铝粉分散过程中粒径效应的三维数值研究

为了研究不同粒径的铝粉在20 L爆炸测试装置中的分散规律,基于计算模型的非结构网格划分,耦合欧拉和拉格朗日方法,实现了描述可压缩气体演化的时间平均Navier-Stokes方程组和粒子运动的DPM动量平衡方程的求解,获得了不同粒径（25,50和100 μm）的铝粉在20 L爆炸仓内分散的三维时空演化规律。研究结果表明:铝粉粒径的差异对爆炸仓点火中心的湍动能和速度的演化过程影响不显著,但对粉尘浓度的变化率和峰值均具有重要影响;随着粒径的增大,峰值浓度越小,但均高于形式浓度0.25 kg/m3,达到峰值浓度的时间越滞后。     

粉尘密度对20 L球罐内粉尘分散规律影响

为分析不同粉尘因密度的差异对20 L球形爆炸装置球罐内粉尘分散过程流场变量变化和点火延迟时间的影响,利用CFD数值模拟的方法,研究了3种不同密度的粉尘在球罐分散过程中湍流动能、流场速度、粉尘浓度3种流场变量在球心处的变化规律。研究结果表明:在其他条件一致的情况下,粉尘密度越小,湍流动能的峰值越小,粉尘云浓度和流场速度的峰值则越大;粉尘密度对湍流动能的增值速率没有影响,而粉尘密度越小,流场速度和粉尘浓度的增值速率越快,粉尘浓度衰减至稳定值的时间也越短。表明粉尘密度越小,点火延迟时间也越小,因此,建议铝粉点火延迟时间在50~60 ms之间,锆粉和锌粉在60~80 ms之间。     

微米级铝粉最低着火温度和爆炸特性试验研究

为更好防治铝粉爆炸,针对不同因素对微米级铝粉的最低着火温度和爆炸特性的影响灵敏度进行试验研究,揭示不同因素对其影响程度大小。最低着火温度和爆炸特性分别由粉尘云最低着火温度测试系统和20 L球爆炸装置测试。试验结果表明:粒径越小,比表面积越大,铝粉越容易发生燃烧爆炸;逐个分析粒径、质量浓度和分散压力这3项影响因素对铝粉尘云最低着火温度影响敏感度,得出敏感度大小为粒径分散压力质量浓度;逐个分析点火延迟时间、粒径和质量浓度这3项影响因素对铝粉爆炸参数的影响灵敏度,得出灵敏度大小为粒径点火延迟时间质量浓度。     

橡胶粉尘的爆炸特性及抑爆的试验研究

为了研究橡胶粉尘的爆炸特性以及惰性粉体对橡胶粉尘的抑爆,用20 L球形爆炸装置测试橡胶粉尘的爆炸特性,分析粉尘浓度和粒径对橡胶粉尘爆炸压力(pmax)和爆炸指数(Kst)的影响,并且探究聚磷酸铵、磷酸二氢铵、碳酸钙和碳酸氢钠4种不同惰性粉体对橡胶粉尘的抑爆效果及不同粒径的聚磷酸铵对橡胶粉尘爆炸压力的影响。结果表明:在爆炸极限范围内,橡胶粉尘的爆炸压力随粉尘质量浓度增加先增大后减小;橡胶粉尘粒径越小,其爆炸后果越严重;聚磷酸铵对橡胶粉尘的抑爆效果相对较好;且在一定质量浓度范围内粒径越小,抑爆效果越好。     

点火延迟时间对粉尘最大爆炸压力测定影响的研究

根据粉尘云形成时颗粒分散及沉降的时间效应,指出目前国际通行的球型爆炸装置采用固定点火延迟时间测定粉尘最大爆炸压力的方法具有不确定性,并以煤粉为介质在20 L标准爆炸球装置上进行系列爆炸实验,研究装置点火延迟时间对粉尘爆炸压力的影响。结果表明:点火延迟时间对粉尘爆炸压力测定有十分显著的影响,不同粒径粉尘的最大爆炸压力有不同点火延迟时间,目前仅以气相湍流度所确定的固定点火延迟时间下,所测粉尘最大爆炸压力可能严重偏离实际。     

超细聚苯乙烯微球粉体的燃爆特性研究

为研究超细聚苯乙烯微球粉体的燃爆特性,通过粉尘层最低着火温度测试装置、MIE-D1.2最小点火能测试装置、20 L球形爆炸测试装置,对其最低着火温度、最大爆炸压力、最小点火能量(MIE)等爆炸特性参数进行测定,探讨了加热温度、点火延滞时间、粉尘质量浓度、粉尘粒径对粉体燃爆特性的影响。结果表明:超细聚苯乙烯微球粉尘层在350℃左右时会发生无焰燃烧,且加热温度越高,粉体粒径越小,粉尘层发生着火时所需的时间越短;当粉体质量浓度为250 g/m3时,最大爆炸压力达到0.65 MPa,质量浓度为500 g/m3时,最大爆炸压力的上升速率达90 MPa/s以上;随点火延滞时间增加,最小点火能表现出先缓慢减小再急剧增大的规律;随粉尘质量浓度增加,最小点火能逐渐降低,当粉尘质量浓度超过500g/m3后逐渐趋于稳定。     

