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1

Lateral dampers for thrust bearings  

Science.gov (United States)

The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

Hibner, D. H.; Szafir, D. R.

1985-01-01

2

Lateral dampers for thrust bearings. Final Report  

Energy Technology Data Exchange (ETDEWEB)

The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

Hibner, D.H.; Szafir, D.R.

1985-08-01

3

Combination radial and thrust magnetic bearing  

Science.gov (United States)

A combination radial and thrust magnetic bearing is disclosed that allows for both radial and thrust axes control of an associated shaft. The combination radial and thrust magnetic bearing comprises a rotor and a stator. The rotor comprises a shaft, and first and second rotor pairs each having respective rotor elements. The stator comprises first and second stator elements and a magnet-sensor disk. In one embodiment, each stator element has a plurality of split-poles and a corresponding plurality of radial force coils and, in another embodiment, each stator element does not require thrust force coils, and radial force coils are replaced by double the plurality of coils serving as an outer member of each split-pole half.

Blumenstock, Kenneth A. (Inventor)

2002-01-01

4

Development of hybrid bearing system with thrust superconducting magnetic bearing and radial active electromagnetic bearing  

Science.gov (United States)

A superconducting/electromagnetic hybrid bearing system is currently under development and test. This system consists of a thrust superconducting magnetic bearing and a double radial active electromagnetic bearing/motor devices. The thrust bearing has been designed using NdFeB permanent magnets levitating on a set of superconducting monoliths of YBCO, prepared by top seeded melt texturing technique, which supports the weight of the rotor. The bearing/motor devices were conceived as 4-pole 2-phase induction machine using stator windings for delivering torque and radial positioning simultaneously. Using this superconducting axial bearing and the active bearings for the rotor radial positioning, a fully levitating vertical-shaft inductive machine has been tested. The tests were successful in reaching a controlled levitation up to 6,300 rpm.

Nicolsky, R.; Pereira, A. S.; de Andrade, R.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Ripper, A.; Gawalek, W.; Habisreuther, T.; Strasser, T.

5

Fatigue Life Analysis of Thrust Ball Bearing Using ANSYS  

Directory of Open Access Journals (Sweden)

Full Text Available This paper compares the total deformation of thrust ball bearing & contact stress b/w ball & raceways & its effect on fatigue life of thrust ball bearing. The 3-Dimensional Modeling has been done through modeling software Pro-e wildfire-5.0. The parts assembly is also done in Pro-e wildfire-5.0 & analysis has been done through ANSYS- 14. An analylitical method is good, less expensive and gives the best results. Analytical results give good agreement with the experimental data. The thrust ball bearings are subjected to various, thrust & dynamic loads, which simulated easily through Pro-E software & analysis because experimentally calculation is very complicated. The general theory used for calculating the Fatigue life of Bearing is basic life rating theory. The material taken for the Bearing is AISI8720H. In this study we have used various analysis codes and got a good result through these codes.

Prabhat Singh*1

2014-01-01

6

Research on Service Life Prediction Model of Thrust Needle Bearing  

Directory of Open Access Journals (Sweden)

Full Text Available Needle roller thrust bear is small in size and of high ability in load bearing, therefore it is widely used in fields of aviation and automobile etc.  But the relation between their service life and pre-tightening torque is not very clear, so the using design of the bear depends mainly on experience of engineer, because of lack of references. In the paper, the theoretical analysis on relation between torque and load is done, special wearing test instrument is developed and wearing test of thrust needle bear is conducted. Based on the results of the test, mathematical model of relation between the losing amount of pre-tightening torque and the pre-tightening torque is built, based on which use of the bear in engineering will be more reasonable, and their pre-tightening torque will be given more accurately.

Li Wei

2012-11-01

7

Fatigue Life Analysis of Thrust Ball Bearing Using ANSYS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper compares the total deformation of thrust ball bearing & contact stress b/w ball & raceways & its effect on fatigue life of thrust ball bearing. The 3-Dimensional Modeling has been done through modeling software Pro-e wildfire-5.0. The parts assembly is also done in Pro-e wildfire-5.0 & analysis has been done through ANSYS- 14. An analylitical method is good, less expensive and gives the best results. Analytical results give good agreement with the experimental data. ...

Prabhat Singh*1; , Prof Upendra Kumar Joshi2

2014-01-01

8

Research on Service Life Prediction Model of Thrust Needle Bearing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Needle roller thrust bear is small in size and of high ability in load bearing, therefore it is widely used in fields of aviation and automobile etc.  But the relation between their service life and pre-tightening torque is not very clear, so the using design of the bear depends mainly on experience of engineer, because of lack of references. In the paper, the theoretical analysis on relation between torque and load is done, special wearing test instrument is developed and wearing test of th...

Li Wei; Fan Bingli; Hu Zhanqi; Qi Xiaowen

2012-01-01

9

Advanced Active-Magnetic-Bearing Thrust-Measurement System  

Science.gov (United States)

An advanced thrust-measurement system utilizes active magnetic bearings to both (1) levitate a floating frame in all six degrees of freedom and (2) measure the levitation forces between the floating frame and a grounded frame. This system was developed for original use in measuring the thrust exerted by a rocket engine mounted on the floating frame, but can just as well be used in other force-measurement applications. This system offers several advantages over prior thrust-measurement systems based on mechanical support by flexures and/or load cells: The system includes multiple active magnetic bearings for each degree of freedom, so that by selective use of one, some, or all of these bearings, it is possible to test a given article over a wide force range in the same fixture, eliminating the need to transfer the article to different test fixtures to obtain the benefit of full-scale accuracy of different force-measurement devices for different force ranges. Like other active magnetic bearings, the active magnetic bearings of this system include closed-loop control subsystems, through which the stiffness and damping characteristics of the magnetic bearings can be modified electronically. The design of the system minimizes or eliminates cross-axis force-measurement errors. The active magnetic bearings are configured to provide support against movement along all three orthogonal Cartesian axes, and such that the support along a given axis does not produce force along any other axis. Moreover, by eliminating the need for such mechanical connections as flexures used in prior thrust-measurement systems, magnetic levitation of the floating frame eliminates what would otherwise be major sources of cross-axis forces and the associated measurement errors. Overall, relative to prior mechanical-support thrust-measurement systems, this system offers greater versatility for adaptation to a variety of test conditions and requirements. The basic idea of most prior active-magnetic-bearing force-measurement systems is to calculate levitation forces on the basis of simple proportionalities between changes in those forces and changes in feedback-controlled currents applied to levitating electromagnetic coils. In the prior systems, the effects of gap lengths on fringing magnetic fields and the concomitant effects on magnetic forces were neglected. In the present system, the control subsystems of the active magnetic bearings are coupled with a computer-based automatic calibration system running special-purpose software wherein gap-length-dependent fringing factors are applied to current and magnetic-flux-based force equations and combined with a multipoint calibration method to obtain greater accuracy.

Imlach, Joseph; Kasarda, Mary; Blumber, Eric

2008-01-01

10

On the Design of Tilting-Pad Thrust Bearings  

DEFF Research Database (Denmark)

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 pad convergence ratio. In this thesis, a theoretical approach is applied in the attempt to quantify the influence of recesses in the pad surfaces. The recesses may be relatively deep and enclosed as is the case with pockets designed for hydrostatic jacking. Such recesses are characterized by low 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 of the bearing length-to-width ratio, pad deformation and injection pocket size are quantified. Suggestions for the design of energy efficient bearings are given. The results show that correctly dimensioned, bearings with oil injection pockets have smaller friction coefficients than bearings with plain pads. Placing the pockets in the high-pressure zones close to the trailing edges of the bearing pads causes a substantial reduction in the friction coefficient. The design of the recess sizes and positions leading to the largest improvements is studied and design suggestions for various pad geometries are given. Parallel-step bearings theoretically have smaller friction coefficients than tilting-pad bearings. A design of a tilting-pad bearing is suggested which combines the benefits of the two types of bearings in a tilting-pad bearing with inlet pockets. This design results in a substantial reduction of the friction loss. Both this bearing and the bearing design with enclosed recesses in the high-pressure regions of the pads suffer from a higher sensitivity to the position of the pivot. The design of such bearing is therefore no trivial task.

Heinrichson, Niels

2007-01-01

11

Numerical analysis on nanoparticles-laden gas film thrust bearing  

Science.gov (United States)

Nanoparticles can be taken as additives and added into various fluids to improve their lubricating performances. At present, researches in this area are mainly concentrated on the improvement effects of nanoparticles on the lubricating performances of liquid such as oil and water. Nanoparticles will also affect gas lubrication, but few related studies have been reported. Nanoparticles-laden gas film (NLGF) is formed when adding nanoparticles into gas bearing. Then, the lubricating performances of gas bearing including pressure distribution and load-carrying capacity will change. The variations of pressure distribution and load-carrying capacity in nanoparticles-laden gas film thrust bearing are investigated by numerical method. Taking account of the compressibility of gas and the interactions between gas and nanoparticles, a computational fluid dynamics model based on Navier-Stokes equations is applied to simulate the NLGF flow. The effects of inlet nanoparticles volume fraction and orifice radius on film pressure distribution and load-carrying capacity of the NLGF are calculated. The numerical calculation results show that both of the film land pressure and the maximum film pressure both increase when the nanoparticles are added into gas bearing, and the film pressures increase with the rising of the inlet nanoparticles volume fraction. The nanoparticles have an enhancement effect on load-carrying capacity of the studied bearing, and the enhancement effect becomes greater as the film thickness decrease. Therefore, nanoparticles can effectively improve the lubricating performance of gas bearing. The proposed research provides a theoretical basis for the design of new-type nanoparticles-laden gas film bearings.

Yang, Zhiru; Diao, Dongfeng; Yang, Lei

2013-07-01

12

Thrust Bearing Governed Clinker Extraction System in Producer Gas Plant  

Directory of Open Access Journals (Sweden)

Full Text Available In the process of Producer Gas Production; clinker/ash is formed as a waste material. This clinker is removed by equipment named as Ash Bowl which rotates on the “Guide Roller” by the application of hydraulic pressure. This process having many problems like formation of large size clinker which require excess hydraulic pressure, guide roller is unable to scatter the hydraulic pressure equally in all the direction on the ash bowl to crush the clinker, more hydraulic pressure is required for the movement of the ash bowl, more time is required to replace the guide roller for its maintenance. In order to eliminate above mention problems, guide roller has been replaced by the thrust bearing which improves productivity by reducing break down time, reducing total man power required & reducing maintenance cost.

Ram Prasad Verma

2013-11-01

13

An Experimental Study on Lubrication Mechanism at Thrust Slide-Bearing of Scroll Compressors  

Science.gov (United States)

This study focuses on the significant effect that a pressure difference across the orbiting thrust plate of a thrust-slide bearing has on the improved lubrication of the bearing in scroll compressor applications. A thrust slide-bearing model submerged in a refrigerant oil VG-56 was operated under pressurized conditions using R-22 as the pressurizing gas, where the pressure difference across the friction surface of the thrust bearing was adjusted from 0 to 1.0 MPa and the friction force and friction coefficient at the thrust slide-bearing were measured over a range of orbiting speeds. As a result, a significant improvement in lubrication at the thrust slide-bearing due to the pressure difference was addressed. Furthermore, a careful observation of wear state at the thrust slide-bearing addressed a significant formation of fluid wedge between the sliding surfaces due to axial loadings, which will definitely induce the addressed significant improvement in lubrication. In addition, the wedge formation was quantitatively addressed with FEM analysis of elastic deformation of the thrust plate, which was verified for its validity with measured strains on the thrust plate.

Oku, Tatsuya; Anami, Keiko; Ishii, Noriaki; Sawai, Kiyoshi; Morimoto, Takashi; Hiwata, Akira

14

An Experimental Study of Lubrication at Thrust Slide-Bearing of Scroll Compressors  

Science.gov (United States)

The previous studies have revealed that the wedge formation at the periphery of the thrust plate, caused by the elastic deformation due to pressure difference across the orbiting thrust plate, is a significant key factor to keep and improve the high performance in lubrication of the thrust-slide bearing. The present study focuses on the effect of the thickness and inner form of the thrust plate upon the lubrication features. A simplified model of cylindrical thrust slide-bearing with thinner thrust plate submerged in a refrigerant oil VG-56 was operated under pressurized conditions using R-22 as the pressurizing gas, where the pressure difference was adjusted from 0 to 1.0 MPa and the friction force and coefficient of friction were measured over a wide range of orbiting speeds, first. The wedge angle by elastic deformation is naturally increased with decreasing the thrust plate thickness, thus resulting in a clear improvement in lubrication at the thrust slide-bearing. On the contrast, secondly, the similar lubrication tests were conducted for the thrust plate with a real inner form, as complicated as in the real scroll compressors, where the thickness of the thrust plate was kept as in the original tests. As a result, no significant change in lubrication features, from those for the simplified cylindrical model, was not addressed, thus confirming that the test results addressed from the simplified cylindrical model tests can be effectively used to examine the basic characteristics in lubrication of thrust slide bearing of scroll compressors.

Ishii, Noriaki; Oku, Tatsuya; Anami, Keiko; Tsuji, Takuma; Ozasa, Toshihiro; Sawai, Kiyoshi; Morimoto, Takashi; Iida, Noboru

15

Experimental equipment for measuring physical properties of the annular hydrostatic thrust bearing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The hydraulic circuit, through which the mineral oil is brought, is an important part of hydrostatic bearings. The annular hydrostatic thrust bearing consists of two sliding plates divided by a layer of mineral oil. In the lower plate, there are oil grooves which distribute the liquid between the sliding areas. The hydraulic circuit is made of two basic parts: the energy source and the controlling part. The hydraulic pump, which brings the liquid into the sliding bearing, is the source of the...

Kozdera Michal; Drábková Sylva; Bojko Marian

2014-01-01

16

A rotary microactuator supported on encapsulated microball bearings using an electro-pneumatic thrust balance  

International Nuclear Information System (INIS)

The development of a rotary microactuator supported on encapsulated microball bearings and driven by electro-pneumatic actuation is reported. The encapsulated bearing provides full support to an encased rotor, while an electro-pneumatic thrust balance is used to minimize rotor normal load. By minimizing normal load, bearing friction is reduced leading to increased speed and performance. Experimental results show that the microactuator is capable of repeatable operation and continuous 360° motion at speeds of 5–2000 rpm. This is the first demonstration of a ball bearing supported electrostatic microactuator with a fully encased rotor, capable of direct mechanical attachment or reliable interaction with external media

17

The Chevron Foil Thrust Bearing: Improved Performance Through Passive Thermal Management and Effective Lubricant Mixing  

Science.gov (United States)

An improved foil thrust bearing is described that eliminates or reduces the need for forced cooling of the bearing foils while at the same time improves the load capacity of the bearing, enhances damping, provides overload tolerance, and eliminates the high speed load capacity drop-off that plagues the current state of the art. The performance improvement demonstrated by the chevron foil thrust bearing stems from a novel trailing edge shape that splays the hot lubricant in the thin film radially, thus preventing hot lubricant carry-over into the ensuing bearing sector. Additionally, the chevron shaped trailing edge induces vortical mixing of the hot lubricant with the gas that is naturally resident within the inter-pad region of a foil thrust bearing. The elimination of hot gas carry-over in combination with the enhanced mixing has enabled a completely passive thermally managed foil bearing design. Laboratory testing at NASA has confirmed the original analysis and reduced this concept to practice.

Bruckner, Robert

2013-01-01

18

A passive magnetic-thrust bearing for energy-storage flywheels  

Science.gov (United States)

Flywheels for the storage and subsequent release of energy in general involve the suspension of rather large masses rotating at speeds limited by the strength of the flywheel material. Since drag torque on the flywheel represents an undesirable energy drain during storage, windage can be eliminated by operation in a vacuum, leaving bearing drag as a significant item. Using a vertical shaft configuration, a passive repulsion-type permanent-magnet thrust bearing is virtually frictionless while small, low-loss, oil-lubricated pintle bearings maintain the shaft radially. This paper discusses the analytical design of the passive magnetic-thrust bearing, including its nonrotating damper. Reliability of the system is high since no servo-control system is required.

Wilcock, D. F.; Eusepi, M.

1980-08-01

19

Experimental equipment for measuring physical properties of the annular hydrostatic thrust bearing  

Directory of Open Access Journals (Sweden)

Full Text Available The hydraulic circuit, through which the mineral oil is brought, is an important part of hydrostatic bearings. The annular hydrostatic thrust bearing consists of two sliding plates divided by a layer of mineral oil. In the lower plate, there are oil grooves which distribute the liquid between the sliding areas. The hydraulic circuit is made of two basic parts: the energy source and the controlling part. The hydraulic pump, which brings the liquid into the sliding bearing, is the source of the pressure energy. The sliding bearing is weighted down by axial force, which can be changed during the process. That´s why in front of the particular oil grooves control components adjusting pressure and flow size are located. This paper deals with a project of a hydraulic circuit for regulation of fluid layer in the annular hydrostatic thrust bearing and the testing equipment for measuring its physical properties. It will include the issue of measuring loading capacity and height of the fluid layer in the annular hydrostatic thrust bearing.

Kozdera Michal

2014-03-01

20

Development of the water-lubricated thrust bearing of the hydraulic turbine generator  

International Nuclear Information System (INIS)

In hydropower plant, a large quantities of turbine oil is used as machine control pressure oil and lubricating oil. If the oil leak out from hydropower plant, it flows into a river. And such oil spill has an adverse effect on natural environment because the oil does not degrade easily. Therefore the KANSAI and Hitachi Mitsubishi Hydro developed the water-lubricated thrust bearing for vertical type hydraulic turbine generator. The water-lubricated bearing has advantages in risk avoidance of river pollution because it does not need oil. For proceeding the development of the water-lubricated thrust bearing, we studied following items. The first is the examination of the trial products of water lubricating liquid. The second is the study of bearing structure which can satisfy bearing performance such as temperature characteristic and so on. The third is the mock-up testing for actual application in the future. As a result, it was found that the water-lubricated thrust bearing was technically applicable to actual equipments.

 
 
 
 
21

Development of the water-lubricated thrust bearing of the hydraulic turbine generator  

Science.gov (United States)

In hydropower plant, a large quantities of turbine oil is used as machine control pressure oil and lubricating oil. If the oil leak out from hydropower plant, it flows into a river. And such oil spill has an adverse effect on natural environment because the oil does not degrade easily. Therefore the KANSAI and Hitachi Mitsubishi Hydro developed the water-lubricated thrust bearing for vertical type hydraulic turbine generator. The water-lubricated bearing has advantages in risk avoidance of river pollution because it does not need oil. For proceeding the development of the water-lubricated thrust bearing, we studied following items. The first is the examination of the trial products of water lubricating liquid. The second is the study of bearing structure which can satisfy bearing performance such as temperature characteristic and so on. The third is the mock-up testing for actual application in the future. As a result, it was found that the water-lubricated thrust bearing was technically applicable to actual equipments.

Inoue, K.; Deguchi, K.; Okude, K.; Fujimoto, R.

2012-11-01

22

Ball to separator contact forces in angular contact ball bearings under thrust and radial loads  

Science.gov (United States)

Experimental data are reported on ball to cage contact forces in a 110 mm bore ball bearing operating at speeds to 12,000 rpm under radial and thrust loads. Information is also reported on cage to inner race land contact force, cage to inner race land clearance, and cage to shaft speed ratios.

Nypan, L. J.

1978-01-01

23

Optimization of residual heat removal pump axial thrust and axial bearing  

Energy Technology Data Exchange (ETDEWEB)

The residual heat removal (RHR) pumps of German 1300 megawatt pressurized-water reactor (PWR) power plants are of the single stage end suction type with volute casing or with diffuser and forged circular casing. Due to the service conditions the pumps have to cover the full capacity range as well as a big variation in suction static pressure. This results in a big difference in the axial thrust that has to be borne by the axial bearing. Because these pumps are designed to operate without auxiliary systems (things that do not exist can not fail), they are equipped with antifriction bearings and sump oil lubrication. To minimize the heat production within the bearing casing, a number of PWR plants have pumps with combined axial/radial bearings of the ball type. Due to the fact that the maximum axial thrust caused by static pressure and hydrodynamic forces on the impeller is too big to be borne by that type of axial bearing, the impellers were designed to produce a hydrodynamic axial force that counteracts the static axial force. Thus, the resulting axial thrust may change direction when the static pressure varies.

Schubert, F.

1996-12-01

24

Detecting thrust bearing failure within a screw compressor  

International Nuclear Information System (INIS)

A 3 1/2 mile ring of over 1000 superconducting magnets are needed to focus and drive the world's highest energy particle smasher. 24 Refrigerators supply liquid helium to the magnets; 34 high pressure oil flooded screw compressors supply 285 psig helium gas to the refrigerators. The 400 h.p. screws are reliable machines that use 45 gallons of oil per minute to seal and lubricate the rotors, lubricate the bearings, and remove the heat of compression. These machines are spaced out in seven buildings over four miles. A minimum of 28 machines must be operating at all times. A contingent of operators start, stop, and monitor any machine from a distant control room. The 34 compressors have an average of 32,000 hours; 9 machines have over 40,000 hours; the highest is 55,000 hours

25

Demonstration, Testing and Qualification of a High Temperature, High Speed Magnetic Thrust Bearing  

Science.gov (United States)

The gas turbine industry has a continued interest in improving engine performance and reducing net operating and maintenance costs. These goals are being realized because of advancements in aeroelasticity, materials, and computational tools such as CFD and engine simulations. These advancements aid in increasing engine thrust-to-weight ratios, specific fuel consumption, pressure ratios, and overall reliability through higher speed, higher temperature, and more efficient engine operation. Currently, rolling element bearing and squeeze film dampers are used to support rotors in gas turbine engines. Present ball bearing configurations are limited in speed (bearings require extensive preventative maintenance in order to assure their safe operation. Since these bearings are at their operational limits, new technologies must be found in order to take advantage of other advances. Magnetic bearings are well suited to operate at extreme temperatures and higher rotational speeds and are a promising solution to the problems that conventional rolling element bearings present. Magnetic bearing technology is being developed worldwide and is considered an enabling technology for new engine designs. Using magnetic bearings, turbine and compressor spools can be radically redesigned to be significantly larger and stiffer with better damping and higher rotational speeds. These advances, a direct result of magnetic bearing technology, will allow significant increases in engine power and efficiency. Also, magnetic bearings allow for real-time, in-situ health monitoring of the system, lower maintenance costs and down time.

DeWitt, Kenneth

2005-01-01

26

Establishing design criteria for crankshaft thrust bearings in gasoline and diesel engines by computer simulations and experiments. Crankshaft thrust bearing design - final report; Auslegungskriterien fuer Kurbelwellenaxiallager in Otto- und Dieselmotoren durch rechnergestuetzte Simulation und experimentelle Untersuchungen. Axialgleitlagerauslegung - Abschlussbericht  

Energy Technology Data Exchange (ETDEWEB)

Aim of the research-project was it to increase the calculation safety of crank shaft thrust bearings in combustion engines. The project was divided in two parts: (1) A simulation program to analyze the load bearing capacity of axial bearings under mixed lubrication has been developed at the Institut fuer Maschinenelemente und Konstruktionstechnik, University of Kassel. This part of the research-project has been presented at the FVV Herbsttagung in 2003. (2) The test runs with original parts were carried out on a newly designed thrust bearing test rig at the Institut fuer Tribologie, University of Applied Sciences in Mannheim. The following presentation shows the results of part 2. The experimental results show the influence of rotational frequency, load, bearing material, lateral run-out of the tread of the crankshaft and groove pattern. These test runs will help to dimension thrust bearings more efficiently. (orig.)

Hunsicker, W. [Fachhochschule Mannheim (Germany). Inst. fuer Tribologie; Backhaus, K. [Univ. GH Kassel (Germany). Inst. fuer Maschinenelemente und Konstruktionstechnik; Schubert, W. [KS Gleitlager GmbH, Papenburg (Germany)

2004-07-01

27

An Optimal Performance Design on Lubrication Mechanism at Thrust Slide-Bearing of Scroll Compressors  

Science.gov (United States)

This study presents an establishment of optimal design method for lubrication at the thrust slide-bearing of scroll compressors, where, the analysis method using the average Reynolds equation by Patir & Cheng and the solid contact theory by Greenwood & Williamson were applied to calculate the resultant lubrication performance. For given values of friction area, thrust load and orbiting speed, the oil film pressure, the solid contact force and the friction forces were calculated to determine the friction coefficient. The friction coefficient decreased gradually with decreasing the friction area, because of decreased oil viscous force. When the friction area became quite small, however, the influence of the effect of surface roughness became large, thus resulting in increased friction coefficient. Thereby, the optimum performance appeared, which changes according to the friction area. In addition, the optimal friction area changed with the orbiting speed, the thrust load, the oil viscosity and the wedge angle. It was concluded that the optimal design values of the thrust slide-bearing can be calculated for given working conditions of the compressor.

Oku, Tatsuya; Ishii, Noriaki; Anami, Keiko; Sawai, Kiyoshi; Morimoto, Takashi; Iida, Noboru

28

Experimental investigation of the flow in a simplified model of water lubricated axial thrust bearing  

Science.gov (United States)

In hydropower plants the axial thrust bearing takes up the hydraulic axial thrust of the runner and, in case of vertical shafts, the entire weight of all rotating masses. The use of water lubricated bearings can eliminate the oil leakage risk possibly contaminating the environment. A complex flow is generated by the smaller film thickness due to the lower viscosity of water compared with oil. Measurements on a simplified hydrostatic axial trust bearing model were accomplished for validating CFD analysis of water lubricated bearings. In this simplified model, fixed pads are implemented and the width of the gap was enlarged to create a higher resolution in space for the measurements. Most parts of the model were manufactured from acrylic glass to get optical access for measurement with PIV. The focus of these measurements is on the flow within the space between two pads. Additional to the PIV- measurement, the pressure on the wall of the rotating disk is captured by pressure transducers. The model bearing measurement results are presented for varied operating conditions.

Kirschner, O.; Ruprecht, A.; Riedelbauch, S.

2014-12-01

29

An Experimental Study of Lubrication in Thrust Slide-Bearings of Scroll Compressors - Effect of Thickness and Inside Form of Thrust Plate -  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The present study focuses on the effect of the thickness and inner form of the thrust plate in a scroll compressor upon the lubrication features. A simplified model of a annular thrust slide-bearing with thinner thrust plate submerged in a refrigerant oil VG-56 was operated under pressure using R-22 as the pressurizing gas, where the pressure difference was adjusted from 0 to 1.0 MPa. The friction force and coefficient of friction were measured over a wide range of orbiting speeds. The wedge ...

Tsuji, Takuma; Ishii, Noriaki; Oku, Tatsuya; Anami, Keiko; Nokiyama, Kouichi

2012-01-01

30

The performance of solid lubricated ball bearings operated in a vacuum under a high thrust load  

Science.gov (United States)

The performance of solid lubricated ball bearings was examined under a high thrust load, up to 3 kN, in a vacuum. Tested bearings were (1) angular contact ball bearings with a sputtered molybdenum disulfide (MoS2) film on balls and races, and with a PTFE based composite cage, and (2) angular contact full complement type ball bearings with an electro-plated lead(Pb) film on balls and races. Low frictional torque of about 1.5 N cm at a load of 3 kN, and a long life of 3 x 10(exp 7) revolutions were obtained with the bearings with a sputtered MoS2 film. However, torque spikes with a duration of about ten seconds and with an interval of several hundred hours were observed. The peak value was as high as 30 times of that in well lubricated state. An electro-plated Pb film also successfully lubricated a bearing for over 6 x 10(exp 6) revolutions under a load of 3 kN, although the frictional torque was about 10 times higher than that obtained with the MoS2 lubricated bearings.

Suzuki, Mineo; Nishimura, Makoto

31

Laminar motion of the incompressible fluids in self-acting thrust bearings with spiral grooves.  

Science.gov (United States)

We analyze the laminar motion of incompressible fluids in self-acting thrust bearings with spiral grooves with inner or external pumping. The purpose of the study is to find some mathematical relations useful to approach the theoretical functionality of these bearings having magnetic controllable fluids as incompressible fluids, in the presence of a controllable magnetic field. This theoretical study approaches the permanent motion regime. To validate the theoretical results, we compare them to some experimental results presented in previous papers. The laminar motion of incompressible fluids in bearings is described by the fundamental equations of fluid dynamics. We developed and particularized these equations by taking into consideration the geometrical and functional characteristics of these hydrodynamic bearings. Through the integration of the differential equation, we determined the pressure and speed distributions in bearings with length in the "pumping" direction. These pressure and speed distributions offer important information, both quantitative (concerning the bearing performances) and qualitative (evidence of the viscous-inertial effects, the fluid compressibility, etc.), for the laminar and permanent motion regime. PMID:24526896

Velescu, Cornel; Popa, Nicolae Calin

2014-01-01

32

Analytic Modeling of the Hydrodynamic, Thermal, and Structural Behavior of Foil Thrust Bearings  

Science.gov (United States)

A simulation and modeling effort is conducted on gas foil thrust bearings. A foil bearing is a self acting hydrodynamic device capable of separating stationary and rotating components of rotating machinery by a film of air or other gaseous lubricant. Although simple in appearance these bearings have proven to be complicated devices in analysis. They are sensitive to fluid structure interaction, use a compressible gas as a lubricant, may not be in the fully continuum range of fluid mechanics, and operate in the range where viscous heat generation is significant. These factors provide a challenge to the simulation and modeling task. The Reynolds equation with the addition of Knudsen number effects due to thin film thicknesses is used to simulate the hydrodynamics. The energy equation is manipulated to simulate the temperature field of the lubricant film and combined with the ideal gas relationship, provides density field input to the Reynolds equation. Heat transfer between the lubricant and the surroundings is also modeled. The structural deformations of the bearing are modeled with a single partial differential equation. The equation models the top foil as a thin, bending dominated membrane whose deflections are governed by the biharmonic equation. A linear superposition of hydrodynamic load and compliant foundation reaction is included. The stiffness of the compliant foundation is modeled as a distributed stiffness that supports the top foil. The system of governing equations is solved numerically by a computer program written in the Mathematica computing environment. Representative calculations and comparisons with experimental results are included for a generation I gas foil thrust bearing.

Bruckner, Robert J.; DellaCorte, Christopher; Prahl, Joseph M.

2005-01-01

33

Experimental Investigation of Friction Effect on Liner Model Rolling Bearings for Large Diameter Thrust Bearing Design  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studying friction coefficient has significant importance, especially when dealing with high load and temperature applications that have frequent starting and stopping points. Towards that, two sets of angular contact Linear Model Mockup Bearings (LMMB) were designed and fabricated. This linear model assembly was made up of high precision, grounded raceways (AISI 4140) and commercially purchased balls (AISI 52100). The experimental studies were carried out by placing different number of balls ...

Babu, S.; Manisekar, K.; Starvin, M. S.

2012-01-01

34

Active control of surge in centrifugal compressors using magnetic thrust bearing actuation  

Science.gov (United States)

This research presents a new method for active surge control in centrifugal compressors with unshrouded impellers using a magnetic thrust bearing to modulate the impeller tip clearance. Magnetic bearings offer the potential for active control of flow instabilities. This capability is highly dependent on the sensitivity of the compressor characteristics to blade tip clearance. If the position of the shaft can be actuated with sufficient authority and speed, the induced pressure modulation makes control of surge promising. The active nature of the magnetic bearing system makes the real-time static and dynamic positioning of the rotor and therefore modulation of the impeller tip clearance possible. A theoretical model is first established that describes the sensitivity of the centrifugal compressor characteristic curve to tip clearance variations induced by axial motion of the rotor. Results from simulation of the nonlinear model for a single stage high-speed centrifugal compressor show that using the proposed control method, mass flow and pressure oscillations associated with compressor surge are quickly suppressed with acceptable tip clearance excursions, typically less than 20% of the available clearance. It is shown that it is possible to produce adequate axial excursions in the clearance between the impeller blades and the adjacent stationary shroud using a magnetic thrust bearing with practical levels of drive voltage. This surge control method would allow centrifugal compressors to reliably and safely operate with a wider range than is currently done in the field. The principal advantage of the proposed approach over conventional surge control methods lies in that, in machines already equipped with magnetic bearing, the method can potentially be implemented by simply modifying controller software. This dispenses with the need to introduce additional hardware, permitting adaptation of existing machinery at virtually no cost. In addition, since the controller is designed with the objective of keeping the trajectories on the compressor characteristic curve, the compressor performance and efficiency are no longer sacrificed by excessive recycling to achieve stability. In order to explore these conjectures experimentally, a high speed centrifugal compressor test facility with active magnetic bearings is developed. The test facility can be used for implementing the proposed surge control method and also for assessing the impeller and bearing loads at off-design conditions. This data can then be used to verify and refine analytical models used in compressor design. (Abstract shortened by UMI.)

Sanadgol, Dorsa

35

Rheodynamic Lubrication of an Externally Pressured Thrust Bearing Using Herschel-Bulkley Fluid with Sinusoidal Injection  

Directory of Open Access Journals (Sweden)

Full Text Available Lubricants with variable viscosity are assuming greater importance for its application in polymer industry, thermal reactors and in biomechanics. With the bearing operations in machines being subject to high speeds, loads, increasing mechanical shearing forces and continually increasing pressure, there has been an increasing interest to use non-Newtonian fluids characterized by a yield value. Some of them, which fit into this class, are Bingham, Casson and Herchel-Bulkley models. In the present work, the problem of an externally pressurized thrust bearing lubricated with Herschel-Bulkley fluid under the sinusoidal flow rate has been investigated. Herschel-Bulkley fluids are characterized by a yield value, which leads to the formation of rigid core in the flow region. The shape and extent of the core has been determined numerically for various values of the Herschel-Bulkley number, power-law index, amplitude of sinusoidal fluid film and time. Numerical solutions have been obtained for the bearing performances such as pressure distribution and load capacity for different values of the Herschel-Bulkley number, power-law index, amplitude of sinusoidal fluid film and time. The effects of sinusoidal injection of the lubricant and the non-Newtonian characteristics on the bearing performances have been discussed.

I.J. Amalraj

2012-01-01

36

A low-friction high-load thrust bearing and the human hip joint  

International Nuclear Information System (INIS)

A hydrostatic thrust bearing operating at a pressure of 130 MPa and with a coefficient of friction rising to 0.004 in 6 days is described. It consists of interleaved oil-coated Mylar and brass sheets, each 0.1 mm thick. At this pressure, the Mylar deforms to reveal a pool of lubricant bounded by contacting layers at its edges where the pressure tapers off to zero. Thus, most of the load is borne by the oil so its effective Coulomb (slip-stick) friction is very low. Expressions for the effective coefficient of friction, the area of the solid-to-solid contact and the torque needed to rotate the bearing are given in terms of its geometry, the viscosity of the lubricant and elapsed time. The mechanism of a bearing with similar geometry and properties, the human hip joint, is compared with this plastic bearing. While their low friction properties arise from the same basic cause, the different natures of their soft deformable materials lead to the hip joint having a much wider range of action. This work is an example of new engineering leading to a fresh insight into an action of Nature, which in turn suggests an improvement in engineering.

37

A Computer Based Approach for the Design of the Orifice-Compensated with Feeding Pocket Annular Hydrostatic Thrust Bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The orifice-compensated with feeding pocket annular hydrostatic (OCFPAH) thrust bearing is a unique type of gas bearingwith many distinguishing characteristics. It is finding many applications in ultra high-speed rotors. A computer code waswritten to overcome the difficulties involved in the design of such a bearing. Initially, the design charts were converted intothe alternative equations using a curve-fitting technique. The program, which is based on these equations, was designed sothat mec...

Al-ajlouni, M.

2007-01-01

38

Design and evaluation of a 3 million DN series-hybrid thrust bearing. [stability tests and fatigue tests  

Science.gov (United States)

The bearing, consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid-film bearing, was fatigue tested. Test conditions were representative of a mainshaft ball bearing in a gas turbine engine operating at maximum thrust load to simulate aircraft takeoff conditions. Tests were conducted up to 16000 rpm and at this speed an axial load of 15568 newtons (3500 lb) was safely supported by the hybrid bearing system. Through the series-hybrid bearing principle, the effective ball bearing speed was reduced to approximately one-half of the shaft speed. It was concluded that a speed reduction of this magnitude results in a ten-fold increase in the ball bearing fatigue life. A successful evaluation of fluid-film bearing lubricant supply failure was performed repeatedly at an operating speed of 10,000 rpm. A complete and smooth changeover to full-scale ball bearing operation was effected when the oil supply to the fluid-film bearing was cut off. Reactivation of the fluid-film oil supply system resulted in a flawless return to the original mode of hybrid operation.

Scibbe, H. W.; Winn, L. W.; Eusepi, M.

1976-01-01

39

Inertia Effects in Rheodynamic Lubrication of an Externally Pressurized Thrust Bearing Using Bingham Lubricant with Sinusoidal Injection  

Directory of Open Access Journals (Sweden)

Full Text Available In the present theoretical investigation, the combined effects of fluid inertia forces and sinusoidal injection of the Bingham lubricant, on the performance of an externally pressurized thrust bearing with circular geometry are studied. Using the conventional two-constant Bingham model and by adopting the method of averaging inertia terms, the reduced Navier-Stokes equations are modified and numerical solutions have been obtained for the bearing performances such as the pressure distribution and the load carrying capacity for different values of Bingham number, Reynolds number, time and amplitude. The effects of fluid inertia forces and the non-Newtonian characteristics of the Bingham lubricant on the bearing performances for different sinusoidal conditions are discussed.

I.J. Amalraj

2013-01-01

40

A Computer Based Approach for the Design of the Orifice-Compensated with Feeding Pocket Annular Hydrostatic Thrust Bearings  

Directory of Open Access Journals (Sweden)

Full Text Available The orifice-compensated with feeding pocket annular hydrostatic (OCFPAH thrust bearing is a unique type of gas bearingwith many distinguishing characteristics. It is finding many applications in ultra high-speed rotors. A computer code waswritten to overcome the difficulties involved in the design of such a bearing. Initially, the design charts were converted intothe alternative equations using a curve-fitting technique. The program, which is based on these equations, was designed sothat mechanical and physical properties of the lubricant and the main dimensions of the bearing can be entered in a userfriendlymanner. Many runs of the code have been carried out successfully. The code has proven to be fast, compatible with CAD and CAD/CAM packages as well as the ability of linking it with data banks and the Internet.

M. Al-Ajlouni

2007-12-01

 
 
 
 
41

Performance of integrated retainer rings in silicon micro-turbines with thrust style micro-ball bearings  

Science.gov (United States)

This work explores the performance of different silicon retainer ring designs when integrated into silicon micro-turbines (SMTs) incorporating thrust style bearings supported on 500 µm diameter steel balls. Experimental performance curves are presented for SMTs with rotor diameters of 5 mm and 10 mm, each with five different retainer designs varying in mechanical rigidity, ball pocket shape and ball complement. It was found that the different retainer designs yielded different performance curves, with the closed pocket designs consistently requiring lower input power for a given rotation speed, and the most rigid retainers giving the best performance overall. Both 5 mm and 10 mm diameter devices have shown repeatable performance at rotation speeds up to and exceeding 20?000 RPM with input power levels below 2 W, and devices were tested for over 2.5 million revolutions without failure. Retainer rings are commonly used in macro-scale bearings to ensure uniform spacing between the rolling elements. The integration of retainers into micro-bearings could lower costs by reducing the number of balls required for stable operation, and also open up the possibility of ‘smart’ bearings with integrated sensors to monitor the bearing status.

Hergert, Robert J.; Hanrahan, Brendan; Ghodssi, Reza; Holmes, Andrew S.

2013-06-01

42

A less expensive solution for thrust-bearing failures at the Sao Simao hydroelectric power plant - Brazil  

Energy Technology Data Exchange (ETDEWEB)

After twenty years without any apparent problems on their combined guides and thrust bearings operations, the six 280 MW hydrogenerators of the Sao Simao Hydroelectric Power Plant of Brazil were failing. Sao Simao is the largest Power Plant of Companhia Energetica de Minas Gerais (CEMIG), one of the major Brazilian electric utility company, with a total installed potential higher than 5,400 MW. The source of the failure was the melting of the thrust pad Babbit lining. The machines began showing performance failures, leading to a sudden interruption in their operations. This caused considerable losses with high direct and indirect costs. The solution proposed by the bearing manufacturer was an improvement to the bearing design and the installation of new water-oil heat exchangers. The direct cost of their solution was estimated at US$ 2,000,000.00 (two million dollars). In a search for a less expensive alternative, CEMIG commenced a parallel study that was to focus on the heat exchangers. A calculation model was used to consider not only the thermal features of the oil circulation system but also the suitability of its pumps and piping system. This model predicted that an increase in the surface of the heat exchange area could solve the problem. A spare heat exchanger was then installed in one machine already possessing two heat exchangers. The rated output test results fulfilled preliminary predictions, eliminating the risk of additional Babbit lining failures. As a consequence of CEMIG's successful modeling test implementation, heat exchangers were added to the remaining machines. This alternative solution had a total direct cost of US$ 600,000.00 (six hundred thousand dollars) with an indirect cost much less than the alternative presented by the manufacturer for its short cessation period. This paper discusses in detail all this study stages. (author)

Porto, Licinio Cesar [Sinergia Engenheiros Consultores Ltda., Belo Horizonte, MG (Brazil)]. E-mail: licinio@sinergia.eng.br; Machado, Luiz; Koury, Ricardo Nicolau Nassar; Porto, Matheus Pereira; Coelho, Fernanda Gomes [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Mecanica]. E-mails: luizm@demec.ufmg.br; koury@ufmg.br; matheusporto@oi.com.br; fernanda@sinergia.eng.br

2008-07-01

43

Robust Optimum Design of Thrust Hydrodynamic Bearings for Hard Disk Drives  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper describes the robust optimum design which combines the geometrical optimization method proposed by Hashimoto and statistical method. Recently, 2.5? hard disk drives (HDDs) are widely used for mobile devices such as laptops, video cameras and car navigation systems. In mobile applications, high durability towards external vibrations and shocks are essentials to the bearings of HDD spindle motor. In addition, the bearing characteristics are influenced by manufacturing error because...

Hiromu Hashimoto; Yuta Sunami

2012-01-01

44

Comparison of Models for the Steady-State Analysis of Tilting-Pad Thrust Bearings  

DEFF Research Database (Denmark)

Prediction of the minimum oil film thickness and the maximum temperature on the surface of the bearing pad is crucial in the design and dimensioning of bearings. Friction loss, oil bath temperature and pad deflection are other parameters of interest. Depending on the desired information a numerical model requires different levels of detail. The two dimensional Reynolds equation for pressure in the oil film can be solved isothermally or considering viscosity variations in two or three dimensions, requiring solution of the equations for thermal equilibrium in oil and pad. Knowing the temperature 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-state operation of a 228 mm outer diameter bearing. It is found that for the given bearing a two dimensional model is sufficient to estimate the minimum oil film thickness and the maximum temperature on the pad surface. Three dimensional modelling does not improve the quality of the results.

Heinrichson, Niels; Santos, Ilmar

2005-01-01

45

Investigation of a saddle node bifurcation due to loss of contact in preloaded spherical roller thrust bearings  

International Nuclear Information System (INIS)

Spherical roller thrust bearings are used as supports in many rotating machineries. By applying an axial preload, clearance between the raceways and the rollers can be avoided. In order to increase the endurance, the preload shall be kept as low as possible. However, a bearing with low preload is sensitive of loosing full contact leading to nonlinear stiffness characteristics. The objective of this paper is to suggest a tool, which can be used to determine suitable preload and to show that a saddle node bifurcation can occur if the preload is too small. Studying the model in a rotating frame leads to an autonomous equation of motion from which stationary points and their stability can be analysed. Some set of parameters give a nonhyperbolic eigenvalue, and by investigating the corresponding central manifold it is found that a saddle node bifurcation occurs. Since explicit equations for the stationary points are derived, they can be used to choose a preload high enough to make sure that full contact always is a possible solution. It is however shown that if the preload becomes too small, the system enters an area of multiple solutions and a saddle node bifurcation can occur.

46

Heterogeneous strength and fault zone complexity of carbonate-bearing thrusts with possible implications for seismicity  

Science.gov (United States)

The understanding of fault-slip behaviour in carbonates has an important societal impact due to the widespread occurrence and propagation of earthquakes in these rocks. Fault rock variations in carbonates are systematically controlled by the lithology of the faulted protolith: cataclasis and hydraulic fracturing with evidence of past seismic slip commonly affect fault rocks in competent limestone formations whereas widespread pressure-solution and sliding along clay foliation are observed in marly rocks. We performed a series of friction experiments on carbonatic fault rocks sampled from mature thrusts (>2 km displacement) in the Apennines of Italy. We sheared both intact wafers and powdered fault materials at low (10 MPa) and in situ (53 MPa) normal stress under room-humidity and water-saturated conditions. We used velocity steps (1 to 300 ?m/s) and slide-hold-slide (3-1000 s holds) to assess the frictional stability and healing behaviour of these rocks. We observe that cataclastic fault rocks derived from competent limestones are characterized by high friction coefficients coupled with significant post-slip restrengthening and velocity-weakening behaviour. Conversely, intact foliated marly tectonites, sheared under the same conditions, show low friction, null post-slip healing and stable velocity-strengthening behaviour suggesting that these rocks deform aseismically. To extrapolate these opposite mechanical behaviours to the entire fault surface we developed a fault model integrating our mechanical data, field observations and balanced geological cross-sections. The mechanical heterogeneities highlighted in the model provide constraints for the distribution of fault patches with higher seismogenic potential.

Tesei, Telemaco; Collettini, Cristiano; Barchi, Massimiliano R.; Carpenter, Brett M.; Di Stefano, Giuseppe

2014-12-01

47

The Development of Open Water-lubricated Polycrystalline Diamond (PCD) Thrust Bearings for Use in Marine Hydrokinetic (MHK) Energy Machines  

Energy Technology Data Exchange (ETDEWEB)

Polycrstalline diamond (PCD) bearings were designed, fabricated and tested for marine-hydro-kinetic (MHK) application. Bearing efficiency and life were evaluated using the US Synthetic bearing test facility. Three iterations of design, build and test were conducted to arrive at the best bearing design. In addition life testing that simulated the starting and stopping and the loading of real MHK applications were performed. Results showed polycrystalline diamond bearings are well suited for MHK applications and that diamond bearing technology is TRL4 ready. Based on life tests results bearing life is estimated to be at least 11.5 years. A calculation method for evaluating the performance of diamond bearings of round geometry was also investigated and developed. Finally, as part of this effort test bearings were supplied free of charge to the University of Alaska for further evaluation. The University of Alaska test program will subject the diamond bearings to sediment laden lubricating fluid.

Cooley, Craig, H.; Khonsari, Michael,, M; Lingwall, Brent

2012-11-28

48

Efecto de la textura superficial en el desempeño a fricción de cojinetes de empuje / Effect of the Surface Texture on Friction Thrust Bearing Performance  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish En este trabajo se presenta un modelo teórico que establece relaciones entre las condiciones de operación de un cojinete de empuje, su micro-topografía acondicionada y el coeficiente de fricción, cuando opera en condiciones de Lubricación Hidrodinámica (HL). Entre los resultados más sobresalientes o [...] btenidos en una exploración efectuada con el modelo están: la construcción de un mapa donde se caracteriza el desempeño de estos componentes y la obtención de algunas relaciones entre diversos grupos adimensionales, los cuales muestran que es factible ampliar el régimen de lubricación hidrodinámica de este tipo de cojinetes mediante el acondicionamiento artificial de sus superficies. Abstract in english This paper shows a theoretical model which stablishes relations among the operational conditions of a thrust bearing, its conditioned microtopography and the friction coeficient when it works under Hydrodynamic Lubrication conditions. Among the most outstanding results obtained from an exploration m [...] ade with the model are: building of a map where the performance of these components is characterized and the obtention of some relations among several adimentional groups that show the possiblility to enhance the hydrodynamic lubrication regime for this sort of bearings by artificial conditioning of their surfaces.

F.A., Suárez-Bustamante; F.M., Toro-Botero; J.M., Vélez-Restrepo.

2012-03-01

49

Splined Ball-Bearing Carrier  

Science.gov (United States)

Ball-bearing carrier includes splined outer surface mating with slightly larger splined inner surface of housing and provides constant deadband, unaffected by movements of other components. Deadband needed to establish radial spring rate and provide for axial movement of bearing for thrust balance. Bearing carrier and bearing intended for use in high-pressure turbopump.

Moore, Jerry H.

1992-01-01

50

Magnetic Bearing  

Directory of Open Access Journals (Sweden)

Full Text Available The use of bearings is essential to all types of machines, especially in marine aspects they provide the function of supporting heavier component in a desired position. These bearings have contact with the rotating part and causes surface wear which can be controlled by lubrication. Researches have raised the standards of performance for rotating equipment by providing robust, cost effective, easy to implement magnetic bearing solutions. Use of magnetic bearings in ships can be more advantageous because it is contact –free resulting in no surface wear and hence no need for lubricant, no servicing and can work in clean environment. It has several other benefits like high reliability, clean environments, high speed applications, position and vibration control and can withstand in extreme conditions. Magnetic bearing will also restrict the translational sliding, which is merely a linear case of supporting a rotating object thus use of thrust block also eliminated. Magnetic bearing technology has become viable because of advances in micro-processing controllers that allows for confident and robust active control. This paper discusses more about the construction, principle and working of magnetic bearing in detail.

Anbuselvan. T

2013-06-01

51

Ball Bearing Mechanics  

Science.gov (United States)

Load-deflection relationships for different types of elliptical contacts such as those found in a ball bearing are developed. Simplified expressions that allow quick calculations of deformation to be made simply from a knowledge of the applied load, the material properties, and the geometry of the contacting elements are presented. Ball bearings subjected to radial, thrust and combined ball loads are analyzed. A design criterion for fatigue life of ball bearings is developed. The section of a satisfactory lubricant, as well as describing systems that provide a constant flow of lubricant to the contact, is considered.

