Coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing

Abstract

A coaxiality adjustment method for testing low-temperature, high-speed bearings for liquid rocket engines comprises installing an x- and y-direction displacement sensor at the head of a drive unit spindle; assembling a low-temperature bearing test apparatus, applying an axial load to the outer ring of the active-point bearing, and simultaneously installing a dial indicator on the end face of the active-point bearing outer ring; completing assembly of the low-temperature bearing test apparatus, installing an x- and y-direction displacement sensor at the extended end of the test apparatus spindle; passing a low-temperature medium through the low-temperature bearing test apparatus, simultaneously collecting and recording the displacement values of the displacement sensors, and cooling the low-temperature bearing test apparatus to obtain preset center height adjustments at room temperature for the main shaft of the low-temperature bearing test apparatus and the main shaft of the drive unit, as well as preset left-right offset adjustments at room temperature for the main shaft of the test apparatus and the main shaft of the drive unit. The present invention achieves coaxiality adjustment between the shaft system of the low-temperature, high-speed bearing test apparatus and the shaft system of the high-speed drive unit, ensuring the coaxiality of the two shaft systems under low-temperature conditions.

Description

Technical Field

[0001] The invention belongs to the field of liquid rocket engine testing and relates to a coaxiality adjustment method for low-temperature and high-speed bearing testing of a liquid rocket engine. Background Art

[0002] Coaxiality is one of the key quality indicators for low-temperature, high-speed bearing testing and is crucial for ensuring the stable operation of high-speed rotating machinery. The low-temperature, high-speed test rotation system connects the drive unit main shaft to the test unit shaft via a coupling. Misalignment can occur in parallel, angular, and a combination of the two. Poor alignment of the rotor shafting will cause the bearings on both shaft systems to bear significant dynamic loads, reducing the lifespan of the drive-end bearings, drive equipment, couplings, and other components. This can also cause premature damage to the turbine pump's low-temperature bearings, making the purpose of the bearing testing impossible.

[0003] Liquid rocket engine cryogenic, high-speed bearings operate at ultra-high speeds (maximum speed >80,000 r / min) and ultra-low temperatures (<-196°C). Under ultra-low temperatures, the bearing test rig experiences significant contraction, and ultra-high-speed operation can also cause significant system vibration. Coaxial misalignment between the cryogenic test rig's shafting and the drive unit's shafting can cause the bearings to bear significant additional dynamic loads during high-speed operation. This is especially true for cryogenic, high-speed bearings, which operate at very high speeds. This can significantly amplify (by a square factor) the eccentric force and additional dynamic loads caused by misalignment, causing significant damage to both the bearing and the test rig's shafting.

[0004] In addition, low-temperature, high-speed bearings operate in extremely harsh environments, such as ultra-low-temperature liquid nitrogen, liquid hydrogen, or liquid oxygen. Their inherent self-lubrication, which relies solely on the solid self-lubrication formed by the transfer film on the cage, is extremely sensitive to coaxiality deviations. If the initial coaxiality is adjusted to an ideal state, the eccentric centrifugal force on the shafting system will be transmitted to the bearing, causing the bearing to bear additional dynamic loads, resulting in premature lubrication problems. In severe cases, the bearing's running trajectory will change, causing damage and locking of the bearing in a short period of time, and even causing fractures in the coupling and rotor of the test rotation system.

[0005] Therefore, achieving accurate adjustment and measurement of the coaxiality of the low-temperature and high-speed test device and the drive device is of great significance for the stable operation, assessment and verification of low-temperature and high-speed bearings and for ensuring space launches. Summary of the Invention

[0006] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, propose a coaxiality adjustment method for low-temperature and high-speed bearing testing of liquid rocket engines, realize the coaxiality adjustment of the shaft system of the low-temperature and high-speed bearing testing device and the shaft system of the high-speed drive device, and ensure the coaxiality of the two shaft systems under low-temperature conditions.

