Experimental and theoretical study of the smoke back-layering length in a tunnel with cross-passage: effects of longitudinal fire source locations

Abstract

The diversion effect caused by the linked structure in a metro tunnel with cross-passage complicates the impact of longitudinal fire source location on the smoke backflow layering behavior that has not been clarified, despite the fact that the scenario exists in practice. A series of laboratory-scale experiments were conducted in this study to investigate the smoke back-layering length in a model tunnel with cross-passage. The heat release rate, the velocity of longitudinal air flow, and the location of the fire source were all varied. It was found that the behavior of smoke backflow for the fire source located at the upstream of bifurcation point resembles a single-hole tunnel fire. As the fire source’s position shifts downstream from the bifurcation point, the length of smoke back-layering progressively increases. A competitive interaction exists between airflow diversion and smoke diversion during smoke backflow, significantly affecting the smoke back-layering length in the main tunnel. The dimensionless smoke back-layering length model was formulated in a tunnel featuring a cross-passage, taking into account the positions of longitudinal fire sources. The dimensionless smoke back-layering length exhibits a positive correlation with the 17/18 power of total heat release rate Q and a negative correlation with the 5/2 power of longitudinal ventilation velocity V.

Keywords

Tunnel fire / Cross-passage / Smoke back-layering length / Fire source location / Longitudinal ventilation

References

[1] LongZ, LiuC, YangY, et al. . Full-scale experimental study on fire-induced smoke movement and control in an underground double-island subway station. Tunn Undergr Sp Technol, 2020, 103: 103508.

[2] QiuP, LongZ, LiuC, et al. . Full-scale experiment on smoke propagation in metro station tunnel fire under opening the platform screen doors. Tunn Undergr Sp Technol, 2021, 107: 103662.

[3] LiuC, ZhongM, TianX, et al. . Experimental and numerical study on fire-induced smoke temperature in connected area of metro tunnel under natural ventilation. Int J Therm Sci, 2019, 138: 84-97.

[4] ThomasPH. The movement of smoke in horizontal passages against an air flow. Fire Saf Sci, 1968, 723: 1-10

[5] VantelonJPA, GuelzimDQ, SomDK, et al. . Investigation of fire-induced smoke movement in tunnels and stations: an application to the Paris Metro. Fire Saf Sci, 1991, 3: 907-918.

[6] Deberteix P, Gabay D, Blay D (2001) Experimental study of five-induced smoke propagation in a tunnel in the presence of longitudinal ventilation. In: Proceedings of the International Conference on Tunnel fires and Escape from Tunnels, Boras, pp 257–265

[7] HuL, PengW, HuoR. Critical wind velocity for arresting upwind gas and smoke dispersion induced by near-wall fire in a road tunnel. J Hazard Mater, 2008, 150: 68-75.

[8] LiY, LeiB, IngasonH. Study of critical velocity and back-layering length in longitudinally ventilated tunnel fires. Fire Saf J, 2010, 45: 361-370.

[9] ChowWK, GaoY, ZhaoJ, et al. . Smoke movement in tilted tunnel fires with longitudinal ventilation. Fire Saf J, 2015, 75: 14-22.

[10] LiuY, FangZ, TangZ, et al. . Analysis of experimental data on the effect of fire source elevation on fire and smoke dynamics and the critical velocity in a tunnel with longitudinal ventilation. Fire Saf J, 2020, 114: 103002.

[11] ZhangT, WangG, LiJ, et al. . Experimental study of back-layering length and critical velocity in longitudinally ventilated tunnel fire with various rectangular cross-sections. Fire Saf J, 2021, 126: 103483.

[12] YanG, WangM, YuL, et al. . Effects of ambient pressure on the critical velocity and back-layering length in longitudinal ventilated tunnel fire. Indoor Built Environ, 2019, 29: 1017-1027.

[13] GuoF, GaoZ, WanH, et al. . Influence of ambient pressure on critical ventilation velocity and back-layering distance of thermal driven smoke in tunnels with longitudinal ventilation. Int J Therm Sci, 2019, 145: 105989.

[14] LiuC, ZhongM, LongZ, et al. . Experimental and numerical study on critical ventilation velocity for confining fire smoke in metro connected tunnel. Tunn Undergr Sp Technol, 2020, 97: 103296.

[15] HuangY, LiY, LiJ, et al. . Experimental investigation of the thermal back-layering length in a branched tunnel fire under longitudinal ventilation. Int J Therm Sci, 2022, 173: 107415.

