RP-3替代燃料自点火燃烧机理构建及动力学模拟

通过对RP-3 航空煤油成分的分析, 以及对8 组替代模型的对比实验, 选取了73.0%(质量分数)正十二烷, 14.7% 1,3,5-三甲基环己烷, 12.3%正丙基苯作为RP-3 航空煤油的替代模型. 使用本课题组自主研发的机理自动生成程序ReaxGen, 构建了RP-3 替代燃料的高温燃烧详细机理, 用该机理模拟了激波管点火延时, 并与实验数据进行比较. 用物质产率分析和近似轨迹优化算法(ATOA)简化方法简化了详细机理. 最后对燃烧机理在不同化学计量比及压力条件下的点火延时做了敏感度分析, 考察了燃烧机理在不同化学计量比下关键反应的异同. 结果表明, 该替代模型的燃烧机理能很好地描述RP-3煤油的高温点火特性.     

甲基环己烷的高温燃烧机理及动力学模拟

本文根据高碳链烷烃和环烷烃高温燃烧的反应类型,开发了高温燃烧反应机理的自动生成程序ReaxGen,并据此建立了甲基环己烷的高温燃烧详细机理。采用激波管反应器模型开展了动力学模拟,研究了燃烧点火温度、点火压力、燃料摩尔分数和当量比对点火延时的影响。通过绝热燃烧平衡计算,得到产物浓度和绝热火焰温度。动力学模拟结果与文献实验结果及国际上同类机理的模拟结果进行了比较和讨论。     

正癸烷加氢裂化集总动力学研究

选用国产３８２５加氢裂化催化剂，对正癸烷加氢裂化动力学进行了研究。根据Ｗｅｅｋ－ｍａｎ集总原理，建立了正癸烷加氢裂化四集总动力学模型。利用Ｍａｒｑｕａｒｄｔ法估计了各反应速度常数，确定了完善的速度表达式。计算了两种压力（６．５和８．５ＭＰａ）下的表观活化能，预测了各反应产物分布，其计算结果与实验值吻合。同时，讨论了空速、温度、压力和反应活化能对产物分布的影响，为重油和渣油加氢裂化集总动力学研究提供     

正癸烷热解的小规模化学动力学机理模型

正癸烷是目前常用的吸热型燃料的替代组分, 但是其热解机理的研究迄今还很少, 且现有的少数几个机理由于规模庞大使用不便. 本文首先构建了一个包含33种组分和75个基元反应的正癸烷热解动力学机理模型(Mech33); 随后, 在该机理的基础上进一步通过灵敏度分析得到影响主要热裂解组分生成的速率控制步, 并采用局部平衡和稳态假设对Mech33机理简化得到了规模更小的、仅包含22种组分和59步反应动力学机理模型(Mech22). 在较宽的温度和压力范围内对流动反应器及激波管中正癸烷热解过程进行了数值模拟, 并与实验数据进行了对比, 结果表明, Mech33和Mech22两个动力学机理模型都能够很好地描述正癸烷热裂解过程,并准确预测主要热裂解产物的浓度分布, 为进一步实现化学反应与计算流体力学(CFD)耦合的工程计算提供了有价值的动力学机理模型.     

