Measurement of the liquid fuel film on the combustion chamber wall of a gasoline engine using a novel capacitance sensor

During a cold start and warm-up operation of an SI gasoline engine, a liquid fuel film is formed on the intake port and piston walls. The liquid fuel film attached to the wall increases exhaust unburned HC, particulate matter (PM) emissions, and oil dilution. It is essential to investigate the formation process of the fuel liquid film to reduce exhaust emissions and improve thermal efficiency. Compact fuel film measurement sensors are required for application in the production engine measurement. In this study, a liquid film sensor detecting changes in capacitance due to the liquid film has been developed. The newly developed liquid film sensor was installed and demonstrated into the combustion chamber wall of a single-cylinder gasoline engine. As a result, the liquid film behavior on the combustion chamber wall was successfully detected.