高海拔隧道施工自卸车CO扩散规律

Numerical Simulation on CO Diffusion in Exhaust Pipe Discharge Process of Dump Trucks in High Altitude Tunnel

为定量分析高海拔隧道出渣过程中自卸车CO排放对施工环境的影响,针对自卸车底部、侧部、尾部安装排气管三种CO排放方式,基于Fluent软件,采用RNGk-ε湍流模型,选取Species Transport模型模拟CO与空气的耦合作用,考虑高海拔低气压和空气密度的影响,运用动网格及用户自定义函数(UDF),模拟自卸车体行驶过程中隧道气流三维速度场、CO浓度场,基于现场实测数据验证模拟结果。结果表明:相同行驶工况下,隧道断面越大,CO沿途扩散越快,较高的CO浓度主要出现在车体高度以下区域;三种排气管中,侧部排气管最有利于沿途CO扩散。自卸车排气管轴向CO浓度的沿途扩散符合e指数衰减规律,根据一维扩散理论,提出CO浓度累积预测计算式。

To quantitatively analyze the impact of CO emission from dump trucks on the construction environment during the slagging process in high altitude tunnel,in response to the three CO emission modes resulted from the installation of exhaust nozzle in the bottom,side and tail of the dump trucks,based on Fluent software and the RNG k-ε turbulence model,the Species Transport model was selected to simulate the coupling of CO and air.Considering the effect of high altitude pressure and air density,the dynamic mesh and User-defined Functions ( UDF) were used to simulate the three-dimensional velocity field and CO concentration field of tunnel airflow during the driving process of dump trucks.The simulation results were verified based on field measured data.The results show that under the same driving conditions,the greater cross-sectional area of the tunnel,the faster the CO emission.The higher CO concentration mainly occurs in the area below the height of the dump truck.Among the three exhaust pipes,the lateral exhaust pipe is most advantageous to the CO diffusion.The attenuation of the axial CO concentration of the exhaust pipe conforms to the e exponential attenuation,based on the one-dimensional diffusion theory,the CO concentration cumulative prediction formula is proposed.