Patent Publication Number: US-10329932-B2

Title: Baffle inserts

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under contract number FA8650-09-D-2923-0021 awarded by the United States Air Force. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to airfoils, and more particularly to vane assemblies for gas turbine engines, for example. 
     2. Description of Related Art 
     Traditionally, turbomachines, as in gas turbine engines, include multiple stages of rotor blades and vanes to condition and guide fluid flow through the compressor and/or turbine sections. Due to the high temperatures in the turbine section, turbine vanes are often cooled with cooling air ducted into an internal cavity of the vane through a vane platform. In order to reduce the amount of cooling air required to cool turbine vanes, space filling baffles can be provided in the vane cavity to reduce the cavity volume, thereby increasing Mach numbers and heat transfer coefficients for the cooling flow. In certain vane designs, Mach numbers and heat transfer coefficients are not always uniform across various regions of the vane. 
     Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved blades and vanes. The present disclosure provides a solution for these problems. 
     SUMMARY OF THE INVENTION 
     An airfoil includes an airfoil body extending from an inner diameter platform to an opposed outer diameter platform along a longitudinal axis. The airfoil body defines a leading edge and a trailing edge and has a cavity defined between the leading edge, the trailing edge, the inner diameter platform and the outer diameter platform. The cavity includes an airfoil protrusion extending inward from an inner surface of the airfoil body. The airfoil includes a baffle body within the cavity extending along a baffle body axis. The baffle body has a baffle protrusion extending along a central protrusion axis at an angle with respect to the baffle body axis. The end of the baffle protrusion abuts an end of the airfoil protrusion to maintain the position of the baffle body within the airfoil body. 
     A flow path can be defined between the inner surface of the airfoil body and the outer surface of the baffle body. The cross-sectional area of the flow path can vary along the baffle body axis to control Mach numbers and heat transfer in the flow path. The distance between the inner surface of the airfoil body and an outer surface of the baffle body varies along the baffle body axis to control heat transfer and Mach numbers of fluid flowing through the cavity. The cross-sectional area of the flow path can converge in a direction from the outer diameter platform toward the inner diameter platform to control Mach numbers and heat transfer in the flow path. The airfoil body can include a fluid inlet proximate to the outer diameter platform. The cross-sectional area of the flow path converges in a direction away from the fluid inlet to control Mach numbers and heat transfer in the flow path. The airfoil body can include a fluid inlet proximate to the inner diameter platform. The cross-sectional area of the flow path can converge in a direction away from the fluid inlet to control Mach numbers and heat transfer in the flow path. 
     In another aspect, the surface area of the end of one of the baffle protrusion or the airfoil protrusion can be greater than the surface area of the end of the other abutting protrusion. The inner surface of the airfoil body can include inwardly extending raised tripping portions. The airfoil protrusion can be one of a plurality of airfoil protrusions and wherein the baffle protrusion is one of a plurality of baffle protrusions. The baffle protrusion can be a first baffle protrusion proximate to a first end of the baffle body. The first baffle protrusion can be shorter than a second baffle protrusion proximate to a second end of the baffle body. The distance between an end of the first protrusion and an outer surface of the baffle body taken along the respective central protrusion axis of the first protrusion is less than that of the second protrusion. The protrusions can extend from a leading edge side of the baffle body, a trailing edge side of the baffle body, a suction side of the baffle body and/or a pressure side of the baffle body. Each airfoil protrusion can abut a respective baffle protrusion. 
     The distance between the inner surface of the airfoil body and the outer surface of the baffle body taken in a direction normal to the inner surface of the airfoil body can be smaller proximate the platform opposite the fluid inlet than proximate to the other platform to maintain a Mach number and heat transfer. The distance between the inner surface of the airfoil body and the outer surface of the baffle body taken in a direction normal to the inner surface of the airfoil body can be smaller proximate the inner diameter platform of the airfoil body than proximate to the outer diameter platform of the airfoil body to a maintain constant Mach numbers and heat transfer. The distance between the outer surface of the baffle body and the baffle body axis taken in a direction normal to the outer surface of the baffle body can vary along the baffle body axis. The maximum distance from the baffle body axis to the outer surface of the baffle body taken in a transverse direction with respect to the baffle body axis can be less than or equal to the minimum distance from the baffle body axis to the end of each one the baffle protrusions taken in a transverse direction with respect to the baffle body axis. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a schematic cross-sectional side elevation view of an exemplary embodiment of a gas turbine engine constructed in accordance with the present disclosure, showing locations of vanes; 
         FIG. 2  is a schematic cross-sectional side elevation view of a portion of the gas turbine engine of  FIG. 1 , showing a vane with baffle inserts; 
         FIG. 3  is a schematic cross-sectional side elevation view of a vane constructed in accordance with the present disclosure, showing vane protrusions extending inward from an inner surface of the vane and baffle protrusions extending outward from an outer surface of the baffle; 
         FIG. 3A  is a schematic cross-sectional front elevation view of a portion of the vane of  FIG. 3 , showing the surface areas of the baffle protrusion and the airfoil protrusion; 
         FIG. 4  is a schematic cross-sectional side elevation view of the vane of  FIG. 3 , showing baffle protrusions of varying lengths extending outward from an outer surface of the baffle; 
         FIG. 5  is a schematic cross-sectional front elevation view of the vane of  FIG. 3 , showing baffle protrusions extending outward from pressure and suction sides of the baffle; and 
         FIG. 6  is a schematic cross-sectional side elevation view of a vane constructed in accordance with the present disclosure, showing a flow channel with a cross-sectional area that converges from both ends towards the middle of the cavity. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a cross-sectional side elevation view of an exemplary embodiment of a gas turbine engine accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  20 . Other embodiments of gas turbine engines in accordance with the disclosure, or aspects thereof, are provided in  FIGS. 2-6 , as will be described. Vanes shown and described herein provide for increased control over Mach numbers and heat transfer between cooling flow paths in the vanes and vane surfaces exposed to high-temperature gases from the gas path. 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B in a bypass duct defined within a fan case  15 , while the compressor section  24  drives air along a core flow path C for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
     With continued reference to  FIG. 1 , the exemplary engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central axis X relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided, and the location of 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 exemplary gas turbine engine  20  is illustrated as a geared architecture  48  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 high pressure turbine  54 . A combustor  56  is arranged in exemplary gas turbine  20  between the high pressure compressor  52  and the high pressure turbine  54 . A mid-turbine frame  58  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  58  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central axis X which is collinear with their longitudinal axes. 
