GB2036363A

GB2036363A - Inspecting Stator Vanes

Info

Publication number: GB2036363A
Application number: GB7937863A
Authority: GB
Original assignee: United Technologies Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1978-12-04
Filing date: 1979-11-01
Publication date: 1980-06-25
Also published as: SE7909841L; IL58599A0; JPS5578127A; FR2443697A1; ES486838A1; BE879820A

Abstract

The stator vanes 26B of a gas turbine engine are inspected by attaching the viewing end 56 of fiber optical inspection apparatus 44 to one or more rotor blades 20A, e.g. by a hook or inflatable bellows and circumferentially displacing the viewing end by rotating the rotor. <IMAGE>

Description

SPECIFICATION Methods and Apparatus for Inspecting Stator Components of Gas Turbine Engines This invention relates to gas turbine engines, 'and more specifically to methods and apparatus for inspecting blades and vanes without disassembly of the engine.

U.S. Patent 4,078,864 to Howell entitled "Method and Apparatus for Viewing and Measuring Damage in an Inaccessible Area", and of common assignee herewith, discloses state of the art methods and apparatus for inspecting inaccessible areas of gas turbine engines. The apparatus disclosed and the method of inspection taught require local access ports for inspection of local components in the areas of the access ports.

To the extent that parts to be inspected can be rotated into view of the optical instrument the apparatus and technique are satisfactory.

Stationary components such as stator vanes, however, are not so adaptable, and generally require disassembly of the engine for inspection.

Disassembly of an engine for inspection is an expensive process depriving the owner of the engine of its use for a substantial period of time.

Manufacturers, operators and owners of engines have been in search of, and continue to seek apparatus and techniques for inspecting internal components without disassembly.

A primary aim of the present invention is to provide a method and apparatus for inspecting blades and vanes of a gas turbine engine.

Techniques for inspecting components which are susceptible to damage without disassembling the engine are sought, and in one aspect of the invention a collateral objective is to enable accurate determination of the specific circumferential location of the component being inspected.

According to the method of the present invention, the viewing end of fiber optic inspection apparatus is inserted through the engine case and is affixed to one or more blades of the rotor such that the viewing end of the apparatus is movable circumferentially about the engine in response to rotation of the engine rotor.

In accordance with detail aspects of the invention the viewing end of the inspection apparatus has a hook for attaching the viewing end to one of the rotor blades, and the inspection technique includes the steps of inserting the viewing end of the apparatus into the engine flow path in proximity to one of the rotor blades; hooking the viewing end of the apparatus to one of the rotor blades in an orientation such that the viewing end faces at least one of the stator vanes to be viewed; viewing the stator vane through the apparatus; displacing the rotor blade to which the end of the apparatus is attached circumferentially to bring the viewing end of the apparatus into optical alignment with a second of the stator vanes to be inspected; and viewing said second stator vane.

A primary feature of the present invention is the technique for advancing the viewing end of the inspection apparatus circumferentially around the engine. The viewing end may be faced in the upstream direction to principally view the trailing edge and suction side surface of the upstream vane and may be faced in the downstream direction to principally view the leading edge and the pressure side surface of the downstream vane. An access port in the approximate region of the components to be inspected is employed. In one embodiment, a guide tube with suitable control features is capable of directing the probe in an upstream or downstream direction from the access port.

A principal advantage of the present method is the ability to inspect heretofore inaccessible components of a gas turbine engine without disassembling the engine. The length of time which an engine need be removed from use for inspection is substantially reduced. Accurate determination of the circumferential location of a component being inspected is enabled by indexing the position of the viewing end to angular movement of the engine rotor or by counting the vanes passed by the viewing end of the apparatus as the rotor is rotated. The concepts are particularly advantageous in inspecting stator vanes of turbine engines and are adaptable to viewing the stator vanes from either the upstream direction or the downstream direction.

The foregoing, and other objects, features and advantages of the present invention will become more apparent in the light of the following detailed description of the preferred embodiment thereof as shown in the accompanying drawing, wherein: Fig. 1 is a simplified, side elevation view of a gas turbine engine including a cut-away segment showing internal portions of the combustion and turbine sections; Fig. 2 is an enlarged view of the portions of the combustion and turbine sections showing disposition of the viewing end of fiber optic inspection apparatus in the turbine section of the engine; Fig. 3 is a sectional view taken along the line 3-3 as shown in Fig. 2; Fig. 4 is an illustration of detailed inspection apparatus constructed in accordance with the concepts of the present invention;; Fig. 5 is an enlarged illustration of the viewing end of the inspection apparatus showing a hook for attaching the viewing end to one of the rotor blades; and Fig. 6 is an enlarged illustration of the viewing end of the inspection apparatus showing an inflatable means for affixing the viewing end of the apparatus to the rotor blades.

