A Study on the Behavior Characteristics of Air Supply during Tunnel Fires under Natural Ventilation with Multiple Vertical Shafts
Abstract
:1. Introduction
2. Theoretical Analysis
3. Numerical Simulation
3.1. Fire Scenarios
3.2. Grid Independence Analysis
4. Results and Interpretation
4.1. Smoke Spread Characteristics under Natural Ventilation Using Multiple Vertical Shafts
4.2. Factors Influencing Smoke/Air Mass Flow Rate in Vertical Shafts
4.3. Prediction of Air Supply Mass Flow Rate for Natural Smoke Extraction with Multiple Vertical Shafts
5. Conclusions
- (1)
- In a multi-shaft ventilation tunnel during a fire, certain shafts are responsible for smoke extraction, while other shafts and tunnel portals not involved in smoke removal provide an air supply. The air supply mass flow rate in the shafts is impacted by various factors, including shaft dimensions and the overall tunnel structure.
- (2)
- The mass flow rates of smoke exhaust and air supply increase as the HRR rises. A slower growth rate of the fire source results in a longer duration of air supply and a lower maximum mass flow rate. Additionally, shafts with larger cross-sectional areas or greater heights demonstrate higher smoke extraction capacities, thus requiring a greater air supply.
- (3)
- Each shaft and tunnel portal has an inflow air supply mass flow rate that matches the discharge rate of hot smoke. The magnitude of inflow air supply in each shaft is determined by its proximity to the fire source. The proposed predictive model, developed based on the ventilation network theory, accurately estimates natural smoke extraction in multi-shaft setups, with its estimates aligning with the numerical simulation outcomes.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Nomenclature
mass flow rate (kg/s) | |
mass flow rate of smoke exhaust (kg/s) | |
mass flow rate of air supply (kg/s) | |
ventilation resistance (kg/(s·m4)) | |
pressure drop (Pa) | |
length (m) | |
perimeter of tunnel cross section (m) | |
heat release rate (MW) | |
gravitational acceleration (m/s2) | |
tunnel cross-sectional area (m2) | |
density (kg/m3) | |
diameter of fire source (m) | |
temperature (K) | |
isobaric heat capacity (kJ/(kg·K)) | |
λ | coefficient of resistance along the course |
ξ | coefficient of local resistance loss |
SUBSCRIPT | |
1~5 | serial number of vertical shafts |
0 | tunnel portal |
F | frictional resistance |
L | local resistance |
∞ | ambient |
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No. | HRR (MW) | Ramp-Up Time (s) | Sizes of Shafts: Height (m) × Length (m) |
---|---|---|---|
1–3 | 1, 2, 5 | 0 | 6 × 6 |
4–5 | 5 | 0, 325 | 6 × 6 |
6–10 | 5 | 0 | 3 × 2 3 × 4 3 × 6 6 × 6 9 × 6 |
HRR (MW) | D* | D*/D |
---|---|---|
1 | 0.959027 | 7.672216 |
2 | 1.265443 | 10.123549 |
5 | 1.825655 | 14.605244 |
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He, L.; Ming, Y.; Liao, K.; Zhang, H.; Jia, C.; Zhu, G.; Tao, H. A Study on the Behavior Characteristics of Air Supply during Tunnel Fires under Natural Ventilation with Multiple Vertical Shafts. Fire 2023, 6, 393. https://doi.org/10.3390/fire6100393
He L, Ming Y, Liao K, Zhang H, Jia C, Zhu G, Tao H. A Study on the Behavior Characteristics of Air Supply during Tunnel Fires under Natural Ventilation with Multiple Vertical Shafts. Fire. 2023; 6(10):393. https://doi.org/10.3390/fire6100393
Chicago/Turabian StyleHe, Lu, Yuyang Ming, Ke Liao, Haojun Zhang, Chenhao Jia, Guoqing Zhu, and Haowen Tao. 2023. "A Study on the Behavior Characteristics of Air Supply during Tunnel Fires under Natural Ventilation with Multiple Vertical Shafts" Fire 6, no. 10: 393. https://doi.org/10.3390/fire6100393
APA StyleHe, L., Ming, Y., Liao, K., Zhang, H., Jia, C., Zhu, G., & Tao, H. (2023). A Study on the Behavior Characteristics of Air Supply during Tunnel Fires under Natural Ventilation with Multiple Vertical Shafts. Fire, 6(10), 393. https://doi.org/10.3390/fire6100393