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.

Nd:YAG water mist laser treatment for giant gestational gingival tumor: A case report

BACKGROUND This case of gestational gingival tumor is huge and extremely rare in clinical practice.As the growth location of this gingival tumor is in the upper anterior tooth area,it seriously affects the pregnant woman's speech and food,causing great pain to the patient.The use of Nd:YGA water mist laser to remove the gingival tumor resulted in minimal intraoperative bleeding,minimal adverse reactions,and good postoperative healing,which is worthy of clinical promotion and application.CASE SUMMARY The patient,a pregnant woman,reported a large lump in her mouth on the first day of postpartum treatment.Based on medical history and clinical examination,the diagnosis was diagnosed as gestational gingival tumor.Postoperative pathological biopsy also confirmed this diagnosis.The use of Nd:YAG water mist laser to remove the tumor resulted in minimal intraoperative bleeding,clear surgical field of view,short surgical time,and good postoperative healing.CONCLUSION In comparison to traditional surgery,Nd:YAG water mist laser surgery is minimally invasive,minimizes cell damage,reduces bleeding,ensures a clear field of vision,and virtually eliminates postoperative edema,carbonization,and the risk of cross infection.It has unique advantages in oral soft tissue surgery for pregnant patients.Therefore,the clinical application of Nd:YAG water mist laser for the treatment of gestational gingival tumors is an ideal choice.

Combined effects of obstacle and fine water mist on gas explosion characteristics

Combined effects of obstacles and fine water mist on a methane-air explosion of a semi-closed pipe were investigated experimentally.In this study,the diameter of the water mist,the location,and the number of obstacles was considered.The results demonstrated that 5 μm water mist present a significant suppression affected while 45 μm shows a slight promotion effected on a gas explosion of the condition without obstacles.In the presence of an obstacle,however,the inhibitory effect of 5 μm water veils of mist dropped significantly during flame propagation,and the effect of 45 μm water veils of mist changed from the enhancement of inhibition,and its inhibitory effect was significant.The inhibitory effect of 45 μm water veils of mist on gas explosion weakened firstly and then enhanced with the increasing distance between obstacle location from the ignition location as well as in several obstacles.

Performance assessment of water mist applied in gas burning suppression in underground coal mine

The main objective of the present study was introduced water mist suppressiontechnology to prevent and control gas burning which occurred during drilling at Wu20160working-face in No.10 coal mine of Pingdingshan Ltd..Based on the self-developed ex-periment platform,a series of fire suppression tests to evaluate the performance of a watermist system were conducted.The detailed measurements of the spray characteristics,i.e.,the Sauter Mean Diameter(SMD),the velocity and spray angle which are the main pa-rameters considered in the Study,were obtained by using LS-2000 Sizer.The amount ofwater consumed and the water flux density distribution over the cross section downstreamthe nozzle exit were measured by cup collector method.The operating pressure of thewater mist nozzle is set to 0.5 MPa,the droplet SMD of 104 pm,the water flux density dis-tribution from 0.71 to 8.47 L/(m^2.min),the average velocity of 2.14 m/s.The experimentalresults show that the averaged time required for extinguishment is 3.14 s,and the corre-sponding amount of water used during fire test is about 0.11 kg.The gas fire suppressionsystem reduces the temperature in combustion chamber of the experimental apparatusbelow the ignition point of the gas,which can effectively avoid the occurrence of the gasfire in coal mine.

Coal combustion restrained by ultra-fine water mist in confined space

In order to apply ultra-fine water mist technology on spontaneous coal combustion in the goaf of a coal mine, we built a small scale compartment with ultra-fine water mist for restraining coal combustion in a confined space and then investigated the restraining efficiency and related factors. The study obtained the following results： a descending rate of heat release, an increase in 02, the production of CO2 decreased gradually, while the production of CO increased dramatically and quickly and then decreased; ultimately it tended to become stable after the discharge of an ultra-fine water mist. The technology showed that the ultra-fine water mist can effectively reduce the heat release rate of coal and the rate to generate components. We found that the restraining effect relied on the mist flux, the discharge time and other factors. A sufficient amount of mist has a better effect compared to an insufficient amount of mist. To combat coal combustion, the greater the discharge time, the better coal flames are extinguished.

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.

Water Content Effect on Oxides Yield in Gas and Liquid Phase Using DBD Arrays in Mist Spray

Electric discharge in and in contact with water can accompany ultraviolet（UV）radiation and electron impact, which can generate a large number of active species such as hydroxyl radicals（OH）, oxygen radical（O）, ozone（O_3） and hydrogen peroxide（H_2O_2）. In this paper, a nonthermal plasma processing system was established by means of dielectric barrier discharge（DBD）arrays in water mist spray. The relationship between droplet size and water content was examined,and the effects of the concentrations of oxides in both treated water and gas were investigated under different water content and discharge time. The relative intensity of UV spectra from DBD in water mist was a function of water content. The concentrations of both O_3 and nitrogen dioxide（NO_2） in DBD room decreased with increasing water content. Moreover, the concentrations of H_2O_2, O_3 and nitrogen oxides（NOx） in treated water decreased with increasing water content,and all the ones enhanced after discharge. The experimental results were further analyzed by chemical reaction equations and commented by physical principles as much as possible. At last,the water containing phenol was tested in this system for the concentration from 100 mg/L to9.8 mg/L in a period of 35 min.

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.

