Experimental Investigation of the Effect of the Impeller Blade Exit Cut on the Performance of a Radial Compressor

Abstract

This study deals with the experimental investigation of the radial compressor characteristics when the blade trailing edge is cut in the radial direction. Five impeller samples, of type, " HOLSET-4 ", are manufactured. One sample is used as a reference and the other 4-samples are changed, by cutting a radial length from one blade while keeping the next blade fixed. At off design speeds ,the maximum efficiency was found to be affected strongly by these cuts. The relation between the cut ratio and the maximum efficiency was reported and correlated. The corresponding mass flow rate and pressure ratio were also determined. It was found that as the cut ratio icreases the mass flow rate decreased with the increase of max. efficiency. The pressure ratio was found to change in an opposite manner to that of mass flow rate. NOMENCLATURE A Coefficient, or area of flow, m. B Coefficient. C Coefficient. cp Specific heat at constant pressure, J/kg K. g Gravitational acceleration, m/s 2. K Trailimg edge cut ratio (T.E.C.) = car/R2 m Mass flow rate, kg/s. mo Mass flow rate at maximum efficiency, kg/s. Nc Compressor speed of rotation, rpm. Ncd Compressor design speed, rpm .