1. Turb4 Tip Cooling
Effects of Guide Ribs on Heat Transfer Enhancement of an Internal Blade Tip
Gongan Xie and Bengt Sundén Division of Heat Transfer, Department of Energy Sciences, Lund University, Lund
Lieke Wang and Esa Utriainen Siemens Industrial Turbomachinery AB, Finspong

2. Fig. 2 A typical serpentine passage
Introduction to Blade Tip Cooling
Fig. 2 A typical serpentine passage
Fig.1 Typical cooling techniques for a blade

3. Fig. 3 Sketch of flow pattern inside a serpentine channel
Need to Be Improvement
Separated flow regions associated with low heat transfer always occur at the corners in the turn region and downstream the turn along the inner wall.
Fig. 3 Sketch of flow pattern inside a serpentine channel

4. Recent work; pin fins

5. Recent work; conjugated heat transfer

6. Recent work; dimples, protrusions.

7. Design Concept
Smooth wall
Guide rib
Smooth wall with guide rib 7

8. Case I Smooth wall Tip-cap Rib Rib Smooth wall Coolant
Guide Rib 1- partial coverage 8

9. Case II Smooth wall Tip-cap Rib Coolant Smooth wall
Guide Rib 2-partial coverage 9

10. Main geometrical parameters
Channel
Aspect ratio = 1:2 (2.75 x 5.5)
= 4 x 2.75/3 = 3.667
Tip clearance = 3.5
Inlet/outlet length = 32
Tip-cap = 5.5 x 6.5
Unit: inch Dh
Rib
Height = (not full)
(blockage rato = 2 x 0.5/2.75=36.4%)
Thickness = 0.2
ReDh = 100,000~600,000

11. Flow Field Smooth wall Cross-section in the turn center
Ribs “compress” the vortices and force them towards the tip-wall 11

12. Ribs “enlarge” low temperature region
Tip Temperature
Smooth wall
Smooth channel
Case I
Case II
In the first-pass tip
Ribs “enlarge” low temperature region 12

13. Heat Transfer and Pressure Drop
Smooth wall
Case I:
Heat Transfer increases: 20%~38%
Pressure drop increases: around 15%
Case II:
Good
Heat Transfer increases: 21%~53%
Pressure drop decreases up to 12% 13

14. Heat Transfer and Pressure Drop
Smooth wall
Comparison of augmentation
Properly designed guide vanes are suitable for improving heat transfer associated with less pressure drop, but is not the most effective way compared to the augmentation by surface modifications imposed on the tip directly. 14

15. Concluding Remarks Smooth wall
1) Guide ribs force vortices towards the to tip-wall.
2) Adding guide ribs in the turn region provides 20~50% higher tip heat transfer.
3) Guide ribs may reduce the pressure if designed and placed properly.
4) The augmentation by guide ribs is much smaller than that by a pin-fin tip.
5) Guide ribs increase blade weight slightly, while pin fins make the tip much heavier. 15

16. Next plan

17. Similar schemes but with full-height guide ribs
Next plan
Similar schemes but with full-height guide ribs
The same height as channel height
( ribs connecting the leading wall and trailing wall)
CFD simulations

18. Comments ?? Thanks for your attention！ Acknowledgement
The research has been funded by the Swedish Energy Agency, Siemens Industrial Turbomachinery AB and Volvo Aero Corporation through the Swedish research program TURBO POWER, the support of which is gratefully acknowledged .