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We investigated the effects of the fuel injection timing — both for early and late injection — in conjunction with the throttle
opening ratio on the fuel-air mixing characteristics, engine power, combustion stability and emission characteristics of a
DI CNG spark engine and control system that had been modified and designed according to the author’s original idea. We verified
that the combustion characteristics were affected by the fuel injection timing and that the engine conditions were affected
by the throttle opening ratios and the rpm. The combustion characteristics were greatly improved for a complete open throttle
ratio with an early injection timing and for a partial throttle ratio with a late injection timing. The combustion duration
was governed by the duration of flame propagation in late injection timing scenarios and by the duration of early flame development
in cases of early injection timing. As the result, the combustion duration is shortened, the lean limit is improved, the air-fuel
mixing conditions are controlled, and the emissions are reduced through control of the fuel injection timing and vary according
to ratio of the throttle opening. 相似文献
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C. W. Park H. C. Oh S. D. Kim H. S. Kim S. Y. Lee C. S. Bae 《International Journal of Automotive Technology》2014,15(4):525-533
To comply with reinforced emission regulations for harmful exhaust gases, including carbon dioxide (CO2) emitted as a greenhouse gas, improved technologies for reducing CO2 and fuel consumption are being developed. Stable lean combustion, which has the advantage of improved fuel economy and reduced emission levels, can be achieved using a sprayguided-type direct-injection (DI) combustion system. The system comprises a centrally mounted injector and closely positioned spark plugs, which ensure the combustion reliability of a stratified mixture under ultra-lean conditions. The aim of this study is to investigate the combustion and emission characteristics of a lean-burn gasoline DI engine. At an excess air ratio of 4.0, approximately 23% improvement in fuel economy was achieved through optimal event timing, which was delayed for injection and advanced for ignition, compared to that under stoichiometric conditions, while NOx and HC emissions increased. The combustion characteristics of a stratified mixture in a spray-guided-type DI system were similar to those in DI diesel engines, resulting in smoke generation and difficulty in three-way catalystutilization. Although a different operating strategy might decrease fuel consumption, it will not be helpful in reducing NOx and smoke emissions; therefore, alternatives should be pursued to achieve compliance with emission regulations. 相似文献
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G. T. Chala A. R. A. Aziz F. Y. Hagos 《International Journal of Automotive Technology》2017,18(1):85-96
There is an increasing interest in supercharging spark ignition engines operating on CNG (compressed natural gas) mainly due to its superior knock resisting properties. However, there is a penalty in volumetric efficiency when directly injecting the gaseous fuel at early and partial injection timings. The present work reports the combined effects of a small boost pressure and injection timing on performance and combustion of CNG fueled DI (direct injection) engine. The experimental tests were carried out on a 4-stroke DI spark ignition engine with a compression ratio of 14. Early injection timing, when inlet valves are still open (at 300°BTDC), and partial injection timing, in which part of the injection occurs after the inlet valves are closed (at 180°BTDC), were varied at each operating speed with variation of the boost pressure from 2.5 to 10 kPa. A narrow angle injector (NAI) was used to increase the mixing rate at engine speeds between 2000 and 5000 rpm. Similar experiments were conducted on a naturally aspirated engine and the results were then compared with that of the boosting system to examine the combined effects of boost pressure and injection timing. It was observed that boost pressure above 7.5 kPa resulted in an improvement of performance and combustion of CNG DI engine at all operating speeds. This was manifested in the faster heat release rates and mass fraction burned that in turn improved combustion efficiency of the boosting system. An increased in cylinder pressure and temperature was also observed with boost pressure compared to naturally aspirated engine. Moreover, the combustion duration was reduced due to concentration of the heat release near to the top dead center as the result of the boost pressure. Supercharging was also found to reduce the penalty of volumetric efficiency at both the simulated port and partial injection timings. 相似文献
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D. Jung W. L. Wang A. Knafl T. J. Jacobs S. J. Hu D. N. Assanis 《International Journal of Automotive Technology》2008,9(1):9-15
The effects of the Abrasive Flow Machining (AFM) process on a direct injection (DI) Diesel engine fuel injector nozzle are
studied. Geometry characterization techniques were developed to measure the microscopic variations inside the nozzle before
and after the process. This paper also provides empirically-based correlations of the nozzle geometry changes due to the AFM
