Experimental and Modeling Study of Premixed Atmospheric-Pressure Dimethyl Ether−Air Flames

Chemical species profiles have been measured at atmospheric pressure for two dimethyl ether (DME)−air flat flames having fuel/air equivalence ratios of 0.67 and 1.49. The samples, obtained with an uncooled quartz probe, were analyzed by either gas chromatography or Fourier transform infrared (FTIR) spectroscopy for CH4, C2H2, C2H4, C2H6, C3H8, DME, CO, CO2, O2, CH2O, and formic acid. A pneumatic probe calibrated at a reference position in the burned gas by a radiation-corrected thermocouple provided temperature profiles for each flame. Species profiles for two methane−air flames with equivalence ratios and cold-gas flow velocities similar to those of the DME flames were also obtained for comparison to the DME results. Mole fractions of C2 product species were similar in DME and methane flames of similar equivalence ratios. However, the CH2O mole fractions were 5−10 times larger in the DME flames. These experimental profiles are compared to profiles generated in a computer modeling study using the best available DME−air chemical kinetic mechanism. The Appendix presents photographs of DME, methane, and ethane diffusion flames. These results show that, while DME produces soot, its yellow flame luminosity is much smaller than that of an ethane flame at the same fuel volume flow rate, consistent with the low soot emission rate observed when DME is used as a diesel fuel.