本文關(guān)鍵詞： 文丘里管 孔板 離心泵 空化發(fā)生器 試驗測試　出處：《江蘇大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：本文在國家自然科學(xué)基金項目(51239005,51309120)、國家留學(xué)基金委公派聯(lián)合培養(yǎng)博士生項目、歐洲太空總署(European Space Agency,ES A)項目"Cavitation in Thermosensible Fluids"和江蘇省高校博士研究生創(chuàng)新基金(CXLX12_0640)的資助下開展工作。隨著科技的進(jìn)步以及工業(yè)制造精度的提高,水力機械得到了迅猛的發(fā)展,然而伴隨著其大型化高速化而產(chǎn)生的空化問題則更加凸顯。空化的存在不僅會降低水泵等水力機械的運行效率,還會產(chǎn)生振動和噪聲,甚至?xí)䦟λC械固體表面造成破壞,嚴(yán)重影響系統(tǒng)的安全穩(wěn)定運行。另一方面,空化由于具有復(fù)雜的物理化學(xué)相變流動特征與特殊的非定常動力特性,已成為污水處理、水下兵器減阻和管道清理等領(lǐng)域的一種高效低能耗新興技術(shù)手段。本文首先對文丘里管和孔板兩種結(jié)構(gòu)簡單的水力裝置進(jìn)行空化空蝕研究,采用理論分析、數(shù)值計算和實驗測量相結(jié)合的方法研究空化空蝕形成機理與相互關(guān)系。隨后以此為基礎(chǔ),對應(yīng)用更為廣泛、結(jié)構(gòu)更為復(fù)雜的旋轉(zhuǎn)類水力機械——離心泵進(jìn)行空化空蝕的研究,改進(jìn)離心泵空化數(shù)值計算模型,揭示離心泵內(nèi)空化的非定常特性,建立離心泵空蝕預(yù)測方法。最后對一種水力空化發(fā)生器進(jìn)行系統(tǒng)研究,為空化應(yīng)用的研究提供一定的參考。本文的主要工作和創(chuàng)新性成果有：1.針對水力裝置與機械空化數(shù)值模擬過程中需人為不斷調(diào)整邊界條件的問題,基于批處理(Batch)和ANSYS-CFX建立了一種空化數(shù)值模擬自動運行方法,實現(xiàn)了CFD計算軟件的自動調(diào)用和邊界條件的自動修改,使計算能夠直接執(zhí)行下一步。該方法保證了數(shù)值模擬過程的無縫銜接,縮短了計算周期。2.通過對文丘里管空化空蝕的研究,建立了一套試驗研究—數(shù)值計算—圖像后處理相結(jié)合的空化空蝕研究方法,具體研究了空泡各發(fā)展階段與空蝕的內(nèi)在聯(lián)系�；赗NG k-ε模型提出了一種考慮空化可壓縮性及湍流粘度修正的CDM湍流模型,有效地解決了常用湍流模型對湍流粘度過預(yù)測的問題：采用兩臺高速相機同時對文丘里管空泡結(jié)構(gòu)演變與空蝕過程進(jìn)行記錄,實現(xiàn)了空化與空蝕的同步測量；采用蝕點計算法對空化空蝕數(shù)據(jù)進(jìn)行分析,并輔以可壓縮數(shù)值模擬方法,研究了空泡不同發(fā)展階段時的空蝕破壞力。研究結(jié)果表明：空泡團的脫落與潰滅過程均會釋放高能量的沖擊波,并對固壁表面造成破壞,且后者為主要原因；蝕點的數(shù)量與面積的增長規(guī)律并非線性,而是呈階梯狀遞增,空蝕大多在空泡潰滅或脫落時發(fā)生。3.基于孔板射流的空化空蝕試驗研究,建立了一種基于空泡圖像的空蝕預(yù)測方法。采用MATLAB軟件對空化試驗數(shù)據(jù),即高速相機采集的連續(xù)空泡圖像進(jìn)行標(biāo)準(zhǔn)方差與平均值處理,預(yù)測出了潛在的空蝕區(qū)域以及相應(yīng)的破壞程度,并反映出空泡的分布情況�？瘴g試驗結(jié)果證明了該方法的有效性與準(zhǔn)確性,孔板射流空化的空蝕區(qū)域位于脫落空泡的潰滅點位置呈環(huán)狀形態(tài),其半徑與采用空泡圖像空蝕預(yù)測方法的半徑相同。試驗研究還揭示了流場速度與空蝕的關(guān)系,在空化數(shù)相同的前提下,流場流速越高,空蝕的程度越嚴(yán)重。4.以本文建立的CDM湍流模型為基礎(chǔ),考慮離心泵的旋轉(zhuǎn)效應(yīng)與大曲率結(jié)構(gòu)特征,建立了一種適用于離心泵空化數(shù)值模擬的RCD湍流模型,并與試驗結(jié)果進(jìn)行了對比,結(jié)果表明：相比標(biāo)準(zhǔn)κ-ε模型與SST k-ω模型,RCD模型有效地抑制了傳統(tǒng)湍流模型對湍流粘度的過預(yù)測,并準(zhǔn)確地捕捉到更為細(xì)致的泵內(nèi)湍流渦團與速度分布,使得數(shù)值計算能夠準(zhǔn)確地模擬出離心泵內(nèi)空化流非定常脫落與潰滅的現(xiàn)象。當(dāng)空化數(shù)不變時,在一個旋轉(zhuǎn)周期內(nèi)每一流道的空泡會依次經(jīng)歷發(fā)展、局部脫落、縮小再發(fā)展的周期性非定常過程。5.研究了ZGB空化模型中空泡半徑、汽化與凝結(jié)經(jīng)驗系數(shù)對離心泵空化揚程下降曲線預(yù)測精度的影響,結(jié)果表明：空泡半徑與汽化經(jīng)驗系數(shù)同時影響空泡的長度及含氣量大小,凝結(jié)系數(shù)主要影響空泡的長度；高空泡含氣量區(qū)域主要影響葉片吸力面進(jìn)口前緣低壓區(qū)的范圍,低壓區(qū)的長度與高空泡含氣量的長度相當(dāng),而高空泡含氣量區(qū)域的大小對離心泵揚程的影響較小,影響揚程預(yù)測精度的主要因素為空泡長度。6.考慮離心泵的旋轉(zhuǎn)運動特性和流體湍動能與空泡結(jié)構(gòu)演變的內(nèi)在聯(lián)系,基于ZGB空化模型發(fā)展了一種適用于離心泵空化數(shù)值模擬的RZGB空化模型,建立了離心泵轉(zhuǎn)速和幾何結(jié)構(gòu)與空泡半徑的函數(shù)關(guān)系。對RZGB模型對不同比轉(zhuǎn)速離心泵的預(yù)測精度進(jìn)行了評估,結(jié)果表明：對于低、中比轉(zhuǎn)速泵,RZGB模型的汽化凝結(jié)項經(jīng)驗系數(shù)分別為5000和0.001時預(yù)測精度更高；對于高比轉(zhuǎn)速泵采用汽化凝結(jié)項經(jīng)驗系數(shù)為50和0.01計算更為準(zhǔn)確。與可視化空化試驗結(jié)果對比表明,RZGB模型能夠更準(zhǔn)確地捕捉到離心泵進(jìn)口空泡的三維特殊結(jié)構(gòu)以及空穴尾端的不穩(wěn)定現(xiàn)象。7.以本文建立的空泡圖像空蝕預(yù)測方法為基礎(chǔ),建立了適用于旋轉(zhuǎn)水力機械的空蝕預(yù)測方法,并通過空蝕試驗證明了該方法的準(zhǔn)確性與可靠性。該方法對連續(xù)的高速攝影圖像或數(shù)值計算圖像進(jìn)行一系列的圖形變換,保證各葉輪流道固定不變,再以圖像標(biāo)準(zhǔn)方差與平均值處理方法進(jìn)行分析,從而獲得了離心泵葉片表面的空蝕區(qū)域與空泡分布。結(jié)果表明空蝕位置與空泡區(qū)域基本相當(dāng),但主體偏向空穴尾端,即離心泵中附著空泡尾端的高湍流不穩(wěn)定現(xiàn)象同樣會對固壁表面造成破壞。8.基于RCD湍流模型與RZGB空化模型,并結(jié)合試驗對一種轉(zhuǎn)子一定子型水力空化發(fā)生器的性能進(jìn)行了系統(tǒng)的研究。研究結(jié)果表明,空化發(fā)生器內(nèi)主要有三種空化類型,即轉(zhuǎn)子與定子相對運動形成的楔形槽空化、轉(zhuǎn)子高速旋轉(zhuǎn)形成的轉(zhuǎn)子葉片前緣空化和尾端低壓區(qū)空化。在相同轉(zhuǎn)速下空化發(fā)生器內(nèi)的壓力脈動隨著流量的增加而增大；在相同流量下空化發(fā)生器內(nèi)的壓力脈動隨著轉(zhuǎn)速的增加而增大；增大轉(zhuǎn)子與定子的間距將小幅度地降低腔內(nèi)的壓力幅值；空化發(fā)生器內(nèi)的主要空蝕區(qū)域為轉(zhuǎn)子葉片尾端,定子葉片前緣空泡附著部分及其尾端；空蝕主要在轉(zhuǎn)子與定子完全交錯時發(fā)生,此時形成的空化強度高且貼近固壁表面,這表明空泡在水力機械近壁面處的潰滅是導(dǎo)致空蝕發(fā)生的必要條件。
