The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts.A three-dimensional numerical model using the dynamic l...The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts.A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train is first developed,and then it is validated against the model tunnel experimental data.With the tunnel and subway train geometries in the numerical model exactly the same as those in the model tunnel experimental test,but with the ventilation ducts being connected to the tunnel ceiling and a barrier placed at the tunnel outlet,the three-dimensional train-induced unsteady tunnel flows are numerically simulated.The computed distributions of the pressure and the air velocity in the tunnel as well as the time series of the mass flow rate at the ventilation ducts reveal the impact of the train motion on the exhaust and suction of the air through ventilation ducts and the effects of a barrier placed at the tunnel outlet on the duct ventilation performance.As the train approaches a ventilation duct,the air is pushed out of the tunnel through the duct.As the train passes the ventilation duct,the exhaust flow in the duct is changed rapidly to the suction flow.After the train passes the duct,the suction mass flow rate at the duct decreases with time since the air pressure at the opening of the duct is gradually recovered with time.A drastic change in the mass flow rate at a ventilation duct while a train passes the corresponding ventilation duct,causes a change in the exhaust mass flow rate at other ventilation ducts.Also,when a barrier is placed at the tunnel outlet,the air volume discharge rate at each ventilation duct is greatly increased,i.e.,the barrier placed at the tunnel outlet can improve remarkably the ventilation performance through each duct.展开更多
Transformers are key components in substations,and their maintenance scheme is very important.Optimizing the transformer maintenance scheme can enhance substation reliability and lower maintenance cost.Current resolut...Transformers are key components in substations,and their maintenance scheme is very important.Optimizing the transformer maintenance scheme can enhance substation reliability and lower maintenance cost.Current resolutions focus on device state evaluation and fault detection,which is ex-post method.However,this paper proposes a LS-SVM algorithm based on deficiencies tree analysis to predict deficiencies in future under certain maintenance scheme,then choose the best maintenance scheme.展开更多
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant No. 2009-0063383)the Seoul R and BD program (Grant No. CS070160)the Leading Academic Discipline Project of Shanghai Municipal Education Commission (Grant No. J50502)
文摘The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts.A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train is first developed,and then it is validated against the model tunnel experimental data.With the tunnel and subway train geometries in the numerical model exactly the same as those in the model tunnel experimental test,but with the ventilation ducts being connected to the tunnel ceiling and a barrier placed at the tunnel outlet,the three-dimensional train-induced unsteady tunnel flows are numerically simulated.The computed distributions of the pressure and the air velocity in the tunnel as well as the time series of the mass flow rate at the ventilation ducts reveal the impact of the train motion on the exhaust and suction of the air through ventilation ducts and the effects of a barrier placed at the tunnel outlet on the duct ventilation performance.As the train approaches a ventilation duct,the air is pushed out of the tunnel through the duct.As the train passes the ventilation duct,the exhaust flow in the duct is changed rapidly to the suction flow.After the train passes the duct,the suction mass flow rate at the duct decreases with time since the air pressure at the opening of the duct is gradually recovered with time.A drastic change in the mass flow rate at a ventilation duct while a train passes the corresponding ventilation duct,causes a change in the exhaust mass flow rate at other ventilation ducts.Also,when a barrier is placed at the tunnel outlet,the air volume discharge rate at each ventilation duct is greatly increased,i.e.,the barrier placed at the tunnel outlet can improve remarkably the ventilation performance through each duct.
文摘Transformers are key components in substations,and their maintenance scheme is very important.Optimizing the transformer maintenance scheme can enhance substation reliability and lower maintenance cost.Current resolutions focus on device state evaluation and fault detection,which is ex-post method.However,this paper proposes a LS-SVM algorithm based on deficiencies tree analysis to predict deficiencies in future under certain maintenance scheme,then choose the best maintenance scheme.
