瓦斯爆炸火焰波与冲击波伴生关系的实验研究.pdf

1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 瓦斯爆炸火焰波与冲击波伴生关系 的实验研究 黎体发1,张莉聪2,徐景德3 ,4 1. 北京科技大学,北京100083; 2.中国矿业大学北京校区 , 北京100083; 3.中国科学技术大学,安徽 合肥230026; 4.华北科技学院,河北 三河101601 摘 要在煤矿瓦斯爆炸过程中,爆炸火焰和冲击波是决定事故危害程度的2个主要因素。作者设 计了氢氧引爆甲烷-空气爆炸的实验方案,对高速瓦斯爆炸参数的变化特征进行了研究。通过实验测 试瓦斯爆炸传播阶段的火焰和压力状态,研究瓦斯爆燃火焰波与冲击波的形成过程及其特性。研究表 明,在瓦斯爆炸火焰传播过程中,湍流效应是加速火焰传播和伴生冲击波的重要因素;爆炸火焰的传播 速度直接影响着爆炸冲击波的生成和加强程度。依据实验研究结果,提出了一些防治煤矿瓦斯爆炸的 建议。 关键词瓦斯爆炸;火焰传播;冲击波;稀疏波;湍流 中图分类号TD712 . 7 文献标识码A 文章编号1008 - 4495200502 - 0004 - 03 收稿日期2004 - 10 - 16 基金项目国家 “973” 重点研究项目200CB4002007 作者简介黎体发1979 - ,男,江西萍乡人,北京科技大 学土木与环境工程学院在读研究生,研究方向为安全技术及 环境工程。 煤矿瓦斯爆炸可看作弱点火点燃甲烷-空气混 合气体引起的爆炸现象[1]。甲烷燃烧火焰在传播过 程中不断加速,一定条件下将形成瓦斯爆炸,具有很 强的破坏作用。通常情况下,煤矿瓦斯爆炸的传播 形式多为亚音速传播的爆燃波,传播阶段的瓦斯爆 燃火焰波和冲击波是造成破坏的主要因素[2]。由于 瓦斯爆炸过程的物理机制非常复杂,目前相关研究 还处于初步探索阶段。作者主要对瓦斯爆炸传播阶 段爆燃火焰波与冲击波的伴生关系展开实验研究。 1 实验系统 实验系统由爆炸点火控制器、 瓦斯爆炸实验管 道、 泄压罐、 压力及火焰数据测量装置组成,见图1。 瓦斯爆炸实验管道是内截面为40 mm40 mm 的方管,总长为9 m。在方管的壁面上布置了压力、 火焰传感器和点火装置的安装孔,方管同一截面的 壁面上安设了压力和火焰传感器,用于测量同一截 面的瓦斯爆炸压力和火焰信号。压力测量采用PCB 压电式压力传感器,该传感器具有很高的响应频率, 抗干扰能力强,信号稳定。火焰测量采用光敏二极 管作为火焰传感器,它对瓦斯爆炸火焰具有较好的 敏感性,响应频率高达106Hz。压力和火焰传感器 通过低噪音信号线连接到电荷放大器,再连接到动 态数据采集分析仪器 10 通道XG B示波器。传感 器PCB1与PD1 ,PCB2与PD2 ,PCB3与PD3分别安装 在测点1 ,2 ,3处,各个测点距点火端的距离分别是 4. 340 ,7. 483 ,7. 728 m。采用高压储能式电火花点 火,点火能可在1～25 J调节。 图1 瓦斯爆炸实验测量系统示意图 2 实验方案 设计了2种实验方案。第一种方案用于研究低 速甲烷-空气爆燃状态,在瓦斯爆炸管道的闭端,通 过弱点火直接点燃甲烷-空气预混气体,见图 2a 。 4 2005年4月 矿业安全与环保 第32卷第2期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 图2 瓦斯爆炸实验方案示意图 第二种方案见图 2b 。由于甲烷是一种低反应 活性的碳氢燃料气体,在弱点火的条件下甲烷-空 气爆燃火焰需要经过较长的传播距离,才能达到较 大的传播速度,形成强冲击波。受实验条件的限制, 点火能量的改变量还不够大,所以实验过程中采用 了氢气-氧气混合气体引爆甲烷-空气预混气体, 使其在较短的距离内达到较高的爆炸传播速度和爆 炸强度,模拟煤矿中的强瓦斯爆炸现象。在引爆段 与试验段之间用涤纶薄膜隔开,引爆段充入反应当 量比的氢气-氧气混合气体,试验段充入甲烷-空 气预混气体,点燃氢氧气体形成较强的爆轰波,用来 点燃甲烷-空气试验气体。该实验方案用来研究瓦 斯的高速爆燃及爆轰特性,具有很高的实用性。 3 实验结果与分析 基于上述2种实验方案,展开了相应的实验研 究。在瓦斯爆炸实验管道上布置了火焰和压力信号 测试传感器,测试高、 低速瓦斯爆炸传播过程中火焰 和压力的变化特性,研究运动火焰与冲击波的形成 过程和相互作用机理。 3. 1 低速瓦斯爆炸的实验结果及分析 依据甲烷-空气爆炸实验方案,在瓦斯爆炸实 验管道的开口端夹上涤纶薄膜,将管道抽为真空后, 充入p0 1. 01105Pa的甲烷-空气预混气体甲 烷体积浓度为9. 5 ,此时管道内外压差为零,再将 膜片刺破,使薄膜不承受冲击,模拟煤矿独头巷道中 的瓦斯爆炸现象。充气后直接对甲烷-空气预混气 体点火,点火能约10 J ,研究瓦斯爆炸的低速传播过 程,试验结果见图3、 图4。数据分析过程中,vf表示 爆炸火焰的传播速度。 由图3和图4可知,在瓦斯爆炸过程中,爆炸火 焰呈加速传播状态,传感器PD1与PD2 ,PD 2与PD3 之间的平均火焰传播速度v1,v2分别为16. 2 m/ s和 28.7 m/ s。由于爆炸火焰的传播速度较低,火焰所 生成的压力波强度还很小,爆炸的超压值不是很明 显,超压仅87. 3 kPa。从图3可知,低速瓦斯爆炸的 开始阶段出现了压力的震荡。压力震荡现象可解释 为火焰面因湍流作用而褶皱、 卷曲,导致火焰传播极 不稳定,这种燃烧火焰的不稳定性形成了压力的脉 动效应,导致开始阶段出现了压力震荡现象。 图3 瓦斯爆炸传播过程中火焰加速关系曲线 图4 测点3处vf 29 m/ s时的压力、 火焰关系曲线 由于管道壁面附近的粘性作用,火焰传播速度 的增大会使管内出现更加剧烈的湍流效应。另外, 管道中存在的障碍物也会加剧火焰传播过程中的湍 流效应。大涡湍流使火焰褶皱,增加燃烧面积,小涡 湍流可提高火焰内部的有效输运能力,这些都有助 于提高燃烧速率。火焰的加速传播将有利于生成较 强的冲击波,使瓦斯爆炸的危害性增大。