共查询到18条相似文献,搜索用时 107 毫秒
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正庚烷燃烧反应中间自由基的光谱测量 总被引:1,自引:0,他引:1
采用ICCD瞬态光谱探测系统和化学激波管,在点火温度1 408K,点火压力2.0atm,燃料摩尔分数1.0%,当量比1.0的条件下,拍摄了正庚烷燃烧过程中不同时刻的瞬态发射光谱,光谱曝光时间6μs,拍谱范围200~850nm。确认了在所拍光谱范围内主要是OH,CH和C2自由基的特征辐射光谱,表明小自由基OH,CH和C2是正庚烷燃烧过程中重要的反应中间产物。所拍时间分辨光谱显示,在正庚烷燃烧反应中,OH,CH和C2自由基一出现很快就达到其浓度峰值,但CH和C2自由基随着反应的进行迅速减少至消失,OH自由基持续的时间却长很多。实验结果为了解正庚烷燃烧反应微观过程和验证其燃烧反应机理提供了实验依据。 相似文献
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利用ReaxFF分子动力学模拟方法对正庚烷在高温条件下的热解行为进行了研究.细致分析了温度对正庚烷高温裂解过程以及产物分布的影响.结果显示温度对正庚烷的热解过程的影响是分阶段的.高温能加速正庚烷的分解,但是当温度达到一定阶段之后这种影响逐渐变小.正庚烷的热解可以分为三个阶段.主要产物C2H4、C3和C4的质量百分数随转化率的变化规律与实验值符合很好.利用一阶动力学模型得到的正庚烷热解的表观活化能和指前因子分别为53.96 kcal/mol和55.34×1013 s-1,与实验值相符. 相似文献
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正癸烷燃烧反应中OH,CH和C2自由基的瞬态发射光谱 总被引:2,自引:0,他引:2
采用ICCD瞬态光谱测量系统和加热激波管,在点火压力2.0atm,点火温度1 100~1 600K,当量比1.0,燃料摩尔分数1.0%条件下,实时测得了正癸烷/氧气/氩气燃烧过程的瞬态发射光谱,光谱范围200~850nm。结果显示燃烧过程中主要发射光谱带归属于小分子中间产物OH,CH和C2自由基,光谱强度的变化反映了燃烧过程中三种自由基浓度的变化历程;正癸烷燃烧过程中光谱强度峰值之比大于同为链烷烃的正庚烷相应OH/CH峰强度之比,揭示出两种链烃燃烧反应机理有较大差异。实验还获得了正癸烷燃烧过程中能显示谱带转动结构的CH和C2高分辨特征发射光谱。实验结果对了解正癸烷燃烧性质和验证正癸烷燃烧反应机理很有意义。 相似文献
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In this work, doped poly(p-phenylene vinylene)/zeolite composites was prepared to detect the three different chemical vapors (acetone, methanol, and n-heptane) and to investigate the effects of zeolite type, chemical vapor type, and vapor concentration based on the electrical conductivity response and selectivity properties of the sensing materials. Before blending with PPV, zeolite Y (Si/Al?=?5.1 and Na+), mordenite (Si/Al?=?18 and Na+), and 5A (LTA) (Si/Al?=?1.0 and Na+) were ion exchanged with Cu2+ at 80 % ion exchanged to prepare 80CuNaY, 80CuNaMOR, and 80CuNa5A. 80CuNaY exhibited the highest electrical conductivity response under acetone and methanol exposures while 80CuNaMOR showed the highest response in n-heptane exposure which depended on the adsorption and solubility properties of each porous material. When adding doped poly(p-phenylene vinylene) (dPPV) into the 80CuNaY matrix, the minimum detection vapor concentration decreased in acetone, methanol, and n-heptane vapors. For the selectivity, the composite between 80CuNaY and dPPV responded only in the polar vapors (acetone, methanol) whereas the composite between dPPV and 80CuNaMOR or dPPV_[90]80CuNaMOR responded only in the nonpolar vapor (n-heptane). The interactions between the sensing materials and the chemical vapors were investigated and identified by FTIR and AFM techniques. 相似文献
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采用分子动力学方法,模拟了CO2膨胀甲醇体系、CO2膨胀乙醇体系的热力学性质和输运性质,以及对氯硝基苯在CO2膨胀甲醇体系、苯甲腈在CO2膨胀乙醇体系中的扩散性质。CO2膨胀甲醇体系的密度模拟值略高于实验值,而CO2膨胀乙醇体系的密度模拟值与实验值非常接近。模拟结果表明:CO2使甲醇和乙醇溶液的膨胀非常明显,当CO2的摩尔分数达到0.5时,溶液膨胀约100%;得到了CO2、甲醇、乙醇、对氯硝基苯以及苯甲腈的扩散系数,其中对氯硝基苯和苯甲腈在两种膨胀液体中的扩散系数与实验结果接近;通过扩散系数关联了两种膨胀液体的粘度,计算结果与修正的Wilke-Chang方程得到的体系粘度规律一致。 相似文献
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Carmelo Corsaro Francesco Mallamace Sow-Hsin Chen H. Eugene Stanley Domenico Mallamace 《Frontiers of Physics》2018,13(1):138201
Herein we study the different microscopic interactions occurring in water/methanol solutions at different methanol molar fractions, using NMR spctroscopy. Temperature was found to determine which interaction dominates. It was found that the mixing between water and methanol is non-ideal because of the presence of interactions like hydrophobicity and hydrophilicity. These results indicate that the competition between hydrophilic and hydrophobic interactions is different in different thermal regions, and that the physical properties of the solution are determined by the character of the solution itself, which in turn depends on the mole fraction of methanol and on the temperature. 相似文献
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Dheeraj K. Singh Shivangi Mishra Animesh K. Ojha Sunil K. Srivastava S. Schlücker B. P. Asthana J. Popp Ranjan K. Singh 《Journal of Raman spectroscopy : JRS》2011,42(4):667-675