A gas turbine engine, of the type to which the method and apparatus of the present invention is well suited, is shown in Fig. 1. The engine principally includes a compression section 10, a combustion section 12 and a turbine section 14.

An engine case 1 6 circumscribes the engine. One or more axially extending rotors 1 8 are contained within the case. One or more rows of rotor blades, as represented by the single blades 20 extend outwardly from the rotor. Each blade has a leading edge 22 and a trailing edge 24. A row of stator vanes, as represented by the single vanes 26 is disposed upstream of each row of rotor blades. A gear box 28 for driving accessory components (not shown) is mechanically joined within the compression section to the rotor via the drive shaft 30.

The internal components of the combustion and turbine sections are shown in greater detail in Fig. 2. A flowpath 32 for working medium gases extends axially through the engine. One or more access ports 34 penetrate the case 1 6 at the combustion section. A combustion chamber 36 inside the combustion section has an inner liner 38 and an outer liner 40. A hole 42 in the outer liner is shown beneath the inspection port. During operation of the engine the hole 42 serves to flow dilution air into the hot working medium gases of the combustion chamber.

During one inspection technique described herein the hole provides access for the inspection apparatus to the engine flowpath. A row of first stage stator vanes, as represented by the single vane 26A is disposed across the flowpath at the downstream end of the combustion chamber. A row of first stage rotor blades, as represented by the single blade 20A extends from the rotor immediately downstream of the first stage stator vanes. A row of second stage stator vanes, as represented by the single vane 26B and a row of second stage rotor blades, as represented by the single blade 20B are disposed immediately downstream of the second stage rotor blades.

Inspection apparatus, such as the fiber optic viewing device 44, for inspecting internal components of the engine extends into the flow path through the port 34 and the hole 42 in the outer liner 40 of the combustion chamber.

Although other points of entry into the flowpath may be employed, entry through the combustion chamber has proven effective with minimal complexity. The viewing device has a housing 46, flexible cable 48 having a viewing end 50, an eyepiece 52 and a light source 54. Attaching means, such as the hook 56 shown, is positioned at the end of the cable for securing the end of the cable to one of the first stage rotor blades 20A. A guide tube 58 having a base portion 60 and an outreach arm 62 extends through the port 34 and the hole 42 for directing the end of the viewing device toward the components to be inspected.

The outreach arm is hingedly joined to the base portion. The guide tube has means, such as the spring 64 and wire 66, for bending the outreach arm angularly with respect to the base portion.

As is shown in Fig. 4 and Fig. 5, the flexible viewing cable 48 has a first fiber optic way 68 .which leads to the eyepiece for viewing the component to be inspected. An objective lens 70 is disposed at the way 68. At least one second fiber optic way, as represented by the two ways 72, lead to the light source 54 for illuminating the component to be inspected. An open tube 74 runs parallel to the optic ways and extends into the housing 46. A spring 76 is disposed in the tube and at one end 78 is formed into the hook 56. The opposite end 80 of the spring extends through the housing. A clamp 82 is slideable on the spring and is capable of holding the hook in a retracted position.

Although not a specific concept of the present invention, fiber optic devices such as that illustrated often include means for articulating the viewing end of the flexible cable. In the illustrated apparatus, a lever 84 is capable of articulating the viewing end and a clamp 86 is capable of holding the articulated viewing end in a set position. The particular fiber optic device illustrated is adapted from instruments utilized in the medical industry.

The optics comprise the principal components of a flexible bronchoscope, such as is procurable from Machida Corporation of Norwood, New Jersey.

The inspection technique of the present invention is particularly advantageous in enabling inspection of components contained deeply within the engine without disassembly of the engine. The time savings in performing this inspection are substantial. For example, inspection of the second stage vanes, as illustrated by Figs. 2 and 3, can be completed in a few hours whereas inspection of second stage vanes by disassembly of the engine may take several days.

Access to the engine flowpath is gained through one of the access ports 34 to the combustion chamber. A guide tube is extended through the case and into the chamber. The guide tube employed has an articulating outreach arm.

