Dynamic and static pressure hybrid thrust bearing structure and design method thereof

Abstract

The invention relates to a dynamic and static pressure hybrid thrust bearing structure and a design method thereof, and the bearing structure, the bearing structure comprises a back plate, a plurality of fan-shaped bosses are uniformly distributed on the circumference of the front surface of the back plate at intervals, gaskets and bottom foils are arranged between two adjacent fan-shaped bosses, fan-shaped flat foils are arranged on the gaskets and the bottom foils, pressure equalizing grooves are formed in the fan-shaped bosses, the pressure equalizing grooves are arc-shaped grooves, and the arc-shaped flat foils are arranged on the back surface of the back plate. Air outlet holes are formed in the pressure equalizing groove and connected with air inlet holes through air supply flow channels, the air supply flow channels are located in the back plate, and the air inlet holes are located in the outer wall of the back plate; an exhaust passage is arranged in the back plate in the radial direction, one end of the exhaust passage is provided with an exhaust hole which is located in the inner wall of the back plate, and fixing threaded holes are formed in the back face of the back plate. The dynamic and static pressure hybrid bearing is of a multi-tile structure, and flexible foils and steps with air inlet holes are distributed in a staggered mode. The working back pressure of the bearing can be improved through external high-pressure air supply of the air inlet holes, the dynamic pressure effect is improved, abrasion of the bearing during starting and stopping is avoided, and therefore the bearing capacity and rigidity of the bearing are improved.

Description

Technical Field

[0001] The invention relates to a dynamic and static pressure mixed thrust bearing structure and a design method thereof. Background Art

[0002] As the core supporting component of high-speed rotor systems, gas bearings are widely used in aerospace, high-speed turbines, cryogenic technology, air circulation, cryogenic refrigeration, micro gas turbines and other fields, and have very good application prospects.

[0003] Gas bearings are generally divided into static pressure gas bearings and dynamic pressure gas bearings.

[0004] Hydrostatic gas bearings use an external gas source to generate a high-pressure gas film to support the rotor. They have the advantages of large load-bearing capacity, long service life, and high rotation accuracy. However, hydrostatic bearings often require an independent high-pressure gas supply system, which increases the complexity of the system. Hydrostatic bearings also consume a lot of gas, are more expensive, and have poor stability under ultra-high-speed conditions.

[0005] The hydrodynamic gas bearing utilizes the relative movement of the bearing mating surfaces to compress the lubricating gas in the wedge-shaped space under the action of viscosity, thereby generating a load-bearing high pressure in the gap. The foil bearing is a typical hydrodynamic gas bearing, usually composed of a flat foil and an elastic support structure. The structural damping and friction damping generated by its elastic deformation can effectively dissipate the unstable eddy energy of the bearing rotor system, thereby improving the high-speed stability and impact resistance of the bearing rotor system. In addition, the elastic surface of the foil bearing can reduce the machining and assembly accuracy requirements of the bearing, and has good adaptability and economy; however, the hydrodynamic gas bearing has the disadvantages of large friction torque during start-stop, insufficient load-bearing capacity, and low stiffness.

[0006] The Chinese patent application with the publication number "CN112762094A" and the invention name "A dynamic and static pressure mixed gas thrust foil bearing and a dynamic and static pressure mixing device" provides a dynamic and static pressure mixed thrust gas foil bearing, which has an air inlet hole on the top foil, and the air supply pipe passes through the bottom foil from the bottom plate and is connected to the air inlet hole. However, due to the elastic surface of the foil, it is difficult for the air supply pipe to ensure air supply.

[0007] A Chinese patent application with publication number "CN115929790A" and invention name "A dynamic and static pressure hybrid foil gas thrust bearing" provides a dynamic and static pressure hybrid thrust gas foil bearing, which has a small hole throttle embedded in the bearing body, a lever displacement amplification mechanism and an air groove. The wedge surface between the foil and the thrust plate can be raised by the lever, thereby effectively improving the bearing capacity of the bearing. However, the solution does not specify the position of the air outlet groove that affects the bearing performance. Summary of the invention

[0008] The present invention proposes a dynamic-static hybrid thrust bearing structure, in which flexible foils and steps with air inlets are alternately distributed. External high-pressure air supply through the air inlets can increase the working back pressure of the bearing, enhance the dynamic pressure effect, and avoid wear of the bearing during start-up and shutdown, thereby improving the bearing capacity and stiffness; at the same time, the flexible foil can provide a certain amount of damping for the bearing, absorb the energy of the rotor vortex, improve the bearing stability, and reduce the air consumption during the operation of the bearing.

