Research On Key Parameters Of Ventilation For High-density Internal Combustion Tractor Hauled Railway Tunnel Operation

The long and large railway tunnels with a single bore and double tracks pose challenges for practical tunnel ventilation due to high traffic density,complex ventilation organization,and high concentrations of pollutant emissions.To address these issues and achieve efficient ventilation,it is crucial to understand the distribution and diffusion patterns of pollutants within such tunnels.In this paper,we present a study based on an actual tunnel ventilation project,using 8.8 km and 11 km tunnels as prototypes.We investigate relevant ventilation parameters through model experiments and numerical simulations.According to the similarity law,a physical model was constructed for one-way and twoway driving trains to conduct model experiments on operating ventilation under different ventilation conditions.By analyzing the results of the model experiments,the distribution of pollutant concentration,the diffusion characteristics of pollutants,the ventilation efficiency under different ventilation conditions,and the optimal location of the vertical shaft were explored.Based on the results of model test and numerical simulation,the distribution of pollutants,the law of pollutant diffusion and the ventilation efficiency under different ventilation conditions were analyzed,and the following conclusions were finally reached:(1)After the train runs under different conditions,under the absence of natural wind,pollutants generally spread in a normal distribution form towards the high portal end,and there is a pollutant concentration peak near the 1/3 position of the distance from the high portal end,which is prone to pollutant accumulation.(2)The optimal layout position of the vertical shaft is near the two ends of the tunnel portal,and the optimal layout position is near the 1/5 position of the distance from the tunnel portal.(3)In this study,we collected,analyzed and calculated the data related to tunnel ventilation under different ventilation conditions.Results showed that running three vertical shaft fans instead of two can improve the ventilation efficiency by an average of 6.4% under different operating conditions.This finding has important implications for improving the ventilation system design and operation in tunnels.Through the study of ventilation technology of high-density internal combustion traction single-hole double-track railway tunnel operation,the distribution law of pollutants discharged by trains in the extra-long tunnel and long tunnel is mastered.Moreover,through the model test of ventilation effect at different shaft locations,the optimal shaft arrangement scheme is given,which provides reference and theoretical basis for tunnel construction.