本文選題：離心泵 + 空化性能�。� 參考：《蘭州理工大學(xué)》2017年碩士論文

【摘要】：隨著科學(xué)技術(shù)的不斷發(fā)展,流體力學(xué)、計(jì)算流體力學(xué)、流體機(jī)械測(cè)試技術(shù)等學(xué)科的理論與應(yīng)用得以有較大進(jìn)步,從而使得離心泵內(nèi)部流動(dòng)問題的研究也得到迅速發(fā)展。目前離心泵的應(yīng)用越來越廣泛,對(duì)離心泵在各個(gè)領(lǐng)域的安全、穩(wěn)定運(yùn)行也提出越來越高的要求。但是,作為水力機(jī)械中的一大難題—空化,一直制約著離心泵的發(fā)展,其不僅對(duì)離心泵的穩(wěn)定運(yùn)行產(chǎn)生影響,還對(duì)離心泵的過流部件造成較大的破壞。影響其內(nèi)部空化發(fā)生的因素有很多,本文以離心泵葉片進(jìn)口邊為研究對(duì)象,采用數(shù)值計(jì)算與理論分析相結(jié)合的方法對(duì)葉片進(jìn)口邊形狀及位置對(duì)離心泵空化性能的影響進(jìn)行研究及分析。具體的研究內(nèi)容有以下幾個(gè)方面:1.通過對(duì)不同離心泵葉片進(jìn)口邊形狀進(jìn)行對(duì)比分析,發(fā)現(xiàn)圓錐型葉片進(jìn)口邊的離心泵具有更優(yōu)秀的空化性能,該葉片在進(jìn)口部分更符合流線形規(guī)律,可改善流體在該處的入流狀態(tài),減少葉片進(jìn)口邊對(duì)流體的沖擊作用。2.保持葉輪軸面截線形狀不變,通過改變軸面截線上葉片進(jìn)口邊在前、后蓋板處的位置,得到具有不同前、后掠角度的葉片進(jìn)口邊,經(jīng)過數(shù)值計(jì)算得到不同葉片樣本的空化性能曲線,并對(duì)離心泵內(nèi)部空泡分布情況進(jìn)行分析,可總結(jié)出當(dāng)葉片進(jìn)口邊在前蓋板處位置改變時(shí)對(duì)空化性能有較大影響,而葉片進(jìn)口邊在后蓋板處位置改變時(shí)對(duì)空化性能影響較小。3.分析了不同葉片樣本的葉片載荷分布情況,葉片進(jìn)口邊在前蓋板處前掠時(shí)具有較好的空化性能,其與原型葉片相比在葉片進(jìn)口部分具有較小的載荷分布,葉片工作面壓力較低,葉片背面壓力較高。從而當(dāng)離心泵進(jìn)口壓力降低時(shí),該葉片與原型葉片相比其背面壓力更難降低到該溫度下液體的汽化壓力,從而在葉片背面進(jìn)口邊附近更難以產(chǎn)生空泡,因此具有較好的空化性能。而葉片進(jìn)口邊沿著后蓋板前掠使得進(jìn)入葉輪的小部分流體受到葉片由后蓋板向前蓋板方向的作用力,并且葉片背面后蓋板處提前受到液流的沖擊使該處壓力比原型更高,這兩個(gè)因素阻止了在進(jìn)口邊前蓋板處產(chǎn)生的氣泡向后蓋板擴(kuò)散,從而可以避免氣泡對(duì)葉片流道的堵塞,因此這種離心泵樣本在內(nèi)部空化有一定程度之后揚(yáng)程下降速率更慢。4.對(duì)具有不同葉片樣本的離心泵蝸殼內(nèi)部非定常壓力脈動(dòng)情況進(jìn)行了分析,具有較好空化性能的葉片樣本,在相同NPSHa時(shí)其葉輪內(nèi)部空化區(qū)域更小,從而對(duì)內(nèi)部流域的流動(dòng)影響較小。而空化性能較差的葉片樣本,葉輪內(nèi)部較大的空化區(qū)域?qū)е氯~輪內(nèi)部流動(dòng)的紊亂,產(chǎn)生較多的漩渦,從而直接影響到蝸殼內(nèi)部壓力脈動(dòng)的程度。5.提出了基于徑向基函數(shù)(RBF)的葉片進(jìn)口邊位置對(duì)離心泵空化性能的影響預(yù)測(cè),將葉片進(jìn)口邊前蓋板處扭掠角度和后蓋板處扭掠角度作為兩個(gè)設(shè)計(jì)變量,將離心泵的必需空化余量NPSHr值作為預(yù)測(cè)值,利用RBF方法建立了不同葉片進(jìn)口邊位置對(duì)離心泵空化性能影響的預(yù)測(cè)模型,取得了較為準(zhǔn)確的預(yù)測(cè)結(jié)果。
[Abstract]:With the continuous development of science and technology, the theory and application of fluid mechanics, computational fluid mechanics, fluid mechanical testing technology and other disciplines have been made great progress, which makes the research on the internal flow of centrifugal pumps developed rapidly. At present, the application of centrifugal pumps is becoming more and more extensive, and the safety and stability of centrifugal pumps in various fields are running steadily. However, as a big problem in the hydraulic machinery, cavitation has been restricting the development of centrifugal pumps, which not only affects the stable operation of centrifugal pumps, but also causes great damage to the overflow parts of centrifugal pumps. There are many factors affecting the cavitation of the centrifugal pump. This paper is based on the inlet edge of the centrifugal pump blade. The influence of the shape and position of the inlet edge of the blade on the cavitation performance of the centrifugal pump is studied and analyzed by the combination of numerical calculation and theoretical analysis. The specific research contents are as follows: 1. through the comparison and analysis of the shape of the inlet edge of the blade of different centrifugal pumps, the inlet edge of the conical blade is found. The centrifugal pump has more excellent cavitation performance. The blade is more consistent with the streamline shape in the inlet part. It can improve the flow status of the fluid in the area, reduce