| Natural gas pipelines may leak due to various reasons during storage and transportation.If it encounters naked flames,it may cause serious fire accidents such as jetting fire,fireball and explosion,which result in huge economic losses.Among them,jet fires not only occur frequently but also cause great damage.A large number of buildings and mechanical equipment are usually found in the fire burning site.The position of the obstacles will change the geometry of the flame and the combustion characteristics.Therefore,it is very important to study the interaction between the barrier and the flame,which is very important to reduce the consequences of the fire.Based on theoretical research,this paper designed and built a small-scale jet fire experimental platform to create obstacles of different sizes and carried out a series of small-scale model experiments.According to the purpose of the experimental study,the inhibitory effect of the obstacles and flames under different operating conditions is discussed in detail.The results show that during the process of flame and obstacle,different degree of deformation will occur,the combustion area of the flame will be reduced,and the flame propagation in the horizontal direction will be effectively blocked.The higher the obstacle height,the better the effect of controlling the flame propagation.However,with the increase of obstacle height,the decrease of rear temperature and radiation decreases.The smaller the width of the obstacle,the larger the concentration of the vortex in the rear of the combustible gas diffused to the obstacle,it is more likely to intensify the combustion in the rear to raise the temperature,while the temperature behind the obstacle is lower but the temperature is smaller than that without the obstacle.The distance between the obstacle and the leak hole increasesin the axial direction,the temperature increases first and then decreases,and the maximum temperature distribution area is about 40%-50% of the flame length.When the obstacles are staggered,the temperature in front of the obstacle is increased by 40% when compared to the parallel and the temperature behind the obstacle is increased by 53.2%.The staggered obstacles greatly increase the turbulence intensity of the flame and increase the temperature and radiation of the surrounding environment,so in the real environment,the obstacles in the environment should be avoided.Secondly,the numerical simulation method is used to simulate the PDF non-premixed combustion model and κ-ε turbulence model.First of all,the validity of the experimental conditions is verified,and the simulation results are in good agreement with the experimental results.The numerical simulation is used to study the flame propagation characteristics under obstacle conditions.The height,width,and leak hole spacing of the obstacles are studied qualitatively to investigate the influence of flame spacing on the flame propagation and combustion characteristics.The above conclusions lay a theoretical foundation for quantifying the effect of obstacles on jet fire control.In addition,the correction formula of flame length and Froude number without barrier,are obtained,and the radiation calculation model is validated by the formula,and the line source model is in good agreement with the experimental values.Finally,the length of the flame is discussed and the formula of the length of the flame under the barrier condition is obtained. |
PDF Full Text Request