Research On The Shape And Stability Of Jet Flame Under The Effect Of Water Mist

The jet flame caused by gas leakage can generate violent heat radiation which could threaten the safety of people and buildings being around.If it was exterminated rashly,the worse consequences may occur due to the explosion caused by the encounter between naked light or spark and the combination of leaked gas and air.Tring to control is a mainstream method to deal with the jet flame caused by gas leakage,and water mist is one of the ideal ways to control it.Therefore,it will have great academic value and practical significance to study the stability of jet flame under the effect of water mist.In this paper,the experimental bench of using water mist to control jet flame has been designed and established.By using experimental measurement means of heat flow meters,thermocouples,etc.and adjusting the gas flow and the water mist pressure to study the shape,temperature,heat radiation and the duration of jet flame come out from three different kinds of nozzle structures shaped in circle,rectangular and triangle under the effects of top spray and lateral spray water mist.Under the influence of top spray water mist,the average height of the jet flame is decreasing along with the increasing of the pressure from water mist.However,relative to jet flow,when the momentum of water mist is seriously deficient the periodic expansion of the flame will occur which can lead to the height increase of flame while raising the pressure of water mist.For lateral spray,the inclination angle will continually increase with the increasing of the pressure from water mist.And the increasing rate will be lower while the pressure from water mist is higher.Water mist can effectively reduce the radiation intensity of jet flame.Take a certain condition of propane jet fire for instance,when the pressure from the water mist has reached 5MPa,all the heat flux densities shown on No.1,No.2 and No.3 heat flow meters have indicated obvious attenuations,which reduced 76.96%,82.17%and 83.70%respectively.This shows that water mist will be a very effective method to control jet flame and reduce the damages from the heat radiation of jet flame for the protected area.Under the effect of top spray water mist,the jet flame from the asymmetric triangle nozzle structure is steadier than others from the circle and rectangular ones.The reason is the asymmetric structure can augment the curl absorb effect for air.For lateral spray,the jet flame from the asymmetric triangle nozzle structure have a worst stability which is because the water mist effect toward the root of the flame from side,massive droplet has been absorbed simultaneous when the flame absorbs air within itself.Furthermore,the numerical simulation model of using water mist to control jet flame has been established.It mainly includes the eddy dissipation combustion model,the discrete phase model and the k-? model.The comparison shows the results achieved from simulations and experiments are consistent.A reliable numerical calculation model can be provided to the forecast and prevention of jet flame.