Evaluation of a Variable Cycle Engine for an EngineIntegrated Thermal Management in Fighter Aircraft

Abstract

Modern fighter aircraft impose thermal loads that challenge conventional cooling concepts. This study evaluates a closed-air thermal management system (TMS) integrated in two engine architectures: a conventional mixed-flow turbofan and a variable cycle engine (VCE). Across sixteen representative operating points, the VCE consistently meets cooling requirements in most segments and achieves twice the capacity of the conventional engine under supercruise conditions. A temperature - mass-flow study for bypass the conditions reveals that, once bypass flow significantly exceeds the TMS stream, additional cooling is obtained almost exclusively by reducing bypass temperature. Optimizing the VCE variabilities further enlarges the cooling margin at negligible fuel burn penalty, underscoring the thermal and operational advantages as well as the flexibility of variable cycle architectures.