Multilayer Shielding Ring For A Flight Driving Mechanism

Abstract

A shielding (6) of a turbine housing (3) of an aircraft engine against radial escape of blade fragments, especially for a high-speed low-pressure turbine, is characterized in that the shielding (6) is embodied as a rigid ring-shaped component of several layers (8). Through the decoupling of the containment function from the design of the turbine exhaust gas channel, which is fabricated as a cast part, the disadvantages of the prior art are avoided. Particularly, the design of the turbine exhaust gas channel can be carried out in a cost- and weight-optimized manner.

Description

[0001] The invention relates to a shielding of a turbine housing or casing of an aircraft engine against the radial escape of blade fragments according to the preamble of the patent claim 1.

[0002] In conventional low-speed low-pressure turbines, the so-called containment protection, i.e. the shielding of the housing or casing against possible radially outwardly ejected blade parts or blade fragments, is to be examined in connection with the designing of the housing. Especially for the connection of the low-pressure turbine (LPT) onto the turbine exhaust gas housing or casing (Turbine Exhaust Case TEC), which is generally embodied as a cast part, often only an examination of the wall thickness is necessary. This examination generally determines that the wall thickness of the connection LPT/TEC is sufficiently strongly dimensioned also as a containment protection.

[0003] Such a shielding from the prior art is shown in a cutaway portion view in FIG. 2. Thereby the low-pressure turbine 1 is shown with turbine blades 2, which are arranged within a turbine housing or casing 3. Thereby the turbine blades are arranged axially after a compressor that is not shown and a combustion chamber that is not shown, and are located on a turbine disk that rotates about the engine axis. The turbine housing 3 is connected via a flange 5 with the turbine exhaust gas channel 10. The turbine exhaust gas channel 10 of the prior art is embodied as a cast part, which also comprises a containment function due to the existing material thickness. That is to say, in the unlikely case of an engine damage with loss of turbine blades or blade parts, the turbine exhaust gas channel with containment function serves to prevent the escape of the blade parts out of the engine housing and thereby to avoid possible damages of the aircraft airframe. In FIG. 2, the impact area that is determinative for the design is identified by the straight lines enclosing an angle .alpha..

[0004] For achieving the required specifications, future engine concepts need low-pressure turbines with high AN.sup.2, high turbine inlet temperatures, and a compact short structure.

[0005] In high-speed low-pressure turbines for such modern engine concepts, the containment protection is, however, a particular design criterium, because the regular cast part thickness of the turbine exhaust gas channel is no longer sufficient to prevent a possible through-penetration of loose blade parts due to the higher momentum of the blade parts. Therefore, according to the present state, no material-, cost- and weight-optimized low-pressure turbine/turbine exhaust gas channel (LPT/TEC) connection is possible. Rather, the material selection and material thickness of the LPT/TEC connection is determined by the required containment thickness and not by the optimized LPT/TEC connection. The material selection is also determined by the higher requirements for the cast material in the containment area and is thereby made more expensive.

[0006] Nonetheless, a containment solution in the area of the low-pressure turbine is known from the U.S. Pat. No. 5,328,324. Therein a glass fiber woven hose is proposed, which is laid onto a carrier element in a multiply-folded configuration, quasi as a collar, whereby the carrier element is located on the outer side of the turbine housing above the low-pressure turbine. In that regard, the glass fiber woven material is produced from a continuous fiber and is heat resistant. The intactness of the continuous fiber is decisive for the functioning of this containment protection. The glass fiber woven hose is thereby dimensioned so that it lies tightly on the carrier element. However, here no special solution for the low-pressure turbine/turbine exhaust gas channel connection is presented. Disadvantageous in this solution, on the one hand, is the unfixed construction of the collar, which is highly sensitive to external influences, for example mechanical influences, moisture, etc. It is a further disadvantage that damages of the continuous fiber of the glass fiber woven hose are not easily noticed and can lead to a total failure of the containment protection in case of need.

