Mixture Preparation Mechanisms in a Port Fuel Injected Engine

An experimental study was carried out that qualitatively examined the mixture preparation process in port fuel injected engines. The primary variables in this study were intake valve lift, intake valve timing, injector spray quality, and injection timing. A special visualization engine was used to obtain high-speed videos of the fuel-air mixture flowing through the intake valve, as well as the wetting of the intake valve and head in the combustion chamber. Additionally, videos were taken from within the intake port using a borescope to examine liquid fuel distribution in the port. Finally, a simulation study was carried out in order to understand how the various combinations of intake valve lifts and timings affect the flow velocity through the intake valve gap to aid in the interpretation of the videos.

The net result of the study was the construction of an “event diagram” for each experimental condition that identifies and explains the sequence of events and interactions affecting the liquid fuel. Six mechanisms that transport liquid fuel into the combustion chamber and four that affect liquid fuel behavior within the combustion chamber were identified.