Euler–Lagrange numerical simulation of a kerosene droplet mist ignition in air using analytically reduced chemistry

High altitude relight is a critical aspect of the aeronautical engine certification and may be addressed with the numerical simulation of two-phase ignition. However, such configurations are stiff and combined with local evaporation may lead to numerical issues. This paper provides several methods to perform two-phase ignition simulations using analytically reduced chemistry in the context of unstructured large Eddy simulation and Euler–Lagrange formalism. Firstly, an exponential formulation combined with a local and dynamic sub-cycling of the stiff chemistry is demonstrated to allow stable integration at the flow time step. Secondly, a particle-bursting method is applied to limit the impact of stiffness induced by the Lagrangian point-source approach in fine meshes. These methods are then applied in the simulation of ignition of a mono-disperse, multi-component kerosene spray in air. The use of the analytically reduced chemistry model enables us to describe in detail the chemical structure of the flame kernel during its formation. Moreover, local increase of fuel concentration is observed as the ignition proceeds which has a large influence on the combustion processes and the flame kernel development.