细水雾对障碍物挡板火灭火有效性的实验研究

在不同障碍物挡板阻隔条件下，就细水雾对油池火的灭火效果进行了实验研究，分析了不同空间位置的障碍物挡板对细水雾灭火效果的影响，采用FDS40对细水雾与不同类型障碍物挡板油池火的相互作用过程的模拟结果表明：障碍物结构与类型影响着细水雾直接作用于油池火上方的水雾通量，油池火上方的水雾卷吸量越大，细水雾对障碍火的灭火效果越明显。     

细水雾灭火技术在电气环境的研究与进展

介绍了细水雾的定义和主导灭火机理，对细水雾、水喷淋及气体灭火技术在电气环境的应用进行了比较，说明了细水雾用于电气环境火灾防治的优点及不足。结合前人实验结果系统地阐述了细水雾的导电性、细水雾作用下电气设备击穿强度变化规律、细水雾的滞空性及烟气冲刷能力。重点回顾了国际上细水雾用于计算机、程控交换机及发电机等电气设备火灾防护的可行性及有效性研究，描述了细水雾作用下带电工作的计算机、发电机、程控交换机等设备的稳定性和可靠性，讨论了雾滴粒径、雾滴速度、雾通量及障碍物遮挡程度等因素对扑灭电气火灾有效性的影响，介绍了国际上细水雾灭火技术在电气环境的应用现状。     

细水雾与火灾烟气相互作用的实验和数值模拟研究

通过模拟实验研究了细水雾与火灾烟气的相互作用,揭示了细水雾作用下烟气温度及组分浓度的变化规律。同时利用FDS程序计算了细水雾作用下烟气温度和组分浓度随时间的变化规律,利用实验数据对计算结果进行了准确性验证。结果表明只要计算网格匹配合理,FDS可以较为准确地预测细水雾作用下烟气温度和组分浓度的变化规律。在实际的细水雾灭火系统工程应用中,可以利用FDS场模拟方法预测灭火过程中火场温度及组分浓度等特性参数的变化规律,这对灭火系统的优化设计具有一定指导意义。     

浅议细水雾灭火系统在商用厨房中的应用

商用厨房火灾绝大多数是食用油燃烧失去控制所致,食用油的闪点和自燃温度较高,一旦发生火灾,难以扑救,而且表面火焰灭熄后需要继续冷却,否则还会复燃。本文从分析商用厨房火灾危险性入手,结合商用厨房火灾灭火技术要求及现状,介绍了细水雾灭火技术的发展和灭火机理,对比了细水雾灭火系统的优势和应用过程中存在的问题,为有效防护和减少厨房火灾提供参考。     

自然通风对细水雾降温速率影响研究

在受限空间通过模拟试验研究细水雾作用下烟气温度的变化规律。实验中通过改变通风口面积、通风口与火源的相对位置及喷雾强度等因素,研究自然通风对细水雾降温速率的影响规律,定量地表征不同自然通风条件下降温速率的衰减比例,实验发现增加喷雾强度可以降低自然通风造成的降温速率衰减。研究结果可为细水雾灭火系统的工程应用和优化设计提供必要的参考依据。     

水雾对黏塑性炸药PBXN-5燃烧的抑制作用研究

为研究水雾对自由堆积状态黏塑性炸药PBXN-5粉末燃烧的抑制作用,搭建了开放式燃烧试验装置,选用了粒度范围D₉₈=425 μm的PBXN-5粉末,分别对无水雾、喷水压力为0.5 MPa和2.0 MPa 3种条件下堆积状态PBXN-5的燃烧过程进行了试验,获得了火焰传播过程及火焰温度随时间的分布曲线。结果表明:在水雾喷水压力为0.5 MPa 和2.0 MPa时,堆积状态PBXN-5的燃烧持续时间分别是自由燃烧时的32.6%和31.8%,说明水雾对于PBXN-5燃烧有很好的抑制作用;灭火时间分别为377.011 ms和115.004 ms,而且2.0 MPa时火焰的最高下降速率较0.5 MPa时有所增加,表明对于堆积状态PBXN-5火焰抑制效果来说,雾动量的影响较雾滴粒径强。     

