addition, we optimized the approximate entropy calculation using two real multi-center databases of fractionated electrogram signals, labeled in 4 levels of fractionation. We found that the values of approximate entropy and the levels of fractionation are positively correlated. This allows the dynamic approximate entropy maps to localize the tips from stable and meandering rotors. Furthermore, we assessed the optimized approximate entropy using bipolar electrograms generated over a vicinity enclosing a rotor, achieving rotor detection. Our results suggest that high approximate entropy values are able to detect a high level of fractionation and to locate rotor tips in simulated atrial fibrillation episodes. We suggest that dynamic approximate entropy maps could become a tool for atrial fibrillation rotor mapping.
Model updating of rotor systems by using Nonlinear least square optimization
Jha, A. K.; Dewangan, P.; Sarangi, M.
2016-07-01
Mathematical models of structure or machineries are always different from the existing physical system, because the approach of numerical predictions to the behavior of a physical system is limited by the assumptions used in the development of the mathematical model. Model updating is, therefore necessary so that updated model should replicate the physical system. This work focuses on the model updating of rotor systems at various speeds as well as at different modes of vibration. Support bearing characteristics severely influence the dynamics of rotor systems like turbines, compressors, pumps, electrical machines, machine tool spindles etc. Therefore bearing parameters (stiffness and damping) are considered to be updating parameters. A finite element model of rotor systems is developed using Timoshenko beam element. Unbalance response in time domain and frequency response function have been calculated by numerical techniques, and compared with the experimental data to update the FE-model of rotor systems. An algorithm, based on unbalance response in time domain is proposed for updating the rotor systems at different running speeds of rotor. An attempt has been made to define Unbalance response assurance criterion (URAC) to check the degree of correlation between updated FE model and physical model.
Energy Level Statistics in Particle—Rotor Model
Institute of Scientific and Technical Information of China (English)
ZHOUXian－Rong; MENGJie; 等
2002-01-01
Energy level statistics of a system consisting of six particles interacting by delta force in a two-j model coupled with a deformed core is studied in particle-rotor model.For single-j shell (i13/2) and two-j shell (g7/2+d5/2) the exact energies for our statistical analysis are obtained from a full diagonalization of the Hamiltonian,whilt in two-j case (i13/2+g9/2) the configuration truncation is used.The nearest-neighbor distribution of energy levels and spectral rigidity are studied as the function of spin.The results of single-j shell are compared with those in two-j case.It is showed that the system becomes more regular when single-j space (i13/2) is replaced by two-j shell (g7/2+d5/2) although the basis size of the configuration space is unchanged.The degree of chaoticity of the system,however,changes slightly when configuration space is enlarged by extending single-j shell (i13/2) to two-j shell (i13/2+g9/2).
Energy Technology Data Exchange (ETDEWEB)
Romero Navarrete, Jose Antonio
1988-09-01
In the operation of complicated systems the simulation has been transformed into an important resource, as much for the aid in the operation of the real plant as for the previous training of the personnel who will have the operation responsibility of the different systems. In this general frame, and particularly in the field referring to the development of models to be used in the simulators for thermal and nuclear power stations future operators training, in this work a general modeling of the rotors orbiting amplitudes of turbogroups, carrying out as a part of the methodology a general typification of the conditions and modifying effects of the dynamic behavior of the rotors of the turbogroups. The mathematical model consists of the handling of an abstracted system of the real system, considering discreet masses united by mass devoid flexible sections. In the bearings, average cutting moments are considered, sensible to linear misalignments of the bearing, as well as to the lubricating oil pressure and temperature. The three-axial states of stresses are taken into account as far as the parameters of the material hardening are set out for each considered segment, leaving this phenomenon based on the radius of the section as well as on the rotation speed. As an influence of the environment, a diminution of the elasticity modulus of the material as the temperature increases, is considered. As faults are studied, on one hand, the influence that the diminution of the diametric moment of inertia, as the result of a cross-sectional fissure has on the critical speeds values and the rotor configurations. The other evaluated fault consists of the linear misalignment of the bearing pedestals, and its influence appears on the orbitation amplitude. The calculation method applied is the one of Prohl, since the alternative method for the mathematical model applied, the one of the transference matrixes, consumes longer run time and memory, which is demonstrated by means of an
A 5-DOF Model for Aeroengine Spindle Dual-rotor System Analysis
Institute of Scientific and Technical Information of China (English)
HU Qinghua; DENG Sier; TENG Hongfei
2011-01-01
This paper develops a five degrees of freedom (5-DOF) model for aeroengine spindle dual-rotor system dynamic analysis.In this system, the dual rotors are supported on two angular contact ball bearings and two deep groove ball bearings, one of the latter-mentioned bearings works as the inter-shaft bearing.Driven by respective motors, the dual rotors have different co-rotating speeds.The proposed model mathematically formulates the nonlinear displacements, elastic deflections and contact forces of beatings with consideration of 5-DOF and coupling of dual rotors.The nonlinear equations of motions of dual rotors with 5-DOF are solved using Runge-Kutta-Fehlberg algorithm.In order to investigate the effect of the introduced 5-DOF and nonlinear dynamic bearing model, we compare the proposed model with two models: the 3-DOF model of this system only considering three translational degrees of freedom (Gupta, 1993, rotational freedom is neglected); the 5-DOF model where the deep groove ball bearings are simplified as linear elastic spring (Guskov, 2007).The simulation results verify Gupta's prediction (1993) and show that the rotational freedom of rotors and nonlinear dynamic model of bearings have great effect on the system dynamic simulation.The quantitative results are given as well.
Directory of Open Access Journals (Sweden)
Farooq Ahmed Arain
2012-01-01
Full Text Available The aim of this study was to develop a statistical model for the effect of RS (Rotor Speed, YT (Yarn Twist and YLD (Yarn Linear Density on production and quality characteristics of rotor spun yarn. Cotton yarns of 30, 35 and 40 tex were produced on rotor spinning machine at different rotor speeds (i.e. 70000, 80000, 90000 and 100000 rpm and with different twist levels (i.e. 450, 500, 550, 600 and 700 tpm. Yarn production (g/hr and quality characteristics were determined for all the experiments. Based on the results, models were developed using response surface regression on MINITAB�16 statistical tool. The developed models not only characterize the intricate relationships among the factors but may also be used to predict the yarn production and quality characteristics at any level of factors within the range of experimental values.
Dynamic modeling and nonlinear control strategy for an underactuated quad rotor rotorcraft
Institute of Scientific and Technical Information of China (English)
Ashfaq Ahmad MIAN; Dao-bo WANG
2008-01-01
In this paper, a nonlinear dynamic MIMO model of a 6-DOF underactuated quad rotor rotorcraft is derived based on Newton-Euler formalism. The derivation comprises determining equations of motion of the quad rotor in three dimensions and seeking to approximate the actuation forces through modeling of the aerodynamic coefficients and electric motor dynamics. The derived model is dynamically unstable, so a sequential nonlinear control strategy is implemented for the quad rotor. The control strategy includes exact feedback linearization technique, using the geometric methods of nonlinear control. The performance of the nonlinear control algorithm is evaluated using simulation and the results show the effectiveness of the proposed control strategy for the quad rotor rotorcraft near quasi-stationary flight.
Energy Level Statistics in Particle-Rotor Model
Institute of Scientific and Technical Information of China (English)
ZHOU Xian-Rong; GUO Lu; MENG Jie; ZHAO En-Guang
2002-01-01
Energy level statistics of a system consisting of six particles interacting by delta force in a two-j modelcoupled with a deformed core is studied in particle-rotor model. For single-j shell (i13/2) and two-j shell (g7/2 + d5/2)the exact energies for our statistical analysis are obtained from a full diagonalization of the Hamiltonian, while in two-jcase (i13/2 + g9/2) the configuration truncation is used. The nearest-neighbor distribution of energy levels and spectralrigidity are studied as the function of spin. The results of single-j shell are compared with those in two-j case. It isshowed that the system becomes more regular when single-j space (i13/2) is replaced by two-j shell (g7/2 +d5/2) althoughthe basis size of the configuration space is unchanged. The degree of chaoticity of the system, however, changes slightlywhen configuration space is enlarged by extending single-j shell (i13/2) to two-j shell (i13/2 + g9/2).
Matrix product states and the non-Abelian rotor model
Milsted, Ashley
2016-04-01
We use uniform matrix product states to study the (1 +1 )D O (2 ) and O (4 ) rotor models, which are equivalent to the Kogut-Susskind formulation of matter-free non-Abelian lattice gauge theory on a "Hawaiian earring" graph for U (1 ) and S U (2 ), respectively. Applying tangent space methods to obtain ground states and determine the mass gap and the β function, we find excellent agreement with known results, locating the Berezinskii-Kosterlitz-Thouless transition for O (2 ) and successfully entering the asymptotic weak-coupling regime for O (4 ). To obtain a finite local Hilbert space, we truncate in the space of generalized Fourier modes of the gauge group, comparing the effects of different cutoff values. We find that higher modes become important in the crossover and weak-coupling regimes of the non-Abelian theory, where entanglement also suddenly increases. This could have important consequences for tensor network state studies of Yang-Mills on higher-dimensional graphs.
Directory of Open Access Journals (Sweden)
Ilker Ercanli
2015-06-01
Full Text Available Diameter at breast height (DBH is the simplest, most common and most important tree dimension in forest inventory and is closely correlated with wood volume, height and biomass. In this study, a number of linear and nonlinear models predicting diameter at breast height from stump diameter were developed and evaluated for Oriental beech (Fagus orientalisLipsky stands located in the forest region of Ayancık, in the northeast of Turkey. A set of 1,501 pairs of diameter at breast height-stump measurements, originating from 70 sample plots of even-aged Oriental beech stands, were used in this study. About 80 % of the otal data (1,160 trees in 55 sample plots was used to fit a number of linear and nonlinear model parameters; the remaining 341 trees in 15 sample plots were randomly reserved for model validation and calibration response. The power model data set was found to produce the most satisfactory fits with the Adjusted Coefficient of Determination, R2adj (0.990, Root Mean Square Error, RMSE (1.25, Akaike’s Information Criterion, AIC (3820.5, Schwarz’s Bayesian Information Criterion, BIC (3837.2, and Absolute Bias (1.25. The nonlinear mixed-effect modeling approach for power model with R2adj(0.993, AIC (3598, BIC (3610.1, Absolute Bias (0.73 and RMSE (1.04 provided much better fitting and precise predictions for DBH from stump diameter than the conventional nonlinear fixed effect model structures for this model. The calibration response including tree DBH and stump diameter measurements of the four largest trees in a calibrated sample plot in calibration produced the highest Bias, -5.31 %, and RMSE, -6.30 %, the greatest reduction percentage.
Directory of Open Access Journals (Sweden)
Arbab Nighat Khizer
2015-01-01
Full Text Available This paper presents a time-domain approach for identification of longitudinal dynamics of single rotor model helicopter. A frequency sweep excitation input signal is applied for hover flying mode widely used for space state linearized model. A fully automated programmed flight test method provides high quality flight data for system identification using the computer controlled flight simulator X-plane©. The flight test data were recorded, analyzed and reduced using the SIDPAC (System Identification Programs for Air Craft toolbox for MATLAB, resulting in an aerodynamic model of single rotor helicopter. Finally, the identified model of single rotor helicopter is validated on Raptor 30-class model helicopter at hover showing the reliability of proposed approach
Thermal Modeling of Disc Brake Rotor in Frictional Contact
Ali, Belhocine; Ghazaly, Nouby Mahdi
2013-01-01
Safety aspect in automotive engineering has been considered as a number one priority in development of new vehicle. Each single system has been studied and developed in order to meet safety requirement. Instead of having air bag, good suspension systems, good handling and safe cornering, there is one most critical system in the vehicle which is brake systems. The objective of this work is to investigate and analyze the temperature distribution of rotor disc during braking operation using ANSYS Multiphysics. The work uses the finite element analysis techniques to predict the temperature distribution on the full and ventilated brake disc and to identify the critical temperature of the rotor. The analysis also gives us, the heat flux distribution for the two discs.
Multi-diameter silicon nanowires: Fabrication, characterization, and modeling
Alagoz, Arif Sinan
Nanotechnology is a rapidly expanding interdisciplinary field offering novel devices for broad range of applications. Quantum effects and surface to volume ratio of nanostructures are strongly size dependent, and redefine material properties at nanoscale. Silicon is one of the most promising materials for next generation nanostructured transistors, photonics devices, Li-ion batteries, photovoltaic solar cells, and thermoelectric energy generators. Since electrical, optical, and mechanical properties of nanostructures strongly depend on their shape, size, periodicity, and crystal structure; it is crucial to control these parameters in order to optimize device performance for targeted applications. This dissertation is intended to develop a low-cost, low-temperature, high-throughput, and large-area nanowire fabrication method that can produce well-ordered arrays of hierarchical single-crystal silicon nanowires at large scale by using nanosphere lithography and metal-assisted chemical etching. Nanowire morphology was characterized by using scanning electron microscope and optical properties of nanowire arrays were modeled with the help of finite-difference-time domain method. These novel multi-diameter silicon nanowire arrays have the potential applications in many fields including but not limited to next generation nanowire solar cells to field ionization gas sensors.
Directory of Open Access Journals (Sweden)
Mohsen Shanbeh
2011-01-01
Full Text Available One of the main methods to reduce the production costs is waste recycling which is the most important challenge for the future. Cotton wastes collected from ginning process have desirable properties which could be used during spinning process. The purpose of this study was to develop predictive models of breaking strength and mass irregularity (CV% of cotton waste rotor-spun yarns containing cotton waste collected from ginning process by using the artificial neural network trained with backpropagation algorithm. Artificial neural network models have been developed based on rotor diameter, rotor speed, navel type, opener roller speed, ginning waste proportion and yarn linear density as input parameters. The parameters of artificial neural network model, namely, learning, and momentum rate, number of hidden layers and number of hidden processing elements (neurons were optimized to get the best predictive models. The findings showed that the breaking strength and mass irregularity of rotor spun yarns could be predicted satisfactorily by artificial neural network. The maximum error in predicting the breaking strength and mass irregularity of testing data was 8.34% and 6.65%, respectively.
Modeling and Analysis of a Micromotor with an Electrostatically Levitated Rotor
Institute of Scientific and Technical Information of China (English)
HAN Fengtian; WU Qiuping; ZHANG Rong
2009-01-01
The modeling and evaluation of a prototype rotary micromotor where the annular rotor is supported electrostatically in five degrees of freedom is presented in order to study the behavior of this levitated micromotor and further optimize the device geometry. The analytical torque model is obtained based on the principle of a planar variable-capacitance electrostatic motor while the viscous damping caused by air film between the stator and rotor is derived using laminar Couette flow model.Simulation results of the closed-loop drive motor, based on the developed dynamic model after eliminating mechanical friction torque via electrostatic suspension, are presented. The effects of the high-voltage drive, required for rotation of the rotor, on overload capacity and suspension stiffness of the electrostatic bearing system are also analytically evaluated in an effort to determine allowable drive voltage and attainable rotor speed in operation. The analytical results show that maximum speed of the micromotor is limited mainly by viscous drag torque and stiffness of the bearing system. Therefore, it is expected to operate the device in vacuum so as to increase the rotor speed significantly, especially for those electrostatically levitated micromotors to be used as an angular rate micro-gyroscope.
Directory of Open Access Journals (Sweden)
Xi Wu
2008-01-01
Full Text Available A mathematical model of a cracked rotor and an asymmetric rotor with two disks representing a turbine and a generator is utilized to study the vibrations due to imbalance and side load. Nonlinearities typically related with a “breathing” crack are included using a Mayes steering function. Numerical simulations demonstrate how the variations of rotor parameters affect the vibration response and the effect of coupling between torsional and lateral modes. Bode, spectrum, and orbit plots are used to show the differences between the vibration signatures associated with cracked shafts versus asymmetric shafts. Results show how nonlinear lateral-torsional coupling shifts the resonance peaks in the torsional vibration response for cracked shafts and asymmetric rotors. The resonance peaks shift depending on the ratio of the lateral-to-torsional natural frequencies with the peak responses occurring at noninteger values of the lateral natural frequency. When the general nonlinear models used in this study are constrained to reduce to linear torsional vibration, the peak responses occur at commonly reported integer ratios. Full spectrum analyses of the X and Y vibrations reveal distinct vibration characteristics of both cracked and asymmetric rotors including reverse vibration components. Critical speeds and vibration orders predicted using the models presented herein include and extend diagnostic indicators commonly reported.
Simplified rotor load models and fatigue damage estimates for offshore wind turbines.
Muskulus, M
2015-02-28
The aim of rotor load models is to characterize and generate the thrust loads acting on an offshore wind turbine. Ideally, the rotor simulation can be replaced by time series from a model with a few parameters and state variables only. Such models are used extensively in control system design and, as a potentially new application area, structural optimization of support structures. Different rotor load models are here evaluated for a jacket support structure in terms of fatigue lifetimes of relevant structural variables. All models were found to be lacking in accuracy, with differences of more than 20% in fatigue load estimates. The most accurate models were the use of an effective thrust coefficient determined from a regression analysis of dynamic thrust loads, and a novel stochastic model in state-space form. The stochastic model explicitly models the quasi-periodic components obtained from rotational sampling of turbulent fluctuations. Its state variables follow a mean-reverting Ornstein-Uhlenbeck process. Although promising, more work is needed on how to determine the parameters of the stochastic model and before accurate lifetime predictions can be obtained without comprehensive rotor simulations.
Modeling and Robust Trajectory Tracking Control for a Novel Six-Rotor Unmanned Aerial Vehicle
Directory of Open Access Journals (Sweden)
Chengshun Yang
2013-01-01
Full Text Available Modeling and trajectory tracking control of a novel six-rotor unmanned aerial vehicle (UAV is concerned to solve problems such as smaller payload capacity and lack of both hardware redundancy and anticrosswind capability for quad-rotor. The mathematical modeling for the six-rotor UAV is developed on the basis of the Newton-Euler formalism, and a second-order sliding-mode disturbance observer (SOSMDO is proposed to reconstruct the disturbances of the rotational dynamics. In consideration of the under-actuated and strong coupling properties of the six-rotor UAV, a nested double loops trajectory tracking control strategy is adopted. In the outer loop, a position error PID controller is designed, of which the task is to compare the desired trajectory with real position of the six-rotor UAV and export the desired attitude angles to the inner loop. In the inner loop, a rapid-convergent nonlinear differentiator (RCND is proposed to calculate the derivatives of the virtual control signal, instead of using the analytical differentiation, to avoid “differential expansion” in the procedure of the attitude controller design. Finally, the validity and effectiveness of the proposed technique are demonstrated by the simulation results.
Model-Based Degree Estimation of Unbalance and Misalignment in Flexible Coupling-rotor System
Institute of Scientific and Technical Information of China (English)
LI Changyou; XU Minqiang; GUO Song; WANG Yuewu; WANG Rixin
2009-01-01
The condition of rotor system must be assessed in order to develop condition-based maintenance for rotating machinery. It is determined by multiple variables such as unbalance degree, misalignment degree, the amount of bending deformation of the shaft, occurrence of shaft crack of rotor system and so on. The estimation of the degrees of unbalance and misalignment in flexible coupling-rotor system is discussed. The model-based approach is employed to solve this problem. The models of the equivalent external loads for unbalance and misalignment are derived and analyzed. Then, the degrees of unbalance and misalignment are estimated by analyzing the components of the equivalent external loads of which the frequencies are equal to the 1 and 2 times running frequency respectively. The equivalent external loads are calculated according to the dynamic equation of the original rotor system and the differences between the dynamical responses in normal case and the vibrations when the degree of unbalance or misalignment or both changes. The denoise method based on bandpass filter is used to decrease the effect of noise on the estimation accuracy. The numerical examples are given to show that the proposed approach can estimate the degrees of unbalance and misalignment of the flexible coupling-rotor system accurately.
Dynamic surface measurements on a model helicopter rotor during blade slap at high angles of attack
Hubbard, J. E., Jr.; Harris, W. L.
1982-01-01
The modern helicopter offers a unique operational capability to both the public and private sectors. However, the use of the helicopter may become severely limited due to the radiated noise generated by the rotor system. A description is presented of some of the experimental results obtained with a model helicopter rotor in an anechoic wind tunnel with regard to blade stall as a source mechanism of blade slap. Attention is given to dynamic rotor blade surface phenomena and the resulting far field impulsive noise from the model helicopter rotor at high angles of attack and low tip speed. The results of the investigation strongly implicates the boundary layer as playing an important role in blade slap due to blade/vortex interaction (BVI) in a highly loaded rotor. Intermittent stall cannot be ruled out as a possible source mechanism for blade slap. This implies that blade surface characteristics, airfoil shape and local Reynolds number may now be used as tools to reduce the resultant far-field sound pressure levels in helicopters.
A comparison of model helicopter rotor Primary and Secondary blade/vortex interaction blade slap
Hubbard, J. E., Jr.; Leighton, K. P.
1983-01-01
A study of the relative importance of blade/vortex interactions which occur on the retreating side of a model helicopter rotor disk is described. Some of the salient characteristics of this phenomenon are presented and discussed. It is shown that the resulting Secondary blade slap may be of equal or greater intensity than the advancing side (Primary) blade slap. Instrumented model helicopter rotor data is presented which reveals the nature of the retreating blade/vortex interaction. The importance of Secondary blade slap as it applies to predictive techniques or approaches is discussed. When Secondary blade slap occurs it acts to enlarge the window of operating conditions for which blade slap exists.
Energy Technology Data Exchange (ETDEWEB)
Breton, S.P.; Watters, C.S.; Masson, C. [Ecole de Technologie Superieure, Montreal, PQ (Canada)
2010-07-01
This presentation discussed the model rotor experiments under controlled conditions (MEXICO) project. The experiments are being conducted in the largest wind tunnel in Europe in order to determine optimal yaw and pitch angles for wind turbines as well as to test the performance of blade aerodynamic profiles and rotor instrumentation. Data obtained during the experiments are used to determine velocity component points in order to develop a greater understanding of wind turbine aerodynamics and improve calculation methods. Blade element momentum (BEM) computational fluid dynamics (CFD) and vortex wake codes are used in the program, which includes an actuator surface method embedded in a customized CFD finite element method. To date, the project has validated various models with experimental data, and mapped the induced velocities upwind and downwind from rotors. Further research is being conducted to compare experimental results with other results in the literature related to blade loading, root bending moments, and detailed flow characteristics. Charts of experimental results were included. tabs., figs.
Numerical and Analytical Analysis of Elastic Rotor Natural Frequency
Directory of Open Access Journals (Sweden)
Adis J. Muminovic
2014-11-01
Full Text Available In this paper simulation model which enables quick analysis of elastic rotor natural frequency modes is developed using Matlab. This simulation model enables users to get dependency diagram of natural frequency in relation to diameter and length of the rotor,density of the material or modulus of elasticity. Testing of the model is done using numerical analysis in SolidWorks software.
Actuator disk model of wind farms based on the rotor average wind speed
DEFF Research Database (Denmark)
Han, Xing Xing; Xu, Chang; Liu, De You;
2016-01-01
Due to difficulty of estimating the reference wind speed for wake modeling in wind farm, this paper proposes a new method to calculate the momentum source based on the rotor average wind speed. The proposed model applies volume correction factor to reduce the influence of the mesh recognition...
Modeling and design strategies for the vibration response of turbine engine rotors
Baik, Sanghum
Efficient, novel design and analysis methods are presented for improving the structural performance of turbine engine rotors with respect to blade vibration response. For a bladed disk, the blades are intended to be identical; however, blade-to-blade structural irregularities, known as blade mistuning, in practice are unavoidable due to manufacturing tolerances and in-service wear. Even small levels of blade mistuning may cause severe increases in blade vibration amplitudes relative to those computed for the ideal, tuned rotor. Thus, the sensitivity of bladed disks to mistuning is a serious safety, readiness, and maintenance concern for turbine engines. Hereby, the effects of blade mistuning are systematically accounted for in searching for a reliable, robust rotor design; that is, a bladed disk less sensitive to mistuning. To this end, design analysis tools are developed for bladed disks. First, as an efficient tool for accurately predicting the vibration response of mistuned rotors, a previously developed reduced-order vibration modeling technique is extended to handle the case of mass mistuning. Even when mass mistuning occurs in small geometric regions of the blades, the enhanced technique can precisely capture free and forced vibration response of the mistuned rotors. Second, as a fast tool for approximately assessing mistuning sensitivity of rotors, a power flow analysis method is proposed. This approach enables the systematic estimation of vibration energy flow within a nominal rotor for excitation cases of interest. This dynamic information is then used to evaluate the robustness of the rotor design with respect to blade mistuning. These tools are incorporated into the design problem of finding an optimal disk geometry to achieve minimum weight while ensuring that blade stress levels of mistuned rotors are kept below a specified safety limit. In doing so, an optimum candidate satisfying the design constraints in an approximate sense is calculated quickly
Computational Study of Flow Interactions in Coaxial Rotors
Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.
2016-01-01
Although the first idea of coaxial rotors appeared more than 150 years ago, most helicopters have used single main-rotor/tail-rotor combination. Since reactive moments of coaxial rotors are canceled by contra-rotation, no tail rotor is required to counter the torque generated by the main rotor. Unlike the single main rotor design that distributes power to both main and tail rotors, all of the power for coaxial rotors is used for vertical thrust. Thus, no power is wasted for anti-torque or directional control. The saved power helps coaxial rotors reach a higher hover ceiling than single rotor helicopters. Another advantage of coaxial rotors is that the overall rotor diameter can be reduced for a given vehicle gross weight because each rotor provides a maximum contribution to vertical thrust to overcome vehicle weight. However, increased mechanical complexity of the hub has been one of the challenges for manufacturing coaxial rotorcraft. Only the Kamov Design Bureau of Russia had been notably successful in production of coaxial helicopters until Sikorsky built X2, an experimental compound helicopter. Recent developments in unmanned aircraft systems and high-speed rotorcraft have renewed interest in the coaxial configuration. Multi-rotors are frequently used for small electric unmanned rotorcraft partly due to mechanical simplicity. The use of multiple motors provides redundancy as well as cost-efficiency. The multi-rotor concept has rarely been used until recently because of its inherent stability and control problems. However, advances in inexpensive electronic flight control systems have opened the floodgates for small drones using multirotors. Coaxial rotors have started to appear in some multi-rotor configurations. Small coaxial rotors have often been designed using a hundred year old approach that is "sketch, build, fly, and iterate." In that approach, there is no systematic way to explore trade-offs or determine logical next steps. It is neither possible to
Loads and Performance Data from a Wind-Tunnel Test of Generic Model Helicopter Rotor Blades
Yeager, William T., Jr.; Wilbur, Matthew L.
2005-01-01
An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to acquire data for use in assessing the ability of current and future comprehensive analyses to predict helicopter rotating-system and fixed-system vibratory loads. The investigation was conducted with a generic model helicopter rotor system using blades with rectangular planform, no built-in twist, uniform radial distribution of mass and stiffnesses, and a NACA 0012 airfoil section. Rotor performance data, as well as mean and vibratory components of blade bending and torsion moments, fixed-system forces and moments, and pitch link loads were obtained at advance ratios up to 0.35 for various combinations of rotor shaft angle-of-attack and collective pitch. The data are presented without analysis.
Gamma-soft Analog of the Confined Beta-soft Rotor Model
Bonatsos, D; Pietralla, N; Terziev, P A
2006-01-01
A gamma-soft analog of the confined beta-soft (CBS) rotor model is developed, by using a gamma-independent displaced infinite well beta-potential in the Bohr Hamiltonian, for which exact separation of variables is possible. Level schemes interpolating between the E(5) critical point symmetry (with R(4/2)=E(4)/E(2)= 2.20) and the O(5) gamma-soft rotor (with R(4/2)=2.50) are obtained, exhibiting a crossover of excited 0+ bandheads which leads to agreement with the general trends of first excited 0+ states in this region and is observed experimentally in 128-Xe and 130-Xe.
Directory of Open Access Journals (Sweden)
Robert Porter
2016-11-01
Full Text Available This paper presents the development and implementation of a single tilting rotor multirotor helicopter. A single tilting rotor multirotor helicopter is proposed that allows for decoupled lateral acceleration and attitude states. A dynamics model of the proposed multirotor helicopter is established to enable control system development. A control system architecture and daisy chaining-based control allocation scheme is developed and implemented. The control architecture facilitates the control of decoupled lateral accelerations and attitudes. Further, a computational and experimental analysis is undertaken and offers evidence that the proposed multirotor helicopter and control system architecture enables the multirotor helicopter to achieve lateral accelerations without requiring attitude actuation.
DEFF Research Database (Denmark)
Sørensen, Dan Nørtoft; Sørensen, Jens Nørkær
2000-01-01
A numerically efficient mathematical model for the aerodynamics of rotor-only axial fans has been developed. The model is based on a blade-elementprinciple whereby the rotor is divided into a number of annular streamtubes. For each of these streamtubes relations for velocity, pressure, and radial......A numerically efficient mathematical model for the aerodynamics of rotor-only axial fans has been developed. The model is based on a blade-elementprinciple whereby the rotor is divided into a number of annular streamtubes. For each of these streamtubes relations for velocity, pressure......, and radialposition are derived from the incompressible conservation laws for mass, tangential momentum, and energy. The resulting system of equations isnonlinear and, due to mass conservation and pressure equilibrium far downstream of the rotor, strongly coupled. The equations are solved using the...
Hodges, Robert V.; Nixon, Mark W.; Rehfield, Lawrence W.
1987-01-01
A methodology was developed for the structural analysis of composite rotor blades. This coupled-beam analysis is relatively simple to use compared with alternative analysis techniques. The beam analysis was developed for thin-wall single-cell rotor structures and includes the effects of elastic coupling. This paper demonstrates the effectiveness of the new composite-beam analysis method through comparison of its results with those of an established baseline analysis technique. The baseline analysis is an MSC/NASTRAN finite-element model built up from anisotropic shell elements. Deformations are compared for three linear static load cases of centrifugal force at design rotor speed, applied torque, and lift for an ideal rotor in hover. A D-spar designed to twist under axial loading is the subject of the analysis. Results indicate the coupled-beam analysis is well within engineering accuracy.
Advanced Model of Squirrel Cage Induction Machine for Broken Rotor Bars Fault Using Multi Indicators
Directory of Open Access Journals (Sweden)
Ilias Ouachtouk
2016-01-01
Full Text Available Squirrel cage induction machine are the most commonly used electrical drives, but like any other machine, they are vulnerable to faults. Among the widespread failures of the induction machine there are rotor faults. This paper focuses on the detection of broken rotor bars fault using multi-indicator. However, diagnostics of asynchronous machine rotor faults can be accomplished by analysing the anomalies of machine local variable such as torque, magnetic flux, stator current and neutral voltage signature analysis. The aim of this research is to summarize the existing models and to develop new models of squirrel cage induction motors with consideration of the neutral voltage and to study the effect of broken rotor bars on the different electrical quantities such as the park currents, torque, stator currents and neutral voltage. The performance of the model was assessed by comparing the simulation and experimental results. The obtained results show the effectiveness of the model, and allow detection and diagnosis of these defects.
Using a cylindrical vortex model to assess the induction zone infront of aligned and yawed rotors
DEFF Research Database (Denmark)
Branlard, Emmanuel Simon Pierre; Meyer Forsting, Alexander Raul
2015-01-01
Analytical formulae for the velocity field induced by a cylindrical vortex wake model areapplied to assess the induction zone in front of aligned and yawed rotors. The results arecompared to actuator disk (AD) simulations for different operating conditions, includingfinite tip-speed ratios...
ROTOR UNBALANCE LOAD CONTROL OF WIND TURBINE BASED ON UNIVERSAL MODEL%基于泛模型的风轮不平衡载荷控制
Institute of Scientific and Technical Information of China (English)
王晓东; 姚兴佳
2012-01-01
针对大型变速变桨风电机组风轮的非线性特征和难以建立精确模型的问题,设计了一种基于泛模型的风轮不平衡载荷自适应控制器.根据传感器测量的叶根载荷,对3个叶片进行独立变桨控制,通过3个叶片的桨距角差异来减小风轮的不平衡载荷.在此基础上,以双馈变速变桨机组为对象,通过仿真对该控制器进行了测试,结果表明该方法用于减小风轮的不平衡载荷是可行且有效的.%With the increasing of wind turbine size and rotor diameter, the wind shear, turbulence and tower shadow more and more affect the load of large scale turbine. Dynamic unbalance load become a key in large scale wind turbine design. It is approved that the pitch control can impact on the rotor loads. Considering the difficulty to build the exact model and non-linear character of rotor, an individual controller banded on universal model was developed in to mitigate the rotor unbalance load for variable speed wind turbine. The controller adjusts the pitch angle of three blades individually based on the measurement load. The pitch angle difference could reduce the effect of wind diversification in the rotor plane. The controller was simulated based on a doubly fed variable speed wind turbine model. The simulation result verified that it is feasible and effective.
Unified continuum damage model for matrix cracking in composite rotor blades
Energy Technology Data Exchange (ETDEWEB)
Pollayi, Hemaraju; Harursampath, Dineshkumar [Nonlinear Multifunctional Composites - Analysis and Design Lab (NMCAD Lab) Department of Aerospace Engineering Indian Institute of Science Bangalore - 560012, Karnataka (India)
2015-03-10
This paper deals with modeling of the first damage mode, matrix micro-cracking, in helicopter rotor/wind turbine blades and how this effects the overall cross-sectional stiffness. The helicopter/wind turbine rotor system operates in a highly dynamic and unsteady environment leading to severe vibratory loads present in the system. Repeated exposure to this loading condition can induce damage in the composite rotor blades. These rotor/turbine blades are generally made of fiber-reinforced laminated composites and exhibit various competing modes of damage such as matrix micro-cracking, delamination, and fiber breakage. There is a need to study the behavior of the composite rotor system under various key damage modes in composite materials for developing Structural Health Monitoring (SHM) system. Each blade is modeled as a beam based on geometrically non-linear 3-D elasticity theory. Each blade thus splits into 2-D analyzes of cross-sections and non-linear 1-D analyzes along the beam reference curves. Two different tools are used here for complete 3-D analysis: VABS for 2-D cross-sectional analysis and GEBT for 1-D beam analysis. The physically-based failure models for matrix in compression and tension loading are used in the present work. Matrix cracking is detected using two failure criterion: Matrix Failure in Compression and Matrix Failure in Tension which are based on the recovered field. A strain variable is set which drives the damage variable for matrix cracking and this damage variable is used to estimate the reduced cross-sectional stiffness. The matrix micro-cracking is performed in two different approaches: (i) Element-wise, and (ii) Node-wise. The procedure presented in this paper is implemented in VABS as matrix micro-cracking modeling module. Three examples are presented to investigate the matrix failure model which illustrate the effect of matrix cracking on cross-sectional stiffness by varying the applied cyclic load.
Lackner, M.A.; van Kuik, G.A.M.
2009-01-01
Modern wind turbines have been steadily increasing in size, and have now become very large, with recent models boasting rotor diameters greater than 120 m. Reducing the loads experienced by the wind turbine rotor blades is one means of lowering the cost of energy of wind turbines. Wind turbines are
Energy Technology Data Exchange (ETDEWEB)
Schepers, J.G.; Boorsma, K. [Energy research Center of the Netherlands ECN, Petten (Netherlands); Munduate, X. [National Renewable Energy Center, CENER, Pamplona (Spain)
2013-02-15
The paper presents the final results from the first phase of IEA Task 29 'Mexnext'. Mexnext was a joint project in which 20 parties from 11 different countries cooperated. The main aim of Mexnext was to analyse the wind tunnel measurements which have been taken in the EU project 'MEXICO'. In the MEXICO project 10 institutes from 6 countries cooperated in doing experiments on an instrumented, three-bladed wind turbine of 4.5 m diameter placed in the 9.5 by 9.5 m{sup 2} open section of the Large Low-speed Facility (LLF) of the test facility DNW (German-Dutch Wind Tunnels). Pressure distributions on the blades were obtained from 148 Kulite pressure sensors, distributed over 5 sections at 25, 35, 60, 82 and 92% radial position respectively. Blade loads were monitored through two strain-gauge bridges at each blade root. Most interesting however are the extensive PIV flow field measurements, which have been taken simultaneously with the pressure and load measurements. As a result of the international collaboration within this task a very thorough analysis of the data could be carried out and a large number of codes were validated not only in terms of loads but also in terms of underlying flow field. The paper will present several results from Mexnext-I, i.e. validation results and conclusion on modelling deficiencies and directions for model improvement. The future plans of the Mexnext consortium are also briefly discussed. Amongst these are Mexnext-II, a project in which also aerodynamic measurements other than MEXICO are included, and 'New MEXICO' in which additional measurement on the MEXICO model are performed.
Some issues on modeling atmospheric turbulence experienced by helicopter rotor blades
Costello, Mark; Gaonkar, G. H.; Prasad, J. V. R.; Schrage, D. P.
1992-01-01
The atmospheric turbulence velocities seen by nonrotating aircraft components and rotating blades can be substantially different. The differences are due to the spatial motion of the rotor blades, which move fore and aft through the gust waves. Body-fixed atmospheric turbulence refers to the actual atmospheric turbulence experienced by a point fixed on a nonrotating aircraft component such as the aircraft's center of gravity or the rotor hub, while blade-fixed atmospheric turbulence refers to the atmospheric turbulence experienced by an element of the rotating rotor blade. An example is presented, which, though overly simplified, shows important differences between blade- and body-fixed rotorcraft atmospheric turbulence models. All of the information necessary to develop the dynamic equations describing the atmospheric turbulence velocity field experienced by an aircraft is contained in the atmospheric turbulence velocity correlation matrix. It is for this reason that a generalized formulation of the correlation matrix describing atmospheric turbulence that a rotating blade encounters is developed. From this correlation matrix, earlier treated cases restricted to a rotor flying straight and level directly into the mean wind can be recovered as special cases.
Tone and Broadband Noise Separation from Acoustic Data of a Scale-Model Counter-Rotating Open Rotor
Sree, David; Stephens, David B.
2014-01-01
Renewed interest in contra-rotating open rotor technology for aircraft propulsion application has prompted the development of advanced diagnostic tools for better design and improved acoustical performance. In particular, the determination of tonal and broadband components of open rotor acoustic spectra is essential for properly assessing the noise control parameters and also for validating the open rotor noise simulation codes. The technique of phase averaging has been employed to separate the tone and broadband components from a single rotor, but this method does not work for the two-shaft contra-rotating open rotor. A new signal processing technique was recently developed to process the contra-rotating open rotor acoustic data. The technique was first tested using acoustic data taken of a hobby aircraft open rotor propeller, and reported previously. The intent of the present work is to verify and validate the applicability of the new technique to a realistic one-fifth scale open rotor model which has 12 forward and 10 aft contra-rotating blades operating at realistic forward flight Mach numbers and tip speeds. The results and discussions of that study are presented in this paper.
Tone and Broadband Noise Separation from Acoustic Data of a Scale-Model Contra-Rotating Open Rotor
Sree, Dave; Stephens, David B.
2014-01-01
Renewed interest in contra-rotating open rotor technology for aircraft propulsion application has prompted the development of advanced diagnostic tools for better design and improved acoustical performance. In particular, the determination of tonal and broadband components of open rotor acoustic spectra is essential for properly assessing the noise control parameters and also for validating the open rotor noise simulation codes. The technique of phase averaging has been employed to separate the tone and broadband components from a single rotor, but this method does not work for the two-shaft contra-rotating open rotor. A new signal processing technique was recently developed to process the contra-rotating open rotor acoustic data. The technique was first tested using acoustic data taken of a hobby aircraft open rotor propeller, and reported previously. The intent of the present work is to verify and validate the applicability of the new technique to a realistic one-fifth scale open rotor model which has 12 forward and 10 aft contra-rotating blades operating at realistic forward flight Mach numbers and tip speeds. The results and discussions of that study are presented in this paper.
Modeling and control of a flexible rotor system with AMB-based sustentation.
Arredondo, I; Jugo, J; Etxebarria, V
2008-01-01
In this work the modeling and basic control design process of a rotary flexible spindle hovered by Active Magnetic Bearings (AMB) whose good capabilities for machine-tool industry extensively treated in the literature is presented. The modeling takes into account the three main behavioral characteristics of such magnetically-levitated rotor: the rigid dynamics, the flexible dynamics and the rotating unbalanced motion. Besides, the gyroscopic coupling is also studied proving that in this case, its effects are not significant and can be neglected. Using this model, a stabilizing controller based on symmetry properties is successfully designed for the system and a complete experimental analysis of its performance is carried out. Also, the predictions of the model are compared with the actual measured experimental results on a laboratory set-up based on the MBC500 Rotor Dynamics. Afterwards, a brief study about some nonlinear behavior observed in the system and its effect over the system stability at the critical speed is included.
Energy Technology Data Exchange (ETDEWEB)
Cheney, M.C. [PS Enterprises, Inc., Glastonbury, CT (United States)
1997-12-31
The cost of energy for renewables has gained greater significance in recent years due to the drop in price in some competing energy sources, particularly natural gas. In pursuit of lower manufacturing costs for wind turbine systems, work was conducted to explore an innovative rotor designed to reduce weight and cost over conventional rotor systems. Trade-off studies were conducted to measure the influence of number of blades, stiffness, and manufacturing method on COE. The study showed that increasing number of blades at constant solidity significantly reduced rotor weight and that manufacturing the blades using pultrusion technology produced the lowest cost per pound. Under contracts with the National Renewable Energy Laboratory and the California Energy Commission, a 400 kW (33m diameter) turbine was designed employing this technology. The project included tests of an 80 kW (15.5m diameter) dynamically scaled rotor which demonstrated the viability of the design.
Estimation of rotor effective wind speeds using autoregressive models on Lidar data
Giyanani, A.; Bierbooms, W. A. A. M.; van Bussel, G. J. W.
2016-09-01
Lidars have become increasingly useful for providing accurate wind speed measurements in front of the wind turbine. The wind field measured at distant meteorological masts changes its structure or was too distorted before it reaches the turbine. Thus, one cannot simply apply Taylor's frozen turbulence for representing this distant flow field at the rotor. Wind turbine controllers can optimize the energy output and reduce the loads significantly, if the wind speed estimates were known in advance with high accuracy and low uncertainty. The current method to derive wind speed estimations from aerodynamic torque, pitch angle and tip speed ratio after the wind field flows past the turbine and have their limitations, e.g. in predicting gusts. Therefore, an estimation model coupled with the measuring capability of nacelle based Lidars was necessary for detecting extreme events and for estimating accurate wind speeds at the rotor disc. Nacelle-mounted Lidars measure the oncoming wind field from utpo 400m(5D) in front of the turbine and appropriate models could be used for deriving the rotor effective wind speed from these measurements. This article proposes an auto-regressive model combined with a method to include the blockage factor in order to estimate the wind speeds accurately using Lidar measurements. An Armax model was used to determine the transfer function that models the physical evolution of wind towards the wind turbine, incorporating the effect of surface roughness, wind shear and wind variability at the site. The model could incorporate local as well as global effects and was able to predict the rotor effective wind speeds with adequate accuracy for wind turbine control actions. A high correlation of 0.86 was achieved as the Armax modelled signal was compared to a reference signal. The model could also be extended to estimate the damage potential during high wind speeds, gusts or abrupt change in wind directions, allowing the controller to act appropriately
Study of △I=2 staggering by perturbed particle-rotor model
Institute of Scientific and Technical Information of China (English)
邢正; 王晓春; 陈星蕖
1996-01-01
AI=2 staggering in superdefonned nuclei has been investigated by a perturbed particle-rotor model, of which all observed features are reproduced in the calculations. It is pointed out that the C4symmetry in Hamiltonian is not the only cause of AI=2 staggering. This model can be used to make a fit to the experimental data in odd-A superdeformed nuclei.
Nuclear Chaotic Behavior in a Two-j Shell Coupled with a Rotor Model
Institute of Scientific and Technical Information of China (English)
GUO Lu; ZHOU XianRong; MENG Jie; ZHAO EnGuang
2002-01-01
The chaotic properties for six particles interacting by a monopolc pairing force in a two-.j stiell modelcoupled with a deformed core are studied in the frame of particle-rotor model. The nearest-neighbor distribution ofenergy levels and spectral rigidity in the two-j shell arc compared with those in the single-j case. The result, s show thatthe system is more regular in the two-j model than that in the single-j case.
Diagnosing Lee Wave Rotor Onset Using a Linear Model Including a Boundary Layer
Directory of Open Access Journals (Sweden)
Miguel A. C. Teixeira
2017-01-01
Full Text Available A linear model is used to diagnose the onset of rotors in flow over 2D hills, for atmospheres that are neutrally stratified near the surface and stably stratified aloft, with a sharp temperature inversion in between, where trapped lee waves may propagate. This is achieved by coupling an inviscid two-layer mountain-wave model and a bulk boundary-layer model. The full model shows some ability to diagnose flow stagnation associated with rotors as a function of key input parameters, such as the Froude number and the height of the inversion, in numerical simulations and laboratory experiments carried out by previous authors. While calculations including only the effects of mean flow attenuation and velocity perturbation amplification within the surface layer represent flow stagnation fairly well in the more non-hydrostatic cases, only the full model, taking into account the feedback of the surface layer on the inviscid flow, satisfactorily predicts flow stagnation in the most hydrostatic case, although the corresponding condition is unable to discriminate between rotors and hydraulic jumps. Versions of the model not including this feedback severely underestimate the amplitude of trapped lee waves in that case, where the Fourier transform of the hill has zeros, showing that those waves are not forced directly by the orography.
Rotordynamic Modelling and Response Characteristics of an Active Magnetic Bearing Rotor System
Free, April M.; Flowers, George T.; Trent, Victor S.
1996-01-01
Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied. These results are presented and discussed.
Study of creep-fatigue behavior in a 1000 MW rotor using a phenomenological lifetime model
Energy Technology Data Exchange (ETDEWEB)
Zhao, Nailong; Wang, Weizhe; Jiang, Jishen; Liu, Yingzheng [School of Mechanical Engineering, Shanghai (China)
2017-02-15
In this study, the phenomenological lifetime model was applied to part of an ultra-supercritical steam turbine rotor model to predict its lifetime as a post processing of the finite element method. To validate the accuracy and adaptation of the post processing program, stress strain hysteresis loops of a cylinderal model under service-like load cycle conditions in cycle N = 1 and 300 were constructed, and the comparison of the results with experimental data on the same cylinderal specimen showed them to be satisfactory. The temperature and von Mises stress distributions of the rotor during a startup-running-shutdown-natural cool process were numerically studied using ABAQUS and the damage caused by the interaction of creep and fatigue was subsequently computed and discussed. It was found that the maximum damage appeared at the inlet notch zone, with the blade groove areas and the front notch areas also suffering a large damage amplitude.
DEFF Research Database (Denmark)
Pierart Vásquez, Fabián Gonzalo
Gas journal bearings have been increasingly adopted in modern turbo-machinery due to their numerous indisputable advantages. They can operate at higher speed than most bearing designs, almost without noise or heat generation and in most cases, as in this work, the gas used is air which is cheap...... work, the control signal design is based on a theoretical model. This approach enables easy modifications of any of the numerous physical parameters in the system if needed. The theoretical model used is based on a modifed version of Reynolds equation where an extra term is added in order to include...... frequencies and damping ratios of the rotor-bearing system) is performed and finally to design controllers that allows improvement of the dynamic properties of the rotor-active gas bearings system and lets the systemto safely cross the critical speeds, using the theoretical model as a design tool. The results...
Institute of Scientific and Technical Information of China (English)
杨璐鸿; 刘顺安; 张冠宇; 王春雪
2015-01-01
To improve the operational efficiency of global optimization in engineering, Kriging model was established to simplify the mathematical model for calculations. Ducted coaxial-rotors aircraft was taken as an example and Fluent software was applied to the virtual prototype simulations. Through simulation sample points, the total lift of the ducted coaxial-rotors aircraft was obtained. The Kriging model was then constructed, and the function was fitted. Improved particle swarm optimization (PSO) was also utilized for the global optimization of the Kriging model of the ducted coaxial-rotors aircraft for the determination of optimized global coordinates. Finally, the optimized results were simulated by Fluent. The results show that the Kriging model and the improved PSO algorithm significantly improve the lift performance of ducted coaxial-rotors aircraft and computer operational efficiency.
Slew, K. Lee; Miller, M.; Matida, E.
2016-09-01
A numerical study was carried out to identify non-dimensional parameters for dual-rotor horizontal axis wind turbines (DRWTs). Based on some important DRWT parameters such as the rotor speeds, rotor diameters and the distance between the rotors, three dimensionless parameters were derived from the Buckingham Pi theorem. Hypothetical DRWT models were created using geometrically-scaled National Renewable Energy Laboratory (NREL) Phase VI rotor geometry and operating conditions in order to confirm the validity of these parameters. The performance of each turbine was simulated using DR_HAWT, an inhouse prediction tool for single and dual-rotor wind turbines created by the current authors. The variation in normalized output power as a function of the dimensionless parameters suggests that an improved performance of DRWTs can be obtained at lower diameter and gap ratios. The NREL Phase VI rotor equipped with a 5 m geometrically-scaled upwind rotor can generate about 88% of the combined power output of two equivalent single-rotors. In addition, the effect of having an auxiliary upwind rotor reduces the angle of attack along the inboard section of the downwind blade.
Modelling and Predictions of Isothermal Flow Inside the Closed Rotor-Stator System
Directory of Open Access Journals (Sweden)
Abdul Fattah Abbasi
2012-01-01
Full Text Available This paper describes the numerical predictions of isothermal closed rotor-stator flows. Steady-state finite-difference solutions are sought for two gap ratios and two rotational Reynolds number in the axisymmetric cylindrical polar coordinate frame of reference. Low Reynolds number models, low Reynolds number k-? and second moment closure models have been used to compute the necessary description of the flow inside the rotor-stator system without superpose flow. The most important dissimilarities among the computational calculations of both the turbulence models obtain at the lower radial locations, where k-? model predicted the premature transitional predictions from laminar to turbulent flow. The major feature of this computational work is the emergence of four regions of the flow i.e. source, sink and two boundary layers. Computed velocity components of both models are compared against the experimental measurements. Low Reynolds number second moment closure shows the improved level of matching with data, particularly on apex of the boundary layers and recirculating core in the middle of the rotor-stator cavity.
