Compartment Fire Research Articles

Temperature evolution, flame behavior and extinction inside compartment with a ceiling vent under the ambient wind

This article presents an experimental and CFD simulation investigation and analysis on temperature evolution and flame behavior inside compartment with a ceiling vent under ambient wind. Experiments were conducted employing a reduced-scale model containing a cubic fire compartment with a ceiling vent under the external wind generated by a wind tunnel. The temperature of windward and leeward inside compartment as well as the flame behavior were recorded for various vent dimensions, heat release rates and wind speeds for a total of 720 test conditions. Results show that there are two types of fire behavior regimes inside the compartment for relatively small- (Bernoulli flow regime) or large vents (oscillatory exchange flow regime). With a relatively small vent, the flame is located at the center of compartment and the temperatures of windward and leeward are almost the same with or without the ambient wind. Then the flame turns to extinct due to lack of oxygen with increasing of fuel supply. However, with a relatively large vent, there is a flame transition from windward to leeward accompanied by the transition of temperature distribution with increasing of fuel supply when subject to ambient wind. Such extinction and transition mechanisms are interpreted by the aid of CFD simulation of global equivalence ratio and flow/oxygen field inside compartment. The critical heat release rate for the occurrence of flame transition decreases with raising wind speed while increases with vent size. Their complex dependence is found to be well represented in terms of a non-dimensional heat release rate as a function of the wind Froude number, employing the vent area-equivalent characteristic diameter as length scale. These new findings facilitate the understanding of the compartment fire evolution with a ceiling vent subject to ambient wind.

Research on Testing and Calculation Analysis of Cargo Bay Fire-Extinguishing Agent Concentration Based on Different Loading in Civil Aircraft

In the history of international aviation, there have been many fire accidents of the cargo compartment. To ensure that the fire is extinguished in time when the cargo compartment is on fire, and to ensure the safety of aircraft and personnel, the design of the cargo compartment fire extinguishing system needs to be verified according to CCAR 25. According to the AC851-1 guidance, the verification of the cargo compartment's fire extinguishing system design aims to test and calculate the concentration of fire extinguishing agents used for the C-class cargo compartment based on different loading conditions of civil aircraft. Through the flight test of the cargo compartment under a no-load condition, it can be seen that the concentration of fire extinguishing agents in the cargo compartment is higher than 5% in the initial phase, higher than 3% in the 39,000ft and 10,000ft level flight phase, and the entire flight test phase is maintained above the suppression concentration required by the test, which meets the system design requirements. The concentration of fire extinguishing agents in the cargo compartment under a no-load condition is calculated and analyzed according to the maximum load rate (full load), and the result is higher than the required 3% suppression concentration.

The Sinkhole Phenomenon—Changes in Compartment Fire Characteristics Due to Incomplete Combustion before Flame Ejection

In this study, experiments and numeric studies were conducted to analyze the causes of abnormal behavior in temperature, heat flux, and combustion efficiency that occurred before a compartment fire was converted to the under-ventilated condition. The fire experiments were performed using a 1/4 reduced-scale ISO 9705 compartment and propane fuel. Considering that the occurrence and termination of abnormal behavior are related to ventilation conditions, vertical openings of various shapes designed to have the identical ventilation factor (0.52Ah) were used. As a result, an abnormal phenomenon was observed in which the measured heat release rate did not increase despite the increase in the fuel flow rate under the over-ventilation condition in all opening shapes. Due to this phenomenon, the combustion efficiency was reduced to 70% regardless of the opening shape. In order to understand these abnormal behaviors and to analyze the causes of their occurrence, the temperature and chemical species concentrations of the opening discharge flow were measured. The results indicated that the abnormal behavior of thermal physical quantities, HRR, and combustion efficiency occurred because fuel that was not burned inside the compartment did not reach the lower combustion limit even outside the compartment and was discharged.

