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This paper presents a brief overview and technical highlights of general aviation (g/a) propulsion research efforts and studies which have been underway at NASA's Lewis Research Center (LeRC) for the past several years. The review covers near-term improvements for current-type piston engines, as well as studies and limited corroborative research on several advanced g/a engine concepts, including diesels, small turboprops and both piston and rotary stratified-charge engines. Also described is basic combustion research, cycle modeling and diagnostic instrumentation work that will be required to make the new engines a reality. The discussion emphasizes the most recently-completed studies and the basic underlying research work, which have not been reported previously.

This paper presents a brief overview and technical highlights of the research efforts and studies on rotary engines over the last several years at the NASA Lewis Research Center. The review covers the test results obtained from turbocharged rotary engines and preliminary results from a high performance single-rotor engine. Combustion modeling studies of the rotary engine and the use of a Laser Doppler Velocimeter to confirm the studies are discussed. An in-house program in which a turbocharged rotary engine was installed in a Cessna Skymaster for ground test studies is also covered. Details are presented on single-rotor stratified-charge rotary engine research efforts, both in-house and on contract.

The National Aeronautics and Space Administration (NASA), Lewis Research Center (LeRC) is responsible for the development, fabrication, and assembly of the electric power system (EPS) for the Space Station Freedom (SSF). The Power Management and Distribution (PMAD) Systems Testbed was assembled to support the design and early evaluation of SSF EPS operating concepts. The PMAD Systems Testbed represents a portion of the SSF EPS, containing intelligent switchgear, power conditioning devices, and the EPS Controllers. The PMAD Systems Testbed facility is discussed, including the power sources and loads available. A description of the PMAD Data System (PDS) is presented. The PDS controls the testbed facility hardware, monitors and records the EPS control data bus and external data. The external data includes testbed voltages and currents along with facility temperatures, pressures, and flow rates. Transient data is collected utilizing digital oscilloscopes.

Two types of turning vane airfoils (a controlled-diffusion shape and a circular-arc shape) have been evaluated in the high-speed and fan-drive corners of a 0.1-scale model of NASA Lewis Research Center's proposed Altitude Wind Tunnel. The high-speed corner was evaluated with and without a simulated engine exhaust removal scoop. The fan-drive corner was evaluated with and without the high-speed corner. Flow surveys of pressure and flow angle were taken for both the corners and the vanes to determine their respective losses. The two-dimensional vane losses were low; however, the overall corner losses were higher because three-dimensional flow was generated by the complex geometry resulting from intersection of the turning vanes with the end wall. The three-dimensional effects were especially pronounced in the outer region of the circular corner.

Jet Engines may experience severe vibration due to the sudden imbalance caused by blade failure. This research investigates employment of on board magnetic bearings or piezolectric actuators to cancel these forces in flight. This operation requires identification of the source of the vibrations via an expert system, determination of the required phase angles and amplitudes for the correction forces, and application of the desired control signals to the magnetic bearings or piezo electric actuators. This paper will show the architecture of the software system, details of the control algorithm used for the sudden imbalance correction project described above, and the laboratory test results.

Joining of a PdCr Strain Gage with a Hastelloy X carrier shim to Inconel by a rapid infrared processing technique has been investigated at 1150 °C using a nickel based brazing alloy AMS 4777, Ni-7Cr-3Fe-3.2B-4.5Si-.06C in wt%. The effects of the infrared joining parameters on the joint and base material microstructure, joint shear strength, and delamination tendency of the PdCr gage was investigated. Results show that the joint shear strength is as high as 503 MPa when processed at approximately 1150 °C for 120 seconds. Microstructural examinations of the joint with both an optical microscope and a scanning electron microscope indicate that good wetting exists between the brazing alloy with both the Hastelloy X and Inconel 718. And, the Hastelloy X and Inconel 718 exhibits no noticeable change in microstructure due to the rapid processing cycle of the infrared heating process while the stabilized PdCr wire gage shows little change in resistance.

Since the beginning of the Space Station Freedom Program (SSFP), the Lewis Research Center (LeRC) has been actively involved in the development of electrical power system test beds to support of the overall design effort. Throughout this time, the SSFP Program has changed the design baseline numerous times, however, the test bed effort has endeavored to track these changes. Beginning in August 1989 with the baselining of an all DC System, a test bed was developed which supported this design baseline. However, about the time of the Test Bed's Completion in December 1990, the SSFP was again going through another design scrub known as Restructure. This paper describes the LeRC PMAD DC Test Bed and highlights the changes that have taken place in the Test Bed configuration and design resulting from the SSFP Restructure Exercise in December 1990.

The steady-state and dynamic performance of a candidate aircraft power distribution system is considered. The system features distribution of both single phase 20-kHz and three-phase 400-Hz power. It is shown that unlike some other recent 20-kHz systems, the power quality of the 20-kHz bus is not a concern due to the use of a synchronous bi-directional rectifier (SBR) as the primary interface to the 20-kHz bus. In addition to showing that the system behaves adequately in the steady-state, the dynamic performance of the system is considered during step changes in load, bolted faults, and sudden variations in jet engine speed.