Details
| Original language | English |
|---|---|
| Article number | 114236 |
| Number of pages | 20 |
| Journal | Combustion and flame |
| Volume | 278 |
| Early online date | 4 Jun 2025 |
| Publication status | Published - Aug 2025 |
Abstract
We report on boundary layer flashback of a turbulent premixed, pure hydrogen flame using well-resolved LES. This numerical work is based on flashback experiments of the TU Delft (TUD) jet flame at a jet Reynolds number of Re=11000. Flashback is a highly sensitive process, which is why (i) the turbulent inflow conditions, (ii) chemistry modeling and (iii) the wall temperatures of the mixing tube are crucial parameters to predict accurately this transient process. The presence of thermo-diffusive flame instabilities is the main contributor for flashback in this setup. We identify quasi-coherent turbulent structures in the mixing tube, namely an ejection event, which transports slow, preheated and hydrogen-enriched fluid away from the wall and triggers the flashback event. As a result, the flame forms a convex cusp upstream of the tube exit pointing towards the unburnt gas mixture. During the transition from unconfined (no walls around the flame) to confined (flame surrounded by walls) boundary-layer flashback, this cusp further bends and propagates towards the jet exit center, while, at the same time, its curvature and the reaction rate of hydrogen significantly increase by a factor of two. We repeated the flashback simulations several times and also for various flow conditions: all cases feature the same FB characteristics and, hence, confirms the generality of the conclusions. Moreover, the numerical flashback mechanism confirms the process hypothesized by the experiments. Based on the identified governing key parameters that affect flame flashback, we performed parametric variations of the Lewis number and wall temperature. By varying the Lewis number, we can clearly state that the flashback is driven by thermo-diffusive instabilities, while a hotter wall significantly deteriorates the flashback behavior of this setup. Novelty and significance statement Hydrogen combustion plays a crucial role in various energy applications due to no CO2 emissions. However, lean premixed hydrogen/air combustion can lead to safety challenges, particularly in the form of flame flashback, potentially causing catastrophic failures in combustion chambers. Understanding and controlling flashback is essential to ensure the safe and efficient use of hydrogen for instance in gas turbines. With this study, we address a number of open questions: (i) root cause of boundary layer flashback in turbulent premixed lean 100% hydrogen jet flames. (ii) transition from unconfined to confined boundary layer flashback. (iii) investigate key parameters that govern flame flashback: Lewis number and wall temperature. This study demonstrates for the first time that flashback in turbulent premixed lean hydrogen combustion is driven by the characteristic behavior of thermo-diffusive instabilities.
Keywords
- Boundary layer flashback, Hydrogen flame, Turbulent premixed combustion
ASJC Scopus subject areas
- Chemistry(all)
- General Chemistry
- Chemical Engineering(all)
- General Chemical Engineering
- Energy(all)
- Fuel Technology
- Energy(all)
- Energy Engineering and Power Technology
- Physics and Astronomy(all)
- General Physics and Astronomy
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In: Combustion and flame, Vol. 278, 114236, 08.2025.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Low velocity streaks combined with intrinsic flame instabilities provoke boundary layer flashback in a turbulent premixed jet-stabilized hydrogen flame
AU - Porath, P.
AU - Altenburg, L. A.
AU - Klein, S. A.
AU - Tummers, M. J.
AU - Ghani, A.
