正十一烷/空气在宽温度范围下着火延迟的激波管研究

在加热激波管上测量了气相正十一烷/空气混合物的着火延迟时间,着火温度为宽温度范围731-1399 K,着火压力在2.02 × 10⁵和10.10 × 10⁵ Pa附近,化学计量比分别为0.5、1.0和2.0。通过监测管侧壁观测点处的反射激波压力和OH^*发射光测出着火延迟时间。实验结果显示：在910 K以上,着火延迟时间随着火温度的降低而变长,从910到780 K,着火延迟时间随着火温度的降低而变短（显示出了负温度系数效应）,在780 K以下,着火延迟时间随着火温度的降低再次变长。在所研究的压力下,着火压力的增加使着火时间变短。化学计量比对着火延迟的影响在着火压力为2.02 × 10⁵和10.10 × 10⁵ Pa时是不同的,与在高温区相比,着火延迟在低温区对化学计量比非常敏感。在整个温度范围内,当前实验结果和LLNL（LawrenceLivermore National Laboratory）机理的预测值表现出了很好的一致性。现在的正十一烷/空气的着火数据和先前实验测量的正庚烷/空气、正癸烷/空气和正十二烷/空气的着火延迟时间相比较显示了着火延迟时间随着直链烷碳原子数的增加而减小。敏感度分析显示,高、低温条件下影响正十一烷着火延迟过程的反应是显著不同的。在高温条件下起最大促进作用的反应是H + O₂=O+OH,然而在低温条件下,起最大促进作用的反应是过氧十一烷基（C₁₁H₂₃O₂）的异构化反应。本文研究首次提供了正十一烷/空气的激波管着火延迟时间。     

戊酸甲酯高温点火的激波管研究

戊酸甲酯是生物柴油和长链脂类燃烧过程中的中间产物之一。迄今为止,文献中还没有戊酸甲酯点火延迟的实验结果,因此对其点火特性的研究是必要的。在本文工作中,于反射激波后测量了戊酸甲酯/空气和戊酸甲酯/4%氧气/氩气的点火延迟时间。实验条件为:戊酸甲酯/空气点火温度1050–1350 K,点火压力1.5 × 10⁵和16 × 10⁵ Pa,当量比0.5、1和2;戊酸甲酯/4%氧气/氩气点火温度1210–1410 K,点火压力3.5 × 10⁵和7 × 10⁵ Pa,当量比0.75和1.25。点火延迟时间由在距离激波管端面15毫米处的测量点测到的反射激波到达信号和CH自由基信号所决定。所得实验结果显示：对于戊酸甲酯/空气和戊酸甲酯/4%氧气/氩气,温度或压力的增加都一定会使它们的点火延迟时间变短,但对于戊酸甲酯/空气,当量比对其点火延迟时间的影响在高低压下却是不同的(16 × 10⁵ Pa: τ_ign = 5.43 × 10⁻⁶Ф^−0.411exp(1.73 × 10²/RT),1.5 × 10⁵ Pa: τ_ign = 7.58 × 10⁻⁷Ф^0.193exp(2.11 × 10²/RT)。当压力为3.5 × 10⁵–7 × 10⁵ Pa时,还获得了戊酸甲酯/4%氧气/氩气点火延迟时间随点火条件的变化关系：τ_ign = 2.80 × 10⁻⁵(10⁻⁵P)^{−0.446±0.032}Ф^0.246±0.044exp((1.88 ± 0.03) × 10²/RT)。这些关系式反映了点火延迟时间对温度、压力和当量比的依赖关系,且有助于将实验数据归一到特定条件下进行比较。在本文实验条件下,由于戊酸甲酯/空气的燃料浓度远大于戊酸甲酯/4%氧气/氩气的燃料浓度,所测戊酸甲酯/空气的点火延迟时间远短于戊酸甲酯/4%氧气/氩气的点火延迟时间。通过对戊酸甲酯和其它长链脂类的点火特性比较,发现在相对低温时(空气中1200 K以下,氩气中1280 K以下),戊酸甲酯的点火延迟时间要长于其它长链脂类的点火延迟时间。已有的两个戊酸甲酯化学动力学机理都不能很好地预测本文实验结果,对戊酸甲酯机理的进一步完善是需要的。敏感度分析结果表明,支链反应H + O₂ = O + OH对戊酸甲酯的高温点火起着最强的促进作用。据我们所知,本文首次报道了戊酸甲酯的高温点火延迟实验数据,研究结果对了解戊酸甲酯的点火特性非常重要,并且为完善戊酸甲酯的化学动力学机理提供了实验依据。     

