Patent Application
20130199040
This invention relates to a device and a method for treatment of high-pressure turbine blades of a gas turbine in order to remove deposits and/or foreign matter coatings in the area of cooling-air recesses or cooling-air holes on the high-pressure turbine blades.
Stator vanes and rotor blades in the high-pressure turbine area feature film cooling of the surface for protection of component surfaces which are in contact with the hot gas flow. This cooling is generated by a varying number of cooling-air holes of the blade.
During operation of an engine, the cooling-air holes are partially or completely closed by various influences.
This leads to a restriction or to a partial loss of the film cooling for the stator vane and rotor blade surfaces, which can result in the destruction of the component. For these reasons, the cooling-air holes on the stator vanes and the rotor blades must be restored to their proper state in the course of repair measures.
To do so, the engine must, according to the state of the art, be removed from the aircraft and transferred to dedicated and authorized workshops. These workshops require a level of equipment almost comparable to that for new part production facilities. In addition, the aircraft must be equipped with a replacement engine for the duration of the engine repair work. The costs for these measures are considerable.
The object underlying the present invention is to provide a device and a method of the type specified at the beginning which are simple to implement and simple in design and which permit dependable clearing and/or treatment of the cooling-air holes on high-pressure turbine blades of a gas-turbine engine.
It is a particular object of the present invention to provide solution to the above problematics by a combination of the features of the independent Claims. Further advantageous embodiments of the present invention become apparent from the sub-claims.
In accordance with the invention, the method for clearing the cooling-air holes on high-pressure turbine blades is performed on a non-removed aircraft engine. It is thus not necessary in accordance with the invention to replace an engine in an aircraft or to transfer the engine to a workshop; instead the method in accordance with the invention is performed on the installed engine.
In accordance with the invention, in the non-removed state of the engine the device in accordance with the invention, i.e. a manual, semi-automated or automated controllable tool, is used to remove the deposits and/or foreign matter coatings only at those points at which they should be removed. The deposits and/or foreign matter coatings are cleaned off by blasting using a compressed fluid jet. The fluid used can be water and/or water with additives, oil, carbon dioxide or nitrogen. Furthermore, the use of high-energy light (laser) is suitable for removing the foreign matter coatings.
After cleaning off or removal of the deposits and/or foreign matter coatings, it is favourable in a development of the invention to conduct additional rinsing or cleaning of the high-pressure turbine blades, in particular also of the interiors of the high-pressure turbine blades, for example by means of a gas flow, for example air, to rinse out or expel where necessary any particles entering through the cooling-air recess.
In accordance with the invention, the method is preferably conducted under visual control, for example with the aid of an endoscope.
Furthermore, it is particularly favourable in accordance with the invention when the tools and/or equipment needed to perform the method are inserted into the area of the high-pressure turbine through boroscope apertures provided in the gas turbine or through burner apertures of the combustion chamber.
The guiding of the tool and/or equipment to the area to be treated is achieved in accordance with the invention by a device having the capability to change its shape individually due to the use of shape memory alloys. For treatment, the fuel injection nozzles of the combustion chamber for the respective sections are removed. An insert sleeve is inserted into the resulting aperture, through which sleeve the tool and/or device is introduced radially. The latter has a 90° angle and is screwed into the aperture of the removed fuel injection nozzles. The tool and/or device is pushed radially and axially through the insert aid and hence directly routed to the appropriate section. The device is controlled by shape memory wires which act as “artificial muscles” in that they contract after heating and thereby bend the device. After cooling, they relax again and resume their original shape. In the device, two wires are arranged offset by 90° on a hose, and positively braced at their start and end. The hose has a stiffness sufficient to apply a resetting force necessary to restore the wires to their original shape after cooling. The wires are pressed using a shrink-on hose directly onto the carrier hose and hence guided to achieve the maximum possible deformation. Thanks to the 90°-offset wires, the tool moves on a circular track. The wire can be positioned accordingly with a controlled heating of the resistor. The combustion chamber is divided into sections, so that the accessibility of all sections of the stator vanes for the tool is assured. By the tangential movement of the tool on a circular track, the cooling-air holes on the leading edge of the stator vanes in this section are reached and then treated. By changing the tool head it is possible to navigate optionally also between the individual stator vanes and to treat the cooling-air holes on the suction and pressure sides. In this way, the rotor blades located axially behind the stator vanes can also be reached and their cooling-air holes can likewise be treated using this method.
