Fire behaviors along timber linings affixed to tunnel walls in mines.

Timber linings are applied as primary supports in the tunnel fault and fracture zones of mines. These linings are essential to prevent broken rock from falling during the occurrence of exogenous fires. In this study, experiments and numerical simulations were carried out using a fire dynamics simulator to investigate the flame-spread rate, flame characteristics, smoke movement, and spread process of timber-lining fires under different wind speeds of 0, 0.25, 0.5, and 0.75 m/s. It was found that cross-section flame spreading follows the three-stage sidewall-ceiling-sidewall pattern. Moreover, the average flame-spread rate increases along the vertical flame-spreading direction and decreases when the flame reaches the timber-lining corners. Moreover, the flame lengths underneath the timber-lining ceiling in the x-direction are longer than those in the y-direction. As the wind speed increases, the normalized flame lengths R(f) in the two directions decrease, and the maximum temperature underneath the ceiling decreases. In addition, the maximum temperature in the three tunnel sections of interest is first recorded in the tunnel cross-section in the initial fire stage. Higher wind speeds correspond to farther distances of the maximum-temperature points of the three timber-lining sections from the fire source.

Effect of triangular roof angle on dispersion of gaseous pollutants and particulate matter.

The Euler-Lagrangian method is adopted to simulate the dispersion of gaseous pollutants and particulate matter (PM) in isolated street canyons, and the influences of the roof angle on the flow structures and distributions of gaseous pollutants and PM are analyzed in detail. Numerical simulation results indicate that gaseous pollutants and PM in the canyons present three typical single main clockwise vortex, transition vortex, and double vortex structures, which are identified at increasing roof slopes. Gaseous pollutants and PM demonstrate the lowest concentration of pollutants when a single vortex structure exists. The concentration of gaseous pollutants and PM reaches the highest value in pedestrian-level areas when the flow field is in a transitional vortex structure. Unlike gaseous pollutants, the concentration of PM does not always decrease with increasing altitude, and higher PM concentrations sometimes occur in the mid-level areas of the canyon. A small roof incline angle is generally recommended for discharging gaseous pollutants and PM.

Numerical study of critical re-entrainment velocity of fire smoke within the street canyons with different building height ratios.

Traffic accident may bring vehicle fire in the street canyons. With its high temperature and numerous hazardous materials, the smoke produced by the vehicle fire may cause serious damage to the human body and the properties nearby, such as the glass curtain walls of buildings. The influence of the ambient air flow speed and street aspect ratio on the dispersion of fire smoke in street canyon has been analyzed by FDS software and theoretical analysis in this study. The impact of different windward building heights and different ambient air flow speeds u0 on the fire smoke were investigated. The results show that the fire smoke tilts towards the opposing direction of the ambient air flow within the street canyon, while the ambient air flow is perpendicular to the windward building. The results indicate that the critical re-entrainment velocity decreases at first, and then increases until it attains a constant with the building height ratio H1/H2. Finally, a predictive model of the critical re-entrainment velocity was developed under different building height ratios H1/H2.

Experimental study on fire smoke control using water mist curtain in channel.

The hazards of the spread of fire smoke in a channel have been recognized. This paper relates to the potential use of a water mist curtain (WMC) for preventing the spread of fire smoke, focusing particularly on smoke control at the early stage of a fire, with the aim of reducing the harm of fire smoke and allowing time for people to escape. Fatal factors for occupant evacuation in a fire, such as carbon monoxide concentration, smoke temperature, and visibility, were measured in the section controlled by the WMC. The results indicate that the WMC can be effective in preventing fire smoke from spreading at the early stage, and may provide a useful reference for developing a novel method of smoke control. Furthermore, the effects of nozzles with different spray characteristics were investigated and an optimal working pressure was suggested. In addition, a mathematical model was simplified and used to analyze the interaction between the fire-induced smoke layer and WMC spray.

Effects of oblique air flow on burning rates of square ethanol pool fires.

The effects of downward airflow on the burning rate and/or burning intensity of square alcohol pool fires for different airflow speeds and directions have been studied experimentally in an inclined wind tunnel. An interesting flame-wrapping phenomenon, caused by impingement of air flow, was observed. The mass burning intensity was found to increase with the airflow speed and the impinging angle. The fuel pan rim temperatures were also measured to study the effect of wind direction and speed on heat transfer from the flame to the fuel source. A model based on heat transfer analysis was developed to correlate the burning intensity with the pan rim characteristic temperature. A good correlation was established between the model results and the experimental results.