[Abstract]:Based on the National Natural Science Fund Project (5123900551309120), joint training doctoral project CSC public school, the European Space Agency (European Space Agency, ES A Cavitation in Thermosensible Fluids) project ", and the Jiangsu Province universities graduate student innovation fund (CXLX12_0640) to carry out the work of funding. With the progress of Science and technology and to improve the manufacturing precision of the hydraulic machinery industry, has been developing rapidly, however, the cavitation problems with its large high-speed and is more prominent. The efficiency of cavitation would not only lower the pumps and other hydraulic machinery, will produce vibration and noise, and even cause damage to the solid surface of hydraulic machinery, serious influence safe and stable operation of the system. On the other hand, because of its physical and chemical characteristics of cavitation flow transition complex and special unsteady dynamic characteristics, has become the For sewage treatment, underwater weapon drag and pipeline cleaning and other fields with high efficiency and low energy consumption in emerging technology. This paper studies on the hydraulic cavitation device two which has the advantages of simple structure of the Venturi tube and hole plate, by theoretical analysis, numerical calculation and experimental measurement of the combination of mechanism and the relationship between the formation of the method study on cavitation. Then on the basis of more extensive application, the structure is more complex on the rotating hydraulic machinery - centrifugal pump cavitation, cavitation of centrifugal pump to improve numerical calculation model, the unsteady characteristics revealed in the centrifugal pump cavitation, a centrifugal pump cavitation prediction method. Finally a systematic study of the hydrodynamic cavitation generator, to provide a reference for the research of cavitation application. The main work and innovative results are as follows: 1. for the hydraulic machinery cavitation device and numerical simulation. People constantly adjust the boundary conditions of the problem should be based on the batch process (Batch) and ANSYS-CFX is built to simulate the automatic operation method of cavitation numerical, automatically modify automatically call and boundary conditions of the CFD calculation software, the calculation can be directly executed next. This method guarantees the seamless process of numerical simulation.2., shorten the calculation period through the study of the Venturi tube cavitation, a combination of cavitation on the image processing method after a test of numerical calculation, relationship specific study of the cavitation and cavitation in different development stage. The RNG k- model based on a compressible turbulence model CDM