[0009] The technical solution of the present invention to solve the above problem is: a dynamic and static pressure hybrid thrust bearing structure, which is special in that:

[0010] It includes a back plate, which is a hollow cylindrical structure, and a plurality of fan-shaped bosses are evenly spaced on the circumference of the front of the back plate. A gasket and a bottom foil are arranged between two adjacent fan-shaped bosses, and a fan-shaped flat foil is arranged on the gasket and the bottom foil. A pressure equalizing groove is arranged on the fan-shaped boss, and the pressure equalizing groove is an arc-shaped groove. An air outlet is arranged on the pressure equalizing groove, and the air outlet is connected to the air inlet through a supply air channel. The supply air channel is located in the back plate, and the air inlet is located on the outer wall of the back plate; an exhaust duct is arranged radially in the back plate, and one end of the exhaust duct is an exhaust hole, and the exhaust hole is located on the inner wall of the back plate. The exhaust hole is used to prevent gas from accumulating and moving inside. The function of the pressure equalizing groove is to make the pressure distribution of the lubrication gap after the high-pressure gas flows into the outlet hole more uniform, reduce the situation of excessive or low local pressure, and can improve the bearing capacity and suppress the micro-vibration of the bearing; a plurality of fixed threaded holes are evenly arranged on the back of the back plate, and the fixed threaded holes are used to fix the dynamic and static pressure hybrid bearing on the rotating machinery housing of the application.

[0011] Furthermore, a positioning slit is radially provided along the back plate between two adjacent sector-shaped bosses, and one end of the sector-shaped flat foil and the bottom foil is flush with the positioning slit.

[0012] Furthermore, the fixed ends of the gasket and the bottom foil are respectively directly fixed to the back plate by welding or riveting, and the fixed end of the fan-shaped flat foil is directly fixed to the gasket by welding or riveting.

[0013] In addition, in view of the problem that the position of the air outlet is the key to the performance of the dynamic and static pressure hybrid bearing, the present invention proposes a design method for the above-mentioned dynamic and static pressure hybrid thrust bearing structure, which can fully consider the geometric parameters of the air outlet, so as to reasonably determine the optimal position of the air outlet. In addition, the design optimization method provided by the present invention also has the advantages of high accuracy, strong applicability, and can give full play to the performance of the dynamic and static pressure hybrid thrust bearing.

[0014] The present invention also proposes a design method for the above-mentioned dynamic and static pressure hybrid thrust bearing structure, which is special in that it includes the following steps:

[0015] Step 1): Determine the bearing mechanical parameters based on the material and working fluid.

[0016] Step 2): Input bearing geometry parameters

[0017] Step 3): Carry out three-dimensional modeling of the bearing according to the geometric parameters;

[0018] Step 4): Assume the initial lubrication clearance h and perform numerical calculation to obtain the bearing pressure distribution.

[0019] Step 5): Calculate the bearing performance parameters according to the pressure distribution, change the geometric parameters within a reasonable range, repeat the modeling and calculation process, and obtain the optimal bearing geometric parameters to determine the location of the vent hole.

[0020] Furthermore, the step 1) is specifically as follows: determining the bearing elastic modulus E, Poisson's ratio μ, fluid dynamic viscosity η, and density ρ according to the bearing material and the lubricating medium.

[0021] Furthermore, in step 5), the performance parameters of the dynamic and static pressure hybrid bearing are determined by 6 geometric parameters: Where D i is the bearing inner diameter, D o is the outer diameter of the bearing, N is the number of bearing pads, is the opening angle of the dynamic pressure area, r is the radial position of the outlet hole, and θ is the circumferential position of the outlet hole; the performance parameters include bearing capacity, friction torque, stiffness and damping, etc.