     The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame includes airfoils which are in the core airflow path C. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. It will be appreciated that each of the positions of the fan section  22 , compressor section  24 , combustor section  26 , turbine section  28 , and fan drive gear system  48  may be varied. For example, gear system  48  may be located aft of combustor section  26  or even aft of turbine section  28 , and fan section  22  may be positioned forward or aft of the location of gear system  48 . 
     Now with reference to  FIGS. 1 and 2 , compressor section  24 , combustor section  26  and turbine section  28  include vanes  100 . Each vane  100  includes a vane body  102  extending from an inner diameter platform  104  to an opposed outer diameter platform  106  along a longitudinal axis A. Vane body  100  defines a leading edge  105  and a trailing edge  107 . A cavity  112  is defined between leading edge  105 , trailing edge  107 , inner diameter platform  104  and outer diameter platform  106 . 
     As shown in  FIGS. 2 and 3 , cavity  112  includes airfoil protrusions  108  extending inward from an inner surface  110  of vane body  102 . Vane  100  includes baffle bodies  114  within cavity  112 . Each baffle body  114  extends from a first end  116  to a second end  118  along respective baffle body axes Z. Each baffle body  114  has baffle protrusions  120  extending along respective central protrusion axes Q at an angle with respect to baffle body axis Z. Protrusions extend from a leading edge side of one of the baffle bodies  114 , e.g. the side proximate to leading edge  105 , and a trailing edge side of the other baffle body  114 , e.g. the side proximate to trailing edge  107 . An end  121  of each baffle protrusion  120  abuts an end  123  of each respective airfoil protrusion  108  to maintain the position of baffle body  114  within vane body  102 . Because both vane and baffle bodies  102  and  114 , respectively, both have protrusions, part of a flow path  124 , described in more detail below, is set by baffle protrusions  120  and part of flow path  124  is set by airfoil protrusions  108 , making insertion of baffle bodies  114  into vane cavity  112  during assembly easier. Inner surface  110  of vane body  102  includes inwardly extending raised tripping portions  128 . Vane body  102  includes cooling holes  140  in fluid communication with flow path  124  to provide cooling air to an exterior surface of vane body  102   
     As shown in  FIG. 3 , a distance d between inner surface  110  of vane body  102  and an outer surface  122  of baffle body  114 , taken in a direction normal to inner surface  110  of vane body  102 , varies along baffle body axis Z to control heat transfer and Mach numbers of fluid flowing through cavity  112 . For example, distance d is smaller proximate inner diameter platform  104  than proximate to outer diameter platform  106 . 
     A flow path  124  is defined between inner surface  110  of vane body  102  and outer surface  122  of baffle body  114 . Vane body  102  includes a fluid inlet  126  proximate to outer diameter platform  106 . The cross-sectional area of flow path  124  converges in a direction away from fluid inlet  126  to control Mach numbers and heat transfer in flow path  124 . For example, cross-sectional area of flow path  124  converges in a direction from outer diameter platform  106  toward inner diameter platform  104 , providing substantially constant Mach numbers and heat transfer throughout flow path  124  as flow is bled off through cooling holes  140 . Whereas, traditionally, the cross-sectional area of flow paths between a baffle body and an inner vane surface have been relatively constant in order to facilitate the insertion of the baffle. Since cooling flow typically enters through a fluid inlet on one side of the vane and is bled out through cooling holes, similar to cooling holes  140 , in the vane, Mach numbers and heat transfer, in traditional embodiments, tend to decrease the further the flow is from the inlet, resulting in high metal temperatures at the end of the flow path. 