多级孔Ni/SAPO-5萘加氢制十氢萘催化剂

以CTAB为改性剂,制备了多级孔SAPO-5-x(x为CTAB与SiO_2的摩尔比,x=0.04~0.10)分子筛和多级孔Ni/SAPO-5-x萘加氢制十氢萘催化剂.加入CTAB后形成了微-介孔多级孔孔道结构,孔容和平均孔径均有增加,但是分子筛的晶相结构没有破坏,层状的外貌没有变化.随x值的增大,SAPO-5-x(x=0~0.10)的孔容和平均孔径先增加后减小,SAPO-5-0.07的最大,Ni/SAPO-5-0.07的平均孔径进一步增大;Ni/SAPO-5-x(x=0~0.10)的强酸位强度先下降后增加,x=0.07时强酸位强度最弱,且以L酸中心为主;催化剂的十氢萘选择性先增大后减小,x=0.07时最大.引入CTAB后催化剂活性略有增加,萘转化率接近100%,十氢萘的选择性可以达到95%以上.     

关于十氢萘的顺反异构

就十氢萘有顺反两种构型为基础展开讨论，说明十氢萘的顺反异构不应被说成是构象异构，指出顺或反十氢萘通常是以各自的诸种构象中最稳定的双椅式构象存在的     

十氢萘选择性开环反应的研究进展

本文介绍了顺式和反式十氢萘的分子结构和反应特性,系统分析了十氢萘在不同催化体系下选择性开环的反应机理,包括在单功能酸性催化剂上的碳正离子机理,在单功能金属催化剂上的氢解反应机理以及基于酸性-金属双功能催化剂的双功能开环反应机理。总结了反应温度、载体酸性和分子筛孔径等工艺条件对十氢萘选择性开环反应性能的影响。最后提出了当前研究存在的不足之处,展望了亟需开展的研究课题。     

反式十氢萘类液晶的合成

以6-烷基-2-十氢萘酮为原料, 经格氏试剂与羰基的加成、脱水、还原及异构化合成系列反式十氢萘类单体液晶 1～12, 产率9.9%～80.8%, 2, 3的产率高于文献值. 结构经过IR, ¹³C NMR, MS鉴定, 并探讨了化合物的相变行为特点和碱催化条件下十氢萘构象异构化的历程.     

四氢萘的加氢与选择性开环

对环境的越来越多的关注，直接导致了燃料油的标准变得越来越严格．柴油中太高含量的芳香烃（尤其是多环芳烃）将导致其密度增大，颜色变暗，尾气中颗粒含量上升，燃烧性能下降．通过传统的深度加氢装置使芳香烃达到饱和也不能有效的提高十六烷值（因为深度加氢的产物-环烷烃同样具有较低的十六烷值）．而环烷烃的开环产物（烷基苯、烷基环己烷、烷基环戊烷、烷烃等）却具有相对较高的十六烷值，这就使得芳香烃饱和加氢后所得环烷烃的进一步开环变得重要起来。     

不同结晶度的WO3负载Pt低温催化萘加氢合成十氢萘

不同温度下直接煅烧偏钨酸铵制备了晶化程度不同的两种氧化钨(WO_3-500和WO_3-900),通过XRD、SEM、TEM、XPS、H_2-TPR和NH_3-TPD手段对WO_3载体负载Pt前后的物化性质进行了系统的表征,低温反应条件下研究了不同氧化钨负载Pt对萘加氢的催化性能。与WO_3-900载体相比,低温煅烧得到具有较低的结晶程度,载体中大量的W~(5+)物种和负载的Pt具有强的相互作用,并显示出较强的酸性。在低的反应温度下(70℃),Pt/WO_3-500催化剂对萘加氢合成十氢萘具有优异的催化性能,萘的转化率和十氢萘的选择性均达到100%;在Pt/WO_3-900催化下萘的转化率和十氢萘的选择性仅为26.7%和1.7%。结合催化剂的表征和催化反应结果,揭示了氧化钨中的氧缺陷位是提升Pt/WO_3催化性能的关键因素,对设计高效的WO_3负载Pt催化剂催化萘合成十氢萘提供了一定的理论指导。     

