仿生波浪前缘在核电汽轮机末级叶片设计中的应用研究

The last stage blade's performance (LSBs) of steam turbine has a great influence on the nuclear power unit's reliability and economy. In recent years, due to its good adaptability to attack angle, bio-inspired wing has become a hot topic in the research field as aeronautics, etc.. Both theoretical investigation and numerical simulation will be performed to study the phenomenon of flow separation, wet steam condensation flow and transonic flow in the last stage of LP steam turbine. By combining the QMOM (Quadrature method of moments) and LES technology, coupling effect of spontaneous condensation and boundary layer separation in wet steam will be considered, and the inhibition effect of the wavy leading edge blades on wet steam boundary layer separation will be studied. The influence of the wavy leading edge's geometry on droplet deposition and liquid film movement mechanism will be dissected by establishing the calculation model and transport equation of liquid film movement equations. Then the effect of wavy leading edge profile on the dewetting performance of nozzles on the last stage will be investigated. By calculating such two-phase flow features as moisture, droplet size and its distribution in the stage, the sensitivity analysis of stage efficiency on such parameters as attack angle of wavy leading edge will also be conducted. In this way, the secondary flow distribution from blade root to tip and the aerodynamic loss in supersonic flow for the bio-wavy leading edge blades on the last stage of LP steam turbine will be revealed. The study proposed above will provide a new idea and theoretical basis for the dewetting performance of nuclear steam turbine blade and optimization of steam turbine blade foil.

汽轮机末级叶片性能对核电机组可靠性和经济性有重要影响。近年来，具有良好冲角适应性的仿生叶型成为航空等领域的研究热点。本项目拟通过数值模拟和理论分析，研究蒸汽在核电汽轮机低压末级长叶片内流动中流动分离、凝结两相流动以及跨音速流动等问题。利用QMOM与LES技术相结合的方法，综合考虑湿蒸汽自发凝结与边界层分离的耦合作用，研究波浪前缘叶型对湿蒸汽边界层分离的抑制机理。构建液滴沉积率计算模型及液膜运动输运方程，对比分析静叶波浪前缘关键参数对液滴沉积及液膜运动的影响机制，探讨其对核电汽轮机末级静叶除湿性能的影响。研究波浪前缘叶型对级内湿度、水滴直径及分布等两相流动的影响规律，分析末级级效率对仿生波浪前缘关键参数的敏感性，重点分析波浪前缘对长叶片叶高方向的二次流分布、以及对控制超音速流动中气动损失的作用。本项目的研究可以为核电汽轮机除湿及叶型优化提供理论依据。

我国能源发展的主要战略措施之一是在确保安全的前提下发展核电。随着电力结构的不断调整，未来核电比例将越来越高。为提高核电汽轮机在变负荷工况下运行的安全性与经济性，开发新型的末级叶片成为业内研究热点。汽轮机在非设计工况下运行时效率降低，主要因为流动分离导致了二次流损失和叶型损失。为了解决上述问题，本项目设计开发了系列核电汽轮机仿生叶型，以期达到改善变工况条件下的攻角适应性和流动分离特性的目的。由于仿生叶型将被应用于湿蒸汽环境下，项目中还探索了仿生结构的除湿效果。本着从简至难的设计思路，本项目分阶段逐步完成对仿生波浪前缘在核电汽轮机末级叶片设计中的应用研究，并研究了不同仿生叶型在汽轮机叶片设计的应用。首先，对直叶片上进行仿生叶型设计，从中研究了仿生结构对流动的作用机理，进而延伸出用仿生结构产生流向涡来对末级级内流场做出控制的设计方法。其次，在叶高较短的核电高压末级动叶上做仿生设计，同时设计了与凸起结构同源的凹陷结构，结果显示：后者在负攻角较小时可更高效地提升叶片做功能力。接着，对核电低压末级动叶进行仿生设计，新设计了更适合于低压级叶型的背压面凸起结构，利用凸起产生的涡对减小背压面所受压力，使长叶片的做功能力得到提升。进而，为探索仿生结构的除湿效果，设计了压力面带仿生凸起的静叶片，发现此型叶片可以有效地聚集一定范围内的表面水膜，与传统的抽吸、吹扫等方法配合，能得到较好的预期效果。总的来说，本项目圆满完成了仿生波浪前缘在核电汽轮机末级叶片设计中的应用研究，探索了仿生叶型在核电汽轮机末级叶片设计中的应用研究，开拓了长叶片设计的思路。研究成果具有重要的科学意义，同时具有独立自主产权，具有广阔的应用前景（包括核电汽轮机、火电汽轮机、舰船汽轮机、太阳能发电汽轮机等）。