通过改变喷油特性曲线形状降低直喷式柴油机的废气排放

本报告为一项研究课题的科研总结,该课题是由德国内燃机研究联合会(简称FVV)提出,奥地利AVL List公司完成的。课题的进行分为三个阶段,即燃烧过程的匹配,各种喷油速率曲线形状的研究;最后再加上废气再循环,充分利用喷油特性曲线形状的改变来降低废气排放。     

简单而有效的废气再循环装置

采用废气再循环能够降低柴油机NOx排放。介绍了一个简单而有效的废气再循环装置,简要列举了该装置装在发动机台架上的部分试验结果,为更好地利用废气再循环技术减少柴油机NOx排放有借鉴作用。     

EGR对双燃料发动机排放特性的影响

废气再循环技术是降低发动机有害排放的有效手段之一。本文介绍了应用于双燃料发动机的废气再循环的装里和实验方法,并详细分析了废气再循环对发动机排放的影响。实验证明朱用废气循环技术降低了发动机的有害排放物。     

通过改变喷油特性曲线形状降低直喷式柴油机的废气排放

本报告为一项研究课题的科研总结,该课题是由德国内燃机研究联合会（简称ＦＶＶ）提出,奥地利ＡＶＬ Ｌｉｓｔ公司完成的。课题的进行分为三个阶段,即燃烧过程的匹配,各种喷油速率曲线形状的研究;最后再加上废气再循环,充分利用喷油特性曲线形状的改变来降低废气排放。     

小型直喷式柴油机的新燃烧概念(2)

为了了解废气再循环对排放的影响，在一台４缸直喷式柴油机上，对一种低温预混合燃烧的新概念进行了试验研究。这种新概念的效果已由延长滞燃期、废气再循环、推迟喷油定时和高涡流比组合的试验结果证明。油耗和可溶性有机物的增加可通过采用大口径的ω型燃烧室来避免。在上述发动机上应用废气再循环已证明新燃烧概念可同时减少ＮＯＸ和颗粒物的排放。     

喷油定时对柴油机超多喷孔预混合燃烧影响研究

柴油机低温预混合燃烧能够同时大幅度降低NOx和碳烟(soot)排放,本研究采用大量废气再循环(EGR)实现低温燃烧来降低NOx排放,采用超多喷孔喷油嘴并结合高压喷射来缩短喷油持续期,实现预混合燃烧从而降低soot排放,主要对喷油定时如何影响柴油机超多喷孔预混合燃烧性能进行了试验研究,选定4个试验工况,通过改变喷油定时来测试柴油机性能,结果显示随着喷油始点从上止点前向后推迟,各工况的NOx和soot排放都有不同程度的同时下降,有别于传统燃烧方式,但HC,CO,比油耗(BSFC)有所升高。     

未来低排放载重车用柴油机喷油系统技术

根据对未来低排放柴油机可能的开发策略的分析,本文讨论在喷油特性和燃烧系统必要的变动之间的相互影响。对于使用象废气再循环(EGR)这样的新技术则是从未来的低排放载重车用柴油机对喷油系统的要求这样的角度进行讨论。 对现有的有效的和正在为开发某些发动机所使用的多种喷油系统进行了比较。最后,可以看出,很多不同的燃油喷射系统将被使用,然而,要特别强调液压喷油系统的电子控制的设计和其他用来降低排放的措施如EGR,DeNOx催化剂或颗粒收集装置的应用。     

机内净化降低船用二冲程柴油机NO_x排放仿真

针对一台满足TierⅡ排放标准的船用二冲程柴油机,建立GT-Power一维仿真模型,研究了废气再循环(EGR)、米勒循环、进气加湿(HAM)以及优化喷油正时等手段对NO_x排放和燃油消耗率的影响,并探讨了通过多种措施耦合来实现TierⅢ排放标准的技术路线.结果表明:单独采用米勒循环或进气加湿难以达到TierⅢ排放标准;通过结合米勒循环和进气加湿,可以将NO_x排放降低至TierⅢ标准,但会导致燃油消耗率大幅增加;废气再循环是降低NO_x排放的最有效措施,通过将其与米勒循环和进气加湿相结合,可有效减小EGR使用率,并适度改善燃油经济性的恶化程度.     

