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。     

汽油替代燃料燃烧过程中多环芳烃生成的化学动力学模型

提出了一个包含103组分和395个基元反应, 能够较好描述多组分汽油替代燃料多环芳烃(PAHs)生成的化学动力学机理模型. 计算结果与实验数据的对比表明, 该机理能够准确地计算乙烯、甲苯、正庚烷预混火焰和正庚烷部分预混对冲火焰中PAHs及其前驱物组分分布. 虽然本文机理目前还无法直接应用于汽油燃烧过程的PAHs多维数值模拟, 但与现有的汽油替代燃料PAHs机理相比, 本文提出的机理规模更小, 距离实际应用的目标更近.     

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.     

RP-3航空煤油高温骨架机理构建及验证

依据RP-3航空煤油的成分,考虑平均分子量及碳氢摩尔比等性质,本文提出其三组分替代燃料模型,其中正癸烷74.24%、1,3,5-三甲基环己烷14.11%和正丙基苯11.65%(质量分数)。采用机理生成程序ReaxGen得到详细化学反应机理;采用机理简化程序ReaxRed,运用直接关系图法与主成分分析法获得高温骨架机理(79物种,311反应)。该机理针对多个工况进行了点火延迟时间与层流火焰速度的验证,能较好地预测实验结果。路径分析结果表明高温下替代燃料通过氢提取反应、单分子裂解反应及β-断键反应消耗。敏感性分析表明高温点火过程由多种小分子自由基(H、CHO、C2H3等)的氧化及分解反应和大分子燃料的氢提取反应控制;影响火焰传播过程的关键反应来源于C0-C3的小分子核心机理。本文所提出的这个尺寸较小但精度较高的骨架机理可用于发动机燃烧过程的高保真数值模拟。     

RP-3航空煤油碳烟机理的构建与验证

燃料燃烧过程中形成的碳烟颗粒是航空发动机中污染物排放的主要成分。RP-3航空煤油作为我国最常用的航空燃料,从微观机理层次研究其碳烟机理对于发动机的污染物减排具有重要意义。本文基于RP-3的三组分替代燃料模型(质量分数为73.0%的正十二烷、14.7%的1,3,5-三甲基环己烷和12.3%的正丙基苯)构建了描述碳烟生成的详细燃烧机理模型,其中包括关键的链烷烃、环烷烃以及芳香烃的多环芳烃(PAHs)生成路径。该机理在多个工况条件下对高温点火延迟时间,层流火焰速度的预测与实验结果符合。碳烟产率的模拟结果表明,该机理能准确再现碳烟的生成。基于该机理对碳烟生成过程中起到关键成核作用的多环芳烃物种芘(A4)进行了敏感性分析,结果表明含有苯环的正丙基苯通过自身裂解产生苯自由基的反应显著促进A4的生成。反应路径分析结果表明在燃烧的不同阶段形成PAHs的各个反应的通量占比有差别,反应前期PAHs的生成主要来源于苯自由基的加成反应过程,而后期主要来源于小分子C₂、C₃、C₄等自由基的加成反应过程。     

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.     

碳氢燃料燃烧机理的自动简化

采用自行开发的碳氢燃料燃烧详细机理自动简化程序ReaxRed分别对包含257个物种和874步反应的RP-3航空煤油替代模型以及包含1389个物种和5935步反应的汽油混合替代模型进行机理自动简化.对RP-3替代模型,分别得到78个物种框架机理和61个物种全局简化机理,在较宽的参数范围内重现RP-3详细机理在点火延迟时间、熄火以及物种浓度分布等方面的模拟结果;通过强制敏感度及物种产率分析进一步说明了简化机理的合理性.对汽油混合替代模型,得到包含266个物种框架机理在较宽范围内重现单组分、两组分及多组分混合的点火延迟时间的模拟结果,并通过元素流动分析阐明了4种单组分燃料的燃烧路径.框架机理保留了详细机理的层级结构以及全局信息,更易于系统分析汽油的燃烧过程.     

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.     

