Patent Application
20160273380
This claims the benefit of German Patent Application DE 10 2015 204 893.4, filed Mar. 18, 2015 and hereby incorporated by reference herein.
The present invention relates to a protective device for a turbomachine. The invention also relates to an aircraft engine.
During the operation of a turbomachine, thermal and mechanical stresses, in particular, can cause structural failure of individual components. For example, a rotor blade of a rotor blade ring may break during operation of the turbomachine. Due to the high peripheral speed of the rotor blade caused by the rotation of the rotor blade ring, a fragment broken off in this manner may radially penetrate a casing element of the turbomachine and be ejected therefrom. Thus may cause further damage to the turbomachine. However, damage may, in particular, also be caused in the vicinity of the turbomachine. For example, if the turbomachine is a gas turbine of an aircraft engine, a radially ejected fragment may injure the passengers of the aircraft and/or damage the aircraft itself. This may also affect systems that are critical to the airworthiness of the aircraft. For example, hydraulic lines of the aircraft may be damaged to such an extent that the control surfaces of the aircraft are then controllable only to a limited extent.
In order to at least substantially prevent a casing element of the turbomachine from being radially penetrated by a fragment of a component of the turbomachine in the event of a structural failure of this component, turbomachines, in particular gas turbines, are provided with protective devices having a containment ring that is disposed on the radially inner side of a casing element of the turbomachine. The containment ring is intended to prevent a broken-off fragment of a component from being ejected radially from the turbomachine.
EP 1 918 531 A2, for example, describes such a containment ring for the fan casing of a gas turbine engine. The containment ring is formed by a single-piece fiber composite ring having a ceramic cover which is arranged on the inner surface facing the fan blades of the gas turbine engine and formed by individual panels embedded in a ductile material. Upon impingement of detached blade fragments, a crack network corresponding to the arrangement of the sintered starting ceramic particles is formed in the ceramic cover, whereupon the ceramic cover disintegrates into small pieces. In the process, the ceramic cover absorbs a large part of the kinetic energy of the impinging blade fragment. This is intended to prevent secondary damage to the containment ring.
Reference is also made to the later-published European Patent Application EP 2 876 262 A1, which relates to a containment system for a fan of an aircraft engine, as well as to the two publications DE 699 08 540 T2 and U.S. Pat. No. 5,336,044A, which also relate to containment systems.
The containment ring described in EP 1 918 531 A2 has the disadvantage that it is particularly costly to manufacture and install. The single-piece fiber composite ring and the ceramic cover must be manufactured separately by a complex process and must subsequently joined together during assembly. A single-piece fiber composite ring is heavily structurally loaded by expansion as a result of thermal loading. This may limit the protective effect of the containment ring. Another consequence of this is that a single-piece fiber composite ring can only be used in turbomachines of limited size.
It is an object of the present invention to provide a protective device for a turbomachine and an aircraft engine which are particularly inexpensive to manufacture and install.
A first aspect of the present invention relates to a protective device for a turbomachine, in particular a gas turbine, having a containment ring which is disposed on the radially inner side of a casing element of the turbomachine and which at least substantially prevents the casing element from being penetrated by a fragment of a component of the turbomachine in the event of a structural failure of this component. In accordance with the present invention, the containment ring is composed, at least in the circumferential direction, of a plurality of ring segments which are form-fittingly interconnected. The multi-piece containment ring provides particular ease of installation even in the case of undercut casing geometries, where known, single-piece containment rings cannot be used or can only be used with great difficulty. The ring segments are coupled to each other by the form-fit. Thus, a full containment function is possible because of the ability to also absorb tensile loads in a containment event. Structural failure of components and the at least substantial prevention of the escape of associated fragments in the radial direction is referred to as a containment event. The form-fit should be designed such that in a containment event, an individual ring segment is not or only insignificantly forced out of the containment ring by the fragment impacting on the ring segment. To this end, the holding force of the form-fit and/or the structure of the form-fit may be selected such that the holding force and/or the structural integrity are/is greater than the force predicted to be exerted on the containment ring by an impacting fragment. In order to provide a form-fit, the individual ring segments may merely be contacted at their end faces that are disposed circumferentially adjacent to each other. The containment ring will then hold together inasmuch as the individual ring segments are jammed against one another at the contacting end faces in response to a force acting in a radial direction.
