Prediction of Sooting Index of Fuel Compounds for Spark-Ignition Engine Applications Based on a Machine Learning Approach

A joint consideration of potential combustion and emission performance in spark-ignition engines is essential for designing gasoline fuel replacements and additives,for which the knowledge of the fuels’characteristic properties forms the backbone.The aim of this study is to predict sooting tendency of fuel molecules for spark-ignition engine applications in terms of their yield sooting indexes(YSI).In conjunction with our previously developed database for gasoline compounds,which includes the physical and chemical properties,such as octane numbers,laminar burning velocity,and heat of vaporization,for more than 600 species,the identification of fuel replacements and additives can thus be performed jointly with respect to both their potential thermal efficiency benefits and emission formation characteristics in spark-ignition engines.For this purpose,a quantitative structure-property relationship(QSPR)model is developed to predict the YSI of fuel species by using artificial neural network(ANN)techniques with 21 well-selected functional group descriptors as input features.The model is trained and cross-validated with the YSI database reported by Yale University.It is then applied to estimate the YSI values of fuels available in the database for gasoline compounds and to explore the sensitivity of fuel’s sooting tendency on molecular groups.In addition,the correlation of YSI values with other properties available in the gasoline fuel database is examined to gain insights into the dependence of these properties.Finally,a selection of potential gasoline blending components is carried out exemplarily,by taking the fuels’potential benefits in thermal engine efficiency and their soot formation characteristics jointly into account in terms of efficiency merit function and YSI,respectively.

An assessment of surrogate fuel using Bayesian multiple kernel learning model in sight of sooting tendency

An integrated and systematic database of sooting tendency with more than 190 kinds of fuels was obtained through a series of experimental investigations. The laser-induced incandescence (LII) method was used to acquire the 2D distribution of soot volume fraction, and an apparatus-independent yield sooting index (YSI) was experimentally obtained. Based on the database, a novel predicting model of YSI values for surrogate fuels was proposed with the application of a machine learning method, named the Bayesian multiple kernel learning (BMKL) model. A high correlation coefficient (0.986) between measured YSIs and predicted values with the BMKL model was obtained, indicating that the BMKL model had a reliable and accurate predictive capacity for YSI values of surrogate fuels. The BMKL model provides an accurate and low-cost approach to assess surrogate performances of diesel, jet fuel, and biodiesel in terms of sooting tendency. Particularly, this model is one of the first attempts to predict the sooting tendencies of surrogate fuels that concurrently contain hydrocarbon and oxygenated components and shows a satisfying matching level. During surrogate formulation, the BMKL model can be used to shrink the surrogate candidate list in terms of sooting tendency and ensure the optimal surrogate has a satisfying matching level of soot behaviors. Due to the high accuracy and resolution of YSI prediction, the BMKL model is also capable of providing distinguishing information of sooting tendency for surrogate design.

拉萨市夏季含碳气溶胶的浓度水平与组成特征研究

利用颗粒物采样器采集拉萨市夏季(2021年8月30日~2021年9月23日)大气细颗粒物(PM_(2.5))样品,并对不同含碳气溶胶组分进行测定和探讨。根据碳组分挥发性的强弱,将有机碳(OC)分为易挥发组分(HOC)、中等挥发组分(MOC)和难挥发组分(LOC),元素碳(EC)分为焦碳(char)和烟炱(soot)。结果显示,拉萨市夏季大气环境白天OC和EC的平均浓度分别为4.39±0.98μg/m^(3)和1.09±0.69μg/m^(3),夜晚OC和EC的平均浓度分别为4.39±1.43μg/m^(3)和1.17±0.57μg/m^(3)。系统比较OC/EC和char/soot源示踪指标在源辨识上的差异,发现char/soot值比OC/EC值可以更准确地识别关键排放源对含碳气溶胶的影响,说明char/soot值是一个可靠的源解析工具。本研究测定的char/soot平均值为0.20,符合机动车尾气污染特征,远小于生物质燃烧和煤炭燃烧特征值,说明拉萨夏季大气环境主要受机动车尾气排放影响。LOC是拉萨夏季含碳气溶胶最丰富的OC组分,在所有碳组分中的占比为47.7%,其次为MOC(18.2%)和HOC(10.8%)。不同碳组分之间的相关性分析表明,HOC主要通过大气化学反应生成,未来可成为评估二次有机气溶胶的一个潜在指标。

