Effect of Inlet-Mixture Stratification and Preheating on a C3H8 Premixer and Bluff-Body Combustor

Abstract

This work presents the computational investigation of the nonreacting flow field and of the fuel–air mixing characteristics in a stratified, premixer/bluff-body combustor configuration under the effect of elevated inlet mixture temperatures. Four levels of preheats of the inlet reactants are investigated, ranging from 300 to 743 K, for lean to ultralean mixture settings. Different fuel–air mixing wake topologies were captured by regulating the fuel injection level, the incoming fuel–air ratio gradient, and the mixture preheat. An implicit, finite-volume-based large eddy simulation method was employed yielding satisfactory agreement between simulations and counterpart experimental data by successfully reproducing the large-scale features of the interaction of the primary afterbody recirculation with the incoming annular shear layer and the impact of preheat on the developing disk wake topology and fuel–air mixing performance. Thus, the effects of inlet mixture stratification, alone or in combination with inlet preheat, on the performance characteristics of the disk stabilizer were elucidated, while parameters controlling the fuel–air mixing in the recirculation zone and the near wake region were also characterized.