EFFECT OF REYNOLDS NUMBER AND TIP CLEARANCE ON THE TRANSONIC AXIAL COMPRESSOR DURING GEOMETRIC SCALING

The compressor often needs to adjust geometric dimensions in the process of design and testing to adapt to different use environments and save design costs. However, low Reynolds number conditions can lead to performance degradation in small-scale machines. At the same time, due to the limitations of processing conditions, the relative tip clearance of small machines is relatively large, which also affects the efficiency and stable working range. Therefore, it is necessary to study the impact of Reynolds number and tip clearance changes on the aerodynamic performance in the process of size scaling. This article first uses the similarity law to geometrically scale down the compressor. The calculated numerical results are used as standards to evaluate the published efficiency correction formula. The results show that the correction error can be controlled within 3%, which meets the engineering application standard. Through flow field analysis, it is found that the decrease of Reynolds number will lead to the increase of boundary layer thickness, the weakness of tip leakage vortex, and the aggravation of corner separation. The accumulation of low-energy fluid in the corner is the main reason for the decrease in flow rate under low Reynolds number. Then, the impact of tip clearance changes on aerodynamic performance under different Reynolds numbers is studied. Under different Reynolds numbers, there is a negative linear correlation between efficiency, pressure ratio and clearance, and the influence of Reynolds number variation on the correlation coefficient is inconspicuous. Under low Reynolds number, increasing relative tip clearance to a certain extent can help improve the stable working range.