Patent Publication Number: US-9850760-B2

Title: Directed cooling for rotating machinery

Description:
TECHNICAL FIELD 
     The present disclosure relates to directed cooling for rotating machinery. More particularly, the present disclosure relates to cooling features incorporated into rotating machinery that collect a cooling fluid from an area of lower relative velocity and increases its kinetic energy/momentum by “pumping” it to a higher radius through operation of the rotating machinery. 
     BACKGROUND 
     Various types of rotating machine require cooling. A subset of such rotating machinery includes those fabricated by metallurgically bonding a hub portion to a ring portion. In these examples, the hub portion includes an outer circumference that is bonded to an inner circumference of the ring portion, thus forming a circumferential bond line at the interface between the outer circumference of the hub and the inner circumference of the ring. Hub/ring fabrication of rotating machinery is desirable because it allows for the use of different alloys for the hub portion and for the ring portion, among other reasons. 
     Non-limiting examples of such rotating machinery that requires cooling, whether they be bonded along a bond line or not, include axial turbines and compressors, radial turbines and impellers, and others as will be appreciated by those having ordinary skill in the art.  FIGS. 1 and 2  are provided for purposes of illustrating some of these examples. More particularly,  FIG. 1  is a perspective view of an axial turbine rotor bladed disk  100  as known in the prior art. The turbine rotor bladed disk  100  has a hub  102 , a ring  104 , and a plurality of blades  106  on the ring  104  that are configured to withstand a wide range of temperatures. Generally, the hub  102  is disk-shaped and surrounded by the ring  104 . The blades  106  extend radially outward from the ring  104 . The hub  102  and ring  104  are diffusion-bonded together along bond line  103  and are generally formed from superalloy materials. Both components may be formed from the same material or may be formed from materials that vary in composition. The hub  102  and/or ring  104  may be cast into equiaxed, directionally solidified, or single crystal components. 
     Additionally,  FIG. 2  is an isometric view of a radial turbine  200  as known in the prior art. As can be seen in  FIG. 2 , radial turbine  200  includes a hub  266  and a ring  256 , with the ring  256  include a plurality of blade segments  258 , which are circumferentially spaced around and extend radially outward on the ring  256 . A bond line  253  illustrates the bonding region between the hub  266  and the ring section  256 . As with the axial turbine example of  FIG. 1 , the radial turbine example of  FIG. 2  has the hub  266  and the ring  256  diffusion-bonded together along the bond line  253  and are generally formed from superalloy metals, which may be the same or different. 
     During operation, rotating machinery is often exposed to elevated temperatures. In the case of the exemplary rotating machinery noted above in  FIGS. 1 and 2 , such elevated temperatures may be caused by the impingement of hot gasses upon the machinery, or by the compression of gasses as a function of the machinery&#39;s operation. As the temperature of the rotating machinery increases, some areas of the rotating machinery, which in some examples may include the bond line (e.g., bond line  103  or  253 ), are less able to withstand structural loads placed on the rotating machinery. Beyond a certain temperature, the rotating machinery could fail at these areas during operation. Further, exposure to high temperatures may cause accelerated low-cycle fatigue (LCF) of the rotating machinery. 
       FIG. 3  is provided to illustrate this problem in the context of the radial turbine  200  shown in  FIG. 2 . More particularly,  FIG. 3  shows a segment  200 A of the radial turbine  200 , with its forward end  285  at left, and it rearward end  286  at right. During operation, hot gasses are directed toward the leading edge of blade segment  258 . These hot gasses cause a temperature maximum at the forward end of bond line  253 , which is illustrated by oval  290 . Such temperature maxima at the bond line  253 , as noted above, may undesirably cause structural failure or accelerated LCF of the radial turbine. 
     As such, it would be desirable to provide rotating machinery that is not susceptible to structural failure or accelerated LCF due to exposure to elevated temperatures. To accomplish the foregoing aim, it would be desirable to provide cooling directed at the heat-susceptible areas of the rotating machinery, which, in the case of rotating machinery including a hub portion bonded to a ring portion, may be a bond line, in order to minimize the temperatures to which such heat-susceptible areas exposed. Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background. 
     BRIEF SUMMARY 
     The present disclosure broadly provides directed cooling for rotating machinery. In one exemplary embodiment, a rotating machine includes a hub portion, wherein the hub portion comprises a forward face and an aft face. The rotating machine further includes a cooling channel formed on either the forward face or the aft face and configured to direct cooling air to a location on the rotating machine, wherein the cooling channel extends from a radially inner location along said face to a radially outer location along said face, and wherein the cooling channel is configured as a recess formed into an outer surface of said face. 