可见火焰 传播过程中的湍流效应是导致爆炸火焰加速传播和 伴生冲击波的重要因素。所以,从防治煤矿瓦斯爆 炸角度考虑,应尽量减小巷道壁面的粗糙度、 及时清 除巷道中的障碍物、 巷道设计应避免大的拐角和巷 道截面的突变等,从而降低火焰传播过程中的湍流 效应。 3. 2 高速瓦斯爆炸的实验结果及分析 根据氢氧引爆甲烷-空气爆炸实验方案,在引 爆段与试验段之间夹上薄膜,将管道抽为真空后,试 验段充入p0 1. 01105Pa的甲烷-空气预混气体, 引爆段根据实验需要充入一定量的氢氧预混气体氢 气与氧气的体积比为2∶ 1 。首先点燃氢氧预混气体, 经传播达到爆轰状态后,破膜点燃甲烷-空气预混气 体,形成高速传播的瓦斯爆炸,见图5、 图6。 5 2005年4月 矿业安全与环保 第32卷第2期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. 图5 测点3处vf 153 m/ s时的压力、 火焰关系曲线 图6 测点3处vf 875 m/ s时的压力、 火焰关系曲线 由图4 ,5 ,6的压力-时间曲线可知,在爆炸传 播过程中,先是爆炸产物膨胀导致压力急速上升形 成超压,紧接着因爆炸形成的向后传播稀疏波的衰 减作用,导致压力又急速下降至低于一个大气压,之 后再回升到一个大气压。在爆炸过程中出现了多次 的压力拉伸破坏作用,特别是随着火焰传播速度的 增大由29 m/ s增大到875 m/ s ,压力拉伸所需时间 却减小了由380 ms降低到40 ms ,这对于煤矿瓦斯 爆炸的防治是极其不利的。 3. 3 爆炸火焰波与冲击波伴生关系探讨 从图4 ,5 ,6火焰与压力的关系曲线分析可知, 瓦斯爆炸火焰处于低速传播状态时,所伴生的压力 波很微弱,超压值仅54. 5 kPa ,没有形成冲击波;当 火焰传播速度达到153 m/ s时,开始形成了爆炸冲 击波,超压186. 4 kPa ,传播速度继续升高到875 m/ s 时,所生成的冲击波的强度明显增强,超压达到 1 245. 4 kPa。 可见,瓦斯爆炸火焰的传播速度直接影响着冲 击波的生成和加强程度,表现为爆炸火焰传播速度 和冲击波强度的不断增大。这主要是因为爆炸火焰 对冲击波起到驱动作用,提供了冲击波传播所需的 能量,火焰加速传播导致了冲击波强度的增大;而冲 击波对火焰起诱导作用,甲烷-空气预混气体质点 经冲击波压缩后,其物理状态发生改变,当火焰面到 达时发生点火,将有利于甲烷-空气预混气体的加 速燃烧,形成了爆炸火焰驱动冲击波、 冲击波诱导火 焰传播的正反馈机制。有关实验数据见表1。 表1 同截面测点瓦斯爆炸火焰阵面与压力波阵面的实验参数 序号vf/ m/ sΔt/ msΔp/ kPa 18854.5054.5 218600.4676.1 329186.2087.3 411828.00148.7 515323.84186.4 63061.06427.6 75100.561 129.5 88750.401 245.4 注vf是火焰测点2 ,3之间的平均速度,相距245 mm;Δt是在测 点3同截面处火焰阵面与压力波阵面的时间差值;Δp是在测点3同 截面处,相对于标准大气压的最大超压值。 由表1可知,在瓦斯爆炸传播过程中,随着爆炸 火焰传播速度增大,在同一时刻爆炸波火焰阵面与 压力波阵面的时间差逐步减小,火焰阵面将逐步接 近压力波阵面,存在火焰面与压力波面耦合的趋势, 在一定条件下,可能达到爆轰状态,形成危害性大、 涉及面广的强瓦斯爆炸。另一方面,随着爆炸火焰 的加速,爆炸压力的超压值不断增大,爆炸强度显著 增强,将会形成较强的爆炸冲击波,其危害性也很 大。所以,在煤矿瓦斯爆炸传播阶段,因火焰加速传 播所导致的破坏效应是较显著的,主要表现为爆炸 冲击波的传播速度加快,爆炸强度增大。因此,在防 治煤矿瓦斯爆炸过程中,应尽量抑制住爆炸过程中 的火焰传播速度,避免火焰加速运动伴生出强的爆 炸冲击波,从而避免造成严重的瓦斯爆炸事故。 4 结论 1 氢氧引爆甲烷-空气爆炸的实验,为研究瓦 斯的高速爆燃及爆轰特性提供了一种便捷、 有效的 方法。 2 湍流效应是加速火焰传播和伴生冲击波的重 要因素。从防治煤矿瓦斯爆炸角度考虑,应尽量降 低火焰传播过程中的湍流效应,采取相应措施,减小 巷道壁面的粗糙度、 清除巷道中的障碍物、 巷道设计 应避免大的拐角和巷道截面的突变。 3 根据所测得的瓦斯爆炸火焰、 压力关系,可得 出爆炸火焰传播速度的大小直接影响着爆炸冲击波 的生成和加强程度。应尽量抑制住爆炸过程中的火 焰传播速度,避免形成强的爆炸冲击波。 参考文献 [1]徐景德.矿井瓦斯爆炸传播规律及影响因素研究[D]. 北京中国矿业大学北京校区 ,2003 [2]周凯元等.丙烷-空气爆燃火焰通过平行板狭缝时的淬 熄研究[J ].爆炸与冲击,1997 ,172 111 - 118 责任编辑熊云威 6 2005年4月 矿业安全与环保 第32卷第2期 1994-2010 China Academic Journal Electronic Publishing House. All rights reserved. English Abstracts of This Issue Study on Relation of Variation of Coal Conductivity with G as Pressure 1 -In this paper , theoretical analysis is made on the gas absorption characteristics of coal and the influence of absorbed gas and free gas upon coal conductivity. Experimental study is made on the variation relation of coal conductivity with gas pressure by measuring the conductivity of different coal