Rotor blade root section with cooling passage and method for supplying cooling fluid to a rotor blade

A root section of a rotor blade for interacting with working fluid upon rotating the rotor blade about a rotation axis oriented in an axial direction, the working fluid streaming in the axial direction, the root section of the rotor blade comprising:

• a curved cooling passage in an inside of the root section for guiding a cooling fluid within the root section from a radially inner end of the root section to a radially outer end of the root section, wherein a radial direction is perpendicular to the axial direction and pointing away from the rotation axis;
• a cooling fluid entry plenum having an entry aperture arranged at the radially inner end of the root section for introducing the cooling fluid into the cooling passage;
• and
• a platform located at a radially outer end of the root section, the platform being in contact with the working fluid, wherein the curved cooling passage penetrates through the platform,
• wherein the following condition is satisfied in a portion ranging from 70% to 100% of a radial extent of the cooling passage:
• 0.25*dr<rc<1.5*dr,
• wherein dr is a radial distance in the radial direction between the platform of the root section and the aperture of the entry plenum and rc is the radius of curvature of the curved cooling passage,
• wherein the cooling fluid is guided within the cooling passage from the radially inner end to the radially outer end of the root section such that the cooling fluid has a movement component in the axial direction and a movement component in the radial direction in a first, radially inner portion of the cooling passage,
• the cooling fluid has a movement component only in the radial direction in a second, radially middle portion of the cooling passage, and
• the cooling fluid has a movement component in a direction opposite to the axial direction and in the radial direction in a third, radially outer portion of the cooling passage.

A method for supplying a cooling fluid to a rotor blade, the rotor blade being adapted for interacting with working fluid upon rotating about a rotation axis oriented in an axial direction, the working fluid streaming in the axial direction, the method comprising:

• guiding the cooling fluid within a curved cooling passage in an inside of a root section of the rotor blade from a radially inner end of the root section to a radially outer end of the root section, wherein a radial direction is perpendicular to the axial direction pointing away from the rotation axis;
• introducing the cooling fluid into the cooling passage via a cooling fluid entry plenum having an entry aperture arranged at the radially inner end of the root section;
• and
• leading the cooling fluid through a platform located at a radially outer end of the root section, the platform being in contact with the working fluid, wherein the curved cooling passage penetrates through the platform,
• wherein the following condition is satisfied in a portion in a range from 70% to 100% of a radial extent of the cooling passage:
• 0.25*dr<rc<1.5*dr, wherein
• dr is a radial distance in the radial direction between the platform of the root section and the aperture of the entry plenum and
• rc is the radius of curvature of the curved cooling passage, wherein the cooling fluid is guided within the cooling passage from the radially inner end to the radially outer end of the root section such that
• the cooling fluid has a movement component in the axial direction and a movement component in the radial direction in a first, radially inner portion of the cooling passage,
• the cooling fluid has a movement component only in the radial direction in a second, radially middle portion of the cooling passage, and
• the cooling fluid has a movement component in a direction opposite to the axial direction and in the radial direction in a third, radially outer portion of the cooling passage.