Research on Internal Flow of Centrifugal Compressor Scroll

Abstract

A centrifugal compressor used in turbochargers, industrial compressors and so on consists of an impeller, which is a rotating part, and a diffuser and a scroll, which are stationary parts. The kinetic energy given to the fluid by the impeller is decelerated and converted to pressure in the diffuser, then collected circumferentially by the scroll, and guided to the discharge pipe finally. In order to improve the aerodynamic performance of centrifugal compressors, the scroll is designed to minimize its pressure loss and also to prevent non-uniform circumferential pressure distribution to suppress the influence on the impeller and diffuser. As a result, the centrifugal compressor scroll has a cross-sectional area distribution which is gradually increased in the circumferential direction toward discharge. However, it is well-known that the off-design performance is deteriorated significantly due to the mismatch of the flow distribution and the area distribution of the scroll. In this study, to clarify a variation of flow distribution in the compressor scroll at the off-design condition, traverse measurements using a 5-hole yaw meter probe were conducted on two types of scrolls with different cross-sectional area and shapes, and the internal flow of the scrolls were investigated in detail when the pressure ratio and flow rate are changed.