1. Cross Flow Turbine Characteristic and layout

2. Cross Flow Turbine - Overview
Advantages:
Simple design
Good standardisation - runner width can be adapted to design flow so it is easy to build the turbine precisely for the specified site needs
Manufacturing without the need for sophisticated manufacturing facilities.
Relative low production costs compared with other turbine designs

3. Cross Flow Turbines
In 1925 Donat Banki received a patent in Budapest for his BANKI-Turbine.
This turbine applied the cross flow principle, where a free jet traverses a cylindrical runner vertical to the turbine shaft.

4. History of Cross Flow Turbine T-series
Local manufacturing of the T3 turbine is established in Nepal and the design is adapted in several steps to optimize production.
More than 100 turbines are built, chiefly for small scale mill operation.
1976
The prototype of the T1 turbine is developed for local manufacturing in Nepal.
Turbines are successfully used for mill operation and village electrification
1980
Operating experience with the T1 turbine leads to the development of the T3 series turbine.
The turbine is tested in the hydraulics laboratory of HTL Brugg, Switzerland. Based on tests, the design is improved

5. History of Cross Flow Turbine T-series
T8 turbines, an improved version of the T7 series, become the standard for village electrification schemes in Indonesia.
1985
The demand for larger output turbines leads to the development of the T7 turbine.
Fabrication is established in Nepal, and later in Indonesia.
Manufacturing of T8 series turbines is also established in Nepal and Argentina.

6. History of Cross Flow Turbine T-series
1995
A research program is started and in collaboration with the hydraulics laboratory of the University of Stuttgart, extensive tests are conducted.
Empirical design improvements result in a new design, the T12 turbine.
1994
Indonesian entrepreneurs acquire the know-how for the implementation of complete SHP projects, using T8 turbines
1995
In Nepal, demand for large turbines is met with a redesigned version of the T8 turbine.

7. History of Cross Flow Turbine T-series
1996
A variety of different hydraulic configurations are tested.
The ultimate goal is to use the optimal configuration for a new, completely re-engineered design.
1996
Further testing, after some critical feedback from the field, leads the way to further design modifications.
The design now becomes the T13 series.

8. T15XFLOW: A new Cross Flow design developed by ENTEC
The T14XFLOW Turbine, was empirically tested in the sophisticated laboratory of the Institute for Hydraulic Machines of Stuttgart University.
The Model Turbine had an output of 15 kW, the runner diameter is mm. The measuring facilities guarantee for reliable results.

9. Efficiency Improvement

10. T15XFLOW: A new Cross Flow design developed by ENTEC
With only 25% of the rated flow, the efficiency is still over 50%. This allow cost reduction, because a single cell CFT will be sufficient in the majority of the applications. Double cell CFT’s have two independent guide vanes, and require two regulation devices as well, which increases cost.
The achieved improvements were the basis for the re-design of the turbine. Two models, with the standard runner diameter of 300 and 500 mm were developed for output above 20kW.
For output up to 25kW models withv runner diameters with 100, 150 and 225mm are available

11. T15XFLOW: A new Cross Flow design developed by ENTEC
General Assembly of T15 Cross Flow Turbine

12. Application limits of T15-150 Turbines

13. Application limits of T15-300 Turbines
Application Limits T15-300

14. Application limits of T15-500 Turbines

15. Summary: Present Application Range T15
150
100
T15-500
T15-300

16. Pelton Turbines T14-800 T14-650 T14-500 T14-300 Pico Piccolo
Future Perspective
Pelton Turbines
T14-800
T14-650
T14-500
T14-300
Pico
Piccolo
Propeller Turbines

17. T15 Calculation: Definition of rated head Hr without draft tube
Penstock
Free water level
Draft Tube Hf
Hg1 Hg
Hg2
~Dt
Tail race canal
CF Turbine
Where:
Hr = Rated head
Hg1 = Level difference between forebay and turbine shaft
Hf = Hydraulic and friction losses in the penstock
(Draft tube not installed)

18. T15 Calculation: Definition of rated head Hr with draft tube (not recommended)
Our laboratory tests proved that the suction head can not be used with the same efficiency as the head acting in the penstock due to following reasons:
A ventilation valve must maintain the water level under the turbine runner free to avoid high losses in the runner. At least one runner diameter must be subtracted from the suction head.
In the remaining part of the draft tube a mixture of air and water will be created. All air flowing through the ventilation valve will even be pumped out of the draft tube. The consequence is, that the density of the water is smaller. A save estimate may be 80%.
Penstock
Free water level
Draft Tube Hf
Hg1 Hg
Hg2
~Dt
Tail race canal
CF Turbine
(Draft tube installed)
Where:
Hg2 = Level difference between turbine shaft and tale race
Dt = Turbine runner diameter
Hf = Hydraulic and friction losses in the penstock

19. The concept of the “Unit Turbine”
To allow using model tests from the laboratory for the dimensioning of turbines with geometrical similar shape, the measuring results are converted to a “Unit Turbine”. This fictive turbine has 1 m widht, 1m diameter and an operation head of 1m.
Unit Machine
Ø1m – Bo 1m
Model Runner
Ø300mm – Bo 160mm
Real Machine
Ø150mm – Bo 200mm

20. Hill Chart of T15 Turbine

21. Basic T15 Calculation (best operation point)
Unit Speed : n11= 38rpm
Unit Flow : p11= 0.8m3/s
Are numerical Values only however in SI units (m)
Runner Width :
Speed :
Run-way Speed :
Power Output :
in kW

22. Hnet = 62.5m Q = 600l/s Dt = 300mm Calculation Example Runner Width :
Speed :

23. Hnet = 62.5m Q = 600l/s Dt = 300mm Calculation Example Runner Width :
Speed :

24. example Runaway Speed :
Attention: If there is a high friction loss in the penstock the runaway speed higher. Maximal
nrmax = nr*sqr(Hg/Hr)
Power Output :

25. Check Application limits of T15-300 Turbines
The calculation of the turbine should be checked in the application diagram. In this case two turbines T are required to produce the power. The application is above the limits in the diagram. The design was reinforced and a stainless steel runner and guide vane was used.

26. Example: recalculation using 2 Turbines with bo=Bt=160mm
Runner Width :
Power Output (per unit) :

27. example
Runner Width :
Power Output :

28. Upgrade of efficiency
The turbine efficiency was determined with a model turbine. In reality the efficiency for larger turbine output and for wider runner is increasing. Parameter for this difference in efficiency is the power output and the specific speed (old definition ns=nt_opt*(Pt_opt)^0.5/Hnet^1.25)

29. T15- calculation tool
A spreadsheet was developed to calculate the suitable T15 Turbine for a certain site application. The blue fields are prepared for data input.
The first step is to calculate the runner width bo and then select it according to the nearest suitable standard width.

30. Determine the upgraded efficiency and enter it ito the blue field

31. Check in the application diagram by moving the green arrows to the site data (in the example the head is quite high but still acceptable if welding and quality is good)

32. Fill in efficiencies of generator and gear/belt

33. Diagram: Efficiency versus flow

34. Diagram: power output versus flow
The rated point of operation is marked in the diagram. There is about 15% safety margin in the power if the turbine is opened above the rated position. This is required to compensate for mistakes in the head calculation or friction losses. In any case the rated power must be reached.

35. Losses at scheme: concerning the energy losses from water intake to the consumers all partial losses must be multiplied to get the over all efficiency (in the example below eta tot=48%)

36. Terima Kasih – Thank You
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