We report on the hydrogen bonding between pyrimidine (Pd) and methanol (M) as H‐donor in this study. Hydrogen bonds between pyrimidine and methanol molecules as well as those between different methanol molecules significantly influence the spectral features at high dilution. The ring‐breathing mode ν1 of the reference system Pd was chosen as a marker band to probe the degree of hydrogen bonding. Polarized Raman spectra in the region 970–1020 cm−1 for binary mixtures of (pyrimidine + methanol) at 28 different mole fractions were recorded. A Raman line shape analysis of the isotropic Raman line profiles at all concentrations revealed three distinct spectral components at mole fractions of Pd below 0.75. The three components are attributed to three distinct groups of species: ‘free Pd’ (pd), ‘Pd with low methanol content’ (pd1) and ‘Pd with high‐methanol content’ (pd2). The two latter species differ considerably in the pattern and the strengths of the hydrogen bonds. The results of density functional theory calculations on structures and vibrational spectra of neat Pd and eight Pd/M complexes with varying methanol content support our interpretations of the experimental results. A nice spectra–structure correlation for the different cluster subgroups was obtained, similar to earlier results obtained for Pd and water. Apart from N···H and O···H hydrogen bonds between pyrimidine and methanol, O···H hydrogen bonds formed among the methanol molecules in the cluster at high methanol content also play a crucial role in the interpretation of the experimental results. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Hugo Ajrouche Ob Nilaphai Camille Hespel Fabrice Foucher 《Proceedings of the Combustion Institute》2019,37(3):3319-3326
A New One Shot Engine (NOSE) was designed to simulate the thermodynamic conditions at High Pressure-High Temperature like an actual common-rail diesel engine in order to study the compression ignition of spray. The volume of the combustion chamber provided with large optical windows simplified the implementation of various optical diagnostics. The advantage of this kind of set-up in comparison to pre-burn or flue chambers is that the initial gas mixture can be well controlled in terms of species and mole fraction. The purpose of this work was to investigate the impact of nitric oxide (NO) on ignition delay (ID) for two fuels with different cetane numbers: n-heptane, and n-dodecane. In the thermodynamic conditions chosen (60?bar and over 800–900?K), NO had a strong effect on ID, with increases in NO tending to reduce the ignition delay. Results showed that ID and Lift-Off Length (LOL) presented the same trend as a function of temperature and NO concentration. Experimentally, at 900?K the ignition of n-dodecane was promoted by NO up to 100?ppm, whilst higher NO levels did not further promote ignition and a stabilization of the value has been noticed. For n-heptane, stronger promoting effects were observed in the same temperature conditions: the ignition delays were monotonically reduced with up to 200?ppm NO addition. At a lower temperature (800?K) the inhibiting effect was observed for n-dodecane for [NO] greater than 40?ppm, whereas only a promoting effect was observed for n-heptane. The experimental results of LOL showed that NO shortened LOL in almost all cases, and this varied with both the NO concentration and the mixture temperature. Thus, fuels with shorter ignition delays produce shorter lift-off lengths. 相似文献
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Dongil Kang Doohyun Kim Kwang Hee Yoo Angela Violi André Boehman 《Proceedings of the Combustion Institute》2019,37(4):4681-4689
