Flexible membrane disc coupling for ultra-high speed cryogenic bearing test and design method thereof

Abstract

A flexible membrane disc coupling for super-high-speed cryogenic bearing test and a design method thereof are disclosed. The coupling is coupled with rotors at two ends. Comprehensive design is performed from two aspects of mechanical performance and dynamic performance to ensure that additional load generated by the coupling on bearings of the rotors at two ends is minimum when the coupling is compensated. Through dynamic optimization design, mass and mass distribution characteristics of the coupling are optimized to ensure that critical speed of the whole rotor system meets rigid design principle. Through setting of a heating belt, temperature of a key part of a membrane disc curved surface of the coupling can be ensured to be in an optimal temperature range of a material when the coupling works in super-low temperature. Changes of material performance and space size caused by use of a previous coupling structure in a super-low temperature environment are overcome. The coupling always maintains an optimal working state to ensure compensation and transmission capacity of the coupling when the double-span rotor system operates at high speed.

Description

Technical Field

[0001] This invention belongs to the field of liquid rocket engine bearing testing technology, and relates to a flexible diaphragm coupling for ultra-high speed, high DN value cryogenic bearing testing and its design method. Background Technology

[0002] To conduct evaluation tests on high-DN value cryogenic bearings for liquid rocket engines, a flexible coupling with high compensation capability needs to be installed between the rotor of the test device and the rotor of the drive device. This coupling compensates for axial, angular, and radial misalignment between the two shaft systems, improving operational dynamic performance. Among various coupling structures, diaphragm couplings offer superior performance, compensating for shaft misalignment and suitable for high-speed applications.

[0003] However, for the operating conditions of cryogenic bearings with high DN values ​​in liquid rocket engines, the DN value (shaft diameter × rotational speed, in mm·r / min) exceeds 3×10. 6 The maximum operating speed is >90000 r / min. However, in previous tests, the shaft system resonated, causing it to break and failing to achieve the purpose of the test.

[0004] Analysis revealed that to achieve bearing testing and verification at ultra-low temperatures (-196℃) and high speeds (>90000 r / min), the diaphragm coupling must be able to adapt to the following operating conditions:

[0005] (1) During operation, the low temperature test device operates in an ultra-low temperature (-196℃) liquid environment, which will transfer the temperature to the coupling through the shaft system, resulting in a decrease in the temperature of the coupling structure, thereby reducing its compensation capability and working performance.

[0006] (2) The compensation capability of the ultra-high speed coupling itself must meet the usage requirements. Although the larger the stiffness value of the coupling, the higher the critical speed of the shaft system, the greater the additional dynamic load on the rotors on both sides when the coupling is working, the greater the additional dynamic load on the rotors on both sides when the stiffness value increases. Therefore, it is necessary to combine the shaft systems on both sides and design their axial stiffness, radial stiffness, and angular stiffness in detail so that the additional load on the bearings of the shaft systems on both sides when compensating under high-speed working conditions is within an acceptable range.

[0007] (3) The critical speed of the ultra-high speed coupling itself should meet the rigid design principle (i.e., it should work below the first critical speed), and after being connected with the rotors on both sides, the critical speed of the entire double-span rotor should meet the rigid design principle.

[0008] Therefore, higher requirements are placed on the surface design, mass design, structural design, and heat transfer design of diaphragm disc couplings. Thus, to achieve experimental verification of high-speed, high-DN value cryogenic bearings for liquid rocket engines, it is necessary to conduct detailed research, develop a design method for diaphragm disc couplings used in cryogenic high-speed bearing testing, and design a specific structure to meet the testing requirements of cryogenic high-speed bearings. Summary of the Invention

[0009] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a flexible diaphragm coupling for ultra-high speed low temperature bearing testing and its design method.

[0010] The solution of the present invention is:

[0011] A flexible diaphragm coupling for ultra-high speed low temperature bearing testing includes a heating belt, a first half-diaphragm coupling, a second half-diaphragm coupling, a third half-diaphragm coupling, a fourth half-diaphragm coupling, a first coupling fastening screw, a second coupling fastening screw, an intermediate shaft, a first positioning screw, a first positioning pressure plate, a second positioning screw, and a second positioning pressure plate.