Facile preparation and efficient MnxCoy porous nanosheets for the sustainable catalytic process of soot

The pursuit of high-performance is worth considerable effort in catalysis for energy efficiency and environmental sustainability. To develop redox catalysts with superior performance for soot combustion, a series of Mn_(x)Co_(y) oxides were synthesized using MgO template substitution.This method greatly improves the preparation and catalytic efficiency and is more in line with the current theme of green catalysts and sustainable development. The resulting Mn_(1)Co_(2.3) has a strong activation capability of gaseous oxygen due to a high concentration of Co^(3+) and Mn^(3+). The Mn doping enhanced the intrinsic activity by prompting oxygen vacancy formation and gaseous oxygen adsorption. The nanosheet morphology with abundant mesoporous significantly increased the solid–solid contact efficiency and improved the adsorption capability of gaseous reactants. The novel design of Mn_(1)Co_(2.3)oxide enhanced its catalytic performance through a synergistic effect of Mn doping and the porous nanosheet morphology, showing significant potential for the preparation of high-performance soot combustion catalysts.

Experimental Study on Gas Flow Uniformity in a Diesel Particulate Filter Carrier

A Diesel Particulate Filter(DPF)is a critical device for diesel engine exhaust products treatment.When using active-regeneration purification methods,on the one hand,a spatially irregular gas flow can produce relatively high local temperatures,potentially resulting in damage to the carrier;On the other hand,the internal temperature field can also undergo significant changes contributing to increase this risk.This study explores the gas flow uniformity in a DPF carrier and the related temperature behavior under drop-to-idle(DTI)condition by means of bench tests.It is shown that the considered silicon carbide carrier exhibits good flow uniformity,with a temperature deviation of no more than 2%with respect to the same radius measurement point at the outlet during the regeneration stage.In the DTI test,the temperature is relatively high within r/2 near the outlet end,where the maximum temperature peak occurs,and the maximum radial temperature gradient is located between r/2 and the edge.Both these quantities grow as the soot load increases,thereby making the risk of carrier burnout greater.Finally,it is shown that the soot load limit of the silicon carbide DPF can be extended to 11 g/L,which reduces the frequency of active regeneration by approximately 40%compared to a cordierite DPF.

Evaluation of the Oxidation Reactivity and Behavior of Exhaust Soot Particles from Diesel Engines with Different Emission Levels

The aim of this study was to investigate the oxidation reactivity and behavior of exhaust particulate matter(PM)from diesel engines.PM samples from two diesel engines(1K,CY4102)with different emission levels were collected by a thermophoretic system and a quartz filter.The oxidation reactivity,oxidation behaviors,and physicochemical properties of the PM samples were analyzed using thermogravimetric analysis(TGA),high-resolution transmission electron microscopy(HRTEM),Fourier-transform infrared spectrometry(FTIR),and Raman spectroscopy.The results showed that there was a great difference in the oxidation reactivity of soot particles emitted by the two different diesel engines.A qualitative analysis of the factors influencing oxidation reactivity showed that the nanostructure,degree of graphitization,and relative concentration of aliphatic C—H functional groups were the most important factors,whereas no significant correlation was found between the primary particle size and activation energy of the diesel soot.Based on the oxidation behavior analysis,the diesel soot particles exhibited both internal and surface oxidation modes during the oxidation process.Surface oxidation was dominant during the initial stage,and as oxidation progressed,the mode gradually changed to internal oxidation.Internal oxidation mode of soot particles from the 1K engine was significantly higher than that of CY4102.

