| Increased Surface Fatigue Lives of Spur Gears by Application of a Coating |
AUG 2003 |
14 pages |
| Authors:
Timothy L. Krantz; Clark V. Cooper; Dennis P. Townsend; Bruce D. Hansen; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
 | Hard coatings have potential for increasing gear surface fatigue lives. Experiments were conducted using gears both with and without a metal- containing, carbon-based coating. The gears were case-carburized AISI 9310 steel spur gears. Some gears were provided with the coating by magnetron sputtering. Lives were evaluated by accelerated life tests. For uncoated gears, all of fifteen tests resulted in fatigue failure before completing 275 million revolutions. For coated gears, eleven ... |
|
| Evaluation of Low-Noise, Improved-Bearing-Contact Spiral Bevel Gears |
JUN 2003 |
27 pages |
| Authors:
Davide G. Lewicki; Ron L. Woods; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Studies to evaluate low-noise, improved-bearing- contact spiral-bevel gears were performed. Experimental tests were performed on the OH-58D helicopter main-rotor transmission in the NASA Glenn 500-hp Helicopter Transmission Test Stand Low-noise, improved-bearing- contact spiral-bevel gears were compared to the baseline OH-58D spiral-bevel gear design, a high-strength design, and previously tested low-noise designs. Noise, vibration, and tooth strain tests were performed. The low-noise, improved-bearing- contact spiral-bevel design showed a decrease in noise ... |
|
| Surface Cracking and Interface Reaction Associated Delamination Failure of Thermal and Environmental Barrier Coatings |
APR 2003 |
12 pages |
| Authors:
Dongming Zhu; Sung R. Choi; Jeffrey I. Eldridge; Kang N. Lee; Robert A. Miller; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| In this paper, surface cracking and interface reactions of a BSAS coating and a multi-layer ZrO2-8wt%Y2O3 and mullite/BSAS/Si thermal and environmental barrier coating system on SiC/SiC ceramic matrix composites were characterized after long-term combined laser thermal gradient and furnace cyclic tests in a water vapor containing environment. The surface cracking was analyzed based on the coating thermal gradient sintering behavior and thermal expansion mismatch stress characteristics under the thermal cyclic ... |
|
| Rotorcraft Damage Tolerance Evaluated by Computational Simulation |
FEB 2000 |
|
| Authors:
Christos C. Chamis; Levon Minnetyan; Frank Abdi; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
 | An integrally stiffened graphite/epoxy composite rotorcraft structure is evaluated via computational simulation. A computer code that scales up constituent micromechanics level material properties to the structure level and accounts for all possible failure modes is used for the simulation of composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulation. Design implications with regard to defect and damage tolerance of integrally stiffened composite ... |
|
| Effects of High Temperature Argon Heat Treatment on Tensile Strength and Microstructure of BN/SiC Coated SiC Fiber Preforms |
JUN 1999 |
15 pages |
| Authors:
Ramalrishna T. Bhatt; Yuan L. Chen; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Preforms of BN/SiC coated Hi-Nicalon and Sylramic SiC fibers were heat treated under 0.1 MPa argon pressure between 1000 deg to 1800 deg C for 1 and 100h. The effects of high temperature exposure on physical dimensions, weight, room temperature tensile strength, and microstructure of preforms have been studied. Both preforms showed shrinkage and weight loss, and microstructural changes beyond 1000 deg C. After 100 hr exposure, the Hi-Nicalon preforms ... |
|
| Pressure Balanced, Low Hysteresis, Finger Seal Test Results |
JUN 1999 |
17 pages |
| Authors:
Gul K. Arora; Margaret P. Proctor; Bruce M. Steinetz; Irebert R. Delgado; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| The finger seal is a revolutionary new technology in air to air sealing for secondary flow control and gas path sealing in gas turbine engines. Though the seal has been developed for gas turbines, it can be easily used in any machinery where a high pressure air cavity has to be sealed from a low pressure air cavity, for both static and rotating applications. This seal has demonstrated air leakage ... |
|
| A Preliminary Study on the Vapor/Mist Phase Lubrication of a Spur Gearbox |
FEB 1999 |
14 pages |
| Authors:
Wilfredo Morales; Robert F. Handschuh; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Organophosphates have been the primary compounds used in vapor/mist phase lubrication studies involving ferrous bearing material. Experimental results have indicated that the initial formation of an iron phosphate film on a rubbing ferrous surface, followed by the growth (by cationic diffusion) of a lubricious pyrophosphate-type coating over the iron phosphate, is the reason organophosphates work well as vapor/mist phase lubricants. Recent work, however, has shown that this mechanism leads to ... |
