公路隧道纵向诱导风速对火灾烟气控制效果影响分析

针对某公路隧道采用集中排烟方式的工程实际,为了分析纵向诱导风速对隧道火灾烟气控制效果的影响规律,进而确定可能的火灾场景时的合理纵向诱导风速,采用火灾动力学模拟软件FDS构建了数值分析模型,并设计了相应的火灾工况.根据隧道实际交通流量、车辆类型及公路等级,确定了模拟火灾规模.分别分析了火灾规模为50 MW时隧道内不同火源位置(排烟阀打开段中部、上游1个/下游5个排烟阀、上游2个/下游4个排烟阀),不同排烟方式下(双向均衡排烟、上游端单向排烟、下游端单向排烟),不同纵向诱导风速情况时的隧道2m高处能见度、烟气蔓延范围及排烟效率,根据模拟分析结果,进而确定了不同火灾工况时的合理纵向诱导风速.结果表明:不同纵向诱导风速对集中排烟模式下烟气控制效果影响显著;特定火灾规模时,火源位置、排烟方式对合理纵向诱导风速的影响不大.     

地铁车站及隧道全尺寸火灾实验研究(3)—车站隧道火灾

为了研究烟气在地铁车站隧道内的蔓延特征,及在车站隧道通风排烟系统、区间隧道通风排烟系统及车站公共区通风排烟系统联合排烟情况下烟气控制效果,在一地铁车站隧道内开展了全尺寸火灾实验.实验研究了车站隧道顶部横向排烟作用下的烟气扩散规律,及烟气的温度变化,分析了屏蔽门开关状态下烟气与空气的卷吸混合特性,及区间风机的气流组织对通风排烟的影响.实验结果对于地铁车站隧道火灾防排烟设计提供了数据支持.     

火源与排烟口布置对隧道火灾排烟影响的数值模拟

运用FDS软件对某半横向通风隧道火灾进行数值模拟,研究了火灾中火源与排烟口布置中烟气蔓延与排烟效果的影响。通过模拟6种不同火源与排烟口布置组合工况下隧道内烟气质量浓度、回流长度的变化规律,得出半横向通风排烟系统排烟效果规律。结果表明:火源位于隧道中间与右车道时,隧道内烟气质量浓度分布基本相同,表明火源位置横向分布对半横向通风系统排烟效果几乎没有影响,而排烟口分布对火灾烟气的蔓延影响较大,排烟口位于烟道板两侧时隧道内烟气质量浓度和回流长度都明显小于当其位于烟道板中部与右侧1/3处时,表明排烟口位于烟道板两侧时隧道排烟系统排烟效果较好,而排烟口位于烟道板中部与右侧1/3处时,两者排烟效果相同,这与文献的小尺寸试验研究结果相吻合。     

水幕排烟系统对烟气控制及排烟效率的影响研究

为探明水幕排烟系统对隧道内烟气控制和排烟效率的影响,通过火灾动力学求解器(FDS)研究不同排烟风量下隧道内烟气、温度和速度分布。结果表明:排烟量小于100 m3/s时,水幕无法有效地阻隔有毒烟气的蔓延;当火源热释放速率(HRR)为10、20及30 MW时,排烟量分别为100、160和180 m3/s,能将烟气限制在水幕排烟系统内;在水幕的作用下,水幕外的温度分布均满足人员逃生的需要(小于80℃),在水幕排烟系统中烟气控制要比温度控制更为重要;相同火源HRR下,排烟口的排烟效率随着排烟量先增大后减小;排烟口的吸穿效应在水幕排烟系统中很难出现,排烟口吸入位于隧道底部混有大量新鲜空气的烟气是造成排烟效率降低的主要原因。     

