An adaptive variable stiffness gas foil bearing

Abstract

This invention relates to the field of hydrodynamic lubrication technology and discloses an adaptive variable stiffness gas foil bearing, comprising a bearing outer sleeve, a contoured transition block, an SMA arched adjusting plate, a metal mesh damping ring, a corrugated foil, and a top foil. The bearing outer sleeve is a hollow cylindrical structure. On the inner side of the bearing outer sleeve, the contoured transition block, the SMA arched adjusting plate, the metal mesh damping ring, the corrugated foil, and the top foil are arranged radially from the outside to the inside. The contoured transition block is embedded in the inner wall of the bearing outer sleeve, and the SMA arched adjusting plate is embedded inside the contoured transition block. The SMA arched adjusting plate is in contact with the outside of the metal mesh damping ring. The corrugated foil and the top foil are nested sequentially inside the metal mesh damping ring. The top foil is assembled and connected to the shaft. This invention solves the contradiction between takeoff and high-speed stability in traditional bearings, and has advantages such as compact structure, reliable assembly, and excellent vibration resistance.

Description

Technical Field

[0001] This invention relates to the field of hydrodynamic lubrication technology, and specifically to an adaptive variable stiffness gas foil bearing. Background Technology

[0002] Gas foil bearings have broad application prospects in high-speed turbine machinery due to their advantages such as oil-free lubrication, high temperature resistance, and high limiting speed.

[0003] However, traditional gas foil bearings face a contradiction in the support stiffness requirements of "takeoff and shutdown" and "high-speed operation" when they are widely used: during the start-stop phase, due to the low speed, the gas film has not yet formed, and the bearing needs to have low stiffness to accommodate rotor deformation, reduce wear, and achieve rapid takeoff; during the high-speed operation phase, as the gas film stiffness increases, the rotor is prone to subsynchronous whirl, and the bearing needs to have high structural stiffness and damping to suppress instability.

[0004] In addition, existing variable stiffness bearing designs mostly use active electric heating of SMA springs (shape memory alloy springs). Although this method offers good controllability, it requires the introduction of complex electronic control systems, power slip rings, and cooling pipes, resulting in a large overall structure that is difficult to apply effectively in space-constrained micro gas turbines.

[0005] In addition, existing multi-layer foil structures often use spot welding connections, which result in low assembly fault tolerance and stress concentration at the weld points, leading to fatigue fracture. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an adaptive variable stiffness gas foil bearing that is compact in structure, requires no external energy source, and passively and adaptively adjusts its stiffness using ambient temperature.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention proposes an adaptive variable stiffness gas foil bearing, comprising a bearing outer sleeve, a contoured transition block, an SMA arched adjustment plate, a metal mesh damping ring, corrugated foil, and a top foil. The bearing outer sleeve is a hollow cylindrical structure. On the inner side of the bearing outer sleeve, the contoured transition block, the SMA arched adjustment plate, the metal mesh damping ring, the corrugated foil, and the top foil are arranged radially from the outside to the inside. The contoured transition block is embedded in the inner wall of the bearing outer sleeve, and the SMA arched adjustment plate is embedded in the inner side of the contoured transition block. The SMA arched adjustment plate is in contact with the outside of the metal mesh damping ring. The corrugated foil and the top foil are nested inside the metal mesh damping ring to form a gas mold working surface. The top foil is assembled and connected to the rotating shaft.

[0009] Furthermore, the gas foil bearing of the present invention also includes an axial baffle in the shape of an annular plate; there are two axial baffles, which are respectively disposed at both ends of the bearing outer sleeve, for limiting and fixing the components inside the bearing outer sleeve in the axial direction.

[0010] Furthermore, the gas foil bearing of the present invention also includes fasteners. The two end faces of the bearing outer sleeve are provided with a plurality of connecting holes. There are a plurality of fasteners arranged in an array. The fasteners and the connecting holes are matched. The fasteners connect the bearing baffle and the bearing outer sleeve by passing through the bearing baffle and being screwed into the connecting holes.

[0011] Furthermore, the axial baffle is provided with several through holes, and the connecting holes are threaded blind holes; fasteners pass through the through holes and are screwed into the threaded blind holes to achieve the connection between the bearing baffle and the bearing outer sleeve.

