Patent Publication Number: US-2020291792-A1

Title: Turbine blade with integral flow meter

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 15/285,347 filed on Oct. 4, 2016. The relevant disclosure of the above application is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to gas turbine engines, and more particularly relates to an axial turbine for use within a gas turbine engine that has one or more turbine blades with an integral flow meter. 
     BACKGROUND 
     Gas turbine engines may be employed to power various devices. For example, a gas turbine engine may be employed to power a mobile platform, such as an aircraft. In certain examples, gas turbine engines include an axial turbine that rotates at a high speed when impinged by high-energy compressed fluid. Generally, higher axial turbine inlet fluid temperature and higher axial turbine speed may be required to improve gas turbine engine efficiency. Increased speeds and higher temperatures, however, may require cooling of a turbine blade associated with the axial turbine. In certain instances, cooling may be provided via an additional external part that serves as a cooling fluid metering device, such as a plate or tube, which is coupled to the axial turbine blade. The additional part, however, may require precise alignment to ensure proper cooling of the axial turbine blade and increases cost and weight associated with the axial turbine. 
     Accordingly, it is desirable to provide improved cooling for an axial turbine blade using an integral flow meter, which supplies cooling fluid to the axial turbine blade without requiring additional parts. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     SUMMARY 
     According to various embodiments, a turbine blade is provided. The turbine blade includes a trailing edge and a leading edge opposite the trailing edge. The turbine blade includes at least one cooling passage defined internally within the turbine blade, and the at least one cooling passage is in fluid communication with a source of cooling fluid via an inlet to receive a cooling fluid. The turbine blade also includes at least one flow meter formed within the turbine blade at the inlet that supplies the cooling fluid to the at least one cooling passage. 
     Also provided according to various embodiments is a method of manufacturing a turbine blade. The method includes forming the turbine blade with at least one integral cooling passage, and the turbine blade has an inlet in fluid communication with a source of a cooling fluid and at least one integrally formed flow meter. The method includes machining at least one flow meter at the inlet to adjust a flow of the cooling fluid into the at least one cooling passage based on a determined cooling requirement for the at least one cooling passage. 
     Further provided according to various embodiments is a turbine blade. The turbine blade includes a trailing edge and a leading edge opposite the trailing edge. The turbine blade also includes at least a first cooling passage and a second cooling passage defined internally within the turbine blade. The first cooling passage is in fluid communication with a source of cooling fluid via an inlet defined in the turbine blade to receive a cooling fluid, and at least one flow meter is formed within the turbine blade at the inlet that supplies the cooling fluid to the second cooling passage. 
     Also provided is a turbine blade. The turbine blade includes a trailing edge and a leading edge opposite the trailing edge. The turbine blade includes a plurality of cooling passages each having a respective inlet in fluid communication with a source of cooling fluid to receive a cooling fluid. The turbine blade includes a plurality of flow meters, with at least a respective one of the plurality of flow meters associated with a respective one of the plurality of cooling passages at the respective inlet. 
     Further provided is a turbine blade. The turbine blade includes a trailing edge and a leading edge opposite the trailing edge. The turbine blade includes a plurality of cooling passages each having a respective inlet in fluid communication with a source of cooling fluid to receive a cooling fluid. The turbine blade includes a plurality of flow meters, with at least a respective one of the plurality of flow meters associated with a respective one of the plurality of cooling passages at the respective inlet. Each of the plurality of flow meters includes a volume of additional material defined about the respective inlet. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a schematic cross-sectional illustration of a gas turbine engine including an axial turbine having a turbine blade according to the various teachings of the present disclosure; 
         FIG. 2  is a detail cross-sectional illustration of a portion of the gas turbine engine of  FIG. 1 , identified at  2  in  FIG. 1 , which includes the axial turbine having the turbine blade, and the turbine blade includes an exemplary cooling passage having an integral flow meter, with the cross-sectional illustration taken along a surface coincident with the camber line of the turbine airfoil at all radial spans; 
         FIG. 3  is a side perspective view of the turbine blade of  FIG. 2 , which includes a portion of a forward seal plate and a rear seal plate; 
         FIG. 4  is a cross-sectional view of the turbine blade of  FIG. 3 , taken along a surface intersecting the camber line of the turbine airfoil at all radial spans; 
         FIG. 5  is a front perspective view of the turbine blade of  FIG. 2 , with the forward seal plate removed to illustrate the integral flow meter; 
         FIG. 6  is a flow chart illustrating an exemplary method of manufacturing the turbine blade of  FIG. 2 ; 
         FIG. 7  is a schematic cross-sectional view of a turbine blade for an axial turbine that includes an exemplary cooling passage having the integral flow meter according to the various teachings of the present disclosure, with the cross-sectional illustration taken along a surface coincident with the camber line of the turbine airfoil at all radial spans; 
         FIG. 8  is a schematic cross-sectional view of a turbine blade for an axial turbine that includes an exemplary cooling passage having an integral flow meter according to the various teachings of the present disclosure with the cross-sectional illustration taken along a surface coincident with the camber line of the turbine airfoil at all radial spans; and 
         FIG. 9  is a flow chart illustrating an exemplary method of manufacturing the turbine blade of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any type of turbine blade that would benefit from an internal flow meter, and that the axial turbine blade described herein for use with a gas turbine engine is merely one exemplary embodiment according to the present disclosure. Moreover, while the turbine blade is described herein as being used with an axial turbine of a gas turbine engine onboard a mobile platform or vehicle, such as a bus, motorcycle, train, motor vehicle, marine vessel, aircraft, rotorcraft and the like, the various teachings of the present disclosure can be used with a gas turbine engine or with an axial turbine associated with a stationary platform. Further, it should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure. In addition, while the figures shown herein depict an example with certain arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment. It should also be understood that the drawings are merely illustrative and may not be drawn to scale. 
