The system of gas turbine supercharging and charge air cooling, by using part of the energy of the exhaust gases, provides the supply of pre-compressed and cooled air to the engine cylinders
Supercharging allows to increase the charge density of the air entering the cylinders and to burn more fuel in the same working volume and increase the liter power of the engine.
The use of supercharged engines expands the operational capabilities when driving on long climbs, on rough terrain and in mountainous conditions.
The engine's gas turbine supercharging system (Figure 1) consists of two interchangeable turbochargers (TCR), exhaust and intake manifolds and pipes, an air-to-air charge air cooler (CAC), and supply and outlet pipelines.
Air enters the turbocharger's centrifugal compressor from the air cleaner, is compressed and supplied under pressure to the CAC, and then the cooled air enters the engine.
Turbochargers are installed on the exhaust pipes, one for each bank of cylinders.
The exhaust manifolds and pipes are made of high-strength cast iron.
The gas joints between the mounting flanges of the turbocharger turbine, exhaust pipes and manifolds are sealed heat-resistant steel gaskets.
The gaskets are single-use parts and are subject to replacement during system overhauls.
The gas joint between the exhaust manifold and the cylinder head is sealed with a gasket made of asbestos-steel sheet edged with metal-clad tape.
The exhaust manifolds are made of one piece and are attached to the cylinder heads with bolts and secured with lock washers.
To compensate for angular movements that occur during heating, special spherical washers are installed under the heads of the exhaust manifold mounting bolts.
The turbocharging and charge air cooling system of the engine must be hermetically sealed. Leakage in the system leads to increased heat stress in the parts, reduced engine power and service life.
In addition, leakage in the intake tract leads to "dust" wear of the cylinder-piston group and premature engine failure.
Turbocharger bearings are lubricated from the engine lubrication system through fluoroplastic tubes with metal braiding.
Oil is drained from the turbochargers through steel tubes into the engine crankcase.
Two TKR 7S-6 turbochargers are installed on the engine. Instead of TKR7S-6 turbochargers, S2B/7624TAE/0.76D9 turbochargers from Schwitzer can be installed.
Technical characteristics of turbochargers are given in the table
The TKR 7S-6 turbocharger consists of a centripetal turbine and a centrifugal compressor connected to each other by a bearing assembly.
Fig. 3. Turbocharger TKR7S: 1 - compressor housing; 2 - cover; 3 - bearing housing; 4 - thrust bearing; 5 - bearing; 6 - retaining ring; 7 - turbine housing; 8 - sealing ring; 9 - turbine wheel; 10 - rotor shaft; 11 - turbine screen; 12 - bar; 13 - bolt; 14 - oil drain screen; 15 - bushing; 16 - oil deflector; 17 - bar; 18 - bolt; 19 - nut; 20 - compressor wheel; 21 - sealing ring; 22 - diffuser
A turbine with a two-pass housing 7 (Figure 3) made of high-strength cast iron converts the energy of the exhaust gases into kinetic energy of the turbocharger rotor rotation, 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 sleeve 15, secured to the shaft with a nut 19.
The turbine wheel is cast from a heat-resistant alloy using investment patterns and is friction welded to the shaft.
The compressor wheel with blades curved backwards in the direction of rotation is made of aluminum alloy and, after mechanical processing, is dynamically balanced to a value of (0.4 g mm).
Bearing journals of the shaft rotors are hardened by high-frequency current to a depth of 1-1.5 mm. After mechanical processing, the rotor is dynamically balanced to a value of (0.5 g/mm).
The bushing, oil deflector, and compressor wheel are installed on the rotor shaft and tightened with a nut to a torque of 7.8-9.8 Nm (0.8-1.0 kgf m).
After assembly, the rotor is not additionally balanced; only the radial runout of the shaft journals is checked.
If the radial runout value is no more than 0.03 mm, marks are applied to the rotor parts in one 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 rotor parts.
The rotor rotates in bearings 5, which are floating rotating bushings.
The axial movements of the rotor are limited by thrust bearing 4, clamped between bearing housing 3 and cover 2. The bearings are made of bronze.
The turbocharger bearing housing is made of a cast iron housing and an aluminum alloy cover to reduce heat transfer from the turbine to the compressor.
A heat-resistant steel screen 11 is installed between the turbine housing and the bearing housing to reduce heat transfer.
An oil-slinging screen 14 is installed in the bearing housing, which, together with elastic split rings 8, prevents oil leakage from the housing cavity.
A rubber sealing ring 21 is installed to eliminate air leaks in the "compressor housing - bearing housing" connection.
The turbine and compressor housings are fastened 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 turbocharger on the engine.
Maintenance of the gas turbine supercharging system and charge air cooling during engine operation, the tightness of the exhaust gas pipeline route and air supply to the engine is checked by visual inspection.
The reliability of fastening of parts and units of these systems is periodically checked, and if necessary, the 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 turbocharger malfunction can lead to engine failure.
Despite the fact that turbochargers do not require adjustments during operation, it is necessary to systematically follow the rules for engine maintenance established by the manufacturer and periodically monitor the operation of the turbochargers by ear.
During TO-2, it is necessary to check the ease of rotation of the turbocharger rotors. To do this, remove the exhaust pipe.
Then check by hand how the rotor rotates in its extreme axial and radial positions.
The rotor should rotate easily, without jamming or touching the stationary parts of the turbocharger.
Turbocharger bearings are very sensitive to the amount and purity of oil, so the necessary conditions for normal operation of the bearing assembly are timely replacement of oil and filter elements of the engine oil filter, as well as the use of oil grades recommended by the manufacturer.
During 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 performed in the following sequence:
- - apply combined marks to the end surfaces of the compressor housing and cover.
- Unscrew the compressor housing fastening bolts.
- Remove the compressor housing by lightly hitting the bosses with a hammer.
- Inspect the rubber sealing ring in the cover groove.
- If defects are found (cuts, loss of elasticity), replace the sealing ring;
- - inspect the compressor wheel blades. If traces of contact with the compressor housing, deformation of the blades or their destruction are detected, the turbocharger is subject to repair at a specialized enterprise or replacement;
- - 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 inter-blade 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, align the marks, install the compressor housing on the cover disk, tighten the bolts with a torque wrench.
Check the ease of rotation of the rotor again. In extreme axial and radial positions, the rotor wheels must not contact the housing parts.
Considering that the turbocharger rotor is balanced with high precision, complete disassembly, repair and maintenance of supercharging units must be carried out at specialized enterprises that have the necessary equipment, tools, devices, instruments and qualified personnel personnel.
During seasonal maintenance, it is necessary to drain the condensate accumulated in the ONV
