瓦斯-煤粉粉尘气固2相爆轰特性测试

研究纯煤粉粉尘爆炸特性和甲烷对煤粉粉尘爆炸的影响。结果表明:煤粉粒径越大,爆炸压力越小,爆炸压力随煤粉粉尘浓度增加先增大后降低;甲烷的加入会增加煤粉粉尘爆炸时的爆炸压力;但是在煤粉浓度很大时,甲烷的提高作用则不明显。     

喷雾爆震起爆过程实验观察

实验测量了爆震室内不同轴向位置的压力和离子信号的演变过程,并利用高速阴影系统直接观察了透明方形管道内汽油/空气两相混合物动态填充过程中,弱火花点火后火焰加速传播、火焰与障碍物的相互作用、激波的出现、热点形成、爆燃向爆震转变、爆震波在障碍物管道中和光滑管道中的传播过程,分析影响爆震波传播速度的关键因素,用烟膜板记录了起爆区的胞格结构.     

爆炸波除灰器中火焰传播及压力波形研究

燃烧气脉冲发生器应用于电站锅炉除灰。其工作原理是预混可燃气体在右端部分开口,内部有障碍物的容器中快速燃烧。形成一定的压力脉冲。并产生作用于积灰表面的射流和冲击波。火焰在湍流扰动装置的作用下不断加速。容器中的压力不断上升。火焰传播愈快,压力波形愈陡。压力锋值愈高。针对这些现象。主要研究了乙块、水煤气、液化石油气和甲烷四种燃料,在不同燃料浓度、不同阻塞比时对火焰传播的影响,分析了不同燃料浓度下对压力波形的影响。     

管道截面突缩对爆轰波起爆特性的影响

为研究管道截面突缩对爆轰波起爆特性的影响,在突缩比为5:3的截面突缩管道及直管内对不同初始压力下甲烷氧气预混气体的起爆特性进行了实验研究,利用离子探针获得管道内火焰传播速度,并通过二维数值模拟探究了3种不同突缩比的截面突缩管道内火焰及压力的传播特性.实验结果表明,截面突缩管道内爆轰波起爆距离随着初始压力的降低而逐渐增加...     

逆风和静止环境中火焰沿柱状燃料传播的实验研究

本文测量不同直径的ＰＭＭＡ燃料捧在逆风和静止环境中的火焰传播速度，裂解长度和火焰形状，实验结果表明，在相同的燃料直径下，逆流风速越大，火焰传播速度较小，裂解区长度越小。火焰形状越平；在相同的逆流风速下，（１）当逆流风速于０．７ｍ／ｓ时，燃料直径越大，火焰传播速度越小；（２）当逆流风速大于０．７ｍ／ｓ时，燃料直径越大，火焰传播速度越大，当逆流风速较大时，不同直径燃料的无因次裂解长度趋现一致。     

多循环喷雾爆震的特性研究

在无阀式脉冲爆震发动机模型机上进行了多循环喷雾两相爆震的实验研究．点火后爆震管内压力上升需要一定的延迟时间,但是迅速增压过程是在火焰传播到一定区域后开始的,在该区域形成向两个方向传播的压缩波,向未燃区传播的压缩波不断加强,形成爆震波,向已燃区传播的压缩波不断衰减;爆震峰值压力沿流向不断增加,压力上升速度加快,峰值随机差异放大;通过对压力历程的分析,用两种方法估算了两相爆震波诱导区的长度．实验中发现,两相爆震的点火延迟时间远大于爆燃向爆震转变的时间,两者之和相对于高频爆震循环非常可观,是限制两相脉冲爆震发动机频率提高的关键因素,并分析了多循环工作时的吸气和排气过程．     

真空腔对爆炸火焰窒息作用研究

采用预装真空腔对管道内瓦斯爆炸后火焰传播进行遏制是一种新型泄爆抑爆技术,从科学实验、理论分析和数值模拟3个方面初步研究了真空腔对爆炸火焰的窒息作用,结果显示一定体积真空腔的介入使其后的实验管道中不再出现火焰传播,真空腔的存在使燃烧过程的氧化工况由剧烈向缓慢转变,阻止燃烧三角形形成闭环,自由基生长的速度小于自由基的消失速度,爆炸火焰在真空腔内被窒息,证明了真空腔泄爆抑爆技术对爆炸火焰具有明显窒息作用的结论。     

