Turbulent hydrogen premixed flames at high pressure and high temperature

TL;DR

This study uses DNS to examine how high pressure and temperature affect turbulent lean premixed hydrogen flames, revealing moderate effects on flame structure and turbulence interaction, with implications for modeling combustion in gas turbines.

Contribution

It provides a detailed analysis of turbulence-flame interactions at high pressure and temperature, highlighting the effects on flame structure and turbulence dissipation.

Findings

Reduced turbulence dissipation at high pressure enhances turbulence-flame coupling.

Tangential strain rate follows universal Kolmogorov scaling.

Moderate overall effects due to compensating influences.

Abstract

The combined influence of elevated pressure and temperature, representative of gas-turbine operating conditions, on lean premixed hydrogen flames is investigated using Direct Numerical Simulations (DNS) of a turbulent jet. Three cases are considered: 1 atm/298 K, 5 atm/472 K, and 20 atm/700 K, scaled to maintain the same jet Reynolds number and nominal Karlovitz number in the unburnt mixture, enabling a direct comparison of flame-turbulence interactions. Although the combined effects are moderate overall due to compensating influences, measurable differences arise in flame structure and turbulence-flame coupling. They are driven by reduced turbulence dissipation within the flame at high pressure and temperature, which enhances the interaction between turbulence and thermodiffusive effects. Finally, the tangential strain rate exhibits the same universal Kolmogorov scaling observed in homogeneous-isotropic turbulence and in methane flames, confirming its robustness for modelling turbulence