The Effects of the Number of Blades/Vanes on the Performance of a Two-Stage Centrifugal Compressor: The CFD Analysis

Abstract

Improving the performance of heavy-duty compressors used in various industries leads to increased efficiency and reliability. Natural gas transmission pipelines are one of the sectors whose performance depends on the stable operation of pressure-boosting stations and their compressors. This paper studies one of the industry's most widely used two-stage centrifugal compressors. Using computational fluid dynamics (CFD) simulations, the effects of changes in various parts have been investigated. The inlet channel, the diffuser between the two stages, and the impellers were studied as the main parts related to the working fluid. The compressor was simulated under different operating conditions and geometries. The results showed that the initial design was based on operation in a specific condition. Compressors perform better at lower flow rates and have significant potential for improving efficiency as flow rates increase. The polytropic efficiency of the primary compressor is 77.04 %. Increasing the number of IGVs to 22 has increased efficiency to 81.43 % (an 8.8 % increase). Modifying the compressor geometry by changing the number of DVs has a limited effect on improving its performance. Increasing the number of DVs to 23 has reduced efficiency by 0.7 %, and reducing their number to 19 has increased efficiency by 1.1 %. By reducing the number of IBs to 15 in the first and second stages, efficiency increased by 2.56 % (from 77.07 % to 79.04 %). The largest negative and positive effects were due to changes in the number of impeller blades (−3.36 %) and inlet guide vanes (+69.5 %), respectively. Since the flow rate of the line was low in most seasons of the year at the time of the initial design and has now increased, the results of this study can have a great impact on reducing power consumption and losses. © 2025 Elsevier B.V., All rights reserved.