惰性气体对容器泄爆收容过程的影响分析

为了考察惰性气体对容器泄爆收容过程的影响,对利用含有惰性气体的容器收容另一个容器内爆炸气体过程中的压力变化规律进行了试验研究。结果表明:收容容器中惰性气体存在时,起爆容器及收容容器内的压力峰值都较低,且泄爆膜破裂后,两容器内的压力上升速率都有所下降,惰性气体的存在能有效抑制泄爆收容过程中的爆炸强度,对起爆容器和收容容器都起到了一定的保护作用;收容容器内的惰性气体体积分数越高,两容器内的压力峰值越低,对两容器的保护作用越好;在一定范围内,随导管长度增加,起爆容器及收容容器内的压力峰值降低,而当导管长度超过某一特定值时,继续增加导管长度,两容器内的压力峰值变化不大;惰性气体的存在能有效抑制火焰的传播,降低火焰传播速率,达到抑制爆炸的目的。     

受限空间内惰性气体对CH4爆炸抑制特性研究

N2和CO2是常用的惰性抑爆气体,为研究两种气体的抑爆特性,采用20L球形爆炸试验装置,分析了不同浓度配比条件下N2/CH4/空气以及CO2/CH4/空气混合气体的爆炸压力,同时采集爆炸后的气体样品,对比分析爆炸后残留气体的主要成分。结果显示:随CH4浓度从5%增加至12.5%时,完全抑制CH4爆炸需要的惰性气体最小量先增大后降低,CH4浓度在6.5%~7.5%之间时,抑爆需要的惰性气体的量最大;在同一CH4浓度条件下,抑爆需要N2的量大于CO2,并且CH4浓度在5%~6.5%时,抑爆需要两种惰性气体的量值差别最大;当CH4浓度一定时,随着加入惰性气体量的增大,爆炸最大超压逐渐降低,惰性气体浓度和爆炸超压之间基本呈线性关系;在同样条件下,相对于N2,CO2为抑爆气体时,爆炸后腔体内残留的CH4浓度较高。研究成果为惰性气体抑爆技术提供技术支撑,同时为揭示惰性气体抑爆机理有一定作用。     

抑制油料洞库油气爆炸传播的新技术设想

针对目前常用的油气爆炸抑制技术在油料洞库应用中存在的不足,提出了一种利用真空腔技术来抑制油料洞库油气爆炸的设想,并对真空腔抑制油气爆炸过程中的传热机理和传质机理进行了详细分析.     

受限空间网状高分子材料抑制油气爆炸实验研究

为研究新型网状高分子材料对油气爆炸的抑制作用,搭建了狭长受限空间油气爆炸抑制实验系统,进行了油气爆炸抑制实验,通过对比是否按留空率规范填充抑爆材料所达到的3种工况,分析了爆炸超压值、升压速率、火焰强度和火焰持续时间等特性参数变化情况。实验结果表明:新型网状高分子材料对油气爆炸产生的最大爆炸超压值、升压速率和火焰强度有明显的抑制作用;新型网状高分子材料对火焰的传播有明显的阻滞作用,使火焰传播速度减小;当新型材料按照规范填充时,最大爆炸超压值和升压速率分别下降了84.36%和 39.18%以上,火焰被完全熄灭,并且距离点火端越远,抑爆效果越明显。     

七氟丙烷对狭长受限空间油气爆炸抑制实验研究

为研究七氟丙烷对油气爆炸的抑制作用,研制了主动式油气爆炸抑制装置,搭建 了狭长受限空间油气爆炸抑制实验系统,进行了油气爆炸抑制实验,并与无抑爆介质条 件进行了对比,分析了爆炸超压值、火焰传播速度和火焰强度等特性参数变化情况。实 验结果表明:当以3、4和5 kg七氟丙烷作为抑爆介质时,最大超压值分别下降34.05%、 50.78%和55.87%,平均火焰传播速度分别下降72.15%、79.87%和89.23%,火焰持续时间 明显缩短,火焰强度减弱;随着七氟丙烷质量的增加,抑爆效果越显著。     

地下储库油气爆炸及抑爆机理与技术研究

针对地下储库受限空间的特点和油气爆炸抑制的需要.在前期所完成的系统油气爆炸试验和理论研究的基础上,采用超细冷气溶胶抑爆新技术,建立地下受限空间油气爆炸及其抑爆模拟试验系统,研制出新型超细冷气溶胶粉体抑爆剂,并对其进行可行性与有效性研究.对地下受限空间油气爆炸抑制的影响因素进行研究,分析了抑爆剂作用机理.结果表明:超细冷气溶胶是一种高效的抑制地下储库油气爆炸的抑爆剂;在相同试验条件下,迎着火焰传播方向喷射抑爆剂的抑爆效果优于垂直火焰传播方向喷射抑爆剂;喷射压力存在临界值,较小较大都不利于油气爆炸抑制,在本文试验条件下.最佳抑爆效果的喷射压力临界值约为0.8 Mpa;抑爆剂用量不能低于临界抑爆浓度,实验得到的抑爆刑临界浓度为0.232 ks/m3;布置方式对抑爆效果具有明显的影响.分散布置比集中布置具有更好的抑爆效果.本文的研究对后续抑爆装置的研制提供了重要的理论参考和关键设计参数.     