[0012] Furthermore, N positioning grooves are evenly provided circumferentially on the inner wall of the bearing outer sleeve, and there are also N contouring transition blocks, which are matched one-to-one with the positioning grooves; the outer side of the contouring transition block is provided with a boss that fits with the positioning groove with a clearance, and the contouring transition block achieves circumferential stop by embedding the boss into the positioning groove of the bearing outer sleeve.

[0013] Furthermore, the inner surface of the contouring adapter block is set as a concave arc surface, and the SMA arched adjustment plate is an arched thin sheet made of two-way shape memory alloy, including an arched back and feet located on both sides. The arched back fits into the concave arc surface of the contouring adapter block. When the feet located on both sides are less than or equal to the martensitic phase transformation end temperature of the SMA arched adjustment plate, they are in a state of complete contraction (i.e., the feet on both sides of the SMA arched adjustment plate are in a state of retraction and relaxation, and the pre-tightening force on the metal wire mesh damping ring is small, or even negligible). When the feet are greater than or equal to the austenitic phase transformation end temperature of the SMA arched adjustment plate, they are in a state of complete expansion and compression with the outer surface of the metal wire mesh damping ring.

[0014] Furthermore, there are N of each of the contour-following adapter block and SMA arched adjustment plate, arranged in a circumferential array.

[0015] Furthermore, the metal mesh damping ring is a complete cylindrical porous elastomer, coaxially disposed on the inner side of all SMA arched adjustment plates, with the two side feet of the SMA arched adjustment plates pressed against the outer cylindrical surface of the metal mesh damping ring.

[0016] Furthermore, the metal wire mesh damping ring is woven and molded from metal wires, and its outer diameter is matched with the cavity size enclosed by the foot span of all SMA arched adjustment plates to ensure that the SMA arched adjustment plates apply radial preload to the metal wire mesh damping ring after assembly.

[0017] Furthermore, the boss of the contouring adapter block is rectangular or dovetail shaped, and the positioning groove on the inner wall of the bearing outer sleeve matches the shape of the boss.

[0018] Furthermore, N positioning grooves are evenly distributed circumferentially on the inner wall of the bearing outer sleeve, and N contouring transition blocks are also provided, corresponding to and matching the positioning grooves one by one; the connecting hole is provided between two adjacent positioning grooves.

[0019] Furthermore, the SMA arched adjustment plate has an arched structure, preferably an Ω-shaped structure, and its phase change temperature range is set within the predetermined operating temperature range of the gas foil bearing.

[0020] It should be noted that the elastic modulus of the SMA arched adjustment plate in the low-temperature martensitic state is lower than that in the high-temperature austenitic state, and it has a shape memory tendency to recover to a higher arch height in the high-temperature state.

[0021] The bearing of this invention can be applied to high-speed rotating machinery such as micro gas turbines and high-speed air compressors. It is an adaptive variable stiffness gas foil bearing technology based on shape memory alloy and metal wire mesh damping.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The gas foil bearing of the present invention adopts a fully mechanical interlock assembly, which is compact in structure, requires no external energy, and can passively and adaptively adjust stiffness by utilizing ambient temperature. It solves the contradiction between take-off and high-speed stability of traditional bearings, and also has reliable assembly and excellent vibration resistance.

[0024] (2) The present invention adopts a mechanical interlocking assembly structure based on geometric shape matching, abandons the traditional spot welding process, effectively eliminates the hidden dangers of thermal stress concentration and weld fatigue failure, and realizes modular rapid disassembly and maintenance of components; by introducing a complete metal wire mesh damping ring, the discrete radial driving force of the SMA arched adjustment plate is transformed into a circumferentially uniformly distributed flexible preload, avoiding local stress concentration and non-uniform deformation of the corrugated foil, and ensuring the consistency of the air film gap; at the same time, the present invention combines the structural hysteresis damping of the metal wire mesh damping ring with the Coulomb friction damping of the corrugated foil to construct a composite damping system, and utilizes the temperature sensitive characteristics of the SMA arched adjustment plate, without the need for external sensors and control circuits, it can drive phase change by relying only on the change of ambient temperature, adaptively realize the variable stiffness adjustment of "low temperature and low stiffness rapid take-off, high temperature and high stiffness stable operation", and significantly improve the vibration resistance and operation stability of the bearing in a wide temperature range and full speed range. Attached Figure Description

