Laminar Burning, Combustion and Emission Characteristics of Premixed Methane- Dissociated Methanol-Air Mixtures

This research presents an experimental study of the laminar burning combustion and emission characteristics of premixed methane -dissociated methanol-air mixtures in a constant volume combustion chamber. All experiments were conducted at 3 bar initial pressure and 373K initial temperature. The dissociated methanol fractions were from 20% to 80% with 20% intervals, and the equivalence ratio varied from 0.6 to 1.8 with 0.2 intervals. The images of flame propagation were visualized by using a schlieren system. The combustion pressure data were measured and exhaust emissions were sampled with a portable exhaust gas analyzer. The results show that the unstretched laminar burning velocities increased significantly with dissociated methanol enrichment. The Markstein length decreased with increasing dissociated methanol fraction and decreasing equivalence ratio. The lewis number decreased with increasing dissociated methanol fraction due to the enhancing of diffusional thermal instability and hydrodynamic instability. The highest maximum combustion pressure was observed when the equivalence ratio was around 1.2 with 80% dissociated methanol added. The ignition delay time decreased with increasing dissociated methanol fraction. As the fraction of dissociated methanol increased in the mixtures, HC and CO₂ decreased but CO and NO_X increased.