对转涡轮盘腔内流动结构转换机理及传热特性的研究

Contra-rotating turbine has already become one of the frontier research of high performance gas turbine technique because of its several excellent advantages. The contra-rotating turbine disk cavity is a new type of rotating cavity formed by two adjacent disks rotating in opposite directions. The fluid flow and heat transfer in contra-rotating disk systems is one class of flow and heat transfer involving most complex underlying physics, and there is comparatively little information on such flow and heat transfer, which needs more researching work. The distribution of rotation-induced forces such as Coriolis force、Centrifugal force and derived buoyancy are numerically investigated. The formation mechanism of Batchelor-type flow and Stewartson-type flow and the transition mechanism between them are analyzed through the research of the coupling effects of the rotating induced forces on the boundary layer flow and the two-cell flow in the core region. The source of the earlier transition to turbulent flow in counter-rotating disk cavity compared with rotor-stator disk cavity is also investigated and explained through the research of instability of the flowing free shear layer formed by the counter secondary circulations. Meanwhile, the effects of flow structure transition on the Nusselt number and frictional moment coefficient on the cooling disk and the pressure in the cavity are experimentally and numerically studied. As the purpose of the researching work, the measures of intensifying the cooling and sealing effects inside contra-rotating disk cavity system will be concluded, thereby increasing the efficiency of the aeroengine.

对转涡轮因为其突出的优点已成为高性能燃气涡轮技术发展的前沿研究方向之一。由于对转涡轮盘腔内流动和换热的复杂性，至今仍有大量问题不甚清楚，尚需进一步深入的研究。本项目通过对对转盘腔内哥氏力等旋转附加力耦合作用对盘面边界层内流动和核心区双涡二次流的影响、旋转附加力对低速盘上滞止点和核心区自由剪切层形成的影响、自由剪切层不稳定性的实验和数值研究，阐明Stewartson型和Batchelor型流动结构的形成机理，揭示Stewartson型和Batchelor型两种流动结构之间的转换机制，探明对转涡轮盘腔内流动相对于转静系由层流向紊流提前转换的原因，并阐释流动结构转换对盘面努塞尔数、力矩系数及盘腔内压力的影响及其机理。综合分析后提出强化对转涡轮盘腔内换热和密封效果的措施，达到延长涡轮盘疲劳寿命、提高发动机性能的目的。

对转涡轮盘腔内的流动及传热特性具有重要的学术价值和工程意义，也是目前国内外研究的一个热点。本项目围绕对转涡轮盘腔内流动及传热所涉及到的三个基础科学问题：对转盘腔内流动结构形成和转换特征、不同流动结构形成机理、流动结构转换对盘腔内冷却和密封特性的影响在此领域展开了一系列的数值模拟和实验研究，主要研究结论如下：获得了转速、转速比及冷却气流流量等参数对封闭旋转盘腔和有进出流旋转盘腔内的流动结构形成和转换的影响规律，同时发现了新的流动结构；探明了作用在流体上的离心力、哥氏力等旋转附加力的分布及与流体流动的耦合作用；揭示了各流动结构的形成机理；并阐明了对转涡轮盘腔内流动相对于转静系由层流向紊流提前转换的原因；提出了对转盘壁面温度分布的无线测量方法，阐释了流动结构转换对盘面努塞尔数、力矩系数及盘腔内压力的影响及其机理；建立了涡轮盘冷却工作参数-盘腔内流动结构-盘腔内冷却和密封性能的内在联系，为发动机对转涡轮盘冷却结构设计提供了有用的参考依据和理论支撑。