Diesel engine pressurization is not increase in diesel engine displacement and speed of the case, to improve power, improve the economy, reduce exhaust pollution and effective means, but also the current development trend of diesel engines. The exhaust turbocharger is a key component of the supercharged engine. It is actually an air compressor that increases the intake air by compressing air. It consists of three parts: turbine, intermediate and compressor.

The turbine is connected to the exhaust pipe of the engine. The compressor is connected with the intake pipe of the engine. The intermediate body is connected with the lubrication system of the engine. Its working principle is: the engine exhaust emissions through the turbine-driven rotor rotation, which drives the coaxial compressor impeller high-speed rotation (30000 ~ 120000r / min), fresh air in the compressor impeller centrifugal force, is compressed to 147 ~ 392kPa after entering the engine cylinder, due to the increase in air density, so that each work cycle into the cylinder to increase the amount of fresh air, which can be injected into the cylinder more diesel to improve the power of diesel engines, combustion has also improved.

Can increase the engine power output 20% to 40%, reduce fuel consumption of about 8%, exhaust smoke reduced by 20% to 50%, exhaust gas in the toxic toxic gases such as CO, SO2 also significantly reduced. In addition, the total displacement of the cylinder under the premise of the increase in power output, can save metal materials, reduce manufacturing costs, so turbocharger is a set of energy saving, environmental protection, materials as one of the high-tech products, Is widely used.

As the supercharger’s technical conditions directly affect the engine’s power, economy, reliability and exhaust emissions, therefore, the correct use of supercharger, supercharger to maintain a good working condition, to prevent early damage and timely and accurate troubleshooting It is very important to use in diesel engines. Supercharger structure Commonly used exhaust turbocharger is divided into ordinary turbocharger and bypass turbocharger two, bypass turbocharger more commonly used.

Exhaust turbochargers are composed of exhaust-driven turbines and radial-type compressors, which are mounted on both ends of the shaft and have their own cast shells. The shaft itself is mounted in the middle shell and supported by the intermediate shell. The sides of the intermediate shell are respectively connected with the compressor housing and the turbine shell, and the typical turbocharger speed can be above 1 x 105 r / min (see Fig. 2). Turbine: composed of turbines and turbo shells. It is the prime mover that drives the compressor impeller device, the exhaust gas enters the turbine, and drives the turbine, which drives the compressor impeller to rotate at high speed by the turbine shaft output.

Compressor: mainly by the compressor impeller, compressor shell and other components.

When the impeller rotates, it begins to inhale the air, and as the blade rotates to compress the air, it enters the intake duct.

Rotor assembly: The turbocharger rotor assembly consists of a turbine and shaft assembly, thrust bearing, thrust ring, seal ring support, compressor impeller, lock nut. It is a component of a turbocharger that requires dynamic balancing.

Bearing mechanism: turbocharger rotor shaft is equipped with a floating bearing, its bore and shaft, outer and intermediate hole with a specified gap, the floating bearing to bear the radial load of the rotor. The intermediate body is provided with a thrust bearing which carries the axial load of the rotor.

Sealing device: In the rotor shaft and seal ring support seal ring groove is equipped with a seal ring, it plays the dual role of oil seal and gas seal.

Intermediate: The intermediate shell is the support mechanism of the turbocharger. The rear plate and the turbine shell are respectively fixed on the intermediate body with bolts. The radial and axial loads of the rotor are respectively driven by the floating bearing and the thrust bearing. Passed to the intermediate. The intermediate body is also the turbocharger lubrication cooling device, its inlet hole connected to the engine lubrication main oil channel.

Lubricants in addition to the floating bearing, thrust bearing lubrication, but also will be exhausted by the heat away to ensure that the turbocharger reliable operation.

Bypass valve: Bypass valve by the bypass membrane box, linkage bar, bypass valve and other components. The bypass valve from the membrane box to the turbine housing is connected by a connecting rod which presses the bleed valve to close it and the supercharging pressure in the intake pipe acts on the air release diaphragm.

The bypass valve controls the opening of the valve at the turbine inlet through the pressure of the compressor outlet. When the boost pressure in the intake pipe reaches the maximum safety limit, the booster pressure pushes the air release diaphragm and opens the bleed Valve, so that part of the exhaust gas does not pass through the turbine impeller from the bypass discharge, thus limiting the turbocharger shaft speed and boost pressure. Its purpose is to limit the engine in the heavy load state of the supercharger speed, while it can reduce the full load and the maximum speed of the engine outbreak pressure. The supercharger with bypass valve improves low speed performance and valve closure improves transient response.

2 turbocharger common faults, causes of damage and preventive measures

Turbocharger is a high temperature environment in the ultra-high-speed rotation of the machine, the working speed of up to 30000 ~ 120000r / min, so high-speed rotation of the machinery often due to improper installation and damage caused by the user to suffer a certain economic loss. The current use of the supercharger, whether domestic or imported, the service life is often less than the expected life, the reason for more than 90% due to improper installation. The following brief description of the turbocharger in the use of some common faults, causes and precautions.

2.1 turbocharger at both ends of the oil spill

Turbocharger at both ends or a side of the oil spill, is one of the most common use of the fault. In theory, the normal pressure into the intermediate of the oil, through the bearing face, the oil has become zero, but by gravity naturally down the engine back to the oil pan. And in normal working conditions at both ends of the impeller at both ends of the impeller has a certain gas pressure, so the oil is not from the low pressure area to the high pressure area of ​​the flow. And the seal ring also plays the role of sealing gas seal oil. Even so, if used improperly, the following conditions can still cause oil leakage at both ends of the supercharger.

