CFD-based Analysis of the Effect of IGV Angle on the Performance Characteristics of a Centrifugal Compressor

In this study, the effects of inlet guide vane (IGV) angle variation on the performance and internal flow characteristics of an industrial centrifugal compressor were investigated using steady-state CFD analysis. Numerical simulations were conducted using ANSYS CFX for IGV angles of 0°, 20°, and 40°. The performance curves, component-wise entropy rise, and internal flow fields at the best efficiency point (BEP) of each IGV angle were compared. As the IGV angle increased, the circumferential component of absolute velocity at the impeller inlet increased, reducing the impeller work and shifting the performance curves and BEP toward lower flow rates. At the BEP of the 40° case, the flow rate, total pressure ratio, and efficiency decreased by 17.6%, 7.7%, and 1.8%, respectively, relative to the 0° case. Increasing the IGV angle promoted flow separation and entropy generation within the IGV passage, particularly at 40°, and also increased the diffuser loss owing to changes in the diffuser inlet flow condition. Although the impeller incidence angle at mid-span for the 40° case differed by approximately 5° from those for the 0° and 20° cases, no distinct leading-edge recirculation was observed, and the overall impeller entropy rise remained nearly unchanged. These results demonstrate a trade-off between shifting the performance curve and BEP toward lower flow rates and the accompanying reductions in pressure ratio and efficiency.