柴油机燃用二元煤基燃料的燃烧和碳烟排放特性

为缓解石油短缺现状并降低柴油机有害物排放,采用二元煤基燃料在1115型单缸柴油机上进行了甲醇均质混合气F-T柴油引燃燃烧试验,对比分析了不同F-T柴油供油时刻和引燃量对燃烧和碳烟排放的影响。研究结果表明:随着供油时刻由16°CA BTDC提前至24°CA BTDC,碳烟排放最高降低27%,滞燃期变长,燃烧持续期先减小后增大,放热率中心先靠近后远离上止点;随着引燃量的增加,放热率中心缓慢接近上止点,滞燃期和燃烧持续期变短,中低负荷下,碳烟排放趋于平稳,高负荷下,碳烟排放逐渐变大。通过调整F-T柴油的供油时刻和引燃量可以对燃烧和碳烟排放进行匹配优化。     

柴油引燃乙醇均质混合气的二元燃料燃烧特性

在一台单缸增压中冷试验柴油发动机上,研究了不同转速和负荷下乙醇在进气道形成均质混合气,然后在气缸内由柴油引燃的二元燃料燃烧特性.结果发现:采用柴油引燃乙醇混合气的二元燃料燃烧方式,在高负荷时预混燃烧量明显增加,扩散燃烧大幅度减少;在低负荷以及整个低速工况下都实现了单峰快速放热.另外,采用这种燃烧模式能够降低绝大部分工况的最高燃烧温度,并缩短高温持续时间.研究还发现,这种二元燃料燃烧大部分工况的最高爆发压力和压力升高率都比原机高,燃烧持续期短于原机,在中高负荷时能大幅度地减少柴油消耗并提高发动机热效率.与原柴油机相比,采用二元燃料燃烧的指示热效率最高提高了11.09%.     

丁醇均质混合气柴油引燃燃烧与排放特性研究

在一台高压共轨柴油机上对丁醇均质混合气柴油引燃(homogeneous charge induced ignition,HCII)的燃烧特性、排放特性和热效率进行了研究。研究结果表明:随着进气道预混丁醇比例的增加,NO和碳烟排放同时显著降低,结合废气再循环技术,丁醇比例超过0.7后可以实现低温燃烧,获得极低的NO和碳烟排放;随着丁醇比例的增加,滞燃期增长,燃烧持续期缩短,最大压力升高率明显降低;随着丁醇比例的增加,指示热效率达到甚至好于原柴油机的水平,提高了丁醇燃料的能量利用率。随着着火相位推后,丁醇/柴油HCII模式的NO和碳烟排放始终未出现折中关系。     

DME/柴油混合燃料HCCI燃烧与排放特性的试验研究

在单缸柴油机上采用轴针式喷嘴进气道燃油喷射方式,开展了二甲醚(DME)/柴油混合燃料预混均质压燃(HCCI)燃烧及其排放特性的试验研究,探讨了喷油嘴启喷压力、进气温度以及进气掺混不同比例CO2对混合气制备率和发动机性能的影响.结果表明:低沸点液相DME在进气道喷射过程中所具有的闪急沸腾效应,可有效强化柴油/DME混合燃料的雾化与蒸发,减少燃油撞击壁面而出现的进气歧管壁湿现象,从而改善柴油HCCI发动机均质混合气的形成与燃烧,拓宽发动机的运行工况范围.进气掺混0~30%的CO2能使HCCI发动机的正常工作范围从0.32MPa提高到0.5MPa,实现高负荷工况下同时降低NOx和碳烟的排放,但CO和未燃HC排放有所增加.     

