Design and Optimization of Primary/Core Heat Exchangers for Turbofan Engine Waste Heat Recovery

Abstract

Waste heat recovery (WHR) is a key pathway to achieving reduced emissions and improved system efficiency through potential conversion of heat to electric or shaft power using a bottoming cycle. A supercritical carbon dioxide (sCO2) power cycle has many advantages, which are key parameters for aviation applications and be realized by compact and lightweight components. The present work focuses on implementing a sCO2 power system into future aircraft engines that may use different fuels, such as sustainable aviation fuel (SAF), hydrogen, natural gas, ammonia, or dual fuels. The first part of the work focuses on steady-state calculations of sCO2 WHR power system operation for a real aircraft engine. The second part of the work focuses on design of WHR heat exchangers, including size, weight, effectiveness, and pressure drop calculations. The last part focuses on optimization of the sCO2 WHR power system using preliminary heat exchanger thermal design data. The results show that the sCO2 WHR power system can generate between 350 and 1100 kW with cycle efficiency between 25% and 28% in ground idling, cruise, landing, and takeoff operating regimes. Effectiveness of the core heat exchanger, which is between 63% and 73 and 81% (2 Engine), and 95 % (1 Engine), drives net power and cycle efficiency of the WHR system.