共查询到19条相似文献,搜索用时 93 毫秒
1.
2.
3.
4.
缸内直喷(GDI)汽油机燃油喷雾和分层燃烧的数值研究 总被引:3,自引:0,他引:3
应用修正的多维流体力学计算程序KIVA-3V对缸内直喷(GDI)汽油机燃油喷雾和混合气分层燃烧过程进行了数值模拟。修正的子模型包括改进的燃油薄膜雾化模型、油滴破碎模型、油滴分布模型、初始缸内气体滚流模型、油滴蒸发模型以及燃烧模型。针对一种典型的三菱缸内直喷汽油机燃烧室结构在部分负荷工况下的燃油喷雾和分层燃烧进行了数值模拟。分析了不同的喷油器位置,缸内逆向滚流强度以及喷油时刻对火花塞附近混合气浓度的影响。计算结果表明,这些参数对燃油分层模式,点火过程以及燃烧特性都有显著影响,不适合的参数将导致火花塞间隙附近燃油空气混合气过稀或过浓从而使燃烧恶化。对缸内直喷汽油机部分负荷工况而言,燃烧室构形、缸内气体流动组织以及喷油时刻的优化设计对实现成功的分层燃烧起着重要作用。 相似文献
5.
电控喷油是二冲程汽油机的一种先进的供油方式。其特点是在保留二冲程机原有优点的同时,可显著降低排放和油耗。本文针对我国情况,建立起一套二冲程汽油机电控喷油系统,现对其基本结构和工作过程进行介绍 相似文献
6.
电控喷油是二冲程汽油机的一种先进的供油方式,其特点是在保留二冲程机原有优点的同时可显著降低排放和油耗。本文针对我国情况,建立起一磁二冲程汽油机电控喷油系统,现对其基本结构和工作过程进行介绍。 相似文献
7.
本文建立了用于小型二冲程汽油机的缸内工作过程计算模型,应用理论计算方法对缸内工作过程进行了较为详尽的描述,计算结果与试验结果基本吻合,为小型二冲程汽油机的设计提供了较好的依据 相似文献
8.
9.
基于两阶段燃油直喷的汽油机研究了首次喷油时刻、第2次喷油时刻、两阶段喷油比例以及点火时刻对起动首循环缸内燃烧离子电流特性的影响.分析了不同燃烧边界条件下直喷汽油机缸内燃烧反相离子电流峰值及其相位的变化,进而探讨了缸内压力及放热率之间的关系.此外,分析了分层燃烧直喷汽油机典型燃烧情况下的离子电流波形特征,并且对比了分层混合气和均质混合气燃烧模式下离子电流波形特征.结果表明,调整首次喷油时刻、第2次喷油时刻以及两阶段喷油比例主要是改变缸内混合气形成特性,尤其是火花塞附近的局部混合气浓度,影响了火焰传播速度,进而也影响了形成的离子电流的强弱.提前和推迟点火时刻均导致反相离子电流峰值减小.另外,4种典型的燃烧(失火、部分燃烧、伴有后燃以及正常燃烧)情况下,离子电流波形特征有着显著的差异,且反相离子电流峰值和积分信号在4种情况下依次增大,伴有后燃的情况下在做功冲程后期再次出现离子电流峰值波形. 相似文献
10.
《内燃机学报》2017,(5)
利用三维数值模拟,研究了小负荷时两次喷油策略对气门式二冲程直喷汽油机缸内混合气形成和火花点火形成的火焰诱发自燃的混合燃烧(SFI)特性的影响.结果表明:缸内燃油和温度的分层形式是影响混合气自燃特性的重要因素.在固定循环喷油量下,随着第二次喷油比例的增大,火花点火时火花塞周围燃空当量比增大,从气缸中心区到外围区的燃油浓度减小,着火时刻先略有提前然后逐步推迟,同时燃烧持续期先减小后增加,而平均指示压力、最大压力升高率和最大气缸压力均呈先增加后降低的趋势.与单次喷油相比,两次喷油更容易实现SFI燃烧.其中,第二次喷油比例为30%,时,火焰传播速度最快、自燃持续期最短.第二次喷油比例大于70%,时,气缸周围的偏稀混合气在火焰传播过程中难以自燃,缸内以火焰传播为主. 相似文献
11.
汽车发动机燃烧技术的新进展 总被引:13,自引:0,他引:13
对近年来汽车发动机燃烧技术的各项新进展进行了介绍和评论。内容包括具有理论空-燃比的均质混合气的燃烧,采用不同分层方法的预混合稀薄燃烧(MPFI),直接喷射式汽油机的燃烧(GDI),直接喷射式柴油机的燃烧(DI Diesel),以及均质混合气压缩点火式发动机的燃烧(HCCI)。最后这些燃烧新技术的今后发展,进行了展望。 相似文献
12.