细水雾作用下烟气组分浓度变化规律的模拟研究

在ISO 9705标准房间通过模拟实验研究了细水雾与火灾烟气的相互作用,揭示了细水雾作用下烟气中氧气、一氧化碳和二氧化碳浓度的变化规律,建立了氧气、一氧化碳和二氧化碳浓度与细水雾工作压力及风机速率的数学模型。实验发现当风机速率达到1.5 kg/s时烟气组分浓度变化规律发生突变,对这一现象进行了深入分析和解释。本文为细水雾技术用于火灾烟气抑制提供了必要的理论基础和科学的参考依据。     

新型细水雾添加剂成分对灭火性能影响研究

为研究自制细水雾添加剂中主要成分对灭火性能的影响,在开放空间,进行了不同工作压力、不同浓度、不同燃料条件下含添加剂细水雾的灭火研究,实验获取了灭火时间、火焰形态、火焰温度等灭火参数。通过对柴油和汽油两种不同燃料的灭火实验发现,使用含添加剂的细水雾对低沸点、高蒸发速率的汽油灭火效果同样较好。根据加入不同浓度的氟表面活性剂的实验结果比照发现,氟表面活性剂是自制添加剂中起到主要提升灭火性能作用的物质,它通过改变细水雾物理性质使加入自制添加剂的细水雾的灭火性能显著提高。对比调整自制添加剂各物质含量的实验数据,进一步确定添加剂各成分最佳灭火性能浓度。     

人造水雾粒度测试及红外消光因子计算分析

在大型半密闭空间内发生具有不同粒度分布的水雾体系,用喷雾激光粒度仪测试粒度分布规律并采用Van Der Hulst公式计算不同大小水雾粒子对红外辐射的散射效率因子、吸收效率因子和消光效率因子。结果表明:试验条件下水雾粒子的平均直径在5~65μm范围内。计算结果显示:水雾粒子对3～5、8～14μm红外辐射的消光作用主要取决于散射效应而非吸收效应。当水雾粒子的直径大于等于红外辐射的波长时,水雾体系对该波长红外辐射能够产生较强的消光效果。综合分析水雾体系的稳定性和消光特性,直径在3~30μm之间的水雾粒子对3～5、8～14μm红外辐射的衰减效果更为明显。     

用锥形量热仪研究细水雾抑制熄灭PVC火

利用锥形量热仪和单流体细水雾系统研究了细水雾抑制PVC火的过程，并观察了重燃现象的发生，测量了实验中热释放速率及O2，CO2，CO和烟气的浓度变化，并对不同细水雾工作压力及不同热辐射流量下的结果进行了比较。由实验可知细水雾能快速扑灭PVC火，且压力越大灭火越迅速，但是在灭火后停止施加细水雾会发生重燃现象，且重燃发生的时间长短与作用在燃料表面的水量有关。     

Delayed thermal explosion in flammable gas containing fuel droplets: Asymptotic analysis

The problem of thermal explosion in a flammable gas mixture with addition of volatile fuel droplets is studied based on the asymptotic method of integral manifolds. The model for the radiative heating of droplets takes into account the semitransparency of droplets. A simplified model for droplet heat-up is used. The results of the analysis are applied to the modelling of thermal explosion in diesel engines. Two distinct dynamical situations have been considered, depending on the initial droplet concentration. These are far zone (small initial liquid volume fraction and small droplet radii) and near zone (large initial liquid volume fraction and large droplet radii). The conditions of the first zone are typical for the areas in the combustion chamber which are far from the fuel injectors, while the conditions of the second zone are typical for the areas in the combustion chamber which are relatively close to the fuel injectors. It has been pointed out that small droplets heating and evaporation time in the far zone is smaller than the chemical ignition delay of the fuel vapor/air mixture. The total ignition delay decreases with increasing initial gas temperature. In the near zone for large droplets, the process starts with the initial gas cooling and slight heating of droplets. This is followed by a relatively slow heating of gas due to the chemical reaction, and further droplet heating. The total ignition delay in the near zone is larger than in the far zone. It is expected that before thermal explosion in the near zone takes place, the droplets break up and are removed from this zone. In optically thick gas effects of thermal radiation are negligible for small droplets but are noticeable for large droplets.     