samples under different gas pressure in the laboratory , and the theoretical study results are thus confirmed. Experimental Study on ation of Flame and Shock Wave in G as Explosion 4 -In the process of a gas explosion , both flame and shock wave are two factors for determining hazard degree of an accident. In this paper , the variation of flame and pressure in gas explosion propagation has been determined experimentally , and research is made on the characters of flame and shock wave in the gas explosion. The research results show that the turbulent effect is the key factor for the acceleration of flame propagation and the ation of shock wave in the process of flame propagation of a gas explosion, and the flame propagating speed has a direct influence upon the ation and enhancement degree of the shock wave in the explosion. On the basis of the experimental study results , the paper putsforward some suggestions for the prevention of gas explosion in coal mines. Criterion for Rock Burst in Tunnel and Its Forecast 7- Rock burst is a common geological disaster of dynamic destabilization in excavation of the underground engineering chamber in high stress area.In this paper , the authors , by analyzing the stress of surrounding rock of a circular tunnel and the characteristics of crack extension within the surrounding rock after excavation and using the destruction criterion of Griffith strength theory , obtained the criterion expressed by the tensile strength of rock for rock burst occurred in the tunnel excavation , which can be used for better prediction of rock burst. The authors put forward the prediction for rock burst by theoretical analysis and site measurement according to the characteristics of rock burst occurred in the tunnel. This research result can be used for similar projects for reference. Research on Water Accumulating Volume in Mine Gob 10 - The mining and water drainage design of a coal mine threatened by water disaster is a complicated systematic project. In this paper , the authors, taking the hydrogeological conditions of Qinshui Coal Field as background , based on deep analysis of the water inrush cause in each mine and through the collection of a great deal of data and simulating tests in the laboratory , put forward such a major conception of water - accumulation coefficient , which is of great importance to the prevention of water inrush in workingfaces and the guaranteeing ofsafe production in mines and has aguiding significance for the mining and water drainage design of mines threatened by water