不同进料方式下气液喷射器内流体流动和混合特征

Hydrodynamic and Mixing Characteristics of Gas-liquid Flow Under Different Feed Types

利用Fluent模拟了喷射器内气液两相在不同进料方式下(气体进口中心线与液体进口中心线偏移量不同)的流体力学和混合特征。其中A方式偏移2.5 mm;B方式偏移0 mm;C方式偏移4.0 mm,此时气体与液体完全相切进料。结果表明:在相同的喷嘴速度时,A方式下喷射器压力降与空气卷吸量最大,C方式下气体和液体的碰撞机会少于其他进料方式,压力和空气卷吸量最小,B方式下喷射器压力降与空气卷吸量居中;而混合效果随着偏移量由大到小(C、B、A)依次增强,但是增强效果不很明显。同时,还以C方式为例讨论了喷射器内喷嘴速度与压力降及空气卷吸量的关系,两者都随着喷嘴速度的增大而增大,且喷射器的压力降与空气卷吸量呈显著的线性相关,相关系数高达0.984。根据模拟结果分析,当3种进料方式压力降相同时,C方式气体卷吸量最大,即相同喷射性能时C方式的能量损失最小。

The hydrodynamics and mixing characteristics of the gas-liquid ejectors at three different feed ways have been simulated by Fluent software： the distance of the gas entrance centerline deviates from the liquid entrance center （deviation distance） is 2.5 mm in the mode A. In the mode B, the deviation distance is 0 mm. Deviation distance is 4.0 mm in the mode C, and in this way the gas was fed in tangentially to the liquid fiow direction. The results show that, at the same nozzle velocity, mode A has the maximum pressure drop and gas entrainment rate. While, Mode C has minimum pres sure drop and entrainment rate because the collision efficiency of gas and liquid under this mode is less than other modes. The mixing effect enhances in the order of mode C, B, A. However the difference is inconspicuous. In the mode C, the effects of the nozzle velocity on the pressure drop and entrainment rate have been discussed. Both of them increase with the increasing nozzle velocity and the correlation between pressure drop and entrainment rate is linear. Based on the simulation analysis, when the three feed methods have the same pressure drop, the gas entrainment rate has maximum value in method C. It is concluded that method C also has the minimum energy consumption under the same jet performance.