Some perspectives on the treatment of three-dimensional flows on axial compressor blading

The unsteady and three-dimensional nature of the flow past axial compressor blading poses substantial challenges to the design of the main flow passage. High aspect ratio blading is amenable to the approach of splitting the design task between the cascade and the meridional planes. However, the three-dimensional flows increasingly affect the st age aerodynamic performance with decreasing blade aspect ratios. At very high load conditions, corner vortices can grow to two-thirds of the blade span, under the influence of the pitchwise pressure gradient, causing significant blockage and loss. A survey of treatments for three - dimensional flows highlights a variety of approaches, including longitudinal and tangential slots for suction and blowing, fences, turning vanes, fillets, and grooves. The merits and issues exposed by past implementations of these end-wall treatments are summarized. Considered together, these arrangements display a variable and open approach, which points towards an opportunity for considering a more common framework, led by a greater understanding of the flow physics. Preliminary work on the parametrization of end-wall grooves has highlighted some promising topological features of end walls generated by using the Beta distribution function as the guide curve. This seemingly unexplored application of the Beta function to axial compressor end wall design promises a better fit with the pitchwise periodic axial compressor geometry than other guide curve functions considered herein and used in the past.

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