甲烷/石墨粉与甲烷/煤粉爆炸特性对比研究

借助20 L球形爆炸系统研究了甲烷/石墨粉和甲烷/煤粉复合体系爆炸特性异同,结果表明：甲烷浓度对甲烷/石墨粉和甲烷/煤粉两相体系的爆炸特性有重要影响,当甲烷的浓度为6%（体积）时,随着石墨粉粒径的增加,甲烷/石墨粉体系的压力曲线由单峰转为双峰,三种粒径的石墨粉（D₅₀：7、18、75 μm）浓度分别在60、200、30 g/m³达到爆炸压力最大值0.691、0.657、0.611 MPa;甲烷/煤粉体系则在400 g/m³达到最大值0.724 MPa,高于甲烷/石墨粉体系。当甲烷浓度接近当量比时,三种粒径石墨粉的爆炸压力峰值均呈现逐渐减小的趋势,石墨粉的粒径越小,甲烷/石墨粉两相体系的爆炸压力峰值越小,甲烷/石墨粉体系在质量浓度为10 g/m³时达到最大值;甲烷/煤粉体系的爆炸压力则在60 g/m³时达到最大值0.776 MPa。甲烷浓度由6%增加至9%时,甲烷/石墨粉和甲烷/煤粉的爆炸火焰由不规则形状转为近似球形发展,火焰表面褶皱消失,同时两相体系的爆燃指数显著增高,当粉尘质量浓度大于30 g/m³时,甲烷/煤粉的爆燃指数大于甲烷/石墨粉体系,这是由于煤粉挥发分含量高,燃烧更为充分,且焦炭参与了爆炸过程;石墨粉本身的挥发分含量低,含碳量远超过煤粉,爆炸中仅有少部分石墨粉参与了爆炸。研究结果将对气粉两相混合物爆炸防治提供指导。     

CO2-双流体细水雾抑制管道甲烷爆炸实验

搭建了尺寸为120 mm×120 mm×840 mm透明有机玻璃瓦斯爆炸管道实验平台,采用双流体喷嘴将二氧化碳和细水雾送入实验系统,从火焰速度、瓦斯爆炸超压两个方面探讨双流体细水雾的抑爆有效性。实验结果表明CO₂双流体细水雾抑制瓦斯爆炸效果显著。随着喷雾时间的延长,火焰传播速度呈缓慢增加趋势,火焰传播速度峰值大幅降低;爆炸超压曲线呈先增大后缓慢减小的趋势,超压峰值大幅降低;当CO₂压力增至0.4 MPa喷雾时间大于3 s时,经多次点火无法引爆, 说明CO₂-双流体细水雾抑制甲烷爆炸时具有协同效应,有利于提高细水雾的抑爆效率。     

基于模糊DEMATEL-ISM的高铁采空区地基注浆治理影响因素研究

高速铁路下伏采空区地基注浆治理的有效性是高速列车安全运行的关键。针对采空区的复杂性、注浆工程的隐蔽性及注浆效果难控制等问题,根据国家及地方规范文件、期刊文献和实证研究成果等3方面的基础资料,结合问卷调查和专家访谈方式构建了高速铁路采空区地基注浆治理影响因素体系。通过模糊DEMATEL方法研究影响因素之间的关联强度并识别关键因素,进一步基于ISM方法分析影响因素间的相互作用关系,建立层次结构模型。研究表明:注浆材料及性能是高铁采空区地基注浆治理的主要影响因素,对注浆效果作用程度最大;岩体基本质量和注浆材料及性能对注浆效果产生直接影响;开采方式、开采深度和煤层倾角等是注浆治理的深层因素;重复采动是影响注浆治理的最根本和最关键的因素。     

Comment on “MoS2/Ti3C2 heterostructure for efficient visible-light photocatalytic hydrogen generation”

In a recent article entitled “MoS₂/Ti₃C₂ heterostructure for efficient visible-light photocatalytic hydrogen generation” published in this journal, MoS₂/Ti₃C₂ heterostructure was prepared with excellent performance as photocatalyst for hydrogen evolution reaction. Although the materials were correctly made and tested, the presentation and explanation of X-ray diffraction (XRD) patterns are not correct. Some diffraction peaks are not indexed correctly. Therefore, better XRD patterns and explanation are suggested to ensure the reliability of the photocatalytic mechanism of MoS₂/Ti₃C₂ in that paper.     

