Abstract
A numerical analysis based on Computational Fluid Dynamics (CFD) is carried out to investigate the influence of the fuselage transition and axial offset, on the inlet distortion and performance of a tail mounted fan, for a short-haul commuter aircraft. For the examined configurations, it is predicted that varying the angle of the fuselage transition does not have a significant impact on the radial distortion, for a typical fan mounted at the centreline of the fuselage. The wake behind the fuselage is predicted to increase in size as the slope of the fuselage is increased, however, the positive suction from the fan is sufficient for the flow to fully recover before the fan duct inlet. Nevertheless, it is predicted that offsetting the fan from the fuselage centreline produces a more significant increase in distortion in the circumferential direction. The propulsive power of the fan is predicted to increase slightly with increasing offset mainly due to the side of the fan which is less obstructed by the fuselage. However, the wake on the opposite side is predicted to increase significantly persisting almost to the inlet of the fan duct. A vortex formed upstream of the fan increases in strength with increasing offset. This vortex helps to offset the increase in circumferential distortion by re-energizing the flow in the wake of the fuselage. This causes the circumferential distortion to remain roughly constant between offsets of 25% and 50% of the fuselage radius. It is likely though that this vortex will deteriorate the performance of the fan.
