Due to constraints imposed by geological and
topographical conditions, urban long-distance
immersed tunnel projects may exist structural characteristics with multiple
slopes forming a W shape, without the installation of wind towers. For such
urban tunnels without wind towers, their opening strategy of fans and pollutant
distribution patterns need to be further studied. In this paper, numerical
simulation is employed, mainly considering different segments with obstruction
(entrance section, middle section, exit section, and full blockage) and varying
numbers of fans (3, 5, 6, and 7 groups) being activated, to investigate the
flow field and pollutant distribution patterns. The results indicate that:
(1)The ceiling tunnel wind speed inside the tunnel increases with the growing
number of activated fans. (2)When considering blockages, it becomes evident
that the obstructed section exerts a more pronounced impact on the flow field
distribution within the expanding fan jet region. The increase in the number of
tunnel fans has a minor impact on the pollutant concentration in the obstructed
segment, primarily affecting the pollutant concentration in the non-obstructed segment. Fans located at the slope change point in the
center of the tunnel have limited effects on the distribution of the flow field
inside the tunnel and the dilution of CO pollutants; This is because the jet is
prematurely impinged on the tunnel wall due to the influence of slope changes,
affecting the jet′s development. (4)Accumulation of
pollutants is anticipated in the latter portion of the tunnel, suggesting the
need to contemplate the incorporation of supplementary jet fans within this
segment during the design. (5)After comprehensively analyzing the exported CO
concentration of similar projects, it was found that the design criteria for CO
concentration adopted in the current domestic specifications are conservative,
which can lead to a waste of resources.
TANG Honghui, WEI Lixin, XU Zhisheng, ZHAO Jiaming, YU Zihan, WANG Juan, XIE Yiqiang
. Opening Strategy of Middle
and Long Distance Immersed Tunnel Ventilation Fans in Urban Areas and Distribution Pattern of Pollutants[J]. Tunnel Construction, 2024
, 44(S1)
: 71
-81
.
DOI: 10.3973/j.issn.2096-4498.2024.S1.008
