Fire Source Location Research Articles

Examination of the Scaling Law of Fire Phenomena in Compartment with Horizontal Natural Opening using Numerical Simulation

The scaling law was examined using numerical simulation for fire phenomena in a compartment with a horizontal natural opening in this study. The results of the large-scale conversion of the scaled model numerical simulation results ([Small-scale] condition) from the earlier studies obtained by applying the scaling law were compared to those of the large-scale numerical simulation performed in this study ([Large-scale] condition). The overall trends for the effects of horizontal natural opening area and fire source location on the discharge mass flow rate through the horizontal natural opening, temperature distribution in the compartment, and flow velocity through the horizontal opening were found to be identical under the [Small-scale] and [Large-scale] conditions. A complex bidirectional flow was observed through the horizontal natural opening under the conditions of this study and the accuracy in predicting the average W-velocity value based on the scaling law was low; however, the accuracy in predicting the range of velocity fluctuation was higher than the average value under certain conditions. Based on the standard deviation of the numerical simulation results, the percentages of the data within ± 30% of the difference between the [Small-scale] and [Large-scale] conditions relative to the total number of data were 100, 75, and 88% for the discharge mass flow rate, temperature, and flow velocity through the horizontal natural opening, respectively. The accuracy of the scaling law was found to be high for the discharge mass flow rate under the conditions considered in this study.

Effects of longitudinal fire source locations on the maximum temperature and longitudinal temperature decay in a mountain tunnel with vertical shaft: an experimental investigation and empirical model

Effects of longitudinal fire source locations on the maximum temperature and longitudinal temperature decay in a mountain tunnel with vertical shaft: an experimental investigation and empirical model

Investigation of changes in steel frames stress state in fire and influence on its vitality

Modern studies of the multi-storey buildings load-bearing structures vitality are analyzed. The shortcomings of the previously studied measures to increase the steel multi-storey frames vitality are identified. The need to study more effective and cost-effective measures have been identified. The change of 2d steel frame various elements loading during a fire is investigated. The dependence of the frame load-bearing capacity on the location of the fire source on different floors and spans is analyzed. 4 scenarios of fire source location in 2d multi-storey frame are considered. The influence of the distribution of the internal forces in the heated beams on the frame stress state, in particular on the local buckling of the I-beam flange and the web is analyzed. It was found that due to temperature expansions due to fire, not only heated elements are can be the first to be damaged in the frame. It is established that during a fire the first destruction occurs faster in the outside span of the frame than in the middle. When comparing the fire scenarios on the lower and upper frame floors, it was determined that on the lower floor the columns are more prone to damage earlier than the beam on the upper floor. When comparing the fire scenarios in the middle and outside frame spans, it was determined that in the middle span the beams are more prone to collapse earlier than the column than in the outside. It has been confirmed that, depending on the fire source location on different floors and spans, both the beam and the column of the frame may be the first to collapse. It is established that depending on the fire source location there may be different mechanisms of multi-storey frame collapse. It is established that the frame structures' stress state is significantly influenced by the distribution of internal forces at temperature loads, and not only fire protection and steel structures fire resistance.

An Intelligent Fire Detection Algorithm and Sensor Optimization Strategy for Utility Tunnel Fires

With the rapid development of utility tunnels, fire safety after construction is increasingly important, especially in the cable compartment. An intelligent fire detection method based on the particle swarm optimization algorithm was proposed for fire state estimation of the utility tunnel, including the fire source location, the maximum temperature value, and the temperature attenuation coefficient. Additionally, a corresponding sensor optimization strategy was also established. The dispersion coefficient of the fire source location was defined as the judgment criteria of sensor optimization. The validity of the proposed algorithm and the sensor optimization strategy were demonstrated in the application of a full-scale experimental example. The maximum errors of the identified fire source location and the maximum temperature value after sensor optimization were 34.7164 m and 8.5403°C, respectively. The total number of temperature sensors was reduced by more than 50%. The proposed intelligent fire detection algorithm can provide precise guidance for fire protection and extinguishing plan. Particularly, the sensor optimization strategy can economize the cost of temperature sensors.

