火花点火发动机未燃碳氢预测模型

本文建立了火花点火发动机顶岸间隙、缸套壁面润滑油膜和缸内壁面积碳层处未燃碳氢生成和释放过程的预测模型以及缸内、排气管中未燃碳氢氧化模型，并利用模型预测了发动机排气未燃碳氢量。计算结果表明，本模型的预测结果能较好地与实验结果吻合。     

冷起动和怠速时火花点火发动机缸内未燃碳氢生成过程的研究

为了更好地弄清起动和怠速时发动机缸内未燃碳氢生成过程以及顶岸间隙和油膜对缸内未燃碳氢的影响，测量了起动和怠速过程活塞顶岸壁面和缸套壁面温度。根据测量结果，预测了起动过程顶岸间隙和壁面油膜处未燃碳氢生成量，发现顶岸和缸套壁温在发动机起动后（１５０～２００）ｓ时达到其稳定状态。起动后顶岸间隙和油膜处生成的碳氢量分别降低至其初始值的２／５和３／４。研究认为：热容量小的活塞能迅速减小顶岸容积和提高其内混合气温度，从而可减少起动期间缸内生成的总未燃碳氢量。     

火花点火式发动机未燃碳氢形成机理及影响因素的研究

详细阐述了火花点火苣了缸内未燃碳氢排放的主要生成源和形成机理，并测量了不同运转参数火花点火式发动机的碳氢排放。     

点燃式发动机燃烧室沉积物的研究综述

本文系统综述了点燃式发动机燃烧室表面沉积物的形成机理、组成以及沉积物对燃料等烷值的要求，沉积物对燃油经济性和未燃碳氢排放的影响，指出了燃烧室表面沉积物对发动机性能的有利于与不利方面。     

火花点火发动机冷启动和暖机过程未燃碳氢排放及控制

火花点火发动机冷启动和暖机瞬态过程中未燃碳氢的排放占整个测试循环总排放量的60％～80％,因而其控制越来越受到广泛的重视。从缸内燃烧过程组织和排气后处理两个方面,阐述近年来国内外火花点火发动机在降低该过程未燃碳氢排放方面的研究成果及存在的问题,并且探讨了寻求新的降低未燃碳氢的方法和技术。     

燃烧室沉积物对火花点火发动机碳氢排放的影响

为了弄清燃烧室沉积物对发动机排气碳氢的影响，使用一台实验用单缸火花点火发动机来形成燃烧室沉积物。在燃烧室沉积物存在的条件下，开展了不同工况下碳氢排放的实验研究，分析了燃烧室沉积物对发动机动力性和燃油经济性的影响。实验结果表明：当发动机运行一段时间后，其燃烧室表面沉积物将达到一稳定平衡厚度，此时排气碳氢浓度随转速的升高、冷却水温的增加以及点火推迟而降低。在本实验各类工况下，沉积物的存在将使发动机排气碳氢浓度增加２０％～３０％。同时沉积物的存在将使发动机的功率和燃油经济性有所提高（功率增加１．１％～１．６％，燃油经济性提高２．７％～３．０％），此现象被认为主要是因沉积物的隔热作用，而不是压缩比的增加所致。     

直喷式柴油机NOx生成及缸内分布研究

建立了柴油机缸内燃烧模型和NOx生成模型,结合实验,对柴油机工作过程以及NOx排放进行了研究.研究结果表明,燃烧初期NOx的生成主要集中在油束外围火焰前锋附近,随着燃烧的扩散NOx的生成主要集中在燃烧室缩口处及中央持续高温、富氧部位;由于缸内未燃碳氢的还原作用,NOx生成总量随曲轴转角增加先增大后减小,且随着缸内气流运动,使NOx在燃烧室内分布趋于均衡.     

运转参数对火花点火发动机未燃碳氢排放影响的实验研究

开展了转速、混合气浓度、点火提前角、节气门开度、润滑油温度对火花点火发动机排气末燃碳氢影响的实验研究，并分析了运转因素对碳氢排放的影响。实验结果表明，提高发动机转速，燃用较稀混合气，适当推迟点火和提高润滑油温度，均可降低发动机排气末燃碳氢浓度。     

火花点火发动机燃用含氧燃料对冷起动和怠速时未燃碳氢排放影响？…

本文以在汽油中掺混不同体积百分比乙醇形成“模型”燃油的方法，研究了含氧燃料对火花点火发动机冷起动和怠速时未燃碳氢排放的影响。实验结果表明：燃油的挥发性和汽化潜热的大小对这两种工况的未燃碳氢排放有很大的影响。掺混１５％的乙醇能有效降低冷起动时的未燃碳氢排放。     