Measurement and Modelling of Multicopter UAS Rotor Blades in Hover
Nowicki, Nathalie
2016-01-01
Multicopters are becoming one of the more common and popular type of unmanned aircraft systems (UAS) which have both civilian and military applications. One example being the concept of drone deliveries proposed by the distribution company Amazon [1]. The electrical propulsion is considered to have both faster and easier deliveries and also environmental benefits compared to other vehicles that still use fossil fuel. Other examples include surveillance and just simple entertainment. The reason behind their success is often said to be due to their small size, relatively low cost, simple structure and finally simple usage. With an increase in the UAS market comes challenges in terms of security, as both people and other aircrafts could be harmed if not used correctly. Therefore further studies and regulations are needed to ensure that future use of drones, especially in the civilian and public sectors, are safe and efficient. Thorough research has been done on full scale, man or cargo transporting, helicopters so that most parts of flight and performance are fairly well understood. Yet not much of it have been verified for small multicopters. Until today many studies and research projects have been done on the control systems, navigation and aerodynamics of multicopters. Many of the methods used today for building multicopters involve a process of trial an error of what will work well together, and once that is accomplished some structural analysis of the multicopter bodies might be done to verify that the product will be strong enough and have a decent aerodynamic performance. However, not much has been done on the research of the rotor blades, especially in terms of structural stress analyses and ways to ensure that the commonly used parts are indeed safe and follow safety measures. Some producers claim that their propellers indeed have been tested, but again that usually tends towards simple fluid dynamic analyses and even simpler stress analyses. There is no real
The molecular asymmetric rigid rotor Hamiltonian as an exactly solvable model
Jarvis, P D
2008-01-01
Representations of the rotation group may be formulated in second-quantised language via Schwinger's transcription of angular momentum states onto states of an effective two-dimensional oscillator. In the case of the molecular asymmetric rigid rotor, by projecting onto the state space of rigid body rotations, the standard Ray Hamiltonian $H(1,\\kappa,-1)$ (with asymmetry parameter $1 \\ge \\kappa \\ge -1$), becomes a quadratic polynomial in the generators of the associated dynamical $su(1,1)$ algebra. We point out that $H(1,\\kappa,-1)$ is in fact quadratic in the Gaudin operators arising from the quasiclassical limit of an associated $su_q(1,1)$ Yang-Baxter algebra. The general asymmetric rigid rotor Hamiltonian is thus an exactly solvable model. This fact has important implications for the structure of the spectrum, as well as for the eigenstates and correlation functions of the model.
Review and analysis of the DNW/Model 360 rotor acoustic data base
Zinner, R. A.; Boxwell, D. A.; Spencer, R. H.
1989-01-01
A comprehensive model rotor aeroacoustic data base was collected in a large anechoic wind tunnel in 1986. Twenty-six microphones were positioned around the azimuth to collect acoustic data for approximately 150 different test conditions. A dynamically scaled, blade-pressure-instrumented model of the forward rotor of the BH360 helicopter simultaneously provided blade pressures for correlation with the acoustic data. High-speed impulsive noise, blade-vortex interaction noise, low-frequency noise, and broadband noise were all captured in this extensive data base. Trends are presentes for each noise source, with important parametric variations. The purpose of this paper is to introduce this data base and illustrate its potential for predictive code validation.
Multidisciplinary Optimization of Tilt Rotor Blades Using Comprehensive Composite Modeling Technique
Chattopadhyay, Aditi; McCarthy, Thomas R.; Rajadas, John N.
1997-01-01
An optimization procedure is developed for addressing the design of composite tilt rotor blades. A comprehensive technique, based on a higher-order laminate theory, is developed for the analysis of the thick composite load-carrying sections, modeled as box beams, in the blade. The theory, which is based on a refined displacement field, is a three-dimensional model which approximates the elasticity solution so that the beam cross-sectional properties are not reduced to one-dimensional beam parameters. Both inplane and out-of-plane warping are included automatically in the formulation. The model can accurately capture the transverse shear stresses through the thickness of each wall while satisfying stress free boundary conditions on the inner and outer surfaces of the beam. The aerodynamic loads on the blade are calculated using the classical blade element momentum theory. Analytical expressions for the lift and drag are obtained based on the blade planform with corrections for the high lift capability of rotor blades. The aerodynamic analysis is coupled with the structural model to formulate the complete coupled equations of motion for aeroelastic analyses. Finally, a multidisciplinary optimization procedure is developed to improve the aerodynamic, structural and aeroelastic performance of the tilt rotor aircraft. The objective functions include the figure of merit in hover and the high speed cruise propulsive efficiency. Structural, aerodynamic and aeroelastic stability criteria are imposed as constraints on the problem. The Kreisselmeier-Steinhauser function is used to formulate the multiobjective function problem. The search direction is determined by the Broyden-Fletcher-Goldfarb-Shanno algorithm. The optimum results are compared with the baseline values and show significant improvements in the overall performance of the tilt rotor blade.
Theoretical Calculation of Rotational Bands of 179Pt in the Particle-Triaxial-Rotor Model
Institute of Scientific and Technical Information of China (English)
CHEN Guo-Jie; SONG Hui-Chao; LIU Yu-Xin
2005-01-01
Theoretical calculations have been performed for nucleus 179Pt in the particle-triaxial-rotor model with variable moment of inertia. The obtained energy spectrum agrees with the experimental data quite well. The calculated results indicate that the bands 1/2- and 7/2+ are triaxial deformation bands and originate mainly from the v[521]1/2- and v[633]7/2+ configurations respectively.
Calculation of Energy Levels of Nucleus 127I in the Particle-Triaxial-Rotor Model
Institute of Scientific and Technical Information of China (English)
SONG Hui-Chao; LIU Yu-Xin; ZHANG Yu-Hu
2004-01-01
@@ Theoretical calculations have been performed for nucleus 127 I in the framework of the particle-triaxial-rotor model.The calculated results indicate that both the 5+2 and 7+2 bands are oblate deformed bands. Their configurations are associated with the πd5/2 [402] 52 and πg7/2[404] 72 orbitals and the strong mixing between them. Meanwhile a possible explanation of the strong mixing is given.
Modelling of the flow at the rotor disc in a geothermal turbine of 110 MW
Energy Technology Data Exchange (ETDEWEB)
Mazur, Z.; Urquiza, G.; Kubiak, J. [Unidad de Turbomaquinaria, Inst. de Investigaciones Electricas, Temixco, Morelos (Mexico); Sierra, F.Z. [Centro de Investigacion en Energia-UNAM, Temixco, Morelos (Mexico)
2001-04-01
To elucidate an excessive erosion damage produced by solid particles in the fourth stage rotor disc of a 110 MW double flow geothermal turbine, a bi-dimensional modelling investigation has been conducted. The study was based on a set of results from a computational model using a Reynolds stress, RSM, turbulence model. The predicted results confirmed characteristic flow conditions that may play a main role in the serious erosion of the fourth stage rotor disc governor side, which has been detected in periodic overhauls. The results show a jet of vapour that hits the disc transition radius surface at velocities around 112 m/s. These conditions are produced by the flow outgoing from the labyrinth seal, which passes through a drastic cross-section reduction in the last seal strip. The flow was then simulated introducing specific changes to the geometry and the grid in order to modify the flow patterns favourably. Actually, the suggested changes have been envisaged indeed to be practically feasible of being implemented. The new results showed that it is possible to reduce the erosion process up to 86% by increasing the distance from the labyrinth seal to the rotor disc, which produces a 38% velocity reduction of the vapour flow in that zone. The design proposed in this work produces a flow pattern of a lower velocity on disc surface together with a modified angle of flow incidence. Furthermore, the proposed design also reduces a recirculating flow at the exit of the last seal strip. Based on these results, an analysis of erosion against velocity demonstrates that the redesigned rotor disc proposed here leads to the duplication of the time period used at present between maintenance repairs. (Author)
The Effects of Ambient Conditions on Helicopter Rotor Source Noise Modeling
Schmitz, Frederic H.; Greenwood, Eric
2011-01-01
A new physics-based method called Fundamental Rotorcraft Acoustic Modeling from Experiments (FRAME) is used to demonstrate the change in rotor harmonic noise of a helicopter operating at different ambient conditions. FRAME is based upon a non-dimensional representation of the governing acoustic and performance equations of a single rotor helicopter. Measured external noise is used together with parameter identification techniques to develop a model of helicopter external noise that is a hybrid between theory and experiment. The FRAME method is used to evaluate the main rotor harmonic noise of a Bell 206B3 helicopter operating at different altitudes. The variation with altitude of Blade-Vortex Interaction (BVI) noise, known to be a strong function of the helicopter s advance ratio, is dependent upon which definition of airspeed is flown by the pilot. If normal flight procedures are followed and indicated airspeed (IAS) is held constant, the true airspeed (TAS) of the helicopter increases with altitude. This causes an increase in advance ratio and a decrease in the speed of sound which results in large changes to BVI noise levels. Results also show that thickness noise on this helicopter becomes more intense at high altitudes where advancing tip Mach number increases because the speed of sound is decreasing and advance ratio increasing for the same indicated airspeed. These results suggest that existing measurement-based empirically derived helicopter rotor noise source models may give incorrect noise estimates when they are used at conditions where data were not measured and may need to be corrected for mission land-use planning purposes.
Liu, Shibing; Yang, Bingen
2015-08-01
Flexible multistage rotating systems that are supported or guided by long water-lubricated rubber bearings (WLRBs) have a variety of engineering applications. Vibration analysis of this type of machinery for performance and duality requires accurate modeling of WLRBs and related rotor-bearing assemblies. This work presents a new model of WLRBs, with attention given to the determination of bearing dynamic coefficients. Due to its large length-to-diameter ratio, a WLRB cannot be described by conventional pointwise bearing models with good fidelity. The bearing model proposed in this paper considers spatially distributed bearing forces. For the first time in the literature, the current study addresses the issue of mixed lubrication in the operation of WLRBs, which involves interactions of shaft vibration, elastic deformation of rubber material and fluid film pressure, and validates the WLRB model in experiments. Additionally, with the new bearing model, vibration analysis of WLRB-supported flexible multistage rotating systems is performed through use of a distributed transfer function method, which delivers accurate and closed-form analytical solutions of steady-state responses without discretization.
Diameter structure modeling and the calculation of plantation volume of black poplar clones
Directory of Open Access Journals (Sweden)
Andrašev Siniša
2004-01-01
Full Text Available A method of diameter structure modeling was applied in the calculation of plantation (stand volume of two black poplar clones in the section Aigeiros (Duby: 618 (Lux and S1-8. Diameter structure modeling by Weibull function makes it possible to calculate the plantation volume by volume line. Based on the comparison of the proposed method with the existing methods, the obtained error of plantation volume was less than 2%. Diameter structure modeling and the calculation of plantation volume by diameter structure model, by the regularity of diameter distribution, enables a better analysis of the production level and assortment structure and it can be used in the construction of yield and increment tables.
Steady state modeling of large diameter crystal growth using baffles
Sahai, Vivek; Williamson, John; Overfelt, Tony
1991-01-01
Buoyancy driven flow in the crystal melt is one of the leading causes of segregation. Natural convection arises from the presence of thermal and/or solutal gradients in the melt and it is not possible to completely eliminate the convection even in the low gravity environment of space. This paper reports the results of computational modeling research that is being done in preparation for space-based experiments. The commercial finite element code FIDAP was used to simulate the steady convection of a gallium-doped germanium alloy in a Bridgman-Stockbarger furnace. In particular, the study examines the convection-suppressing benefits of inserting cylindrical baffles in the molten region to act as viscous dampers. These thin baffles are assumed to be inert and noncontaminating. The results from this study show the manner in which the streamlines, velocities, and temperature fields at various gravity levels are affected by the presence of baffles. The effects of changing both the number and position of the baffles are examined and the advantages and disadvantages of using baffles are considered.
Stringer, David Blake
The overarching objective in this research is the development of a robust, rotor dynamic, physics based model of a helicopter drive train as a foundation for the prognostic modeling for rotary-wing transmissions. Rotorcrafts rely on the integrity of their drive trains for their airworthiness. Drive trains rely on gear technology for their integrity and function. Gears alter the vibration characteristics of a mechanical system and significantly contribute to noise, component fatigue, and personal discomfort prevalent in rotorcraft. This research effort develops methodologies for generating a rotor dynamic model of a rotary-wing transmission based on first principles, through (i) development of a three-dimensional gear-mesh stiffness model for helical and spur gears and integration of this model in a finite element rotor dynamic model, (ii) linear and nonlinear analyses of a geared system for comparison and validation of the gear-mesh model, (iii) development of a modal synthesis technique for potentially providing model reduction and faster analysis capabilities for geared systems, and (iv) extension of the gear-mesh model to bevel and epicyclic configurations. In addition to model construction and validation, faults indigenous to geared systems are presented and discussed. Two faults are selected for analysis and seeded into the transmission model. Diagnostic vibration parameters are presented and used as damage indicators in the analysis. The fault models produce results consistent with damage experienced during experimental testing. The results of this research demonstrate the robustness of the physics-based approach in simulating multiple normal and abnormal conditions. The advantages of this physics-based approach, when combined with contemporary probabilistic and time-series techniques, provide a useful method for improving health monitoring technologies in mechanical systems.
Generic icing effects on forward flight performance of a model helicopter rotor
Tinetti, Ana F.; Korkan, Kenneth D.
1989-01-01
An experimental program using a commercially available model helicopter has been conducted in the TAMU 7 ft x 10 ft Subsonic Wind Tunnel to investigate main rotor performance degradation due to generic ice adhesion. Base and iced performance data were gathered as functions of fuselage incidence, blade collective pitch, main rotor rotational velocity, and freestream velocity. The experimental values have shown that, in general, the presence of generic ice introduces decrements in performance caused by leading edge separation regions and increased surface roughness. In addition to the expected changes in aerodynamic forces caused by variations in test Reynolds number, forward flight data seemed to be influenced by changes in freestream and rotational velocity. The dependence of the data upon such velocity variations was apparently enhanced by increases in blade chord.
Generic icing effects on forward flight performance of a model helicopter rotor
Tinetti, Ana F.; Korkan, Kenneth D.
1989-01-01
An experimental program using a commercially available model helicopter has been conducted in the TAMU 7 ft x 10 ft Subsonic Wind Tunnel to investigate main rotor performance degradation due to generic ice adhesion. Base and iced performance data were gathered as functions of fuselage incidence, blade collective pitch, main rotor rotational velocity, and freestream velocity. The experimental values have shown that, in general, the presence of generic ice introduces decrements in performance caused by leading edge separation regions and increased surface roughness. In addition to the expected changes in aerodynamic forces caused by variations in test Reynolds number, forward flight data seemed to be influenced by changes in freestream and rotational velocity. The dependence of the data upon such velocity variations was apparently enhanced by increases in blade chord.
Comparison with Tilted Axis Cranking and particle rotor model for triaxial nuclei
Energy Technology Data Exchange (ETDEWEB)
Ohtsubo, Shin-ichi; Shimizu, Yoshifumi R. [Kyushu Univ., Fukuoka (Japan). Dept. of Physics
1998-03-01
An extension of the cranking model in such a way to allow a rotation axis to deviate from the principal axes of the deformed mean-field is a promising tool for the spectroscopic study of rapidly rotating nuclei. We have applied such a `Tilted Axis Cranking` (TAC) method to a simple system of one-quasiparticle coupled to a triaxial rotor and compared it with a particle-rotor coupling calculation in order to check whether the spin-orientation degrees of freedom can be well described within the mean-field approximation. The result shows that the TAC method gives a good approximation to observable quantities and it is a suitable method to understand the dynamical interplay between the collective and single-particle angular momenta. (author)
Mathematical Modelling of Unmanned Aerial Vehicles with Four Rotors
Directory of Open Access Journals (Sweden)
Zoran Benić
2016-01-01
Full Text Available Mathematical model of an unmanned aerial vehicle with four propulsors (quadcopter is indispensable in quadcopter movement simulation and later modelling of the control algorithm. Mathematical model is, at the same time, the first step in comprehending the mathematical principles and physical laws which are applied to the quadcopter system. The objective is to define the mathematical model which will describe the quadcopter behavior with satisfactory accuracy and which can be, with certain modifications, applicable for the similar configurations of multirotor aerial vehicles. At the beginning of mathematical model derivation, coordinate systems are defined and explained. By using those coordinate systems, relations between parameters defined in the earth coordinate system and in the body coordinate system are defined. Further, the quadcopter kinematic is described which enables setting those relations. Also, quadcopter dynamics is used to introduce forces and torques to the model through usage of Newton-Euler method. Final derived equation is Newton’s second law in the matrix notation. For the sake of model simplification, hybrid coordinate system is defined, and quadcopter dynamic equations derived with the respect to it. Those equations are implemented in the simulation. Results of behavior of quadcopter mathematical model are graphically shown for four cases. For each of the cases the propellers revolutions per minute (RPM are set in a way that results in the occurrence of the controllable variables which causes one of four basic quadcopter movements in space.
A Viscous-Inviscid Interaction Model for Rotor Aerodynamics
DEFF Research Database (Denmark)
Filippone, Antonino; Sørensen, Jens Nørkær
1994-01-01
A numerical model for the viscous-inviscid interactive computations ofrotor flows is presented. The basic methodology for deriving the outer inviscid solution is a fully three-dimensional boundary element method.The inner viscous domain, i.e. the boundary layer, is described by the two-dimensiona...
Rotor Wake Development During the First Revolution
McAlister, Kenneth W.
2003-01-01
The wake behind a two-bladed model rotor in light climb was measured using particle image velocimetry, with particular emphasis on the development of the trailing vortex during the first revolution of the rotor. The distribution of vorticity was distinguished from the slightly elliptical swirl pattern. Peculiar dynamics within the void region may explain why the peak vorticity appeared to shift away from the center as the vortex aged, suggesting the onset of instability. The swirl and axial velocities (which reached 44 and 12 percent of the rotor-tip speed, respectively) were found to be asymmetric relative to the vortex center. In particular, the axial flow was composed of two concentrated zones moving in opposite directions. The radial distribution of the circulation rapidly increased in magnitude until reaching a point just beyond the core radius, after which the rate of growth decreased significantly. The core-radius circulation increased slightly with wake age, but the large-radius circulation appeared to remain relatively constant. The radial distributions of swirl velocity and vorticity exhibit self-similar behaviors, especially within the core. The diameter of the vortex core was initially about 10 percent of the rotor-blade chord, but more than doubled its size after one revolution of the rotor. According to vortex models that approximate the measured data, the core-radius circulation was about 79 percent of the large-radius circulation, and the large-radius circulation was about 67 percent of the maximum bound circulation on the rotor blade. On average, about 53 percent of the maximum bound circulation resides within the vortex core during the first revolution of the rotor.
The Model of Nonstationary Rotor Magnetic Field Observer in the Induction Motor
Burkov, Alexander; Krasilnikyants, Evgenii; Smirnov, Alexander
2011-01-01
This article is devoted to the questions, associated with observer construction for monitoring the values of rotor magnetic vector magnitude and angular deflection of induction motor oriented on bidimensional convolution on temporal and spatial actual parameters. The interrelation of induction motor breakdown torque and rotor characteristic time and transportation lag is shown. The system of rotor running stream observer on the basis of gage rotor position and stator current is put forward.
Nearfield Unsteady Pressures at Cruise Mach Numbers for a Model Scale Counter-Rotation Open Rotor
Stephens, David B.
2012-01-01
An open rotor experiment was conducted at cruise Mach numbers and the unsteady pressure in the nearfield was measured. The system included extensive performance measurements, which can help provide insight into the noise generating mechanisms in the absence of flow measurements. A set of data acquired at a constant blade pitch angle but various rotor speeds was examined. The tone levels generated by the front and rear rotor were found to be nearly equal when the thrust was evenly balanced between rotors.
Optimization of wind turbine rotors
Energy Technology Data Exchange (ETDEWEB)
Nygaard, Tor Anders
1999-07-01
The Constrained Steepest Descent method has been applied to the optimization of wind turbine rotors through the development of a numerical model. The model consists of an optimization kernel, an aerodynamic model, a structural dynamic model of a rotating beam, and a cost model for the wind turbine. The cost of energy is minimized directly by varying the blade design, the rotational speed and the resulting design of the drive-train and tower. The aerodynamic model is a combination of a fast engineering model based on strip-theory and two and three-dimensional Euler solvers. The two-dimensional Euler solver is used for generation of pre-stall airfoil data. Comparisons with experimental data verify that the engineering model effectively approximates non-stalled flow, except at the blade tip. The three-dimensional Euler solver is in good agreement with the experimental data at the tip, and is therefore a useful supplement for corrections of the tip-loss model, and evaluation of an optimized design. The structural dynamic model evaluates stresses and deformations for the blade. It is based on constitutive relations for a slender beam that are solved with the equations of motions using a finite-difference method. The cost model evaluates the design change of the wind turbine and the resulting costs that occur when a change in blade design modifies the blade mass and the overall forces. The cost model is based on engineering design rules for the drive-train and tower. The model was applied using a Danish 600 kW wind turbine as a reference. Two rotors were optimized using traditional NACA airfoils and a new low-lift airfoil family developed specifically for wind turbine purposes. The cost of energy decreased four percent for the NACA rotor, and seven percent for the low-lift rotor. Optimizations with a high number of degrees of freedom show that a designer has considerable flexibility in choosing some primary parameters such as rated power and rotor diameter, if the rest
Nonlinear dynamic modeling of rotor system supported by angular contact ball bearings
Wang, Hong; Han, Qinkai; Zhou, Daning
2017-02-01
In current bearing dynamic models, the displacement coordinate relations are usually utilized to approximately obtain the contact deformations between the rolling element and raceways, and then the nonlinear restoring forces of the rolling bearing could be calculated accordingly. Although the calculation efficiency is relatively higher, the accuracy is lower as the contact deformations should be solved through iterative analysis. Thus, an improved nonlinear dynamic model is presented in this paper. Considering the preload condition, surface waviness, Hertz contact and elastohydrodynamic lubrication, load distribution analysis is solved iteratively to more accurately obtain the contact deformations and angles between the rolling balls and raceways. The bearing restoring forces are then obtained through iteratively solving the load distribution equations at every time step. Dynamic tests upon a typical rotor system supported by two angular contact ball bearings are conducted to verify the model. Through comparisons, the differences between the nonlinear dynamic model and current models are also pointed out. The effects of axial preload, rotor eccentricity and inner/outer waviness amplitudes on the dynamic response are discussed in detail.
Modelling of 0.5HP Induction Motor using AC Analysis Solver for Rotor Copper Bar material
Directory of Open Access Journals (Sweden)
Ismail Daut
2011-01-01
Full Text Available In this paper a FEM model of a three phase 0.5HP squirrel-cage induction motor is modelled by using FEM software. The model is then used to analyze and investigate the performance of the induction machine using copper rotor bar compared to the conventional aluminium rotor bar material. Calculation using analytical tools could not calculate precisely the required parameters in order to obtain an optimal model to build a prototype model. That is why FEM software has been used to obtain the required data such as the torque vs. speed, torque vs. slip, power loss vs. speed and power loss vs. slip. This work gives some reviews of the advantages by substituting copper for aluminum in the rotor bar of squirrel cage induction motor as a main strategy toward reaching substantially higher efficiency.
Dynamic behavior of dissymmetric rotor bearings modelled with a periodic coefficient large system
Guilhen, P. M.; Berthier, P.; Ferraris, G.; Lalanne, M.
1987-01-01
The instability and unbalance response of dissymmetric rotor-bearing systems containing periodic coefficients when modeling produces matrices with a large number of degrees of freedom are discussed. It is important to solve the equations and then predict the dynamic behavior of the system. This can be done knowing the instability areas and the unbalance response in the stable areas. One deals here with a large number of equations and a reduction of the number of degrees of freedom of the system is achieved through a pseudo modal method. This method is shown to give satisfactory results.
The Acoustic Results of a United Technologies Scale Model Helicopter Rotor Tested at DNW
1990-05-01
Annual Forum of the Amer- Germany (Refs. 3,4). It was this ’ benchmark ’ test ican Helicopter Society, Washington, DC May 1990 which led to the...The au- 2. Schmitz, F.H., Boxwell , DA., Lewy, S., and Da- thors would like to offer sincere thanks to their friends han, C., "A Note on the Generel...W.R., Schultz, K.J., Schmitz, F.H., ing for their contributions made in acquiring the data and Boxwell ,D.A.,"Model Rotor High Speed Im- presented in
Vortex Wake Geometry of a Model Tilt Rotor in Forward Flight
Yamauchi, G. K.; Johnson, W.; Wadcock, A. J.
2002-01-01
The vortex wake trajectory from one rotor of a 0.25-scale V-22 tiltrotor model was measured for four test conditions in the NASA Ames 40- by 80-Foot Wind Tunnel. Vortex wake images were acquired using a laser light sheet and video camera. Wake trajectories were constructed by extracting vortex positions from the video images. Wake trajectories were also calculated using the comprehensive analysis CAMRAD II. Measured and calculated wake geometries exhibit similar trends when advance ratio is varied at fixed thrust or when thrust is varied at fixed advance ratio.
PERFORMANCE ANALYSIS OF A HELICAL SAVONIUS ROTOR WITHOUT SHAFT AT 45° TWIST ANGLE USING CFD
Directory of Open Access Journals (Sweden)
Bachu Deb
2013-06-01
Full Text Available Helical Savonius rotor exhibits better performance characteristics at all the rotor angles compared to conventional Savonius rotor. However studies related to the performance measurement and flow physics of such rotor are very scarce. Keeping this in view, in this paper, a three dimensional Computational Fluid Dynamics analysis using commercial Fluent 6.2 software was done to predict the performance of a two-bucket helical Savonius rotor without shaft and with end plates in a complete cycle of rotation. A two-bucket helical Savonius rotor having height of 60 cm and diameter of 17 cm with 45° bucket twist angle was designed using Gambit. The buckets were connected at the top and bottom circular end plates, which are 1.1 times the rotor diameter. The k-ε turbulence model with second order upwind discretization scheme was adopted with standard wall condition. Power coefficients (Cp and torque coefficients (Ct at different tip speed ratios were evaluated at different rotor angles. From the investigation, it was observed that power coefficient increased with increase of tip speed ratio up to an optimum limit, but then decreased even further tip speed ratio was increased. Further investigation was done on the variations of Cp & Ct in a complete cycle of rotation from 0° to 360° in a step of 45° rotor corresponding to the optimum tip speed ratio. The value of Cp at all the rotor angles is positive. Moreover, velocity magnitude contours were analyzed for each rotor angle and it could be concluded that high aerodynamic torque and power can be expected when the rotor is positioned at 45º & 90º with respect to incoming flow.
PERFORMANCE ANALYSIS OF A HELICAL SAVONIUS ROTOR WITHOUT SHAFT AT 45° TWIST ANGLE USING CFD
Directory of Open Access Journals (Sweden)
Bachu Deb
2013-01-01
Full Text Available Helical Savonius rotor exhibits better performance characteristics at all the rotor angles compared to conventional Savonius rotor. However studies related to the performance measurement and flow physics of such rotor are very scarce. Keeping this in view, in this paper, a three dimensional Computational Fluid Dynamics analysis using commercial Fluent 6.2 software was done to predict the performance of a two-bucket helical Savonius rotor without shaft and with end plates in a complete cycle of rotation. A two-bucket helical Savonius rotor having height of 60 cm and diameter of 17 cm with 45° bucket twist angle was designed using Gambit. The buckets were connected at the top and bottom circular end plates, which are 1.1 times the rotor diameter. The k- ε turbulence model with second order upwind discretization scheme was adopted with standard wall condition. Power coefficients (Cp and torque coefficients (Ct at different tip speed ratios were evaluated at different rotor angles. From the investigation, it was observed that power coefficient increased with increase of tip speed ratio up to an optimum limit, but then decreased even further tip speed ratio was increased. Further investigation was done on the variations of Cp & Ct in a complete cycle of rotation from 0° to 360° in a step of 45° rotor corresponding to the optimum tip speed ratio. The value of Cp at all the rotor angles is positive. Moreover, velocity magnitude contours were analyzed for each rotor angle and it could be concluded that high aerodynamic torque and power can be expected when the rotor is positioned at 45º & 90º with respect to incoming flow.
Splettstoesser, W. R.; Schultz, K. J.; Boxwell, D. A.; Schmitz, F. H.
1984-01-01
Acoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scaling deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.
Bharat Raj Singh,; Onkar Singh
2010-01-01
This paper deals with new concept of compressed air energy storage system using atmospheric air at ambient temperature as a zero pollution power source for running motorbikes. The proposed motorbike is equipped with an air turbine in place of an internal combustion engine, and transforms the energy of the compressed air into shaft work. The mathematical modeling and performance evaluation of such small capacity compressed air driven vaned type novel air turbine is presented here. The effect o...
Mineck, Raymond E.; Gorton, Susan A.
2000-01-01
A wind tunnel test of a generic helicopter fuselage model with an independently mounted rotor has been conducted to obtain steady and periodic pressure data on the helicopter body. The model was tested at four advance ratios and three thrust coefficients. The periodic unsteady pressure coefficients are marked by four peaks associated with the passage of the four rotor blades. Blade passage effects are largest on the nose and tail boom of the model. The magnitude of the pulse increases with rotor thrust coefficient. Tabular listings of the unsteady pressure data are included to permit independent analysis. A CD-rom containing the steady and unsteady pressure data presented in the report is available from the authors.
Institute of Scientific and Technical Information of China (English)
WANG Shunzhong; DAI Limin; LIU Guohua; YUAN Jianqiong; ZHANG Hengmin; WANG Qingli
2006-01-01
The broadleaved-Korean pine mixed forest is a native vegetation in the Changbai Mountains, northeast China. The probability density functions including the normal, negative exponential, Weibull and finite mixture distribution, were used to describe the diameter distributions of the species groups and entire forest stand. There is a strong correlation between parameters and mean DBH except the shape parameters in the mixture distribution. The diameter classes of species and entire forest stand showed not negative exponential but normal and "S" distribution. The mixture function was better than normal and Weibull to describe the model distribution. The location parameter had an effect on the estimated frequency in the first diameter class, when the estimated location parameter was bigger than the lower limit of the first diameter class.
Critical behavior of the XY-rotor model on regular and small-world networks.
De Nigris, Sarah; Leoncini, Xavier
2013-07-01
We study the XY rotors model on small networks whose number of links scales with the system size N(links)~N(γ), where 1≤γ≤2. We first focus on regular one-dimensional rings in the microcanonical ensemble. For γ1.5, the system equilibrium properties are found to be identical to the mean field, which displays a second-order phase transition at a critical energy density ε=E/N,ε(c)=0.75. Moreover, for γ(c)~/=1.5 we find that a nontrivial state emerges, characterized by an infinite susceptibility. We then consider small-world networks, using the Watts-Strogatz mechanism on the regular networks parametrized by γ. We first analyze the topology and find that the small-world regime appears for rewiring probabilities which scale as p(SW)[proportionality]1/N(γ). Then considering the XY-rotors model on these networks, we find that a second-order phase transition occurs at a critical energy ε(c) which logarithmically depends on the topological parameters p and γ. We also define a critical probability p(MF), corresponding to the probability beyond which the mean field is quantitatively recovered, and we analyze its dependence on γ.
Hill, Gary; Du Val, Ronald W.; Green, John A.; Huynh, Loc C.
1990-01-01
A piloted comparison of rigid and aeroelastic blade-element rotor models was conducted at the Crew Station Research and Development Facility (CSRDF) at Ames Research Center. FLIGHTLAB, a new simulation development and analysis tool, was used to implement these models in real time using parallel processing technology. Pilot comments and quantitative analysis performed both on-line and off-line confirmed that elastic degrees of freedom significantly affect perceived handling qualities. Trim comparisons show improved correlation with flight test data when elastic modes are modeled. The results demonstrate the efficiency with which the mathematical modeling sophistication of existing simulation facilities can be upgraded using parallel processing, and the importance of these upgrades to simulation fidelity.
Behavior and sensitivity of an optimal tree diameter growth model under data uncertainty
Don C. Bragg
2005-01-01
Using loblolly pine, shortleaf pine, white oak, and northern red oak as examples, this paper considers the behavior of potential relative increment (PRI) models of optimal tree diameter growth under data uncertainity. Recommendations on intial sample size and the PRI iteractive curve fitting process are provided. Combining different state inventories prior to PRI model...
Energy Technology Data Exchange (ETDEWEB)
Shen, Chen [General Electric Global Research, Niskayuna, NY (United States)
2014-04-01
The goal of this project is to model creep-fatigue-environment interactions in steam turbine rotor materials for advanced ultra-supercritical (A-USC) coal power Alloy 282 plants, to develop and demonstrate computational algorithms for alloy property predictions, and to determine and model key mechanisms that contribute to the damages caused by creep-fatigue-environment interactions.
Cylindrical vortex wake model: skewed cylinder, application to yawed or tilted rotors
DEFF Research Database (Denmark)
Branlard, Emmanuel Simon Pierre; Gaunaa, Mac
2016-01-01
in Blade Element Momentum method codes for yawed conditions. Here, all the components of the full vortex system are analyzed in view of extending Blade Element Momentum models. The main assumptions of the current study are a constant uniform circulation, an infinite number of blades, an un-expanding wake......A vortex system consisting of a bound vortex disk, a root vortex and a vortex cylinder is presented and applied for skewed wake situations. Both the longitudinal and tangential components of vorticity of the cylinder are considered. A subset of this system leads to a model, which is commonly used...... shape and a finite tip-speed ratio. The investigation remains within the context of inviscid potential flow theory. The model is derived for horizontal-axis rotors in general, but results are presented for wind-turbine applications. For each vortex element, the velocity components in all directions...
Unsteady Velocity Measurements Taken Behind a Model Helicopter Rotor Hub in Forward Flight
Berry, John D.
1997-01-01
Drag caused by separated flow behind the hub of a helicopter has an adverse effect on aerodynamic performance of the aircraft. To determine the effect of separated flow on a configuration used extensively for helicopter aerodynamic investigations, an experiment was conducted using a laser velocimeter to measure velocities in the wake of a model helicopter hub operating at Mach-scaled conditions in forward flight. Velocity measurements were taken using a laser velocimeter with components in the vertical and downstream directions. Measurements were taken at 13 stations downstream from the rotor hub. At each station, measurements were taken in both a horizontal and vertical row of locations. These measurements were analyzed for harmonic content based on the rotor period of revolution. After accounting for these periodic velocities, the remaining unsteady velocities were treated as turbulence. Turbulence intensity distributions are presented. Average turbulent intensities ranged from approximately 2 percent of free stream to over 15 percent of free stream at specific locations and azimuths. The maximum average value of turbulence was located near the rear-facing region of the fuselage.
IDENTIFICATION OF CRACKED ROTOR BY WAVELET TRANSFORM
Institute of Scientific and Technical Information of China (English)
邹剑; 陈进; 蒲亚鹏
2002-01-01
The dynamic equation of cracked rotor in rotational frame was modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor were obtained. By the wavelet transform, the time-frequency properties of the cracked rotor and the uncracked rotor were discussed, the difference of the time-frequency properties between the cracked rotor and the uncracked rotor was compared. A new detection algorithm using wavelet transform to identify crack was proposed. The experiments verify the availability and validity of the wavelet transform in identification of crack.
Centrifuge modelling of large diameter pile in sand subject to lateral loading
DEFF Research Database (Denmark)
Leth, Caspar Thrane
Large-diameter (4 to 6 m) rigid monopiles are often used as foundations for offshore wind turbines. The monopiles are subjected to large horizontal forces and overturning moments and they are traditionally designed based on the p-y curve method. The p-y curves recommended in offshore design...... and cyclic behaviour of large diameter rigid piles in dry sand by use of physical modelling. The physical modelling has been carried out at Department of Civil Engineering at the Danish Technical University (DTU.BYG), in the period from 2005 to 2009. The main centrifuge facilities, and especially...... the equipment for lateral load tests were at the start of the research in 2005 outdated and a major part of the work with the geotechnical centrifuge included renovation and upgrading of the facilities. The research with respect to testing of large diameter piles included: Construction of equipment...
On the Elastic Vibration Model for High Length-Diameter Ratio Rocket with Attitude Control System
Institute of Scientific and Technical Information of China (English)
朱伯立; 杨树兴
2003-01-01
An elastic vibration model for high length-diameter ratio spinning rocket with attitude control system which can be used for trajectory simulation is established. The basic theory of elastic dynamics and vibration dynamics were both used to set up the elastic vibration model of rocket body. In order to study the problem more conveniently, the rocket's body was simplified to be an even beam with two free ends. The model was validated by simulation results and the test data.
Tunneling of electrons via rotor-stator molecular interfaces: combined ab initio and model study
Petreska, Irina; Pejov, Ljupco; Kocarev, Ljupco
2015-01-01
Tunneling of electrons through rotor-stator anthracene aldehyde molecular interfaces is studied with a combined ab initio and model approach. Molecular electronic structure calculated from first principles is utilized to model different shapes of tunneling barriers. Together with a rectangular barrier, we also consider a sinusoidal shape that captures the effects of the molecular internal structure more realistically. Quasiclassical approach with the Simmons' formula for current density is implemented. Special attention is paid on conformational dependence of the tunneling current. Our results confirm that the presence of the side aldehyde group enhances the interesting electronic properties of the pure anthracene molecule, making it a bistable system with geometry dependent transport properties. We also investigate the transition voltage and we show that confirmation dependent field emission could be observed in these molecular interfaces at realistically low voltages. The present study accompanies our previ...
Young, L. A.; Lillie, D.; McCluer, M.; Yamauchi, G. K.; Derby, M. R.
2001-01-01
A recent experimental investigation into tiltrotor aerodynamics and acoustics has resulted in the acquisition of a set of data related to tiltrotor airframe aerodynamics and rotor and wing interactional aerodynamics. This work was conducted in the National Full-scale Aerodynamics Complex's (NFAC) 40-by-80 Foot Wind Tunnel, at NASA Ames Research Center, on the Full-Span Tilt Rotor Aeroacoustic Model (TRAM). The full-span TRAM wind tunnel test stand is nominally based on a quarter-scale representation of the V-22 aircraft. The data acquired will enable the refinement of analytical tools for the prediction of tiltrotor aeromechanics and aeroacoustics.
Physical Modelling of Large Diameter Piles in Coarse-Grained Soil
DEFF Research Database (Denmark)
Brødbæk, K. T.; Augustesen, Anders Hust; Møller, M.
2011-01-01
modelling (large- or small-scale). This paper investigates the effects of diameter on the initial part of the p-y curves by small-scale testing. A new and innovative test setup is presented. In order to minimize scale effects the tests are successfully carried out in a pressure tank enabling the possibility...
Directory of Open Access Journals (Sweden)
Natalya Pya
2016-02-01
Full Text Available Background: Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest growth and yield, succession and carbon budget models. However, the diameter at breast height (dbh can be more accurately obtained and at lower cost, than total tree height. Hence, generalized height-diameter (h-d models that predict tree height from dbh, age and other covariates are needed. For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches. We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions. Methods: We develop unconstrained generalized additive models (GAM and shape constrained generalized additive models (SCAM for investigating the possible effects of tree-specific parameters such as tree age, relative diameter at breast height, and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period, on the h-d relationship of forests in Lower Saxony, Germany. Results: Some of the derived effects, e.g. effects of age, index of aridity and sum of daily mean temperature have significantly non-linear pattern. The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges. The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand. The definition of constraints leads only to marginal or minor decline in the model statistics like AIC. An observed structured spatial trend in tree height is modelled via 2-dimensional surface
DEFF Research Database (Denmark)
Santos, Ilmar; Saracho, C.M.; Smith, J.T.
2004-01-01
This work gives a theoretical and experimental contribution to the problem of rotor-blades dynamic interaction. A validation procedure of mathematical models is carried out with help of a simple test rig, built by a mass-spring system attached to four flexible rotating blades. With this test rig,...
A Model Based on Environmental Factors for Diameter Distribution in Black Wattle in Brazil
Sanquetta, Carlos Roberto; Behling, Alexandre; Dalla Corte, Ana Paula; Péllico Netto, Sylvio; Rodrigues, Aurelio Lourenço; Simon, Augusto Arlindo
2014-01-01
This article discusses the dynamics of a diameter distribution in stands of black wattle throughout its growth cycle using the Weibull probability density function. Moreover, the parameters of this distribution were related to environmental variables from meteorological data and surface soil horizon with the aim of finding a model for diameter distribution which their coefficients were related to the environmental variables. We found that the diameter distribution of the stand changes only slightly over time and that the estimators of the Weibull function are correlated with various environmental variables, with accumulated rainfall foremost among them. Thus, a model was obtained in which the estimators of the Weibull function are dependent on rainfall. Such a function can have important applications, such as in simulating growth potential in regions where historical growth data is lacking, as well as the behavior of the stand under different environmental conditions. The model can also be used to project growth in diameter, based on the rainfall affecting the forest over a certain time period. PMID:24932909
A model based on environmental factors for diameter distribution in black wattle in Brazil.
Sanquetta, Carlos Roberto; Behling, Alexandre; Dalla Corte, Ana Paula; Péllico Netto, Sylvio; Rodrigues, Aurelio Lourenço; Simon, Augusto Arlindo
2014-01-01
This article discusses the dynamics of a diameter distribution in stands of black wattle throughout its growth cycle using the Weibull probability density function. Moreover, the parameters of this distribution were related to environmental variables from meteorological data and surface soil horizon with the aim of finding a model for diameter distribution which their coefficients were related to the environmental variables. We found that the diameter distribution of the stand changes only slightly over time and that the estimators of the Weibull function are correlated with various environmental variables, with accumulated rainfall foremost among them. Thus, a model was obtained in which the estimators of the Weibull function are dependent on rainfall. Such a function can have important applications, such as in simulating growth potential in regions where historical growth data is lacking, as well as the behavior of the stand under different environmental conditions. The model can also be used to project growth in diameter, based on the rainfall affecting the forest over a certain time period.
Height-Diameter Models for Mixed-Species Forests Consisting of Spruce, Fir, and Beech
Directory of Open Access Journals (Sweden)
Petráš Rudolf
2014-06-01
Full Text Available Height-diameter models define the general relationship between the tree height and diameter at each growth stage of the forest stand. This paper presents generalized height-diameter models for mixed-species forest stands consisting of Norway spruce (Picea abies Karst., Silver fir (Abies alba L., and European beech (Fagus sylvatica L. from Slovakia. The models were derived using two growth functions from the exponential family: the two-parameter Michailoff and three-parameter Korf functions. Generalized height-diameter functions must normally be constrained to pass through the mean stand diameter and height, and then the final growth model has only one or two parameters to be estimated. These “free” parameters are then expressed over the quadratic mean diameter, height and stand age and the final mathematical form of the model is obtained. The study material included 50 long-term experimental plots located in the Western Carpathians. The plots were established 40-50 years ago and have been repeatedly measured at 5 to 10-year intervals. The dataset includes 7,950 height measurements of spruce, 21,661 of fir and 5,794 of beech. As many as 9 regression models were derived for each species. Although the “goodness of fit” of all models showed that they were generally well suited for the data, the best results were obtained for silver fir. The coefficient of determination ranged from 0.946 to 0.948, RMSE (m was in the interval 1.94-1.97 and the bias (m was -0.031 to 0.063. Although slightly imprecise parameter estimation was established for spruce, the estimations of the regression parameters obtained for beech were quite less precise. The coefficient of determination for beech was 0.854-0.860, RMSE (m 2.67-2.72, and the bias (m ranged from -0.144 to -0.056. The majority of models using Korf’s formula produced slightly better estimations than Michailoff’s, and it proved immaterial which estimated parameter was fixed and which parameters
Zhang, Xuening; Han, Qinkai; Peng, Zhike; Chu, Fulei
2015-05-01
A great deal of research work has been done on the dynamic behaviors of the rotor-bearing system. However, the important effects of load and variation of contact angle on the bearing performance have not been focused on sufficiently. In this paper, a five-degree-of-freedom load distribution model is set up considering the bearing preload and the loads due to the rotor imbalance. Utilizing this model, the variation of the bearing contact angle is investigated thoroughly. The comparisons of the obtained contact angle against the results from literature validate that the proposed load distribution model is effective. With this model, the static ball deformations are obtained considering variation of the contact angle. Through resolving the dynamic displacements of the rotor, the dynamic ball deformations could also be obtained. Then the total restoring forces and moments of the bearings could be formulated. By introducing these nonlinear forces and moments into the rotating system, a new dynamic model considering the preload and the variation of contact angle is set up. The present analyses indicate that the bearing contact angle will be changed remarkably with the effect of bearing load. The deflection vibration of the rotor-bearing system will be underestimated without considering the varying contact angle. With the effect of varying contact angle, the ball passage frequency and its combinations with the shaft rotating frequency become more noticeable. The main resonance regions for the rotor-bearing system shift to the lower speed ranges when the variation of contact angle is taken into account.
DeSmidt, Hans A.; Smith, Edward C.; Bill, Robert C.; Wang, Kon-Well
2013-01-01
This project develops comprehensive modeling and simulation tools for analysis of variable rotor speed helicopter propulsion system dynamics. The Comprehensive Variable-Speed Rotorcraft Propulsion Modeling (CVSRPM) tool developed in this research is used to investigate coupled rotor/engine/fuel control/gearbox/shaft/clutch/flight control system dynamic interactions for several variable rotor speed mission scenarios. In this investigation, a prototypical two-speed Dual-Clutch Transmission (DCT) is proposed and designed to achieve 50 percent rotor speed variation. The comprehensive modeling tool developed in this study is utilized to analyze the two-speed shift response of both a conventional single rotor helicopter and a tiltrotor drive system. In the tiltrotor system, both a Parallel Shift Control (PSC) strategy and a Sequential Shift Control (SSC) strategy for constant and variable forward speed mission profiles are analyzed. Under the PSC strategy, selecting clutch shift-rate results in a design tradeoff between transient engine surge margins and clutch frictional power dissipation. In the case of SSC, clutch power dissipation is drastically reduced in exchange for the necessity to disengage one engine at a time which requires a multi-DCT drive system topology. In addition to comprehensive simulations, several sections are dedicated to detailed analysis of driveline subsystem components under variable speed operation. In particular an aeroelastic simulation of a stiff in-plane rotor using nonlinear quasi-steady blade element theory was conducted to investigate variable speed rotor dynamics. It was found that 2/rev and 4/rev flap and lag vibrations were significant during resonance crossings with 4/rev lagwise loads being directly transferred into drive-system torque disturbances. To capture the clutch engagement dynamics, a nonlinear stick-slip clutch torque model is developed. Also, a transient gas-turbine engine model based on first principles mean
Performance and wake conditions of a rotor located in the wake of an obstacle
Naumov, I. V.; Kabardin, I. K.; Mikkelsen, R. F.; Okulov, V. L.; Sørensen, J. N.
2016-09-01
Obstacles like forests, ridges and hills can strongly affect the velocity profile in front of a wind turbine rotor. The present work aims at quantifying the influence of nearby located obstacles on the performance and wake characteristics of a downstream located wind turbine. Here the influence of an obstacle in the form of a cylindrical disk was investigated experimentally in a water flume. A model of a three-bladed rotor, designed using Glauert's optimum theory at a tip speed ratio λ = 5, was placed in the wake of a disk with a diameter close to the one of the rotor. The distance from the disk to the rotor was changed from 4 to 8 rotor diameters, with the vertical distance from the rotor axis varied 0.5 and 1 rotor diameters. The associated turbulent intensity of the incoming flow to the rotor changed 3 to '6% due to the influence of the disk wake. In the experiment, thrust characteristics and associated pulsations as a function of the incoming flow structures were measured by strain gauges. The flow condition in front of the rotor was measured with high temporal accuracy using LDA and power coefficients were determine as function of tip speed ratio for different obstacle positions. Furthermore, PIV measurements were carried out to study the development of the mean velocity deficit profiles of the wake behind the wind turbine model under the influence of the wake generated by the obstacle. By use of regression techniques to fit the velocity profiles it was possible to determine velocity deficits and estimate length scales of the wake attenuation.
Wind Tunnel Testing of a 120th Scale Large Civil Tilt-Rotor Model in Airplane and Helicopter Modes
Theodore, Colin R.; Willink, Gina C.; Russell, Carl R.; Amy, Alexander R.; Pete, Ashley E.
2014-01-01
In April 2012 and October 2013, NASA and the U.S. Army jointly conducted a wind tunnel test program examining two notional large tilt rotor designs: NASA's Large Civil Tilt Rotor and the Army's High Efficiency Tilt Rotor. The approximately 6%-scale airframe models (unpowered) were tested without rotors in the U.S. Army 7- by 10-foot wind tunnel at NASA Ames Research Center. Measurements of all six forces and moments acting on the airframe were taken using the wind tunnel scale system. In addition to force and moment measurements, flow visualization using tufts, infrared thermography and oil flow were used to identify flow trajectories, boundary layer transition and areas of flow separation. The purpose of this test was to collect data for the validation of computational fluid dynamics tools, for the development of flight dynamics simulation models, and to validate performance predictions made during conceptual design. This paper focuses on the results for the Large Civil Tilt Rotor model in an airplane mode configuration up to 200 knots of wind tunnel speed. Results are presented with the full airframe model with various wing tip and nacelle configurations, and for a wing-only case also with various wing tip and nacelle configurations. Key results show that the addition of a wing extension outboard of the nacelles produces a significant increase in the lift-to-drag ratio, and interestingly decreases the drag compared to the case where the wing extension is not present. The drag decrease is likely due to complex aerodynamic interactions between the nacelle and wing extension that results in a significant drag benefit.
A modified force-balance model for prediction of bubble departure diameter in subcooled flow boiling
Energy Technology Data Exchange (ETDEWEB)
Sugrue, R., E-mail: rsugrue@mit.edu; Buongiorno, J.
2016-08-15
Highlights: • Existing bubble departure models were tested against various experimental databases. • General experimental trends were captured correctly but give large average errors. • A modified bubble departure model is proposed and tested against these databases. - Abstract: Experimental data by Sugrue et al., Klausner et al., Zeng et al., Prodanovic et al., and Situ et al. for bubble departure diameter in subcooled flow boiling in a wide range of orientation angle, subcooling, heat flux, mass flux, and pressure conditions were used to assess the predictive accuracy of the mechanistic force-balance models of Klausner et al. and Yun et al. The results suggested that both models capture the experimental trends correctly, but exhibit large average errors and standard deviations, i.e. 85.5% (σ = 49.7%) and 43.9% (σ = 23.1%) for Klausner’s and Yun’s models, respectively. Since the cube of the bubble departure diameter is used in subcooled flow boiling heat transfer models, such errors are unacceptable, and underscore the need for greater accuracy in predictions. Therefore, the databases were used to (i) identify the dominant forces determining bubble departure at various operating conditions, and (ii) optimize the empirical coefficients describing those forces in Klausner’s model. The modified model considerably lowers prediction error to 22.4% (σ = 19.9%) for all data considered. Application of the modified model is demonstrated for the subcooled flow boiling conditions present in the hot channel of a typical Pressurized Water Reactor (PWR).
Pavlenko, I. V.; Simonovskiy, V. I.; Demianenko, M. M.
2017-08-01
This research paper is aimed to investigating rotor dynamics of multistage centrifugal machines with ball bearings by using the computer programs “Critical frequencies of the rotor” and “Forced oscillations of the rotor,” which are implemented the mathematical model based on the use of beam finite elements. Free and forces oscillations of the rotor for the multistage centrifugal oil pump NPS 200-700 are observed by taking into account the analytical dependence of bearing stiffness on rotor speed, which is previously defined on the basis of results’ approximation for the numerical simulation in ANSYS by applying 3D finite elements. The calculations found that characteristic and constrained oscillations of rotor and corresponded to them forms of vibrations, as well as the form of constrained oscillation on the actual frequency for acceptable residual unbalance are determined.
2006-10-31
Molecular Dipolar Rotors on Insulating Surfaces," Salamanca , Spain. Trends in Nanotechnology Conference. September 5-9, 2003 [86] Laura I. Clarke, Mary Beth...Horansky at the Trends in Nanotechnology Conference, Salamanca , Spain (September 5-9, 2003). [145] Michl, J. “Unusual Molecules: Artificial Surface...temperature and frequency for difluorophenylene rotor crystal. Figure JP6. Monte Carlo results for the local potential asymmetry at
Reinisch, Guillaume; Leyssale, Jean-Marc; Vignoles, Gérard L.
