玉米淀粉粉尘爆炸特性及火焰传播过程的试验研究?

为了全面地认识玉米淀粉粉尘爆炸的敏感性和爆炸破坏效应,分别采用粉尘云着火温度装置、20 L球粉尘爆炸装置和粉尘云火焰传播装置对玉米淀粉的粉尘云着火温度、爆炸下限质量浓度、爆炸压力、爆炸氧极限浓度以及粉尘云火焰传播过程进行了研究。结果表明:玉米淀粉粉尘云最低着火温度在380~390℃之间;粉尘云爆炸氧极限浓度(体积分数)在10%~11%之间;爆炸下限质量浓度和最大爆炸压力随着化学点火具质量的增加而呈现出不同的变化特征,随着化学点火具质量的增加,玉米淀粉的爆炸下限质量浓度逐渐降低,而玉米淀粉爆炸压力逐渐升高。在不同的粉尘质量浓度条件下,粉尘云火焰传播速度和火焰温度有一定的变化,在粉尘质量浓度为500 g/m3时,火焰传播速度和火焰温度均达到最大值,分别为13.81 m/s和1 107℃。     

石松子粉爆炸过程中火焰传播特性研究

为了研究石松子粉火焰传播特征,采用哈特曼管装置对石松子粉在燃烧管中进行试验,利用高速摄影和红外热成像技术记录石松子粉火焰传播过程,并对石松子粉火焰传播速度和火焰温度变化情况进行了分析。结果表明:点火能量为200mJ,粉尘浓度在125~500g/m~3范围内,火焰在燃烧管中向上传播所达到的最大速度随着粉尘浓度的增加先增大后减小;在石松子粉浓度为250g/m~3时达到最大速度11.08m/s;火球的面积随着时间变化呈现先增大后减小的趋势,在60ms时达到最大,同时达到最高温度1100℃;随着火焰的向上传播,火焰的最高温度区域也随之向上移动。     

石松子粉爆炸过程中火焰传播特性研究

为了研究石松子粉火焰传播特征,采用哈特曼管装置对石松子粉在燃烧管中进行试验,利用高速摄影和红外热成像技术记录石松子粉火焰传播过程,并对石松子粉火焰传播速度和火焰温度变化情况进行了分析。结果表明:点火能量为200mJ,粉尘浓度在125⁵00g/m500g/m³范围内,火焰在燃烧管中向上传播所达到的最大速度随着粉尘浓度的增加先增大后减小;在石松子粉浓度为250g/m3范围内,火焰在燃烧管中向上传播所达到的最大速度随着粉尘浓度的增加先增大后减小;在石松子粉浓度为250g/m³时达到最大速度11.08m/s;火球的面积随着时间变化呈现先增大后减小的趋势,在60ms时达到最大,同时达到最高温度1100℃;随着火焰的向上传播,火焰的最高温度区域也随之向上移动。     

初始湍流对粉尘爆炸影响的实验研究

采用大型实验装置对管道相连的粉尘操作设备中粉尘爆炸的火焰和压力传播过程及其影响因素进行实验研究。实验装置由两个通过管道连接的不同体积容器构成,爆炸从一个容器中通过管道传播到另一个容器中。在不同的初始湍流度条件下进行粉尘爆炸实验,测试不同位置的火焰和压力信号。结果表明:随着初始湍流度的增大,爆炸的猛烈程度增强,火焰和冲击波的传播速度加快,初始湍流作为影响粉尘爆炸发展过程的重要因素之一,在进行粉尘爆炸的安全防护和设计时必须考虑其作用。     

褐煤煤尘爆炸火焰传播特性及燃烧热分解机理研究

煤尘爆炸是矿井安全开采的主要危险源之一。以褐煤煤尘为研究对象,探究煤尘粒径对煤尘火焰传播过程的影响。用高速摄影装置记录火焰的传播过程,进而分析不同粒径下煤尘爆炸火焰传播的高度和速度。为进一步分析煤尘燃烧过程中的化学反应机理,借助反应分子动力学方法对煤分子燃烧中的初始热分解过程进行了模拟。研究结果表明:爆炸火焰传播高度呈先增加、后稳定的趋势,传播速度呈先增大、后减小的趋势;随着煤尘粒径的减小,火焰传播高度和传播速度均呈增大的趋势;当煤尘粒径为10.5 μm时,火焰传播高度和传播速度的峰值分别为623 mm和4.3 m/s;煤尘热分解主要产物为H₂、H₂O、CO₂和CH₂O,这些产物进一步与氧气的结合会促进煤尘燃烧和火焰传播过程,使得整个体系燃速加快。为煤尘热分解和燃烧提供了较为充分的数据基础。     

