Evaluation of Surfactant Enhanced Water Mist Performance

Water-mist technology provides efficient fire suppression for compartments while minimizing water usage. Even with the many advantages of water mist systems, there is still room for improvement. Water mist systems have demonstrated effectiveness at suppressing flammable liquids (Class B) fires in compartments. However, an especially challenging fire suppression scenario for water mist systems is the small Class B fire. This scenario is often realized after a large fire has been reduced in size or ‘controlled’ by water mist. The small fire scenario is challenging because a small fire may not be able to generate enough vaporized water to displace sufficient oxygen for complete extinction. It should also be noted that even if the Class B fire is extinguished with a water mist system, re-ignition from the hot surrounding surfaces may occur at any time. In the present work, an additive is introduced into the water supply and its effect on the water mist suppression performance is studied. This Forafac^TM additive is a specific formulation, which includes fluorinated surfactants for creating a robust fire suppression foam. The enhanced suppressant exiting the mist nozzle is dispersed in the form of small droplets (not as a continuous foam) similar to a pure water mist spray. However, these droplets create a foam blanket on the surface of the fire, which acts to isolate the fuel from the air. With this formulation, the efficiency of the water mist system is improved even on small fires and most importantly the re-ignition of class B fires is prevented.

高压细水雾灭火系统在档案库的灭火试验研究

细水雾灭火系统已被建议用于保护对水敏感的区域,如档案库房。通过试验研究了细水雾灭火系统控制与扑灭档案库房火灾的可能性,并比较不同喷头形式的细水雾灭火系统在扑救档案库房火灾中的局限性,为细水雾灭火系统在档案库房内的推广应用提供建议。     

大流量液氮泡沫灭火装备在化工园区的应用研究

介绍了液氮泡沫灭火技术原理,研究了液氮泡沫发泡倍数、析液时间、微观状态等,搭建了泡沫长距离输送管路系统,研究了液氮泡沫的长距离输送性能,通过多尺度储罐灭火实验验证了液氮泡沫灭火能力。实验表明：液氮泡沫的气泡直径在20~50 μm,气泡直径相对均匀;发泡倍数在7~8,25%析液时间在3~5 min。液氮泡沫可在消防带内输送1 000 m,无析出分层,泡沫性能保持不变。液氮泡沫较压缩空气泡沫的灭火能力提升1.6倍以上,较吸气式泡沫的灭火能力提升2.5倍以上。该大流量液氮泡沫灭火系统可用于扑救大型储罐火灾、地面池火、流淌火及大型生产装置立体火灾等。     

Extinguishment of Cooking Oil Fires by Water Mist Fire Suppression Systems

A series of full-scale experiments were conducted in a mock-up commercial cooking area to study extinguishing mechanisms and effectiveness of water mist against cooking oil fires. The impact of water mist characteristics, such as spray angle, droplet size, flow rate, discharge pressure and type of nozzle, on the effectiveness of water mist against cooking oil fires was investigated. A series of oil splash experiments were also conducted to determine if the oil was splashed by water mist. In addition, the change in oil composition during heating and fire suppression was determined using Fourier Transform Infrared (FTIR) technique.The study showed that cooking oil fires were very difficult to extinguish, because they burned at high temperature and re-ignited easily due to changes in oil composition during heating and fire suppression. The water mist systems developed in the present work effectively extinguished cooking oil fires and prevented them from re-ignition. The spray angle, discharge pressure, and water flow rate were important factors to determine the effectiveness of water mist in extinguishing cooking oil fires.     

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.     

Experimental study of water mist fire suppression in tunnels under longitudinal ventilation

This paper studies water mist fire suppression under different longitudinal ventilation velocities in tunnels by small-scale experiments. After a scaling study, two mist nozzles are used for suppressing crib fires under 5 ventilation speeds. The result comes out that fire suppression process can be divided into three stages including flame unitary restraining stage, surface flame extinguishing stage and inside flame suppression stage. Several factors influencing efficiency are investigated. When the interval between mist nozzle and fire source enlarges, the relationship curve between fire suppression time and ventilation velocity shows a ‘V’ figure. The best ventilation speed exists. Following the rules summarized, a coupling system of water mist and ventilation may increase fire suppression efficiency remarkably.     

