A Study on the Rotating Stall in Vaneless Diffusers of Centrifugal Fans : 2nd Report. An Analysis of Pressure Fluctuations

Abstract

The unique peripheral distribution of the amplitudes of pressure fluctuations on a diffuser wall was observed under the rotating stall of a diffuser. The distribution changed according to the number of cells for the same scroll. The reason why the distribution occurs is not evident. A study is carried out to clarify the principal cause for the unique distribution. The instantaneous pressure distributions on the diffuser wall are measured and they are analized by the authors' original technique. The measured pressure fluctuation is separated into two components and the factors for the above unique distribution are made clear. The mechanism of the occurrence of the unique distribution is clarified by the experiment and the numerical analysis. Some interesting facts observed in the experiment are also presented.