Description:AN AIR FOIL RADIAL BEARING FOR HIGH-SPEED ROTATING MACHINES AND OPERATION METHOD THEREOF
FIELD OF INVENTION
The present invention generally relates to the field of bearings. Specifically, the present invention relates to radial bearings. Particularly, the present invention relates to air foil radial bearing assembly. More particularly, the present invention relates to an axial air foil radial bearing assembly for enhancing thermal management in high-speed rotating system.
BACKGROUND OF THE INVENTION
From the emergence of mechanics, a radial bearing is a type of rolling element bearing that is specifically designed to support radial loads, which are forces acting perpendicular to the axis of rotation. These bearings are commonly used in various industrial applications, including automotive, aerospace, and machinery.
In general, radial bearings are crucial components in many mechanical systems as they enable smooth rotation and reduce friction between moving parts. They consist of an inner and outer, with a set of rolling elements, such as balls or cylindrical rollers, positioned between them, also the rolling elements distribute the load evenly across the rings, allowing for efficient transmission of radial forces.
In particular, one of the key advantages of radial bearings is their ability to withstand high radial loads while maintaining low friction levels. This is achieved through careful design and selection of materials, ensuring optimal contact between the rolling elements and the rings. Additionally, radial bearings are typically designed to operate at high speeds, making them suitable for applications where rotational speed is a critical factor.

Over the years, there have been numerous advancements in the design and manufacturing of radial bearings. These developments have led to improved performance, increased durability, and enhanced efficiency. Closest prior art refers to existing patents or technical publications that are similar to the invention in question. Here are some examples of closest prior arts for radial bearings:
US4029368A discloses radial bearings, the present invention includes that, radial bearings are in a combination of a housing member, a shaft member, a radial bearing mounted between the housing member and the shaft member, said radial bearing including a sleeve member comprising matrix bonded hard particles, a complementary bearing member comprising matrix bonded hard particles mounted in said bearing in bearing relationship with said sleeve, passageways extending through one of said members.
CN212079928U discloses air foil radial bearing based on hierarchical deformation, the present invention includes the device which comprises a bearing shell, an outer foil, a bump foil elastic component, a top foil, an elastic sleeve, a rotor and a pressing device; the bump foil elastic member is arranged between the outer foil and the top foil; the bump foil elastic member includes: more than 3 wave foils which are uniformly distributed along the inner wall of the outer foil; the bump foil includes: at least 1 group of wave foil combined segments; the wave foil combined section includes: a first construction section, a second construction section, a third construction section; the first construction section, the second construction section and the third construction section are all bent and are bent towards the inner side of the bearing shell; the first construction section, the second construction section and the third construction section respectively comprise 2 feet and a top. The utility model aims at providing an air foil journal bearing based on hierarchical deformation improves the stability of rotor when high-speed operation.
US8845193B2 discloses radial foil bearing, the present invention also includes a top foil, a back foil, and a bearing housing accommodating the top and back foils, and supports a rotary shaft. Engagement grooves are formed on both side surfaces of the bearing housing to extend from the outer circumferential edge to the inner circumferential edge of the side surface. Notches are formed in circumferential edges on both sides of the back foil. A locking member is locked into the engagement grooves of the bearing housing and the notches of the back foil, and includes a pair of engagement legs engaging with the engagement grooves and the notches, and a connection portion connecting the engagement legs together to be disposed near one ends of the engagement legs.
CN109812493B discloses an air foil radial bearing, the present invention comprising: a bearing housing having a hollow portion in which a rotating body is arranged; and a pair of top foils having different lengths, formed inside the hollow portion, thereby enhancing ease of assembly due to a reduction in length and increasing stability at high-speed rotation by adjusting the position of the slot into which the top foil is inserted.
Moreover, the available radial bearings are in need of enhanced, design for manufacturability, thermal management and load capacity.
Hence, there exists an urgent need in the state of art to develop a novel air foil radial bearing for supporting high-speed rotating system to devoid from the above said drawbacks.
OBJECTIVES OF THE INVENTION:
The main objective of the present invention is to develop a novel air foil radial bearing assembly.
Another objective of the present invention is to develop an air foil radial bearing assembly for enhancing thermal management in high-speed rotating system.
Another objective of the present invention is to develop a radial bearing assembly for manufacturability, assembly, and functionality.
Another objective of the present invention is to develop a radial bearing assembly comprising an L- shaped fixation to fixate the foils.
Yet another objective of the present invention is to develop a radial bearing assembly comprising few components such as top foil, bump foil, sleeve housing, O-ring and connecting units.
Further objective of the present invention is to utilize the developed radial bearing assembly for enhancing thermal management in high-speed rotating system.
SUMMARY OF THE INVENTION
According to an aspect of the present invention discloses a novel air foil radial bearing assembly (100), comprising:
a) a sleeve housing (1);
b) bump foil (2);
c) a top foil (3);
d) washer/gasket or axial end cap(4);
e) connecting units (5);
f) anti rotating feature (6a, 6b);
g) cooling channels (7);
h) L – shaped fixation (8);
i) circumferential O-ring (9a) in the O-ring grooves (9);