Ni/γ-Al2O3催化剂上萘加氢生成十氢萘的催化反应研究

采用Ni/Al₂O₃催化剂,在高压固定床反应器中考察了反应温度、压力、空速和氢油体积比比等因素对萘饱和加氢反应行为的影响,尤其是反应条件对反式十氢萘和顺式十氢萘选择性的影响。研究表明,反式十氢萘和顺式十氢萘的选择性与反应操作条件密切相关;反式十氢萘与顺式十氢萘的比例随着氢油比和温度的升高而增加,而随着压力和空速的增加而减小。在反应温度260-290℃、反应压力为5-7 MPa、空速为1-1.5 h^-1及氢油体积比大于250时,十氢萘的选择性最高可达99%以上,萘的转化率接近100%,产物中反式和顺式十氢萘的比例最高,可达4.0左右。对Ni/γ-Al₂O₃催化剂稳定性进行了考察,初步发现催化活性组分的烧结或流失是催化剂失活和影响产物中反式十氢萘和顺式十氢萘比例的主要原因。     

煤油裂解产物/空气与煤油/空气在宽温度范围内点火延迟的对比研究

Kerosene is an ideal endothermic hydrocarbon. Its pyrolysis plays a significant role in the thermal protection for high-speed aircraft. Before it reacts, kerosene experiences thermal decomposition in the heat exchanger and produces cracked products. Thus, to use cracked kerosene instead of pure kerosene, knowledge of their ignition properties is needed. In this study, ignition delay times of cracked kerosene/air and kerosene/air were measured in a heated shock tube at temperatures of 657–1333 K, an equivalence ratio of 1.0, and pressures of 1.01 × 10⁵–10.10 × 10⁵ Pa. Ignition delay time was defined as the time interval between the arrival of the reflected shock and the occurrence of the steepest rise of excited-state CH species (CH*) emission at the sidewall measurement location. Pure helium was used as the driver gas for high-temperature measurements in which test times needed to be shorter than 1.5 ms, and tailored mixtures of He/Ar were used when test times could reach up to 15 ms. Arrhenius-type formulas for the relationship between ignition delay time and ignition conditions (temperature and pressure) were obtained by correlating the measured high-temperature data of both fuels. The results reveal that the ignition delay times of both fuels are close, and an increase in the pressure or temperature causes a decrease in the ignition delay time in the high-temperature region (> 1000 K). Both fuels exhibit similar high-temperature ignition delay properties, because they have close pressure exponents (cracked kerosene: τ_ign∝P^-0.85; kerosene:τ_ign∝P^-0.83) and global activation energies (cracked kerosene: E_a = 143.37 kJ·mol^-1; kerosene: E_a = 144.29 kJ·mol^-1). However, in the low-temperature region (< 1000 K), ignition delay characteristics are quite different. For cracked kerosene/air, while the decrease in the temperature still results in an increase in the ignition delay time, the negative temperature coefficient (NTC) of ignition delay does not occur, and the low-temperature ignition data still can be correlated by an Arrhenius-type formula with a much smaller global activation energy compared to that at high temperatures. However, for kerosene/air, this NTC phenomenon was observed, and the Arrhenius-type formula fails to correlate its low-temperature ignition data. At temperatures ranging from 830 to 1000 K, the cracked kerosene ignites faster than the kerosene; at temperatures below 830 K, kerosene ignition delay times become much shorter than those of cracked kerosene. Surrogates for cracked kerosene and kerosene are proposed based on the H/C ratio and average molecular weight in order to simulate ignition delay times for cracked kerosene/air and kerosene/air. The simulation results are in fairly good agreement with current experimental data for the two fuels at high temperatures (> 1000 K). However, in the low-temperature NTC region, the results are in very good agreement with kerosene ignition delay data but disagree with cracked kerosene ignition delay data. The comparison between experimental data and model predictions indicates that refinement of the reaction mechanisms for cracked kerosene and kerosene is needed. These test results are helpful to understand ignition properties of cracked kerosene in developing regenerative cooling technology for high-speed aircraft.     