the modified and turbulent viscosity considering cavitation is proposed to effectively solve the problem of the prediction of turbulence models of turbulent viscosity by two high-speed camera and cavity structure of Venturi tube The evolution was recorded and the cavitation process, realize the synchronous measurement of cavitation; cavitation corrosion was used to analyze the data of calculation method, supplemented by compressible numerical simulation method of cavitation bubble in different stages of development of the destructive force. The results show that shock wave cavitation shedding and group collapse of will release high energy, and caused damage to the wall surface, and the latter is the main reason; the number and area of the corrosion spot growth law and nonlinear, but the ladder was increasing, mostly in the cavitation bubble collapse or fall off occurs when the.3. experimental study on cavitation jet orifice based on established a prediction method of cavitation bubble image based on cavitation. The test data using MATLAB software, the continuous acquisition of the bubble image high speed camera standard deviation and average value, predict the cavitation region of potential And the corresponding damage degree, and reflect the distribution of cavitation. Cavitation test results prove the validity and accuracy of this method, the collapse point of cavitation cavitation jet orifice area is located in the form of a ring cavity shedding, the same radius and the cavitation cavitation image prediction method study radius. It reveals the relationship between flow velocity and cavitation, cavitation number in the premise of the same flow rate, the higher the CDM turbulence model of cavitation more serious degree of.4. basing on the view of the rotating effect of centrifugal pump with large curvature structural features, establish a suitable numerical cavitation of centrifugal pump simulation of the RCD turbulence model, and compared with the test results showed that: compared to the standard k-e model and SST k- turbulence model, RCD model can effectively suppress the traditional turbulence model to predict turbulent viscosity, and accurately. To capture more detailed pump turbulent eddies and the velocity distribution, the numerical calculation can accurately simulate the centrifugal pump cavitation flow unsteady shedding and collapse phenomenon. When the cavitation number is constant, in a revolving cycle cavity of each flow passage will in turn experience Development Bureau of the Ministry, fall off, narrow the unsteady process of.5. on the ZGB cavitation model of hollow bubble radius periodic RE development, vaporization and condensation experience coefficient decline, precision curve prediction of centrifugal pump cavitation bubble radius and the results show that the lift coefficient and cavitation effect experience of vaporization length and gas bubble size, length of condensation coefficient has great effect on high altitude; global gas range mainly affects the area of the suction side of the blade inlet front low pressure area, and the length of the high altitude area of the global air content length, while a high global content area size of centrifugal pump Less