Search

In order to study the influence of wind direction on fire spread on building facades, a three-dimensional model of a high-rise building was built with PyroSim software. Numerical simulations were conducted with five wind directions (0°, 45°, 90°, 135° and 180°) and a reference wind speed of 3 m/s. The results show that the fire spread on the building facade was most significant on the leeward side, followed by the upwind condition. The horizontal spread of fire was promoted by crosswinds at 45°, 90° and 135°, while its vertical spread was inhibited. Among these, the inhibitory effect of the 45° crosswind was the greatest. The fire spread area under the leeward condition was the greatest at approximately 341.3 m2, accounting for 17.1% of the facade, and the vertical spread velocity under the condition of no wind was the fastest at 0.075 m/s. In this study, the motion characteristics of facade fire spread under different wind directions were determined, providing supporting evidence to enhance fire safety prevention and control measures in high-rise buildings.

Once a fire breaks out in an electric bus, it can easily lead to mass casualties and severe injuries, resulting in significant property damage and social impact. The high-temperature smoke and toxic gases in an electric bus fire are key factors that cause a large number of casualties, both of which are closely related to ventilation conditions. In view of this, this study utilized the Fire Dynamics Simulator (FDS 6) software to establish a three-dimensional experimental model of an electric bus. Numerical simulations of the fire combustion process in the electric bus under different ventilation conditions were conducted. Multiple fire scenes were established based on varying ventilation areas, different wind speeds, and diverse window opening positions. This study specifically analyzed the temperature and CO concentration variations under different fire scenes. By comparing the simulation results under different ventilation conditions, it can be concluded that when an electric bus catches fire, opening 100% of the windows, the wind speed is 8 m/s, and opening the rear window of the electric bus first can minimize the fire risk. Through the numerical simulation of electric bus fires under various conditions, this study analyzed the impact of different ventilation conditions on electric bus fires, providing a theoretical basis for firefighting and rescue efforts as well as personnel evacuation in electric bus fire incidents, with the ultimate goal of maximizing public safety.

In a long and narrow corridor, the installation of roof smoke blocking structures is a measure to slow down the spread of fire smoke. When employing multiple smoke blocking structures, the spacing between these structures is a critical parameter that needs to be considered for optimal effectiveness. This paper analyzes the smoke blocking performance of double structures at different spacing and measures the smoke flow velocity both upstream and downstream of the double structures. According to the analysis of the smoke velocity vector obtained from numerical simulation, the smoke can be divided into three zones based on the flow state of the smoke after passing through the front smoke screen structure, namely the vortex zone, surge wave zone, and steady flow zone. When the rear smoke screen is located in the surge zone, the smoke blocking effect is optimal. Analysis of the morphology of the smoke layer indicates that the length of the vortex region is directly proportional to the upstream smoke flow velocity. The numerical and experimental results both indicate that an excessively large or small spacing between the structures fails to achieve optimal smoke control effectiveness. When the spacing is within an optimal range, the smoke velocity is the lowest. Finally, using a real architectural corridor as a case background, this paper presents a design example of roof smoke blocking structures. In order to arrange as many smoke blocking structures as possible, an appropriate spacing between the structures should be slightly larger than the vortex region. The smoke control effectiveness of multiple roof structures was validated through numerical simulation. As a result, the time required for smoke to pass through the corridor increases by 110 s.

In the context of a fire emergency, safe and efficient exits are of paramount importance for pedestrian evacuation. The recent rapid development in the construction industry has rendered exit structures more diverse and complex. However, little attention has been paid to the influence of exit structures on the efficiency of crowd evacuation processes. In this paper, a tentative experiment was designed to preliminarily reveal the effects of five exit structures (Exit 1, Exit 2, Exit 4, Exit 5, and Exit 3 as examples for comparison) on crowd evacuation. Exit 1 has door leaves opening outward. Exit 2 has door leaves opening inward. Exit 3 has no leaves. Exit 4 consists of double-layer exit doors with the doors opening outward. Exit 5 comprises double-layer exit doors with the doors opening both sides outwards Subsequently, according to the properties of this experiment, a social force-based simulation model was established using the AnyLogic software 8.8.4. By changing the exit width and the crowd density, data such as evacuation time, flow rate, crowd density, and time delay were investigated in detail. The results revealed a notable variation in the evacuation efficiency depending on the deign of the exit. The respective flow rates for Exits 1, 2, 3, 4, and 5 were 0.66 people/(m·s), 0.77 people/(m·s), 0.80 people/(m·s), 0.71 people/(m·s), and 0.66 people/(m·s). Although Exit 3 excelled in terms of evacuation efficiency, it is not directly applicable to real architectural structures. Therefore, Exit 2 emerged as a highly promising solution in terms of flow rate and population control in the exit area, underscoring the effectiveness and practicality of its structural design. It is prospective that the results of this study can offer engineering and technical professionals valuable references and guidance concerning the design of exit structures.

