An improved stall prediction model for axial compressor stage based on diffuser analogy

Stall represents a limit to the useful operation of the axial compressor. Despite its difficulty, a rational and effective stall prediction model is an urgent requirement for compressor designers. In this paper, a stall prediction model for determining the maximum static pressure rise capability of axial flow compressor stage is presented based on Koch’s two dimensional diffuser analogy concept. Compared with the original Koch’s model, where the flow angles are only used to consider the increase of inlet dynamic pressure factor caused by high stagger angle, this paper takes into account the effect of flow angles on the diffusion length, and derives the mathematical expression of the modified non-dimensional diffusion length. A semi-empirical correlation is presented to account for the effect of camber angle on the stalling static-pressure-rise coefficient of axial compressor stages. By re-evaluating the Reynolds number effect,blockage indicator is proposed to determine the effect of boundary layer blockage on stalling capability. Good agreement is demonstrated between the predicted and test stalling pressure rise data for a wide range of axial compressor stages and a 4-stage low speed research compressor. Compared with the original Koch’s model, the relative error of the modified model in predicting the stall margin is reduced from 22.5% to 3.5%. This model has a guiding significance for the selection of initial design variables in the axial compressor design process.