Numerical and experimental study on flame spread over conveyor belts in a large-scale tunnel

Conveyor belt fires in an underground mine pose a serious life threat to the miners. This paper presents numerical and experimental results characterizing a conveyor belt fire in a large-scale tunnel. A computational fluid dynamics (CFD) model was developed to simulate the flame spread over the conveyor belt in a mine entry. Thermogravimetric analysis (TGA) tests were conducted for the conveyor belt and results were used to estimate the kinetic properties for modeling the pyrolysis process of the conveyor belt burning. The CFD model was calibrated using results from the large-scale conveyor belt fire experiments. The comparison between simulation and test results shows that the CFD model is able to capture the major features of the flame spread over the conveyor belt. The predicted maximum heat release rate, and maximum smoke temperature are in good agreement with the large-scale tunnel fire test results. The calibrated CFD model can be used to predict the flame spread over a conveyor belt in a mine entry under different physical conditions and ventilation parameters to aid in the design of improved fire detection and suppression systems, mine rescue, and mine emergency planning.     

Control of exhaled SARS-CoV-2-laden aerosols in the interpersonal breathing microenvironment in a ventilated room with limited space air stability

The Coronavirus Disease 2019 (COVID-19) highlights the importance of understanding and controlling the spread of the coronavirus between persons. We experimentally and numerically investigated an advanced engineering and environmental method on controlling the transmission of airborne SARS-CoV-2-laden aerosols in the breathing microenvironment between two persons during interactive breathing process by combining the limited space air stability and a ventilation method. Experiments were carried out in a full-scale ventilated room with different limited space air stability conditions, i.e., stable condition, neutral condition and unstable condition. Two real humans were involved to conducted normal breathing process in the room and the exhaled carbon dioxide was used as the surrogate of infectious airborne SARS-CoV-2-laden aerosols from respiratory activities. A correspondent numerical model was established to visualize the temperature field and contaminated field in the test room. Results show that the performance of a ventilation system on removing infectious airborne SARS-CoV-2-laden aerosols from the interpersonal breathing microenvironment is dependent on the limited space air stability conditions. Appropriate ventilation method should be implemented based on an evaluation of the air condition. It is recommended that total volume ventilation methods are suitable for unstable and neutral conditions and local ventilation methods are preferable for stable conditions. This study provides an insight into the transmission of airborne SARS-CoV-2-laden aerosols between persons in ventilated rooms with different limited space air stability conditions. Useful guidance has been provided to cope with COVID-19 in limited spaces.     

突然进风对室内火灾影响的实验研究

以工业酒精为燃料，在一房间与走廊相联的模型中，研究了封闭燃烧一定时间后，突然进风对室内火灾的影响。分别在走廊进风。起火室进风等情况下，观察了燃烧状况的变化，测量了典型截面的温度分布，并对一些现象出现的原因作了分析。指出这种突然进风，可在短时间、一定范围内降低温度，但主要效果是促进燃烧。当室内有明火源时还会引发烟气回燃，致使其中的温度急剧升高。     

基于RS-ANN的通风系统可靠性预警系统

系统可靠性预警是度量系统运行状态偏离可靠性指标界线的强弱程度,确定预警等级和做出决策警示的过程。笔者在对目前国内外有关系统预警方法的分析比较基础上,针对矿井通风系统可靠性运行的实际状况,应用了粗糙集(RS)理论和神经网络(ANN)技术,提出了一种基于粗糙集神经网络(RSANN)的矿井通风系统可靠性预警方法:首先,建立了一套适合于矿井通风系统可靠性的预警指标体系;然后,利用人工神经网络与粗糙集理论的优势互补,以粗糙集作为前置处理系统优化指标结构,构建了基于RSANN的通风系统可靠性预警仿真模型,并应用该模型进行了实例验证。其结果表明,该模型的仿真结论与基于ANN的结论十分吻合,训练效率提高了667倍。     

矿井通风系统与耗散结构理论

把通风系统看成一个开放系统 ,利用耗散结构理论 ,对通风系统的耗散条件和耗散行为进行研究 ,得到了通风系统稳定工作的条件以及通风参量与非平衡相变的关系 ,为矿井通风系统优化和日常通风管理工作提供指导 ,同时为通风系统数值模拟的参数选定提供理论依据。通过对耗散参量的研究 ,认识通风系统中参数作用方式 ,了解系统有序相变临界耗散趋势 ,理解整个通风系统的演化规律。     

层次性通风网络平衡图的自动生成

风网平衡图是矿井通风管理的一种重要手段。笔者首次创造性的提出层次性的风网平衡图 ,把风网平衡图做成一个具有层次图形显示、连续双向查询、自动优化网络、数据管理的图形数据库。利用VLISP语言在AutoCAD平台上开发一套矿井通风平衡图的层次性生成及优化软件 ,可以扩展AutoCAD的数据接口、充分发挥它的图形功能、数据管理功能 ,使通风网络平衡图成为一个具有自动优化功能的数据库系统。软件具有可视化、自动风网优化、数据管理、效率高的特点     

国内现有露天矿大气污染源防治技术的调查与分析

在现场调查和函凋及查阅大量的文献资料的基础上,较全面地掌握了国内露天矿通风防尘实用技术措施的实施状况,分析了国内露天矿通风防尘实用技术措施的特点及其适用性。     

隧道电除尘器的应用及其安装计算

介绍了电除尘器在公路长隧道中的应用，对隧道电除尘器在隧道中的安装位置和台数进行了公式推导，并给出了应用实例。     

基于通路法的通风网络最大流求解方法

最大流问题属于网络优化的范畴 ,在通风系统改造等方面具有重要作用 ,为此 ,笔者对网络最大流的算法进行了研究和探讨。利用图论和集合论的知识 ,结合通风网络特点 ,对通风网络最大流问题进行了深入研究 ,提出适合求解通风网络最大流问题的通路法。用通路法求解通风网络最大流时 ,用节点邻接矩阵 ,通过矩阵运算确定通路 ;通过对最小可增广通路 ,依次进行增广求得最大流 ,该方法简便快捷 ,易于程序实现。与Edmonds Karp修正算法相比 ,通路法具有运算量小的优点 ;与Dinic算法相比 ,通路法具有无需分层和无需确定向前边、后退边的优点。通路法对教学和科研具有重要意义和实用价值     

新类型混流风机除尘器的研制与应用

摒弃国内外惯用除尘器加风机的技术路线,研制具有除尘通风双重功能的混流风机除尘器,它可干湿两用除尘,除尘效率达98％以上。整机结构简单,体积小,易于维护,能耗低,造价低,是工矿企业一种新型的除尘器。