This paper investigates the sensitivity of factors influencing the transport of smoke in subway station fires by developing a three-dimensional physical model of a subway station using Building Information Modeling (BIM) technology and importing it into Fire Dynamics Simulator (FDS) software for numerical simulation. The orthogonal test method analyzes the effects of four common factors on temperature, CO concentration, and visibility. These factors are the mode of opening the screen door, the number of smoke vents opened, the number of smoke barriers, and the wind speed of the smoke vents. The results show that the smoke control system and the building structure influence smoke transport in subway stations, while the temperature and CO concentration gradually decrease as the distance from the fire source increases. In addition, the mode of opening the screen door is the most significant factor influencing temperature, CO concentration, and visibility using range and variance analysis. Moreover, the sensitivity analysis indicates that the optimal combination of all factors can significantly enhance the smoke exhaust efficiency. Compared with the average, the temperature optimal combination increases the smoke exhaust efficiency by 20.8%, CO concentration by 56.59%, and visibility by about 13.41%. This study provides a foundation for optimizing smoke control systems and formulating personnel evacuation strategies in subway stations.

Rapid perception of the location of the fire point is crucial to building fire emergency response in the process of building fire emergency response, which can help firefighters direct fire-fighting operations, effectively control fire sources, and provide strong evidence for the analysis and investigation of fire causes. This paper uses acoustic CT temperature measurement technology to determine the fire source location of a building fire and verifies its validity and applicability as follows: we construct various fire point numerical models based on the fire dynamics simulator (FDS) and obtain temperature data at different times; neural network means were used to obtain the time-of-flight (TOF) of an acoustic wave traveling; the large ill-conditioned matrix equation of acoustic flight under different meshing schemes was constructed and solved based on the simultaneous algebraic reconstruction technique (SART) and least squares QR-decomposition (LSQR), and then reconstruction temperature data under each scheme were obtained. Through the error analysis, the reconstruction effect of each reconstruction scheme is evaluated, and then the applicability of the location coordinate determination of the fire point is analyzed. The results show that the determination of the fire location under the conditions of various fire points in the building space can be realized by acoustic CT temperature measurement technology.

With the long-term running of the subway, the soil layer around the tunnel takes on the thermal deposition effect, which can lead the air in the tunnel to heat up and pose a serious threat to the safety operation of trains. Through taking some subway tunnels from typical zones as an example, the influence of tunnel depth on the heat storage characteristics of the surrounding soil mass was analyzed in the paper. The results indicate that the temperature field of the surrounding soil mass was thermally disturbed by both the ground air temperature and the tunnel air temperature, and there was a significant coupling point ‘O’ located at the center of the tunnel overburden. With the extension of the heat-exchange time, the shape of the cooling ring around the tunnel gradually changed from a circle to an oval. For the analysis of cases, from the space aspect, when the tunnel depth was less than 30 m, the wall temperature increased gradually with the increase of tunnel depth. From the time aspect, over time, the wall temperature gradually rose and finally reached a fixed value. From the region aspect, the heat absorption capacity of different areas decreased gradually with the increase of tunnel depth. When the depth exceeded 45 m, the heat absorption capacity of certain cities became negative. In addition, three typical boundaries were discussed, and the optimal method for evaluating the heat absorption capacity of the tunnel soil was ultimately determined. This study has important reference value for temperature control and positioning problems in the process of tunnel construction and operation.

