The common failure forms of diesel generator engine parts include wear.deformation, fatigue fracture and corrosion. The damage of the genset refers to the phenomenon that the material gradually loses from one surface to the other when the object is in contact with each other and moves relative to each other, resulting in the operation of the surface. Generally,damage is divided into four categories according to its surface failure mechanism and characteristic, including abrasive fatigue damage and corrosion damage.
The loss of surface material caused by friction between object surface and abrasive is called abrasive damage. Abrasive damage is a kind of mechanical damage, which is very common and harmful. According to statistics, abrasive wear accounts for more than 50% of the total wear. When diesel generator set is supplying power in the field, because of the bad working conditions, it often has direct contact with mud sand, ore and ash, which abrasive wear.
Abrasive wear is the result of mechanical action of abrasive particles, which is related to the relative hardness, shape, size and mechanical properties of abrasive surface under load. Abrasive materials come from outside dust, chip invasion, fluid brought in, surface wear products, surface hard spots and inclusions of material structure, etc. Abrasive wear consists of two cases. The first case is the wear of rough metal surfaces on relatively soft metal surfaces. The second case is the wear caused by free hard abrasive on the surface of hard metal against soft metal such as bearing and cylinder wear. Generally, measures are taken to reduce abrasive wear from two aspects. One is to prevent or reduce the abrasive particles into the friction surface; the other is to enhance the wear resistance of the parts.
When the friction surface is running relatively, a large amount of heat will be produced locally by friction, which leads to a sharp rise in temperature and the melting of the surface metal. As the heat continues to pass around, the temperature on the surface of the part will gradually drop, resulting in joint welding, which is torn apart in subsequent motion. The phenomenon that leads to the transfer of materials from one surface to another is called adhesion wear, such as clasp, cylinder, etc.
When two contact surfaces are rolling or sliding, the fatigue of the surface of the material will be caused by the effect of cylinder contact stress. With the crack propagation, and because of the high pressure of lubricating oil in the crack, the phenomenon of spot wear is produced, which is called surface fatigue wear. Such as bearing surface wear, gear surface wear.
During friction, metals react chemically or electrochemically with surrounding media. Due to the joint action of corrosion and wear, the loss of surface matter of parts is called corrosion wear. Corrosion wear is a kind of mechanochemical wear. The pure abrasion phenomenon can not be defined as corrosion wear. It can be formed only when the corrosion phenomenon is combined with the mechanical wear process. The mechanism of corrosion wear is different from that of the above three kinds of wear. It is a very complicated wear process, which often occurs in high temperature or wet environment, and is more likely to occur in special medium conditions such as acid, alkali, salt and so on.
Because of the nature of the medium, the action state of the medium on the friction surface and the different properties of the friction material, the appearance of the friction surface is also different. Therefore, corrosion wear is often divided into oxidation wear, special medium corrosion wear and fretting corrosion wear.
The process of diesel generator set is also a wear process of its own parts. How to use diesel generator set reasonably and correctly is the first condition to reduce wear, and it is also a method to prolong the service life of diesel generator set.
It is normal phenomenon that the generator set will wear out after a period of use. However, if there is unreasonable excessive wear and tear, such as situation is abnormal. It may be due to improper use of the user or to some malfunction of the machine. Therefore, users should know what causes diesel generator set show sign of wear and tear to avoid excessive wear.
The wear and tear of diesel generators such as Cummins generator, Richardo generator and Yuchai generator are generally affected by the quality of fuel and lubricating oil, the running speed and load of diesel engine, the environmental conditions and operating conditions.
The quality of fuel and lubrication oil should be adapted to the structure of the diesel engine. If the diesel oil contains sulfur or other impurities, it will produce acids and other corrosive substances during combustion, thus accelerating the wear and tear of the cylinder. If there is too much heavy fraction in diesel oil, it is easy to form carbon deposit after combustion, which causes abrasive wear between piston ring and cylinder. The viscosity of oil affects the formation of gas mixture and the reliability of oil supply equipment. For lubricating oil, viscosity and oxidation resistance are the most important factors, which should be reasonably used according to the working conditions of diesel engine, and must not be used randomly.
The test results show that the friction of diesel engine increase with the increase of speed and load. As the load increases, the genset pressure on the friction surface increases and the thermal condition is bad. With the increase of rotational speed, the number of friction times per genset is half plus, and at the same power, the increase of rotational speed is larger than the wear when load is increased. However, too low rotational speed can not guarantee good liquid lubrication conditions, also increase wear. In addition, when the diesel engine often works unsteadily, such as acceleration, deceleration, stopping and starting, the lubricating condition of diesel engine is poor, the thermal state is unstable, and the wear increases due to the frequent changes of speed and load. Especially when starting, the speed of crankshaft is low, the oil supply of engine oil pump is not timely, the oil temperature is low, the oil viscosity is large, the friction surface is difficult to establish liquid lubrication, and the wear is very serious. Ambient temperature also affect the wear and tear of diesel generator set. When the temperature is high, the engine is easy to overheat, the viscosity of lubricating oil is low, and the wear of parts increase. When the temperature is low, the viscosity of lubricating oil increases, the diesel engine starts difficult, the cooling water can not keep the normal temperature while working, and the wear and corrosion of parts are increased. When the diesel engine starts at low temperature, the wear is more serious.
The working temperature of generator set is one of the important factors affecting wear and tear. In the process of use, due to the limitation of cooling system structure, the change of working load and speed, and the change of ambient temperature of diesel engine is very large. The practice shows that the temperature of cooling water is controlled at 75-85 ℃, and the temperature of lubricating oil is at 75-95 ℃.
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