Contents: Purpose ↡ Functioning ↡
Air supply system (functional diagram, the arrangement of elements is shown conditionally)
VN 2.108
1. Intake manifold
2. Exhaust manifold
3. Turbocharger
4. Charge air cooler
5. Compressed air duct
6. Vacuum boost control device
7. Intake manifold pressure sensor (B28)
8. Vacuum converter controlling the boost pressure control flap ATM. Atmospheric pressure output OUT. Control vacuum output VAK. Vacuum supply from the vacuum pump (Y31/5)
Constant Geometry Turbocharger for Gas Turbine
VN 2.109
1. Vacuum boost pressure control device
2. Bypass line valve
3. Supercharger housing
4. Compressor wheel
5. Gas turbine housing
6. Turbine wheel
7. Turbine bearing housing
8. Turbine aal
9. Supercharger inlet (outside air)
10. Supercharger outlet (compressed air)
11. Feed exhaust gases to the turbine wheel
12. Exhaust gas outlet
13. Bypass hole
14. Oil supply
15. Returning oil to the engine crankcase
Variable Geometry Turbocharger for Gas Turbine
VN 2.110
1. Compressor inlet (outside air)
2. Compressor outlet (forced air)
3. Supply of exhaust gases to the turbine wheel
4. Exhaust gas outlet
5. Turbine housing
6. Turbine wheel
7. Compressor housing (supercharger)
8. Control rod
9. Synchronizing ring drive lever
10. Synchronizing (regulating) ring
11. Guide vane rotary lever
12. Guide vane
13. Air gap in the "closed" position of the blades
14. Air gap in the "open" position of the blades
15. Guide vanes "closed"
16, Guide vanes "open"
17. Boost pressure control vacuum chamber
[Material taken from a web resource: mercedesman.ru]
Purpose
The boost pressure supply system is designed to bring the amount of air supplied to the cylinders in line with the required power at the given moment and with external conditions.
The boost pressure is regulated by means of a valve starting from an engine speed of approximately 2000 rpm, depending on the engine load and the engine speed, by opening it in the turbocharger bypass line. Until the rotation speed reaches 2000 rpm, the control valve is closed (boost pressure is not yet sufficient).
Functioning
The exhaust gases are directed through the exhaust manifold into the turbine housing onto the turbine wheel. The energy of the exhaust gas flow causes the turbine wheel to rotate. On the same shaft as the turbine wheel is the supercharger turbine wheel, which, when rotating, creates a flow of air directed under pressure into the engine cylinders. Maximum turbine speed (in high altitude conditions) can reach 18000 rpm.
Boost pressure regulation is performed in various ways.
The first method uses a controlled valve to regulate the capacity of the bypass hole that directs exhaust gases around the turbine, thus reducing its performance.
The second method regulates the direction and intensity of the gas flow directly in front of the turbine wheel blades. Figure VN 2.110 shows how, when the installation angle of the guide blades changes, the flow cross-section of the gap between the blades and the angle at which the gas flow is directed to each blade of the turbine wheel change.
The advantages of a turbocharger with variable geometry turbine guide vane are:
- increasing boost pressure, especially in the low engine speed range;
- increased torque as a result of improved cylinder filling;
- reduction of harmful emissions in the exhaust gases as a result of increasing the amount of air supplied to the cylinders;
- increased engine power as a result of higher boost pressure combined with reduced exhaust back pressure