Results of experiments and computations are presented in
Figs. 4 and 5. Decreasing F has obvious effects: the air flow
increases because the hydrogen flow reduces, the energy available for combustion reduces, the laminar flame speed
reduces, the combustion rate deteriorates, the spark timing is
advanced to compensate the reduced rate of combustion, the
peak pressure reduces, IMEP reduces. As MAP increases, the
air flow rate increases. However, IMEP does not increase proportionally
to the air flow rate because of the different
combustion rate and spark advance. Experimental and
computational results agree surprisingly well.