[0012] The front end of the main shaft of the test device is connected to the drive main shaft through an intermediate shaft, and the intermediate shaft is designed with circumferential flanges at both ends. The first half-diaphragm coupling is fixed to the front end of the main shaft of the test device through the first positioning plate and the first positioning screw. The second half-diaphragm coupling is connected to the first half-diaphragm coupling by electron beam welding. The flange of the second half-diaphragm coupling is fixed to the flange on the intermediate shaft by the first coupling fastening screw. The third half-diaphragm coupling is fixed to the end of the drive main shaft through the second positioning plate and the second positioning screw. The fourth half-diaphragm coupling is connected to the third half-diaphragm coupling by electron beam welding. The flange of the fourth half-diaphragm coupling is fixed to the flange on the intermediate shaft by the second coupling fastening screw.

[0013] The heating belt has a circular structure and is fitted at the junction of the first half-diaphragm disc coupling and the main shaft of the test device, with a clearance fit between the first half-diaphragm disc coupling and the main shaft of the test device; the lower part of the heating belt is connected to the base, and when working, the heating belt is supplied with direct current to achieve heating and release of heat and emit infrared radiation; the voltage and current are adjusted by a voltage regulator to achieve different heat output and different thermal radiation from the heating belt.

[0014] Preferably, the flange of the second half-diaphragm coupling and the flange of the intermediate shaft are provided with stepped stops to achieve radial positioning of the intermediate shaft and the second half-diaphragm coupling, prevent excessive shear stress on the bolts during operation, and improve service life.

[0015] Preferably, the raised portion of the stepped stop is located on the flange of the intermediate shaft, and the recessed portion is located on the second half-diaphragm disc coupling.

[0016] Preferably, the first half-diaphragm disc coupling and the main shaft of the test device, and the third half-diaphragm disc coupling and the drive main shaft are both self-centering spline interference fits to achieve circumferential positioning and torque transmission.

[0017] A design method for a flexible diaphragm coupling used in ultra-high speed cryogenic bearing testing, wherein the diaphragm coupling has a hyperbolic profile, and the design method includes the following steps:

[0018] (1) Obtain the nominal torque T, maximum torque, and required compensation value of the connected test device;

[0019] (2) Calculate the critical speed of the test device rotor and the drive rotor in advance, and couple the test device rotor and the drive rotor into a whole. Adjust the shaft head distance, the connection stiffness of the two shaft systems and the mass of the intermediate accessories of the two shaft systems to obtain the mass of the diaphragm coupling and the shaft head distance that meet the critical speed requirements.

[0020] (3) Initially set the thickness d0 at the thinnest part of the diaphragm coupling profile. The larger the torque value, the larger d0 will be. Initially set the radius r2 at the thinnest part of the profile curve and the radius r1 at the thickest part of the profile curve.

[0021] (4) The shear stress τ of the diaphragm coupling is initially calculated using the formula;

[0022] (5) If the shear stress τ is within an acceptable range, then establish the curve equation f of the diaphragm coupling, which is used to characterize the relationship between thickness and radius;

[0023] (6) Establish the spatial curve equation of the diaphragm coupling in 3D software;

[0024] (7) In the three-dimensional software, the sketch curve of the space curve on the two-dimensional plane is obtained by sketching and projection. Another curve of the diaphragm coupling is obtained by mirroring. Based on these two curves, combined with the aforementioned shaft head distance and mass requirements of the diaphragm coupling, the three-dimensional structure of the diaphragm coupling is initially designed, and the concentrated mass of the diaphragm coupling is made close to the two shaft systems.

[0025] (8) Couple the diaphragm coupling structure with the rotors on both sides, establish a diaphragm coupling compensation mechanical calculation model, and apply radial displacement x1 and axial displacement x2 respectively according to the compensation capacity of the diaphragm coupling to calculate the axial support reaction force F1 and radial support reaction force F2 generated by the diaphragm coupling under the rated compensation axial displacement and radial displacement.

[0026] (9) Verify the influence of the additional load generated by the diaphragm coupling on the additional load generated by the shaft system on both sides, and establish a calculation model of the influence of the additional load of the diaphragm coupling on the shaft system. The radial support reaction force F2 is a rotational load, and the additional dynamic loads generated by it on the bearings on the shaft system are F3 and F4, respectively. The additional dynamic loads F3 and F4 will change with the rotation direction of the shaft system, resulting in the bearings bearing alternating additional dynamic loads. Through optimized design, the range of alternating additional dynamic loads of the diaphragm coupling support reaction force on the bearings is reduced to an acceptable range.

