Patent Publication Number: US-8966756-B2

Title: Gas turbine engine stator vane assembly

Description:
BACKGROUND 
     This disclosure relates to a gas turbine engine front architecture. More particularly, the disclosure relates to a stator vane assembly and a method of installing stators vanes within a front architecture. 
     One type of gas turbine engine includes a core supported by a fan case. The core rotationally drives a fan within the fan case. Multiple circumferentially arranged stator vanes are supported at an inlet of the core by its front architecture. 
     The stator vanes are supported to limit displacement of the vane, and the vanes are subjected to vibratory stress by the supporting structure. That is, loads are transmitted through the front architecture to the stator vanes. Typically, the stator vanes are constructed from titanium, stainless steel or a high grade aluminum, such as a 2618 alloy, to withstand the stresses to which the stator vanes are subjected. 
     Some front architectures support the stator vanes relative to inner and outer fairings using rubber grommets. A fastening strap is wrapped around the circumferential array of stator vanes to provide mechanical retention of the stator vanes with respect to the fairings. As a result, mechanical loads and vibration from the fairings are transmitted to the stator vanes through the fastening strap. 
     SUMMARY 
     A method of assembling gas turbine engine front architecture includes positioning inner and outer fairings relative to one another. Multiple vanes are arranged circumferentially between the inner and outer fairings. A liquid sealant is applied around a perimeter of the vanes to seal between the vanes and at least one of the fairings. 
     A gas turbine engine front architecture includes an inlet case having first and second inlet flanges integrally joined by inlet vanes. Outer and inlet fairings respectively fastened to the first and second inlet flanges. The outer and inner fairings respectively include first and second walls having first and second slots respectively. Multiple stator vanes are arranged upstream from the inlet vanes and are circumferentially spaced from one another. Each of the stator vanes extend radially between the inner and outer fairings and include outer and inner perimeters respectively within the first and second slots. Sealant is provided about the inner and outer perimeters at the inner and outer fairings. 
     The stator vanes include inner and outer ends and provide leading and trailing edges. A notch is provided on the inner end at the trailing edge and seated over the inner fairing. Opposing tabs extend from opposing sides of the stator vanes at the out end. The sealant is provided beneath the notch and the opposing tabs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a schematic view of an example gas turbine engine. 
         FIG. 2A  is a partial perspective view of a stator vane assembly before applying sealant. 
         FIG. 2B  is a cross-sectional view of the stator vane assembly shown in  FIG. 2A . 
         FIG. 3A  is a top front perspective view of an inner end of the stator vane supported by an inner fairing. 
         FIG. 3B  is a bottom front perspective view of the inner stator vane shown in  FIG. 3A . 
         FIG. 4  is a top front perspective view of an outer end of the stator vane installed in an outer fairing. 
         FIG. 5  is a side perspective view of a portion of the stator vane assembly with the sealant applied. 
         FIG. 6  is a cross-sectional view of a front architecture with the stator vane assembly shown in  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION 
     A gas turbine engine  10  is illustrated schematically in  FIG. 1 . The gas turbine engine  10  includes a fan case  12  supporting a core  14  via circumferentially arranged flow exit guide vanes  16 . A bypass flow path  18  is provided between the fan case  12  and the core  14 . A fan  20  is arranged within the fan case  12  and rotationally driven by the core  14 . 
     The core  14  includes a low pressure spool  22  and a high pressure spool  24  independently rotatable about an axis A. The low pressure spool  22  rotationally drives a low pressure compressor section  26  and a low pressure turbine section  34 . The high pressure spool  24  supports a high pressure compressor section  28  and a high pressure turbine section  32 . A combustor  30  is arranged between the high pressure compressor section  28  and the high pressure turbine section  32 . 
     The core  14  includes a front architecture  36 , having fixed structure, provided within the fan case  12  downstream from the fan  20 . The front architecture  36  includes stator vanes  44  arranged upstream from inlet guide vanes  84 , which are also arranged upstream from the first stage of the low compressor section  26 . 
     The front architecture  36  supports a stator vane assembly  38 , which is shown in  FIGS. 2A ,  2 B and  6 . The stator vane assembly  38  includes inner and outer fairings  40 ,  42  radially spaced from one another. Multiple stator vanes  44  are arranged circumferentially relative to one another about the axis A and extend between the inner and outer fairings  40 ,  42 . The stator vanes  44  provide an airfoil having opposing sides extending between leading and trailing edges LE, TE ( FIG. 6 ). 
     Each stator vane  44  includes opposing inner and outer ends  46 ,  48 . The outer fairing  42  has a first wall  50  that includes circumferential first slots  52  for receiving the outer ends  48  of the stator vane  44 . A first flange  54  extends from the first wall  50  and includes first and second attachment features  56 ,  58 . 
     The inner fairing  40  is provided by a second wall  60  that includes circumferentially arranged second slots  62  for receiving the inner ends  46  of the stator vanes  44 . A second flange  64  extends from the second wall  60  and provides a third attachment feature  66 . 
