Estimation of Running Resistance in Train Tunnels
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The research is initiated with the aim to make the tunnel resistance estimations more accurate. Tunnel resistance is measured to calculate running times and energy consumption. From previous studies performed by Norges Statsbaner-NSB, it is found that the standard methods in Open Track and Viriato 6 simulation tools, used to measure tunnel resistance overestimate its value which leads to higher estimation of running times and energy consumption. But in reality, train experiences less resistance while crossing the tunnels. With the purpose to measure tunnel resistance more accurately, an attempt is made to develop new methodology that can eliminate the overestimation of tunnel resistance thus making the railway system more efficient. In order to establish the methodology of calculating tunnel resistance, train resistance, its types and extent to which these resistances effect train motion inside tunnels are investigated. Running resistance value changes significantly inside the tunnels mainly because of change in aerodynamics. Running resistance depends on three coefficients A, B and C and among these three coefficients, C shows more variations as it depends on aerodynamics inside the tunnel. Therefore, efforts have been made out to measure the new value of coefficient C and tunnel factor is estimated using the new value of this coefficient C. Data for the research work was gathered both from NSB and Stadler. NSB conducted the test runs on NSB Type 73 and 75 while Stadler performed the test runs only on Type 75. On the basis of available data sets, direct and velocity fitting approaches are developed for tunnel resistance calculations. Direct and velocity fitting approaches are compared with each other and also with standard Open Track and Viriato 6 methods based on tunnel factors. Results show that both the methods provide lower tunnel factors than standard values used in Open Track and Viriato 6 thus eliminating the overestimation problem. It is also found from the results that the velocity fitting method has less variations in tunnel factors for same tunnel type and provides better estimation of tunnel resistance than direct method. Therefore, tunnel factors are calculated using velocity fitting approach based on tunnel types and it ranges from 4.1 to 7.7 kg/m. Based on the results, it is suggested to use 7.7 kg/m for single track tunnels with small cross-section, 6.4 kg/m for double track tunnels with small cross-section and 4.1 kg/m for double track tunnels with large cross-section to calculate the tunnel resistance more accurately.