点火发动机碳氢排放的数值模拟

为了弄清发动机气缸内未燃碳氢uHC的主要生成源和它们在废气排放中所占有的比例 ,有针对性地采取措施降低缸内uHC生成量 ,详细的分析了uHC排放生成机理 ;结合前人的研究成果 ,根据燃烧过程中所体现的物理学知识 ,建立了包括HC逃离正常燃烧、缸内氧化、缸内残留和排气管氧化等在内的一系列模型。通过此模型可非常清楚的了解发动机运行时缸内uHC的具体情况 ,并能定量分析各参数对HC排放的影响     

降低汽油机起动及暖机过程中HC排放的探讨

根据实测的催化器入口、出口 HC排放浓度及排气管不同位置的温度 ,结合示功图对电喷汽油机冷起动时 HC排放量在台架上进行了模拟分析 ,将起动过程以节气门突开为界划分为 3个阶段 ,其中HC的主要排放量发生在开始起动到节气门开这一段时间内。通过控制点火提前角使缸内发生不完全燃烧 ,将燃烧延续到排气管内 ,即可降低 HC排放量 ,也有助于加速催化器起燃。     

Characterization of flame front propagation during early and late combustion for methane-hydrogen fueling of an optically accessible SI engine

In recent years, hybrid and fully electric vehicles have received significant consideration since they represent an alternative sustainable transport to the conventional fossil-fuel powered vehicles. However, a worldwide implementation of this alternative propulsion can induce large and undesirable peak demands in distributed power systems. In this context, natural gas spark ignition engines are a promising form of technology to supply part of the energy demand. The main limitations related to low laminar flame propagation speed and poor lean-burn capabilities of natural gas can be overcome by using hydrogen as additional fuel. In this paper, a comparison was carried out between methane and different CH₄/H₂ mixtures. Specifically, low levels of hydrogen addition were used (5%, 10%, 20% volumetric basis) in stoichiometric and lean burn conditions. The measurements were carried out in an optically accessible single-cylinder port fuel injection spark ignition engine. Optical measurements were performed to analyze the combustion process with high spatial and temporal resolution. In particular, optical techniques based on 2D-digital imaging with two different combustion chamber views were used. Macroscopic (global) and microscopic (local) post-processing tools were implemented to provide a detailed analysis of the flame front propagation process. Moreover, an in-depth analysis was performed to study the flame penetration in the piston top-land crevice. Exhaust gas emissions were also characterized and linked with thermodynamic and optical data. In order to evaluate the combustion process in similar fluid-dynamic conditions, all measurements were performed under steady-state conditions at fixed engine speed, load and spark advance. All the results highlight fast combustion promotion due to the hydrogen addition. In addition, hydrogen reduces the preferential propagation of the flame in a certain direction and increases the flame front wrinkling. Flame propagation in the top-land crevice region was measured for methane and its blends with hydrogen, which represents an original contribution to the literature. An inverse trend was seen between flame penetration in the crevice and unburned hydrocarbon emissions. Lastly, tests in lean conditions demonstrate the potential to decrease nitrogen oxides emissions when methane and methane-hydrogen blends are used.     

The effect of hydrogen addition on combustion and emission characteristics of an n-heptane fuelled HCCI engine

The mechanisms of the influence of hydrogen enrichment on the combustion and emission characteristics of an n-heptane fuelled homogeneous charge compression ignition (HCCI) engine was numerically investigated using a multi-zone model. The model calculation successfully captured the most available experimental data. The results show that hydrogen addition retards combustion phasing of an n-heptane fuelled HCCI engine due to the dilution and chemical effects, with the dilution effect being more significant. It is because of the chemical effect that combustion duration is reduced at a constant compression ratio if an appropriate amount of hydrogen is added. As a result of retarded combustion phasing and reduced combustion duration, hydrogen addition increases indicated thermal efficiency at a constant combustion phasing. Hydrogen addition reduces indicated specific unburned hydrocarbon emissions, but slightly increases normalized unburned hydrocarbon emissions that are defined as the emissions per unit burned n-heptane mass. The increase in normalized unburned hydrocarbon emissions is caused by the presence of more remaining hydrocarbons that compete with hydrogen for some key radicals during high temperature combustion stage. At a given hydrogen addition level, N₂O emissions increases with overly retarding combustion phasing, but hydrogen addition moderates this increase in N₂O emissions.     