2010-10-01
We present an extension of some popular hindered rotor (HR) models, namely, the one-dimensional HR (1DHR) and the degenerated two-dimensional HR (d2DHR) models, allowing for a simple and accurate treatment of internal rotations. This extension, based on the use of a variable kinetic function in the Hamiltonian instead of a constant reduced moment of inertia, is extremely suitable in the case of rocking/wagging motions involved in dissociation or atom transfer reactions. The variable kinetic function is first introduced in the framework of a classical 1DHR model. Then, an effective temperature and potential dependent constant is proposed in the cases of quantum 1DHR and classical d2DHR models. These methods are finally applied to the atom transfer reaction SiCl3+BCl3→SiCl4+BCl2. We show, for this particular case, that a proper accounting of internal rotations greatly improves the accuracy of thermodynamic and kinetic predictions. Moreover, our results confirm (i) that using a suitably defined kinetic function appears to be very adapted to such problems; (ii) that the separability assumption of independent rotations seems justified; and (iii) that a quantum mechanical treatment is not a substantial improvement with respect to a classical one.
Directory of Open Access Journals (Sweden)
Hao Xu
2014-04-01
Full Text Available Tree height and diameter at breast height are two important forest factors. The best model from 23 height-diameter equations was selected as the basic model to fit the height-diameter relationships of Chinese fir with one level (sites or plots effects and nested two levels (nested effects of sites and plots Nonlinear Mixed Effects (NLME models. The best model was chosen by smaller Bias, RMSE and larger Radj2. Then the best random-effects combinations for the NLME models were determined by AIC, BIC and -2LL. The results showed that the basic model with three random effects parameters &Phi &Phi &Phi1 &Phi2 and &Phi3 was considered the best mixed model. The nested two levels NLME model considering heteroscedasticity structure (power function possessed with higher predictable accuracy and significantly improved model performance (LRT = 469.43, p<0.0001. The NLME model would be allowed for estimating accuracy the height-diameter relationships of Chinese fir and provided better height predictions than the models using only fixed-effects parameters.
Directory of Open Access Journals (Sweden)
E. S. Ferreira Jr.
Full Text Available Abstract CFD modelling combines transport phenomena and numerical approaches to solve physical problems. Although numerical modelling of flow scenarios is the cutting edge of flow modelling, there seems to be room for improvement. This paper proposes an approach for jet modelling in a low Mach number computational code. The methodology is based on the equivalent diameter and velocity profile calculated downstream from the jet leak orifice. The novel model DESQr (Diameter of Equivalent Simulation for Quicker Run is combined with LES (Large Eddy Simulation to calculate the gas jet profile due to accidental releases. The model is implemented in the framework of FDS (Fire Dynamics Simulator and the open source code is modified to handle gas dispersion scenarios. Numerical findings for jet modelling and gas dispersion are compared with experimental data. The results are also compared with a commercial CFD tool. Good agreement is observed. Significant computational time reduction is achieved. A free open source CFD tool emerges and the results presented in this work are promising.
Directory of Open Access Journals (Sweden)
Tatiana Vassileva Stankova
2013-05-01
Full Text Available The height-diameter relationship is an important and extensivelyinvestigated forest model, but generalized and mixed-effects models of wider applicability are currently lacking in the forest modeling literature for Scots pine (Pinus sylvestris L. plantations in Bulgaria. Considering the practical advantages of deterministic and mixed-effects models, the present study aims to derive a generalized deterministic height-diameter relationship and a simple mixed-effects model for plantation-grown Scots pine in Bulgaria. Ten generalized and six local models of adequate mathematical properties were selected and examined in several subsequent steps with a representative data set.A deterministic model was derived for tree height reconstruction fromthe individual tree diameters, stand dominant height and diameter,number of trees per hectare and stand age. Mixed-effects models weredeveloped from the individual-tree and stand diameters and heights applicable to determine the height-diameter relationship in field surveys. Both types of models can be applied with confidence, according to their advantages and specifications, for estimating the height-diameter relationship of Scots pine plantations in Bulgaria, presenting a unique contribution for the particular species, study area and type of model. The choice of the tested models is relevant to the height-diameter relationship investigation of biologically related and geographically close species and types of stands and the study procedure allows repetition of the work to provide reliable solutions of the problem where information on such type of model is deficient or incomplete.
Rotor-Router Aggregation on the Comb
Huss, Wilfried; Sava, Ecaterina
2011-01-01
We prove a shape theorem for rotor-router aggregation on the comb, for a specific initial rotor configuration and clockwise rotor sequence for all vertices. Furthermore, as an application of rotor-router walks, we describe the harmonic measure of the rotor-router aggregate and related shapes, which is useful in the study of other growth models on the comb. We also identify the shape for which the harmonic measure is uniform. This gives the first known example where the rotor-router cluster ha...
Tunneling of electrons via rotor-stator molecular interfaces: Combined ab initio and model study
Petreska, Irina; Ohanesjan, Vladimir; Pejov, Ljupčo; Kocarev, Ljupčo
2016-07-01
Tunneling of electrons through rotor-stator anthracene aldehyde molecular interfaces is studied with a combined ab initio and model approach. Molecular electronic structure calculated from first principles is utilized to model different shapes of tunneling barriers. Together with a rectangular barrier, we also consider a sinusoidal shape that captures the effects of the molecular internal structure more realistically. Quasiclassical approach with the Simmons' formula for current density is implemented. Special attention is paid on conformational dependence of the tunneling current. Our results confirm that the presence of the side aldehyde group enhances the interesting electronic properties of the pure anthracene molecule, making it a bistable system with geometry dependent transport properties. We also investigate the transition voltage and we show that conformation-dependent field emission could be observed in these molecular interfaces at realistically low voltages. The present study accompanies our previous work where we investigated the coherent transport via strongly coupled delocalized orbital by application of Non-equilibrium Green's Function Formalism.
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Juing-Shian Chiou
2013-01-01
Full Text Available This paper has implemented nonlinear control strategy for the single tilt tri-rotor aerial robot. Based on Newton-Euler’s laws, the linear and nonlinear mathematical models of tri-rotor UAVs are obtained. A numerical analysis using Newton-Raphson method is chosen for finding hovering equilibrium point. Back-stepping nonlinear controller design is based on constructing Lyapunov candidate function for closed-loop system. By imitating the linguistic logic of human thought, fuzzy logic controllers (FLCs are designed based on control rules and membership functions, which are much less rigid than the calculations computers generally perform. Effectiveness of the controllers design scheme is shown through nonlinear simulation model on each channel.
Kazin, S. B.; Paas, J. E.; Minzner, W. R.
1973-01-01
A scale model of the bypass flow region of a 1.5 pressure ratio, single stage, low tip speed fan was tested with a serrated rotor leading edge to determine its effects on noise generation. The serrated rotor was produced by cutting teeth into the leading edge of the nominal rotor blades. The effects of speed and exhaust nozzle area on the scale models noise characteristics were investigated with both the nominal rotor and serrated rotor. Acoustic results indicate the serrations reduced front quadrant PNL's at takeoff power. In particular, the 200 foot (61.0 m) sideline noise was reduced from 3 to 4 PNdb at 40 deg for nominal and large nozzle operation. However, the rear quadrant maximum sideline PNL's were increased 1.5 to 3 PNdb at approach thust and up to 2 PNdb at takeoff thust with these serrated rotor blades. The configuration with the serrated rotor produced the lowest maximum 200 foot (61.0 m) sideline PNL for any given thust when the large nozzle (116% of design area) was employed.
An, Taeyang; Cha, Min-Chul
2013-03-01
We study the superfluid-insulator quantum phase transition in a disordered two-dimensional quantum rotor model with random on-site interactions in the presence of particle-hole symmetry. Via worm-algorithm Monte Carlo calculations of superfluid density and compressibility, we find the dynamical critical exponent z ~ 1 . 13 (2) and the correlation length critical exponent 1 / ν ~ 1 . 1 (1) . These exponents suggest that the insulating phase is a incompressible Mott glass rather than a Bose glass.
Rotational Bands of Some Neutron Deficient Odd-A Pt Isotopes in Particle-Triaxial-Rotor Model
Institute of Scientific and Technical Information of China (English)
WU Xian-Ming; LIU Yu-Xin
2008-01-01
Theoretical calculations are performed for neutron deficient Pt isotopes 177pt and 175,173,171pt in the particle-triaxial-rotor model with variable moment of inertia. The obtained energy spectra agree with experimental data quite well. The calculated results indicate that all these nuclei are in triaxial rotation with 177pt being in prolate and 175,173,171pt in oblate. Several levels are predicted for the 13/2+ band in 169pt.
Rotor/Wing Interactions in Hover
Young, Larry A.; Derby, Michael R.
2002-01-01
Hover predictions of tiltrotor aircraft are hampered by the lack of accurate and computationally efficient models for rotor/wing interactional aerodynamics. This paper summarizes the development of an approximate, potential flow solution for the rotor-on-rotor and wing-on-rotor interactions. This analysis is based on actuator disk and vortex theory and the method of images. The analysis is applicable for out-of-ground-effect predictions. The analysis is particularly suited for aircraft preliminary design studies. Flow field predictions from this simple analytical model are validated against experimental data from previous studies. The paper concludes with an analytical assessment of the influence of rotor-on-rotor and wing-on-rotor interactions. This assessment examines the effect of rotor-to-wing offset distance, wing sweep, wing span, and flaperon incidence angle on tiltrotor inflow and performance.
Modeling and Analysis of Double Stator Slotted Rotor Permanent Magnet Generator
Directory of Open Access Journals (Sweden)
Suhairi Rizuan Che Ahmad
2017-03-01
Full Text Available This paper discusses the modeling and analysis of three phase double stator slotted rotor permanent magnet generator (DSSR-PMG. The use of double stator topology through the double magnetic circuit helps to maximize the usage of flux linkage in the yoke structure of the single stator topology. The analytical computation is done using Permeance Analysis Method (PAM. Finite Element Analysis (FEA is used for numerical verifications and to verify the design structure a prototype laboratory is performed. The analysis is done with various loading conditions to derive the electromagnetic torque, output power and efficiency for the proposed structure. The analytical, numerical and experimental results from the analysis are found to be in good agreement. The maximum power developed by this generator at rated speed of 2000 rpm is of 1 kW with the operational efficiency of 75%. A rectifier bridge circuit is used to make the generated voltage a storage capable constant voltage to make it suitable for mobile applications (such as Direct Current DC generator. The proposed generator structure is highly recommended for applications such as micro-hydro and small renewable plants.
Ohara, Masaki; Noguchi, Toshihiko
This paper describes a new method for a rotor position sensorless control of a surface permanent magnet synchronous motor based on a model reference adaptive system (MRAS). This method features the MRAS in a current control loop to estimate a rotor speed and position by using only current sensors. This method as well as almost all the conventional methods incorporates a mathematical model of the motor, which consists of parameters such as winding resistances, inductances, and an induced voltage constant. Hence, the important thing is to investigate how the deviation of these parameters affects the estimated rotor position. First, this paper proposes a structure of the sensorless control applied in the current control loop. Next, it proves the stability of the proposed method when motor parameters deviate from the nominal values, and derives the relationship between the estimated position and the deviation of the parameters in a steady state. Finally, some experimental results are presented to show performance and effectiveness of the proposed method.
Don C. Bragg
2002-01-01
This article is an introduction to the computer software used by the Potential Relative Increment (PRI) approach to optimal tree diameter growth modeling. These DOS programs extract qualified tree and plot data from the Eastwide Forest Inventory Data Base (EFIDB), calculate relative tree increment, sort for the highest relative increments by diameter class, and...
High-fidelity linear time-invariant model of a smart rotor with adaptive trailing edge flaps
DEFF Research Database (Denmark)
Bergami, Leonardo; Hansen, Morten Hartvig
2017-01-01
aero-servo-elastic model support the design, systematic tuning and model synthesis of smart rotor control systems. As an example application, the gains of an individual flap controller are tuned using the Ziegler-Nichols method for the full-order poles. The flap controller is based on feedback...... of inverse Coleman transformed and low-pass filtered flapwise blade root moments to the cyclic flap angles through two proportional-integral controllers. The load alleviation potential of the active flap control, anticipated by the frequency response of the linear closed-loop model, is also confirmed by non...
Modelling thermal radiation from one-meter diameter methane pool fires
Consalvi, J. L.; Demarco, R.
2012-06-01
The first objective of this article is to implement a comprehensive radiation model in order to predict the radiant fractions and radiative fluxes on remote surfaces in large-scale methane pool fires. The second aim is to quantify the importance of Turbulence-Radiation Interactions (TRIs) in such buoyant flames. The fire-induced flow is modelled by using a buoyancy-modified k-ɛ model and the Steady Laminar Flamelet (SLF) model coupled with a presumed probability density function (pdf) approach. Spectral radiation is modelled by using the Full-Spectrum Correlated-k (FSCK) method. TRIs are taken into account by considering the Optically-Thin Fluctuation Approximation (OTFA). The emission term and the mean absorption coefficient are closed by using a presumed pdf of the mixture fraction, scalar dissipation rate and enthalpy defect. Two 1m-diameter fires with Heat Release Rates (HRR) of 49 kW and 162 kW were simulated. Predicted radiant fractions and radiative heat fluxes are found in reasonable agreement with experimental data. The importance of TRIs is evidenced, computed radiant fractions and radiative heat fluxes being considerably higher than those obtained from calculations based on mean properties. Finally, model results show that the complete absorption coefficient-Planck function correlation should be considered in order to properly take into account the influence of TRIs on the emission term, whereas the absorption coefficient self-correlation in the absorption term reduces significantly the radiant fractions.
Directory of Open Access Journals (Sweden)
Tatiana Vassileva Stankova
2013-07-01
Full Text Available The height-diameter relationship is an important and extensively investigated forest model, but generalized and mixed-effects models of wider applicability are currently lacking in the forest modeling literature for Scots pine (Pinus sylvestris L. plantations in Bulgaria. Considering the practical advantages of deterministic and mixed-effects models, the present study aims to derive a generalized deterministic height-diameter relationship and a simple mixed-effects model for plantation-grown Scots pine in Bulgaria. Ten generalized and six local models of adequate mathematical properties were selected and examined in several subsequent steps with a representative data set. A deterministic model was derived for tree height reconstruction from the individual tree diameters, stand dominant height and diameter, number of trees per hectare and stand age. Mixed-effects models were developed from the individual-tree and stand diameters and heights applicable to determine the height-diameter relationship in field surveys. Both types of models can be applied with confidence, according to their advantages and specifications, for estimating the height-diameter relationship of Scots pine plantations in Bulgaria, presenting a unique contribution for the particular species, study area and type of model. The choice of the tested models is relevant to the height-diameter relationship investigation of biologically related and geographically close species and types of stands and the study procedure allows repetition of the work to provide reliable solutions of the problem where information on such type of model is deficient or incomplete.
Directory of Open Access Journals (Sweden)
Ning Yan
2012-12-01
Full Text Available The magnetically suspended Control Moment Gyroscope (CMG has the advantages of long-life, micro-vibration and being non-lubricating, and is the ideal actuator for agile maneuver satellite attitude control. However, the stability of the rotor in magnetic bearing and the precision of the output torque of a magnetically suspended CMG are affected by the rapid maneuvers of satellites. In this paper, a dynamic model of the agile satellite including a magnetically suspended single gimbal control moment gyroscope is built and the equivalent disturbance torque effected on the rotor is obtained. The feedforward compensation control method is used to depress the disturbance on the rotor. Simulation results are given to show that the rotor displacement is obviously reduced.
Zhang, Zhongrui; Zhong, Quanlin; Niklas, Karl J.; Cai, Liang; Yang, Yusheng; Cheng, Dongliang
2016-08-01
Metabolic scaling theory (MST) posits that the scaling exponents among plant height H, diameter D, and biomass M will covary across phyletically diverse species. However, the relationships between scaling exponents and normalization constants remain unclear. Therefore, we developed a predictive model for the covariation of H, D, and stem volume V scaling relationships and used data from Chinese fir (Cunninghamia lanceolata) in Jiangxi province, China to test it. As predicted by the model and supported by the data, normalization constants are positively correlated with their associated scaling exponents for D vs. V and H vs. V, whereas normalization constants are negatively correlated with the scaling exponents of H vs. D. The prediction model also yielded reliable estimations of V (mean absolute percentage error = 10.5 ± 0.32 SE across 12 model calibrated sites). These results (1) support a totally new covariation scaling model, (2) indicate that differences in stem volume scaling relationships at the intra-specific level are driven by anatomical or ecophysiological responses to site quality and/or management practices, and (3) provide an accurate non-destructive method for predicting Chinese fir stem volume.
Zhang, Zhongrui; Zhong, Quanlin; Niklas, Karl J; Cai, Liang; Yang, Yusheng; Cheng, Dongliang
2016-08-24
Metabolic scaling theory (MST) posits that the scaling exponents among plant height H, diameter D, and biomass M will covary across phyletically diverse species. However, the relationships between scaling exponents and normalization constants remain unclear. Therefore, we developed a predictive model for the covariation of H, D, and stem volume V scaling relationships and used data from Chinese fir (Cunninghamia lanceolata) in Jiangxi province, China to test it. As predicted by the model and supported by the data, normalization constants are positively correlated with their associated scaling exponents for D vs. V and H vs. V, whereas normalization constants are negatively correlated with the scaling exponents of H vs. D. The prediction model also yielded reliable estimations of V (mean absolute percentage error = 10.5 ± 0.32 SE across 12 model calibrated sites). These results (1) support a totally new covariation scaling model, (2) indicate that differences in stem volume scaling relationships at the intra-specific level are driven by anatomical or ecophysiological responses to site quality and/or management practices, and (3) provide an accurate non-destructive method for predicting Chinese fir stem volume.
Institute of Scientific and Technical Information of China (English)
Lu Yuanchang; Lei Xiangdong; Jiang Lei
2003-01-01
Permanent plots in the montane tropical rain forests in Xishuangbanna, southwest China, were established, and different empirical models, based on observation data of these plots in 1992, were built to model diameter frequency distributions. The focus of this study is on predicting accuracy of stem number in the larger diameter classes, which is much more important than that of the smaller trees, from the view of forest management, and must be adequately considered in the modelling and estimate. There exist 3 traditional ways of modelling the diameter frequency distribution: the negative exponential function model, limiting line function model, and Weibull distribution model. In this study, a new model, named as the logarithmic J-shape function, together with the others, was experimented and was found as a more suitable model for modelling works in the tropical forests.
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Shilin Chen
1994-01-01
Full Text Available An exact and direct modeling technique is proposed for modeling of rotor-bearing systems with arbitrary selected degrees-of-freedom. This technique is based on the combination of the transfer and dynamic stiffness matrices. The technique differs from the usual combination methods in that the global dynamic stiffness matrix for the system or the subsystem is obtained directly by rearranging the corresponding global transfer matrix. Therefore, the dimension of the global dynamic stiffness matrix is independent of the number of the elements or the substructures. In order to show the simplicity and efficiency of the method, two numerical examples are given.
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Zapoměl J.
2013-12-01
Full Text Available Unbalance is the principal source of increase of time varying forces transmitted between the rotor and its stationary part. Their magnitudes can be considerably reduced if the rotor is flexibly suspended and if the damping devices are added to the support elements. Their damping effect must be high for low rotor velocities and small for velocities approximately higher than the critical one to minimize the transmitted forces and the vibrations amplitude. This implies to achieve maximum efficiency of the damping elements, their damping effect has to be adaptable to the current operating conditions. Such technological solution is offered by application of a squeeze film magnetorheological damper. Its hybrid variant consisting of two damping units (one controllable in a serial arrangement is investigated in this paper. The damping takes place in two concentric lubricating films formed by normal and magnetorheological oils. The damper is equipped with an electric coil generating magnetic flux passing through the layer of the magnetorheological fluid. As resistance against its flow depends on magnetic induction, changing magnitude of the applied current enables to control the damping force. In the computational model, the rotor is considered to be absolutely rigid, unbalanced and the damping elements are represented by force couplings. The goal of the analysis is to study influence of the investigated magnetorheological damper on behaviour of a rigid rotor during different transient regimes. A special attention is focused on passing the rotor through the critical speed and on planning the dependence of the applied current on speed of the rotor rotation to achieve the optimum compromise between minimizing the transmitted forces and maximum attenuation of the rotor vibrations.
Actuator line/Navier–Stokes computations for the MEXICO rotor: comparison with detailed measurements
DEFF Research Database (Denmark)
Shen, Wen Zhong; Zhu, Wei Jun; Sørensen, Jens Nørkær
2012-01-01
In the European collaborative MEXICO (Model Experiments in Controlled Conditions) project, a series of experiments was carried out on a 4.5 m diameter wind turbine rotor to validate numerical diagnostics tools. Here, some of the measured data are compared with computations of the combined actuator...... line/Navier–Stokes (AL/NS) model developed at the Technical University of Denmark. The AL/NS model was combined with a large eddy simulation technique and used to compute the flow past the MEXICO rotor in free air and in the DNW German‐Dutch wind tunnel for three commonly defined test cases at wind...
Rotor damage detection by using piezoelectric impedance
Qin, Y.; Tao, Y.; Mao, Y. F.
2016-04-01
Rotor is a core component of rotary machinery. Once the rotor has the damage, it may lead to a major accident. Thus the quantitative rotor damage detection method based on piezoelectric impedance is studied in this paper. With the governing equation of piezoelectric transducer (PZT) in a cylindrical coordinate, the displacement along the radius direction is derived. The charge of PZT is calculated by the electric displacement. Then, by the use of the obtained displacement and charge, an analytic piezoelectric impedance model of the rotor is built. Given the circular boundary condition of a rotor, annular elements are used as the analyzed objects and spectral element method is used to set up the damage detection model. The Electro-Mechanical (E/M) coupled impedance expression of an undamaged rotor is deduced with the application of a low-cost impedance test circuit. A Taylor expansion method is used to obtain the approximate E/M coupled impedance expression for the damaged rotor. After obtaining the difference between the undamaged and damaged rotor impedance, a rotor damage detection method is proposed. This method can directly calculate the change of bending stiffness of the structural elements, it follows that the rotor damage can be effectively detected. Finally, a preset damage configuration is used for the numerical simulation. The result shows that the quantitative damage detection algorithm based on spectral element method and piezoelectric impedance proposed in this paper can identify the location and the severity of the damaged rotor accurately.
DEFF Research Database (Denmark)
Salazar, Jorge Andrés González; Santos, Ilmar
2017-01-01
This is part II of a twofold paper series dealing with the design and implementation of model-based controllers meant for assisting the hybrid and developing the feedback-controlled lubrication regimes in active tilting pad journal bearings (active TPJBs). In both papers theoretical and experimen......This is part II of a twofold paper series dealing with the design and implementation of model-based controllers meant for assisting the hybrid and developing the feedback-controlled lubrication regimes in active tilting pad journal bearings (active TPJBs). In both papers theoretical...... and experimental analyses are presented with focus on the reduction of rotor lateral vibration. This part is devoted to synthesising model-based LQG optimal controllers (LQR regulator + Kalman Filter) for the feedback-controlled lubrication and is based upon the mathematical model of the rotor-bearing system...... derived in part I. Results show further suppression of resonant vibrations when using the feedback-controlled or active lubrication, overweighting the reduction already achieved with hybrid lubrication, thus improving the whole machine dynamic performance....
Energy Technology Data Exchange (ETDEWEB)
Afungchui, David [University of Buea, Faculty of Science, Department of Physics, UB Street, PO Box 63, Molyko, Buea, South West (Cameroon); Kamoun, Baddreddinne; Helali, Ali; Ben Djemaa, Abdellatif [Faculte des Sciences de Sfax, Departement de Physique, Laboratoire de Physique, Appliquee (L.P.A.), Sfax (Tunisia)
2010-01-15
The aim of this paper is to numerically explore the non-linear two-dimensional unsteady potential flow over a Savonius rotor and to develop a code for predicting its aerodynamics performances. In the model developed, the rotor is represented in a median plane by two semicircles, displaced along their common diameter. The two semicircles can be considered to produce lifting effects. As a result, they are modelled by a collection of discrete vortices on their contours. The flow field is then governed by the Laplace equation. The versatile Neumann boundary condition, applied over the contour of the semicircles and the Kutta Joukowsky condition applied at the four extremities of the semicircles have been used in the modelling. The torque distribution of the stationary rotor and the unsteady pressure field on the blades of the rotating rotor, predicted by the code developed, have been compared and validated by some experimental data. (author)
Assessment of the Effect of Blast Hole Diameter on the Number of Oversize Boulders Using ANN Model
Dhekne, Prakash; Pradhan, Manoj; Jade, Ravi Krishnarao
2016-04-01
Now-a-days, blasts are planned using large diameter blast holes. The loading density (kg/m) and subsequently the energy available for the breakage of the rockmass increase with the diameter. The in-hole velocity of detonation (VoD) of non-ideal explosive also boosts up with the increase in diameter till the optimum diameter is reached. The increase in the energy content and in-hole VoD cause a sizable effect on the rock fragmentation. The effect can be assessed by counting the number of oversize boulders. This paper explains as to how the technique of artificial neural network modeling was used to predict the number of oversize boulders resulting from ANFO and SME blasts with blast holes of different diameters. The results from ANFO blasts indicated that there was no significant variation in the number of oversize boulders with the diameter whereas a perceptible variation was noticed in case of SME blasts with the change in the diameter. The change in the number of oversize boulders in ANFO blasts was negligible because mean energy factor remained almost same even when the diameter of the blast holes was altered. The decrease in the number of oversize boulders in SME blasts was on account of increase in mean energy factor when the blast hole diameter was increased. The increase in the in-hole VoD due to increase in the diameter of the hole was not found to have an effect on the generation of oversize boulders as this increase was not substantial both in SME and ANFO blasts.
Advances in tilt rotor noise prediction
George, A. R.; Coffen, C. D.; Ringler, T. D.
The two most serious tilt rotor external noise problems, hover noise and blade-vortex interaction noise, are studied. The results of flow visualization and inflow velocity measurements document a complex, recirculating highly unsteady and turbulent flow due to the rotor-wing-body interactions characteristic of tilt rotors. The wing under the rotor is found to obstruct the inflow, causing a deficit in the inflow velocities over the inboard region of the rotor. Discrete frequency harmonic thickness and loading noise mechanisms in hover are examined by first modeling tilt rotor hover aerodynamics and then applying various noise prediction methods using the WOPWOP code. The analysis indicates that the partial ground plane created by the wing below the rotor results in a primary sound source for hover.
Indian Academy of Sciences (India)
Long Zhang; Guoliang Xiong; Hesheng Liu; Huijun Zou; Weizhong Guo
2010-04-01
A parametric time-frequency representation is presented based on timevarying autoregressive model (TVAR), followed by applications to non-stationary vibration signal processing. The identiﬁcation of time-varying model coefﬁcients and the determination of model order, are addressed by means of neural networks and genetic algorithms, respectively. Firstly, a simulated signal which mimic the rotor vibration during run-up stages was processed for a comparative study on TVAR and other non-parametric time-frequency representations such as Short Time Fourier Transform, Continuous Wavelet Transform, Empirical Mode Decomposition, Wigner–Ville Distribution and Choi–Williams Distribution, in terms of their resolutions, accuracy, cross term suppression as well as noise resistance. Secondly, TVAR was applied to analyse non-stationary vibration signals collected from a rotor test rig during run-up stages, with an aim to extract fault symptoms under non-stationary operating conditions. Simulation and experimental results demonstrate that TVAR is an effective solution to non-stationary signal analysis and has strong capability in signal time-frequency feature extraction.
Richardson, Robin A; Papachristos, Konstantinos; Read, Daniel J; Harlen, Oliver G; Harrison, Michael; Paci, Emanuele; Muench, Stephen P; Harris, Sarah A
2014-12-01
Advances in structural biology, such as cryo-electron microscopy (cryo-EM) have allowed for a number of sophisticated protein complexes to be characterized. However, often only a static snapshot of a protein complex is visualized despite the fact that conformational change is frequently inherent to biological function, as is the case for molecular motors. Computer simulations provide valuable insights into the different conformations available to a particular system that are not accessible using conventional structural techniques. For larger proteins and protein complexes, where a fully atomistic description would be computationally prohibitive, coarse-grained simulation techniques such as Elastic Network Modeling (ENM) are often employed, whereby each atom or group of atoms is linked by a set of springs whose properties can be customized according to the system of interest. Here we compare ENM with a recently proposed continuum model known as Fluctuating Finite Element Analysis (FFEA), which represents the biomolecule as a viscoelastic solid subject to thermal fluctuations. These two complementary computational techniques are used to answer a critical question in the rotary ATPase family; implicit within these motors is the need for a rotor axle and proton pump to rotate freely of the motor domain and stator structures. However, current single particle cryo-EM reconstructions have shown an apparent connection between the stators and rotor axle or pump region, hindering rotation. Both modeling approaches show a possible role for this connection and how it would significantly constrain the mobility of the rotary ATPase family. © 2014 Wiley Periodicals, Inc.
Directory of Open Access Journals (Sweden)
T. Sghaier
2013-12-01
Full Text Available Aim of study: The aim of the work was to develop an individual tree diameter-increment model for Thuya (Tetraclinis articulata in Tunisia.Area of study: The natural Tetraclinis articulata stands at Jbel Lattrech in north-eastern of Tunisia.Material and methods: Data came from 200 trees located in 50 sample plots. The diameter at age t and the diameter increment for the last five years obtained from cores taken at breast height were measured for each tree. Four difference equations derived from the base functions of Richards, Lundqvist, Hossfeld IV and Weibull were tested using the age-independent formulations of the growth functions. Both numerical and graphical analyses were used to evaluate the performance of the candidate models.Main results: Based on the analysis, the age-independent difference equation derived from the base function Richards model was selected. Two of the three parameters (growth rate and shape parameter of the retained model were related to site quality, represented by a Growth Index, stand density and the basal area in larger trees divided by diameter of the subject tree expressing the inter-tree competition.Research highlights: The proposed model can be useful for predicting the diameter growth of Tetraclinis articulata in Tunisia when age is not available or for trees growing in uneven-aged stands.Keywords: Age-independent growth model; difference equations; Tetraclinis articulata; Tunisia.
Hill, Gary; Duval, Ronald W.; Green, John A.; Huynh, Loc C.
1991-01-01
A piloted comparison of rigid and aeroelastic blade-element rotor models was conducted at the Crew Station Research and Development Facility (CSRDF) at Ames Research Center. A simulation development and analysis tool, FLIGHTLAB, was used to implement these models in real time using parallel processing technology. Pilot comments and quantitative analysis performed both on-line and off-line confirmed that elastic degrees of freedom significantly affect perceived handling qualities. Trim comparisons show improved correlation with flight test data when elastic modes are modeled. The results demonstrate the efficiency with which the mathematical modeling sophistication of existing simulation facilities can be upgraded using parallel processing, and the importance of these upgrades to simulation fidelity.
Hill, Gary; Du Val, Ronald W.; Green, John A.; Huynh, Loc C.
1991-01-01
A piloted comparison of rigid and aeroelastic blade-element rotor models was conducted at the Crew Station Research and Development Facility (CSRDF) at Ames Research Center. A simulation development and analysis tool, FLIGHTLAB, was used to implement these models in real time using parallel processing technology. Pilot comments and qualitative analysis performed both on-line and off-line confirmed that elastic degrees of freedom significantly affect perceived handling qualities. Trim comparisons show improved correlation with flight test data when elastic modes are modeled. The results demonstrate the efficiency with which the mathematical modeling sophistication of existing simulation facilities can be upgraded using parallel processing, and the importance of these upgrades to simulation fidelity.
On Cup Anemometer Rotor Aerodynamics
Santiago Pindado; Sergio Avila-Sanchez; Javier Pérez
2012-01-01
The influence of anemometer rotor shape parameters, such as the cups’ front area or their center rotation radius on the anemometer’s performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a lin...
Wang, Shuai; Wang, Yu; Zi, Yanyang; Li, Bing; He, Zhengjia
2015-10-01
A novel reduced-order modeling method is presented in this paper for dynamics analysis of rotating impeller-shaft-bearing assembly with cracked impellers. Based on three-dimensional finite element model, the complex component mode synthesis (CMS) method is employed to generate an efficient reduced-order model (ROM) for studying the effects of crack on the global vibration of the rotating assembly. First, a modeling framework for impeller-shaft-bearing systems in rotating frame is presented. Rotational effects, including Coriolis matrix and centrifugal softening, have been taken into account. Then, the governing equation of motion of the damped gyroscopic system is reduced by the complex CMS method. Finally, the obtained ROM is employed to study the effects of crack on assembly's vibration. During the steady-state response analysis, external excitations on the impeller due to rotor-stator interactions have been taken into account, which was however neglected in previous investigations on rotordynamics. Numerical results show that the lower-order eigenvalues and the unbalance response of the assembly are not sensitive to the local crack on impeller. Nevertheless, the flexible coupling between impeller and shaft becomes more complex when the air flow-induced excitations are considered. Under EO1 traveling wave excitations, a crack leads to slight changes in the assembly's response. In contrast, the effect of crack becomes significant when the assembly is excited by EO2 and higher EO excitations. Moreover, the nonlinear crack breathing effects affect the assembly's response obviously. Finally, a potential technique for detecting the crack on impeller during operation is discussed.
Numerical Modelling of Large-Diameter Steel Piles at Horns Rev
DEFF Research Database (Denmark)
Augustesen, Anders Hust; Brødbæk, K. T.; Møller, M.;
2009-01-01
Today large-diameter monopiles are the most common foundation type used for large offshore wind farms. This paper aims to investigate the behaviour of monopiles under monotonic loading taking the interaction between the pile and the subsoil into account. Focus is paid to a monopile used as founda......Today large-diameter monopiles are the most common foundation type used for large offshore wind farms. This paper aims to investigate the behaviour of monopiles under monotonic loading taking the interaction between the pile and the subsoil into account. Focus is paid to a monopile used...... as foundation for a wind turbine at Horns Rev located in the Danish sector of the North Sea. The outer diameter of the pile is 4 m and the subsoil at the location consists primarily of sand. The behaviour of the pile is investigated under realistic loading conditions by means of a traditional Winkler...
Fabian C.C. Uzoh; William W. Oliver
2008-01-01
A diameter increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in the United States using a multilevel linear mixed model. Stochastic variability is broken down among period, locale, plot, tree and within-tree components. Covariates acting at tree and stand level, as breast height diameter, density, site index...
Institute of Scientific and Technical Information of China (English)
Hong Tang; Xiaogang Sun; Guibin Yuan
2007-01-01
In total light scattering particle sizing technique, the relationship among Sauter mean diameter D32, mean extinction efficiency Q, and particle size distribution function is studied in order to inverse the mean diameter and particle size distribution simply. We propose a method which utilizes the mean extinction efficiency ratio at only two selected wavelengths to solve D32 and then to inverse the particle size distribution associated with (Q) and D32. Numerical simulation results show that the particle size distribution is inversed accurately with this method, and the number of wavelengths used is reduced to the greatest extent in the measurement range. The calculation method has the advantages of simplicity and rapidness.
Innovative multi rotor wind turbine designs
Energy Technology Data Exchange (ETDEWEB)
Kale, S.A.; Sapali, S.N. [College of Engineering. Mechanical Engineering Dept, Pune (India)
2012-07-01
Among the renewable energy sources, today wind energy is the most recognized and cost effective. Developers and researchers in this sector are optimistic and continuously working innovatively to improve the technology. The wind power obtained is proportional to the swept area of wind turbine. The swept area is increased by using a single rotor of large diameter or multi rotors in array. The rotor size is growing continuously with mature technology. Multi rotor technology has a long history and the multi rotor concept persists in a variety of modern innovative systems but the concept has fallen out of consideration in mainstream design from the perception that is complex and unnecessary as very large single rotor units are now technically feasible. This work addresses the evaluation of different multi rotor wind turbine systems. These innovative wind turbines are evaluated on the basis of feasibility, technological advantages, security of expected power performance, cost, reliability, impact of innovative system, comparison with existing wind turbine design. The findings of this work will provide guidelines for the practical and economical ways for further research on the multi rotor wind turbines. (Author)
The strain energy release approach for modeling cracks in rotors: A state of the art review
Papadopoulos, Chris A.
2008-05-01
The strain energy release rate (SERR) theory, combined with Linear Fracture Mechanics and Rotordynamics theories, has been widely used over the last three decades in order to calculate the compliance that causes a transverse surface crack in a rotating shaft. In this paper, the basic theory of this approach is presented, along with some extensions and limitations of its usage. The SERR theory is applied to a rotating crack and gives good results. The linear or nonlinear cracked rotor behavior depends on the mechanism of opening and closure of the crack during the shaft rotation. A brief history of the SERR theory is presented. In the 1970s, this theory met with rotordynamics as a result of research conducted on the causes of rotor failures in power industries. The main goal of this research was to give the engineer an early warning about the cracked situation of the rotor—in other words, to make the identification of the crack possible. Different methods of crack identification are presented here as well as those for multi-crack identification.
The effect of blade pitch in the rotor hydrodynamics of a cross-flow turbine
Somoano, Miguel; Huera-Huarte, Francisco
2016-11-01
In this work we will show how the hydrodynamics of the rotor of a straight-bladed Cross-Flow Turbine (CFT) are affected by the Tip Speed Ratio (TSR), and the blade pitch angle imposed to the rotor. The CFT model used in experiments consists of a three-bladed (NACA-0015) vertical axis turbine with a chord (c) to rotor diameter (D) ratio of 0.16. Planar Digital Particle Image Velocimetry (DPIV) was used, with the laser sheet aiming at the mid-span of the blades, illuminating the inner part of the rotor and the near wake of the turbine. Tests were made by forcing the rotation of the turbine with a DC motor, which provided precise control of the TSR, while being towed in a still-water tank at a constant Reynolds number of 61000. A range of TSRs from 0.7 to 2.3 were covered for different blade pitches, ranging from 8° toe-in to 16° toe-out. The interaction between the blades in the rotor will be discussed by examining dimensionless phase-averaged vorticity fields in the inner part of the rotor and mean velocity fields in the near wake of the turbine. Supported by the Spanish Ministry of Economy and Competitiveness, Grant BES-2013-065366 and project DPI2015-71645-P.
Leighton, K. P.; Harris, W. L.
1984-01-01
An investigation of blade slap due to blade vortex interaction (BVI) has been conducted. This investigation consisted of an examination of BVI blade slap for two, three, and four-bladed model rotors at tip Mach numbers ranging from 0.20 to 0.50. Blade slap contours have been obtained for each configuration tested. Differences in blade slap contours, peak sound pressure level, and directivity for each configuration tested are noted. Additional fundamental differences, such as multiple interaction BVI, are observed and occur for only specific rotor blade configurations. The effect of increasing the Mach number on the BVI blade slap for various rotor blade combinations has been quantified. A peak blade slap Mach number scaling law is proposed. Comparison of measured BVI blade slap with theory is made.
Directory of Open Access Journals (Sweden)
Bangcheng Han
2013-01-01
Full Text Available We firstly report on an investigation into the unbalanced magnetic pull (UMP effect on the static stiffness models of radial active magnetic bearing (RAMB in brushless DC motor (BDCM in no-loaded and loaded conditions using the finite element method (FEM. The influences of the UMP on the force-control current, force-position, current stiffness, and position stiffness of RAMB are clarified in BDCM with 100 kW rated power. We found the position stiffness to be more susceptible to UMP. The primary source of UMP is the permanent magnets of BDCM. In addition, the performance of RAMB is affected by the UMP ripples during motor commutation and also periodically affected by the angular position of rotor. The characteristic curves of RAMB force versus control current (or rotor position and angular position of rotor affected by the UMP are given. The method is useful in design and optimization of RAMB in magnetically suspended BDCMs.
Study of the Standard k-ɛ Model for Tip Leakage Flow in an Axial Compressor Rotor
Gao, Yanfei; Liu, Yangwei; Zhong, Luyang; Hou, Jiexuan; Lu, Lipeng
2016-12-01
The standard k-ɛ model (SKE) and the Reynolds stress model (RSM) are employed to predict the tip leakage flow (TLF) in a low-speed large-scale axial compressor rotor. Then, a new research method is adopted to "freeze" the turbulent kinetic energy and dissipation rate of the flow field derived from the RSM, and obtain the turbulent viscosity using the Boussinesq hypothesis. The Reynolds stresses and mean flow field computed on the basis of the frozen viscosity are compared with the results of the SKE and the RSM. The flow field in the tip region based on the frozen viscosity is more similar to the results of the RSM than those of the SKE, although certain differences can be observed. This finding indicates that the non-equilibrium turbulence transport nature plays an important role in predicting the TLF, as well as the turbulence anisotropy.
Rotor for a line start permanent magnet machine
Energy Technology Data Exchange (ETDEWEB)
Melfi, Mike; Schiferl, Rich; Umans, Stephen
2017-07-11
A rotor comprises laminations with a plurality of rotor bar slots with an asymmetric arrangement about the rotor. The laminations also have magnet slots equiangularly spaced about the rotor. The magnet slots extend near to the rotor outer diameter and have permanent magnets disposed in the magnet slots creating magnetic poles. The magnet slots may be formed longer than the permanent magnets disposed in the magnets slots and define one or more magnet slot apertures. The permanent magnets define a number of poles and a pole pitch. The rotor bar slots are spaced from adjacent magnet slots by a distance that is at least 4% of the pole pitch. Conductive material is disposed in the rotor bar slots, and in some embodiments, may be disposed in the magnet slot apertures.
Rafal Podlaski; Francis A. Roesch
2013-01-01
Study assessed the usefulness of various methods for choosing the initial values for the numerical procedures for estimating the parameters of mixture distributions and analysed variety of mixture models to approximate empirical diameter at breast height (dbh) distributions. Two-component mixtures of either the Weibull distribution or the gamma distribution were...
Directory of Open Access Journals (Sweden)
Jun Sun
2016-08-01
Conclusion: Gene enhanced tissue engineering followed mosaicplasty could restore a 9 mm diameter osteochondral defects in a goat model effectively. With the reduction of covering area of the graft, the advantages of the combined gene enhanced tissue engineering method can be better reflected.
Indian Academy of Sciences (India)
Smitadhi Ganguly; A Nandi; S Neogy
2014-06-01
Unlike structural dynamics, the three-dimensional finite-element model of non-axisymmetric rotors on orthotropic bearings generates a large gyroscopic system with parametric stiffness. The present work explores the use of mass-lumping in stability analysis of such systems. Using a variant of Hill’s method, the problem reduces to a generalized Eigen value problem of order $nm \\times nm$, with as the order of the system in state vector representation and as the number of terms in the assumed solution. The matrices in both the sides of the Eigen value problem are expressed in terms of Kronecker products where the mass-matrix appears twice as a sub-matrix in both the sides of the equation. A particular one or both of them can be made diagonal. Both options produce sufficiently accurate results with considerable savings, even with a coarse mesh.
THE DESIGN OF AXIAL PUMP ROTORS USING THE NUMERICAL METHODS
Directory of Open Access Journals (Sweden)
Ali BEAZIT
2010-06-01
Full Text Available The researches in rotor theory, the increasing use of computers and the connection between design and manufacturing of rotors, have determined the revaluation and completion of classical rotor geometry. This paper presents practical applications of mathematical description of rotor geometry. A program has been created to describe the rotor geometry for arbitrary shape of the blade. The results can be imported by GAMBIT - a processor for geometry with modeling and mesh generations, to create a mesh needed in hydrodynamics analysis of rotor CFD. The results obtained are applicable in numerical methods and are functionally convenient for CAD/CAM systems.
Institute of Scientific and Technical Information of China (English)
Seyed Mostafa Hosseinalipour; Hadiseh Karimaei; Ehsan Movahednejad
2016-01-01
The maximum entropy principle (MEP) is one of the first methods which have been used to predict droplet size and velocity distributions of liquid sprays. This method needs a mean droplets diameter as an input to predict the droplet size distribution. This paper presents a new sub-model based on the deterministic aspects of liquid atom-ization process independent of the experimental data to provide the mean droplets diameter for using in the maximum entropy formulation (MEF). For this purpose, a theoretical model based on the approach of energy conservation law entitled energy-based model (EBM) is presented. Based on this approach, atomization occurs due to the kinetic energy loss. Prediction of the combined model (MEF/EBM) is in good agreement with the avail-able experimental data. The energy-based model can be used as a fast and reliable enough model to obtain a good estimation of the mean droplets diameter of a spray and the combined model (MEF/EBM) can be used to wel predict the droplet size distribution at the primary breakup.
Sree, Dave
2015-01-01
Near-field acoustic power level analysis of F31A31 open rotor model has been performed to determine its noise characteristics at simulated cruise flight conditions. The non-proprietary parts of the test data obtained from experiments in the 8x6 supersonic wind tunnel were provided by NASA-Glenn Research Center. The tone and broadband components of total noise have been separated from raw test data by using a new data analysis tool. Results in terms of sound pressure levels, acoustic power levels, and their variations with rotor speed, freestream Mach number, and input shaft power, with different blade-pitch setting angles at simulated cruise flight conditions, are presented and discussed. Empirical equations relating models acoustic power level and input shaft power have been developed. The near-field acoustic efficiency of the model at simulated cruise conditions is also determined. It is hoped that the results presented in this work will serve as a database for comparison and improvement of other open rotor blade designs and also for validating open rotor noise prediction codes.
Directory of Open Access Journals (Sweden)
Sacramento Corral-Rivas
2014-02-01
Full Text Available Background We used mixed models with random components to develop height-diameter (h-d functions for mixed, uneven-aged stands in northwestern Durango (Mexico, considering the breast height diameter (d and stand variables as predictors. Methods The data were obtained from 44 permanent plots used to monitor stand growth under forest management in the study area. Results The generalized Bertalanffy-Richards model performed better than the other generalized models in predicting the total height of the species under study. For the genera Pinus and Quercus, the models were successfully calibrated by measuring the height of a subsample of three randomly selected trees close to the mean d, whereas for species of the genera Cupressus, Arbutus and Alnus, three trees were also selected, but they are specifically the maximum, minimum and mean d trees. Conclusions The presented equations represent a new tool for the evaluation and management of natural forest in the region.
Bifurcation and chaos of the bladed overhang rotor system with squeeze film dampers
Institute of Scientific and Technical Information of China (English)
CAO DengQing; WANG LiGang; CHEN YuShu; HUANG WenHu
2009-01-01
To study the nonlinear dynamic behavior of the bladed overhang rotor system with squeeze film damper (SFD), a blade-overhang rotor-SFD model is formulated using the lumped mass method and the Lagrange approach. The cavitated short bearing model is employed to describe the nonlinear oil force of the SFD. To reduce the scale of the nonlinear coupling system, a set of orthogonal transformations is employed to decouple the one nodal diameter equations of blades, which are coupled with the dy-namical equations of the rotor, with other equations of blades. In this way, the original system with 16+4n (n≥3) degrees of freedom (DoF) is reduced to a system with 24 DoF only. Then the parametric excitation terms in the blade-overhang rotor-SFD model are simplified in terms of periodic transforma-tions. The coupling equations are numerically solved and the solutions are used to analyze the dy-trum plot. A variety of motion types are found such as multi-periodic, quasi-periodic, and chaotic mo-tions. Moreover, the typical nonlinear dynamic evolutions including the periodic-doubling bifurcation and reverse bifurcation are noted. It is noticed that there exist apparent differences in the dynamic behavior between the blade-overhang rotor-SFD models without and with considering the effect of blades.
Bifurcation and chaos of the bladed overhang rotor system with squeeze film dampers
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
To study the nonlinear dynamic behavior of the bladed overhang rotor system with squeeze film damper (SFD), a blade-overhang rotor-SFD model is formulated using the lumped mass method and the Lagrange approach. The cavitated short bearing model is employed to describe the nonlinear oil force of the SFD. To reduce the scale of the nonlinear coupling system, a set of orthogonal transformations is employed to decouple the one nodal diameter equations of blades, which are coupled with the dy- namical equations of the rotor, with other equations of blades. In this way, the original system with 16+4n (n≥3) degrees of freedom (DoF) is reduced to a system with 24 DoF only. Then the parametric excitation terms in the blade-overhang rotor-SFD model are simplified in terms of periodic transforma- tions. The coupling equations are numerically solved and the solutions are used to analyze the dy- namic behavior of the system in terms of the bifurcation diagram, whirl orbit, Poincaré map and spec- trum plot. A variety of motion types are found such as multi-periodic, quasi-periodic, and chaotic mo- tions. Moreover, the typical nonlinear dynamic evolutions including the periodic-doubling bifurcation and reverse bifurcation are noted. It is noticed that there exist apparent differences in the dynamic behavior between the blade-overhang rotor-SFD models without and with considering the effect of blades.
Use of the method of Boolean models to study different methods of drilling wells of large diameter
Energy Technology Data Exchange (ETDEWEB)
Selivanov, A.N.; Ryabinin, A.I.
1981-01-01
A description is made of the method of statistical modeling using the method of Boolean models as an example of processing and analyzing the results of drilling wells of large diameter by different methods. It is indicated that this method as compared to traditional methods of multiple-factor analysis with comparatively small volume of experimental data makes it possible to obtain a complete qualitative and quantitative characterization of the studied phenomenon.
Directory of Open Access Journals (Sweden)
Ahmadi, K.
2013-01-01
Full Text Available The relationship between tree height and diameter is an important element in growth and yield models, in carbon budget and timber volume models, and in the description of stand dynamics. Six non-linear growth functions (i.e. Chapman-Richards, Schnute, Lundqvist/Korf, Weibull, Modified Logistic and Exponential were fitted to tree height-diameter data of oriental beech in the Hyrcanian mixed hardwood forests of Iran. The predictive performance of these models was in the first place assessed by means of different model evaluation criteria such as adjusted R squared (adjR2, root mean square error (RMSE, Akaike information criterion (AIC, mean difference (MD, mean absolute difference (MAD and mean square (MS error criteria. Although each of the six models accounted for approximately 75% of total variation in height, a large difference in asymptotic estimates was observed. Apart from this, the predictive performance of the models was also evaluated by means of cross-validation and by splitting the data into 5-cm diameter classes. Plotting the MD in relation to these diameter at breast height (DBH classes showed for all growth functions, except for the Modified Logistic function, similar mean prediction errors for small- and medium-sized trees. Large-sized trees, however, showed a higher mean prediction error. The Modified Logistic function showed the worst performance due to a large model bias. The Exponential and Lundqvist/Korf models were discarded due to their showing biologically illogical behavior and unreasonable estimates for the asymptotic coefficient, respectively. Considering all the above-mentioned criteria, the Chapman-Richards, Weibull, and Schnute functions provided the most satisfactory height predictions. However, we would recommend the Chapman-Richards function for further analysis because of its higher predictive performance.
Kommajosyula, Ravikishore; Mazzocco, Thomas; Ambrosini, Walter; Baglietto, Emilio
2016-11-01
Accurate prediction of Bubble Departure and Lift-off Diameters is key for development of closures in two-phase Eulerian CFD simulation of Flow Boiling, owing to its sensitivity in the Heat Flux partitioning approach. Several models ranging from simple correlations to solving complex force balance models have been proposed in literature; however, they rely on data-fitting for specific databases, and have shown to be inapplicable for general flow applications. The aim of this study is to extend the approach by proposing a more consistent and general formulation that accounts for relevant forces acting on the Bubble at the point of Departure and Lift-off. Among the key features of the model, the Bubble Inclination angle is treated as an unknown to be inferred along with the Departure Diameter, and the relative velocity of the bubble sliding on the surface, is modeled to determine the Lift-off Diameter. A novel expression is developed for the bubble growth force in terms of flow quantities, based on extensive data analysis. The model has been validated using 6 different experimental databases with varying flow conditions and 3 fluids. Results show high accuracy of predictions over a broad range, outperforming existing models both in terms of accuracy and generality. CASL - The Consortium for Advanced Simulation of LWRs.
