The piston is a reciprocating part in the cylinder block of an automobile engine. The basic structure of the piston can be divided into top, head and skirt. The top of the piston is the main part of the combustion chamber, and its shape is related to the selected combustion chamber form. Gasoline engines mostly use flat-top pistons, which have the advantage of small heat absorption area. There are often various pits on the top of diesel engine pistons, and their specific shape, location and size must be adapted to the requirements of diesel engine mixture formation and combustion.