燃料高速燃料动态温度的测量

利用多通道高温计测量燃料高速燃烧动态温度的方法，在爆炸激波管中模拟异辛烷，正庚烷、正辛烷、正庚烷＋异辛烷混合物等烷烃高速燃烧。并用该方法考察了氧气对异辛烷高速燃烧温度的影响，及上述烷烃的辛烷值与高速燃烧温度的关系。结果表明，对于富含异辛烷 合物，增加氧含量可以使高速燃烧温度增加；随着烷烃辛烷值的增加，高速燃烧温度下降，与利用传感器测量结果相吻合。本文所述的方法可以用于各种气－液相混合物高速燃烧温度的测量。     

火焰原子吸收光谱法测定汽油中铅

汽油中最具代表性的组分是辛烷。辛烷值是[1]表示汽油在汽油机中燃烧时的抗震性的指标。它是将汽油样品与抗震性很好的异辛烷(辛烷值规定为100)和抗震性很小的正庚烷配合成的混合液在标准汽油机中进行比较而得。例如一种汽油样品的抗震性与95%异辛烷和5%正庚烷的混合液相等,该样品的辛烷值即为95,就称为95号汽油。直馏汽油的辛烷值在55~72之间。在每升汽油中加入0.6 g“铅”可以将辛烷值提高79~88。加入汽油中的铅主要含有约60%(质量分数)的四乙基铅Pb(C2H5)4或四甲基铅Pb(CH3)4和约40%的二溴乙烷(或二氯乙烷)的混合物。四乙基铅阻止提前…     

采用系统的方法自动构建链烷烃高温燃烧反应机理

为了得到合理可靠和简化的反应机理,利用反应机理自动生成程序ReaxGen,构建了正庚烷、异辛烷、正癸烷和正十二烷的高温燃烧反应详细机理;同时分别采用物质产率分析和反应路径流量分析的方法对详细机理进行简化,得到了半详细机理和骨架机理. 在较宽的温度和压力条件下,对半详细机理和骨架机理进行了点火延时、层流火焰传播速度和重要物种浓度曲线的模拟并与实验结果比较;最后,图示说明了这些烷烃的主要高温燃烧路径,给出了点火延迟时间的敏感度分析. 结果表明：这些机理能够合理描述链烷烃的自点火特性,文中提出的结合ReaxGen程序的机理构建方法和反应路径流量分析的简化方法也可以用于其它烃类的高温燃烧机理构建.     

采用系统的方法自动构建链烷烃高温燃烧反应机理（英文）

为了得到合理可靠和简化的反应机理,利用反应机理自动生成程序ReaxGen,构建了正庚烷、异辛烷、正癸烷和正十二烷的高温燃烧反应详细机理;同时分别采用物质产率分析和反应路径流量分析的方法对详细机理进行简化,得到了半详细机理和骨架机理.在较宽的温度和压力条件下,对半详细机理和骨架机理进行了点火延时、层流火焰传播速度和重要物种浓度曲线的模拟并与实验结果比较;最后,图示说明了这些烷烃的主要高温燃烧路径,给出了点火延迟时间的敏感度分析.结果表明:这些机理能够合理描述链烷烃的自点火特性,文中提出的结合ReaxGen程序的机理构建方法和反应路径流量分析的简化方法也可以用于其它烃类的高温燃烧机理构建.     

噻吩分子及其与异辛烷二元混合物在MCM-22分子筛中吸附的蒙特卡罗模拟

应用巨正则蒙特卡罗模拟方法研究了噻吩分子以及噻吩与异辛烷混合物在MCM-22分子筛中的吸附和分布. 通过模拟获得了噻吩分子在MCM-22分子筛中不同温度(298、363 和393 K)下的吸附等温线和等量吸附热, 以及298 K时噻吩和异辛烷分子二元混合物在MCM-22分子筛中的吸附及分布情况. 结果表明, 吸附温度和吸附压力对噻吩分子在MCM-22分子筛吸附都有影响, 但等量吸附热受温度和吸附量影响较小. 对于二元混合物的吸附, 噻吩和异辛烷在分子筛中存在竞争吸附过程, 噻吩能够大量吸附在MCM-22分子的十元环和超笼中, 而异辛烷主要吸附在MCM-22分子筛的超笼系统, 从而可以将噻吩分子与异辛烷分子分离开来.     

