Study of inter-sector spray flame propagation in a linear arrangement of swirled burners

Driven by pollutant emissions stringent regulations, engine manufacturers rely on lean combustion and aim to reduce the number of injectors, both affecting the light-round phase of ignition. This work focuses on inter-injector spray flame propagation in a linear multi-injector n-heptane/air spray burner measured at CORIA. Large Eddy Simulation (LES) are performed together with a complex chemistry description and a Lagrangian formalism of the spray in order to account for fuel droplet polydispersion. First, a non-reacting case enables to evaluate the numerical approach by comparison with measurements, and to analyse the influence of inter-injector spacing on both the flow dynamics and the local fuel distribution. Second, the comparison of numerical fully transient ignition sequences with experimental data shows that LES recovers the inter-injector spray propagation features found in the experiment such as flame propagation modes from radial to progressively arc-like, and total ignition time delay. However due to important pre-evaporation, liquid fuel does not significantly impact the overall ignition process, which exhibits the same driving mechanisms as in purely gaseous flows.