Stator wake research in an axial-radial combined compressor with inlet distortion

A combined compressor consisting of an axial rotor, a stator and a centrifugal rotor was used in a vehicle engine turbocharger because of its better performance compared with a single stage compressor under space restrictions. There have been many studies on the inlet distortion effect on multistage axial compressors; however, few studies have been performed for axial-radial combined compressors. To investigate stator wake characteristics, an axial-radial compressor was unsteadily simulated with three-dimensional Reynolds averaged Navier-Stokes equations by "domain-scaling" the rotor/stator interface method under uniform, circumferential distorted and combined distorted total pressure inlet conditions. In addition to the axial-radial configuration, the unsteady method of analysis was applied to a stand-alone axial stage by the same unsteady method. A comparison shows that at the vane stator outlet, a radial distortion is formed and different total pressure loss occurs at different spans. The circumferential interfaces between the distorted and non-distorted regions generate different flow characteristics due to different pitchwise pressure gradient directions and the absence of a downstream rotor. The stator wake causes more flow loss in the distorted case but less flow angle fluctuation compared to the uniform inlet condition. The downstream potential effect and inlet distortion creates strong pressure pulsation at the stator blade surface. A stator wake oscillation characteristics study shows disturbing effects on the stator wake from the upstream axial rotor, and the downstream radial rotor acts differently both spanwise and pitchwise.