射流式離心泵氣液兩相流動特性研究
發(fā)布時間：2018-08-01 18:45
【摘要】：射流式離心泵作為節(jié)水灌溉的主要設備之一,提高其自吸性能對于節(jié)水灌溉的發(fā)展起到至關重要的作用。本文采用CFX軟件所提供的雙歐拉多相流模型對射流式離心泵進行氣液兩相流模擬。并對數(shù)值模擬結果進行對比分析,得到射流式離心泵內(nèi)部氣液兩相流的流動規(guī)律,為后續(xù)優(yōu)化自吸性能提供借鑒。本文選擇浙江某企業(yè)的JET750射流式離心泵作為主要研究對象。其主要研究內(nèi)容和創(chuàng)新成果如下:1)采用流場分析軟件CFX對JET750射流式離心泵進行液相模擬,分析發(fā)現(xiàn),噴嘴出口的循環(huán)流量隨著運行工況增大,逐漸減小,對應的噴嘴出口處的渦量值以及喉管處的靜壓、射流器內(nèi)部的湍流強度逐漸降低。射流器出口流體的速度趨向于均勻流,擴散段的流動分離逐漸減小,流體過流能力增強。2)為了研究射流式離心泵內(nèi)部氣液兩相流動規(guī)律,對泵進口分別設置不同氣相濃度同一運行工況以及同種進口氣相濃度不同運行工況下的氣液兩相模擬。當對進口不同含氣率模擬結果進行分析,發(fā)現(xiàn)隨著進口氣相含氣率的增加,噴嘴循環(huán)流量逐漸降低,葉輪流道內(nèi)的含氣率以及射流器內(nèi)部各截面上的氣相含氣率也逐漸增加,氣相平均速度逐漸減小。當對同種進口含氣率不同運行工況模擬結果分析發(fā)現(xiàn),隨著運行工況的增加,噴嘴出口的循環(huán)流量逐漸增加的,葉輪內(nèi)部的氣相過流能力加強,揚程下滑相對小流量工況要小。3)將射流式離心泵中射流器部分提取出來,單獨進行氣液相兩相流數(shù)值模擬。以射流器噴嘴直徑0P、喉管直徑1P、喉管長度2P、喉嘴距3P四個參數(shù)為試驗因素,出口氣相的流速為目標函數(shù),設置正交試驗樣本,根據(jù)模擬結果通過Isight軟件對射流器的四個因素以及目標函數(shù)進行擬合得到近似模型。R-squared可到0.88,擬合優(yōu)度滿足求解要求,并得到各因素對射流器氣相過流能力的影響程度,從大到小分別為P_o、P_o~2、P_1~2、P_1、P_1~*P_3、P_0~* P_1、P_1~*P_2 、P_2~2、P_3 、P_3~2。然而修改噴嘴直徑以及喉管直徑將改變面積比,面積比的變化對于外特性影響很大。在試驗部分對候嘴距以及喉管長度這兩個因素進行修改,通過自吸性能以及外特性性能試驗,發(fā)現(xiàn)適當?shù)脑黾雍砉荛L度有利于改善自吸性能,自吸高度由原來的7.45米提高到9.1米,自吸時間也由原來的145s縮短到90s,而外特性基本保持不變,若繼續(xù)增加喉管長度,射流器內(nèi)流損失急劇增大,外特性開始下滑。通過模擬發(fā)現(xiàn),適當?shù)募娱L喉管長度不僅使過流能力上有所提升,喉管處的壓力有所降低,卷吸能力有所提升,這對于氣相過流能力都是有利的。本次對于自吸性能的優(yōu)化已經(jīng)應用到公司產(chǎn)品當中。
[Abstract]:As one of the main equipment of water-saving irrigation, jet centrifugal pump plays an important role in the development of water-saving irrigation. In this paper, the two-Euler multiphase flow model provided by CFX software is used to simulate the gas-liquid two-phase flow in the ejection centrifugal pump. By comparing and analyzing the numerical simulation results, the flow law of gas-liquid two-phase flow in the jet centrifugal pump is obtained, which provides a reference for the subsequent optimization of self-priming performance. In this paper, the JET750 jet centrifugal pump of a Zhejiang enterprise is chosen as the main research object. The main research contents and innovative results are as follows: (1) the liquid phase simulation of JET750 jet centrifugal pump is carried out by using the flow field analysis software CFX. It is found that the circulating flow rate at the nozzle outlet decreases gradually with the increase of the operating condition. The vorticity at the nozzle outlet and the static pressure at the throat reduce the turbulent intensity of the jet. In order to study the gas-liquid two-phase flow in the jet centrifugal pump, the velocity of the fluid at the outlet of the jet tends to be uniform, the flow separation of the diffusion section decreases gradually, and the flow capacity of the fluid overflows increases by .2) in order to study the gas-liquid two-phase flow in the jet centrifugal pump, The gas-liquid two-phase simulation was carried out at the pump inlet under the same operating condition with different gas concentration and different operating conditions with the same inlet gas concentration. When the simulation results of different inlet gas holdup are analyzed, it is found that with the increase of inlet gas holdup, the flow rate of nozzle cycle decreases gradually, and the gas holdup in impeller channel and in each section of the jet is gradually increased. The gas phase average velocity decreases gradually. When the simulation results of the same inlet gas content and different operating conditions are analyzed, it is found that with the increase of the operating conditions, the circulating flow rate of the nozzle outlet increases gradually, and the gas phase overflow capacity inside the impeller is strengthened. Compared with the low flow rate, the head slide is smaller than that of the small flow rate (3. 3) the jet part of the jet centrifugal pump is extracted and the gas-liquid two-phase flow numerical simulation is carried out separately. Taking the four parameters of jet nozzle diameter 0 P, throat pipe diameter 1 P, throat length 2 P, throat distance 3 P as test factors, and the velocity of gas phase at outlet as objective function, the orthogonal test samples were set up. According to the simulation results, the four factors and the objective function of the jet were fitted by Isight software to get the approximate model. R-squared can reach 0.88. The goodness of fit meets the requirements of the solution, and the degree of influence of each factor on the gas phase overflow capacity of the jet is obtained. From the big to the small, to the next, to the second, to the flesh, to the flesh; to the flesh, to the number of people; However, the area ratio will be changed by modifying the nozzle diameter and the throat diameter, and the change of the area ratio will have a great influence on the external characteristics. In the test part, two factors, the distance between the nozzle and the length of the pipe, are modified. Through the self-priming performance and the external characteristic test, it is found that the proper increase of the length of the pipe is beneficial to the improvement of the self-priming performance. The self-priming height is increased from 7.45 m to 9.1 m, and the self-priming time is shortened from 145s to 90s, but the external characteristic remains unchanged. If the length of the throat is increased, the loss of the inner flow of the jet will increase sharply, and the external characteristic will begin to decline. It is found by simulation that the proper length of the long pipe not only increases the overcurrent capacity, but also reduces the pressure and the entrainment capacity of the pipe, which is beneficial to the gas phase overcurrent capacity. This self-priming performance optimization has been applied to the company's products.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH311
