Experimental research on combined effect of obstacle and local spraying water fog on hydrogen/air premixed explosion

In order to reveal the mechanism of water fog explosion suppression and research the combined effect of water fog and obstacle on hydrogen/air deflagration, multiple sets of experiments were set up. The results show that the instability of thermal diffusion under lean combustion conditions is the main influencing factor of hydrogen/air flame surface instability, and the existence of water fog will aggravate the hydrogen/air flame surface instability. When obstacle is not considered, 8 μm, 15 μm, 30 μm water fog can significantly reduce the flame velocity and explosion overpressure of hydrogen/air, 45 μm fine water fog plays the opposite role. When considering the relative position of the water fog release position and the obstacle, the 8 μm, 15 μm, 30 μm water fog has almost no suppression effect when released near the obstacle, but a significant suppression effect occur, when using the 45 μm water fog. In the field of theoretical research, the research results not only provide an experimental basis for the fine water fog to reduce the consequences of hydrogen explosion accidents, and the optimal diameter range used by the water fog, but also provide experimental reference for the numerical simulation of hydrogen/air explosion suppression in semi-open space, and promote the development of hydrogen explosion suppression theory. In terms of engineering applications, this study can provide a theoretical basis for the layout of fire fighting equipment in the engine room of nuclear power plants or hydrogen-powered ships.     

煤尘爆炸固态产物的矿物质特性研究

利用20 L球形爆炸装置对来自老虎台和新密矿区的2种煤尘进行爆炸实验，并对其爆炸固态产物进行收集分析。采用X射线衍射技术对2个矿区的煤尘原样和爆炸固态产物的矿物质特性进行分析研究。研究发现，煤尘爆炸后，爆炸固态产物中挥发分和固定碳等有机组分较煤尘原样均明显减少，而主要由矿物质组成的灰分却明显增加;矿物质物相定性和定量分析结果表明，煤尘原样主要由高岭石、石英等常见矿物质组成;爆炸固态产物中的矿物质组成和含量均发生了明显变化，主要由稳定、耐高温的硅酸盐矿物和氧化物矿物组成;且通过对矿物质演化行为的分析认为煤尘爆炸固态产物应该是一种掺杂有部分煤尘原样颗粒的混合物,且与煤尘原样中的矿物质存在一定的转化关系。     

蒸汽爆破技术对苹果果胶乳化特性的影响

明确蒸汽爆破处理对苹果果胶乳化性的影响。对苹果果胶进行蒸汽爆破处理,研究汽爆压力和汽爆时间对果胶乳化活性和乳化稳定性的影响,并比较汽爆前后果胶粒径和果胶表观黏度,通过显微镜观察乳化液的微观结构。结果表明,果胶乳化活性和乳化稳定性随着爆破压力和爆破时间的增加而增加,与未汽爆处理的果胶相比,在0.6 MPa/120 s处理条件下,果胶乳化活性由21.05 m2/g增加至43.61 m2/g;乳化稳定性由89.60 min增加到125.92 min;乳化液平均粒径由143.1 μm减少为100 μm;乳化液表观黏度显著上升,显微观察显示汽爆后的苹果果胶乳化液滴更加均匀细密。蒸汽爆破处理苹果果胶提高了乳化性,使果胶乳化性整体改善。     

蒸汽爆破处理对香菇成分及香菇蛋糕品质的影响

目的研究蒸汽爆破处理对香菇成分及香菇蛋糕品质的影响。方法采用酸水解法、苯酚硫酸法和凯氏定氮法及索氏提取法测定香菇中总糖、多糖和蛋白质、脂肪含量,并采用感官评定法对蛋糕品质进行评定。结果蒸汽爆破处理后香菇营养成分发生变化,其中香菇多糖、总糖、蛋白质均有所增加,脂肪含量和纤维素含量变化不大。汽爆处理后香菇蛋糕中香菇粉添加量略有下降,在汽爆香菇粉与低筋粉比例为6:94(m:m)时,蛋糕感官评分最高。结论蒸汽爆破处理对香菇成分释放及香菇蛋糕品质均产生有利影响。     

爆炸防控技术在爆破工程警务规划和技术评估中应用

通过介绍爆炸防控技术概念的内涵和外延,说明了爆破工程警务规划设计和技术评估的目的,就是有效防止或遏制涉爆事故,维护社会公共安全。在对一项复杂环境下的基础开挖爆破工程实施警务规划设计和技术评估时,警务技术民警对照爆破作业设计施工单位技术方案中的参数,现场核实需要保护的建筑和重要设施,准确测量保护目标与爆区的实际距离,分析是否存在影响爆破工程实施的不稳定因素,确认上述参数符合安全要求后做出准予爆破许可的建议。爆破工程警务规划设计和技术评估的要点就是要通过现场核查,核实爆破有害效应是否可控,能否确保爆破施工时周边保护目标的安全。     