Preferably, the individual ring segments of the containment ring are disposed on the radially inner side of a casing element in such a manner that they cannot leave their intended normal position during a normal operating condition; i.e., during an operating condition without failure event. In particular, none of the ring segments should be able to fall out of the substantially circular containment ring. This may be achieved, for example, by providing that the ring segments forming the containment ring be bounded radially outwardly by the casing element that they are intended to protect, axially by a clamping device, which will be described in more detail below, and radially inwardly by a cover structure made of, for example, sheet metal, such as a liner. The radially inwardly disposed cover structure can prevent the ring segments from falling out radially inwardly. Furthermore, in the containment event, the cover structure can contribute to better distribution of the impact force over the ring segments.
The axis of the turbomachine, and thus also the radial direction spatially orthogonal thereto, is defined, for example, by the axis of rotation of a central shaft of the turbomachine. The individual ring segments are preferably made of a high-strength material. In the event of a structural failure of the component, the ring segments distribute the kinetic energy of the impacting fragment over a large area. This, first of all, prevents penetration of the casing element disposed radially outwardly of the respective ring segment. The containment ring, composed of a plurality of ring segments, is particularly inexpensive to manufacture and install, and particularly less expensive than a single-piece containment ring.
The turbomachine may include, for example, an airfoil ring, in particular a rotor blade ring and/or a stator vane ring. The protective device including the containment ring at least substantially prevents airfoil ring fragments of the turbomachine from escaping radially from a casing of the turbomachine. The containment ring may extend over the same axial distance as an airfoil ring. However, the containment ring may also extend axially beyond the airfoil ring, and in particular also over respective stators of the turbomachine. This markedly enhances the protective effect of the protective device. It is also possible to arrange a plurality of containment rings axially adjacent to each other. It is also conceivable that one containment ring may extend over the entire length of the turbomachine casing. The use of a containment ring having a particularly large extent and/or a plurality of containment rings arranged adjacent to each other makes it possible to protect a particularly large area of the turbomachine from being penetrated by a broken-off fragment in the event of a structural failure of a component.
A further risk posed by a structural failure of a turbomachine component is that a fragment broken off from this component may get stuck in the turbomachine casing and/or in the containment ring. In this case, the fragment may project into the interior of the turbomachine in such a way that other rotor blades of a rotor blade ring will strike against the inwardly projecting fragment. This may cause further fragments to break off, which are then prone to being ejected radially from the casing of the turbomachine. This results in considerably increased structural loading of the turbomachine and/or in a significantly increased risk of fragments escaping radially from the turbomachine. Therefore, a ring segment of the protective device according to the present invention may advantageously be designed such that in the event of an impact of a broken-off fragment of the turbomachine, the ring segment may deform to such an extent that no fragment stuck in the ring segment can project into the interior of the turbomachine. This prevents the interior from being further damaged by the broken-off fragment. Such deformation may, in particular, be confined to a localized area and/or have a curved shape. In addition, a bulge formed in the material of a ring segment as a result of an impact of a broken-off fragment may seal an opening formed in the radially outer casing element.
In another advantageous embodiment of the protective device according to the present invention, some play is provided between the individual ring segments in the circumferential direction to allow compensation for expansions of the ring segments caused by thermal loading. In particular, the play also makes it possible to compensate for differences in the thermal expansion characteristics between the casing element and the containment ring. Combustion processes can produce particularly high temperatures in the interior of a turbomachine. These temperatures cause particularly high thermal loading of the containment ring, thereby also causing expansion. However, the play should be kept to a minimum. For example, when in the normal position, the ring segments should remain in abutment under normal thermal loads. Thus, no view-through gap should be present, even when the temperatures are particularly low, for example, when the turbomachine is not in operation. The play must be carefully dimensioned according to the inside temperature expected during operation of the turbomachine and according to the coefficient of expansion of the material of the ring segments. A coefficient of expansion of the material of the casing element and its expected temperature during operation of the turbomachine may also be taken into account. In particular, the play should be smaller than the fragments to be expected in the event of a structural failure of a component. For example, the play should be smaller than the respective tips of blades of the airfoil ring. In this way, fragments are advantageously prevented from entering the gap between two ring segments and getting jammed therein and/or from penetrating through the containment ring and subsequently through the casing of the turbomachine. In the case of a plurality of rows of ring segments arranged adjacent to each other, a corresponding play may advantageously also be provided axially between these rows.
