共查询到20条相似文献,搜索用时 15 毫秒
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Recently, to reduce environmental pollution and the waste of limited energy resources, there is an increasing requirement
for higher engine efficiency and lower levels of harmful emissions. A premixed charge compression ignition (PCCI) engine,
which uses a 2-stage type injection, has drawn attention because this combustion system can simultaneously reduce the amount
of NOx and PM exhausted from diesel engines. It is well known that the fuel injection timing and the spray angle in a PCCI
engine affect the mixture formation and the combustion. To acquire two optimal injection timings, the combustion and emission
characteristics of the PCCI engine were analyzed with various injection conditions. The flame visualization was performed
to validate the result obtained from the engine test. This study reveals that the optimum injection timings are BTDC 60° for
the first injection and ATDC 5° for the second injection. In addition, the injection ratio of 3 to 7 showed the best NOx and
PM emission results. 相似文献
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U. Egüz N. C. J. Maes C. A. J. Leermakers L. M. T. Somers L. P. H. De Goey 《International Journal of Automotive Technology》2013,14(5):693-699
The objective of new combustion concepts is to meet emission standards by improving fuel air mixing prior to ignition. Since there is no overlap between injection and ignition, combustion is governed mainly by chemical kinetics and it is challenging to control the phasing of ignition. Reactivity Controlled Compression Ignition (RCCI) combustion aims to control combustion phasing by altering the fuel ratios of the high- and low octane fuel and injection timings. In this study the dual fuel blend is prepared with gasoline and diesel fuels. The applied injection timings of the diesel are very early (90 to 60° CA bTDC). In the detailed reaction mechanism, n-heptane and iso-octane represent diesel and gasoline fuel, respectively. A multi-zone model approach is implemented to perform RCCI combustion simulation. Ignition characteristics are analyzed by using CA50 as the main parameter. In the experiments for the early direct injection (DI) timing advancing the injection time results in a later ignition. Qualitatively, the trend effect of the diesel injection timing and the effect of the ratio gasoline/diesel are captured accurately by the multi-zone model. 相似文献
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Lean burn is an effective way to improve spark ignition engine fuel economy. In this paper, the combustion and emission characteristics
of a lean burn natural gas fuelled spark ignition engine were investigated at various throttle positions, fuel injection timings,
spark timings and air fuel ratios. The results show that ignition timings, the combustion duration, the coefficient of variation
(COV) of the indicated mean effective pressure (IMEP) and engine-out emissions are dependent on the overall air fuel ratio,
spark timings, throttle positions and fuel injection timings. With the increase of the air fuel ratio, the ignition delays
and combustion duration increases. Fuel injection timings affect ignition timings, combustion duration, IMEP, and the COV
of the IMEP. Late fuel injection timings can decrease the COV of the IMEP. Moreover, the change in the fuel injection timings
reduces the engine-out CO, total hydrocarbon (THC) emissions. Lean burn can significantly reduce NOx emissions, but it results
in high cyclic variations. 相似文献
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L. D. K. Nguyen N. W. Sung S. S. Lee H. S. Kim 《International Journal of Automotive Technology》2011,12(3):339-350
The effects of split injection, oxygen enriched air, and heavy exhaust gas recirculation (EGR) on soot emissions in a direct
injection diesel engine were studied using the KIVA-3V code. When split injection is applied, the second injection of fuel
into a cylinder results in two separate stoichiometric zones, which helps soot oxidation. As a result, soot emissions are
decreased. When oxygen enriched air is applied together with split injection, a higher concentration of oxygen causes higher
temperatures in the cylinder. The increase in temperature promotes the growth reaction of acetylene with soot. However, it
does not improve acetylene formation during the second injection of fuel. As more acetylene is consumed in the growth reaction
with soot, the concentration of acetylene in the cylinder is decreased, which leads to a decrease in soot formation and thus
soot emissions. A combination of split injection, a high concentration of oxygen, and a high EGR ratio shows the best results
