Numerical Simulation of Ignition Mechanism in the Main Chamber of Turbulent Jet Ignition System

The ignition mechanism of a lean premixed CHVair mixture by a hot turbulent jet issued from the pre-chamber combustion is investigated using 3D combustion CFD. The turbulent jet ignition experiments conducted in the rapid compression machine (RCM) at Michigan State University (MSU) were simulated. A full simulation was carried out first using RANS model for validation, the results of which were then taken as the boundary condition for the detailed simulations using both RANS and LES. To isolate the thermal and chemical kinetic effects from the hot jet, two different inlet conditions of the chamber were considered: inert case (including thermal effects only) and reactive case (accounting for both thermal and chemical kinetic effects). It is found that the chemical kinetic effects are important for the ignition in the main chamber. Comparison of OH and HRR (heat release rate) computed by RANS and LES shows that RANS predicts slightly faster combustion, which implies higher predicted turbulent flame speed. Correlations between vorticity, mixing field, and temperature field are observed, which indicate that the flow dynamics strongly influence the mixing process near the flame front, and consequently affect flame propagation.