航空煤油裂解产物燃烧机理构建与动力学模拟

针对航空煤油典型裂解工况的裂解产物,本文提出了以2.99%氢气、45.05%甲烷、36.96%乙烯、0.76%环己烯、8.89%甲苯和5.35%正十二烷(摩尔分数)的六组分煤油裂解产物替代模型,构建了包含323个物种,1544步反应的化学动力学机理。使用Chemkin-pro程序进行宽温度范围裂解产物的动力学模拟,点火延迟模拟结果与实验值吻合较好;点火延迟敏感性分析的结果表明HO_2+OH=H_2O+O_2是机理中的关键反应,同时燃烧中间产物与氧气、HO_2和OH自由基的反应也对点火影响较大。该机理模拟精度较高,能够较好的再现航空煤油裂解产物的燃烧特性。     

正十二烷高温机理简化及验证

由于详细化学反应机理在模拟燃烧室燃烧时,计算量极大,很难被广泛运用。为了满足工程设计要求,采用替代燃料的简化机理进行计算不失为一种行之有效的方法。本文基于误差传播的直接关系图法和敏感性分析法对正十二烷180组分1962步高温机理(温度大于1100 K)进行简化,获得40组分234步化学反应机理。在温度为1100–1650 K,压力为0.1–4 MPa条件下,采用简化机理及详细机理对不同当量比、压力下着火延迟时间进行模拟,模拟结果与实验数据吻合得较好。通过对不同压力及温度下火焰传播速度进行模拟,验证了简化机理能够正确地反映正十二烷的燃烧特性。利用C_(12)H_(26)/OH/H_2O/CO_2等重要组分随时间变化的数据,验证了简化机理能够准确描述燃烧过程反应物消耗、基团变化、生成物产生的过程,并表明该机理具有较高的模拟精度。利用该简化机理对本生灯进行数值分析,结果表明该机理能够准确地反映火焰区温度和组分浓度的变化。紧凑的正十二烷高温简化机理不仅能够正确体现其物理化学特性,而且能够用于三维数值模拟,具有较高的工程运用价值和应用前景。     

Construction of a Chemical Kinetic Model of Five-Component Gasoline Surrogates under Lean Conditions

The requirements for improving the efficiency of internal combustion engines and reducing emissions have promoted the development of new combustion technologies under extreme operating conditions (e.g., lean combustion), and the ignition and combustion characteristics of fuels are increasingly becoming important. A chemical kinetic reduced mechanism consisting of 115 species and 414 elementary reactions is developed for the prediction of ignition and combustion behaviors of gasoline surrogate fuels composed of five components, namely, isooctane, n-heptane, toluene, diisobutylene, and cyclohexane (CHX). The CHX sub-mechanism is obtained by simplifying the JetSurF2.0 mechanism using direct relationship graph error propagating, rate of production analysis, and temperature sensitivity analysis and CHX is mainly consumed through ring-opening reactions, continuous dehydrogenation, and oxygenation reactions. In addition, kinetic parameter corrections were made for key reactions R14 and R391 based on the accuracy of the ignition delay time and laminar flame velocity predictions. Under a wide range of conditions, the mechanism’s ignition delay time, laminar flame speed, and the experimental and calculated results of multi-component gasoline surrogate fuel and real gasoline are compared. The proposed mechanism can accurately reproduce the combustion and oxidation of each component of the gasoline-surrogate fuel mixture and real gasoline.     

NOFBX新型绿色推进剂燃烧化学反应动力学模型

本文以具有绿色无毒、高性能、低成本等诸多优势的N_2O-C_2烃类燃料单元复合推进剂(即NOFBX)为对象,首先发展了包含52组分、325反应的燃烧化学反应机理模型。该机理不仅能够准确计算N_2O热解过程中重要组分的分布,而且能够在较宽的温度、压力、化学计量比范围内准确预测N_2O-C_2烃类燃料体系的着火延迟时间和层流火焰传播速度。鉴于本文提出的N_2O-C_2烃类燃料反应机理具有机理规模小、实验验证充分的特点,有望在NOFBX发动机的多维燃烧数值模拟中得到广泛应用。     

