Patent Publication Number: US-9422819-B2

Title: Rotor blade root spacer for arranging between a rotor disk and a root of a rotor blade

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. patent application Ser. No. 13/718,719 filed Dec. 18, 2012, which is hereby incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This disclosure relates generally to rotational equipment and, more particularly, to a root spacer for arranging between a rotor disk and a root of a rotor blade. 
     2. Background Information 
     A fan assembly for a typical turbine engine includes a plurality of fan blades arranged circumferentially around a rotor disk. Each of the fan blades may include an airfoil connected to a dovetail root. The root is inserted into a respective dovetail slot within the rotor disk to connect the fan blade to the rotor disk. A radial height of the root is typically less than a radial height of the slot. A gap therefore extends between a radial inner surface of the root and a radial inner surface of the slot. Such a gap is typically filled with a root spacer, which is sometimes also referred to as a fan blade spacer. 
     A typical root spacer is configured to reduce slippage and wear between the root and the rotor disk during engine operation where centrifugal loading on the fan blade is relatively low; e.g., during wind milling. By filling the gap, for example, the root spacer reduces space that would otherwise be available for rotating of the root within the slot. Such a rigid connection between the rotor disk and the fan blade, however, may increase internal stresses on the fan blade where an object such as a bird or a released fan blade collides with the fan blade. 
     There is a need in the art for an improved rotor spacer. 
     SUMMARY OF THE DISCLOSURE 
     According to an aspect of the invention, a rotor assembly is provided that includes a rotor disk, a rotor blade, and a root spacer. The rotor disk includes a slot. The rotor blade includes a blade root arranged within the slot. The blade root includes a root base segment and a pair of root side segments. The root base segment is laterally separated from the rotor disk by the root side segments. The root spacer is arranged within the slot, and includes a side surface that extends radially between an inner surface and an outer surface. The side surface is approximately laterally aligned with an intersection between the root base segment and a first of the root side segments. The outer surface engages the root base segment. 
     According to another aspect of the invention, another rotor assembly is provided that includes a rotor disk, a rotor blade and a root spacer. The rotor disk includes a slot. The rotor blade includes a blade root arranged within the slot. The blade root includes a root base segment and a pair of root side segments. The root side segments extend laterally between and laterally separate the root base segment and the rotor disk. The root spacer is arranged within the slot. The root spacer includes a side surface that extends radially between an inner surface and an outer surface that engages the root base segment. A gap, located adjacent the side surface, extends radially between a first of the root side segments and the rotor disk. 
     According to still another aspect of the invention, a turbine engine is provided that includes a fan section, a compressor section, a combustor section and a turbine section that are arranged along an axis. The fan section includes a rotor disk, a fan blade and a root spacer. The rotor disk includes a slot. The fan blade includes a blade root arranged within the slot. The blade root includes a root base segment and a pair of root side segments, where the root base segment is laterally separated from the rotor disk by the root side segments. The root spacer is arranged within the slot, and includes a side surface that extends radially between an inner surface and an outer surface. The side surface is approximately laterally aligned with an intersection between the root base segment and a first of the root side segments. The outer surface engages the root base segment. 
     A gap, located adjacent the side surface, may extend radially between the first of the root side segments and the rotor disk. 
     The side surface may be configured as a first side surface, and the root spacer may include a second side surface that extends radially between the inner surface and the outer surface. The second side surface may be approximately laterally aligned with an intersection between the root base segment and a second of the root side segments. The outer surface may have a substantially flat cross-sectional geometry. The slot may extend radially into the rotor disk from an opening with a first lateral width. The root spacer may have a second lateral width that extends between the first and the second side surfaces. The second lateral width may be between about 80 and about 110 percent of the first lateral width. 
     The root spacer may include a spacer base segment and a spacer side segment. The spacer base segment may be arranged radially between the root base segment and the rotor disk. The spacer side segment may be arranged radially between a second of the root side segments and the rotor disk. The spacer base segment may include a portion of the outer surface having a substantially flat cross-sectional geometry. The slot may extend radially into the rotor disk from an opening with a first lateral width. The portion of the outer surface may have a second lateral width. The second lateral width may be between about 80 and about 110 percent of the first lateral width. 
