Experimental determination of laminar burning velocities and Markstein lengths for 75% hydrous-ethanol, hydrogen and air gaseous mixtures

Hydrogen-rich mixtures generated by the on-board reforming of biomass-derived hydrous-ethanol can be used as a potential alternative fuel (i.e., reformed ethanol fuel, RE fuel). In this paper, outwardly propagating spherical flames were employed to observe the laminar flame characteristics of the gaseous mixtures composed of simulated RE fuel (mixture of 75% hydrous-ethanol and hydrogen) and air in a constant-volume combustion vessel at an initial temperature of 383 K, a pressure of 0.1 MPa, a hydrogen fraction from 0% to 80%, and an equivalence ratio from 0.6 to 1.6. The results show that the unstretched flame propagation speeds and burning velocities increase with increasing hydrogen fraction, especially when the fraction is above 40%. When the hydrogen fraction is less than 40%, the Markstein length and flame instability decrease and increase with the equivalence ratio, respectively, while the reverse holds when the hydrogen fraction is greater than 40%. At an equivalence ratio below 1.4, the Markstein length decreases with increasing hydrogen fraction, indicating a positive correlation between the flame instability and hydrogen fraction. At an equivalence ratio above 1.4, a negative relationship is observed. Finally, it is concluded that a hydrogen fraction of approximately 40% in simulated RE fuel is feasible for spark ignition engines by comparing the laminar burning characteristics of ethanol-air mixtures.     

甲烷火焰中氢气对着火与燃尽的影响

利用化学反应动力学机理研究了甲烷－空气预混火焰添加H2的着火和燃尽特性。通过分析计算,讨论了氢气对甲烷燃烧过程及着火温度、燃烧速率、燃尽时间的影响。结果表明,甲烷火焰中少量氢气的存在不仅可以降低甲烷的着火温度,而且可以显著增大燃烧速率,缩短燃尽时间,这些结果与已有的实验结果吻合。     

柴油油池火功率特性

在一些柴油油池火实验数据基础上,分析了油池火的初期增长过程以及影响油池火燃烧的因素．油池火由引燃至开始稳定燃烧的增长过程分为两个阶段:第一阶段约占增长过程的1／3,可通过时间平方增长来近似,其增长系数介于0．12-0．28之间;第二阶段约占增长过程的2／3,也可用时间的二次曲线来模拟其增长过程．油池火的稳定燃烧速率和热释放速率随着油面面积的增大、通风条件的改善而增大,其燃烧效率介于0．68-0．85之间．     

一种新型聚酯钝感剂在发射药中的应用

采用水相钝感法工艺制备了含新型聚酯钝感剂的单基药和高能硝胺发射药,通过常规理化性能测试、密闭爆发器和加速长贮等实验研究了聚酯钝感剂对两种发射药性能的影响。结果表明,聚酯钝感剂与单基药和高能硝胺药相容性良好,具有挥发性小、抗迁移性能强等优点,能够显著提高单基药的燃烧渐增性;含聚酯钝感剂的发射药加速老化长贮实验前后,初速跳差小于10m/s,其内弹道性能几乎无变化。     

改善AP-CMDB高燃速推进剂低温力学性能技术

探讨了溶剂压伸工艺成型压力和加入补强剂等技术对AP-CMDB高燃速推进剂的力学性能影响。研究结果表明,采用加入功能添加剂的方法．有效地提高了该推进剂的力学性能,可将-40℃的抗冲击强度由3．38kJ／m^2提高到6．17kJ／m^2,其它性能与原配方相比基本相当。该技术为解决此类推进剂毛刷式或悬壁梁式发动机装药低温工作易产生碎药问题及拓宽其应用领域奠定了技术基础。     

烧成制度对BaTiO3介电性能的影响

烧成制度对BaTiO3质PTC陶瓷的介电性能有重要影响,详细讨论了烧成温度、保温时间、冷却速度以及烧结气氛等因素对BaTiO3质陶瓷室温电阻和PTC效应的影响,并对其影响机制给出了合理解释。研究结果表明,陶瓷的半导化与烧成温度密切相关,适当保温对传质有很大影响,冷却速度和烧结气氛对室温电阻和PTC效应有一定影响。     

兖矿国泰多喷嘴对置式水煤浆气化装置运行总结

兖矿国泰化工有限公司多喷嘴对置式水煤浆气化装置经历了近5 a的工业生产运行。通过优化与改进,该气化装置已实现良好的稳定运行。     

催化剂对太根发射药燃速的影响

为探讨调节发射药燃气生成规律的途径,采用催化剂调节太根发射药的燃速,通过密闭爆发器实验测试了不同催化剂对太根发射药燃速调节的效果。结果表明,使用催化剂可以有效调节太根发射药的燃速,当测试压力为50~150M Pa时,碳酸镍可使太根发射药的燃速提高8%以上,二茂铁可使太根发射药的燃速降低10%。所研究的6种催化剂对发射药燃速压力指数的影响均小于0.02。     

Nonlinear effects of stretch on the flame front propagation

In all experimental configurations, the flames are affected by stretch (curvature and/or strain rate). To obtain the unstretched flame speed, independent of the experimental configuration, the measured flame speed needs to be corrected. Usually, a linear relationship linking the flame speed to stretch is used. However, this linear relation is the result of several assumptions, which may be incorrected. The present study aims at evaluating the error in the laminar burning speed evaluation induced by using the traditional linear methodology. Experiments were performed in a closed vessel at atmospheric pressure for two different mixtures: methane/air and iso-octane/air. The initial temperatures were respectively 300 K and 400 K for methane and iso-octane. Both methodologies (linear and nonlinear) are applied and results in terms of laminar speed and burned gas Markstein length are compared. Methane and iso-octane were chosen because they present opposite evolutions in their Markstein length when the equivalence ratio is increased.The error induced by the linear methodology is evaluated, taking the nonlinear methodology as the reference. It is observed that the use of the linear methodology starts to induce substantial errors after an equivalence ratio of 1.1 for methane/air mixtures and before an equivalence ratio of 1 for iso-octane/air mixtures. One solution to increase the accuracy of the linear methodology for these critical cases consists in reducing the number of points used in the linear methodology by increasing the initial flame radius used.     

国内外电缆及光缆燃烧性能分级体系探讨

对国际电工委员会(IEC)、美国、欧盟及中国的电缆及光缆燃烧性能分级体系进行分析、比较和综述。通过研究发现:IEC仅发布了考核电缆的火焰蔓延距离、烟密度和无卤特性等单一的试验方法标准;美国主要针对电缆的火焰蔓延、产烟等特性分为4个级别;欧盟于2014年颁布了新的燃烧性分级体系,该分级体系主要从电缆的火焰蔓延和热释放等特性分为7个级别,同时针对不同场所又从电缆的产烟、燃烧滴落物和酸度进行了附加分级;我国新发布的电缆及光缆燃烧性能分级体系与欧盟类似。