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1.
《JSAE Review》1994,15(2):109-116
Simultaneous measurements were made in the same cycle of the light absorption and emission behavior of the OH (characteristic spectrum of 306.4 nm), CH (431.5 nm) and C2 (516.5 nm) radicals in the end-gas region using spectroscopic methods. The data obtained with absorption spectroscopy in particular made the following clear. First, the changes observed in the absorbance behavior of the radicals during combustion in an actual engine corresponded to the phenomena associated with the degeneracy of a cool flame. Secondly, prior to the occurrence of auto-ignition under abnormal combustion characterized by knocking, the absorbance waveforms showed distinct evidence of a behavior corresponding to that of a blue flame. 相似文献
2.
S. W. Lee Y. S. Cho W. C. Choi J. H. Lee Y. J. Park 《International Journal of Automotive Technology》2012,13(7):1149-1157
This study aims to investigate the combustion characteristics of mixed fuel of liquefied propane gas (LPG) and biodiesel under compression ignition (CI) in an effort to develop highly efficient and environmentally friendly mixed fuelbased CI engines. Although LPG fuel is known to be eco-friendly due to its low CO2 emission, LPG has not yet been widely applied for highly efficient CI engines because of its low cetane number and is usually mixed with other types of CI-friendly fuels. In this study, a number of experiments were prepared with a constant volume chamber (CVC) setup to understand the fundamental combustion characteristics of mixed fuel with LPG and biodiesel in two weight-based ratios and exhaust gas recirculation (EGR) conditions. The results from the current investigations verify the applicability of mixed fuel of LPG and biodiesel in CI engines with a carefully designed combustion control strategy that maximizes the benefits of the mixed fuel. Based on the results of this study, ignition is improved by increasing the cetane value by using higher blending ratios of biodiesel. As the blending ratios of biodiesel increased, CO and HC decreased and CO2 and NOx increases. 相似文献
3.
This research investigated the spray and combustion characteristics of compressed ignition type LPG fuel when a cetane number
enhancing additive was applied to a constant volume chamber. Because LPG has a lower cetane number, DTBP and alpha olefin
were added to the LPG (100% butane) to enhance the cetane number and viscosity. By adding the cetane enhancer, stable combustion
over the wide range of the ambient conditions was possible as well. According to the blending rates of DTBP and alpha olefin,
various proportions of LPG blended fuels were obtained. In a constant volume chamber, a high speed digital camera was also
employed to visualize the combustion characteristics of LPG fuel. The combustion pressures and heat-release rates of the LPG
blends were also compared at various ambient pressures. As the results of measurements of exhaust emissions, CO and HC were
reduced considerably, but CO2 was increased by blending LPG with DTBP and alpha olefin. 相似文献
4.
《JSAE Review》2002,23(2):195-203
It is recognized that alternative fuels such as liquid petroleum gas (LPG) have less polluting combustion characteristics than diesel fuel. In this study, LPG was injected into a high pressure and temperature chamber to reproduce the stratification processes in an engine. The spray images were taken by the use of a PLIF method with Nd:YAG laser to analyze their penetration and evaporation characteristics. Also the characteristics of combustion were investigated by simultaneous visualization of OH radical and flames.The results show that the mixture moves along the impingement wall that reproduced the piston bowl and reaches the ignition spark plug. Also, OH fluorescence rises sharply and then decreases gradually when the combustion is carried out actively. 相似文献
5.
Bin Yang Wu Qiang Zhan Xiao Yang Yu Wen Yu Gu Min Zhang Wanhua Su 《International Journal of Automotive Technology》2018,19(4):605-614
In-cylinder charge density at top dead center is an important parameter of diesel engines and is influenced by intake pressure, intake temperature, and compression ratio. The effects of charge density on fuel spray, combustion process, and emissions were investigated by using a constant volume bomb and a heavy-duty diesel engine. Spray development resistance increased with the increase of the charge density in the constant volume bomb. It was found that short spray penetration was accompanied by a large spray cone angle in the former stage with high charge density. However, the equivalence ratio was lowered and the degree of homogeneity of the mixture was increased in the later stage owing to the rapid interaction of fuel and gas at a high mixing rate. Combining the first law of thermodynamics and the second law of thermodynamics for analysis, as the charge density increased, the gross indicated thermal efficiency (ITEg) was improved. However, pumping loss had to be considered with higher charge density. Under this condition, the brake thermal efficiency (BTE) trend was increased initially and decreased subsequently. Under high-load operation (1200 r/min BMEP, 2.0 MPa), the minimum charge density value of 44.8 kg/m3 was found to be reasonable. This charge density was suitable for combustion and brought about minimum exhaust energy and trade-off emissions. Moreover, by analyzing two operation conditions in terms of the maximum BTE with the Miller and the conventional cycles, compression temperature and combustion temperature were reduced in the Miller cycle with the charge density 44.8 kg/m3. A high Cp/Cv could improve the cylinder exergy/power conversion process by its positive effect of increasing the specific heat ratio. Owing to the interaction between a high Cp/Cv and exergy loss to heat transfer, the condition with the minimal charge density could produce more piston work. 相似文献
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Fuel injection during negative valve overlap period was used to realize diesel homogeneous charge compression ignition (HCCI)
combustion. In order to control the combustion, CO2 in-cylinder injection was used to simulate external EGR. Effects of CO2 injection parameters (injection timing, quantity, pressure) on HCCI combustion and emission characteristics were investigated.