|
| Three-Dimensional Gear Crack Propagation Studies |
DEC 1998 |
15 pages |
| Authors:
David G. Lewicki; Ashok D. Sane; Raymond J. Drago; Paul A. Wawrzynek; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Three-dimensional crack growth simulation was performed on a split- tooth gear design using boundary element modeling and linear elastic fracture mechanics. Initial cracks in the fillet of the teeth produced stress intensity factors of greater magnitude (and thus, greater crack growth rates) than those in the root or groove areas of the teeth. Crack growth simulation was performed on a case study to evaluate crack propagation paths. Tooth fracture was ... |
|
| A Framework for a Supervisory Expert System for Robotic Manipulators with Joint-Position Limits and Joint-Rate Limits |
DEC 1998 |
22 pages |
| Authors:
Arthur G. Mutambara; Jonathan Litt; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| This report addresses the problem of path planning and control of robotic manipulators which have joint-position limits and joint-rate limits. The manipulators move autonomously and carry out variable tasks in a dynamic, unstructured and cluttered environment. The issue considered is whether the robotic manipulator can achieve all its tasks, and if it cannot, the objective is to identify the closest achievable goal. This problem is formalized and systematically solved for ... |
|
| A Framework for a Supervisory Expert System for Robotic Manipulators with Joint-Position Limits and Joint-Rate Limits. |
DEC 1998 |
|
| Authors:
A. Mutambara; J. Litt; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| This report addresses the problem of path planning and control of robotic manipulators which have joint-position limits and joint-rate limits. The manipulators move autonomously and carry out variable tasks in a dynamic, unstructured and cluttered environment. The issue considered is whether the robotic manipulator can achieve all its tasks, and if it cannot, the objective is to identify the closest achievable goal. This problem is formalized and systematically solved for ... |
|
| Model-Based Fault Diagnosis for Turboshaft Engines |
NOV 1998 |
12 pages |
| Authors:
Michael D. Green; Ahmet Duyar; Jonathan S. Litt; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Tests are described which, when used to augment the existing periodic maintenance and pre-flight checks of T700 engines, can greatly improve the chances of uncovering a problem compared to the current practice. These test signals can be used to expose and differentiate between faults in various components by comparing the responses of particular engine variables to the expected. The responses can be processed on-line in a variety of ways which ... |
|
| Neural Network-Based Sensor Validation for Turboshaft Engines |
NOV 1998 |
13 pages |
| Authors:
James C. Moller; Jonathan S. Litt; Ten-Huei Guo; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Sensor failure detection, isolation, and accommodation using a neural network approach is described. An autoassociative neural network is configured to perform dimensionality reduction on the sensor measurement vector and provide estimated sensor values. The sensor validation scheme is applied in a simulation of the T700 turboshaft engine in closed loop operation. Performance is evaluated based on the ability to detect faults correctly and maintain stable and responsive engine operation. The ... |
|
| Simulation of Crack Propagation in Engine Rotating Components Under Variable Amplitude Loading |
OCT 1998 |
20 pages |
| Authors:
P. J. Bonacuse; L. J. Ghosn; J. Telesman; A. M. Calomino; P. Kantzos; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| The crack propagation life of tested specimens has been repeatedly shown to strongly depend on the loading history. Overloads and extended stress holds at temperature can either retard or accelerate the crack growth rate. Therefore, to accurately predict the crack propagation life of an actual component, it is essential to approximate the time loading history. In military rotorcraft engine applications, the loading profile (stress amplitudes, temperature, and number of excursions) ... |
|
| Wave Turbine Analysis Tool Development |
JUL 1998 |
18 pages |
| Authors:
Gerard E. Welch; Daniel E. Paxson; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A quasi-one-dimensional (Q-1-D) computational fluid dynamic solver, previously developed and validated for pressure-exchanger wave rotors, is extended in the present work to include the blade forces of power producing wave rotors (i.e., wave turbines). The accuracy of the single-passage Q-1-D solver is assessed relative to two two-dimensional solvers: a single-passage code and a multi-block stator/rotor/stator code. Comparisons of computed results for inviscid, steady and unsteady flows in passage geometries typical ... |
