1. Variable Geometry Turbocharger

2. Content Introduction Turbocharging History
Problems with simple turbocharging
Working of VGT
Benefits
Designing of VGT
Summary and Conclusion
References
Common questions

3. Introduction
Variable-geometry turbochargers (VGTs) also known as variable nozzle turbines/VNTs), are a family of turbochargers
Designed to allow the effective aspect ratio (A:R) of the turbo to be altered as conditions change
It produces variations in the flow of inlet air mass by geometry change of inlet conditions of turbine blades according to requirement.

4. Turbocharger A turbocharger consist of four parts: Turbine Compressor
Common axle
Sub assemblies
Air cooler
WORKING
The turbine inlet receives exhaust gases from the engine exhaust manifold
causing the turbine wheel to rotate
This rotation drives the compressor, compressing ambient air
After it delivers it to the air intake manifold of the engine at higher pressure,
resulting in a greater amount of the air and fuel entering the cylinder

5. Problems with simple Turbochargers
Difference in the optimum aspect ratio of nozzle at different running conditions
Low boost at slow running conditions
Choking at high speed
Variation in the inlet air mass according to engine performance
Starting lag
Do internet search and add more

6. Turbocharger configuration

7. Turbocharger integration
Linking of engine performance with turbocharger performance

8. Variable geometry turbocharger
In variable geometry turbocharger the variation in inlet air mass is brought by compressor speed
Changes is done on the turbine
Nozzle angle is changed by stator vane, operated by ECU unit of vehicle
For low speed, the vane is brought in closed position so that boosting can be done by compressor
At high speed ,the vane comes at open condition allowing most of the exhaust to impact on the blades ,and the pressure decreases of exhaust gases and choking is avoided

9. Working of VGT Low speed run condition
Engine running parameters is taken by
ECU as input and send direction to vane
to close
High speed run condition

10. Benefits No throttling loss of the waste gate valve
Higher air–fuel ratio and higher peak torque at low engine speeds
Improved vehicle accelerations without the need to resort to turbines with high pumping loss at high engine speeds
Potential for lower engine ΔP (the difference between exhaust manifold and intake manifold pressures)
Control over engine ΔP that can be used to drive EGR flow in diesel engines with high pressure loop (HPL) EGR systems
A better ability to cover a wider region of low BSFC in the engine speed–load domain
Ability to provide engine braking
Ability to raise exhaust temperature for after treatment system management

11. Designing of the VGT Three parts Electronic control unit
Compressor designing
Turbine designing

12. Electronic control unit
The opening of the guide vanes is commanded by the electronic control unit (ECU) of the car
Aspects of engine performance that ECU consider for the varying the nozzle angle
1) the instant and quantity of injected fuel
2) the opening and closing of the intake and exhaust valves
3) pressures, temperatures, flow rates
Mass flow rate is given by
Add diagrams and notes about ecu

13. Compressor design Flow coefficient Circumferential Mach number
Isentropic work coefficient

14. Turbine design Parameters: Pressure ratio Corrected mass flow rate
Isentropic efficiency
Corrected speed
VNT positions

15. Conclusion
An VGT is designed to position the nozzle to attain the optimum air mass flow inside the engine and improving the break specific fuel consumption.
An VGT, under low running speed, provides closing of vane blades to allow more impact of exhaust gases on it improving intake air mass..
Designing of the compressor and turbine include the study of there design parameter on the maps which allow us to decide standards for the components.
Pumping losses , pressure energy loss, engine noise and heat energy loss is recovered by VGT. These problems commonly occur on vehicle with conventional turbocharging system or in case of no turbocharging.
If there occurs VGT failure, the system will revert to normal turbocharging operation. Normally the ECU unit will turn on the light in case of any fault.

16. Thank you