Soot size distribution in lightly sooting premixed flames of benzene and toluene

The evolution of particle size distribution function(PSDF)of soot in premixed flames of benzene and toluene was studied on a burner stabilized stagnation(BSS)flame platform.The cold gas velocities were changed to hold the maximum flame temperatures of different flames approximately constant.The PSDFs of all the test flames exhibited a bimodal distribution,i.e.,a small-size nucleation mode and a large-size accumulation mode.It was observed that soot nucleation and particle growth in the benzene flame were stronger than those in the toluene flame at short residence times.At longer residence times,the PSDFs of the two flames were similar,and the toluene flame showed a larger particle size distribution range and a higher particle volume fraction than the benzene flame.

Investigation of Detailed Kinetic Scheme Performance on Modelling of Turbulent Non-Premixed Sooting Flames

This paper presents the results of an application of a first-order conditional moment closure （CMC） approach coupled with a semi-empirical soot model to investigate the effect of various detailed combustion chemistry schemes on soot formation and destruction in turbulent non-premixed flames. A two-equation soot model repre- senting soot particle nucleation, growth, coagulation and oxidation, was incorporated into the CMC model. The turbulent flow-field of both flames is described using the Favre-averaged fluid-flow equations, applying a stan- dard k-c turbulence model. A number of five reaction kinetic mechanisms having 50 - 100 species and 200 - 1000 elementary reactions called ABF, Miller-Bowman, GRI-Mech3.0, Warnatz, and Qin were employed to study the effect of combustion chemistry schemes on soot predictions. The results showed that of various kinetic schemes being studied, each yields similar accuracy in temperature prediction when compared with experimental data. With respect to soot prediction, the kinetic scheme containing benzene elementary reactions tends to result in a better prediction on soot concentrations in comparison to those contain no benzene elementary reactions. Among five kinetic mechanisms being studied, the Qin combustion scheme mechanism turned to yield the best prediction on both flame temperature and soot levels.

Cool Sooting Flames of Hydrocarbons

This paper presents the study of polycyclic aromatic hydrocarbons (PAH) and paramagnetism of soot particles sampled from cool sooting flames of methane and propane in a separately-heated two-sectional reactor under atmospheric pressure at the reactor temperatures of 670-1170 K. The temperature profiles of the flames were studied. The sampling was carred out with a quarts sampler and the samples were frozen with liquid nitrogen. A number of polyaromatic hydrocarbons such as pyrene. fluoranthene, coronene, anthanthrene, 1,1 2-benzperylene, were identified by spectroscopic methods in the extract of soot. The processes of soot formation at methane- oxygen mixture combustion in the electric field with applied potential changed from 0 to 2,2 kV at different polarity of electrodes have been investigated. It has been stated that at the electrical field application, an increase in soot particle sizes and soot yield occurs; besides, at the application of the field, speeding up the positively charged particles, the interplanar distance decreases. On the basis of investigation of soot particles paramagnetism, it was shown that initially soot particles have high carcinogetic activity and pollute the environment owing to a rapid decrease of the number of these radical centers. The reduction of the radical concentration is connected with radical recombination on soot.

满足非四排放标准的农用柴油机试验研究

随着非四排放法规的实施,对农用柴油机排放提出了新的要求。研究了采用EGR技术路线的某农用柴油机喷油器安装深度、EGR对发动机排放的影响以及在等NOx排放条件下喷油提前角和EGR共同作用对燃油经济性、碳烟(Soot)等的影响。通过研究发现:在非道路瞬态排放测试循环(non-road transient cycle, NRTC)下,喷油器垫片在1 mm厚度时发动机的经济性和排放最优;与发动机在低负荷工况下运行相比较,发动机在中高负荷运行时,EGR率每升高1%,发动机排气温度降低40%,NOx的排放降低3%;在保证NOx排放满足法规要求的前提下,可以适当提高EGR率和延迟喷油提前角,低负荷时发动机EGR率通常设定在7.5%~10%,喷油提前角在4°~6°,中高负荷时EGR率通常设定在10.5%~12%,喷油提前角在8°~11°;发动机排气温度在420~460℃,满足发动机排气系统要求。

