共查询到19条相似文献,搜索用时 786 毫秒
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进气可变滚流系统应用于缸内直喷汽油机的数值模拟 总被引:1,自引:0,他引:1
建立了缸内直喷(GDI)汽油机三维数值模型,在分析原机工作过程的基础上引入了可变进气滚流系统(VITS)。首先采用稳态CFD方法对两种方案进行了分析,进气可变滚流系统工作时气门最大升程的流量系数降低56%,滚流比提高221%。然后对该发动机进气、压缩和油气混合过程进行了瞬态CFD分析,结果显示,可变进气滚流系统工作时,在缸内能形成更规则的大尺度漩涡,与原机相比燃油蒸发速度更快,混合气均匀性更好,适用于GDI发动机均质燃烧模式。 相似文献
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Pop-Paul Ewphun Chau Tan Vo Prathan Srichai Chinda Charoenphonphanich Susumu Sato Hidenori Kosaka 《International Journal of Automotive Technology》2017,18(4):643-652
This paper investigates the effects of Hydrotreated vegetable oil-diesel blend to combustion characteristics under various ambient oxygen concentrations and ambient pressure. Combustion characteristics were investigated using heat release rate analysis, two color method, soot concentration measurement and NOx concentration measurement. The experiments were carried out on a rapid compression expansion machine to simulate the ambient condition of a CI engine at TDC. Synthetic gas with oxygen concentrations of 21 %, 15 % and 10 % were used to simulate EGR conditions. A single hole injector was used with five different fuels: commercial diesel, HVO-commercial diesel blends and HVO. The results showed that increasing HVO blending percentages decreased ignition delay, flame temperature, soot concentration and NOx concentration. Heat release at oxygen concentration of 10 % dramatically dropped due to a shortened ignition delay, which resulted in less combustion. A decreased oxygen concentration from applied EGR conditions not only increased ignition delay, heat release, flame temperature and NOx concentration, but also increased soot concentration. A combination of EGR and supercharged conditions by increasing ambient pressure and decreasing oxygen concentrations resulted in increased heat release, decreased flame temperature, ignition delay and soot concentration, compared to EGR conditions. 相似文献
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In this study, a 3-D CFD simulation and laser diagnostics were developed to understand the characteristics of soot generation
in a diesel diffusion flame. The recently developed RANS (Reynolds-averaged Navier-Stokes equations) hybrid combustion model
(Extended Coherent Flame Model — 3 Zones, ECFM-3Z model) was used. This industrial, state-ofthe-art model of the diffusion
flame is commonly used in diesel combustion models as well as for propagating (premixed) flame combustion. The simulation
results were validated with measurements from a constant volume combustion chamber. The experiment revealed that soot accumulated
in the chamber where the temperature decreased. Where the temperature increased rapidly, only a little soot accumulated. The
temperature and soot distribution were independently examined using both the two-color method and a 3-D CFD simulation for
a turbulent diesel diffusion flame. 相似文献
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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
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针对掺混甲烷的乙烯层流火焰中的炭烟颗粒从形貌角度进行了研究,构建了具有相同当量比(2.07)、火焰温度、气体流速的层流预混乙烯火焰和掺混甲烷的乙烯火焰,并各自选取了3个高度进行热泳探针取样,采用TEM和AFM方法对各个工况的炭烟颗粒粒径分布、平均粒径、平均体积当量球径进行了对比。发现少量的甲烷掺混会令乙烯火焰中炭烟颗粒的尺寸变大,而当甲烷掺混量变多时该现象消失。而通过对颗粒的圆度、球度和分形维数计算和分析,发现即使是很小的颗粒也具有相似的不规则形状,这一现象广泛存在于各种火焰和各种大小的颗粒中,不受掺混比的影响,并且越大的颗粒结构越松散。 相似文献
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《JSAE Review》2002,23(3):291-296
Effects of squish area location on tumble and squish flow were investigated to control the knock in an SI engine. For the exhaust squish piston, tumble flow is collapsed by the exhaust squish clearance during the compression stroke, so that the compression-squish flow is strong. For the intake squish piston, tumble flow impinges on the edge of squish area and the induction of it into the squish area is controlled. The compression-squish flow is weakened and reverse-squish flow grows strong. This led to realization of a high heat release at late stage combustion. Simultaneously, the decrease of cycle-by-cycle variation of initial burn is realized. Consequently, knocking is controlled compared with a flat piston. 相似文献
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The objective of this work was to investigate the effects of injection conditions and swirl on D.I. diesel combustion using
a transparent engine system. The test engine is equipped with a common rail injection system to control injection conditions
and to obtain split injection characteristics. A combustion analysis and steady flow test were conducted to measure the heat
release rate due to cylinder pressure and the swirl ratio. In addition, spray and diffusion flame images were obtained using
a high speed camera. The LII & LIS methods were also used to obtain 2-D soot and droplet distributions. High injection pressure
was found to shorten ignition delay, as well as to enhance peak pressure. The results also revealed that the heat release
rate in the premixed combustion region was markedly reduced through the use of pilot injection, while the soot distribution
and the heat release rate in the diffusion combustion region were increased. The swirl effect was found to shorten ignition
delay at certain injection timings, and to enhance the heat release rate in all experimental conditions. 相似文献
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在YC6A220C柴油机上进行了进气道喷甲醇结合EGR的试验研究,在保持原柴油机动力性基本不变的基础上,研究了在不同负荷下,选用不同的EGR率和不同甲醇消耗率对原机的动力性、经济性、NOx和炭烟排放的影响。研究结果表明:单纯地使用EGR对于降低NOx效果比较明显,但是难以同时降低炭烟的排放,尤其当EGR率超过30%时,随着EGR率或者负荷的增加炭烟也急剧增加。向回路喷入适量甲醇后,不但可以保证NOx排放减少,而且炭烟排放也可以大幅度降低。在1 500r/min(最大扭矩转速)下,在EGR率为20%~35%,甲醇消耗率为50~70g/(kW·h)范围内,可以同时降低NOx和炭烟排放。发动机的动力性和燃油消耗略有降低,排放水平均低于燃用0号柴油。 相似文献