Patent Publication Number: US-11028728-B2

Title: Strut dampening assembly and method of making same

Description:
BACKGROUND 
     1. Technical Field 
     This disclosure relates generally to gas turbine engines, and more particularly to dampers for supporting tubes therein. 
     2. Background Information 
     A gas turbine engine may include one or more frames including an inner hub, an outer casing, and a plurality of spaced-apart struts connecting the hub and casing. One or more of the struts may contain an internal tube configured to convey a fluid. For example, the tube may convey oil to a bearing supported by the hub. 
     Due to the length and thickness of internal tubes such as those described above, the tubes may have a resonance frequency corresponding to one of the gas turbine engine operating modes. Accordingly, the internal tubes may be susceptible to vibratory fatigue, as a result of normal engine operation, which can degrade the structural integrity of the internal tubes potentially leading to tube fracture. Further, the hollow passage within the strut may have a very small cross-sectional area into which the internal tube must fit. 
     SUMMARY 
     According to an embodiment of the present disclosure, a strut includes a strut passage extending through the strut along a radial length of the strut. A tube is disposed within the strut passage and is spaced from an interior surface of the strut passage. A grommet is disposed about the tube and is in communication with the interior surface of the strut passage. The grommet defines a compressible zone including a hollow space extending radially through the grommet. The compressible zone is disposed between the tube and the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the grommet includes a first portion disposed about a perimeter of the tube and at least one second portion extending from the first portion away from the tube. An exterior surface of the first portion and an interior surface of the second portion define the compressible zone therebetween. An exterior surface of the second portion forms an interface with the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the second portion is in communication with the interior surface of the strut passage and the first portion is spaced from the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the strut further includes at least one retention plate projecting outward from the tube proximate a radial end of the grommet. The at least one retention plate is configured to limit radial motion of the grommet along the tube. 
     In the alternative or additionally thereto, in the foregoing embodiment, the grommet is bonded to the tube. 
     In the alternative or additionally thereto, in the foregoing embodiment, the strut passage includes an opening to the strut passage through an outer radial end of the strut. 
     In the alternative or additionally thereto, in the foregoing embodiment, the opening has a first width and the strut passage has a second width greater than the first width. 
     In the alternative or additionally thereto, in the foregoing embodiment, the grommet is configured to be compressed such that a width of the grommet is less than the first width when the grommet is in a compressed state and greater than the first width when the grommet is in an uncompressed state. 
     According to another embodiment of the present disclosure, a gas turbine engine includes an inner hub, an outer casing, and a plurality of struts extending radially between and connecting the inner hub to the outer casing. At least one strut of the plurality of struts includes a strut passage extending through the strut along a radial length of the strut. A tube is disposed within the strut passage and is spaced from an interior surface of the strut passage. A grommet is disposed within the strut passage and is spaced from an interior surface of the strut passage. The grommet defines a compressible zone including a hollow space extending radially through the grommet. The compressible zone is disposed between the tube and the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the grommet includes a first portion disposed about a perimeter of the tube and at least one second portion extending from the first portion away from the tube. An exterior surface of the first portion and an interior surface of the second portion define the compressible zone therebetween. An exterior surface of the second portion forms an interface with the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the gas turbine engine further includes at least one retention plate projecting outward from the tube proximate a radial end of the grommet. The at least one retention plate is configured to limit radial motion of the grommet along the tube. 
     In the alternative or additionally thereto, in the foregoing embodiment, the strut passage includes an opening to the strut passage through the outer casing and an outer radial end of the strut. 
     In the alternative or additionally thereto, in the foregoing embodiment, the opening has a first width and the strut passage has a corresponding second width greater than the first width. 
     In the alternative or additionally thereto, in the foregoing embodiment, the grommet is configured to be compressed such that a width of the grommet is less than the first width when the grommet is in a compressed state and greater than the first width when the grommet is in an uncompressed state. 
