Abstract
For short take-off and landing (STOL) aircraft, a parallel hybrid-electric propulsion system potentially offers superior performance compared to a conventional propulsion system, because the short-take-off power requirement is much higher than the cruise power requirement. This power-matching problem can be solved with a balanced hybrid propulsion system. However, there is a trade-off between wing loading, power loading, the level of hybridization, as well as range and take-off distance. An optimization method can vary design variables in such a way that a minimum of a particular objective is attained. In this paper, a comparison between the optimization results for minimum mass, minimum consumed primary energy, and minimum cost is conducted. A new initial sizing algorithm for general aviation aircraft with hybrid-electric propulsion systems is applied. This initial sizing methodology covers point performance, mission performance analysis, the weight estimation process, and cost estimation. The methodology is applied to the design of a STOL general aviation aircraft, intended for on-demand air mobility operations. The aircraft is sized to carry eight passengers over a distance of 500 km, while able to take off and land from short airstrips. Results indicate that parallel hybrid-electric propulsion systems must be considered for future STOL aircraft.
Highlights
For any short take-off and landing (STOL) aircraft, a hybrid-electric propulsion system is expected to deliver superior performance compared to a conventional propulsion system, because the power needed for a short take-off is much greater than the power needed for cruise, while this excess power is only required for a fraction of the total flight time
It has been shown that the traditional sizing optimization assumptions should not be used for future hybrid-electric aircraft
For conventional designs, selecting the design point, which allows the lowest installed power-to-weight ratio (P/W) does result in the lightest aircraft, which will be the cheapest design to produce
Summary
The optimization problem during initial sizing can be stated as minimize MTOM by varying P/W and W/S while satisfying performance and mission constraints. These parameters are selected because the installed power and wing reference area are the main design drivers of conventional aircraft. The optimization problem during the initial sizing for hybrid-electric aircraft must be stated as minimize MTOM by varying P/W, HP, and W/S while satisfying performance and mission constraints. It is uncertain if the best optimization strategy for hybrid-electric aircraft is the same as for conventional aircraft.
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