A forced ignition probability analysis method using LES and Lagrangian particle monitoring

Abstract A large eddy simulations-based methodology is developed for predicting the probability of igniting a turbulent non-premixed jet flame with a localized spark. The method couples the LES to a Lagrangian monitoring of fluid particles and explores, through a sub-grid turbulent flame speed model, the local turbulent flow properties on upstream and downstream flame propagation in the axial direction following radial kernel growth. The velocity and mixing fields are validated by using experimental measurements. The predicted region of possible upstream flame propagation, characterized by near-stoichiometric mixture and low velocity flow, compares well with the available experimental data regarding its form and upstream flame speed. The probabilistic generation of a kernel, its convection and the subsequent flame propagation are investigated and the conditional statistics of the mixture at the ignition location, and the convection and transition to upstream propagating flame are determined. The conditional probability of formation, convection, growth and stabilization of flame kernels results in a prediction of the overall flame ignition probability, which agrees well with experiment.