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
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.
