Experimental research on the mixture mechanism of polluted and fresh air at the portal of small-space road tunnels

Tan, Xianjun; Chen, Weizhong; Dai, Yonghao; Wu, Guojun; Yang, Jianping; Jia, Shanpo; Yu, Hongdan; Li, Fēi

doi:10.1016/j.tust.2015.07.009

Cited by 15 publications

(10 citation statements)

References 29 publications

(34 reference statements)

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“…Existing literature [13] has also shown that when uin = uout, for closely spaced twin tunnels with aligned inlet and outlet air tunnel portals, φc does not change with the change of air velocity value but is related to the ratio of uin and uout. Figure 10 shows the variation of φc with air velocity at the closely spaced twin tunnels with staggered inlet and outlet.…”

Section: The Relationship Between Circulating Air Mixing Ratio and Thmentioning

confidence: 97%

“…It shows that CFD simulation results are consistent with the trend of the test data, with a maximum error of only 5.2%. In addition to the above, this paper also used the scale model test results of the circulating air in closely spaced twin tunnels in the existing literature [13] Figure 6. Results show that change patterns are roughly consistent, with a maximum error of only 5.5%, which indicates that the mathematical model adopted by this paper In addition to the above, this paper also used the scale model test results of the circulating air in closely spaced twin tunnels in the existing literature [13] to verify the species transport model.…”

Section: Validationmentioning

confidence: 99%

“…In addition to the above, this paper also used the scale model test results of the circulating air in closely spaced twin tunnels in the existing literature [13] Figure 6. Results show that change patterns are roughly consistent, with a maximum error of only 5.5%, which indicates that the mathematical model adopted by this paper In addition to the above, this paper also used the scale model test results of the circulating air in closely spaced twin tunnels in the existing literature [13] to verify the species transport model. The scale model was 10-m long, and the section was a semicircle with a radius of 0.5 m. The lateral distance between the portals d = 4 m, and the front slope of the tunnel portal was perpendicular to the ground.…”

Section: Validationmentioning

confidence: 99%

“…They concluded that the mixed proportion of the polluted airflow could be reduced by increasing the outlet air velocity and lateral distance of the tunnel portals as well as decreasing the inlet air velocity. Through a model test, Tan et al [13] established a testing ventilation system of a close tunnel model and conducted a series of experiments. The results showed that when inlet and outlet airflow velocity were equal, the mixed volume of pollutants was barely influenced by the airflow velocity but would decrease with the increase of the tunnel spacing.…”

Section: Introductionmentioning

confidence: 99%

“…The circulating air can be effectively influenced by staggering the inlet and outlet air tunnel portals. For example, by increasing the length of outlet air tunnel portal and repositioning it at a point 5 m away from the inlet, the proportion of polluted airflow mixed with fresh airflow will be lower than 5% [13]. However, previous research mostly focused on closely spaced twin tunnels with aligned inlet and outlet air tunnel portals, and studies relating to the circulating air of the staggered inlet and outlet are still inadequate.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Research on the Mixture Mechanism of Polluted and Fresh Air at the Staggered Tunnel Portals

Zhang

Zhu

et al. 2018

Applied Sciences

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Abstract:In longitudinal ventilation, circulating air is formed in portals for closely spaced twin tunnels, which causes mixing between the polluted air exhausted from one tunnel and the fresh air flow of another tunnel, thus leading to the rising costs of ventilation system construction and operation. In this study, for the closely spaced tunnel with staggered inlet and outlet, the computational fluid dynamics (CFD) numerical simulation method was adopted to reveal flow characteristics of the circulating air as well as variation rules of the circulating air mixing ratio ϕ c with tunnel structure and operation parameters. Results show that both reducing inlet air velocity and increasing outlet air velocity and lateral distance can reduce the impact of the negative-pressure zone at the tunnel entrance on the jet flow structure at the tunnel exit, thus weakening the circulating air. When the inlet is placed behind or aligned with the outlet (staggered distance ∆l ≤ 0), ϕ c will increase linearly along with the increase of staggered distance; when the inlet is placed before the outlet (∆l > 0), ϕ c will first increase and then decrease with the increase of staggered distance. An expression to predict circulating air mixing ratio was created by sections. The predictions show a good correlation with the measurements and indicate that the front slope gradient of the tunnel portal is also one of the factors affecting the circulating air mixing ratio.

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Section: The Relationship Between Circulating Air Mixing Ratio and Thmentioning

confidence: 97%

Section: Validationmentioning

confidence: 99%