The role and working conditions of piston of Marine diesel engine fittings

Piston in short

Piston is one of the main moving parts of diesel engine, and is a component of combustion chamber. The piston of diesel engine can be divided into two categories: crosshead type diesel engine piston and barrel type diesel engine piston. The former is composed of a piston head, a piston skirt, a piston ring, a piston rod and a piston cooler, and the latter is composed of a piston body, a piston ring and a piston pin.

Piston action

The piston is not only a component part of the combustion chamber, but also with the connecting rod, crankshaft and other components to form a motion machine. The main function of the piston is to complete the compression and expansion process under the condition of ensuring the seal, and to transfer the air force to the crankshaft through the connecting rod. In a cylindrical piston diesel engine, the piston acts as a sliding block under side thrust. In the two-stroke diesel engine, the air port is also opened and closed to control the air exchange.

Piston operating conditions

In diesel engine operation, piston is subjected to high temperature, high pressure, ablation and corrosion of gas. Its thermal load and mechanical load are very high, and the mechanical properties of the piston material are reduced at high temperatures, so the piston is prone to cracks and deformation during work. Friction and impact occur between piston and cylinder in relative motion. In the cylinder, the piston cannot establish hydrodynamic lubrication between it and the cylinder due to high temperature, gas erosion, reciprocating motion, etc., so the friction loss is large and the wear is serious. In medium and high speed diesel engines, the piston has a large reciprocating inertia force, which makes the vibration of the diesel engine intensified.