Patent Publication Number: US-9410576-B2

Title: Compact bearing assemblies including superhard bearing surfaces, bearing apparatuses, and methods of use

Description:
BACKGROUND 
     Subterranean drilling systems can employ various tools that require electrical power. In some instances, a drilling system includes a power generation unit. Fluid, such as drilling fluid, may flow through a turbine of the power generation unit, thereby producing rotation of a shaft, which may be converted into electrical power (e.g., the power generation unit may drive an alternator). Bearing apparatuses (e.g., thrust, radial, tapered, and other types of bearings) also may be operably coupled to the shaft and may assist in maintaining the shaft in a substantially stationary lateral and/or axial position, for instance, relative to a housing, while allowing the shaft to rotate. 
     A typical bearing apparatus includes a stator that does not rotate and a rotor that is attached to the shaft and rotates with the shaft. The operational lifetime of the bearing apparatuses often determines the useful life of the power generation unit as well as of the subterranean drilling system. Therefore, manufacturers and users of subterranean drilling systems and power generation units continue to seek improved bearing apparatuses to extend the useful life of such bearing apparatuses. 
     SUMMARY 
     Embodiments of the invention are directed to compact bearing assemblies configured to operate in small spaces and/or in harsh environments, bearing apparatuses including such bearing assemblies, and methods of operating such bearing assemblies and apparatuses. For instance, one or more compact bearing assemblies may at least partially rotatably secure a shaft of a power generation unit to a housing thereof. In an embodiment, a first compact bearing assembly may connect or couple to the shaft and may rotatably engage a second compact bearing assembly, which may be connected or otherwise secured to the housing. Furthermore, when engaged with one another, the first and second compact bearing assemblies may have limited or no lateral movement relative to one another. Hence, a bearing apparatus that may include the first and second bearing assemblies may rotatably secure the shaft to the housing, while limiting lateral movement of the shaft relative to the housing. 
     An embodiment includes a bearing apparatus including a first bearing assembly and a second bearing assembly. The first bearing assembly includes a first support structure. The first bearing assembly further includes a first superhard body secured to the first support structure and protruding above a top surface thereof and defining a convex radial-bearing surface. The second bearing assembly includes a second superhard body secured within the recess. In addition, the second superhard body includes an opening defined by a concave radial-bearing surface that is sized and configured to rotatably engage the first radial-bearing surface. 
     Embodiments also include a power generation unit including a housing and a first bearing assembly attached to the housing. The first radial bearing assembly includes a first single superhard body that defines a first radial-bearing surface. The power generation unit also includes a shaft rotatably secured within the housing in a manner that flow of fluid through the power generation unit produces rotation of the shaft. Furthermore, the power generation unit includes a second bearing assembly attached to the shaft. The second bearing assembly includes a second single superhard body that defines a second radial-bearing surface, the second radial-bearing surface being rotatably engaged with the first radial-bearing surface. In addition, the power generation unit includes an alternator operably connected to the shaft. 
     Another embodiment is directed to a method of rotating a shaft within a housing. The method includes attaching a first bearing assembly to the shaft and attaching a second bearing assembly to the housing. Additionally, the method includes positioning a first radial-bearing surface of the first bearing assembly inside an opening defined by a second radial-bearing surface of the second bearing assembly. Moreover, one or more of the first radial-bearing surface or the second radial-bearing surface include superhard material. The method also includes forming a fluid film between the first radial-bearing surface and the second radial-bearing surface during the rotation of the shaft within the housing, thereby producing hydrodynamic operation between the first radial-bearing surface and the second radial-bearing surface. 
     Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate several embodiments of the present disclosure, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings. 
         FIG. 1A  is an isometric view of a first bearing assembly according to an embodiment; 
         FIG. 1B  is a cross-sectional view of the first bearing assembly of  FIG. 1A ; 
         FIG. 1C  is an isometric view of a first bearing assembly according to another embodiment; 
         FIG. 2A  is a cross-sectional view of a second bearing assembly according to an embodiment; 
         FIG. 2B  is a cross-sectional view of a second bearing assembly according to another embodiment; 
         FIG. 2C  is a cross-sectional view of a second bearing assembly according to yet another embodiment; 
         FIG. 3A  is a cross-sectional view of a bearing apparatus according to an embodiment; 
         FIG. 3B  is a cross-sectional view of a bearing apparatus according to another embodiment; 
         FIG. 3C  is a cross-sectional view of a bearing apparatus according to yet another embodiment; 
         FIG. 3D  is a cross-sectional view of a bearing apparatus according to still one other embodiment; and 
         FIG. 4  is a partial cross-sectional view of a power generation unit according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention are directed to compact bearing assemblies configured to operate in small spaces and/or in harsh environments, bearing apparatuses including such bearing assemblies, and method of operating such bearing assemblies and apparatuses. For instance, one or more compact bearing assemblies may at least partially rotatably secure a shaft of a power generation unit to a housing thereof. In an embodiment, a first compact bearing assembly may connect or couple to the shaft and may rotatably engage a second compact bearing assembly, which may be connected or otherwise secured to the housing. Furthermore, when engaged with one another, the first and second compact bearing assemblies may have limited or no lateral movement relative to one another. Hence, a bearing apparatus that may include the first and second bearing assemblies may rotatably secure the shaft to the housing, while limiting lateral movement of the shaft relative to the housing. 