Suarez Mullins, Astrid
Terrain-induced gravity waves and rotor circulations have been hypothesized to enhance the generation of submeso motions (i.e., nonstationary shear events with spatial and temporal scales greater than the turbulence scale and smaller than the meso-gamma scale) and to modulate low-level intermittency in the stable boundary layer (SBL). Intermittent turbulence, generated by submeso motions and/or the waves, can affect the atmospheric transport and dispersion of pollutants and hazardous materials. Thus, the study of these motions and the mechanisms through which they impact the weakly to very stable SBL is crucial for improving air quality modeling and hazard predictions. In this thesis, the effects of waves and rotor circulations on submeso and turbulence variability within the SBL is investigated over the moderate terrain of central Pennsylvania using special observations from a network deployed at Rock Springs, PA and high-resolution Weather Research and Forecasting (WRF) model forecasts. The investigation of waves and rotors over central PA is important because 1) the moderate topography of this region is common to most of the eastern US and thus the knowledge acquired from this study can be of significance to a large population, 2) there have been little evidence of complex wave structures and rotors reported for this region, and 3) little is known about the waves and rotors generated by smaller and more moderate topographies. Six case studies exhibiting an array of wave and rotor structures are analyzed. Observational evidence of the presence of complex wave structures, resembling nonstationary trapped gravity waves and downslope windstorms, and complex rotor circulations, resembling trapped and jump-type rotors, is presented. These motions and the mechanisms through which they modulate the SBL are further investigated using high-resolution WRF forecasts. First, the efficacy of the 0.444-km horizontal grid spacing WRF model to reproduce submeso and meso
Liu, Jing; Shao, Yimin
2017-06-01
Rotor bearing systems (RBSs) play a very valuable role for wind turbine gearboxes, aero-engines, high speed spindles, and other rotational machinery. An in-depth understanding of vibrations of the RBSs is very useful for condition monitoring and diagnosis applications of these machines. A new twelve-degree-of-freedom dynamic model for rigid RBSs with a localized defect (LOD) is proposed. This model can formulate the housing support stiffness, interfacial frictional moments including load dependent and load independent components, time-varying displacement excitation caused by a LOD, additional deformations at the sharp edges of the LOD, and lubricating oil film. The time-varying displacement model is determined by a half-sine function. A new method for calculating the additional deformations at the sharp edges of the LOD is analytical derived based on an elastic quarter-space method presented in the literature. The proposed dynamic model is utilized to analyze the influences of the housing support stiffness and LOD sizes on the vibration characteristics of the rigid RBS, which cannot be predicted by the previous dynamic models in the literature. The results show that the presented method can give a new dynamic modeling method for vibration formulation for a rigid RBS with and without the LOD on the races.
Chen, Ting; Li, Liqing; Huang, Xiubao
2005-06-01
Physical, statistical and artificial neural network (ANN) models are established for predicting the fibre diameter of melt blown nonwovens from the processing parameters. The results show that the ANN model yields a very accurate prediction (average error of 0.013%), and a reasonably good ANN model can be achieved with relatively few data points. Because the physical model is based on the inherent physical principles of the phenomena of interest, it can yield reasonably good prediction results when experimental data are not available and the entire physical procedure is of interest. This area of research has great potential in the field of computer assisted design in melt blowing technology.
Institute of Scientific and Technical Information of China (English)
Zhang Ying; Ye Liang; Yang Shuo
2015-01-01
A method combining rotor actuator disk model and embedded grid technique is pre-sented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more efficiently and effectively. In this method, rotor’s influence is con-sidered in terms of the momentum it impacts to the fluid around it;transformation matrixes among different coordinate systems are deduced to extend actuator method’s utility to conversion mode flow fields’ calculation. Meanwhile, an embedded grid system is designed, in which grids generated around fuselage and actuator disk are regarded as background grid and minor grid respectively, and a new method is presented for‘donor searching’ and‘hole cutting’ during grid assembling. Based on the above methods, flow fields of tilt rotor aircraft in conversion mode are simulated, with three-dimensional Navier–Stokes equations discretized by a second-order upwind finite-volume scheme and an implicit lower–upper symmetric Gauss–Seidel (LU-SGS) time-stepping scheme. Numerical results demonstrate that the proposed CFD method is very effective in simulating the conversion mode flow fields of tilt rotor aircraft.
Directory of Open Access Journals (Sweden)
Zhang Ying
2015-02-01
Full Text Available A method combining rotor actuator disk model and embedded grid technique is presented in this paper, aimed at predicting the flow fields and aerodynamic characteristics of tilt rotor aircraft in conversion mode more efficiently and effectively. In this method, rotor’s influence is considered in terms of the momentum it impacts to the fluid around it; transformation matrixes among different coordinate systems are deduced to extend actuator method’s utility to conversion mode flow fields’ calculation. Meanwhile, an embedded grid system is designed, in which grids generated around fuselage and actuator disk are regarded as background grid and minor grid respectively, and a new method is presented for ‘donor searching’ and ‘hole cutting’ during grid assembling. Based on the above methods, flow fields of tilt rotor aircraft in conversion mode are simulated, with three-dimensional Navier–Stokes equations discretized by a second-order upwind finite-volume scheme and an implicit lower–upper symmetric Gauss–Seidel (LU-SGS time-stepping scheme. Numerical results demonstrate that the proposed CFD method is very effective in simulating the conversion mode flow fields of tilt rotor aircraft.
Directory of Open Access Journals (Sweden)
Feng Chai
2016-10-01
Full Text Available High power density outer-rotor motors commonly use water or oil cooling. A reasonable thermal design for outer-rotor air-cooling motors can effectively enhance the power density without the fluid circulating device. Research on the heat dissipation mechanism of an outer-rotor air-cooling motor can provide guidelines for the selection of the suitable cooling mode and the design of the cooling structure. This study investigates the temperature field of the motor through computational fluid dynamics (CFD and presents a method to overcome the difficulties in building an accurate temperature field model. The proposed method mainly includes two aspects: a new method for calculating the equivalent thermal conductivity (ETC of the air-gap in the laminar state and an equivalent treatment to the thermal circuit that comprises a hub, shaft, and bearings. Using an outer-rotor air-cooling in-wheel motor as an example, the temperature field of this motor is calculated numerically using the proposed method; the results are experimentally verified. The heat transfer rate (HTR of each cooling path is obtained using the numerical results and analytic formulas. The influences of the structural parameters on temperature increases and the HTR of each cooling path are analyzed. Thereafter, the overload capability of the motor is analyzed in various overload conditions.
Bharadwaj, Sudarsh; Dullin, Holger R; Leung, Karen; Tong, William
2015-01-01
We present and analyse a simple model for the twisting somersault. The model is a rigid body with a rotor attached which can be switched on and off. This makes it simple enough to devise explicit analytical formulas whilst still maintaining sufficient complexity to preserve the shape-changing dynamics essential for twisting somersaults in springboard and platform diving. With `rotor on' and with `rotor off' the corresponding Euler-type equations can be solved, and the essential quantities characterising the dynamics, such as the periods and rotation numbers, can be computed in terms of complete elliptic integrals. Thus we arrive at explicit formulas for how to achieve a dive with m somersaults and n twists in a given total time. This can be thought of as a special case of a geometric phase formula due to Cabrera 2007.
On cup anemometer rotor aerodynamics.
Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio
2012-01-01
The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.
Hi-Q Rotor - Low Wind Speed Technology
Energy Technology Data Exchange (ETDEWEB)
Todd E. Mills; Judy Tatum
2010-01-11
The project objective was to optimize the performance of the Hi-Q Rotor. Early research funded by the California Energy Commission indicated the design might be advantageous over state-of-the-art turbines for collecting wind energy in low wind conditions. The Hi-Q Rotor is a new kind of rotor targeted for harvesting wind in Class 2, 3, and 4 sites, and has application in areas that are closer to cities, or 'load centers.' An advantage of the Hi-Q Rotor is that the rotor has non-conventional blade tips, producing less turbulence, and is quieter than standard wind turbine blades which is critical to the low-wind populated urban sites. Unlike state-of-the-art propeller type blades, the Hi-Q Rotor has six blades connected by end caps. In this phase of the research funded by DOE's Inventions and Innovation Program, the goal was to improve the current design by building a series of theoretical and numeric models, and composite prototypes to determine a best of class device. Development of the rotor was performed by aeronautical engineering and design firm, DARcorporation. From this investigation, an optimized design was determined and an 8-foot diameter, full-scale rotor was built and mounted using a Bergey LX-1 generator and furling system which were adapted to support the rotor. The Hi-Q Rotor was then tested side-by-side against the state-of-the-art Bergey XL-1 at the Alternative Energy Institute's Wind Test Center at West Texas State University for six weeks, and real time measurements of power generated were collected and compared. Early wind tunnel testing showed that the cut-in-speed of the Hi-Q rotor is much lower than a conventional tested HAWT enabling the Hi-Q Wind Turbine to begin collecting energy before a conventional HAWT has started spinning. Also, torque at low wind speeds for the Hi-Q Wind Turbine is higher than the tested conventional HAWT and enabled the wind turbine to generate power at lower wind speeds. Based on the data
Directory of Open Access Journals (Sweden)
Jose Javier Gorgoso-Varela
2016-04-01
Full Text Available Aim of study: In this study we compare the accuracy of three bivariate distributions: Johnson’s SBB, Weibull-2P and LL-2P functions for characterizing the joint distribution of tree diameters and heights.Area of study: North-West of Spain.Material and methods: Diameter and height measurements of 128 plots of pure and even-aged Tasmanian blue gum (Eucalyptus globulus Labill. stands located in the North-west of Spain were considered in the present study. The SBB bivariate distribution was obtained from SB marginal distributions using a Normal Copula based on a four-parameter logistic transformation. The Plackett Copula was used to obtain the bivariate models from the Weibull and Logit-logistic univariate marginal distributions. The negative logarithm of the maximum likelihood function was used to compare the results and the Wilcoxon signed-rank test was used to compare the related samples of these logarithms calculated for each sample plot and each distribution.Main results: The best results were obtained by using the Plackett copula and the best marginal distribution was the Logit-logistic.Research highlights: The copulas used in this study have shown a good performance for modeling the joint distribution of tree diameters and heights. They could be easily extended for modelling multivariate distributions involving other tree variables, such as tree volume or biomass.
A Recurrent Rotor-Router Configuration in Z^3
A, Tulasi Ram Reddy
2010-01-01
Rotor Router models were first introduced by James Propp in 2002. A recurrent Rotor configuration is the one in which every state is visited infinitely often. In this project we investigated whether there is a recurrent Rotor configuration in Z^d (d>2).
Van Zante, Dale E.; Rizzi, Stephen A.
2016-01-01
The ERA project executed a comprehensive test program for Open Rotor aerodynamic and acoustic performance. System studies used the data to estimate the fuel burn savings and acoustic margin for an aircraft system with open rotor propulsion. The acoustic measurements were used to produce an auralization that compares the legacy blades to the current generation of open rotor designs.
Energy Technology Data Exchange (ETDEWEB)
Ramirez Solis, Jose Antonio; Munoz Quezada, Rodolfo; Franco Nava, Jose Manuel [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
1993-01-01
At the Instituto de Investigaciones Electricas (IIE), the experimental modal tests were initiated in order to validate the numerical models used by computer programs for the study of the rotor dynamic behavior. In order to contribute to the application of the rotor balancing methods based in the calculation of their modal forms, currently the capacity to determine these modal forms and the natural frequencies of turbogenerator rotors, is being developed, through experimental modal tests. In this paper a short description is made of the technique and the results of its application in an experimental rotor and in one of the rotors of a turbogenerator, are presented. [Espanol] En el Instituto de Investigaciones Electricas (IIE), las pruebas modales experimentales se iniciaron con la finalidad de validar los modelos numericos empleados por programas de computo para el estudio del comportamiento dinamico de rotores. Con objeto de contribuir a la aplicacion de los metodos de balanceo de rotores basados en el calculo de sus formas modales, actualmente esta desarrollandose la capacidad para determinar esas formas modales y las frecuencias naturales de rotores de turbogeneradores, a traves de las pruebas modales experimentales. En este trabajo se describe brevemente la tecnica y se presentan los resultados de su aplicacion en un rotor experimental y en uno de los tres rotores de un turbogenerador.
Energy Technology Data Exchange (ETDEWEB)
Doessing, M.
2011-05-15
During the last decades the annual energy produced by wind turbines has increased dramatically and wind turbines are now available in the 5MW range. Turbines in this range are constantly being developed and it is also being investigated whether turbines as large as 10-20MW are feasible. The design of very large machines introduces new problems in the practical design, and optimization tools are necessary. These must combine the dynamic effects of both aerodynamics and structure in an integrated optimization environment. This is referred to as aeroelastic optimization. The Risoe DTU optimization software HAWTOPT has been used in this project. The quasi-steady aerodynamic module have been improved with a corrected blade element momentum method. A structure module has also been developed which lays out the blade structural properties. This is done in a simplified way allowing fast conceptual design studies and with focus on the overall properties relevant for the aeroelastic properties. Aeroelastic simulations in the time domain were carried out using the aeroelastic code HAWC2. With these modules coupled to HAWTOPT, optimizations have been made. In parallel with the developments of the mentioned numerical modules, focus has been on analysis and a fundamental understanding of the key parameters in wind turbine design. This has resulted in insight and an effective design methodology is presented. Using the optimization environment a 5MW wind turbine rotor has been optimized for reduced fatigue loads due to apwise bending moments. Among other things this has indicated that airfoils for wind turbine blades should have a high lift coefficient. The design methodology proved to be stable and a help in the otherwise challenging task of numerical aeroelastic optimization. (Author)
Ledo, Alicia; Cornulier, Thomas; Illian, Janine B; Iida, Yoshiko; Kassim, Abdul Rahman; Burslem, David F R P
2016-12-01
Accurate estimation of tree biomass is necessary to provide realistic values of the carbon stored in the terrestrial biosphere. A recognized source of errors in tree aboveground biomass (AGB) estimation is introduced when individual tree height values (H) are not directly measured but estimated from diameter at breast height (DBH) using allometric equations. In this paper, we evaluate the performance of 12 alternative DBH : H equations and compare their effects on AGB estimation for three tropical forests that occur in contrasting climatic and altitudinal zones. We found that fitting a three-parameter Weibull function using data collected locally generated the lowest errors and bias in H estimation, and that equations fitted to these data were more accurate than equations with parameters derived from the literature. For computing AGB, the introduced error values differed notably among DBH : H allometric equations, and in most cases showed a clear bias that resulted in either over- or under-estimation of AGB. Fitting the three-parameter Weibull function minimized errors in AGB estimates in our study and we recommend its widespread adoption for carbon stock estimation. We conclude that many previous studies are likely to present biased estimates of AGB due to the method of H estimation. © 2016 by the Ecological Society of America.
Interpreting stem diameter changes
Hölttä, T.; Sevanto, S.; Nikinmaa, E.
2009-12-01
Detecting phloem transport in stem diameter changes Teemu Hölttä1, Sanna Sevanto2, Eero Nikinmaa1 1Department of Forest Ecology, P.O. Box 27, FIN-00014 University of Helsinki, Finland 2Department of Physics, P.O. Box 48, FIN-00014 University of Helsinki, Finland Introduction The volume of living cells and xylem conduits vary according to pressures they are subjected to. Our proposition is that the behavior of the inner bark diameter variation which cannot be explained by changes in xylem water status arise from changes in the osmotic concentration of the phloem and cambial growth. Materials and methods Simultaneous xylem and stem diameter measurements were conducted between June 28th to October 4th 2006 in Southern Finland on a 47-year old, 15 meter tall, Scots pine tree (DBH 15 cm) at heights of 1.5 and 10 meters. The difference between the measured inner bark diameter and the inner bark diameter predicted from xylem diameter change with a simple model (assuming there was no change in the osmotic concentration of the phloem) is hypothesized to give the changes in the osmotic concentration of the inner bark. The simple model calculates the radial water exchange between the xylem and phloem driven by the water potential changes in the xylem. Results and Discussion The major signal in the inner bark diameter was the transpiration rate as assumed, but also a signal arising from the change in the osmotic concentration (Fig 1a). The predicted osmotic concentration of the phloem typically increased during the afternoon due to the loading of photosynthesized sugars to the phloem. Inner bark osmotic concentration followed the photosynthesis rate with a 3 and 4 hour time-lag at the top and base, respectively (Fig 1b). The connection between photosynthesis and the predicted change in phloem osmotic concentration was stronger in the upper part of the tree compared to lower part. The changes in the predicted osmotic concentration were not similar every day, indicating that
Naderi, Peyman
2016-09-01
The inter-turn short fault for the Cage-Rotor-Induction-Machine (CRIM) is studied in this paper and its local saturation is taken into account. However, in order to observe the exact behavior of machine, the Magnetic-Equivalent-Circuit (MEC) and nonlinear B-H curve are proposed to provide an insight into the machine model and saturation effect respectively. The electrical machines are generally operated near to their saturation zone due to some design necessities. Hence, when the machine is exposed to a fault such as short circuit or eccentricities, it is operated within its saturation zone and thus, time and space harmonics are integrated and as a result, current and torque harmonics are generated which the phenomenon cannot be explored when saturation is dismissed. Nonetheless, inter-turn short circuit may lead to local saturation and this occurrence is studied in this paper using MEC model. In order to achieve the mentioned objectives, two and also four-pole machines are modeled as two samples and the machines performances are analyzed in healthy and faulty cases with and without saturation effect. A novel strategy is proposed to precisely detect inter-turn short circuit fault according to the stator׳s lines current signatures and the accuracy of the proposed method is verified by experimental results.
Energy Technology Data Exchange (ETDEWEB)
Melin, Alexander M [ORNL; Kisner, Roger A [ORNL; Fugate, David L [ORNL; Holcomb, David Eugene [ORNL
2015-01-01
Embedding instrumentation and control Embedding instrumentation and control (I\\&C) at the component level in nuclear power plants can improve component performance, lifetime, and resilience by optimizing operation, reducing the constraints on physical design, and providing on-board prognostics and diagnostics. However, the extreme environments that many nuclear power plant components operate in makes embedding instrumentation and control at the component level difficult. Successfully utilizing embedded I\\&C requires developing a deep understanding of the system's dynamics and using that knowledge to overcome material and physical limitations imposed by the environment. In this paper, we will develop a coupled dynamic model of a high temperature (700 $^\\circ$C) canned rotor pump that incorporates rotordynamics, hydrodynamics, and active magnetic bearing dynamics. Then we will compare two control design methods, one that uses a simplified decoupled model of the system and another that utilizes the full coupled system model. It will be seen that utilizing all the available knowledge of the system dynamics in the controller design yield an order of magnitude improvement in the magnitude of the magnetic bearing response to disturbances at the same level of control effort, a large reduction in the settling time of the system, and a smoother control action.
Directory of Open Access Journals (Sweden)
Unger Laura Anna
2015-09-01
Full Text Available This work aimed at the detection of rotor centers within the atrial cavity during atrial fibrillation on the basis of phase singularities. A voxel based method was established which employs the Hilbert transform and the phase of unipolar electrograms. The method provides a 3D overview of phase singularities at the endocardial surface and within the blood volume. Mapping those phase singularities from the inside of the atria at the endocardium yielded rotor center trajectories. We discuss the results for an unstable and a more stable rotor. The side length of the areas covered by the trajectories varied from 1.5 mm to 10 mm. These results are important for cardiologists who target rotors with RF ablation in order to cure atrial fibrillation.
The near-field acoustic levitation of high-mass rotors.
Hong, Z Y; Lü, P; Geng, D L; Zhai, W; Yan, N; Wei, B
2014-10-01
Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.
The near-field acoustic levitation of high-mass rotors
Energy Technology Data Exchange (ETDEWEB)
Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)
2014-10-15
Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.
Time Frequency Features of Rotor Systems with Slowly Varying Mass
Directory of Open Access Journals (Sweden)
Tao Yu
2011-01-01
Full Text Available With the analytic method and numerical method respectively, the asymptotic solutions and finite element model of rotor system with single slowly varying mass is obtained to investigate the time frequency features of such rotor system; furthermore, with given model of slowly varying mass, the rotor system with dual slowly varying mass is studied. For the first order approximate solution is used, there exists difference between the results with analytic method and numerical method. On the base of common characteristics of rotor system with dual slowly varying mass, the general rules and formula describing the frequency distribution of rotor system with multiple slowly varying mass are proposed.
Directory of Open Access Journals (Sweden)
Maulana Arifin
2015-07-01
Full Text Available Organic Rankine Cycle (ORC is one of the most promising technology for small electric power generations. The geometry analysis and the effect of turbulence model on the radial turbo-expanders design for small ORC power generation systems were discussed in this paper. The rotor blades and performance were calculated using several working fluids such as R134a, R143a, R245fa, n-Pentane, and R123. Subsequently, a numerical study was carried out in the fluid flow area with R134a and R123 as the working fluids. Analyses were performed using Computational Fluid Dynamics (CFD ANSYS Multiphysics on two real gas models, with the k-epsilon and SST (shear stress transport turbulence models. The result shows the distribution of Mach number, pressure, velocity and temperature along the rotor blade of the radial turbo-expanders and estimation of performance at various operating conditions. The operating conditions are as follow: 250,000 grid mesh flow area, real gas model SST at steady state condition, 0.4 kg/s of mass flow rate, 15,000 rpm rotor speed, 5 bar inlet pressure, and 373K inlet temperature. By using those conditions, CFD analysis shows that the turbo-expander able to produce 6.7 kW and 5.5 kW of power when using R134a and R123, respectively.
Directory of Open Access Journals (Sweden)
Sghaier T
2016-10-01
Full Text Available The objective of this study was to evaluate the effectiveness of both Normal and two-parameter Weibull distributions in describing diameter distribution of Tetraclinis articulata stands in north-east Tunisia. The parameters of the Weibull function were estimated using the moments method and maximum likelihood approaches. The data used in this study came from temporary plots. The three diameter distribution models were compared firstly by estimating the parameters of the distribution directly from individual tree measurements taken in each plot (parameter estimation method, and secondly by predicting the same parameters from stand variables (parameter prediction method. The comparison was based on bias, mean absolute error, mean square error and the Reynolds’ index error (as a percentage. On the basis of the parameter estimation method, the Normal distribution gave slightly better results, whereas the Weibull distribution with the maximum likelihood approach gave the best results for the parameter prediction method. Hence, in the latter case, the Weibull distribution with the maximum likelihood approach appears to be the most suitable to estimate the parameters for reducing the different comparison criteria for the distribution of trees by diameter class in Tetraclinis articulata forests in Tunisia.
Computational Analysis of Multi-Rotor Flows
Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.
2016-01-01
Interactional aerodynamics of multi-rotor flows has been studied for a quadcopter representing a generic quad tilt-rotor aircraft in hover. The objective of the present study is to investigate the effects of the separation distances between rotors, and also fuselage and wings on the performance and efficiency of multirotor systems. Three-dimensional unsteady Navier-Stokes equations are solved using a spatially 5th order accurate scheme, dual-time stepping, and the Detached Eddy Simulation turbulence model. The results show that the separation distances as well as the wings have significant effects on the vertical forces of quadroror systems in hover. Understanding interactions in multi-rotor flows would help improve the design of next generation multi-rotor drones.
Hettrick, D A; Battocletti, J; Ackmann, J; Warltier, D C
1999-01-01
Traditional methods for estimating the slope alpha and offset volume Vp for determining real-time chamber volume by the conductance catheter technique are not suited to measurements made in the aorta due to the relatively low resistivity of the aortic wall. We developed three distinct three-dimensional finite element models of the conductance catheter and surrounding tissues in order to predict alpha and Vp and to examine the nature of the electric field near the aortic wall. A heterogeneous isotropic model of the catheter, aorta and surrounding tissues accurately predicted the values of alpha and Vp. A homogeneous anisotropic model was developed to examine the effects of anisotropy of blood and the layers of the aortic wall on measured values of resistance, alpha and Vp. This model demonstrated that anisotropy of blood and aortic wall tissue can increase the values of both alpha and Vp. Finally, a three-dimensional homogeneous isotropic rectangular model allowed examination of the effects of catheter position. This model showed small effects of catheter position on measured resistance (9.7% increase) and larger effects on alpha (21.2% decrease) and Vp (41.9% increase). We conclude the following: the FEA models may lead to accurate estimate values of alpha and Vp in vivo. The unique anisotropic conductive properties of the layers of the aortic wall contribute to the high observed values of alpha and Vp in the aorta. Finally, catheter position has a proportionately greater effect on alpha and Vp than on measured resistance. The results of this study should assist in the determination of aortic mechanical properties using conductance catheter measurements of vessel dimension.
呼吸性椭圆裂纹转子弯曲刚度模型%Bending stiffness model of a breathing elliptical cracked rotor
Institute of Scientific and Technical Information of China (English)
刘政; 王建军
2016-01-01
Usually a fatigue crack on a rotor shaft has an elliptical tip,while the current literatures at home and abroad mostly focus on straight-tip crack rotors,very few articles built models to study elliptical-tip crack breathing behavior.Here,a new breathing model of an elliptical crack on a cylindrical shaft was proposed to modify the neutral axis's position and determine crack open area.Based on the crack strain energy,the elliptical crack's additional flexibility coefficient was calculated,and the bending stiffness model of the elliptical cracked rotor was also established.It was shown that the proposed crack's breathing laws agree well with those of literatures and the finite element results,the crack's additional flexibility and rotor's dimensionless deflection both meet the requirements of computing,the effectiveness and feasibility of the model are validated.%通常转子轴上的疲劳裂纹为椭圆形尖端，而国内外现有文献大多关注直裂纹转子，很少对椭圆裂纹呼吸行为建立模型。提出了新的圆柱轴椭圆裂纹呼吸模型，修正中性轴位置确定裂纹张开面积，并基于裂纹应变能计算出椭圆裂纹附加柔性系数，建立了该类裂纹转子弯曲刚度模型。进一步，与文献和有限元结果进行对比，裂纹呼吸规律完全符合，裂纹附加柔度、转子无量纲挠度满足计算要求，验证了该模型有效可行。
Al-Qahtani, Saad Mubarak; Abdullah, Abdulmuin Mostafa A.; Nishat, Md. Rezaul Karim; Ahmed, Shaikh S.
2017-03-01
A multiscale computational study is performed to investigate how electronic structure, optical transitions, and terminal characteristics of nanostructured ZnO/MgO disk-in-wire emitters are governed by an intricate coupling of size-quantization, atomicity, and built-in structural and polarization fields. As for the models, an 8-band sp3 (with spin) atomistic tight-binding basis set was used to construct the Hamiltonian of the device in wurtzite crystal symmetry. Strain and the associated distortions of bond directions and bond lengths were modeled via the valence force-field (VFF) molecular mechanics framework. Specifically, in this work, a recently proposed ab initio based diameter-dependent model for the piezoelectric fields was implemented, which, as compared to the conventional diameter-independent model, was found to curb the influence of spontaneous (pyroelectric) polarization significantly. This particular finding is further illustrated through the calculation of electronic bandgap and localization of wavefunctions, optical emission characteristics, and the internal quantum efficiency of the device.
Dynamic modelling of rotor in non-inertia system%转子在非惯性系中的动力学建模
Institute of Scientific and Technical Information of China (English)
惠旭升; 蔡安江; 张小龙
2009-01-01
以Jeffcott转子为模型,对其在非惯性系中进行了动力学研究.提出在非惯性系中,对于转子应考虑非惯性力和陀螺力矩的影响,采用包括陀螺近似原理在内的一些相关理论来分析.文中从非惯性参考系中质点的运动微分方程出发,推导出转子考虑非惯性力及陀螺力矩影响条件下的盘心运动分量方程函数.在模型建立过程中,还考虑了转子的偏心、初弯和阻尼力.这对进一步在非惯性系中研究转子的动力特性有一定的裨益.%Taking Jeffcott rotor as a model, the dynamics re-search of rotor in the non-inertia system was carried out. It has been brought forward that within the non-inertia system the rotor should be analyzed by adopting some oorrelated theories that includes the gyro approximation principle and with the consideration on the influ-ences of non-inertia force and gyro moment. Proceed from the mo-tion differential equation of particle in the non-inertia reference-system this paper derived the equation function of motion component of rotor' s disk center under the condition of considering the influ-ences of the non-inertia force and the gyro moment. The eccentrici-ty, initial bending and damping force of rotor had been considered as well during the course of model establishment. There exist cer-tain benefits on further study of the rotor' s dynamic characters in the non-inertia system.
Institute of Scientific and Technical Information of China (English)
Long DI; Zongli LIN
2014-01-01
Active magnetic bearings (AMBs) have found a wide range of applications in high-speed rotating machinery industry. The instability and nonlinearity of AMBs make controller designs difficult, and when AMBs are coupled with a flexible rotor, the resulting complex dynamics make the problems of stabilization and disturbance rejection, which are critical for a stable and smooth operation of the rotor AMB system, even more difficult. Proportional-integral-derivative (PID) control dominates the current AMB applications in the field. Even though PID controllers are easy to implement, there are critical performance limitations associated with them that prevent the more advanced applications of AMBs, which usually require stronger robustness and performance offered by modern control methods such as H-infinity control andμ-synthesis. However, these advanced control designs rely heavily on the relatively accurate plant models and uncertainty characterizations, which are sometimes difficult to obtain. In this paper, we explore and report on the use of the characteristic model based all-coefficient adaptive control method to stabilize a flexible rotor AMB test rig. In spite of the simple structure of such a characteristic model based all-coefficient adaptive controller, both simulation and experimental results show its strong performance.
Directory of Open Access Journals (Sweden)
S. Babu
2012-12-01
Full Text Available Studying friction coefficient has significant importance, especially when dealing with high load and temperature applications that have frequent starting and stopping points. Towards that, two sets of angular contact Linear Model Mockup Bearings (LMMB were designed and fabricated. This linear model assembly was made up of high precision, grounded raceways (AISI 4140 and commercially purchased balls (AISI 52100. The experimental studies were carried out by placing different number of balls between the raceways under different loads at dry lubricating condition. The static friction coefficients were measured using two different experiments: viz gravitation-based experiment and direct linear force measurement experiment. And Digital Image Correlation (DIC technique was used to find the stiffness of LMMB set.
Rafal Podlaski; Francis Roesch
2014-01-01
In recent years finite-mixture models have been employed to approximate and model empirical diameter at breast height (DBH) distributions. We used two-component mixtures of either the Weibull distribution or the gamma distribution for describing the DBH distributions of mixed-species, two-cohort forest stands, to analyse the relationships between the DBH components,...
Nonlinear dynamic analysis of a rotor-bearing-seal system under two loading conditions
Ma, Hui; Li, Hui; Niu, Heqiang; Song, Rongze; Wen, Bangchun
2013-11-01
The operating speed of the rotating machinery often exceeds the second or even higher order critical speeds to pursue higher efficiency. Thus, how to restrain the higher order mode instability caused by the nonlinear oil-film force and seal force at high speed as far as possible has become more and more important. In this study, a lumped mass model of a rotor-bearing-seal system considering the gyroscopic effect is established. The graphite self-lubricating bearing and the sliding bearing are simulated by a spring-damping model and a nonlinear oil-film force model based on the assumption of short bearings, respectively. The seal is simulated by Muszynska nonlinear seal force model. Effects of the seal force and oil-film force on the first and second mode instabilities are investigated under two loading conditions which are determined by API Standard 617 (Axial and Centrifugal Compressors and Expander-compressors for Petroleum, Chemical and Gas Industry Services, Seventh Edition). The research focuses on the effects of exciting force forms and their magnitudes on the first and second mode whips in a rotor-bearing-seal system by using the spectrum cascades, vibration waveforms, orbits and Poincaré maps. The first and second mode instability laws are compared by including and excluding the seal effect in a rotor system with single-diameter shaft and two same discs. Meanwhile, the instability laws are also verified in a rotor system with multi-diameter shaft and two different discs. The results show that the second loading condition (out-of-phase unbalances of two discs) and the nonlinear seal force can mainly restrain the first mode instability and have slight effects on the second mode instability. This study may contribute to a further understanding about the higher order mode instability of such a rotor system with fluid-induced forces from the oil-film bearings and seals.
Blackwell, Mark W.; Tutty, Owen R.; Rogers, Eric; Sandberg, Richard D.
2016-01-01
The inclusion of smart devices in wind turbine rotor blades could, in conjunction with collective and individual pitch control, improve the aerodynamic performance of the rotors. This is currently an active area of research with the primary objective of reducing the fatigue loads but mitigating the effects of extreme loads is also of interest. The aerodynamic loads on a wind turbine blade contain periodic and non-periodic components and one approach is to consider the application of iterative learning control algorithms. In this paper, the control design is based on a simple, in relative terms, computational fluid dynamics model that uses non-linear wake effects to represent flow past an airfoil. A representation for the actuator dynamics is included to undertake a detailed investigation into the level of control possible and on how performance can be effectively measured.
Nonlinear Vibration of Rotor Rubbing Stator Caused by Initial Perturbation
Institute of Scientific and Technical Information of China (English)
张小章; 隆锦胜; 李正光
2001-01-01
The vibration of a rotor rubbing a stator caused by an initial perturbation was studied analytically.The analytical model consists of a simple disc shaft rotor and a fixed stator. The perturbation is aninstantaneous change of the radial velocity when the rotor is operating in its normal steady state. The analysisshowed that the rotor may continue rubbing the stator for small clearance, even if the initial perturbation nolonger exists. For the interest of engineering applications, we investigated various rotating speeds,perturbation amplitudes and clearances between the rotor and the stator. Various friction coefficients on thecontact surface were also considered. The graphical results can be used for the design of rotating machines.``
Directory of Open Access Journals (Sweden)
Hao Xu
Full Text Available An individual-tree diameter growth model was developed for Cunninghamia lanceolata in Fujian province, southeast China. Data were obtained from 72 plantation-grown China-fir trees in 24 single-species plots. Ordinary non-linear least squares regression was used to choose the best base model from among 5 theoretical growth equations; selection criteria were the smallest absolute mean residual and root mean square error and the largest adjusted coefficient of determination. To account for autocorrelation in the repeated-measures data, we developed one-level and nested two-level nonlinear mixed-effects (NLME models, constructed on the selected base model; the NLME models incorporated random effects of the tree and plot. The best random-effects combinations for the NLME models were identified by Akaike's information criterion, Bayesian information criterion and -2 logarithm likelihood. Heteroscedasticity was reduced with two residual variance functions, a power function and an exponential function. The autocorrelation was addressed with three residual autocorrelation structures: a first-order autoregressive structure [AR(1], a combination of first-order autoregressive and moving average structures [ARMA(1,1] and a compound symmetry structure (CS. The one-level (tree NLME model performed best. Independent validation data were used to test the performance of the models and to demonstrate the advantage of calibrating the NLME models.
DEFF Research Database (Denmark)
Sessarego, Matias; Ramos García, Néstor; Yang, Hua;
2016-01-01
In this paper a surrogate optimization methodology using a three-dimensional viscous-inviscid interaction code for the aerodynamic design of wind-turbine rotors is presented. The framework presents aunique approach because it does not require the commonly-used blade element momentum (BEM)method. ......In this paper a surrogate optimization methodology using a three-dimensional viscous-inviscid interaction code for the aerodynamic design of wind-turbine rotors is presented. The framework presents aunique approach because it does not require the commonly-used blade element momentum (BEM...... performance can be achieved using the new design method and that themethodology is effective for the aerodynamic design of wind-turbine rotors....
Splettstoesser, W. R.; Lehmann, G.; van der Wall, B.
1989-09-01
Initial acoustic results are presented from a higher harmonic control (HHC) wind tunnel pilot experiment on helicopter rotor blade-vortex interaction (BVI) impulsive noise reduction, making use of the DFVLR 40-percent-scaled BO-105 research rotor in the DNW 6m by 8m closed test section. Considerable noise reduction (of several decibels) has been measured for particular HHC control settings, however, at the cost of increased vibration levels and vice versa. The apparently adverse results for noise and vibration reduction by HHC are explained. At optimum pitch control settings for BVI noise reduction, rotor simulation results demonstrate that blade loading at the outer tip region is decreased, vortex strength and blade vortex miss-distance are increased, resulting altogether in reduced BVI noise generation. At optimum pitch control settings for vibration reduction adverse effects on blade loading, vortex strength and blade vortex miss-distance are found.
Directory of Open Access Journals (Sweden)
Ed VanBavel
Full Text Available Organ perfusion is regulated by vasoactivity and structural adaptation of small arteries and arterioles. These resistance vessels are sensitive to pressure, flow and a range of vasoactive stimuli. Several strongly interacting control loops exist. As an example, the myogenic response to a change of pressure influences the endothelial shear stress, thereby altering the contribution of shear-dependent dilation to the vascular tone. In addition, acute responses change the stimulus for structural adaptation and vice versa. Such control loops are able to maintain resistance vessels in a functional and stable state, characterized by regulated wall stress, shear stress, matched active and passive biomechanics and presence of vascular reserve. In this modeling study, four adaptation processes are identified that together with biomechanical properties effectuate such integrated regulation: control of tone, smooth muscle cell length adaptation, eutrophic matrix rearrangement and trophic responses. Their combined action maintains arteries in their optimal state, ready to cope with new challenges, allowing continuous long-term vasoregulation. The exclusion of any of these processes results in a poorly regulated state and in some cases instability of vascular structure.
Steady-state modeling of large-diameter crystal growth using baffles
Sahai, Vivek; Williamson, John W.; Overfelt, Tony
1991-12-01
Buoyancy driven flow in the crystal melt is one of the leading causes of segregation. Natural convection arises from the presence of thermal and/or solutal gradients in the melt and it is not possible to completely eliminate the convection even in the low gravity environment of space. This paper reports the results of computational modeling research that is being done in preparation for space-based experiments. The commercial finite element code FIDAP was used to simulate the steady convection of a gallium-doped germanium alloy in a Bridgman- Stockbarger furnace. In particular, the study examines the convection-suppressing benefits of inserting cylindrical baffles in the molten region to act as viscous dampers. These thin baffles are assumed to be inert and noncontaminating. The results from this study show the manner in which the streamlines, velocities, and temperature fields at various gravity levels are affected by the presence of baffles. The effects of changing both the number and position of the baffles are examined and the advantages and disadvantages of using baffles are considered.
Balch, D. T.; Lombardi, J.
1985-01-01
A model scale hover test was conducted in the Sikorsky Aircraft Model Rotor hover Facility to identify and quantify the impact of the tail rotor on the demonstrated advantages of advanced geometry tip configurations. The existence of mutual interference between hovering main rotor and a tail rotor was acknowledged in the test. The test was conducted using the Basic Model Test Rig and two scaled main rotor systems, one representing a 1/5.727 scale UH-60A BLACK HAWK and the others a 1/4.71 scale S-76. Eight alternate rotor tip configurations were tested, 3 on the BLACK HAWK rotor and 6 on the S-76 rotor. Four of these tips were then selected for testing in close proximity to an operating tail rotor (operating in both tractor and pusher modes) to determine if the performance advantages that could be obtained from the use of advanced geometry tips in a main rotor only environment would still exist in the more complex flow field involving a tail rotor. This volume contains the test run log and tabulated data.
Dynamic Gust Load Analysis for Rotors
Directory of Open Access Journals (Sweden)
Yuting Dai
2016-01-01
Full Text Available Dynamic load of helicopter rotors due to gust directly affects the structural stress and flight performance for helicopters. Based on a large deflection beam theory, an aeroelastic model for isolated helicopter rotors in the time domain is constructed. The dynamic response and structural load for a rotor under the impulse gust and slope-shape gust are calculated, respectively. First, a nonlinear Euler beam model with 36 degrees-of-freedoms per element is applied to depict the structural dynamics for an isolated rotor. The generalized dynamic wake model and Leishman-Beddoes dynamic stall model are applied to calculate the nonlinear unsteady aerodynamic forces on rotors. Then, we transformed the differential aeroelastic governing equation to an algebraic one. Hence, the widely used Newton-Raphson iteration algorithm is employed to simulate the dynamic gust load. An isolated helicopter rotor with four blades is studied to validate the structural model and the aeroelastic model. The modal frequencies based on the Euler beam model agree well with published ones by CAMRAD. The flap deflection due to impulse gust with the speed of 2m/s increases twice to the one without gust. In this numerical example, results indicate that the bending moment at the blade root is alleviated due to elastic effect.
Aerodynamics of Rotor Blades for Quadrotors
Bangura, Moses; Naldi, Roberto; Mahony, Robert
2016-01-01
In this report, we present the theory on aerodynamics of quadrotors using the well established momentum and blade element theories. From a robotics perspective, the theoretical development of the models for thrust and horizontal forces and torque (therefore power) are carried out in the body fixed frame of the quadrotor. Using momentum theory, we propose and model the existence of a horizontal force along with its associated power. Given the limitations associated with momentum theory and the inadequacy of the theory to account for the different powers represented in a proposed bond graph lead to the use of blade element theory. Using this theory, models are then developed for the different quadrotor rotor geometries and aerodynamic properties including the optimum hovering rotor used on the majority of quadrotors. Though this rotor is proven to be the most optimum rotor, we show that geometric variations are necessary for manufacturing of the blades. The geometric variations are also dictated by a desired th...
Performance investigation of the S-Rotors
Bhayo, B. A.; Al-Kayiem, H. H.; Yahaya, N. Z.
2015-12-01
This paper presents and discusses results from an experimental investigation of three models of wind S-rotors. Models 1 is modified from conventional Savonius rotor with a single stage and zero offsets zero overlaps; model 2 is three blade single stage wind rotor; and model 3 is double stage conventional Savonius rotor. The three models were designed, fabricated and characterized in terms of their coefficient of performance and dynamic torque coefficient. A special open wind simulator was designed for the test. The optimum parameters for the models were based on previous studies. The results showed that the model 1, model 2 and model 3 has the maximum power coefficient of 0.26, 0.17, and 0.21 at the correspondence tip speed ratio (TSR) of 0.42, 0.39 and 0.46, respectively. Model 1 is further optimized in terms of the aspect ratio resulting in improved power coefficient by 24%. The maximum dynamic torque coefficient of model 1, model 2 and model 3 was found as 0.81, 0.56 and 0.67 at the correspondence minimum TSR of 0.28, 0.21 and 0.17, respectively. It was noted that the all three models have high torque coefficient because the models were tested at higher applied torque on the rotors.
Bin Hassan, M. F.; Bonello, P.
2017-05-01
Recently-proposed techniques for the simultaneous solution of foil-air bearing (FAB) rotor dynamic problems have been limited to a simple bump foil model in which the individual bumps were modelled as independent spring-damper (ISD) subsystems. The present paper addresses this limitation by introducing a modal model of the bump foil structure into the simultaneous solution scheme. The dynamics of the corrugated bump foil structure are first studied using the finite element (FE) technique. This study is experimentally validated using a purpose-made corrugated foil structure. Based on the findings of this study, it is proposed that the dynamics of the full foil structure, including bump interaction and foil inertia, can be represented by a modal model comprising a limited number of modes. This full foil structure modal model (FFSMM) is then adapted into the rotordynamic FAB problem solution scheme, instead of the ISD model. Preliminary results using the FFSMM under static and unbalance excitation conditions are proven to be reliable by comparison against the corresponding ISD foil model results and by cross-correlating different methods for computing the deflection of the full foil structure. The rotor-bearing model is also validated against experimental and theoretical results in the literature.
Gori, R.; Gennaretti, M.; Pavel, M.D.; Stroosma, O.; Miletovic, I.
2015-01-01
Among the many fundamental components of a flight simulator, the mathematical representation of the vehicle dynamics stands out for complexity and importance. This is especially true for helicopters, for which the complex dynamics involved prevents simple models to be sufficiently accurate without t
Simulation of a MW rotor equipped with vortex generators using CFD and an actuator shape model
DEFF Research Database (Denmark)
Troldborg, Niels; Zahle, Frederik; Sørensen, Niels N.
2015-01-01
This article presents a comparison of CFD simulations of the DTU 10 MW reference wind turbine with and without vortex generators installed on the inboard part of the blades. The vortex generators are modelled by introducing body forces determined using a modified version of the so-called BAY mode...
Duval, R. W.; Bahrami, M.
1985-01-01
The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission systm from the fuselage. A mathematical model relating applied rotor loads and inertial loads of the rotor/transmission system to the load cell response is required to allow the load cells to be used to estimate rotor loads from flight data. Such a model is derived analytically by applying a force and moment balance to the isolated rotor/transmission system. The model is tested by comparing its estimated values of applied rotor loads with measured values obtained from a ground based shake test. Discrepancies in the comparison are used to isolate sources of unmodeled external loads. Once the structure of the mathematical model has been validated by comparison with experimental data, the parameters must be identified. Since the parameters may vary with flight condition it is desirable to identify the parameters directly from the flight data. A Maximum Likelihood identification algorithm is derived for this purpose and tested using a computer simulation of load cell data. The identification is found to converge within 10 samples. The rapid convergence facilitates tracking of time varying parameters of the load cell model in flight.
Valbuena, Rubén; Heiskanen, Janne; Aynekulu, Ermias; Pitkänen, Sari; Packalen, Petteri
2016-01-01
It has been suggested that above-ground biomass (AGB) inventories should include tree height (H), in addition to diameter (D). As H is a difficult variable to measure, H-D models are commonly used to predict H. We tested a number of approaches for H-D modelling, including additive terms which increased the complexity of the model, and observed how differences in tree-level predictions of H propagated to plot-level AGB estimations. We were especially interested in detecting whether the choice of method can lead to bias. The compared approaches listed in the order of increasing complexity were: (B0) AGB estimations from D-only; (B1) involving also H obtained from a fixed-effects H-D model; (B2) involving also species; (B3) including also between-plot variability as random effects; and (B4) involving multilevel nested random effects for grouping plots in clusters. In light of the results, the modelling approach affected the AGB estimation significantly in some cases, although differences were negligible for some of the alternatives. The most important differences were found between including H or not in the AGB estimation. We observed that AGB predictions without H information were very sensitive to the environmental stress parameter (E), which can induce a critical bias. Regarding the H-D modelling, the most relevant effect was found when species was included as an additive term. We presented a two-step methodology, which succeeded in identifying the species for which the general H-D relation was relevant to modify. Based on the results, our final choice was the single-level mixed-effects model (B3), which accounts for the species but also for the plot random effects reflecting site-specific factors such as soil properties and degree of disturbance.
Directory of Open Access Journals (Sweden)
Rubén Valbuena
Full Text Available It has been suggested that above-ground biomass (AGB inventories should include tree height (H, in addition to diameter (D. As H is a difficult variable to measure, H-D models are commonly used to predict H. We tested a number of approaches for H-D modelling, including additive terms which increased the complexity of the model, and observed how differences in tree-level predictions of H propagated to plot-level AGB estimations. We were especially interested in detecting whether the choice of method can lead to bias. The compared approaches listed in the order of increasing complexity were: (B0 AGB estimations from D-only; (B1 involving also H obtained from a fixed-effects H-D model; (B2 involving also species; (B3 including also between-plot variability as random effects; and (B4 involving multilevel nested random effects for grouping plots in clusters. In light of the results, the modelling approach affected the AGB estimation significantly in some cases, although differences were negligible for some of the alternatives. The most important differences were found between including H or not in the AGB estimation. We observed that AGB predictions without H information were very sensitive to the environmental stress parameter (E, which can induce a critical bias. Regarding the H-D modelling, the most relevant effect was found when species was included as an additive term. We presented a two-step methodology, which succeeded in identifying the species for which the general H-D relation was relevant to modify. Based on the results, our final choice was the single-level mixed-effects model (B3, which accounts for the species but also for the plot random effects reflecting site-specific factors such as soil properties and degree of disturbance.
ÇATAL, Yılmaz
2012-01-01
The height of a tree is important for assessing tree volume and site index. Diameter of breast height-tree height releation equations are often used to predict the mean tree height for trees in case only diameter at breast height is measured. This study aim describes between the tree heights with diameter of breast height relationships for artificially grown black locust (Robinia pseudoacacia L.), Anatolian black pine (Pinus nigra Arnold. subsp. pallasiana (Lamb.) Holmboe) and Taurus cedar (C...
Structural modelling of composite beams with application to wind turbine rotor blades
DEFF Research Database (Denmark)
Couturier, Philippe
represented within the elements. A post processing scheme is also presented to recover inter laminar stresses via equilibrium equations of 3D elasticity derived in the laminate coordinate system.In the final part of the thesis a flexible method for analysing two types of instabilities associated with bending...... of thin-walled prismatic beams is presented. First, the flattening instability from the Brazier effect is modelled by representing the cross-section by two-dimensional non-linear co-rotating beam elements with imposed in-plane loads proportional to the curvature. Second, the bifurcation instability from...... distributions.In the second part a formulation developed for analysis of the stiffness properties of general cross-sections with arbitrary geometry and material distribution is presented.The full six by six cross-section stiffness matrix is obtained by imposing simple deformation modes on a single layer of 3D...
Characteristics of drift-flux models for the 3' diameter vertical-upward air-water flow condition
Energy Technology Data Exchange (ETDEWEB)
Nguyen, V. T.; Euh, D. J.; Song, C. H. [KAERI, Daejeon (Korea, Republic of)
2009-07-01
One of the more complex aspects of two-phase flow calculations is the determination of the void fraction. An accurate estimation of this parameter is important for understanding and predicting the behavior of systems during a wide variety of transient conditions. The drift-flux models are based on correlations to compute the void fraction distribution and slip in a two-phase flow needed to obtain the relative velocity between the phases. Thus, the accuracy of the correlation has a decisive role in determining the correct transport of the two-phases in the system. In this paper, the assessment of 7 correlations based on the Zuber-Findlay model has been done by using the experimental data which were performed on the 3' diameter vertical-upward air-water test facility in KAERI. The void fraction was measured by using the impedance void meter which has a good dynamic resolution to get the values directly without any further data treatment. A total of 28 flow conditions have been performed at 2 bar and 3 bar inlet pressure conditions with temperature of 30 .deg. C, superficial liquid and gas velocity range of 0.5-2.8 m/s and 0.044-1.025 m/s. Some physical phenomena relevant to inlet flow condition and pressure effect were investigated. The results of assessment show a good predictive capability of Bestion model, which is currently used in the system code CATHARE.
Balch, D. T.; Lombardi, J.
1985-01-01
A model scale hover test was conducted in the Sikorsky Aircraft Model rotor hover Facility to identify and quantify the impact of the tail rotor on the demonstrated advantages of advanced geometry tip configurations. The test was conducted using the Basic Model Test Rig and two scaled main rotor systems, one representing a 1/5.727 scale UH-60A BLACK HAWK and the others a 1/4.71 scale S-76. Eight alternate rotor tip configurations were tested, 3 on the BLACK HAWK rotor and 6 on the S-76 rotor. Four of these tips were then selected for testing in close proximity to an operating tail rotor (operating in both tractor and pusher modes) to determine if the performance advantages that could be obtained from the use of advanced geometry tips in a main rotor only environment would still exist in the more complex flow field involving a tail rotor. The test showed that overall the tail rotor effects on the advanced tip configurations tested are not substantially different from the effects on conventional tips.