[0027] (10) After completing the verification of the compensation capacity and mechanical model of the diaphragm coupling, the coupling structure is coupled with the two rotors to establish a dynamic calculation model of the test device rotor + diaphragm coupling + drive rotor. The critical speed of the double-span rotor system is calculated. Based on the results, the structural mass, mass distribution and stiffness of the diaphragm coupling are optimized and designed to finally obtain a diaphragm coupling that meets the requirements.

[0028] (11) Calculate the temperature transmitted from the main shaft 1 of the test device to the first half-diaphragm coupling 31, the heat radiation of the heating belt 2 to the first half-diaphragm coupling 31, and the heat exchange between the first half-diaphragm coupling 31 and the room temperature. Verify the heating power and heat generation of the heating belt to ensure that the working temperature of the coupling under steady state is >-20℃.

[0029] Preferably, in step (3), the value of r1 / r2 should be 0.4 to 0.5.

[0030] Preferably, in step (4),

[0031]

[0032] Preferably, in step (5),

[0033]

[0034] In the formula: r is the radius value at any point on the curve of the diaphragm coupling.

[0035] Preferably, in step (6), the equation of the space curve is:

[0036] y = r b +(r a -r b )t

[0037]

[0038] In the formula: y is the ordinate of the diaphragm disc coupling curve; r a r is the radius at the thinnest point of the profile curve. b Let be the radius of the thickest part of the profile curve, and t be the independent variable.

[0039] Preferably, t∈[0,1].

[0040] The advantages of this invention compared to the prior art are:

[0041] (1) The diaphragm disc coupling structure of the present invention can achieve a DN value greater than 3.5 × 10 6 For transmissions operating at ultra-low temperatures (-196℃) with speeds greater than 100,000 r / min, the diaphragm coupling structure of this invention, by incorporating a heating belt, ensures that the temperature of the diaphragm disc surface in critical areas remains within the optimal temperature range of the material when the coupling operates at ultra-low temperatures. This overcomes the changes in material properties and spatial dimensions caused by the application of previous coupling structures in ultra-low temperature environments, maintaining optimal working conditions and ensuring compensation and transmission capabilities during high-speed operation of the dual-span rotor system.

[0042] (2) In the design of the diaphragm coupling structure of the present invention, the coupling is coupled with the rotors at both ends, and the design is carried out in a comprehensive manner from the aspects of mechanical performance and dynamic performance, so as to ensure that the additional load on the bearings of the rotors on both sides is minimized when the coupling is compensated; through dynamic optimization design, the mass and mass distribution characteristics of the coupling are optimized to ensure that the critical speed of the entire rotor system meets the rigid design principle.

[0043] (3) The design method of the diaphragm coupling structure proposed in this invention couples the coupling structure with the rotors at both ends into a whole. It comprehensively designs the coupling based on the temperature characteristics, mechanical characteristics, and dynamic characteristics, and optimizes the curved surface, stiffness, and mass. The proposed design method and process of the diaphragm coupling structure can provide theoretical support for the field of ultra-high speed diaphragm couplings and ultra-high speed rotation. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the diaphragm disc coupling structure.

[0045] Figure 2 This is a partial structural diagram of the diaphragm disc coupling;

[0046] Figure 3 It consists of a diaphragm disc coupling with a curved surface structure;

[0047] Figure 4 This is a schematic diagram of the heating element;

[0048] Figure 5 A mechanical calculation model for diaphragm disc coupling compensation;

[0049] Figure 6 A calculation model for the effect of additional load on the shaft system of the diaphragm coupling;

[0050] Figure 7 For system dynamics calculation model;

[0051] Figure 8 Flowchart of the design method for flexible diaphragm disc couplings. Detailed Implementation

[0052] The invention will now be further described with reference to the accompanying drawings.

[0053] The purpose of this invention is to provide an ultra-high-speed (DN value greater than 3.5 × 10⁻⁶) system. 6 A low-temperature (-196℃) flexible diaphragm coupling with a speed greater than 100,000 r / min (mm.r / min) is used to test and verify the bearing of the turbopump of a high-speed liquid rocket engine and to provide theoretical support for the structural design of the high-speed diaphragm coupling.

