Coupled Transient and Dynamic Modelling of a Retrofit Hybrid Electric Turbofan Engine

Hybrid electric propulsion systems can potentially reduce the aviation sector’s emissions by decreasing the fuel consumption and lowering maximum temperatures within the aero engine’s combustor. The development of hybrid electric propulsion systems requires modelling methods capable of depicting the complex interdependencies between the electric and gas turbine systems. State-of-the-art models mostly incorporate steady-state simulations. However, the transient operation of the electric components and the dynamic behaviour of the conventional aero engine are expected to impact the electric component degradation and the formation of emission species caused by short peaks in temperature and load. This paper presents a novel combined model of a retrofit parallel hybrid electric turbofan engine capable of simulating the coupled transient and dynamic behaviour of the propulsion system. The model results are compared to a state-of-the-art approach, which employs steady-state performance maps to represent the electric motor. Deviations between the two modelling approaches of up to 2 % are observed during acceleration and deceleration of the propulsion system. These deviations can be traced to the direct interface representation in the combined model. The results emphasise the necessity to incorporate coupled transient and dynamic modelling of hybrid electric propulsion systems.