Parametric Study of Autoigniting Hydrogen-Methane Jets in Direct-Injection Engine Conditions

This work investigates the effects of ambient and injection parameters on the ignition and combustion characteristics of hydrogen (H-2)- methane (CH4) jet (50% H-2 by volume, with the remaining CH4) in simulated direct-injection, compression-ignition conditions. Parameter variations include ambient gas temperature (1060-1200 K), ambient oxygen (O-2) concentration (10-21 vol %), and injection pressure (10-20 MPa reservoir pressure). The results show that the ignition delay of the H-2-CH4 jet decreases with increasing ambient temperature. In most cases, the ignition initiates from a localized kernel before spreading across the jet volume downstream. The lower ambient O-2 cases display a more voluminous ignition sequence. The results also show that the jet flame recesses upstream to attach or stabilize close to the nozzle but becomes increasingly lifted with lower ambient temperature and O-2 conditions. The flame autoignition process displays increased variation at the lowest tested ambient temperature condition in this work, which affects the ensuing flame evolution and heat release profile.