A numerical study of the autoignited laminar DME lifted jet flames in heated coflow air

Abstract

The liftoff characteristics of autoignited laminar dimethyl ether (DME) jet flames in heated coflow air is numerically investigated with openFOAM-based laminar reacting flow solver, laminarSMOKE. According to a previous experimental study on autoignited laminar DME jet flame, decreasing liftoff height trend of the lifted jet flames is observed with the increase of fuel jet velocity at relatively-low jet velocities. To understand the unusual liftoff characteristics of the autoignited Lifted DME jet flames, various numerical simulations have been carried out. From additional simulations with modified mass diffusivity of hydrogen, it is found that the decreasing liftoff height behavior is mainly attributed to the high diffusive nature of hydrogen molecule, which is generated by the DME pyrolysis. The temperature profile along the streamline passing through the flamebase shows that actual autoignition delay time deviates from the 0-D ignition delay time trend due to the preferential diffusion effect of hydrogen molecule, leading to the decreasing HL behavior.