Design Methodology and Parametric Design Study of the On-Board Electrical Power System for Hybrid Electric Aircraft Propulsion

This paper presents parametric design studies of the on-board Electrical Power System (EPS) for a distributed hybrid aircraft propulsion. The work presents the methodology that has been adopted to develop the physics-based models of the EPS components that comprise the electrical machines, power electronic converters, batteries, solid state circuit breakers and power cables. The EPS model is a sizing tool that can be used to evaluate the mass and dimensions of its main components. In addition, it determines the thermal performance of the EPS over six key flight stages of the aircraft mission. The EPS model has been created within a wider multidisciplinary design platform with the aim of sizing the overall aircraft configuration including the aircraft thermal system, the gas turbines and the electrically propelled fans together with the aircraft structure. This paper focusses on the EPS and presents the assessments of three key parameters which are the battery specific energy density, the electric propulsion power and the power split ratio between the generator and the battery. The assessment results demonstrate the significant impact the aforementioned parameters can have on the weight of the battery, the electrical power system and hence the aircraft fuel burn. The work developed within the Clean Sky 2 TRADE project is vital as it develops and applies important physics-based multidisciplinary tools that are required to identify optimum solutions amidst the large number of available conceptual hybrid aircraft architectures.