Gas Ring of Piston Ring in Diesel Generator Set Part 1

Piston rings are elastic metal open circular rings, which can be divided into two types according to their functions: gas rings and oil rings. The 2-4 air rings are installed at the upper end of the piston head, and the 1-2 oil rings are installed at the lower end.

The function of the gas ring is to ensure the sealing between the piston and the cylinder wall, preventing high-pressure gas from leaking into the crankcase from the upper part of the piston. When the seal is poor, more gas leaks out during the compression stroke, causing a decrease in the pressure at the end of compression and making it difficult to start the internal combustion engine. High temperature gas leakage into the crankcase can also increase the temperature of the piston, causing the oil to oxidize and deteriorate due to heating. In addition to its sealing function, the gas ring also plays a role in heat transfer. The heat absorbed by the top of the piston is mostly transmitted to the cylinder wall through the gas ring (as the piston head does not touch the cylinder wall), and then carried away by the external cooling medium.

The gas ring, especially the first gas ring, is not only subjected to high-speed reciprocating linear motion along the cylinder wall with the piston, but also affected by factors such as high temperature and high pressure gas pressure, poor lubrication conditions, etc., which reduces the mechanical properties and elasticity of the gas ring, and may cause carbonization of the lubricating oil, and even lead to cylinder pulling and leakage. Therefore, it is required that the gas ring has sufficient elasticity to make the ring tightly adhere to the cylinder wall around it, so that high-pressure gas cannot leak out through the contact surface between the gas ring and the cylinder wall. The gas acting on the upper end face of the ring presses the ring tightly into the piston ring groove, causing the lower end face to closely adhere to the ring groove. The gas entering between the inner surface of the ring and the ring groove has an outward pressure, making the ring more tightly adhere to the cylinder wall. Therefore, by utilizing the elasticity of the gas ring itself and the pressure of the gas, the leakage of high-pressure gas can be prevented.

Piston rings are usually made of high-quality gray cast iron or alloy cast iron. In order to improve the working performance and wear resistance of the first gas ring, a porous chromium or molybdenum layer is often plated on the surface of the first gas ring. In recent years, the first gas ring has also been made of ductile iron or steel. In the free state, the outer diameter of the ring is slightly larger than the cylinder diameter. After being installed in the cylinder, the piston ring generates elastic force and presses against the cylinder wall. A certain gap (called end gap or opening gap, the opening gap of the internal combustion engine piston ring is usually 0.4-0.8mm) should be retained at the opening to prevent the piston ring from getting stuck in the cylinder when it expands due to heat. After the piston ring is installed in the ring groove, there should also be a certain clearance in the height direction (called side clearance, which is usually 0.08-0.16mm for internal combustion engine piston rings). When the piston ring is installed on the piston, the openings of each ring should be staggered by 120 ° to 180 ° according to regulations, and the opening of the piston ring should be staggered by more than 45 ° from the piston pin seat hole to prevent air leakage after the piston ring is installed in the cylinder.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.