Experimental study of temperature profile in underground corridor of various widths induced by fire in an adjacent compartment

Corridor-compartment fire, i.e., fire plume ejected through the door of the compartment and spread along the adjacent corridor, is a fundamental scientific problem in underground space, which is very important for the evacuation and firefighting. Nevertheless, the relevant studies are still very limited for quantifying the temperature evolutions inside the compartment as well as the corridor ceiling flow induced by corridor-compartment fire scenarios for various compartment door sizes and corridor widths. In the present study, a reduced-scale corridor-compartment experimental model was established, with four opening (door) sizes and eight corridor widths considered. The fuel burning mass loss rate (or instantaneous HRR) and the temperature profile inside the compartment and corridor were measured and analyzed. Results show that: (1) A non-dimensional correlation of the upper-part temperature rise inside the compartment could be found for various opening sizes and corridor widths in over-ventilated and under-ventilated condition, respectively. (2) The temperatures of the ceiling flow at the corner between corridor wall and corridor ceiling increases slowly before over-ventilated and then increases significantly after reaching under-ventilated condition with fire growth, it decreases significantly with the corridor width increasing, due to the change of ventilation condition. A non-dimensional model which considering the effect of corridor width for different opening sizes is proposed for the temperature decay profile of ceiling flow at the corner between corridor wall and corridor ceiling. This model could predict the temperature in underground corridor of various widths induced by a fire in an adjacent compartment, and then analyze and assess the fire thermal hazard on the compartment and corridor.

Study on the effects of cooling phase and construction technology on the fire performance of R/C tunnels

Fire performance of tunnels can represent a critical issue in the design phase, even more than for other structures and infrastructures, due to some inherent features such as (a) the fire compartment geometry often leading to very high temperature (also making difficult the intervention of fire brigades), (b) the structural redundancy caused by soil restraint fostering the development of relevant indirect actions, and (c) the high compression state in the lining (all the more during the fire exposure) that increases the spalling propensity and severity. Within this context, the role played by key parameters such as lining thickness and stiffness are investigated by comparing the fire performance of two different technological solutions for the lining: (1) traditional cast-in-situ lining and (2) pre-cast segmental tunnel lining. The fire scenario also considers the cooling phase, in order to discuss the main critical points to be solved when facing the final stage of the fire. 3D finite element analyses have been performed, proving that (I) higher thickness and stiffness does not necessarily correspond to a higher safety factor due to the indirect actions, and (II) fire cooling phase (if any) can be even more critical than the heating phase.

Application of travelling behaviour models for thermal responses in large compartment fires

Large open-plan compartment fires in modern buildings may exhibit a local burning region travelling across the floor plan as a ‘travelling fire’. This phenomenon has been found in the forensic investigations of fire accidents and in the large compartment fire tests. The fire impact in a large compartment is spatially non-uniform and time-variant, which can cause severe local damage to structural components. Advanced from the previous models assuming constant travelling, the natural fire model established in this paper comprises time-variant and test-based travelling behaviour models and localised fire models of various modes. It is demonstrated with the fast-spread Veselí fire test and the slow-spread Malveira fire test. A generic structural model is set up within OpenSees for fire to examine the thermal impact on structural members under various travelling fire scenarios of different travelling parameters, fire travelling directions, and beam sizes. Locally much higher thermal responses are represented after introducing behaviour models while adopting the same design fire load. Based on the work in this paper, a library of design fire models can be potentially enabled to examine the fire safety performance of structures regarding the realistic fire load and fire impact aiming for discovering unknown worse fire scenarios.

Analysis of Domestic and Foreign Standards and Conditions for the Prevention of Fire through Ducts

Ducts penetrating the fire compartment are passageways for spreading the flames and smoke of igniting deposits attached to the inside or fires from outside. Fires through ducts have a fast flame propagation speed and are difficult to extinguish quickly because of the high-temperature heat. Therefore, in this study, to improve the fire risk of ducts, the need for institutional improvement is confirmed by analyzing fire cases, comparing domestic and foreign laws and standards, and analyzing the current situation. As a result, a blind spot is evident in domestic law at the location of the fire damper installation because of the mitigating condition of fire compartments. There is also a gap regarding the need to prepare preventive systems such as maintenance standards inside ducts and installation standards for fire suppression systems in commercial restaurant kitchens.