|
| Experimental Performance of a Micromachined Heat Flux Sensor |
APR 1998 |
16 pages |
| Authors:
S. Stefanescu; R. G. DeAnna; M. Mehregany; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Steady-state and frequency response calibration of a microfabricated heat-flux sensor have been completed. This sensor is batch fabricated using standard, micromachining techniques, allowing both miniaturization and the ability to create arrays of sensors and their corresponding interconnects. Both high-frequency and spatial response is desired, so the sensors are both thin and of small cross-sectional area. Thin-film, temperature-sensitive resistors are used as the active gauge elements. Two sensor configurations are investigated: ... |
|
| New Intense Light Source: Use of Dielectric Solids to Power Thermophotovoltaic Electric Generators and to Pump Lasers |
13 FEB 98 |
67 pages |
| Authors:
L. G. DeShazer; A. S. Kushch; K. C. Chen; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A new light source using dielectric solids has been developed to power thermophotovoltaics (TPV) and to pump lasers. The light source is a refractory solid emitter heated to relatively high temperature by combustion. The dielectric solid was chosen to have selective thermal emission with nearly narrowband emission peaked at various visible and IR wavelengths. The combination of the selective emitter with an optical waveguide is called a 'superemissive light pipe" ... |
|
| Development of Gear Technology and Theory of Gearing |
DEC 1997 |
120 pages |
| Authors:
Faydor L. Litvin; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| This book presents recent developments in the theory of gearing and the modifications in gear geometry necessary to improve the conditions of meshing. Highlighted are low-noise gear drives that have a stable contact during meshing and a predesigned parabolic transmission error function that can handle misalignment during operation without sacrificing the low-noise aspects of operation. This book also provides a comprehensive history of the development of the theory of gearing ... |
|
| Measurements of Heat Transfer, Flow, and Pressures in a Simulated Turbine Blade Internal Cooling Passage |
DEC 97 |
25 pages |
| Authors:
Louis M. Russell; Douglas R. Thurman; Philip E. Poinsatte; Steven A. Hippensteele; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| An experimental study was made to obtain quantitative information on heat transfer, flow, and pressure distribution in a branched duct test section that had several significant features of an internal cooling passage of a turbine blade. The objective of this study was to generate a set of experimental data that could be used for validation of computer codes that would be used to model internal cooling. Surface heat transfer coefficients ... |
|
| Determination of Creep Behavior of Thermal Barrier Coatings Under Laser Imposed Temperature and Stress Gradients |
NOV 97 |
46 pages |
| Authors:
Dongming Zhu; Robert A. Miller; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| In the present study, a laser sintering/creep technique has been established to quantitatively determine the creep behavior of thermal barrier coatings under steady state high heat flux/high thermal gradient conditions. An approach is proposed to separate the strong influence of stress relaxation, based on the deduced strain rate changes with respect to time and temperature during testing. For a plasma sprayed zirconia-8wt.% yttria ceramic coating, a large primary creep strain ... |
|
| Compliant Metal Enhanced Convection Cooled Reverse-Flow Annular Combustor |
JUN 1994 |
26 pages |
| Authors:
Marc D. Paskin; Waldo A. Acosta; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A joint Army/NASA program was conducted to design, fabricate, and test an advanced, reverse-flow, small gas turbine combustor using a compliant metal enhanced (CME) convection wall cooling concept. The objectives of this effort were to develop a design method (basic design data base and analysis) for the CME cooling technique and then demonstrate its application to an advanced cycle, small, reverse-flow combustor with 3000 deg F (1922 K) burner outlet ... |
|
| Evaluation of an Oil-Debris Monitoring Device for Use in Helicopter Transmissions |
AUG 1992 |
20 pages |
| Authors:
David G. Lewicki; Donald M. Blanchette; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Experimental tests were performed on an OH-58A helicopter main-rotor transmission to evaluate an oil-debris monitoring device (ODMD). The tests were performed in the NASA 500-hp Helicopter Transmission Test Stand. Five endurance tests were run as part of a U.S. Navy/NASA/Army advanced lubricants program. The tests were run at 100-percent design speed, 117-percent design torque, and 121 deg C (250 deg F) oil inlet temperature. Each test lasted between 29 and ... |
|
| Multi-Megawatt Inverter/Converter Technology for Space Power Applications |
01 JAN 92 |
13 pages |
| Authors:
I. T. Myers; B. D. Baumann; R. Kraus; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Large power conditioning mass reductions will be required to enable megawatt power systems envisioned by the Strategic Defense Initiative, the Air Force and NASA. Phase I of a proposed two phase interagency program has been completed to develop an 0.1 kg/kW DC/DC converter technology base for these future space applications. Three contractors, Hughes, General Electric (GE), and Maxwell were Phase I contractors in a competitive program to develop a megawatt ... |
|
| Low-Density, High-Strength Intermetallic Matrix Composites by XD(TM) synthesis |
01 JAN 91 |
101 pages |
| Authors:
K. S. Kumar; M. S. Dipietro; S. A. Brown; J. D. Whittenberger; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| There is an increasing need for lightweight high performance materials in today's aerospace arena. High temperature engine designs, for example, require engine materials with elevated temperature strength, creep resistance, damage tolerance, oxidation resistance, and low density. Ordered intermetallics are considered potential alternatives to superalloys because they exhibit many of these properties. A major problem with most ordered alloys is their tendency toward inherently low ductility. The reasons can be quite ... |
|
| Summary and Evaluation of the Strategic Defense Initiative Space Power Architecture Study |
01 MAR 89 |
419 pages |
| Authors:
M. Edenburn; J. M. Smith; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| The Space Power Architecture Study (SPAS) identified and evaluated power subsystem options for multimegawatt electric (MMWE) space based weapons and surveillance platforms for SDI applications. Steady state requirements of <1 MMWE are adequately covered by the SP-100 nuclear space power program and hence were not addressed in the SPAS. Four steady state power systems <1 MMWE were investigated with little difference between them on a mass basis. The majority of ... |
|
| Refractory Metal Alloys and Composites for Space Power Systems |
09 APR 1988 |
33 pages |
| Authors:
Joseph R. Stephens; Donald W. Petrasek; Robert H. Titran; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Space power requirements for future NASA and other United States missions will range from a few kilowatts to megawatts of electricity. Maximum efficiency is a key goal of any power system in order to minimize weight and size so that the space shuttle may be used a minimum number of times to put the power supply into orbit. Nuclear power has been identified as the primary power source to meet ... |
|
| Thermo-Oxidatively Stable Condensation Polyimides Containing 1,1,1- Triaryl-2,2,2-Trifluoroethane Dianhydride and Diamine Monomers |
JUL 87 |
|
| Authors:
William B. Alston; Roy F. Gratz; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Nine new condensation polyimides containing the trifluorophenylethylidene linkage were synthesized by the amic-acid route. Several other polyimides, including some with the hexafluoroisopropylidene linkage, were also prepared as controls. Amic-acid solutions were characterized by determining their inherent viscosities prior to thermal conversion into polyimide films. Glass transition temperatures (Tg), thermogravimetric analysis (TGA), and isothermal weight loss data (at 316 C, 371 C, 371 C under 0.5 MPa air pressure) were obtained ... |
|
| Composite Grid and Finite-Volume LU (Lower-Upper) Implicit Scheme for Turbine Flow Analysis |
JUN 87 |
|
| Authors:
Yung K. Choo; Seokkwan Yoon; Kestutis C. Civinskas; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A composite grid was generated in an attempt to improve grid quality for a typical turbine blade with large camber in terms of mesh control, smoothness, and orthogonality. This grid consists of the C-grid in the immediate vicinity of the blade and the H-grid in the upstream region and in the middle of the blade passage between the C-grids. It provides good boundary layer resolution around the leading-edge region for ... |
|
| Vibration Characteristics of OH-58A Helicopter Main Rotor Transmission |
APR 87 |
|
| Authors:
David G. Lewicki; John J. Coy; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration ... |
|
| Viscous Analyses for Flow through Subsonic and Supersonic Intakes, |
