【作者】 李进博；

【导师】 梁武科； 赵道利；

【作者基本信息】 西安理工大学 ， 水利水电工程， 2009， 硕士

【摘要】 针对我国某电站混流式水轮机因密封间隙引起的机组振动问题,采用计算流体动力学软件CFX,基于N-S方程和RNGκ-ε湍流模型，将含密封间隙的原型水轮机进行了全流道的定常、非定常数值计算,主要成果包括以下几部分：通过对原型水轮机定常流动计算,发现密封间隙的泄漏量和机组轴向水推力在同一出力工况下与密封间隙值有关,间隙值越大,泄漏量和机组轴向水推力越大。在同一间隙值下,密封间隙的泄漏量和机组轴向水推力随出力的增加而增大,其增大的幅度与密封间隙值密切相关。分析了密封间隙值对水轮机稳定流场的影响。密封间隙对转轮前流场有明显的扰动作用,这种扰动作用受密封间隙值和位置的影响。越小的间隙值扰动作用越强烈,越靠近间隙进、口扰动效果越明显。密封间隙对尾水管的影响主要在靠近尾水管进口边壁区,随着密封间隙值的加大,尾水管进口边壁附近的压力分布得以改善。对比了不同密封间隙值的流场分布,得出密封间隙进口轴向平均压力变化与间隙值有关,小间隙值时平均压力轴向梯度大,流场不稳定。密封间隙压力腔内压力分布沿径向成梯级减小趋势,这种趋势仍然与密封间隙值有关。对原型水轮机几个典型工况进行了非定常计算。探讨了密封间隙值对机组压力脉动的影响。在密封间隙内得到了与现场试验测得机组振动主频接近的压力脉动频率,证明原型水轮机的振动是由密封间隙内的压力脉动引起的,并对机组振动的解决方案进行了验证。将所计算结果与现场实验对比后得出：转轮密封间隙值与机组匹配存在着稳定区和非稳定区的概念。所以在机组设计时需要对转轮密封间隙值的大小进行综合考虑,避免密封间隙匹配不合理引起的振动问题,以保证机组安全稳定的运行。更多还原

【Abstract】 To the vibration of a power plant turbine caused by sealing clearance, the whole flow passage steady and unsteady numerical calculation of the turbine including sealing clearance is calculated by CFD software CFX, based on N-S equation and RNGκ-εturbulence model. The main research findings are as follows:Based on the steady flow calculation results of the prototype turbine, the leakage rate and the axial hydraulic thrust are related with the value of sealing clearance under the same output condition. The more sealing clearance value, the more leakage rate and the axial hydraulic thrust the turbine has. With the same clearance value, the leakage rate of the sealing clearance and the axial hydraulic thrust will increase as the increase of the output. The increasing rang is significantly attributed to the value of sealing clearance.The effect of the steady flow of the turbine caused by the sealing clearance is analyzed. Sealing clearance has obvious disturbance effect on flow field in front of inlet of runner, which is related to the sealing clearance value and position. The smaller sealing clearance value is, the more obvious the disturbance effect is as well as the nearer to the inlet of the sealing clearance is. The effect of the sealing clearance to the draft tube is occurred in boundary wall near the inlet of draft tube. As the sealing clearance increased, the pressure distribution of the inlet of the draft tube near the boundary wall improved as well as its tangential velocity. The contrast of the flow field distribution of the different sealing clearance value is completed with the conclusion that the gradient of average pressure in axial of sealing clearance inlet is related with sealing clearance value. The smaller sealing clearance value is, the greater axial gradient of average pressure which leading to the flow field unsteady. The trend of pressure distribution of the pressure chamber of the sealing clearance is reduction in radial direction, which is attributed to the sealing clearance value. Some typical unsteady working condition of prototype turbine is calculated. The effect of the unit pressure fluctuation caused by sealing clearance is discussed. The paper got the frequency of pressure in sealing clearance which is approached to vibration frequency of unit. It proved that the vibration of prototype turbine is caused by pressure fluctuation in sealing clearance. At the same time, the project solution is validated. After contrasting of calculated and tested results, we found that:there is a concept about steady and unsteady area between sealing clearance and unit stability.Therefore the design of crown’s sealing clearance value should be considered in a comprehensive way to prevent the vibration caused by the caused by runner crown’s sealing clearance. Consequently the unit can be operated safely and stably.更多还原