Influence of the root fillet on the flow pattern of an axial turbine rotor

The influences of the root fillet on the aerodynamic performance and vortex patterns of an axial turbine rotor were investigated by numerical simulation,and different root fillet radii were taken into account.Results show that the efficiency of the turbine rotor could decrease due to the root fillet.And the efficiency could further decrease with bigger fillet radius.The root fillet could make a significant influence on the cascade secondary flow patterns.In the case of small radius of the fillet,the separation bubble before the rotor leading edge near the endwall could increase markedly,resulting in the intensification of horseshoe vortex and lower passage vortex.And the lower passage vortex could move away from the rotor suction side.The pressure distribution near the trailing edge region changes due to the strengthening passage vortex;pressure at the region of the lower passage vortex reduces;meanwhile the pressure at the upper passage increases,leading to the decrease of the upper passage vortex for the fillet rotor compared with the unfilleted rotor.The fillet near the trail edge could increase the turbine rotor wake and induce more wake losses.However,comparisons of different fillet radii indicate that,as the fillet radius increases,the separation bubble decreases along with the correlative horseshoe vortex and lower passage vortex,and the upper passage vortex increase along with the rotor wake.