梧桐树粉尘爆炸特性研究

以梧桐树粉尘为例,研究了可作为工业粉状炸药添加剂的木粉粉尘的爆炸特性。运用哈特曼管测试了粉尘云的最小点火能,得出样品1#、样品2#和样品3#的最小点火能分别为70、90 m J和150 m J。将响应面法中的Box-Behnken试验设计应用于粉尘爆炸压力的测试,用20 L爆炸球进行试验,并从试验结果中拟合回归方程,由此判断出粉尘浓度对爆炸压力的影响最大,其次是点火能量,再次是粉尘粒径。对爆炸压力的试验条件进行优化,试验测得压力值为0.795 9 MPa,试验值与预测值之间的误差仅为1.28%,证明了该模型非常有效。     

纤维板砂光粉尘的燃爆特性

以某纤维板生产线的速生杨、马尾松、南方硬杂木的混合砂光粉尘作为研究对象,在分析粉尘粒径及其分布、可挥发分及形貌特征的基础上,采用20 L爆炸球对砂光粉尘进行燃爆实验,探索砂光粉尘的浓度对粉尘燃爆特征的影响,并对爆炸前、后粉尘的热稳定性和特征官能团进行探讨。结果表明,当砂光粉尘质量浓度增加到1 000 g/m3,最大爆炸压力达到最大值0.761 MPa;此后,粉尘浓度的增加反而使砂光粉的最大爆炸压力减小;当粉尘质量浓度增加到1 250 g/m3时,爆炸指数达到最大值17.62 MPa·m/s,且爆炸危险分级为St1(弱爆炸)。实验还采用最小点火能测试系统、热板炉和GodbertGreenwald炉研究了砂光粉尘的燃烧特性,结果表明,粉尘最小点火能为30~100 m J,粉尘层最低着火温度为300℃,粉尘云最低着火温度为420℃。     

石松子粉粉尘爆炸试验研究

该论文采用20 L球形爆炸测试装置对粒径在75μm以下的石松子粉的粉尘爆炸下限浓度、爆炸压力和爆炸指数随粉尘浓度的变化规律等进行了研究。研究结果表明:石松子粉粉尘爆炸下限浓度在20～40 g/m3之间,在粉尘浓度相对较低的60～500 g/m3时,粉尘的爆炸压力和爆炸指数随着粉尘浓度的提高而急速上升,在浓度为500 g/m3时达到最大,此时最大爆炸压力为0.69 MPa,爆炸指数为17.20 MPa.m/s;继续增加粉尘浓度,爆炸压力和爆炸指数略有下降,但仍维持在较高值;并判定石松子粉粉尘爆炸危险性分级为Ⅰ级。     

密闭空间镁粉爆炸压力特性研究

为研究镁粉粉尘爆炸最大压力与最大压力上升速率特性参数变化规律,使用标准20 L球形爆炸装置进行爆炸试验分析。通过对试验数据进行理论分析,探讨了点火延迟时间td、粉尘浓度c和粉尘粒径d等因素对镁粉爆炸压力特性的变化规律及产生原因。最后通过对金属镁粉爆炸试验数据进行回归分析,得到合适的回归模型。回归模型的R2值均在0.9以上,该回归模型的预测具有一定的合理性和准确性,为镁粉抑爆研究提供理论基础。     

石松子粉尘爆炸危险性及抑爆研究

为了研究粒径对石松子粉尘爆炸危险性的影响,采用Godbert-Greenwald(G-G)炉和20 L球爆炸装置对石松子粉尘云进行了试验,分析了粒径对爆炸特性的影响,并探讨了Si O2和NH4H2PO4对石松子粉的抑爆效果。结果表明:粒径越小的粉尘着火温度越低,潜在危险性更大;粒径小于48μm的粉尘,在质量浓度为750 g/m3时达到最大爆炸指数22.61 MPa·m/s,其爆炸危险性为Ⅱ级,相比于粒径小于75μm的粉尘,爆炸危险性更高;添加Si O2和NH4H2PO4后,能够显著降低石松子粉的爆炸压力和爆炸指数;与Si O2相比,NH4H2PO4具有更好的抑爆效果。     