利用EGR降低柴油机排放的研究

介绍了废气再循环（ＥＧＲ）降低柴油机ＮＯｘ排放的原理和控制方法,考察了不同工况下柴油机废气污染物的排放分布情况,并进行了柴油机废气再循环的试验。试验结果表明,在柴油机稍作更改,成本增加不多的基础上,采用ＥＧＲ能够较有效地降低ＮＯｘ排放。     

喷油策略与EGR对柴油机低温燃烧影响试验研究

为研究喷油策略及废气再循环(exhaust gas recirculation,EGR)对柴油机低温燃烧特性和排放特性的影响,在一台电控高压共轨柴油机上进行了试验研究。研究结果表明:EGR率的升高提高了进气比热容,降低了缸内最高燃烧压力及缸内平均温度,延长了滞燃期,降低了NOx排放,由于进气氧浓度及碳烟氧化速率的降低,增加了碳烟排放;中小EGR率下,提高喷油压力,加速油气混合程度,可以有效降低碳烟排放;推迟燃烧重心CA50到上止点后7°之后造成燃烧效率降低,扩散燃烧持续期延长,导致碳烟排放升高。     

Effect of exhaust gas recirculation on diesel engine nitrogen oxide reduction operating with jojoba methyl ester

Jojoba methyl ester (JME) has been used as a renewable fuel in numerous studies evaluating its potential use in diesel engines. These studies showed that this fuel is good gas oil substitute but an increase in the nitrogenous oxides emissions was observed at all operating conditions. The aim of this study mainly was to quantify the efficiency of exhaust gas recirculation (EGR) when using JME fuel in a fully instrumented, two-cylinder, naturally aspirated, four-stroke direct injection diesel engine. The tests were carried out in three sections. Firstly, the measured performance and exhaust emissions of the diesel engine operating with diesel fuel and JME at various speeds under full load are determined and compared. Secondly, tests were performed at constant speed with two loads to investigate the EGR effect on engine performance and exhaust emissions including nitrogenous oxides (NO_x), carbon monoxide (CO), unburned hydrocarbons (HC) and exhaust gas temperatures. Thirdly, the effect of cooled EGR with high ratio at full load on engine performance and emissions was examined. The results showed that EGR is an effective technique for reducing NO_x emissions with JME fuel especially in light-duty diesel engines. With the application of the EGR method, the CO and HC concentration in the engine-out emissions increased. For all operating conditions, a better trade-off between HC, CO and NO_x emissions can be attained within a limited EGR rate of 5–15% with very little economy penalty.     

多次喷油实现清洁高效柴油预混燃烧的机理

采用试验和数值模拟方法研究了多次喷油模式耦合高EGR率和进气增压实现高效清洁柴油机预混燃烧的潜力.结果表明,EGR可以推迟高温反应定时,降低化学反应速率,特别是在较高负荷时,EGR还明显降低NOx排放.平均指示压力(IMEP)为0.4,MPa左右时,较少的喷油量使得单次喷油和多次喷油模式着火前一时刻形成的混合气均在当量比φ<2之内,故排放差别不大.氧体积分数为10%左右时,提高喷油量,进入侧隙内的气相燃油量增加并形成φ>2的浓区,两模式的碳烟、CO和UHC排放均升高.但IMEP为0.7 MPa左右时,多次喷油更有利于生成稀且均匀的混合气,减少局部过浓区,故其碳烟、CO和UHC排放远低于单次喷油.高EGR率时,多次喷油耦合进气增压,混合气形成得到进一步改善,可在更高负荷下实现高效清洁燃烧.     

Analysis of exhaust waste heat recovery from a dual fuel low temperature combustion engine using an Organic Rankine Cycle

