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.     

Flame propagation enhancement by plasma excitation of oxygen. Part I: Effects of O3

The thermal and kinetic effects of O₃ on flame propagation were investigated experimentally and numerically by using C₃H₈/O₂/N₂ laminar lifted flames. Ozone produced by a dielectric barrier plasma discharge was isolated and measured quantitatively by using absorption spectroscopy. Significant kinetic enhancement by O₃ was observed by comparing flame stabilization locations with and without O₃ production. Experiments at atmospheric pressures showed an 8% enhancement in the flame propagation speed for 1260 ppm of O₃ addition to the O₂/N₂ oxidizer. Numerical simulations showed that the O₃ decomposition and reaction with H early in the pre-heat zone of the flame produced O and OH, respectively, from which the O reacted rapidly with C₃H₈ and produced additional OH. The subsequent reaction of OH with the fuel and fuel fragments, such as CH₂O, provided chemical heat release at lower temperatures to enhance the flame propagation speed. It was shown that the kinetic effect on flame propagation enhancement by O₃ reaching the pre-heat zone of the flame for early oxidation of fuel was much greater than that by the thermal effect from the energy contained within O₃. For non-premixed laminar lifted flames, the kinetic enhancement by O₃ also induced changes to the hydrodynamics at the flame front which provided additional enhancement of the flame propagation speed. The present results will have a direct impact on the development of detailed plasma-flame kinetic mechanisms and provided a foundation for the study of combustion enhancement by O₂(a¹Δ_g) in part II of this investigation.     

煤粉复合旋流火焰燃烧特性研究（1）：实验研究

本文实验研究了煤粉复合旋流火焰燃烧特性，进行了包括３个典型煤种：褐煤、烟煤和无烟煤，在不同煤粉浓度下的燃烧试验，测量了火焰场的温度分布、气体组份分布、火焰周界辐射和煤颗粒燃烧参数，对火焰场特性、不同煤种影响和煤粉浓度作用做了较系统的试验研究，揭示了该燃烧方式的稳定着火、强化燃烧机理，获得了这种煤粉火焰的燃烧特性。     

环保型阻燃聚丙烯的研制

应对欧盟RoHS环保要求,对环保型阻燃聚丙烯的研制进行了研究;并探讨了六溴环十二烷和三氧化二锑对PP材料阻燃性及物理性能的影响,得到了一种性能优良的环保型阻燃PP。     

钛酸酯偶联剂在膨胀型阻燃聚丙烯中的偶联作用

研究了钛酸酯偶联剂（TTOPP）对聚丙烯/膨胀型阻燃剂（PP/IFR）复合材料阻燃性能和力学性能的影响,并采用扫描电子显微镜、偏光显微镜和X射线衍射研究了复合材料的微观形态和结晶行为。结果表明,加入TTOPP后,IFR在PP中的分散更加均匀,PP球晶的大小趋于一致,适量的TTOPP改善了IFR与PP间的相容性,促进了IFR对PP形成β晶的诱导作用。当PP/IFR/TTOPP为75/25/0.375时,复合材料的综合性能最佳,自熄时间降到24 s,拉伸强度和冲击强度比PP/IFR分别提高了14.0 %和12.0 %。     

无卤膨胀阻燃剂在低密度聚乙烯中的应用研究

以干法合成的P-N无卤膨胀阻燃剂(IFR)为基础,配合聚磷酸胺(APP)并且将金属氧化物(ZnO)作为协效剂阻燃改性低密度聚乙烯(PE-LD)。采用扫描电子显微镜对该体系燃烧后的炭层结构进行了分析。通过红外光谱和X射线光电子能谱研究了该体系在不同温度热处理后的残炭组成,并分析了该膨胀型阻燃体系对PE-LD的阻燃机理。结果表明,PE-LD/IFR/APP/ZnO体系的极限氧指数可以达到27.9%,垂直燃烧性能达到UL 94V-0级。     

溴/氮本质阻燃环氧树脂的热性能和阻燃性能研究

采用热分析仪、傅里叶变换红外光谱仪(FTIR)、极限氧指数仪和综合垂直燃烧测定仪研究了反应型磷/氮阻燃剂聚N-(2,3,5,6-四溴对二亚甲基苯基)-N-乙基胺(BNFR)阻燃环氧树脂的热性能、阻燃性能、成烟性能等。结果表明,BNFR分子通过参与固化反应而以化学键键合于固化树脂的立体网络结构之中,无迁移,通过改变固化树脂的热降解过程提高树脂的热稳定性能以及阻燃性能;BNFR分子结构中含有Br和N两种阻燃元素,气相和固相阻燃机理同时起作用,因此阻燃效率较高,环氧树脂中添加12%的BNFR可以使极限氧指数达到30%,600℃成炭量高于10%。     

电缆用高阻燃耐热软质PVC的制备及性能研究

以软质PVC为基体,选用氢氧化铝-氢氧化镁(ATH/MDH)为复配阻燃剂、硼酸锌(ZB)为阻燃协效剂及钙锌材料为复合热稳定剂(Ca-Zn),通过共混法对PVC进行改性,制备PVC/ATH/MDH、PVC/ATH/MDH/ZB及PVC/ATH/MDH/ZB/Ca-Zn等软质PVC复合电缆料。分析3种电缆料的阻燃性能、拉伸性能及热稳定性。结果表明:相较纯软质PVC,PVC/ATH/MDH与PVC/ATH/MDH/ZB的阻燃性能提高,拉伸性能显著下降,且热稳定性改善不明显。而PVC/ATH/MDH/ZB/Ca-Zn的阻燃性能显著提升,与纯软质PVC相比,其极限氧指数(LOI)增加34.90%,烟密度等级下降29.50%,复合材料的炭层更连续且致密;PVC/ATH/MDH/ZB/Ca-Zn的拉伸强度和断裂伸长率分别提高1.78%和2.48%。Ca-Zn的添加提高软质PVC的残炭率,热稳定性增强。PVC/ATH/MDH/ZB/Ca-Zn的综合性能最佳。     

纳米材料复合改性阻燃聚丙烯的研究进展

综述了近年来纳米无机阻燃剂及其复合阻燃体系对聚丙烯的阻燃性能研究进展。重点介绍了氢氧化铝、氢氧化镁和蒙脱土及其复合卤系、磷系、膨胀型阻燃剂对阻燃聚丙烯材料的阻燃性能及力学性能的影响。并指出纳米复合改性阻燃聚丙烯不仅能提高阻燃性能，还具有增强、增韧作用，是实现阻燃聚丙烯高性能化及低成本的一个重要方向。     

环保膨胀型阻燃PP母料的研制

以三聚氰胺聚磷酸(MPP)/季戊四醇(PT)为复配阻燃剂,氧化锌为催化协效剂,聚乙烯蜡为分散剂,并添加一定量载体树脂,制备了环保膨胀型阻燃聚丙烯(PP)母料,运用氧指数法、UL94垂直燃烧法、热失重分析法和扫描电子显微镜研究了阻燃PP母料的阻燃性能。结果表明:当MPP∶PT=2∶1且MPP与PT占母料总量的72%时,将该类母料添加到PP中制得的复合材料的综合性能最好;阻燃PP母料的最佳载体树脂为PP/PP-g-MAH(1/1),将25%PP/PP-g-MAH基阻燃PP母料添加到PP中,复合材料的阻燃等级可达到UL94V—0级。