Aerodynamic interactions between compressor blades and circumferential temperature distortions

A unifying principle was discovered to treat square-wave, steady state, circumferential temperature distortions at arbitrary levels of distorted stagnation pressure, applicable to the low speed range., ' ' A velocity transformation was found to relate the physical 4 properties of a two-dimensional, non-viscous flow field collectively, to the\introduced modified velocity. Furthermore, the flow in the modified plane retains the characteristics of classical incompressible flow and, in general, is rotational. The flow was divided into regions of either constant or linearly â º varying modified velocities. Each two regions were separated by a free streamline initíally of unknown position. A non-linear,large disturbance,mathematical model was set-up to find out the correct free streamlines location in the presence of a single aerofoil. Considering first order derivatives of the induced modified velocities of the flow modified vortices and the aerofoil,.when applying a modified continuity equation,_the model converges rapidly.

.Results showed the aerofoil lift coefficient to fluctuate above and below its undistorted value, near the regions of shear flow,~º - depending on the relative directions of the flow modified vortices, and the circulation around the aerofoil - « . . Experimental investigations included tests on«a single blade' 'mounted near the intake of an axial compressor of constant annulus - height. Results showed that at this level of temperature distortions _ the stagnation pressure of the distorted flow had a dominant effect on the behaviour of the lift coefficient.