1. Aerodynamic and Heat Transfer Validation of LPT-OGVs (TURB34−LTH part) Chenglong Wang, Lei Wang, and Bengt Sundén Department of Energy Sciences, Lund University, Lund, 22100, Sweden

2. Background
Low pressure turbine (LPT) outlet guide vanes (OGVs) are positioned in the turbine rear frame.
The purpose of OGVs is to remove the swirl from the incoming flow and straighten the air into an axial outflow (nozzle).
OGVs

3. Challenges
The flow around OGVs is challenging because it requires tight separation margins and low pressure losses.
However, at some conditions (e.g., ground idle), the inlet incidence angles are far from what the OGV is designed for and fully separated flow would be expected.
The accurate prediction of the thermal load on the OGVs is essential for aerodynamic designers, both for on- and off-design conditions.

4. Objectives
To investigate the heat transfer on the OGV for both on- and off-design conditions.
To investigate the endwall heat transfer for both on- and off-design conditions.
To demonstrate and apply the Liquid Crystal Thermography (LCT) method to measure the surface temperature and obtain the local heat transfer coefficients.

5. Test rig
flow
The measurements were conducted in the large-scale linear cascade located at Chalmers.
By varying the incident angles, both on- and off-design conditions could be tested.

6. Measurements in situ: Chalmers

7. Profile of an OGV
The axial chord of the considered OGV is mm and the spanwise width is 200 mm.

8. On-design condition, α = 25°
Suction side.
Pressure side.
The flow is from the right to the left. Re = 300,000.

9. Mid-span distributions for α = 25°
Nu number distributions for different Re numbers.
Pressure coefficient distributions for Re = 300,000.

10. Off-design condition, α = -25°
Suction side.
Pressure side.
The flow is from the right to the left. Nusselt number distributions at Re = 300,000.

11. Mid-span distributions for α = -25°

12. Off-design II: α = 40°, Re = 300,000
Suction side.
Pressure side.

13. Mid-span distributions for α = 40°

14. Endwall: on-design, α = 25°
The flow is from the right to the left. Nusselt number distribution at Re = 300,000.

15. Endwall: on-design, α = -25°
The flow is from the right to the left. Nusselt number distribution at Re = 300,000.

16. Endwall: on-design, α = 40°
The flow is from the right to the left. Nusselt number distributions at Re = 300,000.

17. Summary I: heat transfer on the OGV
For α = 25° and 40 °, the stagnation point is located at the pressure side. For α = -25°, the stagnation point is located at the suction side.
For α = 25°, the transition position is at x/L = 0.4 on the suction side. The heat transfer on the pressure side exhibits a plateau.
For α = -25°, the transition position is shifted downstream at about x/L = 0.6 on the suction side. On the pressure side, the heat transfer undergoes a gradual increase after a sharp decrease from the stagnation point.
For α = 40°, the transition position is shifted upstream at about x/L = 0.2 on the suction side. On the pressure side, the plateau still exists but significantly shrunk compared to α = 25°.

18. Summary II: heat transfer on the endwall
For the on-design condition α = 25°, there is no obvious separation from the vane.
For the off-design condition α = -25°, the flow is significantly detached from both sides of the vane. The local minimum heat transfer is found close to the pressure side.
For the off-design condition α = 40°, the flow first separates from the suction side but subsequently reattaches on the surface.

19. Thank for your attention！
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