Numerical Analysis of the Tip Clearance Effect on the Stall Process in a Low Speed Axial Compressor

Blade row tip clearance height and the associated tip leakage flow is well known as an important factor impacting the stall inception process of compressors, thus there has been a large amount of research in this area. The relationship between tip leakage flow and spike initiated rotating stall has been confirmed, and there has been some work trying to explain the mechanism by numerical simulation approach. It would be helpful for optimizing the design if the stall process can be simulated during the preliminary design phase. However, general CFD methods are not suitable for this. Since stall inception is a highly unsteady process, unsteady CFD method is required to get accurate results. But unsteady RANS and LES both require significant computational resources, are unrealistic to be used during the preliminary design phase. TUSIAC (Three Dimensional and Unsteady Stall Inception Analysis Code) is a numerical simulation program developed by Tu, for simulating the whole stall process. It solves the Euler equations in the flow field, and modeled the rotor/stator as a three-dimensional actuator disk, thus the computational resources required is low, and is ideal for use during the preliminary design phase. In this article, the tip leakage flow model developed by Martinez-Sanchez and Gothier is modified and incorporated into TUSIAC, and the stall inception processes of a low speed axial compressor, with different tip clearance heights of the blade, are simulated using TUSIAC. The influence of tip clearance on the flow around it, the performance of the compressor, and the stall inception process are analyzed. It is shown that the newly developed model can describe the effect of tip clearance on the stability of the compressor correctly, thus providing a practical approach to investigate the compressor stability and optimize the compressor design during the preliminary design phase.