     According to another embodiment of the present disclosure, a method for assembly of a strut for a gas turbine engine is disclosed. A strut including a strut passage extending through the strut along a radial length of the strut and an opening to the strut passage through an outer radial end of the strut is provided. The opening has a first width. At least one grommet is attached to a tube. The at least one grommet defines a compressible zone including a hollow space extending radially through the at least one grommet. The at least one grommet is compressed such that the at least one grommet has a width less than the first width. The tube is inserted into the strut passage via the opening such that the compressible zone is disposed between the tube and an interior surface of the strut passage and the tube is spaced from the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the at least one grommet, in an uncompressed state, is in communication with the interior surface of the strut passage when the tube has been inserted into the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the grommet includes a first portion disposed about a perimeter of the tube and at least one second portion extending from the first portion away from the tube. An exterior surface of the first portion and an interior surface of the second portion define the compressible zone therebetween. An exterior surface of the second portion forms an interface with the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the second portion is in communication with the interior surface of the strut passage and the first portion is spaced from the interior surface of the strut passage. 
     In the alternative or additionally thereto, in the foregoing embodiment, the strut passage has a second width greater than the first width. 
     In the alternative or additionally thereto, in the foregoing embodiment, the step of attaching the at least one grommet to the tube includes bonding the at least one grommet to the tube with an adhesive. 
     The present disclosure, and all its aspects, embodiments and advantages associated therewith will become more readily apparent in view of the detailed description provided below, including the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side cross-sectional view of a portion of a gas turbine engine. 
         FIG. 2  illustrates a fan frame for a gas turbine engine. 
         FIG. 3A  illustrates a portion of the fan frame of  FIG. 2 . 
         FIG. 3B  illustrates a portion of the fan frame of  FIG. 2   
         FIG. 4  illustrates a tube of the fan frame of  FIG. 2 . 
         FIG. 5  illustrates a side cross-sectional view of a strut of the fan frame of  FIG. 2 . 
         FIGS. 6A-E  illustrate exemplary grommets. 
         FIG. 7  is a flowchart for a method of assembling a strut for a fan frame. 
     
    
    
     DETAILED DESCRIPTION 
     It is noted that various connections are set forth between elements in the following description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. It is further noted that various method or process steps for embodiments of the present disclosure are described in the following description and drawings. The description may present the method and/or process steps as a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation. 
     Referring to  FIG. 1 , a gas turbine engine  10  having a two-spool turbofan configuration is shown. This exemplary embodiment of a gas turbine engine includes a fan section  12 , a compressor section  14 , a combustor section  16 , and a turbine section  18 . The fan section  12  drives air along a bypass flow path B in a bypass duct, while the compressor section  14  drives air along a core flow path C for compression and communication into the combustor section  16  then expansion through the turbine section  18 . 
     The exemplary gas turbine engine  10  includes a low-speed spool  20  and a high-speed spool  22  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  24 . Core airflow is compressed by the low-pressure compressor  26  then the high-pressure compressor  28 , mixed and burned with fuel in the combustor  30 , then expanded over the high-pressure turbine  32  and low-pressure turbine  34 . The turbines  32 ,  34  rotationally drive the respective low-speed spool  20  and high-speed spool  22  in response to the expansion. The low-low-speed spool  20  generally includes a fan shaft  36  from which extends a fan  38 . The fan shaft  36  drives the fan  38  directly or indirectly (e.g., through a geared architecture to drive the fan  38  at a lower speed than the low-speed spool  20 ). 
     Referring to  FIG. 2 , the forward end of the fan shaft  36  (see  FIG. 1 ) may be supported by bearings which may in turn be supported by one or more parts of the engine static structure  24 , such as fan frame  40 . The fan frame  40  includes a radially inner hub  42  and a radially outer casing  44  disposed about the longitudinal axis A. A plurality of circumferentially spaced-apart struts  46  extend radially between and connect the inner hub  42  and the outer casing  44 . The inner hub  42  supports a bearing  48  for the rotating fan shaft  36 , with the loads therefrom being channeled through the inner hub  42  and the struts  46  to the outer casing  44 . While aspects of the present disclosure will be discussed with respect to gas turbine engines  10 , and more specifically to fan frames  40 , it should be understood that the present disclosure is also applicable to other types of rotational machinery. For example, aspects of the present disclosure could be applicable to a frame of a rotational equipment assembly such as an industrial gas turbine engine, wind turbine, etc. 
