Integrated Power and Thermal Management System for A Hybrid-Electric Aircraft: Integrated Modeling and Passive Cooling Analysis
Authors: Ouyang Zeyu , Nikolaidis Theoklis , Jafari Soheil 
Published: July 2024

Abstract
Aircraft electrification introduces challenges in power and thermal management. In a hybrid-electric aircraft (HEA), the additional heat loads generated by the high-power electrical components in the propulsion system can negate the benefits of the HEA. Consequently, an integrated energy management system is required for the HEA to reject the additional heat loads while minimizing energy consumption. This paper presents the integrated modeling method for an integrated power and thermal management system (IPTMS) for HEA. With this method, a platform can be developed to assess the varying efficiencies of the components in the electrical propulsion system (EPS), such as the battery, motor, bus, and converter, and the performance of the thermal management system (TMS), such as passive cooling, during a flight mission. This makes it applicable to modular designs and optimizations of the IPTMS. A small/medium range (SMR) aircraft similar to ATR72 is studied to demonstrate the platform's capabilities. In this study, the EPS operates only during takeoff and climb. It provides supplementary propulsive power, which declines linearly from 924 kW to zero. Therefore, the platform assesses the heat and power loads of the IPTMS for a typical flight mission (takeoff and climb) in this study. The performance of passive cooling is also analyzed across this typical flight mission and under normal, hot-day, and cold-day conditions. It was found that under the normal condition, after the midclimb flight mission, the EPS components except for the motor and the inverter can be cooled sufficiently by the passive cooling mechanism without any need for active cooling. However, the battery temperature decreases below its minimum operating temperature (15 °C) after the late-climb segment indicating the need for active temperature control to prevent damage. The passive cooling is still sufficient under the hot-day and cold-day conditions. Additionally, compared with the normal condition, the points at which passive cooling is sufficient to cool the component move forward in the hot-day condition and backward in the cold-day condition, respectively. Under the hot-day condition, the battery temperature is below its minimum temperature after the late-climb, still requiring active temperature control. In the cold-day condition, the bus, the converter, and the battery require active temperature control to prevent their temperatures below the minimum temperatures. Additionally, the heat from the gas turbine (GT) engine has a positive impact to ensure the motor and the inverter operate at their operating temperatures in cold conditions. The studied aircraft can be assessed with the integrated model under normal, hot-day, and cold-day conditions for heat and power loads, as well as passive TMS performance. This demonstrates the adaptability of the integrated modeling method. These findings imply the potential to minimize TMS weight and energy consumption, providing an insight for further research on IPTMS.