A visualization study of mixture preparation mechanisms for port fuel injected spark ignition engines

Abstract

An experimental study was carried out that examined qualitatively the mixture preparation process in port fuel injected spark ignition 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 enable high-speed video 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, video was 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 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 five that affect liquid fuel within the combustion chamber were identified.