Performance Evaluation of an Engine-Integrated and Bleed Air-Driven Thermal Management System in Fighter Aircraft

Abstract

In modern supersonic fighter aircraft, the increasing use of high-performance electronics leads to a significant demand for heat dissipation. This requires the integration of an advanced Thermal Management System (TMS) utilizing multiple heat sinks. This paper investigates an engine-integrated TMS that employs a bleed air-driven open reverse Brayton cycle to reject heat loads into the engine bypass stream. This study explores the interrelations between TMS cooling capacity and engine performance for a fighter configuration developed at the German Aerospace Center (DLR). Key aspects include the TMS behavior with respect to its compressor pressure ratio as one of the main design parameters and the interaction with the engine throughout a flight mission. The TMS performance is first examined under constant flight conditions to evaluate the system’s thrust dependence. These results are then compared with those of a representative flight mission. Evaluations on the TMS compressor design pressure ratio reveal no clear design optimum. Higher ratios improve the cooling capacity at high engine loads under constant ambient conditions but offer no benefit during the flight mission, while increasing fuel consumption up to 1.2 % with minimal loss in cooling capacity. It becomes clear that system adjustments, such as bypass control options, are required to enable flexible TMS operation across the widest possible operating range during a mission. The results show the performance limitations of a simple reverse Brayton cycle and highlight the relevance of advanced system controls to maximize efficiency and cooling capacity.