多点法测定可燃物质自燃特性的可靠性研究

多点法是一种新提出的自热反应动力学分析方法。采用实验研究和理论分析相结合的方式对多点法的操作过程以及实验结果的可靠性展开研究。通过构建一维导热系统、采用不同形式的热电偶布设方式,对烟叶粉末的自燃临界环境温度、活化能以及反应热与指前因子的乘积等参数进行了测定。研究表明:所构建的一维系统能较好地模拟一维导热;热电偶的分布方式对测量结果有较大影响,对称分布状况下,温度结果与经典的F-K对称模型一致;多点法相比于传统方法省时省力,测定结果有较好的线性拟合相关度,求解的动力学参数较为可靠。     

不同环境激素吸附行为及机理的对比研究

文章研究了环境激素类污染物在土壤中吸附的动力学、热力学过程,并进行相关参数分析和模型构建。结果显示,5种环境激素的吸附过程分为快速吸附、慢速吸附、平衡3个阶段,动力学过程均符合二级动力学方程;Freundlich等温模型的拟合度最高,吸附过程均为物理过程,并且放出热量。     

甲烷水合物恒压分解动力学研究进展

相比气体水合物生成过程的研究,对分解过程的研究起步较晚且不深入,而研究水合物分解特征有助于水合物的开发、利用。为此,对甲烷水合物恒压分解动力学研究现状进行了分析和评价,主要评述了甲烷水合物恒压分解实验方法、恒压分解动力学参数的测定、恒压分解动力学模型构建等方面的内容,以期能够加深对甲烷水合物恒压分解动力学的理解及引起科研工作者的重视。最后,展望了未来气体水合物分解动力学的研究方向。     

桥式起重机吊物摆动影响因素的动力学研究

以桥式起重机为例,对吊物摆动的影响进行了动力学研究。基于Matlab/Simulink模块搭建了仿真模型,针对影响吊物摆动的关键参数进行了仿真分析及对比。本研究对于各类起重机械作业中吊物摆动控制、动态优化以及系统参数的选择具有借鉴意义。     

基于子集模拟的埋地管道失效概率评估

对失效概率的评估是管道系统风险评价的核心内容,针对目前对埋地管道失效概率问题研究的不足,采用子集模拟方法（SS）建立埋地管道失效概率的定量评估模型以及参数敏感度模型,并对随机变量进行敏感分析。研究结果表明:子集模拟能利用少量样本定量计算出管道失效概率,有效弥补了管道结构可靠性模型中的不足;在管道运行中期,工作压力、腐蚀速率、管道壁厚和屈服强度是对管道失效概率影响较大的4个因素,而腐蚀因素在管道运行后期成为对系统失效概率影响最大的因素。     

汽车制动系统缺陷风险传递动力学分析

为有效预防汽车产品缺陷的产生,分析缺陷风险的变化过程,首先采用风险传递理论和系统动力学方法,利用汽车制动系统工作原理,分析缺陷风险的变化特征;其次综合考虑缺陷因素和人、机、环、管等影响因素与激发因素对风险的作用,分析从出现风险到导致事故和伤害过程的风险传递和演变机制,建立制动系统缺陷的风险传递动力学模型;最后利用仿真软件验证该模型。仿真结果表明:零部件缺陷风险在制动系统中按一定方向传递和演变;在影响因素和激发因素的催化作用下,风险按能量逐渐增大的方向传递;应根据风险传递特点,在传递过程中采取措施,阻断风险的正常传递。     

砂石过滤河水中COD的动力学与热力学研究

为研究砂石过滤吸附水中有机物的规律和性能,以西宁市湟水河水为研究对象,研究其对水溶液中COD的等温吸附特性,利用一级动力学模型、二级动力学模型对慢砂吸附COD动力学过程进行分析。结果表明:砂石对水溶液中COD的等温吸附特征符合非线性的Langmuir方程,通过Langmuir方程相关参数和试验校对得出二级动力学模型能更好地反映砂石对水溶液中COD的吸附动力学过程,并得出该条件下最大COD吸附量为36.36 mg/kg,而一级动力学模型的误差较大。在热力学分析过程中ΔH为负值说明净砂对水中COD的吸附为放热过程,ΔG也为负值说明吸附可自发进行,ΔS为正值说明吸附过程增加了固液界面的混乱度。     

