Establishment of standard model of linear cascade wind tunnel for subsonic compressor（NPU-MGS1））

The standard model for linear cascade wind tunnel is the key to the construction of axial compressor design system and the standardization of linear cascade testing technique. The standard model of compressor cascade with a typical controlled diffusion airfoil is designed and tested based on linear cascade wind tunnel of Northwestern Polytechnical University. The flow quality of the standard cascade consists of inflow precision, flow periodicity, and two-dimensionality are adjusted by a self-established integrated control system. On the basis of examining the flow quality, the performance of the standard cascade is measured, including the features of incidence and axial velocity density ratio, as well as the distributions of surface isentropic Mach number and wake, and compared to the reference cascade data published by DLR. The results show that the standard cascade exhibits good flow periodicity and homogeneity, including a uniform region over four successive blade passages upstream and a periodicity range over two successive blade passages downstream, and the periodicity index of outflow is less than 2. The deviation of inlet Mach number and axial velocity density ratio in the measuring blade passage is no more than 0.005 and 0.02, respectively. At the design inlet Mach number of 0.62, the variation laws of the loss, exit flow angle and static pressure ratio with inlet flow angle are essentially the same between standard cascade and reference cascade. The loss and exit flow angle of the standard cascade are larger than those of the reference cascade due to the difference of measuring position downstream of cascade, but the static pressure ratio is basically the same. The distributions of the surface isentropic Mach numbers for the two sets of cascades are highly consistent. The test data for the established standard cascade is comprehensive and reliable.