C2H6/C3H8影响CH4爆炸极限参数及动力学特性研究

为研究C₂H₆/C₃H₈对甲烷爆炸极限参数及动力学特性的影响，采用标准的可燃气体爆炸极限测定装置测定了不同配比的C₂H₆/C₃H₈混合气体对甲烷爆炸极限的影响规律，同时得出了氮气惰化条件下甲烷爆炸临界参数的变化规律。此外，利用Chemkin软件模拟了C₂H₆/C₃H₈混合气体对甲烷爆炸过程中中间产物浓度的影响情况，并进行了敏感性分析。结果表明，C₂H₆/C₃H₈的存在降低了甲烷的爆炸上下限，增大了甲烷的爆炸危险度；在氮气惰化过程中甲烷的爆炸上限下降，爆炸下限上升，最终爆炸上下限重合，重合点处甲烷浓度和氮气临界浓度均随C₂H₆/C₃H₈的添加而逐渐减小；此外，C₂H₆/C₃H₈混合气体使甲烷爆炸过程中CO和·H的生成量逐渐增大，而CO₂、·O和·OH的生成量则有下降趋势，通过对爆炸过程中甲烷体积的敏感性分析，发现C₂H₆/C₃H₈的存在在某种程度上促进了甲烷爆炸。对比不同配比的C₂H₆/C₃H₈混合气体，发现C₃H₈含量越高，其对甲烷爆炸过程中相关参数的影响越大，这可为工矿企业的安全生产提供一定的理论依据。     

Experimental investigation on the dynamic responses of vented hydrogen explosion in a 40-foot container

To investigate the structural dynamics of a container subjected to a vented hydrogen explosion, 48 field tests were conducted in a 40-foot container with roof vents and an end vent. The effects of the hydrogen concentration, ignition position, and obstacles on the evolution of the dynamic responses were investigated. Three stages were generally observed for displacements: (1) At the stage of the vent rupture, the displacement could be approximated as a quasi-static response, and there was a linear relationship between the peaks of positive overpressure and displacement. (2) Structural deformation appeared as reciprocating vibration at the stage of Helmholtz oscillation. (3) The structure exhibited relatively weak irregular fluctuation when high-frequency acoustic oscillation occurred. Two types of the structural acceleration with low and high amplitudes resulting from Helmholtz oscillation and acoustic oscillation, respectively, were clearly observed. For the end-vented explosion, multiple peaks were observed for the displacement at the quasi-static stage due to the rupture, discharge, and external explosion. Moreover, the displacement was sensitive to hydrogen concentration, whereas the number of obstacles and the ignition position had significant influences on the peak acceleration for roof venting. This work conducted the fundamental explanation for the evolution law of structural responses induced by vented hydrogen explosions from the perspective of structural dynamics and enriched the experimental accumulation in a large-scale container with congestion in this field.     

Qualitative analysis of thermal explosion of sodium droplet with variable thermophysical properties and thermal radiations

There are many coolants frequently used in the industry for controlling not only heat transfer, but also temperature distribution in a confined domain. However, little is known on the thermal properties of sodium droplets. The qualitative analysis of differential equations that model the thermal explosion, nonlinear dynamic of sodium droplet with variable thermophysical properties when thermal radiations are considered as suggested by Cogley et al, Sohrab et al, and P‐1 approximation Sazhin et al is deliberated upon in this study. The governing equations, first‐order nonlinear ordinary differential equations, are nondimensionalized using the appropriate similarity variables. The existence and uniqueness of the solutions, concavity, and convexity of the temperature distribution, and positivity nature of the solutions of the dimensionless governing equations are established. It is concluded that there exists a solution for a certain range of the admissible parameters and when the reduced activation energy is negative and temperature distribution fits concavity. More so, the major criteria to obtain a positive solution are outlined in this study.     

A simple and effective approach for evaluating unconfined hydrogen/air cloud explosions

The topic of hydrogen safety assessment has been focused by many researchers. The overpressure evaluation of vapor cloud explosion (VCE), is an important issue for both designing and evaluating on chemical plants, as well as buildings. Unknown flame radius history limits the original acoustic approximation model's application. The objective of this work is to develop an achievable model for hydrogen/air deflagration assessment in engineering applications, and the model should have high computational efficiency. A tentative scheme that starts from flame/piston speed history solving was adopted, and the flame/piston radius and acceleration history will be obtained subsequently. Thus, the overpressure history for far field could be gotten based on the acoustic approximation model. A simplified scheme was employed for the region inside the flame cloud. The model proposed in this paper could be solved in several seconds, because there are no differential equations but only algebraic equations. The model was verified by hydrogen/air deflagration tests from small scale to large scale. Compared with the experimental data, the model appeared well agreements in the medium and large scale cases. In the small scale cases, the model obtained acceptable solutions.