N1 - Publisher Copyright: © 2025 The Authors
PY - 2025/8
Y1 - 2025/8
N2 - We report on boundary layer flashback of a turbulent premixed, pure hydrogen flame using well-resolved LES. This numerical work is based on flashback experiments of the TU Delft (TUD) jet flame at a jet Reynolds number of Re=11000. Flashback is a highly sensitive process, which is why (i) the turbulent inflow conditions, (ii) chemistry modeling and (iii) the wall temperatures of the mixing tube are crucial parameters to predict accurately this transient process. The presence of thermo-diffusive flame instabilities is the main contributor for flashback in this setup. We identify quasi-coherent turbulent structures in the mixing tube, namely an ejection event, which transports slow, preheated and hydrogen-enriched fluid away from the wall and triggers the flashback event. As a result, the flame forms a convex cusp upstream of the tube exit pointing towards the unburnt gas mixture. During the transition from unconfined (no walls around the flame) to confined (flame surrounded by walls) boundary-layer flashback, this cusp further bends and propagates towards the jet exit center, while, at the same time, its curvature and the reaction rate of hydrogen significantly increase by a factor of two. We repeated the flashback simulations several times and also for various flow conditions: all cases feature the same FB characteristics and, hence, confirms the generality of the conclusions. Moreover, the numerical flashback mechanism confirms the process hypothesized by the experiments. Based on the identified governing key parameters that affect flame flashback, we performed parametric variations of the Lewis number and wall temperature. By varying the Lewis number, we can clearly state that the flashback is driven by thermo-diffusive instabilities, while a hotter wall significantly deteriorates the flashback behavior of this setup. Novelty and significance statement Hydrogen combustion plays a crucial role in various energy applications due to no CO2 emissions. However, lean premixed hydrogen/air combustion can lead to safety challenges, particularly in the form of flame flashback, potentially causing catastrophic failures in combustion chambers. Understanding and controlling flashback is essential to ensure the safe and efficient use of hydrogen for instance in gas turbines. With this study, we address a number of open questions: (i) root cause of boundary layer flashback in turbulent premixed lean 100% hydrogen jet flames. (ii) transition from unconfined to confined boundary layer flashback. (iii) investigate key parameters that govern flame flashback: Lewis number and wall temperature. This study demonstrates for the first time that flashback in turbulent premixed lean hydrogen combustion is driven by the characteristic behavior of thermo-diffusive instabilities.
AB - We report on boundary layer flashback of a turbulent premixed, pure hydrogen flame using well-resolved LES. This numerical work is based on flashback experiments of the TU Delft (TUD) jet flame at a jet Reynolds number of Re=11000. Flashback is a highly sensitive process, which is why (i) the turbulent inflow conditions, (ii) chemistry modeling and (iii) the wall temperatures of the mixing tube are crucial parameters to predict accurately this transient process. The presence of thermo-diffusive flame instabilities is the main contributor for flashback in this setup. We identify quasi-coherent turbulent structures in the mixing tube, namely an ejection event, which transports slow, preheated and hydrogen-enriched fluid away from the wall and triggers the flashback event. As a result, the flame forms a convex cusp upstream of the tube exit pointing towards the unburnt gas mixture. During the transition from unconfined (no walls around the flame) to confined (flame surrounded by walls) boundary-layer flashback, this cusp further bends and propagates towards the jet exit center, while, at the same time, its curvature and the reaction rate of hydrogen significantly increase by a factor of two. We repeated the flashback simulations several times and also for various flow conditions: all cases feature the same FB characteristics and, hence, confirms the generality of the conclusions. Moreover, the numerical flashback mechanism confirms the process hypothesized by the experiments. Based on the identified governing key parameters that affect flame flashback, we performed parametric variations of the Lewis number and wall temperature. By varying the Lewis number, we can clearly state that the flashback is driven by thermo-diffusive instabilities, while a hotter wall significantly deteriorates the flashback behavior of this setup. Novelty and significance statement Hydrogen combustion plays a crucial role in various energy applications due to no CO2 emissions. However, lean premixed hydrogen/air combustion can lead to safety challenges, particularly in the form of flame flashback, potentially causing catastrophic failures in combustion chambers. Understanding and controlling flashback is essential to ensure the safe and efficient use of hydrogen for instance in gas turbines. With this study, we address a number of open questions: (i) root cause of boundary layer flashback in turbulent premixed lean 100% hydrogen jet flames. (ii) transition from unconfined to confined boundary layer flashback. (iii) investigate key parameters that govern flame flashback: Lewis number and wall temperature. This study demonstrates for the first time that flashback in turbulent premixed lean hydrogen combustion is driven by the characteristic behavior of thermo-diffusive instabilities.
KW - Boundary layer flashback
KW - Hydrogen flame
KW - Turbulent premixed combustion
UR - http://www.scopus.com/inward/record.url?scp=105007156644&partnerID=8YFLogxK
U2 - 10.1016/j.combustflame.2025.114236
DO - 10.1016/j.combustflame.2025.114236
M3 - Article
AN - SCOPUS:105007156644
VL - 278
JO - Combustion and flame
JF - Combustion and flame
SN - 0010-2180
M1 - 114236
ER -