Research On Flow Analysis And Design Method Of Centrifugal Compressor Conformal Passage Diffuser

Conformal passage diffuser is a new kind of vaned diffuser which has been proposed byNanjing University of Aeronautics and Astronautics, the passage is a three-dimensional squareexpansion tube which turns in the meridian plane and rotary surface. In order to analyze the importantflow structures in diffuser and the main design factors impact on the diffuser performanceindependently, this paper firstly decoupled out two important factors as curvature and expansion ratiofrom complex relationship of the flow property of the diffuser, then a single passage of conformalpassage diffuser was simplified to a90°turn expansion tube. Finally, some conclusions were appliedto conformal passage diffuser and got a good verification. The main research work that has been donein this paper includes:1. The study on the turning expansion pipe with inlet aspect ratio of2, the turning radius from5cm~,expansion ratio in the range of0.024to0.074has been done, the results showed that:the best expansion ratio was in the range of0.065to0.072when inlet Mach number was0.9; The curvature had a great impact on the expansion pipe’s performance, but it didn’t change the bestexpansion ratio; Better performance was obtained by expending in meridian plane as well as sidewall at the same time. These laws could provide a reference for the diffuser design.2. According to the analysis and summarize inner flow condition of the two types of turning tubewhich were the meridian plane expansion and the side wall expansion at the high subsonic, theflow structure of a turn expansion tube was obtained, the main flow characteristics containingchannel vortex, separation vortex inside and outside the corner area at the beginning of turningand the separation in inner wall turn; study about the mechanism how expansion ratio, turningradius and the expansion form impacted on the performance would provide a basis for theanalysis of complex diffuser flow field.3. The investigation of the conformal passage diffuser performance and the structure of the flowfield when the expansion ratio was in the range of0.045to0.11showed that: the best expansionratio of conformal passage diffuser was in the expansion range of turn tube; the main flow fieldcharacteristics of conformal passage diffuser were spiral forward secondary flow, separationvortex at the dorsal casing and flow separation at the hub.4. The study, carried out in conformal passage diffuser at the expansion ratio was0.07and exitaspect ratio was in the range of8.22~1.01, found that: In the meridian plane, a given expansionmade exit aspect ratio not too big could obtain higher performance. In the condition of inletaspect ratio2and inlet geometry angle of conformal passage diffuser66°, exit aspect ratio3,the highest pressure coefficient could be obtained.