A reduced-scale experimental investigation of facade flame behavior ejected from a top-hung window of fire compartment

In case of a room fire, facade flame ejected from a window could lead to catastrophic consequence. Top-hung window is a common feature in modern buildings. This paper investigates, for the first time, the ejected facade flame behavior from a top-hung window. Experiments are performed by a cubic scale model compartment with a top-hung window of four opening angles and four dimensions under various heat release rates (HRR). A total of 119 test conditions are involved to quantify generally the ejected facade flame behavior and morphological characteristics, characterized by its vertical height and horizontal depth (normal to facade). It is found that the position of neutral plane between the inflow and outflow at the top-hung window increases with opening angle, while being smaller as the window width is larger or the window height is smaller. The critical HRR for flame ejection is higher as the top-hung window opening angle is larger. The facade flame depth increases, while the flame height decreases, with increasing of opening angle of the top-hung window. A new characteristic length taking into account both the top-hung window dimensions and window opening angle is deduced by the mass balance analysis of the inflow and outflow as well as ventilation factor through the top-hung window. New dimensionless models are established to describe the critical HRR for flame ejection, the height of the facade flame and flame depth as a function of the newly derived top-hung window ventilation factor as well as characteristic length, showing good fitting of experimental results. The present study provides the basic data, understanding and model of facade flame characteristics from a top-hung window of a fire compartment, which is essential in estimation of its risk and adverse impact to urban environment as a new supplementary over previous knowledge limited for freely opened windows.

Validating hybrid fire testing with full-physical twin experiments

Real fire incidents show that structural systems have specific fire-induced redundancies that make them perform better than classical structural fire analysis predicts. Properly validated hybrid fire testing has the potential to tap into such redundancies for designs. In this study, we conceived and implemented a comprehensive and novel physics-based validation strategy for hybrid fire testing. We developed a laboratory-scale thermo-mechanical proof-of-concept problem that is representative for structural systems exposed to compartment fires. We solved the proof-of-concept problem using our novel thermo-mechanical hybrid solution procedure (Schulthesset al.2020Comput. Struct.238, 106301 (doi:10.1016/j.compstruc.2020.106301)) and compared the resulting hybrid model response against the results from a full-physical laboratory set-up of the same proof-of-concept problem, which we call a full-physical twin experiment. Full-physical twin experiments constitute the top layer of a suite of benchmark tests any specific hybrid fire testing procedure must pass to qualify not only as theoretically accurate and correctly functioning but also (and more importantly) as physically sound and able to yield realistic simulation results. This paper delivers such a first-of-its-kind physics-based validation, and in doing so, the first comprehensively validated method for hybrid fire testing—a method that now allows fire test facilities to conduct meaningful full-scale hybrid fire tests of entire structural systems.

Compartment Fire Behavior at the Stages of Detection, Containment and Suppression Using Water Mist

This paper presents experimental research findings regarding the characteristics of fire safety equipment activation before and after a water-based fire suppression system is triggered. A group of typical indoor combustible materials (wood, linoleum, cardboard, paper) were used to construct Class A model fires in the experiments. The three most frequent fire causes were reproduced: the careless handling of fire (open flame), the unsafe operation of heating equipment and electrical short circuits. To identify the fire behavior, an automated system including fire (heat, smoke, flame) detectors, contact and non-contact temperature measurement instruments, a gas analysis system and video recording equipment was employed. Following the experiments, the most efficient (in terms of detection speed and reliability) combinations of technical equipment that are necessary and sufficient to identify all the combustion stages of substances and materials were determined. The efficient consumption of a fire-extinguishing agent was found to be possible when fire development stages were controlled. Guidelines on creating automated fire prevention systems in buildings were provided. These have the potential to significantly speed up compartment fire suppression.