[0007] The solution of the present invention is:

[0008] The coaxiality adjustment method for liquid rocket engine cryogenic and high-speed bearing testing includes:

[0009] A first x-direction displacement sensor and a first y-direction displacement sensor are provided at the spindle head of the driving device. The first x-direction displacement sensor is used to measure the horizontal displacement from the driving device to the test device, and the first y-direction displacement sensor is used to measure the vertical displacement. An initial value x1 of the first x-direction displacement sensor and an initial value y1 of the first y-direction displacement sensor are recorded. The driving device is then idled at the rated operating speed until the temperatures of the driving device bearings and lubricating oil stabilize, and a displacement value x2 of the first x-direction displacement sensor and a displacement value y2 of the first y-direction displacement sensor are recorded.

[0010] Assemble a low-temperature bearing test device, apply an axial load to the outer ring of the active point bearing 2 through the force-applying mechanism 1, and set a dial indicator on the end face of the outer ring of the active point bearing to monitor the axial movement of the outer ring of the bearing;

[0011] After the cryogenic bearing test device is assembled, a second x-direction displacement sensor and a second y-direction displacement sensor are installed at the extended end of the main shaft of the cryogenic bearing test device. The second x-direction displacement sensor is used to measure the horizontal displacement from the drive device to the test device, and the second y-direction displacement sensor is used to measure the vertical displacement. The initial value x3 of the first x-direction displacement sensor and the initial value y3 of the first y-direction displacement sensor are recorded.

[0012] Passing a cryogenic medium into the cryogenic bearing test apparatus, while simultaneously collecting and recording the displacement value of the second displacement sensor, cooling the cryogenic bearing test apparatus to ensure that the temperature of the cryogenic bearing test apparatus is less than -190°C, and when the values of the second x-direction displacement sensor and the second y-direction displacement sensor do not change over time, recording the displacement value x4 of the second x-direction displacement sensor and the displacement value y4 of the second y-direction displacement sensor;

[0013] Through the above test, the center height pre-adjustment value of the main shaft of the low-temperature bearing test device and the main shaft of the drive device at room temperature is obtained, and the center height pre-adjustment value is (y3-y4)+(y2-y1);

[0014] Through the above test, the pre-adjusted value of the left and right offset of the main shaft of the low-temperature bearing test device and the main shaft of the driving device at room temperature is obtained.

[0015] Preferably, an axial load is applied to the outer ring of the live point bearing in the following manner: gradually apply a load step of 1000N to the full load of the live point bearing, and then completely remove the axial load; then apply the load to the full load, and repeat 2-3 times to ensure that the axial displacement of the outer ring end face of the live point bearing each time is within the envelope range, ensure that the load is applied to both live point bearings in place, ensure that the axial clearance of the two live point bearings is completely eliminated and the end faces do not tilt.

[0016] Preferably, the calculation method of the pre-adjusted values of the left and right offsets is as follows:

[0017] ① Calculate the left and right displacements of the low-temperature bearing test device and the drive device spindle head respectively, where the drive device spindle displacement is X1 = x2 - x1, and the low-temperature bearing test device spindle displacement is X2 = x4 - x3;

[0018] ② If X1>X2, the pre-adjustment amount of the test device spindle is X1-X2 offset to the right relative to the drive device spindle; if X2>X1, the pre-adjustment amount of the test device spindle is X2-X1 offset to the left relative to the drive device spindle, where the definition of left and right is based on looking at the test device from the drive device.

[0019] Preferably, before adjusting the coaxiality of the low-temperature bearing test device and the driving device, the concentricity of the front and rear bearing seats of the test device should be adjusted first.

[0020] Preferably, during the process of adjusting the coaxiality, the coaxiality of the low-temperature bearing test device and the driving device is measured in real time using a coaxiality tool.

[0021] Preferably, the coaxiality tooling includes a shaft sleeve tightening structure, a first adapter structure, a second adapter structure, an amplifying disk, a first dial indicator, a second dial indicator, a third adapter structure, a fourth adapter structure, and a flat head screw;

[0022] The shaft sleeve tightening structure is installed on the main shaft of the test device and tightened by bolts; the first adapter structure is installed on the shaft sleeve tightening structure and tightened by nuts; the second adapter structure is installed on the upper end of the first adapter structure, and the third adapter structure is installed on the lower end of the first adapter structure, and both are tightened by nuts; the first dial indicator is installed on the second adapter structure and tightened by bolts; the fourth adapter structure is installed on the third adapter structure and tightened by nuts; the second dial indicator is installed on the fourth adapter structure and tightened by bolts; the amplifying disk is installed on the main shaft of the driving device and tightened by a flat head screw.

