共查询到20条相似文献,搜索用时 62 毫秒
1.
基于某高速汽油机,对燃烧室结构、燃油喷射特性、凸轮型线改型设计为稀薄燃烧发动机。提出利用响应面模型对正时策略进行分析和优化的研究方法,并建立利用响应面进行多目标优化计算的流程。以提高有效功率和降低有效燃油消耗率为优化目标,以点火正时、空燃比和进排气正时为设计变量,建立了发动机性能与响应面耦合优化模型。分析与试验结果表明:较标准混合比燃烧时,稀薄燃烧发动机的进排气提前角减小,点火正时提前,最低燃油消耗率下降3.9%,最大功率提升9.7%;同时利用响应面优化方法提高了优化效率。 相似文献
2.
点火正时对电控稀燃天然气发动机性能的影响 总被引:1,自引:0,他引:1
试验研究了点火正时对电控稀燃多点喷射天然气发动机燃烧及排放性能的影响规律。对该发动机转速为1 450 r/min,1 750 r/min,2 050 r/min,负荷为25%,50%,75%,100%的12个工况点进行了试验研究。研究结果表明,在其他燃烧边界条件不变的情况下,点火正时对该发动机输出扭矩及CH4排放影响不大,但是在2 050 r/min,100%负荷工况下,随着点火正时的进一步后移,出现扭矩下降及CH4排放增加的现象。点火正时对NOx排放有显著的影响,同一工况下,随着点火正时的推移,NOx排放明显降低。 相似文献
3.
4.
C. W. Park H. C. Oh S. D. Kim H. S. Kim S. Y. Lee C. S. Bae 《International Journal of Automotive Technology》2014,15(4):525-533
To comply with reinforced emission regulations for harmful exhaust gases, including carbon dioxide (CO2) emitted as a greenhouse gas, improved technologies for reducing CO2 and fuel consumption are being developed. Stable lean combustion, which has the advantage of improved fuel economy and reduced emission levels, can be achieved using a sprayguided-type direct-injection (DI) combustion system. The system comprises a centrally mounted injector and closely positioned spark plugs, which ensure the combustion reliability of a stratified mixture under ultra-lean conditions. The aim of this study is to investigate the combustion and emission characteristics of a lean-burn gasoline DI engine. At an excess air ratio of 4.0, approximately 23% improvement in fuel economy was achieved through optimal event timing, which was delayed for injection and advanced for ignition, compared to that under stoichiometric conditions, while NOx and HC emissions increased. The combustion characteristics of a stratified mixture in a spray-guided-type DI system were similar to those in DI diesel engines, resulting in smoke generation and difficulty in three-way catalystutilization. Although a different operating strategy might decrease fuel consumption, it will not be helpful in reducing NOx and smoke emissions; therefore, alternatives should be pursued to achieve compliance with emission regulations. 相似文献
5.
6.
7.
射流点火是实现稳定的稀薄燃烧,大幅度提升发动机热效率的有效技术途径。该文利用设计的一种射流点火器,对气相射流点火(GJI)的燃烧开展研究,揭示了主动式射流点火(射流室内有补充燃料)和被动式射流点火(射流室内无补充燃料)的燃烧和排放特性。结果表明:相比于被动式射流点火,主动式射流点火将过量空气系数拓展至2.0,热效率提升1.5%;进一步引入废气再循环(EGR)后,热效率提升至44.5%。主动式射流点火时,最高热效率点NOx排放较被动式射流点火下降低66%,THC及CO排放的增加使燃烧效率降低3%;引入EGR后,NOx进一步降低79%,燃烧效率保持稳定在96%。 相似文献
8.
9.
对预燃室壁涂有催化剂的均质压燃(HCCI)发动机的燃烧过程进行了数值计算,分析了催化燃烧对HCCI发动机燃烧特性的影响;同时分析了预燃室内催化剂种类、过量空气系数、进气温度、进气速度、缸径以及预燃室壁温对HCCI发动机燃烧特性的影响。结果表明,预燃室存在催化燃烧时对HCCI发动机的着火时刻有很大的影响:随着过量空气系数及预燃室进气速度的增加,HCCI发动机的着火时刻提前;催化剂种类、预燃室缸径以及预燃室壁温对HCCI发动机着火时刻影响不显著,但对缸内燃烧温度影响显著。 相似文献
10.
