共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Jung M. Ishida S. Yamamoto H. Ueki D. Sakaguchi 《International Journal of Automotive Technology》2010,11(5):611-616
For realizing a premixed charge compression ignition (PCCI) engine, the effects of bio-ethanol blend oil and exhaust gas recirculation
(EGR) on PM-NOx trade-off have been investigated in a single cylinder direct injection diesel engine with the compression
ratio of 17.8. In the present experiment, the ethanol blend ratio and the EGR ratio were varied focusing on ignition delay,
premixed combustion, diffusive combustion, smoke, NOx and the thermal efficiency. Very low levels of 1.5 [g/kWh] NOx and 0.02
[g/kWh] PM, which is close to the 2009 emission standards imposed on heavy duty diesel engines in Japan, were achieved without
deterioration of the thermal efficiency in the PCCI engine operated with the 50% ethanol blend fuel and the EGR ratio of 0.2.
It is found that this improvement can be achieved by formation of the premixed charge condition resulting from a longer ignition
delay. A marked increase in ignition delay is due to blending ethanol with low cetane number and large latent heat, and due
to lowering in-cylinder gas temperature on compression stroke based on the EGR. It is noticed that smoke can be reduced even
by increasing the EGR ratio under a highly premixed condition. 相似文献
2.
Jaegu Kang Sanghyun Chu Jeongwoo Lee Gyujin Kim Kyoungdoug Min 《International Journal of Automotive Technology》2018,19(1):27-35
In this research, the effects of three operating parameters (Diesel injection timing, propane ratio, and exhaust gas recirculation (EGR) rates) in a diesel-propane dual fuel combustion were investigated. The characteristics of dual-fuel combustion were analyzed by engine parameters, such as emission levels (Nitrogen oxides (NOx) and particulate matter (PM)), gross indicated thermal efficiency (GIE) and gross IMEP Coefficient of Variance (CoV). Based on the results, improving operating strategies of the four main operating points were conducted for dual-fuel PCCI combustion with restrictions on the emissions and the maximum pressure rise rate. The NOx emission was restricted to below 0.21 g/kWh in terms of the indicated specific NOx (ISNOx), PM was restricted to under 0.2 FSN, and the maximum pressure rise rate (MPRR) was restricted to 10 bar/deg. Dual-fuel PCI combustion can be available with low NOx, PM emission and the maximum pressure rise rate in relatively low load condition. However, exceeding of PM and MPRR regulation was occurred in high load condition, therefore, design of optimal piston shape for early diesel injection and modification of hardware optimizing for dual-fuel combustion should be taken into consideration. 相似文献
3.
J. Lee S. Choi H. Kim D. Kim H. Choi K. Min 《International Journal of Automotive Technology》2013,14(4):551-558
Recent studies on dual-fuel combustion in compression-ignition (CI) engines, also known as diesel engines, fall into two categories. In the first category are studies focused on the addition of small amounts of gaseous fuel to CI engines. In these studies, gaseous fuel is regarded as a secondary fuel and diesel fuel is regarded as the main fuel for combustion. The objectives of these studies typically involve reducing particulate matter (PM) emissions by using gaseous fuel as a partial substitution for diesel fuel. However, the addition of gaseous fuel raises the combustion temperature, which increases emissions of nitrogen oxides (NOx). In the second category are studies focused on reactivity-controlled compression-ignition (RCCI) combustion. RCCI combustion can be implemented by early diesel injection with a large amount of low-reactivity fuel such as gasoline or gaseous fuel. Although RCCI combustion promises lower NOx and PM emissions and higher thermal efficiency than conventional diesel combustion, it requires a higher intake pressure (usually more than 1.7 bars) to maintain a lean fuel mixture. Therefore, in this study, practical applications of dual-fuel combustion with a low air-fuel ratio (AFR), which implies a low intake pressure, were systemically evaluated using propane in a diesel engine. The characteristics of dualfuel combustion for high and low AFRs were first evaluated. The proportion of propane used for four different operating conditions was then increased to decrease emissions and to identify the optimal condition for dual-fuel combustion. Although the four operating conditions differ, the AFR was maintained at 20 (? approximately equal to 0.72) and the 50% mass fraction burned (MFB 50) was also fixed. The results show that dual-fuel combustion can reduce NOx and PM emissions in comparison to conventional diesel combustion. 相似文献
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J. W. Chung J. H. Kang N. H. Kim W. Kang B. S. Kim 《International Journal of Automotive Technology》2008,9(1):1-8
Currently, due to the severity of world-wide air pollution by substances emitted from vehicles, emission control is being
enforced more strictly, and it is expected that the regulation requirements for emission will become even more severe. A new
concept combustion technology that can reduce the Nitrogen oxides (NOx) and PM in relation to combustion is urgently required.