[0023] Preferably, the method of using the coaxiality tool is as follows:

[0024] Adjust the needles of the first and second dial indicators to the appropriate compression position, and tighten each fastening component according to the specified pre-tightening force;

[0025] Apply the bearing axial load to the test device to full load, rotate the main shaft of the test device, and adjust the coaxiality of the main shaft of the test device and the main shaft of the drive device according to the pre-obtained coaxiality adjustment value; the first dial indicator is used to measure the center height deviation between the main shaft of the test device and the main shaft of the drive device, and the second dial indicator is used to measure the end face deviation between the main shaft of the test device and the main shaft of the drive device.

[0026] Preferably, the amplifying disk is a hollow "convex" type rotating body structure, with a tapered hole at the center of its outer end face with a larger diameter; the parallel position tolerance between the outer end face and the inner end face in contact with the main shaft of the test device should be <0.001mm.

[0027] Preferably, if the axial distance L from the needle of the first dial indicator to the shaft sleeve tightening structure is greater than 50 mm, the displacement D at the needle of the first dial indicator caused by elastic deformation is calculated. When adjusting the coaxiality, it should be ensured that the center height of the main shaft of the test device is higher than the main shaft of the driving device by an amount of (y3-y4)+(y2-y1)+D / 2.

[0028] Preferably, the material of the coaxiality tooling is titanium alloy or aluminum alloy.

[0029] The beneficial effects of the present invention compared with the prior art are:

[0030] (1) The present invention conducts in-depth research on the coaxiality of the high-speed test rotation system, conducts detailed theoretical analysis on the working characteristics of the low-temperature high-speed bearing test device and the high-speed drive device, and extracts the pre-compensation value for the coaxiality of the low-temperature high-speed bearing test rotation system, providing basic support for the precise control of the coaxiality.

[0031] (2) Through long-term experimental verification, the present invention has refined a coaxiality adjustment method for low-temperature bearing test equipment, and through structural design, a tooling structure and usage method for coaxiality adjustment of low-temperature and high-speed bearing test systems have been developed, ensuring the safety and reliability of low-temperature and high-speed bearing test operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the test device and driving device structure;

[0033] Figure 2 This is a schematic diagram of the drive device shaft head displacement sensor monitoring;

[0034] Figure 3 This is a schematic diagram of the test device's shaft head displacement sensor monitoring;

[0035] Figure 4 This is a schematic diagram of the concentricity measurement structure of the front and rear bearing seats;

[0036] Figure 5This is the coaxiality tooling structure diagram;

[0037] Figure 6 Schematic diagram of the shaft sleeve tightening structure;

[0038] Figure 7 Schematic diagram of the first transfer structure;

[0039] Figure 8 Schematic diagram of the second transfer structure;

[0040] Figure 9 1 is a schematic diagram of a fourth transfer structure;

[0041] Figure 10 It is a schematic diagram of the enlarged disk;

[0042] Figure 11 Schematic diagram of axial distance verification. DETAILED DESCRIPTION

[0043] The present invention will be further described below with reference to the accompanying drawings.

[0044] Figure 1 The diagram below shows the structure of the test device and the drive device. To obtain the pre-adjusted coaxiality value of the test device and the drive device at room temperature, the pre-adjustment method steps of the present invention are as follows:

[0045] (1) A first x-direction displacement sensor and a first y-direction displacement sensor are set at the position where the drive device extends the shaft head at high speed, such as Figure 2 As shown, the view is from the drive unit toward the test unit. The first x-direction displacement sensor is used to measure the horizontal displacement from the drive unit to the test unit, and the first y-direction displacement sensor is used to measure the vertical displacement. The initial value x1 of the first x-direction displacement sensor and the initial value y1 of the first y-direction displacement sensor are recorded. The drive unit is then idled at the rated operating speed until the bearing and lubricating oil temperatures of the drive unit stabilize, and the displacement value x2 of the first x-direction displacement sensor and the displacement value y2 of the first y-direction displacement sensor are recorded.

