Research on the correlation between passive pre-chamber turbulent jet and combustion through decoupling analysis

Low-carbon gas engines show great potential in future marine propulsion and power generation applications. Passive pre-chamber jet ignition technology is one of an important approach to enhance ignition reliability and enabling stable lean combustion. Although extensive research has been conducted on pre-chamber jet ignition, most studies have focused on main chamber ignition experiments without decoupling the dynamics of hot turbulent jets from subsequent combustion processes. As a result, the influence of early jet evolution on later flame development remains insufficiently understood. In this work, a novel decoupling methodology is proposed to isolate and analyze early jet evolution independently of subsequent ignition and combustion phases. The optical diagnostics for high-speed photography of the Z-type schlieren image system is established. By comparing jet penetration and morphological characteristics under different ambient densities, which demonstrates that jet development remains consistent between inert and flammable main chamber environments when densities are similar. This finding validates the feasibility of decoupling early jet development from later combustion events. Based on this, the study systematically investigates jet characteristics and flame development, revealing a strong correlation between ignition delay and early jet morphology. Notably, under lean conditions (λ = 1.4), the propagation rate of the jet area significantly influences the axial flame development rate, while under near-stoichiometric conditions (λ = 1.2), radial flame propagation is more closely governed by early jet behavior. These insights provide a foundational understanding of the coupled mechanisms governing turbulent jet ignition and offer new perspectives for optimizing pre-chamber designs in next generation low-carbon engines.