the impact of the inlet of the blade on the fluid, and keep the axial plane of the impeller to keep the shape of the interception of the impeller. By changing the position of the inlet edge of the blade at the front and the rear cover, the position of the blade at the front and the rear cover is obtained by changing the position of the blade inlet on the axis of the axis. The cavitation performance curves of different blade samples are obtained by numerical calculation, and the distribution of cavitation in the centrifugal pump is analyzed by numerical calculation. It is concluded that when the position of the blade inlet is changed at the front cover, the cavitation performance is greatly influenced, while the inlet side of the blade is changed at the back plate position. The cavitation performance is less affected by the.3. analysis of the blade load distribution of different blade samples. The blade inlet side has better cavitation performance at the front of the front cover plate. Compared with the prototype blade, it has a smaller load distribution in the inlet part of the blade, the pressure of the blade working face is lower, and the back pressure of the blade is higher. When the pressure is reduced, the back pressure of the blade is more difficult to reduce to the vaporization pressure of the liquid at this temperature, so it is more difficult to produce vacuoles near the inlet side of the blade. Therefore, it has better cavitation performance. The blade inlet border along the back cover makes the small part of the fluid entering the impeller from the rear cover. The force in the direction of the plate forward and the rear cover plate at the back of the blade causes the pressure to be higher than the prototype at the back of the rear cover. These two factors prevent the diffusion of the bubble back at the front cover plate at the inlet side, thus avoiding the plugging of the air bubble on the blade runner, so the centrifugal pump sample is cavitating inside. The unsteady pressure fluctuation in the centrifugal pump volute with different blade samples is analyzed by.4. to a certain extent. The blade samples with better cavitation performance have smaller cavitation area at the same NPSHa, which has less influence on the flow field in the internal flow field, and the cavitation performance is poor. The blade sample, the larger cavitation area inside the impeller leads to the disturbance of the flow inside the impeller and produces more whirlpools, which directly affects the degree of pressure pulsation in the inner shell of the worm.5.. The influence of the inlet position of the blade on the cavitation performance of the centrifugal pump is predicted based on the radial basis function (RBF), and the swept angle of the front cover plate at the inlet of the blade is made. As two design variables, the NPSHr value of the necessary cavitation allowance of the centrifugal pump is taken as the predictive value, and the prediction model of the influence of the inlet position of different blades on the cavitation performance of the centrifugal pump is established by RBF method, and a more accurate prediction result has been obtained.

【學(xué)位授予單位】：蘭州理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TH311

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