A Comparison of Manufacturing Methods, Accuracy, Quality Control and Testing Methods a They Relate to High Head Low Flow Impeller Efficiency and Overall Compressor Performance

Abstract

This paper presents a detailed analysis and evaluation of impeller efficiency and overall compressor performance as they relate to specific impeller manufacturing methods, manufacturing tolerances, and quality control. The manufacturing process used in the construction of an impeller has a direct influence on the impeller’s performance The authors explain and compare different manufacturing methods and introduce the Taguchi Method Application as an available tool for statistical evaluation of key manufacturing parameters influence on impeller performance. As a best practice, manufacturing techniques for one piece impeller production are presented. In the case of high pressure centrifugal compressor applications with very narrow tip width impellers, and corrosive gas applications requiring special materials, EDM (Electrical Discharge Machining) and ECM (Electrolytic Machining) can be applied as a manufacturing process to improve quality control over conventional manufacturing methods. In response to a compressor performance discrepancy encountered during OEM FAT, a review was initiated into improving quality control and performance prediction based on enhanced impeller manufacturing processes for narrow tip width impellers. In this analysis, two compressor rotors are evaluated and compared; the first using traditional, two piece welded impellers and the second with one piece impellers machined via EDM and ECM. The resulting data from both series of tests suggests a significant improvement in individual impeller performance, as well as overall compressor performance for the single piece impeller compared to the two piece impeller.