     In an embodiment, one of the first bearing assembly and the second bearing assembly may include a protrusion that may have a convex substantially cylindrical bearing surface, while the other of the first and second bearing assemblies may include an opening defined by a concave substantially cylindrical bearing surface that may rotatably engage the protrusion. As such, the first bearing assembly may rotate relative to the second bearing assembly, as described above. In additional or alternative embodiments, the first and/or the second bearing assembly may include superhard material that may form or define at least a portion of the bearing surfaces thereof. For example, the first and/or second bearing assembly may include a superhard body bonded to a substrate. The respective superhard bodies may include superhard material that forms/defines bearing surfaces of the first and second bearing assemblies. 
     In some embodiments, the first bearing assembly may include a superhard body that protrudes away from the support structure, thereby forming a protrusion with a convex bearing surface that may enter and/or engage the second bearing assembly. For example, the second bearing assembly may include an interior surface that may form/define a concave bearing surface of the second bearing assembly. For example, the protrusion of the first bearing assembly may enter an opening in the second bearing assembly and may engage the bearing surface of the second bearing assembly. 
     Furthermore, as noted above, in an embodiment, the respective bearing surfaces of the first and second bearing assemblies may be formed/defined by superhard material (e.g., superhard material of respective superhard bodies). As such, the bearing surface defined or formed by the opening in the second bearing assembly may include superhard material. In an embodiment, the superhard material may be a body of superhard material mounted on or within the support structure. Such superhard body may form a hole or an opening that may rotatably at least partially engage the protrusion of the first bearing assembly. 
     Also, in some embodiments, the first bearing assembly may be a rotor, while the second bearing assembly may be a stator (e.g., the second bearing assembly may be substantially stationary relative to a housing or other machine component, while the first bearing assembly may rotate together with the shaft) or vice versa. In any event, at least a portion of a protrusion of the first bearing assembly may rotatably at least partially engage an opening in the second bearing assembly in a manner that allows the first and second bearing assemblies to rotate relative to each other, while preventing or limiting lateral movement thereof. 
       FIGS. 1A-1C  illustrate an embodiment of a first bearing assembly  100 . The first bearing assembly  100  may include a first radial-bearing surface  110 , which may at least partially engage a corresponding bearing surface of the second bearing assembly, as described below in more detail. 
     In an embodiment, the first radial-bearing surface  110  may be convex and approximately cylindrical. Furthermore, in some instance, the first radial-bearing surface  110  may be substantially continuous or uninterrupted. Accordingly, rotation of the first radial-bearing surface  110  about an axis  10  may cause the first radial-bearing surface  110  to be in at least partial contact with the opposing bearing surface of the second bearing assembly. Alternatively, however, the first radial-bearing surface  110  may be discontinuous and/or interrupted (e.g., the first radial-bearing surface  110  may include groove). 
     Additionally, the first radial-bearing surface  110  may include superhard material, such that the first radial-bearing surface  110  may exhibit a hardness that is at least as hard as tungsten carbide. In any of the embodiments disclosed herein, the superhard material may include one or more of polycrystalline diamond, polycrystalline cubic boron nitride, silicon carbide, tungsten carbide, or any combination of the foregoing superhard materials. 
     For instance, the first bearing assembly  100  may have a superhard body  120  that may include the first radial-bearing surface  110 . Particularly, a peripheral surface of the superhard body  120  may form/define the first radial-bearing surface  110 . In addition, the superhard body  120  may include a chamfer  121  extending between the first radial-bearing surface  110  and a top surface  122  of the superhard body  120 . Under some operating conditions, the chamfer  121  may prevent or eliminate chipping of the superhard body  120  that may, otherwise, affect continuity of the first radial-bearing surface  110 . 
     In an embodiment, the superhard body  120  may be bonded to a substrate  130 , which may be secured to a support structure  140 . The support structure  140  may have any suitable shape, which may vary from one embodiment to the next. In an embodiment, the support structure  140  may have a generally cylindrical shape. Moreover, the support structure  140  may include multiple sections connected together or integrated with one another, such as sections  141 ,  142 , and  143 . Thickness of each section (as measured along the axis  10 ) as well as the overall thickness of the support structure  140  may vary one embodiment to another, and may depend on a particular application and load experienced by the support structure  140 , among other factors or considerations. 
     Similarly, as mentioned above, the shapes of the sections  141 ,  142 ,  143  may vary depending on particular application of the first bearing assembly  100 . In some instances, the peripheral surface of the section  141  may have one or more flat or planar portions, which may facilitate engagement of a tool therewith (e.g., a wrench may engage the planar portions(s) in a manner that allows the tool to rotate the support structure  140  about the axis  10 ). For example the section  141  may be a hexagonal prismoid. Additionally or alternatively, the section  141  may have at least partially cylindrical shape (e.g., in high speed operation a cylindrical shape may improve balance of the first bearing assembly  100  and/or reduce vibration thereof). In any event, a tool may be used to hold and/or assemble the first bearing assembly  100  for operation (e.g., to rotate the first bearing assembly  100  such as to screw the first bearing assembly  100  onto a shaft). 
