Tilt Rotor Aeroacoustic Model (TRAM): A New Rotorcraft Research Facility
National Research Council Canada - National Science Library
Young, Larry A
1998-01-01
...". These two test stands are inclusively called the Tilt Rotor Aeroacoustic Model "TRAM". The baseline proprotors and airframe of the TRAM test stands are nominally 1/4-scale representations of the V-22 Osprey aircraft...
Analysis of the wind tunnel test of a tilt rotor power force model
Marr, R. L.; Ford, D. G.; Ferguson, S. W.
1974-01-01
Two series of wind tunnel tests were made to determine performance, stability and control, and rotor wake interaction on the airframe, using a one-tenth scale powered force model of a tilt rotor aircraft. Testing covered hover (IGE/OCE), helicopter, conversion, and airplane flight configurations. Forces and moments were recorded for the model from predetermined trim attitudes. Control positions were adjusted to trim flight (one-g lift, pitching moment and drag zero) within the uncorrected test data balance accuracy. Pitch and yaw sweeps were made about the trim attitudes with the control held at the trimmed settings to determine the static stability characteristics. Tail on, tail off, rotors on, and rotors off configurations were testes to determine the rotor wake effects on the empennage. Results are presented and discussed.
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)
Wind Tunnel Testing of a 6%-Scale Large Civil Tilt Rotor Model in Airplane and Helicopter Modes
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... 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...airframe models were tested without rotors in the U.S. Army 7- by 10-foot wind tunnel at NASA Ames Research Center. This test entry represents the first
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.
Directory of Open Access Journals (Sweden)
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.
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...... 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.......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...
Directory of Open Access Journals (Sweden)
Ying Zhang
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.
Vibration reduction in a tilting rotor using centrifugal pendulum vibration absorbers
Shi, Chengzhi; Shaw, Steven W.; Parker, Robert G.
2016-12-01
This paper investigates vibration reduction in a rigid rotor with tilting, rotational, and translational motions using centrifugal pendulum vibration absorbers (CPVAs). A linearized vibration model is derived for the system consisting of the rotor and multiple sets of absorbers tuned to different orders. Each group of absorbers lies in a given plane perpendicular to the rotor rotation axis. Gyroscopic system modal analysis is applied to derive the steady-state response of the absorbers and the rotor to external, rotor-order, periodic forces and torques with frequency mΩ, where Ω is the mean rotor speed and m is the engine order (rotor-order). It is found that an absorber group with tuning order m is effective at reducing the rotor translational, tilting, and rotational vibrations, provided certain conditions are met. When the periodic force and torque are caused by N substructures that are equally spaced around the rotor, the rotor translational and tilting vibrations at order j are addressed by two absorber groups with tuning orders jN±1. In this case, the rotor rotational vibration at order j can be attenuated by an absorber group with tuning order jN. The results show how the response depends on the load amplitudes and order, the rotor speed, and design parameters associated with the sets of absorbers, most importantly, their tuning, mass, and plane of placement. In the ideal case with zero damping and exact tuning of the absorber sets, the vibrations can be eliminated for a range of loads over which the linearized model holds. The response for systems with detuned absorbers is also determined, which is relevant to applications where small detuning is employed due to robustness issues, and to allow for a larger range of operating loads over which the absorbers are effective. The system also exhibits undesirable resonances very close to these tuning conditions, an issue that is difficult to resolve and deserves further investigation.
Position, Attitude, and Fault-Tolerant Control of Tilting-Rotor Quadcopter
Kumar, Rumit
flight. Further, the performance of the controller and the tilt-rotor design has been compared with respect to the conventional quadcopter in the presence of wind disturbances and sensor uncertainties. In this work, another novel feed-forward control design approach is presented for complex trajectory tracking during autonomous flight. Differential flatness based feed-forward position control is employed to enhance the performance of the UAV during complex trajectory tracking. By accounting for differential flatness based feed-forward control input parameters, a new PD controller is designed to achieve the desired performance in autonomous flight. The results for tracking complex trajectories have been presented by performing numerical simulations with and without environmental uncertainties to demonstrate robustness of the controller during flight. The conventional quadcopters are under-actuated systems and, upon failure of one propeller, the conventional quadcopter would have a tendency of spinning about the primary axis fixed to the vehicle as an outcome of the asymmetry in resultant yawing moment in the system. In this work, control of tilt-rotor quadcopter is presented upon failure of one propeller during flight. The tilt-rotor quadcopter is capable of handling a propeller failure and hence is a fault-tolerant system. The dynamic model of tilting-rotor quadcopter with one propeller failure is derived and a controller has been designed to achieve hovering and navigation capability. The simulation results of way point navigation, complex trajectory tracking and fault-tolerance are presented.
Control techniques of tilt rotor unmanned aerial vehicle systems: A review
Directory of Open Access Journals (Sweden)
Zhong Liu
2017-02-01
Full Text Available The tilt rotor unmanned aerial vehicle (TRUAV exhibits special application value due to its unique rotor structure. However, varying dynamics and aerodynamic interference caused by tiltable rotors are great technical challenges and key issues for TRUAV’s high-powered flight controls, which have attracted the attention of many researchers. This paper outlines the concept of TRUAV and some typical TRUAV platforms while focusing on control techniques. TRUAV structural features, dynamics modeling, and flight control methods are discussed, and major challenges and corresponding developmental tendencies associated with TRUAV flight control are summarized.
Kottapalli, Sesi; Meza, Victor
1992-01-01
A rotorcraft analysis is conducted to assess tilt-rotor stability and conversion loads for the XV-15 rotor with metal blades within its specified test envelope. A 38-DOF flutter analysis based on the code by Johnson (1988) is developed to simulate a wind-tunnel test in which the rotor torque is constant and thereby study stability. The same analytical model provides the simulated loads including hub loads, blade loads, and oscillatory pitch-link loads with attention given to the nonuniform inflow through the proprotor in the presence of the wing. Tilt-rotor stability during the cruise mode is found to be sensitive to coupling effects in the control system stiffness, and a stability problem is identified in the XV-15 Advanced Technology Blades. The present analysis demonstrates that the tilt-rotor is stable within the specified test envelope of the NASA 40 x 80-ft wind tunnel.
Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2005-01-01
In the present paper the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted...... lubricated tilting-pad bearing. By applying a simple proportional controller it is possible to reach 30% reduction of the resonance peak associated with the first rigid body mode shape of the system. One of the most important consequences of such a vibration reduction in rotating machines is the feasibility...
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
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...
Adaptive Neural Network Sliding Mode Control for Quad Tilt Rotor Aircraft
Yanchao Yin; Hongwei Niu; Xiaobao Liu
2017-01-01
A novel neural network sliding mode control based on multicommunity bidirectional drive collaborative search algorithm (M-CBDCS) is proposed to design a flight controller for performing the attitude tracking control of a quad tilt rotors aircraft (QTRA). Firstly, the attitude dynamic model of the QTRA concerning propeller tension, channel arm, and moment of inertia is formulated, and the equivalent sliding mode control law is stated. Secondly, an adaptive control algorithm is presented to eli...
Effects of rotor location, coning, and tilt on critical loads in large wind turbines
Spera, D. A.; Janetzke, D. C.
1978-01-01
Several large (1500 kW) horizontal rotor configurations were analyzed to determine the effects on dynamic loads of upwind downwind rotor locations, coned and radial blade positions, and tilted and horizontal rotor axis positions. Loads were calculated for a range of wind velocities at three locations in the structure: (1) the blade shank; (2) the hub shaft; and (3) the yaw drive. Blade axis coning and rotor axis tilt were found to have minor effects on loads. However, locating the rotor upwind of the tower significantly reduced loads at all locations analyzed.
Wind Tunnel Interference Effects on Tilt Rotor Testing Using Computational Fluid Dynamics
Koning, Witold J. F.
2016-01-01
Experimental techniques to measure rotorcraft aerodynamic performance are widely used. However, most of them are either unable to capture interference effects from bodies, or require an extremely large computational budget. The objective of the present research is to develop an XV-15 Tiltrotor Research Aircraft rotor model for investigation of wind tunnel wall interference using a novel Computational Fluid Dynamics (CFD) solver for rotorcraft, RotCFD. In RotCFD, a mid-fidelity Unsteady Reynolds Averaged Navier-Stokes (URANS) solver is used with an incompressible flow model and a realizable k-e turbulence model. The rotor is, however, not modeled using a computationally expensive, unsteady viscous body-fitted grid, but is instead modeled using a blade-element model (BEM) with a momentum source approach. Various flight modes of the XV-15 isolated rotor, including hover, tilt, and airplane mode, have been simulated and correlated to existing experimental and theoretical data. The rotor model is subsequently used for wind tunnel wall interference simulations in the National Full-Scale Aerodynamics Complex (NFAC) at Ames Research Center in California. The results from the validation of the isolated rotor performance showed good correlation with experimental and theoretical data. The results were on par with known theoretical analyses. In RotCFD the setup, grid generation, and running of cases is faster than many CFD codes, which makes it a useful engineering tool. Performance predictions need not be as accurate as high-fidelity CFD codes, as long as wall effects can be properly simulated. For both test sections of the NFAC wall, interference was examined by simulating the XV-15 rotor in the test section of the wind tunnel and with an identical grid but extended boundaries in free field. Both cases were also examined with an isolated rotor or with the rotor mounted on the modeled geometry of the Tiltrotor Test Rig (TTR). A "quasi linear trim" was used to trim the thrust
Energy Technology Data Exchange (ETDEWEB)
Sambell, K.W.
1976-04-01
A conceptual design study is presented of 1,985 commercial tilt rotor STOL transports for a NASA 200 n. mi. (370 km) STOL Mission. A 100-passenger STOL Variant (Bell D313) of the Phase I VTOL Tilt Rotor Aircraft is defined. Aircraft characteristics are given; with the aircraft redesigned to meet 2,000-foot (610 m) field criteria, with emphasis on low fuel consumption and low direct operating cost. The 100-passenger STOL Tilt Rotor Aircraft was analyzed for performance, weights, economics, handling qualities, noise footprint and aeroelastic stability. (GRA)
A comparison of optimal and noise-abatement trajectories of a tilt-rotor aircraft
Schmitz, F. H.; Stepniewski, W. Z.; Gibs, J.; Hinterkeuser, W. Z.
1972-01-01
The potential benefits of flight path control to optimize performance and/or reduce the noise of a tilt-rotor aircraft operating in the takeoff and landing phases of flight are investigated. A theoretical performance-acoustic model is developed and then mathematically flown to yield representative takeoff and landing profiles. Minimum-time and minimum-fuel trajectories are compared to proposed noise-abatement profiles to assess the reductions in annoyance possible through flight path control. Significant reductions are feasible if a nearly vertical-takeoff flight profile is flown near the landing site; however, the time expended and fuel consumed increase.
Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2004-01-01
In the present paper, the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted......-pad bearing. By applying a simple proportional controller, it is possible to reach 30% reduction of the resonance peak associated with the first rigid body mode shape of the system. One of the most important consequences of such a vibration reduction in rotating machines is the feasibility of increasing...
Modeling of Tilting-Pad Journal Bearings with Transfer Functions
Directory of Open Access Journals (Sweden)
J. A. Vázquez
2001-01-01
Full Text Available Tilting-pad journal bearings are widely used to promote stability in modern rotating machinery. However, the dynamics associated with pad motion alters this stabilizing capacity depending on the operating speed of the machine and the bearing geometric parameters, particularly the bearing preload. In modeling the dynamics of the entire rotor-bearing system, the rotor is augmented with a model of the bearings. This model may explicitly include the pad degrees of freedom or may implicitly include them by using dynamic matrix reduction methods. The dynamic reduction models may be represented as a set of polynomials in the eigenvalues of the system used to determine stability. All tilting-pad bearings can then be represented by a fixed size matrix with polynomial elements interacting with the rotor. This paper presents a procedure to calculate the coefficients of polynomials for implicit bearing models. The order of the polynomials changes to reflect the number of pads in the bearings. This results in a very compact and computationally efficient method for fully including the dynamics of tilting-pad bearings or other multiple degrees of freedom components that interact with rotors. The fixed size of the dynamic reduction matrices permits the method to be easily incorporated into rotor dynamic stability codes. A recursive algorithm is developed and presented for calculating the coefficients of the polynomials. The method is applied to stability calculations for a model of a typical industrial compressor.
Frequency Response Analysis of an Actively Lubricated Rotor/Tilting-Pad Bearing System
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2004-01-01
In the present paper, the dynamic response of a rotor supported by an active lubricated tilting-pad bearing is investigated in the frequency domain. The theoretical part of the investigation is based on a mathematical model obtained by means of rigid body dynamics. The oil film forces are inserted...... into the model by using two different approaches: (a) linearized active oil film forces and the assumption that the hydrodynamic forces and the active hydraulic forces can be decoupled; (b) equivalent dynamic coefficients of the active oil film and the solution of the modified Reynolds' equation for the active......-pad bearing. By applying a simple proportional controller, it is possible to reach 30% reduction of the resonance peak associated with the first rigid body mode shape of the system. One of the most important consequences of such a vibration reduction in rotating machines is the feasibility of increasing...
Nonlinear Dynamics Analysis of Tilting Pad Journal Bearing-Rotor System
Directory of Open Access Journals (Sweden)
Jiayang Ying
2011-01-01
Full Text Available The nonlinear dynamics theory is increasingly applied in the dynamics analysis of tilting pad journal bearing-rotor system. However, extensive work on system dynamics done previously neglects the influence caused by the moment of inertia of the pad. In this paper, a comparison is made between the responses of the rotor in the bearings with and without pad inertia effect. Taking the Jeffcott rotor system as an example, the characteristics of bearing-rotor system, such as bifurcation diagram, cycle response, frequency spectrum, phase trajectories, and Poincaré maps, were attained within a certain rotation rate range. The pivotal oil-film force of tilting pad journal bearing was calculated by database method. The results directly demonstrate that considering the influence of the pad moment of inertia, system dynamics characteristics are found more complicated when rotor-bearing system works around natural frequency and system bifurcation is observed forward when rotor-bearing system works on high-speed range.
Definition and analytical evaluation of a power management system for tilt-rotor aircraft
Morris, J. J.; Alexander, H. R.
1978-01-01
The paper reviews the special design criteria which apply to power management in a tilt-rotor aircraft. These include the need for accurate and fast control of rpm and thrust, while accounting for the dynamic interactions between rotor systems caused by cross-shafting and aircraft lateral/directional response. The power management system is also required to provide acceptable high speed sensitivity to longitudinal turbulence. It is shown that the criteria can best be met using a single governor adjusting the collective pitch by an amount proportional to a combination of the average rpm and the integral of the average rpm of the two rotors. This system is evaluated and compared with other candidate systems in hover and cruise flight.
Control of a Quadrotor Equipped with a Fixed-wing by Tilting Some of Four Rotors
Directory of Open Access Journals (Sweden)
Yoshikazu Nakamura
2017-03-01
Full Text Available Abstract—Unmanned aerial vehicles (UAVs are beingexpected to be used for the vegetational observation and theinformation collection of disaster sites. Especially, rotorcraftstypified by helicopters are attractive, because they are able tohover and achieve vertical take-off and landing (VTOL.However, rotorcrafts have a disadvantage that it cannot have along-distance flight, because they fly by the thrust of upwarddirection. Aircrafts with tilt rotors are developed in order toovercome such disadvantages. Such aircrafts can be hovering andtake a VTOL and also a long-distance flight by changing theangle of the rotor. In this research, it is aimed at proposing aVTOL-type UAV with a fixed-wing and four tiltable rotors andcontrolling it.
Adaptive Neural Network Sliding Mode Control for Quad Tilt Rotor Aircraft
Directory of Open Access Journals (Sweden)
Yanchao Yin
2017-01-01
Full Text Available A novel neural network sliding mode control based on multicommunity bidirectional drive collaborative search algorithm (M-CBDCS is proposed to design a flight controller for performing the attitude tracking control of a quad tilt rotors aircraft (QTRA. Firstly, the attitude dynamic model of the QTRA concerning propeller tension, channel arm, and moment of inertia is formulated, and the equivalent sliding mode control law is stated. Secondly, an adaptive control algorithm is presented to eliminate the approximation error, where a radial basis function (RBF neural network is used to online regulate the equivalent sliding mode control law, and the novel M-CBDCS algorithm is developed to uniformly update the unknown neural network weights and essential model parameters adaptively. The nonlinear approximation error is obtained and serves as a novel leakage term in the adaptations to guarantee the sliding surface convergence and eliminate the chattering phenomenon, which benefit the overall attitude control performance for QTRA. Finally, the appropriate comparisons among the novel adaptive neural network sliding mode control, the classical neural network sliding mode control, and the dynamic inverse PID control are examined, and comparative simulations are included to verify the efficacy of the proposed control method.
Design Study of Propulsion and Drive Systems for the Large Civil TiltRotor (LCTR2) Rotorcraft
Robuck, Mark; Wilkerson, Joseph; Zhang, Yiyi; Snyder, Christopher A.; Vonderwell, Daniel
2013-01-01
Boeing, Rolls Royce, and NASA have worked together to complete a parametric sizing study for NASA's Large Civil Tilt Rotor (LCTR2) concept 2nd iteration. Vehicle gross weight and fuel usage were evaluated as propulsion and drive system characteristics were varied to maximize the benefit of reduced rotor tip speed during cruise conditions. The study examined different combinations of engine and gearbox variability to achieve rotor cruise tip speed reductions down to 54% of the hover tip speed. Previous NASA studies identified that a 54% rotor speed reduction in cruise minimizes vehicle gross weight and fuel burn. The LCTR2 was the study baseline for initial sizing. This study included rotor tip speed ratios (cruise to hover) of 100%, 77% and 54% at different combinations of engine RPM and gearbox speed reductions, which were analyzed to achieve the lightest overall vehicle gross weight (GW) at the chosen rotor tip speed ratio. Different engine and gearbox technology levels are applied ranging from commercial off-the-shelf (COTS) engines and gearbox technology to entry-in-service (EIS) dates of 2025 and 2035 to assess the benefits of advanced technology on vehicle gross weight and fuel burn. Interim results were previously reported1. This technical paper extends that work and summarizes the final study results including additional engine and drive system study accomplishments. New vehicle sizing data is presented for engine performance at a single operating speed with a multispeed drive system. Modeling details for LCTR2 vehicle sizing and subject engine and drive sub-systems are presented as well. This study was conducted in support of NASA's Fundamental Aeronautics Program, Subsonic Rotary Wing Project.
Collins, Nathan Scott
Surrey Space Centre (SSC) has been working on an autonomous fixed-wing all-electric vertical take-off and landing (VTOL) aerobot for the exploration of Mars for several years. SSC's previous designs have incorporated separate vertical lift and horizontal pusher rotors as well as a mono tilt-rotor configuration. The Martian aerobot's novel Y-4 tilt-rotor (Y4TR) design is a combination of two previous SSC designs and a step forward for planetary aerobots. The aerobot will fly as a Y4 multi-rotor during vertical flight and as a conventional flying wing during horizontal flight. The more robust Y4TR configuration utilizes two large fixed coaxial counter rotating rotors and two small tilt-rotors for vertical takeoff. The front tilt-rotors rotate during transition flight into the main horizontal flight configuration. The aerobot is a blended wing design with the wings using the "Zagi 10" airfoil blended to a center cover for the coaxial rotors. The open source design and analysis programs XROTOR, CROTOR, Q-BLADE, XFLR5, and OpenVSP were used to design and model the aerobot's four rotors and body. The baseline mission of the Y4TR remains the same as previously reported and will investigate the Isidis Planitia region on Mars over a month long period using optical sensors during flight and a surface science package when landed. During flight operations the aerobot will take off vertically, transition to horizontal flight, fly for around an hour, transition back to vertical flight, and land vertically. The flight missions will take place close to local noon to maximize power production via solar cells during flight. A nonlinear six degree of freedom (6DoF) dynamic model incorporating aerodynamic models of the aerobot's body and rotors has been developed to model the vertical, transition, and horizontal phases of flight. A nonlinear State-Dependent Riccati Equation (SDRE) controller has been developed for each of these flight phases. The nonlinear dynamic model was
DEFF Research Database (Denmark)
Salazar, Jorge Andrés González; Santos, Ilmar
2015-01-01
function is optimized in the stabilizing gain domain and then chosen from a subdomain imposed by servovalve restrictions. This work demonstrates enhancements of the dynamic response of flexible rotor-bearing systems supported by an active tilting-pad journal bearing by means of the feedback...
Active tilting-pad journal bearings supporting flexible rotors: Part I – The hybrid lubrication
DEFF Research Database (Denmark)
Salazar, Jorge Andrés González; Santos, Ilmar
2017-01-01
This is part I of a twofold paper series, of theoretical and experimental nature, presenting 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...
An Investigation of Large Tilt-Rotor Hover and Low Speed Handling Qualities
Malpica, Carlos A.; Decker, William A.; Theodore, Colin R.; Lindsey, James E.; Lawrence, Ben; Blanken, Chris L.
2011-01-01
A piloted simulation experiment conducted on the NASA-Ames Vertical Motion Simulator evaluated the hover and low speed handling qualities of a large tilt-rotor concept, with particular emphasis on longitudinal and lateral position control. Ten experimental test pilots evaluated different combinations of Attitude Command-Attitude Hold (ACAH) and Translational Rate Command (TRC) response types, nacelle conversion actuator authority limits and inceptor choices. Pilots performed evaluations in revised versions of the ADS-33 Hover, Lateral Reposition and Depart/Abort MTEs and moderate turbulence conditions. Level 2 handling qualities ratings were primarily recorded using ACAH response type in all three of the evaluation maneuvers. The baseline TRC conferred Level 1 handling qualities in the Hover MTE, but there was a tendency to enter into a PIO associated with nacelle actuator rate limiting when employing large, aggressive control inputs. Interestingly, increasing rate limits also led to a reduction in the handling qualities ratings. This led to the identification of a nacelle rate to rotor longitudinal flapping coupling effect that induced undesired, pitching motions proportional to the allowable amount of nacelle rate. A modification that counteracted this effect significantly improved the handling qualities. Evaluation of the different response type variants showed that inclusion of TRC response could provide Level 1 handling qualities in the Lateral Reposition maneuver by reducing coupled pitch and heave off axis responses that otherwise manifest with ACAH. Finally, evaluations in the Depart/Abort maneuver showed that uncertainty about commanded nacelle position and ensuing aircraft response, when manually controlling the nacelle, demanded high levels of attention from the pilot. Additional requirements to maintain pitch attitude within 5 deg compounded the necessary workload.
Directory of Open Access Journals (Sweden)
Yongliang Wang
2015-01-01
Full Text Available Tilting pad bearings offer unique dynamic stability enabling successful deployment of high-speed rotating machinery. The model of dynamic stiffness, damping, and added mass coefficients is often used for rotordynamic analyses, and this method does not suffice to describe the dynamic behaviour due to the nonlinear effects of oil film force under larger shaft vibration or vertical rotor conditions. The objective of this paper is to present a nonlinear oil force model for finite length tilting pad journal bearings. An approximate analytic oil film force model was established by analysing the dynamic characteristic of oil film of a single pad journal bearing using variable separation method under the dynamic π oil film boundary condition. And an oil film force model of a four-tilting-pad journal bearing was established by using the pad assembly technique and considering pad tilting angle. The validity of the model established was proved by analyzing the distribution of oil film pressure and the locus of journal centre for tilting pad journal bearings and by comparing the model established in this paper with the model established using finite difference method.
Malcipa, Carlos; Decker, William A.; Theodore, Colin R.; Blanken, Christopher L.; Berger, Tom
2010-01-01
A piloted simulation investigation was conducted using the NASA Ames Vertical Motion Simulator to study the impact of pitch, roll and yaw attitude bandwidth and phase delay on handling qualities of large tilt-rotor aircraft. Multiple bandwidth and phase delay pairs were investigated for each axis. The simulation also investigated the effect that the pilot offset from the center of gravity has on handling qualities. While pilot offset does not change the dynamics of the vehicle, it does affect the proprioceptive and visual cues and it can have an impact on handling qualities. The experiment concentrated on two primary evaluation tasks: a precision hover task and a simple hover pedal turn. Six pilots flew over 1400 data runs with evaluation comments and objective performance data recorded. The paper will describe the experiment design and methodology, discuss the results of the experiment and summarize the findings.
MODELLING AND CONTROL OF H-SHAPED RACING QUADCOPTER WITH TILTING PROPELLERS
Directory of Open Access Journals (Sweden)
Ahmed Alkamachi
2017-08-01
Full Text Available Traditional quadcopter suffers terribly from its underactuation which implies the coupling between the rotational and the translational motion. In this paper, we present a quadcopter with dynamic rotor tilting capability in which the four propellers are allowed to tilt together around their arm axis. The proposed model provides leveled forward/backward horizontal motion and therefore, ensures a correct view of the onboard camera, and increases the vehicle speed by reducing the air drag. The rotor tilt mechanism also provides an instant high speed in the forward or reverse direction and offers a quick and solid air brake to restrain that fast moving speed. The nonlinear dynamical model for the quadcopter under consideration is derived using Newton-Euler formalization. A control strategy is then proposed aimed to control the altitude, attitude, and the forward speed of the obtained model. Finally, a numerical simulation is used to integrate the system model with the controller and to test the system performance. Simulation results are reported to demonstrate the advantages of the proposed novel configuration.
Numerical modelling of the tilt casting processes of titanium alumindes
Wang, Hong
2008-01-01
This research has investigated the modelling and optimisation of the tilt casting process of Titanium Aluminides (TiAl). This study is carried out in parallel with the experimental research undertaken in IRC at the University of Birmingham. They propose to use tilt casting inside a vacuum chamber and attempt to combine this tilt casting process with Induction Skull Melting (ISM). A totally novel process is developing for investment casting, which is suitable for casting gamma TiAl.\\ud \\ud As ...
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
Tilted-ring modelling of disk galaxies : Anomalous gas
Jozsa, G. I. G.; Niemczyk, C.; Klein, U.; Oosterloo, T. A.
We report our ongoing work on kinematical modelling of HI in disk galaxies. We employ our new software TiRiFiC (Tilted-Ring-Fitting-Code) in order to derive tilted-ring models by fitting artificial HI data cubes to observed ones in an automated process. With this technique we derive very reliable
Stability of Rotor Systems: A Complex Modelling Approach
DEFF Research Database (Denmark)
Kliem, Wolfhard; Pommer, Christian; Stoustrup, Jakob
1996-01-01
with the results of the classical approach using Rayleighquotients. Several rotor systems are tested: a simple Laval rotor, a Laval rotor with additional elasticity and damping in thr bearings, and a number of rotor systems with complex symmetric 4x4 randomly generated matrices.......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...
International Nuclear Information System (INIS)
Gronert, H.; Vetter, J.; Eckert, M.
1978-01-01
In the field of hollow high speed rotors there is an increasing demand for progressively higher speeds of safe operation. High speed operation causes support bearings to be carefully designed if the rotor speed is to pass safely through its critical speed of operation where intense vibration is experienced. Also the rotational speed is limited by the peripheral velocity and strength of the outside surface portion of the rotor. The invention proposes that elemental boron, which has great tensile strength and lightness be used to provide a major part of a hollow rotor so that increased operating speeds can be attained. Such a rotor is usable to provide a high speed centrifuge drum. (author)
Directory of Open Access Journals (Sweden)
Hui-Hui Feng
2014-01-01
Full Text Available The water-lubricated bearings have been paid attention for their advantages to reduce the power loss and temperature rise and increase load capacity at high speed. To fully study the complete dynamic coefficients of two water-lubricated, hydrostatic journal bearings used to support a rigid rotor, a four-degree-of-freedom model considering the translational and tilting motion is presented. The effects of tilting ratio, rotary speed, and eccentricity ratio on the static and dynamic performances of the bearings are investigated. The bulk turbulent Reynolds equation is adopted. The finite difference method and a linear perturbation method are used to calculate the zeroth- and first-order pressure fields to obtain the static and dynamic coefficients. The results suggest that when the tilting ratio is smaller than 0.4 or the eccentricity ratio is smaller than 0.1, the static and dynamic characteristics are relatively insensitive to the tilting and eccentricity ratios; however, for larger tilting or eccentricity ratios, the tilting and eccentric effects should be fully considered. Meanwhile, the rotary speed significantly affects the performance of the hydrostatic, water-lubricated bearings.
Modeling of high speed micro rotors in moderate flow confinement
Dikmen, E.; van der Hoogt, Peter; Aarts, Ronald G.K.M.; Sas, P.; Bergen, B.
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
Thermal modeling of a mini rotor-stator system
Dikmen, E.; van der Hoogt, Peter; de Boer, Andries; Aarts, Ronald G.K.M.; Jonker, Jan B.
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
Robuck, Mark; Wilkerson, Joseph; Snyder, Christopher A.; Zhang, Yiyi; Maciolek, Bob
2013-01-01
In a series of study tasks conducted as a part of NASA's Fundamental Aeronautics Program, Rotary Wing Project, Boeing and Rolls-Royce explored propulsion, drive, and rotor system options for the NASA Large Civil Tilt Rotor (LCTR2) concept vehicle. The original objective of this study was to identify engine and drive system configurations to reduce rotor tip speed during cruise conditions and quantify the associated benefits. Previous NASA studies concluded that reducing rotor speed (from 650 fps hover tip speed) during cruise would reduce vehicle gross weight and fuel burn. Initially, rotor cruise speed ratios of 54% of the hover tip speed were of most interest during operation at cruise air speed of 310 ktas. Interim results were previously reported1 for cruise tip speed ratios of 100%, 77%, and 54% of the hover tip speed using engine and/or gearbox features to achieve the reduction. Technology levels from commercial off-the-shelf (COTS), through entry-in-service (EIS) dates of 2025 and 2035 were considered to assess the benefits of advanced technology on vehicle gross weight and fuel burn. This technical paper presents the final study results in terms of vehicle sizing and fuel burn as well as Operational and Support (O&S) costs. New vehicle sizing at rotor tip speed reduced to 65% of hover is presented for engine performance with an EIS 2035 fixed geometry variable speed power turbine. LCTR2 is also evaluated for missions range cases of 400, 600, 800, 1000, and 1200 nautical miles and cruise air speeds of 310, 350 and 375 ktas.
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.
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...
Tilted dipole model for bias-dependent photoluminescence pattern
Fujieda, Ichiro; Suzuki, Daisuke; Masuda, Taishi
2014-12-01
In a guest-host system containing elongated dyes and a nematic liquid crystal, both molecules are aligned to each other. An external bias tilts these molecules and the radiation pattern of the system is altered. A model is proposed to describe this bias-dependent photoluminescence patterns. It divides the liquid crystal/dye layer into sub-layers that contain electric dipoles with specific tilt angles. Each sub-layer emits linearly polarized light. Its radiation pattern is toroidal and is determined by the tilt angle. Its intensity is assumed to be proportional to the power of excitation light absorbed by the sub-layer. This is calculated by the Lambert-Beer's Law. The absorption coefficient is assumed to be proportional to the cross-section of the tilted dipole moment, in analogy to the ellipsoid of refractive index, to evaluate the cross-section for each polarized component of the excitation light. Contributions from all the sub-layers are added to give a final expression for the radiation pattern. Self-absorption is neglected. The model is simplified by reducing the number of sub-layers. Analytical expressions are derived for a simple case that consists of a single layer with tilted dipoles sandwiched by two layers with horizontally-aligned dipoles. All the parameters except for the tilt angle can be determined by measuring transmittance of the excitation light. The model roughly reproduces the bias-dependent photoluminescence patterns of a cell containing 0.5 wt. % coumarin 6. It breaks down at large emission angles. Measured spectral changes suggest that the discrepancy is due to self-absorption and re-emission.
Tilted dipole model for bias-dependent photoluminescence pattern
International Nuclear Information System (INIS)
Fujieda, Ichiro; Suzuki, Daisuke; Masuda, Taishi
2014-01-01
In a guest-host system containing elongated dyes and a nematic liquid crystal, both molecules are aligned to each other. An external bias tilts these molecules and the radiation pattern of the system is altered. A model is proposed to describe this bias-dependent photoluminescence patterns. It divides the liquid crystal/dye layer into sub-layers that contain electric dipoles with specific tilt angles. Each sub-layer emits linearly polarized light. Its radiation pattern is toroidal and is determined by the tilt angle. Its intensity is assumed to be proportional to the power of excitation light absorbed by the sub-layer. This is calculated by the Lambert-Beer's Law. The absorption coefficient is assumed to be proportional to the cross-section of the tilted dipole moment, in analogy to the ellipsoid of refractive index, to evaluate the cross-section for each polarized component of the excitation light. Contributions from all the sub-layers are added to give a final expression for the radiation pattern. Self-absorption is neglected. The model is simplified by reducing the number of sub-layers. Analytical expressions are derived for a simple case that consists of a single layer with tilted dipoles sandwiched by two layers with horizontally-aligned dipoles. All the parameters except for the tilt angle can be determined by measuring transmittance of the excitation light. The model roughly reproduces the bias-dependent photoluminescence patterns of a cell containing 0.5 wt. % coumarin 6. It breaks down at large emission angles. Measured spectral changes suggest that the discrepancy is due to self-absorption and re-emission
Modelling and Simulations of a Narrow Track Tilting Vehicle
Directory of Open Access Journals (Sweden)
JJ Chong
2016-10-01
Full Text Available Narrow track tilting vehicle is a new category of vehicle that combines the dynamical abilities of a passenger car with a motorcycle. In the presence of overturning moments during cornering, an accurate assessment of the lateral dynamics plays an important role to improve their stability and handling. In order to stabilise or control the narrow tilting vehicle, the demand tilt angle can be calculated from the vehicle’s lateral acceleration and controlled by either steering input of the vehicle or using additional titling actuator to reach this desired angle. The aim of this article is to present a new approach for developing the lateral dynamics model of a narrow track tilting vehicle. First, this approach utilises the well-known geometry ‘bicycle model’ and parameter estimation methods. Second, by using a tuning method, the unknown and uncertainties are taken into account and regulated through an optimisation procedure to minimise the model biases in order to improve the modelling accuracy. Therefore, the optimised model can be used as a platform to develop the vehicle control strategy. Numerical simulations have been performed in a comparison with the experimental data to validate the model accuracy.
Conformally flat tilted Bianchi Type-V cosmological models in ...
Indian Academy of Sciences (India)
The model starts expanding with a big-bang at М = 0 and the expansion in the model stops at М = ∞ and = -2(Т + 2)¬. The model in general represents shearing, non-rotating and tilted universe. The expansion in the model decreases as time increases. For = 1 Т = 1, we have heat conduction vector Х1 = 0 Х4 = 0. When М ...
Modeling Flow Past a Tilted Vena Cava Filter
Energy Technology Data Exchange (ETDEWEB)
Singer, M A; Wang, S L
2009-06-29
Inferior vena cava filters are medical devices used to prevent pulmonary embolism (PE) from deep vein thrombosis. In particular, retrievable filters are well-suited for patients who are unresponsive to anticoagulation therapy and whose risk of PE decreased with time. The goal of this work is to use computational fluid dynamics to evaluate the flow past an unoccluded and partially occluded Celect inferior vena cava filter. In particular, the hemodynamic response to thrombus volume and filter tilt is examined, and the results are compared with flow conditions that are known to be thrombogenic. A computer model of the filter inside a model vena cava is constructed using high resolution digital photographs and methods of computer aided design. The models are parameterized using the Overture software framework, and a collection of overlapping grids is constructed to discretize the flow domain. The incompressible Navier-Stokes equations are solved, and the characteristics of the flow (i.e., velocity contours and wall shear stresses) are computed. The volume of stagnant and recirculating flow increases with thrombus volume. In addition, as the filter increases tilt, the cava wall adjacent to the tilted filter is subjected to low velocity flow that gives rise to regions of low wall shear stress. The results demonstrate the ease of IVC filter modeling with the Overture software framework. Flow conditions caused by the tilted Celect filter may elevate the risk of intrafilter thrombosis and facilitate vascular remodeling. This latter condition also increases the risk of penetration and potential incorporation of the hook of the filter into the vena caval wall, thereby complicating filter retrieval. Consequently, severe tilt at the time of filter deployment may warrant early clinical intervention.
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....
Stability of rotor systems: A complex modelling approach
DEFF Research Database (Denmark)
Kliem, Wolfhard; Pommer, Christian; Stoustrup, Jakob
1998-01-01
The dynamics of a large class of rotor systems can be modelled by a linearized complex matrix differential equation of second order, Mz + (D + iG)(z) over dot + (K + iN)z = 0, where the system matrices M, D, G, K and N are real symmetric. Moreover M and K are assumed to be positive definite and D...... approach applying bounds of appropriate Rayleigh quotients. The rotor systems tested are: a simple Laval rotor, a Laval rotor with additional elasticity and damping in the bearings, and a number of rotor systems with complex symmetric 4 x 4 randomly generated matrices.......The dynamics of a large class of rotor systems can be modelled by a linearized complex matrix differential equation of second order, Mz + (D + iG)(z) over dot + (K + iN)z = 0, where the system matrices M, D, G, K and N are real symmetric. Moreover M and K are assumed to be positive definite and D......, G and N to be positive semidefinite. The complex setting is equivalent to twice as large a system of second order with real matrices. It is well known that rotor systems can exhibit instability for large angular velocities due to internal damping, unsymmetrical steam flow in turbines, or imperfect...
Rotordynamic Evaluation of Full Scale Rotor on Tilting Pad Bearings with 0.1 and 0.3 Preload
Directory of Open Access Journals (Sweden)
Weimin Wang
2014-01-01
Full Text Available A system identification method for rotating machinery stability evaluation is investigated based on sine sweep excitation testing with electromagnetic actuator. The traditional MIMO FRF is transformed into dFRF from real number field to complex field with a transformation matrix, eliminating the influence of forward and backward modal overlap and providing higher accuracy to identify rotor’s first forward modal parameters using the rational polynomial method. The modal parameters are acquired for stability estimation. Furthermore, two sets of bearing with preloads of 0.1 and 0.3 under both load-on-pad (LOP and load-between-pad (LBP conditions are investigated. The effects of oil inlet pressure (1.0 bar–1.75 bar and temperature (43°C–51°C on the stability of rotor are investigated in detail. Results indicate that the stability of rotor will be improved by increasing the oil inlet temperature and pressure. It is found that the rotor is more stable on bearing with 0.1 preload than that of 0.3 preload. Load-on-pad provides more damping to rotor than load-between-pad. The method and outcomes of this paper can provide both theory basis and technology foundation for improving the rotor stability of centrifugal compressors.
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
Linear Time Invariant Models for Integrated Flight and Rotor Control
Olcer, Fahri Ersel
2011-12-01
Recent developments on individual blade control (IBC) and physics based reduced order models of various on-blade control (OBC) actuation concepts are opening up opportunities to explore innovative rotor control strategies for improved rotor aerodynamic performance, reduced vibration and BVI noise, and improved rotor stability, etc. Further, recent developments in computationally efficient algorithms for the extraction of Linear Time Invariant (LTI) models are providing a convenient framework for exploring integrated flight and rotor control, while accounting for the important couplings that exist between body and low frequency rotor response and high frequency rotor response. Formulation of linear time invariant (LTI) models of a nonlinear system about a periodic equilibrium using the harmonic domain representation of LTI model states has been studied in the literature. This thesis presents an alternative method and a computationally efficient scheme for implementation of the developed method for extraction of linear time invariant (LTI) models from a helicopter nonlinear model in forward flight. The fidelity of the extracted LTI models is evaluated using response comparisons between the extracted LTI models and the nonlinear model in both time and frequency domains. Moreover, the fidelity of stability properties is studied through the eigenvalue and eigenvector comparisons between LTI and LTP models by making use of the Floquet Transition Matrix. For time domain evaluations, individual blade control (IBC) and On-Blade Control (OBC) inputs that have been tried in the literature for vibration and noise control studies are used. For frequency domain evaluations, frequency sweep inputs are used to obtain frequency responses of fixed system hub loads to a single blade IBC input. The evaluation results demonstrate the fidelity of the extracted LTI models, and thus, establish the validity of the LTI model extraction process for use in integrated flight and rotor control
Modelling of Rotor-gas bearings for Feedback Controller Design
DEFF Research Database (Denmark)
Theisen, Lukas Roy Svane; Niemann, Hans Henrik
2014-01-01
Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which ca...... and are shown to accurately describe the dynamical behaviour of the rotor-gas bearing. Design of a controller using the identied models is treated and experiments verify the improvement of the damping properties of the rotor-gas bearing.......Controllable rotor-gas bearings are popular oering adaptability, high speed operation, low friction and clean operation. Rotor-gas bearings are however highly sensitive to disturbances due to the low friction of the injected gas. These undesirable damping properties call for controllers, which can...... be designed from suitable models describing the relation from actuator input to measured shaft position. Current state of the art models of controllable gas bearings however do not provide such relation, which calls for alternative strategies. The present contribution discusses the challenges for feedback...
DEFF Research Database (Denmark)
Salazar, Jorge Andrés González; Santos, Ilmar
2014-01-01
to experimentally characterized multi-input multi-output systems is used to determine the stabilizing PD gain domain. The main contribution of this work is to demonstrate the enhancement of the dynamic response of a flexible rotor-bearing system supported by an active TPJB by means of the feedback...
Rigid finite element model of a cracked rotor
Kulesza, Zbigniew; Sawicki, Jerzy T.
