Patent Application
20190321934
The present disclosure relates generally to apparatus and methods for abrasive flow machining and, more particularly, to apparatus and methods for abrasive flow machining used to polish or finish surfaces of airfoil clusters for gas turbine engines.
Abrasive flow machining is a process with application to polishing or finishing surfaces of metal parts following initial fabrication through, for example, casting or additive manufacturing. The process has been found to be advantageous for polishing or finishing of manufactured parts having complex structural features such as, for example, internal passages or buried cavities that include surfaces that are difficult to access by other surface finishing techniques.
Abrasive flow machining has been employed as a manufacturing step in the production of surface finished airfoil clusters for gas turbine engines. The airfoil clusters may consist of a plurality of airfoils attached to a supporting rail to form a unitary structure. Due to the complex structural features of the airfoil clusters, surface polishing by abrasive flow machining may prove more effective than other polishing methods that exhibit difficulties in finishing or polishing various regions of the airfoil cluster to a desired degree.
While abrasive flow machining may provide an effective method for surface polishing of airfoil clusters, differential finishing (or uneven surface polishing) of various regions of the airfoil clusters may occur in certain cases. As a result, various surfaces of the airfoil cluster may receive more surface polishing and more difficult to reach surfaces may be left with undesirable surface roughness. Difficult to reach surface areas may include, for example, the concave surfaces and the root radii of the airfoils and the platforms located on the support rail between each adjacent pair of airfoils.
A cluster-tool assembly for abrasive flow machining of a plurality of airfoils is disclosed. In various embodiments, the cluster-tool assembly includes an airfoil cluster, the airfoil cluster including a supporting rail and the plurality of airfoils spaced about the supporting rail, and a sacrificial tool unitarily formed with the airfoil cluster, the sacrificial tool including a body and a plurality of prongs extending from the body.
In various embodiments, a first airfoil of the plurality of airfoils is positioned between a first prong and a second prong of the plurality of prongs. In various embodiments, the first airfoil includes a foil tip portion unitarily connected to the body of the sacrificial tool. In various embodiments, the first airfoil defines a length from a leading edge to a trailing edge and a first side channel extends along the length between a convex foil surface of the first airfoil and a concave prong surface of the first prong. In various embodiments, a second side channel extends along the length between a concave foil surface of the first airfoil and a convex prong surface of the second prong.
In various embodiments, the first prong includes a first prong tip portion positioned adjacent a first platform portion of the supporting rail, defining a first platform channel that extends along the length proximate a first base portion of the convex foil surface of the first airfoil. In various embodiments, the second prong includes a second prong tip portion positioned adjacent a second platform portion of the supporting rail, defining a second platform channel that extends along the length proximate a second base portion of the concave foil surface of the first airfoil. In various embodiments, the first side channel defines a channel width along the length, the first platform channel defines a height along the length and the height is greater than the width.
In various embodiments, each one of the plurality of airfoils includes a foil tip portion unitarily connected to the body of the sacrificial tool and each one of the plurality of airfoils is positioned between a first prong and a second prong. In various embodiments, each one of the plurality of airfoils includes a convex foil surface positioned adjacent a concave prong surface of the first prong and a concave foil surface positioned adjacent a convex prong surface of the second prong. In various embodiments, each one of the plurality of airfoils defines a length from a leading edge to a trailing edge and a first side channel extends along the length between a first foil surface of each one of the plurality of airfoils and a first prong surface of an adjacent prong of the plurality of prongs.
In various embodiments, each one of the plurality of airfoils defines a length from a leading edge to a trailing edge, a first side channel extends along the length between a convex foil surface of each one of the plurality of airfoils and a concave prong surface of a first adjacent one of the plurality of prongs and a second side channel extends along the length between a concave foil surface of each one of the plurality of airfoils and a convex prong surface of a second adjacent one of the plurality of prongs.
