Emissions and fuel consumption characteristics of an HCNG-fueled heavy-duty engine at idle
Emissions and fuel consumption characteristics of an HCNG-fueled heavy-duty engine at idle
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DOI：
10.1016/j.ijhydene.2014.03.079
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发表时间：
2014-05
影响因子：
7.2
通讯作者：
Sunyoup Lee;Chang-gi Kim;Y. Choi;Gihun Lim;Cheolwoong Park
中科院分区：
文献类型：
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作者：
Sunyoup Lee;Chang-gi Kim;Y. Choi;Gihun Lim;Cheolwoong Park
在一台装有增压器和中冷器的6缸11缸L发动机上，研究了压缩天然气和掺氢天然气燃料的怠速性能。HCNG由70%的CNG和30%的氢气组成，根据作者之前的研究，这不仅是因为它确保了每次加油有足够的行驶距离，还因为它是满足欧6排放法规的最佳掺混比。发动机试验结果表明，使用均质天然气提高了怠速燃烧稳定性，并将稀薄运行极限从过量空气系数(λ)=11.5(CNG)扩大到1.6。与CNG相比，HCNG怠速运行的油耗率降低了25%以上。在怠速状态下燃用HCNG时，由于碳含量低，燃烧特性增强，碳氢化合物和一氧化碳排放减少。特别是，尽管氢气浓缩，但由于稳定怠速的燃料量低于CNG操作，最终导致气缸内最高燃烧温度较低，所以HCNG操作排放的氮氧化物(NOx)较少。在怠速状态下的低燃料量也导致了NOx排放的持续下降，同时λ的增加。怠速发动机试验结果还表明，燃用HCNG时，由于排气温度低，发动机的冷启动性能会变差。因此，讨论了可能的解决方案，包括燃烧策略，如延迟火花点火正时和降低空气/燃料比。
The idle performance of an 11-L, 6-cylinder engine equipped with a turbocharger and an intercooler was investigated for both compressed natural gas (CNG) and hydrogen-blended CNG (HCNG) fuels. HCNG, composed of 70% CNG and 30% hydrogen in volume, was used not only because it ensured a sufficient travel distance for each fueling, but also because it was the optimal blending rate to satisfy EURO-6 emission regulation according to the authors' previous studies. The engine test results demonstrate that the use of HCNG enhanced idle combustion stability and extended the lean operational limit from excess air ratio (λ) = 1.5 (CNG) to 1.6. A decrease of more than 25% in the fuel consumption rate was achieved in HCNG idle operations compared to CNG. Total hydrocarbon and carbon monoxide emissions decreased when fueled with HCNG at idle because of the low carbon content and enhanced combustion characteristics. In particular, despite hydrogen enrichment, less nitrogen oxides (NOx) were emitted with HCNG operations because the amount of fuel supplied for a stable idle was lower than with CNG operations, which eventually induced lower peak in-cylinder combustion temperature. This low HCNG fuel quantity in idle condition also induced a continuous decrease in NOxemissions with an increase inλ. The idle engine test results also indicate that cold-start performance can deteriorate owing to low exhaust gas temperature, when fueled with HCNG. Therefore, potential solutions were discussed, including combustion strategies such as retardation of spark ignition timing combined with leaner air/fuel ratios.