Experimental investigation on the propagation of flow and flame in a confined combustion chamber equipped with a single-hole perforated plate

The effects of the hole size and perforated plate position on the propagation of flame and flow and pressure oscillation were explored in a constant volume combustion chamber (CVCB) with a single-hole perforated plate. Stoichiometric hydrogen-air mixture was used in the experiments, and the propagation of the flame and jet flow were recorded by high-speed schlieren photography. The results demonstrated that the flame velocity firstly increases and then decreases with the increasing hole size. With the hole size of 13 mm, the flame velocity, peak pressure, and pressure oscillation reached the maximum under the current experimental conditions. Moreover, the influence of the position of the perforated plate was investigated. It was found that the jet flow before the flame front is prominently distinct when the perforated plate is in positions A and B, resulting in an apparent difference in the flame shape behind the perforated plate, which means that the movement of the jet flow plays a leading role in the development of the flame. In Position B, the flame front overlapped with the jet flow and has the same shape. Besides, an interesting phenomenon was captured: with perforated plate in Position B, a secondary flame front was generated with higher flame tip velocity before the primary flame front under the effect of the flame-vortex interaction.     

Effect of high silicon-aluminum coal ashes on sintering and fusion characteristics of a potassium-rich biomass ash

The effects of high silicon-aluminum coal ashes (Shajuzi coal ash (SJZA) and Pingshuo coal ash (PSA)) on the sintering and fusion behaviors of a potassium-rich biomass ash (cotton stalk ash (CSA)) were investigated by a horizontal tube furnace and an ash fusion temperature (AFT) analyzer. X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC) techniques were applied to analyze the mineral transformations and thermal behaviors of the ash samples. As the coal ash mass ratio varied from 0 to 50%, the sintering degree of CSA/SJZA and CSA/PSA mixtures gradually mitigated. The AFTs of the two groups of mixtures all presented parabolic with respect to coal ash ratio. The potassium content in CSA was very high (K₂O, 39.55%), and K-containing minerals mainly existed as low melting point (MP) matters, i.e., sylvite (KCl), arcanite (K₂SO₄), potassium carbonate (K₂CO₃), and fairchildite (K₂Ca(CO₃)₂). The mitigation of sintering degree was ascribed to a decrease in KCl content with increasing coal ash ratio. When the coal ash ratio was less than 20%, the decrease in AFT was due to the consumption of alkaline earth metal oxide and the formation of K silicate. The conversions of low MP K salts to high MP K–Al silicates (kalsite (KAlSiO₄) and nepheline (KNa₃Al₄Si₄O₁₆)) and the formations of other high MP minerals increased the AFTs after adding 20% coal ash. The thermogravimetric analysis showed that the endothermic peak of KCl evaporation weakened to disappear and the exothermic peaks of some reactions enhanced with rising coal ash ratio.     

TiO2光催化强化[HO2MMim][HSO4]?H2O2脱除煤中有机硫的研究

燃煤中的硫严重影响了煤炭的高效利用,将光催化氧化引入到萃取脱硫体系,可以显著地提高离子液体萃取脱硫效率。为了进一步研究脱硫机理,采用实验结合计算机仿真模拟对其进行了分析。实验结果表明将光催化反应过程与离子液体萃取过程耦合,可有效脱除煤中的有机硫,[HO₂MMim][HSO₄]?H₂O?H₂O₂?TiO₂（质量比5∶5∶10∶4）光催化处理后的煤的有机硫脱硫率最高可达12.40%。Materials Studio分析得出由光催化产生的羟基自由基(·OH)具有较强的氧化性,·OH的氧原子附近所在区域呈负电性,容易与噻吩中S原子的正电势点产生静电力并形成S=O双键;另外,离子液体的加入使得原本噻吩环上的最低空轨道消失,还降低了最高占据分子轨道（HOMO）和最低未占分子轨道（LUMO）的能级差,使反应更容易进行。使用COSMO软件分析发现离子液萃取作用体现在[HO₂MMim][HSO₄]中咪唑的五元杂环结构通过范德华力与噻吩、砜分子之间成键,使硫化物不断被萃取到离子液体相中;外加氧化剂使反应中化学势较高的砜比噻吩更容易进入到化学势低的离子液[HO₂MMim][HSO₄]中。      

无触点开关在煤矿提升机电控系统改造中的应用

平煤五矿原电控系统采用继电器-接触器切换转子电阻方式调速,控制方式落后.采用无触点开关方式进行改造,重点分析了无触点开关的工作原理,给出了一种新的触发电路.     

串并联型机床运动学参数标定的一种建模方法

基于局部POE(product-of-exponential)公式,建立局部坐标系对3-DOF串并联型机床进行了误差建模,研究了分支末端点距离误差与运动误差间的关系,从而得到线性标定模型。此模型为串并联型机床敏感性分析、误差补偿和几何参数标定等提供了新的方法和手段。