Turbine blade creep monitoring

A method of monitoring turbine blade creep in a gas turbine engine, the method including:

• receiving stereo images of a turbine blade of a row of turbine blades, the stereo images having been obtained using a stereo borescope located in the engine adjacent a row of turbine blades, and the stereo images including a seal segment located radially outwardly of the blades, in use the blades moving past the seal segment as the row of turbine blades rotates;
• identifying same features of the blade in each of the stereo images;
• identifying the seal segment in each of the stereo images;
• mapping each of the identified features by triangulation onto a 3D space to produce a 3D depth map of at least part of the blade, the 3D depth map including a shroud of the blade;
• mapping the seal segment by triangulation onto the 3D space such that the produced 3D depth map also includes the seal segment;
• providing a 3D reference model of the blade and the seal segment;
• and
• comparing the 3D reference model with the 3D depth map to measure one or more deviations in shape of the blade to determine an amount of creep-induced distortion of the blade, wherein the creep-induced distortion is determined by measuring relative twisting between the shroud and the seal segment.

A system for monitoring turbine blade creep in a gas turbine engine, the system including:

• a computer readable medium for storing stereo images of a turbine blade of a row of turbine blades, the stereo images being over a whole radial length of the turbine blade, and having been obtained using a stereo borescope located in the engine adjacent the row of turbine blades;
• and
• a processor-based sub-system operationally connected to the computer readable medium and adapted to:
• identify a trailing edge, a platform edge and a shroud edge of the blade in each of the stereo images;
• map each of the trailing edge, the platform edge and the shroud edge by triangulation onto a 3D space;
• measure in the 3D space a distance between a radially inner landmark at a corner of the platform edge closes to the trailing edge on the blade, and a radially outer land mark at a corner of the shroud edge closest to the trailing edge on the blade;
• and
• compare the measured distance with the distance between the radially inner landmark and the radially outer landmark for a turbine blade that has not experienced creep to determine an amount of creep-induced distortion of the blade.

A system for monitoring turbine blade creep in a gas turbine engine, the system including:

• a computer readable medium for storing stereo images of a turbine blade of a row of turbine blades, the images having been obtained using a stereo borescope located in the engine adjacent the row of turbine blades, and the stereo images including a seal segment located radially outwardly of the blades, in use the blades moving past the seal segment as the row of turbine blades rotates;
• and
• a processor-based sub-system operationally connected to the computer readable medium and adapted to:
• identify same features of the blade in each of the stereo images;
• identify the seal segment in each of the stereo images;
• map each of the identified features by triangulation onto a 3D space to produce a 3D depth map of at least part of the blade, the 3D depth map including a shroud of the blade;
• map the seal segment by triangulation onto the 3D space such that the produced 3D depth map also includes the seal segment;
• provide a 3D reference model of the blade and the seal segment;
• and
• compare the 3D reference model with the 3D depth map to measure one or more deviations in shape of the blade to determine an amount of creep-induced distortion of the blade, wherein the creep-induced distortion is determined by measuring relative twisting between the shroud and the seal segment.