本文選題：壅塞空化器　切入點(diǎn)：空化機(jī)理　出處：《湖南工業(yè)大學(xué)》2014年碩士論文

【摘要】：壅塞空化器是一種新型的水力空化發(fā)生裝置，它充分利用壅塞空化產(chǎn)生的特殊流場(chǎng)有效地加強(qiáng)了水力空化強(qiáng)度，但對(duì)產(chǎn)生壅塞空化的機(jī)理還有待進(jìn)一步加深認(rèn)識(shí)。 將氣液兩相臨界流的壅塞現(xiàn)象和液體的空化現(xiàn)象結(jié)合起來進(jìn)行研究，針對(duì)不同壅塞空化器的結(jié)構(gòu)和尺寸，通過CFD軟件數(shù)值模擬壅塞空化器的空化流場(chǎng)，利用U型管壓差計(jì)測(cè)量壅塞管壁面沿程靜壓力的分布，分析壅塞管內(nèi)沿程壓力和空隙率的變化規(guī)律，研究空泡生成和氣液兩相流及其臨界流壅塞現(xiàn)象形成的機(jī)理；通過水聽器測(cè)試壅塞空化器產(chǎn)生的空化噪聲信號(hào)，分析空化噪聲的功率譜特性、空化噪聲能量比值和潰滅空泡數(shù)量和尺寸，并結(jié)合壅塞現(xiàn)象的特性研究壅塞空化的空泡潰滅機(jī)理，并把數(shù)值模擬結(jié)果和實(shí)驗(yàn)結(jié)果進(jìn)行相互驗(yàn)證。研究結(jié)果表明，壅塞管的上游區(qū)域形成接近或低于飽和蒸汽壓的低壓區(qū)域，同時(shí)管內(nèi)的含氣率迅速升高，管內(nèi)由單相流動(dòng)轉(zhuǎn)變?yōu)闅庖簝上嗔�，�?dǎo)致壅塞管內(nèi)兩相流的當(dāng)?shù)匾羲偌眲∠陆�，形成了�?dāng)?shù)伛R赫數(shù)接近于1的壅塞截面。在壅塞截面的上下游間高達(dá)108Pa/m的壓力恢復(fù)梯度作用下，使得管內(nèi)有數(shù)量多達(dá)106級(jí)和直徑為10-6m級(jí)的空泡迅速潰滅，形成了劇烈空化的壅塞空化現(xiàn)象�？栈鞅硥菏芹杖栈瘡�(qiáng)度的重要影響因素，在一定的空化器結(jié)構(gòu)和水動(dòng)力參數(shù)下背壓存在相應(yīng)的最佳范圍。流量越大越有利于壅塞空化的形成，，大流量下空化器潰滅的空泡數(shù)量更多；壅塞環(huán)可以在背壓和流量不變的條件下影響壅塞截面的位置以及增大壅塞截面處的壓力恢復(fù)梯度，且背壓越低時(shí)效果越明顯。
[Abstract]:Choking cavitation device is a new type of hydraulic cavitation device. It makes full use of the special flow field produced by choking cavitation to effectively strengthen the intensity of hydraulic cavitation, but the mechanism of producing choking cavitation needs to be further understood.The choking phenomenon of gas-liquid two-phase critical flow is combined with the cavitation phenomenon of liquid. According to the structure and size of different choking cavitation device, the cavitation flow field of choking cavitation device is numerically simulated by CFD software.The distribution of static pressure along the wall of choked pipe is measured by U-tube pressure difference meter. The variation law of pressure and voidage in choked pipe is analyzed, and the formation mechanism of cavitation and gas-liquid two-phase flow and its critical choking phenomenon is studied.The cavitation noise signal produced by choked cavitation device is measured by hydrophone. The power spectrum characteristics of cavitation noise, the ratio of cavitation noise energy and the number and size of cavitation bubble are analyzed.Combined with the characteristics of choking phenomenon, the cavitation collapse mechanism of choked cavitation is studied, and the numerical simulation results and experimental results are verified.The results show that a low pressure region close to or below the saturated vapor pressure is formed in the upstream region of the choked pipe, and the gas holdup in the pipe increases rapidly, and the flow in the pipe changes from a single-phase flow to a gas-liquid two-phase flow.The local sonic speed of the two-phase flow in the choked pipe drops sharply and the local Mach number is close to 1.Under the pressure recovery gradient of up to 108Pa/m between upstream and downstream of the choked section, the number of cavitation bubbles of up to 106m and the diameter of 10-6m are rapidly collapsing, and the phenomenon of choking cavitation is formed.The backpressure of cavitation device is an important factor affecting the choking cavitation intensity. The optimum range of backpressure exists under certain cavitation structure and hydrodynamic parameters.The larger the flow rate is, the more favorable the formation of choking cavitation is, and the more cavitation bubbles are destroyed under the large flow rate, the choking ring can influence the position of the choked section and increase the pressure recovery gradient of the choked section under the condition of constant back pressure and flow rate.And the lower the back pressure, the more obvious the effect is.
【學(xué)位授予單位】：湖南工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TV131.32;TV136

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