Numerical Simulation Analysis of the Transformer Fire Extinguishing Process with a High-Pressure Water Mist System under Different Conditions

To thoroughly study the extinguishing effect of a high-pressure water mist fire extinguishing system when a transformer fire occurs,a 3D experimental model of a transformer is established in this work by employing Fire Dynamics Simulator(FDS)software.More specifically,by setting different parameters,the process of the highpressure water mist fire extinguishing system with the presence of both diverse ambient temperatures and water mist sprinkler laying conditions is simulated.In addition,the fire extinguishing effect of the employed high-pressure water mist system with the implementation of different strategies is systematically analyzed.The extracted results show that a fire source farther away fromthe centerline leads to a lower local temperature distribution.In addition,as the ambient temperature increases,the temperature above the fire source decreases,while the temperature and the concentrationof theupperflue gas layer bothdecrease.Interestingly,after thehigh-pressurewatermist sprinkler begins to operate,both the temperature distribution above the fire source and the concentration of the flue gas decrease,which indicates that the high-pressure water mist system plays the role of cooling and dust removal.By comparing various sprinkler laying methods,it is found that the lower sprinkler height has a better effect on the temperature above the fire source,the temperature of the upper flue gas layer,and the concentration of the flue gas.Moreover,when the sprinkler is spread over thewhole transformer,the cooling effect on both the temperature above the fire source and the temperature of the upper flue gas layer is good,whereas the change in the concentration of the flue gas above the fire source is not obvious compared to the case where the sprinkler is not fully spread.

A Numerical Study on the Extinguishing Performances of High-Pressure Water Mist on Power-Transformer Fires for Different Flow Rates and Particle Velocities

In order to study the extinguishing performance of high-pressure-water-mist-based systems on the fires originating from power transformers the PyroSim software is used.Different particle velocities and flow rates are considered.The evolution laws of temperature around transformer,flue gas concentration and upper layer temperature of flue gas are analyzed under different boundary conditions.It is shown that the higher the particle velocity is,the lower the smoke concentration is,the better the cooling effect on the upper layer temperature of flue gas layer is,the larger the flow rate is and the better the cooling effect is.

Research on the effect of the component proportion in the new water mist additive on firefighting performance

Water mist technology provides efficient firefighting performance while there is still room for improvement. So varieties of additives have been studied in recent years both at home and abroad. The self-made additives are used to compare the firefighting performance of diesel and heptane fire in open space. By adjusting the concentration of substance in the additives and conducting the experiment under the pressure of 0.3 MPa,0.5 MPa and 0.7 MPa,extinguish time and temperature are measured in the experiment. Through the experiments using different fuels,it can be found when the fuel is heptane that has a lower ignition point and a higher evaporation rate, the water mist additive can still significantly improve the firefighting performance. According to the data based on different concentrations of fluorinated surfactants,we find that fluorinated surfactants are the main substance to improve the performances by changing physical property of water mist. Optimal proportion of the additives for firefighting performance is found by experiment results.

Analysis of Water Mist Suppression with Foam Additive in Wind Generator

The study adopted a 20-foot long container to simulate the situation inside a turbine cabin. Water mist sprays were installed internally and used to perform fire extinguishing tests. Under these different scenarios, several operating factors were adjusted with the results of each adjustment subsequently measured. The operating factors studied included： operating pressures, foam concentrations, cabin opening issues, and obstacles. Each of the factors was compared with the others so as to find out which combinations would be most suitable for a water mist spray system installed inside a wind turbine cabin. The presence of obstructions hinders the direct impact of the mist spray on the fire source and in average an additional 2 to 3 minutes is required to put out the fire. This study found that the effect of the foam-water ratio is linear. Regardless of the scenario, the optimum mixture ratio is 3%. The line graph shows that the most unsuitable aqueous film-forming mixture ratio is 6%. This experiment found that the main fire extinguishing mechanism of water mist spray is the cooling of a large area via water droplets. This system is very effective in bringing down the temperature. The addition of foam in water mist spray, however, impaired the effectiveness of the cooling effect although the fire control mechanism via emulsification markedly reduced the time required to put out the fire. The increase in foam magnification will considerably enhance the fire extinguishing efficiency.

Study on fire extinguishing performance of ultrafine water mist in a cup burner

Two simplified models for predicting minimum extinguishing concentration(MEC) of ultrafine water mist(UFM)(<10 m) were developed based on limiting oxygen concentration(LOC) and combustion limit temperature(CLT),respectively.Experiment was conducted using a modified cup burner which can reduce the surface adsorption of UFM.Two typical liquid fuels,n-heptane and ethanol,were used in the experiment.Tests using the same scenario were repeated 20 times or 10 times according to the variance of extinguishing time.The average and the standard deviations of extinguishing time were used to evaluate the fire extinguishing performance of UFM.Experimental results agree well with the model based on LOC,and disagree with the model based on CLT.The disagreements were explained by analyzing flow behavior of UFM.It was concluded that the primary mechanism of fire extinguishment with UFM was oxygen dilution.

