共查询到19条相似文献,搜索用时 779 毫秒
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基于一台三缸1.5TGDI增压直喷发动机研究了三火花塞点火均质稀燃对发动机性能的影响。结果表明:三火花塞可有效拓展稀燃极限,压缩比15时,采用三火花塞在2 000 r/min、8 bar BMEP的特征工况点可实现lambda 1.95的稳定燃烧,最低油耗相比单火花塞降低约5 g/(k W·h),NOx原始排放可降低至约50×10-6,此时lambda受增压能力限制难以进一步增加;压缩比增加至16所能实现的最低油耗相比压缩比15改善不明显,且稀燃极限有所下降。三火花塞对爆震倾向改善作用较小,但可显著加快稀混合气的燃烧速率,相同lambda条件下其燃烧持续期相比单火花塞可缩短约3-6°CA,lambda 1.95时的燃烧持续期相比当量燃烧仅增加约2°CA。通过对潜在最高热效率的研究表明,采用三火花塞设计可在压缩比15条件下最终实现45.02%的有效热效率。 相似文献
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介绍了天然气发动机激光点火的基本工作原理、基本过程、不同的引燃点火方式以及影响激光点火的3个特性参数(气体不均一指数、水的吸光度、火焰发射);对激光点火系统与传统的火花塞点火系统在天然气发动机燃烧和排放性能方面进行了燃烧持续期、失火极限、敲缸极限、NOx排放等参数的比较;总结了激光点火的优缺点及其在天然气发动机中的应用前景。 相似文献
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CNG缸内直喷发动机稀薄燃烧火焰传播过程影响因素的研究 总被引:1,自引:0,他引:1
在试验用单缸光学发动机上,采用可视化技术研究缸内CNG直喷稀薄燃烧过程中喷射方式和点火方式对火焰传播过程的影响,同时采用双喷油器、双火花塞,分析研究喷射时刻、喷射位置和点火时刻等参数对稀薄燃烧特性和NOx排放特性的影响。结果表明,在稀薄燃烧过程中,火花塞附近的混合气浓度梯度对火焰传播和燃烧稳定性影响很大;混合气浓度梯度越大,循环变动越小,燃烧更稳定,但NOx排放量也增加。可见,控制稀薄燃烧过程的关键是控制火花塞附近的混合气浓度梯度,而它又直接影响NOx的生成。 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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Lean burn is an effective way to improve spark ignition engine fuel economy. In this paper, the combustion and emission characteristics
of a lean burn natural gas fuelled spark ignition engine were investigated at various throttle positions, fuel injection timings,
spark timings and air fuel ratios. The results show that ignition timings, the combustion duration, the coefficient of variation
(COV) of the indicated mean effective pressure (IMEP) and engine-out emissions are dependent on the overall air fuel ratio,
spark timings, throttle positions and fuel injection timings. With the increase of the air fuel ratio, the ignition delays
and combustion duration increases. Fuel injection timings affect ignition timings, combustion duration, IMEP, and the COV
of the IMEP. Late fuel injection timings can decrease the COV of the IMEP. Moreover, the change in the fuel injection timings
reduces the engine-out CO, total hydrocarbon (THC) emissions. Lean burn can significantly reduce NOx emissions, but it results
in high cyclic variations. 相似文献
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《JSAE Review》1996,17(3):251-258
Natural gas is very different from liquid fuels, such as gasoline and diesel fuel, in ignition characteristics, mixture formation process, combustion speed and so on. These characteristics greatly influence the cycle variation in the engine. The influence on lean-burn combustion is larger than that on stoichiometric combustion and the influence has not yet been sufficiently studied. In this paper, several factors for the stabilization of combustion of spark ignition natural gas lean-burn engines are clarified by means of experimental investigations using such parameters as ignition condition, swirl and compression ratio. 相似文献
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为降低HCNG发动机NOx排放,采用负阀重叠EGR策略,利用AVL-Fire软件对HCNG发动机不同进气门开启角(θIVO)下的进气过程和燃烧过程进行了三维仿真计算,对比分析了采用负阀重叠前后发动机缸内EGR分布和燃烧过程。仿真结果表明:负阀重叠EGR策略下,排气门关闭角(θEVC)固定为340°曲轴转角不变,当θIVO为380°曲轴转角时,既可避免发生回火又能保证一定的进气量及充气效率;采用负阀重叠后,在压缩冲程后期,缸内EGR率呈梯度分布(靠近火花塞位置EGR率较低),更有利于着火及火焰传播;采用负阀重叠可降低缸内最高燃烧压力及最高温度,但会减少进入气缸的新鲜工质,降低发动机功率;通过负阀重叠实现内部EGR可降低NOx排放,但会导致着火困难,燃烧速度变慢;提高点火能量可缩短着火落后期和燃烧持续期,加快燃烧速度。 相似文献
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对一台点燃式多点电喷天然气发动机在稀燃工况下进行试验,获得了各工况下的连续循环缸内压力数据,并计算了每循环与压力相关的燃烧循环变动特征参数及循环变动系数,进而研究了稀燃工况下天然气发动机的燃烧循环变动特性。结果表明,在稀燃条件下,每循环缸内峰值压力与平均指示压力有稳定的线性相关关系,每循环缸内峰值压力出现时刻与峰值压力和平均指示压力的线性相关关系随当量比的减小,均出现了由负相关到正相关的转变,并且混合气当量比越小,天然气发动机的燃烧循环变动越明显,在当量比为0.60~0.65时,平均指示压力变动系数有加速增长的趋势。 相似文献
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G. D’Errico T. Lucchini S. Merola C. Tornatore 《International Journal of Automotive Technology》2012,13(3):389-399
A combination of experimental and numerical methodologies is proposed for the investigation of knocking in spark ignition