In another advantageous embodiment of the protective device according to the present invention, the ring segments are form-fittingly interconnected by notched engagement and/or toothed engagement. Due to the notched engagement and/or the toothed engagement, individual ring segments are connected to other ring segments in a manner that allows the force of an impacting fragment to be distributed over a plurality of ring segments, and thus over a particularly large area. This markedly enhances the protective effect of the containment ring and, in addition, makes the containment ring particularly easy to install. Moreover, a notched engagement and/or a toothed engagement makes it possible to particularly reliably prevent individual ring segments from being forced out of the containment ring by an impacting fragment. This also markedly enhances the protective effect of the containment ring.
In another advantageous embodiment of the protective device according to the present invention, the containment ring is axially clamped by a clamping device. This allows the containment ring to be fixed in position in a particularly simple manner. Moreover, as a result of a considerable wall friction in the case of a clamping device, the tensile forces in the ring segments are smaller than in an equivalent single-piece containment ring due to the redirection of forces. At the same time, this provides a particularly simple way of establishing a predetermined holding force by which an individual ring segment is held in its position. Using the clamping device, it is possible, in particular, to adjust the strength of a notched engagement and/or a toothed engagement. In this manner, the containment ring having the plurality of ring segments can be given substantially the properties of a closed containment ring.
In another advantageous embodiment of the protective device according to the present invention, the clamping device includes at least one stator, in particular a root of a stator vane, a casing projection, a hook and/or a baffle, which at least partially engages the containment ring axially. Thus, existing components of the turbomachine can be used as part of the clamping device, which makes the clamping device particularly inexpensive to manufacture. Moreover, the space requirement of the protective device can thereby be kept particularly low.
In another advantageous embodiment of the protective device according to the present invention, the containment ring has at least two rows of ring segments, with at least the axially adjacent side faces of the ring segments being interconnected by a notched engagement, a toothed engagement and/or a staggered arrangement along the circumferential direction. On the one hand, this prevents rotation of the at least two rows relative to one another. On the other hand, this inventive design produces a self-locking action, in particular a form-fit-type self-locking action, between the two rows with respect to one another. Moreover, the respective rows are held in a defined position. In addition, this makes the containment ring particularly easy to install. By means of the notched engagement, toothed engagement and/or staggered arrangement of the ring segments with respect to one another in accordance with the present invention, individual ring segments and individual rows are connected to other ring segments and other rows in a manner that allows the force of an impacting fragment to be distributed over a particularly large area. This markedly enhances the protective effect of the containment ring. A plurality of rows of ring segments makes it possible to use axially smaller ring segments, thereby notably reducing the manufacturing costs. Moreover, this makes it possible to particularly easily, in particular modularly, increase the axial extent of the containment ring so as to protect a larger portion of the turbomachine casing from being penetrated by broken-off fragments from the interior of the turbomachine.
In another advantageous embodiment of the protective device according to the present invention, the at least two rows have an undulating profile at their side faces that are adjacent each other along the circumferential direction. This enables particularly effective self-locking of the at least two rows against rotation relative to each other. Moreover, the undulating profile of the adjacent side faces results in a particularly uniform transfer of force at these side faces.
In another advantageous embodiment of the protective device according to the present invention, the at least two rows have a sawtooth profile at their side faces that are adjacent each other along the circumferential direction. Ring segments having side faces with such a profile are particularly inexpensive to manufacture.
In another advantageous embodiment of the protective device according to the present invention, the at least two rows have corresponding shoulders at their side faces that are adjacent each other along the circumferential direction. Such shoulders provide particularly effective self-locking against rotation of the at least two rows relative to each other and are capable of absorbing particularly high forces. Moreover, a containment ring of this type is particularly easy to install.
