Performance characteristics of mixed-flow impeller and vaned diffuser with several modifications

The performance of a mixed-flow impeller and vaned diffuser unit with several modifications was investigated in an KACA vari[1ble-component supercharger test rigo The inves ti ga tion covered impeller tip speeds from 800 to 1200 feet per second over the range of nir flows from wide-open throttle to incipient surge 0 Several di':'ferent frontal clearances VJere tried, surveys were taken to detelmine the losses in the various components , and, finally, two 7aneless extensions of different diameter were added to the diffuser.The results showed the supercharger to have a peak efficiency of 0~77 ~ld a peak pres sure coefficient of 0.61 with the impeller frontal clearance at 0 .. 035 inch , The supercherger "'as fairly sensi ti ve to clearance! the peak efficiency fal ling off about two points at a mean clearance of 0,070 inch.The use of the vaneless extension to the stpr,dC1.rddiffuser increased the effi ciency to 0. 80.