A Reduction of Tip Mach number in Lift Fan Rotor for Jet VTOL Aircraft

摘要

The very small bellmouse shaped Lift Fan Engines of JAXA's conceptual Jet VTOL aircraft increases relative tip Mach number and causes supersonic regions on the rotor blades. The last report has studied rotor work input patterns to lower the tip Mach number. Although the tip Mach number has been lowered from 0.98 to 0.93, there are still some supersonic regions on the rotor blades. To lower the tip Mach number to around 0.80, this paper performs a numerical analysis of the throughflow on a lift fan as a two-dimensional axisymmetrical flow. Based on the last report focusing on the work input pattern tests, three life fan designs are tested: normal fan (radius 1.20m, revolution 2000rpm), low speed fan (1.20m, 1600rpm), and low speed large-scale fan (1.30m, 1600rpm). The low speed large-scale fan lowers the tip Mach number to 0.82 and shows no supersonic regions on the rotor.