Effect of methane-dimethyl ether fuel blends on flame stability, laminar flame speed, and Markstein length

Binary fuel blends provide challenges to chemical kinetics models not seen by testing only pure fuels, allowing them to be verified over a wider range of inputs. The effect of adding dimethyl ether (DME) to methane on the laminar flame speed, Markstein length, and Lewis number was studied experimentally and numerically over a range of initial pressures from 1 to 10 atm, with the volumetric ratios of the fuel blends ranging from 60% CH₄/40% DME to 80% CH₄/20% DME. The experimental results were compared to an improved kinetics model, an ongoing effort spanning the past few years. The fuel blends showed a large change in the laminar flame speed with DME addition, and the model captured this increase in flame speed. Agreement between the model and experimental results was excellent for all cases. In addition, the Markstein lengths were greatly affected by the blending of the fuels. A small amount of DME addition caused the Markstein lengths to change by a large value. Finally, a rigorous uncertainty analysis was performed on the experimental data, giving the error with respect to the true value rather than the standard deviation of repeated experiments.