Water Mist Suppression Research Articles

Experimental study on temperature control of cable tunnel fire under the combined effect of fine water mist and mechanical ventilation

AbstractElectricity is an important energy supply for industry, and long‐distance transmission in China mainly relies on cable tunnels, while cable tunnel fires occur frequently. A 1:1 scale tunnel model with a length of 20 m, a width of 2.5 m, and a height of 2.5 m was used to conduct experimental research on the temperature field of the ceiling of a high‐voltage fine water mist suppression cable tunnel. The article conducted experimental research on parameters, such as nozzle pressure, nozzle position, and longitudinal ventilation speed in high‐pressure water mist systems using n‐hexane as the ignition source. The results indicate that the high‐pressure water mist system can effectively reduce the ceiling temperature during cable tunnel fires. When the mechanical smoke evacuation system is activated, it leads to a reduction in the overall temperature within the tunnel. When the mechanical smoke extraction system is integrated with the high‐pressure water mist system, therefore, it is feasible to integrate the high‐pressure water mist system with the mechanical smoke exhaust system in engineering applications.

Fire prevention and mitigation technologies in high-rise buildings: A bibliometric analysis from 2010 to 2023

PurposeThis study provides a comprehensive bibliometric analysis for research in the area of fire prevention and mitigation in high-rise buildings, an emerging crucial subject. The analysis covers the period between 2010 and 2023, with the main goal of classifying and evaluating the efficacy of fire prevention and mitigation technologies. MethodsThe current study contributes a methodological approach for analyzing fire safety measures and highlighting the critical necessity for multidisciplinary approaches in enhancing fire safety protocols, with a special focus on the integration of advanced fire detection, suppression, and evacuation technologies. The investigation indicates a steady 10 % growth rate in scholarly production on this topic. ResultsResearch on active fire prevention technologies has focused on the technologies including; 1) water mist suppression, 2) unmanned aerial vehicles, 3) Artificial Intelligence (AI) algorithms, and 4) Internet of Things (IoT) frameworks, while research on passive technologies has trended toward fire compartmentation and fire-resistant materials. The study identifies 6 passive technologies and 14 active technologies, with active technologies focusing on water mist suppression, AI algorithms, and IoT frameworks. On the other hand, passive technologies focus on risk assessment, fire protection, and management. ConclusionsThe current study analyzes the role of risk assessment, fire protection, and management in the development of the field of fire mitigation and prevention. The study highlights research collaboration toward reducing risk and fatalities by fire prevention and mitigation solutions. The US and China have the highest collaboration in these technologies, while the UK and the US have the highest publications. Research implicationsThe provided analysis ultimately serves as guidance for stakeholders involved in the design, policy-making, and implementation of fire safety measures in urban high-rise environments, and can give insight on future research direction toward effective strategies and technologies for fire mitigation and prevention in high-rise buildings.

Experimental and Numerical Studies on the Efficacy of Water Mist to Suppress Hydrocarbon Fires in Enclosures

Fire is one of the most undesirable events onboard a ship. The engine room is one of the most critical spaces in the ship in terms of fire protection, as it includes machinery, hydrocarbon fuel systems, and different electrical equipment. With the phasing out of Halon 1301 as a fire suppressant over recent decades, there has been an intensive effort to explore the efficacy of water-mist spray in mitigating fires within machinery spaces. This exploration entails a comprehensive investigation through experimental and simulation studies aimed at identifying suppression mechanisms and evaluating their effectiveness. While experimental setups typically encompass measurements of gas temperature, thermal radiation heat flux, oxygen concentration, and fire extinction time, limited attention has been paid to quantifying the heat release rate (HRR), a crucial indicator of fire magnitude. Furthermore, research into shielded fire scenarios remains sparse, despite their significance in maritime fire dynamics. Addressing shielded fires with water mist proves particularly challenging due to the potential obstruction impeding the direct interaction between the fire source and the water droplets. In the existing literature, most of the computational fluid dynamics (CFD) modelling of fires and suppression was performed using a Fire Dynamics Simulator (FDS). Alternate studies were performed using FireFOAM. and very few employed FLUENT and other analogous software codes. In the majority of reported computational studies, the determination of HRR was typically relied upon for its calculation derived from the measured data of fuel mass loss rate. Moreover, certain studies were undertaken for numerical simulations without conducting thorough model validation, either by omitting validation altogether or solely validating against dry fire experiments (i.e., without water-mist suppression). This critical review of the literature has identified several notable research gaps in the context of extinguishing hydrocarbon fires utilising water-mist spray, warranting further investigations. Additionally, this review paper highlights recent advancements in both experimental and numerical investigations pertaining to the efficacy of water-mist fire-suppression systems in enclosed spaces regarding hydrocarbon fires.

