The Effect of Distance between Jet Fans on Gas Transport, Energy Conservation, and Emission Reduction in Long Highway Tunnels

Abstract

With the rapid development of the national economy, China’s transportation industry is experiencing accelerated development, and, at the same time, the number of long tunnels is constantly increasing. In order to examine the influence of jet fan spacing on gas transport law during the construction of long highway tunnels, this study used the Baima Highway Tunnel in Sichuan as an engineering prototype and established a numerical tunnel ventilation model based on Fluent numerical simulation software. The gas transport characteristics of jet fans in tunnels at different spacings (200 m, 400 m, 600 m, and 800 m) were studied. The results showed that with the increase in jet fan spacing (200 m, 400 m, 600 m, and 800 m), the gas concentration at the tunnel face showed a trend of decreasing and then increasing. Moreover, by analyzing the gas distribution cloud map and the wind flow line diagram, it was determined that the ventilation system effect was the best when the jet fan spacing was 600 m, which met the requirements of a gas concentration of less than 0.5% at the tunnel face and a minimum wind speed of 0.25 m/s. At the same time, according to the optimal spacing for the optimization of the site ventilation system, it was observed that after the ventilation was stabilized (after 600 s), the minimum value of the gas concentration in the left and right tunnel holes diminished from 0.38% to 0.31% and from 0.41% to 0.31%, with rates of reduction of 18.42% and 24.39%, respectively. This indicated that after optimizing the ventilation system at the tunnel site, the concentration significantly decreased compared with before the optimization. Moreover, when the jet fan spacing was 600 m compared with 200 m and 400 m, the annual energy savings were 1900.8 MW·h and 950.4 MW·h, respectively. The research results clarified the optimal layout parameters of jet fans in the Baima Highway Tunnel, providing a reference for the rational layout of jet fans in long-distance tunnels. In addition, the results of this study provide an important theoretical basis for the gas prevention and safe construction of long highway tunnels. Furthermore, this study contributes to research in energy conservation, emission reduction, and sustainable development of energy in the ventilation process during tunnel construction.