闭环回旋控尘技术的三维数值模拟研究

针对输煤皮带转载点粉尘污染大的问题,提出一种新型粉尘控制技术。以霍州煤电集团木瓜煤矿为例,以气固两相流理论的颗粒轨道模型为基础,结合现场实际粉尘扩散规律,三维数值模拟皮带转载点的粉尘逸散规律。根据粉尘颗粒在皮带转载点的运移规律,提出了闭环回旋控尘技术,通过气固两相流和颗粒碰撞理论的三维数值模拟对该技术的控尘机理进行研究,并在木瓜煤矿进行试验应用。结果表明:闭环回旋控尘技术能有效控制粉尘扩散和降低粉尘颗粒动能,其降尘效率达到88%以上,同时,该技术无需任何动力,是未来节能型除尘产品的发展方向。     

转载点粉尘颗粒扩散运动规律的数值模拟

为解决车间转载点粉尘污染问题,利用数值模拟方法计算小空间粉尘颗粒的扩散规律和颗粒运动轨迹,同时借助虚拟现实和现代计算机技术进行颗粒运动轨迹的再现.转载点气流一般处于湍流状态,很难掌握全部粉尘颗粒的扩散规律,只能进行单个粉尘颗粒的受力分析,建立颗粒的一般性运动方程,再利用Lagrange法研究颗粒的运动轨迹方程,然后通过编程语言和虚拟现实技术反映到计算机上,把粉尘扩散轨迹呈现出来.研究成果对转载点粉尘的处理具有一定的实用价值.     

爆破掘进空间内粉尘非稳态运移规律研究

为促进井下粉尘防治工作,对爆破掘进面粉尘非稳态运移规律进行研究。基于控制方程与RNG k-ε湍流模型,选择欧拉-拉格朗日法进行模拟。构建1100工作面三维几何模型并划分网格,确定气相流场边界条件。引入粉尘运动模型进行非稳态计算,利用CFD软件得到气相流场风速分布规律,得出掘进面60m范围内粉尘沿巷道纵向、垂向扩散规律及巷道沿程粉尘粒径分布规律与空间分布规律。此外,还得到爆破后50min内巷道沿程粉尘浓度随时间变化规律。     

基于真三维GIS的危险化学气体泄漏扩散动态模拟仿真系统

针对传统危险化学气体泄漏扩散软件在模拟表现力方面的不足,提出将改进的随机游走大气泄漏扩散模型集成到真三维地理环境信息系统中,完成了基于真三维GIS环境下的危险化学品泄漏扩散模拟仿真系统的设计与开发.该系统能够在真三维场景中直观地展示危险化学气体的三维扩散过程,实时显示危险化学品泄漏扩散浓度分布图及事故不同程度的危害范围.同时通过与PHAST软件模拟结果对比,验证了该系统的可靠性.系统可以直观地、有效地帮助应急指挥人员组织应急救援和疏散,为企业、政府在危险化学品泄漏事故预防、预测和评估以及应急预案的制定提供参考.     

小粒径粉尘粒子扩散沉降量的计算

本文将空气动力学边界层理论，浓度边界层理论和小粉尘粒子扩散理论相结合，详细研究了微小粉尘在平板边界层内的运动规律，推导出微小粉尘在平板上扩散沉降量的计算公式。该空气动力流型可以模拟粉尘在肺叶中的扩散沉降机理以及大气中粉尘向平板上的沉降。其思路，方法和公式也可用于计算管道内的粉尘沉降问题。希望该文对于从事劳动保护的科研人员和工作人员以及通风除尘人员有所帮助。     

高含硫天然气站场泄漏扩散数值模拟分析

为研究不同泄漏场景下的硫化氢泄漏扩散特性,采用计算流体力学软件FLACS对站内设备进行了三维建模,并对站内分离器及管道开展了泄漏扩散模拟,通过分析模拟结果得到了不同泄漏速率及时间下硫化氢扩散规律。研究结果对于预测高含硫天然气站场泄漏事故影响范围及开展后续应急工作具有一定的实际意义。     

热喷涂粉尘质量浓度分布规律数值模拟及实验研究

基于气固两相流理论,采用仿真软件Fluent对热喷涂粉尘的扩散过程进行了数值模拟,分析了热喷涂车间气流速度对粉尘质量浓度分布的影响规律,并通过实验测定了车间呼吸层风速与粉尘质量浓度沿程分布,通过与模拟结果作对比分析,验证了数值模型的可行性。结果表明:粉尘颗粒自尘源处沿径向周围扩散,高质量浓度区域集中在尘源附近;车间气流速度越大,高质量浓度粉尘区域越小,车间粉尘质量浓度越低;当车间出风口风速为12 m/s时,除尘源区域外,呼吸层粉尘质量浓度已明显低于标准限值;通过对比分析,实测数据与数值模拟结果基本吻合,表明采用数值模拟方法研究热喷涂粉尘扩散规律是一种行之有效的方法。     

通风除尘中气体的力学性质和运动特性

通风除尘中气体的力学性质和运动特性首都经济贸易大学安全工程系王希鼎除尘技术的研究对象为含尘气体（主要是空气）的运动和粉尘的运动、沉降、扩散和凝并的规律。作为运载粉尘的气体在通风除尘中占有极为重要的地位。本文对于通常状态下气体的物理性质和基本运动方程不...     

