Design Optimization of Shock Control Bumps for Efficiency and Stability Enhancement of Transonic Axial Compressor

Abstract In the interior of supersonic/transonic axial compressor, implementing shock control bumps (SCBs) on the blade suction surface holds great promise for delaying shock waves and shrinking boundary-layer separation regions. However, conventional approaches to SCBs design optimization have shown limited effectiveness in simultaneously enhancing peak efficiency and expanding the operating range, because of the incomplete physical mechanisms underlying the separation suppression by SCBs and the lack of quantitative flow-field metrics for assessing operating stability. Building on the previous research into the stall flow mechanisms in the axial compressor, the present study introduces both shroud endwall blockage attenuation and suction surface separation suppression as key metrics for optimizing the operating stability of SCBs. On this basis, an efficient design optimization method for SCBs is proposed by integrating a classification-based surrogate-assisted evolutionary algorithm with an adaptive filling strategy. The developed optimization framework is applied to the SCBs design on a transonic compressor rotor, resulting in a 5.55% increase in the stall margin and a 1.71% improvement in the adiabatic efficiency. Separation flow topology analysis, based on the critical point theory, reveals that the enhanced efficiency and expanded stable operating range are primarily due to delayed shock-induced boundary-layer separation and the formation of a reattachment zone on the blade suction surface. These improvements are attributed to the transformation from an unstable saddle-point topology to a stable node-point topology, occurring in the mid-span region at the peak efficiency point and near the blade tip at the near-stall point.