高危岗位矿工个体风险感知影响因素仿真研究

为探索高危岗位矿工风险感知的影响因素,在文献研究和复杂适应系统理论分析基础上,从个体角度构建矿工风险感知影响因素的系统动力学模型。运用Vensim 软件模拟仿真各工作时间段中,矿工风险感知水平及各因素对其影响的动态演化过程。研究表明:工作初期,情绪稳定性水平对风险感知水平促进效果显著,工作倦怠的抑制作用较突出;在工作后期,自我效能感对风险感知水平的削弱影响显著,风险规避态度则发挥较大的促进作用;风险知识经验超出一定范围会对风险感知水平起到反作用;安全教育培训与安全监管对风险感知水平的促进作用相对稳定持久。因此,煤矿企业应根据各因素在工作时间段的不同作用,采取相应措施以提高矿工风险感知水平。     

相对两面受火的方钢管钢筋混凝土柱耐火极限

目前有关方钢管钢筋混凝土柱抗火性能的研究主要是针对四面均匀受火的情况,而在实际中,会出现相对两面受火这一情况。为此,利用ABAQUS分析软件建立了方钢管钢筋混凝土柱在相对两面受火作用下高温反应有限元模型,在验证模型正确性的基础上,对其耐火极限进行参数分析,包括荷载比、截面边长、长细比、荷载偏心率、钢材和混凝土强度及配筋率等,得到了相对两面火灾作用下方钢管钢筋混凝土柱耐火极限的主要影响参数和影响规律,并给出了该受火条件下方钢管钢筋混凝土柱耐火极限的简化计算方法。研究结果表明:荷载比、截面边长、长细比是相对两面火灾作用下方钢管钢筋混凝土柱耐火极限的主要影响参数,表现为截面边长越大,荷载比和长细比越小,构件的耐火极限越大。     

碱性水对煤自燃特性影响实验研究

为了研究碱性水对煤自燃特性的影响,选取葫芦素煤矿102工作面煤样作为实验煤样,利用STA-449C型同步热分析仪进行热重实验,研究加入PH=8 NaOH的煤样与原煤以及加入蒸馏水煤样在空气氛围中燃烧失重、放热量、特征温度点等变化规律,并根据Coats-Redfern积分模型计算了3种煤样燃烧反应动力学参数（活化能、指前因子）。研究结果表明:加入碱性水的2号煤样失重量较1,3号少,燃烧失重速率更低;2号煤氧化燃烧温度区间缩短,着火温度点升高,放热量少,比1,3号煤分别少485.0,480.4 J/g;3种煤样反应机理基本遵循一级化学反应函数,2号煤各段活化能高于1,3号煤,但2号煤失水活化能小于3号,表明碱性水具有抑制煤自燃效应。     

Modeling the initial flame acceleration in an obstructed channel using large eddy simulation

The propagation and acceleration of a flame surface past obstructions in a closed square channel was investigated using large eddy simulation. The dynamic Smagorinsky–Lilly subgrid model and the Boger flame surface density combustion model were used. The geometry is essentially two-dimensional with fence-type obstacles distributed on the top and bottom surfaces, equally spaced along the channel length at the channel height. Flame propagation, however, is three dimensional as ignition occurs at a point at the center of the channel cross-section. The effect of obstacle blockage ratio on the development of the flame structure was investigated by varying the obstacle height. Three-dimensional cases were simulated from the initiation of a combustion kernel through spark ignition to the acceleration of the flame front at speeds up to 80 m/s. The transition from laminar flame propagation to turbulent flame propagation within the “thin reaction zone” regime was observed in the simulations. By analyzing the development of the three dimensional flame surface and unburned gas flow field, the formation of several flame structures observed experimentally are explained. Global quantities such as the total flame area and centerline flame velocity were ascertained and compared to the experimental data. High amplitude oscillations in the centerline flame velocity were found to occur from a combination of the unburned gas flow field and fluctuations in the volumetric burning rate.     