Hamrock, B. J.; Dowson, D.

1981-01-01

52

A MICRO TURBINE DEVICE WITH ENHANCED MICRO AIR-BEARINGS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As part of progress in developing a micro gas turbine engine, this paper presents the design, fabrication and testing of a silicon-based micro turbine device, which is driven by compressed air. To improve its rotational speed and stability, the turbine device has enhanced journal air bearing and thrust air bearings. The thrust air bearings are utilized for supporting the rotor from both its top- and bottom- sides. The top thrust air bearing employs pump-in type spiral grooves, and the bottom ...

Shan, X. -c; Zhang, Qide; Sun, Y. F.; Maeda, R.

2006-01-01

53

Hydrostatic and hybrid bearing design  

CERN Document Server

Hydrostatic and Hybrid Bearing Design is a 15-chapter book that focuses on the bearing design and testing. This book first describes the application of hydrostatic bearings, as well as the device pressure, flow, force, power, and temperature. Subsequent chapters discuss the load and flow rate of thrust pads; circuit design, flow control, load, and stiffness; and the basis of the design procedures and selection of tolerances. The specific types of bearings, their design, dynamics, and experimental methods and testing are also shown. This book will be very valuable to students of engineering des

Rowe, W B

1983-01-01

54

Big bearings. Unsung hero; Kyodaina jikuuke. Hitome ni tsukanai hatarakimono  

Energy Technology Data Exchange (ETDEWEB)

This paper introduces examples of the use of big bearings. Bearings are divided largely into those used for radial load supporting and those used for thrust load supporting, while big bearings are often used for the latter usage. Thrust bearings include a cutter heat supporting bearing for tunnel excavator working underground, in addition to those used for swing motion of parabolic antennas and tower cranes. A bearing used in an excavator has an outer diameter of about half that of the excavator. The outer diameter of a shielding machine practically used in tunnel drilling currently has an outer diameter of 14,140 mm, and the outer diameter of the bearing is 7200 mm (bearing weighing 45 tons). Other big thrust bearings may include a swing tower swinging thrust bearing used in a continuous casting facility. Big radial bearings are used in iron and steel making facilities. This paper describes two examples of bearings used in this application. A spherical roller bearing to support converter trunion should be of an ultra big size to withstand total weight of about 1400 tons composed of a converter weight and weight of steel to be processed. A four-row cylindrical roller bearing to support the backup roll of a thick plate rolling mill is a bearing with durability against large loads to support reduction rolls whose size have become increasingly large. 2 refs., 5 figs.

Nanba, S. [Koyo Seiko Co. Ltd., Osaka (Japan)

1997-03-05

55

Experimental Evaluation of Journal Bearing Stability and New Gas Bearing Material  

Science.gov (United States)

It has been estimated that the noise levels in aircraft engine transmissions can be reduced by as much as 10 dB through the use of journal bearings. The potential benefits of lower noise levels include reduced wear, longer gear life and enhanced comfort for passengers and crew. Based on this concept the journal-thrust wave bearing was analyzed and its performance was evaluated. Numerical codes, developed over the past 30 years by Dr. Dimofte, were used to predict the performance of the bearing. The wave bearing is a fluid film bearing and therefore was analyzed using the Reynolds pressure equation. The formulation includes turbulent flow concepts and possesses a viscosity-temperature correction. The centrifugal growth of the bearing diameter and the deformation of the bearing under gear loads were also incorporated into the code. An experimental rig was developed to test the journal-thrust wave bearing.

Keith, Theo G., Jr.; Dimofte, Florin

2001-01-01

56

Thrusting, halotectonics, and sedimentation in the Spanish Pyrenees  

Energy Technology Data Exchange (ETDEWEB)

The Spanish Pyrenees are a linked system of regional thrust sheets and intermontane basins which formed during the Tertiary collision of the European and Iberian plates. The structural evolution of the Pyrenees was controlled by Mesozoic extensional structures and evaporite-bearing strata which served as the regional decollement and produced widespread pre- to postthrusting halotectonic folds. Palinspastic restoration of Cretaceous strata from the Pyrenean realm delineates a large normal-faulted embayment in the northern Iberian margin. Thicker sediments within the bay, coupled with the southward emplacement of the Cotiella-Montsec thrust sheet, caused underlying evaporites to flow toward the basin margins, producing folds such as the Mediano anticline.

Anastasio, D.J.

1988-08-01

57

Micro thrust and heat generator  

Science.gov (United States)

A micro thrust and heat generator have a means for providing a combustion fuel source to an ignition chamber of the micro thrust and heat generator. The fuel is ignited by a ignition means within the micro thrust and heat generator`s ignition chamber where it burns and creates a pressure. A nozzle formed from the combustion chamber extends outward from the combustion chamber and tappers down to a narrow diameter and then opens into a wider diameter where the nozzle then terminates outside of said combustion chamber. The pressure created within the combustion chamber accelerates as it leaves the chamber through the nozzle resulting in pressure and heat escaping from the nozzle to the atmosphere outside the micro thrust and heat generator. The micro thrust and heat generator can be microfabricated from a variety of materials, e.g., of polysilicon, on one wafer using surface micromachining batch fabrication techniques or high aspect ratio micromachining techniques (LIGA). 30 figs.

Garcia, E.J.

1998-11-17

58

Thrust Force Analysis of Tripod Constant Velocity Joint Using Multibody Model  

Science.gov (United States)

A tripod constant velocity joint is used in the driveshaft of front wheel drive vehicles. Thrust force generated by this joint causes lateral vibration in these vehicles. To analyze the thrust force, a detailed model is constructed based on a multibody dynamics approach. This model includes all principal parts of the joint defined as rigid bodies and all force elements of contact and friction acting among these parts. This model utilizes a new contact modeling method of needle roller bearings for more precise and faster computation. By comparing computational and experimental results, the appropriateness of this model is verified and the principal factors inducing the second and third rotating order components of the thrust force are clarified. This paper also describes the influence of skewed needle rollers on the thrust force and evaluates the contribution of friction forces at each contact region to the thrust force.

Sugiura, Hideki; Matsunaga, Tsugiharu; Mizutani, Yoshiteru; Ando, Yosei; Kashiwagi, Isashi

59

Thrust Bearing Governed Clinker Extraction System in Producer Gas Plant  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the process of Producer Gas Production; clinker/ash is formed as a waste material. This clinker is removed by equipment named as Ash Bowl which rotates on the “Guide Roller” by the application of hydraulic pressure. This process having many problems like formation of large size clinker which require excess hydraulic pressure, guide roller is unable to scatter the hydraulic pressure equally in all the direction on the ash bowl to crush the clinker, more hydraulic pressure is required fo...

Ram Prasad Verma; Prof. Manish Verma; Dr. Arvind Dewangan

2013-01-01

60

Direct measurement of MPD thrust  

Science.gov (United States)

An integrally mounted accelerometer has been used to obtain direct thrust measurements during operation of a magnetoplasmadynamic (MPD) thruster. The structural oscillations which can mask the accelerometer output have been ameliorated by stiffening the thruster to increase the lowest resonant frequency above the 1kHz region of interest. In addition, signal conditioning is used to provide a high signal-to-noise accelerometer output waveform. Impulse response measurement of the thruster frequency response function has proven to be an effective means of selecting the signal filter and estimating measurement errors. Comparison of the total impulse derived from the accelerometer output with that from a swinging arm thrust stand indicates 3 percent agreement, providing some confidence in the viability of the accelerometer thrust measurement technique.

Berg, J. M.; Kelly, A. J.; Jahn, R. G.

1984-01-01

 
 
 
 
61

Magnetic Bearing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The use of bearings is essential to all types of machines, especially in marine aspects they provide the function of supporting heavier component in a desired position. These bearings have contact with the rotating part and causes surface wear which can be controlled by lubrication. Researches have raised the standards of performance for rotating equipment by providing robust, cost effective, easy to implement magnetic bearing solutions. Use of magnetic bearings in ships can be more advantag...

Anbuselvan. T; Vinothkumar.K; Sai Vikash. M

2013-01-01

62

Pulsed Electric Propulsion Thrust Stand Calibration Method  

Science.gov (United States)

The evaluation of the performance of any propulsion device requires the accurate measurement of thrust. While chemical rocket thrust is typically measured using a load cell, the low thrust levels associated with electric propulsion (EP) systems necessitate the use of much more sensitive measurement techniques. The design and development of electric propulsion thrust stands that employ a conventional hanging pendulum arm connected to a balance mechanism consisting of a secondary arm and variable linkage have been reported in recent publications by Polzin et al. These works focused on performing steady-state thrust measurements and employed a static analysis of the thrust stand response. In the present work, we present a calibration method and data that will permit pulsed thrust measurements using the Variable Amplitude Hanging Pendulum with Extended Range (VAHPER) thrust stand. Pulsed thrust measurements are challenging in general because the pulsed thrust (impulse bit) occurs over a short timescale (typically 1 micros to 1 millisecond) and cannot be resolved directly. Consequently, the imparted impulse bit must be inferred through observation of the change in thrust stand motion effected by the pulse. Pulsed thrust measurements have typically only consisted of single-shot operation. In the present work, we discuss repetition-rate pulsed thruster operation and describe a method to perform these measurements. The thrust stand response can be modeled as a spring-mass-damper system with a repetitive delta forcing function to represent the impulsive action of the thruster.

Wong, Andrea R.; Polzin, Kurt A.; Pearson, J. Boise

2011-01-01

63

Another Look at Rocket Thrust  

Science.gov (United States)

Rocket propulsion is often introduced as an example of Newton's third law. The rocket exerts a force on the exhaust gas being ejected; the gas exerts an equal and opposite force--the thrust--on the rocket. Equivalently, in the absence of a net external force, the total momentum of the system, rocket plus ejected gas, remains constant. The law of…

Hester, Brooke; Burris, Jennifer

2012-01-01

64

Superconducting bearings  

International Nuclear Information System (INIS)

The physics and technology of superconducting bearings is reviewed. Particular attention is given to the use of high-temperature superconductors (HTSs) in rotating bearings. The basic phenomenology of levitational forces is presented, followed by a brief discussion of the theoretical models that can be used for conceptual understanding and calculations. The merits of various HTS bearing designs are presented, and the behaviour of HTS bearings in typical situations is discussed. The article concludes with a brief survey of various proposed applications for HTS bearings. (author)

65

Fatigue life of double row slewing ball bearing with irregular geometry  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Standard procedure for bearing life calculation, as described in standard ISO281:2008, was developed for standard, rather small axial or thrust rolling bearings. Since the geometry and manufacturing procedures of large rolling slewing bearings are considerably different from those of standard rolling bearings, different calculation procedures have to be used. The paper describes a computational procedure, where the geometry of the bearing is described with vectors, which enables modelling of ...

Potoc?nik, Rok; Go?ncz, Pe?ter; Flas?ker, Joz?e; Glodez?, Srec?ko

2012-01-01

66

The R and D D's bearing test benches  

International Nuclear Information System (INIS)

In power generation plants, rotating machines are involved in energy transformation processes and safety systems. The bearings supporting the rotors and the thrust bearings play a crucial role in the reliability of these machines. The phenomena encountered straddle several disciplines: hydrodynamics, tribology, thermomechanics, materials and vibrations in a specific environment, namely: thin fluid film, solid mechanical components and shaft rotation. Means of analysing the behaviour of these components (bearings and thrust bearings) have been developed and implemented. These consists of the EDYOS (Etude Dynamique des Organes de Supportage) code for dynamically studying bearing devices and several related bench tests. In reality, in order to understand the complex physical phenomena encountered in these components, it is vital to carry out analyses and experimental validations. Since these investigations cannot be carried out on actual machines, test benches have been built which can subject the sample bearings to the equivalent stresses. (author)

67

Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig  

Science.gov (United States)

The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig is an apparatus for vibration testing of turbomachine blades in a vacuum at rotational speeds from 0 to 40,000 rpm. This rig includes (1) a vertically oriented shaft on which is mounted an assembly comprising a rotor holding the blades to be tested, (2) two actively controlled heteropolar radial magnetic bearings at opposite ends of the shaft, and (3) an actively controlled magnetic thrust bearing at the upper end of the shaft. This rig is a more capable successor to a prior apparatus, denoted the Dynamic Spin Rig (DSR), that included a vertically oriented shaft with a mechanical thrust bearing at the upper end and a single actively controlled heteropolar radial magnetic bearing at the lower end.

Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Mehmed, Oral; Johnson, Dexter; Montague, Gerald; Duffy, Kirsten; Jansen, Ralph

2005-01-01

68

Foil bearings  

Science.gov (United States)

The rolling element bearings (REB's) which support many turbomachinery rotors offer high load capacity, low power requirements, and durability. Two disadvantages of REB's are: (1) rolling or sliding contact within the bearing has life-limiting consequences; and (2) REB's provide essentially no damping. The REB's in the Space Shuttle Main Engine (SSME) turbopumps must sustain high static and dynamic loads, at high speeds, with a cryogenic fluid as lubricant and coolant. The pump end ball bearings limit the life of the SSME high pressure oxygen turbopump (HPOTP). Compliant foil bearing (CFB) manufacturers have proposed replacing turbopump REB's with CFB's CFB's work well in aircraft air cycle machines, auxiliary power units, and refrigeration compressors. In a CFB, the rotor only contracts the foil support structure during start up and shut down. CFB damping is higher than REB damping. However, the load capacity of the CFB is low, compared to a REB. Furthermore, little stiffness and damping data exists for the CFB. A rotordynamic analysis for turbomachinery critical speeds and stability requires the input of bearing stiffness and damping coefficients. The two basic types of CFB are the tension-dominated bearing and the bending-dominated bearing. Many investigators have analyzed and measured characteristics of tension-dominated foil bearings, which are applied principally in magnetic tape recording. The bending-dominated CFB is used more in rotating machinery. This report describes the first phase of a structural analysis of a bending-dominated, multileaf CFB. A brief discussion of CFB literature is followed by a description and results of the present analysis.

Elrod, David A.

1993-11-01

69

Lubrication of an 85-mm ball bearing with RP-1  

Science.gov (United States)

A parametric experimental investigation of an 85 millimeter bore angular contact ball bearing running in RP-1 fuel was performed at speeds of 10,000 to 24,000 rpm. Thrust loads were varied from 4450 to 17,800 Newtons (1000 to 4000 lbs.). Radial loads were varied from 1335 to 13,350 Newtons (300 to 3000 lbs.). RP-1 lubrication for the bearing was provided through a stationary jet ring located adjacent to the test bearing outer ring. Increases in both the thrust and radial loads resulted in increased bearing temperature, while increases in shaft speed resulted in much more dramatic increases in bearing temperature. These trends are typical for ball bearings operating under these types of conditions. Results are given for outer ring temperatures of the test bearing at the various test conditions employed. In addition, the heat energy removed from the bearing by the RP-1 was determined by measuring the increase in temperature as the RP-1 passed through the bearing. Results showed that the amount of heat energy removed by the RP-1 increased with both shaft speed and RP-1 flow rate to the bearing.

Addy, Harold E., Jr.; Schuller, Fredrick T.

1993-01-01

70

The preliminary design of bearings for the control system of a high-temperature lithium-cooled nuclear reactor  

Science.gov (United States)

The design of bearings for the control system of a fast reactor concept is presented. The bearings are required to operate at temperatures up to 2200 F in one of two fluids, lithium or argon. Basic bearing types are the same regardless of the fluid. Crowned cylindrical journals were selected for radially loaded bearings and modified spherical bearings were selected for bearings under combined thrust and radial loads. Graphite and aluminum oxide are the materials selected for the argon atmosphere bearings while cermet compositions (carbides or nitrides bonded with refractory metals) were selected for the lithium lubricated bearings. Mounting of components is by shrink fit or by axial clamping utilizing differential thermal expansion.

Yacobucci, H. G.; Waldron, W. D.; Walowit, J. A.

1973-01-01

71

Static Load Distribution in Ball Bearings  

Science.gov (United States)

A numerical procedure for computing the internal loading distribution in statically loaded, single-row, angular-contact ball bearings when subjected to a known combined radial and thrust load is presented. The combined radial and thrust load must be applied in order to avoid tilting between inner and outer rings. The numerical procedure requires the iterative solution of Z + 2 simultaneous nonlinear equations - where Z is the number of the balls - to yield an exact solution for axial and radial deflections, and contact angles. Numerical results for a 218 angular-contact ball bearing have been compared with those from the literature and show significant differences in the magnitudes of the ball loads, contact angles, and the extent of the loading zone.

Ricci, Mario

2010-01-01

72

Measuring Model Rocket Engine Thrust Curves  

Science.gov (United States)

This paper describes a method and setup to quickly and easily measure a model rocket engine's thrust curve using a computer data logger and force probe. Horst describes using Vernier's LabPro and force probe to measure the rocket engine's thrust curve; however, the method of attaching the rocket to the force probe is not discussed. We show how a…

Penn, Kim; Slaton, William V.

2010-01-01

73

Computer-aided selection of materials for cryogenic turbopump bearings  

Science.gov (United States)

The life requirement for the angular contact ball bearings in the Space Shuttle Main Engine (SSME) high-pressure-oxygen turbopump (HPOTP) is 7.5 hours. In actual operation, significantly shorter service life has been experienced. The objective of this current program is to identify bearing materials and/or materials processing techniques offering significant potential for extending HPOTP bearing performance life. A thermomechanical analysis of the HPOTP shaft/bearing system was performed with the SHABERTH (SHaft-BEaring-THermal) computer program. Bearing fatigue life, ball-race contact stress, heat generation rate, bulk ring temperatures, and circumferential stress in the inner rings were quantified as functions of radial load, thrust load, and ball-race contact friction. The analysis results were used to formulate criteria that are being used for the selection of special materials for future turbopump bearings.

Maurer, R. E.; Pallini, R. A.

1985-01-01

74

Low thrust chemical rocket technology  

Science.gov (United States)

An on-going technology program to improve the performance of low thrust chemical rockets for spacecraft on-board propulsion applications is reviewed. Improved performance and lifetime is sought by the development of new predictive tools to understand the combustion and flow physics, introduction of high temperature materials and improved component designs to optimize performance, and use of higher performance propellants. Improved predictive technology is sought through the comparison of both local and global predictions with experimental data. Predictions are based on both the RPLUS Navier-Stokes code with finite rate kinetics and the JANNAF methodology. Data were obtained with laser-based diagnostics along with global performance measurements. Results indicate that the modeling of the injector and the combustion process needs improvement in these codes and flow visualization with a technique such as 2-D laser induced fluorescence (LIF) would aid in resolving issues of flow symmetry and shear layer combustion processes. High temperature material fabrication processes are under development and small rockets are being designed, fabricated, and tested using these new materials. Rhenium coated with iridium for oxidation protection was produced by the Chemical Vapor Deposition (CVD) process and enabled an 800 K increase in rocket operating temperature. Performance gains with this material in rockets using Earth storable propellants (nitrogen tetroxide and monomethylhydrazine or hydrazine) were obtained through component redesign to eliminate fuel film cooling and its associated combustion inefficiency while managing head end thermal soakback. Material interdiffusion and oxidation characteristics indicated that the requisite lifetimes of tens of hours were available for thruster applications. Rockets were designed, fabricated, and tested with thrusts of 22, 62, 440 and 550 N. Performance improvements of 10 to 20 seconds specific impulse were demonstrated. Higher performance propellants were evaluated: Space storable propellants, including liquid oxygen (LOX) as the oxidizer with nitrogen hydrides or hydrocarbon as fuels. Specifically, a LOX/hydrazine engine was designed, fabricated, and shown to have a 95 pct theoretical c-star which translates into a projected vacuum specific impulse of 345 seconds at an area ratio of 204:1. Further performance improvment can be obtained by the use of LOX/hydrogen propellants, especially for manned spacecraft applications, and specific designs must be developed and advanced through flight qualification.

Schneider, Steven J.

1992-01-01

75

Pulsed Ejector Thrust Amplification Tested and Modeled  

Science.gov (United States)

There is currently much interest in pulsed detonation engines for aeronautical propulsion. This, in turn, has sparked renewed interest in pulsed ejectors to increase the thrust of such engines, since previous, though limited, research had indicated that pulsed ejectors could double the thrust in a short device. An experiment has been run at the NASA Glenn Research Center, using a shrouded Hartmann-Sprenger tube as a source of pulsed flow, to measure the thrust augmentation of a statistically designed set of ejectors. A Hartmann- Sprenger tube directs the flow from a supersonic nozzle (Mach 2 in the present experiment) into a closed tube. Under appropriate conditions, an oscillation is set up in which the jet flow alternately fills the tube and then spills around flow emerging from the tube. The tube length determines the frequency of oscillation. By shrouding the tube, the flow was directed out of the shroud as an axial stream. The set of ejectors comprised three different ejector lengths, three ejector diameters, and three nose radii. The thrust of the jet alone, and then of the jet plus ejector, was measured using a thrust plate. The arrangement is shown in this photograph. Thrust augmentation is defined as the thrust of the jet with an ejector divided by the thrust of the jet alone. The experiments exhibited an optimum ejector diameter and length for maximizing the thrust augmentation, but little dependence on nose radius. Different frequencies were produced by changing the length of the Hartmann-Sprenger tube, and the experiment was run at a total of four frequencies. Additional measurements showed that the major feature of the pulsed jet was a starting vortex ring. The size of the vortex ring depended on the frequency, as did the optimum ejector diameter.

Wilson, Jack

2004-01-01

76

May the Force Be With You: Thrust  

Science.gov (United States)

In this lesson, students will study how propellers and jet turbines generate thrust. This lesson focuses on Isaac Newton's 3rd Law of Motion, which states that for every action there is an equal and opposite reaction.

Integrated Teaching and Learning Program,

77

Evolution of the Puente Hills Thrust Fault  

Science.gov (United States)

This study aims to assess the evolution of the blind Puente Hills thrust fault system (PHT) by determining its age of initiation, lateral propagation history, and changes in slip rate over time. The PHT presents one of the largest seismic hazards in the United States, given its location beneath downtown Los Angeles. The PHT is comprised of three fault segments: the Los Angeles (LA), Santa Fe Springs (SFS), and Coyote Hills (CH). The LA and SFS segments are characterized by growth stratigraphy where folds formed by uplift on the fault segments have been continually buried by sediment from the Los Angeles and San Gabriel rivers. The CH segment has developed topography and is characterized by onlapping growth stratigraphy. This depositional setting gives us the unique opportunity to measure uplift on the LA and SFS fault segments, and minimum uplift on the CH fault segment, as the difference in sediment thicknesses across the buried folds. We utilize depth converted oil industry seismic reflection data to image the fold geometries. Identifying time-correlative stratigraphic markers for slip rate determination in the basin has been a problem for researchers in the past, however, as the faunal assemblages observed in wells are time-transgressive by nature. To overcome this, we utilize the sequence stratigraphic model and well picks of Ponti et al. (2007) as a basis for mapping time-correlative sequence boundaries throughout our industry seismic reflection data from the present to the Pleistocene. From the Pleistocene to Miocene we identify additional sequence boundaries in our seismic reflection data from imaged sequence geometries and by correlating industry well formation tops. The sequence and formation top picks are then used to build 3-dimensional surfaces in the modeling program Gocad. From these surfaces we measure the change in thicknesses across the folds to obtain uplift rates between each sequence boundary. Our results show three distinct phases of deformation on the LA and SFS segments: an early period characterized by fault-propagation or structural wedge kinematics that terminates in the early Pleistocene, followed by a period of quiescence. The faults were subsequently reactivated in the middle Pleistocene and propagated upward to detachments, with the deformation characterized by fold-bend folding kinematics. Slip on the LA segment decreases to the West, suggesting lateral growth in that direction. Our work highlights the need to assess along-strike variability in slip rate when assessing the seismic hazard of a compressional fault, as marginal sites may significantly underestimate fault activity. Ponti, D. J. et al. A 3-Dimensional Model of Water-Bearing Sequences in the Dominguez Gap Region, Long Beach, California. US Geological Survey Open-File Report 1013 (2007).

Bergen, K. J.; Shaw, J. H.; Dolan, J. F.

2013-12-01

78

FROM STUDIES ON THE THRUST IN SWIMMING  

Directory of Open Access Journals (Sweden)

Full Text Available Swimming speed is determined by many factors, including weight preparation of the swimmer which is one of the most important ones. This power is directly related to the speed a swimmer can reach in water, that is the value of thrust. The aim of the study was to establish the level of thrust and swimming speed of the 2nd year students (n=20 of the University School of Physical Education (USPE in Pozna? and to compare them with the results of study from 1983 in which the 4th year students (n=20 of the USPE in Pozna? were studied. The current study was carried out in the context of the long-term changes in swimming technique. Research methods: measurement of thrust in real conditions was performed using a prototype device for the measurement of thrust of a swimmer which makes it possible to register the force in the water environment; swimming speed was established on the basis of the time needed to cover the distance of 25 metres, according to the regulations of the Polish Swimming Association. Conclusions: the students taking part in the 1983 study had higher values of thrust, but a lower speed than the students taking part in the 2006 study, which suggests that apart from the thrust the technique of swimming has a important influence of the swimming speed.

Strzelczyk, R.

2008-07-01

79

Assessment of natural crack initiation and its propagation in slow speed bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Monitoring of bearings is an essential part of most condition monitoring programmes in rotating machinery. This paper demonstrates the use of acoustic emission (AE) measurements to detect, monitor and locate natural defect initiation and propagation in a thrust rolling element bearing. To undertake this task a special purpose test-rig was built that allowed for accelerated natural degradation of a bearing race. It is concluded that sub-surface initiation and subsequent crack...

Elforjani, Mohamed; Mba, David

2009-01-01

80

Effect of blade outlet angle on radial thrust of single-blade centrifugal pump  

International Nuclear Information System (INIS)

Single-blade centrifugal pumps are widely used as sewage pumps. However, a large radial thrust acts on a single blade during pump operation because of the geometrical axial asymmetry of the impeller. This radial thrust causes vibrations of the pump shaft, reducing the service life of bearings and shaft seal devices. Therefore, to ensure pump reliability, it is necessary to quantitatively understand the radial thrust and clarify the behavior and generation mechanism. This study investigated the radial thrust acting on two kinds of single-blade centrifugal impellers having different blade outlet angles by experiments and computational fluid dynamics (CFD) analysis. Furthermore, the radial thrust was modeled by a combination of three components, inertia, momentum, and pressure, by applying an unsteady conservation of momentum to this impeller. As a result, the effects of the blade outlet angle on both the radial thrust and the modeled components were clarified. The total head of the impeller with a blade outlet angle of 16 degrees increases more than the impeller with a blade outlet angle of 8 degrees at a large flow rate. In this case, since the static pressure of the circumference of the impeller increases uniformly, the time-averaged value of the radial thrust of both impellers does not change at every flow rate. On the other hand, since the impeller blade loading becomes large, the fluctuation component of the radial thrust of the impeller with the blade outlet anglef the impeller with the blade outlet angle of 16 degrees increases. If the blade outlet angle increases, the fluctuation component of the inertia component will increase, but the time-averaged value of the inertia component is located near the origin despite changes in the flow rate. The fluctuation component of the momentum component becomes large at all flow rates. Furthermore, although the time-averaged value of the pressure component is almost constant, the fluctuation component of the pressure component becomes large at a large flow rate. In addition to the increase of the fluctuation component of this pressure component, because the fluctuation component of the inertia and momentum components becomes large (as mentioned above), the radial thrust increases at a large flow rate, as is the case for the impeller with a large blade outlet angle.

 
 
 
 
81

Misalignment in Gas Foil Journal Bearings: An Experimental Study  

Science.gov (United States)

As gas foil journal bearings become more prevalent in production machines, such as small gas turbine propulsion systems and microturbines, system-level performance issues must be identified and quantified in order to provide for successful design practices. Several examples of system-level design parameters that are not fully understood in foil bearing systems are thermal management schemes, alignment requirements, balance requirements, thrust load balancing, and others. In order to address some of these deficiencies and begin to develop guidelines, this paper presents a preliminary experimental investigation of the misalignment tolerance of gas foil journal bearing systems. Using a notional gas foil bearing supported rotor and a laser-based shaft alignment system, increasing levels of misalignment are imparted to the bearing supports while monitoring temperature at the bearing edges. The amount of misalignment that induces bearing failure is identified and compared to other conventional bearing types such as cylindrical roller bearings and angular contact ball bearings. Additionally, the dynamic response of the rotor indicates that the gas foil bearing force coefficients may be affected by misalignment.

Howard, Samuel A.

2008-01-01

82

Thrust Augmentation with Mixer/Ejector Systems  

Science.gov (United States)

Older commercial aircraft often exceed FAA (Federal Aviation Administration) sideline noise regulations. The major problem is the jet noise associated with the high exhaust velocities of the low bypass ratio engines on such aircraft. Mixer/ejector exhaust systems can provide a simple means of reducing the jet noise on these aircraft by mixing cool ambient air with the high velocity engine gases before they are exhausted to ambient. This paper presents new information on thrust performance predictions, and thrust augmentation capabilities of mixer/ejectors. Results are presented from the recent development program of the patented Alternating Lobe Mixer Ejector Concept (ALMEC) suppressor system for the Gulfstream GII, GIIB and GIII aircraft. Mixer/ejector performance procedures are presented which include classical control volume analyses, compound compressible flow theory, lobed nozzle loss correlations and state of the art computational fluid dynamic predictions. The mixer/ejector thrust predictions are compared to subscale wind tunnel test model data and actual aircraft flight test measurements. The results demonstrate that a properly designed mixer/ejector noise suppressor can increase effective engine bypass ratio and generate large thrust gains at takeoff conditions with little or no thrust loss at cruise conditions. The cruise performance obtained for such noise suppressor systems is shown to be a strong function of installation effects on the aircraft.

Presz, Walter M., Jr.; Reynolds, Gary; Hunter, Craig

2002-01-01

83

The two intracrustal boundary thrusts of the Himalaya  

Science.gov (United States)

The series of four different, steeply inclined thrusts which sharply sever the youthful autochthonous Cenozoic sedimentary zone, including the Siwalik, from the mature old Lesser Himalayan subprovince is collectively known as the Main Boundary Thrust (MBT). In the proximity of this trust in northwestern and eastern sectors, the parautochtonous Lesser Himalayan sedimentary formations are pushed up and their narrow frontal parts split into imbricate sheets with attendant repetition and inversion of lithostratigraphic units. The superficially steeper thrust plane seems to flatten out at depth. The MBT is tectonically and seismically very active at the present time. The Main Central Thrust (MCT), inclined 30° to 45° northwards, constitutes the real boundary between the Lesser and Great Himalaya. Marking an abrubt change in the style and orientation of structures and in the grade of metamorphism from lower amphibolitefacies of the Lesser Himalayan to higher metamorphic facies of the Great Himalayan, the redefined Main Central Thrust lies at a higher level as that originally recognized by A. Heim and A. Gansser. They had recognized this thrust as the contact of the mesozonal metamorphics against the underlying sedimentaries or epimetamorphics. It has now been redesignated as the Munsiari Thrust in Kumaun. It extends northwest in Himachal as the Jutogh Thrust and farther in Kashmir as the Panjal Thrust. In the eastern Himalaya the equivalents of the Munsiari Thrust are known as the Paro Thrust and the Bomdila Thrust. The upper thrust surface in Nepal is recognized as the Main Central Thrust by French and Japanese workers. The easterly extension of the MCT is known as the Khumbu Thrust in eastern Nepal, the Darjeeling Thrust in the Darjeeling-Sikkim region, the Thimpu Thrust in Bhutan and the Sela Thrust in western Arunachal. Significantly, hot springs occur in close proximity to this thrust in Kumaun, Nepal and Bhutan. There are reasons to believe that movement is taking place along the MCT, although seismically it is less active than the MBT.

Valdiya, K. S.

1980-07-01

84

Axisymmetric thrust-vectoring nozzle performance prediction  

International Nuclear Information System (INIS)

Throat-hinged geometrically variable converging-diverging thrust-vectoring nozzles directly affect the jet flow geometry and rotation angle at the nozzle exit as a function of the nozzle geometry, the nozzle pressure ratio and flight velocity. The consideration of nozzle divergence in the effective-geometric nozzle relation is theoretically considered here for the first time. In this study, an explicit calculation procedure is presented as a function of nozzle geometry at constant nozzle pressure ratio, zero velocity and altitude, and compared with experimental results in a civil thrust-vectoring scenario. This procedure may be used in dynamic thrust-vectoring nozzle design performance predictions or analysis for civil and military nozzles as well as in the definition of initial jet flow conditions in future numerical VSTOL/TV jet performance studies

85

Thrust cell technology for modular engines  

Science.gov (United States)

A modular platelet engine is a new generation propulsion system which finds potential application in three major space flight vehicles: the airbreathing National AeroSpace Plane, an all rocket propelled Single Stage To Orbit system, and a new Upper Stage propulsion system. A modular platelet engine system consists of several self-contained linear engine arrays. Each engine array contains a set of small thrust cells consisting of an injector with integrated igniter, a regeneratively cooled chamber, and an internal nozzle expansion section with a square or rectangular exit plane. This paper discusses the critical design aspects of these thrust cells, and the underlying platelet etching, diffusion bonding, and cold forming fabrication technology which assures the simultaneous benefits of high performance, long life, and low weight. Two thrust cell generations will be presented; the first has been developed and evaluated, and the second, an extension and improvement, is presently being defined and developed.

Siebenhaar, A.; Orton, George F.; Leonard, James R.

1993-06-01

86

Low thrust NTP for manned Mars operations  

International Nuclear Information System (INIS)

The impact on manned Mars operations of selecting a nuclear thermal propulsion (NTP) module with a relatively low total thrust, in the 222--445 kN (50--100 klbf) range, is explored. The propulsion module may consist of one or more engines. Selection of a low total thrust is robust across a wide range of payload masses provided perigee kicks are utilized for trans-Mars insertion (TMI). The longer time taken for TMI when using a low total thrust and perigee kicks allows for extensive system evaluation before commitment to Earth escape, but will require fuels with lifetimes of at least a few hours. Longer fuel life could be obtained without using advanced fuels by operating at lower fuel temperatures later in the mission. The additional traversals through the Van Allen belts inherent with using perigee kicks for TMI does not significantly increase the radiation exposure of the crew. Negative reactivity from xenon buildup between perigee kicks can be mitigated by coasting on the intermediate orbits, by altering the selection of the intermediate orbits, by deep throttling, or by building in sufficient excess reactivity. Thrust misalignments of a realistic magnitude do not pose an Earth impact hazard. Engine crosstalk in clusters is a very manageable problem. High propulsion module reliability can be achieved with a propulsion module consisting of a cluster of three or four small engines without dropping the module thrust-to-weight ratio below an acceptable level. A total dratio below an acceptable level. A total design thrust in the 222--445 kN range is high enough for Earth return with only one of the engines of the cluster operating

87

A six degree-of-freedom thrust sensor for a labscale hybrid rocket  

Science.gov (United States)

A six degree-of-freedom thrust sensor was designed, constructed, calibrated, and tested using the labscale hybrid rocket at the University of Arkansas at Little Rock. The system consisted of six independent legs: one parallel to the axis of symmetry of the rocket for main thrust measurement, two vertical legs near the nozzle end of the rocket, one vertical leg near the oxygen input end of the rocket, and two separated horizontal legs near the nozzle end. Each leg was composed of a rotational bearing, a load cell, and a universal joint above and below the load cell. The leg was designed to create point contact along only one direction and minimize the non-axial forces applied to the load cell. With this system, force in each direction and moments for roll, pitch, and yaw can be measured. The system was calibrated and tested using a labscale hybrid rocket using gaseous oxygen and hydroxyl-terminated polybutadiene solid fuel. The thrust stand proved to be stable during calibration tests. Thrust force vector components and roll, pitch, and yaw moments were calculated for test firings with an oxygen mass flow rate range of 0.0174-0.0348 kg s-1.

Wright, Ann M.; Wright, Andrew B.; Born, Traig; Strickland, Ryan

2013-12-01

88

A microNewton thrust stand for average thrust measurement of pulsed microthruster.  

Science.gov (United States)

A torsional thrust stand has been developed for the study of the average thrust for microNewton pulsed thrusters. The main body of the thrust stand mainly consists of a torsional balance, a pair of flexural pivots, a capacitive displacement sensor, a calibration assembly, and an eddy current damper. The behavior of the stand was thoroughly studied. The principle of thrust measurement was analyzed. The average thrust is determined as a function of the average equilibrium angle displacement of the balance and the spring stiffness. The thrust stand has a load capacity up to 10 kg, and it can theoretically measure the force up to 609.6 ?N with a resolution of 24.4 nN. The static calibrations were performed based on the calibration assembly composed of the multiturn coil and the permanent magnet. The calibration results demonstrated good repeatability (less than 0.68% FSO) and good linearity (less than 0.88% FSO). The assembly of the multiturn coil and the permanent magnet was also used as an exciter to simulate the microthruster to further research the performance of the thrust stand. Three sets of force pulses at 17, 33.5, and 55 Hz with the same amplitude and pulse width were tested. The repeatability error at each frequency was 7.04%, 1.78%, and 5.08%, respectively. PMID:24387476

Zhou, Wei-Jing; Hong, Yan-Ji; Chang, Hao

2013-12-01

89

Bearing endurance tests in vacuum for sputtered molybdenum disulfide films  

Science.gov (United States)

Angular-contact, 440C stainless steel, ball bearings with sputtered MoS2 films 0.0000006 x 10-7m (6000 A) thick were evaluated in a vacuum bearing chamber (1750 rpm, 137.9-N- (31-lbf-) thrust load) for endurance. Two types of sputtered films were evaluated: (1) MOS2 sputtered directly onto bearing components, and (2) a thin 0.0000001 x 10-7m (1000 A) underlayer of Cr3Si2 subsequently sputtered with MoS2. Bearing test evaluations in vacuum showed that endurance lives of more than 1000 hours (105,000,000 cycles) were obtained with bearings (cage, races, and balls) directly sputtered with MoS2. The same endurance lives were also obtained when only the races and cage were sputtered with an underlayer of Cr3Si2 and subsequently with MoS2.

Spalvins, T.

1975-01-01

90

Development of an indirect counterbalanced pendulum optical-lever thrust balance for micro- to millinewton thrust measurement  

International Nuclear Information System (INIS)

This paper describes the design and testing of an indirect hanging pendulum thrust balance using a laser-optical-lever principle to provide micro- to millinewton thrust measurement for the development of electric propulsion systems. The design philosophy allows the selection of the total thrust range in order to maximize resolution through a counterbalanced pendulum principle, as well as passive magnetic damping in order to allow relatively rapid transient thrust measurement. The balance was designed for the purpose of hollow cathode microthruster characterization, but could be applied to other electric propulsion devices in the thrust range of micro- to millinewtons. An initial thrust characterization of the T5 hollow cathode is presented

91

Fluid Film Bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A hydrodynamic fluid film bearing in which a plurality of circumferentially spaced bearing elements are provided, defining areas of support for the rotating part of the bearing. At least some of the bearing elements are adjustable during operation to vary lubrication conditions in the fluid film. The bearing elements are of sufficiently high stiffness that the position of the entire bearing surface of each element is essentially independent of the pressure in the fluid film encountered during...

Martin, James Keith; Parkins, David Walter

1995-01-01

92

Application of thrust vector control on airships  

Directory of Open Access Journals (Sweden)

Full Text Available  Concepts of manual and automatic thrust vector control of a modern airship are investigated and compared by simulation of the vehicle movement dynamics. Airship movement simulation with application of the mathematical apparatus of differential transformations is carried out.

?.?. ???????

2005-03-01

93

Thrust Stand for Electric Propulsion Performance Evaluation  

Science.gov (United States)

An electric propulsion thrust stand capable of supporting testing of thrusters having a total mass of up to 125 kg and producing thrust levels between 100 microN to 1 N has been developed and tested. The design features a conventional hanging pendulum arm attached to a balance mechanism that converts horizontal deflections produced by the operating thruster into amplified vertical motion of a secondary arm. The level of amplification is changed through adjustment of the location of one of the pivot points linking the system. Response of the system depends on the relative magnitudes of the restoring moments applied by the displaced thruster mass and the twisting torsional pivots connecting the members of the balance mechanism. Displacement is measured using a non-contact, optical linear gap displacement transducer and balance oscillatory motion is attenuated using a passive, eddy-current damper. The thrust stand employs an automated leveling and thermal control system. Pools of liquid gallium are used to deliver power to the thruster without using solid wire connections, which can exert undesirable time-varying forces on the balance. These systems serve to eliminate sources of zero-drift that can occur as the stand thermally or mechanically shifts during the course of an experiment. An in-situ calibration rig allows for steady-state calibration before, during and after thruster operation. Thrust measurements were carried out on a cylindrical Hall thruster that produces mN-level thrust. The measurements were very repeatable, producing results that compare favorably with previously published performance data, but with considerably smaller uncertainty.

Polzin, Kurt A.; Markusic, Thomas E.; Stanojev, Boris J.; Dehoyos, Amado; Spaun, Benjamin

2006-01-01

94

Rocketdyne LOX bearing tester program  

Science.gov (United States)

The cause, or causes, for the Space Shuttle Main Engine ball wear were unknown, however, several mechanisms were suspected. Two testers were designed and built for operation in liquid oxygen to empirically gain insight into the problems and iterate solutions in a timely and cost efficient manner independent of engine testing. Schedules and test plans were developed that defined a test matrix consisting of parametric variations of loading, cooling or vapor margin, cage lubrication, material, and geometry studies. Initial test results indicated that the low pressure pump thrust bearing surface distress is a function of high axial load. Initial high pressure turbopump bearing tests produced the wear phenomenon observed in the turbopump and identified an inadequate vapor margin problem and a coolant flowrate sensitivity issue. These tests provided calibration data of analytical model predictions to give high confidence in the positive impact of future turbopump design modification for flight. Various modifications will be evaluated in these testers, since similar turbopump conditions can be produced and the benefit of the modification will be quantified in measured wear life comparisons.

Keba, J. E.; Beatty, R. F.

1988-01-01

95

Defining the Himalayan Main Central Thrust in Nepal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An inverted metamorphic field gradient associated with a crustal-scale south-vergent thrust fault, the Main Central Thrust, has been recognized along die Himalaya for over 100 years. A major problem in Himalayan structural geology is that recent workers have mapped the Main Central Thrust within the Greater Himalayan Sequence high-grade metamorphic sequence along several different structural levels. Some workers map the Main Central Thrust as coinciding with a lithological contact, others as ...

Searle, Mp; Law, Rd; Godin, L.; Larson, Kp; Streule, Mj; Cottle, Jm; Jessup, Mj

2008-01-01

96

Spiral Groove Aerodynamic Bearings  

Directory of Open Access Journals (Sweden)

Full Text Available In order to research the conical spiral groove aerodynamic bearings, the bearing's lubrication analysis mathematical model is established. The Reynolds equation of the laminar flow condition is used to calculate the 3D pressure distribution by the locally finite difference method. The influence law of the gas film pressure distribution on the bearing performance is revealed by researching the nonlinear dynamic characteristic of gas film. It reveals the laws that the effect of the bearing structural parameters on the gas film pressure distribution and the bearing capacity. The results show that the spiral groove change the gas film thickness distribution and the gas film pressure distribution and achieve good bearing dynamic pressure effect, which improve the bearing performance and the bearing stability; The structure parameters affect the gas film pressure distribution and the static characteristics. Therefore, a reasonable choice of bearing structural parameters contributes to improve the bearing's static characteristics and bearing capacity.

Jia Chen-Hui

2013-01-01

97

Conical Magnetic Bearings Developed for Active Stall Control in Gas Turbine Engines  

Science.gov (United States)

Active stall control is a current research area at the NASA Glenn Research Center that offers a great benefit in specific fuel consumption by allowing the gas turbine to operate beyond the onset of stall. Magnetic bearings are being investigated as a new method to perform active stall control. This enabling global aviation safety technology would result in improved fuel efficiency and decreased carbon dioxide emissions, as well as improve safety and reliability by eliminating oil-related delays and failures of engine components, which account for 40 percent of the commercial aircraft departure delays. Active stall control works by perturbing the flow in front of the compressor stage such that it cancels the pressure wave, which causes the compressor to go into stall. Radial magnetic bearings are able to whirl the shaft so that variations in blade tip leakage would flow upstream causing a perturbation wave that could cancel the rotating stall cell. Axial or thrust magnetic bearings cannot be used to cancel the surge mode in the compressor because they have a very low bandwidth and thus cannot modulate at a high enough frequency. Frequency response is limited because the thrust runner cannot be laminated. To improve the bandwidth of magnetic thrust bearings, researchers must use laminations to suppress the eddy currents. A conical magnetic bearing can be laminated, resulting in increased bandwidth in the axial direction. In addition, this design can produce both radial and thrust force in a single bearing, simplifying the installation. The proposed solution combines the radial and thrust bearing into one design that can be laminated--a conical magnetic bearing. The new conical magnetic bearing test rig, funded by a Glenn fiscal year 2002 Director's Discretionary Fund, was needed because none of the existing rigs has an axial degree of freedom. The rotor bearing configuration will simulate that of the main shaft on a gas turbine engine. One conical magnetic bearing replaces the ball bearing in front of the compressor, and the second replaces the roller bearing behind the burner. The rig was made operational to 10,000 rpm under Smart Efficient Components funding, and both position and current adaptive vibration control have been demonstrated. Upon program completion, recommendations will be made as to the efficacy of the conical magnetic bearing for active stall control.

Trudell, Jeffrey J.; Kascak, Albert F.; Provenza, Andrew J.; Buccieri, Carl J.

2004-01-01

98

Recent research and development of bearings for helium circulator  

International Nuclear Information System (INIS)

This paper mainly describes recent studies and successful applications of water lubricated bearing and gas lubricated bearing. Both types of bearing seem to be suitable for a turbo machine installed in an atomic energy plant - such as the helium circulator of a HTGR - not to be affected by radioactivity, so we have been attracted by them for about 10 years. The former was investigated theoretically taking account of turbulent flow due to the low viscosity of water, and compared with the experimental data. Good agreement was obtained, and a successful example applied to a small-sized high speed air compressor is shown. The latter was investigated using a large-sized bearing test rig simulated to an actual machine. The tilting pad journal bearing and the tilting pad thrust bearing were taken and improved for some aspects. These bearings have been taken into service on an actual circulator and are now operating successfully. Currently, a magnetic bearing is being studied to pay special attention to endurance for an earthquake and catcher bearing system. We would like to have an opportunity to present these results in the near future. (author). 5 refs, 15 figs, 2 tabs

99

Lubrication of Space Shuttle Main Engine Turbopump Bearings  

Science.gov (United States)

The Space Shuttle has three main engines that are used for propulsion into orbit. These engines are fed propellants by four turbopumps on each engine. A main element in the turbopump is the bearings supporting the rotor that spins the turbine blades and the pump impeller. These bearings are required to spin at very high speeds, support radial and thrust loads, and have high wear resistance without the benefit of lubrication. The liquid hydrogen and oxygen propellants flow through the bearings to cool the surfaces. The volatile nature of the propellants excludes any conventional means of lubrication. Lubrication for these bearings is provided by the ball separator inside the bearing. The separator is a composite material that supplies a transfer film of lubrication to the rings and balls. New separator materials and lubrication schemes have been investigated at Marshall Space Flight Center in a bearing test rig with promising results. Hybrid bearings with silicon nitride balls have also been evaluated. The use of hybrid, silicon nitride ball bearings in conjunction -with better separator materials has shown excellent results. The work that Marshall has done is being utilized in turbopumps flying on the space shuttle fleet and will be utilized in future space travel. This result of this work is valuable for all aerospace and commercial applications where high-speed bearings are used.

Gibson, Howard; Munafo, Paul (Technical Monitor)

2001-01-01

100

Passive magnetic bearing configurations  

Science.gov (United States)

A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

Post, Richard F. (Walnut Creek, CA)

2011-01-25

 
 
 
 
101

Introduction to ball bearings  

Science.gov (United States)

The purpose of a ball bearing is to provide a relative positioning and rotational freedom while transmitting a load between two structures, usually a shaft and a housing. For high rotational speeds (e.g., in gyroscope ball bearings) the purpose can be expanded to include rotational freedom with practically no wear in the bearing. This condition can be achieved by separating the bearing parts with a coherent film of fluid known as an elastohydrodynamic film. This film can be maintained not only when the bearing carries the load on a shaft, but also when the bearing is preloaded to position the shaft to within micro- or nano-inch accuracy and stability. Background information on ball bearings is provided, different types of ball bearings and their geometry and kinematics are defined, bearing materials, manufacturing processes, and separators are discussed. It is assumed, for the purposes of analysis, that the bearing carries no load.

Hamrock, B. J.; Dowson, D.

1981-01-01

102

MATERIALS PERFORMANCE TARGETED THRUST FY 2004 PROJECTS  

Energy Technology Data Exchange (ETDEWEB)

The Yucca Mountain site was recommended by the President to be a geological repository for commercial spent nuclear fuel and high-level radioactive waste. The multi-barrier approach was adopted for assessing and predicting system behavior, including both natural barriers and engineered barriers. A major component of the long-term strategy for safe disposal of nuclear waste is first to completely isolate the radionuclides in waste packages for long times and then to greatly retard the egress and transport of radionuclides from penetrated packages. The goal of the Materials Performance Targeted Thrust program is to further enhance the understanding of the role of engineered barriers in waste isolation. In addition, the Thrust will explore technical enhancements and seek to offer improvements in materials costs and reliability.

DOE

2005-09-13

103

NATURAL BARRIERS TARGETED THRUST FY 2004 PROJECTS  

Energy Technology Data Exchange (ETDEWEB)

This booklet contains project descriptions of work performed by the Department of Energy (DOE), Office of Civilian Radioactive Waste Management (OCRWM), Office of Science and Technology and International's (OST&I) Natural Barriers Targeted Thrust during Fiscal Year (FY) 2004. The Natural Barriers Targeted Thrust is part of OST&I's Science and Technology Program which supports the OCRWM mission to manage and dispose of high-level radioactive waste and spent nuclear fuel in a manner that protects health, safety, and the environment; enhances national and energy security; and merits public confidence. In general, the projects described will continue beyond FY 2004 assuming that the technical work remains relevant to the proposed Yucca Mountain Repository and sufficient funding is made available to the Science and Technology Program.