铣销镁粉爆炸危险性及防爆措施

小型爆炸容器内测试了镁粉最大爆炸压力 ,在实际工业规模所使用的振动筛中 ,对镁粉半成品的筛分分级的爆炸性等进行了测试 ,分析了生产线粉尘爆炸的危险性 ,提出了相应的防爆措施     

玉米淀粉电火花点火数值模拟

在粉尘云电火花点火实验研究的基础上,结合粉尘云点火机理,建立完整的粉尘云点火模型。通过模型计算玉米淀粉的最小点火能,并模拟点火过程中颗粒温度随时间的变化过程,同时分析在无粉尘粒子情况下电火花温度的变化情况。通过模拟计算,得到玉米淀粉在敏感条件下的点火能为2.9 mJ,计算结果与实验数据基本一致,由此可以进一步理解粉尘云的点火过程及电火花放电过程。     

粉尘爆炸防护措施的研究进展

随着工业现代化的发展,粉末技术应用越来越广泛。由于人们对不同物料粉尘的危害认识不清,特别是粮食粉尘和金属粉尘爆炸机理和防治技术研究不够系统、深入,缺乏有效的粉尘爆炸安全防护,导致最近几年粉尘爆炸事故频繁发生。为预防和控制粉尘爆炸事故,更加深入地了解粉尘爆炸,首先从粉尘爆炸的机理和必要条件介绍了粉尘爆炸;其次,总结了粉尘爆炸防护措施的试验研究现状,对惰化技术、泄爆技术、抑爆技术3个方面进行阐述。此外,分析目前防护措施的不足,并提出将来发展的方向,为粉尘爆炸防护研究提供引导作用。     

典型爆炸粉尘的危险性预测

本文在国际通用的Siwek 20-L球形爆炸装置内系统研究工业生产中典型爆炸粉尘的危险性,包括粉尘爆炸下限,粉尘层最低着火温度,最大爆炸压力和爆炸指数。结果表明随着粉尘浓度的增加,其爆炸威力呈先增后减的趋势。对粉尘的惰化实验研究表明,惰性介质的添加能有效降低粉尘爆炸威力,混合体系在高添加量下甚至失去可爆性。     

密闭空间煤粉爆炸特性的实验研究

为了探明煤粉在密闭空间中的爆炸特性参数,利用20 L球形爆炸装置进行实验测试,实验研究了不同点火能量对煤粉爆炸行为的影响,对比CaCO_3和Al(OH)_3两种惰性介质的抑爆效果及惰性介质的抑爆效力随点火能量的变化规律进行了重点探讨。结果表明:随着点火能量的增加,爆炸压力随着煤粉浓度的增加呈现先上升后下降的趋势,在同一浓度下,粉尘最大爆炸压力和最大升压速率呈线性上升,在高浓度下,粉尘爆炸压力受点火能量的影响更显著;添加CaCO_3和Al(OH)_3能够降低煤粉的爆炸压力,相对于CaCO_3的物理抑爆而言,Al(OH)_3的物理-化学抑爆效果更佳;惰性介质抑爆效力随点火能量增加而下降,建议采用5~10 k J点火能量考察惰性介质对煤粉爆炸的抑制效力。     

Explosion dust particle size measurements

In situ measurements of the sizes and concentrations of dust particles generated by the detonation of high explosives in clay soil near Leesville, La., sandy clay soil near Huntsville, Ala., and sandy soils near Orogrande, N.M. are reported. Measurements were generally made within 1 m of the surface (in one case 10 m) at distances ranging from 10 to approximately 50 m from the detonation point with a combination of Knollenberg lightscattering counters (for particles with equivalent radius in the submicron to 15-microm range) and a Knollenberg optical array probe (for particles of 10-150 microm). Measurements were made for periods of several tens of seconds following detonation. All dust size distributions, irrespective of soil or explosive type, exhibit a bimodal character with mass mean radii of approximately 7 and 70 microm. Peak aerosol mass loadings inferred from the distributions have values ranging from 0.05 to 10 g gm-3 with the larger mode of particles contributing most to the mass loading. Predictions of dust extinction coefficients at visible (0.55-microm) and IR (10.4-microm) wavelengths were made using the measured size distributions together with estimates of dust refractive indices. These predictions suggest that extinction should be nearly neutral (wavelength independent) in agreement with transmission measurements made during some of the tests. Predicted mass extinction coefficients, under the assumption of dust material density of 2.5 g cm-3, are of the order of 0.05 m2 g-1 at both visible and IR wavelengths. This value is also in good agreement with a test-averaged measured value of 0.03 m3 g-1 (at lambda = 10.6 microm) obtained using a short path transmissometer and hi-vol sampler.     

