Interrelation Between Dilatation Rate and Displacement Speed in Premixed Turbulent Flames

Area of Science:

• Combustion Science
• Turbulence Modeling
• Chemical Kinetics

Background:

• Understanding turbulent flame dynamics is crucial for combustion efficiency and safety.
• The relationship between flame propagation speed and fluid dilatation is complex in turbulent flows.

Purpose of the Study:

• To analyze the interrelation between displacement speed and dilatation rate in premixed turbulent flames.
• To investigate the influence of chemistry models and flame regimes on this relationship.

Main Methods:

• Three-dimensional Direct Numerical Simulation (DNS) data.
• Analysis of statistically planar turbulent premixed flames with single-step and detailed chemistry (NH3-air).
• Investigation under unity Lewis number and near-unity effective Lewis number conditions.

Main Results:

• Density-weighted displacement speed positively correlates with fluid velocity-based dilatation rate, though non-linearly.
• Negative correlation observed between displacement speed and flame propagation velocity-based dilatation in wrinkled flamelets.
• Curvature stretch rate, influenced by Karlovitz number, drives correlation branches in thin reaction zones.

Conclusions:

• The study demonstrates a link between density-weighted displacement speed and dilatation rate in turbulent flames.
• Flame curvature and turbulence intensity significantly modulate these correlations.
• Findings suggest potential for mean dilatation rate closure in Reynolds Averaged Navier-Stokes simulations.