NA

2005-07-27

104

Thrust production by a mechanical swimming lamprey  

Science.gov (United States)

To develop a comprehensive model of lamprey locomotion, we use a robotic lamprey to investigate the formation of the wake structure, the shedding vorticity from the body, and the relationship between thrust production and pressure on the surface of the robot. The robot mimics the motion of living lamprey in steady swimming by using a programmable microcomputer to actuate 13 servomotors that produce a traveling wave along the length of the lamprey body. The amplitude of the phase-averaged surface pressure distribution along the centerline of the robot increases toward the tail, which is consistent with previous momentum balance experiments. This indicates that thrust is produced mainly at the tail. The phase relationship between the pressure signal and the vortex shedding from the tail is also examined, showing a clear connection between the location of vortex structures and the fluctuations of the pressure signal.

Leftwich, M. C.; Smits, A. J.

2011-05-01

105

Thrust vector control using electric actuation  

Science.gov (United States)

Presently, gimbaling of launch vehicle engines for thrust vector control is generally accomplished using a hydraulic system. In the case of the space shuttle solid rocket boosters and main engines, these systems are powered by hydrazine auxiliary power units. Use of electromechanical actuators would provide significant advantages in cost and maintenance. However, present energy source technologies such as batteries are heavy to the point of causing significant weight penalties. Utilizing capacitor technology developed by the Auburn University Space Power Institute in collaboration with the Auburn CCDS, Marshall Space Flight Center (MSFC) and Auburn are developing EMA system components with emphasis on high discharge rate energy sources compatible with space shuttle type thrust vector control requirements. Testing has been done at MSFC as part of EMA system tests with loads up to 66000 newtons for pulse times of several seconds. Results show such an approach to be feasible providing a potential for reduced weight and operations costs for new launch vehicles.

Bechtel, Robert T.; Hall, David K.

1995-01-01

106

MATERIALS PERFORMANCE TARGETED THRUST FY 2004 PROJECTS  

International Nuclear Information System (INIS)

The Yucca Mountain site was recommended by the President to be a geological repository for commercial spent nuclear fuel and high-level radioactive waste. The multi-barrier approach was adopted for assessing and predicting system behavior, including both natural barriers and engineered barriers. A major component of the long-term strategy for safe disposal of nuclear waste is first to completely isolate the radionuclides in waste packages for long times and then to greatly retard the egress and transport of radionuclides from penetrated packages. The goal of the Materials Performance Targeted Thrust program is to further enhance the understanding of the role of engineered barriers in waste isolation. In addition, the Thrust will explore technical enhancements and seek to offer improvements in materials costs and reliability

107

THRUST PREDICTION PROGRAM FOR MARINE JET POWER  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Marine Jet Power, MJP wishes to investigate the possibility of transforming their current Thrust Prediction Program, TPP written in C++ source code into a more up to date tool for their sales staff. The old TPP, though an accurate and precise tool, is not documented and lacks commentaries in the source code. Therefore the beginning of this master thesis was about documenting and investigates what methods were used to calculate the performance of the water jet system.The next step was splittin...

Bergsek, Mattias

2011-01-01

108

Lightweight Chambers for Thrust Cell Applications  

Science.gov (United States)

Traditional metals like steel and copper alloys have been used for many years to fabricate injector and chamber components of thruster assemblies. While the materials perform well, reducing engine weights would help existing and future vehicles gain performance and payload capability. It may now be possible to reduce current thruster weights up to 50% by applying composite materials. In this task, these materials are being applied to an existing thrust cell design to demonstrate new fabrication processes and potential weight savings. Two ceramic matrix composite (CMC) designs, three polymer matrix composite (PMC) designs, and two metal matrix composite (MMC) designs are being fabricated as small chamber demonstration units. In addition, a new alloy of copper, chrome, and niobium (Cu-8Cr-4Nb) is being investigated for thrust chamber liners since it offers higher strength and increased cycle life over traditional alloys. This new alloy is being used for the liner in each MMC and PMC demonstration unit. During June-August of 2000, hot-fire testing of each unit is planned to validate designs in an oxygen/hydrogen environment at chamber pressures around 850 psi. Although the weight savings using CMC materials is expected to be high, they have proven to be much harder to incorporate into chamber designs based on current fabrication efforts. However, the PMC & MMC concepts using the Cu-8Cr-4Nb liner are nearly complete and ready for testing. Additional efforts intend to use the PMC & MMC materials to fabricate a full size thrust chamber (60K lb(sub f) thrust class). The fabrication of this full size unit is expected to be complete by October 2000, followed by hot-fire testing in November-December 2000.

Elam, S.; Effinger, M.; Holmes, R.; Lee, J.; Jaskowiak, M.

2000-01-01

109

Feasibility of magnetic bearings for advanced gas turbine engines  

Science.gov (United States)

The application of active magnetic bearings to advanced gas turbine engines will provide a product with major improvements compared to current oil lubricated bearing designs. A rethinking of the engine rotating and static structure design is necessary and will provide the designer with significantly more freedom to meet the demanding goals of improved performance, increased durability, higher reliability, and increased thrust to weight ratio via engine weight reduction. The product specific technology necessary for this high speed, high temperature, dynamically complex application has been defined. The resulting benefits from this approach to aircraft engine rotor support and the complementary engine changes and improvements have been assessed.

Hibner, David; Rosado, Lewis

1992-01-01

110

Rotational infrared polarization modulator using a MEMS-based air turbine with different types of journal bearing  

Science.gov (United States)

This paper describes rotational infrared polarization modulators using a micro-electromechanical-system-based (MEMS-based) air turbine with different types of journal bearing. Three types of journal bearing, circular, symmetrical two-lobed and asymmetrical seven-lobed journal bearing, were compared. Using an optical displacement meter and a high speed camera, it was confirmed that all turbines exhibit three modes of rotation: (a) low speed mode, (b) intermediate mode and (c) high speed mode in this order, when decreasing N2 flow rate to an aerostatic thrust bearing. In the low speed mode, the rotor is lifted up by excess flow to the thrust bearing, making a contact with an upper layer. In the high speed mode, the rotor is levitated without any contact to the upper and lower layers by balanced flow to the thrust bearing, and the maximum rotational speed of 74000 rpm was achieved using the asymmetrical seven-lobed bearing. The rotation in this mode is, however, discontinuous due to the collision between the rotor and the journal bearing. It was concluded that a journal bearing with sufficient load capacity is necessary for continuous high speed rotation.

Hara, Motoaki; Tanaka, Shuji; Esashi, Masayoshi

2003-03-01

111

The Zagros hinterland fold-and-thrust belt in-sequence thrusting, Iran  

Science.gov (United States)

The collision of the Iranian microcontinent with the Afro-Arabian continent resulted in the deformation of the Zagros orogenic belt. The foreland of this belt in the Persian Gulf and Arabian platform has been investigated for its petroleum and gas resource potentials, but the Zagros hinterland is poorly investigated and our knowledge about its deformation is much less than other parts of this orogen. Therefore, this work presents a new geological map, stratigraphic column and two detailed geological cross sections. This study indicates the presence of a hinterland fold-and-thrust belt on northeastern side of the Zagros orogenic core that consists of in-sequence thrusting and basement involvement in this important part of the Zagros hinterland. The in-sequence thrusting resulted in first- and second-order duplex systems, Mode I fault-bend folding, fault-propagation folding and asymmetric detachment folding which indicate close relationships between folding and thrusting. Study of fault-bend folds shows that layer-parallel simple shear has the same role in the southeastern and northwestern parts of the study area (?e = 23.4 ± 9.1°). A major lateral ramp in the basement beneath the Talaee plain with about one kilometer of vertical offset formed parallel to the SW movement direction and perpendicular to the major folding and thrusting.

Sarkarinejad, Khalil; Ghanbarian, Mohammad Ali

2014-05-01

112

Vacuum Thrust Optimised Expansion Deflection Nozzles  

Science.gov (United States)

ED nozzles have long been considered for launch vehicle applications, due to their postulated twin benefits of reduced length and altitude compensating capability. However, the difficulties involved in modelling the inviscid/viscous jet boundaries and associated flow phenomena during wake closure, have prevented the creation of a reliable method for the prediction of the performance characteristics of the type through atmospheric flight. However, if the operating regime of the nozzle is restricted to vacuum conditions (e.g. upper stages, and OTVs, etc), the wake region of the ED nozzle is permanently closed. Under these circumstances, the prediction of the pressure distribution along the viscous/inviscid flow boundary, and the complex interaction of the fluid flows during wake closure, becomes unnecessary. Therefore thrust calculation may be accomplished by conventional techniques, provided reliable methods are available for the prediction of the flow in the throat region (which may be arbitrarily displaced and inclined to the axis of revolution), and estimation of the pressure acting on the base of the central pintle. Prediction of ED nozzle throat flows has been accomplished by the use of CFD techniques, described in a previous paper. The analysis in this paper has been extended to complete nozzles by including a conventional method of characteristics based optimisation routine for the outer shroud contour, and a semi-empirical method for prediction of pintle base pressures. A brief parametric study is presented, outlining the effects of throat configuration (including throat wall radii, and radial displacement and inclination) on the performance of axisymmetric and planar ED nozzles under vacuum conditions. Whilst the method used for base pressure prediction requires several simplifying assumptions which affect the accuracy, results from an ongoing experimental program are reducing this uncertainty. Further as nozzles designed for vacuum operation are likely to have extremely high area ratios to maximise thrust coefficient, the relative magnitude of the pintle base pressure is small compared to the forces generated on the shroud, reducing the sensitivity of overall thrust calculations to errors in base pressure prediction. A comparison of thrust performance of bell and ED nozzles reveals that considerable reductions in length are possible, in the region of 30%. By implication this should result in a significant lowering of system mass. This conclusion is further supported by consideration of the unrealistic worst case scenario, which is the assumption of zero thrust contribution from the pintle. This analysis still produces length savings of over 20% when compared to conventional optimised bell nozzles.

Taylor, N. V.; Hempsell, C. M.

2002-01-01

113

Paleostress analysis of the Osning Thrust, Germany  

Science.gov (United States)

The Osning Thrust is a 100 km-scale NW-SE fault separating the Lower Saxony Basin to the NE from the Münsterland Basin to the SE. The fault has accommodated a polyphase deformation that started at least when it acted as one of the normal border faults of the Jurassic Lower Saxony Basin. Tectonic inversion of the basin in Late Cretaceous-Early Paleocene times led to the development of the SE-vergent Osning Thrust and to folding of rocks. A paleostress analysis was carried out in order to decipher the polyphase kinematics of the Osning Thrust. The fault slip data were collected in the folded Albian to Turonian stratigraphic units of the Münsterland basin, in the SE vicinity of a 20 km-long steep segment of the Osning Thrust. Fault slip data in sufficient amount to perform paleostress inversion were collected in 10 sites among 23 visited outcrops. Abundant minor faults trend sub-parallel to the NW-SE steep segment of the Osning Thrust but, surprisingly, they are dextral (and not reverse) in type. Another major set of E-W striking minor faults is remarkable. It corresponds to conjugate systems of either reverse or normal faults and to oblique- to strike-slip faults in a less extent. The paleostress tensors reveal a ca. N-S compression recorded in 5 locations under which the NW-SE steep faults were dextral and the E-W striking S- and N- dipping faults were reverse. Six stress tensors fit with a ca. N-S extension. They are calculated from E-W striking S- and N- dipping normal to oblique normal faults. The same N-S trend of minimum stress axis is also recorded with NNE-SSW dextral and E-W sinistral faults. We propose that along the studied segment of the Osning Thrust a N-S compressional stress field led to the inversion of the Lower Saxony Basin and that slip along the Osning Thrust was oblique reverse. At two locations, the N-S compressive stress states affected the rock prior to tilting of the beds (herein, due to folding) and at one site, the normal faults of the N-S extension clearly cut across reverse faults of the N-S compression. These two observations allow to propose a chronology between the reconstructed stress fields. While the N-S compression is presumably linked to the Late Cretaceous-Early Palaeocene inversion of the Lower Saxony Basin, the successive E-W extension is not constrained in age. However, it is known that tensional stresses have largely affected the west European platform in Oligocene times and this N-S extension revealed by the present study might be related to this tectonic event.

Saintot, Aline; Kozakovski, Anna; Pascal, Christophe

2013-04-01

114

Development and Testing of an Axial Halbach Magnetic Bearing  

Science.gov (United States)

The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2006-01-01

115

THE INFLUENCE OF THE ROLLER GEOMETRY ON THE STRESS FIELD IN LARGE SLEWING BEARINGS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The subject of this diploma work is to identify the impact of roller geometry on the stress field for large axial cylindrical roller bearings. A numerical calculation model is presented in order to parametrically examine the impact of roller geometry (profile, fillets), and variable material properties of raceway (case-hardened layer thickness) on the stress field in the raceway of the large thrust bearing.

Pavlic?, Lio

2011-01-01

116

Nanomechanical and analytical investigations on tribological layers for wear protection in slow running roller bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract In a tribological system consisting of roller thrust bearings and various lubricants, we investigated reaction layers formed under the presence of lubricants with low wear protection, high wear and fatigue protection as well as high wear but low fatigue protection. The bearings were tested under heavy-duty conditions in a FE-8 test rig in order to asses rapidly the efficiency of different reaction layer-systems. Chemical composition and microstructure analysis of the layer...

Reichelt, Manuela; Weirich, Thomas; Richter, Silvia; Aretz, Anke; Bueckins, Matthias; Wolf, Thomas; Gold, P. W.; Mayer, Joachim

2006-01-01

117

High-power, null-type, inverted pendulum thrust stand.  

Science.gov (United States)

This article presents the theory and operation of a null-type, inverted pendulum thrust stand. The thrust stand design supports thrusters having a total mass up to 250 kg and measures thrust over a range of 1 mN to 5 N. The design uses a conventional inverted pendulum to increase sensitivity, coupled with a null-type feature to eliminate thrust alignment error due to deflection of thrust. The thrust stand position serves as the input to the null-circuit feedback control system and the output is the current to an electromagnetic actuator. Mechanical oscillations are actively damped with an electromagnetic damper. A closed-loop inclination system levels the stand while an active cooling system minimizes thermal effects. The thrust stand incorporates an in situ calibration rig. The thrust of a 3.4 kW Hall thruster is measured for thrust levels up to 230 mN. The uncertainty of the thrust measurements in this experiment is +/-0.6%, determined by examination of the hysteresis, drift of the zero offset and calibration slope variation. PMID:19485530

Xu, Kunning G; Walker, Mitchell L R

2009-05-01

118

Optimum Staging with Varying Thrust Attitude Angle  

Directory of Open Access Journals (Sweden)

Full Text Available Optimum staging programme for step rockets of arbitrary number of stages having different specific impulses and mass fractions with stages is derived, the optimization criterion being minimum take-off weight for a desired burntout velocity at an assigned altitude. Variation of thrust attitude angle from stage to stage and effects of gravity factor are taken into account. Analysis is performed for a degenerate problem obtained by relaxing the altitude constraint and it has been shown that problems of Weisbord, Subotowicz, Hall & Zambelli and Malina & Summerfield are the particular cases of the degenerate problem.

T. N. Srivastava

2014-05-01

119

Factorization and resummation for transverse thrust  

CERN Document Server

We analyze transverse thrust in the framework of Soft Collinear Effective Theory and obtain a factorized expression for the cross section that permits resummation of terms enhanced in the dijet limit to arbitrary accuracy. The factorization theorem for this hadron-collider event-shape variable involves collinear emissions at different virtualities and suffers from a collinear anomaly. We compute all its ingredients at the one-loop order, and show that the two-loop input for next-to-next-to-leading logarithmic accuracy can be extracted numerically, from existing fixed-order codes.

Becher, Thomas

2015-01-01

120

Axial Halbach Magnetic Bearings  

Science.gov (United States)

Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2008-01-01

 
 
 
 
121

Effect of Tongue Thrust Swallowing on Position of Anterior Teeth  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background and aims. There is no consensus about the effect of tongue thrusting on incisor position. The purpose of this study was to evaluate the position of anterior teeth in growing children with tongue thrust swallowing. Materials and methods. In the present study 193 subjects with an age range of 9 to 13 years participated. All the patients were examined by a trained investigator and those having tongue thrust swallowing were selected and the position of their anterior teeth was com...

Tahereh Jalaly; Farzaneh Ahrari; Foroozandeh Amini

2009-01-01

122

Quadratic Programming Thrust Allocation and Management for Dynamic Positioning Ships  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To solve the complex thrust allocation problems of dynamic positioning ship with azimuth thrusters, the quadratic programming thrust allocation and management system was built. The power optimal thrust allocation was formulated as a quadratic programming problem by the linear treatments of inequality constraints and the optimal solution could be found in a finite amount of time. And some influence factors of thruster allocation were separated from algorithms and treated as a superstratum m...

Yushi Wei; Mingyu Fu; Jipeng Ning; Xingyan Sun

2013-01-01

123

Measurement of ice thrusts on dams  

Energy Technology Data Exchange (ETDEWEB)

Ice loads exerted on dams are not well understood. Measuring ice pressure is a challenge, especially when the ice environment is highly subject to creep. This paper discussed a program to evaluate ice load thrust on dams that was undertaken during the winter of 2007 to 2008 at La Gabelle and 2008 to 2009 at Beaumont and La Gabelle. The project involved measuring ice load thrust on the dam face in order to harmonize different design load criteria put forward by experts. The paper presented the preliminary results on the objectives of establishing maximum load levels and harmonizing ice load design criteria. Field program and instrumentation and the physical behaviour of ice were outlined. Ice pressure and ice load measurements were also discussed. It was concluded that the measurements near the dams yielded peak values of less than 150 kN/m, which was compatible with previous studies. Non-uniform distributions of the ice loads along the dam were observed, indicating that measurements at many points are needed in order to be meaningful. 10 refs.

Taras, A.; Cote, A.; Noel, P.; Lupien, R. [Institut de Recherche d' Hydro-Quebec, Varennes, PQ (Canada); Morse, B.; Pratt, Y. [Laval Univ., Quebec City, PQ (Canada); Stander, E. [State Univ. of New York Cobleskill College, Cobleskill, NY (United States); Comfort, G. [Fleet Technologies, Ottawa, ON (Canada)

2009-07-01

124

OMV/VTE variable thrust engine analysis  

Science.gov (United States)

The objective of the present work is to develop a predictive CFD based analytical tool for the Variable Thrust Engine (VTE) in the Orbital Maneuvering Vehicle (OMV). This objective is being accomplished within the framework of the Los Alamos KIVA computer code for chemically reactive flows with sprays. For the OMV application, the main structure of KIVA is to be retained while reformulating many of the phenomenological submodels, enhancing some of the numerics, and adding more features. The analytical model consists of the general conservation equations for two-phase reactive flows and of submodels for turbulence, chemical reactions, and bipropellant sprays. Tailoring this model to the OMV engine brings about the added complexities of combustion and flow processes that occur in a liquid hypergolic propellant rocket chamber. This report exposes the foundation upon which the analytical tool is being constructed and developed. Results from a cursory computational exercise involving the simulation of the flow and combustion processes in a hypothetical N2H4/N204 rocket engine thrust chamber is presented and discussed.

Larosillere, L.; Litchford, R.; Jeng, S. M.

1995-01-01

125

Emergency Control Aircraft System Using Thrust Modulation  

Science.gov (United States)

A digital longitudinal Aircraft Propulsion Control (APC system of a multiengine aircraft is provided by engine thrust modulation in response to comparing an input flightpath angle signal (gamma)c from a pilot thumbwheel. or an ILS system with a sensed flightpath angle y to produce an error signal (gamma)e that is then integrated (with reasonable limits) to generate a drift correction signal to be added to the error signal (gamma)e after first subtracting a lowpass filtered velocity signal Vel(sub f) for phugoid damping. The output error signal is multiplied by a constant to produce an aircraft thrust control signal ATC of suitable amplitude to drive a throttle servo for all engines. each of which includes its own full-authority digital engine control (FADEC) computer. An alternative APC system omits sensed flightpath angle feedback and instead controls the flightpath angle by feedback of the lowpass filtered velocity signal Vel(sub f) which also inherently provides phugoid damping. The feature of drift compensation is retained.

Burken, John J. (Inventor); Burcham, Frank W., Jr. (Inventor)

2000-01-01

126

Quantification of mass transfers and mineralogical transformations in a thrust fault (Monte Perdido thrust unit, southern Pyrenees, Spain)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In fold-and-thrust belts, shortening is mainly accommodated by thrust faults which are preferential zones for recrystallisation and mass transfer. This study focuses on a detachment fault related to the emplacement of the Monte Perdido thrust unit in the southern Pyrenees. The studied fault zone consists of a 10 m thick intensively foliated phyllonite developed within the Millaris marls, of Eocene age. The lithological homogeneity of the hanging wall and footwall allows us to compare the Mill...

Trincal, Vincent; Charpentier, Delphine; Buatier, Martine D.; Grobety, Bernard; Lacroix, Brice; Labaume, Pierre; Sizun, Jean-pierre

2014-01-01

127

Hot gas thrust vector control motor  

Science.gov (United States)

A hot gas thrust vector control (HGTVC) motor developed in the framework of a Foreign Weapon Evaluation program is discussed. Two HGTVC versions were evaluated on the two nozzles of the program, normal injection with a blunt pintle and 10 deg upstream injection with a tapered pintle. The HGTVC system was tested on a modified ORBUS-1 motor which is based on two technologies, namely, a composite chamber polar boss (CPB) and a two-piece C-C nozzle which threads to the CPB and receives two HGVs embedded into its exit cone, 180 deg apart. It is concluded that the composite polar bosses and C-C nozzles performed successfully in both firings.

Berdoyes, Michel; Ellis, Russell A.

1992-07-01

128

Thrust Production in a Mechanical Swimming Lamprey  

Science.gov (United States)

To develop a comprehensive model of lamprey locomotion, we use a robotic lamprey as a means of investigating the surface pressure and wake structure during swimming. A programmable microcomputer actuates 11 servomotors that produce a traveling wave along the length of the lamprey body. The waveform is based on the motion of the American eel (Anguilla rostrata), as described by Tytell and Lauder (2004) and kinematic studies of living lamprey. The amplitude of the phase-averaged surface pressure distribution along the centerline of the robot increases toward the tail, which is consistent with previous momentum balance experiments indicating that thrust is produced mainly at the tail. The phase relationship between the pressure signal and the vortex shedding from the tail is also examined. The project is supported by NIH CNRS Grant 1R01NS054271.

Leftwich, Megan; Smits, Alexander

2008-11-01

129

Secondary Production of Massive Quarks in Thrust  

CERN Document Server

We present a factorization framework that takes into account the production of heavy quarks through gluon splitting in the thrust distribution for e+ e- --> hadrons. The explicit factorization theorems and some numerical results are displayed in the dijet region where the kinematic scales are widely separated, which can be extended systematically to the whole spectrum. We account for the necessary two-loop matrix elements, threshold corrections, and include resummation up to N3LL order. We include nonperturbative power corrections through a field theoretical shape function, and remove the O(Lambda_QCD) renormalon in the partonic soft function by appropriate mass-dependent subtractions. Our results hold for any value of the quark mass, from an infinitesimally small (merging to the known massless result) to an infinitely large one (achieving the decoupling limit). This is the first example of an application of a variable flavor number scheme to final state jets.

Hoang, Andre H; Pietrulewicz, Piotr

2014-01-01

130

Electronics Engineering Department Thrust Area report FY'84  

Energy Technology Data Exchange (ETDEWEB)

This report describes the work of the Electronics Engineering Department Thrust Areas for FY'84: diagnostics and microelectronic engineering; signal and control engineering; microwave and pulsed power engineering; computer-aided engineering; engineering modeling and simulation; and systems engineering. For each Thrust Area, an overview and a description of the goals and achievements of each project is provided.

Minichino, C.; Phelps, P.L. (eds.)

1984-01-01

131

Thrust augmentation nozzle (TAN) concept for rocket engine booster applications  

Science.gov (United States)

Aerojet used the patented thrust augmented nozzle (TAN) concept to validate a unique means of increasing sea-level thrust in a liquid rocket booster engine. We have used knowledge gained from hypersonic Scramjet research to inject propellants into the supersonic region of the rocket engine nozzle to significantly increase sea-level thrust without significantly impacting specific impulse. The TAN concept overcomes conventional engine limitations by injecting propellants and combusting in an annular region in the divergent section of the nozzle. This injection of propellants at moderate pressures allows for obtaining high thrust at takeoff without overexpansion thrust losses. The main chamber is operated at a constant pressure while maintaining a constant head rise and flow rate of the main propellant pumps. Recent hot-fire tests have validated the design approach and thrust augmentation ratios. Calculations of nozzle performance and wall pressures were made using computational fluid dynamics analyses with and without thrust augmentation flow, resulting in good agreement between calculated and measured quantities including augmentation thrust. This paper describes the TAN concept, the test setup, test results, and calculation results.

Forde, Scott; Bulman, Mel; Neill, Todd

2006-07-01

132

Bearing Rigidity and Almost Global Bearing-Only Formation Stabilization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper studies the distributed control of bearing-constrained multi-agent formations using bearing-only measurements. In order to analyze bearing-constrained formations, we first present a bearing rigidity theory that is applicable to arbitrary dimensions. Based on the proposed bearing rigidity theory, we analyze two bearing-only formation control problems. In the first, each agent can measure the relative bearings to their neighbors in a global reference frame, while in...

Zhao, Shiyu; Zelazo, Daniel

2014-01-01

133

Thrust Measurements for a Pulse Detonation Engine Driven Ejector  

Science.gov (United States)

Results of an experimental effort on pulse detonation driven ejectors aimed at probing different aspects of PDE ejector processes, are presented and discussed. The PDE was operated using ethylene as the fuel and an equimolar oxygen/nitrogen mixture as the oxidizer at an equivalence ratio of one. The thrust measurements for the PDE alone are in excellent agreement with experimental and modeling results reported in the literature and serve as a Baseline for the ejector studies. These thrust measurements were then used as a basis for quantifying thrust augmentation for various PDE/ejector setups using constant diameter ejector tubes and various detonation tube/ejector tube overlap distances. The results show that for the geometries studied here, a maximum thrust augmentation of 24% is achieved. The thrust augmentation results are complemented by shadowgraph imaging of the flowfield in the ejector tube inlet area and high frequency pressure transducer measurements along the length of the ejector tube.

Santoro, Robert J.; Pak, Sibtosh; Shehadeh, R.; Saretto, S. R.; Lee, S.-Y.

2005-01-01

134

Thrust and efficiency of a self-field MPD thruster  

Science.gov (United States)

Thrust and efficiency of a quasi-steady multi-MW argon MPD thruster are determined for one-millisecond current pulses. Terminal voltage and impulse bit per pulse are measured for a benchmark thruster geometry on a swinging gate thrust stand in a dielectric vacuum tank, at a background pressure of 0.0001 torr, for a range of argon flow rates and arc currents. The quasi-steady thrust data scale quadratically with arc current, and confirm previous estimates of the electromagnetic and electrothermal components of thrust from magnetic and pressure probe measurements. Thruster efficiency is found to increase monotonically with specific impulse, reaching a value of 25% for 4.5 to 6.0 g/sec at 2000 seconds. Results of further experiments show that the inferred specific impulse for voltage fluctuation onset can be increased to 3000 seconds, and the thrust efficiency to above 30%.

Burton, R. L.; Clark, K. E.; Jahn, R. G.

1981-01-01

135

Redefining Medlicott-Wadia's main boundary fault from Jhelum to Yamuna: An active fault strand of the main boundary thrust in northwest Himalaya  

Science.gov (United States)

The MBT demarcates a tectonic boundary between the Tertiary Sub Himalaya and the pre-Tertiary Lesser Himalaya. South of the MBT, another tectonically important fault extends from Muzaffarabad and Riasi in Jammu-Kashmir to Bilaspur and Nahan in Himachal. Medlicott and Wadia had designated this fault the Main Boundary Fault (MBF) in Simla Hills and Jammu region respectively. In between these two areas, later workers gave local-area names to the MBF as the Riasi Thrust in Jammu, Palampur Thrust in Kangra, Bilaspur Thrust in Simla Hills and Nahan Thrust in Sirmur. We have reviewed and established the tectonostratigraphic framework and physical continuity of the lower Tertiary belt and the MBF. The lower Tertiary belt, lying south of the MBT, has characteristic tectonostratigraphic setting with discontinuous bodies of stromatolite-bearing Proterozoic limestone overlain with depositional contact by the Paleocene-lower part Middle Eocene marine Subathu/Patala formation which in turn overlain by the Upper Oligocene-Lower Miocene non-marine Dharamsala/Murree Formation. To avoid confusion with the MBT, we designate collectively the MBF and related faults as the Medlicott-Wadia Thrust (MWT). The MWT extends east of Hazara-Kashmir syntaxis to river Yamuna, covering a distance of ˜ 700 km. Further east of Yamuna, the lower Tertiary belt pinches out and the MWT merges with the sensuo-stricto MBT. The Proterozoic limestone represents the basement over which the lower Tertiary sediments were deposited. The limestone basement with its cover was detached by the MWT, exhuming to the surface and thrusting over largely the Siwalik group. The reactivated Balakot-Bagh Fault, causative fault for the 2005 Kashmir earthquake, extends southeast with right-step to the Riasi Thrust. The Riasi Thrust shows evidence of reactivation and active tectonic activity in Jammu region. It extends further east to the Palampur Thrust in Kangra reentrant, which lies within the 1905 Kangra earthquake rupture zone. The Bilaspur Thrust, continuation of the Palampur Thrust, shows active faulting south of Simla hills between Sataun and Yamuna River. These observations indicate that the MWT represents a southern strand of the sensuo-stricto MBT and shows active faulting in some segments.

Thakur, V. C.; Jayangondaperumal, R.; Malik, M. A.

2010-06-01

136

The Incredible Water Bear  

Science.gov (United States)

This image-rich Micscape Magazine article explores how water bears can be found almost everywhere yet are still unknown to almost everybody, why there are relatively few light microscope photographs of water bears in the literature and on the Web, and how light microscopy can outperform scanning electron microscopy when viewing these animals. It includes a list of historical references, early sketches, and colorful images of water bears, also known as tardigrades.

Martin Mach

137

Bearing restoration by grinding  

Science.gov (United States)

A joint program was undertaken by the NASA Lewis Research Center and the Army Aviation Systems Command to restore by grinding those rolling-element bearings which are currently being discarded at aircraft engine and transmission overhaul. Three bearing types were selected from the UH-1 helicopter engine (T-53) and transmission for the pilot program. No bearing failures occurred related to the restoration by grinding process. The risk and cost of a bearing restoration by grinding programs was analyzed. A microeconomic impact analysis was performed.

Hanau, H.; Parker, R. J.; Zaretsky, E. V.; Chen, S. M.; Bull, H. L.

1976-01-01

138

14 CFR 23.934 - Turbojet and turbofan engine thrust reverser systems tests.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Turbojet and turbofan engine thrust reverser systems... Powerplant General § 23.934 Turbojet and turbofan engine thrust reverser systems tests. Thrust reverser systems of turbojet or turbofan engines must meet the...

2010-01-01

139

14 CFR 25.934 - Turbojet engine thrust reverser system tests.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Turbojet engine thrust reverser system tests...Powerplant General § 25.934 Turbojet engine thrust reverser system tests. Thrust reversers installed on turbojet engines must meet the...

2010-01-01

140

Effect of cage design on characteristics of high-speed-jet-lubricated 35-millimeter-bore ball bearing. [turbojet engines  

Science.gov (United States)

Parametric tests were conducted with a 35 mm bore angular contact ball bearing with a double outer land guided cage. Provisions were made for jet lubrication and outer-ring cooling of the bearing. Test conditions included a combined thrust and radial load at nominal shaft speeds of 48,000 rpm, and an oil-in temperature of 394 K (250 F). Successful operation of the test bearing was accomplished up to 2.5 million DN. Test results were compared with those obtained with similar bearing having a single outer land guided cage. Higher temperatures were generated with the double outer land guided cage bearing, and bearing power loss and cage slip were greater. Cooling the outer ring resulted in a decrease in overall bearing operating temperature.

Schuller, F. T.; Pinel, S. I.; Signer, H. R.

1980-01-01

 
 
 
 
141

Anatomy of the Main Martir Thrust: a Non-terminal Suture in the Peninsular Ranges, Baja California, Mexico.  

Science.gov (United States)

We investigate part of the exhumed Peninsular Ranges batholith, a Mesozoic-Cenozoic continental margin magmatic arc. We use structural and microstructural data to constrain the displacement and kinematics of the Main Martir thrust (MMt) and compare these to a model. The thrust, which has been interpreted as a non-terminal suture, is a one to two kilometer-wide shear zone that divides the batholith into an eastern part underlain by continental crust and a western part underlain by juvenile oceanic crust. The thrust is not associated with any known occurrences of ophiolites or deep marine sediments, which could be expected if the oceanic arc had accreted with a continental margin above a subduction zone. From east to west the shear zone includes orthogneisses, epidote-bearing metavolcanic gneisses, migmatites, and garnet amphibolites in the hanging wall, as well as a 50m section of calc-silicates mostly underlain by upper greenschist-facies metavolcanic phyllites in the footwall. Phyllites form a continuous footwall assemblage in all traverses and are part of the Albian Alisitos Formation, which towards the thrust shows a progressive increase in metamorphic grade consistent with juxtaposition against hotter rocks of the hanging wall. Within the hanging wall some units are attenuated, discontinuous, or pinch out and the metamorphic grade varies from andalusite-bearing schists to sillimanite-bearing metapelitic migmatites. Metamorphism appears to have accompanied deformation. Oriented rock samples from both sides of the MMt record mylonitic fabrics with shallowly plunging mineral lineations. Rounding a bend in the MMt these lineations swing from northeast-plunging in the western segment to north-plunging in the southern segment. Our work shows that significant differences in lithology, metamorphic grade, and lineation orientation occur along strike of the MMt. The diverse lithologies suggest that some components of a subduction complex might be present, whereas the different peak metamorphic temperatures recorded could suggest that hanging wall metamorphism occurred during periodic, variable heating episodes. Our study area spans a sharp bend in the thrust, and we explore the possibility that an indentor corner caused the distinctive lineation pattern and variation in metamorphic grade.

Melis, E. A.; Johnson, S. E.; Koons, P. O.

2004-05-01

142

Early history and reactivation of the rand thrust, southern California  

Science.gov (United States)

The Rand thrust of the Rand Mountains in the northwestern Mojave Desert separates an upper plate of quartz monzonite and quartzofeldspathic to amphibolitic gneiss from a lower plate of metagraywacke and mafic schist (Rand Schist). The Rand thrust is considered part of the regionally extensive Vincent/Chocolate Mountain thrust system, which is commonly believed to represent a Late Cretaceous subduction zone. The initial direction of dip and sense of movement along the Vincent/Chocolate Mountain thrust are controversial. Microfabrics of mylonites and quartzites from the Rand Mountains were analyzed in an attempt to determine transport direction for this region, but the results are ambiguous. In addition, the southwestern portion of the Rand thrust was found to have been reactivated as a low-angle normal fault after subduction. Reactivation might have occurred shortly after subduction, in which case it could account for the preservation of high-pressure mineral assemblages in the Rand Schist, or it could be related to mid-Tertiary extension in the western United States. In either event, the reactivation might be responsible for the complicated nature of the microfabrics. The Rand Schist exhibits an inverted metamorphic zonation. Isograds in the schist are not significantly truncated by the reactivated segment of the Rand thrust. This indicates that other segments of the Vincent/Chocolate Mountain thrust should be re-evaluated for the possibility of late movement, even if they show an apparently undisturbed inverted metamorphic zonation.

Postlethwaite, Clay E.; Jacobson, Carl E.

143

Thrust stand for high-power electric propulsion devices  

Science.gov (United States)

A thrust stand for use with magnetoplasmadynamic (MPD) thrusters operated at powers up to 250 kW steady state has been built and tested. The stand was based on an inverted pendulum configuration which resulted in large displacements and high resolution. Up to 50 mm of deflection was observed under a force of 5 N. This large range of displacement significantly reduced the effects of facility induced vibrations on thrust measurements. A remotely operated system was provided for in situ calibration of the thrust stand prior to and immediately after data were obtained. Calibrations showed that thrust measurements were linear and repeatable to within a fraction of 1%. Structural distortions of the vacuum facility due to pumpdown were detected with an inclinometer located in the thrust stand base. Slope deviations as small as 10 arcsec could be compensated using a remotely controlled leveling motor. Early problems with magnetically induced tares caused by the thruster discharge current were reduced by rerouting high-current cables to decrease stray fields. Tares due to discharge current were on the order of 26 mN at 3000 A, and those due to an applied field current were 63 mN at 1400 A. The thrust stand was used with a water-cooled, applied field, steady-state MPD device at power levels up to 125 kW. Hot thruster firings as long as 1 h were performed. By precisely maintaining a level thrust stand base, thermal drift was held to about 2% of the full scale reading over this period. The remaining thermal drift could be subtracted from the thrust measurement to further reduce systematic error. Tares caused by the applied magnetic field were similarly removed. By subtracting tabulated discharge current magnetic tares, thrust measurement uncertainty was reduced to approximately 2% of the measured value.

Haag, T. W.

1991-05-01

144

Thrust Steering of a Gridded Ion Engine  

Science.gov (United States)

In any spacecraft installation of an ion propulsion system it is likely that there will be a need to alter the position of the thrust vector with respect to the centre of the vehicle, in order to minimise attitude and orbital perturbations during operation. Of most importance is the need to correct for the movements of the centre of mass of the spacecraft during operation. These movements are caused by the consumption of propellant, by the deployment and rotation of solar arrays, and by the varying radiation flux from the sun. As an example of the seriousness of this problem, the consumption due to this cause for an Intelsat VII class satellite with a lifetime of 15 years would be 26kg for an excursion of the centre of mass of just 1cm. As a consequence, large gimbal systems (approximately 10kg) are employed. Whilst these devices can perform perfectly well, they do represent a considerable mass overhead, amplify launch vibrations to the thrusters, as well as occupying a large volume, and presenting large cost (0.8Meuro) and additional reliability concerns. Consequently a method for providing direct vectoring of the ion beam has been developed using the technique of relative grid translation.

Jameson, P.

2004-10-01

145

Experimental Investigation of Thrust Faults in Homalite  

Science.gov (United States)

A sound interplay between experimental observations and numerical simulations can reveal a much greater insight into a scientific problem than either methodology alone, where numerics may direct the next experiment or vise-versa. With this motivation, experiments are designed to study the ground motion of thrust faults near the fault trace and to compare with true-to-life numerical simulation results. Through the application of an external load with a press to a thin sheet of Homalite, a high-density polymer, and discharging a capacitor across a wire, slip is initiated along a carefully treated interface. Several key parameters such as the angle of the interface and the applied load may be varied to achieve fundamentally different wave phenomenon, namely a super shear or sub-Rayleigh event. Laser vibrometers are used to record the velocity normal to the free surface on the hanging wall and the footwall. With high-speed cameras, photoelastic fringes are obtained in transmission through the Homalite slab, outputting information about the stress state in the material. Discoveries on the material response to the applied wave field are possible with the information from the photoelastic images in conjunction with the velocity traces, especially in the differences between a super shear and a sub Rayleigh event. Experimental results validate the salient features of the numerical simulations in 2D and even more closely in 3D.

Gabuchian, V.; Rosakis, A.; Lapusta, N.; Oglesby, D. D.

2010-12-01

146

Cretaceous biostratigraphy in the Wyoming thrust belt.  

Science.gov (United States)

In the Cretaceous section of the thrust belt, fossils are especially useful for dating and correlating repetitive facies of different ages in structurally complex terrain. The biostratigraphic zonation for the region is based on megafossils (chiefly ammonites) , which permit accurate dating and correlation of outcrop sections, and which have been calibrated with the radiometric time scale for the Western Interior. Molluscan and vertebrate zone fossils are difficult to obtain from the subsurface, however, and ammonites are restricted to rocks of marine origin. Palynomorphs (plant microfossils) have proven to be the most valuable fossils in the subsurface because they can be recovered from drill cuttings. Palynomorphs also are found in both marine and nonmarine rocks and can be used for correlation between facies. Stratigraphic ranges of selected Cretaceous marine and nonmarine palynomorphs in previously designated reference sections in Fossil Basin, Wyoming are correlated with the occurrence of ammonites and other zone fossils in the same sections. These correlations can be related to known isotopic ages, and they contribute to the calibration of palynomorph ranges in the Cretaceous of the Western Interior. -from Authors

Nichols, D.J.; Jacobson, S.R.

1982-01-01

147

Touchdown Ball-Bearing System for Magnetic Bearings  

Science.gov (United States)

The torque-limited touchdown bearing system (TLTBS) is a backup mechanical-bearing system for a high-speed rotary machine in which the rotor shaft is supported by magnetic bearings in steady-state normal operation. The TLTBS provides ball-bearing support to augment or supplant the magnetic bearings during startup, shutdown, or failure of the magnetic bearings. The TLTBS also provides support in the presence of conditions (in particular, rotational acceleration) that make it difficult or impossible to control the magnetic bearings or in which the magnetic bearings are not strong enough (e.g., when the side load against the rotor exceeds the available lateral magnetic force).

Kingsbury, Edward P.; Price, Robert; Gelotte, Erik; Singer, Herbert B.

2003-01-01

148

Ball and Roller Bearings. A Teaching Reference.  

Science.gov (United States)

The manual provides a subject reference for ball and roller bearings. The following topics are included: (1) bearing nomenclature, (2) bearing uses, (3) bearing capacities, (4) shop area working conditions, (5) bearing removal, (6) bearing cleaning and inspection, (7) bearing replacement, (8) bearing lubrication, (9) bearing installation, (10)…

American Association for Vocational Instructional Materials, Athens, GA.

149

Cryogenic magnetic bearing  

Science.gov (United States)

Magnetic suspension provides an alternative to rolling-element bearings for some precision gimbal applications. The Cryogenic Magnetic Bearing program includes studies of magnetic suspension for a gimbal bearing requiring long life (greater than 7 years); low runout (less than 5 microrads bore-sight error due to runout); and low, uniform drag torque. Additionally, the bearing is to operate in an oscillating mode, from room-ambient (300 K) to liquid nitrogen (77 K) temperatures at ambient pressure and in a hard vacuum (10 (exp-6) torr). Two magnetic suspension alternatives were studied: an all-active approach using electromagnets to control all five bearing degrees-of-freedom and a Passive-Radial Active-Axial (PRAA) approach using passive magnetics to stabilize four of the five bearing degrees-of-freedom and an electromagnet to control the fifth. The all-active approach provides a lower weight, better-accuracy bearing system than the PRAA system, but requires more quiescent operating power and is electrically more complex. The PRAA was selected for hardware study to produce a simple, low-power magnetic system.

Andrus, James; Kendig, John; Kroeger, John

1992-12-01

150

Rapid prototype fabrication processes for high-performance thrust cells  

Science.gov (United States)

The Thrust Cell Technologies Program (Air Force Phillips Laboratory Contract No. F04611-92-C-0050) is currently being performed by Rocketdyne to demonstrate advanced materials and fabrication technologies which can be utilized to produce low-cost, high-performance thrust cells for launch and space transportation rocket engines. Under Phase 2 of the Thrust Cell Technologies Program (TCTP), rapid prototyping and investment casting techniques are being employed to fabricate a 12,000-lbf thrust class combustion chamber for delivery and hot-fire testing at Phillips Lab. The integrated process of investment casting directly from rapid prototype patterns dramatically reduces design-to-delivery cycle time, and greatly enhances design flexibility over conventionally processed cast or machined parts.

Hunt, K.; Chwiedor, T.; Diab, J.; Williams, R.

1994-01-01

151

Thrust Characteristics of Water/Liquid Nitrogen Rocket Engine  

Science.gov (United States)

When liquid nitrogen and heated water are mixed in a chamber, pressure increase due to evaporation expansion inside the chamber becomes high enough to generate thrust force for rocket propulsion. This thrust system is safer and environment-friendly compared to conventional rocket engines utilizing combustion process. This new type of rocket engine system is called "Water-Liquid Nitrogen rocket engine system" and it can be used for small payload mission with expected altitude of several kilometers. In this paper, experimentally obtained thrust characteristics are shown and analyzed. As a result, relations between the thrust force and the mixing chamber pressure are clarified. Also, it is found that the present injector can attain only half of the theoretically expected specific impulse due to insufficient mixing efficiency.

Watanabe, Rikio; Hayashi, Kohei; Iwao, Masaki; Ikawa, Keita; Tomita, Nobuyuki

152

The Development of NASA's Low Thrust Trajectory Tool Set  

Science.gov (United States)

Highly efficient electric propulsion systems can enable interesting classes of missions; unfortunately, they provide only a limited amount of thrust. Low-thrust (LT) trajectories are much more difficult to design than impulsive-type (chemical propulsion) trajectories. Previous low-thrust (LT) trajectory optimization software was often difficult to use, often had difficulties converging, and was somewhat limited in the types of missions it could support. A new state-of-the-art suite (toolbox) of low-thrust (LT) tools along with improved algorithms and methods was developed by NASA's MSFC, JPL, JSC, and GRC to address the needs of our customers to help foster technology development in the areas of advanced LT propulsion systems, and to facilitate generation of similar results by different analysts.

Sims, Jon; Artis, Gwen; Kos, Larry

2006-01-01

153

Quadratic Programming Thrust Allocation and Management for Dynamic Positioning Ships  

Directory of Open Access Journals (Sweden)

Full Text Available To solve the complex thrust allocation problems of dynamic positioning ship with azimuth thrusters, the quadratic programming thrust allocation and management system was built. The power optimal thrust allocation was formulated as a quadratic programming problem by the linear treatments of inequality constraints and the optimal solution could be found in a finite amount of time. And some influence factors of thruster allocation were separated from algorithms and treated as a superstratum management module. In this system, online adjustment of input constraints and singularity avoidance could be realized, and the reliability and adaptability of thrust allocation were improved consequently. Finally, the validity and excellent performance of this method was proved by the simulation.

Yushi Wei

2013-01-01

154

High Speed Operation and Testing of a Fault Tolerant Magnetic Bearing  

Science.gov (United States)

Research activities undertaken to upgrade the fault-tolerant facility, continue testing high-speed fault-tolerant operation, and assist in the commission of the high temperature (1000 degrees F) thrust magnetic bearing as described. The fault-tolerant magnetic bearing test facility was upgraded to operate to 40,000 RPM. The necessary upgrades included new state-of-the art position sensors with high frequency modulation and new power edge filtering of amplifier outputs. A comparison study of the new sensors and the previous system was done as well as a noise assessment of the sensor-to-controller signals. Also a comparison study of power edge filtering for amplifier-to-actuator signals was done; this information is valuable for all position sensing and motor actuation applications. After these facility upgrades were completed, the rig is believed to have capabilities for 40,000 RPM operation, though this has yet to be demonstrated. Other upgrades included verification and upgrading of safety shielding, and upgrading control algorithms. The rig will now also be used to demonstrate motoring capabilities and control algorithms are in the process of being created. Recently an extreme temperature thrust magnetic bearing was designed from the ground up. The thrust bearing was designed to fit within the existing high temperature facility. The retrofit began near the end of the summer, 04, and continues currently. Contract staff authored a NASA-TM entitled "An Overview of Magnetic Bearing Technology for Gas Turbine Engines", containing a compilation of bearing data as it pertains to operation in the regime of the gas turbine engine and a presentation of how magnetic bearings can become a viable candidate for use in future engine technology.

DeWitt, Kenneth; Clark, Daniel

2004-01-01

155

Correlating the Ultrasonic Thrust Force with Acoustic Streaming Velocity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The UltraSonic Thruster (UST) is an actuator which employs a piezoelectric transducer to generate a highly directive ultrasonic wave so as to produce bulk fluid movement. This streaming phenomenon can be utilized underwater for thrusting or maneuvering purposes in marine applications, and particularly at very small scale. We make a new connection between fluid flow and forces, establishing a specific formula for estimating overall thrust from the velocity field. Using Par...

Tan, Alfred C. H.; Hover, Franz S.

