Numerical Simulation Of Vehicle Exhaust Pollutants And Fire Smoke Diffusion In Kaiyuan Tunnel

In recent years,with the continuous advancement of urban modernization construction,urban traffic congestion has become a common phenomenon,and more and more cities have begun to build urban tunnels to improve urban traffic problems.Due to its special building structure,the internal pollutants are not easy to spread.Once the concentration reaches a certain amount,it will pose a threat to the physical and mental health of the passing personnel.The daily traffic volume of Jinan City Tourist Road is very large.The Kaiyuan Tunnel,as the "throat" of the tourist road,often has congestion at the peak period,causing the concentration of pollutants in the tunnel to rise sharply and the accident rate to increase,posing a safety hazard.Taking the representative Kaiyuan tunnel in Jinan as an example,this paper uses numerical simulation method to clarify the diffusion law of pollutants in tunnels under different driving conditions and different traffic conditions.The research results of the thesis have important reference value for the traffic operation of general tunnels and the emergency handling of sudden accidents in tunnels.Firstly,the feasibility of the numerical simulation method used in this study was verified by comparing the numerical simulation results with the wind tunnel test data.The numerical simulation study on the driving of the vehicles in the Kaiyuan tunnel shows that the pedestrians in the tunnel are greatly affected by the medium and large vehicles driving on the outermost lane,which is almost unaffected by the driving of the small car.Therefore,it is recommended to reduce the outermost lanes appropriately.The number of medium and large vehicles.In addition,the diffusion law of CO in the exhaust pollutants of vehicles is analyzed.Compared with the non-tunnel environment,the existence of the tunnel wall hinders the dilution of CO by the lateral air flow.In the tunnel,CO's concentration is 60PPM higher than that outside the tunnel;the CO concentration in the tunnel has exceeded 50PPM,which is harmful to pedestrian health.Standards,so the exposure time of personnel in the tunnel should be strictly limited to a safe range.After that,the traffic volume of the Kaiyuan tunnel was investigated.It was found that the normal hour traffic volume of the Kaiyuan tunnel was 1252 veh/h,and the peak hour traffic volume was 2260 veh/h.Using the measured traffic volume,the CO emission of the Kaiyuan tunnel during the peak period was calculated to be 0.0077m3/s and the particulate matter emission was 0.0438m3/s.According to the standard of dilution of CO and particulate matter,the required air volume at this time is 67.655m3/s and 5.84m3/s,and the larger value of 50.25 m3/s is taken as the required air volume of the tunnel.The jet fan model is simplified.On the basis of this,the ventilation in the front,middle and back sections of the tunnel is simulated.The average pressure rise of the tunnel exit section of the jet fan is compared with the lateral clearance of the jet fan from 1 to 5.5 m.It is the most efficient boosting solution between 2 and 2.5 m.The diffusion law of pollutants in the exit section of the tunnel during the peak period is simulated,and the dilution effect of natural ventilation and mechanical ventilation on the exhaust pollutants of the motor vehicle is compared.It is concluded that if the fan spacing is less than 20m when the fan is not turned on,When the waiting time reaches 20s,the exhaust pollutants of the vehicle will spread to the preceding vehicle,which will cause harm to the physical and mental health of the driver of the preceding vehicle.After that,the traffic volume of the Kaiyuan Tunnel was investigated,and the number of different models during the normal hours and peak hours was counted.Using the measured traffic volume,the tunnel ventilation demand in the peak period is calculated according to the standard of diluted particulate matter concentration and CO concentration,and the larger value of the two is taken as the required air volume of the tunnel.The jet fan model is simplified.On the basis of this,the ventilation in the front,middle and back sections of the tunnel is simulated.The average boost of the tunnel exit section under the lateral clearance of different jet fans is compared,and the jet fan clearance with the highest boosting efficiency is found.The diffusion law of pollutants in the tunnel exit section during the peak period is simulated,and the dilution effect of natural ventilation and mechanical ventilation on vehicle exhaust pollutants is compared,and the time when the pollutants are diluted to a safe degree after the jet fan is turned on is obtained.Finally,the paper also simulates the diffusion law of high temperature flue gas inside the tunnel caused by the sudden accident of Kaiyuan Tunnel,and compares with the data of foreign tunnel fire test,which verifies the validity of the numerical method of this study.On this basis,the critical wind speed values of 5MW,20MW and 50MW fires in the front,middle and back sections of the tunnel were obtained by numerical simulation,which were 1.451m/s,2.165m/s and 2.715m/s respectively.The difference between the numerical simulation results and the empirical formula calculation results is analyzed,and the results calculated by the empirical formula for the curve tunnel are found to be small.The safety situation of personnel escape under different longitudinal wind speeds in the 5MW,20MW and 50MW fires on the congested sections of the tunnel exit is studied.The simulation results show that when a small fire of 5MW occurs,personnel can escape safely.When a medium-sized fire of 20MW and 50MW occurs,if the person is within 15m of the fire position,more than 3min,the safety condition will be affected when the escape occurs.It is also concluded that after the medium-sized fire occurs,the escape safety of the personnel will not be affected after the jet fan is turned on for 5 minutes,so the jet fan should not be turned on immediately when the fire occurs.