基于氦气热物性的氦气压气机叶栅流动特性解析与实验验证

HTGR is a kind of next generation reactor(Generation IV)that proposed by IAEA. Helium is a monoatomic and inert gas. The specific heat of helium is 5 times that of air. Those make helium a ideal coolant of High Temperature Gas Reactor (HTGR). However, the helium is diffcult to be compressed due to its larger specific heat and smaller molecular weight, which results in a number of compressor stages and slender compressor rotor if the compressor is designed based on the principle of air compressor despite of the compression ratio is not so high. The rotor will run at designated speed that will pass over several critical speeds and the manufacture is diffcult and costly as well. Therefore the research of flow characteristics of helium compressor is a basic scientific topic for HTGR. This research will investigate and improve the performance of helium compressor cascade with theoretical, numerical and experimental methods. The development and transition of boundary layer on the surface of helium compressor cascade will be investigated with theoretical and experimental methods. The performance and loss characteristics of helium compressor cascade will be measured. The separations of boundary layers of general compressor cascade and high-loaded compressor cascade will be observed and displayed. The distribution of loads along the span and stream wise will be researched. The conclusions of these researches will deepen the recognization of the flow mechanism of helium compressor and provide fundamental data to improve the performance of helium compressor.

高温气冷堆是国际原子能机构推荐的第四代核反应堆。作为冷却工质的氦气是单原子气体和惰性气体，其导热性能好，比热是空气的5倍，是高温气冷堆的理想冷却剂。但是大比热、大绝热指数和小分子量也同时意味着氦气十分难压缩,其结果是基于常规空气压气机原理所设计的氦气压气机，即使压比不大所得到的氦气压气机级数很多、效率较低、转子细长，及工作转速要跨过数阶临界转速的转子动力学问题。因此，氦气压气机叶栅流动特性研究就成为该领域重要的基础科学问题。 本课题从氦气热物性对氦气压气机叶栅性能影响分析出发，进行氦气压气机叶栅边界层发展与转捩的理论与实验研究；探索氦气压气机叶栅的氦气流动规律与损失特性；进行常规设计氦气压气机叶栅与高负荷叶栅三维分离模式研究与实验；进行载荷的展向与流向分配对氦气压气机叶栅流场结构的影响研究。研究结论可以深化对扩压叶栅内氦气流动机理的认识，为提高氦气压气机性能提供参考与基础数据。

高温气冷堆是最具有应用前景的第四代核反应堆之一。作为其堆芯冷却介质及循环工作介质的氦，由于比热比和定压比热均明显大于空气，因此采用空气压气机设计方法设计的氦气压气机具有级数多的特点。众多的级数使得氦气压气机转子细长，细长的转子诱发了严重的转子动力学问题。本项目从氦气的物性出发首先对氦气物性对氦气压气机叶栅边界层流动和发展进行了详细研究；其次利用氦气音速高的特点发展了氦气压气机的高负荷设计方法，并对高负荷氦气压气机的分离流结构后损失特点与常规氦气压气机进行了比较研究；然后从理论上揭示了氦气所具有的大比热比对氦气压气机性能（效率、压比、喘振边界和堵塞边界）的影响；最后分别采用氦气工质和空气工质对高负荷氦气压气机进行了试验对比研究。通过本项目的研究得出如下结论：1、雷诺数是影响叶栅边界层流动的关键因素之一，随着雷诺数的减小，吸力面转捩点位置靠前，转捩过渡段变长，转捩过程加剧。低雷诺数下，总压损失系数急剧增大，吸力面附面层位移厚度明显增加。在雷诺数很低的情况下，叶栅吸力面气流从分离点直接分离，将不会发生再附。2、氦气压气机的高负荷设计方法能够有效的解决氦气难压缩的问题，成功的将某型传统设计的16级氦气压气机的级数减少到了3级。3、在亚音速条件并且满足几何相似、马赫数相似和雷诺数相似的条件下，氦气的大比热比使氦气压气机较空气压气机相比具有较低的效率和较小的堵塞流量，而喘振裕度和压比则有所增加。