Commercial Hybrid Electric Aircraft Thermal Management Sensitivity Studies

Weight sensitivity studies were carried out on a Thermal Management System (TMS) of a parallel Hybrid Electric Propulsion (HEP) system of a commercial single aisle aircraft. The HEP system features a battery that feeds a Low Spool Motor (LSM) to assist the fan of a high bypass ratio geared turbofan. The first study gauged the impact of the Energy Storage, Conversion, & Distribution (ECS&D) system on the size of the Air Oil Cooler (AOC) and the Fuel Oil Cooler (FOC). The HEP system results in decreased FOC weight by 11% due to lower fuel flow at higher temperature due to the LSM and its heat load. Conversely, AOC weight increased by 32% also due to the higher heat load. A second study examines the effect of efficiency of the battery and motor drive on the TMS. Increases in efficiency of the battery from 95% to 96% and the motor drive (MD) from 96% to 98% decrease the weights of their Ram air Coolant Coolers (RCC) by 26% and 38%, respectively, as well as the heat sink air flow through them. Lastly, the altitude at which the Battery ram air Cooled Cooler (Bat RCC) was sized to reject the full heat load on a hot day (8 kft vs 20 kft) was examined. A TMS weight decrease in excess of 50 lbs. is possible for the 20 kft case provided that batteries are sufficiently pre-cooled below ambient temperature prior to take-off.