Fast detection of compartment fires under different heating conditions of materials

The paper presents experimental findings for the characteristics of equipment activation for the detection of pyrolysis and flame combustion under different heating conditions of materials. Class A model fires in the experiments involved a group of typical indoor combustible materials (wood, linoleum, cardboard, paper). Three most common causes of fires were reproduced: careless handling of fire (open flame), unsafe operation of heating equipment and electrical short circuits. To identify the characteristics of pyrolysis and ignition (i.e., stages preceding a fire), an automated system featuring fire (heat, smoke, flame) detectors, contact and non-contact temperature measurement instruments, a gas analysis system (CO, CO2, O2) and video recording equipment was used. Following the experiments, the scope of technical equipment (smoke, heat and flame detectors, gas analytical sensors, video recording systems) for the detection of pyrolysis of combustible materials and flame combustion start was determined. The most efficient combinations of equipment, necessary and sufficient for the identification of pyrolysis of combustible materials, were established for different fire causes. The values of the efficiency coefficients of fire detectors are calculated. It is shown that their values for different types of detectors can vary in a wide range (0.1–0.9). Recommendations were made on upgrading the existing fire prevention systems in buildings and creating new automated ones, allowing faster identification of an incipient fire, considering the specific character of the fire hazard source: open flame, heating equipment, electrical overload.

An Experimental and Modeling Study on the Effect of Wall Opening Location on the Under-Ventilated Compartment Fire

An experimental and modeling study was carried out to investigate the effect of wall opening location on the mass flow rates of gases through the opening and the associated fire phenomena, such as compartment temperature, projected flame height through the opening, and the heat release rates inside and outside the compartment. A 0.3 m by 0.3 m opening was placed at three different elevations—bottom, middle, and top—of a narrow end wall of a 0.8 m by 1.2 m by 0.8 m (H) compartment. A propane gas burner was used to provide four different fire sizes in the compartment: 90, 110, 130, and 150 kW. The existing correlations for mass flow rates and heat release rates generally do not include the wall opening location as a variable and are functions of only the opening area and height. Based on the experimental and modeling analysis, it is found that the wall opening location affects the internal and external fire phenomena. Two fundamental factors, K and O, are introduced to explain the effect quantitatively. Factor K is the ratio of the air inflow predicted by Fire Dynamics Simulator (FDS) to the existing correlation (0.5AoHo), and Factor O is the ratio of the oxygen consumption rate in the compartment to the oxygen flow rate into the compartment, indicating combustion efficiency. Factor K ranges from 0.78 to 0.94, and O ranges from 0.67 to 0.85 for different opening locations, which suggests that the existing correlations may overestimate the amount of airflow to and the combustion efficiency within the compartment.

Structural integrity of composite floors in fire: A comparison of two large-scale experiments with varying slab reinforcement

This paper presents a comparison of two compartment fire experiments performed on the 9.1 m × 6.1 m composite floors using a full-scale two-story steel gravity frame to study the influence of slab reinforcement on the overall structural integrity. The floor specimens were designed to achieve a 2-h fire rating but had dissimilar slab reinforcement. The Test #1 specimen had steel wire reinforcement of 60 mm2/m width as the minimum permitted in the United States practice whereas the Test #2 specimen was reinforced with deformed steel bars (230 mm2/m) determined by incorporating tensile membrane action. The Test #1 specimen exhibited mid-panel slab integrity failure before reaching the specified fire rating period. However, the Test #2 specimen exhibited much smaller concrete cracks until it was heated up to 131 min and retained the post-fire residual strength at least two times greater than the design demand at ambient temperature. This unique large-scale testing demonstrated that the appropriate slab reinforcement scheme can delay the vertical deflection of the heated composite floor and maintain the structural integrity at large vertical displacements over a longer duration of fire exposure.

