Numerical investigation on combustion and knock formation mechanism of hydrogen direct injection engine

• Published in: Fuel (Guildford) Vol. 316; p. 123302
• Main Authors: Li, Yong, Gao, Wenzhi, Li, Yuhuai, Fu, Zhen, Zou, Jiahua
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.05.2022; Elsevier BV
• Subjects: Alternative fuels; Combustion; Detonation; Elastic waves; Emissions; Flame propagation; High temperature; High-temperature reaction; Hydrogen; Hydrogen peroxide; Internal combustion engines; Knock; Low temperature; Low-temperature reaction; Pressure; Pressure wave; Spontaneous combustion; Thermodynamic efficiency; Wave propagation; Knock; Pressure wave; Low-temperature reaction; High-temperature reaction
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2022.123302

[Display omitted] •The interaction of pressure wave and flame can also develop into knock.•The radicals H2O2 and HO2 have a crucial influence on flame development.•OH plays a significant role in the production of heat.•The increase of H2O2 before the flame is the direct cause of accelerating the flame. Hydrogen is an ideal alternative fuel of internal combustion engine because of its high thermal efficiency and no carbon emissions, but knock has become one of the main obstacles restricting its application in engines. The characteristic of flame propagation and the interaction of flame and pressure wave during knocking development was studied numerically in a hydrogen fueled engine. The results showed that the knock is caused by the spontaneous combustion of the end mixture and the interaction between flame and pressure wave. HO2 and H2O2 play a significant role in the flame development by affecting the formation of OH in low-temperature reaction zone. Because the low-temperature reaction zone is preheated by reaction heat of the chain reaction, H2+OH=H2O+H, to prepare for the subsequent high-temperature reactions. Therefore, the faster pressure wave accelerates the flame propagation by promoting the generation of HO2 and H2O2 in the unburned zone at the flame front. The accelerated flame in turn further enhances the pressure wave. Like this, the pressure wave and flame promote and strengthen each other, and finally develop into detonation.