Energy performance optimization of combined Brayton and two parallel inverse Brayton cycles with regeneration before the inverse cycles

This paper proposes combined regenerative Brayton and two parallel inverse Brayton cycles with regeneration before the inverse cycles. Performance analysis and optimization for the combined cycle are performed based on the first law. The analytical formulae of thermal efficiency and specific work are derived. The performance analysis and optimization of thermal efficiency and specific work are carried out by adjusting the compressor pressure ratios of the bottom cycles. The influences of the effectiveness of the regenerator and other parameters on the optimal thermal efficiency and the optimal specific work are analyzed by numerical examples. It is found that the combined regenerative cycle can obtain higher thermal efficiency than that of the base cycle but with smaller specific work. It is revealed that if the effectiveness of regenerator equals to 0.9, the combined cycles will attain an optimal thermal efficiency of 51.2%.