Investigation of the Influence of Active Pre-Chamber Fuel Injection Strategy Considering Flame Kernel Position on the In-Cylinder Combustion

Lean combustion improves thermal efficiency by increasing the specific heat ratio and reducing pumping and heat transfer losses. However, it is limited by the lean-burn limit. Among potential solutions, pre-chamber turbulent jet ignition (TJI) combines high-energy ignition and mixture stratification, offering large ignition energy and fast flame propagation. An active pre-chamber, equipped with a fuel injector to precisely control the mixture, is more complex than a passive one but significantly extends the lean-burn limit, thereby improving efficiency and reducing emissions. Using 3D Computational Fluid Dynamics (CFD) method with detailed chemical kinetics, this study investigates the effects and underlying mechanisms of pre-chamber injection pressure, timing, and spark plug position on combustion in a hybrid dedicated gasoline engine. Injection pressure governs mixture formation: low pressure causes poor atomization; high pressure reduces mixing efficiency due to small pre-chamber volume; moderate pressure provides a near-stoichiometric mixture at the spark plug. Injection timing trades off mixture homogeneity and combustion phasing: too early leaks mixture to the main-chamber; too late causes stratification; moderate timing achieves a well-mixed pre-chamber charge and symmetric rapid jet flames, yielding higher peak pressure and internal thermal efficiency. Changing spark plug position has two distinct effects. First, altered pre-chamber geometry affects fuel diffusion and mixture distribution. Second, shifted flame kernel location influences flame propagation and jet symmetry. However, when the mixture is highly non-uniform, the kernel location effect is masked. Thus, pre-chamber design must ensure a uniformly distributed, combustible mixture while minimizing fuel leakage to the main-chamber.