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1.
Modeling of nitromethane flame structure and burning behavior   总被引:1,自引:0,他引:1  
Nitromethane was investigated in this study due to the push for higher performance and reduced toxicity monopropellant. A comprehensive detailed model for its flame structure and linear regression rate was developed and validated with experimental data. The model considered one-dimensional behavior with surface vaporization and detailed gas-phase kinetics based on the RDX mechanism of Yetter et al. combined with the nitromethane decomposition mechanism of Glarborg, Bendtsen, and Miller, resulting in a mechanism consisting of 47 species and 250 elementary reactions. The predictive model was implemented using a custom FORTRAN code wrapping the CHEMKIN 4 PREMIX gas-phase solver coupled with the condensed-phase solution. Predicted burning rates using the model showed good agreement with measured rates up to 15 MPa. Calculated species and temperature profiles showed three distinct regions based upon the appearance and consumption of certain species. The first region was marked by decomposition of nitromethane, the second region by consumption of all intermediate species except CH4 and NO, and the third region by the rise to final temperature and species concentrations near the equilibrium values. Among the intermediate species, CH4 and NO had higher concentrations than those of CH2O, N2O, HNO, and HONO. CH4 served as fuel species and NO provided a portion of the oxidizer for the third-region reactions to reach equilibrium composition. Sensitivity analysis identified the importance of two elementary reactions involving HNO to the temperature profile, and therefore the burning rate. Although the absolute level of NH and HCO were low, they served as an important intermediate species transporting nitrogen and carbon, respectively, between other higher-concentration species. The calculated flame zone thickness is consistent with that measured by microthermocouples.  相似文献
2.
固相硝基甲烷相变的第一性原理计算   总被引:1,自引:0,他引:1       下载免费PDF全文
张力  陈朗 《物理学报》2014,63(9):98105-098105
研究极端条件下固相分子晶体含能材料的相变机理,对于人们认识固相含能材料的爆轰反应有着重要的意义. 采用基于校正密度泛函理论的第一性原理方法研究固相硝基甲烷在静水压下的行为. 分析晶格参数a,bc 轴随压强的变化,发现在1 GPa到12 GPa时晶格参数出现不连续的变化,表明体系发生相变. 在相变时最大的二面角从155.3°增加到177.5°,二面角的增加限制CH3官能团自由旋转,使得C–N和C–H键的键长发生变化. 在相变之前,体系主要存在由C–H…O组成的分子间的氢键,而在相变之后存在分子内的H…O和分子间C–H…O组成的氢键. 此外通过对硝基甲烷体系的电子结构进行计算,发现相变会影响带隙随压强的变化,而且还会影响费米能级附近的态密度结构. 关键词: 相变 硝基甲烷 校正密度泛函理论  相似文献
3.
The adsorption and reaction of the isomers nitromethane (CH3NO2) and methyl nitrite (CH3ONO) on two ordered Sn/Pt(111) surface alloys were studied using TPD, AES, and LEED. Even though the Sn–O bond is stronger than the Pt–O bond and Sn is more easily oxidized than Pt, alloying with Sn reduces the reactivity of the Pt(111) surface for both of these oxygen-containing molecules. This is because of kinetic limitations due to a weaker chemisorption bond and an increased activation energy for dissociation for these molecules on the alloys compared to Pt(111). Nitromethane only weakly adsorbs on the Sn/Pt(111) surface alloys, shows no thermal reaction during TPD, and undergoes completely reversible adsorption under UHV conditions. Methyl nitrite is a much more reactive molecule due to the weak CH3O–NO bond, and most of the chemisorbed methyl nitrite decomposes below 240 K on the alloy surfaces to produce NO and a methoxy species. Surface methoxy is a stable intermediate until 300 K on the alloys, and then it dehydrogenates to evolve gas phase formaldehyde with high selectivity against complete dehydrogenation to form CO on both alloy surfaces.  相似文献
4.
建立了一套高分辨的离子速度影像装置。在这套装置中,离了透镜的设计是利用Simion7.0应用程序对电场中离子的空间分布进行模拟“聚焦”得到的,达到了将离了源空间分布中速度相同而位置不同的离子聚焦在同一点上的效果。利用这套装置研究了CCl3Br在267nm附近的光解反应产物Br(^2P3.2)和Br^*(^2P1.2)的速度和角度的分布,得到了β(Br)=-0.48,β(Br^*)=1.44。  相似文献
5.
