Ignition control in a gasoline compression ignition engine with ozone addition combined with a two-stage direct-injection strategy

To control the ignition timing in a gasoline compression ignition (GCI) engine, ozone (O₃) was introduced into the intake air. The O-radicals are decomposed from the O₃ above 550 K during the compression stroke, and combine into oxygen (O₂) in a very short time. The authors adopted two-stage direct injection to mix the fuel injected into the cylinder at very early timings with the O-radicals, before a reduction of the O-radicals would take place. The ignition timing of the second fuel injection for the main combustion is controlled by the heat release from the first fuel injection. In this paper, engine experiments were performed to examine the feasibility of the ignition control with a primary reference fuel, octane number 90 (PRF90). The O₃ concentration, the quantity, and the timing of the first injection were changed as experimental parameters. The results showed that a very small quantity of O₃, tens of ppm, is sufficient to promote the heat release of the first injected fuel. The heat release increases with the O₃ concentration and the quantity of fuel in the first injection. The addition of O₃ has no other impact on the ignition when the first injection timing is retarded to around −40°CA ATDC. In this manner, it is possible to control the ignition delays and to alter the combustion state from typical diesel combustion to premixed compression ignition combustion.