Effect of Shear Flows on the Outlet Angle in Axial Compressor Cascades—Methods of Prediction and Correlation With Experiments

A theory is presented for accurate prediction of the spanwise variation of outlet angle in axial compressor cascades, taking into account the effects of secondary flow, Bernoulli surface rotation, and spanwise flow displacement due to tangential vorticity and viscosity. The values of outlet angle predicted by this method are compared with experimental results obtained in various cascades (Louis [13], Soderberg [16], and Lakshminarayana [7]) in which the approach velocity was varied artificially in the spanwise direction by creation of a wake. The strength of secondary vorticity is reduced substantially by viscous effects and to a small extent by Bernoulli surface rotation. Conventional secondary flow theories which ignore these effects tend to overestimate the spanwise variation in outlet angle. An accurate estimate of the kinetic energy of the secondary flow is made.