An experimental research on combustion instability of a spark ignited single cylinder
engine operating on biogas with different distribution ratio of hydrogen (15%, 20%, 25%,
30%, 35% in volume) is studied. The results show that the increase of the hydrogen fraction
in the fuel blends leads to the decrease of the cyclic variation coefficient of indicated mean
effective pressure in a certain fraction range (15% w 35%).The combustion heat release
rate accelerates. The flame development angle shortens because the chemical reaction
takes the dominant effects. Increasing the ignition advance angle can decrease the cyclic
variation. The engine work stability is largely improved with the higher hydrogen fraction
in the fuel blends.