一种快速冷却超高温流体方法的数值模拟

发布时间：2018-06-21 22:35

本文选题：气体动力学 + 收缩型喷嘴　；参考：《化工学报》2017年11期

【摘要】：在许多强吸热化学反应的化工过程中,常常需要对反应流体流出反应器时进行快速急冷来避免副反应或逆反应发生,以期最终获得可观的目标产物。在本实验室前期开展的热等离子体裂解二氧化碳实验研究中,采取在高温反应器出口加装收缩喷管将裂解气高速导入夹套水冷管的方法,实现了对高温裂解气的快速急冷,显著地避免了裂解气中CO与O的逆反应,获得了意想不到的CO_2高转化率。本文利用计算流体力学软件模拟这一过程,以期揭示这种新的冷却方法导致极快速冷却的机制。模拟结果表明,加装收缩喷嘴确实可以期待对高温射流产生10~7 K·s~(-1)量级的温降速率。深入分析表明,仅仅靠气体动力学效应不能完全解释如此快速的冷却速率。从喷管高速喷出的黏性流体在夹套水冷管内形成高速涡流,这种涡流一方面增强了主流体对周围气体的卷吸,另一方面加强了被卷吸流体在被卷入之前与夹套水冷管壁面的强制换热过程,是导致快速急冷的主要机制。
[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.
【作者单位】：四川大学化学工程学院等离子体技术中心;
【基金】：国家自然科学基金项目(11375123)~~
【分类号】：TQ025

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