the sleeve housing (1) secured for assembling the foils (2,3), comprises;
the separate single piece bump foil (2) acts as a spring and provides stiffness and a simplified single piece top foil (3) expands outwards when the shaft rotates at a predetermined speed to generate an air film,

the L- shaped fixation (8) configured to fixate the foils (2,3) in a mobile phase, the anti-rotating feature (6a, 6b) connected by the connecting units to prevent mobility of the sleeve housing (1), the circumferential O-ring (4) secured on the outer diameter of the sleeve (1) configured to provide additional damping, the in-built cooling channels (7) for thermal management,

the end washer or axial end cap is a gasket (4) configured to control the axial movement of the foils (2,3) wherein locked by the connecting units (5) on both sides of the radial bearing assembly (100) thereby achieves thermal capability in high-speed rotating system.

In an aspect of the present invention, in the air foil radial bearing assembly (100), the top foil (3) and bump foil (2) are serially assembled with both fixed at same or opposite ends.

In an aspect of the present invention, in the air foil radial bearing assembly (100), the cooling channels (7) comprises axial slots 3x on outer body of sleeve will act as a thermal decoupling channels also consists axial slots 3x on foil locking plate will act as a thermal decoupling channels.

In an aspect of the present invention, in the air foil radial bearing assembly (100), the anti-rotating feature (6a, 6b) consisting of axial and/or radial restriction mechanism.

In an aspect of the present invention, in the air foil radial bearing assembly (100), the cooling channels on the outer diameter of sleeve is arranged in dimensions by providing optimal temperature boundaries to the load carrying air film and foils.

In an aspect of the present invention, in the air foil radial bearing assembly (100), the shaft said shaft attains DN greater than 3.5 million.

In an aspect of the present invention, in the air foil radial bearing assembly (100), the hard coating is selected from diamond like carbon or equivalent for the rotating shaft and PTFE or equivalent coating on the top foil.

Additionally, in another aspect, the present invention discloses a method for operating air foil radial bearings (AFBs), comprising the steps of:
a) providing a rotor having a rotation surface;
b) applying a hard coating on the rotation surface of the radial contact surface and applying a soft coating on a top foil of the air foil radial bearing;
c) initiating rotation of the rotor in an anti-clockwise direction; thereby as the rotor speed increases, a converging wedge forces air into a reducing cross-sectional area, thereby developing an air film with sufficient pressure to levitate the rotor, known as lift-off speed;
d) adjusting the stiffness of the bump foil (2) and top foil (3) to accommodate rotor eccentricities.
e) below the lift-off speed, a frictional contact occurs between the top foil (3) and the rotor surfaces; followed by maintaining the rotor in steady operation to obtain an air foil radial bearing which is operated at high speeds and stabilized higher temperatures, thereby thermal management and durability is obtained.

In an aspect of the present invention, in the method of operation of air foil radial bearing assembly, the hard coating on the rotation surface is coated with diamond-like carbon (DLC) or equivalent.

In an aspect of the present invention, in the method of operation of air foil radial bearing assembly, the soft coating on top foil is coated with Mos2 or Teflon coating like PTFE or equivalent.
BRIEF DESCRIPTION OF DRAWINGS

Figure: 1 depicts the perspective view of the radial bearing assembly of the present invention.

Figure: 2 illustrates the Radial bearing assembly of the present invention with axial slots on the outer body of the sleeves and foil locking plate.

Figure 3 illustrates the O-rings and the O-ring grooves acting as damping.

