Asymmetric flow in a double-suction centrifugal fan induced by an inclined impeller

Abstract

The impeller and volute of a centrifugal fan are designed to be coaxially placed; however, the impeller might be inclined about the central axis of the volute due to installation fault, inducing asymmetric flow in the left and right halves of the fan. We performed a detailed numerical investigation on the non-uniform and asymmetric flow in a double-suction multi-blade centrifugal fan with a slightly inclined impeller using the unsteady Reynolds-averaged Navier–Stokes simulation approach. The impeller is assumed to rotate about each of the two minor axes perpendicular to the central axis to model the inclination. This work aims to quantify the influence of the impeller inclination on the aerodynamic performance of the centrifugal fan and to reveal the physics of transient flow in the two halves of the fan to demonstrate the impact of various inclination ways. Numerical results denote that a slight impeller inclination could stabilize the flow in the fan, while the flow is highly asymmetric as the inclination is enhanced, and the efficiency of the fan decreases due to the recirculation generated by the interaction of flow exiting from the impeller. An in-depth inspection shows sharply intensified pressure fluctuation at the collector, where the local clearance varies. The flow entering the collector and impeller substantially decreases in velocity, resulting in separated flow in part of the blade passages. The flow in the volute is also asymmetric since the impeller outlet is biased toward the volute wall.