As a core combustion technology among new combustion technologies for the next generation engine, the homogenous charge compression
ignition (HCCI) is expanding its application range by adopting a multiple combustion mode, a catalyst, direct fuel injection
and partially premixed charge compression ignition combustion using the split injection method. This paper used a split injection
method in order to apply the partially premixed charge compression ignition combustion method without significantly altering
engine specifications of the multiple combustion mode and practicality by referring to the results of studies on the HCCI
engine. Furthermore, the effects of the ratio of the fuel injection amount on split injection are investigated. From the test
results, the adequate combination of the ratio of the fuel injection amount for the split injection method has some benefit
on exhaust and fuel economy performance in a naturally aspirated single cylinder diesel engine. 相似文献
8.
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
9.
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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This study summarizes engine speed and load effects on HC species emissions from premixed charge compression ignition (PCI)
and conventional diesel combustion, and it evaluates diesel oxidation catalyst (DOC) formulations on a gas flow reactor for
the purpose of diesel particulate filter regeneration or lean NOx trap desulfation. HC emissions are sampled simultaneously by a Tedlar bag for light HC species and by a Tenax TA™ adsorption
trap for semi-volatile HC species, and they are analyzed by gas chromatography with a flame ionization detector. The bulk
temperature and residence time during combustion are key parameters that are important for understanding the effects of speed
and load on engine-out HC emissions. The degree of post-flame oxidation is higher in PCI than in conventional combustion,
and it is increased for PCI with a higher speed and load, as indicated by a lower fuel alkanes/THC ratio, a higher alkenes/fuel
alkanes ratio, and a higher methane/THC ratio. Ethene and n-undecane are two representative HC species, and they are used
as a surrogate mixture in the gas flow reactor to simulate PCI and conventional combustion with in-cylinder post fuel injection.
Among the three DOC formulations tested, the catalyst with constituent precious metals of platinum and palladium (PtPd) showed
the best light-off performance, followed by PtPd with an addition of cerium dioxide (PtPd+CeO2), and platinum (Pt), regardless of exhaust compositions. Conventional combustion exhaust composition shows a lower light-off
temperature than that of PCI, regardless of catalyst formulation. 相似文献
13.
H. Q. Yang S. J. Shuai Z. Wang J. X. Wang 《International Journal of Automotive Technology》2013,14(1):19-27
A novel combustion concept namely “multiple premixed compression ignition” (MPCI) in gasoline direct injection compression ignition (GDICI) regime is proposed. Its predominant feature is the first premixed and followed quasipremixed combustion processes in a sequence of “spray-combustion-spray-combustion”. The multiple-stage premixed combustion decouples the pressure rise with pollutants formation process, which means the pressure rise rate and emissions can be reduced simultaneously, while achieving a high thermal efficiency. The gasoline MPCI mode has been demonstrated in a research engine with a compression ratio of 18.5. Gasoline with the research octane number (RON) of 94.4 was tested under 1400 rpm, 0.6 MPa IMEP conditions, without EGR and intake boosting. A parameter study of common rail pressure and intake temperature was implemented to investigate their effects on the performance of MPCI mode. Compared to the single-stage diffusion combustion in traditional diesel engines, the gasoline MPCI mode achieves lower emissions of soot, NO, CO, as well as slightly higher indicated efficiency, with a penalty of higher THC emissions when the common rail pressure is larger than 80 MPa in this study. With intake temperature sweeping, the gasoline MPCI mode also has the foregoing advantages compared to the diesel under the same operating conditions. 相似文献
14.