     In some embodiments, the sections  142 ,  143  may have approximately cylindrical shapes. Moreover, in an embodiment, the sections  142  and  143  may have dissimilar diameters and/or thicknesses. For example, the outside diameter of section  142  may be larger than the outside diameter of section  143 . Moreover, in some instances, the section  143  may at least partially enter an opening in the second bearing assembly, while the section  142  may be larger than such opening. Likewise, the section  141  may be larger than section  142 , such as to provide sufficient surface area for engaging a tool that may be used to secure the first bearing assembly  100  to a shaft (as discussed in greater detail hereinbelow). 
     Furthermore, in an embodiment, one, some, or all of the sections  141 ,  142 ,  143  may be generally concentric with one another. For instance, the sections  141 ,  142 ,  143  may be substantially centered about the axis  10 . Alternatively, however, some or all of the sections  141 ,  142 ,  143  may be off-center relative to one another. In addition, one or more of the sections may include an opening, such as an opening  144  in the section  141 , which may accept a shaft and/or a fastener that may secure the first bearing assembly  100  to a machine element or component. 
     As described above, the first bearing assembly  100  may include the superhard body  120  that may be bonded to the substrate  130 . For example, the superhard body  120  may comprise polycrystalline diamond and the substrate  130  may comprise cobalt-cemented tungsten carbide. Other carbide materials may be used with tungsten carbide or as an alternative, such as chromium carbide, tantalum carbide, vanadium carbide, titanium carbide, or combinations thereof cemented with iron, nickel, cobalt, or alloys thereof. Furthermore, in any of the embodiments disclosed herein, the polycrystalline diamond body may be leached to at least partially remove or substantially completely remove a metal-solvent catalyst (e.g., cobalt, iron, nickel, or alloys thereof) that was used to initially sinter precursor diamond particles to form the polycrystalline diamond. In another embodiment, an infiltrant used to re-infiltrate a preformed leached polycrystalline diamond body may be leached or otherwise at least partially removed to a selected depth from a bearing surface. Moreover, in any of the embodiments disclosed herein, the polycrystalline diamond may be un-leached and include a metal-solvent catalyst (e.g., cobalt, iron, nickel, or alloys thereof) that was used to initially sinter the precursor diamond particles that form the polycrystalline diamond and/or an infiltrant used to re-infiltrate a preformed leached polycrystalline diamond body. Examples of methods for fabricating the superhard bearing elements and superhard materials and/or structures from which the superhard bearing elements may be made are disclosed in U.S. Pat. Nos. 7,866,418; 7,998,573; 8,034,136; and 8,236,074; the disclosure of each of the foregoing patents is incorporated herein, in its entirety, by this reference. 
     The diamond particles that may be used to fabricate the superhard body  150   a  in a high-pressure/high-temperature process (“HPHT”) may exhibit a larger size and at least one relatively smaller size. As used herein, the phrases “relatively larger” and “relatively smaller” refer to particle sizes (by any suitable method) that differ by at least a factor of two (e.g., 30 μm and 15 μm). According to various embodiments, the diamond particles may include a portion exhibiting a relatively larger size (e.g., 70 μm, 60 μm, 50 μm, 40 μm, 30 μm, 20 μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at least one relatively smaller size (e.g., 15 μm, 12 μm, 10 μm, 8 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In an embodiment, the diamond particles may include a portion exhibiting a relatively larger size between about 10 μm and about 40 μm and another portion exhibiting a relatively smaller size between about 1 μm and 4 μm. In another embodiment, the diamond particles may include a portion exhibiting the relatively larger size between about 15 μm and about 50 μm and another portion exhibiting the relatively smaller size between about 5 μm and about 15 μm. In another embodiment, the relatively larger size diamond particles may have a ratio to the relatively smaller size diamond particles of at least 1.5. In some embodiments, the diamond particles may comprise three or more different sizes (e.g., one relatively larger size and two or more relatively smaller sizes), without limitation. The resulting polycrystalline diamond or superabrasive body formed from HPHT sintering the aforementioned diamond particles may also exhibit the same or similar diamond grain size distributions and/or sizes as the aforementioned diamond particle distributions and particle sizes. Such polycrystalline diamond includes a plurality of diamond grains exhibiting diamond-to-diamond bonding (e.g., sp 3  bonding) therebetween and defining interstitial regions having a catalyst therein (e.g., a metal-solvent catalyst or carbonate catalyst). Other superabrasive/superhard materials may include a plurality of superabrasive grains bonded together to define interstitial regions having a catalyst therein. Additionally, in any of the embodiments disclosed herein, the superhard bearing elements may be free-standing (e.g., substrateless) and optionally may be at least partially leached or fully leached to remove a metal-solvent catalyst initially used to sinter the polycrystalline diamond body. 
     In some embodiments, the substrate  130  may be secured within the support structure  140 . For example, the support structure  140  may include a recess  145  that can at least partially accommodate the substrate  130  therein. As such, at least a portion of the substrate  130  may be positioned and secured within the recess  145 . In an embodiment, the recess  145  may be generally concentric with the opening  144 . Hence, the recess  145  may generally concentrically locate the substrate  130  relative to the opening  144 . For instance, the recess  145  may be centered about the axis  10 . 