Fire accidents due to oil-immersed transformers seriously threaten the safe operation of power systems. In this paper, the similarity principle was used to design a high-pressure water mist fire-extinguishing test platform for a small-scale transformer fire, and the design method achieved a good fire extinguishing effect. The results indicate that a deflagration phenomenon, lasting about 2–4 s, could be observed after activating the high-pressure water mist system; the flame temperature rose rapidly at first, then dropped sharply, and finally cooled to the indoor temperature. The nozzle’s flow rate in this system has a significant impact on the fire extinguishing time. Meanwhile, the adjustment of the upper nozzle height also influenced the fire suppression effectiveness of the system, where a height of 1800 mm achieved the best performance compared to the others. In addition, the ambient wind speed is a very unfavorable factor for transformer fire suppression, where the fire extinguishing efficiency decreases rapidly with the increase in wind speed. Therefore, under low wind speed conditions, the high-pressure water mist system has great advantages in the fire suppression of outdoor oil-immersed transformers, and the above research results can provide a reference for the optimization design of this system.

In order to cope with limited land availability and the increasing urban population, more high-rise buildings are being built throughout cities, but this has also led to new challenges in the emergency evacuation of people. Therefore, we conducted an evacuation experiment of a group of people in the stairwells of high-rise buildings to explore the movement law of groups in stairwells. The experiment had 18 scenes, including the evacuation movement of an independent group and the crowd evacuation movement of different groups. Analyzing the independent groups’ movement showed that regardless of the type of group, the average speed of the crowd was more than 1.2 m/s, which was longer than that of previous studies. The more constraints in the evacuation process, the smaller the speed difference between males and females. Group cohesion was mostly concentrated at about 1 s. Moreover, group velocity and cohesion were found to have no significant correlation in stairwell movement. Analyzing the crowd evacuation time of eight different scenes showed that it took longer for crowds bearing weight to evacuate than those not bearing weight. According to the spatiotemporal evolution of crowd evacuation in stairwells, the crowd moves intermittently in the evacuation process, especially in the early and middle stages of evacuation, and the influence of group factors on this process was not obvious. Regardless of the kind of scene or stairwell, the number of pedestrians generally first increased and then decreased to a significantly low value, and the number of pedestrians reached about 30 in the scenario of people without any load. Additionally, the speed of the pedestrians entering the stairwell in the back of the group was not faster than that of the pedestrians in the front, which showed that pedestrians rarely engaged in overtaking behavior. The research results of this paper not only enrich evacuation research but also provide support for the design of high-rise stairs.

Due to hot toxic smoke and unknown risks under fire conditions, detection and relevant reconnaissance are significant in avoiding casualties. A fire reconnaissance robot was therefore developed to assist in the problem by offering important fire information to fire fighters. The robot consists of three main systems, a display operating system, video surveillance, and mapping and positioning navigation. Augmented reality (AR) goggle technology with a display operating system was also developed to free fire fighters’ hands, which enables them to focus on rescuing processes and not system operation. Considering smoke disturbance, a thermal imaging video surveillance system was included to extract information from the complicated fire conditions. Meanwhile, a simultaneous localization and mapping (SLAM) technology was adopted to build the map, together with the help of a mapping and positioning navigation system. This can provide a real-time map under the rapidly changing fire conditions to guide the fire fighters to the fire sources or the trapped occupants. Based on our experiments, it was found that all the tested system components work quite well under the fire conditions, while the video surveillance system produces clear images under dense smoke and a high-temperature environment; SLAM shows a high accuracy with an average error of less than 3.43%; the positioning accuracy error is 0.31 m; and the maximum error for the navigation system is 3.48%. The developed fire reconnaissance robot can provide a practically important platform to improve fire rescue efficiency to reduce the fire casualties of fire fighters.