engines to aid in better understanding the physical and chemical processes that occur and to exploit the capabilities of a
developed computational tool. The latter consists of a thermo-fluid dynamics model, which is part of an advanced 1-D fluid
dynamics code for the simulation of the entire engine, and a complex chemistry model, which can be embedded into the thermo-fluid
dynamics model using the same integration algorithm for the conservation equations and the reacting species. Their mutual
interaction in the energy balance will be considered. The experimental activity was carried out in the combustion chamber
of an optically accessible, single-cylinder P.F.I. engine equipped with a commercial head. The experimental data consisted
of optical measurements correlated to the combustion and auto-ignition processes within the cylinder. The optical measurements
were based on 2-D digital imaging, UV visible natural emission spectroscopy and the chemiluminescence of radical species (OH
and HCO). The engine parameters, the pressure signals of the related data and optical acquisition are compared on an individual
cycle basis in the simulation by running the engine at a constant speed and varying the spark advance from normal combustion
to heavy knock conditions. 相似文献
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基于一台汽油/天然气两用燃料的涡轮增压三缸发动机,建立 GT-Power仿真模型,研究喷水对准氩气动力循环发动机工作过程的影响。结果表明,在低负荷工况下,喷水后缸内的温度和压力都下降;增大水气比 (水和甲烷的质量比) 和推迟点火则传热损失减少但排气损失增加,存在热效率提升的较宽水气比范围和最优的水气比,推迟点火时刻和喷水对于爆震有良好的抑制作用。在大负荷爆震工况下,喷水能够显著抑制爆震,提前点火时刻可以得到更优的燃烧效率,喷水可使制动平均有效压力 (Brake Mean Effective Pressure,BMEP) 为0.6 MPa时指示热效率提高0.2%、有效热效
率提高0.1%,0.8 MPa工况的指示热效率提高0.4%、有效热效率提高0.2%,1.2 MPa工况的指示热效率提高1.2%、有效热效率提高0.8% (水气比为1工况相对于水气比为0.4工况)。结合低负荷工况和高负荷工况的表现,发现喷水能有效抑制发动机的爆震,并能提升发动机的热效率。 相似文献
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G. T. Chala A. R. A. Aziz F. Y. Hagos 《International Journal of Automotive Technology》2017,18(1):85-96
There is an increasing interest in supercharging spark ignition engines operating on CNG (compressed natural gas) mainly due to its superior knock resisting properties. However, there is a penalty in volumetric efficiency when directly injecting the gaseous fuel at early and partial injection timings. The present work reports the combined effects of a small boost pressure and injection timing on performance and combustion of CNG fueled DI (direct injection) engine. The experimental tests were carried out on a 4-stroke DI spark ignition engine with a compression ratio of 14. Early injection timing, when inlet valves are still open (at 300°BTDC), and partial injection timing, in which part of the injection occurs after the inlet valves are closed (at 180°BTDC), were varied at each operating speed with variation of the boost pressure from 2.5 to 10 kPa. A narrow angle injector (NAI) was used to increase the mixing rate at engine speeds between 2000 and 5000 rpm. Similar experiments were conducted on a naturally aspirated engine and the results were then compared with that of the boosting system to examine the combined effects of boost pressure and injection timing. It was observed that boost pressure above 7.5 kPa resulted in an improvement of performance and combustion of CNG DI engine at all operating speeds. This was manifested in the faster heat release rates and mass fraction burned that in turn improved combustion efficiency of the boosting system. An increased in cylinder pressure and temperature was also observed with boost pressure compared to naturally aspirated engine. Moreover, the combustion duration was reduced due to concentration of the heat release near to the top dead center as the result of the boost pressure. Supercharging was also found to reduce the penalty of volumetric efficiency at both the simulated port and partial injection timings. 相似文献