Joint OH-PLIF and Mie scattering imaging of enhanced water mist suppression of buoyant fires

This study presents the first near-field measurements of interactions between reaction layers and water mist droplets suppressing a buoyant turbulent diffusion flame that is representative of a fire. Joint Mie scattering and OH-PLIF are employed at a high repetition rate of 400 Hz to image the droplet field and OH structure, which are deemed here to approximate the high-temperature reaction zone. Compressed natural gas (CNG) buoyant diffusion flames are stabilised on the Sydney Turbulent Buoyant Fire Burner, which is surrounded by a low-velocity air co-flow that is seeded with fine water mist droplets (d32 ∼ 50 µm). The water mist is doped with varying concentrations of metal alkali salts (NaHCO3, KHCO3) that release radical scavenging molecules, providing enhanced suppression capabilities through chemical inhibition in addition to the quenching effect from the water droplets. The spray boundary condition across the wind tunnel exit plane is quantified using Phase Doppler Interferometry. Flame extinction limits are measured by defining the critical condition at which the flame destabilises and lifts off the burner exit plane. A stability map is developed to quantify suppression efficacy in terms of the water mist flow rate and inhibitor concentration. Joint Mie-OH images of selected cases at varying extinction levels show that the addition of inhibitor introduces frequent breakages in the OH layers, marking regions of local extinction and reignition. Large mass fractions of inhibitor in the water, which, once evaporated, produces excess salt crystals in the local extinction zones that causes streaks of salt clouds that line both the lean and rich side of the flame. The chemical scavenging effects of the OH radical by NaHCO3 and KHCO3 is quantified by evaluating the reduction of the mean OH fluorescence signal in the flame at varying locations. Probability density functions for the OH area characterise local extinction in the flame due to the radical scavengers. The order of OH radical depletion and localised extinction in the flame due to the water mist follows: KHCO3 > NaHCO3 > H2O.

Numerical Simulation on Methane Coal Dust Composite Explosion in Restricted Space by Ultrafine Water Mist Suppression

The purpose of this experimental investigation was to examine the effects of ultrafine water mist on explosions caused by methane and coal dust hybrids that occurred inside of a closed vessel. In this study, we built a small-scale semi-closed visualization experimental platform and ran simulations to study the effects of four factors on the explosion of methane coal mixtures: the amount of ultra-fine water mist sprayed, the volume fraction of methane, the position of the methane inlet, and the amount of time it took to premix. This allowed us to gain a deeper understanding of the repressive effect of this water mist on methane explosion. The findings demonstrate that ultrafine water mist is capable of suppressing methane explosions, with a notable inhibitory effect on 10% methane. This inhibitory effect becomes stronger with increasing amounts of sprayed ultrafine water mist. The effect of methane volume fraction on the maximum explosion overpressure Δ

ANALYSIS OF HEAT RELEASE RATE IN ENGINE ROOM FIRES OF 300 GT FERRY RO-RO PASSENGER BY USING WATER MIST SYSTEM AND CO2 SYSTEM