[0025] Figure 1 This is a three-dimensional structural diagram of the gas foil bearing in Embodiment 1 of the present invention;

[0026] Figure 2 This is an exploded view of the gas foil bearing structure in Embodiment 1 of the present invention;

[0027] Figure 3 This is a schematic diagram of the radial cross-section of the gas foil bearing in Embodiment 1 of the present invention;

[0028] Figure 4 This is a partially enlarged schematic diagram illustrating the working mechanism of the SMA arched adjustment plate and the metal wire mesh damping ring in Embodiment 1 of the present invention;

[0029] Figure 5 This is a comparison curve showing the equivalent stiffness of the gas foil bearing and a conventional bearing in Embodiment 1 of the present invention as a function of ambient temperature. The meanings of the reference numerals in the figure are as follows:

[0030] 1-Bearing outer sleeve; 2-Contouring adapter block; 3-SMA arched adjusting plate; 4-Metal wire mesh damping ring; 5-Wave foil; 6-Top foil; 7-Axial baffle; 8-Fastener. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may include different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of the present invention and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, this embodiment proposes an adaptive variable stiffness gas foil bearing, which has a multi-layer coaxial nested structure. The outermost layer is the bearing outer sleeve 1, which serves as the main load-bearing component. On the inner side of the bearing outer sleeve 1, a contoured transition block 2, an SMA arched adjusting plate 3, a metal wire mesh damping ring 4, a corrugated foil 5, and a top foil 6 are distributed radially from the outside to the inside. An axial baffle 7 is fitted to both end faces of the bearing outer sleeve 1, and fasteners 8, which pass through the axial baffle 7, are screwed into threaded holes on the end faces of the bearing outer sleeve 1, thereby limiting and fixing the internal components axially to prevent axial movement during operation.

[0036] like Figure 2 As shown, the bearing outer sleeve 1 is a cylindrical body with six axial through grooves uniformly machined along its inner circumference as positioning grooves. The outer surface of the contouring adapter block 2 is designed as a rectangular boss that fits with the positioning grooves with clearance, and the number of bosses is the same as the number of positioning grooves. The SMA arched adjusting plates 3 have an arched structure, and their number corresponds one-to-one with the contouring adapter blocks 2. The metal wire mesh damping ring 4 is a complete cylindrical part located inside all the SMA arched adjusting plates 3. During assembly, it is carried out by a fully mechanical interlocking method: the contouring adapter block 2 is radially embedded into the bearing outer sleeve 1; the SMA arched adjusting plates 3 are radially embedded into the contouring adapter block 2; the metal wire mesh damping ring 4, the corrugated foil 5, and the top foil 6 slide in axially in sequence; finally, the axial baffles 7 at both ends are locked.

[0037] like Figure 3 As shown, the rectangular boss of the contouring adapter block 2 is embedded in the positioning groove of the bearing outer sleeve 1, achieving circumferential stopping. The inner surface of the contouring adapter block 2 is machined with a concave arc surface, the radius of curvature of which matches the radius of curvature of the arch back of the SMA arched adjustment piece 3, thereby providing stable back support for the SMA arched adjustment piece 3. The outer cylindrical surface of the wire mesh damping ring 4 maintains contact with the inwardly contracting two sides of the SMA arched adjustment piece 3. In addition, the mounting holes of the fastener 8 are located in the thicker solid part of the bearing outer sleeve 1, that is, in the middle of two adjacent positioning grooves, avoiding structural interference with the mounting groove and ensuring connection strength.

[0038] It should be noted that: in order to illustrate the internal structure of the gas foil bearing in this embodiment, Figures 1 to 3 An axial baffle at one end is not shown.

