A study on combustion chamber deposit formation on a piston crown of a small two-stroke cycle engine (relation between a lubricant oil flow and CCD formation pattern in a cylinder)

We made a study on the combustion chamber deposit (CCD) formation pattern on a piston crown surface in a small two-stroke spark ignition engine. Generation of the CCD is influenced by the temperature, pressure, gas flow conditions or retention period of the lubrication oil in the cylinder. Lubrication oil flows were observed by generating CCD streaks (CCDS) from many small drilled holes on the piston crown. To understand the temperature influence on the heat degradation of the lubricant oil, the oil on the conical cavity was heated statically in an electric furnace, and the oil was also dropped on the heated incline plate. Using separated a piston crown and a cylinder head, the characteristic properties of deposited sediments in the combustion chamber were surveyed and analyzed in a such operation load. In the results, (1) the oil flow-pattern of a piston surface flow is the average direction of gas flow there, (2) Most of CCD is formatted at about 275°C, (3) CCDS formed on the heated plate along the oil flow line is a distant every angle, (4) CCD on higher-heating area is formed heat-proof in a higher-boiling point-composition concentrated by a metallic detergent, and (5) CCD is many on lower-middle operation load and less on higher operation load.