     In another exemplary embodiment, a rotating machine includes a hub portion, wherein the hub portion includes an outer circumference, an inner circumference, a forward face, and an aft face. The rotating machine further includes a ring portion, wherein the ring portion includes an inner circumference that is metallurgically bonded to the outer circumference of the hub portion along a circumferential bond line. Furthermore, the rotating machine includes a cooling channel formed on either the forward face or the aft face and configured to direct cooling air to the bond line, wherein the cooling channel extends from a radially inner location along said face to a radially outer location along said face, and wherein the cooling channel is configured as a recess formed into an outer surface of said face. 
     In yet another exemplary embodiment, a rotating machine includes a hub portion, wherein the hub portion includes an outer circumference, an inner circumference, a forward face, and an aft face. The rotating machine further includes a ring portion, wherein the ring portion includes an inner circumference that is metallurgically bonded to the outer circumference of the hub portion along a circumferential bond line. Furthermore, the ring portion additionally includes a forward end and an aft end, wherein either the forward end or the aft end includes a circumferential flange extending outward from said end and positioned radially above the bond line, and wherein said face includes a circumferential recess radially below the bond line. The flange and the recess define a circumferential bond line channel along both said end and said face that distributes cooling air circumferentially along the bond line. 
     This brief summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventive subject matter will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a perspective view of an axial turbine rotor as known in the prior art; 
         FIG. 2  is an isometric view of a radial turbine as known in the prior art; 
         FIG. 3  is a view of a segment of the radial turbine of  FIG. 2  provided to illustrate bond line high temperature exposure problems encountered in the prior art; and 
         FIGS. 4A-4C  are exemplary perspective, cross-sectional, and end views, respectively, of a rotating machine that includes bond line cooling in accordance with embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the inventive subject matter or the application and uses of the inventive subject matter. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
     The present disclosure broadly provides directed cooling for rotating machinery, including but not limited to rotating machinery provided in a bonded hub/ring configuration. Examples of such rotating machinery include, but are not limited to, axial turbines and compressors, radial turbines and impellers. Regardless of the particular implementation, in each embodiment of the present disclosure the rotating machine includes what will be referred to herein as a “hub” portion. The term “hub,” as used herein, should not be thought of as limited to the context of hub/ring bonded configurations, but should be understood merely to refer to a central member of the rotating machine, onto which a fluid “pumping” or cooling channel may be provided. Typically, the hub portion includes an outer circumference, an inner circumference, a forward face, and an aft face. Further, in some embodiments of the present disclosure that are in fact directed to bonded hub/ring rotating machine configurations, the rotating machine further includes a ring portion. When provided, the ring portion typically includes an inner circumference that is metallurgically bonded to the outer circumference of the hub portion along a circumferential bond line. In the case of turbines, compressors, and impellers, the ring portion will also include a plurality of blades extending radially outward therefrom. 
     To achieve the desire aim of directed cooling as set forth herein, embodiments may include the aforementioned cooling channel formed on either the forward face or the aft face (depending on the particular implementation), which is configured to direct or “pump” a cooling fluid, typically cooling air, to the desired location on the rotating machine. Where the rotating machine is in the exemplary hub/ring bonded configuration, this desired location may optionally be the bond line. The cooling channel is provided so as to extend from a radially inner location along the face (again, either forward or aft, depending on the particular implementation) to a radially outer location along the face. The cooling channel is configured as a recess formed into an outer surface of the face, and in this manner can be easily machined into the appropriate face during the manufacturing process. Thus, it should be understood that the general purpose of the subject cooling channel is to collect a cooling fluid from an area of lower relative velocity and increase its kinetic energy/momentum by “pumping” it to a higher radius by taking advantage of the rotation inherent in the operation of a rotating machine. 
     For purposes of illustrating the inventive subject matter, the reader is directed to  FIGS. 4A-4C  which provide various views of the cooling channel implemented in the context of a hub/ring bonded radial turbine  400 . However, it should be appreciated that the skilled artisan, based on this illustration, will easily be able to implement such a cooling channel in accordance with the principles of the present disclosure on any other rotating machine, whether turbine or otherwise, whether having a bond line between the hub portion and the ring portion or otherwise. 
