Investigations on the Influence of Fuel Oil Interaction on Preignition Events in highly boosted DI Gasoline Engines
Premature and uncontrolled flame initiation, called preignition (PI), is a prominent issue in the development of spark-ignited engines. It is commonly assumed that this abnormal combustion mode hinders progress in engine downsizing, thus inhibiting development of more efficient engines. The phenomenon is primarily observed in highly turbocharged spark ignited (SI) engines in the full load regime at low engine speeds. Subsequent engine knock induces extremely high peak pressures, potentially causing severe engine damage. The mechanisms leading to this phenomenon are not completely understood. It seems to be common sense that a multiphase process is responsible for the preignition. One effect could be the interaction between injected fuel droplets and the oil film at the cylinder liner. Under certain conditions droplets of oil or oil fuel mixture can be detached leading to a preignition at the droplet surface towards the end of the compression phase.