Role Of Acoustic Wave On The Response Of Flames And Extinguishing Flames Coupling With Water Mist

With the continuous development of the economy and society,fire scenes are becoming more and more diversified and complicated.In order to meet the special fire-fighting needs of the scene with the limited water or the sensitivity of water consumption,acoustic wave,as an emerging firefighting technology,is gradually favored.At the same time,water mist fire extinguishing technology as a conventional fire extinguishing technology plays an indispensable role in various vehicle fire scenarios such as parking lots,tunnels,factories,warehousing,and logistics.However,for pure water mist,the fire extinguishing efficiency is limited by factors such as the area of spray,the flow rate and the spray pressure.Therefore,how to improve the fire extinguishing efficiency of water mist has become an important research topic.Because of its potential fire extinguishing function,acoustic wave has been proposed as an important new technology to improve the fire extinguishing efficiency of water mist.However,the disturbance characteristics of acoustic wave on the flame and its influence mechanism on the fire extinguishing efficiency of water mist are still unclear.So,it is necessary to further explore the relationship between acoustic wave,flames and the water mist.In this paper,a visual experimental bench consisting of the flame device,the water mist system,and the acoustic wave generating system is built.On the one hand,the behavior of the flame under the action of acoustic wave generated by different input signals is explored,including the morphological analysis of the flame and the periodic motion distance of the flame.In the experiments,not only the adopted fuel of flame includes hydrogen and ethanol but also the influence of layout about acoustic wave generating system and the flame device was considered.On the other hand,the influence mechanism on the fire extinguishing efficiency of water mist by acoustic wave generated by different input signals is studied,and reasonable explanations are put forward from the aspects of flame behaviors,acoustic characteristics,and water mist characteristics.As a note,the ethanol fueled flame is taken as the research object,and the influence of the layout about the flame device,the water mist system,and the acoustic wave generating system is considered.The study found that the main factor driving the periodic motion of the flame with different fuels is the wind speed induced by acoustic wave according to the behavior of the flame under the action of acoustic wave.Under the same signal peak-peak value,the lower the signal frequency,the stronger the wind speed and the greater the flame movement.In the study of the influence mechanism on the fire extinguishing efficiency of water mist by acoustic wave,when the flames are in the edge of spray area,they cannot be extinguished by water mist alone in 1 minute.And their response is greatly affected by acoustic wave by the water mist in collaboration with the acoustic field,so it needs to explain by the behavior of the flame under the action of acoustic wave.Flame A can be stably extinguished under the combined action of water mist and acoustic wave.The average fire extinguishing time under the external acoustic field with the signal frequency of30 Hz is 14.21 s,and the fire extinguishing success rate is as high as 95%.This is probably due to the fact that the acoustic wave increases the proportion of water mist over the wick,while the periodic motion of the flame makes part of the wick exposed outside the flame area.Therefore,the water mist can more adequately cool the wick,cutting off the continuous fuel supply.The results of research can provide reference for the design of acoustic wave assisted water mist fire extinguishing devices in practical engineering applications.