Numerical study on the influence of the layout of jet fans on the ventilation effect in tunnel

Abstract

In order to optimize the spatial layout of jet fans in the tunnel, the influence of the location of jet fans on the air flow and vehicle exhaust in the tunnel are studied in this paper. Firstly, the three-dimensional physical model of tunnel and mathematical model of jet fan ventilation and vehicle exhaust emissions are established. Then the effects of fan longitudinal spacing and transverse spacing on the velocity distribution, pressure-rise coefficient of jet fans and vehicle exhaust in the tunnel are studied through CFD numerical simulation, so as to obtain the optimal layout parameters. The results show that when the fan longitudinal spacing is 110-m to approximately 140-m, the pressure-rise coefficients of fans are 0.880 to approximately 0.891, which increase first and then decrease as the longitudinal spacing increasing, and the optimal longitudinal spacing is 130-m. When the transverse spacing of fans are 1.68-m, 2.24-m, 2.8m and 3.36-m, the pressure-rise coefficients of fans are 0.918 to approximately 0.936, which increase first and then decrease as the transverse spacing increasing. The transverse spacing of fans should be set between 2.24-m and 3.36-m, and the pressure-rise coefficients can reach above 9.2, and the optimal transverse spacing is 2.8-m. When the jet fans are arranged horizontally and longitudinally, the concentration of CO in the tunnel presents zigzag fluctuations. When the transverse spacing of fans are 1.68-m to approximately 3.36-m and the longitudinal spacing are 110-m approximately 130-m, the concentration of CO in the tunnel is far lower than the safety concentration. The research results can be used for reference and guidance in the layout and installation of jet fans in tunnels.