The viewing cable is inserted through the tube and into the chamber. The cable may be inserted prior to articulation of the guide tube, or may be inserted after the articulated tube is in position between adjacent vanes. The flexible cable is next advanced from the end of the guide tube with the viewing end of the cable being directed rearwardly through the flowpath. The viewing end of the device is passed between a pair of adjacent first stage blades and is affixed to one or more of the blades in an orientation enabling the viewing end of the device to face rearwardly toward the second stator stage. The engine rotor is next rotated to bring the viewing end of the device into optical alignment with one of the vanes of the second stator stage to be inspected. The vane in optical alignment is examined for structural damage or deterioration. The rotor is next advanced to bring the viewing end of the device into optical alignment with a second of the vanes of the stator stage and the second vane is examined for structural damage or deterioration.

The rotating and viewing steps are repeated until all of the vanes to be inspected have been examined.

Experimentation with the techniques taught herein has shown that insertion and rotation of the viewing end of the probe from two circumferential locations about the flowpath is desirable. The two locations are preferably positioned approximately one hundred eighty degrees (1800) apart so as to limit the internal resistance encountered in dragging the flexible cable around the engine. In accordance with this technique, the viewing end is inserted at one location and is rotated one hundred eighty degrees (1800) with the engine rotor so as to view all vanes within that arcuate sector. The viewing end is then withdrawn from the engine and reinserted at a location approximately one hundred eighty degrees (1800) apart from the original point of insertion. The rotating and viewing steps are repeated.

The rotor 18 of the engine illustrated is mechanically coupled to the gear box 28 via the shaft 30. Additional shafting, not shown, extends radially inward to the rotor within the compression section. Gas turbine mechanics will recognize that the rotor 1 8 is rotatable by externally driving components of the gear box.

The position of the rotor may be indexed to these components to accurately determine the precise vane being inspected. Alternatively, the circumferential position in the flowpath may be determined by counting the number of vanes as the viewing end 50 of the device is rotated past the vanes.

An alternate technique for attaching the viewing end of the fiber optic device to the rotor blades is illustrated in Fig. 6. Inflatable means, such as the bladder 88 circumscribes the viewing end of the fiber optic device. A tube 90 extends from the bladder through the flexible cable to provide a conduit for inflating the bladder.

Although the invention has been shown and described with respect to preferred embodiments thereof, it should be understood by those skilled in the art that various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.

Claims

1. A method for viewing stator vanes of a gas turbine engine of the type having rotor blades disposed adjacent to the vanes to be viewed, comprising the steps of: inserting the viewing end of a fiber optic device into the engine flowpath in proximity to one of the rotor blades; affixing the viewing end of the fiber optic device to said rotor blade in an orientation such that the viewing end faces at least one of the stator vanes to be viewed; viewing said stator vane through the fiber optic device; displacing said rotor blade to which the end of the fiber optic device is attached circumferentially to bring the viewing end of the device into optical alignment with a second of the stator vanes to be inspected; and viewing said second stator vane through the fiber optic device.

2. The method according to claim 1 which includes repeating the steps of displacing said rotor blade to which the viewing end is attached and viewing stator vanes until all vanes to be viewed have been brought into view of the fiber optic device.

3. The method according to claims 1 or 2 wherein the step of affixing the viewing end of the fiber optic scope includes the step of hooking the viewing end of the device to said rotor blade.

4. The method according to claim 3 wherein the rotor blade to which the fiber optic device is attached is located upstream of the stator vanes to be inspected and wherein the step of hooking the viewing end of the device to said rotor blade includes the step of hooking the viewing end of the device to the downstream end of said rotor blade.

5. The method according to claims 1, 2, 3 or 4 wherein the step of inserting the viewing end of a fiber optic device into the engine flowpath includes the steps of: inserting a guide tube through the engine case and into the flowpath; and passing the viewing end of the fiber optic device through the guide tube.

6. Apparatus for inspecting internal, stationary components of a gas turbine engine having rotatable engine components in proximity to the stationary components to be inspected, comprising: a viewing device including an eyepiece, a light source, and a flexible cable having a viewing end for disposition in proximity with the component to be inspected wherein said cable has a first fiber optic way leading from the viewing end of the cable to the eyepiece for viewing of the component to be inspected, at least one second fiber optic way leading from the light source to the viewing end of the cable for illuminating the component to be inspected, and means for attaching the viewing end of the cable to a rotatable component of the engine.

7. The invention according to claim 6 wherein the apparatus further has an elongated tube through which the viewing cable is insertable for guiding the cable toward the component to be inspected.

8. The invention according to claims 6 or 7 wherein said means for attaching the viewing end of the cable to the rotating component includes a hook at the end of the cable.