disasters. ExperimentalStudyonCatalyticOxidationwith Fentong Reagent for Treatment of Coking Wastewater 12 - Based on the experiment of treatment of coking wastewater through catalytic oxidation with Fenton Fe2 H2O2 reagent , this paper emphatically compares treatment results under different reaction conditions and discusses their influencing factors. Experiments of removing COD and phenol fromwastewater from Chongqing Steel and Iron Group’Coking works were conducted under 6 different reaction conditions , i. e. reaction time , pH, the plunged quantity of Fenton reagent , the dosing of Fenton reagent , reaction temperature ,and the way of plunging.Raw wastewater was used in the experimental removal of COD and diluted wastewater with as much distilled water in the experimental removal of phenol. The experiment results show that the removal rate of COD and phenol stands at 88.12 and 89. 45 respectively , an optimum treatment , with reaction temperature at 25℃,pH at 3 , reaction time lasting 5 minutes and the ratio of H2O2to COD and Fe2 to H2O2being 2∶1 and 10∶1 respectively. Probing intoIndustrialInjuryInsuranceRateSystem of Chongqing 14 -This paper made an analysis on the industrial injury insurance rate system based on the investigation on industrial injury situation of 102 enterprises in 39 trades from 1988 to 2000 in Chongqing. The target of this investigation can be divided into 12 risk grades be ed into different rate. The supreme rate thus ed is 7.0 and minimum rate is 0.2 . Application of Assessment with Fire and Explosion Inds in Safety Assessment on Dangerous Chemical Production Enterprise20 -This paper gives a description of the application of assessment with DOW chemical fire and explosion inds in safety assessment of dangerous chemical production unit. Study results show that the use of DOW chemical fire and explosion inds to assess the safety situation of the dangerous chemical production unit can not only more accurately reflect the actual situation of the unit to be assessed , but also predict the economic loss caused by the safety accident once it happened. Discussion on H azard uation of Mine G as Accumulation Based on Ination Entropy 25 -Gas accumulation in a mine roadway is a prerequisite condition for the occurrence of gas accidents.In this paper , the authors defined the conception of ination entropy ofminegasaccumulationandgavethe calculation ula.The analysis on the actual cases of gas accumulation in the winning district shows that this index can reflect not only the hazard degree of gas accumulation , but also