Using a specific numerical example, we consider and discuss a problem of correction of quantum–chemical force fields because of the ambiguous selection of the systems of scaling factors. Additional conditions are suggested that make it possible to narrow noticeably the regions of solutions of the inverse vibrational problem.  相似文献
6.
 对高压下液态硝基甲烷的性质进行经典和基于第一性原理计算的Car-Parrinello分子动力学(CPMD)模拟。利用经典势的分子动力学(MD)模拟研究了高压压缩状态下液态硝基甲烷的结构和热力学性质,得到了高达14.2 GPa压力下的理论Hugoniot数据。对于一些热力学函数,如总能和粒子速度,经典势模拟给出了很好的总趋势,基本特征和实验观测一致。但是在给定的密度下,经典模拟预言的Hugoniot压力偏高。在几个选定的密度下,进行了CPMD模拟,得到了二体相关函数、速度自相关函数、振动光谱和其它的热力学性质,并与经典模拟结果进行了比较。对二体相关函数的分析表明经典势的短程部分的刚性可能太强,从而导致了比实验值高的理论压力值。对于某些二体相关函数,CPMD模拟和经典模拟结果差别很大,可以归结为量子效应。当压力增高时,量子模拟得到的振动光谱向高频部分移动的现象与实验观测相符合。  相似文献
7.
实验研究射流冷却CH3S自由基eA2A1态在352 nm的光解动力学. 应用氢原子产额谱和光碎片平动能谱方法第一次直接观察到氢原子产物解离通道.CH3S自由基eA2A1态2132振动能级解离为H和H2CS产物.H+H2CS产物平动能释放较小,平动能峰值接近33.4 kJ/mol.氢原子产物角分布是各向同性.H+H2CS产物是经eA2A1激发态向X2E基态内转变,紧接着在基态势能面上解离产生.  相似文献
8.
利用氢原子里德堡态飞行时间谱技术研究HN3分子在紫外光(190?248 nm)光照射下的H+N3通道的光解动力学结果.通过测量H+N3通道的产物平动能分布以及产物的角分布,得到了在不同波长光解下N3产物分子的振动态分布. 实验结果表明, 在大于225 nm时,HN3分子主要是通过一个排斥态解离的.而在低于225 nm时,有一个慢的通道从220 nm 开始出现.这一新的解离通道是一个闭环产生环状N3产物的通道.当光解能量增加时,这一新通道相对的变得越来越重要.  相似文献
9.
利用高里德堡态氢原子飞行时间 (HRTOF)探测技术 ,研究了正丙醇和异丙醇的紫外光解动力学过程 .在 193.3nm光辐射下 ,O -H键快速断裂过程构成主要的氢原子生成通道 .伴随O -H键的碎裂 ,相当大的一部分能量转换成氢原子及其相应碎片的平动能 (正丙醇〈fv〉 =0 .76 ;异丙醇〈fv〉 =0 .78) .氢原子碎片具有各向异性的角度分布 ;其角分布异向因子 β分别为 - 0 .79(正丙醇 )和 - 0 .77(异丙醇 ) .研究结果表明 ,吸收 1个 193.3nm光子后 ,丙醇分子跃迁到一个寿命很短的电子激发态 ;沿着O -H反应坐标 ,该激发态势能面是排斥的 ,因而O -H键快速断裂 .此外 ,还得到了丙醇的O -H键离解能 :(432± 2 )kJ/mol(正丙醇 )和 (433± 2 )kJ/mol(异丙醇 ) .  相似文献
10.
cndo/Force method is used to evaluate the redundancy free internal valence force fields for two conformers of nitromethane. The initial force field is set up by taking the interaction and bending force constants from this method and transferring the stretching force constants from the force fields of chemically related molecules. The final force field is obtained by refining the initial force field using vibrational frequencies of isotopic speciesviz CH3NO2, CD3NO2, CH3 15NO2 and CH3N18O2. The final force field thus obtained is reasonable on the basis of frequency fit and potential energy distribution. The barrier to internal rotation is found to be 0.048 kcal mol−1.  相似文献
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