Mechanism of Low-Frequency Oscillation in the Compressor Corner Region and Its Deterministic Impact on Loss Generation

Abstract

Abstract. The loss generation in the corner region of compressors is highly dependent on vortex dynamics. When the Reynolds number (Re) decreases to a critical value, the flow unsteadiness induced by multiscale vortex structures changes significantly, resulting in difficulties in loss quantification and control. In this study, a high-subsonic compressor cascade was taken as the research object, and the low-Re-effects on the flow unsteadiness and loss generation in the corner region were clarified. A new source of flow unsteadiness in the corner region, namely,, low-frequency oscillation (LFO), which is induced by the resonance among multiple vortex structures with different frequencies, is first identified. When Re decreases from 5.6 × 105 to 2.5 × 105, more energy is transferred to LFO through the resonance process. As such, the region of LFO is distinctly extended, which becomes the most important source of flow unsteadiness in the corner region at a low Re. Furthermore, the contributions of various flow unsteadiness on the generation of TKE are quantified via multiscale proper orthogonal decomposition (mPOD) analysis, with the results showing that LFO contributes the largest proportion to TKE at a low Re. Thus, the loss increases or performance deterioration caused by the low-Re-effect is attributed mainly to the enhancement of LFO. That is to, say, the top priority of loss reduction in the corner region at a low Re is to suppress LFO growth by weakening the multiscale vortex-induced resonance process.