点火能量对粉尘爆炸下限浓度的影响

运用20L标准粉尘爆炸特性测试装置对不同粉尘在不同点火能量时的爆炸下限浓度进行测试,以此方法研究粉尘爆炸下限浓度随点火能量的变化规律。试验过程分别采用2. 5 k J、5 k J、10 k J点火能量对石松子粉、石墨粉、铝粉、金属打磨粉尘、纸粉、PVC粉、纺织粉、烟叶粉的爆炸下限浓度进行测试。试验结果显示粉尘爆炸下限浓度随点火能量的增加总体呈下降趋势;对于不易点燃的粉尘,其爆炸下限浓度随点火能量的增加将急剧下降。石墨粉随点火能量增加爆炸下限浓度急剧下降,铝粉、石松子粉和金属打磨粉尘受点火能量影响较小,对纸粉、纺织、烟叶粉尘影响中等。高点火能量可以扩大点火源波及的区域,从而使更多粉尘参与初始爆炸及其后的传播过程,这对于不易点燃粉尘的爆炸传播影响较大,而对于易燃粉尘的爆炸传播影响不大。为了更好的涵盖各种粉样的测试情况,也为了更加安全的指导作业现场粉尘防爆实践,推荐采用10 k J点火能量测试不易点燃的粉尘的爆炸下限。     

三环唑粉尘爆炸特性研究

利用激光粒度仪对三环唑粉尘的粒径分布进行分析,并用20 L爆炸球测试装置、哈特曼管装置探讨了粉尘质量浓度、点火延迟时间、点火能量、粒径分布对粉尘爆炸的影响并总结了相关规律。实验结果表明:粉尘粒度是影响粉尘最小点火能和爆炸下限的单调因素,粉尘质量浓度是影响粉尘爆炸压力的极值因素,点火延迟时间是影响粉尘最小点火能的极值因素。     

基于正交实验的面粉爆炸特性研究

为探究面粉爆炸实验中粉尘质量浓度、点火能量、点火延迟时间对面粉爆炸的影响,采用正交实验法并利用20 L球形爆炸测试装置比较研究了粉尘质量浓度、点火延迟时间以及点火能对面粉爆炸的影响程度。结果表明:对最大爆炸压力影响最为显著的因素是点火延迟时间,对最大爆炸指数影响最为显著的因素是粉尘质量浓度;在实验浓度范围内,存在最佳实验条件。当粉尘质量浓度500 g/m3、点火延迟时间100 ms时,面粉爆炸最剧烈。     

1．2L Harttman管式与20L球型爆炸测试装置爆炸猛度实验研究

随着现代工业的发展，粉尘爆炸的危险性几乎涉及到所有的粉体工业部门，因此对粉尘爆炸危险场所进行危险性分析成为一种必然。粉尘爆炸的猛度参数是危险性分析的重要参数，反应了粉尘爆炸的猛烈程度，同时也是设计和选用泄爆、隔爆、抑爆等不同防爆技术方法的基础。然而，对于不同的测试装置所测得猛度参数有所不同。本文分别利用1．2L Haitmann管与20L球形爆炸装置对玉米淀粉的爆炸猛度参数进行了测试，并对相应结果进行了对比分析。     

CFD modeling and simulation of turbulent fluid flow and dust dispersion in the 20-L explosion vessel equipped with the perforated annular nozzle

A three-dimensional CFD model was developed to simulate the turbulent flow field induced by dust feeding and the associated dust dispersion within the 20-L explosion vessel equipped with the perforated annular nozzle. The model was validated against experimental data for pressure and root mean square velocity.Simulation results have shown that the turbulent kinetic energy is rather uniformly distributed and its values are significantly lower than those attained with the rebound nozzle. Furthermore, the perforated annular nozzle is able to generate a uniform dust/air cloud. However, a consistent fraction of the dust remains trapped inside the nozzle and, thus, it does not contribute to the explosion process.     

