Airfoil with improved cooling
The present invention relates to an airfoil for a gas turbine, including an improved turbulator arrangement formed on an inner cooling channel of the airfoil. According to preferred embodiments of the invention, in order to ensure a constant angle of the cooling flow inside the channel relative to each turbulator, the angle formed between the turbulator and the vertical axis is advantageously adapted, in the curved area, for every single turbulator. Furthermore, the same principle may be applied to all the cooling channels present within the airfoil.
1. An airfoil for a gas turbine, the airfoil comprising:
at least one inner cooling channel arranged along a longitudinal axis, the at least one cooling channel having a bent portion where the longitudinal axis is curved and deviates from a vertical axis of a design axis of the gas turbine, and
a plurality of longitudinally spaced turbulators distributed on at least a wall of said inner cooling channel and inclined such that each turbulator forms a tilt angle with the longitudinal axis,
wherein the inclination of each turbulator is adapted such that the tilt angle is constant along the curved longitudinal axis.
2. The airfoil according to claim 1 , wherein said tilt angle varies along the longitudinal axis within a range of +/−3° around a mean value.
3. The airfoil according to claim 1 , wherein said tilt angle is selected within a range 40°-70°.
4. The airfoil according to claim 1 , wherein said tilt angle is equal to 60° with a range of +/−3°.
5. The airfoil according to claim 1 , wherein said turbulators are equally spaced between each other in the direction of the longitudinal axis of the inner cooling channel, such that a pitch determined on the longitudinal axis between subsequent turbulators is constant along the inner cooling channel.
6. The airfoil according to claim 1 , wherein a second tilt angle associated to a variation of relative inclination between two subsequent turbulators is equal or smaller than 3°.
7. The airfoil according to claim 1 , wherein the airfoil comprises a plurality of inner cooling channels.
8. The airfoil according to claim 7 , wherein said plurality of inner cooling channels are connected to each other in series in a serpentine-type configuration.
9. The airfoil according to claim 1 , wherein said turbulators are ribs.
10. The airfoil according to claim 1 , wherein said cooling channel is defined by first and second opposed walls, the airfoil comprising:
turbulators distributed on each wall, wherein the turbulators distributed on the first wall are staggered relative to the turbulators distributed on the opposed second wall.
11. A rotor of a gas turbine, the rotor comprising an airfoil according to claim 1 .
12. The airfoil according to claim 1 , wherein a ratio between a pitch of the turbulators and a height of each turbulator is within a range of 5-12.
13. The airfoil according to claim 12 , wherein a ratio of a width of each turbulator and the height of each turbulator is within a range of 0.8-1.2.
14. The airfoil according to claim 13 , wherein each turbulator is trapezoidal in lateral cross-section and has a draft angle γ within a range of 2°-5°.