本文選題：熱氨融霜　切入點：液擊　出處：《南昌大學》2017年碩士論文　論文類型：學位論文

【摘要】：本文針對預(yù)防熱氨制冷系統(tǒng)氨融霜過程液擊誘發(fā)的系統(tǒng)爆炸事故頻發(fā)的安全隱患所遇到的關(guān)鍵科學與技術(shù)瓶頸問題,研究構(gòu)建了多相相變分層流動液擊形成理論模型和相應(yīng)的模擬方法,并通過數(shù)值模擬和實驗研究揭示了熱氨融霜過程中多相相變液擊形成機理,明晰了影響液擊的關(guān)鍵調(diào)控參數(shù),提出了抑制液擊沖擊形成的關(guān)鍵技術(shù)和方法�；诨貧饪偣芤簱魶_擊的安全評估,闡述了熱氨制冷系統(tǒng)氨融霜過程液擊誘發(fā)的系統(tǒng)爆炸事故頻發(fā)的力學機理,研究結(jié)果為建立我國預(yù)防融霜過程中液擊沖擊失效的氨制冷裝置的設(shè)計準則奠定了科學的理論基礎(chǔ)和技術(shù)支撐。首次研究建立了綜合考慮熱氨融霜急劇相變影響的汽液二相分層流動液擊形成機理理論模型,并依此研究建立了熱氨融霜液擊形成過程的虛擬仿真平臺。研究發(fā)現(xiàn)了熱氨融霜過程中回氣總管液擊形成的二個直接驅(qū)動力為:1)熱氨總閥突然開啟形成的熱氨蒸汽進口流速的突變;2)高溫熱氨蒸汽與深冷液氨瞬間接觸誘發(fā)的劇烈相變。研究建立了熱氨融霜液擊壓力與急劇相變、熱氨蒸汽進口流速突變、深冷液氨殘余體積分數(shù)、熱氨蒸汽氣泡瞬態(tài)破裂、段塞流關(guān)聯(lián)關(guān)系,明晰了熱氨融霜液擊壓力的關(guān)鍵調(diào)控參數(shù),揭示了具有相變的多相分層流動液擊形成的機理,并提出了抑制液擊沖擊形成的關(guān)鍵技術(shù)和方法。構(gòu)建了回氣總管熱氨沖霜液擊形成機理的實驗研究平臺,研究提出了高溫熱氨蒸汽進口流速、突增加速度、液擊壓力和液位檢測、顯示和控制系統(tǒng)以及檢測數(shù)據(jù)同步采集顯示系統(tǒng),回氣總管熱氨沖霜液擊實驗研究表明高溫熱氨蒸汽進口流速突變會導(dǎo)致回氣總管在熱氨沖霜過程中形成明顯的液擊現(xiàn)象,高溫熱氨蒸汽進口流速自動控制系統(tǒng)的過調(diào)糾偏導(dǎo)致的電動流量控制閥開啟趨勢的突變也會導(dǎo)致明顯的液擊,通過高溫熱氨蒸汽進口流速自動控制難以消除回氣總管的液擊現(xiàn)象,且實驗檢測的液擊壓強與本文理論模型按實驗工況模擬預(yù)測的液擊壓強吻合。深冷液氨與高溫熱氨蒸汽的多相流動所形成的段塞流是由分層界面不穩(wěn)定波動所誘發(fā),而分層界面不穩(wěn)定直接驅(qū)動力是二相流速速度差和分層界面的急劇相變。有相變與無相變多相流動液擊模擬對比分析研究表明:在其他條件一定時,考慮高溫熱氨蒸汽與深冷液氨劇烈相變的回氣總管管內(nèi)第一峰值最大液擊平均壓強是不考慮相變情況下的管內(nèi)第一峰值最大液擊平均壓強的四至五倍,是回氣總管正常工作操作壓力的65倍左右,因而熱氨融霜過程誘發(fā)的液擊易導(dǎo)致爆管與封頭脫落的脆性斷裂爆炸事故頻發(fā),準確預(yù)測熱氨融霜液擊沖擊壓強的理論前提是要建立綜合考慮高溫熱氨蒸汽和深冷液氨劇烈相變的多相流動液擊形成機理理論模型。
[Abstract]:This paper aims at the key scientific and technical bottleneck problems of preventing the safety hidden danger of frequent explosion accidents caused by liquid strike in ammonia melting frost process of hot ammonia refrigeration system. The theoretical model and corresponding simulation method of liquid shock formation in multiphase phase change stratified flow were established. The mechanism of liquid shock formation in the process of hot ammonia melting was revealed by numerical simulation and experimental study. The key control parameters affecting liquid impact are clarified, and the key technologies and methods to restrain the formation of liquid impact are put forward. Based on the safety evaluation of hydraulic impact of return gas manifold, The mechanical mechanism of frequent explosion accidents induced by liquid shock during ammonia defrosting in hot ammonia refrigeration system is described. The results laid a scientific theoretical foundation and technical support for the establishment of the design criteria for ammonia refrigeration units for preventing the failure of liquid impact impact in the process of defrosting. For the first time, a comprehensive consideration of the effect of rapid phase transition of hot ammonia thawing frost was established. A theoretical model for the formation mechanism of liquid shock in vapor-liquid two-phase stratified flow, The virtual simulation platform of hot ammonia thawing frost forming process was established. It was found that the two direct driving forces of hot ammonia thawing process were: 1) the hot ammonia total valve suddenly opened and formed hot ammonia steam. The abrupt change of inlet velocity of steam (2) the abrupt phase transition induced by the instantaneous contact of hot ammonia steam with cryogenic liquid ammonia. The