考虑热斑和冷气掺混的多级燃气透平非定常流动与传热机理研究

Unsteady flow is an intrinsic characteristics for the internal flow of turbomachinery. However, for gas turbine, the inlet (or the combustion outlet) hot streak (nonuniform temperature profile) and the cascade cooling air mixing (nonuniform velocity and temperature profiles) intensify the complexity of the unsteady flow and heat transfer, thus significantly affect the efficiency and reliability of the heat-work conversion in gas turbine with multistage feature. Because of the incomprehension for influence mechanism of the hot streak and cooling air mixing, it is difficult to completely take these impacts into account in the related design theory for designer at present. With the increasing of gas turbine inlet temperature, the nonuniformity of temperature profile with the hot streak and the flow rate of cooling air increase, thus greatly affect the flow and heat transfer in gas turbine. Therefore, based on the one and a half axial turbine stage test rig with the hot streak generation simulator and the cascade heat transfer test rig combined with the cascade cooling air mixing model, by means of experimental measurement techniques and numerical simulation methods, this project aims to investigate the unsteady flow and heat transfer mechanism in multistage turbine considering the hot streak and cooling air mixing, reveal the influence of the clocking effect and the cooling air injection parameter on unsteady flow and heat transfer, subsequently provide solid theoretical basis and experimental verification for the development of efficient cooling technology as well as the unsteady aerodynamic optimization design method for turbine cascade, thus providing related theoretical fundation for increasing heat-work conversion efficiency in gas turbine.

透平机械级内的流动具有固有的非定常流动特点，而燃气透平进口（燃烧室出口）的高温热斑（非均匀温度场）和透平叶栅冷气掺混（非均匀速度场和温度场）加剧了其非定常流动和传热的复杂性，从而对多级燃气透平的热-功转换效率与可靠性产生重要的影响。由于对热斑和冷气掺混的影响机理尚不清楚，目前相关的设计理论还无法充分考虑其实际影响。随着透平进口温度的提高，热斑温度不均匀程度与冷却所需冷气量的增加，对流动与换热的影响越趋明显。为此，本项目拟在一级半轴流式透平试验台和叶栅传热试验台上，通过热斑生成模拟器及冷气掺混叶栅模型，应用试验测量和数值模拟相结合的方法，重点研究考虑热斑和冷气掺混的多级透平非定常流动和传热机理，深入揭示时序效应与冷气出流参数对非定常流动传热特性的影响规律，以期为发展透平叶栅高效冷却技术和非定常气动优化设计方法，提供充分的理论依据和实验验证，为燃气轮机热-功转换效率的进一步提升奠定理论基础。

燃气透平工作在高温、高压、高转速的恶劣环境中，内部流动具有固有的非定常流动特点，且受到燃烧室燃气出流非均匀性（热斑、旋流和总压梯度等）和叶片冷气出流掺混的显著影响，进一步加剧了透平内部流动和传热的非定常性和复杂性，极大的增加了叶片气动和冷却设计的难度，从而影响到透平气动效率和可靠性。本项目以发展综合考虑热斑和冷气掺混的多级燃气透平气动和冷却设计方法为出发点，针对多级燃气透平内部复杂非定常流动和传热冷却机理开展了系统深入的理论分析、试验测试和数值仿真研究。首先，对一级半透平试验台进行了系统改造，设计搭建了透平进口热斑模拟及试验测试系统，结合非定常数值仿真，深入揭示了燃烧室内部气流组织、扩散掺混等机理，得到了燃烧室出口热斑、湍流强度、旋流和总压分布的典型物理模型，解决了热斑试验和数值研究缺乏边界条件的难题。其次，采用高频快速响应气动探针和热电偶，实现了一级半透平叶片出口非定常瞬时流场和时均温度场的高精度测量，结合数值仿真，揭示了热斑在多级叶栅中的迁移衰减机理并指出了影响热斑衰减数值预测的关键参数，阐明了热斑等进口非均匀性引起的叶栅流动结构和传热机理变化，提出了利用热斑与叶排时序位置提升透平效率并降低叶片热负荷的可行性方案。然后，基于平板和平面叶栅气膜冷却试验与脱体涡模拟等数值方法，掌握了级环境下冷气出流与主流的干涉机理及上游冷气在下游透平级中的非定常迁移机理，获得了冷气掺混损失受冷气出流参数影响的敏感性，掌握了上游冷气对下游多级叶排流动和传热的影响机理。最后，研究了综合考虑热斑和冷气掺混的透平叶片传热冷却特性，建立了透平叶栅冷却工程一维和二维设计方法，搭建了端壁气热耦合试验台，提出并试验验证了端壁一体化复合冷却强化技术和均匀化设计方案，在透平工程设计中得到了应用。通过上述工作，完成了既定目标，研究结果为发展综合考虑热斑和冷气掺混的透平气动冷却设计方法提供了基础理论和技术支撑。