CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No.

61/719,250, filed on October 26, 2012, entitled "Radiated and Thermal Expansion

Compensating Gas Bearing," the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER

FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

[0002] The United States Government has rights in this invention pursuant to Contract No.

DE-AC52-07NA27344 between the United States Department of Energy and Lawrence

Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.

BACKGROUND OF THE INVENTION

[0003] The National Ignition Facility (NIF) is a laser-based inertial confinement fusion research machine located at the Lawrence Livermore National Laboratory in Livermore, California. NIF uses lasers to heat and compress a capsule of deuterium and tritium (DT) fuel held in a hohlraum to the temperatures and pressures to cause a nuclear fusion reaction.

[0004] Inertial confinement fusion power plants have been proposed. The equipment, systems and support necessary for the deployment of such a fusion power plant are now being investigated and designed at LLNL. In the indirect drive approach to inertial confinement fusion (often "ICF" herein), a fusion fuel capsule containing DT is held inside a hohlraum; the two together being referred to as a "target." The targets are injected into a fusion chamber and fired upon by a bank of lasers. The hohlraum absorbs and re-radiates the energy as x-rays onto the fuel capsule. The outer surface of the fuel capsule ablates, compressing and heating the DT fuel to cause a fusion reaction. Coolants to control the fusion chamber environment and fluids used for transfer of thermal energy produced from the reaction become activated during plant operation. These activated fluids travel through processing equipment that must be developed to handle thermal gradients and irradiation. SUMMARY OF THE INVENTION

[0005] This invention relates to the injection of targets used as fuel for fusion reactions, and in particular to gas-bearing or air-bearings used in injectors for such applications, including self-compensating or self-regulating gas bearings. Embodiments of the present invention are applicable to process equipment for fusion energy production such as gas separation centrifuges, reactor coolant pumping, and the injection of targets used as fuel for fusion reactions, and in particular to gas-bearing or air-bearings used in such applications. More particularly, embodiments of the present invention relate to gas bearing, for example, air bearings, that compensate for expansion resulting from neutron absorption and thermal load. In a particular embodiment, a gas bearing includes flexure elements that balance flexural stiffness with gas-bearing pressure. In another particular embodiment, a gas bearing element includes bifurcated radial arms that deform to balance internal pressure with the pressure at the bearing interface. Embodiments of the present invention are applicable to a wide variety of bearing applications including radial and longitudinal bearings. [0006] According to an embodiment of the present invention, a gas bearing is provided. The gas bearing includes a central hub operable to receive a pressurized gas and a gas containment structure disposed around the central hub. The gas containment structure comprises a plurality of flexural elements each having an entrance orifice adjacent the central hub, a central region including a set of cantilevered spring elements extending distally from the entrance orifice, and a distal nozzle surrounded by a bearing pad. The gas bearing also includes a bearing race surrounding the gas containment structure.

[0007] In an embodiment, the gas bearing also includes a set of toroidal discs, each of the set of toroidal discs being adjacent a side of the gas containment structure. The plurality of flexural elements can be self-sealed in other embodiments. The bearing pad can be made of porous material and the distal nozzle can be formed as a plurality of openings in the porous material, providing for diffuse flow through the bearing pad. The plurality of flexural elements can each comprise two cantilevered spring elements separated by a gas passage.

[0008] According to another embodiment of the present invention, a gas bearing is provided. The gas bearing includes a central hub operable to receive a pressurized gas and a bearing element disposed around the central hub. The bearing element comprises a plurality of bifurcated flexure elements each having an entrance orifice adjacent the central hub, a central region extending distally from the entrance orifice, and a distal nozzle. The gas bearing also includes a bearing race surrounding the bearing element. [0009] The gas bearing can also include a set of toroidal discs on opposing sides of the bearing element. The bifurcated flexure elements can be self-sealed in other embodiments. In some embodiments, the pressurized gas can include at least one of air, nitrogen, argon, or combinations thereof. The plurality of birfurcated flexure elements can further include a bearing plate surrounding the nozzle. In this embodiment, the bearing plate forms a hydrostatic pressure region between the bearing plate and the bearing race.

