Experimental Study on the Impact of Smoke Exhaust Rate and Exhaust Vent Opening Mode on the Smoke Control Effect of the Point Smoke Exhaust System in an Asymmetric V-Shaped Tunnel

Small-scale model experiments were conducted to examine the effectiveness of a point smoke exhaust system in an asymmetrical V-shaped tunnel. Using a design fire power of 20 MW as a reference, the study explored the optimal smoke exhaust rate for the point exhaust system in tunnels. Additionally, the impact of different slope combinations and various smoke vent opening configurations on the smoke control efficiency was analyzed when the fire source was positioned at the slope transition point of the V-shaped tunnel. The results indicate that an exhaust rate of approximately 140–160 m3/s is effective in controlling smoke for a 20 MW fire. In V-shaped tunnels, when three exhaust vents are symmetrically opened on both sides of the fire source, smoke diffusion on the large slope side remains uncontrolled. To address this issue, increasing the number of smoke exhaust vents on the large slope side can enhance smoke control. However, when the slope difference between the two sides of an asymmetrical V-shaped tunnel is excessively large—especially when the large side has a very high inclination—effective smoke control becomes significantly more challenging.