REFERENCE NUMERALS:
Reference numerals for different part numbers of air foil radial bearing assembly of the present invention:

S. No PART NAME PART NUMBER
1. Air foil radial bearing assembly (100)
2. A sleeve housing (1)
3. Bump foil (2)
4. A top foil (3)
5. Washer/gasket or axial end cap (4)
6. Connecting units (5)
7. Anti rotating feature on sleeve (6a, 6b)
8. Cooling channels (7) or
Axial slots 3x on outer body of sleeve will act as a thermal decoupling channels (7)
9. Axial slots 3x on foil locking plate will act as a thermal decoupling channels 7a
10. L – shaped fixation (8); (8)
11. Circumferential o-ring groove(9); (9)
12. O-ring acting has a damping (9a)

DETAILED DESCRIPTION OF THE INVENTION:
The present invention as embodied by an “AN AIR FOIL RADIAL BEARING FOR HIGH SPEED ROTATING MACHINES AND OPERATION METHOD THEREOF”” succinctly fulfills the above-mentioned need[s] in the art. The present invention has objective[s] arising as a result of the above-mentioned need[s], said objective[s] being enumerated below. In as much as the objective[s] of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective[s] are not exhaustive of the present invention in its entirety and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative[s] and/or any functional equivalent[s] even though, such structural alternative[s] and/or any functional equivalent[s] are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation[s]/modification[s] applied to the structural alternative[s]/functional alternative[s] within its scope and purview. The present invention may be embodied in other specific form[s] without departing from the essential attributes thereof.

Throughout this specification, the use of the word "comprises" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
A bearing is a mechanical element that fixes a rotary shaft of a rotating machine at a fixed position and supports the shaft while supporting a load applied to the shaft.

Among the bearings, the airfoil bearing is a bearing which supports the load by introducing air, between the foil and the foil in contact with the rotor or the bearing disk due to high-speed rotation of the rotor or rotary shaft to form a pressure. Among these airfoil bearings, the airfoil journal bearings are bearings configured to support a radial load in the vertical direction. The airfoil journal bearing has a bump foil provided along the inner circumference of the hollow circumference of the bearing housing and a top foil provided above the bump foil. A rotor (or rotary shaft) is disposed inside the top foil. The rotor rotates in a state in which the outer peripheral surface of the rotor and the inner peripheral surface of the top foil are spaced apart.

The bump foil and the top foil form a bending portion in which the circumferential end portion is curved radially outward. The bent portion is engaged with a slot formed along the axial direction on the inner circumferential surface of the bearing housing. The bending portion allows the bump foil and the top foil to be fixed to the bearing housing without being rotated or pushed in the circumferential direction when the rotor is rotated. Both the bump foil and the Top foil are single 360 degrees units which are circumferential and circular with ends in engagement with the bearing housing.

The slot of the bearing housing to which the bending of the bump foil and the top foil are engaged is provided in the form of a closed both front and rear sides in the axial direction in order to prevent axial disengagement of the bump foil and the top foil. The bumps on the bump foil are configured to compress under the load.

Therefore, in order to assemble the bump foil and the top foil to the bearing housing, the bump foil and the top foil are wound in the circumferential direction and axially inserted into the hollow of the bearing housing, and then the bent portions of the bump foil and the top foil are radially engaged. This is accomplished by coupling the bending portion of the bump foil and the top foil to the slot in which both the front and rear sides of the axial direction are closed, the bump foil and the top foil can be fixed to the bearing housing and maintained in position by the anti-rotation arrangement.

The present invention discloses a radial air foil bearing assembly that offers enhanced manufacturability, assembly, and functionality. The novelty of the invention lies in the fixation of the top and bump foil insertion into the surrounding, further there is a cooling arrangement in the housing and the foils are arrested from slipping out of the housing, as compared to the prior art.

A comprehensive specification of the present invention includes its unique features and advantages as follows,

Air foil radial bearing assembly (100):
It consists of a simplified single piece top foil and a separate single piece bump foil arranged in series. This configuration ensures high load capacity, low friction, and ease of handling.

Sleeve housing (1):

The bearing is mounted within a sleeve that incorporates in-built cooling channels (7). These channels enhance the thermal behavior of the assembly, promoting efficient heat dissipation and temperature regulation. Reference is drawn to figure 2, depicting the Axial slots 3x on outer body of sleeve will act as a thermal decoupling and 7a depicting the Axial slots 3x on foil locking plate will act as a thermal decoupling. The sleeve has an anti-rotation pin slot and a pin 6a and 6b that could be axial and/or radial in nature to arrest the rotational movement of the sleeve.