Explosion and detonation characteristics of dimethyl ether

In this study, the explosion and detonation characteristics of dimethyl ether (DME) were experimentally investigated. A spherical pressure vessel with an internal volume of 180L was used as the explosion vessel. Therefore, tubes 10m in length with internal diameters of 25mm and 50mm were used as detonation tubes. In addition, we compared the characteristics of DME with those of propane since DME is considered as a substitute fuel for liquid petroleum gas (LPG). At room temperature and atmospheric pressure, the maximum explosive pressure increased tenfold. The explosion index (K(G) values), an indicator of the intensity of an explosion, was larger than that of propane, indicating that the explosion was intense. No experimental study has been conducted on the detonation behavior of DME so far, but this research confirmed a transition to detonation. The detonation characteristics were similar to the characteristics of the Chapman-Jouguet detonation, and the concentration range for detonation was from 5.5% to 9.0%.     

Explosion characteristics of synthesised biogas at various temperatures

Biogas is considered as a valuable source of renewable energy. Indeed, it can be turned into useful energy (heat, electricity, fuel) and can contribute to reduce greenhouse gas emissions. Knowledge of its safety characteristics is a very important practical issue. Experimental investigation of synthesised biogas explosion characteristics was conducted in a 20-L sphere at various temperatures (30-70 degrees C) and at atmospheric pressure. The studied biogas was made of 50% methane (CH(4)) and 50% carbon dioxide (CO(2)). It was also saturated with humidity: this composition is frequently met in digesters during waste methanisation. There are two inert gases in biogas: water vapour and carbon dioxide. Its vapour water content rises along with temperature. The presence of these inert gases modifies considerably biogas characteristics compared to the ones of pure methane: explosion limits are lowered and beyond 70 degrees C, water vapour content is sufficient to inert the mixture. Furthermore, explosion violence (estimated with the maximum rate of pressure rise values, (dp/dt)(max)) is three times lower for biogas than for pure methane at ambient temperature.     

Processing property characteristics for long glass fibre reinforced polyamide

The influence of microstructure on the stiffness and toughness of ‘long’ glass fibre reinforced nylon 66 mouldings was studied. Using the results of previous work which established the influence of processing conditions on moulding microstructure, the effects of processing on resulting mechanical properties are inferred. Whilst impact toughness is shown to be insensitive to processing conditions, slow crack propagation toughness is greatest in situations where the processing produces a pronounced core region of long fibres orthogonally aligned to the direction of crack propagation. Model studies of the influence of microstructure on stiffness suggests little sensitivity of modulus to likely variations in the processing parameters.     

Inhibition characteristics of coal dust explosion at the gasification atmosphere

The risk of coal dust explosion threatens the safety of coal gasification process. To reveal the inhibition of carrageenan dry-water material (CDM) on coal dust explosion, a 20 L spherical explosive device was adopted to compare with SiO₂ and NH₄H₂PO₄ at the atmosphere of coal gasification. The thermal decomposition behavior and chemical structures of the explosion residues were characterized by synchronous thermal analyzer, X-ray photoelectron spectroscopy and FTIR. The results indicate that the CDM showed the optimal inhibiting effect on 300 mesh and the maximum explosion pressure of anthracite coal dust was reduced to 0.02 MPa with the percentage of 97.53%. At the same concentration, the inhibiting effect of CDM on the coal dust explosion was better than that of SiO₂ and weaker than that of NH₄H₂PO₄. Through the residues analysis, the CDM mainly prevented the volatilization of C-H and consumption of oxygen-containing groups and sulfur-containing groups contributing to the inhibition of coal dust explosion.     

