Reduced-scale experimental and numerical study of fire in a hybrid ventilation system in a large underground subway depot with superstructures under fire scenario

Abstract To reduce energy consumption and improve the safety and reliability of ventilation systems in underground subway depots, a hybrid ventilation (HV) system composed of natural ventilation, mechanical fans, and flow deflectors was proposed and tested. A reduced-scale (1:50) experiment and a full-scale numerical simulation were conducted, wherein four heat release rates (HRRs; 281 W, 380 W, 531 W, and 866 W) of the fire source and five ventilation velocities (0.7 m/s, 1.0 m/s, 1.4 m/s, 1.9 m/s, and 2.4 m/s) were tested. The temperature distributions under the ceiling were measured. Smoke movement and smoke layer stability were visualized using a laser sheet. The smoke layer height, gas flux of shafts, and smoke movement route were recorded from the simulation. Under HV, the ceiling temperature decreased significantly with increasing ventilation velocity; however, changes in temperature were different at different locations. With appropriate ventilation velocity (1.4 m/s), HV effectively controlled the smoke temperature of the bottom layer and ensured the stability of the smoke layer in the interlayer. However, the stability of the smoke layer was disrupted at higher ventilation velocities, which caused the smoke to sink, whereas a lower velocity could not slow the rise in temperature. The relationship among ventilation velocity, HRR, ceiling temperature, and smoke layer stability was analysed. A new criterion, N (N = 0.62), was proposed to determine the critical ventilation velocity associated with a lower ceiling temperature and improved smoke layer stability.

[1]  Angui Li,et al.  Fire-induced smoke control via hybrid ventilation in a huge transit terminal subway station , 2012 .

[2]  Wan Ki Chow,et al.  Scale modeling studies on stack effect in tall vertical shafts , 2011 .

[3]  Jie Ji,et al.  A study of the effect of plug-holing and boundary layer separation on natural ventilation with vertical shaft in urban road tunnel fires , 2012 .

[4]  Shen-Wen Chien,et al.  Smoke Control of Fires in Subway Stations , 2003 .

[5]  Angui Li,et al.  Prediction of the spread of smoke in a huge transit terminal subway station under six different fire scenarios , 2012 .

[6]  Ping Jiang,et al.  Effects of cross air flow on mass loss rates of circular aviation fuel pool fires in large open space , 2013 .

[7]  C. K. Chan,et al.  Numerical simulation of the spread of smoke in an atrium under fire scenario , 2009 .

[8]  F. Plourde,et al.  Smoke spreading analysis from an experimental subway scale model , 2016 .

[9]  Siuming Lo,et al.  Influence of fire power and window position on smoke movement mechanisms and temperature distribution in an emergency staircase , 2014 .

[10]  Olivier Vauquelin,et al.  Definition and experimental evaluation of the smoke "confinement velocity" in tunnel fires , 2005 .

[11]  Bo Lei,et al.  Experimental and Theoretical Study for Tunnel Fires with Natural Ventilation , 2013, Fire Technology.

[12]  Wei Tang,et al.  Numerical study on the optimization of smoke ventilation mode at the conjunction area between tunnel track and platform in emergency of a train fire at subway station , 2014 .

[13]  H. Sanada,et al.  Excavation cycle times recorded during sinking of a deep shaft in crystalline rock – A case example at Ventilation Shaft of Mizunami URL, Japan , 2015 .

[14]  C. K. Chan,et al.  Numerical simulations on fire spread and smoke movement in an underground car park , 2007 .

[15]  Jie Ji,et al.  A simplified calculation method on maximum smoke temperature under the ceiling in subway station fires , 2011 .

[16]  J. Viegas.  The use of impulse ventilation for smoke control in underground car parks , 2010 .

[17]  Longhua Hu,et al.  Characterization of buoyant flow stratification behaviors by Richardson (Froude) number in a tunnel fire with complex combination of longitudinal ventilation and ceiling extraction , 2017 .

[18]  Futoshi Tanaka,et al.  Performance validation of a hybrid ventilation strategy comprising longitudinal and point ventilation by a fire experiment using a model-scale tunnel , 2015 .

[19]  Xu-hai Pan,et al.  Feasibility analysis on natural ventilation scheme for large underground spaces based on the top cover design , 2014 .

[20]  Wei Zhang,et al.  Performance of smoke elimination and confinement with modified hybrid ventilation for subway station , 2014 .

[21]  Bin Zhou,et al.  Study on pollution control in residential kitchen based on the push-pull ventilation system , 2016 .

[22]  Yasushi Oka,et al.  Ceiling-jet thickness and vertical distribution along flat-ceilinged horizontal tunnel with natural ventilation , 2016 .

[23]  H. Awbi.  Ventilation of buildings , 1873 .

[24]  Jie Ji,et al.  Large Eddy Simulation of stack effect on natural smoke exhausting effect in urban road tunnel fires , 2013 .

[25]  Olivier Vauquelin,et al.  Experimental simulations of fire-induced smoke control in tunnels using an “air–helium reduced scale model”: Principle, limitations, results and future , 2008 .

[26]  B. P. Kazakov,et al.  Stability of natural ventilation mode after main fan stoppage , 2015 .

[27]  Lizhong Yang,et al.  Vertical temperature distributions in ventilation shafts during a fire , 2016 .

[28]  Kaiyuan Li,et al.  Study on air entrainment coefficient of one-dimensional horizontal movement stage of tunnel fire smoke in top central exhaust , 2016 .