The effect of lubricating oil
Lubricating oil can be divided into animal oil, vegetable oil, petroleum lubricating oil and synthetic lubricating oil according to the source. Among them, the amount of petroleum lubricating oil accounts for more than 90% of the total amount, so the lubricating oil often refers to petroleum lubricating oil. It is mainly used to reduce the friction between the surface of moving parts, and at the same time it has the functions of cooling, sealing, anti-corrosion, anti-rust, insulation, power transmission and cleaning impurities. The raw material is mainly derived from a lubricating oil fraction and a residue fraction from a crude oil distillation unit. The most important properties of lubricating oils are viscosity, oxidation stability and lubricity, which are closely related to the composition of the lubricating oil fraction. Viscosity is an important quality indicator that reflects the fluidity of a lubricant. Different conditions of use have different viscosity requirements. Heavy-duty and low-speed machines use high-viscosity lubricants. Oxidation stability indicates the antioxidant capacity of the oil in the environment of use due to temperature, oxygen in the air, and metal catalysis. After the oil is oxidized, a fine carbonaceous substance mainly composed of asphaltenes is formed according to the use conditions, and is a viscous lacquer-like substance or a paint film, or a viscous aqueous substance, thereby reducing or losing the use property. Lubricity means the wear reduction performance of the lubricating oil. The concept of a lubricant additive is one or more compounds added to the lubricant to give the lubricant some new properties or to improve some of the properties already present in the lubricant. The additives are mainly composed of antioxidant and metal reducing agent, extreme pressure antiwear agent, friction ameliorative agent (also known as oil agent), detergent dispersant, foam inhibitor, antirust agent, antiseptic, flow point improvement agent, viscosity index enhancer, antiemulsive agent and so on. The additives sold in the market are generally composites of the above single additives, the difference being that the composition of the single additive is different and the ratio of several single additives inside the composite additive is different.
The main effect of lubricating oil
When the engine is running, if some of the friction parts are not properly lubricated, dry friction will occur. It has been proved that the heat generated by dry friction in a short time can cause the metal to melt, and cause damage or even death of the machine parts (many leaking or oil leaking vehicles have the failure of the cylinder, the shaft and so on. The main reason is that). Therefore, it is necessary to give good lubrication to the friction parts in the engine. When the lubricating oil flows to the friction part, it will adhere to the friction surface to form an oil film, which reduces the resistance between the friction parts, and the strength and toughness of the oil film is the key to exert its lubricating effect. However, it can not be used too much, because the resistance of squared relation will be great when the volume is too large, so it has great influence on the speed, so we should pay special attention to the dosage.
Only a small part of the heat generated by the combustion of the fuel in the engine is used for the power output and the frictional resistance consumption and the drive of the auxiliary mechanism; the rest of the heat is discharged into the atmosphere by the exhaust gas, and is also used by the cooling medium belt in the engine. Take a part. Excess heat in the engine must be exhausted from the body, otherwise the engine will burn out due to excessive temperature. This aspect is accomplished by the engine cooling system. On the other hand, the lubricating oil absorbs heat from the surfaces of the cylinder, the piston, the crankshaft and the like and is then taken to the oil sump for dissipation.
When the engine is working, it will produce a lot of dirt. Such as inhalation of sand, dust, air formed by the combustion of the mixture, the formation of a gel after the oxidation of the lubricating oil, friction between the parts to produce metal chips and so on. The dirt will be attached to the friction surface of the machine. If it is not cleaned, it will increase the wear and tear of the machine parts. In addition, a large number of gum will make the piston ring stuck, leading to engine failure. Therefore, these contaminants must be cleaned up in time. This cleaning process is completed by the circulation of lubricating oil in the body.
There is a certain gap between the cylinder and the piston of the engine, the piston ring and the ring groove, and between the valve and the valve seat, so that the movement pairs are not stuck. However, these gaps can cause poor cylinder seals, and the result of combustion chamber leakage is to reduce cylinder pressure and engine output. The oil film formed by these lubricants in these gaps ensures the tightness of the cylinder, maintains cylinder pressure and engine output, and prevents exhaust gas from falling down into the crankcase.
When the engine is running or storing, the moisture in the atmosphere, lubricating oil, fuel oil and the acid gas generated by the combustion will cause corrosion and rust on the machine parts, thus increasing the damage of the friction surface. The oil film formed on the surface of the lubricating oil can avoid direct contact between the machine and water and acid gas to prevent corrosion and rust.
Eliminate impact load
At the end of the compression stroke, the mixture begins to burn and the cylinder pressure rises sharply. At this time, the lubricating oil in the bearing clearance will alleviate the impact load on the piston, piston pin, connecting rod, crankshaft and other parts, so that the engine can work smoothly and prevent direct metal contact and reduce wear.