       FIG. 3A  shows a cross-sectional view of the contact surfaces for airfoil and baffle protrusions,  108  and  120 , respectively. As shown, the surface area  130  of end  121  of baffle protrusion  120  is greater than the surface area  132  of end  123  of airfoil protrusion  108 . However, it is contemplated that in alternate embodiments, surface area  132  of end  123  of airfoil protrusion  108  can be greater than surface area  130  of end  121  of baffle protrusion  120 . This difference in area ensures that end surfaces  121  of baffle protrusions  120  and end surfaces  123  of airfoil protrusions  108  abut one another despite manufacturing tolerances and thermal growth that occurs during engine operation. While both baffle protrusion  120  and airfoil protrusion  108  are shown as having a rectangular cross-sectional shape with rounded corners it is contemplated that baffle protrusions  120  and airfoil protrusions  108  can have a variety of cross-sectional shapes, for example, circular, oval, ellipse, and the like. 
     As shown in  FIG. 4 , the distance f taken between outer surface  122  of baffle body  114  and baffle body axis Z in a direction normal to outer surface  122  of each baffle body  114  varies along baffle body axis Z. The distance p represents the maximum distance taken from baffle body axis Z to outer surface  122  of baffle body  114  in a transverse direction with respect to baffle body axis Z. In order to insert baffle  114 , distance p is less than or equal to the minimum of distances h taken from the baffle body axis Z to the end  121  of each baffle protrusion  120  in a transverse direction with respect to baffle body axis Z. Furthermore, the distance l between an end  121  of a first one of baffle protrusions  120  and an outer surface  122  of baffle body  114 , e.g. also at the base of protrusion  120 , taken along the respective central protrusion axis Q of the first protrusion is greater than a similar distance l taken along the respective central protrusion axis Q of a second one of baffle protrusions  120 . For example, baffle protrusions  120  proximate to second end  118  of baffle body  114  are longer than baffle protrusions  120  proximate to first end  116  of baffle body  114 . 
     With reference now to  FIG. 5 , baffle protrusions  120  and corresponding airfoil protrusions  108  also extend from a suction side of baffle body  114 , e.g. the side facing a suction side  134  of vane body  102 , and a pressure side of baffle body  114 , e.g. the side facing a pressure side  136  of vane body  102 . Those skilled in the art will readily appreciate that baffle protrusions  120  can be positioned in a variety of places with respect to the airfoil body, e.g. vane body  102 , in which they are disposed, depending on the alignment and cooling required. 
     With reference now to  FIG. 6 , vane  200  includes a vane body  202  extending from an inner diameter platform  204  to an opposed outer diameter platform  206  along a longitudinal axis A. Vane body  200  defines a leading edge  205  and a trailing edge  207 . A cavity  212  is defined between leading edge  205 , trailing edge  207 , inner diameter platform  204  and outer diameter platform  206 . Vane body  202  includes a fluid inlet  226 , similar to fluid inlet  126 , proximate to inner diameter platform  204  instead of outer diameter platform  206 . Vane cavity  212  includes baffle bodies  214  that increase in width approaching the center of baffle body  114 . 
     With continued reference to  FIG. 6 , a flow path  224  is defined between inner surface  210  of vane body  202  and outer surface  222  of baffle body  214 . The cross-sectional area of flow path  224  first converges in a radial direction away from fluid inlet  226  toward the center of baffle bodies  214  and then diverges from the center of the baffle bodies  214  towards outer diameter platform  206 . The configuration of vane  200  tends to assist in aiding heat transfer when the temperature of gas path, e.g. core flow path C, is hottest at midspan of vane body  202 . Thus, vanes  100  and  200  show that embodiments of the present disclosure allow the flow path to be tailored to meet heat transfer requirements. While vane bodies, e.g. vane bodies  102  and  202 , are shown and described herein as having fluid inlets, e.g. fluid inlets  126  and  226 , proximate to an inner diameter platform, e.g. inner diameter platform  104  or  204 , or an outer diameter platform, e.g. outer diameter platform  106  or  206 , of the vane body, it is contemplated that the vane body can include fluid inlets proximate to both the inner diameter platform and the outer diameter platform of the vane body. Moreover, while shown and described herein, cooling holes  140  may not be necessary in the vane bodies. In which case, the cooling flow can enter either the inner diameter platform or outer diameter platform and exit at the respective opposite end. 
     Those skilled in the art will readily appreciate that baffles, e.g. baffles  114  and  214 , and their respective protrusions, e.g. baffle protrusions  120  and  220 , can be manufactured in a variety of ways. For example, baffles can be made from sheet metal and protrusions can be stamped in before forming the baffle shape, baffles and protrusions can be cast together, and/or baffles and protrusions can be additively manufactured. Additionally, the baffles can be used in conjunction with other baffles that do not include baffle protrusions. It is also contemplated that embodiments described herein can readily be used in airfoils other than turbine vanes. For example, they can be used in turbine blades, compressor blades, compressor vanes, or any other suitable airfoil application. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for airfoils with superior properties including improved heat transfer coefficients and higher Mach numbers, resulting in more efficient cooling. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.