ON AIR FLOW STRUCTURE IN STATION VENTILATION CONNECTIONS OF SUBWAYS

Abstract

One of the important microclimatic criteria for the comfort and safety of passenger transportation in subways is dust concentration in passenger and staff area. It is known that fine dust concentration in subways is significantly exceeded relative to the permissible regulatory level. To reduce the dust concentration to the maximum allowable level, it is necessary to filter the tunnel air not only for the systems of local ventilation of staff rooms, but also for tunnel ventilation and general ventilation of passenger rooms at the stations. It is better to install filters in station ventilation connections, since significant circulating air flows pass through them. To determine the type and parameters of filters, it is required to know the magnitude and direction of an airflow rate, i.e. the structure of its velocity field. Due to the complex topology and presence of separation zones, the airflow structure, gradient of air velocities in the cross-section of ventilation connections and, accordingly, justification of filter installation locations in a ventilation connection requires a separate study. The paper substantiates a decomposition approach to mathematical modeling of aerodynamic processes by transition from a linear open-loop model of the subway line to a closed circular one; geometric parameters of the adopted design model; mathematical statement of the problem. Computational aerodynamics methods allowed determining the minimum, average and maximum projections of air velocity on the normal to the cross section of a ventilation connection and air flows through this cross section. This makes it possible to justify the requirements for the placement and operating parameters of the filtration equipment.