Analysis of Ventilating Network for an Urban Underground Road with Multi-point Entry and Exit

Due to the existence of the converging intersections and diverging intersections, the urban underground road of multi-point entry and exit can show complicated forms in the air flow rate and smoke movement in a comparison with the underground road with single-point entry and exit. In this paper, the strategies of original ventilating and exhausting smoke of a certain urban underground of multi-point entry and exit road were simulated and evaluated by using ventilation simulation software IDA RTV. The partial ventilation scheme where the number of fans was reduced was analyzed. The running strategy of fans in the tunnel under three conditions was determined. And the influence of the fans in ramp tunnel on the wind speed of main road was studied. Results indicate that when exhausting smoke in branch section, The mode of operation where jet fan in the section is fully operated is unreasonable, which would lead to excessive wind speed downstream of the shaft. The running of the ramp fan has a certain influence on the wind speed of the main tunnel. In the ventilation and smoke control design, the ramp position and the operating mode of the ramp fan should be fully considered. Operating fans downstream of the shaft reversely can exhaust smoke more effectively. The results provide the theoretical basis for the ventilation and exhaust design of other complicated underground roads.