[0054] This invention relates to a diaphragm disc coupling structure for ultra-high-speed operation testing of cryogenic high-speed bearings in liquid rocket engines. It comprises four identical half-diaphragm disc couplings, an intermediate shaft, a heating belt, and fastening and positioning elements. During testing, the two ends of the diaphragm disc coupling are respectively installed on the drive spindle and the test device spindle, and axial positioning is achieved using screws, positioning plates, and other components. A heating belt is installed at the test device spindle end to heat the coupling structure through thermal radiation, ensuring its operating environment temperature is >-10℃. During rotation, the drive rotor drives the test device rotor to rotate and accelerate through the coupling, compensating for misalignment during high-speed operation of the two rotors.

[0055] like Figure 1 , 2 As shown in Figure 3, the diaphragm disc coupling of the present invention comprises a heating belt 2, a first half-diaphragm disc coupling 31, a second half-diaphragm disc coupling 41, a third half-diaphragm disc coupling 32, a fourth half-diaphragm disc coupling 42, a first coupling fastening screw 51, a second coupling fastening screw 52, ​​an intermediate shaft 6, a first positioning screw 71, a first positioning pressure plate 81, a second positioning screw 72, and a second positioning pressure plate 82.

[0056] The front end of the main shaft 1 of the test device is connected to the drive main shaft 9 via an intermediate shaft 6. The intermediate shaft 6 has circumferential flanges at both ends. The first half-diaphragm coupling 31 is fixed to the front end of the main shaft 1 via a first positioning plate 81 and a first positioning screw 71. The second half-diaphragm coupling 41 is connected to the first half-diaphragm coupling 31 by electron beam welding. The flange of the second half-diaphragm coupling 41 is fixed to the flange on the intermediate shaft 6 via the first fastening screw 51. The third half-diaphragm coupling 32 is fixed to the end of the drive main shaft 9 via a second positioning plate 82 and a second positioning screw 72. The fourth half-diaphragm coupling 42 is connected to the third half-diaphragm coupling 32 by electron beam welding. The flange of the fourth half-diaphragm coupling 42 is fixed to the flange on the intermediate shaft 6 via the second fastening screw 52. Both the first fastening screw 51 and the second fastening screw 52 are hexagonal head screws, arranged evenly around the circumference, with a total of 12 screws.

[0057] The flange of the second half-diaphragm coupling 41 and the flange of the intermediate shaft 6 are provided with a stepped stop 13 to achieve radial positioning of the intermediate shaft 6 and the second half-diaphragm coupling 41, preventing excessive shear stress on the bolts during operation and improving service life. The protruding part of the stepped stop is located on the flange of the intermediate shaft 6, and the recessed part is located on the second half-diaphragm coupling 41, with a radial clearance of less than 0.01 mm.

[0058] The axial distance d2 of the recessed part at the bottom of the second half-diaphragm coupling 41 is 2mm, which can meet the space machining requirements of the minimum tool and ensure that the overall added mass of the coupling is as close as possible to the two shaft systems.

[0059] The first half-diaphragm disc coupling 31 is clamped to the test device main shaft 1 and the third half-diaphragm disc coupling 32 is clamped to the drive main shaft 9 by positioning screws and positioning pressure plates to fix the axial position. The first half-diaphragm disc coupling 31 and the test device main shaft 1, and the third half-diaphragm disc coupling 32 and the drive main shaft 9 are all self-centering spline interference fits to achieve circumferential positioning and torque transmission.

[0060] The heating band 2 is located between the end of the main shaft 1 of the test device and the first half-diaphragm disc coupling 31. Its fit with the main shaft 1 and the first half-diaphragm disc coupling 31 is a clearance fit, and its structure is a ring-shaped structure.

[0061] like Figure 4 As shown, the lower part of the heating belt 2 is connected to the base, and its main structural components include a quartz tube 14 and a carbon fiber filament 15. When working, the heating belt 2 is supplied with direct current to achieve heating and release of heat and emit infrared radiation. The heat generation of the heating belt 2 can be adjusted by a voltage regulator to adjust the voltage and current to achieve different heat generation and different thermal radiation.