Design of intelligent fire-fighting robot based on multi-sensor fusion and experimental study on fire scene patrol

Based on the current situation that most fire-fighting robots are operated by humans and do not have independent planning and operation abilities, in this paper an intelligent fire-fighting robot is designed using multi-sensor fusion. The robot has the functions of automatic inspection and fire-fighting, and can integrate the information of the operational environment and make decisions based multi-sensor fusion. An improved path-planning mechanism is proposed in order to overcome some disadvantages of the ant colony optimization algorithm, such as its easy tendency to reach local optimal solutions, slow convergence speed and weak global searching ability. A comprehensive evaluation method of the improved ACO is established to quantify its relevance and effectiveness. A joint calibration scheme for the color and temperature information obtained using an infrared thermal imager and a binocular vision camera was designed, and the internal and external parameters and distortion coefficient of the camera were successfully obtained. Based on the principle of binocular vision, a fire source detection and location strategy is proposed. When a fire source is detected, the location of the fire source is determined quickly and rescue path planning can be carried out, which improves the intelligence level of the fire-fighting robot. Finally, MATLAB and ROS are used to analyze the improved algorithm, and a fire site patrolling experiment is carried out. The results showed that the improved ACO greatly improves the convergence, reduces the number of iterations and greatly shortens the length of the patrol path, while the robot can effectively determine the location of the fire source efficiently during independent patrols and sound alarms, which will save precious time for fire-fighting and emergency rescue personnel.

Semi-empirical correlations for predicting hot gas layer temperature in pre-flashover compartment fires considering fire source location

A series of numerical experiments have been carried out through a CFD code, namely Fire Dynamics Simulator (FDS), to analyze the influence of the fire heat source location (transversal, longitudinal and vertical positions) on the hot gas layer temperature (HGLT) in pre-flashover compartment fires. Knowing the HGLT helps engineers to predict the onset of flashover and to design fire safety systems, which give more time for evacuation procedures. Using these numerical data, and based on an energy balance on the upper layer, new semi-empirical correlations were developed to predict the HGLT in pre-flashover compartment fires, as a function of the fire source location, heat release rate, ventilation factor, surface area, effective heat transfer coefficient and ambient thermal properties. As an external validation of the newly developed correlations, their outcomes were tested against several sets of experimental data available in the literature, showing a good agreement. So, it is concluded that these improved correlations are capable to predict the HGLT for different pre-flashover fire scenarios, accounting to the position where the fire started.

Predicting the Fire Source Location by Using the Pipe Hole Network in Aspirating Smoke Detection System

The aspirating smoke detector (ASD) is one of the most critical pieces of equipment for detecting smoke in a protected area when a fire occurs. It has more advantages than a conventional smoke detector because it can be used in extreme conditions, such as cold storage facilities or hot aisle containment areas. ASD uses a fan to draw air from the protected area into the pipe network system via pipe holes. The sucked air is transported into the sensing chamber to detect smoke. If the obscuration in the sensing chamber is greater than the setpoint, the ASD will sound an alarm so that people realize there is a fire. For this reason, investigating the effect of the pipe hole network on obscuration in the ASD is critical. In this study, a Pipe Hole Network Program was developed to consider the pipe flow parameter. A numerical study based on the program and an experimental study was performed. The results showed that the numerical results had the same trend as the experimental study. The further the location of the fire source was, the lower the obscuration was. In addition, the correlation between the obscuration parameter and the fire source distance was also derived. It could be used to predict the fire source location in the aspirating smoke detection system.

Justifying calculations of people warning and evacuation algorithms in case of fire in accordance with its source location variants and combustion development dynamic

Modern warning and people evacuation management systems in case of fire are able to implement different notification options (with a start evacuation delay) and different people groups routing, which reduces their flows density and the critical congestions formation probability on the evacuation routes. For these systems potential technical capabilities practical realization, warning and evacuation algorithms are required in accordance with the fire source location, the combustion development dynamic, the characteristic parameters of the object and the evacuating people. Such algorithms generation is possible on the basis of information about the current values and fire hazards increase dynamic in the premises and on the evacuation routes. The necessary information can be obtained as a result of numerical studies using software tools that implement mathematical models of heat and mass transfer and gas dynamic processes, as well as the evacuating people flows movement processes in case of fire. One of the algorithms examples for alerting and evacuating people for the educational institution building is presented. The calculated data make it possible to predict and evaluate the people safe evacuation fundamental possibility in case of fire and to propose space-planning, technical and organizational solutions and measures for its successful implementation.

