摘要
为了评估上游台阶结构对端壁气膜冷却性能的影响,采用商用CFD软件ANSYS FLUENT数值研究了上游后向台阶结构对跨声速透平叶栅端壁上游双排离散气膜孔冷却效率的影响。模拟某工业燃气透平真实运行工况(进口湍流度Tu=16%、出口马赫数Maex=0.85、出口雷诺数Reex=1.5×10^6),采用基于两类热边界条件模型的壁面换热系数和绝热冷却效率数值预测方法,计算分析了在设计工况吹风比为2.5下,具有不同上游台阶高度(ΔH=0,3,6.78,10 mm)的跨声速透平叶栅端壁热负荷分布、气膜冷却效率分布和近端壁二次流场结构。研究结果表明:上游台阶结构改变了近端壁流场,在台阶下游形成强度较大的空腔涡等复杂涡系结构,显著影响了端壁的热负荷和冷却气膜覆盖分布;随上游台阶高度的增加,叶栅通道上游端壁传热逐渐增强,形成显著的条状高传热区;端壁冷却效率呈现先增大后减小的变化趋势,在ΔH=6.78 mm时,端壁气膜覆盖效果最好;在ΔH=10 mm时,上游离散孔冷却射流被限制在近吸力面三角区域,端壁冷却效率低于无进口台阶结构。
To evaluate the influences of the upstream step geometry on the endwall film cooling performance of the upstream double-row film holes,the commercial CFD software ANSYS FLUENT was used to predict the endwall film cooling efficiency.The endwall thermal load distribution,film cooling efficiency distribution and the secondary flow field were calculated and analyzed for four different upstream step heights(ΔH=0,3,6.78,10 mm)at the practical design condition of an industrial gas turbine with the blowing ratioγBR=2.5,inlet turbulence Tu=16%,exit Mach number Maex=0.85,exit Reynolds number Reex=1.5×10^6 by using the numerical method based on two types of thermal boundaries.Results show that flow filed near endwall is significantly influenced by the upstream step geometry due to the complex vortex structure such as the large cavity vortex downstream of the step,which obviously changes the endwall thermal load and film cooling distribution.As the upstream step height is increased,the complex vortexes located downstream of the step are significantly enhanced,resulting in a series of striped high heat transfer regions located at the upstream of the cascade passage.Due to the influence of the upstream step geometry,the endwall film cooling efficiency first increases and then decreases with the increase of step height,and the endwall obtains the best film cooling coverage when the step height is 6.78 mm.When the upstream step height is 10 mm,the coolant jet is confined to the triangle region near the vane suction side,which results in an obvious decrease in the film cooling efficiency compared with the case ofΔH=0 mm.
作者
白波
李志刚
李军
BAI Bo;LI Zhigang;LI Jun(School of Energy and Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China;Collaborative Innovation Center of Advanced Aero-Engine,Beijing 100191,China)
出处
《西安交通大学学报》
EI
CAS
CSCD
北大核心
2020年第5期1-8,共8页
Journal of Xi'an Jiaotong University
基金
国家自然科学基金资助项目(51776152)。
关键词
上游台阶结构
双排离散气膜孔
端壁传热
气膜冷却
upstream step geometry
double-row discrete film cooling hole
endwall heat transfer
film cooling
