Experiment And Numerical Simulation Research On Fire Ventilation In Underground Road Tunnel

With the rapid economic development and the urbanization in China, traffic has becomea conspicuous problem in metropolis. Urban underground road has advantages of both viaductand subway, it improves the quality of urban environment and urban life, also solve the trafficcongestion. Besides, the underground road has little influence to urban buildings. But the riskof tunnel fires cannot be ignored, so the research on underground road tunnel fires isimportant for safety.This thesis introduced the main underground road tunnels at home and abroad anddiscussed the methods and current researches about tunnel fires. Numerical simulation andexperimental method were used to study tunnel fires in this thesis. Aim at the project ofunderground road tunnel of east2ed ring road in Beijing, a series of full-scale tunnel fire testswere completed in an experimental tunnel in Tongzhou Area of Beijing. Temperaturedistribution near the fire and smoke settlement times downstream the tunnel under differentlongitudinal velocities were obtained. The experimental results showed that the verticaltemperature stratification were obvious on the same section and the temperature rising rates athigher positions were greater than those at lower positions in the fire developing stage. It wasalso showed that the relation between smoke settlement height and time was almost linear.The greater longitudinal velocity contributed to reducing the temperature in tunnel，but couldimprove the smoke settlement downstream the tunnel. Numerical simulations were carried outby using ANSYS CFX and reliability of the CFD simulation was validated.Physical model of the underground road tunnel of east2ed ring road was established andits critical velocity of20MW heat release rate under longitudinal ventilation system wassimulated. Three kinds of exhaust valves with different size were designed, and their smokeexhaust effects under central smoke extraction system were carried out by CFD simulation.The results showed the exhaust valve with larger opening had a better exhaust effect. Thetemperature distribution and smoke concentration distribution under longitudinal ventilationwith critical velocity and central smoke extraction system with different valve openings werecarried out respectively by CFD simulation. The results showed that the smoke spreadingdistance under the longitudinal ventilation was longer and the temperature at1.6m high in themain area downstream the tunnel was more than60℃which was defined as the safetytemperature limit. So the longitudinal ventilation system was not beneficial to personnelevacuation downstream the tunnel. When the distance and opening of the valves were fixed,the smoke spreading distance increased with the increasing of open number of smoke exhaust valves under bidirectional central smoke extraction system. When2or4exhaust valves nearthe fire source were opened, smoke temperature higher than60℃area were controlled within140m and the smoke spreading distance was short.