The guiding of the tool and/or equipment to the area to be treated can also be achieved in accordance with the invention by using rail systems to be inserted and which can be of rigid, flexible or also volume-increasing design. The rail systems are designed such that individual and prefabricated tube sections are successively inserted through the boroscope aperture or the aperture of the removed fuel injection nozzles. The tube sections should here ideally be rigidly connected to one another. The device is based on the fact that the appropriate area to be cleaned is approached depending on the preceding visual inspection. In the same way, prefabricated elastic devices can be inserted into the combustion chamber and inflated using compressed air. With these devices, the tool proper can then be guided to its intended destination.
It is furthermore possible to use cable pull systems for guidance and navigation of the tools and/or equipment inserted into the engine through various apertures. To do so, in accordance with the invention a device should be fastened above the boroscope aperture or an aperture of a removed fuel injection nozzle and/or the engine outlet, and a further device also fastened to the engine outlet for guidance of the cable system. The tool and ideally an optical unit is fastened to the cable system and is guided by the movement of the cable to the appropriate blade.
After the removal of engine attachments too, such as fuel injection nozzles, igniter plugs etc., the aforementioned apertures are obtained and can be used in accordance with the invention. The high-pressure turbine area is readily accessible through these apertures, without additional or extensive removal work being necessary. The method in accordance with the invention is thus distinguished by rapid and inexpensive performability. By restoring the function of the cooling-air holes on the engine while it is installed in the aircraft, any removal of the engine and any repair in specially authorized workshops, as well as installation of a leased or substitute engine in the aircraft, are avoided. The method in accordance with the invention thus results on the one hand in a considerable cost reduction and on the other hand in a considerable shortening of the down time of the aircraft.
The present invention is described in the following in light of the accompanying drawing, showing exemplary embodiments. In the drawing,
To dispense with the need to remove engines, visual inspections are conducted using a boroscope or flexoscope. This thin tube, which originates in medical endoscopy, is equipped on the inside with an optical lens which can be inserted into a cavity to be tested. Optic fibers enclose the optical unit and supply the light from a connected source to the point of inspection, from where a reflected image passes through the optical unit back to the eye of the beholder or into a camera with connected monitor. In this way, boroscopic testing supplies images of places that would never have been accessible without removing major components.
An aircraft engine has, for boroscopic investigation, a plurality of special apertures allowing the optical unit to be guided directly to the point to be tested, for example into any individual compressor stage. A single aperture is sufficient for the latter, since the blades to be tested can be rotated manually in front of the optical unit of the boroscope. Rigid components without direct access are inspected using a flexoscope. Instead of the rigid tube, this tool has a flexible hose in which glass fibers replace the optical lens. With a working length of several meters, it can also be used to inspect components not reachable in a straight line.
Low-pressure turbine rotor blades, stage 2, trailing edge.
The manipulator 6 can be linked to a tool for removing and extracting/analysing particles. A display and actuation unit or the control unit 7 permits checking and controlling of the work by means of the monitor 9.
It is understood that the representation in
The invention makes it possible to perform cleaning of the cooling-air holes without removing the engine from the aircraft. To do so, miniaturized tools are supplied to the repair/cleaning area via boroscope apertures located on the engine. It is possible with the aid of the boroscope to remove particles from contamination using a tool and to collect them in combination with a local extraction device. An analysis of the contamination particles permits differentiated selection of an appropriate cleaning medium. With the aid of the boroscope, the suitable cleaning medium (pasty form or snow blasting or dry ice blasting) is applied to the affected area of the high-pressure turbine stator vane or rotor blade. By specific selection of the cleaning medium, initial dissolving of the contamination or a neutralization of the adhesive mechanism between component and contamination particles is achieved. By mechanical reworking, e.g. by a micro-blasting medium supplied with the aid of the boroscope in combination with an effective extraction device, the component surface or the cooling-air hole is cleaned. Alternatively to mechanical reworking, it is also possible to use a cleaning fluid adapted to the selected cleaning medium. With the aid of the boroscope, this fluid can be targeted at the area to be cleaned. Using an extraction device, a major part of the dissolved contamination particles together with the cleaning fluid are extracted. A concluding visual check ensures that the area to be cleaned is again largely adapted to drawing requirements and hence restored to a proper state.
The invention makes it possible to perform the clearing of the cooling-air holes without removing the engine from the aircraft. To do so, miniaturized tools are moved to the repair/treatment area via the boroscope apertures located on the engine. A concluding visual inspection ensures that the area to be treated is again adjusted largely to comply with drawing requirements and hence restored to its proper state.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 002 275.1 | Feb 2012 | DE | national |