基于LaGrange-SUMT方法的全电控柴油引燃天然气发动机MAP优化标定技术

利用非线性规划理论，采用LaGrange-SUMT方法建立了电控发动机全工况范围内多变量、多目标的优化模型，并在全电控柴油引燃天然气发动机上进行了应用。试验结果证明，该方法可以减少优化参数的试验量，在较少的试验量基础上获得最优控制MAP。发动机的NOχ、碳烟排放明显优于欧洲Ⅱ排放标准，经济性与原柴油机相当。     

进气预混乙醇对柴油机碳烟与NOx排放的影响参数研究

在一台自然吸气式直喷柴油机上，按照组合燃烧的要求．全面、系统地研究了不同喷嘴孔径、不同供油定时、不同喷醇的始点对发动机碳烟、NOx排放以及经济性的影响．研究结果表明，为了获得更低的碳烟和NOx排放以及优越的能量经济性，与燃用纯柴油的发动机相比，采用进气预混乙醇的组合燃烧发动机的柴油供油定时可以稍迟或保持不变，燃油喷嘴的孔径应适当减小，预混乙醇的发动机负荷起点应适中．     

甲醇均质混合气F-T柴油引燃发动机排放特性研究

针对F-T柴油和煤基甲醇在发动机中燃烧时的各自优势,在一台CY25TQ型柴油机上,研究了甲醇占能比及F-T柴油喷油时刻对甲醇均质混合气F-T柴油引燃燃烧方式下发动机排放特性的影响。试验结果表明:随甲醇占能比增加,碳烟和NOx排放明显下降,而THC,HCHO,CO排放上升;F-T柴油喷油时刻提前,CO和NOx排放上升,而碳烟,HCHO,THC排放呈先降低后升高趋势。     

均质混合气压燃汽油机燃烧特性和碳烟的生成

作者将一台单缸四冲程试验用汽油机改造成均质混合气压燃点火发动机。在大量试验的基础上,证明柴油均质混合气压燃点火在技术上可以实现。利用该燃烧模型进一步研究柴油机的燃烧和碳烟生成中的一些问题:如点火延迟时间与混合气浓度的关系,排气中的碳烟浓度与混合气油气当量比的关系。     

车用增压二甲醚发动机燃烧和排放特性的试验研究

在一台D6114ZLQB柴油机上进行了燃用二甲醚（DME）的燃烧和排放特性的试验研究。研究结果表明：二甲醚发动机的外特性转矩特别是低速转矩比柴油机高;二甲醚喷油延迟角比柴油大,最高爆发压力、最大压力升高率、燃烧噪声比柴油低;二甲醚扩散燃烧速率比柴油快,燃烧持续期比柴油短。和柴油机相比,二甲醚发动机的NO,排放显著下降,其欧洲稳态测试循环（ESC的NOx排放比原柴油机降低41．6％;二甲醚发动机在全工况范围内碳烟排放为零。     

柴油机双燃料复合燃烧的最佳运行范围研究

通过在进气过程中加入容易汽化的燃料与空气形成一定浓度的预混合气进入燃烧室，利用压燃喷入的柴油形成着火源向整个燃烧室传播，以完成燃烧过程的部分预混双燃料燃烧模式可能是减少柴油机碳烟排放的有效措施。而在该燃烧方案中过低的预混浓度可因火焰无法传播到整个燃烧室而增加HC排放，在保持柴油机压缩比的条件下，过高的预混合气浓度可能使燃烧最高温度上升而对NOx排放不利，甚至在柴油喷入前压燃预混合气而发生爆震。燃烧模式的改变对CO排放水平的影响也可能不利；因此，确定双燃料的最佳运行范围是建立双燃料过程控制的基础，介绍了以液化气和柴油形成双燃料系统时的最佳运行范围的初步研究结果。     

不同喷醇方式对柴油机实行柴油/醇组合燃烧时性能的影响

提出了柴油／甲醇的组合燃烧方式。在一台高速非增压直喷柴油机上采用组合燃烧方式进行了柴油机燃用甲醇的试验，对比了不同喷醇方式(单点喷醇和多点喷醇)对柴油机实行组合燃烧时性能的影响。试验结果表明，采用组合燃烧方式的柴油机燃用甲醇时，多点喷醇方式获得的动力性、经济性以及排放品质等综合性能要优于单点喷醇方式。     

