Rotating Stall Caused by Pressure Surface Flow Separation on Centrifugal Fan Blades

Abstract

A rotating stall associated with massive flow separation on the pressure surface (p-stall) of a centrifugal fan blade is identified. The stall cell rotates in the same sense as the rotation of the impeller. The frequency of pressure pulsation is greater than the running frequency and approaches 4/3rds the running frequency. It is proposed that the mechanism of p-stall propagation is similar to that of the classical rotating stall caused by flow separation on the suction surface (s-stall). However, it is emphasized that the cause of p-stall is different from s-stall and any corrective treatment applied should take its nature into consideration. In the present work, pressure surface stall was induced by pre-rotating the inlet flow using inlet guide vanes and operating the fan against a low system resistance. Heuristic models are proposed for the inception and propagation of p-stall, and computational predictions of the flow fields, along with experimental results, are presented to support the model.

Rotating Stall in Centrifugal Compressor Vaneless Diffuser: Experimental Analysis of Geometrical Parameters Influence on Phenomenon Evolution

“…20). Madhavan and Wright (1985), the last reference in a completely different situation (blower, high flow rate). When the configurations with DR = 1.3 were tested, things changed considerably in terms of machine working range: stall occurs for greater flow coefficient.…”

Analysis of Vaneless Diffuser Stall Instability in a Centrifugal Compressor

“…The theory [1] also states that it occurs with steady, uniform inflow and outflow conditions and thus independent of the interaction with the rotating impeller. A criticism is that inflow periodic unsteadiness may trigger a diffuser instability, see e.g., [3]. Another criticism is that the theory assumes diffuser flow as inviscid.…”