| In recent years,with the quickening pace of people's life,the use of high temperature cooking technology is becoming more and more common,and kitchen fires often occur.Nearly half of the fires caused by the kitchen are caused by high temperature oil,which poses a great threat to people's lives and property.Traditional kitchen extinguishing agents are deficient in rapid cooling,prevention of reignition and environmental friendliness.As the most ideal fire extinguishing agent,water mist has been widely applied in industrial fires,but its application in cooking oil fires is close to blank.Firstly,the atomization process and spray extinguishing mechanism of the premixed nozzle device for compressed air and low pressure water were analyzed.The premixing performance of the three premix was compared by spray experiment.The spray performance of different spray nozzles,different apertures and different water and gas ratio conditions was compared.At the same time,compared with high pressure water spray.The FDS was used to simulate the change of space temperature,smoke movement and gas quality of free combustion,high pressure water spray fire extinguishing and compressed air and low pressure water premixed spray fire extinguishing.The fire extinguishing performance of different spray nozzles,different apertures,different gas water ratios and different coverage conditions was compared by spray extinguishing cooking oil fire experiment.At the same time,the fire extinguishing performance of high pressure water with water flow is compared.The results show that the atomization process includes premixed atomization,conveying section atomization and nozzle atomization.The mechanism of spray extinguishing is cooling surface,cooling flame,dynamic effect and attenuated thermal radiation.The premixing effect of rotating jet premixer in the three premixers is the best.The spray effect of the solid X nozzle with 3mm aperture in the conventional atomizer is the best.The pressure and flow rate of the best matched are pressure 0.45MPa,water pressure 0.6MPa,gas flow 10m~3/h and water flow6L/min.Spray effect is superior to high pressure water spray with water flow.The atomization performance of the fan nozzle is second only to the solid X nozzle,and the optimum matching flow and pressure for an effective spray is present in each aperture,of which the effective spray diffuse height of the 3mm aperture fan nozzle is 2.5m-3.0m.Compared with free combustion,high pressure water spray and compressed air and low pressure water premixed spray can effectively reduce space temperature,suppress smoke layer and effectively control space gas quality.However,the performance of compressed air and low pressure water premix spray is superior to that of high-pressure water spray in these three aspects.The heating and burning of edible oil has six processes:oil temperature rise,oil vapour evaporation,initial combustion,combustion enhancement,combustion peak value and combustion stability.The process of spray fire extinguishing of the device involves five stages:flame deflation,flame expansion,flame tearing,plane flame and flame extinction.solid X nozzles and fan-shaped nozzles with good spray extinguishing performance in solid X nozzle,fan-shaped nozzle,direct nozzle,hollow nozzle and external spiral nozzle,in which 3mm aperture of solid X nozzle has the best fire extinguishing performance,and its corresponding optimum matching parameters are water flow 6L/min,gas flow 10m~3/h,water pressure 0.6MPa and air pressure0.45MPa,and the corresponding effective fire extinguishing radius under this working condition is 96.24cm.The 3mm aperture nozzle has the best fire extinguishing performance in the fan-shaped nozzles with different aperture.The corresponding optimum matching parameters are water pressure 0.6MPa,pressure0.45MPa,water flow 4.0L/min and gas flow 12m~3/h.At the same time,compared with the same volume of high pressure water spray,the fire suppression performance of the compressed air and low pressure water premix spray is superior. |
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