Extensive usage of automobiles has certain disadvantages and one of them is its negative effect on environment. Carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx), sulphur dioxide (SO2) and particulate matter (PM) come out as harmful products during incomplete combustion from internal combustion (IC) engines. As these substances affect human health, regulatory bodies impose increasingly stringent restrictions on the level of emissions coming out from IC engines. This trend suggests the urgent need for the investigation of all aspects relevant to emissions. It is required to modify existing engine technologies and to develop a better after-treatment system to achieve the upcoming emission norms. Diesel engines are generally preferred over gasoline engines due to their undisputed benefit of fuel economy and higher torque output. However, diesel engines produce higher emissions, particularly NOx and PM. Aftertreatment systems are costly and occupy more space, hence, in-cylinder solutions are preferred in reducing emissions. Exhaust gas recirculation (EGR) technology has been utilized previously to reduce NOx. Though it is quite successful for small engines, problem persists with large bore engines and with high rate of EGR. EGR helps in reducing NOx, but increases particulate emissions and fuel consumption. Many in-cylinder solutions such as lower compression ratios, modified injection characteristics, improved air intake system etc. are required along with EGR to accomplish the future emission norms. Modern combustion techniques such as low temperature combustion (LTC), homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI) etc. would be helpful for reducing the exhaust emissions and improving the engine performance. However, controlling of autoignition timing and achieving wider operating range are the major challenges with these techniques. A comprehensive review of diesel engine performance and emission characteristics is given in this paper. 相似文献
15.
This paper reviews the particle emissions formed during the combustion process in spark ignition and diesel engine. Proposed
legislation in Europe and California will impose a particle number requirement for GDI (gasoline direct injection) vehicles
and will introduce the Euro 6 and LEV-III emission standards. More careful optimization for reducing particulate emission
on engine hardware, fuel system, and control strategy to reduce particulate emissions will be required during cold start and
warm-up phases. Because The diesel combustion inherently produces significant amounts of PM as a result of incomplete combustion
around individual fuel droplets in the combustion zone, much attention has been paid to reducing particle emissions through
electronic engine control, high pressure injection systems, combustion chamber design, and exhaust after-treatment technologies.
In this paper, recent research and development trends to reduce the particle emissions from internal combustion engines are
summarized, with a focus on PMP activity in EU, CARB and SAE papers and including both state-of-the-art light-duty vehicles
and heavy-duty engines. 相似文献
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C. B. Yin Z. D. Zhang N. L. Xie Y. D. Sun T. Sun 《International Journal of Automotive Technology》2016,17(4):591-604
In this paper, knocking combustion in dual-fuel diesel engine is modeled and investigated using the CFD code coupled with detailed chemical kinetics. The ethanol/gasoline blend E85 is used as the primary fuel in a dual-fuel combustion concept based on a light-duty diesel engine equipped with a common-rail injection system. The E85 blend is injected and well mixed with intake air in the intake manifold and is ignited by the direct injection diesel fuel. A 46-species, 187-reaction Multicomponent mechanism is adopted to model the auto-ignition process of the E85/air/diesel mixture ahead of the flame front. Based on the model validation, knocking combustion under boost and full load operating condition for 0 %, 20 %, 50 %, as well as 70 % E85 substitute energy is simulated. The effects of E85 substitute rate and two stage injection strategies on knock intensity, power output, as well as location of the auto-ignition initiation is clearly reproduced by the model. The calculation result shows that, for a high E85 rate of 50 % and 70 % with single injection strategies, the most serious knock and the origin of auto-ignition always occurs far away from where the flame of diesel spray is first generated, at the center of combustion chamber, due to higher pressure wave, relatively richer E85 mixture and longer distances of flame propagation. The two stage injection strategies with a small amount of diesel pilot injection ahead of the main injection primarily influence the ignition behavior of the directly injected fuel, leads to a lower pressure rise rate and a reduced propagation distance, both of which contribute to the attenuation of knock intensity for a higher E85 rate. 相似文献
18.
《JSAE Review》1998,19(4):311-317
We have investigated combustion characteristics of lean gasoline–air pre-mixture ignited by diesel fuel injection using a high compression direct injection diesel engine. Gasoline was supplied as a uniform lean mixture by using carburetors, and diesel fuel was directly injected into the cylinder. It was confirmed that the lean mixture of air–fuel ratio between 150 and 35 could be ignited and burned by this ignition method. As the diesel fuel injection increased, HC concentration decreased, and NO and CO concentration increased. The exhaust gas emission of pollutants could be reduced when lean mixture was ignited by an optimum diesel fuel injection. 相似文献
19.
