The engine air supply system consists of a filter, a seal, an air intake, pipes and pipes connecting the air intake and air cleaner with turbochargers
Its design is determined by the vehicle configuration.
The air filter (Figure 1) is a dry type, two-stage, designed to clean the air entering the engine from dust.
It consists of a body 3 with a swirler 4, a cover 8, a precleaner 1, a filter element 2. The tightness of the connection of the cover with the body is ensured by the sealing ring 5.
The cover is attached to the body with four spring clips 6. The main parts of the filter are made of sheet steel
1.2 mm thick. To increase the efficiency of cleaning the air entering the engine, a precleaner 1 is put on the filter element - a sheath made of non-woven filter cloth.
Air cleaning in the filter is two-stage.
The first stage of purification is a monocyclone containing a swirler 4 installed behind the inlet pipe and providing a helical movement of the air flow in the annular gap between the filter housing and element 2.
Due to the action of centrifugal forces, dust particles are thrown to the wall of the housing and driven into the hopper. The dust collector is formed by a cover 8, a partition 7 and a removable plug 9.
The second stage of cleaning is filter element 2, which has outer and inner casings.
They are made of perforated steel sheet and corrugated filter paper, connected at the ends with metal caps, which are glued with special glue.
The filter element is tightly pressed against the bottom of the housing 3 and sealed with an end rubber ring. The filter element is fixed in the housing with a self-locking nut 10.
The air pre-cleaned in the first stage enters the second stage with a replaceable cardboard filter element for finer cleaning, where, penetrating through the pores of the cardboard, it leaves fine dust particles on its surface.
The purified air enters through a tee to two centrifugal compressors and, under excess pressure, through the charge air cooler pipe to the engine cylinders.
The air supply system of the engine provides for the installation of a clogged filter element indicator.
If the clogging indicator works, then the air filter element needs to be serviced or replaced.
The gas turbine pressurization and charge air cooling system, due to the use of part of the energy of the exhaust gases, provides the supply of pre-compressed and cooled air to the engine cylinders.
Supercharging allows you to increase the charge density of the air entering the cylinders, and in the same working volume, burn more fuel and increase the engines liter power.
The use of supercharged engines expands the operational capabilities when driving on long slopes, over rough terrain and in mountainous conditions.
The gas turbine engine pressurization system (Figure 2) consists of two interchangeable turbochargers (TKR), exhaust and intake manifolds and nozzles, an air-to-air charge air cooler (CAC), inlet and outlet pipelines.
The air in the centrifugal compressor of the turbocharger comes from the air cleaner, is compressed and pressurized in the CAC, and then the cooled air enters the engine.
Turbochargers are mounted on the exhaust pipes, one for each bank of cylinders. Exhaust manifolds and pipes are made of ductile iron.
The sealing of gas joints between the mounting flanges of the turbine of turbochargers, exhaust pipes and manifolds is carried out with gaskets made of heat-resistant steel.
Gaskets are disposable parts and must be replaced when the system is overhauled.
The gas joint between the exhaust manifold and the cylinder head is sealed with a gasket made of asbestos sheet, edged with metal clad tape.
The exhaust manifolds are made of one piece and are bolted to the cylinder heads and secured with lock washers.
Special spherical washers are installed under the heads of the exhaust manifold mounting bolts to compensate for the angular displacements that occur during heating.
The engines turbocharging and charge air cooling system must be sealed. Leakage of the system leads to an increase in the thermal stress of parts, a decrease inyu power and engine resource.
In addition, leakage of the intake tract leads to "dusty" wear of the cylinder-piston group and premature engine failure.
The turbocharger bearings are lubricated from the engine lubrication system through fluoroplastic tubes with a metal braid. Oil is drained from the turbochargers through steel pipes into the crankcase.
The engine is equipped with two TKR 7S-6 turbochargers. Instead of the TKR7S-6 turbocharger, Schwitzer S2B/7624TAE/0.76D9 turbochargers can be installed.
Technical characteristics of turbochargers are shown in table 2.
The TKR 7S-6 turbocharger consists of a centripetal turbine and a centrifugal compressor connected to each other by a bearing assembly.
A turbine with a two-way housing 7 (Figure 3) made of ductile iron converts the energy of the exhaust gases into the kinetic energy of rotation of the turbocharger rotor, which is then converted into air compression work in the compressor stage.
The turbocharger rotor consists of a turbine wheel 9 with a shaft 10, a compressor wheel 20, an oil deflector 16 and a bushing 15, fixed to the shaft with a nut 19.