In another advantageous embodiment of the protective device according to the present invention, the ring segments have corresponding indentations and/or projections at their contacting side faces and/or end faces at least in portions thereof. A form-fitting connection of this type is particularly inexpensive and particularly easy to produce. Furthermore, it is particularly easy to obtain the desired strength for such a form-fit.
In another advantageous embodiment of the protective device according to the present invention, the containment ring is disposed radially outwardly of an abradable coating for a stator vane ring. The space required for the protective device may be particularly small when the containment ring is disposed in a clearance, in particular a gap, of the abradable coating. This also makes it possible to use a particularly hard material for the ring segments, since this material and the ring segments are separated by the abradable coating from the stator vanes.
In another advantageous embodiment of the protective device according to the present invention, the ring segments are formed from a ceramic material, in particular a fiber-reinforced ceramic material, an oxide ceramic material, and/or a silicon carbide. Silicon carbide is also a kind of ceramic material. A ceramic material may be particularly rigid, lightweight and temperature-resistant. This makes ceramic particularly suitable for the ring segments. Moreover, ceramic may be thermally insulating, in particular depending on its porosity. Thus, the containment ring may also be used as thermal insulation, also referred to as thermal insulation packing. In some instances, this may advantageously eliminate the need for additional elements for thermal insulation. This makes the turbomachine particularly inexpensive and lightweight. In addition, it is possible to reduce space requirements. A fiber-reinforced ceramic material is particularly resistant to penetration. Moreover, the fiber reinforcement may ensure that an impact of a fragment on a ring segment does not cause individual pieces to spall off the ring segment, which otherwise could cause further damage in the turbomachine. This is particularly advantageous when a ring segment is locally deformed by an impact. An oxide ceramic material is less brittle and has a higher ductility than non-oxide ceramic materials and, in particular, provides better thermal insulation. Silicon carbide is particularly hard and particularly resistant to very high temperatures.
In another advantageous embodiment of the protective device according to the present invention, each ring segment extends circumferentially over 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°, 95°, 100°, 105°, 110°, 115°, or 120°. The smaller the extent of a ring segment, the less expensive it is to manufacture. In particular, it is possible to use smaller manufacturing machines. In the case of larger ring segments, a smaller number of parts has to be installed, which makes installation particularly easy. However, this effect is limited by the increasing weight of an individual ring segment. Furthermore, larger ring segments distribute the load resulting from impact of a fragment over a larger area, thereby enhancing the protective effect. However, this advantage may also be obtained with smaller ring segments by means of a suitably designed form-fitting connection. In addition, in the case of larger ring segments, and thus a smaller number of ring segments, it is particularly difficult to provide sufficient play for thermal expansion between the ring segments. In particular, in the case of particularly large ring segments, the required play between two ring segments can become so large that a view-through gap is created and/or that a gap is present through which fragments may penetrate or in which fragments may get stuck.
Considering these opposite effects, a good compromise for the size of an individual ring segment is 30°. The optimal extent of a ring segment in the circumferential direction may preferably also be determined empirically and/or analytically for each turbomachine.
In another advantageous embodiment of the protective device according to the present invention, the containment ring is disposed radially between at least one airfoil ring of the turbomachine and the casing element. The airfoil ring may, for example, be part of a fan, a compressor and/or a turbine of the turbomachine. Such positioning of the containment ring makes it particularly easy to install. The containment ring may, for example simply be introduced between the casing element and the airfoil ring.
A second aspect of the present invention relates to an aircraft engine having at least one protective device as described above. This makes the aircraft engine particularly inexpensive and safe. The features and advantages derived from the protective device according to the first inventive aspect are apparent from the descriptions of the first inventive aspect. Advantageous embodiments of the first inventive aspect are considered to be advantageous embodiments of the second inventive aspect and vice versa.
Other features of the present invention will become apparent from the exemplary embodiments, and from the drawings. The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the exemplary embodiments may be used not only in the particular stated combination, but also in other combinations, without departing from the scope of the present invention.
In the drawing,
Further provided is a cover structure 112 to ensure that ring segments 16 do not leave their intended position in containment ring 12, even in a condition where no forces act thereupon as a result of a containment event. This cover structure 112 bounds ring segments 16 radially inwardly, thereby closing the space in which the ring segments are received. The cover structure 112 may be a thin sheet-metal component, in particular a liner which may have an abradable coating 114 for the radially outer tips of rotor blades 116, as schematically shown. In the containment event, such a cover structure causes a certain distribution of the impact forces over ring segments 16.
