The system of gas turbine supercharging and cooling of the charge air, due to the use of part of the exhaust gas energy, provides 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 liter power of the engine.
The use of supercharged engines expands operational capabilities when driving on long ascents, over rough terrain and in mountainous conditions.
The gas turbine engine boost system (Figure 1) consists of two interchangeable turbochargers, exhaust and intake manifolds and nozzles, an air-to-air charge air cooler, supply and discharge pipelines.
The air in the centrifugal compressor of the turbocharger comes from the air purifier, is compressed and supplied under pressure to the ONV, and then the cooled air enters the engine.
Turbochargers are installed on the exhaust pipes, one for each row of cylinders.
Exhaust manifolds and pipes are made of high-strength cast iron.
The gas joints between the turbine mounting flanges of turbochargers, exhaust pipes and manifolds are sealed with gaskets made of heat-resistant steel.
Gaskets are single-use parts and must be replaced during system bulkheads.
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.
Exhaust manifolds are made solid and are attached to the cylinder heads with bolts and buttressed with lock washers.
To compensate for the angular displacements that occur during heating, special spherical washers are installed under the bolt heads of the exhaust manifold mounting.
The turbocharging and cooling system of the engine charge air must be sealed. The leakiness of the system leads to an increase in the heat stress of the parts, a decrease in engine power and resource.
In addition, leakage of 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 braid.
Oil is drained from turbochargers through steel tubes into the crankcase of the engine.
Two TKR 7C-6 turbochargers are installed on the engine. Instead of TKR7C-6 turbochargers, S2B/7624TAE/0,76D9 turbochargers from Schwitzer can be installed.
The technical characteristics of turbochargers are given in the table
The TKR 7C-6 turbocharger consists of a centripetal turbine and a centrifugal compressor connected by a bearing assembly.
A turbine with a two-way housing 7 (Figure 2) made of high-strength cast iron converts the energy of exhaust gases into the kinetic energy of rotation of the turbocharger rotor, which then turns 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 reflector 16 and a sleeve 15 fixed to the shaft by a nut 19.
The turbine wheel is cast from a heat-resistant alloy according to the smelted models and is welded to the shaft by friction.
The compressor wheel with blades bent backward in the direction of rotation is made of aluminum alloy and, after machining, is dynamically balanced to a value of (0.4 g mm).
The bearing trunnions of the rotor shaft are hardened by HDPE to a depth of 1-1.5 mm. After machining, the rotor is dynamically balanced to a value of (0.5 gmm).
The bushing, oil reflector, 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 kgf m).
After assembly, the rotor is not additionally balanced, only the radial runout of the shaft trunnions is checked.
If the radial runout value is not 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.
Axial movements of the rotor are limited by a thrust bearing 4, pinched between the bearing housing 3 and the cover 2. The bearings are made of bronze.
In order to reduce the heat transfer from the turbine to the compressor, the turbocharger bearing housing is made of a composite cast-iron housing and an aluminum alloy cover.
To reduce heat transfer, a heat-resistant steel shield 11 is installed between the turbine housing and the bearing housing.
An oil discharge 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 O-ring 21 is installed in the connection "compressor housing - bearing housing".
The turbine and compressor housings are attached to the bearing housing using bolts 13,18 and slats 12,17. This design allows the housings to be installed at any angle to each other, which in turn facilitates the installation of the TCR on the engine.
Maintenance of the gas turbine boost and charge air cooling system during engine operation is checked by an external inspection tightness of the exhaust gas pipeline route, air supply to the engine.
Periodically, the reliability of fastening parts and assemblies of these systems is 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 turbocharger malfunction can lead to engine failure.
Despite the fact that turbochargers do not require adjustments in operation, it is necessary to systematically comply with the rules of engine maintenance established by the manufacturer and periodically monitor the operation of turbochargers by ear.
At TO-2, it is necessary to check the ease of rotation of the turbocharger rotors. To do this, remove the intake 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 stationary parts of the turbocharger.
Turbocharger bearings are very sensitive to the amount and purity of oil, therefore, the necessary conditions for the 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 brands recommended by the manufacturer.
During seasonal maintenance, it is recommended to remove 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.
The cleaning of the centrifugal compressor must be carried out in the following sequence:
- - apply combined risks to the end surfaces of the compressor housing and cover.
- Unscrew the bolts securing the compressor housing.
- With light blows of a hammer on the bosses, remove the compressor housing.
- Inspect the rubber O-ring in the slot of the lid.
- If defects are detected (incisions, loss of elasticity), replace the O-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 must be repaired at a specialized enterprise or replaced;
- - rinse the inner cavity of the compressor housing, the surface of the lid 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 O-ring with engine oil, combine the risks, install the compressor housing on the cover disc, tighten the bolts with a torque wrench.
Once again check 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 accuracy, complete disassembly, repair and maintenance of boost units should be carried out at specialized enterprises with the necessary equipment, tools, fixtures, appliances and qualified personnel.
During seasonal maintenance, it is necessary to drain the condensate accumulated in the ONV