Visualization of end wall flow in a large deflection turbine rotor cascade: Effect of tip clearance and incidence angle

Experimental investigations were carried out on a two-dimensional cascade fitted with 120° deflection rotor blades to study the effect of incidence angle on the end wall flow in the presence of tip clearance. A total of five incidence angles, -10°, -5°, 0°, 5°, and 10°, were chosen, and for each incidence angle, experiments were conducted for five tip clearance values at a constant space-chord ratio of 0.79. The end wall flow is visualized for all the incidence angles and tip gap heights. The variation of static pressure coefficient ahead of the blade leading edge and the discharge coefficient at various axial stations are also presented. For zero clearance, the primary and secondary separation lines are observed. The adverse pressure gradient upstream of the leading edge is reduced as the tip clearance is increased. The origin of the corner vortex moves toward the leading edge and the size of the tip clearance vortex increases as the incidence angle is changed from negative to positive values. The maximum value of discharge coefficient increases and the point at which maximum value occurs shifts toward the leading edge when incidence angle is changed from -10° to 10°.