Study On The Effect Of The Mechanical Smoke Exhaust And The Water Mist On Building Fire Control

The population in the city is increasing,the demand for construction is increasing,the types of buildings are becoming more and more complex and changing,the interior decoration is becoming more and more colorful,and there are more and more combustible materials that cause fires in the building.The probability of fires in buildings increases frequently,so it is particularly important to study fire extinguishing systems.Water mist fire extinguishing system,as an environmentally friendly fire extinguishing technology with multiple fire extinguishing mechanisms,is extremely popular in the field of fire protection.However,the gas flow characteristics of the coupling of water mist and fire smoke are still lacking;the combined effect of mechanical exhaust and water mist on fire extinguishing is not perfect,especially for the change of fire source location and building structure in small buildings The study of change.Use CFD dynamics calculation software to simulate the combustion and fireextinguishing model in the case of different fire sources inside the building and the presence or absence of structural beams in the building,and explore whether the structure is added with beams,and the mechanical smoke exhaust and water mist are common in the case of different fire sources.The effect of the effect on the smoke diffusion characteristics of building fires.Gambit software was used to establish a structural building fire model,and FLUENT simulated and calculated the influence of the change of the fire source position and the addition of building structural beams on the smoke distribution of the building fire.When the fire source position is shifted to the south wall and the fire source position is not shifted,when the combustion reaches the full development stage,the temperature difference between the upper and lower directions and the north-south direction is smaller,and the smoke velocity gradient at the exit decreases;adding beams and not Compared with the working condition of adding beams,the smoke velocity near the two sides of the beam decreases,and the smoke velocity near the air inlet and the free exit area increases.The smoke temperature from the air inlet to the front of the beam is lower than that behind the beam.It shows that the structural beams of the building affect the smoke distribution of the fire site.On the basis of this geometric model,water mist nozzles and smoke exhaust vents were added to further study the influence of water mist and mechanical smoke exhaust on fire extinguishing.Based on the above-mentioned structural building fire model,according to the conclusion that the water mist fire extinguishing model with the exhaust air volume equal to0.38 has the highest fire extinguishing efficiency and the technical specifications of the water mist system,the position of the exhaust outlet and the nozzle are set up and established The two fire extinguishing models verify that the fire extinguishing model with the combined action of mechanical smoke exhaust and water mist extinguishes fire faster than the fire extinguishing model with only water mist to a certain extent.At the same time,the fire extinguishing model was simulated to obtain the influence of the change of the fire source position and the installation of the structural beams on the smoke temperature distribution in the fire site.The fire source is in the middle of the ground,the middle of the east wall,and the middle of the west wall.The difference between smoke and air temperature at the same building height can reach 35.7% and 38.5%;when the fire source is blocked by the wall,when the combustion is fully developed During the phase,the overall flue gas temperature distribution is lower than the working condition of the fire source in the middle of the indoor ground.In the above working conditions of the fire source location,the water mist fire extinguishing model under natural ventilation conditions is adopted.The addition of structural beams will reduce the overall indoor temperature by 14.2%,15.7% and21.2% respectively;if it is mechanical exhaust and fine The combined effect of water mist,the addition of structural beams will reduce the overall indoor temperature by 23.3%,14.6%and 23.4%,respectively.In addition,the presence of beams enables the indoor space with a height greater than or equal to 2.5m to achieve a maximum cooling effect of 34.8%,while the entire space has a maximum cooling effect of only 23.4%.The results show that the presence of beams has a positive effect on fire extinguishing.When a fire occurs,the damage to the ceiling of the building is less than that without beams.