核电汽轮机高压级内非定常流动对自发凝结的影响

为研究核电汽轮机高压级内非定常流动对湿蒸汽凝结流动液滴直径、压力以及湿汽损失等参数分布的影响,采用湿蒸汽非平衡凝结相变模型,对定常与非定常流动状态下湿蒸汽自发凝结流动进行三维数值分析。结果表明:非定常凝结流动趋于稳定时,各项参数的分布呈现周期性变化规律。非定常流动的动静干涉现象导致周向流场具有非均匀性,湿蒸汽级内的轴端功率下降0.266%。非定常流动过程中的静叶尾迹现象致使下游动叶通道内自发凝结的液滴直径减小。非定常凝结流动的压力位势作用使得动叶出口平均压力提高。非定常流动引起湿蒸汽凝结的热力学损失与制动损失分别升高62.27%和1.88%,疏水损失降低0.233%。     

湿蒸汽两相流动的非定常数值模拟

应用两相均质混合模型、湿蒸汽平衡相变模型以及双时间步长法,对某超临界汽轮机末级叶栅流场进行了全三维非定常的数值计算.计算结果表明:湿蒸汽流动与流场内的非定常特性密切相关,其定常计算结果与非定常的时均结果不相一致.由于动静叶干涉的影响,动叶栅出口由非定常计算得到的湿度值小于定常计算得到的结果.     

基于双流体模型的湿蒸气凝结流动三维数值模拟

建立湿蒸气凝结流动的双流体模型,考虑了湿蒸气汽液两相流动中相间速度滑移、耦合以及湍流扩散作用的影响。针对蒸汽透平叶栅中流动的湍流特性,在单相湍流计算中数值模拟精度相对良好的两方程SSTk-ω湍流模型基础上,参照颗粒湍能输运方程理论,推导建立了湿蒸气两相流动SSTk-ω-kp湍流模型,模型中引入了液相粘性、导热及扩散系数等拟流体概念。对一直列叶栅中存在自发凝结的湿蒸气流动进行了三维数值模拟,结果表明:与中心截面相比,端壁附近汽流首先出现大量凝结核,并较早恢复到平衡状态,由于涡系结构的存在使得沿叶高汽液两相叶栅出口马赫数之间存在一定差异。本文建立的模型提高了湿蒸气凝结流动三维数值模拟的精度,更好地揭示叶栅中凝结流动的相间作用。     

汽轮机轴封漏汽对调节级静叶栅二次流及出口流场的影响

以一台３００ＭＷ汽轮机组的调节级静叶栅为研究对象,就轴封漏汽对叶栅二次流及出口流场的影响进行了数值模拟,计算结果表明,漏汽加快了叶栅出口区域二次流动的衰减,使出口气流角沿叶高方向的分布产生较大变化,对损失系数的分布影响较小。     

汽轮机湿蒸汽两相凝结流动数值研究的现状与进展

着重针对汽轮机中存在自发凝结的湿蒸汽两相流动 ,论述了湿蒸汽两相流动数值研究进展现状及其待解决的问题 ,以期对此方面的研究及其工程应用起到促进作用。文中结合作者目前进行的有关湿蒸汽两相凝结流动数值研究 ,对湿蒸汽透平级中两相流动的数值模型、求解方法等关键问题进行了阐述和探讨 ,给出了作者对一维喷管、二维喷管以及叶栅进行数值模拟的部分算例结果 ,以说明所发展的数值模拟方法的可行性和准确程度。     

海豚型叶片对动叶栅流场的影响

采用遗传算法及人工神经网络的优化算法,把某汽轮机末级常规静叶片改型设计成海豚仿生型叶片。利用两相均质数值方法和湿蒸汽平衡相变模型,以商用软件CFX为计算平台,模拟了常规原型与新设计的海豚型叶栅流场。通过对计算结果进行比较,分析该海豚型叶片与常规叶片在气动性能上的异同,探索海豚型叶片是如何通过改变叶栅流道内蒸汽湿度的分布状况来更好地适应叶栅内湿蒸汽跨音速流动。     

某汽轮机中的湿蒸汽流动研究

按照平衡凝结流动设计方法设计的低压汽轮机实际按照非平衡凝结流动规律运行,因此会带来额外的损失。为了评估两种凝结方式的差异,对某汽轮机低压缸内的平衡凝结和非平衡凝结流动进行了对比研究。结果表明：与平衡凝结流动相比,非平衡凝结流动中汽轮机低压缸各级透平焓降、反动度、湿度分布以及各叶栅表面压力分布、叶栅进口攻角、出口气流角、末级出口余速及低压缸内热力过程线均有明显差异。按照非平衡凝结流动规律设计低压汽轮机是进一步提高其效率的一个途径。     

大功率汽轮机湿蒸汽级两相凝结流动的数值模拟与分析

采用真实气体平衡态计算模式和非平衡态自发凝结两相流动计算模式两种不同的计算方法对某大功率汽轮机低压末两级内三维湿蒸汽两相凝结流动进行了模拟和分析。计算表明非平衡效应引起湿蒸汽级组内流量、焓降在各级之间的分配、叶栅出口气流角、各级反动度都有发生变化。     

光热汽轮机低压进汽结构气动性能分析与优化设计

为满足新能源汽轮机低压进汽系统的开发,采用数值求解三维Reynolds-Averaged Navier-Stokes(RANS)方程研究了耦合第一级的光热汽轮机低压进汽结构的气动性能,并对无叶通道进行了优化设计,同时考虑了不同蒸汽调节阀结构对低压进汽系统通流能力的影响。结果表明:原始低压进汽结构会造成较宽跨度的静叶进汽攻角和较大的进汽不均匀度,最大汽流角分布在蜗壳的左右两侧;优化的策略在于增大进汽弯管的出流面积和倾角,通过减小滞止涡来降低汽流角跨度和进汽不均匀度,这样可以有效地改善第一级静叶进口的汽流组织;随着调节阀门偏心度的增加,蒸汽阀通流能力增大,且总压损失降低。研究方法和结果为高性能光热汽轮机通流设计提供了技术支撑。     

