【摘要】：水能資源是我國能源結(jié)構(gòu)的重要組成部分,隨著我國西南一大批巨型水電站規(guī)劃上馬和南水北調(diào)工程許多大型泵站相繼建成,大型水利工程中水力機(jī)組運(yùn)行的安全性和穩(wěn)定性顯得尤為重要。而水力機(jī)械具有良好的的空化性能是保證整個水利水電工程與機(jī)組安全可靠運(yùn)行的關(guān)鍵因素之一。在我國水利水電工程大規(guī)模建設(shè)的同時,一個不容忽視的問題是目前我國諸多河流與湖庫面臨著嚴(yán)峻的水污染形勢,水體富營養(yǎng)化嚴(yán)重,主要污染物為總磷、總氮和重金屬絡(luò)合物等。此前,水力機(jī)械的設(shè)計(jì)、試驗(yàn)、模擬等大多以清水為基礎(chǔ)進(jìn)行。當(dāng)引用水質(zhì)遭受化學(xué)污染性質(zhì)發(fā)生變化時,對水力機(jī)械的空化性能是否造成影響和造成何種影響是一個亟待研究的問題。本文重點(diǎn)就以遭受嚴(yán)重總磷污染的烏江流域內(nèi)的電站為例,研究總磷污染水體的空化壓力特性以及對水輪機(jī)空化性能的影響,并將試驗(yàn)結(jié)果運(yùn)用到空化流的數(shù)值模擬中去,取得較好的效果。為了了解烏江流域的總磷污染形勢,實(shí)地采樣考察了流域中、下游梯級電站引用水的總磷含量和底泥情況,并對流域內(nèi)主要支流的污染情況作了資料收集和取樣化驗(yàn)�；�(yàn)結(jié)果表明：烏江流域中、下游總磷污染嚴(yán)重,水質(zhì)為劣V類,底泥重金屬含量高。為了研究化學(xué)污染的水對水力機(jī)械空化性能的影響,在射流試驗(yàn)裝置中對比了引用水質(zhì)為磷石膏懸濁液和清水時空化初生的條件和空化發(fā)展的狀態(tài),高速攝影觀察到射流裝置內(nèi)引用水為總磷懸濁液時更容易發(fā)生初生空化,相同工況下空化發(fā)展更為強(qiáng)烈,空泡云體積明顯變大。同時對總磷污染水的空化壓力特性進(jìn)行了專項(xiàng)實(shí)測,表明水體的初生空化壓力與臨界空化壓力較清水時壓力值明顯增大,且在飽和濃度內(nèi),空化壓力值隨著總磷濃度的提高而增大。長期以來,許多水力機(jī)械書籍以及論述空化與空蝕的文獻(xiàn)中,都將空化與水的汽化混為一談,將發(fā)生空化時的水壓認(rèn)定為當(dāng)時溫度下水的汽化壓力或飽和蒸汽壓力,并將該壓力值應(yīng)用到水力機(jī)械的空化計(jì)算中。根據(jù)以上試驗(yàn)結(jié)果,考慮水質(zhì)因素對描述水力機(jī)械空化性能的主要參數(shù)如空化數(shù)、水輪機(jī)空化系數(shù)、水輪機(jī)吸出高度等值做了必要的修正,并應(yīng)用修正值對遭受總磷污染的構(gòu)皮灘電站和三峽電站的空化性能做了評價分析。繞流物體如水輪機(jī)與葉片泵轉(zhuǎn)輪葉片,當(dāng)沿流面所截的翼型吸力面發(fā)生空化且來流沖角不大時,便可形成猶如附著在固體表面上的空穴。通過試驗(yàn)觀察空化發(fā)生時空泡的變化過程,得到了空化壓力與單位體積內(nèi)空泡的數(shù)量和直徑的關(guān)系。實(shí)驗(yàn)證實(shí),空穴內(nèi)部為含有很多空泡的混合水體,而不是以往普遍認(rèn)為的氣體,空穴的形狀和尺寸同空穴內(nèi)部的空泡尺寸與數(shù)量直接相關(guān),空泡的尺寸與數(shù)量則由引用水的空化壓力特性和吸力面壓力分布決定,將引用水空化壓力特性與三維湍流數(shù)值模擬結(jié)合起來模擬了葉輪內(nèi)部的空化流動,與實(shí)際情況相符。
[Abstract]:Hydropower resources are an important part of China's energy structure. As a large number of large-scale hydropower stations in southwest China have been planned and many large-scale pumping stations have been built in succession for the South-to-North Water Transfer Project, the safety and stability of the operation of hydraulic units in large-scale water conservancy projects are particularly important. One of the key factors for the safe and reliable operation of the whole water conservancy and hydropower project is the large-scale construction of the water conservancy and hydropower project in China. At present, many rivers and lakes in China are facing severe water pollution situation. The eutrophication of the water body is serious. The main pollutants are total phosphorus, total nitrogen and heavy metal complexes. Previously, the design, test and Simulation of hydraulic machinery were mostly based on clean water. Whether or not the cavitation performance of hydraulic machinery will be affected and what kind of influence will be caused when the quality of water quoted is changed by chemical pollution is an urgent problem to be studied. In order to understand the situation of total phosphorus pollution in the Wujiang River basin, the total phosphorus content in the water of cascade hydropower stations in the middle and lower reaches of the basin was investigated by field sampling. The results show that the total phosphorus pollution is serious in the middle and lower reaches of Wujiang River basin, the water quality is inferior V and the content of heavy metals in the sediment is high. The water quality is phosphogypsum suspension and clean water, and the condition of cavitation development. High-speed photography shows that when the water is the total phosphorus suspension, the primary cavitation is more likely to occur, the cavitation development is more intense and the volume of cavitation cloud is obviously larger. The special measurement shows that the primary and critical cavitation pressures of water body are obviously higher than those of clean water, and the cavitation pressure increases with the increase of total phosphorus concentration in saturated concentration. The water pressure at the time of cavitation is defined as the vaporization pressure or saturated vapor pressure of the water at the temperature at that time and applied to the cavitation calculation of hydraulic machinery. The cavitation performance of Goupitan Hydropower Station and Three Gorges Hydropower Station polluted by total phosphorus is evaluated and analyzed. When the suction surface of the airfoil intercepted along the flow surface is cavitated and the inflow angle is small, the flow around the object such as the turbine and the blade pump runner blade can be formed as if it is attached to the solid surface. Cavitation. The relationship between cavitation pressure and the number and diameter of cavitation in a unit volume is obtained by observing the process of cavitation. It is confirmed by experiments that the cavitation is a mixture of water with many cavitations, rather than the gas generally believed in the past. The cavitation pressure and suction surface pressure distribution determine the size and quantity of the cavitation. The cavitation flow in the impeller is simulated by combining the cavitation pressure characteristics of the water and the three-dimensional turbulent numerical simulation.
【學(xué)位授予單位】：中國農(nóng)業(yè)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：X524;TV136

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本文編號：2181249