System and method for inspecting turbine blades

1. A system for inspecting surfaces of rotor blades for a surface characteristic, the system including: an assembly comprising a movable arm and, mounted on the movable arm, a scanner; and

a row of the rotor blades desirably positioned near the assembly for inspection, the row including at least a plurality of the rotor blades circumferentially spaced about a center axis;

wherein at least one of the row of the rotor blades and the assembly is moved relative to the other so as to index the row of the rotor blades relative to the assembly;

a rotor disc having an outer periphery on which the rotor blades of the row of the rotor blades are mounted;

wherein the each of the rotor blades include an airfoil defined between a concave pressure side face and a laterally opposed convex suction side face, the pressure side face and the suction side face extending axially between opposite leading and trailing edges and radially between an outboard tip and a platform of a root configured for mounting the rotor blade to the rotor disc;

and wherein the surfaces for inspection comprises as least one of: the pressure side face of the airfoil;

the suction side, face of the airfoil; the outboard tip of the airfoil; and the platform;

wherein the row of the rotor blades includes multiple neighboring pairs of the rotor blades; and

wherein a gap is formed between the airfoils of each of the neighboring pairs of the rotor blades, the gap being defined:

circumferentially between the pressure side face and the suction side face of the neighboring pairs of the rotor blades;

radially between the platforms of the neighboring pairs of the rotor blades and a reference, plane connecting the outboard tips of the neighboring pairs of the rotor blades; and

axially between a reference plane connecting the leading edges of the neighboring pairs of the rotor blades and a reference plane connecting the trailing edges of the neighboring pairs of the rotor blades;

wherein the movable arm is configured for controllably moving the scanner between an indexing position and a scanning position, wherein: the indexing position comprising a position outside of any of the gaps formed between the neighboring pairs of the rotor blades; and the scanning position comprising a position inside one of the gaps formed between the neighboring pairs of the rotor blades.

2. The system according to claim 1 , further comprising a gear mechanism connected to the rotor disc for rotating the row of the rotor blades about the central axis;

wherein the assembly comprises a stationary base to which the movable arm attaches and the indexing the row of the rotor blades relative to the assembly comprises rotating the rotor disc via the gear mechanism.

3. The system according to claim 2 , wherein the outboard tips of the airfoils of each of the neighboring pairs of the rotor blades define an outboard mouth of the gap;

wherein, in moving the scanner between the indexing position to the scanning position, the movable arm passes the scanner through the outboard mouth of the gap; and

wherein the gear mechanism comprises a shaft on which the rotor disc is mounted, the shaft comprising a central shaft of a gas turbine engine on which the rotor disc mounts during operation.

4. The system according to claim 2 , wherein the surface characteristics include at least one of a tear, rip, hole, crack, pit, creep elongation, and deformity; and

the movable arm comprises a retractable arm;

wherein the gear mechanism comprises a shaft on which the rotor disc is mounted, the shaft comprising a separate shaft as a central shaft of a gas turbine engine on which the rotor disc mounts during operation.

5. The system according to claim 2 , wherein the scanner further comprises a light source, the light source comprising at least one of: a structured light source, a laser light source, and a visible light source.

6. The system according to claim 5 , wherein the scanner further comprises a proximity sensor that includes at least one of an infrared proximity sensor, eddy current proximity sensor, capacitive proximity sensor, photoelectric proximity sensor, and inductive proximity sensor; and

wherein the proximity sensor is configured to assist in positioning the scanner in moving between the indexing position and the scanning position.

7. The system according to claim 5 , wherein the indexing of the row of the rotor blades by the gear mechanism comprises an intermittent rotation in which rotating periods alternate with stationary periods; and

wherein the movable arm is configured to operate relative the intermittent rotation such that the scanner is positioned at the indexing position during the rotating periods and at the scanning position during the stationary periods.

8. The system according to claim 7 , wherein the scanner is rotatably mounted on the movable arm; and

wherein, upon achieving the scanning position, the scanner is configured to rotate at least once so to adjust an aim of the scanner such that multiple ones of the surfaces of the rotor blades are scanned while the scanner is in the scanning position.

