Effect of vaned diffuser throat area on surge flow rate of centrifugal compressor

摘要

The centrifugal compressor for the turbocharger with its design pressure ratio of 3.2 was tested with vaned diffusers. Throat area of the vaned diffuser was chosen as the geometric parameter. The smallest throat area which was selected covered 40% of its design flow rate. The analysis of the static pressure ratio in the impeller and the diffusing system-consists of the diffuser and the scroll-showed that there were four possible combinations of characteristics of impeller pressure ratio and that of diffusing system pressure ratio.In spite of reduction of the diffuser throat area, the compressor stable operating range could not be extended less than Q{sub}p within a certain range of the diffuser throat. Although it was possible to get the negative slope on the stage pressure ratiobelow Q{sub}p by use of the diffuser whose choke flow rate near Q{sub}p or less than Q{sub}p, the cost of the compressor efficiency was inevitable. The flow rate, Q{sub}p, where the