Studies Of Smoke Control For Methanol-gasoline Blends Pool Fire In A Long-narrow Confined Space

In recent years,the long-narrow confined space has been developed and applied in many fields.The long-narrow confined space provides convenience for the production and life of human beings with huge fire hazards as well.The characteristics of long-narrow confined space fire are difficult to fight,spread quickly,difficult to evacuation and so on.At the same time,methanol gasoline blends has broad application prospects as clean energy,and there is also a huge fire hazard in the process of production,storage and transportation.Therefore,the extensive application of long-narrow confined space,the broad prospects for the application of methanol gasoline blends and the danger of fire show that it is of great significance to study the fire smoke diffusion characteristics and smoke control methods for long-narrow confined space blends pool fire.The research about fire in long-narrow confined space mainly begins with three aspects of fire source,space structure,fire prevention and smoke control based on the theoretical analysis,numerical simulations,model experiments and full-scale experiments methods.The methanol,gasoline and methanol gasoline blends pool are chosen as fire sources acoording different research needs.In terms of fire source,from a point of view of the diversity of fire sources in long-narrow confined space fire,the combustion characteristics of blends pool fire and the influence of the concentration of fire smoke on the smoke diffusion are studied.Firstly,the combustion characteristics of the combustion characteristics of methanol-gasoline blends pool fire under natural ventilation were studied by means of full-scale experiments and theoretical analysis.The influence of azeotrope on the fire combustion characteristics of blends is analyzed by measuring the fuel mass loss rate,ceiling temperature,fire plume temperature,smoke layer temperature profile,flame height and smoke layer height.The combustion mechanism of fire in long-narrow confined space is revealed,and the critical temperature criterion and the criterion of smoke layer height is obtained.Secondly,full-scale experimental study on the smoke diffusion in the stable flow zone under the longitudinal ventilation is carried out.The influence of smoke concentration on the smoke diffusion along the ceiling is theoretically analyzed by considering the difference of smoke concentration produced by different fuels.A theoretical model for one-dimensional diffusion of smoke along the ceiling is derived.The ceiling temperature profile,smoke layer temperature profile and smoke concentration are measured in experiments.The ceiling temperature decay model considering the smoke concentration is obtained by using the method of data fitting based on the theoretical model.In terms of structure of long-narrow confined space,in view of the influence of the ceiling structure on the fire smoke diffusion in of the long-narrow confined space,the smoke diffusion characteristics of the long-narrow confined spaces with a ceiling screen and multiple ceiling beams are carried out by the model experiments and numerical simulations methods.The influence of a ceiling screen on the airflow structure of long-narrow confined space is analyzed,and the air flow re-circulation length model considering the parameters of screen is established.The dimensionless ceiling temperature decay model for the long-narrow confined space with a ceiling screen is established by considering the two parameters of the height of the screen and the distance between the screen and the fire source.The maximum excess ceiling temperature model and the dimensionless ceiling temperature decay model for the long-narrow confined space with multiple ceiling beams are established by considering two characteristic parameters of the height of beam and the interval of beams.In terms of fire prevention and smoke control,the water mist system and the longitudinal ventilation system are used to control the methanol-gasoline blends pool fire in the long-narrow confined space.The longitudinal ventilation system is adopted to control the smoke induced by the long-narrow confined space fire.The effect of water mist to extinguish different fuel pool fires is studied.The suppression effects of water mist system with multiple nozzles on long-narrow confined space fire with ventilation have been studied for the cases that fire could be more difficult to extinguish.In view of the effects of ceiling structures on smoke diffusion,the critical longitudinal wind speed models to control smoke diffusion for the long-narrow confined space with different ceiling structure are proposed separately.For the long-narrow confined space with a ceiling screen,the lower boundary temperature of the screen is predicted based on the ceiling temperature decay model for the long-narrow confined space with a ceiling screen.The critical wind speed model to suppress the fire smoke diffusion is established using assuming a virtual fire source.For the long-narrow confined space with multiple ceiling beams,the critical wind speed model to suppress the fire smoke diffusion is established considering the blockage effects of ceiling beam,the blockage ratio is lower than 0.25.The results provide the methods for controlling smoke in a rectangular long-narrow confined space with different ceiling structures.In summary,with the combination of theoretical analysis,numerical simulations,model experiments and full-scale experiments,the smoke diffusion law and smoke control methods for long-narrow confined space fire has been studied.The combustion characteristics of blends pool fire in long-narrow confined space are revealed.The smoke diffusion models for long-narrow confined space fire considering the smoke concentration and the characteristic parameters of ceiling structure are established.The fire smoke control methods considering the characteristics of fire source and ceiling structure are proposed.The results are of great significance for expanding the application of smoke diffusion models and fire smoke control methods in the long-narrow confined limited space.It provides a scientific basis for the prevention and control of fire and smoke control in the long-narrow confined space.