Numerical Simulation Of Dust-reducing Mechanism Of High-pressure Spray In Building Construction

Since the reform and opening up,China’s economy has developed at a high speed,and the modernization process has gradually accelerated.Large-scale construction of roads,bridges,and civil buildings has been carried out.However,the problem of atmospheric particulate matter pollution has become very prominent and has to attract the attention of the whole people and even the world.Especially in recent years,large-scale smog incidents occurred in many central and eastern cities in China,and the frequency of outbreaks has become higher and higher,and the scope has become wider and wider,which seriously threatens human health.Building dust is one of the main causes of atmospheric particulate pollution.In order to completely control the hidden haze,it is necessary to strictly control the emission of building dust and strengthen measures to suppress dust and dust.In this thesis,the numerical simulation method is used to explore the mechanism of high-pressure spray dust reduction,so as to guide the measures of high-pressure spray dust reduction to reduce the adverse effects of building dust on the atmosphere.This research relies on the research and demonstration of pollutant control technology and monitoring system in the whole process of construction of the 13 th Five-Year National Key Research and Development Project.The key work of this paper is: Based on the national questionnaire survey and the on-site monitoring of several demonstration projects in Changsha City,the causes,characteristics,hazards and evaluation of existing dust control measures were analyzed;On the basis of extensive research on the mechanism of high pressure spray dust reduction at home and abroad,the mechanism of liquid atomization and crushing and the mechanism of high pressure spray dust reduction are summarized;High-pressure spray dust reduction simulation of building dust is carried out by means of computational fluid dynamics numerical simulation.The main research content of this paper is to explore the mechanism of high pressure spray dust reduction.Taking dust particles and water mist particles as the research object,on the basis of mastering the characteristics of two different particle particles,the coupling mechanism of dust particles and water mist particles is analyzed.Through the investigation of the dust-reducing mechanism of high-pressure spray,the key influencing factors of high-pressure spray dust reduction are obtained,which provides basic parameters for the numerical simulation process of high-pressure spray dust-reducing mechanism and the basis for coupling model selection.The main conclusions of this paper are:(1)Basic law of wind field in deep foundation pit of building construction: In the vicinity of the foundation pit wall of the deep foundation pit,the airflow is vortex-like,forming a local “quiet wind zone”,and most of the dust particles are trapped in the“quiet wind zone”,which is expressed as The diffusion velocity of the upwind dust particles is slowed down;the middle part of the deep foundation pit is in the airflow acceleration zone,which will accelerate the downward diffusion of the dust particles;the airflow “acceleration zone” appears in the wind direction of the deep foundation pit,which will accelerate the outward diffusion of the dust particles,but Due to the obstruction of the foundation wall by the downwind,part of the dust particles will accumulate in the downwind wall of the foundation pit and cannot be diffused outside the foundation pit in time.It is called the “stacking area” of the dust particles;after the deep foundation pit is subjected to the wind field The dust particles are mainly concentrated in the up-and-down wind direction foundation pit wall,especially the dust particle concentration in the downwind direction is high.The dust-reducing key area of high-pressure spray dust reduction in building construction should be mainly concentrated around the wind direction of the foundation pit.(2)Basic law of dust diffusion in deep foundation pits of building construction:With the decrease of particle size of dust particles,the easier it is to diffuse dust particles from the deep foundation pit to the outside of the foundation pit;and the particle size is reduced from 100 to 10,and the effect of diffusion enhancement is obvious.However,the dust particle size is reduced from 10 to 2.5,and the effect of continuing to enhance diffusion is not obvious.The dust particles with particle sizes of10 and 2.5 are more likely to diffuse outside the pit.(3)The basic mechanism of high pressure spray dust reduction: Under the same simulated conditions,after the dust is sprayed,the combination of spray and dust reduces the diffusion of dust particles to the outside of the foundation pit;the smaller the particle size of the dust particles,the more sprays need to be combined.The smaller the particle size,the more obvious the dust reduction effect.(4)The effect of spray speed on the dust-reducing effect of the high-pressure spray of the surrounding spray system: the spray water discharge speed has a great influence on the high-pressure spray dust reduction efficiency,and the high-pressure spray dust reduction efficiency increases with the increase of the spray speed;the spray speed is from the initial value.When the lower the initial increase,the dust reduction rate is more obvious,but to a certain value,the faster the spray speed,the effect of continuing the dust reduction will be greatly reduced.(5)The effect of spray height on the high-pressure spray dust reduction effect of the surrounding spray system: the efficiency of high-pressure spray dust reduction decreases with the increase of spray height;the spray height should take the same value as the height of the enclosure,when the spray height is greater than At this value,the improvement of the dust reduction efficiency of the high pressure spray is not obvious.