Modified Reacting Solver: A Simplified Approach for Capturing the Molecular and Flow Diffusivities for the...

Area of Science:

• Combustion Science
• Computational Fluid Dynamics

Background:

• Nonpremixed moderate and intense low oxygen dilution (MILD) flames present unique combustion challenges.
• Accurate prediction of MILD flames requires robust computational models.

Purpose of the Study:

• To investigate the applicability of the inlet boundary species Lewis number for MILD flames.
• To develop and validate a modified reactive solver for MILD combustion simulations.
• To assess the solver's accuracy in predicting velocity, temperature, and flame lift-off height while reducing computational cost.

Main Methods:

• A modified reactive solver, modifiedReactingFoam, was developed in OpenFOAM by incorporating enthalpy flux and modified constants.
• Numerical simulations were performed for the delft-jet-in-hot-coflow burner under MILD conditions.
• The solver was tested using methane Lewis numbers ranging from 0.9 to 1.14.

Main Results:

• The modified solver demonstrated improved predictions compared to existing models, particularly with the modified eddy dissipation concept.
• Predictions using a methane Lewis number of 1.12 showed close agreement with experimental results, with lift-off height deviations within ±3%.
• Computational time was reduced up to 10 times when combined with DLBFoam.

Conclusions:

• The modified solver is effective for simulating MILD flames.
• The inlet boundary species Lewis number is a critical parameter for accurate MILD flame predictions.
• The developed solver offers a computationally efficient and accurate alternative for MILD combustion research.