液体射流的破碎是一个复杂的非线性动力学问题。为研究破碎过程中气液间的动量交换机制,利用Fluent软件进行数值模拟,得到不同气流冲击液体过程中动量交换量和动量交换效率的变化规律,并进一步通过VOF to DPM模型对规律进行了验证。结...液体射流的破碎是一个复杂的非线性动力学问题。为研究破碎过程中气液间的动量交换机制,利用Fluent软件进行数值模拟,得到不同气流冲击液体过程中动量交换量和动量交换效率的变化规律,并进一步通过VOF to DPM模型对规律进行了验证。结果表明:在气流速度为40~90 m/s,气流密度为1.177~7.356 kg/m^(3)的工况范围内,动量交换效率在62%~83%变化。气液之间的动量交换量随着气流速度的增大而增大,气体密度不变时,随着气流速度的增大,气液间的动量交换效率逐渐降低,最后趋于稳定;气流速度一致时,动量交换效率随气体密度的增大而减小,最后逐渐趋于稳定。在气流物性不变时,增大液体的密度和黏度均会导致气液动量交换效率的增大。将雾滴粒径分布作为液体破碎效果的计算指标,对动量交换机制进行验证,发现在气液动量交换量相等时,液体破碎后的粒径规律基本一致,最大误差为15.3%。展开更多
In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are desi...In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are designed by using the orthogonal design method. The Eulerian-Lagrangian formulation is employed for modeling the droplets-crossflow two-phase flow while the realizable k-ε turbulence model is used to describe the turbulence. A new index, mixedness quality, is proposed to assess the overall mixing of the droplets in the crossflow. The simulation results demonstrate that the counter-rotating vortex pair (CVP) imposes a more significant impact on the spatial distribution than on the size distribution of the droplets. Pairs of CVP with smaller scales are preferable for achieving a better mixing. The influencing factors are listed in the following order in terms of the degree of their impact from the greatest to the least: the Sauter diameter of the initial droplets, the mixing tube diameter, the spray angle, the velocity of the inlet crossflow, and the vertical velocity of the initial droplets. A moderate droplet diameter, a smaller tube diameter, a moderate spray angle, a greater crossflow velocity and a moderate vertical velocity of the droplet are favorable for achieving a higher mixedness quality of the jet spray in a confined crossflow.展开更多
In order to characterize the mechanics of jet breakup, the finite volume formulations were employed to solve the Navier-Stokes equations and continuity equation of jet. The volume of fluid(VOF) method was used to trac...In order to characterize the mechanics of jet breakup, the finite volume formulations were employed to solve the Navier-Stokes equations and continuity equation of jet. The volume of fluid(VOF) method was used to track the free surface of jet. The spray process of the molten Pb63Sn37 alloy was simulated based on the mathematical model by means of FLUENT code. The configuration of jets generated in different disturbance ratios and modulation ratios was obtained. The theoretical results show that the droplets merge together by the number of disturbance ratio N, which agrees with the corresponding picture captured in the experiment. In addition, the droplet streams broken at non-optimal frequency are also uniform according to simulation results, which proves that the A-M disturbance can increase the width of the uniform droplet generating frequency.展开更多
以脱酸塔内旋转雾化器为研究对象,基于VOF(Volume of fluid)和DPM(Discrete particle model)方法,采用Fluent软件模拟了石灰浆液的一次破碎过程和雾化后的粒径分布特征,分析了雾化盘转速、单喷孔、平行双/3喷孔及孔间距对喷孔射流一次...以脱酸塔内旋转雾化器为研究对象,基于VOF(Volume of fluid)和DPM(Discrete particle model)方法,采用Fluent软件模拟了石灰浆液的一次破碎过程和雾化后的粒径分布特征,分析了雾化盘转速、单喷孔、平行双/3喷孔及孔间距对喷孔射流一次破碎效果和粒径分布的影响。结果表明,高速射流条件下的液滴破碎主要由周向表面波和轴向波叠加导致,并呈现出关于主流对称的形态;多喷孔射流的聚合射程与孔间距成正比关系,增加喷孔数将导致射流提前聚合;提高雾化盘转速、喷孔间距和喷孔数目均有利于减小雾化后液滴平均直径;多喷孔结构下的液滴平均直径与孔间距呈简单的线性关系。展开更多
