共查询到17条相似文献,搜索用时 171 毫秒
1.
在微尺度催化燃烧中,由于燃料和氧气对于催化剂表面活性位的竞争,导致了可燃下限为富燃的情况。为了提高燃料利用率,拓宽可燃范围,本文在正丁烷/空气的混合气中加入一定量的氢气,在Swiss-roll燃烧器内研究了氢气/正丁烷/空气预混气的燃烧特性。结果表明,氢气能够有效拓宽正丁烷的可燃范围,可燃下限能够低于1,以贫燃的条件实现高燃料利用率。对于稳定燃烧温度的实验结果表明,燃烧器最高温度出现在富燃料一侧。 相似文献
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Total cross sections for scattering of electrons from O2, H2O, H2, O3, CO and CO2 at 100-2000eV 下载免费PDF全文
A complex optical model potential rewritten by the concept of bonded atom, which considers the overlap of electron clouds, is employed to calculate the total cross sections for electron scattering from several simple molecules (O_2, H_2O, H_2, O_3, CO and CO_2) consisting of C, H and O atoms in an incident energy range of 100-2000eV by the use of the additivity rule at Hartree-Fock level. In the study, the complex optical potential composed of static, exchange, correlation polarization plus absorption contributions firstly uses the bonded-atom concept. The quantitative molecular total cross section results are compared with experimental data and with the other calculations wherever available and good agreement is obtained. It is shown that the additivity rule along with the complex optical model potential rewritten by the concept of bonded atom can be used successfully to calculate the total cross section of electron-molecule scattering above 100eV, whereas the rule together with the complex optical model potential not rewritten by the concept of bonded atom is only successfully used above 300-500eV. So, the introduction of the bonded-atom concept in the complex optical potential can improve the accuracy of the total cross section calculations. 相似文献
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掺氢天然气在稀释气体作用下的熄灭特性研究对实际燃烧设备的设计和优化具有重要的指导意义。本文利用对冲火焰法测量了掺氢天然气层流火焰在N2和CO2作用下的熄灭拉伸率,并采用数值模拟耦合详细化学反应机理对N2,CO2和He的稀释剂效应展开研究。结果表明,Li、GRI Mech 3.0和FFCM-1机理均能定性反映燃料熄灭拉伸率随当量比的变化规律,且FFCM-1机理综合预测精度最高。实验和模拟发现,不同稀释剂气体对掺氢天然气熄灭拉伸率降低幅度满足:He22。进一步研究发现,CO2由于热容大,在反应体系中会降低火焰温度,同时增强了链终止反应强度,通过热效应和化学效应两方面对火焰熄灭特性起作用。He则能显著改变燃料混合物的平均摩尔质量,从而改变体系中重要反应物和自由基的扩散特性,从扩散效应方面影响火焰的熄灭特性。 相似文献
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光谱技术的发展使得连续测量环境大气中的稳定同位素成为可能。描述了应用傅里叶变换红外(FTIR)光谱技术测量环境大气中稳定同位素的方法。为了验证该方法对环境大气中的稳定同位素进行连续测量的可行性,在七天的外场实验中,应用开放光程FTIR系统直接测量环境大气中CO2的稳定同位素12 CO2,13 CO2和H2O的稳定同位素H216 O和HD16 O,并得到大气中碳同位素比值δ13 C和氘同位素比值δD。对同位素比值δ13 C和δD,系统的测量精度分别约为1.08‰和1.32‰。采用Keeling图方法,在不同的时间尺度上对CO2和H2O的同位素数据进行分析,得到了水汽地表蒸散的氘同位素特征δET。外场实验的结果证明了开放光程FTIR系统长期测量环境大气中稳定同位素的潜力。 相似文献
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本文分别采用考虑辐射重吸收的谱带辐射(SNBCK)模型及未考虑辐射重吸收的光学薄辐射(OPT)模型,对0.1~4 MPa,CO2稀释比为0%和20%的一维预混层流合成气/空气火焰进行数值分析,研究辐射重吸收效应对可燃极限及极限处的火焰传播速度和温度的影响。结果表明,辐射重吸收效应能有效拓宽贫可燃极限,提高燃料中CO2比例或提高CO/H2比例都会加剧上述效果。辐射重吸收效应随压力增大而逐渐增强,并造成可燃极限处最大火焰温度随压力先增加后减小,在1 MPa左右达到峰值。 相似文献
6.
