Study of Simulated Distortion Waves in an Axial Flow Fan

Abstract

Inflow distortion is a problem encountered during axial fan/compressor operation. There are a large number of experimental studies that have been carried out to study the distortion effects on the axial fan/compressor performance by using wire mesh screens, by blocking inlet passage and physically disturbing the inlet flow. When the compressor experiences off design operation, it is likely to experience an inlet distortion, which determines its operational sustainability. Every compressor in each flight segment undergoes non-uniform inlet flow fields and responds differently to that of a clean inlet flow, for which it is designed. To meet specific performance requirements, it is often required for a compressor to pass through off-design environments. Distortion, simulated as waves or combination of waves in propagation, have been studied in this work. It has been observed that the effect of distortion depends on types of waves applied, area covered by distortion, operating speed of the fan/compressor & location of the distortion waves with respect to blade profile. For a given velocity in distorted passages spike wave has more detrimental effect compare to normal distortion wave or a triangular wave. A few combination distortion waves have been studied too.

Experimental Investigation of Stall Inception Mechanisms of Low Speed Contra Rotating Axial Flow Fan Stage

“…Modal waves and spikes are the two main known stall inception patterns or stall precursors so far identified [5,6]. Modal waves (long length scale disturbances) are gradual and progressive type of stall inception with a small amplitude and low frequency disturbance, which propagates at approximately 20-45% of a rotor speed and increases to 40-60% when it grows to fully develop rotating stall [7]. Camp and Day [8] have identified the spike type short length scale disturbance, which rotates at 70-80% of the rotor speed and originates near tip region because of tip vortices.…”