共查询到19条相似文献,搜索用时 203 毫秒
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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。 相似文献
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为控制汽油机稀燃NOx排放,对Ir-ZSM5分子筛催化剂在实际稀燃排气条件下进行了试验研究.试验结果表明,应用Ir-ZSM5催化剂,可以实现CO对稀燃NOx的选择催化还原反应.在空燃比为15~20时,空速为30000/h时,NOx最高转化效率可达50%~80%,并且具有较宽的高活性温度窗口.随着空燃比的增加,NOx转化效率减小.Ir-ZSM5催化剂对HC、CO也可以实现较高的转化率,有望应用于当量空燃比条件,从而降低空燃比控制精度.该催化剂尤其适合稀燃汽油机的需要. 相似文献
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吸附还原催化系统降低稀燃汽油机NOx排放试验研究 总被引:4,自引:0,他引:4
采用NOx吸附还原催化器和传统的三效催化器组合而形成的新型催化转化系统,在一台改装的产品四气门电控燃油喷射准均质稀燃汽油机上进行了催化技术降低稀燃汽油机NOx排放的试验研究.试验结果表明当t稀t浓=200 s20 s时,仅用NOx吸附还原催化器或三效催化器位于吸附还原催化器之后的催化器布置可以使稀燃汽油机的NOx排放降低到300×10-6左右,降低62.5%,而三效催化器位于吸附还原催化器之前的催化器布置可以大幅降低稀燃汽油机的NOx排放,达到50×10-6左右,降低93%.而且随着t稀t浓绝对时间的减小,稀燃汽油机的NOx排放浓度降低.稀燃汽油机转速和负荷增大,NOx排放浓度增大,NOx催化转化率CNox减小. 相似文献
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汽油机燃用乙醇和含水乙醇与汽油的混合燃料的试验研究 总被引:8,自引:0,他引:8
报导了在摩托车汽油机中燃用乙醇-汽油混合燃料的试验结果,并与燃用汽油时的结果进行了对比分析。结果显示,汽油机燃用乙醇和汽油的混合燃料,当纯乙醇或含水5%的工业乙醇在混合燃料的比例为10%的时候,即使发动机的结构不变、燃油系统和点火系统不作任何调整动的时候,发动机的全负荷输出不受影响,发动机的能耗率得到改善、HC和CO排放有所降低,但是NOx排放会有显著的增加。 相似文献
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为了在电控汽油机上优化M85甲醇汽油的应用,利用发动机台架试验,分析了电控汽油机直接燃用M85的主要问题,并通过放大喷油脉宽,增加M85甲醇汽油的喷油量来改善发动机性能。试验结果表明:与燃用汽油相比,喷油脉宽放大1.3倍时,发动机燃用M85甲醇汽油的功率和扭矩分别平均降低了6.83%和7.15%;小时燃油消耗量与有效燃油消耗率增大,但有效能耗平均降低6%;CO和HC排放分别平均降低11.28%和0.64%;NOx排放平均增加55.56%。 相似文献
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利用二次喷油稀燃实验系统研究了二次喷油对可变滚流进气发动机稀燃特性的影响情况。首先,采用纯滚流可变滚流进气系统时,采用较大比例的二次喷油量可以获得更好的稀燃经济性。第二,最低油耗点所对应的喷油正时按照T1、T2和T3顺序依次提前;负荷较大时,对应的最低油耗点喷油正时也相应提前。第三,在可变滚流结构中,二次喷油可能造成局部混合气过浓.导致CO排放增加:同时.在稀燃情况下.增大滚流比可以降低发动机HC和NOχ排放。第四,增大滚流比可以改善发动机低速工况条件下的性能,但应避免机构对燃油喷注的阻隔作用。 相似文献
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在一台直列4缸增压直喷汽油机上针对万有特性最低油耗工况点,进行了稀薄燃烧与废气再循环(exhaust gas recirculation,EGR)提高发动机热效率的对比试验研究。试验结果表明:稀薄燃烧及EGR均能有效降低发动机燃油消耗率,稀释率分别为33%和19%时,采用稀燃和EGR时的最高有效热效率绝对值分别增加2.8%和1.7%,其中稀燃的有效热效率达到了39.9%,稀燃实现更高热效率主要归因于较低的传热损失和未燃损失。从燃烧角度来看,稀燃及EGR稀释都延长了燃烧滞燃期及持续期,但同样稀释率下稀燃的滞燃期更短,稀燃更高的稀释极限实现了更低的传热损失;但EGR抑制爆震,提前燃烧相位,使采用EGR时的排气能量损失低于稀燃。从排放角度来看,稀燃及EGR在高稀释率下均显著降低NO_x排放,而受益于高氧气浓度,相同稀释率下稀燃的HC及CO排放均低于采用EGR时,从而使稀燃的未燃损失更低。 相似文献
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Cheolwoong Park Seunghyun Park Changgi Kim Sunyoup Lee 《International Journal of Hydrogen Energy》2012
In this study, the effects of exhaust gas recirculation (EGR) on the behavior of a spark ignition engine fueled by hydrogen-blended low-calorific biogas were investigated, and its performance and emission characteristics were compared with those of the lean burn engine investigated in our previous work. The engine was operated at a constant rotational speed of 1800 rpm under a 60 kW power output condition, and a simulated biogas containing H2 was used to realize a wide range of gas compositions. The engine test results demonstrate that when less than 20% H2 was added to the biogas, the EGR operations had inferior fuel economy to the lean burn technique. However, when the H2 blending ratio was increased, the EGR method achieved higher engine performance with lower NOx emissions than the legal standard. Analyses of