Investigation of the dynamic airtightness coefficient of high-speed trains traveling through a tunnel : a field study

Abstract

Determining the dynamic airtightness coefficient (τdyn) of train carriages using a high-accuracy and high- efficiency method is essential regarding the study of the dynamic airtightness performance of high-speed trains (HSTs) traveling through tunnels. This study set out to provide a systematic elaboration and investigation of the whole process of establishing the calculation methodology of τdyn of HST carriages. Moreover, the applicability of three different typical optimization algorithms in the calculation of τdyn was explored and compared. These were the traversal algorithm (TRAA), the trichotomy algorithm (TRIA), and the genetic algorithm (GA). Using the established calculation method, the values of τdyn of different HST carriages for tunnels with different lengths were calculated based on field test data of pressure outside and inside HST carriages. Results revealed that the selection of optimization algorithms had significant effects on the calculation process of τdyn because of their different optimization mechanisms. These three optimization algorithms were proven to be feasible for establishing the calculation method of τdyn and gave the same calculation result of τdyn for the calculation example within the expected accuracy. The elapsed time of the TRAA and GA were approximately 100 and 80 times that of the TRIA regarding the calculation example. The TRIA was the preferable choice for the calculation of τdyn among the three algorithms because of its uncomplicated implementation logic and high efficiency. Within the tunnel-length range involved, the tunnel length itself had no significant effect on τdyn of HST carriages. A significant increasing trend in τdyn of HST carriages was found along the train length. Compared to the head car, the increasing ratio of τdyn of the second car was varying from 0.2 to 0.5, while the increasing ratio of the seventh car was ranging from 0.8 to 1.7 considering different tunnel lengths. These findings provide a reference basis for the design of the calculation method of τdyn of HST carriages and also enhance understanding of τdyn of HST carriages under different operating circumstances.