【作者】 王健；

【导师】 王福利； 李新光；

【作者基本信息】 东北大学 ， 控制理论与控制工程， 2010， 博士

【摘要】 粉尘爆炸危害对众多涉及易燃粉体制备、使用和处理的行业一直构成持续的安全威胁。粮食行业是粉尘爆炸的多发行业,随着新技术的应用和生产规模的扩大,粉尘爆炸事故日益频繁。粉尘爆炸事故通常会造成严重的人员伤亡及财产损失,甚至导致灾难性的后果。因此,深入开展粮食粉尘爆炸的研究对于预防和控制此类工业灾害性事故具有重要的理论意义和工程价值。本文的特色和创新性工作成果如下：开发了一套基于以太网与OPC技术的多功能粉尘爆炸测定系统。采用LabVIEW虚拟仪器软件平台开发的数据采集与控制系统具有人机界面友好、操作方便安全,实验测试效率较高等优点,可实现实验过程控制、自动数据采集、曲线分析、数据库管理等功能；采用OPC接口技术实现测试计算机和控制箱之间的通讯,使测试系统具有良好的一致性、扩展性和可维护性；采用以太网技术将各子测试系统的控制系统连为一个整体,方便了实验数据的综合分析,保证了测试数据的完整性和一致性。开发了具有特色功能的20L球形爆炸测试装置,该装置是目前唯一支持液体分散的爆炸测试系统,可实现粉尘\气体\液体蒸汽的爆炸测试；该装置同时还集成了自主研发的大能量电火花发生系统,是目前唯一支持1OkJ大能量静电点火的粉尘爆炸测试装置。所开发的最小点火能测试装置集成了多种放电触发方式,用户可根据需要选择合适的触发方式。对大型管道相连容器系统中的粮食粉尘爆炸进行了实验分析,研究了复杂结构中粮食粉尘爆炸过程的基本规律和影响因素,所用实验粉尘为玉米淀粉和土豆淀粉。研究表明：粉尘反应性、点火位置、初始湍流和粉尘浓度等因素对爆炸发展过程均有重要影响。粉尘的反应性越强,爆炸的猛烈程度越强,火焰传播速度越快,二次爆炸的猛烈程度也越强；点火位置离泄爆口越远,初级容器中的最大泄爆压力Pred,max越高,爆炸通过管道传播后引发的二次爆炸越猛烈；初始湍流对粉尘的爆炸性参数特别是压力上升速率有重要影响,随着初始湍流度的增大,爆炸的猛烈程度增强,火焰和冲击波的传播速度加快；在合适的粉尘浓度条件下,粉尘爆炸程度较为猛烈,火焰传播导致的最终火焰速度和压力峰值均较大。对于管道互连装置,初始爆炸能够引起压力和火焰在连接管道中传播,火焰在管道中传播时会形成正反馈的加速机制,最终引发二次爆炸。本实验研究增进了对管道互连装置中粮食粉尘爆炸发展过程及其影响因素的理解,为粮食工业中复杂结构系统的粉尘爆炸安全防护和优化设计提供了有价值的信息,并为深入的数值模拟研究提供了宝贵的实验校验数据。建立了一个完备的描述淀粉爆炸过程的数学模型。采用了基于欧拉-拉格朗日方法的气固两相流模型,并采用随机轨道模型来描述粒子相,其主要优点是计算简单,当颗粒有较复杂的变化经历时,能较好的追踪颗粒的运动,数值计算时也不会产生伪扩散,并且考虑了气相湍流脉动对颗粒的影响。淀粉粒子的燃烧模型考虑了水分蒸发、挥发分分解、气相反应和颗粒表面反应。气相燃烧模型采用EBU-Arrhenius模型,解决了以往数值模型中不能合理地计算湍流燃烧反应速率的问题,提高了数值模拟的精度。所建立的数学模型是一种通用的有机粉尘爆炸模型,对粮食粉尘爆炸的研究具有重要的实用意义和理论价值。利用CFD软件FLUENT完成了所开发数学模型的计算机实现,对不同情况下的玉米淀粉粉尘爆炸进行了数值模拟研究,并利用实验数据对数值模型的有效性进行了校验。对1m3密闭容器粉尘爆炸的数值研究表明,数值模拟能够全面反映密闭容器中的粉尘爆炸过程,可对密闭空间粉尘爆炸危险性进行预测。对9.63m3容器泄爆过程的数值研究表明,数值模拟可以较好地反映出泄爆过程的流动和燃烧特性,计算结果模拟出了泄爆时的压力波动状况。研究还表明,点火位置对爆炸发展有明显影响,随着点火位置远离泄爆口,Pred,max逐渐增加。对管道中火焰传播的数值研究表明,数值模拟捕获了火焰在长管中传播的主要特征,在整个爆炸过程中,火焰始终是加速传播的,火焰前方的压力波幅值逐渐增强,且压力上升速率越来越快。模拟结果与实验结果符合得较好,说明了本论文建立的粉尘爆炸数学模型的适用性和准确性,应用该模型可以很好地对粮食粉尘爆炸过程进行模拟计算和数值分析。本论文的研究工作填补了国内粮食粉尘爆炸研究领域的空白。论文研究结果具有重要的实用价值,为粮食工业中粉尘爆炸灾害的研究、预防和控制提供了一定的理论基础和科学依据,并为后续的深入研究奠定了坚实的基础。更多还原

