Study on the effect of high-pressure methane jet on lean burn laminar flame

Abstract

High-pressure gas fuel direct injection (HPDI) technology benefits the engine with high efficiency and great output power. During the initial ignition process of the gas fuel jet ignited by the pre-ignition flame, the gas jet interacts with the pre-ignition flame, and causes important effects on the flame propagation and stability. This work aims to investigate the effects of the high-pressure gas fuel (methane) jet on the premixed methane flame with an equivalence ratio of 0.7 in a constant volume bomb (CVB) based on a three-dimensional numerical model. The results indicate that there is a complex interaction between the high-pressure methane jet and the premixed flame. The dominant combustion mode within the CVB changes from the premixed flame surface to the diffusion flame surface, which results in two different combustion behaviors in different regions along the methane jet direction, that is, primary ignition and secondary ignition. The methane jet flame development is divided into three regions, that is, laminar combustion laminar-turbulent combustion, turbulent combustion. Reynolds number of the main region of turbulent combustion ranges within Re = 2300–6000, which means that this flame is a small-scale turbulent flame. These findings contribute to understanding the combustion characteristics under high-pressure direct injection natural gas engine conditions, particularly in lean burn conditions, providing valuable insights for natural gas lean-burn flame stability.