本文關(guān)鍵詞：基于兩相流的多級(jí)離心泵汽蝕性能分析　出處：《華南理工大學(xué)》2011年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 多級(jí)離心泵 汽蝕 兩相流模型 數(shù)值模擬

【摘要】：多級(jí)離心泵在運(yùn)轉(zhuǎn)過程中,有時(shí)會(huì)出現(xiàn)水力機(jī)械特有的汽蝕現(xiàn)象。汽蝕現(xiàn)象改變了流道內(nèi)的速度分布,使離心泵的效率下降、揚(yáng)程降低,引起機(jī)器振動(dòng),同時(shí)也會(huì)使葉輪遭受破壞,嚴(yán)重影響工作性能,并妨礙其正常運(yùn)行。所以如何準(zhǔn)確地預(yù)測泵的汽蝕性能,防止汽蝕的發(fā)生是一個(gè)重要的研究方向。 由于汽蝕現(xiàn)象本身的復(fù)雜性以及測量的困難性,要對(duì)汽蝕現(xiàn)象準(zhǔn)確的定量分析還很難。隨著計(jì)算流體動(dòng)力學(xué)(CFD)技術(shù)在水力機(jī)械內(nèi)部流場計(jì)算中應(yīng)用日益廣泛,CFD成為優(yōu)化設(shè)計(jì)的重要工具。所以使用數(shù)值模擬研究多級(jí)離心泵內(nèi)部的汽蝕流動(dòng),預(yù)測泵的汽蝕性能,對(duì)汽蝕現(xiàn)象進(jìn)行準(zhǔn)確地定量分析已經(jīng)成為可能。 本文利用CFX軟件的RNG k-ε湍流模型和SIMPLEC算法,采用Rayleigh-Plesset汽蝕模型對(duì)多級(jí)離心泵的首級(jí)葉輪進(jìn)行了汽蝕模擬。分析了壓力場和速度場,得到了不同壓力、不同流量下的氣泡分布和速度矢量分布。還對(duì)9個(gè)流量工況下的葉輪進(jìn)行了完整的汽蝕模擬計(jì)算,從汽蝕未發(fā)生、汽蝕初生到汽蝕發(fā)展,找到了臨界汽蝕余量點(diǎn),得到了NPSH-Q曲線,并和實(shí)驗(yàn)曲線進(jìn)行了比對(duì)。 本文得到的結(jié)論如下： 1、為了驗(yàn)證模擬軟件和模型的準(zhǔn)確性,先對(duì)多級(jí)離心泵的兩級(jí)葉輪和導(dǎo)葉進(jìn)行無汽蝕模型的單相流動(dòng)數(shù)值模擬,把模擬結(jié)果和實(shí)驗(yàn)結(jié)果進(jìn)行了對(duì)比,模擬曲線和實(shí)驗(yàn)曲線的趨勢一致,誤差較小,證明了模擬的有效性和可行性。從模擬結(jié)果發(fā)現(xiàn)泵壓力最低的地方在多級(jí)離心泵首級(jí)葉輪葉片進(jìn)口處,為下面的工作打下了基礎(chǔ)。 2、對(duì)多級(jí)離心泵的首級(jí)葉輪進(jìn)行了汽蝕模擬。得到了壓力分布圖和速度矢量分布圖,知道了汽蝕初生的位置在葉片背面進(jìn)口稍后處。調(diào)節(jié)出口壓力和流量,得到了汽蝕隨壓力和流量變化圖。利用模擬計(jì)算可以觀察到汽蝕初生,找到汽蝕初生點(diǎn),這對(duì)防止離心泵的汽蝕有重要的意義。 3、對(duì)9個(gè)流量工況下的葉輪進(jìn)行了汽蝕模擬,找到臨界汽蝕余量得到NPSH-Q曲線并與實(shí)驗(yàn)曲線進(jìn)行對(duì)比,兩條曲線的趨勢基本一致,在大流量工況下誤差較大,在小流量工況,特別是額定工況下模擬結(jié)果和實(shí)驗(yàn)結(jié)果較為接近。說明該模擬方法可以準(zhǔn)確預(yù)測離心泵的汽蝕性能,也說明數(shù)值模擬預(yù)測可以代替繁瑣而又復(fù)雜的泵汽蝕實(shí)驗(yàn)。
[Abstract]:During the operation of multi - stage centrifugal pump , cavitation phenomenon which is peculiar to the hydraulic machinery can sometimes occur . The cavitation phenomenon changes the velocity distribution in the flow channel , so that the efficiency of the centrifugal pump is reduced , the lift is reduced , the machine vibration is caused , meanwhile , the impeller is damaged , the working performance is seriously affected , and the normal operation of the pump is hindered . As the computational fluid dynamics ( CFD ) technology is widely used in the calculation of the flow field in the hydraulic machinery , the computational fluid dynamics ( CFD ) technology has been widely used in the calculation of the internal flow field of the hydraulic machinery , and the CFD has become an important tool for the optimization design . In this paper , the first - stage impeller of multi - stage centrifugal pump is simulated by using the rng k - 蔚 turbulence model and SIMPLEC algorithm of CFX software . The pressure field and velocity field are analyzed . The conclusions are as follows : 1 . In order to verify the accuracy of the simulation software and the model , the single - phase flow numerical simulation of the non - cavitation model is carried out on the two - stage impeller and the guide vane of the multistage centrifugal pump . The simulation results and the experimental results are compared , the simulation curves and the experimental curves are consistent , the errors are small , the simulation results are proved to be valid and feasible . 2 . The cavitation simulation of the first impeller of the multistage centrifugal pump is carried out . The pressure distribution map and velocity vector distribution map are obtained . It is known that the position of the cavitation is at a later stage at the back of the blade . The pressure and flow rate of the cavitation are adjusted . The cavitation inception can be observed by using the simulated calculation , and the cavitation inception point can be found , which is of great significance to prevent cavitation erosion of the centrifugal pump . 3 . The cavitation simulation of the impeller under 9 flow conditions is carried out , the critical cavitation margin is found to be compared with the experimental curve , the trend of the two curves is basically consistent , and the simulation results and the experimental results are close to the experimental results under the condition of large flow conditions . The simulation method can accurately predict the cavitation performance of the centrifugal pump , but also the numerical simulation prediction can replace the tedious and complicated pump cavitation experiment .

【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2011
【分類號(hào)】：TH311

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