Resistance and serviceability assessment of innovative composite slab exposed to standard compartment fire

The resistance and serviceability of an innovative flat profile steel–concrete composite slab fabricated with fire-resistant weathering (FRW) steel are investigated in depth. A total of five composite slabs are subject to full-process standard fire tests, with another five slabs for comparative tests under room temperature. The full-process fire tests include 60-minute heating, 180-minute forced cooling, 24-hour natural cooling test. The heating and cooling curves are recorded and simulated by a series of logarithmic functions. Based on the test results, an exponential model is proposed in terms of deflection rebounding ratio to evaluate the capability of self-restoration after fire exposure. The residual loading ratio is defined to describe and assess the robustness of the slab after fire. Analysis results show that this new type of composite slab exhibits very strong resilience and robustness after exposure to standard fire. Finally, based on sufficient standard fire tests and shear-bond tests, the specific post-fire serviceability performances are formulated, including flexural capacity, shear-bonding action, shear capacity, limiting deflection under normal service condition. The post-fire assessment method is further proposed, characterizing with resilience, robustness and reusability in terms of deformation restoration, residual loading capacity and serviceability both under normal service and fire resistance limit conditions, respectively. These research findings are of great significance in assessing the resistance and serviceability of horizontal separating elements after timely fire extinguishing, proper repairing and rehabilitation.

A Study of Fire Safety in Hostel Design: Case Study of Nnamdi Azikiwe University, Anambra State, Nigeria

In addition to offering residents a comfortable indoor environment, a hostel structure must also secure their safety. Hostel buildings should be made to be easily able to handle such emergencies and prevent unfavorable fire incidence since it concerns the safety of the building's residents. This is due to the necessity of fire safety and protection. The study aims to determine what causes fires and how to make hostels safer. Through case studies and interviews, data for the study was gathered. A case study was carried out in hostel in three universities: Nnamdi Azikiwe University, Awka, University of Nigeria Enugu campus, and Babcock University, Ogun state. The analysis of the data showed that both passive and active methods are used to ensure fire safety in buildings. The active measures include the control of smoke and heat propagation in buildings by either the natural or forced ventilation of fire compartments. In contrast, the passive measures are related to building materials and the response of the building construction to the fire. The study suggests that a comprehensive approach should be used to ensure fire safety in hostel buildings and designs, taking into account factors like building compartmentalization, fire-resistant building components, automatic sprinkler, and fire alarm systems, fire hydrants, firefighting appliances, providing open spaces, and muster points with proper signages.

Influence of test parameters on the high-temperature material properties of G550 CFS

Cold-formed steel (CFS) members generally present rising and falling temperature periods during full-range compartment fires. This study conducted 78 experiments of 1.0 mm thick G550 CFS during rising and falling temperature periods and quantitatively estimated the influence of the holding time of peak temperature, cooling rate, temperature history, and test methods. The results show that the temperature history plays an important role in the steady-state results. If the G550 CFS members are exposed to fire multiple times, the maximum temperature and tensile temperature can be used to represent the influence of temperature histories on the material properties of G550 CFS. Additionally, the temperature history also has a significant influence on the transient-state test strains. Under the same tensile temperature, the relative deviation between transient-state test strains during rising and falling temperature periods can reach 99,642%. In addition, when the tensile temperature is not lower than 300 °C, the transient-state test strain is obviously higher than the steady-state test strain under the same tensile temperature and stress level. Therefore, the steady-state and transient-state test methods are not equivalent. After collecting approximately 250 groups of test data, a data-driven model of G550 CFS under full-range fires was developed based on the BP neural network. The peak temperature, tensile temperature, steel position and thickness were taken as input parameters, and typical expressions of stress-strain curves were taken as the output parameters. The proposed data-driven model could give an acceptable prediction of the material properties and stress-strain curves of G550 CFS during full-range fires.

