Simulation Test Study On Push-pull Ventilation For Control Of Internal Span Welding Fumes In Multi-span Workshop

Welding is an important basic technology in the machining industry.It has been continuously developed and widely used in China with the development of industry.Welding can be regarded as a small metallurgical process,which is accompanied by the production of a large amount of toxic and harmful soot particles diffused and suspended in the working space.Long-term exposure to welding fumes with excessive concentrations may pose a threat to the health of workers and may lead to a variety of occupational diseases such as pneumoconiosis.Ventilation and purification is an effective means to reduce the concentration of welding fume and ensure the hygienic conditions of the working environment.With the expansion of production scale and the complexity of the process,large-scale machinery manufacturing plants are increasingly using multi-span plants for joint production.The space is high,and the characteristics of the opening and closing of various industrial departments make it difficult to ventilate and collect the electric welding fumes in the inner cross-welding section.The common comprehensive ventilation and local ventilation methods are not effective.Therefore,studying the law of diffusion and movement of electric welding fumes in space,selecting appropriate ventilation methods,and designing reasonable airflow organization to effectively capture welding fumes is of great significance to reduce the risk of occupational diseases among workers.In this paper,the CFD numerical simulation method is used to analyze the movement and diffusion characteristics of welding fume under the natural ventilation of the factory building with the model of multi-span factory building of a certain mechanical manufacturing enterprise.Based on the relevant theoretical knowledge,the original local ventilation plan is analyzed and improved.The orthogonal simulation test method is used to study the importance of the influencing factors of the suction and ventilation ventilation collection efficiency,and the improvement scheme is optimized accordingly.Based on the orthogonal simulation test results,the prediction model of the capture efficiency is obtained through multiple regression analysis.The content is as follows:（1）From the theoretical aspect,the composition,properties,formation process,diffusion mechanism,force and the law of airflow movement of localized ventilation of welding fumes are analyzed and introduced.The welding fumes are composed of metal particles,various metal oxides,fluorides,chlorides,and toxic gases,and are turbulently diffused after leaving the high temperature arc zone.Ventilation control of welding fumes is generally carried out by local ventilation airflow.This ventilation method requires a small amount of air and good effect,and is the most effective ventilation method for preventing industrial harmful substances from polluting indoor air and improving the working environment.（2）Establish a physical model,simulate the welding soot concentration distribution under natural ventilation and the original local ventilation scheme,and obtain the concentration distribution data.The simulation results show that natural ventilation can not effectively control your concentration of welding fumes,and the local concentration exceeds the standard seriously,up to 7.0 mg/m³.Under natural ventilation,the welding fume now moves in the vertical direction,and rises to 4.0⁸.0m,then spreads in the horizontal direction with the natural ventilation airflow,and the smoke accumulation above the workshop is serious.The existing local ventilation adopts the suction and suction ventilation mode,and the blowing and suction air outlets are alternately arranged,and a certain smoke control effect is obtained.However,due to the insufficient air volume and the unsatisfactory sealing size,the control effect on the welding dust is not good,only 3.0⁴.0 mg/m³,close to occupational health exposure limits.（3）According to the diffusion characteristics of welding fume under natural ventilation and original local ventilation scheme,determine the suction and suction ventilation mode and design the ventilation system parameters.The six-factor and three-level orthogonal tables are designed.The factors affecting the efficiency of the suction-type ventilation collection are studied by orthogonal simulation test.The results show that the importance of each factor is ranked as the suction port wind speed,the suction port height,the air outlet height,and the suction port.The installation height,the air outlet speed and the air outlet installation height were numerically simulated based on the experimental analysis.The capture efficiencyηwas 99.98%,which verified the rationality of the orthogonal simulation test results.（4）Based on the results of orthogonal experiment,the multivariate regression analysis method is used to establish the multi-linear regression prediction model with the capture efficiency as the objective function and the influencing factors as independent variables asη=0.046×v₂+0.001×b₂-0.001×b₁-0.052 provides reference for pre-judgment of engineering applications.