2012-08-01
The article introduces a new mathematical model for the cracked rotating shaft. The model is based on the rigid finite element (RFE) method, which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. In this article, the RFE method is extended and adopted for the modeling of rotating machines. An original concept of crack modeling utilizing the RFE method is developed. The crack is presented as a set of spring-damping elements of variable stiffness connecting two sections of the shaft. An alternative approach for approximating the breathing mechanism of the crack is introduced. The approach is simple and allows one to intuitively and systematically prepare and analyze the model of a cracked rotor. The proposed method is illustrated with numerical and experimental results. The experiments conducted for the uncracked free-free rotor as well as the numerical results obtained with other software confirm the accuracy of the RFE model. The numerical analysis conducted for a set of cracked rotors has shown that, depending on the eccentricity and its angular location, the breathing behavior of the crack may take different forms. In spite of this, the frequency spectra for different cracks are almost identical. Due to its simplicity and numerous advantages, the proposed approach may be useful for rotor crack detection, especially if methods utilizing the mathematical model of the rotor are applied.
Model-based monitoring of rotors with multiple coexisting faults
International Nuclear Information System (INIS)
Rossner, Markus
2015-01-01
Monitoring systems are applied to many rotors, but only few monitoring systems can separate coexisting errors and identify their quantity. This research project solves this problem using a combination of signal-based and model-based monitoring. The signal-based part performs a pre-selection of possible errors; these errors are further separated with model-based methods. This approach is demonstrated for the errors unbalance, bow, stator-fixed misalignment, rotor-fixed misalignment and roundness errors. For the model-based part, unambiguous error definitions and models are set up. The Ritz approach reduces the model order and therefore speeds up the diagnosis. Identification algorithms are developed for the different rotor faults. Hereto, reliable damage indicators and proper sub steps of the diagnosis have to be defined. For several monitoring problems, measuring both deflection and bearing force is very useful. The monitoring system is verified by experiments on an academic rotor test rig. The interpretation of the measurements requires much knowledge concerning the dynamics of the rotor. Due to the model-based approach, the system can separate errors with similar signal patterns and identify bow and roundness error online at operation speed. [de
Effective ellipsoidal models for wavefield extrapolation in tilted orthorhombic media
Waheed, Umair Bin
2016-04-22
Wavefield computations using the ellipsoidally anisotropic extrapolation operator offer significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate wavefield representation or imaging for media of orthorhombic symmetry. Therefore, we propose the use of ‘effective ellipsoidally anisotropic’ models that correctly capture the kinematic behaviour of wavefields for tilted orthorhombic (TOR) media. We compute effective velocities for the ellipsoidally anisotropic medium using kinematic high-frequency representation of the TOR wavefield, obtained by solving the TOR eikonal equation. The effective model allows us to use the cheaper ellipsoidally anisotropic wave extrapolation operators. Although the effective models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including frequency dependency and caustics, if present, with reasonable accuracy. The proposed methodology offers a much better cost versus accuracy trade-off for wavefield computations in TOR media, particularly for media of low to moderate anisotropic strength. Furthermore, the computed wavefield solution is free from shear-wave artefacts as opposed to the conventional finite-difference based TOR wave extrapolation scheme. We demonstrate applicability and usefulness of our formulation through numerical tests on synthetic TOR models. © 2016 Institute of Geophysics of the ASCR, v.v.i
Probabilistic Rotor Life Assessment Using Reduced Order Models
Directory of Open Access Journals (Sweden)
Brian K. Beachkofski
2009-01-01
Full Text Available Probabilistic failure assessments for integrally bladed disks are system reliability problems where a failure in at least one blade constitutes a rotor system failure. Turbine engine fan and compressor blade life is dominated by High Cycle Fatigue (HCF initiated either by pure HCF or Foreign Object Damage (FOD. To date performing an HCF life assessment for the entire rotor system has been too costly in analysis time to be practical. Although the substantial run-time has previously precluded a full-rotor probabilistic analysis, reduced order models make this process tractable as demonstrated in this work. The system model includes frequency prediction, modal stress variation, mistuning amplification, FOD effect, and random material capability. The model has many random variables which are most easily handled through simple random sampling.
Patient Specific Modeling of Head-Up Tilt
DEFF Research Database (Denmark)
Williams, Nakeya; Wright, Andrew; Mehlsen, Jesper
2014-01-01
blood pressure. The model contains five compartments representing arteries and veins in the upper and lower body of the systemic circulation, as well as the left ventricle facilitating pumping of the heart. A physiologically based sub-model describes gravitational effects on pooling of blood during......Short term cardiovascular responses to head-up tilt (HUT) experiments involve complex cardiovascular regulation in order to maintain blood pressure at homeostatic levels. This manuscript presents a patient specific compartmental model developed to predict dynamic changes in heart rate and arterial...... that it is possible to estimate a subset of model parameters that allows prediction of observed changes in arterial blood pressure. Furthermore, the model adequately predicts arterial and venous blood pressures, as well as cardiac output in compartments for which data are not available....
3 QP plus rotor model and high spin states
International Nuclear Information System (INIS)
Mathur, Tripti
1995-01-01
Nuclear models are approximate methods to describe certain properties of a large number of nuclei. In this paper details of 3 QP (three quasi particle) plus rotor model and high spin state are discussed. The band head energies for the 3 QP rotational bands for 157 Ho and 159 Tm are also given. 5 refs., 8 figs
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...
A new dynamic model of rotor-blade systems
Ma, Hui; Lu, Yang; Wu, Zhiyuan; Tai, Xingyu; Li, Hui; Wen, Bangchun
2015-11-01
A new dynamic model of rotor-blade systems is developed in this paper considering the lateral and torsional deformations of the shaft, gyroscopic effects of the rotor which consists of shaft and disk, and the centrifugal stiffening, spin softening and Coriolis force of the blades. In this model, the rotating flexible blades are represented by Timoshenko beams. The shaft and rigid disk are described by multiple lumped mass points (LMPs), and these points are connected by massless springs which have both lateral and torsional stiffness. LMPs are represented by the corresponding masses and mass moments of inertia in lateral and rotational directions, where each point has five degrees of freedom (dofs) excluding axial dof. Equations of motion of the rotor-blade system are derived using Hamilton's principle in conjunction with the assumed modes method to describe blade deformation. The proposed model is compared with both finite element (FE) model and real experiments. The proposed model is first validated by comparing the model natural frequencies and vibration responses with those obtained from an FE model. A further verification of the model is then performed by comparing the model natural frequencies at zero rotational speed with those obtained from experimental studies. The results shown a good agreement between the model predicted system characteristics and those obtained from the FE model and experimental tests. Moreover, the following interesting phenomena have been revealed from the new model based analysis: The torsional natural frequency of the system decreases with the increase of rotational speed, and the frequency veering phenomenon has been observed at high rotational speed; The complicated coupling modes, such as the blade-blade coupling mode (BB), the coupling mode between the rotor lateral vibration and blade bending (RBL), and the coupling mode between the rotor torsional vibration and blade bending (RBT), have also been observed when the number of
Modeling and simulation of coaxial helicopter rotor aerodynamics
Gecgel, Murat
A framework is developed for the computational fluid dynamics (CFD) analyses of a series of helicopter rotor flowfields in hover and in forward flight. The methodology is based on the unsteady solutions of the three-dimensional, compressible Navier-Stokes equations recast in a rotating frame of reference. The simulations are carried out by solving the developed mathematical model on hybrid meshes that aim to optimally exploit the benefits of both the structured and the unstructured grids around complex configurations. The computer code is prepared for parallel processing with distributed memory utilization in order to significantly reduce the computational time and the memory requirements. The developed model and the simulation methodology are validated for single-rotor-in-hover flowfields by comparing the present results with the published experimental data. The predictive merit of different turbulence models for complex helicopter aerodynamics are tested extensively. All but the kappa-o and LES results demonstrate acceptable agreement with the experimental data. It was deemed best to use the one-equation Spalart-Allmaras turbulence model for the subsequent rotor flowfield computations. First, the flowfield around a single rotor in forward flight is simulated. These time---accurate computations help to analyze an adverse effect of increasing the forward flight speed. A dissymmetry of the lift on the advancing and the retreating blades is observed for six different advance ratios. Since the coaxial rotor is proposed to mitigate the dissymmetry, it is selected as the next logical step of the present investigation. The time---accurate simulations are successfully obtained for the flowfields generated by first a hovering then a forward-flying coaxial rotor. The results for the coaxial rotor in forward flight verify the aerodynamic balance proposed by the previously published advancing blade concept. The final set of analyses aims to investigate if the gap between the
Quad-Rotor Unmanned Aerial Vehicle Helicopter Modelling & Control
Directory of Open Access Journals (Sweden)
Yogianandh Naidoo
2011-09-01
Full Text Available This paper presents the investigation of the modelling and control of a quad-rotor helicopter and forms part of research involving the development of an unmanned aerial vehicle (UAV to be used in search and rescue applications. Quad-rotor helicopters consist of two pairs of counter rotating rotors situated at the ends of a cross, symmetric about the centre of gravity, which coincides with the origin of the reference system used. These rotors provide the predominant aerodynamic forces which act on the rotorcraft, and are modelled using momentum theory as well as blade element theory. From this, one can determine the expected payload capacity and lift performance of the rotorcraft. The Euler-Lagrange method has been used to derive the defining equations of motion of the six degree-of-freedom system. The Lagrangian was obtained by modelling the kinetic and potential energy of the system and the external forces obtained from the aerodynamic analysis. Based on this model, a control strategy was developed using linear PD controllers. A numerical simulation was then conducted using MATLAB® Simulink®. First, the derived model was simulated to investigate the behaviour of the rotorcraft, and then a second investigation was conducted to determine the effectiveness of the implemented control system. The results and findings of these investigations are then presented and discussed.
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...
International Nuclear Information System (INIS)
Yadav, P.; Chandel, S.S.
2014-01-01
Tilt angle and orientation greatly are influenced on the performance of the solar photo voltaic panels. The tilt angle of solar photovoltaic panels is one of the important parameters for the optimum sizing of solar photovoltaic systems. This paper analyses six different isotropic and anisotropic diffused solar radiation models for optimum tilt angle determination. The predicted optimum tilt angles are compared with the experimentally measured values for summer season under outdoor conditions. The Liu and Jordan model is found to exhibit t lowest error as compared to other models for the location. (author)
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
-blade/control-system aeroelastic analysis. The rotor blade analysis was in good agreement and validated by comparing with DYMORE. Numerical results were obtained for a four-bladed, small-scale, articulated rotor rotating in vacuum and in a wind tunnel to simulate forward-flight conditions and its aerodynamic effects. The complete......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...
1988-06-01
virtually conventional airplane performance when operating with its rotors partially tilted forward. In this configuration on a very short runway it can...Pto. Ayacucho to San Fernando de Atabapo. In areas where landing is virtually impossible transportation, recovery and resupply of critically needed...Venezuela 4. Jefatura de Educacion 2 Comandancia General de la Armada Avenida Vollmer San Bernardino Caracas, Venezuela 5. Escuela Superior de Guerra Naval
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.
Modelling the influence of yaw using a simple vortex rotor model
DEFF Research Database (Denmark)
Troldborg, Niels; Gaunaa, Mac; Guntur, Srinivas
2012-01-01
A simple analytical rotor model based on vortex theory is briefly presented and used to investigate the main mechanisms for wind turbine rotors operating at yaw misalignment. The overall findings of the model is verified by comparing with an existing model as well as with results obtained using...
General model and control of an n rotor helicopter
International Nuclear Information System (INIS)
Sidea, A G; Brogaard, R Yding; Andersen, N A; Ravn, O
2014-01-01
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
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.
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.
Effects of Different Rub Models on Simulated Rotor Dynamics
1984-02-01
bearings that were mounted in a squeeze - film damper common are blade tip and seal rubs, which are caused by with centering springs. Two of the...disks mounted on .0 .0 two axially stiff bearings (fig. 3). In this rotor- bearing model the bearings were mounted in squeeze - film damper where r(x,h,t...smearing and the abrading rub models into the analysis squeeze - film bearing . Assuming the ratio of blade width used in reference 5 and to compare
DEFF Research Database (Denmark)
Cerda Varela, Alejandro Javier; Fillon, Michel; Santos, Ilmar
2012-01-01
The relevance of calculating accurately the oil film temperature build up when modeling tilting-pad journal bearings is well established within the literature on the subject. This work studies the feasibility of using a thermal model for the tilting-pad journal bearing which includes a simplified...
MODELING, CONTROL AND NAVIGATION OF AN AUTONOMOUS QUAD-ROTOR HELICOPTER
Directory of Open Access Journals (Sweden)
Damir Šoštarić
2016-06-01
Full Text Available Autonomous outdoor quad-rotor helicopters increasingly attract the attention of potential researchers. Several structures and configurations have been developed to allow 3D movements. The quadrotor helicopter is made of a rigid cross frame equipped with four rotors. The autonomous quad-rotor architecture has been chosen for this research for its low dimension, good manoeuvrability, simple mechanics and payload capability. This article presents the modelling, control and navigation of an autonomous outdoor quad-rotor helicopter.
Efficient Beam-Type Structural Modeling of Rotor Blades
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 ...
Validation of Tilt Gain under Realistic Path Loss Model and Network Scenario
DEFF Research Database (Denmark)
Nguyen, Huan Cong; Rodriguez, Ignacio; Sørensen, Troels Bundgaard
2013-01-01
Despite being a simple and commonly-applied radio optimization technique, the impact on practical network performance from base station antenna downtilt is not well understood. Most published studies based on empirical path loss models report tilt angles and performance gains that are far higher...... than practical experience suggests. We motivate in this paper, based on a practical LTE scenario, that the discrepancy partly lies in the path loss model, and shows that a more detailed semi-deterministic model leads to both lower gains in terms of SINR, outage probability and downlink throughput...... and lower optimum tilt settings. Furthermore, we show that a simple geometrically based tilt optimization algorithm can outperform other tilt profiles, including the setting applied by the cellular operator in the specific case. In general, the network performance is not highly sensitive to the tilt...
The modeling of the dynamic behavior of an unsymmetrical rotor
Pǎrǎuşanu, Ioan; Gheorghiu, Horia; Petre, Cristian; Jiga, Gabriel; Crişan, Nicoleta
2018-02-01
The purpose of this article is to present the modeling of the dynamic behaviour of unsymmetrical rotors in relatively simple quantitative terms. Numerical simulations show that the shaft orthotropy produces a peak of resonant vibration about half the regular critical speed and, for small damping, a range of possible unstable behavior between the two critical speeds. Rotors having the shaft and/or the disks with unequal diametral moments of inertia (e.g., two-bladed small airplane propellers, wind turbines and fans) are dynamically unstable above a certain speed and some of these may return to a stable condition at a sufficiently high speed, depending on the particular magnitudes of the gyroscopic coupling and the inertia inequality.
Spectral statistics in particles-rotor model and cranking model
Zhou Xian Rong; Zhao En Guang; Guo Lu
2002-01-01
Spectral statistics for six particles in single-j and two-j model coupled with a deformed core are studied in the frames of particles-rotor model and cranking shell model. The nearest-neighbor-distribution of energy levels and spectral rigidity are studied as a function of the spin or cranking frequency, respectively. The results of single-j shell are compared with those in two-j case. The system becomes more regular when single-j space (i sub 1 sub 3 sub / sub 2) is replaced by two-j shell (g sub 7 sub / sub 2 + d sub 5 sub / sub 2), although the basis size of the configuration space is unchanged. However, the degree of chaoticity of the system changes slightly when configuration space is enlarged by extending single-j shell (i sub 1 sub 3 sub / sub 2) to two-j shell (i sub 1 sub 3 sub / sub 2 + g sub 9 sub / sub 2). Nuclear chaotic behavior is studied when authors take a two-body interaction as delta force and pairing interaction, respectively
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.
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.
Modelling of LEG tilting pad journal bearings with active lubrication
DEFF Research Database (Denmark)
Cerda Varela, Alejandro Javier; García, Asier Bengoechea; Santos, Ilmar
2017-01-01
This work constitutes the first step in a research effort aimed at studying the feasibility of introducing an active lubrication concept in tilting pad journal bearings (TPJBs) that feature the leading edge groove (LEG) lubrication system. The modification of the oil flow into each pad supply gro...
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...
Modeling and Robust Trajectory Tracking Control for a Novel Six-Rotor Unmanned Aerial Vehicle
Yang, Chengshun; Yang, Zhong; Huang, Xiaoning; Li, Shaobin; Zhang, Qiang
2013-01-01
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 ...
Tilt aftereffects in a self-organizing model of the primary visual cortex.
Bednar, J A; Miikkulainen, R
2000-07-01
RF-LISSOM, a self-organizing model of laterally connected orientation maps in the primary visual cortex, was used to study the psychological phenomenon known as the tilt aftereffect. The same self-organizing processes that are responsible for the long-term development of the map are shown to result in tilt aftereffects over short timescales in the adult. The model permits simultaneous observation of large numbers of neurons and connections, making it possible to relate high-level phenomena to low-level events, which is difficult to do experimentally. The results give detailed computational support for the long-standing conjecture that the direct tilt aftereffect arises from adaptive lateral interactions between feature detectors. They also make a new prediction that the indirect effect results from the normalization of synaptic efficacies during this process. The model thus provides a unified computational explanation of self-organization and both the direct and indirect tilt aftereffect in the primary visual cortex.
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.
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.
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.
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.
Dynamics Modeling and Control of a Quad-rotor Helicopter
Hossain, Mohammed Raju
Unmanned Aerial Vehicles (UAVs) have become a promising field of research due to the enormous potential for both military and civilian applications. This thesis focuses on increasing the autonomy of one type of rotary wing UAV; namely a Quad-rotor Helicopter. In this work a detailed mathematical model was introduced for simulation of the dynamics and control of this system. The dynamic model evolved from a simple set of equations, valid only for hovering, to a complex mathematical model with more realistic aerodynamic factors like thrust factor and drag factor. A simple yet precise tool was developed to measure these aerodynamic factors. An intelligent vision based control technique has been proposed for the critical, near-hovering flight of the vehicle. Finally, a platform was developed and a PD controller was implemented with inertial sensors in order to prepare the platform for implementing the vision-based control in the future.
Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock-Leighton Solar Dynamo Model
Karak, Bidya Binay; Miesch, Mark
2017-09-01
We present results from a three-dimensional Babcock-Leighton (BL) dynamo model that is sustained by the emergence and dispersal of bipolar magnetic regions (BMRs). On average, each BMR has a systematic tilt given by Joy’s law. Randomness and nonlinearity in the BMR emergence of our model produce variable magnetic cycles. However, when we allow for a random scatter in the tilt angle to mimic the observed departures from Joy’s law, we find more variability in the magnetic cycles. We find that the observed standard deviation in Joy’s law of {σ }δ =15^\\circ produces a variability comparable to the observed solar cycle variability of ˜32%, as quantified by the sunspot number maxima between 1755 and 2008. We also find that tilt angle scatter can promote grand minima and grand maxima. The time spent in grand minima for {σ }δ =15^\\circ is somewhat less than that inferred for the Sun from cosmogenic isotopes (about 9% compared to 17%). However, when we double the tilt scatter to {σ }δ =30^\\circ , the simulation statistics are comparable to the Sun (˜18% of the time in grand minima and ˜10% in grand maxima). Though the BL mechanism is the only source of poloidal field, we find that our simulations always maintain magnetic cycles even at large fluctuations in the tilt angle. We also demonstrate that tilt quenching is a viable and efficient mechanism for dynamo saturation; a suppression of the tilt by only 1°-2° is sufficient to limit the dynamo growth. Thus, any potential observational signatures of tilt quenching in the Sun may be subtle.
Vibration model of rolling element bearings in a rotor-bearing system for fault diagnosis
Cong, Feiyun; Chen, Jin; Dong, Guangming; Pecht, Michael
2013-04-01
Rolling element bearing faults are among the main causes of breakdown in rotating machines. In this paper, a rolling bearing fault model is proposed based on the dynamic load analysis of a rotor-bearing system. The rotor impact factor is taken into consideration in the rolling bearing fault signal model. The defect load on the surface of the bearing is divided into two parts, the alternate load and the determinate load. The vibration response of the proposed fault signal model is investigated and the fault signal calculating equation is derived through dynamic and kinematic analysis. Outer race and inner race fault simulations are realized in the paper. The simulation process includes consideration of several parameters, such as the gravity of the rotor-bearing system, the imbalance of the rotor, and the location of the defect on the surface. The simulation results show that different amplitude contributions of the alternate load and determinate load will cause different envelope spectrum expressions. The rotating frequency sidebands will occur in the envelope spectrum in addition to the fault characteristic frequency. This appearance of sidebands will increase the difficulty of fault recognition in intelligent fault diagnosis. The experiments given in the paper have successfully verified the proposed signal model simulation results. The test rig design of the rotor bearing system simulated several operating conditions: (1) rotor bearing only; (2) rotor bearing with loader added; (3) rotor bearing with loader and rotor disk; and (4) bearing fault simulation without rotor influence. The results of the experiments have verified that the proposed rolling bearing signal model is important to the rolling bearing fault diagnosis of rotor-bearing systems.
Vishwakarma, Vinod
Modified Modal Domain Analysis (MMDA) is a novel method for the development of a reduced-order model (ROM) of a bladed rotor. This method utilizes proper orthogonal decomposition (POD) of Coordinate Measurement Machine (CMM) data of blades' geometries and sector analyses using ANSYS. For the first time ROM of a geometrically mistuned industrial scale rotor (Transonic rotor) with large size of Finite Element (FE) model is generated using MMDA. Two methods for estimating mass and stiffness mistuning matrices are used a) exact computation from sector FE analysis, b) estimates based on POD mistuning parameters. Modal characteristics such as mistuned natural frequencies, mode shapes and forced harmonic response are obtained from ROM for various cases, and results are compared with full rotor ANSYS analysis and other ROM methods such as Subset of Nominal Modes (SNM) and Fundamental Model of Mistuning (FMM). Accuracy of MMDA ROM is demonstrated with variations in number of POD features and geometric mistuning parameters. It is shown for the aforementioned case b) that the high accuracy of ROM studied in previous work with Academic rotor does not directly translate to the Transonic rotor. Reasons for such mismatch in results are investigated and attributed to higher mistuning in Transonic rotor. Alternate solutions such as estimation of sensitivities via least squares, and interpolation of mass and stiffness matrices on manifolds are developed, and their results are discussed. Statistics such as mean and standard deviations of forced harmonic response peak amplitude are obtained from random permutations, and are shown to have similar results as those of Monte Carlo simulations. These statistics are obtained and compared for 3 degree of freedom (DOF) lumped parameter model (LPM) of rotor, Academic rotor and Transonic rotor. A state -- estimator based on MMDA ROM and Kalman filter is also developed for offline or online estimation of harmonic forcing function from
Jambunathan, V.; Murthy, V. R.
1993-01-01
A generic mathematical model that is capable of accurately modeling the multiple load path bearingless rotor blade is developed. A comprehensive, finite element based solution for the natural vibration of the rotor blade is developed. An iterative scheme based on harmonic balance is used to evaluate the nonlinear response of the rotor to control inputs and a Newton-Raphson procedure is employed to evaluate the trim of rotorcraft. Linearized perturbation model of the nonlinear system are presented. The model is validated by comparing with existing whirl tower, wind tunnel and flight test results of BMR/BO-105 helicopter. Frequencies of two bearingless rotor blades compare well with results from experiments. Nonlinear response and trim results are presented for the bearingless BMR/BO-105 rotor. Aeroelastic stability in forward flight, evaluated using floquet theory agrees with test data in general.
Tilted Bianchi type I dust fluid cosmological model in general relativity
Indian Academy of Sciences (India)
Abstract. In this paper, we have investigated a tilted Bianchi type I cosmological model filled with dust of perfect fluid in general relativity. To get a determinate solution, we have assumed a condition. A. Bn between metric potentials. The physical and geometrical aspects of the model together with singularity in the model are ...
Tilted Bianchi type I dust fluid cosmological model in general relativity
Indian Academy of Sciences (India)
In this paper, we have investigated a tilted Bianchi type I cosmological model ﬁlled with dust of perfect ﬂuid in general relativity. To get a determinate solution, we have assumed a condition = between metric potentials. The physical and geometrical aspects of the model together with singularity in the model are also ...
Monte Carlo modelling of germanium crystals that are tilted and have rounded front edges
Energy Technology Data Exchange (ETDEWEB)
Gasparro, Joel [EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Hult, Mikael [EC-JRC-IRMM, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium)], E-mail: mikael.hult@ec.europa.eu; Johnston, Peter N. [Applied Physics, Royal Melbourne Institute of Technology, GPO Box 2476V, Melbourne 3001 (Australia); Tagziria, Hamid [EC-JRC-IPSC, Institute for the Protection and the Security of the Citizen, Via E. Fermi 1, I-21020 Ispra (Vatican City State, Holy See,) (Italy)
2008-09-01
Gamma-ray detection efficiencies and cascade summing effects in germanium detectors are often calculated using Monte Carlo codes based on a computer model of the detection system. Such a model can never fully replicate reality and it is important to understand how various parameters affect the results. This work concentrates on quantifying two issues, namely (i) the effect of having a Ge-crystal that is tilted inside the cryostat and (ii) the effect of having a model of a Ge-crystal with rounded edges (bulletization). The effect of the tilting is very small (in the order of per mille) when the tilting angles are within a realistic range. The effect of the rounded edges is, however, relatively large (5-10% or higher) particularly for gamma-ray energies below 100 keV.
Monte Carlo modelling of germanium crystals that are tilted and have rounded front edges
International Nuclear Information System (INIS)
Gasparro, Joel; Hult, Mikael; Johnston, Peter N.; Tagziria, Hamid
2008-01-01
Gamma-ray detection efficiencies and cascade summing effects in germanium detectors are often calculated using Monte Carlo codes based on a computer model of the detection system. Such a model can never fully replicate reality and it is important to understand how various parameters affect the results. This work concentrates on quantifying two issues, namely (i) the effect of having a Ge-crystal that is tilted inside the cryostat and (ii) the effect of having a model of a Ge-crystal with rounded edges (bulletization). The effect of the tilting is very small (in the order of per mille) when the tilting angles are within a realistic range. The effect of the rounded edges is, however, relatively large (5-10% or higher) particularly for gamma-ray energies below 100 keV
Dynamic model of cage induction motor with number of rotor bars as parameter
Directory of Open Access Journals (Sweden)
Gojko Joksimović
2017-05-01
Full Text Available A dynamic mathematical model, using number of rotor bars as parameter, is reached for cage induction motors through the use of coupled-circuits and the concept of winding functions. The exact MMFs waveforms are accounted for by the model which is derived in natural frames of reference. By knowing the initial motor parameters for a priori adopted number of stator slots and rotor bars model allows change of rotor bars number what results in new model parameters. During this process, the rated machine power, number of stator slots and stator winding scheme remain the same. Although presented model has a potentially broad application area it is primarily suitable for the analysis of the different stator/rotor slot combination on motor behaviour during the transients or in steady-state regime. The model is significant in its potential to provide analysis of dozen of different number of rotor bars in a few tens of minutes. Numerical example on cage rotor induction motor exemplifies this application, including three variants of number of rotor bars.
A dynamical systems approach to the tilted Bianchi models of solvable type
Coley, Alan; Hervik, Sigbjørn
2005-02-01
We use a dynamical systems approach to analyse the tilting spatially homogeneous Bianchi models of solvable type (e.g., types VIh and VIIh) with a perfect fluid and a linear barotropic γ-law equation of state. In particular, we study the late-time behaviour of tilted Bianchi models, with an emphasis on the existence of equilibrium points and their stability properties. We briefly discuss the tilting Bianchi type V models and the late-time asymptotic behaviour of irrotational Bianchi type VII0 models. We prove the important result that for non-inflationary Bianchi type VIIh models vacuum plane-wave solutions are the only future attracting equilibrium points in the Bianchi type VIIh invariant set. We then investigate the dynamics close to the plane-wave solutions in more detail, and discover some new features that arise in the dynamical behaviour of Bianchi cosmologies with the inclusion of tilt. We point out that in a tiny open set of parameter space in the type IV model (the loophole) there exist closed curves which act as attracting limit cycles. More interestingly, in the Bianchi type VIIh models there is a bifurcation in which a set of equilibrium points turns into closed orbits. There is a region in which both sets of closed curves coexist, and it appears that for the type VIIh models in this region the solution curves approach a compact surface which is topologically a torus.
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....
Wind-Tunnel Survey of an Oscillating Flow Field for Application to Model Helicopter Rotor Testing
Mirick, Paul H.; Hamouda, M-Nabil H.; Yeager, William T., Jr.
1990-01-01
A survey was conducted of the flow field produced by the Airstream Oscillator System (AOS) in the Langley Transonic Dynamics Tunnel (TDT). The magnitude of a simulated gust field was measured at 15 locations in the plane of a typical model helicopter rotor when tested in the TDT using the Aeroelastic Rotor Experimental System (ARES) model. These measurements were made over a range of tunnel dynamic pressures typical of those used for an ARES test. The data indicate that the gust field produced by the AOS is non-uniform across the tunnel test section, but should be sufficient to excite a model rotor.
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.
DEFF Research Database (Denmark)
Cerda, Alejandro; Santos, Ilmar
2012-01-01
This work is aimed at a theoretical study of the dynamic behavior of a rotor-tilting pad journal bearing (TPJB) system under different lubrication regimes, namely, thermohydrodynamic (THD), elastohydrodynamic (EHD), and hybrid lubrication regime. The rotor modeled corresponds to an industrial...... compressor. Special emphasis is put on analyzing the stability map of the rotor when the different lubrication regimes are included into the TPJB modeling. Results show that, for the studied rotor, the inclusion of a THD model is more relevant when compared to an EHD model, as it implies a reduction...... on the instability onset speed for the rotor. Also, results show the feasibility of extending the stable operating range of the rotor by implementing a hybrid lubrication regime. [DOI: 10.1115/1.4004214]...
Tilted Bianchi Type III Wet Dark Fluid Cosmological Model in Saez and Ballester Theory
Sahu, Subrata Kumar; Kantila, Endale Nigatu; Gebru, Dawit Melese
2016-01-01
Tilted Bianchi-III wet dark fluid cosmological model is investigated in the frame work of Saez and Ballester theory (Phys. Lett. A. 113:467, 1986). Exact solutions to the field equations are derived when the metric potentials are functions of cosmic time only. Some physical and geometrical properties of the solutions are also discussed.
Tilted Kantowski-Sachs cosmological model in Brans-Dicke theory of gravitation
Pawar, D. D.; Shahare, S. P.; Dagwal, V. J.
2018-02-01
Tilted Kantowski-Sachs cosmological model in Brans-Dicke theory for perfect fluid has been investigated. The general solution of field equations in Brans-Dicke theory for the combined scalar and tensor field are obtained by using power law relation. Also, some physical and geometrical parameters are obtained and discussed.
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)
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.
2017-01-01
for a rigid symmetric top rotor can be derived by replacing τc in eq 8 with an effective correlation time that relates the 13C–1H relaxation vector...of internal motions (θ = ε = 0°), the expression that is derived from substituting τc in eq 8 with τe reduces to the symmetric top rotor J(ω) in eq... SYMMETRIC TOP ROTOR MODELS AND THE FLEXIBLE SYMMETRIC TOP ROTOR MODEL ECBC-TR-1428 Terry J. Henderson RESEARCH AND TECHNOLOGY DIRECTORATE
Conformally flat tilted Bianchi Type-V cosmological models in ...
Indian Academy of Sciences (India)
the complete determination of these quantities, we assume two extra conditions. First we assume that the space-time is conformally flat which leads to. 1008 .... Discussions. The model starts expanding with a big-bang at М = 0 and the expansion in the model stops at М = ∞ and = -2(Т + 2)¬. The model in general represents.
Tilted Bianchi type-I wet dark fluid model in Saez and Ballester theory
Sahu, S. K.; Tole, T. T.; Balcha, M.
2018-01-01
Tilted Bianchi-I wet dark fluid cosmological model is investigated in Saez and Ballester scalar theory of gravitation. Background cosmologies are obtained for a constant deceleration parameter. We consider a linear relationship between the shear scalar and the expansion scalar. We have discussed some physical and geometrical properties of the models. In our models, equation of state of the dark energy is observed to behave like a cosmological constant at late times.
A note on tilted Bianchi type VIh models: the type III bifurcation
Coley, A. A.; Hervik, S.
2008-10-01
In this note we complete the analysis of Hervik, van den Hoogen, Lim and Coley (2007 Class. Quantum Grav. 24 3859) of the late-time behaviour of tilted perfect fluid Bianchi type III models. We consider models with dust, and perfect fluids stiffer than dust, and eludicate the late-time behaviour by studying the centre manifold which dominates the behaviour of the model at late times. In the dust case, this centre manifold is three-dimensional and can be considered a double bifurcation as the two parameters (h and γ) of the type VIh model are varied. We therefore complete the analysis of the late-time behaviour of tilted ever-expanding Bianchi models of types I VIII.
Directory of Open Access Journals (Sweden)
Birgit Wieland
2017-10-01
Full Text Available The production of rotor blades for wind turbines is still a predominantly manual process. Process simulation is an adequate way of improving blade quality without a significant increase in production costs. This paper introduces a module for tolerance simulation for rotor-blade production processes. The investigation focuses on the simulation of temperature distribution for one-sided, self-heated tooling and thick laminates. Experimental data from rotor-blade production and down-scaled laboratory tests are presented. Based on influencing factors that are identified, a physical model is created and implemented as a simulation. This provides an opportunity to simulate temperature and cure-degree distribution for two-dimensional cross sections. The aim of this simulation is to support production processes. Hence, it is modelled as an in situ simulation with direct input of temperature data and real-time capability. A monolithic part of the rotor blade, the main girder, is used as an example for presenting the results.
Wieland, Birgit; Ropte, Sven
2017-10-05
The production of rotor blades for wind turbines is still a predominantly manual process. Process simulation is an adequate way of improving blade quality without a significant increase in production costs. This paper introduces a module for tolerance simulation for rotor-blade production processes. The investigation focuses on the simulation of temperature distribution for one-sided, self-heated tooling and thick laminates. Experimental data from rotor-blade production and down-scaled laboratory tests are presented. Based on influencing factors that are identified, a physical model is created and implemented as a simulation. This provides an opportunity to simulate temperature and cure-degree distribution for two-dimensional cross sections. The aim of this simulation is to support production processes. Hence, it is modelled as an in situ simulation with direct input of temperature data and real-time capability. A monolithic part of the rotor blade, the main girder, is used as an example for presenting the results.
Directory of Open Access Journals (Sweden)
Jiang Xiangwen
2015-06-01
Full Text Available Based on computational fluid dynamics (CFD method, electromagnetic high-frequency method and surrogate model optimization techniques, an integration design method about aerodynamic/stealth has been established for helicopter rotor. The developed integration design method is composed of three modules: integrated grids generation (the moving-embedded grids for CFD solver and the blade grids for radar cross section (RCS solver are generated by solving Poisson equations and folding approach, aerodynamic/stealth solver (the aerodynamic characteristics are simulated by CFD method based upon Navier–Stokes equations and Spalart–Allmaras (S–A turbulence model, and the stealth characteristics are calculated by using a panel edge method combining the method of physical optics (PO, equivalent currents (MEC and quasi-stationary (MQS, and integrated optimization analysis (based upon the surrogate model optimization technique with full factorial design (FFD and radial basis function (RBF, an integrated optimization analyses on aerodynamic/stealth characteristics of rotor are conducted. Firstly, the scattering characteristics of the rotor with different blade-tip swept and twist angles have been carried out, then time–frequency domain grayscale with strong scattering regions of rotor have been given. Meanwhile, the effects of swept-tip and twist angles on the aerodynamic characteristic of rotor have been performed. Furthermore, by choosing suitable object function and constraint condition, the compromised design about swept and twist combinations of rotor with high aerodynamic performances and low scattering characteristics has been given at last.
Modelling multi-rotor UAVs swarm deployment using virtual pheromones.
Aznar, Fidel; Pujol, Mar; Rizo, Ramón; Rizo, Carlos
2018-01-01
In this work, a swarm behaviour for multi-rotor Unmanned Aerial Vehicles (UAVs) deployment will be presented. The main contribution of this behaviour is the use of a virtual device for quantitative sematectonic stigmergy providing more adaptable behaviours in complex environments. It is a fault tolerant highly robust behaviour that does not require prior information of the area to be covered, or to assume the existence of any kind of information signals (GPS, mobile communication networks …), taking into account the specific features of UAVs. This behaviour will be oriented towards emergency tasks. Their main goal will be to cover an area of the environment for later creating an ad-hoc communication network, that can be used to establish communications inside this zone. Although there are several papers on robotic deployment it is more difficult to find applications with UAV systems, mainly because of the existence of various problems that must be overcome including limitations in available sensory and on-board processing capabilities and low flight endurance. In addition, those behaviours designed for UAVs often have significant limitations on their ability to be used in real tasks, because they assume specific features, not easily applicable in a general way. Firstly, in this article the characteristics of the simulation environment will be presented. Secondly, a microscopic model for deployment and creation of ad-hoc networks, that implicitly includes stigmergy features, will be shown. Then, the overall swarm behaviour will be modeled, providing a macroscopic model of this behaviour. This model can accurately predict the number of agents needed to cover an area as well as the time required for the deployment process. An experimental analysis through simulation will be carried out in order to verify our models. In this analysis the influence of both the complexity of the environment and the stigmergy system will be discussed, given the data obtained in the
Modelling multi-rotor UAVs swarm deployment using virtual pheromones
Pujol, Mar; Rizo, Ramón; Rizo, Carlos
2018-01-01
In this work, a swarm behaviour for multi-rotor Unmanned Aerial Vehicles (UAVs) deployment will be presented. The main contribution of this behaviour is the use of a virtual device for quantitative sematectonic stigmergy providing more adaptable behaviours in complex environments. It is a fault tolerant highly robust behaviour that does not require prior information of the area to be covered, or to assume the existence of any kind of information signals (GPS, mobile communication networks …), taking into account the specific features of UAVs. This behaviour will be oriented towards emergency tasks. Their main goal will be to cover an area of the environment for later creating an ad-hoc communication network, that can be used to establish communications inside this zone. Although there are several papers on robotic deployment it is more difficult to find applications with UAV systems, mainly because of the existence of various problems that must be overcome including limitations in available sensory and on-board processing capabilities and low flight endurance. In addition, those behaviours designed for UAVs often have significant limitations on their ability to be used in real tasks, because they assume specific features, not easily applicable in a general way. Firstly, in this article the characteristics of the simulation environment will be presented. Secondly, a microscopic model for deployment and creation of ad-hoc networks, that implicitly includes stigmergy features, will be shown. Then, the overall swarm behaviour will be modeled, providing a macroscopic model of this behaviour. This model can accurately predict the number of agents needed to cover an area as well as the time required for the deployment process. An experimental analysis through simulation will be carried out in order to verify our models. In this analysis the influence of both the complexity of the environment and the stigmergy system will be discussed, given the data obtained in the
Modelling of rotor speed transient with shaft-to-stator contact
International Nuclear Information System (INIS)
Roques, S.
2007-12-01
This research thesis first reports the development of a one-dimensional model of a rotor where variables to be computed are the displacements of a beam in a three-dimensional space, and the rotor angular position. After a description of the industrial context (the turbo-alternator group which transforms the thermal energy into electrical energy within the secondary circuit of a nuclear plant), and starting with an energy formulation, the rotor movement equations are established for a speed transient. The second part deals with the contact mechanics and the time resolution of a rotor-stator interaction problem. Contactless speed transients on rotor simple models are then presented, where the equation enables the calculation of the shaft rotational speed. The author then explores interaction cases. The reliability of results is assessed by studying their evolution with respect to the time step. The convergence of different interesting quantities such as the rotor rotational speed, shaft line displacements, and stresses (bearings and contact) is shown
Sun, Guangyoung
2006-01-01
Catcher bearings (CBs) or auxiliary bearings provide mechanical backup protection in the events of magnetic bearing failure. This paper presents numerical analysis for a rotor drop on CBs and following thermal growths due to their mechanical rub using detailed CB and damper models. The detailed CB model is determined based on its material, geometry, speed and preload using the nonlinear Hertzian load-deflection formula, and the thermal growths of bearing components during the rotor drop are estimated using a 1D thermal model. A finite-element squeeze film damper provides the pressure profile of an annular oil film and the resulting viscous damping force. Numerical simulations of an energy storage flywheel with magnetic suspensions failed reveal that an optimal CB design using the detailed simulation models stabilizes the rotor drop dynamics and lowers the thermal growths while preventing the high-speed backward whirl. Furthermore, CB design guides based on the simulation results are presented.
Mechanical model development of rolling bearing-rotor systems: A review
Cao, Hongrui; Niu, Linkai; Xi, Songtao; Chen, Xuefeng
2018-03-01
The rolling bearing rotor (RBR) system is the kernel of many rotating machines, which affects the performance of the whole machine. Over the past decades, extensive research work has been carried out to investigate the dynamic behavior of RBR systems. However, to the best of the authors' knowledge, no comprehensive review on RBR modelling has been reported yet. To address this gap in the literature, this paper reviews and critically discusses the current progress of mechanical model development of RBR systems, and identifies future trends for research. Firstly, five kinds of rolling bearing models, i.e., the lumped-parameter model, the quasi-static model, the quasi-dynamic model, the dynamic model, and the finite element (FE) model are summarized. Then, the coupled modelling between bearing models and various rotor models including De Laval/Jeffcott rotor, rigid rotor, transfer matrix method (TMM) models and FE models are presented. Finally, the paper discusses the key challenges of previous works and provides new insights into understanding of RBR systems for their advanced future engineering applications.
