Numerical Study Of The Motion Characteristics Of Water Droplets In Heat Flow Field

In recent years,the fine water mist fire extinguishing system is widely used in all kinds of typical places of prevention work.Its own resource-saving,non-toxic and non-hazardous and efficient advantages,gradually become one of the mainstream alternatives to halon fire extinguishing agent.In the heat flow field,the water mist droplet particle-related parameters of the law of change carried out in-depth research,can be to enhance the system fire efficiency;improve the safety of the system work process;reduce the side effects of the fire fighting process and the cost of consumption has a positive significance.Therefore,for the water mist droplet particles in motion accompanied by changes in the key parameters of targeted research,combined with the corresponding fire extinguishing mechanism to analyze the results for the optimization and enhancement of fine water mist fire extinguishing system performance has important engineering significance.The mainly used method in our study is numerical simulation.Firstly,the heat flux field formed by combustion is simulated to obtain a stable combustion heat flow field.The stable field provides initial conditions for the subsequent movement of fine water mist particles.Then,numerical simulations were conducted on the motion process of single water mist particle in the combustion heat flux field under different conditions.The changes in the parameters of single water mist particle include four types: the height of the droplet entering the heat flow field,the initial velocity of the particle,the particle diameter,and the axial distance of the droplet entering.Conclusions have been obtained in this paper as follows:(1)single particle water mist droplets from the center of the fire source released vertically and lateral release into the combustion heat flow field research shows that: droplets released vertically into the combustion heat flow field,droplet particle Reynolds number with the release height decreases,droplet particle momentum change rate and evaporation rate with the release height decreases and increases;droplets released from the side of the fire source into the combustion heat flow field,droplet particle Reynolds number,droplet particle momentum change rate and evaporation rate with the release height decreases and increases rate and evaporation rate increase with decreasing release height,but the latter two are generally lower in magnitude than those calculated for droplet particles released vertically above.(2)The orthogonal test method was used to analyze the correspondence between the four influencing factors,and the results showed that: the droplet particle momentum change rate was influenced by droplet initial velocity,release height,axial distance and droplet particle size in descending order;the droplet particle evaporation rate was influenced by release height,droplet particle size,initial velocity and axial distance in descending order.(3)The analysis of different release heights of droplets shows that the Reynolds number of droplet particles,the rate of change of droplet particle momentum and the release height are exponential functions;by using dimensionless means,the corresponding functions of Reynolds number and the rate of change of droplet momentum are obtained for four different release heights.(4)The analysis of the initial velocity of droplets shows that the evaporation rate produced by droplet particles with higher initial velocity cannot reach the maximum value at low release heights;however,the evaporation rate produced by droplet particles with lower initial velocity is less affected.In this paper,numerical simulation of the motion of fine water mist droplet particles in the combustion heat flow field under different circumstances,the analysis of the change of droplet parameters,the results of this paper can be improved to improve the effectiveness of fine water mist fire fighting to provide reference advice.