Apparatus and method for rejuvenating cooling passages within a turbine airfoil

An electrochemical machining method for rejuvenating at least one cooling passage within an airfoil, said electrochemical machining method comprising:

• preparing an inner surface of the cooling passage for electrochemical machining, including removing residue from the inner surface;
• positioning an electrode in the cooling passage, the electrode comprising a conductive core and an insulating coating, the insulating coating exposing a plurality of exposed portions of the conductive core;
• and
• machining a groove pattern on the inner surface of the cooling passage using the exposed portions of the conductive core by passing an electric current between the electrode and the airfoil while circulating an electrolyte solution through the cooling passage, said machining producing a rejuvenated cooling passage,
• wherein the electrode further comprises a tip and an end, the conductive core extending between the tip and the end, wherein the exposed portions comprise conductive strips of the conductive core extending between the tip and the end of the electrode, wherein the insulating coating comprises a plurality of insulating portions which substantially extend between the tip and the end of the electrode, the insulating portions being positioned between the conductive strips to form an alternating pattern, wherein said machining of the groove pattern uses the alternating pattern, and wherein the groove pattern comprises a plurality of alternating grooves and fins, and
• wherein the conductive strips and the insulating portions are configured so that said machining forms the grooves having dimensions of about 0.01 cm to about 0.06 cm in width and about 0.01 cm to about 0.06 cm in depth and forms the fins having dimensions of about 0.01 cm to about 0.06 cm in width and about 0.01 cm to about 0.06 cm in depth.

An electrochemical machining method for rejuvenating at least one cooling passage within an airfoil, said electrochemical machining method comprising:

• preparing an inner surface of the cooling passage for electrochemical machining, including removing residue from the inner surface;
• positioning an electrode in the cooling passage, the electrode comprising a conductive core and an insulating coating, the insulating coating exposing a plurality of exposed portions of the conductive core;
• and
• machining a groove pattern on the inner surface of the cooling passage using the exposed portions of the conductive core by passing an electric current between the electrode and the airfoil while circulating an electrolyte solution through the cooling passage, said machining producing a rejuvenated cooling passage,
• wherein the electrode further comprises a tip and an end, the conductive core extending between the tip and the end, wherein the exposed portions comprise conductive strips of the conductive core extending between the tip and the end of the electrode, wherein the insulating coating comprises a plurality of insulating portions which substantially extend between the tip and the end of the electrode, the insulating portions being positioned between the conductive strips to form an alternating pattern, wherein said machining of the groove pattern uses the alternating pattern, and wherein the groove pattern comprises a plurality of alternating grooves and fins, and
• wherein the airfoil comprises a blade airfoil, the cooling passage comprises a radial cooling hole, and the electrode is so dimensioned so as to have a diameter, which is within a range of about 0.008 to about 0.015 cm less that the diameter of the cooling passage.

An electrochemical machining method for rejuvenating at least one cooling passage within an airfoil, said electrochemical machining method comprising:

• preparing an inner surface of the cooling passage for electrochemical machining, including removing residue from the inner surface;
• positioning an electrode in the cooling passage, the electrode comprising a conductive core and an insulating coating, the insulating coating exposing a plurality of exposed portions of the conductive core;
• and
• machining a groove pattern on the inner surface of the cooling passage using the exposed portions of the conductive core by passing an electric current between the electrode and the airfoil while circulating an electrolyte solution through the cooling passage, said machining producing a rejuvenated cooling passage,
• wherein the electrode further comprises a tip and an end, the conductive core extending between the tip and the end, wherein the exposed portions comprise conductive strips of the conductive core extending between the tip and the end of the electrode, wherein the insulating coating comprises a plurality of insulating portions which substantially extend between the tip and the end of the electrode, the insulating portions being positioned between the conductive strips to form an alternating pattern, wherein said machining of the groove pattern uses the alternating pattern, and wherein the groove pattern comprises a plurality of alternating grooves and fins, and
• wherein the airfoil comprises a vane airfoil having a central passage and a trailing edge, the cooling passage extends between the central passage and the trailing edge, and the electrode is so dimensioned so as to have a diameter, which is within a range of about 0.008 to about 0.015 cm less that the diameter of the cooling passage.

An electrochemical machining method for rejuvenating at least one cooling passage within an airfoil, said electrochemical machining method comprising:

• preparing an inner surface of the cooling passage for electrochemical machining, including removing residue from the inner surface;
• positioning an electrode in the cooling passage, the electrode comprising a conductive core and an insulating coating, the insulating coating exposing a plurality of exposed portions of the conductive core;
• and
• machining a groove pattern on the inner surface of the cooling passage using the exposed portions of the conductive core by passing an electric current between the electrode and the airfoil while circulating an electrolyte solution through the cooling passage, said machining producing a rejuvenated cooling passage,
• wherein the electrode further comprises a tip and an end, the conductive core extending between the tip and the end, wherein the exposed portions comprise conductive strips of the conductive core extending between the tip and the end of the electrode, wherein the insulating coating comprises a plurality of insulating portions which substantially extend between the tip and the end of the electrode, the insulating portions being positioned between the conductive strips to form an alternating pattern, wherein said machining of the groove pattern uses the alternating pattern, and wherein the groove pattern comprises a plurality of alternating grooves and fins,
• wherein the insulating coating further exposes a plurality of spacer portions of the conductive core, the spacer portions being longitudinally positioned between the insulating portions, and wherein the groove pattern further includes a plurality of connectors, each connector being longitudinally positioned between two of the fins and connecting two of the grooves,
• wherein the conductive strips and the insulating portions are dimensioned so that said machining forms the grooves having dimensions of about 0.01 cm to about 0.06 cm in width and about 0.01 cm to about 0.06 cm in depth and forms the fins having dimensions of about 0.01 cm to about 0.06 cm in width and about 0.01 cm to about 0.06 cm in depth, and wherein the spacer portions are dimensioned so that the fins are spaced by about 0.01 cm to about 0.06 cm along a longitudinal direction.