Alkylbenzenes are major aromatic constituents of real transportation fuels and important surrogate components. In this study, the structural impact of nine alkylbenzenes on their ignition characteristics is experimentally and computationally investigated with particular emphasis on the blending effect with significantly more reactive normal alkanes. Experimental comparisons of mono-alkylbenzenes (toluene, ethylbenzene, n-propylbenzene, iso-propylbenzene) from a modified CFR engine showed that the difference in pure alkylbenzene reactivity significantly diminished when blended with n-heptane, as the strength of the radical scavenging effect of all three alkylbenzenes is similar. Among C8H10 isomers, the reactivity of pure ethylbenzene and o-xylene and their blends with n-heptane showed a complex competing effect between the difference in CH bond energy and the existence of intermediate/low-temperature chemistry caused by adjacent methyl pairs. A similar structural impact was also observed for C9H12 isomers and their blends with n-heptane, while the influence of CH bond energy was more noticeable than C8H10 molecules. Kinetic simulations of the alkylbenzene/n-heptane blends highlighted the effect caused by adjacent methyl pairs that is referred to as the “ortho effect”. Analysis of ethylbenzene and o-xylene showed that o-xylene's intermediate/low-temperature pathways initiated by benzylperoxy radical – benzylhydroperoxide isomerization (RO2 – QOOH) produce additional active radicals such as OH and CH2O, which accelerates the oxidation chemistry of more reactive n-heptane. This study provides knowledge on the blending effect of alkylbenzene compounds with n-heptane on their ignition characteristics that is useful to develop surrogates that can better mimic the reactivity of real fuels. 相似文献
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利用OH自由基特征发射谱测量正庚烷的点火延迟时间 总被引:2,自引:0,他引:2
在化学激波管中利用反射激波进行点火,采用OH自由基在306.4nm处特征发射谱线强度的急剧变化标志燃料的着火,由光谱单色仪、光电倍增管、压力传感器和示波器组成测量系统,测量了正庚烷/氧气的点火延迟时间,点火压力(1.0±0.1)和(0.75±0.05)atm,点火温度1 170~1 730K,当量比1.0,得到了在此实验条件下正庚烷/氧气点火延迟时间随温度变化的关系式。研究结果表明正庚烷/氧气点火延迟时间随温度的增加呈指数减小,点火压力为0.75atm时,随着点火温度的增加,点火延迟时间的变化率要小于1.0atm条件时。实验结果为建立正庚烷燃烧反应动力学模型,验证正庚烷燃烧反应机理提供了实验依据。 相似文献
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M. Gizdavic-Nikolaidis P. A. Kilmartin Z. D. Zujovic J. Travas-Sejdic R. P. Cooney G. A. Bowmaker 《Applied magnetic resonance》2005,29(4):729-739
Aniline oligomers, which are formed in the reaction of aniline with 1,1-diphenyl-2-picrylhydrazyl (DPPH) in methanol and chloroform
as solvents, are investigated by means of magnetic resonance techniques. The electron paramagnetic resonance (EPR) spectrum
of the products of the reaction of aniline with DPPH (mole ratio, 2∶1) in chloroform solution, and of aniline with DPPH (mole
ratio, 1∶2) in methanol solution, were recorded as the reaction progressed, and after the reaction was finished. The spectra
of the products after reaction were resolved into the spectra of two species. For the acidified methanol solution the spectrum
of one of the species shows hyperfine coupling to two nitrogen atoms with a coupling constanta(2·14N)=5.8 G, in good agreement with previously reported observations for the radical cation of model aniline trimers. A species
is observed in the chloroform solution witha(1·14N)=11.4 G, which suggests the presence of aniline dimers. Both solutions also show a second signal which is attributed to
higher oligomer radical cations with unresolved14N hyperfine structure.1H nuclear magnetic resonance (NMR) spectra of aniline and aniline-DPPH solutions in CDCl3 with the peaks due to DPPHH, the product of reduction of DPPH, were observed. The1H NMR experiments show that only 15% of the available aniline was consumed, in agreement with the theoretical calculations
for the formation of polyaniline-emeraldine base salt under these conditions rather than the sole formation of dimers, which
would be expected to consume 33% of the available aniline. This is probably due to formation of partially oxidized long-chain
aniline oligomers as the main reaction product. 相似文献