Flame Structure Analysis and Flamelet/Progress Variable Modelling of DME/Air Flames with Different Degrees of Premixing

Abstract

Laminar dimethyl ether (DME) coflow jet flames, defined by different levels of partial premixing in the fuel stream, provide canonical test cases for studying conditions in between perfectly premixed and non-premixed characteristics. This work investigates the structure of DME/air flames and the evaluation of suitable flamelet modeling approaches. Three laminar, partially premixed DME/air flames are studied using fully resolved numerical simulations and the flamelet/progress variable (FPV) approach. The flame structure of the partially premixed DME/air flames is discussed and selected slices are compared to each other as well as to Raman/Rayleigh data. Overall, the experimental data is well predicted and the local flame structure is represented by the fully resolved simulations. In the context of the FPV approach, an a priori analysis of the underlying tabulated manifold is carried out. Lookup tables based on strained counterflow flames were identified as the most suitable candidate for the fully coupled FPV simulations of all three partially premixed DME/air flames. The FPV results are further compared a posteriori to the fully resolved simulation data. The flame structure of the partially premixed DME/air flames was reproduced and good results were obtained for the temperature and the species mass fractions. This numerical investigation contributes to the understanding of local flame structures in partially premixed DME/air flames and has the potential to support model selection in complex combustion processes.