An experimental study of determining friction force between ring and cylinder by ‎measuring piston movement

The cylinder-piston reciprocating mechanism has been one of the most dominant designs since the invention of internal combustion engines. By reducing friction between the cylinder and piston of the engine, the reciprocating movement of the piston can be made possible, easily. The pressure inside the cylinder during the compression and expansion strokes is much higher than in the crankcase. Due to the movement of the piston inside the cylinder and its temperature change during the engine operation, a clearance needs to be between them. The clearance creates some crevices between the cylinder chamber and the crankcase. By placing the open-mouthed elastic rings in their special grooves on the piston, some serious flowing obstacles are created. However, in addition to the loss of work, the friction between the rings and cylinder can cause the relative motion of the rings in their grooves during the reciprocating movement of the piston and change the blowby geometry, so the ring friction forces are important. In the present work, an accurate experimental method is proposed and used to measure the friction of a ring with a cylinder applying a mass-pulley-string set, equipped with a displacement measurement sensor. After the experimental-analytical estimation of pulley-resistant torques, to extract the friction force of the ring, the friction force was measured and calculated in two states piston without ring and piston with ring. The results showed that the friction force of a compression ring was 2.87 N and although the piston under vertical movement had no noticeable lateral load, it was observed that its friction force was about 77% of the compression ring friction.