     With reference to  FIG. 1 , a partial, cross-sectional view of an exemplary gas turbine engine  100  is shown with the remaining portion of the gas turbine engine  100  being axi-symmetric about a longitudinal axis  140 , which also comprises an axis of rotation for the gas turbine engine  100 . In the depicted embodiment, the gas turbine engine  100  is an annular multi-spool turbofan gas turbine jet engine  100  within an aircraft  99 , although other arrangements and uses may be provided. The gas turbine engine  100  may be, for example, an auxiliary power unit (“APU”). As will be discussed herein, one or more axial turbine blades of the gas turbine engine  100  includes an integral flow meter, which supplies cooling fluid to a portion of the axial turbine blade. By using an integral flow meter, an external part is not required to meter cooling fluid to the turbine blade, thereby reducing cost and complexity associated with cooling the axial turbine blade. As used herein, the term “integral” denotes a component, such as the flow meter, which is formed within the turbine blade or defined within the turbine blade so as to be a part of the turbine blade and is not separate from the turbine blade itself. Stated another way, the term “integrally formed” and “integral” mean one-piece and excludes brazing, fasteners, or the like for coupling components in a fixed relationship as a single unit. 
     In this example, the gas turbine engine  100  includes fan section  102 , a compressor section  104 , a combustor section  106 , a turbine section  108 , and an exhaust section  110 . The fan section  102  includes a fan  112  mounted on a rotor  114  that draws air into the gas turbine engine  100  and accelerates it. A fraction of the accelerated air exhausted from the fan  112  is directed through an outer (or first) bypass duct  116  and the remaining fraction of air exhausted from the fan  112  is directed into the compressor section  104 . The outer bypass duct  116  is generally defined by an inner casing  118  and an outer casing  144 . In the embodiment of  FIG. 1 , the compressor section  104  includes an intermediate pressure compressor  120  and a high pressure compressor  122 . However, in other embodiments, the number of compressors in the compressor section  104  may vary. In the depicted embodiment, the intermediate pressure compressor  120  and the high pressure compressor  122  sequentially raise the pressure of the air and direct a majority of the high pressure air into the combustor section  106 . A fraction of the compressed air bypasses the combustor section  106  and is used to cool, among other components, turbine blades in the turbine section  108  via an inner bypass duct. 
     In the embodiment of  FIG. 1 , in the combustor section  106 , which includes a combustion chamber  124 , the high pressure air is mixed with fuel and combusted. The high-temperature combusted air is then directed into the turbine section  108 . In this example, the turbine section  108  includes three turbines disposed in axial flow series, namely, a high pressure turbine  126 , an intermediate pressure turbine  128 , and a low pressure turbine  130 . However, it will be appreciated that the number of turbines, and/or the configurations thereof, may vary. In this embodiment, the high-temperature combusted air from the combustor section  106  expands through and rotates each turbine  126 ,  128 , and  130 . As the turbines  126 ,  128 , and  130  rotate, each drives equipment in the gas turbine engine  100  via concentrically disposed shafts or spools. In one example, the high pressure turbine  126  drives the high pressure compressor  122  via a high pressure shaft  134 , the intermediate pressure turbine  128  drives the intermediate pressure compressor  120  via an intermediate pressure shaft  136 , and the low pressure turbine  130  drives the fan  112  via a low pressure shaft  138 . 
     With reference to  FIG. 2 , a portion of the high pressure turbine  126  of the gas turbine engine  100  of  FIG. 1  is shown in greater detail. In this example, the high pressure turbine  126  is an axial turbine. It should be understood that while the high pressure turbine  126  is described herein as comprising a dual alloy axial turbine, the high pressure turbine  126  may comprise a single alloy, which may be cast or machined, or it may be an inserted blade and disk arrangement. In addition, while the high pressure turbine  126  is illustrated herein as being used with the gas turbine engine  100 , which can be included with an auxiliary power unit, the high pressure turbine  126  can be employed with various types of engines, including, but not limited to, turbofan, turboprop, turboshaft, and turbojet engines, whether deployed onboard an aircraft, watercraft, or ground vehicle (e.g., a tank), included within industrial power generators, or utilized within another platform or application. 
     The turbine section  108  includes a turbine duct section  200 , which is in fluid communication with the combustor section  106  to receive combustive gases from the combustion chamber  124 . A second turbine duct section  202  is positioned downstream from the high pressure turbine  126 , and is in fluid communication with the intermediate pressure turbine  128  ( FIG. 1 ). The second turbine duct section  202  directs the combustive gas flow  204  from the high pressure turbine  126  to the intermediate pressure turbine  128 . 
     The combustive gas flow  204  drives rotation of the high pressure turbine  126 , which drives the high pressure compressor  122 . In this example, a first, forward seal plate  206  is coupled to the high pressure turbine  126  so as to be upstream from the high pressure turbine  126  in a direction of airflow, and a second, rear seal plate  208  is coupled to the high pressure turbine  126  so as to be downstream from the high pressure turbine  126  in the direction of air flow. Generally, the forward seal plate  206  at least partially defines a cooling fluid plenum  210 . In this example, the cooling fluid plenum  210  receives cooling fluid or air from a source upstream from the high pressure turbine  126  and cooperates with the forward seal plate  206  to direct the cooling fluid into each of a plurality of blades  212  of the high pressure turbine  126 . Thus, in this embodiment, each of the plurality of blades  212  comprise forward-fed turbine blades. 
     In one example, the cooling fluid plenum  210  is in fluid communication with an outlet  214 , which provides cooling fluid, as indicated in  FIG. 2  by arrows  216 , bled from a section of the gas turbine engine  100  upstream of the combustor section  106 . In this example, a portion of the airflow flowing within compressor section  104  ( FIG. 1 ) is diverted into the inner bypass duct  118  to provide the cooling fluid  216 . The cooling fluid  216  flowing from the inner bypass duct  118  is directed radially inward toward the engine centerline via the outlet  214  and an inlet  218  defined through a portion of the forward seal plate  206 . From the inlet  218 , the cooling fluid  216  flows axially along the high pressure shaft  134  and ultimately flows into an inlet  220  of each of the plurality of blades  212 . The inlet  220  provides each of the plurality of blades  212  with cooling fluid to internally cool the plurality of blades  212 . 
     With continued reference to  FIG. 2 , the high pressure turbine  126  includes a turbine rotor  224  having a hub  226  and the plurality of blades  212 . The hub  226  is substantially annular about the axis of rotation or longitudinal axis  140 , and is coupled to the high pressure shaft  134 . In one example, the hub  226  is substantially one-piece or monolithic. In one example, the hub  226  is composed of a nickel-based superalloy, having a relatively high Low Cycle Fatigue (LCF) resistance and moderate thermal tolerance. The hub  226  defines a throughbore  230  and an outer peripheral surface  232 . The throughbore  230  is generally defined near the axial centerline of the turbine rotor  224 , and enables the turbine rotor  224  to be positioned about at least the intermediate pressure shaft  136  ( FIG. 1 ). The outer peripheral surface  232  is coupled to the plurality of blades  212 . 
