Coating of finely dispersed particles by two-fluid nozzle

Particle coatings are used extensively to generate dispersed solids with well-defined properties, e.g., to protect active ingredients, with most coating processes using core particles of a diameter larger than 200 μm. This work contributes to the development of a coating process for fine dispersed particles (diameter less than 50 μm) by combining two particle-formulation processes, namely, coating and spray drying. The feasibility of the operation is based on and demonstrated by the innovative application of a two-fluid nozzle. Experiments were conducted by using glass particles as core particles and sodium benzoate as the coating agent. The coating of finely dispersed particles is achieved by the spraying of particles and coating solution as a homogeneous suspension. The aim is to create droplets with only one contained particle at the nozzle outlet. After evaporation of the water in the droplet, a thin solid film is built on the particle surface. The suspension viscosity was measured and compared with empirical equations from the literature. The liquid-film thickness on the particle surface was calculated to predict the building of a uniform coating layer or agglomerates. In this study, the feasibility of pneumatic transport through the nozzle and an investigation of the process were illustrated. The agglomeration fraction and degree of coating of the particle surface were analyzed optically by scanning electron microscopy. In this way, the influence of different processes and suspension parameters on the product quality were determined.     

水下超声速气体射流回击现象的实验研究

对水下超声速气体射流的动力学行为进行了实验研究.通过流动可视化揭示了回击现象的演化过程,利用探针排获得了射流近场区的脉动压力分布,实验结果表明:在超声速喷管出口两倍直径处,射流形貌的变化导致气体中出现了大幅值压力脉冲.通过流场可视化与压力测量的同步校验,证实了喷口端面处回击事件与流场气相区中压力脉动之间相关性.     

基区无吹氦环柱型高超音速低温喷管流场分析

设计了小基区、基区不吹He的环柱型高能化学激光器环形HYLTE喷管 阵列,并使用数值模拟的方法对环形HYLTE喷管阵列流场的气动性能和光学性能进行了分 析. 结果表明,该设计有利于形成ν= 1 →ν = 0之间振转跃迁谱线,不利 于ν = 2→ν =1之间振转跃迁谱线的形成,由于光腔区绝大多数的HF(2)分 子碰撞去激活后成为HF(1)分子,从而使1P谱线的小信号增益倍增,无基 区吹He的设计有利于提高高能化学激光 器的效率. 采用小基区的设计可以增大喷管阵列的功率流密度,无基区吹He的设计不但可 以使复杂的环形高超音速低温喷管叶片的加工与装配得到简化,而且降低了激光器工作 气体的消耗. 因此该设计不但有利于实现高能激光器的紧凑化设计,还有利于节省高能 激光器建造和运行的成本.     

流动注射微分光度法测定钛酸钡烧结物中微量钡

分析速度快、精密度好的流动注射分析技术(FIA),在光度法分析中得到了广泛应用和迅速发展[1-3]。就测试技术而言是在一个非平衡单光束动态检测完成的,而应用双光束检测器建立的分析方法报道很少[4,5]。本文自行研制两组流动比色装置,分别安置在检测器的样品池和参比池,实现了微