Experimental study of the effect of water spray on the spread of smoldering in Indonesian peat fires

Peatland fires remain a major contributor of environmental problems in Indonesia. Several studies on peat fire suppression have been conducted with multiple methods, such as quarrying, water spray, artificial rain, and foam spray. This research is focused on laboratory scaled experiments of Indonesian peat smoldering fire behaviour and suppression by a water mist system. The peat used in this work was obtained from two different locations, namely Papua and South Sumatra, Indonesia. During the suppression tests, the intensity of the water mist spray was varied by changing the distance between the nozzle and the peat surface. Meanwhile, the time periods of spray were 15 min (short period of suppression) and approximately 2 h for full suppression until the peat fire was extinguished. The peat temperature and the total mass lost during the smoldering reaction were recorded to get the burning rate ratio for each sample. The spread rate of the smoldering process was identified by the changes in the local temperatures of the peat bed. The results show that the spread rate of the smoldering combustion front was affected by particle size and permeability of peat material. The short duration of water suppression failed to extinguish the peat fires. A re-ignition phenomenon was identified due to the persistence of stored heat in the core of the peat. In addition, the total water required to fully suppress both peat fires is about 6 L/kg peat.     

高压细水雾灭火系统用于绍兴市档案馆库房

细水雾灭火系统是一种灭火效率高、耗水量少、绿色环保的新型灭火系统。结合绍兴市综合档案馆大型库房消防设计实例,介绍了高压细水雾灭火系统的组成、工作原理、设计参数、计算公式、控制方式等,提出了高压细水雾灭火系统在实际应用中存在的问题和相关建议。     

Fixed Fire Protection Systems in Tunnels: Issues and Directions

Fire protection practices for highway tunnels have been undergoing significant changes in the last decade, largely in response to a number of catastrophic fires that caused tunnel authorities to thoroughly review their fire safety assumptions. One of the fire safety issues currently receiving much attention includes the installation of “active” fire protection systems in addition to the “passive” fire protection features that were until recently considered to be sufficient to mitigate fire risk in tunnels. Passive fire protection measures include the use of fire resistive construction materials which help protect the critical structural elements from damage due to high temperatures. Active fire protection systems include fixed piping systems to deliver water sprays, such as deluge sprinklers and water mist, or other water-based agents such as compressed air or high expansion foam (CAF or Hi-Ex respectively). Active fire protection systems for tunnels are currently referred to as water based fixed fire fighting systems, or FFFS for short. Fire research suggests that measures based solely on passive protection are not likely to be sufficient to protect life and property to the degree warranted by the high monetary and strategic value of modern tunnel infrastructure. Full-scale fire testing and engineering analysis indicate that FFFS have the potential to reduce the impact of a severe fire on the tunnel structure from catastrophic to manageable at an affordable cost. Fire testing with CAF and Hi-Ex foam systems has shown them capable of actually extinguishing very large fires, including hydrocarbon pool fires. Systems based on water sprays on the other hand are not expected to extinguish fires, but rather to control the fire, limit fire growth and heat release rate, prevent fire propagation and provide thermal management. Although there are a few years of experience internationally that have proven sprinkler and deluge sprinkler system to be effective in mitigating tunnel fires, recent testing of FFFS in Europe has concentrated on water mist. One reason is the perception that water mist systems may involve less complex piping and agent storage than CAF or Hi-Ex foam, and may provide equivalent or superior performance with less water and smaller pipes than conventional sprinkler deluge systems. However, many engineering challenges remain to be resolved, such as how much credit to grant to the FFFS in terms of reduced criteria for passive protection, and how exactly to integrate active protection systems with traditional fire safety measures such as the ventilation systems. This article examines some recent developments in understanding how active fire-fighting systems might alter the impact of fires in tunnels.     

含添加剂高压细水雾抑灭乙醇池火性能研究

为探究含NaCl、KCl、Na2CO3、K2CO3、NaHCO3、KHCO3六种碱金属盐以及SDBS、CAB35、APG0810三种起泡剂对高压细水雾抑灭乙醇池火性能的影响,在空间尺寸为6 m×6 m×4 m的受限空间内开展纯高压细水雾与含不同添加剂的高压细水雾对乙醇池火抑灭性能的对比实验。结果显示：相比纯高压细水雾灭火,添加碱金属盐与起泡剂的高压细水雾的灭火时间明显缩短,并且缩短的主要是处在火焰被撕裂抑制、火焰向周围游走阶段的时间;其他条件不变时,灭火时间随着添加剂浓度的增加先减小后增大,与纯高压细水雾相比,两类添加剂中各自灭火时间最短的分别为含3%KHCO3、3%SDBS的高压细水雾,可分别缩短灭火时间57.4%、64.6%;平均降温速率随着添加剂浓度的增加先增大后减小,降温速率最高的为含3%SDBS的细水雾,相较于纯高压细水雾提高了217.54%;含不同碱金属盐与起泡剂的高压细水雾对乙醇池火的抑灭性能各不相同,但与纯高压细水雾相比都得到显著提高。     

Assessment of the Fire Dynamics Simulator for Modeling Fire Suppression in Engine Rooms of Ships with Low-Pressure Water Mist