Directory of Open Access Journals (Sweden)
Dan A. MacIsaac
2011-09-01
Full Text Available We investigated the relationship of stem diameter to tree, site and stand characteristics for six major tree species (trembling aspen, white birch, balsam fir, lodgepole pine, black spruce, and white spruce in Alberta (Canada with data from Alberta Sustainable Resource Development Permanent Sample Plots. Using non-linear mixed effects modeling techniques, we developed models to estimate diameter at breast height using height, crown and stand attributes. Mixed effects models (with plot as subject using height, crown area, and basal area of the larger trees explained on average 95% of the variation in diameter at breast height across the six species with a root mean square error of 2.0 cm (13.4% of mean diameter. Fixed effects models (without plot as subject including the Natural Sub-Region (NSR information explained on average 90% of the variation in diameter at breast height across the six species with a root mean square error equal to 2.8 cm (17.9% of mean diameter. Selected climate variables provided similar results to models with NSR information. The inclusion of nutrient regime and moisture regime did not significantly improve the predictive ability of these models.
Directory of Open Access Journals (Sweden)
Guangtao Zhang
2017-05-01
Full Text Available Inter-turn short circuit of field windings (ISCFW may cause the field current of a generator to increase, output reactive power to decrease, and unit vibration to intensify, seriously affecting its safe and stable operation. Full integration of mechanical and electrical characteristics can improve the sensitivity of online monitoring, and detect the early embryonic period fault of small turns. This paper studies the calculations and variations of unbalanced magnetic pull (UMP, of which the excitation source of rotor vibration is the basis and key to online fault monitoring. In grid load operation, ISCFW are first calculated with the multi-loop method, so as to obtain the numerical solutions of the stator and the rotor currents during the fault. Next, the air-gap magnetic field of the ISCFW is analyzed according to the actual composition modes of the motor loops in the fault, so as to obtain the analytic expressions of the air-gap magnetic motive force (MMF and magnetic density. The UMP of the rotor is obtained by solving the integral of the Maxwell stress. The correctness of the electric quantity calculation is verified by the ISCFW experiment, conducted in a one pair-pole non-salient pole model machine. On this basis, comparing the simulation analysis with the calculation results of the model in this paper not only verifies the accuracy of the electromagnetic force calculation, but also proves that the latter has the advantages of a short time consumption and high efficiency. Finally, the influencing factors and variation law of UMP are analyzed by means of an analytic model. This develops a base for the online monitoring of ISCFW with the integration of mechanical and electrical information.
On Cup Anemometer Rotor Aerodynamics
Directory of Open Access Journals (Sweden)
Santiago Pindado
2012-05-01
Full Text Available The influence of anemometer rotor shape parameters, such as the cups’ front area or their center rotation radius on the anemometer’s performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal, tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups’ center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor’s cup.
Rotor dynamic analysis of main coolant pump
Energy Technology Data Exchange (ETDEWEB)
Lee, Chong Won; Seo, Jeong Hwan; Kim, Choong Hwan; Shin, Jae Chul; Wang, Lei Tian [Korea Advanced Institute of Science and Technology, Taejon (Korea)
1999-03-01
A rotor dynamic analysis program DARBS/MCP, for the main coolant pump of the integral reactor, has been developed. The dynamic analysis model of the main coolant pump includes a vertical shaft, three grooved radial journal bearings and gaps that represent the structure-fluid interaction effects between the rotor and the lubricant fluid. The electromagnetic force from the motor and the hydro-dynamic force induced by impeller are the major sources of vibration that may affect the rotor system stability. DARBS/MCP is a software that is developed to effectively analyze the dynamics of MCP rotor systems effectively by applying powerful numerical algorithms such as FEM with modal truncation and {lambda}-matrix method for harmonic analysis. Main design control parameters, that have much influence to the dynamic stability, have been found by Taguchi's sensitivity analysis method. Design suggestions to improve the stability of MCP rotor system have been documented. The dynamic bearing parameters of the journal bearings used for main coolant pump have been determined by directly solving the Reynolds equation using FDM method. Fluid-structure interaction effect that occurs at the small gaps between the rotor and the stator were modeled as equivalent seals, the electromagnetic force effect was regarded as a linear negative radial spring and the impeller was modeled as a rigid disk with hydrodynamic and static radial force. Although there exist critical speeds in the range of operational speeds for type I and II rotor systems, the amplitude of vibration appears to be less than the vibration limit set by the API standards. Further more, it has been verified that the main design parameters such as the clearance and length of journal bearings, and the static radial force of impeller should be properly adjusted, in order to the improve dynamic stability of the rotor system. (author). 39 refs., 81 figs., 17 tabs.
Mahanti, P.; Robinson, M. S.; Boyd, A. K.
2013-12-01
Craters ~20-km diameter and above significantly shaped the lunar landscape. The statistical nature of the slope distribution on their walls and floors dominate the overall slope distribution statistics for the lunar surface. Slope statistics are inherently useful for characterizing the current topography of the surface, determining accurate photometric and surface scattering properties, and in defining lunar surface trafficability [1-4]. Earlier experimental studies on the statistical nature of lunar surface slopes were restricted either by resolution limits (Apollo era photogrammetric studies) or by model error considerations (photoclinometric and radar scattering studies) where the true nature of slope probability distribution was not discernible at baselines smaller than a kilometer[2,3,5]. Accordingly, historical modeling of lunar surface slopes probability distributions for applications such as in scattering theory development or rover traversability assessment is more general in nature (use of simple statistical models such as the Gaussian distribution[1,2,5,6]). With the advent of high resolution, high precision topographic models of the Moon[7,8], slopes in lunar craters can now be obtained at baselines as low as 6-meters allowing unprecedented multi-scale (multiple baselines) modeling possibilities for slope probability distributions. Topographic analysis (Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) 2-m digital elevation models (DEM)) of ~20-km diameter Copernican lunar craters revealed generally steep slopes on interior walls (30° to 36°, locally exceeding 40°) over 15-meter baselines[9]. In this work, we extend the analysis from a probability distribution modeling point-of-view with NAC DEMs to characterize the slope statistics for the floors and walls for the same ~20-km Copernican lunar craters. The difference in slope standard deviations between the Gaussian approximation and the actual distribution (2-meter sampling) was
Estimation of wake propagation behind the rotors of wind-powered generators
DEFF Research Database (Denmark)
Naumov, I. V.; Mikkelsen, Robert Flemming; Okulov, Valery
2016-01-01
in the experimental research in order to define the degree of self-damping of perturbations generated by oneself wind-powered generator. The obtained experimental data for the wake dynamics behind the model of wind-powered generator allowed ascertaining its impact on slowing down of incident vortex flow......The objectives of this work are to develop the experimental model of wake behind the wind-power generator rotor to estimate its propagation distance and the impact on the average and pulsation characteristics of incident flow with the possibility of further use of these data in the calculation...... and changes in the wake structure in the distance of more than 40 rotor diameters downstream with a slight level of turbulent pulsations (less than 2%) of free flow were investigated. A significant impact of external intense pulsations typical for natural atmospheric conditions was purposely excluded...
Institute of Scientific and Technical Information of China (English)
王少波; 孟成; 苏明
2013-01-01
重型燃气轮机通常采用拉杆转子结构,此类转子-支撑系统的临界转速的分析计算与整体结构转子不同.以Riccati传递矩阵法为框架,对某燃气轮机中心拉杆转子结构进行分析并离散,考虑轴承支撑以及端面齿啮合对转子动力学特性的影响,建立转子-支撑系统的动力学计算模型.利用该模型对临界转速以及相应的振型进行计算,并通过与试验台实测结果的对比,验证了计算模型和方法的正确性,该方法可应用于类似结构转子动力学特性的分析研究.%Rod fastening rotor is usually used in heavy duty gas turbine rotor-support system, of which critical speed calculation differs from that of the integral rotor. In the framework of Riccati transfer matrix method, discretization of central tie-rod fastening rotor structure with detailed analysis was conducted. Taking into account the impacts which are brought by bearing support and meshing face tooth on dynamic characteristics of rotor system, a computation model of rotor-support system was further established. In this way, critical speeds and the corresponding modes were obtained. The calculated result shows a good a-greement with the test measurement result, which implies that the method is accurate and computation model is reliable. This approach can also be applied to analyze dynamic characteristics of rotors with homogenous structure.
Open Rotor Noise Shielding by Blended-Wing-Body Aircraft
Guo, Yueping; Czech, Michael J.; Thomas, Russell H.
2015-01-01
This paper presents an analysis of open rotor noise shielding by Blended Wing Body (BWB) aircraft by using model scale test data acquired in the Boeing Low Speed Aeroacoustic Facility (LSAF) with a legacy F7/A7 rotor model and a simplified BWB platform. The objective of the analysis is the understanding of the shielding features of the BWB and the method of application of the shielding data for noise studies of BWB aircraft with open rotor propulsion. By studying the directivity patterns of individual tones, it is shown that though the tonal energy distribution and the spectral content of the wind tunnel test model, and thus its total noise, may differ from those of more advanced rotor designs, the individual tones follow directivity patterns that characterize far field radiations of modern open rotors, ensuring the validity of the use of this shielding data. Thus, open rotor tonal noise shielding should be categorized into front rotor tones, aft rotor tones and interaction tones, not only because of the different directivities of the three groups of tones, but also due to the differences in their source locations and coherence features, which make the respective shielding characteristics of the three groups of tones distinctly different from each other. To reveal the parametric trends of the BWB shielding effects, results are presented with variations in frequency, far field emission angle, rotor operational condition, engine installation geometry, and local airframe features. These results prepare the way for the development of parametric models for the shielding effects in prediction tools.
Federal Laboratory Consortium — This test apparatus, when combined with the National Full-Scale Aerodynamics Complex, produces a thorough, full-scale test capability. The Large Rotor Test Apparatus...
Investigation of rotor control system loads
Institute of Scientific and Technical Information of China (English)
Sun Tao; Tan Jianfeng; Wang Haowen
2013-01-01
This paper concentrates on the aeroelasticity analysis of rotor blade and rotor control systems. A new multi-body dynamics model is established to predict both rotor pitch link loads and swashplate servo loads. Two helicopter rotors of UH-60A and SA349/2, both operating in two critical flight conditions, high-speed flight and high-thrust flight, are studied. The analysis shows good agreements with the flight test data and the calculation results using CAMRAD II. The mechanisms of rotor control loads are then analyzed in details based on the present predictions and the flight test data. In high-speed conditions, the pitch link loads are dominated by the integral of blade pitching moments, which are generated by cyclic pitch control. In high-thrust conditions, the positive pitching loads in the advancing side are caused by high collective pitch angle, and dynamic stall in the retreating side excites high-frequency responses. The swashplate servo loads are predominated by the rotor pitch link loads, and the inertia of the swashplate has significant effects on high-frequency harmonics of the servo loads.
Energy Technology Data Exchange (ETDEWEB)
Song, Jun Beom [Dept. of Aviation Maintenance, Dongwon Institute of Science and Technology, Yangsan (Korea, Republic of); Byun, Young Seop; Jeong, Jin Seok; Kim, Jeong; Kang, Beom Soo [Dept. of Aerospace Engineering, Pusan National University, Busan (Korea, Republic of)
2016-11-15
This paper proposes a cascaded control structure and a method of practical application for attitude control of a multi-rotor Unmanned aerial vehicle (UAV). The cascade control, which has tighter control capability than a single-loop control, is rarely used in attitude control of a multi-rotor UAV due to the input-output relation, which is no longer simply a set-point to Euler angle response transfer function of a single-loop PID control, but there are multiply measured signals and interactive control loops that increase the complexity of evaluation in conventional way of design. However, it is proposed in this research a method that can optimize a cascade control with a primary and secondary loops and a PID controller for each loop. An investigation of currently available PID-tuning methods lead to selection of the Simple internal model control (SIMC) method, which is based on the Internal model control (IMC) and direct-synthesis method. Through the analysis and experiments, this research proposes a systematic procedure to implement a cascaded attitude controller, which includes the flight test, system identification and SIMC-based PID-tuning. The proposed method was validated successfully from multiple applications where the application to roll axis lead to a PID-PID cascade control, but the application to yaw axis lead to that of PID-PI.
Performance of Savonius Rotor for Environmentally Friendly Hydraulic Turbine
Nakajima, Miyoshi; Iio, Shouichiro; Ikeda, Toshihiko
The aim of this investigation was to develop an environmentally friendly nano-hydraulic turbine. A model of a two-bucket Savonius type hydraulic turbine was constructed and tested in a water tunnel to arrive at an optimum installation condition. Effects of two installation parameters, namely a distance between a rotor and a bottom wall of the tunnel, a rotation direction of the rotor, on the power performance were studied. A flow field around the rotor was examined visually to clarify influences of installation conditions on the flow field. The flow visualization showed differences of flow pattern around the rotor by the change of these parameters. From this study it was found that the power performances of Savonius hydraulic turbine were changed with the distance between the rotor and the bottom wall of the tunnel and with a rotation direction of the rotor.
Dynamic Analysis of Darrieus Vertical Axis Wind Turbine Rotors
Lobitz, D. W.
1981-01-01
The dynamic response characteristics of the vertical axis wind turbine (VAWT) rotor are important factors governing the safety and fatigue life of VAWT systems. The principal problems are the determination of critical rotor speeds (resonances) and the assessment of forced vibration response amplitudes. The solution to these problems is complicated by centrifugal and Coriolis effects which can have substantial influence on rotor resonant frequencies and mode shapes. The primary tools now in use for rotor analysis are described and discussed. These tools include a lumped spring mass model (VAWTDYN) and also finite-element based approaches. The accuracy and completeness of current capabilities are also discussed.
Eigenfrequency sensitivity analysis of flexible rotors
Directory of Open Access Journals (Sweden)
Šašek J.
2007-10-01
Full Text Available This paper deals with sensitivity analysis of eigenfrequencies from the viewpoint of design parameters. The sensitivity analysis is applied to a rotor which consists of a shaft and a disk. The design parameters of sensitivity analysis are the disk radius and the disk width. The shaft is modeled as a 1D continuum using shaft finite elements. The disks of rotating systems are commonly modeled as rigid bodies. The presented approach to the disk modeling is based on a 3D flexible continuum discretized using hexahedral finite elements. The both components of the rotor are connected together by special proposed couplings. The whole rotor is modeled in rotating coordinate system with considering rotation influences (gyroscopic and dynamics stiffness matrices.
Fontana, R. R.; Hubbard, J. E., Jr.
1983-01-01
Mini-tuft and smoke flow visualization techniques have been developed for the investigation of model helicopter rotor blade vortex interaction noise at low tip speeds. These techniques allow the parameters required for calculation of the blade vortex interaction noise using the Widnall/Wolf model to be determined. The measured acoustics are compared with the predicted acoustics for each test condition. Under the conditions tested it is determined that the dominating acoustic pulse results from the interaction of the blade with a vortex 1-1/4 revolutions old at an interaction angle of less than 8 deg. The Widnall/Wolf model predicts the peak sound pressure level within 3 dB for blade vortex separation distances greater than 1 semichord, but it generally over predicts the peak S.P.L. by over 10 dB for blade vortex separation distances of less than 1/4 semichord.
Analysis on structural characteristics of rotors in twin-rotor cylinder-embedded piston engine
Institute of Scientific and Technical Information of China (English)
陈虎; 潘存云; 徐海军; 邓豪; 韩晨
2014-01-01
Twin-rotor cylinder-embedded piston engine is proposed for dealing with the sealing problems of rotors in twin-rotor piston engine where the existent mature sealing technologies for traditional reciprocating engine can be applied. The quantity and forms of its sealing surfaces are reduced and simplified, and what’s more, the advantages of twin-rotor piston engine are inherited, such as high power density and no valve mechanism. Given the motion law of two rotors, its kinematic model is established, and the general expression for some parameters related to engine performance, such as the trajectory, displacement, velocity and acceleration of the piston and centroid trajectory, angular displacement, velocity and acceleration of the rod are presented. By selecting different variation patterns of relative angle of two rotors, the relevant variables are compared. It can be concluded that by designing the relative angle function of two rotors, the volume variation of working chamber can be changed. However, a comprehensive consideration for friction and vibration is necessary because velocity and acceleration are quite different in the different functions, the swing magnitude of rod is proportional to link ratioλ, and the position of rod swing center is controlled by eccentricitye. In order to reduce the lateral force, a smaller value ofλshould be selected in the case of the structure, and the value ofe should be near 0.95. There is no relationship between the piston stroke and the variation process of relative angle of two rotors, the former is only proportional to the amplitude of relative angle of two rotors.
Directory of Open Access Journals (Sweden)
Xiangbo Xu
2015-08-01
Full Text Available Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs, offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously.
Xu, Xiangbo; Chen, Shao
2015-08-31
Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously.
Institute of Scientific and Technical Information of China (English)
Vindhya Prasad Tewari
2007-01-01
Four generalised diameter-height equations were developed and compared for pure and even-aged stands of Tecomella undulata in hot arid region of Rajasthan State in India. The data used to fit the equations consisted of 1 540 diameter-height observations collected from the plots laid out in uniformly stocked stands of varying age and density. The performance of four equations was tested by non-linear least squares regression and evaluated using different statistical criteria. Finally, these equations, with the same values of coefficients obtained during the fitting phase, were validated by an independent data set consisting of 854 diameter-height observations. Overall, equation (4) (Hui and Gadow function) was found to perform best for both the fitting data set as well as validation data set.
APPLICATION OF MECHANIZED MATHEMATICS TO ROTOR DYNAMICS
Institute of Scientific and Technical Information of China (English)
胡超; 王岩; 王立国; 黄文虎
2002-01-01
Based on the mechanized mathematics and WU Wen-tsun elimination method,using oil film forces of short-bearing model and Muszynska's dynamic model, the dynamical behavior of rotor-bearing system and its stability of motion are investigated. As example,the concept of Wu characteristic set and Maple software, whirl parameters of short- bearing model, which is usually solved by the numerical method, are analyzed. At the same time,stability of zero solution of Jeffcott rotor whirl equation and stability of self-excited vibration are studied. The conditions of stable motion are obtained by using theory of nonlinear vibration.
Institute of Scientific and Technical Information of China (English)
鲍建成
2012-01-01
Asynchronous motor rotor resistance changes affect the control precision of the system, because temperature and skin effect, rotor resistance changes has nonlinear. In order to identificate the rotor resistance accurately and rapidly, an asynchronous motor rotor resistance identificate method was proposed based on extended kalman filter in this paper. Taking Rotor resistance as a system state variable, a rotor resistance identification was designed base on extended Kalman filtering technology. Through the measuring the voltage and curren of the motor stator, the rotor resistance identification value was obtained. The simulation model was built with MATLAB/Simulink system, and the simulation results show that the proposed mehod can rapidly and accurately identify rotor resistance and improve the precision of rotor resistance.%研究异步电机稳定性优化控制问题,异步电机转子电阻受温度变化、集肤效应等影响,具有时变性和非线性,影响系统稳定性分析.传统方法对异步电机转子电阻状态辩识准确率低.为了准确和快速对转子电阻进行状态辩识,提出一种扩展卡尔曼滤波的异步电机转子电阻辩识方法.将转子电阻看成系统状态变量,设计一种扩展卡尔曼滤波技术的转子电阻估计器,通过测量电机定子电压、电流,实现对转子电阻在线辩识.在MATLAB/Simulink中建立仿真模型,仿真结果表明,异步电机转子电阻改进辩识方法可提高转子电阻辨识准确率.
Effect of Bearing Housings on Centrifugal Pump Rotor Dynamics
Yashchenko, A. S.; Rudenko, A. A.; Simonovskiy, V. I.; Kozlov, O. M.
2017-08-01
The article deals with the effect of a bearing housing on rotor dynamics of a barrel casing centrifugal boiler feed pump rotor. The calculation of the rotor model including the bearing housing has been performed by the method of initial parameters. The calculation of a rotor solid model including the bearing housing has been performed by the finite element method. Results of both calculations highlight the need to add bearing housings into dynamic analyses of the pump rotor. The calculation performed by modern software packages is more a time-taking process, at the same time it is a preferred one due to a graphic editor that is employed for creating a numerical model. When it is necessary to view many variants of design parameters, programs for beam modeling should be used.
STABILITY OF ROTOR-BEARING SYSTEMS
Directory of Open Access Journals (Sweden)
Uğur YÜCEL
2003-03-01
Full Text Available In various industrial applications there is a need for higher speed, yet reliably operating rotating machinery. A key factor in achieving this type of machinery continues to be the ability to accurately predict the dynamic response and stability of a rotor-bearing system. This paper introduces and explains the nature of rotordynamic phenomena from comparatively simple analytic models. Starting with the most simple rotor model that is supported in two rigid bearings at its ends, the more realistic and more involved cases are considered by incorporating the effects of flexible bearings. Knowledge of these phenomena is fundamental to an understanding of the behavior of complex models, which corresponds to the real rotors of turbomachines.
Energy Technology Data Exchange (ETDEWEB)
Martinez Guillen, Miguel A.; Paz Comech, M.; Ruiz Guillen, Javier; Giraut Ruso, Elizabeth; Garcia-Gracia, Miguel
2009-07-01
The present wind energy penetration into the electrical network has forced system operators to adapt their Grid Codes to this new generation, preventing an unacceptable effect on the system safety and reliability. There are several wind turbine models that can be used to study the effects of voltage dips and the corresponding wind turbine responses but these models need to be validated by comparing their results with the data obtained during field tests. This paper describe the process followed for the validation of a Resistance-Commutated rotor wind turbine generator from in-field testing results according to the Spanish procedure for verification, validation and certification of the requirements of the P.O. 12.3 on the response of wind farms in the event of voltage dips. (orig.)
Response studies of rotors and rotor blades with application to aeroelastic tailoring
Friedmann, P. P.
1982-01-01
Various tools for the aeroelastic stability and response analysis of rotor blades in hover and forward flight were developed and incorporated in a comprehensive package capable of performing aeroelastic tailoring of rotor blades in forward flight. The results indicate that substantial vibration reductions, of order 15-40%, in the vibratory hub shears can be achieved by relatively small modifications of the initial design. Furthermore the optimized blade can be up to 20% lighter than the original design. Accomplishments are reported for the following tasks: (1) finite element modeling of rotary-wing aeroelastic problems in hover and forward flight; (2) development of numerical methods for calculating the aeroelastic response and stability of rotor blades in forward fight; (3) formulation of the helicopter air resonance problem in hover with active controls; and (4) optimum design of rotor blades for vibration reduction in forward flight.
小管径冷凝管的数学模型%Mathematical model of small diameter condenser pipes
Institute of Scientific and Technical Information of China (English)
柏立战; 林贵平
2009-01-01
Based on the annular flow pattern, the mathematical model of condenser pipes with small diameters was established. The effect of surface tension on the liquid/vapor interface causing the pressure difference between liquid and vapor phases on the same cross section and the interaction between the liquid and vapor phases including the frictional and momentum-transfer shear stresses were considered in the model. The variations of the liquid and vapor phase pressure drops, the thickness of the liquid film, shear stress on the liquid/vapor interface and so on along the pipe length can be obtained by solving the model. Based on the modeling results, the conclusions below can be drawn: the two-phase pressure drop along the pipe length increases nearly linearly; the average velocity of vapor phase first increases and then decreases, but the variation range is small and far bigger than that of liquid phase; the momentum-transfer shear stress increases as the thickness of the liquid film increases, and can not be ignored compared to the frictional shear stress; the con-vective heat transfer coefficient at the inner wall of the pipe decreases as the thickness of the liquid film increases, but i is still comparatively bigger when the condensation is almost completed.%基于环状流流型建立了小管径冷凝管的数学模型.模型考虑了气液界面表面张力的作用,在同一横截面上气相与液相存在压力差.对两相压降的计算,考虑了气液两相间的相互作用,包括摩擦切应力和动量转移切应力.应用该模型,可考察气相与液相压降、液膜厚度、气相与液相平均速度、气液界面切应力以及管内壁换热系数等的沿程变化情况.根据模拟结果可得:两相压降沿管长呈近似线性增加;气相平均速度沿管长先增大后逐渐减小,但变化范围很小,且远大于液相平均速度;动量转移切应力随液膜厚度增加而增大,同摩擦切应力相比不可忽略;管内壁对流
Energy Technology Data Exchange (ETDEWEB)
Gupta, R.; Biswas, A.; Sharma, K.K. [Department of Mechanical Engineering, National Institute of Technology (NIT), Silchar 788 010, Assam (India)
2008-09-15
The vertical axis wind turbines are simple in construction, self-starting, inexpensive and can accept wind from any direction without orientation. A combined Savonius-Darrieus type vertical axis wind rotor has got many advantages over individual Savonius or individual Darrieus wind rotor, such as better efficiency than Savonius rotor and high starting torque than Darrieus rotor. But works on the combined Savonius-Darrieus wind rotor are very scare. In view of the above, two types of models, one simple Savonius and the other combined Savonius-Darrieus wind rotors were designed and fabricated. The Savonius rotor was a three-bucket system having provisions for overlap variations. The Savonius-Darrieus rotor was a combination of three-bucket Savonius and three-bladed Darrieus rotors with the Savonius placed on top of the Darrieus rotor. The overlap variation was made in the upper part, i.e. the Savonius rotor only. These were tested in a subsonic wind tunnel available in the department. The various parameters namely, power coefficients and torque coefficients were calculated for both overlap and without overlap conditions. From the present investigation, it is seen that with the increase of overlap, the power coefficients start decreasing. The maximum power coefficient of 51% is obtained at no overlap condition. However, while comparing the power coefficients (C{sub p}) for simple Savonius-rotor with that of the combined configuration of Savonius-Darrieus rotor, it is observed that there is a definite improvement in the power coefficient for the combined Savonius-Darrieus rotor without overlap condition. Combined rotor without overlap condition provided an efficiency of 0.51, which is higher than the efficiency of the Savonius rotor at any overlap positions under the same test conditions. (author)
Design, analysis and testing of small, affordable HAWT rotors
Pricop, Mihai V.; Niculescu, Mihai L.; Cojocaru, Marius G.; Barsan, Dorin
2012-09-01
The paper presents affordable technologies dedicated to design, CAD modelling and manufacturing of the small-medium HAWT rotors. Three numerical tools are developed: blade/rotor design, blade modelling for industry CATIA(CATScript) and blade modelling for small scale developers. Numerical analysis of the rotors is accomplished for both performance and noise level estimation using XFLOW (LES) and an in-house code (URANS). Results are presented for a 5KW rotor at the design point only, since computations are expensive. Developement examples are included as two rotors are designed, manufactured and tested for 1.5 and 5KW. A third one, rated for 20KW is under developement. Basic testing results are also included.
Rotor balancing apparatus and system
Lyman, Frank (Inventor); Lyman, Joseph (Inventor)
1976-01-01
Rotor balancing apparatus and a system comprising balance probes for measuring unbalance at the ends of a magnetically suspended rotor are disclosed. Each balance probe comprises a photocell which is located in relationship to the magnetically suspended rotor such that unbalance of the rotor changes the amount of light recorded by each photocell. The signal from each photocell is electrically amplified and displayed by a suitable device, such as an oscilloscope.
Diagnosis of wind turbine rotor system
DEFF Research Database (Denmark)
Niemann, Hans Henrik; Mirzaei, Mahmood; Henriksen, Lars Christian
2016-01-01
This paper describes a model free method for monitoring and fault diagnosis of the elements in a rotor system for a wind turbine. The diagnosis as well as the monitoring is done without using any model of the wind turbine and the applied controller or a description of the wind profile. The method...... is based on available standard sensors on wind turbines. The method can be used both on-line as well as off-line. Faults or changes in the rotor system will result in asymmetries, which can be monitored and diagnosed. This can be done by using the multi-blade coordinate transformation. Changes in the rotor...... system that can be diagnosed and monitored are: actuator faults, sensor faults and internal blade changes as e.g. change in mass of a blade....
Sree, Dave
2015-01-01
Far-field acoustic power level and performance analyses of open rotor model F31/A31 have been performed to determine its noise characteristics at simulated scaled takeoff, nominal takeoff, and approach flight conditions. The nonproprietary parts of the data obtained from experiments in 9- by 15-Foot Low-Speed Wind Tunnel (9?15 LSWT) tests were provided by NASA Glenn Research Center to perform the analyses. The tone and broadband noise components have been separated from raw test data by using a new data analysis tool. Results in terms of sound pressure levels, acoustic power levels, and their variations with rotor speed, angle of attack, thrust, and input shaft power have been presented and discussed. The effect of an upstream pylon on the noise levels of the model has been addressed. Empirical equations relating model's acoustic power level, thrust, and input shaft power have been developed. The far-field acoustic efficiency of the model is also determined for various simulated flight conditions. It is intended that the results presented in this work will serve as a database for comparison and improvement of other open rotor blade designs and also for validating open rotor noise prediction codes.
Energy Technology Data Exchange (ETDEWEB)
Myrent, Noah J. [Vanderbilt Univ., Nashville, TN (United States). Lab. for Systems Integrity and Reliability; Barrett, Natalie C. [Vanderbilt Univ., Nashville, TN (United States). Lab. for Systems Integrity and Reliability; Adams, Douglas E. [Vanderbilt Univ., Nashville, TN (United States). Lab. for Systems Integrity and Reliability; Griffith, Daniel Todd [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technology Dept.
2014-07-01
Operations and maintenance costs for offshore wind plants are significantly higher than the current costs for land-based (onshore) wind plants. One way to reduce these costs would be to implement a structural health and prognostic management (SHPM) system as part of a condition based maintenance paradigm with smart load management and utilize a state-based cost model to assess the economics associated with use of the SHPM system. To facilitate the development of such a system a multi-scale modeling and simulation approach developed in prior work is used to identify how the underlying physics of the system are affected by the presence of damage and faults, and how these changes manifest themselves in the operational response of a full turbine. This methodology was used to investigate two case studies: (1) the effects of rotor imbalance due to pitch error (aerodynamic imbalance) and mass imbalance and (2) disbond of the shear web; both on a 5-MW offshore wind turbine in the present report. Sensitivity analyses were carried out for the detection strategies of rotor imbalance and shear web disbond developed in prior work by evaluating the robustness of key measurement parameters in the presence of varying wind speeds, horizontal shear, and turbulence. Detection strategies were refined for these fault mechanisms and probabilities of detection were calculated. For all three fault mechanisms, the probability of detection was 96% or higher for the optimized wind speed ranges of the laminar, 30% horizontal shear, and 60% horizontal shear wind profiles. The revised cost model provided insight into the estimated savings in operations and maintenance costs as they relate to the characteristics of the SHPM system. The integration of the health monitoring information and O&M cost versus damage/fault severity information provides the initial steps to identify processes to reduce operations and maintenance costs for an offshore wind farm while increasing turbine availability
Dynamics of the rotor on elastic-damping supports under action of kinematic effects
Chernyshev, V.; Savin, L.; Fominova, O.
2017-08-01
The article describes the elements of the theory of dynamic analysis of rotor systems. The mathematical model of a gyroscopic rotor as an elementary object on elastic-damping supports. The results of simulation of the trajectories of the rotor under kinematic loading with amplitude commensurate with the clearance in bearing assemblies of fluid friction.
Large Wind Turbine Rotor Design using an Aero-Elastic / Free-Wake Panel Coupling Code
DEFF Research Database (Denmark)
Sessarego, Matias; Ramos García, Néstor; Shen, Wen Zhong;
2016-01-01
Despite the advances in computing resources in the recent years, the majority of large wind-turbine rotor design problems still rely on aero-elastic codes that use blade element momentum (BEM) approaches to model the rotor aerodynamics. The present work describes an approach to wind-turbine rotor...
NUMERICAL AND EXSPERIMENTAL ASPECTS OF THERMALLY INDUCED VIBRATION IN REAL ROTORS
Milenko B Jevtić; Ljiljana Z Radovanović; Zivoslav Z Adamović
2011-01-01
Temperature fields in electric energy generators may lead to mechanical dissbalance of an already balanced rotor. The author collected information in a number of steam power plants and confirmed the existence of the problem. This paper is presents the specific case of thermal deformation of the rotor, caused by an asymmetrical temperature field in scale of rotor. On the grounds of the relevant physical aspects, we propose a mathematical model identifying fields in a turbo generator rotor and ...
Behar, M.; Filevich, A.; Macchiavelli, A. O.; Szybisz, L.; Thieberger, P.
1982-10-01
Nuclear states of 79Kr were studied through the 78Se(α, 3n) reaction at an energy of 45 MeV. Excitation functions, γ-ray angular distributions, and γ-γ coincidences were performed. Three bands based on the g.s. (12-), 147.1 keV (52-), and 129.7 keV (72+) states were identified. Leading order analysis and quasiparticle-plus-rotor model calculations were performed. A good overall agreement was found between the experimental data and the theoretical predictions. NUCLEAR REACTIONS 78Se(α, 3n), E=30-55 MeV; measured σ(E, Eγ, θ), Eγ, Iγ, γ-γ coin. 79Kr deduced levels J. Enriched targets.
Semirigid vibrating rotor target model for atom-polyatom reactions: Application to F+CH4→CH3+HF
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The semirigid vibrating rotor target (SVRT) model for the polyatomic reaction has been applied to the reaction of F+CH4→HF+CH3. The time-dependent wave packet approach has also been used in the calculation. In the current study, reaction probability, cross-section, and rate constant are calculated for the title reaction on the modified J1 (MJ1) potential energy surface (PES). Numerical calculation shows oscillatory structures in the energy dependence of the calculated reaction probability. Those structures are generally associated with broad dynamical resonance. They are almost washed-out in the energy dependence of integral cross-sections due to summation over partial waves. The calculated rate constant is in good agreement with experimental measurement.
Directory of Open Access Journals (Sweden)
Borkowski Paweł
2016-03-01
Full Text Available This paper is concerned with the 1st stage of HP rotor blade assembly steam turbine TK 120. The methodology was focused on the selection of mechanical properties and the way of the rotor disc modeling and estimating the degree of damage caused by creep. Then the dynamic interference between the frequencies of excitation and the natural frequencies was assessed. Static calculations were performed for the cyclic sectors consisting of the disc, disc blades, spacers and shrouding, including loads as temperature, mass forces from the angular velocity and the pressure on the blades. Then, the creep analysis using a Norton’s model and the modal analysis were performed. Static analysis gave information concerning the distributions of displacements, stress and strain components. In the creep analysis, the creep displacements and stress relaxation versus time were determined and the estimated degree of damage caused by creep was evaluated at each part of the rotor disc. In the modal analysis, the natural frequencies and modes of vibrations corresponding to the nodal diameters were found. The results of modal analysis were shown in the SAFE graph. Numerical calculations have shown that the rotor disc was a well-designed structure and did not reveal any dynamic interference.
Directory of Open Access Journals (Sweden)
Paulo JA
2016-06-01
Full Text Available A generalized non-linear tree crown diameter model was developed with the aim of allowing the computation of tree crown diameter over a large range of tree dimensions, and allowing its inclusion in forest growth and yield models. The model was formulated to provide biological meaning to the predicted values. Due to the nested structure of the data analyzed (trees within stands, both mixed- and fixed-effect models were developed. Since tree crown diameter is not frequently measured in forest inventories, the validation of the mixed model was carried out by considering the population specific response. The results demonstrate that when the measurements required for the mixed model calibration are not available, the use of the fixed effect model results in less biased and more accurate estimates. The fixed model was applied to the data from the two last Portuguese National Forest Inventories (NFI to analyze the change in stand crown cover and assess the stocking evolution of cork oak stands in Portugal between 1996 and 2006. Results showed an increase in the frequency of stands with crown cover lower than 20%, as well as a decrease in the frequency of stands with crown cover between 20 and 40%. Average crown cover values were significantly different in the two NFI, with a decrease from 28.0 to 26.5% over the considered period.
Jia, Mei-Hui; Wang, Cheng-Lin; Ren, Bin
2017-07-01
Stress, strain and vibration characteristics of rotor parts should be changed significantly under high acceleration, manufacturing error is one of the most important reason. However, current research on this problem has not been carried out. A rotor with an acceleration of 150,000 g is considered as the objective, the effects of manufacturing errors on rotor mechanical properties and dynamic characteristics are executed by the selection of the key affecting factors. Through the force balance equation of the rotor infinitesimal unit establishment, a theoretical model of stress calculation based on slice method is proposed and established, a formula for the rotor stress at any point derives. A finite element model (FEM) of rotor with holes is established with manufacturing errors. The changes of the stresses and strains of a rotor in parallelism and symmetry errors are analyzed, which verify the validity of the theoretical model. The pre-stressing modal analysis is performed based on the aforementioned static analysis. The key dynamic characteristics are analyzed. The results demonstrated that, as the parallelism and symmetry errors increase, the equivalent stresses and strains of the rotor slowly increase linearly, the highest growth rate does not exceed 4%, the maximum change rate of natural frequency is 0.1%. The rotor vibration mode is not significantly affected. The FEM construction method of the rotor with manufacturing errors can be utilized for the quantitative research on rotor characteristics, which will assist in the active control of rotor component reliability under high acceleration.
Effects of increasing tip velocity on wind turbine rotor design.
Energy Technology Data Exchange (ETDEWEB)
Resor, Brian Ray [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Berg, Jonathan Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Richards, Phillip William [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-05-01
A reduction in cost of energy from wind is anticipated when maximum allowable tip velocity is allowed to increase. Rotor torque decreases as tip velocity increases and rotor size and power rating are held constant. Reduction in rotor torque yields a lighter weight gearbox, a decrease in the turbine cost, and an increase in the capacity for the turbine to deliver cost competitive electricity. The high speed rotor incurs costs attributable to rotor aero-acoustics and system loads. The increased loads of high speed rotors drive the sizing and cost of other components in the system. Rotor, drivetrain, and tower designs at 80 m/s maximum tip velocity and 100 m/s maximum tip velocity are created to quantify these effects. Component costs, annualized energy production, and cost of energy are computed for each design to quantify the change in overall cost of energy resulting from the increase in turbine tip velocity. High fidelity physics based models rather than cost and scaling models are used to perform the work. Results provide a quantitative assessment of anticipated costs and benefits for high speed rotors. Finally, important lessons regarding full system optimization of wind turbines are documented.
Towards More Efficient Comprehensive Rotor Noise Simulation Project
National Aeronautics and Space Administration — Rotorcraft design and optimization currently still rely largely on simplified (low-fidelity) models, such as rotor disk or wake models to reduce the turn-around time...
Rotor Vibration Reduction via Active Hybrid Bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2002-01-01
The use of fluid power to reduce and control rotor vibration in rotating machines is investigated. An active hybrid bearing is studied, whose main objective is to reduce wear and vibration between rotating and stationary machinery parts. By injecting pressurised oil into the oil film, through...... orifices machined in the bearing pads, one can alter the machine dynamic characteristics, thus enhancing its operational range. A mathematical model of the rotor-bearing system, as well as of the hydraulic system, is presented. Numerical results of the system frequency response show good agreement...
Directory of Open Access Journals (Sweden)
K. Siva Kumar
2012-01-01
Full Text Available Problem statement: The Rotor reactance control by inclusion of external capacitance in the rotor circuit has been in recent research for improving the performances of Wound Rotor Induction Motor (WRIM. The rotor capacitive reactance is adjusted such that for any desired load torque the efficiency of the WRIM is maximized. The rotor external capacitance can be controlled using a dynamic capacitor in which the duty ratio is varied for emulating the capacitance value. This study presents a novel technique for tracking maximum efficiency point in the entire operating range of WRIM using Artificial Neural Network (ANN. The data for ANN training were obtained on a three phase WRIM with dynamic capacitor control and rotor short circuit at different speed and load torque values. Approach: A novel neural network model based on the back-propagation algorithm has been developed and trained in determining the maximum efficiency of the motor with no prior knowledge of the machine parameters. The input variables to the ANN are stator current (Is, Speed (N and Torque (Tm and the output variable is the duty ratio (D. Results: The target is pre-set and the accuracy of the ANN model is measured using Mean Square Error (MSE and R2 parameters. The result of R2 value of the proposed ANN model is found to be 0.99980. Conclusion: The optimal duty ratio and corresponding optimal rotor capacitance for improving the performances of the motor are predicted for low, medium and full loads by using proposed ANN model.
Dynamic response of a rub-impact rotor system under axial thrust
Energy Technology Data Exchange (ETDEWEB)
An, Xueli; Zhou, Jianzhong; Xiang, Xiuqiao; Li, Chaoshun; Luo, Zhimeng [Huazhong University of Science andTechnology, College of Hydroelectric and Digitalization Engineering, Wuhan, Hubei (China)
2009-11-15
A model of a rigid rotor system under axial thrust with rotor-to-stator is developed based on the classic impact theory and is analyzed by the Lagrangian dynamics. The rubbing condition is modeled using the elastic impact-contact idealization, which consists of normal and tangential forces at the rotor-to-stator contact point. Mass eccentricity and rotating speed are used as control parameters to simulate the response of rotor system. The motions of periodic, quasi-periodic and chaotic are found in the rotor system response. Mass eccentricity plays an important role in creating chaotic phenomena. (orig.)
Simulation of blood flow in a small-diameter vascular graft model with a swirl (spiral) flow guider
Institute of Scientific and Technical Information of China (English)
Robert; GUIDOIN
2008-01-01
Small-diameter vascular grafts are in large demand for coronary and peripheral bypass procedures, but present products still fail in long-term clinical application. In the present communication, a new type of small-diameter graft with a swirl flow guider was proposed to improve graft patency rate. Flow pattern in the graft was simulated numerically and compared with that in a conventional graft. The numerical results revealed that the swirl flow guider could indeed make the blood flow rotate in the new graft. The swirling flow distal to the flow guider significantly altered the flow pattern in the new graft and the ve- locity profiles were re-distributed. Due to the swirling flow, the blood velocity near the vessel wall and wall shear rate were greatly enhanced. We believe that the increased blood velocity near the wall and the wall shear rate can impede the occurrence of acute thrombus formation and intimal hyperplasia, hence can improve the graft patency rate for long-term clinical use.
Directory of Open Access Journals (Sweden)
Silvia Chiesa
2013-01-01
Full Text Available Purpose. To correlate site and diameter of brain metastases with hippocampal sparing in patients treated by RapidArc (RA technique on whole brain with simultaneously integrated boost (SIB. Methods and Materials. An RA plan was calculated for brain metastases of 1-2-3 cm of diameter. The whole brain dose was 32.25 Gy (15 fractions, and SIB doses to brain metastases were 63 Gy (2 and 3 cm or 70.8 Gy (1 cm. Plans were optimized and evaluated for conformity, target coverage, prescription isodose to target volume, homogeneity index, and hippocampal sparing. Results. Fifteen brain lesions and RA plan were generated. Hippocampal volume was 4.09 cm3, and hippocampal avoidance volume was 17.50 cm3. Related to site of metastases, the mean hippocampal dose was 9.68 Gy2 for occipital lobe, 10.56 Gy2 for frontal lobe, 10.56 Gy2 for parietal lobe, 10.94 Gy2 for deep brain structures, and 40.44 Gy2 for temporal lobe. The mean hippocampal dose was 9.45 Gy2, 10.15 Gy2, and 11.70 Gy2 for diameter’s metastases of 1.2 and 3 cm, respectively, excluding results relative to temporal brain lesions. Conclusions. Location more than size of metastases can adversely influence the hippocampus sparing. Further investigation is necessary to meet definitive considerations.
A numerical investigation of the role of the turbine rotor scale and the nacelle on wake meandering
Foti, Daniel; Yang, Xiaolei; Shen, Lian; Sotiropoulos, Fotis
2016-11-01
Recent analysis of a hydrokinetic turbine and laboratory scale wind turbine reveal that the turbine nacelle has a considerable effect on the turbulence kinetic energy and wake meandering. However, the role of the nacelle on wake meandering for utility-scale wind turbines has not been fully investigated. In this work, a numerical investigation using large eddy simulations of four wind turbines with rotor diameters ranging from laboratory to utility scale reveals similar turbulent structures in the far wake and a comparable wake meandering Strouhal number regardless of rotor size. By reconstructing the wake meandering with three dimensional spatio-temporal filtering process, first proposed in Foti et al., the statistics of the dynamics of the wake meandering are quantified in terms of amplitude and wavelength. Results indicate that the wavelength of wake meandering can be properly scaled by rotor diameter of the turbines for both simulations with and without a nacelle model. The meandering amplitude, on the other hand, is larger for the simulation with a nacelle. This is further quantitative evidence that a nacelle model is imperative to accurately capturing wake meandering. This work was supported by Department of Energy (DE-EE0002980, DE-EE0005482 and DE-AC04-94AL85000), and Sandia National Laboratories.
Institute of Scientific and Technical Information of China (English)
高军龙; 胡国才; 吴靖
2016-01-01
Rotor mass unbanlance leads to dynamic unbalance of rotor-system, thus it causes helicopter vibration. Accord-ing to the faults of rotor dynamic unbalance, the dynamics model of helicopter was constructed to simulate and analyze mass unbalance of blade,and the relation was found out between the mass unbalance and adjusting weight . And then a methodology of rotor adjustment was presented based on the combination of BP neural network and genetic algorithm, and a model was established between the inputs and weights that included the flapping angles of 4 blades and the accelerations and phases of body roll and pitch. The model would predict the adjustment weights throught learning and training, so as to reduce the vibration of the helicopter, and solve the problem of rotor unbalance.%旋翼桨叶质量不平衡造成旋翼动不平衡,从而引起直升机振动.针对旋翼动不平衡故障,建立直升机动力学模型,对桨叶质量不平衡进行故障仿真及分析,建立质量不平衡故障与调整配重的对应关系;进而提出一种BP神经网络和遗传算法结合的旋翼调整方法,建立输入参数与桨叶配重之间的模型,将四片桨叶的挥舞角和机体横滚、俯仰2个方向的加速度值及相位作为网络输入,通过学习训练,根据输入数据预测调整配重,从而减小直升机振动,解决旋翼动不平衡问题.
Dynamical localization of coupled relativistic kicked rotors
Rozenbaum, Efim B.; Galitski, Victor
2017-02-01
A periodically driven rotor is a prototypical model that exhibits a transition to chaos in the classical regime and dynamical localization (related to Anderson localization) in the quantum regime. In a recent work [Phys. Rev. B 94, 085120 (2016), 10.1103/PhysRevB.94.085120], A. C. Keser et al. considered a many-body generalization of coupled quantum kicked rotors, and showed that in the special integrable linear case, dynamical localization survives interactions. By analogy with many-body localization, the phenomenon was dubbed dynamical many-body localization. In the present work, we study nonintegrable models of single and coupled quantum relativistic kicked rotors (QRKRs) that bridge the gap between the conventional quadratic rotors and the integrable linear models. For a single QRKR, we supplement the recent analysis of the angular-momentum-space dynamics with a study of the spin dynamics. Our analysis of two and three coupled QRKRs along with the proved localization in the many-body linear model indicate that dynamical localization exists in few-body systems. Moreover, the relation between QRKR and linear rotor models implies that dynamical many-body localization can exist in generic, nonintegrable many-body systems. And localization can generally result from a complicated interplay between Anderson mechanism and limiting integrability, since the many-body linear model is a high-angular-momentum limit of many-body QRKRs. We also analyze the dynamics of two coupled QRKRs in the highly unusual superballistic regime and find that the resonance conditions are relaxed due to interactions. Finally, we propose experimental realizations of the QRKR model in cold atoms in optical lattices.
Eigenvalue assignment strategies in rotor systems
Youngblood, J. N.; Welzyn, K. J.
1986-01-01
The work done to establish the control and direction of effective eigenvalue excursions of lightly damped, speed dependent rotor systems using passive control is discussed. Both second order and sixth order bi-axis, quasi-linear, speed dependent generic models were investigated. In every case a single, bi-directional control bearing was used in a passive feedback stabilization loop to resist modal destabilization above the rotor critical speed. Assuming incomplete state measurement, sub-optimal control strategies were used to define the preferred location of the control bearing, the most effective measurement locations, and the best set of control gains to extend the speed range of stable operation. Speed dependent control gains were found by Powell's method to maximize the minimum modal damping ratio for the speed dependent linear model. An increase of 300 percent in stable speed operation was obtained for the sixth order linear system using passive control. Simulations were run to examine the effectiveness of the linear control law on nonlinear rotor models with bearing deadband. The maximum level of control effort (force) required by the control bearing to stabilize the rotor at speeds above the critical was determined for the models with bearing deadband.
Rotor Systems of Aircraft Jet Engines
Directory of Open Access Journals (Sweden)
Ján Kamenický
2000-01-01
engine's both coaxial rotors, their supports (including their hydrodynamic dampers, and its casing as well. Besides the short description of the engine design peculiarities and of its calculating model, there is also a short description of the used method of calculations, with focus on its peculiarities as well. Finally, some results of calculations and conclusions that follow from them are presented.
Usage of modal synthesis method with condensation in rotor
Directory of Open Access Journals (Sweden)
Zeman V.
2008-11-01
Full Text Available The paper deals with mathematical modelling of vibration and modal analysis of rotors composed of a flexible shaft and several flexible disks. The shaft is modelled as a one dimensional continuum whereon flexible disks modelled as a three dimensional continuum are rigid mounted to shaft. The presented approach allows to introduce continuously distributed centrifugal and gyroscopic effects. The finite element method was used for shaft and disks discretization. The modelling of such flexible multi-body rotors with large DOF number is based on the system decomposition into subsystems and on the modal synthesis method with condensation. Lower vibration mode shapes of the mutually uncoupled and non-rotating subsystems are used for creation of the rotor condensed mathematical model. An influence of the different level of a rotor condensation model on the accuracy of calculated eigenfrequencies and eigenvectors is discussed.
Institute of Scientific and Technical Information of China (English)
焦卫东; 郭红祥
2013-01-01
裂纹转子旋转过程中,由于裂纹的非线性开/合行为导致转子刚度的变化,进而导致转子复杂的非线性振动.文章研究存在横向表面裂纹转子的纵-弯-扭耦合振动建模,并对裂纹引发的转子变刚度特性进行综合分析.转子建模采用欧拉梁单元模型,并考虑了轴向力、截面剪力、弯矩以及扭矩作用下转子运动的六个方向的自由度.裂纹单元的刚度矩阵采用柔度系数法导出,而柔度系数则由应变能理论求得.在此基础上,对一些影响裂纹转子刚度变化的主要因素如裂纹深度,梁单元长度等进行了数值分析.所得研究结果,有助于理解和揭示具有横向表面裂纹转子的非线性振动响应特性.%During the rotation of a cracked rotor, its stiffness will change because of the nonlinear opening/closing behavior of the crack. Furthermore, the cracked rotor shows strong nonlinear vibration. In this paper, coupled longitudinal-bending-torsion vibration of the rotor with transverse surface crack is first modeled. Then, comprehensive analysis is made on crack-related stiffness variation characteristics of the cracked rotor. . In the modeling of the cracked rotor, Euler beam element is used. Especially, six degrees of freedom, including axial force, section shear, bending and the torque, are considered. Stiffness matrix of the cracked element is derived by the flexibility coefficients method, and these flexibility coefficients are computed by the strain energy theory. Based on the stiffness computation of the cracked rotor, numerical evaluation is made for some influence factors, such as length of beam element and depth of crack, etc. This study is helpful to understanding and revealing the nonlinear vibration characteristics of the rotor with transverse surface crack.
Rotor for a pyrolysis centrifuge reactor
DEFF Research Database (Denmark)
2015-01-01
The present invention relates to a rotor for a pyrolysis centrifuge reactor, said rotor comprising a rotor body having a longitudinal centre axis, and at least one pivotally mounted blade being adapted to pivot around a pivot axis under rotation of the rotor body around the longitudinal centre axis....... Moreover, the present invention relates to a pyrolysis centrifuge reactor applying such a rotor....