【Abstract】 The dust explosion hazard continues to represent a constant threat to process industries that manufacture, use and/or handle powders and dusts of combustible materials. Grain industry is a high dust explosion probability industry. With the application of new technology and the expansion of production scale, dust explosion accidents occur frequently and would usually cause heavy casualties and loss of property, and even catastrophic effect. Thus, intensive research work on grain dust explosion has important theoretical significance and engineering value for prevent and control of such hazardous industrial disaster. The features and innovative work product of the thesis are as follwos:A multi-function dust explosion test system was developed based on Ethernet and OPC technique. The data acquisition and control system developed in Lab VIEW has advantages as user-friendly GUI, easy to operate, efficient work, and has functions of experimental process control, automatic data acquiring, curve analysis, database management, etc. The communication between test computer and control box was achieved by OPC technique, which gives the test system good consistency, extensibility and maintainability. The control system of sub-system was connected in LAN, which facilitates comprehensive analysis of experimental data and ensure the integrity and consistency of test data. The 20L spherical explosion test apparatus with certain specific functions was developed, which is by far the only apparatus that support liquid dispersing of similar products and can determine explosion characteristics of combustible dust, gas and vapor. It is also by far the only apparatus that support large energy electrostatic ignition in lOkJ with integrated home-grown large energy electrostatic spark generator of similar products. The developed dust cloud minimum ignition energy test apparatus has a spark generator that integrated several triggering modes and users can select suitable one as needed.The experimental analysis about grain dust explosion in large scale interconnected vessels was conducted to study the fundamental law and influencing factors of grain dust explosion in complex configuration. The test dust is maize and potato starch. Study shows that factors as dust reactivity, ignition location, initial turbulence and dust concentration have important influence on development process of dust explosion. The more explosible a dust tends to be, the more violent is the explosion, and the faster is flame propagating velocity, and the more violent is the secondary explosion. The farther the ignition location is away from vent, the higher is the maximum reduced overpressure Pred,max in primary vessel, and the more violent is the secondary explosion. Initial turbulence has an important influence on dust explosion characteristics and especially on pressure rise rate. With increasing initial turbulence level, the explosion become more violent and propagating velocity of flame and shock wave increase. With suitable dust concentration, the final flame velocity and peak pressure caused by flame propagation are both higher. For interconnected equipments, primary explosion can cause pressure and flame to propagate through pipe. A positive feedback acceleration mechanism can be formed during flame propagating along pipe and lead to a secondary explosion finally. The experimental investigation promote greater understanding of grain dust explosion process and its influencing factors, and provide valuable information for safety protection and optimal design of dust explosion in complex configuration in grain industry, and accumulate valuable experimental data which can be used for validation in further numerical simulation investigation.A comprehensive mathematical model that describes explosion process of starch dust is established. Eulerian-Lagrangian two phase flow model is adopted and the particle phase is modeled by discrete random walk (DRW) model. The DRW model has the following advantages:easy to calculate; the motion of particle can be tracked better when particle undergoing complex change; numerical calculation won’t produce false diffusion; the effect of fluid’s turbulent pulsation on particle can be accounted for. Combustion model of starch particle takes account into detail mechanisms of water vaporization, volatile decomposition, gas phase reaction and surface reaction of carbon. EBU- Arrhenius model is used to simulate the reaction of gas phase which can solve the problem of inaccuracy calculation of turbulent combustion rate and thus improving the precision of numerical simulation. The developed model is a general one for organic dust explosion and is of great theoretical value and practical significance for grain dust explosion investigation.Numerical simulation of different dust explosion case has been carried out by using CFD code FLUENT, and the validity of numerical model has been checked by experimental data. Simulation of dust explosion in 1m3 closed vessel showed that numerical simulation can fully reflect deveploment process of explosion and predict the hazards of dust explosion in closed space. Simulation of dust explosion in 9.63m3 vented vessel showed that numerical simulation is well able to reflect flow and combustion features of explosion venting process. The fluctuation of pressure druing venting can be modelled well. It also shows that igniton location has remarkable effect on explosion development process. Th farther the ignition location is away from vent, the higher is Prcd.max value. Simulation of flame propagation in pipe showed that numerical simulation has reflected main feature of flame propagation in long pipe. In the whole explosion process, flame velocity continued to accelarate, the magnitude of pressure wave ahead flame front increased gradually and pressure rise rate become steeper and steeper. It also indicated that dust concentration has important influence on development of flame propagation. The simulated results have relative good agreement with experimental results and that turns out the applicability and accuracy of the developed model and shows that it can be good in use of numerical simulation and analysis of dust explosion.The study of this thesis fills the gap of domestic investigation on grain dust explosion. The research results have important practical value, and provide certain theoretical foundation and scientific evidence for study, prevent and control of dust explosion hazard in grain industry, and lay a foundation for the further research更多还原