基于不同燃料PAH特性改进的适用于多组分燃料的碳烟模型

将多环芳烃(PAH)骨架模型与甲苯参比燃料(TRF)氧化模型耦合,构建了一个新的TRF-PAH骨架模型.以新的TRF-PAH骨架模型作为燃料燃烧的气相化学反应模型,基于不同分子结构的燃料氧化过程中生成PAHs和碳烟的路径也不同的研究结论,本文进一步优化了以PAHs为碳烟前驱生成物的碳烟半经验模型.通过甲苯在流动反应器、搅拌反应器和激波管中的氧化/裂解实验验证发现,新的TRF-PAH骨架模型可以相对准确地预测小分子PAHs和重要中间组分的浓度.通过对比烷烃和芳香烃氧化过程中生成苯的计算值可以发现,燃料的分子结构对PAHs的生成路径影响很大.另外,改进后的碳烟模型利用甲苯、正庚烷/甲苯及异辛烷/甲苯混合物为燃料的激波管中裂解和氧化实验验证,结果表明在较宽的工况内碳烟模拟值与实验值吻合较好.最后,将新的碳烟模型应用于KIVA程序,模拟以TRF20为燃料的柴油机碳烟排放,结果表明TRF-PAH骨架模型和碳烟模型能重现缸内燃烧和排放的特性.     

双燃料发动机缸内分层激光诱导荧光实验及化学动力学模拟研究

双燃料压燃（RCCI）是一种很有前景的发动机新型燃烧方式,能在小负荷到中高负荷范围内实现发动机高效清洁燃烧,为了将RCCI拓展到更高负荷,需要对其缸内燃油分层和燃烧过程开展更深入研究。本文在一台双燃料光学发动机上采用燃油-示踪剂平面激光诱导荧光法（PLIF）,对RCCI着火前缸内燃油分层进行定量测量,选用甲苯作为示踪剂,利用266 nm脉冲激光激发甲苯荧光,发动机转速1200 r·min^-1,平均指示压力6.9×10⁵ Pa,气道喷射异辛烷,缸内在上止点前10°喷射正庚烷。采用燃油-气体绝热混合假设,对PLIF测量结果进行温度不均匀性修正,以上止点后5°曲轴转角下的测量结果为例,不修正相比修正测试区域内的最大当量比高估15%。根据实验结果,利用Chemkin软件分析了活性、浓度和温度分层对燃烧滞燃期的影响,结果显示燃料活性分层和浓度分层共同决定RCCI的着火滞燃期,其中活性分层影响要大于浓度分层,而温度分层对着火滞燃期影响很小。RCCI燃烧过程自发光的高速成像结果表明,着火过程首先出现在燃烧室边缘的高活性区域,随后火焰向燃烧室中心处的低活性区域发展,碳烟辐射光图像显示碳烟主要形成于燃烧室边缘的高活性区域。     

低温燃料化学特性对湍流预混火焰传播的影响

大分子碳氢燃料的低温化学反应及两阶段点火特性会显著影响火焰的分区及燃烧情况。本文采用数值模拟的方法探究了正庚烷/空气预混混合气在RATS燃具上的湍流火焰传播,与试验结果具有一致性。模拟使用的是44种物质,112步的正庚烷简化动力学机理。使用Open FOAM的reacting Foam求解器建立了简化模拟流道及出口的三维模型,模拟了在大气环境下,初始反应温度450–700 K、入口速度6 m·s~(-1)与10 m·s~(-1)、焰前流动滞留时间100 ms及60 ms、当量比φ=0.6的正庚烷/空气混合气湍流火焰燃烧情况。结果发现,标准化湍流燃烧速度与混合气初始温度以及流动滞留时间有关。在低温点火阶段,正庚烷氧化程度受到初始温度与速度的影响,燃料分解并在预热区中产生大量中间物质如CH_2O,继而会影响湍流火焰燃烧速度。随着初始反应温度的升高,湍流燃烧火焰逐渐由化学反应冻结区过渡到低温点火区;温度超过一定数值后,燃料不再发生低温反应,此时燃烧位于高温点火区域。     

分子动力学模拟烷烃混合物在石墨烯表面取向

采用分子动力学模拟方法研究了烷烃混合物在石墨烯表面取向的过程.研究结果表明,模拟温度能够改变链取向的方向,相对较低的温度对链垂直表面取向有利,相对较高的温度对链平行于表面取向有利;温度升高短链烷烃会发生脱离混合物的情况,且温度越高发生脱离行为的烷烃数目越多.烷烃链与石墨烯的相互作用在此过程中起重要作用.     