the O2 fraction and thermal capacity variations of the inlet charge also indicated that a dilution (O2 replacement) effect rather than a thermal effect was the dominant factor when EGR was introduced in a low-calorific biogas engine. Subsequently, in order to improve the engine efficiency as well as combustion characteristics, the spark gap was projected further into the combustion chamber with EGR engine operations. The engine test results show that repositioning the discharge location improved the thermal efficiency, and the maximum tolerable EGR rate increased because of spatial advantages such as relatively short flame propagation lengths and high electrode temperatures. 相似文献
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A comparison between EGR and lean-burn strategies employed in a natural gas SI engine using a two-zone combustion model 总被引:1,自引:0,他引:1
Exhaust gas recirculation (EGR) strategy has been recently employed in natural gas SI engines as an alternative to lean burn technique in order to satisfy the increasingly stringent emission standards. However, the effect of EGR on some of engine performance parameters compared to lean burn is not yet quite certain. In the current study, the effect of both EGR and lean burn on natural gas SI engine performance was compared at similar operating conditions. This was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. The combustion model was validated using experimental data and a good agreement between the results was found. It was demonstrated that adding EGR to the stoichiometric inlet charge at constant inlet pressure of 130 kPa decreased power more rapidly than excess air; however, the power loss was recovered by increasing the inlet pressure from 130 kPa at zero dilution to 150 kPa at 20% EGR dilution. The engine fuel consumption increased by 10% when 20% EGR dilution was added at inlet pressure of 150 kPa compared to using 20% air dilution at 130 kPa. However, it was found that EGR dilution strategy is capable of producing extremely lower NO emission than lean burn technique. NO emission was reduced by about 70% when the inlet charge was diluted at a rate of 20% using EGR instead of excess air. 相似文献
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基于某一直喷增压发动机,研究了EGR对发动机小负荷油耗的影响。结果表明:在改善油耗方面,原发动机使用进气门晚关策略优于使用内部EGR策略;在低转速小负荷工作区域,外部中冷EGR对油耗的贡献主要来自于降低了泵气功,但是过多的EGR气体引入容易导致燃烧不稳;使用高压EGR时,最佳的进排气VVT角度与无EGR时相同。 相似文献
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基于一台带有低压废气再循环系统的1.5 L涡轮增压直喷汽油发动机进行了稀燃和废气再循环(EGR)影响发动机燃烧性能的试验研究。结果表明,随着稀释率的上升,EGR和稀燃均导致发动机滞燃期、燃烧持续期延长,燃烧重心提前,有效燃油消耗率下降,排气温度下降,平均绝热指数上升。相同稀释率下,相比稀燃,EGR的滞燃期长,燃烧重心提前,两者燃烧持续期基本相等,稀释极限低,绝热指数小,排气温度低。在稀释率分别为20%、35.9%时,最大可减小有效燃油消耗率4.7%、7.2%。热容对燃油经济性的影响占主导地位,相同稀释率下,循环变动系数小于3%时,相比稀燃,EGR具有更好的燃油经济性。 相似文献
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H.E. Saleh 《Renewable Energy》2009,34(10):2178-2186
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 (NOx), 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 NOx 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 NOx emissions can be attained within a limited EGR rate of 5–15% with very little economy penalty. 相似文献