[0022] Further, in step 5), D i and D o The bearing parameters are input according to the design requirements to determine the size of the bearing. The position of the vent is determined by the parameters r and θ, and its range is And assume that the initial lubrication gap h = 0.01 mm.

[0023] Further, in step 5), the optimal geometric parameters of the final design are set within the limited range. The largest set of parameter values ​​is the vent position determined by the above design method.

[0024] Advantages of the present invention:

[0025] The dynamic-static hybrid bearing proposed in the present invention is a multi-tile structure, with flexible foils and steps with air inlets staggered. The external high-pressure air supply through the air inlet can increase the working back pressure of the bearing, enhance the dynamic pressure effect, avoid wear of the bearing during start-up and shutdown, and thus improve the bearing capacity and stiffness; at the same time, the flexible foil can provide a certain damping for the bearing, absorb the energy of the rotor vortex, enhance the bearing stability, and reduce the gas consumption during the operation of the bearing. In view of the problem that the position of the air outlet is the key to the performance of the dynamic-static hybrid bearing, the design method provided by the present invention can fully consider the geometric parameters of the air outlet, so as to reasonably determine the optimal position of the air outlet. In addition, the design optimization method provided by the present invention also has the advantages of high precision and strong applicability, and can give full play to the performance of the dynamic-static hybrid thrust bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an exploded view of the overall structure of the dynamic and static pressure hybrid thrust bearing provided by the present invention;

[0027] Figure 2 is a top view of the dynamic and static pressure hybrid thrust bearing provided by the present invention;

[0028] Figure 3 is another angle view of the dynamic and static pressure hybrid thrust bearing provided by the present invention;

[0029] Figure 4 is another angle view of the dynamic and static pressure hybrid thrust bearing provided by the present invention;

[0030] Figure 5 yes Figure 4 The enlarged view of point B in the middle;

[0031] Figure 6 It is a schematic flow chart of the design method of the dynamic and static pressure hybrid thrust bearing provided by the present invention;

[0032] Figure 7 It is a front view and an isometric view of a back plate of a dynamic and static pressure hybrid thrust bearing provided by the present invention;

[0033] Figure 8 yes Figure 3 The enlarged view of point A in the middle;

[0034] Fig. 9 It is a schematic diagram of the bearing geometric parameters provided by the present invention.

[0035] In the figure: 1- flat foil; 2- gasket; 3- bottom foil; 4- back plate; 41- boss; 42- air outlet; 43- air inlet; 44- exhaust hole; 45- positioning slit; 46- fixing threaded hole. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0037] Example 1

[0038] See also Figure 1-Figure 5 , a dynamic-static hybrid thrust bearing structure, including a back plate 4, the back plate 4 is a hollow cylindrical structure, a plurality of fan-shaped bosses 41 are evenly spaced on the circumference of the front of the back plate 4, a gasket 2 and a bottom foil 3 are arranged between two adjacent fan-shaped bosses 41, a fan-shaped flat foil 1 is arranged on the gasket 2 and the bottom foil 3, and a gasket 2 and a bottom foil 3 correspond to each fan-shaped flat foil 1. The fan-shaped boss 41 is provided with a pressure equalizing groove, the pressure equalizing groove is an arc-shaped groove, and an air outlet 42 is provided on the pressure equalizing groove, and the air outlet 42 is connected to the air inlet 43 through a supply air channel, the supply air channel is located in the back plate 4, and the air inlet 43 is located on the outer wall of the back plate 4. An exhaust duct is radially penetrated in the back plate 4, and one end of the exhaust duct is an exhaust hole 44, and the exhaust hole 44 is located on the inner wall of the back plate 4. Referring to 7, a plurality of fixed threaded holes 46 are evenly arranged on the back of the back plate, and the fixed threaded holes 46 are used to fix the dynamic-static hybrid bearing on the rotating machinery housing of the application.

[0039] The arc-shaped pressure-equalizing groove on the boss 41 can make the pressure distribution of the lubrication gap after the high-pressure gas flows from the outlet hole 42 more uniform, reduce the situation where the local pressure is too high or too low, and can improve the bearing capacity and suppress the micro-vibration of the bearing.

