Abstract
The influence of additives including dimethyl ether (DME), formaldehyde (CH
2
O), and hydrogen peroxide (H
2
O
2
) for the control of ignition of methane fuel in HCCI engines has been investigated numerically. The chemical kinetic mechanisms incorporated GRI-Mech 3.0 which considers 53 species and 325 reactions together with the DME reaction scheme consisting of 79 species and 351 reactions. Computations were carried out in a constant-volume bomb at engine-like conditions to assess the ignition delay times with the additives at various initial temperatures, pressures, equivalence ratios, and compositions. Comparison between the two kinetic mechanisms was first carried out to examine the validity using available experimental data. Reasonable agreement was observed between the simulation and experiment. The effect of H
2
O
2
addition in reducing the ignition delay time was most pronounced in comparison with the other two additives DME and CH
2
O for all conditions examined. Sensitivity analyses were performed to identify important reactions in reducing ignition delays. The present study demonstrated the possibility of controlling and improving the ignition characteristics of natural gas homogeneous charge compression ignition engines by means of the additives.