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

摘要

The effects of elevated reactant temperatures on soot formation in a laminar coflow ethylene flamewere 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. Inthe 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 HeatTransfer (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 experimentaland numerical data suggests that soot formation is promoted by enhanced soot surface growth. The numericalsimulation reveals that PAH (polycyclic aromatic hydrocarbon) adsorption, which is a function ofPAH 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.