[0046] (2) Assemble the low-temperature bearing test device and apply an axial load to the outer ring of the active point bearing 2 through the force-applying mechanism 1. At the same time, set a dial indicator on the end face of the outer ring of the active point bearing to monitor the axial movement of the outer ring of the bearing. The axial load is applied in steps of 1000N until the full load of the bearing is applied, and then the axial load is completely removed; then the load is applied to the full load again, and repeated 2-3 times, ensuring that the axial displacement of the outer ring end face of the active point bearing 2 is within the envelope range each time, ensuring that the load is applied to both bearings in place, ensuring that the axial clearance of the two bearings is completely eliminated, and that the end faces do not tilt. Figure 1 The number 4 in the middle is the dead point bearing, which is a fixed bearing;

[0047] (3) After the test device is assembled, a second x-direction displacement sensor and a second y-direction displacement sensor are set at the protruding end of the test device main shaft 13, such as Figure 3 As shown, the viewing direction is from the driving device to the test device. The second x-direction displacement sensor is used to measure the horizontal displacement from the driving device to the test device, and the second y-direction displacement sensor is used to measure the vertical displacement; the initial value x3 of the first x-direction displacement sensor and the initial value y3 of the first y-direction displacement sensor are recorded;

[0048] (4) Passing a low-temperature medium into the bearing test device, while collecting and recording the displacement value of the second displacement sensor, cooling the test device for more than 30 minutes to ensure that the temperature of the test device is less than -190°C, and when the values of the second x-direction displacement sensor and the second y-direction displacement sensor do not change over time, record the displacement value x4 of the second x-direction displacement sensor and the displacement value y4 of the second y-direction displacement sensor;

[0049] (5) Through the above test, the pre-adjusted value of the center height of the test device spindle 13 and the drive device spindle 21 at room temperature should be: the value of the test device spindle higher than the drive device spindle is (y3-y4)+(y2-y1);

[0050] (6) Through the above test, the calculation method for obtaining the pre-adjustment value of the left and right offset of the main shaft of the test device and the main shaft of the drive device at room temperature should be: ① Calculate the left and right displacement of the test device and the main shaft of the drive device respectively, where the displacement of the main shaft of the drive device is X1=x2-x1, X2=x4-x3; ② If X1>X2, the pre-adjustment amount of the test device is the rightward offset relative to the main shaft of the drive device (looking from the drive device to the test device) X1-X2; if X2>X1, the pre-adjustment amount of the test device is the leftward offset relative to the main shaft of the drive device X2-X1.

[0051] Before adjusting the coaxiality of the test device and the drive device, the concentricity of the front and rear bearing seats should be adjusted first.

[0052] The concentricity measurement structure of the front and rear bearing seats 7 and 12 of the test device is shown as follows: Figure 4 The front and rear bearing seat concentricity adjustment structure includes dial indicators 6 and 11, L-shaped adapter structures 8 and 10, and a rotating structure 9.

[0053] The dial indicator 6 is mounted on the L-shaped adapter structure 8, and the dial indicator 11 is mounted on the L-shaped adapter structure 10. The L-shaped adapter structures 8 and 10 are mounted on the threaded holes at both ends of the main shaft of the rotating structure 9 and tightened with nuts. After being installed, the entire structure is placed between the front bearing seat 7 and the rear bearing seat 12, and the axial centerline of the main shaft of the rotating structure 9 coincides with the axial centerlines of the front bearing seat 7 and the rear bearing seat 12.

[0054] The installation angles of the L-shaped transfer structures 8 and 10 should be consistent and at the same azimuth angle, and the dial indicators should be adjusted to zero before testing.

