Experimental analysis and thermodynamic modeling for multilevel heat exchange system with multifluid in aero engines

Efficient thermal management systems (TMS) are crucial for advanced aerospace vehicles to handle the increased thermal loads from engine combustion and aerodynamic heating. Aero-engine TMS are uniquely characterized by their high compactness, reliability, and stringent safety requirements. This study proposes a multilevel heat exchange system using endothermic hydrocarbon fuel, air, and high-pressure water. An experimental platform was constructed to analyze the effects of mass flow rates and inlet temperatures on the system's thermodynamic characteristics. Thermal management strategies were developed to optimize these parameters, significantly reducing thermal loads during high-speed flight and enhancing system efficiency and safety. Results indicate that variations in thermal energy input to a heat exchanger on one branch have a limited impact on another branch. The fuel mass flow rate can modulate the temperature of all working fluids in the system, but it also affects combustion characteristics. A transfer matrix-based system model with high accuracy was established, coupled with a genetic algorithm to achieve holistic identification of the heat exchanger heat transfer characteristics in practical applications, achieving a maximum parameter deviation of −4.79 %. The results contribute to optimizing TMS for aero engines, improving thermal stability, and enhancing energy utilization efficiency.