叶根倒角对轴流涡轮转子流场的影响

通过对某一亚声速轴流涡轮转子进行数值模拟,研究了涡轮转子根部倒角对涡轮叶栅流场的影响.研究结果表明:叶根倒角改变通道内的涡系结构,使叶栅通道内的流动重新分布,并降低了涡轮效率.当叶片根部存在较小半径的倒角时,倒角使叶片前缘近轮毂处的分离程度加剧,分离涡强度增加,并导致前缘马蹄涡和下通道涡强度和范围都增加,下通道涡增强导致叶片尾缘处通道下方静压降低,而通道上方静压相应升高,通道上半部流道前后压差减小,上通道涡的形成和发展受到抑制,上通道涡强度和分布范围都减小.随着倒角半径的增加,根部前缘分离程度先略有增加,然后减小,导致马蹄涡和下通道涡的强度先增加后减小,上通道涡强度先减小后增加.倒角还会使轮毂附近尾迹的强度和范围都加强,使尾迹损失增加. 

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.