This paper examines the exhaust waste heat recovery potential of a high-efficiency, low-emissions dual fuel low temperature combustion engine using an Organic Rankine Cycle (ORC). Potential improvements in fuel conversion efficiency (FCE) and specific emissions (NO_x and CO₂) with hot exhaust gas recirculation (EGR) and ORC turbocompounding were quantified over a range of injection timings and engine loads. With hot EGR and ORC turbocompounding, FCE improved by an average of 7 percentage points for all injection timings and loads while NO_x and CO₂ emissions recorded an 18 percent (average) decrease. From pinch-point analysis of the ORC evaporator, ORC heat exchanger effectiveness (?), percent EGR, and exhaust manifold pressure were identified as important design parameters. Higher pinch point temperature differences (PPTD) uniformly yielded greater exergy destruction in the ORC evaporator, irrespective of engine operating conditions. Increasing percent EGR yielded higher FCEs and stable engine operation but also increased exergy destruction in the ORC evaporator. It was observed that hot EGR can prevent water condensation in the ORC evaporator, thereby reducing corrosion potential in the exhaust piping. Higher ? values yielded lower PPTD and higher exergy efficiencies while lower ? values decreased post-evaporator exhaust temperatures below water condensation temperatures and reduced exergy efficiencies.     

Effect of addition of hydrogen and exhaust gas recirculation on characteristics of hydrogen gasoline engine

The effects of exhaust gas recirculation (EGR) on combustion and emissions under different hydrogen ratios were studied based on an engine with a gasoline intake port injection and hydrogen direct injection. The peak cylinder pressure increases by 9.8% in the presence of a small amount of hydrogen. The heat release from combustion is more concentrated, and the engine torque can increase by 11% with a small amount of hydrogen addition. Nitrogen oxide (NOx) emissions can be reduced by EGR dilution. Hydrogen addition offsets the blocking effect of EGR on combustion partially, therefore, hydrogen addition permits a higher original engine EGR rate, and yields a larger throttle opening, which improves the mechanical efficiency and decreases NOx emissions by 54.8% compared with the original engine. The effects of EGR on carbon monoxide (CO) and hydrocarbon (HC) emissions are not obvious and CO and HC emissions can be reduced sharply with hydrogen addition. CO, HC, and NOx emissions can be controlled at a lower level, engine output torque can be increased, and fuel consumption can be reduced significantly with the co-control of hydrogen addition and EGR in a hydrogen gasoline engine.     

Influence of high rates of supplemental cooled EGR on NOx and PM emissions of an automotive HSDI diesel engine using an LP EGR loop

Previous experimental studies on diesel engine have demonstrated the potential of exhaust gas recirculation (EGR) as an in‐cylinder NO_x control method. Although an increase in EGR at constant boost pressure (substitution EGR) is accompanied with an increase in particulate matter (PM) emissions in the conventional diesel high‐temperature combustion (HTC), the recirculation of exhaust gases supplementary to air inlet gas (supplemental EGR) by increasing the boost pressure has been suggested as a way to reduce NO_x emissions while limiting the negative impact of EGR on PM emissions. In the present work, a low‐pressure (LP) EGR loop is implemented on a standard 2.0 l automotive high‐speed direct injection (HSDI) turbocharged diesel engine to study the influence of high rates of supplemental cooled EGR on NO_x and PM emissions. Contrary to initial high‐pressure (HP) EGR loop, the gas flow through the turbine is unchanged while varying the EGR rate. Thus, by closing the variable geometry turbine (VGT) vanes, higher boost pressure can be reached, allowing the use of high rates of supplemental EGR. Furthermore, recirculated exhaust gases are cooled under 50°C and water vapour is condensed and taken off from the recirculated gases. An increase in the boost pressure at a given inlet temperature and dilution ratio (DR) results in most cases an increase in NO_x emissions and a decrease in PM emissions. The result of NO_x–PM trade‐off, while varying the EGR rate at fixed inlet temperature and boost pressure depends on the operating point: it deteriorates at low load conditions, but improves at higher loads. Further improvement can be obtained by increasing the injection pressure. A decrease by approximately 50% of NO_x emissions while maintaining PM emission level, and brake specific fuel consumption can be obtained with supplemental cooled EGR owing to an LP EGR loop, compared with the initial engine configuration (HP moderately cooled EGR). Copyright © 2008 John Wiley & Sons, Ltd.     