Based on statistical data in recent years, there are still quite a number of ship accidents due to fires, including on passenger ships. The water mist system is a fire suppression system that allows it to be used in the engine room with the advantage that it can keep the heat production rate low during the extinguishing process and can be operated earlier than the CO2 system. The research is conducted by using fire dynamic simulator in the engine room of a 300 GT ferry ro-ro passenger to compare the heat release rate of fire without an extinguishing system, an existing CO2 system, and a water mist system. The result shows that the CO2 fire suppression system reduces the heat release rate more rapidly to the decay phase at 375 seconds while the water mist takes more than 900 seconds. However, the fully developed phase of the water mist suppression system occurs more quickly than CO2 because the sprinklers are activated shortly after a fire occurs. Unlike water mist, the CO2 system is activated at 60 seconds so that the pre-combustion, growth, flashover, and fully developed phases are at the same HRR and time as the natural one.

Water Mist Fire Suppression Systems for Building and Industrial Applications: Issues and Challenges

Interest in water mist fire suppression has increased within the fire protection industry due to its ability to control the spread and development of fire without using environmentally damaging agents. Water mist fire suppression has been used for many years in various applications such as machinery spaces, combustion turbine enclosures, and onboard passenger sea vessels. Now there is a demand to use this firefighting method to protect other fire risks such as cooking areas, commercial buildings, residential buildings, electrical equipment, road tunnels, bushfire (wildland fire) protection, and nuclear power generation facilities. To support this industry demand, this review covers the fundamentals of water mist, its suppression mechanisms, areas of application, existing research and development, and the codes and standards related to design. This comprehensive review provides a clear history of water mist suppression. It is able to identify the issues and challenges related to the technology to help pave the way for future research and development that will improve these systems to a level so that they are suitable for these new applications and meet the industry demand for nontoxic fire suppression systems.

The investigation of the water mist suppression pool fire process's flame expansion characteristics

Flame expansion is a typical fire suppression phenomenon that happens during the water mist suppression of liquid fuel fires, particularly heavy oil fires, and poses a risk to process safety. A series of transformer oil fire expansion experiments were carried out to study the mechanism of flame expansion in the process of water mist suppression pool fires. A theoretical model of the interaction of water mist with flame and hot fuel was developed after a quantitative investigation of flame structure changes during expansion. According to the results of the study, the presence of a fuel-rich vapor layer on the oil pool's surface is a prerequisite for flame intensification, and the thickness of this layer is proportional to the height of the transformer oil flame, Lc=0.195Lf. Furthermore, the impact of water mist on the fuel-rich vapor layer is found to be the principal cause of flame expansion, and the transformer oil flame expansion rate is determined using a combination of theoretical and experimental methods, φv=13.9−41.8. Finally, one of the factors that aggravates flame expansion is the overpressure on the fuel surface caused by the water-oil mixture. Droplet size reduces as water mist pressure rises, and flame expansion shifts from the parallel effect of jet impact and water-oil mixing to the serial effect, lowering the flame expansion rate. As a result, reducing droplet size causes flame expansion to weaken.

Influence of Water Mist Temperature Approach on Fire Extinguishing Effect of Different Pool Fires

The aim of this paper was to study the suppression influence of water mist on oil pool fires, taking diesel fires and n-heptane fires as experimental objects. The effects of spray pressure and temperature on water mist suppression were examined, and an experimental platform for the suppression of water mist in a small space was set up. Their fire prevention performance and fire extinguishing mechanisms were analyzed by comparing the flame temperature and extinguishing time of diesel and n-heptane pool fire. Three types of spray pressure were set. Water mist was designed at different temperatures and design experiments were carried out for this purpose. The change process of smoke concentration, thermocouple temperature, and flame combustion under different working conditions were analyzed, and the factors affecting the fire extinguishing effect of water mist on oil pool fire were discussed. The results show that 20 °C water mist is more effective at medium and high pressure than at low pressure. Moreover, 80 °C water mist at 9 MPa is more effective in extinguishing n-heptane fire. The flame extinction time is about 10 s, which is more than 40 s higher than that of cold water.

