Brayton rotating units for space reactor power systems

Designs and analyses models of centrifugal-flow compressor and radial-inflow turbine of 40.8 kW e Brayton Rotating Units (BRUs) are developed for 15 and 40 g/mole He–Xe working fluids. Also presented are the performance results of a space power system with segmented, gas cooled fission reactor heat source and three Closed Brayton Cycle loops, each with a separate BRU. The calculated performance parameters of the BRUs and the reactor power system are for shaft rotational speed of 30–55 krpm, reactor thermal power of 120 – 471 kW th , and turbine inlet temperature of 900–1149 K. With 40 g/mole He–Xe, a power system peak thermal efficiency of 26% is achieved at rotation speed of 45 krpm, compressor and turbine inlet temperatures of 400 and 1149 K and 0.93 MPa at exit of the compressor. The corresponding system electric power is 122.4 kW e , working fluid flow rate is 1.85 kg/s and the pressure ratio and polytropic efficiency are 1.5% and 86.3% for the compressor and 1.42% and 94.1% for the turbine. For the same nominal electrical power of 122.4 kW e , decreasing the molecular weight of the working fluid (15 g/mole) decreases its flow rate to 1.03 kg/s and increases the system pressure to 1.2 MPa.