Numerical simulation research on the fire in cable cabin of utility tunnel with different longitudinal fire source locations

A full-scale model was established by the Fire Dynamics Simulator (FDS) to study the fire characteristics in the cable cabin of utility tunnel with different longitudinal fire source locations. Five fire sources at different locations were placed in a 200-meter-long fire compartment. Several important parameters were obtained and analyzed, including temperature distribution, smoke concentration, and fire self-extinguishing. The results present that the fire source located at 1/2 of the longitudinal direction has the largest range of high-temperature smoke, which leads to the largest damage range of the concrete structure. The reverse filling of the smoke in the utility tunnel leads to the longitudinal CO peak concentration first decreasing and then increasing from the fire source to the end. When the fire source is located at 1/8 of the longitudinal direction, the fire self-extinguishing time is the longest. These encouraging results could provide significant references for the fire protection design and fire control of the utility tunnel.

Research on fire source localization in confined space based on the fire characteristic physical quantity information

Fire source localization is of great significance to the firefighting and evacuation. In order to resolve the problem of precise localization of fire source in confined space, a method based on the diffusion law of hot smoke flow in the early stage of fire is proposed in this paper. According to the fire characteristic physical quantity information collected by the sensor array, the relative variability correlation degree is used to obtain the signal time delays between the sensor units. Then, the direction angle of the sensor units and fire source can be determined through the geometric relationship, and the angular localization principle is used to obtain the fire source localization results. Finally, according to the fire source localization results obtained in different sets of time delays, the localization estimation area is selected based on the dynamic clustering, and the center of this area is output as the comprehensive localization result. The testing results show that this method performs well and achieves a high localization accuracy.

Numerical Simulation of the Evacuation Process in a Tunnel during Contraflow Traffic Operations

The purpose of this numerical research is to assess the evacuation process in a tunnel under the contraflow condition. Numerical simulations utilizing FDS+Evac codes associated with a fire dynamic simulator (FDS) model simulating a fire scenario are used to simulate evacuation and to predict the impact of a 100 MW fire scenario on the occupants inside the tunnel. Traffic and passenger conditions are based on real data from a tunnel in the UK. Two fire loads, 100 MW and 5 MW, are studied to represent an HGV and a passenger car fire. The 100 MW fire source, caused by an unexpected heavy good vehicle (HGV) catching fire, is located in the middle of the tunnel and at 20% of tunnel length to study the effect of fire source location on the usage of emergency exits and tenability thresholds. The dimensions and the inclination angle of the existing roadway tunnel are 1836 m (L) × 7.3 m (W) × 5 m (H) and 4%, respectively. It should be noted that the 4% inclination of the tunnel causes asymmetry propagation of smokes thus the visibility of the downstream and upstream from the fire behave differently. The maximum needed time to evacuate using all egress, the amount of fractional effective dose and visibility at the human’s height are analyzed. Simulation results indicate that when a realistic worst-case fire scenario is modeled, all evacuees can survive before the combustion gases and heat influence their survivability.

An adaptive Particle Swarm Optimization algorithm for fire source identification of the utility tunnel fire

In order to overcome serious utility tunnel fires and minimize economic loss, it is essential to establish an effective and practical method for finding the fire source. An adaptive Particle Swarm Optimization (PSO) algorithm was proposed for fire source identification of utility tunnel fires, whose inertia weight and learning factors were adjusted dynamically. In comparison with traditional fire detection methods, the proposed algorithm is immune to the specific environment and complicated fire propagation mechanisms, the fire source location can be identified only based on several temperature values. The proposed algorithm was applied in both numerical and experimental scenarios. The results showed that the adaptive algorithm showed greater global searchability in the early exploration, and stronger local searchability in the later exploration compared with the basic one, the improvement ratio of convergence performance could achieve 50%. Additionally, all of the cases demonstrated that the fire source location can be identified by the proposed algorithm with good accuracy. Critically, the spatial temperature distribution of the whole utility tunnel was obtained based on the fire source location and the attenuation coefficient. The reasonable results indicate that the proposed algorithm can provide a reference for fire protection and intervention in the utility tunnel.

Influence of the competitive effect of V-shaped slope tunnel on smoke characteristics

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.

