细水雾灭火系统在电缆隧道中的应用研究

电缆隧道由于其火灾的特殊性对火灾保护系统有特殊的要求.细水雾灭火技术作为一种清洁、高效的灭火技术适合于在电缆隧道中应用.通过缩小尺度的细水雾灭电缆隧道火灾模拟实验,证实细水雾能够快速有效地扑灭电缆隧道火灾,灭火效果受可燃物数量、摆放方式和隧道通风条件的影响.     

客栈中细水雾灭火技术有效性实验研究

在搭建细水雾和传统闭式喷头的实验平台上,对比细水雾灭火系统和传统的水喷淋系统的控火、灭火性能,研究细水雾灭火抑制客栈火灾的有效性,并对其进行分析。研究发现:在水雾足量的情况下,与传统的水喷淋系统相比,细水雾灭火系统能快速、有效的抑制客栈中的火灾,降低烟气温度。     

高压细水雾系统的研究

本文简述了细水雾系统的发展历程及其对水喷淋系统的技术突破点,以我国研制的气水同管高压两相流预安装细水雾系统实体灭火实验为依据,阐述了该系统的成雾原理、灭火机理、灭火效能、工程应用范围及其与气体灭火系统和水喷雾灭火系统的工程造价比,确定了该系统替代卤代烷系统的可能性,展示了该系统远大的工程应用前景。     

高压细水雾——档案馆和图书馆的安全保护

传统灭火技术如喷淋灭火系统、气体、粉末及泡沫系统,因导致水破坏、环境破坏,毒性或再次填充的成本等问题,显现出一些不尽人意的地方。灭火剂造成的间接破坏通常比火灾造成的潜在损失更大。因此,大部分存放高附加值物品的建筑只使用火灾探测系统进行保护。细水雾灭火的好处自20世纪30年代起逐渐开始为人所知,     

细水雾灭火系统在电厂电缆大厅中的应用

细水雾灭火系统是一种新兴的灭火技术，它在灭火效果、工程造价、环境保护、二次灾害损失等方面都有较大的应用空间。介绍了细水雾灭火系统在电厂电缆大厅中的应用及灭火试验。     

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。     

综合管廊电缆舱灭火系统效果研究

针对某综合管廊的电缆舱室,采取全尺寸实验和数值模拟结合的方法,探究综合管廊内电缆舱的火灾特性,对比分析干粉灭火系统和高压细水雾灭火两种灭火系统的灭火效果。将火源功率为0.7 MW 的乙醇火设置于电缆架底部,观察火灾发展和烟气蔓延情况,分析电缆舱火灾特性;对比两种灭火系统开启后管廊内的温度和烟气变化规律,分析灭火效果。在实验基础上利用FDS 软件进行数值模拟以补充验证多工况火灾灭火结果。结果表明,电缆舱关闭防火门后,火灾不会持续发展,舱内温度稳定在600～700 ℃之间;干粉灭火系统有效灭火时间较短,且降温效果有限,火源上方温度降至440 ℃后发生了复燃现象;高压细水雾系统有效灭火时间较长,可以持续进行灭火,降温效果较为明显,且对于烟气蔓延有较明显的抑制作用,能为后续消防队员进入创造有利条件。     

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泡沫-水喷淋联用灭火系统在汽车库中的应用

分析了汽车库火灾的特点和现状,介绍了泡沫一水喷淋联用灭火系统的组成和特性,指出了泡沫-水喷淋联用灭火系统应用的相关问题。     

基于综合管廊火灾特性的细水雾灭火系统应用研究

综合管廊电力电缆舱室具有较高的火灾危险性,一旦发生火情,极易酿成重大火灾事故。笔者研建了综合管廊实体火灾试验平台,开展了不同工况条件下的细水雾灭火系统局部应用与全淹没应用灭火试验研究。研究表明,对于综合管廊电力舱,细水雾灭火系统宜采用全淹没灭火方式;若需采用局部应用灭火方式,应对着火分区与相邻分区同时喷射细水雾,并保证一定的灭火区间长度和喷雾强度。灭火过程中,通风排烟系统与门窗洞口严重影响细水雾灭火性能,火灾时应及时联动关闭;全淹没应用时,适当增大系统喷雾强度,是保障细水雾高效能灭火的关键。     

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.     