Middle or low water pressure direct spiral double helix converging nozzle structure optimization and flow field analysis

In order to solve the problem of using new nozzle is proposed in fire rescue robot. middle or low water pressure to form fine water mist, a Existing water mist nozzles are basically used for high pressure and in large size, complex structure and poor low pressure atomization effect in comparison with requirement of snake-like fire rescue robots. On the basis of comprehensive typical spray noz- zles, a direct spiral double helix converging nozzle （DSDHCN） is proposed, which has the advanta- ges of small volume, light weight, simple structure, and convenient installation. To make the spray nozzle have good performance, and meet the requirements of more efficient fire extinguishing, a nu- merical study is carried out to analyze the internal and external full flow field of nozzle. A gas-liquid two-phase flow is applied to simulate the external full flow field of nozzle with VOF model in fluent software. The simulation results show the real situation of water flow out of the atomization nozzle and the water jet trajectory. Some simulations about middle or low water pressure direct spiral double he- lix converging optimized nozzle have been done in 30bar pressure. The simulation results show that the optimized nozzle structure not only makes the spray droplets have a good cone angle, but also have a sufficient axial velocity,which proves the structure rationality of the proposed optimized nozzle.

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.

地铁车站高压细水雾灭火系统设计探讨

高压细水雾式灭火系统在地铁车站中作为一种新型替代性技术,已经显示出了极其优越的性能,并且引发了国际消防学界的广泛重视。在现行设计规范中,对于高压细水雾灭火系统在地铁车站的应用还没有详细规定。论文将结合地铁车站的特殊应用环境,以及设计实例,重点讨论高压细水雾灭火系统在设计中的参数选择和设备布置原则等相关问题,深入分析高压细水雾灭火系统的技术优势和特点。

分布式电源(DPS)机房的高压细水雾灭火试验研究

随着网络技术的快速发展,越来越多的数据机房采用分布式电源(DPS)机房。而由于DPS机房内存在磷酸铁锂电池,导致DPS机房火灾特点区别于传统以电缆为主的数据机房火灾,因此应对DPS机房磷酸铁锂电池火灾展开试验研究。重点试验研究了DPS机房磷酸铁锂过充火灾下的探测系统报警及高压细水雾系统灭火效果、可燃气体浓度研究,并对比了高压细水雾系统不同布置方式下的灭火效果,给出了探测系统设计意见,从而为工程项目应用提供技术支撑。

细水雾抑制石化污水系统内油气爆炸的实验与模拟

为研究石化污水系统内细水雾抑制油气爆炸的冲击规律,搭建10 m×1.5 m×1.5 m真实尺度污水系统模型,并开展细水雾抑制油气燃爆实验,结合数值模拟方法研究了细水雾覆盖区域、细水雾喷雾流量、可燃气初始浓度等因素爆炸冲击的影响。结果表明,通道前端覆盖细水雾使得腔体峰值超压明显增强,后端覆盖细水雾腔体内部爆炸超压被显著抑制;随着水雾起始位置距点火点距离D的增加,通道内爆炸超压峰值出现时间明显延后,且爆炸峰值超压逐渐减弱;腔体前端施加细水雾时,随着喷雾流量的增加爆炸超压峰值出现时间明显提前,且爆炸峰值超压逐渐增加,而后端施加细水雾时,规律相反;细水雾施加下,随着可燃气初始燃料配比ER增加,通道内爆炸超压峰值呈现先增后减、超压峰值出现时间先减小后增大。

单相高压与两相雾化方式对地铁车厢火灾抑制效果的对比实验研究

目前地铁车厢内细水雾灭火系统以单相高压雾化方式为主,高压管路一旦破损可对乘客生命安全构成潜在威胁。以行李袋和汽油作为燃烧物开展了全尺寸实验研究。分别从冷却能力、热辐射衰减效果及烟气抑制效果方面分析对比了单相雾化和两相雾化方式对车厢内火灾的抑制效果。结果表明单相雾化和两相雾化冷却效果相当,但两相雾化在热辐射衰减、烟气洗消效果方面较高压单相雾化更优,且安全性更好。

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。

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。

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。

某火电厂集控室消防细水雾抑制火灾模拟分析

以某火电厂建设工程集控室消防系统设计为例,利用PyroSim火灾模拟软件建立试验模型,模拟研究在不同压力和角度下细水雾对T^(2)模式自由火的抑制过程,对比分析细水雾在喷头角度为45°、60°、90°和喷头压力为1 MPa、2 MPa、5 MPa时的火焰温度变化曲线,模拟空间内的CO、O_(2)浓度变化、灭火时间和灭火用水量等情况。结果表明:灭火过程可以分为喷雾初期的抑制阶段、火焰强化膨胀阶段和细水雾再次抑制阶段3个阶段;水雾压力越大,灭火效果越明显;喷射角度为90°的细水雾灭火过程中火焰温度变化平稳,适合作为集控室的自动灭火喷头参数;垂直布设的中压细水雾具有更好的实用价值。

基于轨道客车防火技术标准体系的消防设施配置研究

党中央、国务院印发的《交通强国建设纲要》中指出要建设现代化综合交通体系和城市群一体化交通网,提升交通装备安全水平和安全防护能力。文章基于轨道客车防火相关技术标准的制修订现状,对轨道客车消防设施配置进行了研究,对灭火器、安全锤、紧急呼吸面罩、细水雾灭火系统等消防设施的参数、性能展开了论述,对消防设置的选型、配置、安装和维修保养解决方案提出了建议。可以确保紧急情况下能够快速、有效地扑灭火灾,同时降低火灾造成的损失及人员伤亡,有助于提高轨道客车消防设施配置规范性,提高轨道客车的安全水平和安全防护能力,助力交通强国战略的实施。

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。