Flamelet/progress variable modelling of turbulent non-premixed cool flames of dimethyl-ether/methane mixtures

In present work, the turbulent non-premixed cool flames of dimethyl-ether (DME)/methane mixtures are studied within the framework of flamelet/progress variable modelling and chemical kinetic analyses. The numerical setup is based on the Princeton CARAT burner configuration, and the accuracy of the hpmech-V3.3 chemistry to model turbulent low-temperature combustion is validated against the reference experiments and DNS. The simulation results reveal that turbulent cool flame structures are modified (lifted) by methane addition owing to the decline of cool flame extinction limits. The different flame regions associated with differing thermochemical characteristics for the dual-fuel lifted cool flames are uncovered. The DME/methane consumption trends suggest that methane addition inhibits the DME low-temperature oxidation. Through the kinetic analyses, the mechanisms are identified to be two-fold: methane competes with the DME H-abstraction reaction for OH radicals and the reaction of QOOH <=> O 2 + 2CH 2 O is significantly slowed down with the methane addition. The mechanisms also kinetically explain the finding that the formation of CH 2 O, CO, CO 2 in cool flames decline in response to the increase of methane blending ratios. The correlation between temperature and key intermediate formation is discovered. • Turbulent cool flame structures are modified (lifted) by methane addition through the decline of cool flame extinction limits. • The different flame regions associated with differing thermochemical characteristics for the dual-fuel lifted cool flames are uncovered. • Methane addition inhibits the DME low-temperature oxidation. • The kinetic mechanisms behind are identified: CH 4 competes with the DME H-abstraction reaction for OH radicals and the reaction of QOOH <=> O 2 + 2CH 2 O is significantly slowed down with the methane addition.