On the use of flamelet model approach in analyzing the mixing-controlled spray flame dynamics

This research examines the application of unsteady flamelet modeling to consider the impact of turbulent-chemistry interaction (TCI) on a mixing-controlled spray flame. The model incorporates the Representative Interactive Flamelets (RIF) approach to represent the sub-grid scaled heterogeneous mixture along with chemical reactions. This is combined with an Eulerian Particle Flamelet Model (EPFM), which uses multiple flamelets to account for the history of unsteady flames. The results are compared with those of a first-order moment method known as the Well-Stirred Reactor (WSR) model. The numerical simulations were carried out using a Reynolds Averaged Navier–Stokes (RANS) solver incorporated in two different CFD platforms, a commercially available CFD code, CONVERGE, and C++ based open-source CFD code, OpenFOAM. The test conditions were employed based on the Engine Combustion Network (ECN) Spray-A setup. The simulation results obtained interchangeably using both CFD software are investigated to address essential aspects of the RIF model. In order to ensure accurate predictions in the mixing field, adjustments were made to the original OpenFOAM code to enhance the treatment of time-stepping for spray source terms. This refinement allows for an adequate resolution of spray-induced mixing. While there are slight variations in the implementation of the RIF model between OpenFOAM and CONVERGE, both CFD codes effectively reproduce the physics of mixing-controlled combustion. This includes accurately representing important phenomena like mixing-controlled turbulent spray flame and combustion recession.