Energy distribution analysis on suppressing a shielded fire with water mist in a tunnel rescue station

In real tunnel fire scenarios, water mist has little opportunities to directly apply to train fires shielded by a carriage body. However, most models for heat transfer analysis assume direct contact between fire source and mist droplets. It is of interest to find a method to evaluate the energy exchange between water mist and a shielded fire. To investigate the water mist suppression performance on a shielded fire, a full-scale experimental and theoretical study was performed by varying the activation time of water mist system, working pressure, and the diameter of mist droplets. The suppression performance is found to be dependent on the working pressure for the small mist droplets, and sensitive to the size of mist droplets at high working pressure. Moreover, the suppression performance is also influenced by the water mist activation time due to the competition of fuel cooling and the inhibition effect of the smoke layer. A theoretical model was developed to predict the energy exchange among smoke, water mist, and surroundings. It was found that in comparison to the indirectly restricted effect of cooling the carriage and fire, the direct heat loss between water mist and smoke is the main controlling mechanism. This study provides an important reference for the design of fire water system in the tunnel rescue station and is beneficial to the environmental protection of fire extinguishing sites.

Performance Test and Application Research of New Gemini Wetting Dust Suppressant

In order to solve the problem of low efficiency of dust-catching by water mist to the hard-to-wetting and respirable dust, a new wetting type dust suppressant of Gemini was proposed based on the analysis of the wetting effect of water mist. Based on the evaluation indexes of surface tension, contact Angle, wetting and settling rate of dust spray, the performance of polyquaternary ammonium salt AG-101, dodecanol polyoxyethylene etheryl dimethyl ammonium chloride, octyl alcohol polyoxyethylene etheryl dimethyl decyl ammonium chloride and macromolecular cationic PCD Gemini surfactants were optimized, and had carried on the dust-suppression performance in a certain open-pit iron mine field experiment research. The results show that the comprehensive dust suppression performance of mass concentration of 2.0% of quaternary ammonium salt polymer AG-101 is the best, indoor experimental tests showed the dust rate is 4.2 times the speed of water, the field test showed that the initial wetting speed is 4.4 times the speed of water, and the action time of dust and water mist suppression is shortened obviously. The field application proves that the total dust removal efficiency is 82.3% (water is 56.6%), which is 45.4% higher than that of water. The dust removal efficiency of respirable dust is 92.1%, which is 16.5% higher than that of water. The research results provide a new dust suppressing agent for optimization of mine spray dust removal.

Research on explosion suppression technology of low-concentration gas transmission pipeline

In order to effectively control the explosion accident disasters of low-concentration gas transmission pipelines and improve the safety of low-concentration gas transmission and utilization process, the paper has summarized and analyzed the current three types of low-concentration gas transmission pipeline explosion suppression technologies and devices used in the field, including powder suppression, inert gas suppression and fine water mist suppression, and put forward the problems of coal mine gas transmission pipeline explosion suppression technologies. It is of great practical significance to pipeline transmission and utilization of low-concentration gas.

Analysis of the Impact of Water Flow Rate on the Temperature Variability in a Closed Room during the Extinguishing of A-Group Fire Using a Hybrid Water Mist Suppression System

The advantage of hybrid fire suppression systems is that they combine the advantages of both water mist and clean agent systems. Currently, this innovative technology is increasingly used in fixed firefighting systems. Available literature both in Polish and around the world describes this issue in a fragmentary way. Extinguishing system tests were carried out at the Main School of Fire Service in Warsaw. The impact of water mist flow rate on the temperature variability in a closed room during the extinguishing of group A fires using a hybrid water mist system was analyzed. Four different flow rates 0.5, 1.0, 1.5 and 3.0 dm3/min were applied. The temperature variability of selected points of a closed test chamber during extinguishing process are presented. The extinguishing efficiency, taking into account extinguishing time, average speed of temperature drop and other parameters, was estimated on the basis of proposed original criterion. The results obtained showed that water flow rate has a significant impact on temperature variability and included the determination of optimal water flow rate at which the extinguishing efficiency is the highest. The conducted research proved that the hybrid system is more effective than classic mist and gas systems when extinguishing group A fires.

