Abstract:
A gas turbine engine stator segment has a shroud band and a plurality of blade sections. Each of the blade sections has a first section with a first thickness, second section with a second thickness and a fairing section transitioning between the first and second section. The second section thickness is less than the first section thickness.

Description:
BACKGROUND 
     The present application is directed toward a gas turbine engine stator segment, and more particularly, toward a cast stator shroud band and stator blade. 
     Gas turbine engines, such as those commonly used in aircraft are typically segmented with the engine segments being isolated from each other with a seal. Dividing the segments are rotor/stator pairs that combine to form the seal. The rotor/stator seal arrangement allows rotation of an inner aperture to be passed between engine segments without compromising the integrity of the seal. One example seal configuration used in gas turbine engines is a blade seal. A blade seal uses contact between stator blades and rotors to create the seal. Use of a blade seal introduces friction between the stator blades and the rotor, thereby generating heat and wearing the stator blades. In order to reduce friction, the tip of the stator blade is often milled such that the tip is thinner and therefore has a lower contact surface area, leading to less friction and less heat. 
     SUMMARY 
     Disclosed is a stator segment having a shroud band, and a plurality of blades protruding radially inward from the shroud band, each of the blades is defined by a first section having a first thickness, a second section having a second thickness, and a faired section transitioning from the first section to the second section. The second thickness is less than the first thickness. 
     Also disclosed is a turbine engine assembly having a rotor extending radially outward from an inner aperture to an outer periphery, and a stator having a shroud band and a plurality of blades extending inward from the shroud band toward the inner aperture. Each of the blades is defined by a first section having a first thickness, a second section having a second thickness, and a faired section transitioning from the first section to the second section, with the second thickness being less than the first thickness. 
     Also disclosed is a method for creating a stator shroud band having a plurality of radially inward protruding blades. The method has the steps of: casting a single piece having a stator shroud and multiple radially inward protruding blades; and trimming a tip end of each of the protruding blades such that each tip end is a desired length. 
    
    
     