文曲利管排气再循环系统在涡轮增压柴油机上的应用研究

以一台 D6 114涡轮增压柴油机为研究对象 ,采用了一套带文曲利管的排气再循环系统进行了试验研究。试验结果表明 ,该系统在高工况下能克服平均排气压力低于平均进气压力的困难 ,方便地实现排气再循环。研究了在不同工况下柴油机的 NOx 排放、烟度和比油耗随 EGR率的变化规律以及 EGR的冷却效果对 NOx 排放的影响     

直喷汽油机采用不同缸内稀释技术的性能研究

针对一款4缸1.5L废气涡轮增压缸内直喷汽油(GDI)发动机,进行了废气再循环(EGR)缸内稀释燃烧技术、空气缸内稀释燃烧技术与原机燃烧的经济性、排放特性对比试验研究。研究了不同缸内稀释技术对发动机性能和排放影响的变动规律,并对比分析了相同稀释率下、采用不同稀释技术时发动机的性能变化。结果表明:空气稀释率在49.5%时比油耗相比原机下降6.2%,而EGR稀释率在20.5%时经济性改善4.2%,在相同稀释率时,EGR稀释可采用更为提前的点火角实现更优的燃烧相位,但空气稀释所带来的多变指数提升使其经济性优于EGR稀释,且发动机燃烧系统对空气稀释程度具有更强的容忍性;NOx排放在空气稀释率为11.0%时达到峰值水平,随后随着稀释率的提高不断下降,而EGR稀释的NOx排放随着稀释率的提高持续大幅下降;空气稀释的CO排放水平远低于原机,EGR稀释的CO排放随着稀释率的增加而略有下降;对于HC排放,空气稀释的排放量低于EGR稀释,而当空气稀释率由49.5%增加为68.0%时,HC排放出现较大幅度上升。     

电控五气门汽油机稀燃与废气再循环性能对比研究

在一电控喷射稀薄燃烧五气门汽油机上，以稀薄燃烧汽油机电控开发系统及相应的废气再循环系统为试验平台，对五气门汽油机在各种进气模式下实施稀混合气燃烧及废气再循环时的燃油消耗率和排放性能进行了详细的试验研究，进而对本发动机的稀燃性能与废气再循环性能进行了比较，分析实施不同方法对发动机性能的不同影响效果，实验结果表明，采用分层EGR技术以后，EGR比率可达32％，稀燃和分层废气再循环都有效地降低了NOx排放，分层废气再循环对NOx降低的效果更为明显，而且降低速度更快，尤其在中、低负荷，可以使排气中的NOx降低85％～95％．对于油耗，稀燃的效果显然要好于废气再循环，在较高负荷尤为明显，稀燃可显著降低HC、CO，分层EGR对HC、CO排放降低幅度不大。     

低压EGR对GDI增压汽油机外特性下性能和排放影响

通过一款涡轮增压汽油直喷(gasoline direct injection,GDI)发动机低压废气再循环(exhaust gas recirculation,EGR)的试验,研究了EGR率和点火提前角的综合作用对增压GDI发动机的燃烧、缸压、排放和油耗等方面的影响。结果表明,在GDI增压发动机中加入EGR后,由于废气的稀释和热容作用,使缸内燃烧持续期增大,排气温度下降,燃烧相位也发生了改变。这对发动机外特性的有利影响是油耗减少,CO和NO_x排放也明显减少;不利影响是EGR的加入提高了增压发动机的排气压力,导致泵气损失增加。此外,总碳氢(total hydro carbons,THC)排放也有所增加。在GDI增压汽油机中使用EGR系统并配合点火角的调节能够有效提高热效率,降低NO_x排放。     

进气加湿结合废气再循环技术对高压直喷双燃料低速机燃烧及排放的影响

基于CONVERGE软件建立了高压直喷双燃料船用发动机三维仿真模型,研究了空气加湿技术和废气再循环(exhaust gas recirculation,EGR)对发动机燃烧过程及排放的影响,并通过耦合进气加湿、EGR和天然气喷射策略等技术,最终得到满足TierⅢ排放法规的可行性技术路线。结果表明,进气加湿降低NOx排放潜力较大(约55%),且对燃料经济性恶化程度较小(约1.6%);单独采用进气加湿技术难以满足TierⅢ排放标准,60%进气加湿程度结合较低程度EGR率(20%)可进一步提高降低NOx排放的潜力(78%);为降低进气加湿和EGR带来的功率损失,在20%EGR率耦合60%进气加湿氛围下,提前2°曲轴转角喷射天然气可使天然气消耗率可降低约1g/(kW·h),同时NOx排放满足TierⅢ排放法规要求。