[0039] like Figure 4 As shown, during rotor start-up or low-speed operation, the ambient temperature is low, and the SMA arched regulating plate 3 is in the martensitic phase (low stiffness soft state). At this time, its two sides are in a retracted and relaxed state, with a small preload on the internal components, and the overall bearing has a low structural stiffness. At this time, the innermost top foil 6 serves as the air film working surface, and the structure below it has a large deformation margin, which can effectively accommodate the eccentricity and deformation of the rotor in the early stage of start-up, reduce the mechanical wear between the top foil 6 and the shaft, and help the rotor achieve low-speed and rapid "take-off".

[0040] As the gas turbine enters a high-speed, stable operating state, and the ambient temperature rises above the phase transformation temperature of the SMA arched regulating plate 3, the material undergoes a reverse martensitic phase transformation to austenite, causing the SMA arched regulating plate 3 to tend to revert to its high-arched shape memory. Because its arched back is rigidly constrained by the concave arc surface of the contoured transition block 2, it cannot expand outwards, forcing its two sides to extend radially inwards and press against each other, applying a significant radial compressive force to the metal mesh damping ring 4. This radial compressive force compresses the metal mesh damping ring 4, increasing the dry friction damping between the microwires inside the metal mesh damping ring 4, and uniformly transmitting the preload to the internal corrugated foil 5, providing a solid bottom layer support for the top foil 6. This significantly improves the overall structural stiffness of the bearing, achieving the goal of suppressing high-speed rotor whirling and maintaining high-speed stable operation. During equipment shutdown, as the temperature decreases, the SMA arched regulating plate 3 transforms back into the martensitic phase, the radial preload is unloaded, and the bearing stiffness decreases again, safely and smoothly accommodating the vibration during rotor deceleration.

[0041] To further verify the beneficial effects of the present invention, such as Figure 5 The figure shows a comparison curve of the equivalent stiffness of the gas foil bearing (referred to as Composite Bearings in the figure) and the traditional gas foil bearing (referred to as Traditional Bearings in the figure) as a function of ambient temperature. The horizontal axis represents the ambient temperature, the vertical axis represents the equivalent stiffness, and the SMA Phase Transformation Region represents the SMA phase transformation region.

[0042] from Figure 5The test curves show that the equivalent stiffness of traditional bearings remains basically unchanged and at a low level within the ambient temperature range of 24℃ to 100℃, which cannot simultaneously meet the requirements of low-speed rotor take-off and high-speed stable operation. Conversely, the gas foil bearing of the present invention exhibits extremely significant temperature-adaptive variable stiffness characteristics: in the low-temperature stage (e.g., 24℃~40℃), the SMA arched adjusting plate 3 is in the martensitic state and no phase transformation occurs. The overall equivalent stiffness of the gas foil bearing of the present invention is low, which is beneficial for the rotor to take off smoothly at low speed and accommodate deformation. When the ambient temperature rises and enters the SMA phase transformation region (i.e., the gray shaded area of ​​about 50℃~65℃ in the figure), the SMA arched adjusting plate 3 undergoes a rapid reverse martensitic phase transformation. The radial elongation and restoring force generated at its foot increase significantly with temperature, strongly compressing the metal wire mesh damping ring 4, resulting in a nonlinear and rapid increase in the equivalent stiffness of the gas foil bearing of the present invention. When the ambient temperature further rises to the high-temperature stage (e.g., 80℃~100℃), the phase transformation is basically completed, and the equivalent stiffness of the gas foil bearing of the present invention reaches and is maintained at an extremely high level (e.g., about 15×10^5 N / m at 100℃, far exceeding the stiffness level of traditional bearings).

[0043] The comparative curve data intuitively and fully demonstrates that the present invention can passively and smoothly achieve adaptive adjustment of "low temperature and low stiffness, high temperature and high stiffness" by relying solely on changes in ambient temperature without any external electronic control intervention, thus perfectly solving the core contradiction between the stability of traditional bearings during low-speed take-off and high-speed operation.

