Blade-end treatment to improve the performance of axial compressors: An overview

This paper reviews the literature published over the past 30 years on the blade-end treatment in axial compressors. The blade-end treatment reduces the endwall losses and extends the stable margin by modifying the blade shape near the endwall region with end-bend, end-dihedral and end-sweep flow control measures. The end-bend improves the overall performance by aligning the blade inlet/outlet to the flow stream direction. The end-dihedral reduces the blade force on the endwalls, while the end-sweep not only reduces the shock losses, but also controls the spanwise migration of the blade surface boundary layer. All these effects strongly influence the compressor performance by modifying the blading loading distribution in the streamwise or spanwise directions. However, the benefit of the endwall flow control comes with increased losses in the mainstream so there is a trade-off between the improved endwall region flows and the degraded mid-span flows. Thus, how to combine end-bend, end-dihedral and end-sweep to achieve the correct balance of loss distribution, appears to be the key to a successful three-dimensional compressor design.