Instantaneous DNS iso-surfaces of the flame (red, 1700K) and turbulent vorticity (blue) inside the flashback region — the raw simulation output this entire study was built on.
How does the presence of a wall boundary influence the topology and frequency of flame self-interaction (FSI) events during turbulent boundary-layer flashback of hydrogen-rich premixed combustion?
Hydrogen is one of the leading clean fuels for future power generation and aviation propulsion, but its high reactivity and low quenching distance make it far more prone to boundary-layer flashback — the uncontrolled upstream propagation of a flame — than conventional hydrocarbon fuels. Flashback is a critical failure mode for hydrogen combustors, and accurately modelling it requires a detailed understanding of how flame topology behaves right at the wall, where current turbulence models are weakest.
- Interrogated a ~0.4 billion grid-point Direct Numerical Simulation (DNS) database of hydrogen-air boundary-layer flashback
- Applied critical-point theory to classify flame self-interaction topologies via the eigenvalues of the Hessian of the reaction progress variable
- Conducted statistical analysis — probability density functions, histograms, and curvature statistics — across six wall-normal distances through the channel flow
- First study to examine flame self-interaction topology distributions specifically within hydrogen-rich boundary-layer flashback
Tunnel Formation topologies dominate, accounting for over 50% of all flame self-interaction events at every distance from the wall — with the wall boundary shown to have a significant influence on flame surface geometry and the overall turbulent burning rate.
The findings have direct implications for flame-surface-based combustion models used in industrial combustor design. This project also marked an early engagement with hydrogen combustion physics — a thread that carried directly into the DPhil's later work on thermal solutions for liquid hydrogen jet engines.