Numerical Simulation Of On Descentional Ventilation Fire

Mine fire is one of the main disasters in the process of production of mineral resources,which has many special sharacter such as breaking out suddenly,fire developing quickly,putting out fire and rescuing hard.In the event of mine fire,the additional heating effect resulting from the fire will change the direction and the flow of wind in the mine if the fire can not be control in time,and then the flow disorder will occur in the mine,which even change the whole ventilation system in the mine.In all forms of mine fire, the descensional ventilation fire extremely has the particularity and complexity.Due to the direction of fan pressure and the fire pressure is opposite,the tow inerraction will lead to a variety of results.when the fire is small,the fan pressure is higher than the fire pressure,in this condition,the air flow will be decrease and the smoke rollback will occur in the roadway but will not appear the airflow reversal in the roadway.when the fire get larger,the fire pressure higher than the fan pressure,in the condition,the airflow reversal will occur in the roadway.Under the circumstances, a large high temperature and toxic smoke will flow into the intake airflow roadway,which will lead to enlarging the smoke influence area,and a large of fresh air will flow into the quenched area,which will lead to backflash and explosion.Due to the great fire hazard in the descensional ventilation roadway and it is difficult to control the fire in this situation,therefor,it is necessary to master the distribution law of temperature,smoke concentration and spread,which provide the theoretical guidance for determining the route for avoiding disaster,effectively preventing and controlling the development and progression of fire and fire disaster rescue in mine.Limited by lots of fact,it is difficult to achieve the fire experiment in mine. In recent years, with the development and application of the computing technology, the level of numerical simulation is higher and higher. So it is available of directly simulating the air distribution with the hydrodynamics, CFD(Computational Fluid Dynamics) has grown a new subject following the development of computer.The theses use the FDS software, based on computational fluid mechanics and heat transfer theory,to found the partial three-dimensinal model of descensional ventilation roadway and simulate the turbulent flow of ventilated tunnel based on the theory of computational fluid dynamics.The theses has certain innovation in the process of modeling.Although much study on the mine fire,less special study on the fire in the descensional ventilation roadway due to the limitation of experimental conditions,high cost and the difficulty of modeling. The roadways has been separately modeled in most simulation study on the mine fire,which the mutual influence among lots of tunnels. In the theses,in order to systematically analyse the effect of mine fire,the model include descensional ventilation roadway,working face and ventilation roadway.At the same time,on the basis of previous researches,different control measures will be put forward in this paper and the condition of model will be change based on the control measure.Three different working condition will be set up:the first condition which haven’t any control measure,the second condition in which the fan pressure is higher than the fire pressure and the third condition in which the exhaust branch will be set up in addition to the higher fan pressure. According to the results of the simulation data,the rule of temperature,smoke concentration and the smoke spread in different working condition will be research and the advantage and disadvantage of three control measure will be analysised.The results show that the high temperature and toxic smoke counter flow into the intake air roadways in the first condition;in the second condition the high temperature and toxic smoke dose not counter flow,but the fire will affect the working face which is detrimental to operating personnel in this place;in the third condition the smoke reversely flowing into intake airflow roadway can be effectively controlled and the working face destruction is minimum due to the smoke has been led to the the exhaust branch and then flow into the ventilation roadway, which is useful for evacuation.Finally, this paper also analyzed the effection on the result of simulation if the types of descentional Ventilation roadway are different.This paper discussed what effection on the result of simulation if the descentional Ventilation roadway in the coal mine or the slope,height and cross sectional area of mine are different. It is found that the factors of coal and gas must be considered if the roadway in the coal mine,which can’t simulate directly.Howerve,it is can be simulate indirectly by taking the temperature and pressure.It is also found that the slope,height and cross sectional area has the positive correlation with the critical wind velocity,and the factor of slope has greater influence on it than the other factors.This paper includes five chapters.Chapter1, introduction. This chapter mainly introduces the harmfulness of mine fire, and the particularity and complexity of the fire in the descentional ventilation tunnel, research status of mine fire domestic and international, and the research method, content and resolve the problem, to pave the way for the further study of this thesis.Chapter2, introduces the basic theory of underground mine fires, the particularity of the fire in the descentional ventilation tunnel, the basic form and reason and occurrence of conditions for the disordered airflow. It also presents the critical wind velocity equation to control the backflow of the high temperature smoke, as well as measures to control the fire in the descentional ventilation tunnel.Chapter3, basic introduction of FDS and the setting of the model boundary condition, and according to the related control measures set in three different conditions, and fire dynamics simulation for this three working status respectively.Chapter4, analysis of the temperature distribution, smoke concentration distribution and flow conditions under the three different working conditions after the fire in the descentional ventilation tunnel and the neighbouring tunnel. Summary the change rules of all parameters after the fire in the descentional ventilation tunnel. Meanwhile, compared with the change of all parameters in different conditions, and summarize the advantages and disadvantages of different control measures, and to provide a basis for the taking control measures of descentional ventilation tunnel fire in the different underground mines. Finally, the chapter also analyzed the effection on the result of simulation if the types of descentional Ventilation roadway are different.Chapter5,summary.The main conclusions of the thesis are concluded and the prospect of researching in the future are presented.