impact head, considering the inner relation between the centrifugal pump rotating motion and fluid turbulent kinetic energy and cavity structure of the cavity length of.6. main factors affecting the accuracy of the predicted head, ZGB cavitation model based on the development of a suitable for the numerical simulation of the RZGB centrifugal pump cavitation cavitation model, establishes the function relation of centrifugal pump speed and geometry the structure and bubble radius. The RZGB model for different prediction accuracy over speed centrifugal pump were evaluated, the results show that: for the low specific speed pump, empirical coefficient were 5000 and 0.001 when setting higher prediction accuracy of RZGB model for vaporization; high specific speed pump uses the experience of vaporization condensation coefficient is 50 0.01 and the calculation is more accurate. Compared with the visualization of cavitation test results, RZGB model can more accurately capture the special three-dimensional structure of imported centrifugal pump cavitation and air hole Bubble image cavitation instabilities in the.7. at the end of this prediction method based on prediction method of cavitation was established for hydraulic machinery, and proves the accuracy and reliability of this method through the test. The method of image graphic transformation of a series of continuous high speed photography or numerical calculation, ensure the impeller is fixed, then the standard deviation and image processing method of the average value were analyzed to obtain the centrifugal pump blade surface cavitation region and void distribution. The results show that the cavitation and cavitation region location is quite basic, but the main bias hole end, high turbulence is the tail end of the attached cavitation in centrifugal pump the unstable phenomenon also will damage the.8. model and RZGB RCD model based on turbulence cavitation on the solid wall surface, combined with the test of a rotor stator generator of cavitation It was systematically studied. The results show that the cavitation generator has three main types: wedge groove cavitation cavitation, the rotor and the stator relative motion of formation of the rotor blade leading edge and end area of low pressure cavitation cavitation high-speed rotating rotor formation. The pressure fluctuation at the same speed of cavitation in the generator increases with the increase of flow rate at the same flow; pressure fluctuation of cavitation in the generator increases with increasing engine speed; increasing the distance between the rotor and the stator will be a small decrease in amplitude of pressure chamber; the main cavitation region within the cavitation generator for the rotor blade end, stator blade leading edge and the end part of the bubble attached; cavitation occurs mainly in the rotor and the stator completely staggered, the cavitation intensity high and close to the wall surface, which indicates that the cavitation in hydraulic machinery near the wall is the cause of cavitation bubble collapse The necessary conditions for the occurrence.

【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TH311;TK72

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