Multi-objective parameter optimization and performance evaluation of indirect precooled engine with multi-branch closed Brayton cycle

Indirect precooled engines (IPE) with a multi-branch closed Brayton cycle (MBCBC) have potential performance advantages in air-breathing hypersonic propulsion due to complex cycle configurations. This paper conducts a design performance evaluation and cycle parameter optimization for the IPE with MBCBC. A mathematical model is established, and a composite optimization framework integrating sensitivity analysis and multi-objective optimization (MOP) is proposed. Sensitivity analysis results identify the optimal design parameters as: air precooling temperature, helium-air mass flow ratio, flow distribution ratio of the tandem cooling-compression system, and helium compressor pressure ratio. Under identical hydrogen consumption, MOP increases specific thrust by 3.329 % and specific impulse by 3.071 %. But the further performance improvement is limited by hydrogen path components and overall work capacity. A comparison of MOP results demonstrates that the composite optimization framework enhances convergence and can provide critical design insights for performance improvement of other systems with complex cycle configurations.