高碳烃宽温度范围燃烧机理构建及动力学模拟

发动机中燃料点火特性以及燃烧能量的释放对于发动机设计具有非常重要的作用,为了提高燃料的燃烧效率以及减少燃料在燃烧过程中污染物的排放,基于反应动力学机理对燃料燃烧过程的模拟就显得十分必要。因此需要更加深入的认识碳氢燃料的燃烧机理,探索其在燃烧过程中十分复杂的化学反应网络。为了发展能够适用于实际燃料多工况条件(宽温度范围、宽压力范围和不同当量比)燃烧的燃烧机理,基于碳氢燃料机理自动生成程序ReaxGen构建了正癸烷燃烧详细机理(包含1499个物种,5713步反应)和正十一烷燃烧详细机理(包含1843个物种,6993步反应)。详细机理主要由小分子核心机理和高碳烃类(C5以上)机理两部分组成。为了验证机理的合理性与可靠性,本文对于高碳烃燃烧新机理在点火延时时间以及物种浓度曲线进行了动力学分析,并与实验数据及国内外同类机理进行了对比,结果表明本文提出的正癸烷和正十一烷燃烧新机理在比较宽泛的温度、压力和当量比条件下都具有较高的模拟精度,为发展精确航空煤油燃烧模型提供了基础数据。同时考虑到详细机理的复杂性以及机理分析的计算量大和时耗长,本文基于误差传播的直接关系图形(Directed Relation Graph with Error Propagation,DRGEP)方法简化得到的包含709组分2793反应的正癸烷和包含820组分3115反应的正十一烷简化机理,使用DRGEP方法时所采用的数据点选自压力范围从1.0×10~5 Pa到1.0×10~6Pa,当量比范围从0.5到2.0,初始温度范围从600到1400时恒压点火的模拟结果在点火延迟时间附近区域的抽样,同时在正癸烷机理简化中选取正癸烷、O_2和N_2作为初始预选组分,正十一烷的机理简化中主要选取正十一烷、O_2和N_2作为初始预选组分,得到的简化机理在比较宽泛的条件下的预测结果与详细机理吻合很好。最后结合敏感度分析方法分析了正癸烷和正十一烷的点火延迟敏感性,考察了机理中影响点火的关键反应。结果表明:这些机理能够合理描述正癸烷和正十一烷的自点火特性,在工程计算流体力学仿真设计中有很好的应用前景。     

正癸烷着火及燃烧的化学动力学模型

构建了一个包含46组分和167反应的描述正癸烷着火与燃烧过程的化学反应动力学机理模型, 该机理是在通过路径分析和灵敏度分析对Peters 机理(118组分和527反应)进行较大程度简化的基础上, 对低温着火和火焰传播速度影响较大的部分基元反应进行修正和改进后得到的. 与文献给出的实验结果对比表明, 该机理不仅比现有的机理具有较少的组分数和基元反应数, 而且能够更准确地预测正癸烷低温和高温条件下的着火延迟时间和火焰传播速度. 该机理为进一步实现总包简化机理与计算流体力学(CFD)的耦合计算奠定了基础.     

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.     

正癸烷热裂解实验和动力学模拟

采用自制常压裂解装置, 研究了正癸烷在温度范围为973-1123 K, 停留时间为0.5-2 s时, 热裂解主要气相产物氢气、甲烷和乙烯的分布情况. 根据自主开发的机理生成软件ReaxGen, 构建了正癸烷热裂解的详细机理, 该机理包含1072步反应和281个物种. 进一步进行动力学模拟, 并用实验结果进行了初步验证. 结果表明, 在反应的温度区间内, 短的停留时间有利于乙烯和氢气的生成. 通过敏感度分析, 确定了常压下973 K, 停留时间为1 s时影响氢气、甲烷和乙烯产量的主要反应步骤是烷基的重排和β裂解反应.     

正十二烷高温燃烧机理的构建及模拟

基于燃料燃烧反应机理的计算机自动生成方法,构建了正十二烷高温燃烧的详细反应机理; 分别采用物质产率分析和反应路径流量分析方法对详细机理进行简化,得到包含202个物种、738步反应的半详细机理和53个物种、228步反应的骨架机理; 对正十二烷点火延时、高温裂解以及层流火焰速度的模拟结果表明半详细机理和骨架机理具有很高的模拟精度,在工程计算流体力学仿真设计中有很好的应用前景.最后分析了正十二烷高温燃烧的反应路径,并对点火延时做了敏感度分析,考查了机理中的关键反应.     