pressure and sharp phase transition of hot ammonia melting frost-liquid were studied. The sudden change of inlet flow rate of hot ammonia steam, the residual volume fraction of cryogenic liquid ammonia, the transient rupture of hot ammonia steam bubble and the correlating relationship of slug flow reveal the key control parameters of the impact pressure of hot ammonia thawing frost. The mechanism of liquid hammer formation in multiphase stratified flow with phase transition is revealed, and the key technologies and methods to restrain liquid impact formation are proposed. An experimental research platform for the mechanism of liquid shock formation of hot ammonia scouring frost in return gas manifold is constructed. In this paper, the inlet velocity of hot ammonia steam at high temperature, sudden acceleration, liquid hammer pressure and liquid level detection, display and control system, and synchronous data acquisition and display system are proposed. The experimental study of hot ammonia scouring frost in gas return manifold shows that the sudden change of inlet velocity of hot ammonia steam at high temperature will lead to the obvious liquid hammer phenomenon in the hot ammonia scouring process of the gas return manifold. The sudden change in the opening trend of the electric flow control valve caused by the overadjustment and correction of the inlet flow rate of high temperature ammonia steam will also lead to obvious liquid hammer. Through the automatic control of inlet velocity of ammonia steam at high temperature, it is difficult to eliminate the phenomenon of liquid shock in the return gas manifold. The measured pressure coincides with that predicted by the theoretical model in this paper. The slug flow caused by the multiphase flow of cryogenic liquid ammonia and high temperature hot ammonia steam is induced by the instability of stratified interface. The direct driving force of the instability of stratified interface is the velocity difference of two phases and the sharp phase transition of the stratified interface. The comparative analysis of liquid shock simulation of multiphase flow with and without phase transition shows that: when other conditions are fixed, The average pressure of the first peak value in the return gas manifold considering the intense phase transition between the hot ammonia steam and the cryogenic liquid ammonia is four to five times that of the first maximum maximum liquid hammer average pressure in the tube without taking into account the phase change. It is about 65 times as high as the normal operating pressure of the return gas manifold. Therefore, the liquid shock induced by the hot ammonia defrosting process is liable to lead to brittle fracture and explosion accidents of the tube and the head falling off. The theoretical premise of accurately predicting the impact pressure of hot ammonia melting frost is to establish a theoretical model for the formation mechanism of liquid shock in multiphase flow considering the severe phase transition of high temperature hot ammonia steam and cryogenic liquid ammonia.
【學位授予單位】：南昌大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB657

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本文編號：1575863