     Furthermore, the superhard body  120  may be generally concentric within the substrate  130 . For example, the first radial-bearing surface  110  of the superhard body  120  may be centered about the axis  10 . Thus, in one or more embodiments, the first radial-bearing surface  110  may be generally concentric with the opening  144 , such that rotation of the shaft secured within the opening  144  may produce a rotation of the first bearing assembly  100  during which the first radial-bearing surface  110  rotates approximately concentrically within the support structure  140  and/or with the shaft. 
     In an embodiment, the recess  145  may be approximately cylindrical (i.e., may have an approximately circular cross-section). Likewise, the substrate  130  may have approximately cylindrical cross-section and may have a similar size to the recess  145 . For example, the recess  145  may have sufficient clearance to accommodate the substrate  130  therein. The substrate  130  may be brazed, soldered, welded, fastened, press-fit, or otherwise secured to the support structure  140  (e.g., within the recess  145 ). It should be also appreciated that the recess  145  may have any suitable shape, which may vary from one embodiment to the next. Correspondingly, the substrate  130  also may have any suitable shape that may be mountable inside the recess  145 . In any event, the superhard body  120  may be secured to or incorporated with the support structure  140 . Thus, rotation of the first bearing assembly  100  may produce a corresponding rotation of the first radial-bearing surface  110 , which may be approximately concentrically aligned with the axis of rotation of the shaft. 
     In some embodiments, the clearance between the recess  145  and the substrate  130  may be substantially small to allow final finishing of the first radial-bearing surface  110  before securing the substrate  130  within the recess  145 . Additionally or alternatively, the substrate  130  may be first secured within the recess  145 , and the first radial-bearing surface  110  may be finished (e.g., ground) thereafter. Similarly, in an embodiment, the top surface  122  of the superhard body  120  also may be finished after securing the substrate  130  in the recess  145 . In an embodiment, the top surface  122  also may be unfinished or may be finished before securing the substrate  130  to the support structure  140 . 
     In some embodiments, the substrate  130  may protrude above a top surface  146  ( FIG. 1B ) of the support structure  140 . Alternatively, the substrate  130  may be entirely within the support structure  140 , such that an interface between the substrate  130  and superhard body  120  may be located approximately in plane with top surface  146 . In any case, in one or more embodiments, the superhard body  120  may be located entirely above the top surface  146  of the support structure  140 . In other embodiments, the superhard body  120  may be partially located in the recess  145 . 
     Referring still to  FIG. 1B , in an embodiment, the superhard body  120  may have a thickness  123  (measured from the substrate  130  to the top surface  122 ) that is similar to or the same as the height of the substrate  130 . For example, the thickness of the superhard body  120  may be approximately 0.25 inches, while the thickness of the substrate  130  may be between 0.23 inches to 0.27 inches. Additional examples of suitable thicknesses of the superhard body  120  and/or substrate  130  may include the following: about 0.05 inches to about 0.10 inches; about 0.08 inches to about 0.15 inches; about 0.12 inches to about 0.2 inches; about 0.18 inches to about 0.25 inches; about 0.20 inches to about 0.30 inches; or about 0.25 inches to about 0.50 inches. It should be appreciated that the superhard body  120  and/or substrate  130  may be thicker than 0.50 inches or thinner than 0.08 inches. 
     It should be appreciated that in some embodiments, the superhard body  120  may be bonded directly to the support structure  140 . For example, the support structure  140  may comprise stainless steel and a substrateless superhard body  120  may be brazed, press-fitted, or otherwise attached directly to the support structure  140 . Alternatively, the support structure  140  may comprise tungsten carbide, and the superhard body  120  may be bonded to the support structure  140  (e.g., using HPHT process described above). In any event, the first bearing assembly  100  may include the first radial-bearing surface  110 , formed/defined by the superhard body  120 , which may engage the corresponding second radial-bearing surface of the second bearing assembly. 
     Moreover, in an embodiment, the first bearing assembly  100  may include a thrust-bearing surface. In particular, the first radial-bearing surface  110  may carry a radial load, thereby preventing or limiting lateral movement of the shaft, for example, relative to the housing, while the thrust-bearing surface may prevent or limit axial movement of the shaft during rotation thereof. For instance, the top surface  146  of the support structure  140  may be a thrust-bearing surface and may engage an opposing or corresponding thrust-bearing surface of the second bearing assembly or of another (e.g., third) bearing assembly. Furthermore, the top surface  146  may include superhard material, such as polycrystalline diamond, which may be bonded or otherwise secured thereto. 
     As noted above, the first bearing assembly may include one or more groves on a bearing surface thereof. For example, as illustrated in  FIG. 1C , a first bearing assembly  100   a  may include a bearing surface  110   a  formed by a superhard body  120   a , which includes a plurality of grooves  111   a . Except as otherwise described below, the first bearing assembly  100   a  and its materials, elements, and components may be similar to or the same as materials, elements, or components of the first bearing assembly  100  ( FIGS. 1A and 1B ). 
