气膜孔布置对透平端壁冷却和气动性能影响的研究

Study on Effects of Film Hole Arrangements on Film Cooling and Aerodynamic Characteristics of Turbine Endwall

为了研究燃机透平端壁气膜冷却特性,对存在装配间隙泄漏流条件下端壁不同气膜孔布置的气膜冷却进行了分析。采用压敏漆技术对端壁气膜冷却效率进行了测量,并利用实验结果对湍流模型进行了校核;对所研究模型的网格无关性进行了验证,在此基础上,采用实验给定的边界条件,研究了存在装配间隙泄漏流的端壁在不同气膜孔布置下的气膜冷却特性及气动损失特性,详细分析了5种冷气吹风比(M=0.5,1.0,1.5,2.0,2.5)和4种气膜孔布置下端壁气膜冷却特性和气动特性。结果表明:对于气膜孔布置A(S=0.065C_(ax),γ_(2)=-56.6°,S为第二组气膜孔到装配间隙的距离,C_(ax)为叶片轴向弦长,γ_(2)为第二组气膜孔复合角),吹风比为0.5时,端壁气膜冷却效率最大,随着吹风比的增大,气膜孔出口冷气脱离端壁表面,气膜孔周围的气膜冷却效率下降;4种不同气膜孔布置下叶栅出口处近端壁区域的总压损失系数均随着吹风比的增大而降低,其中气膜孔布置A的降低幅度最大;低吹风比(M=0.5)时,气膜孔布置对端壁气膜冷却特性影响较小;高吹风比(M=2.5)时,气膜孔布置D(S=0.1C_(ax),γ_(2)=30°)端壁气膜冷却效率最高。

A numerical study was carried out for the effects of different film hole arrangements on film cooling characteristics of turbine endwall with midpassage gap leakage.Firstly,the film cooling effectiveness of a gas turbine endwall was measured with PSP method,and the results was adopted for turbulence model validation.Then mesh independence analysis was carried out for the model under study.On this basis,the film cooling and aerodynamic loss characteristics under different film hole arrangements of the endwall with midpassage gap leakage were studied.The film cooling and aerodynamic characteristics under five different blowing ratios(M=0.5,1.0,1.5,2.0,2.5)and four film hole arrangements were analyzed in detail.Results show that when the blowing ratio is 0.5,the endwall film cooling effectiveness reaches its maximum value under arrangement A(S=0.065Cax,γ_(2)=-56.6°;S is the distance between second group film holes and midpassage gap,Cax is the axial chord length of the blade,andγ_(2) is the compound angles of the second group film holes).With the increase of blowing ratio,the film coolant jets off from the endwall surface,and the film cooling effectiveness near the film hole decreases.Under the four different film hole arrangements,the total pressure loss coefficient in the near wall area decreases with the increase of the blowing ratio.The decrease amplitude under arrangement A is the greatest.The film hole arrangement has little effect on the endwall film cooling under a low blowing ratio(M=0.5).The film cooling effectiveness(S=0.1Cax,γ_(2)=30°)is the highest under arrangement D and a high blowing ratio(M=2.5).