Multipoint aerodynamic design of a nacelle for an electric fan

Attention to aircraft electrification has been growing quickly since such technology carries the potential of drastically reducing the environmental impact of aviation. This paper describes the re-design of a nacelle for an electric fan, which is developed as part of the EleFanT (Electric Fan Thruster) project. A multipoint nacelle design approach was carried out. Initially the nacelle shapes were optimized for a cruise condition by employing an evolutionary genetic algorithm (GA). The flow field around the nacelles was calculated by conducting 2D axisymmetric computational fluid dynamics (CFD) simulations, and the objective functions were computed by means of thrust and drag bookkeeping. It was found that the optimizer favored two types of nacelle shapes that differed substantially in geometry. The designs were referred to as low spillage and high spillage types. The optimum low spillage and high spillage cases were selected and investigated further by the means of 3D CFD simulations at cruise and at an end of runway takeoff condition, where the nacelle is subjected to high angle of attack. Whilst the low spillage case provided a slightly better performance at cruise, it presented high levels of distortion and boundary layer separation at takeoff, requiring a substantial shape modification. The high spillage case performed well at takeoff; however, supersonic velocities could be observed at the cowling when it was subjected to incoming flow at an angle of attack. Nonetheless, such problem was easily corrected by drooping the inlet. Due to its superior performance at takeoff, the drooped high spillage design type was recommended