The principle analysis of methane explosion suppressed by water column curtain in coal mining

The principles of fine water mist explosion-extinguishing system was introduced. The defects of current systems were analyzed. The concept of a new water column cur-tain and the explosion-extinguishing mechanism were given. Using water column curtain to suppress methane explosion in experiment pipes was conducted. The photos were written with schlieren photograph system. The results of experiment show that the effect is perfect.

气凝胶灭火剂抑制锂离子储能电池热失控特性研究

通过对比试验探究了气凝胶灭火剂对锂离子储能电池热失控的抑制效果。研究满荷电状态下的100 Ah磷酸铁锂储能电池热失控演变过程特征参数,识别出3个灾害演变特征拐点作为灭火剂施加的指导节点。在相同节点分别施加灭火参数一致的气凝胶灭火剂与细水雾开展灭火对比测试。结果表明:触发明火前施加灭火剂均可有效阻断电池内部放热副反应,两者表现出相似的冷却效能;电池起火后,气凝胶灭火剂展现出更为出色的明火抑制效果,其接触电池表面形成的致密泡沫可有效阻隔氧气,实现快速灭火;对于已经触发热失控的情形,气凝胶灭火剂凭借预热覆盖效果,显著缩短电池射流火持续时间,可大幅降低电池火灾危害。

城市地下综合管廊电缆火灾低压细水雾灭火效能研究

为了研究城市地下综合管廊电缆火灾低压细水雾灭火的有效性、明确影响低压细水雾灭火效能的关键因素,搭建了缩尺寸综合管廊低压细水雾灭火试验平台并开展了灭火试验。试验结果表明,低压细水雾能够快速有效地扑灭综合管廊电缆火灾,灭火时间最快为7 s,在启动灭火系统后50 s即可将管廊内部最高温度从650℃降至40℃。压力与喷头流量系数的改变对低压细水雾灭火效能影响较大,灭火时间分别最多缩短75.0%和66.7%,平均降温速率最高为8.2℃/s和7.43℃/s;喷头间距的改变对灭火效能影响相对较小,灭火时间最多缩短47.3%,平均降温速率最高为6.1℃/s。

含添加剂水雾抑灭单基药火焰的小尺度实验研究

为探究含不同性质添加剂的水雾对单基火药燃烧抑灭性能的影响,在自主搭建的火药燃烧及灭火平台上开展纯水雾与含Na_(2)SO_(3)、FeCl_(2)、K_(2)CO_(3)、KHCO_(3)添加剂的水雾对单基火药燃烧抑灭性能的对比实验,研究灭火过程中温度、辐射热流、火焰形态等的变化。结果表明:含还原性(Na_(2)SO_(3)、FeCl_(2))和非还原性(K_(2)CO_(3)、KHCO_(3))添加剂的水雾抑灭性能明显优于纯水雾,灭火时间更短。含非还原性添加剂的水雾在低浓度下抑灭效果较差,当添加质量分数提升至3%以上时,抑灭效果显著提升;含还原性添加剂水雾对单基药的抑灭性能在各添加剂浓度下均优于含非还原性添加剂的水雾,且随着添加剂浓度的增大,抑灭性能表现出饱和性。

文物建筑内移动式高压细水雾灭火装置设计参数研究

为了研究移动式高压细水雾灭火装置在文物建筑内的设计参数,搭建了6A木垛火试验台,研究在不同喷射距离和模式下,该装置应对大规模火灾时适合的喷射流量与距离,并采用FDS,以北京某古建筑为模型进行模拟,从喷射强度、喷射距离、喷射时机、雾化粒径等方面验证并补充移动式高压细水雾灭火装置的设计参数。结果显示,喷射强度可设定为4.4~6.6 L/(min.m^(2));喷射距离可设定为5 m,尽可能采用近距离喷射策略;灭火时机应尽早,至少在起火后300 s内;雾化粒径的选择需根据具体情况权衡考虑。

超声波细水雾灭火技术试验研究

利用超声波技术产生的细水雾可作为一种灭火剂,通过冷却、窒息等作用实施灭火。搭建试验平台,分析超声波雾化装置产生细水雾的特性,并设计灭火试验,研究局部应用和全淹没两种形式的灭火有效性和影响因素。结果表明:利用超声波雾化技术产生细水雾并确保足够雾化量和适宜的喷射方向,实施局部应用灭火是可行的;采用全淹没灭火时,灭火效果取决于场所通风情况和空间大小,在相对封闭空间内灭火效果较好。

Calculation of fire extinguishment time with water mist in an enclosed room

The fire extinguishment time is a major factor to evaluate the efficiency of fire extinguishment with water mist. In this paper the fire extinguishment time with water mist in an enclosed room is calculated. Before adding water mist, the chemical kinetics plays the role in combustion, where a dimensionless math model is established by us-ing the Semenov theory. After adding water mist, the diffusion plays the role instead. Then another math model containing water mist and dominated by oxygen concentration is established. The fire temperature is integrated from Tm to extinguishment temperature TB and the extinguishment time can be obtained. The calculated values are compared with the experimental data under different conditions. The results show that this model can predict the fire extinguishment time accurately. Besides, this model also can be used to determine the critical water mist flux and evaluate which fire extinguishment mechanisms dominate the extinguishment.

