Experimental and modeling studies of C_2H_4/O_2/Ar, C_2H_4/methylal/O_2/Ar and C_2H_4/ethylal/O_2/Ar rich flames and the effect of oxygenated additives

摘要

The addition of dimethoxymethane (DMM or methylal) and diethoxymethane (DEM or ethylal) to a rich ethylene/oxygen/argon flame has been investigated by measuring the depletion of soot precursors. Three rich premixed ethylene/oxygen/argon (with and without added methylal or ethylal) flat flames have been stabilized at low-pressure (50 mbar) on a Spalding-Botha type burner with the same equivalence ratio of 2.50. Identification and monitoring of signal intensity profiles of species within the flames have been carried out by using molecular beam mass spectrometry (M.B.M.S.). The replacement of some C_2H_4 by C_3H_8O_2 or C_5H_(12)O_2 is responsible for a decrease of the maximum mole fractions of the detected intermediate species. This phenomenon is noticeable for C_2-C_4 intermediates and becomes more effective for C5-C10 species, mainly when C_3H_8O_2 added. A new kinetic mode! has been elaborated and contains 546 reactions and 107 chemical species in order to simulate the three investigated flames: C_2H_4/O_2/Ar, C_2H_4/DMM/02/Ar and C_2H_4/DEM/O_2/Ar. The reaction mechanism well reproduces experimental mole fraction profiles of major and intermediate species, and underlines the effect of methylal and ethylal addition on species concentration profiles for these flames.