Large Eddy Simulation of Mild Combustion Using PDF-Based Turbulence–Chemistry Interaction Models

Abstract

The present work reports on large eddy simulation (LES) of turbulent reacting flow of the Delft-jet-in-hot-coflow (DJHC) burner, emulating moderate and intense low oxygen dilution (MILD) combustion, with transported probability density function-based (PDF) combustion models using ANSYS FLUENT 13.0. Two different eddy viscosity models for LES (dynamic Smagorinsky and kinetic energy transport) along with two solution approaches for the PDF transport equation, i.e., Eulerian and Lagrangian, have been used in the present study. Moreover, the effects of chemical kinetics and the micro-mixing models have also been investigated for two different fuel jet Reynolds numbers (Re = 4100 and Re = 8800). The mean velocity and turbulent kinetic energy predicted by the different models are in good agreement with experimental data. Both the composition PDF models predict an early ignition resulting in higher radial mean temperature predictions at the burner exit. The models, however, correctly predict the formation mechanism of ignition kernels and the decreasing trend of the lift-off height with increasing jet Reynolds number, as observed experimentally.

Keywords:

• Composition probability density function transport model
• Large eddy simulation
• Moderate and intense low oxygen dilution combustion
• Turbulence–chemistry interaction