Study Of Numerical Simulation On Cooking Oil Fire By Water Mist Protection And Building Complex Fire Based On FDS

Cooking oil fire is most common in kitchen,and it is very different from ordinary liquid fires.During fire,the flame temperature is higher,it is difficult to quickly extinguish but easy to re-ignite.The current fire extinguishers have no very good effect on it.The building complex are integrated with various functions,so it is also called “city in the city”.The complexity of its functions must be accompanied by the complexity of structure and the increasing fire risk.The open fire in the kitchen is a dangerous source that must be pay attention.After verifying the numerical simulation model,The FDS(Fire Dynamics Simulator)is applied to simulate the interaction between water mist and cooking oil fire.By changing the characteristics of water mist,including discharge pressure,spray angle,the relative distance between nozzle and fire and flow rate,the numerical simulations are conducted to analyze the impact of these important factor on the effectiveness of water mist against cooking oil fires.Then based on the ground floor and underground two-story garage were selected for the fire.The smoke spread,the smoke visibility and the smoke temperature at the height of the personal are monitored and analyzed.The simulation is verified by the former experiment.It is showed that cooking oil fires can be extinguished by water mist,and its temperature can be significantly reduced,so it is difficult to re-ignite.In water mist characteristics,fire extinguishing time is shortened with the increase of discharge pressure and flow rate in general,but,the reduction of fire extinguishing time is not obvious when the discharge pressure increased from 1.5MPA to 2.0MPA,as well as,the flow rate increase from 5m/s to 8m/s.The smaller the spray angle and the distance between nozzle and fire,the shorter the fire extinguishing time.Therefore,water mist characteristics have a great impact on effectiveness of water mist against cooking oil fires.It is better to reduce the fire extinguishing time by increasing the discharge pressure and flow rate within a certain range,but the reduction effect is not clear when they increased to a certain value.Under the premise of covering the fire field with water mist,it is economical and effective to extinguish the cooking oil fire,reducing spray angle and distance between nozzle and fire as far as possible.Water mist is an efficient and environmental friendly fire extinguishing agent for cooking oil fires.The numerical simulation study of fire spreading in building complex shows that smoke visibility reaches the dangerous critical point first and smoke temperature is far from the critical threshold during the numerical simulation time.The verification of the numerical simulation model on extinguishing cooking oil fires with water mist with former experiment,the study of the impact of the changes of water mist characteristics on the effectiveness of water mist against cooking oil fire,and the analysis of fire spreading rules,are all aimed to provide guidance for extinguishing cooking oil fire,so as to find out the most economical and efficient water mist characteristics integrations,and provide theoretical support for the design and development of the cooking oil fire extinguisher equipment on water mist,and further promote the water mist extinguishing agent to apply widely.Taking the fire spreading in building complex as an example,the numerical simulation results of smoke spreading and fire development can be used as a part of quantitative fire safety demonstration to provide guidance for the evacuation of people,so as to better plan comprehensive fire strategies.