International Nuclear Information System (INIS)
Khorasanizadeh, H.; Mohammadi, K.; Mostafaeipour, A.
2014-01-01
Highlights: • Optimum tilt angles of solar surfaces in the Iranian city of Tabass are determined. • Due to lack of measured diffuse data, a new two variables diffuse model is established. • The monthly optimum tilt varies between 0° and 64° and the best annual tilt is 32°. • The semi-yearly tilt strategy of 10° for warm and 55° for cold periods are suggested. • Radiation components obtained for horizontal, tilted and vertical surfaces are compared. - Abstract: In this study the optimum tilt angle for south-facing solar surfaces in Tabass, Iran, for the fixed monthly, seasonal, semi-yearly and yearly adjustments were calculated. Due to lack of measured diffuse solar radiation data, to predict the horizontal diffuse radiation nine diffuse models from three different categories were established. Based on some statistical indicators the three degree model, in which both clearness index and relative sunshine duration are variables, was recognized the best. The monthly optimum tilt varies from 0° in June and July up to 64° in December and the yearly optimum tilt is around 32°, which is very close to latitude of Tabass (33.36°). For different adjustments, particularly for a vertically mounted surface, the received monthly mean daily solar radiation components and the annual solar energy gains were calculated and compared. Total yearly extra solar gain for the monthly, seasonal, semi-yearly and yearly optimally adjusted surfaces compared to that of horizontal surface are 23.15%, 21.55%, 21.23% and 13.76%, respectively. The semi-yearly tilt adjustment of 10° for warm period (April–September) and 55° for cold period (October–March) is highly recommended, since it provides almost the same level of annual solar energy gain as those of monthly and seasonal adjustments
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. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
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.
Tipjet 80-inch Model Rotor Hover Test: Test No. 1198
1993-09-01
CONTZNT0 (Continued) Page A- A. -Derived p t andEquatio qo ...................... 33 AB . u iLog ............................................ 3D Appendix...pressure, a Druck PPCR 920-series 100-psig unit (S/N 238784), calibrated to 70 psig (about 85 psia) in 7-psi increments; a transducer used to measure...pressure in the I rotor mast plenum, a Druck PDCR 920-series 30-psig unit (S’N 227480), calibrated to 30 psig (about 45 psia) in 3.0-psi increments. 5
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...
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...
Waheed, Umair bin
2014-08-01
The wavefield extrapolation operator for ellipsoidally anisotropic (EA) media offers significant cost reduction compared to that for the orthorhombic case, especially when the symmetry planes are tilted and/or rotated. However, ellipsoidal anisotropy does not provide accurate focusing for media of orthorhombic anisotropy. Therefore, we develop effective EA models that correctly capture the kinematic behavior of the wavefield for tilted orthorhombic (TOR) media. Specifically, we compute effective source-dependent velocities for the EA model using kinematic high-frequency representation of the TOR wavefield. The effective model allows us to use the cheaper EA wavefield extrapolation operator to obtain approximate wavefield solutions for a TOR model. Despite the fact that the effective EA models are obtained by kinematic matching using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including the frequency dependency and caustics, if present, with reasonable accuracy. The methodology developed here offers a much better cost versus accuracy tradeoff for wavefield computations in TOR media, particularly for media of low to moderate complexity. We demonstrate applicability of the proposed approach on a layered TOR model.
Analytical model of tilted driver–pickup coils for eddy current nondestructive evaluation
Cao, Bing-Hua; Li, Chao; Fan, Meng-Bao; Ye, Bo; Tian, Gui-Yun
2018-03-01
A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil. It is frequently observed in an eddy current (EC) array probe. In this work, a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evaluation. Basically, the core of the formulation is to obtain the projection of magnetic vector potential (MVP) from the driver coil onto the vector along the tilted pickup coil, which is divided into two key steps. The first step is to make a projection of MVP along the pickup coil onto a horizontal plane, and the second one is to build the relationship between the projected MVP and the MVP along the driver coil. Afterwards, an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields. The calculated values from the resulting model indicate good agreement with those from the finite element model (FEM) and experiments, which validates the developed analytical model. Project supported by the National Natural Science Foundation of China (Grant Nos. 61701500, 51677187, and 51465024).
Wake Geometry Measurements and Analytical Calculations on a Small-Scale Rotor Model
Ghee, Terence A.; Berry, John D.; Zori, Laith A. J.; Elliott, Joe W.
1996-01-01
An experimental investigation was conducted in the Langley 14- by 22-Foot Subsonic Tunnel to quantify the rotor wake behind a scale model helicopter rotor in forward level flight at one thrust level. The rotor system in this test consisted of a four-bladed fully articulated hub with blades of rectangular planform and an NACA 0012 airfoil section. A laser light sheet, seeded with propylene glycol smoke, was used to visualize the vortex geometry in the flow in planes parallel and perpendicular to the free-stream flow. Quantitative measurements of wake geometric proper- ties, such as vortex location, vertical skew angle, and vortex particle void radius, were obtained as well as convective velocities for blade tip vortices. Comparisons were made between experimental data and four computational method predictions of experimental tip vortex locations, vortex vertical skew angles, and wake geometries. The results of these comparisons highlight difficulties of accurate wake geometry predictions.
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.
Modeling the starting performance of high power solid rotor salient pole synchronous motors
Energy Technology Data Exchange (ETDEWEB)
Carlson, R.; Sadowski, N. [GRUCAD/Federal University of Santa Catarina, Florianopolis, SC 88040-970 (Brazil); Grander, L.O. [ELETROSUL Power Stations S.A., Florianopolis, SC 88040-901 (Brazil); Ruencos, F.; Ogawa, C.; Fo, F.J. Doubrawa [WEG Energy, Jaragua do Sul, SC 89256-900 (Brazil)
2009-12-15
A computer model, including analytical and FEM formulations, was developed to calculate the starting performance of synchronous motors with solid rotor salient poles. Using quasi-steady state equations, the average and the envelope of the oscillating electromagnetic torque as well as the stator rms current are calculated. With the stator current, the rotor pole losses are evaluated by FEM. The complete simulation process is performed by self-contained software composed by several computational modules properly tiled to simplify the work of a design engineer. The calculated starting performance was compared to experimental results showing satisfactory consistency. (author)
A mechanical model of biomimetic adhesive pads with tilted and hierarchical structures.
Schargott, M
2009-06-01
A 3D model for hierarchical biomimetic adhesive pads is constructed. It is based on the main principles of the adhesive pads of the Tokay gecko and consists of hierarchical layers of vertical or tilted beams, where each layer is constructed in such a way that no cohesion between adjacent beams can occur. The elastic and adhesive properties are calculated analytically and numerically. For the adhesive contact on stochastically rough surfaces, the maximum adhesion force increases with increasing number of hierarchical layers. Additional calculations show that the adhesion force also depends on the height spectrum of the rough surface.
A mechanical model of biomimetic adhesive pads with tilted and hierarchical structures
Energy Technology Data Exchange (ETDEWEB)
Schargott, M [Institute of Mechanics, Technische Universitaet Berlin, Strd 17 Juni 135, 10623 Berlin (Germany)], E-mail: martin.schargott@tu-berlin.de
2009-06-01
A 3D model for hierarchical biomimetic adhesive pads is constructed. It is based on the main principles of the adhesive pads of the Tokay gecko and consists of hierarchical layers of vertical or tilted beams, where each layer is constructed in such a way that no cohesion between adjacent beams can occur. The elastic and adhesive properties are calculated analytically and numerically. For the adhesive contact on stochastically rough surfaces, the maximum adhesion force increases with increasing number of hierarchical layers. Additional calculations show that the adhesion force also depends on the height spectrum of the rough surface.
A mechanical model of biomimetic adhesive pads with tilted and hierarchical structures
International Nuclear Information System (INIS)
Schargott, M
2009-01-01
A 3D model for hierarchical biomimetic adhesive pads is constructed. It is based on the main principles of the adhesive pads of the Tokay gecko and consists of hierarchical layers of vertical or tilted beams, where each layer is constructed in such a way that no cohesion between adjacent beams can occur. The elastic and adhesive properties are calculated analytically and numerically. For the adhesive contact on stochastically rough surfaces, the maximum adhesion force increases with increasing number of hierarchical layers. Additional calculations show that the adhesion force also depends on the height spectrum of the rough surface
Application of engineering models to predict wake deflection due to a tilted wind turbine
DEFF Research Database (Denmark)
Guntur, Srinivas; Troldborg, Niels; Gaunaa, Mac
2012-01-01
such a mechanism introduces control complications due to changing wind directions. Deflecting the wake in the vertical direction using tilt, on the other hand, overcomes this challenge. In this paper, the feasibility of steering wake is explored in a simple uniform inflow case. This is done by trying to model......It is a known fact that the power produced by wind turbines operating inside an array decreases due to the wake effects of the upstream turbines. It has been proposed previously to use the yaw mechanism as a potential means to steer the upstream wake away from downstream turbines, however...
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.
Development of Virtual Blade Model for Modelling Helicopter Rotor Downwash in OpenFOAM
2013-12-01
Georgia Tech rotor - airframe interaction wind tunnel experimental setup – reproduced from Reference 23... Rotor - Airframe Interaction Experimental Setup The wind tunnel experiment in Reference 20 involves placement of a simple fuselage body in a 2.3 m...Laser Doppler Velocimetry (LDV) technique. Figure 5.1: Georgia Tech rotor - airframe interaction wind tunnel experimental setup – reproduced
Hohenemser, K. H.; Banerjee, D.
1977-01-01
An introduction to aircraft state and parameter identification methods is presented. A simplified form of the maximum likelihood method is selected to extract analytical aeroelastic rotor models from simulated and dynamic wind tunnel test results for accelerated cyclic pitch stirring excitation. The dynamic inflow characteristics for forward flight conditions from the blade flapping responses without direct inflow measurements were examined. The rotor blades are essentially rigid for inplane bending and for torsion within the frequency range of study, but flexible in out-of-plane bending. Reverse flow effects are considered for high rotor advance ratios. Two inflow models are studied; the first is based on an equivalent blade Lock number, the second is based on a time delayed momentum inflow. In addition to the inflow parameters, basic rotor parameters like the blade natural frequency and the actual blade Lock number are identified together with measurement bias values. The effect of the theoretical dynamic inflow on the rotor eigenvalues is evaluated.
DEFF Research Database (Denmark)
Santos, Ilmar; Saracho, C.M.; Smith, J.T.
2004-01-01
, it is possible to highlight some dynamic effects and experimentally simulate the structural behavior of a windmill in two dimensions (2D-model). Only lateral displacement of the rotor in the horizontal direction is taken into account. Gyroscopic effect due to rotor angular vibrations is eliminated in the test......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...... linear, non-linear and time-depending terms in a very transparent way. Although neither gyroscopic effect due to rotor angular vibrations nor higher blade mode shapes are considered in the analysis, the equations of motion of the rotor-blades system are still general enough for the purpose of the work...
Benaarbia, A.; Rae, Y.; Sun, Wei
2018-01-01
This paper presents an elasto-visco-plastic finite element modelling framework including the associated UMAT codes to investigate the high temperature behaviour of gas turbine rotor steels. The model used in the FE study is an improved and unified multi-axial Chaboche-Lemaitre model which takes into account non-linear kinematic and isotropic hardening. The computational methodology is a three-dimensional framework following an implicit formulation and based on a radial return mapping algorith...
A discontinuous Galerkin method for P-wave modeling in tilted TI media
Amler, Thomas
2014-01-01
The acoustic approximation is an efficient alternative to the equations of elastodynamics for modeling Pwave propagation in weakly anisotropic media. We present a stable discontinuous Galerkin (DG) method for solving the acoustic approximation in tilted TI media (acoustic TI approximation). The acoustic TI approximation is considered as a modification of the equations of elastodynamics from which a modified energy is derived. The modified energy is obtained by eliminating the shear stress in the coordinates determined by the tilt angle and finding an energy for the remaining unknowns. This construction is valid if the medium is not elliptically anisotropic, a requirement frequently found in the literature. In the fully discrete setting, the modified energy is also conserved in time the presence of sharp contrasts in material parameters. By construction, the scheme can be coupled to the (fully) acoustic wave equation in the same way as the equations of elastodynamics. Hence, the number of unknowns can be reduced in acoustic regions. Our numerical examples confirm the conservation of energy in the discrete setting and the stability of the scheme.
Cardiovascular models of simulated moon and mars gravities: head-up tilt vs. lower body unweighting.
Kostas, Vladimir I; Stenger, Michael B; Knapp, Charles F; Shapiro, Robert; Wang, Siqi; Diedrich, André; Evans, Joyce M
2014-04-01
In this study we compare two models [head-up tilt (HUT) vs. body unweighting using lower body positive pressure (LBPP)] to simulate Moon, Mars, and Earth gravities. A literature search did not reveal any comparisons of this type performed previously. We hypothesized that segmental fluid volume shifts (thorax, abdomen, upper and lower leg), cardiac output, and blood pressure (BP), heart rate (HR), and total peripheral resistance to standing would be similar in the LBPP and HUT models. There were 21 subjects who were studied while supine (simulation of spaceflight) and standing at 100% (Earth), 40% (Mars), and 20% (Moon) bodyweight produced by LBPP in Alter-G and while supine and tilted at 80 degrees, 20 degrees, and 10 degrees HUT (analogues of Earth, Mars, and Moon gravities, respectively). Compared to supine, fluid shifts from the chest to the abdomen, increases in HR, and decreases in stroke volume were greater at 100% bodyweight than at reduced weights in response to both LBPP and HUT. Differences between the two models were found for systolic BP, diastolic BP, mean arterial BP, stroke volume, total peripheral resistance, and thorax and abdomen impedances, while HR, cardiac output, and upper and lower leg impedances were similar. Bodyweight unloading via both LBPP and HUT resulted in cardiovascular changes similar to those anticipated in actual reduced gravity environments. The LBPP model/Alter-G has the advantage of providing an environment that allows dynamic activity at reduced bodyweight; however, the significant increase in blood pressures in the Alter-GC may favor the HUT model.
Noise Benefits of Rotor Trailing Edge Blowing for a Model Turbofan
Woodward, Richard P.; Fite, E. Brian; Podboy, Gary G.
2007-01-01
An advanced model turbofan was tested in the NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) to explore far field acoustic effects associated with rotor Trailing-Edge-Blowing (TEB) for a modern, 1.294 stage pressure ratio turbofan model. The TEB rotor (Fan9) was designed to be aerodynamically similar to the previously tested Fan1, and used the same stator and nacelle hardware. Fan9 was designed with trailing edge blowing slots using an external air supply directed through the rotor hub. The TEB flow was heated to approximate the average fan exit temperature at each fan test speed. Rotor root blockage inserts were used to block TEB to all but the outer 40 and 20% span in addition to full-span blowing. A configuration with full-span TEB on alternate rotor blades was also tested. Far field acoustic data were taken at takeoff/approach conditions at 0.10 tunnel Mach. Far-field acoustic results showed that full-span blowing near 2.0% of the total flow could reduce the overall sound power level by about 2 dB. This noise reduction was observed in both the rotor-stator interaction tones and for the spectral broadband noise levels. Blowing only the outer span region was not very effective for lowering noise, and actually increased the far field noise level in some instances. Full-span blowing of alternate blades at 1.0% of the overall flow rate (equivalent to full-span blowing of all blades at 2.0% flow) showed a more modest noise decrease relative to full-span blowing of all blades. Detailed hot film measurements of the TEB rotor wake at 2.0% flow showed that TEB was not every effective for filling in the wake defect at approach fan speed toward the tip region, but did result in overfilling the wake toward the hub. Downstream turbulence measurements supported this finding, and support the observed reduction in spectral broadband noise.
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.
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.
Nonlinear Transient Modeling and Design of Turbocharger Rotor/Semi-Floating Bush Bearing System
Directory of Open Access Journals (Sweden)
Jianming Cao
2017-06-01
Full Text Available This work presents the bearing design and analysis of radial semi-floating bush oil lubricated bearings for a typical industrial turbocharger configuration. Initially, the stability analysis for a linear rotor/bearing system is evaluated through eigenvalues and eigenvectors. The stiffness and damping coefficients of the inner oil film are obtained for the linear modeling process. The operating speed range of the turbocharger is high enough, at 21,000 to 24,000 rpm, to be unstable, indicating that the analysis should be and is carried out with nonlinear transient modeling. The nonlinear transient analysis evaluates the rotor and bush limit cycle orbits, rotor dynamics, the forces acting on the rotor and semi-floating bush surfaces, the oil flow through the bearing, the oil temperatures, and the power loss of the two oil films. The optimum design of a set of semi-floating bush bearings for this application depends strongly upon the clearances of the bush and squeeze film damper, usually expressed as the non-dimensional clearance to radius ratio. A typical clearance is evaluated to determine the bearing performance in terms of orbit size, forces acting on the bush and squeeze damper surfaces, oil flow through the bearing, power loss, and thermal heating. The nonlinear transient orbit values are evaluated for frequency content using the FFT to determine which orbits show both the synchronous and sub-synchronous vibration components and the associated rotor modes excited. These results are compared to the linear analysis over the operating speed range. The oil flow through the bearing component is much larger than the squeeze film damper. The forces acting on the bush and squeeze damper surfaces are related to the fatigue life of the bearing.
DEFF Research Database (Denmark)
Pierart Vásquez, Fabián Gonzalo
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...... the critical speeds. In order to overcome such limitations, a mechatronic device has been proposed as a possible solution. This device named "hybrid active radial gas bearing" or simply "active gas bearing", combines an aerodynamic gas journal bearing with piezoelectrically controlled injectors. In the present...... 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...
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.
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
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.
A method of LED free-form tilted lens rapid modeling based on scheme language
Dai, Yidan
2017-10-01
According to nonimaging optical principle and traditional LED free-form surface lens, a new kind of LED free-form tilted lens was designed. And a method of rapid modeling based on Scheme language was proposed. The mesh division method was applied to obtain the corresponding surface configuration according to the character of the light source and the desired energy distribution on the illumination plane. Then 3D modeling software and the Scheme language programming are used to generate lens model respectively. With the help of optical simulation software, a light source with the size of 1mm*1mm*1mm in volume is used in experiment, and the lateral migration distance of illumination area is 0.5m, in which total one million rays are computed. We could acquire the simulated results of both models. The simulated output result shows that the Scheme language can prevent the model deformation problems caused by the process of the model transfer, and the degree of illumination uniformity is reached to 82%, and the offset angle is 26°. Also, the efficiency of modeling process is greatly increased by using Scheme language.
Nonlinear Transient Modeling and Design of Turbocharger Rotor/Semi-Floating Bush Bearing System
Jianming Cao; Saeid Dousti; Paul Allaire; Tim Dimond
2017-01-01
This work presents the bearing design and analysis of radial semi-floating bush oil lubricated bearings for a typical industrial turbocharger configuration. Initially, the stability analysis for a linear rotor/bearing system is evaluated through eigenvalues and eigenvectors. The stiffness and damping coefficients of the inner oil film are obtained for the linear modeling process. The operating speed range of the turbocharger is high enough, at 21,000 to 24,000 rpm, to be unstable, indicating ...
Non-linear journal bearing model for analysis of superharmonic vibrations of rotor systems
Energy Technology Data Exchange (ETDEWEB)
Hannukainen, P.
2008-07-01
A rotating machine usually consists of a rotor and bearings that supports it. The nonidealities in these components may excite vibration of the rotating system. The uncontrolled vibrations may lead to excessive wearing of the components of the rotating machine or reduce the process quality. Vibrations may be harmful even when amplitudes are seemingly low, as is usually the case in superharmonic vibration that takes place below the first critical speed of the rotating machine. Superharmonic vibration is excited when the rotational velocity of the machine is a fraction of the natural frequency of the system. In such a situation, a part of the machineAEs rotational energy is transformed into vibration energy. The amount of vibration energy should be minimised in the design of rotating machines. The superharmonic vibration phenomena can be studied by analysing the coupled rotor-bearing system employing a multibody simulation approach. This research is focused on the modelling of hydrodynamic journal bearings and rotorbearing systems supported by journal bearings. In particular, the non-idealities affecting the rotor-bearing system and their effect on the superharmonic vibration of the rotating system are analysed. A comparison of computationally efficient journal bearing models is carried out in order to validate one model for further development. The selected bearing model is improved in order to take the waviness of the shaft journal into account. The improved model is implemented and analyzed in a multibody simulation code. A rotor-bearing system that consists of a flexible tube roll, two journal bearings and a supporting structure is analysed employing the multibody simulation technique. The modelled non-idealities are the shell thickness variation in the tube roll and the waviness of the shaft journal in the bearing assembly. Both modelled non-idealities may cause subharmonic resonance in the system. In multibody simulation, the coupled effect of the non
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......Newton-Raphson method, and solutions converged to machine accuracy are found at small computing costs. Calculations are found to agree well withpublished measurements....
Offset, tilted dipole models of Uranian smooth high-frequency radio emission
International Nuclear Information System (INIS)
Schweitzer, A.E.; Romig, J.H.; Evans, D.R.; Sawyer, C.B.; Warwick, J.W.
1990-01-01
During the Voyager 2 encounter with Uranus in January 1986, the Planetary Radio Astronomy (PRA) experiment detected a complex pattern of radio emissions. Two types of emissions were seen: smooth and bursty. The smooth emission has been divided into smooth high-frequency (SHF) and smooth low-frequency (SLF) components which are presumed to come from different sources because of their distinctly different characteristics. The SHF component is considered in this paper. The SHF emission has been modeled by many authors on OTD (offset, tilted dipole (Ness et al., 1986)) L shells ranging from 5 to 40. However, the bursts have been modeled at much higher L shells. The authors complete an OTD investigation of the SHF emission at high L shells within the range of the bursty source locations, and present a viable high L shell model. This model has fundamentally the same longitudinally symmetric net emission pattern in space as the L shell 5 model presented in Romig et al. (1987) and Barbosa (1988). However, they were unable to produce an acceptable model on intermediate L shells without restricting source longitude. They discuss the similarities and distinctions between their two models and the models of other authors. They believe that the high L shell model (and others similar to it) cannot account for the observed smoothness and periodicity of the SHF emissions because it has open field lines containing untrapped particles, which should produce more variable emission than that seen in the SHF data. Therefore, the authors prefer models at L shells less than 18, the boundary for closed field lines (Ness et al., 1986). They then discuss and contrast two models within this boundary: the L = 5 model and an L ∼ 12 model by Kaiser et al. (1987) and Farrell and Calvert (1989b). The main distinction between these two models is the longitudinal extent of the source location
Modelling and robust control of an unmanned coaxial rotor helicopter with unstructured uncertainties
Directory of Open Access Journals (Sweden)
Zhi-Yan Dong
2017-01-01
Full Text Available A complete methodology for an unmanned coaxial rotor helicopter with unstructured uncertainties was proposed to achieve high-accuracy tracking performance from modelling to robust control. An integrative approach was introduced to systematically construct a whole dynamic model. The key parameters were selected carefully after iteratively being checked by empirical coefficients to decrease the budget and risk of programme. Moreover, a new control scheme is proposed to simultaneously incorporate six inputs to control six states based on the investment of singularity value responses and the general rule of relative gain array. Coprime factor uncertainty model is considered to represent a class of unstructured uncertainties, such as unmolded actuator dynamics and unpredicted interferences between two rotors. Furthermore, the H ∞ loop-shaping control was proposed to apply the control design of the coaxial rotor helicopter to manage complicated uncertainties and multivariable coupling. Finally, simulation results show the effectiveness of the proposed controller design in the step response of the closed loop. The stable closed-loop plant is achieved and the tolerant size of unstructured uncertainty is up to 36.09%. Good step responses and satisfied decoupling were also investigated in detail.
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.
Chu, Chunlei
2012-01-01
Discrete earth models are commonly represented by uniform structured grids. In order to ensure accurate numerical description of all wave components propagating through these uniform grids, the grid size must be determined by the slowest velocity of the entire model. Consequently, high velocity areas are always oversampled, which inevitably increases the computational cost. A practical solution to this problem is to use nonuniform grids. We propose a nonuniform grid implicit spatial finite difference method which utilizes nonuniform grids to obtain high efficiency and relies on implicit operators to achieve high accuracy. We present a simple way of deriving implicit finite difference operators of arbitrary stencil widths on general nonuniform grids for the first and second derivatives and, as a demonstration example, apply these operators to the pseudo-acoustic wave equation in tilted transversely isotropic (TTI) media. We propose an efficient gridding algorithm that can be used to convert uniformly sampled models onto vertically nonuniform grids. We use a 2D TTI salt model to demonstrate its effectiveness and show that the nonuniform grid implicit spatial finite difference method can produce highly accurate seismic modeling results with enhanced efficiency, compared to uniform grid explicit finite difference implementations. © 2011 Elsevier B.V.
The Influence of Rotor Unbalance on Turbocharger Rotor Dynamics
Directory of Open Access Journals (Sweden)
Knotek Jiří
2015-12-01
Full Text Available This paper describes the influence of an unbalance on turbocharger rotor dynamics. The structural model of the turbocharger rotor and the hydrodynamic model of the journal floating ring bearing are described and assembled in multibody dynamics software. Moreover, the paper presents various results describing rotor dynamics where the influence of an unbalance is discussed.
Design model for bending vibrations of single-stage tunnel fan rotor
Krasyuk, AM; Kosykh, PV
2018-03-01
Using of one-mass model of tunnel fan rotor is justified for estimation calculation of the natural bending vibrations frequency during the design stage. It’s shown that the evaluative computation of the main axial tunnel fan at the early design stage yields the acceptable accuracy. It is shown that after completion of the design, the mass of the stepped-type shaft differs from the mass of the calculated uniform-diameter shaft no more than by 40%. Inclusion of this additional mass in the estimation calculation makes it possible to improve the calculation accuracy. The region of the dimensionless rotor design parameters at which the relative difference of frequency in the evaluative and verification calculations is not higher than 5 % is determined.
CFD Modeling and Simulation of Aeorodynamic Cooling of Automotive Brake Rotor
Belhocien, Ali; Omar, Wan Zaidi Wan
Braking system is one of the important control systems of an automotive. For many years, the disc brakes have been used in automobiles for the safe retarding of the vehicles. During the braking enormous amount of heat will be generated and for effective braking sufficient heat dissipation is essential. The thermal performance of disc brake depends upon the characteristics of the airflow around the brake rotor and hence the aerodynamics is an important in the region of brake components. A CFD analysis is carried out on the braking system as a case study to make out the behavior of airflow distribution around the disc brake components using ANSYS CFX software. We are interested in the determination of the heat transfer coefficient (HTC) on each surface of a ventilated disc rotor varying with time in a transient state using CFD analysis, and then imported the surface film condition data into a corresponding FEM model for disc temperature analysis.
Tilt - ellips and rho - phase modelling of VLF EM and VLF R in Candi Umbul Magelang
Affanti, Adella Putri; Niasari, Sintia Windhi
2017-07-01
A research for geothermal energy is increased due to the need of green energy. The presence of geothermal manifestations indicate the existence of geothermal system. One of the geothermal manifestations is warm spring. CandiUmbul area which located in Telomoyo, Magelang has warm spring as the geothermal manifestation. Very Low Frequency (VLF) is one of geophysical method that can be used to map the subsurface in Candi Umbul, Telomoyo. VLF is a method using electromagnetic field that powered and transferred by the transmitter. The receiver read the electromagnetic signal which induce the rock and give information about the conductivity as the physical property measurred. In this research, after collecting and processing data, we modeled tilt-ellips data of VLF-EM and rho-phase data of VLF-R to explain the geothermal system of Candi Umbul. Both VLF-EM and VLF-R model were correlated for the interpretation. The model showed an anomalous conductive feature beneath the research area. The result of this research showed that the anomaly is oriented in NW-SE direction. This direction is assumed as a fluid path way of Candi Umbul which became the outflow of Telomoyo geothermal system. To prove the early deduction this research is still on going.
Late-time behaviour of the tilted Bianchi type VIh models
Hervik, S.; van den Hoogen, R. J.; Lim, W. C.; Coley, A. A.
2007-08-01
We study tilted perfect fluid cosmological models with a constant equation of state parameter in spatially homogeneous models of Bianchi type VIh using dynamical systems methods and numerical experimentation, with an emphasis on their future asymptotic evolution. We determine all of the equilibrium points of the type VIh state space (which correspond to exact self-similar solutions of the Einstein equations, some of which are new), and their stability is investigated. We find that there are vacuum plane-wave solutions that act as future attractors. In the parameter space, a 'loophole' is shown to exist in which there are no stable equilibrium points. We then show that a Hopf-bifurcation can occur resulting in a stable closed orbit (which we refer to as the Mussel attractor) corresponding to points both inside the loophole and points just outside the loophole; in the former case the closed curves act as late-time attractors while in the latter case these attracting curves will co-exist with attracting equilibrium points. In the special Bianchi type III case, centre manifold theory is required to determine the future attractors. Comprehensive numerical experiments are carried out to complement and confirm the analytical results presented. We note that the Bianchi type VIh case is of particular interest in that it contains many different subcases which exhibit many of the different possible future asymptotic behaviours of Bianchi cosmological models.
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.
Transverse Crack Modeling and Validation in Rotor Systems, Including Thermal Effects
Directory of Open Access Journals (Sweden)
N. Bachschmid
2003-01-01
Full Text Available This article describes a model that allows the simulation of the static behavior of a transverse crack in a horizontal rotor under the action of weight and other possible static loads and the dynamic behavior of cracked rotating shaft. The crack breathes—that is, the mechanism of the crack's opening and closing is ruled by the stress on the cracked section exerted by the external loads. In a rotor, the stresses are time-dependent and have a period equal to the period of rotation; thus, the crack periodically breathes. An original, simplified model allows cracks of various shapes to be modeled and thermal stresses to be taken into account, as they may influence the opening and closing mechanism. The proposed method was validated by using two criteria. First the crack's breathing mechanism, simulated by the model, was compared with the results obtained by a nonlinear, threedimensional finite element model calculation, and a good agreement in the results was observed. Then the proposed model allowed the development of the equivalent cracked beam. The results of this model were compared with those obtained by the three-dimensional finite element model. Also in this case, there was a good agreement in the results.
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...
Generalized two axes model of a squirrel-cage induction motor for rotor fault diagnosis
Directory of Open Access Journals (Sweden)
Samir Hamdani
2008-01-01
Full Text Available A generalized two axes model of a squirrel-cage induction motor is developed This model is based on a winding function approach and the coupled magnetic circuit theory and takes into account the stator and the rotor asymmetries due to faults. This paper presents a computer simulation and experimental dynamic characteristics for a healthy induction machine, machine with one broken bar and a machine with two broken bars. The results illustrate good agreement between both simulated and experimental results. Also, the power spectral density PSD was performed to obtain a stator current spectrum.
DEFF Research Database (Denmark)
Sørensen, Niels N.
2009-01-01
When predicting the flow over airfoils and rotors, the laminar-turbulent transition process can be important for the aerodynamic performance. Today, the most widespread approach is to use fully turbulent computations, where the transitional process is ignored and the entire boundary layer...... on the wings or airfoils is handled by the turbulence model. The correlation based transition model has lately shown promising results, and the present paper describes the effort of deriving the two non-public empirical correlations of the model to make the model complete. To verify the model it is applied...... to flow over a flat plate, flow over the S809 and the NACA63-415 airfoils, flow over a prolate spheroid at zero and thirty degrees angle of attack, and finally to the NREL Phase VI wind turbine rotor for the zero yaw upwind cases from the NREL/NASA Ames wind tunnel test. Copyright © 2009 John Wiley & Sons...
Head-Down Tilt with Balanced Traction as a Model for Simulating Spinal Acclimation to Microgravity
Ballard, R. E.; Styf, J. R.; Watenpaugh, D. E.; Fechner, K.; Haruna, Y.; Kahan, N. J.; Hargens, A. R.
1994-01-01
Astronauts experience total body height increases of 4 to 7 cm in microgravity. Thus, stretching of the spinal cord, nerve roots, and muscular and ligamentous tissues may be responsible for the hyperreflexia, back pain, and muscular atrophy associated with exposure to microgravity. Axial compression of the spine makes 6 deg. head-down tilt (HDT) an unsuitable model for spinal acclimation to microgravity. However, this axial compression may be counteracted by balanced traction consisting of 10% body weight (sin 6 deg. = 0.1) applied to the legs. Six healthy male subjects underwent 3 days each of 60 HDT with balanced traction and horizontal bed rest (HBR), with a 2 week recovery period between treatments. Total body and spine length, lumbar disc height, back pain, erector spinae intramuscular pressure, and ankle joint torque were measured before, during and after each treatment. Total body and spine (processes of L5 - C7) lengths increased significantly more during HDT with balanced traction (22 +/- 8 mm and 25 +/- 8 mm, respectively) than during HBR (16 +/- 4 mm and 14 +/- 9 mm, respectively). Back and leg pain were significantly greater during HDT with balanced traction than during HBR. The distance between the lower end plate of L4 and the upper endplate of S1, as measured by sonography, increased significantly in both treatments to the same degree (2.9 +/- 1.9 mm, HDT with balanced traction; 3.3 +/- 1.5 mm, HBR). Intramuscular pressure of the erector spinae muscles and maximal ankle joint torque were unaltered with both models. While neither model increased height to the magnitude observed in microgravity, HDT with balanced traction may be a better model for simulating the body lengthening and back pain experienced in microgravity.
Transverse Crack Modeling and Validation in Rotor Systems Including Thermal Effects
Directory of Open Access Journals (Sweden)
N. Bachschmid
2004-01-01
Full Text Available In this article, a model is described that allows one to simulate the static behavior of a transversal crack in a horizontal rotor, under the action of the weight and other possible static loads and the dynamical behavior of the rotating cracked shaft. The crack “breaths,” i.e., the mechanism of opening and closing of the crack, is ruled by the stress acting on the cracked section due to the external loads; in a rotor the stress is time-depending with a period equal to the period of rotation, thus the crack “periodically breaths.” An original simplified model is described that allows cracks of different shape to be modeled and thermal stresses to be taken into account, since they may influence the opening and closing mechanism. The proposed method has been validated using two criteria. Firstly, the crack “breathing” mechanism, simulated with the model, has been compared with the results obtained by a nonlinear 3-D FEM calculation and a good agreement in the results has been observed. Secondly, the proposed model allows the development of the equivalent cracked beam. The results of this model are compared with those obtained by the above-mentioned 3-D FEM. There is a good agreement in the results, of this case as well.
International Nuclear Information System (INIS)
Posadillo, R.; Lopez Luque, R.
2009-01-01
The performance of three diffuse hourly irradiation models on tilted surfaces was evaluated by making a database of hourly global and diffuse solar irradiation on a horizontal surface, as well as global solar irradiation on a tilted surface, recorded in a solar radiation station located at Cordoba University (Spain). The method for a comparison of the performance of these models was developed from a study of the 'utilizable energy' statistics, a value representing, for a specific period of time, the mean monthly radiation that exceeded a critical level of radiation. This model comparison method seemed to us to be highly suitable since it provides a way of comparing the capacity of these models to estimate, however, much energy is incident on a tilted surface above a critical radiation level. Estimated and measured values were compared using the normalized RMBE and RRMSE statistics. According to the results of the method let us verify that, of the three models evaluated, one isotropic and two anisotropic, the Reindl et al. anisotropic model was the one giving the best results.
Rothhaar, Paul M.; Murphy, Patrick C.; Bacon, Barton J.; Gregory, Irene M.; Grauer, Jared A.; Busan, Ronald C.; Croom, Mark A.
2014-01-01
Control of complex Vertical Take-Off and Landing (VTOL) aircraft traversing from hovering to wing born flight mode and back poses notoriously difficult modeling, simulation, control, and flight-testing challenges. This paper provides an overview of the techniques and advances required to develop the GL-10 tilt-wing, tilt-tail, long endurance, VTOL aircraft control system. The GL-10 prototype's unusual and complex configuration requires application of state-of-the-art techniques and some significant advances in wind tunnel infrastructure automation, efficient Design Of Experiments (DOE) tunnel test techniques, modeling, multi-body equations of motion, multi-body actuator models, simulation, control algorithm design, and flight test avionics, testing, and analysis. The following compendium surveys key disciplines required to develop an effective control system for this challenging vehicle in this on-going effort.
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.
International Nuclear Information System (INIS)
JianPing, Jing; Guang, Meng; Yi, Sun; SongBo, Xia
2003-01-01
A nonlinear Continuum Damage Mechanics model is proposed to assess the creep-fatigue life of a steam turbine rotor, in which the effects of complex multiaxial stress and the coupling of fatigue and creep are taken into account. The nonlinear evolution of damage is also considered. The model is applied to a 600 MW steam turbine under a practical start-stop operation. The results are compared with those from the linear accumulation theory that is dominant in life assessment of steam turbine rotors at present. The comparison show that the nonlinear continuum damage mechanics model describes the accumulation and development of damage better than the linear accumulation theory
DEFF Research Database (Denmark)
Andersen, Elsa; Lund, Hans; Furbo, Simon
2004-01-01
in the calculation. The weather data are measured at the solar radiation measurement station, SMS at the Department of Civil Engineering at the Technical University of Denmark. In this study the weather data are combined with solar collector calculations based on solar collector test carried out at Solar Energy...... Center, SEC, Denmark. With measured solar radiation on horizontal and the different solar radiation processing models the total radiation is calculated on differently tilted and oriented surfaces and compared with the measured solar radiation on the different surfaces. Further, the impact on the yearly......Measured solar radiation data are most commonly available as total solar radiation on a horizontal surface. When using solar radiation measured on horizontal to calculate the solar radiation on tilted surfaces and thereby the thermal performance of different applications such as buildings and solar...
DEFF Research Database (Denmark)
Sørensen, Jens Nørkær
2016-01-01
The finite-bladed optimum Betz rotor is treated. It is first very recently that a complete description of this rotor has been derived. In the chapter, a full analytical solution to the Betz rotor problem will be given, and the results will be compared to other optimum rotor models, both with resp......The finite-bladed optimum Betz rotor is treated. It is first very recently that a complete description of this rotor has been derived. In the chapter, a full analytical solution to the Betz rotor problem will be given, and the results will be compared to other optimum rotor models, both...... with respect to performance and resulting rotor geometry. It is here shown that for tip speed ratios greater than three, all models result in the same geometry at the outer part of the rotor, whereas the inner part always is different, both with respect to plan form and with respect to twist distribution....
Design, construction and characterization of a flightworthy piezoelectric solid state adaptive rotor
Barrett, Ron; Frye, Phillip; Schliesman, Michael
1998-06-01
The development of a new type of flightworthy adaptive rotor system is presented. By building upon earlier adaptive rotor work, a new miniature solid state adaptive rotor (SSAR) was built using directionally attached piezoelectric (DAP) torque-plates controlling Hiller servopaddles. These servopaddles change the rotor disk tilt and thereby induce changes in forces and moments for flight control. To demonstrate the concept, a 23.5 in diameter helicopter rotor was built using DAP servopaddles at the hub. The servopaddles were constructed from PZT-5H piezoceramic actuator sheets bonded symmetrically at 0964-1726/7/3/017/img1. An aluminum substrate and a high temperature cure was used to provide precompression. Analytical modeling was accomplished by laminated plate theory along with strip theory aerodynamics and inertial relations. Because propeller moments are proportional to servopaddle deflections at a fixed rotational speed, it was possible to cancel them out by balancing an aeroelastic coupling between the center of mass, aerodynamic center and elastic axis. Bench testing of the SSAR showed that the rotor system could produce static servopaddle deflections in excess of 0964-1726/7/3/017/img2 with good agreement between theory and experiment. With the spinning rotor, the servopaddles demonstrated dynamic capability in excess of 0964-1726/7/3/017/img3. As the rotor speed was increased, deviations between linear theory and experiment also increased. Nonetheless, the rotor still demonstrated 0964-1726/7/3/017/img4 servopaddle deflections at full rotor speed (1600 RPM). A detailed weight statement of the conventional and SSAR systems shows that the SSAR helicopter experienced a 40% reduction in flight control system weight, which resulted in an 8% cut in total aircraft gross weight, a 26% drop in parasite drag and a drop in flight control system part count from 94 components down to five.
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.
A review of ice accretion data from a model rotor icing test and comparison with theory
Britton, Randall K.; Bond, Thomas H.
1991-01-01
An experiment was conducted by the Helicopter Icing Consortium (HIC) in the NASA Lewis Icing Research Tunnel (IRT) in which a 1/6 scale fuselage model of a UH-60A Black Hawk helicopter with a generic rotor was subjected to a wide range of icing conditions. The HIC consists of members from NASA, Bell Helicopter, Boeing Helicopter, McDonnell Douglas Helicopters, Sikorsky Aircraft, and Texas A&M University. Data was taken in the form of rotor torque, internal force balance measurements, blade strain gage loading, and two dimensional ice shape tracings. A review of the ice shape data is performed with special attention given to repeatability and correctness of trends in terms of radial variation, rotational speed, icing time, temperature, liquid water content, and volumetric median droplet size. Moreover, an indepth comparison between the experimental data and the analysis of NASA's ice accretion code LEWICE is given. Finally, conclusions are shown as to the quality of the ice accretion data and the predictability of the data base as a whole. Recommendations are also given for improving data taking technique as well as potential future work.
