Restaggering of IGV blade row to mitigate distortion effects on a highly loaded axial compressor stage

Topic: MSc Seminar Simão Gonçalves (KTH & VKI)
Title: "Restaggering of IGV blade row to mitigate distortion effects on a highly loaded axial compressor stage"
Time: Oct 16, 2025 10:00 AM Stockholm

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Abstract:
"Current research on next-generation aircraft engines focuses on reducing emissions and fuel consumption through innovative concepts such as open-rotor architectures, Short Nacelle High-Bypass (SNHB) turbofans, and Boundary-Layer Ingestion (BLI) engines. However, these solutions force engines to operate under distorted inlet flow conditions that can compromise compressor performance and stability. The present work investigates whether performance recovery can be achieved by restaggering the inlet guide vanes (IGVs) of a low-pressure compressor stage, adopting a local design strategy to correct velocity triangles at the rotor inlet. By correcting local rotor incidence in specific parts of the annulus, this approach seeks to mitigate secondary flows and thus improve the overall performance of the stage under realistic distortion conditions. The study employed 2D unsteady full-annulus simulations to assess multiple IGV restaggering strategies, each based on a local correction: (i) Reducing incidence in the distorted sector while maintaining the same average stagger around the annulus as the clean configuration; (ii) Reducing incidence only in the distorted region, without preserving the average stagger around the annulus; (iii) Reducing incidence uniformly across the entire annulus. Results revealed that the restagger strategy was successful in correcting incidence in some regions of the annulus. However, when the restaggering caused significant blockage or triggered flow separation, the incidence correction was no longer effective. This thesis emphasises the limitations of pure local incidence correction and proposes an alternative design strategy that considers the annular behaviour of the stage. It demonstrates that robust incidence correction requires restagger methodologies that explicitly account for the coupled effects of stagger angle, blockage, and mass-flow redistribution, rather than relying solely on local flow angle adjustments."