[0007] Therefore, it is the underlying object of the invention to avoid the disadvantages of the known solutions of the prior art, and to make available an improved solution for a containment protection on the LPT/TEC connection especially of high-speed low-pressure turbines.

[0008] This object is achieved according to the invention by a multilayer shielding for an aircraft engine with features of the patent claim 1. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0009] The inventive shielding of a turbine housing of an aircraft engine against radial escape of blade fragments, especially for a high-speed low-pressure turbine, is characterized in that the shielding is embodied as a rigid ring-shaped component of several layers. Thereby the ring-shaped shielding can be arranged radially within or outside of the turbine housing. In connection with mounting on the turbine housing, the shielding can also direct cooling air, for example from the fan stream flow, in a targeted manner onto the outer skin of the housing. It is further possible that the ring-shaped shielding consists of several segments, whereby production and assembly are simplified. Due to the stiff embodiment, the shielding is protected against external influences, and can be embodied in a self-supporting manner.

[0010] An advantageous embodiment of the inventive shielding provides that the shielding is arranged on the turbine exhaust gas channel. By the decoupling of the containment function from the design of the turbine exhaust gas channel, which is fabricated as a cast part, the disadvantages of the prior art are avoided. Especially the design of the turbine exhaust gas channel can be carried out in a cost- and weight-optimized manner, i.e. more-economical materials and material thicknesses can be utilized here, in comparison to what would be the case with an integrated containment function. The containment function is then exercised alone by the ring-shaped multilayer shielding.

[0011] An advantageous embodiment of the inventive shielding provides that the shielding is embodied as a forged component. This makes possible a multilayer construction with selection of suitable material layers. In that regard, on the one hand the strength is a defining factor, as well as the temperatures present in the area of the low-pressure turbine on the housing or on the LPT/TEC connection. In that regard, the possibility of the temperature expansion is to be taken into account for a shielding ring having multiple parts in the circumferential direction.

[0012] A further advantageous embodiment of the inventive shielding provides that the shielding is arranged within the turbine housing. On the one hand this avoids interfering additional structural components outside of the turbine housing, and on the other hand it is hereby prevented that the housing or the LPT/TEC connection is penetrated through in the case of a blade damage, whereby the costs of an engine failure rise further.

[0013] Still another advantageous embodiment of the inventive shielding provides that the shielding is embodied as a flow guide element. This can be the case both for the application of the shielding within or outside of the housing. Thereby additional flow guide elements can be applied on the shielding, or alternatively the shielding itself is formed or mounted in a flow-advantageous manner.

[0014] Still a further advantageous embodiment of the inventive shielding provides that the shielding is embodied as a heat shield. This is especially necessary for the installation in the flow channel, i.e. within the turbine housing. However, this can also be suitable for the purpose for installation on the outer circumference of the turbine housing, in order to prevent injuries due to burns on hot engine components during maintenance work.

[0015] An advantageous embodiment of the inventive shielding provides that the layers are constructed of different materials. For example, highly heat resistant forgeable alloys come into consideration as materials. Thereby the strength characteristics, temperature expansion and weight of the shielding can be influenced to the desired extent. This is especially expedient in the sense of a weight- and cost-optimization.

[0016] An advantageous embodiment of the inventive shielding provides that the layers comprise different thicknesses. Like the material selection, the strength and the weight of the shielding can also be optimized by the selection of the layer thickness, and thereby the costs of the component can be reduced.

[0017] An advantageous embodiment of the inventive shielding provides that the layers are adapted or tuned to one another in a vibration-optimized manner. Thereby the layers of the multilayer shielding ring are connected in a resonance-free manner in the shielding housing. Hereby both the vibration characteristics of the shielding alone, as well as the vibration characteristics of the components coupled with the shielding, can be taken into consideration. Furthermore, the variation of the vibration characteristics due to fluid flow thereon and temperature expansion can be taken into consideration in the design and adaptation or tuning of the layers.