L- shaped Fixation (8):
It is a major aspect of the present invention configured to secure the foils within the sleeve, an L-shaped axial slot is employed. This fixation method ensures a stable and reliable connection between the foils and the housing, preventing axial displacement during operation. The top foil and the bump foil are inserted into the L shaped axial groove (8). Fixation provides durability.

Air Foil Radial Bearings (AFBs) :
AFBs are self-acting hydrodynamic compliant bearings that utilize ambient air or gas as lubricants. Compared to traditional oil bearings and rolling bearings, AFBs offer several advantages, including high reliability, extremely low friction during steady operation, and the ability to operate at high speeds and temperatures.

Radial Bearing Operation:
As the rotor initiates anti-clockwise rotation, a converging wedge design forces air into a reducing cross-sectional area. This generates an air film with sufficient pressure to achieve lift-off, allowing the shaft to levitate. The stiffness of the bump foil and top foil can be adjusted to accommodate rotor eccentricities.
During startup, below the lift-off speed, the top foil comes into frictional contact with the rotor surfaces. To mitigate wear, a hard coating such as DLC (diamond-like carbon) or similar hard coats is applied to the rotation surface of the thrust runner. The top foil is coated with a soft material like Mos2 or PTFE (polytetrafluoroethylene) or similar soft coats to enhance wear resistance.
From the figure 1 it is clearly inferred that Fixation of foils to the housing using an L-shaped axial cut is a major merit factor of the present invention.
Housing assembly has cooling channels (labeled as 7) on the outer diameter of the sleeve.
Figure 1 illustrates Implementation of "special axial end caps" to prevent foils from coming out axially. The end caps (4) are configured to be fixed in such a way that they secure the foils by dowel pins.

In one of the preferred embodiment, the present invention discloses an air foil radial bearing assembly (100), comprising:
a) a sleeve housing (1);
b) bump foil (2);
c) a top foil (3);
d) washer/gasket (4); or Axial End caps
e) connecting units (5);
f) anti rotating feature on sleeve (6a, 6b);
g) cooling channels (7);
h) L – shaped fixation (8);
i) circumferential O-ring (9);
in which the sleeve housing (1) secured for assembling the foils (2,3), comprises;
the separate single piece bump foil (2) acts as a spring and provides stiffness and a simplified single piece top foil (3) expands outwards when the shaft rotates at a predetermined speed to generate an air film, this lift-off speed is function of bearing diameter and shaft static loads,

the L- shaped fixation (8) configured to fixate the foils (2,3) in a mobile phase, the anti-rotating feature / stator (6a, 6b) connected by the connecting units to avoid rotation of the bearing housing during high speed and start – stop operations. (1),

the circumferential O-ring (4) secured on the outer diameter of the sleeve (1) configured to provide additional damping, the in-built cooling channels (7) secured to remain in stationary phase, configured for thermal management configured for controlling thermal expansion by providing air film and foil loads to maintain ideal temperature,

the end washer / gasket (4) configured to control the axial movement of the foils (2,3) wherein locked by the connecting units on both sides of the radial bearing assembly (100) ensures stable operation in high-speed rotating system.

In the preferred embodiment, the top foil (3) and bump foil (2) are serially assembled.

In preferred embodiment, the cooling channels on the outer diameter of sleeve is arranged in predetermined dimension, each slot dimensions are selected from the range of 5 degrees to 10 degrees circumferentially

In the preferred embodiment, the shaft comprising turbine side and compressor side on both free ends mounted directly on clamped with tie rod mechanism, and each with or without a motor magnet arrangement at the center.

In the preferred embodiment, the shaft spins in the range of 10 rpm to 140k rpm or higher.

In the preferred embodiment, the hard coating is selected from diamond like carbon or equivalent on the shaft.

In another preferred embodiment of the present invention, a method for operating air foil radial bearings (AFBs), comprising the steps of:
a) providing a rotor (6a) having a rotation surface.
b) applying a hard coating on the rotation surface of the rotor and applying a soft coating on a top foil of the air foil radial bearing;
c) initiating rotation of the rotor in an anti-clockwise direction; thereby as the rotor speed increases, a converging wedge forces air into a reducing cross-sectional area, thereby developing an air film with sufficient pressure to levitate the rotor, known as lift-off speed;
d) adjusting the stiffness of the bump foil (2) and top foil (3) to accommodate rotor eccentricities;
e) below the lift-off speed, a frictional contact occurs between the top foil (3) and the rotor surfaces; followed by maintaining the rotor in steady operation to obtain an air foil radial bearing which is operated at high speeds and high temperatures, thereby thermal management and durability is obtained.

