| More than 75% of people killed in mine fires and explosions die due to CO poisoning or asphyxiation.The emergency refuge system is a vital part of the mine life support system.A safe breathing environment is a prerequisite for the safety and security of the refuge,but with CO concentrations in the tunnel reaching up to 1% or more after a mine fire or explosion,CO gas will enter the refuge with the personnel,putting the breathing environment at risk.As the main emergency refuge,a mine refuge provides a supply of oxygen and other supplies for at least 96 hours of life safety.When people enter the refuge from a high concentration of toxic and hazardous gases,these gases can follow them into the refuge and contaminate the air inside.The air curtain creates an air barrier to prevent the flow of toxic and hazardous gases.Despite the fact that most mine refuge chambers are fitted with air curtains,the use of air curtains is not always random and there is a lack of standardization,resulting in a high level of barrier performance.Currently,there are a number of factors that affect the performance of air curtains,including jet velocity,jet angle and installation location,but these are not systematically studied.In this paper,we use CFD software to study the effects of changes in jet velocity,installation position,structural parameters and jet angle on the performance of the air curtain system after a gas explosion in a 50-person refuge in China.The effect of temperature and CO concentration changes on the performance of the air curtain was also investigated.The main findings of this paper are as follows:(1)Introduce the air infiltration theory and air curtain system barrier theory driven by thermal pressure,and propose indicators for evaluating the barrier performance of air curtain;establish physical and numerical models including external environment,transition chamber and air curtain,and compare the numerical simulation results with the results of previous experimental studies on the barrier performance of air curtain system to verify the accuracy of the simulation results;(2)Increasing the jet velocity of the air curtain will not increase the efficiency of the air curtain;increasing the jet angle of the air curtain will increase the efficiency of the air curtain and then decrease it.A high concentration of CO gas from the external environment enters the transition chamber from the upper side of the refuge door frame under thermal pressure,and an air curtain installed on the upper side with a jet velocity of 22m/s and a jet angle of 10° has the best barrier efficiency of 69.9%;(3)Increasing the hole diameter of the air curtain will increase the barrier efficiency of the air curtain;increasing the hole spacing of the air curtain will decrease the barrier efficiency of the air curtain.The mathematical relationship between the hole diameter,hole spacing and the barrier efficiency of the air curtain is fitted,which provides reference suggestions for the subsequent structural design of the air curtain;(4)Keeping the concentration of the transition chamber and the external environment constant,the barrier efficiency of the air curtain decreases with the increase in the temperature of the external environment.Based on the data of the external ambient temperature and the barrier efficiency,an equation was fitted to predict the relationship between the change in external ambient temperature and the barrier efficiency;keeping the temperature of the transition chamber and the external ambient constant,the change in the external ambient concentration had no effect on the barrier efficiency of the air curtain. |
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