热力学数据精度对正庚烷燃烧模拟结果的影响

为了探讨热力学数据的精度对正庚烷燃烧模拟结果的影响,本文分别在B3LYP/6-31G(d,p)水平和G3水平上计算了正庚烷燃烧反应机理中物种的热力学数据,分别用这些数据模拟了正庚烷在不同条件下的绝热火焰温度和点火延时。同时对正庚烷燃烧反应的点火延时做了敏感度分析,探讨了对点火影响较大的物种。模拟结果表明:核心机理(C0-C4)的物种的热力学数据精度对正庚烷燃烧的模拟结果具有较大影响,而C4以上物种的热力学数据精度对结果影响不大。     

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.     

On-line determination of fuel quality parameters using near-infrared spectrometry with fibre optics and multivariate calibration

Near-infrared spectrometry with multivariate calibration has been widely used in the food and chemical industries for the determination of quality parameters. The use of fibre optics opens the possibility of using this technique for on-line analysis. With fuels such as gasoline and diesel, most of the parameters used for their characterization are measured using empirical and sometimes subjective tests. These tests might also require costly and complicated equipment as in the measurement of octane number, cetane number and paraffin, olefin, naphthene and aromatics content (PONA). Near-infrared spectrometry using fibre optics in combination with multivariate calibration was used for the determination of fuel quality parameters. The octane number of gasolines was measured. The sampling problems encountered when this method is implemented on-line were evaluated by monitoring the research and motor octane numbers in a gasoline line. Other applications, such as the determination of PONA in gasolines and the measurement of cetane number in diesel fuels, are discussed. In all instances the results obtained by the proposed technique agree with the values measured with conventional methods.     

超临界条件下正庚烷的裂解与结焦

以正庚烷为碳氢燃料模型化合物, 考察其在超临界条件下的裂解和结焦情况, 着重探讨了裂解温度和雷诺数(Re)对裂解反应的影响. 在4.0 MPa和500～650 ℃范围内, 随着反应温度升高, 正庚烷的裂解转化率大幅度提高, 裂解反应及其产物的二次反应使结焦前驱物增加, 最终导致结焦严重; 在超临界条件下, 提高流体的湍动程度, 有利于抑制结焦. 采用扫描电镜(SEM)、透射电镜(TEM)、差示扫描量热(DSC)和X射线衍射(XRD)等技术分析固体焦的形貌特性, 结果表明正庚烷裂解结焦主要以金属催化作用产生的丝状焦为主, 丝状焦的生长是不锈钢发生渗碳现象的重要原因.     

Computational Kinetic Study for the Unimolecular Decomposition of Cyclopentanone

Among various categories of potential biofuel molecules, ketones are of significant interest. Cyclopentanone is a cyclic ketone that can be produced from biomass, and its combustion is still unknown. Moreover, its cyclic configuration makes it an interesting feedstock for the further production of high‐density fuels such as bi(cyclopentane). This study reports the first computational kinetic investigation of the unimolecular decomposition pathways of cyclopentanone by using the compound G3B3 method. The rate constants were calculated using Rice–Ramsperger–Kassel–Marcus theory in the temperature range of 800–2000 K. The results presented here can be used in a future kinetic combustion mechanism.     

Dipole moments and molecular conformations ofO-vinyl- andO-ethylacetoximes in solutions

Dipole moments of the molecules ofO-vinyl- andO-ethylacetoximes in octane and THF were measured at different temperatures. In octane, the equilibrium mixture of stableO-vinylacetoxime conformers consists of forms with different polarity. Polarity of these conformers, which are due to rotation about the C−O and N−O bonds, is mainly determined by the relative position of the lone electron pairs of nitrogen and oxygen atoms. The fraction of the polar conformer increases as temperature increases, as well as on going from octane to THF. Saturation of the vinyl group in theO-vinylacetoxime molecule nearly halves the molecular dipole moment in the nonpolar medium, which radically differentiates this compound from vinyl ethers. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1685–1690, September, 1999.     

