Chemical processing and micromixing in confined impinging jets
Chemical processing and micromixing in confined impinging jets
复制标题
DOI：
10.1002/aic.690490905
复制
发表时间：
2003-09-01
期刊：
影响因子：
3.7
通讯作者：
Prud'homme, RK
中科院分区：
文献类型：
--
作者：
Johnson, BK;Prud'homme, RK
快速过程（例如某些有机反应或高过饱和度下的沉淀）需要喷射混合器提供快速混合。使用 Damkohler 数来关联加工，对受限冲击射流 (CH) 混合器中的微混合进行了表征。特征微混合时间的比例理论与从 Kolmogorov 微尺度开始的动量扩散成正比，足以表达 CH 混合器的微混合性能。最近表征的二阶竞争反应装置被用作“化学标尺”，为 CH 混合器中的混合时间分配绝对值。使用盐酸竞争氢氧化钠中和或 2,2-二甲氧基丙酸催化水解来评估宽范围的特征时间（320 至 5 ms）。该反应组足够灵敏，可以在 Re 为 90 时检测类湍流的开始，并且能够证明不需要的产物减少，直至测试的最高 Re 3,800 或喷射速度 19 m/s。它代表了对先前混合研究所使用的反应装置和技术的重大进步，对此进行了审查。实验验证了 CH 混合器中的特征混合时间与喷射速度的三倍幂的倒数成正比，并且“介混体积”（消散大部分流动能量的体积）最好近似为与喷嘴间间隔的立方成正比。对于所测试的每种不同的喷射直径、室直径和出口配置，反应的选择性与达姆科勒数成线性比例，如根据已知的反应动力学和计算的柯尔莫哥洛夫扩散时间确定的。提供了冲击射流中微混合的第一个完整表征，可以预测混合性能、反应选择性和放大标准。
Rapid processes such as certain organic reactions or precipitations at high supersaturation require the rapid mixing provided by jet mixers. Micromixing in a confined impinging jets (CH) mixer was characterized employing the Damkohler number to correlate processing. A scaling theory for the characteristic micromixing time, proportional to momentum diffusion starting at the Kolmogorov microscale, is shown as sufficient to express the micromixing performance of the CH mixer. A recently characterized second-order competitive reaction set is used as a "chemical ruler" to assign an absolute value to the mixing time in the CH mixer. A wide range of characteristic time (320 to 5 ms) is evaluated with hydrochloric acid competing for sodium hydroxide neutralization or 2,2-dimethoxypropane acid catalyzed hydrolysis. This reaction set was sensitive enough to detect the onset of a turbulent-like flow at a Re of 90 and was able to demonstrate a decrease in undesired products up to the highest Re tested, 3,800 or a jet velocity of 19 m/s. It represents a significant advancement to the reaction sets and techniques used for previous mixing studies, which are reviewed. Experiments verify the characteristic mixing time in a CH mixer scales as the inverse of the jet velocity to the three halves power, and the "mesomixing volume" (the volume over which the majority of flow energy was dissipated) is best approximated as proportional to the internozzle separation cubed. For each of the different jet diameters, chamber diameters and outlet configurations tested, the selectivity of the reaction scaled linearly with the Damkohler number, as determined from the known reaction kinetics and the calculated Kolmogorov diffusion time. The first full characterization is provided of micromixing in impinging jets that allows the prediction of mixing performance, reaction selectivity, and scale-up criteria.