On displacement speed correlations for statistically planar turbulent premixed flames of NH3 and H2 fuel blends
Proceedings of the Combustion Institute, cilt.42, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 42
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.proci.2026.106778
- Dergi Adı: Proceedings of the Combustion Institute
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
- Anahtar Kelimeler: Correlation relation, Curvature, Density-weighted displacement speed, Direct Numerical Simulation, Stretch-rate
- Bilecik Şeyh Edebali Üniversitesi Adresli: Evet
Özet
The performance of different correlations for parameterising the flame stretch rate K and curvature κm dependences of the density-weighted displacement speed Sd* has been analysed using Direct Numerical Simulation (DNS) data of statistically planar premixed flames of NH3 and representative NH3–H2–N2 blends. The linear stretch-rate model is found to be insufficient to predict the behaviour of Sd* due to strong non-linear stretch-rate effects linked to the negative correlation between displacement speed and curvature. A non-linear stretch-based formulation provides improved predictions of stretch rate dependence of Sd*. By contrast, a formulation assuming linear curvature dependence performs satisfactorily despite the non-linear relationship between Sd* and κm, because of the negative correlation coefficient between these quantities being close to -1.0 for the cases considered. As a result, a non-linear curvature-based relation offers no significant advantage and yields similar Markstein length scale LM values to the linear curvature relation. The Markstein length scale LM decreases with increasing hydrogen content, reflecting the reduction in effective Lewis number. Further analysis shows that the curvature dependence of Sd* arises mainly from the tangential diffusion component, while the combined contribution of reaction and normal diffusion is only weakly curvature dependent, indicating modest non-unity Lewis number effects. Based on these findings, a simplified model that accounts solely for tangential diffusion is identified and shown to provide reliable predictions for NH3/H2 blends under the conditions studied. Novelty and significance statement The present work quantifies both stretch rate- and curvature-dependences of density-weighted displacement speed Sd* via the Markstein length across different blend ratios and progress variable definitions for premixed turbulent NH₃/H₂ flames —an aspect not previously addressed for NH₃/H₂ blends. Results show that density-weighted displacement speed Sd* exhibits nearly linear curvature dependence but strongly nonlinear stretch rate dependence, governed by tangential diffusion. These findings provide guidance for improving level-set and Flame Surface Density closures in Reynolds Averaged Navier-Stokes and Large Eddy Simulations, ensuring reliable predictive modelling of premixed combustion of zero-carbon NH₃/H₂ fuel blends for power and propulsion applications. The framework also highlights when non-linear relations are necessary, offering a pathway for future model development for fuels with near-unity Lewis number.