Directory of Open Access Journals (Sweden)
Lijun ZHANG
2014-09-01
Full Text Available Reliability of rotating machinery has a significant relation with personal safety and economic efficiency. With the development of science and technology, the improvement of performance degradation of machinery becomes increasingly higher. Research of traditional reliability theory depends on failure data. Some lifetime data result in little or even no failure. For mechanical equipment, degradation data may contain useful information about machinery reliability. Service condition of rotating machinery suffers from a long period of deterioration time until functional failure occurs. However, normal or failure status of rotating machinery is simply defined by traditional fault diagnosis methods. A machinery performance degradation assessment method for the cracked rotor based on multi-observation Hidden Markov Model is proposed for rotating machinery in run-up and shutdown processes. The proposed method can reflect the change of the performance of rotating machinery effectively. Finally, dynamics simulation data of the cracked rotor with gradually decreasing stiffness is used to validate the feasibility of the proposed method.
Nguyen, Louis H.; Ramakrishnan, Jayant; Granda, Jose J.
2006-01-01
The assembly and operation of the International Space Station (ISS) require extensive testing and engineering analysis to verify that the Space Station system of systems would work together without any adverse interactions. Since the dynamic behavior of an entire Space Station cannot be tested on earth, math models of the Space Station structures and mechanical systems have to be built and integrated in computer simulations and analysis tools to analyze and predict what will happen in space. The ISS Centrifuge Rotor (CR) is one of many mechanical systems that need to be modeled and analyzed to verify the ISS integrated system performance on-orbit. This study investigates using Bond Graph modeling techniques as quick and simplified ways to generate models of the ISS Centrifuge Rotor. This paper outlines the steps used to generate simple and more complex models of the CR using Bond Graph Computer Aided Modeling Program with Graphical Input (CAMP-G). Comparisons of the Bond Graph CR models with those derived from Euler-Lagrange equations in MATLAB and those developed using multibody dynamic simulation at the National Aeronautics and Space Administration (NASA) Johnson Space Center (JSC) are presented to demonstrate the usefulness of the Bond Graph modeling approach for aeronautics and space applications.
Meimon, Serge; Petit, Cyril; Fusco, Thierry; Kulcsar, Caroline
2010-11-01
Adaptive optics (AO) systems have to correct tip-tilt (TT) disturbances down to a fraction of the diffraction-limited spot. This becomes a key issue for very or extremely large telescopes affected by mechanical vibration peaks or wind shake effects. Linear quadratic Gaussian (LQG) control achieves optimal TT correction when provided with the temporal model of the disturbance. We propose a nonsupervised identification procedure that does not require any auxiliary system or loop opening and validate it on synthetic profile as well as on experimental data.
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
Magee, J. P.; Clark, R. D.; Widdison, C. A.
1975-01-01
Conceptual design studies are summarized of tandem-rotor helicopter and tilt-rotor aircraft for a short haul transport mission in the 1985 time frame. Vertical takeoff designs of both configurations are discussed, and the impact of external noise criteria on the vehicle designs, performance, and costs are shown. A STOL design for the tilt-rotor configuration is reported, and the effect of removing the vertical takeoff design constraints on the design parameters, fuel economy, and operating cost is discussed.
Buoyancy-Induced Heat Transfer inside Compressor Rotors: Overview of Theoretical Models
Directory of Open Access Journals (Sweden)
J. Michael Owen
2018-03-01
Full Text Available Increasing pressures in gas-turbine compressors, particularly in aeroengines where the pressure ratios can be above 50:1, require smaller compressor blades and an increasing focus on blade-clearance control. The blade clearance depends on the radial growth of the compressor discs, which in turn depends on the temperature and stress in the discs. As the flow inside the disc cavities is buoyancy-driven, calculation of the disc temperature is a conjugate problem: the heat transfer from the disc is coupled with the air temperature inside the cavity. The flow inside the cavity is three-dimensional, unsteady and unstable, so computational fluid dynamics is not only expensive and time-consuming, it is also unable to achieve accurate solutions at the high Grashof numbers found in modern compressors. Many designers rely on empirical equations based on inappropriate physical models, and recently the authors have produced a series of papers on physically-based theoretical modelling of buoyancy-induced heat transfer in the rotating cavities found inside compressor rotors. Predictions from these models, all of which are for laminar flow, have been validated using measurements made in open and closed compressor rigs for a range of flow parameters representative of those found inside compressor rotors. (The fact that laminar buoyancy models can be used for large Grashof numbers (up to 10 12 , where most engineers expect the flow to be turbulent, is attributed to the large Coriolis accelerations in the fluid core and to the fact that there is only a small difference between the rotational speed of the core and that of the discs. As many as 223 separate tests were analysed in the validation of the models, and good agreement between the predictions and measurements was achieved for most of these cases. This overview paper has collected together the equations from these papers, which should be helpful to designers and research workers. The paper also points out
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.
Nonlinear dynamics and health monitoring of 6-DOF breathing cracked Jeffcott rotor
Zhao, Jie; DeSmidt, Hans; Yao, Wei
2015-04-01
Jeffcott rotor is employed to study the nonlinear vibration characteristics of breathing cracked rotor system and explore the possibility of further damage identification. This paper is an extension work of prior study based on 4 degree-of-freedom Jeffcott rotor system. With consideration of disk tilting and gyroscopic effect, 6-dof EOM is derived and the crack model is established using SERR (strain energy release rate) in facture mechanics. Same as the prior work, the damaged stiffness matrix is updated by computing the instant crack closure line through Zero Stress Intensity Factor method. The breathing crack area is taken as a variable to analyze the breathing behavior in terms of eccentricity phase and shaft speed. Furthermore, the coupled vibration among lateral, torsional and longitudinal d.o.f is studied under torsional/axial excitation. The final part demonstrates the possibility of using vibration signal of damaged system for the crack diagnosis and health monitoring.
Sabaapour, Mohammad Reza; Zohoor, Hassan
Swashplate mechanism is the steering control mechanism used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. This paper aimed at the kinematic analysis of one of the latest architectures of the swashplate mechanism, used for hingeless rotor with the flybar. Hence, the position analysis of each module and whole mechanism, based on parallel manipulators concept with more details involved than other works, was presented here. The kinematic model was further developed to obtain Jacobian matrices, velocity and acceleration analysis in detail. Finally, a particular example was conducted and compared with an ADAMS rigid body dynamic model, to verify the analytical model. In many simulated cases, the results matched.
Directory of Open Access Journals (Sweden)
Tiago Henrique Machado
Full Text Available ABSTRACT The present work gives continuity in the analysis of the wear influence on cylindrical hydrodynamic bearings by presenting an experimental validation of the wear model previously proposed by the authors. This validation is carried on using the frequency response of the rotor-bearings system in directional coordinates. For this purpose, a test rig was assembled in order to evaluate the behavior of the rotating system when supported by hydrodynamic bearings with different wear patterns. The experimental measurements are used to validate the wear model, comparing the anisotropy influence on the experimental and numerical responses. The simulated directional frequency responses showed a good agreement with the experimental ones, demonstrating the potential of the proposed wear model in satisfactorily represent its influence on the rotor-bearings system response in the frequency range where the numerical model was validated.
Machado, Tiago Henrique; Cavalca, Katia L
2016-01-01
The present work gives continuity in the analysis of the wear influence on cylindrical hydrodynamic bearings by presenting an experimental validation of the wear model previously proposed by the authors. This validation is carried on using the frequency response of the rotor-bearings system in directional coordinates. For this purpose, a test rig was assembled in order to evaluate the behavior of the rotating system when supported by hydrodynamic bearings with different wear patterns. The experimental measurements are used to validate the wear model, comparing the anisotropy influence on the experimental and numerical responses. The simulated directional frequency responses showed a good agreement with the experimental ones, demonstrating the potential of the proposed wear model in satisfactorily represent its influence on the rotor-bearings system response in the frequency range where the numerical model was validated.
Hydrogen migration modeling in a symmetric tilt boundary of the Iron-Chromium system
Ramunni, V. P.
2018-03-01
Previous experimental studies of H permeation in 9%Cr-Fe alloys have found a permeation coefficient 10 times lower and a diffusion coefficient 200 times lower than in pure annealed Fe. In an effort to shed some light on the microscopic origin of these findings, we perform an extensive study of Fe, Cr, and H migration in a high-angle symmetric tilt grain boundary in bcc Fe, both via vacancy and interstitial mechanism. This is undertaken in the framework of transition state theory with the relevant energies obtained from classical interatomic potentials, and partially from Density Functional Theory calculations, in order to check the consistency of structures. Trapping sites for H and possible migration paths are explored. We find that the presence of Cr and its migration via vacancy and interstitials creates the conditions in produce stable preferential trapping sites for H in the grain boundary, that delay the H migration, thereby explaining the experimental results.
International Nuclear Information System (INIS)
Mayer, T.
2012-01-01
This dissertation deals with the effective mechanical analysis of steam turbine parts which is not only required for the reliable and safe use of newly built steam turbines, but also for the remaining life assessment of components that have been exposed to service duty over long periods of time. This Thesis aims to develop a physically motivated evolutionary constitutive model for a low-alloy bainitic 2CrMoNiWV (23CrMoNiWV8-8) steam turbine rotor steels. A comprehensive experimental characterisation is performed concerning the mechanical and microstructural evolution of 2CrMoNiWV as subjected to low cycle fatigue (LCF) deformation at elevated temperatures, at different strain rates and for various strain amplitudes. This cyclic plastic deformation causes the rearrangement of dislocations in the microstructure of the steels used for such rotor applications. Symmetric, strain controlled LCF experiments have been carried out in the Laboratory of the High Temperature Integrity Group at the Swiss Federal Laboratories for Materials Science and Technology EMPA. These include mechanical tests in the temperature range between 20 °C to 600 °C at strain rates of 0.001%/s to 1.0%/s and strain amplitudes of ±0.25% to ±1.0%. The LCF experiments reported on comprehensively characterise the temperature, strain rate and strain amplitude dependent cyclic elastic-plastic behaviour of 2CrMoNiWV. Both complete single-specimen endurance tests and interrupted multi-specimen tests have been performed. On the basis of this experimental evidence, an evolutionary formulation of the model is further developed that excellently reproduces the strain amplitude dependent mechanical evolution of 2CrMoNiWV when subjected to LCF loading at different constant strain amplitudes but equal temperature and strain rate. The simulation of benchmark experiments introducing increasing or decreasing strain amplitude steps into the LCF deformation history provide promising results. A further important
Wang, Chi; Tan, Zhiqiang; Louis, Thomas A
2014-01-01
Evaluating the effect of a treatment on a time-to-event outcome is the focus of many randomized clinical trials. It is often observed that the treatment effect is heterogeneous, where only a subgroup of the patients may respond to the treatment due to some unknown mechanism such as genetic polymorphism. In this paper, we propose a semiparametric exponential tilt mixture model to estimate the proportion of patients who respond to the treatment and to assess the treatment effect. Our model is a natural extension of parametric mixture models to a semiparametric setting with a time-to-event outcome. We propose a nonparametric maximum likelihood estimation approach for inference and establish related asymptotic properties. Our method is illustrated by a randomized clinical trial on biodegradable polymer-delivered chemotherapy for malignant gliomas patients.
Analytical calculation of the vibrator-rotor transition in the sdg interacting boson model
International Nuclear Information System (INIS)
Wang Baolin
1992-01-01
Analytical calculation of the vibrator-rotor transition is given by utilizing the 1/N expansion technique in the sdg IBM. The phase transition of low-lying energy spectrum and E2 transition for Sm isotopes are calculated
Sabaapour, Mohammad Reza; Zohoor, Hassan
Swashplate mechanism is the steering control mechanism, used in most helicopters. It is a complex multi-loop closed kinematic chain which controls the angles of attack of the main rotor blades. In most new model helicopters, this mechanism is also equipped with the bell-hiller stabilizer bar (flybar), to improve the stability. The main purpose of this paper is the dynamic analysis of a swashplate mechanism, one of the latest architectures, used for hingeless rotor with the flybar. The underlying kinematics has been discussed in Part I. Thus, the detailed dynamic analysis of the whole mechanism and each part are presented here. The analyses are based on the parallel manipulators concept and the virtual work principle. Also an ADAMS rigid body dynamic model was developed to verify the results of the analytical model. In many simulated cases, the results matched.
Truncated exponential-rigid-rotor model for strong electron and ion rings
International Nuclear Information System (INIS)
Larrabee, D.A.; Lovelace, R.V.; Fleischmann, H.H.
1979-01-01
A comprehensive study of exponential-rigid-rotor equilibria for strong electron and ion rings indicates the presence of a sizeable percentage of untrapped particles in all equilibria with aspect-ratios R/a approximately <4. Such aspect-ratios are required in fusion-relevant rings. Significant changes in the equilibria are observed when untrapped particles are excluded by the use of a truncated exponential-rigid-rotor distribution function. (author)
impedance calculations of induction machine rotor conductors.
African Journals Online (AJOL)
Dr Obe
This paper describes a method of' calculating the impedance of Rectangular and Trapezoidal rotor bars. An R-L parallel network is used to model each of the Rotor bars. A computer optimisation Algorithm is developed and from which the Rotor circuit parameters at several frequencies are estimated. The model solutions ...
Teixeira, Miguel A. C.
2017-04-01
A linear model is used to diagnose the onset of rotors in flow over 2D ridges, 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 with a bulk boundary-layer model. The full model shows some ability to detect flow stagnation as a function of key input parameters, such as the Froude number and the height of the inversion, by comparison with results from numerical simulations and laboratory experiments carried out by previous authors. The effect of a boundary layer is essential to correctly predict flow stagnation, as the inviscid version of the model severely overestimates the dimensionless critical mountain height necessary for stagnation to occur. An improved model that includes only the effects of mean flow deceleration and amplification of the velocity perturbation within the boundary layer predicts flow stagnation much better in the most non-hydrostatic cases treated here, where waves appear to be directly forced by the orography. However, in the most hydrostatic case, only the full model, taking into account the feedback of the boundary layer on the inviscid flow, satisfactorily predicts flow stagnation, although the corresponding stagnation condition is unable to discriminate between rotors and hydraulic jumps. This is due to the fact that the trapped lee waves associated with the rotors are not forced directly by the orography in this case, but rather seem to be generated indirectly by nonlinear processes. This mechanism is, to a certain extent, mimicked by the modified surface boundary condition adopted in the full model, where an "effective orography" that differs from the real one forces the trapped lee waves. Versions of the model not including this feedback severely underestimate the amplitude of the trapped lee waves in the most hydrostatic case, partly
DEFF Research Database (Denmark)
Cerda Varela, Alejandro Javier; Santos, Ilmar
2014-01-01
In recent years, a continuous research effort has transformed the conventional tilting-pad journal bearing into a mechatronic machine element. The addition of electromechanical elements provides the possibility of generating controllable forces over the rotor as a function of a suitable control...... directly into the bearing clearance. The injected flow is controlled by means of a servovalve. The theoretical model includes the dynamics of servovalves and pipelines using a lumped parameter approach, whereas the coupling between the hydraulic system and the bearing oil film is modeled using a modified...
National Research Council Canada - National Science Library
Maglieri, Domenic
1955-01-01
Preliminary investigations have been made in the Langley gust tunnel to determine the effects of a sharp-edge vertical gust on the blade flapwise vibratory bending moments of small model rotors having...
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.
Modeling and Analysis of Micro-Spacecraft Attitude Sensing with Gyrowheel
Directory of Open Access Journals (Sweden)
Xiaokun Liu
2016-08-01
Full Text Available This paper proposes two kinds of approaches of angular rate sensing for micro-spacecraft with a gyrowheel (GW, which can combine attitude sensing with attitude control into one single device to achieve a compact micro-spacecraft design. In this implementation, during the three-dimensional attitude control torques being produced, two-dimensional spacecraft angular rates can be sensed from the signals of the GW sensors, such as the currents of the torque coils, the tilt angles of the rotor, the motor rotation, etc. This paper focuses on the problems of the angular rate sensing with the GW at large tilt angles of the rotor. For this purpose, a novel real-time linearization approach based on Lyapunov’s linearization theory is proposed, and a GW linearized measurement model at arbitrary tilt angles of the rotor is derived. Furthermore, by representing the two-dimensional rotor tilt angles and tilt control torques as complex quantities and separating the twice periodic terms about the motor spin speed, the linearized measurement model at smaller tilt angles of the rotor is given and simplified. According to the respective characteristics, the application schemes of the two measurement models are analyzed from the engineering perspective. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed strategy.
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.
A four degrees-of-freedom model for a misaligned electrical rotor
Xu, Xueping; Han, Qinkai; Chu, Fulei
2015-12-01
The eccentricity is one of the most common trouble sources in the rotor of electrical machine. This paper aims to investigate the vibration characteristics of an inclined rotor with both the static displacement eccentricity and the static angle eccentricity in the three-dimensional space. The air-gap length of an eccentric rotor is derived and the electromagnetic excitation which consists of the unbalanced magnetic pull (UMP) and the electromagnetic torque is obtained. The gyroscopic effect is taken into consideration and dynamic equations of the rotor system with four degrees of freedom are established. The static displacement eccentricity, static angle eccentricity, coexistence of static displacement and angle eccentricity, rotor location, unbalanced mass eccentricity and the rotating frequency are investigated for their effects on the dynamic responses in both the time domain and the frequency domain, respectively. Simulation results illustrate that both the static displacement eccentricity and the static angle eccentricity can lead to the increase in amplitudes of the dynamic displacement response and the angle response. The displacement and angle parameters are interactive in both the time domain and the frequency domain. The frequency components contained in the dynamic responses are related to multiples of the supply frequency and the rotating frequency. High integer multiples of rotating frequency are found when amplitudes of dynamic responses increase.
Study on Creep Damage Model of 1Cr1Mo1/4V Steel for Turbine Rotor
International Nuclear Information System (INIS)
Choi, Woo Sung; Song, Gee Wook; Kim, Bum Shin; Chang, Sung Ho; Fleury, Eric
2011-01-01
It is well known that the dominant damage mechanisms in high-temperature steam turbine facilities such as rotor and casing are creep and fatigue damages. Even though coupling of creep and fatigue should be considered while predicting the life of turbine facilities, the remaining life of large steam turbine facilities is generally determined on the basis of creep damage because the turbines must generate stable base-load power and because they are operated at a high temperature and pressure for a long time. Almost every large steam turbine in Korea has been operated for more than 20 years and is made of steel containing various amounts of principal alloying elements nickel, chromium, molybdenum, and vanadium. In this study, creep damage model of 1Cr1Mo1/4V steel for turbine rotor is proposed and that can assess the high temperature creep life of large steam turbine facilities is proposed
... test may also be appropriate to investigate the cause of fainting if you've fainted only once, but another ... recommend a tilt table test to evaluate the cause of syncope. A tilt table test may also be recommended ...
Modelling high frequency phenomena in the rotor of induction motors under no-load test conditions
International Nuclear Information System (INIS)
Boglietti, Aldo; Bottauscio, Oriano.; Chiampi, Mario; Lazzari, Mario
2003-01-01
The paper aims to deep the electromagnetic phenomena in the rotor of induction motors produced during the no-load test by the high-order harmonics of the spatial distribution of magnetic flux. The analysis is carried out by a flux driven finite element procedure, which can take into account the hysteresis of magnetic material, the induced currents in rotor cage and the eddy currents in the laminations. The computed results, including losses and local waveforms of electrical and magnetic quantities, are finally discussed
Numerical modeling of a pulsed asynchronous generator with iron-free cylindrical solid rotor
Energy Technology Data Exchange (ETDEWEB)
Guettafi, A. [Inst. d' Electrotechnique, Univ. de Batna, Batna (Algeria); Delmas, A.; Quichaud, G. [Lab. de Physique des Gaz et des Plasmas, Univ. Paris Sud, Orsay (France)
2001-01-01
This article presents the numerical simulation with finite element method of the transient regime of an asynchronous generator with iron-free cylindrical solid rotor. During this operation kinetic energy of the rotor is transferred through the ideal rectifier bridge to a load-inductance in order to create a high magnetic field pulse. The interest of this device is the less value of capacitors battery for self-oscillations of the asynchronous generator compared to this one necessary for direct transfer of its energy to the load-inductance. (orig.)
Nonlinear dynamic model of a gear-rotor-bearing system considering the flash temperature
Gou, Xiangfeng; Zhu, Lingyun; Qi, Changjun
2017-12-01
The instantaneous flash temperature is an important factor for gears in service. To investigate the effect of the flash temperature of a tooth surface on the dynamics of the spur gear system, a modified nonlinear dynamic model of a gear-rotor-bearing system is established. The factors such as the contact temperature of the tooth surface, time-varying stiffness, tooth surface friction, backlash, the comprehensive transmission error and so on are considered. The flash temperature of a tooth surface of pinion and gear is formulated according to Blok's flash temperature theory. The mathematical expression of the contact temperature of the tooth surface varied with time is derived and the tooth profile deformation caused by the change of the flash temperature of the tooth surface is calculated. The expression of the mesh stiffness varied with the flash temperature of the tooth surface is derived based on Hertz contact theory. The temperature stiffness is proposed and added to the nonlinear dynamic model of the system. The influence of load on the flash temperature of the tooth surface is analyzed in the parameters plane. The variation of the flash temperature of the tooth surface is studied. The numerical results indicate that the calculated method of the flash temperature of the gear tooth surface is effective and it can reflect the rules for the change of gear meshing temperature and sliding of the gear tooth surface. The effects of frequency, backlash, bearing clearance, comprehensive transmission error and time-varying stiffness on the nonlinear dynamics of the system are analyzed according to the bifurcation diagrams, Top Lyapunov Exponent (TLE) spectrums, phase portraits and Poincaré maps. Some nonlinear phenomena such as periodic bifurcation, grazing bifurcation, quasi-periodic bifurcation, chaos and its routes to chaos are investigated and the critical parameters are identified. The results provide an understanding of the system and serve as a useful reference
Molecular tilt on monolayer-protected nanoparticles
Giomi, L.
2012-02-01
The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.
Cui, Peiling; Yan, Ning
2012-12-12
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.
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.
Modelling of magnetorheological squeeze film dampers for vibration suppression of rigid rotors
Czech Academy of Sciences Publication Activity Database
Zapoměl, Jaroslav; Ferfecki, Petr; Kozánek, Jan
2017-01-01
Roč. 127, Jul SI (2017), s. 191-197 ISSN 0020-7403 R&D Projects: GA ČR GA15-06621S Institutional support: RVO:61388998 Keywords : squeeze film damper * magnetorheological fluid * bilinear material * rigid rotor * frequency response Subject RIV: JR - Other Machinery OBOR OECD: Mechanical engineering Impact factor: 2.884, year: 2016
Fu, Jicheng; Jones, Maria; Jan, Yih-Kuen
2014-01-01
Wheelchair tilt and recline functions are two of the most desirable features for relieving seating pressure to decrease the risk of pressure ulcers. The effective guidance on wheelchair tilt and recline usage is therefore critical to pressure ulcer prevention. The aim of this study was to demonstrate the feasibility of using machine learning techniques to construct an intelligent model to provide personalized guidance to individuals with spinal cord injury (SCI). The motivation stems from the clinical evidence that the requirements of individuals vary greatly and that no universal guidance on tilt and recline usage could possibly satisfy all individuals with SCI. We explored all aspects involved in constructing the intelligent model and proposed approaches tailored to suit the characteristics of this preliminary study, such as the way of modeling research participants, using machine learning techniques to construct the intelligent model, and evaluating the performance of the intelligent model. We further improved the intelligent model's prediction accuracy by developing a two-phase feature selection algorithm to identify important attributes. Experimental results demonstrated that our approaches held the promise: they could effectively construct the intelligent model, evaluate its performance, and refine the participant model so that the intelligent model's prediction accuracy was significantly improved.
Tilting Saturn without Tilting Jupiter: Constraints on Giant Planet Migration
Brasser, R.; Lee, Man Hoi
2015-11-01
The migration and encounter histories of the giant planets in our solar system can be constrained by the obliquities of Jupiter and Saturn. We have performed secular simulations with imposed migration and N-body simulations with planetesimals to study the expected obliquity distribution of migrating planets with initial conditions resembling those of the smooth migration model, the resonant Nice model and two models with five giant planets initially in resonance (one compact and one loose configuration). For smooth migration, the secular spin-orbit resonance mechanism can tilt Saturn’s spin axis to the current obliquity if the product of the migration timescale and the orbital inclinations is sufficiently large (exceeding 30 Myr deg). For the resonant Nice model with imposed migration, it is difficult to reproduce today’s obliquity values, because the compactness of the initial system raises the frequency that tilts Saturn above the spin precession frequency of Jupiter, causing a Jupiter spin-orbit resonance crossing. Migration timescales sufficiently long to tilt Saturn generally suffice to tilt Jupiter more than is observed. The full N-body simulations tell a somewhat different story, with Jupiter generally being tilted as often as Saturn, but on average having a higher obliquity. The main obstacle is the final orbital spacing of the giant planets, coupled with the tail of Neptune’s migration. The resonant Nice case is barely able to simultaneously reproduce the orbital and spin properties of the giant planets, with a probability ˜ 0.15%. The loose five planet model is unable to match all our constraints (probability <0.08%). The compact five planet model has the highest chance of matching the orbital and obliquity constraints simultaneously (probability ˜0.3%).
Comparison of Models for the Steady-State Analysis of Tilting-Pad Thrust Bearings
DEFF Research Database (Denmark)
Heinrichson, Niels; Santos, Ilmar
2005-01-01
distribution the deflection of the pad due to pressure and thermal bending can be calculated using a flat plate approximation. At the five free sides of the pad heat transfer can be modelled. The temperature distribution at the inlet to the pad can be calculated through equilibrium of thermal energy...... for the groove between pads and the oil bath temperature from energy equilibrium for the entire bearing. The main theoretical contribution of this paper is the elaboration and comparison of 7 different mathematical models of increasing complexity. The results are compared to experimental data for steady...
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.
Complex double-mass dynamic model of rotor on thrust foil gas dynamic bearings
Sytin, A.; Babin, A.; Vasin, S.
2017-08-01
The present paper considers simulation of a rotor’s dynamics behaviour on thrust foil gas dynamic bearings based on simultaneous solution of gas dynamics differential equations, equations of theory of elasticity, motion equations and some additional equations. A double-mass dynamic system was considered during the rotor’s motion simulation which allows not only evaluation of rotor’s dynamic behaviour, but also to evaluate the influence of operational and load parameters on the dynamics of the rotor-bearing system.
Experimental investigation of main rotor wake
Directory of Open Access Journals (Sweden)
Stepanov Robert
2017-01-01
Full Text Available In this work, experimental results of rotor wake in hover mode are presented. The experiments were carried out with a rotor rig model in the T-1K wind tunnel in Kazan National Research Technical University (Kazan Aviation Institute. The rotor consisted of four identical blades. The Q-criterion was used to identify tip vortices for a 2D case. The results were then compared with two different wake models.
Experimental investigation of main rotor wake
Stepanov Robert; Mikhailov Sergey
2017-01-01
In this work, experimental results of rotor wake in hover mode are presented. The experiments were carried out with a rotor rig model in the T-1K wind tunnel in Kazan National Research Technical University (Kazan Aviation Institute). The rotor consisted of four identical blades. The Q-criterion was used to identify tip vortices for a 2D case. The results were then compared with two different wake models.
DEFF Research Database (Denmark)
Jannati, Mohammad; Monadi, Ali; Nik Idris, Nik Rumzi
2016-01-01
This paper discusses the d-q model and winding function method (WFM) for modeling and a rotor eld-oriented control (RFOC) system for controlling a faulty three-phase induction motor (three-phase IM when one of the phases is disconnected). In the adapted scheme for controlling the faulty IM...
Cross, Rod
2017-01-01
If a small object is placed under the front leg of a chair, the chair tilts backwards. If the object is placed under a rear leg, the chair tilts sideways. The effect is surprising but can be analysed in terms of elementary physics.
Jin, Yulin; Lu, Kuan; Hou, Lei; Chen, Yushu
2017-12-01
The proper orthogonal decomposition (POD) method is a main and efficient tool for order reduction of high-dimensional complex systems in many research fields. However, the robustness problem of this method is always unsolved, although there are some modified POD methods which were proposed to solve this problem. In this paper, a new adaptive POD method called the interpolation Grassmann manifold (IGM) method is proposed to address the weakness of local property of the interpolation tangent-space of Grassmann manifold (ITGM) method in a wider parametric region. This method is demonstrated here by a nonlinear rotor system of 33-degrees of freedom (DOFs) with a pair of liquid-film bearings and a pedestal looseness fault. The motion region of the rotor system is divided into two parts: simple motion region and complex motion region. The adaptive POD method is compared with the ITGM method for the large and small spans of parameter in the two parametric regions to present the advantage of this method and disadvantage of the ITGM method. The comparisons of the responses are applied to verify the accuracy and robustness of the adaptive POD method, as well as the computational efficiency is also analyzed. As a result, the new adaptive POD method has a strong robustness and high computational efficiency and accuracy in a wide scope of parameter.
Vibration response of misaligned rotors
Patel, Tejas H.; Darpe, Ashish K.
2009-08-01
Misalignment is one of the common faults observed in rotors. Effect of misalignment on vibration response of coupled rotors is investigated in the present study. The coupled rotor system is modelled using Timoshenko beam elements with all six dof. An experimental approach is proposed for the first time for determination of magnitude and harmonic nature of the misalignment excitation. Misalignment effect at coupling location of rotor FE model is simulated using nodal force vector. The force vector is found using misalignment coupling stiffness matrix, derived from experimental data and applied misalignment between the two rotors. Steady-state vibration response is studied for sub-critical speeds. Effect of the types of misalignment (parallel and angular) on the vibration behaviour of the coupled rotor is examined. Along with lateral vibrations, axial and torsional vibrations are also investigated and nature of the vibration response is also examined. It has been found that the misalignment couples vibrations in bending, longitudinal and torsional modes. Some diagnostic features in the fast Fourier transform (FFT) of torsional and longitudinal response related to parallel and angular misalignment have been revealed. Full spectra and orbit plots are effectively used to reveal the unique nature of misalignment fault leading to reliable misalignment diagnostic information, not clearly brought out by earlier studies.
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.
Frutos-Alfaro, Francisco
2007-03-01
The gravitational lens equation for the tilted Plummer family of models can be reduced to a one-dimensional non-linear equation. For certain values of the slope of the radial profile it can be reduced to a polynomial form. Both forms are advantageous to find the roots, i.e. the images for a given model. The critical curve equations can also be reduced to a non-linear or polynomial form, and therefore it is useful to find the caustics. This lens model family has ample use in gravitational lens theory, and can produce up to five images.
DEFF Research Database (Denmark)
Døssing, Mads
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...... 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 eective 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 coecient. The design methodology proved to be stable and a help in the otherwise challenging task of numerical aeroelastic optimization....
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.
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.
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.
Tilting-Pad Guide Bearing in Large Hydro-unit
Directory of Open Access Journals (Sweden)
Li-Feng Ma
2000-01-01
Full Text Available A new numerical method is proposed for predicting the nonlinearity of tilting-pad guide bearing oilfilm force in the rotor-bearing system in a large hydro-unit. Nonlinear displacement and velocity of the journal center, as well as nonlinear tilting angles and angular velocities of the pads in non-stationary Reynolds equation are taken into account. This method is also suited for other small rotor-bearing system. As an example, the response due to a momentarily created unbalance is Calculated. The nonlinear motion patterns of the pad and journal whirling orbit are obtained. Finally, the nonlinear orbit is compared to the linear one that could be calculated from linear stiffness and damping coefficients. It is shown that there are important differences between those two orbits and that the nonlinear simulation is more accurate.
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
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.
Tip Vortex and Wake Characteristics of a Counterrotating Open Rotor
VanZante, Dale E.; Wernet, Mark P.
2012-01-01
One of the primary noise sources for Open Rotor systems is the interaction of the forward rotor tip vortex and blade wake with the aft rotor. NASA has collaborated with General Electric on the testing of a new generation of low noise, counterrotating Open Rotor systems. Three-dimensional particle image velocimetry measurements were acquired in the intra-rotor gap of the Historical Baseline blade set. The velocity measurements are of sufficient resolution to characterize the tip vortex size and trajectory as well as the rotor wake decay and turbulence character. The tip clearance vortex trajectory is compared to results from previously developed models. Forward rotor wake velocity profiles are shown. Results are presented in a form as to assist numerical modeling of Open Rotor system aerodynamics and acoustics.
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.
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)
Internal rotor friction instability
Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.
1990-01-01
The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.
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)
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.
National Research Council Canada - National Science Library
Young, L. A; Lillie, D; McCluer, M; Yamauchi, G. K; Derby, M. R
2002-01-01
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...
DEFF Research Database (Denmark)
Salazar, Jorge Andrés González; Cerda Varela, Alejandro Javier; Santos, Ilmar
2013-01-01
This paper reports the dynamic study of a flexible rotor-bearing test rig which resembles a large overhung centrifugal compressor. The rotor is supported by an active tilting pad journal bearing (TPJB) able to perform the adjustable lubrication regime. Such a regime is obtained by injecting...
Wind Tunnel Evaluation of a Model Helicopter Main-Rotor Blade With Slotted Airfoils at the Tip
Noonan, Kevin W.; Yeager, William T., Jr.; Singleton, Jeffrey D.; Wilbur, Matthew L.; Mirick, Paul H.
2001-01-01
Data for rotors using unconventional airfoils are of interest to permit an evaluation of this technology's capability to meet the U.S. Army's need for increased helicopter mission effectiveness and improved safety and survivability. Thus, an experimental investigation was conducted in the Langley Transonic Dynamics Tunnel (TDT) to evaluate the effect of using slotted airfoils in the rotor blade tip region (85 to 100 percent radius) on rotor aerodynamic performance and loads. Four rotor configurations were tested in forward flight at advance ratios from 0.15 to 0.45 and in hover in-ground effect. The hover tip Mach number was 0.627, which is representative of a design point of 4000-ft geometric altitude and a temperature of 95 F. The baseline rotor configuration had a conventional single-element airfoil in the tip region. A second rotor configuration had a forward-slotted airfoil with a -6 deg slat, a third configuration had a forward-slotted airfoil with a -10 slat, and a fourth configuration had an aft-slotted airfoil with a 3 deg flap (trailing edge down). The results of this investigation indicate that the -6 deg slat configuration offers some performance and loads benefits over the other three configurations.
Helicopter rotor induced velocities theory and experiment
Berry, John D.; Hoad, Danny R.; Elliott, Joe W.; Althoff, Susan L.
1987-01-01
An investigation has been performed to assess methods used for rotor inflow modeling. A key element of this assessment has been the recent acquisition of high quality experimental measurements of inflow velocities taken in the proximity of a lifting rotor in forward flight. Widely used rotor performance predictive methods are based on blade element strip theory coupled with an inflow model. The inflow prediction models assessed in this paper include the uniform inflow based on momentum, a skewed disk model, and two methods based on a vortex wake structure.
Amezquita-Brooks, Luis; Liceaga-Castro, Eduardo; Gonzalez-Sanchez, Mario; Garcia-Salazar, Octavio; Martinez-Vazquez, Daniel
2017-11-01
Applications based on quad-rotor-vehicles (QRV) are becoming increasingly wide-spread. Many of these applications require accurate mathematical representations for control design, simulation and estimation. However, there is no consensus on a standardized model for these purposes. In this article a review of the most common elements included in QRV models reported in the literature is presented. This survey shows that some elements are recurrent for typical non-aerobatic QRV applications; in particular, for control design and high-performance simulation. By synthesising the common features of the reviewed models a standard generic model SGM is proposed. The SGM is cast as a typical state-space model without memory-less transformations, a structure which is useful for simulation and controller design. The survey also shows that many QRV applications use simplified representations, which may be considered simplifications of the SGM here proposed. In order to assess the effectiveness of the simplified models, a comprehensive comparison based on digital simulations is presented. With this comparison, it is possible to determine the accuracy of each model under particular operating ranges. Such information is useful for the selection of a model according to a particular application. In addition to the models found in the literature, in this article a novel simplified model is derived. The main characteristics of this model are that its inner dynamics are linear, it has low complexity and it has a high level of accuracy in all the studied operating ranges, a characteristic found only in more complex representations. To complement the article the main elements of the SGM are evaluated with the aid of experimental data and the computational complexity of all surveyed models is briefly analysed. Finally, the article presents a discussion on how the structural characteristics of the models are useful to suggest particular QRV control structures.
Lieb's correlation inequality for plane rotors
International Nuclear Information System (INIS)
Rivasseau, V.
1980-01-01
We prove a conjecture by E. Lieb, which leads to the Lieb inequality for plane rotors. As in the Ising model case, this inequality implies the existence of an algorithm to compute the transition temperature of this model. (orig.)
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.
DEFF Research Database (Denmark)
Haahr Andersen, Henning; Kaneda, Masaharu
Let $U_q$ denote the quantum group associated with a finite dimensional semisimple Lie algebra. Assume that $q$ is a complex root of unity of odd order and that $U_q$ is %the quantum group version obtained via Lusztig's $q$-divided powers construction. We prove that all regular projective (tilting...
Mapping of moveout in tilted transversely isotropic media
Stovas, A.
2013-09-09
The computation of traveltimes in a transverse isotropic medium with a tilted symmetry axis tilted transversely isotropic is very important both for modelling and inversion. We develop a simple analytical procedure to map the traveltime function from a transverse isotropic medium with a vertical symmetry axis (vertical transversely isotropic) to a tilted transversely isotropic medium by applying point-by-point mapping of the traveltime function. This approach can be used for kinematic modelling and inversion in layered tilted transversely isotropic media. © 2013 European Association of Geoscientists & Engineers.
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 model....... The vortex generator model is validated by applying it for modelling an array of VGs on an airfoil section compared to both wind tunnel measurements and fully gridded CFD....
Rotating Shaft Tilt Angle Measurement Using an Inclinometer
Luo Jun; Wang Zhiqian; Shen Chengwu; Wen Zhuoman; Liu Shaojin; Cai Sheng; Li Jianrong
2015-01-01
This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendic...
DEFF Research Database (Denmark)
von Osmanski, Alexander Sebastian; Larsen, Jon Steffen; Santos, Ilmar
2017-01-01
Despite decades of research, the dynamics of air foil bearings (AFBs) are not yet fully captured by any model,suggesting that the fundamental mechanisms of the AFB and their relative merits are not yet fully understood. The recent years have seen promising results from nonlinear time domain models......, allowing the dynamic pressure–compliance interaction and the unsteady terms of the compressible Reynolds equation to be considered. By including the simple elastic foundation model (SEFM) in a fully coupled simultaneous time integration, the dynamics of a rotor supported by industrial AFBs have previously...
A state-space free-vortex hybrid wake model for helicopter rotors
Wasileski, Bryan J.
This paper presents the development of a new hybrid wake model merging two distinctly different modeling approaches into a single, more comprehensive solution. The objective of the work was to leverage the strengths of each individual wake model creating a more flexible and extensible solution that could be used across the entire flight envelope of a helicopter. The results of the work indicate that the two wakes models can be successfully merged. The results also show that hybrid wake provides a mechanism by which finite-state wake imparts a level of stability on the free wake solution allowing the free wake to provide consistent, repeatable results from hover through high speed forward flight. While the new hybrid wake includes the geometric distortion needed for predicting the off-axis control response, the new model, as configured in this work, shows no sign of improvement in this area.
Directory of Open Access Journals (Sweden)
Lutz Sperling
2000-01-01
Full Text Available Synchronous elimination as one of the possible methods of cancelling any harmful vibration resulting from the unbalance of rotary machines is considered. This method, introduced by Fesca and Thearle, involves the placement of unbalanced elements (e.g. ring, pendulum, ball balancers on the rotor axis, which can occupy any angular position in relation to the rotor. Under defined conditions in the postcritical frequency range, there is a spontaneous placement of the corection elements such that they balance the rotor unbalance. Hedaya and Sharp generalized this method by combining two force balancers to compensate the unbalanced moment as well as the unbalanced force of a rigid rotor.
Topological dynamics in supramolecular rotors.
Palma, Carlos-Andres; Björk, Jonas; Rao, Francesco; Kühne, Dirk; Klappenberger, Florian; Barth, Johannes V
2014-08-13
Artificial molecular switches, rotors, and machines are set to establish design rules and applications beyond their biological counterparts. Herein we exemplify the role of noncovalent interactions and transient rearrangements in the complex behavior of supramolecular rotors caged in a 2D metal-organic coordination network. Combined scanning tunneling microscopy experiments and molecular dynamics modeling of a supramolecular rotor with respective rotation rates matching with 0.2 kcal mol(-1) (9 meV) precision, identify key steps in collective rotation events and reconfigurations. We notably reveal that stereoisomerization of the chiral trimeric units entails topological isomerization whereas rotation occurs in a topology conserving, two-step asynchronous process. In supramolecular constructs, distinct displacements of subunits occur inducing a markedly lower rotation barrier as compared to synchronous mechanisms of rigid rotors. Moreover, the chemical environment can be instructed to control the system dynamics. Our observations allow for a definition of mechanical cooperativity based on a significant reduction of free energy barriers in supramolecules compared to rigid molecules.
Internal Friction And Instabilities Of Rotors
Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.
1992-01-01
Report describes study of effects of internal friction on dynamics of rotors prompted by concern over instabilities in rotors of turbomachines. Theoretical and experimental studies described. Theoretical involved development of nonlinear mathematical models of internal friction in three joints found in turbomachinery - axial splines, Curvic(TM) splines, and interference fits between smooth cylindrical surfaces. Experimental included traction tests to determine the coefficients of friction of rotor alloys at various temperatures, bending-mode-vibration tests of shafts equipped with various joints and rotordynamic tests of shafts with axial-spline and interference-fit joints.