MAR 1987 |
|
| Authors:
Louis A. Povinelli; Charles E. Towne; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A parabolized Navier-Stokes code was used to analyze a number of diffusers typical of a modern inlet design. The effect of curvature of the diffuser centerline and transitioning cross sections was evaluated to determine the primary cause of the flow distortion in the duct. Results are presented for S-shaped intakes with circular and transitioning cross sections. Special emphasis is placed on verification of the analysis to accurately predict distorted flow ... |
|
| Summary of Investigations of Engine Response to Distorted Inlet Conditions, |
MAR 1987 |
|
| Authors:
Thomas J. Biesiadny; Willis M. Braithwaite; Ronald H. Soeder; Mahmood Abdelwahab; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A survey is presented of experimental and analytical experience of the NASA Lewis Research Center in engine response to inlet temperature and pressure distortions. There has been a continuing NASA effort over the past decade and a half to improve the understanding of the effects of inlet distortion on engine performance, particularly on the compression system performance. Results of experimental investigations and analytical modeling work at NASA are reviewed together ... |
|
| Shock Structure Measured in a Transonic Fan Using Laser Anemometry, |
MAR 1987 |
|
| Authors:
Jerry R. Wood; Anthony J. Strazisar; P. S. Simonyi; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Shock structure measurements acquired in a low aspect ratio transonic fan rotor are presented and analyzed. The rotor aspect ratio in 1.56 and the design tip relative Mach number is 1.38. the rotor flowfield was surveyed at near maximum efficiency and near still operating conditions. Intra-blade velocity measurements acquired with a laser fringe anemometer on blade-to-blade planes in the supersonic region from 10 to 60 percent span are presented. The ... |
|
| APS-Workshop on Characterization of MMIC (Monolithic Microwave Integrated Circuit) Devices for Array Antenna, |
FEB 1987 |
|
| Authors:
Jerry Smetana; Raj Mittra; Nick Laprade; Bryan Edward; Amir Zaghloul; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| The IEEE AP-S ADCOM is attempting to expand its educational, tutorial and information exchange activities as a further benefit to all members. To this end, ADCOM will be forming specialized workshops on topics of interest to its members. The first such workshop on Characterization and Packaging of MMIC Devices for Array Antennas was conceived. The workshop took place on June 13, 1986 as part of the 1986 International Symposium sponsored ... |
|
| A Design Concept for an MMIC (Monolithic Microwave Integrated Circuit) Microstrip Phased Array. |
FEB 1987 |
|
| Authors:
Richard Q. Lee; Jerry Smetana; Roberto Acosta; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A conceptual design for a microstrip phased array with monolithic microwave integrated circuit (MMIC) amplitude and phase controls is described. The MMIC devices used are 20 GHz variable power amplifiers and variable phase shifters recently developed by NASA contractors for applications in future Ka band advanced satellite communication antenna systems. The proposed design concept is for a general NxN element array of rectangular lattice geometry. Subarray excitation is incorporated in ... |
|
| Swept Frequency Technique for Dispersion Measurement of Microstrip Lines. |
FEB 1987 |
|
| Authors:
Richard Q. Lee; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity ... |
|
| A Method for Calculating Turbulent Boundary Layers and Losses in the Flow Channels of Turbomachines |
87 |
|
| Authors:
Lawrence F. Schumann; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| An interactive inviscid core flow boundary layer method is presented for the calculation of turbomachine channel flows. For this method, a one- dimensional inviscid core flow is assumed. The end wall and blade surface boundary layers are calculated using an integral entrainment method. The boundary layers are assumed to be collateral and thus are two-dimensional. The boundary layer equations are written in a streamline coordinate system. The streamwise velocity profiles ... |
|
| Automated Acoustic Intensity Measurements and the Effect of Gear Tooth Profile on Noise |
87 |
|
| Authors:
William J. Atherton; Adam Pintz; David G. Lewicki; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Acoustic intensity measurements were made at NASA Lewis Research Center on a spur gear test apparatus. The measurements were obtained with the Robotic Acoustic Intensity Measurement System developed by Cleveland State University. This system provided dense spatial positioning, and was calibrated against a high quality acoustic intensity system. The measured gear noise compared gearsets having two different tooth profiles. The tests evaluated the sound field of the different gears for ... |