     In an embodiment, the grooves  111   a  may be approximately parallel to the axis  10  and may be spaced and arranged thereabout. For instance, the grooves  111   a  may be evenly spaced about the bearing surface  110   a , such that the distance between any two adjacent grooves  111   a  is the same as the distance between any two other adjacent grooves  111   a . It should be appreciated, however, that the bearing surface  110   a  may include any number of grooves, which may have any suitable size, orientation (e.g., horizontal), configuration (e.g., spiral, arcuate, etc.), and combinations thereof. 
     As mentioned above, the first bearing assembly  100  may rotatably engage the second bearing assembly.  FIG. 2A  illustrates an embodiment of a second bearing assembly  200 . Generally, except as otherwise described below, the second bearing assembly  200  and its materials, elements, and components may be similar to or the same as materials, elements, or components of the first bearing assembly  100  ( FIGS. 1A and 1B ). In some embodiments, a superhard body  220  and/or a substrate  230  of the second bearing assembly  200  may include materials similar to or the same as the superhard body  120  and substrate  130 , respectively. Also, in one example, the second bearing assembly  200  may include a second radial-bearing surface  210 , which may engage the first radial-bearing surface  110  ( FIGS. 1A and 1B ). Embodiments may include the superhard body  220  that may form or define the second radial-bearing surface  210 . The superhard body  220  may be bonded to the substrate  230 , which may be secured to a support structure  240 . 
     The second radial-bearing surface  210  may have a concave and approximately cylindrical shape that may span about an axis  10   a  in a manner that defines an opening in the second bearing assembly  200 . Particularly, the cylindrical shape of the second radial-bearing surface  210  may at least partially engage the corresponding first radial-bearing surface of the first bearing assembly. In other words, the protruding superhard body that may form/define the first radial-bearing surface may be positioned at least partially within an opening  211  in the second bearing assembly  200  and the first radial-bearing surface may at least partially contact the second radial-bearing surface  210 . In some instances, the opening  211  may have an approximately cylindrical shape, such as to define an inside diameter  224 . 
     When at least partially engaged, the first radial-bearing surface and the second radial-bearing surface  210  may be substantially concentric with each other, such that the axis  10   a  is generally aligned with the axis  10  ( FIGS. 1A and 1B ). In any event, the first radial-bearing surface  110  ( FIGS. 1A and 1B ) may at least partially contact the second radial-bearing surface  210 , such that the second bearing assembly  200  and the first bearing assembly may rotate relative to each other with limited relative lateral movement. In some embodiments, the second radial-bearing surface  210  may be substantially continuous. Alternatively, the second radial-bearing surface  210  may have groves or other interruptions (e.g., to supply fluid between the second radial-bearing surface  210  and the first radial-bearing surface). 
     In an embodiment, the support structure  240  may have an approximately cylindrical shape. Furthermore, the support structure  240  may include a recess  241  that may secure the superhard body  220  and/or the substrate  230  therein. The superhard body  220  and/or substrate  230  may be press-fitted, brazed, fastened, or otherwise secured in the recess  241 . Moreover, the second bearing assembly  200  may include the superhard body  220  that is substrateless, which may be bonded or otherwise secured directly to the support structure  240 . In any event, the superhard body  220  may be secured to the support structure  240  and may have a suitable shape and size that may allow the first radial-bearing surface to at least partially enter the opening  211  formed in the superhard body  220  as well as at least partially contact the second radial-bearing surface  210 . In another embodiment, the substrate  230  may be an annular substrate (e.g., ring-shaped) that is attached to the support structure  240  and the superhard body  220  may be received by and bonded with the annular substrate. 
     As shown in  FIG. 2A , the second bearing assembly  200  may include a through hole  250 . In some instances, the through hole  250  may allow fluid (e.g., drilling fluid) to enter and/or exit the second bearing assembly  200 . For instance, the through hole  250  may be in fluid communication with the opening  211  defined by the second radial-bearing surface  210 . Furthermore, any debris or dust generated during operation of the second bearing assembly  200  and the first bearing assembly may exit through the through hole  250 , which may reduce wear of the second radial-bearing surface  210  and/or of the first radial-bearing surface. Moreover, the through hole  250  may include a female thread, which may be accept a fastener that may secure the second bearing assembly  200  to a machine element or component. 
     In some instances, the second bearing assembly  200  may include a chamfer  260  extending between a peripheral surface thereof and a top surface  270 . Additionally or alternatively, the second bearing assembly  200  may include a second chamfer or lead-in  280 , which may extend between the top surface  270  and a peripheral surface of the recess  241 . The chamfer  260  and/or lead-in  280  may reduce or eliminate chipping or breaking of otherwise sharp corners or edges of the second bearing assembly  200 . 
     In an embodiment, the top surface of the superhard body  220  also may form/define a thrust-bearing surface  221 , which may at least partially contact the thrust-bearing surface of the first bearing assembly to limit or prevent relative axial movement of the first and second bearing assemblies. Hence, in one or more embodiments, the thrust-bearing surface  221  may include superhard material, such as polycrystalline diamond. 
     In some embodiments, the superhard body may include a chamfer to prevent chipping or cracking thereof during assembly and/or operation. For instance,  FIG. 2B  illustrates a second bearing assembly  200   a  that includes a superhard body  220   a , which has a bearing surface  210   a , and which may be bonded to a substrate  230   a . Except as otherwise described herein, the second bearing assembly  200   a  and its materials, elements, and components may be similar to or the same as materials, elements, or components of the second bearing assembly  200  ( FIG. 2A ). In an embodiment, the superhard body  220   a  may include a chamfer  222   a , which may be positioned at the top of an opening  211   a  defined by the bearing surface  210   a.    