Containment ring 12 is characterized in that it is composed, at least in the circumferential direction, of a plurality of ring segments 16 which are form-fittingly interconnected. The form-fit is created in particular at facing end faces 40 of ring segments 16. In
The containment ring 12 assembled from ring segments 16 obtains its containment function by means of a form-fit featuring a circumferential-type notched engagement. Some play is provided between ring segments 16, the play being just sufficient to allow compensation for thermal expansions of containment ring 12. This play is provided, in particular, in the circumferential direction between end faces 40 of ring segments 16, and is so small no view-through gap can form under any conditions. Furthermore, the play also makes it possible to compensate for differences in the thermal expansion characteristics of casing element 14 and containment ring 12. This is not as easily possible with a similar but single-piece continuous containment ring.
Containment ring 12, respectively ring segments 16, are made of a ceramic material. A ceramic material may be exceptionally rigid, temperature-resistant and thermally insulating. This makes it possible, in particular, to dispense with an additional thermal insulation packing, whereby the engine may be particularly lightweight. However, the production of particularly large ceramic parts can be very costly. Therefore, containment ring 12, which is composed of a plurality of ring segments 16, is also particularly inexpensive to manufacture.
Multi-piece containment ring 12 is also particularly easy to install, even in the case of undercut casing geometries. Individual ring segments 16 can be easily introduced or inserted. In particular, ring segments 16 can be introduced between an abradable coating for a stator vane ring and the respective casing elements 14. This is not as easily possible with a single-piece containment ring. In the case of undercut casing geometries, a single-piece containment ring can, in any case, only be installed with very high effort.
By means of a circumferential-type notched engagement and/or locking engagement of ring segments 16 with each other, it is possible to give containment ring 12 substantially the properties of a closed ring. In this manner, the so-configured containment ring 12 obtains its full containment capability. In addition, this enables the individual ring segments 16 to absorb tensile forces in the circumferential direction, such as may occur in a containment event. In the event of an impact of a fragment upon structural failure of a component of the turbomachine, the containment ring 12 composed of a plurality of coupled ring segments 16, contains these fragments and prevents casing element 14 from being locally sharply penetrated by fragment edges.
This containment capability of containment ring 12 may be further enhanced by a clamping device 20. To this end, clamping device 20 may include a stator 24 having circumferential ribs. Stator 24 bears axially against containment ring 12 and clamps it against casing element 14. As a result, ring segments 16 are radially restrained from movement in the tangent plane. Alternatively or additionally, it is also possible to use casing element 14 and/or other components as elements of clamping device 20. Clamping device 20 clamps ring segments 16 axially, thereby creating a considerable wall friction. Moreover, due to the resulting redirection of forces, the tensile forces in ring segments 16 are smaller than in an equivalent single-piece containment ring.
In particular, clamping device 20 may contribute to the containment capability of containment ring 12 by preventing or at least substantially limiting axial displacement of individual ring segments 16 in the containment event. In the containment event, radially outwardly acting forces are exerted on containment ring 12 by the impacting component. Since, as explained above, the individual ring segments 16 of containment ring 12 act in the manner of a closed ring because of their form-fitting connection, containment ring 12 is subjected to tensile stress. In embodiments such as are illustrated, for example, in
In
In the embodiment shown in
In the embodiment shown in
Similarly to the play in the circumferential direction between end faces 40 of ring segments 16, an axial play may be provided between adjacent side faces 32, 34, 36 of the two rows 30. This play makes it possible to compensate for differences in the thermal expansion characteristics of casing element 14, containment ring 12, rows 30 and/or other elements of the turbomachine, particularly in the axial direction.
It is particularly advantageous to use the inventive protective device 10 in an aircraft engine. A failure of the containment of an aircraft engine, in particular, can result in significant safety hazards. Protective device 10 makes it possible to provide such containment in a particularly inexpensive manner.
| Number | Date | Country | Kind |
|---|---|---|---|
| DE102015204893.4 | Mar 2015 | DE | national |
