THE AERODYNAMIC DESIGN AND PERFORMANCE OF CENTRIFUGAL AND MIXED-FLOW COMPRESSORS

This paper presents an analytical method and aerodynamic design criteria) as applied to the design of centrifugal and mixed-flow compressors. Included are the basic design criteria and test results of 12 compressors, comprising altogether a range of impellers of various configurations consisting of backward/curved and straight radial vanes and a special group of research mixed-flow impellers. The compressors shown include current AiResearch production models used in small gas turbines for both bleed air and shaft power application. The test results of these compressors show that, by following the aerodynamic design criteria with respect to impeller blade loading distribution, high over-all compressor stage efficiencies (from 80 to 85 percent) are obtainable, the highest being 85 percent at 3.0 pressure ratio with a mixed-flow impeller and vaneless diffuser combination. Impellers designed with non-optimized blade loading criteria show considerably lower efficiencies.

The first successful effort to apply strictly aerodynamic design criteria to establish the impeller blade shape started at AiResearch nearly 10 years ago, and has undergone continuous improvement since that time in regard to both the mathematical solution of the three-dimensional flow involved and the knowledge gained from the test results of each succeeding compressor. As a result of this continuing effort, it is felt that centrifugal compressors of very high efficiency can be designed with a high degree of assurance by following the technique and aerodynamic criteria presented herein.