Numerical study on the indoor flow field and ventilation performance in the power room of a hybrid locomotive that passes through a tunnel

Under the background of energy saving, emission reduction, and green transportation, the electrification construction of railway lines is difficult owing to long cycles and high costs. Hybrid locomotives have emerged as fuel locomotives that can run on electrified lines and that achieve energy saving, emission reduction, and railway emergency on non-electrified lines. Train power equipment is highly integrated in the locomotive power room, which leads to the ventilation and heat dissipation performance of indoor high-heat equipment becoming one of the main factors that affect the safe operation of trains. This study focuses on the flow field and ventilation of locomotive power rooms in railway vehicle/tunnel systems and explores the variation of the ventilation flow rate and flow field in a power room when trains pass through a tunnel at different speeds. Based on the unsteady Reynold-averaged Navier–Stokes (RANS) equations and shear-stress transformation (SST) k-ω turbulence model, the relative motion between a train and a tunnel is simulated by sliding mesh, and the related algorithm settings are verified through experiments. The results show that: train speed is linearly related to the air inlet flow rate, and trains have a critical speed, which affects the original indoor air-cooling circulation system. This critical speed is reduced by the tunnel environment; The propagation and superposition of the pressure wave in a tunnel have no evident effect on the flow rate of the power room vent; Train speed is negatively correlated with the fan efficiency; thus, it deteriorates the fan efficiency in the tunnel environment; The symmetrical distribution of ventilation openings in a power room can effectively balance the fresh-air flow, but it is not conducive to cooling equipment located near the locomotive. These conclusions can contribute to improving future designs of the ventilation systems of hybrid electric locomotive power rooms.