11.
《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
12.
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
13.
The in-cylinder RGF (residual gas fraction) of internal combustion engines for new combustion concepts, such as CAI (controlled
auto ignition) or HCCI (homogenous charged compression ignition), is a major parameter that affects the combustion characteristics.
Thus, measurement or prediction of the cycle-by-cycle RGF and investigation into the relation between the RGF and the combustion
phenomena are critical issues. However, on-line prediction of the cycle-by-cycle RGF during engine testing is not always practical
due to the requirement of expensive, fast response exhaust-gas analyzers and/or theoretical models that are just too slow
for application. In this study, an on-line model that can predict the RGF of each engine cycle and cylinder during the experiment
in the test cell has been developed. This enhanced model can predict the in-cylinder charge conditions of each engine cycle
during the test in three seconds by using the measured dynamic pressures of the intake, exhaust, and cylinder as the boundary
conditions. A Fortran77 code was generated to solve the 1-D MOC (method of characteristics). This code was linked to Labview
DAQ as a form of DLL (dynamic link library) to obtain three boundary pressures for each cycle. The model was verified at various
speeds and valve timings under the CAI mode by comparing the results with those of the commercial code, GT-Power. 相似文献
14.
15.
16.
柴油机HCCI燃烧的均质混合气制备 总被引:3,自引:0,他引:3
介绍了均质充量压缩着火燃烧的概念、优缺点及其良好的发展前途与当前面临的困难。分析了HCCI混合气制备的重要性,总结了柴油机HCCI混合气制备的典型方法和成功经验,并分析了混合气制备对HCCI燃烧排放、着火相位的控制以及功率输出的影响,探讨并展望了HCCI混合气制备的可能发展方向。 相似文献
17.
18.
大气压力和冷却液温度对柴油机性能影响的试验研究 总被引:1,自引:0,他引:1
利用内燃机高海拔(低气压)模拟试验系统,研究了大气压力和冷却液温度对柴油机性能与燃烧特性的影响规律。试验结果表明:随着进气压力降低,柴油机最高燃烧压力下降,缸内平均温度大幅升高,燃烧始点推迟且持续期延长,后燃严重,燃烧过程未能及时释放热量,动力性能和燃料经济性下降明显;随着冷却液温度的升高,最高燃烧压力增大,燃烧始点提前且持续期略有延长,燃烧重心略微前移,燃烧放热率减小,且大气压力越低冷却液温度对柴油机燃烧过程的影响越明显。在高海拔(低气压)条件下,提高柴油机冷却液工作温度,可以明显减少冷却液散热量,提高柴油机的热-功转换效率,显著改善柴油机的高原动力性和经济性,同时柴油机热负荷升高幅度并不大。 相似文献
19.
Y. Tsutsumi A. Iijima K. Yoshida H. Shoji J. T. Lee 《International Journal of Automotive Technology》2009,10(6):645-652
The Homogeneous Charge Compression Ignition (HCCI) engine has attracted much interest because it can simultaneously achieve
high efficiency and low emissions. However, the ignition timing is difficult to control because this engine has no physical
ignition mechanism. In addition, combustion proceeds very rapidly because the premixed mixture ignites simultaneously at multiple
locations in the cylinder, making it difficult to increase the operating load. In this study, an HCCI engine was operated
using blended test fuels comprised of dimethyl ether (DME) and methane, each of which have different ignition characteristics.
The effects of mixing ratios and absolute quantities of the two types of fuel on the ignition timing and rapidity of combustion
were investigated. Cool flame reaction behavior, which significantly influences the ignition, was also analyzed in detail
on the basis of in-cylinder spectroscopic measurements. The experimental results revealed that within the range of the experimental
conditions used in this study, the quantity of DME supplied substantially influenced the ignition timing, whereas there was
little observed effect from the quantity of methane supplied. Spectroscopic measurements of the behavior of a substance corresponding
to HCHO also indicated that the quantity of DME supplied significantly influenced the cool flame behavior. However, the rapidity
of combustion could not be controlled even by varying the mixing ratios of DME and methane. It was made clear that changes
in the ignition timing substantially influence the rapidity of combustion. 相似文献