Flow Field And Dust Migration Law Of Forced Ventilation In Fully Mechanized Heading Face

Coal is one of the main energy sources in China.With the deepening of the concept of green environment and sustainable development,the clean,efficient and safe utilization of coal resources is also increasingly valued.In order to ensure safe production,the ventilation environment in the excavation roadways is very important.Forced ventilation is widely used in local ventilation of mine,and the key factors affecting the pressurized ventilation are the flow structure and dust accumulation area.Therefore,the flow field structure and dust migration rule of the pressed ventilation in the heading face are systematically analyzed in this paper.Based on the theory of fluid mechanics,gas-solid two phase flow and similarity modeling,and the basic conditions of pressed ventilation in fully mechanized face,a similarity criterion and similarity ratio of similar parameters for a fully mechanized working face have been established;Through similar experimental platform for tunneling laneway,wind speed and dust sensor were used to measure wind speed distribution characteristics and dominant factors,dust concentration variation and sedimentary area of pressed ventilation.;the flow field structure of pressure entry ventilation is analyzed in detail by numerical simulation,and the zoning characteristics of the flow field are obtained by the experimental data.;On the basis of the research above,the simulation analysis of different duct height and flow and dust away from the head field at different distance characteristics,draw ventilation and dust distribution regularity of air duct position;The distribution of dust under different wind conditions is analyzed,and the influence of wind speed on the migration and deposition of dust is obtained.The results are as follows:(1)Based on the similarity theory,the model experiment of pressurized ventilation in excavation roadway need to meet four similarity criteria by dimensional analysis method.It is calculated that when the geometric ratio is 0.3,the similarity ratio of wind speed is 2.62,and the Reynolds number is verified in the self-mode area,which ensures the motion similarity and dynamic similarity of the model experiment.(2)The flow field can be divided into the attached jet area,the impinging jet attachment area,the reflux area and the eddy current zone.The percentage of the backflow area accounts of the cross section increase along the way.The stagnation and descent of the curve correspond to the location and range of the vortex structure.The larger the axial length of the vortex structure is,the longer the reflux area is.(3)As air duct t moves down,the proportion of the reflux area to the section of the roadway increases gradually.When the air duct is 75 cm from the roof,the wind speed is the most concentrated and the reflux development is good,which makes the effect of dust removal the best.When the distance between the air duct and the head is increased in the range of 2.5m,the main jet length increases,and the wind speed in the middle section of the roadway decreases.Among them,when the air duct is 2m from the front,the number of particles presenting at the top and tail of the boring machine is the least.(4)Under the condition of different air volume,the distribution of wind speed has similarities,and the structure of flow field has nothing to do with the change of air volume;dusts of large particle size are mainly deposited in the lane of 3~4m.With the increase of wind speed,the probability of random diffusion of dust becomes smaller,which enhance the ability of the wind flow carrying dust,and the dust concentration on the soleplate also decreases gradually.The distribution of wind speed is basically consistent with the simulation results.The dust deposition rule of the floor is measured in the experiment and the reliability of the numerical simulation is verified.