The complex unsteady flow exploration of a contra-rotating rotor under inlet distortion

Abstract

This article explores the relationship between stall types and speed ratios in contra-rotating boost stages, discovering stationary circumferential stall cells and dual stall cell phenomena, and examines the relationship between stall characteristics and inlet distortions. These stall characteristics of counter-rotating boost stages are markedly different from the single stall patterns of traditional compressor rotor-stator structures, highlighting the complexity of the flow field in counter-rotating stages. The study uses the experimental methods to investigate different speed ratios under both uniform and distorted inlet conditions, conducting both accelerating and decelerating stall tests, with each stall condition analyzed using data from 25 s. The main focus is on the stall types, frequencies, and development patterns under different distortion conditions at various speed ratios, filling a research gap in counter-rotating boost stages. It explores the unstable flow characteristics of counter-rotating boost stages under distorted conditions, particularly the stall disturbance characteristics and pressure fluctuation patterns at the blade tip during stall entry and recovery under distortions. Comparing distortions with uniform inlet conditions provides an intuitive understanding of the influence of various types of distortions on wall pressure and stall in the flow field. Researchers can use this knowledge to design casings or blowing devices to suppress stall disturbances, thereby achieving stall prevention and enhancing stability.