[0010] According to a particular embodiment of the present invention, method of operating a gas bearing is provided. The method includes providing a source of pressurized gas and pressurizing a central hub of the gas bearing with the pressurized gas. The method also includes flowing the gas through a plurality of flexural elements in fluid communication with the central hub and forming a bearing region characterized by a pressure equal to a first hydrostatic pressure and disposed between each of the flexural elements and a bearing race. The method further includes increasing the pressure in the bearing region to a second hydrostatic pressure greater than the first hydrostatic pressure, deforming the plurality of flexural elements, and restoring the pressure in the bearing region to the first hydrostatic pressure.

[0011] According to an embodiment of the present invention, an air bearing structure which compensates for temperature induced expansion and contraction is provided. The air bearing structure includes a plurality of members each including an inlet for allowing pressurized gas to enter the element and a nozzle to provide the air bearing by allowing the pressurized gas to escape against an air bearing surface. The flexural stiffness of each element between the inlet and the nozzle balances with air-bearing pressure to maintain a constant air-bearing separation between the nozzle and the air bearing surface.

[0012] According to an embodiment of the present invention, a gas bearing is provided. The gas bearing includes a pressure source region operable to receive a pressurized gas and a gas containment structure in fluid communication with the pressure source region. The gas containment structure comprises a plurality of flexural elements each having an entrance orifice adjacent the pressure source region, a central region including a set of cantilevered spring elements extending distally from the entrance orifice, and a distal nozzle surrounded by a bearing pad. The gas bearing also includes a bearing race adjacent the bearing pads of the plurality of flexural elements.

[0013] According to another specific embodiment of the present invention, a gas bearing is provided. The gas bearing includes a pressure source region operable to receive a pressurized gas and a bearing element in fluid communication with the pressure source region. The bearing element comprises a plurality of bifurcated flexure elements each having an entrance orifice adjacent the pressure source region, a central region extending distally from the entrance orifice, and a distal nozzle. The gas bearing also includes a bearing race adjacent the distal nozzle.

[0014] Numerous benefits are achieved by way of the present invention over conventional techniques. For example, embodiments of the present invention provide gas bearings that are self-compensating for neutron absorption and thermal expansion. These and other embodiments of the present invention, along with many of its advantages and features, are described in more detail in conjunction with the text below and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 A is a simplified schematic diagram illustrating an exploded view of a gas bearing according to an embodiment of the present invention. [0016] FIG. IB is a simplified schematic diagram of a flexural element undergoing deflection according to an embodiment of the present invention.

[0017] FIG. 1C is a simplified schematic diagram illustrating components of the flexural element illustrated in FIG. IB.

[0018] FIG. 2A is a simplified plan view of a gas bearing including bearing elements with bifurcated radial arms according to an embodiment of the present invention.

[0019] FIG. 2B is a simplified schematic diagram illustrating self-regulation of a gas bearing element according to an embodiment of the present invention.

[0020] FIG. 2C is a simplified schematic diagram illustrating flexing of a gas bearing element during operation. [0021] FIG. 3 is a simplified flowchart illustrating a method of operating a gas bearing according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] As presently contemplated, a megawatt size ICF power plant will require on the order of 10 to 15 targets per second. Thus, inertial confinement fusion target designers must consider many engineering requirements in addition to the physics requirements for a successful target implosion. Among these considerations is injection of the targets to the center of the chamber where the laser beams can implode the fusion fuel. For the fuel to implode and create a fusion reaction, the fuel capsule must be irradiated evenly with energy to ablate its surface to compress and heat the DT fuel. [0023] In such a system, the 10-15 fusion reactions per second in the chamber create intense heat and radiation which can damage targets waiting to be injected. Systems may protect the targets from damage from the fusion reactions by providing a "shutter" to block the heat and radiation from the fusion reaction from reaching targets yet to be injected. These targets are positioned immediately outside the fusion chamber in the injector mechanism. One such shutter provides a revolving structure which enables the targets to pass from the injection mechanism and into the chamber without ever exposing yet-to-be-injected targets to the heat and radiation. Such a shutter is described in commonly assigned and co-pending PCT Patent Application No. PCT/US2013/064544, filed on October 11, 2013, and entitled "Irradiation Shutter for Target Injection into a Fusion Chamber," the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

[0024] A design challenge in implementing such a shutter is to provide a low friction mechanism for rotating the shutter, for example, by using an air bearing or gas bearing. The design challenges to implementing such a shutter, however, are numerous. The large thermal variations and radiation cause any shutter materials to expand and contract. The tolerances required for a properly functioning gas-bearing or air-bearing drive the need to develop a solution for these expansions and contractions occurring in the bearing components.