本文通过实验研究了CO2质量分数为11.39%~70.95%,壁面过冷度为5~25 K,总压力为5~15 kPa的CO2/H2O混合气体自然对流条件下在水平管外的凝结换热规律,结果表明CO2/H2O的凝结换热系数随CO2含量和壁面过冷度的增大而降低,但随总压力的增大而增大。根据实验结果建立了新关联式,将关联式应用到凝汽器的设计计算与分析,且对凝汽器进行了分离特性和经济性分析。 相似文献
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极紫外光刻技术是我国当前面临35项“卡脖子”关键核心技术之首.高极紫外光转换效率和低离带热辐射的激光等离子体极紫外光源是极紫外光刻系统的重要组成部分.本文通过采用激光作用固体Sn和低密度SnO2靶对极紫外光源以及其离带热辐射进行研究.实验结果表明,两种形式Sn靶在波长为13.5 nm附近产生了强的极紫外光辐射.由于固体Sn靶等离子体具有较强自吸收效应,在光刻机中心工作波长13.5 nm处的辐射强度处于非光谱峰值位置.而低密度SnO2靶具有较弱的自吸收效应,其所辐射光谱的峰值恰好位于13.5 nm处.相比于固体Sn靶,低密度SnO2靶中处于激发态的Sn离子发生跃迁所产生的伴线减弱,使其在13.5 nm处的光谱效率提升了约20%.另一方面,开展了极紫外光源离带热辐射(400—700 nm)的实验研究,光谱测量结果表明离带热辐射主要是由连续谱所主导,低密度SnO2靶中含有部分低Z元素O(Z=8),导致其所形成的连续谱强度低,同时离带辐射时间短,因而激光作用低密度SnO2靶所产生的离带... 相似文献
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本文采用实验测量和数值模拟结合的方法,对NSD等离子体–催化剂协同重整CH4/CO2过程中的协同效应以及积碳动力学进行研究。构建了包含中性分子、自由基、振动激发态、电子激发态、带电粒子、表面吸附态等物质在内的详细动力学机理。采用ZDPlasKin-CHEMKIN耦合的方法迭代求解等离子体放电过程、气相反应动力学及表面反应动力学在内的详细动力学机理。在300~700 K的温度范围内,该动力学模型能较好地预测反应物的消耗和产物的生成,路径通量分析表明CH3在催化剂表面上的直接吸附反应以及CH4振动激发态分子的吸附态CH4(vs)在催化剂表面上的解离吸附均可促进吸附态CH3(s)的生成。积碳动力学研究表明催化剂上的积碳主要来源于吸附态CH(s)的脱氢反应CH(s)+Ni(s)→C(s)+H(s)。 相似文献
11.
A study of the adsorption/desorption behavior of CO, H2O, CO2 and H2 on Ni(110)(4 × 5)-C and Ni(110)-graphite was made in order to assess the importance of desorption as a rate-limiting step for the decomposition of formic acid and to identify available reaction channels for the decomposition. The carbide surface adsorbed CO and H2O in amounts comparable to the clean surface, whereas this surface, unlike clean Ni(110), did not appreciably adsorb H2. The binding energy of CO on the carbide was coverage sensitive, decreasing from 21 to 12 as the CO coverage approached 1.1 × 1015 molecules cm?2 at 200K. The initial sticking probability and maximum coverage of CO on the carbide surface were close to that observed for clean Ni(110). The amount of H2, CO, CO2 and H2O adsorbed on the graphitized surface was insignificant relative to the clean surface. The kinetics of adsorption/desorption of the states observed are discussed. 相似文献
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Infrared spectroscopic evidence is presented for the formation of linearly bonded CO species, as a result of surface interaction between H2 and CO2 at room temperature over silicalite-supported Pt. Comparison with direct CO adsorption results suggests that the active sites for this CO2 reaction are the corner or step sites on platinum particles. The CO formed on these active sites then migrates to other sites on the surface of Pt particles. Co-adsorbed hydrogen and water make the linearly bonded CO species more strongly adsorbed on Pt particles. However, exposure to oxygen or air at room temperature effectively removes these CO species. 相似文献
13.