     As will be discussed further herein, each of the plurality of blades  212  is coupled to the outer peripheral surface  232  of the hub  226  so as to be spaced apart about a circumference of the hub  226 . As each of the plurality of blades  212  are substantially the same or similar, for ease of description, a single blade  212  will be discussed in detail herein. With reference to  FIG. 3 , the blade  212  has an airfoil  238  extending outwardly from a root  240 . The airfoil  238  includes a leading edge  242 , a trailing edge  244 , a first or pressure side  246  and a second or suction side  248 . At least one cooling passage  250  is defined internally within the blade  212  and is in fluid communication with the inlet  220  to receive the cooling fluid  216 . The cooling passage  250  extends from the root  240  to a tip or tip portion  262  of the airfoil  238  to direct cooling fluid through the blade  212 . As will be discussed further herein, at least one flow meter is formed or defined within the blade  212  at the inlet  220  to supply the cooling fluid  216  to the at least one cooling passage  250 . 
     A first or top surface  252  of the root  240  is coupled to a bottom surface  254  of the airfoil  238 . A second or bottom surface  256  of the root  240  is in contact with the outer peripheral surface  232  of the hub  226  to couple the blade  212  to the hub  226 . For example, with reference to  FIG. 2 , the root  240  may be metallurgically bonded to the outer peripheral surface  232  of the hub  226  via diffusion bonding along a bond line BL. It should be understood that various other techniques may be employed to couple the blade  212  to the hub  226 , such as through blade attachment slots that receive the bottom surface  256  of the root  240 . 
     The root  240  also includes a first or forward side  258  and a second or aft side  260 . Each of the first side  258  and the second side  260  define annular flanges  261 , which extend outwardly from the first side  258  and the second side  260  to project over the forward seal plate  206  and the rear seal plate  208 . The first side  258  is coupled to the forward seal plate  206 , and is upstream from the second side  260  in a direction of airflow A. The first side  258  defines the inlet  220  for the cooling passage  250 . Generally, the cooling passage  250  of the blade  212  includes only a single inlet, the inlet  220 . The second side  260  is coupled to the rear seal plate  208 . 
     The leading edge  242  of the airfoil  238  extends from the tip portion  262  to the bottom surface  254 . The trailing edge  244  comprises the distalmost portion of the airfoil  238 . The pressure side  246  is substantially opposite the suction side  248 . Each of the pressure side  246  and the suction side  248  extend along the airfoil  238  from the leading edge  242  to the trailing edge  244 . 
     The cooling passage  250  is defined within the root  240  and the airfoil  238  to direct cooling fluid through the blade  212 . Generally, the cooling passage  250  is defined wholly or entirely within the blade  212 . With reference to  FIG. 4 , the cooling passage  250  is shown in greater detail. In this example, the cooling passage  250  includes the inlet  220 , a first, leading cooling passage  270 , a second, secondary cooling passage  272 , a third, tip plenum  274  and at least one fourth, trailing cooling passage  276 . Each of the cooling passages  270 - 276  receive the cooling fluid  216  from the inlet  220  and cooperate to cool the blade  212 . It should be noted that although while not illustrated herein for clarity, the airfoil  238  generally includes a plurality of film cooling holes over an exterior surface of the airfoil  238  to direct cooling fluid over the exterior surface of the airfoil  238 . 
     The leading cooling passage  270  is defined along the first side  258  of the root  240  and adjacent to the leading edge  242  of the airfoil  238 . The leading cooling passage  270  has an inlet  278 . The inlet  278  is downstream from the inlet  220  and is in fluid communication with the inlet  220  to receive the cooling fluid  216 . In certain embodiments, the leading cooling passage  270  is also in fluid communication with a leading edge cooling passage  280  via a plurality of conduits  282 . The leading edge cooling passage  280  receives a portion of the cooling fluid  216  from the leading cooling passage  270  via the conduits  282  to assist in further cooling the leading edge  242  of the airfoil  238 . The leading cooling passage  270  also includes a conduit  284  defined near the tip portion  262 , which is in fluid communication with the tip plenum  274 . Thus, the conduit  284  directs a portion of the cooling fluid  216  from the leading cooling passage  270  to the tip plenum  274  to cool the tip portion  262  of the blade  212 . 
     The secondary cooling passage  272  is defined through the airfoil  238  and the root  240  so as to be downstream from the leading cooling passage  270 , between the leading cooling passage  270  and the trailing edge  244  of the blade  212 . In this example, the secondary cooling passage  272  comprises a serpentine passage. In other examples, the secondary cooling passage  272  comprises a radial passage. The secondary cooling passage  272  is in fluid communication with an integral flow meter  288  to receive the cooling fluid  216 . In this regard, the flow meter  288  is defined through a portion of the airfoil  238  between the leading cooling passage  270  and the secondary cooling passage  272  to supply the secondary cooling passage  272  with a predefined amount of the cooling fluid  216 . In one example, the flow meter  288  comprises a bore defined through a dividing wall  289  of the airfoil  238  that has a predetermined diameter to direct a particular flow rate of the cooling fluid  216  into the secondary cooling passage  272 . The dividing wall  289  separates the leading cooling passage  270  from the secondary cooling passage  272 , and is defined within the airfoil  238 . In one embodiment, there may be two cooling passages and one flow meter  288 . In other embodiments there may be more than two cooling passages and more than one flow meter  288 . 
     While the flow meter  288  is illustrated herein as having a diameter D 2  that is substantially the same over a length L 2  of the flow meter  288 , the flow meter  288  can have a diameter that varies over the length L 2  of the integral flow meter  288 . Moreover, while the flow meter  288  is illustrated herein as comprising a cylindrical bore ( FIG. 5 ), the flow meter  288  can be formed with any desired shape, such as elliptical, triangular, etc. Further, with reference to  FIG. 2 , while the flow meter  288  is illustrated herein as being defined along an axis A 2  substantially parallel to the longitudinal axis  140  of the gas turbine engine, the flow meter  288  can be defined along an axis that is transverse to or oblique to the longitudinal axis  140 . The cross sectional flow area of the meter restricts the flow, and is sized based on the needs of the cooling circuit(s), in this example, the secondary cooling passage  272 . Generally, the area of the flow meter  288  is directly proportional to a flow rate of the cooling fluid  216  that is supplied to the secondary cooling passage  272 . In the example of a cylindrical bore for the flow meter  288 , the cross-sectional area of the flow meter  288  is defined as: 
     
