【作者】 毛宁；

【导师】 谭春青； 张冬阳；

【作者基本信息】 中国科学院研究生院（工程热物理研究所） ， 工程热物理， 2011， 硕士

【摘要】 为了减少间隙泄漏损失和振动,在条件许可的情况下,现代燃气涡轮一般将转子叶片设计成顶部带冠结构,并在叶冠上添加篦齿加以密封。这形成了叶冠密封容腔内及进出口流动特有的复杂流动现象,而且叶冠容腔结构和泄漏流仍然对涡轮气动损失有很大影响。因此,对于叶冠密封容腔流动的研究有着很重要的实际意义,也是近年来国际燃气轮机和蒸汽轮机领域的热点研究方向之一。本文采用数值模拟和分析的方法对涡轮叶冠容腔流动、叶冠的几何形状影响以及模拟叶冠容腔流影响的边界源方法等方面进行了研究。首先对国内外有关叶冠容腔流动的文献进行了综述和分析,总结了国内外学者所采用的研究方法和研究方向,结合论文依托项目研究内容,确立了本文的研究方法和主要研究内容。本文首先对所采用的数值计算方法进行了实验校验。在此基础上,本文对一三级燃气涡轮进行了几何建模、网格划分及网格无关性验证后,对各级动叶的叶冠容腔流动特性进行了研究。研究表明,涡轮的叶冠结构形成了较为复杂的流场结构,形成了相关流动损失,减小了动叶载荷,叶冠容腔的泄漏流影响了动叶和下一级静叶交界面的总压和熵分布,使得近机匣处的相对总压降低,熵增大。泄漏流与主流流动方向的差异使泄漏流进入下一级静叶时增大了近机匣区域的负攻角,产生了攻角损失和增强的二次流损失。在对三级涡轮叶冠容腔流动特性研究的基础上,对改进叶冠几何结构的性能进行了研究。基于减小叶冠质量的需求,对两种不同的部分冠结构进行数值计算,并对流场进行了对比研究和分析。结果表明,改进的部分冠减小了10%的叶冠的质量,但是与全冠密封相比,气动性能没有降低,涡轮等熵效率与全冠基本相等。与原始部分冠密封相比,改进的部分冠减小了近机匣区域泄漏流与主流的掺混损失,以及减弱了部分冠所带来的横向窜流。由于工程应用的需要,本文还对采用边界源等效叶冠容腔流动效应的方法进行了研究,分析了不同参数的影响。在本文研究的影响涡轮特性的几个因素中,进口面积对涡轮等熵效率的影响最大,其涡轮等熵效率最接近带冠涡轮的效率；泄漏流进口的总温对效率影响最小,进口位置的影响也很小。文中还对两种具有代表性的工况进行了流场的详细分析和对比,研究表明：两种工况在动叶出口近机匣的损失比带冠涡轮小,但是20%有效进口面积的工况在第二级静叶95%叶高位置有很大的负攻角,流动损失较大。在静叶下游,三者均能观察到在70%叶高处有泄漏流形成的损失区,相对于两种计算工况,带冠涡轮的损失区更大,效率更低。更多还原

【Abstract】 In order to reduce the leakage flow and vibration, the modern gas turbine is normally designed with blade shroud and labyrinth seal structure, which still induces complex flow phenomena around it and ignorable impact on flow loss of turbine. The investigation on this kind of leakage flow is no doubt of importance and has become one of the hot research directions in gas turbine and steam turbine fields in recent years.In this thesis, numerical simulation and analysis are conducted for the researcher on the shroud seal cavity flow, the impact of shroud geometry shape and boundary source method. The related domestic and foreign reference papers are analyzed and summarized in this thesis. Referred to the research requirement of relative projects, the following research works are conducted in this thesis.The numerical method and software are validated firstly. Then the flow in a three stage turbine with rotor shroud is simulated and analyzed after the geometry, grid generation and grid independence verification. The results show that the leakage flow forms the complex flow structure and leads to a decrease of blade loading and total pressure loss downstream rotor in the area near the shroud. The mixing of leakage flow and main flow results in negative incidence and enhanced secondary flow loss for the downstream blade row.For the investigating the partial shroud performance, the numerical study is conducted for the 1.5 stage turbine with two different partial shrouds. The results show the modified partial shroud, with a 10% reduction of mass, has the almost same performance with the fully shroud. Compared with the original partial shroud, the modified partial shroud reduces the mixing loss of the leakage flow and main flow, and wakens the circumferential flow in original partially shrouded turbine.For the engineering application purpose, the boundary source method for modeling tip shroud effect is studied and developed in this thesis. Several factors that influence the performance of turbine are analyzed. The results show that the leakage flow entrance area has the significant impact, whereas the flow total temperature and entrance location have the much less magnitude. Flow fields and characteristics under tow representative working conditions are compared and analyzed. More total pressure loss is observed for all these two conditions than the shrouded turbine in the area near the shroud, and large negative incidence into the second stage stator at 95% span under the condition of 20% of leakage entrance area. A loss region, which is resulted from the shroud leakage flow, is observed in the exit of second stage stator under the two conditions.更多还原