[16] YangX, LuoY, LiZ, et al. . Experimental investigation on the smoke back-layering length in a branched tunnel fire considering different longitudinal ventilations and fire locations. Case Stud Therm Eng, 2021, 28: 101497.

[17] HuL, HuoR, ChowWK. Studies on buoyancy-driven back-layering flow in tunnel fires. Exp Therm Fluid Sci, 2008, 32: 1468-1483.

[18] HuL, HuoR, ChowWK, et al. . Decay of buoyant smoke layer temperature along the longitudinal direction in tunnel fires. J Appl Fire Sci, 2005, 13: 53-77.

[19] LiZ, GaoY, LiX, et al. . Effects of transverse fire locations on flame length and temperature distribution in a bifurcated tunnel fire. Tunn Undergr Sp Technol, 2021, 112: 103893.

[20] FanW, WangQ, JiangF, et al. Concise tutorial of fire science, 1995HefeiChina University of Science and Technology Press

[21] WangY, SunX, LiuS, et al. . Simulation of back-layering length in tunnel fire with vertical shafts. Appl Therm Eng, 2016, 109: 344-351.

[22] HeL, XuZ, ChenH, et al. . Analysis of entrainment phenomenon near mechanical exhaust vent and a prediction model for smoke temperature in tunnel fire. Tunn Undergr Sp Technol, 2018, 80: 143-150.

[23] LiY, LeiB, IngasonH. The maximum temperature of buoyancy-driven smoke flow beneath the ceiling in tunnel fires. Fire Saf J, 2011, 46: 204-210.

[24] HuangY, LiY, LiJ, et al. . Experimental investigation on maximum gas temperature beneath the ceiling in a branched tunnel fire. Int J Therm Sci, 2019, 145: 105997.

[25] VauquelinO, WuY. Influence of tunnel width on longitudinal smoke control. Fire Saf J, 2006, 41: 420-426.

[26] ChenL, HuL, TangW, et al. . Studies on buoyancy driven two-directional smoke flow layering length with combination of point extraction and longitudinal ventilation in tunnel fires. Fire Saf J, 2013, 59: 94-101.

[27] TangF, LiL, MeiF, et al. . Thermal smoke back-layering flow length with ceiling extraction at upstream side of fire source in a longitudinal ventilated tunnel. Appl Therm Eng, 2016, 106: 125-130.

[28] HinkleyPL. The flow of hot gases along an enclosed shopping mall a tentative theory. Fire Saf Sci, 1970, 807: 1-10

[29] HuL, HuoR, WangH, et al. . Experimental and numerical studies on longitudinal smoke temperature distribution upstream and downstream from the fire in a road tunnel. J Fire Sci, 2007, 25: 23-43.

[30] DuT, YangD, DingY. Driving force for preventing smoke back-layering in downhill tunnel fires using forced longitudinal ventilation. Tunn Undergr Sp Technol, 2018, 79: 76-82.

[31] BassettMD, WinterboneDE, PearsonRJ. Calculation of steady flow pressure loss coefficients for pipe junctions. Proc Inst Mech Eng C J Mech Eng Sci, 2001, 215: 861-881.

[32] LiZ, LuoY, GaoY, et al. . Experimental and theoretical studies of the effects of fire location on the smoke temperature distribution in a branched tunnel. Fire Technol, 2021, 58: 1265-1284.

[33] LiZ, ZhangY, JiangH, et al. . Effect of fire source elevation on the smoke spreading characteristics in an extra-long tunnel. Fire Technol, 2022, 6021313-1332.

[34] GannouniS. Critical velocity for preventing thermal back-layering flow in tunnel fire using longitudinal ventilation system: effect of floor-fire separation distance. Int J Therm Sci, 2022, 171: 107192.

[35] LiH, TangF. Numerical and experimental study on the critical velocity and smoke maximum temperature in the connected area of branch tunnel. Build Simul, 2021, 15: 525-536.

[36] LiY, IngasonH. The maximum ceiling gas temperature in a large tunnel fire. Fire Saf J, 2012, 48: 38-48.

Funding

National Natural Science Foundation of China(52278415)

National Key Research and Development Program of China(2022YFC3801104)

Innovation Fund Project of Hebei University of Engineering(SJ2401002066)

Sichuan Science and Technology Program(2023YFS0407)

Hebei Provincial Department of Education Project(QN2025304)

RIGHTS & PERMISSIONS

The Author(s)