Reducing casualties and property losses through effective evacuation route planning has been a key focus for researchers in recent years. As part of this effort, an enhanced sparrow search algorithm (MSSA) was proposed. Firstly, the Golden Sine algorithm and a nonlinear weight factor optimization strategy were added in the discoverer position update stage of the SSA algorithm. Secondly, the Cauchy-Gaussian perturbation was applied to the optimal position of the SSA algorithm to improve its ability to jump out of local optima. Finally, the local search mechanism based on the mountain climbing method was incorporated into the local search stage of the SSA algorithm, improving its local search ability. To evaluate the effectiveness of the proposed algorithm, the Whale Algorithm, Gray Wolf Algorithm, Improved Gray Wolf Algorithm, Sparrow Search Algorithm, and MSSA Algorithm were employed to solve various test functions. The accuracy and convergence speed of each algorithm were then compared and analyzed. The results indicate that the MSSA algorithm has superior solving ability and stability compared to other algorithms. To further validate the enhanced algorithm's capabilities for path planning, evacuation experiments were conducted using different maps featuring various obstacle types. Additionally, a multi-exit evacuation scenario was constructed according to the actual building environment of a teaching building. Both the sparrow search algorithm and MSSA algorithm were employed in the simulation experiment for multi-exit evacuation path planning. The findings demonstrate that the MSSA algorithm outperforms the comparison algorithm, showcasing its greater advantages and higher application potential. [ABSTRACT FROM AUTHOR]

Urban utility tunnels have developed rapidly in recent years. The effective ventilation system maintains the air quality of the utility tunnel. In order to improve the ventilation performance of utility tunnel, a three-dimensional model of utility tunnel was established according to the design drawings. Based on Fluent 14.0 software, a flow model was established. And numerical simulation methods were used to study the optimization of air ducts and ventilation methods. The utility tunnel used top ventilation and interlayer ventilation. The ventilation methods of different ventilation areas of urban utility tunnels are compared. The results showed that the combination of operational gain and ventilation zone length mainly affected the ventilation effect. Based on the simulation results, a comprehensive ventilation mode consisting of top ventilation, natural ventilation at 400 m long entrance and mechanical outlet exhaust was proposed. Electric valve, fire door, exhaust fan and induction fan could be opened in the urban public utility tunnel at low speed. This new combination method is considered the optimal combination method for the maximum ventilation speed of urban utility tunnels. [ABSTRACT FROM AUTHOR]

The purpose of this article is is to investigate the critical speed and back-layer length of smoke propagation during fires of lithium-ion battery vehicles in tunnels. The combustion of lithium-ion battery vehicles in tunnels is numerically simulated. This article uses heat release rate (HRR) and ventilation rate to predict the length of smoke counterflow in tunnel fires with new energy vehicles. Temperature is an important parameter for calculating smoke counterflow. The temperature in the tunnel is measured by thermocouples. The results showed that dimensionless critical velocity influences dimensionless HRR. The numerical simulation results indicated that there is a certain correlation between the HRR variable, which corresponds to the dimensionless smoke counterflow length and the critical speed in the tunnel. This article proposed a computational model for predicting the length of smoke counterflow. This paper contributes to the prevention of tunnel fires and reduction of social and economic losses. Therefore, this paper guides the propagation of smoke under the roof of lithium-ion battery vehicle fires in tunnels. [ABSTRACT FROM AUTHOR]

The accuracy of heat load calculation directly affects the effectiveness of the heating system. The design specifications for Heating, Ventilation, and Air Conditioning (HVAC) building load calculations utilized the Tianzheng HVAC software (THS) load calculations and HDY-SMAD software (HSS). A 14-story residential building in Qingdao was taken as an example. The calculation of the heat load was biased and the results were compared with those calculated by the THS and HSS. The results showed that the winter load calculated was 251.3 kW by using HSS. The heat index per unit area in winter was 49.9 W/m2. The heat index per unit area was 32.6 W/m2 in summer. [ABSTRACT FROM AUTHOR]

This paper evaluates the influence of natural ventilation on the longitudinal temperature attenuation of cable tunnel wall fires. It took into account the effects of different fuel quantities, cable types, cable layers, and the number of cables per layer. Experimental tests were carried out in a cable tunnel. Results indicated that under natural ventilation the cable burns well. The cable total mass loss rate varies under different conditions. Moreover, under natural ventilation, cable combustion was affected by many factors. This paper analyzed the effect of natural ventilation on longitudinal dimensionless temperature attenuation. A mathematical model was proposed for longitudinal dimensionless temperature attenuation under natural ventilation cases. In addition, a predictive model for maximum temperature rise below the ceiling was proposed to address the effects of heat release rate (HRR) and ventilation on cable tunnel fires. The experimental results were compared with previous research results. Finally, this paper established a calculation equation for dimensionless fire source heat release rate. This paper provides guidance for the fire prevention of cable tunnels. [ABSTRACT FROM AUTHOR]