The honeycomb seals (HS) are the heavy duty elements of modern gas turbine engines (GTE). Usually HS is produced from the corrugated metal ribbons as honeycombed structures, by subsequential fastening by means of soldering on an inner side of GTE stator. Soldering defects (local absence of welding alloy, violation of the thermal mode, etc) result in HS disbonding and separation, and this, in its turn, has the fatal influence on GTE operation. Regarding to this, the inspection of HS is an actual task. At the present moment, acoustic and visual methids are the basic ones for HS inspection. The perspective photothermal method is not applied widely due to complication of control procedures. In some cases (inaccessibility HS for ultrasonic inspection because of rising tides and similar elements on the rotor, small size of honeycombs, etc) visual method (VM) is widely used. The VM is realized in two ways - honeycombs inspection in reflected light, and observation of the effect of light "infiltration" from honeycombs illuminated locally by optical light-guide, into adjacent cells, that takes place in case of absence of welding alloy. By the inspection in reflected light, HS with defectous soldering form the characteristic image with an obvious point in center of each cell. Absence of welding alloy and other defects result in leaps in the structure of light dazzles from a cell (general brightness fades, the spot in center disappears, etc). However by the existing methods (visual inspection) the foregone modifications of observation conditions (geometry, brightness) result in operator fatigue, missing of defects, especially in HS with small cells.
展开▼