       
         
           
             
               
                 
                   A 
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                         ( 
                         
                           
                             D 
                             2 
                           
                           2 
                         
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                     2 
                   
                 
               
               
                 
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     Wherein, D 2  is the diameter of the flow meter  288 . With reference back to  FIG. 4 , the flow meter  288  includes a flow meter inlet  290  and a flow meter outlet  292 . The flow meter inlet  290  is in fluid communication with the inlet  220  to receive the cooling fluid  216 , and the flow meter outlet  292  is in fluid communication with a secondary passage inlet  294  to provide the secondary cooling passage  272  with the cooling fluid  216 . Thus, in one embodiment, the flow meter  288  is the primary supply or source of cooling fluid  216  into the secondary cooling passage  272 . Stated another way, the flow meter  288  controls substantially a majority of the flow of the cooling fluid  216  into the secondary cooling passage  272 , as the secondary cooling passage  272  is divided from the leading cooling passage  270  by the dividing wall  289  and is not in direct fluid communication with the leading cooling passage  270 . Rather, the secondary passage inlet  294  of the secondary cooling passage  272  is primarily in fluid communication with the flow meter  288 , and secondarily in fluid communication with the leading cooling passage  270  at a secondary location  299 . Generally, the flow meter  288  provides about 60% to about 100% of the flow of the cooling fluid  216  into the secondary cooling passage  272 , while the secondary location  299  provides about 0% to about 40% of the flow of the cooling fluid  216  into the secondary cooling passage  272 . In one embodiment, the flow meter  288  controls all of the flow of the cooling fluid  216  at a first location between the leading cooling passage  270  and the secondary cooling passage  272 , but the leading cooling passage  270  and the secondary cooling passage  272  may communicate at other locations, which are spaced apart from the first location. As will be discussed, the flow meter  288  can be machined to control an amount or flow rate of the cooling fluid  216  received into the secondary cooling passage  272 . 
     Although the flow rate through the flow meter  288  is generally proportional to the cross-sectional area of the flow meter  288 , the flow rate is also a function of aerodynamic flow characteristics within the metering hole that is the flow meter  288 . Because these flow characteristics can be affected by the metering hole inlet and exit geometries, the flow rate through the flow meter  288  can also be affected by these geometries. The aerodynamic flow characteristics are generally quantified as the hole flow, or discharge, coefficient where the flow rate is directly proportional to the flow coefficient. Thus, flow rate can also be modified by changes to the shape of the flow meter inlet  290  or flow meter outlet  292  of the flow meter  288 , in addition to the area of the hole that is the flow meter  288 . In this embodiment, the flow rate through the metering hole that is the flow meter  288  can be both increased and reduced depending upon the cooling requirements for the secondary cooling passage  272 . 
     For example, by making the inlet geometry of the flow meter  288  near or at the flow meter inlet  290  the shape of a bellmouth in the cast form, one can ensure the flow coefficient is relatively high. However, if one were to remove the bellmouth shape that were cast and machine a smaller inlet fillet radius at the inlet  290  of the flow meter  288 , the flow coefficient could be reduced. Similarly, by shaping the inlet  220  and/or the region adjacent to the inlet  220  as needed, the cooling fluid  216  would interact with the metering location or the flow meter  288  in a manner that would either increase or decrease, as intended, the flow coefficient. In this example, a passage  221  between the inlet  220  of the blade  212  and the metering location or flow meter  288  is treated as a single inlet to the flow meter  288  for metering of the cooling fluid  216 . Therefore, any modification to this geometry has the potential to increase or decrease the flow rate of the flow meter  288 . For example, one or more disruptive features can be cast or machined within the passage  221  to disrupt the flow of the cooling fluid  216  into the flow meter  288 . These modifications can be modeled with fluid dynamics based computation modeling or empirically derived through testing. Thus, the geometry of the inlet  290  of the flow meter  288 , the geometry of the inlet  220  and the geometry of the passage  221  can each be modified, via machining or casting, in a predetermined manner to change a flow coefficient through the flow meter  288 , and thereby increase or decrease a flow rate of the cooling fluid  216  that is the primary source of the cooling fluid  216  supplied to the secondary cooling passage  272 . In addition, the flow meter outlet  292  of the flow meter  288  can be machined to change the flow coefficient, and thus, the flow rate through the flow meter  288  as determined by the fluid dynamics based computation modeling or testing. 
     The secondary cooling passage  272  also includes one or more trailing conduits  296  downstream from the secondary passage inlet  294  and one or more tip conduits  298 . The trailing conduits  296  direct a portion of the cooling fluid  216  from the secondary cooling passage  272  to the at least one trailing cooling passage  276 . The tip conduits  298  direct a portion of the cooling fluid  216  from the secondary cooling passage  272  to the tip plenum  274 . 
     The tip plenum  274  is in fluid communication with the conduit  284  of the leading cooling passage  270  and the tip conduits  298  of the secondary cooling passage  272  to receive the portion of the cooling fluid  216 . The tip plenum  274  generally extends along the tip portion  262  from the leading edge  242  to the trailing edge  244  to cool the tip portion  262  of the airfoil  238 . 