2.1.1 long-term idle operation of the engine

Baotou North Ben heavy truck accessories engine for a long time idle operation, turbocharger turbo and impeller rounds will have a certain negative pressure, which led to the middle of the oil out of the oil leakage, so should avoid the engine for a long time idle operation.

2.1.2 poor oil return

In the use of oil if the oil return pipe deformation or obstruction, will make the oil return oil is not smooth, the middle of the oil pressure is too high, the compressor oil along the rotor at both ends of the flow out of the seal ring caused by oil spills. So often check the return line is smooth, to ensure that the oil can be normal flow back to the oil pan.

2.1.3 engine crankcase pressure is too high

Crankcase exhaust gas pressure exceeds the specified value, will increase the pressure inside the supercharger return line, back to the oil caused by poor oil leakage. Should always check the crankcase ventilation, and the lower exhaust pipe is smooth.

2.1.4 air filter obstruction or poor air intake

After the long-term use of the engine, the air filter cartridge will be due to excessive dust caused by blocking, or the intake hose through the soft suction caused by poor air intake, etc., resulting in the compressor air pressure is too high, the wheel back There will be due to high pressure caused by the seal ring leakage, so to regularly check the maintenance of air filters and intake hose, so that the filter does not block, hose smooth, to maintain normal gas supply.

2.1.5 Seal ring wear or failure

Long-term do not replace the oil, so that the impurities in the oil too much from the role of abrasive, resulting in increased wear ring seal, thinning, and gradually lost sealing, sealing oil and lead to oil spills.

2.2 wear of floating bearings

Floating bearing wear is one of the most common faults in the turbocharger. After such failure, the gap between the bearing and the shaft is too large, oil film instability, carrying capacity decreased, the rotor shaft vibration intensified, undermine the dynamic balance. Excessive rotation radius makes both ends sealed and damaged, which may cause damage to the entire supercharger. The main reason for this failure is the following reasons.

2.2.1 does not use the supercharger oil according to the instructions

After the engine pressurized its heat load and mechanical load increased significantly, the working temperature is very high, so that the oil temperature, viscosity decreased, carrying capacity decreased, while the supercharger speed higher than the engine speed of nearly 40 times The temperature at the bearing is much higher than the temperature at the engine crankshaft. Therefore, the supercharger oil must be used correctly as instructed in the instructions.

2.2.2 oil cleanliness is too bad

As mentioned earlier, the oil contains too much impurities will accelerate the wear of bearings and shafts, maintenance in the engine oil pan often found in the oil black, thinning, or even black mud, such as oil continue to use No doubt will make the bearing in a short time due to wear and tear scrapped.

2.2.3 oil shortage dry grinding

Baotou North Ben heavy truck accessories supercharger oil from the engine oil pump, if the oil valve business “> pump work is not normal, resulting in insufficient fuel or oil pressure is too low, and the oil pipeline deformation, blocking, cracks and other phenomena lead to oil Insufficient supply, can make the supercharger bearings and shaft damage due to poor lubrication in the maintenance often found that some bearings and shafts have obvious dry friction marks, serious will see the phenomenon of burning blue, so should always Check the oil into the pipeline, a timely removal of problems.

Supercharger oil inlet pressure should be greater than 0.2MPa in order to ensure that the oil supply and bearing and other rotating parts of the normal lubrication. In addition, when checking the supercharger rotor, if the axial clearance is too large, it indicates that the thrust bearing wear is too large, if the radial clearance is too large, then the floating bearing wear is too large.

2.3 Turbine or compressor impeller is damaged

2.3.1 engine exhaust pipe into the metal

Supercharger in the normal high-speed operation, if the engine exhaust pipe nuts, screws and the like, will inevitably cause damage to the turbine blades, serious can also damage the turbine shell, the same compressor blade encountered this The situation will be damaged, if the impeller is damaged, then the rotor’s dynamic balance immediately destroyed, the supercharger rotor shaft vibration intensified, the supercharger can not continue to use. In use, such as hearing a different response immediately stop the inspection to prevent the falling compressor blades into the cylinder of the engine, causing serious accidents.

2.3.2 does not use the air filter or intake pipe seal is not strict

In the desert area or operating environment harsh areas of the use of pressurized engine, fine sand dust through the air filter or pipe in the gap into the supercharger, can cause the supercharger impeller inlet at the uniform wear of the leaves, Pressure regulator to reduce the effect of serious damage to the rotor balance, it should always check the intake and air filter and maintenance, timely replacement of filter, tighten the pipeline interface to reduce the occurrence of such failures.

2.3.3 not timely removal of sludge

Baotou North Ben heavy truck accessories supercharger long-term use, the dust in the air will be formed with the oil mist, gradually gathered in the supercharger shell inlet channel, so that the impeller and the shell without gaps, or blades and supercharger Shell contact and produce friction, causing the supercharger rotor shaft vibration, aggravate the wear of the shaft, it should always check the timely removal of sludge.

2.3.4 Exhaust temperature is too high

As the supercharger engine fuel system failure, such as fuel supply delay, the oil supply is too large or exhaust valve leakage and other phenomena, can lead to exhaust temperature is too high, so that the turbine inlet leaves burned deformation. Excessive exhaust temperature can also make the turbine side of the oil at the oil seal, and the turbine end of the local overheating, resulting in premature failure of the seal and bearing.