Development and verification of simplified methane/dimethyl ether mechanism for micro-combustion

In this work, a simplified mechanism for simulating methane/dimethyl ether micro-flames is developed by validating the flame speed and ignition delay time. Towards this goal, DRGEPSA is used to simplify the pure dimethyl ether mechanism proposed by Zhao. Then the simplified mechanism is coupled with the existing pure methane mechanism (kee-58 mechanism) to obtain the blended fuel mechanism. The sensitivity analysis indicates that the chemical reaction HCOOH = HCO + OH is most beneficial to the optimization of the blended fuel mechanism. By adjusting this reactions reaction rate, the dynamic characteristics and applicability of the blended fuel mechanism in the numerical simulation are adjusted, resulting in a simplified mechanism containing 25 species and 96 chemical reactions. The predicted ignition delay time and laminar flame speed are well matched with the experimental results under certain conditions, showing the capability of this simplified mechanism in describing the combustion characteristics. Finally, this mechanism is applied to predict the transition rules of flame structure, flame location, and blowout limit of methane/dimethyl ether flames under micro-scale conditions using a three-dimensional model. A good agreement between calculations and experimental measurements is achieved, demonstrating the reliability of the simplified mechanism developed in the present work.