Abstract: The computational fluid dynamics (CFD) method is used to simulate the influence of the emergency exhaust pipe on the gas component mixing inside the main chimney. The coefficient of variation (COV) of velocity and tracer gas concentration are used to represent the mixing uniformity on each surface. Three typical working conditions were compared and studied, namely high wind speed (about 13.1 m/s), medium wind speed (about 8.2 m/s) and low wind speed (about 0.56 m/s). The results show that when the wind speed is 13.1 m/s and there is no internal pipe, the distribution of velocity and gas concentration is more uniform, and the COV values on each surface are reduced by 2.8% and 2.0% respectively; When the wind speed is 8.2 m/s and there is no internal pipe, it is conducive to the uniform distribution of velocity (COV value decreases by 1.5%), but reduces the mixing uniformity of gas components (COV value increases by 3.1%); When the wind speed is 0.56 m/s and there is no emergency exhaust pipe, the velocity and gas components show better mixing uniformity, and the COV values are reduced by 4.8% and 0.02% respectively. Comparing the simulation results with experimental data, more than 92.5% of the simulation data has a deviation of less than 15% from the experimental values.

Key words: computational fluid dynamics, internal structure of chimney, gas mixing uniformity