二次流对六喷嘴冲击式水轮机性能影响的研究

发布时间：2018-02-04 02:15

本文关键词： 二次流冲击式水轮机气液两相流射流形状不良流动　出处：《哈尔滨工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着中国经济的快速发展和人们生活水平的不断提高,人们对电力的需求量不断增长,电能正成为人们需求增长最快的能源。我国水电开发逐步由低水头大流量向高水头发展,冲击式水轮机具有适应高水头运行的特点,多喷嘴冲击式水轮机能有效提高冲击式水轮机的出力特性,冲击式水轮机也逐步由单喷嘴向多喷嘴发展。我国对冲击式水轮机的研究相比技术成熟的混流式水轮机还属于起步阶段。由于冲击式水轮机在工作的过程中属于三维非定常的两相流动,流动的复杂性也增加了对冲击式水轮机研究的困难。冲击式水轮机的给水机构中既有典型的弯管流动,也有分岔管流动,两种流动产生的二次流会对进入喷嘴前的流态分布造成的影响,这种影响不断向下游发展会影响射流的形状,造成射流质量下降。冲击式水轮机的效率是由给水单元效率和转轮区效率共同决定,转轮区的效率与射流质量密切相关。所以研究二次流在冲击式水轮机给水单元的发展、变化过程就显得很重要。本文对某一型号的六喷嘴冲击式数轮机模型进行了数值模拟,具体研究内容如下:1.通过分析六喷嘴冲击式水轮机给水机构能量损失情况,找出造成六喷嘴冲击式水轮机给水机构能量损失的原因;2.通过研究二次流在六喷嘴冲击式水轮机给水机构中产生,发展和变化的过程,探究二次流向下游的发展过程及射流内部流态的发展过程,找出上游来流对射流流态和形状的影响;3.对六喷嘴冲击式水轮机进行全流域数值模拟,通过分析射流在水斗上的工作过程,找出冲击式水轮机的工作特性和内部的不良流动现象。研究结果表明,六喷嘴冲击式水轮机给水机构的能量损失主要分为配水环管能量损失和喷嘴能量损失,其中喷嘴能量损失是给水机构的主要损失,且喷嘴损失量在相同开度时随着水头的增加而增加,但占总水头比基本保持恒定。六喷嘴冲击式水轮机由于配水环管属于典型的弯管流动,内部会产生典型的沿水平面对称的迪恩涡对。由于分岔管处过渡不均匀和流体的转向,这种对称的迪恩涡对会向分岔管内侧偏移,并不断向后发展,造成射流在内侧产生分岔流动;对于六喷嘴冲击式水轮机,其内部存在严重的不良流动现象,其中水斗背面打水现象在本文水斗模型中较为严重,射流在水斗背面的不断流动还会造成水斗背面产生一个持续的低压区,低压区可能会发生气蚀现象。
[Abstract]:With the rapid development of Chinese economy and the improvement of people's living standard, the demand for electricity is increasing. Electric energy is becoming the fastest growing energy. Hydropower development in China is gradually from low head large flow to high water head. Impact turbine has the characteristics of adapting to high water head operation. Multi-nozzle impact turbine can effectively improve the performance of impact turbine. The research of impact-type turbine in our country is still in the initial stage compared with the developed Francis turbine, because the impact-type turbine is in the process of operation. Three-dimensional unsteady two-phase flow. The complexity of the flow also makes it difficult to study the impact-type turbine. In the feed water mechanism of the impact-type turbine, there are both typical bends flow and bifurcation pipe flow. The influence of the secondary flow produced by the two flows on the distribution of the flow pattern before entering the nozzle will affect the shape of the jet. The efficiency of the impingement turbine is determined by the efficiency of the feed unit and the efficiency of the runner zone. The efficiency of runner zone is closely related to the quality of jet, so the development of secondary flow in the feed unit of impinging turbine is studied. The change process is very important. In this paper, the numerical simulation of a certain type of six-nozzles impact-type turbine model is carried out. The specific research contents are as follows: 1. By analyzing the energy loss of the feed mechanism of the six-nozzle impingement turbine, the causes of the energy loss of the water-supply mechanism of the six-nozzle impact-type turbine are found out. 2. By studying the process of producing, developing and changing secondary flow in the feed mechanism of six-nozzle impingement turbine, the development process of secondary flow downstream and the development process of internal flow state of jet are explored. The influence of upstream flow on the flow pattern and shape of jet was found out. 3. The whole basin numerical simulation of six-nozzles impingement turbine is carried out. By analyzing the working process of jet on the bucket, the working characteristics of the impingement turbine and the bad flow phenomenon inside the turbine are found out. The results show that. The energy loss of six nozzle impingement turbine feed mechanism is mainly divided into distribution loop energy loss and nozzle energy loss, in which nozzle energy loss is the main loss of water supply mechanism. The nozzle loss increases with the increase of the water head, but the ratio of the nozzle to the total head remains constant. The six-nozzles impingement turbine belongs to the typical curved pipe flow due to the water distribution loop. Due to the non-uniform transition at the bifurcation tube and the fluid steering, the symmetrical Dean vortex pair will shift to the inner side of the bifurcation pipe and continue to develop backward. The flow of the jet in the inner side is caused by bifurcation. For the six-nozzle impingement turbine, there is a serious bad flow phenomenon inside the turbine, in which the backside water pumping phenomenon of the bucket is more serious in the model of the water bucket in this paper. The continuous flow of the jet on the back of the bucket will also result in a continuous low pressure region on the back of the bucket, and cavitation may occur in the low pressure region.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK735

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