汽轮机内蒸汽瞬变凝结流动及其对叶片高周疲劳影响的研究

Wet-steam problem has a strong impact on the the economy and security of steam turbine units and it has puzzled the steam turbine designer and manufacturer for a long time.Both therotical investigation and numerical simulation will be undertaken to study the steam transient condensation flow in steam turbine and its effect on high cycle fatigue of blade. The relationship between the surface tension of a water droplet and its radius as well as the quantity of the impurity contained in it in the stage of actual turbine units, which will be used to calculate the homogeneous and heterogeneous nucleation rate, will be computed through both molecular dynamics and Monte Carlo method. Quadrature method of moments(QMOM) combined with nucleation theory will be used to build three-dimensional numerical calculation model of steam transient condensation flow considering the effect of homogeneous and heterogeneous nucleation. The model will be used to study the impact of heterogeneous nucleation on steam transient condensation flow.Computations on steam transient condensation flow are used to analyze its effect on stage efficiency. Furthermore, the 3D fluid-stucture interaction model of steam turbine blade will be built to study the impact of homogeneous nucleation and heterogeneous nucleation on the blade surface load and forced response of wet-steam stage under different conditions and the sensitivity of blade high cycle fatigue to steam transient flow. The studies proposed above will provide therotical basis for the optimal design of steam turbine wet steam stage blade.

湿蒸汽问题长期以来一直困扰汽轮机设计和制造技术人员，是影响汽轮发电机组经济性和安全性的难题。本课题拟通过理论研究、数值计算，研究汽轮机内蒸汽瞬变凝结流动及其对叶片高周疲劳影响。运用物理学研究中所采用的分子动力学和Monte Carlo方法研究实际机组级内蒸汽凝结形成的水滴表面张力与其半径及可溶性杂质含量的关系，并用其计算同相成核率和异相成核率。将QMOM方法与成核理论相结合，建立考虑蒸汽杂质影响的瞬变凝结流动的三维数值计算模型，研究异相成核对蒸汽瞬变凝结流动的影响；通过研究机组内蒸汽瞬变凝结流动状况，分析其对级效率的影响；建立适用于对汽轮机叶栅进行三维流固耦合分析的计算模型，研究两种成核现象对不同工况下湿蒸汽级叶片表面载荷和强迫响应的影响，同时研究叶片高周疲劳对蒸汽瞬变流场的敏感性。本课题的研究可为汽轮机湿蒸汽级叶片的优化设计提供理论基础和依据。

湿蒸汽问题长期以来是影响汽轮发电机组经济性和安全性的难题。在基金资助下，本课题通过理论研究、数值计算和相关实验，研究了汽轮机内蒸汽瞬变凝结流动特性及其对叶片高周疲劳影响。在理论研究方面：应用分子动力学方法研究了水蒸气的非平衡凝结过程，推导得到球面表面张力的修正公式的求积公式，分析了水滴表面张力对非平衡凝结过程的影响进而分析对级效率的影响；将QMOM方法与成核理论相结合，建立考虑蒸汽杂质影响的瞬变凝结流动的三维数值计算模型，研究异相成核对蒸汽瞬变凝结流动的影响；采用湿汽损失的3D精确计算方法计算了各项湿汽损失随入口水滴直径的变化曲线；此外，研究了叶片表面上粗糙度的大小和粗糙度在叶片表面上的位置对自发凝结级性能的影响、小流量工况下汽轮机内部凝结流动特性以及动、静叶栅间势干涉的强度和影响范围，分析了叶片颤振发生的机理并深入探讨了水蒸气跨音速流动过程中尾缘波系与自发凝结的交互作用。在实验研究方面：采用光学非接触方法测量了水蒸气浓度、水蒸气流速及微小液滴浓度；采用频谱分析发测量某核电叶片高压第一级和低压末级叶片高频振动特性；上述实验研究为研究凝结流动以及湿蒸汽级叶片“高周疲劳”提供了实测数据。本课题的研究成果可为汽轮机湿蒸汽级叶片的优化设计提供理论基础和依据。