Impact of Non-Axisymmetric Inlet Guide Vane Stagger Angle on the Performance and Stability of a Low-Speed Research Compressor

Abstract

Abstract The paper examines the impact of non-axisymmetric inlet guide vanes (IGV) stagger angle on the performance and flow behaviors of a 4-stage low-speed research compressor at Shanghai Jiao Tong University. The One-ninth entire annulus of the IGV row and the first stage are modeled as the computational domain. The stagger angle of one in nine IGV blades is varied by 1.5 and 3 degrees in the anticlockwise direction from the datum case. The sensitivities of these non-axisymmetric configurations to two different total pressure inlet profiles (the datum and defective ones) are analyzed using RANS and URANS numerical methods. Results indicate that the impact of IGV stagger angle deviations on overall performance is negligible under the datum inlet. However, the performance and internal flow behaviors are significantly influenced by the defective inflow, especially in the 3-degree configuration. When stagger angle varies by 3 degrees, an approximately 2.39% efficiency penalty at the near stall condition and a 1.58% reduction in stall margin occur. The analysis on the internal flow behaviors shows that, with the datum inlet, only neutral trailing edge separations are observed in both design and near stall conditions. While under the defective inflow, a large corner separation exists near the rotor suction surface, resulting in a distinct performance degradation. The dynamic pressure signals at the rotor tip are examined to investigate the unsteadiness inside the rotor passage under both inlet conditions. It is demonstrated that for both inlet, the 3-degree deviation of IGV blade magnifies the intensity of the prominent frequency around the period of 2/3 blade-passing-frequency, which represents the generation, oscillation, and shedding of leakage vortices. Furthermore, a characteristic frequency 2044 Hz is newly observed in the 3-degree configuration under defective inflow. It might be brought by the radial migration and fluctuation of low-energy fluid separated from the rotor suction surface. Further investigations are required to study the effects of varied IGV staggers on rotor-stator matching and stall inception mode.