     In additional or alternative embodiments, the second bearing assembly may include grooves, which may be similar to or the same as the grooves of the first bearing assembly. For example,  FIG. 2C  illustrates a second bearing assembly  200   b  that has a superhard body  220   b  that forms or defines a bearing surface  210   a , and which includes a plurality of grooves  212   b . Except as otherwise described herein, the second bearing assembly  200   b  and its materials, elements, and components may be similar to or the same as materials, elements, or components of any of the second bearing assemblies  200 ,  200   a  ( FIGS. 2A and 2B ). In some embodiments, the grooves  212   b  may extend into and through a substrate  230   b . Accordingly, for example, fluid may flow through the groove  212   b  and into and/or out of an opening  211   b  of the second bearing assembly  200   b . Moreover, it should be appreciated, however, that the bearing surface  210   b  may include any number of grooves, which may have any suitable size, orientation (e.g., horizontal), configuration (e.g., spiral, arcuate, etc.), and combinations thereof. 
     As noted above, the first and second bearing assemblies rotate with respect to one another, wherein the first radial-bearing surface and the second radial-bearing surface  210  at least partially contact one another.  FIG. 3A  illustrates an embodiment of a bearing apparatus  300  that includes the first bearing assembly  100  and second bearing assembly  200  assembled with one another. In some embodiments, the first bearing assembly  100  may be a rotor, while the second bearing assembly  200  may be a stator. Alternatively, the first bearing assembly  100  may be a stator, while the second bearing assembly  200  may be a rotor (e.g., the second bearing assembly  200  may be attached to the shaft). Furthermore, in an embodiment, both the first bearing assembly  100  and the second bearing assembly  200  may rotate relative to a machine or mechanism incorporating the bearing apparatus  300 . In any case, the first bearing assembly  100  and second bearing assembly  200  may rotate relative to one another. 
     Particularly, the superhard body  120  may be positioned at least partially within the opening in the second bearing assembly  200  defined by the superhard body  220 . As mentioned above, the superhard body  220  and the superhard body  120  may at least partially contact one another, thereby providing a rotatable bearing between the first bearing assembly  100  and the second bearing assembly  200 . In some embodiments, diameter  124  of the superhard body  120  may be sufficiently small to accommodate compact spaces. For instance, the diameter  124  of the superhard body  120  may be in one or more of the following ranges: about 0.08 inches to 0.15 inches; about 0.10 inches to 0.20 inches; about 0.18 inches to about 0.38 inches; about 0.30 inches to 0.50 inches; about 0.40 inches to 0.80 inches; less than 2 inches; or less than 1 inch. In some instances, the diameter  124  of the superhard body  120  may be smaller than 0.08 inches or greater than 0.80 inches. 
     Similarly, the superhard body  120  may have a suitable thickness  123 , which may vary from one embodiment to another. For example, the thickness  123  of the superhard body  120  may be in one or more of the following ranges: about 0.05 inches to about 0.09 inches; about 0.08 inches to about 0.12 inches; about 0.09 inches to about 0.15 inches; about 0.15 inches to about 0.25 inches; less than 0.15 inches; less than 0.20 inches; or less than 0.50 inches. It should be appreciated that in some embodiments, the thickness  123  may be less than 0.05 inches or greater than 0.50 inches. 
     As mentioned above, the second radial-bearing surface  210  may define an opening that is sufficiently shaped and sized to accept and at least partially contact the first radial-bearing surface  110  during operation (e.g., the opening may have the diameter  224 ). Furthermore, in some embodiments, the bearing apparatus  300  may include a clearance or a gap between the first radial-bearing surface  110  and the second radial-bearing surface  210  (measured by the difference between the outside diameter defined by the first radial-bearing surface  110  and inside diameter defined by the second radial-bearing surface  210 ). For example, the gap between the first radial-bearing surface  110  and the second radial-bearing surface  210  may be in one or more of the following ranges (provided as a percentage of the diameter defined by the first radial-bearing surface  110 ): about 0.5% to 1.0%; about 0.8% to 1.5%; about 1.2% to 2.5%; about 2% to 3%; or about 2.7% to 3.5%. In some instances, the gap between the first radial-bearing surface  110  and the second radial-bearing surface  210  may be less than 0.5% or greater than 3.5% of the diameter defined by the first radial-bearing surface  110 . In a specific embodiment, the first radial-bearing surface  110  may define an outside diameter of about 0.249 inches, while the second radial-bearing surface  210  may define an inside diameter of about 0.256 inches, forming a gap of about 0.007 inches. 
     Although the gap of about 0.007 inches may be atypical for radial bearing assemblies, such gap may facilitate development of fluid film between the first radial-bearing surface  110  and the second radial-bearing surface  210 , thereby producing a hydrodynamic operation of the bearing apparatus  300 . In some instances, the fluid may be introduced between the first radial-bearing surface  110  and the second radial-bearing surface  210  through a space  310  between the first bearing assembly  100  and the second bearing assembly  200 . Alternatively, the fluid may be introduced through the through hole  250  in the second bearing assembly  200 . It should be also appreciated that the fluid may be introduced between the first radial-bearing surface  110  and second radial-bearing surface  210  in any number of suitable ways, which may vary from one embodiment to the next. Additionally, in some embodiments the drilling fluid may be channeled to enter the space between the first radial-bearing surface  110  and second radial-bearing surface  210  and may form the fluid film, which may facilitate hydrodynamic operation of the bearing apparatus  300 . 