the influence of uncertain factors of gas accumulation hazard , so the analysis and uation ofgas accumulation hazard based on ination entropy have further value for theoretical exploration. Inquiring into Development of Processing Industry of Superior Mineral Resources in Chongqing 27 - This paper , starting with the analysison the superior mineral resources and the present state of the processing industry of superior mineral resources in Chongqing , points out the problems present in the development of the processing industry of superior mineral resources in Chongqing in the face of both the international and domestic markets , and puts forward the development orientation and guarantee measures for the processing industry of 8 superior mineral resources in Chongqing. Review on Artificial Wetland for Treatment of Acid Mime Water 40 -This paper summarized the treatment for acid mine water with artificial wetland , mainly including the basic structure and type of the artificial wetland , its decontaminating mechanism, the factors that affect decontamination effect as well as the technological design , treatment effect and development trend of the artificial wetland. Length Determination of Super - long Fully Mechanized Caving Face of Inflammable Thick Seam and Its Layout 64 -This paper analyzed the ability of production , transport and support of the super - long fully mechanized caving face of inflammable thick seam, its mining and technology , the requirements for gas , ventilation and fire control as well as the ability of production , on - the - spot and technical management so as to determine the length of the super - long fully mechanized caving face and the layout requirement and reliability in the inflammable thick seam. This can be used by similar coal mining areas for reference. Distribution Characteristics of F02 Fault in Nappe Structure of Xinji Mine Field 66 -Based on the analysis and exploratory verification of the mechanism of the nappe structure of Huainan coal field , this paper made research on the occurrence and distribution characteristics of F02 fault in the nappe structure , negated the existence of plane structural surface on the two sides of Xinji “structural window”and put forward the possibility of F02 fault position shifting towards north. The fact showed that this research result is correct and can be used as the technical basis for determining the position of the open - off cut of 1309 fully mechanized caving face of Xinji No.1 Mine. Vol.32 No.2 2005 MINING SAFETY ENVIRONMENTAL PROTECTION April 2005