沉管隧道内车厢火羽流的临界风速研究

为探究纵向通风与侧向集中排烟协同作用下,沉管隧道内车厢火羽流的临界控制风速特征,首先,建立1∶8缩尺寸隧道试验模型;然后,选取3种车厢开口尺寸及9组火源功率,并考虑侧向集中排烟系统开启和关闭2种状态,采集沉管隧道内不同纵向风速下顶棚烟气温度数据;同时,通过火灾动力学模拟软件(FDS)模拟沉管隧道内车厢火羽流的速度场和温度场分布特征;最后,分析临界风速演化的物理影响机制。结果表明：无论侧向集中排烟系统是否开启,隧道顶棚下方烟气最大温升均会随纵向风速增加而下降,同时隧道内烟气逆流长度也会不断缩短直至为0;随隧道内车厢火源功率的增加,临界风速均呈现先增大后不变的趋势;在相同火源功率条件下,侧向排烟系统开启时对应的临界风速明显大于其关闭的情况;在侧向排烟与纵向通风协同作用下,随火源功率增加,沉管隧道车厢火羽流临界风速呈现先增加、后不变的分段函数关系。     

地铁停车线区域通风排烟模式研究

为明确复杂结构、多排烟系统联动作用下,地铁停车线区域火灾烟气扩散特性,优化停车线通风排烟策略,针对广州某停车线区域开展了火灾现场实验和数值模拟研究。首先,基于全尺寸火灾试验结果,获取停车线区域典型火灾场景下的烟气扩散和沉降特性,并测量停车线区域不同通风模式下的气流流速;随后,运用数值模拟方法对比多种排烟模式下的烟气控制效果,并分析隧道风机和射流风机排烟风量对烟气扩散特征的影响形式。研究结果表明：自然通风场景下,火灾烟气起火后180 s内即可进入区间隧道及配线隧道,而启动隧道风机排烟可以减缓烟气扩散速率和沉降速率,但隧道风速未达到临界风速时,无法控制烟气向外扩散;隧道风机排烟组合区间射流风机向停车线送风的工作模式是停车线区域最佳排烟模式,建议隧道风机采用2台60 m³/s风量风机,射流风机采用2台30 m³/s风量风机,可同时降低停车线区域、区间隧道及配线隧道区域的烟气扩散和沉降速率,延长各区域可用疏散时间。研究结果可用于指导停车线风机选型及排烟模式设计,提升停车线区域火灾烟气控制能力。     

地铁区间隧道半横向排烟方式的数值模拟研究

为了研究地铁区间隧道半横向排烟方式对排烟效果的影响,利用火灾动力学模拟软件FDS研究在车厢内部着火且火源功率为5 MW的情况下,不同的排烟道高度、排烟风速、排烟口开启个数对隧道内烟气控制的影响,即对不同工况下,隧道内烟气蔓延情况、人眼特征高度处的CO浓度、温度进行研究并作对比分析。结果表明,综合考虑排烟效果与隧道挖掘成本,排烟道设置高度为1.6 m较为合适;排烟风速控制为10 m/s并且开启火源附近2个排烟口能获得较好的排烟效果。     

地铁车站及隧道全尺寸火灾实验研究(2)——区间隧道火灾

为了研究强制通风情况下地铁区间隧道火灾时的烟气扩散规律,在一实际地铁区间隧道内开展了全尺寸火灾实验。实验改变火源功率,在区间隧道通风排烟系统启动状态下,研究了区间烟气纵向蔓延速度、烟气竖直温度分布和水平温度变化,分析了烟气火焰倾斜角,顶棚烟气温升的纵向指数变化特征。实验结果对于地铁区间隧道火灾烟流控制及防排烟设计提供了数据支持。     

地铁长大区间隧道火灾风机启动方案数值模拟研究

为了研究地铁长大区间隧道火灾烟控模式,以国内某一在建地铁长大区间隧道为研究案例,选取不利起火位置,设置了7种风机启动方案,研究不同风机启动方案下,隧道内顶棚温度,疏散平台人员高度烟气温度、CO浓度、可见度的变化,获得不同风机启动方案情况下排烟效果。研究表明:当开启了火源附近足够数量的送风风机后,额外增加距离火源较远的送风风机并不会显著改善排烟效率;即使开启风机台数一致,开启火源所在区段两端的风机效果明显好于开启其他风机。     