A Review of Lithium-Ion Battery Fire Suppression

Lithium-ion batteries (LiBs) are a proven technology for energy storage systems, mobile electronics, power tools, aerospace, automotive and maritime applications. LiBs have attracted interest from academia and industry due to their high power and energy densities compared to other battery technologies. Despite the extensive usage of LiBs, there is a substantial fire risk associated with their use which is a concern, especially when utilised in electric vehicles, aeroplanes, and submarines. This review presents LiB hazards, techniques for mitigating risks, the suppression of LiB fires and identification of shortcomings for future improvement. Water is identified as an efficient cooling and suppressing agent and water mist is considered the most promising technique to extinguish LiB fires. In the initial stages, the present review covers some relevant information regarding the material constitution and configuration of the cell assemblies, and phenomenological evolution of the thermal runaway reactions, which in turn can potentially lead to flaming combustion of cells and battery assemblies. This is followed by short descriptions of various active fire control agents to suppress fires involving LiBs in general, and water as a superior extinguishing medium in particular. In the latter parts of the review, the phenomena associated with water mist suppression of LiB fires are comprehensively reviewed.

Pool fire suppression performance by twin‐fluid water mist under low pressures in an altitude chamber

AbstractFire suppression tests using low pressure twin‐fluid water mist under low pressure environments were carried out to exam the performance of water mist systems at low pressure environments. The experiment results show that the suppression time gets shorter for lower chamber pressure, and relevant total weight of water and nitrogen used decreases as the chamber pressure gets lower. For the case of 30‐cm diameter pool fire, the suppression times are 20.19, 7.5, and 2.24 under the chamber pressure of 60, 38, and 24 kPa, respectively. In case of a cargo compartments fire, it is suggested to open the ventilation valve of the cargo compartment at a high cruising altitude to relieve pressure, so as to achieve rapid fire suppression. When a fire happens at the position off the center below the water mist nozzle, the water mist suppression effects will be weakened. The fire size has little effects on the fire extinguishing process under pressure of 24 kPa. Under the critical atomization condition with the pressure differential between the inlet and outlet of the nozzle for water as 0.05 MPa (5.04 L/min), and the pressure differential for nitrogen as 0.10 MPa (10.97 L/min), the suppression time is the shortest as 18.66 seconds.

Numerical simulation and mechanism analysis of gas explosion suppression by ultrasonic water mist

ABSTRACTAimed at reducing the occurrence of gas explosion accidents, this work explored the mechanism and effect of ultrasonic water mist suppression on gas explosion. On the basis of EDC combustion model, the experimental and numerical results are compared and verified. It shows that the flame temperature, flame propagation velocity, and maximum explosion pressure are obviously decreased when ultrasonic water mist is added into the pipeline, and the descending proportion increases with the increment of the water mist concentration, which implies the ultrasonic water mist can effectively restrain gas explosion. The maximum error of the flame propagation time and the flame propagation velocity is within 10%, the maximum error of the explosion pressure is about 10%, which means the model is reliable and the numerical simulation results are in good agreement with the experimental results. Furthermore, the reaction rate of the generated water and the evaporation rate of water mist were studied, the mechanism and effect of the ultrasonic water mist on gas explosion suppression were further discussed.

Performance evaluation of water mist fire suppression: A clean and sustainable fire-fighting technique in mechanically-ventilated place