S. Jones J. Melguizo-Gavilanes J.E. Shepherd 《Proceedings of the Combustion Institute》2019,37(2):1597-1604
A combined experimental and numerical study was carried out to investigate thermal ignition by millimeter size ( mm) moving hot spheres in H2-O2-N2 environments over a range of equivalence ratios. The mixtures investigated were diluted with N2 to keep their laminar flame speed constant and comparable to the sphere fall velocity (2.4 m/s) at time of contact with the reactive mixture. The ignition thresholds (and confidence intervals) were found by applying a logistic regression to the data and were observed to increase from lean (; Tsphere = 963 K) to rich (; Tsphere = 1007 K) conditions. Experimental temperature fields of the gas surrounding the hot sphere during an ignition event were, for the first time, extracted using interferometry and compared against simulated fields. Numerical predictions of the ignition thresholds were within 2% of the experimental values and captured the experimentally observed increasing trend between lean and rich conditions. The effect of stoichiometry and dilution on the observed variation in ignition threshold was explained using 0-D constant pressure delay time computations. 相似文献
14.
Tanh Le Cong 《Proceedings of the Combustion Institute》2009,32(1):427-435
An experimental investigation of the oxidation of hydrogen diluted by nitrogen in presence of CO2 was performed in a fused silica jet-stirred reactor (JSR) over the temperature range 800-1050 K, from fuel-lean to fuel-rich conditions and at atmospheric pressure. The mean residence time was kept constant in the experiments: 120 ms at 1 atm and 250 ms at 10 atm. The effect of variable initial concentrations of hydrogen on the combustion of methane and methane/carbon dioxide mixtures diluted by nitrogen was also experimentally studied. Concentration profiles for O2, H2, H2O, CO, CO2, CH2O, CH4, C2H6, C2H4, and C2H2 were measured by sonic probe sampling followed by chemical analyses (FT-IR, gas chromatography). A detailed chemical kinetic modeling of the present experiments and of the literature data (flame speed and ignition delays) was performed using a recently proposed kinetic scheme showing good agreement between the data and this modeling, and providing further validation of the kinetic model (128 species and 924 reversible reactions). Sensitivity and reaction paths analyses were used to delineate the important reactions influencing the kinetic of oxidation of the fuels in absence and in presence of additives (CO2 and H2). The kinetic reaction scheme proposed helps understanding the inhibiting effect of CO2 on the oxidation of hydrogen and methane and should be useful for gas turbine modeling. 相似文献
15.
Measurements in SF6?H2 mixtures of HF1 fluorescence at 2.8 μm induced by pulsed CO2 laser radiation are reported. The dependence of fluorescence intensity on laser fluence is found to be strongly affected by the laser beam geometry in the interaction region. Our results show that the technique of HF1 fluorescence intensity detection can be a sensitive and reliable single-shot measure of multiple-photon dissociation of SF6 in a collisionless regime on condition that the laser fluence is uniform along the interaction region which is monitored. 相似文献
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G.K. Johri R.P. Rishishwar 《Journal of Quantitative Spectroscopy & Radiative Transfer》1984,32(4):371-372
Microwave linewidths of C2H4O (κ = -0.41) broadened by H2, N2, O2, and CO2 and considering dipole-quadrupole interactions have been calculated using the Mehrotra-Boggs theory (1977). This theory accounts satisfactorily for observed linewidths 相似文献
17.
Dong-Chan Park Stuart J. Day Peter F. Nelson 《Proceedings of the Combustion Institute》2005,30(2):2169-2175
The chemistry of char-N release and conversion to nitrogen-containing products has been probed by studying its release and reactions with O2, CO2, and H2O. The experiments were performed in a fixed bed flow reactor at pressures of up to 1.0 MPa. The results show that the major nitrogen-containing products observed depend on the reactant gas; with O2, NO, and N2 being the major species observed. Char-N reaction with CO2 produces N2 with very high selectivity over a broad range of pressures and CO2 concentrations, and reaction with H2O gives rise to HCN, NH3, and N2. Observed distributions of nitrogen-containing products are little affected by pressure when O2 and CO2 are the reactant gases, but increasing pressures in the reaction with H2O results in the formation of increasing proportions of NH3. Formation of NH3 is also promoted by increasing concentrations of H2O in the feed gas. The results suggest that NO and HCN are primary products when O2 and H2O, respectively, are used as the reactant gases, and that the other observed products arise from interactions of these primary products with the char surface. 相似文献