The chemical kinetic and heating effects decoupling of pilot diesel in a diesel ignited natural gas engine under various pilot diesel injection timing

• Published in: Fuel (Guildford) 2024-10, Vol.374, p.132408, Article 132408
• Main Authors: You, Jinwen, Liang, Ruquan, Shi, Jianhui, Song, Yuanmei, Zhang, Dengbo, Yang, Liu
• Format: Article
• Language: English
• Subjects: Chemical kinetic effect; Diesel pilot-ignited; Heating effect; Natural gas
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.132408

•The chemical kinetic and heating effects decoupling of pilot diesel in dual fuel engine were analyzed.•The application of chemical inertness method is the key to decoupling the two effects of pilot diesel.•The changes of chemical kinetic effect and heating effect exhibit opposite trends with injection timing advanced.•The cylinder concentration and distribution of pilot diesel are strongly related to the magnitude of the chemical kinetic. The diesel ignited natural gas engine suffers from low load low thermal efficiency and high load knocking problems. The solution to these problems requires control of the combustion process. The combustion of pilot diesel plays an important role in the natural gas combustion process. The combustion of pilot diesel not only provides heat for the natural gas combustion process (heating effect), but also provides highly intermediate chemicals for the chemical reaction of natural gas (chemical kinetic effect). However, the mechanism of this effect under various pilot diesel injection timing is unclear. To decouple the heating effect and chemical kinetic effect of pilot diesel, a detailed study was conducted by numerical simulation combined with chemical inertness method. A 6-cylinder turbocharged intercooler diesel/natural gas dual fuel heavy-duty engine was used in this study, and the pilot diesel injection timing was controlled over a very wide range. The result shows that the chemical kinetic effect of pilot diesel increases while the heating effect shows the opposite trend with the advance of injection timing. When the fuel injection timing is 40° CABTDC, the pilot diesel chemical kinetic effect begins to exceed 50%. This may serve as judging the start timing of RCCI combustion mode. The low concentration and wide distribution of pilot diesel at the beginning of natural gas combustion is the leading reason for the increase of chemical kinetic effect. When the fuel injection timing is advanced, the high concentration area and distribution of highly active intermediate CH2O show an increasing trend, while the high-temperature area decreases and the low-temperature area gradually increases. There is a strong correlation between strong chemical kinetic effect and low-temperature combustion.