發(fā)布時間：2018-03-08 20:53

  本文選題：流動模擬　切入點：低溫等離子體　出處：《北京理工大學》2015年碩士論文　論文類型：學位論文

【摘要】：膜分離作為一種新型的分離技術(shù),具有能耗低、分離效率高等優(yōu)點。不同膜材料的親疏水性能不同,為了減輕使用過程中的膜污染和應(yīng)對不同分離體系所需膜的親疏水性能要求,提高分離效率,故需對膜進行一定的修飾改性。其中,等離子體改性技術(shù)應(yīng)用甚為廣泛。本文主要針對低溫等離子體親水改性中空纖維膜內(nèi)表面的問題,使用FLUENT軟件對細管內(nèi)空氣的流動狀態(tài)進行模擬,在此基礎(chǔ)上,利用遠程動態(tài)低溫等離子體對細管管道內(nèi)表面進行活化改性實驗研究。首先,利用FLUENT流體流動模擬軟件對空氣介質(zhì)(密度取理想密度)在不同管徑內(nèi)的流動進行模擬,分別對流動的壓力場、密度場和速度場進行了研究;同時,將計算機模擬輸出的出口質(zhì)量流量與泊肅葉公式計算得到的質(zhì)量流量進行了對比。驗證了低壓下空氣流動基本符合連續(xù)流體流動規(guī)律,并對比模擬與計算結(jié)果得到在一定的低壓下,長度為500 mm內(nèi)徑大于10 mm時使用FLUENT模擬是可行的。當內(nèi)徑為5-8 mm時,模擬誤差約為10%,但結(jié)果仍然可以為細徑管內(nèi)低溫等離子體的輸運規(guī)律提供一定的指導(dǎo)作用。然后,采用本研究組的遠程動態(tài)低溫等離子體發(fā)生裝置,對不同內(nèi)徑的替代膜—硅橡膠管內(nèi)表面進行活化,在空氣中暴露后進行體現(xiàn)親水性變化的水接觸角測試,并對改性前后的膜管內(nèi)表面進行了傅里葉紅外光譜(FTIR)、X-射線光電子能譜(XPS)、掃描電鏡(SEM)等性能的表征。此外,分別研究了等離子體操作條件和組件結(jié)構(gòu)對活化改性效果的影響,并對改性后管壁面親水穩(wěn)定性進行了考察。結(jié)果表明,有效改性距離與功率呈正相關(guān),但功率越大表面刻蝕越嚴重;在壓力20±5 pa下,流量控制在1 sccm的有效改性距離達到最長;在一定的操作條件下,管內(nèi)徑越大其有效改性距離越長,當內(nèi)徑大于等于5 mm時有效距離達到10 cm以上,硅橡膠管只經(jīng)活化處理而不進行后續(xù)接枝,其疏水性恢復(fù)時間接近20天;在所研究的范圍內(nèi),有效改性距離比輝光距離長7 cm至10.5 cm。綜上所述,如果對膜管組件采取兩端處理,組件的有效改性距離可達到20cm-30 cm,有望滿足實際應(yīng)用組件改性的要求。本文的研究結(jié)果對實際中空纖維膜內(nèi)表面改性研究有一定的指導(dǎo)意義。
[Abstract]:As a new separation technology, membrane separation has the advantages of low energy consumption and high separation efficiency. In order to reduce the membrane fouling during use, to meet the hydrophobic performance requirements of different separation systems and to improve the separation efficiency, it is necessary to modify the membrane to a certain extent. Plasma modification technology is widely used. In this paper, the flow state of air in a thin tube is simulated by FLUENT software, aiming at the problem of low temperature plasma hydrophilic modification of the inner surface of hollow fiber membrane. An experimental study on the activation modification of the inner surface of a tube by remote dynamic low-temperature plasma was carried out. Firstly, the flow of air medium (density with ideal density) in different pipe diameters was simulated by FLUENT fluid flow simulation software. The pressure field, density field and velocity field of the flow are studied respectively. The mass flow at the outlet of the simulated output is compared with the mass flow calculated by the Poisson's formula. It is verified that the air flow under low pressure basically accords with the law of continuous fluid flow. The results of simulation and calculation show that it is feasible to use FLUENT simulation when the length is 500mm or more than 10mm at a certain low pressure, when the inner diameter is 5-8 mm. The simulation error is about 10, but the results can still provide some guidance for the transport law of low temperature plasma in fine diameter tube. Then, the remote dynamic low temperature plasma generator of this research group is used. The inner surface of silicone rubber tube with different internal diameters was activated, and the hydrophilic contact angle was measured after exposure to air. The properties of the inner surface of the membrane tube before and after modification were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), etc. In addition, the effects of plasma operating conditions and component structure on the activation modification effect were studied, respectively. The hydrophilic stability of the modified tube wall was investigated. The results showed that the effective modification distance was positively correlated with the power, but the more power the surface etching was, the more serious the surface etching was, the longest effective modification distance was obtained when the flow rate was controlled at 1 sccm under the pressure of 20 鹵5pa. Under certain operating conditions, the larger the inner diameter of the tube is, the longer the effective modification distance is. When the inner diameter is greater than or equal to 5 mm, the effective distance is more than 10 cm, and the silicone rubber pipe is only activated without subsequent grafting. The hydrophobicity recovery time is close to 20 days; in the range studied, the effective modification distance is 7 cm to 10.5 cm longer than the glow distance. The effective modification distance of the module can reach 20cm-30 cm, which is expected to meet the requirements of practical application. The results of this paper have a certain guiding significance for the study of internal surface modification of hollow fiber membrane.
【學位授予單位】：北京理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ028.8

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本文編號：1585502