N2 O-C2 H4预混气体火焰的传播特性

运用标准k-ε模型,对N₂O-C₂H₄预混气体在水平半封闭管道内火焰传播过程进行了数值模拟,得到了火焰锋面结构、传播速度、出口压力和燃烧区的气流速度随时间的变化规律。研究结果表明,管道内预混火焰传播过程分为3个阶段:点火初期的平面火焰传播阶段、Tulip火焰传播阶段和指形火焰传播阶段;火焰传播速度呈指数增长,管道出口处压力和气流速度均呈现出先增大后减小的趋势。同时,采用高速摄影系统、压力传感器、有机玻璃管等装置对预混气体的火焰加速进程和压力演变过程进行了验证,实验结果与数值模拟结果一致。     

燃烧管长度对煤粉火焰传播规律的影响

为评价煤粉爆炸的危险性,掌握煤粉爆炸过程中火焰传播的规律,实验采用垂直的哈特曼管,选择褐煤为研究对象,研究燃烧管长度对煤粉火焰传播的影响,并使用高速摄影机记录火焰的传播过程.结果表明:随着燃烧管长度的增加,煤粉火焰在传播过程中逐渐变细,同时煤粉火焰前锋阵面的最大高度、火焰传播的最大速度不断增加.火焰传播速度整体呈现先增大后减小的趋势.当燃烧管的长度分别为300 mm、 600 mm、 750 mm和900 mm时,煤粉云的火焰前锋阵面的最大高度分别达到649 mm、 808 mm、 1 003 mm和1 010 mm,煤粉云的火焰传播的最大速度分别为5.4 m/s、 12.09 m/s、 15.0 m/s和18.61 m/s.研究结果可以为保证煤炭的安全开采提供理论支撑.     

瓦斯爆炸火焰厚度的实验研究

本文对水平管道中瓦爆炸传播火焰的厚度进行了实验研究,对不同浓度的瓦斯／空气爆炸火焰的厚度及传播速度进行了实际的测量,得到了火焰厚度变化的基本规律。在本实验条件下所测得的实际火焰厚度较厚, 而且变化范围较大,其厚度比按传统的静态火焰模型计算出的结果大得多。该实验结果为泊瓦斯爆炸机理的研究、瓦斯爆炸模型的建立以及数值模拟提供了可靠的实验数据。     

不同位置分支管道对油气爆炸强度的影响

为研究不同位置分支管道对油气爆炸强度的影响,搭建了不同分支管道实验系统。分别在直管道和具有不同位置分支管道的直管道中进行了油气浓度为1.75%的爆炸实验,并分析了爆炸超压值、升压速率、火焰传播速度以及火焰强度等特性参数变化情况。实验结果表明:分支管道对直管内的爆炸超压、升压速率、火焰传播速度、火焰强度和火焰持续时间有强化作用,并且距离点火端越远,强化作用越显著,火焰传播速度对火焰持续时间也有重要影响;分支管道前的爆炸超压变化曲线可以分为加速上升、膨胀泄压、振荡强化和振荡衰减等4个阶段,分支管道后的爆炸超压变化曲线可以分为加速上升、振荡强化和振荡衰减等3个阶段。     

磁场对瓦斯爆炸过程中火焰传播影响的实验研究

在实验研究的基础上,分析了磁场对瓦斯爆炸过程中火焰传播规律的重要影响.研究结果表明,磁场对瓦斯爆炸过程的影响很大,相比光滑管道,加磁场后火焰传播速度大幅度提高,而且随磁场强度的增加影响加剧;对于管道终端开口和闭口系统的瓦斯爆炸过程,磁场对两种系统的影响规律是一致的,影响程度比较接近,基于磁场强度对瓦斯爆炸影响的实验理论,从理论上分析了磁场强度对瓦斯爆炸传播速度的影响,并对实验现象作出了合理的解释.     

Experimental study on flames propagating through zirconium particle clouds

To reveal the mechanisms of flame propagation through the hardly volatile metal dust clouds clearly, the flame propagating through zirconium particle clouds has been examined experimentally. A high-speed video camera was used to record the propagation process of the flame. Combustion zone temperature was detected by a fine thermocouple. Based on the experimental results, structure of flame and combustion courses of zirconium particles were analyzed, the combustion propagation in zirconium dust was investigated, and the velocity and temperature characteristics of the combustion zone were also elucidated. The combustion zone propagating through zirconium particle clouds consists of luminous particles. Particle concentration plays an important role in the combustion zone propagation process. With the increase of zirconium particle concentration, the maximum temperature of the combustion zone increases at the lower concentration, takes a maximum value, and then decreases at the higher concentration. It is also found that the propagation velocity of the combustion zone has a linear relationship with its maximum temperature.     