Embodiments of the present invention utilize compliant features within the bearing design to balance bearing gas pressure and compliant component spring rates to compensate for changes in the materials during bearing operation. [0025] The invention herein has applicability for use in environments that would typically disable the use of close-tolerance air/gas bearing concepts due to thermal load or irradiated material deformations. Mechanical operation in a high energy, high flux neutron

environment such as a fusion reactor will produce significant swelling of mechanical components, thereby necessitating solutions that are tolerant to such challenging

environments. The concepts described herein, however, have widespread uses, potentially dealing with not only thermal and radiative material expansions, but dealing with bearing misalignment or relieving tolerances in gas-bearing assembly, manufacturing, and similar applications. [0026] In development of fusion fuel injection apparatus concepts, the issue of material damage and swelling due to high energy neutron flux gives rise to potential concerns. In anticipation of potential bearing failures where close tolerances are required in such environments, concepts for self-compensating gas-bearings are described herein. Typical tolerances for gas-pressure bearings, specifically static pressure bearings, are on the order of 0.1 mm flow gaps. Coefficients of thermal expansion and swelling due to atom

displacements and decays would quickly eliminate the tolerances required for proper bearing operation using conventional designs.

[0027] FIG. 1 A is a simplified schematic diagram illustrating an exploded view of a gas bearing according to an embodiment of the present invention. As discussed herein, the gas bearing 100 balances flexural stiffness with gas bearing pressure to maintain desired bearing surfaces. In other words, the force of the hydrostatic effect on the bearing plate reacts against the flexural stiffness in the flexural element, analogous to a leaf spring. This hydrostatic force counteracts the stiffness of the flexural element to maintain the preloading in the gas bearing.

[0028] The gas bearing 100 illustrated in FIG. 1 A, which may be an air bearing, is suitable for applications in which neutron flux and thermal load result in expansion or swelling and/or contraction of the bearing during operation. The gas bearing 100 includes a gas containment structure 110 and two toroidal discs 120 and 122. The gas containment structure 110 is made up of a plurality of radially disposed flexural elements that are described more fully in relation to FIGS. IB and 1C. The gas containment structure 110 is surrounded by a bearing race 112 that opposes the bearing plates to provide a gas bearing effect. In FIG. 1 A, the bearing race 112 has been slid to a position below the gas bearing for purposes of clarity.

[0029] FIG. IB is a simplified schematic diagram of a flexural element of the gas bearing undergoing deflection according to an embodiment of the present invention. As stated above, flexural element 150 is one of the plurality of flexural elements making up the gas containment structure 110. The flexural element 150 includes a radial arm 160 with a nozzle plate 165 (also referred to as a bearing plate) including a nozzle 170. During operation, pressurized gas flows from the central region 105 of the gas bearing 100 through a gas passage 193 in the center of the radial arm 160 and out the nozzle 170.

