Large Eddy Simulation of Bluff-Body Flame Approaching Blow-Off: A Sensitivity Study

Abstract

As almost all combustion processes of practical interest take place in the presence of turbulence, the development of the increasingly refined turbulence-chemistry interaction (TCI) models has led to highly sophisticated approaches. Nearly all of the studies comparing different models focus on stable premixed/nonpremixed flame configurations. In this work, the focus is on well-documented, lean premixed bluff-body stabilized flames approaching blow-off and on the blow-off sequence itself. Large Eddy Simulations (LES) have been used to capture the time-dependent, three-dimensional flow-field using Transported Probability Density Function (TPDF), Partially Stirred Reactor Model (PaSR) and Implicit LES (ILES) models. Furthermore, the influence of finite-rate chemistry and different chemical mechanisms is evaluated to determine the limitation and capability of the different TCI approaches for modelling flames just prior to and during the transient blow-off process. While the average flow-fields do not reveal any significant differences between modelling approaches, detailed analysis of the flame reveals that there are differences in the predicted flame thickness and composition. The ability of the considered TCI models to predict local as well as full flame extinction during the blow-off is investigated as well. It is demonstrated that such a blow-off sequence is not always governed by complex chemistry.

Near-lean blowoff dynamics in a liquid fueled combustor

“…Combustion only occurs in the recirculation zone, which is sometimes referred to as the "residual flame". Continued reactant entrainment cools the residual flame such that the recirculation zone eventually becomes a soup of fresh reactants, partially burned reactants, and local heat release parcels that are unable to ignite the incoming mixture [37,42,43].…”

Learning Flame Evolution Operator under Hybrid Darrieus Landau and Diffusive Thermal Instability

“…In conclusion, this work showcases the potential of operator learning methodologies for analyzing complex flame dynamics arising from hybrid instabilities. While challenges persist, particularly related to noise overestimation, these methods offer assisting tools for understanding and predicting real-world flame behavior in combustion systems [36][37][38][39][40][41][42][43]. Realistic flame development can be influenced by various factors beyond the two intrinsic flame instability mechanisms considered in this study.…”