定容弹内柴油/丁醇混合燃料燃烧特性研究

In this paper,the spray and combustion characteristics of diesel/butanol-blended fuels were studied within a high-temperature and high-pressure constant volume chamber equipped with a single-hole injector.Two blends with 80%diesel/20%butanol and 60%diesel/40%butanol mixed by volume were tested in this study.The pure diesel B0 was also tested here as a reference.The spray penetration,flame lift-off length,and soot optical thickness were obtained through high-speed schlieren imaging,OH*chemiluminescence,and diffused back-illumination extinction imaging technique,respectively.The thermogravimetric curves of different fuels were obtained through a thermogravimetric analyzer.The results showed that butanol/diesel blends presented a longer ignition delay(ID)and flame lift-off length compared with pure diesel,and such finding was mainly caused by the lower cetane number and higher latent heat of vaporization of n-butanol.With the increase in the n-butanol ratio,soot production in the combustion process decreased significantly.Given the shorter ID period,the soot distribution of pure diesel reached a steady state earlier than the blends.

柴油机燃烧室结构对混合气形成及燃烧特性的影响

针对已开发的2.0L型高压共轨直喷柴油机燃烧室,利用FIRE软件建立其仿真计算模型,仿真分析了不同燃烧室结构对缸内速度场以及湍流特性的影响,并引入与混合气形成和燃烧过程密切相关的无量纲参数Da数,研究了燃烧室结构形状对混合气形成机理、燃烧过程以及NO和SOOT生成率的影响。结果表明:通过合理设计燃烧室的结构形状可以有效组织混合气的形成和燃烧过程,从而抑制NO和SOOT的生成。

发动机排气系统及尾喷流的流场和红外特征数值模拟

建立了发动机排气系统及尾喷流的内外流一体化流场数值模拟计算模型，得到了发动机排气系统及尾喷流的流场．然后采用辐射传递方程（RTE）积分法研究了发动机排气系统及尾喷流的红外辐射特征，开发了相应的红外辐射特征计算源程序．程序可以计算加力和非加力两种状态下的红外光谱辐射特征，在加力状态下主要增加考虑了soot粒子的光谱吸收与发射．气体介质考虑了水蒸气、二氧化碳、一氧化碳和一氧化氮的红外光谱吸收与发射．最后给出了在光谱3～5μm范围内，某发动机在高空飞行时其排气系统及尾喷流在加力和非加力状态下的红外辐射特征的模拟结果．

Ce/Zr系列催化剂上碳颗粒物燃烧行为

分别在TG和TPO上考察了CeO2,ZrO2及不同Ce/Zr比的CexZr1-xO2固溶体催化剂上soot的燃烧性能,同时考察了反应气氛对活性的影响.结果表明:Ce基催化剂能明显降低soot的起燃温度,Ce/Zr比的不同导致CexZr1-xO2催化剂性能的差异.反应的速度控制步骤随O2浓度的不同而改变;H2O对Ce0.5Zr0.5O2上soot的氧化活性基本没有影响;由于NO氧化产生的NO2具有更强的的氧化能力,因此NO对soot的燃烧具有促进作用,起燃温度降低了30℃.催化剂上的β氧种参与了soot燃烧过程.

Soot的Java程序控制流分析及图形化输出

Soot是一个Java编译优化框架,可以利用它实现Java字节码程序的数据流分析和控制流分析。在深入分析Soot控制流生成机制的基础上,详细叙述了利用Soot分析Java类的控制流并生成其控制流图的方法和过程,同时提出了将Soot生成的抽象的控制流图进行图形化输出的方法。

Catalytic performance of Ag/Co-Ce composite oxides during soot combustion in O_2 and NO_x:Insights into the effects of silver