[0030] FIG. 1C is a simplified schematic diagram illustrating components of the flexural element illustrated in FIG. IB. In the embodiment illustrated in FIG. 1C, two cantilever spring elements 190 and 192 extend from the base of the flexural element where pressurized gas enters from the central region 105 of the gas bearing and passes to the nozzle 170. The two cantilever springs can be compared to leaf springs. An air gap 193 is formed between the two cantilever spring elements providing a passage for the gas from the entrance orifice 167 to the nozzle 170. Referring to FIG. 1A, the two toroidal discs provide covers that define the top and bottom of the gas passage. In other embodiments, the flexure element can be fabricated with a central gas passage surrounded on four sides by flexible materials that provide the spring action desired and confine the gas flowing through the hollow fiexure element to and subsequently through the nozzle in the bearing plate. Thus, embodiments provide multiple ways to transport the gas from the pressurized gas source to the bearing surface defined by the bearing plate and the bearing race, thereby providing a hydrostatic effect at each bearing plate. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0031] As shown in FIG. IB, pressure induced deflection of the flexural element occurs as the flexural elements expands, for example, from neutron absorption and/or thermal swell. Embodiments balance flexural stiffness with gas bearing pressure as described herein. As shown in FIG. IB, the initial (unflexed) position of the flexural element is illustrated using dashed lines 180 and the position of the flexural element after expansion is illustrated using solid lines 185. As the flexural element expands due to thermal expansion or other causes, including neutron flux, the gap between the bearing plate and the bearing race decreases. This results in an increase in pressure in the bearing region between the bearing plate and bearing race. This increase in pressure results in compression of the flexure element, which increases the gap, thereby decreasing the pressure in the bearing region. The balance between increased pressure in the bearing region and increased compression in the flexure element thus provides for self-regulation. [0032] In some embodiments, the flexure elements is designed to enable the bearing plate 165 to maintain a constant orientation during expansion and contraction. In order to provide the desired hydrostatic pressure between the bearing plate and the bearing race, the fiexure element is designed such that during expansion and contraction, the bearing plate moves in a substantially radial direction while maintaining substantially the same orientation. In other words, expansion of the flexure element decreases the gap between the bearing plate and the bearing race, but maintains the orientation of the bearing plate with respect to the bearing race. Referring to FIG. IB, the normal to the bearing plate in the radial direction is substantially aligned with the normal to the bearing race to keep the bearing plate and the bearing race substantially parallel to each other. [0033] As illustrated in FIG. 1 A and FIG. IB, an embodiment of the present invention uses the bearing material spring-rate and deflection force to counteract the force generated within the bearing race to maintain the gas-bearing flow gaps. Geometry optimization with regard to material selection and material coefficients of thermal expansion and irradiation effects impact the final performance of the bearing design. In the gas bearing illustrated FIG. 1 A and FIG. IB, the flexural stiffhess on each of the flexural elements 150, as shown in FIG. IB, compensates for expansion of the materials. This compensation is achieved by the balance between the flexural stiffness and the pressure of the air or gas ejected from the nozzle 170 of the flexural element. [0034] Referring to FIG. 1A, the pressurized gas enters the gas bearing 100 in the center 105 of the containment structure 110 and is trapped between the two toroidal discs 120 and 122. The gas enters entrance orifices (illustrated as reference number 167 in FIG. 1C) on the portion of the flexural elements proximal to the center 105, passes through a gas passage 193 defined in the central region of the radial arm 160, which can also be referred to as the central regions of the flexural elements, and emerges from the nozzles 170. In an embodiment, there is one nozzle 170 in each of the flexural elements although the present invention is not limited to this design and multiple nozzles per flexural element can be provided in other embodiments. In other embodiments, the bearing plate 165 can be fabricated from a porous material, providing a porous media through with gas flows from the gas passage to the bearing race. In these embodiments, the "nozzle" may be a plurality of openings in the porous media, providing for diffuse gas flow through the "nozzles" of the bearing plate. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0035] The embodiment of the present invention illustrated in FIG. 1 A operates using static pressure. An external pressure source (not shown) provides pressurized gas that is fed into the center bearing cavity 105. The high-pressure gas flows outward radially through the flexure elements and the nozzles 170 of the flexure elements to the bearing plates, which can also be referred to as bearing race pads. The pressure force on the bearing plate is then used to regulate flow gaps. It should be appreciated that although FIG. 1 A illustrates a gas bearing utilizing a circular race bearing and a radial configuration, embodiments of the present invention can be adapted to linear configurations for thrust and linear bearings as appropriate to the particular application. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0036] According to another embodiment of the present invention, the internal bearing cavity pressure forces are used to generate deflections that regulate the gas-bearing race flow gaps. In this embodiment, changes in the hydrostatic pressure at the bearing plate / bearing race region result in pressure changes in a region of the flexure element, resulting in deformation of the flexure element and self-regulation.