基于FLUENT的炼钢电炉车间粉尘控制措施优化*

为降低炼钢电炉车间粉尘对作业人员的危害,通过对某钢铁厂电炉车间实际情况为研究背景,利用现场调研与数值模拟对炼钢电炉车间的粉尘空间分布以及粒子运动规律进行分析。在采用FLUENT粒子流场综合计算的理论基础上,利用DPM颗粒运动轨道中的离散运动模型,加载粒子相,并综合计算两相流,最终得到粒子的运动规律。通过分析逃逸扩散粉尘在不同空间分布中的情况以及扩散粉尘颗粒物逃逸率的情况,综合分析对车间环境造成的影响。结果表明:粉尘粒径越小,对气流的跟随性越好,排风口对粉尘的捕集效果越差;集气罩的安装位置距离污染源越近捕集效果越好;集气罩的尺寸越大对粉尘的捕集效果越好。     

一种新型的工业粉尘控制装置

本文论述了由LSR技术公司的S.RonaldWysk,Leo A.Smolensky和Bradford金属公司的Andrew Murison研制的芯形分离器在控制粉尘方面的应用。 鉴于对人类生命健康的空气质量要求,因而控制粉尘的扩散,已成为重大社会需要。近年来粉尘控制设备费用约占空气污染控制市场总费用的60％,实际上在整个工业中控制粉尘排放的费用高于控制所有气体扩散费用的总和。这也许反映了使用低成本的气固分离技术的相对困难性。     

Numerical study on dust movement and dust distribution for hybrid ventilation system in a laneway of coal mine

Coal dust disaster is the most serious problem in a laneway of coal mine. Dust movement regularity for comprehensive mechanized heading face is the key scientific issues for the principle and technology of dust prevention. The special topic on systematic study of the variation regularity of dust movement and dust distribution is presented with hybrid ventilation for the comprehensive mechanized heading face: Euler–Euler method was firstly established on the numerical platform for gas–solid two phase flow in a laneway. And the forces and the dynamic model of dust particles were performed in three-dimensional flow field. Then based on the visible simulations, the movement characteristics of diffusion, sedimentation and accumulation of dust particles were investigated under the action of the complex air flow, and the spatiotemporal variation of dust distribution was studied with hybrid ventilation system. Meanwhile, the obtained dust distribution regularities were compared with the obtainable experimental results. Finally, selected method on different ventilation patterns for dust control was brought out for the heading face according to the gained regularity. The research results is helpful for further understanding of the essence of dust movement with air flow, which could provide more suitable guidance for the principle of dust control and technology of ventilation.     

灵泉煤矿粉尘浓度分布规律的实测研究

为解决大流量工序定点短时测尘结果与工人实际接尘情况存在差距的问题,本文对综放工作面粉尘浓度现场测量,应用全工班呼吸性粉尘监测方法进行测尘。在实测和分析的基础上,采用平均数、标准差、累计百分比等统计学方法对监测结果进行了深入的分析,得出了综放工作面粉尘浓度的分布规律。以一定初速度从滚筒割煤处抛出的粉尘,在风流作用力、重力、底板和煤壁的吸附以及对落尘的反弹作用下沿程扩散。靠近底板和煤壁处的总粉尘浓度沿程分布曲线是双峰型曲线,距底板和煤壁较远处的总粉尘浓度沿程分布曲线是单峰型曲线。按粉尘粒径大小,双峰型总粉尘浓度沿程分布曲线可以分为两个区域,一个是可沉降的大颗粒粉尘为主的区域,另一个是难以沉降的微细颗粒粉尘为主的区域。从而有利于矿山管理者有的放矢地采取防尘措施,减少投资,提高效率,确保劳动者健康。     

Effect of pressure for dust dispersion on minimum ignition temperature

The existing technical standards for determining the minimum ignition temperature (MIT) of dust clouds are inadequate. According to existing technical standards, this study expands the test pressure conditions. The MIT of dust clouds can be determined by a variety of different dispersion pressures, that is, 0.02, 0.04, 0.06, 0.08 and 0.1 MPa. But, whether the MIT of dust clouds tested under different dispersion pressures is consistent is lacking in the corresponding exploration. In this study, a set of measurement system of instantaneous concentration and particle size was established, which can observe the flow of dust clouds and the distribution of the instantaneous particle size and concentration of dust clouds in the heating furnace tube. On this basis, the MIT of dust clouds is determined, and the physical mechanism of dispersion pressure affecting the MIT of dust clouds is revealed. The results show that the MIT of dust clouds is consistent when the dispersion pressure in the range of 0.02–0.06 MPa. When the dispersion pressure is not in this range, the MIT of the dust clouds is very different due to the obvious increase of the instantaneous particle size of the dust clouds.     

