Study On The Effectiveness Of Water Mist Curtain To Control The Fire Development Of High-speed Rail Carriage

The high-speed railway carriage is long and narrow with airtightness,when it runs on the open field or viaduct at high speed,the external environment wind field has a significant impact on the fire of carriage,which aggravates the complexity of the development of high-speed railway carriage fire and the difficulty of fire inhibition and extinguishment.Based on the background of the complex wind in the field,this paper analyzes the influence of the external wind field on the development of carriage fire,and analyzes the efficiency and determinants of water mist curtain in inhibiting carriage fire,so as to provide technical support for the application of fire safety technology of water mist curtain in high-speed railway carriage.Firstly,the FDS numerical simulation model of carriage fire in wind environment was verified by small-scale experiments.The luggage fire scene of second-class highspeed railway was established.The external environment wind with different speeds and directions was applied outside the carriage,and the parameters of the carriage fire heat release rate(HRR),smoke temperature of ceiling,smoke field temperature of eye characteristic height,CO concentration and visibility were tested,the influence of wind environment on the development and spread of high-speed railway luggage fire and safety of people evacuation in carriage is analyzed.The results show that when the HRR reaches 1108 kW without influence of wind,the fire flashover bursts out;And there is a critical value between the longitudinal wind of 4-4.5 m/s and the transverse wind of 2.3-3 m/s,when the wind speed is lower than the critical value,the ambient wind sucks fresh air to promote the development of fire;When the wind speed is higher than the critical value,the smoke exhaustion and heat dissipation effect of external environment wind is more significant,which inhibits the development of fire;The longitudinal wind aggravates the declination of visibility and the spread of smoke,which is not conducive to the people’s evacuation to the downwind side.The disturbance of transverse wind on smoke makes the local visibility low,but the overall disturbance is small.Based on the experimental verification,the FDS simulation model of water mist curtain fire inhibition in high-speed railway carriage is established to analyze the fire inhibition efficiency of water mist curtain with different spray pressure and droplet size when fire occurs in the head and middle of carriage.The results show that in the scene of fire in the head of carriage,when the droplet size of water mist curtain is 300μm,water mist curtain with the injection pressure of 1MPa can promote CO accumulation within 300s after the ignition of luggage,however when the injection pressure is higher than 5MPa,the phenomenon does not appear.With the increase of injection pressure,the efficiency of inhibiting the fire characterization parameters is higher,the maximum attenuation efficiency of water mist curtain with injection pressure of 1,5 and 10 MPa on HRR,temperature and CO is less than 50%.However,the inhibition efficiency of water mist curtain on heat radiation intensity is more than 70%under all simulation conditions;When the injection pressure is 1MPa,the droplet size decreases from the second stage to the first stage,and the temperature control efficiency increases by nearly 40%.When the injection pressure is 5MPa,the water curtain with 100μm droplet size can eliminate the promoting effect on CO in part time;In the middle compartment fire scene,when the droplet size of water mist curtain is 300μm,the inhibition efficiency of 1MPa water mist curtain for temperature and CO is less than 50%,and the inhibition efficiency of 5 and 10MPa water mist curtain for fire characterization parameters is higher than 60%.