Aerodynamic design and investigation of two counter-rotating fans

The design rotating speed ratio of forward and afterward rotors was discussed based on one-dimensional analysis.The variations of pressure ratios,adiabatic efficiencies,diffusion losses and shock losses at the streamline of half-annulus-area radius against the varied design rotating speed ratios were studied.The flow fields of these two contra-stages were numerically simulated and the detailed flow physics was investigated at the design and off-design conditions.The simulations reveal that these two stages are quite well performed.For the civil engine contra-stage test fan,both rotors are conventional transonic rotors due to the low pressure ratio and low tip speed.For the military engine contra-stage fan different from the conventional transonic forward rotor,the afterward rotor is a full-span relative supersonic rotor in which both the leading edge shock and the passage shock extend from the casing to the hub.Furthermore,these two contra-stages exhibit stall margins competitive to conventional rotor-stator stages.For the civil test fan of low pressure ratio at the stall point,both the forward and afterward rotors are stall and the shocks are detached,correspondingly;for the military fan of high pressure ratio,only the afterward rotor is stall,determining the stage stall point.