Indirect engine sizing via distributed hybrid-electric unmanned aerial vehicle state-of-charge-based parametrisation criteria

Abstract

This paper presents a design process for the challenging problem of sizing the engine pack for a distributed series hybrid-electric propulsion system of unmanned aerial vehicle. Sizing the propulsion system for hybrid-electric unmanned aerial vehicles is a demanding problem because of the two different categories of propulsion (the engine and the motor), and the electrical system characteristics. Furthermore, what adds to the difficulty is that the internal combustion engine does not directly drive the propellers, but it is connected to an electrical generator and therefore provides electrical power to the electric motors and propellers. Hence there is a clear distinction from the traditional engine solutions which are mechanically coupled to the propeller. This paper addresses this specific distinction and proposes an indirect solution based on properties on the electrical part of the system. In particular, a novel parametric characterisation engine sizing approach is presented using the battery pack state-of-charge during a realistic unmanned aerial vehicle flight scenario. Five candidate engine options were considered with different starting conditions for the electrical system. The results show that by using the state-of-charge properties it is possible to select an appropriate size of engine pack while carrying a suitable electrical propulsion pack. However, the solutions are not unique and are appropriate for given design criteria clearly indicated in the paper.

Design of a Distributed Hybrid Electric Propulsion System for a Light Aircraft based on genetic algorithm

“…The second part consists of outside electrical loads, such as an electric taxiing system. Electric taxiing refers to an aircraft uses a motor to directly drive wheels during taxiing stage instead of using propellers [21]. The new taxiing method is more efficient and allows to switch off engine earlier due to the battery pack can provide energy for taxiing.…”

“…, will lead to a better battery performance, as shown in Eq. (6) [21]. The selected engine is small and it is not capable to generate enough power for high-powerful missions, such as take-off or climbing.…”

“…Assuming cruise is steady and no acceleration, the power requirement for a common flight can be determined. Calculations are mentioned in paper [17,21]. Fig.…”