Effect of Varying Diffuser Vane Height on NASA CC3 4:1 Centrifugal Stage Performance

This work is aimed at conducting a computational study to find out the effect of vaneless space downstream of the Diffuser vane trailing edge, by varying the height of diffuser vane viz. 50%, 75%, and 100% diffuser height, on centrifugal stage performance. The considered centrifugal compressor stage in this study is NASA CC3 4:1 centrifugal stage. In all the cases diffuser leading-edge radius is the same. The compressor performance with full diffuser vane configuration (100% diffuser height) is computed and initially compared with test data. The diffuser vane height is then reduced to 50% and 75% of the original length from the diffuser leading edge. Hence, the diffuser leading-edge location remains the same as the original 100% diffuser vane height geometry whereas the location of the trailing edge changes according to vane height. Another part of the study is to model the 75% & 100% diffuser vane height with hub and shroud gaps respectively. The computational study is carried out using CFX v19.1. The paper presents performance comparisons viz. speedline and 2D pitch averaged profile data of different variables for the above discussed five configurations.