     In some embodiments, a portion of the substrate  130  may be positioned at least partially within the opening defined by the second radial-bearing surface  210 . Alternatively, the substrate  130  may be outside of or above the opening formed by the second radial-bearing surface  210  and may not contact the second radial-bearing surface  210  during operation of the bearing apparatus  300 . Accordingly, the substrate  130  may not experience wear during operation of the bearing apparatus  300 . 
     In addition, as mentioned above, the chamfer  121  may prevent the superhard body  120  from chipping and/or cracking during the operation of the bearing apparatus  300 . Moreover, in some embodiments, the chamfer  121  may start below the second radial-bearing surface  210 . As such, in some embodiments, the entire first radial-bearing surface  110  may be in contact with the second radial-bearing surface  210 . 
     In some embodiments, the bearing apparatus may carry both a radial load and a thrust load. For instance, as illustrated in  FIG. 3B , a bearing apparatus  300   a  may include opposing thrust-bearing surfaces  115   a ,  215   a  of first and second bearing assemblies  100   a ,  200   a . Except as otherwise described herein, materials, elements, or components of the bearing apparatus  300   a  may be similar to or the same as materials, elements, or components of the bearing apparatus  300  ( FIG. 3A ). For instance, the first and second bearing assemblies  100   a ,  200   a  also may include radial bearing surfaces  110   a ,  210   a  that may carry the radial load exerted onto the bearing apparatus  300   a.    
     Moreover, in an embodiment, both the thrust-bearing surface  115   a  and the radial bearing surface  110   a  may be formed by the same superhard body  120   a  of the first bearing assembly  100   a . In an embodiment, the superhard body  120   a  may be bonded to a substrate  130   a . The thrust-bearing surface  215   a  and the radial bearing surface  210   a  of the second bearing assembly  200   a  may be formed/defined by a superhard body  220   a . In some instance, the superhard body  220   a  may be bonded directly to a support structure  240 . 
     As noted above, bearing surfaces of the first and/or second bearing assembly may include one or more grooves therein. For example,  FIG. 3C  illustrates a bearing apparatus  300   b  that includes a first bearing assembly  100   b  and a second bearing assembly  200   b , either or both of which may include grooves in the bearing surfaces thereof. In particular, an embodiment includes grooves  211   b  in a superhard body  220   b  of the second bearing assembly  200   b . It should be also appreciated that, in one or more embodiments, the first bearing assembly  100   b  also may include grooves in the bearing surface thereof (e.g., as described above in connection with  FIG. 1C ). 
     In any event, fluid may be circulated through one or more grooves in the bearing surfaces of the second bearing assembly  200   b  and/or in the first bearing assembly  100   b . Providing fluid flow through the grooves  211   b  may produce hydrodynamic operation of the bearing apparatus  300   b . For example, the fluid may be directed through the first bearing assembly  100   b  and into the second bearing assembly  200   b  (e.g., into the grooves  211   b  of the second bearing assembly  200   b ). In an embodiment, the first bearing assembly  100   b  may include an opening  109 , which may pass through the first bearing assembly  100   b  (e.g., through substrate  130   b  and/or through superhard body  120   b  of the first bearing assembly  100   b ). Particularly, the opening  109  may be in fluid communication with the grooves  211   b , and the fluid may pass through the opening  109  and into the grooves  211   b.    
     While the bearing assemblies and bearing apparatuses described above may include support structures, it should be appreciated that this invention is not so limited. For instance,  FIG. 3D  illustrates an embodiment of a bearing apparatus  300   c  that includes a first bearing assembly  100   c  and a second bearing assembly  200   c  assembled with one another, either or both of which may not include a support structure. Except as described herein, material, elements, or components of the bearing apparatus  300   c  may be similar to or the same as materials, elements, or components of any of the bearing apparatuses  300 ,  300   a ,  300   b  ( FIGS. 3A-3C ). 
     In some embodiments, the first bearing assembly  100   c  may include a superhard body  120   c  bonded to a substrate  130   c , which may be substantially cylindrical. The first bearing assembly  100   c  may be secured to or otherwise incorporated directly into moving (e.g., rotating) or stationary machine component. Likewise, the second bearing assembly  200   c  may include a hollow cylindrical or tubular superhard body  220   c  that may be bonded to a substrate  230   c . In some instances, the substrate  230  also may be at least partially tubular. The second bearing assembly  200   c  also may be directly attached to or incorporated into a moving (e.g., rotating) or stationary machine component. In any event, at least a portion of the superhard body  120   c  may enter the opening in the superhard body  220   c.    