Laval喷管内蒸汽凝结流动的数值研究

为了研究缩放喷管中湿蒸汽的自发凝结流动,对某Laval喷管中的几何参数及实验工况进行喷管中湿蒸汽凝结两相流动的三维数值模拟。通过以数值模拟结果结合部分工况的压力实验数据进行对比,讨论了喷管中蒸汽自发凝结流动的物理现象。     

Numerical study and control method of interaction of nucleation and boundary layer separation in condensing flow

The spontaneous nucleation flow in turbine cascade was numerically studied. The model was implemented within a full Navier–Stokes viscous flow solution procedure and the process of condensation was calculated by the quadrature method of moments that shows good accuracy with very broad size distributions. Results were presented for viscous and inviscous flow, showing the influence of boundary layer separation and wake vortices on spontaneous nucleation. The results show that the degree of flow separation in wet steam flow is greater than that in superheated steam flow due to condensation shock and that the loss cannot be neglected. Furthermore, the impact of boundary layer separation and wake vortices on velocity profiles and its implications for profile loss were considered. The calculations showed that layer separation and wake vortices influence nucleation rate, leading to different droplet distributions. A method for controlling homogeneous nucleation and for reducing degree of flow separation in high-speed transonic wet steam flow was presented. The liquid phase parameter distribution is sensitive to the suction side profile of turbine cascade, which impacts the nucleation rate distribution leading to different droplet distributions and affects the degree of flow separation. The numerical study provides a practical design method for turbine blade to reduce wetness losses.     

Numerical study and control method of interaction of nucleation and boundary layer separation in condensing flow

The spontaneous nucleation flow in turbine cascade was numerically studied. The model was implemented within a full Navier-Stokes viscous flow solution procedure and the process of condensation was calculated by the quadrature method of moments that shows good accuracy with very broad size distributions. Results were presented for viscous and inviscous flow, showing the influence of boundary layer separation and wake vortices on spontaneous nucleation. The results show that the degree of flow separation in wet steam flow is greater than that in superheated steam flow due to condensation shock and that the loss cannot be neglected. Furthermore, the impact of boundary layer separation and wake vortices on velocity profiles and its implications for profile loss were considered. The calculations showed that layer separation and wake vortices influence nucleation rate, leading to different droplet distributions. A method for controlling homogeneous nucleation and for reducing degree of flow separation in high-speed transonic wet steam flow was presented. The liquid phase parameter distribution is sensitive to the suction side profile of turbine cascade, which impacts the nucleation rate distribution leading to different droplet distributions and affects the degree of flow separation. The numerical study provides a practical design method for turbine blade to reduce wetness losses.     

某型高压汽轮机动叶栅的气动优化设计

利用CFD(计算流体力学)技术对某冲动式汽轮机的高压级动叶进行了改型设计。对比数值模拟结果,优化后有效地改善了叶栅流道中的流动状况,级性能有了显著的提高。     

三维湿蒸汽自发凝结流动的数值模拟

采用完全欧拉坐标系下的数值模型描述湿蒸汽两相自发凝结流动过程，对某汽轮机低压部分三维静叶栅中内复杂的自发凝结流动进行了模拟和分析。与忽略自发凝结的计算结果相比，叶片表面的压力分布有所不同，吸力面侧尤为明显；自发凝结的发生引起气流角的变化，直接导致作功能力的变化；由于流动参数沿径向分布不均，自发凝结引起的湿度沿径向分布也明显不同；计算结果同时显示边界层对自发凝结有很大的影响。     

Numerical investigation on wet steam non-equilibrium condensation flow in turbine cascade

Based on the two-phase wet steam flow with spontaneous condensation,experimental verification and flow analysis on nozzle and 2D cascade are carried out.The 3D Reynolds-Averaged gas-liquid two-phase flow control equation solver is explored with k ε k p turbulence model.Furthermore,3D flow numerical simulation on the last stage stator of the steam turbine is carried out.The results show that a sudden pressure rise on blade suction surface is mainly caused by the droplet growth in condensation flow.The more backward the condensation position is in cascade passage,the less the sudden pressure rise from condensation is,and the larger the nucleation rate is,the maximum under-cooling and the number of droplets per unit volume are.Interaction of condensation wave and shock wave has imposed greater influence on the parameters of the blade cascade outlet.     

跨音速向心汽轮机气动设计分析

通过一维设计与三维数值模拟分析相结合的方法,对一台300kW向心汽轮机进行了气动设计。汽轮机整级焓降达到248.5kJ,压比达到4.17,为了提高整级效率,反动度值比较小,致使导叶栅中存在超音速流。对导叶和叶轮内部流动特性进行具体分析,并对设计过程中碰到的一些问题进行探讨。     

Analysis of the superheated steam cycle of a PWR secondary system

The impacts of variations of turbine exhaust steam wetness, live steam parameters, and the turbine sectional pressure ratio on the thermodynamic efficiency of the saturated steam cycle in a PWR secondary system are analyzed. The effects of live steam parameters and turbine sectional pressure ratio on the thermodynamic efficiency and the turbine exhaust steam wetness for the superheated steam cycle are also investigated. The optimum ranges of operating parameters are proposed based on the comparison of the performance of the superheated steam cycle with that of the saturated steam cycle. © 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 185–194, 2001