纵向风速对隧道内烟气发展影响的实验研究

通过在鹰嘴岩隧道内的现场模拟火灾试验,对不同纵向通风速率下隧道内烟气发展过程进行了研究。结果表明,纵向风速和火源大小均对烟气层沉降有重要影响。相比之下,纵向风速对烟气层沉降的影响更大;火源位置较高时,烟气层热膨胀力较大,在距离火源一定距离外仍可产生上游方向的烟气逆流;一定坡度的隧道在某种条件下可以产生"弱烟囱效应",导致烟气向下游方向的流速增加。在隧道设计中可以考虑利用这一点来增加排烟效率。     

Characteristic overpressure–impulse–distance curves for the detonation of explosives, pyrotechnics or unstable substances

A number of models have been proposed to calculate overpressure and impulse from accidental industrial explosions. When the blast is produced by explosives, pyrotechnics or unstable substances, the TNT equivalent model is widely used. From the curves given by this model, data are fitted to obtain equations showing the relationship between overpressure, impulse and distance. These equations, referred to here as characteristic curves, can be fitted by means of power equations, which depend on the TNT equivalent mass. Characteristic curves allow determination of overpressure and impulse at each distance.     

围压作用下自振空化射流脉动特性实验研究

就围压下自振空化射流动压力特性进行了实验研究,其实验结果表明：在围压作用下,自振空化射流脉动幅度存在最优喷距,并且最优喷距随围压的增大而增大;在压降一定情况下,脉动幅度随围压的增加而减小;在围压和压降一定时,自振空化射流的最大冲击压力明显高于普通连续射流;自振空化射流的脉动频率,基本不随围压、压降和喷距的变化而变化,在本实验条件下,基本保持在１．３８ＫＨｚ 左右     

爆震雾化射流用于灭火的可行性研究

脉冲细水雾灭火技术在国内外已获得成功应用 ,为进一步提高其灭火效果和简化装备 ,笔者提出了一种基于爆炸推进原理的爆震雾化射流发生装置 ,对其工作原理、动力特性进行了分析。理论分析与初步实验结果表明 ,爆震流体动力源可获得极高的能量密度和输出功率 ,爆震雾化射流具有直流水与雾状水的双重灭火性能 ,其灭火机理是脉冲雾化水的强水力冲击、高效冷却、隔氧阻燃、吸收热辐射及火焰拉伸的共同作用 ,该技术适于开发高效、清洁的便携式个人消防装备     

Influence of laneway support spacing on methane/air explosion shock wave

A laneway support system provides an available way to solve problems related to ground movements in underground coal mines, but also poses another potential hazard. Once a methane/air explosion occurs in a laneway, inappropriate design parameters of the support system, especially the support spacing, likely have a negative influence on explosion disaster effects. The commercial software package AutoReaGas, a computational fluid dynamics code suitable for gas explosions, was used to carry out the numerical investigation for the methane/air explosion and blast process in a straight laneway with different support spacing. The validity of the numerical method was verified by the methane/air explosion experiment in a steel tube. Laneway supports can promote the development of turbulence and explosion, and also inhibit the propagation of flame and shock wave. For the design parameters in actual laneway projects, the fluid dynamic drag due to the laneway support plays a predominant role in a methane/air explosion. There is an uneven distribution of the peak overpressure on the same cross section in the laneway, and the largest overpressure is near the laneway walls. Different support spacing can cause obvious differences for the distributions of the shock wave overpressure and impulse. Under comparable conditions, the greater destructive effects of explosion shock wave are seen for the laneway support system with larger spacing. The results presented in this work provide a theoretical basis for the optimized design of the support system in coal laneways and the related safety assessments.     