     The rotor blade may be configured as a turbine engine fan blade. 
     The slot may be one of a plurality of slots that extend longitudinally into the rotor disk. The rotor blade may be one of a plurality of rotor blades that are arranged circumferentially around an axis, where each of the rotor blades includes a respective blade root that is arranged within a respective one of the slots. The root spacer may be one of a plurality of root spacers, where each of the root spacers is arranged within a respective one of the slots between the rotor disk and a respective one of the blade roots. 
     The side surface may be approximately laterally aligned with an intersection between the root base segment and the first of the root side segments. 
     The side surface may be configured as a first side surface, and the root spacer may include a second side surface that extends radially between the inner surface and the outer surface. A gap, located adjacent the second side surface, may extend radially between a second of the root side segments and the rotor disk. The outer surface may have a substantially flat cross-sectional geometry. The slot may extend radially into the rotor disk from an opening with a first lateral width. The root spacer may have a second lateral width that extends between the first and the second side surfaces. The second lateral width may be between about 80 and about 110 percent of the first lateral width. 
     The foregoing features and the operation of the invention will become more apparent in light of the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side sectional illustration of a geared turbine engine; 
         FIG. 2  is a perspective illustration of a partially assembled rotor assembly for the turbine engine of  FIG. 1 ; 
         FIG. 3  is a side sectional illustration of a portion of the rotor assembly of  FIG. 2 ; 
         FIG. 4  is a perspective illustration of an end of a portion of the rotor assembly of  FIG. 2  during a first mode of operation; 
         FIG. 5  is an illustration of an inner surface of a root spacer for the rotor assembly of  FIG. 2 ; 
         FIG. 6  is a perspective illustration of an end of a portion of the rotor assembly of  FIG. 2  during a second mode of operation; 
         FIG. 7  is an illustration of an end of an alternative embodiment root spacer for the rotor assembly of  FIG. 2 ; and 
         FIG. 8  is a perspective illustration of an end of a portion of the rotor assembly of  FIG. 2  with an alternative embodiment root spacer. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a sectional illustration of a geared turbine engine  20  that extends along an axis  22  between a forward airflow inlet  24  and an aft airflow exhaust  26 . The engine  20  includes a fan section  28 , a low pressure compressor (LPC) section  29 , a high pressure compressor (HPC) section  30 , a combustor section  31 , a high pressure turbine (HPT) section  32 , and a low pressure turbine (LPT) section  33 . These engine sections  28 - 33  are arranged sequentially along the axis  22  and housed within an engine case  34 . Each of the engine sections  28 - 30 ,  32  and  33  includes a respective rotor  36 - 40 . Each of the rotors  36 - 40  includes a plurality of rotor blades arranged circumferentially around and connected (e.g., mechanically fastened, welded, brazed or otherwise adhered) to one or more respective rotor disks. The fan rotor  36  is connected to a gear train  42 . The gear train  42  and the LPC rotor  37  are connected to and driven by the LPT rotor  40  through a low speed shaft  44 . The HPC rotor  38  is connected to and driven by the HPT rotor  39  through a high speed shaft  45 . 
     Air enters the engine  20  through the airflow inlet  24 , and is directed through the fan section  28  and into an annular core gas path  46  and an annular bypass gas path  48 . The air within the core gas path  46  may be referred to as “core air”. The air within the bypass gas path  48  may be referred to as “bypass air” or “cooling air”. The core air is directed through the engine sections  29 - 33  and exits the engine  20  through the airflow exhaust  26 . Within the combustion section  31 , fuel is injected into and mixed with the core air and ignited to provide forward engine thrust. The bypass air is directed through the bypass gas path  48  and out of the engine  20  to provide additional forward engine thrust or reverse thrust via a thrust reverser. The bypass air may also be utilized to cool various turbine engine components within one or more of the engine sections  29 - 33 . 