[0044] This invention utilizes a geometric interlocking structure to achieve fully mechanical, weld-free assembly. It leverages the thermal environment of the gas turbine to trigger a phase change in the SMA arched regulating plate 3. At high temperatures, the foot of the SMA arched regulating plate 3 expands radially inward, compressing the metal mesh damping ring 4, passively increasing the structural stiffness and damping of the gas foil bearing, thus resolving the contradiction between takeoff and high-speed stability in traditional bearings. Simultaneously, this invention exhibits excellent vibration resistance. This superior vibration resistance primarily stems from the fact that when the SMA arched regulating plate 3 presses against the metal mesh damping ring 4, it not only enhances the overall stiffness but also generates significant structural hysteresis damping due to the mutual slippage between the microfilaments within the metal mesh damping ring 4. Combined with the Coulomb friction damping between the corrugated foil 5 and the top foil 6, a highly efficient composite damping system is constructed, capable of dissipating a large amount of vibration energy from the rotor during high-speed operation.

[0045] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An adaptive variable stiffness gas foil bearing, characterized in that, The bearing includes a bearing outer sleeve, a contoured transition block, an SMA arched adjusting plate, a metal mesh damping ring, a corrugated foil, and a top foil. The bearing outer sleeve is a hollow cylindrical structure. On the inner side of the bearing outer sleeve, the contoured transition block, the SMA arched adjusting plate, the metal mesh damping ring, the corrugated foil, and the top foil are arranged radially from the outside to the inside. The contoured transition block is embedded in the inner wall of the bearing outer sleeve. The SMA arched adjusting plate is embedded in the inner side of the contoured transition block. The SMA arched adjusting plate is in contact with the outside of the metal mesh damping ring. The corrugated foil and the top foil are nested inside the metal mesh damping ring. The top foil is assembled and connected to the rotating shaft.

2. The adaptive variable stiffness gas foil bearing according to claim 1, characterized in that, It also includes an axial baffle in the shape of an annular plate; there are two axial baffles, which are respectively disposed at both ends of the bearing outer sleeve.

3. The adaptive variable stiffness gas foil bearing according to claim 2, characterized in that, It also includes fasteners, and the two ends of the bearing outer sleeve are provided with a number of connecting holes. There are a number of fasteners arranged in an array, and the fasteners are matched with the connecting holes. The fasteners pass through the bearing baffle and are screwed into the connecting holes.

4. The adaptive variable stiffness gas foil bearing according to claim 1, characterized in that, The inner wall of the bearing outer sleeve is uniformly provided with N positioning grooves along the circumference, and there are also N contouring transition blocks, which are matched one-to-one with the positioning grooves; the outer side of the contouring transition block is provided with a boss that fits with the positioning groove with a clearance.

5. The adaptive variable stiffness gas foil bearing according to claim 1, characterized in that, The inner surface of the contouring adapter block is set as a concave arc surface. The SMA arched adjustment plate is an arched plate made of two-way shape memory alloy, including an arched back and feet located on both sides. The arched back fits into the concave arc surface of the contouring adapter block. When the feet located on both sides are less than or equal to the martensitic phase transformation end temperature of the SMA arched adjustment plate, they are in a fully contracted state. When they are greater than or equal to the austenitic phase transformation end temperature of the SMA arched adjustment plate, they are in a fully expanded state and are squeezed against the outer surface of the metal wire mesh damping ring.

6. The adaptive variable stiffness gas foil bearing according to claim 1, characterized in that, There are N of each of the contour-following adapter block and SMA arched adjustment plate, arranged in a circumferential array.

7. The adaptive variable stiffness gas foil bearing according to claim 6, characterized in that, The metal mesh damping ring is cylindrical and coaxially arranged inside all SMA arched adjustment plates. The two sides of the SMA arched adjustment plates are pressed against the outer cylindrical surface of the metal mesh damping ring.

8. The adaptive variable stiffness gas foil bearing according to claim 4, characterized in that, The protrusion of the contouring adapter block is rectangular or dovetail shaped, and the positioning groove on the inner wall of the bearing outer sleeve matches the protrusion shape.

9. The adaptive variable stiffness gas foil bearing according to claim 3, characterized in that, The inner wall of the bearing outer sleeve is provided with N positioning grooves evenly distributed along the circumference, and there are also N contouring transition blocks, which are matched one-to-one with the positioning grooves; the connecting hole is provided between two adjacent positioning grooves.

10. The adaptive variable stiffness gas foil bearing according to claim 1, characterized in that, The SMA arched adjustment plate has an arched structure.

Images