Fuel stratification has the potential to extend the high load limits of homogeneous charge compression ignition (HCCI) combustion by improving the control over the combustion phase as well as reducing the maximum rate of pressure rise. In this work, experiments were carried out on a single-cylinder engine equipped with a dual-fuel-injection system – a port injector for preparing a homogeneous charge and a direct in-cylinder injector for creating the desired fuel stratification. The homogeneous charge was prepared using gasoline fuel while the fuel stratification was created with the in-cylinder injection of either gasoline or methanol during the compression stroke. The test results indicate that high load extension using gasoline for fuel stratification is limited by the trade-off between CO and NOx emissions. Weak gasoline stratification leads to an advanced combustion phase and an increase in NOx emission, while increasing the stratification with a higher quantity of gasoline direct injection, results in a significant deterioration in both the combustion efficiency and the CO emission. Engine tests using methanol for the stratification retarded the ignition timing and prolonged the combustion duration, resulting in a substantial reduction in the maximum rate of pressure rise and the maximum cylinder pressure – a prerequisite for HCCI high load extension. Further tests were then conducted with methanol stratification to extend the HCCI load limit and to optimize the stratified methanol-to-gasoline fuel ratio. Compared to gasoline HCCI, a 50% increase in the maximum IMEP attained was achieved with an acceptable maximum pressure rise rate of 0.5 MPa/°CA while maintaining a high thermal efficiency. 相似文献
13.
14.
在一电控喷射稀薄燃烧五气门汽油机上,以稀薄燃烧汽油机电控开发系统及相应的废气再循环系统为试验平台,对五气门汽油机在各种进气模式下实施稀混合气燃烧及废气再循环时的燃油消耗率和排放性能进行了详细的试验研究,进而对本发动机的稀燃性能与废气再循环性能进行了比较,分析实施不同方法对发动机性能的不同影响效果,实验结果表明,采用分层EGR技术以后,EGR比率可达32%,稀燃和分层废气再循环都有效地降低了NOx排放,分层废气再循环对NOx降低的效果更为明显,而且降低速度更快,尤其在中、低负荷,可以使排气中的NOx降低85%~95%.对于油耗,稀燃的效果显然要好于废气再循环,在较高负荷尤为明显,稀燃可显著降低HC、CO,分层EGR对HC、CO排放降低幅度不大。 相似文献
15.
A thermodynamic model considering flame propagation is presented to predict SI engine characteristics for hydrogen-methane blends. The partially charge stratification approach which involves micro direct injection of pure fuel or a fuel–air mixture, to create a rich zone near the spark plug, is proposed as a method to improve engine performance. Presented approach was validated with experimental data for the natural gas at lean condition. The model was generalized to predict the performance of engine for a variety of hydrogen contents in hydrogen-methane blends. Hydrogen molar concentrations of 0%, 15%, 30%, and 45% were used in the simulations. Results showed that partially charge stratification improves engine performance by increasing indicated mean effective pressure and decreasing specific fuel consumption. The results indicated that increasing mole fraction of hydrogen content would improve the PSC effect on engine performance. An advantage of the presented model is the flexibility and simplicity that make it possible to investigate several effects such as mixture distribution and fuel constituents on engine performance more practical than other types of simulation. 相似文献
16.
Zhijun Peng 《Frontiers of Energy and Power Engineering in China》2009,3(3):353-358
The influences of charge stratification on spark ignition (SI) engine combustion and NO emission were analyzed using a phenomenological
model. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air-fuel
charge, a dilution region without any combustible charge, and a mixing region lying between the core and the dilution region.
Three mixture stratification parameters such as the extent of dilution in the mixing region, the extent of combustible charge
in the mixing region, and the gradient of stratification in the mixing region were investigated. The results indicate that
the extent of combustible charge in the mixing region could reduce in-cylinder NO formation significantly, compared with the
extent of dilution in the mixing region. As long as the degree of dilution in the mixing region is within the dilution limit
of the combustible charge, the gradient of dilution has little effect on combustion and NO formation. 相似文献
17.
Zhijun PENG 《Frontiers in Energy》2009,3(3):353
The influences of charge stratification on spark ignition (SI) engine combustion and NO emission were analyzed using a phenomenological model. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air-fuel charge, a dilution region without any combustible charge, and a mixing region lying between the core and the dilution region. Three mixture stratification parameters such as the extent of dilution in the mixing region, the extent of combustible charge in the mixing region, and the gradient of stratification in the mixing region were investigated. The results indicate that the extent of combustible charge in the mixing region could reduce in-cylinder NO formation significantly, compared with the extent of dilution in the mixing region. As long as the degree of dilution in the mixing region is within the dilution limit of the combustible charge, the gradient of dilution has little effect on combustion and NO formation. 相似文献
18.
缸内燃油分层是改善HCCI燃烧控制的常用方法,为了解决燃油分层的控制问题,应用激光诱导荧光法研究了气道喷射和缸内直接喷射的缸内燃油分布,同时结合粒子图像测速技术分析了缸内流场对缸内燃油分布的影响.测量结果表明,气道喷射时缸内燃油分布较为均匀,难以形成燃油分层.而缸内直接喷射形成的燃油分层较为明显,且涡流流场测量结果表明,进气涡流对浓区位置分布有明显引导作用.同时采用缸内直喷时燃油的不均匀度的循环变动要比气道喷射的大,且随着缸内直喷喷油时刻的推迟,不均匀度的循环变动增大. 相似文献