2009-01-01

156

Thrust enhancement of the gasdynamic mirror (GDM) fusion propulsion system  

International Nuclear Information System (INIS)

The gasdynamic mirror propulsion system is a device that utilizes a magnetic mirror configuration to confine a hot plasma to allow fusion reactions to take place while ejecting a fraction of the energetic charged particles through one end to generate thrust. Because the fusion fuel is generally an isotope of hydrogen, e.g., deuterium or tritium, this propulsion device is capable of producing very large specific impulses (e.g., 200,000 seconds) but at modest thrusts. Since large thrusts are desirable, not only for reducing travel time but also for lifting sizable payloads, we have examined methods by which GDM close-quote s thrust could be enhanced. The first consists of utilizing the radiation generated by the plasma, namely bremsstrahlung and synchrotron radiation, to heat a hydrogen propellant which upon exhausting through a nozzle produces the additional thrust. We asses the performance in this case by using an ideal model that ignores heat transfer considerations of the chamber wall, and one that takes into account heat flow and wall temperature limitations. We find in the case of a DT burning plasma that although thrust enhancement is significant, it was more than offset by the large drop in the specific impulse and a concomitant increase in travel time. The second method consisted of not altering the original GDM operation, but simply increasing the density of the injected plasma to achieve higher thrust. It is shown that the latter approach is more effective sit the latter approach is more effective since it is compatible with improved performance in that it reduces trip time but at the expense of larger vehicle mass. For a D-He3 burning device the use of hydrogen to enhance thrust appears to be more desirable since the radiated power that goes into heating the hydrogen propellant is quite large. copyright 1997 American Institute of Physics

157

Thrust enhancement of the gasdynamic mirror (GDM) fusion propulsion system  

International Nuclear Information System (INIS)

The gasdynamic mirror propulsion system is a device that utilizes a magnetic mirror configuration to confine a hot plasma to allow fusion reactions to take place while ejecting a fraction of the energetic charged particles through one end to generate thrust. Because the fusion fuel is generally an isotope of hydrogen, e.g., deuterium or tritium, this propulsion device is capable of producing very large specific impulses (e.g., 200,000 seconds) but at modest thrusts. Since large thrusts are desirable, not only for reducing travel time but also for lifting sizable payloads, we have examined methods by which GDM's thrust could be enhanced. The first consists of utilizing the radiation generated by the plasma, namely bremsstrahlung and synchrotron radiation, to heat a hydrogen propellant which upon exhausting through a nozzle produces the additional thrust. We asses the performance in this case by using an ideal model that ignores heat transfer considerations of the chamber wall, and one that takes into account heat flow and wall temperature limitations. We find in the case of a DT burning plasma that although thrust enhancement is significant, it was more than offset by the large drop in the specific impulse and a concomitant increase in travel time. The second method consisted of not altering the original GDM operation, but simply increasing the density of the injected plasma to achieve higher thrust. It is shown that the latter approach is more effective since it is co approach is more effective since it is compatible with improved performance in that it reduces trip time but at the expense of larger vehicle mass. For a D-He3 burning device the use of hydrogen to enhance thrust appears to be more desirable since the radiated power that goes into heating the hydrogen propellant is quite large

158

Bilateral and multiple cavitation sounds during upper cervical thrust manipulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background The popping produced during high-velocity, low-amplitude (HVLA) thrust manipulation is a common sound; however to our knowledge, no study has previously investigated the location of cavitation sounds during manipulation of the upper cervical spine. The primary purpose was to determine which side of the spine cavitates during C1-2 rotatory HVLA thrust manipulation. Secondary aims were to calculate the average number of pops, the duration of upper cervical t...

Dunning James; Mourad Firas; Barbero Marco; Leoni Diego; Cescon Corrado; Butts Raymond

2013-01-01

159

The Prevalence of Tongue Thrusting in Patients with Periodontal Disease  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Statement of Problem: Tongue thrust and/or its consequent swallowing pattern are amongst the parafunctional habits that have always been considered as etiological factors for dental disorders by different investigators.Purpose: The aim of this study was to investigate the prevalence of tongue thrusting and the incidence of periodontal disorders associated with this habit among patients referred to the Department of Periodontology, School of Dentistry, Tehran University of Medical Sciences.Mat...

Miremadi, S. A.; Khoshkhounejad, A. A.; Mahdavi, E.

2005-01-01

160

Exploring fold and thrust belts in Google Earth  

Science.gov (United States)

Google Earth enhances traditional geologic maps by allowing the viewer to explore three-dimensional map patterns and the interaction between structure and topography in dictating those map patterns. This activity overlays 4, 7.5' USGS quadrangles on Google Earth terrain and imagery data and encourages students to investigate common features of fold-and-thrust belts. Keywords: Google Earth, fold-and-thrust belt, visualization

Jack Loveless

 
 
 
 
161

A double pendulum plasma thrust balance and thrust measurement at a tandem mirror exhaust  

International Nuclear Information System (INIS)

For the purpose of measuring the plasma momentum flux in a plasma system, a highly sensitive and precision balance has been developed. It can measure a force, an impulse, or thrust as low as 0.1 mN free of mechanical noise, electrical and magnetic pickups. The double pendulum system consists of two parallel conducting plates. One or both of the plates can be suspended by needles. The needle suspended plate (or plates) can swing freely with negligible friction because of the sharp points of the needles. When one of the plates is impacted by an impulse it will swing relatively to the fixed plate or other movable plate. The capacitance between the plates changes as a result of such a motion. The change of capacitance as a function of time is recorded as an oscillating voltage signal. The amplitude of such a voltage signal is proportional to the impacting force or impulse. The proportional factor can be calibrated. The forces can thus be read out from the recorded value of the voltage. The equation of motion for the pendulum system has been solved analytically. The circuit equation for the electronic measurement system has been formulated and solved numerically. Using this balance the thrust at the exhaust of a Tandem Mirror plasma thruster has been measured. The analytical solution of the overall characteristics agrees greatly with the measurement. copyright 1995 American Institute of Physics

162

Thrust stand for vertically oriented electric propulsion performance evaluation  

Energy Technology Data Exchange (ETDEWEB)

A variation of a hanging pendulum thrust stand capable of measuring the performance of an electric thruster operating in the vertical orientation is presented. The vertical orientation of the thruster dictates that the thruster must be horizontally offset from the pendulum pivot arm, necessitating the use of a counterweight system to provide a neutrally stable system. Motion of the pendulum arm is transferred through a balance mechanism to a secondary arm on which deflection is measured. A noncontact light-based transducer is used to measure displacement of the secondary beam. The members experience very little friction, rotating on twisting torsional pivots with oscillatory motion attenuated by a passive, eddy-current damper. Displacement is calibrated using an in situ thrust calibration system. Thermal management and self-leveling systems are incorporated to mitigate thermal and mechanical drifts. Gravitational force and torsional spring constants associated with flexure pivots provide restoring moments. An analysis of the design indicates that the thrust measurement range spans roughly four decades, with the stand capable of measuring thrust up to 12 N for a 200 kg thruster and up to approximately 800 mN for a 10 kg thruster. Data obtained from calibration tests performed using a 26.8 lbm simulated thruster indicated a resolution of 1 mN on 100 mN level thrusts, while those tests conducted on a 200 lbm thruster yielded a resolution of roughly 2.5 mN at thrust levels of 0.5 N and greater.

Moeller, Trevor [University of Tennessee Space Institute, Tullahoma, Tennessee 37388 (United States); Polzin, Kurt A. [NASA, Marshall Space Flight Center, Huntsville, Alabama 35812 (United States)

2010-11-15

163

Thrust stand for vertically oriented electric propulsion performance evaluation  

Science.gov (United States)

A variation of a hanging pendulum thrust stand capable of measuring the performance of an electric thruster operating in the vertical orientation is presented. The vertical orientation of the thruster dictates that the thruster must be horizontally offset from the pendulum pivot arm, necessitating the use of a counterweight system to provide a neutrally stable system. Motion of the pendulum arm is transferred through a balance mechanism to a secondary arm on which deflection is measured. A noncontact light-based transducer is used to measure displacement of the secondary beam. The members experience very little friction, rotating on twisting torsional pivots with oscillatory motion attenuated by a passive, eddy-current damper. Displacement is calibrated using an in situ thrust calibration system. Thermal management and self-leveling systems are incorporated to mitigate thermal and mechanical drifts. Gravitational force and torsional spring constants associated with flexure pivots provide restoring moments. An analysis of the design indicates that the thrust measurement range spans roughly four decades, with the stand capable of measuring thrust up to 12 N for a 200 kg thruster and up to approximately 800 mN for a 10 kg thruster. Data obtained from calibration tests performed using a 26.8 lbm simulated thruster indicated a resolution of 1 mN on 100 mN level thrusts, while those tests conducted on a 200 lbm thruster yielded a resolution of roughly 2.5 mN at thrust levels of 0.5 N and greater.

Moeller, Trevor; Polzin, Kurt A.

2010-11-01

164

Optimal synchronizability of bearings.  

Science.gov (United States)

Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with asymmetrically weighted couplings. Accordingly, these networks can exhibit optimal synchronization properties through fine-tuning of the local interaction strength as a function of node degree [Motter, Zhou, and Kurths, Phys. Rev. E 71, 016116 (2005)]. We show that, in analogy, the synchronizability of bearings can be maximized by counterbalancing the number of contacts and the inertia of their constituting rotor disks through the mass-radius relation, m~r(?), with an optimal exponent ?=?(×) which converges to unity for a large number of rotors. Under this condition, and regardless of the presence of a long-tailed distribution of disk radii composing the mechanical system, the average participation per disk is maximized and the energy dissipation rate is homogeneously distributed among elementary rotors. PMID:23432250

Araújo, N A M; Seybold, H; Baram, R M; Herrmann, H J; Andrade, J S

2013-02-01

165

Optimal synchronizability of bearings  

CERN Document Server

Bearings are mechanical dissipative systems that, when perturbed, relax toward a synchronized (bearing) state. Here we find that bearings can be perceived as physical realizations of complex networks of oscillators with asymmetrically weighted couplings. Accordingly, these networks can exhibit optimal synchronization properties through fine tuning of the local interaction strength as a function of node degree [Motter, Zhou, and Kurths, Phys. Rev. E 71, 016116 (2005)]. We show that, in analogy, the synchronizability of bearings can be maximized by counterbalancing the number of contacts and the inertia of their constituting rotor disks through the mass-radius relation, $m\\sim r^{\\alpha}$, with an optimal exponent $\\alpha=\\alpha_{\\times}$ which converges to unity for a large number of rotors. Under this condition, and regardless of the presence of a long-tailed distribution of disk radii composing the mechanical system, the average participation per disk is maximized and the energy dissipation rate is homogeneo...

Araújo, N A M; Baram, R M; Herrmann, H J; Andrade, J S

2013-01-01

166

Fractured carbonates in the Mediumfjellet thrust-stack in the Tertiary fold-and-thrust belt of Spitsbergen  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis describes a study that was carried out in the Tertiary fold-and-thrust belt of Svalbard, in the mountain range of Mediumfjellet summer 2007 and 2008. The focuses were on: i) further describing the larger structures of the Mediumfjellet, ii) analyze the fracture distribution in the limestone beds associated with the major structures in the area. Available data sets are based on photo textured Lidar scan and extensive field observations. The Mediumfjellet thrust stack is situated i...

Larsen, Tine

2009-01-01

167

Gear bearing drive  

Science.gov (United States)

A gear bearing drive provides a compact mechanism that operates as an actuator providing torque and as a joint providing support. The drive includes a gear arrangement integrating an external rotor DC motor within a sun gear. Locking surfaces maintain the components of the drive in alignment and provide support for axial loads and moments. The gear bearing drive has a variety of applications, including as a joint in robotic arms and prosthetic limbs.

Weinberg, Brian (Inventor); Mavroidis, Constantinos (Inventor); Vranish, John M. (Inventor)

2011-01-01

168

Synkinematic phyllosilicates in a thrust fault zone : good proxy for PT conditions, deformation mechanism and mass transfers (example of the Monte perdido Thrust in southern Pyrenees)  

Science.gov (United States)

Thrust fault zones in foreland basins are often characterized by highly foliated shear bands generally enriched in phyllosilicates which can play a major role on the mechanical behaviour of the fault. These textural modifications, as well as the chemical modifications in the core zone of the fault, depend on the mechanisms of deformation and fluid-sediment interactions. In this context, investigations of synkinematic clay minerals allow determining the origin of the fluid from which they precipitated, the PT conditions as well as the mechanisms of deformation. Our study is focused on clay mineral assemblages (illite and chlorite) in two thrust faults located in the Monte Perdido massif (southern Pyrenees): (i) the major Torla fault (kilometric offset)that affects Upper Cretaceous -Paleocene platform carbonates and lower Eocene marls and turbidites and (ii) a detachment fault which affects the lower Eocene Millaris marls. The core zone of these two faults consists of an interval of intensely foliated clays-bearing rocks bounded by major shear surfaces. The deformed sediment is markedly darker than the protolith. Calcite-quartz shear veins along the shear planes are abundant. Bulk chemical analyses and Rietveld refinement of the bulk rock XRD from the highly deformed sediments and hanging wall and footwall protoliths has allowed a quantification of the mineral proportions and mass balance calculation. Mineralogical variations between the protolith and fault zone samples have been estimated by the Gresens calculation (Gresens, 1967). According to this calculation, the highly deformed sediments registered volume reduction of up to 50% but without important chemical variations except calcium and LOI loss. However, SEM and TEM investigations of the deformed sediments show that chlorite precipitated coevally to the shear displacement and small crystals (<2 ?m) of authigenic illite underline the cleavage. The newly formed chlorite is a Fe-rich chlorite (Si2.86Al1.14O10(Al1.67Fe2.31Mg1.71)6(OH)8). Temperatures of chlorite formation calculated by thermodynamic models range from 210°C to 265°C. Taking into account thermometric data from fluid inclusions in calcite and quartz veins, we established that the formation of the synkinematic chlorite occurred under about 6.5km burial. These data suggest that calcite and quartz pressure solution was not the only mechanism of deformation but that thrust fault activity induced mineralogical reactions implying partial dissolution and recrystallisation of phyllosilicates in the presence of fluid in a relatively closed system.

Buatier, Martine; Lacroix, Brice; Trincal, Vincent; Charpentier, Delphine; Labaume, Pierre; Trave, Anna

2013-04-01

169

Strain path partitioning within thrust sheets: microstructural and petrofabric evidence from the Moine Thrust zone at Loch Eriboll, northwest Scotland  

Science.gov (United States)

Quartz c axis fabrics and microstructures have been investigated within a suite of quartzites collected from the Loch Eriboll area of the Moine Thrust zone and are used to interpret the detailed processes involved in fabric evolution. The intensity of quartz c axis fabrics is directly proportional to the calculated strain magnitude. A correlation is also established between the pattern of c axis fabrics and the calculated strain symmetry. Two kinematic domains are recognized within one of the studied thrust sheets which outcrops immediately beneath the Moine Thrust. Within the upper and central levels of the thrust sheet coaxial deformation is indicated by conjugate, mutually interfering shear bands, globular low strain detrital quartz grains whose c axes are aligned sub-parallel to the principal finite shortening direction ( Z) and quartz c axis fabrics which are symmetric (both in terms of skeletal outline and intensity distribution) with respect to mylonitic foliation and lineation. Non-coaxial deformation is indicated within the more intensely deformed and recrystallized quartzites located near the base of the thrust sheet by single sets of shear bands and c axis fabrics which are asymmetric with respect to foliation and lineation. Tectonic models offering possible explanations for the presence of kinematic (strain path) domains within thrust sheets are considered.

Law, R. D.; Knipe, R. J.; Dayan, H.

170

An Assessment of Gas Foil Bearing Scalability and the Potential Benefits to Civilian Turbofan Engines  

Science.gov (United States)

Over the past several years the term oil-free turbomachinery has been used to describe a rotor support system for high speed turbomachinery that does not require oil for lubrication, damping, or cooling. The foundation technology for oil-free turbomachinery is the compliant foil bearing. This technology can replace the conventional rolling element bearings found in current engines. Two major benefits are realized with this technology. The primary benefit is the elimination of the oil lubrication system, accessory gearbox, tower shaft, and one turbine frame. These components account for 8 to 13 percent of the turbofan engine weight. The second benefit that compliant foil bearings offer to turbofan engines is the capability to operate at higher rotational speeds and shaft diameters. While traditional rolling element bearings have diminished life, reliability, and load capacity with increasing speeds, the foil bearing has a load capacity proportional to speed. The traditional applications for foil bearings have been in small, lightweight machines. However, recent advancements in the design and manufacturing of foil bearings have increased their potential size. An analysis, grounded in experimentally proven operation, is performed to assess the scalability of the modern foil bearing. This analysis was coupled to the requirements of civilian turbofan engines. The application of the foil bearing to larger, high bypass ratio engines nominally at the 120 kN (approx.25000 lb) thrust class has been examined. The application of this advanced technology to this system was found to reduce mission fuel burn by 3.05 percent.

Bruckner, Robert J.

2010-01-01

171

Design and Operating Characteristics of High-Speed, Small-Bore, Angular-Contact Ball Bearings  

Science.gov (United States)

The computer program SHABERTH was used to analyze 35-mm-bore, angular-contact ball bearings designed and manufactured for high-speed turbomachinery applications. Parametric tests of the bearings were conducted on a high-speed, high-temperature bearing tester and were compared with the computer predictions. Four bearing and cage designs were studied. The bearings were lubricated either by jet lubrication or through the split inner ring with and without outer-ring cooling. The predicted bearing life decreased with increasing speed because of increased operating contact stresses caused by changes in contact angle and centrifugal load. For thrust loads only, the difference in calculated life for the 24 deg. and 30 deg. contact-angle bearings was insignificant. However, for combined loading, the 24 deg. contact-angle bearing gave longer life. For split-inner-ring bearings, optimal operating conditions were obtained with a 24 deg. contact angle and an inner-ring, land-guided cage, using outer-ring cooling in conjunction with low lubricant flow rates. Lower temperature and power losses were obtained with a single-outer-ring, land-guided cage for the 24 deg. contact-angle bearing having a relieved inner ring and partially relieved outer ring. Inner-ring temperatures were independent of lubrication mode and cage design. In comparison with measured values, reasonably good engineering correlation was obtained using the computer program SHABERTH for predicted bearing power loss and for inner- and outer-ring temperatures. The Parker formula for XCAV (used in SHABERTH, a measure of oil volume in the bearing cavity) may need to be refined to reflect bearing lubrication mode, cage design, and location of cage-controlling land.

Pinel, Stanley I.; Signer, Hans R.; Zaretsky, Erwin V.

1998-01-01

172

Thrust stand for vertically oriented electric propulsion performance evaluation  

International Nuclear Information System (INIS)

A variation of a hanging pendulum thrust stand capable of measuring the performance of an electric thruster operating in the vertical orientation is presented. The vertical orientation of the thruster dictates that the thruster must be horizontally offset from the pendulum pivot arm, necessitating the use of a counterweight system to provide a neutrally stable system. Motion of the pendulum arm is transferred through a balance mechanism to a secondary arm on which deflection is measured. A noncontact light-based transducer is used to measure displacement of the secondary beam. The members experience very little friction, rotating on twisting torsional pivots with oscillatory motion attenuated by a passive, eddy-current damper. Displacement is calibrated using an in situ thrust calibration system. Thermal management and self-leveling systems are incorporated to mitigate thermal and mechanical drifts. Gravitational force and torsional spring constants associated with flexure pivots provide restoring moments. An analysis of the design indicates that the thrust measurement range spans roughly four decades, with the stand capable of measuring thrust up to 12 N for a 200 kg thruster and up to approximately 800 mN for a 10 kg thruster. Data obtained from calibration tests performed using a 26.8 lbm simulated thruster indicated a resolution of 1 mN on 100 mN level thrusts, while those tests conducted on a 200 lbm thruster yielded a resolution of roughly 2.5 mN at thrust levelsolution of roughly 2.5 mN at thrust levels of 0.5 N and greater.

173

Methods for determining atypical gate valve thrust requirements  

International Nuclear Information System (INIS)

Evaluating the performance of rising stem, wedge type, gate valves used in nuclear power plant is not a problem when the valves can be design-basis tested and their operability margins determined diagnostically. The problem occurs when they cannot be tested because of plant system limitations or when they can be tested only at some less-than-design-basis condition. To evaluate the performance of these valves requires various analytical and/or extrapolation methods by which the design-basis stem thrust requirement can be determined. This has been typically accomplished with valve stem thrust models used to calculate the requirements or by extrapolating the results from a less-than-design-basis test. The stem thrust models used by the nuclear industry to determine the opening or closing stem thrust requirements for these gate valves have generally assumed that the highest load the valve experiences during closure (but before seating) is at flow isolation and during unwedging or before flow initiation in the opening direction. However, during full-scale valve testing conducted for the USNRC, several of the valves produced stem thrust histories that showed peak closing stem forces occurring before flow isolation in the closing direction and after flow initiation in the opening direction. All of the valves that exhibited this behavior in the closing direction also showed signs of internal damage. Initially, we dismissed the early peak in the closing stem thrust requirementeak in the closing stem thrust requirement as damage-induced and labeled it nonpredictable behavior. Opening responses were not a priority in our early research, so that phenomenon was set aside for later evaluation

174

Bilateral and multiple cavitation sounds during upper cervical thrust manipulation  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The popping produced during high-velocity, low-amplitude (HVLA thrust manipulation is a common sound; however to our knowledge, no study has previously investigated the location of cavitation sounds during manipulation of the upper cervical spine. The primary purpose was to determine which side of the spine cavitates during C1-2 rotatory HVLA thrust manipulation. Secondary aims were to calculate the average number of pops, the duration of upper cervical thrust manipulation, and the duration of a single cavitation. Methods Nineteen asymptomatic participants received two upper cervical thrust manipulations targeting the right and left C1-2 articulation, respectively. Skin mounted microphones were secured bilaterally over the transverse process of C1, and sound wave signals were recorded. Identification of the side, duration, and number of popping sounds were determined by simultaneous analysis of spectrograms with audio feedback using custom software developed in Matlab. Results Bilateral popping sounds were detected in 34 (91.9% of 37 manipulations while unilateral popping sounds were detected in just 3 (8.1% manipulations; that is, cavitation was significantly (P Conclusions Cavitation was significantly more likely to occur bilaterally than unilaterally during upper cervical HVLA thrust manipulation. Most subjects produced 3–4 pops during a single rotatory HVLA thrust manipulation targeting the right or left C1-2 articulation; therefore, practitioners of spinal manipulative therapy should expect multiple popping sounds when performing upper cervical thrust manipulation to the atlanto-axial joint. Furthermore, the traditional manual therapy approach of targeting a single ipsilateral or contralateral facet joint in the upper cervical spine may not be realistic.

Dunning James

2013-01-01

175

Simple modeling of hydrostatic bearings  

Science.gov (United States)

Hydrostatic bearings are a key component for many large telescopes due to their high load bearing capacity, stiffness and low friction. A simple technique is presented to model these bearings to understand the effects of geometry, oil viscosity, flow control, temperature, etc. on the bearings behavior.

Hull, Charlie

2014-07-01

176

Relationships between the Loch Ailsh and Borralan alkaline intrusions and thrusting in the Moine Thrust zone, southern Assynt culmination, NW Scotland  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Moine Thrust zone ofNWScotland marks the Caledonian orogenic front and in the Assynt region consists of several west-vergent major thrust sheets (Moine, Ben More, Glencoul and Sole Thrust sheets) that place allochthonous rocks onto the Lewisian basement and Torridon Group cover in the west. Here we present two new balanced and restored sections across the Moine Thrust zone in the region of the Loch Ailsh and Loch Borralan alkali intrusions. Syenites and alkaline pyroxenites intrude up to ...

Searle, Mp; Law, Rd; Dewey, Jf; Streule, Mj

2010-01-01

177

Study of superconducting magnetic bearing applicable to the flywheel energy storage system that consist of HTS-bulks and superconducting-coils  

Energy Technology Data Exchange (ETDEWEB)

The Railway Technical Research Institute conducted a study to develop a superconducting magnetic bearing applicable to the flywheel energy-storage system for railways. In the first step of the study, the thrust rolling bearing was selected for application, and adopted liquid-nitrogen-cooled HTS-bulk as a rotor, and adopted superconducting coil as a stator for the superconducting magnetic bearing. Load capacity of superconducting magnetic bearing was verified up to 10 kN in the static load test. After that, rotation test of that approximately 5 kN thrust load added was performed with maximum rotation of 3000rpm. In the results of bearing rotation test, it was confirmed that position in levitation is able to maintain with stability during the rotation. Heat transfer properties by radiation in vacuum and conductivity by tenuous gas were basically studied by experiment by the reason of confirmation of rotor cooling method. The experimental result demonstrates that the optimal gas pressure is able to obtain without generating windage drag. In the second stage of the development, thrust load capacity of the bearing will be improved aiming at the achievement of the energy capacity of a practical scale. In the static load test of the new superconducting magnetic bearing, stable 20kN-levitation force was obtained.

Seino, Hiroshi; Nagashima, Ken; Tanaka, Yoshichika; Nakauchi, Masahiko, E-mail: seino@rtri.or.j [Railway Technical Research Institute, Hikari-cho 2-8-38, Kokubunji-shi, Tokyo (Japan)

2010-06-01

178

Study of superconducting magnetic bearing applicable to the flywheel energy storage system that consist of HTS-bulks and superconducting-coils  

International Nuclear Information System (INIS)

The Railway Technical Research Institute conducted a study to develop a superconducting magnetic bearing applicable to the flywheel energy-storage system for railways. In the first step of the study, the thrust rolling bearing was selected for application, and adopted liquid-nitrogen-cooled HTS-bulk as a rotor, and adopted superconducting coil as a stator for the superconducting magnetic bearing. Load capacity of superconducting magnetic bearing was verified up to 10 kN in the static load test. After that, rotation test of that approximately 5 kN thrust load added was performed with maximum rotation of 3000rpm. In the results of bearing rotation test, it was confirmed that position in levitation is able to maintain with stability during the rotation. Heat transfer properties by radiation in vacuum and conductivity by tenuous gas were basically studied by experiment by the reason of confirmation of rotor cooling method. The experimental result demonstrates that the optimal gas pressure is able to obtain without generating windage drag. In the second stage of the development, thrust load capacity of the bearing will be improved aiming at the achievement of the energy capacity of a practical scale. In the static load test of the new superconducting magnetic bearing, stable 20kN-levitation force was obtained.

179

Thrust Augmentation Measurements for a Pulse Detonation Engine Driven Ejector  

Science.gov (United States)

Thrust augmentation results of an ongoing study of pulse detonation engine driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE) setup with various ejector configurations. The PDE used in these experiments utilizes ethylene (C2H4) as the fuel, and an equi-molar mixture of oxygen and nitrogen as the oxidizer at an equivalence ratio of one. High fidelity thrust measurements were made using an integrated spring damper system. The baseline thrust of the PDE engine was first measured and agrees with experimental and modeling results found in the literature. Thrust augmentation measurements were then made for constant diameter ejectors. The parameter space for the study included ejector length, PDE tube exit to ejector tube inlet overlap distance, and straight versus rounded ejector inlets. The relationship between the thrust augmentation results and various physical phenomena is described. To further understand the flow dynamics, shadow graph images of the exiting shock wave front from the PDE were also made. For the studied parameter space, the results showed a maximum augmentation of 40%. Further increase in augmentation is possible if the geometry of the ejector is tailored, a topic currently studied by numerous groups in the field.

Pal, S.; Santoro, Robert J.; Shehadeh, R.; Saretto, S.; Lee, S.-Y.

2005-01-01

180

Thrust Augmentation Measurements Using a Pulse Detonation Engine Ejector  

Science.gov (United States)

Results of an experimental effort on pulse detonation driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE)/ejector setup that was specifically designed for the study and operated at frequencies up to 50 Hz. The results of various experiments designed to probe different aspects of the PDE/ejector setup are reported. The baseline PDE was operated using ethylene (C2H4) as the fuel and an oxygen/nitrogen O2 + N2) mixture at an equivalence ratio of one. The PDE only experiments included propellant mixture characterization using a laser absorption technique, high fidelity thrust measurements using an integrated spring-damper system, and shadowgraph imaging of the detonation/shock wave structure emanating from the tube. The baseline PDE thrust measurement results at each desired frequency agree with experimental and modeling results reported in the literature. These PDE setup results were then used as a basis for quantifying thrust augmentation for various PDE/ejector setups with constant diameter ejector tubes and various ejector lengths, the radius of curvature for the ejector inlets and various detonation tube/ejector tube overlap distances. For the studied experimental matrix, the results showed a maximum thrust augmentation of 106% at an operational frequency of 30 Hz. The thrust augmentation results are complemented by shadowgraph imaging of the flowfield in the ejector tube inlet area and high frequency pressure transducer measurements along the length of the ejector tube.

Santoro, Robert J.; Pal, Sibtosh

2005-01-01

 
 
 
 
181

Engineering research, development and technology: Thrust area report FY 91  

International Nuclear Information System (INIS)

The mission of the Engineering Research, Development, and Technology Program at Lawrence, Livermore National Laboratory (LLNL) is to develop the technical staff and the technology needed to support current and future LLNL programs. To accomplish this mission, the Engineering Research, Development, and Technology Program has two important goals: (1) to identify key technologies and (2) conduct high quality work to enhance our capabilities in these key technologies. To help focus our efforts, we identify technology thrust areas and select technical leaders for each area. The thrust areas are integrated engineering activities and, rather than being based on individual disciplines, they are staffed by personnel from Electronics Engineering, Mechanical Engineering, and other LLNL organizations, as appropriate. The thrust area leaders are expected to establish strong links to LLNL program leaders and to industry; to use outside and inside experts to review the quality and direction of the work; to use university contacts to supplement and complement their efforts; and to be certain that we are not duplicating the work of others. The thrust area leader is also responsible for carrying out the work that follows from the Engineering Research, Development, and Technology Program so that the results can be applied as early as possible to the needs of LLNL programs. This annual report, organized by thrust area, describes activities conducted within the Program for the fiscal year, 1991. Its intent is to provide timely summaries of objectives, theories, methods, and results

182

Characterisation of Materials Used in Flex Bearings of Large Solid Rocket Motors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Solid rocket motors are propulsion devices for both satellite launchers and missiles, which require guidance and steering to fly along a programmed trajectory and to compensate for flight disturbances. A typical solid rocket motor consists of motor case, solid propellant grain, motor insulation, igniter and nozzle. In most solid rocket motors, thrust vector control (TVC) is required. One of the most efficient methods of TVC is by flex nozzle system. The flex nozzle consists of a flexible bear...

Ram Mohan, Ch V.; Ramanathan, J.; Satish Kumar; Gupta, A. V. S. S. K. S.

2011-01-01

183

Rotordynamics of automotive turbochargers. Linear and nonlinear rotordynamics - Bearing design - Rotor balancing  

Energy Technology Data Exchange (ETDEWEB)

Describes the rotordynamics of automotive turbochargers. Requires only a minimum of mathematical background. Written by an R and D expert from industry. This book deals with rotordynamics of automotive turbochargers while encompassing the analysis of the dynamics of rotating machines at very high rotor speeds of 300,000 rpm and above. This interdisciplinary field involves 1. thermodynamics and turbo-matching knowledge to compute working conditions of turbochargers, 2. fluid and bearing dynamics to calculate various operating thrust loads and to design the rotating floating ring bearings (two-oil-film bearings), and 3. tribology to improve the rotor stability and to reduce the bearing friction. Mathematical background in modeling and simulation methods is necessary; however, the prerequisites have been kept to a minimum. The book addresses both practitioners working in the field of rotordynamics of automotive turbochargers and graduate students in mechanical engineering.

Nguyen-Schaefer, Hung [Bosch Mahle Turbo Systems GmbH und Co. KG, Stuttgart (Germany)

2012-11-01

184

Radial Halbach Magnetic Bearings  

Science.gov (United States)

Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while minimizing it on the opposite side. The advantage of this configuration is that it makes it possible to approach the theoretical maximum force per unit area that could be exerted by a given amount of permanent-magnet material. The configuration is named after physicist Klaus Halbach, who conceived it for use in particle accelerators. Halbach arrays have also been studied for use in magnetic-levitation ("maglev") railroad trains. In a radial Halbach magnetic bearing, the basic Halbach arrangement is modified into a symmetrical arrangement of sector-shaped permanent magnets mounted on the outer cylindrical surface of a drum rotor (see Figure 2). The magnets are oriented to concentrate the magnetic field on their radially outermost surface. The stator coils are mounted in a stator shell surrounding the rotor.

Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

2009-01-01

185

Viscoplastic analysis of an experimental cylindrical thrust chamber liner  

Science.gov (United States)

A viscoplastic stress-strain analysis of an experimental cylindrical thrust chamber is presented. A viscoelastic constitutive model incorporating a single internal state variable that represents kinematic hardening was employed to investigate whether such a viscoplastic model could predict the experimentally observed behavior of the thrust chamber. Two types of loading cycles were considered: a short cycle of 3.5-s duration that corresponded to the experiments, and an extended loading cycle of 485.1 s duration that is typical of the Space Shuttle Main Engine (SSME) operating cycle. The analysis qualitatively replicated the deformation behavior of the component as observed in experiments designed to simulate SSME operating conditions. The analysis also showed that the mode and location of failure in the component may depend on the loading cycle. The results indicate that using viscoplastic models for structural analysis can lead to a more realistic life assessment of thrust chambers.

Arya, Vinod K.; Arnold, Steven M.

1992-01-01

186

Dynamic Model for Thrust Generation of Marine Propellers  

DEFF Research Database (Denmark)

Mathematical models of propeller thrust and torque are traditionally based on steady state thrust and torque characteristics obtained in model basin or cavitation tunnel tests. Experimental results showed that these quasi steady state models do not accurately describe the transient phenomena in a thruster. A recently published dynamic model was based on the experimental observations. Describing zero advance speed conditions accurately, this model, however, does not work for a vessel at non- zero relative water speed. This paper derives a large signal dynamic model of propeller that includes the eects of transients in the ow over a wide range of operation. The results are essential for accurate thrust control in dynamic positioning and in underwater robotics.

Blanke, Mogens; Lindegaard, Karl-Petter

2000-01-01

187

Separability of drag and thrust in undulatory animals and machines  

CERN Document Server

For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal- istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation fram...

Bale, Rahul; Neveln, Izaak D; Bhalla, Amneet Pal Singh; MacIver, Malcolm A; Patankar, Neelesh A

2014-01-01

188

Parametric study of thermal behavior of thrust chamber cooling channels  

Directory of Open Access Journals (Sweden)

Full Text Available A numerical investigation is adopted for two dimensional thermal analysis of rocket thrust chamber wall (RL10, employing finite difference model with iterative scheme (implemented under relaxation factor of 0.9 for convergence to compute temperature distribution within thrust chamber wall (which is composed of Nickel and Copper layers. The analysis is conducted for different boundary conditions: only convection boundary conditions then combined radiation, convection boundary conditions also for different aspect ratio (AR of cooling channel. The results show that Utilizing cooling channels of high aspect ratio leads to decrease in temperature variation across thrust chamber wall, while no effects on heat transferred to the coolant is indicated. The radiation has a considerable effect on the computed wall temperature values.

Karima E. Amori

2007-01-01

189

Optimization of Flapping Airfoils for Maximum Thrust and Propulsive Efficiency  

Directory of Open Access Journals (Sweden)

Full Text Available A numerical optimization algorithm based on the steepest decent along the variation of the optimization function is implemented for maximizing the thrust and/or propulsive efficiency of a single flapping airfoil. Unsteady, low speed laminar flows are computed using a Navier-Stokes solver on moving overset grids. The flapping motion of the airfoil is described by a combined sinusoidal plunge and pitching motion. Optimization parameters are taken to be the amplitudes of the plunge and pitching motions, and the phase shift between them. Computations are performed in parallel in a work station cluster. The numerical simulations show that high thrust values may be obtained at the expense of reduced efficiency. For high efficiency in thrust generation, the induced angle of attack of the airfoil is reduced and large scale vortex formations at the leading edge are prevented. 

I. H. Tuncer

2004-01-01

190

Modular gear bearings  

Science.gov (United States)

A gearing system using modular gear bearing components. Each component is composed of a core, one or more modules attached to the core and two or more fastening modules rigidly attaching the modules to the core. The modules, which are attached to the core, may consist of gears, rollers or gear bearing components. The core orientation affects the orientation of the modules attached to the core. This is achieved via the keying arrangement of the core and the component modules that attach to the core. Such an arrangement will also facilitate the phase tuning of gear modules with respect to the core and other gear modules attached to the core.

Vranish, John M. (Inventor)

2009-01-01

191

Imaging deformation in submarine thrust belts using seismic attributes  

Science.gov (United States)

Uncertainty exists as to the patterns of deformation that develop within submarine thrust belts. This case study uses a large-scale gravity-driven fold-thrust structure as an analogue for submarine fold thrust systems in general. Seismic attribute analysis and mapping provide ways of identifying complex fault patterns and associated deformation that are otherwise unresolved in conventional amplitude displays. These methods are developed and applied to a 3D dataset and used to investigate the geometry, internal architecture and the nature of the low signal/noise incoherency and discontinuities observed on the km-scale. Semblance (coherency), curvatures and spectral decomposition were all computed and used as attributes. Collectively these define volumes within the seismic data where the signal is greatly reduced — features termed here "disturbance geobodies". The study shows that thrust faults that, on conventional amplitude displays appear to be simple and continuous, are likely to consist of complex arrays of anastamosing fault strands. Adjacent to these composite fault zones are greater volumes of deformed rocks (disturbance geobodies) across which there are only minor stratal offsets. Similarly volumes of high stratal curvature coincide with disturbance geobodies, again interpreted as zones of weak, distributed deformation. These relationships between narrow thrust faults and broader zones of deformation are broadly comparable to those observed in outcrops within exhumed thrust systems. Application of the seismic imaging techniques developed here will improve the understanding of the localization of deformation in sedimentary successions with important implications for predicting fluid flow within other deep water structures such as subduction accretion complexes.

Iacopini, David; Butler, Robert W. H.

2011-02-01

192

Improvement of Rocket Performance by Increasing the Thrust  

International Nuclear Information System (INIS)

This paper describes one of the methods to increase the performance of the rocket. Based of the result of the static test, the measure of the combustion chamber pressure and the thrust of the rocket will increase, if the throat diameter was decreased. The result of the static test showed that the throat diameter of the nozzle was smaller, where as the combustion chamber pressure, the thrust and the specific Impulse were higher. Its mean that the performance of the rocket was increased. (author)

193

Problems of millipound thrust measurement. The "Hansen Suspension"  

Energy Technology Data Exchange (ETDEWEB)

Considered in detail are problems which led to the need and use of the 'Hansen Suspension'. Also discussed are problems which are likely to be encountered in any low level thrust measuring system. The methods of calibration and the accuracies involved are given careful attention. With all parameters optimized and calibration techniques perfected, the system was found capable of a resolution of 10 {mu} lbs. A comparison of thrust measurements made by the 'Hansen Suspension' with measurements of a less sophisticated device leads to some surprising results.

Carta, David G.

2014-03-31

194

Beryllium satellite thrust cone design, manufacture and test  

International Nuclear Information System (INIS)

Pre-formed beryllium sheet material has been used in the design, manufacturing and test of a satellite thrust cone structure. Adhesive bonding was used for attachment of aluminium flanges and conical segment lap strips. Difficulties in beryllium structure design such as incompatibilities with aluminium and handling problems are discussed. Testing to optimize beryllium-beryllium and beryllium-aluminium adhesive bonds is described. The completed thrust cone assembly has been subjected to static load testing and the results are presented. A summary of the relative merits of the use of beryllium in satellite structures is given with recommendations for future users. (author)

195

A balanced cross section across the Himalayan frontal fold-thrust belt, Subathu area, Himachal Pradesh, India: thrust sequence, structural evolution and shortening  

Science.gov (United States)

The structural evolution of the frontal fold-thrust belt in the NW Himalayas has been deciphered through the construction of a balanced cross section, which incorporates all the Tertiary and the Precambrian sedimentary rock units belonging to the Sub-Himalaya Zone and the Lesser Himalaya Zone, respectively. Towards the foreland the structural geometry is rather simple with widely spaced thrust ramps and simple fault-bend folds in the hangingwall. In the central sector, the structural geometry seen at the surface is essentially controlled by a thrust system that can be approximately described as a buried hinterland-dipping duplex. The structural geometry becomes extremely complex in the northeastern sector (i.e. towards the hinterland) owing to out-of-sequence thrusting, low ramp spacing leading to dislocation of older thrusts and related structures by younger thrusts, folded thrusts, and breached horses. Stacked-up horses, occupied by Lesser Himalaya Zone formations, dominate the structural geometry in this sector. An in-sequence thrusting event followed by out-of-sequence thrusting in an approximately break-back style best describe the structural evolution of the fold-thrust belt in this area. A total slip of about 96 km occurred along the detachment and the shortening partitioned within the fold-thrust belt is about 72 km or about 71%.

Mukhopadhyay, Dilip K.; Mishra, Premanand

2005-08-01

196

Bearing-Cartridge Damping Seal  

Science.gov (United States)

In proposed design for improved ball-bearing cartridge, damping seal in form of thin-layer fluid journal bearing incorporated into cartridge. Damping seal acts as auxiliary bearing, relieving bearing balls of significant portions of both static and dynamic bearing loads. Damping from seal reduces dynamic loads even further by reducing amplitude of vibrations in second vibrational mode of rotor, which mode occurs when rotor turning at nearly full operating speed. Intended for use in high-pressure-oxygen turbopump of Space Shuttle main engine, also applicable to other turbomachinery bearings.

Goggins, David G.; Scharrer, Joseph K.; Chen, Wei C.

1991-01-01

197

Flexure Bearing Reduces Startup Friction  

Science.gov (United States)

Design concept for ball bearing incorporates small pieces of shim stock, wire spokes like those in bicycle wheels, or other flexing elements to reduce both stiction and friction slope. In flexure bearing, flexing elements placed between outer race of ball bearing and outer ring. Elements flex when ball bearings encounter small frictional-torque "bumps" or even larger ones when bearing balls encounter buildups of grease on inner or outer race. Flexure of elements reduce high friction slopes of "bumps", helping to keep torque between outer ring and inner race low and more nearly constant. Concept intended for bearings in gimbals on laser and/or antenna mirrors.

Clingman, W. Dean

1991-01-01

198

Predicted and experimental performance of jet-lubricated 120-millimeter-bore ball bearings operating to 2.5 million DN  

Science.gov (United States)

Bearing inner- and outer-race temperatures and friction power losses were calculated using two computer programs. The values obtained were compared with previously reported experimental data for 120 mm bore bearings which operated at thrust loads to 22 240 N (5000 lb), shaft speeds to 20 800 rpm, and with two lubricant flow rates. One program severely underestimated the power loss, while the other, called SHABERTH, provided a good prediction of both race temperatures and power losses.

Coe, H. H.; Zaretsky, E. V.

1978-01-01

199

Development of Flexible Bearing  

Directory of Open Access Journals (Sweden)

Full Text Available Elastomeric base isolation systems are proven to be effective in reducing seismic forces transmitted to buildings. However, due to their cost, the use of these devices is currently limited to large and expensive buildings. A fiber reinforced elastomeric isolator utilizes fiber fabric, such as carbon fiber, glass fibre, and etc. as the reinforcement material instead of solid steel plates. The fibre fabric reinforcement is extensible in tension and has no flexural rigidity. Elastomers normally used in the isolator are natural rubber; neoprene, butyl rubber and nit rile rubber etc. These devices were fabricated by binding alternating layers of rubber and fibre mesh. The fibre mesh is used to increase the vertical stiffness of the bearings while maintaining low lateral stiffness. Characterizing the behaviour of a fibre reinforced bearing “shape factor” of the bearing, Poisson’s ratio of the elastomeric material and flexibility of the reinforcing sheets and investigate the effect of reinforcement flexibility on compressive behaviour of elastomeric bearings with different geometrical and material properties. Bonding with fibre reinforcements can increase the stiffness of elastic layers only when the elastic layer is compressed.

K.S.Mohanraj

2014-06-01

200

Tardigrada (Water Bears)  

Science.gov (United States)

This reference page offers a brief description of Tardigrades, also known as water bears. It includes information about their physical appearance, an explanation of their name, likely habitats, internal organs and other distinguishing features, and a few images. A diagram of a common tardigrade, Macrobiotus macronyx, is also provided via an internal link.

Micrographia

 
 
 
 
201

Magnetically leviated superconducting bearing  

Science.gov (United States)

A magnetically levitated superconducting bearing includes a magnet (2) mounted on a shaft (12) that is rotatable around an axis of rotation and a Type II superconductor (6) supported on a stator (14) in proximity to the magnet (2). The superconductor (6) is positioned so that when it is cooled to its superconducting state in the presence of a magnetic field, it interacts with the magnet (2) to produce an attractive force that levitates the magnet (2) and supports a load on the shaft (12). The interaction between the superconductor (6) and magnet(2) also produces surface screening currents (8) that generate a repulsive force perpendicular to the load. The bearing also has means for maintaining the superconductor at a temperature below its critical temperature (16, 18). The bearing could also be constructed so the magnet (2) is supported on the stator (14) and the superconductor (6) is mounted on the shaft (12). The bearing can be operated by cooling the superconductor (6) to its superconducting state in the presence of a magnetic field.

Weinberger, Bernard R. (Avon, CT); Lynds, Jr., Lahmer (Glastonbury, CT)

1993-01-01

202

Bear vs Bee  

Science.gov (United States)

This interactive Java applet is a game that challenges a student to solve problems by using logic and rudimentary engineering skills. The goal in each case is to create a conveyance that gets the bear to the pot of honey, avoiding the bees. The game has 32 stages of increasing complexity.

2012-01-01

203

History of ball bearings  

Science.gov (United States)

The familiar precision rolling-element bearings of the twentieth century are products of exacting technology and sophisticated science. Their very effectiveness and basic simplicity of form may discourage further interest in their history and development. Yet the full story covers a large portion of recorded history and surprising evidence of an early recognition of the advantages of rolling motion over sliding action and progress toward the development of rolling-element bearings. The development of rolling-element bearings is followed from the earliest civilizations to the end of the eighteenth century. The influence of general technological developments, particularly those concerned with the movement of large building blocks, road transportation, instruments, water-raising equipment, and windmills are discussed, together with the emergence of studies of the nature of rolling friction and the impact of economic factors. By 1800 the essential features of ball and rolling-element bearings had emerged and it only remained for precision manufacture and mass production to confirm the value of these fascinating machine elements.

Dowson, D.; Hamrock, B. J.

1981-01-01

204

Component test results from the bearing life improvement program for the Space Shuttle Main Engine oxidizer turbopumps  

Science.gov (United States)

Interim results from a component test program to improve ball bearing life in the Space Shuttle Main Engine oxygen turbopumps are presented. Two specific bearing applications, using liquid oxygen as the bearing coolant, are addressed. The first, the thrust bearing of the low pressure pump, operates at relatively slow speed with predominantly axial load and little temperature rise in the bulk coolant. Testing has demonstrated a very significant reduction in bearing wear by increasing the bearing internal clearance. Heat generation data was obtained that indicates heavy, intermittent cage-to-ball contact occurs, providing a possible explanation for the observed wear. The second application is the turbine end bearings of the high pressure pump. These bearings operate at high speed and load with the possibility of significant coolant vaporization. Tests on production bearings and bearings having modified internal clearance and curvature yielded scattered but generally poor lives. A dramatic improvement was achieved by coating the standard cage with a thin film of fluorinated ethylene propylene and 15 percent molybdenum disulfide. Very promising results have also been obtained by replacing the standard balls with ones made of silicon nitride, especially in combination with the coated cage.

Keba, John E.

1992-01-01

205

Measuring ball-bearing loads  

Science.gov (United States)

Contour of wear-path boundary in bearing race gives precise information about magnitude, direction and imbalance of load. Simple tool measures height of path perimeter as bearing race is rotated manually on flat surface.

Butner, M. F.

1980-01-01

206

A Regeneratively Cooled Thrust Chamber For The Fastrac Engine  

Science.gov (United States)

Abstract This paper presents the development of a low-cost, regeneratively-cooled thrust chamber for the Fastrac engine. The chamber was fabricated using hydraformed copper tubing to form the coolant jacket and wrapped with a fiber reinforced polymer composite Material to form a structural jacket. The thrust chamber design and fabrication approach was based upon Space America. Inc.'s 12,000 lb regeneratively-cooled LOX/kerosene rocket engine. Fabrication of regeneratively cooled thrust chambers by tubewall construction dates back to the early US ballistic missile programs. The most significant innovations in this design was the development of a low-cost process for fabrication from copper tubing (nickel alloy was the usual practice) and use of graphite composite overwrap as the pressure containment, which yields an easily fabricated, lightweight pressure jacket around the copper tubes A regeneratively-cooled reusable thrust chamber can benefit the Fastrac engine program by allowing more efficient (cost and scheduler testing). A proof-of-concept test article has been fabricated and will he tested at Marshall Space Flight Center in the late Summer or Fall of 2000.

Brown, Kendall K.; Sparks, Dave; Woodcock, Gordon

2000-01-01

207

Effect of Operating Frequency on PDE Driven Ejector Thrust Performance  

Science.gov (United States)

Results of an on-going study of pulse detonation engine driven ejectors are presented and discussed. The experiments were conducted using a pulse detonation engine (PDE) designed to operate at frequencies up to 50 Hz. The PDE used in these experiments utilizes an equi-molar mixture of oxygen and nitrogen as the oxidizer, and ethylene (C2H4) as the fuel, with the propellant mixture having an equivalence ratio of one. A line of sight laser absorption technique was used to determine the time needed for proper filling of the tube. Thrust measurements were made using an integrated spring damper system coupled with a linear variable displacement transducer. The baseline thrust of the PDE was first measured at each desired frequency and agrees with experimental and modeling results found in the literature. Thrust augmentation measurements were then made for constant diameter ejectors. The ejectors had varying lengths, and two different inlet geometries were tested for each ejector configuration. The parameter space for the study included PDE operation frequency, ejector length, overlap distance and the radius of curvature for the ejector inlets. For the studied experimental matrix, the results showed a maximum thrust augmentation of 106% at an operational frequency of 30 Hz.

Santoro, Robert J.; Pal, Sibtosh; Landry, K.; Shehadeh, R.; Vouvet, N.; Lee, S.-Y.

2005-01-01

208

Engineering Research, Development and Technology, FY95: Thrust area report  

Energy Technology Data Exchange (ETDEWEB)

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the knowledge base, process technologies, specialized equipment, tools and facilities to support current and future LLNL programs. Engineering`s efforts are guided by a strategy that results in dual benefit: first, in support of Department of Energy missions, such as national security through nuclear deterrence; and second, in enhancing the nation`s economic competitiveness through their collaboration with US industry in pursuit of the most cost-effective engineering solutions to LLNL programs. To accomplish this mission, the Engineering Research, Development, and Technology Program has two important goals: (1) identify key technologies relevant to LLNL programs where they can establish unique competencies, and (2) conduct high-quality research and development to enhance their capabilities and establish themselves as the world leaders in these technologies. To focus Engineering`s efforts, technology thrust areas are identified and technical leaders are selected for each area. The thrust areas are comprised of integrated engineering activities, staffed by personnel from the nine electronics and mechanical engineering divisions, and from other LLNL organizations. This annual report, organized by thrust area, describes Engineering`s activities for fiscal year 1995. The report provides timely summaries of objectives methods, and key results from eight thrust areas: computational electronics and electromagnetics; computational mechanics; microtechnology; manufacturing technology; materials science and engineering; power conversion technologies; nondestructive evaluation; and information engineering.

