This article studies numerically a familiar important phenomenon in spray combustion which is deformation and breakup of liquid drops in gas flow. The SIMPLER method is used to solve the two-dimensional （2D） unstead...This article studies numerically a familiar important phenomenon in spray combustion which is deformation and breakup of liquid drops in gas flow. The SIMPLER method is used to solve the two-dimensional （2D） unsteady axisymmetric Navier-Stokes equations for both the drop and the ambient gas flow. The level set method is applied to capturing the liquid/gas interface. Through calculation are obtained four typical breakup modes--oscillation, bag breakup, sheet stripping breakup and shear breakup governed by four non-dimensional numbers which are gas Weber number （Weg）, liquid Reynolds number （Rel）, gas Reynolds number （Reg） and density ratio （γ）. Their effects upon each mode are analyzed. The results indicate that among the four numbers, Weg is of the highest importance with Rel, Reg and γfollowing up. By widening the range of the density ratio up to 1 000, the breakup mode is discovered to be so complicated that a new one called multimode breakup mode turns up. This mode contains the shearing breakup and piercing breakup, which successively happen. The calculation results agree well with what is observed from the experiments.展开更多
The experimental investigation on a liquid-liquid spray process by dispersing water in corn oil was conducted.The drop formation in the spraying process was observed through analyzing photographs from camera.The obser...The experimental investigation on a liquid-liquid spray process by dispersing water in corn oil was conducted.The drop formation in the spraying process was observed through analyzing photographs from camera.The observation showed that with increase of electrostatic voltage,the drop formation presented a dripping mode as well as cloudy spraying mode in turn and the drops displayed different characteristics in pattern and movement under two kinds of modes.The existing condition and the characteristics of two modes were presented.The quantitative analysis of spraying droplet diameter distributions was performed at different voltages by means of particle image analyzer and the theory of spraying droplet distribution.The result showed that for liquid-liquid electrostatic spray,the droplet size distribution could be mathematically described by Rosin-Rammler distribution.With increase of voltage,the droplet became fine in size and uniform in size distribution.Comparing with water-in-gas spray,the probability density function curve for droplet size distribution was not symmetrical with respect to its peak value,viz,the diameter distribution for the relatively smaller droplets was narrower than that for other larger droplets.With increase of voltage,the distribution for larger droplets became narrow and the curve shape of probability density function became nearly symmetric.展开更多
本文基于VOF(Volume of Fluid)相界面追踪方法,建立了不可压缩W_1/O/W_2双乳液液滴动力学模型并进行了数值求解,模拟了双板平行剪切流条件下液滴在流场中的稳定变形与破碎过程。研究结果表明:液滴的稳定变形程度随着毛细数的增大而加剧...本文基于VOF(Volume of Fluid)相界面追踪方法,建立了不可压缩W_1/O/W_2双乳液液滴动力学模型并进行了数值求解,模拟了双板平行剪切流条件下液滴在流场中的稳定变形与破碎过程。研究结果表明:液滴的稳定变形程度随着毛细数的增大而加剧,且双乳液内液滴的变形程度要明显小于液滴整体变形程度;液滴雷诺数为0.05时,存在一个0 57～0.58之间的临界毛细数,当液滴毛细数小于临界毛细数时,液滴只发生稳定变形,反之则发生破碎。展开更多
文摘This article studies numerically a familiar important phenomenon in spray combustion which is deformation and breakup of liquid drops in gas flow. The SIMPLER method is used to solve the two-dimensional （2D） unsteady axisymmetric Navier-Stokes equations for both the drop and the ambient gas flow. The level set method is applied to capturing the liquid/gas interface. Through calculation are obtained four typical breakup modes--oscillation, bag breakup, sheet stripping breakup and shear breakup governed by four non-dimensional numbers which are gas Weber number （Weg）, liquid Reynolds number （Rel）, gas Reynolds number （Reg） and density ratio （γ）. Their effects upon each mode are analyzed. The results indicate that among the four numbers, Weg is of the highest importance with Rel, Reg and γfollowing up. By widening the range of the density ratio up to 1 000, the breakup mode is discovered to be so complicated that a new one called multimode breakup mode turns up. This mode contains the shearing breakup and piercing breakup, which successively happen. The calculation results agree well with what is observed from the experiments.
文摘The experimental investigation on a liquid-liquid spray process by dispersing water in corn oil was conducted.The drop formation in the spraying process was observed through analyzing photographs from camera.The observation showed that with increase of electrostatic voltage,the drop formation presented a dripping mode as well as cloudy spraying mode in turn and the drops displayed different characteristics in pattern and movement under two kinds of modes.The existing condition and the characteristics of two modes were presented.The quantitative analysis of spraying droplet diameter distributions was performed at different voltages by means of particle image analyzer and the theory of spraying droplet distribution.The result showed that for liquid-liquid electrostatic spray,the droplet size distribution could be mathematically described by Rosin-Rammler distribution.With increase of voltage,the droplet became fine in size and uniform in size distribution.Comparing with water-in-gas spray,the probability density function curve for droplet size distribution was not symmetrical with respect to its peak value,viz,the diameter distribution for the relatively smaller droplets was narrower than that for other larger droplets.With increase of voltage,the distribution for larger droplets became narrow and the curve shape of probability density function became nearly symmetric.
文摘本文基于VOF(Volume of Fluid)相界面追踪方法,建立了不可压缩W_1/O/W_2双乳液液滴动力学模型并进行了数值求解,模拟了双板平行剪切流条件下液滴在流场中的稳定变形与破碎过程。研究结果表明:液滴的稳定变形程度随着毛细数的增大而加剧,且双乳液内液滴的变形程度要明显小于液滴整体变形程度;液滴雷诺数为0.05时,存在一个0 57～0.58之间的临界毛细数,当液滴毛细数小于临界毛细数时,液滴只发生稳定变形,反之则发生破碎。
