An experimental and numerical study of the effects of reactant temperatures on soot formation in a coflow diffusion ethylene flame

Abstract The effects of elevated reactant temperatures on soot formation in a laminar coflow ethylene flame were experimentally and numerically investigated. Ethylene flames at the reference reactant temperatures (both air and fuel), T r , of 300K (LT), 473K (MT), 673K (HT), and 713K (UHT) were established. In the experiment, soot volume fractions ( f v ), primary particle diameters ( d p ), and soot (flame) temperatures ( T F ) were measured. The flames were also simulated by the CoFlame code with the Conjugate Heat Transfer (CHT) condition. The experimental results show that elevating T r positively affects soot formation. The increase in the maximum f v is greater on the wing pathline ( ∼ 1.9 times) than on the centerline ( ∼ 1.2 times) when the adiabatic flame temperature increases by ∼ 100K. An analysis of the experimental and numerical data suggests that soot formation is promoted by enhanced soot surface growth. The numerical simulation reveals that PAH (polycyclic aromatic hydrocarbon) adsorption, which is a function of PAH concentration, becomes important at high T r as its mass contribution increases from ∼ 50% to ∼ 70%. This may be attributed to early fuel pyrolysis within the fuel tube.