     Referring to  FIGS. 3A-3B , the inner ends  46  are secured relative to the inner fairing  40  within the second slots  62  with a liquid sealant  74  that provides a bonded joint. In one example, the liquid sealant is a silicone rubber having, for example, a thicksotropic formulation or a room temperature vulcanization formulation. The liquid sealant cures to a solid state subsequent to its application about an inner perimeter  72  at the inner fairing  40 , providing a filleted joint. 
     The inner end  46  includes a notch  68  at a trailing edge TE ( FIG. 6 ) providing an edge  70  that is in close proximity to the wall  60 , as illustrated in  FIG. 2B , for example. The edge  70  provides an additional safeguard that prevents the stator vanes  44  from being forced inward through the inner fairing  40  during engine operation. 
     The stator vane  44  is supported relative to the inner fairing  40  such that a gap  71  is provided between the inner end  46  and the inner fairing  40  about the inner perimeter  72 . Said another way, a clearance is provided about the inner perimeter  72  within the second slot  62 . The liquid sealant  74  is injected into the gap  71  to vibrationally isolate the inner end  46  from the inner fairing  40  during the engine operation and provide a seal. 
     Referring to  FIGS. 4-5 , the outer ends  48  are secured relative to the outer fairing  42  within the first slots  52  with the liquid sealant  80  that provides a bonded joint. The liquid sealant cures to a solid state subsequent to its application about the outer perimeter  78  at the outer fairing  42 , providing a filleted joint. 
     The stator vane  44  is supported relative to the outer fairing  42  such that a gap  79  is provided between the outer end  48  and the outer fairing  42  about the outer perimeter  78 . Said another way, a clearance is provided about the outer perimeter  78  within the first slot  52 . The liquid sealant  80  is injected into the gap  79  to vibrationally isolate the outer end  48  from the outer fairing  42  during the engine operation and provide a seal. 
     The outer end  48  includes opposing, laterally extending tabs  76  arranged radially outwardly from the outer fairing  42  and spaced from the first wall  50 . The tabs  76  also prevent the stator vanes  44  from being forced radially inward during engine operation. The liquid sealant is provided between the tabs  76  and the first wall  50 . 
     The front architecture  36  is shown in more detail in  FIG. 6 . An inlet case  82  includes circumferentially arranged inlet vanes  84  radially extending between and integrally formed with first and second inlet flanges  86 ,  88 . The inlet case  82  provides a compressor flow path  100  from the bypass flow path  18  to the first compressor stage. The outer fairing  42  is secured to the first inlet flange  86  at the first attachment feature  56  with fasteners  87 . The inner fairing  40  is secured to the second inlet flange  88  at the third attachment feature  66  with fasteners  89 . 
     A splitter  90  is secured over the outer fairing  42  to the second attachment feature  58  with fasteners  91 . The splitter  90  includes an annular groove  92  arranged opposite the second attachment feature  58 . The outer fairing  42  includes a lip  94  opposite the first flange  54  that is received in the annular groove  92 . A projection  96  extends from an inside surface of the splitter  90  and is arranged in close proximity to, but spaced from, an edge  98  of the outer ends  48  to prevent undesired radial outward movement of the stator vanes  44  from the outer fairing  42 . The inner and outer fairings  40 ,  42  and splitter  90  are constructed from an aluminum 6061 alloy in one example. 
     The front architecture  36  is assembled by positioning the inner and outer fairings  40 ,  42  relative to one another. The stator vanes  44  are arranged circumferentially and suspended between the inner and outer fairings  40 ,  42 . That is, the stator vanes  44  are mechanically isolated from the inner and outer fairings  40 ,  42 . The liquid sealant is applied and layed in the gaps  71 ,  79 , which are maintained during the sealing step, to vibrationally isolate the stator vanes  44  from the adjoining structure. The sealant adheres to and bonds the stator vanes and the inner and outer fairings to provide a flexible connection between these components. In the example arrangement, there is no direct mechanical engagement between the stator vanes and fairings. The sealant provides the only mechanical connection and support of the stator vanes relative to the fairings. 
     Since the sealant bonds the stator vanes to the inner and outer fairings, the stator vane ends are under virtually no moment constraint such that there is a significant reduction in stress on the stator vanes. No precision machined surfaces are required on the stator vanes for connection to the fairings. In one example, a stress reduction of over four times is achieved with the disclosed configuration compared with stator vanes that are mechanically supported in a conventional manner at one or both ends of the stator vanes. As a result of being subjected to considerably smaller loads, lower cost, lighter materials can be used, such as an aluminum 2014 alloy, which is also more suitable to forging. Since the liquid sealant is applied after the stator vanes  44  have been arranged in a desired position, any imperfections or irregularities in the slots or stator vane perimeters are accommodated by the sealant, unlike prior art grommets that are preformed. 
     Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.