初始扰动对CO2抑制瓦斯爆炸特性研究*

为了预防实际生产过程中发生的瓦斯爆炸事故,利用20 L球形爆炸装置,通过改变粉尘仓充压压力产生不同的扰动,研究9.5%CH4浓度下不同扰动条件对CO2抑爆特性的影响。通过对所得参数进行分析,得到CO2抑爆特性与初始扰动的关系。研究结果表明:相较于均匀静置状态,初始扰动的存在均能提高CH4的爆炸强度,当引发初始扰动的粉尘仓压力为1.5 MPa时,最大爆炸压力达到0.78 MPa;随CO2浓度增大,爆炸强度整体下降,呈二次下降趋势、最大爆炸压力时间呈上升趋势,且各初始扰动压力间爆炸强度均大于均匀静置状态、最大爆炸压力时间小于均匀静置状态;同时利用CHEMKIN软件得到绝热平衡压力,计算热损失参数发现,同一气体混合比例工况下,初始扰动状态的热损失及热损失分数明显低于均匀静置状态的,且当CO2浓度为15%时,差距最大,不同初始扰动间热损失及热损失分数最小值分别为0.013 19 kJ/m2,17.9%,远小于静置状态下0.036 29 kJ/m2,46.4%,说明初始扰动对于CO2抑爆效果存在削弱作用。     

基于20 L球罐的多相混合物扩散模拟

为更好地探索多相混合物的爆炸特性，以铝粉、乙醚、空气为研究对象，基于20 L球型爆炸罐建立三维计算模型，对气固两相和气液固三相混合物的分散过程进行数值模拟，以分析不同多相混合物分散过程的差异，并为测量多相混合物爆炸下限时的点火延迟时间设定提供参考。监测分析铝粉浓度粒子分布、流场内部湍流动能以及液相体积百分数等的演化过程，讨论混合物分散效果的差异，并确定测量爆炸下限的点火延迟时间。研究结果表明:实验工况下，液相的存在会降低粉尘云团的湍流动能、降低其扩散速度，并使粉尘云内部浓度更均匀。测量多相混合物爆炸下限时，三相混合物的最佳点火延迟时间早于气固两相混合物10~20 ms。     

Effectiveness of dust dispersion in the 20-L Siwek chamber

The Siwek 20-L chamber is widely used throughout the world to evaluate the explosibility of dusts. This research evaluated the quality of dust dispersion in the Siwek 20-L chamber using Pittsburgh coal, Gilsonite, and purple K dusts. A Pittsburgh Research Laboratory (PRL) optical dust probe was used to measure optical transmittance through the dust cloud at various locations within the chamber. A total of 540 tests were performed, with triplicate tests at five nominal dust concentrations and six locations. The two standard dispersion nozzles (rebound and perforated annular nozzle) were compared. The transmissions corresponding to the normal ignition delay period were used to: (a) determine variations in spatial uniformity of dispersion obtained with both nozzles; (b) make comparisons between the experimental transmission data and those calculated from theory for the three dusts; and (c) make comparisons with transmission data measured in the PRL 20-L and Fike 1-m³ dust explosion chambers.The uniformity of dispersion for the three dusts was similar with both nozzles, despite the differences in nozzle geometry and mode of operation. Transmission data of the three dusts were all significantly lower than those calculated from theory. This was discovered to be, in part, due to significant reduction in particle size that occurred during dispersion. By measuring particle sizes before and after dispersion, values of 60%, 50%, and 20% reduction in particle size (based on the surface-weighted mean diameter) were obtained for Pittsburgh coal, Gilsonite, and purple K, respectively. Transmission data from the PRL 20-L, Fike 1-m³ and the Siwek 20-L chambers indicated comparable results in terms of uniformity of dispersion. However, transmission data from the Siwek 20-L chamber were significantly lower than those of the PRL and Fike chambers. Again, this was attributed, in part, to the significant reduction in particle size that occurred during dispersion in the Siwek chamber. The design of the outlet (dispersion) valve of the Siwek 20-L apparatus charge vessel was largely responsible for the particle break-up. The contribution to particle break-up by the dispersion nozzles and the high level of turbulence in the chamber were found to be minimal. This is a significant finding in that the dust particle size tested for explosibility in the Siwek chamber is considerably smaller than the original dust sample.     

Visualization and analysis of dispersion process of combustible dust in a transparent Siwek 20-L chamber

Dust explosion severities are closely associated with dust dispersion behaviors. To characterize the dispersion process of dust cloud, visualization experiments were conducted by using a transparent Siwek 20-L chamber. Dispersion processes of typical carbonaceous dust were recorded by a high-speed camera and, with the image processing technique, the qualitative analysis based on the transmission of dust cloud was carried out. Results have evidenced the three consecutive stages of dust dispersion process: the fast injection stage of dust particles, the stabilization stage and the sedimentation stage of dust cloud. The motion of dust particles and the variations of dust cloud in space and time can be clearly distinguished. In the stabilization stage, the good uniformity of dust dispersion is achieved when the deviation of transmission data at different locations reaches to the minimum value. Under different nominal dust concentrations, the time periods for dust dispersion stabilization are found to be significantly different, suggesting that different dust concentrations should correspond to different ignition delay in order to accurately measure the explosion characteristics in the Siwek 20-L chamber. Moreover, it is found that the decrease trend of transmission with increasing nominal dust concentration will become gradually leveling off, different from the inversely proportional relationship according to the Bouguer's law, and this indicates that the actual dust concentration will be lower than the nominal concentration or the dust cannot be fully dispersed at the case of high dust concentration. According to the experiment, when the nominal dust concentration exceeds to 1000 g/m³, the transmission will no longer vary visibly.     

