Numerical and experimental investigation of quantitative relationship between secondary flow intensity and inviscid blade force in axial compressors

The secondary flow attracts wide concerns in the aeroengine compressors since it has become one of the major loss sources in modern high-performance compressors. But the research about the quantitative relationship between secondary flow and inviscid blade force needs to be more detailed. In this paper, a database of 889 three-dimensional linear cascades was built. An indicator, called Secondary Flow Intensity (SFI), was used to express the loss caused by secondary flow. The quantitative relationship between the SFI and inviscid blade force deterioration was researched. Blade oil flow and Computation Fluid Dynamics (CFD) results of some cascades were also used to cross-validate. Results suggested that all numerical cascade cases can be divided into 3 clusters by the SFI, which are called Clusters A, B and C in the order of the increasing SFI indicator. The corner stall, known as the strong corner separation, only happens when the SFI is high. Both calculations and oil flow experiments show that the SFI would stay at a low level if the vortex core at the endwall surface does not appear. The strong interaction of Kutta condition and endwall cross-flow is considered the dominant mechanism of higher secondary flow losses, rather than the secondary flow penetration depth on the suction surface. In conclusion, the inviscid blade force spanwise deterioration is strongly related to the SFI. The correlation of the SFI and spanwise inviscid blade force deterioration is given in this paper. The correlation could provide a quantitative reference for estimating secondary flow losses in the design.