During the train meeting events,train equipment compartments are exposed to the worst pressure changes,potentially affecting the ventilation performance of equipment,particularly for electrical facilities equipped wit...During the train meeting events,train equipment compartments are exposed to the worst pressure changes,potentially affecting the ventilation performance of equipment,particularly for electrical facilities equipped with independent air ducts.In this paper,a two-step method is used for numerical computation:(1)obtaining the temporal and spatial transient node data of the flow field sections during the train-passing simulation and(2)using the data as the input data for the equipment compartment simulation.In addition,this paper also compares the difference in equipment ventilation between the single-train and trainpassing scenarios in real vehicle tests.The results indicate that the primary factors influencing ventilation effectiveness are the aerodynamic compression and deceleration of airflow induced by the other train's nose,as well as the instability of the external flow field in the wake of the other train.During train crossing,the air is forced into the air duct,with a maximum ratio of the airflow in-duct to the airflow out-duct reaching 3.2.The average mass flow falls below the rated mass flow for the converter.Compared to the rated air volume of converter,the maximum suppression rates obtained from testing and simulation are-24.5%and-16.8%,respectively.Compared to the single-train operation,the maximum suppression rates obtained from testing and simulation are-15%and-18%,respectively.These findings provide valuable insights into the design and operation of high-speed trains.展开更多
Previous research was limited to flat-façade buildings when evaluating the indoor and outdoor ventilation performance in a multi-story building.However,envelope features can provide the shading effect to induce t...Previous research was limited to flat-façade buildings when evaluating the indoor and outdoor ventilation performance in a multi-story building.However,envelope features can provide the shading effect to induce the temperature difference between surfaces exposed to direct solar radiation and those without solar radiation.This temperature difference between surfaces can enhance the thermal buoyancy and change indoor and outdoor ventilation performance.We conducted scaled outdoor experiments to examine the impact of various envelope features on indoor and outdoor ventilation performance in multi-story buildings.Compared to the flat-façade multi-building,the average normalized horizontal airflow velocity of overhang,small wing wall,and large wing wall multi-buildings increased by 12.41%,10.56%,and 5.56%,respectively.Cross-ventilation is more susceptible to envelope features than single-sided ventilation in air change per hour(ACH).Specifically,the ACH values of cross-ventilation for large wing wall,small wing wall,and balcony multi-buildings decreased by 69.98%,25.79%,and 12.12%relative to the flat-façade building.For the same envelope feature building,the ACH values of single-sided ventilation on the windward side are better than those on the leeward side,particularly the building with small wing walls,with an improvement of 12.77%compared to flat-façade.This study contributes to advancing the understanding of urban ventilation,and provides a valid basis for designing envelope features in urban buildings.展开更多
An unsteady three-dimensional analysis of the ventilation performance is carried out for different ventilation strategies to find out a ventilation method with a high performance in a subway tunnel.The natural ventila...An unsteady three-dimensional analysis of the ventilation performance is carried out for different ventilation strategies to find out a ventilation method with a high performance in a subway tunnel.The natural ventilation performance associated with a train-induced air flow in a subway tunnel is examined.The dynamic layering method is used to consider the moving boundary of a train in the current CFD method.The geometries of the modeled tunnel and the subway train are partially based on those of the Seoul subway.The effects of the structure of the ventilation duct and the geometry of the partitions on the ventilation performance are evaluated.The results show that the combined ventilation ducts （to be designed）,and the partitioning blocks installed along the middle of tunnel （already in existences） are helpful for air exchange.This study can provide some guidance for the design of ventilation ducts in a subway system.展开更多
Large space circular coal storage dome(LSCCSD)offers an environmental and dependable alternative to open stockpiles,and it has been consequently widely applied in China.However,due to the lack of scientific guidelines...Large space circular coal storage dome(LSCCSD)offers an environmental and dependable alternative to open stockpiles,and it has been consequently widely applied in China.However,due to the lack of scientific guidelines,its natural ventilation performance is lower than expected.Natural ventilation potential strongly depends on the roof geometry and opening mode,which have not yet been investigated for LSCCSD.This paper presents a detailed evaluation of the impact of dome geometry(rise span ratio),opening height,and opening modes on the ventilation performance of LSCCSD.The evaluation is based on computational fluid dynamics(CFD)methods and is validated by available wind tunnel testing.We employed three evaluation indicators,which are wind pressure coefficient,effective ventilation rate,and wind speed ratio.The results demonstrate that the rise span ratio has a significant effect on the wind pressure difference and the effective ventilation rate increases by approximately 9%–42%with a single-annular opening.When double-annular openings are set in a strong positive pressure zone,the effective ventilation rate increases by 100%and the average wind speed ratio increases by 50%.When it is compared with single one with similar opening height,the effective ventilation rate increases by 25%.The optimum natural ventilation performance for LSCCSD is achieved at a rise span ratio of 0.37.In addition,the lateral middle opening is kept higher than the ridge top of the coal pile.The proposed evaluation approach and design parameters provided instructive information in the building design and ventilation control for LSCCSDs.展开更多
A virtual instrument system is proposed to test the performance parameters of local-ventilator installed under coal mines,which can do ventilator parameter acquisition automatically,as well as plot and analyze the ven...A virtual instrument system is proposed to test the performance parameters of local-ventilator installed under coal mines,which can do ventilator parameter acquisition automatically,as well as plot and analyze the ventilator performance curve.The whole system is designed using the virtual instrument technology combined with network technology based on Labview platform.Experimental results show that it can monitor and evaluate ventilator’s performance parameters automatically and efficiently,which provides critical information for ventilator safety under coal mine.展开更多
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
基金support by Technology R&D Program of China State Railway Group Co.,Ltd(Grant number N2022J013)the Hunan Provincial Innovation Foundation for Postgraduate(Grant number CX20220279)+1 种基金the Fundamental Research Funds for the Central Universities of Central South University(Grant number 2022ZZTS0193)China Scholarship Council(202106370112)。
文摘During the train meeting events,train equipment compartments are exposed to the worst pressure changes,potentially affecting the ventilation performance of equipment,particularly for electrical facilities equipped with independent air ducts.In this paper,a two-step method is used for numerical computation:(1)obtaining the temporal and spatial transient node data of the flow field sections during the train-passing simulation and(2)using the data as the input data for the equipment compartment simulation.In addition,this paper also compares the difference in equipment ventilation between the single-train and trainpassing scenarios in real vehicle tests.The results indicate that the primary factors influencing ventilation effectiveness are the aerodynamic compression and deceleration of airflow induced by the other train's nose,as well as the instability of the external flow field in the wake of the other train.During train crossing,the air is forced into the air duct,with a maximum ratio of the airflow in-duct to the airflow out-duct reaching 3.2.The average mass flow falls below the rated mass flow for the converter.Compared to the rated air volume of converter,the maximum suppression rates obtained from testing and simulation are-24.5%and-16.8%,respectively.Compared to the single-train operation,the maximum suppression rates obtained from testing and simulation are-15%and-18%,respectively.These findings provide valuable insights into the design and operation of high-speed trains.
