Numerically investigation of ignition process in a premixed methane-air swirl configuration

Ignition process in a premixed methane-air swirl configuration is studied using a large eddy simulation method with Smagorinsky sub-grid scale model. A developed thickened flame combustion approach with two-step methane-air mechanism is used. Non-reacting mean and RMS axial, tangential and radial velocity profiles are validated against the experimental results. It is shown that the flow field consists of four zones: Inner Recirculation Zone, Inner Shear Layer, Outer Shear Layer and Corner Recirculation Zone. The mean and RMS of velocities and temperature in reacting flow are then validated against the experimental data. Large eddy simulation is used to investigate the ignition sequence by sparking in the four zones in the flow field. Flame growth, propagation and stabilization are studied for these cases. Results show that sparking in IRZ has the fastest flame growth and takes the minimum time to reach flame stabilization. Propagating flame surface in all cases has sharp flame edges, without any hysteresis for flame position. Finally, flame structures are analyzed by flame curvature and the effect of flow field velocity on the flame surface. •Ignition process is investigated by large eddy simulation and thickened flame model.•Sparking in IRZ has the fastest flame growth and minimum time to flame stabilization.•Flame attachment position doesn't show any hysteresis with respect to spark position.•The major controlling mechanism is the velocity direction in the propagation phase.