An abrasive flow machine for polishing surfaces of a plurality of airfoils is disclosed. In various embodiments, the machine comprises a housing; an abrasive media contained within the housing; a driver operatively associated with the abrasive media to cause the abrasive media to flow over the surfaces of the plurality of airfoils; and a fixture configured to retain a cluster-tool assembly within the flow of the abrasive media, the cluster-tool assembly comprising an airfoil cluster and a sacrificial tool unitarily formed with the airfoil cluster.
In various embodiments, the airfoil cluster comprises a supporting rail, the plurality of airfoils being equally spaced about the supporting rail, and the sacrificial tool comprises a body and a plurality of prongs extending from the body. In various embodiments, each one of the plurality of airfoils includes a foil tip portion unitarily connected to the body of the sacrificial tool and each one of the plurality of airfoils is positioned between a first prong and a second prong. In various embodiments, each one of the plurality of airfoils includes a convex foil surface positioned adjacent a concave prong surface of the first prong and a concave foil surface positioned adjacent a convex prong surface of the second prong.
A method for polishing surfaces of a plurality of airfoils is disclosed. In various embodiments, the method comprises fabricating a cluster-tool assembly, the cluster-tool assembly including an airfoil cluster and a sacrificial tool unitarily formed with the airfoil cluster, where the airfoil cluster includes a supporting rail and the plurality of airfoils is spaced about the supporting rail, where the sacrificial tool comprises a body and a plurality of prongs extending from the body, where a first airfoil of the plurality of airfoils is positioned between a first prong and a second prong of the plurality of prongs and where the first airfoil includes a foil tip portion unitarily connected to the body of the sacrificial tool. In various embodiments, the method further comprises positioning the cluster-tool assembly within an abrasive flow machine and flowing an abrasive media through a first side channel extending between a convex foil surface of the first airfoil and a concave prong surface of the first prong and a second side channel extending between a concave foil surface of the first airfoil and a convex prong surface of the second prong.
In various embodiments, the first prong includes a first prong tip portion positioned adjacent a first platform portion of the supporting rail, defining a first platform channel that extends proximate a first base portion of the convex foil surface of the first airfoil, and the abrasive media is urged through the first platform channel. In various embodiments, the second prong includes a second prong tip portion positioned adjacent a second platform portion of the supporting rail, defining a second platform channel that extends proximate a second base portion of the concave foil surface of the first airfoil, and the abrasive media is urged through the second platform channel. In various embodiments, the method further comprises terminating the flow of abrasive media and removing any portion of the sacrificial tool that remains connected to the airfoil cluster.
The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the following detailed description and claims in connection with the following drawings. While the drawings illustrate various embodiments employing the principles described herein, the drawings do not limit the scope of the claims.
The following detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that changes may be made without departing from the scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. It should also be understood that unless specifically stated otherwise, references to “a,” “an” or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural. Further, all ranges may include upper and lower values and all ranges and ratio limits disclosed herein may be combined.
Referring now to the drawings,
The gas turbine engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems at various locations may alternatively or additionally be provided and the location of the several bearing systems 38 may be varied as appropriate to the application. The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism, which in this gas turbine engine 20 is illustrated as a fan drive gear system 48 configured to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 and a high pressure turbine 54. A combustor 56 is arranged in the gas turbine engine 20 between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46 and may include airfoils 59 in the core flow path C for guiding the flow into the low pressure turbine 46. The mid-turbine frame 57 further supports the several bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via the several bearing systems 38 about the engine central longitudinal axis A, which is collinear with their longitudinal axes.
The air in the core flow path is compressed by the low pressure compressor 44 and then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, and then expanded over the high pressure turbine 54 and low pressure turbine 46. The low pressure turbine 46 and the high pressure turbine 54 rotationally drive the respective low speed spool 30 and the high speed spool 32 in response to the expansion. It will be appreciated that each of the positions of the fan section 22, the compressor section 24, the combustor section 26, the turbine section 28, and the fan drive gear system 48 may be varied. For example, the fan drive gear system 48 may be located aft of the combustor section 26 or even aft of the turbine section 28, and the fan section 22 may be positioned forward or aft of the location of the fan drive gear system 48.