     At least one trailing cooling passage  276  is in fluid communication with the secondary cooling passage  272  via the trailing conduits  296 . In this example, the at least one trailing cooling passage  276  comprises four trailing flow passages  276   a - d , which are each in fluid communication with one or more of the trailing conduits  296  to receive the cooling fluid  216 . Each of the trailing flow passages  276   a - d  receive the cooling fluid  216  from the secondary cooling passage  272  to cool the airfoil  238  along the trailing edge  244 . Thus, generally, the trailing flow passages  276   a - d  are defined within the airfoil  238  along the trailing edge  244  from the tip portion  262  to the bottom surface  254 . 
     With reference to  FIG. 2 , the forward seal plate  206  defines the inlet  218  at a distal end  300  and is coupled to the first side  258  of the blade  212  at a proximal end  302 . The distal end  300  can also define a first plurality of sealing teeth  304  and a second plurality of sealing teeth  306 . The sealing teeth  304 ,  306  extend outwardly from the forward seal plate  206  and seal against adjacent structures within the gas turbine engine  100  to ensure that a substantial majority of the cooling fluid  216  is directed into the inlet  218 . The proximal end  302  defines a groove  308 , which receives a sealing member  310 . The sealing member  310  seats against the first side  258  and forms a seal that substantially prevents leakage of the cooling fluid  216  from the cooling fluid plenum  210 . 
     The rear seal plate  208  is coupled to the second side  260  of the blade  212  at a proximal end  312 , and is coupled to an adjacent forward seal plate (not shown) at a distal end  314 . The proximal end  312  defines a groove  316 , which receives a second sealing member  318 . The second sealing member  318  seats against the second side  260  and forms a seal that substantially prevents leakage of a cooling fluid for an adjacent rotor (not shown). The distal end  314  defines a passage  320  for cooling fluid for the adjacent rotor, and can also define one or more sealing fins  322  that extend outwardly from the rear seal plate  208 . The sealing fins  322  seal against adjacent structures within the gas turbine engine  100  to ensure that a substantial majority of the cooling fluid for the adjacent rotor is directed from the passage  320  into the corresponding inlet for the cooling passage of the adjacent rotor. The forward seal plate  206  and the rear seal plate  208  can be composed of any suitable material, such as a metal or metal alloy. 
     With reference to  FIG. 6 , and with continued reference to  FIGS. 1-5 , in accordance with one example, a method  399  of manufacturing the blade  212  with the flow meter  288  is shown. The method begins at  400 . At  402 , the blade  212  is formed. In one example, the blade  212  is formed using investment casting. In this example, a core is formed from a ceramic material, which may be cast, molded, or manufactured from a ceramic using ceramic additive manufacturing or selective laser sintering. Generally, the core comprises the inverse of the cooling passage  250  shown in  FIG. 4  without the flow meter  288 . Stated another way, the core comprises the inlet  220 , the leading cooling passage  270 , the secondary cooling passage  272 , the tip plenum  274  and the at least one trailing cooling passage  276 , but does not include the flow meter  288 . With the core formed, the core is positioned within a die. With the core positioned within the die, the die is injected with liquid wax such that liquid wax surrounds the core. A wax sprue or conduit may also be coupled to the core within the die to aid in the formation of the blade  212 . Once the wax has hardened to form a wax pattern, the wax pattern is coated or dipped in ceramic to create a ceramic mold about the wax pattern. After coating the wax pattern with ceramic, the wax pattern may be subject to stuccoing and hardening until the ceramic mold has reached the desired thickness. 
     With the ceramic mold at the desired thickness, the wax is heated to melt the wax out of the ceramic mold. With the wax melted out of the ceramic mold, voids remain surrounding the core. The ceramic mold is filled with molten metal or metal alloy. In one example, the molten metal is poured down an opening created by the wax sprue. Once the metal or metal alloy has solidified, the ceramic is removed from the metal or metal alloy, through chemical leaching, for example, leaving the cooling passage  250  formed in the metal or metal alloy, as illustrated in  FIG. 4 . 
     It should be noted that alternatively the blade  212  may be formed using conventional dies with one or more portions of the cooling passage  250  (or portions adjacent to the cooling passage  250 ) comprising a fugitive core insert. 
     With the blade  212  formed, at  404 , the cooling requirements for the secondary cooling passage  272  are determined. In one example, the cooling requirements are pre-defined, via a fluid dynamics analysis performed using a computer model of the blade  212 . In other embodiments, the cooling requirements are pre-defined based on experimental testing and simulation. In still other embodiments, the cooling requirements are defined based on a regulation from one or more governing agencies. 
     At  406 , the flow meter  288  is machined through the inlet  220  of the blade  212 . In this regard, given the determined cooling requirements for the secondary cooling passage  272 , the flow meter  288  is defined through the inlet  220  to fluidly couple the inlet  220  to the secondary cooling passage  272 . In this example, with reference to  FIG. 4 , the inlet  220  has a diameter D 3 , which is sized to enable a tool to be inserted into the inlet  220  to form or define the flow meter  288 . Generally, the diameter D 3  of the inlet  220  is greater than the diameter D 2  of the flow meter  288 . In one example, the flow meter  288  is machined through the dividing wall  289  by drilling, grinding and/or milling the bore that defines the flow meter  288  through the dividing wall  289 . In other embodiments, the flow meter  288  is formed by electrical discharge machining (EDM). With reference to  FIG. 6 , optionally at  407 , one or more of the geometry of the flow meter inlet  290  of the flow meter  288 , the flow meter outlet  292  of the flow meter  288 , the geometry of the inlet  220  and the geometry of the passage  221  are machined, via EDM for example, to change the flow coefficient through the flow meter  288 , and thereby increase or decrease a flow rate of the cooling fluid  216  that is the primary source of the cooling fluid  216  supplied to the secondary cooling passage  272 . 
