Failure analysis of diesel engine caused by improp

2022-08-14
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Analysis of diesel engine faults caused by improper operation

diesel engine faults caused by improper operation account for a large proportion of diesel engine faults, which are mainly manifested in the following aspects:

1) the throttle slamming after the cold start of the diesel engine. Some drivers always blow the accelerator after cold starting the diesel engine, which is a bad problem. Because the lubricating oil on each friction surface has been lost after the diesel engine has been parked for a period of time, and the lubricating oil cannot flow smoothly to each lubrication part due to low temperature, high oil viscosity and poor fluidity when the cold engine is started. With the increase of the speed of the diesel engine, although the oil supply volume and pressure of the engine oil pump will also increase, it always lags behind the needs of friction surface lubrication, resulting in the lack of oil on the friction surface at the moment of starting. If the throttle is slammed, the speed of the diesel engine will rise sharply, and some friction surfaces will produce dry friction, causing severe wear. In addition, the force on the piston, connecting rod and crankshaft changes greatly when the throttle is blown, causing severe impact and easy to damage the parts. Therefore, it is strictly forbidden to blow the throttle after the diesel engine is started

2) operate with load without warming up after cold start. When the diesel engine is cold started, due to low temperature, high oil viscosity and poor fluidity, the oil pump is insufficient in oil supply, resulting in lack of oil on the friction surface and no lubrication, resulting in rapid wear, and even cylinder pulling, Bush burning and other faults. Therefore, after the diesel engine is cold started, it should be idled and heated up, and then run with load when the oil temperature reaches more than 40 ℃; When starting the vehicle, shift to low gear and drive for a certain mileage in each gear in sequence until the oil temperature is normal and the oil supply is sufficient

3) the diesel engine stops suddenly with load or immediately after suddenly unloading the load. After the diesel engine stalls, the cooling system water circulation stops, and the heat dissipation capacity decreases sharply. 6. The temperature rise and fall method causes the cooling water to boil and produce blisters, and the heated parts lose cooling, which is easy to cause overheating of cylinder head, cylinder liner, cylinder block and other parts, resulting in cracks, or excessive expansion of the piston and seizure in the cylinder liner. On the other hand, the diesel engine was not cooled by idling when it stopped. Due to insufficient oil retention on the friction surface, the diesel engine was aggravated by poor lubrication when it was restarted. Therefore, before the diesel engine stalls, the load should be removed, and the speed should be gradually reduced. The engine can be stopped only after the engine oil temperature drops below 40 ℃

4) don't worry about using insufficient engine oil. These points must be done when the diesel engine runs. At this time, due to insufficient oil supply, the oil supply on the surface of each friction pair will be insufficient, making the lubrication worse, resulting in abnormal wear or burns. Therefore, before starting the vehicle and during the operation of the diesel engine, pay attention to observe the oil level of the engine oil to prevent cylinder pulling and Bush burning faults caused by lack of oil

5) when the cooling water volume of diesel engine is insufficient or the temperature of cooling water and oil is too high, a - constant rotation. Insufficient cooling water of the diesel engine affects the cooling effect, and the diesel engine cannot be cooled properly, resulting in overheating of the diesel engine. If the temperature of cooling water and oil is too high, the diesel engine will overheat. At this time, the heat load of main heating parts such as cylinder head, cylinder liner, piston assembly and valve is large, and its mechanical properties, such as strength and toughness, decline sharply, which increases the deformation of parts, destroys the cooperation gap between parts, and accelerates the wear of parts. In serious cases, it will also produce cracks, or the failure of mechanical parts stuck due to thermal expansion, such as the seizure of pistons, piston rings and cylinder liners and the seizure of valves. The high temperature of cooling water and engine oil will accelerate the aging, deterioration and burning of engine oil, and the viscosity of engine oil will decrease, making it difficult for the oil film on the friction surface to form and maintain. Sometimes, it oxidizes and gels, and even loses its lubrication effect, thus deteriorating the lubrication conditions of cylinder liners, pistons and main friction pairs, resulting in abnormal wear, cylinder pulling, Bush burning, shaft holding and other faults. Overheating of the diesel engine will also worsen the combustion process of the diesel engine, resulting in abnormal operation of the fuel injector, poor atomization, increased carbon deposition, and serious "burning" and "sticking" phenomena. Therefore, before starting the diesel engine, pay attention to check the cooling water surface to prevent the diesel engine from overheating due to water shortage; Pay attention to the temperature of cooling water and engine oil during driving. If the temperature of cooling water and engine oil is too high (greater than 95 ℃), take measures in time to avoid greater accidents

6) the diesel engine operates when the temperature of cooling water and oil is too low. During the operation of the diesel engine, the temperature of the cooling water is too low, and the temperature of the cylinder wall decreases accordingly. The water vapor generated by combustion condenses into droplets, which contact with the exhaust gas to form acidic substances, which are attached to the cylinder wall, and loose substances are produced by corrosion and wear. The lower the temperature is, the easier the acidic substances are generated, and the greater the corrosion is. Practice has proved that when the diesel engine is often used at the cooling water temperature of ℃, the wear of its parts is several times greater than that at the normal operating temperature (℃). When the water temperature is too low, the temperature in the cylinder is low, and the ignition delay period of the diesel engine is prolonged. Once it is on fire, the pressure rises rapidly, the diesel engine burns violently, and the moving parts such as pistons and connecting rods are subjected to strong impact loads, which is easy to cause mechanical damage to parts and components. The diesel engine operates under the condition of low temperature cooling water for a long time, and the gap between the piston and the cylinder liner is large, which is prone to cylinder knocking and vibration, causing cavitation damage to the cylinder liner. According to experience, the cavitation damage is the most serious when the cooling water temperature of the diesel engine is lower than 50 ℃ for a long time. The oil temperature is too low, the viscosity of the oil is high and the fluidity is poor, and the oil quantity of the lubricating parts is insufficient, which makes the lubrication worse, causes the wear of the friction pair to increase, and shortens the service life of the diesel engine. Therefore, frequent cold start or low-temperature operation should be avoided as far as possible to maintain the normal working temperature of the diesel engine

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