[0055] The concentricity measurement of the front and rear bearing seats 7 and 12 should rotate the rotating structure, and the concentricity of the front and rear bearing seats 7 and 12 should be adjusted and tightened by analyzing the changes in the readings of the dial indicator.

[0056] After the pre-adjusted coaxiality value between the test device and the driving device is obtained, the coaxiality value should be measured and adjusted using a coaxiality adjustment method suitable for the transmission device.

[0057] The coaxiality adjustment method should be designed and selected according to the space size and structural characteristics of the test device and the drive device, and the corresponding coaxial adjustment structure and adjustment method should be selected.

[0058] The space size between the test device and the drive device mainly depends on their axial distance and center height. If the space distance is sufficient, the drive device axis should be used as a reference, a coaxiality tooling structure should be adopted, a coaxiality adjustment amplifying disc structure should be set, and a transfer tooling and a dial indicator structure should be set on the test device axis to realize the measurement and adjustment of coaxiality.

[0059] The coaxiality tooling structure is as follows Figure 5 The components include a bolt 14, a shaft sleeve tightening structure 15, a nut 16, a first transition structure 17, a second transition structure 18, an amplifying plate 19, dial indicators 20 and 23, a third transition structure 22, a fourth transition structure 24, and a flat head screw 25.

[0060] The installation method of the coaxiality tooling structure is as follows: the shaft sleeve tightening structure 15 is installed on the main shaft 13 of the test device and is tightened by the bolt 14; the first adapter structure 17 is installed on the shaft sleeve tightening structure 15 and is tightened by the nut; the second adapter structure 18 and the third adapter structure 22 are installed on the first adapter structure 17, and are all tightened by the nuts; the dial indicator 20 is installed on the second adapter structure 18 and is tightened by the bolt 14; the fourth adapter structure 24 is installed on the third adapter structure 22 and is tightened by the nut; the dial indicator 23 is installed on the adapter structure 22 and is tightened by the bolt 14; the amplifying disk 19 is installed on the main shaft 21 of the driving device and is tightened by the flat head screw 25.

[0061] The coaxiality fixture is used by adjusting the dial indicators 20 and 23 to the appropriate compression position and tightening all fastening components to the specified preload. Applying a full axial load to the bearings of the test device and rotating the test device spindle 13 will achieve coaxiality adjustment between the test device spindle 13 and the drive device spindle 21. Adjust the test device end according to the pre-determined coaxiality deviation value to ensure that the final adjusted coaxiality is within the theoretical pre-determined coaxiality deviation value.

[0062] The shaft sleeve tightening structure 15 is as follows Figure 6 The shaft sleeve tightening structure is a hollow rotating body structure, with three threaded holes distributed along the circumference at two cross-section positions along its axial direction. The threaded holes are connected to the bolts 14, and the right end is provided with an external threaded protrusion structure, which is connected to the first adapter structure 17 through a nut.

[0063] The structure of the first transfer structure 17 is as follows Figure 7 The overall shape of the first adapter structure is a rectangular parallelepiped structure, with a through hole 26 provided at the center. The through hole 26 is connected to the external threaded protrusion structure at the right end of the shaft sleeve tightening structure 15. Two oblong hole structures 27 of the same size are provided above and below the through hole. The oblong hole structures are connected to the second adapter structure 18 via nuts 16.

[0064] The second transfer structure 18 is as follows Figure 8 The overall shape of the second adapter structure 18 is a rectangular parallelepiped with a cylindrical external thread structure. Threaded through holes 29 and through holes 30 are provided at both ends of the rectangular parallelepiped structure 28 at a 90° angle. The through holes 30 are used to mount the dial indicator 20, and bolts are screwed into the threaded through holes 29 to tighten the dial indicator 20.

[0065] The third transition structure 22 is a cylindrical external thread structure. The fourth transition structure 24 has a structural shape as shown in FIG. Figure 9 As shown; the overall structure of the transition structure 4 is a rectangular structure, on which rectangular protrusions 31 and 33 are provided, and threaded through holes 32 and through holes 34 are respectively provided on two surfaces with an angle of 90° on the rectangular protrusion 31, wherein the through hole 34 is used to install the dial indicator 23, and the threaded through hole 32 is used to install the bolt, and the bolt presses the dial indicator 23; on the rectangular protrusion 33, three evenly distributed and uniformly sized cylindrical through holes 35 are provided for installing the third transition structure 22 and tightening it by nuts.

