小型通用二冲程汽油机排放控制的试验研究

本文针对小型通用机械用二冲程小汽油机的使用要求及排放特点，提出通过优化空燃比等机内净化和应用还原型Rh催化转化器氧化转化HC和还原NOx的方法，达到大幅度降低CO、HC排放之目的。1E45排放控制试验结果表明，这是国产二冲程小汽油机排放达到美国EPA第二阶段排放要求的有效控制方法。     

汽油机掺烧CO2对NOx排放影响的实验研究

本文进行EGR的基础研究,单纯从CO2的加入入手,主要以进气掺烧CO2减排汽油机NOx的特性为研究对象,在HODNA G200单缸四冲程发动机上进行系列实验.并通过理论和实验分析了进气掺烧不同流量CO2对NOx、HC、CO和CO2的排放以及燃烧过程的影响.研究结果表明,汽油机进气掺烧适量CO2减排NOx效果明显,对HC排放影响不大,CO排放略有增加,发动机输出功率有所下降.     

分层扫气技术在小型二冲程汽油机上的应用

本文为应对欧洲、美国的汽油机排放法规,提出一种分层扫气技术,利用这项技术,可以最大限度降低小型二冲程汽油机在扫气时未燃烧混合气的短路损失和提高燃烧效率,从而实现减少汽油机的HC和NOx排放指标的目的,并能大幅降低汽油机燃油消耗率,达到使小型二冲程汽油机即环保又节能的目的,为小型二冲程汽油机进入欧美市场扫清技术障碍。     

分层扫气技术在小型二冲程汽油机上的应用

摘本文为应对欧洲、美国的汽油机排放法规，提出一种分层扫气技术，利用这项技术，可以最大限度降低小型二冲程汽油机在扫气时未燃烧混合气的短路损失和提高燃烧效率，从而实现减少汽油机的HC和NOx排放指标的目的，并能大幅降低汽油机燃油消耗率，达到使小型二冲程汽油机即环保又节能的目的，为小型二冲程汽油机进入欧美市场扫清技术障碍。     

分层进气二冲程汽油机的试验研究

本文介绍了应用分层进气提高二冲程汽油机性能的试验研究结果;讨论了分层进气主要参数的确定及其对发动机性能的影响;分析了分层进气汽油机的基本特性。分层进气汽油机的最低油耗率为334g/(kW·h),较原机降低了29.7%。     

快速空气加热器减少汽油机冷起动排放的试验研究

利用汽油机自身的燃油供应系统,建立了高压点火、低压喷射的快速空气加热器(RAH),使用这种加热器对汽油机冷起动过程的排放进行了试验研究.研究表明:RAH能快速加热进气,并且本身排放量较少.在环境温度为-2 ℃时,仅需加热32 s就能使进气温度由9 ℃上升至30 ℃,在发动机起动后还会继续升高.在发动机起动后最初40 s内,经预热的进气可使HC和CO排放分别降低46 %和36.4 %,在同样的时间燃用乙醇汽油,可使HC和CO排放分别降低33.4 %和11.1 %.结果表明RAH为有效的降低汽油机冷起动排放的装置.     

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。     

汽油机排放性能连续测量研究

使用AVL4000型五气分析仪连续测量了492QBW车用汽油机在多种稳定工况和启动工况下排气中有害成分CO，HC和NO的量。稳定工况试验结果表明：汽油机的转速和负荷都对CO，HC，NO排放产生影响，负荷变化对排放浓度变化的影响大于转速变化带来的影响；同时工况稳定情况下连续测量的一段时间内，各排气成分会产生一定波动，尤其是HC排放波动最大。冷启动、热启动试验结果显示，在启动过程中汽油机的CO和HC排放较高，尤其是冷启动时CO和HC排放出现峰值。     

小排量增压汽油机进气压力对性能的影响研究

对465Q汽油机进行废气涡轮增压改造,研究了进气压力对增压发动机性能及排放的影响。增压后,发动机动力性能明显提升,增压压比越大,发动机的比功率越高;热效率提高,燃油消耗率下降,经济性改善;在低进气压力时,随进气压力增大,CO,HC排放减少,NOx排放增多;高进气压力时,随进气压力增大,CO,HC排放增多,NOx排放减少;CO,HC,NOx排放随转速的提高呈先增多后减少的规律;进气压力越大,发动机的放热率、压升率越高。     

进气预热降低汽油机冷起动排放的研究

研究了不同进气温度、加热方式和蓄热箱容积对发动机冷起动排放的影响规律。结果表明，提高进气温度有利于减少冷起动阶段的HC、CO排放。最初参与缸内燃烧的新鲜空气的温度对冷起动HC排放有重要影响，对发动机进气歧管内的冷空气进行加热可以大幅度降低HC排放。蓄热箱容积一定时（30L），存在一个进气温度（70℃）可以使HC、CO排放改善得到最佳效果（分别降低36％和13％）。较强的蓄热能力，可以在较大温度范围内减少排放。     

