Numerical Investigation of Self-Driven Fan Performance With Tip-Jet

Tip-jet rotor system has unique potential value in the area of vertical take-off and landing (VTOL) or short take-off and landing (STOL) concept aircraft. The main objective of the current work is to investigate the aerodynamic properties of a self-driven fan with tip-jet (SDF_TJ) in hover by numerical experiments. In order to obtain the detailed flow phenomena of SDF_TJ, CFD method is performed, which is conducted by solving three-dimensional Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. For the purpose of investigation, the analysis of SDF_TJ performances with different nozzle configurations have been carried out. Current results indicate the conformal tip-jet not only provide the reaction torque, but also augment the fan lift via entraining the main flow above the suction surface of blade. The rotation speed of fan is mainly determined by bleed air parameters and nozzle area, so as to torque self-balance. The total torque produced by jets contains rotor required torque and penalty torque induced by Coriolis force. The blade lift coefficient and the ratio with jet momentum coefficient are influenced by the distance from the nozzle downstream edge to blade trailing. As the lift of SDF_TJ is larger than the thrust generated by jets alone, which could benefit the take-off and landing capability of VTOL concept aircraft.