Investigation and optimization on performance of an innovative Brayton cycle in space nuclear power system

Abstract

As space exploration advances, the need for robust and dependable energy sources continues to grow. Due to its exceptional energy density, substantial output power, prolonged operational lifespan, and remarkable adaptability to environmental conditions, the space nuclear power system (SNPS) stands out as the ideal energy solution for future deep-space missions. At the same time, the Brayton cycle is an ideal thermoelectric conversion method for megawatt SNPS. However, for the Brayton system, the circulating working fluid still has high energy quality after heating by the reactor and doing work by the turbine. And the compressor is the main power consumption equipment in the Brayton system, it is necessary to reduce its inlet temperature as much as possible. In this paper, under the background of SNPS, a multi-compression Brayton cycle was proposed. Based on the simple Brayton cycle structure, the circulating working fluid was bled and multiple compressed. Utilizing He-Xe mixture as the working fluid, thermodynamic and mass estimation models were developed to analyze how bleeding ratio, turbine inlet temperature, recuperator effectiveness, compressor inlet temperature and pressure ratio, influence the thermal efficiency, overall mass, and specific power of the multi-compression Brayton system. Taking thermal efficiency, total mass and specific power of the system as optimization objectives, the non-dominated sorting whale optimization algorithm (NSWOA) was used for multi-objective optimization. Under the compromise of maximum thermal efficiency, minimum total mass and maximum specific power, the optimal value of system thermal efficiency, total mass, specific power was 61.04 %, 1266.53 kg and 0.31 kWe/kg, respectively.