LES flamelet-progress variable modeling and measurements of a turbulent partially-premixed dimethyl ether jet flame

Abstract

In the present study the flame structure of a piloted partially-premixed dimethyl ether flame (DME-D), which is based on the Sydney/Sandia piloted jet burner flame series, is investigated using an LES-flamelet-progress variable approach (LES-FPV). Simulation results are used together with a comprehensive experimental data set including multi-scalar measurements of temperature and major species from Raman/Rayleigh scattering, intermediate species CH2O and OH from laser induced fluorescence (LIF) and velocity data from particle image velocimetry (PIV). The comparison between numerical and experimental data includes the mean and the root mean square (RMS) radial profiles for velocity, mixture fraction, temperature and mole fractions of major species at different downstream locations. Furthermore, species distributions conditioned on the experimentally accessible mixture fraction are compared and differences between DME and methane flames are discussed. In addition to this comparison, the computation of CH2O-LIF and OH-LIF signals as well as the effective Rayleigh cross-section was incorporated into the flamelet-progress variable approach. The filtered and time-averaged numerical results are then directly compared with the corresponding experimental signals at different axial positions. The characteristic separation of instantaneous CH2O and OH fields, which was previously observed in simultaneous LIF measurements, is discussed and analyzed based on the underlying flamelet structures. Finally, modeling assumptions from the experimental post-processing for the effective Rayleigh cross-section, which were introduced to account for the experimentally inaccessible intermediate hydrocarbons, are evaluated using the detailed species composition from the numerical simulations.