Combustion chamber geometry effects in spark ignition engine exhaust emissions

The paper presents experimental results showing the effect of hemispherical, cylindrical and oval bowls-in-piston on exhaust gases within the cylinder of spark ignition engines. Results indicate that bowls increase both heat transfer and flame speed. Consequently, flame ability must become wide to reduce both engine emissions and cycle combustion variability. Hemispherical effect ranked first on hydrocarbon and carbon monoxide emissions, followed by cylindrical then oval. Nitrogen oxides are in opposite direction, with oval ranked first, followed by cylindrical then hemispherical.