in terms of diesel emissions. In this paper, the split injection scheme of 75.8.25, in which 75% of total fuel is injected
in the first pulse, followed by 8°CA of dwell time, and 25% of fuel is injected in the second pulse, with an oxygen concentration
of 23% in volume and an EGR ratio of 30% shows a 45% reduction in soot emissions, with the same NOx emissions as in single
injection. 相似文献
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Jeongwoo Lee Sanghyun Chu Jaegu Kang Kyoungdoug Min Hyunsung Jung Hyounghyoun Kim Yohan Chi 《International Journal of Automotive Technology》2017,18(6):943-950
Environmental problems have become a major issue for diesel engine development. Although emission aftertreatment systems such as DPFs (diesel particulate filters), LNTs (lean NOx traps) and SCR (selective catalytic reduction) have been used in diesel vehicles, the manufacturing cost increase caused by this equipment can be hard to be control. Thus, it is better for engine emissions to be reduced by improving the combustion system. A dual-fuel combustion concept is a recommended method to improve a combustion system and effectively reduce emissions. Low reactivity fuel including gasoline and natural gas, which was supplied to the intake port by the FPI (port fuel injector), improved the premixed air-fuel mixture conditions before ignition. Additionally, a small amount of high reactivity fuel, in this case diesel, was injected into the cylinder directly as an ignition source. This dual-fuel combustion promises lower levels of NOx (nitrogen oxide) and PM (particulate matter) emissions due to the elimination of local rich regions in the cylinder. However, it is challenging to control the dual-fuel combustion because the combustion stability and efficiency deteriorate due to the lack of ignition source and reactivity. Thus, it is important to establish an appropriate dual-fuel operating strategy to achieve stable, high efficiency and low emission operation. As a result of this research, a detailed operating method of dual-fuel PCI (premixed compression ignition) was introduced in detail at a low speed and low load condition by using a single cylinder diesel engine. Engine operating parameters including the gasoline ratio, a diesel injection strategy consisting of multiple injectors and timing, the EGR (exhaust gas recirculation) rate and the intake pressure were controlled to satisfy the low ISNOx (indicated specific NOx) and PM emissions levels (0.21 g/kWh and 0.1 FSN, 0.040 g/kWh, respectively) as per the EURO-6 regulation without any after-treatment systems. The results emphasized that a well-constructed dual-fuel PCI operating strategy showed low NOx and PM emissions and high GIE (gross indicated fuel conversion efficiency) with excellent combustion stability. 相似文献
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改善柴油机排放的核心是对燃烧过程进行优化,通过改善燃烧过程来降低柴油机排放是当前柴油机研究中的重要课题。本文主要从优化进气系统、优化喷油系统、优化燃烧室结构、燃料的改质及优化润滑系统五个方面进行分析,综合这些相互制约的优化措施优化柴油机的燃烧过程,降低颗粒物质PM和NOx的直接排放。 相似文献
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柴油微引燃乙醇发动机采用进气道喷射乙醇、缸内直喷微量柴油引燃的方式进行燃料供给。基于单缸四冲程柴油机,对其燃烧、性能及排放特性进行研究,固定引燃柴油喷射量为发动机能实现压燃着火的最小值,在进气压力为0.15 MPa时比较不同乙醇喷射量的工况组,通过改变柴油喷射时刻进行工况扫描。结果表明,引燃柴油的喷射时刻对发动机的燃烧、性能和排放影响显著。柴油微引燃乙醇发动机在中高负荷能够稳定运行,指示热效率可达34%以上,通过适当调节柴油喷射时刻,可以有效控制未燃碳氢(UHC)、NO_x与CO排放,同时可以实现极低的炭烟排放。柴油微引燃乙醇发动机燃烧模式为预混合或部分预混合燃烧,燃烧有两阶段放热特征,改变引燃柴油喷射时刻,可以有效控制燃烧相位。 相似文献
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《JSAE Review》2002,23(3):297-302
In recent DI diesel engines designed to achieve high output and meet future exhaust regulation, the pilot injection control using a common-rail injection system is adopted. In this research, we developed visualization equipment for pilot combustion behavior of non-luminous flame to clarify the influence of pilot injection parameters (timing and quantity) on engine performance. As a result of this analysis, we clarified the influence of pilot injection parameters on pilot-main combustion and found the optimum pilot injection controlling method. 相似文献
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比较了客车燃用两种不同比例二甲醚—柴油混合燃料及普通柴油的能耗与排放。结合燃料生产阶段和运输过程的数据,分析和比较了不同燃料在客车上应用的全生命周期指标。结果表明,与柴油车相比,在全生命周期内二甲醚—柴油混合燃料车的VOC,CO,NOx和PM的排放分别降低,且随着混合燃料中二甲醚比例的增加,有害排放物下降得更多,但混合燃料车的总能耗、CO2和SO2排放分别增加。 相似文献
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The purpose of this study is to understand the operational characteristics of a diesel engine that uses BD20 reformed by ultrasonic
energy irradiation. In particular we study the effects of tuning injection delay and EGR rate. BD containing about 10% oxygen
has attracted attention due to soaring crude oil prices and environmental pollution. This oxygen decreases soot by promoting
combustion, but it also increases NOx. To solve this problem, injection timing may be delayed or an EGR system may be applied.
