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Secondary Power System Evaluations for an Unmanned Air Vehicle Configuration

UES, Inc.-Mysore Ramalingam
Wright Patterson AFB-Brian Donovan, Thomas Lamp
Published 1999-08-02 by SAE International in United States
A Thermodynamic analytical program has been developed to help investigate the impact of power system requirements on Tactical Aircraft (TA) and Unmanned Aerial Vehicle (UAV) performance. The Visual Basic for Applications (VBA) program has a user interface that operates in MS-Excel, linking several subsystem analysis programs for execution and data transfer in the power systems analysis. The analytical model is configured to include a UAV encoded propulsion engine cycle code, which allows the inspection of power extraction effects on engine performance. The model was benchmarked by validating the results of the encoded engine program for a TA with an investigation of the separate effects of shaft power extraction and pneumatic bleed air power extraction of power. The selected engine cycle for this purpose was that of the standard TA fighter. The altitude was varied from sea level (SL) to 40,000 ft with a constant Mach number of 0.9. This analysis was then repeated with an encoded UAV engine cycle code to investigate UAV Secondary Power System (SPS) performance in the range of SL to 67000…
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Preliminary Thermodynamic Analysis of Power System Impact on Tactical Aircraft Performance

UES, Inc.-Mysore Ramalingam
Power Division, US Air Force Research Laboratory-Brian Donovan, Edward Durkin, Jerry Beam
Published 1998-04-01 by SAE International in United States
A computerized thermodynamic analytical program is being developed to help investigate the impact of power system requirements on aircraft performance. The Visual Basic for Applications (VBA) program has a user interface that operates in MS-EXCEL, linking several subsystem analysis programs for execution and data transfer in the power systems analysis. The program presently includes an encoded propulsion engine cycle code, which allows the inspection of power extraction effects on engine performance. To validate the results of the encoded engine program, a study was conducted to investigate the separate effects of shaft power extraction and pneumatic bleed. The selected engine cycle was that for a standard tactical fighter, with a flight condition of varied altitude (sea level to 40k-ft.) and constant Mach Number(0.9). As expected, the resultant data showed that the engine performance was more sensitive to pneumatic bleed than to shaft power extraction. Fuel inventory comparisons for a given mission were made for three different secondary power system configurations. The lower fuel consumption of the more-electric secondary power system succinctly reflects the sensitivity of the…
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Rolling Contact Evaluation of Self-Lubricating Ball Bearing Retainer Materials at 482°C and 650°C

UES, Inc.-Hitesh K. Trivedi
Desilube, Inc.-James King
Published 1996-10-01 by SAE International in United States
High temperature lubrication of ceramic and metal surfaces is critical technology for many developing commercial, military, space and aerospace applications. Conventional lubricants will not be effective for many of these applications and hostile bearing environments. An alternative approach to conventional lubrication systems is the use of a self-lubricating retainer. This paper describes rolling contact evaluation of three high temperature self-lubricating bearing retainers fabricated by a hot isostatic pressing (HIP) technique. Rolling contact tests were conducted using a micromelt T-15 tool steel rod-silicon nitride (Si3N4) balls at 482°C and Si3N4 rod-Si3N4 balls at 650°C using a ball-on-rod type rolling fatigue tester. Transfer of lubricating material from retainer to the rod via the balls was observed. The transfer films were analyzed using surface profile traces, Auger Electron Spectroscopy (AES) and Energy Dispersive X-ray (EDAX) analysis. EDAX showed the presence of retainer material on the rods and balls. Two retainers disintegrated completely during the 650°C test. The feasibility of a self-lubricating composite retainer to meet the demanding thermal, oxidative and tribological requirements up to 650°C was shown.
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Effect of Gas Turbine Engine Lubricant Viscosity on Rolling Contact Fatigue (RCF) Life

UES, Inc.-Hitesh K. Trivedi
UDRI-Costandy S. Saba
Published 1996-10-01 by SAE International in United States
The effect of gas turbine engine lubricant viscosity on rolling contact fatigue (RCF) life was studied using four fully formulated synthetic ester based lubricants with the same additive package. The lubricants were evaluated using a modified ball-on-rod type rolling contact fatigue tester for fatigue and wear characteristics, at a maximum hertzian stress of 4.8 GPa and at a speed of 3600 rpm. Weibull analysis and analysis of variance (ANOVA) were performed on the data to determine any significant difference in performance. The lubricant deposits formed at the tribocontact were examined by Auger Electron Spectroscopy (AES). At ambient temperature, viscosity had no effect on both RCF life and wear. However, at 177°C the higher viscosity lubricants formed thicker lubricant film deposits and showed superior fatigue life and reduction in wear rate.
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High Speed Rotating Heat Pipe for Aircraft Applications

UES, Inc.-Rengasamy Ponnappan
Wright-Patterson Air Force Base-John E. Leland
Published 1995-05-01 by SAE International in United States
The rotating heat pipe (RHP) technology is revisited in the context of finding a suitable thermal management solution for the advanced electrical machines such as switched reluctance and permanent magnet types. These machines, with potential applications involving direct mounting to gas turbine main shaft, have very high operating speeds and rotor thermal loads requiring new research studies on the use of RHP technology. The RHP literature data of the 1970's and 1980's are mostly limited to low speeds and off-axis mode tests. In this paper, results of a stainless steel - water on-axis RHP are presented. Also, potential application areas are identified.
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A Modified Ball-on-Rod Type Rolling Contact Fatigue (RCF) Tester for Accelerated Testing of Candidate Lubricants and Bearing Materials

