Cooling circuits for a gas turbine blade

1. A gas turbine blade for a turbomachine, the blade having an aerodynamic surface which extends radially between a blade root and a blade tip, which surface presents a leading edge and a trailing edge interconnected by a pressure side face and by a suction side face, and is closed at the blade tip by a transverse wall, said aerodynamic surface extending radially beyond said transverse wall so as to form a bathtub,

the blade further comprising, in its central portion, a centrally-located first cooling circuit comprising:

at least one suction side cavity extending radially on the suction side of the blade;

at least one pressure side cavity extending radially on the pressure side of the blade;

at least one central cavity extending radially in the central portion of the blade between the suction side cavity and the pressure side cavity;

a first air admission opening at a radially bottom end of the suction side cavity to feed cooling air to said suction side cavity;

a second air admission opening at a radially bottom end of the pressure side cavity to feed cooling air to said pressure side cavity;

at least one first passage putting a radially top end of the suction side cavity into communication with a radially top end of the central cavity;

at least one second passage putting a radially top end of the pressure side cavity into communication with the radially top end of the central cavity; and

outlet orifices opening out both into the central cavity and into the pressure side face of the blade.

2. A blade according to claim 1 , further comprising a second cooling circuit independent of the first cooling circuit, said second cooling circuit comprising:

at least one trailing edge cavity extending radially beside the trailing edge of the blade;

an air admission opening at a radially bottom end of the trailing edge cavity to admit cooling air into said trailing edge cavity; and

outlet slots opening out both into the trailing edge cavity and into the pressure side face of the blade.

3. A blade according to claim 2 , wherein the transverse wall of the blade includes at least one emission hole opening out both into the trailing edge cavity of the second cooling circuit and into the blade tip.

4. A blade according to claim 2 , wherein at least the outlet slot closest to the blade tip presents an angle of inclination towards the blade tip relative to a longitudinal axis of the turbomachine.

5. A blade according to claim 4 , wherein said angle of inclination towards the blade tip lies in the range 10° to 30° relative to said longitudinal axis of the turbomachine.

6. A blade according to claim 2 , wherein the trailing edge cavity of the second cooling circuit includes baffles on its pressure side and suction side walls so as to increase heat transfer along said walls.

7. A blade according to claim 2 , further comprising a third cooling circuit independent of the first and second cooling circuits, said third cooling circuit comprising:

at least one leading edge cavity extending radially in the vicinity of the leading edge of the blade;

an air admission opening at a radially bottom end of the leading edge cavity to feed cooling air into said leading edge cavity; and

outlet orifices opening out both into the leading edge cavity and into the leading edge in the pressure side and in the suction side of the blade.

8. A blade according to claim 7 , wherein the transverse wall of the blade includes at least one emission hole opening out both into the leading edge cavity of the third cooling circuit and into the bathtub so as to cool it.

9. A blade according to claim 8 , wherein said emission hole is of right section greater than that of the outlet orifices of the third cooling circuit so as to enable impurities coming from the cooling air to be exhausted, which might otherwise close off said outlet orifices.

10. A blade according to claim 7 , wherein the leading edge cavity includes baffles on its pressure side and suction side walls so as to increase heat exchange along said walls.

11. A blade according to claim 1 , wherein the transverse wall of the blade includes a plurality of emission holes opening out both into the pressure side, suction side, and central cavities of the first cooling circuit and into the bathtub in order to cool it.

12. A blade according to claim 1 , wherein the pressure side cavity of the first cooling circuit includes bridges extending between its side walls in order to increase internal heat transfer.

13. A blade according to claim 1 , wherein the suction side cavity of the first cooling circuit includes bridges extending between its side walls in order to increase internal heat transfer.

14. A blade according to claim 1 , wherein the pressure side cavity and the suction side cavity of the first cooling circuit have a high aspect ratio so as to increase internal heat transfer.