Performance assessment of a hybrid electric-powered long-range commercial airliner
Despite the recent increase in the amount of smaller electric general aviation aircrafts, a fully electric airliner is not likely to fly in the near future. Partially inspired by the automotive industry’s success with the hybrid car, this thesis investigated the feasibility of an electric-hybrid propulsion system for an Airbus A340-600 on a long-haul flight and its effect on the aircraft’s performance. First, an analysis was done of the reference aircraft, A340-600, using conventional propulsion. Second, a 5700 nautical miles flight was modelled to determine performance data such as the power and thrust requirements during the different flight phases. Third, the flight phases where electric propulsion would be implemented were identified and an optimum ratio between conventional and electric propulsion was calculated. Finally, a detailed performance analysis of the new hybrid electric aircraft comparing it to a conventional aircraft was conducted.
The maximum available conventional thrust was reduced to a certain percentage of the maximum thrust. Primarily conventional thrust is used, however when it is no longer sufficient, additional thrust is gained through electric propulsion. Conventional thrust ratio of 69.5%, 63.5% and 59.5% of total thrust was investigated yielding 8680 kg, 10500kg and 8585kg of payload decrease respectively. Net energy of 6.70MWh, 11.71MWh and 31.06MWh is required and the electric engines need to provide 21.3 MW, 25.5 MW and 28.3 MW of net power respectively.
Partial electric propulsion will result in increased weight; however, it will also give room for further performance optimisation and technical innovations. On the one hand, the conventional engines will run at a constant speed throughout the flight allowing for better optimisation at a specific design point. On the other hand, electric engines are more reliable and require less maintenance than conventional engines. Furthermore, lower fuel consumption means less carbon-dioxide emissions. An exemption from CO2-taxes, similar to measures implemented for hybrid cars in certain countries, could financially justify use of the aircraft by airlines and compensate for the decrease in payload. Since a fully electric propelled airliner is not likely to fly for several decades, a hybrid-airliner would be a suitable alternative for the transition period from fossil fuels to electric energy.
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