某客滚船低压水雾灭火系统设计

本文以某客滚船为例,介绍低压水雾灭火系统的组成及保护分类、系统水量估算方法、系统满足客船安全返港要求的布置特点以及设计过程碰到的有关问题。

细水雾工作压力对综合管廊火场温度与烟气运移影响

为探究细水雾压力对综合管廊火灾温度场和烟气的影响,通过搭建1∶6缩尺管廊试验台,采用流量系数为3的细水雾喷头,设计了5种不同细水雾工作压力下的管廊火灾试验,对比分析5种工况下的管廊火灾温度场和烟气的变化规律。结果表明:适当增加喷雾压力能够提高细水雾的灭火效率,且随着细水雾压力的增加,管廊内烟气温度先大幅下降后缓慢降低,烟气流速减慢,烟气层高度下降;细水雾压力为2 MPa时,烟气温度比无细水雾时提前达到峰值,且峰值大幅降低,当压力达到4 MPa以后,温度峰值下降趋势变缓;温度分布呈逐渐衰减趋势,横向上火源中心处温度最高;在竖向上,距顶棚越近温度越高;不同细水雾压力作用下管廊顶棚横向温度分布和竖向温度分布均与指数模型拟合良好,通过指数模型能够预测出不同细水雾压力作用下的顶棚横向温度和竖向温度;压力为3 MPa时,细水雾对火灾的抑制作用和对烟气的排出效率均较高,设定细水雾压力参数时不应过大,以保证对烟气影响较小的基础上完成对火灾的抑制降温。研究结果为实际管廊细水雾灭火系统的设计优化和提高排烟效率提供参考。

文物古建筑高压细水雾灭火系统应用探讨

古建筑作为我国历史文物的主要构成部分,其具备历史、社会、艺术等多个方面的价值。随着社会发展,许多庙宇、殿堂古建筑群被开发为景点,人们可以通过对古建筑的瞻仰来缅怀学习历史文化。由于文物古建筑自身的特点及管理上存在的一些缺失,使其存在着大量的火灾隐患,极易诱发火灾事故,且难以及时扑救会造成难以弥补的火灾损失。建造在先,防消在后,是文物古建筑的消防安全工作有别于现代建筑的最大特点。笔者总结多年来文物古建筑消防工程设计经验,发现传统水灭火系统在扑救文物古建筑火灾存在诸多弊端,欲探索一种更适用于文物古建筑的灭火系统。

DF4型内燃机车灭火系统应用方案研究

随着铁路运输业的飞速发展,内燃机车在铁路运输系统中占据了举足轻重的地位,其安全性和稳定性日益成为公众瞩目的焦点。特别是中国广泛应用的DF4型内燃机车,其灭火系统的设计与运用在确保机车安全运行、预防火灾事故方面起到了至关重要的作用。基于前期的研究成果,进一步深入探讨DF4型内燃机车灭火系统的装车与应用策略,旨在通过理论与实践的双重探索,为提升内燃机车的安全性能提供坚实的理论支撑和实用的实践指导,从而确保铁路运输的顺畅与安全。

高压细水雾灭火机泵内机油温度及温升测量结果不确定度评定

根据林业行业标准LY/T 2232-2013《林业机械以汽油机为动力的背负式高压细水雾灭火机》,进行高压细水雾灭火机的检测试验,为了提高压细水雾灭火机液泵泵内机油温升测量结果的准确性,针对在测量过程中不确定度情况进行分析,准确评估高压细水雾灭火机泵内机油温升检测项目试验结果,尤其是当测量值处于标准规定限制临界点时。

气体灭火系统和细水雾灭火系统在医院建筑中的应用及对比分析

介绍了气体灭火系统和细水雾灭火系统的灭火原理;以重庆某大型综合医院为例,对医疗设备、电气机房等进行消防灭火设计和对比分析,研究气体灭火系统和细水雾灭火系统的适用性及经济性;通过对比分析,对两种系统的选用提出相关建议。

高压细水雾灭火系统与气体灭火系统的对比分析

高压细水雾灭火系统,作为一种新型的灭火系统,现已广泛运用于大型综合医院、图书馆等场所的消防保护中。本文将从灭火机制、设备与人员安全性、适用性以及经济性等多个维度,对高压细水雾灭火系统与传统气体灭火系统进行深入的综合对比分析。

电缆竖井细水雾灭火系统数值模拟研究

利用数值模拟技术研究了电缆竖井不同高度和通风条件对细水雾灭火效果的影响,按典型高低压电缆井断面情况,基于火灾动力学软件,模拟了细水雾灭火系统在电缆竖井中不同通风条件下的控火和灭火效果,同时对细水雾灭火系统在电缆竖井中的形式、喷头布置方式等进行说明,得到在限定条件下的火灾规律性结果和相应的应用边界条件等结论,为电缆竖井防火实验研究和工程设计提供参考。