Aero-Propulsive Efficiency Requirements for Turboelectric Transport Aircraft

In this paper a design-of-experiments is performed with the objective of determining the improvements in aeropropulsive efficiency required for a reduction in the energy consumption of turboelectric transport aircraft, when compared to conventional, gas-turbine based alternatives. Simplified representations of the powertrain and the aeropropulsive interaction effects are used, such that the results are independent of the design of the electrical system or the external layout of the propulsion-system. An evaluation of different mission requirements confirms that the turboelectric architecture presents the largest benefit for long ranges, and that the aeropropulsive benefit required for a predefined reduction in energy consumption increases with increasing cruise Mach number. Moreover, the impact of different technology maturity levels of the electrical drivetrain components is assessed. The results show that the shaft power ratio necessary to achieve a determined aeropropulsive benefit is a decisive factor, and that for a shaft power ratio of 20%, a 5% reduction in energy consumption is possible on the mid-term (circa 2035) if an 11% increase in aeropropulsive efficiency is achieved. A 15% reduction in energy consumption is only possible with extremely optimistic powertrain technology assumptions, and requires and increase in aeropropulsive efficiency of at least 14%, for the missions considered.