     With continued reference to  FIG. 6 , at  408 , it is determined whether there is sufficient cooling flow into the secondary cooling passage  272 . In one example, this determination can be made by testing the blade  212  in a test rig, in which a cooling flow through the blade  212 , including the secondary cooling passage  272 , is measured. In another example this determination may be made by dimensional inspection of the flow meter  288  and the inlet  220 . 
     Based on the determination at  408 , if the secondary cooling passage  272  is receiving the desired amount of the cooling fluid  216  from the flow meter  288 , at  410 , the method ends. Otherwise, at  412 , the flow meter  288  is further machined through the inlet  220 , the inlet  220  is further machined and/or the passage  221  is further machined to adjust the cooling fluid  216  supplied to the secondary cooling passage  272 . In one example, the diameter D 2  of the bore of the flow meter  288  is enlarged to increase the flow rate of the cooling fluid  216  to the secondary cooling passage  272 ; however, one or more of the inlet  290 , the outlet  292 , the inlet  220  of the blade  212  and the passage  221  can be modified to reduce the flow rate of the cooling fluid  216  to the secondary cooling passage  272 . The method proceeds back to  408 . 
     The method of  FIG. 6  can be repeated to form any number of blades  212  for use with the turbine rotor  224 . With the desired number of blades  212  formed, the blades  212  are consolidated into a ring, and coupled together through any conventional technique to form a blade ring. The blade ring comprising the blades  212  is coupled to the hub  226  to form the turbine rotor  224 . With the turbine rotor  224  formed and assembled, the turbine rotor  224  can be installed in the gas turbine engine  100 . 
     As each of the blades  212  of the turbine rotor  224  include the cooling passage, having the integral flow meter  288 , the cooling fluid  216  is supplied to the blades  212  without requiring additional metering plates or metering components. By forming the flow meter  288  integrally with the blade  212  to provide the desired cooling flow, the amount of cooling fluid  216  used by the blade  212  substantially comports with the amount of cooling flow needed by the blade  212 , thereby reducing instances where the blade  212  is receiving more cooling fluid  216  than needed, which may impact fuel consumption of the gas turbine engine  100 . Moreover, the integrally formed flow meter  288  ensures the proper amount of the cooling fluid  216  is supplied to the secondary cooling passage  272  of the blade  212 , thereby reducing the likelihood that the blade  212  is insufficiently cooled. 
     It should be noted that while the flow meter  288  is described herein as being separately defined after the formation of the blade  212 , it will be understood that the present disclosure is not so limited. In this regard, the flow meter  288  can be part of the core used with the investment casting of the blade  212  such that the flow meter  288  is integrally formed or defined during the investment casting of the blade  212 . In this example, the flow meter  288  defined by the investment casting can be separately machined via drilling, grinding, milling and/or EDM to tune the amount of cooling fluid  216  received by the secondary cooling passage  272  in a separate step after formation of the blade  212 . 
     It should be noted that the cooling passage  250  described with regard to  FIGS. 1-6  is merely exemplary, and depending upon the shape and size of the axial turbine, the shape of the cooling passage  250  may vary. For example, with reference to  FIG. 7 , a cross-section of a blade  500  of an axial turbine is shown. As the blade  500  includes components that are the same or substantially similar to the blade  212  discussed with regard to  FIGS. 1-6 , the same reference numerals will be used herein to denote the same or similar components. In this example, the blade  500  is metallurgically bonded to an outer peripheral surface of a hub via diffusion bonding along a bond line BL 2 , and does not include the root  240  as discussed with regard to  FIGS. 1-6 . 
     The blade  500  includes an airfoil  502  having a leading edge  504 , the trailing edge  244 , the first or pressure side  246  and the second or suction side  248 . In this example, due to the shape of the blade  500 , an inlet  508  is defined through a portion of the airfoil  502  below the leading edge  504 . Thus, in this example, the cooling fluid  216  flows axially along the high pressure shaft  134  and ultimately flows into the inlet  508  of each of the plurality of blades  500  adjacent to or near the leading edge  504 . The inlet  508  provides each of the plurality of blades  500  with cooling fluid to internally cool the plurality of blades  500 . At least one cooling passage  510  is defined internally within the blade  500  and is in fluid communication with the inlet  508 . 
     The cooling passage  510  is defined within the airfoil  502  to direct cooling fluid through the blade  212 . Generally, the cooling passage  510  is defined wholly or entirely within the airfoil  502 . The cooling passage  510  includes the inlet  508 , the leading cooling passage  270 , the secondary cooling passage  272 , the tip plenum  274  and the at least one trailing cooling passage  276 . Each of the cooling passages  270 - 276  receive the cooling fluid  216  from the inlet  508  and cooperate to cool the blade  500 . It should be noted that although while not illustrated herein for clarity, the airfoil  502  generally includes a plurality of film cooling holes over an exterior surface of the airfoil  502  to direct cooling fluid over the exterior surface of the airfoil  502 . As the cooling passage  510 , including the integral flow meter  288 , is substantially the same as the cooling passage  250  and the flow meter  288  discussed with reference to  FIGS. 1-6  with the exception of the location of the inlet  508 , the cooling passage  510  will not be discussed in detail herein. Moreover, as the blade  500  with the integral flow meter can be formed using the method of blocks  400 - 412  of  FIG. 6 , the method of manufacturing the blade  500  will also not be discussed in detail herein. 
     It should be noted that the present disclosure is not limited to forward fed turbine blades  212 ,  500 , but is equally applicable to bottom fed turbine blades as well. In this regard, with reference to  FIG. 8 , a bottom fed turbine blade  600  is shown. The blade  600  is coupled to a hub to form a turbine rotor (not shown), and can be used with the gas turbine engine  100  of  FIGS. 1-6 . The blade  600  has an airfoil  602  extending outwardly from a root  604 . The airfoil  602  includes a leading edge  606 , a trailing edge  608 , a first or pressure side  610  and a second or suction side  612 . At least one or a plurality of cooling passages  614  are defined internally within the blade  600 , and each of the plurality of cooling passages  614  are in fluid communication with respective ones of a plurality of integral flow meters  616 . As will be discussed, the plurality of cooling passages  614  extend from the root  604  to a tip or tip portion  618  of the airfoil  602  to direct cooling fluid through the blade  600 . 
