Researchonthecharacteristics Of The Natural Ventilation In The Subway Station With Cpsds

Subway ventilation system is an indispensable component in the subway tunnel, which accounts for a large amount of energy consumption during the operation of the subway system. In general, platform screen doors (PSDs) system and automatic platform gates system are typical ventilation systems in subway. Nevertheless the energy saving potential of these two systems is inverse under different climatic conditions, and a debate of the selection of subway environment control system using PSDs or automatic platform gates system has arisen recently. Based on this background, a new combined platform screen doors (CPSDs) system integrating the advantages of these two systems has emerged. CPSDs system not only holds the energy saving potential of PSDs system in air-conditioning season, but also can transform from PSDs mode to automatic platform gates mode through opening the vents on the upper part of platform screen doors during the transitional season. Multi-modes operation of the ventilation system is capable of reducing the initial investment and using the piston ventilation more effectively to save energy.In this thesis, natural ventilation in subway stations with CPSDs system was studied with the help of one-dimensional network model tool and three-dimensional CFD tool. The results obtained from CFD and one-dimensional method have shown that the air flow patterns at the vents were identical as well as the air change rate in the public area. Consequently, one-dimensional simulation was chosen as the prior method to investigate the ventilation characteristics of CPSDs system.The air exchange patterns of the vents on the platform screen doors in a typical subway station were evaluated by subway environment simulation (SES) tool. The air flow of vents and air exchange volume in the station under different vent location, vent area, and vent number were considered, and a simplified method for the vent models was presented. Based on the typical subway network, the influence of dispatch density, tunnel length, the location and number of piston ventilation shafts were discussed. The results showed that it was not beneficial for the air exchange in the platform section under the short-term operation (10trains per hour), while it was beneficial for the air exchange in the station hall under the long-term operation (30trains per hour). Besides, under long-term operation the air exchange in the station hall of some stations could not satisfy the fresh air required, so the mechanical ventilation is necessary. Furthermore, the longer the tunnel length is the larger the air exchange volume in the station is, and the effective method to increase the air exchange in the station hall is to optimize the location of piston ventilation shafts. Take the Cheng Du metro for example, the air exchange volume and the mean air temperature in the station public area under initial stage, short-term and long-term operation were evaluated as well as the mean air velocity in the stairway. The results showed that the air exchange volume could not meet the requirement only in some station halls under long-term operation. However, after moving the ventilation shafts to the entrance end of the station, air volume flowing into the station hall significantly increases. In addition, the mean air temperature in the platform section will increase, but it is still within the design standard.