防爆门质量对瓦斯爆燃泄爆特性影响实验研究

对透明玻璃空腔中的甲烷-空气预混气体爆燃的泄爆过程进行了实验研究。通过在腔体顶部安装不同质量的防爆门,对预混可燃气体的爆燃压力、火焰速度等参数进行了测量,分析了防爆门在开启过程中火焰结构、爆燃压力和火焰传播速度随时间的变化规律。结果表明:防爆门质量越大,腔体内部的爆燃超压越高,开启防爆门所需时间越长,火焰锋面传播速度的峰值也越大。此外,与质量对称防爆门相比,质量不对称防爆门在泄爆过程中的开启时刻和火焰速度达到最大值时刻均更为提前。     

高温高压下二甲醚—空气预混层流燃烧特性研究

在定容燃烧弹内研究了初始压力为0.5 MPa时,不同初始温度和燃空当量比下二甲醚-空气混合气预混层流火焰的层流燃烧速率和马克斯坦长度,分析了火焰拉伸对火焰传播速率的影响.基于容弹燃烧的双区模型计算了预混层流燃烧的燃烧特性参数.结果表明:随着初始温度的增加,二甲醚-空气预混合气的无拉伸火焰传播速率和无拉伸层流燃烧率增加;对于给定的初始温度,在化学当量比偏浓混合气一侧存在一个层流燃烧速度的峰值;随初始温度和当最比增加,马克斯坦长度值减小,火焰前锋面的不稳定性增加;最大燃烧压力随初始温度的增加而下降,压力升高率随初始温度的增加而降低.     

密闭燃烧室内压力和预混火焰表面积的关系推导及应用

对密闭燃烧室内的预混火焰传播来说,火焰表面积是一个十分重要同时难以测量的动态参数.本文通过数学推导,得到了预混火焰表面积和压力之间的关系表达式,并采用数值模拟验证了推导结果的有效性.结果表明压力上升速率与火焰表面积呈正相关.结合该表达式和实验结果对密闭管道内甲烷-空气预混火焰传播进行了定量分析,发现在障碍物作用下,预混火焰表面积急剧增长,火焰面积和火焰面积增长速率随障碍物阻塞比增大而增大.     

Experimental and theoretical investigation on hydrogen cloud explosion subjected to external turbulence

This work is to experimentally and theoretically explore the hydrogen cloud explosion subjected to external turbulence. In the experiments, the flame characteristics and explosion pressure are obtained using high-speed camera and pressure sensor. In the theoretical calculation, the peak explosion pressure is obtained using LM, LMIET and TM method. The results indicated that most flame characteristics in the experiments are located in the zone of wrinkled flamelets. The explosion-related parameters including flame propagation velocity, peak explosion pressure and peak rate of pressure rise continue to increase as the gear level increases from G0 to G3, increase firstly and then decrease as the equivalence ratio increases from Φ = 0.5 to Φ = 3.0. Due to ignoring flame acceleration propagation induced by flame instabilities, external turbulence and flame-induced turbulence, the peak explosion pressure obtained using experimental method is significantly larger than that obtained using LM method. Owing to considering the limit value of flame wrinkling level induced flame instabilities and flame-induced turbulence, the peak explosion pressure obtained using experimental method is significantly lower than that obtained using LMIET and TM method.     

Effects of hydrogen concentration and film thickness on the vented explosion in a small obstructed rectangular container

The explosion venting is an effective way to reduce hydrogen-air explosion hazards, but the explosion venting has been less touched in an obstructed container. The present study mainly focused on the effects of hydrogen concentration and film thickness on the explosion venting in a small obstructed rectangular container. High speed schlieren photography was employed to obtain the flame fine structure and velocity. Pressure transducers were used to measure the overpressure nearby the obstacle. The experimental results show that the obstacle has a significant effect on the flame shape, tip speed and overpressure. In the process of flame evolution, the flame surface becomes more wrinkled with time after the tulip flame. Compared with the cases without the obstacle, the flame surface becomes more distorted and wrinkled downstream of the obstacle under the influence of obstacle enhanced turbulence and flow instability. Upstream of the obstacle, the lower part of the flame surface becomes concave while the upper part shows convex. The pressure histories show that the maximum overpressure increases with the hydrogen concentration in the range of 11.8%–23.7%. Two main pressure peaks were observed for all hydrogen concentrations in the presence of the obstacle. The Helmholtz oscillations appear after the second pressure peak and its duration increases slightly when the hydrogen concentration increases. The combined effect of the obstacle and hydrogen concentration on the second peak overpressure is more significant than on the first peak overpressure. Moreover, the maximum overpressure shows a monotonic increase with the film thickness.     