NONE

1996-02-01

209

Design of an ion thruster movable grid thrust vectoring system  

Science.gov (United States)

Several reasons justify the development of an ion propulsion system thrust vectoring system. Spacecraft launched to date have used ion thrusters mounted on gimbals to control the thrust vector within a range of about ±5°. Such devices have large mass and dimensions, hence the need exists for a more compact system, preferably mounted within the thruster itself. Since the 1970s several thrust vectoring systems have been developed, with the translatable accelerator grid electrode being considered the most promising. Laboratory models of this system have already been built and successfully tested, but there is still room for improvement in their mechanical design. This work aims to investigate possibilities of refining the design of such movable grid thrust vectoring systems. Two grid suspension designs and three types of actuators were evaluated. The actuators examined were a micro electromechanical system, a NanoMuscle shape memory alloy actuator and a piezoelectric driver. Criteria used for choosing the best system included mechanical simplicity (use of the fewest mechanical parts), accuracy, power consumption and behaviour in space conditions. Designs of systems using these actuators are proposed. In addition, a mission to Mercury using the system with piezoelectric drivers has been modelled and its performance presented.

Kural, Aleksander; Leveque, Nicolas; Welch, Chris; Wolanski, Piotr

2004-08-01

210

Separability of drag and thrust in undulatory animals and machines  

Science.gov (United States)

For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal-istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation framework helps to predict the observed height of the ribbon fin of electric knifefish, a diverse group of neotropical fish which are an important model system in sensory neurobiology. We also show how drag-thrust separation leads to models that can predict the swimming velocity of an organism or a robotic vehicle.

Bale, Rahul; Shirgaonkar, Anup A.; Neveln, Izaak D.; Bhalla, Amneet Pal Singh; Maciver, Malcolm A.; Patankar, Neelesh A.

2014-12-01

211

Solid rocket booster thrust vector control subsystem description  

Science.gov (United States)

Major Solid Rocket Booster-Thrust Vector Control (SRB-TVC) subsystem components and subcomponents used in the Space Transportation System (STS) are identified. Simplified schematics, detailed schematics, figures, photographs, and data are included to acquaint the reader with the operation, performance, and physical layout as well as the materials and instrumentation used.

Redmon, J., Jr. (compiler)

1983-01-01

212

Compliant hydrodynamic fluid journal bearing  

Science.gov (United States)

An air bearing structure is described that prevents destructive bending moments within the top foil. Welds are eliminated by mounting the top bearing foil in the bearing cartridge sleeve without using a space block. Tabs or pins at the end of the top bearing foil are restrained by slots or stops formed in the cartridge sleeve. These structural members are free to move in a direction normal to the shaft while being restrained from movement in the direction of shaft rotation.

Warren, E. L. (inventor)

1985-01-01

213

First order ball bearing kinematics  

Science.gov (United States)

Two first order equations are given connecting geometry and internal motions in an angular contact ball bearing. Total speed, kinematic equivalence, basic speed ratio, and modal speed ratio are defined and discussed; charts are given for the speed ratios covering all bearings and all rotational modes. Instances where specific first order assumptions might fail are discussed, and the resulting effects on bearing performance reviewed.

Kingbury, E.

1984-01-01

214

Thrust Area Report, Engineering Research, Development and Technology  

Energy Technology Data Exchange (ETDEWEB)

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the knowledge base, process technologies, specialized equipment, tools and facilities to support current and future LLNL programs. Engineering`s efforts are guided by a strategy that results in dual benefit: first, in support of Department of Energy missions, such as national security through nuclear deterrence; and second, in enhancing the nation`s economic competitiveness through our collaboration with U.S. industry in pursuit of the most cost- effective engineering solutions to LLNL programs. To accomplish this mission, the Engineering Research, Development, and Technology Program has two important goals: (1) identify key technologies relevant to LLNL programs where we can establish unique competencies, and (2) conduct high-quality research and development to enhance our capabilities and establish ourselves as the world leaders in these technologies. To focus Engineering`s efforts technology {ital thrust areas} are identified and technical leaders are selected for each area. The thrust areas are comprised of integrated engineering activities, staffed by personnel from the nine electronics and mechanical engineering divisions, and from other LLNL organizations. This annual report, organized by thrust area, describes Engineering`s activities for fiscal year 1996. The report provides timely summaries of objectives, methods, and key results from eight thrust areas: Computational Electronics and Electromagnetics; Computational Mechanics; Microtechnology; Manufacturing Technology; Materials Science and Engineering; Power Conversion Technologies; Nondestructive Evaluation; and Information Engineering. Readers desiring more information are encouraged to contact the individual thrust area leaders or authors. 198 refs., 206 figs., 16 tabs.

Langland, R. T.

1997-02-01

215

14 CFR 23.1155 - Turbine engine reverse thrust and propeller pitch settings below the flight regime.  

Science.gov (United States)

...false Turbine engine reverse thrust and propeller pitch settings below the flight regime...1155 Turbine engine reverse thrust and propeller pitch settings below the flight regime...each control for reverse thrust and for propeller pitch settings below the...

2010-01-01

216

Centrifugally decoupling touchdown bearings  

Science.gov (United States)

Centrifugally decoupling mechanical bearing systems provide thin tensioned metallic ribbons contained in a support structure. This assembly rotates around a stationary shaft being centered at low speeds by the action of the metal ribbons. Tension springs are connected on one end to the ribbons and on the other end to the support structure. The ribbons pass through slots in the inner ring of the support structure. The spring preloading thus insures contact (or near-contact) between the ribbons and the shaft at rotation speeds below the transition speed. Above this speed, however, the centrifugal force on the ribbons produces a tensile force on them that exceeds the spring tensile force so that the ribbons curve outward, effectively decoupling them from mechanical contact with the shaft. They still remain, however, in position to act as a touchdown bearing in case of abnormally high transverse accelerations.

Post, Richard F

2014-06-24

217

Magnetic bearing and motor  

Science.gov (United States)

A magnetic bearing assembly (10) has an intermediate rotatable section (33) having an outer cylindrical member (30) coaxially suspended by a torsion wire (72) around an axially polarized cylindrical magnet (32). Axial alignment between the pole faces (40-43) of the intermediate section (33) and end surfaces (50-53) of opposed end bells (20, 22) provides a path of least reluctance across intervening air gaps (60-63) for the magnetic flux emanating from magnet (32). Radial dislocation increases the reluctance and creates a radial restoring force. Substitution of radially polarized magnets 107 fixed to a magnetically permeable cylinder (32') and insertion of pairs of armature coil windings (109-112) between the cylinder pair (33') provides an integral magnetic bearing and torsion motor (100) able to provide arcuately limited rotational drive.

Studer, Philip A. (Inventor)

1983-01-01

218

Bears in a Boat  

Science.gov (United States)

In this math activity, learners are challenged to create aluminum foil boats that will hold plastic bears until the boats sink. The lesson serves as a fun, hands-on way to collect data. Data from two attempts is collected and used to make two class box-and-whisker plots with some surprising results. This lesson guide includes questions for learners, assessment options, extensions, and reflection questions.

Rubillo, Jim

2012-01-01

219

Cavitation in short bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this note we obtain the boundaries of the cavitation bubbles when the Reynolds conditions are used to treat the problem of the cavitation, in short journal bearings and in mechanical face seals. A universal solution to this problem is presented in some detail, in the sense that the solution of an ordinary nonlinear first order differential equation, that is necessary to describe the downstream boundary of the cavity, only depends on the eccentricity ratio, but not on the cavitation incipie...

Rodri?guez Ferna?ndez, Manuel; Lin?a?n Marti?nez, Amable

1985-01-01

220

Syntectonic sedimentation effects on the growth of fold-and-thrust belts  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We use two-dimensional mechanical models to investigate the effects of syntectonic sedimentation on fold-and-thrust belt development, testing variable syntectonic (wedge-top and foredeep) sediment thicknesses and flexural rigidities. Model results indicate a first-order control of syntectonic sedimentation on thrust-sheet length and thrust spacing. Thrust sheets are longer when syntectonic sediment thickness and/or flexural rigidity increase. Comparison with observations from several fold-and...

Fillon, Charlotte; Huismans, Ritske; Beek, Pieter

2013-01-01

 
 
 
 
221

Magnetic translator bearings  

Science.gov (United States)

A magnetic bearing system for enabling translational motion includes a carriage and a shaft for movably supporting the carriage; a first magnetic bearing fixed to one of the carriage and shaft and slidably received in a first channel of the other of the carriage and shaft. The first channel is generally U shaped with two side walls and a back wall. The magnetic bearing includes a pair of spaced magnetic pole pieces, each pole piece having a pair of electromagnetic coils mounted on poles on opposite ends of the pole piece proximate the side walls, and a third electromagnetic coil mounted on a pole of the pole piece proximate the backwall; a motion sensor for sensing translational motion along two axes and rotationally about three axes of the carriage and shaft relative to each other; and a correction circuit responsive to the sensor for generating a correction signal to drive the coils to compensate for any misalignment sensed between the carriage and the shaft.

Hockney, Richard L. (Inventor); Downer, James R. (Inventor); Eisenhaure, David B. (Inventor); Hawkey, Timothy J. (Inventor); Johnson, Bruce G. (Inventor)

1990-01-01

222

Anti-backlash gear bearings  

Science.gov (United States)

A gear bearing having a first gear and a second gear, each having a plurality of teeth. Each gear operates on two non-parallel surfaces of the opposing gear teeth to perform both gear and bearing functions simultaneously. The gears are moving at substantially the same speed at their contact points. The gears may be roller gear bearings or phase-shifted gear bearings, and may be arranged in a planet/sun system or used as a transmission. One preferred embodiment discloses and describes an anti-backlash feature to counter ''dead zones'' in the gear bearing movement.

Vranish, John M. (Inventor)

2009-01-01

223

Bearing for liquid metal pump  

Science.gov (United States)

A liquid metal pump bearing support comprises a series of tangentially oriented spokes that connect the bearing cylinder to the pump internals structure. The spokes may be arranged in a plurality of planes extending from the bearing cylinder to the pump internals with the spokes in one plane being arranged alternately with those in the next plane. The bearing support structure provides the pump with sufficient lateral support for the bearing structure together with the capability of accommodating differential thermal expansion without adversely affecting pump performance.

Dickinson, Robert J. (Shaler Township, Allegheny County, PA); Wasko, John (Plum Borough, PA); Pennell, William E. (Unity Township, Allegheny County, PA)

1984-01-01

224

Interseismic Strain Accumulation Across Metropolitan Los Angeles: Puente Hills Thrust  

Science.gov (United States)

Twelve years of observation of the Southern California Integrated GPS Network (SCIGN) are tightly constraining the distribution of shortening across metropolitan Los Angeles, providing information on strain accumulation across blind thrust faults. Synthetic Aperture Radar Interferometry (InSAR) and water well records are allowing the effects of water and oil management to be distinguished. The Mojave segment of the San Andreas fault is at a 25° angle to Pacific-North America plate motion. GPS shows that NNE-SSW shortening due to this big restraining bend is fastest not immediately south of the San Andreas fault across the San Gabriel mountains, but rather 50 km south of the fault in northern metropolitan Los Angeles. The GPS results we quote next are for a NNE profile through downtown Los Angeles. Just 2 mm/yr of shortening is being taken up across the San Gabriel mountains, 40 km wide (0.05 micro strain/yr); 4 mm/yr of shortening is being taken up between the Sierra Madre fault, at the southern front of the San Gabriel mountains, and South Central Los Angeles, also 40 km wide (0.10 micro strain/yr). We find shortening to be more evenly distributed across metropolitan Los Angeles than we found before [Argus et al. 2005], though within the 95% confidence limits. An elastic models of interseismic strain accumulation is fit to the GPS observations using the Back Slip model of Savage [1983]. Rheology differences between crystalline basement and sedimentary basin rocks are incorporated using the EDGRN/EDCMP algorithm of Wang et al. [2003]. We attempt to place the Back Slip model into the context of the Elastic Subducting Plate Model of Kanda and Simons [2010]. We find, along the NNE profile through downtown, that: (1) The deep Sierra Madre Thrust cannot be slipping faster than 2 mm/yr, and (2) The Puente Hills Thrust and nearby thrust faults (such as the upper Elysian Park Thrust) are slipping at 9 ±2 mm/yr beneath a locking depth of 12 ±5 km (95% confidence limits). Incorporating sedimentary basin rock either reduces the slip rate by 10 per cent or increases the locking rate by 20 per cent. The 9 mm/yr rate for the Puente Hills Thrust and nearby faults exceeds the cumulative 3-5 mm/yr rate estimated using paleoseismology along the Puente Hills Thrust (1.2-1.6 mm/yr, Dolan et al. 2003), upper Elysian Park Thrust (0.6-2.2 mm/yr, Oskin et al. 2000), and western Compton Thrust (1.2 mm/yr, Leon et al. 2009], though all the paleoseismic estimates are minimums. We infer that M 7 earthquakes in northern metropolitan Los Angeles may occur more frequently that previously thought.

Argus, D.; Liu, Z.; Heflin, M. B.; Moore, A. W.; Owen, S. E.; Lundgren, P.; Drake, V. G.; Rodriguez, I. I.

2012-12-01

225

Development of superconducting magnetic bearing using superconducting coil and bulk superconductor  

Energy Technology Data Exchange (ETDEWEB)

The authors conducted a study on superconducting magnetic bearing, which consists of superconducting rotor and stator to apply the flywheel energy-storage system for railways. In this study, high temperature bulk superconductor (HTS bulk) was combined with superconducting coils to increase the load capacity of the bearing. In the first step of the study, the thrust rolling bearing was selected for application by using liquid nitrogen cooled HTS bulk. 60mm-diameter HTS bulks and superconducting coil which generated a high gradient of magnetic field by cusp field were adopted as a rotor and a stator for superconducting magnetic bearing, respectively. The results of the static load test and the rotation test, creep of the electromagnetic forces caused by static flux penetration and AC loss due to eccentric rotation were decreased to the level without any problems in substantial use by using two HTS bulks. In the result of verification of static load capacity, levitation force (thrust load) of 8900N or more was supportable, and stable static load capacity was obtainable when weight of 460kg was levitated.

Seino, H; Nagashima, K; Arai, Y [Railway Technical Research Institute, Hikari-cho 2-8-38, Kokubunji-shi, Tokyo (Japan)], E-mail: seino@rtri.or.jp

2008-02-01

226

14 CFR 25.1155 - Reverse thrust and propeller pitch settings below the flight regime.  

Science.gov (United States)

...2010-01-01 false Reverse thrust and propeller pitch settings below the flight regime...Accessories § 25.1155 Reverse thrust and propeller pitch settings below the flight regime. Each control for reverse thrust and for propeller pitch settings below the...

2010-01-01

227

The Butte Valley and Layton Well Thrusts of eastern California: Distribution and regional significance  

Science.gov (United States)

The Butte Valley and Layton Well Thrusts are major structural features in two adjacent mountain ranges west of southern Death Valley. The Butte Valley Thrust in the southern Panamint Range underlies most of the range and emplaces Proterozoic rocks over strata as young as Jurassic(?) in age. The Layton Well Thrust to the southwest in the Slate Range has been interpreted to have Proterozoic rocks juxtaposed on rocks as young as Jurassic, suggesting that the Butte Valley Thrust and the Layton Well Thrust might be correlative. New information indicates that the allochthonous rocks of the Layton Well Thrust are Mesozoic in age and are not likely part of the same allochthon as that above the Butte Valley Thrust. In addition, the Butte Valley Thrust cuts sharply downward to the north and west across lower plate Paleozoic strata, suggesting that the fault roots beneath the Layton Well Thrust. The Layton Well Thrust probably belongs to the East Sierran thrust system and thus would be in the upper plate of the Butte Valley Thrust.

Wrucke, Chester T.; Stevens, Calvin H.; Wooden, Joseph L.

1995-10-01

228

Evaluation of various thrust calculation techniques on an F404 engine  

Science.gov (United States)

In support of performance testing of the X-29A aircraft at the NASA-Ames, various thrust calculation techniques were developed and evaluated for use on the F404-GE-400 engine. The engine was thrust calibrated at NASA-Lewis. Results from these tests were used to correct the manufacturer's in-flight thrust program to more accurately calculate thrust for the specific test engine. Data from these tests were also used to develop an independent, simplified thrust calculation technique for real-time thrust calculation. Comparisons were also made to thrust values predicted by the engine specification model. Results indicate uninstalled gross thrust accuracies on the order of 1 to 4 percent for the various in-flight thrust methods. The various thrust calculations are described and their usage, uncertainty, and measured accuracies are explained. In addition, the advantages of a real-time thrust algorithm for flight test use and the importance of an accurate thrust calculation to the aircraft performance analysis are described. Finally, actual data obtained from flight test are presented.

Ray, Ronald J.

1990-01-01

229

Advances in Thrust-Based Emergency Control of an Airplane  

Science.gov (United States)

Engineers at NASA's Dryden Flight Research Center have received a patent on an emergency flight-control method implemented by a propulsion-controlled aircraft (PCA) system. Utilizing the preexisting auto-throttle and engine-pressure-ratio trim controls of the airplane, the PCA system provides pitch and roll control for landing an airplane safely without using aerodynamic control surfaces that have ceased to function because of a primary-flight-control-system failure. The installation of the PCA does not entail any changes in pre-existing engine hardware or software. [Aspects of the method and system at previous stages of development were reported in Thrust-Control System for Emergency Control of an Airplane (DRC-96-07), NASA Tech Briefs, Vol. 25, No. 3 (March 2001), page 68 and Emergency Landing Using Thrust Control and Shift of Weight (DRC-96-55), NASA Tech Briefs, Vol. 26, No. 5 (May 2002), page 58.]. Aircraft flight-control systems are designed with extensive redundancy to ensure low probabilities of failure. During recent years, however, several airplanes have exhibited major flight-control-system failures, leaving engine thrust as the last mode of flight control. In some of these emergency situations, engine thrusts were successfully modulated by the pilots to maintain flight paths or pitch angles, but in other situations, lateral control was also needed. In the majority of such control-system failures, crashes resulted and over 1,200 people died. The challenge lay in creating a means of sufficient degree of thrust-modulation control to safely fly and land a stricken airplane. A thrust-modulation control system designed for this purpose was flight-tested in a PCA an MD-11 airplane. The results of the flight test showed that without any operational control surfaces, a pilot can land a crippled airplane (U.S. Patent 5,330,131). The installation of the original PCA system entailed modifications not only of the flight-control computer (FCC) of the airplane but also of each engine-control computer. Inasmuch as engine-manufacturer warranties do not apply to modified engines, the challenge became one of creating a PCA system that does not entail modifications of the engine computers.

Creech, Gray; Burken, John J.; Burcham, Bill

2003-01-01

230

Testing of Bearing Materials for Large Two-stroke Marine Diesel Engines  

DEFF Research Database (Denmark)

In large two-stroke marine diesel engines bearings are designed with the intention that these need not be replaced during the life of the engine. The design has shown very good service experiences. The design parameters of the main bearings are, among others, based on the average maximum specific load which the bearing should operate under. In general, the frictional loss is less than 1% of the nominal power of the engine but is still a target for optimization. Fatigue mechanisms of bearing lining material are not fully understood and the design limits with regards to minimum oil film thickness, max oil film pressure and oil film pressure gradient is not established. Large two-stroke journal bearings are not suitable for fatigue test due to the size, the low rotational speed and the complexity of such test-rig. The Disc Fatigue Test Rig (DFTR) was designed with the purpose to test white metal coatings under realistic bearing conditions, in a confined time-frame. The test-rig simulates a scale model of a thrust bearing, in contrary to standard design the bearing lining material is applied to the rotating collar. On each side of the disc three stationary tilting-pads applies a load to the test disc, with a rotational speed of 2000 rpm. Parameters, such as bearing load, rotational speed, oil temperature, oil contamination is controlled/monitored in order to achieve repeatability and a systematic approach to the experiments. Test performed on the test-rig shows good correlation on the fatigue cracks with those experienced on large two-stroke journal bearings.

Klit, Peder; Persson, Sebastian

2013-01-01

231

Characterization of Space Shuttle Reusable Rocket Motor Static Test Stand Thrust Measurements  

Science.gov (United States)

Space Shuttle Reusable Solid Rocket Motors (RSRM) are static tested at two ATK Thiokol Propulsion facilities in Utah, T-24 and T-97. The newer T-97 static test facility was recently upgraded to allow thrust measurement capability. All previous static test motor thrust measurements have been taken at T-24; data from these tests were used to characterize thrust parameters and requirement limits for flight motors. Validation of the new T-97 thrust measurement system is required prior to use for official RSRM performance assessments. Since thrust cannot be measured on RSRM flight motors, flight motor measured chamber pressure and a nominal thrust-to-pressure relationship (based on static test motor thrust and pressure measurements) are used to reconstruct flight motor performance. Historical static test and flight motor performance data are used in conjunction with production subscale test data to predict RSRM performance. The predicted motor performance is provided to support Space Shuttle trajectory and system loads analyses. Therefore, an accurate nominal thrust-to-pressure (F/P) relationship is critical for accurate RSRM flight motor performance and Space Shuttle analyses. Flight Support Motors (FSM) 7, 8, and 9 provided thrust data for the validation of the T-97 thrust measurement system. The T-97 thrust data were analyzed and compared to thrust previously measured at T-24 to verify measured thrust data and identify any test-stand bias. The T-97 FIP data were consistent and within the T-24 static test statistical family expectation. The FSMs 7-9 thrust data met all NASA contract requirements, and the test stand is now verified for future thrust measurements.

Cook, Mart L.; Gruet, Laurent; Cash, Stephen F. (Technical Monitor)

2003-01-01

232

Investigation of Thrust Augmentation of a 1600-pound Thrust Centrifugal-flow-type Turbojet Engine by Injection of Refrigerants at Compressor Inlets  

Science.gov (United States)

Investigations were conducted to determine effectiveness of refrigerants in increasing thrust of turbojet engines. Mixtures of water an alcohol were injected for a range of total flows up to 2.2 lb/sec. Kerosene was injected into inlets covering a range of injected flows up to approximately 30% of normal engine fuel flow. Injection of 2.0 lb/sec of water alone produced an increase in thrust of 35.8% of rate engine conditions and kerosene produced a negligible increase in thrust. Carbon dioxide increased thrust 23.5 percent.

Jones, William L.; Dowman, Harry W.

1947-01-01

233

Thrust structure in Michigan could point toward more targets  

Energy Technology Data Exchange (ETDEWEB)

During the drilling of an Ordovician St. Peter development well in AuGres field of Arenac County, Mich., an unexpected, duplicate section of Silurian A-1 carbonate was encountered. This duplicate section has been interpreted to have been formed by thrusting that was caused by a nonlinear, right-lateral wrench fault. Wrench faulting in Michigan is well documented, but transpression -- resulting in thrusted structures -- is rare. Shear-zone fracturing along this wrench fault has enhanced hydrocarbon accumulation within the A-1 carbonate as well as the A-2 evaporite. Reservoirs associated with wrenching are not new to Michigan. The state's largest oil field, Albion-Scipio, is producing from fractures and porosity enhancement resulting from wrench movement. Exploring for such features, however, could be shifted to other parts of the Michigan basin.

DesAutels, D. (Qatar General Petroleum Corp., Doha (Qatar))

1993-08-16

234

Design of Low-Thrust Gravity Assist Trajectories to Europa  

CERN Document Server

This paper presents the design of a mission to Europa using solar electric propulsion as main source of thrust. A direct transcription method based on Finite Elements in Time was used for the design and optimisation of the entire low-thrust gravity assist transfer from the Earth to Europa. Prior to that, a global search algorithm was used to generate a set of suitable first guess solutions for the transfer to Jupiter, and for the capture in the Jovian system. In particular, a fast deterministic search algorithm was developed to find the most promising set of swing-bys to reach Jupiter A second fast search algorithm was developed to find the best sequence of swing-bys of the Jovian moons. After introducing the global search algorithms and the direct transcription through Finite Elements in Time, the paper presents a number of first guess Solutions and a fully optimised transfer from the Earth to Europa.

Vasile, Massimiliano

2011-01-01

235

Nonlinear structural analysis of cylindrical thrust chambers using viscoplastic models  

Science.gov (United States)

The results are presented of a viscoplastic stress-strain analysis of a cylindrical thrust chamber used in experiments that were designed to simulate the SSME operating conditions. The inelastic strain was calculated by using a viscoplastic model, and a quasi-three-dimensional structural analysis was performed by using a finite element program MARC. The temperatures and pressures were calculated by using the loading cycles of experiments, and these temperatures and pressures were used in the computations. The deformed shape of the component was predicted after the end of each loading cycle. The predicted shape qualitatively replicated the deformed shape of the component as observed in experiments. The results indicate that the use of viscoplastic models for structural analysis may lead to more realistic life assessments of experimental thrust chambers.

Arya, Vinod K.

1991-01-01

236

Engineering research, development and technology. Thrust area report, FY93  

Energy Technology Data Exchange (ETDEWEB)

The mission of the Engineering Research, Development, and Technology Program at Lawrence Livermore National Laboratory (LLNL) is to develop the technical staff, tools, and facilities needed to support current and future LLNL programs. The efforts are guided by a dual-benefit research and development strategy that supports Department of Energy missions, such as national security through nuclear deterrence and economic competitiveness through partnerships with U.S. industry. This annual report, organized by thrust area, describes the activities for the fiscal year 1993. The report provides timely summaries of objectives, methods, and results from nine thrust areas for this fiscal year: Computational Electronics and Electromagnetics; Computational Mechanics; Diagnostics and Microelectronics; Fabrication Technology; Materials Science and Engineering; Power Conversion Technologies; Nondestructive Evaluation; Remote Sensing, Imaging, and Signal Engineering; and Emerging Technologies. Separate abstracts were prepared for 47 papers in this report.

1994-05-01

237

Optimization of Low-Thrust Spiral Trajectories by Collocation  

Science.gov (United States)

As NASA examines potential missions in the post space shuttle era, there has been a renewed interest in low-thrust electric propulsion for both crewed and uncrewed missions. While much progress has been made in the field of software for the optimization of low-thrust trajectories, many of the tools utilize higher-fidelity methods which, while excellent, result in extremely high run-times and poor convergence when dealing with planetocentric spiraling trajectories deep within a gravity well. Conversely, faster tools like SEPSPOT provide a reasonable solution but typically fail to account for other forces such as third-body gravitation, aerodynamic drag, solar radiation pressure. SEPSPOT is further constrained by its solution method, which may require a very good guess to yield a converged optimal solution. Here the authors have developed an approach using collocation intended to provide solution times comparable to those given by SEPSPOT while allowing for greater robustness and extensible force models.

Falck, Robert D.; Dankanich, John W.

2012-01-01

238

Erosion influences the seismicity of active thrust faults  

Science.gov (United States)

Assessing seismic hazards remains one of the most challenging scientific issues in Earth sciences. Deep tectonic processes are classically considered as the only persistent mechanism driving the stress loading of active faults over a seismic cycle. Here we show via a mechanical model that erosion also significantly influences the stress loading of thrust faults at the timescale of a seismic cycle. Indeed, erosion rates of about ~0.1–20?mm?yr?1, as documented in Taiwan and in other active compressional orogens, can raise the Coulomb stress by ~0.1–10?bar on the nearby thrust faults over the inter-seismic phase. Mass transfers induced by surface processes in general, during continuous or short-lived and intense events, represent a prominent mechanism for inter-seismic stress loading of faults near the surface. Such stresses are probably sufficient to trigger shallow seismicity or promote the rupture of deep continental earthquakes up to the surface.

Steer, Philippe; Simoes, Martine; Cattin, Rodolphe; Shyu, J. Bruce H.

2014-11-01

239

Kinematic structural restorations and discrete fracture modeling of a thrust trap: a case study from the Tarija Basin, Argentina  

Energy Technology Data Exchange (ETDEWEB)

The integration between kinematic structural restorations and discrete fracture simulation is applied to a thrusted and fractured fault block in the Tarija basin, Northern Argentina. The emphasis is on the influence of the factor time on the deformation history and fracture growth. The structural evolution of the gas bearing Santa Rosa reservoir forms the basis for understanding the development of the 3D fracture system, as simulated with 3D kinematic restorations. During the restoration, the cumulative dilatational strain was calculated and mapped and compared to traditional curvature analyses. The strain maps are subsequently used to simulate geologically realistic discrete fracture networks that form the basis for further exploration and development of the field. (author)

Sanders, C.; Bonora, M.; Richards, D. [Midland Valley Ltd., Glasgow (United Kingdom); Kozlowski, E.; Sylwan, C.; Cohen, M. [Pan American Energy, Buenos Aires (Argentina)

2004-08-01

240

Uranium favorability of tertiary rocks in the Badger Flats, Elkhorn Thrust Area, Park and Teller Counties, Colorado  

International Nuclear Information System (INIS)

Uranium potential of Tertiary rocks in the Badger Flats--Elkhorn Thrust area of central Colorado is closely related to a widespread late Eocene erosion surface. Most uranium deposits in the area are in the Eocene Echo Park Alluvium and Oligocene Tallahassee Creek Conglomerate, which were deposited in paleodrainage channels on or above this surface. Arkosic detritus within the channels and overlying tuffaceous sedimentary rocks of the Antero and Florissant Formations of Oligocene age and silicic tuffs within the volcanic units provide abundant sources of uranium that could be concentrated in the channels where carbonaceous debris facilitates a reducing environment. Anomalous soil, water, and stream-sediment samples near the Elkhorn Thrust and in Antero basin overlie buried channels or are offset from them along structural trends; therefore, uranium-bearing ground water may have moved upward from buried uranium deposits along faults. The area covered by rocks younger than the late Eocene erosion surface, specifically the trends of mapped or inferred paleochannels filled with Echo Park Alluvium and Tallahassee Creek Conglomerate, and the Antero Formation are favorable for the occurrence of uranium deposits

 
 
 
 
241

A Comparison Study of Magnetic Bearing Controllers for a Fully Suspended Dynamic Spin Rig  

Science.gov (United States)

NASA Glenn Research Center (GRC) has developed a fully suspended magnetic bearing system for the Dynamic Spin Rig (DSR) that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteropolar radial magnetic bearings and a thrust bearing and the associated control system were integrated into the DSR to provide noncontact magnetic suspension and mechanical excitation of the 35 lb vertical rotor with blades to induce turbomachinery blade vibration. A simple proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked very well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, and energy savings for the system. The test results of a variety of controllers we demonstrated up to the rig's maximum allowable speed of 10,000 rpm are shown.

Choi, Benjamin; Johnson, Dexter; Morrison, Carlos; Mehmed, Oral; Huff, Dennis (Technical Monitor)

2002-01-01

242

YBCO texturation and applications of superconducting magnetic bearings in flywheels for energy storage  

International Nuclear Information System (INIS)

A thrust bearing has been built consisting of 6 melt-textured YBCO pellets (diameter 30 x 18 mm) and a Nd-Fe-B ring magnet. The maximum levitation force of the bearing was 65 N at zero gap. Vertical stiffness at 1 mm gap was 440 N/cm, lateral stiffness was 130 N/cm. The bearing has been integrated into a flywheel system rotating a 2.8 kg disk at speeds up to 15 000 rpm. The maximum energy capacity was 4.8 Wh. It can be expected that further refinement of this technology should allow the operation of superconducting flywheels in the kWh range. (orig.)

243

Aerospace applications of magnetic bearings  

Science.gov (United States)

Magnetic bearings have traditionally been considered for use in aerospace applications only where performance advantages have been the primary, if not only, consideration. Conventional wisdom has been that magnetic bearings have certain performance advantages which must be traded off against increased weight, volume, electric power consumption, and system complexity. These perceptions have hampered the use of magnetic bearings in many aerospace applications because weight, volume, and power are almost always primary considerations. This paper will review progress on several active aerospace magnetic bearings programs at SatCon Technology Corporation. The magnetic bearing programs at SatCon cover a broad spectrum of applications including: a magnetically-suspended spacecraft integrated power and attitude control system (IPACS), a magnetically-suspended momentum wheel, magnetic bearings for the gas generator rotor of a turboshaft engine, a vibration-attenuating magnetic bearing system for an airborne telescope, and magnetic bearings for the compressor of a space-rated heat pump system. The emphasis of these programs is to develop magnetic bearing technologies to the point where magnetic bearings can be truly useful, reliable, and well tested components for the aerospace community.

Downer, James; Goldie, James; Gondhalekar, Vijay; Hockney, Richard

1994-05-01

244

Secondary injection fluidic thrust vectoring of an axisymmetric supersonic nozzle  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Secondary injection into the divergent section of a supersonic rocket nozzle is investigated for the fluidic thrust vectoring effects. The study was conducted in the framework of CNES PERSEUS program and was motivated by the need for an alternative vectoring solution aimed for a small space launcher. The thesis work, based on the combined experimental and numerical approaches, essentially comprises of a wide parametric study mainly concerning the position of the injection, the shape of the pr...

Zmijanovic, Vladeta

2013-01-01

245

Low-thrust chemical propulsion system pump technology  

Science.gov (United States)

A study was conducted within the thrust range 450 to 9000 N (100 to 2000 pounds). Performance analyses were made on centrifugal, pitot, Barske, drag, Tesla, gear, piston, lobe, and vane pumps with liquid hydrogen, liquid methane, and liquid oxygen as propellants. Gaseous methane and hydrogen driven axial impulse turbines, vane expanders, piston expanders, and electric motors were studied as drivers. Data are presented on performance, sizes, weights, and estimated service lives and costs.

Meadville, J. W.

1980-01-01

246

Lift, drag and thrust measurement in a hypersonic impulse facility  

Science.gov (United States)

This paper reports the extension of the stress wave force balance to the measurement of forces on models which are non-axisymmetric or which have non-axisymmetric load distributions. Recent results are presented which demonstrate the performance of the stress wave force balance for drag measurement, for three-component force measurement and preliminary results for thrust measurement on a two-dimensional scramjet nozzle. In all cases, the balances respond within a few hundred microseconds.

Tuttle, S. L.; Mee, D. J.; Simmons, J. M.

1995-01-01

247

Thrust Production and Wake Structure of an Actuated Lamprey Model  

Science.gov (United States)

Thrust generation is studied for a flexible lamprey model which is actuated periodically to produce a streamwise traveling wave. Shape memory alloy actuators are used to achieve this deformation. The flow field is investigated using DPIV and flow visualization for a range of Strouhal numbers based on peak-to-peak amplitude of the trailing edge. The vortex kinematics in the spanwise and streamwise planes are examined, and a three-dimensional unsteady vortex model of the wake will be discussed.

Buchholz, James; Smits, Alexander

2004-11-01

248

The Prevalence of Tongue Thrusting in Patients with Periodontal Disease  

Directory of Open Access Journals (Sweden)

Full Text Available Statement of Problem: Tongue thrust and/or its consequent swallowing pattern are amongst the parafunctional habits that have always been considered as etiological factors for dental disorders by different investigators.Purpose: The aim of this study was to investigate the prevalence of tongue thrusting and the incidence of periodontal disorders associated with this habit among patients referred to the Department of Periodontology, School of Dentistry, Tehran University of Medical Sciences.Material and Methods: Two hundred and eighty patients, undergoing first phase of periodontal therapy, were selected. Among them, those who had tongue thrusting were diagnosed and periodontal indices (probing depth, gingival recession, spacing and gingival enlargement were measured. Also, crown-root ratio was assessed for each anterior tooth.Results: Tongue thrusting was seen in 27.3%of patients, whereas 29.8% and 33.8% of them showed an increase in periodontal pocket depths in their upper and lower jaws,respectively. Gingival recession was found in the upper jaw in 12.98% and in the lowerjaw in 49.35% of the cases. Crown to root length ratio in 24.6% of the upper incisors and 35.1% of the lower incisors were found to be higher than normal. Spacing was observed between the incisors in 31.2% and 41.6% of the patients in the upper and lower jaws, respectively. Finally 31.2% of the patients showed gingival enlargement.Conclusion: The results of the present study revealed a considerable increase in the prevalence of various periodontal diseases among these subjects. To minimize the clinical problems of such patients, prevention of periodontal diseases through excellent oral hygiene and regular dental visits are suggested.

S.A. Miremadi

2005-06-01

249

Energy from sea wave thrust and flow of water  

International Nuclear Information System (INIS)

The area adjacent to the tidal rivers, irrigational canal, drain and also the seashore may be energized harnessing the energy from the flow/wave thrust by simply converting it into unidirectional rotating force to drive the generator for power generation. The existing plants are big in size and also fixed in place. A plant which will be a small/portable type is described. 7 refs., figs

250

Effect of thrust chamber configuration on MPD arcjet performance  

Science.gov (United States)

The performance of quasisteady multimegawatt MPD thrusters is significantly affected by anode thickness, location, and orifice radius, and by cathode length. Terminal voltage oscillations and electrode erosion are deferred until higher currents by anodes at more downstream locations and of smaller orifice radius and by cathodes of greater length. Without an optimized geometry, specific impulses of 3300 s and thrust efficiencies up to 31% are implied by the best data.

King, D. Q.; Jahn, R. G.; Clark, K. E.; Smith, W. W.

1981-01-01

251

PNA bearing 5-azidomethyluracil  

Science.gov (United States)

Fmoc- and Boc-protected modified monomers bearing 5-azidomethyluracil nucleobase were synthesized. Four different solid-phase synthetic strategies were tested in order to evaluate the application of this series of monomers for the solid-phase synthesis of modified PNA. The azide was used as masked amine for the introduction of amide-linked functional groups, allowing the production of a library of compounds starting from a single modified monomer. The azide function was also exploited as reactive group for the modification of PNA in solution via azide-alkyne click cycloaddition. PMID:22772040

Manicardi, Alex; Accetta, Alessandro; Tedeschi, Tullia; Sforza, Stefano; Marchelli, Rosangela; Corradini, Roberto

2012-01-01

252

A Simple Model of Pulsed Ejector Thrust Augmentation  

Science.gov (United States)

A simple model of thrust augmentation from a pulsed source is described. In the model it is assumed that the flow into the ejector is quasi-steady, and can be calculated using potential flow techniques. The velocity of the flow is related to the speed of the starting vortex ring formed by the jet. The vortex ring properties are obtained from the slug model, knowing the jet diameter, speed and slug length. The model, when combined with experimental results, predicts an optimum ejector radius for thrust augmentation. Data on pulsed ejector performance for comparison with the model was obtained using a shrouded Hartmann-Sprenger tube as the pulsed jet source. A statistical experiment, in which ejector length, diameter, and nose radius were independent parameters, was performed at four different frequencies. These frequencies corresponded to four different slug length to diameter ratios, two below cut-off, and two above. Comparison of the model with the experimental data showed reasonable agreement. Maximum pulsed thrust augmentation is shown to occur for a pulsed source with slug length to diameter ratio equal to the cut-off value.

Wilson, Jack; Deloof, Richard L. (Technical Monitor)

2003-01-01

253

Electric sail control mode for amplified transverse thrust  

CERN Document Server

The electric solar wind sail produces thrust by centrifugally spanned high voltage tethers interacting with the solar wind protons. The sail attitude can be controlled and attitude maneuvers are possible by tether voltage modulation synchronous with the sail rotation. Especially, the sail can be inclined with respect to the solar wind direction to obtain transverse thrust to change the osculating orbit angular momentum. Such an inclination has to be maintained by a continual control voltage modulation. Consequently, the tether voltage available for the thrust is less than the maximum voltage provided by the power system. Using a spherical pendulum as a model for a single rotating tether, we derive analytical estimations for the control efficiency for two separate sail control modes. One is a continuous control modulation that corresponds to strictly planar tether tip motion. The other is an on-off modulation with the tether tip moving along a closed loop on a saddle surface. The novel on-off mode is introduce...

Toivanen, Petri; Envall, Jouni

2014-01-01

254

The 7.5K lbf thrust engine preliminary design for Orbit Transfer Vehicle  

Science.gov (United States)

This document summarizes the preliminary design of the Aerojet version of the Orbit Transfer Vehicle main engine. The concept of a 7500 lbf thrust LO2/GH2 engine using the dual expander cycle for optimum efficiency is validated through power balance and thermal calculations. The engine is capable of 10:1 throttling from a nominal 2000 psia to a 200 psia chamber pressure. Reservations are detailed on the feasibility of a tank head start, but the design incorporates low speed turbopumps to mitigate the problem. The mechanically separate high speed turbopumps use hydrostatic bearings to meet engine life requirements, and operate at sub-critical speed for better throttling ability. All components were successfully packaged in the restricted envelope set by the clearances for the extendible/retractable nozzle. Gimbal design uses an innovative primary and engine out gimbal system to meet the +/- 20 deg gimbal requirement. The hydrogen regenerator and LOX/GH2 heat exchanger uses the Aerojet platelet structures approach for a highly compact component design. The extendible/retractable nozzle assembly uses an electric motor driven jack-screw design and a one segment carbon-carbon or silicide coated columbium nozzle with an area ratio, when extended, of 1430:1. A reliability analysis and risk assessment concludes the report.

Hayden, Warren R.; Sabiers, Ralph; Schneider, Judy

1994-01-01

255

EVALUATION OF A LOW FRICTION - HIGH EFFICIENCY ROLLER BEARING ENGINE  

Energy Technology Data Exchange (ETDEWEB)

This Low Friction (High Efficiency Roller Bearing) Engine (LFE) report presents the work done by The Timken Company to conduct a technology demonstration of the benefits of replacing hydrodynamic bearings with roller bearings in the crankshaft and camshaft assemblies of an internal combustion engine for the purpose of collecting data sufficient to prove merit. The engines in the present study have been more extensively converted to roller bearings than any previous studies (40 needle roller bearings per engine) to gain understanding of the full potential of application of bearing technology. The project plan called for comparative testing of a production vehicle which was already respected for having demonstrated low engine friction levels with a rollerized version of that engine. Testing was to include industry standard tests for friction, emissions and fuel efficiency conducted on instrumented dynamometers. Additional tests for fuel efficiency, cold start resistance and other measures of performance were to be made in the actual vehicle. Comparative measurements of noise, vibration and harshness (NVH), were planned, although any work to mitigate the suspected higher NVH level in the rollerized engine was beyond the scope of this project. Timken selected the Toyota Avalon with a 3.5L V-6 engine as the test vehicle. In an attempt to minimize cost and fabrication time, a ‘made-from’ approach was proposed in which as many parts as possible would be used or modified from production parts to create the rollerized engine. Timken commissioned its test partner, FEV Engine Technology, to do a feasibility study in which they confirmed that using such an approach was possible to meet the required dimensional restrictions and tolerances. In designing the roller bearing systems for the crank and cam trains, Timken utilized as many production engine parts as possible. The crankshafts were produced from production line forgings, which use Timken steel, modified with special machining and heat treatment. Timken designed and manufactured all of the roller bearing related components such as the thrust bearing package. The production connecting rods and camshafts could not be used for the roller bearing engine, so new ones were produced according to the team’s designs using Timken steel. The remaining miscellaneous components were designed and procured by FEV. Timken prepared a display version of the crankshaft portion of the production engine without connecting rods which could be driven by a motor through a cogged-belt and electrically actuated clutch arrangement. A modified version was also made in which the engine was outfitted with roller bearings on the main bearing positions. Preliminary tests showed that the rollerized engine was running with 1/3 less friction than the standard display engine. Additional friction testing and noise characterization was cut short because of shipping damage to the rollerized engine display and because of other project priorities. The team did successfully demonstrate the ability to package roller bearings satisfactorily in numerous locations in a typical automotive engine. The scope of this project did not include durability demonstration and that subject would have to be addressed in any follow-on work. In the actual test phase, the rollerized engine did show significantly less friction in motored dynamometer tests compared to its production equivalent. The 5-10% improvement measured in this study was about half that seen in other studies. However, the fired test results did not show a reduction in friction which did not match prior experience or expectations. Subsequent teardown and inspection of the rollerized engine revealed potential sources of excessive friction in the experimental application. These features would be eliminated in a design not based on modification of production parts. The team is confident (based on experience) that friction reduction would be realized with proper modifications.

Kolarik, Robert V. II; Shattuck, Charles W.; Copper, Anthony P.

2009-06-30

256

Evaluation of an Outer Loop Retrofit Architecture for Intelligent Turbofan Engine Thrust Control  

Science.gov (United States)

The thrust control capability of a retrofit architecture for intelligent turbofan engine control and diagnostics is evaluated. The focus of the study is on the portion of the hierarchical architecture that performs thrust estimation and outer loop thrust control. The inner loop controls fan speed so the outer loop automatically adjusts the engine's fan speed command to maintain thrust at the desired level, based on pilot input, even as the engine deteriorates with use. The thrust estimation accuracy is assessed under nominal and deteriorated conditions at multiple operating points, and the closed loop thrust control performance is studied, all in a complex real-time nonlinear turbofan engine simulation test bed. The estimation capability, thrust response, and robustness to uncertainty in the form of engine degradation are evaluated.

Litt, Jonathan S.; Sowers, T. Shane

2006-01-01

257

Segmented Hybrid Gasostatic Bearing Optimization  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of research-development of methods of numerical optimization rotatable support pads gasostatic hybrid bearing. In the world‘s aerospace engineering the gas-dynamic bearings are currently most common. They are characterized by the supporting layer of different designs, which ensures the workability of the rotors during starts and stops. The main problem of this bearing type, apart from the construction complexity is the wear of this supporting layer. Gas-static bearing has no such defect, since there is no physical contact between solid surfaces. This study presents the results of the hybrid bearing’s calculation, combining both technologies. The slotted nozzle of non-conventional shape that mirrors the solution of Reynolds equation’s isoline is studied. The dependences of the main parameters on the speed of the shaft’s rotation are discussed. The aerodynamic resistance of pads for different regimes of operation is investigated.

Prodan Nikolay Vasilevich

2014-07-01

258

Grease lubrication in rolling bearings  

CERN Document Server

The definitive book on the science of grease lubrication for roller and needle bearings in industrial and vehicle engineering. Grease Lubrication in Rolling Bearings provides an overview of the existing knowledge on the various aspects of grease lubrication (including lubrication systems) and the state of the art models that exist today. The book reviews the physical and chemical aspects of grease lubrication, primarily directed towards lubrication of rolling bearings. The first part of the book covers grease composition, properties and rheology, including thermal

Lugt, Piet M

2012-01-01

259

Thermal barrier coatings (TBC's) for high heat flux thrust chambers  

Science.gov (United States)

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the harmful emissions to protect the environment. Airfoils or blades tend to be the limiting factor when it comes to the performance of the turbine because of their complex design making them difficult to cool as well as limitations of their thermal properties. Key tasks for space transportation it to lower costs while increasing operational efficiency and reliability of our space launchers. The important factor to take into consideration is the rocket nozzle design. The design of the rocket nozzle or thrust chamber has to take into account many constraints including external loads, heat transfer, transients, and the fluid dynamics of expanded hot gases. Turbine engines can have increased efficiencies if the inlet temperature for combustion is higher, increased compressor capacity and lighter weight materials. In order to push for higher temperatures, engineers need to come up with a way to compensate for increased temperatures because material systems that are being used are either at or near their useful properties limit. Before thermal barrier coatings were applied to hot-section components, material alloy systems were able to withstand the service conditions necessary. But, with the increased demand for performance, higher temperatures and pressures have become too much for those alloy systems. Controlled chemistry of hot-section components has become critical, but at the same time the service conditions have put our best alloy systems to their limits. As a result, implementation of cooling holes and thermal barrier coatings are new advances in hot-section technologies now looked at for modifications to reach higher temperature applications. Current thermal barrier coatings used in today's turbine applications is known as 8%yttria-stabilized zirconia (YSZ) and there are no coatings for current thrust chambers. Current research is looking at the applicability of 8%yttria-stabilized hafnia (YSH) for turbine applications and the implementation of 8%YSZ onto thrust chambers. This study intends to determine if the use of thermal barrier coatings are applicable for high heat flux thrust chambers using industrial YSZ will be advantageous for improvements in efficiency, thrust and longer service life by allowing the thrust chambers to be used more than once.

Bradley, Christopher M.

260

Evaluation of shuttle turbopump bearings  

Science.gov (United States)

Because the high pressure turbopumps used on the space shuttle main engine (SSME) are high speed machines and rotor dynamics analysis of these units is very complicated, it was considered necessary to verify calculated turbomachinery shaft bearing loads by analysis of ball bearing load tracks. This report presents the methods used and the results of load track analysis on one set of bearings removed from a high pressure liquid oxygen turbopump which had been subjected to SSME static firing tests. This type of analysis was found useful in determining bearing operating conditions and for verifying rotor dynamics computer models.

Dufrane, K. F.; Kannel, J. W.

1978-01-01

 
 
 
 
261

Performance of jet- and inner-ring-lubricated 35 millimeter bore ball bearings operating to 2.5 million DN  

Science.gov (United States)

Parametric tests were conducted with a 35 millimeter bore, angular contact ball bearing having a single outer land guided cage. Lubrication was achieved by flowing oil through axial grooves and radial holes machined in the inner ring of the bearing. Test conditions were a thrust load of 667 N (150 lb), shaft speeds from 48,000 to 72,000 rpm, and an oil inlet temperature of 394 K (250 F). Data from tests where the distribution of the total oil supplied to the inner ring was 50 percent for bearing lubrication and 50 percent for bearing inner ring cooling were compared with those where the distribution pattern was 25 percent lubrication and 75 percent cooling. Successful operation was experienced with both the 50-50 and 25-75 percent flow distribution patterns to 2.5 million DN. The 50-50 percent flow pattern provided the cooler bearing operation of the two inner ring lubricated bearings. The jet lubricated bearing had lower outer ring and higher inner ring temperatures than the inner ring lubricated bearings. Maximum power loss of 2.8 kW (3.7 hp) was experienced with the 25-75 percent flow distribution, and maximum percent cage slip of 7.0 occurred at 72,300 rpm with the 50-50 percent flow distribution.

