基于PLIF的水平三向撞击流径向流型的研究

Study on Radial Stream Patterns in Three-Jet Impinging Stream Mixers Using Planar Laser Induced Fluorescence

利用平面激光诱导荧光技术(PLIF)测量了水平三向撞击流反应器内液体混合时变化的二维浓度场,发现了其内部存在两种不同的径向流型:漏斗径向射流和自由径向射流。借助径向射流偏转角β对两种流型的变化规律进行了探索,实验结果表明等效喷嘴间距L*=1D时,偏转角变化范围Δβ很小;L*增大到2D时,Δβ急剧增大,出现峰值。当L*继续增大到3D、4D和5D时,Δβ略微下降,最终趋于稳定。流速u的变化对Δβ的影响较小。小喷嘴直径D工况下,最佳喷嘴间距为L*=2D或L*=3D;中等喷嘴直径D工况下,最佳喷嘴间距为L*=2D。通过计算离析度IOS得到完全混合所需时间t,发现Δβ越大,混合所需时间t越短,混合效果越好。

The flow field distribution in a three-jet impinging stream mixer was studied by applying planar Laser Induced Fluorescence（PLIF）. The two-dimension concentration change of liquid-liquid mixing was directly observed, and two radial stream patterns（funnel radial stream and free radial stream） were discovered with profiles studied by radial stream deflection angle β. When the equivalent jet separation distance L^＊= 1D, Δβ hardly changes, and when L^＊ increases to 2D, Δβ increases rapidly and reaches maximum. When L^＊continues to increase to 3D, 4D and 5D, Δβ decreases slightly and stabilizes. The best L^＊ values are L^＊ = 2D or L^＊ = 3D when the D value is relatively low, but when the D value is in the middle range, the best L^＊ value is L^＊ = 2D. The intensity of segregation（IOS） was calculated to obtain total mixing time t and the results show that the increase of Δβ can reduce mixing time which gives better mixing effects.