[0040] See also Figure 3 An exhaust duct is arranged on the back plate 4 between two adjacent fan-shaped bosses 41. The exhaust duct is arranged to penetrate the inside of the back plate from the inner circle to the outer circle in the radial direction, and its function is to prevent the gas from accumulating and moving inside.

[0041] Specifically, see 2, Figure 3 , Figure 4 and Figure 5 A positioning slit 45 is radially opened along the back plate 4 between two adjacent fan-shaped bosses 41. The positioning slit 45 penetrates the back plate 4. One end of the fan-shaped flat foil 1 and the bottom foil 3 is flush with the positioning slit 45. The positioning slit 45 increases the heat dissipation channel inside the bearing and enhances the heat dissipation effect of the bearing.

[0042] Specifically, see 2, Figure 3 and Figure 5 The fixed ends of the gasket 2 and the bottom foil 3 are directly fixed to the back plate 4 by welding or riveting, and the fixed end of the fan-shaped flat foil 1 is directly fixed to the gasket 2 by welding or riveting.

[0043] When the dynamic-static hybrid thrust bearing is working, external high-pressure gas flows into the back plate from the air inlet 43 and flows into the lubrication gap between the bearing and the rotor from the air outlet 42, which can increase the pressure in the air film gap and increase the dynamic pressure effect, thereby improving the bearing capacity and rigidity of the bearing and avoiding bearing wear during start-stop; at the same time, the flexible foil structure including the flat foil 1 and the bottom foil 3 can provide a certain damping for the bearing, absorb the vortex energy during the operation of the rotor, and improve the stability of the system.

[0044] In addition, in view of the problem that the position of the air outlet is the key to the performance of the dynamic and static pressure hybrid bearing, the present invention proposes a design method for the above-mentioned dynamic and static pressure hybrid thrust bearing structure, which can fully consider the geometric parameters of the air outlet, so as to reasonably determine the optimal position of the air outlet. In addition, the design optimization method provided by the present invention also has the advantages of high accuracy, strong applicability, and can give full play to the performance of the dynamic and static pressure hybrid thrust bearing.

[0045] The present invention also proposes a design method for the above-mentioned dynamic and static pressure hybrid thrust bearing structure, see Figure 6-Figure 9 , simplifying the bearing with periodic structure in the circumferential direction into a single design model, including the following steps:

[0046] Step 1): Determine the bearing mechanical parameters according to the material and working fluid, select the required bearing material and lubricating working fluid, and thus determine the bearing elastic modulus E, Poisson's ratio μ, fluid dynamic viscosity η, and density ρ;

[0047] Step 2): Input bearing geometry parameters Assuming a set of bearing geometry parameters Where D i is the bearing inner diameter, D o is the outer diameter of the bearing, N is the number of bearing pads, the number of bearing pads refers to the number of basic working elements of the bearing, which is also equivalent to the number of flat foil 1, gasket 2, and bottom foil 3. is the opening angle of the dynamic pressure area, r is the radius of the center of the air outlet 42, and θ is the circumferential angle of the air outlet 42;

[0048] Step 3): establishing a three-dimensional geometric model of the bearing and a finite element physical calculation model according to the geometric parameters;

[0049] Step 4): Assuming the initial lubrication clearance h, solve the Reynolds equation and perform numerical calculations to obtain the bearing pressure distribution.

[0050]

[0051] Step 5): Calculate bearing performance parameters (e.g. bearing capacity) based on pressure distribution ), change the geometric parameters within a reasonable range, repeat the modeling and calculation process, and obtain the optimal bearing geometric parameters, thereby determining the position of the air outlet 42. The bearing performance parameters include bearing load capacity, friction torque, stiffness and damping.

[0052] Furthermore, under the dynamic pressure effect, the lubricating gas film presents a non-uniform pressure distribution. For different pad numbers N and dynamic pressure area angles, The range of bearing geometric parameters is: By controlling the radius r and circumferential angle θ of the center of the air outlet 42, it is matched with the high-pressure area of ​​the lubricating gas film. Under the dynamic pressure effect, the high-pressure area of ​​the gas film often appears in the middle section of the fan-shaped area close to the outer edge. The reasonable position of the air outlet 42 should be in the middle section of the bearing close to the outer edge and close to the fixed end of the foil. This can maximize the pressure and effective bearing area of ​​the high-pressure area, and obtain a set of geometric parameters that optimize the target performance parameters.