[0066] The structure of the amplifying disk 19 is as follows Figure 10The amplifying disk structure is a hollow rotating body structure, with a tapered hole 37 set at the center of the end face 36 with a larger diameter; the parallel position tolerance of the end face 36 and the end face 39 should be less than 0.001mm, and the perpendicularity tolerance of the end faces 36, 39 and the outer cylindrical surface 38 should be less than 0.001mm; the parallel tolerance of the end face 36 and the end face 40 should be less than 0.001mm.

[0067] The coaxiality fixture structure should be checked during design. Figure 11 The axial distance L from the dial indicator needle 41 to the shaft sleeve tightening structure 15, as well as the cross-sectional moment, are used to calculate the displacement of the needle due to elastic deformation under the action of gravity, and the deformation is reduced to within the error range through optimized design.

[0068] The axial distance L of the coaxiality fixture is greater than 50 mm, and the displacement D of the dial indicator needle caused by elastic deformation needs to be accurately calculated and verified. Therefore, when adjusting the coaxiality, the center height of the test device should be ensured to be higher than the gearbox shaft by an amount of (y3-y4)+(y2-y1)+D / 2.

[0069] The materials of the above-mentioned structures should be titanium alloy or aluminum alloy.

[0070] After actual verification, the coaxiality tooling structure and coaxiality adjustment method of the present invention have been widely used in various models and types of low-temperature and high-speed bearing tests, and have strong practicality and popularization.

[0071] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications 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 scope of protection of the technical solutions of the present invention.

Claims

1. A method for adjusting the coaxiality of a liquid rocket engine low-temperature high-speed bearing test, characterized in that: include: A first x-direction displacement sensor and a first y-direction displacement sensor are provided at the spindle head of the driving device. The first x-direction displacement sensor is used to measure the horizontal displacement from the driving device to the test device, and the first y-direction displacement sensor is used to measure the vertical displacement. An initial value x1 of the first x-direction displacement sensor and an initial value y1 of the first y-direction displacement sensor are recorded. The driving device is then idled at the rated operating speed until the temperatures of the driving device bearings and lubricating oil stabilize, and a displacement value x2 of the first x-direction displacement sensor and a displacement value y2 of the first y-direction displacement sensor are recorded. Assemble a low-temperature bearing test device, apply an axial load to the outer ring of the active point bearing (2) through a force-applying mechanism (1), and simultaneously set a dial indicator on the end face of the outer ring of the active point bearing to monitor the axial movement of the outer ring of the bearing; After the cryogenic bearing test device is assembled, a second x-direction displacement sensor and a second y-direction displacement sensor are installed at the extended end of the main shaft of the cryogenic bearing test device. The second x-direction displacement sensor is used to measure the horizontal displacement from the drive device to the test device, and the second y-direction displacement sensor is used to measure the vertical displacement. The initial value x3 of the first x-direction displacement sensor and the initial value y3 of the first y-direction displacement sensor are recorded. Passing a cryogenic medium into the cryogenic bearing test apparatus, while simultaneously collecting and recording the displacement value of the second displacement sensor, cooling the cryogenic bearing test apparatus to ensure that the temperature of the cryogenic bearing test apparatus is less than -190°C, and when the values of the second x-direction displacement sensor and the second y-direction displacement sensor do not change over time, recording the displacement value x4 of the second x-direction displacement sensor and the displacement value y4 of the second y-direction displacement sensor; Through the above test, the center height pre-adjustment value of the main shaft of the low-temperature bearing test device and the main shaft of the drive device at room temperature is obtained, and the center height pre-adjustment value is (y3-y4)+(y2-y1); Through the above test, the pre-adjusted value of the left and right offset of the main shaft of the low-temperature bearing test device and the main shaft of the driving device at room temperature is obtained.

2. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 1, characterized in that: Apply axial load to the outer ring of the live point bearing in the following manner: gradually apply load steps of 1000N to the full load of the live point bearing, and then completely remove the axial load; then apply the load to the full load, and repeat 2-3 times to ensure that the axial displacement of the outer ring end face of the live point bearing each time is within the envelope range, ensure that the load is applied to both live point bearings in place, ensure that the axial clearance of the two live point bearings is completely eliminated and the end faces do not tilt.

3. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 1, characterized in that: The calculation method for the left and right offset pre-adjustment values is as follows: ① Calculate the left and right displacements of the low-temperature bearing test device and the drive device spindle head respectively, where the drive device spindle displacement is X1 = x2 - x1, and the low-temperature bearing test device spindle displacement is X2 = x4 - x3; ② If X1>X2, the pre-adjustment amount of the test device spindle is X1-X2 offset to the right relative to the drive device spindle; if X2>X1, the pre-adjustment amount of the test device spindle is X2-X1 offset to the left relative to the drive device spindle, where the definition of left and right is based on looking at the test device from the drive device.

4. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 1, characterized in that: Before adjusting the coaxiality of the low-temperature bearing test device and the drive device, the concentricity of the front and rear bearing seats of the test device should be adjusted first.

5. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 1, characterized in that: During the coaxiality adjustment process, the coaxiality of the low-temperature bearing test device and the drive device is measured in real time using the coaxiality tooling.

6. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 5, characterized in that: The coaxiality tooling comprises a shaft sleeve tightening structure (15), a first transfer structure (17), a second transfer structure (18), an amplifying disk (19), a first dial indicator (20), a second dial indicator (23), a third transfer structure (22), a fourth transfer structure (24), and a flat head screw (25); The shaft sleeve tightening structure (15) is installed on the main shaft (13) of the test device and is tightened by the bolt (14); the first transfer structure (17) is installed on the shaft sleeve tightening structure (15) and is tightened by the nut; the second transfer structure (18) is installed on the upper end of the first transfer structure (17) and the third transfer structure (22) is installed on the lower end of the first transfer structure (17), and both are tightened by the nut; the first dial indicator (20) is installed on the second transfer structure (18) and is tightened by the bolt; the fourth transfer structure (24) is installed on the third transfer structure (22) and is tightened by the nut; the second dial indicator (23) is installed on the fourth transfer structure (24) and is tightened by the bolt; the amplifying disk (19) is installed on the main shaft (21) of the driving device and is tightened by the flat head screw (25).

7. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 6, characterized in that: The method of using the coaxiality tool is as follows: Adjust the needles of the first dial indicator (20) and the second dial indicator (23) to appropriate compression positions, and tighten each fastening component according to the specified pre-tightening force; The test device applies a bearing axial load to full load, rotates the test device main shaft (13), and adjusts the coaxiality of the test device main shaft (13) and the drive device main shaft (21) according to a pre-obtained coaxiality adjustment value; wherein the first dial indicator (20) is used to measure the center height deviation of the test device main shaft and the drive device main shaft, and the second dial indicator (23) is used to measure the end face deviation of the test device main shaft and the drive device main shaft.

8. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 6, characterized in that: The amplifying disk (19) is a hollow "convex" rotating body structure, and a tapered hole (37) is provided at the center of its outer end surface (36) with a larger diameter; the parallel position tolerance between the outer end surface (36) and the inner end surface (39) in contact with the main shaft of the test device should be less than 0.001mm.

9. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 6, characterized in that: If the axial distance L between the needle (41) of the first dial indicator (20) and the shaft sleeve tightening structure (15) is greater than 50 mm, the displacement D at the needle of the first dial indicator caused by the elastic deformation is calculated. When adjusting the coaxiality, it should be ensured that the center height of the main shaft of the test device is higher than the main shaft of the driving device by an amount of (y3-y4)+(y2-y1)+D / 2.

10. The coaxiality adjustment method for liquid rocket engine low-temperature high-speed bearing testing according to claim 6, characterized in that: The material of the coaxial tooling is titanium alloy or aluminum alloy.

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