     A first or top surface  620  of the root  604  is coupled to the airfoil  602 . A second or bottom surface  622  of the root  604  defines the plurality of flow meters  616 , as will be discussed further herein. The root  604  also includes a first side  624  opposite a second side  626 . The leading edge  606  of the airfoil  602  extends from the tip portion  618  to the top surface  620  of the root  604 . The trailing edge  608  comprises the distalmost portion of the airfoil  602 . The pressure side  610  is substantially opposite the suction side  612 . Each of the pressure side  610  and the suction side  612  extend along the airfoil  602  from the leading edge  606  to the trailing edge  608 . 
     The plurality of cooling passages  614  are defined within the root  604  and the airfoil  602  to direct cooling fluid through the blade  600 . Generally, the plurality of cooling passages  614  are defined wholly or entirely within the blade  600 . In this example, the plurality of cooling passages  614  include a first cooling passage  614   a , a second cooling passage  614   b , a third cooling passage  614   c  and a fourth cooling passage  614   d . It will be understood, however, that the blade  600  can include more or less cooling passages, if desired. Each of the cooling passages  614   a - d  receive the cooling fluid  216  from a respective inlet  619   a - e , and each of the plurality of flow meters  616   a - e  are defined at the respective inlet  619   a - e  that supplies the cooling fluid  216  to the respective one of the plurality of cooling passages  614   a - d . It should be noted that although while not illustrated herein for clarity, the airfoil  602  generally may include a plurality of film cooling holes over an exterior surface of the airfoil  602  to direct cooling fluid over the exterior surface of the airfoil  602 . 
     The first cooling passage  614   a  is adjacent to the leading edge  606  and includes a first branch  628  and a second branch  629  that merge into a main branch  631 . The first branch  628  and the second branch  629  are defined in the root  604 , and merge into the main branch  631  adjacent to the top surface  620  of the root  604  such that the main branch  631  extends through the airfoil  602 . The first branch  628  and the second branch  629  each receive the cooling fluid  216  from a respective one of the plurality of flow meters  616 , such as flow meter  616   a ,  616   b . Each of the second cooling passage  614   b , the third cooling passage  614   c  and the fourth cooling passage  614   d  extend from the root  604  to the tip portion  618  of the airfoil  602 , and are each in fluid communication with a respective one of the plurality of flow meters  616 , for example, flow meter  616   c , flow meter  616   d  and flow meter  616   e , respectively. 
     Each of the plurality of flow meters  616   a - e  is formed within or defined in the bottom surface  622  of the root  604  about a respective one of the inlets  619   a - e  to supply each of the plurality of cooling passages  614   a - d  with a predefined amount of the cooling fluid  216 . In one example, each of the plurality of flow meters  616   a - e  comprise a volume of additional material M defined about the respective inlet  619   a - e  that is able to be machined to a predetermined diameter to direct a particular flow rate of the cooling fluid  216  into the respective one of the plurality of cooling passages  614   a - d . The additional material M may cover about 10% to about 100% of the area of the inlet  619   a - e  prior to machining the additional material M at the respective inlet  619   a - e  to achieve the final configuration for the respective inlet  619   a - e  that corresponds to the predetermined flow requirement for the particular cooling passage  614   a - d . While each of the plurality of flow meters  616   a - e  are illustrated herein as having a thickness D 6  (i.e. (D 5 −D 4 )/2) that is substantially the same over a height h 4  of the flow meters  616   a - e , the plurality of flow meters  616   a - e  can have a diameter that varies over the height h 4  of the plurality of flow meters  616   a - e . Generally, each of the plurality of flow meters  616   a - e  are defined with the diameter D 6 , which can be machined in various amounts to create the respective inlet  619   a - e  with a diameter as needed for the selected amount of the cooling fluid  216 . Stated another way, each of the plurality of flow meters  616   a - e  can be initially defined as the additional material M that surrounds the respective inlets  619   a - e  with the diameter D 4 , and the additional material M surrounding each of the inlets  619   a - e  can be machined up to a diameter D 5  as needed to provide a predetermined amount of the cooling fluid  216  to the respective one of the plurality of cooling passages  614   a - d.    
     Moreover, while the plurality of flow meters  616   a - e  are illustrated herein as being machinable into a cylindrical bore, the plurality of flow meters  616   a - e  can be formed with any desired shape, such as elliptical, triangular, etc. Further, while the plurality of flow meters  616   a - e  are illustrated herein as being defined along an axis A 4  substantially perpendicular to the longitudinal axis  140  of the gas turbine engine, the additional material M of the plurality of flow meters  616   a - e  can be defined along an axis that is transverse to or oblique to the longitudinal axis  140 . In addition, while each of the plurality of flow meters  616   a - e  are illustrated as having substantially the same size and shape (i.e. the same diameter D 6  and the same height h 4 ), one or more of the plurality of flow meters  616   a - e  can have a different shape, diameter and/or height. Generally, the cross-sectional area of each of the inlets  619   a - e  is directly proportional to the flow rate of the cooling fluid  216  that is supplied to the respective ones of the plurality of cooling passages  614   a - d . In the example of a cylindrical bore for each of the plurality of flow meters  616   a - e , the cross-sectional flow area of a single one of the inlets is defined as: 
     
