Study On Performance Optimization And Evaluation Index Of Local Exhaust Hood At Welding Station

Welding is the most common production process in industrial production.Various occupational hazard factors generated during welding process can cause serious damage to the physical and mental health of workers.Therefore,it is very important to study the pollutant capture performance of local exhaust hoods at welding station.The research object of the article is the smoke emission point and the local exhaust hood arranged on the welding station of an automobile manufacturing enterprise.The specific research content includes the following three aspects:1)Research on smoke exhaust performance of exhaust hood.In an ideal state where there is no interference from ambient airflow at the welding station,the effects of exhaust volume and temperature on the capture efficiency of the exhaust hood and the effects of temperature on the flue gas diffusion process are studied.The research shows that the capture efficiency of flue gas and the degree of energy utilization are high when the exhaust volume is within the range of 0.12-0.20m~3/s;when the exhaust volume is constant,the morphological changes of flue gas diffusion process within the range of 40-80℃are basically consistent,but the higher the temperature,the faster flue gas diffusion speed.Based on the above research results,flue gas temperature and exhaust volume parameters were selected to conduct a study on the impact of transverse airflow interference at different speeds at the welding station on the capture efficiency of flue gas and soot particles.Research shows that once there is transverse airflow at the welding station,the capture efficiency of both will decrease.And with the increase of the transverse airflow,the decreasing regularity of the capture efficiency of both is consistent.In addition,the greater the velocity of the transverse airflow,the greater the impact on the capture efficiency of both.2)Performance optimization of exhaust hood.The performance is optimized through orthogonal tests of the structural parameters of the exhaust hood,and the optimal structural parameters are selected:outer edge size of the hood opening is 900×900mm,and outer diameter of exhaust duct is 380mm.Compared to the previous optimization,the capture efficiency increased by 23.1%.Secondly,movable baffles with different heights are added around the edges of hood opening to further optimize performance.The research shows that the increase of movable baffles is beneficial to improving the capture efficiency of flue gas.When the baffle height is 200mm,the efficiency is the highest,which is 6.0%higher than the above optimized structure.Finally,when the amount of flue gas released is different,and it is impossible to change the structure and add auxiliary facilities,performance optimization can be carried out by optimizing exhaust volume.Establish a fitting formula between the flue gas release amount and the required exhaust volume to obtain the optimal exhaust volume under any flue gas release amount.3)Performance evaluation of exhaust hood.Based on the above research results,the section proposes three indicators:"concentration of the respiratory zone","surface average concentration of the exhaust outlet",and"concentration in the exhaust hood".The performance of the exhaust hood is comprehensively evaluated by combining the three indicators with the capture efficiency.The"concentration of the respiratory zone"can measure the health risk of welding fume to human health.The"surface average concentration of the exhaust outlet"can replace capture efficiency and indirectly measure capture performance.The"concentration in the exhaust hood"can evaluate the impact of transverse airflow on the vertical diffusion of flue gas,and indirectly measure the pollutant removal performance of exhaust hood when there is transverse airflow interference.Conduct testing and research on three different welding implementation conditions on site based on the"concentration of the respiratory zone"indicator.Setting up the ventilation system has a certain effect on capturing welding fume compared to not opening it.The concentration of welding fume in the respiratory zone is lower,but still exceeds the occupational health exposure limit.And under the disturbance of airflow with a fan,it can promote the capture of welding fume,and reduce the concentration of welding fume in the respiratory zone to within the short-term exposure limit.