1. Micro Turbines : Turbo-expanders New Solutions for Distributed Green & Waste Resources….. P M V Subbarao Professor Mechanical Engineering Department

2. Selection of An Expander

3. In search of A Suitable Principle of Momentum Exchange/Direction of Fluid Flow Primary characteristics of a source or need. The cause/effect:  p or  h The Capacity: Flow rate, Q (m 3 /s ). Density of fluid:  (kg/m 3 ).

4. Time Scale of a Machine to Resource Speed: N (rpm) or n (rps) of a turbo machine: This is named as Specific Speed, N s

5. Selection of An Expander

6. Why Radial Flow Turbines Better ability to guide flow in an optimal direction into the expansion turbine wheel, Variable inlet guide vanes present the most important advantage of a radial turbine over an axial turbine. Suitable for highly variable natural sources of energy/waste energy recovery.

7. Turbo-Expanders

8. Compressible Flow Francis Turbine Through minor modifications standard radial inflow turbines can be optimized for different renewable thermal resources. They enable to smooth the seasonal variations by maintaining high efficiency levels at off-design conditions through the use of variable inlet guide vanes. Radial inflow turbines are less sensitive to blade profile in accuracies than axial turbines, which enable high efficiencies to be maintained as size decreases. Radial-inflow turbines are more robust under increased blade road caused by using high-density fluids as either subcritical or supercritical conditions.

9. Compressible Flow Francis Turbine Radial inflow turbines are easier to manufacture relative to axial turbines as the blades are attached to the hub. The rotor dynamic stability of the system is also improved due to a higher stiffness.

10. Parts of A Turbo-expander

11. Design of Spiral Casing R casing R isv d pipe Q Select a suitable value of mass flow rate.

12. At any angle , the radius of casing is: A full spiral is generally recommended for high head 300m, semi-spiral is recommended for low head < 50m. In general  =1.0, however corrected using CFD.

13. Flow Distribution Analysis of Casing Stay vanes or Guide vanes

14. Parts of A Turbo-expander

15. Geometrical Description of A Turbo-expander

16. Water from spiral casing Water particle

17. Design of the Details of Stay Vanes r exit stay Vane r inlet Stay Vane B esv Theory of Relatively Whirling flow: B isv

18. Runner inlet (Φ 0.870m) Guide vane outlet for designα) (Φ 0.913m) Closed Position Max. Opening Position

19. Operation of Guide Vanes.

20. Design of the Guide Vanes The outlet angle can be calculated by assuming a vortex from the flow in the gap between the runner and the guide vanes r egv r igv B egv Select appropriate value of n

21. The correlation between the turbine discharge and the guide vane opening angle.

22. Pressure drop versus guide vane angle

23. Velocity triangles r ri r re U ri V wi V ri V fi V ai U re V we V re V fe V ae ii ii ee ee

24. Inlet Velocity Triangles Vs Ns Low Specific Speed : Slow Francis Runner V wi V ai V fi

25. Inlet Velocity Triangles Vs Ns Low Specific Speed : Normal Francis Runner V wi V ai V fi

26. Inlet Velocity Triangles Vs Ns High Specific Speed : Fast Francis Runner V wi V ai V fi

27. Specfic Speed Vs Runner Shape

28. 3D Reconstruction of Runner with Blades

29. Study of Velocity distribution on runner for improvement

30. Design Rule 1 90-  i

31. Design Rule 2

32. Design Rule 3