基于仿生微细通道结构的透平叶片蒸汽高效冷却机理研究

The tree-like branching network systems widely around in the natural world have the high cooling efficiency and the low flow resistance as well as the uniform temperature distribution characteristics. Utilizing the efficient transportation branching network as the internal cooling structure for the gas turbine steam-cooled blade, can provide the optimal resolution for solving the uneven and insufficient cooling problems on the high thermal load region of the steam-cooled blade. Based on the energy transport dynamics and the fractal geometry theory, the main research work is to find the convective heat transfer scaling law of tree-like fractal branching channel applied to the high temperature gas turbine; investigate the steam heat transfer mechanism in considering the effects of mesoscopic scale and imperfect gas by adopting the experimental and numerical method, and systematically analyze the influence of the variation of microchannel structure parameters and cooling conditions on the steam cooling performance, thus,obtained the bionic microchannel structure optimized method; then by utilizing the above research results, construct the new cooling blade model using the effective internal convective cooling passages and perform the blade comprehensive cooling efficiency test; explore the regularity of the internal cooling configuration placement and cooling steam flow rate distribution in harmony. The final objective of the current project is to establish a scientific and reasonable design method of the effective steam-cooled blade of the gas turbine, and provide the foundation and support for the application of the bionic microchannel to the steam-cooled blade of the high temperature gas turbines.

借鉴自然界广泛存在的树状分叉微网络设计高温透平蒸汽冷却叶片的内冷通道，使其具有高冷效、低流阻和温度分布均匀的特性，能够解决蒸汽冷却叶片在高热负荷区域存在冷却不均匀和冷效不足的问题。本项目拟结合能量输运动力学和分形几何理论，提出适用于高温透平叶片蒸汽冷却的树状分形分叉微通道的对流换热标度律；采用试验与数值计算相结合的方法，研究冷却通道的介观尺度效应，以及蒸汽作为实际气体对传热机理的影响，并系统分析微通道结构参数和冷却工况变化对蒸汽冷却效果的影响规律，构建系统的微通道单元冷却结构优化方法；在单元冷却结构研究结果的基础上，设计具有仿生微通道冷却结构的新型叶片模型，对其进行综合冷效试验，得到冷却结构与蒸汽流量的协调配置规律，从而建立科学合理的叶片蒸汽高效冷却结构设计方法，为仿生微通道应用于高温透平蒸汽冷却叶片提供依据和支撑。

针对高温透平叶片的冷却问题，设计了树状分形分叉微细通道的拓扑结构，并对其进行流动和换热特性的数值模拟与实验分析，阐明树状分形分叉微细通道的换热强化机理。对树状分形分叉微细通道和蛇形通道的壁面温度进行预测，发现采用蒸汽冷却的仿生微细通道的壁面温度分布最均匀。在相同的进口质量流量下，蒸汽的平均换热系数比空气的高大约49.2%。分析通道的结构参数对流体流动和换热特性的影响，研究工况变化下的摩擦阻力系数，换热系数和强化换热因子的变化规律，得到优化结果。在叶片上布置优化后的树状分形分叉微细通道冷却结构，并分析其冷却特性，为实现新型高效叶片冷却提供了设计方法和理论基础。