     With particular attention now to  FIG. 4A , radial turbine  400  includes hub portion  466 . Hub portion  466  should be understood as having a forward face, which is generally understood as that portion of the hub facing at directional arrow  485 , and an aft face, which is generally understood as that portion of the hub facing at directional arrow  486 , the forward and aft faces being on axially opposite sides of the hub portion  466  from one another. Moreover, hub portion  466  should be understood as having an outer circumference, which is generally understood as encompassing portions of the bond line  453  and portions of the “saddle” region  420  between blades, and an inner circumference, which, although not visible in any illustration, is generally understood as a hollow cavity of the hub portion  466  through which a shaft or other suitable rotating object may be inserted. It is noted that, with particular regard to the outer circumference, it should not be understood that the term “circumference” implies a perfectly circular profile. Rather, as clear from  FIG. 4A , the outer circumference includes various contours and shaping to allow for improved bonding and manufacturing characteristics. 
     Additionally, radial turbine  400  includes a ring portion  456 . Ring portion  456  should be understood as having a forward end, which is generally understood as that end oriented towards directional arrow  485 , and an aft end, which is generally understood as that end oriented towards directional arrow  486 . Moreover, ring portion  456  should be understood as including an inner circumference, which is generally understood as that portion disposed along bond line  453 . However, like the hub portion  466 , the term “circumference” does not mean to imply the need for a perfectly circular profile, with contours and shaping being allowable for improved bonding and manufacturing characteristics. In some embodiments of the present disclosure, as with radial turbine  400 , the ring portion  456  includes a plurality of blades  458  extending radially outward from the ring portion  456 . The shape and configuration of these blades depends on the particular style of rotating machine, and in the present case of a radial turbine the blades are configured having inducer and exducer portions, as well-known in the art. In the alternative case of an axial turbine, the blades would be configured as airfoils, having a leading edge and a trailing edge, as also well-known in the art. 
     With continued reference to  FIG. 4A , and with further reference now to  FIG. 4B , the cross-sectional profile of the hub portion  466  and the ring portion  456  (as bonded together along bond line  453 ) will be presently discussed, and in particular the cross-sectional profile at the forward face/end thereof, which in this implementation includes the novel bond line cooling features of the present disclosure. (In other implementations, the cooling features may be at the aft face/end.) Broadly, the forward face of the hub portion  466  may be considered to have three concentric, annular regions  411 ,  412 , and  413 , with annular region  411  being the inner most region, and annular region  413  being the outermost region. In terms of axial position (forward or aft), the middle annular region  412  has the most axially-forward extending face profile, whereas annular regions  411  and  413  have faces that are axially-aft of the axial face of the middle annular region  412 .  FIG. 4A  shows all three concentric, annular regions  411 - 413 , whereas  FIG. 4B  only shows all of region  413  and part of region  412 . 
     As further evidenced in  FIGS. 4A and 4B , along the forward face of the hub  466  and within outer annular region  413 , there is a circumferential recess  432  that causes the forward face to recess axially aftward (forming a small, radially-outward facing surface  434 ) as it adjoins with the outer circumference of the hub  466 . This recess  432  extends circumferentially about the entire hub  466 . The recess  432  may be formed by machining the hub portion  466  after bonding with the ring portion  456 . 
     Turning now to the forward-end profile of the ring portion  456  as illustrated in  FIGS. 4A and 4B , it is evidenced that the ring portion  456  forward end is configured so as to be axially flush with the recess  432  of the hub portion  466  at the bond line  453 , as indicated by region  430 . However, radially above the bond line  453 , the forward end of the ring portion  456  includes a circumferential flange  435  that extends axially forward of the region  431 , and is defined by a radially lower surface  433  and a radially upper surface  436 . Above the radially upper surface  436  of the flange  435 , the ring  456  resumes the forward end profile, which may or may not be coplanar with region  431 . The flange  435  extends aftward to a distance so as to be coplanar or staggered with the face profile of annular region  413  of the hub portion  466 . As such, when the hub portion  466  is bonded to the ring portion  456 , the recess  432  and the flange  435  cooperate to form a bond line channel  430  that extends circumferentially along the bond line. More particularly, the bond line channel is defined by the radially lower surface  433  of flange  435 , the region  431  of the forward end of the ring  456  adjacent the bond line  453 , the recess  432  of the hub  466 , and the radially-outward facing surface  434  of hub  466  adjacent the recess  432 . Being that the bond line  453  is radially above the saddle  420  of the hub  466 , it should be appreciated that the circumferential bond line channel  430  does not form a completed circle, but rather is intermittent along an imaginary circle that passes through each forward end portion of the bond line  453 . The bond line channel  430  functions to distribute cooling air along the bond line  453 , thereby maintain the bond line at acceptable temperatures in terms of operating stresses and LCF when the radial turbine  400  is impinged with hot gasses during operation. The bond line channel  430  is fed with cooling air from a cooling channel formed into the forward face of the hub  466 , as will be described in greater detail below. This cooling air that feeds the cooling channel is supplied from a separation space between the rotor and an adjacent static structure axially forward of the rotor, as best illustrated in  FIG. 4B . 