JP-10点火延时的激波管研究

JP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen.     

Shock Tube Measurement of Ethylene Ignition Delay Time and Molecular Collision Theory Analysis

In this study, 75% and 96% argon diluent conditions were selected to determine the ignition delay time of stoichiometric mixture of C₂H₄/O₂/Ar within a range of pressures (1.3-3.0 atm) and temperatures (1092-1743 K). Results showed a logarithmic linear relationship of the ignition delay time with the reciprocal of temperatures. Under both two diluent conditions, ignition delay time decreased with increased temperature. By multiple linear regression analysis, the ignition delay correlation was deduced. According to this correlation, the calculated ignition delay time in 96% diluent was found to be nearly five times that in 75% diluent. To explain this discrepancy, the hard-sphere collision theory was adopted, and the collision numbers of ethylene to oxygen were calculated. The total collision numbers of ethylene to oxygen were 5.99×10³⁰ s^-1cm^-3 in 75% diluent and 1.53×10²⁹ s^-1cm^-3 in 96% diluent (about 40 times that in 75% diluent). According to the discrepancy between ignition delay time and collision numbers, viz. 5 times corresponds to 40 times, the steric factor can be estimated.     

正癸烷燃烧机理及航空煤油点火延时动力学模拟

以单一正癸烷作为国产航空煤油的单组分替代模型, 应用自有的碳氢燃料反应机理生成程序ReaxGen-Combustion构建了燃烧反应的详细机理. 以国产煤油在加热型激波管上的燃烧实验为参考, 对比研究了文献报道的3组分替代模型(模型Ⅰ)、2组分替代模型(模型Ⅱ)以及本文的单组分替代燃烧反应机理(模型Ⅲ)在预测我国航空煤油点火延时特性方面的实用性. 结果表明, 温度在1052~1538 K时, 模型Ⅰ预测的点火延时与实验值相差较大; 模型Ⅲ在温度高于1176 K时的预测值与实验值符合较好, 在1052~1176 K之间时则相差较大; 模型Ⅱ与模型Ⅲ预测值符合很好, 由于前者考虑了低温反应机理, 因而对1052~1176 K区间的预测精度与模型Ⅲ相比有所改善. 计算还发现, 模型Ⅱ中添加的20%(质量分数)1,2,4-三甲基苯对高温段点火延时未产生明显影响.     

煤油自点火特性的实验研究

在加热激波管中利用反射激波点火,采用壁端压力和CH*发射光作为点火指示信号,测量了气相煤油/空气混合物的点火延时,点火温度为1100-1500K,压力为2.0×105和4.0×105Pa,化学计量比(Φ)为0.2、1.0和2.0.分析了点火温度、压力和化学计量比对点火延时的影响.结果显示,化学计量比为1.0和2.0时活化能几乎是相同的,但与化学计量比为0.2时的活化能差异很大,拟合得到了不同化学计量比条件下点火延时随温度变化的关系式.点火延时与已有的动力学机理进行对比,实验结果与Honnet等人的动力学机理吻合得很好.对不同化学计量比条件下的反应进行了敏感度分析,结果表明在化学计量比为0.2时,对点火延时敏感的关键反应与化学计量比为1.0时的有很大差异.     