Plasma Assisted Low Temperature Combustion

This paper presents recent kinetic and flame studies in plasma assisted low temperature combustion. First, the kinetic pathways of plasma chemistry to enhance low temperature fuel oxidation are discussed. The impacts of plasma chemistry on fuel oxidation pathways at low temperature conditions, substantially enhancing ignition and flame stabilization, are analyzed base on the ignition and extinction S-curve. Secondly, plasma assisted low temperature ignition, direct ignition to flame transition, diffusion cool flames, and premixed cool flames are demonstrated experimentally by using dimethyl ether and n-heptane as fuels. The results show that non-equilibrium plasma is an effective way to accelerate low temperature ignition and fuel oxidation, thus enabling the establishment of stable cool flames at atmospheric pressure. Finally, the experiments from both a non-equilibrium plasma reactor and a photolysis reactor are discussed, in which the direct measurements of intermediate species during the low temperature oxidations of methane/methanol and ethylene are performed, allowing the investigation of modified kinetic pathways by plasma-combustion chemistry interactions. Finally, the validity of kinetic mechanisms for plasma assisted low temperature combustion is investigated. Technical challenges for future research in plasma assisted low temperature combustion are then summarized.     

A high-temperature sensor analyzer: Determination of difficult volatile organic impurities in solvents

It was shown that an automated analyzer with solid-electrolyte sensor cells can be used to determine difficult volatile organic impurities (technical oils, gasoline, and kerosene) in organic solvents (alcohols, acetone, and turpentine) by their two-stage oxidation with atmospheric oxygen at 100 °C (evaporation of a light fraction) and at a temperature of 900 °C and higher (burning impurities). Optimum conditions are found for the rapid determination of trace amounts of MS-20 oil in washing solvents (ethanol, benzene): time of determination, 5 min/sample; aliquot portion, 10 μL; linearity range of the calibration graph, from 20 to 100 mg/L of organic impurity; detection limit, 2.5 mg/L; RSD ≥ 8%. The results of determining the concentrations of gasolines of different grades and other organic mixtures for identifying substance grades are discussed. The novelty and advantages of the developed method consist in the rapid and quantitative determination of the octane number and other parameters of hydrocarbon fuels without preliminary sample preparation and also in the possibility of analyzing liquid samples of any other origin without resorting to the chemical methods of analysis. The ecological safety of the method is also important.     

掺混含氧燃料的柴油替代物部分预混火焰中多环芳香烃的荧光光谱和碳烟浓度

为研究不同含氧燃料与柴油掺混后碳烟降低机理, 本文在自行设计的燃烧器上构建部分预混层流火焰, 采用甲苯和正庚烷混合物(T20, 20%(体积分数)甲苯、80%正庚烷)作为柴油替代物,并分别添加甲醇、乙醇、正丁醇、丁酸甲酯和2,5-二甲基呋喃(DMF), 且保证混合燃料的含氧量均为4%. 进而应用激光诱导荧光法和激光诱导炽光法分别测量不同混合燃料的火焰中多环芳香烃(PAHs)的荧光光谱和碳烟浓度. 结果表明: 通过PAHs的荧光光谱可测量不同燃料火焰中PAHs的生成和增长历程. 四环芳香烃(A4)的生成氧化规律和碳烟基本一致, 说明通过分析A4变化可以预测碳烟变化. 添加含氧燃料后, T20燃料中甲苯含量降低是导致PAHs的荧光光谱强度降低和碳烟生成量减少的主要原因; 同时不同含氧燃料本身对多环芳香烃的生成贡献能力也是影响PAHs的荧光强度和碳烟生成的重要原因. 含氧量相当时, 掺混正丁醇后PAHs的荧光光谱强度和碳烟浓度比添加甲醇、乙醇、丁酸甲酯和DMF这四种含氧燃料的更低. 因此从含氧燃料结构来讲, 正丁醇掺混入T20燃料中降低PAHs和碳烟作用最显著.     

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.