Large eddy simulation of methane–air deflagration in an obstructed chamber using different combustion models

In this paper, simulations of methane–air deflagration inside a semi-confined chamber with three solid obstacles have been carried out with large eddy simulation (LES) technique. Three sub-grid scale (SGS) combustion models, including power-law flame wrinkling model by Charlette et al., turbulent flame speed closure (TFC) model, and eddy dissipation model (EDM), are applied. All numerical results have been compared to literature experimental data. It is found that the power-law flame wrinkling model by Charlette et al. is able to better predict the generated pressure and other flame features, such as flame structure, position, speed and acceleration against measured data. Based on the power-law flame wrinkling model, the flame–vortex interaction during the deflagration progress is also investigated. The results obtained have demonstrated that higher turbulence levels, induced by obstacles, wrinkle the flame and then increase its surface area, the burning rates and the flame speed.     

基于神经网络的煤与瓦斯突出预测模型

在全面分析了煤与瓦斯突出影响因素的基础上 ,提出了煤与瓦斯突出预测的人工神经网络模型。介绍了突出特征指标的选取及表示方法与推理过程。实例分析表明 ,模型精度很高 ,可用于工作面煤与瓦斯突出预测 ,并分别给出图 2 ,表 3,文献 5     

高层建筑管道井内烟气运动大涡模拟

采用火灾过程的场模拟理论,以大涡模拟为基础,分析了火灾烟气流动过程的动力学特征;为了验证大涡模拟数值方法的准确性,针对Mercier和Jaluria竖井内的实验工况进行了模拟研究,其模拟结果与试验结果吻合较好,表明大涡模拟可以较好地预测竖井内烟气流动情况;通过设定不同的火灾场景,对不同火源功率和不同几何尺寸条件下管道井内烟气的流动过程进行了数值模拟,其结果给出了不同的几何尺寸和火源功率对管道井内所形成“烟囱效应”的影响情况。笔者的模拟和研究表明:大涡模拟可较准确地预测高层建筑管道井内烟气的流动状态,对高层建筑的防火设计具有指导性作用。     

Quantification of turbulence in cryogenic liquid using high speed flow visualization

A high speed flow visualization experiment was conducted to characterize the boiling induced turbulence when a cryogenic liquid is released on water. The advective transport of turbulent structures traversing through the liquid was captured and reconstructed using image processing software to obtain information on velocity components. The numerical results obtained from image processing were used to determine turbulence parameters like turbulent intensity, turbulent kinetic energy and eddy dissipation rate. An interesting aspect of the study was the formation of wavy structures called ‘thermals’ which were characteristic of turbulent convection. The thermals were found to act as a catalyst in increasing heat transfer and turbulence between water and cryogenic pool. The turbulent intensity was influenced by the turbulent velocity and had direct effects on the vaporization flux. Among the turbulence parameters, increase in turbulent kinetic energy resulted in faster vaporization of cryogenic liquid through enhanced mixing, whereas variations in the eddy dissipation rate had weak dependence on vaporization. Additionally, the initial height of cryogenic liquid was also found to strongly affect the vaporization mass flux.     