Effect of obstacle arrangement on premixed hydrogen flame: Eddy-dissipation concept model based numerical simulation

In this paper, computational fluid dynamics (CFD) numerical simulation is used to analyze and discuss the horizontal propagation process of premixed hydrogen flame with obstacles. A total of three different obstacle channel arrangements at the blocking ratio of 0.5, which will affect the explosion flame and pressure development. The results show that the premixed flame is affected by flow instabilities and vortices when propagating through the obstacle channel, thereby distorting the flame. The vortices outside the flame boundary are more conducive to the acceleration of the flame. The continuous acceleration and synergistic promotion of the flame is more prominent due to the existence of the channel in the central axis of flame propagation, and the maximum velocity even achieved 307.91  m/s. The degree of the wrinkle of flame increases with the number of obstacle channels. The flame propagation process is always accompanied by pressure variations, and the dynamic pressure builds up at the flame front and intensifies periodically. But the downstream pressure gradually increases as the number of obstacle channels increases. CFD simulation of the explosion process clearly reveals the changing trends and interactions of explosion characteristic factors.     

Experimental study of explosion dynamics of syngas flames in the narrow channel

This article introduced the experimental study of the propagation of a syngas premixed flame in a narrow channel. The structural evolution, flame front position and velocity characteristics of lean and rich premixed flames were investigated at different hydrogen volume fractions as the flame was ignited at the open end of the pipe and propagated to the closed end. The comparative study of the syngas fuel characteristics, flame oscillation frequency and overpressure oscillation frequency prove that the syngas explosion flame oscillation in the narrow passage has a strong coupling relationship with overpressure and fuel heat release rate. The results was shown that the flame structure was strongly influenced by the hydrogen volume fraction of the syngas and the fuel concentration. The distorted tulip flame only appears in lean mixture. At 30% of hydrogen volume fraction, the flame exhibits intense and unstable propagation, manifested as the reciprocating and alternating movement of the flame front. As the volume fraction of hydrogen increased, the velocity of flame propagation and the frequency of oscillation increased. When the hydrogen volume fraction γ ≥ 0.4 at the equivalence ratio of Φ = 0.8, the pressure oscillation amplitude gradually increases and reaching the peak after 200–320 ms. Significantly, when γ = 0.3, the pressure peak increases abnormally. This work can provide support for the safe use of syngas in industry by experimental study of various explosion parameters in the narrow channel.     

Experimental research on hydrogen/air explosion inhibition by the ultrafine water mist

This experimental study focused on the inhibition of ultrafine water mist on hydrogen explosion inside the closed vessel. The inhibition law and mechanism were studied through changes of explosion intensity, flame propagation velocity and temperature under different mist concentrations. Results indicate that flame propagation and pressure rise inside the closed vessel were corresponding. Explosion intensity was reduced after adding mist, which was mainly manifested in the reductions of explosion pressure and flame propagation velocity. Flame was accelerated to extinguish and the inhibition effect was enhanced with increasing mist concentration. However, the explosion prussure did not present obvious reduction as the mist concentration reached a certain value. Besides, it indicates that the absoption heat effect of ultrafine water mist was an important factor on hydrogen explosion inhibition by the reductions of flame temperature and propagation velocity. The inhibition effect was mainly attributed to the combination effect of physical and chemical inhibitions.     

