Hydrogen turbulent nonpremixed flames blended with spray or prevapourised biofuels

Abstract

The low radiant intensity of hydrogen flames may be enhanced by adding biofuels with a high sooting propensity. This paper reports the effect of biofuel concentration and phase on the combustion characteristics of turbulent nonpremixed hydrogen-based flames. The 0.2 and 1 mol% vapourised/spray biofuel surrogates blended flames exhibit limited soot loading, except for 1 mol% spray toluene and anisole blends where soot starts to form. Spray additives benefit the formation of soot by creating localised fuel-rich conditions. Blending 3.5 and 4 mol% vapourised toluene attains a sooting flame and significantly enhances the luminosity and radiant fraction. The global NOx emissions increase with prevapourised/spray biofuel surrogates due to the enhanced NO formation via thermal and prompt routes. Reducing the hydrogen concentration from 9:1 to 7:3 in H2/N2 (by mole) leads to large increases in luminosity and radiant fraction by 34 times and 135%, respectively, and a reduction in NOx emissions by 68%.