Characteristics of wheat dust flame with the influence of ceramic foam

A vertical dust combustion pipeline with high-speed photography, micro-thermocouple and pressure sensor was built to investigate the influence of ceramic foam on the wheat dust explosion flame. Ceramic foams with different parameters were adopted in this paper, and compared with metal mesh. The chemical structures of dust explosion residue were characterized by X-ray photoelectron spectroscopy. Results indicate that the wheat dust flame propagation and structure were significantly destroyed by ceramic foam. With the decreasing aperture or increasing layer, the blocking effect of ceramic foam was aggravated on the dust flame. The flame cannot pass through the ceramic foam with 20 PPI and 3 layers. On the upper end of ceramic foam, the flame temperature is positively proportional to the aperture but inversely proportional to the layers. With the PPI and layers of ceramic foam increases, the combustion pressure firstly increases and then decreases when the dust combustion intensity is strong. Ceramic foam shows the incentive effect to some extent on the combustion pressure, but the continuous inhibition effect is found for the metal mesh.     

Explosion propagation in inert porous media

Porous media are often used in flame arresters because of the high surface area to volume ratio that is required for flame quenching. However, if the flame is not quenched, the flow obstruction within the porous media can promote explosion escalation, which is a well-known phenomenon in obstacle-laden channels. There are many parallels between explosion propagation through porous media and obstacle-laden channels. In both cases, the obstructions play a duel role. On the one hand, the obstruction enhances explosion propagation through an early shear-driven turbulence production mechanism and then later by shock-flame interactions that occur from lead shock reflections. On the other hand, the presence of an obstruction can suppress explosion propagation through momentum and heat losses, which both impede the unburned gas flow and extract energy from the expanding combustion products. In obstacle-laden channels, there are well-defined propagation regimes that are easily distinguished by abrupt changes in velocity. In porous media, the propagation regimes are not as distinguishable. In porous media the entire flamefront is affected, and the effects of heat loss, turbulence and compressibility are smoothly blended over most of the propagation velocity range. At low subsonic propagation speeds, heat loss to the porous media dominates, whereas at higher supersonic speeds turbulence and compressibility are important. This blending of the important phenomena results in no clear transition in propagation mechanism that is characterized by an abrupt change in propagation velocity. This is especially true for propagation velocities above the speed of sound where many experiments performed with fuel-air mixtures show a smooth increase in the propagation velocity with mixture reactivity up to the theoretical detonation wave velocity.     

变阻障碍物对管道内瓦斯爆炸的影响

为探究障碍物阻塞比变化率对瓦斯爆炸的影响,分别建立平均阻塞比为0.6、 0.3的受限空间物理模型,基于Charlette湍流燃烧模型,利用Fluent软件对阻塞比变化率依次为0、 0.05、 0.10、 0.15的障碍物条件下的爆炸火焰、湍流转捩、压力波耦合过程进行大涡模拟(LES)。研究结果表明：火焰经过障碍物会产生回流卷吸效应。在平均阻塞比为0.6的工况组A中,当阻塞比变化率为0.10、 0.15时,火焰锋面更加尖锐,火焰传播速度峰值更高,平均传播速度更高,到达超压所需时间更短,超压峰值更大。在平均阻塞比为0.3的工况组B中,各工况平均传播速度相同,随着阻塞比变化率的增大,到达超压所需时间更长,超压峰值更大。     

角联管网瓦斯爆炸冲击波与火焰波的传播特性

为了得出实际管网中瓦斯爆炸冲击波、火焰波的普适性传播特性,搭建了角联管网实验系统。通过平均升压速率和爆炸威力指数表征冲击波传播特性;通过火焰传播速率表征火焰波传播特性。结果表明:冲击波在角联管网中传播时出现了多次衰减与叠加,冲击波的正向传播和冲击波在管网所有互连管道中的反向传播叠加在一起,导致冲击波的传播呈现复杂无序状态。冲击波传播在不同的管道结构时,经过45°分岔管道时爆炸威力最大;在斜角联支管中,压力损失最大,超压爆炸威力下降幅度最大,火焰波传播速率最快;底部直管中的火焰波传播速率最慢。可为瓦斯爆炸灾害发生后应急救援方案的制定提供理论参考。     

Suppression of methane/coal dust deflagration flame propagation by CO2/fly ash as a flue gas layer

To reveal the suppression characteristics of methane/coal dust deflagration flame propagation by the flue gas loading in local zones. The suppression experiments of flue gas layer (CO₂ and fly ash) with different thicknesses and fly ash concentrations were conducted in semi-open vertical combustion pipe. The flue gas layer was produced by self-designed flue gas layer generator. Flame propagation characteristics which including the flame image, velocity, the ion current and temperature were recorded by the high-speed photography, the ion current probe and the thermocouple. The residues after coal dust deflagration were characterized by FTIR (Fourier transform infrared spectroscopy). The results show that the flue gas layer has a significant suppression on deflagration flame propagation. With the increasing of flue gas layer thickness and fly ash concentration, the flame velocity, height, temperature and the ion current gradually decreases, and the suppression effect was enhanced. The asphyxiation of CO₂, heat absorption and insulation of fly ash were mainly methods for the suppression of coal dust deflagration flame.