process. The resulting impact of the process on the engine performance and emissions are also assessed with a DI Diesel engine
test setup. This study shows that properly AFM-processed injectors can enhance engine performance and improve emissions due
to the improved quality of the nozzle characteristics. However, an extended process can also cause enlargement of the nozzle
hole as a side effect, which can adversely affect emissions. Emission measurements show the trade-off for the minimum levels
as the process proceeds. Since the enlargement of the hole during the AFM process is not avoidable and must be minimized,
strict control over the process is required. This control can be enforced by either limiting the AFM processing period, or
by properly preparing the initial hole diameter so as to accommodate the inevitable changes in the nozzle geometry. 相似文献
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Q. Fan J. Bian H. Lu L. Li J. Deng 《International Journal of Automotive Technology》2012,13(4):523-531
The first firing cycle is very important during cold-start for all types of spark ignition engines. In addition, the combustion characteristics of the first firing cycle affect combustion and emissions in the following cycles. However, the first-cycle fuel-air mixing, combustion and emissions generation within the cylinder of a two-stage direct-injection (TSDI) engine during cold start is not completely understood. Based on the total stoichiometric air-fuel ratio and local richer mixture startup strategy, the first-cycle firing and combustion characteristic at cold start were investigated in a two-stage direct injection (TSDI) gasoline engine. In addition, the effects of the first injection timing, second injection timing, 1st and 2nd fuel injection proportion and total excess air ratio on the in-cylinder pressure, heat release rate and accumulated heat release were analyzed on the basis of a cycle-by-cycle analysis. It is shown that a larger 2nd fuel injection amount and later 2nd injection timing are more beneficial to the firing of the first cycle in the case of a total excess air ratio of 1.0. The optimum 1st and 2nd injection timing fuel injection proportions are 120°CA ATDC during the intake stroke, 60°CA BTDC during the compression stroke and 1:1. In addition, the firing boundary is a 2nd injection timing later than 90°CA BTDC during the compression stroke in the case of the 1st injection timing from 60°CA to 180°CA ATDC during an intake stroke and involves a 1st and 2nd fuel injection proportion of 1:1 and an excess air ratio of 1.0. The study provides a detailed understanding of cold-start combustion characteristics and a guide for optimizing the reliable first-cycle firing at cold start. 相似文献
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In this work a two-stroke scooter engine was modified to work with semi-direct injection of gasoline at a pressure of 8 bar
from an injector in the cylinder barrel pointed toward the cylinder head. The influence of injection timing, injection pressure,
spark plug location and air-fuel ratio, on performance, emissions and combustion characteristics has been investigated. In
addition, a comparison has been made with manifold injection of gasoline on the same engine at a given speed and various outputs.
A significant reduction in HC emissions and fuel consumption with no adverse effects on NOx emissions and combustion stability
was observed. A small drop in power and increase in CO emission were observed disadvantages of the new injection system. Injection
timing was found to be the most important factor and a balance between reduction in shortcircuited fuel by late injection,
and time for mixture preparation by advancing the injection, was found to be essential. 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
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G. S. Jung Y. H. Sung B. C. Choi M. T. Lim 《International Journal of Automotive Technology》2009,10(1):1-7
Compression ignition of homogeneous charges in internal combustion (IC) engines is expected to offer high efficiency of DI
diesel engines without high levels of NOx and particulate emissions. This study is intended to find ways of extending the
rich limit of HCCI operation, one of the problems yet to be overcome. Exhaust emissions characteristics are also explored
through analyses of the combustion products. DME fuel, either mixed with air before induction or directly injected into the
combustion chamber of a rapid compression and expansion machine, is compressed to ignite under various conditions of compression
ratio, equivalence ratio, and injection timing. The characteristics of the resulting combustion and exhaust emissions are
discussed in terms of the rate of heat release computed from the measured pressure, and the concentrations of THC, CO, and
NOx are measured by FT-IR and CLD. The experimental data to date show that operation without knock is possible with mixtures
of higher equivalence ratio when DME is directly injected rather than when it is inducted in the form of a perfectly homogeneous
fuel-air mixture. Although fuel injected early in the compression stroke promotes homogeneity of the DME-air mixture in the
cylinder, it causes the mixture to ignite too early to secure good thermal efficiency and knock-free operation at high loads.