基金supported by the Key Laboratory of Ecology and Energy Saving Study of Dense Habitat,Ministry of Education,Tongji University(Grant No.20220104)the National Natural Science Foundation of China(Grant Nos.52378026 and 42175095)the Shenzhen Science and Technology Program(No.20220809120650001).
文摘Previous research was limited to flat-façade buildings when evaluating the indoor and outdoor ventilation performance in a multi-story building.However,envelope features can provide the shading effect to induce the temperature difference between surfaces exposed to direct solar radiation and those without solar radiation.This temperature difference between surfaces can enhance the thermal buoyancy and change indoor and outdoor ventilation performance.We conducted scaled outdoor experiments to examine the impact of various envelope features on indoor and outdoor ventilation performance in multi-story buildings.Compared to the flat-façade multi-building,the average normalized horizontal airflow velocity of overhang,small wing wall,and large wing wall multi-buildings increased by 12.41%,10.56%,and 5.56%,respectively.Cross-ventilation is more susceptible to envelope features than single-sided ventilation in air change per hour(ACH).Specifically,the ACH values of cross-ventilation for large wing wall,small wing wall,and balcony multi-buildings decreased by 69.98%,25.79%,and 12.12%relative to the flat-façade building.For the same envelope feature building,the ACH values of single-sided ventilation on the windward side are better than those on the leeward side,particularly the building with small wing walls,with an improvement of 12.77%compared to flat-façade.This study contributes to advancing the understanding of urban ventilation,and provides a valid basis for designing envelope features in urban buildings.
文摘An unsteady three-dimensional analysis of the ventilation performance is carried out for different ventilation strategies to find out a ventilation method with a high performance in a subway tunnel.The natural ventilation performance associated with a train-induced air flow in a subway tunnel is examined.The dynamic layering method is used to consider the moving boundary of a train in the current CFD method.The geometries of the modeled tunnel and the subway train are partially based on those of the Seoul subway.The effects of the structure of the ventilation duct and the geometry of the partitions on the ventilation performance are evaluated.The results show that the combined ventilation ducts （to be designed）,and the partitioning blocks installed along the middle of tunnel （already in existences） are helpful for air exchange.This study can provide some guidance for the design of ventilation ducts in a subway system.
文摘Large space circular coal storage dome(LSCCSD)offers an environmental and dependable alternative to open stockpiles,and it has been consequently widely applied in China.However,due to the lack of scientific guidelines,its natural ventilation performance is lower than expected.Natural ventilation potential strongly depends on the roof geometry and opening mode,which have not yet been investigated for LSCCSD.This paper presents a detailed evaluation of the impact of dome geometry(rise span ratio),opening height,and opening modes on the ventilation performance of LSCCSD.The evaluation is based on computational fluid dynamics(CFD)methods and is validated by available wind tunnel testing.We employed three evaluation indicators,which are wind pressure coefficient,effective ventilation rate,and wind speed ratio.The results demonstrate that the rise span ratio has a significant effect on the wind pressure difference and the effective ventilation rate increases by approximately 9%–42%with a single-annular opening.When double-annular openings are set in a strong positive pressure zone,the effective ventilation rate increases by 100%and the average wind speed ratio increases by 50%.When it is compared with single one with similar opening height,the effective ventilation rate increases by 25%.The optimum natural ventilation performance for LSCCSD is achieved at a rise span ratio of 0.37.In addition,the lateral middle opening is kept higher than the ridge top of the coal pile.The proposed evaluation approach and design parameters provided instructive information in the building design and ventilation control for LSCCSDs.
文摘A virtual instrument system is proposed to test the performance parameters of local-ventilator installed under coal mines,which can do ventilator parameter acquisition automatically,as well as plot and analyze the ventilator performance curve.The whole system is designed using the virtual instrument technology combined with network technology based on Labview platform.Experimental results show that it can monitor and evaluate ventilator’s performance parameters automatically and efficiently,which provides critical information for ventilator safety under coal mine.
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.