Schuller, F., T.; Signer, H. R.

1981-01-01

262

Kinematic history of the ongoing growth of Himalayan fold-thrust belt  

Science.gov (United States)

Ongoing growth of the Himalayan fold-thrust belt since the Middle Miocene is mostly accomplished by the deformation of the Lesser Himalayan Sequence (a deformed package of rocks which dominates the southern half of the Himalaya). However, the first-order kinematic evolution of this process remains unclear. Four end-member models are proposed: frontal accretion through forward-propagation of a basal thrust; discrete underplating of thrust horses from the downgoing plate to the fold-thrust belt; expansion of the orogen via incremental accretion along the basal shear zone; and out-of-sequence faulting. Both the underplating and out-of-sequence models can explain the rapid uplift and exhumation observed along the central belt of the Himalaya. We test these models by determining the relationship between major thrust faults within the Lesser Himalayan sequence: the Berinag thrust and Tons thrust. Map geometries require >40 km and >80 km displacements along the Berinag and Tons thrusts, respectively. Field mapping along the Tons Valley and the lower Pabbar valley across the Lesser Himalayan Sequence reveals a new first-order thrust fault, which we term the Pabbar thrust. The Pabbar thrust is a ~300 m thick ductile shear zone separating the hanging wall of the Tons thrust (the Outer Lesser Himalayan Sequence) above from the hanging wall of the Berinag thrust (the Berinag Group) below, marked by S-C fabrics, mylonitic fabrics, and sheath folds, demonstrating top-to-the-southwest thrusting. Sheath folds, with hinges parallel to the stretching lineations defined by strongly elongated quartz grains in NE-SW direction, developed at cm to m scale of wavelength and amplitude within the shear zone. The Berinag and Tons thrust zones display both brittle features and ductile shear fabrics including southwest-directed brittle faults, southwest verging tight to open folds, and week southwest-trending stretching lineations. The ductile nature of the Pabbar thrust and the brittle-ductile nature of both the Berinag thrust and Tons thrust suggest that the Pabbar thrust developed first, followed by underplating of the Berinag sheet to the Pabbar thrust. Continued motion along the new sole thrust toward the foreland becomes the brittle-ductile Tons and Berinag thrusts, operating as a single structure. The kinematic history of the Pabbar thrust and the Berinag-Tons thrust suggests that the ongoing growth of the Himalayan fold-thrust belt since the Middle Miocene most likely occurred through the discrete underplating of thrust horses from the downgoing plate, not by out-of-sequence faulting. Expansion of the orogen by incremental accretion model is also invalid here since the expected pervasive shear features through the LHS are not observed in the field. Instead, shear is only concentrated in discrete fault zones.

Yu, H.; Webb, A. G.

2012-12-01

263

Structural evidence for northeastward movement on the Chocolate Mountains thrust, southeasternmost Calfornia  

Energy Technology Data Exchange (ETDEWEB)

The Late Cretaceous Chocolate Mountains thrust of southeastern California and southwestern Arizona places a block of Proterozoic and Mesozoic continental crust over the late Mesozoic continental margin oceanic sedimentary and volcanic rocks of the regionally distinctive Orocopia Schist. The Chocolate Mountains thrust is interpreted as a thrust (burial, subduction) fault rather than a low-angle normal (exhumation, unroofing, uplift) fault. The Chocolate Mountains thrust zone contains sparse to locally abundant mesoscopic asymmetric folds. Fabric relations indicate that these folds are an integral part of and coeval with the thrust zone. On a lower hemisphere equal-area plot representing the orientation and sense of asymmetry of 80 thrust zone folds from 36 localities, spread over an area 60 by 10 km, Z folds plot northwest of and S folds plot southeast of a northeast-southwest striking vertical plane of overall monoclinic symmetry. The only sense of movement consistent with the collective asymmetry of the thrust zone folds is top to the northeast. Paleomagnetic data suggest that the original sense of thrusting, prior to Neogene vertical axis tectonic rotation related to the San Andreas fault system, was northward. The essential point is that movement of the upper plate of the Chocolate Mountains thrust evidently was continentward. Continentward thrusting suggests a tectonic scenario in which an insular or peninsular microcontinental fragment collided with mainland southern California. Alternative tectonic models involving subduction of the Orocopia Schist eastward beneath continental southern California circumvent the suture problem but are presently not supported by any direct structural evidence.

Dillon, J.T. (Alaska Div. of Geological and Geophysical Surveys, Fairbanks (USA)); Haxel, G.B. (Geological Survey, Flagstaff, AZ (USA)); Tosdal, R.M. (Geological Survey, Menlo Park, CA (USA))

1990-11-10

264

High-Performance Ball Bearing  

Science.gov (United States)

High-performance bearing features strong, lightweight, self-lubricating cage with self-lubricating liners in ball apertures. Designed to operate at high speed (tens of thousands of revolutions per minute) in cryogenic environment like liquid-oxygen or liquid-hydrogen turbopump. Includes inner race, outer race, and cage keeping bearing balls equally spaced.

Bursey, Roger W., Jr.; Haluck, David A.; Olinger, John B.; Owen, Samuel S.; Poole, William E.

1995-01-01

265

Acoustic Coupler for Monitoring Bearing Wear  

Science.gov (United States)

Concept for acoustic coupler allows sound efficiently conveyed from bearings to external sensor. Noise from bearings in bearing test machine monitored for signs of incipient failure. Straight through acoustic-coupler assembly inserted through existing ports in housing of bearing-testing machine. Threaded electrical connector at top rotated to adjust force applied to sensing element and contact bearing.

Jolly, W.

1986-01-01

266

Nonlinear control of magnetic bearings  

Science.gov (United States)

In this paper we present a variety of nonlinear controllers for the magnetic bearing that ensure both stability and robustness. We utilize techniques of discontinuous control to design novel control laws for the magnetic bearing. We present in particular sliding mode controllers, time optimal controllers, winding algorithm based controllers, nested switching controllers, fractional controllers, and synchronous switching controllers for the magnetic bearing. We show existence of solutions to systems governed by discontinuous control laws, and prove stability and robustness of the chosen control laws in a rigorous setting. We design sliding mode observers for the magnetic bearing and prove the convergence of the state estimates to their true values. We present simulation results of the performance of the magnetic bearing subject to the aforementioned control laws, and conclude with comments on design.

Pradeep, A. K.; Gurumoorthy, R.

1994-01-01

267

Large-scale geometry of Montana thrust belt  

Energy Technology Data Exchange (ETDEWEB)

Regional plunge of a structural culmination in the Sawtooth Mountains, combined with seismic profiles and borehole data, show that the imbricated faults of the Montana Disturbed belt gather upward to merge into a duplex beneath a large thrust plate dominated by the Precambrian Belt Supergroup. The duplex formed after deposition of the Paleocene St. Mary River Formation. This thrust plate overlies the Lewis, Hoadley, El dorado, Steinbach, and related thrust faults and forms the main ranges of the Montana Rocky Mountains. The plate is shaped like a northeasterly tapering wedge; it is 3 to 4 km (10,000 to 13,000 ft) thick at its leading edge, but thickens to more than 25 km (15 mi) to the southwest. At its leading edge, the plate carries lower parts of the Belt supergroup, including the Greyson, Empire, and Spokane formations. These units and overlying parts of the Belt Supergroup thicken dramatically westward within the plate, and the older, very thick, metamorphosed Prichard Formation emerges along the Purcell and related anticlinoria. The plate forms a south-facing monocline along the Lewis and Clark line. The monocline is corrugated into a series of southeast-plunging en echelon folds of Late Cretaceous age and merges with the southern terminus of the Purcell anticlinorium. Along these folds, metamorphosed Belt strata of the plate plunge systematically beneath Paleozoic and Mesozoic rocks that are preserved in a regional structural depression at the foot of the monocline. Geometric constructions based on areal geology suggest that the monocline has 25 km (15 mi) of structural relief and overlies a major footwall ramp that continues northward beneath the Purcell anticlinorium. This footwall ramp corresponds to the depositional locus for the easterly tapering belt strata of the plate, suggesting a total northeasterly displacement of about 50 km (30 mi) for the plate.

Sears, J.W.; Dolberg, D.M.

1986-08-01

268

Variable thrust/specific-impulse of multiplexed electrospray microthrusters  

Science.gov (United States)

We report on the development of a single-propellant ElectroSpray (ES) microthruster able to: (a) cover a wide range of specific impulse (Isp) and thrust at high propulsion efficiency, and (b) provide macroscopic thrust via micro-fabricated emitter arrays. The electrospray is a mature technology for the emission of fast nanodroplets at a propulsive efficiency larger than 50% over the full Isp range. The size of the droplets depends on the propellant flow rate and the physical properties of the electrolyte, especially the electric conductivity. To achieve a useful thrust one needs to multiplex the ES by operating many in parallel, which we achieve via silicon microfabrication of arrays of multiple and identical nozzles. The Multiplexed Electrospray (MES) micro-thruster is composed mainly of two electrodes: a nozzle-array and an extractor electrode, between which the electric field needed to form the ES is established. We tested nozzle arrays with up to 37 capillaries, that are spaced 1mm apart, with ID/OD = 10/30? m. The capillaries are filled with 2.01? m silicon dioxide beads to increase the hydraulic impedance and ensure uniform flow rate through the different emitters. A third electrode (accelerator) is mounted downstream the extractor to accelerate the droplets, thereby increasing the microthruster performance. The system is packaged in an alumina casing for electrical insulation and propellant feed. Tests run in a vacuum chamber at a pressure ? 10-5 mbar demonstrated reliable operation for several hours with a relatively high beam energy of 7.56kV. The 37-nozzle MES device was tested with the ionic liquid ethylammonium nitrate (EAN), at estimated total flow rates between 1.2 and 14 ? L/h, emitted currents between 14.2 and 23.0 ? A, specific impulse ranging between 710 and 1930s, and thrust ranging between 7.5 and 33 ? N. EAN is well suited to cover a relatively broad range of charge/mass- at an average propulsion efficiency of 66%. With further scale-up to a 600-MES system, the device would be suitable for micro-satellites missions such as attitude control and station keeping.

Lenguito, G.; Fernandez de la Mora, J.; Gomez, A.

269

Design of high power electromechanical actuator for thrust vector control  

Science.gov (United States)

NASA-Marshall has undertaken the development of electromechanical actuators (EMAs) for thrust vector control (TVC) augmentation system implementation. The TVC EMA presented has as its major components two three-phase brushless dc motors, a two-pass gear-reduction system, and a roller screw for rotary-to-linear motion conversion. System control is furnished by a solid-state electronic controller and power supply; a pair of resolvers deliver position feedback to the controller, such that precise positioning is achieved. Peformance comparisons have been conducted between the EMA and comparable-performance hydraulic systems applicable to TVCs.

Cowan, J. R.; Myers, W. N.

1991-01-01

270

Control of Ducted Fan Flying Object Using Thrust Vectoring  

Science.gov (United States)

Recently, R/C helicopter is used in fields of aerial photography and aerial investigation. But helicopter rotor blades are not covered, and the thrust is generated by high rotational speed. Thus R/C helicopter has a high risk of damage. In this study, we developed a new flying object using ducted fans instead of rotor blades. At first, PD control was employed for pitch and roll attitude control, but it caused steady state error. Moreover, PI-D control was used instead of PD control, and it reduced the steady state error. We succeeded to achieve stable hovering by 3-axes (roll, pitch and yaw axis) attitude control.

Miwa, Masafumi; Shigematsu, Yuki; Yamashita, Takashi

271

Thrust sequences and evolution of the external sector of a fold and thrust belt: An example from the Southern Apennines (Italy)  

Science.gov (United States)

The Southern Apenninic chain was built up from the late Oligocene-early Miocene to the middle Pleistocene. It consists of an upper wedge composed of strongly deformed deep marine and carbonate platform successions and a buried thrust and fold belt in the carbonate rocks of the Apulian Platform. This paper analyzes the frontal part of the Southern Apennines, where contractional structures display complex geometries related to progressive incorporation of accreted material, internal shortening and gravitational processes. Late normal faults, which hinder the interpretation of contractional structures in other sectors of the chain, are scarcely represented in the frontal part of the Southern Apennines. This allows a detailed analysis of thrust and fold geometry. In particular it is possible to recognize the relationships between gravity-driven nappes, foreland-vergent thrusts and backthrusts. New field observations allow us to depict a detailed structural framework of this area and to construct regional cross-sections, which illustrate the inferred evolution of the frontal sector of the Apenninic chain. The chronological constraints are given by the age of thrust-top basins and foredeep deposits of middle-late Miocene to Pleistocene age. Deepening of the décollement level during thrusting creates complicate overprinting relationships connected to the deformation of the older thrust surfaces. The inferred evolution can be summarized in two stages. During the first stage shortening of the wedge was associated to emplacement of thin thrust sheets, interpreted as gravity-driven nappes, before sedimentation of middle-late Miocene thrust top basins. The second stage, of middle Pliocene-middle Pleistocene age, was characterized by folding and breaching of the pre-existing structures, related to deep thrusting in the Apulian Platform. The examples shown suggest the presence of transfer zones and lateral ramps to explain lateral variations in thrust geometry and shortening amount. The along strike geometry of non-cylindrical structures provides a valuable tool to decipher the tectonic evolution of the thrust belt. The proposed scheme is well suited to interpret the structural setting of thin-skinned thrust and fold belts characterised by change in the geometry of the thrust systems through time.

Piedilato, Simone; Prosser, Giacomo

2005-05-01

272

Direct thrust measurements and modelling of a radio-frequency expanding plasma thruster  

Energy Technology Data Exchange (ETDEWEB)

It is shown analytically that the thrust from a simple plasma thruster (in the absence of a magnetic field) is given by the maximum upstream electron pressure, even if the plasma diverges downstream. Direct thrust measurements of a thruster are then performed using a pendulum thrust balance and a laser displacement sensor. A maximum thrust of about 2 mN is obtained at 700 W for a thruster length of 17.5 cm and a flow rate of 0.9 mg s{sup -1}, while a larger thrust of 4 mN is obtained at a similar power for a length of 9.5 cm and a flow rate of 1.65 mg s{sup -1}. The measured thrusts are in good agreement with the maximum upstream electron pressure found from measurements of the plasma parameters and in fair agreement with a simple global approach used to model the thruster.

Lafleur, T.; Charles, C.; Boswell, R. W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Takahashi, K. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia); Department of Electrical Engineering and Computer Science, Iwate University, Morioka 020-8551 (Japan)

2011-08-15

273

Thrust Generation with Low-Power Continuous-Wave Laser and Aluminum Foil Interaction  

International Nuclear Information System (INIS)

The micro-newton thrust generation was observed through low-power continuous-wave laser and aluminum foil interaction without any remarkable ablation of the target surface. To evaluate the thrust characteristics, a torsion-balance thrust stand capable for the measurement of the thrust level down to micro-Newton ranges was developed. In the case of an aluminum foil target with 12.5 micrometer thickness, the maximum thrust level was 15 micro-newtons when the laser power was 20 W, or about 0.75 N/MW. It was also found that the laser intensity, or laser power per unit area, irradiated on the target was significantly important on the control of the thrust even under the low-intensity level.

274

Direct thrust measurements and modelling of a radio-frequency expanding plasma thruster  

International Nuclear Information System (INIS)

It is shown analytically that the thrust from a simple plasma thruster (in the absence of a magnetic field) is given by the maximum upstream electron pressure, even if the plasma diverges downstream. Direct thrust measurements of a thruster are then performed using a pendulum thrust balance and a laser displacement sensor. A maximum thrust of about 2 mN is obtained at 700 W for a thruster length of 17.5 cm and a flow rate of 0.9 mg s-1, while a larger thrust of 4 mN is obtained at a similar power for a length of 9.5 cm and a flow rate of 1.65 mg s-1. The measured thrusts are in good agreement with the maximum upstream electron pressure found from measurements of the plasma parameters and in fair agreement with a simple global approach used to model the thruster.

275

Experimental results for a two-dimensional supersonic inlet used as a thrust deflecting nozzle  

Science.gov (United States)

Nearly all supersonic V/STOL aircraft concepts are dependent on the thrust deflecting capability of a nozzle. In one unique concept, referred to as the reverse flow dual fan, not only is there a thrust deflecting nozzle for the fan and core engine exit flow, but because of the way the propulsion system operates during vertical takeoff and landing, the supersonic inlet is also used as a thrust deflecting nozzle. This paper presents results of an experimental study to evaluate the performance of a supersonic inlet used as a thrust deflecting nozzle for this reverse flow dual fan concept. Results are presented in terms of nozzle thrust coefficient and thrust vector angle for a number of inlet/nozzle configurations. Flow visualization and nozzle exit flow survey results are also shown.

Johns, Albert L.; Burstadt, Paul L.

1984-01-01

276

Thrust-breakthrough of asymmetric anticlines: Observational constraints from surveys in the Brooks Range, Alaska  

Science.gov (United States)

To gain insights into the processes governing the thrust-truncation of anticlines, we conducted a field study of the thrust-truncated folds in the remote Brooks Range of northern Alaska, where there is a transition in fold style from symmetric detachment folds to thrust-truncated asymmetric folds. In order to document the detailed geometry of the km-scale folds exposed in cliff-forming, largely inaccessible outcrops, a new surveying technique was developed that combines data from a theodolite and laser range finder. The field observations, survey profiles, and cross section reconstructions, indicate that late-stage thrust breakthrough of the anticlines within the mechanically competent Lisburne Group carbonates accommodated continued shortening when other mechanisms became unfeasible, including fold tightening, forelimb rotation, and parasitic folding in the anticline forelimbs. These results provide constraints on the processes that govern the transition from buckle folding to thrust truncation in fold-and-thrust belts worldwide.

Jadamec, Margarete A.; Wallace, Wesley K.

2014-05-01

277

Three-dimensional geometry of thrust surfaces and the origin of sinuous thrust traces in orogenic belts: Insights from scaled sandbox experiments  

Science.gov (United States)

Sinuous traces of emerging thrust tips, comprising multiple salients and recesses, are commonly observed in orogenic belts (e.g. Lesser Himalayas of India, Nepal and Bhutan) and in accretionary prisms (e.g. Nankai Trough off the coast of Japan). Lateral (along the strike of the deformation zone) variation in the depths of foreland basins (i.e. variable sediment thickness) or in the strength of the basal detachment, or presence of a curved indenter has been traditionally cited to explain the formation of salients in fold-and-thrust belts, although they are not applicable in all cases. In the present work, we have carried out four series of scaled analog model experiments using dry quartz sand, changing the dip of the basal decollément (? = 0° or 5°) and the basal friction (?b = 0.5 or 0.3) to investigate the 3D shape of thrust surfaces under varying overall boundary conditions, but without any lateral variation of these parameters, within the models. The experimental results show that under all boundary conditions, thrust surfaces are curved both in their dip and strike directions (i.e. spoon-shaped in 3D). Multiple concave-upward and convex-upward segments constitute a thrust surface, which produces a sinuous trace when the tip line intersects the Earth's surface. It is also shown that thrust surface curvatures occur at different scales, and the overall thrust surface roughness (corrugations) has a self-affine fractal geometry.

Chattopadhyay, A.; Jain, M.; Bhattacharjee, D.

2014-12-01

278

Neandertal Humeri May Reflect Adaptation to Scraping Tasks, but Not Spear Thrusting  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Unique compared with recent and prehistoric Homo sapiens, Neandertal humeri are characterised by a pronounced right-dominant bilateral strength asymmetry and an anteroposteriorly strengthened diaphyseal shape. Remodeling in response to asymmetric forces imposed during regular underhanded spear thrusting is the most influential explanatory hypothesis. The core tenet of the “Spear Thrusting Hypothesis”, that underhand thrusting requires greater muscle activity on the right side of the body ...

Shaw, Colin N.; Hofmann, Cory L.; Petraglia, Michael D.; Stock, Jay T.; Gottschall, Jinger S.

2012-01-01

279

Thrust Ripples Reduction for a Vector Controlled Permanent Magnet Linear Synchronous Motor with IMC Controller  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The significant drawback of PMLSM is thrust ripples, which is mainly generated by the detent force caused by the interaction of the permanent magnet and iron core without input current in armature winding. It is the function of mover position relative to the stator. This will deteriorate the performance of the drive system in high precision applications. This paper focus on the thrust ripples reduction. To minimize the thrust ripples and realize the high-precision control, the components of t...

RAMESH BABU.DEVA; Arundhati, B.; Alice Mary, K.

2013-01-01

280

Is tongue thrust that develops during orthodontic treatment an unrecognized potential road block?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The role of tongue thrust has often been suspected, long debated and largely dispelled as a primary etiological factor of malocclusion. However, tongue thrust may contribute to poor occlusal intercuspation both during and after treatment. A tongue thrust may also develop during orthodontic mechanotherapy as a result of the transient creation of intra and interarch spaces and this little recognized phenomenon was found to occur in many randomly followed cases. In many instances, this seemingly...

Chawla H; Suri Sanjay; Utreja A

2006-01-01

 
 
 
 
281

Structural evidence for northeastward movement on the Chocolate Mountains Thrust, southeasternmost California  

Science.gov (United States)

The Late Cretaceous Chocolate Mountains thrust of southeastern California and southwestern Arizona places a block of Proterozoic and Mesozoic continental crust over the late Mesozoic continental margin oceanic sedimentary and volcanic rocks of the regionally distinctive Orocopia Schist. The Chocolate Mountains thrust is interpreted as a thrust (burial, subduction) fault rather than a low-angle normal (exhumation, unroofing, uplift) fault. An important parameter required to understand the tectonic significance of the Chocolate Mountains and related thrusts is their sense of movement. The Chocolate Mountains thrust zone contains sparse to locally abundant mesoscopic asymmetric folds. Fabric relations, supported by regional geologic evidence, indicate that these folds are an integral part of and coeval with the thrust zone. On a lower hemisphere equal-area plot representing the orientation and sense of asymmetry of 80 thrust zone folds from 36 localities, spread over an area 60 by 10 km, Z folds plot northwest of and S folds plot southeast of a northeast-southwest striking vertical plane of overall monoclinic symmetry. The only sense of movement consistent with the collective asymmetry of the thrust zone folds is top to the northeast. Asymmetric microstructures studied at several localities also indicate top to the northeast movement. Paleomagnetic data suggest that the original sense of thrusting, prior to Neogene vertical axis tectonic rotation related to the San Andreas fault system, was northward. The essential point is that movement of the upper plate of the Chocolate Mountains thrust evidently was continentward. Continentward thrusting suggests a tectonic scenario in which an insular or peninsular microcontinental fragment collided with mainland southern California. The suture predicted by this model is elusive; but the Chocolate Mountains thrust and underlying Orocopia Schist themselves may represent the suture, at the present level of exposure. Alternative tectonic models involving subduction of the Orocopia Schist eastward beneath continental southern California circumvent the suture problem but are presently not supported by any direct structural evidence.

Dillon, John T.; Haxel, Gordon B.; Tosdal, Richard M.

1990-11-01

282

Simulations of Pulse Detonation Engines with MHD Thrust Augmentation  

Science.gov (United States)

Pulse detonation rocket engines (PDREs) have received significant attention in recent years due to their potentially superior performance over constant-pressure engines. Yet unsteady chamber pressures cause the PDRE flow to be either over-expanded or under-expanded for the majority of the cycle, with substantial performance loss in atmospheric flight applications. The present computational studies examine the potential benefits of using magneto-hydrodynamic (MHD) thrust augmentation by extracting energy via a generator in the PDRE nozzle and applying it to a separate, secondary stream. In the present studies, which involve both transient quasi-1D and 2D numerical simulations, the energy extracted from the nozzle flow is directly applied to a by-pass air stream through an MHD accelerator. The air stream is first shocked by the under-expanded nozzle flow and raised to high temperature, allowing thermal ionization. The specific conditions for thrust augmentation are examined. Alternative configurations utilizing a magnetic piston in the PDRE chamber are also explored. Results show potential performance gains but with significant challenges, depending on the operating and flight conditions.

Zeineh, Christopher; Roth, Timothy; Cole, Lord; Karagozian, Ann; Cambier, Jean-Luc

2008-11-01

283

Preliminary Assessment of Thrust Augmentation of NEP Based Missions  

Science.gov (United States)

Science Applications International Corporation (SAIC), with support from NASA Marshall Space Flight Center, has conducted a preliminary study to compare options for augmenting the thrust of a conventional nuclear electric propulsion (NEP) system. These options include a novel nuclear propulsion system concept known as Hybrid Indirect Nuclear Propulsion (HINP) and conventional chemical propulsion. The utility and technical feasibility of the HINP concept are assessed, and features and potential of this new in-space propulsion system concept are identified. As part of the study, SAIC developed top-level design tools to model the size and performance of an HINP system, as well as for several chemical propulsion options, including liquid and gelled propellants. A mission trade study was performed to compare a representative HINP system with chemical propulsion options for thrust augmentation of NEP systems for a mission to Saturn's moon Titan. Details pertaining to the approach, features, initial demonstration results for HINP model development, and the mission trade study are presented. Key technology and design issues associated with the HINP concept and future work recommendations are also identified.

Chew, Gilbert; Pelaccio, Dennis G.; Chiroux, Robert; Pervan, Sherry; Rauwolf, Gerald A.; White, Charles

2005-01-01

284

Precision electromagnetic calibration technique for micro-Newton thrust stands  

Science.gov (United States)

This paper introduces a new direct non-contact electromagnetic calibration technique for high precision measurements of micro-thrust and impulse. A ring-shaped electromagnet with an air gap is used in the calibration. The calibration force is produced by the interaction of a uniform magnetic field with a copper wire current in the air gap. This force depends linearly on this current as well as the steady angular displacement of the torsion arm of the thrust stand. The range of calibration force is very large and the calibration force is easy to generate and insensitive to the arm displacement. The calibration uncertainty for a 150-?N force is 4.17 ?N. The more influential factor on the calibration uncertainty is the magnetization of the electromagnet core due to the copper wire current. In the impulse calibration, the exerted impulse is linearly dependent on the maximal angular displacement of the torsion arm. The uncertainty in the impulse calibration is determined by uncertainties in both the force calibration and the pulse time.

He, Zhen; Wu, Jianjun; Zhang, Daixian; Lu, Gaofei; Liu, Zejun; Zhang, Rui

2013-05-01

285

Design and test of electromechanical actuators for thrust vector control  

Science.gov (United States)

New control mechanisms technologies are currently being explored to provide alternatives to hydraulic thrust vector control (TVC) actuation systems. For many years engineers have been encouraging the investigation of electromechanical actuators (EMA) to take the place of hydraulics for spacecraft control/gimballing systems. The rationale is to deliver a lighter, cleaner, safer, more easily maintained, as well as energy efficient space vehicle. In light of this continued concern to improve the TVC system, the Propulsion Laboratory at the NASA George C. Marshall Space Flight Center (MSFC) is involved in a program to develop electromechanical actuators for the purpose of testing and TVC system implementation. Through this effort, an electromechanical thrust vector control actuator has been designed and assembled. The design consists of the following major components: Two three-phase brushless dc motors, a two pass gear reduction system, and a roller screw, which converts rotational input into linear output. System control is provided by a solid-state electronic controller and power supply. A pair of resolvers and associated electronics deliver position feedback to the controller such that precise positioning is achieved. Testing and evaluation is currently in progress. Goals focus on performance comparisons between EMA's and similar hydraulic systems.

Cowan, J. R.; Weir, Rae Ann

1993-01-01

286

Development of a two-dimensional dual pendulum thrust stand for Hall thrusters  

Science.gov (United States)

A two-dimensional dual pendulum thrust stand was developed to measure thrust vectors [axial and horizontal (transverse) direction thrusts] of a Hall thruster. A thruster with a steering mechanism is mounted on the inner pendulum, and thrust is measured from the displacement between inner and outer pendulums, by which a thermal drift effect is canceled out. Two crossover knife-edges support each pendulum arm: one is set on the other at a right angle. They enable the pendulums to swing in two directions. Thrust calibration using a pulley and weight system showed that the measurement errors were less than 0.25mN (1.4%) in the main thrust direction and 0.09mN (1.4%) in its transverse direction. The thrust angle of the thrust vector was measured with the stand using the thruster. Consequently, a vector deviation from the main thrust direction of ±2.3° was measured with the error of ±0.2° under the typical operating conditions for the thruster.

Nagao, N.; Yokota, S.; Komurasaki, K.; Arakawa, Y.

2007-11-01

287

Development of a two-dimensional dual pendulum thrust stand for Hall thrusters  

International Nuclear Information System (INIS)

A two-dimensional dual pendulum thrust stand was developed to measure thrust vectors (axial and horizontal (transverse) direction thrusts) of a Hall thruster. A thruster with a steering mechanism is mounted on the inner pendulum, and thrust is measured from the displacement between inner and outer pendulums, by which a thermal drift effect is canceled out. Two crossover knife-edges support each pendulum arm: one is set on the other at a right angle. They enable the pendulums to swing in two directions. Thrust calibration using a pulley and weight system showed that the measurement errors were less than 0.25 mN (1.4%) in the main thrust direction and 0.09 mN (1.4%) in its transverse direction. The thrust angle of the thrust vector was measured with the stand using the thruster. Consequently, a vector deviation from the main thrust direction of ±2.3 deg. was measured with the error of ±0.2 deg. under the typical operating conditions for the thruster

288

Research on axial thrust of the waterjet pump based on CFD under cavitation conditions  

Science.gov (United States)

Based on RANS equations, performance of a contra-rotating axial-flow waterjet pump without hydrodynamic cavitation state had been obtained combined with shear stress transport turbulence model. Its cavitation hydrodynamic performance was calculated and analysed with mixture homogeneous flow cavitation model based on Rayleigh-Plesset equations. The results shows that the cavitation causes axial thrust of waterjet pump to drop. Furthermore, axial thrust and head cavitation characteristic curve is similar. However, the drop point of the axial thrust is postponed by 5.1% comparing with one of head, and the critical point of the axial thrust is postponed by 2.6%.

Shen, Z. H.; Pan, Z. Y.

2015-01-01

289

Thrust Ripples Reduction for a Vector Controlled Permanent Magnet Linear Synchronous Motor with IMC Controller  

Directory of Open Access Journals (Sweden)

Full Text Available The significant drawback of PMLSM is thrust ripples, which is mainly generated by the detent force caused by the interaction of the permanent magnet and iron core without input current in armature winding. It is the function of mover position relative to the stator. This will deteriorate the performance of the drive system in high precision applications. This paper focus on the thrust ripples reduction. To minimize the thrust ripples and realize the high-precision control, the components of thrust ripples are extracted first and then compensate with PI and IMC (Internal Model Control controller

RAMESH BABU.DEVA

2013-06-01

290

Seafloor expression and shallow structure of a fold-and-thrust system, Isfjorden, west Spitsbergen  

Directory of Open Access Journals (Sweden)

Full Text Available A detailed map of the structure of the west Spitsbergen fold-and-thrust belt in the Isfjorden area, Spitsbergen, is presented. The map was constructed from a dense grid of two-dimensional multichannel reflection seismic and bathymetric data. Joint interpretation of two data sets allowed a comparison of tectonic structures detected along the uppermost parts of the seismic sections and those reflected in the morphology of the seafloor. Three major, predominantly north-west–south-east striking faults were identified. The westernmost fault (T1 is a hinterland-directed (most likely out of sequence thrust, while the central and easternmost faults (T2 and T3 are foreland-directed (in-sequence thrusts. The thrusts divide Isfjorden into three subareas. Subarea 1 is bounded by thrust faults T1 and T2 and comprises Tertiary rocks surrounded by Jurassic–Cretaceous strata. The structural signature of Subarea 1 is that of a system of hinterland- and foreland-directed thrust faults, resulting in a seafloor relief characterized by parallel ridges and troughs. Subarea 2 is limited by thrust faults T2 and T3 and shows Jurassic–Cretaceous outcrops on the seafloor. Subarea 3 is situated east of the main thrust fault T3 and mainly involves outcrops of Triassic–Jurassic rocks. Together, Subareas 2 and 3 are dominated by foreland-directed, north-west–south-east and NNW–SSE-striking thrusts that are hardly detectable in bathymetric data.

Maria Blinova

2012-09-01

291

Finite-thrust optimization of interplanetary transfers of space vehicle with bimodal nuclear thermal propulsion  

Science.gov (United States)

The nuclear thermal rocket (NTR) propulsion is one of the leading promising technologies for primary space propulsion for manned exploration of the solar system due to its high specific impulse capability and sufficiently high thrust-to-weight ratio. Another benefit of NTR is its possible bimodal design, when nuclear reactor is used for generation of a jet thrust in a high-thrust mode and (with an appropriate power conversion system) as a source of electric power to supply the payload and the electric engines in a low-thrust mode. The model of the NTR thrust control was developed considering high-thrust NTR as a propulsion system of limited power and exhaust velocity. For the proposed model the control of the thrust value is accomplished by the regulation of reactor thermal power and propellant mass flow rate. The problem of joint optimization of the combination of high- and low-thrust arcs and the parameters of bimodal NTR (BNTR) propulsion system is considered for the interplanetary transfers. The interplanetary trajectory of the space vehicle is formed by the high-thrust NTR burns, which define planet-centric maneuvers and by the low-thrust heliocentric arcs where the nuclear electric propulsion (NEP) is used. The high-thrust arcs are analyzed using finite-thrust approach. The motion of the corresponding dynamical system is realized in three phase spaces concerning the departure planet-centric maneuver by means of high-thrust NTR propulsion, the low-thrust NEP heliocentric maneuver and the approach high-thrust NTR planet-centric maneuver. The phase coordinates are related at the time instants of the change of the phase spaces due to the relations between the space vehicle masses. The optimal control analysis is performed using Pontryagin's maximum principle. The numerical results are analyzed for Earth-Mars "sprint" transfer. The optimal values of the parameters that define the masses of NTR and NEP subsystems have been evaluated. It is shown that the low-thrust NEP subsystem with Brayton cycle power conversion system is preferable in comparison with NEP subsystem with thermoemission power conversion system.

Kharytonov, Oleksii M.; Kiforenko, Boris M.

2011-08-01

292

Structural framework of the Cenozoic QILIAN SHAN-Nan Shan thrust belt, NORTHEASTERN TIBETAN PLATEAU  

Science.gov (United States)

The Qilian Shan- Nan Shan thrust belt defines the northern margin of the Tibetan Plateau and results from Cenozoic India-Asia collision. The thrust belt is constructed in a region that had experienced early Paleozoic collisional tectonics and Jurassic-Cretaceous extension. This complexity has made the evaluating the magnitude of the Cenozoic shortening across the thrust belt difficult. In order to address this issue, we conduct detailed field mapping in a north-south traverse across the Shule Nan Shan in the north and Tuolai Nan Shan in the south in the central Qilian Shan-Nan Shan thrust belt (N38°39'-29' E99°21'-04'). Our work reveals that the Cenozoic thrusts in the study area are dominantly north-dipping. The Shule thrust bounds the southern edge of the Shule Nan Shan and strikes northwest. The fault places primarily Ordovician volcanic rocks and Carboniferous strata over Cenozoic sediments; the latter are largely covered by Quaternary deposits. As the fault does not cut Quaternary sediments, it appears that the Shule thrust is inactive. Cenozoic and Cretaceous redbeds are locally exposed below the Shule thrust in deep-cut valleys. In contrast to the northwest strike, north-dipping thrusts along the south edge and within the Tuolai Nan Shan in the south are dominantly east-striking. These thrusts merge with one another to the east and terminate at the northwest-striking Shule thrust. This relationship may be explained by the development of a crustal-scale duplex system with the Shule thrust as a roof structure. The hanging wall of the Tuolai thrust comprises a high-grade metamorphic complex within which an east-striking right-slip ductile shear zone occurs. A sample from mylonitized granitoid in the shear zone yields a U-Pb zircon age of ~920 Ma. The metamorphic complex is overlain by Permian to Jurassic strata that are complexly folded and together thrust over Neogene strata in the south. A regionally extensive unconformity, which lies between Ordovician-Silurian strata below and Carboniferous-Permian strata and ¬¬is repeated Cenozoic thrusts, is recognized during mapping. This marker together with scattered Mesozoic strata is being used in constructing a balanced cross section across the central Qilian Shan-Nan Shan thrust belt with the aim of establishing the magnitude of Cenozoic shortening.

Reith, R. C.; Yin, A.; Dong, S.; Liu, W.; Zuza, A. V.; Zhang, J.; Wu, C.; Wu, L.; Gong, J.

2012-12-01

293

Random bearings and their stability  

CERN Document Server

Self-similar space-filling bearings have been proposed some time ago as models for the motion of tectonic plates and appearance of seismic gaps. These models have two features which, however, seem unrealistic, namely, high symmetry in the arrangement of the particles, and lack of a lower cutoff in the size of the particles. In this work, an algorithm for generating random bearings in both two and three dimensions is presented. Introducing a lower cutoff for the sizes of the particles, the instabilities of the bearing under an external force such as gravity are studied.

Baram, R M

2005-01-01

294

Bear River/Bear Lake Operation - A Historical Perspective  

Digital Repository Infrastructure Vision for European Research (DRIVER)

PacifiCorp and its predecessor companies have managed and operated Bear Lake and the Bear River downstream since the early 1900’s. The system operation has evolved over the past 85 years from a joint irrigation and power project to an irrigation and flood control project with environmental and fish and wildlife issues becoming more important in recent years. This presentation will provide a perspective on the historical changes in river and lake operation and will address the impacts of rec...

Burton, Carly

2004-01-01

295

Correlation of asperity contact-time fraction with elastohydrodynamic film thickness in a 20-millimeter-bore ball bearing  

Science.gov (United States)

Elastohydrodynamic film thicknesses and asperity contact-time fractions were measured for a 20 mm bore ball bearing by using the capacitance and conductance techniques. The bearing was thrust loaded to 90, 445, and 778 N. The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa. The test speed ranged from 400 to 15,000 rpm. The test bearing was mist lubricated with a MIL-L-23699A turbine oil. The temperature was 27 C. The experimental results were correlated to give the percent film (no-contact-time fraction) as a function of measured film thickness. Measurements were made for three test series that represented the test bearing in various conditions of run-in. The measurements show that the percent film changes with bearing run-in time. The experimental results agreed well with theoretical predictions based on surface trace analysis for a new bearing. For the run-in state, they agreed with previously reported experimental results. The results show that asperity contact existed at a film thickness-roughness ratio lambda of 6.0 or less for a new bearing. After run-in, no asperity contact occurred at a lambda of 3.5 or greater.

Coy, J. J.

1979-01-01

296

Was Himalayan normal faulting triggered by initiation of the Ramgarh-Munsiari thrust and development of the Lesser Himalayan duplex?  

Science.gov (United States)

The Ramgarh-Munsiari thrust is a major orogen-scale fault that extends for more than 1,500 km along strike in the Himalayan fold-thrust belt. The fault can be traced along the Himalayan arc from Himachal Pradesh, India, in the west to eastern Bhutan. The fault is located within the Lesser Himalayan tectonostratigraphic zone, and it translated Paleoproterozoic Lesser Himalayan rocks more than 100 km toward the foreland. The Ramgarh-Munsiari thrust is always located in the proximal footwall of the Main Central thrust. Northern exposures (toward the hinterland) of the thrust sheet occur in the footwall of the Main Central thrust at the base of the high Himalaya, and southern exposures (toward the foreland) occur between the Main Boundary thrust and Greater Himalayan klippen. Although the metamorphic grade of rocks within the Ramgarh-Munsiari thrust sheet is not significantly different from that of Greater Himalayan rock in the hanging wall of the overlying Main Central thrust sheet, the tectonostratigraphic origin of the two different thrust sheets is markedly different. The Ramgarh-Munsiari thrust became active in early Miocene time and acted as the roof thrust for a duplex system within Lesser Himalayan rocks. The process of slip transfer from the Main Central thrust to the Ramgarh-Munsiari thrust in early Miocene time and subsequent development of the Lesser Himalayan duplex may have played a role in triggering normal faulting along the South Tibetan Detachment system.

Robinson, Delores M.; Pearson, Ofori N.

2013-04-01

297

A Passive Magnetic Bearing Flywheel  

Science.gov (United States)

A 100 percent passive magnetic bearing flywheel rig employing no active control components was designed, constructed, and tested. The suspension clothe rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm, which is 65 percent above the first critical speed of 3336 rpm. Operation was not continued beyond this point because of the excessive noise generated by the air impeller and because of inadequate containment in case of failure. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.

Siebert, Mark; Ebihara, Ben; Jansen, Ralph; Fusaro, Robert L.; Morales, Wilfredo; Kascak, Albert; Kenny, Andrew

2002-01-01

298

Testing and Lubrication for Single Race Bearings  

Energy Technology Data Exchange (ETDEWEB)

Three ES and H-compatible lubricants (Environment, Safety and Health) for single race bearing applications and one hybrid-material single race bearings were evaluated and compared against single race bearings with trichlorotrifluoroethane (Freon) deposition of low molecular weight polytetrafluoroethylene (PTFE) bearing lubricant extracted from Vydax{trademark}. Vydax is a product manufactured by DuPont consisting of various molecular weights of PTFE suspended in trichlorotrifluoroethane (Freon), which is an ozone-depleting solvent. Vydax has been used as a bearing lubricant in stronglink mechanisms since 1974. Hybrid bearings with silicon nitride balls and molded glass-nylon-Teflon retainers, bearings lubricated with titanium carbide (TiC) on the balls, bearings lubricated with sputtered MoS{sub 2} on races and retainers, and bearings lubricated with electrophoretically deposited MoS{sub 2} were evaluated. The bearings were maintained in a preloaded state in bearing cartridges during cycling and vibration tests. Bearings with electrophoretically deposited MoS{sub 2} performed as well as bearings lubricated with Vydax and were the best performing candidate. All candidates were suitable for low preload applications. Bearings with TiC coated balls and bearings lubricated with sputtered MoS{sub 2} on the races and retainers performed well at high preloads, though not as well as bearings lubricated with electrophoretic deposition of MoS{sub 2}. Bearings with silicon nitride balls were not suitable for high preload applications.

Steinhoff, R.G.

1998-03-04

299

Implementation of a magnetic bearing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The idea of a magnetic bearing is to make the rotating part hover so that it won’t touch the stator part. Minimal friction and wear and independence of lubrication are among the largest advantages. Marcus Granström has in a present Master of Science Thesis showed that it is theoretical possible to build a magnetic bearing. Marcus Granström has made a Simulinkmodel over the process, the controller included. Further Marcus Granström has suggested some alternative controllers. This Master o...

Ymerson, Madeleine

2007-01-01

300

Computational analysis of Variable Thrust Engine (VTE) performance  

Science.gov (United States)

The Variable Thrust Engine (VTE) of the Orbital Maneuvering Vehicle (OMV) uses a hypergolic propellant combination of Monomethyl Hydrazine (MMH) and Nitrogen Tetroxide (NTO) as fuel and oxidizer, respectively. The performance of the VTE depends on a number of complex interacting phenomena such as atomization, spray dynamics, vaporization, turbulent mixing, convective/radiative heat transfer, and hypergolic combustion. This study involved the development of a comprehensive numerical methodology to facilitate detailed analysis of the VTE. An existing Computational Fluid Dynamics (CFD) code was extensively modified to include the following models: a two-liquid, two-phase Eulerian-Lagrangian spray model; a chemical equilibrium model; and a discrete ordinate radiation heat transfer model. The modified code was used to conduct a series of simulations to assess the effects of various physical phenomena and boundary conditions on the VTE performance. The details of the models and the results of the simulations are presented.

Giridharan, M. G.; Krishnan, A.; Przekwas, A. J.

1993-02-01

 
 
 
 
301

Cooling of high pressure rocket thrust chambers with liquid oxygen  

Science.gov (United States)

An experimental program using hydrogen and oxygen as the propellants and supercritical liquid oxygen (LOX) as the coolant was conducted at 4.14 and 8.274 MN/sq m chamber pressure. It was aimed to demonstrate the effect of LOX leaking into the combustion region through small cracks in the chamber wall, and to verify the supercritical oxygen heat transfer correlation developed from heated tube experiments. Four thrust chambers with throat diameters of 0.066 m were tested; three of these were cyclically tested to 4.14 MM/sq m chamber pressure until a crack developed; the fourth chamber was operated at 8.274 MM/sq m pressure to obtain steady state heat transfer data. Wall temperature measurements confirmed the heat transfer correlation.

Price, H. G.

1980-01-01

302

Mechanical properties of foliated cataclasites from the Nobeoka thrust  

Science.gov (United States)

Understanding the mechanics of plate boundary earthquakes requires a sound investigation of the deformation style and mechanical behavior not only within plate boundary faults but also in the surrounding rocks. It is critical to quantify the strain accumulation and accommodation in the entire subduction systems. Recent studies suggest that heterogeneous deformation and strain distribution in mélanges observed in many ancient accretionary prism outcrops are related to slow slip events and low frequency earthquakes [Fagereng and Sibson, 2010; Kitamura and Kimura, 2011]. However, there are few experimental studies to describe mechanical properties of mélanges and foliated cataclasites. Here, we report on triaxial deformation experiments on foliated cataclasites from the footwall of the Nobeoka thrust, Japan. The Nobeoka thrust, which is exhumated in Kyushu, southwest Japan, is considered as one of the ancient out-of-sequence faults. The Nobeoka thrust fault core, hanging wall, and foot wall rocks were recently cored and logged in a vertical borehole as a NOBELL project [Hamahashi et al., in press]. The Nobeoka thrust is recovered at 41.3 m from the ground. The hanging wall (0-41.3 m coring interval) is composed of the Kitagawa Group of phyllite of alternating beds of sandstone and shale, while the footwall (41.3-255 m) is composed of the Hyuga Group of foliated cataclasite consisting of scaly shale, tuffacious shale, sandstone, and acidic tuff. For deformation experiments, we used foliated catacalsite core samples, which are in better quality and less weathered than outcrop samples. Cylindrical samples with a diameter of 20 mm and a length of 30 mm were subsampled from the cores. The cylindrical specimen were deformed at an axial displacement rate of 0.05-0.5 ?m/s, corresponding to strain rates of 1.6 ×10-6-1.6 ×10-5 s-1, and at a temperature of 250 ° C and an effective pressure (Pe) of 120 MPa (confining pressure of 200 MPa and pore pressure of 80 MPa) or 20 MPa (confining pressure of 200 MPa and pore pressure of 180 MPa). The temperature was chosen based on the estimated temperature (250-300 ° C) at which the footwall foliated cataclasites were formed [Kondo et al., 2005]. The two different effective pressures of 120 MPa and 20 MPa correspond to the stress conditions at ~8 km (geothermal gradient of ~30 ° C/km) with hydrostatic pore pressure and lithostatic pore pressure, respectively. The preliminary results show that the foliated cataclasite samples, taken from the coring interval of 153 m, deform in a brittle manner at Pe = 20 MPa. The strengths reach at 80-90 MPa at peak following a strain weakening to residual strengths of 40-60 MPa. At Pe = 120 MPa, on the other hand, the foliated cataclasite deforms in a brittle-ductile transition manner and steady-state strength is ~ 300 MPa. We will present more experimental results and microstructure observations of the experimentally deformed samples.

Kitajima, Hiroko; Takahashi, Miki; Kimura, Gaku; Yamaguchi, Asuka; Saito, Saneatsu; Hamahashi, Mari; Fukuchi, Rina; Kameda, Jun; Hamada, Yohei; Fujimoto, Koichiro; Hashimoto, Yoshitaka; Kitamura, Yujin; Hina, Shoko; Eida, Mio

2014-05-01

303

Hudson Valley Fold and Thrust Belt Field Trip (Structural Geology)  

Science.gov (United States)

This structural geology field trip in the Hudson Valley region reinforces class discussions about fold and thrust belts and thin-skinned tectonics. Students observed a ramp anticline over a ramp-flat geometry fault. The anticline has minor faulting and veining in the hinge zone and folding occurred by flexural slip (evident from down-dip slickenlines on bedding surfaces). Students make observations and sketches of the outcrop and take strike and dip measurements of bedding and fault surfaces. Students can also look for a very weak cleavage. Students can use attitude measurements to reinforce key principles of stereonets including plotting lines, planes, and poles and interpreting the orientation of the fold axis (or other information) from these nets.

Growdon, Martha

304

Thrust Measurements in Ballistic Pendulum Ablative Laser Propulsion Experiments  

International Nuclear Information System (INIS)

This paper describes a setup for thrust measurement in ablative laser propulsion experiments, based on a simple ballistic pendulum associated to an imaging system, which is being assembled at IEAv. A light aluminium pendulum holding samples is placed inside a 100 liters vacuum chamber with two optical windows: the first (in ZnSe) for the laser beam and the second (in fused quartz) for the pendulum visualization. A TEA-CO2 laser beam is focused to the samples providing ablation and transferring linear moment to the pendulum as a whole. A CCD video camera captures the oscillatory movement of the pendulum and the its trajectory is obtained by image processing. By fitting the trajectory of the pendulum to a dumped sinusoidal curve is possible to obtain the amplitude of the movement which is directly related to the momentum transfered to the sample

305

Use of structured surfaces for friction and wear control on bearing surfaces  

Science.gov (United States)

Surface texturing with purposely made regular micropatterns on flat or curved surfaces, as opposed to random roughness inherited from machining processes, has attracted significant attention in recent years. At the 2013 World Tribology Congress in Turin alone there were over 40 presentations related to surface texturing for tribological applications, from magnetic hard discs and hydrodynamic bearings to artificial joints. Although surface texturing has been reported being successfully applied in industrial applications such as seals, pistons, and thrust pad bearings, the demand for robust design is still high. Etsion has recently reviewed the modeling research mainly conducted by his group Etsion I (2013 Friction 1 195–209). This paper aims to review the state-of-the-art development of surface texturing made by a wider range of researchers.