Experimental results revealed that CO2 in-cylinder injection can control the start of combustion and effectively reduce NOx emission. Either advancing CO2 injection timing or increasing CO2 injection quantity can reduce peak cylinder pressure and mean gas temperature, delay the starts of low temperature reaction
(LTR) and high temperature reaction (HTR), and lower pressure rise rate; NOx emission was reduced, while smoke, HC, and CO emissions increased. Since the combustion phase was improved, the indicated
thermal efficiency was also improved. Injection pressure determines the amount of disturbance introduced into the cylinder.
Generally, with the same injection quantity, higher injection pressure results in higher momentum flux and total momentum.
Larger momentum flux and momentum has a stronger disturbance to air-fuel mixture, resulting in a more homogeneous mixture;
therefore, larger injection pressure leads to lower NOx and smoke emissions. 相似文献
8.
B. C. Choi S. K. Choi S. H. Chung J. S. Kim J. H. Choi 《International Journal of Automotive Technology》2011,12(2):183-191
Experimental and numerical analyses of laminar diffusion flames were performed to identify the effect of fuel mixing on soot
formation in a counterflow burner. In this experiment, the volume fraction, number density, and particle size of soot were
investigated using light extinction/scattering systems. The experimental results showed that the synergistic effect of an
ethylene-propane flame is appreciable. Numerical simulations showed that the benzene (C6H6) concentration in mixture flames was higher than in ethylene-base flames because of the increase in the concentration of
propargyl radicals. Methyl radicals were found to play an important role in the formation of propargyl, and the recombination
of propargyl with benzene was found to lead to an increase in the number density for cases exhibiting synergistic effects.
These results imply that methyl radicals play an important role in soot formation, particularly with regard to the number
density. 相似文献
9.
在1台经过改装的单缸柴油机上,采用气相色谱和FT-IR红外光谱检测技术,开展了进气道喷射DME和甲醇双燃料HCCI燃烧方式,以及进气道喷射DME、缸内直喷甲醇双燃料复合燃烧方式下,非常规污染物排放特性的试验研究。结果表明,在不同的燃烧方式下均检测到甲醛、乙醛、甲酸、甲酸甲酯等非常规排放物,且甲醛是非常规排放物中的主要成分。DME—甲醇HCCI燃烧方式下,在同一负荷下随着甲醇喷射量的增加,甲醛、乙醛、甲酸甲酯的排放都有所增加;在同一甲醇浓度下随着发动机负荷的增加,甲醛的排放增加,乙醛的排放减少,甲酸甲酯的排放先减少后增加。复合式燃烧方式下,甲醛的排放随着有效功率的增大呈先降低后升高的趋势;甲酸甲酯和甲酸的排放均随着有效功率的增加而减少,随着DME喷射比例的增加而增加。DME—甲醇HCCI燃烧方式下,甲醇排放量增加十分明显。 相似文献
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Y. X. Shi Y. X. Cai X. H. Li Y. Y. Chen D. W. Ding W. Tang 《International Journal of Automotive Technology》2014,15(6):871-876
By using a self-designed non-thermal plasma (NTP) injection system, an experimental study of the regeneration of DPF was conducted at different temperatures, where oxygen as the gas source. The results revealed that PM can be decomposed to generate CO and CO2 by these active substances O3, O which was generated through the discharge reaction of NTP reactor. With the increasing of test temperature, the mass of C1 (C in CO) shows a overall downward trend while the mass of C2 (C in CO2) and C12 (C1 and C2) increase firstly and then decrease. When the test temperature is 80°C, the backpressure of DPF decreases fastest and the regenerative effect is remarkable. DPF can be regenerated by NTP technology without any catalyst at a lower temperature. Compared with the traditional regeneration method, the NTP technology has its superiority. 相似文献
12.
S. Abdullah W. H. Kurniawan M. Khamas Y. Ali 《International Journal of Automotive Technology》2011,12(1):29-38
In an era in which environmental pollution and depletion of world oil reserves are of major concern, emissions produced by
automotive vehicles need to be controlled and reduced. An ideal solution is to switch to a cleaner fuel such as natural gas,
which generates cleaner emissions. In addition, control over the in-cylinder air-fuel mixture can be best achieved through
a direct-injection mechanism, which can further improve combustion efficiency. This need for cleaner automobiles provides
the motivation for this paper’s examination of the use of computational fluid dynamic (CFD) simulations to analyze the concentrations
of the exhaust gases produced by a compressed natural gas engine with a direct-fuel-injection system. In this work, a compressed
natural gas direct-injection engine has been designed and developed through a numerical simulation using computational fluid
dynamics (CFD) to provide an insight into complex in-cylinder behavior. The emissions analyzed in this study were carbon monoxide
(CO), nitric oxide (NO) and carbon dioxide (CO2), i.e. the main pollutants produced by natural gas combustion. Based on a stoichiometric mixture, the concentrations of CO
and NO were computed using the dissociation of carbon dioxide and the extended Zeldovich mechanism. CO2 was calculated using a mass balance of the species involved in the combustion process. The simulation results were then compared
with the experimental data generated by a single-cylinder research engine test rig. A good agreement was obtained with the
experimental data for the engine speeds considered for all emissions concentrations. 相似文献
13.
