Effects of the Reynolds Number on the Efficiency and Stall Mechanisms in a Three-stage Axial Compressor

Abstract

The Reynolds number ( R e) is an important parameter that can affect compressor performance. This study experimentally and numerically investigated the effect of R e variations on the efficiency and stall mechanisms for a three-stage axial flow compressor. In the experiment, the total pressure ratio, polytropic efficiency, and stalling mass flow rate were measured in a R e range varying from 1,100,000 to 55,000 to elucidate the R e effects. Unsteady three-dimensional numerical simulations were implemented to understand the stall mechanisms. The results indicate that the compressor efficiency and stall– pressure ratio begin to decrease remarkably as R e is reduced below a critical value, which is 220,000 in the case of the compressor studied. At a low R e, losses caused by the secondary flow near the hub and shroud increase remarkably, and the extended boundary layer separations at the blade suction surface further decrease the efficiency. The variation in R e changes the stall-initiated location. At higher Reynolds numbers, the interaction between the corner separation at the hub of stator 1 and the leakage flow through the blade tip gap induces a large vortex, which seriously blocks the blade passage. The blocking effect spreads to the aft stage and extends to higher spans, which results in the stall of the whole compressor. However, the blocking effect at the hub disappears at R e =55,000, and the interaction of the blade boundary layer separation near the shroud of rotor 1 and the tip leakage vortex causes a large blockage and then induces stall. The R e variation