[0062] The heat generation of the heating belt 2 is calculated using thermal analysis to establish a heat transfer calculation model for the heating belt 2, the first half-diaphragm disc coupling 31, and the main shaft 1 of the test device. The heat transfer calculation model is as follows: the heating belt 2 is set as a constant-temperature heat source, the heat generation is set as W1, and the surface of the main shaft 1 within the shaft seal is set to a boundary condition of -196℃. Thermal radiation boundary conditions are established between the heating belt 2 and the air, as well as the first half-diaphragm disc coupling 31. Heat transfer boundary conditions are also established between the main shaft 1 of the test device and the first half-diaphragm disc coupling 31. By changing the heat generation of the heating belt 2, the temperature of the first half-diaphragm disc coupling 31 is ultimately maintained above 0℃.

[0063] The curved structure of the diaphragm coupling includes a transition fillet I10, a profile curve segment 11, and a transition fillet II12. Its key dimensions include the radius r1 at the thickest point of the profile curve, the radius r2 at the thinnest point of the profile curve, the thickness d0 at the thinnest point of the profile curve, and the axial distance d1 from the lowest point of the transition fillet I near the electron beam welding side to the electron beam welding.

[0064] In a preferred embodiment, the ratio of the radius r1 at the thickest point of the profile curve to the radius r2 at the thinnest point of the profile curve is 0.45, the thickness d0 at the thinnest point of the profile curve is 0.3 mm, and the value of d1 is 0.5 mm.

[0065] The coupling profile is a hyperbolic profile, such as... Figure 8 As shown, its design method is as follows:

[0066] (1) Obtain the nominal torque T, maximum torque, and required compensation value of the connected test device.

[0067] (2) Calculate the critical speed of the test device rotor and the drive rotor in advance, and couple the test device rotor and the drive rotor into a whole. Adjust the shaft head distance, the connection stiffness of the two shaft systems and the mass of the intermediate accessories of the two shaft systems to obtain the coupling mass and shaft head distance that meet the critical speed requirements.

[0068] (3) Initially set the thickness d0 at the thinnest part of the profile. The general range is 0.3 to 0.6 mm. The larger the torque value, the larger d0 should be. Initially set the radius r2 at the thinnest part of the profile curve and the radius r1 at the thickest part of the profile curve. The value of r1 / r2 should be 0.4 to 0.5.

[0069] (4) The shear stress of the coupling is initially calculated using the formula.

[0070]

[0071] In the formula:

[0072] T – Nominal torque value of the coupling;

[0073] d0—Thickness at the thinnest point of the profile curve;

[0074] r2—radius at the thinnest point of the profile curve;

[0075] (5) If the shear stress τ is within an acceptable range, then establish the curve equation f of the hyperbolic diaphragm coupling, that is, the relationship between thickness and radius, and obtain...

[0076]

[0077] Where: r—radius value at any point on the membrane disc curve, mm;

[0078] (6) Establish the spatial curve equation of the hyperbolic membrane disk in 3D software.

[0079] y = r b +(r a -r b )t

[0080]

[0081] t∈[0,1]

[0082] In the formula: y is the ordinate of the diaphragm disc coupling curve; r a r is the radius at the thinnest point of the profile curve. b Let be the radius of the thickest part of the profile curve, and t be the independent variable.

[0083] (7) In the three-dimensional software, the sketch curve of the space curve on the two-dimensional plane is obtained by sketching and projection. Another hyperbolic diaphragm disc curve is obtained by mirroring. Based on these two curves, combined with the aforementioned shaft head distance and mass requirements of the diaphragm disc coupling, the three-dimensional structure of the hyperbolic diaphragm disc coupling is initially designed, and the concentrated mass of the coupling is made close to the two shaft systems.

[0084] (8) Couple the coupling structure with the rotors on both sides to establish a connection as shown in the figure. Figure 5 The model for calculating the compensating mechanics of the coupling is shown. Based on the compensation capacity of the coupling, radial displacement x1 and axial displacement x2 are applied respectively, and the axial support reaction force F1 and radial support reaction force F2 generated by the coupling under the rated compensated axial and radial displacements are calculated.