       FIG. 2  is a perspective illustration of a partially assembled rotor assembly  50  for one of the rotors  36 - 40  (e.g., the fan rotor  36 ). In the embodiment of  FIG. 2 , the rotor assembly  50  includes the rotor disk  52 , the rotor blades  54  (e.g., fan blades), and one or more root spacers  56  (e.g., fan blade spacers). 
     The rotor disk  52  extends axially between a disk forward end  57  and a disk aft end  58 . The rotor disk  52  extends radially out to a disk outer surface  60 . The rotor disk  52  includes one or more slots  62  (e.g., dovetail slots) arranged circumferentially around the axis  22 . Referring to  FIG. 3 , one or more of the slots  62  each extends longitudinally into the rotor disk  52 ; e.g., through the rotor disk  52  between the forward end  57  and the aft end  58 . Referring now to  FIG. 4 , one or more of the slots  62  each extends radially into the rotor disk  52  from an opening  64  in the outer surface  60  to a slot base surface  66 . One or more of the slots  62  each extends laterally (e.g., circumferentially or tangentially) between opposing slot side surfaces  68 . The base surface  66  extends laterally between the side surfaces  68 . 
     Referring to  FIG. 3 , one or more of the rotor blades  54  each includes a blade root  70  and an airfoil  72 . The blade root  70  extends longitudinally between a root forward end  73  and a root aft end  74 . Referring to  FIG. 4 , the blade root  70  includes a root base segment  76  and a pair of root side segments  78  and  79 . The base segment  76  extends radially between the airfoil  72  and a root base surface  80 . The side segments  78  and  79  respectively extend laterally from the base segment  76  to opposing root side surfaces  82  and  83 . The base surface  80  extends laterally between the side surfaces  82  and  83 , and may have a substantially flat cross-sectional geometry. The side surface  82  includes an intermediate portion  84  that extends radially between inner and outer portions  85  and  86 . The inner portion  85  extends laterally between the base surface  80  and the intermediate portion  84 . The inner portion  85  may have a substantially flat cross-sectional geometry that is angularly offset from the base surface  80  by, for example, between about 135 and about 160 degrees. The side surface  83  includes an intermediate portion  88  that extends radially between inner and outer portions  89  and  90 . The inner portion  89  extends laterally between the base surface  80  and the intermediate portion  88 . The inner portion  89  may have a substantially flat cross-sectional geometry that is angularly offset from the base surface  80  by, for example, between about 135 and about 160 degrees. 
     Referring to  FIGS. 4 and 5 , one or more of the root spacers  56  each extends longitudinally between a spacer forward end  92  and a spacer aft end  93 . One or more of the root spacers  56  extends laterally between opposing spacer side surfaces  94  and  95 . One or more of the root spacers  56  includes a spacer base segment  96  and a spacer side segment  98 . These segments  96  and  98  extend radially between a spacer inner surface  100  and a spacer outer surface  102 , which surfaces  100  and  102  extend laterally between the side surfaces  94  and  95 . The base segment  96  extends laterally between the side surface  94  and the side segment  98 , and respectively defines base portions  104  and  106  of the inner and the outer surfaces  100  and  102 . The base portion  106  may have a substantially flat cross-sectional geometry, and a lateral width that is substantially equal to (or is between about 80 and about 110 percent of) a lateral width of the opening  64 . The side segment  98  extends laterally between the side surface  95  and the base segment  96 . The side segment  98  defines side portions  108  and  110  of the inner and the outer surfaces  100  and  102 . The side portion  110  may have a substantially flat cross-sectional geometry that is angularly offset from the base portion  106  by, for example, between about 135 and about 160 degrees. 
