Simplified Numerical Models of the Unsteady Tip Leakage Flow in Compressor

Tip leakage flow (TLF) in compressors, which can cause flow blockage in blade passage and induce efficiency loss, is also a potential threat to the unsteady flow stability of modern aeroengines. This paper provides an overview of the significance of tip leakage flow research, and introduces relevant previous studies. After calculating by different methods, large eddy simulation (LES) is demonstrated again as a suitable compromise between accuracy and computational cost for the unsteady flow study. Two types of simplified tip leakage flow models using LES are adopted with a focus on the unsteady characteristics of shedding vortices in a cavity plane. This paper applies these models to study the unsteady tip leakage flow which triggers the onset of acoustic resonance in a multistage axial compressor. Compared with the detected acoustic resonance frequency of 5.22 rotational frequency (RF) in the previous experiment, the computed combination frequency in the 2-D model is equal to 5.232RF, and the simplified 3-D unsteady tip leakage flow model results in a combination frequency of 5.316RF. Therefore, based on the small relative error between model results and experimental results, the simplified numerical models are validated to be sufficiently accurate, and theoretically provide a useful basis for the subsequent research of unsteady tip leakage flow in turbomachinery.