UES, Inc.-Hitesh K. Trivedi, David T. Gerardi
U.S. Air Force-Nelson H. Forster, Lewis Rosado, Garry D. Givan
Published 1995-02-01 by SAE International in United States
This paper describes the modified ball-on-rod type rolling contact fatigue (RCF) tester for accelerated screening of candidate lubricants and materials. The modified tester has the capability to evaluate three different lubrication methods that include liquid lubrication, solid lubrication (both coatings and powders) and vapor phase lubrication. The tribological properties such as friction force, wear volume and rolling contact fatigue life at different temperatures and loading conditions can be obtained. Test results are presented for liquid, coating and powder lubrication methods for VIMVAR M50 bearing steel. Results for the vapor phase test are based on a test conducted using T-15 bearing steel. The simple, expendable test specimen geometry reduces the testing variables and allows for easy post test evaluations.
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A Novel Electronic Cooling Concept

UES, Inc.-R. Ponnappan
Wright-Patterson AFB-J. E. Beam
Published 1992-08-03 by SAE International in United States
Advanced electrical power conditioning systems for the More Electric Aircraft Initiative involve high currents and high voltages with the attendant waste heat generation and cooling problems. The use of solid state switching devices such as MCTs for these systems will result in power dissipation of several hundred Watts per square centimeter. Conventional forced air or low velocity single phase fluid cooling is inadequate to handle the waste heat dissipation of these high power devices. More advanced and innovative methods of cooling which can use fluids available in the aircraft and also easy to package are sought. A new approach called “venturi flow cooling concept” is described. It is shown that localized cooling up to 200 W/cm2 is possible at the venturi throat region where the MCTs can be mounted. PAO coolant with Pr = 56 at 40°C can be conveniently used in aircraft.
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Recrystallization Characteristics of Mo-W-Re-HfC Alloys for Thermionic Applications

UES, Inc.-Bang-Hung Tsao, Mysore L. Ramalingam
Wright Patterson AFB-Brian D. Donovan, Thomas R. Lamp
Published 1992-08-03 by SAE International in United States
Microstructural evolution of a Mo-10W-2Re-0.5HfC alloy was studied in the temperature range of 298 K to 2200 K. The typical characteristics of the microstructure were curly deformation bands, with nucleation at boundaries and subgrain coalescence. The recrystallization temperature of the Mo-10W-2Re-0.5HfC alloy was determined to be near 1950 K, which is comparable with 2125 K for W-4Re-0.35 HfC and 2000 K for W-0.35 HfC. Microhardness tests were performed before and after 1 hour of vacuum annealing and the results indicate that the mechanical strength of Mo-10W-2Re-0.5HfC is lower than that of W-4Re-0.35 HfC or W-0.35 HfC. X-ray diffraction and pole figures indicate that this particular alloy exhibits the primary texture (110) and secondary texture (112) which is normally observed in B.C.C. metals such as Molybdenum. The creep strengths of W-4Re-0.35HfC, TZM-Mo, and W-25Re-30Mo were evaluated and compared at the same stress level. The W-4Re-0.35HfC alloy was found to have the superior creep strength. The creep strength of the Mo-10W-2Re-0.5HfC alloy is comparable to that of TZM-Mo or W-25Re-30Mo making it a suitable alternative for thermionic…
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Orientational Effects on the Performance of a Heat Pipe Coupled Thermionic Converter

UES, Inc.-Mysore L. Ramalingam, Bang-Hung Tsao
Wright Lab.-Timothy J. Young
Published 1992-08-03 by SAE International in United States
The effects of collector heat pipe orientation upon the electrical and thermal performance of a planar thermionic converter were investigated. The high heat throughput of the converter must be carried away from the collector following electrical power production.The planar thermionic converter tested employs chemical-vapor-deposited rhenium on molybdenum electrodes, a separately heated two-phase cesium reservoir, and a radiantly coupled, electric emitter heater. The collector also functions as the evaporator end cap for the liquid sodium heat pipe. The converter fixture places the heat pipe in the reflux mode (evaporator below the condenser) and allows orientational changes of 15, 30, 45, and 60 degrees from the vertical.It was determined that the thermionic output performance is a relatively weak function of orientation angle in the range of 0 to 60°. As the emitter temperature increased, the effect of orientation on the converter performance increases. The trend is that maximum power and output voltage decreases as orientation increases.The performance of the heat pipe was also monitored at various emitter temperatures and orientations. The difference in the temperatures of the…
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Parallel ALPID-3D: A 3-D Metal Forming Program for Parallel Computers

UES, Inc.-Alpesh Amin, Anil Chaudhary
Ohio State Univ.-P. Sadayappan
Published 1992-06-01 by SAE International in United States
A three dimensional nonlinear rigid-viscoplastic metal forming Finite Element (FE) simulation package, ALPID-3D, is being developed to run on distributed memory Multiple Instruction Multiple Data (MIMD) parallel computers. Efficient parallelization of this application requires automatic partitioning of the finite element domain into sub-domains and solving the compute intensive parts of these sub-domains concurrently while minimizing inter-processor communication. Domain decomposition of the FE graph is accomplished by creating an Element Interaction Graph (EIG) and partitioning the EIG into sub-graphs. The most compute intensive part of any FE analysis consists of the generation and solution of FE matrix governing equations. In order to minimize the communication overhead during the solution of these equations, a Coarse Grain Element By Element Preconditioned Conjugate Gradient (CG-EBE-PCG) method is used. Experimentally measured performance on a Meiko i860 system is reported.
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