[0018] Finally an advantageous embodiment of the inventive shielding provides that the shielding comprises an enclosure or mounting frame for different functional layers. In that regard, enclosure or mounting frame can also encompass a shielding housing with which different layers are connected in a joint-technical manner. In that regard, the ring-shaped layers can be encased or enclosed or surrounded quasi from three sides, and if applicable can also be received in a floating manner in the mounting frame.

[0019] Further measures improving the invention are explained more closely in the following together with the description of a preferred example embodiment of the invention in connection with the figures. It is shown by:

[0020] FIG. 1 an advantageous embodiment of the present invention, schematically in a cutaway portion;

[0021] FIG. 2 a schematic partial sectional illustration of a shielding of the prior art.

[0022] In the depicted figures, the same or similar components are identified with the same reference numbers. Direction indications refer to the axes of the aircraft engine.

[0023] FIG. 1 schematically shows in the manner of a cutaway portion, an advantageous embodiment of an inventive shielding 6 on a high-speed low-pressure turbine 1. In that regard, the compressor which is not shown in the drawing and the combustion chamber, as well as the high- and medium-pressure turbine which is similarly not shown, are located in the drawing plane on the left hand side, that is to say upstream with regard to the flow. Thereby the FIG. 1 shows a cutaway portion of a half-section.

[0024] In FIG. 1, a part of a turbine blade 2 is illustrated, which is arranged within a turbine housing 3 that surrounds the turbine stage in the circumferential direction. The turbine housing 3 is connected with the turbine exhaust gas channel 4 or connected thereto via a material-technically optimized flange connection 5.

[0025] The shielding 6 is arranged on the connection of the low-pressure turbine 1 to the turbine exhaust gas channel 4 within the turbine housing 3. A flange 9 protrudes inwardly in the radial direction on the turbine exhaust gas channel 4, and the shielding 6 or the shielding housing 7 is flange-connected on the flange 9.

[0026] The shielding 6 or the containment ring, which is illustrated L-shaped in section and is ring-shaped in the circumferential direction, is embodied as a multilayer forged part in the present example embodiment. In that regard, the two layers 8 of the shielding 6 are received in a shielding housing 7 and are connected therewith in a forging-technological manner. Both the type of the alloy as well as the layer thickness/number of layers differ from one another in the two layers 8 shown in the example embodiment. In that regard, the resonance-free shielding 6 in the present example embodiment also comprises integrated heat-shield and flow-guiding function in addition to the containment function. The containment function is presently not integrated in the connection of low-pressure turbine 1/turbine exhaust gas channel 4, whereby this connection can be embodied as a weight-optimized cast part.

[0027] The invention is not limited in its embodiment to the preferred example embodiment set forth above. Rather, a number of variants is conceivable, which also makes use of the solution claimed in the patent claims, also in embodiments of a different type.

Claims

1. Shielding (6) of a turbine housing (3) of an aircraft engine against radial escape of blade fragments, especially for a high-speed low-pressure turbine (1), characterized in that the shielding (6) is embodied as a rigid ring-shaped component of several layers (8).

2. Shielding (6) according to patent claim 1, characterized in that the shielding is arranged on the turbine exhaust gas channel.

3. Shielding (6) according to patent claim 1, characterized in that the shielding (6) is embodied as a forged component.

4. Shielding (6) according to patent claim 1, characterized in that the shielding (6) is arranged within the turbine housing (3).

5. Shielding (6) according to patent claim 1, characterized in that the shielding (6) is embodied as a flow guiding element.

6. Shielding (6) according to patent claim 1, characterized in that the shielding (6) is embodied as a heat shield.

7. Shielding (6) according to patent claim 1, characterized in that the layers (8) are made of different materials.

8. Shielding (6) according to patent claim 1, characterized in that the layers (8) comprise different thicknesses and/or numbers.

9-10. (canceled)

11. Shielding (6) according to patent claim 1, characterized in that the layers (8) are tuned to one another in a vibration-optimized manner.

12. Shielding (6) according to patent claim 1, characterized in that the shielding (6) comprises a mounting frame (7) for different functional layers.