Model of large pool fires

A two zone entrainment model of pool fires is proposed to depict the fluid flow and flame properties of the fire. Consisting of combustion and plume zones, it provides a consistent scheme for developing non-dimensional scaling parameters for correlating and extrapolating pool fire visible flame length, flame tilt, surface emissive power, and fuel evaporation rate. The model is extended to include grey gas thermal radiation from soot particles in the flame zone, accounting for emission and absorption in both optically thin and thick regions. A model of convective heat transfer from the combustion zone to the liquid fuel pool, and from a water substrate to cryogenic fuel pools spreading on water, provides evaporation rates for both adiabatic and non-adiabatic fires. The model is tested against field measurements of large scale pool fires, principally of LNG, and is generally in agreement with experimental values of all variables.     

The Dynamics of Vapor Void under Conditions of Thermal Interaction of a Hot Spherical Particle with Ambient Water

The problem on the thermal interaction of a hot spherical particle with ambient water heated to the boiling point is solved. The level of physical parameters is treated that corresponds to the interaction between molten core droplets and cooling water in the case of severe accident in a nuclear reactor. In calculating the heat transfer via the vapor shell, the thermal radiation of the particle is included. An analytical solution in isobaric approximation is derived for the initial stage of interaction. As demonstrated by the results of comparison with a complete numerical solution, the oscillations of vapor pressure and vapor shell thickness do not affect the mean parameters of heat transfer from particle to water. Results are obtained that illustrate the damping effect of thermal radiation of the particle on the oscillation of the particle vapor shell. The possible destruction of a melt droplet under the effect of oscillation of pressure in the vapor shell is estimated, and the value of the droplet size is obtained at which its further destruction is unlikely.     

Modeling of explosion thermal radiation

The hydrodynamic and radiation processes accompanying explosions of chemical explosives and fuel-air mixtures have been considered. Computer modeling of the radiation from a fire ball of explosion and a flame of diffusion combustion of a hydrocarbon fuel has been performed. The dependences of the heat flux density from the region occupied by explosion and combustion products on its temperature and geometric characteristics have been determined. Thermal load distributions on targets of different orientations in the vicinity of the energy release zone have been obtained. A comparison of the thermal parameters on radiation detectors with the criteria of thermal affection of people and ignition of combustible materials has been made.     

组分含量对水基热气溶胶灭火剂燃速影响规律的研究

水基热气溶胶灭火剂是以替代哈龙为目的而研制的新一代灭火剂。通过水基热气溶胶灭火剂在燃烧器中燃烧，产生以水蒸气和惰性气体为主体的气溶胶灭火介质，经冷却后，排放到被保护空间，对火灾实施有效扑救。因此，水基热气溶胶灭火剂在燃烧器中的燃烧速度，对其灭火效率有重要影响。研究了硝酸钾、催化剂（caty1）、水分、淀粉等组分含量对水基热气溶胶灭火剂的平均质量燃速的影响规律。     

Large hydrocarbon fuel pool fires: physical characteristics and thermal emission variations with height

In a recent paper [P.K. Raj, Large LNG fire thermal radiation-modeling issues and hazard criteria revisited, Process Safety Progr., 24 (3) (2005)] it was shown that large, turbulent fires on hydrocarbon liquid pools display several characteristics including, pulsating burning, production of smoke, and reduced thermal radiation, with increasing size. In this paper, a semi-empirical mathematical model is proposed which considers several of these important fire characteristics. Also included in this paper are the experimental results for the variation of the fire radiance from bottom to top of the fire (and their statistical distribution) from the largest land spill LNG pool fire test conducted to date. The purpose of the model described in this paper is to predict the variation of thermal radiation output along the fire plume and to estimate the overall thermal emission from the fire as a function its size taking into consideration the smoke effects. The model utilizes experimentally measured data for different parameters and uses correlations developed from laboratory and field tests with different fuels. The fire dynamics and combustion of the fuel are modeled using known entrainment and combustion efficiency parameter values. The mean emissive power data from field tests are compared with model predictions. Model results for the average emissive powers of large, hypothetical LNG fires are indicated.