Fuel modification flash boiling atomization and combustion in reciprocating engines

With the current goals and regulations in reducing carbon emissions, flash boiling atomization is considered a promising method for liquid fuel energy conversions, for instance, alternative fuel combustions and zero/negative carbon fuel combustions. One scheme to enable flash boiling atomization is to dope highly volatile fuel into low volatile fuels and trigger phase change during combustion, but the impacts of such modifications on the performance of the combustor, especially soot formation mechanisms and gaseous emissions characteristics, are not illustrated systematically yet. This investigation focuses on the combustion of commercial gasoline fuel doped with iso-pentane at different volume fractions. The combustion experiments are made using a reciprocating optical engine facility with spark-ignition direct-injection combustion modes. Typical engine conditions such as low fuel temperature and high ambient pressure conditions are examined. The flame chemiluminescence is captured by a high-speed color camera, and the emission characteristics are quantified by emission analyzers. The results show that flash boiling achieved via fuel modification can generally reduce soot formation by suppressing spray impingement and wall film combustion. A more homogenous fuel-air mixture can further reduce the hot spots/rich combustions from unburnt droplets or fuel-rich zones.