Injection and ignition characteristics of gaseous fuel jets for low-emission engines

Application of renewable natural gas (RNG) and hydrogen (H2) in internal combustion engines with a direct injection (DI) configuration leads to improved thermal efficiency and reduced CO2. Because of the high nozzle pressure ratios (NPR) relevant to DI, typically an under-expanded jet is formed past the nozzle exit. Transient jet development affects ignition and combustion properties, and consequently performance and emissions of the engines significantly. In this research, the effects of parameters including injection pressure, gas type and composition, and back pressure on the characteristics of the gaseous jets have been experimentally investigated. The ignition properties of these jets have been studied using a hot surface. Results indicate that the NPR has the most significant effect on the jets' penetration rate. Additionally, adding H2 to natural gas contributes considerably to improve ignition properties of the gaseous mixture. The results are of value to support future modeling and engine development.