Coupling Effect between Inlet Distortion Vortex and Fan

In the process of inlet/engine matching, large-scale distortion vortexes would be generated due to lip separation, curved duct, shock-wave boundary layer interaction and other factors of inlet, resulting in complex combination distortion of total pressure and swirl, which would affect the stable and efficient operation of fans/compressors of aero-engine. On the basis of main distortion vortex characteristics of a typical S-shape inlet and its theoretical model of velocity and pressure distribution, this paper establishes an inlet boundary condition definition method to generate three-dimensional distortion vortex, and presents a study of coupling effect between steady distortion vortex and NASA Rotor 67. The results show that the fan's performance curve would move to smaller mass flow direction under the influence of the co-rotating distortion vortex, while fan's operation curve would change to the opposite direction if the inlet distortion vortex direction is opposite to the fan's rotating direction. Compared with co-rotating distortion vortex, the efficiency loss caused by counter-rotating distortion vortex would be larger and total pressure ratio loss would be smaller. The vortex core size has significant influence on the stability margin of the fan, but has little influence on the efficiency and total pressure ratio characteristic. As the vortex core size increases, the range of fan's tip region with high attack angle would become larger and cause the fan to stall in advance. Due to the non-uniform suction of the downstream fan, the inlet distortion vortex accelerates to mix with the surrounding main flow. The total pressure distortion decreases and swirl distortion increases along sections from inlet boundary to the fan leading edge.