Numerical investigations on turbulent jet ignition with gasoline as an auxiliary fuel in rapid compression machines

Abstract

ABSTRACT Lean burning as one of the low-temperature combustion strategies has the potential to reduce pollution emissions and improve fuel efficiency. However, highly diluted mixtures cause internal combustion engines to suffer from severe combustion instabilities. Turbulent jet ignition (TJI) technology is considered an effective way to solve these issues, but most previous work mainly considers the passive TJI systems fueled by gaseous fuel. In this work, an active TJI system with gasoline as an auxiliary fuel was investigated using three-dimensional computational fluid dynamics (CFD) simulations in rapid compression machines (RCM). High-pressure low-temperature operating conditions were established to mimic the combustion situation of supercharged spark-ignition engines. Different injection parameters for pre-chamber were considered, including injection timing, injection angle, and injection pulse width, and the influence of injection parameters on the evolution of turbulent jet flame in the main chamber with lean mixtures was investigated. The results show that the hedging effect between reverse squeezed flow and high-speed fuel spray during piston compression promotes gasoline spray atomization, evaporation, and mixing in the pre-chamber. The initial lambda of the pre-chamber plays a significant role in the jet exit velocity, while the initial lambda of the main chamber exhibits a greater impact on the jet propagation distance. Meanwhile, there are generally three stages for the entire combustion in the main chamber, including jet penetration, jet ignition, and spontaneous combustion. The present work can provide useful insights into the optimization and design of active TJI systems in realistic engines.