The Effect of Hydrogen Addition on Confined Turbulent Boundary Layer Flashback Studied with a Critically Strained Flame Model

The addition of hydrogen fuel to gas turbines otherwise operating on natural gas is a practical technique for the reduction of carbon emissions. However, hydrogen addition also modifies flame properties and leads to a significantly higher boundary layer flashback propensity. Robust methods to accurately predict these flashback limits are thus important to reducing emissions. In this work, a quantitative model for confined turbulent boundary layer flashback based on critically strained flames is presented. The model is based on the idea that strained flame extinction is directly responsible for controlling the flashback limit. The model predicts the occurrence of flashback when the one-dimensional strained flame speed at the extinction limit matches the axial flow velocity one thermal distance from the wall. The model agrees well with measurements of hydrogen-air flames in a non-swirling burner, and can be extended to methane-hydrogen-air flames in a swirling burner through minimal experimental data