直喷式柴油机燃用F-T柴油时的性能与排放

煤通过Fischer-Tropsch（F-T）合成可以获得十六烷值高、硫和芳香烃含量极低的F-T柴油.在一台未作改动的单缸直喷式柴油机上对燃用F-T柴油时发动机的性能和排放进行了研究.结果表明,在相同工况下与燃用常规柴油相比,燃用F-T柴油时的滞燃期较短,预混燃烧放热峰值较低,扩散燃烧放热峰值较高,最高燃烧压力略低,最大压力升高率显著下降,燃油消耗率和热效率都得到了改善.燃用F-T柴油可同时降低CO、HC、NOx和碳烟排放,其中NOx和碳烟排放分别平均降低了16.7%和40.3%.研究表明F-T柴油是柴油机优秀的清洁代用燃料.     

Soot processes in compression ignition engines

While diesel engines are arguably superior to any other power-production device for the transportation sector in terms of efficiency, torque, and overall driveability, they suffer from inferior performance in terms of noise, NO_x and particulate emissions. The majority of particulate originates with soot particles which are formed in fuel-rich regions of burning diesel jets. Over the past two decades, our understanding of the formation process of soot in diesel combustion has transformed from inferences based on exhaust measurements and laboratory flames to direct in-cylinder observations that have led to a transformation in diesel engine combustion. In-cylinder measurements show the diesel spray to produce a jet which forms a lifted, partially premixed, turbulent diffusion flame. Soot formation has been found to be strongly dependent on air entrainment in the lifted portion of the jet as well as by oxygen in the fuel and to a lesser extent the composition and structure of hydrocarbons in the fuel. Soot surviving the combustion process and exiting in the exhaust is dominated by soot from fuel-rich pockets which do not have time to mix and burn prior to exhaust valve opening. Higher temperatures at the end of combustion enhance the burnout of soot, while high temperatures at the time of injection reduce air entrainment and increase soot formation. Using a conceptual model based on in-cylinder soot and combustion measurements, trends seen in exhaust particulate can be explained. The current trend in diesel engine emissions control involves multi-injection combustion strategies which are transforming the picture of diesel combustion rapidly into a series of low temperature, stratified charge, premixed combustion events where NO_x formation is avoided because of low temperature and soot formation is avoided by leaning the mixture or increasing air entrainment prior to ignition.     

生物制气-柴油双燃料发动机NOx计算模型

采用气化炉热解气化各种农林废弃的生物质,产生可燃生物制气,作为双燃料发动机的主要燃料。双燃料发动机由单缸、四冲程、水冷、直喷式柴油机改装,生物制气通入发动机进气管,在进气过程中吸入气缸。在油滴蒸发准维燃烧模型的基础上,结合单区模型和详细化学反应动力学机理,建立生物制气-柴油双燃料发动机的NOx生成模型,计算结果与试验结果吻合较好。供油提前角提前,生物制气-柴油双燃料发动机NOx排放量增加;引燃柴油量减小时,NOx排放量减小。     

柴油机燃烧多环芳香烃前驱体等物质的化学动力学研究

为了揭示混合气浓度对柴油机排放的影响规律,采用正庚烷氧化详细反应机理及化学动力学分析软件对不同燃空当量比下柴油机燃烧初级碳烟粒子前驱体等重要反应中间产物或自由基的形成及发展历程进行了数值模拟．模拟结果表明,降低混合气浓度可以实现低温燃烧,使燃烧温度远离“碳烟形成温度窗”,大幅度降低柴油机碳烟排放．混合气浓度对反应中间产物或自由基有重要影响,通过改变混合气浓度可以控制燃烧过程中多环芳香烃(PAH)前体物乙炔(C2H2)、炔丙基(C3H3)及其他重要物质羟基(OH)、过氧羟自由基(HO2)、过氧化氢(H2O2)、甲醛(CH2O)和一氧化碳(CO)等的生成量,从而实现控制柴油机排放．     

