| As an advanced metal material,aluminum powder is widely used in production,life and cutting-edge industries.However,due to the special properties of aluminum powder relative to non-metallic dust,it is very easy to induce dust explosion accidents during production and use.Explosion pressure venting technology not only improves the safety of equipment,but also poses potential threats to the surrounding environment and personnel.Factors such as the characteristic parameters of the explosion venting surface,the location of the ignition source,the dust mass concentration,and the initial turbulence intensity(which can be described by the dust dispersion time)are very important.The pressure venting process of aluminum powder explosion and its induced external disaster effects have important influences.In addition,the outdoor safety distance design and evaluation of various industrial buildings in China do not consider the outdoor disaster effect and its influence range caused by explosions,resulting in a lack of scientific and quantitative reference for the safety distance design of industrial buildings involving aluminum powder.Therefore,this paper conducts research based on the computational fluid dynamics software FLUENT 19.0,and on the basis of verifying the accuracy of the numerical method,summarizes the external disaster effects induced by the explosion of aluminum powder in large-scale installations under different influencing factors and the distribution law of outdoor safety distances,the specific findings are as follows.(1)The influence of the characteristic parameters of the explosion venting surface on the outdoor disaster effect and safety distance is studied.It was found that the indoor explosion peak overpressure and peak temperature increases with the increase in opening pressure and the decrease in the venting coefficient,while the external explosion peak overpressure increases with the increase in the venting coefficient and opening pressure,respectively.The maximum peak dynamic pressure and wind speed,respectively,decreases with the increase of the venting coefficient,while the opening pressure of the explosion surface has the opposite effect on the law.In addition,the safety distance of outdoor overpressure hazard determined based on the explosion injury criterion increases monotonously with the increase of venting coefficient and opening pressure,and the safety distance of high-speed airflow increases with the decrease of venting coefficient and the increase of opening pressure,while the change rule of safety distance of outdoor thermal radiation hazard is complicated,which decreases first and then increases with the increase of venting coefficient,and the opening pressure of explosion surface has little influence on safety distance of outdoor thermal radiation hazard.Comprehensive comparison shows that the safety distance of high-speed airflow is wider than that of overpressure and high temperature,and the longest distance can reach 38.9 m outdoors,which is 6.48 times of the length of explosion chamber.(2)The influence law of ignition position on the evolution process of explosion hazard effect and the distribution of outdoor safe distance is revealed.When the front end is ignited,the indoor explosion peak overpressure and the dynamic pressure near the outdoor explosion vent both reach the maximum value,followed by the rear end ignition,and the smallest during the center ignition.In addition,the safety distances of outdoor overpressure hazards,thermal radiation hazards,and high-speed airflow hazards are all maximized when the front end is ignited.Therefore,when the aluminum powder process or ignition source is located near the indoor explosion vent,the outdoor safe distance margin should be increased as much as possible,so as to reduce the possibility of injury to personnel and equipment caused by outdoor disaster effect caused by explosion vent.(3)The influence law of aluminum powder concentration on various disaster effects and outdoor safety distance is clarified.As the concentration of aluminum powder increases,outdoor explosion overpressure,thermal radiation,high-speed airflow,dynamic pressure and other disaster effects and their outdoor safety distance all show a changing trend of first increasing and then decreasing.Compared to the overpressure hazard and thermal radiation hazard safety distance,high-speed airflow hazard safety distance range is greater,is 6.82 times the length of the explosion chamber.500 g/m~3 for the best mass concentration of aluminum powder explosion,but also the most dangerous concentration,the actual production process should try to control the concentration of aluminum powder in the 500 g/m~3 below.(4)The influence law of initial turbulence intensity(aluminum powder dispersion time)on various disaster effects and their corresponding outdoor safe distances was explored.120 ms for the most dangerous aluminum powder dispersion time,the moment under the aluminum powder dispersion reached the best state,the disaster effects induced by the release of the explosion and its impact range also reached a critical value.With the increase of aluminum powder dispersion time,each disaster effect and its outdoor safety distance are shown first increased to a critical value and then basically remain stable evolutionary trend.(5)Summarize the influence range of high-speed airflow hazard induced by explosion venting and the influence degree of main factors on the safety distance of high-speed airflow hazard.Among all kinds of disaster effects induced by explosion,the outdoor safety distance range of high-speed airflow is the largest.The degree of influence of various factors on the safety distance of high-speed airflow hazards:aluminum powder mass concentration>aluminum powder dispersion time>opening pressure>ignition location>venting coefficient.Therefore,the explosion protection design of places involving aluminum powder should focus on the explosion of high-speed airflow in the outdoor disaster range and the impact of the mass concentration of aluminum powder on the distribution range of disaster effects. |
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