Effects of rotor-rotor interactions in a counter-rotating fan

Taking a two-stage counter-rotating fan as the test case, the rotor-rotor interactions have been studied. A steady simulation and unsteady numerical simulation based on the non-linear harmonic method have been presented and discussed. The comparison between the steady and unsteady flow field shows that upstream wake is the main influencing factor in the rotor-rotor interactions effects. Specifically, the unsteady effects reduce the efficiency of the 2nd blade row above midspan, which is attributed to the interactions of wake-shock, wake-boundary layer, and wake-passage vortex. In addition, the efficiency of the 2nd row below midspan is increased by the wake-boundary interaction which could enhance the exchange of energy between boundary layer and mainstream, add energy to the boundary layer and delay the hub corner separation.