进气预混乙醇降低柴油机碳烟与NOx排放的试验研究

通过开发的控制系统在485QDI发动机上研究了不同喷嘴、不同喷油定时、不同喷醇的起点对发动机碳烟、NOx排放和经济性的影响。经过优化供油参数和喷醇起点的喷醇发动机与原柴油机进行的对比试验,证明采用进气预混乙醇发动机在碳烟、NOx排放明显优于原柴油机,经济性也好于原柴油机,并在柴油机燃用可再生的含氧燃料方面做了很多有益的探索。     

柴油机燃用柴油/甲醇混合燃料时的性能与排放研究

通过添加助溶剂形成一种稳定的柴油／甲醇混合燃料，并开展了柴油机燃用此混合燃料的性能与排放研究。研究结果表明：发动机热效率和柴油等热值燃油消耗率随混合燃料中甲醇含量的增加而改善，这是由于预混燃烧量的增加，燃料富氧以及扩散燃烧的改善所致。适当增加供油提前角可使柴油／甲醇混合燃料发动机热效率提高。燃用柴油／甲醇混合燃料可显著降低发动机CO和烟度，而对碳氢排放影响不大；在相同平均有效压力的条件下，N0x随甲醇含量的增加而增加，添加甲醇对N0x的影响在大负荷下更为明显。柴油／甲醇混合燃料燃烧时存在一个较为平坦的N0x／烟度关系曲线。     

Preparation,characterization, engine combustion and emission characteristics of rapeseed oil based hybrid fuels

In this study, hybrid fuels consisting of rapeseed oil/diesel blend, 1% aqueous ethanol and a surfactant (oleic acid/1-butanol mixture) were prepared and tested as a fuel in a direct injection (DI) diesel engine. The main fuel properties such as the density, viscosity and lower heating value (LHV) of these fuels were measured, and the engine performance, combustion and exhaust emissions were investigated and compared with that of diesel fuel. The experimental results showed that the viscosity and density of the hybrid fuels were decreased and close to that of diesel fuel with the increase of ethanol volume fraction up to 30%. The start of combustion was later than that of diesel fuel and the peak cylinder pressure, peak pressure rise rate and peak heat release rate were higher than those of diesel fuel. The brake specific fuel consumption (BSFC) of hybrid fuels was increased with the volume fraction of ethanol and higher than that of diesel. The brake specific energy consumption (BSEC) was almost identical for all test fuels. The smoke emissions were lower than those for diesel fuel at high engine loads, the NO_x emissions were almost similar to those of diesel fuel, but CO and HC emissions were higher, especially at low engine loads.     

Numerical Investigation of the Effect of Hydrogen Enrichment on an Opposed-Piston Compression Ignition Diesel Engine

High power-to-weight and fuel efficiency are bounded with opposed-piston compression ignition(OPCI) engine, which makes it ideal in certain applications. In the present study, a dynamic three-dimensional CFD model was established to numerically investigate the combustion process and emission formation of a model OPCI engine with hydrogen enrichment. The simulation results indicated that a small amount of hydrogen was efficient to improve the indicated power owing to the increased in-cylinder pressure. Hydrogen tended to increase the ignition delay of diesel fuel due to both dilution and chemical effect. The burning rate of diesel fuel was apparently accelerated when mixing with hydrogen and premixed combustion became dominated. NO_x increased sharply while soot was sufficiently suppressed due to the increase of in-cylinder temperature. Preliminary modifications on diesel injection strategy including injection timing and injection pressure were conducted. It was notable that excessive delayed injection timing could reduce NO_x emission but deteriorate the indicated power which was mainly attributed to the evident decline of hydrogen combustion efficiency. This side effect could be mitigated by increasing the diesel injection pressure. Appropriate delay of injection coupled with high injection pressure was suggested to deal with trade-offs among NO_x, soot and engine power.