Utilizing hydrogen as a fuel is a promising option for the paradigm shift toward a carbon-neutral aviation industry. However, a variety of problems could emerge as hydrogen flames are prone to thermodiffusive instabilities. In this work, transported probability density function (TPDF) simulations are carried out in conjunction with a direct numerical simulation dataset of lean premixed turbulent hydrogen/air flames. This provides a clean evaluation of the models for conditional molecular diffusion, including the micromixing in composition space and the molecular transport in physical space. It is found that the mixing formulations ignoring the localness in composition space are incapable of reproducing the overall combustion process. Applying the mechanical-to-scalar timescale ratio indicated by the mixing frequency of hydrogen is superior to a constant ratio, implying that hydrogen is the controlling species for scalar mixing. More interestingly, it is found that the superequilibrium phenomenon cannot be captured regardless of the treatment for micromixing if the molecular transport in physical space is ignored, highlighting the importance of spatial transport due to molecular diffusion, which is typically ignored in TPDF simulations. This study demonstrates the capability of the TPDF method to reproduce the key features of synergistic interactions between turbulence and thermodiffusive instabilities.
Transported Probability Density Function Investigation on Turbulent Premixed Hydrogen Flames with Thermodiffusive Instability
AIAA Journal ; 1-16
2025-05-01
Article (Journal)
Electronic Resource
English
Density fluctuations in premixed turbulent flames
Automotive engineering | 1984
|AIAA | 2014
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