Abstract
Technological development of the past decades has made it possible in the case of railway vehicles to continually improve dynamic and traction performance. This has determined, in the case of the conventional system (the railway vehicle on rails) a steady increase in travel speeds, reaching the record value 578 km/h. The current trend, in the case of the conventional classical trains composed from the locomotives and wagons are the maximum travel speeds to be at values of 200 - 250km/h. In the case of Electric multiple unit (EMU), the maximum speeds allowed in the current traffic are between 300 - 450 km/h. These increases in travel speeds would not have been possible without first studying in more detail the aerodynamic phenomena that act on the vehicles during their travel. This paper intends to analyses how the aerodynamic forces acts in the case of a classic passenger train formed up of a motor vehicles (locomotive) and three towed vehicles. For the determination of aerodynamic force values, an air flow simulation program will be used in case the train moves under normal atmospheric conditions.
Highlights
During the movement of a train, on the railway vehicles that make up, are a few forces that allow its movement. The arrangement of these forces is done as follows: in the sense of the movement of the train, is the traction force (F0(v)) developed by the power equipment placed on the motor vehicles, and in the opposite direction to the train movement are the sum of the resistance forces (∑Rt(v)), which opposes the displacement and the braking force (Ff(v)) used to reduce the speed or to stop the train
The largest share of the values of this force has the component determined by the motor vehicle
Using the analysis model resulting from Davis's relationship, it is found that at higher speeds the share of aerodynamic forces becomes significant, reaching 82% of the total value of the resistances to advancement
Summary
During the movement of a train, on the railway vehicles that make up, are a few forces that allow its movement. At any time of the train movement, the values corresponding to these forces must be lower or at a limit equal to the limit of the adhesion force (Fa(v)) of the track wheel contact. Under these conditions, the equilibrium equation for the forces acting on the vehicle in the longitudinal direction (the direction of travel of the train) can be written in mathematical form according to [1,2,3,4,5,6] as follows: F0(v) – ∑Rt(v) – Ff(v) ≤ Fa(v). Where: ∑Rt-v(v) - the sum of the total rolling resistance of a railway vehicle; A - mechanical rolling resistance [N]; B - coefficient of non-aerodynamic drag resistance [N/(km/h)]; C - drag coefficient determined by aerodynamic phenomena [N/(km/h)2]; v - vehicle speed [km/h]
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