缸内直喷式汽油机燃用当量空燃比混合气的试验研究

缸内直接喷射式汽油机，要求部分负荷时在压缩过程后期喷入燃油，实现混合气分层燃烧，以获得好的经济性；在全负荷时，燃油在进气过程中喷入，采用化学计量比混合气，实现均质预混合燃烧，以保持汽油机升功率高和排放低的优点。本文将一台柴油机改装为缸内直接喷射汽油机，在试验台架上进行了高负荷时燃用当量空燃比混合气的试验研究，结果表明，与化油器式汽油机相比，高负荷时油耗降低了6％，未燃碳氢降低了31％，NOx排放降低了10％，取得了较为满意的结果。     

Study on combustion and emission characteristics of a n-butanol engine with hydrogen direct injection under lean burn conditions

The n-butanol fuel, as a renewable and clean biofuel, could ease the energy crisis and decrease the harmful emissions. As another clean and renewable energy, hydrogen properly offset the high HC emissions and the insufficient of dynamic property of pure n-butanol fuel in SI engines, because of the high diffusion coefficient, high adiabatic flame velocity and low heat value. Hydrogen direct injection not only avoids backfire and lower intake efficiency but also promotes to form in-cylinder stratified mixture, which is helpful to enhance combustion and reduce emissions. This experimental study focused on the combustion and emissions characteristics of a hydrogen direct injection stratified n-butanol engine. Three different hydrogen addition fractions (0%, 2.5%, 5%) were used under five different spark timing (10° ,15° ,20° ,25° ,30° CA BTDC). Engine speed and excess air ratio stabled at 1500 rpm and 1.2 respectively. The direct injection timing of the hydrogen was optimized to form a beter stratified mixture. The obtained results demonstrated that brake power and brake thermal efficiency are increased by addition hydrogen directly injected. The BSFC is decreased with the addition of hydrogen. The peak cylinder pressure and the instantaneous heat release rate raises with the increase of the hydrogen addition fraction. In addition, the HC and CO emissions drop while the NOx emissions sharply rise with the addition of hydrogen. As a whole, with hydrogen direct injection, the power and fuel economy performance of n-butanol engine are markedly improved, harmful emissions are partly decreased.     

Improvement of thermal efficiency and reduction of NOx emissions by burning a controlled jet plume in high-pressure direct-injection hydrogen engines

A new combustion process called the Plume Ignition Combustion Concept (PCC), in which the plume tail of the hydrogen jet is spark-ignited immediately after the completion of fuel injection to accomplish combustion of a rich mixture has been proposed by the authors. This PCC combustion process markedly reduces nitrogen oxides (NOx) emissions in the high-output region while maintaining high levels of thermal efficiency and power. On the other hand, as burning lean mixture of fuel and air is the conventional way to improve thermal efficiency and reduce NOx, a high λ premixed mixture of hydrogen and air formed by injecting hydrogen in the early stage of the compression stroke has been used in direct-injection hydrogen engines. It was recently reported, however, that this mixture condition does not always offer expected improved thermal efficiency under even lean mixture conditions by increasing unburned hydrogen emissions caused by incomplete flame propagation in the non-uniform and extremely lean portion of the mixture. In this study, the effect of retarding the injection timing to late in the compression stroke but slightly advanced from original PCC was examined as a way of reducing unburned hydrogen emissions and improving thermal efficiency. These effects result from a centroidal axially stratified mixture that positions a fairly rich charge near the spark plug. This stratified mixture is presumably effective in reducing incomplete flame propagation thought to be the cause of unburned hydrogen emissions and also promoting increasing burning velocity of the mixture that improve thermal efficiency. Finally, this research is characterized by measuring the hydrogen fuel concentration at the point and the time of spark ignition quantitatively by spark-induced breakdown spectroscopy in order to identify the changes in mixture ratio mentioned above caused by the parameters involved.     

可变涡流进气系统及其在直喷式汽油机中的应用

设计了一种简单的阀片式变涡流控制系统。在螺旋气道中安装一适当形状的阀片,可在较大范围内连续调节涡流比。在充气效率不受影响的情况下,本涡流控制系统可使涡流比在０．３５～１．６８之间变化。通过在稳流吹风试验台上的大量试验,对阀片形状,包括阀片外形和逆流弯角进行了优化。将本系统应用在汽油机直接喷射分层燃烧系统中,发动机的综合性能,尤其是低负荷下的排放性能有了较大的改善。试验表明,当涡流比在１．０～１．５之间变化时,所研究的直接喷式汽油机在低负荷工况下ＣＯ、ＨＣ和ＮＯｘ的排放水平较低。     

Flame inertia into lean region in stratified hydrogen mixture

In hydrogen engines, the direct-injection stratified charge system has the ability to realize a more lean operation than homogeneous charge systems. Flame propagation into the lean region in the stratified hydrogen mixture was investigated in this study. Hydrogen was injected into a lean hydrogen–air premixed mixture charge of the equivalence ratio of 0.074–0.257. This stratified hydrogen mixture was ignited by an electric spark. The flame generated in the hydrogen jet propagated into the lean premixed mixture charge as if it had “inertia”, even though the stoichiometry of the premixed mixture charge was less than the lower flammability limit. The amount of burned hydrogen in the case of a stratified mixture was greater than that in the case of the homogeneous mixture. The flame seems to be supported from behind by the burned gas in the rich region until the decay of this support.     

