A previously tested 30-kw shaft output engine has been fitted with a closed-loop gas management system for power control. The closed-cycle engine operates at essentially constant speed and turbine inlet temperature, and power capability is a function of pressure level. The gas management system compresses and stores excess argon working fluid during load removal and injects on demand in response to load application. The system consists of a low, medium and high pressure storage accumulator, piston-type motor-driven compressor, valving and electronic control unit for sequencing the accumulators. Peak storage pressures at minimum power (10kw) are 765, 1076, and 1517 kPa (111, 156, and 220 psia). The engine and control system were run for a total of 57 hr over numerous transients of varying duration and range. Operation was characterized by quick response, smooth switching, and effective control. During load removal, the compressor required up to 3 min. to reduce full inventory to minimum power while turbine bypass valves allowed immediate engine response without excessive overspeed. Manually adjustable inject orifices allowed system response to closely follow load applications of 15 sec to 3 min. Compression heating in the accumulators during charging tended to elevate the switch points slightly, altering the storage capacities after repeated transients.

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