Experimental investigation of the wake decay process in an axial pump with varied rotor-stator axial spacings

For a compressor stage, the mechanism of wake recovery leads the rotor wakes to decay in a reversible process through the stator passage. Based on this theory, the rotor-stator axial spacing is believed to be a significant factor bound up with the wake mixing loss. In this paper, the wake decay processes in a tiny axial pump with varied rotor-stator axial spacings are studied using particle image velocimetry (PIV) measurement. PIV results indicate that the rotor wakes interact with the stator blade and generate flow regions with elevated turbulence. This interaction is enhanced when the axial spacing is close. The attenuation process of the disturbance kinetic energy (DKE) and the relative wake depth demonstrate that the axial spacing significantly affects the proportion of the wakes that decay in the stator passage. Close rotor-stator axial spacing is proposed to increase the recovery rate of the rotor wakes. Supplementary CFD computation is conducted to certify that the experimental results are universal for pumps with and without splitters.