Fast and predictive simulation tools are prerequisites for pursuing simulation based engine control development. A particularly
attractive tradeoff between speed and fidelity is achieved with a co-simulation approach that marries a commercial gas dynamic
code WAVE™ with an in-house quasi-dimensional combustion model. Gas dynamics are critical for predicting the effect of wave
action in intake and exhaust systems, while the quasi-D turbulent flame entrainment model provides sensitivity to variations
of composition and turbulence in the cylinder. This paper proposes a calibration procedure for such a tool that maximizes
its range of validity and therefore achieves a fully predictive combustion model for the analysis of a high degree of freedom
(HDOF) engines. Inclusion of a charge motion control device in the intake runner presented a particular challenge, since anything
altering the flow upstream of the intake valve remains “invisible” to the zero-D turbulence model applied to the cylinder
control volume. The solution is based on the use of turbulence multiplier and scheduling of its value. Consequently, proposed
calibration procedure considers two scalar variables (dissipation constant C
β
and turbulence multiplier C
M
), and the refinements of flame front area maps to capture details of the spark-plug design, i.e. the actual distance between
the spark and the surface of the cylinder head. The procedure is demonstrated using an SI engine system with dual-independent
cam phasing and charge motion control valves (CMCV) in the intake runner. A limited number of iterations led to convergence,
thanks to a small number of adjustable constants. After calibrating constants at the reference operating point, the predictions
are validated for a range of engine speeds, loads and residual fractions. 相似文献
14.
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
15.
《JSAE Review》2002,23(1):9-14
Characteristics of NOx formation in a gas turbine fuelled with hydrogen were analyzed with both an experimental and a numerical approach. This research experimentally investigated NOx reduction effect of rich–lean combustion in a coaxial burner. Hydrogen emits no Prompt NO even in rich mixture conditions, and can be more effective to reduce NOx in the rich–lean combustion system than hydrocarbons. The results show that the rich–lean combustion of hydrogen successfully reduces NOx emission compared with diffusive combustion. In the rich–lean combustion, hydrogen combustion has lower NOx emission compared to methane combustion, especially with larger equivalence ratio of richer side mixture. Calculations of NOx formation in the rich–lean combustion were also done employing the extended Zel’dovich NO formation mechanism. 相似文献
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In lean-DeNOX catalysis reactions, hydrogen is a good reducing agent in PGM catalysts as well as an effective promoter in
selective catalytic reduction reactions over base metal oxide catalysts. However, such a lean-DeNOX system, which uses hydrogen,
requires an on-board fuel reforming system applicable to internal combustion engines. In this study, catalytic partial oxidation
(CPOx) performance was tested in a laboratory for various reactants and hydrocarbon conditions. Volume concentrations of 5–10%
oxygen and 0-5% water vapor were used to simulate diesel exhaust, and n-C12H26 was used as the feedstock for the reforming reaction. In the CPOx of n-C12H26, the highest hydrogen selectivity was 64% and was achieved at 100,000 h-1 GHSV. Additionally, the C/O ratio was less than
unity in the absence of water vapor. However, as the water concentration was increased to 2.5 and 5.0 vol. % in the n-C12H26 CPOx reactions, the maximum hydrogen selectivity was increased from 64% in the absence of water to 70% and 75%, respectively.
This effect is a consequence of the water-gas shift reaction over the catalyst bed. Regarding oxygen concentration effects,
hydrogen selectivity slightly increased with increasing oxygen concentration from 10% to 15%. It was also found that the CPOx
reaction of n-C12H26 can be ignited at temperatures below 300 C. Accordingly, it can be concluded that CPOx is a useful and feasible device for
promoting diesel DeNOx catalysis in terms of hydrogen productivity and reaction initiation. 相似文献
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20.
点火正时对电控稀燃天然气发动机性能的影响 总被引:1,自引:0,他引:1
试验研究了点火正时对电控稀燃多点喷射天然气发动机燃烧及排放性能的影响规律。对该发动机转速为1 450 r/min,1 750 r/min,2 050 r/min,负荷为25%,50%,75%,100%的12个工况点进行了试验研究。研究结果表明,在其他燃烧边界条件不变的情况下,点火正时对该发动机输出扭矩及CH4排放影响不大,但是在2 050 r/min,100%负荷工况下,随着点火正时的进一步后移,出现扭矩下降及CH4排放增加的现象。点火正时对NOx排放有显著的影响,同一工况下,随着点火正时的推移,NOx排放明显降低。 相似文献