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Low NOx stratified combustion of a compressed natural gas with an over-expansion injector

使用过膨胀喷射器进行压缩天然气的低氮氧化物分层燃烧

基本信息

批准号：
15560168
负责人：
SHIGA Seiichi
金额：
$ 2.11万
依托单位：
Gunma University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560168/
关键词：
Over-expansion flow Air introduction Compressed natural gas Direct-injection engine NOx

项目摘要

The present study aimed at revealing the feasibility of utilizing over-expansion behavior of supersonic gas flow. It would generate lower pressure area at the fuel jet than the ambient air, the ambient air was expected to be sucked into the fuel jet, and the richer zone in the central region of the fuel jet would become leaner resulting in lower combustion temperature and lower NOx formation. On the basis of the estimation of this behavior on the pressure ratio and the mach number plane, the shock wave pattern was predicted under the condition of high pressure and temperature ambient realized by a rapid compression machine. When the reduced compression ratio of 5.8 in the rapid compression machine was applied, slight increase of combustion efficiency and reduction of CO were observed, which suggested the effect of formation of over-expansion condition. However, little variation of NOx level was detected. Thus the over-expansion effect was realized at lower compression ratio and the ext … More ent is not so remarkable.For introducing ambient air into the fuel jet at subsonic condition, utilization of air entrainment with turbulent mixing, so-called Bunsen burner mechanism, was also tested. Under atmospheric condition with steady-state test rig experiment, the phenomenon of air introduction was successfully observed. However, in the experiment of rapid compression machine, little effect of such air introduction was obtained. Thus it was also shown that the air introduction is not so effective enough to reduce NOx emission.In terms of application to engine combustion, effect of injector positioning was examined since it is normally limited to cylinder head. Comparison study of injector positioning, side and central injection was carried out. With the central injection, combustion efficiency was increased at higher equivalence ratio condition but it deteriorated much at leaner condition. This would be generated by the better mixing of central injection due to the interaction between the fuel jet and the combustion chamber wall. Thus the importance of fuel injector positioning was clearly shown and the need of the future strategy of injection parameter determination was suggested. Less

本研究旨在揭示利用超音速气流过度膨胀行为的可行性。它会在燃料射流处产生比环境空气更低的压力区域，环境空气预计会被吸入燃料射流中，并且燃料射流中心区域中的较浓区域将变得较稀薄，从而导致较低的燃烧温度和较低的氮氧化物形成。基于对压力比和马赫数平面上这种行为的估计，预测了快速压缩机在高压和高温环境条件下的冲击波模式。当在快速压缩机中应用降低的压缩比5.8时，观察到燃烧效率略有提高并且CO减少，这表明过度膨胀条件形成的影响。然而，检测到 NOx 水平变化很小。因此，在较低的压缩比下实现了过度膨胀效应，并且外部膨胀并不那么显着。为了在亚音速条件下将环境空气引入到燃料喷射中，还测试了利用湍流混合的空气夹带，即所谓的本生燃烧器机制。在大气条件下进行稳态试验台实验，成功观察到了空气引入现象。但在快速压缩机的实验中，这种空气引入效果甚微。因此也表明，空气引入对于减少NOx排放不够有效。在发动机燃烧的应用方面，由于喷油器定位通常仅限于气缸盖，因此检查了喷油器定位的效果。对喷油器定位、侧喷和中央喷油进行了比较研究。采用中央喷射，燃烧效率在较高当量比工况下有所提高，但在稀薄工况下燃烧效率大大恶化。由于燃料射流和燃烧室壁之间的相互作用，中央喷射的更好混合会产生这种情况。因此，清楚地表明了喷油器定位的重要性，并提出了未来喷射参数确定策略的需要。较少的