Finite element analysis of two disk rotor system
Dixit, Harsh Kumar
2016-05-01
A finite element model of simple horizontal rotor system is developed for evaluating its dynamic behaviour. The model is based on Timoshenko beam element and accounts for the effect of gyroscopic couple and other rotational forces. Present rotor system consists of single shaft which is supported by bearings at both ends and two disks are mounted at different locations. The natural frequencies, mode shapes and orbits of rotating system for a specific range of rotation speed are obtained by developing a MATLAB code for solving the finite element equations of rotary system. Consequently, Campbell diagram is plotted for finding a relationship between natural whirl frequencies and rotation of the rotor.
Computations of Torque-Balanced Coaxial Rotor Flows
Yoon, Seokkwan; Chan, William M.; Pulliam, Thomas H.
2017-01-01
Interactional aerodynamics has been studied for counter-rotating coaxial rotors in hover. The effects of torque balancing on the performance of coaxial-rotor systems have been investigated. The three-dimensional unsteady Navier-Stokes equations are solved on overset grids using high-order accurate schemes, dual-time stepping, and a hybrid turbulence model. Computational results for an experimental model are compared to available data. The results for a coaxial quadcopter vehicle with and without torque balancing are discussed. Understanding interactions in coaxial-rotor flows would help improve the design of next-generation autonomous drones.
开式转子发动机计算模型及调节研究%Research on Open Rotor Engine Caculating Model and Control Schedule
Institute of Scientific and Technical Information of China (English)
屠秋野; 倪力伟; 杨祥明; 郑恒; 蒋平
2016-01-01
目前先进的开式转子发动机多采用变桨距、双排共轴对转桨作为推进部件。采用双排桨的气动计算方法，根据单排桨特性图计算对应的双排对转桨特性图，验证对转桨性能计算模型。在双轴涡轮喷气发动机计算模型的基础上，添加动力涡轮、行星差动齿轮和双排对转桨，组成开式转子发动机计算模型。采用该模型研究了开式转子发动机的调节计划，对比了等转速和等叶尖速度调节的不同，以及对开式转子发动机高度速度特性的影响，并使用美国PROOSIS模型对计算结果进行验证。结果表明：开式转子发动机模型计算精度较高，可较准确地研究不同设计参数和调节规律下发动机的总体性能，其中固定桨扇叶尖速度的调节计划在较低飞行速度下具有高推力、低油耗的优点，可以获得较好的全包线性能。%Counter-rotating coaxial propellers with variable pitch blades are mostly implemented in the current advanced open rotor engine. An aerodynamic computing method of counter rotating propellers was verified through calculating the counter-rotating propeller map using two single propeller maps. Basing on the aerodynamic and thermal model of a two-spool turbojet engine, an open rotor performance model was established by adding a power turbine, a differential planetary gearbox and a pair of counter rotating propellers. With this model, the control schedules were studied. The difference between constant propeller speed strategy and constant tip speed strategy , their influences to the altitude and velocity characteristics were compared respectively. The results were demonstrated to be accurate by using the data of PROOSIS model, and the performance of open rotor engine under various design parameters and different control schedules could be precisely studied. Results show that the constant tip speed strategy had advantage of high thrust with low fuel
Vorotnikov, V. I.; Martyshenko, Yu. G.
2013-09-01
The nonlinear game problem of the three-axis reorientation of an asymmetric solid body with three flywheels (rotors) has been solved. Acceptable levels of uncontrollable noise depending on given constraints of control moments have been estimated.
Yeager, William T., Jr.; Noonan, Kevin W.; Singleton, Jeffrey D.; Wilbur, Matthew L.; Mirick, Paul H.
1997-01-01
An investigation was conducted in the Langley Transonic Dynamics Tunnel to obtain data to permit evaluation of paddle-type tip technology for possible use in future U.S. advanced rotor designs. Data was obtained for both a baseline main-rotor blade and a main-rotor blade with a paddle-type tip. The baseline and paddle-type tip blades were compared with regard to rotor performance, oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Data was obtained in hover and forward flight over a nominal range of advance ratios from 0.15 to 0.425. Results indicate that the paddle-type tip offers no performance improvements in either hover or forward flight. Pitch-link oscillatory loads for the paddle-type tip are higher than for the baseline blade, whereas 4-per-rev vertical fixed-system loads are generally lower.
Energy Technology Data Exchange (ETDEWEB)
Ebert, C.; Friedmann, H.; Henkel, F.O. [Woelfel Beratende Ingenieure GmbH und Co.KG, Hoechberg (Germany); Frankenstein, B.; Schubert, L. [Fraunhofer-Institut fuer Zerstoerungsfreie Pruefverfahren, Dresden (Germany)
2010-07-01
The authors of the contribution under consideration report on a development of a Structural-Health-Monitoring-System which is to supervise the condition of the rotor blades of wind power plants and to detect in time structural changes before total failures. It is based on a combination of measuring techniques from the areas of the led rollers in the ultrasonic range and low-frequency modal analysis. The combination of both techniques was already promisingly used with past investigations of rotor blades. By means of modal analysis, statements to the total behaviour of the structure of rotor blades are possible. Endangered and strongly stressed areas additionally are supervised by led rollers within the ultrasonic range. The authors also report on the conception and execution of a fatigue test at a material rotor blade with a length by 39.1 m.
Institute of Scientific and Technical Information of China (English)
J.D.Denton
1997-01-01
NASA rotor 37 was used as a blind test case for turbomachinery CFD by the Turbomachinery Committee of the IGTI.The rotor is a transonic compressor with a tip speed of 454 m/s(1500ft/s)and a relatively high pressure ratio of 2.1.It was tested in isolation with a circumferentially uniform inlet flow so that the flow through it should be steady apart from and effects of passage to passage geometry variation and mechanical vibration.As such it represents the simplest possible type of test for three-dimensional turbomachinery flow solvers.Howerver,the rotor still presents a real challenge to 3D viscous flow solvers because the shock wave-boudary layer interaction is strong and the effects of viscosity are dominant in determining the flow deviation and hence the pressure ration.Eleven blind solutions were submittewd and in addition a non-blind solution was used to prepare for the exercies.This paper reviews the flow in the test case and the comparisons of the CFD solutions with the test data.Lessons for both the Flow physics in transonic fans and for the application of CFD to such machines are pointed out.
Simulation of blood flow in a small-diameter vascular raft model with a swirl (spiral) flow guider
Institute of Scientific and Technical Information of China (English)
ZHANG ZhiGuo; FAN YuBo; DENG XiaoYan; WANG GuiXue; ZHANG He; Robert GUIDOIN
2008-01-01
Small-dlameter vascular grafts are in large demand for coronary and peripheral bypass procedures, but present products still fail in long-term clinical application. In the present communication, a new type of small-diameter graft with a swirl flow guider was proposed to improve graft patency rate. Flow pattern in the graft was simulated numerically and compared with that in a conventional graft. The numerical results revealed that the swirl flow guider couldindeed make the blood flow rotate in the new graft. The swirling flow distal to the flow guider significantly altered the flow pattern in the new graft and the ve-locity profiles were re-distributed. Due to the swirling flow, the blood velocity near the vessel wall and wall shear rate were greatly enhanced. We believe that the increased blood velocity near the wall and the wall shear rate can impede the occurrence of acute thrombus formation and intimal hyperplasia, hence can improve the graft patency rate for long-term clinical use.
Flettner Rotor Concept for Marine Applications: A Systematic Study
Directory of Open Access Journals (Sweden)
A. De Marco
2016-01-01
Full Text Available The concept of Flettner rotor, a rotating cylinder immersed in a fluid current, with a top-mounted disk, has been analyzed by means of unsteady Reynolds averaged Navier-Stokes simulations, with the aim of creating a suitable tool for the preliminary design of the Flettner rotor as a ship’s auxiliary propulsion system. The simulation has been executed to evaluate the performance sensitivity of the Flettner rotor with respect to systematic variations of several parameters, that is, the spin ratio, the rotor aspect ratio, the effect of the end plates, and their dimensions. The Flettner rotor device has been characterized in terms of lift and drag coefficients, and these data were compared with experimental trends available in literature. A verification study has been conducted in order to evaluate the accuracy of the simulation results and the main sources of numerical uncertainty. All the simulation results were used to achieve a surrogate model of lift and drag coefficients. This model is an effective mathematical tool for the preliminary design of Flettner rotor. Finally, an example of assessment of the Flettner rotor performance as an auxiliary propulsion device on a real tanker ship is reported.
CFD simulations of the MEXICO rotor
DEFF Research Database (Denmark)
Bechmann, Andreas; Sørensen, Niels N.; Zahle, Frederik
2011-01-01
The wake behind a wind turbine model is investigated using Computational Fluid Dynamics (CFD), and results are compared with measurements. The turbine investigated is the three‐bladed test rotor (D = 4.5 m) used in the Model Experiments in Controlled Conditions (MEXICO) wind tunnel experiment....... During the MEXICO experiment, particle image velocimetry measurements of the induction upstream and downstream of the rotor were performed for different operating conditions, giving a unique dataset to verify theoretical models and CFD models. The present paper first describes the efforts in reproducing...... the experimental results using the Reynold‐Averaged Navier‐Stokes method. Second, three‐dimensional airfoil characteristics are extracted that allow simulations with simpler wake models. Copyright © 2011 John Wiley & Sons, Ltd....
Homopolar motor with dual rotors
Energy Technology Data Exchange (ETDEWEB)
Hsu, John S. (Oak Ridge, TN)
1998-01-01
A homopolar motor (10) has a field rotor (15) mounted on a frame (11) for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor (17) mounted for rotation on said frame (11) within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor (15). The two rotors (15, 17) are coupled through a 1:1 gearing mechanism (19), so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed.
Homopolar motor with dual rotors
Energy Technology Data Exchange (ETDEWEB)
Hsu, J.S.
1998-12-01
A homopolar motor has a field rotor mounted on a frame for rotation in a first rotational direction and for producing an electromagnetic field, and an armature rotor mounted for rotation on said frame within said electromagnetic field and in a second rotational direction counter to said first rotational direction of said field rotor. The two rotors are coupled through a 1:1 gearing mechanism, so as to travel at the same speed but in opposite directions. This doubles the output voltage and output power, as compared to a motor in which only the armature is rotated. Several embodiments are disclosed. 7 figs.
Rotor/body aerodynamic interactions
Betzina, M. D.; Smith, C. A.; Shinoda, P.
1985-01-01
A wind tunnel investigation was conducted in which independent, steady state aerodynamic forces and moments were measured on a 2.24 m diam. two bladed helicopter rotor and on several different bodies. The mutual interaction effects for variations in velocity, thrust, tip-path-plane angle of attack, body angle of attack, rotor/body position, and body geometry were determined. The results show that the body longitudinal aerodynamic characteristics are significantly affected by the presence of a rotor and hub, and that the hub interference may be a major part of such interaction. The effects of the body on the rotor performance are presented.
Variable Speed Rotor System Project
National Aeronautics and Space Administration — Variable speed rotors will give helicopters several advantages: higher top speed, greater fuel efficiency, momentary emergency over-power, resonance detuning...
Neradilek, Moni B; Polissar, Nayak L; Einstein, Daniel R; Glenny, Robb W; Minard, Kevin R; Carson, James P; Jiao, Xiangmin; Jacob, Richard E; Cox, Timothy C; Postlethwait, Edward M; Corley, Richard A
2012-06-01
We examine a previously published branch-based approach for modeling airway diameters that is predicated on the assumption of self-consistency across all levels of the tree. We mathematically formulate this assumption, propose a method to test it and develop a more general model to be used when the assumption is violated. We discuss the effect of measurement error on the estimated models and propose methods that take account of error. The methods are illustrated on data from MRI and CT images of silicone casts of two rats, two normal monkeys, and one ozone-exposed monkey. Our results showed substantial departures from self-consistency in all five subjects. When departures from self-consistency exist, we do not recommend using the self-consistency model, even as an approximation, as we have shown that it may likely lead to an incorrect representation of the diameter geometry. The new variance model can be used instead. Measurement error has an important impact on the estimated morphometry models and needs to be addressed in the analysis.
Directory of Open Access Journals (Sweden)
Eberhard P Scholz
Full Text Available Inhibition of the atrial ultra-rapid delayed rectifier potassium current (I Kur represents a promising therapeutic strategy in the therapy of atrial fibrillation. However, experimental and clinical data on the antiarrhythmic efficacy remain controversial. We tested the hypothesis that antiarrhythmic effects of I Kur inhibitors are dependent on kinetic properties of channel blockade. A mathematical description of I Kur blockade was introduced into Courtemanche-Ramirez-Nattel models of normal and remodeled atrial electrophysiology. Effects of five model compounds with different kinetic properties were analyzed. Although a reduction of dominant frequencies could be observed in two dimensional tissue simulations for all compounds, a reduction of spiral wave activity could be only be detected in two cases. We found that an increase of the percent area of refractory tissue due to a prolongation of the wavelength seems to be particularly important. By automatic tracking of spiral tip movement we find that increased refractoriness resulted in rotor extinction caused by an increased spiral-tip meandering. We show that antiarrhythmic effects of I Kur inhibitors are dependent on kinetic properties of blockade. We find that an increase of the percent area of refractory tissue is the underlying mechanism for an increased spiral-tip meandering, resulting in the extinction of re-entrant circuits.
Podlaski, Rafał; Roesch, Francis A
2014-03-01
In recent years finite-mixture models have been employed to approximate and model empirical diameter at breast height (DBH) distributions. We used two-component mixtures of either the Weibull distribution or the gamma distribution for describing the DBH distributions of mixed-species, two-cohort forest stands, to analyse the relationships between the DBH components, age cohorts and dominant species, and to assess the significance of differences between the mixture distributions and the kernel density estimates. The data consisted of plots from the Świętokrzyski National Park (Central Poland) and areas close to and including the North Carolina section of the Great Smoky Mountains National Park (USA; southern Appalachians). The fit of the mixture Weibull model to empirical DBH distributions had a precision similar to that of the mixture gamma model, slightly less accurate estimate was obtained with the kernel density estimator. Generally, in the two-cohort, two-storied, multi-species stands in the southern Appalachians, the two-component DBH structure was associated with age cohort and dominant species. The 1st DBH component of the mixture model was associated with the 1st dominant species sp1 occurred in young age cohort (e.g., sweetgum, eastern hemlock); and to a lesser degree, the 2nd DBH component was associated with the 2nd dominant species sp2 occurred in old age cohort (e.g., loblolly pine, red maple). In two-cohort, partly multilayered, stands in the Świętokrzyski National Park, the DBH structure was usually associated with only age cohorts (two dominant species often occurred in both young and old age cohorts). When empirical DBH distributions representing stands of complex structure are approximated using mixture models, the convergence of the estimation process is often significantly dependent on the starting strategies. Depending on the number of DBHs measured, three methods for choosing the initial values are recommended: min.k/max.k, 0.5/1.5/mean
Institute of Scientific and Technical Information of China (English)
张世海; 刘雄彪; 李录平; 晋风华; 梁伟
2016-01-01
The 3D model of rotor system of a domestic 600MW steam turbine has been modeled by using the Solidworks software.The analysis of dynamic characteristics of rotors and shaft system of this unit are completed by using the FEA software Algor.The results shows that the arrangement of modal frequency values of each order of the shaft system is roughly in ascending order according to the modal frequency values of each single rotor .And the distribution of the modal shape of each order of the shaft system with the trend that each modal shape matches the single rotor ’ s one,if the modal frequency value close to the signal rotor's one.The natural frequencies of the rotors and the shaft system are satisfied with the requirements that the values are far from with the operating frequency value .The work of this article offered a reference for the 3D modeling concrete bodies and the analysis of dynamic characteristics of large turbo machines .The results of this study provides theoretical basis for operation of this unit .%采用Solidworks软件对国产某600MW汽轮发电机组转子系统进行三维实体建模。运用Algor有限元软件对该机组各转子及轴系进行了动力特性分析。结果表明：该机组轴系的各阶模态频率值有按照各单转子各阶模态频率值由小到大顺序排列、各阶模态振型相对应的分布趋势；该机组的各转子及轴系的固有频率均满足远离工作频率的要求。为大型汽轮发电机组转子系统的三维实体建模及其动力特性有限元分析提供了一定的参考，研究结果为该机组的运行提供了理论依据。
Rotor-rotor interaction for counter-rotating fans. Part 1: Three-dimensional flowfield measurements
Shin, Hyoun-Woo; Whitfield, Charlotte E.; Wisler, David C.
1994-11-01
The rotor wake/vortex flowfield generated in a scale model simulator of General Electric's counter-rotating unducted fan (UDF) engine was investigated using three-dimensional hot-wire anemometry. The purpose was to obtain a set of benchmark experimental aerodynamic data defining the rotor wake and vortex structure, particularly in the tip region, and to relate this observed flow structure to its acoustic signature. The tests were conducted in a large, freejet anechoic chamber. Measurements of the three components of velocity were made at axial stations upstream and downstream of each rotor for conditions that simulate takeoff, cutback, and approach power. Two different forward blade designs were evaluated. The tip vortices, the axial velocity defect in the vortex core, and differences in the interaction of the wakes and vortices generated by the forward and aft rotor are used to explain differences in noise generated by the two different rotor designs. Part 1 presents the three-dimensional flowfield measurements. Part 2 (aeroacoustic prediction and analysis), which will be presented later, will give an acoustic prediction using the measured data.
Rotor Design for Diffuser Augmented Wind Turbines
Directory of Open Access Journals (Sweden)
Søren Hjort
2015-09-01
Full Text Available Diffuser augmented wind turbines (DAWTs can increase mass flow through the rotor substantially, but have often failed to fulfill expectations. We address high-performance diffusers, and investigate the design requirements for a DAWT rotor to efficiently convert the available energy to shaft energy. Several factors can induce wake stall scenarios causing significant energy loss. The causality between these stall mechanisms and earlier DAWT failures is discussed. First, a swirled actuator disk CFD code is validated through comparison with results from a far wake swirl corrected blade-element momentum (BEM model, and horizontal-axis wind turbine (HAWT reference results. Then, power efficiency versus thrust is computed with the swirled actuator disk (AD code for low and high values of tip-speed ratios (TSR, for different centerbodies, and for different spanwise rotor thrust loading distributions. Three different configurations are studied: The bare propeller HAWT, the classical DAWT, and the high-performance multi-element DAWT. In total nearly 400 high-resolution AD runs are generated. These results are presented and discussed. It is concluded that dedicated DAWT rotors can successfully convert the available energy to shaft energy, provided the identified design requirements for swirl and axial loading distributions are satisfied.
MODIFIED SAVONIUS ROTOR FOR DOMESTIC POWER PRODUCTION
Directory of Open Access Journals (Sweden)
VINAY P V
2012-07-01
Full Text Available Conventional fuels which are fast depleting, have ever fluctuating price and polluting characteristic of theirs is pushing mankind towards energies which are renewable and green. Wind being one of the renewable energies among solar, geothermal, biomass, ocean and others is being more patronized in places where wind is copious by governmental and with private partnership to generate electricity. Vertical axis rotor was selected over the horizontal ones due to its simplicity and reliability. At a selected location a prototype was built and installed. The design and development process and the need of the new type of machine will be described in this paper. This paper produces an investigational exploration of a vertical axis rotor (Savonius rotor wind turbine adapted for household/domestic electricity generation. The model machine collects wind energy and generates a 12 volt output which is used to charge one heavy duty battery. As a result, the home is served simultaneously by the wind turbine and the utility. The wind turbine responds well to low wind velocities and also various materials for vanes, various transmission mechanisms were also tried to evaluate the performance of the rotor.
Power Properties of Two Interacting Wind Turbine Rotors
DEFF Research Database (Denmark)
Okulov, Valery; Mikkelsen, Robert Flemming; Sørensen, Jens Nørkær
2016-01-01
In the current experiments, two identical wind turbine models were placed in uniform flow conditions in a water flume. The initial flow in the flume was subject to a very low turbulence level, limiting the influence of external disturbances on the development of the inherent wake instability. Both...... rotors are threebladed and designed using blade element/lifting line (BE/LL) optimum theory at a tip speed ratio, λ, of 5 with a constant design lift coefficient along the span, CL= 0.8. Measurements of the rotor characteristics were conducted by strain sensors installed in the rotor mounting...
Power Properties of Two Interacting Wind Turbine Rotors
DEFF Research Database (Denmark)
Okulov, Valery; Mikkelsen, Robert Flemming; Sørensen, Jens Nørkær
2017-01-01
In the current experiments, two identical wind turbine models were placed in uniform flow conditions in a water flume. The initial flow in the flume was subject to a very low turbulence level, limiting the influence of external disturbances on the development of the inherent wake instability. Both...... rotors are three-bladed and designed using blade element/lifting line (BE/LL) optimum theory at a tip-speed ratio, λ, of 5 with a constant design lift coefficient along the span, CL = 0.8. Measurements of the rotor characteristics were conducted by strain sensors installed in the rotor mounting...
Energy Technology Data Exchange (ETDEWEB)
Neradilek, Moni B.; Polissar, Nayak L.; Einstein, Daniel R.; Glenny, Robb W.; Minard, Kevin R.; Carson, James P.; Jiao, Xiangmin; Jacob, Richard E.; Cox, Timothy C.; Postlethwait, Edward M.; Corley, Richard A.
2012-04-24
We examine a previously published branch-based approach to modeling airway diameters that is predicated on the assumption of self-consistency across all levels of the tree. We mathematically formulate this assumption, propose a method to test it and develop a more general model to be used when the assumption is violated. We discuss the effect of measurement error on the estimated models and propose methods that account for it. The methods are illustrated on data from MRI and CT images of silicone casts of two rats, two normal monkeys and one ozone-exposed monkey. Our results showed substantial departures from self-consistency in all five subjects. When departures from selfconsistency exist we do not recommend using the self-consistency model, even as an approximation, as we have shown that it may likely lead to an incorrect representation of the diameter geometry. Measurement error has an important impact on the estimated morphometry models and needs to be accounted for in the analysis.
Directory of Open Access Journals (Sweden)
Uğbreve;ur Dalli
2011-01-01
Full Text Available An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.
Jordon, D. E.; Patterson, W.; Sandlin, D. R.
1985-01-01
The XV-15 Tilt Rotor Research Aircraft download phenomenon was analyzed. This phenomenon is a direct result of the two rotor wakes impinging on the wing upper surface when the aircraft is in the hover configuration. For this study the analysis proceeded along tow lines. First was a method whereby results from actual hover tests of the XV-15 aircraft were combined with drag coefficient results from wind tunnel tests of a wing that was representative of the aircraft wing. Second, an analytical method was used that modeled that airflow caused gy the two rotors. Formulas were developed in such a way that acomputer program could be used to calculate the axial velocities were then used in conjunction with the aforementioned wind tunnel drag coefficinet results to produce download values. An attempt was made to validate the analytical results by modeling a model rotor system for which direct download values were determinrd..
Directory of Open Access Journals (Sweden)
Kang L. Wang
2012-08-01
Full Text Available The use of a functional molecular unit acting as a state variable provides an attractive alternative for the next generations of nanoscale electronics. It may help overcome the limits of conventional MOSFETd due to their potential scalability, low-cost, low variability, and highly integratable characteristics as well as the capability to exploit bottom-up self-assembly processes. This bottom-up construction and the operation of nanoscale machines/devices, in which the molecular motion can be controlled to perform functions, have been studied for their functionalities. Being triggered by external stimuli such as light, electricity or chemical reagents, these devices have shown various functions including those of diodes, rectifiers, memories, resonant tunnel junctions and single settable molecular switches that can be electronically configured for logic gates. Molecule-specific electronic switching has also been reported for several of these device structures, including nanopores containing oligo(phenylene ethynylene monolayers, and planar junctions incorporating rotaxane and catenane monolayers for the construction and operation of complex molecular machines. A specific electrically driven surface mounted molecular rotor is described in detail in this review. The rotor is comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly-doped P^{+} Si. This electrically driven sandwich-type monolayer molecular rotor device showed an on/off ratio of approximately 10^{4}, a read window of about 2.5 V, and a retention time of greater than 10^{4} s. The rotation speed of this type of molecular rotor has been reported to be in the picosecond timescale, which provides a potential of high switching speed applications. Current-voltage spectroscopy (I-V revealed a temperature-dependent negative differential resistance (NDR associated with the device. The analysis of the device
Flowers, George T.
1995-02-01
This semiannual status report lists specific accomplishments made on the research of the influence of backup bearings and support structure dynamics on the behavior of rotors with active supports. Papers have been presented representing work done on the T-501 engine model; an experimental/simulation study of auxiliary bearing rotordynamics; and a description of a rotordynamical model for a magnetic bearing supported rotor system, including auxiliary bearing effects. A finite element model for a foil bearing has been developed. Additional studies of rotor/bearing/housing dynamics are currently being performed as are studies of the effects of sideloading on auxiliary bearing rotordynamics using the magnetic bearing supported rotor model.
DEFF Research Database (Denmark)
Yang, Hua; Shen, Wen Zhong; Sørensen, Jens Nørkær
2012-01-01
on rotor blades developed by SHEN, et al is successfully used to extract airfoil data from experimental characteristics on the MEXICO (Model experiments in controlled conditions) rotor. Detailed surface pressure and particle image velocimetry (PIV) flow fields at different rotor azimuth positions...
EVALUATION OF PERFORMANCE OF HORIZONTAL AXIS WIND TURBINE BLADES BASED ON OPTIMAL ROTOR THEORY
Directory of Open Access Journals (Sweden)
Nitin Tenguria
2011-01-01
Full Text Available Wind energy is a very popular renewable energy resource. In order to increase the use of wind energy, it is important to develop wind turbine rotor with high rotations rates and power coefficient. In this paper, a method for the determination of the aerodynamic performance characteristics using NACA airfoils is given for three bladed horizontal axis wind turbine. Blade geometry is obtained from the best approximation of the calculated theoretical optimum chord and twist distribution of the rotating blade. Optimal rotor theory is used, which is simple enough and accurate enough for rotor design. In this work, eight different airfoils are used to investigate the changes in performance of the blade. Rotor diameter taken is 82 m which is the diameter of VESTAS V82-1.65MW. The airfoils taken are same from root to tip in every blade. The design lift coefficient taken is 1.1. A computer program is generated to automate the complete procedure.
EVALUATION OF PERFORMANCE OF HORIZONTAL AXIS WIND TURBINE BLADES BASED ON OPTIMAL ROTOR THEORY
Directory of Open Access Journals (Sweden)
Nitin Tenguria
2011-06-01
Full Text Available Wind energy is a very popular renewable energy resource. In order to increase the use of wind energy, it is important to develop wind turbine rotor with high rotations rates and power coefficient. In this paper, a method for the determination of the aerodynamic performance characteristics using NACA airfoils is given for three bladed horizontal axis wind turbine. Blade geometry is obtained from the best approximation of the calculated theoretical optimum chord and twist distribution of the rotating blade. Optimal rotor theory is used, which is simple enough and accurate enough for rotor design. In this work, eight different airfoils are used to investigate the changes in performance of the blade. Rotor diameter taken is 82 m which is the diameter of VESTAS V82-1.65MW. The airfoils taken are same from root to tip in every blade. The design lift coefficient taken is 1.1. A computer program is generated to automate the complete procedure.
Robust stabilization of rotor-active magnetic bearing systems
Li, Guoxin
Active magnetic bearings (AMBs) are emerging as a beneficial technology for high-speed and high-performance suspensions in rotating machinery applications. A fundamental feedback control problem is robust stabilization in the presence of uncertain destabilizing mechanisms in aeroelastic, hydroelastic dynamics, and AMB feedback. As rotating machines are evolving in achieving high speed, high energy density, and high performance, the rotor and the support structure become increasingly flexible, and highly coupled. This makes rotor-AMB system more challenging to stabilize. The primary objective of this research is to develop a systematic control synthesis procedure for achieving highly robust stabilization of rotor-AMB systems. Of special interest is the stabilization of multivariable systems such as the AMB supported flexible rotors and gyroscopic rotors, where the classical control design may encounter difficulties. To this end, we first developed a systematic modeling procedure. This modeling procedure exploited the best advantages of technology developed in rotordynamics and the unique system identification tool provided by the AMBs. A systematic uncertainty model for rotor-AMB systems was developed, eliminating the iterative process of selecting uncertainty structures. The consequences of overestimation or underestimation of uncertainties were made transparent to control engineers. To achieve high robustness, we explored the fundamental performance/robustness limitations due to rotor-AMB system unstable poles. We examined the mixed sensitivity performance that is closely related to the unstructured uncertainty. To enhance transparency of the synthesis, we analyzed multivariable controllers from classical control perspectives. Based on these results, a systematic robust control synthesis procedure was established. For a strong gyroscopic rotor over a wide speed range, we applied the advanced gain-scheduled synthesis, and compared two synthesis frameworks in
Suppression of Base Excitation of Rotors on Magnetic Bearings
2007-01-01
This paper deals with rotor systems that suffer harmonic base excitation when supported on magnetic bearings. Magnetic bearings using conventional control techniques perform poorly in such situations mainly due to their highly nonlinear characteristics. The compensation method presented here is a novel optimal control procedure with a combination of conventional, proportional, and differential feedback control. A four-degree-of-freedom model is used for the rotor system, and the bearings a...
Koobatian, Maxwell T; Row, Sindhu; Smith, Randall J; Koenigsknecht, Carmon; Andreadis, Stelios T; Swartz, Daniel D
2016-01-01
The large number of coronary artery bypass procedures necessitates development of off-the-shelf vascular grafts that do not require cell or tissue harvest from patients. However, immediate thrombus formation after implantation due to the absence of a healthy endothelium is very likely. Here we present the successful development of an acellular tissue engineered vessel (A-TEV) based on small intestinal submucosa that was functionalized sequentially with heparin and VEGF. A-TEVs were implanted into the carotid artery of an ovine model demonstrating high patency rates and significant host cell infiltration as early as one week post-implantation. At one month, a confluent and functional endothelium was present and the vascular wall showed significant infiltration of host smooth muscle cells exhibiting vascular contractility in response to vaso-agonists. After three months, the endothelium aligned in the direction of flow and the medial layer comprised of circumferentially aligned smooth muscle cells. A-TEVs demonstrated high elastin and collagen content as well as impressive mechanical properties and vascular contractility comparable to native arteries. This is the first demonstration of successful endothelialization, remodeling, and development of vascular function of a cell-free vascular graft that was implanted in the arterial circulation of a pre-clinical animal model. Copyright © 2015 Elsevier Ltd. All rights reserved.
Method for predicting impulsive noise generated by wind turbine rotors
Viterna, L. A.
1982-01-01
Large wind turbines can generate both broad band and impulsive noises. These noises can be controlled by proper choice of rotor design parameters such as rotor location with respect to the supporting tower, tower geometry and tip speed. A method was developed to calculate the impulsive noise generated when the wind turbine blade experiences air forces that are periodic functions of the rotational frequency. This phenomenon can occur when the blades operate in the wake of the support tower and the nonuniform velocity field near the ground due to wind shear. Results from this method were compared with measured sound spectra taken at locations of one to two rotor diameters from the DOE/NASA Mod-1 wind turbine. The calculated spectra generally agreed with the measured data in both the amplitude of the predominant harmonics and the roll of rate with frequency. Measured sound pressure levels far from the Mod-1 (15 rotor diameters), however, were higher than predicted. Simultaneous measurements in the near and far field indicated that the propagation effects could enhance the sound levels by more than 10 dB above that expected by spherical dispersion. These propagation effects are believed to be due to terrain and atmospheric characteristics of the Mod-1 site.
Directory of Open Access Journals (Sweden)
Mohd Afaque Iqbal
2014-06-01
Full Text Available Single-phase induction motor (SPIM has very crucial role in industrial, domestic and commercial sectors. So, the efficient SPIM is a major requirement of today’s market. For efficient motors, many research methodologies and suggestions have been given by researchers in past. Various parameters like as stator/rotor slot variation, size and shape of stator/rotor slots, stator/rotor winding configuration, choice of core material etc. have significant impact on machine design. Rotor slot geometry influences the distribution of the magnetic field to a degree. Even a little difference of the magnetic field distribution can make big difference on the performance of the induction motor. The rotor slot geometry influences the skin effect and slot leakage flux in order to increase the torque and efficiency. In this paper, three types of rotor slot configurations are designed and simulated with different rotor slot configuration and rotor bars composition by changing the rotor slot configuration of base model. Aluminum and Copper are used simultaneously as rotor winding material. The rotor bar is a composite conductor which carries Aluminum as well as Copper sub-conductors running parallel in the same slot. Overall cross section area of rotor bar in each model kept same and work is carried out with difference proportion of Aluminum and Copper sub conductors. All models are investigated and simulated in FEMM and finally the simulated results are compared for optimal solution.
Validation of a three-dimensional viscous-inviscid interactive solver for wind turbine rotors
DEFF Research Database (Denmark)
Ramos García, Néstor; Sørensen, Jens Nørkær; Shen, Wen Zhong
2014-01-01
measurements and/or CFD simulations for five wind turbine rotors, including three experimental model rotors [20-22], the 2.5 MW NM80 machine [23] and the NREL 5 MW virtual rotor [24]. Such a broad set of operational conditions and rotor sizes constitutes a very challenging validation matrix, with Reynolds......MIRAS is a newly developed computational model that predicts the aerodynamic behavior of wind turbine blades and wakes subject to unsteady motions and viscous effects. The model is based on a three-dimensional panel method using a surface distribution of quadrilateral singularities with a Neumann...
Wind Turbine Rotors with Active Vibration Control
DEFF Research Database (Denmark)
Svendsen, Martin Nymann
are assumed to be proportional to the relative inflow angle, which also gives a linear form with equivalent stiffness and damping terms. Geometric stiffness effects including the important stiffening from tensile axial stresses in equilibrium with centrifugal forces are included via an initial stress......This thesis presents a framework for structural modeling, analysis and active vibration damping of rotating wind turbine blades and rotors. A structural rotor model is developed in terms of finite beam elements in a rotating frame of reference. The element comprises a representation of general...... formulation. The element provides an accurate representation of the eigenfrequencies and whirling modes of the gyroscopic system, and identifies lightly damped edge-wise modes. By adoption of a method for active, collocated resonant vibration of multi-degree-of-freedom systems it is demonstrated...
Modeling and Position Tracking Control for Six-Rotors%六旋翼飞行器建模及位置跟踪控制
Institute of Scientific and Technical Information of China (English)
王伟; 邱启明
2014-01-01
为实现六旋翼的位置跟踪与控制功能，对六旋翼飞行器的数学模型进行了分析，通过线性化得到了其简单数学模型。在简化的数学模型基础之上设计了基于PID(比例-积分-微分控制器)控制算法的姿态控制器和位置控制器，控制器仿真结果表明位置跟踪误差小于2%。飞行实验中飞行器准确追踪给定的姿态角精度大于80%，飞行器性能稳定，实现方法合理。%In order to accomplish control functions,a simple mathematical model was achieved after the model of six-rotor unmanned aerial( UAVs) vehicle was analyzed and linearnized. Attitude controller and position controller was designed based on PID ( Proportional-Integral-Derivative ) control algorithm and the simply mathematical mentioned above. The results of simulation putted on position controller showed that position error is less than two percent. The degree of accuracy on the fact that the reference input was correctly traced by UAVs is greater than eighty percent during the flight test. The performance is stable,and the implementation method is reasonable.
Investigation of a new model accounting for rotors of finite tip-speed ratio in yaw or tilt
DEFF Research Database (Denmark)
Branlard, Emmanuel; Gaunaa, Mac; Machefaux, Ewan
2014-01-01
from the MEXICO experiment are used as a basis for validation. Three tools using the same 2D airfoil coefficient data are compared: a BEM code, an Actuator-Line and a vortex code. The vortex code is further used to validate the results from the newly implemented BEM yaw-model. Significant improvements......The main results from a recently developed vortex model are implemented into a Blade Element Momentum(BEM) code. This implementation accounts for the effect of finite tip-speed ratio, an effect which was not considered in standard BEM yaw-models. The model and its implementation are presented. Data...
Energy Technology Data Exchange (ETDEWEB)
Jeon, Sang Hyeon; Kim, Bum Suk; Huh, Jong Chul [Jeju National Univ., Jeju (Korea, Republic of); Go, Young Jun [Hanjin Ind, Co., Ltd., Yangsan (Korea, Republic of)
2016-01-15
The wake effects behind wind turbines were investigated by using data from a Met Mast tower and the SCADA (Supervisory Control and Data Acquisition) system for a wind turbine. The results of the wake investigations and predicted values for the velocity deficit based on the eddy viscosity model were compared with the turbulence intensity from the Lange model. As a result, the velocity deficit and turbulence intensity of the wake increased as the free stream wind speed decreased. In addition, the magnitude of the velocity deficit for the center of the wake using the eddy viscosity model was overestimated while the turbulence intensity from the Lange model showed similarities with measured values.
Spectral Analysis of Two Coupled Diatomic Rotor Molecules
Directory of Open Access Journals (Sweden)
Horace T. Crogman
2014-10-01
Full Text Available In a previous article the theory of frame transformation relation between Body Oriented Angular (BOA states and Lab Weakly Coupled states (LWC was developed to investigate simple rotor–rotor interactions. By analyzing the quantum spectrum for two coupled diatomic molecules and comparing it with spectrum and probability distribution of simple models, evidence was found that, as we move from a LWC state to a strongly coupled state, a single rotor emerges in the strong limit. In the low coupling, the spectrum was quadratic which indicates the degree of floppiness in the rotor–rotor system. However in the high coupling behavior it was found that the spectrum was linear which corresponds to a rotor deep in a well.
Assessment of Scaled Rotors for Wind Tunnel Experiments.
Energy Technology Data Exchange (ETDEWEB)
Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kelley, Christopher Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Chiu, Phillip [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-07-01
Rotor design and analysis work has been performed to support the conceptualization of a wind tunnel test focused on studying wake dynamics. This wind tunnel test would serve as part of a larger model validation campaign that is part of the Department of Energy Wind and Water Power Program’s Atmosphere to electrons (A2e) initiative. The first phase of this effort was directed towards designing a functionally scaled rotor based on the same design process and target full-scale turbine used for new rotors for the DOE/SNL SWiFT site. The second phase focused on assessing the capabilities of an already available rotor, the G1, designed and built by researchers at the Technical University of München.
TORNADO concept and realisation of a rotor for small VAWTs
Directory of Open Access Journals (Sweden)
Horia DUMITRESCU
2013-09-01
Full Text Available The concept of a three-tier configuration for a vertical axis rotor was successfully developed into a experimental model. The rotor assembly is divided into three tiers with three straight blades in each tier. The three-tiers are shifted by an angle of 400 generating a full helical flow field inside the rotor. Thereby the new configuration has some different mechanism of torque generation as other Darrieus rotors. The three-tier configuration facilitates the operation by enabling the turbine to self-start at wind velocity as low as 2 m/s with good performance and a smoother driving torque. At the same time the design couples an esthetic appearance with low noise level.
Extension of Goldstein's circulation function for optimal rotors with hub
Okulov, V. L.; Sørensen, J. N.; Shen, W. Z.
2016-09-01
The aerodynamic interaction or interference between rotor blades and hub body is usually very complicated, but some useful simplifications can be made by considering the hub with an infinite cylinder. Various attempts to find the optimum distribution of circulation by the lifting vortex lines method have been previously proposed to describe the blade interaction with the hub modeled by the infinite cylinder. In this case, the ideal distribution of bound circulation on the rotor blades is such that the shed vortex system in the hub-area is a set of helicoidal vortex sheets moving uniformly as if rigid, exactly as in the case where there is no influence of the streamtube deformations by the central hub-body. In the present investigation, we consider a more specific problem of the rotor-hub interaction where the initial flow streamtubes and the rotor slipstream submitted strong deformations at the nose-area of the semi-infinite hub.
Rafal Podlaski; Francis A. Roesch
2014-01-01
Two-component mixtures of either the Weibull distribution or the gamma distribution and the kernel density estimator were used for describing the diameter at breast height (dbh) empirical distributions of two-cohort stands. The data consisted of study plots from the Å wietokrzyski National Park (central Poland) and areas close to and including the North Carolina section...
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor speed. 27.1509 Section 27.1509... Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be established... minimum power-off rotor speed must be established so that it is not less than 105 percent of the...
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Rotor speed. 29.1509 Section 29.1509....1509 Rotor speed. (a) Maximum power-off (autorotation). The maximum power-off rotor speed must be... minimum power-off rotor speed must be established so that it is not less than 105 percent of the...
Performance tests on helical Savonius rotors
Energy Technology Data Exchange (ETDEWEB)
Kamoji, M.A.; Kedare, S.B. [Department of Energy Science and Engineering, Indian Institute of Technology, Bombay (India); Prabhu, S.V. [Department of Mechanical Engineering, Indian Institute of Technology, Bombay (India)
2009-03-15
Conventional Savonius rotors have high coefficient of static torque at certain rotor angles and a negative coefficient of static torque from 135 to 165 and from 315 to 345 in one cycle of 360 . In order to decrease this variation in static torque from 0 to 360 , a helical Savonius rotor with a twist of 90 is proposed. In this study, tests on helical Savonius rotors are conducted in an open jet wind tunnel. Coefficient of static torque, coefficient of torque and coefficient of power for each helical Savonius rotor are measured. The performance of helical rotor with shaft between the end plates and helical rotor without shaft between the end plates at different overlap ratios namely 0.0, 0.1 and 0.16 is compared. Helical Savonius rotor without shaft is also compared with the performance of the conventional Savonius rotor. The results indicate that all the helical Savonius rotors have positive coefficient of static torque at all the rotor angles. The helical rotors with shaft have lower coefficient of power than the helical rotors without shaft. Helical rotor without shaft at an overlap ratio of 0.0 and an aspect ratio of 0.88 is found to have almost the same coefficient of power when compared with the conventional Savonius rotor. Correlation for coefficient of torque and power is developed for helical Savonius rotor for a range of Reynolds numbers studied. (author)
Directory of Open Access Journals (Sweden)
Bošeľa Michal
2014-06-01
Full Text Available Smrek je jednou z najrozšírenejších a ekonomicky najdôležitejších ihličnatých drevín v Európe. Taktiež je drevinou veľmi často poškodzovanou vetrovými kalamitami. Štíhlostný kvocient (pomer výšky a hrúbky stromu sa považuje za vhodný indikátor statickej stability jednotlivých stromov a porastov. Preto cieľom práce bola identifikácia hlavných faktorov, ktoré majú významný vplyv na hodnoty kvocientu. Jednoduchý model bol vytvorený ako pomôcka pre lesníka pri rozhodovaní o intenzite prebierok v smrekových porastoch s cieľom potenciálneho zvýšenia statickej stability a zachovania optimálnej produkcie. Využili sa údaje Národnej inventarizácie a monitoringu lesov SR (260 plôch a taktiež údaje z predchádzajúcich výskumných projektov (48 plôch tak aby reprezentovali čo najširšie rozpätie ekologických podmienok, v ktorých smrek v súčasnosti rastie. Výsledky ukázali, že najvýznamnejšími ekologickými faktormi boli: nadmorská výška a bonita stanovišťa. Taktiež niektoré porastové charakteristiky sa významne podieľali na variabilite kvocientu: podiel koruny z výšky stromu, hustota porastu a stredná porastová výška reprezentujúca rastovú fázu porastu. Výsledky ďalej preukázali, že ekologické podmienky sú významnejšie ako porastové charakteristiky, a preto tieto treba brať do úvahy pri rozhodovacom procese. To znamená, že ak sa porast nachádza na pre smrek veľmi bonitnom stanovišti, sú potrebné silnejšie prebierky od mladých rastových fáz, aby sa ovplyvňovaním hrúbkového prírastku vyrovnal vplyv rýchleho výškového rastu. Zároveň je dôležitá rozdielna intenzita výškového a hrúbkového rastu počas vývoja porastu
Dynamic Analysis of a Helicopter Rotor by Dymore Program
Doğan, Vedat; Kırca, Mesut
The dynamic behavior of hingeless and bearingless blades of a light commercial helicopter which has been under design process at ITU (İstanbul Technical University, Rotorcraft Research and Development Centre) is investigated. Since the helicopter rotor consists of several parts connected to each other by joints and hinges; rotors in general can be considered as an assembly of the rigid and elastic parts. Dynamics of rotor system in rotation is complicated due to coupling of elastic forces (bending, torsion and tension), inertial forces, control and aerodynamic forces on the rotor blades. In this study, the dynamic behavior of the rotor for a real helicopter design project is analyzed by using DYMORE. Blades are modeled as elastic beams, hub as a rigid body, torque tubes as rigid bodies, control links as rigid bodies plus springs and several joints. Geometric and material cross-sectional properties of blades (Stiffness-Matrix and Mass-Matrix) are calculated by using VABS programs on a CATIA model. Natural frequencies and natural modes of the rotating (and non-rotating) blades are obtained by using DYMORE. Fan-Plots which show the variation of the natural frequencies for different modes (Lead-Lag, Flapping, Feathering, etc.) vs. rotor RPM are presented.
Fuzzy control of attitude of four - rotor UAV
Zhang, Zexiang; Hu, Shengbin
2017-08-01
The four - rotor unmanned aerial vehicle (UAV) is the object of study, in this paper. In order to solve the problem of poor robustness and low control precision of the four-rotor unmanned aerial vehicle (UAV) control system, and realized the stability control problem of the four-rotor UAV attitude. First, the dynamic model of the four-rotor unmanned aerial vehicle is established. And on this basis, a fuzzy controller is designed, and used to control the channel. Then, the simulation platform is built by Matlab / Simulink simulation software, and the performance of the designed fuzzy controller is analyzed comprehensively. It is also determined whether the algorithm can control the attitude of the four rotor unmanned aerial vehicle. The simulation results fully verify the accuracy of the model, and proved fuzzy controller has better dynamic performance and robustness under appropriate parameters so that UAVs can fly stable. The algorithm can improve the anti-jamming performance and control accuracy of the system, it has a certain significance for the actual four-rotor aircraft attitude control.
Development of a Wind Turbine Rotor Flow Panel Method
Energy Technology Data Exchange (ETDEWEB)
Van Garrel, A. [ECN Wind Energy, Petten (Netherlands)
2011-12-15
The ongoing trend towards larger wind turbines intensifies the demand for more physically realistic wind turbine rotor aerodynamics models that can predict the detailed transient pressure loadings on the rotor blades better than current engineering models. In this report the mathematical, numerical, and practical aspects of a new wind turbine rotor flow simulation code is described. This wind turbine simulation code is designated ROTORFLOW. In this method the fluid dynamics problem is solved through a boundary integral equation which reduces the problem to the surface of the configuration. The derivation of the integral equations is described as well as the assumptions made to arrive at them starting with the full Navier-Stokes equations. The basic numerical aspects in the solution method are described and a verification study is performed to confirm the validity of the implementation. Example simulations with the code show the flow solutions for a stationary wing and for a rotating wing in yawed conditions. With the ROTORFLOW code developed in this project it is possible to simulate the unsteady flow around wind turbine rotors in yawed conditions and obtain detailed pressure distributions, and thus blade loadings, at the surface of the blades. General rotor blade geometries can be handled, opening the way to the detailed flow analysis of winglets, partial span flaps, swept blade tips, etc. The ROTORFLOW solver only requires a description of the rotor surface which keeps simulation preparation time short, and makes it feasible to use the solver in the design iteration process.
Numerical Study of Stratified Charge Combustion in Wave Rotors
Nalim, M. Razi
1997-01-01
A wave rotor may be used as a pressure-gain combustor effecting non-steady flow, and intermittent, confined combustion to enhance gas turbine engine performance. It will be more compact and probably lighter than an equivalent pressure-exchange wave rotor, yet will have similar thermodynamic and mechanical characteristics. Because the allowable turbine blade temperature limits overall fuel/air ratio to sub-flammable values, premixed stratification techniques are necessary to burn hydrocarbon fuels in small engines with compressor discharge temperature well below autoignition conditions. One-dimensional, unsteady numerical simulations of stratified-charge combustion are performed using an eddy-diffusivity turbulence model and a simple reaction model incorporating a flammability limit temperature. For good combustion efficiency, a stratification strategy is developed which concentrates fuel at the leading and trailing edges of the inlet port. Rotor and exhaust temperature profiles and performance predictions are presented at three representative operating conditions of the engine: full design load, 40% load, and idle. The results indicate that peak local gas temperatures will result in excessive temperatures within the rotor housing unless additional cooling methods are used. The rotor itself will have acceptable temperatures, but the pattern factor presented to the turbine may be of concern, depending on exhaust duct design and duct-rotor interaction.
Balancing of machinery with a flexible variable-speed rotor
Sève, F.; Andrianoely, M. A.; Berlioz, A.; Dufour, R.; Charreyron, M.
2003-07-01
The balancing procedure of machines composed of a flexible rotating part (rotor) and a non-rotating part (stator) mounted on suspensions is presented. The rotating part runs at a variable speed of rotation and is mounted on bearings with variable-speed-dependent characteristics. Assuming that the unbalance masses are relatively well defined, such as in the case of a crank-shaft, the procedure is based on a numerical approach using rotordynamics theory coupled with the Finite Element and Influence Coefficient Methods. An academic rotor/stator model illustrates the procedure. Moreover, the industrial application concerns a refrigerant rotary compressor whose experimental investigation permits validating the model. Assuming that the balancing planes are located on the rotor, it is shown that reducing the vibration level of both rotor and stator requires a balancing procedure using target planes on the rotor and on the stator. In the case of the rotary compressor, this avoids rotor-to-stator rubs and minimizes vibration transmission through pipes and grommets.
Li, Yan-qiong; Deng, Xiang-wen; Huang, Zhi-hong; Xiang, Wen-hua; Yan, Wen-de; Lei, Pi-feng; Zhou, Xiao-lu; Peng, Chang-hui
2015-01-01
Tree diameter at breast height (dbh) and height are the most important variables used in forest inventory and management as well as forest carbon-stock estimation. In order to identify the key stand variables that influence the tree height-dbh relationship and to develop and validate a suit of models for predicting tree height, data from 5961 tree samples aged from 6 years to 53 years and collected from 80 Chinese-fir plantation plots were used to fit 39 models, including 33 nonlinear models and 6 linear models, were developed and evaluated into two groups. The results showed that composite models performed better in height estimate than one-independent-variable models. Nonlinear composite Model 34 and linear composite Model 6 were recommended for predicting tree height in Chinese fir plantations with a dbh range between 4 cm and 40 cm when the dbh data for each tree and the quadratic mean dbh of the stand (Dq) and mean height of the stand (Hm) were available. Moreover, Hm could be estimated by using the formula Hm = 11.707 × l n(Dq)-18.032. Clearly, Dq was the primary stand variable that influenced the height-dbh relationship. The parameters of the models varied according to stand age and site. The inappropriate application of provincial or regional height-dbh models for predicting small tree height at local scale may result in larger uncertainties. The method and the recommended models developed in this study were statistically reliable for applications in growth and yield estimation for even-aged Chinese-fir plantation in Huitong and Changsha. The models could be extended to other regions and to other tree species only after verification in subtropical China.
Rotor blade assembly having internal loading features
Energy Technology Data Exchange (ETDEWEB)
Soloway, Daniel David
2017-05-16
Rotor blade assemblies and wind turbines are provided. A rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge and a trailing edge each extending between a tip and a root, the rotor blade defining a span and a chord, the exterior surfaces defining an interior of the rotor blade. The rotor blade assembly further includes a loading assembly, the loading assembly including a weight disposed within the interior and movable generally along the span of the rotor blade, the weight connected to a rotor blade component such that movement of the weight towards the tip causes application of a force to the rotor blade component by the weight. Centrifugal force due to rotation of the rotor blade biases the weight towards the tip.
