| As a typical structure,the shaft structure is widespread in the interior of the building.Domestic and foreign scholars have carried out a lot of research on the single shaft structure,but the research on the typical structure of double shafts is relatively weak.Based on smallscale experiments,numerical simulation and theoretical analysis,this paper studies the smoke transport law in double shaft structures.It mainly includes the influence of single and double shaft structures on the temperature distribution in the shaft,the influence of pressure and the influence of air supply velocity.According to the temperature distribution in the single and double shaft structures,it is found that the temperature increases first,then decreases and then continues to increase with the increase of time under different working conditions.It is also found that the temperature in the shaft structure decreases exponentially with the increase of height and the temperature attenuation model in the single and double shaft structure is obtained.From the results of pressure distribution and neutral surface height,it is found that the hot pressure at the bottom of the shaft is always greater than that at the top,the bottom pressure in the double shaft structures is always greater than that in the single shaft structure,and the change rate of bottom pressure increases with the increase of fire source position,and decreases with the increase of the fire power.The neutral plane of double shaft structure is higher than that of single shaft structure,and it is found that the neutral surface height calculated by the neutral surface calculation model has small deviation compared with the simulation results,and the model is universal.By comparing the velocity of air supply at the vent of single and double shaft structure,it is found that the velocity of air supply in double shaft structures is higher than that in single shaft structure.By using the smoke overflow judgment model,the gas at the vent of double shaft structures under different fire power is analyzed.It is found that the thermal buoyancy is greater than the wind pressure force in the shaft structure at the beginning of the fire,and the thermal buoyancy plays a leading role at this time.The smoke flows from the inside of the building to the outside.With the increase of time,the stack effect forms,and the air supply begins.Then the wind pressure force is gradually greater than the thermal buoyancy,and the wind pressure force plays a leading role at the time.The air at the vent flows into the structure. |