     Referring to  FIG. 2 , the rotor blades  54  are arranged circumferentially around the axis  22 . The blade roots  70  and the root spacers  56  are respectively arranged within the slots  62 . Referring to  FIG. 4 , the root side segments  78  and  79  respectively extend laterally between and separate the root base segment  76  and the rotor disk  52 . The outer portions  86  and  90  may respectively engage (e.g., contact) the slot side surfaces  68 . The root spacer  56  is arranged radially between the blade root  70  and the rotor disk  52 . The spacer side surface  94  is approximately laterally aligned with (e.g., laterally on, adjacent or proximate) an intersection  112  between the root base segment  76  and the root side segment  78 . An intersection  114  between the spacer base segment  96  and the spacer side segment  98  is approximately laterally aligned with an intersection  116  between the root base segment  76  and the root side segment  79 . This intersection  114  is also laterally offset from a lateral centroid  118  of the blade root  70  by a lateral distance. The side portion  110  engages the inner portion  89 . The base portion  106  engages the root base surface  80 . The base and side portions  104  and  108  may engage the slot base surface  66 . A gap  120 , located adjacent the spacer side surface  94 , extends radially between and separates the inner portion  85  and the slot base surface  66 . 
       FIG. 4  illustrates an end of a portion of the rotor assembly  50  during a first mode of operation; e.g., during nominal flight conditions.  FIG. 6  illustrates an end of a portion of the rotor assembly  50  during a second mode of operation; e.g., during non-nominal flight conditions such as after a foreign object collides with one or more of the rotor blades  54 . During the first mode of operation of  FIG. 4 , the spacer side segment  98  may substantially prevent the blade root  70  from rotating within the slot  62  by radially supporting the root side segment  79  and/or substantially filling the radial space within the slot  62  between the blade root  70  and the rotor disk  52 . In contrast, during the second mode of operation of  FIG. 6 , a shock load generated by the collision of the foreign object against the rotor blades  54  causes the blade root  70  to shift the root spacer  56  towards the left-hand side of the page. The blade root  70  therefore may rotate clockwise within the slot  62  by pivoting about a corner between the spacer outer and side surfaces  94  and  102 . This rotating of the blade root  70  may enable the rotor blade  54  to substantially absorb the shock load without breaking and causing additional harm to the engine  20 . 
     One or more of the root spacers  56  may have various configurations other than those described above. For example, as illustrated in  FIG. 7 , the base and/or side portions  106 ′ and  110 ′ may each have a curved cross-sectional geometry. In the embodiment of  FIG. 7 , the side portion  110 ′ has a chord  122  that is angularly offset from a chord  124  of the base portion  106 ′. In addition or alternatively, for example as illustrated in  FIG. 8 , one or more of the root spacers  56 ′ may omit the spacer side segment  98  (see  FIG. 4 ). The spacer base segment  96 ′ and the base portions  104  and  106  therefore extend laterally between the spacer side surfaces  94  and  95 ′. The spacer side surface  95 ′ is approximately laterally aligned with the intersection  116  between the root base segment  76  and the root side segment  79 . A gap  126 , located adjacent the spacer side surface  95 ′, extends radially between and separates the inner portion  89  and the slot base surface  66 . The present invention therefore is not limited to any particular root spacer configurations. 
     The root spacers  56  may be constructed from a variety of materials such as metal and/or polymer. The present invention therefore is not limited to any particular root spacer materials. 
     The terms “upstream”, “downstream”, “inner” and “outer” are used to orientate the components of the rotor assembly  50  described above relative to the turbine engine  20  and its axis  22 . A person of skill in the art will recognize, however, the rotor assembly components such as the root spacer  56  may be utilized in other orientations than those described above. The spacer side segment, for example, may be arranged radially between the root side segment  78  and the rotor disk. The present invention therefore is not limited to any particular rotor assembly or root spacer spatial orientations. 
     A person of skill in the art will recognize the rotor assembly  50  may be included in one or more sections of the engine  20  other than the fan section  28  as well as in various turbine engines other than that described above. A person of skill in the art will also recognize the rotor assembly  50  may be included in various types of rotational equipment other than a turbine engine. The present invention therefore is not limited to any particular types or configurations of rotational equipment. 
     While various embodiments of the present invention 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 invention. For example, the present invention as described herein includes several aspects and embodiments that include particular features. Although these features may be described individually, it is within the scope of the present invention that some or all of these features may be combined within any one of the aspects and remain within the scope of the invention. Accordingly, the present invention is not to be restricted except in light of the attached claims and their equivalents.