DEFF Research Database (Denmark)
Troldborg, Niels; Zahle, Frederik; Réthoré, Pierre-Elouan
2015-01-01
The wake of the 5MW reference wind turbine designed by the National Renewable Energy Laboratory (NREL) is simulated using computational fluid dynamics with a fully resolved rotor geometry, an actuator line method and an actuator disc method, respectively. Simulations are carried out prescribing...
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.
A review of research in rotor loads
Bousman, William G.; Mantay, Wayne R.
1988-01-01
The research accomplished in the area of rotor loads over the last 13 to 14 years is reviewed. The start of the period examined is defined by the 1973 AGARD Milan conference and the 1974 hypothetical rotor comparison. The major emphasis of the review is research performed by the U.S. Army and NASA at their laboratories and/or by the industry under government contract. For the purpose of this review, two main topics are addressed: rotor loads prediction and means of rotor loads reduction. A limited discussion of research in gust loads and maneuver loads is included. In the area of rotor loads predictions, the major problem areas are reviewed including dynamic stall, wake induced flows, blade tip effects, fuselage induced effects, blade structural modeling, hub impedance, and solution methods. It is concluded that the capability to predict rotor loads has not significantly improved in this time frame. Future progress will require more extensive correlation of measurements and predictions to better understand the causes of the problems, and a recognition that differences between theory and measurement have multiple sources, yet must be treated as a whole. There is a need for high-quality data to support future research in rotor loads, but the resulting data base must not be seen as an end in itself. It will be useful only if it is integrated into firm long-range plans for the use of the data.
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...
Rotor Mass Eccentricity Vibration Compensation Control in Bearingless Induction Motor
Directory of Open Access Journals (Sweden)
Zebin Yang
2015-01-01
Full Text Available In the process of motor rotation, the vibration caused by the rotor mass eccentricity seriously affects the dynamic characteristics and safety operation of system. So rotor mass eccentricity vibration compensation control on rotating machine has great significance, especially for the high speed bearing less induction motor (BIM. A rotor mass eccentricity compensation control strategy was presented to restrain the vibration of suspended rotor for BIM. Firstly, the suspension rotor dynamical model was deduced and unbalanced vibration mechanism was analyzed. Secondly, based on decoupling control between electromagnetic torque and radial force, the obtained vibration signal from the displacement sensor was put into the original radial force control system. Then, a feedforward compensator was set up to increase the same period component of the given radial force signal and enlarge the stiffness of the vibration signal. Finally, the compensation control of rotor vibration was realized by forcing the rotor shaft rotation around its geometric center. The simulation results show that the presented feedforward compensator can suppress the vibration of rotor under different speed and improve the precision of rotor suspension. The further experimental results also show that the control method can obviously reduce the peak-peak value of rotor radial displacement and effectively restrain rotor vibration.
Computational Study of Flow Interactions in Coaxial Rotors
Yoon, Seokkwan; Lee, Henry C.; Pulliam, Thomas H.
2016-01-01
account for multiple real-world constraints up front in design nor possible to know what performance is possible with a given design. Since unmanned vehicles are sized and optimized for the particular mission, a modern low-fidelity conceptual design and sizing tool that has been used for the design of large helicopters can be used for design of small coaxial rotorcraft. However, unlike most helicopters with single main rotor, the interactions between the upper and lower rotors emerge as an important factor to consider in design because an increase in performance of a multi-rotor system is not proportional to the number of rotors. Interference losses and differences in thrusts between the upper and lower rotors were investigated by theoretical methods as well as a computational fluid dynamics (CFD) method using the Reynolds-Averaged Navier-Stokes (RANS) equations. In this work, hybrid turbulence models are used to investigate the physics of interactions between coaxial rotors and a fuselage that are not well understood. Present study covers not only small-scale drones but also large-scale coaxial rotors for heavy-lifting missions. Considering the recently proposed FAA drone rules that require the flight only in visual line-of-sight, a large multirotor might be used as an airborne carrier for launch and recovery of unmanned aircraft systems with a human operator onboard. For applications to civil operations, their aerodynamic performance and noise levels need to be assessed. Noise is one of the largest limiting factors to rotorcraft operations in urban area. Since the high-frequency noise of multi-rotors may increase the annoyance, noise may turn out to be a key issue that must be addressed for market acceptability. One of the objectives of the present work is to study the effects of inter-rotor spacing and collectives on the performance, efficiency, and acoustics of coaxial rotor systems.
Coupled Dynamics of a Rotor-Journal Bearing System Equipped with Thrust Bearings
Yu Lie; R.B. Bhat
1995-01-01
The rotordynamic coefficients of fixed-pad thrust bearing are introduced and calculated by using the out-domain method, and a general analysis method is developed to investigate the coupled dynamics of a rotor equipped with journal and thrust bearings simultaneously. Considerations include the effects of static tilt parameters of the rotor on rotordynamic coefficients of thrust bearing and the action of thrust bearing on system dynamics. It is shown that thrust bearing changes the load distri...
Structural modelling of composite beams with application to wind turbine rotor blades
DEFF Research Database (Denmark)
Couturier, Philippe
The ever changing structure and growing size of wind turbine blades put focus on the accuracy and flexibility of design tools. The present thesis is organized in four parts - all concerning the development of efficient computational methods for the structural modelling of composite beams which...... 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...... longitudinal stresses is modelled with a Finite Strip buckling analysis based on the deformed cross-section. The analysis is well suited for early stages of design as it only requires a simple 2D line mesh of the cross-section....
Unique parity states in 109Pd as a test of particle-rotor and IBFA models
International Nuclear Information System (INIS)
Casten, R.F.
1980-01-01
Calculations were performed for anti-aligned levels in 109 Pd. For a Nilsson model with pairing, variable moment of inertia, and Coriolis coupling, the favored levels were well reproduced, but the low-spin unfavored states exhibited serious disagreement with experiment results. Calculations with the IBFA were a significant improvement, in particular a regards the splitting of states of common spin. Comments on the source of this improvement are offered. 2 figures, 1 table
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
DEFF Research Database (Denmark)
Wang, K.; Hansen, Martin Otto Laver; Moan, T.
2015-01-01
in skewed flow conditions. Three different dynamic stall models are also integrated into the DMS model: Gormont's model with the adaptation of Strickland, Gormont's model with the modification of Berg and the Beddoes-Leishman dynamic stall model. Both the small Sandia 17m wind turbine and the large Deep...
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.
de Santiago Duran, Oscar Cesar
Experimental identification of fluid film bearing parameters is vital to validate predictions from often restrictive computational fluid film bearing models and is also promising for condition monitoring and troubleshooting. This dissertation presents the analytical bases of two procedures for bearing supports parameter identification with potential for in-situ implementation. Bearing support coefficients are derived from measurements of rotor responses to impact loads and due to calibrated imbalances in characteristic planes. Subsequent implementation of the procedures to measurements performed in a rigid massive rotor traversing two critical speeds provides force coefficients for a novel bearing support comprising a tilting pad bearing (TPJB ) in series with an integral squeeze film damper (SFD). At a constant rotor speed, the first method requires impacts loads exerted along two lateral planes for identification of frequency-dependent force coefficients. Simulation numerical examples show the method is reliable with a reduced sensitivity to noise as the number of impacts increases (frequency averaging). In the experiments, an ad-hoc fixture delivers impacts to the rotor middle disk at speeds of 2,000 and 4,000 rpm. The experimentally identified force coefficients are in close agreement with predicted coefficients for the series support TPJB-SFD. In particular, damping coefficients are best identified around the system first natural frequency. Bearing stiffness are correctly identified in the low frequency range, but show a marked reduction at higher frequencies apparently due to inertial effects not accounted for in the model. Measurements of rotor response to calibrated imbalances allow identification of speed-dependent force coefficients. The procedure requires a minimum of two different imbalance distributions for identification of force coefficients from the two bearing supports. The rotor responses show minimal cross-coupling effects, as also predicted by
High resolution flow field prediction for tail rotor aeroacoustics
Quackenbush, Todd R.; Bliss, Donald B.
The prediction of tail rotor noise due to the impingement of the main rotor wake poses a significant challenge to current analysis methods in rotorcraft aeroacoustics. This paper describes the development of a new treatment of the tail rotor aerodynamic environment that permits highly accurate resolution of the incident flow field with modest computational effort relative to alternative models. The new approach incorporates an advanced full-span free wake model of the main rotor in a scheme which reconstructs high-resolution flow solutions from preliminary, computationally inexpensive simulations with coarse resolution. The heart of the approach is a novel method for using local velocity correction terms to capture the steep velocity gradients characteristic of the vortex-dominated incident flow. Sample calculations have been undertaken to examine the principal types of interactions between the tail rotor and the main rotor wake and to examine the performance of the new method. The results of these sample problems confirm the success of this approach in capturing the high-resolution flows necessary for analysis of rotor-wake/rotor interactions with dramatically reduced computational cost. Computations of radiated sound are also carried out that explore the role of various portions of the main rotor wake in generating tail rotor noise.
Tilted-axis wobbling in odd-mass nuclei
Budaca, R.
2018-02-01
A triaxial rotor Hamiltonian with a rigidly aligned high-j quasiparticle is treated by a time-dependent variational principle, using angular momentum coherent states. The resulting classical energy function has three unique critical points in a space of generalized conjugate coordinates, which can minimize the energy for specific ordering of the inertial parameters and a fixed angular momentum state. Because of the symmetry of the problem, there are only two unique solutions, corresponding to wobbling motion around a principal axis and, respectively, a tilted axis. The wobbling frequencies are obtained after a quantization procedure and then used to calculate E 2 and M 1 transition probabilities. The analytical results are employed in the study of the wobbling excitations of 135Pr nucleus, which is found to undergo a transition from low angular momentum transverse wobbling around a principal axis toward a tilted-axis wobbling at higher angular momentum.
Analysis of the Strength on the Rotor Punching Sheet of Nuclear Reactor Cooling Medium Driving Motor
Directory of Open Access Journals (Sweden)
GE Bao-jun
2017-02-01
Full Text Available A strong stress is withstood by the rotor punching sheet during the running of nuclear reactor cooling medium driving motor. In order to study the strength on the rotor punching sheet and the influential factor of its stress，the rotor of driving motor was the research object, the three-dimensional rotor model of driving motor is established by the finite element method to obtain the Mires equivalent stress nephogram and check the rotor’s strength with setting parameters and constraints. According to different rotor speeds，the different average temperatures of rotor punching sheet and shaft and the different static magnitude of interference between rotor punching sheet and shaft，the research about how the contact pressure of matching surface between rotor punching sheet and shaft and the Mires equivalent stress are impacted is carried on. The results show that the maximum Miser equivalent stress value of rotor punching sheet emerges on the axial vents，the stress value is beyond the tensile limit of the materialand. The greater the static magnitude of interference and the smaller temperature difference of rotor punching sheet and shaft lead to the greater interface compressive stress of rotor punching sheet and shaft and the greater maximum Mires equivalent stress value of rotor punching sheet. The higher the rotor speed lead to the smaller interface compressive stress of rotor punching sheet and shaft and the greater equivalent stress value of rotor punching sheet.
Coupled Dynamics of a Rotor-Journal Bearing System Equipped with Thrust Bearings
Directory of Open Access Journals (Sweden)
Yu Lie
1995-01-01
Full Text Available The rotordynamic coefficients of fixed-pad thrust bearing are introduced and calculated by using the out-domain method, and a general analysis method is developed to investigate the coupled dynamics of a rotor equipped with journal and thrust bearings simultaneously. Considerations include the effects of static tilt parameters of the rotor on rotordynamic coefficients of thrust bearing and the action of thrust bearing on system dynamics. It is shown that thrust bearing changes the load distribution of journal bearings and the static deflection of the rotor and delays the instability of the system considerably in lateral shaft vibration.
Viana, Ilisio; Orteu, Jean-José; Cornille, Nicolas; Bugarin, Florian
2015-11-01
We focus on quality control of mechanical parts in aeronautical context using a single pan-tilt-zoom (PTZ) camera and a computer-aided design (CAD) model of the mechanical part. We use the CAD model to create a theoretical image of the element to be checked, which is further matched with the sensed image of the element to be inspected, using a graph theory-based approach. The matching is carried out in two stages. First, the two images are used to create two attributed graphs representing the primitives (ellipses and line segments) in the images. In the second stage, the graphs are matched using a similarity function built from the primitive parameters. The similarity scores of the matching are injected in the edges of a bipartite graph. A best-match-search procedure in the bipartite graph guarantees the uniqueness of the match solution. The method achieves promising performance in tests with synthetic data including missing elements, displaced elements, size changes, and combinations of these cases. The results open good prospects for using the method with realistic data.
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.
Fast Fourier transform analysis of rotor-bearing systems
Choy, K. C.; Gunter, E. J.; Allaire, P. E.
1978-01-01
Nonlinear transient analysis of rotor-bearing systems is becoming increasingly important in the analysis of modern-day rotating machinery to model such phenomena as oil film whirl. This paper develops an analysis technique incorporating modal analysis and fast Fourier transform techniques to analyze rotors with residual shaft bow and realistic nonlinear bearings. The technique is demonstrated on single-mass and three-mass rotor examples. Comparisons of the theoretical results with experimental data give excellent agreement.
Aeromechanics of a High Speed Coaxial Helicopter Rotor
Schmaus, Joseph Henry
The current work seeks to understand the aeromechanics of lift offset coaxial rotors in high speeds. Future rotorcraft will need to travel significantly faster that modern rotorcraft do while maintaining hovering efficiency and low speed maneuverability. The lift offset coaxial rotor has been shown to have those capabilities. A majority of existing coaxial research is focused on hovering performance, and few studies examine the forward flight performance of a coaxial rotor with lift offset. There are even fewer studies of a single rotor with lift offset. The current study used comprehensive analysis and a new set of wind tunnel experiments to explore the aeromechanics of a lift offset coaxial rotor in high speed forward flight. The simulation was expanded from UMARC to simultaneously solve multiple rotors with coupled aerodynamics. It also had several modifications to improve the aerodynamics of the near-wake model in reverse flow and improve the modeling of blade passages. Existing coaxial hovering tests and flight test data from the XH-59A were used to validate the steady performance and blade loads of the comprehensive analysis. It was used to design the structural layout of the blades used in the wind tunnel experiment as well as the test envelope and testing procedure. The wind tunnel test of a model rotor developed by the University of Texas at Austin and the University of Maryland was performed in the Glenn L Martin Wind Tunnel. The test envelope included advance ratios 0.21-0.53, collectives 4°- 8°, and lift offsets 0%-20% for both rotors tested in isolation and as a coaxial system operating at 900 RPM. Rotating frame hub loads, pushrod loads, and pitch angle were recorded independently for each rotor. Additional studies were performed at 1200 RPM to isolate Reynold effects and with varying rotor-to-rotor phase to help quantify aerodynamic interactions. Lift offset fundamentally changes the lift distribution around the rotor disk, doing so increases the
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.
International Nuclear Information System (INIS)
Song, Jun Beom; Byun, Young Seop; Jeong, Jin Seok; Kim, Jeong; Kang, Beom Soo
2016-01-01
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
Generator rotor dovetail cracking
International Nuclear Information System (INIS)
Toth, J.
2004-01-01
In the presentation the dovetail control and recommended arrangements of the large steam turbine generators are described. The company General Electric established a complete package comprising working schedule of rotor control and solutions of the problems of the dovetail cracking of the large steam turbine generator rotors with long-term operation. A part of the article is also the recommended packet including more items. (author)
Measurement of electrical polar symmetry in turbogenerator rotors
International Nuclear Information System (INIS)
Ramírez-Niño, J; González Vázquez, A
2012-01-01
This paper presents a measurement technique and an analysis of the electrical polar symmetry in turbogenerator rotors using the so-called recurrent pulse comparison with the injection of charge as the excitation source. The polar symmetry should be measured because it provides information that allows electrical insulation failures in the rotor winding to be detected. A simple electrical model for the rotor is introduced, and the technique for comparing the recurrent pulses is analysed in detail. The particular measurement instrumentation and the analysis of the results obtained in the time and frequency domains, including their relation to the rotor failures, are also described. (paper)
Conceptual design studies of 1985 commercial VTOL transports that utilized rotors, Volume 2
Magee, J. P.; Clark, R.; Alexander, H. R.
1974-01-01
Results of conceptual design studies of tilt rotor and tandem helicopter aircraft for a 200 nautical mile commercial short haul transport mission are presented. The trade study data used in selecting the design point aircraft and technology details necessary to support the design conclusions are included.
Control system design for flexible rotors supported by actively lubricated bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2008-01-01
and keeping the lengths of the two eigenvalues constant in the real-imaginary plane. The methodology is applied to an industrial gas compressor supported by active tilting-pad journal bearings. The unbalance response functions and mode shapes of the flexible rotor with and without active control are presented...
Opatrný, Tomáš; Richterek, Lukáš; Opatrný, Martin
2018-01-31
We show that the classical model of Euler top (freely rotating, generally asymmetric rigid body), possibly supplemented with a rotor, corresponds to a generalized Lipkin-Meshkov-Glick (LMG) model describing phenomena of various branches of quantum physics. Classical effects such as free precession of a symmetric top, Feynman's wobbling plate, tennis-racket instability and the Dzhanibekov effect, attitude control of satellites by momentum wheels, or twisting somersault dynamics, have their counterparts in quantum effects that include spin squeezing by one-axis twisting and two-axis countertwisting, transitions between the Josephson and Rabi regimes of a Bose-Einstein condensate in a double-well potential, and other quantum critical phenomena. The parallels enable us to expand the range of explored quantum phase transitions in the generalized LMG model, as well as to present a classical analogy of the recently proposed LMG Floquet time crystal.
Evaluating Tilt for Wind Plants
Energy Technology Data Exchange (ETDEWEB)
Annoni, Jennifer [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Scholbrock, Andrew K. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Churchfield, Matthew J. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Fleming, Paul A. [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-07-03
The objective of this work is to demonstrate the feasibility of tilt in a wind plant. Tilt control, much like other wind plant control strategies, has the potential to improve the performance of a wind plant. Tilt control uses the tilt angle of the turbine to direct the wake above or below the downstream turbines. This paper presents a study of tilt in two- and three-turbine arrays. Specifically, the authors show that the power production of a two-turbine array can be increased by tilting turbines in a specific orientation. When adding more turbines, as is shown with the three-turbine array, the overall percentage of power gain increases. This outcome deviates from some of the results seen in typical wind plant control strategies. Finally, we discuss the impact this type of control strategy has on the aerodynamics in a wind plant. This analysis demonstrates that a good understanding of wake characteristics is necessary to improve the plant's performance. A tilt strategy such as the one presented in this paper may have implications for future control/optimization studies including optimization of hub heights in a wind plant and analysis of deep array effects.
Modeling and inversion of PS-wave moveout asymmetry for tilted TI media: Part 2: Dipping TTI layer
Digital Repository Service at National Institute of Oceanography (India)
Dewangan, P.; Tsvankin, I.
, where the cubic H20849equation 3H20850 and higher-order terms in xSS do not go to zero. Figure 1 shows H9004tPS computed for a typical dipping TTI model from the exact equations 1 and A-1, as well as from the weak-aniso- tropy approximation H20849... equation 3H20850. While the initial slope of H9004tPS is well-described by the linear term in equation 3 even for large abso- lute values of H9254 and H9268, the cubic and higher-order terms make a sig- nificant contribution at far offsets that correspond...
Digital Repository Service at National Institute of Oceanography (India)
Dewangan, P.; Tsvankin, I.
arrowright H11009, we add a denominator H208491+Cx2H20850 to the cubic term in equation C-14: H9004tPS = Ax + Bx 3 1+Cx2 , H2084920H20850 Figure 5. Polar plot H20849in kilometersH20850 of the offset xminH20849H9251H20850 for the model from Figure 3. The stars... FoothillsH20850. D108 DewanganandTsvankin Application of equation 1 produces reflection SS data with the traveltimes of SS primaries but generally distorted amplitudes. The moveout of the constructed SS-waves in common-midpoint H20849CMPH20850 geometry...
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.
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.
Flocking of quad-rotor UAVs with fuzzy control.
Mao, Xiang; Zhang, Hongbin; Wang, Yanhui
2018-03-01
This paper investigates the flocking problem of quad-rotor UAVs. Considering the actual situations, we derived a new simplified quad-rotor UAV model which is more reasonable. Based on the model, the T-S fuzzy model of attitude dynamic equation and the corresponding T-S fuzzy feedback controller are discussed. By introducing a double-loop control construction, we adjust its attitude to realize the position control. Then a flocking algorithm is proposed to achieve the flocking of the quad-rotor UAVs. Compared with the flocking algorithm of the mass point model, we dealt with the collision problem of the quad-rotor UAVs. In order to improve the airspace utilization, a more compact configuration called quasi e-lattice is constructed to guarantee the compact flight of the quad-rotor UAVs. Finally, numerical simulations are provided to illustrate the effectiveness of the obtained theoretical results. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.
Elliott, David M.
2012-01-01
A counter-rotating open rotor scale model was tested in the NASA Glenn Research Center 9- by 15-Foot Low-Speed Wind Tunnel (LSWT). This model used a historical baseline blade set with which modern blade designs will be compared against on an acoustic and aerodynamic performance basis. Different blade pitch angles simulating approach and takeoff conditions were tested, along with angle-of-attack configurations. A configuration was also tested in order to determine the acoustic effects of a pylon. The shaft speed was varied for each configuration in order to get data over a range of operability. The freestream Mach number was also varied for some configurations. Sideline acoustic data were taken for each of these test configurations.
Wang, Shuai; Wang, Yu; Zi, Yanyang; He, Zhengjia
2015-12-01
A generalized and efficient model for rotating anisotropic rotor-bearing systems is presented in this paper with full considerations of the system's anisotropy in stiffness, inertia and damping. Based on the 3D finite element model and the model order reduction method, the effects of anisotropy in shaft and bearings on the forced response and whirling of anisotropic rotor-bearing systems are systematically investigated. First, the coefficients of journal bearings are transformed from the fixed frame to the rotating one. Due to the anisotropy in shaft and bearings, the motion is governed by differential equations with periodically time-variant coefficients. Then, a free-interface complex component mode synthesis (CMS) method is employed to generate efficient reduced-order models (ROM) for the periodically time-variant systems. In order to solve the obtained equations, a variant of Hill's method for systems with multiple harmonic excitations is developed. Four dimensionless parameters are defined to quantify the types and levels of anisotropy of bearings. Finally, the effects of the four types of anisotropy on the forced response and whirl orbits are studied. Numerical results show that the anisotropy of bearings in stiffness splits the sole resonant peak into two isolated ones, but the anisotropy of bearings in damping coefficients mainly affect the response amplitudes. Moreover, the whirl orbits become much more complex when the shaft and bearings are both anisotropic. In addition, the cross-coupling stiffness coefficients of bearings significantly affect the dynamic behaviors of the systems and cannot be neglected, though they are often much smaller than the principle stiffness terms.
Montgomery, M. M.; Martin, E. L.
2010-01-01
Many different system types retrogradely precess, and retrograde precession could be from a tidal torque by the secondary on a misaligned accretion disk. However, a source to cause and maintain disk tilt is unknown. In this work, we show that accretion disks can tilt due to a force called lift. Lift results from differing gas stream supersonic speeds over and under an accretion disk. Because lift acts at the disk's center of pressure, a torque is applied around a rotation axis passing through...
Design of a wind turbine rotor for maximum aerodynamic efficiency
DEFF Research Database (Denmark)
Johansen, Jeppe; Aagaard Madsen, Helge; Gaunaa, Mac
2009-01-01
maximum aerodynamic efficiency. The rotor is designed assuming constant induction for most of the blade span, but near the tip region, a constant load is assumed instead. The rotor design is obtained using an actuator disc model, and is subsequently verified using both a free-wake lifting line method...
Motion sickness on tilting trains.
Cohen, Bernard; Dai, Mingjia; Ogorodnikov, Dmitri; Laurens, Jean; Raphan, Theodore; Müller, Philippe; Athanasios, Alexiou; Edmaier, Jürgen; Grossenbacher, Thomas; Stadtmüller, Klaus; Brugger, Ueli; Hauser, Gerald; Straumann, Dominik
2011-11-01
Trains that tilt on curves can go faster, but passengers complain of motion sickness. We studied the control signals and tilts to determine why this occurs and how to maintain speed while eliminating motion sickness. Accelerometers and gyros monitored train and passenger yaw and roll, and a survey evaluated motion sickness. The experimental train had 3 control configurations: an untilted mode, a reactive mode that detected curves from sensors on the front wheel set, and a predictive mode that determined curves from the train's position on the tracks. No motion sickness was induced in the untilted mode, but the train ran 21% slower than when it tilted 8° in either the reactive or predictive modes (113 vs. 137 km/h). Roll velocities rose and fell faster in the predictive than the reactive mode when entering and leaving turns (0.4 vs. 0.8 s for a 4°/s roll tilt, P<0.001). Concurrently, motion sickness was greater (P<0.001) in the reactive mode. We conclude that the slower rise in roll velocity during yaw rotations on entering and leaving curves had induced the motion sickness. Adequate synchronization of roll tilt with yaw velocity on curves will reduce motion sickness and improve passenger comfort on tilting trains.
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
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.
GAS MOVEMENT IN ROTARY TILTING FURNACES
Directory of Open Access Journals (Sweden)
S. L. Rovin
2016-01-01
Full Text Available The article presents the results of studies of gas movement and heat and mass transfer processes in the rotary tilting furnace (RTF at the heat treatment of disperse materials. The study was performed through computer modeling using software packages ANSYS CFX and Solid Works Flow Simulation. The results were used to design RTF with different capacity and application and helped to improve their technical and economic characteristics.
Hotta, Kohei; Iguchi, Masato; Ohkura, Takahiro; Yamamoto, Keigo
2016-01-01
We herein propose a three-pressure-source model for ground inflation with highly eruptive activity at the Showa crater of Sakurajima volcano, Japan. We applied a model of stacked spherical sources to continuous combined geodetic data from a global navigation satellite system, tilt and strainmeters. The data were recorded during ground inflation throughout an eruptive episode that began in October 2011 and ended in March 2012. Using a genetic algorithm, we obtained the locations and volumes of three sources. A pressure source analysis of ground inflation during the period from October 2011 to March 2012 revealed inflation sources to be located at a depth of 9.6 km beneath Aira caldera (A-source) and 3.3 km beneath Kita-dake (K-source), and a shallow deflation source is located at a depth of 0.7 km beneath Minami-dake (M-source). The A-source corresponds to the main magma reservoir at a depth of 10 km beneath the Aira caldera inferred by previous geophysical studies. The K-source is a-reservoir of Sakurajima volcano, where magma intrudes from the main magma reservoir beneath the Aira caldera during the first stage of eruptive activity. The M-source is the uppermost part of a conduit from the K-source to the summit and the Showa crater. Magma injection into the A-source started in mid-November 2011, instantly triggering the migration of increased volumes of magma from the A-source to the K-source. Approximately one month later, in mid-December 2011, an increased volume of magma started migrating from the K-source to the M-source and finally erupted at the surface. The accumulation rate for the A-source is comparable to the magma supply rate for the past 100 years (0.8 to 1.6 × 107 m3). The three-pressure-source model was applied to inflation events before the 2011 event in order to reconstruct the magma migration process. Applying our source model to earlier activity phases, we found that injected magma from the A-source remained at the K-source and a small amount of
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...
Theory/test correlation of helicopter rotor blade element airloads in the blade stall regime
Bobo, C. J.
1972-01-01
The effects of stall on a rotor blade element in a three-dimensional rotating environment was investigated. The model rotor test provided blade element airloads and local boundary layer flow characteristics at the three-quarter blade radius position for a wide range of rotor operating conditions. A description of the test program and the test results are presented.
DEFF Research Database (Denmark)
Enemark, Søren; Santos, Ilmar F.
2016-01-01
Helical pseudoelastic shape memory alloy (SMA) springs are integrated into a dynamic system consisting of a rigid rotor supported by passive magnetic bearings. The aim is to determine the utility of SMAs for vibration attenuation via their mechanical hysteresis, and for adaptation of the dynamic...... nonlinear coupled dynamics of the rotor-bearing system. The nonlinear forces from the thermomechanical shape memory alloy springs and from the passive magnetic bearings are coupled to the rotor and bearing housing dynamics. The equations of motion describing rotor tilt and bearing housing lateral motion...
DEFF Research Database (Denmark)
Barlas, Thanasis K.; van Wingerden, W.; Hulskamp, A.W.
2013-01-01
In this paper, the proof of concept of a smart rotor is illustrated by aeroelastic simulations on a small-scale rotor and comparison with wind tunnel experiments. The application of advanced feedback controllers using actively deformed flaps in the wind tunnel measurements is shown to alleviate d...
Stability Analysis of a Turbocharger Rotor System Supported on Floating Ring Bearings
International Nuclear Information System (INIS)
Zhang, H; Shi, Z Q; Zhen, D; Gu, F S; Ball, A D
2012-01-01
The stability of a turbocharger rotor is governed by the coupling of rotor dynamics and fluid dynamics because the high speed rotor system is supported on a pair of hydrodynamic floating ring bearings which comprise of inner and outer fluid films in series. In order to investigate the stability, this paper has developed a finite element model of the rotor system with consideration of such exciting forces as rotor imbalance, hydrodynamic fluid forces, lubricant feed pressure and dead weight. The dimensionless analytical expression of nonlinear oil film forces in floating ring bearings have been derived on the basis of short bearing theory. Based on numerical simulation, the effects of rotor imbalance, lubricant viscosity, lubricant feed pressure and bearing clearances on the stability of turbocharger rotor system have been studied. The disciplines of the stability of two films and dynamic performances of rotor system have been provided.
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.
Hotta, K.; Iguchi, M.; Ohkura, T.; Yamamoto, K.
2014-12-01
During frequent vulcanian activity at the Minami-dake crater at Sakurajima during the period of 1974 - 1992, ground subsidence was observed and its pattern was modeled by two deflation sources: located in Aira caldera at a depth of about 10 km, about 6 km north from Minami-dake, and beneath Minami-dake at a depth of about 3 km [Eto, 1989]. Eruptive activities at Showa crater, about 500 m east of Minami-dake, since 2006 increased, accompanying ground inflation in October 2009 - May 2010 (2009 event) in contrast to the Minami-dake period. Similar inflation occurred in October 2011 - March 2012 (2011 event). In this study, we analyzed GPS, tilt and strain data synthetically to obtain pressure sources around Sakurajima during the periods of high explosivity with ground inflation. We applied 3-pressure-source model to the deformation of 2009 and 2011 events. Main inflation source is located beneath Aira caldera at a depth of 9.6 km, similar to previous study. In Sakurajima, inflation pressure source is located beneath Kita-dake 1 km north of Minami-dake at a depth of 3.3 km (K-source), and deflation source is located beneath Minami-dake at a depth of 0.7 km (M-source). We estimated temporal change of volume of K- and M-sources fixing inflation rate of Aira source for 2011 event. Inflation rate of K-source increased in November 2011 and kept at a constant rate until January 2012. Deflation rate of M-source increased at the same time as inflation rate of K-source increased, and kept at a constant rate until March 2012. Amount of volume increase of K-source is nearly 20 times larger than that of volume decrease of M-source. Magma was thought to migrate from Aira source to K-source in November 2011 and continued until January 2012. Due to higher eruptive volume from Showa crater than migration of magma from K-source, M-source deflated slightly from late November 2011 to March 2012.
Towards More Efficient Comprehensive Rotor Noise Simulation, Phase I
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...
Directory of Open Access Journals (Sweden)
Mattias Nässelqvist
2014-01-01
Full Text Available In vertically oriented machines with journal bearing, there are no predefined static radial loads, such as dead weight for horizontal rotor. Most of the commercial software is designed to calculate rotordynamic and bearing properties based on machines with a horizontally oriented rotor; that is, the bearing properties are calculated at a static eccentricity. For tilting-pad bearings, there are no existing analytical expressions for bearing parameters and the bearing parameters are dependent on eccentricity and load angle. The objective of this paper is to present a simplified method to perform numerical simulations on vertical rotors including bearing parameters. Instead of recalculating the bearing parameters in each time step polynomials are used to represent the bearing parameters for present eccentricities and load angles. Numerical results are compared with results from tests performed in a test rig. The test rig consists of two guide bearings and a midspan rotor. The guide bearings are 4-pad tilting-pad bearings. Shaft displacement and strains in the bearing bracket are measured to determine the test rig’s properties. The comparison between measurements and simulated results shows small deviations in absolute displacement and load levels, which can be expected due to difficulties in calculating exact bearing parameters.
An efficient eikonal solver for tilted transversely isotropic and tilted orthorhombic media
Waheed, Umair bin
2014-01-01
Computing first-arrival traveltimes in the presence of anisotropy is important for high-end near surface modeling, microseismic source localization, and fractured reservoir characterization. Anisotropy deviating from elliptical anisotropy introduces higher-order nonlinearity into the eikonal equation, which makes solving the equation a challenging task. We address this challenge by iteratively solving a sequence of simpler tilted elliptically anisotropic eikonal equations. At each iteration, the source function is updated to capture the effects due to the higher order nonlinear terms in the anisotropy. We use Aitken extrapolation to speed up the convergence rate of the iterative algorithm. The result is an efficient algorithm for firstarrival traveltime computations in tilted anisotropic media. We demonstrate the proposed method for the tilted transversely isotropic media and the tilted orthorhombic media. Numerical tests show that the proposed method is feasible and produces results that are comparable to wavefield extrapolation, even for strongly anisotropic and complex structures. Therefore, for the cases where one or two-point ray tracing fails, our method may be a potential substitute for computing traveltimes.
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.
Rotor Vibration Reduction via Active Hybrid Bearings
DEFF Research Database (Denmark)
Nicoletti, Rodrigo; Santos, Ilmar
2002-01-01
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...
Prediction of aerodynamic performance for MEXICO rotor
DEFF Research Database (Denmark)
Hong, Zedong; Yang, Hua; Xu, Haoran
2013-01-01
The aerodynamic performance of the MEXICO (Model EXperiments In Controlled cOnditions) rotor at five tunnel wind speeds is predicted by making use of BEM and CFD methods, respectively, using commercial MATLAB and CFD software. Due to the pressure differences on both sides of the blade, the tip-fl...
Development and tests of large nuclear turbo-generator welded rotors
International Nuclear Information System (INIS)
Colombie, H.; Thiery, M.; Rotzinger, R.; Pelissou, C.; Tabacco, C.; Fernagut, V.
2015-01-01
Turbo-generators require large forgings for the rotor and it is a worldwide practice to manufacture turbo-generator rotor bodies as single piece forgings. Rotors for nuclear applications (4-pole rotors design, 1500/1800 rpm) require forgings of up to 2.0 m diameter and ultra large ingots with weight more than 500 tons. Nowadays only few forge masters can deliver such forgings in the world. Based on the large welding experience Alstom has gained over decades on steam and gas turbines and Alstom's multi piece shrunk turbo-generator rotors, it was suggested to manufacture 4-pole turbo-generator rotors by welding the shaft from aligned cylindrical forgings. Compared to turbine welded rotors, the shaft of a turbo-generator rotor presents differences linked to dimensions/weight, weld depth and electrical application. The manufacture of a 2 disc model allowed to prove through electrical and mechanical analysis the reliability of the concept as well as the reliability of the manufacturing processes through material tests, micro sections, electrical component tests, weld geometry, welding processes (TIG,SAW,...), weld inspection (Ultrasonic testing, radiographic inspection,...) weld heat treatments and machining. Then a full rotor able to replace a single forging rotor was manufactured in order to validate and prove to potential customers the validity of the welded rotor technology. During the first order from EDF of a welded 900 MW spare rotor, the procedure for the Non Destructive Test on a slotted rotor was developed upon EDF request in order to compare future Non Destructive Testing with the finger print of the new rotor. This complete rotor was delivered to EDF in January 2013. This rotor is in operation in a nuclear unit since November 2013. (authors)
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.
Energy Technology Data Exchange (ETDEWEB)
Ramirez-Argaez, M. A.; Conteras, F.; Gonzalez, C.
2006-07-01
In this work a fundamental Eulerian mathematical model was developed to study fluid flow and mixing phenomena in aluminium 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-Stockers and the k{epsilon} turbulence model for a two-phase fluid flow problem using the Inter Phase Slip Algorithm (IPSA). (Author). 20 refs.
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....
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.
Refined Performance and Loads of a Mach-Scale Rotor at High Advance Ratios
Trollinger, Lauren N.
This work will investigate the performance and vibratory loads of a Mach-scale rotor with highly similar, non-instrumented blades at advance ratios (micro) up to 0.9. Wind tunnel tests were performed on a 4-bladed, articulated rotor with a diameter of 2.78 ft. The slowed rotor was operated at 30%, 40%, and 50% of nominal speed,corresponding to advancing tip Mach numbers up to 0.53, and shaft tilt angles of -4°, 0°, and 4° were tested. Collective sweeps from -2° to 12° were performed for each flight condition, and blade motion, control cyclics, and hub loads were measured. Blade similarity was shown to improve rotor track and trim at high micro. Thrust reversal was observed at micro = 0.9, but positive (aft) shaft tilt increased lift at high micro. Vibratory hubloads are shown to increase with advance ratio. Correlations performed using the comprehensive analysis code UMARC show good agreement for rotor performance.
Height and Tilt Geometric Texture
DEFF Research Database (Denmark)
Andersen, Vedrana; Desbrun, Mathieu; Bærentzen, Jakob Andreas
2009-01-01
compromise between functionality and simplicity: it can efficiently handle and process geometric texture too complex to be represented as a height field, without having recourse to full blown mesh editing algorithms. The height-and-tilt representation proposed here is fully intrinsic to the mesh, making...
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.
Individual Blade Control of a 5-bladed Rotor Using the Multiple Swashplate System
Küfmann, Philip; Bartels, Rainer; van der Wall, Berend G.; Schneider, Oliver; Holthusen, Hermann; Postma, Jos
2017-01-01
After its first wind tunnel test in 2015, the multiple swashplate system (META) as well as the DLR's rotor test rig were modified and upgraded extensively to allow IBC operation on a five-bladed rotor system. In late 2016 a second wind tunnel test was performed on a Mach-scaled, five-bladed model rotor with the goal to reduce Vibration, noise and required rotor power on a five-bladed rotor in different flight conditions using proven IBC strategies. Highlights of the test matrix were 2/rev swe...
Performance and wake conditions of a rotor located in the wake of an obstacle
DEFF Research Database (Denmark)
Naumov, I. V.; Kabardin, I. K.; Mikkelsen, Robert Flemming
2016-01-01
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......, 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...
Platts, David A.
2002-01-01
There has been invented a turbine engine with a single rotor which cools the engine, functions as a radial compressor, pushes air through the engine to the ignition point, and acts as an axial turbine for powering the compressor. The invention engine is designed to use a simple scheme of conventional passage shapes to provide both a radial and axial flow pattern through the single rotor, thereby allowing the radial intake air flow to cool the turbine blades and turbine exhaust gases in an axial flow to be used for energy transfer. In an alternative embodiment, an electric generator is incorporated in the engine to specifically adapt the invention for power generation. Magnets are embedded in the exhaust face of the single rotor proximate to a ring of stationary magnetic cores with windings to provide for the generation of electricity. In this alternative embodiment, the turbine is a radial inflow turbine rather than an axial turbine as used in the first embodiment. Radial inflow passages of conventional design are interleaved with radial compressor passages to allow the intake air to cool the turbine blades.
Nonlinear analysis of a rub-impact rotor-bearing system with initial permanent rotor bow
Energy Technology Data Exchange (ETDEWEB)
Shen, Xiaoyao; Jia, Jiuhong; Zhao, Mei [Shanghai Jiaotong University, State Key Laboratory of Vibration, Shock and Noise, Shanghai (China)
2008-03-15
A general model of a rub-impact rotor-bearing system with initial permanent bow is set up and the corresponding governing motion equation is given. The nonlinear oil-film forces from the journal bearing are obtained under the short bearing theory. The rubbing model is assumed to consist of the radial elastic impact and the tangential Coulomb type of friction. Through numerical calculation, rotating speeds, initial permanent bow lengths and phase angles between the mass eccentricity direction and the rotor permanent bow direction are used as control parameters to investigate their effect on the rub-impact rotor-bearing system with the help of bifurcation diagrams, Lyapunov exponents, Poincare maps, frequency spectrums and orbit maps. Complicated motions, such as periodic, quasi-periodic even chaotic vibrations, are observed. Under the influence of the initial permanent bow, different routes to chaos are found and the speed when the rub happens is changed greatly. Corresponding results can be used to diagnose the rub-impact fault in this kind of rotor systems and this study may contribute to a further understanding of the nonlinear dynamics of such a rub-impact rotor-bearing system with initial permanent bow. (orig.)
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...... 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....
Controlling the quantum rotational dynamics of a driven planar rotor ...
Indian Academy of Sciences (India)
Archana Shukla
driven planar rotor, a model for rigid diatomic molecules, by rebuilding barriers in the classical phase space. The barriers are invariant tori with irrational winding ratios which are perturbatively constructed at desired locations in the phase space. We.