T. Fang R. E. Coverdill C. -F. F. Lee R. A. White 《International Journal of Automotive Technology》2008,9(5):551-561
An optically accessible single-cylinder high speed direct-injection (HSDI) Diesel engine equipped with a Bosch common rail
injection system was used to study low temperature Modulated Kinetics (MK) combustion with a retarded single main injection.
High-speed liquid fuel Mie-scattering was employed to investigate the liquid distribution and evolution. By carefully setting
up the optics, three-dimensional images of fuel spray were obtained from both the bottom of the piston and the side window.
The NOx emissions were measured in the exhaust pipe. The influence of injection pressure and injection timing on liquid fuel
evolution and combustion characteristics was studied under similar fuel quantities. Interesting spray development was seen
from the side window images. Liquid impingement was found for all of the cases due to the small diameter of the piston bowl.
The liquid fuel tip hits the bowl wall obliquely and spreads as a wall jet in the radial direction of the spray. Due to the
bowl geometry, the fuel film moves back into the central part of the bowl, which enhances the air-fuel mixing process and
prepares a more homogeneous air-fuel mixture. Stronger impingement was seen for high injection pressures. Injection timing
had little effect on fuel impingement. No liquid fuel was seen before ignition, indicating premixed combustion for all the
cases. High-speed combustion video was taken using the same frame rate. Ignition was seen to occur on or near the bowl wall
in the vicinity of the spray tip, with the ignition delay being noticeably longer for lower injection pressure and later injection
timing. The majority of the flame was confined to the bowl region throughout the combustion event. A more homogeneous and
weaker flame was observed for higher injection pressures and later injection timing. The combustion structure also proves
the mixing enhancement effect of the liquid fuel impingement. The results show that ultra-low sooting combustion is feasible
in an HSDI diesel engine with a higher injection pressure, a higher EGR rate, or later injection timing, with little penalty
on power output. It was also found that injection timing has more influence on HCCI-like combustion using a single main injection
than the other two factors studied. Compared with the base cases, simultaneous reductions of soot and NOx were obtained by
increasing EGR rate and retarding injection timing. By increasing injection pressure, NOx emissions were increased due to
leaner and faster combustion with better air-fuel mixing. However, smoke emissions were significantly reduced with increased
injection pressure. 相似文献
20.
为了改善发动机燃用高比例生物质混合燃料的性能,在中等比例的生物柴油-柴油混合燃料中分别添加5%、10%和20%体积比的乙醇(分别用BD50E5,BD50E10和BD50E20表示),在一台6缸增压共轨柴油机上,将发动机的转速稳定在1 600 r·min-1,选择7个不同的负荷点测定不同掺混比生物柴油-柴油-乙醇混合燃料的燃烧与排放性能,并将其与柴油进行对比。结果表明:在平均有效压力为0.322 MPa的低负荷条件下,发动机为预喷加主喷喷油策略,在预喷的低温反应阶段生物柴油-柴油-乙醇混合燃料产生了大量羟基自由基,因此混合燃料的缸内最大压力和最大瞬时放热率均高于柴油;随着负荷的增大,当平均有效压力为0.805 MPa时,发动机的喷油策略转变为单段喷射,乙醇的热值较低导致生物柴油-柴油-乙醇混合燃料的缸内最大压力和最大瞬时放热率低于柴油;随着乙醇掺混比的增大,受乙醇低十六烷值和高汽化潜热的影响,生物柴油-柴油-乙醇混合燃料的滞燃期明显延长;强烈的预混燃烧和乙醇的高含氧量使混合燃料的燃烧速度明显加快,乙醇的添加有利于燃料集中放热从而缩短燃烧持续期;与纯柴油相比,BD50E5,BD50E10和BD50E20的NOx排放量分别升高了10.46%、12.59%和17.52%,碳烟排放量分别降低了37.91%、45.85%和49.25%,CO排放量分别降低了20.24%、36.43%和46.43%,HC排放量分别降低了12.53%、4.40%和0.76%。 相似文献