     Referring to  FIGS. 3A, 3B, 4, and 5 , one or more of the struts  46  may be hollow to provide a reduction in the weight of the gas turbine engine  10  or to permit the passage of air, oil, or other fluids through the struts  46 . Struts  46  having a hollow configuration may include a strut passage  50  extending through the strut  46  along a radial length of the strut  46 . The strut passage  50  may extend radially between the inner hub  42  and the outer casing  44  for the full radial length of the struts  46 . The strut passage  50  may include one or both of an outer strut opening  52  and an inner strut opening  54  extending through a respective first radial end  46 E 1  and second radial end  46 E 2  of the struts  46 . One or both of the outer strut opening  52  and the inner strut opening  54  may correspond to and be aligned with an opening in the outer casing  44  and the inner hub  42 , respectively. 
     In some embodiments, inlet air to the gas turbine engine  10  may first pass through the fan frame  40  prior to reaching the fan  38 . Accordingly, the struts  46  may have an airfoil shape. As shown in  FIG. 3A , the strut passage  50  may have a substantially elliptical cross-sectional shape corresponding to the airfoil shape of the struts  46 . With reference to the x-y-z axes illustrated in  FIG. 5 , the strut passage  50  may have a z-width (i.e., a width extending substantially along the z-axis) having a greater magnitude than an x-width (i.e., a width extending substantially along the x-axis) of the strut passage  50 . One or both of the z-width and the x-width of the strut passage  50  may vary along the radial length of the strut passage  50 . For example, the z-width of the strut passage  50  may be greater proximate the inner hub  42  than the z-width of the strut passage  50  proximate the outer casing  44 . As used herein, the term “substantially” with regard to an angular relationship refers to the noted angular relationship +/−10 degrees. 
     In some embodiments, one or both of the openings  52 ,  54  may have a size and/or shape which is different than the size and/or shape of the respective strut passage  50 . For example, the outer strut opening  52  may have a z- and/or x-width that is less than the z- and/or x-width of the corresponding strut passage  50 . Additionally, in some embodiments, one or both of the openings  52 ,  54  may have a different shape than the strut passage  50 . For example, the strut passage  50  may have a substantially elliptical shape while the outer strut opening  52  may have a substantially circular shape. 
     One or more of the struts  46  includes a tube  60  disposed within the strut passage  50  and spaced from an interior surface  66  of the strut passage  50 . The tube  60  may be configured, to convey oil or other fluids (e.g., cooling air), for example, to the bearing  48  in communication with the fan shaft  36 . As shown in  FIG. 3A , the tube  60  may extend from a position radially outside of the outer casing  44  to a position radially inside of the inner hub  42 . The tube may include a mounting fixture  62  configured to mount the tube to the outer casing  44  or the inner hub  42 . The mounting fixture  62  may be mounted to the outer casing  44 , for example, by one or more fasteners. 
     In some embodiments, the tube  60  may have, for example, an elliptical or obround cross-sectional shape corresponding to the shape of the respective strut passage  50  (i.e., the tube  50  may have a greater z-width than x-width). In other embodiments, the tube  60  may have a round cross-sectional shape or any other suitable shape for disposition within the strut passage  50  while being spaced from the interior surface  66  of the strut passage. 
     The tube  60  may include one or more grommets  64  configured to dampen vibrational forces between the tube  60  and the respective strut  46 . The grommet  64  may be disposed about the tube  60  (e.g., a perimeter of the tube  60 ) and in communication with the interior surface  66  of the strut passage  50 . The grommet  64  may further maintain an interface  68  between the grommet  64  and the interior surface  66  throughout a range of gas turbine engine operating modes so as to prevent contact between the tube  60  and the interior surface  66 . Accordingly, the grommet  64  may prevent rubbing between the tube  60  and the interior surface  66  thereby preventing the formation of wear particles within the strut passage  50 . In some embodiments, the grommet  64  may be bonded to the tube  60  with a suitable adhesive. 
     In some embodiments, the tube  60  may include one or more retention plates  72  disposed along the tube  60  and projecting outward from the tube  60  proximate a radial end of the grommet  64 . The retention plate  72  may be configured to limit radial motion of the grommet  64  along the tube  60 . For example, as shown in  FIGS. 4 and 5 , one or more retention plates  72  may be disposed on the tube  60  radially above and/or below the grommet  64  in order to limit radial movement of the grommet  64 . In some embodiments, the retention plate  72  may be bonded or braised to the exterior surface of the tube  60 . 