CFD simulation of rotor aerodynamic performance when using additional surface structure array
Wang, Bing; Kong, Deyi
2017-10-01
The present work analyses the aerodynamic performance of the rotor with additional surface structure array in an attempt to maximize its performance in hover flight. The unstructured grids and the Reynolds Average Navier-Stokes equations were used to calculate the performance of the prototype rotor and the rotor with additional surface structure array in the air. The computational fluid dynamics software FLUENT was used to simulate the thrust of the rotors. The results of the calculations are in reasonable agreement with experimental data, which shows that the calculation model used in this work is useful in simulating the performance of the rotor with additional surface structure array. With this theoretical calculation model, the thrusts of the rotors with arrays of surface structure in three different shapes were calculated. According to the simulation results and the experimental data, the rotor with triangle surface structure array has better aerodynamic performance than the other rotors. In contrast with the prototype rotor, the thrust of the rotor with triangle surface structure array increases by 5.2% at the operating rotating speed of 3000r/min, and the additional triangle surface structure array has almost no influence on the efficiency of the rotor.
Rotor Performance of a UH-60 Rotor System in the NASA Ames 80- by 120-Foot Wind Tunnel
National Research Council Canada - National Science Library
Shinoda, Patrick M; Yeo, Hyeonsoo; Norman, Thomas R
2002-01-01
.... To evaluate the NASA Ames 80- by 120- Foot Wind Tunnel as a hover testing facility, rotor performance data were compared with predictions, UH-60 aircraft flight test data, and UH-60 model-scale data...
Stability Analysis of the Slowed-Rotor Compound Helicopter Configuration
Floros, Matthew W.; Johnson, Wayne
2007-01-01
The stability and control of rotors at high advance ratio are considered. Teetering, articulated, gimbaled, and rigid hub types are considered for a compound helicopter (rotor and fixed wing). Stability predictions obtained using an analytical rigid flapping blade analysis, a rigid blade CAMRAD II model, and an elastic blade CAMRAD II model are compared. For the flapping blade analysis, the teetering rotor is the most stable, showing no instabilities up to an advance ratio of 3 and a Lock number of 18. A notional elastic blade model of a teetering rotor is unstable at an advance ratio of 1.5, independent of pitch frequency. Analysis of the trim controls and blade flapping shows that for small positive collective pitch, trim can be maintained without excessive control input or flapping angles.
Integrated technology rotor/flight research rotor concept definition study
Carlson, R. G.; Beno, E. A.; Ulisnik, H. D.
1983-01-01
As part of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) Program a number of advanced rotor system designs were conceived and investigated. From these, several were chosen that best meet the started ITR goals with emphasis on stability, reduced weight and hub drag, simplicity, low head moment stiffness, and adequate strength and fatigue life. It was concluded that obtaining low hub moment stiffness was difficult when only the blade flexibility of bearingless rotor blades is considered, unacceptably low fatigue life being the primary problem. Achieving a moderate hub moment stiffness somewhat higher than state of the art articulated rotors in production today is possible within the fatigue life constraint. Alternatively, low stiffness is possible when additional rotor elements, besides the blades themselves, provide part of the rotor flexibility. Two primary designs evolved as best meeting the general ITR requirements that presently exist. An I shaped flexbeam with an external torque tube can satisfy the general goals but would have either higher stiffness or reduced fatigue life. The elastic gimbal rotor can achieve a better combination of low stiffness and high fatigue life but would be a somewhat heavier design and possibly exhibit a higher risk of aeromechanical instability.
Real-Time Simulation of Coaxial Rotor Configurations with Combined Finite State Dynamic Wake and VPM
Zhao, Jinggen; He, Chengjian
2017-01-01
This paper describes a first-principle based finite state dynamic rotor wake model that addresses the complex aerodynamic interference inherent to coaxial rotor configurations in support of advanced vertical lift aircraft simulation, design, and analysis. The high fidelity rotor dynamic wake solution combines an enhanced real-time finite state dynamic wake model (DYW) with a first-principle based viscous Vortex Particle Method (VPM). The finite state dynamic wake model provides a state-spa...
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
A novel micro-mixer with a quasi-active rotor: fabrication and design improvement
Kim, Yongdae; Lee, Jongkwang; Kwon, Sejin
2009-10-01
In the present paper, a novel micro-mixer with a quasi-active rotor for micro-plant applications is proposed and design considerations for the improvement of the mixing performance of the proposed micro-mixer are derived. The proposed micro-rotor mixer combines an active micro-mixer with a passive micro-mixer. The micro-rotor, which is a moving part of an active micro-mixer, is added to the micro-chamber of a passive micro-mixer. The micro-rotor was rotated by inflows tangential to the chamber, causing strong perturbations. Two models of the micro-rotor mixer were fabricated with six layers of photosensitive glass which were individually fabricated and thermally bonded together. Improvement in the design of the micro-rotor mixer was achieved after the fabrication and experimental testing of the first model. In the design of the second model, the channel width and the rotor diameter were diminished and the number of rotor blades was increased from four to five. Through these design improvements, the micro-rotor started rotating at a lower Reynolds number; the rotor rotated at Re 1000 in the first model, whereas it did so at Re 200 in the second model. The mixing efficiency values of the micro-mixers were measured using an image analysis method. In the results, the mixing performance was dominated by molecular diffusion in the low Reynolds number region. On the other hand, convection flows such as twisted flows and Coanda flows dominated the mixing performance in the higher Reynolds number region. In the upper Reynolds number region, the micro-rotor was rotated and strong perturbations were induced. The mixing efficiency values of the micro-rotor mixers were found to exceed 90% when the rotor was rotated.
Flexible-Rotor Balancing Demonstration
Giordano, J.; Zorzi, E.
1986-01-01
Report describes method for balancing high-speed rotors at relatively low speeds and discusses demonstration of method on laboratory test rig. Method ensures rotor brought up to speeds well over 20,000 r/min smoothly, without excessive vibration amplitude at critical speeds or at operating speed.
Rotor and wind turbine formalism
DEFF Research Database (Denmark)
Branlard, Emmanuel Simon Pierre
2017-01-01
The main conventions used in this book for the study of rotors are introduced in this chapter. The main assumptions and notations are provided. The formalism specific to wind turbines is presented. The forces, moments, velocities and dimensionless coefficients used in the study of rotors...
Study on the prevention of spragging in a tilting pad journal bearing using the variation of preload
International Nuclear Information System (INIS)
Yang, Seong Heon; Park, Chul Hyun; Ha, Hyun Cheon; Kim, Chae Sil
2001-01-01
Tilting pad journal bearings have been widely used in a high speed rotating machinery, such as steam turbines and gas turbines, owing to their inherent stability characteristics. However, some peculiar fatigue failure in the babbitt metal due to spragging has been continuously occurred at the leading edge of the upper pads. The spragging is defined as the pad vibration initiated on the upper unloaded pads in tilting pad journal bearing. This paper describes both several kinds of bearing failure related with spragging and the theoretical investigation on the prevention of the spragging phenomenon using the variation of preload. Results show that positive preload(m>0.5) assures all pads remain statically loaded under all operating conditions. For the change of design parameter to prevent spragging, thermo-hydrodynamic lubrication and rotor dynamic analysis were performed to verify temperature limitation on bearing and vibration problems on rotor bearing system
Conceptual design studies of 1985 commercial VTOL transports that utilized rotors, Volume 1
Magee, J. P.; Clark, R. D.; Alexander, H. R.
1974-01-01
Results of conceptual design studies of commercial rotary wing transport aircraft for the 1985 time period are presented. Two aircraft configurations, a tandem helicopter and a tilt rotor, were designed for a 200 nautical mile short haul mission with an upper limit of 100 passengers. In addition to the baseline aircraft two further designs of each configuration are included to assess the impact of external noise design criteria on the aircraft size, weight, and cost.
Yeager, W. T., Jr.; Mantay, W. R.
1983-01-01
A passive means of tailoring helicopter rotor blades to improve performance and reduce loads was evaluated. The parameters investigated were blade torsional stiffness, blade section camber, and distance between blade structural elastic axis and blade tip aerodynamic center. This offset was accomplished by sweeping the tip. The investigation was conducted at advance ratios of 0.20, 0.30, and 0.40. Data are presented without analysis; however, cross referencing of performance data and harmonic loads data may be useful to the analyst for validating aeroelastic theories and design methodologies as well as for evaluating passive aeroelastic tailoring or rotor blade parameters.
THE MODEL OF THE RADIAL-THRUST BALL BEARING FOR ANALYSIS OF NONLINEAR VIBRATIONS OF THE ROTOR
Directory of Open Access Journals (Sweden)
S. Filipkovskyi
2015-12-01
Full Text Available The non-linear model of resilient forces of pre-loaded ball bearing is developed. The contact forces are obtained and arranged in the Heyn’s row on the basis of Herts theory. The obtained model is used for solving the problem of non-linear dynamics of vehicles. The design samples correspond to calculations performed with the help of the traditional model.
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.
Dynamic rotor mode in antiferromagnetic nanoparticles
DEFF Research Database (Denmark)
Lefmann, Kim; Jacobsen, H.; Garde, J.
2015-01-01
measured neutron data and reveal that thermally activated spin canting gives rise to an unusual type of coherent magnetic precession mode. This "rotor" mode can be seen as a high-temperature version of superparamagnetism and is driven by exchange interactions between the two magnetic sublattices......We present experimental, numerical, and theoretical evidence for an unusual mode of antiferromagnetic dynamics in nanoparticles. Elastic neutron scattering experiments on 8-nm particles of hematite display a loss of diffraction intensity with temperature, the intensity vanishing around 150 K....... The frequency of the rotor mode behaves in fair agreement with a simple analytical model, based on a high-temperature approximation of the generally accepted Hamiltonian of the system. The extracted model parameters, such as the magnetic interaction and the axial anisotropy, are in excellent agreement...
Integrated technology rotor/flight research rotor hub concept definition
Dixon, P. G. C.
1983-01-01
Two variations of the helicopter bearingless main rotor hub concept are proposed as bases for further development in the preliminary design phase of the Integrated Technology Rotor/Flight Research Rotor (ITR/FRR) program. This selection was the result of an evaluation of three bearingless hub concepts and two articulated hub concepts with elastomeric bearings. The characteristics of each concept were evaluated by means of simplified methodology. These characteristics included the assessment of stability, vulnerability, weight, drag, cost, stiffness, fatigue life, maintainability, and reliability.
Rotating Shaft Tilt Angle Measurement Using an Inclinometer
Luo, Jun; Wang, Zhiqian; Shen, Chengwu; Wen, Zhuoman; Liu, Shaojin; Cai, Sheng; Li, Jianrong
2015-10-01
This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendicular to the rotating shaft. The reversal measurement method is applied to decrease the effect of inclinometer drifts caused by temperature, to eliminate inclinometer and rotating shaft mechanical error and inclinometer systematic error to attain high measurement accuracy. The uncertainty estimation shows that the accuracy of rotating shaft tilt angle measurement depends mainly on the inclinometer uncertainty and its uncertainty is almost the same as the inclinometer uncertainty in the simulation. The experimental results indicate that measurement time is 4 seconds; the range of rotating shaft tilt angle is 0.002° and its standard deviation is 0.0006° using NS-5/P2 inclinometer, whose precision and resolution are ±0.01° and 0.0005°, respectively.
Rotating Shaft Tilt Angle Measurement Using an Inclinometer
Directory of Open Access Journals (Sweden)
Luo Jun
2015-10-01
Full Text Available This paper describes a novel measurement method to accurately measure the rotating shaft tilt angle of rotating machine for alignment or compensation using a dual-axis inclinometer. A model of the rotating shaft tilt angle measurement is established using a dual-axis inclinometer based on the designed mechanical structure, and the calculation equation between the rotating shaft tilt angle and the inclinometer axes outputs is derived under the condition that the inclinometer axes are perpendicular to the rotating shaft. The reversal measurement method is applied to decrease the effect of inclinometer drifts caused by temperature, to eliminate inclinometer and rotating shaft mechanical error and inclinometer systematic error to attain high measurement accuracy. The uncertainty estimation shows that the accuracy of rotating shaft tilt angle measurement depends mainly on the inclinometer uncertainty and its uncertainty is almost the same as the inclinometer uncertainty in the simulation. The experimental results indicate that measurement time is 4 seconds; the range of rotating shaft tilt angle is 0.002° and its standard deviation is 0.0006° using NS-5/P2 inclinometer, whose precision and resolution are ±0.01° and 0.0005°, respectively.
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
A high-fidelity linear time-invariant model of the aero-servo-elastic response of a wind turbine with trailing-edge flaps is presented and used for systematic tuning of an individual flap controller. The model includes the quasi-steady aerodynamic effects of trailing-edge flaps on wind turbine bl...
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.
Modal Characteristics of Novel Wind Turbine Rotors with Hinged Structures
Lu, Hongya; Zeng, Pan; Lei, Liping
2018-03-01
The vibration problems of the wind turbine rotors have drawn public attention as the size of wind turbine has increased incredibly. Although various factors may cause the vibration problems, the flexibility is a big threat among them. Therefore, ensuring the high stiffness of the rotors by adopting novel techniques becomes a necessity. The study was a further investigation of several novel designs regarding the dynamic behaviour and the influencing mechanism. The modal testing experiments were conducted on a traditional blade and an isolated blade with the hinged rods mounted close to the root. The results showed that the rod increased both the modal frequency and the damping of the blade. More studies were done on the rods’ impact on the wind turbine rotor with a numerical model, where dimensionless parameters were defined to describe the configuration of the interveined and the bisymmetrical rods. Their influences on the modal frequencies of the rotor were analyzed and discussed.
Transient rotor dynamic rub phenomena - Theory and test
Kascak, A. F.; Montaque, G.; Palazzolo, A. B.
1987-01-01
This paper develops an implicit integration scheme for transient rotor dynamic rub prediction and includes a correlation study with actual test results. A Nordsieck-like numerical integration scheme is applied directly to the second-order equations of motion. The assumption that forces and torques on the rotor are functions of the position and velocity at the point of application and its nearest neighbor is made in order to make the computational time proportional to the number of elements in the rotor dynamics model rather than the cube of the number. The test rig consists of a turbine driven, flexible shaft supported by squeeze film dampers. The blade loss event occurs due to collision of a balance bolt on one of the disks with a high speed plunger. The rotor is seen to spiral outward and contact against a stationary assemblage of seal shoes.
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...... 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...
A soft rotor concept - design, verification and potentials
Energy Technology Data Exchange (ETDEWEB)
Rasmussen, F.; Thirstrup Petersen, J. [Risoe National Lab., Roskilde (Denmark)
1999-03-01
This paper contains results from development and testing of a two-bladed soft rotor for an existing 15 kW flexible wind turbine. The new concept is characterised as a free yawing down wind turbine with nacelle tilting flexibility and a two-bladed teetering rotor with three-point supported flexible blades with built-in structural couplings. The power and the loads are controlled by active stall and active coning. The concept has been developed by extensive application of aero-elastic predictions, numerical optimisation and stability analysis in order to obtain optimal aero-elastic response and minimal loads. The flexible blades and the principle of active coning allow the blades to deflect with the wind to such an extent that the loads are reduced to between 25 and 50% of the loads for a similar rigid rotor. All conceptual design principles have been focused on application to large MW turbines, and aero-elastic predictions for an upscale 1 MW version show that this would have approximately identical characteristisc, without being particularly optimised for the actual size. (au)
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 greater...
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 greater...
Modern rotor balancing - Emerging technologies
Zorzi, E. S.; Von Pragenau, G. L.
1985-01-01
Modern balancing methods for flexible and rigid rotors are explored. Rigid rotor balancing is performed at several hundred rpm, well below the first bending mode of the shaft. High speed balancing is necessary when the nominal rotational speed is higher than the first bending mode. Both methods introduce weights which will produce rotor responses at given speeds that will be exactly out of phase with the responses of an unbalanced rotor. Modal balancing seeks to add weights which will leave other rotor modes unaffected. Also, influence coefficients can be determined by trial and error addition of weights and recording of their effects on vibration at speeds of interest. The latter method is useful for balancing rotors at other than critical speeds and for performing unified balancing beginning with the first critical speed. Finally, low-speed flexible balancing permits low-speed tests and adjustments of rotor assemblies which will not be accessible when operating in their high-speed functional configuration. The method was developed for the high pressure liquid oxygen turbopumps for the Shuttle.
International Nuclear Information System (INIS)
Iudice, N.L.
1993-01-01
It is shown by a model independent numerical estimate that the TRM expression of the M1 strength is fully consistent with the recently discovered saturation properties of the M1 excitations knows as scissors mode
Reverse time migration in tilted transversely isotropic media
Energy Technology Data Exchange (ETDEWEB)
Zhang, Linbing; Rector III, James W.; Hoversten, G. Michael
2004-07-01
This paper presents a reverse time migration (RTM) method for the migration of shot records in tilted transversely isotropic (TTI) media. It is based on the tilted TI acoustic wave equation that was derived from the dispersion relation. The RTM is a full depth migration allowing for velocity to vary laterally as well as vertically and has no dip limitations. The wave equation is solved by a tenth-order finite difference scheme. Using 2D numerical models, we demonstrate that ignoring the tilt angle will introduce both lateral and vertical shifts in imaging. The shifts can be larger than 0.5 wavelength in the vertical direction and 1.5 wavelength in the lateral direction.
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.
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.
Czech Academy of Sciences Publication Activity Database
Zapoměl, Jaroslav; Ferfecki, Petr; Kozánek, Jan
2013-01-01
Roč. 7, č. 2 (2013), s. 223-234 ISSN 1802-680X. [COMPUTATIONAL MECHANICS 2012 /28./. Špičák, 12.11.2012-14.11.2012] Institutional support : RVO:61388998 Keywords : rigid rotors * controllable damping * hybrid magnetorheological dampers * transient response Subject RIV: JR - Other Machinery
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.
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.
Gravito-Inertial Force Resolution in Perception of Synchronized Tilt and Translation
Wood, Scott J.; Holly, Jan; Zhang, Guen-Lu
2011-01-01
Natural movements in the sagittal plane involve pitch tilt relative to gravity combined with translation motion. The Gravito-Inertial Force (GIF) resolution hypothesis states that the resultant force on the body is perceptually resolved into tilt and translation consistently with the laws of physics. The purpose of this study was to test this hypothesis for human perception during combined tilt and translation motion. EXPERIMENTAL METHODS: Twelve subjects provided verbal reports during 0.3 Hz motion in the dark with 4 types of tilt and/or translation motion: 1) pitch tilt about an interaural axis at +/-10deg or +/-20deg, 2) fore-aft translation with acceleration equivalent to +/-10deg or +/-20deg, 3) combined "in phase" tilt and translation motion resulting in acceleration equivalent to +/-20deg, and 4) "out of phase" tilt and translation motion that maintained the resultant gravito-inertial force aligned with the longitudinal body axis. The amplitude of perceived pitch tilt and translation at the head were obtained during separate trials. MODELING METHODS: Three-dimensional mathematical modeling was performed to test the GIF-resolution hypothesis using a dynamical model. The model encoded GIF-resolution using the standard vector equation, and used an internal model of motion parameters, including gravity. Differential equations conveyed time-varying predictions. The six motion profiles were tested, resulting in predicted perceived amplitude of tilt and translation for each. RESULTS: The modeling results exhibited the same pattern as the experimental results. Most importantly, both modeling and experimental results showed greater perceived tilt during the "in phase" profile than the "out of phase" profile, and greater perceived tilt during combined "in phase" motion than during pure tilt of the same amplitude. However, the model did not predict as much perceived translation as reported by subjects during pure tilt. CONCLUSION: Human perception is consistent with
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.
DEFF Research Database (Denmark)
Salazar, Jorge G.; Santos, Ilmar F.
2016-01-01
This paper presents the identified dynamic coefficients of a lightly loaded actively lubricated bearing under three lubrication regimes: passive, hybrid and feedback-controlled. The goal is to experimentally demonstrate the feasibility of modifying the bearing dynamic properties via active...... lubrication. Dominated by the latest two regimes, the bearing properties become adjustable or controllable due to the injection of either a constant or variable pressurized oil flow. Such a flow is regulated by a hydraulic control system composed of (a) a high-pressure oil supply unit, (b) servovalves, (c......) radial injection nozzles, (d) displacement sensors and (e) well-tuned digital controllers. A scaled-down industrial rotor featuring active lubrication, composed of a flexible rotor supported by a four-rocker load-between-pads tilting-pad bearing under light load condition, is used for this objective...
Downward continuation and tilt derivative of magnetic data for ...
Indian Academy of Sciences (India)
S K Pal
2017-06-12
Jun 12, 2017 ... are corroborated with multi-seam occurrences, mine working levels and surface manifestation which are also correlated well with 3D model of downward continued anomaly distribution. Keywords. Downward continuation; tilt derivative; magnetic data; coal fire mapping; Jharia coal field;. India. 1.
The impact of gravity during head-up tilt
DEFF Research Database (Denmark)
Ottesen, Johnny T.; Olufsen, Mette; Smith, Brittany
The impact of gravity during head-up tilt, a test often used in the clinic to diagnose patients who suffer from dizziness or frequent episodes of syncope, is not well described. This study uses mathematical modeling to analyze experimental blood pressure data measured at the level of the aorta...
Conservative treatment of excessive anterior pelvic tilt
DEFF Research Database (Denmark)
Brekke, Anders Falk
, DK-5000 Odense C, Denmark ABSTRACT (1795 anslag) Background: Excessive anterior pelvic tilt has been linked to pain and dysfunction of the hip and pelvic region. Conservative treatment (e.g. manual therapy and physical training) is suggested in correcting the tilt and eventually related symptoms....... However, the effectiveness in reducing excessive anterior pelvic tilt in adults is unknown. Purpose: To systematically review studies investigating the effectiveness of conservative treatment in reducing anterior pelvic tilt in adults and evaluate the quality of evidence. Materials and methods: MEDLINE...
Capacitive micromachined ultrasonic transducer based tilt sensing
Yu, Hongbin; Guo, Bin; Haridas, Kuruveettil; Lin, Tsu-Hui; Hao Cheong, Jia; Lin Tsai, Ming; Boon Yee, Tack
2012-10-01
In this paper, a tilt sensing mechanism based on the capacitive micromachined ultrasound transducers (CMUTs) is presented. By measuring the difference in the time of flight of various pulse-echo signals from different CMUT transmitting elements to one common receiving element in the oil bath, the tilt angle of the oil surface can be determined. With the proposed device, the maximum tilt angles of 20° and 28° have been measured in the clockwise and counterclockwise directions, respectively, and the difference between the measured and the theoretical values of the tilt angle was found to be within 0.05° during the whole test.
Investigation on the Dynamics of an On-Board Rotor-Bearing System
Dakel, M. Zaki; Baguet, Sébastien; Dufour, Régis
2012-01-01
International audience; In ship and aircraft turbine rotors, the rotating mass unbalance and the different movements of the rotor base are among the main causes of vibrations in bending. The goal of this paper is to investigate the dynamic behavior of an on-board rotor under rigid base excitations. The modeling takes into consideration six types of base deterministic motions (rotations and translations) when the kinetic and strain energies in addition to the virtual work of the rotating flexi...
Rigsby, James Michael
Interest in high speed rotorcraft has directed attention toward the slowed-rotor, high advance ratio compound autogyro concept as evidenced by the current DARPA Heliplane project. The behavior of partially unloaded rotors, autorotating at high advance ratio is not well understood and numerous technical issues must be resolved before the vehicle can be realized. Autorotation in helicopters usually indicates an emergency loss of power. For the concept vehicle autorotation is the normal working state of the rotor. The necessity for a reduction in rotor speed with increasing flight speed results in high advance ratio operation where the retreating side of the rotor is dominated by the reverse flow region. Further, rotor speed changes also affect the rotor dynamics and the associated hub moments generated by cyclic flapping. The result is rotor characteristics that vary widely depending on advance ratio. In the present work, rotor behavior is characterized in terms of issues relevant to the control system conceptual design and the rotor impact on the intrinsic vehicle flight dynamics characteristics. A series of trim, stability, and control analyses, based on features inherent in the concept vehicle, are performed. Trends are identified through parametric variation of rotor operating conditions, augmented by inclusion of the sensitivities to blade mass and blade stiffness properties. In this research, non-linear models, including the rotor speed degree of freedom, were created and analyzed with FLIGHTLAB(TM) rotorcraft modeling software. Performance analysis for rotors trimmed to autorotate with zero average hub pitching and rolling moments indicates reduced rotor thrust is achieved primarily through rotor speed reduction at lower shaft incidence angle, and imposing hub moment trim constraints results in a thrust increment sign reversal with collective pitch angle above advance ratio mu ˜ 1.0. Swashplate control perturbations from trim indicate an increase in control
Critical speed analysis of rotors
Cavicchi, R. H.
1970-01-01
General frequency equation is developed for both forward and backward precession of rigid rotors in undamped bearings on flexible foundations. As well as major critical speeds, nonsynchronous critical speeds that may result from bearing defects can be located.
Design Optimization of Tilting-Pad Journal Bearing Using a Genetic Algorithm
Directory of Open Access Journals (Sweden)
Hamit Saruhan
2004-01-01
Full Text Available This article focuses on the use of genetic algorithms in developing an efficient optimum design method for tilting pad bearings. The approach optimizes based on minimum film thickness, power loss, maximum film temperature, and a global objective. Results for a five tilting-pad preloaded bearing are presented to provide a comparison with more traditional optimum design methods such as the gradient-based global criterion method, and also to provide insight into the potential of genetic algorithms in the design of rotor bearings. Genetic algorithms are efficient search techniques based on the idea of natural selection and genetics. These robust methods have gained recognition as general problem solving techniques in many applications.
CFD Analysis of A Starved Four-Pad Tilting-Pad Journal Bearing with An Elastic Support of Pads
Parovay, E. F.; Falaleev, S. V.
2018-01-01
Tilting-pad journal bearings are widely used in technics. Oil starvation operation regime is not common for hydrodynamic bearings. However, correctly designed low-flow journal bearing have to operate efficiently and consistently on high rotor speeds. An elastic support of bearing pads is a set of elastic pins made of steel. Elastic support allows pads to self-align and achieve an optimal operational mode. The article presents the thermohydrodynamic performance of an axial journal bearing. The study deals with 60 mm diameter four-pad tilting-pad journal bearing, submitted to a static load varying from 1000 to 30000 N with a rotating speed varying from 1000 to 10000 rpm. The investigation focuses on numerical studying the characteristics of low-flow tilting-pad journal bearings under oil starvation conditions. Dependencies of the bearing performance on the load, rotational speed of the shaft, and the size of the radial clearance are presented.
Helicopter rotor noise investigation during ice accretion
Cheng, Baofeng
An investigation of helicopter rotor noise during ice accretion is conducted using experimental, theoretical, and numerical methods. This research is the acoustic part of a joint helicopter rotor icing physics, modeling, and detection project at The Pennsylvania State University Vertical Lift Research Center of Excellence (VLRCOE). The current research aims to provide acoustic insight and understanding of the rotor icing physics and investigate the feasibility of detecting rotor icing through noise measurements, especially at the early stage of ice accretion. All helicopter main rotor noise source mechanisms and their change during ice accretion are discussed. Changes of the thickness noise, steady loading noise, and especially the turbulent boundary layer - trailing edge (TBL-TE) noise due to ice accretion are identified and studied. The change of the discrete frequency noise (thickness noise and steady loading noise) due to ice accretion is calculated by using PSU-WOPWOP, an advanced rotorcraft acoustic prediction code. The change is noticeable, but too small to be used in icing detection. The small thickness noise change is due to the small volume of the accreted ice compared to that of the entire blade, although a large iced airfoil shape is used. For the loading noise calculation, two simplified methods are used to generate the loading on the rotor blades, which is the input for the loading noise calculation: 1) compact loading from blade element momentum theory, icing effects are considered by increasing the drag coefficient; and 2) pressure loading from the 2-D CFD simulation, icing effects are considered by using the iced airfoil shape. Comprehensive rotor broadband noise measurements are carried out on rotor blades with different roughness sizes and rotation speeds in two facilities: the Adverse Environment Rotor Test Stand (AERTS) facility at The Pennsylvania State University, and The University of Maryland Acoustic Chamber (UMAC). In both facilities the
Using collisions and resonances to tilting Uranus
Rogoszinski, Zeeve; Hamilton, Douglas
2018-01-01
Uranus’ large obliquity (98°) is widely thought to have occurred from a polar strike with an Earth sized object. Morbidelli et al. (2012) argue that two or more collisions are required in order to explain the prograde motion of Uranus’ satellites. These impactors could have been less massive by about a factor of ten, but multiple polar strikes are still improbable as even larger mass impactors would be needed for more equatorial collisions. Here we explore an alternative non-collisional model inspired by the explanation to Saturn’s significant tilt (27°). Ward and Hamilton (2004) & Hamilton and Ward (2004) argue that a secular resonance currently between Saturn’s spin axis and Neptune’s orbital pole is responsible for Saturn’s large obliquity. Unfortunately, Uranus’ axial precession frequency today is too long to match any of the current planets’ fundamental frequencies. Boué and Laskar (2010) explain that Uranus may have harbored an improbably large moon in the past which could have sped up the planet’s axial precession frequency enough to resonate with the regression of its own orbital pole. We explore another scenario which requires only the interactions between the giant planets.Thommes et al. (1999, 2002, 2003) argue that at least the cores of Uranus and Neptune were formed in between Jupiter and Saturn, as the density of the protoplanetary disk was greater there. If Neptune was scattered outward before Uranus, then a secular spin-orbit resonance between the two planets is possible. However, driving Uranus’ obliquity to near 90° with a resonance capture requires a timescale on the order of 100 Myr. If Neptune migrated out quicker or its orbital inclination was initially larger, then we find that the resulting resonance kick can tilt Uranus more than 40° in a reasonable timespan. This could replace one of the impactors required in the collisional scenario described by Morbidelli et al. (2012), but in most situations the effect of such a
Assessment of community noise for a medium-range airplane with open-rotor engines
Kopiev, V. F.; Shur, M. L.; Travin, A. K.; Belyaev, I. V.; Zamtfort, B. S.; Medvedev, Yu. V.
2017-11-01
Community noise of a hypothetical medium-range airplane equipped with open-rotor engines is assessed by numerical modeling of the aeroacoustic characteristics of an isolated open rotor with the simplest blade geometry. Various open-rotor configurations are considered at constant thrust, and the lowest-noise configuration is selected. A two-engine medium-range airplane at known thrust of bypass turbofan engines at different segments of the takeoff-landing trajectory is considered, after the replacement of those engines by the open-rotor engines. It is established that a medium-range airplane with two open-rotor engines meets the requirements of Chapter 4 of the ICAO standard with a significant margin. It is shown that airframe noise makes a significant contribution to the total noise of an airplane with open-rotor engines at landing.
An influence of the different incoming wake-like flows on the rotor vibrations
DEFF Research Database (Denmark)
Naumov, I. V.; Kabardin, Ivan K.; Mikkelsen, Robert Flemming
2017-01-01
The aim of the current investigation is the rotor vibrations generated by the disturbances caused the different types of incoming wake-like flows. Those wakes arriving at the tested rotor were created by two ways: a passive wake generator (immobile disk) and an upstream rotating rotor as an activ...... wake generator. The influence of both wakes on the tested rotor was studied in a water flume. A model of the tested three-bladed rotor designed using Glauert’s optimum theory at an optimal tip speed ratio λ = 5 was placed in both “passive” and “active” wakes to recognize dissimilarities...... accuracy using LDA. The turbulent intensity of the incoming wake flows changed from 3 to 16% due to the types of the wake generators. Power and thrust characteristics and their pulsations of the tested rotor were measured by strain gauges. The dependences of power coefficients from tip speed ratios...
Mokhtar, Md Asjad; Kamalakar Darpe, Ashish; Gupta, Kshitij
2017-08-01
The ever-increasing need of highly efficient rotating machinery causes reduction in the clearance between rotating and non-rotating parts and increase in the chances of interaction between these parts. The rotor-stator contact, known as rub, has always been recognized as one of the potential causes of rotor system malfunctions and a source of secondary failures. It is one of few causes that influence both lateral and torsional vibrations. In this paper, the rotor stator interaction phenomenon is investigated in the finite element framework using Lagrange multiplier based contact mechanics approach. The stator is modelled as a beam that can respond to axial penetration and lateral friction force during the contact with the rotor. It ensures dynamic stator contact boundary and more realistic contact conditions in contrast to most of the earlier approaches. The rotor bending-torsional mode coupling during contact is considered and the vibration response in bending and torsion are analysed. The effect of parameters such as clearance, friction coefficient and stator stiffness are studied at various operating speeds and it has been found that certain parameter values generate peculiar rub related features. Presence of sub-harmonics in the lateral vibration frequency spectra are prominently observed when the rotor operates near the integer multiple of its lateral critical speed. The spectrum cascade of torsional vibration shows the presence of bending critical speed along with the larger amplitudes of frequencies close to torsional natural frequency of the rotor. When m × 1/n X frequency component of rotational frequency comes closer to the torsional natural frequency, stronger torsional vibration amplitude is noticed in the spectrum cascade. The combined information from the stator vibration and rotor lateral-torsional vibration spectral features is proposed for robust rub identification.
Truhins, Kaspars; McCaffery, Anthony J.; Alwahabi, Zeyad T.; Rawi, Zaid
1997-07-01
We report measurements of the linear and circular polarization ratios from fully resolved rotational levels of the asymmetric rotor NH2 populated by collisions with H atoms. The results compare well with a theoretical model that includes the depolarizing effects of intramolecular coupling of rotational angular momentum N to nuclear and to electron spin. These have a very significant influence on fluorescence polarization. The model also incorporates the tilting of the N vector in the molecule frame that occurs when inter-k stack transitions take place. Changes in N vector orientation are described with the aid of the angular momentum sphere, a classical representation of the motion of the N vector in a molecule fixed frame. The theoretical treatment assumes the classically impulsive limit for the collisional interaction with conservation of the m quantum number along the kinematic apse. This description of the fate of the N vector under the influence of intra- and intermolecular interactions allows stereodynamical conclusions to be drawn from experimental observations of fluorescence polarization.
DYNAMIC ANALYSIS OF HYDRAULIC DRIVE OF TILTING PLATFORM MECHANISM OF DUMP TRUCK
Directory of Open Access Journals (Sweden)
P. Kishkevich
2011-01-01
Full Text Available Object of research – hydraulic drive of tilting platform mechanism of dump truck. We pro-pose a dynamic model of the hydraulic system. The model takes into account the cyclic operation (lifting, lowering the platform.
DYNAMIC ANALYSIS OF HYDRAULIC DRIVE OF TILTING PLATFORM MECHANISM OF DUMP TRUCK
P. Kishkevich; A. Safonau; I. Selivonchik; P. Bartosh
2011-01-01
Object of research – hydraulic drive of tilting platform mechanism of dump truck. We pro-pose a dynamic model of the hydraulic system. The model takes into account the cyclic operation (lifting, lowering the platform).
Sedimentary basins reconnaissance using the magnetic Tilt-Depth method
Salem, A.; Williams, S.; Samson, E.; Fairhead, D.; Ravat, D.; Blakely, R.J.
2010-01-01
We compute the depth to the top of magnetic basement using the Tilt-Depth method from the best available magnetic anomaly grids covering the continental USA and Australia. For the USA, the Tilt-Depth estimates were compared with sediment thicknesses based on drilling data and show a correlation of 0.86 between the datasets. If random data were used then the correlation value goes to virtually zero. There is little to no lateral offset of the depth of basinal features although there is a tendency for the Tilt-Depth results to be slightly shallower than the drill depths. We also applied the Tilt-Depth method to a local-scale, relatively high-resolution aeromagnetic survey over the Olympic Peninsula of Washington State. The Tilt-Depth method successfully identified a variety of important tectonic elements known from geological mapping. Of particular interest, the Tilt-Depth method illuminated deep (3km) contacts within the non-magnetic sedimentary core of the Olympic Mountains, where magnetic anomalies are subdued and low in amplitude. For Australia, the Tilt-Depth estimates also give a good correlation with known areas of shallow basement and sedimentary basins. Our estimates of basement depth are not restricted to regional analysis but work equally well at the micro scale (basin scale) with depth estimates agreeing well with drill hole and seismic data. We focus on the eastern Officer Basin as an example of basin scale studies and find a good level of agreement between previously-derived basin models. However, our study potentially reveals depocentres not previously mapped due to the sparse distribution of well data. This example thus shows the potential additional advantage of the method in geological interpretation. The success of this study suggests that the Tilt-Depth method is useful in estimating the depth to crystalline basement when appropriate quality aeromagnetic anomaly data are used (i.e. line spacing on the order of or less than the expected depth to
Experimental Investigation of a Helicopter Rotor Hub Flow
Reich, David
The rotor hub system is by far the largest contributor to helicopter parasite drag and a barrier to increasing helicopter forward-flight speed and range. Additionally, the hub sheds undesirable vibration- and instability-inducing unsteady flow over the empennage. The challenges associated with rotor hub flows are discussed, including bluff body drag, interactional aerodynamics, and the effect of the turbulent hub wake on the helicopter empennage. This study was conducted in three phases to quantify model-scale rotor hub flows in water tunnels at The Pennsylvania State University Applied research lab. The first phase investigated scaling and component interaction effects on a 1:17 scale rotor hub model in the 12-inch diameter water tunnel. Effects of Reynolds number, advance ratio, and hub geometry configuration on the drag and wake shed from the rotor hub were quantified using load cell measurements and particle-image velocimetry (PIV). The second phase focused on flow visualization and measurement on a rotor hub and rotor hub/pylon geometry in the 12-inch diameter water tunnel. Stereo PIV was conducted in a cross plane downstream of the hub and flow visualization was conducted using oil paint and fluorescent dye. The third phase concentrated on high accuracy load measurement and prediction up to full-scale Reynolds number on a 1:4.25 scale model in the 48-inch diameter water tunnel. Measurements include 6 degree of freedom loads on the hub and two-component laser-Doppler velocimetry in the wake. Finally, results and conclusions are discussed, followed by recommendations for future investigations.
Coupled bending and torsional vibration of a rotor system with nonlinear friction
Energy Technology Data Exchange (ETDEWEB)
Hua, Chunli; Cao, Guohua; Zhu, Zhencai [China University of Mining and Technology, Xuzhou (China); Rao, Zhushi; Ta, Na [Shanghai Jiao Tong University, Shanghai (China)
2017-06-15
Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating ma- chinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose self- excited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.
Optic flow induced self-tilt perception
Bos, J.E.
2008-01-01
Roll optic flow induces illusory self-tilt in humans. As far as the mechanism underlying this visual-vestibular interaction is understood, larger angles of self-tilt are predicted than observed. It is hypothesized that the discrepancy can be explained by idiotropic (i.e., referring to a personal
Lake-tilting investigations in southern Sweden
International Nuclear Information System (INIS)
Paasse, T.
1996-04-01
The main aim of lake-tilting investigations is to determine the course of the glacio-isostatic uplift, i.e. to find a formula for the uplift. Besides the lake-tilting graphs, knowledge of the recent relative uplift and the gradient of some marine shorelines are used for solving this problem. This paper summarizes four investigations. 23 refs, 10 figs
Lake-tilting investigations in southern Sweden
Energy Technology Data Exchange (ETDEWEB)
Paasse, T. [Sveriges Geologiska Undersoekning, Goeteborg (Sweden)
1996-04-01
The main aim of lake-tilting investigations is to determine the course of the glacio-isostatic uplift, i.e. to find a formula for the uplift. Besides the lake-tilting graphs, knowledge of the recent relative uplift and the gradient of some marine shorelines are used for solving this problem. This paper summarizes four investigations. 23 refs, 10 figs.
Large optics inspection, tilting, and washing stand
Ayers, Marion Jay [Brentwood, CA; Ayers, Shannon Lee [Brentwood, CA
2010-08-24
A large optics stand provides a risk free means of safely tilting large optics with ease and a method of safely tilting large optics with ease. The optics are supported in the horizontal position by pads. In the vertical plane the optics are supported by saddles that evenly distribute the optics weight over a large area.
Uncertainty analysis of flexible rotors considering fuzzy parameters and fuzzy-random parameters
Directory of Open Access Journals (Sweden)
Fabian Andres Lara-Molina
Full Text Available Abstract The components of flexible rotors are subjected to uncertainties. The main sources of uncertainties include the variation of mechanical properties. This contribution aims at analyzing the dynamics of flexible rotors under uncertain parameters modeled as fuzzy and fuzzy random variables. The uncertainty analysis encompasses the modeling of uncertain parameters and the numerical simulation of the corresponding flexible rotor model by using an approach based on fuzzy dynamic analysis. The numerical simulation is accomplished by mapping the fuzzy parameters of the deterministic flexible rotor model. Thereby, the flexible rotor is modeled by using both the Fuzzy Finite Element Method and the Fuzzy Stochastic Finite Element Method. Numerical simulations illustrate the methodology conveyed in terms of orbits and frequency response functions subject to uncertain parameters.
Rotor/stator unsteady calculation
Energy Technology Data Exchange (ETDEWEB)
Denis, C.; Dejean, F. [Electricite de France, 78 - Chatou (France). Direction des Etudes et Recherches
1997-12-31
The flow prediction involves the use of the three-dimensional Navier-Stokes solver N3S-NATUR. This compressible and turbulent finite volume / finite element code is able to perform multi-domain steady and now unsteady calculations through the external coupling module CALCIUM. The later is based on PVM (Parallel Virtual Machine). The originality of the method is the use of this external coupling module in such a way that each domain is computed with its own N3S code. Of course, a turbomachinery stage flow is always unsteady because of the rotor. When dealing with steady computations, the principal assumption is that the flow is steady relative to each domain individually and that each domain can communicate via mixing planes. These planes introduce circumferential averaging of the flow properties but preserve quite general radial variations. For unsteady calculations, the same method is used but without any circumferential averaging. Here, two fixed and three rotating blades are taken into account which involves the use of five different N3S-NATUR codes (one code for one blade). Of course, in order to perform such a calculation without any hypothesis, all the blades have to be modelled. Actually, such a calculation is done for a turbine stage of 23 fixed and 37 rotating blades (VEGA 2 turbine). In order to perform such a calculation in a realistic time, 60 processors of a parallel architecture computer are used. (authors)
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.
