In view of some distinctive characteristics of the early-stage flame image, a corresponding method of characteristic extraction is presented. Also introduced is the application of the improved BP algorithm based on th...In view of some distinctive characteristics of the early-stage flame image, a corresponding method of characteristic extraction is presented. Also introduced is the application of the improved BP algorithm based on the optimization theory to identifying fire image characteristics. First the optimization of BP neural network adopting Levenberg-Marquardt algorithm with the property of quadratic convergence is discussed, and then a new system of fire image identification is devised. Plenty of experiments and field tests have proved that this system can detect the early-stage fire flame quickly and reliably.展开更多
The fire behaviour involving multiple fires in a mine drift with longitudinal ventilation was analysed. The conditions and fire phenomena occurring were described. The analysis was based upon experimental data from mo...The fire behaviour involving multiple fires in a mine drift with longitudinal ventilation was analysed. The conditions and fire phenomena occurring were described. The analysis was based upon experimental data from model-scale fire experiments. A fire involving several fuel items may lead to flames tilted horizontally and filling up the entire cross section, leading to earlier ignition, higher fire growth rates, higher fire spread rate and severe fire behaviour. Longer flame lengths will also result due to decreased air entrainment. A correlation for the continuous flame length was proposed. The results of the analysis will help identifying and preventing potentially dangerous fire situations with several large combustible items distributed along a mine drift.展开更多
文摘In view of some distinctive characteristics of the early-stage flame image, a corresponding method of characteristic extraction is presented. Also introduced is the application of the improved BP algorithm based on the optimization theory to identifying fire image characteristics. First the optimization of BP neural network adopting Levenberg-Marquardt algorithm with the property of quadratic convergence is discussed, and then a new system of fire image identification is devised. Plenty of experiments and field tests have proved that this system can detect the early-stage fire flame quickly and reliably.
文摘氨煤混燃作为新型低碳技术备受关注,其与传统煤燃烧相比可减少碳排放,但目前氨煤混燃中氨与煤粉的交互作用仍不明确,高掺氨燃烧仍存在着火、稳燃和燃烬等问题尚未解决。该文基于平焰燃烧器实验平台,借助扫描电子显微镜-能谱仪(scanning electron microscope-energy dispersive spectrometer,SEM-EDS)及热重分析,系统探讨掺氨比(0~0.6)与氧浓度(0.1、0.15、0.2)对煤粉颗粒燃烧行为的影响。结果表明,随着掺氨比提高,煤焦颗粒粒径减小,最大失重速率对应温度降低,C含量先增加后减少;这是由于火焰温度上升、传热增强与挥发分快速析出使焦炭破碎应力加大,小粒径颗粒反应加快令热重曲线第3阶段由单峰变为双峰、峰值温度偏低。同时,提升氧浓度使颗粒表面孔隙度增大,C含量略升,最大失重速率对应温度提高,热重过程偏向高温区进行。当掺氨比0.4、氧浓度0.2时,颗粒反应温度最低,表明该条件下氨煤混燃活性与燃烧速率均更优。该研究可为深入理解氨煤协同燃烧机制及优化实际锅炉运行参数提供一定依据,助力低碳燃烧技术的推广与应用。
文摘The fire behaviour involving multiple fires in a mine drift with longitudinal ventilation was analysed. The conditions and fire phenomena occurring were described. The analysis was based upon experimental data from model-scale fire experiments. A fire involving several fuel items may lead to flames tilted horizontally and filling up the entire cross section, leading to earlier ignition, higher fire growth rates, higher fire spread rate and severe fire behaviour. Longer flame lengths will also result due to decreased air entrainment. A correlation for the continuous flame length was proposed. The results of the analysis will help identifying and preventing potentially dangerous fire situations with several large combustible items distributed along a mine drift.