Effects of ignitors and turbulence on dust explosions

The aim of this work is in an attempt to increase the understanding of the acting behaviour of pyrotechnic ignitors and their effects on confined dust explosions. Flame visualization has shown that pyrotechnic ignitors can initiate an explosion by instantaneous jet-like volumetric and/or multipoint ignition. Hence, the rate of pressure rise and also the apparent burning velocity will be increased to some extent, depending on the ignitor energy and the reactivity of the mixtures. The ignitor effect is more important for the early stages of flame propagation and would be more significant in small explosion chambers. Thus, for dust explosion tests with various purposes, use of pyrotechnic ignitors should be made carefully, and the ignitor effect must be accounted for in the data interpretation. Turbulence induced by dust dispersion is a dominant factor in affecting dust explosions. At different ignition delays, however, the turbulence influence will be coupled with that of ignitors. This complicates further the interpretation of explosion data measured under turbulent conditions.     

Classification of dispersibility for combustible dust based on Hausner ratio

Mixing of combustible dust and oxidant is one of five essential prerequisites in the dust explosion pentagon, requiring that particles originally in mutual contact within the deposits be separated and suspended in the air. However, dust dispersion never proceeds with 100% efficiency, with inevitable particle agglomeration, and an inherent trend toward settling out of suspension. Dispersibility is defined to describe the ease of dispersion of a dust and the tendency of the particulate matter to remain airborne once a dust cloud has been formed. Pioneers made contributions to classify dust dispersibility by introducing dustiness group (DG), dustability index (DI), NIOSH dispersion chamber and in-situ particle size analysis. Issues remained including the difficulty in comparing results from different methods, as well as the availability of some high-tech testing apparatus.This study aims to provide a quick and universal testing method to estimate the dispersion property of combustible dust. A new dispersibility classification was developed based on dimensionless numbers Hausner ratio and Archimedes number. Four dispersibility classes (DCs) were proposed from one to four, with a larger number meaning better dispersibility. Results for more than a dozen dust samples and mixtures thereof showed the new method is useful in dust explosion research. The consistency in classifying dust dispersion properties between the DC method and previous methods was good. Changes in DC well explained our earlier findings on suppressant enhanced explosion parameter (SEEP) phenomenon attributed to the improvement in dust dispersibility. Hausner ratio and Archimedes number, as easily measured parameters, can be quite advantageous to assess dust dispersibility, permitting a proper risk assessment for the formation of explosible dust clouds.     

CFD Simulation of the Dispersion of Binary Dust Mixtures in the 20 L Vessel

There are at least two main requirements for repeatable and reliable measurements of flammability and explosibility parameters of dusts: a uniform dispersion of solid particles inside the test vessel, and a homogeneous degree of turbulence. In several literature works, it has been shown that, in the standard 20 L sphere, the dust injection system generates a non-uniform dust cloud, while high gradients characterize the turbulent flow field. In this work, the dust dispersion inside the 20 L sphere was simulated for nicotinic acid/anthraquinone mixtures (with different pure dust ratios, while keeping the total dust concentration constant) with a validated three-dimensional CFD model. Numerical results show that the fields of dust concentration, flow velocity and turbulence are strongly affected by both diameter and density of the pure dusts. These different dust properties lead to segregation phenomena with the formation of zones richer in one component and leaner in the other one and vice versa, and also result in preferential paths for the solid particles inside the sphere. Overall, the obtained results highlight the need for developing a dust injection system able to overcome the shortcomings of the actual one even when testing dust mixtures.     

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。     

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.     

Numerical simulation study of dust concentration distribution regularity in cavern stope

Based on the theory of gas-solid two-phase flow and the characteristics of cavern stope a model of dust migration was established. The dust concentration changing of cavern stope by ventilation in 20 min after blasting and the dust trajectory in different wind speed were simulated by Fluent Software. The results show that distribution of dust concentration is significantly affected by flow field of airway in cavern, and the dust concentration of inlet is higher than that of outlet and the highest one on the corner of inlet’s side. In the stope, the smaller the wind speed of inlet is, the shorter of dust can be captured, settled and discharged, the more obviously affected by the trajectory of gas flow field. It goes into the stage of clean cycle emissions after 60 s, the speed of dust concentration dropped is the biggest between 0 s and 70 s, the main dust in stope is respirable dust after 70 s, it needs much time to settlement.According to the measured data of metal mining, approximately 87% of dust was generated during the drilling and blasting in the mine (Wang, 1979). A lot of dust with high concentrations was produced during the cavern stope blasting and it was difficult to be discharged. It can help choose the right speed to rule out the dust quickly which produced during cavern blasting, if the dust concentration distribution and the dust migration law of different inlet velocity in the cavern can be verified, what’s more, the labor productivity can be increased. It has great significance for choosing reasonable ventilation parameters, reducing dust hazards of stope to researching the dust concentration distribution regularity in the stope.     

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.