Water mist-based fire-extinguishing systems are gaining acceptance for the protection of ship machinery spaces. The use of simulation tools presents a great potential for taking a performance-based design (PBD) approach to these fire scenarios. The Fire Dynamics Simulator (FDS) is the most frequently used and validated fire modeling software; however, studies of low-pressure water mist fire suppression modeling in ship engine rooms are rare. This paper contributes to the current literature by using the FDS to model a series of fire suppression scenarios defined by the International Maritime Organization (IMO) Circulars, including spray and pool fires with heptane and diesel oil, as well as exposed and obstructed fires. The simulation results are compared to data from full-scale tests conducted at recognized fire testing laboratories. Furthermore, an analysis of both the experimental and model uncertainties is carried out to assess the simulations performance. In general, a good agreement in compartment temperature evolution and fire extinguishing time is found for the modeled fire scenarios. The results support the application of FDS in a PBD approach for the design of water mist fire extinguishing systems for machinery spaces in ships. In this way, designers and engineers could model different machinery volumes and nozzles spacings that differ from those prescribed for a one story square engine room of the IMO, and, thus, predict the evolution of temperatures and extinguishing times for get the authorities approval.     

Examination of the Extinguishment Performance of a Water Mist System Using Continuous and Cycling Discharges

We conducted a series of full-scale fire tests of a twin-fluid water mist system in an empty enclosure and in a simulated machinery space. During the tests, two water mist discharge modes, continuous and cycling, were used. We investigated the extinguishment performance of the water mist system using these two discharge modes under various fire scenarios, including different fire sizes, types, and locations, and different ventilation conditions. Test results showed that use of the cycling discharge substantially improved the effectiveness of the water mist system for fire suppression, in comparison to the continuous discharge. The corresponding extinguishing time and water requirement for fire suppression were significantly reduced, and some fires that could not be extinguished with the continuous discharge were extinguished with the cycling discharge. The improvement in fire suppression was attributed to high depletion and dilution rate of oxygen and the recurrent dynamic mixing generated by the cycling water mist discharge in the compartment.     

A study of portable water mist fire extinguishers used for extinguishment of multiple fire types

This paper describes both theoretical and experimental studies on the application of a portable water mist extinguisher in suppressing multiple fire types. Two prototype portable water mist fire extinguishers were developed and their feasibility in extinguishing flammable liquid, cooking oil and wood crib fires, and for use in fires associated with an energized target was investigated. The interaction between water mist and the fire plume was studied by analyzing the instantaneous process of fire extinction, and fire and fuel temperature profiles. Both theoretical analysis and experimental results showed that the extinguishing mechanisms and process as well as water mist characteristics required (such as water flux density, droplet size and spray coverage) change with the types of fires encountered. The portable water mist extinguisher with appropriate mist characteristics was able to extinguish multiple fire types.     

Simulation of water mist suppression of small scale methanol liquid pool fires

The focus of this paper is on numerical modeling of methanol liquid pool fires and the suppression of these fires using water mist. A mathematical model is first developed to describe the evaporation and burning of liquid methanol. The complete set of unsteady, compressible Navier–Stokes equations are solved along with an Eulerian sectional water mist model. Heat transfer into the liquid pool and the metal container through conduction, convection and radiation are modeled by solving a modified form of the energy equation. Clausius–Clapeyron relationships are invoked to model the evaporation rate of a two-dimensional pool of pure liquid methanol.The interaction of water mist with pulsating fires stabilized above a liquid methanol pool and steady fires stabilized by a strong co-flowing air jet are simulated. Time-dependent heat release/absorption profiles indicate the location where the water droplets evaporate and absorb energy. The relative contribution of the various suppression mechanisms such as oxygen dilution, radiation and thermal cooling is investigated. Parametric studies are performed to determine the effect of mist density, injection velocity and droplet diameter on entrainment and suppression of pool fires. These results are reported in terms of reduction in peak temperature, effect on burning rate and changes in overall heat release rate. Numerical simulations indicate that small droplet diameters exhibit smaller characteristic time for decrease of relative velocity with respect to the gas phase, and therefore entrain more rapidly into the diffusion flame than larger droplet. Hence for the co-flow injection case, smaller diameter droplets produce maximum flame suppression for a fixed amount of water mist.     

