Study On The Influence Of Smoke Exhaust Device Setting On Efficiency Of Smoke Exhaust

With the rapid development of the country's economic construction,a large number of complex buildings have risen from the ground.Many buildings use some combustible materials.Once burned,they are usually accompanied by a large amount of toxic and harmful fumes,so the smoke in the building fire.Control problems are one of the key points of fire prevention and control at this stage.In terms of mechanical exhaust system in modern buildings,the specification stipulates that the height of the pipe of the mechanical exhaust system shall not exceed 50m in public buildings and 100m in civil buildings.We studied the influence of the pipe height of the mechanical exhaust system on the effect of the fan.Through the experimental method,the smoke exhaustion of different floors under the same mechanical exhaust system is measured.It is found that at the pipeline heights of 50m and 100m,the wind speed of the exhaust outlet was attenuated by 15%and 33%respectively compared with 0m.After that,we found through numerical simulation that the fan air volume is linear with the pipe height.As the pipe height increases,the fan air volume are reduce continuously.From the results obtained in this paper,when the pipeline height is 50m,the actual air volume of the wind turbine is about 90.1%of the rated air volume,and when the pipeline height reaches 100m,the working air volume of the wind turbine is only 81%of the rated air volume.That is to say,in the design of the mechanical exhaust system,it is necessary to consider the loss caused by the fan pipeline in advance,and appropriately increase the rated air volume of the fan to meet the requirements of the specification for the air volume of the mechanical exhaust system.For natural smoke exhaust,the specification considers that except for the flat push window,which calculated according to the actual opening size,the other hanging windows is calculated based on the projected area after the opening.In fact,the effect of the natural smoke exhaust windows is also affected by the type.In this paper,the influence of the top-hung windows and the bottom-hung windows on the smoke exhausting effect are mainly studied by numerical simulation method.By changing the opening angle of the upper hanging window,we found that the main exhaust area of the top-hung windows is the two sides of the window,and the efficiency of the exhaust of the top-hung windows is linear with the sine value of the opening angle,but has little relationship with the length of the window.Based on this,a method for improving the efficiency of exhausting the top-hung windows in buildings are proposed.The simulation results of the bottom-hung windows show that when the opening angle of the window is greater than 23°,the smoke exhausting effect is basically the same as when there is no window occlusion.