Determining Attenuation of Impulse Noise With an Electrical Equivalent of a Hearing Protection Device

Determining the effectiveness of impulse noise attenuation with hearing protection devices (HPDs) is an important part of their selection. Measuring impulse noise parameters under an HPD would involve exposing subjects to impulses with a high peak sound pressure level. This paper presents a computational method of determining impulse noise parameters under the cups of earmuffs. Calculations are done using the transfer function of earmuffs, determined with Shaw’s electrical equivalent of an HPD, taking into account the design parameters of earmuffs. The developed method was used for calculations in the presence of impulse noise generated by gunshots. To verify the computational method, the results of these calculations were compared with the results of measurements.     

密闭管道瓦斯爆炸冲击波冲量及压力上升速率的实验研究

针对矿井瓦斯爆炸破坏模式主要在压力破坏和冲量破坏的研究,实验分析瓦斯在密闭管道发生爆炸时瓦斯浓度对冲击波冲量及压力上升速率的影响,利用管道中距离点火源不同位置的压力传感器测试了不同浓度瓦斯的爆炸压力,对冲击波冲量及压力上升速率进行分析,为防爆抑爆提供依据。研究结果显示:在管道中距离点火源的不同位置上,当浓度为9.5%时,瓦斯爆炸冲击波冲量及压力上升速率最大;由于超压衰减和传播距离的增加,在距离点火源4m和8m时压力冲量较大;在瓦斯浓度较低的范围内瓦斯爆炸时,其压力上升速率增长较快,而随着浓度的增加在较宽的浓度范围内,能较稳定地维持在高位值。     

滑坡涌浪灾害物理模型试验研究综述

为有效预防和减少滑坡涌浪灾害，采用定性文献综述方法从涌浪的产生、传播与衰减、爬高3个阶段对国内外物理模型试验相关文献进行全面梳理分析。结果表明:涌浪产生阶段的研究主要集中在波形特征的识别和初始波高/波幅的公式表达上，传播阶段的研究主要聚焦在涌浪形态和波高在空间的衰减上，而爬高阶段则主要关注爬高的求解。在现状分析的基础上，从致灾因子、承灾体、防灾减灾角度提出关注泥岩质滑坡体、滑坡体淹没率等具体的未来研究建议。     

Consequence analysis by means of characteristic curves to determine the damage to humans from the detonation of explosive substances as a function of TNT equivalence

In a previous paper, the characteristic overpressure–impulse–distance curves for the detonation of explosive substances were presented. They allow the overpressure and impulse to be determined at each distance from the detonation. When combined with damage criteria (such as those shown by the Probit equations), the characteristic curves allow consequence analysis for this kind of explosion to be carried out in only one step, as the damage is shown in the same diagram as the overpressure, impulse and distance. In this paper, diagrams and equations are presented to determine the damage to humans (eardrum rupture, death due to displacement and skull fracture, death due to displacement and whole body impact, and death due to lung damage or lung haemorrhage).     

低压脉冲袋式除尘器在硅铁电炉烟气中的应用

介绍了低压脉冲袋式除尘器在6300 kVA半封闭式硅铁电炉烟气除尘系统中的应用,通过对铁合金半封闭式硅铁电炉烟气性质的分析,对除尘系统在运行过程中出现的问题以及解决方案进行了分析和阐述,最后指出低压脉冲袋式除尘器在半封闭式硅铁电炉除尘系统中使用时应该注意的问题。     

Accuracy of assessing the level of impulse sound from distant sources.

Impulse sound events are characterised by ultra high pressures and low frequencies. Lower frequency sounds are generally less attenuated over a given distance in the atmosphere than higher frequencies. Thus, impulse sounds can be heard over greater distances and will be more affected by the environment. To calculate a long-term average immission level it is necessary to apply weighting factors like the probability of the occurrence of each weather condition during the relevant time period. This means that when measuring impulse noise at a long distance it is necessary to follow environmental parameters in many points along the way sound travels and also to have a database of sound transfer functions in the long term. The paper analyses the uncertainty of immission measurement results of impulse sound from cladding and destroying explosive materials. The influence of environmental conditions on the way sound travels is the focus of this paper.