1. Design Analysis of Axial Flow Gas Turbines
P M V Subbarao
Professor
Mechanical Engineering Department
A Sustainable Non-Biological Muscle by Sir Charles Parson…..

2. Compressor – Turbine Rotor

3. Infrastructure for Realization of Newton's’ Laws
Stator
Rotor

4. Classification of Gas Turbines

5. Impulse-Reaction turbine
This utilizes the principle of impulse and reaction.
There are a number of rows of moving blades attached to the rotor and and equal number of fixed blades attached to the casing.
The fixed blades are set in a reversed manner compared to the moving blades, and act as nozzles.
The fixed blade channels are of nozzle shape and there is a some drop in pressure accompanied by an increase in velocity.
The fluid then passes over the moving blades and, as in the pure impulse turbine, a force is exerted on the blades by the fluid.
There is further drop in pressure as the fluid passes through the moving blades, since moving blade channels are also of nozzle shape.
The relative velocity increases in the moving blades.

6. Velocity triangles for turbine model stage
Vr2
Va2
Va1
Velocity triangles for turbine model stage
Vr2
Vr3
Va3
Vr2
Va2
Vr3
Va3 Vf
Vw

7. Selection of Blade & Flow Angles
The gas is delivered to the wheel at an angle a2 and velocity Va2.
The selection of angle a2 is a compromise.
An increase in a2, increases the value of useful component (Absolute circumferential Component).
This is also called Inlet Whirl Velocity, Vw2 = Va2 sin (a2).
An increase in a2, decreases the value of axial component, also called as flow component.
This is responsible for definite mass flow rate between to successive blades.
Flow component Vf2 = Va2cos(a2) = Vr2 cos(b2).
The absolute inlet velocity can be considered as a resultant of blade velocity and inlet relative velocity.
The two points of interest are those at the inlet and exit of the blade.

8. Impulse-Reaction Stage of ATurbine
Vr2
Va2
Vr3
Va3 Vf
Vw
The reaction effect is an addition to impulse effect.
The degree of reaction p va vr
A Physical Linking of Momentum and Energy transactions

9. First law for fixed blades:
First law for moving blades: 1 3 2
Total enthalpy drop in a stage:

10. Vr2 should enter at an angle b2, the inlet blade angle.
Va2
Vr3
Va3 Vf
Vw
If the gas is to enter and leave the blades without shock or much losses, then relative velocity should be tangential to the blade inlet tip.
Vr2 should enter at an angle b2, the inlet blade angle.
Similarly, Vr3 should leave at b3, the exit blade angle.
In an impulse reaction blade, Vr3 > Vr2
The flow velocities between two successive blade at inlet and exit are Vf2 & Vf3.
The axial (basic useful) components or whirl velocities at inlet and exit are Vw2 & Vw3.

11. The Driving Force on Wheel
Vr2
Va2
Vr3
Va3 Vf
Vw
Power Output of the blade :

12. Sequence of Energy Losses
Gas
Thermal
Power
Blade
kinetic
Power
Gas
kinetic
Power
Nozzle Losses
Stage Losses
Moving Blade
Losses
Isentropic efficiency of
Nozzle
Blade Friction Factor

13. Irreversible Adiabatic Flow Through A Turbine Stage : SSSF
Ideal work wiso = h01 –h03ss
Actual work wact = h01 – h03a
Isetropic Efficiency of a stage h s 1 2s
3ss 2a 3a 3s

14. Stage Loading and Flow Coefficient
Stage Loading Coefficient: Ratio of specific stage work output and square of mean rotor speed.
Flow Coefficient: Ratio of the axial velocity entering to the mean rotor speed.

15. Sizing of A Turbine Stagey F

16. Theoretical Model for Loss Estimation
The losses in any blade row will be proportional to the dynamic head or kinetic energy in the row.
Define the coefficient fs as the ratio of the shaft work output to the sum of the mean kinetic energies within stator + rotor.
For a 50% reaction turbine:

17. Performance Vs Size of A Turbiney
fs = F

18. Vr2
Va2
Vr3
Va3 Vf
Vw

19. Vr2
Va2
Vr3
Va3 Vf
Vw

20. Selection of Geometrical Parametersb2
90-a2

21. Selection of Geometrical Parameters
/
(b2+b2) b2

22. Selection of Geometrical Parameters
L/F=2
L/F=1
L/F=0.5
L/F=0
(b2+b3) b2

23. Design Algorithm

24. Design Algorithm

25. Model turbine instrumentation

26. Design validation