Experimental and numerical simulation investigation of a counter-rotating fan stage

Counter-rotating fans are widely implemented in ventilation systems in mine and ship industries due to the characteristics of compact structure, high pressure and high efficiency. This paper investigates the aerodynamic performance and internal flow fields of a typical counter-rotating fan using both experimental and numerical methods. The theoretical analysis about the velocity triangle is carried out to deduce that the load ratio of two rotors should be in the range of 0.7 to 1 to improve the counter-rotating fan's performance. The fan of load ratio of 0.8 is introduced in the paper. The numerical result shows good agreement with experimental result. The stage isentropic efficiency is as high as 88% and the fan assembly efficiency reaches 86%. The fan has high efficiency in a large operation range. The radial profile of relative total pressure loss of two rotors shows that loss in aft rotor increases remarkably than fore rotor, especially in the hub region. Loss mechanism and vortex structure across the counter-rotating fan stage are revealed based on the limiting streamline analysis. The research indicates that increasing the aft rotor efficiency is the key point to improve the counter-rotating fan performance.