Detecting Rotating Stall Precursors in Axial Compressors via Perturbations Part 2: Experiments

Abstract

In Part 1 of this paper by Dong and Wang (“Detection of Rotating Stall Precursors in Axial Compressors via Periodic Perturbation Part 1: General Theory of Nonlinear Dynamics,” Journal of Propulsion and Power.), a general theoretic framework is established for prediction of the imminence of a subcritical Hopf bifurcation by using the properties of the dynamic response to periodic and small-amplitude random disturbances. In this paper (Part 2), experiments are carried out on a single-stage low-speed high hub-to-tip ratio compressor by using different levels of static circumferential inlet distortions. Based on the experimental data, a modified Moore–Greitzer model is proposed to accommodate the effects of the distortions on both the mean flow and the first spatial mode. The general theory is then applied to the model, and it is found that the theoretical formula for the sensitivity of amplitude of the first spatial mode to the variation of the bifurcation parameter predicts qualitatively well when compared with numerical simulations and the experiments. By using the sensitivity as the criterion, the imminence of rotating stall can be identified well before its inception, whereas without inlet distortion, the amplification of the first spatial model cannot be detected until at stall inception.