Investigation of chemical pathways for turbulent Hydrogen-Air premixed flames

Abstract

This paper considers the kinetic pathways of hydrogen oxidation in turbulent, premixed H2-air flames. It assesses the relative roles of different reaction steps in H2 oxidation relative to laminar flames, and the degree to which turbulence-chemistry interactions alters the well understood oxidation pathway that exist in laminar flames. This is done by analysing turbulent, lean (φ =0.4), H2-Air flame DNS database from Aspden et al. (Proc. Combust. Inst. 35 (2015) 1321–1329). The relative roles of dominant reaction steps in heat release and radical formation/consumption are analysed at different Karlovitz numbers and compared with laminar stretched flame calculations from counterflow flames and perfectly stirred reactors. It is found that both the progress variable conditioned and spatially integrated contributions of the dominant reactions remain qualitatively similar between a highly turbulent and a laminar unstretched flame. Larger changes, up to a factor of about two, occur in the relative roles of reactions with secondary influences on heat release and radical production/consumption. These results suggest that the kinetic routes through which H2 is oxidized remain essentially constant between laminar, unstretched flames and high Karlovitz number flames.