Effects of Inlet Tip Clearance on Internal Flow Characteristic and Aerodynamic Performance of Centrifugal Compressor

Abstract

In this study, numerical simulations of centrifugal compressors are carried out using ANSYS-CFX software. The focus lies in investigating the impact of the inlet tip-clearance (ITC) on the characteristics of the internal complex flow and the aerodynamic performance of centrifugal compressors. Specifically, the paper mainly emphasizes the influence of ITC on the polytropic efficiency and total pressure ratio of a centrifugal compressor, as well as the variations in velocity and pressure at the blade tip, the spatiotemporal evolution of the tip-leakage vortex (TLV), and fluctuations in pressure and velocity downstream of the passage near the blade surface. Analysis of tip-leakage flow (TLF) and TLV motion patterns at rated operating conditions reveals the spatiotemporal evolution within one revolution. Results from Fast Fourier Transform (FFT) spectrum analysis indicate that the TLV motion pattern may be affected by the ITC size. The fluid flow resistance and backflow in the blade tip region are gradually reduced, the flow field stability is effectively enhanced, and the reflux vortex at the volute outlet is eliminated, thereby the working range of the centrifugal compressor is effectively extended by decreasing the ITC. The aerodynamic performance of the centrifugal compressor is effectively increased in the range of the medium and high flow rates by decreasing ITC. Additionally, it is observed that pressure, velocity, and load in the blade tip region do not exhibit a linear relationship with ITC, resulting in a nonlinear change in aerodynamic performance concerning ITC. Pressure and velocity spectrum analysis suggests that the effect of TLF is stronger at the top of the flow passage compared to the middle. Moreover, with the increase of ITC, the effect of TLF decreases at the middle and top of the pressure side (PS) while increasing at the bottom of PS and the suction side (SS).

Keywords

• numerical simulation
• centrifugal compressor
• inlet tip clearance (itc)
• spatiotemporal evolution
• fast fourier transform (fft)
• nonlinear relationship