In the preferred embodiment, the hard coating on the rotation surface is coated with diamond-like carbon (DLC) or equivalent

In the preferred embodiment, the soft coating on top foil is coated with Mos2 or Teflon coating like PTFE or equivalent

Example
The present invention has improved the DN value to over 3.5 million.

, Claims:WE CLAIM:
1. An air foil radial bearing assembly (100), comprising:
a) a sleeve housing (1);
b) bump foil (2);
c) a top foil (3);
d) washer/gasket or axial end cap(4);
e) connecting units (5);
f) anti rotating feature (6a, 6b);
g) cooling channels (7);
h) L – shaped fixation (8);
i) circumferential O-ring (9a) in the O-ring grooves (9);

wherein the sleeve housing (1) secured for assembling the foils (2,3), comprises;
the separate single piece bump foil (2) acts as a spring and provides stiffness and a simplified single piece top foil (3) expands outwards when the shaft rotates at a predetermined speed to generate an air film,

the L- shaped fixation (8) configured to fixate the foils (2,3) in a mobile phase, the anti-rotating feature (6a, 6b) connected by the connecting units to prevent mobility of the sleeve housing (1), the circumferential O-ring (4) secured on the outer diameter of the sleeve (1) configured to provide additional damping, the in-built cooling channels (7) for thermal management,

the end washer or axial end cap is a gasket (4) configured to control the axial movement of the foils (2,3) wherein locked by the connecting units (5) on both sides of the radial bearing assembly (100) thereby achieves thermal capability in high-speed rotating system.

2. The air foil radial bearing assembly (100), as claimed in claim 1 wherein the said top foil (3) and bump foil (2) are serially assembled with both fixed at same or opposite ends.

3. The air foil radial bearing assembly (100), as claimed in claim wherein the said cooling channels (7) comprises axial slots 3x on outer body of sleeve will act as a thermal decoupling channels also consists axial slots 3x on foil locking plate will act as a thermal decoupling channels.

4. The air foil radial bearing assembly (100), as claimed in claim 1 wherein the anti-rotating feature (6a, 6b) consisting of axial and/or radial restriction mechanism.

5. The air foil radial bearing assembly (100), as claimed in claim 1 wherein the cooling channels on the outer diameter of sleeve is arranged in dimensions by providing optimal temperature boundaries to the load carrying air film and foils.

6. The air foil radial bearing assembly (100), as claimed in claim 1 wherein the said shaft said shaft attains DN greater than 3.5 million.

7. The air foil radial bearing assembly (100), as claimed in claim 1 wherein the said hard coating is selected from diamond like carbon or equivalent for the rotating shaft and PTFE or equivalent coating on the top foil.

8. A method for operating air foil radial bearings (AFBs), comprising the steps of:
a) providing a rotor having a rotation surface;
b) applying a hard coating on the rotation surface of the radial contact surface and applying a soft coating on a top foil of the air foil radial bearing;
c) initiating rotation of the rotor in an anti-clockwise direction; thereby as the rotor speed increases, a converging wedge forces air into a reducing cross-sectional area, thereby developing an air film with sufficient pressure to levitate the rotor, known as lift-off speed;
d) adjusting the stiffness of the bump foil (2) and top foil (3) to accommodate rotor eccentricities.
e) below the lift-off speed, a frictional contact occurs between the top foil (3) and the rotor surfaces; followed by maintaining the rotor in steady operation to obtain an air foil radial bearing which is operated at high speeds and stabilized higher temperatures, thereby thermal management and durability is obtained.

9. The method of operation of air foil radial bearing assembly as claimed in claim 8, wherein the hard coating on the rotation surface is coated with diamond-like carbon (DLC) or equivalent.

10. The method of operation of air foil radial bearing assembly as claimed in claim 8, wherein the soft coating on top foil is coated with Mos2 or Teflon coating like PTFE or equivalent.

Dated this 22nd day of January 2024 -SD-
Kalyanchand Jhabakh (IN/PA-830)
Agent for Applicant