Investigation on the performance and flow structure of centrifugal compressor-understand the inlet bent duct configurations

In turbocharger systems, the inlets of centrifugal compressor often connect with bent ducts, producing a non-uniform flow field distribution at the compressor impeller inlet, which degrades the compressor performance and deteriorate the flow structure of the compressor significantly. In present work, a group of typical bent ducts is designed by adjusting the torsion angle of the U-shaped duct to investigate the effects of these bent ducts on the performance and flow field of the compressor. The experimental tests of the compressor with various inlet bent duct configurations were carried out to obtain the aerodynamic performance and pressure distributions. The experimental performance curves showed the bent ducts affect the aerodynamic performance and surge margin of the compressor. To understand these effects fundamentally, the unsteady flow calculations were conducted to capture the detailed flow in the bent ducts and compressor internal. The flow distortion distributions and swirl patterns in various bent ducts were compared by numerical calculation results and analyzed in theory. The results showed the total pressure distorted region at the duct exit expands along the circumferential direction and distortion degree is weakened with the torsion angle of bent duct increases. Moreover, the swirl distortion patterns vary in different inlet ducts. The further analysis showed that an appropriate bent duct configuration is helpful for improving the surge margin of the compressor effectively. By observing the static pressure in the impeller inlet and shroud region, it found that the bent ducts produce non-uniform static pressure at impeller inlet and reduce the static pressure in shroud wall. It also found that the change of the pressure in compressor internal has some relation with the swirl structure of bent duct exit.