Wang, Ling

2014-10-01

306

Momentum Management Tool for Low-Thrust Missions  

Science.gov (United States)

A momentum management tool was designed for the Dawn low-thrust interplanetary spacecraft en route to the asteroids Vesta and Ceres, in an effort to better understand the early creation of the solar system. Momentum must be managed to ensure the spacecraft has enough control authority to perform necessary turns and hold a fixed inertial attitude against external torques. Along with torques from solar pressure and gravity-gradients, ion-propulsion engines produce a torque about the thrust axis that must be countered by the four reaction wheel assemblies (RWA). MomProf is a ground operations tool built to address these concerns. The momentum management tool was developed during initial checkout and early cruise, and has been refined to accommodate a wide range of momentum-management issues. With every activity or sequence, wheel speeds and momentum state must be checked to avoid undesirable conditions and use of consumables. MomProf was developed to operate in the MATLAB environment. All data are loaded into MATLAB as a structure to provide consistent access to all inputs by individual functions within the tool. Used in its most basic application, the Dawn momentum tool uses the basic principle of angular momentum conservation, computing momentum in the body frame, and RWA wheel speeds, for all given orientations in the input file. MomProf was designed specifically to be able to handle the changing external torques and frequent de - saturations. Incorporating significant external torques adds complexity since there are various external torques that act under different operational modes.

Swenka, Edward R.; Smith, Brett A.; Vanelli, Charles A.

2010-01-01

307

Modeling two sequential coaxial phases of shortening in a foreland thrust belt  

Science.gov (United States)

Analog sandbox models are used to simulate two sequential coaxial phases of shortening in a foreland thrust belt. A sufficient hiatus is considered so that erosion and sedimentation after the first phase create an angular unconformity that is subsequently deformed. The effect of variation in thickness of post-erosional sediment package and presence of a weak layer at the unconformity level are analyzed. During the second phase, some first phase thrusts are reactivated and new thrusts are also initiated. Thrust reactivation results in a structure spacing that is smaller than the expected spacing for a thicker sediment package. Reactivation of pre-existing structures prevents the weak layer from acting as an intermediate décollement. An increase in thickness ratio tends to weaken reactivation of pre-existing thrusts. Model results also show that total displacement along individual reactivated thrusts generally increases downwards across the unconformity, which could be used to distinguish thrust reactivation in the field. Two regional examples from the northern Eastern Cordillera in Colombia and from the Variscan frontal zone in Western Europe, respectively, where multiphase coaxial shortening occurred, are compared with model results. Both natural cases show features, such as partially eroded first-generation folds and truncated first-generation thrusts that are indicators for two sequential phases of deformation as observed in the models.

Deng, Hongling; Koyi, Hemin A.; Froitzheim, Nikolaus

2014-09-01

308

A thrust formula for an MPD thruster with applied-magnetic field  

Science.gov (United States)

In this paper a thrust formula for applied field MPD will be presented. The swirling velocity will be derived from the magnetic stress tensor and its conversion into axial energy into the magnetic nozzle will be analytically treated. The theoretical prediction of both swirling velocity and thrust will be compared to the measurements showing a reasonable agreement.

Coletti, M.

2012-12-01

309

"Null-E" magnetic bearings  

Science.gov (United States)

Using electromagnetic forces to suspend rotating objects (rotors) without mechanical contact is often an appealing technical solution. Magnetic suspensions are typically required to have adequate load capacity and stiffness, and low rotational loss. Other desired features include low price, high reliability and manufacturability. With recent advances in permanent-magnet materials, the required forces can often be obtained by simply using the interaction between permanent magnets. While a magnetic bearing based entirely on permanent magnets could be expected to be inexpensive, reliable and easy to manufacture, a fundamental physical principle known as Earnshaw's theorem maintains that this type of suspension cannot be statically stable. Therefore, some other physical mechanisms must be included. One such mechanism employs the interaction between a conductor and a nonuniform magnetic field in relative motion. Its advantages include simplicity, reliability, wide range of operating temperature and system autonomy (no external wiring and power supplies are required). The disadvantages of the earlier embodiments were high rotational loss, low stiffness and load capacity. This dissertation proposes a novel type of magnetic bearing stabilized by the field-conductor interaction. One of the advantages of this bearing is that no electric field, E, develops in the conductor during the rotor rotation when the system is in no-load equilibrium. Because of this we refer to it as the Null-E Bearing. Null-E Bearings have potential for lower rotational loss and higher load capacity and stiffness than other bearings utilizing the field-conductor interaction. Their performance is highly insensitive to manufacturing inaccuracies. The Null-E Bearing in its basic form can be augmented with supplementary electronics to improve its performance. Depending on the degree of the electronics involvement, a variety of magnetic bearings can be developed ranging from a completely passive to an active magnetic bearing of a novel type. This dissertation contains theoretical analysis of the Null-E Bearing operation, including derivation of the stability conditions and estimation of some of the rotational losses. The validity of the theoretical conclusions has been demonstrated by building and testing a prototype in which non-contact suspension of a 3.2-kg rotor is achieved at spin speeds above 18 Hz.

Filatov, Alexei Vladimirovich

2002-09-01

310

Ball-and-Socket-Bearing Wear Test  

Science.gov (United States)

Series of experiments to measure wear life of spherical bearing summarized. Report designed to establish clearance, contour, finish, and lubricant parameters for highly-loaded, compact plain spherical bearing. Information useful in design of bearings for helicopter control linkages, business machines, nuclear reactor, and rotor bearings.

Graham, W. G.

1984-01-01

311

Liquid oxygen cooled bearing ignition potential assessment  

Science.gov (United States)

Space Shuttle Main Engine High Pressure Oxygen Turbopump bearings have shown evidence of heavy oxidation on the surfaces of the balls and races. Extensive analyses were performed to assess the ignition potential in the bearing system during normal and off-nominal operation. Test programs and analyses were used to determine the bearing thermal condition and bearing material ignition characteristics.

Page, Arthur T.; Goode, Brian K.; Owen, James W.

1990-01-01

312

Damping Seals And Bearings For A Turbomachine  

Science.gov (United States)

Improved design for support of rotor in turbopump integrates ball bearings with damping seals and damping bearings. Reduces radial (side) loads on ball bearings, making it possible to increase contact angles to withstand increased transient axial loads. Service lives of bearings prolonged.

Von Pragenau, George L.

1990-01-01

313

Journal gas bearing for curved surfaces  

Science.gov (United States)

Optimizing bearing length and permissible axis curvature alleviates distortion of film gap of gas lubricated journal bearing in deployment mechanisms. Required bearing length is divided into two shorter bearings interconnected by links which allow satisfactory conformity with the bent, load-carrying member.

Redmon, J. W.

1969-01-01

314

Master ``blind'' thrust faults hidden under the Zagros folds: active basement tectonics and surface morphotectonics  

Science.gov (United States)

The basement-involved active fold-thrust belt of the Zagros in southwest Iran is underlain by numerous seismogenic blind basement thrust faults covered by the folded Phanerozoic sedimentary rocks. Meizoseismal regions of moderate- to large-magnitude earthquakes in the Zagros are localized and concentrated along particular structural-geomorphological features and topographic fronts at the surface. The study reveals at least four active SW-vergent segmented master blind thrusts in the Zagros collisional belt, along which different morphotectonic units are thrusting over the deforming regions. These boundary thrusts, which make contiguous frontal asymmetric anticlines, prominent escarpments and Quaternary deformation, mark topographic fronts at the surface, and have vertically displaced geologic marker beds for more than 6000 m, include: the High Zagros (with a maximum recorded historic earthquake of Ms = 6.0 at Daryan); the Mountain Front ( Ms = 7.0 at Khurgu); the Dezful Embayment ( Ms = 5.7); and the Foredeep ( Ms = 6.5 at Ahwaz) thrusts. Three other seismogenic blind thrusts responsible for the Qir ( Ms = 6.9), the Lar ( Ms = 6.5) and the Beriz-Dehkuyeh ( Ms = 5.7) earthquakes are also documented in this study. The master faults, as evidenced by deformation of the asymmetric anticlines in the hanging wall of the blind thrusts, are segmented and discontinuous, and are separated by gaps in faulting that have presumably controlled the extent of rupture and the magnitude of earthquakes. The master seismic thrusts are displaced right-laterally by deep-seated active transverse faults of Kazerun ( Io = VIII), Sarvestan ( Ms = 6.4?) and Sabz Pushan. The study shows that active deformation in the Zagros is dominated by: (1) prevalent subsurface blind thrusting; (2) occasional surface strike-slip faulting; (3) coseismic asymmetric folding and uplift of sedimentary cover; and (4) surface thrusting ramping up from at least two regional upper (Miocene Gachsaran) and lower (Lower Cambrian Hormoz) décollement detachments. The active master thrust faults have implications for seismic hazard assessment that were not previouly appreciated. The possibility of large compressive earthquakes ( Ms ˜ 7.0) along the introduced blind thrusts must be considered. Locations of other unknown segmented blind thrusts in the belt, which have distinct effects on the surface morphotectonics and topography, and on the structures at depth, could be easily based on meizoseismal maps of the earthquakes combined with active morphotectonic features, morphometric analyses and accurate aftershock sequence studies.

Berberian, Manuel

1995-01-01

315

Ultrasonic measurement of lubricant film thickness in sliding bearings with thin liners  

Science.gov (United States)

When conducting ultrasonic measurements of the lubricant film thickness in sliding bearings with thin liners, the ultrasonic pulse reflected from the bearing liner–lubricant film interface will superimpose on the pulse reflected from the bearing substrate–liner interface. The thickness information of the lubricant film is contained in the reflected pulse from the liner–lubricant film interface. In this case, the film thickness could not be obtained directly from the superimposed reflected signals. The thin liner indicates that the thickness of the bearing liner is less than half the ultrasonic pulse width. Based on the spectrum analysis method of superimposed signals, a new method is proposed to measure the lubricant film thickness in sliding bearings with thin liners. The frequency-domain amplitude ratio between the echo component containing thickness information and the steady echo component from the bearing substrate–liner interface is extracted from the superimposed signal. The reflection coefficient of the liner–lubricant film interface is obtained by this amplitude ratio to determine the film thickness. The lubricant films of different thicknesses in a thin-liner thrust pad were measured in a high-precision experimental apparatus. The measurement results were compared with the known film thickness set by the experimental apparatus. In the thinner film region, the measurement results agreed well with the set film thickness. In the thicker film region, the mean values of the multiple measurement results represented the film thickness. The experimental results show that the method can be used to measure the lubricant film thickness in sliding bearings with thin liners.

Geng, Tao; Meng, Qingfeng; Zhang, Kai; Yuan, Xiaoyang; Jia, Qian

2015-02-01

316

Measurement effects on the calculation of in-flight thrust for an F404 turbofan engine  

Science.gov (United States)

A study was performed that investigates parameter measurement effects on calculated in-flight thrust for the General Electric F404-GE-400 afterburning turbofan engine which powered the X-29A forward-swept wing research aircraft. Net-thrust uncertainty and influence coefficients were calculated and are presented. Six flight conditions were analyzed at five engine power settings each. Results were obtained using the mass flow-temperature and area-pressure thrust calculation methods, both based on the commonly used gas generator technique. Thrust uncertainty was determined using a common procedure based on the use of measurement uncertainty and influence coefficients. The effects of data nonlinearity on the uncertainty calculation procedure were studied and results are presented. The advantages and disadvantages of using this particular uncertainty procedure are discussed. A brief description of the thrust-calculation technique along with the uncertainty calculation procedure is included.

Conners, Timothy R.

1989-01-01

317

Bearing damage versus central lubrication system  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The examination paper which has been carried out at Stora Enso illustrates the difficulties around surveillance of bearing condition and the short length of bearing lives in the press section on the cardboard machines. This paper also illustrates if the short bearing lives are lubrication related, and how the lubrication funds affect the length of the bearing lives. There is a complication with finding bearing failures at the using vibration analysis on relatively low revolution machines, thi...

Egestrand, Jens

2012-01-01

318

Development of porous-ceramic hydrostatic bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Porous-ceramic hydrostatic bearings have been recently developed. These bearings have demonstrated an exceptional overall performance when compared with conventional technology bearings. However, despite all the benefits, porous-ceramic hydrostatic bearings have yet to find widespread acceptance due to the problems found in tailoring the bearings geometry and size to suit precision engineering applications, while producing porous-structures with consistent and reproducible p...

Durazo-cardenas, Isidro Sergio

2003-01-01

319

Bearing Cartridge Designed To Reduce Wear  

Science.gov (United States)

Bearing cartridge holding outer races of two ball bearings in turbopump designed to prevent unloading of bearings during operating transients. Cartridge and bearings replace two ball bearings, whose outer races mounted in cylinder called "isolator" and preloaded by single spring mount holding isolator and reacting radial loads. Cartridge slides axially in bore of isolator during transients and forces outer races to move as pair. Necessary to eliminate unloading because unloading initiates wear.

Krieg, Eric J.

1992-01-01

320

Development of porous ceramic air bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Porous air bearings enjoy some important advantages over conventional air bearing types such as increased load carrying capacity, higher stiffness and improved damping. However, these types of bearings have yet to find widespread acceptance due to problems with obtaining materials with consistent permeability, instability issues relating to the volume of gas trapped at the bearing surface in the pores, and manufacturing the bearing without altering the permeability. Using...

Roach, Christopher James

2001-01-01

 
 
 
 
321

Active Magnetic Bearings – Magnetic Forces  

DEFF Research Database (Denmark)

Parameter identification procedures and model validation are major steps towards intelligent machines supported by active magnetic bearings (AMB). The ability of measuring the electromagnetic bearing forces, or deriving them from measuring the magnetic flux, strongly contributes to the model validation and leads to novel approaches in identifying crucial rotor parameters. This is the main focus of this paper, where an intelligent AMB is being developed with the aim of aiding the accurate identification of damping and stiffness coefficients of journal bearings and seals. The main contribution of the work is the characterization of magnetic forces by using two experimental different experimental approaches. Such approaches are investigated and described in details. A special test rig is designed where the 4 poles - AMB is able to generate forces up to 1900 N. The high precision characterization of the magnetic forces are led by using different experimental tests: (I) by using hall sensors mounted directly on the poles (precise measurements of the magnetic flux) and by an auxiliary system, composed of strain gages and flexible beams attached to the rotor; (II) by measuring the input current and bearing gap variations, monitoring the bearing input signals. Advantages and drawbacks of the different methodologies are critically discussed. The experimental determination of linearity ranges is found and the characterization of magnetic forces with a high accuracy of less than 1% is achieved.

KjØlhede, Klaus

2006-01-01

322

Superconductor bearings, flywheels and transportation  

International Nuclear Information System (INIS)

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

323

Numerical modeling of sedimentation controls on the growth of the fold-and-thrust belts  

Science.gov (United States)

In the Southern Central Pyrenees, a major phase of late syn-orogenic sedimentation may have influenced the wedge growth and propagation. During Middle Eocene times, thrust deformation in the Pyrenean fold-and-thrust belt propagated to the south with long thrust sheets and significant wedge-top sedimentation. From Late Eocene to Oligo-miocene times, combined thermochronometric, modeling and field studies have shown that a thick pile of conglomerates sourced from the hinterland buried the fold-and-thrust belt until and the Ebro foreland basin. Simultaneously, thrust activity migrated from the front to the internal parts of the orogen reactivating major proximal thrusts, but the reason for the out-of-sequence activity is still a matter of debate. The main objective of this study is to understand the coupling between tectonics and surface processes during formation of a thin-skinned fold-and-thrust belt. To that purpose, we focus on the controls of syn-orogenic sedimentation on thrust development during wedge building before applying a more quantitative study to the southern Pyrenees. There, we investigate the causes for out-of-sequence thrust activity, and the relationship with conglomeratic wedge-top sedimentation. We use an Arbitrary LagrangianEulerian finite-element model (Sopale) to model the thin-skinned fold-and-thrust belt at upper crustal scales (7 km depth and 200 km length). Sopale takes into account the main features and processes that influence the development of a fold-and-thrust belt including detachment horizons, strain-softening, flexural isostasy, and erosion and sedimentation processes. Initial, more conceptual modeling focuses on wedge development coupled with syn-orogenic sedimentation. Wedge-top sedimentation directly affects the taper angle and clearly modifies the behavior of the wedge; a clear relationship between average thrust-sheet length and the thickness of syn-tectonic sediments is highlighted. Subsequently, a sediment cover that progrades towards the foreland with time is added to reproduce the late syn-orogenic burial of the southern Pyrenean fold-and-thrust belt by conglomerates. By perturbing the forward progression of the wedge, this pattern of sedimentation can explain the out-of-sequence activity in the southern central Pyrenees.

Fillon, C.; Huismans, R.; van der Beek, P.

2012-04-01

324

Experimental Study of an Axisymmetric Dual Throat Fluidic Thrust Vectoring Nozzle for Supersonic Aircraft Application  

Science.gov (United States)

An axisymmetric version of the Dual Throat Nozzle concept with a variable expansion ratio has been studied to determine the impacts on thrust vectoring and nozzle performance. The nozzle design, applicable to a supersonic aircraft, was guided using the unsteady Reynolds-averaged Navier-Stokes computational fluid dynamics code, PAB3D. The axisymmetric Dual Throat Nozzle concept was tested statically in the Jet Exit Test Facility at the NASA Langley Research Center. The nozzle geometric design variables included circumferential span of injection, cavity length, cavity convergence angle, and nozzle expansion ratio for conditions corresponding to take-off and landing, mid climb and cruise. Internal nozzle performance and thrust vectoring performance was determined for nozzle pressure ratios up to 10 with secondary injection rates up to 10 percent of the primary flow rate. The 60 degree span of injection generally performed better than the 90 degree span of injection using an equivalent injection area and number of holes, in agreement with computational results. For injection rates less than 7 percent, thrust vector angle for the 60 degree span of injection was 1.5 to 2 degrees higher than the 90 degree span of injection. Decreasing cavity length improved thrust ratio and discharge coefficient, but decreased thrust vector angle and thrust vectoring efficiency. Increasing cavity convergence angle from 20 to 30 degrees increased thrust vector angle by 1 degree over the range of injection rates tested, but adversely affected system thrust ratio and discharge coefficient. The dual throat nozzle concept generated the best thrust vectoring performance with an expansion ratio of 1.0 (a cavity in between two equal minimum areas). The variable expansion ratio geometry did not provide the expected improvements in discharge coefficient and system thrust ratio throughout the flight envelope of typical a supersonic aircraft. At mid-climb and cruise conditions, the variable geometry design compromised thrust vector angle achieved, but some thrust vector control would be available, potentially for aircraft trim. The fixed area, expansion ratio of 1.0, Dual Throat Nozzle provided the best overall compromise for thrust vectoring and nozzle internal performance over the range of NPR tested compared to the variable geometry Dual Throat Nozzle.

Flamm, Jeffrey D.; Deere, Karen A.; Mason, Mary L.; Berrier, Bobby L.; Johnson, Stuart K.

2007-01-01

325

Controls on the architecture of the Himalayan thrust belt, NW India  

Science.gov (United States)

In the Himalayan-Tibetan orogen, the syntaxes at the eastern and western terminations of the orogen connect a 2400 km long thrust belt. If the two syntaxes are locked, the behavior of the thrust belt may be different in the syntaxes than in the central part of the thrust belt. In fact, recent work in the central part of the Himalayan thrust belt reveals shortening estimates of ~700-900 km while closer to the syntaxes, the amount of shortening may be nearly half that (~470 km). Thus, there should be an identifiable region where the character of the thrust belt changes from that of the syntaxes to that of the central part of the thrust belt. In the Himachal Pradesh region of NW India, a transition exists in the architecture of the thrust belt. North of the Kanga reentrant, the high mountains are close to the frontal part of the thrust belt; yet, near the Beas River, ~90 km to the east, and further east still in the Sutlej and Yamuna valleys, the high mountains of the thrust belt are located far into the hinterland. The presence or absence of the Greater Himalayan rocks at the surface appears to control this pattern: when Greater Himalayan rocks are absent at the surface, as near the town of Dharamsala, the thrust belt is very narrow (150 km) and the high mountains are located in the hinterland. The presence/absence of Greater Himalayan rocks at the surface also appears to control where focused erosion is presently occurring and, subsequently, the erosional exposure of Lesser Himalayan rocks. Three models reveal the possible kinematic roles of the Greater Himalayan rocks and its subsequent control of the architecture of the thrust belt: 1) the fault that carries Greater Himalayan rocks may tip out at depth; 2) slip on that fault may continue to the surface; 3) the fault tips out and slip is transferred to a different fault. In addition, the presence or absence of Greater Himalayan rocks may control the sub-supracrustal architecture of the Himalayan-Tibetan orogen, and thus provides insight into the evolution of the orogen. For example, the presence of Greater Himalayan rocks at the surface may indicate more melt to lubricate thrusting, whereas the absence of Greater Himalayan rocks at the surface may indicate a significantly different in thermal structure in that part of the thrust belt.

Robinson, D. M.; Paul, S. K.; Chambers, J. A.; Kohn, M. J.

2009-12-01

326

'Dodo' and 'Baby Bear' Trenches  

Science.gov (United States)

NASA's Phoenix Mars Lander's Surface Stereo Imager took this image on Sol 11 (June 5, 2008), the eleventh day after landing. It shows the trenches dug by Phoenix's Robotic Arm. The trench on the left is informally called 'Dodo' and was dug as a test. The trench on the right is informally called 'Baby Bear.' The sample dug from Baby Bear will be delivered to the Phoenix's Thermal and Evolved-Gas Analyzer, or TEGA. The Baby Bear trench is 9 centimeters (3.1 inches) wide and 4 centimeters (1.6 inches) deep. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

2008-01-01

327

Tribo-characteristics of self-lubricating ball bearings for the LE-7 liquid hydrogen rocket-turbopump  

Science.gov (United States)

The tribo characteristics of self-lubricating 40-mm-bore ball bearings with a retainer of glass cloth-polytetrafluoroethylene (PTFE) laminate, which has elliptical pockets with a large pocket clearance, were tested under thrust loads at speeds up to 50,000 rpm, 2 million DN, in liquid hydrogen (LH2) and in liquid nitrogen (LN2). During testing, the bearing torque, outer-race temperature, and electric resistance between the inner and outer races were monitored to verify the formation and rupture of a PTFE transfer film. Testing showed that the bearings having the elliptical retainer pockets were superior to the conventional bearings with circular pockets. It was determined that, at the maximum inner race spinning velocity of about 5 m/s, a PTFE transfer film could sustain the maximum Hertz stress, up to about 2000 N/sq mm, in LH2, without severe film rupture resulting in bearing seizure. In LN2, the critical load capacity of PTFE transfer film with bearing seizure was about 2700 N/sq mm.

Nosaka, Masataka; Oike, Mamoru; Kikuchi, Masataka; Kamijo, Kenjiro; Tajiri, Masanori

1993-07-01

328

Air bearing vacuum seal assembly  

International Nuclear Information System (INIS)

An air bearing vacuum seal assembly is described that is capable of rotating at the speed of several thousand revolutions per minute using an air cushion to prevent the rotating and stationary parts from touching, and a two stage differential pumping arrangment to maintain the pressure gradient between the air cushion and the vacuum so that the leak rate into the vacuum is, for example, less than 1 x 10-4Pa m3/s. The air bearing vacuum seal has particular application for mounting rotating targets to an evacuated accelerator beam tube for bombardment of the targets with high-power charged particle beams in vacuum

329

Low eddy loss axial hybrid magnetic bearing with gimballing control ability for momentum flywheel  

International Nuclear Information System (INIS)

For a magnetically suspended momentum flywheel (MSMF), the spinning rotor can be tilted by a pair of the presented axial hybrid magnetic bearing (AHMB) with eight poles and rotates around the radial axes to generate a large torque to maneuver the spacecraft. To improve the control performance and gimballing control ability of the AHMB, characteristics such as magnetic suspension force, angular stiffness and tilting momentum are researched. These segmented stator poles cause the magnetic density in the thrust rotor plate to be uneven unavoidably and the rotational loss is large at high speed, but we optimized the stator poles configuration and caused the thrust rotor plate formed by bulk DT4C and laminated material to make the magnetic density in the thrust rotor plate change less and be smoother. Laminated material such as 1J50 film with a thickness of 0.1 mm can make the variation of the magnetic density in DT4C become very small and the eddy loss of it be negligible, but the stress produced in the “O” shape stacks by reeling has a bad effect on its power loss. Nanocrystalline can reduce eddy losses and is not affected by the reeling process. Based on the AHBM consisting of the stator with eight improved poles and the presented thrust rotor plate with DT4 and nanocrystalline, the rotational loss of 5-DOF magnetically suspended momentum flywheel with angular momentum of 15 N m s at 5000 rpm has reduced from 23.4 W to 3.2 W, which proved that this AHMB has low eddyich proved that this AHMB has low eddy loss for the gimballing control ability. - Highlights: ? Control methods of rotor driven by AHMBs and their characteristics are researched. ? Optimized stator and rotor of AHMB reduce its eddy losses greatly. ? Presented the factors affecting the eddy losses of AHMBs. ? The good performances of AHMB with low eddy loss are proved by experiments.

330

Computational Study of an Axisymmetric Dual Throat Fluidic Thrust Vectoring Nozzle for a Supersonic Aircraft Application  

Science.gov (United States)

A computational investigation of an axisymmetric Dual Throat Nozzle concept has been conducted. This fluidic thrust-vectoring nozzle was designed with a recessed cavity to enhance the throat shifting technique for improved thrust vectoring. The structured-grid, unsteady Reynolds- Averaged Navier-Stokes flow solver PAB3D was used to guide the nozzle design and analyze performance. Nozzle design variables included extent of circumferential injection, cavity divergence angle, cavity length, and cavity convergence angle. Internal nozzle performance (wind-off conditions) and thrust vector angles were computed for several configurations over a range of nozzle pressure ratios from 1.89 to 10, with the fluidic injection flow rate equal to zero and up to 4 percent of the primary flow rate. The effect of a variable expansion ratio on nozzle performance over a range of freestream Mach numbers up to 2 was investigated. Results indicated that a 60 circumferential injection was a good compromise between large thrust vector angles and efficient internal nozzle performance. A cavity divergence angle greater than 10 was detrimental to thrust vector angle. Shortening the cavity length improved internal nozzle performance with a small penalty to thrust vector angle. Contrary to expectations, a variable expansion ratio did not improve thrust efficiency at the flight conditions investigated.

Deere, Karen A.; Flamm, Jeffrey D.; Berrier, Bobby L.; Johnson, Stuart K.

2007-01-01

331

Analytical guidance for spacecraft relative motion under constant thrust using relative orbit elements  

Science.gov (United States)

Proximity control of modern nano-spacecraft often relies on low and discrete thrust engines that are characterized by low consumption, and generate on-off force profiles. New guidance solutions must take into account the nature of this type of orbital engines. This paper introduces novel analytical guidance solutions for spacecraft relative motion considering continuous, on-off thrust, and using relative orbit elements as a geometrical representation of the dynamics. The solutions provide the relative state vector at any given time, accommodating any thrust magnitude along the three directions of the relative frame, as well as generic activation times and durations. Relative orbit elements geometrically interpret key aspects of the relative motion, including for example, the relative ellipse size, and the evolution of its center in time. The new solutions provide the guidance designer with a direct visualization of the thrust effects on the relative motion geometry, offering new possibilities for analytical guidance in the presence of continuous thrust engines, such as low thrust engines on nano-spacecraft. The paper presents the analytical solutions, and tests their effectiveness using a sample thrust profile based on input-shaping, previously developed by one of the authors using classical Cartesian coordinates. The use of relative orbit elements shows substantial benefits and added simplicity with respect to Cartesian-based approaches, holding the promise for straightforward onboard spacecraft implementation. The software developed for this research will be available open source1

Bevilacqua, Riccardo; Lovell, Thomas Alan

2014-09-01

332

Wave Journal Bearing. Part 1: Analysis  

Science.gov (United States)

A wave journal bearing concept features a waved inner bearing diameter of the non-rotating bearing side and it is an alternative to the plain journal bearing. The wave journal bearing has a significantly increased load capacity in comparison to the plain journal bearing operating at the same eccentricity. It also offers greater stability than the plain circular bearing under all operating conditions. The wave bearing's design is relatively simple and allows the shaft to rotate in either direction. Three wave bearings are sensitive to the direction of an applied stationary side load. Increasing the number of waves reduces the wave bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the wave bearing design for a specific application. It is concluded that the stiffness of an air journal bearing, due to hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.

Dimofte, Florin

1995-01-01

333

Non-Contact Thrust Stand Calibration Method for Repetitively-Pulsed Electric Thrusters  

Science.gov (United States)

A thrust stand calibration technique for use in testing repetitively-pulsed electric thrusters for in-space propulsion has been developed and tested using a modified hanging pendulum thrust stand. In the implementation of this technique, current pulses are applied to a solenoidal coil to produce a pulsed magnetic field that acts against the magnetic field produced by a permanent magnet mounted to the thrust stand pendulum arm. The force on the magnet is applied in this non-contact manner, with the entire pulsed force transferred to the pendulum arm through a piezoelectric force transducer to provide a time-accurate force measurement. Modeling of the pendulum arm dynamics reveals that after an initial transient in thrust stand motion the quasisteady average deflection of the thrust stand arm away from the unforced or zero position can be related to the average applied force through a simple linear Hooke s law relationship. Modeling demonstrates that this technique is universally applicable except when the pulsing period is increased to the point where it approaches the period of natural thrust stand motion. Calibration data were obtained using a modified hanging pendulum thrust stand previously used for steady-state thrust measurements. Data were obtained for varying impulse bit at constant pulse frequency and for varying pulse frequency. The two data sets exhibit excellent quantitative agreement with each other as the constant relating average deflection and average thrust match within the errors on the linear regression curve fit of the data. Quantitatively, the error on the calibration coefficient is roughly 1% of the coefficient value.

Wong, Andrea R.; Toftul, Alexandra; Polzin, Kurt A.; Pearson, J. Boise

2011-01-01

334

Design Enhancements of the Two-Dimensional, Dual Throat Fluidic Thrust Vectoring Nozzle Concept  

Science.gov (United States)

A Dual Throat Nozzle fluidic thrust vectoring technique that achieves higher thrust-vectoring efficiencies than other fluidic techniques, without sacrificing thrust efficiency has been developed at NASA Langley Research Center. The nozzle concept was designed with the aid of the structured-grid, Reynolds-averaged Navier-Stokes computational fluidic dynamics code PAB3D. This new concept combines the thrust efficiency of sonic-plane skewing with increased thrust-vectoring efficiencies obtained by maximizing pressure differentials in a separated cavity located downstream of the nozzle throat. By injecting secondary flow asymmetrically at the upstream minimum area, a new aerodynamic minimum area is formed downstream of the geometric minimum and the sonic line is skewed, thus vectoring the exhaust flow. The nozzle was tested in the NASA Langley Research Center Jet Exit Test Facility. Internal nozzle performance characteristics were defined for nozzle pressure ratios up to 10, with a range of secondary injection flow rates up to 10 percent of the primary flow rate. Most of the data included in this paper shows the effect of secondary injection rate at a nozzle pressure ratio of 4. The effects of modifying cavity divergence angle, convergence angle and cavity shape on internal nozzle performance were investigated, as were effects of injection geometry, hole or slot. In agreement with computationally predicted data, experimental data verified that decreasing cavity divergence angle had a negative impact and increasing cavity convergence angle had a positive impact on thrust vector angle and thrust efficiency. A curved cavity apex provided improved thrust ratios at some injection rates. However, overall nozzle performance suffered with no secondary injection. Injection holes were more efficient than the injection slot over the range of injection rates, but the slot generated larger thrust vector angles for injection rates less than 4 percent of the primary flow rate.

Flamm, Jeffrey D.; Deere, Karen A.; Mason, Mary L.; Berrier, Bobby L.; Johnson, Stuart K.

2006-01-01

335

Climate Change, Polar Bears and their management  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This is a literature study of polar bears in the context of climate change: what kind of creatures are polar bears, what are the main interpretations of current climate change, how might the polar bear adapt to these changes (feeding strategies) and how are the bears being managed (hunting)? These are relevant questions , since climate change is on the agenda, and polar bears being the apex predators of the Arctic are a key representation of the wildlife there. The third element of polar bear...

Derenchenko, Liza

2010-01-01

336

Estimating Wear Of Installed Ball Bearings  

Science.gov (United States)

Simple inspection and measurement technique makes possible to estimate wear of balls in ball bearing, without removing bearing from shaft on which installed. To perform measurement, one observes bearing cage while turning shaft by hand to obtain integral number of cage rotations and to measure, to nearest 2 degrees, number of shaft rotations producing cage rotations. Ratio between numbers of cages and shaft rotations depends only on internal geometry of bearing and applied load. Changes in turns ratio reflect changes in internal geometry of bearing provided measurements made with similar bearing loads. By assuming all wear occurs on balls, one computes effective value for this wear from change in turns ratio.

Keba, John E.; Mcvey, Scott E.

1993-01-01

337

A METHOD OF COMPUTER CALCULATION OF AXIAL THRUST AND INTERNAL LEAKAGE IN CENTRIFUGAL PUMPS  

Directory of Open Access Journals (Sweden)

Full Text Available A simple method of calculation of radial pressure distribution on a disc rotating in a casing and then the axial thrust in centrifugal pumps is presented. The method is based on integral relations and allows to estimate rapidly the axial thrust value with accuracy sufficient for technical applications (the error less than 15%. The method allows to compute simultaneously Internal leakage losses in centrifugal pumps. The presented method may also be useful for the calculation of the pressure distribution and the axial thrust in other rotating machines, such as compressors, gas turbines, water turbines, hydraulic torque convertors and paper-pulp mills.

Waldemar J?dral

1991-01-01

338

Is tongue thrust that develops during orthodontic treatment an unrecognized potential road block?  

Science.gov (United States)

The role of tongue thrust has often been suspected, long debated and largely dispelled as a primary etiological factor of malocclusion. However, tongue thrust may contribute to poor occlusal intercuspation both during and after treatment. A tongue thrust may also develop during orthodontic mechanotherapy as a result of the transient creation of intra and interarch spaces and this little recognized phenomenon was found to occur in many randomly followed cases. In many instances, this seemingly adaptive and secondary response of the tongue posture and function may persist and thereafter impede the resolution of intra and interarch problems. PMID:16823232

Chawla, H S; Suri, S; Utreja, A

2006-06-01

339

Net thrust calculation sensitivity of an afterburning turbofan engine to variations in input parameters  

Science.gov (United States)

The calculated value of net thrust of an aircraft powered by a General Electric F404-GE-400 afterburning turbofan engine was evaluated for its sensitivity to various input parameters. The effects of a 1.0-percent change in each input parameter on the calculated value of net thrust with two calculation methods are compared. This paper presents the results of these comparisons and also gives the estimated accuracy of the overall net thrust calculation as determined from the influence coefficients and estimated parameter measurement accuracies.

Hughes, D. L.; Ray, R. J.; Walton, J. T.

1985-01-01

340

Kinematics of the Main Caucasus Thrust near Baku, Azerbaijan  

Science.gov (United States)

The Absheron Peninsula lies at the junction of the ˜ E-W striking, north-verging, intra-continental Main Caucasus Thrust Fault (MCTF) and the Central Caspian Seismic Zone (CCSZ). The MCTF accommodates shortening between the Lesser and Greater Caucasus Mountains, and the CCSZ is thought to reflect the early stages of subduction of the southern Caspian ocean basin beneath the northern Caspian continental lithosphere. Both structures accommodate ongoing, roughly N-S continent-continent collision between the Arabian and Eurasian plates. GPS measurements along an ~ N-S traverse crossing the Lesser Caucasus, Kura Depression, and Absheron Peninsula near the city of Baku, Azerbaijan, indicate high strain rates that appear to be continuous with high strain rates along the MCTF located west of the Peninsula. Simple models for strain accumulation along an ESE extension of the MCTF and a SSE-striking, predominantly right-lateral strike-slip fault (both structures being consistent with the regional tectonics) provide reasonable fits to the observed deformation. The MCTF has experienced a number of M > 6.5 historic earthquakes, including the 1991, M=7.1 Racha, Georgia event. Due to the close proximity of the strain anomaly to Baku, and the potential environmental and economic impact from damage to the petroleum infrastructure in this highly industrialized area, further studies are needed to determine better the kinematics of this "transition" zone and possible implications for future earthquake activity.

Floyd, M. A.; Kadirov, F. A.; Alizada, A.; Guliev, I.; Reilinger, R. E.; Kuleli, S.; King, R. W.; Toksoz, M. N.

2011-12-01

 
 
 
 
341

Influence of variable thrust parameters on swirl injector fluid mechanics  

Science.gov (United States)

Current swirl injector design methodologies do not consider elevated chamber pressure and less than design mass flow rate operation found in variable thrust liquid rocket engines. The objective of this work is to study the effects of elevated chamber pressure and off-design mass flow rate operation on swirl injector fluid mechanics. Using a high pressure chamber, water flowed through a swirl injector at various combinations of elevated chamber pressure and reduced mass flow rate. The optically-accessible swirl injector allowed for determination of the film thickness profile down the swirl injector nozzle section. High speed video and digital stills showed significant increases in the film thickness profile at high chamber pressure and low mass flow rate operation. At prescribed combinations of chamber pressure and mass flow rate, a jump was noted in the film thickness profile. This jump was assumed related to a vortex breakdown phenomenon. Measured injector discharge coefficient values showed different trends with increasing chamber pressure at low mass flow rate operation as opposed to near-design mass flow rate operation. Downstream spray angles showed classic changes in morphology as the mass flow rate was decreased below the design value. Increasing chamber pressure worked to decrease the spray angle at any injection mass flow rate. A new set of fundamental relations linking swirl injector design parameters to injector geometry and flow conditions were derived. Impacts of the research findings to the swirl injector design process were assessed.

Kenny, Robert J.

342

SOURCE TERM TARGETED THRUST FY 2005 NEW START PROJECTS  

International Nuclear Information System (INIS)

While a significant amount of work has been devoted to developing thermodynamic data. describing the sorption of radionuclides to iron oxides and other geomedia, little data exist to describe the interaction of key radionuclides found in high-level radioactive waste with the uranium surfaces expected in corroded spent nuclear fuel (SNF) waste packages. Recent work indicates that actinide adsorption to the U(VI) solids expected in the engineered barrier system may play a key role in the reduction of dissolved concentrations of radionuclides such as Np(V). However, little is known about the mechanism(s) of adsorption, nor are the thermodynamic data available to represent the phenomenon in predictive modeling codes. Unfortunately, this situation makes it difficult to consider actinide adsorption to the U(VI) silicates in either geochemical or performance assessment (PA) predictions. The primary goal in the Source Term Targeted Thrust area is to ''study processes that control radionuclide release from the waste form''. Knowledge of adsorption of actinides to U(VI) silicate solids its and parameterization in geochemical models will be an important step towards this goal

343

Radiative Thrust Chamber -enthalpy gain by absorption of electromagnetic radiation  

Science.gov (United States)

Propulsion systems in aerospace engineering either use chemical, thermal or electrical energy to accelerate a medium in order to create thrust. In the first case the energy is already contained in the propulsive medium itself whereas for the latter two the energy is stored externally and provided to the driving medium via different ways. This paper discusses an unconventional, purely radiation-based method to convey energy to the mass flow via electromagnetic interaction. Depending on the wavelength of the incident radiation, it can interact with the medium in different ways. Among these are absorption and scattering. The first mechanism always leads to an increase of the atoms' and molecules' energy, whereas the second can be elastic or inelastic. Depending on the atomic or molecular structure of the driving medium, different degrees of freedom are energized. Whereas atomic particles possess translational and electronic degrees of freedom, molecules exhibit rotational and vibrational modes. We intend to focus the discussion on possibilities to enhance the mass flow enthalpy by absorp-tion as an alternative to the conventional methods. It is outlined whether certain degrees of freedom can be thermalized efficiently to provide momentum.

Gamgami, Farid; Scharringhausen, Marco

344

Low-thrust trajectories for human missions to Ceres  

Science.gov (United States)

A low-thrust trajectory design study is performed for a mission to send humans to Ceres and back. The flight times are constrained to 270 days for each leg, and a grid search is performed over propulsion system power, ranging from 6 to 14 MW, and departure V?, ranging from 0 to 3 km/s. A propulsion system specific mass of 5 kg/kW is assumed. Each mission delivers a 75 Mg payload to Ceres, not including propulsion system mass. An elliptical spiral method for transferring from low Earth orbit to an interplanetary trajectory is described and used for the mission design. A mission with a power of 11.7 MW and departure V? of 3 km/s is found to offer a minimum initial mass in low Earth orbit of 289 Mg. A preliminary supply mission delivering 80 Mg of supplies to Ceres is also designed with an initial mass in low Earth orbit of 127 Mg. Based on these results, it appears that a human mission to Ceres is not significantly more difficult than current plans to send humans to Mars.

Laipert, Frank E.; Longuski, James M.

2014-02-01

345

SOURCE TERM TARGETED THRUST FY 2005 NEW START PROJECTS  

Energy Technology Data Exchange (ETDEWEB)

While a significant amount of work has been devoted to developing thermodynamic data. describing the sorption of radionuclides to iron oxides and other geomedia, little data exist to describe the interaction of key radionuclides found in high-level radioactive waste with the uranium surfaces expected in corroded spent nuclear fuel (SNF) waste packages. Recent work indicates that actinide adsorption to the U(VI) solids expected in the engineered barrier system may play a key role in the reduction of dissolved concentrations of radionuclides such as Np(V). However, little is known about the mechanism(s) of adsorption, nor are the thermodynamic data available to represent the phenomenon in predictive modeling codes. Unfortunately, this situation makes it difficult to consider actinide adsorption to the U(VI) silicates in either geochemical or performance assessment (PA) predictions. The primary goal in the Source Term Targeted Thrust area is to ''study processes that control radionuclide release from the waste form''. Knowledge of adsorption of actinides to U(VI) silicate solids its and parameterization in geochemical models will be an important step towards this goal.

NA

2005-10-05

346

Tardigrades: Bears of the Moss  

Science.gov (United States)

This online PowerPoint presentation is dedicated to the phylum Tardigrada. It discusses distinguishing characteristics of Tardigrades (also known as water bears), their relationship to arthropods and nematodes, internal structures, life stages, cryptobiosis, research opportunities, classification, identification, habitat, distribution, ease of study in the lab, and more. Each slide contains illustrations and descriptions of the microscopic animal.

William Miller

347

Fuzzy control of magnetic bearings  

Science.gov (United States)

The use of an adaptive fuzzy control algorithm implemented on a VLSI chip for the control of a magnetic bearing was considered. The architecture of the adaptive fuzzy controller is similar to that of a neural network. The performance of the fuzzy controller is compared to that of a conventional controller by computer simulation.

Feeley, J. J.; Niederauer, G. M.; Ahlstrom, D. J.

1991-01-01

348

Journal and Wave Bearing Impedance Calculation Software  

Science.gov (United States)

The wave bearing software suite is a MALTA application that computes bearing properties for user-specified wave bearing conditions, as well as plain journal bearings. Wave bearings are fluid film journal bearings with multi-lobed wave patterns around the circumference of the bearing surface. In this software suite, the dynamic coefficients are outputted in a way for easy implementation in a finite element model used in rotor dynamics analysis. The software has a graphical user interface (GUI) for inputting bearing geometry parameters, and uses MATLAB s structure interface for ease of interpreting data. This innovation was developed to provide the stiffness and damping components of wave bearing impedances. The computational method for computing bearing coefficients was originally designed for plain journal bearings and tilting pad bearings. Modifications to include a wave bearing profile consisted of changing the film thickness profile given by an equation, and writing an algorithm to locate the integration limits for each fluid region. Careful consideration was needed to implement the correct integration limits while computing the dynamic coefficients, depending on the form of the input/output variables specified in the algorithm.

Hanford, Amanda; Campbell, Robert

2012-01-01

349

A major synmetamorphic Early Devonian thrust and extensional fault system in the Mid-Norway Caledonides: Key to exhumation of HP and UHP rocks  

Science.gov (United States)

The northern ('Nordoyane') UHP domain of the Western Gneiss Region contains occurences of microdiamonds, coesite and quartz pseudomorphs after coesite, and petrologically based peak P estimates 3-6 GPa. The structure is dominated by post-peak, near orogen-parallel, sub-horizontal, ductile sinistral-shear and top-SW extensional fabrics, overprinted locally by amphibolite-facies mylonites. Thus, earlier features related to subduction and exhumation are greatly obscured, and complicating segmentation was created. Nevertheless, top-SE eclogite-facies fabrics are locally preserved in Nordøyane, that can be equated with subduction and earliest exhumation. Zones preserving evidence of top-NW transport in early extension are also identified. Robust U-Pb zircon chronology indicates peak UHP eclogite-facies crystallization at 415-410 Ma (Early Devonian Lochkovian to Pragian, cf. Kauffmann 2006), followed by pegmatite crystallization at 395 Ma (late Emsian) in neck lines of boudins produced in ductile subhorizontal extension, thus limiting the process to 15-20 million years. In coastal areas north and west of Trondheim, the postulated Agdenes extensional detachment is identified by a major break in titanite U-Pb geochronology. Basement gneisses below contain Mesoproterozoic igneous titanite fully reset at 395Ma, as well as significant development of Devonian pegmatites. Ordovician granitoids of the Støren Nappe of the Upper Allochthon, just above the detachment, contain igneous titanite barely influenced by Devonian recrystallization and no evidence of post-Ordovician melts, implying removal of a significant section on a very- large-scale detachment. Rocks both above and below the detachment are overprinted by the same late, subhorizontal, sinistral ductile extensional fabric, obscuring any fabrics produced during development of the detachment itself. Notably, deep-seated metamorphism overlaps the Late Emsian (403-392 Ma) age of sandstones and conglomerates determined by plant fossils that lie unconformably on parts of the Upper Allochthon. When traced as the base of the Upper Allochthon, the detachment covers a present minimum area of 450 x 180 km. The eastern part of the region in Trollheimen escaped the late strong subhorizontal overprint, and shows this sequence of deformations: 1) Early emplacement of thrust nappes of Lower and Middle Allochthons over Baltican basement with Late Neoproterozoic quartzite cover. 2) Major SE-directed recumbent folding of the entire thrust-imbricated sequence including basement. 3) Major out-of-sequence SE-directed thrusting (Storli thrust) of the recumbent-folded sequence over deeper, less deformed, lower basement gneisses and unconformable Neoproterozoic quartzite cover. This thrust has a minimum transport of 80 km across strike. Upper basement contains boudins of eclogite and garnet-corona gabbro that are lacking in lower basement. With respect to Trollheimen, similar thrust imbrication of basement is documented 190 km NE in the Tømmerås window, 240 km NE in the Grong-Olden culmination, where a minimum of 100 km across-strike transport is demonstrated, and 100 km W at Reksdalshesten. We suggest that crustal imbrication by the Storli and related thrusts, covering a conservatively estimated present minimum area of 400 x 100 km, provided gravitational potential to trigger the overlying Agdenes detachment, leading toward exhumation of a large region of eclogite-bearing rocks.

Robinson, P.; Tucker, R. D.; Terry, M. P.; Kamo, S. L.; Roberts, D.; Gee, D. G.; Butler, J. P.

2012-04-01

350

Development of sputtered techniques for thrust chambers, task 1. [evaluation of filler materials for regeneratively cooled thrust chambers  

Science.gov (United States)

Filler materials proposed for use in the sputter fabrication regeneratively cooled thrust chambers were evaluated. Low melting castable alloys, CERROBEND. CERROCAST, and CERROTRU, slurry applied SERMETEL 481 and flame-sprayed aluminum were investigated as filler materials. Sputter deposition from a cylindrical cathode inverted magnestron was used to apply an OFHC copper closeout layer to filled OFHC copper ribbed-wall cylindrical substrates. The sputtered closeout layer structure was evaluated with respect to filler material contamination, predeposition machining and finishing operations, and deposition parameters. The application of aluminum by flame-spraying resulted in excessiver filler porosity. Though the outgassing from this porosity was found to be detrimental to the closeout layer structure, bond strengths in excess of 10,500 psi were achieved. Removal of the aluminum from the grooves was readily accomplished by leaching in a 7.0 molar solution of sodium hydroxide at 353 K. Of the other filler materials evaluated, CERROTRU was found to be the most suitable material with respect to completely filling the ribbed-wall cylinders and vacuum system compatibility. However, bond contamination resulted in low closeout layer bond strength with the CERROTRU filler. CERROBEND, CERROCAST, and SERMETEL 481 were found to be unacceptable as filler materials.

Mullaly, J. R.; Schmid, T. E.; Hecht, R. J.

1974-01-01

351

Alex the Bear Goes to Child Care  

Medline Plus

Full Text Available ... Quality Child Care Videos Child Care Aware Public Service Announcements Meet Alex the Bear Resources Resources for ... Quality Child Care Videos Child Care Aware Public Service Announcements Meet Alex the Bear Child Care Aware ...

352

Alex the Bear Goes to Child Care  

Medline Plus

Full Text Available ... Alex the Bear Meet Alex the Bear, a new friend of Child Care Aware® Going to child care for the first time or entering a new child care setting can be a daunting experience ...

353

Hunting for 'bears' in the backyard  

Science.gov (United States)

This Micscape Magazine article offers practical hints about how to collect and study tardigrades, or water bears, from mosses in your backyard. It features a general introduction of water bears, a video, and a section of references for further reading.

Walker, Dave; Magazine, Micscape

354

Detecting Wear In Ball Bearings During Operation  

Science.gov (United States)

Strain-gauge signals at harmonics of ball-bearing-cage frequencies signify wear. Brief report describes experiments in continuing effort to interpret vibrations of machinery in terms of wear in ball bearing.

Hine, Michael J.