文摘液体射流的破碎是一个复杂的非线性动力学问题。为研究破碎过程中气液间的动量交换机制,利用Fluent软件进行数值模拟,得到不同气流冲击液体过程中动量交换量和动量交换效率的变化规律,并进一步通过VOF to DPM模型对规律进行了验证。结果表明:在气流速度为40~90 m/s,气流密度为1.177~7.356 kg/m^(3)的工况范围内,动量交换效率在62%~83%变化。气液之间的动量交换量随着气流速度的增大而增大,气体密度不变时,随着气流速度的增大,气液间的动量交换效率逐渐降低,最后趋于稳定;气流速度一致时,动量交换效率随气体密度的增大而减小,最后逐渐趋于稳定。在气流物性不变时,增大液体的密度和黏度均会导致气液动量交换效率的增大。将雾滴粒径分布作为液体破碎效果的计算指标,对动量交换机制进行验证,发现在气液动量交换量相等时,液体破碎后的粒径规律基本一致,最大误差为15.3%。
基金Supported by the National Natural Science Foundation of China(50823002)
文摘In order to achieve uniform mixing between spray droplets and crossflow, cold-model experiment of a hollow-cone water spray in an air crossflow is investigated via a numerical simulation. The simulation cases are designed by using the orthogonal design method. The Eulerian-Lagrangian formulation is employed for modeling the droplets-crossflow two-phase flow while the realizable k-ε turbulence model is used to describe the turbulence. A new index, mixedness quality, is proposed to assess the overall mixing of the droplets in the crossflow. The simulation results demonstrate that the counter-rotating vortex pair (CVP) imposes a more significant impact on the spatial distribution than on the size distribution of the droplets. Pairs of CVP with smaller scales are preferable for achieving a better mixing. The influencing factors are listed in the following order in terms of the degree of their impact from the greatest to the least: the Sauter diameter of the initial droplets, the mixing tube diameter, the spray angle, the velocity of the inlet crossflow, and the vertical velocity of the initial droplets. A moderate droplet diameter, a smaller tube diameter, a moderate spray angle, a greater crossflow velocity and a moderate vertical velocity of the droplet are favorable for achieving a higher mixedness quality of the jet spray in a confined crossflow.
基金Project(20070699076) supported by Specialized Research Fund of the Doctoral Program of Higher Education of ChinaProject supported by the Innovation Foundation by Northwestern Polytechnical University, China
文摘In order to characterize the mechanics of jet breakup, the finite volume formulations were employed to solve the Navier-Stokes equations and continuity equation of jet. The volume of fluid(VOF) method was used to track the free surface of jet. The spray process of the molten Pb63Sn37 alloy was simulated based on the mathematical model by means of FLUENT code. The configuration of jets generated in different disturbance ratios and modulation ratios was obtained. The theoretical results show that the droplets merge together by the number of disturbance ratio N, which agrees with the corresponding picture captured in the experiment. In addition, the droplet streams broken at non-optimal frequency are also uniform according to simulation results, which proves that the A-M disturbance can increase the width of the uniform droplet generating frequency.
文摘以脱酸塔内旋转雾化器为研究对象,基于VOF(Volume of fluid)和DPM(Discrete particle model)方法,采用Fluent软件模拟了石灰浆液的一次破碎过程和雾化后的粒径分布特征,分析了雾化盘转速、单喷孔、平行双/3喷孔及孔间距对喷孔射流一次破碎效果和粒径分布的影响。结果表明,高速射流条件下的液滴破碎主要由周向表面波和轴向波叠加导致,并呈现出关于主流对称的形态;多喷孔射流的聚合射程与孔间距成正比关系,增加喷孔数将导致射流提前聚合;提高雾化盘转速、喷孔间距和喷孔数目均有利于减小雾化后液滴平均直径;多喷孔结构下的液滴平均直径与孔间距呈简单的线性关系。