Critical velocity for preventing thermal backlayering flow in tunnel fire using longitudinal ventilation system: Effect of floor-fire separation distance

To design a reliable longitudinal ventilation system in a roadway tunnel, it is crucial to know the optimum value of the forced airflow velocity which must be applied to minimize hazards to users trapped in the building during a fire. This optimal value known as the critical longitudinal ventilation velocity, is a crucial criterion for tunnel safety when designing ventilation systems. Analysis of the influence of the fire development location from the tunnel floor on the critical velocity has rarely been studied, although this situation really exists due to the difference in vehicle sizes in practice. CFD simulations were performed in this paper to study this scenario and to estimate the critical velocity for a fire developing in different locations relative to the tunnel floor. The results indicate that as the elevation of the fire location increases from the tunnel floor, the critical velocity decreases. A new model involving the separation distance of the fire location on the tunnel floor and relating the critical velocity to the fire heat release rate is proposed. Furthermore, under critical conditions of ventilation velocity, the results show that the elevation of the fire source location from the floor has a significant effect on the maximum smoke temperature rise below the tunnel ceiling.

Experimental and numerical studies on the smoke extraction strategies by longitudinal ventilation with shafts during tunnel fire

With the surge of extra-long tunnels, the vertical shafts are widely used to shorten the construction period and become a part of the ventilation system during the operation period. Because of the towering mountains, the depth of vertical shafts is usually about 100 m or more, which is quite different from those of urban road tunnels. As a result, it is indispensable to set up perfect smoke extraction strategies, including exhaust velocity and supply velocity, featuring longitudinal ventilation system with vertical shafts to reduce the great loss during tunnel fire. To control smoke better, 1: 4.8 reduced-scale tests were carried out. In addition, a series of full-scale numerical simulations were established, using FDS, to refine the supply velocity of three HRRs of three fire source locations. From this study, some conclusions were drawn: (1) Without ventilation system, the temperature at the junction of the main tunnel and shaft is higher, because of more smoke vents and stronger stack effect provided by vertical shafts. (2) Due to the stack effect of vertical shafts, the exhaust velocity is smaller than the supply velocity under a bigger HRR. (3) The HRRs and the fire locations made no difference to the exhaust velocity which is 3 m/s. When the fire source is located at the exhaust region and middle region, the respective supply velocity is in the range of 3 ~ 4 m/s and 4 ~ 6 m/s. When the fire source is situated in the supply region, the supply velocity of 6 m/s is suitable for all three HRRs. (4) The fitting formulas of the exhaust region and middle region are expressed. The results in this work will provide references for tunnel designers and engineers to devise smoke extraction strategies during tunnel fires.

Investigation on temperature distribution under the coupling action of transverse position and fire sealing of linear fire in tunnel

By sealing the portal at one end of tunnel and changing the transverse location of linear fire source in tunnel, the hot smoke layer, longitudinal temperature distribution and maximum temperature of linear fire source were investigated. It is found that the flame will bend under the influence of curved ceiling and hot smoke layer will be thicker when the linear fire source approaches to the side wall. The variation law of heat release rate is analyzed by considering the limiting effect of side wall and thermal feedback. By modifying the previous formula of effective ceiling height, an empirical formula for predicting longitudinal temperature distribution of linear fire sources with different aspect ratios is proposed, and the ventilation coefficient is obtained to characterized the temperature under sealing and without sealing. Moreover, the accuracy of predicted temperature under sealing is verified by using the ventilation coefficient. Based on dimensional analysis, it's concluded that the maximum temperature mainly depends on the heat release rate, and an empirical formula is proposed to predict the maximum temperature rise of linear fire sources with different aspect ratios in several transverse positions. The error of predicted values and actual values is within 13%.

