摘要
目前主流CFD计算软件中基于拉格朗日框架的碰撞模型不够准确,难以对液液栓式喷雾的宏观特性进行仿真.故本文基于开源软件OpenFOAM植入了复合碰撞模型,考虑了卫星液滴和四种不同的碰撞模式:聚合(Ⅰ,Ⅲ)、反弹(Ⅱ)、自反分离(Ⅳ)和拉伸分离(Ⅴ),修正了反弹模式中液滴的速度方向;通过纯轨迹法(改进的Nordin模型)检测液滴碰撞.该碰撞模型在不同模式的液滴碰撞和栓式喷雾上都与实验吻合较好,如液滴的运动过程、喷雾分布和喷雾锥角等.不同工况下对比表明,复合碰撞模型能合理地将液滴碰撞动力学应用于栓式喷雾,预示结果明显优于CFD软件中的O'Rourke碰撞模型,准确预示出喷雾锥角随有效动量比的变化趋势以及径向液柱、轴向液膜的混合分布.
Abstract
The collision model based on the Lagrangian framework in the current mainstream CFD software is not accurate enough to simulate the macroscopic characteristics of liquid-liquid pintle spray.Therefore,based on the open-source software OpenFOAM,this paper implants a composite collision model,which considers the formation of satellite droplets and four different collision regimes:coalescence(Ⅰ,Ⅲ),bouncing(Ⅱ),reflexive separation(Ⅳ)and stretching separation(Ⅴ).Moreover,this paper corrects the velocity direction of droplets in the bouncing regime and detects collision pairs by an absolutely deterministic trajectory method(improved Nordin model).Furthermore,experimental verifications of the composite collision model are carried out for binary droplet collisions and pintle sprays,such as collision processes of droplets in all regimes,spray distribution,spray angle,etc.The composite collision model can effectively apply the droplet collision dynamics to pintle sprays under different conditions.Compared with the O'Rourke model,the composite collision model is more outstanding,and can accurately predict the trends of spray angle with effective momentum ratio as well as the mixed distribution of radial liquid column and axial liquid sheet.
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