Proposal and Experimental Verification of Design Guidelines for Centrifugal Compressor Impellers With Curvilinear Element Blades to Improve Compressor Performance

Abstract

This study numerically and experimentally examines the effects of applying curvilinear element blades to fully-shrouded centrifugal impellers on the performance of the centrifugal compressor stages. The design suction coefficient of the target impellers was 0.073. Our previous study confirmed that the application of curvilinear element blades could improve the stage efficiency of similar types of centrifugal compressors. However, a detailed explanation of the relation between the stall margin and the application of the curvilinear element blades remains to be given. The purpose of this study is to investigate the effects of using these blades on the impeller flow field and the stall margin in further detail.The curvilinear element blades we developed for centrifugal turbomachinery were defined by the coordinate transformations between a revolutionary flow-coordinate system and a cylindrical coordinate system. All the blade sections in the transferred cylindrical coordinate system were moved and stacked spanwise in accordance with the given "lean profile," which meant the spanwise distribution profile of movement of the blade sections, to form a new leaned blade surface. The effects of the curvilinear element blades on the impeller flowfield were investigated by conducting numerical simulations using this method. We next considered the optimum design guidelines for impellers with curvilinear element blades. Then we designed a new impeller using these design guidelines and evaluated the performance improvement of a new compressor stage by conducting numerical simulations.As mentioned in several papers, we numerically confirmed that curvilinear element blades with a negative tangential lean profile improved the velocity distribution and stage efficiency INTRODUCTIONCentrifugal compressors are widely used in various industrial fields. These centrifugal compressors require a higher efficiency and a wider operating range to reduce their life cycle costs and their influence on the environment.

Influence of blade geometry on secondary flow development in a transonic centrifugal compressor

“…The authors concluded that an efficiency increase of about 1.5% was mainly achieved due to a shock strength reduction in the inducer of the impeller. Another remarkable optimization of a process gas compressor with a shrouded impeller was made by Hiradate et al (2014), which was later experimentally verified by Tsukamoto et al (2015). Due to the use of curvilinear blade stacking and thus a modification of lean, an efficiency improvement of 2.1% could be achieved.…”