The composite oxides xAg/Co_（0.93）Ce_（0.07）（x=Ag/（Co＋Ce） molar ratio）,intended for use as high performance catalytic materials,were successfully prepared via citric acid complexation.The effects of silver on the performance of these substances during soot combustion were subsequently investigated.Under O_2,the 0.3Ag/Co_（0.93）Ce_（0.07） catalyst resulted in the lowest ignition temperature,T_（10）,of197 ℃,while the minimum light-off temperature was obtained from both 0.2Ag/Co_（0.93）Ce_（0.07） and0.3Ag/Co_（0.93）Ce_（0.07） in the NO_x atmosphere.These materials were also characterized by various techniques,including H_2,soot and NO_x temperature programmed reduction,X-ray diffraction,and electron paramagnetic resonance,Raman,X-ray photoelectron,and Fourier transform infrared spectroscopic analyses.The results demonstrated that silver significantly alters the catalytic behavior under both O_2 and NO_x,even though the lattice structure of the mixed oxide is not affected.Surface silver oxides generated under the O_2 atmosphere favor soot combustion by participating in the redox cycles between soot and the silver oxide,whereas the AgNO_3 that forms in a NO_x-rich atmosphere facilitates soot abatement at a lower temperature.The inferior activity of AgNO_3 relative to that of Ag_2O results in the different catalytic performance in the presence of NO_x or O_2.

基于对象跟踪的J2EE程序动态污点分析方法

Web程序的安全威胁主要是由外部输入未验证引发的安全漏洞,如数据库注入漏洞和跨站脚本漏洞,动态污点分析可有效定位此类漏洞。提出一种基于对象跟踪的动态分析方法,与现有动态方法跟踪字符和字符串对象不同,追踪所有可能被污染的Java对象。方法应用对象哈希值表示污点对象,定义方法节点和方法坐标记录污点传播时的程序位置,支持污点传播路径追踪,针对Java流对象装饰模式提出流家族污点传播分析。方法设计一种语言规范对Java类库中污点传播相关的方法集合以及用户自定义方法建模,按照污点引入、传播、验证和使用,对方法集分类后设计和形式化定义各类方法的污点传播语义。在SOOT平台实现对J2EE源码或字节码插桩框架,使用静态分析计算可达方法集以减少插桩规模,应用原型系统对真实网站的测试结果表明该方法可有效发现注入漏洞。

基于Soot控制流图的函数调用路径分析

每个应用系统中存在多条基于函数的调用路径,这些路径的准确提取对于程序的理解、测试和维护起着重要的作用。文章利用开源的Java程序编译优化框架-Soot,对java程序的数据流及控制流进行分析,提取函数间关联信息写入中间文件,并对文件中的数据进行了分析,阐述了程序函数调用路径生成的流程及Soot的优点。最后通过实验验证,相比其他程序调用分析软件,基于Soot调用路径分析的软件测试工具-JSFUNP,对程序调用路径的分析更加准确、高效。

燃烧室缩口位置对重型柴油机影响的数值模拟研究

柴油机的燃烧过程主要受控于燃油空气混合速率,为了进一步改善重型柴油机的燃烧和排放,在合理提高压缩比的基础上,设计了5种新型燃烧室,并基于三维计算流体力学软件CONVERGE,通过数值模拟的方法,研究了燃烧室内缩口位置,包括缩口直径和深度对缸内混合、燃烧和排放过程的影响。研究结果表明:采用合理的缩口位置,可以明显提高缸内的涡流比,促进对燃油的利用,加快油气混合过程。与原机基础燃烧室相比,热效率可提高约2%。

柴油机喷孔夹角对燃烧过程的影响

本文建立了某四缸增压直喷柴油机的三维模型,研究喷孔夹角α对燃烧过程的影响,分别选取α=140°、α=150°和α=160°三种喷孔夹角模拟计算。研究结果表明:喷孔夹角α对燃油的空间分布影响很大。喷孔夹角α=140°时,过多燃油进入燃烧室底部,略微提升动力性的同时造成NOx和Soot的排放升高;喷孔夹角α=160°时,会造成大量燃油进入余隙容积,动力性下降,NOx和Soot的减少。综合考虑各种因素,本文选取的最佳喷孔夹角α=150°。