Study on the effect of hydrogen addition to dimethyl ether homogeneous charge compression ignition combustion engine

The auto-ignition characteristics of dimethyl ether (DME)/H₂/Air blends (hydrogen blending ratio ranging from 0% to 70%) in homogeneous charge compression ignition (HCCI) combustion engine are investigated by calculation method using zero-dimension single-zone model. All the simulated mixtures demonstrated a two-stage heat release phenomenon at different crank angles. The results show that the hydrogen addition can retard the auto-ignition timing of DME in HCCI combustion engine. The ignition timing at low temperature is retarded slightly with the hydrogen addition, and the ignition timing at high temperature is delayed significantly due to the increased negative temperature coefficient duration. Chemical kinetic analysis reveals that the competition of OH radicals between hydrogen and DME could be the reason why the low temperature reactions of DME are mitigated. H₂O₂ molecules decompose at about 1000 K and initiate the high temperature reactions of the mixtures.