抛光铝粉爆炸及ABC粉体抑爆特性的实验研究

为研究抛光铝粉的爆炸危险和ABC粉体的抑爆特性，在对实验粉体粒径分布进行分析的基础上，采用20 L粉尘爆炸特性实验装置，分别对不同铝粉尘浓度、不同抑爆剂浓度条件下的爆炸特性参数进行测试。研究结果表明:在实验条件下，铝粉的爆炸下限为45 g/m3＜C＜60 g/m3；随铝粉浓度增加，爆炸烈度呈现出先增强后减弱的变化趋势，在浓度为400 g/m3时爆炸烈度最大。ABC抑爆剂能够有效抑制铝粉爆炸超压和爆炸反应进程，随着惰性粉体浓度的增加，抑制效果愈加明显，爆炸逐渐减弱。当ABC惰性粉体的质量占比增加到50%时，相较单一铝粉爆炸，反应过程时间由72 ms增加至785 ms，爆炸最大压力、最大压力上升速率分别下降了61.7%，89.5%；当ABC粉体质量占比为53%时，铝粉被完全惰化，未发生爆炸。     

碳酸氢钠及其固态分解产物对玉米淀粉爆炸抑制实验研究*

为研究NaHCO3对玉米淀粉爆炸的抑制效果,采用20 L球形爆炸装置测试玉米淀粉在添加不同抑制比NaHCO3及其固态分解产物Na2CO3后爆炸参数变化规律,并分析NaHCO3抑制淀粉爆炸过程。结果表明:NaHCO3及Na2CO3对玉米淀粉爆炸均有抑制作用,NaHCO3抑制效果优于Na2CO3;混合粉尘的最大爆炸压力、最大爆炸压力上升速率与爆炸指数随抑制比增大而逐渐减小,爆炸时间随抑制比增大而逐渐延长。随着NaHCO3浓度增加,物理抑制效果逐渐增加,化学抑制效果基本保持不变。NaHCO3浓度不同时,其抑制主导过程不同,当抑制比为0.1~0.5时,NaHCO3抑制效果以化学抑制为主,物理抑制为辅;抑制比为0.8和1.2时,NaHCO3抑制效果以物理抑制为主,化学抑制为辅;当抑制比为1.2时,玉米淀粉爆炸完全被NaHCO3抑制,此时物理抑制起主导作用。     

含磷酸盐对聚乙烯粉尘爆燃的抑制影响实验研究

为了揭示含磷酸盐（KH_{2PO4,NH4H2PO4,Ca(H2PO4)2）对聚乙烯粉尘爆炸的抑制作用,通过哈特曼管实验装置和20 L球形爆炸罐,研究含磷酸盐对聚乙烯粉尘爆炸火焰和压力传播特性的抑制效果。采用高速摄影方法记录含磷酸盐对聚乙烯粉尘爆炸火焰传播的影响;采用20 L球形爆炸罐,收集压力传感器数据,分析含磷酸盐对聚乙烯粉尘爆炸压力的影响;采用同步热分析仪研究聚乙烯粉尘和含磷酸盐的热解行为。研究结果表明:含磷酸盐对聚乙烯粉尘爆炸火焰传播特性参数和爆炸压力特性参数均有显著的影响,通过对比得到NH4H2PO4抑制效果相对最好。研究结果可为含磷酸盐在抑爆剂工程应用提供理论基础。}     

CFD simulations of dust dispersion in the 1 m3 explosion vessel

According to standard procedures, flammability and explosion parameters for dusts and dust mixtures are evaluated in 20 L and/or 1 m³ vessels, with equivalent results provided a correct ignition delay time (60 ms in the 20 L vessel; 600 ms in the 1 m³ vessel). In this work, CFD simulations of flow field and dust concentration distribution in the 1 m³ spherical vessel are performed, and the results compared to the data previously obtained for the 20 L. It has been found that in the 1 m³ vessel, the spatial distribution of the turbulent kinetic energy is lower and much more uniform. Concerning the dust distribution, as in the case of the 20 L, dust is mainly concentrated at the outer zones of the vortices generated inside the vessel. Furthermore, an incomplete feeding is attained, with most of the dust trapped in the perforated annular nozzle. Starting from the maps of dust concentration and turbulent kinetic energy, the deflagration index K_St is calculated in both vessels. In the conditions of the present work, the K_St is found to be 2.4 times higher in the 20 L than in the 1 m³ vessel.