惰性气体-水雾协同抑爆甲烷研究

采用自行改造的20 L球形爆炸容器进行瓦斯抑爆研究，试验中采用分压法来制备混合气体，定量描述了爆炸压力、爆炸压力上升速率及抑爆效率等特征，分析了在3种惰性气体(CO₂、N₂和Ar)作用下CH₄的最大爆炸压力和最大爆炸压力上升速率。结果表明，CO₂的抑爆效果优于其他两种惰性气体，当CO₂的体积分数达到6%时，CH₄的最大爆炸压力和最大爆炸压力上升速率分别降为0.113 MPa和1.58 MPa/s,下降了78.6%和86.4%。通过试验可知，3种惰性气体均能延缓瓦斯爆炸的发生，降低爆炸的强度，但对于N₂和Ar而言则需要增加惰性气体的体积分数以达到与CO₂相同的抑爆效果。基于上述单相抑爆结果，选择3种惰性气体中抑爆效果最佳的CO₂来进行惰性气体-水雾协同抑爆效率的研究。通过大量重复性试验得出，2%CO₂-1 MPa水雾抑爆效率由单相体积分数为2%的CO₂     

大长径比管道汽油-空气混合气爆炸与抑制实验研究*

为探究狭长受限空间中油气爆炸失控时的发展状态,探索高效环保的油气爆炸抑制方法,利用长径比155的管道开展92号汽油-空气混合气爆炸发展规律和七氟丙烷主动抑爆技术研究。通过测量不同端部开口条件下油气爆炸超压、火焰传播速度、火焰强度等参数,对比研究空爆和抑爆工况下的油气爆炸变化规律,探讨长直管道中的油气爆炸特性,分析七氟丙烷抑爆效果。结果表明:大长径比管道中,端部开口泄爆对降低油气爆炸破坏能力的作用较小,开口与否对最大超压峰值的出现位置有影响;长直管道空爆时,油气爆炸由爆燃发展成爆轰,管道尾部的爆轰波速可达近2 000 m/s;密闭管道中,爆轰发生前火焰传播呈“已燃区-火焰锋面-待燃区-前驱激波-未燃区”的2波3区结构;主动抑爆方式下七氟丙烷抑爆效果良好,最大超压峰值降低幅度可达90%,火焰传播被及时阻断。     

长径比对管道油气爆炸特性与火焰传播规律影响研究*

为了探究长径比对油气爆炸传播特性与火焰传播规律的影响，为复杂管道受限空间油气爆炸防控提供理论参考，结合油气爆炸与爆炸抑制工程实际需要，构建不同长径比管道油气爆炸模拟实验系统,在此基础上开展不同初始浓度的预混油气-空气混合气爆炸实验。研究结果表明:管道内部的预混油气爆炸超压信号呈先上升后下降的趋势，由于耗散以及憋压效应导致超压下降平稳后仍大于初始压力；同时长径比增加会导致达到最大爆炸超压的油气浓度增加，油气爆炸超压峰值随着长径比的增加呈现上升→下降→上升的规律，小长径比管道的油气爆炸超压峰值高于大长径比管道，但同为小长径比管道或大长径比管道工况的实验结果对比显示爆炸超压峰值随着长径比增加而提升；而超压上升速率则会随着长径比的增加而上升；长径比的增加同时也会促进火焰的加速传播并减小火焰持续时间。     

原油管道氮气抑爆实验研究

为了探究不同浓度下的氮气对管道受限空间内油气爆炸的影响作用，通过原油实验管道测得不同油气浓度下的最大爆炸压力值，研究氮气对原油管道爆炸特性的抑制作用。研究结果表明:实验原油管道油气浓度在4.32%~14.25%区间管道油气发生爆炸，在低油气浓度的爆炸区间内，相近油气浓度的爆炸压力等爆炸特性上升较快，高浓度的爆炸区间内，变化较缓慢，在9.23%的油气浓度时爆炸特性变化最明显；在爆炸区间内充入浓度为0%~30%的不同浓度的氮气，随原油管道内氮气浓度的扩充，实验所测得爆炸区间不断压缩，在26%的氮气浓度时几乎不发生油气爆炸，且实验研究的爆炸特性均有所减弱。     