       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 an illustration of an example turbine engine. 
         FIG. 2  is a sectional view of a blade seal portion of the example turbine engine of  FIG. 1 . 
         FIG. 3  is an isometric view of an example stator shroud band and stator blades. 
         FIG. 4  is a side view of the example stator shroud band and stator blades of  FIG. 3 . 
         FIG. 5  is a sectional view of a fairing section and tip end of an example stator blade. 
         FIG. 6  is an end view of an example stator shroud band and stator blade in contact with a rotor. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example turbine engine  10  having an inner aperture  20 . The inner aperture  20  transmits rotational movement through the turbine engine  10  to multiple engine sections  32 ,  34 . The engine sections  32 ,  34  are isolated from each other with a stator  42  and a rotor  44  arranged in a blade seal configuration  60  according to known sealing techniques. The rotor  44  and the inner aperture  20  rotate about an axis  50 . The blade seal configuration  60  can be seen in greater detail in  FIG. 2 , which is a sectional view of the blade seal configuration  60  of the turbine engine  10  of  FIG. 1 . The blade seal  60  is made up of multiple rotor disc  110  and stator segment  120  pairs. Each of the stator segments  120  has a blade component  122  and a stator shroud band component  124 . During operation of the engine  10 , the rotors  110  rotate about the axis  50  along with the inner aperture  20 . The stator blades  122  contact the rotors  110  at a radially inward end  130 , thereby creating a blade seal. An example configuration illustrating the contact between the stator blades  122  and the rotors  110  is illustrated in  FIG. 6 , and described below. 
     An isometric view of an exemplary stator segment  200  is illustrated in  FIG. 3 . The stator segment  200  has a bowed shroud band  210  from which multiple stator blades  260  protrude radially inward. The stator blades  260  each are composed of a base section  220 , which forms the majority of the blade  260 , a tip end  230  for contacting the rotor  110  (illustrated in  FIG. 2 ), and a fairing section  240  transitioning between the base section  220  and the tip end  230 . The stator segment  200  is cast as a single piece resulting in a solid unit of both the blades  260  and the shroud band  210 . The fairing section  240  causes the cast piece to be within acceptable variances by allowing a cast material to flow smoothly and evenly from the base section  220  of the mold into the tip section  230  of the mold. Even flow of the cast material reduces variance in the tip ends  230  of the finished stator segment  200  and ensures that the stator segment  200  falls within design tolerance. 
       FIG. 4  illustrates a cross-sectional side view of the stator segment  200  of  FIG. 3  along view line  250 , with like numerals indicating like elements. Each of the stator blades includes a base section  320 , a fairing section  340 , and a tip end  330 . Additionally indicated in  FIG. 3 , is an expected direction of rotation  360  of contacting rotor. The contacting rotor forms the other half of the blade seal  60  (illustrated in  FIG. 1 ). The blade tip ends  330  have a radial tip length  372  and are angled relative to the rotor to allow for the tip ends  330  to flex with the expected rotation of the rotor. The material used to cast the stator segment  300 , along with the angle of the blade tips  330  allows the tips  330  to flex either with the rotation of the rotor, when the rotor is rotating in an expected direction  360  or in a direction opposing the expected direction  360  of rotation of the rotor when the rotor is rotating a reverse direction. Furthermore, each of the fairing sections has a radial fairing length  374 . 
       FIG. 5  illustrates a single blade tip  400  in contact with a rotating member  470 , which is not drawn to scale with certain features exaggerated for explanation purposes. The illustrated tip end  430  has a radial tip end length  482  of X relative to a base end  420  width  484  of X. This results in a ratio of approximately 1:1 radial tip end length  482  to base end width  484 . Actual implementations include variance and therefore do not have the exact ratio described above. For this reason, a thickness ratio within the range of 0.5:1 to 1.5:1 falls within the present disclosure. Additionally, the tip end  430  has a width  432  of ½X in the illustrated example, thereby improving the performance of the seal. It is understood that the tip end  430  width  432  could fall anywhere within the range of ¼X to ¾X in an alternate embodiment. The base length “X” is determined based on the width of the blade at the base end  420 . Alternately, a value X can be used for the tip end  430  length and the fairing section  440  that is proportional to the base end width  484  without being identical to the base end width  484 . 
       FIG. 6  illustrates a contextual drawing of a stator shroud band  510  and blade  580  relative to a rotor  570 . Included on the rotor  570  is a stator blade contact pad  560 . The contact pad  560  provides a contact surface for the rotor  570 /stator  580  pair that allows for controlled wear of the tip end  530  and the contact pad  560  as a result of friction. The contact pad  560  is constructed of any suitable material that demonstrates desired properties relative to the material of the stator blade  540 . In one example, the contact pad  560  is constructed out of a material that is abrasive to the tip end  530  of the stator blade  540  thereby causing the stator blade  540  to wear during rotation. In another example, the contact pad  560  is abratable relative to the stator blade  540 , thereby causing the contact pad  560  to wear, during rotation. 
     In order to create the above described stator segment  580 , the stator segment  580 , including the stator shroud band  510  and the stator blades, is cast as a single piece. The inclusion of the fairing section  540  of the blade allows the cast material to flow evenly into the section of the mold corresponding to the tip end  530  from the section of the mold corresponding to a blade section  520 , thereby reducing variance of the thickness of the tip end  530  as described above. In addition to the fairing section  540 , the tip ends  530  are cast at a length longer than the desired length. The excess length of the tip ends  530  is then cut off using any known cutting technique, resulting in a desired tip end  530  length. The excess length of the cast tip end  530  reduces variance of the tip end  530  thickness by allowing the cast material to be drawn further into the tip of the mold and ensuring an even thickness at least to the desired length of the tip end. Aside from cutting the tip end  530  to the desired length, the stator segment  580  does not undergo any milling or alterations after it is cast. 
     The above example illustrations show a partial ring stator segment that is combined with other identical stator segments  580  to form a full stator ring. However, it is understood that the stator segment  580  can be cast as a full stator ring rather than the illustrated partial segment and fall within the above disclosure. 
     Although an example 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.