     With particular attention now to  FIGS. 4A and 4C , the above-noted cooling channel, indicated with reference numeral  440 , is formed into portions of the forward face of the hub  466 . Of course, in other appropriate embodiments, the cooling channel could be at the aft face. In either case, as illustrated, the cooling channel  440  extends radially outward along the face from a radially inner location  441  along the face to a radially outer location  442  along the face. In the illustrated embodiment, the radially inner location  441  is provided between annular regions  411  and  412  of the forward face of the hub  466 , and the radially outer location  442  is provided radially below the bond line channel  430  within annular region  413  (i.e., between the low-point of the saddle  420  and the bond line  453 ). The cooling channel  440  may be formed by machining the hub portion  466  after bonding with the ring portion  456 , and as such is configures as a recess formed into the surface of the forward face of the hub portion  466 . Of course, with regard to the entire radial turbine  400 , multiple cooling channels  440  may be formed, one for each of the intermittent segments of the bond line channel. 
     With particular attention to  FIG. 4C , it is evidenced that the cooling channel  440  does not form a linear path (extending radially outwardly) between the radially inner location  441  and the radially outer location  442 , but rather follows a curved path. At this point in the discussion, it should be noted that arrow  460  indicates the direction of rotation of the radial turbine  400 . As such, the curved path of the cooling channel  440  may be defined as having various portions which, while always extending radially outward, also extend at an angle that is either with the direction of rotation or against the direction of rotation. The illustrated cooling channel  440  may thus be defined as having a radially inner portion  461  and a radially outer portion  462 . The radially inner portion  461  may be angled against the direction of rotation (arrow  460 ), while the radially outer portion  462  may be angled with the direction of rotation. The mid-point between the portions  461  and  462  may be appropriately disposed within annular region  412  of the hub  466 . 
     It should be noted that, axially forward of the hub portion  466  (but not separately illustrated), a cavity may exist that encloses air at a temperature less than that of the hot air impinging upon the blades  458  (i.e., which is referred to herein as “cooling air”). This cooling air may be supplied to the cavity from any suitable location of the apparatus in which the rotating machine is operating. For example, in the context of a turbine rotor operating in a turbine engine, the cooling air may be supplied from an appropriate bypass duct, or the like. Thus, the source of the cooling air forward of the hub  466  should not be considered limiting of the described embodiments in sense. 
     In operation, therefore, the rotation of hub portion  466  causes the cooling air to be forced through the cooling channel  440  from the radially inner location  441  to the radially outer location  442 . The curvature of the cooling channel  440 , with the radially inner portion  461  thereof being angled against the direction of rotation, causes the cooling air to be efficiently directed into the channel upon rotation. In the illustrated embodiment, the cooling air is then pushed back with the direction of rotation and radially outward through the channel  440 . Thereafter, upon exiting the channel  440  through the radially outer location  442 , the cooling air is ideally positioned for intake into the bond line channel  430 , located radially there-above. The cooling air thus passes into the bond line channel  430 , where it performs the desired function of maintaining the temperature of the bond line at a suitably low temperature to prevent device failure and/or accelerated LCF. 
     Broadly speaking, the general purpose of the cooling channel is to collect the cooling air from an area of low relative velocity and increase its kinetic energy/momentum by “pumping” it to a higher radius. While the “inlet” of the channel  440  (i.e., location  441 ) should have in general a strong tangential component (i.e., be directed against the rotational direction  460 ), the “exit” of the channel  440  (i.e., location  442 ) may be directed as preferred to infer radial, tangential, and axial velocity components. The cross sectional area of the channel  440  may also be optimized to achieve the desired effect, in a given embodiment. On average, the channel  440  will start relatively wide and will then progressively narrow as the cooling air is pumped to a higher radius. This will accelerate the relative velocity of the flow, therefore increasing momentum. The cross sectional shape can also be optimized to achieve the most desirable “pumping” effect. 
     Accordingly, the present disclosure has provided embodiments of rotating machines that include directed cooling features. Desirably, the provided cooling features prevent structural failure of the rotating machine during operation, as well as inhibit LCF. The embodiments are easily manufactured by the simple machining of the disclosed features onto portions of a rotating machine. The described embodiments desirably achieve the dual benefits of selectively cooling certain portions of rotating machines and actively controlling cooling flow in rotating machines. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description of the disclosure, 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 an exemplary embodiment of the disclosure. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the disclosure as set forth in the appended claims.