Dynamics of upstream flame propagation in a hydrogen-enriched premixed flame

TL;DR

This study uses Large Eddy Simulation with a Thickened Flame model to analyze how hydrogen addition affects upstream flame propagation in a methane-air premixed flame within a swirled combustor, validating results with experimental data.

Contribution

It demonstrates the application of LES-TF modeling to capture upstream flame dynamics and the impact of hydrogen enrichment on flame stability and propagation.

Findings

Hydrogen enrichment leads to more unstable upstream flame behavior.

The LES-TF model accurately predicts experimental RMS fluctuations.

Upstream propagation is linked to recirculation bubble dynamics.

Abstract

An unconfined strongly swirled flow is investigated to study the effect of hydrogen addition on upstream flame propagation in a methane-air premixed flame using Large Eddy Simulation (LES) with a Thickened Flame (TF) model. A laboratory-scale swirled premixed combustor operated under atmospheric conditions for which experimental data for validation is available has been chosen for the numerical study. In the LES-TF approach, the flame front is resolved on the computational grid through artificial thickening and the individual species transport equations are directly solved with the reaction rates specified using Arrhenius chemistry. Good agreement is found when comparing predictions with the published experimental data including the predicted RMS fluctuations. Also, the results show that the initiation of upstream flame propagation is associated with balanced maintained between hydrodynamics and reaction. This process is associated with the upstream propagation of the center recirculation bubble, which pushes the flame front in the upstream mixing tube. Once the upstream movement of the flame front is initiated, the hydrogen-enriched mixture exhibits more unstable behavior; while in contrast, the CH4 flame shows stable behavior.