本文選題：氣體動力學 + 收縮型噴嘴��； 參考：《化工學報》2017年11期

【摘要】：在許多強吸熱化學反應的化工過程中,常常需要對反應流體流出反應器時進行快速急冷來避免副反應或逆反應發(fā)生,以期最終獲得可觀的目標產物。在本實驗室前期開展的熱等離子體裂解二氧化碳實驗研究中,采取在高溫反應器出口加裝收縮噴管將裂解氣高速導入夾套水冷管的方法,實現(xiàn)了對高溫裂解氣的快速急冷,顯著地避免了裂解氣中CO與O的逆反應,獲得了意想不到的CO_2高轉化率。本文利用計算流體力學軟件模擬這一過程,以期揭示這種新的冷卻方法導致極快速冷卻的機制。模擬結果表明,加裝收縮噴嘴確實可以期待對高溫射流產生10~7 K·s~(-1)量級的溫降速率。深入分析表明,僅僅靠氣體動力學效應不能完全解釋如此快速的冷卻速率。從噴管高速噴出的黏性流體在夾套水冷管內形成高速渦流,這種渦流一方面增強了主流體對周圍氣體的卷吸,另一方面加強了被卷吸流體在被卷入之前與夾套水冷管壁面的強制換熱過程,是導致快速急冷的主要機制。
[Abstract]:In the chemical process of many strong endothermic chemical reactions, it is often necessary to rapidly cool the reaction fluid out of the reactor in order to avoid the side reaction or reverse reaction, in order to obtain a considerable target product. In the experimental study of thermal plasma pyrolysis of carbon dioxide in our laboratory, the rapid cooling of high temperature cracking gas was realized by adding shrinkage nozzle to the outlet of the high temperature reactor and introducing the cracking gas into the jacket water cooled pipe at high speed. The inverse reaction of CO and O in cracking gas was avoided significantly, and the unexpected high conversion rate of COS _ 2 was obtained. In this paper, the computational fluid dynamics software is used to simulate this process in order to reveal the mechanism of this new cooling method leading to extremely fast cooling. The simulation results show that the temperature drop rate of 107Ks ~ (-1) for high temperature jet can be expected by adding shrinkage nozzle. Further analysis shows that such a rapid cooling rate cannot be fully explained by gas dynamics alone. The viscous fluid ejected from the nozzle at high speed forms a high speed eddy current in the clamped water cooled pipe, which on the one hand enhances the entrainment of the surrounding gas by the mainstream. On the other hand, the forced heat transfer process between the entrained-fluid and the jacketed water-cooled pipe wall before being involved is strengthened, which is the main mechanism leading to rapid cooling.
【作者單位】： 四川大學化學工程學院等離子體技術中心;
【基金】：國家自然科學基金項目(11375123)~~
【分類號】：TQ025

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