CFD investigation of a Stirling engine flexi-fuel burner based on MILD combustion

Paper in proceeding, 2015

This paper presents comparisons of results from tests and 3D CFD combustion simulations based on both RANS and hybrid URANS/LES (SAS-SST model) turbulence models applied to an industrial Stirling engine combustion chamber at atmospheric pressure. Both methane gas and landfill gas were simulated. The combustor is designed to operate in the MILD combustion mode which is characterized by low flame temperatures and low NOx emissions. A 4-step reduced reaction mechanism, named AAT4NR, involving seven species was developed to represent the landfill gas. The optimization was performed at atmospheric pressure for a range of fresh gas temperatures [300 K - 1000 K] and equivalence ratios [0.15 - 1]. Comparisons with detailed chemistry solutions of a planar propagating flame front show that the laminar flame speed, the adiabatic flame temperature, the ignition delay time and the species concentration at equilibrium are adequately predicted. There is good agreement between the quantities predicted with URANS/LES and experimental data, in terms of flow and flame dynamics, averaged temperatures, NOX-levels and the concentrations of some major species.