     Referring to  FIGS. 6A-6E , several non-limiting exemplary embodiments of the grommet  64  are illustrated. The grommet  64  includes a first portion  76  having an interior surface  86  configured for disposition about the perimeter of the tube  60 . The first portion  76  may include a grommet opening  74  configured to allow the first portion  76  to be opened and positioned about the tube  60 . A second portion  78  of the grommet  64  extends from the first portion  76  in a direction generally away from the tube  60 . An exterior surface  80  of the first portion  76  and in interior surface  82  of the second portion  78  define a compressible zone  70  defined by a hollow space extending radially through the grommet  64  and disposed between the tube  60  and the interior surface  66  of the strut passage  50 . An exterior surface  84  of the second portion  78  forms the interface  68  between the grommet  64  and the interior surface  66  of the strut passage  50  (see  FIG. 5 ). 
       FIGS. 6A-6E  illustrate several non-limiting exemplary embodiments of the grommet  64 . The grommet  64  may include two second portions  78  extending from the first portion  76  opposite one another with respect to the tube  60 . In some embodiments, the second portion  78  may include two or more independent portions extending from the first portion  76 . In operation, the compressible zone  70  may expand or contract (i.e., the volume of the compressible zone  70  may increase or decrease) in response to external forces such as vibratory forces within the struts  46 , thereby dampening the vibratory forces applied to the tube  60 . As will be discussed, the compressible zone  70  may also expand and contract as a result of forces applied during assembly of the struts  46 . The first and second portions  76 ,  78  may be of any suitable thickness. In some embodiments, the first and second portions  76 ,  78  may have different thicknesses while in some other embodiments they may have a same thickness. 
     Referring again to  FIGS. 3A and 3B , the outer strut opening  52  may have a width which is smaller than a respective width of the strut passage  50 . Accordingly, in order to maintain contact with the interior surface  66  of the strut passage  50  during gas turbine engine  10  operation, the grommet may be compressible such that, during installation, it can pass through the outer strut opening  52  and subsequently expand to form the interface  68  with the interior surface  66 . 
     In some embodiments, the grommet  64  may be made of silicone, rubber, or any other suitable material for constraining vibratory amplitude of the tube  60  while being capable of compression for insertion into the strut passage  50 . The dampers  60  may be procured by a number of different methods, for example, additive manufacturing, laser cutting, milling, water jetting, casting, etc. In some embodiments, the interior surface  66  of the strut passage  50  may have a rough surface finish. Accordingly, the material of the grommet  64  may be selected such that the interface between the grommet  64  and the interior surface  66  of the strut passage  50  does not cause the formation of wear particles as a result of relative motion between the grommet  64  and the interior surface  66 . 
     Referring to  FIG. 7 , a method  700  for assembling a strut  50  for a gas turbine engine  10  is illustrated. In block  702 , the strut  46  having a strut passage  50  is provided. In block  702 , at least one grommet  64  is attached to the tube  60  in preparation for insertion of the tube  60  into the strut passage  50 . As previously discussed, in some embodiments, the grommet  64  may be bonded to the tube  60 . In block  706 , the grommet  64  is compressed such that the grommet  64  has a width that is less than a corresponding width of the outer strut opening  52 . For example, the compressible zone  70  of the grommet  64  may be compressed such that the width of the grommet  64  between opposing distal surfaces of the second portions  78  of the grommet  64  is less than a corresponding (e.g., tangential) width of the outer strut opening  52 . In block  708 , the tube  60  is inserted into the strut passage  50  via the outer strut opening  52 . Subsequent to insertion into the strut passage  50 , the grommet returns to an uncompressed state thereby forming the interface  68  with the interior surface  66  of the strut passage  50 . As used herein, the “uncompressed state” refers to the condition of the grommet  64  absent the compressive force applied for inserting the grommet  64  through the outer strut opening  52 . As one of ordinary skill in the art will understand, the grommet  64  may still be compressed to some degree within the strut passage  50  by the interior surface  66 . 
     While various aspects of the present disclosure have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these particular features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the present disclosure. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents.