Effect of tip injection on an axial flow fan under distorted inflow

The present CFD analysis is aimed at studying the effect of tip injection on the performance and flow characteristics in the tip region of an axial flow fan under distorted inflow condition. Inlet flow distortions are flow non-uniformities that cause a reduction in performance and operating flow ranges of axial flow fan. CFD simulations were carried out for the following configurations: (a) 90° circumferential extent steady total pressure distortion without tip injection and (b) 90° circumferential extent steady total pressure distortion with tip injection. The configuration with six injectors, injector velocity of 60 m/s, 0° pitch angle, and injector skew angle of-15° (in an orientation opposing the direction of rotor rotation) is used for tip injection study. Total pressure values have been noted down from Ansys CFX post at the exit of the axial fan, both in distorted and uniform regions (with and without tip injection case). The simulation results are analyzed to obtain axial fan performance parameters like the pressure rise coefficient, flow coefficient. The result of the present analysis shows that the tip injection increases the pressure rise by 4.04% in distorted inflow for pitch angle of 0° and skew angle of -15°. Also there is a slight increment in the stall margin of the axial flow fan under distorted inflow.