Abstract
Protecting the infrastructure of the metro from unauthorized actions with the help of ventilation openings of the systems is one of the main security problems of this type of transport. This article discusses the problem of the dynamics of distribution of the mass flow rate of ventilation air in a two-component system “tunnel vertical ventilation shaft”, due to the piston effect of a moving train. The dependence of the mass flow rate of ventilation air passing in both directions in short ventilation shafts (up to 10 m), on the speed, location of the rolling stock and cross-sectional area of the ventilation shaft is investigated. It is shown, that at speeds of 10–20 m / s of rolling stock and sections of the ventilation shaft of more than 4 m2, the mass flow rate of air passing through the ventilation shaft must be taken into account with the mass flow rate of ventilation air in the transport tunnel for assessing the safety of the harmful aerosols. These processes can have a significant impact on the air quality of the underground infrastructure of the metro.
Highlights
Under the conditions of modern technological development, the most important task of the metro is to provide security measures in the context of growing environmental and terrorist threats
Through the vertical ventilation shafts, depending on the location of the trains, the effect of the piston caused by the movement of trains changes the direction of the air flow several times, which in certain cases can be considered as the possibility of distribution of uncontrolled air into the underground space
S0 = 20 m2; Perimeter - P0 = 18 m, Ventilation shaft is located in the central part of the transport tunnel, which is separated from the portal - Lc = L0/2; The shaft cross section is variable and takes values - Sc = 1, 4, 9, 16 m2, and the vertical height of the shaft hc = 10 m from the tunnel ceiling; - On the left portal of the tunnel there are the different meanings of excessive dynamic pressure ∆Pk = 10, 30, 50
Summary
Under the conditions of modern technological development, the most important task of the metro is to provide security measures in the context of growing environmental and terrorist threats. To overcome the noted difficulties, in the present work it is assumed that similar processes take place in similar systems, and using numerical and analytical methods, depending on the location of the train in the tunnel, the resistance coefficients are estimated, which can be interpreted as the first correlation. As it is known, the indicated coefficients are widely used in the traditional practice of aeromechanics. In the paper [14], as well as in [11] noted that particle generation in underground space occurs by mechanical wear at the brake–wheel and wheel–rail interfaces, where magnetic metallic flakes and splinters are released and undergo progressive atmospheric oxidation
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