9. The system according to claim 8 , wherein the multiple ones of the surfaces that are scanned while the scanner is in the scanning position include the pressure side of a first rotor blade of one of the neighboring pairs of rotor blades and a suction side of a second rotor blade of the one of the neighboring pairs of rotor blades.

10. The system according to claim 7 , wherein the scanner comprises a plurality of scanners aimed in a plurality of directions for simultaneously scanning a plurality of the surfaces of the rotor blades with one of the gaps while the scanner is in the scanning position.

11. The system according to claim 10 , wherein the multiple ones of the surfaces that are simultaneously scanned while the scanner is in the scanning position include the pressure side of a first rotor blade of one of the neighboring pairs of rotor blades and a suction side of a second rotor blade of the one of the neighboring pairs of rotor blades.

12. The system according to claim 7 , further comprising multiple ones of the assembly such that a first assembly includes a first movable arm and a first scanner and a second assembly includes a second movable arm and a second scanner;

wherein the first assembly is configured to simultaneously scan one of the surfaces in a first one of the gaps while the second assembly scans one of the surfaces in a second one of the gaps.

13. The system according to claim 7 , further comprising a computer operably connected to the assembly, wherein the computer is configured to:

analyze input regarding the surface characteristics of the surfaces as scanned by the scanner;

calculate differences between the input from the scanner and a reference blade surface; and

compare the differences between the input from the scanner and the reference blade surface against predetermined thresholds.

14. The system according to claim 13 , wherein the computer is further configured to:

given the comparisons of the differences against the predetermined thresholds, determine repair areas on the surfaces and, for each repair area, repair type;

create a report that includes a predicted performance characteristic related to repairing the repair areas per the repair type that corresponds thereto; and

output the report to a system user.

15. The system according to claim 4 , wherein the assembly comprises a movable base to which the movable arm attaches and the indexing the row of the rotor blades relative to the assembly comprises moving the movable base about a periphery of the row of rotor blades.

16. A method of inspecting surfaces of rotor blades mounted on a rotor disc for a surface characteristic, the method comprising the steps of:

desirably positioning an assembly that includes a scanner mounted on a movable arm near the rotor blades;

rotating the rotor disc so to index the rotor blades relative to the assembly;

controllably moving the scanner via the moveable arm between an indexing position and a scanning position, wherein:

the indexing position comprises a position outside of any of the gaps formed between the neighboring pairs of the rotor blades; and

the scanning position comprises a position inside one of the gaps formed between the neighboring pairs of the rotor blades; and

scanning the surfaces of the rotor blades when the scanner maintains the indexing position.

17. The method according to claim 16 , wherein each of the rotor blades include an airfoil defined between a concave pressure side face and a laterally opposed convex suction side face, the pressure side face and the suction side face extending axially between opposite leading and trailing edges and radially between an outboard tip and a platform of a root configured for mounting the rotor blade to the rotor disc; and

wherein the surfaces for inspection comprises as least one of: the pressure side face of the airfoil;

the suction side face of the airfoil; the outboard tip of the airfoil; and the platform.

18. The method according to claim 17 , wherein the rotor blades include multiple neighboring pairs of the rotor blades; and

wherein a gap is formed between the airfoils of each of the neighboring pairs of the rotor blades, the gap being defined:

circumferentially between the pressure side face and the suction side face of the neighboring pairs of the rotor blades;

radially between the platforms of the neighboring pairs of the rotor blades and a reference plane connecting the outboard tips of the neighboring pairs of the rotor blades; and

axially between a reference plane connecting the leading edges of the neighboring pairs of the rotor blades and a reference plane connecting the trailing edges of the neighboring pairs of the rotor blades; and

wherein, in controllably moving the scanner between the indexing position and the scanning position, the movable arm passes the scanner through the reference plane connecting the outboard tips of the neighboring pairs of the rotor blades.

19. The method according to claim 18 , wherein the scanner further comprises a structured light source;

wherein the rotating the rotor disc comprises an intermittent rotation in which rotating periods alternative with stationary periods; and

wherein the controllably moving the scanner via the moveable arm between the indexing position and the scanning position includes: timing the movement pursuant to the intermittent rotation such that the scanner comprises the indexing position during the rotating periods and the scanning position during the stationary periods.