[0085] (9) Verify the effect of the additional load generated by the coupling on the additional load generated by the shaft systems on both sides. Establish as follows: Figure 6The diagram shows a calculation model for the impact of additional loads from the coupling on the shaft system. The radial support reaction force F2 is a rotating load, and the additional dynamic loads F3 and F4 it generates on the bearings in the shaft system are respectively. These additional dynamic loads F3 and F4 change with the rotation direction of the shaft system, causing the bearings to bear alternating additional dynamic loads. Through calculation and optimization design, the range of alternating additional dynamic loads on the bearings caused by the coupling support reaction force is reduced to an acceptable range.

[0086] (10) After completing the verification of the coupling compensation capacity and mechanical model, couple the coupling structure with the two rotors to establish a dynamic calculation model of the test device rotor + diaphragm coupling + drive rotor, as follows: Figure 7 As shown, the critical speed of the combined double-span rotor system is calculated. Based on the results, the structural mass, mass distribution, stiffness and other characteristics of the coupling are optimized and designed to finally obtain a diaphragm coupling structure that meets the requirements.

[0087] (11) Calculate and verify the heating power and heat output of the heating tape. Perform comprehensive calculations on the low temperature transmitted from the main shaft 1 of the test device to the first half-diaphragm coupling 31, the heat radiation of the heating tape 2 to the first half-diaphragm coupling 31, and the heat exchange between the first half-diaphragm coupling 31 and the room temperature to ensure that the working temperature of the coupling under steady state is >-20℃.

[0088] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A flexible diaphragm coupling for ultra-high speed cryogenic bearing testing, characterized in that: Includes heating belt (2), first half-diaphragm disc coupling (31), second half-diaphragm disc coupling (41), third half-diaphragm disc coupling (32), fourth half-diaphragm disc coupling (42), first coupling fastening screw (51), second coupling fastening screw (52), intermediate shaft (6), first positioning screw (71), first positioning pressure plate (81), second positioning screw (72), and second positioning pressure plate (82); The front end of the main shaft (1) of the test device is connected to the drive main shaft (9) through the intermediate shaft (6). The intermediate shaft (6) is designed with circumferential flanges at both ends. The first half-diaphragm coupling (31) is fixed to the front end of the main shaft (1) of the test device through the first positioning plate (81) and the first positioning screw (71). The second half-diaphragm coupling (41) is connected to the first half-diaphragm coupling (31) by electron beam welding. The flange of the second half-diaphragm coupling (41) is fixed to the flange on the intermediate shaft (6) through the first coupling fastening screw (51). The third half-diaphragm coupling (32) is fixed to the end of the drive main shaft (9) through the second positioning plate (82) and the second positioning screw (72). The fourth half-diaphragm coupling (42) is connected to the third half-diaphragm coupling (32) by electron beam welding. The flange of the fourth half-diaphragm coupling (42) is fixed to the flange on the intermediate shaft (6) through the second coupling fastening screw (52). The heating belt (2) has a circular structure and is fitted at the junction of the first half-diaphragm disc coupling (31) and the main shaft (1) of the test device, with clearance fit between the first half-diaphragm disc coupling (31) and the main shaft (1) of the test device; the lower part of the heating belt (2) is connected to the base, and when working, the heating belt (2) is supplied with DC current to realize the heating of the heating belt and release heat and emit infrared radiation; the voltage and current are adjusted by the voltage regulator to realize different heat output and different thermal radiation of the heating belt (2).

2. The flexible diaphragm coupling for ultra-high speed cryogenic bearing testing according to claim 1, characterized in that: The flange of the second half-diaphragm coupling (41) and the flange of the intermediate shaft (6) are provided with stepped stop (13) to achieve radial positioning of the intermediate shaft (6) and the second half-diaphragm coupling (41), prevent excessive shear stress on the bolts during operation, and improve service life.

3. The flexible diaphragm coupling for ultra-high speed cryogenic bearing testing according to claim 2, characterized in that: The raised portion of the stepped stop is located on the flange of the intermediate shaft (6), and the recessed portion is located on the second half-diaphragm coupling (41).

4. The flexible diaphragm coupling for ultra-high speed cryogenic bearing testing according to claim 1, characterized in that: The first half-diaphragm coupling (31) and the test device main shaft (1), and the third half-diaphragm coupling (32) and the drive main shaft (9) are both self-centering spline interference fits to achieve circumferential positioning and torque transmission.

