本文關(guān)鍵詞： 二次流 沖擊式水輪機(jī) 氣液兩相流 射流形狀 不良流動(dòng)　出處：《哈爾濱工業(yè)大學(xué)》2016年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：隨著中國(guó)經(jīng)濟(jì)的快速發(fā)展和人們生活水平的不斷提高,人們對(duì)電力的需求量不斷增長(zhǎng),電能正成為人們需求增長(zhǎng)最快的能源。我國(guó)水電開(kāi)發(fā)逐步由低水頭大流量向高水頭發(fā)展,沖擊式水輪機(jī)具有適應(yīng)高水頭運(yùn)行的特點(diǎn),多噴嘴沖擊式水輪機(jī)能有效提高沖擊式水輪機(jī)的出力特性,沖擊式水輪機(jī)也逐步由單噴嘴向多噴嘴發(fā)展。我國(guó)對(duì)沖擊式水輪機(jī)的研究相比技術(shù)成熟的混流式水輪機(jī)還屬于起步階段。由于沖擊式水輪機(jī)在工作的過(guò)程中屬于三維非定常的兩相流動(dòng),流動(dòng)的復(fù)雜性也增加了對(duì)沖擊式水輪機(jī)研究的困難。沖擊式水輪機(jī)的給水機(jī)構(gòu)中既有典型的彎管流動(dòng),也有分岔管流動(dòng),兩種流動(dòng)產(chǎn)生的二次流會(huì)對(duì)進(jìn)入噴嘴前的流態(tài)分布造成的影響,這種影響不斷向下游發(fā)展會(huì)影響射流的形狀,造成射流質(zhì)量下降。沖擊式水輪機(jī)的效率是由給水單元效率和轉(zhuǎn)輪區(qū)效率共同決定,轉(zhuǎn)輪區(qū)的效率與射流質(zhì)量密切相關(guān)。所以研究二次流在沖擊式水輪機(jī)給水單元的發(fā)展、變化過(guò)程就顯得很重要。本文對(duì)某一型號(hào)的六噴嘴沖擊式數(shù)輪機(jī)模型進(jìn)行了數(shù)值模擬,具體研究?jī)?nèi)容如下:1.通過(guò)分析六噴嘴沖擊式水輪機(jī)給水機(jī)構(gòu)能量損失情況,找出造成六噴嘴沖擊式水輪機(jī)給水機(jī)構(gòu)能量損失的原因;2.通過(guò)研究二次流在六噴嘴沖擊式水輪機(jī)給水機(jī)構(gòu)中產(chǎn)生,發(fā)展和變化的過(guò)程,探究二次流向下游的發(fā)展過(guò)程及射流內(nèi)部流態(tài)的發(fā)展過(guò)程,找出上游來(lái)流對(duì)射流流態(tài)和形狀的影響;3.對(duì)六噴嘴沖擊式水輪機(jī)進(jìn)行全流域數(shù)值模擬,通過(guò)分析射流在水斗上的工作過(guò)程,找出沖擊式水輪機(jī)的工作特性和內(nèi)部的不良流動(dòng)現(xiàn)象。研究結(jié)果表明,六噴嘴沖擊式水輪機(jī)給水機(jī)構(gòu)的能量損失主要分為配水環(huán)管能量損失和噴嘴能量損失,其中噴嘴能量損失是給水機(jī)構(gòu)的主要損失,且噴嘴損失量在相同開(kāi)度時(shí)隨著水頭的增加而增加,但占總水頭比基本保持恒定。六噴嘴沖擊式水輪機(jī)由于配水環(huán)管屬于典型的彎管流動(dòng),內(nèi)部會(huì)產(chǎn)生典型的沿水平面對(duì)稱(chēng)的迪恩渦對(duì)。由于分岔管處過(guò)渡不均勻和流體的轉(zhuǎn)向,這種對(duì)稱(chēng)的迪恩渦對(duì)會(huì)向分岔管內(nèi)側(cè)偏移,并不斷向后發(fā)展,造成射流在內(nèi)側(cè)產(chǎn)生分岔流動(dòng);對(duì)于六噴嘴沖擊式水輪機(jī),其內(nèi)部存在嚴(yán)重的不良流動(dòng)現(xiàn)象,其中水斗背面打水現(xiàn)象在本文水斗模型中較為嚴(yán)重,射流在水斗背面的不斷流動(dòng)還會(huì)造成水斗背面產(chǎn)生一個(gè)持續(xù)的低壓區(qū),低壓區(qū)可能會(huì)發(fā)生氣蝕現(xiàn)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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TK735

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