对含添加剂细水雾灭火系统的分析

含添加剂细水雾灭火系统是当今火灾科学研究的热点之一。结合细水雾灭火系统的灭火机理对碱金属化舍物和泡沫添加剂的灭火效果进行了分析，指出了影响含添加剂细水雾灭火系统灭火性能的主要因素。讨论了目前含添加剂细水雾存在的问题，并展望了系统今后的研究方向和发展趋势。     

细水雾灭火技术在华东电网调度大楼中的应用

对细水雾灭火技术的灭火机理及技术特点进行了简要概括,以华东电网调度中心大楼为例,着重介绍了高压细水雾灭火系统的系统组成、系统控制方式及工作原理、系统设计流量及工作压力计算、系统应用条件及要求,以推广细水雾灭火技术的应用。     

A Study of Total Flooding Water Mist Fire Suppression System Performance Using a Transient One-Zone Computer Model

Due to the intense R&D activity in the field of water mist fire suppression during the past decade, the qualitative and quantitative understanding on the performance of water mist has increased significantly. This development has led to a point in which quantitative theoretical models describing large-scale water mist fire suppression systems begin to emerge. This paper describes the composition and validation of one such model, designed for total flooding water mist applications, especially against flammable liquid hazards in enclosures. The basic construction of the model is first described, followed by an example on the validation of the model using full-scale experimental data. The model is then used to investigate the limitations to the maximum possible mist concentration in the protected space. The potential of the model as an engineering tool is illustrated by making predictions on the scaling laws associated with water mist systems in the framework of IMO MSC/Circ.668/728 as the enclosure volumes and ventilation conditions are varied. The predictions are found to be in agreement with what is indicated by the recent US Coast Guard test series in very large machinery spaces.     

A numerical study of water-mist suppression of large scale compartment fires

The focus of this paper is on simulating water mist suppression of fires in large enclosures. A two-continuum formulation is used in which the gas phase and the water-mist are both described by equations of the Eulerian form. The water-mist model is coupled with previously developed codes based on the multi- block Chimera technique for simulating fires. Computations are performed to understand the various physical processes that occur during the interaction of water-mist and fires in large enclosures. Droplet sectional density contours and velocity vectors are used to track the movement of water-mist and to identify the regions of the fire compartment where the droplets evaporate and absorb energy. Parametric studies are performed to optimize various water-mist injection characteristics for maximum suppression. The effects of droplet diameter, mist injection velocity, injection density, nozzle locations and injection orientation on mist entrainment and flame suppression are quantified. Numerical results indicate that for similar injection parameters such as mist injection density, injection velocity and droplet diameter, the time for suppression was smallest for the top injection configuration. Water-mist injection through the side walls, the front and rear walls and through the floor were found to be less efficient than the top injection configuration. These results are compared with our earlier predictions on water-mist suppression of small scale methanol pool fires and other experimental studies.     

Water Spray Protection of Machinery Spaces

This report provides an evaluation of the firefighting capabilities of fixed pressure water spray systems for machinery spaces as described in Regulation 10 of Safety of Life at Sea (SOLAS). The objective of this evaluation was to determine if a system meeting the minimum SOLAS requirement can provide adequate protection of shipboard machinery spaces. To meet this objective, the capabilities and limitations of twelve water spray systems were determined using the International Maritime Organization (IMO) test protocol for water mist systems (MSC 668 and 728) as the basis for this analysis. The tests were conducted in a simulated 500-m³ machinery space onboard the U.S. Coast Guard's test vessel STATE OF MAINE. Generally speaking, the trends in performance of water spray systems were similar to those observed for water mist systems. All systems were capable of extinguishing larger fires (4 kW/m³ and greater) with variations in system capabilities becoming apparent as the fire size was reduced (2 kW/m³ and below). Only about half of the systems were capable of extinguishing the 1.0 MW obstructed spray fire located on the side of the engine mock-up (similar to IMO-6). Water mist systems typically exhibit slightly better capabilities primarily against the smaller fires. It was concluded that the capabilities of these systems cannot be associated with a single parameter such as application rate and must be determined empirically. As a result, the approval of these systems needs to be performance based as with all other fire suppression systems required by SOLAS. It was recommended that SOLAS Regulation 10 be re-written to cover all water based machinery space systems with the caveat that they pass a modified IMO test protocol based on the one currently used for approving water mist systems [MSC 668 and 728].     

不同气源压缩气体泡沫灭B类火灾性能比较

采用实验室压缩气体泡沫系统，通过油盘火对比试验，分别考察基于不同气源的压缩气体泡沫对于120#溶剂油火灾的灭火性能，分析探讨适用于常规B类火灾扑救的气源类型和供气方案。结果表明，在泡沫溶液供给强度为2.5 L/（min·m²）的条件下，压缩氮气泡沫和压缩空气泡沫均可扑灭120#溶剂油火灾，都具有良好的抗烧和抗复燃性能；压缩氮气泡沫比压缩空气泡沫的控灭火性能略有提升，但二者差别不大；对于常规B类非极性燃料火灾，实际工程中有氮气源的场所建议直接采用已有供氮气设备作为供气源。