Mach number scaling of helicopter rotor blade/vortex interaction noise
Leighton, Kenneth P.; Harris, Wesley L.
1985-01-01
A parametric study of model helicopter rotor blade slap due to blade vortex interaction (BVI) was conducted in a 5 by 7.5-foot anechoic wind tunnel using model helicopter rotors with two, three, and four blades. The results were compared with a previously developed Mach number scaling theory. Three- and four-bladed rotor configurations were found to show very good agreement with the Mach number to the sixth power law for all conditions tested. A reduction of conditions for which BVI blade slap is detected was observed for three-bladed rotors when compared to the two-bladed baseline. The advance ratio boundaries of the four-bladed rotor exhibited an angular dependence not present for the two-bladed configuration. The upper limits for the advance ratio boundaries of the four-bladed rotors increased with increasing rotational speed.
APPLICATION OF WAVELET TIME-FR EQUENCY ANALYSIS TO IDENTIFICATION OF CRACKED ROTOR
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Based on the simple hinge crack model and the local flexibility theorem, the corresponding dynamic equation of the cracked rotor is modelled, the numerical simulation solutions of the cracked rotor and the uncracked rotor are obtained. By the continuous wavelet time-frequency transform, the wavelet time-frequency properties of the uncracked rotor and the cracked rotor are discussed. A new detection algorithm that uses the wavelet time-frequency transform to identify the crack is proposed. The influence of the sampling frequency on the wavelet time-frequency transform is analyzed by the numerical simulation research. The valid sampling frequency is suggested. Experiments demonstrate the validity and availability of the proposed algorithm in identification of the cracked rotor for engineering practices.
Dynamic Characteristics of Flow Induced Vibration in a Rotor-Seal System
Directory of Open Access Journals (Sweden)
Nan Zhang
2011-01-01
Full Text Available Flow induced vibration is an important factor affecting the performance of the rotor-seal system. From the point of view of flow induced vibration, the nonlinear models of the rotor-seal system are presented for the analysis of the fluid force, which is induced by the interaction between the unstable fluid flow in the seal and the vibrating rotor. The nonlinear characteristics of flow induced vibration in the rotor-seal system are analyzed, and the nonlinear phenomena in the unbalanced rotor-seal system are investigated using the nonlinear models. Various nonlinear phenomena of flow induced vibration in the rotor-seal system, such as synchronization phenomenon and amplitude mutation, are reproduced.
Jahandar Lashaki, Masoud; Fayaz, Mohammadreza; Niknaddaf, Saeid; Hashisho, Zaher
2012-11-30
This paper investigates the effect of the kinetic diameter (KD) of the reference adsorbate on the accuracy of the Dubinin-Radushkevich (D-R) equation for predicting the adsorption isotherms of organic vapors on microporous activated carbon. Adsorption isotherms for 13 organic compounds on microporous beaded activated carbon were experimentally measured, and predicted using the D-R model and affinity coefficients. The affinity coefficients calculated based on molar volumes, molecular polarizabilities, and molecular parachors were used to predict the isotherms based on four reference compounds (4.3≤KD≤6.8 Å). The results show that the affinity coefficients are independent of the calculation method if the reference and test adsorbates are from the same organic group. Choosing a reference adsorbate with a KD similar to that of the test adsorbate results in better prediction of the adsorption isotherm. The relative error between the predicted and the measured adsorption isotherms increases as the absolute difference in the kinetic diameters of the reference and test adsorbates increases. Finally, the proposed hypothesis was used to explain reports of inconsistent findings among published articles. The results from this study are important because they allow a more accurate prediction of adsorption capacities of adsorbents which allow for better design of adsorption systems.
Aerodynamic design of the National Rotor Testbed.
Energy Technology Data Exchange (ETDEWEB)
Kelley, Christopher Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-10-01
A new wind turbine blade has been designed for the National Rotor Testbed (NRT) project and for future experiments at the Scaled Wind Farm Technology (SWiFT) facility with a specific focus on scaled wakes. This report shows the aerodynamic design of new blades that can produce a wake that has similitude to utility scale blades despite the difference in size and location in the atmospheric boundary layer. Dimensionless quantities circulation, induction, thrust coefficient, and tip-speed-ratio were kept equal between rotor scales in region 2 of operation. The new NRT design matched the aerodynamic quantities of the most common wind turbine in the United States, the GE 1.5sle turbine with 37c model blades. The NRT blade design is presented along with its performance subject to the winds at SWiFT. The design requirements determined by the SWiFT experimental test campaign are shown to be met.
Dynamic Characteristics and Experimental Research of Dual-Rotor System with Rub-Impact Fault
Directory of Open Access Journals (Sweden)
Hongzhi Xu
2016-01-01
Full Text Available Rub-impact fault model for dual-rotor system was further developed, in which rubbing board is regarded as elastic sheet. Sheet elastic deformation, contact penetration, and elastic damping support during rubbing of sheet and wheel disk were considered. Collision force and friction were calculated by utilizing Hertz contact theory and Coulomb model and introducing nonlinear spring damping model and friction coefficient. Then kinetic differential equations of rub-impact under dry rubbing condition were established. Based on one-dimensional finite element model of dual-rotor system, dynamic transient response of overall structure under rub-impact existing between rotor wheel and sheet was obtained. Meanwhile, fault dynamic characteristics and impact of rubbing clearance on rotor vibration were analyzed. The results show that, during the process of rub-impact, the spectrums of rotor vibration are complicated and multiple combined frequency components of inner and outer rotor fundamental frequencies are typical characteristic of rub-impact fault for dual-rotor system. It also can be seen from rotor vibration response that the rubbing rotor’s fundamental frequency is modulated by normal rotor double frequency.
A study of EV induction motor controller based on rotor flux oriented control
Institute of Scientific and Technical Information of China (English)
Song Jianguo; Chen Quanshi
2006-01-01
Induction motor is a multi-parameter, non-linear and strong coupling system, which requires efficient control algorithms. In this paper, rotor flux oriented control (FOC) algorithm based on voltage source inverter-fed is deduced in detail, including stator voltage compensation, closed-loop PI parameters' calculation of torque and rotor flux. FOC's Simulink model is setup to simulate torque and rotor flux's response. At last, the experimental results are shown.
Rotor-stator contact dynamics using a non-ideal drive—Theoretical and experimental aspects
Lahriri, Said; Weber, Hans I.; Santos, Ilmar F.; Hartmann, Henning
2012-09-01
The possible contact between rotor and stator is considered a serious malfunction that may lead to catastrophic failure. Rotor rub is seen as a secondary phenomenon caused by a primary source, i.e. sudden mass unbalance, instabilities generated by aerodynamic and hydrodynamic forces in seals and bearings among others. The contact event gives rise to normal and friction forces exerted on the rotor at impact events. The friction force plays a significant role by transferring some rotational energy of the rotor to lateral motion. A mathematical model has been developed to capture this for a conventional backup annular guide setup. It is reasonable to superpose an impact condition to the rub, where the rotor spin energy can be fully transformed into rotor lateral movements. Using a nonideal drive, i.e. an electric motor without any kind of velocity feedback control, it is even possible to stop the rotor spin under rubbing conditions. All the rotational energy will be transformed in a kind of "self-excited" rotor lateral vibration with repeated impacts against the housing. This paper studies the impact motion of a rotor impacting a conventional backup annular guide for the case of dry and lubricated inner surface of the guide. For the dry surface case, the experimental and numerical analysis shows that the rotational energy is fully transformed into lateral motion and the rotor spin is stopped. Based on this study this paper proposes a new unconventional backup bearing design in order to reduce the rub related severity in friction and center the rotor at impact events. The analysis shows that the rotor at impacts is forced to the center of the backup bearing and the lateral motion is mitigated. As a result of this, the rotor spin is kept constant.
Woodward, R. P.; Lucas, J. G.; Balombin, J. R.
1977-01-01
The fan was externally driven by an electric motor. Design features for low-noise generation included the elimination of inlet guide vanes, long axial spacing between the rotor and stator blade rows, and the selection of blade-vane numbers to achieve duct-mode cutoff. The fan QF-2 results were compared with those of another full-scale fan having essentially identical aerodynamic design except for nozzle geometry and the direction of rotation. The fan QF-2 aerodynamic results were also compared with those obtained from a 50.8 cm rotor-tip-diameter model of the reverse rotation fan QF-2 design. Differences in nozzle geometry other than exit area significantly affected the comparison of the results of the full-scale fans.
Model of open rotor engine for aircraft conceptual design%面向飞机总体设计的开式转子发动机分析模型
Institute of Scientific and Technical Information of China (English)
张帅; 余雄庆
2012-01-01
A rapid analysis model of the open rotor engine, which can be used in aircraft conceptual design, was established by the combination of the test data of high speed propfan and approximate model of turboshaft. The performance, mass and size of the open rotor en- gine were able to be predicted quickly by this model with a small amount of input parame- ters. The precision of the model was validated by the experimental data from the references. The model developed in the paper can be used in the aircraft conceptual design to evaluate the benefits of using open rotor engines.%应用高速桨扇试验数据与涡轴核心机估算模型相结合的方法，建立了一种快速的、能用于飞机总体方案论证阶段的开式转子发动机分析模型．它使用少量的总体参数即可估算出开式转子发动机推力与耗油率特性、质量和外形尺寸，计算速度快．通过对比模型的估算结果与文献的试验数据，证明其精度能够满足飞机总体初步方案论证的要求，可用于评估采用开式转子发动机带来的收益．
Mahoney, John J; Dugan, Paul D; Budinger, Raymond E; Goelzer, H Fred
1950-01-01
A 30-inch tip-diameter axial-flow compressor stage was investigated with and without rotor to determine individual blade-row performance, interblade-row effects, and outer-wall boundary-layer conditions. Velocity gradients at guide-vane outlet without rotor approximated design assumptions, when the measured variation of leaving angle was considered. With rotor in operation, Mach number and rotor-blade effects changed flow distribution leaving guide vanes and invalidated design assumption of radial equilibrium. Rotor-blade performance correlated interpolated two-dimensional results within 2 degrees, although tip stall was indicated in experimental and not two-dimensional results. Boundary-displacement thickness was less than 1.0 and 1.5 percent of passage height after guide vanes and after rotor, respectively, but increased rapidly after rotor when tip stall occurred.
Feedback Control of Rotor Overspeed
Churchill, G. B.
1984-01-01
Feedback system for automatically governing helicopter rotor speed promises to lessen pilot's workload, enhance maneuverability, and protect airframe. With suitable modifications, concept applied to control speed of electrical generators, automotive engines and other machinery.
Design of composite flywheel rotor
Institute of Scientific and Technical Information of China (English)
Yue BAI; Qingjia GAO; Haiwen LI; Yihui WU; Ming XUAN
2008-01-01
A design method for a flywheel rotor com-posed of a composite rim and a metal hub is proposed by studying the connection between the rotor and the driving machine. The influence of some factors such as the rotor material, configuration, connection, and frac-ture techniques on energy density is analyzed. The results show that the ratio of the inner radius to outer radius of the rim is the key factor, and is determined by the rim material. Optimizing the hub can further efficiently improve energy density. The composite flywheel rotor is produced and its rotation stress has been tested at the speed of 20 krpm. The emulation results are consistent with testing results, which proves that the introduced design method is useful.
Saxena, Anand
The focus of this research was to demonstrate a four blade rotor trim in forward flight using integrated trailing edge flaps instead of using a swashplate controls. A compact brushless DC motor was evaluated as an on-blade actuator, with the possibility of achieving large trailing edge flap amplitudes. A control strategy to actuate the trailing edge flap at desired frequency and amplitude was developed and large trailing edge flap amplitudes from the motor (instead of rotational motion) were obtained. Once the actuator was tested on the bench-top, a lightweight mechanism was designed to incorporate the motor in the blade and actuate the trailing edge flaps. A six feet diameter, four bladed composite rotor with motor-flap system integrated into the NACA 0012 airfoil section was fabricated. Systematic testing was carried out for a range of load conditions, first in the vacuum chamber followed by hover tests. Large trailing edge flap deflections were observed during the hover testing, and a peak to peak trailing edge flap amplitude of 18 degree was achieved at 2000 rotor RPM with hover tip Mach number of 0.628. A closed loop controller was designed to demonstrate trailing edge flap mean position and the peak to peak amplitude control. Further, a soft pitch link was designed and fabricated, to replace the stiff pitch link and thereby reduce the torsional stiffness of the blade to 2/rev. This soft pitch link allowed for blade root pitch motion in response to the trailing edge flap inputs. Blade pitch response due to both steady as well as sinusoidal flap deflections were demonstrated. Finally, tests were performed in Glenn L. Martin wind tunnel using a model rotor rig to assess the performance of motor-flap system in forward flight. A swashplateless trim using brushless DC motor actuated trailing edge flaps was achieved for a rotor operating at 1200 RPM and an advance ratio of 0.28. Also, preliminary exploration was carried out to test the scalability of the motor
Directory of Open Access Journals (Sweden)
Ramírez-Argáez, M. A.
2006-06-01
Full Text Available In this work a fundamental Eulerian mathematical model was developed to study fluid flow and mixing phenomena in aluminum ladles equipped with impeller for deshidrogenization treatment. The effect of critical process parameters such as rotor speed, depth of immersion, gas flow rate, and type of rotor on the mixing behavior and vortex formation was analyzed with this model. The model simulates operation with and without gas injection and it was developed on the commercial CFD code PHOENICS 3.4 in order to solve all conservation equations governing the process, i.e. continuity, 3D turbulent Navier-Stokes and the k-e turbulence model for a two-phase fluid flow problem using the Inter Phase Slip Algorithm (IPSA. In order to realistically represent the process, shape of the furnace and three kinds of impellers were drawn by employing Body Fitted Coordinates (BFC. From the results it was concluded that mixing behavior is highly dependent on the rotor speed and on the rotor type. Mixing time is improved when: 1 Impeller is located at a depth of 0.229m into the aluminum bath, 2 By using high rotor speeds, 3 By using ladles with a high aspect ratio of Diameter to Height, and 4By using an impeller with notches.
Se desarrolló un modelo matemático Euleriano para analizar el flujo de fluidos y el mezclado en ollas (cucharas de tratamiento de aluminio equipadas con rotor-inyector, variando parámetros del proceso como la velocidad de giro del rotor, la distancia de inmersión de la flecha, el flujo de gas, el tipo de rotor y el factor de forma de la olla (cuchara (relación altura/diámetro. El modelo matemático simula la operación, con y sin inyección de gas, a través del rotor, empleando el código comercial PHOENICS donde se resolvieron las ecuaciones de continuidad, momento, especies químicas y turbulencia, k-e, de forma simultánea, tanto para la fase líquida como para la gaseosa. El dominio se dibujó, realistamente, empleando coordenadas
Energy Technology Data Exchange (ETDEWEB)
Paquette, J. A.
2012-03-01
Sandia National Laboratories (SNL) and Verdant Power Inc. (VPI) have partnered under a Cooperative Research and Development Agreement (CRADA) to develop a new kinetic hydropower rotor. The rotor features an improved hydrodynamic and structural design which features state-of-the-art technology developed for the wind industry. The new rotor will have higher energy capture, increased system reliability, and reduction of overall cost of energy. This project was divided into six tasks: (1) Composite Rotor Project Planning and Design Specification; (2) Baseline Fatigue Testing and Failure analysis; (3) Develop Blade/Rotor Performance Model; (4) Hydrofoil Survey and Selection; (5) FEM Structural Design; and (6) Develop Candidate Rotor Designs and Prepare Final Report.
A New Soft Starting Method for Wound-Rotor Induction Motor
Sharifian, Mohammad Bagher Bannae; Feyzi, Mohammad Reza; Sabahi, Mehran; Farrokhifar, Meysam
2011-01-01
Starting of a three-phase Induction motor using a starter rheostat in rotor circuit has some disadvantages. A new method for starting of a three-phase motor by using a parallel combination of resistors, self-inductors and capacitors in rotor circuit is proposed in this paper. The proposed method ensures the soft and higher starting torque as well as limited starting current as compared to shorted rotor method. The characteristic curves for both methods (shorted rotor and rotor with added elements) are provided. The mathematical model based on the steady-state equivalent circuit of the induction motor is expanded in frequency domain and the required computer program is prepared using an optimization method. The values for added elements to rotor circuit are calculated in such a way that minimum starting time considering current and torque limitations are achieved.
Efficiency of operation of wind turbine rotors optimized by the Glauert and Betz methods
Okulov, V. L.; Mikkelsen, R.; Litvinov, I. V.; Naumov, I. V.
2015-11-01
The models of two types of rotors with blades constructed using different optimization methods are compared experimentally. In the first case, the Glauert optimization by the pulsed method is used, which is applied independently for each individual blade cross section. This method remains the main approach in designing rotors of various duties. The construction of the other rotor is based on the Betz idea about optimization of rotors by determining a special distribution of circulation over the blade, which ensures the helical structure of the wake behind the rotor. It is established for the first time as a result of direct experimental comparison that the rotor constructed using the Betz method makes it possible to extract more kinetic energy from the homogeneous incoming flow.
Performance of Double-step Savonius Rotor for Environmentally Friendly Hydraulic Turbine
Nakajima, Miyoshi; Iio, Shouichiro; Ikeda, Toshihiko
The aim of this investigation is to develop an environmentally friendly nano-hydraulic turbine. Three type models of Savonius rotor are constructed and tested in a water tunnel to improve and clarify the power performance. Flow field around the rotor is examined visually to reveal the enhancement mechanisms of power coefficient using the double-step rotor. Flow visualization showed the difference of flow patterns at the central section between the standard (single-step) rotor and the double-step one. A meandering flow in the axial direction of the rotor was observed only for the double-step rotor. This flow had the pressure restoration effect at the returning blade's concave side and the torque strengthened effect at the advancing blade's convex side. As a consequence, the power coefficient was 10% improved.
Directory of Open Access Journals (Sweden)
Jingwei Cai
2016-01-01
Full Text Available For large-diameter, cast-in-place concrete piles, the end bearing capacity of a single pile is affected by discontinuous surfaces that exist in natural rock masses when the bearing layer of the pile end is located in the rock layer. In order to study the influence of the jointed dip angle on the bearing characteristics of the pile end, the discrete element models are adopted to simulate the mechanical characteristics of the jointed rock masses, and the model tests of the failure mode of the jointed rock masses were also designed. The results of the numerical calculations and modeling tests show that the joints, which have a filtering effect on the internal stress of the bedrock located at the pile end, change the load transferring paths. And the failure mode of the jointed rock foundation also changes as jointed dip angle changes. The rock located at the pile end generally presents a wedge failure mode. In addition, the Q-S curves obtained by model tests show that the ultimate end bearing capacity of a single pile is influenced by the jointed dip angle. The above results provide an important theoretical basis for how to correctly calculate end resistance for a cast-in-place concrete pile.
Directory of Open Access Journals (Sweden)
B. Hribar-Lee
2013-01-01
Full Text Available Very recently the effect of equisized charged hard sphere solutes in a mixture with core-softened fluid model on the structural and thermodynamic anomalies of the system has been explored in detail by using Monte Carlo simulations and integral equations theory (J. Chem. Phys., Vol. 137, 244502 (2012. Our objective of the present short work is to complement this study by considering univalent ions of unequal diameters in a mixture with the same soft-core fluid model. Specifically, we are interested in the analysis of changes of the temperature of maximum density (TMD lines with ion concentration for three model salt solutes, namely sodium chloride, potassium chloride and rubidium chloride models. We resort to Monte Carlo simulations for this purpose. Our discussion also involves the dependences of the pair contribution to excess entropy and of constant volume heat capacity on the temperature of maximum density line. Some examples of the microscopic structure of mixtures in question in terms of pair distributions functions are given in addition.
König, S.; Suriyah, M. R.; Leibfried, T.
2015-05-01
Model based design and optimization of large scale vanadium redox flow batteries can help to decrease system costs and to increase system efficiency. System complexity, e.g. the combination of hydraulic and electric circuits requires a multi-physic modeling approach to cover all dependencies between subsystems. A Matlab/Simulink model is introduced, which covers a variable number of stacks and their hydraulic circuit, as well as the impact of shunt currents. Using analytic approaches that are afterward crosschecked with the developed model, a six-stack, 54 kW/216 kWh system is designed. With the simulation results it is demonstrated how combining stacks to strings and varying pipe diameters affects system efficiency. As cell voltage is comparatively low, connecting stacks in series to strings seems reasonable to facilitate grid connection. It is shown that this significantly lowers system efficiency. Hydraulic circuit design is varied to lower efficiency drop. In total, four different electric designs are equipped with 21 hydraulic design variations to quantify dependencies between electric and hydraulic subsystems. Furthermore, it is examined whether additional shunt current losses through stack series connection can be compensated by more efficient energy conversion systems.
Institute of Scientific and Technical Information of China (English)
王铁成; 李伟力; 孙建伟
2003-01-01
A mathematical model has been built up for compound cage rotor induction machine with the rotor re-sistance and leakage inductance in the model identified through Kalman filtering method. Using the identifiedparameters, simulation studies are performed, and simulation results are compared with testing results.
Rothberg, Steve J.; Halkon, Ben J.; Tirabassi, Mario; Pusey, Chris
2012-11-01
Laser Doppler vibrometry (LDV) offers an attractive solution when radial vibration measurement directly from a rotor surface is required. Research to date has demonstrated application on polished-circular rotors and rotors coated with retro-reflective tape. In the latter case, however, a significant cross-sensitivity to the orthogonal radial vibration component occurs and post-processing is required to resolve individual radial vibration components. Until now, the fundamentally different behaviour observed between these cases has stood as an inconsistency in the published literature, symptomatic of the need to understand the effect of surface roughness. This paper offers the first consistent mathematical description of the polished-circular and rough rotor behaviours, combined with an experimental investigation of the relationship between surface roughness and cross-sensitivity. Rotors with surface roughness up to 10 nm satisfy the polished-circular rotor definition if vibration displacement is below 100% beam diameter, for a 90 μm beam, and below 40% beam diameter, for a 520 μm beam. On rotors with roughness between 10 nm and 50 nm, the polished-circular rotor definition is satisfied for vibration displacements up to 25% beam diameter, for a 90 μm beam, and up to 10% beam diameter, for a 520 μm beam. As roughness increases, cross-sensitivity increases but only rotors coated in retro-reflective tape satisfied the rough rotor definition fully. Consequently, when polished-circular surfaces are not available, rotor surfaces must be treated with retro-reflective tape and measurements post-processed to resolve individual vibration components. Through simulations, the value of the resolution and correction algorithms that form the post-processor has been demonstrated quantitatively. Simulations incorporating representative instrument misalignments and measurement noise have enabled quantification of likely error levels in radial vibration measurements. On a polished
An investigation of rotor tip leakage flows in the rear-block of a multistage compressor
Brossman, John Richard
An effective method to improve gas turbine propulsive efficiency is to increase the bypass ratio. With fan diameter reaching a practical limit, increases in bypass ratio can be obtained from reduced core engine size. Decreasing the engine core, results in small, high pressure compressor blading, and large relative tip clearances. At general rule of 1% reduction in compressor efficiency with a 1% increase in tip clearance, a 0.66% change in SFC indicates the entire engine is sensitive to high pressure compressor tip leakage flows. Therefore, further investigations and understanding of the rotor tip leakage flows can help to improve gas turbine engine efficiency. The objectives of this research were to investigate tip leakage flows through computational modeling, examine the baseline experimental steady-stage performance, and acquire unsteady static pressure, over-the rotor to observe the tip leakage flow structure. While tip leakage flows have been investigated in the past, there have been no facilities capable of matching engine representative Reynolds number and Mach number while maintaining blade row interactions, presenting a unique and original flow field to investigate at the Purdue 3-stage axial compressor facility. To aid the design of experimental hardware and determine the influence of clearance geometry on compressor performance, a computational model of the Purdue 3-stage compressor was investigated using a steady RANS CFD analysis. A cropped rotor and casing recess design was investigated to increase the rotor tip clearance. While there were small performance differences between the geometries, the tip leakage flow field was found independent of the design therefore designing future experimental hardware around a casing recess is valid. The largest clearance with flow margin past the design point was 4% tip clearance based on the computational model. The Purdue 3-stage axial compressor facility was rebuilt and setup for high quality, detailed flow
Directory of Open Access Journals (Sweden)
Wu Zaixin
2016-01-01
Full Text Available High-speed motorized spindle is a multi-variable, non-linear and strong coupling system. The rotor static eccentricity is inevitable because of machining or assembling error. The rotor static eccentricities have an important effect on the electromechanical coupled characteristics of the motorized spindle. In this paper, the electromechanical coupled mathematical model of the motorized spindle was set up. The mathematical model includes mechanical and electrical equation. The mechanical and electrical equation is built up by the variational principle. Furthermore, the inductance parameters without the rotor static eccentricity and the inductance parameters with rotor static eccentricity have been calculated by the winding function method and the high speed motorized spindle was simulated. The result show that the rotor static eccentricity can delay the starting process of the motorized spindle, and at steady state, the rotor circuit currents are still large because of the rotor static eccentricity.
Ashbaugh, Fred N.; Murry, Kenneth R.
1988-12-27
A boring tool and a method of operation are provided for boring two concentric holes of precision diameters and depths in a single operation. The boring tool includes an elongated tool body, a shank for attachment to a standard adjustable boring head which is used on a manual or numerical control milling machine and first and second diametrically opposed cutting edges formed for cutting in opposite directions. The diameter of the elongated tool body is substantially equal to the distance from the first cutting edge tip to the axis of rotation plus the distance from the second cutting edge tip to the axis of rotation. The axis of rotation of the tool is spaced from the tool centerline a distance substantially equal to one-half the distance from the second cutting edge tip to the axis of rotation minus one-half the distance from the first cutting edge tip to the axis of rotation. The method includes the step of inserting the boring tool into the boring head, adjusting the distance between the tool centerline and the tool axis of rotation as described above and boring the two concentric holes.
Control of Magnetic Bearings for Rotor Unbalance With Plug-In Time-Varying Resonators.
Kang, Christopher; Tsao, Tsu-Chin
2016-01-01
Rotor unbalance, common phenomenon of rotational systems, manifests itself as a periodic disturbance synchronized with the rotor's angular velocity. In active magnetic bearing (AMB) systems, feedback control is required to stabilize the open-loop unstable electromagnetic levitation. Further, feedback action can be added to suppress the repeatable runout but maintain closed-loop stability. In this paper, a plug-in time-varying resonator is designed by inverting cascaded notch filters. This formulation allows flexibility in designing the internal model for appropriate disturbance rejection. The plug-in structure ensures that stability can be maintained for varying rotor speeds. Experimental results of an AMB-rotor system are presented.
Jet engine performance enhancement through use of a wave-rotor topping cycle
Wilson, Jack; Paxson, Daniel E.
1993-01-01
A simple model is used to calculate the thermal efficiency and specific power of simple jet engines and jet engines with a wave-rotor topping cycle. The performance of the wave rotor is based on measurements from a previous experiment. Applied to the case of an aircraft flying at Mach 0.8, the calculations show that an engine with a wave rotor topping cycle may have gains in thermal efficiency of approximately 1 to 2 percent and gains in specific power of approximately 10 to 16 percent over a simple jet engine with the same overall compression ratio. Even greater gains are possible if the wave rotor's performance can be improved.
Design Considerations for a Stopped-Rotor Cyclocopter for Venus Exploration
Husseyin, S.; Warmbrodt, William G.
2016-01-01
This paper considers the use of a cycloidal blade system as a means of providing lift and propulsive thrust as well as combined with a stopped rotor system, to create a stopped-rotor cyclocopter vehicle, during a mission to Venus. This stopped-rotor cyclocopter will be capable of flying at all atmospheric levels of Venus as well as landing on the surface for scientific investigation. Three reference conceptual designs with different stopped-rotor cyclocopter yaw angles are tested in RotCFD as well as a model of a hovering cyclorotor for comparison with past work in the literature and innovative study for future projects.
NUMERICAL AND EXSPERIMENTAL ASPECTS OF THERMALLY INDUCED VIBRATION IN REAL ROTORS
Directory of Open Access Journals (Sweden)
Milenko B Jevtić
2011-01-01
Full Text Available Temperature fields in electric energy generators may lead to mechanical dissbalance of an already balanced rotor. The author collected information in a number of steam power plants and confirmed the existence of the problem. This paper is presents the specific case of thermal deformation of the rotor, caused by an asymmetrical temperature field in scale of rotor. On the grounds of the relevant physical aspects, we propose a mathematical model identifying fields in a turbo generator rotor and suggest the optimum control by which the unwanted effects are eliminated.
Hoad, D. R.
1979-01-01
The effect of tip-shape modification on blade-vortex interaction-induced helicopter blade-slap noise was investigated. The general rotor model system (GRMS) with a 3.148 m (10.33 ft) diameter, four-bladed fully articulated rotor was installed in the Langley V/STOL wind tunnel. The tunnel was operated in the open-throat configuration with treatment to improve the semi-anechoic characteristics of the test chamber. Based on previous investigation, four promising tips (ogee, sub-wing, 60 deg swept-tapered, and end-plate) were used along with a standard square tip as a baseline configuration. Aerodynamic and acoustical data concerning the relative applicability of the various tip configurations for blade-slap noise reduction are presented without analysis or discussion.
Development of a 32 Inch Diameter Levitated Ducted Fan Conceptual Design
Eichenberg, Dennis J.; Gallo, Christopher a.; Solano, Paul A.; Thompson, William K.; Vrnak, Daniel R.
2006-01-01
The NASA John H. Glenn Research Center has developed a revolutionary 32 in. diameter Levitated Ducted Fan (LDF) conceptual design. The objective of this work is to develop a viable non-contact propulsion system utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels, and mitigate many of the concerns and limitations encountered in conventional aircraft propulsors. The physical layout consists of a ducted fan drum rotor with blades attached at the outer diameter and supported by a stress tuner ring at the inner diameter. The rotor is contained within a stator. This concept exploits the unique physical dimensions and large available surface area to optimize a custom, integrated, electromagnetic system that provides both the levitation and propulsion functions. The rotor is driven by modulated electromagnetic fields between the rotor and the stator. When set in motion, the time varying magnetic fields interact with passive coils in the stator assembly to produce repulsive forces between the stator and the rotor providing magnetic suspension. LDF can provide significant improvements in aviation efficiency, reliability, and safety, and has potential application in ultra-efficient motors, computers, and space power systems.
Jin, Qiuxue; Liu, Bo; Liu, Yan; Wang, Heng; Xu, Zhen; Gao, Dan; Wang, Qing; Xia, Yangyang; Wang, Weiwei; Song, Zhitang; Feng, Songlin
2016-10-01
A three-dimensional finite element model for Phase-Change Random Access Memory (PCRAM) is established to simulate thermal and electrical distribution during RESET operation. The establishment of the model is highly in accordance with the manufacture of PCRAM cell in the 40nm process and the model is applied to simulate the RESET behaviors of 35 nm diameter of titanium nitride (TiN) bottom electrode in the conventional mushroom structure (MS). By the simulations of thermal and electrical distribution, the highest temperature is observed in TiN bottom electrode contactor and meanwhile the voltage of the TiN bottom electrode accounts for as high as 65 percent of the total voltage. It induces high RESET current which suggests that the thermoelectric conductivity of MS is crucial in improving the heating efficiency in RESET process. Simulation results of RESET current and high resistance distribution during RESET operation are close to the data from the actual measurement. However those two values of low resistance are slightly different, probably due to the interface resistance between Ge2Sb2Te5 (GST) and other materials and the resistance caused by microstructural defects. This work reveals the importance of the thermoelectrical properties of materials in PCRAM cells and improves the quality of PCRAM simulations in industrial application.
Control of flexible rotor systems with active magnetic bearings
Lei, Shuliang; Palazzolo, Alan
2008-07-01
An approach is presented for the analysis and design of magnetic suspension systems with large flexible rotordynamics models including dynamics, control, and simulation. The objective is to formulate and synthesize a large-order, flexible shaft rotordynamics model for a flywheel supported with magnetic bearings. A finite element model of the rotor system is assembled and then employed to develop a magnetic suspension compensator to provide good reliability and disturbance rejection. Stable operation over the complete speed range and optimization of the closed-loop rotordynamic properties are obtained via synthesis of eigenvalue analysis, Campbell plots, waterfall plots, and mode shapes. The large order of the rotor model and high spin speed of the rotor present a challenge for magnetic suspension control. A flywheel system is studied as an example for realizing a physical controller that provides stable rotor suspension and good disturbance rejection in all operating states. The baseline flywheel system control is determined from extensive rotordynamics synthesis and analysis for rotor critical speeds, mode shapes, frequency responses, and time responses.
Dynamics of the interaction between the rotor and the induction zone
Mirzaei, Mahmood; Meyer Forsting, Alexander R.; Troldborg, Niels
2016-09-01
Traditionally met masts are used for power and load verifications. They are normally placed 2-4 rotor diameters ahead of the turbine. However in complex terrain this can lead to complex analysis of the effect of the terrain on the flow field. A nacelle mounted lidar can provide a better tool for wind field measurements in all terrains. Provided that the measurement is close enough to the rotor disc, the uncertainty in the flow field measurement can be reduced significantly. Therefore any complex terrain calibration and changes in the wind direction can be avoided. However, close distance lidar measurements are affected by the presence of the wind turbine, due to its induction zone. In this work, the dynamic coupling between changes in the wind turbine operating point and the velocities inside the induction zone is studied. Reynolds-Averaged Navier-Stokes (RANS) simulations are used to investigate this interaction. Thereafter, system identification is used to fit first order dynamic models to the simulation results. The parameters of the model are given for the turbine induction zone. These results possibly reduce the uncertainty in lidar measurements, arising from wind turbine blockage.
MODELING AND SIMULATION OF WIND ROTOR FOR VARIABLE SPEED AND PITCH WIND TURBINE%大型变速变桨距风机风轮的建模与仿真
Institute of Scientific and Technical Information of China (English)
宁祎; 李红刚; 李富生; 陶学军; 周伟
2012-01-01
针对风机实验建模的复杂性、得到结果的长期性和结论应用的局限性,提出在叶素-动量理论基础上利用Schmitz理论建立变桨风机气动性能模型的方案.该模型考虑了叶尖损失、轮毂损失、翼型厚度和宽度的影响,同时也考虑了风机在启动时风的实度和空载时的圆盘效应；考虑了在风轮结构参数的基础上坐标变换后偏航和风剪切的影响,并根据不同叶素产生转矩不同的现象,应用权系数分配叶素的方法,解决了在有限叶素数内的计算精度问题.利用Simulink仿真工具和许继集团提供的2MW风机参数,验证了风机仿真模型的正确性,得出气动模型能快速简便地仿真大多类型风机的结论.%Because of the complexity and long-term of modeling for wind turbine experimentally, the momentum-blade element theory, aerodynamic model of variable pitch wine turbine was established using Schmitz theory by considering the effect of tip losses, hub losses, thickness and width of airfoil and furthermore, the effect of rotor solidity when the turbine start and disc effect when the turbine idles. The effect of yawing and wind shear on rotor was modeled by changing the coordinates on the basis of the parameter of turbine structure. According to the different torque generated from different blade element, different weight factors were distributed by different blade elements to solve the accuracy problem within limited blade-elements. Simulink rotor model was established by using 2MW wind turbine parameter provided by XJ Group Corporation. Analysis theory can rapidly and easily simulate any type of wind rotors by simulating operation curves during the rated power and below rated wind speed.
Energy Technology Data Exchange (ETDEWEB)
Behar, M.; Filevich, A.; Macchiavelli, A.O.; Szybisz, L.; Thieberger, P.
1982-10-01
Nuclear states of /sup 79/Kr were studied through the /sup 78/Se(..cap alpha..,3n) reaction at an energy of 45 MeV. Excitation functions, ..gamma..-ray angular distributions and ..gamma..-..gamma.. coincidences were performed. Three bands based on the g.s. (1/2/sup -/), 147.1 keV (5/2/sup -/) and 129.7 keV (7/2/sup +/) states, were identified. Leading order analysis and quasiparticle-plus-rotor model calculations were performed. A good overall agreement was found between the experimental data and the theoretical predictions.
Experimental Investigation of a Shrouded Rotor Micro Air Vehicle in Hover and in Edgewise Gusts
Hrishikeshavan, Vikram
Due to the hover capability of rotary wing Micro Air Vehicles (MAVs), it is of interest to improve their aerodynamic performance, and hence hover endurance (or payload capability). In this research, a shrouded rotor configuration is studied and implemented, that has the potential to offer two key operational benefits: enhanced system thrust for a given input power, and improved structural rigidity and crashworthiness of an MAV platform. The main challenges involved in realising such a system for a lightweight craft are: design of a lightweight and stiff shroud, and increased sensitivity to external flow disturbances that can affect flight stability. These key aspects are addressed and studied in order to assess the capability of the shrouded rotor as a platform of choice for MAV applications. A fully functional shrouded rotor vehicle (disk loading 60 N/ m2) was designed and constructed with key shroud design variables derived from previous studies on micro shrouded rotors. The vehicle weighed about 280 g (244 mm rotor diameter). The shrouded rotor had a 30% increase in power loading in hover compared to an unshrouded rotor. Due to the stiff, lightweight shroud construction, a net payload benefit of 20-30 g was achieved. The different components such as the rotor, stabilizer bar, yaw control vanes and the shroud were systematically studied for system efficiency and overall aerodynamic improvements. Analysis of the data showed that the chosen shroud dimensions was close to optimum for a design payload of 250 g. Risk reduction prototypes were built to sequentially arrive at the final configuration. In order to prevent periodic oscillations in ight, a hingeless rotor was incorporated in the shroud. The vehicle was successfully ight tested in hover with a proportional-integralderivative feedback controller. A flybarless rotor was incorporated for efficiency and control moment improvements. Time domain system identification of the attitude dynamics of the flybar and
Design of the Active Elevon Rotor for Low Vibration
Fulton, Mark V.; Rutkowski, Michael (Technical Monitor)
2000-01-01
Helicopter fuselages vibrate more than desired, and traditional solutions have limited effectiveness and can impose an appreciable weight penalty. Alternative methods of combating high vibration, including Higher Harmonic Control (HHC) via harmonic swashplate motion and Individual Blade Control (IBC) via active pitch links, have been studied for several decades. HHC via an on-blade control surface was tested in 1977 on a full scale rotor using a secondary active swashplate and a mechanical control system. Recent smart material advances have prompted new research into the use of on-blade control concepts. Recent analytical studies have indicated that the use of on-blade control surfaces produces vibration reduction comparable to swashplate-based HHC but for less power. Furthermore, smart materials (such as piezoceramics) have been shown to provide sufficient control authority for preliminary rotor experiments. These experiments were initially performed at small scale for reduced tip speeds. More recent experiments have been conducted at or near full tip speeds, and a full-scale active rotor is under development by Boeing with Eurocopter et al. pursuing a similarly advanced full-scale implementation. The US Army Aeroflightdynamics Directorate has undertaken a new research program called the Active Elevon Rotor (AER) Focus Demo. This program includes the design, fabrication, and wind. tunnel testing of a four-bladed, 12.96 ft diameter rotor with one or two on-blade elevons per blade. The rotor, which will be Mach scaled, will use 2-5/rev elevon motion for closed-loop control and :will be tested in late 2001. The primary goal of the AER Focus Demo is the reduction of vibratory hub loads by 80% and the reduction of vibratory blade structural loads. A secondary goal is the reduction of rotor power. The third priority is the measurement and possible reduction of Blade Vortex Interaction (BVI) noise. The present study is focused on elevon effectiveness, that is, the elevon
Measurements of wakes originated from 2-bladed and 3-bladed rotors
Wu, Yu-Ting; Lyu, Shao-Dong; Chen, Bo-Wei
2016-04-01
Measurements of wakes originated from 2-bladed and 3-bladed rotors were carried out using a hot-wire probe system in an open jet wind tunnel. Hot-wire anemometry was adopted to characterize the spanwise profiles of mean wind speed, turbulence intensity and momentum flux for downwind locations at 0.5, 1, 2, 3, and 4 rotor diameters. The results showed that the 2-bladed rotor spun faster than the 3-bladed one, where the ratio of the two blade angular velocities was 1.065:1 under the same inflow condition with a uniform distribution of 5.4 m/s flow velocity. The turbulence flow statistics of the rotor wakes showed that the wake originated from the 3-bladed rotor has larger velocity deficit, streamwise turbulence intensity, momentum flux magnitude, but smaller spanwise turbulence intensity. The velocity spectrum showed peaks associated with the presence of the blade-induced tip vortices in the near wake region (approximately within 3 rotor diameters).
Institute of Scientific and Technical Information of China (English)
杨毅; 刘石; 高庆水; 张楚; 邓小文; 蔡笋
2015-01-01
In allusion to defect of traditional spring-damp element building wheel disc junction model in dynamics analysis on rod fastening rotor,a kind of dynamics model for junction surface of rod fastening rotor based on virtual isotropic material was built. Considering affect of wheel disc junction surface,this method was used for analyzing natural vibration characteris-tic of some rod fastening rotor under the condition of stretch pressure of different wheel discs. By means of calculating,er-ror between the first four natural frequency and the experimental value was worked out which was less than 5% and the mo-dal vibration type was identical to the testing result.%针对拉杆转子动力学分析中所采用的传统弹簧–阻尼单元建立轮盘间结合面模型的不足，发展了一种基于虚拟各项同性材料的拉杆转子结合面动力学模型。考虑轮盘间结合面的影响，采用该方法对某模型拉杆转子在不同轮盘预紧压力条件下的固有振动特性进行分析，计算得到前4阶固有频率与试验值的误差均小于5%，模态振型与测试结果吻合良好。
Effect of fluid damping on vibration response of immersed rotors
Directory of Open Access Journals (Sweden)
Mahmud Rasheed Ismail, Mustafa Asaad Hussein
2016-01-01
Full Text Available As immersed rotors vibrate in a viscous media such as fluid, a considerable amount of damping may be generated due to the interaction phenomena between the rotor components and the fluid media.Such damping is depending on many factors such as; fluid drag,fluid friction,turbulence, vortex and so on. Immersed rotors find their application in many engineering fields such as Marines machines, gear box, turbine and pumps.In the presentwork, a mathematical modelis attempted to investigate the dynamical behaviorimmersed rotor.The model takes into account the effects of the most rotordynamic parameters, namely; fluid drag,damping and stiffness of bearing,unbalance and gyroscopic effects of the attacheddisc, and elastic bending and internal damping of rotor shaft.Four types of fluid are employed as a fluid immersing media which are; Air, Water, SAE 20 andSAE 40oils.The experimental apparatus includes a sample rotor with single disc and plastic fluid container.Two proximate sensors are employed for measuring the unbalance response and orbits shapes under different rotor speeds, and discs size and locations.Modal analysis is employed for solving the governing equation of vibration motion. To check the validity of the mathematical model the theoretical results are compared with the experimental results. It is found that; the theoretical results are in a good agreement with the experimental ones, where the maximum error is not exceeded (6.8 %, and that;the fluid damping can highly reduce the peak amplitude of the unbalance response (up to 60 % however, it has slight effect on the critical speeds which are highly affected by the size and location of the attached disc.
Acoustic performance of two 1.83-meter-diameter fans designed for a wind-tunnel drive system
Soderman, P. R.; Page, V. R.
1977-01-01
A parametric study was made of the noise generated by two 1.83-m (6-ft) diameter fans operating up to a maximum pressure ratio of 1.03. One fan had 15 rotor blades, 23 stator blades, and a maximum rotational speed of 1200 rpm. The other fan had 9 rotor blades, 13 stator blades, and a maximum speed of 2,000 rpm. The fans were approximately 1/7-scale models of the 12.2-m (40-ft) diameter fans proposed for repowering the NASA-Ames 40- by 80 foot wind tunnel. The fans were operated individually in a 23.8-m (78-ft) long duct. Sound pressure levels in the duct were used to determine radiated acoustic power as fan speed, blade angle, and mass flow were varied. Results show that the low speed fan was slightly quieter than the high speed fan and, when scaled to full scale, would be 16 db quieter than the present wind tunnel fans. The fan noise varied directly with thrust regardless of whether thrust was varied by rotational speed or blade setting for the ranges studied.
Directory of Open Access Journals (Sweden)
Rajat Gupta, Sukanta Roy, Agnimitra Biswas
2010-11-01
Full Text Available H-Darrieus rotor is a lift type device having two to three blades designed as airfoils. The blades are attached vertically to the central shaft through support arms. The support to vertical axis helps the rotor maintain its shape. In this paper, Computational Fluid Dynamics (CFD analysis of an airfoil shaped two-bladed H-Darrieus rotor using Fluent 6.2 software was performed. Based on the CFD results, a comparative study between experimental and computational works was carried out. The H-Darrieus rotor was 20cm in height, 5cm in chord and twisted with an angle of 30° at the trailing end. The blade material of rotor was Fiberglass Reinforced Plastic (FRP. The experiments were earlier conducted in a subsonic wind tunnel for various height-to-diameter (H/D ratios. A two dimensional computational modeling was done with the help of Gambit tool using unstructured grid. Realistic boundary conditions were provided for the model to have synchronization with the experimental conditions. Two dimensional steady-state segregated solver with absolute velocity formulation and cell based grid was considered, and a standard k-epsilon viscous model with standard wall functions was chosen. A first order upwind discretization scheme was adopted for pressure velocity coupling of the flow. The inlet velocities and rotor rotational speeds were taken from the experimental results. From the computational analysis, power coefficient (Cp and torque coefficient (Ct values at ten different H/D ratios namely 0.85, 1.0, 1.10, 1.33, 1.54, 1.72, 1.80, 1.92, 2.10 and 2.20 were calculated in order to predict the performances of the twisted H-rotor. The variations of Cp and Ct with tip speed ratios were analyzed and compared with the experimental results. The standard deviations of computational Cp and Ct from experimental Cp and Ct were obtained. From the computational analysis, the highest values of Cp and Ct were obtained at H/D ratios of 1.0 and 1.54 respectively. The
旋翼结冰对直升机飞行动力学特性的影响%Effect of Rotor Icing on Helicopter Flight Dynamic Characteristics
Institute of Scientific and Technical Information of China (English)
李国知; 曹义华
2011-01-01
基于旋翼冰风洞试验数据,考虑桨叶表面附着冰脱落及桨叶表面局部温度对结冰的影响,提出了旋翼结冰的工程模型,建立了直升机旋翼结冰后的飞行动力学模型,以UH-60A为样机,研究了直升机旋翼结冰后的平衡特性,分析了结冰对直升机稳定性的影响.根据有人驾驶垂直/短距起落飞机军用品质规范(MIL-F-83300)与军用旋翼飞行器驾驶品质要求(ADS-33E-PRF),分析了结冰时间、环境温度、液态水含量以及平均水滴直径对旋翼结冰后的直升机开环状态下的操纵特性、姿态敏捷性、轴间耦合特性以及垂直轴操纵功效的影响.计算结果的对比分析显示,旋翼结冰模型合理,直升机飞行动力学模型计算精度高,能够用来研究直升机旋翼结冰后的飞行动力学问题.%Based on the rotor icing tunnel data, and considering the effect of rotor blade ice shedding and local temperature variation on the rotor blade icing, an engineering rotor icing model is advanced. Then a flight dynamics modal is built of a single rotor helicopter due to icing. The trim characteristics and stability of a UH-60A helicopter in icing conditions at the hover and in the forward flight are studied in detail. Using the military specification flying qualities of piloted V/STOL aircraft (MIL-F-83300) and the handling qualities requirements for military helicopters (ADS-33E-PRF), the effect of icing on the controllability, attitude quickness, interaxis coupling, and vertical axis control power of the helicopter open-loop system are analyzed in terms of icing time, atmospheric temperature, liquid water content, and median volumetric diameter. Calculation results indicate that the rotor icing model and the iced helicopter dynamics model are feasible and effective, and that they can be used to investigate issues in helicopter dynamics in rotor icing conditions.
Wind Turbine Rotor Simulation via CFD Based Actuator Disc Technique Compared to Detailed Measurement
Directory of Open Access Journals (Sweden)
Esmail Mahmoodi
2015-10-01
Full Text Available In this paper, a generalized Actuator Disc (AD is used to model the wind turbine rotor of the MEXICO experiment, a collaborative European wind turbine project. The AD model as a combination of CFD technique and User Defined Functions codes (UDF, so-called UDF/AD model is used to simulate loads and performance of the rotor in three different wind speed tests. Distributed force on the blade, thrust and power production of the rotor as important designing parameters of wind turbine rotors are focused to model. A developed Blade Element Momentum (BEM theory as a code based numerical technique as well as a full rotor simulation both from the literature are included into the results to compare and discuss. The output of all techniques is compared to detailed measurements for validation, which led us to final conclusions.
On utilizing the orbital motion in water waves to drive a Savonius rotor
Energy Technology Data Exchange (ETDEWEB)
Faizal, Mohammed; Rafiuddin Ahmed, M. [The University of the South Pacific, Laucala Campus, Suva (Fiji); Lee, Young-Ho [Korea Maritime University, 1 Dongsam-dong, Youngdo-Ku, Busan 606-791 (Korea)
2010-01-15
In wave motion, the water particles are known to follow orbital paths. This orbital motion was studied and a five bladed Savonius rotor was built to extract energy from the orbiting particles. Experiments were performed on a rotor placed parallel to the incoming waves in a two-dimensional wave channel by varying the frequency of the wave generator, which produced sinusoidal waves. The rotor submergence below the mean level was varied. The flow around the rotor was studied with particle image velocimetry (PIV) measurements. It was found that the rpm of the rotor (N{sub n}) increases with an increase in wave frequency. An increase in wave height also increases the N{sub n} values, as the kinetic energy of the particles' orbital motion increases. The optimum N{sub n} values are obtained when the rotor is placed close to the water surface at the minimum submergence of 1.06d where 'd' is the rotor diameter. (author)
Thermoelastic steam turbine rotor control based on neural network
Rzadkowski, Romuald; Dominiczak, Krzysztof; Radulski, Wojciech; Szczepanik, R.
2015-12-01
Considered here are Nonlinear Auto-Regressive neural networks with eXogenous inputs (NARX) as a mathematical model of a steam turbine rotor for controlling steam turbine stress on-line. In order to obtain neural networks that locate critical stress and temperature points in the steam turbine during transient states, an FE rotor model was built. This model was used to train the neural networks on the basis of steam turbine transient operating data. The training included nonlinearity related to steam turbine expansion, heat exchange and rotor material properties during transients. Simultaneous neural networks are algorithms which can be implemented on PLC controllers. This allows for the application neural networks to control steam turbine stress in industrial power plants.
