Study On Diffusion And Control Of Large Proportion Gaseous Pollutants Based On Main Transformer Room Of Underground Hydropower Station

Large proportion gaseous pollutants refer to gaseous pollutants with higher density than air,which are produced by heavy gas leakage.With the increasingly wide use of heavy gas in chemical industry,energy and other fields,the frequency of heavy gas leakage accidents increases due to equipment aging or improper operation,and the research on the leakage and diffusion characteristics of large proportion gaseous pollutants and the corresponding accident exhaust system has gradually become an important topic in the field of public safety.Therefore,in order to reduce the impact of such accidents,based on the structure of the main transformer room of the Rudila underground hydropower station,this study analyzes the leakage and diffusion process of several kinds of common heavy gas（sulfur hexafluoride（SF₆）,chlorine gas（Cl₂）and carbon dioxide（CO₂））under various working conditions by numerical simulation,which provides a theoretical basis for the setting of early warning monitoring points for heavy gas leakage accidents and the design of large proportion gaseous pollutants push-pull ventilation system.The attached ventilation airflow organization model is introduced,and the exhaust system is designed by numerical simulation combined with orthogonal test,that is,the large proportion gaseous pollutants push-pull ventilation system.The main research contents are as follows:（1）Through numerical simulation and verification,the concentration distribution characteristics of three kinds of pollutants（SF₆,Cl₂,CO₂）with different relative molecular weights after leakage are obtained when the leakage orifice is located at the center of the body source side surface.Under this working condition,the concentration distribution of heavy gas in the vertical direction is affected by the ratio of relative molecular mass to air relative molecular mass.At the lower horizontal height,the concentration of heavy gas with relatively large molecular weight accumulates significantly,but with the increase of height,the concentration of heavy gas with relatively large molecular weight decreases obviously.In addition,under this working condition,the plane average concentration of heavy gas shows a fluctuating upward trend with the change of time,and the concentration fluctuation is more obvious at the height above the ground.The fluctuation trend of heavy gas with small relative molecular weight will lag behind that with large relative molecular weight,and the order in this working condition is SF₆,Cl₂ and CO₂.（2）By numerical simulation,the concentration distribution characteristics of three kinds of pollutants（SF₆,Cl₂,CO₂）with different relative molecular weights are analyzed when the orifice at the center of the upper surface of the body source leaks.Under this working condition,the increase of the average concentration of heavy gas in the low-level plane comes from the sliding of heavy gas accumulated on the upper surface of the container.Therefore,under this working condition,it takes a long time for the average concentration of heavy gas in the low plane to increase greatly,and the smaller the relative molecular weight of heavy gas is,the longer it stays on the upper surface of the body source.The change of the average concentration at each height plane with time can be divided into two processes:the rapid growth process of concentration and the slow growth process.In the slow growth process,due to the obvious gravity settlement of the high-level plane gas cloud,the concentration change process of the pollutants will be accompanied by significant fluctuations.（3）According to the diffusion characteristics of large proportion gaseous pollutants,combined with this research model（1.1 m×1 m×1.23 m）,the air distribution of attached ventilation mode,which has been studied by our group for a long time,is introduced,and SF₆ is taken as a typical large proportion gaseous pollutants to complete the preliminary design of the large proportion gaseous pollutants push-pull ventilation system.Through numerical simulation,the performance of the system under different air exchange times is obtained,and the air exchange times n,which is economical and efficient,is determined to be 10 times per hour.Then,the optimum combination of parameters of air supply and exhaust ports is obtained by orthogonal test:the length of air supply port is 0.25 m,the distance between air exhaust ports is 0.00 m,and the length of air exhaust port is 0.50 m;At the same time,it is found that adding suitable deflector can reduce the obstacle to airflow organization;Finally,it is proved by numerical simulation that the large proportion gaseous pollutants push-pull ventilation system is also suitable for the leakage of large proportion gaseous pollutants（Cl₂ and CO₂）with different relative molecular weights.