The turbine wheel is cast from a heat-resistant investment alloy and welded to the shaft by friction.
The compressor wheel with backward-curved blades is made of aluminum alloy and, after machining, is dynamically balanced to a value of (0.4 g mm).
The bearing journals of the rotor shaft are hardened by HDTV to a depth of 1...1.5 mm. After machining, the rotor is dynamically balanced to a value (0.5 g mm).
Technical characteristics of turbochargers
The bushing, oil deflector, compressor wheel are mounted on the rotor shaft and tightened with a nut with a torque of 7.8 ... 9.8 Nm (0.8 ... 1.0 kgcm).
After assembly, the rotor is not additionally balanced, only the radial runout of the shaft pins is checked.
When the value of the radial runout is not more than 0.03 mm, marks are applied to the parts of the rotor in the same plane, and the rotor is allowed to assemble the turbocharger.
When installing the rotor in the bearing housing, it is necessary to align the marks on the parts of the rotor. The rotor rotates in 5 bearings, which are floating rotating bushings.
Axial movement of the rotor is limited by thrust bearing 4, pinched between bearing housing 3 and cover 2. Bearings are made of bronze.
The turbocharger bearing housing, in order to reduce heat transfer from the turbine to the compressor, is made of a cast-iron housing and an aluminum alloy cover.
To reduce heat transfer, a screen 11 made of heat-resistant steel is installed between the turbine housing and the bearing housing.
An oil-rejecting screen 14 is installed in the bearing housing, which, together with elastic split rings 8, prevents oil leakage from the housing cavity.
To eliminate air leaks, a rubber sealing ring 21 is installed in the connection "compressor housing - bearing housing".
Turbine and compressor housings are attached to the bearing housing using bolts 13, 18 and strips 12, 17. This design allows the housings to be installed at any angle to each other, which in turn facilitates the installation of the TKR on the engine.
Maintenance of the gas turbine pressurization system and charge air cooler
During the operation of the engine, external inspection checks the tightness of the exhaust gas pipeline route, the air supply to the engine.
The reliability of fastening parts and assemblies of these systems is periodically checked, and, if necessary, bolts, fastening nuts and clamps are tightened.
The operation of the turbocharger has a significant impact on the parameters and performance of the engine. A malfunctioning turbocharger can lead to engine damage.
Despite the fact that turbochargers do not require adjustments in operation, it is necessary to systematically follow the engine maintenance rules established by the manufacturer and periodically monitor the operation of turbochargers by ear.
For TO-2, it is necessary to check the ease of rotation of the turbocharger rotors.
For this it is necessary to remove the exhaust pipe of the exhaust system.
Then check with your hand how the rotor rotates in its extreme axial and radial positions.
The rotor should rotate easily, without jamming and touching the fixed parts of the turbocharger.
Turbocharger bearings are very sensitive to the quantity and purity of oil, therefore, the necessary conditions for the normal operation of the bearing assembly are the timely replacement of oil and filter elements of the engine oil filter, as well as the use of oils recommended by the manufacturer.
For seasonal maintenance, it is recommended to remove the turbochargers from the engine once every two years to clean the centrifugal compressor. It is advisable to remove the unit together with the exhaust manifold.
Cleaning the centrifugal compressor must be done in the following sequence:
- apply combined risks on the end surfaces of the compressor housing and cover.
Remove the bolts securing the compressor housing. Remove the compressor housing with light blows of a wooden hammer on the bosses.
Inspect the rubber o-ring in the cover groove.
If defects are found (cuts, loss of elasticity), replace the sealing ring with a new one;
- - inspect the compressor wheel blades. If traces of contact with the compressor housing, deformation of the blades or their destruction are found, the turbocharger must be repaired at a specialized company or replaced;
- - wash the internal cavity of the compressor housing, the surface of the cover with a rag soaked in diesel fuel.
When cleaning the compressor wheel, it is recommended to clean the interblade surfaces with a hair brush using diesel fuel;
- - check the ease of rotation of the rotor, jamming of the rotor is not allowed;
- - before assembly, it is necessary to lubricate the sealing ring with engine oil, combine the risks, install the compressor housing on the cover disc, tighten the bolts with a torque wrench.
Recheck the ease of rotation of the rotor. In the extreme axial and radial positions, the rotor wheels should not come into contact with the body parts.
Due to the fact that the turbocharger rotor is balanced with high precision, complete disassembly, repair and maintenance of boost units should be carried out at specialized enterprises with the necessary equipment, tools, fixtures, devices and qualified personnel.
During seasonal maintenance, it is necessary to drain the condensate accumulated in the CAC.