An Optimal Design of Aircraft Hybrid Powertrain Based on a Coupled Method

Abstract Hybrid aircraft can better meet the future needs of green aviation. The range and payload of battery electric aircraft are limited by the low energy density of the battery. Gas turbine hybrid systems can reduce the battery weight and increase the range and payload. In the engineering design aspect, how to select the optimal gas turbine power at design point and determine suitable off-design output power characteristics at different flight phases based on a specific mission profile is a worthy research topic. This paper presents a coupled optimization method for hybrid powertrain. Firstly, a component model of the gas turbine generator system and a battery model based on test data are established. Secondly, A design point power optimization method based on the bisection method is proposed. Further, an off-design output power optimization method based on the particle swarm optimization algorithm is also established. Based on the maximum and minimum output power capability of the gas turbine, a general table of numerical results of the non-linear equations is generated to accelerate the calculation of the off-design points based on the flight mission. Finally, based on the mission profile of NASA-X57, this paper designs the corresponding hybrid power system and compares its performance with the battery electric system, and the results show that the aircraft with optimized hybrid powertrain could increase the efficient payload (people and cargo) by 25%, the specific transportation cost (RMB/kg/km) is increased by 19%. The method proposed in this paper could provide a fast optimal design and performance evaluation of the hybrid powertrain based on a certain flight mission profile, which could provide the aircraft and powertrain manufacturers an efficient design tool.