CeO_(2)纳米燃油单液滴蒸发数值模拟研究

Study on Numerical Simulation of Single Droplet Evaporation of CeO_(2) Nano-fuel

基于单液滴蒸发可视化试验,应用ANSYS FLUENT计算流体力学模拟软件,建立纳米燃油单液滴蒸发模型,探究纳米粒子质量浓度和粒径对燃油液滴蒸发过程中温度和燃油蒸气质量浓度的影响.结果表明,纳米燃油液滴中的纳米粒子质量浓度越高、粒径越小,燃油液滴的蒸发平衡温度越高,相同时间内的燃油蒸气气相体积分数越高.在环境温度573 K下,纳米燃油液滴从外界环境吸收热量使自身温度不断升高,在计算域内沿液滴表面向外延伸形成质量浓度边界层和温度边界层,促进液相向气相的转化.在蒸发初始阶段,蒸发速率较低,燃油蒸气气相体积分数较小;随着蒸发过程持续进行,由于纳米粒子增强传热传质的作用,液相组分蒸发汽化加快,液滴蒸发速率加快.

A model of the single droplet evaporation of nano-fuel was conducted based on ANSYS FLUENT soft⁃ware with reference to the visualized evaporation experiments.The effects of nanoparticle mass concentration and size on the temperature distribution and fuel-vapor mass concentration during droplet evaporation were discussed.It was revealed by the simulation results that the evaporation equilibrium temperature of droplets tended to rise up with the increasing nanoparticle mass concentration or the size of the diminishing nanoparticle,and the vapor volume frac⁃tion was higher during the same evaporation period.At the ambient temperature of 573 K,the temperature inside the nano-fuel droplet was raised by absorbing heat from the external environment.And within the computational domain,the temperature boundary layer and mass concentration boundary layer were formed along the outward droplet surface,which promoted the conversion of liquid to gas.At the initial evaporation of nano-fuel droplet,the vapor volume frac⁃tion,as well as the evaporation rate was relatively low,while during the proceeding of evaporation,with the assistance of nanoparticles in enhancing heat and mass transfer,the liquids were evaporated to vapors with increasing rate.