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Summary: In more and more tunnels, natural ventilation mode with vertical shafts has been gradually employed. However, there are few studies investigating the influences of fire and shaft positions on natural ventilation performance currently. Therefore, this study investigated the effects of the transverse distance from fire source to tunnel sidewall, the longitudinal distance from fire source to shaft, and the transverse distance from shaft to sidewall on natural ventilation effectiveness in a tunnel fire by using Fire Dynamics Simulator. The typical characteristic parameters of smoke, such as mass flow rate, temperature distribution, and velocity vector were analyzed; besides, the phenomenon of plug‐holing was discussed. The results have shown that the mass flow rate of gas exhausted by the shaft decreases slightly with the increase of longitudinal distance from fire source to shaft. When the longitudinal distance from fire source to shaft is constant, changing the transverse distance from shaft to sidewall will have a more obvious effect on the effectiveness of exhausting smoke than changing the transverse distance from fire source to sidewall; in addition, the phenomenon of plug‐holing is more serious when the shaft is close to the sidewall. [ABSTRACT FROM AUTHOR]

A computational model is developed to estimate the heat release rate and fuel type of circular pool fires by analyzing the videos with recognizable flames. The model can be used in both static and mobile platforms. The pool diameter, mean flame height, heat release rate and fuel type are estimated using image recognition technique on flame videos and inverse modelling with traditional fire dynamics theories. A set of experimental videos from different sources are used to validate the model. During image recognition, the model isolates the flame from the non-flame elements in each frame using the "automatic seed placement and region growing" method. The method is found to be effective in non-flame elements removal and improves the flexibility of the model to wide range of flame videos. To automatically determine the pool diameter, fast Fourier transform (FFT) is involved to identify the flame pulsation frequency that is used as the input of inverse modelling. It is found that a sampling duration of 10 s to 20 s gives the most reliable predictions to the flame pulsation frequency for the current set of videos. A shorter duration is not sufficient for FFT to recognize the correct main frequency of the signal while a longer duration increases the low frequency components caused by the unsteady flame. Compared to the traditional fire dynamics theories with power indexes of input variables less than 1, the inverse modelling enlarges the error in the modelling results. Therefore, the main weakness of current model is perhaps the enlarged uncertainty led by the inverse modelling conducted with the traditional theories which are empirical, although the current predictions to the experiments are acceptable. Moreover, the current model divides the pool fires into three categories and based on the predicted pool diameter and heat release rate the fuel type can be estimated, which might benefit the hazard analysis in certain circumstances. Finally, a cross-platform comparison shows that the mobile devices can be considered for fire applications although it is still less powerful than personal computers. [ABSTRACT FROM AUTHOR]

This paper investigates the temperature profile of large scale RP – 5 aviation kerosene pool fire in an open space through a series of large scale experiments of 1 m2, 5 m2, 10 m2, 25 m2 pool sizes. The temperature profile is acquired by thermocouple trees positioned in various distances to the pool centerline, while the ambient wind velocity is captured by four transducers in the experimental field. Results show that the large scale pool fire behaves different to the used small to medium scale experiments. The mass loss rate is in good agreement with Blinov and Khudyakov's results, but the vertical temperature is much lower than the McCaffery's results due to the reduced global combustion efficiency as more sooty smoke produced. The three regimes in McCaffery's model is redefined, correlating well with the vertical temperature profile upon the pool centerline. Gaussian Fit is well proposed for the lateral temperature profile at the pool base level, however as the ambient wind inevitable, the fire plume would be tilted to the downstream direction. Finally, the isothermal diagrams of fire plume for various pool sizes are plotted showing the temperature field of plumes, and also the tilt angle of plumes is presented. [ABSTRACT FROM AUTHOR]