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喷射器作为气液混合装置,比传统接触混合器具有更高的混合强度和传质系数。计算流体力学(computational fluid dy- namics,CFD)模拟作为研究气液混合流的方法,有助于理解喷射器的流体力学和混合特征。它能提供详细的信息来量化操作条件对喷射器性能的影响。本文利用CFD模拟了上喷式喷射器内的气液两相流的流体力学特征。结果表明在较高的混合段长径比下,混合段入口处的压力较低。但是存在一个最大的压力降,此时混合段长径比约为4.0。在相同的喷嘴速度下,混合段入口处压力降最低,气体卷吸量最大。模拟中混合管与喷嘴面积比范围为1～16。无论是保持喷嘴直径不变还是混合管直径不变,混合段入口处的压力都随着D_M~2/D_N~2的增加而增加。但是对应的最大气体卷吸率发生在面积比为4.0。当喷射器的结构参数不变,混合段入口处的压力降和气体卷吸率随着喷嘴速度的增加而增大。
The ejector, as a gas-liquid mixing device, has a higher mixing strength and mass transfer coefficient than a conventional contact mixer. Computational fluid dynamics (CFD) simulations as a method of studying the gas-liquid mixing flow help to understand the fluid dynamics and mixing characteristics of the ejector. It provides detailed information to quantify the effect of operating conditions on injector performance. In this paper, CFD is used to simulate the hydrodynamic characteristics of the gas-liquid two-phase flow in an upper jet injector. The results show that at the higher mixing section aspect ratio, the pressure at the inlet of the mixing section is lower. However, there is a maximum pressure drop at which time the aspect ratio of the mixing section is about 4.0. At the same nozzle velocity, the pressure drop at the inlet of the mixing section is the lowest, and the amount of gas entrainment is the largest. The mixing tube and nozzle area ratio ranged from 1 to 16 in the simulation. The pressure at the inlet of the mixing section increases with the increase of D_M ~ 2 / D_N ~ 2, no matter the nozzle diameter is kept or the diameter of the mixing tube is constant. However, the corresponding maximum gas entrainment rate occurs at an area ratio of 4.0. When the structural parameters of the ejector remain the same, the pressure drop at the inlet of the mixing section and the gas entrainment rate increase with the increase of nozzle velocity.