Inhibiting effects of gas–particle mixtures containing CO2, Mg(OH)2 particles,and NH4H2PO4 particles on methane explosion in a 20-L closed vessel

The main risk factors from methane explosion are the associated shock waves, flames, and harmful gases. Inert gases and inhibiting powders are commonly used to prevent and mitigate the damage caused by an explosion. In this study, three inhibitors (inert gas with 8.0 vol% CO₂, 0.25 g/L Mg(OH)₂ particles, and 0.25 g/L NH₄H₂PO₄ particles) were prepared. Their inhibiting effects on methane explosions with various concentrations of methane were tested in a nearly spherical 20-L explosion vessel. Both single-component inhibitors and gas–particle mixtures can substantially suppress methane explosions with varying degrees of success. However, various inhibitors exhibited distinct reaction mechanisms for methane gas, which indicated that their inhibiting effects for methane explosion varied. To alleviate amplitude, the ranking of single-component inhibitors for both explosion pressure (P_ex) and the rate of explosion pressure rise [(dP/dt)_ex] was as follows: CO₂, NH₄H₂PO₄ particles, and Mg(OH)₂ particles. In order of decreasing amplitude, the ranking of gas‒particle mixtures for both P_ex and (dP/dt)_ex was as follows: CO₂–NH₄H₂PO₄ mixture, CO₂‒Mg(OH)₂ mixture, and pure CO₂. Overall, the optimal suppression effect was observed in the system with the CO₂–NH₄H₂PO₄ mixture, which exhibited an eminent synergistic effect on methane explosions. The amplitudes of P_ex with methane concentrations of 7.0, 9.5, and 11.0 vol% decreased by 37.1%, 42.5%, and 98.6%, respectively, when using the CO₂–NH₄H₂PO₄ mixture. In addition, an antagonistic effect was observed with CO₂‒Mg(OH)₂ mixtures because MgO, which was generated by the thermal decomposition of Mg(OH)₂, can chemically react with water vapor and CO₂ to produce basic magnesium carbonate (xMgCO₃·yMg(OH)₂·zH₂O), thereby reducing the CO₂ concentration in a reaction system. This research revealed the inhibiting effects of gas‒particle mixtures (including CO₂, Mg(OH)₂ particles, and NH₄H₂PO₄ particles) on methane explosions and provided primary experimental data.     

Effect of separation distance on gas dispersion and vapor cloud explosion in a storage tank farm determined using computational fluid dynamics

Storage tank separation distance, which considerably affects forestalling and mitigating accident consequences, is principally determined by thermal radiation modeling and meeting industry safety requirements. However, little is known about the influence of separation distance on gas dispersion or gas explosion, which are the most destructive types of accidents in industrial settings. This study evaluated the effect of separation distance on gas dispersion and vapor cloud explosion in a storage tank farm. Experiments were conducted using Flame Acceleration Simulator, an advanced computational fluid dynamics software program. Codes governing the design of separation distances in China and the United States were compared. A series of geometrical models of storage tanks with various separation distances were established. Overall, increasing separation distance led to a substantial reduction in vapor cloud volume and size in most cases. Notably, a 1.0 storage diameter separation distance appeared to be optimal. In terms of vapor cloud explosion, a greater separation distance had a marked effect on mitigating overpressure in gas explosions. Therefore, separation distance merited consideration in the design of storage tanks to prevent gas dispersion and explosion.     

Effect of inert species on the laminar burning velocity of hydrogen and ethylene

The maximum laminar burning velocity (LBV) of a fuel-air mixture is an important input parameter to vapor cloud explosion (VCE) blast load prediction methods. In particular, the LBV value has a significant impact on the predicted blast loads for high reactivity fuels with the propensity to undergo a deflagration-to-detonation transition (DDT). Published data are available for the maximum LBV of many pure fuel-air mixtures. However, little test data are available for mixtures of fuels, particularly for mixtures of fuels and inert species. Such mixtures are common in the petroleum refining and chemical processing industries. It is therefore of interest to be able to calculate the maximum LBV of a fuel/inert mixture based on the mixture composition and maximum LBV of each component.This paper presents measured test data for the maximum LBV of H₂/inert and C₂H₄/inert mixtures, with both nitrogen and carbon dioxide as the inert species. The LBV values were determined using a constant-volume vessel and the pressure rise method. This paper also provides a comparison of the measured LBV values with simplified LBV prediction methods.     

