Abstract: The pressing demand for future advanced gas turbine requires to identify the losses in a turbine and to understand the physical mechanisms producing them. In gas turbines with shrouded blades, a large portion of losses is generated by tip shroud leakage flow. In order to analyze the loss sources and physical mechanisms induced by shroud leakage flow, a computational study for a highly-loaded turbine was presented and discussed. Three dimensional steady multistage calculations using mixing plane approach and entropy analysis method were performed. Detailed tip shroud geometry is taken into consideration which overcomes most of the limitations of simple shroud empirical correlation in modeling leakage flow over tip shroud. Results show that turbine with shrouded blades show 0.9% higher in efficiency than the unshrouded one. Furthermore, cavity loss, leakage loss, mixing loss and incidence loss are the four major components of shroud related losses. Loss mechanisms breakdown analysis demonstrates that various loss sources account for different portions according to the tip clearance levels. Therefore, full calculation of shroud leakage flow is necessary in turbine performance prediction and the shroud geometric features need to be considered seriously during turbine design process. 

Key words: Shroud leakage flow; Leakage loss; Tip radial clearance; Entropy analysis; Highly-loaded turbine CLC number:V231.3Document code:AArticle number:1001-4055(2014)01-0033-10

摘要： 高性能燃气轮机的发展迫切要求对涡轮内部损失来源及其物理机制有更清楚的认识。采用带冠设计的涡轮中,气动损失的很大一部分来自叶冠的泄漏流动。为了深入分析叶冠泄漏损失对涡轮性能的影响,选取高负荷涡轮,采用带有掺混面模型的三维定常 计算方法和熵增的分析方法来研究叶冠泄漏的损失来源和损失机理。计算中考虑了详细的叶冠几何结构,打破了经验公式在模拟叶冠泄漏流时的局限性。结果表明,带冠涡轮比不带冠涡轮的气动效率高出约0.9%。叶冠泄漏所带来的损失主要分为腔体损失、泄漏损失、掺混损失和攻角损失四个部分,这四种损失来源在不同间隙下所占比例并不相同。因此,考虑完整的叶冠几何结构对涡轮性能的预测和气动设计至关重要。 

关键词: 叶冠泄漏流; 泄漏损失; 叶尖间隙；熵增分析方法; 高负荷涡轮