Fundamental Experiment of Ignition and Flame Development in Turbulent Jet Ignition Ignited Methane Jet Flame

In heavy-duty natural gas engines, diesel is usually injected before natural gas to initiate methane combustion. However, such an approach requires additional fuel and precise injection strategies. In the present work, an alternative approach of pre-chamber turbulent jet ignition (TJI) ignited methane jet flame is performed experimentally. The underlying mechanism of TJI-HPDI jet combustion is investigated in an optically visualized constant-volume combustion chamber with an active pre-chamber. It is found that with the increase of the injection-ignition delay (ti), the combustion process undergoes several transitions. In addition, the success ignition region and ignition failure region separated by ti and TMI are discerned on the ti-TMI diagram. As ti increases, there is an initial rise in both the mean flame front velocity and peak pressure, followed by a subsequent decrease This behavior highlights the TJI-HPDI system's notable advantages in expanding the lean combustion limit and enhancing overall combustion characteristics compared to premixed combustion. These advantages can be attributed to the mixture stratification and turbulence. Furthermore, pre-chambers fueled with hydrogen can further improve the intensity and energy of the turbulent hot jet, which further decreases the critical injection-ignition delay to initiate global flame propagation in the TJI-HPDI system. The present work deals with real engineering technologies, and it will provide new insights into the design and control of TJI-HPDI engines, especially for heavy-duty natural gas engines.