The effect of vent burst pressure on a vented hydrogen–air deflagration in a 1 m3 vessel

A series of experiments are conducted to investigate the effect of vent burst pressure on stoichiometric hydrogen–air premixed flame propagation and pressure history in a 1 m³ rectangular vessel in this paper. Pressure buildup and flame evolution are recorded using piezoelectric pressure transducers and a high-speed camera, respectively. The results show typical pressure peaks of three different mechanisms for all vent burst pressures in the experiments. The first pressure peak, generated by the rupture of the vent cover, increases with the vent failure pressure, with the subsequent outflow inertia of combustion products giving rise to a negative pressure. The second pressure peak results from the constant bulk motion of the flame bubble (the Helmholtz oscillation), and the third is produced by the interaction between the combustion waves and the acoustic waves. The time interval between the first pressure peak and the second pressure transient remained nearly constant. The Helmholtz oscillation always appears as the vent ruptures and its magnitude increases with the vent burst pressure. Furthermore, the lower the vent failure pressure, the longer the Helmholtz oscillation is sustained. The peak of the acoustically enhanced pressure always occurs within several milliseconds of the flame front touching the vessel. From a theoretical perspective, Rasbash's equation models the relationship between the maximum reduced explosion overpressure and the vent burst pressure precisely. Also, it is observed that the maximum lengths of the external flames were found to be nearly identical in all tests, but the average propagation rate of the flame front increases with the vent burst pressure. It is interesting that a phenomenon of intense oscillation of internal flame bubble was observed with the increase of vent burst pressure.     

Inerting effect of carbon dioxide on confined hydrogen explosion

Taking maximum flame propagation velocity, maximum explosion pressure, maximum rate of pressure rise and time-average of rising pressure impulse as index, this paper is aimed at evaluating the inerting effects of carbon dioxide on confined hydrogen explosion by varying initial pressure, carbon dioxide addition and equivalence ratio. The results indicated that under enhancing hydrodynamic instability, the stronger flame destabilization occurs with the increase of initial pressure. At Φ = 0.8 and Φ = 1.0, the destabilization effect of thermodiffusive instability continues to increase with the increase of carbon dioxide addition. At all equivalence ratios, the destabilization effect of hydrodynamic instability decreases monotonously with the increase of carbon dioxide addition. All of maximum flame propagation velocity, maximum explosion pressure, maximum rate of pressure rise and time-average of rising pressure impulse reach the peak value at Φ = 1.5, and decrease significantly with increasing carbon dioxide addition. The inerting effect of carbon dioxide could be attributed to the reduction of thermal diffusivity, flame temperature and active radicals. The chemical effect of carbon dioxide reaches the peak value at Φ = 1.0. With the increase of carbon dioxide addition, the chemical effect continues to decrease at Φ = 0.8 and Φ = 1.0, and increase monotonously at Φ = 2.5.     

Flame characteristics of premixed H2-air mixtures explosion venting in a spherical container through a duct

The explosion venting duct can effectively reduce the hazard degree of a gas explosion and conduct the venting energy to the safe area. To investigate the flame quantitative propagation law of explosion venting with a duct, the effects of hydrogen fraction and explosion venting duct length on jet flame propagation characteristics of premixed H₂-air mixtures were analyzed through experiment and simulation. The experiment results under initial conditions of room temperature and 1 atm show that when hydrogen fraction was high enough, part of the unburned hydrogen was mixed with air again to reach an ignitable concentration, resulting in the secondary combustion was easier produced and the duration of the secondary flame increased. With the increase of venting duct length, the flame front distance and propagation velocity increased. Meanwhile, the spatial distribution of pressure field and temperature field, and the propagation process and mechanism of the flame venting with a duct were analyzed using FLUENT software. The variation of the pressure wave and the pressure reflection oscillation law in the explosion venting duct was captured. Therefore, in the industrial explosion venting design with a duct, the hazard caused by the coupling of venting pressure and venting flame under different fractions should be considered comprehensively.     

随机堆积床内过滤燃烧特性的实验研究

本文提出了一种可视化燃烧室,用于对3种尺寸的随机堆积结构开展过滤燃烧实验,该结构分别由直径为5,10,15 mm的氧化铝颗粒堆积而成。通过搭建燃烧平台,研究了不同颗粒直径堆积床中火焰的燃烧波高度、火焰传播速度、火焰温度及排放特性。结果表明：在可燃工况下,颗粒直径5 mm堆积床中火焰最高温度随火焰传播过程减小,火焰传播速度变快;而在颗粒直径10和15 mm堆积床中火焰最高温度随火焰传播过程增大,火焰传播速度变慢。