Effects of Mixed Inert Gases on Design of Centrifugal Compressors for Space Nuclear Reactor

Abstract The aerospace industry considers nuclear reactor as the prime candidate to extend mission durations and enhance the energy supply for spacecraft. Among the power conversion systems for space reactors, the direct closed Brayton cycle stands out for its compactness, lightness, safety, and high power density, making it exceptionally well-suited to these applications. Centrifugal compressor is a key component of the Brayton cycle, whose performance is pivotal in the system efficiency. Researches on compressors utilizing inert gases has predominantly concentrated on helium-xenon mixtures, leaving other inert gas combinations less explored. Moreover, the influence of inert gas mixture proportions on compressor design has not been adequately addressed in the literature. To fill this research gap, this paper established models of the inert gas mixtures properties and design of centrifugal compressors, and investigated the effects of inert gas mixtures, including helium-argon and helium-neon mixtures, on performance and geometric parameters of the centrifugal compressor. The results indicated that helium-argon or helium-neon mixtures working fluid could significantly reduce the number of compressor stages, thus potentially minimizing the compressor’s volume and mass compared to pure helium working fluid. The increase in the molar mass of the gas mixture decreased the rotational speed and maximum circumferential velocity of the compressor and increase the mass flow rate and the Mach number at the exit of the final-stage impeller. This study provides a reference for the selection of working fluids in space reactor Brayton cycles and the design of centrifugal compressors.