Integrated agent-based simulation and evacuation risk-assessment model for underground building fire: A case study

To reduce the casualties of underground shopping malls after a fire and provide a reference for better emergency decision-making, this paper undertakes an in-depth study of the fire evacuation risk in underground shopping malls. First, no theoretical model exists for selecting the fire source location of the existing building evacuation fire. Considering the approach-avoidance behavior of people toward fires during evacuation and assuming the worst-case scenario, the authors propose a multi-exit fire-source-location-selection model. This study then simulates an underground shopping-mall fire using Pyrosim software. Finally, this study improves the existing evacuation risk-assessment model based on previous research and studies on underground buildings using this new model. The model presents the evacuation risk distribution in various areas within the building clearly, providing references for both the fire protection design for underground shopping malls and forming fire-emergency plans. Moreover, the number of people in the building, pre-movement time, and safety exit widths significantly influence fire evacuation risk in underground shopping malls; specifically, the number of people in the building and the pre-movement time are positively correlated with the evacuation risk, whereas the width of safety exits is negatively correlated. The number of people inside the building has the greatest impact on the evacuation risk.

Experimental study on the effect of canyon cross wind yaw angle on airflow and flame characteristics in a tunnel

The effect of canyon cross wind yaw angle on airflow and flame characteristics of ethanol pool fires in a tunnel was investigated. The fire source location and canyon cross wind speed were studied as factors. The wind yaw angle was ranged in 45°–135° with an interval of 15°. The results showed that the flow field in the tunnel presented three different conditions with the boundaries of wind yaw angles 60° and 90°. The mass burning rate and flame tilt characteristics were affected by the flow field near the fire source. The mass burning rate decreased with the increasing wind yaw angle when the wind yaw angle was in 45°–90°, but remained steady when the angle was in 90°–135°. Additionally, a normalized mass burning rate model considering normalized distance to the upstream portal and the wind yaw angle was developed. The flame close to the upstream portal wiggled, rotated and oscillated irregularly due to the influence of turbulence induced by the external canyon cross wind. This made mean flame length and flame tilt angle in turbulence zone different from those in other zones. A prediction correlation between the flame tilt angle and the canyon cross wind speed and yaw angle was established.

Experimental Investigation on Diesel Fire Toxicity in a Compartment Under Different Pool Locations

The objective of this study is to investigate how the location of fire source impacts the species generation. From the standpoint of fire safety, toxicity need to be estimated from the product gases evolved under different conditions of pool fire inside the compartment. However, industries like chemical, nuclear and thermal power plants also possess fuel positions significantly above the floor level inside an enclosure. Also, marine diesel fuel storage position in the ship cabin is just above the base, which implies an elevated pool fire conditions. In the present investigation, the severity of product gases with different pan diameters (ranges from 0.2 to 0.8 m) along with diesel fuel pan elevations in terms of toxicity were analysed. In order to study the behaviour of various fuel position, a large pool diameter 0.8 m was burned in centre, corner and rear wall centre along with six different fire source elevation. Results were analysed in terms of heat release rate (HRR), ratio of CO2/CO, upper hot gas temperature, residence time of upper hot gas, CO yield, CO2 yield and fractional effective dose (FED). The maximum HRR was obtained in the range of 10 kW to 1100 kW. For large pool diameter, results of CO2/CO ratio shows exponential decay trend along with fuel pan elevation, the maximum concentration of CO increased with increase in ceiling temperature showed parabolic trend. Moreover, lower CO2/CO ratio addresses incomplete combustion and thereby leads to higher toxicity inside the compartment.

Effects of transverse fire locations on flame length and temperature distribution in a bifurcated tunnel fire

In this paper, a series of experiments were conducted in a 1:10 reduced scale bifurcated tunnel to investigate transverse flame length and temperature field distribution under the ceiling with different transverse fire source locations. Five fire locations were considered and the corresponding distances (D) between the fire source centerline and sidewall are 0.1 m, 0.3 m, 0.5 m, 0.7 m and 0.9 m respectively. It is found that the predicted value by Gao’s model overestimates the ceiling jet flame extension length, thus a modified correlation considering the influence of the branch tunnel is established, which includes a sidewall and non-sidewall region. Moreover, a simplified equation for predicting the dimensionless maximum ceiling jet temperature by taking transverse fire locations into account is developed based on Ji’s model. Besides, the longitudinal temperature decay coefficient in the main tunnel ceiling shows a non-monotonous trend with D, exhibiting a maximum value at the condition for D is 0.3 m. However, there is a linear relationship between the longitudinal temperature decay coefficient and the ratio of the distance from sidewall and tunnel width. Meanwhile, based on Hu’s model, a revised formula for predicting the dimensionless longitudinal temperature rise by considering the effect of transverse fire location is established.