基于特征值分析的正癸烷骨架和总包简化机理

使用基于特征值分析的骨架简化方法对由118个组分和527个反应构成的正癸烷详细机理进行了简化,获得了一个由70个组分、327个基元反应组成的骨架机理;采用基于特征值分析的计算奇异摄动(CSP)简化方法对骨架机理进行进一步简化,得到一个38组分、34步的总包简化机理.通过对简化机理、骨架机理和详细机理的对比发现,简化机理和骨架机理能够很好地再现详细机理的特性,并能够描述正癸烷的主要燃烧特性,为进一步实现耦合化学反应动力学与流体力学的工程计算,提高计算效率提供了可用的燃烧模型.     

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.     

十氢萘/空气混合物高温着火延迟的激波管测量

在激波管上进行了气相十氢萘/空气混合物的着火延迟测量, 着火温度为950-1395 K, 着火压力为1.82×10⁵-16.56×10⁵ Pa, 化学计量比分别为0.5、1.0 和2.0. 在侧窗处利用反射激波压力和CH^*发射光来测出着火延迟时间. 系统研究了着火温度、着火压力和化学计量比对十氢萘着火延迟时间的影响. 实验结果显示着火温度和着火压力的升高均会缩短着火延迟时间. 首次在相对高和低压的条件下观察到了化学计量比对十氢萘着火延迟的影响是完全相反的. 当压力为15.15×10⁵ Pa时, 富油混合物呈现出最短的着火延迟时间, 而贫油混合物的着火延迟时间却是最长的. 相反, 当压力为2.02×10⁵ Pa时, 富油混合物的着火延迟时间最长. 着火延迟数据与已有的动力学机理的预测值进行对比, 结果显示机理在所有的实验条件下均很好地预测了实验着火延时趋势. 为了探明化学计量比对着火延迟时间影响的本质, 对高、低压条件下的着火延时进行了敏感度分析.结果显示, 压力为2.02×10⁵ Pa时, 控制着火延迟的关键反应为H+O₂=OH+O, 而涉及十氢萘及其相应自由基的反应在15.15×10⁵ Pa时对着火延迟起主要作用.     

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.     

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。     

航空煤油替代燃料模型构建方法及HEF航空煤油替代燃料模型

本文在完善燃烧化学特性参数,发展更准确的混合物特性参数计算方法的基础上,提出一套完整的、精确的航煤替代燃料模型构建方法。并采用定容燃烧弹实验系统首次测量了初始温度420和460 K、压力0.1 MPa,实际HEF航煤以及代表性组分十氢萘的层流火焰传播速度,为本文发展和验证替代燃料模型提供充分的实验数据。依据该方法提出了摩尔分数为65%正十二烷、10%正十四烷、25%十氢萘三组分HEF航煤替代燃料模型。充分的的实验和计算结果验证表明,替代燃料模型与实际HEF航煤在物理特性和燃烧化学特性方面有很高的相似性。本文提出的HEF航煤替代燃料模型和实验测量的层流火焰传播速度,为后续化学反应机理的发展与验证奠定了基础。     

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.     

Comparative study of the high-temperature auto-ignition of cyclopentane and tetrahydrofuran

Cyclopentane (C₅H₁₀) and tetrahydrofuran (C₄H₈O) are both five-membered ring compounds. The present study compares the auto-ignition of cyclopentane and tetrahydrofuran in a high-pressure shock-tube (20 atm). Twelve different mixtures were investigated at two different fuel initial mole fractions (1% and 2%): at X_fuel = 1%, three equivalence ratios, kept constant between cyclopentane and tetrahydrofuran, were studied (0.5, 1, and 2), whereas three X_fuel/X_O2 were investigated when X_fuel = 2%. A detailed kinetic mechanism was developed to reproduce cyclopentane and tetrahydrofuran auto-ignition. The agreement between our experimental results and the modeling is very good. This mechanism was used to explain the similarities and differences observed between cyclopentane and tetrahydrofuran auto-ignition.