【摘要】：隨著微納米技術(shù)的發(fā)展,空泡技術(shù)在生物醫(yī)學(xué)、化學(xué)工程和國防軍事等領(lǐng)域發(fā)揮著巨大的作用。空泡技術(shù)的關(guān)鍵是如何實現(xiàn)對空泡動力學(xué)特性的有效控制,本文針對微通道構(gòu)型對空泡動力學(xué)特性的影響以及壁面潤濕性的調(diào)控技術(shù)進行了系統(tǒng)研究,對微流控系統(tǒng)的設(shè)計具有重要意義。利用高速攝像技術(shù)對通氣空泡在T型微通道處的產(chǎn)生過程進行了研究,重點分析了流速、氣液流速比以及通道尺寸對空泡動力學(xué)特性的影響。結(jié)果表明,空泡的產(chǎn)生方式包括四種,其對應(yīng)的生成機制分別為擠壓、剪切、擠壓和剪切共同作用以及壁面阻力�？张荽笮‰S著流速、氣液流速比以及通道寬度的增大而增大。借助高速攝像技術(shù)并結(jié)合計算流體動力學(xué)方法研究了通氣空泡在T型、Y型和文丘里管型微通道中發(fā)生形變或分裂的動力學(xué)特性。研究發(fā)現(xiàn),T型和Y型通道中空泡的分裂機理主要包含通道結(jié)構(gòu)和流場兩種,文丘里管型通道中空泡的分裂機理為流場作用�？张莅l(fā)生形變或分裂的強度隨著流速的增大而增強,隨著空泡體積和通道尺寸的增大而減弱。采用激光加工和自組裝技術(shù)制備了具有不同潤濕性的微通道壁面,借助高速攝像系統(tǒng)著重分析了流速和壁面疏水性對空泡動態(tài)接觸角的影響。試驗結(jié)果表明,隨著流速的增大,空泡在壁面處的動態(tài)接觸角和兩側(cè)壁面處的動態(tài)接觸角比值均減小�？张菰谕ǖ纼蓚�(cè)壁面處的動態(tài)接觸角比值與通道左側(cè)壁面潤濕性之間存在著對應(yīng)關(guān)系,此對應(yīng)關(guān)系可用于微通道壁面潤濕性的表征。利用薄片組裝結(jié)合自組裝分子膜沉積的方法設(shè)計并制作了一種表面潤濕性可調(diào)控的疏水／超疏水表面,借助接觸角測量儀對表面具有不同肋板高度時對應(yīng)的靜態(tài)接觸角進行測量。測量結(jié)果表明,通過精確控制表面微肋板高度,可快速實現(xiàn)表面潤濕性在弱疏水和強疏水甚至超疏水之間的可逆調(diào)控,且調(diào)控效果具有連續(xù)性。將設(shè)計的潤濕性可調(diào)控表面進行改進并集成到微通道中作為通道一側(cè)壁面,研究了流速和壁面疏水性對空泡動態(tài)接觸角的影響。研究發(fā)現(xiàn),通過控制微肋板結(jié)構(gòu)可改變氣液固三相的接觸狀態(tài),從而實現(xiàn)壁面實際潤濕性在強疏水和親水之間的可逆調(diào)控。另外,壁面潤濕性的調(diào)控效果和壁面處的空泡動態(tài)接觸角均受薄片厚度和流速二者的影響。
[Abstract]:With the development of micro / nano technology, cavitation technology plays an important role in biomedicine, chemical engineering and national defense. The key of cavitation technology is how to effectively control the dynamic characteristics of cavitation. In this paper, the influence of micro-channel configuration on the dynamic characteristics of cavitation and the control technology of wall wettability are systematically studied. It is of great significance to the design of microfluidic system. The formation process of aerated vacuoles at T-type microchannels was studied by using high-speed camera technology. The effects of velocity of flow, gas-liquid velocity ratio and channel size on the dynamic characteristics of the vacuoles were analyzed with emphasis on the flow rate, gas-liquid velocity ratio and channel size. The results show that there are four types of cavitation formation, and the corresponding mechanisms are extrusion, shear, extrusion and shear together, and wall resistance. The bubble size increases with the increase of flow velocity, gas-liquid velocity ratio and channel width. The dynamic characteristics of deformation or splitting of aerated vacuoles in T-type Y-type and Venturi-type microchannels were studied by means of high-speed camera technique and computational fluid dynamics (CFD) method. It is found that the splitting mechanism of vacuoles in T-type and Y-type channels mainly consists of two kinds of channel structure and flow field, and the splitting mechanism of vacuoles in Venturi-type channel is flow field. The strength of void deformation or splitting increases with the increase of flow velocity and decreases with the increase of bubble volume and channel size. The micro-channel walls with different wettability were fabricated by laser processing and self-assembly technology. The effects of velocity and wall hydrophobicity on the dynamic contact angle of cavitation were analyzed by means of high-speed camera system. The experimental results show that the dynamic contact angle at the wall surface and the dynamic contact angle ratio at both sides of the cavity decrease with the increase of the velocity of flow. There is a corresponding relationship between the dynamic contact angle ratio at both sides of the channel and the wettability of the left side of the channel, which can be used to characterize the wettability of the micro-channel wall. A hydrophobic / superhydrophobic surface with adjustable wettability was designed and fabricated by using the method of thin film assembly and self-assembled molecular film deposition. By means of contact angle measuring instrument, the static contact angle of the surface with different height of rib plate is measured. The measurement results show that the reversible regulation of surface wettability between weak hydrophobic and strong hydrophobic or even superhydrophobic can be realized quickly by accurately controlling the height of the surface micro-rib, and the control effect is continuous. The designed wettability adjustable surface was improved and integrated into the micro-channel as one side of the channel. The effects of flow velocity and wall hydrophobicity on the dynamic contact angle of the cavitation were studied. It is found that the contact state of gas-liquid-solid three-phase can be changed by controlling the structure of micro-ribbed plate, so that the reversible regulation of the actual wettability of the wall between strong hydrophobic and hydrophilic can be realized. In addition, the governing effect of wall wettability and the dynamic contact angle of vacuoles on the wall surface are affected by the thickness and velocity of the film.
【學(xué)位授予單位】：大連海事大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：O359.1;O352

【引證文獻】

相關(guān)碩士學(xué)位論文 前1條

1 石棟棟;Y型微通道中空泡動力學(xué)特性研究[D];大連海事大學(xué);2017年

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本文編號：2447074