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The alpha cup method was employed to delineate spontaneous combustion areas in three coal mines. Following this, cores were drilled to measure radon concentration at various depths using the RAD7 radon detector. Subsequently, the results were then combined with the equation of radon concentration distribution with depth in a semi-infinite medium, demonstrating the equation's suitability for shallow coal seams. Thereafter, numerical models of radon migration were constructed. The study found that the upward migration of radon is weakened and adsorbed by rock formations, and faults, altering the migration path of radon. [ABSTRACT FROM AUTHOR]

Traditional video surveillance, temperature-based or smoke-based fire source location methods are difficult to timely and accurately locate the fire source in warehouses with the characteristics of burning intensely, smoke spreading quickly, and being sheltered by shelves and goods. To overcome the drawbacks, a deep-learning-based fire source localization algorithm with temperature and smoke sensor data fusion according to the different stages of the combustion process is proposed in this paper. The temperature and smoke concentration information are collected from sensors distributed in different spatial locations of a warehouse. A convolutional neural network is used to exact the fusion data feature. The deep learning algorithm is adopted to construct the fire source localization model where the fusion data feature of temperature and smoke concentrations are the inputs and the fire source coordinates are the outputs. By using Fire Dynamics Simulator, a warehouse that meets the practical application is constructed and kinds of fire scenes are simulated. The experimental results show that the RMSE of the model localization reaches 0.63, 0.08, and 0.17 in three stages respectively, which verifies the effectiveness of the proposed fire source localization algorithm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigated the fuel combustion behavior inside a compartment. • Observed the flame traveling behavior with fire growth for various fire source locations. • Revealed the flow dynamic conditions inside the compartment for various fire source locations. • Characterized the fire transition behavior inside compartment by two non-dimensional groups. The temperature evolution and flame traveling structure with fire growth from the fuel combustion of various source locations inside a compartment with a front opening at one end-side wall was explored in the present study. Concerning the compartment complex combustion (fire) dynamics, the temperature in a fire compartment based on the thermocouple array and the isotherm plane across the compartment center plane, flame appearance/structure obtained from the video camera and a critical heat release rate (HRR) for flame transition along the longitudinal direction of compartment were presented and discussed for a total of 329 experimental conditions. The flow dynamics conditions and combustion structures inside the compartment is presented to better interpret the experimental observation of the flame traveling/transition phenomenon. It is found that: (1) A flame traveling behavior was witnessed with increasing HRR, i.e. , the flame first moves to the inner-side and then travels to the front-wall/opening of the compartment. This behavior is also reflected by the high temperature zone. (2) The temperature in a fire compartment first rises then varies little, eventually decreases with fire growth for all burner locations. Nevertheless, the temperature at the inner-side (closer to the backwall) decreases with the burner moving from the backwall to the front-wall/opening of the compartment. The temperature at the outer-side (closer to the front-wall/opening) changes little with HRR. A dimensionless correlation was raised according to the non-dimensional fire source location. (3) The flow field inside the compartment shows a significant difference for various burner locations. The flame traveling behavior from the inner-side to the outer-side of the compartment is characterized by a critical HRR, which first increases then decreases with the burner moving from the backwall to the front-wall/opening, and increases with the opening ventilation factor. A non-dimensional correlation was proposed by two non-dimensional quantities of the critical HRR and the fire source location. These novel findings facilitate the understanding of fire dynamics concerning various fire source locations in a compartment with an opening. [ABSTRACT FROM AUTHOR]

This work presents an experimental investigation on ceiling-vented compartment fire behavior and thermal characteristics with different fire source locations under the effect of wind associated by CFD simulations. Experiments were carried out under the ambient wind condition, and the fire source was respectively set at windward side, center and leeward side. Results show that: (1) In no-wind cases, a critical heat release rate is found at which the inside temperature decreases with the increasing of fire heat release rate indicating flame flows outside. The critical HRR for fire source attached to sidewall is slightly larger than that when the fire source is located at compartment center, and it increases as vent dimension increases. (2) In ambient wind condition, there is a travelling process that the flame transfers from windward side to leeward side with the increasing of fire HRR. The critical HRR for the transition increases as vent size increases, and decreases as wind speed increases, and is basically independent of fire source location, which is proved to be related to air inflow rate. A Froude number is proposed to characterize the wind effect based on air inflow analysis, and the critical HRR for transition is represented well by the Froude number. • Ceiling-vented fire with different fire source locations under wind was studied. • Temperature profile and flame transition behavior were characterized. • Effects of wind and vent dimension on air inflow and flow field were analyzed. • Prediction model for flame transition based on the air inflow rate was proposed. [ABSTRACT FROM AUTHOR]