Fire disasters occurring in the ventilated places often feature the harmless and pollution-free fire extinguishing methods, one of which is water mist. However, the application of water mist system in the forced-ventilated places is still a controversial issue. The main objective of this study is to present a systematic experimental investigation on water mist suppression performance in the mechanical ventilation conditions. A series of full-scale experiments were conducted in a glass-walled cabin with dimension of 3 m × 3 m × 3 m, measuring instantaneous flame height, smoke temperature, radiative and convective heat flux, and concentrations of oxygen and carbon monoxide. The coupling effect of water mist and mechanical smoke exhaust was revealed. Experimental results show that all the dimensionless maximum temperature rise, dimensionless rising and descending rates decline linearly with exhaust rate. Moreover, the dimensionless maximum temperature rise correlates well with the dimensionless height in a cubical relationship. The inhibitive effect of convective heat transfer is enhanced gradually with the increased mechanical exhaust rate. Both the turbulent mixing and radiation attenuation play significant roles in water mist fire suppression. Furthermore, the minimum value and descending rate of O2 concentration both tend to increase with exhaust rate, while the maximum value and rising rate of CO concentration change inversely. It is implied that the coupling of mechanical ventilation and water mist system is beneficial for personnel evacuation, and it provides a reference for the clean and sustainable fire-extinguishing system design.

Acoustically Enhanced Water Mist Suppression of Heptane Fueled Flames

Recent research has shown that acoustics can be used to suppress flames from a liquid fuel source. The results of these experiments indicated that acoustics alone are insufficient to control flames beyond the incipient stage. Recent research has also shown that variations in the delivery of water mist to a fire can enhance the mist’s efficiency. Therefore, the addition of acoustics to water mist may be an effective means of enhancing an established fire protection technology. For the first time, acoustics and water mist have been combined and studied as a flame suppression strategy. A series of experiments were conducted that explored the potential for coupling acoustics with water mist as means of flame suppression. Heptane fueled flames were created from two different sized ceramic fiber wicks: 30 mm × 50 mm with 5 mL of fuel, and 60 mm × 100 mm with 20 mL of fuel. The flames were then exposed to water mist delivered at a constant rate, which was found to be incapable of suppressing the flames. Next, low frequency sound waves at 62 Hz and 80 Hz were used to suppress flames from both wicks, with each frequency being generated by a different resonator. Finally, acoustics from both resonators were combined with water mist, and used to suppress flames from both wicks. The results showed that a combination of acoustic waves and water mist suppressed the flames more effectively than each individual technique on its own. This finding opens the possibility of developing more efficient ways to use water mist technology.

Physical scaling of water mist fire extinguishment in industrial machinery enclosures

Froude-based scaling relationships had previously been theoretically extended to, and experimentally validated in the laboratory for, water mist suppression of fires in open environment and in enclosures, which were shown applicable to gas, liquid and solid combustible fires. Before applying these relationships to real-world settings, their applicability needs to be further evaluated for the intended protection. This paper presents such an evaluation on scaling water mist fire extinguishment in an industrial machinery enclosure. In this evaluation exercise, a full-scale water mist protection set-up tested for a 260-m3 machinery enclosure was selected as the benchmark. A ½-scale machinery enclosure test replica was then constructed, together with a ½-scale nozzle whose orifices were geometrically similar to those of the full-scale nozzle. Spray measurements indicated that the ½-scale spray closely met the scaling requirements, in terms of discharge K-factor, water mist flux, droplet velocity and droplet size distribution. Two spray fires and one pool fire, which were scaled with the respective full-scale fires, were used to challenge the water mist protection in the ½-scale enclosure. At least five replicated tests were conducted for each of the four tested fire scenarios. Overall, the instantaneous local gas temperature and oxygen concentration measured inside the ½-scale enclosure for each fire scenario agreed reasonably well with those measured at the corresponding locations inside the full-scale enclosure, meeting Froude modeling's requirement that scalar quantities be preserved in different scales. The fire extinguishment times obtained from the ½-scale tests for each fire scenario were also statistically consistent with that observed in the corresponding full-scale test. Based on the obtained results, it is concluded that, for machinery enclosures and other similar occupancies, the previously laboratory-validated scaling relationships for water mist fire suppression can be used to determine the fire extinguishing performance of a full-scale water mist protection in a ½-scale test facility.

Экспериментальные исследования метода подавления возгорания маслонаполненного трансформатора тонкораспыленной водой

Экспериментальные исследования метода подавления возгорания маслонаполненного трансформатора тонкораспыленной водой