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.
Flow-driven simulation on variation diameter of counter rotating wind turbines rotor
Directory of Open Access Journals (Sweden)
Littik Y. Fredrika
2018-01-01
Full Text Available Wind turbines model in this paper developed from horizontal axis wind turbine propeller with single rotor (HAWT. This research aims to investigating the influence of front rotor diameter variation (D1 with rear rotor (D2 to the angular velocity optimal (ω and tip speed ratio (TSR on counter rotating wind turbines (CRWT. The method used transient 3D simulation with computational fluid dynamics (CFD to perform the aerodynamics characteristic of rotor wind turbines. The counter rotating wind turbines (CRWT is designed with front rotor diameter of 0.23 m and rear rotor diameter of 0.40 m. In this research, the wind velocity is 4.2 m/s and variation ratio between front rotor and rear rotor (D1/D2 are 0.65; 0.80; 1.20; 1.40; and 1.60 with axial distance (Z/D2 0.20 m. The result of this research indicated that the variation diameter on front rotor influence the aerodynamics performance of counter rotating wind turbines.
Aerodynamic Characteristic Analysis of Multi-Rotors Using a Modified Free-Wake Method
Lee, Jaewon; Yee, Kwanjung; Oh, Sejong
Much research is in progress to develop a next-generation rotor system for various aircrafts, including unmanned aerial vehicles (UAV) with multi-rotor systems, such as coaxial and tandem rotors. Development and design of such systems requires accurate estimation of rotor performance. The most serious problem encountered during analysis is wake prediction, because wake-wake and wake-rotor interactions make the problem very complex. This study analyzes the aerodynamic characteristics based on the free-wake method, which is both efficient and effective for predicting wake. This code is modified to include the effect of complex planforms as well as thickness by using an unsteady 3D panel method. A time-marching free-wake model is implemented based on the source-doublet panel method that assigns panels to the surface and analyzes them. The numerical wake instability, the most critical problem for analysis, is resolved by adopting slow start-up and by including viscous effects. Also, the instability due to wake interference in tandem rotor analysis is resolved by configuring the initial shapes of the multi-rotor wake as that of a single rotor wake trajectory. The developed code is verified by comparing with previous experimental data for coaxial and tandem rotors.
Finite element analysis of misaligned rotors on oil-film bearings
Indian Academy of Sciences (India)
degree of freedom rotor model to more general finite element model of shaft disc systems on multiple bearings. The present work first proposes a fairly general coupling misalignment model using Lagrange multipliers. For an integrated analysis of the ...
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.
A Novel Numerical Approach for Generation and Propagation of Rotor-Stator Interaction Noise
Patel, Krishna
As turbofan engine designs move towards bypass ratios ≥12 and corresponding low pressure ratios, fan rotor blade tip Mach numbers are reduced, leading to rotor-stator interaction becoming an important contributor to tonal fan noise. For future aircraft configurations employing boundary layer ingestion, non-uniform flow enters the fan. The impact of such non-uniform flows on the generation and propagation of rotor-stator interaction tones has yet to be assessed. In this thesis, a novel approach is proposed to numerically predict the generation and propagation of rotor-stator interaction noise with distorted inflow. The approach enables a 42% reduction in computational cost compared to traditional approaches employing a sliding interface between the rotor and stator. Such an interface may distort rotor wakes and can cause non-physical acoustic wave reflections if time steps are not sufficiently small. Computational costs are reduced by modelling the rotor using distributed, volumetric body forces. This eliminates the need for a sliding interface and thus allows a larger time step size. The force model responds to local flow conditions and thus can capture the effects of long-wavelength flow distortions. Since interaction noise is generated by the incidence of the rotor wakes onto the stator vanes, the key challenge is to produce the wakes using a body force field since the rotor blades are not directly modelled. It is shown that such an approach can produce wakes by concentrating the viscous forces along streamtubes in the last 15% chord. The new approach to rotor wake generation is assessed on the GE R4 fan from NASA's Source Diagnostic Test, for which the computed overall aerodynamic performance matches the experiment to within 1%. The rotor blade wakes are generated with widths in excellent agreement and depths in fair agreement with the experiment. An assessment of modal sound power levels computed in the exhaust duct indicates that this approach can be used
Discontinuity effects in dynamically loaded tilting pad journal bearings
DEFF Research Database (Denmark)
Thomsen, Kim; Klit, Peder; Vølund, Anders
2011-01-01
This paper describes two discontinuity effects that can occur when modelling radial tilting pad bearings subjected to high dynamic loads. The first effect to be treated is a pressure build-up discontinuity effect. The second effect is a contact-related discontinuity that disappears when a contact...... force is included in the theoretical model. Methods for avoiding the pressure build-up discontinuity effect are proposed....
DEFF Research Database (Denmark)
Cheng, Shuangyin; Luo, Derong; Huang, Shoudao
2015-01-01
This study presents an investigation into the control of an axial-flux permanent magnet synchronous machine (PMSM) with contra-rotating rotors fed by a single inverter, which corresponds to two PMSM connected in series. In this study, the mathematic model of the PMSM with contra-rotating rotors...
Detection of a fatigue crack in a rotor system using full-spectrum ...
Indian Academy of Sciences (India)
methods and it is the main motivation of the present work. 3. System modeling of a cracked rotor with transverse crack. A Laval rotor with a centrally located rigid disc and a mass- less elastic shaft is considered, which is supported on rigid bearings (figure 1). Transverse translation displacements in two orthogonal directions ...
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...
Two-Degree-of-Freedom Active Vibration Control of a Prototyped “Smart” Rotor
Van Wingerden, J.W.; Hulskamp, A.; Barlas, A.; Houtzager, I.; Bersee, H.; Van Kuik, G.; Verhaegen, M.
2010-01-01
This paper studies the load reduction potential of a prototyped “smart” rotor. This is, a rotor where the blades are equipped with a number of control devices that locally change the lift profile on the blade, combined with appropriate sensors and controllers. Experimental models, using dedicated
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...
Finite element analysis of misaligned rotors on oil-film bearings
Indian Academy of Sciences (India)
Al-Hussain K M 2003 Dynamic stability of two rigid rotors connected by a flexible coupling with angular misalignment. J. Sound and Vibration 266: 217–234. Ding J, Krodkiewski J M 1990 Inclusion of static indetermination in the mathematical model for nonlinear dynamic analyses of multi-bearing rotor system. J. Sound and ...
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)
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
Comparison of the far wake behind dual rotor and dual disk configurations
DEFF Research Database (Denmark)
Okulov, Valery; Mikkelsen, Robert Flemming; Naumov, I. V.
2016-01-01
wake features for two rotors subjected to different operating and spatial conditions. As a part of this, a comparison with the wake development behind two disks replacing the rotor models was performed to determine the difference between the two wake systems.LDA and Stereo PIV experiments were carried...
Evaluating Tilt for Wind Farms: Preprint
Energy Technology Data Exchange (ETDEWEB)
Annoni, Jennifer; Scholbrock, Andrew; Churchfield, Matthew; Fleming, Paul
2017-06-29
The objective of this work is to demonstrate the feasibility of tilt in a wind plant. Tilt control, much like other wind plant control strategies, has the potential to improve the performance of a wind plant. Tilt control uses the tilt angle of the turbine to direct the wake above or below the downstream turbines. This paper presents a study of tilt in two- and threeturbine arrays. Specifically, the authors show that the power production of a two-turbine array can be increased by tilting turbines in a specific orientation. When adding more turbines, as is shown with the three-turbine array, the overall percentage of power gain increases. This outcome deviates from some of the results seen in typical wind plant control strategies. Finally, we discuss the impact this type of control strategy has on the aerodynamics in a wind plant. This analysis demonstrates that a good understanding of wake characteristics is necessary to improve the plant's performance. A tilt strategy such as the one presented in this paper may have implications for future control/optimization studies including optimization of hub heights in a wind plant and analysis of deep array effects.
Unilateral otolith centrifugation by head tilt.
Winters, Stephanie M; Bos, Jelte E; Klis, Sjaak F L
2014-01-01
To test for otolith asymmetries, several studies described horizontal translation of the body and head en bloc during fast vertical axis rotation. This stimulus causes one otolithic organ to rotate on-axis, and the other to experience centripetal acceleration. To test a new, more simple method of unilateral stimulation with head tilt and the body remaining on axis. During stationary and during 360 deg/s rotation, 12 healthy blindfolded subjects had their heads tilted 30 degrees sideways, positioning one otolithic organ on the axis of rotation after the other. The haptic subjective vertical (SV) was recorded several times by means of a manually adjustable rod. It was found that during stationary the SV tilted about 4 degrees on average in the direction of the head. During rotation, the SV tilted about 9 degrees on average. We therefore estimate the effect of eccentric otolith rotation to be 5 degrees on average. Tilt of the subjective vertical induced by head tilt during on-axis body rotation can provide a relatively uncomplicated alternative to test unilateral otolithic function as compared to body and head translation during rotation. Moreover, unlike eccentric rotation of the entire body, somatosensory cues are minimized by keeping the body fixed on axis and by subtracting the effect of head tilt per se.
Experimental studies of octahedral tilting in perovskites
International Nuclear Information System (INIS)
Howard, C.J.; Kennedy, B.J.; Chakoumakos, B.C.
1999-01-01
Full text: Structures of the perovskite family, ABX 3 , have interested crystallographers over many years, and continue to attract attention on account of their fascinating electrical and magnetic properties, and their significance in the earth sciences. The ideal perovskite (cubic) is a particularly simple structure, but also a demanding one, since aside from the lattice parameter there are no variable parameters in the structure. Consequently, the majority of perovskite structures show departures from the ideal, the most common distortion being the comer-linked tilting of the practically rigid BX 6 octahedral units. Following a group theoretical study in 1997, a number of experimental investigations of octahedral tilting have been undertaken in 1998, and these are reported in this presentation. The studies are of the perovskites, SrZrO 3 , SrHfO 3 , CaTiO 3 , NaTaO 3 and LaGaO 3 . In each case, the crystal structures have been followed at high temperatures, with particular attention being paid to temperature regimes in which only the simplest octahedral tilt (only one tilt axis) pertains. Neutron powder diffraction patterns have been recorded on the medium/high resolution diffractometer installed at beam port HB4 at the High Flux Isotope Reactor, at the Oak Ridge National Laboratory. Crystal structures have been refined by the Rietveld method, and angles of tilt of the oxygen octahedra derived from the atomic position parameters. Each of the first four perovskites listed above transforms from tetragonal (with a single tilt axis) to cubic, and in each case, as far as can be determined from our measurements, the tilt angle in the tetragonal phase decreases continuously towards zero. There are interesting differences, however, in the functional form of this variation. The LaGaO 3 transforms at modest temperature to a rhombohedral phase, also characterised by a single tilt axis, but though the tilt angle decreases slowly with increasing temperature, the sample
Sensor fusion for structural tilt estimation using an acceleration-based tilt sensor and a gyroscope
Liu, Cheng; Park, Jong-Woong; Spencer, B. F., Jr.; Moon, Do-Soo; Fan, Jiansheng
2017-10-01
A tilt sensor can provide useful information regarding the health of structural systems. Most existing tilt sensors are gravity/acceleration based and can provide accurate measurements of static responses. However, for dynamic tilt, acceleration can dramatically affect the measured responses due to crosstalk. Thus, dynamic tilt measurement is still a challenging problem. One option is to integrate the output of a gyroscope sensor, which measures the angular velocity, to obtain the tilt; however, problems arise because the low-frequency sensitivity of the gyroscope is poor. This paper proposes a new approach to dynamic tilt measurements, fusing together information from a MEMS-based gyroscope and an acceleration-based tilt sensor. The gyroscope provides good estimates of the tilt at higher frequencies, whereas the acceleration measurements are used to estimate the tilt at lower frequencies. The Tikhonov regularization approach is employed to fuse these measurements together and overcome the ill-posed nature of the problem. The solution is carried out in the frequency domain and then implemented in the time domain using FIR filters to ensure stability. The proposed method is validated numerically and experimentally to show that it performs well in estimating both the pseudo-static and dynamic tilt measurements.
CT patellar cortex tilt angle: A radiological method to measure patellar tilt
International Nuclear Information System (INIS)
Mirza Toluei, F.; Afshar, A.; Salarilak, S.; Sina, A.
2005-01-01
Background/Objectives: the role of patellar tilt in the anterior knee pain is indisputable. Traditionally. the lateral patello-femoral angle of Laurin has been defined in both the axial view and CT images for measuring the tilt of patella. We present a new angle. which is independent of the morphology of patella and directly relates to clinical assessment of the tilt. which is appreciated from palpation of the edges of the patella. Patients and Methods: 38 patients with anterior knee pain and forty normal control subjects were examined using CT scan of patello-femoral joint in 15 degrees of knee flexion. The amount of lateral patellar tilt was quantitatively assessed using the lateral patello-femoral angle, as described by Laurin et al, and the newly defined patellar cortex tilt angle. This angle is subtended by the line drawn along the posterior femoral condyles and the one parallel to the subchondral bone of patellar cortex. The fifteen-degree tilt was taken as normal cut-off point for patellar cortex tilt angle in the control group. Results: in patients, the average tilt of patella. using the patellar cortex tilt angle was 15.26 versus 7.05 in the control group. Using Student's t test, the difference between the two means was significant (P<0.001). The sensitivity and specificity of patellar cortex tilt angle were 40 and 90 percent, respectively There was a moderate agreement between our presented test and the lateral tilt angle test (kappa=0.40. P<0.001). Conclusion: our results indicate that patellar tilt can also be detected using patellar cortex tilt angle. We need more specific studies ta determine the validity of the test
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.
In-vitro hemodynamics of stented bioprosthetic heart valves in the tilted implantation position.
Babin-Ebell, Joerg; Sievers, Hans H; Misfeld, Martin; Runge, Maike; Vogt, Paul Robert; Scharfschwerdt, Michael
2008-09-01
Although, in small aortic annulus or aortic annulus calcification, it is recommended that valves are implanted in a tilted position, mechanical valves show impaired hemodynamic performance when positioned in this way. To date, no investigations have been conducted with biological valves implanted in a tilted position. Measurements were performed in a pulsatile flow simulator. The aortic roots were mounted in a fluid reservoir and tested with bioprosthetic valves implanted in the regular position (21 mm; n = 7) or at a 200 tilt (23 mm; n = 7). Additional 21 mm valves were implanted in both positions with a systemic pressure of 120/80 mmHg. Subsequently, the valves were implanted into a glass model and flow visualization monitored by adding air bubbles illuminated with a laser diode. The 21 mm valves showed a slightly higher transvalvular gradient in the tilted than in the regular position, while 23 mm valves in a tilted position showed a lower gradient than 21 mm valves in the regular position. Flow in the regular position was seen to be straight and central, but in the tilted position was diverted and impacted on the aortic wall. Vortex formation in the tilted position was more pronounced than in the regular position, with certain low-flow areas being observed. The implantation of a one size-larger bioprosthetic valve at a 20 degree tilt in a small aortic root resulted in a slight reduction in transvalvular gradient compared to a smaller valve implanted in the regular position. Whilst mechanical valve performance is markedly compromised in the tilted position, the bioprosthetic valve showed only minor impairment of transvalvular pressure gradient due to tilting, and this was overcompensated by the larger valve size. However, the advantage of a greater orifice area must be traded against the consequences of the observed flow disturbances.
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.
Parametric analyses on dynamic stall control of rotor airfoil via synthetic jet
Directory of Open Access Journals (Sweden)
Qijun ZHAO
2017-12-01
Full Text Available The effects of synthetic jet control on unsteady dynamic stall over rotor airfoil are investigated numerically. A moving-embedded grid method and an Unsteady Reynolds Averaged Navier-Stokes (URANS solver coupled with k-Ï Shear Stress Transport (SST turbulence model are established for predicting the complex flowfields of oscillatory airfoil under jet control. Additionally, a velocity boundary condition modeled by sinusoidal function has been developed to fulfill the perturbation effect of periodic jet. The validity of present CFD method is evaluated by comparisons of the calculated results of baseline dynamic stall case for rotor airfoil and jet control case for VR-7B airfoil with experimental data. Then, parametric analyses are conducted emphatically for an OA212 rotor airfoil to investigate the effects of jet control parameters (jet location, dimensionless frequency, momentum coefficient, jet angle, jet type and dual-jet on dynamic stall characteristics of rotor airfoil. It is demonstrated by the calculated results that efficiency of jet control could be improved with specific momentum coefficient and jet angle when the jet is located near separation point of rotor airfoil. Furthermore, the dual-jet could improve control efficiency more obviously on dynamic stall of rotor airfoil with respect to the unique jet, and the influence laws of dual-jetâs angles and momentum coefficients on control effects are similar to those of the unique jet. Finally, unsteady aerodynamic characteristics of rotor via synthetic jet which is located on the upper surface of rotor blade in forward flight are calculated, and asÂ a result, the aerodynamic characteristics of rotor are improved compared with the baseline. The results indicate that synthetic jet has the capability in improving aerodynamic characteristics of rotor. Keywords: Airfoil, Dynamic stall characteristics, Flow control, Moving-embedded grid methodology, Navier-Stokes equations, Parametric
Filter type rotor for multistation photometer
Shumate, II, Starling E.
1977-07-12
A filter type rotor for a multistation photometer is provided. The rotor design combines the principle of cross-flow filtration with centrifugal sedimentation so that these occur simultaneously as a first stage of processing for suspension type fluids in an analytical type instrument. The rotor is particularly useful in whole-blood analysis.
Cao, Hao; Cao, Xiaoyu; Chen, Fei; Li, Ming; Zhang, Bolin; Wei, Jilong
2017-12-01
This paper presents a new kind of tilting-pad gas seal. This design is introduced to reduce the tangential seal force and to improve the stability of rotor system finally. A seal test rig is set up. The paper compares the leakage between tilting-pad seal and fixed pad seal. The result shows that the leakage ratio of the tilting-pad seal is close to the leakage ratio of the fixed pad seal. The work done by seal force on the cylinder system is calculated as an index of comparison between these two seals. Result shows that the work done by the fixed pad seal is greater than the work done by the tilting-pad seal. Moreover, system damping factor is used to compare the stabilities of these two seals. The impact tests on the cylinder system are done under different conditions. The system damping factors are calculated from the damped waves of system vibration. Test results show that the damping factor of the tilting pad seal is higher than that of the fixed pad seal in both the vertical and the horizontal directions.
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.
Synthesis of Triptycene-Based Molecular Rotors for Langmuir-Blodgett Monolayers.
Kaleta, Jiří; Kaletová, Eva; Císařová, Ivana; Teat, Simon J; Michl, Josef
2015-10-16
We describe syntheses of six triptycene-containing molecular rotors with several single-crystal X-ray diffraction analyses. These rod-shaped molecules carrying an axial rotator are designed to interleave on an aqueous surface into Langmuir-Blodgett (LB) monolayers containing a two-dimensional trigonal array of dipoles rotatable about an axis normal to the surface. Monolayer formation was verified with the simplest of the rotor structures. On an aqueous subphase containing divalent cations (Mg(2+), Ca(2+), Zn(2+), Sr(2+), or Cd(2+)), the LB isotherm yielded an area of 53 ± 3 Å(2)/molecule (monolayer of type A), compatible with the anticipated triangular packing of axes normal to the surface. On pure water, the area is 30 ± 3 Å(2)/molecule, and it is proposed that in this monolayer (type B), the molecular axes are tilted by 40-45° to a structure similar to those observed in single crystals of related triptycenes. After transfer to a gold surface, ellipsometry and PM IRRAS yield tilt angles of 29 ± 4° (monolayers of type A) and 38 ± 4° (type B). A full-scale examination of monolayers from all the rotors on a subphase and after transfer is underway and will be reported separately.
Patterns of the Rotor-over-Stator Rolling under Change in the Damping Components
Shatokhin, V. F.
2018-03-01
As experimental studies show, the rubbing of the rotor against the structure usually excites harmonics of different frequencies. In high-frequency regions, the power of the vibration signal appears to be considerable. The rotor—supports—stator system is in an unstable equilibrium state during the contact interaction between the rotor and the stator. The forces exerted on the rotor facilitate the excitation of the asynchronous rolling and its damping. The forces have been determined that facilitate the excitation of the progressive and retrograde rotor precession. The consideration of these forces in the algorithm for modeling the rotor-over-stator rolling development allows investigation of the impact of the components of the above forces on the behavior of the rotor system. The initial excitation—disturbance of the normal operation—of the rotor and subsequent unsteady oscillations of it result from sudden imbalance in the second span. The results of numerical modeling of the rubbing in the second span and the rotor-over-stator rolling upon change in the damping components of secondary (gyroscopic) components b ij ( i ≠ j) of the damping matrix are presented for the rotor on three bearing-supports considering the synergetic effect of the forces of various types exerted on the rotor. It is shown that change in one of the parameters of the excitation forces leads to ambiguity of the pattern (manifestation form) of the asynchronous rotor-over-stator rolling and proves the existence of more than one states towards which the rotor—supports—stator system tends. In addition to the rolling with a constant rotor—stator contact, oscillations of the rotor develop in the direction perpendicular to the common trajectory of the precession motion of the rotor's center with transition to the vibro-impact motion mode. The oscillations of the rotor tend towards the symmetry center of the system (the stator bore center). The reason is the components of the stiffness
A bistable mechanism for chord extension morphing rotors
Johnson, Terrence; Frecker, Mary; Gandhi, Farhan
2009-03-01
Research efforts have shown that helicopter rotor blade morphing is an effective means to improve flight performance. Previous example of rotor blade morphing include using smart-materials for trailing deflection and rotor blade twist and tip twist, the development of a comfortable airfoil using compliant mechanisms, the use of a Gurney flap for air-flow deflection and centrifugal force actuated device to increase the span of the blade. In this paper we explore the use of a bistable mechanism for rotor morphing, specifically, blade chord extension using a bistable arc. Increasing the chord of the rotor blade is expected to generate more lift-load and improve helicopter performance. Bistable or "snap through" mechanisms have multiple stable equilibrium states and are a novel way to achieve large actuation output stroke. Bistable mechanisms do not require energy input to maintain a stable equilibrium state as both states do not require locking. In this work, we introduce a methodology for the design of bistable arcs for chord morphing using the finite element analysis and pseudo-rigid body model, to study the effect of different arc types, applied loads and rigidity on arc performance.
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.
Combined Influence of Visual Scene and Body Tilt on Arm Pointing Movements: Gravity Matters!
Scotto Di Cesare, Cécile; Sarlegna, Fabrice R.; Bourdin, Christophe; Mestre, Daniel R.; Bringoux, Lionel
2014-01-01
Performing accurate actions such as goal-directed arm movements requires taking into account visual and body orientation cues to localize the target in space and produce appropriate reaching motor commands. We experimentally tilted the body and/or the visual scene to investigate how visual and body orientation cues are combined for the control of unseen arm movements. Subjects were asked to point toward a visual target using an upward movement during slow body and/or visual scene tilts. When the scene was tilted, final pointing errors varied as a function of the direction of the scene tilt (forward or backward). Actual forward body tilt resulted in systematic target undershoots, suggesting that the brain may have overcompensated for the biomechanical movement facilitation arising from body tilt. Combined body and visual scene tilts also affected final pointing errors according to the orientation of the visual scene. The data were further analysed using either a body-centered or a gravity-centered reference frame to encode visual scene orientation with simple additive models (i.e., ‘combined’ tilts equal to the sum of ‘single’ tilts). We found that the body-centered model could account only for some of the data regarding kinematic parameters and final errors. In contrast, the gravity-centered modeling in which the body and visual scene orientations were referred to vertical could explain all of these data. Therefore, our findings suggest that the brain uses gravity, thanks to its invariant properties, as a reference for the combination of visual and non-visual cues. PMID:24925371
Wind-tunnel tests of the XV-15 tilt rotor aircraft
Weiberg, J. A.; Maisel, M. D.
1980-01-01
The XV-15 aircraft was tested in the Ames 40 by 80 Foot Wind Tunnel for preliminary evaluation of aerodynamic and aeroelastic characteristics prior to flight. The tests were undertaken to investigate the aircraft performance, stability, control and structural loads for flight modes from helicopter through transition and airplane mode up to the tunnel capability of 170 knots. Results from these tests are presented.
Conservative treatment of excessive anterior pelvic tilt
DEFF Research Database (Denmark)
Brekke, Anders Falk
quality by two reviewers using Cochrane Collaboration’s tool for assessing risk of bias in RCT’s and the ROBINS-I tool (Risk Of Bias In Non-randomized Studies - of interventions). Data was synthesized qualitatively. The GRADE approach was used to determine the overall quality of the evidence. PROSPERO...... treatment may reduce anterior pelvis tilt and reduce symptoms in relation to faulty posture. Keywords: pelvis, anterior tilt, anteversion, posture...
On the Design of Tilting-Pad Thrust Bearings
DEFF Research Database (Denmark)
Heinrichson, Niels
2007-01-01
Pockets are often machined in the surfaces of tilting-pad thrust bearings to allow for hydrostatic jacking in the start-up phase. Pockets and other recesses in the surfaces of bearing pads influence the pressure distribution and thereby the position of the pivot resulting in the most advantageous...... friction and a small pressure build-up. As in parallel-step bearings the recesses may also have a depth of the same order of magnitude as the oil film thickness. Such recesses are characterized by a strong pressure build-up caused by the reduction of the flow area at the end of the recess. Numerical models...... based on the Reynolds equation are used. They include the effects of variations of viscosity with temperature and the deformation of the bearing pads due to pressure and thermal gradients. The models are validated using measurements. Tilting-pad bearings of standard design are studied and the influences...
International Nuclear Information System (INIS)
Singh, M.; Pradeep Kumar; Singh, Y.; Varshney, A.K.; Gupta, D.K.
2014-01-01
We undertake the present work to treat 232 Th with a soft rotor formula used recently by C. Bihari et. al for γ-band and modified by J.B. Gupta et. al. It describes energy in terms of moment of inertia and softness parameter
Dynamic Analysis of Composite Rotors
Directory of Open Access Journals (Sweden)
S. P. Singh
1996-01-01
accounted for. Material damping is also taken into account. The layerwise theory is compared with conventionally used equivalent modulus beam theory. Some interesting case studies are presented. The effect of various parameters on dynamic behavior and stability of a composite rotor is presented.
Tilt stability of rotating current rings with passive conductors
International Nuclear Information System (INIS)
Zweibel, E.G.; Pomphrey, N.
1984-12-01
We study the combined effects of rotation and resistive passive conductors on the stability of a rigid current in an external magnetic field. We present numerical and approximate analytical solutions to the equations of motion, which show that the ring is always tilt unstable on the resistive decay timescale of the conductors, although rotation and eddy currents may stabilize it over short times. Possible applications of our model include spheromaks which rotate or which are encircled by energetic particle rings
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.
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.
Lifting to cluster-tilting objects in higher cluster categories
Liu, Pin
2008-01-01
In this note, we consider the $d$-cluster-tilted algebras, the endomorphism algebras of $d$-cluster-tilting objects in $d$-cluster categories. We show that a tilting module over such an algebra lifts to a $d$-cluster-tilting object in this $d$-cluster category.
International Nuclear Information System (INIS)
Xu, X P; Zhang, G Y; Zhang, N; Wang, L Y
2006-01-01
Tilt angle of scanning mirror is one of the important qualifications of performance measurement on the earth surface for swing scanning mode infrared the earth sensor. In order to settle the problem of measuring the tilt angle of scanning mirror in dynamic, real-time and non-contact, based on laser inspecting technology and CCD probing technology, a method of laser dynamical measurement for tilt angle of scanning mirror of the infrared earth sensor is presented. The measurement system developed in this paper can accomplish the dynamic and static laser non-contact measurement for the parameters of scanning mirror such as tilt angle, swing frequency, etc. In this paper the composition and overall structure of system are introduced. Emphasis on analyzing and discussing the theory of dynamically measuring tilt angle of scanning mirror, the problems of data processing and error correction are settled by established mathematic model of system. The accuracy of measurement system is verified by experiment, the results indicated that measurement range of system for tilt angle is 0∼±12 0 , accuracy of dynamic and static measurement is less than ±0.05 0 , this method of dynamically measuring tilt angle is suitable
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.
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.
International Nuclear Information System (INIS)
Wang, C.-C.; Jang, M.-J.; Yeh, Y.-L.
2007-01-01
This paper studies the bifurcation and nonlinear behaviors of a flexible rotor supported by relative short gas film bearings. A time-dependent mathematical model for gas journal bearings is presented. The finite difference method with successive over relation method is employed to solve the Reynolds' equation. The system state trajectory, Poincare maps, power spectra, and bifurcation diagrams are used to analyze the dynamic behavior of the rotor and journal center in the horizontal and vertical directions under different operating conditions. The analysis reveals a complex dynamic behavior comprising periodic and subharmonic response of the rotor and journal center. This paper shows how the dynamic behavior of this type of system varies with changes in rotor mass and rotational velocity. The results of this study contribute to a further understanding of the nonlinear dynamics of gas film rotor-bearing systems
Direct cone beam SPECT reconstruction with camera tilt
International Nuclear Information System (INIS)
Jianying Li; Jaszczak, R.J.; Greer, K.L.; Coleman, R.E.; Zongjian Cao; Tsui, B.M.W.
1993-01-01
A filtered backprojection (FBP) algorithm is derived to perform cone beam (CB) single-photon emission computed tomography (SPECT) reconstruction with camera tilt using circular orbits. This algorithm reconstructs the tilted angle CB projection data directly by incorporating the tilt angle into it. When the tilt angle becomes zero, this algorithm reduces to that of Feldkamp. Experimentally acquired phantom studies using both a two-point source and the three-dimensional Hoffman brain phantom have been performed. The transaxial tilted cone beam brain images and profiles obtained using the new algorithm are compared with those without camera tilt. For those slices which have approximately the same distance from the detector in both tilt and non-tilt set-ups, the two transaxial reconstructions have similar profiles. The two-point source images reconstructed from this new algorithm and the tilted cone beam brain images are also compared with those reconstructed from the existing tilted cone beam algorithm. (author)
Isolated Open Rotor Noise Prediction Assessment Using the F31A31 Historical Blade Set
Nark, Douglas M.; Jones, William T.; Boyd, D. Douglas, Jr.; Zawodny, Nikolas S.
2016-01-01
In an effort to mitigate next-generation fuel efficiency and environmental impact concerns for aviation, open rotor propulsion systems have received renewed interest. However, maintaining the high propulsive efficiency while simultaneously meeting noise goals has been one of the challenges in making open rotor propulsion a viable option. Improvements in prediction tools and design methodologies have opened the design space for next generation open rotor designs that satisfy these challenging objectives. As such, validation of aerodynamic and acoustic prediction tools has been an important aspect of open rotor research efforts. This paper describes validation efforts of a combined computational fluid dynamics and Ffowcs Williams and Hawkings equation methodology for open rotor aeroacoustic modeling. Performance and acoustic predictions were made for a benchmark open rotor blade set and compared with measurements over a range of rotor speeds and observer angles. Overall, the results indicate that the computational approach is acceptable for assessing low-noise open rotor designs. Additionally, this approach may be used to provide realistic incident source fields for acoustic shielding/scattering studies on various aircraft configurations.
Directory of Open Access Journals (Sweden)
Adilson Pacheco de Souza
2010-04-01
Full Text Available O objetivo deste trabalho foi avaliar o desempenho de modelos isotrópicos de estimativa do total de radiação incidente em superfícies inclinadas e propor estimativas com base nas correlações entre os índices de claridade horizontais e inclinados, em diferentes condições de cobertura de céu, em Botucatu, SP. Foram avaliadas superfícies com inclinação de 12,85º, 22,85º e 32,85º, pelos modelos isotrópicos propostos por Liu & Jordan, Revfeim, Jimenez & Castro, Koronakis, a teoria Circunsolar, e a correlação entre os índices de claridade horizontais e inclinados, para diferentes condições de cobertura de céu. O banco de dados de radiação global utilizado corresponde ao período de 1998 a 2007, com intervalos de 4/1998 a 8/2001 para a inclinação de 22,85º, de 9/2001 a 2/2003 para 12,85º e de 1/2004 a 12/2007 para 32,85º. O desempenho dos modelos foi avaliado pelos indicadores estatísticos erro absoluto médio, raiz quadrada do quadrado médio do erro e índice "d" de Wilmott. Os modelos de Liu & Jordan, Koronakis e de Revfeim apresentaram os melhores desempenhos em dias nublados, em todas as inclinações. As coberturas de céu parcialmente difuso e parcialmente aberto, nos maiores ângulos de inclinação, apresentaram as maiores dispersões entre valores estimados e medidos, independentemente do modelo. As equações estatísticas apresentaram bons resultados em aplicações com agrupamentos de dados mensais.The objective of this work was to evaluate the performance of isotropic models estimative of the global radiation on tilted surfaces and to propose estimations based on correlation between the clearness index for horizontal and tilted surfaces, for different sky conditions, in Botucatu, SP, Brazil. The isotropic model proposed by Liu & Jordan, Revfeim, Jimenez & Castro, Koronakis, the Circunsolar theory and the correlation between the clearness index for horizontal and tilted surfaces, for different sky conditions
A New Sensorless MRAS Based on Active Power Calculations for Rotor Position Estimation of a DFIG
Directory of Open Access Journals (Sweden)
Gil Domingos Marques
2011-01-01
Full Text Available 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 quantity in function of electromotive forces and rotor currents that are measurable on the rotor position, which is under estimation. The method does not need any information about the stator or rotor flux and can be implemented in the rotor or in the stator reference frames with a hysteresis or with a PI controller. The stability analysis gives an unstable region on the rotor current dq plane. Simulation and experimental results show that the method is appropriate for the vector control of the doubly fed induction machine under the stability region.
DEFF Research Database (Denmark)
Venturoli, M.; Smit, B.; Sperotto, Maria Maddalena
2005-01-01
in membranes, we considered proteins of different hydrophobic length ( as well as different sizes). We studied the cooperative behavior of the lipid-protein system at mesoscopic time-and lengthscales. In particular, we correlated in a systematic way the protein-induced bilayer perturbation, and the lipid......Biological membranes are complex and highly cooperative structures. To relate biomembrane structure to their biological function it is often necessary to consider simpler systems. Lipid bilayers composed of one or two lipid species, and with embedded proteins, provide a model system for biological...... membranes. Here we present a mesoscopic model for lipid bilayers with embedded proteins, which we have studied with the help of the dissipative particle dynamics simulation technique. Because hydrophobic matching is believed to be one of the main physical mechanisms regulating lipid-protein interactions...
Heat transfer in rotor/stator cavity
Tuliszka-Sznitko, Ewa; Majchrowski, Wojciech; Kiełczewski, Kamil
2011-12-01
In the paper we analyze the results of DNS/LES of the flow with heat transfer in the rotor/stator cavity. The rotor and the outer cylinder are heated. Computations have been performed for wide range of Reynolds numbers and aspect ratios. Computations are based on the efficient pseudo-spectral Chebyshev-Fourier method. In LES we used a Lagrangian dynamic subgrid-scale model of turbulence. Analysis allowed to check the influence of the aspect ratio and Reynolds number on the statistics and the structure of the flow. We analyzed all six Reynolds stress tensor components, turbulent fluctuations, three turbulent heat fluxes and different structural parameters which can be useful for modeling purposes. The distributions of Nusselt numbers obtained for different Re and aspect rations along disks are given. We also investigated influence of thermal Rosssby number as well as distributions of temperature along heated disk on statistics. Computations have shown that turbulence is mostly concentrated in the stator boundary layer with a maximum at the junction between the stator and the outer cylinder. The results are compared to the experimental and numerical data taken from literature.
Quad-rotor flight path energy optimization
Kemper, Edward
Quad-Rotor unmanned areal vehicles (UAVs) have been a popular area of research and development in the last decade, especially with the advent of affordable microcontrollers like the MSP 430 and the Raspberry Pi. Path-Energy Optimization is an area that is well developed for linear systems. In this thesis, this idea of path-energy optimization is extended to the nonlinear model of the Quad-rotor UAV. The classical optimization technique is adapted to the nonlinear model that is derived for the problem at hand, coming up with a set of partial differential equations and boundary value conditions to solve these equations. Then, different techniques to implement energy optimization algorithms are tested using simulations in Python. First, a purely nonlinear approach is used. This method is shown to be computationally intensive, with no practical solution available in a reasonable amount of time. Second, heuristic techniques to minimize the energy of the flight path are tested, using Ziegler-Nichols' proportional integral derivative (PID) controller tuning technique. Finally, a brute force look-up table based PID controller is used. Simulation results of the heuristic method show that both reliable control of the system and path-energy optimization are achieved in a reasonable amount of time.
Directory of Open Access Journals (Sweden)
Pierre Tchakoua
2015-09-01
Full Text Available Models are crucial in the engineering design process because they can be used for both the optimization of design parameters and the prediction of performance. 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. The proposed model was built from the mechanical description given by the Paraschivoiu double-multiple streamtube model and is based on the analogy between mechanical and electrical circuits. This work addresses the physical concepts and theoretical formulations underpinning the development of the model. After highlighting the working principle of the DTVAWT, the step-by-step development of the model is presented. For assessment purposes, simulations of aerodynamic characteristics and those of corresponding electrical components are performed and compared.
Mancuso, Peter Timothy
Fixed-wing unmanned aerial vehicles (UAVs) that offer vertical takeoff and landing (VTOL) and forward flight capability suffer from sub-par performance in both flight modes. Achieving the next generation of efficient hybrid aircraft requires innovations in: (i) power management, (ii) efficient structures, and (iii) control methodologies. Existing hybrid UAVs generally utilize one of three transitioning mechanisms: an external power mechanism to tilt the rotor-propulsion pod, separate propulsion units and rotors during hover and forward flight, or tilt body craft (smaller scale). Thus, hybrid concepts require more energy compared to dedicated fixed-wing or rotorcraft UAVs. Moreover, design trade-offs to reinforce the wing structure (typically to accommodate the propulsion systems and enable hover, i.e. tilt-rotor concepts) adversely impacts the aerodynamics, controllability and efficiency of the aircraft in both hover and forward flight modes. The goal of this research is to develop more efficient VTOL/ hover and forward flight UAVs. In doing so, the transition sequence, transition mechanism, and actuator performance are heavily considered. A design and control methodology was implemented to address these issues through a series of computer simulations and prototype benchtop tests to verify the proposed solution. Finally, preliminary field testing with a first-generation prototype was conducted. The methods used in this research offer guidelines and a new dual-arm rotor UAV concept to designing more efficient hybrid UAVs in both hover and forward flight.
Profile stabilization of tilt mode in a Field Reversed Configuration
Energy Technology Data Exchange (ETDEWEB)
Cobb, J.W.; Tajima, T. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies; Barnes, D.C. [Los Alamos National Lab., NM (United States)
1993-06-01
The possibility of stabilizing the tilt mode in Field Reversed Configurations without resorting to explicit kinetic effects such as large ion orbits is investigated. Various pressure profiles, P({Psi}), are chosen, including ``hollow`` profiles where current is strongly peaked near the separatrix. Numerical equilibria are used as input for an initial value simulation which uses an extended Magnetohydrodynamic (MHD) model that includes viscous and Hall terms. Tilt stability is found for specific hollow profiles when accompanied by high values of separatrix beta, {beta}{sub sep}. The stable profiles also have moderate to large elongation, racetrack separatrix shape, and lower values of 3, average ratio of Larmor radius to device radius. The stability is unaffected by changes in viscosity, but the neglect of the Hall term does cause stable results to become marginal or unstable. Implications for interpretation of recent experiments are discussed.
TILT-BASED PREDICTIVE TEXT INPUT CONCEPT FOR MOBILE DEVICES
Directory of Open Access Journals (Sweden)
Marcin Badurowicz
2017-06-01
Full Text Available In the paper authors are introducing the concept of usage of physical orientation of a mobile device, calculated using built-in environmental sensors like accelerometer, gyroscope and magnetometer for detection of tilting gesture. This gesture is used as an acceptance factor for the two next probable word solutions suggested to the user during text input. By performing the device tilt, the first or second word is being automatically put into the desired text field and new prediction is performed. The text predictions are calculated and stored directly on the device to maintain privacy protection. The founding concept of the software is being presented, as well as initial considerations and further plans. This solution is recommended especially to smartphone manufacturers like Microsoft, Samsung and Apple to deploy in their latest models.
Pulse Front Tilt and Laser Plasma Acceleration
Mittelberger, Daniel; Thévenet, Maxence; Nakamura, Kei; Lehe, Remi; Gonsalves, Anthony; Benedetti, Carlo; Leemans, Wim
2017-10-01
Pulse front tilt (PFT) is potentially present in any CPA laser system, but its effects may be overlooked because spatiotemporal pulse characterization is considerably more involved than measuring only spatial or temporal profile. PFT is particularly important for laser plasma accelerators (LPA) because it influences electron beam injection and steering. In this work, experimental results from the BELLA Center will be presented that demonstrate the effect of optical grating misalignment and optical compression, resulting in PFT, on accelerator performance. Theoretical models of laser and electron beam steering will be introduced based on particle-in-cell simulations showing distortion of the plasma wake. Theoretical predictions will be compared with experiments and complimentary simulations, and tolerances on PFT and optical compressor alignment will be developed as a function of LPA performance requirements. This work was supported by the Office of High Energy Physics, Office of Science, US Department of Energy under Contract DE-AC02-05CH11231 and the National Science Foundation under Grant PHY-1415596.