Referring now to
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In various embodiments, the airfoil cluster 200 may be formed from metal and be manufactured by a 3D-printing or additive manufacturing technique, such as, for example, direct metal laser sintering (DMLS). Following manufacture, in some circumstances, certain regions of the airfoil cluster 200 such as, for example, the concave surface 212, the convex surface 214, the platform 216 and the root radii 210 of each of the plurality of airfoils 202 may have rough surfaces. In order to bring the surface roughness of the various regions of the airfoil cluster 200 to a desired smoothness or to remove excess material to meet part specifications and quality regulations, the airfoil cluster 200 may require surface polishing prior to distribution and incorporation into the airfoil assembly 250 and the gas turbine engine. Typically, such surface polishing will target areas of the airfoil cluster 200 that may be characterized by high surface roughness following manufacture (e.g., the concave surface 212, the convex surface 214, the platform 216 and the root radii 210 of each of the plurality of airfoils 202). The below disclosure provides apparatus and methods that may be employed to finish or polish the regions of high surface roughness to desirable levels, in accordance with various embodiments.
Referring now to
More specifically, each of the plurality of prongs 366 may be configured to reside between a convex surface 314 of an airfoil from the plurality of airfoils 302 and a concave surface 312 of an immediately adjacent airfoil from the plurality of airfoils 302 without coming into physical contact with the concave and convex surfaces of the airfoils. Each of the plurality of prongs 366 may have a length 340 in an axial direction that equals or exceeds a length of each of the plurality of airfoils 302, as measured from a leading edge to a trailing edge, such as the leading edge 206 and the trailing edge 208 described above with reference to
Still referring to
With continued reference to
When manufactured as a unitary component, the cluster-tool assembly 330, comprising the airfoil cluster 300 and the sacrificial tool 320, may assist in targeting certain surfaces of the airfoil cluster 300 for enhanced polishing. More specifically, given that the velocity of the flow of the abrasive media through the side channels 375 and each platform channel 382 may be directly correlated with the channel width, W, and the channel height, H, and that each platform channel 382 may be wider than the side channels 375, the abrasive media may flow with higher velocities in the platform channel 382 than in the side channels 375 during the abrasive flow polishing process. Consequently, the surfaces of the airfoil cluster 300 that are located in each platform channel 382 may experience greater abrasive wear and enhanced polishing as compared to the surfaces located in the side channels 375. In similar fashion, the channel width, W, and the channel height, H, may be adjusted relative to one another to enhance the polishing of the concave and convex surfaces of each airfoil relative to the platform and root radii surfaces. In various embodiments, the channel width, W, may vary along the span or length of each airfoil, from root to tip, to enhance polishing at, for example, the tip of the airfoil relative to the root of the airfoil. As can be appreciated, the sacrificial tool 320 may have alternative configurations creating different flow channel geometries to direct enhanced abrasive activity to other selected regions of the airfoil cluster 300.
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The foregoing provides an apparatus and method that may be used to enhance post-processing (e.g., finishing or polishing) of components by abrasive flow machining. In various embodiments, this is accomplished by fabricating a sacrificial tool into the component (e.g., an airfoil cluster) and exposing the combination to abrasive flow media. The sacrificial component is configured to beneficially guide the abrasive flow media toward regions of the component that are either difficult to reach or require focused smoothing or polishing of undesired roughness. Although this approach is particularly amenable to components made through additive manufacturing, the same principles according to the disclosure may be applied to other methods of manufacture, such as casting, used to create the combination of a desired component and sacrificial tool having a geometry configured to tailor the flow of abrasive material about various surfaces of the component.
Finally, it should be understood that any of the above described concepts can be used alone or in combination with any or all of the other above described concepts. Although various embodiments have been disclosed and described, one of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. Accordingly, the description is not intended to be exhaustive or to limit the principles described or illustrated herein to any precise form. Many modifications and variations are possible in light of the above teaching.
Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.
Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.
Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