These adjustments normally lower engine power and increase exhaust emission but, in using fuel reformed by ultrasonic energy
irradiation (which is changed physically and chemically to promote combustion), we may hope to circumvent this problem. To
control the duration of the ultrasonic energy irradiation, the capacity of the chamber in an ultrasonic energy fuel supply
system was tested at 550cc and 1100cc capacities. As for the results of the experiment, we could identify the optimum EGR
rate by investigating the engine performance and the characteristics of exhaust emissions according to the injection timing
and the EGR rate while ultrasonically irradiated BD20 was fed to a commercial diesel engine. With UBD20 (at an injection timing
of BTDC 16°), the optimum EGR rate, giving satisfactory engine performance and exhaust emissions characteristics, was in the
range of 15∼20%. 相似文献
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二甲醚/柴油混合燃料在压燃式发动机上的应用 总被引:1,自引:0,他引:1
为探索二甲醚/柴油混合燃料作为柴油机替代燃料的应用性能,对D20二甲醚/柴油混合燃料的喷雾特性进行了试验研究;同时,开展了直喷式柴油机燃用二甲醚/柴油混合燃料动力性能、经济性能及排放性能研究。结果表明:在同样的环境背压下,D20混合燃料的油束与柴油相比较,贯穿度有所缩短,喷雾锥角有所增大;柴油机燃用二甲醚/柴油混合燃料时,通过适当调整循环油量,发动机的动力性可以超过原柴油机,最低当量比油耗下降4.5%,烟度指标下降70%以上,NOx排放降低30%~50%;二甲醚/柴油混合燃料是一种能实现高比功率、低排放的石油替代燃料。 相似文献
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《JSAE Review》2002,23(4):407-414
Fuel properties play a dominant role in the spray, mixture formation and combustion process, and are a key to emission control and efficiency optimization. This paper deals with the influence of the fuel properties on the spray and combustion characteristics in a high-pressure and temperature chamber. Light diesel fuel spray and combustion images were taken by using a high-speed video camera and analyzed by their penetration and evaporation characteristics in comparison with current diesel fuel. Then, a single-cylinder DI engine was used to investigate combustion and exhaust characteristics. The mixture formation of the light diesel fuel is faster than that of the current fuel depending on physical properties like boiling point, density, viscosity and surface tension. Engine test results show that smoke is reduced without an increase in other emissions. 相似文献
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喷油正时对电控共轨柴油机燃用LNG-柴油双燃料的影响 总被引:1,自引:0,他引:1
为了在电控共轨柴油机上应用LNG,将电控共轨柴油机改装为柴油引燃天然气双燃料发动机,研究了引燃柴油喷油正时对双燃料发动机性能与排放的影响。试验选取最大扭矩转速1 600r/min和标定转速2 500r/min,在不同油门开度工况下研究了双燃料发动机的功率、燃料消耗量、有效燃料消耗率和排放。试验结果表明:随喷油正时的提前,双燃料发动机的输出功率先增大后降低;有效燃料消耗率先降低后增大,并在最大功率正时处达到最低;HC,CO和炭烟排放降低,CO2排放升高;油门开度较小时的NOx排放降低,而油门开度较大时升高。 相似文献