Study On Disturbance Characteristics Of Cross Flow To Diffusion Flame

Because of the influence of transverse wind the behavior of the flame becomes more complex.Compared with the stationary flame,the flame affected by transverse wind swept is more popular in life,its characteristics study has a more practical meaningful.In this paper,the disturbance characteristics of transverse wind to diffuse flame are studied by the combination of experimental and numerical simulation,including the influence of transverse wind on the fractal dimension of the diffusion flame projection gray-scale,the characteristics of the flame image(flame shape,flame height,flame area,flame lateral offset length)and ceiling airflow vortex characteristics of the diffuse flame.The results will provide the theoretical basis for the development of fire science.The influence of transverse wind on the fractal dimension of the diffusion flame projection gray-scale is studied by using a linear motion diffusion flame device.The results show that the tangential force produced by transverse sweeping winds and the buoyancy produced by combustion cause the flame fractal to change,which is more complex than that of stationary flame.The fractal dimension of the diffusion flame projection gray-scale under the influence of transverse wind can be divided into three stages,that is,the combustion control zone where the fractal dimension increases with the velocity increasing,the transition zone where the fractal dimension decreases with the velocity increasing,and the transverse wind control zone where the fractal dimension tends to be stable with the velocity increasing.The characteristics of the fire diffusion image of oil pool under the influence of transverse wind were analyzed in the wind tunnel experiment system.The results show that the wind speed is equal to 0 m/s,the oil pool flame is in the middle with no offset,and the height of the flame fluctuates periodicity.As the wind speed increases,the flame is shiftes,then the velocity of the airflow around the flame increases and the degree of turbulence increases,and irregular vortices occur at the edge of the flame.The fluctuation range of the flame height and area is the largest with no transverse wind effects,and it decreases with the increase of wind speed.The maximum value of the flame height and area is the largest with the wind speed of 0.5 m/s,and it decreases with the increases of wind speed.When the wind speed increases,the maximum value and fluctuation range of the lateral offset length of the oil pool flame show a trend of first increase and then decrease.The experimental system model of the diffusion flame wind tunnel is established by using the Pyrosim which is a FDS simulation software to study the influence of cross-wind on the vortex characteristics of diffuse flame.The results show that the existence and the size of the transverse wind have a significant effect on the generation and propagation of the ceiling airflow vortex of the diffusion flame.The vortex motion cycle decreases with the wind speed increasing,the position where the vortex appears is closer to the outlet of the wind tunnel as the wind speed increases,and the initial time when the vortex appears increases with the wind speed increasing.Through the above research,a more comprehensive understanding of the characteristics of the diffusion flame under the influence of cross-wind is gotten,which can provide some theoretical basis for fire flame spread and extinguishing.