基于激波管装置的乙烯氧化实验研究与动力学机理分析

在乙烯/氧气化学计量比为1,温度1092-1743 K,压力1.3-3.0 atm (1 atm = 101325 Pa)范围内,利用激波管测量了在摩尔分数为96%和75%两种不同氩气稀释度工况下的乙烯/氧气/氩气反应体系的着火延迟时间。实验结果表明,乙烯着火延迟时间在低稀释度下比高稀释度下短,着火延迟时间的对数与温度的倒数成良好线性关系,随着温度增加着火延迟时间缩短。此外,低稀释度下,能观察到爆轰(或者爆燃转爆轰)现象,而在高稀释度下,未发生爆轰现象。将四种不同机理模拟结果与实验结果比较,发现LLNL机理与实验结果吻合得较好。反应路径分析研究表明,稀释度对乙烯氧化反应路径无影响,而温度影响较大,温度增加,乙烯消耗路径由四条减少为三条,反应C₂H₄ + H (+ M) = C₂H₅ (+ M)由正向消耗乙烯变为逆向生成乙烯。     

高温非平衡条件下氟原子亲电动力学的激波管研究

To study electron affinity kinetics, a shock tube method was applied, in which the test gas was ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave. As the quenching speed of 106 K/s was reached, a nonequilibrium ionization recombination process occurred, which was dominated by ion recombination with electrons. A Langmuir electrostatic probe was used to monitor variation in the ion number density at the reflection shock region. The working state of the probe was analyzed, and a correction was introduced for reduction of the probe current due to elastic scattering in the probe sheath. The three body electron affinity rate coefficient of the fluorine atom over the temperature range 1200 to 2200 K in an ambiance of argon gas was directly determined. The temperature dependence of electron affinity rate coefficient was discussed.     

典型燃料点火延迟时间的一阶和二阶局部和全局敏感度分析

Sensitivity analysis is an important tool in model validation and evaluation that has been employed extensively in the analysis of chemical kinetic models of combustion processes. The input parameters of a chemical kinetic model are always associated with some uncertainties, and the effects of these uncertainties on the predicted combustion properties can be determined through sensitivity analysis. In this work, first- and second-order global and local sensitivity coefficients of ignition delay time with respect to the scaling factor for reaction rate constants in chemical kinetic mechanisms for combustion of H₂, methane, n-butane, and n-heptane are examined. In the sensitivity analysis performed here, the output of the model is taken to be natural logarithm of ignition delay time and the input parameters are the natural logarithms of the factors that scale the reaction rate constants. The output of the model is expressed as a polynomial function of the input parameters, with up to coupling between two input parameters in the present sensitivity analysis. This polynomial function is determined by varying one or two input parameters, and allows the determination of both local and global sensitivity coefficients. The order of the polynomial function in the present work is four, and the factor that scales the reaction rate constant is in the range from 1/e to e, where e is the base of the natural logarithm. A relatively small number of sample runs are required in this approach compared to the global sensitivity analysis based on the highly dimensional model representation method, which utilizes random sampling of input (RS-HDMR). In RS-HDMR, sensitivity coefficients are determined only for the rate constants of a limited number of reactions; the present approach, by contrast, affords sensitivity coefficients for a larger number of reactions. Reactions and reaction pairs with the largest sensitivity coefficients are listed for ignition delay times of four typical fuels. Global sensitivity coefficients are always positive, while local sensitivity coefficients can be either positive or negative. A negative local sensitivity coefficient indicates that the reaction promotes ignition, while a positive local sensitivity coefficient suggests that the reaction actually suppresses ignition. Our results show that important reactions or reaction pairs identified by global sensitivity analysis are usually rather similar to those based on local sensitivity analysis. This finding can probably be attributed to the fact that the values of input parameters are within a rather small range in the sensitivity analysis, and nonlinear effects for such a small range of parameters are negligible. It is possible to determine global sensitivity coefficients by varying the input parameters over a larger range using the present approach. Such analysis shows that correlation effects between an important reaction and a minor reaction can have relatively sizable second-order sensitivity coefficient in some cases. On the other hand, first-order global sensitivity coefficients in the present approach will be affected by coupling between two reactions, and some results of the first-order global sensitivity analysis will be different from those determined by local sensitivity analysis or global sensitivity analysis under conditions where the correlation effects of two reactions are neglected. The present sensitivity analysis approach provides valuable information on important reactions as well as correlated effects of two reactions on the combustion characteristics of a chemical kinetic mechanism. In addition, the analysis can also be employed to aid global sensitivity analysis using RS-HDMR, where global sensitivity coefficients are determined more reliably.