细水雾控制高层住宅烟道火灾的有效性及参数优化

为了有效控制高层住宅厨房烟道火灾,构建细水雾控制厨房食用油火和带分支烟道的高层住宅厨房烟道油垢火的FDS数值模型,分析高层住宅厨房烟道细水雾灭火系统有效性的影响因素及最佳设计参数。结果表明,如果未能即时扑灭高层住宅底层厨房食用油火,在强烈的烟囱效应作用下,高温火焰和烟气会引燃烟道内油垢,造成火势的迅速蔓延。本文所建的30 m高厨房烟道火模型中,最佳细水雾灭火系统运行模式为关闭厨房抽油烟机,即时开启厨房灶台上方和主烟道内分段设置的细水雾喷头,雾流量分别为0.6,10 L/min,细水雾最佳参数为喷射流速10 m/s、喷射角度60°、水雾粒径500 μm。     

原木楞堆细水雾灭火过程数值模拟

采用FDS模拟对原木楞堆细水雾灭火过程.通过分析雾滴直径、喷雾速率和喷头与楞堆顶面距离不同情况下楞堆燃烧周围温度的变化规律,选定了贮木场楞堆细水雾化灭火系统的合理参数.模拟结果表明,雾滴直径在100～150 m、喷头与楞堆顶面距离约5m时,细水雾灭火系统的灭火效果最好;雾滴速率为30～70 m/s时对灭火能力的影响不走,在设计细水雾灭火系统时可不予考虑.     

Modeling of fire suppression by fuel cooling

Fire suppression with water spray was investigated, focusing on cases where fuel cooling is the dominant suppression mechanism, with the aim to add a specific suppression model addressing this mechanism in Fire Dynamics Simulator (FDS), which already involves a suppression model addressing effects related to flame cooling. A series of experiments was selected, involving round pools of either 25 or 35 cm diameter and using both diesel and fuel oil, in a well-ventilated room. The fire suppression system is designed with four nozzles delivering a total flow rate of 25 l/min and injecting droplets with mean Sauter diameter 112 μm. Among the 74 tests conducted in various conditions, 12 cases with early spray activation were especially considered, as suppression was observed to require a longer time to cool the fuel surface below the ignition temperature. This was quantified with fuel surface temperature measurements and flame video recordings in particular. A model was introduced simulating the reduction of the pyrolysis rate during the water spray application, in relation to the decrease of the fuel local temperature. The numerical implementation uses the free-burn step of the fire to identify the relationship between pyrolysis rate and fuel surface temperature, assuming that the same relationship is kept during the fire suppression step. As expected, numerical simulations reproduced a sharp HRR decrease following the spray activation in all tests and the suppression was predicted in all cases where it was observed experimentally. One specific case involving a water flow rate reduced such that it is too weak to allow complete suppression was successfully simulated. Indeed, the simulation showed a reduced HRR but a fire not yet suppressed. However, most of the tests showed an under-estimated duration before fire suppression (discrepancy up to 26 s for a spray activation lasting 73 s), which demonstrates the need for model improvement. In particular the simulation of the surface temperature should require a dedicated attention. Finally, when spray activation occurred in hotter environments, probably requiring a combination of fuel cooling and flame cooling effects, fire suppression was predicted but with an over-estimated duration. These results show the need for further modeling efforts to combine in a satisfactory manner the flame cooling model of FDS and the present suggested model for fuel cooling.     

