Low-power baseline test results for the GPU 3 Stirling engine
In support of the Department of Energy's Stirling Engine Highway Vehicle Systems Program, the NASA Lewis Research Center has converted a 7.5-kilowatt (10-hp) Stirling engine to a research configuration in order to obtain data for validating Stirling-cycle computer simulations. The engine was originally built by General Motors Research Laboratories for the US Army in 1965 as part of a 3-kW engine-generator set that was designated the GPU 3 (Ground Power Unit 3). Baseline tests were run to map the engine over a range of heater-tube gas temperatures, mean compression-space pressures, and engine speeds with both helium and hydrogen as the working fluid. Tests were limited to the lower power levels because the original alternator and a resistance load bank were used and they were not capable of absorbing the full engine output power. Test results show that engine output and engine efficiency increased with increasing pressure level. However, the relative gain in power and, particularly, the relative gain in efficiency decreased as pressure increased. The maximum efficiency for a given pressure level was obtained at intermediate speeds. Flow losses caused the efficiency to decrease at high speeds, and conduction losses caused it to decrease at low speeds. The hydrogen power curves were more linear with speed than were the corresponding helium curves - an indication of the lower flow losses associated with hydrogen. The maximum power obtained with hydrogen was 4.48 kW (6.0 hp) at 4.1 megapascals (600 psi) mean compression-space pressure; the maximum power output with helium was 3.92 kW (5.25 hp) at 6.9 megapascals (1000 psi).
- Research Organization:
- National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
- DOE Contract Number:
- EC-77-A-31-1040
- OSTI ID:
- 6262023
- Report Number(s):
- DOE/NASA/1040-79/6; NASA-TM-79103
- Country of Publication:
- United States
- Language:
- English
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