Simulation And Experimental Research On Fine Water Extinguish Effect Of Belt Conveyor Fire

As the belt conveyor application scope has been more and more wide under the coal mine, its fire hazard problems gradually turned to be highlights with its frequent use which caused the wide attention of the researchers. People attaches great importance to the the belt fire mainly includes: the irritated odor gases during the fire period caused serious damage to respiratory system; At the same time, with the development of fire, a lot of smoke sharply reduced visibility along the roadway, which made people escape and fire fighting and rescue more difficult; In addition, the fire may thread the safety of the mine ventilation,if a fire broke out in the mine with a gas and dust explosion risk, it can cause secondary disasters such as gas and coal dust explosion accidents.In order to find the belt fire harm, this article adopts the numerical simulation and experimental research method, to explore the underground belt development rule and water mist, to master the belt fire features, to improve water mist fire extinguishing efficiency. In numerical simulation, FDS and auxiliary software PyroSim were used to build belt roadway physical model, the temperature distribution inside the tunnel fire period was studied, flue gas flow and wind speed, the influence of different spray pressure, droplet size, water flow and the characteristics of water mist location of nozzle.simulation results showed that: in the fire power of 1200 kw, the wind speed 1 m/s, namely the upper hand side, the phenomenon of the reversal smoke came out, Inverse distance back 10 m, when the wind speed increased to 2 m/s in roadway, smoke reversal phenomenon disappeared; Under a certain fire power the temperature and smoke layer is obvious, the greater the wind speed was, the temperature and smoke layer sinked more quickly; When different pressure water mist was used, the fire area and the surrounding temperature can be significantly reduced, and the higher press,the more temperature drop,; Different particle size of water mist had fire suppression effect,the particle size of under 200 microns had almost same extinguishing effect, suppression of 400 microns water mist was poor, flow rate and position of the nozzle layout were also the important factors influencing the water mist fire extinguishing, Increase the flow may improve the efficiency of fire extinguishing, but with the increase of water, it will eventually reach a gradual extinguishing time.In experiments, according to relevant data,we determined the water droplet diameter and spray cone angle,water droplet momentum and mist flux were the characteristic parameters which influenced the effect of water mist fire extinguishing, the results showed that increasing the spray pressure helps to reduce the droplet size and optimize the uniformity of droplet group, when the pressure increased to 6 MPa, if we continue to increase the pressure,the particle size had no obvious change, the nozzle on the center line of the radial distribution of droplet group, the farther distance away from the center line the particle sizes were bigger; Increase the flow, water mist particle size turned bigger and the water group enjoyed better uniformity; Increasing pressure is advantageous to improve the spray cone Angle, but when pressure increased to 6 MPa, The influence of flow for the spray cone Angle became smaller.By using water mist generator for different working conditions of water mist,the fire extinguishing effectiveness was investigated, the results showed that when spray pressure of 4 MPa, 5 MPa, 6 MPa, 7 MPa were used, water mist fire extinguishing time were respectively 10 min, 8 min, 6 min, 5 min, time reduced more than 50% compared with normal water mist, water mist fire extinguishing time increased with higher pressure, But when the presser increased to 6MPa pressure, extinguishing time can not effectively reduce further; Adding the amount of water will help to improve the effect of water mist fire extinguishing, but along with the increasing water mist flow, extinguishing time will eventually reach a gradual value; When burning area is located down the nozzle directly or deviating from the center line of 0.5 m, within the level of the water mist range, the extinguishing time was short: when the deviation of the sample was 2 m in the edge of the water mist level scope, fire extinguishing took a long time; The experimental results showed that water mist under different pressure and flow rate can reduce CO and CO₂ and smoke effectively.