Boeing Smart Rotor Full-scale Wind Tunnel Test Data Report
Kottapalli, Sesi; Hagerty, Brandon; Salazar, Denise
2016-01-01
A full-scale helicopter smart material actuated rotor technology (SMART) rotor test was conducted in the USAF National Full-Scale Aerodynamics Complex 40- by 80-Foot Wind Tunnel at NASA Ames. The SMART rotor system is a five-bladed MD 902 bearingless rotor with active trailing-edge flaps. The flaps are actuated using piezoelectric actuators. Rotor performance, structural loads, and acoustic data were obtained over a wide range of rotor shaft angles of attack, thrust, and airspeeds. The primary test objective was to acquire unique validation data for the high-performance computing analyses developed under the Defense Advanced Research Project Agency (DARPA) Helicopter Quieting Program (HQP). Other research objectives included quantifying the ability of the on-blade flaps to achieve vibration reduction, rotor smoothing, and performance improvements. This data set of rotor performance and structural loads can be used for analytical and experimental comparison studies with other full-scale rotor systems and for analytical validation of computer simulation models. The purpose of this final data report is to document a comprehensive, highquality data set that includes only data points where the flap was actively controlled and each of the five flaps behaved in a similar manner.
A comparison between 2-and 3-bladed wind turbine rotors with focus on wake characteristics
Mühle, Franz; Adaramola, Muyiwa Samuel; Sætran, Lars
2016-11-01
Due to cost benefit and weight reduction, 2-bladed wind turbines have the potential to become more important for offshore wind applications. In order to optimize the arrangement of wind turbines in wind farms and for accurate forecasts of the power production, a detailed knowledge of the wake flow is needed. In the presented study, three different rotors with varying number of blades and similar performance behavior have been designed and manufactured using the 3-dimensional (3D) printing technology. The performance characteristics of these rotors as well as their wake features are measured experimentally in wind tunnel tests and compared. The velocity deficit is seen to vary only insignificantly for the wakes in distances of 3D (where D is the rotor diameter), 5D and 7D behind the turbine. However, higher turbulence intensity levels are recorded in the wake of the 2-bladed rotors. This could have potential for a faster wake recovery and thus a narrower turbine spacing.
Energy Technology Data Exchange (ETDEWEB)
Inayat-Hussain, Jawaid I. [School of Engineering, Monash University Malaysia, No. 2, Jalan Kolej, Bandar Sunway, 46150 Petaling Jaya, Selangor Darul Ehsan (Malaysia)]. E-mail: jawaid.inayat-hussain@eng.monash.edu.my
2007-02-15
This work reports on a numerical study undertaken to investigate the response of an imbalanced rigid rotor supported by active magnetic bearings. The mathematical model of the rotor-bearing system used in this study incorporates nonlinearity arising from the electromagnetic force-coil current-air gap relationship, and the effects of geometrical cross-coupling. The response of the rotor is observed to exhibit a rich variety of dynamical behavior including synchronous, sub-synchronous, quasi-periodic and chaotic vibrations. The transition from synchronous rotor response to chaos is via the torus breakdown route. As the rotor imbalance magnitude is increased, the synchronous rotor response undergoes a secondary Hopf bifurcation resulting in quasi-periodic vibration, which is characterized by a torus attractor. With further increase in the rotor imbalance magnitude, this attractor is seen to develop wrinkles and becomes unstable resulting in a fractal torus attractor. The fractal torus is eventually destroyed as the rotor imbalance magnitude is further increased. Quasi-periodic and frequency-locked sub-synchronous vibrations are seen to appear and disappear alternately before the emergence of chaos in the response of the rotor. The magnitude of rotor imbalance where sub-synchronous, quasi-periodic and chaotic vibrations are observed in this study, albeit being higher than the specified imbalance level for rotating machinery, may possibly occur due to a gradual degradation of the rotor balance quality during operation.
Directory of Open Access Journals (Sweden)
Shekhar Kumar
2013-01-01
Full Text Available For design and development of liquid-liquid extraction systems, it is essential to have an accurate estimation of hydrodynamic and mass transfer characteristics of the employed contactor. In the present study, experimental evaluations consisted primarily of determining the maximum solution throughput that could be processed without cross-phase contamination at a given rotor speed, O/A flow ratio, and organic-aqueous solution pair in a 30 mm bowl diameter centrifugal contactor. In addition, analysis included experimental drop size determinations as well as holdup determination. The experimental drop size distributions are expected to be helpful for modeling work.
SU (3) realization of the rigid asymmetric rotor within the IBM
Energy Technology Data Exchange (ETDEWEB)
Smirnova, N.A.; Van Isacker, P. [Grand Accelerateur National d' Ions Lourds (GANIL), 14 - Caen (France); Smirnov, Y.F. [Instituto de Ciencias Nucleares, UNAM (Mexico)
1999-07-01
It is shown that the spectrum of the asymmetric rotor can be realized quantum mechanically in terms of a system of interacting bosons. This is achieved in the SU(3) limit of the interacting boson model by considering higher-order interactions between the bosons. The spectrum corresponds to that of a rigid asymmetric rotor in the limit of infinite boson number. (author)
Actuator Line/Navier-Stokes Computations for Flows past the Yawed MEXICO Rotor
DEFF Research Database (Denmark)
Shen, Wen Zhong; Sørensen, Jens Nørkær; Yang, H.
2011-01-01
In the paper the Actuator Line/Navier-Stokes model has been used to simulate flows past the yawed MEXICO rotor. The computed loads as well as the velocity field behind the yawed rotor are compared to detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project...
Determination of the angle of attack on the mexico rotor using experimental data
DEFF Research Database (Denmark)
Yang, Hua; Shen, Wen Zhong; Sørensen, Jens Nørkær
2010-01-01
characteristics from experimental data on the MEXICO (Model Experiments in controlled Conditions) rotor. Detailed surface pressure and Particle Image Velocimetry (PIV) flow field at different rotor azimuth positions were examined for determining the sectional airfoil data. It is worthwhile noting that the present...
Institute of Scientific and Technical Information of China (English)
师名林; 王德忠; 张继革
2012-01-01
The lumped parameter model of large -scale canned motor pump rotor system is established,and the critical speeds and modal shapes are calculated based on Riccati transfer matrix method. The calculated results show the critical rotary speeds can effectively avoid the operation speed,thus the critical rotary speed design of large-scale canned motor pump rotor system k sufficient in design capacity. In addition,the locations of upper and lower flywheels are the sensitive part of radical vibration of rotor system and should be monitored to avoid collision with pressure casing in operation.%建立了大型屏蔽电机泵转子系统的集总参数模型,并采用Riccati传递矩阵法对转子系统的临界转速及振型进行了计算.计算结果表明:(1)采用Riccati传递矩阵法编制的转子系统临界转速求解程序计算稳定,计算精度足够高；(2)大型屏蔽电机泵转子系统的临界转速为设计超速的1.2倍,能够有效避开工作转速,设计裕量足够；(3)在正常工作下,转子系统上、下飞轮处为振动敏感部位,应重点监测,以免和承压壳体发生碰磨.
Active control for performance enhancement of electrically controlled rotor
Institute of Scientific and Technical Information of China (English)
Lu Yang; Wang Chao
2015-01-01
Electrically controlled rotor (ECR) system has the potential to enhance the rotor perfor-mance by applying higher harmonic flap inputs. In order to explore the feasibility and effectiveness for ECR performance enhancement using closed-loop control method, firstly, an ECR rotor perfor-mance analysis model based on helicopter flight dynamic model is established, which can reflect the performance characteristics of ECR helicopter at high advance ratio. Based on the simulation platform, an active control method named adaptive T-matrix algorithm is adopted to explore the feasibility and effectiveness for ECR performance enhancement. The simulation results verify the effectiveness of this closed-loop control method. For the sample ECR helicopter, about 3%rotor power reduction is obtained with the optimum 2/rev flap inputs at the advance ratio of 0.34. And through analyzing the distributions of attack of angle and drag in rotor disk, the underlying physical essence of ECR power reduction is cleared. Furthermore, the influence of the key control parameters, including convergence factor and weighting matrix, on the effectiveness of closed-loop control for ECR performance enhancement is explored. Some useful results are summarized, which can be used to direct the future active control law design of ECR performance enhancement.
Thermodynamic wetness loss calculation in a steam turbine rotor tip section: nucleating steam flow
Joseph, Joby; Sathyanarayanan, S.; K, Vigney; Prasad, B. V. S. SS; Biswas, D.; Jimbo, T.
2016-09-01
Rapid expansion of steam in the last stages of a steam turbine causes condensation. The formation of liquid droplets due to condensation results in wetness losses, which include aerodynamic losses (due to friction between liquid droplets and the vapour), thermodynamic losses (due to irreversible heat addition), and braking losses (due to the impact of liquid droplets on the blade). The thermodynamic loss contributes up to 80% to the wetness losses when the diameter of the droplets formed is less than 1 μm. In this study, the thermodynamic loss in a two-dimensional steam turbine rotor tip section is numerically investigated for various operating and off-design conditions. A pressure based, Eulerian-Eulerian approach is used to model the non-equilibrium condensation process. The entropy change due to condensation is used to compute the thermodynamic losses.
A review of current finite difference rotor flow methods
Caradonna, F. X.; Tung, C.
1986-01-01
Rotary-wing computational fluid dynamics is reaching a point where many three-dimensional, unsteady, finite-difference codes are becoming available. This paper gives a brief review of five such codes, which treat the small disturbance, conservative and nonconservative full-potential, and Euler flow models. A discussion of the methods of applying these codes to the rotor environment (including wake and trim considerations) is followed by a comparison with various available data. These data include tests of advancing lifting and nonlifting, and hovering model rotors with significant supercritical flow regions. The codes are also compared for computational efficiency.
Transonic Axial Splittered Rotor Tandem Stator Stage
2016-12-01
compressor rotor was designed incorporating a splitter vane between the principal blades . Historical experiments conducted by Dr. Arthur J...conventional rotor design . The stage is composed of the rotor and stator. The flow of the air passing through the rotor is turned, and the flow is required...derived results achieved the best blade geometry for design continuation. The best circumferential and axial placement for the splitter blade was
Lift capability prediction for helicopter rotor blade-numerical evaluation
Rotaru, Constantin; Cîrciu, Ionicǎ; Luculescu, Doru
2016-06-01
The main objective of this paper is to describe the key physical features for modelling the unsteady aerodynamic effects found on helicopter rotor blade operating under nominally attached flow conditions away from stall. The unsteady effects were considered as phase differences between the forcing function and the aerodynamic response, being functions of the reduced frequency, the Mach number and the mode forcing. For a helicopter rotor, the reduced frequency at any blade element can't be exactly calculated but a first order approximation for the reduced frequency gives useful information about the degree of unsteadiness. The sources of unsteady effects were decomposed into perturbations to the local angle of attack and velocity field. The numerical calculus and graphics were made in FLUENT and MAPLE soft environments. This mathematical model is applicable for aerodynamic design of wind turbine rotor blades, hybrid energy systems optimization and aeroelastic analysis.
Assessment of Geometry and In-Flow Effects on Contra-Rotating Open Rotor Broadband Noise Predictions
Zawodny, Nikolas S.; Nark, Douglas M.; Boyd, D. Douglas, Jr.
2015-01-01
Application of previously formulated semi-analytical models for the prediction of broadband noise due to turbulent rotor wake interactions and rotor blade trailing edges is performed on the historical baseline F31/A31 contra-rotating open rotor configuration. Simplified two-dimensional blade element analysis is performed on cambered NACA 4-digit airfoil profiles, which are meant to serve as substitutes for the actual rotor blade sectional geometries. Rotor in-flow effects such as induced axial and tangential velocities are incorporated into the noise prediction models based on supporting computational fluid dynamics (CFD) results and simplified in-flow velocity models. Emphasis is placed on the development of simplified rotor in-flow models for the purpose of performing accurate noise predictions independent of CFD information. The broadband predictions are found to compare favorably with experimental acoustic results.
Small diameter carbon nanopipettes
Singhal, Riju; Bhattacharyya, Sayan; Orynbayeva, Zulfiya; Vitol, Elina; Friedman, Gary; Gogotsi, Yury
2010-01-01
Nanoscale multifunctional carbon probes facilitate cellular studies due to their small size, which makes it possible to interrogate organelles within living cells in a minimally invasive fashion. However, connecting nanotubes to macroscopic devices and constructing an integrated system for the purpose of fluid and electrical signal transfer is challenging, as is often the case with nanoscale components. We describe a non-catalytic chemical vapor deposition based method for batch fabrication of integrated multifunctional carbon nanopipettes (CNPs) with tip diameters much smaller (10-30 nm) than previously reported (200 nm and above) and approaching those observed for multiwalled carbon nanotubes. This eliminates the need for complicated attachment/assembly of nanotubes into nanofluidic devices. Variable tip geometries and structures were obtained by controlled deposition of carbon inside and outside quartz pipettes. We have shown that the capillary length and gas flow rate have a marked effect on the carbon deposition. This gives us a flexible protocol, useful for growing carbon layers of different thicknesses at selective locations on a glass pipette to yield a large variety of cellular probes in bulk quantities. The CNPs possess an open channel for fluid transfer with the carbon deposited inside at 875 °C behaving like an amorphous semiconductor. Vacuum annealing of the CNP tips at temperatures up to 2000 °C yields graphitic carbon structures with an increase in conductivity of two orders of magnitude. Penetration of the integrated carbon nanoprobes into cells was shown to produce minimal Ca2+ signals, fast recovery of basal Ca2+ levels and no adverse activation of the cellular metabolism during interrogation times as long as 0.5-1 h.
Institute of Scientific and Technical Information of China (English)
房建成; 张会娟; 刘虎
2014-01-01
By the virtue of active magnetic bearing, magnetically suspended inertia actuators can make micro-vibration come true through active vibration control. However, there still exist vibrations with some frequencies in magnetically suspended inertia actuators. Firstly, the vibration mechanism of Magnet Runout is analyzed based on the analysis of rotor unbalance and Sensor Runout, then the dynamic model of the magnetically suspended rigid rotor system composing of three vibration sources is developed and divided into translational motion and torsional motion. The analysis dedicates that rotor unbalance, Magnet Runout and Sensor Runout will arise vibrations through different channels, and that the vibrations include the fundamental frequencies and their harmonics. Lastly, the requirements of active vibration control are proposed for the magnetically suspended rigid rotor system, and are useful for the future research.%磁悬浮惯性执行机构采用磁轴承支承，可通过主动控制实现极微振动，但磁悬浮惯性执行机构仍存在频谱分量丰富的振动。首先在转子动静不平衡和Sensor Runout振动机理分析的基础上，重点分析了Magnet Runout产生振动机理；然后，建立包含多振动源的系统动力学建模，并将整个动力学模型分解为平动和转动子系统，分析表明转子动静不平衡、Sensor Runout和Magnet Runout是通过不同的途径产生振动，不仅产生同频振动还包含倍频振动；最后，提出磁悬浮刚性转子系统主动振动控制的要求，为以后的主动振动控制研究奠定基础。
Institute of Scientific and Technical Information of China (English)
Han Dong
2015-01-01
To reduce the pitch link loads of variable speed rotors, variable tuning frequency fluid-lastic isolators are proposed. This isolator utilizes the variation of centrifugal force due to the change of rotor speed to change the tuning port area ratio, which can change the tuning frequency of the isolator. A rotor model including the model of fluidlastic isolator is coupled with a fuselage model to predict the steady responses of the rotor system in forward flight. The aeroelastic analyses indicate that distinct performance improvement in pitch link load control can be achieved by the utilization of variable frequency isolators compared with the constant tuning frequency isolators. The 4/rev (per revolution) pitch link load is observed to be reduced by 87.6%compared with the increase of 56.3%by the constant frequency isolator, when the rotor speed is reduced by 16.7%. The isolation ability at different rotor speeds in different flight states is investigated. To achieve overall load reduction within the whole range of rotor speed, the strategy of the variation of tuning frequency is adjusted. The results indicate that the 4/rev pitch link load within the whole rotor speed range is decreased.
Directory of Open Access Journals (Sweden)
Han Dong
2015-10-01
Full Text Available To reduce the pitch link loads of variable speed rotors, variable tuning frequency fluidlastic isolators are proposed. This isolator utilizes the variation of centrifugal force due to the change of rotor speed to change the tuning port area ratio, which can change the tuning frequency of the isolator. A rotor model including the model of fluidlastic isolator is coupled with a fuselage model to predict the steady responses of the rotor system in forward flight. The aeroelastic analyses indicate that distinct performance improvement in pitch link load control can be achieved by the utilization of variable frequency isolators compared with the constant tuning frequency isolators. The 4/rev (per revolution pitch link load is observed to be reduced by 87.6% compared with the increase of 56.3% by the constant frequency isolator, when the rotor speed is reduced by 16.7%. The isolation ability at different rotor speeds in different flight states is investigated. To achieve overall load reduction within the whole range of rotor speed, the strategy of the variation of tuning frequency is adjusted. The results indicate that the 4/rev pitch link load within the whole rotor speed range is decreased.
Alexander, B. X. S.
Flywheel energy storage has distinct advantages over conventional energy storage methods such as electrochemical batteries. Because the energy density of a flywheel rotor increases quadratically with its speed, the foremost goal in flywheel design is to achieve sustainable high speeds of the rotor. Many issues exist with the flywheel rotor operation at high and varying speeds. A prominent problem is synchronous rotor vibration, which can drastically limit the sustainable rotor speed. In a set of projects, the novel Active Disturbance Rejection Control (ADRC) is applied to various problems of flywheel rotor operation. These applications include rotor levitation, steady state rotation at high speeds and accelerating operation. Several models such as the lumped mass model and distributed three-mass models have been analyzed. In each of these applications, the ADRC has been extended to cope with disturbance, noise, and control effort optimization; it also has been compared to various industry-standard controllers such as PID and PD/observer, and is proven to be superior. The control performance of the PID controller and the PD/observer currently used at NASA Glenn has been improved by as much as an order of magnitude. Due to the universality of the second order system, the results obtained in the rotor vibration problem can be straightforwardly extended to other vibrational systems, particularly, the MEMS gyroscope. Potential uses of a new nonlinear controller, which inherits the ease of use of the traditional PID, are also discussed.
Fan Noise Source Diagnostic Test: Rotor Alone Aerodynamic Performance Results
Hughes, Christopher E.; Jeracki, Robert J.; Woodward, Richard P.; Miller, Christopher J.
2005-01-01
The aerodynamic performance of an isolated fan or rotor alone model was measured in the NASA Glenn Research Center 9- by 15- Foot Low Speed Wind Tunnel as part of the Fan Broadband Source Diagnostic Test conducted at NASA Glenn. The Source Diagnostic Test was conducted to identify the noise sources within a wind tunnel scale model of a turbofan engine and quantify their contribution to the overall system noise level. The fan was part of a 1/5th scale model representation of the bypass stage of a current technology turbofan engine. For the rotor alone testing, the fan and nacelle, including the inlet, external cowl, and fixed area fan exit nozzle, were modeled in the test hardware; the internal outlet guide vanes located behind the fan were removed. Without the outlet guide vanes, the velocity at the nozzle exit changes significantly, thereby affecting the fan performance. As part of the investigation, variations in the fan nozzle area were tested in order to match as closely as possible the rotor alone performance with the fan performance obtained with the outlet guide vanes installed. The fan operating performance was determined using fixed pressure/temperature combination rakes and the corrected weight flow. The performance results indicate that a suitable nozzle exit was achieved to be able to closely match the rotor alone and fan/outlet guide vane configuration performance on the sea level operating line. A small shift in the slope of the sea level operating line was measured, which resulted in a slightly higher rotor alone fan pressure ratio at take-off conditions, matched fan performance at cutback conditions, and a slightly lower rotor alone fan pressure ratio at approach conditions. However, the small differences in fan performance at all fan conditions were considered too small to affect the fan acoustic performance.
Directory of Open Access Journals (Sweden)
Yan Wei
2015-10-01
Full Text Available The uniform distribution and experimental design is employed to study the thermo-hydraulic characteristics of a heat exchanger, which consists of the rotor-assembled strands mounted in circular smooth tubes. The uniform distribution and experimental design parameters include multiple rotor parameters such as rotor diameters, rotor lead, and height of blade, with the aim of studying their influence on the PEC, that is, ( ( Nu z / Nu g / ( f g / f z 1 / 3 , which stands for the heat transfer and friction characteristics. The best matching schemes of rotor-assembled strand, which significantly improves PEC to 2.01, are given by the regression analysis of uniform distribution and experimental design table. The single-factor experiments are performed to compare a tube installed with different kinds of rotor-assembled strands with a smooth tube without any strands when the Reynolds number changes between 20,000 and 60,000. The experimental result is in good agreement with the result obtained by the regression analysis of uniform distribution and experimental design. It is shown that the rotor diameters play important role in the heat transfer, and the optimal PEC value is obtained under the case that the rotor diameter is 21 mm. The rotor lead also contributes to the improvement of heat transfer and its optimal value is 700 mm in this study. The Nusselt number, friction factor and PEC increase with the increase in blade height. It shows that the uniform distribution and experimental design is an efficient method to find out the optimal parameters.
Analysis of a Compessor Rotor using Finite Element Analysis
Directory of Open Access Journals (Sweden)
Munagunuri Suneel Babu
2014-11-01
Full Text Available The compressor compresses its working fluid by first accelerating the fluid and then diffusing it to obtain a pressure increase. In an axial flow compressor, air passes from one stage to the next, each stage raising the pressure slightly. The energy level of air or gas flowing through it is increased by the action of the rotor blades which exert a torque on the fluid which is supplied by an electric motor or a steam or a gas turbine. In this present work we are taken the existing model of transonic compressor test rotors which contains 18 blades. The model was modeled in Pro-E Creo 5.0 with existing dimensions and analyzed using Ansys14.5. For the analysis we are taken two different materials and compared the values. For the further extension we changed the existing mode by decreasing the number of blades and analyzed with different materials. The developed stress values of the existing model are compares with the modified models. Our objective is to increase the performance of the rotor blade by changing the materials and the model. From the observation we will suggest which model is suitable for the compressor rotor.
Prospects for Brushless ac Motors with HTS Rotors
McCulloch, M. D.; Jim, K.; Kawai, Y.; Dew-Hughes, D.; Morgan, C.; Goringe, M. J.; Grovenor, C. R. M.
1997-03-01
There is a superconducting equivalent for every type of brushless ac motor; permanent magnet, reluctance, hysteresis and induction (squirrel cage) motor. The particular advantage of superconducting versions of these machines is that they are expected to provide much higher power densities than their conventional equivalents. The behaviour of superconducting rotors fabricated in the form of (a) squirrell cages from silver coated with melt-processed Bi-2212, (b) tubes cast centifugally from Bi-2212, and (c) small cylinders of melt-processed and seeded YBCO has been studied in rotating magnetic fields provided by conventional motor coils. Measurements of static torque, and values of dynamic torque deduced from angular velocity and acceleration have been used to characterise the potential performance of these embryonic machines. Two broad types of behaviour have been observed. In the Bi-2212 rotors the torque decreases with increasing rotor speed; this behaviour is believed due to flux creep. By contrast the strong-pinning YBCO rotors maintain a constant torque up to synchronous speed. Mathematical modelling of flux penetration and distribution within the rotors is able to reproduce both types of the observed behaviour. Power densities some 5 to 10 times that of conventional machines are predicted to be achievable in optimised prototype machines.
Liquid Self-Balancing Device Effects on Flexible Rotor Stability
Directory of Open Access Journals (Sweden)
Leonardo Urbiola-Soto
2013-01-01
Full Text Available Nearly a century ago, the liquid self-balancing device was first introduced by M. LeBlanc for passive balancing of turbine rotors. Although of common use in many types or rotating machines nowadays, little information is available on the unbalance response and stability characteristics of this device. Experimental fluid flow visualization evidences that radial and traverse circulatory waves arise due to the interaction of the fluid backward rotation and the baffle boards within the self-balancer annular cavity. The otherwise destabilizing force induced by trapped fluids in hollow rotors, becomes a stabilizing mechanism when the cavity is equipped with adequate baffle boards. Further experiments using Particle Image Velocimetry (PIV enable to assess the active fluid mass fraction to be one-third of the total fluid mass. An analytical model is introduced to study the effects of the active fluid mass fraction on a flexible rotor supported by flexible supports excited by bwo different destabilizing mechanisms; rotor internal friction damping and aerodynamic cross-coupling. It is found that the fluid radial and traverse forces contribute to the balancing action and to improve the rotor stability, respectively.
Egolf, T. A.; Landgrebe, A. J.
1982-01-01
A user's manual is provided which includes the technical approach for the Prescribed Wake Rotor Inflow and Flow Field Prediction Analysis. The analysis is used to provide the rotor wake induced velocities at the rotor blades for use in blade airloads and response analyses and to provide induced velocities at arbitrary field points such as at a tail surface. This analysis calculates the distribution of rotor wake induced velocities based on a prescribed wake model. Section operating conditions are prescribed from blade motion and controls determined by a separate blade response analysis. The analysis represents each blade by a segmented lifting line, and the rotor wake by discrete segmented trailing vortex filaments. Blade loading and circulation distributions are calculated based on blade element strip theory including the local induced velocity predicted by the numerical integration of the Biot-Savart Law applied to the vortex wake model.
Xu, Yuanping; Zhou, Jin; Di, Long; Zhao, Chen
2017-01-01
Active magnetic bearings (AMBs) support rotors using electromagnetic force rather than mechanical forces. It is necessary to accurately identify the AMBs force coefficients since they play a critical role in the rotordynamic analysis including system stability, bending critical speeds and modes of vibrations. This paper proposes a rotor unbalance response based approach to identifying the AMBs stiffness and damping coefficients during rotation. First, a Timoshenko beam finite element (FE) rotor model is created. Second, an identification procedure based on the FE model is proposed. Then based on the experimental rotor unbalance response data from 1200 rpm to 30,000 rpm, the AMBs dynamic force parameters (stiffness and damping) are obtained. Finally, the identified results are verified by comparing the estimated and experimental rotor unbalance responses, which shows high accuracy.
Development of a 5.5 m diameter vertical axis wind turbine, phase 3
Dekitsch, A.; Etzler, C. C.; Fritzsche, A.; Lorch, G.; Mueller, W.; Rogalla, K.; Schmelzle, J.; Schuhwerk, W.; Vollan, A.; Welte, D.
1982-06-01
In continuation of development of a 5.5 m diameter vertical axis windmill that consists in conception, building, and wind tunnel testing, a Darrieus rotor windpowered generator feeding an isolated network under different wind velocity conditions and with optimal energy conversion efficiency was designed built, and field tested. The three-bladed Darrieus rotor tested in the wind tunnel was equiped with two variable pitch Savonius rotors 2 m in diameter. By means of separate measures of the aerodynamic factors and the energy consumption, effect of revisions and optimizations on different elements was assessed. Pitch adjustement of the Savonius blades, lubrication of speed reducer, rotor speed at cut-in of generator field excitation, time constant of field excitation, stability conditions, switch points of ohmic resistors which combined with a small electric battery simulated a larger isolated network connected with a large storage battery, were investigated. Fundamentals for the economic series production of windpowered generators with Darrieus rotors for the control and the electric conversion system are presented.
A New Sensorless MRAS Based on Active Power Calculations for Rotor Position Estimation of a DFIG
Gil Domingos Marques; Duarte Mesquita e Sousa
2011-01-01
A sensorless method for the estimation of the rotor position of the wound-rotor induction machine is described in this paper. The method is based on the MRAS methodology and consists in the comparison of two models for the evaluation of the active power transferred across the air gap: the reference model and the adaptive model. The reference model obtains the power transferred across the air gap using directly available and measured stator variables. The adaptive model obtains the same quanti...
Directory of Open Access Journals (Sweden)
A. Calzado
2013-04-01
Full Text Available Aim of study: The aim of this work was to model diameter distributions of Quercus suber stands. The ultimate goal was to construct models enabling the development of more affordable forest inventory methods. This is the first study of this type on cork oak forests in the area.Area of study: The area of study is “Los Alcornocales” Natural Park (Cádiz-Málaga, Spain.Material and methods: The diameter distributions of 100 permanent plots were modelled with the two-parameter Weibull function. Distribution parameters were fitted with the non-linear regression, maximum likelihood, moment and percentile-based methods. Goodness of fit with the different methods was compared in terms of number of plots rejected by the Kolmogorov-Smirnov test, bias, mean square error and mean absolute error. The scale and shape parameters in the Weibull function were related to the stand variables by using the parameter prediction model.Main results: The best fitting was obtained with the non-linear regression approach, using as initial values those obtained by maximum likelihood method, the percentage of rejections by the Kolmogorov-Smirnov test was 2% of the total number of cases. The scale parameter (b was successfully modelled in terms of the quadratic mean diameter under cork (R2 adj = 0.99. The shape parameter (c was modelled by using maximum diameter, minimum diameter and plot elevation (R2 adj = 0.40.Research highlights: The proposed model diameter distribution can be a highly useful tool for the inventorying and management of cork oak forests.Key words: maximum likelihood method; moment method; non linear regression approach; parameter prediction model; percentile method; scale parameter; shape parameter.
Design optimization for active twist rotor blades
Mok, Ji Won
This dissertation introduces the process of optimizing active twist rotor blades in the presence of embedded anisotropic piezo-composite actuators. Optimum design of active twist blades is a complex task, since it involves a rich design space with tightly coupled design variables. The study presents the development of an optimization framework for active helicopter rotor blade cross-sectional design. This optimization framework allows for exploring a rich and highly nonlinear design space in order to optimize the active twist rotor blades. Different analytical components are combined in the framework: cross-sectional analysis (UM/VABS), an automated mesh generator, a beam solver (DYMORE), a three-dimensional local strain recovery module, and a gradient based optimizer within MATLAB. Through the mathematical optimization problem, the static twist actuation performance of a blade is maximized while satisfying a series of blade constraints. These constraints are associated with locations of the center of gravity and elastic axis, blade mass per unit span, fundamental rotating blade frequencies, and the blade strength based on local three-dimensional strain fields under worst loading conditions. Through pre-processing, limitations of the proposed process have been studied. When limitations were detected, resolution strategies were proposed. These include mesh overlapping, element distortion, trailing edge tab modeling, electrode modeling and foam implementation of the mesh generator, and the initial point sensibility of the current optimization scheme. Examples demonstrate the effectiveness of this process. Optimization studies were performed on the NASA/Army/MIT ATR blade case. Even though that design was built and shown significant impact in vibration reduction, the proposed optimization process showed that the design could be improved significantly. The second example, based on a model scale of the AH-64D Apache blade, emphasized the capability of this framework to
Falls, Jaye
This work studies the design of trailing edge controls for swashplateless helicopter primary control, and examines the impact of those controls on the performance of the rotor. The objective is to develop a comprehensive aeroelastic analysis for swashplateless rotors in steady level flight. The two key issues to be solved for this swashplateless control concept are actuation of the trailing edge controls and evaluating the performance of the swashplateless rotor compared to conventionally controlled helicopters. Solving the first requires simultaneous minimization of trailing flap control angles and hinge moments to reduce actuation power. The second issue requires not only the accurate assessment of swashplateless rotor power, but also similar or improved performance compared to conventional rotors. The analysis consists of two major parts, the structural model and the aerodynamic model. The inertial contributions of the trailing edge flap and tab are derived and added to the system equations in the structural model. Two different aerodynamic models are used in the analysis, a quasi-steady thin airfoil theory that includes arbitrary hinge positions for the flap and the tab, and an unsteady lifting line model with airfoil table lookup based on wind tunnel test data and computational fluid dynamics simulation. The design aspect of the problem is investigated through parametric studies of the trailing edge flap and tab for a Kaman-type conceptual rotor and a UH-60A swashplateless variant. The UH-60A model is not changed except for the addition of a trailing edge flap to the rotor blade, and the reduction of pitch link stiffness to imitate a soft root spring. Study of the uncoupled blade response identifies torsional stiffness and flap hinge stiffness as important design features of the swashplateless rotor. Important trailing edge flap and tab design features including index angle, aerodynamic overhang, chord and length are identified through examination of coupled
Design of a wind turbine rotor for maximum aerodynamic efficiency
DEFF Research Database (Denmark)
Johansen, Jeppe; Aagaard Madsen, Helge; Gaunaa, Mac;
2009-01-01
The design of a three-bladed wind turbine rotor is described, where the main focus has been highest possible mechanical power coefficient, CP, at a single operational condition. Structural, as well as off-design, issues are not considered, leading to a purely theoretical design for investigating...... and a full three-dimensional Navier-Stokes solver. Excellent agreement is obtained using the three models. Global CP reaches a value of slightly above 0.51, while global thrust coefficient CT is 0.87. The local power coefficient Cp increases to slightly above the Betz limit on the inner part of the rotor......; the local thrust coefficient Ct increases to a value above 1.1. This agrees well with the theory of de Vries, which states that including the effect of the low pressure behind the centre of the rotor stemming from the increased rotation, both Cp and Ct will increase towards the root. Towards the tip, both...
Design modification in rotor blade of turbo molecular pump
Energy Technology Data Exchange (ETDEWEB)
Iqbal, Munawar, E-mail: muniqbal@yahoo.com [Centre for High Energy Physics, University of the Punjab, Quaid-e-Azam, Campus, Lahore 54590 (Pakistan); Wasy, Abdul [Department of Mechanical Engineering, University of Engineering and Technology, Taxila 47050 (Pakistan); Batani, Dimitri [Centre Lasers Intenses et Applications, Universite Bordeaux 1, Liberation, 33405 Talence cedex (France); Rashid, Haris [Centre for High Energy Physics, University of the Punjab, Quaid-e-Azam, Campus, Lahore 54590 (Pakistan); Lodhi, M.A.K. [Department of Physics, Texas Tech University, Lubbock Texas, 79409 (United States)
2012-06-21
Performance of a Turbo Molecular Pump (TMP) is strongly related to the frequency of the rotor. As rpm increases deflection in the rotor blades starts to occur. Therefore, quality of material and blade design has been modified in order to obtain stable performance at higher speed. To reduce the deformation, stiffer material and change in blade design have been calculated. Significant improvement has been achieved in modeling the blade design using CATIA software. The analysis has been performed by ANSYS workbench. It is shown that the modification in the blade design of TMP rotor has reduced the structural deformation up to 66 percent of the deformation produced in the original blade design under the same conditions. Modified design achieved additional 23 percent rpm which increased TMP's efficiency.
Design modification in rotor blade of turbo molecular pump
Iqbal, Munawar; Wasy, Abdul; Batani, Dimitri; Rashid, Haris; Lodhi, M. A. K.
2012-06-01
Performance of a Turbo Molecular Pump (TMP) is strongly related to the frequency of the rotor. As rpm increases deflection in the rotor blades starts to occur. Therefore, quality of material and blade design has been modified in order to obtain stable performance at higher speed. To reduce the deformation, stiffer material and change in blade design have been calculated. Significant improvement has been achieved in modeling the blade design using CATIA software. The analysis has been performed by ANSYS workbench. It is shown that the modification in the blade design of TMP rotor has reduced the structural deformation up to 66 percent of the deformation produced in the original blade design under the same conditions. Modified design achieved additional 23 percent rpm which increased TMP's efficiency.
Genetics Home Reference: Rotor syndrome
... of these proteins. Without the function of either transport protein, bilirubin is less efficiently taken up by the ... Schinkel AH. Complete OATP1B1 and OATP1B3 deficiency causes human Rotor syndrome by interrupting conjugated bilirubin reuptake into ...
开式转子发动机对转桨扇性能建模研究%Modeling of Counter-Rotating Prop-Fan Performance of Open Rotor Engine
Institute of Scientific and Technical Information of China (English)
祁宏斌; 周人治; 黄红超; 李刚团
2012-01-01
对转桨扇开式转子发动机性能计算的难点在于对转桨扇部件的性能计算。传统方法是将对转桨扇简化处理为涡轮螺桨进行计算，但精度较低。本文基于传统涡轮螺桨性能模拟方法，考虑前排桨扇出口气流对后排桨扇的影响，对前、后排桨扇进行独立建模，建立了开式转子发动机对转桨扇部件级性能计算模型，并使用美国NASA风洞试验数据进行验证。结果表明，对转桨扇性能模型计算精度较高，采用此模型可较准确地模拟不同设计参数和不同控制规律下的对转桨扇性能，并评估其对开式转子发动机总体性能的影响。%The prop-fan performance calculation is the most difficult part of the performance prediction of open rotor engine with counter-rotating prop-fan. To simplify a prop-fan as a propeller is a usually used method which is not so precise. Based on the traditional method, considering the influence of outlet airflow from the front blades on the rear blades, the front model and rear model were built separately. Then the open rotor engine counter-rotating prop-fan component performance model was established and demonstrat- ed by wind tunnel test data from NASA. The counter-rotating prop-fan model was proved to be precise. With this model, various design parameters and different performance under control laws could be precisely simulated, and its influence on the overall performance of open rotor engine could be evaluated.
Institute of Scientific and Technical Information of China (English)
陆洋; 王超; 赵鑫
2013-01-01
首先基于Peters He广义动态尾迹理论,建立了电控旋翼动态尾迹入流模型,进一步结合电控旋翼襟翼操纵与桨叶变距之间的关系、桨叶挥舞运动方程和带襟翼翼型非定常气动力模型建立了适用于飞行力学分析的电控旋翼气动力模型.在此基础上,结合机身、尾桨、尾面的气动力模型,建立了完整的电控旋翼直升机飞行动力学分析模型.以Z-11直升机为基准改造为电控旋翼直升机作为算例,计算了前飞状态下电控旋翼直升机的诱导速度分布和桨盘迎角分布,对比了电控旋翼与常规旋翼的气动特性差异；在此基础上,进一步分析了电控旋翼直升机的配平特性随前飞速度的变化规律以及与常规直升机的差异.%Firstly,a dynamic inflow model for electrically controlled rotor (ECR) is developed based on the "Peters-He" generalized dynamic wake theory,and an accurate aerodynamics model of ECR,which is suited for the analysis of ECR helicopter flight dynamics,is built combined with the relationship between flap deflection and blade pitch,the blade flapping equation and the unsteady aerodynamic model of airfoil with trailing-edge flap.Then,on this basis,an ECR helicopter flight dynamics model is established combined with the aerodynamics models of airframe,tail rotor,horizontal and vertical tail.Taking Z-11 helicopter as a numerical example,the distributions of ECR induced velocity and angles of attack variations with advance speed are calculated and compared with the baseline rotor.Furthermore,the trim characteristics of the ECR helicopter is investigated.
National Research Council Canada - National Science Library
Pierre Tchakoua; Rene Wamkeue; Mohand Ouhrouche; Tommy Andy Tameghe; Gabriel Ekemb
2015-01-01
.... Thus, models can significantly reduce design, development and optimization costs. This paper proposes a novel equivalent electrical model for Darrieus-type vertical axis wind turbines (DTVAWTs...
Fractional Identification of Rotor Skin Effect in Induction Machines
Directory of Open Access Journals (Sweden)
Jean-Claude Trigeassou
2011-07-01
Full Text Available Fractional identification of rotor skin effect in induction machines is presented in this paper. Park transformation is used to obtain a system of differential equations which allows to include the skin effect in the rotor bars of asynchronous machines. A transfer function with a fractional derivative order has been selected to represent the admittance of the bar by the help of a non integer integrator which is approximated by a J+1 dimensional modal system. The machine parameters are estimated by an output-error technique using a non linear iterative optimization algorithm. Numerical simulations and experimental results show the performance of the modal approach for modeling and identification.
Extension of Goldstein's circulation function for optimal rotors with hub
DEFF Research Database (Denmark)
Okulov, Valery; Sørensen, Jens Nørkær; Shen, Wen Zhong
2016-01-01
The aerodynamic interaction or interference between rotor blades and hub body is usually very complicated, but some useful simplifications can be made by considering the hub with an infinite cylinder. Various attempts to find the optimum distribution of circulation by the lifting vortex lines...... method have been previously proposed to describe the blade interaction with the hub modeled by the infinite cylinder. In this case, the ideal distribution of bound circulation on the rotor blades is such that the shed vortex system in the hub-area is a set of helicoidal vortex sheets moving uniformly...... at the nose-area of the semi-infinite hub....
NRT Rotor Structural / Aeroelastic Analysis for the Preliminary Design Review
Energy Technology Data Exchange (ETDEWEB)
Ennis, Brandon Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Paquette, Joshua A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-10-01
This document describes the initial structural design for the National Rotor Testbed blade as presented during the preliminary design review at Sandia National Laboratories on October 28- 29, 2015. The document summarizes the structural and aeroelastic requirements placed on the NRT rotor for satisfactory deployment at the DOE/SNL SWiFT experimental facility to produce high-quality datasets for wind turbine model validation. The method and result of the NRT blade structural optimization is also presented within this report, along with analysis of its satisfaction of the design requirements.
Study of nonlinear dynamic characteristics of rotor-bearing systems
Institute of Scientific and Technical Information of China (English)
焦映厚; 陈照波; 曲秀全
2004-01-01
Based on the short-bearing model, the stability of a rigid Jeffcott rotor system is studied in a relatively wide parameter range by using Poincare maps and the numerical intrgration method. The results of the calculation show that the period doubling bifurcation, quasi-periodic and chaotic motions may occur. In some typical system are acquired with the numerical integration method. They demonstrate some motion state of the system.The fractal dimension concept is used to determine whether the system is in a state of chaotic motion. The analysis result of this paper provides the theoretical basis for qualitatively controlling the stable operating states ofthe rotors.
Energy Technology Data Exchange (ETDEWEB)
Jacques, R.; Le Quere, P.; Daube, O. [Centre National de la Recherche Scientifique (CNRS), 91 - Orsay (France)
1997-12-31
Turbulent flows between a fixed disc and a rotating disc are encountered in various applications like turbo-machineries or torque converters of automatic gear boxes. These flows are characterised by particular physical phenomena mainly due to the effects of rotation (Coriolis and inertia forces) and thus, classical k-{epsilon}-type modeling gives approximative results. The aim of this work is to study these flows using direct numerical simulation in order to provide precise information about the statistical turbulent quantities and to improve the k-{epsilon} modeling in the industrial MATHILDA code of the ONERA and used by SNECMA company (aerospace industry). The results presented are restricted to the comparison between results obtained with direct simulation and results obtained with the MATHILDA code in the same configuration. (J.S.) 8 refs.
Shaft Diameter Measurement Using Structured Light Vision
2015-01-01
A method for measuring shaft diameters is presented using structured light vision measurement. After calibrating a model of the structured light measurement, a virtual plane is established perpendicular to the measured shaft axis and the image of the light stripe on the shaft is projected to the virtual plane. On the virtual plane, the center of the measured shaft is determined by fitting the projected image under the geometrical constraints of the light stripe, and the shaft diameter is meas...
Energy Technology Data Exchange (ETDEWEB)
Werner, Ulrich [Siemens AG, Nuernberg (Germany). Industry, Drive Technologies, Large Drives, Industry Development
2010-03-15
The paper shows a computational methodology for calculating the relative shaft vibrations in the sleeve bearings of two-pole induction machines regarding excitation due to an electromagnetic force, which is caused by static rotor eccentricity. For a worst case calculation concerning the height of exciting magnetic force electromagnetic field damping effects and magnetic resistance concerning the homopolar flux are neglected. The calculated magnetic force, acting on the rotor core with double supply frequency in direction of the smallest air gap, is implemented into a finite element rotor dynamic model. With this model the influence of the rotor speed as well as influence of the direction of the magnetic force on the relative shaft displacements can be analyzed. Therefore the paper shows a computational methodology to check, whether the rotor-bearing design is sensitive for electromagnetic excitations due to static rotor eccentricity and prepares therefore the possibility to introduce improvements during the design phase of the induction motor. (orig.)
Directory of Open Access Journals (Sweden)
Zhentao Wang
2012-01-01
Full Text Available Fault detection and isolation (FDI in rotor systems often faces the problem that the system dynamics is dependent on the rotor rotary frequency because of the gyroscopic effect. In unbalance excited rotor systems, the continuously distributed unbalances are hard to be determined or estimated accurately. The unbalance forces as disturbances make fault detection more complicated. The aim of this paper is to develop linear time invariant (LTI FDI methods (i.e., with constant parameters for rotor systems under consideration of gyroscopic effect and disturbances. Two approaches to describe the gyroscopic effect, that is, as unknown inputs and as model uncertainties, are investigated. Based on these two approaches, FDI methods are developed and the results are compared regarding the resulting FDI performances. Results are obtained by the application in a rotor test rig. Restrictions for the application of these methods are discussed.
Energy Technology Data Exchange (ETDEWEB)
Inayat-Hussain, J I [School of Engineering, Monash University, Jalan Lagoon Selatan, 46150 Bandar Sunway, Selangor Darul Ehsan (Malaysia)], E-mail: jawaid.inayat-hussain@eng.monash.edu.my
2008-02-15
Numerical results on the response of a flexible rotor supported by nonlinear active magnetic bearings are presented. Nonlinearity arising from the magnetic actuator forces that are nonlinear functions of the coil current and the air gap between the rotor and the stator, and from the geometric coupling of the magnetic actuators is incorporated into the mathematical model of the flexible rotor - active magnetic bearing system. For relatively large values of the geometric coupling parameter, the response of the rotor with the variation of the speed parameter within the range 0.05 {<=}{omega} {<=} 5.0 displayed a rich variety of nonlinear dynamical phenomena including sub-synchronous vibrations of periods -2, -3, -6, -9, and -17, quasi-periodicity and chaos. Numerical results also reveal the occurrence of bi-stable operation within certain ranges of the speed parameter where multiple attractors may co-exist at the same speed parameter value depending on the operating speed of the rotor.
Hybrid Configuration of Darrieus and Savonius Rotors for Stand-alone Power Systems
Wakui, Tetsuya; Tanzawa, Yoshiaki; Hashizume, Takumi; Nagao, Toshio
The suitable hybrid configuration of Darrieus lift-type and Savonius drag-type rotors for stand-alone wind turbine-generator systems is discussed using our dynamic simulation model. Two types of hybrid configurations are taken up: Type-A installs the Savonius rotor inside the Darrieus rotor and Type-B installs the Savonius rotor outside the Darrieus rotor. The computed results of the output characteristics and the dynamic behaviors of the system operated at the maximum power coefficient points show that Type-A, which has fine operating behavior to wind speed changes and can be compactly designed because of a shorter rotational shaft, is an effective way for self-controlled stand-alone small-scale systems.
Ezell, M. J.; Johnson, S. N.; Yu, Y.; Pokkunuri, P.; Perraud, V.; Bruns, E.; Alexander, M.; Zelenyuk, A.; Dabdub, D.; Finlayson-Pitts, B. J.
2008-12-01
A unique, high-volume, low-flow, stainless steel aerosol flow system for the study of the formation and reactions of aerosols relevant to the troposphere has been constructed, modeled and experimentally tested. The total flow tube length is 7.3 m which includes a 1.2 m section used for mixing. The flow tube is equipped with ultraviolet lamps for photolysis. The diameter of 0.45 m results in a smaller surface to volume ratio than is found in many other flow systems and reduces the contribution of wall reactions. The latter is also reduced by frequent cleaning of the flow tube walls which is feasible due to the ease of disassembly of the flow tube. Flow systems present a major advantage over chamber studies in that continuous sampling under stable conditions over long periods of time is possible, increasing the amount of sample available for analysis and permitting a wide variety of analytical techniques to be applied simultaneously. In this system, the large volume (1000 L) and low flow speed (2 cm/minute) result in a residence time of nearly an hour; and equally spaced sampling ports allow for time-resolved measurements of aerosol and gas-phase products. The central features of this system have been modeled using computational fluid dynamics software and experimentally probed using inert gases and aerosols. Instrumentation attached directly to this flow system includes a NOx analyzer, an ozone analyzer, relative humidity and temperature probes, a scanning mobility particle sizer (SMPS) spectrometer, an aerodynamic particle sizer (APS) spectrometer, GC-MS, integrating nephelometer, and FTIR. Particles are collected using impactors and filters, and analyzed by a variety of techniques including FTIR, electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), GC-MS, HPLC-UV and HPLC-MS. In addition, for selected studies, an aerosol mass spectrometer (AMS), a single particle mass spectrometer (SPLAT II) and
Stall Characteristics and Tip Clearance Effects in Forward Swept Axial Compressor Rotors
Institute of Scientific and Technical Information of China (English)
Ramakrishna PV; Govardhan M
2009-01-01
Tilting the blade sections to the flow direction (blade sweep) would increase the operating range of an axial com-pressor due to modifications in the pressure and velocity fields on the suction surface. On the other hand, blade tip gap, though finite, has great influence on the performance of a turbomachine. The present paper investigates the combined effect of these two factors on various flow characteristics in'a low speed axial flow compressor. For this present study, nine computational domains were modeled; three rotor sweep configurations (0°, 20° and 30°) and for three different clearance levels for each rotor. Commercial CFD solver ANSYS CFX 11.0 is used for the simulations. Results indicated that tip chordline sweep is found to improve the stall margin of the compressor by modifying the suction surface boundary layer migration phenomenon. Diffusion Factor (DF) contours showed the severity of stalling with unswept rotor. For the swept rotors, the zones of high probable stall are less severe and they become less in size with increasing sweep. Increment in the tip gap is found to gradually affect the perform-ance of unswept rotor, while the effect is very high for the two swept rotors for the earlier increments. As a mini-mum clearance is unavoidable, swept rotors suffer relatively higher deviation from the idealistic behavior than the unswept rotor due to tip clearance.
Numerical simulation of aerodynamic interaction for a tilt rotor aircraft in helicopter mode
Institute of Scientific and Technical Information of China (English)
Ye Liang; Zhang Ying; Yang Shuo; Zhu Xinglin; Dong Jun
2016-01-01
A rotor CFD solver is developed for simulating the aerodynamic interaction phe-nomenon among rotor, wing and fuselage of a tilt rotor aircraft in its helicopter mode. The unsteady Navier–Stokes equations are discretized in inertial frame and embedded grid system is adopted for describing the relative motion among blades and nacelle/wing/fuselage. A combination of multi-layer embedded grid and‘‘extended hole fringe”technique is complemented in original grid system to tackle grid assembly difficulties arising from the narrow space among different aerody-namic components, and to improve the interpolation precision by decreasing the cell volume dis-crepancy among different grid blocks. An overall donor cell searching and automatic hole cutting technique is used for grid assembly, and the solution processes are speeded up by introduc-tion of OpenMP parallel method. Based on this solver, flow fields and aerodynamics of a tilt rotor aircraft in hover are simulated with several rotor collective angles, and the corresponding states of an isolated rotor and rotor/wing/fuselage model are also computed to obtain reference solution. Aerodynamic interference influences among the rotor and wing/fuselage/nacelle are analyzed, and some meaningful conclusions are drawn.
Turbulent Flow Characteristics and Dynamics Response of a Vertical-Axis Spiral Rotor
Directory of Open Access Journals (Sweden)
Yuli Wang
2013-05-01
Full Text Available The concept of a vertical-axis spiral wind rotor is proposed and implemented in the interest of adapting it to air flows from all directions and improving the rotor’s performance. A comparative study is performed between the proposed rotor and conventional Savonius rotor. Turbulent flow features near the rotor blades are simulated with Spalart-Allmaras turbulence model. The torque coefficient of the proposed rotor is satisfactory in terms of its magnitude and variation through the rotational cycle. Along the height of the rotor, distinct spatial turbulent flow patterns vary with the upstream air velocity. Subsequent experiments involving a disk generator gives an in-depth understanding of the dynamic response of the proposed rotor under different operation conditions. The optimal tip-speed ratio of the spiral rotor is 0.4–0.5, as is shown in both simulation and experiment. Under normal and relative-motion flow conditions, and within the range of upstream air velocity from 1 to 12 m/s, the output voltage of the generator was monitored and statistically analyzed. It was found that normal air velocity fluctuations lead to a non-synchronous correspondence between upstream air velocity and output voltage. In contrast, the spiral rotor’s performance when operating from the back of a moving truck was significantly different to its performance under the natural conditions.