[0037] FIG. 2A is a simplified plan view of a gas bearing with bearing elements including bifurcated radial arms according to an embodiment of the present invention. This top view illustrates a central hub 205, which is in fluid communication with a source of pressurized gas, for example, pressurized air, nitrogen, argon, or the like. The gas bearing includes a plurality of bearing elements that are attached to the central hub and arrayed substantially radially. The gas bearing includes a bearing race 203 that surrounds the bearing elements and opposes the plurality of bearing plates 221. A gas bearing is thus provided between the bearing plates and the bearing race. Although not shown in this plan view, the gas bearing includes a set of toroidal discs that provide top and bottom seals to the bearing elements. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0038] Although the embodiment illustrated in FIG. 2 utilizes a gas flow from the central hub through the bearing elements to the bearing race, this particular outward flow

implementation is not required by the present invention. In other embodiments, pressurized gas is provided to the region between the bearing race and the bearing elements, which can be referred to as a peripheral ring. The pressurization of the peripheral ring serves as a pressure source for gas flow through the bearing elements, which are reversed with respect to the implementation illustrated in FIG. 2A, with the entrance orifice facing the illustrated bearing race and the nozzle facing the illustrated central hub. In this alternative implementation, the bearing region is formed between the nozzles and a bearing race positioned where the central hub s illustrated in FIG. 2A. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. [0039] As described below, the pressure inside a cavity in the bearing elements and deformation of this cavity will provide for a self-regulation of the gas bearing as the bearing plate position changes with respect to the bearing race.

[0040] FIG. 2B is a simplified schematic diagram illustrating self-regulation of an element of a gas bearing according to an embodiment of the present invention. Referring to FIG. 2B, the gas enters at the entrance orifice 218 of the element, which is in fluid communication with a pressure source, flows through the central portion 220 of the element between the bifurcated radial arms 230 and 232, and emerges from the nozzle 223 in the bearing plate 221, also referred to as an exit orifice, of the element. As the flow gap 222 between the bearing plate 221 and the bearing race 203 decreases, the pressure in the central portion 220 of the flexure element increases, i.e., the pressures within the bearing components increase, creating deformations in the bifurcated radial arms 230 and 232 that act to increase the bearing flow gaps, thus providing self-regulating bearing gaps. Although the bifurcated arms are referred to as bifurcated radial arms in this radial configuration, this is not required by the present invention and they may be utilized in non-radial implementations while still serving their function as bifurcated arms. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

[0041] FIG. 2C is a simplified schematic diagram illustrating flexing of a gas bearing element during operation. As the radial arms flex, the flexing maintains the gas bearing clearance between the bearing plates and the bearing race as described herein. In FIG. 2C, the position of the bifurcated arms is shown at an initial position 212 as well as a flexed position 214 after expansion of the central region 220. The separation of the bifurcated arms results in radial contraction of the bearing plate 221 as illustrated by the solid lines in FIG. 2C.

[0042] Thus, the embodiment illustrated in FIGS. 2A-2C provides for pressure balanced compensation. As described above, the internal pressure in curved tubes can be used to cause a straightening effect in the tubes. As swelling due to thermal expansion, neutron absorption, and the like, occurs, the swelling changes the hydrostatic pressure in the gap between the bearing plates and the bearing race. As an example and as discussed in relation to FIGS. 2A through 2C, an increase in the internal channel pressure in the bearing flow gaps will result in an increase in pressure in the central portion 220 of the flexure element, forcing the arms of the element to increase their separation. The increased bowing of the arms will result in shortening of the flexure element, producing a decrease in the internal channel pressure in the bearing flow gaps. Thus, self-regulation and compensation is provided by the embodiment illustrated in FIGS. 2A-2C.

