Technical Paper
Mechanism Triggering Pre-Ignition in a Turbo-Charged Engine
2019-04-02
2019-01-0255
Pre-ignition in modern engines is largely attributed to oil-fuel mixture droplets igniting before the spark timing. Researchers have also found pre-ignition events to be triggered by high hydrocarbon emissions from the previous cycle as well as late spark timing in the previous cycle. Additionally, an ideally scavenged engine was not found to be limited by pre-ignition. These observations point to a significant role of residuals in triggering pre-ignition events. Current work studies pre-ignition in a probabilistic approach. The effect of residuals and in-cylinder thermodynamic state is studied by varying the exhaust back pressure and intake air temperature respectively. Experiments were performed with a fixed mass flow rate of air + fuel and intake air temperature while the exhaust back pressure was varied. Intake air pressure varied in response to fixed intake temperature. Pre-ignition and super-knock count increased with increasing exhaust back pressure.