• piston
• Piston ring
• Cylinder liner combination

The piston is a hollow cylinder that slides inside the cylinder. The outer diameter of the piston is approximately equal to the inner diameter of the cylinder. The function is to change the volume enclosed by the cylinder or the pressure exerted by the fluid in the cylinder. The piston comes into contact with the burning high-pressure gas, withstands the impact pressure at the time of the explosion of the gas mixture, and reciprocates in the cylinder at a very high speed with rapid relative motion and friction with the cylinder wall.