Effect of organoclay addition on the two-body abrasive wear characteristics of polyamide 6 nanocomposites

Polymer clay nanocomposites (PCN) exhibit improved mechanical properties due to nanolevel dispersion of clay in the polymer matrix. They also exhibit good tribological performance under dry sliding conditions. Abrasive wear behaviour of these materials would be different from dry sliding behaviour as the mechanisms of the both are entirely different. Hence the abrasive wear behaviour of these materials needs to be investigated. The abrasive wear characteristics of polyamide 6 nanocomposites, with 1, 3 and 5% (wt.) clay prepared by melt intercalation technique, under two-body abrasive wear conditions have been reported. Abrasive wear tests were conducted using a pin-on-disc tribometer containing an abrasive counterface. All the polyamide nanocomposites investigated exhibited a low abrasive wear resistance compared with pristine Nylon. The wear performance of the nanocomposites was correlated with the mechanical properties. Dominant ploughing and cutting wear were observed in polymer clay nanocomposites. The amount of clay present alters the wear mechanism.     

Study on dynamic and mechanical characteristics of carbon fiber- and polyamide fiber-reinforced seismic isolators

Seismic isolators are used to decrease the energy and forces of earthquakes. The weight of conventional steel-reinforced elastomeric isolators (SREIs) is high, mostly due to the use of multiple steel shim plates. On the contrary, the damping ratio of SREIs is relatively low. Accordingly, this research utilizes a new approach in which the steel shim plates are replaced by carbon and polyamide fibers. This study attempts to obtain the dynamic and mechanical properties of such carbon fiber- and polyamide fiber-reinforced elastomeric isolators, in comparison with SREIs. In this work, a number of specimens were initially designed and manufactured. Afterwards, compression and cyclic shear tests were performed on them. In the shear tests, due to the limitations of the testing machine, a constant vertical load was not applied. All three types of isolator specimen were cylindrical, with identical diameter and height. The steel-, carbon fiber-, and polyamide fiber-reinforced elastomeric isolator specimens had 16, 23, and 23 reinforcement layers, respectively. To decrease the effect of manufacturing errors on the dynamic and mechanical characteristics of the specimens, 6 samples of each isolator type were manufactured, i.e., a total of 18 samples. The outcome of the experiments revealed that the use of flexible reinforcement resulted in a damping increase of up to 20 and 30 % for the carbon fiber- and polyamide fiber-reinforced elastomeric isolators, respectively. Furthermore, the carbon fiber design provides more reasonable performance for the isolators compared with the use of polyamide fiber.     

Approximate analytical scattering phase function dependent on microphysical characteristics of dust particles

The approximate bulk-scattering phase function of a polydisperse system of dust particles is derived in an analytical form. In the theoretical solution, the particle size distribution is modeled by a modified gamma function that can satisfy various media differing in modal radii. Unlike the frequently applied power law, the modified gamma distribution shows no singularity when the particle radius approaches zero. The approximate scattering phase function is related to the parameters of the size distribution function. This is an important advantage compared to the empirical Henyey-Greenstein (HG) approximation, which is a simple function of the average cosine. However, any optimized value of average cosine of the HG function cannot provide the information on particle microphysical characteristics, such as the size distribution function. In this paper, the mapping between average cosine and the parameters of size distribution function is given by a semianalytical expression that is applicable in rapid numerical simulations on various dust populations. In particular, the modal radius and half-width can be quickly estimated using the presented formulas.     

Charging,movement and lifetime characteristics of dust in magnetic fusion devices

Charging, movement and lifetime characteristics of spherical dust grains generated in magnetic fusion devices are discussed. A universal charging equation of the dust grain is given. The simulation results show that the charge quantity of the dust grain changes along with the ratio of electron and ion temperature, and decreases due to secondary electron emission, the charging relaxation time of dust grain in fusion devices is much shorter than that in laboratory plasma, that, under the effect of ion drag force, dust speed reaches hundreds of metres per second and the lifetime of carbon dust in fusion devices is at the millisecond scale. The results are consistent with experimental observations.