Low temperature reactions occur at about 660K regardless of the fueling methods, fuel injection timing and equivalence ratio.
The main components of hydrocarbon emissions turned out to be unburned fuel (DME), formaldehyde and methane. 相似文献
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Seunghyun Lee Hoimyung Choi Kyoungdoug Min 《International Journal of Automotive Technology》2017,18(4):571-578
Vehicle emissions regulations are becoming increasingly severe and remain a principal issue for vehicle manufacturers. Since, WLTP (Worldwide harmonized Light vehicles Test Procedures) and RDE (real driving emission) regulations have been recently introduced, the engine operating conditions have been rapidly changed during the emission tests. Significantly more emissions are emitted during transient operation conditions compared to those at steady state operation conditions. For a diesel engine, combustion control is one of the most effective approaches to reduce engine exhaust emissions, particularly during the transient operation. The concern of this paper is about reducing emissions using a closed loop combustion control system which includes a EGR rate estimation model. The combustion control system calculates the angular position where 50 % of the injected fuel mass is burned (MFB50) using in-cylinder pressure for every cycle. In addition, the fuel injection timing is changed to make current MFB50 follow the target values. The EGR rate can be estimated by using trapped air mass and in-cylinder pressure when the intake valves are closed. When the EGR rate is different from the normal steady conditions, the target of MFB50 and the fuel injection timing are changed. The accuracy of the model is verified through engine tests, as well as the effect of combustion control. The peaks in NO level was decreased during transient conditions after adoption of the EGR model-based closed loop combustion control system. 相似文献
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Zhong Chang Liu Xing Yuan Jing Tian Yong Qiang Han Kai Bo Yu Peng Kun Teng 《International Journal of Automotive Technology》2018,19(5):783-794
The object of this paper is to reduce soot emissions under typical 5s transient conditions of constant speed and increasing torque. And effects of fuel injection timing on combustion and emissions parameters were experimentally and numerically studied in a regulated two-stage turbocharged diesel engine with a turbine bypass valve (TBV). The test results indicated that: the smaller TBV opening could improve deterioration of smoke emissions and BSFC at medium and heavy loads. Afterward, the full-stage injection timing (FSIT) strategies (delaying injection timing during the entire transient process) could reduce soot and NOX emissions simultaneously. However, when TBV opening became larger, smoke emissions and BSFC were deteriorated gradually. Moreover, the sectional-stage injection timing (SSIT) strategies (advancing injection timing from 10 % load to a preset load and delaying injection timing from the preset load to 100 % load) could markedly reduce soot emissions by 75.8 % with TBV opening 20 %; the degradation of fuel consumption could be effectively suppressed. Finally, coupling the SSIT strategies with the TBV control strategies could significantly improve the transient performance. 相似文献
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介绍了共轨蓄压式电控喷油系统的工作原理。共轨蓄压式电控喷油系统喷油正时的控制采用开环控制方案,喷油正时的控制精度主要取决于喷油延迟时间的准确度,而喷油延迟时间主要受共轨油压和发动机转速的影响。具体分析了通过优化喷油延迟角MAP图来实现共轨蓄压式电控喷油系统喷油正时精确控制的方法。 相似文献
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