5. The design method of a flexible diaphragm disc coupling for ultra-high speed cryogenic bearing testing according to any one of claims 1-4, characterized in that, The diaphragm disc coupling has a hyperbolic profile, and the design method includes the following steps: (1) Obtain the nominal torque T, maximum torque, and required compensation value of the connected test device; (2) Calculate the critical speed of the test device rotor and the drive rotor in advance, and couple the test device rotor and the drive rotor into a whole. Adjust the shaft head distance, the connection stiffness of the two shaft systems and the mass of the intermediate accessories of the two shaft systems to obtain the mass of the diaphragm coupling and the shaft head distance that meet the critical speed requirements. (3) Initially set the thickness d0 at the thinnest part of the diaphragm coupling profile. The larger the torque value, the larger d0 will be. Initially set the radius r2 at the thinnest part of the profile curve and the radius r1 at the thickest part of the profile curve. (4) The shear stress τ of the diaphragm coupling is initially calculated using the formula; (5) If the shear stress τ is within an acceptable range, then establish the curve equation f of the diaphragm coupling, which is used to characterize the relationship between thickness and radius; (6) Establish the spatial curve equation of the diaphragm coupling in 3D software; (7) In the three-dimensional software, the sketch curve of the space curve on the two-dimensional plane is obtained by sketching and projection. Another curve of the diaphragm coupling is obtained by mirroring. Based on these two curves, combined with the aforementioned shaft head distance and mass requirements of the diaphragm coupling, the three-dimensional structure of the diaphragm coupling is initially designed, and the concentrated mass of the diaphragm coupling is made close to the two shaft systems. (8) Couple the diaphragm coupling structure with the rotors on both sides, establish a diaphragm coupling compensation mechanical calculation model, and apply radial displacement x1 and axial displacement x2 respectively according to the compensation capacity of the diaphragm coupling to calculate the axial support reaction force F1 and radial support reaction force F2 generated by the diaphragm coupling under the rated compensation axial displacement and radial displacement. (9) Verify the influence of the additional load generated by the diaphragm coupling on the additional load generated by the shaft system on both sides, and establish a calculation model of the influence of the additional load of the diaphragm coupling on the shaft system. The radial support reaction force F2 is a rotational load, and the additional dynamic loads generated by it on the bearings on the shaft system are F3 and F4, respectively. The additional dynamic loads F3 and F4 will change with the rotation direction of the shaft system, resulting in the bearings bearing alternating additional dynamic loads. Through optimized design, the range of alternating additional dynamic loads of the diaphragm coupling support reaction force on the bearings is reduced to an acceptable range. (10) After completing the verification of the compensation capacity and mechanical model of the diaphragm coupling, the coupling structure is coupled with the two rotors to establish a dynamic calculation model of the test device rotor + diaphragm coupling + drive rotor. The critical speed of the double-span rotor system is calculated. Based on the results, the structural mass, mass distribution and stiffness of the diaphragm coupling are optimized and designed to finally obtain a diaphragm coupling that meets the requirements. (11) Calculate the temperature transmitted from the main shaft of the test device to the first half-diaphragm coupling, the heat radiation of the heating belt to the first half-diaphragm coupling, and the heat exchange between the first half-diaphragm coupling and room temperature. Verify the heating power and heat output of the heating belt to ensure that the working temperature of the coupling under steady state is >-20℃.

6. The design method of a flexible diaphragm coupling for ultra-high speed cryogenic bearing testing according to claim 5, characterized in that, In step (3), the value of r1 / r2 should be 0.4 to 0.

5.

7. The design method of a flexible diaphragm disc coupling for ultra-high speed cryogenic bearing testing according to claim 5, characterized in that, In step (4), 8. The design method of a flexible diaphragm disc coupling for ultra-high speed cryogenic bearing testing according to claim 5, characterized in that, In step (5), In the formula: r is the radius value at any point on the curve of the diaphragm coupling.

9. The design method of a flexible diaphragm coupling for ultra-high speed cryogenic bearing testing according to claim 5, characterized in that, In step (6), the equation of the space curve is: y=r b +(r a -r b )t In the formula: y is the ordinate of the diaphragm disc coupling curve; r a r is the radius at the thinnest point of the profile curve. b Let be the radius of the thickest part of the profile curve, and t be the independent variable.

10. The design method of a flexible diaphragm disc coupling for ultra-high speed cryogenic bearing testing according to claim 9, characterized in that, t∈[0,1]。

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