共查询到20条相似文献,搜索用时 15 毫秒
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M. Xu Y. C. Sun Y. Cui K. Y. Deng L. Shi 《International Journal of Automotive Technology》2016,17(1):109-118
In diesel engine, spray penetration is usually changed by in-cylinder gas flow. Accurate prediction on diesel spray with gas flow is important to the optimal design of diesel fuel injection system. This paper presents a theory investigation focusing on the penetration of diesel spray with gas flow. In order to understand the effect of gas flow on the penetration of diesel spray, a one-dimensional spray model is developed from an idealized diesel spray, which is able to predict the spray behavior under different gas flow conditions. The ambient gas flow is simplified as ideal flow that has only constant flow velocity along x-axial and y-axial directions of spray. The x-axial and y-axial directions are respectively defined as along and vertical spray directions. The main assumption is that the y-axial direction gas flow has no effect on the penetration of spray along x-axial direction. The principles of conservation of mass and momentum are used in the derivation. Momentum of in-cylinder air flow is also taken into consideration. Validation of the model at stable condition is achieved by comparing model predictions with experimental measurements of diesel spray without gas flow from Naber's experiments. Furthermore, CFD simulations on penetration of diesel spray with gas flow were performed with the commercial code AVL-fire. The onedimensional model is validated by the penetration results with gas flow from CFD calculation. Results show that a reasonable estimation of the spray evolution can be obtained for both with and without ambient gas flow conditions. 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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高原环境柴油机喷嘴内部流场与缸内温度场的三维数值模拟 总被引:1,自引:0,他引:1
采用广安博之等准维模型,建立柴油机高原运行工作过程模型;通过环境模拟台架试验验证了模型的可信性。将准维计算结果作为喷嘴内部气液两相流动和缸内燃烧三维模拟的初始条件,就高原低压、低温、低氧条件对喷孔内燃油流动状态与分布、缸内燃烧过程的影响进行三维数值模拟。海拔3 700m计算结果表明:与平原环境相比,柴油机喷嘴内空穴现象加剧,燃油流动速度增加,喷孔出口燃油分布不均匀度增加;缸内燃烧平均温度比平原最多高出300℃且分布不均匀,燃烧室局部热负荷偏高。研究初步揭示了高原环境柴油机性能劣化机理,为通过优化缸内喷雾和燃烧过程改善高原运行发动机性能提供参考。 相似文献
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《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
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利用定容弹、纹影仪以及高速相机等装置,就柴油转子发动机工况下的喷雾过程进行了试验研究,重点分析了喷雾环境背压和喷射压力对喷雾特性的影响。结果表明:在转子发动机喷雾过程中,喷雾扩散速度先快速增大后逐渐减小;喷雾锥角在初次雾化阶段内急剧减小,然后在二次雾化作用下保持相对稳定。喷雾环境背压的增大,有效减小了喷雾贯穿距离,增大了喷雾锥角,说明喷雾环境背压的增大对喷雾贯穿距离和锥角都有显著的影响,从而为转子发动机喷油正时的优化提供了试验数据支持;随着喷射压力提高,喷雾贯穿距离和喷雾锥角都增大,并且增大喷射压力加强了燃油的初次雾化和二次雾化,有利于提高转子发动机喷雾质量,为优化柴油转子发动机油气混合状态创造了条件。 相似文献
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发动机燃用水乳化柴油的研究进展 总被引:1,自引:0,他引:1
综述了柴油机燃用水乳化柴油的燃烧与喷雾特性、动力性与经济性及排放特性,对比分析了发动机燃用水乳化柴油与普通柴油在性能上的差异及其原因,总结了水乳化柴油在柴油机上的应用优化方法。结果表明:与柴油相比,乳化柴油着火滞燃期延迟,燃烧持续期缩短,喷雾贯穿距变长或相差不大,火焰升起高度增加;燃用乳化柴油时动力性下降,但有效热效率较柴油升高;乳化柴油可以明显降低NOx和炭烟排放,但多数工况下HC和CO排放有所升高,低转速和中低负荷工况下尤为明显;燃用乳化柴油时颗粒物数量浓度增加,体积浓度减小,且对于醛类和噪声排放并没有改善作用;添加合适添加剂或结合发动机技术协同作用,可以针对性地改善乳化柴油的燃烧过程,进一步起到节能减排的效果。基于燃料稳定性与燃料理化特性综合优化目标的燃料设计,以及适用于乳化柴油的高压共轨柴油机燃烧组织参数优化是未来的研究方向。 相似文献