[0043] Embodiments of the present invention as illustrated in FIG. 2A are applicable for use in several portions of the LIFE architecture, including as bearings for the loading mechanism, bearings for the rotating shutter mechanism, or the like. As illustrated in FIG. 2A, the geometry is suitable (e.g., optimized) to create the correct bearing surface motion as pressure due to thermal expansion and expansion resulting from neutron absorption causes deformation of the gas bearing elements. [0044] The embodiment of the present invention illustrated in FIG. 2A operates using static pressure. An external pressure source (not shown) provides pressurized gas that is fed into the center bearing cavity 205. The high-pressure gas then flows outward radially through the central portion of the element and exits at the nozzle 221 to the bearing race. The pressure within the central portion of the element and the channel is then used to regulate flow gaps. It should be appreciated that although FIG. 2A illustrates a circular race bearing and a radial configuration, embodiments of the present invention can be adapted to linear configurations for thrust and linear bearings as appropriate to the particular application. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. [0045] FIG. 3 is a simplified flowchart illustrating a method of operating a gas bearing according to an embodiment of the present invention. The method includes pressurizing a pressure source of the gas bearing with pressurized gas (312). The pressure source can be a central hub of the gas bearing or a peripheral ring of the gas bearing. The method also includes flowing the gas through a plurality of flexural elements in fluid communication with the pressure sournce (314) and forming a bearing region characterized by a pressure equal to a first hydrostatic pressure and disposed between each of the flexural elements and a bearing race (316). The first hydrostatic pressure can be a preload pressure for the gas bearing.

[0046] Flowing the gas through the plurality of flexural elements can include, for each of the plurality of flexural elements, flowing the gas through an orifice in each of the plurality of flexural elements, flowing the gas through a radial portion of each of the plurality of flexural elements, and flowing the gas through a nozzle in each of the plurality of flexural elements. In an embodiment, the nozzle is a porous bearing plate.

[0047] The method further includes increasing the pressure in the bearing region to a second hydrostatic pressure greater than the first hydrostatic pressure (318), deforming the plurality of flexural elements (320), and restoring the pressure in the bearing region to the first hydrostatic pressure (322). Increasing the pressure in the bearing region can result from thermal expansion of the plurality of flexure elements.

[0048] Deforming the plurality of flexural elements can include compressing the plurality of elements as discussed in relation to FIG. IB. Thus, each of the plurality of flexure elements can include a set of radially arrayed cantilevered springs having a radial gas passage disposed therebetween. Additionally, deforming the plurality of flexural elements can include increasing the flexure in a set of cantilevered springs as discussed in relation to FIGS. 2B and 2C. In these embodiments, increasing the flexure in the set of cantilevered springs results from an increase in pressure in a region between the set of cantilevered springs.

[0049] In an embodiment, each of the plurality of flexure elements comprises a plurality of bifurcated flexure elements each having an entrance orifice adjacent the pressure source, a central region extending distally from the entrance orifice, and a distal nozzle.

[0050] It should be appreciated that the specific steps illustrated in FIG. 3 provide a particular method of operating a gas bearing according to an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the individual steps illustrated in FIG. 3 may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. Furthermore, additional steps may be added or removed depending on the particular applications. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. [0051] It should be noted that although some embodiments of the present invention are discussed in terms of providing the source of pressurized gas to the central hub and out to the bearing regions between the bearing plates and the bearing race, this is not required by the present invention and, in fact, pressurized gas could be supplied to the bearing region and flow from there through the flexure elements to the central hub. It should also be appreciated that the motion of the gas bearing can be such that the bearing race can move with respect to the central hub or the central hub can move with respect to the bearing race. Moreover, the bearing pads can be oriented to oppose a central bearing race rather than the circumferential bearing race illustrated in some embodiments herein.

[0052] As an example, the pressure source region, rather than being the central hub, with the bearing element being disposed around the central hub, and the bearing race surrounding the bearing element, could be a peripheral ring, with the bearing element disposed inside the peripheral ring, and the bearing race being disposed inside the bearing element. Thus, implementations in which the flow is radially outward as well as radially inward are included within the scope of the present invention. Thus, the flexural elements / bifurcated flexure elements described in relation to FIGS. 1A-1B and 2A-2C can either be oriented with the entrance orifice on the periphery of the bearing element or on the inner portion of the bearing element as illustrated in the figures. One of ordinary skill in the art would recognize many variations, modifications, and alternatives. [0053] It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.