采煤工作面瓦斯爆炸事故树分析

根据矿井采煤面瓦斯爆炸的一些典型事例，概括出导致瓦斯爆炸的基本事件，编制了采煤工作面瓦斯爆炸事故树。应用事故树分析中的最小割集、最小径集和结构重要度，对矿井采煤工作面瓦斯爆炸事故进行了研究。结论表明，严格控制瓦斯浓度，杜绝一切火源，是预防矿井瓦斯爆炸的基本途径。     

Gas explosions caused by gasification of condensed phase combustibles

For reasonable explanation about recent accidental gas explosions caused by condensed phase combustibles occurred in Japan, the processes of such gas explosions have been investigated. When the combustible is of condensed phase at its initial state, gasification is necessary to form a flammable mixture causing a gas explosion. The process of gasification characterizes such a gas explosion. When the combustible is RDF (refuse derived fuel), the temperature was inferred to spontaneously increase. Also, the flammable gas should be generated within a confined high temperature region in the pile and come through a low temperature layer without combustion. The growth of a flammable layer after gasoline is spread over floor is analytically evaluated. The flame propagation through the flammable layer established over the floor enhances the pressure enough to break the structure of the office. Long-term heating is inferred to cause ignition of dried garbage, and the mechanism of flammable gas generation would be similar to that in the case of the RDF explosion. For prevention of losses at accidental explosions caused by gasification of condensed phase combustibles, understanding of the phenomena is the most important.     

Evaluating the potential for overpressures from the ignition of an LNG vapor cloud during offloading

Ignition of natural gas (composed primarily of methane) is generally not considered to pose explosion hazards when in unconfined and low- or medium-congested areas, as most of the areas within LNG regasification facilities can typically be classified. However, as the degrees of confinement and/or congestion increase, the potential exists for the ignition of a methane cloud to result in damaging overpressures (as demonstrated by the recurring residential explosions due to natural gas leaks). Therefore, it is prudent to examine a proposed facility’s design to identify areas where vapor cloud explosions (VCEs) may cause damage, particularly if the damage may extend off site.An area of potential interest for VCEs is the dock, while an LNG carrier is being offloaded: the vessel hull provides one degree of confinement and the shoreline may provide another; some degree of congestion is provided by the dock and associated equipment.In this paper, the computational fluid dynamics (CFD) software FLACS is used to evaluate the consequences of the ignition of a flammable vapor cloud from an LNG spill during the LNG carrier offloading process. The simulations will demonstrate different approaches that can be taken to evaluate a vapor cloud explosion scenario in a partially confined and partially congested geometry.     

Computational modeling of vapor cloud explosions in off-shore rigs using a flame-speed based combustion model

Computational modeling is a useful tool in determining the consequences from vapor cloud explosions. Here an approach that uses a flame-speed based combustion model is evaluated. Various scenarios of explosions in full-scale off-shore modules are simulated and compared to available test data. The ignition location of the cloud and available venting paths are found to affect the overpressure field in and outside the module. For end ignition cases, the combustion of gas pushed out of the module is found to play a key role. Using the flame-speed based model with appropriate effective flame speeds is found to provide accurate simulations.     

Advanced CFD modeling on vapor dispersion and vapor cloud explosion

The main objective of this study is to quantify the potential overpressures due to Vapor Cloud Explosions (VCEs) and the potential gas buildup by using Computation Fluid Dynamics (CFD) for onshore or offshore facilities.A series of CFD simulations and analyses have been performed for the various vapor dispersion scenarios, covering different release rates and release locations. The overpressure that could result from the potential VCE is assessed by CFD simulation for the largest explosive transient gas cloud. The results from the analyses also comprise an extensive picture of probable leak scenarios having the potential to make an explosive gas cloud.The CFD analysis results could be applied to provide input for detailed risk-based design and risk analysis, to find safe and cost-optimal design against explosions.     

因果图和模糊综合风险评价在城市燃气输配系统的应用

针对复杂的城市燃气输配系统,利用因果图和模糊综合评价相结合的方法对其进行风险分析.因果图能找出影响城市燃气输配系统失效的因素,模糊综合评价则可在其基础上对风险量化.以某市的燃气输配系统为例描述了该方法的步骤.结果表明,因果图和模糊综合评价相结合的方法合理且易于工程应用.     

液化石油气事故机理及模拟评价方法

液化石油气的生产、储运过程中蒸气爆炸事故屡有发生,并导致其他类型的爆炸.结合液化石油气的典型案例,对液化石油气火灾爆炸事故发生的过程、机理和评价模型进行了研究与分析.