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B. H. Lee J. H. Song Y. J. Chang C. H. Jeon 《International Journal of Automotive Technology》2010,11(6):783-791
The diesel combustion process is highly dependent on fuel injection parameters, and understanding fuel spray development is
essential for proper control of the process. One of the critical factors for controlling the rate of mixing of fuel and air
is the number of injector holes in a diesel engine. This study was intended to explore the behavior of the formation of spray
mixtures, combustion, and emissions as a function of the number of injector hole changes; from this work, we propose an optimal
number of holes for superior emissions and engine performance in diesel engine applications. The results show that increasing
the number of holes significantly influences evaporation, atomization, and combustion. However, when the number of holes exceeds
a certain threshold, there is an adverse effect on combustion and emissions due to a lack of the air entrainment required
for the achievement of a stoichiometric mixture. 相似文献
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通过柴油机工作过程测量分析系统对一台直喷式车用柴油机加速时的喷油和燃烧过程进行了试验研究和计算,并计算了其加速过程中的总声压级;利用油滴蒸发准维燃烧模型对柴油机加速过程NOx 排放进行了模拟计算。研究结果表明,柴油机喷油和燃烧特性参数的综合效果对NOx排放值产生影响;柴油机加速时的燃烧噪声大于标定工况,加速工况时的NOx 排放浓度值变化较大,有时大于标定工况。 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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以Hiroyasu喷雾和燃烧模型为基础,建立了适应不同海拔环境的特种车辆增压柴油机模型,并利用平原台架试验和海拔3 700 m实车试验对计算结果进行了验证。计算了该柴油机在0~5 000 m海拔实际运行时的动力性、经济性和排放性,预测了不同环境下柴油机热负荷、机械负荷主要参数的变化规律。结果表明,当海拔高度为5 000 m时,柴油机动力性、经济性比平原恶化10%以上;柴油机缸内燃烧温度峰值上升235℃以上,涡前排气温度最多增加150℃左右;最大压升率比平原升高15%以上,NOx排放减少,碳烟排放剧增。 相似文献
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环境对大功率柴油机缸内喷雾、燃烧与传热的影响 总被引:2,自引:0,他引:2
采用准维多区数值仿真和环境模拟试验的方法,研究了不同海拔环境对某大功率柴油机缸内喷雾、燃烧和传热的影响。结果表明:在高原环境下,油核破裂滞后期比平原最大延长9.1°曲轴转角,油滴分裂长度增加29%以上,贯穿度明显增加,一次雾化后,SMD直径显著增加;海拔4 500m,瞬时放热率峰值降低18.4%,放热率重心后移近4°,最高燃烧压力降低18.8%,位置滞后0.6°;缸内对流换热和辐射换热都比平原明显增强。研究结果为探明特殊环境下柴油机性能劣化与故障机理提供了理论参考。 相似文献
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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
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高强化柴油机双卷流燃烧系统喷油参数匹配试验研究 总被引:1,自引:0,他引:1
针对采用双卷流燃烧系统的单缸柴油机进行了强化燃烧试验研究,研究内容包括不同喷雾锥角燃烧特性试验和相同负荷下不同转速的燃烧特性试验。研究发现,柴油机喷雾锥角的合理设计对燃烧特性具有重要影响,提高转速是提高柴油机强化程度的有效途径,但是转速提高会带来排温升高及燃油经济性恶化等问题。通过调节喷油定时可以在提高发动机转速时使排温及燃油经济性的问题在一定程度上得以改善。采用双卷流燃烧系统并配以合适的喷油参数(喷雾锥角、喷油定时)可以达到提高柴油机强化程度的目的。 相似文献
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针对1台6缸增压中冷电控高压共轨柴油机,在不改变原柴油机结构和喷油参数的条件下,研究了生物柴油的掺混比例对发动机燃烧特性的影响。结果表明:小负荷时发动机有预喷射,随着生物柴油掺混比的增大,生物柴油-柴油混合燃料的滞燃期缩短、缸内最高燃烧压力下降,预喷阶段压力升高率峰值和瞬时燃烧放热率峰值减小,且对应的相位提前;主喷阶段压力升高率峰值和瞬时燃烧放热率峰值增大,且对应的相位后移。随着负荷的增大,发动机喷油策略改为单次喷射,随着生物柴油掺混比的增大,缸内最高燃烧压力下降,燃烧持续期缩短,压力升高率峰值略有增大,瞬时燃烧放热率峰值逐渐减小且对应的相位前移。两种不同负荷条件下,随着生物柴油掺混比的增大,混合燃料的指示热效率逐渐下降。 相似文献