Characterizing the influence of thermodiffusive effects on turbulent burning velocity of lean hydrogen/air mixtures using critically stretched laminar flames

Artikel i vetenskaplig tidskrift, 2025

This work focuses on characterizing the influence of thermodiffusive effects on turbulent burning velocity (𝑆𝑇 ) of lean hydrogen/air mixtures, employing the so-called leading point concept. To this end, the flame characteristics of 1-D critically stretched laminar flames, including the flame consumption velocity and flame thickness, are extracted from two flame configurations: counter-flow twin premixed flames and spherically expanding flames. The former configuration is solely subject to strain-related stretch, whereas the latter configuration is subject to both strain-related and curvature-related stretches. Lean hydrogen/air mixtures are considered at a wide range of temperatures and pressures, addressed in recent direct numerical simulations
(DNS) of turbulent, premixed, lean hydrogen/air flames (Wang et al., 2024). It is found that the critically stretched flame consumption velocities obtained from these two configurations are closely aligned, while the flame thickness obtained from the spherically expanding flames is substantially greater than that from the counter-flow twin premixed flames. Capabilities of these flame characteristics for capturing the thermodiffusive effects on 𝑆𝑇 are demonstrated by incorporating these characteristics into fits to 𝑆𝑇 dataset obtained from the aforementioned DNS study. Various definitions of flame thickness are also examined, with the thickness of fuel consumption zone showing the best performance. These findings support the leading point concept and imply that both critically strained planar flames and highly curved spherically expanding flames could be used to characterize the local burning state at the leading edges of turbulent lean premixed hydrogen flames.