Properties of in-cylinder fuel reformation and ignition characteristics of CO/H2/CH4 mixtures

In-cylinder fuel reformation and reactivity of reformate gases were investigated. Compositions of reformate gases derived from in-cylinder fuel reformation were numerically investigated over a wide range of initial temperatures and equivalence ratios. The computational results showed that products of fuel reformation were mainly CO and H2 at low equivalence ratios. At high equivalence ratios, on the other hand, mole fractions of CH4 and C2H4 became large, H2 mole fraction became small and CO mole fraction was almost constant. To investigate the effects of CH4 on reactivity of reformate gas, CO, H2 and CH4 were chosen as representative components of reformate gases in this study. Then four types of CO/H2/CH4 compositions were selected to investigate the effects of H2-to-CH4 ratios on reactivity at a constant fraction of CO. For the investigation on the ignition properties, a micro flow reactor with a controlled temperature profile was adopted and weak flames of CO/H2/CH4/air mixtures were observed. Experimental and computational results showed that the positions of weak flames shifted to the downstream side with the increase of CH4 fraction, which means reactivity of CO/H2/CH4/air mixtures was reduced.