填充床中气体渗流与化学波耦合问题的研究

研究等温和显著气固反应条件下填充床内反应气体浓度(物质)波推进与混合气体渗流的相互作用,指出化学反应对流动的影响包括两个方面,反应过程中混合气体质量的变化和密度的变化。混合气体流动将反过来影响反应进程。分析表明,按耦合模型和非耦合模型得到的速度场完全不同;按耦合模型,反应气体的浓度(物质)波阵面的推进对混合气体的流场有显著影响,因此按耦合模型计算的混合气体流场强烈地依赖于时间;忽略化学反应引起的混合气体密度变化的耦合模型,将导致一个质量消失的汇(或质量生成的源),因此将引起混合气体渗流速度的明显变化,并可能导致物理上不合理的结果;按耦合模型和非耦合模型计算的浓度场也有很大差别;当反应气体与惰性气体摩尔质量相差较大时,不能忽略反应过程中混合气体密度的变化;研究表明对于显著气固反应不能忽略化学反应与气体渗流的相互作用。

Interaction between Gas Mixture Flows and Concentration Wave in Packed-bed with Gas-Solid Reaction

Under isothermal and rapid gas-solid reaction the interaction between the concentration (substance) wave front advancing and gas mixture flow in a packed bed is investigated,where both the changes of mass and the density of the gas mixture due to chemical reaction influence the flow of gas mixture considerably,and the flow of gas mixture affects the gas-solid reaction in turn. The numerical results show that the velocity profiles of gas mixture obtained with coupled model are quite different from that with uncoupled model,not only in magnitude but also in the velocity variation trend in the packed bed. The advancing of concentration (substance) wave front affects the flow of gas mixture considerably,so,the velocity of gas mixture depends strongly upon time. The ignorance of the density change of gas mixture duo to chemical reaction would lead to an extra sink of gas mass dissipation or a source of gas mass generation to become physically irrational. In case of an obvious difference between the molar masses of gaseous reactant and inert gas,the density change of the gas mixture in reaction process is unnegligible.