Comparative Study of Vaneless and Vaned Diffusers in a Transonic Centrifugal Compressor With Real Gas

Abstract

Vaneless and vaned diffusers in a transonic centrifugal compressor with the refrigerant HFC-134a were studied experimentally and numerically. The compressor was tested on a closed-loop stand instrumented to obtain both overall performance data and local flow field quantities. In numerical studies, the thermodynamic and transport properties of the refrigerant gas were modeled by the Martin-Hou equation of state and power laws, respectively. To include the interaction of the compressor components in these analyses, a unified three-dimensional numerical model was built for the complete compressor stage. The flow field was calculated with a Navier-Stokes solver using the k-ε turbulent model. The impact of the different diffusers on both local flow field and overall performance is analyzed comparatively for each component. The experimental and numerical results agree well. The correlation between the overall compressor performance and local flow field quantities is defined. The methodology developed and data obtained in these studies can be applied to centrifugal compressor design and optimization.