Exhaust gas turbocharger (hereinafter referred to as turbocharger) is a very precise device, widely used in construction machinery, generating sets and other power equipment, without changing the basic structure of the diesel engine, the turbocharger can increase power by 30% or more, so that fuel consumption can be reduced by about 5%, and receive good economic benefits. However, due to improper installation and use, the supercharger often fails to achieve the desired effect. Based on the structure and principle of the supercharger, this paper analyzes the common faults of the supercharger.

The turbocharger uses the exhaust gas from the exhaust pipe to drive the turbine to rotate at high speed. At the same time, the rotor shaft drives the compressor impeller to rotate at high speed. The speed of the turbocharger can be as high as 50000~230000r/min. The compressor impeller which rotates at high speed will pressurize the air sucked into the cylinder, so that the air density into the cylinder is greatly increased and the power of the diesel engine is increased.

1 common faults of supercharger

1.1 supercharging effect is poor.

Mainly in the dynamic decline, black smoke, poor fuel economy.

1.2 oil leakage at one end or two sides of the supercharger.

This is a common failure, and it is also the main reason that affects the service life of turbocharger.

1.3 supercharger life expectancy is far from ideal value.

When a turbocharger is replaced, the floating bearing is damaged, oil leakage at both ends, and power down.

2 cause of failure

2.1 supercharging effect is poor.

(1) the air filter is too dirty to provide high density clean air to the engine.

(2) impeller failure causes insufficient air intake.

(3) There is too much dust in the inlet, and there is mud in the joint between the impeller and the supercharger shell, which affects the speed of the supercharger impeller, resulting in insufficient air intake.

2.2 oil leakage at one end or two sides of the supercharger.

The turbocharger has a high speed, and the lubrication of its floating bearing is lubricated by lubricating oil from the oil pan. When the oil with normal pressure enters the bearing clearance passes through the bearing working face, the oil pressure becomes zero and flows back to the oil pan by its own gravity, and it will not flow out from both ends of the supercharger. And in normal operation, there is a certain pressure between the two impellers of the supercharger, the oil will not flow from the low-pressure bearing area to the two ends of the high-pressure area, and there are sealing rings between the two impellers and floating bearings, the general situation will not occur oil leakage. However, under the following circumstances, oil may leak out from both ends of the turbocharger.

(1) wear of floating bearing. Long-term failure to replace oil or air filter causes too much dust into the supercharger, serious wear and tear of floating bearings, resulting in excessive bearing clearance, oil film instability, in the supercharger at high speed, the supercharger will soon appear unbalanced, resulting in increased vibration of the rotor shafting, damage to both ends of the seal, resulting in oil leakage Leakage.

(2) air filters are too dirty or blocked. When the air filter due to excessive dust or other reasons for poor air supply, will lead to compressor inlet negative pressure is too high, so that the compressor pressure at one end of the internal pressure is higher than the external pressure, the oil under the pressure difference from the inlet pipe at one end.

(3) oil return is not smooth. When the oil flows out of the supercharger floating bearing, it flows back to the oil pan on its own gravity. When the return pipeline is deformed or blocked, or when there is pressure in the return pipeline due to excessive exhaust gas pressure in the crankcase, the oil flowing out of the floating bearing will not flow back to the oil pan very smoothly, but will flow out of the sealing ring along the axial ends of the rotor, causing oil leakage.

(4) engine idle for a long time will also cause turbocharger oil leakage. When the engine is idling for a long time, negative pressure will be generated behind the turbocharger turbine and compressor impeller, resulting in oil leakage from the floating bearing under the action of pressure difference.

3 shortening service life of turbocharger

3.1 incorrect installation.

According to the requirements, when the supercharger is installed, the floating bearing should be first filled with oil to avoid the engine starting oil can not be supplied to the floating bearing in time, resulting in dry grinding and damage to the floating bearing.

3.2 incorrect startup.

The supercharged engine must idle for several minutes after starting to ensure that the oil reaches the floating bearing before the supercharger can run at high speed.

3.3 shutdown is incorrect.

It should be idle for several minutes before shutting down, so that the rotor of the turbocharger will gradually slow down and cool down. When the engine stops suddenly, the oil supply stops, and the rotor rotates at a high speed under inertia, which will cause the floating bearings to wear out or even ablate due to high temperature and lack of oil.

3.4 incorrect oil selection.

The thermal and mechanical loads of an engine equipped with a supercharger are greatly increased, requiring good viscosity-temperature characteristics, oxidation resistance and wear resistance of the lubricating oil, so it is necessary to select good quality oil.

In view of the above faults, when installing and using the turbocharger, it should strictly follow the instructions for correct operation; regularly check and clean the air filter to ensure smooth air intake; regularly remove the oil sludge on the compressor impeller, while checking the use of compressor impeller fixed screws and blades to prevent impeller shedding caused by Major accidents; use the regular manufacturer's standard oil, according to the operating rules to operate the engine start and stop, to avoid long idle engine operation.

In short, as long as the use of the supercharger strictly in accordance with the instructions and operating procedures, you can avoid some failures, so that the supercharger to maximize the role and prolong its service life.