       
         
           
             
               
                 
                   A 
                   = 
                   
                     
                       π 
                        
                       
                         ( 
                         
                           
                             D 
                             4 
                           
                           2 
                         
                         ) 
                       
                     
                     2 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     Each of the plurality of flow meters  616   a - e  includes a flow meter inlet  630   a - e  and a flow meter outlet  632   a - e . The respective flow meter inlet  630   a - e  is in fluid communication with the cooling fluid  216  at the respective inlet  619   a - e , and the respective flow meter outlet  632   a - e  is in fluid communication with the respective one of the plurality of cooling passages  614   a - d . The respective one or more of the plurality of flow meters  616   a - e  cooperate with the respective inlet  619   a - e  to control all of the flow of the cooling fluid  216  into the respective one of the plurality of cooling passages  614   a - d . As will be discussed, the additional material M can be machined to control an amount or flow rate of the cooling fluid  216  received into the respective one of the plurality of cooling passages  614   a - d  at the respective inlet  619   a - e . In one example, the flow rate may be reduced in the flow meters  616   a - e  by modifying the inlet  619   a - e  at the bottom surface  622 . In this regard, one or more fillets, bumps or contours may be defined on the bottom surface  622  adjacent to, near or around one or more of the inlets  619   a - e  to alter the flow through the respective flow meters  616   a - e.    
     With reference to  FIG. 9 , and with continued reference to  FIG. 8 , in accordance with one example, a method  799  of manufacturing the blade  600  with the plurality of flow meters  616   a - e  is shown. The method begins at  800 . At  802 , the blade  600  is formed. In one example, the blade  600  is formed using investment casting, as discussed with regard to  FIG. 6 , above. As the remainder of the investment casting process for the blade  600  is substantially similar to the process discussed with regard to  FIG. 6 , the method of investment casting the blade  600  will not be discussed in great detail herein. Briefly, however, the core that is formed in investment casting the blade  600  comprises the inverse of the plurality of cooling passages  614   a - d , including the extra material M of the plurality of flow meters  616   a - e  that surrounds each of the inlets  619   a - e . With the core positioned within the die, the die is injected with liquid wax such that liquid wax surrounds the core. Once the wax has hardened to form a wax pattern, the wax pattern is coated or dipped in ceramic to create the ceramic mold about the wax pattern. With the ceramic mold at the desired thickness, the wax is heated to melt the wax out of the ceramic mold. The ceramic mold is filled with molten metal or metal alloy. Once the metal or metal alloy has solidified, the ceramic is removed from the metal or metal alloy, through chemical leaching, for example, leaving the plurality of cooling passages  614   a - d , including the extra material M surrounding each of the inlets  619   a - e  of the plurality of cooling passages  614   a - d  formed in the metal or metal alloy. 
     It should be noted that alternatively the blade  600  may be formed using conventional dies with one or more portions of the plurality of cooling passages  614   a - d , including the extra material M surrounding each of the inlets  619   a - e  (or portions adjacent to the plurality of cooling passages  614   a - d ) comprising a fugitive core insert. 
     With the blade  600  formed, at  804 , the cooling requirements for each of the plurality of cooling passages  614   a - d  are determined. In one example, the cooling requirements are pre-defined, via a fluid dynamics analysis performed using a computer model of the blade  600 . In other embodiments, the cooling requirements are pre-defined based on experimental testing and simulation. In still other embodiments, the cooling requirements are defined based on a regulation from one or more governing agencies. 
     At  806 , based on the determination at  804 , the additional material M of one or more of the plurality of flow meters  616   a - e  is machined to adjust the amount or flow rate of the cooling fluid  216  received by the particular one of the plurality of cooling passages  614   a - d  at the respective inlet  619   a - e . In this regard, given the determined cooling requirements for each of the plurality of cooling passages  614   a - d , the additional material M is removed, if necessary, to provide for a greater flow rate of the cooling fluid  216  to enter the respective one of the plurality of cooling passages  614   a - d  at the respective inlet  619   a - e . In one example, the additional material M of the plurality of flow meters  616   a - e  is machined by drilling, grinding and/or milling about the respective one of the inlets  619   a - e . In other embodiments, the additional material M is removed by electrical discharge machining (EDM). 
     With continued reference to  FIG. 9 , at  808 , it is determined whether there is sufficient cooling flow into each of the plurality of cooling passages  614   a - d . In one example, this determination can be made by testing the blade  600  in a test rig, in which a cooling flow through the blade  600 , including the plurality of cooling passages  614   a - d , is measured. It may also be determined through dimensional inspection. 
     Based on the determination at  808 , if each of the plurality of cooling passages  614   a - d  are receiving the desired amount of the cooling fluid  216  from the respective ones of the inlets  619   a - e , at  810 , the method ends. Otherwise, at  812 , the additional material M of respective ones of the plurality of flow meters  616   a - e  is further removed by machining to increase the cooling fluid  216  flow rate supplied to the respective ones of the plurality of cooling passages  614   a - d . The method proceeds back to  808 . 
     The method of  FIG. 9  can be repeated to form any number of blades  600  for use with a turbine rotor of the gas turbine engine  100 . With the desired number of blades  600  formed, the blades  600  are consolidated into a ring, and coupled together to form a blade ring, which is coupled to the hub of the turbine rotor as discussed above with regard to the blades  212 . With the turbine rotor formed and assembled, the turbine rotor can be installed in the gas turbine engine  100 . 
     As each of the blades  600  include the plurality of cooling passages  614   a - d , each having one or more of the plurality of integral flow meters  616   a - e , the cooling fluid  216  is supplied to the blades  600  without requiring additional metering plates or metering components. By forming the plurality of flow meters  616   a - e  integrally with the blade  600  with the additional material M, one or more of the plurality of flow meters  616   a - e  can be machined to remove portions of the additional material M to adjust the cooling fluid  216  individually for each of the plurality of cooling passages  614   a - d . This adjustability reduces instances where one or more of the plurality of cooling passages  614   a - d  is receiving more cooling fluid  216  than needed, which may impact fuel consumption of the gas turbine engine  100 . Moreover, the plurality of flow meters  616   a - e  having the additional material M which is removable ensures the proper amount of the cooling fluid  216  is supplied to each of the plurality of cooling passages  614   a - d  of the blade  600 , thereby reducing the likelihood that the blade  600  is insufficiently cooled. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.