涡流热成像动态检测模式的缺陷信号重构方法研究

在涡流热成像检测中,缺陷信号重构可以有效评定结构的安全性和可靠性,及时预防生产中安全事故的发生,目前大多数信号重构方法都不适用于动态模式的涡流热成像检测。为了对动态模式涡流热成像检测的信号进行重构,提出了1种基于区域扫描的方法,选定区域大小及划分准则,在每帧图像相同位置划分区域,对各个区域内的温度数据进行相应的运算处理并提取结果,以此作为每个区域的重构温度,进而重构出包含所有缺陷温度信息的热像图。结果表明:该方法可以对动态模式下的涡流热成像温度信号进行重构,并能在一定程度上消除噪声,有利于后续的图像处理。     

Experimental and LES investigation of premixed methane/air flame propagating in a chamber for three obstacle BR configurations

The paper aims at revealing the effect of blockage ratio (BR) on the flame acceleration process and the flame-vortex mechanism in an obstructed chamber based essentially on the experimental and numerical methods. In the experiments, high-speed video photography and pressure transducer are used to study the flame shape changes and pressure dynamics. In the numerical simulations, large eddy simulation (LES) with the flame surface density (FSD) model is applied to investigate the interaction between the moving flame and vortices induced by obstacle. The results demonstrate that the flame propagation process can be divided into four stages, namely spherical flame, finger-shaped flame, jet flame and volute flame for three obstacle BR configurations, and a small recirculation zone is observed above the obstacle only for BR = 0.5. The peak of flame tip speed and pressure growth rate increases with the blockage ratio. The generation and evolution of the vortex behind the obstacle can be attributed to the initial flame acceleration, while the subsequent flame deceleration is due to the flame-vortex interaction. In addition, the transition from a “thin reaction zones” to a “broken reaction zones” is also observed in the simulation.     

Prediction of the relief of gas explosion in a tubular vessel by venting using a mathematical model

The relief of a gas explosion in a tubular vessel by venting can be predicted by using a mathematical model. In this model, the flame acceleration is represented by an increase in the burning velocity. The movement of a vent cover can be included. The model assumes that the vent is blocked by the vent cover prior to the explosion. the venting ratio was the most influential parameter in terms of relieving the pressure. In the case of a large venting ratio, the flame acceleration made a highly significant contribution, whereas for small venting ratios, the weight of the vent cover contributed to the relief more than the flame acceleration. When the pressure is required to be reduced significantly, the venting ratio, the vent open pressure and the weight of the vent cover must all be reduced.     

人工神经网络对矿山安全状态的评判能力分析

通过改变神经网络训练样本等方法,对比分析了神经网络对不同训练样本的反映能力,讨论了人工神经网络对矿山安全程度进行评价的适应性.为了研究人工神经网络用于矿山安全评价时的优化设计,通过改变神经网络的神经元数目及初值赋值方式等方法,测试了不同结构、不同参数的神经网络对相同训练样本的评价结论.本文的研究为人工神经网络用于矿山安全评价时的进一步改进及其优化设计提出了合理的建议.     

The acceleration of flames in tube explosions with two obstacles as a function of the obstacle separation distance

The separation distance (or pitch) between two successive obstacles or rows of obstacles is an important parameter in the acceleration of flame propagation and increase in explosion severity. Whilst this is generally recognised, it has received little specific attention by investigators. In this work a vented cylindrical vessel 162 mm in diameter 4.5 m long was used to study the effect of separation distance of two low blockage (30%) obstacles. The set up was demonstrated to produce overpressure through the fast flame speeds generated (i.e. in a similar mechanism to vapour cloud explosions). A worst case separation distance was found to be 1.75 m which produced close to 3 bar overpressure and a flame speed of about 500 m/s. These values were of the order of twice the overpressure and flame speed with a double obstacle separated 2.75 m (83 characteristic obstacle length scales) apart. The profile of effects with separation distance was shown to agree with the cold flow turbulence profile determined in cold flows by other researchers. However, the present results showed that the maximum effect in explosions is experienced further downstream than the position of maximum turbulence determined in the cold flow studies. It is suggested that this may be due to the convection of the turbulence profile by the propagating flame. The present results would suggest that in many previous studies of repeated obstacles the separation distance investigated might not have included the worst case set up, and therefore existing explosion protection guidelines may not be derived from worst case scenarios.