A probabilistic inferential framework is proposed to utilize transient temperature data measured at the ceiling of the compartment to determine location of fire source, as well as size of fire, based on Bayesian inferential theory. This approach treats the problem as one of parameter estimation, expressed as a function of posterior probability distribution based on the qualitative of agreement between predicted temperatures and observed temperatures at the sensor locations. A comparison of the measured temperature from full-scale burn tests with predicted temperatures from in verse problem solution algorithm indicate the error to be less than 5% when fires are small, but the error increases to more than 10% for large size fires. The accuracy of the inverse problem solution algorithm can be improved by utilizing data from sensitivity studies carried out on fire source location errors and heat release rate errors. [ABSTRACT FROM AUTHOR]

Since there exists few effective fire detection technologies for underground pipe gallery application, a temperature data-driven bio-inspired artificial intelligence algorithm is developed to detect fire source in 3D space of the underground pipe gallery, in which a simple physical model is used. In the developed algorithm, Ant colony optimization (ACO) is the first time to be used to determine tunnel fire source, and the new and special pheromone evaporation method and heuristic factor are developed for fitting the concerned problem here. Three fire experiments are used to support the ability of the algorithm. Satisfactory results can always be obtained, which shows that the developed algorithm can be used to estimate the tunnel fire source as well as temperature prediction. In addition, since only temperature data at several sensors is necessary in the developed algorithm, it has a very wide popularization and engineering application prospects due to its advantages of the global optimal ability and computational efficiency as well as the low economic cost. [ABSTRACT FROM AUTHOR]

• Simulate competitive effect of the V-shaped slope tunnel. • Study variation of the downstream back-layering length. • Propose partition of the smoke movement behavior. • Present relationship between mass flow rate and tunnel slope. Numerical simulations are conducted to study the influence of the heat release rate, the fire source location, and the tunnel slope on the smoke spread characteristics of V-shaped slope tunnels. Theoretical analysis and simulation results show that the smoke movement in the V-shaped slope tunnel is affected by the competition effect on both sides, which leads to the fact that the smoke only overflows from the tunnel portal closer to the fire source, and a large amount of air flows into the tunnel from the other portal. Due to the competition effect, the downstream smoke back-layering length first decreases and then increases slightly with the increasing distance between the fire source and the grade change point (refering to the intersection point of two adjacent slope lines). As the tunnel slope increases, both the back-layering length and the influence of the fire source location on the smoke spread decrease gradually. Besides, the heat release rate has little effect on the smoke movement characteristics. Based on the back-layering length and the mass flow rate distribution, the smoke movement behaviors in the V-shaped tunnel can be divided into the double-slope control zone, the transition zone, and the single-slope control zone. When the vertical distance between the fire source and the grade change point is more than 2.1 m, the smoke movement can be classified in the single-slope control zone. The mass flow rate reaches the peak value when the fire source is located in the transition zone, and the dimensionless mass flow rate is proportional to the tunnel slope and the 0.3 power of the dimensionless heat release rate. [ABSTRACT FROM AUTHOR]

• The fire smoke backflow in inclined tunnel is mainly driven by downstream length. • A non-dimensional empirical correlation of back-layering length and downstream length is established. • A new prediction formula of back-layering length account for tunnel slopes and downstream length is developed. To investigate the vehicle fire hazard at different locations in inclined tunnels, the effect of longitudinal fire locations on smoke behavior characteristics induced by inclined tunnel fires was proposed by simulation and theoretical analysis. A series of tunnel models with slope of 4% was conducted by Fire Dynamics Simulator (FDS) software for fire simulation, in which three fire scenarios were considered corresponding to the variation of fire location, upstream length and downstream length respectively. The results show that smoke back-layering length drops progressively with increasing of downstream length, and upstream inlet airflow velocity is linearly positively correlated with downstream length, while the upstream length has a limited impact on smoke movement. A new prediction equation of the dimensionless smoke back-layering length account for downstream length and tunnel slope was established, through the addition of height difference between fire source and downstream exit. The established correlation shows that the dimensionless smoke back-layering length is logarithmically related to cubic power of downstream length, and the predicted results agreed well with simulated data as tunnel slope from 3.5% to 7.5%. The results can provide beneficial suggestion in ventilation system design and emergency evacuation for inclined tunnels. [ABSTRACT FROM AUTHOR]