The main role of diesel generator set valve set is used to control the intake and exhaust tract and cylinder access, open should be smooth, after closing should ensure sealing. Valve set is composed of valve, valve seat, valve guide, valve spring, spring tray and locking plate and other parts.
Valve working conditions
When the diesel generator set work, the valve top directly in contact with the combustion gas, will be subject to high temperature and high pressure. In the work, the exhaust valve to be subject to the impact of high-speed hot exhaust gas, the temperature can reach 800 ° C -900 ° C, easy to make the working surface ablation. Intake valve to be subject to the role of alternating hot and cold gas, will make the valve warp deformation, damage or reduce the valve seal, the temperature in 300 ° C-400 ° C. In order to make the valve to adapt to the above working conditions, in high temperature can wear-resistant, corrosion-resistant, to maintain the mechanical properties of the valve and valve seal, the valve is usually made of high-quality alloy steel.
Valve stem structure is relatively simple, but the valve stem and valve top must be concentric and vertical, the end of the valve stem (valve foot) is often hit (because the valve foot and tappet clearance). Therefore, the valve foot has to undergo surface heat treatment to improve the hardness.
Valve seat is the valve seat that fits with the valve. In the medium and small diesel generator set, if the cylinder block, cylinder head for cast iron manufacturing.
Then the valve seat can be directly bored out on the steam surface cover or cylinder block. Valve seat is also subject to high temperature, and continuous impact by the valve, requiring it to have sufficient strength and wear resistance, in order to facilitate the maintenance of the valve seat, in some diesel generator sets use the valve seat inserted. This valve seat is mostly made of chrome steel or special cast iron, and then inserted by cold pressing method.
Typical valve construction usually consists of valve stem end or rocker contact area, valve spring seat locking groove, valve stem, valve head, rounded corner (neck), tapered surface, valve thickness, etc. The head of the valve is the part inside the combustion chamber, which must be able to withstand extremely high temperatures, ranging from 1300°F to 1500°F. It has many shapes, such as oval head, flat head, concave head, flared head, etc., the more metal in the head of the valve, the greater the valve stiffness, stiffness of the valve life is long, but the seal is not good. Valve taper refers to the part of the cylinder head in contact with and play a sealing role.
The rounded corner is the curved part between the valve stem and the inside of the valve cone, the rounded corner increases the strength of the valve. The role of the valve rod is to support the valve in the cylinder head, and the role of the valve spring seat locking groove is to keep the valve spring attached to the valve during engine operation.
Valve material
The valves are made of a very strong metal containing nickel, chromium and small amounts of manganese and other materials. This metal must be able to conduct heat quickly. If the heat is not conducted quickly enough, the valve will be burned. Some exhaust valves are also filled with sodium metal inside the valve stem. The sodium metal becomes liquid at the engine’s operating temperature, and the liquid sodium allows for faster heat transfer from the valve stem to the valve guides.
