The cylinder head of the diesel engine is installed on the upper part of the cylinder block and is fastened to the cylinder block with the cylinder head bolts according to the specified torque. Its function is to close the upper plane of the cylinder and form a combustion chamber with the cylinder and the top of the piston. It is often in contact with high temperature and high-pressure gas, so it bears a large thermal load and mechanical load. A cooling water jacket is made inside the cylinder head of the water-cooled engine, and the cooling water hole on the lower end face of the cylinder head communicates with the cooling water hole of the cylinder block. Use circulating water to cool high-temperature parts such as the combustion chamber.
The cylinder head is also equipped with intake and exhaust valve seats, valve guide holes for installing intake and exhaust valves, as well as intake and exhaust passages. The cylinder head of a gasoline engine is machined with holes for installing spark plugs, while the cylinder head of a diesel engine is machined with holes for installing fuel injectors. The cylinder head of the overhead camshaft engine is also machined with a camshaft bearing hole for installing the camshaft.
The cylinder head is an integral part of the combustion chamber. The shape of the combustion chamber has a great influence on the operation of the engine. Due to the different combustion methods of gasoline engines and diesel engines, the parts of the cylinder head that make up the combustion chamber are quite different. The combustion chamber of a gasoline engine is mainly located on the cylinder head, while the combustion chamber of a diesel engine is mainly located in the pit on the top of the piston.
Three Common Types of Cylinder Head Structures:
- Single-cylinder type, each cylinder has a separate cylinder head
- Double cylinder type, each two cylinders share a cylinder head, like the cylinder head for Yanmar 3tnv70 in the picture below
- Multi-cylinder type (integral type), each row of cylinders shares a cylinder head
The thermal load of the diesel engine cylinder head is very serious. It is equipped with parts such as intake and exhaust valves, valve rocker arms, and injectors, and the cylinder head is equipped with intake and exhaust passages and oil passages. Especially in the cylinder head of the air-cooled diesel engine, it is difficult to arrange the heat sink. If the cooling effect of the fuel injector is not good and the temperature is too high, the needle valve of the fuel injector is easy to be seized or other failures occur. Due to the serious heating of the exhaust valve, such poor cooling will increase wear and reduce its service life. Therefore, it is necessary to ensure a sufficient cooling effect for some important components.
Common materials for cylinder heads are high-strength gray cast iron HT20-40 and HT25-47. Alloy cast iron or ductile iron is used for large or fortified diesel engines. Aluminum alloy cast iron cylinder heads are commonly used in air-cooled diesel engines or special-purpose diesel engines.
In order to ensure the sealing between the cylinder block and the cylinder head, a cylinder gasket needs to be installed between them. The cylinder head gasket requires high-temperature resistance, corrosion resistance, and certain elasticity. Commonly used cylinder heads are metal-asbestos cylinder heads. The size of the outer gallery of this cylinder head gasket is the same as that of the underside of the cylinder head, and in the free state, the thickness is about 3 mm. It is about 1.5-2mm after pressing. The inside of the cylinder head gasket is asbestos fiber, and the outside is copper or steel.
The above is the structure of the diesel engine cylinder head introduced by Landtopmall. We Landtopmall is a professional engine supplier, with a complete supply chain, advanced production technology, perfect quality management system, and considerate after-sales service, we can provide users with one-stop service at any time. For more engine accessories, please subscribe to our Landtopmall.