Rotor Rolling over a Water-Lubricated Bearing
Shatokhin, V. F.
2018-02-01
The article presents the results of studying the effect of forces associated with secondary damping coefficients (gyroscopic forces) on the development of asynchronous rolling of the rotor over a water-lubricated bearing. The damping forces act against the background of other exciting forces in the rotor-supports system, in particular, the exciting forces of contact interaction between the rotor and bearing. The article considers a rotor resting on supports rubbing against the bearing and the occurrence of self-excited vibration in the form of asynchronous roll-over. The rotor supports are made in the form of plain-type water-lubricated bearings. The plain-type bearing's lubrication stiffness and damping forces are determined using the wellknown algorithms taking into account the physical properties of water serving as lubrication of the bearing. The bearing sliding pair is composed of refractory materials. The lubrication layer in such bearings is thinner than that used in oil-lubricated bearings with white metal lining, and there is no white metal layer in waterlubricated bearings. In case of possible deviations from normal operation of the installation, the rotating rotor comes into direct contact with the liner's rigid body. Unsteady vibrations are modeled using a specially developed software package for calculating the vibration of rotors that rub against the turbine (pump) stator elements. The stiffness of the bearing liner with the stator support structure is specified by a dependence in the force-deformation coordinate axes. In modeling the effect of damping forces, the time moment corresponding to the onset of asynchronous rolling-over with growing vibration amplitudes is used as the assessment criterion. With a longer period of time taken for the rolling-over to develop, it becomes possible to take the necessary measures in response to actuation of the equipment set safety system, which require certain time for implementing them. It is shown that the
Development of Precision Rotor Experiment for Matter Creation Test.
Jones, George Robert, Jr.
An apparatus designed to test for spontaneous matter creation by the spin-down of an ultra-low friction precision rotor has been made functional and tested extensively. Modifications to an earlier system allow true corotation of the gas atmosphere around the inner test rotor while removing a previous dynamic type of coupling-"cranking" by the rotating magnetic suspension. A computerized data acquisition system allows for the gathering of huge amounts of information on these precisions rotations. Inherent limits, however, make it unlikely that this room temperature model can reach a target rate of m/m = 10('-10) yr('-1). The sensitivity of this realization of the experiment for yielding an estimate of matter creation is presently limited by a torsional coupling between the inner rotor and corotating vacuum chamber which was persistent, and which caused an oscillation in the angular position of the rotor with respect to the chamber while rotating. The focus of the present study was therefore on how various physical conditions, such as magnetic, thermal, and acoustic shielding, affected the properties of this oscillation. Oscillation properties of interest included the amplitude of the oscillation, and its minimum residual noise level of excitation, the period of the oscillation, and the drift in the average relative position between the rotor and the rotating vacuum chamber. The minimum residual amplitude of the 28 min oscillation was (TURN)0.5(DEGREES), which for this rotor, with a 3 s rotational period, corresponds to 7.6 x 10(' -7) erg, 10('-10) of the rotational energy. The decay rate of the energy of the oscillation approaching this level is (TURN)10('-19) W. The ability of the measurements to imply matter exchange or creation was in addition limited by inordinately high thermal drifts. Information on much of the behavior of the corotations was obtained, however, and several concrete suggestions can be made for large -scale improvements in sensitivity to m/m.
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
A Survey of Theoretical and Experimental Coaxial Rotor Aerodynamic Research
Coleman, Colin P.
1997-01-01
The recent appearance of the Kamov Ka-50 helicopter and the application of coaxial rotors to unmanned aerial vehicles have renewed international interest in the coaxial rotor configuration. This report addresses the aerodynamic issues peculiar to coaxial rotors by surveying American, Russian, Japanese, British, and German research. (Herein, 'coaxial rotors' refers to helicopter, not propeller, rotors. The intermeshing rotor system was not investigated.) Issues addressed are separation distance, load sharing between rotors, wake structure, solidity effects, swirl recovery, and the effects of having no tail rotor. A general summary of the coaxial rotor configuration explores the configuration's advantages and applications.
Influence of Turbine and Compressor Wheel Mass and Inertia on the Rotor Dynamics of Turbocharger
Directory of Open Access Journals (Sweden)
J. Knotek
2016-03-01
Full Text Available This paper describes the influence of the compressor and turbine wheel mass and inertia change on the turbocharger rotor dynamics. The model of the turbocharger is presented, the hydrodynamic model of the journal bearing is described and assembly of the whole model in MBS is also presented. The article presents various results describing rotor dynamics on which the influence of compressor and turbine wheel mass and inertia change is discussed.
Analysis of fixed tilt and sun tracking photovoltaic–micro wind based hybrid power systems
International Nuclear Information System (INIS)
Sinha, Sunanda; Chandel, S.S.
2016-01-01
Graphical abstract: 6 kW p photovoltaic–micro wind based hybrid power system analysis in a Indian Western Himalayan location. - Highlights: • Power generation by a roof mounted photovoltaic–micro wind hybrid system is explored. • Optimum hybrid configurations using fixed and sun tracking photovoltaic systems are determined. • Analysis of hybrid systems with optimally tilted and different sun tracking systems is presented. • Two axis sun tracking systems are found to generate 4.88–26.29% more energy than fixed tilt system. • Hybrid system installed at optimum tilt angle is found to be cost effective than a sun tracking system. - Abstract: In this study fixed tilt and sun tracking photovoltaic based micro wind hybrid power systems are analyzed along with determining the optimum configurations for a 6 kW p roof mounted micro wind based hybrid system using fixed and tracking photovoltaic systems to enhance the power generation potential in a low windy Indian hilly terrain with good solar resource. The main objective of the study is to enhance power generation by focusing on photovoltaic component of the hybrid system. A comparative power generation analysis of different configurations of hybrid systems with fixed tilt, monthly optimum tilt, yearly optimum tilt and 6 different sun tracking photovoltaic systems is carried out using Hybrid Optimization Model for Electric Renewables. Monthly and seasonal optimum tilt angles determined for the location vary between 0° and 60° with annual optimum tilt angle as 29.25°. The optimum configurations for all sun tracking systems except for the two axis tracking system is found to be 7 kW p photovoltaic system, one 5 kW p wind turbine, 10 batteries and a 2 kW p inverter. The optimum configuration for two axis tracking system and two types of fixed tilt systems, is found to be a 8 kW p photovoltaic system, one 5 kW p wind turbine, 10 batteries and a 2 kW p inverter. The results show that horizontal axis with
Theoretical study of simultaneous water and VOCs adsorption and desorption in a silica gel rotor
DEFF Research Database (Denmark)
Zhang, G.; Zhang, Y.F.; Fang, Lei
2008-01-01
One-dimensional partial differential equations were used to model the simultaneous water and VOC (Volatile Organic Compound) adsorption and desorption in a silica gel rotor which was recommended for indoor air cleaning. The interaction among VOCs and moisture in the adsorption and desorption...... be prolonged to allow complete removal of the VOC pollutants from the rotor. The regeneration temperature designed for dehumidification provides considerable efficiency for indoor air cleaning. The application of the model in estimating the cleaning capacity of the rotor for VOC pollutants was demonstrated....
The impact of gravity during head-up tilt
DEFF Research Database (Denmark)
Ottesen, Johnny T.; Olufsen, Mette; Smith, Brittany
2011-01-01
and the carotid sinuses in a healthy volunteer. During head-up tilt the head is lifted above the heart stimulating gravitational pooling of blood in the lower extremities. This shift in volume is followed by an increase in blood pressure in the lower body, while the pressure in the head decreases, while...... a model predicting hydrostatic height between the two locations. Results from this model were compared with measurements. Furthermore, we show, using a differential equations model predicting blood pressure, that it is possible to predict blood pressure measured at the level of the carotid sinuses using...
Reducing friction in tilting-pad bearings by the use of enclosed recesses
DEFF Research Database (Denmark)
Heinrichson, Niels; Santos, Ilmar
2008-01-01
A three-dimensional thermoelastohydrodynamic model is applied to the analysis of tilting-pad bearings with spherical pivots and equipped with deep recesses in the high-pressure regions. A potential for a 10-20% reduction in the friction loss compared to conventional plain bearing pads is documented....... Design suggestions minimizing the power loss are given for various length-to-width ratios. The tilting angle in the sliding direction is more sensitive to correct positioning of the pivot point than conventional bearing pads. Improving the performance by equipping a tilting-pad bearing with a deep recess...... therefore requires accurate analysis and design of the bearing. Similarly, a high sensitivity perpendicular to the sliding direction suggests that this method of reducing friction is more feasible when using line pivots or spring beds than when using spherical pivots for controlling the tilting angle....
FUN3D Airload Predictions for the Full-Scale UH-60A Airloads Rotor in a Wind Tunnel
Lee-Rausch, Elizabeth M.; Biedron, Robert T.
2013-01-01
An unsteady Reynolds-Averaged Navier-Stokes solver for unstructured grids, FUN3D, is used to compute the rotor performance and airloads of the UH-60A Airloads Rotor in the National Full-Scale Aerodynamic Complex (NFAC) 40- by 80-foot Wind Tunnel. The flow solver is loosely coupled to a rotorcraft comprehensive code, CAMRAD-II, to account for trim and aeroelastic deflections. Computations are made for the 1-g level flight speed-sweep test conditions with the airloads rotor installed on the NFAC Large Rotor Test Apparatus (LRTA) and in the 40- by 80-ft wind tunnel to determine the influence of the test stand and wind-tunnel walls on the rotor performance and airloads. Detailed comparisons are made between the results of the CFD/CSD simulations and the wind tunnel measurements. The computed trends in solidity-weighted propulsive force and power coefficient match the experimental trends over the range of advance ratios and are comparable to previously published results. Rotor performance and sectional airloads show little sensitivity to the modeling of the wind-tunnel walls, which indicates that the rotor shaft-angle correction adequately compensates for the wall influence up to an advance ratio of 0.37. Sensitivity of the rotor performance and sectional airloads to the modeling of the rotor with the LRTA body/hub increases with advance ratio. The inclusion of the LRTA in the simulation slightly improves the comparison of rotor propulsive force between the computation and wind tunnel data but does not resolve the difference in the rotor power predictions at mu = 0.37. Despite a more precise knowledge of the rotor trim loads and flight condition, the level of comparison between the computed and measured sectional airloads/pressures at an advance ratio of 0.37 is comparable to the results previously published for the high-speed flight test condition.
Preliminary analysis of turbochargers rotors dynamic behaviour
Monoranu, R.; Ştirbu, C.; Bujoreanu, C.
2016-08-01
Turbocharger rotors for the spark and compression ignition engines are resistant steels manufactured in order to support the exhaust gas temperatures exceeding 1200 K. In fact, the mechanical stress is not large as the power consumption of these systems is up to 10 kW, but the operating speeds are high, ranging between 30000 ÷ 250000 rpm. Therefore, the correct turbochargers functioning involves, even from the design stage, the accurate evaluation of the temperature effects, of the turbine torque due to the engine exhaust gases and of the vibration system behaviour caused by very high operating speeds. In addition, the turbocharger lubrication complicates the model, because the classical hydrodynamic theory cannot be applied to evaluate the floating bush bearings. The paper proposes a FEM study using CATIA environment, both as modeling medium and as tool for the numerical analysis, in order to highlight the turbocharger complex behaviour. An accurate design may prevent some major issues which can occur during its operation.
Rotors fault detection using vibration methods
Directory of Open Access Journals (Sweden)
Andrzej GRZADZIELA
2009-01-01
Full Text Available Ships’ propulsion plant usually works in a hard environment caused by static forces and permanent dynamic loads. Basic elements of propulsion systems are rotation machines like gas turbine engines, gear boxes, propulsion shafts etc. Another loads coming from technological faults of rotation machines like misalignment, unbalancing or resonance. Exciding of tolerated values of shaft alignments or unbalancing can cause a damage of radial and thrust bearings in relative short time. Similar situation is occurred when the mode or modes of rotors natural resonances are in the range of operational speed. The paper compares three methods of calculating and recognizing modes of rotors’ natural frequencies using laboratory model of rotational machine. Results of FEM modeling, modal hammers measurements and synchronous vibration measurement show that free stop-down process is an interesting area for the vibration diagnosing of rotational machines.
Energy from Swastika-Shaped Rotors
Directory of Open Access Journals (Sweden)
McCulloch M. E.
2015-04-01
Full Text Available It is suggested here that a swastika-shaped rotor exposed to waves will rotate in the di- rection its arms are pointing (towards the arm-tips due to a sheltering effect. A formula is derived to predict the motion obtainable from swastika rotors of different sizes given the ocean wave height and phase speed and it is suggested that the rotor could provide a new, simpler method of wave energy generation. It is also proposed that the swastika rotor could generate energy on a smaller scale from sound waves and Brownian motion, and potentially the zero point field.
Variable Speed Rotor System, Phase I
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...
Balancing High-Speed Rotors at Low Speed
Giordano, J.; Zorzi, E.
1986-01-01
Flexible balancing reduces vibrations at operating speeds. Highspeed rotors in turbomachines dynamically balanced at fraction of operating rotor speed. New method takes into account rotor flexible rather than rigid.
Quantum molecular dynamics of methyl rotors in peptide links
International Nuclear Information System (INIS)
Del-Mar, Jon
2002-01-01
A particles wavefunction extends beyond the classically accessible regions of the potential energy surface. Quantum mechanical tunnelling is the result of this partial delocalisation, which enables the surpassing of classically inaccessible potential barriers. A particles mass is an important aspect, reflecting the tunnelling probability; a consequence of this is that a proton is ideally suited to this behaviour. Symmetrical molecular rotors such as Ch 3 provide a clear example of quantum mechanical tunnelling, seen in their motional spectrum. The advantage of the methyl rotor is that it's found in a wide range of organic compounds, giving a wide range in hindering potentials. It is effectively a proton rotor, and is easily observed using techniques such as Nuclear Magnetic Resonance (NMR), and Inelastic Neutron Scattering (INS). Both NMR and INS techniques are sensitive to molecular motion, and as they measure the tunnel frequencies in different energy windows, are complementary. Of central importance to many biological processes and structures is the peptide unit, -CONH-. Of particular significance are the intermolecular networks that are often formed by the NHO hydrogen bonds, the peptide links. The molecules were chosen for the research in this thesis to form a tractable model for polypeptides and alpha-helix proteins. Methyl rotor tunnelling frequencies have been used, which are very sensitive to the potential energy surface, as a probe of the electronic and molecular structure associated with the peptide links. Quantum chemistry calculations were then utilized to connect experiments to theory to learn about the hydrogen bond. (author)
Loss of efficiency in a coaxial arrangement of a pair of wind rotors
DEFF Research Database (Denmark)
Okulov, V. L.; Naumov, I. V.; Tsoy, M. A.
2017-01-01
The efficiency of a pair of wind turbines is experimentally investigated for the case when the model of the second rotor is coaxially located in the wake of the first one. This configuration implies the maximum level of losses in wind farms, as in the rotor wakes, the deceleration of the freestream...... is maximum. As a result of strain gauge measurements, the dependences of dimensionless power characteristics of both rotors on the distances between them were determined for different modes at different tip speed ratios. The obtained results are of interest for further development of aerodynamics of wind...
Deflection Shape Reconstructions of a Rotating Five-blade Helicopter Rotor from TLDV Measurements
International Nuclear Information System (INIS)
Fioretti, A.; Castellini, P.; Tomasini, E. P.; Di Maio, D.; Ewins, D. J.
2010-01-01
Helicopters are aircraft machines which are subjected to high level of vibrations, mainly due to spinning rotors. These are made of two or more blades attached by hinges to a central hub, which can make the dynamic behaviour difficult to study. However, they share some common dynamic properties with the ones expected in bladed discs, thereby the analytical modelling of rotors can be performed using some assumptions as the ones adopted for the bladed discs. This paper presents results of a vibrations study performed on a scaled helicopter rotor model which was rotating at a fix rotational speed and excited by an air jet. A simplified analytical model of that rotor was also produced to help the identifications of the vibration patterns measured using a single point tracking-SLDV measurement method.
Spatial coherence profilometry on tilted surfaces
Czech Academy of Sciences Publication Activity Database
Pavlíček, Pavel; Halouzka, M.; Duan, Z.; Takeda, M.
2009-01-01
Roč. 48, č. 34 (2009), H40-H47 ISSN 0003-6935 R&D Projects: GA MŠk(CZ) 1M06002 Institutional research plan: CEZ:AV0Z10100522 Keywords : tilted surface * spatial coherence profilometry * spatial coherence * measurement error * shape measurement Subject RIV: BH - Optics, Masers, Lasers Impact factor: 1.410, year: 2009
"Happiness and Education": Tilting at Windmills?
Verducci, Susan
2013-01-01
This essay explores the question: Is Nel Noddings a visionary who sees past the constraints of contemporary education or is she, like Don Quixote, madly tilting at windmills in her description and defense of happiness as an educational aim? Viewing the educational aim of happiness as an ideal raises substantial challenges for the practicality of…
Effect of manual tilt adjustments on incident irradiance on fixed and tracking solar panels
International Nuclear Information System (INIS)
Lubitz, William David
2011-01-01
Hourly typical meteorological year (TMY3) data was utilized with the Perez radiation model to simulate solar radiation on fixed, azimuth tracking and two axis tracking surfaces at 217 geographically diverse temperate latitude sites across the contiguous United States of America. The optimum tilt angle for maximizing annual irradiation on a fixed south-facing panel varied from being equal to the latitude at low-latitude, high clearness sites, to up to 14 o less than the latitude at a north-western coastal site with very low clearness index. Across the United States, the optimum tilt angle for an azimuth tracking panel was found to be on average 19 o closer to vertical than the optimum tilt angle for a fixed, south-facing panel at the same site. Azimuth tracking increased annual solar irradiation incident on a surface by an average of 29% relative to a fixed south-facing surface at optimum tilt angle. Two axis tracking resulted in an average irradiation increase of 34% relative to the fixed surface. Introduction of manual surface tilt changes during the year produced a greater impact for non-tracking surfaces than it did for azimuth tracking surfaces. Even monthly tilt changes only resulted in an average annual irradiation increase of 5% for fixed panels and 1% for azimuth tracked surfaces, relative to using a single optimized tilt angle in each case. In practice, the decision whether to manually tilt panels requires balancing the added cost in labor and the panel support versus the extra energy generation and the cost value of that energy. A spreadsheet file is available that gives individual results for each of the 217 simulated sites.
A novel method of measuring spatial rotation angle using MEMS tilt sensors
International Nuclear Information System (INIS)
Cao, Jian’an; Zhu, Xin; Zhang, Leping; Wu, Hao
2017-01-01
This paper presents a novel method of measuring spatial rotation angle with a dual-axis micro-electro-mechanical systems tilt sensor. When the sensor is randomly mounted on the surface of the rotating object, there are three unpredictable and unknown mounting position parameters: α , the sensor’s swing angle on the measuring plane; β , the angle between the rotation axis and the horizontal plane; and γ , the angle between the measuring plane and the rotation axis. Thus, the sensor’s spatial rotation model is established to describe the relationship between the measuring axis, rotation axis, and horizontal plane, and the corresponding analytical equations are derived. Furthermore, to eliminate the deviation caused by the uncertain direction of the rotation axis, an extra perpendicularly mounted, single-axis tilt sensor is combined with the dual-axis tilt sensor, forming a three-axis tilt sensor. Then, by measuring the sensors’ three tilts and solving the model’s equations, the object’s spatial rotation angle is obtained. Finally, experimental results show that the developed tilt sensor is capable of measuring spatial rotation angle in the range of ±180° with an accuracy of 0.2° if the angle between the rotation axis and the horizontal plane is less than 75°. (paper)
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.
Study of the Effect of Centrifugal Force on Rotor Blade Icing Process
Directory of Open Access Journals (Sweden)
Zhengzhi Wang
2017-01-01
Full Text Available In view of the rotor icing problems, the influence of centrifugal force on rotor blade icing is investigated. A numerical simulation method of three-dimensional rotor blade icing is presented. Body-fitted grids around the rotor blade are generated using overlapping grid technology and rotor flow field characteristics are obtained by solving N-S equations. According to Eulerian two-phase flow, the droplet trajectories are calculated and droplet impingement characteristics are obtained. The mass and energy conservation equations of ice accretion model are established and a new calculation method of runback water mass based on shear stress and centrifugal force is proposed to simulate water flow and ice shape. The calculation results are compared with available experimental results in order to verify the correctness of the numerical simulation method. The influence of centrifugal force on rotor icing is calculated. The results show that the flow direction and distribution of liquid water on rotor surfaces change under the action of centrifugal force, which lead to the increasing of icing at the stagnation point and the decreasing of icing on both frozen limitations.
Ueno, Yutaka; Mine, Shouhei; Kawasaki, Kazunori
2015-04-01
In this article, we describe an improved method to assign the projection angle for averaged images using tilt-pair images for three-dimensional reconstructions from randomly oriented single-particle molecular images. Our study addressed the so-called 'initial volume problem' in the single-particle reconstruction, which involves estimation of projection angles of the particle images. The projected images of the particles in different tilt observations were mixed and averaged for the characteristic views. After the ranking of these group average images in terms of reliable tilt angle information, mutual tilt angles between images are assigned from the constituent tilt-pair information. Then, multiples of the conical tilt series are made and merged to construct a network graph of the particle images in terms of projection angles, which are optimized for the three-dimensional reconstruction. We developed the method with images of a synthetic object and applied it to a single-particle image data set of the purified deacetylase from archaea. With the introduction of low-angle tilt observations to minimize unfavorable imaging conditions due to tilting, the results demonstrated reasonable reconstruction models without imposing symmetry to the structure. This method also guides its users to discriminate particle images of different conformational state of the molecule. © The Author 2015. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
Rotor theories by Professor Joukowsky: Momentum theories
DEFF Research Database (Denmark)
van Kuik, G. A. M.; Sørensen, Jens Nørkær; Okulov, V. L.
2015-01-01
This paper is the first of two papers on the history of rotor aerodynamics with special emphasis on the role of Joukowsky. The present one focuses on the development of the momentum theory while the second one surveys the development of vortex theory for rotors. Joukowsky has played a major role ...
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)
High-Temperature Hybrid Rotor Support System Developed
Montague, Gerald T.
2004-01-01
The Army Research Laboratory Vehicle Technology Directorate and the NASA Glenn Research Center demonstrated a unique high-speed, high-temperature rotor support system in September 2003. Advanced turbomachinery is on its way to surpassing the capabilities of rolling-element bearings and conventional dampers. To meet these demands, gas turbine engines of the future will demand increased efficiency and thrust-to-weight ratio, and reduced specific fuel consumption and noise. The more-electric engine replaces oil-lubricated bearings, dampers, gears, and seals with electrical devices. One such device is the magnetic bearing. The Vehicle Technology Directorate and Glenn have demonstrated the operation of a radial magnetic bearing in combination with a hydrostatic bearing at 1000 F at 31,000 rpm (2.3 MDN1). This unique combination takes advantage of a high-temperature rub surface in the event of electrical power loss or sudden overloads. The hydrostatic bearings allow load sharing with the magnetic bearing. The magnetic-hydrostatic bearing combination eliminates wear and high contact stress from sudden acceleration of the rolling-element bearings and overheating. The magnetic bearing enables high damping, adaptive vibration control, and precise rotor positioning, diagnostics, and health monitoring. A model of the test facility used at Glenn for this technology demonstration is shown. A high-temperature heteropolar radial magnetic bearing is located at the center of gravity of the test rotor. There is a 0.022-in. radial air gap between the rotor and stator. Two rub surface hydrostatic bearings were placed on either side of the magnetic bearing. The rotor is supported by a 0.002-in. hydrostatic air film and the magnetic field. The prototype active magnetic bearing cost $24,000 to design and fabricate and a set of four high temperature, rub-surface, hydrostatic bearings cost $28,000. This work was funded by the Turbine-Based Combined Cycle program.
Rotor speed estimation for indirect stator flux oriented induction motor drive based on MRAS scheme
Directory of Open Access Journals (Sweden)
Youssef Agrebi
2007-09-01
Full Text Available In this paper, a conventional indirect stator flux oriented controlled (ISFOC induction motor drive is presented. In order to eliminate the speed sensor, an adaptation algorithm for tuning the rotor speed is proposed. Based on the model reference adaptive system (MRAS scheme, the rotor speed is tuned to obtain an exact ISFOC induction motor drive. The reference and adjustable models, developed in stationary stator reference frame, are used in the MRAS scheme to estimate induction rotor peed from measured terminal voltages and currents. The IP gains speed controller and PI gains current controller are calculated and tuned at each sampling time according to the new estimated rotor speed. The proposed algorithm has been tested by numerical simulation, showing the capability of driving active load; and stability is preserved. Experimental results obtained with a general-purpose 1-kW induction machine are presented showing the effectiveness of the proposed approach in terms of dynamic performance.
Mechanisms of Günther Tulip filter tilting during transfemoral placement.
Matsui, Y; Horikawa, M; Ohta, K; Jahangiri Noudeh, Y; Kaufman, J A; Farsad, K
The purpose of this study was to characterize the mechanisms of Günther Tulip filter (GTF) tilting during transfemoral placement in an experimental model with further validation in a clinical series. In an experimental study, 120 GTF placements in an inferior vena cava (IVC) model were performed using 6 configurations of pre-deployment filter position. The angle between the pre-deployment filter axis and IVC axis, and the proximity of the constrained filter legs to IVC wall prior to deployment were evaluated. The association of those pre-deployment factors with post-deployment filter tilting was analyzed. The association noted in the experimental study was then evaluated in a retrospective clinical series of 21 patients. In the experimental study, there was a significant association between the pre-deployment angle and post-deployment filter tilting (P<0.0001). With a low pre-deployment angle (≤5°), a significant association was noted between filter tilting and the proximity of the constrained filter legs to the far IVC wall (P=0.001). In a retrospective clinical study, a significant association between the pre-deployment angle and post-deployment filter tilting was also noted with a linear regression model (P=0.026). Significant association of the pre-deployment angle with post-deployment GTF tilting was shown in both the experimental and clinical studies. The experimental study also showed that proximity of filter legs is relevant when pre-deployment angle is small. Addressing these factors may result in a lower incidence of filter tilting. Copyright © 2017 Editions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.
Francis, Patrick; Martinez, D Mark; Taghipour, Fariborz; Bowen, Bruce D; Haynes, Charles A
2006-12-20
Controlled shear affinity filtration (CSAF) is a novel integrated processing technology that positions a rotor directly above an affinity membrane chromatography column to permit protein capture and purification directly from cell culture. The conical rotor is intended to provide a uniform and tunable shear stress at the membrane surface that inhibits membrane fouling and cell cake formation by providing a hydrodynamic force away from and a drag force parallel to the membrane surface. Computational fluid dynamics (CFD) simulations are used to show that the rotor in the original CSAF device (Vogel et al., 2002) does not provide uniform shear stress at the membrane surface. This results in the need to operate the system at unnecessarily high rotor speeds to reach a required shear stress of at least 0.17 Pa at every radial position of the membrane surface, compromising the scale-up of the technology. Results from CFD simulations are compared with particle image velocimetry (PIV) experiments and a numerical solution for low Reynolds number conditions to confirm that our CFD model accurately describes the hydrodynamics in the rotor chamber of the CSAF device over a range of rotor velocities, filtrate fluxes, and (both laminar and turbulent) retentate flows. CFD simulations were then carried out in combination with a root-finding method to optimize the shape of the CSAF rotor. The optimized rotor geometry produces a nearly constant shear stress of 0.17 Pa at a rotational velocity of 250 rpm, 60% lower than the original CSAF design. This permits the optimized CSAF device to be scaled up to a maximum rotor diameter 2.5 times larger than is permissible in the original device, thereby providing more than a sixfold increase in volumetric throughput. Copyright 2006 Wiley Periodicals, Inc.
Open Rotor - Analysis of Diagnostic Data
Envia, Edmane
2011-01-01
NASA is researching open rotor propulsion as part of its technology research and development plan for addressing the subsonic transport aircraft noise, emission and fuel burn goals. The low-speed wind tunnel test for investigating the aerodynamic and acoustic performance of a benchmark blade set at the approach and takeoff conditions has recently concluded. A high-speed wind tunnel diagnostic test campaign has begun to investigate the performance of this benchmark open rotor blade set at the cruise condition. Databases from both speed regimes will comprise a comprehensive collection of benchmark open rotor data for use in assessing/validating aerodynamic and noise prediction tools (component & system level) as well as providing insights into the physics of open rotors to help guide the development of quieter open rotors.
Substantially parallel flux uncluttered rotor machines
Hsu, John S.
2012-12-11
A permanent magnet-less and brushless synchronous system includes a stator that generates a magnetic rotating field when sourced by polyphase alternating currents. An uncluttered rotor is positioned within the magnetic rotating field and is spaced apart from the stator. An excitation core is spaced apart from the stator and the uncluttered rotor and magnetically couples the uncluttered rotor. The brushless excitation source generates a magnet torque by inducing magnetic poles near an outer peripheral surface of the uncluttered rotor, and the stator currents also generate a reluctance torque by a reaction of the difference between the direct and quadrature magnetic paths of the uncluttered rotor. The system can be used either as a motor or a generator
Development of tilted fibre Bragg gratings using highly coherent 255 ...
Indian Academy of Sciences (India)
2014-02-06
Feb 6, 2014 ... This paper reports the study on development of tilted fibre Bragg gratings using highly coherent 255 nm radiation, obtained from the second harmonic generation (SHG) of copper vapour laser (CVL). The transmission and reflection spectra of the tilted fibre Bragg gratings (TFBG) were studied for the tilt ...
Directory of Open Access Journals (Sweden)
Rob Eling
2016-09-01
Full Text Available Journal bearings are used to support rotors in a wide range of applications. In order to ensure reliable operation, accurate analyses of these rotor-bearing systems are crucial. Coupled analysis of the rotor and the journal bearing is essential in the case that the rotor is flexible. The accuracy of prediction of the model at hand depends on its comprehensiveness. In this study, we construct three bearing models of increasing modeling comprehensiveness and use these to predict the response of two different rotor-bearing systems. The main goal is to evaluate the correlation with measurement data as a function of modeling comprehensiveness: 1D versus 2D pressure prediction, distributed versus lumped thermal model, Newtonian versus non-Newtonian fluid description and non-mass-conservative versus mass-conservative cavitation description. We conclude that all three models predict the existence of critical speeds and whirl for both rotor-bearing systems. However, the two more comprehensive models in general show better correlation with measurement data in terms of frequency and amplitude. Furthermore, we conclude that a thermal network model comprising temperature predictions of the bearing surroundings is essential to obtain accurate predictions. The results of this study aid in developing accurate and computationally-efficient models of flexible rotors supported by plain journal bearings.
Edge Waves and Localization in Lattices Containing Tilted Resonators
Directory of Open Access Journals (Sweden)
Domenico Tallarico
2017-06-01
Full Text Available The paper presents the study of waves in a structured geometrically chiral solid. A special attention is given to the analysis of the Bloch-Floquet waves in a doubly periodic high-contrast lattice containing tilted resonators. Dirac-like dispersion of Bloch waves in the structure is identified, studied, and applied to wave-guiding and wave-defect interaction problems. The work is extended to the transmission problems and models of fracture, where localization and edge waves occur. The theoretical derivations are accompanied with numerical simulations and illustrations.
Nonlinear dynamics of a support-excited flexible rotor with hydrodynamic journal bearings
Dakel, Mzaki; Baguet, Sébastien; Dufour, Régis
2014-05-01
The major purpose of this study is to predict the dynamic behavior of an on-board rotor mounted on hydrodynamic journal bearings in the presence of rigid support movements, the target application being turbochargers of vehicles or rotating machines subject to seismic excitation. The proposed on-board rotor model is based on Timoshenko beam finite elements. The dynamic modeling takes into account the geometric asymmetry of shaft and/or rigid disk as well as the six deterministic translations and rotations of the rotor rigid support. Depending on the type of analysis used for the bearing, the fluid film forces computed with the Reynolds equation are linear/nonlinear. Thus the application of Lagrange's equations yields the linear/nonlinear equations of motion of the rotating rotor in bending with respect to the moving rigid support which represents a non-inertial frame of reference. These equations are solved using the implicit Newmark time-step integration scheme. Due to the geometric asymmetry of the rotor and to the rotational motions of the support, the equations of motion include time-varying parametric terms which can lead to lateral dynamic instability. The influence of sinusoidal rotational or translational motions of the support, the accuracy of the linear 8-coefficient bearing model and the interest of the nonlinear model for a hydrodynamic journal bearing are examined and discussed by means of stability charts, orbits of the rotor, time history responses, fast Fourier transforms, bifurcation diagrams as well as Poincaré maps.
Directory of Open Access Journals (Sweden)
Ruhai Li
2017-12-01
Full Text Available The electromagnetic vibration caused by electromagnetic force on the stator has threatened large hydro generators operating safely and stably. At the Zhexi hydropower station, the hydro generator was beset by electromagnetic vibration for a long time. Therefore, the paper provided a new method to help to find the vibration source and detect the hydro generator fault, through the combination of simulation and experiments. In this paper, the 3D stator pack structure model and the 2D hydro generator electromagnetic models under rotor eccentricity and rotor ellipse deformation conditions were built. Then, electromagnetism simulations were conducted to study the characteristics of the electromagnetic flux and electromagnetic force under different conditions by using the finite element method (FEM. Lastly, the vibration testing experiments and harmonic response simulations of stator frame were performed to present the characteristics of vibration distribution in frequency conditions. The simulation results were compared with the generator measured data to try to find out the main vibration source and guide the overhaul.
Design and Development of Tilting Rotary Furnace
Sai Varun, V.; Tejesh, P.; Prashanth, B. N.
2018-02-01
Casting is the best and effective technique used for manufacturing products. The important accessory for casting is furnace. Furnace is used to melt the metal. A perfect furnace is one that reduces the wastage of material, reduces the cost of manufacturing and there by reduces the cost of production. Of all the present day furnaces there may be wastage of material, and the chances of increasing the time of manufacturing as the is continuous need of tilting of the furnace for every mould and then changing the moulds. Considering these aspects, a simple and least expensive tilting rotary furnace is designed and developed. The Tilting and Rotary Furnace consists of mainly melting chamber and the base. The metal enters the melting chamber through the input door that is provided on the top of the melting chamber. Inside the melting chamber there is a graphite furnace. The metal is melted in the graphite crucible. An insulation of ceramic fibre cloth is provided inside the furnace. The metal is melted using Propane gas. The propane gas is easily available and economic. The gas is burned using a pilot burner. The pilot burner is more efficient that other burners. The pilot burner is lit with a push button igniter. The pilot burner is located at the bottom of the combustion chamber. This enables the uniform heating of the metal inside the crucible. The temperature inside the melting chamber is noted using a temperature sensor. The gas input is cut-off if the temperature is exceeding a specific temperature. After the melting of the metal is done the furnace is tilted and after the mould is filled it is rotated. The external gears are used to controlling the tilting. The results of studies carried out for the design & development of low cost, simple furnace that can be mounted anywhere on the shop floor and this can be very much useful for the education purposes and small scale manufacturing. The furnace can be rotated in 360 degrees and can help in reducing the time taken
Optimal Aerodynamic Design of Conventional and Coaxial Helicopter Rotors in Hover and Forward Flight
Giovanetti, Eli B.
This dissertation investigates the optimal aerodynamic performance and design of conventional and coaxial helicopters in hover and forward flight using conventional and higher harmonic blade pitch control. First, we describe a method for determining the blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), and division of propulsive and lifting forces among the components that minimize the total power for a given forward flight condition. The optimal design problem is cast as a variational statement that is discretized using a vortex lattice wake to model inviscid forces, combined with two-dimensional drag polars to model profile losses. The resulting nonlinear constrained optimization problem is solved via Newton iteration. We investigate the optimal design of a compound vehicle in forward flight comprised of a coaxial rotor system, a propeller, and optionally, a fixed wing. We show that higher harmonic control substantially reduces required power, and that both rotor and propeller efficiencies play an important role in determining the optimal shaft angle, which in turn affects the optimal design of each component. Second, we present a variational approach for determining the optimal (minimum power) torque-balanced coaxial hovering rotor using Blade Element Momentum Theory including swirl. We show that the optimal hovering coaxial rotor generates only a small percentage of its total thrust on the portion of the lower rotor operating in the upper rotor's contracted wake, resulting in an optimal design with very different upper and lower rotor twist and chord distributions. We also show that the swirl component of induced velocity has a relatively small effect on rotor performance at the disk loadings typical of helicopter rotors. Third, we describe a more refined model of the wake of a hovering conventional or coaxial rotor. We approximate the rotor or coaxial rotors as actuator disks (though not necessarily uniformly loaded
An efficient wave extrapolation method for anisotropic media with tilt
Waheed, Umair bin
2015-03-23
Wavefield extrapolation operators for elliptically anisotropic media offer significant cost reduction compared with that for the transversely isotropic case, particularly when the axis of symmetry exhibits tilt (from the vertical). However, elliptical anisotropy does not provide accurate wavefield representation or imaging for transversely isotropic media. Therefore, we propose effective elliptically anisotropic models that correctly capture the kinematic behaviour of wavefields for transversely isotropic media. Specifically, we compute source-dependent effective velocities for the elliptic medium using kinematic high-frequency representation of the transversely isotropic wavefield. The effective model allows us to use cheaper elliptic wave extrapolation operators. Despite the fact that the effective models are obtained by matching kinematics using high-frequency asymptotic, the resulting wavefield contains most of the critical wavefield components, including frequency dependency and caustics, if present, with reasonable accuracy. The methodology developed here offers a much better cost versus accuracy trade-off for wavefield computations in transversely isotropic media, particularly for media of low to moderate complexity. In addition, the wavefield solution is free from shear-wave artefacts as opposed to the conventional finite-difference-based transversely isotropic wave extrapolation scheme. We demonstrate these assertions through numerical tests on synthetic tilted transversely isotropic models.
Optimization of wind turbine rotors
Energy Technology Data Exchange (ETDEWEB)
Holmkvist, Jonas
1998-05-01
A computer program for aerodynamic optimization of wind turbine rotors has been written in Fortran with the purpose to maximize the annual energy production. The constraints is the maximum power output from the turbine and maximum and minimum values on the design variables. The design of the rotor is described by the chord- and twist distribution. The chord- and twist distributions are described with Bezier splines which, with a few number of control points, are very flexible. The Bezier control points are the design variables which are optimized by the optimization program. The optimization method used in the program is the Method of Moving Asymptotes, MMA, suggested by Krister Svanberg at the Royal Institute of Technology in Stockholm. MMA is a stable method and it seems suitable for this application. It is also in general easy to implement constraints. It seems like there are many local maximum points and the variations in the annual energy production between the total maximum points are very small, so there are many solutions to choose between and finding the global maximum point can be a problem. The problem could possibly be avoided with smaller wind steps near the rated wind. In future versions of the optimization program the Reynolds number dependents of the aerodynamic coefficients should be taken into consideration. Constraints for the thrust and the aerodynamic noise should also be implemented in the program 8 refs, 8 figs, 13 tabs, 14 appendixes
Kumaravelu, Uma Devi; Mohamed Yakub, Sanavullah
2012-01-01
A method of simulation and modeling outer rotor permanent magnet brushless DC (ORPMBLDC) motor under dynamic conditions using finite element method by FEMM 4.2 software package is presented. In the proposed simulation, the torque developed at various positions of the rotor, under a complete cycle of excitation of the stator, is analysed. A novel method of sinusoidal excitation is proposed to enhance the overall torque development of ORPMBLDC motor.
Directory of Open Access Journals (Sweden)
Uma Devi Kumaravelu
2012-01-01
Full Text Available A method of simulation and modeling outer rotor permanent magnet brushless DC (ORPMBLDC motor under dynamic conditions using finite element method by FEMM 4.2 software package is presented. In the proposed simulation, the torque developed at various positions of the rotor, under a complete cycle of excitation of the stator, is analysed. A novel method of sinusoidal excitation is proposed to enhance the overall torque development of ORPMBLDC motor.
Development of a Driving Electric Dynamometer Rotor Emulator for MHK In‐Stream Turbines
Laing, William, E., Jr.; VanSwieten, James H.
2014-01-01
As marine and hydrokinetic (MHK) technologies which convert the flow of fluid into useful electrical power are developed, it is desirable to simulate drivetrain performance and refine control strategies in a laboratory prior to field installation. This paper presents and evaluates a technique developed to operate the prime mover of a dynamometer so that it drives a machine under test like an MHK turbine's rotor. The approach utilizes environmental and rotor numerical models to calculate hydro...
Bifurcation Analysis of a Non-linear On-Board Rotor-Bearing System
Dakel, M. Zaki; Baguet, Sébastien; Dufour, Régis
2014-01-01
International audience; The non-linear dynamic behavior of an on-board rotor mounted on hydrodynamic journal bearings and subject to rigid base excitations is investigated in this work. The proposed finite element rotor model takes into account the geometric asymmetry of shaft and/or rigid disk and considers six types of base deterministic motions (rotations and translations) and non-linear fluid film forces obtained from the Reynoldsequation. The equations of motion contain time-varying para...