机械排烟下高压细水雾对地下商场火灾灭火效果的数值模拟

运用 FDS 模拟在特定机械排烟量下地下商场发生火灾时,观察不同细水雾喷头间距对火场烟气的控制影响。分析得到,在5 MW火灾功率下,排烟量60 m^3/（h·m^2）时,喷头间距2.0 m灭火效果较好,对大空间消防设计中喷头间距3.0 m更经济。     

Experimental and numerical study on water mist suppression system on room fire

Full-scale experiment and numerical simulations are carried out on a room fire to study water mist suppression system with heat release rate of 6 MW. A computational fluid dynamics (CFD) model of fire-driven fluid flow, FDS (Fire Dynamics Simulator), is used to solve numerically a form of the Navier–Stokes equations for fire. A fire experiment without water mist is performed and the temperatures are measured to validate the predictions of FDS code against the experimental data. Then a fire experiment with water mist suppression system is performed and the temperatures and extinguishing time are measured. The validated numerical model is used to simulate the experiment; the temperatures, oxygen concentration and extinguishing time are compared and studied. In numerical simulations, the cell size sensitivity is analyzed. The experimental results of temperatures and extinguishing time are compared with the results of numerical simulations. It appears that the numerical results are in good agreement (qualitatively) with the experimental data in temperature fields. These useful data can be helpful in accomplishing the design of water mist suppression system and the design regulations for fire safety management.     

武汉长江隧道通风排烟问题的数值模拟研究

采用大涡模拟火灾分析软件(FDS)分析不同火灾功率时通风速度对隧道烟气流动及温度分布的影响,可为今后的日常管理提供相关的运行控制参数。研究表明,在20MW的火灾规模条件下,隧道通风速度以控制在2.5m/s为宜。     

Testing Water Mist Systems Against Large Fires in Tunnels: Integrating Test Data with CFD Simulations

The high cost of conducting large, full-scale fire tests for the evaluation of suppression systems in tunnels tends to limit both the extent of the instrumentation provided and the number of tests that are conducted. Because of the variability of the large fires, performance criteria based on single point measurements derived from experience with smaller test fires were not reliable indicators of performance. Yet decisions about the acceptability of suppression systems must be based on the limited amount of performance information available. A means was sought to reduce the reliance on single point instrumentation readings, and to augment the value of the limited amount of test data by integrating the field testing with CFD modeling. In this study a computational fluid dynamic (CFD) model was used to simulate a series of full-scale fire tests of water mist systems conducted in 2006 in a highway test tunnel. The NIST Fire Dynamics Simulator version 4 (FDS4) was used to simulate five of the tunnel fire tests. The task was to confirm that the simulations could achieve a reasonable degree of agreement with the conditions measured in the tests. The model could then be used to evaluate the performance of the water mist system over a broader range of performance indicators than were measured. This paper illustrates what is unique about very large fire tests and presents highlights of the modeling. The level of agreement between simulation and test results is demonstrated for one test. Agreement was deemed to be good enough to establish confidence in applying the model to examine the conditions that would occur with an unsuppressed fire, which had not been tested. CFD modeling can be used to improve the understanding of the performance of the suppression system, and to augment the value of the test results. A second, complementary paper has been submitted to the SFPE Journal of Fire Protection Engineering to provide more detailed information about the FDS4 modeling than can be covered in this paper.     

Evaluation of FDS V.4: Upward Flame Spread

NIST’s Fire Dynamics Simulator (FDS) is a powerful tool for simulating the gas phase fire environment of scenarios involving realistic geometries. If the fire engineer is interested in simulating fire spread processes, FDS provides possible tools involving simulation of the decomposition of the condensed phase: gas burners and simplified pyrolysis models. Continuing to develop understanding of the capability and proper use of FDS related to fire spread will provide the practicing fire engineer with valuable information. In this work three simulations are conducted to evaluate FDS V.4’s capabilities for predicting upward flame spread. The FDS predictions are compared with empirical correlations and experimental data for upward flame spread on a 5 m PMMA panel. A simplified flame spread model is also applied to assess the FDS simulation results. Capabilities and limitations of FDS V.4 for upward flame spread predictions are addressed, and recommendations for improvements of FDS and practical use of FDS for fire spread are presented.