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Exhaust gas turbocharger is a very precise device, widely used in engineering machinery, generators and other power equipment, on the basis of not changing the basic structure of the diesel engine, turbocharger can increase power by 30% or more, so that fuel The fuel consumption is reduced by about 5% and it has received very good economic benefits. However, the supercharger is often installed and used improperly during its use, and it cannot achieve the expected results. Based on the structural principle of the supercharger, the turbocharger is analyzed for common failures.
The supercharger utilizes the exhaust gas discharged from the exhaust pipe to push the turbine to rotate at a high speed. At the same time, the rotor shaft drives the compressor wheel to rotate at a high speed. The speed of the supercharger can be as high as 50,000 to 230,000 r/min, and the high-speed rotating compressor wheel will increase the air intake. Pressure, so that the air density into the cylinder greatly increased, increasing the diesel engine power.
1 Turbocharger common fault
1.1 poor pressure booster
Mainly in the decline in power, black smoke, poor fuel economy.
1.2 Turbocharger leaks at one or both ends
This is a relatively common failure, and it is also the main reason that affects the service life of the supercharger.
1.3 The service life of the supercharger is too different from the ideal value
Put on a supercharger, and soon there are failures such as floating bearing damage, oil leakage at both ends, and power drop.
2 cause of failure
2.1 Poor pressure effect
(1) The air cleaner is too dirty to provide high-density clean air to the engine.
(2) The impeller is damaged, causing insufficient air intake.
(3) There is too much dust in the air intake, there is sludge at the joint between the impeller and the supercharger shell, which affects the speed of the turbocharger impeller, resulting in insufficient air intake.
2.2 Turbocharger leaks at one or both ends
The supercharger rotates at a very high speed, and its floating bearing is lubricated by the lubrication oil from the oil pan. When the oil that enters the bearing clearance at normal pressure passes through the bearing face, the oil pressure becomes zero and flows back to the oil pan by its own gravity, and does not flow out from both ends of the booster. In normal operation, there is a certain pressure between the two impellers of the supercharger, and the oil does not flow from the low-pressure bearing region to the high-pressure region at both ends. In addition, there is a seal ring between the two impellers and the floating bearings. Oil leakage can occur. However, oil may leak from both ends of the supercharger under the following conditions:
(1) Floating bearing wear. Failure of long-term oil change or air filter failure causes too much dust to enter the supercharger, causing severe wear of the floating bearing, resulting in excessive bearing clearance and unstable oil film. Under the high speed of the supercharger, supercharging will soon occur. The unbalance of the device causes the vibration of the rotor shaft system to increase, destroying the seal at both ends and causing leakage of the lubricant.
(2) The air cleaner is dirty or clogged. When the air filter is too bad due to excessive dust or other reasons, it will cause the compressor intake negative pressure is too high, so that the internal pressure of the compressor is higher than the external pressure, the oil under the pressure difference from the intake pipe Outflow at one end.
(3) Poor oil return. When the oil flows out of the supercharger floating bearing, it flows back to the oil pan by its own gravity. When the oil return pipeline is deformed or blocked, or when pressure in the return pipeline is caused by high exhaust gas pressure in the crankcase, the oil flowing out of the floating bearing will not flow back to the oil pan very quickly, but two axially along the rotor shaft. Outflow of the seal ring at the end causes oil leakage.
(4) If the engine runs idle for a long time, it will also cause the turbocharger to leak oil. When the engine runs idle for a long time, a negative pressure is generated behind the turbocharger turbine and the compressor impeller, which causes the oil flowing out of the floating bearing to leak out under the influence of the pressure difference.
3 Reduced service life of turbocharger
3.1 Incorrect Installation
According to the requirements, the supercharger should be filled with oil before the floating bearing is installed to prevent the oil from being supplied to the floating bearing in time when the engine is started, resulting in dry grinding and damaging the floating bearing.
3.2 Incorrect Startup
After the supercharged engine starts, it must idle for a few minutes to ensure that the supercharger can run at high speed after the oil reaches the floating bearing.
3.3 Incorrect shutdown
Before stopping the machine, idle for a few minutes to make the supercharger rotor gradually decelerate and cool down. When the engine suddenly stops, the oil supply stops, and the rotor rotates at a high speed under inertia. At this time, the floating bearing will wear due to high temperature and lack of oil, and even cause ablation.
3.4 Incorrect oil selection
The engine with a supercharger greatly increases the thermal load and mechanical load, and requires a good viscosity-temperature characteristic, oxidation resistance, and wear resistance of the lubricating oil. Therefore, a good quality oil must be used.
For the above faults, when installing or using a supercharger, it should be operated in strict accordance with the requirements of the user's manual; regular inspection, cleaning the air filter to ensure smooth flow of intake air; regularly remove the sludge on the compressor wheel, and check the compressor wheel at the same time Fix the screws and the use of blades to prevent the impeller from escaping and causing major accidents. Use the oil that meets the standards of use from the regular manufacturers and operate the engine's start and stop according to the operating rules to prevent the engine from idling for a long time.
In short, as long as the supercharger is used strictly in accordance with the operating instructions and operating procedures, some failures can be avoided, allowing the supercharger to function to its maximum extent and prolong its service life.