本文編號：2158497
[Abstract]:As one of the main equipment of water-saving irrigation, jet centrifugal pump plays an important role in the development of water-saving irrigation. In this paper, the two-Euler multiphase flow model provided by CFX software is used to simulate the gas-liquid two-phase flow in the ejection centrifugal pump. By comparing and analyzing the numerical simulation results, the flow law of gas-liquid two-phase flow in the jet centrifugal pump is obtained, which provides a reference for the subsequent optimization of self-priming performance. In this paper, the JET750 jet centrifugal pump of a Zhejiang enterprise is chosen as the main research object. The main research contents and innovative results are as follows: (1) the liquid phase simulation of JET750 jet centrifugal pump is carried out by using the flow field analysis software CFX. It is found that the circulating flow rate at the nozzle outlet decreases gradually with the increase of the operating condition. The vorticity at the nozzle outlet and the static pressure at the throat reduce the turbulent intensity of the jet. In order to study the gas-liquid two-phase flow in the jet centrifugal pump, the velocity of the fluid at the outlet of the jet tends to be uniform, the flow separation of the diffusion section decreases gradually, and the flow capacity of the fluid overflows increases by .2) in order to study the gas-liquid two-phase flow in the jet centrifugal pump, The gas-liquid two-phase simulation was carried out at the pump inlet under the same operating condition with different gas concentration and different operating conditions with the same inlet gas concentration. When the simulation results of different inlet gas holdup are analyzed, it is found that with the increase of inlet gas holdup, the flow rate of nozzle cycle decreases gradually, and the gas holdup in impeller channel and in each section of the jet is gradually increased. The gas phase average velocity decreases gradually. When the simulation results of the same inlet gas content and different operating conditions are analyzed, it is found that with the increase of the operating conditions, the circulating flow rate of the nozzle outlet increases gradually, and the gas phase overflow capacity inside the impeller is strengthened. Compared with the low flow rate, the head slide is smaller than that of the small flow rate (3. 3) the jet part of the jet centrifugal pump is extracted and the gas-liquid two-phase flow numerical simulation is carried out separately. Taking the four parameters of jet nozzle diameter 0 P, throat pipe diameter 1 P, throat length 2 P, throat distance 3 P as test factors, and the velocity of gas phase at outlet as objective function, the orthogonal test samples were set up. According to the simulation results, the four factors and the objective function of the jet were fitted by Isight software to get the approximate model. R-squared can reach 0.88. The goodness of fit meets the requirements of the solution, and the degree of influence of each factor on the gas phase overflow capacity of the jet is obtained. From the big to the small, to the next, to the second, to the flesh, to the flesh; to the flesh, to the number of people; However, the area ratio will be changed by modifying the nozzle diameter and the throat diameter, and the change of the area ratio will have a great influence on the external characteristics. In the test part, two factors, the distance between the nozzle and the length of the pipe, are modified. Through the self-priming performance and the external characteristic test, it is found that the proper increase of the length of the pipe is beneficial to the improvement of the self-priming performance. The self-priming height is increased from 7.45 m to 9.1 m, and the self-priming time is shortened from 145s to 90s, but the external characteristic remains unchanged. If the length of the throat is increased, the loss of the inner flow of the jet will increase sharply, and the external characteristic will begin to decline. It is found by simulation that the proper length of the long pipe not only increases the overcurrent capacity, but also reduces the pressure and the entrainment capacity of the pipe, which is beneficial to the gas phase overcurrent capacity. This self-priming performance optimization has been applied to the company's products.
【學位授予單位】：江蘇大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TH311
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