Experimental Investigation of a Truncated Pipe Diffuser With a Tandem Deswirler in a Centrifugal Compressor Stage

The subject of this paper is the experimental investigation of three different geometric configurations of the diffusing system in a high pressure centrifugal compressor stage for a jet engine application. The objective of this study is twofold. On the one hand, it seeks to explain the impact of truncating a diffuser and a redesigned tandem deswirler on the global stage performance; on the other hand, it aims to correlate the performance differences with local flow phenomena. For this purpose, a state-of-the-art centrifugal compressor test rig was used. Particle image velocimetry measurements visualize the separation behavior in the pipe diffuser passage. Thereby it is shown that the truncation of the diffuser changed the boundary conditions for the downstream deswirler including a high incidence. Thus, a new tandem deswirler design was implemented and measured. Moreover, the relative position of the two tandem rows is investigated. An optimal relative circumferential position for the stage efficiency and static pressure rise was found. This paper gives fundamental insight into the physical mechanisms of the influence of three geometric configurations in a centrifugal compressor stage, especially in the pipe diffuser and the deswirler. Hence, this study contributes in furthering knowledge of the fundamental principles of flow phenomena in the diffusing system of a centrifugal compressor.