Abstract: The piston ring and cylinder of a four-stroke four-cylinder engine is taken as the research object. A study on effect of non-circular cylinder bore on oil consumption in cylinder is carried out, taking into account the non-circularity of the cylinder bore under real working condition. The oil film thickness between piston ring and non-circular cylinder is firstly calculated. Then, major oil consumption patterns are identified and characterized. A numerical model to calculate oil consumption in cylinder is proposed and demonstrated. Compared with the oil consumption in the ideal round cylinder bore, the effect of non-circular cylinder bore on oil consumption is discussed. Results indicate that non-uniform distribution of the film thickness between piston ring and cylinder along the circumferential direction is quite remarkable. Overall, compared with that between piston ring and ideal round cylinder, mean value of oil film thickness along circumferential direction between piston ring and non-circular cylinder bore is bigger. The amount of oil scrapped by top ring, thrown by inertial force or pushed by reversed gas pressure in non-circular cylinder is bigger than the corresponding one in ideal round cylinder. The oil consumption calculation considering non-circular cylinder bore is much closer to the real one. Non-circularity of the cylinder bore plays a very important role in oil consumption calculation, and should not be neglected.

Key words: Non-circular cylinder bore, Non-uniform distribution of oil film thickness along circumferential direction, Oil consumption in cylinder