[0053] Specifically, the design parameters and calculated values ​​in this example are:

[0054]

[0055]

[0056] The above descriptions are merely embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related system fields, are also included in the protection scope of the present invention.

Claims

1. A dynamic and static pressure hybrid thrust bearing structure, characterized in that: The invention comprises a back plate (4), wherein the back plate (4) is a hollow cylindrical structure, and a plurality of fan-shaped bosses (41) are evenly spaced on the circumference of the front side of the back plate (4), a gasket (2) and a bottom foil (3) are provided between two adjacent fan-shaped bosses (41), a fan-shaped flat foil (1) is provided on the gasket (2) and the bottom foil (3), a pressure equalizing groove is provided on the fan-shaped boss (41), the pressure equalizing groove is an arc-shaped groove, an air outlet (42) is provided on the pressure equalizing groove, the air outlet (42) is connected to the air inlet (43) through an air supply channel, the air supply channel is located in the back plate (4), and the air inlet (43) is located on the outer wall of the back plate (4); an exhaust channel is radially provided in the inner side of the back plate (4), one end of the exhaust channel is an exhaust hole (44), and the exhaust hole (44) is located on the inner wall of the back plate (4); and a plurality of fixed threaded holes (46) are evenly arranged on the back side of the back plate.

2. The dynamic and static pressure hybrid thrust bearing structure according to claim 1, characterized in that: Between two adjacent sector-shaped bosses (41), a positioning slit (45) is provided along the back plate (4) in a radial direction, and one end of the sector-shaped flat foil (1) and the bottom foil (3) is flush with the positioning slit (45).

3. The dynamic and static pressure hybrid thrust bearing structure according to claim 2, characterized in that: The fixed ends of the gasket (2) and the bottom foil (3) are respectively directly fixed to the back plate (4) by welding or riveting, and the fixed end of the fan-shaped flat foil (1) is directly fixed to the gasket (2) by welding or riveting.

4. A design method for a dynamic and static pressure hybrid thrust bearing structure, characterized in that: The following steps are involved: Step 1): Determine the bearing mechanical parameters based on the material and working fluid. Step 2): Input bearing geometry parameters Step 3): Carry out three-dimensional modeling of the bearing according to the geometric parameters; Step 4): Assume the initial lubrication clearance h and perform numerical calculation to obtain the bearing pressure distribution. Step 5): Calculate the bearing performance parameters according to the pressure distribution, change the geometric parameters within a reasonable range, repeat the modeling and calculation process, and obtain the optimal bearing geometric parameters, thereby determining the position of the air outlet (42).

5. The design method of a dynamic and static hybrid thrust bearing structure according to claim 4, characterized in that: The step 1) specifically includes: determining the bearing elastic modulus E, Poisson's ratio μ, fluid dynamic viscosity η, and density ρ according to the bearing material and lubricating medium.

6. The design method of a dynamic and static hybrid thrust bearing structure according to claim 5, characterized in that: In step 5), the bearing performance parameters are determined by 6 geometric parameters Where D i is the bearing inner diameter, D o is the outer diameter of the bearing, N is the number of bearing pads, is the opening angle of the dynamic pressure area, r is the radial position of the outlet hole (42), and θ is the circumferential position of the outlet hole (42); the performance parameters include bearing capacity, friction torque, stiffness and damping.

7. The design method of a dynamic and static hybrid thrust bearing structure according to claim 6, characterized in that: In step 5): D i and D o The bearing parameters are input according to the design requirements to determine the size of the bearing. The position of the air outlet (42) is determined by the parameters r and θ, and the range is And assume that the initial lubrication gap h = 0.01 mm.

8. The design method of a dynamic and static hybrid thrust bearing structure according to claim 7, characterized in that: In step 5), the optimal geometric parameters of the final design are set within the limited range. The maximum set of parameter values ​​ultimately determines the position of the air outlet (42).

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