Influence of uncertain inflow conditions on a subsonic compressor cascade based on wind tunnel experiment

The intended inflow condition of compressors is subject to the uncertain inflow Mach number (Ma₁) and incidence angle (i). To quantify the effects of uncertain inflow conditions, real-time measuring experiments of Ma₁ and i are performed under various operating conditions to extract the statistical characteristics of the uncertainties. Statistical analysis shows that Ma₁ and i follow Gaussian distribution. 0.005 and 0.125 are chosen as the standard deviation of Ma₁ and i, respectively. Based on these data, an in-house code of non-intrusive polynomial chaos and Sobol’ indices are employed to quantify the variability in the aerodynamic performance of a compressor cascade caused by uncertain Ma₁ and i. The results show that the inflow uncertainties narrow the steady working range of the compressor cascade and lead to fluctuation in the aerodynamic performance. The fluctuation amplitude of the total pressure loss coefficient increases about 15.8 times and tenfold while the static pressure ratio increases just double and 1.3 times under various Ma₁ and i conditions, respectively. An analysis of flow field under various operating conditions shows that the uncertainties change the peak isentropic Mach number on the suction surface alter the location and size of the boundary layer separation and reattachment, and shift the interference between the wake and suction surface separation vortex. The sensitivity analysis reveals that as Ma₁ increases from 0.5 to 0.6, the dominant parameter affecting the uncertainty of the flow field changes from i to Ma₁. When Ma₁ increases to 0.75, the coupling effect of Ma₁ and i dominates the flow field.