Flow control mechanism of compressor cascade: A new leading-edge tubercles profiling method based on sine and attenuation function

Abstract

Leading-edge tubercles are an effective method to improve the stall margin in a compressor. In existing studies on leading-edge tubercles, achieving a better control on all conditions is a huge difficulty and challenge. Hence, a new method of leading-edge tubercles profiling based on sine and attenuation functions is introduced in this paper. First, the wavelength and amplitude of the leading-edge tubercles were varied by sine function to study their effects on compressor performance. The research reveals uniform tubercles with small amplitude and large wavelength can delay stall incidence from 7.9° to 8.8° and increase it by 10% compared to the baseline. A small amplitude is beneficial to reduce the additional loss caused by the leading-edge tubercles near the blade middle, and a large wavelength is conducive to the development of separation vortex. Then, the leading-edge tubercles were further modified and investigated by introducing some attenuation functions. A suitable attenuation function is introduced to the uniform tubercles with small amplitude and large wavelength so that stall incidence is delayed to 9.7° and increased by 21.25% compared with the baseline. Finally, the vorticity transport equation and three-dimensional streamline reveal that the formation and development of leading-edge vortex pairs are mainly related to the axial bending of the circumferential vortex, the axial stretching of the axial vortex, and vortex viscous dissipation. For this paper, the principal purpose is to offer useful design guidelines, study flow control mechanisms, and achieve better aerodynamic performances under all working conditions for the leading-edge tubercles in the compressor.