An experimental investigation of fuel-injection-pressure and engine-speed effects on the performance and emission characteristics of a divided-chamber diesel engine

An experimental study is conducted to investigate the fuel-injection-pressure and engine-speed effects on the performance and exhaust emissions of a naturally aspirated four-stroke indirect-injection (IDI) diesel engine with a swirl combustion chamber. The influence of the injection pressure and the engine rotational speed on fuel consumption, exhaust-gas temperature, exhaust smokiness and exhaust-gas emissions (nitrogen oxides and unburned hydrocarbons) is examined, following a detailed experimental investigation. Empirical easy-to-use correlations are produced, expressing the variation of the various parameters with injection pressure, by applying a regression analysis on the curves fitting the relevant experimental data. Theoretical aspects of diesel fuel spray progress (atomization, evaporation and mixing), combustion and emissions formation are used for the interpretation of the observed engine behaviour.     

点燃式发动机燃烧过程模拟分析及临界爆震预测

建立了火花点火式发动机的双区燃烧模型，其中包括化学动力学模型和湍流火焰燃烧模型．改进的双区燃烧模型中，区别于以往的绝热模型，考虑了已燃区向未燃区的传热．该模型通过模拟火花点火式发动机的燃烧过程，尝试性地进行了临界爆震预测和爆震分析工作．模型的计算结果与实验结果吻合得较好，验证了该模型分析的可行性．     

Hydrogen–natural gas blends fuelling passenger car engines: Combustion,emissions and well-to-wheels assessment

In this study, a state of the art passenger car natural gas engine was optimized for hydrogen–natural gas mixtures and high exhaust gas recirculation (EGR) rates in the major part of the engine map. The investigations involved stoichiometric combustion. With optimal combinations of spark timing and EGR rate, the achievements are efficiency increase with substantially lower engine-out NO_x while total unburned hydrocarbons or CO-engine-out emissions are only modestly affected. The efficiency is increased by 3% in the low load and by more than 5% in the medium-load domain. Increasing hydrogen content of the fuel accelerates combustion leading to the efficiency improvements. Combustion analysis showed that the increasing burning rates mainly affected the initial combustion phase (duration for 5% mass-fraction burned). Nevertheless, increase of the hydrogen fraction in the fuel over a certain threshold did not result in any efficiency increase in the medium loads. Loss analysis identified high wall heat losses as the main reason. Dedicated combustion chamber design may be able to avoid these losses and lead to additional efficiency benefits. Well-to-wheel analysis revealed paths for the production of the fuel blends still having overall energy requirements slightly higher than a diesel benchmark vehicle but reducing by 7% overall green house gas emissions.     

进气道和燃烧室形状对火花点火发动机燃烧过程影响的研究

本文针对ＣＡ６１０２发动机燃烧慢、循环变动率偏大等问题，对进气道和燃烧室进行了改进。研究了不同进气道和燃烧结构（六种匹配方案）对燃烧过程和性能的影响，发现涡流比和性能之间无单调的相关关系，与燃烧期之间存在二次抛物线型的逆变相关关系，ＣＡ６１０２发动机合适的涡流比在０．９左右，燃烧室设计因素中火花塞的位置对燃烧过程和性能影响最大，火花塞靠近中心布置方案同原机相比，最低燃油消耗率降低了４．１％，最大扭     

采用离子电流分析法实现发动机爆震信号的正确检测

本描述了了种直接利用火花塞电极作为传感器检测发动机爆震的方法。作在章中详细分析及讨论了离子电流的产生机理及影响其测量的因素，并利用这一方法在发动机做了大量的试验研究，获得了宝贵的第一手资料。为了获得正确的信号检测，作在火花塞电极上加一定的直汉电压、使其能灵敏的感受燃气密度的变化。     

火花点火发动机准维湍流卷吸燃烧模型的适用性研究（二）

本文利用作者提出的火花点火发动机准维湍流卷吸燃烧模型，对压缩比为１０和１２的火球形燃烧室以及压缩比为１０的碗形燃烧室变工况进行了计算，将计算得到的示功图、质量燃烧率等与实验值进行了对比对分析。结果表明，合理选取与燃烧室结构相对应的四个经验常数，准维湍流卷吸燃烧模型完全适用于火花点火发动机变工况及不同燃烧室结构工作过程的计算，能够正确反映火花点火发动机结构参数和运转参数对燃烧过程的影响。