     Moreover, a bearing surface  110   c  of the first bearing assembly  100   c  may engage a corresponding bearing surface  210   c  of the second bearing assembly  200   c . For example, the bearing surfaces  110   c  and  210   c  may have an overlap  305  therebetween. In other words, the bearing surfaces  110   c  and  210   c  may engage or at least partially contact each other along the overlap  305 . For example, the overlap  305  may be greater than or less than 0.50 inches, such as 0.3 inches to about 0.7 inches, 0.2 inches to about 0.35 inches, or about 0.15 inches to about 0.30 inches. 
     The bearing apparatus  300  or any other bearing apparatus disclosed herein may be incorporated into any number of machines or mechanisms to rotatably secure rotating components or elements thereof.  FIG. 4  illustrates an embodiment of a power generation unit  400  that includes the bearing apparatus  300 . In particular, the bearing apparatus  300  may rotatably connect a shaft  410  within a housing  420 . For example, the second bearing assembly  200  may be a stator and may be secured to and/or within the housing  420 , such as to remain substantially stationary relative to the housing  420 . The first bearing assembly  100  may be a rotor and may be secured to the shaft  410  in a manner that allows the housing  420  to rotate within the shaft  410 . In an embodiment, the shaft  410  may be secured within the section  141 . 
     It should be appreciated that the first bearing assembly  100  may be attached to the shaft  410  in any number of suitable ways. In an embodiment, as noted above, the section  141  includes the opening  144  that may accept a portion of the shaft  410 . Moreover, the opening  144  may position the first bearing assembly  100  relative to the shaft  410 . For example, the opening  144  may align the first bearing assembly  100  relative to the shaft  410 , such that the first bearing assembly  100  is concentric with the shaft  410 . Accordingly, rotation of the shaft  410  about center axis there may produce rotation of the first bearing assembly  100  about the axis  10 . 
     Furthermore, the shaft  410  may be secured within the opening  144 . For example, the opening  144  may include female threads that may engage with male threads on an end of the shaft  410 , thereby connecting the first bearing assembly  100  to the shaft  410 . In some instances, the threads also may align the first bearing assembly  100  relative to the shaft, such that the first bearing assembly  100  is concentric with the shaft  410 . Other fastening configurations (e.g., with screws) also may connect the first bearing assembly  100  to the shaft  410 . In additional or alternative embodiments, the shaft  410  may be press-fitted into the opening  144  of the first bearing assembly  100 . Likewise, the first bearing assembly  100  may be brazed, welded, or otherwise connected to or integrated with the shaft  410  (e.g., the support structure  140  of the first bearing assembly  100  may be integrated with the shaft  410 ). In any event, the first bearing assembly  100  may be attached or secured to the shaft  410  in a manner that rotation of the shaft  410  produces a corresponding rotation of the first bearing assembly  100  and vice versa. 
     The term “housing” is not intended to be limiting and is provided only as an example component of the power generation unit  400 . It should be appreciated that the shaft may be rotatably connected to any element or component of a machine that may remain stationary relative to the shaft during operation of such machine. In other words, the housing  420  may be any other stationary element or component that may secure a stator of the bearing apparatus  300 , which may be rotatably engaged with a rotor of the bearing apparatus  300 . 
     In an embodiment, the power generation unit  400  may include a turbine  430  attached to the shaft  410 . As fluid flows through the power generation unit  400  (as indicated by the arrows), the turbine  430  may be induced to rotate together with the shaft  410 . In an embodiment, the housing  420  may include one or more openings, which may channel the fluid toward the turbine  430  and, subsequently, out of the power generation unit  400 . The shaft  410  may be operably connected to an alternator in a manner that rotation of the shaft  410  may drive the alternator (e.g., the shaft  410  may include a magnetic rotor that may be surrounded by windings), thereby converting mechanical energy into electrical power. Additionally, a portion of the fluid may be diverted or may otherwise flow between the first bearing assembly  100  and second bearing assembly  200 , as described above, thereby producing hydrodynamic operation of the bearing apparatus  300 . 
     It should be appreciated that any of the bearing apparatuses  300 ,  300   a ,  300   b ,  300   c  ( FIGS. 3A-3D ) may be used in the power generation unit described above. Furthermore, even though the bearing apparatuses are described above as used in a power generation unit (e.g., in the power generation unit  400 ), the embodiments of the invention are not so limited. Hence, any of the bearing apparatuses  300 ,  300   a ,  300   b ,  300   c  ( FIGS. 3A-3D ) may be used in any suitable machine or mechanism to facilitate rotation of one or more elements or components thereof. For instance, any of the bearing apparatuses  300 ,  300   a ,  300   b ,  300   c  ( FIGS. 3A-3D ) may be used a blood pump, such as a cardiopulmonary bypass blood pump described in U.S. patent application Ser. No. 13/761,944, entitled “Bearing Assembly For Use In Axial-Flow Cardiopulmonary Bypass Blood Pumps And Related Pumps,” filed on Feb. 7, 2013, the entire content of which is incorporated herein by this reference. For instance, any of the bearing apparatuses  300 ,  300   a ,  300   b ,  300   c  ( FIGS. 3A-3D ) may rotatably secure the shaft of the blood pump within and relative to the housing thereof. 
     While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. Additionally, the words “including,” “having,” and variants thereof (e.g., “includes” and “has”) as used herein, including the claims, shall be open ended and have the same meaning as the word “comprising” and variants thereof (e.g., “comprise” and “comprises”).