Research On Diffusion Mechanism And Ventilation Of Welding Fume In Limited Space Of Pumped Storage Power Plant

Welding technology is an important technical means of connecting metals in modern industrial engineering,while generating a large number of high-temperature toxic particulate smoke,gas pollutants will be coupled with low-temperature ambient air,resulting in a highly complex process of diffusion of pollutants,therefore,it is extremely important to study the diffusion mechanism of various types of pollutants in welding smoke.During the electromechanical installation period of pumped storage power plants,large-scale unit welding operations are required in the limited underground space,which will continue to generate a large amount of high-temperature pollutants,and the current ventilation and smoke exhaust in pumped storage power plants is mainly based on experience,which is ineffective and poses a serious threat to the physical and mental health of the construction workers in the plants.Therefore,it is important to study the mechanism of welding fume diffusion and the effect of ventilation and smoke exhaust during the electromechanical installation period,and the thesis investigates the mechanism of welding fume diffusion and ventilation in a limited space of a pumped storage power plant.Firstly,we analyzed the forces on the diffusion of welding fume in the limited space of the pumped storage power plant,based on which we established a mathematical model of the diffusion of welding fume in two-phase flow and verified it,numerically studied the temperature distribution and velocity distribution of the fume and solid particles,the rising height of the fume plume and the width of the flow section,the rising height of the particles and the diffusion radius and other physical quantities during continuous welding;and further studied the four important influencing factors of the release temperature,release velocity,release time and particle size of solid particles that affect the diffusion of welding fume;based on the analysis of the simulation results,we arranged the main plant ventilation and fume exhaust scheme and simulated a better ventilation and fume exhaust scheme.The research results show that:1)When the release temperature of welding fume is 473K,the release speed is 0.5m/s,the release time is 10s and the initial particle size is 10μm,during the two-phase flow release phase,the temperature of welding fume gas can reach up to 473K,the gas flow speed can increase to more than 1m/s,and the growth rate of flow section width（ζ_c）and rise height（H）are larger,0.269m/s and 0.7m/s respectively;while During the stop-release two-phase flow phase,the temperature and flow velocity of the solder fume gas gradually become the same as those of the ambient air,and the growth rates of the flow section width（ζ_c）and rise height（H）are smaller,0.079m/s and 0.41m/s,respectively;in any phase,the temperature and velocity of the solder fume particles change in the same trend as those of the solder fume gas,and the motion behavior of most of the solder fume particles is determined by the diffusion process of the solder fume gas.The majority of the motion behavior of the welding fume particles is determined by the diffusion process of the welding fume gas.2)When the four factors of welding fume release temperature,release velocity,release time and particle size affect the two-phase pollutant transport,the diffusion ability of welding fume gas is determined by the total heat released within the two-phase flow release phase itself,when T₀,v₀ and t₀ are larger,the diffusion ability of the gas is stronger;and the diffusion ability of welding fume particles is determined by their own temperature and velocity characteristics,when T₀,v₀ and t₀ are larger and d_p is smaller,the ability of the particle mass to follow the gas flow is stronger.3)When different ventilation and smoke exhaust methods are used in the main plant,the smoke exhaust fan is installed at a height of 16m from the ground or 70.1m away from the welding position,and multiple smoke exhaust fans are set to induce ventilation（multiple fans are arranged at the same time at the same horizontal height）,while the ventilation angle of the smoke exhaust fan is adjusted to 15°,and the smoke exhaust effect is best when the air supply outlet sent into the plant is moved down to a height of 4m from the ground of the secondary plant.The findings of the study provide important technical support and ideas for the design of welding construction ventilation in the underground plant during the electromechanical installation period of this hydropower station,and the findings of the study provide reference for similar projects.