The Four Components of a Diesel Engine Piston Part 1

When we talk about pistons, they will be lifted up to the piston connecting rod assembly. The piston connecting rod assembly consists of a piston assembly (piston, piston ring, piston pin) and a connecting rod assembly (connecting rod small head, connecting rod body, connecting rod large head, connecting rod bearing). Dingbo Electric will share with you the structure of the piston assembly. For more professional information on diesel generator sets, please follow the Dingbo Electric Power website. Today, we will mainly introduce in detail the structure of the pistons in the piston group.

The function of the piston is to withstand the pressure of the gas and transmit the force to the crankshaft through the connecting rod. The working conditions of the piston are extremely harsh. It constantly undergoes high-speed reciprocating linear motion under the action of high temperature and high pressure gas. Due to the periodic changes in gas pressure and reciprocating inertia force, the piston bears a large mechanical and thermal load. In addition, uneven temperature distribution can cause thermal stress. Therefore, it is required that the piston must have a relatively light weight and sufficient stiffness and rigidity. The piston works under high temperature, high pressure, and high speed conditions, and its lubrication conditions are poor, resulting in severe friction between the piston and the cylinder wall. To reduce wear, the surface of the piston must be wear-resistant.

The pistons of high-speed diesel engines are usually made of cast aluminum alloy. With the continuous strengthening of diesel engines, the use of forged aluminum alloy or eutectic aluminum silicon alloy pistons is increasing. However, high turbocharged internal engines often use cast iron pistons to improve their strength and reduce their thermal expansion coefficient. The basic structure of the piston can be divided into four parts: top, ring groove (leak proof part or head), piston pin seat, and skirt.

1. Top

The top is a part of the combustion chamber, and its structural shape is related to the type of engine and combustion chamber. There are several different structural shapes of the piston top. Most small internal combustion engines use flat top pistons, which have the advantages of simple manufacturing and small heating area. Most internal combustion engines have complex shapes on the top of the piston due to the formation of specially shaped combustion chambers, which are generally made with various pits. The pit is designed to improve the combustion condition of the engine, making the formation of combustible mixture more favorable and the combustion process more complete. Some internal combustion engines also have shallow valve collision avoidance pits on the top to avoid collision between the valves and the piston crown.

The high thermal load on the pistons of internal combustion engines (especially direct injection engines) often causes thermal fatigue and cracking of the pistons. Therefore, some internal combustion engines can spray oil from the fuel injection holes on the connecting rod tip to cool the inner wall of the piston crown. Some internal combustion engines are equipped with specialized fuel injection mechanisms in the body, which can also serve the same purpose. The top of the piston is generally thicker due to the gas pressure it bears; Some piston tops also have reinforcing ribs inside.

We will continue to introduce the relevant content in the next article, If you would like to get more information welcome to contact us via sales@dieselgeneratortech.com.