Investigation for the effect of variations in heat exchange parameters on the performance of precooled combined engines

The closed helium Brayton cycle is essential for thermal and mechanical energy transfer in precooled combined cycle engines. However, the impact of heat exchanger parameter variations on engine performance and system matching remains unclear. Therefore, a mathematical simulation model of a precooled airbreathing combined engine (PATR engine) including a closed helium Brayton cycle is established using the component method. The influence of key parameters in the precooler, helium heater, and hydrogen-helium regenerator on engine performance is analyzed, along with the safety boundaries for component matching. Results indicate that the hydrogen-helium regenerator has the most significant impact on engine performance, primarily due to changes in the air compressor inlet temperature. Optimal hydrogen flow is achieved when the heat capacity rates of hydrogen and helium are equal. Engine component matching exhibits low tolerance for deviations in the hydrogen-helium regenerator's effectiveness but high tolerance for the precooler and helium heater. The safe deviation range for the regenerator's heat exchange effectiveness is -10 % to +5 %, while negative deviations in hydrogen flow should not exceed -15 %. The optimal helium outlet temperature from the heater occurs at +3 % deviation, whereas exceeding a -3.4 % deviation leads to mismatch due to insufficient power for the helium turbine.