1988-01-01

355

Rolling Element Bearing Stiffness Matrix Determination (Presentation)  

Energy Technology Data Exchange (ETDEWEB)

Current theoretical bearing models differ in their stiffness estimates because of different model assumptions. In this study, a finite element/contact mechanics model is developed for rolling element bearings with the focus of obtaining accurate bearing stiffness for a wide range of bearing types and parameters. A combined surface integral and finite element method is used to solve for the contact mechanics between the rolling elements and races. This model captures the time-dependent characteristics of the bearing contact due to the orbital motion of the rolling elements. A numerical method is developed to determine the full bearing stiffness matrix corresponding to two radial, one axial, and two angular coordinates; the rotation about the shaft axis is free by design. This proposed stiffness determination method is validated against experiments in the literature and compared to existing analytical models and widely used advanced computational methods. The fully-populated stiffness matrix demonstrates the coupling between bearing radial, axial, and tilting bearing deflections.

Guo, Y.; Parker, R.

2014-01-01

356

Simulation analysis of pressure regulation of hydraulic thrust system on a shield tunneling machine  

Science.gov (United States)

Hydraulic thrust system is an important system in a shield tunneling machine. Pressure regulation of thrust cylinders is the most important function for thrust system during tunnel excavation. In this paper, a hydraulic thrust system is explained, and a corresponding simulation model is carried out in order to study the system characteristics. Pressure regulation of a certain group's cylinders has little influence on regulation of the other groups' cylinders. The influence will not affect the process much during tunnel excavation. Pump displacement may have a greater effect on pressure regulation and oil supply flow rate should be adaptive to the system's demand. A exacting situation is simulated to explain how pressure regulation works during tunnel excavation.

Liu, Zhibin; Xie, Haibo; Yang, Huayong

2011-09-01

357

14 CFR Appendix I to Part 25 - Installation of an Automatic Takeoff Thrust Control System (ATTCS)  

Science.gov (United States)

...Automatic Takeoff Thrust Control System (ATTCS). An ATTCS is defined as the entire automatic system used on takeoff...signals, actuate fuel controls or power levers or...performance, all-engine flight path where,...

2010-01-01

358

Unbalance Response Prediction for Rotors on Ball Bearings Using Speed- and Load-Dependent Nonlinear Bearing Stiffness  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus, an accurate rotordynamic analysis requires that bearing forces corresponding to the actual bearing deflection be utilized. For this work, bearing forces were calculated by COBRA-AHS, a recently developed rolling-element bearing analysis code. Bearing stiffness was found to be a strong function of bearing deflection, with higher deflection producing markedly higher stiffness. Curves fitted to the bearing data for...

Fleming David P.; Poplawski J. V.

2005-01-01

359

Theory of the Ultimate Bearing Capacity Calculation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The traditional formula and calculation method for calculating the ultimate bearing capacity is not scientific. According to the research, the ultimate bearing capacity is equal to the real degree of the material and detection force product. Ultimate bearing capacity is not for the change of detecting the force. On the basis of this understanding, a new theory of the study bearing capacity of rock-soil and new methods is generated.

Chang Yi Wang; Ben Jun Wang; Shu Zun Jiang

2012-01-01

360

Theory of the Ultimate Bearing Capacity Calculation  

Directory of Open Access Journals (Sweden)

Full Text Available The traditional formula and calculation method for calculating the ultimate bearing capacity is not scientific. According to the research, the ultimate bearing capacity is equal to the real degree of the material and detection force product. Ultimate bearing capacity is not for the change of detecting the force. On the basis of this understanding, a new theory of the study bearing capacity of rock-soil and new methods is generated.

Chang Yi Wang

2012-01-01

 
 
 
 
361

Technology development for indigenous water lubricated bearings  

International Nuclear Information System (INIS)

Water Lubricated Bearings (WLB) are used in various mechanisms of fuel handling systems of PHWRs and AHWR. Availability and random failures of these bearings was a major factor in refuelling operations. Indigenous development of these bearings was taken up and 7 types of antifriction bearings in various sizes (totaling 37 variants) for PHWR, AHWR and Dhruva applications were successfully developed. This paper deals with various aspects of WLB development. (author)

362

Journal bearing performance and metrology issues  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: In this paper, a radial clearance of a journal bearings and the metrology of the radial clearance measurement is described.Design/methodology/approach: In this experimental study out-of-roundness and radial clearance of journal bearings were measured with high precision and the impact of their metrology was examined on the specific oil film thickness of the bearing. Some metrological issues were emerged and these should be taken into account when bearings are designed.Findings: An in...

Sharma, S.; Hargreaves, D.; Scott, W.

2009-01-01

363

Oil film pressure in hydrodynamic journal bearings  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Hydrodynamic journal bearings are critical power transmission components that are carrying increasingly high loads because of the increasing power density in various machines. Therefore, knowing the true operating conditions of hydrodynamic journal bearings is essential to machine design. Oil film pressure is one of the key operating parameters describing the operating conditions in hydrodynamic journal bearings. Measuring the oil film pressure in bearings has been a demanding task and theref...

Valkonen, Antti

2009-01-01

364

A Control Approach for Thrust-Propelled Underactuated Vehicles and its Application to VTOL Drones  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A control approach is proposed for a class of underactuated vehicles in order to stabilize reference trajectories either in thrust direction, velocity, or position. The basic modeling assumption is that the vehicle is propulsed via a thrust force along a single body-fixed direction and that it has full torque actuation for attitude control (i.e., a typical actuation structure for aircrafts, Vertical Take-Off and Landing (VTOL) vehicles, submarines, etc.). Additional assumptions on the externa...

Hua, Minh-duc; Hamel, Tarek; Morin, Pascal; Samson, Claude

2009-01-01

365

Tectonic History and Present-Day Deformation in the Zagros Fold-Thrust Belt  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis uses various approaches such as observation of satellite images, field investigations, analogue modeling and GPS measurements to constrain deformation of the basement and sedimentary cover of the Zagros fold-thrust belt in time and space. Focal mechanism solutions of most earthquakes indicate that deformation in the Zagros basement is due to shortening and thickening through numerous thrust faults. However, observations of strike-slip faulting recognized on satellite images imply ...

Hessami, Khaled

2002-01-01

366

Static performance investigation of a skewed-throat multiaxis thrust-vectoring nozzle concept  

Science.gov (United States)

The static performance of a jet exhaust nozzle which achieves multiaxis thrust vectoring by physically skewing the geometric throat has been characterized in the static test facility of the 16-Foot Transonic Tunnel at NASA Langley Research Center. The nozzle has an asymmetric internal geometry defined by four surfaces: a convergent-divergent upper surface with its ridge perpendicular to the nozzle centerline, a convergent-divergent lower surface with its ridge skewed relative to the nozzle centerline, an outwardly deflected sidewall, and a straight sidewall. The primary goal of the concept is to provide efficient yaw thrust vectoring by forcing the sonic plane (nozzle throat) to form at a yaw angle defined by the skewed ridge of the lower surface contour. A secondary goal is to provide multiaxis thrust vectoring by combining the skewed-throat yaw-vectoring concept with upper and lower pitch flap deflections. The geometric parameters varied in this investigation included lower surface ridge skew angle, nozzle expansion ratio (divergence angle), aspect ratio, pitch flap deflection angle, and sidewall deflection angle. Nozzle pressure ratio was varied from 2 to a high of 11.5 for some configurations. The results of the investigation indicate that efficient, substantial multiaxis thrust vectoring was achieved by the skewed-throat nozzle concept. However, certain control surface deflections destabilized the internal flow field, which resulted in substantial shifts in the position and orientation of the sonic plane and had an adverse effect on thrust-vectoring and weight flow characteristics. By increasing the expansion ratio, the location of the sonic plane was stabilized. The asymmetric design resulted in interdependent pitch and yaw thrust vectoring as well as nonzero thrust-vector angles with undeflected control surfaces. By skewing the ridges of both the upper and lower surface contours, the interdependency between pitch and yaw thrust vectoring may be eliminated and the location of the sonic plane may be further stabilized.

Wing, David J.

1994-01-01

367

Design, fabrication and thrust measurement of a micro liquid monopropellant thruster  

Science.gov (United States)

A liquid monopropellant MEMS thruster was designed, fabricated and tested. For application on a nanosatellite for orbit control, a liquid propellant MEMS thruster delivers better performance than a solid thruster. Two issues must be addressed for a liquid monopropellant MEMS thruster: high energy content of the monopropellant to overcome the excessive heat loss associated with the small scale of the thruster, and repeatability of generated thrust force. The present study proposed blending 90?wt% hydrogen peroxide with ethanol at an oxidizer to fuel ratio of 30 to enhance the energy content of the propellant. The thruster structure was constructed using glass layers that were individually patterned by wet etching. The decomposition catalyst was separately prepared by wet impregnation of the active material, Pt, on the gamma alumina pellets and inserted into the thrust chamber before the UV bonding process of the glass layers. The firing test of the assembled MEMS thruster was conducted and thrust was measured both with ethanol blended hydrogen peroxide and pure hydrogen peroxide as a reference monopropellant. The measured thrusts were approximately 30?mN for both 1.7?ml?min?1 flow rate of blended hydrogen peroxide and 2.0?ml?min?1 flow rate of pure hydrogen peroxide. The measured thrust for 1.7?ml?min?1 pure hydrogen peroxide was approximately 24?mN. The measured thrust was 40% less than the design thrust for both monopropellants. The uncertainty of the thrust was less with blended monopropellant than with pure hydrogen peroxide.

Huh, Jeongmoo; Kwon, Sejin

2014-10-01

368

Low-thrust trajectory design and optimization of lunar south pole coverage missions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A framework for designing and optimizing low-thrust trajectories for lunar south pole coverage missions is developed. Such missions may involve three, two, or even one satellite to maintain continuous communications between a lunar ground station and the Earth. Special emphasis is dedicated to single satellite communication links, which involve the design and discovery of novel pole-sitter orbits. Pole-sitters are possible, given the availability of an efficient low-thrust force in the model....

Ozimek, Martin T.

2010-01-01

369

Thrust Enhancement in Hypervelocity Nozzles by Chemical Catalysis  

Science.gov (United States)

In the hypersonic flight regime, the air-breathing supersonic combustion ramjet (scramjet) has been shown to be a viable propulsion system. The current designs of scramjet engines provide performance benefits only up to a Mach number of 14. Performance losses increase rapidly as the Mach number increases. To extend the applicability of scram'jets beyond Mach 14, research is being conducted in the area of inlet and wave drag reduction, skin-friction and heat-transfer reduction, nozzle loss minimization, low-loss mixing, and combustion enhancement. For high Mach number applications, hydrogen is the obvious fuel choice because of its high energy content per unit mass in comparison with conventional fuels. These flight conditions require engines to operate at supersonic internal velocities, high combustor temperatures, and low static pressures. The high static temperature condition enhances the production of radicals such as H and OH, and the low-pressure condition slows the reaction rates, particularly the recombination reactions. High-temperature and low-pressure constraints, in combination with a small residence time, result in a radical-rich exhaust gas mixture exiting the combustor. At high Mach number conditions (due to low residence time), H and OH do not have enough time to recombine ; thus, a significant amount of energy is lost as these high-energy free radical are exhausted. The objective of the present study is to conduct a flowfield analysis for a typical nozzle geometry for NASP-type vehicle to assess for thrust enhancement in hypervelocity nozzles by substituting small amount of phosphine for hydrogen.

Singh, D. J.; Carpenter, Mark H.; Drummond, J. P.

1997-01-01

370

Seismic variability of subduction thrust faults: Insights from laboratory models  

Science.gov (United States)

Laboratory models are realized to investigate the role of interface roughness, driving rate, and pressure on friction dynamics. The setup consists of a gelatin block driven at constant velocity over sand paper. The interface roughness is quantified in terms of amplitude and wavelength of protrusions, jointly expressed by a reference roughness parameter obtained by their product. Frictional behavior shows a systematic dependence on system parameters. Both stick slip and stable sliding occur, depending on driving rate and interface roughness. Stress drop and frequency of slip episodes vary directly and inversely, respectively, with the reference roughness parameter, reflecting the fundamental role for the amplitude of protrusions. An increase in pressure tends to favor stick slip. Static friction is a steeply decreasing function of the reference roughness parameter. The velocity strengthening/weakening parameter in the state- and rate-dependent dynamic friction law becomes negative for specific values of the reference roughness parameter which are intermediate with respect to the explored range. Despite the simplifications of the adopted setup, which does not address the problem of off-fault fracturing, a comparison of the experimental results with the depth distribution of seismic energy release along subduction thrust faults leads to the hypothesis that their behavior is primarily controlled by the depth- and time-dependent distribution of protrusions. A rough subduction fault at shallow depths, unable to produce significant seismicity because of low lithostatic pressure, evolves into a moderately rough, velocity-weakening fault at intermediate depths. The magnitude of events in this range is calibrated by the interplay between surface roughness and subduction rate. At larger depths, the roughness further decreases and stable sliding becomes gradually more predominant. Thus, although interplate seismicity is ultimately controlled by tectonic parameters (velocity of the plates/trench and the thermal regime), the direct control is exercised by the resulting frictional properties of the plate interface.

Corbi, F.; Funiciello, F.; Faccenna, C.; Ranalli, G.; Heuret, A.

2011-06-01

371

14 CFR 29.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 29.623 Section 29.623...Construction General § 29.623 Bearing factors. (a) Except as provided...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

372

14 CFR 23.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 23.623 Section 23.623...Design and Construction § 23.623 Bearing factors. (a) Each part that has...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

373

14 CFR 27.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 27.623 Section 27.623...Construction General § 27.623 Bearing factors. (a) Except as provided...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

374

14 CFR 25.623 - Bearing factors.  

Science.gov (United States)

...2010-01-01 2010-01-01 false Bearing factors. 25.623 Section 25.623...Construction General § 25.623 Bearing factors. (a) Except as provided...to pounding or vibration, must have a bearing factor large enough to provide for...

2010-01-01

375

Developing stochastic model of thrust and flight dynamics for small UAVs  

Science.gov (United States)

This thesis presents a stochastic thrust model and aerodynamic model for small propeller driven UAVs whose power plant is a small electric motor. First a model which relates thrust generated by a small propeller driven electric motor as a function of throttle setting and commanded engine RPM is developed. A perturbation of this model is then used to relate the uncertainty in throttle and engine RPM commanded to the error in the predicted thrust. Such a stochastic model is indispensable in the design of state estimation and control systems for UAVs where the performance requirements of the systems are specied in stochastic terms. It is shown that thrust prediction models for small UAVs are not a simple, explicit functions relating throttle input and RPM command to thrust generated. Rather they are non-linear, iterative procedures which depend on a geometric description of the propeller and mathematical model of the motor. A detailed derivation of the iterative procedure is presented and the impact of errors which arise from inaccurate propeller and motor descriptions are discussed. Validation results from a series of wind tunnel tests are presented. The results show a favorable statistical agreement between the thrust uncertainty predicted by the model and the errors measured in the wind tunnel. The uncertainty model of aircraft aerodynamic coefficients developed based on wind tunnel experiment will be discussed at the end of this thesis.

Tjhai, Chandra

376

Structure, burial history, and petroleum potential of frontal thrust belt and adjacent foreland, southwest Montana.  

Science.gov (United States)

The frontal thrust belt in the Lima area of SW Montana consists of blind (nonsurfacing) thrusts of the Lima thrust system beneath the Lima anticline and the Tendoy thrust sheet to the W. The Tendoy sheet involves Mississippian through Cretaceous rocks of the SW-plunging nose of the Mesozoic Blacktail-Snowcrest uplift that are thrust higher (NE) onto the uplift. The front of the Tendoy sheet W of Lima locally has been warped by later compressive deformation which also involved synorogenic conglomerates of the structurally underlying Beaverhead Formation. To the N, recent extension faulting locally has dropped the front of the Tendoy sheet beneath Quaternary gravels. Rocks of the exposed Tendoy sheet have never been deeply buried, based on vitrinite relectance of = or burial depth is indicated by higher conodont CAI values. W-dipping post-Paleocene extension faults truncate much of the rear part of the Tendoy sheet and also separate the Medicine Lodge sheet from thrust sheets of the Beaverhead Range still farther W. -from Authors

Perry, W.J., Jr.; Wardlaw, B.R.; Bostick, N.H.; Maughan, E.K.

1983-01-01

377

A Computational Study of a New Dual Throat Fluidic Thrust Vectoring Nozzle Concept  

Science.gov (United States)

A computational investigation of a two-dimensional nozzle was completed to assess the use of fluidic injection to manipulate flow separation and cause thrust vectoring of the primary jet thrust. The nozzle was designed with a recessed cavity to enhance the throat shifting method of fluidic thrust vectoring. Several design cycles with the structured-grid, computational fluid dynamics code PAB3D and with experiments in the NASA Langley Research Center Jet Exit Test Facility have been completed to guide the nozzle design and analyze performance. This paper presents computational results on potential design improvements for best experimental configuration tested to date. Nozzle design variables included cavity divergence angle, cavity convergence angle and upstream throat height. Pulsed fluidic injection was also investigated for its ability to decrease mass flow requirements. Internal nozzle performance (wind-off conditions) and thrust vector angles were computed for several configurations over a range of nozzle pressure ratios from 2 to 7, with the fluidic injection flow rate equal to 3 percent of the primary flow rate. Computational results indicate that increasing cavity divergence angle beyond 10 is detrimental to thrust vectoring efficiency, while increasing cavity convergence angle from 20 to 30 improves thrust vectoring efficiency at nozzle pressure ratios greater than 2, albeit at the expense of discharge coefficient. Pulsed injection was no more efficient than steady injection for the Dual Throat Nozzle concept.

Deere, Karen A.; Berrier, Bobby L.; Flamm, Jeffrey D.; Johnson, Stuart K.

2005-01-01

378

Constraints on the tectonics of the Mule Mountains thrust system, southeast California and southwest Arizona  

Science.gov (United States)

The Mule Mountains thrust system crops out discontinuously over a 100-km-strike length in this Blythe-Quartzsite region. Along the thrust system, middle and upper crustal metamorphic and plutonic rocks of Proterozoic and Mesozoic age are thrust N-NE (015??-035??) over a lower plate metamorphic terrane. Stratigraphic, petrologic, and Pb isotopic ties for Jurassic granitoids and for Jurassic(?) and Cretaceous sedimentary rocks across the various parts of the thrust system indicate that related crustal blocks are superposed and preclude it from having large displacements. Deformation occurred under low greenschist facies metamorphic conditions in the upper crust. Movement along the thrust system was probably limited to no more than a few tens of kilometers and occurred between 79??2 Ma and 70??4 Ma. Results suggest that the thrust system forms the southern boundary of the narow zone of Cretaceous intracratonic deformation, and it is one of the last tectonic events in the zone prior to regional cooling. -from Author

Tosdal, R.M.

1990-01-01

379

Thin film superconductor magnetic bearings  

Science.gov (United States)

A superconductor magnetic bearing includes a shaft (10) that is subject to a load (L) and rotatable around an axis of rotation, a magnet (12) mounted to the shaft, and a stator (14) in proximity to the shaft. The stator (14) has a superconductor thin film assembly (16) positioned to interact with the magnet (12) to produce a levitation force on the shaft (10) that supports the load (L). The thin film assembly (16) includes at least two superconductor thin films (18) and at least one substrate (20). Each thin film (18) is positioned on a substrate (20) and all the thin films are positioned such that an applied magnetic field from the magnet (12) passes through all the thin films. A similar bearing in which the thin film assembly (16) is mounted on the shaft (10) and the magnet (12) is part of the stator (14) also can be constructed.

Weinberger, Bernard R. (Avon, CT)

1995-12-26

380

Improvement of journal bearing operation at heavy misalignment using bearing flexibility and compliant liners  

DEFF Research Database (Denmark)

A flexure journal bearing design is proposed that will improve operational behaviour of a journal bearing at pronounced misalignment. Using a thermoelastohydrodynamic model, it is shown that the proposed flexure journal bearing has vastly increased the hydrodynamic performance compared to the stiff bearing when misaligned. The hydrodynamic performance is evaluated on lubricant film thickness, pressure and temperature. Furthermore, the influence of a compliant bearing liner is investigated and it is found that it increases the hydrodynamic performance when applied to a stiff bearing, whereas the liner has practically no influence on the flexure journal bearing's performance.

Thomsen, Kim; Klit, Peder

2012-01-01

 
 
 
 
381

Crustal Shortening in the Himalayan Fold-Thrust Belt, Eastern and Central Bhutan  

Science.gov (United States)

Studies that present retro-deformable balanced cross-sections have estimated the crustal shortening accommodated by the Himalayan fold-thrust belt, but the majority of data has come from the central and western portions of the orogen in Pakistan, northwest Indian, and Nepal. In contrast, in the eastern quarter of the orogen, in Sikkim, Bhutan, and northeast India, only preliminary data on structural geometry and shortening are available. Shortening estimates collected across the full length of the orogen can be used to test predictions of systematic variation, including: 1) shortening should increase from west to east, as a result of post-collisional rotation of India or an eastward increase in convergence and erosion rates, or 2) shortening magnitude should mimic the width of the Tibetan Plateau measured in an arc-normal direction. In this study, we present a new 1:250,000-scale geologic map of eastern and central Bhutan and four balanced cross-sections through the Himalayan fold-thrust belt. Major structural features, from south to north, include: 1) the 2-7 km-thick Subhimalayan thrust sheet above the Main Frontal Thrust and below the Main Boundary Thrust; 2) the upper Lesser Himalayan (LH) duplex system, which repeats 2-3 km-thick thrust sheets of the Neoproterozoic (?) to Cambrian Baxa Group below a roof thrust, the Shumar Thrust, that carries the Paleoproterozoic Daling-Shumar Group in its hanging wall; 3) the lower LH duplex system, which repeats 4-9 km-thick thrust sheets of the Daling-Shumar Group and Ordovician Jaishidanda Formation, with the Main Central Thrust (MCT) acting as the roof thrust; 4) the 5-11 km-thick structurally-lower Greater Himalayan (GH) thrust sheet above the MCT and below the South Tibetan Detachment (STD); 5) Tethyan Himalayan (TH) rock in stratigraphic contact above the lower GH section in central Bhutan and in structural contact above the STD in eastern Bhutan; and 6) the >13 km-thick structurally-higher GH thrust sheet above the Kakhtang Thrust (KT) and below the STD. Cross-sections show 185-292 km of shortening in Subhimalayan and LH rocks, 74-144 km structural overlap across the MCT, and 17-40 km structural overlap across the KT, indicating that a total of 343-397 km of minimum crustal shortening (70-75%) has been accommodated by the Bhutan fold-thrust belt. Our data show an eastward continuation of LH duplexing identified in northwest India, Nepal, and Sikkim, and that this duplexing accommodates between 52-65% of total shortening, and passively folds the overlying GH and TH sections. A compilation of shortening estimates across the orogen does not indicate a systematic west to east increase, and the data more closely approximate the arc-normal width of the Tibetan Plateau. Finally, though precipitation increases from west to east along-strike, a compilation of percent shortening across the orogen does not indicate a systematic west to east increase, which would be predicted if precipitation magnitude exerts a first-order control on orogen width.

Long, S. P.; McQuarrie, N.; Tobgay, T.; Grujic, D.

2009-12-01

382

The BEAR Beamline at Elettra  

International Nuclear Information System (INIS)

The BEAR (Bending Magnet for Emission Absorption and Reflectivity) beamline is installed at the right exit of the 8.1 bending magnet at ELETTRA. The beamline - in operation since January 2003 - delivers linear and circularly polarized radiation in the 5 - 1600 eV energy range. The experimental station is composed of a UHV chamber for reflectivity, absorption, fluorescence and angle resolved photoemission measurements and a UHV chamber for in-situ sample preparation

383

Fault Tolerant Homopolar Magnetic Bearings  

Science.gov (United States)

Magnetic suspensions (MS) satisfy the long life and low loss conditions demanded by satellite and ISS based flywheels used for Energy Storage and Attitude Control (ACESE) service. This paper summarizes the development of a novel MS that improves reliability via fault tolerant operation. Specifically, flux coupling between poles of a homopolar magnetic bearing is shown to deliver desired forces even after termination of coil currents to a subset of failed poles . Linear, coordinate decoupled force-voltage relations are also maintained before and after failure by bias linearization. Current distribution matrices (CDM) which adjust the currents and fluxes following a pole set failure are determined for many faulted pole combinations. The CDM s and the system responses are obtained utilizing 1D magnetic circuit models with fringe and leakage factors derived from detailed, 3D, finite element field models. Reliability results are presented vs. detection/correction delay time and individual power amplifier reliability for 4, 6, and 7 pole configurations. Reliability is shown for two success criteria, i.e. (a) no catcher bearing contact following pole failures and (b) re-levitation off of the catcher bearings following pole failures. An advantage of the method presented over other redundant operation approaches is a significantly reduced requirement for backup hardware such as additional actuators or power amplifiers.

Li, Ming-Hsiu; Palazzolo, Alan; Kenny, Andrew; Provenza, Andrew; Beach, Raymond; Kascak, Albert

2003-01-01

384

Polar Bears International: Wrangel Island, Russia  

Science.gov (United States)

This site describes the ongoing research of the polar bears in the Russian High Arctic. Wrangel Island with neighboring small island, Herald Island, are the key reproductive areas for the Chukchi-Alaskan polar bear population. Marine areas and Wrangel and Herald islands provide optimum foraging habitats for polar bears, and polar bear densities in these marine habitats are high all year round. Approximately 350-500 pregnant female polar bears construct their maternity dens on Wrangel and Herald islands every fall, emerging with their cubs in spring. The research is described in terms of goals and objectives, structure, methods, equipment, staff, and implementations.

385

A motor with superconducting magnetic bearings  

International Nuclear Information System (INIS)

Superconducting bearings may be one of the most promising near term applications of HTSC. For use at liquid nitrogen temperature and below, they offer the advantage of lower energy consumption and higher reliability. Different bearing configurations have been proposed. But in order to substitute for conventional bearings a further increase in the critical current density of the superconductor and improved bearing concepts are necessary. For this it is necessary to take into account the peculiarities of the interaction between permanent magnets and bulk superconductors. As a contribution to this programme we present the model of a motor with superconducting magnetic bearings. (orig.)

386

Fail-Safe Operation of a High-Temperature Magnetic Bearing Investigated for Gas Turbine Engine Applications  

Science.gov (United States)

The Structural Mechanics and Dynamics Branch at the NASA Glenn Research Center has developed a three-axis high-temperature magnetic bearing suspension rig to enhance the safety of the bearing system up to 1000 F. This test rig can accommodate thrust and radial bearings up to a 22.84 cm (9 in.) diameter with a maximum axial loading of 22.25 kN (5000 lb) and a maximum radial loading up to 4.45 kN (1000 lb). The test facility was set up to test magnetic bearings under high-temperature (1100 F) and high-speed (20,000 rpm) conditions. The magnetic bearing is located at the center of gravity of the rotor between two high-temperature grease-packed mechanical ball bearings. The drive-end duplex angular contact ball bearing, which is in full contact, acts as a moment release and provides axial stability. The outboard end ball bearing has a 0.015-in. radial clearance between the rotor to act as a backup bearing and to compensate for axial thermal expansion. There is a 0.020-in. radial air gap between the stator pole and the rotor. The stator was wrapped with three 1-kW band heaters to create a localized hot section; the mechanical ball bearings were outside this section. Eight threaded rods supported the stator. These incorporated a plunger and Bellville washers to compensate for radial thermal expansion and provide rotor-to-stator alignment. The stator was instrumented with thermocouples and a current sensor for each coil. Eight air-cooled position sensors were mounted outside the hot section to monitor the rotor. Another sensor monitored this rotation of the outboard backup bearing. Ground fault circuit interrupts were incorporated into all power amplifier loops for personnel safety. All instrumentation was monitored and recorded on a LabView-based data acquisition system. Currently, this 12-pole heteropolar magnetic bearing has 13 thermal cycles and over 26 hr of operation at 1000 F.

Choi, Benjamin B.; Montague, Gerald T.

2002-01-01

387

Foil bearing research at Penn State  

Science.gov (United States)

Foil journal bearings consist of a compliant metal shell or foil which supports a rigid journal by means of a fluid film. Foil bearings are considered to be a potential alternative to rolling element or traditional rigid surface bearings in cryogenic turbomachinery applications. The prediction of foil bearing performance requires the coupled solution of the foil deflection and the fluid flow in the bearing clearance between the rotor and the foil. The investigations being conducted in the Department of Mechanical Engineering at Penn State are focused in three areas: theoretical prediction of steady state bearing performance, modeling of the dynamic bearing characteristics to determine performance in rotor systems, and experimental verification of analysis codes. The current status and results from these efforts will be discussed.

Carpino, Marc

1993-01-01

388

Wave Journal Bearings Under Dynamic Loads  

Science.gov (United States)

The dynamic behavior of the wave journal bearing was determined by running a three-wave bearing with an eccentrically mounted shaft. A transient analysis was developed and used to predict numerical data for the experimental cases. The three-wave journal bearing ran stably under dynamic loads with orbits well inside the bearing clearance. The orbits were almost circular and nearly free of the influence of, but dynamically dependent on, bearing wave shape. Experimental observations for both the absolute bearing-housing-center orbits and the relative bearing-housing-center-to-shaft-center orbits agreed well with the predictions. Moreover, the subsynchronous whirl motion generated by the fluid film was found experimentally and predicted theoretically for certain speeds.

Hendricks, Robert C.; Dimofte, Florin

2002-01-01

389

Determination of ball bearing dynamic stiffness  

Science.gov (United States)

The dynamic radial stiffness characteristics of rolling element bearings are currently determined by analytical methods that have not been experimentally verified. These bearing data are vital to rotating machinery design integrity because accurate critical speeds and rotor stability predictions are highly dependent on the bearing stiffness. A tester was designed capable of controlling the bearing axial preload, speed, and rotor unbalance. The rotor and support structures were constructed to permit critical speeds that are predominantly determined by a 57 mm test bearing. A curve of calculated critical speed versus stiffness was used to determine the actual bearing stiffness from the empirical data. The results of extensive testing are used to verify analytical predictions, increase confidence in existing bearing computer programs, and to serve as a data base for efforts to correct these programs.

Beatty, R. F.; Rowan, B. F.

1982-01-01

390

Contact Sensors on Ceramic Ball Bearings  

Science.gov (United States)

Integration of micro contact sensors onto a ball bearing is a critical technology necessary for on-line bearing health monitoring in an industrial harsh environment and evaluation of the bearing performance and design. The current planner fabrication methods offered by the MEMS technology restrict the possibility of integrating micro sensor onto a double contoured bearing surface in a more traditional manufacturing environment. We have developed an unique technique to directly fabricate micron-sized pressure and temperature sensors onto a miniature ceramic ball bearing. A complete fabrication process, based on sensor design, surface preparation, optimized sputtering parameters, photolithographic techniques and sensor post-treatment, is described. Pressure and temperature measurement results on a miniature ceramic ball bearing show good correlation with numerical thermal-EHL analysis and good wear resistance. Keywords: Ball Bearing, Thin film Sensor, Pressure sensor, Temperature Sensor, adhesion, wear resistance, Non-developable surface, and thermal-EHL.

Yi, Jia; Just-Agosto, Frederick; Romero, Edwar

2002-01-01

391

??????–????????????????—????????? Evolution and Later Reformation of Early-Middle Jurassic Coal-Bearing Basins in Western Mongolia—A Case Study from the Shinejinst Basin  

Directory of Open Access Journals (Sweden)

Full Text Available ?????????????????????????????–??????????????????????????????????????????????????????–?????????????????????????–???????????????–??????????????????????????????????(??????????????????????????????????????????????????????????????????????–???????????????????????????????????????????????–?????????????????????????????????????????????????????????????Owing to variation of the basement structures, syn-orogenic stress fields and regional tectonic evolution, the Early-Middle Jurassic coal-bearing basins in western Mongoliashow different geometric and kinematic features from the simultaneous molasse basins in easternMongolia. The west segment of the Mongolia-Okhotsk suture is a NW- striking transfer zone, which constraints two transpressional fracture belts developing in western Mongolia. The tran- spressional fracture consists of the oblique thrust with NWW- to nearly E-W-striking, and the NW-orientated oblique thrust-strike slipping fault. The front fault of the oblique thrust controls a coal-forming basin in its lower plate. The ba- sin-controlling fault thrusts north(eastwards, with the basin dynamics resulting from a northward push-compression caused by closure of Tethyan ocean in the end of Early Jurassic in western China and followed continent-continent col- lision. The evolution of the Shinejinst Basin can be divided into three stages, which experiences four episodes of refor- mation after its reversion. The coal-search direction for the Lower-Middle Jurassic large coal fields in western Mongo- lia should be a kind of the South Sub-Basin of Shinejinst Basin, which could be indicated by three characters: 1 the basin-controlling faults being NWW- to nearly E-W-striking oblique thrust as well as NE-striking sinistral shearing fault, 2 to be situated at upper side of normal fault in Early Cretaceous extension, and 3 to be located along the piedmont belt of thrust or foothill of range in the Cenozoic uplifting.

???

2013-08-01

392

Fully Suspended, Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig With Forced Excitation  

Science.gov (United States)

The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig, a significant advancement in the Dynamic Spin Rig (DSR), is used to perform vibration tests of turbomachinery blades and components under rotating and nonrotating conditions in a vacuum. The rig has as its critical components three magnetic bearings: two heteropolar radial active magnetic bearings and a magnetic thrust bearing. The bearing configuration allows full vertical rotor magnetic suspension along with a feed-forward control feature, which will enable the excitation of various natural blade modes in bladed disk test articles. The theoretical, mechanical, electrical, and electronic aspects of the rig are discussed. Also presented are the forced-excitation results of a fully levitated, rotating and nonrotating, unbladed rotor and a fully levitated, rotating and nonrotating, bladed rotor in which a pair of blades was arranged 180 degrees apart from each other. These tests include the bounce mode excitation of the rotor in which the rotor was excited at the blade natural frequency of 144 Hz. The rotor natural mode frequency of 355 Hz was discerned from the plot of acceleration versus frequency. For nonrotating blades, a blade-tip excitation amplitude of approximately 100 g/A was achieved at the first-bending critical (approximately 144 Hz) and at the first-torsional and second-bending blade modes. A blade-tip displacement of 70 mils was achieved at the first-bending critical by exciting the blades at a forced-excitation phase angle of 908 relative to the vertical plane containing the blades while simultaneously rotating the shaft at 3000 rpm.

Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Montague, Gerald; Duffy, Kirsten; Mehmed, Oral; Johnson, Dexter; Jansen, Ralph

2004-01-01

393

Chromatographic (TLC) differentiation of grizzly bear and black bear scats  

Science.gov (United States)

While past work concluded that thin-layer chromatography (TLC) was inadequate for the separation of grizzly (Ursus arctos horribilis) and black bear (U. americanus) scats, our study found differences adequate for species separation. A key was constructed using 19 of 40 data points recorded on each(N)=356 profiles of 178) know-species scat. Accuracy was best for late summer scats (94%). Methods for specimen preparation, analysis, and reading the TLC profiles are discussed. Factors involved in scat variation were tested.

Picton, Harold D.; Kendall, Katherine C.

1994-01-01

394

Structural geology and tectonic significance of foreland thrust belts, Tarim and Junggar basins, northwest China  

Energy Technology Data Exchange (ETDEWEB)

The Kalpin uplift, located on the northwestern margin of the Tarim basin is characterized by a series of thin, southeast-vergent thrust plates modified by strike-slip faults. Each thrust plate repeats a sedimentary sequence consisting of upper Proterozoic through Permian shallow marine to nonmarine carbonates and clastics. Tertiary rocks as young as Neogene are affected by the deformation. The most basinward thrust sheet abuts the Bachu uplift, an older structural feature trending almost perpendicular to the thrusts. Sedimentary rocks as old as late Proterozoic are exposed in the Bachu uplift, which apparently represents a west-vergent Late Silurian to Early Devonian thrust belt. An unconformable Silurian-Devonian contact, the presence of Devonian red beds, and another unconformable contact separating Devonian from Upper Carboniferous strata support the interpretation of a middle Paleozoic deformational event. Another unconformity, at the Carboniferous-Permian boundary, apparently coincides with the time of collision of the Tarim craton with the southern margin of central Asia. The Shihezi fold trend, located in the southern Junggar basin, consists of three lines of surface anticlines trending parallel to the axis of the Urumqi foredeep. A thick sequence of Mesozoic and Cenozoic nonmarine sedimentary rocks accumulated in the growing foredeep. Mesozoic and Paleogene strata are deformed in the southern foldbelt, with Jurassic rocks forming the cores of these thrusted anticlines. The Qigu oil field is located in this southern belt. Deformed Neogene and Quaternary strata are exposed in the thrusted anticlines of the middle and northern foldbelts. The Dushanzi oil field is located in the northern belt. The episodic development of compressional structures in northwestern China documents the accretion of a number of tectonic units to the growing southern margin of central Asia through time.

McKnight, C.L.; Chu, J.; Corroll, A.R.; Hendrix, M.S.; Wang, X.; Graham, S.A.; Liang, Y.H.; Wang, Z.X.; Xiao, X.

1989-03-01

395

Subduction, platform subsidence, and foreland thrust loading: The late Tertiary development of Taranaki Basin, New Zealand  

Science.gov (United States)

Borehole, seismic, and gravity data are used to investigate deformation of continental lithosphere at a Miocene collisional zone. Deformation is manifested in the three following principal forms: a long wavelength (>500 km) platform subsidence ascribed to mantle convection; flexural deformation on a scale of 100-200 km due to crustal thrusting at the eastern boundary of the Taranaki Basin; and a ductile thickening, evident on the deep seismic section of Taranaki Basin, that occurs on a scale of ˜10 km. Evidence for flexural deformation principally comes from the deep seismic section that shows a 150-km wavelength bending of the Moho down toward the major zone of thrusting within the Taranaki Fault Zone. Paleowater depths, however, provide evidence for an initial early Miocene regional subsidence that is too long in wavelength to be explained by flexure induced from thrust sheet loading. Instead, we propose that this broad "platform subsidence" was driven by loading from a deep source, probably subduction-induced flow in the mantle. By ˜22-19 Ma, 1-2 km of water existed over most of the area now occupied by South Taranaki Basin. By ˜19-17 Ma the water depth in the zone east of the Taranaki Basin, the Taranaki Fault Zone, had been replaced by rock due to submarine thrusting and crustal thickening. This build up of submarine topography in the Taranaki Fault Zone constitutes part of the load (25±8 MPa) that created and maintains South Taranaki Basin. Gravity data place further constraints on loading at the thrust front and point to an additional intracrustal loading, equivalent to 15±7 MPa over a 50-km-wide zone. This intracrustal load is explained as being due to thick-skinned thrusting bringing denser, lower-crustal rocks nearer to the surface in the thrust zone. The complete load on the Taranaki foreland is therefore in three parts; the submarine-topographic load, the intracrustal load, and the loading of infilling sediments.

Holt, W. E.; Stern, T. A.

1994-10-01

396

Control Study for Five-axis Dynamic Spin Rig Using Magnetic Bearings  

Science.gov (United States)

The NASA Glenn Research Center (GRC) has developed a magnetic bearing system for the Dynamic Spin Rig (DSR) with a fully suspended shaft that is used to perform vibration tests of turbomachinery blades and components under spinning conditions in a vacuum. Two heteropolar radial magnetic bearings and a thrust magnetic bearing and the associated control system were integrated into the DSR to provide magnetic excitation as well as non-contact mag- netic suspension of a 15.88 kg (35 lb) vertical rotor with blades to induce turbomachinery blade vibration. For rotor levitation, a proportional-integral-derivative (PID) controller with a special feature for multidirectional radial excitation worked well to both support and shake the shaft with blades. However, more advanced controllers were developed and successfully tested to determine the optimal controller in terms of sensor and processing noise reduction, smaller rotor orbits, more blade vibration amplitude, and energy savings for the system. The test results of a variety of controllers that were demonstrated up to 10.000 rpm are shown. Furthermore, rotor excitation operation and conceptual study of active blade vibration control are addressed.

Choi, Benjamin; Johnson, Dexter; Provenza, Andrew; Morrison, Carlos; Montague, Gerald

2003-01-01

397

Conditioning of alpha bearing wastes  

International Nuclear Information System (INIS)

Alpha bearing wastes are generated during the reprocessing of spent fuel, mixed oxide fuel fabrication, decommissioning and other activities. The safe and effective management of these wastes is of particular importance owing to the radiotoxicity and long lived characteristics of certain transuranic (TRU) elements. The management of alpha bearing wastes involves a number of stages which include collection, characterization, segregation, treatment, conditioning, transport, storage and disposal. This report describes the currently available matrices and technologies for the conditioning of alpha wastes and relates them to their compatibility with the other stages of the waste management process. The selection of a specific immobilization process is dependent on the waste treatment state and the subsequent handling, transport, storage and disposal requirements. The overall objectives of immobilization are similar for all waste producers and processors, which are to produce: (a) Waste forms with sufficient mechanical, physical and chemical stability to satisfy all stages of handling, transport and storage (referred to as the short term requirements), and (b) Waste forms which will satisfy disposal requirements and inhibit the release of radionuclides to the biosphere (referred to as the long term requirements). Cement and bitumen processes have already been successfully applied to alpha waste conditioning on the industrial scale in many of the IAEA Member States. Cement sn many of the IAEA Member States. Cement systems based on BFS and pozzolanic cements have emerged as the principal encapsulation matrices for the full range of alpha bearing wastes. Alternative technologies, such as polymers and ceramics, are being developed for specific waste streams but are unlikely to meet widespread application owing to cost and process complexity. The merits of alpha waste conditioning are improved performance in transport, storage and disposal combined with enhanced public perception of waste management operations. These factors need to be assessed in relation to the economic and radiological implications of conditioning. 104 refs, 26 figs, 17 tabs

398

Current Status of Hybrid Bearing Damage Detection  

Science.gov (United States)

Advances in material development and processing have led to the introduction of ceramic hybrid bearings for many applications. The introduction of silicon nitride hybrid bearings into the high pressure oxidizer turbopump, on the space shuttle main engine, led NASA to solve a highly persistent and troublesome bearing problem. Hybrid bearings consist of ceramic balls and steel races. The majority of hybrid bearings utilize Si3N4 balls. The aerospace industry is currently studying the use of hybrid bearings and naturally the failure modes of these bearings become an issue in light of the limited data available. In today s turbine engines and helicopter transmissions, the health of the bearings is detected by the properties of the debris found in the lubrication line when damage begins to occur. Current oil debris sensor technology relies on the magnetic properties of the debris to detect damage. Since the ceramic rolling elements of hybrid bearings have no metallic properties, a new sensing system must be developed to indicate the system health if ceramic components are to be safely implemented in aerospace applications. The ceramic oil debris sensor must be capable of detecting ceramic and metallic component damage with sufficient reliability and forewarning to prevent a catastrophic failure. The objective of this research is to provide a background summary on what is currently known about hybrid bearing failure modes and to report preliminary results on the detection of silicon nitride debris, in oil, using a commercial particle counter.

Dempsey, Paula J.; Certo, Joseph M.; Morales, Wilfredo

2004-01-01

399

Interference Fit Life Factors for Roller Bearings  

Science.gov (United States)

The effect of hoop stresses in reducing cylindrical roller bearing fatigue life was determined for various classes of inner ring interference fit. Calculations were performed for up to seven interference fit classes for each of ten bearing sizes. Each fit was taken at tightest, average and loosest values within the fit class for RBEC-5 tolerance, thus requiring 486 separate analyses. The hoop stresses were superimposed on the Hertzian principal stresses created by the applied radial load to calculate roller bearing fatigue life. The method was developed through a series of equations to calculate the life reduction for cylindrical roller bearings based on interference fit. All calculated lives are for zero initial bearing internal clearance. Any reduction in bearing clearance due to interference fit was compensated by increasing the initial (unmounted) clearance. Results are presented as tables and charts of life factors for bearings with light, moderate and heavy loads and interference fits ranging from extremely light to extremely heavy and for bearing accuracy class RBEC 5 (ISO class 5). Interference fits on the inner bearing ring of a cylindrical roller bearing can significantly reduce bearing fatigue life. In general, life factors are smaller (lower life) for bearings running under light load where the unfactored life is highest. The various bearing series within a particular bore size had almost identical interference fit life factors for a particular fit. The tightest fit at the high end of the RBEC-5 tolerance band defined in ANSI/ABMA shaft fit tables produces a life factor of approximately 0.40 for an inner-race maximum Hertz stress of 1200 MPa (175 ksi) and a life factor of 0.60 for an inner-race maximum Hertz stress of 2200 MPa (320 ksi). Interference fits also impact the maximum Hertz stress-life relation.

Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.

2008-01-01

400

Quaternary deformation of the Mushi thrust-related fold, northeastern margin of the Pamir  

Science.gov (United States)

The Pamir salient defines the northwestern end of the Himalayan-Tibetan orogen and has overthrust the Tajik-Tarim basin to the north by ~300km along a late Cenozoic, south-dipping intracontinental subduction zone (Burtman and Molnar, 1993). The Quaternary deformation of the salient are concentrated on the outer margins: the sinistral Darvaz fault on the northwestern margin, the Trans-Alai thrust on the north margin and the northeast margin. The GPS-based plate tectonic model indicates the convergence rate is of 8-12mm/a in an N-S direction, nearly 1/4 of that between the Indian plate and the Eurasian plate (DeMets et al., 1990; Reigber et al., 2001; Yang et al., 2008). Previous studies focused on the northwestern margin and the north margin revel their spatial distribution, temporal evolution and kinematic patterns (Burtman and Molnar, 1993; Strecker et al., 1995; Arrowsmith and Strecker, 1999; Coutand et al., 2002). Deformed strata and GPS data indicate Quaternary deformations on the northeastern margin are concentrated on the PFT (the Pamir Front Thrust), the foreland thrust system generated by the latest advancing migration of the Pamir salient, whose kinematic patterns are still poor understood. Integrated by the Mushi thrust and the Mushi anticline, the Mushi thrust-related fold located at eastern end of the PFT. Simple structure, well outcrops and evident deformed terraces make it an excellent place to recognize deformation characters and kinematic patterns of the PFT. The Mushi thrust is north-vergent, roughly parallel with the anticline axis, and west part forming several subparallel fault scarps on the terrace surface and east part buried under the late-Quaternary deposits. The Mushi thrust is north-plunging, with a gentle south limb and a steep north limb. Combining field mapping data and neighboring seismic reflection profiles, following the cross-section balance principle, we can confine the Mushi thrust-related fold is a fault propagation fold evaluating from a detachment fold, the total shortening is ~0.7km, and the total uplift is ~1.5km. The shortening of the Mushi thrust-related fold is absorbed by strata folding and slipping along the thrust surface. According to the offset and the age of the terrace surface near the dam of the Kashi power station, the shortening rate of the Mushi thrust is ~0.7mm/a. On the basis of terraces deformation analysis, the Mushi anticline grows through limb rotation in late-Quaternary, and the minimum shortening rate is ~0.6mm/a. Then the total shortening rate is ~1.3mm/a. Although the growth strata cannot be found in the field work, the comfortable contacts between the Atushi formation and the Xiyu formation at both limbs indicate the growth inception of the Mushi thrust-related fold later than the base age of the Xiyu formation, which is ~1.6Ma (Chen et al., 2007). If the shortening rate is constant during growth of the thrust-related fold, the growth inception should be earlier than 0.5-0.6Ma.

Li, T.; Chen, J.; Huang, D. M.; Thompson, J.; Xiao, P. W.; Yuan, D. Z.; Burbank, D. W.

2010-12-01

 
 
 
 
401

Undulating fins produce off-axis thrust and flow structures.  

Science.gov (United States)

While wake structures of many forms of swimming and flying are well characterized, the wake generated by a freely swimming undulating fin has not yet been analyzed. These elongated fins allow fish to achieve enhanced agility exemplified by the forward, backward and vertical swimming capabilities of knifefish, and also have potential applications in the design of more maneuverable underwater vehicles. We present the flow structure of an undulating robotic fin model using particle image velocimetry to measure fluid velocity fields in the wake. We supplement the experimental robotic work with high-fidelity computational fluid dynamics, simulating the hydrodynamics of both a virtual fish, whose fin kinematics and fin plus body morphology are measured from a freely swimming knifefish, and a virtual rendering of our robot. Our results indicate that a series of linked vortex tubes is shed off the long edge of the fin as the undulatory wave travels lengthwise along the fin. A jet at an oblique angle to the fin is associated with the successive vortex tubes, propelling the fish forward. The vortex structure bears similarity to the linked vortex ring structure trailing the oscillating caudal fin of a carangiform swimmer, though the vortex rings are distorted because of the undulatory kinematics of the elongated fin. PMID:24072799

Neveln, Izaak D; Bale, Rahul; Bhalla, Amneet Pal Singh; Curet, Oscar M; Patankar, Neelesh A; MacIver, Malcolm A

2014-01-15

402

Hunting Bears with a Microscope  

Science.gov (United States)

In this online activity, students use lichens and tardigrades (water bears) to investigate their use as bioindicators of key air pollutants. When lichens are exposed to some kinds of air pollutants, especially to sulfur dioxide, the lichens are injured and die. The lichen coverage in a specified area should be a good indicator of the level of air quality. The diversity of the tardigrade species on the lichens will be used to develop another level for bioindication of air quality. Sections of this activity include: introduction, sulfur dioxide and lichens, sampling procedure for lichen coverage, tardigrade sampling, sampling procedure for tardigrades, calculating diversity using the Simpson Diversity Index, interpretation of results, and references.

Case, Steve; Excellence, The N.

403

Current leads and magnetic bearings  

Energy Technology Data Exchange (ETDEWEB)

Since the discovery of high-temperature superconductors (HTSs), Argonne National Laboratory (ANL) has been active in a broad spectrum of activities in developing these materials for applications. Work at every stage of development has involved industrial collaboration in order to accelerate commercialization. While most of the development work has been devoted to improving the properties of current-carrying wires, some effort has been devoted to applications that can utilize HTSs with properties available now or in the near future. In this paper, I discuss advances made at my laboratory in the area of current leads and magnetic bearings.

Hull, J.R.

1993-12-31

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