Experimental and chemical kinetic modeling study of 3-pentanone oxidation

Shock tube ignition delay times have been measured for 3-pentanone at a reflected shock pressure of 1 atm (±2%), in the temperature range 1250-1850 K, at equivalence ratios of 0.5-2.0 for O(2) mixtures in argon with fuel concentrations varying from 0.875 to 1.3125%. Laminar flame speeds have also been measured at an initial pressure of 1 atm over an equivalence ratio range. Complementary to previous studies [Pichon S., Black, G., Chaumeix, N., Yahyaoui, M., Simmie, J. M., Curran, H. J., Donohue, R. Combust. Flame, 2009, 156, 494-504; Serinyel, Z.; Black, G.; Curran, H. J.; Simmie, J. M. Combustion Sci. Tech., 2010, 182, 574-587], laminar flame speeds of 2-butanone have also been measured, and relative reactivities of these ketones have been compared and discussed. A chemical kinetic submechanism describing the oxidation of 3-pentanone has been developed and detailed in this paper; rate constants for unimolecular fuel decomposition reactions have been treated for falloff in pressure with nine-parameter fits using the Troe Formulism. Both compounds treated in this work may be used as fuel tracers, thus further ignition delay time measurements have been carried out by adding 3-pentanone to n-heptane in order to test the effect of the blend on ignition delay timing. It was found that the autoignition characteristics of n-heptane remained unaffected in the presence of 15% 3-pentanone in the fuel, consistent with results obtained using acetone and 2-butanone [Pichon S., Black, G., Chaumeix, N., Yahyaoui, M., Simmie, J. M., Curran, H. J., Donohue, R. Combust. Flame, 2009, 156, 494-504; Serinyel, Z.; Black, G.; Curran, H. J.; Simmie, J. M. Combustion Sci. Tech., 2010, 182, 574-587].     

Investigation on 1-Heptene/Air Laminar Flame Propagation under Elevated Pressures

The laminar flame propagation of 1-heptene/air mixtures covering equivalence ratios from 0.7 to 1.5 is investigated in a constant-volume cylindrical combustion vessel at 373 K and elevated pressures (1, 2, 5, and 10 atm). Laminar flame speed and Markstein length are derived from the recorded schlieren images. A kinetic model of 1-heptene combustion is developed based on our previous kinetic model of 1-hexene. The model is validated against the laminar flame speed data measured in this work and the ignition delay time data in literature. Modeling analyses, such as sensitivity analysis and rate of production analysis, are performed to help understand the high temperature chemistry of 1-heptene under various pressures and its influence on the laminar flame propagation. Furthermore, the laminar flame propagation of 1-heptene/air mixtures is compared with that of n-heptane/air mixtures reported in our previous work. The laminar flame speed values of 1-heptene/air mixtures are observed to be faster than those of n-heptane/air mixtures under most conditions due to the enhanced exothermicity and reactivity.     

Quenching of Flame Propagation Through Endothermic Reaction

The propagation of a premixed laminar flame supported by an exothermic chemical reaction under adiabatic conditions but subject to inhibition through a parallel endothermic chemical process is considered. The temperature dependence of the reaction rates is assumed to have a generalised Arrhenius type form with an ignition temperature, below which there is no reaction. The heat loss through the endothermic reaction, represented by the dimensionless parameter , has a strong quenching effect on wave initiation and propagation. The temperature profile can have a front or a pulse structure depending on the relative value of the ignition temperatures and on the value of the parameters and , the latter represents the rate at which inhibitor is consumed relative to the consumption of fuel. The wave speed-cooling parameter () curves are determined for various values of the other parameters. These curves can have three different shapes: monotone decreasing, -shaped or S-shaped, with the possibility of having one, two or three different flame velocities for the same value of the cooling parameter .     

ChemKED: A Human‐ and Machine‐Readable Data Standard for Chemical Kinetics Experiments

Fundamental experimental measurements of quantities such as ignition delay times, laminar flame speeds, and species profiles (among others) serve important roles in understanding fuel chemistry and validating chemical kinetic models. However, despite both the importance and abundance of such information in the literature, the community lacks a widely adopted standard format for this data. This impedes both sharing and wide use by the community. Here we introduce a new chemical kinetics experimental data format, ChemKED and the related Python‐based package for validating and working with ChemKED‐formatted files called PyKED. We also review past and related efforts and motivate the need for a new solution. ChemKED currently supports the representation of autoignition delay time measurements from shock tubes and rapid compression machines. ChemKED‐formatted files contain all of the information needed to simulate experimental data points, including the uncertainty of the data. ChemKED is based on the YAML data serialization language and is intended as a human‐ and machine‐readable standard for easy creation and automated use. Development of ChemKED and PyKED occurs openly on GitHub under the BSD 3‐clause license, and contributions from the community are welcome. Plans for future development include support for experimental data from laminar flame, jet‐stirred reactor, and speciation measurements.