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions of a gasoline/hydrogen SI engine

A comparative study on effects of homogeneous or stratified hydrogen on combustion and emissions was presented for a gasoline/hydrogen SI engine. Three kinds of injection modes (gasoline, gasoline plus homogeneous hydrogen and gasoline plus stratified hydrogen) and five excess air ratios were applied at low speed and low load on a dual fuel SI engine with hydrogen direct injection (HDI) and gasoline port injection. The results showed that, with the increase of excess air ratio, the brake thermal efficiency increases firstly then decreases and reaches the highest when the excess air ratio is 1.1. In comparison with pure gasoline, hydrogen addition can make the ignition stable and speed up combustion rate to improve the brake thermal efficiency especially under lean burn condition. Furthermore, it can reduce the CO and HC emissions because of more complete combustion, but produce more NO_X emissions due to the higher combustion temperature. Since, in the gasoline plus stratified hydrogen mode, the hydrogen concentration near the sparking plug is denser than that of homogeneous hydrogen, the ignition is more stable and faster, which further speed up the combustion rate and improve the brake thermal efficiency. In the gasoline plus stratified hydrogen mode, the brake thermal efficiency increases by 0.55%, the flame development duration decreases by 1.0°CA, rapid combustion duration decreases by 1.3°CA and the coefficient of variation (COV) decreases by 9.8% on average than that of homogeneous hydrogen. However, in the gasoline plus stratified hydrogen mode, due to the denser hydrogen concentration near the sparking plug and leaner hydrogen concentration near the wall, the combustion temperature and the wall quenching distance increase, which make the NO_X and HC emissions increase by 14.3% and 12.8% on average than that of homogeneous hydrogen.     

Mixture distribution measurement using laser induced breakdown spectroscopy in hydrogen direct injection stratified charge

Reduction in cooling loss due to the heat transfer from burning gas to the combustion chamber wall is very important for improving the thermal efficiency in hydrogen engines. The previous research has shown that the direct injection stratified charge can be a technique to reduce the cooling loss and improve thermal efficiency in hydrogen combustion. For effective reductions in cooling loss by the stratified charge, it is very important to know the relation between the fuel injection conditions and mixture distribution. The current research employs the laser induced breakdown spectroscopy as a method to measure the hydrogen concentration distribution in the direct injection stratified charge. Measurement of instantaneous local equivalence ratio by the method clears the characteristics of mixture formation in hydrogen direct injection stratified charge. This research also tries to actively control the mixture distribution using a split fuel injection.     

基于缸内直喷的甲醇汽油混合燃料HCCI燃烧排放特性研究

在缸内直喷发动机上研究甲醇汽油混合燃料的HCCI燃烧排放特性,分析了其非常规排放的性能。试验中选用汽油、M10(甲醇体积分数10%)、M20(甲醇体积分数20%)3种燃料,并通过FTIR方法测量甲醇及甲醛等非常规排放。研究结果表明:在汽油中添加甲醇可以有效拓展HCCI燃烧的高负荷范围,M20燃料的高负荷范围比汽油提高近9%,指示燃油消耗率比汽油高5%～10%,但指示能量消耗率比汽油低2%～6%。CO、THC、NOx等常规排放随甲醇添加比例的增加而降低,而甲醇和甲醛等非常规排放随甲醇添加比例的增加而增加,并随负荷增高呈先增加后减少的趋势。     

利用火花点火式快速压缩装置进行天然气直喷分层燃烧可行性的研究

利用快速压缩装置进行了天然气直喷分层燃烧可行性的研究。结果表明 :天然气分层燃烧具有短的初期火焰发展期和主燃期以及高的燃烧压力。分层燃烧可使稀燃极限延伸到很小的当量比。由于过度分层 ,CO在当量比大于 0 .8时急剧增加 ,而 NOx 的峰值也因充量分层而出现在小当量比处。燃烧效率在当量比处于0 .1～ 0 .9范围时高于 0 .92 ,在极小当量比时由于未燃混合气淬熄 ,在当量比时由于过度分层而使燃烧效率降低。根据燃烧产物计算的燃烧效率与根据放热分析获得的燃烧效率一致。因此 ,天然气直喷分层燃烧在宽广的当量比范围内可望实现高效燃烧火花助燃发动机的宽广的高效燃烧。