|
| Generation of a Composite Grid for Turbine Flows and Consideration of a Numerical Scheme |
NOV 86 |
|
| Authors:
Y. Choo; S. Yoon; C. Reno; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A composite grid was generated for flows in turbines. It consisted of the C-grid (or O-grid) in the immediate vicinity of the blade and the H-grid in the middle of the blade passage between the C-grids and in the upstream region. This new composite grid provides better smoothness, resolution, orthogonality than any single grid for a typical turbine blade with a large camber and rounded leading and trailing edges. The ... |
|
| New Generation Methods for Spur, Helical, and Spiral-Bevel Gears |
NOV 86 |
|
| Authors:
F. L. Litvin; W. J. Tsung; J. J. Coy; R. F. Handschuh; C. B. Tsay; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Research was directed at finding new methods for generating spur, helical, and spiral-bevel gears that would provide conjugate gear tooth surfaces and localized bearing contact and would reduce kinematic errors (gear noise) caused by gear misalignment. Tooth contact analysis (TCA) computer programs have been developed for these gears. These programs make it possible to simulate gear meshing and bearing contact and to investigate the influence of gear misalignment on kinematic ... |
|
| Laser Fringe Anemometry for Aero Engine Components, |
NOV 1986 |
|
| Authors:
Anthony J. Strazisar; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Advances in flow measurement techniques in turbomachinery continue to be paced by the need to obtain detailed data for use in validating numerical predictions of the flowfield and for use in the development of empirical models for those flow features which cannot be readily modelled numerically. This paper reviews the key issues which are involved when considering the application of laser anemometry to the measurement of turbomachinery flowfields. Aspects of ... |
|
| Combined Fringe and Fabry-Perot Laser Anemometer for Three Component Velocity Measurements in Turbine Stator Cascade Facility, |
NOV 1986 |
|
| Authors:
Richard G. Seasholtz; Louis J. Goldman; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| A laser anemometer is described that was developed for use in a 508 mm diameter annular turbine stator cascade facility. All three velocity components are measured through a single restricted optical port, both within the stator vane row and downstream of the vanes. The measurements are made through a cylindrical window in the casing that matches the tip radius of the cascade. The stator tested has a contoured hub endwall ... |
|
| Beam-Modulation Methods in Quantitative and Flow-Visualization Holographic Interferometry, |
NOV 1986 |
|
| Authors:
Arthur J. Decker; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| This report discusses heterodyne holographic interferometry and time-average holography with a frequency shifted reference beam. Both methods will be used for the measurement and visualization of internal transonic flows, where the target facility is reviewed. Measurements using heterodyne holographic interferometry are presented. Performance of the laser required for time-average holography of time-varying transonic flow is discussed. |
|
| The Effect of Cr, Co, Al, Mo, and Ta on a Series of Cast Ni-Base Superalloys on the Stability of an Aluminide Coating During Cyclic Oxidation in Mach 0.3 Burner Rig, |
OCT 1986 |
|
| Authors:
I. Zaplatynsky; C. A. Barrett; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-base gamma/gamma prime superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on full 2(super 5)-fractional statistical design supplemented by 10 star point alloys ... |
|
| Micromechanisms of Thermomechanical Fatigue-A Comparison With Isothermal Fatigue |
11 JUN 86 |
|
| Authors:
Robert C. Bill; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Thermomechanical Fatigue (TMF) experiments were conducted on Mar-M 200, B-1900, and PWA-1480 (single crystal) over temperature ranges representative of gas turbine airfoil environments. The results were examined from both a phenomenological basis and a micromechanistic basis. Depending on constituents present in the superalloy system, certain micromechanisms dominated the crack initiation process and significantly influenced the TMF lives as well as sensitivity of the material to the type of TMF cycle ... |
|
| Predicted Effect of Dynamic Load on Pitting Fatigue Life for Low- Contact-Ratio Spur Gears |
JUN 86 |
|
| Authors:
David G. Lewicki; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| How dynamic load affects the surface pitting fatigue life of external spur gears was predicted by using NASA computer program TELSGE. Parametric studies were performed over a range of various gear parameters modeling low- contact-ratio involute spur gears. In general, gear life predictions based on dynamic loads differed significantly from those based on static loads, with the predictions being strongly influenced by the maximum dynamic load during contact. Gear mesh ... |
|
| Small Gas Turbine Combustor Experimental Study--Compliant Metal/Ceramic Liner and Performance Evaluation |
JUN 86 |
16 pages |
| Authors:
Waldo A. Acosta; Carl T. Norgren; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Combustor research relating to the development of fuel efficient small gas turbine engines capable of meeting future commercial and military aviation needs is currently underway at NASA Lewis. As part of this combustor research, a basic reverse-flow combustor has been used to investigate advanced liner wall cooling techniques. Liner temperature, performance, and exhaust emissions of the experimental combustor utilizing compliant metal/ceramic liners were determined and compared with three previously reported ... |
|
| COMPUTATIONAL ENGINE STRUCTURAL ANALYSIS |
JUN 86 |
|
| Authors:
Christos C. Chamis; Robert H. Johns; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| a significant research activity at the nasa lewis research center is the computational simulation of complex multidisciplinary engine structural problems. this simulation is performed using computational engine structural analysis (cesa) which consists of integrated multidisciplinary computer codes in conjunction with computer post-processing for problem-specific application. a variety of the computational simulations of specific cases are described in some detail in this paper. these case studies include (1) aeroelastic behavior of ... |
|
| COMPUTATIONAL SIMULATION OF PROGRESSIVE FRACTURE IN FIBER COMPOSITES |
MAY 86 |
|
| Authors:
Christos C. Chamis; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| computational methods for simulation and predicting progressive fracture in fiber composite structures are presented. these methods are integrated into a computer code of modular form. the modules include composite mechanics, finite element analysis, and fracture criteria. the code is used to computationally simulate progressive fracture in composite laminates with and without defects. the simulation tracks the fracture progression in terms of modes initiating fracture, damage growth, and imminent global (catastrophic) ... |
|
| FIBER COMPOSITE SANDWICH THERMOSTRUCTURAL BEHAVIOR: COMPUTATIONAL SIMULATION |
MAY 86 |
|
| Authors:
C. C. Chamis; R. A. Aiello; P. L. N. Murthy; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| several computational levels of progressive sophistication/ simplification are described to computationally simulate composite sandwich hygral, thermal, and structural behavior. the several computational levels of sophistication include: (1) three-dimensional detailed finite element modeling of the honeycomb, the adhesive and the composite faces; (2) three-dimensional finite element modeling of the honeycomb assumed to be an equivalent continuous, homogeneous medium the adhesive and the composite faces; (3) laminate theory simulation where the honeycomb ... |
|
| CONCEPTS FOR INTERRELATING ULTRASONIC ATTENUATION, MICROSTRUCTURE, AND FRACTURE TOUGHNESS IN POLYCRYSTALLINE SOLIDS |
MAY 86 |
|
| Authors:
Alex Vary; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| conceptual models are advanced for explaining and predicting empirical correlations found between ultrasonic measurements and fracture toughness of polycrystalline solids. the models lead to insights concerning microstructural factors governing fracture processes and associated stress wave interactions. analysis of the empirical correlations suggested by the models indicates that, in addition to grain size and shape, grain boundary reflections, elastic anisotropy, and dislocation damping are factors that underlie both fracture toughness and ... |
|
| Computational Simulation of Progressive Fracture in Fibre Composites, |
MAY 1986 |
|
| Authors:
C. C. Chamis; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
|
| Computational methods for simulating and predicting progressive fracture in fiber composite structures are presented. These methods are integrated into a computer code of modular form. The modules include composite mechanics, finite element analysis, and fracture criteria. The code is used to computationally simulate progressive fracture in composite laminates with and without defects. The simulation tracks the fracture progression in terms of modes initiating fracture, dmaage growth, and imminent global (catastrophic) ... |
|
Reports by Corporate Author