An engineering CFD model for fire spread on wood cribs for travelling fires

The temperature heterogeneity due to fire in large open-plan office compartments is closely associated with fire spread behaviour and has been historically limited to experimental investigations using timber cribs. This study explores the ability of Computational Fluid Dynamics (CFD) models, specifically the Fire Dynamics Simulator (FDS), to reproduce the results of full-scale tests involving fire spread over timber cribs for continuous fuel-beds. Mesh schemes are studied, with a fine mesh over the crib and 2 × 2 cells in the wood stick cross-section by default, this being relaxed in the surrounding regions to enhance computational efficiency. The simple pyrolysis model considers the charring phase and moisture. In application to the TRAFIR-Liège LB7 test, this calibrated “stick-by-stick” representation shows a good agreement for interrelated parameters of heat release rate, fire spread, gas phase temperature, and burn-away, a set of agreements which has not been demonstrated in previous studies. Fire spread shows relatively high sensitivities to: heat of combustion, ignition temperature, thermal inertia, radiation fraction, heat release rate per unit area, and the fuel load density. An approximately linear regression was found between the different fire modes and the thermal exposures, with “travelling” (and decaying) fires characterised by heat fluxes associated with the fire plume, while the growing fires were associated with proportionally higher heat fluxes on the horizontal surfaces of the sticks, in conditions where these receive more pre-heating. The trends in the overall HRR are more dependent on the fire spread rates than variations in the stick burning rates.

Identifying products of pyrolysis and combustion of materials at incipient stages of fires

The paper presents experimental research findings for the concentrations of the main gases in the products of pyrolysis and combustion of individual materials typical of compartment fires, as well as their combinations. Information for facilities and typical materials has been arranged into categories. In each group of premises, the most common materials have been distinguished. The concentrations of gas mixture components have been established for each material at three temperatures, corresponding to its ignition, average combustion temperature and typical temperature of fire. A possibility of identifying the source of fire and type of dominant material in it by the concentration of gases in pyrolysis and combustion products has been substantiated. Recommendations have been produced on using gas analyzing equipment when identifying the products of pyrolysis and combustion of materials at incipient stages of compartment fires for their efficient extinguishing. It has been established that obtaining well-timed information on the dominant material in the combustion source makes it possible to determine the conditions of supplying a water with efficient discharge density.

Experimental study on transverse temperature profile of spill plume and thermal characteristic difference with lateral direction

The present research investigated theoretically and experimentally the transverse temperature profiles of spill buoyant plume ejected from a fire compartment, as well as the thermal characteristic difference between the transverse and lateral direction. The previous literatures only focused on the vertical and lateral (normal to facade) temperature profiles; although the transverse (parallel to facade) temperature profiles will also have a significant impact on the thermal expansion, and it could be essentially different from the lateral temperature profile due to the existence of facade (air entrainment restricted), however, this topic has not been revealed yet. Hence, in present study, the plume thickness of transverse direction was theoretically analyzed, and a model for transverse temperature profile using the Gaussian function was established using the new effective plume thickness. Experiments were then conducted by using a reduced-scaled fire compartment with one opening attached on the facade wall. The transverse and lateral temperature profile of the spill fire plume along the facade wall were measured and analyzed. The model for transverse temperature profile can be well verified by obtained data. And it is found that the transverse temperature decay slower than the lateral temperature due to the Coanda effect caused by the one-side air entrainment. The obtained experimental data and proposed transverse temperature profile function in this work provide a basic understanding for the thermal characteristics of spill buoyant plume ejected from a fire compartment, and the proposed function can be applied to predict the spread possibility of building facade fire.

Application of multi-parametric characterization to water-based fire suppression systems in compartment fire scenarios

A new predictive fire suppression model has been developed and applied to a compartment room environment with various fire locations to clarify the suppression mechanisms of water mist and sprinkler systems. To effectively mitigate the combustion process, an in-depth framework has been developed, which includes the thermal fluidic interactions and utilizes statistical approaches for water droplets characterization. Efficiencies and effectiveness of both systems under different operating conditions were investigated with a multi-parametric approach that uniquely traces the accumulative mass fluxes, penetrability and number counts of droplets. Different fire suppression scenarios were identified based on combustion behaviors, and the suppression systems’ performance was evaluated based on spray coverage, penetrability, water utilization rate and potential water damage. The current study finds that water mist systems significantly outperform sprinkler systems in suppressing centered fires from both time (within 0.55 s) and utilization rate (up to 6.78%) perspective, while sprinkler systems can effectively suppress fires within a larger area, but their water utilization rate is as low as 0.07%. For water mist systems, although the water utilization rate can be 37 times higher than sprinkler systems, their effective suppression coverage area is small, which provided directions for future improvement.