共查询到20条相似文献,搜索用时 716 毫秒
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基于定容燃烧弹试验平台,采用燃烧可视化方法研究了预混式单孔主动预燃室的几何参数对预燃室点火特性的影响。在火焰发展初期的定压燃烧过程中,将从点火开始到火焰面积达到燃烧弹可视窗口面积一半所用的时间定义为初期火焰发展时间,作为衡量不同几何参数下主动预燃室点火效果的参考指标:在不同喷孔孔径(2.0~4.0 mm)、不同预燃室通道内径(3.0~5.5 mm)、不同下端开口角度(0°~75°)的试验条件下,初期火焰发展时间的最大差异分别为9.3 ms、6.8 ms、2.9 ms,最终得出3个几何参数对单孔主动预燃室点火效果的影响程度排序由大到小依次为喷孔孔径、预燃室通道内径、下端开口角度。 相似文献
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本文采用湍流火焰传播速度模型描述火花点燃(SI)燃烧,针对单个自燃点仍采用湍流火焰传播速度模型,将所有自燃点的当量湍流火焰速度集合作为总当量湍流火焰速度用来描述压燃燃烧,进而建立了火花辅助压燃(SACI)准维燃烧模型。基于该模型研究了空气、外部废气再循环(EGR)稀释对SACI的影响,仿真和实验匹配良好。计算表明:SACI的火焰传播速度高于SI,随点火提前而增大,外部EGR稀释的火焰传播速度低于空气稀释;点火推迟或者增加外部EGR都会导致火焰前锋面面积峰值升高,衰减速度减慢,燃烧等容度减弱;稀释率相当时,空气稀释的热效率更高,但外部EGR稀释的尾气后处理更容易。 相似文献
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分别介绍了预混层流、紊流燃烧研究的现状和动向,指出了几种不同湍流产生方式的容弹装置及预混湍流燃烧研究的主要实验手段和方法,并提出了预混燃烧研究发展的动向。 相似文献
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LJ276QA发动机直接点火系统设计研究 总被引:2,自引:1,他引:2
本文分析了目前国产LJ276QA发动机点火系统存在的问题,提出了新的采用直接点火系统(DIS)的点火方案,建立了直接点火系统次级电压特性的计算模型,应用该模型对该发动机直接点火系统参数进行了设计计算,确定了系统主要参数。本文的设计分析方法可以用于其它汽油发动机直接点火系统的设计,也可作为电喷系统点火问题的设计参考。 相似文献
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在预混合燃烧中,每缸单点点火或多点点火的多点直喷的燃烧过程能够得到很好改变,试验结果表明,通过点火正时,燃烧的热释放率可以在很大范围内改变,这种改变也可以带来更好的燃烧。通过一种专门开发的模拟装置,我们可以模拟多种多样的循环过程,包括多区域燃烧模式。对多区域模式的燃烧的计算结果表明,在早期燃烧阶段中形成的区域内会有大量的氮氧化物形成。 相似文献
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无触点点火系统的评估 总被引:1,自引:0,他引:1
针对目前发动机制造厂对无触点分电器的触发方式、点火模块和安装方式等方面提出的诸多要求,从火花参数、可靠的点火正时、能量转换效率、可靠性和生产成本方面,对无触点分电器点火系统进行了综合评述,并给出了设计实例。 相似文献
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在传统的节气门式发动机上,发动机的控制装置是同步而协同地进行控制的(按照适当的燃烧管理策略),使所有的参数都适合于燃烧,这当然要通过各个专用的子系统的完满执行。这些子系统例如燃油喷射(燃油的数量和质量),用于空气动作的传统装备,点火装置(点火定时),EGR废气再循环装置,废气涡轮增压(增压压力)装置。 相似文献
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开发了1种用于研究气体燃料燃烧特性的定容燃烧装置。该装置主要由燃烧弹本体、进排气、温控、压力采集、高速摄影及同步控制等系统组成。在该装置上进行了甲烷—空气混合气的燃烧试验,研究了混合气的初始压力、初始温度及当量比对燃烧压力的影响。结果表明:相同初始压力下,燃烧压力及压力峰值随初始温度的升高而降低,压力升高率有所增大;相同初始温度下,整个燃烧过程中的压力随初始压力升高而增大,压力升高率基本不随初始压力变化;随着的增加,燃烧压力峰值和压力升高率先增加后减小,并在φ=1.0时取得最大值,同时,燃烧压力出现峰值所用的时间随的增加先减少后增加,在φ=1.0时取得最小值。 相似文献
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基于进气道三维流场测试装置、定容弹喷雾试验台和光学单缸机测试系统组成的缸内直喷汽油机燃烧系统可视化开发平台,开发设计了满足设计要求的高性能进气道,并匹配了缸盖燃烧室和活塞,有助于缸内混合气的形成,提高燃烧速率;综合考虑排放与机油稀释量的基础上,优化设计了喷雾靶点。对所设计的燃烧系统进行了光学单缸机试验和热力学多缸机试验验证。结果表明,进气道和燃烧室组织引导的气流在缸内形成高滚流,对喷雾油束有强烈的弯卷作用,极大促进了均质混合气的形成,并减小喷雾碰壁的风险;喷雾靶点的合理设计有效避免喷雾油束与壁面的碰撞,减少了机油稀释率和起燃工况HC排放;所设计的燃烧系统搭载1.5TGDI发动机实现了80kW/L、最大扭矩250N·m、排放较低的性能指标。 相似文献
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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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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