A method for aligning shafts in a low-speed machine including a large flexible coupling

Abstract

This invention relates to a method for aligning a low-speed engine shaft system including a large flexible coupling. First, based on the overall shaft system layout, the deviation between the center of each bearing and the center of the shaft axis is designed. The bearing stress in the final aligned state is calculated to ensure that the stress on each bearing meets the usage requirements. Then, ensuring that the deviation between the center of each bearing and the center of the shaft axis remains unchanged, the flexible coupling in the shaft system is removed. The opening value and displacement value of the flanges before and after the flexible coupling, as well as the load on each bearing in this state, are calculated. This method for aligning a low-speed engine shaft system can meet the alignment requirements and accuracy of low-speed engine shaft systems including large flexible couplings. It is particularly suitable for aligning low-speed engine shaft systems with large mass, large inertia, high elasticity, and high damping of the flexible coupling.

Description

Technical Field

[0001] This invention relates to a method for aligning shafts in a low-speed machine, and more particularly to a method for aligning shafts in a low-speed machine that includes a large flexible coupling. Background Technology

[0002] Current methods for aligning low-speed engine shaft systems typically involve sequentially designing flange openings at the crankshaft, intermediate shaft, and output shaft. The flanges are then aligned according to their offset and opening values. Finally, the flanges are bolted together to complete the entire shaft alignment. However, when the shaft system includes large flexible couplings, the high elasticity of these couplings means that the flange offset and opening values ​​during alignment cannot guarantee the shaft system will be in its designed stable state. Therefore, simply connecting the flanges sequentially using the traditional method will not achieve the desired alignment. Flexible couplings used in low-speed engines generally possess characteristics such as large mass, high inertia, high elasticity, high damping, and high alignment accuracy. Summary of the Invention

[0003] The present invention provides a method for aligning the shaft system of a low-speed engine, which includes a large flexible coupling. This method can meet the requirements of the flexible coupling of the low-speed engine, which has large mass, large inertia, large elasticity, large damping, and high alignment accuracy.

[0004] To achieve the above objectives, the technical solution of the present invention is: a method for aligning a low-speed machine shaft system including a large flexible coupling. First, based on the overall shaft system arrangement, the deviation between the center of each bearing and the center of the shaft axis is designed, and the bearing stress in the final aligned state is calculated to ensure that the stress of each bearing meets the usage requirements. Then, ensuring that the deviation between the center of each bearing and the center of the shaft axis remains unchanged, the flexible coupling in the shaft system is removed, and the opening value and displacement value of the flange pair before and after the flexible coupling, as well as the load of each bearing in this state, are calculated.

[0005] Furthermore, the specific steps of this low-speed machine shaft alignment method are as follows:

[0006] The first step is to bolt the intermediate shaft and crankshaft together at the flange. Then, install the intermediate bearing on the intermediate shaft, adjust the intermediate bearing according to the calculated deviation between the center of the intermediate bearing and the center of the shaft axis, and then measure the load on the intermediate bearing.

[0007] The second step is to adjust the position of the output shaft, leaving axial space for the flexible coupling between the rear flange of the intermediate shaft and the front flange of the output shaft. Fix the laser alignment sensor on the surface of the rear flange of the intermediate shaft and the front flange of the output shaft, set the mode of the laser alignment instrument, and adjust the beam position of the laser alignment instrument so that the opening and displacement of the rear flange of the intermediate shaft and the front flange of the output shaft meet the opening and displacement values ​​of the front and rear flanges of the flexible coupling obtained in the calculation of the flexible coupling in the shaft system.

[0008] The third step is to install the flexible coupling, and bolt the two ends of the flexible coupling to the rear flange of the intermediate shaft and the front flange of the output shaft.

[0009] Furthermore, in the first step, the intermediate bearing load should be consistent with the intermediate bearing load calculated in the case of canceling the flexible coupling in the shaft system before proceeding to the next step.

[0010] Furthermore, in the third step, after completing the shaft connection, the load on each bearing is measured.

[0011] Furthermore, the measured loads of each bearing should be consistent with the bearing loads in the final alignment state calculated in the entire shaft system arrangement, which indicates that the shaft system alignment is complete.

[0012] Furthermore, based on the overall shaft system layout, the deviation between the center of each bearing and the center of the shaft axis is designed, and the bearing stress in the final aligned state is calculated to ensure that the stress of each bearing meets the usage requirements.

[0013] Furthermore, the flexible coupling in the shaft system is removed. The opening and displacement values ​​of the flange pairs before and after the flexible coupling, as well as the specific method for calculating the load of each bearing under this condition, are as follows: The shaft system is regarded as a continuous beam placed on multiple rigid hinge supports. The engineering mechanics theory for solving planar rod systems can be used to solve for the reaction forces on each support and the bending moment, shear force, deflection, and rotation angle parameters on each specified section. The reasonable or optimal values ​​of the above parameters are obtained according to the optimization theory.

[0014] Furthermore, the entire calculation process is as follows:

[0015] 1) Establish a physical model for the centering calculation of the entire shaft system;

[0016] 2) Determine the constraints, including bearing allowable load limits, maximum shaft bending stress limits, maximum shaft bending angle limits, and maximum coupling torque limits;

[0017] 3) Determine the basic parameters such as the number of nodes, shaft diameter, span, concentrated force, and bearing position;

[0018] 4) Calculate the parameters affecting the cross-sectional moment of inertia, uniformly distributed load, and buoyancy correction factor;

[0019] 5) Calculate the coefficients and constants of the variable to be determined;

[0020] 6) Calculate the bending moment, rotation angle, deflection, and support reaction force of each node when the shaft system is connected by a straight line;

[0021] 7) Calculate the bearing load influence number based on the relationship between bearing load and bearing displacement;

[0022] 8) Use the trial-and-error method to determine the reasonable displacement of the bearing;

[0023] 9) Calculate the bending moment, rotation angle, deflection, and support reaction force of the bearing in the hot state after displacement;

[0024] 10) Calculate the bending moment, rotation angle, deflection, and support reaction force of the bearing in the cold state after displacement;

[0025] 11) Calculate the reasonable opening and displacement values ​​of the connecting flanges between shaft segments.

[0026] Furthermore, in step 2) above, the constraints include bearing allowable load limits, maximum shaft bending stress limits, maximum shaft bending angle limits, and maximum coupling torque limits.

[0027] Furthermore, in step 9) above, if all the calculation results meet the constraints, proceed to step 10); otherwise, return to step 8) and change the bearing displacement.

[0028] The beneficial effects of this invention are:

[0029] The low-speed engine shaft alignment method of the present invention can meet the alignment requirements and alignment accuracy of low-speed engine shaft installation including large flexible couplings. It is particularly suitable for the alignment of low-speed engine shafts with large mass, large inertia, large elasticity and large damping of flexible couplings. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the shaft system arrangement of a low-speed machine, which includes a large flexible coupling.

[0031] Figure 2 This is a typical shaft system diagram for a low-speed machine;

[0032] Figure 3 This is a schematic diagram of a laser alignment instrument installed in the shaft system of a low-speed machine;

[0033] Figure 4 This is the jack-load curve from the first step of the embodiment;

[0034] Figure 5 This is a schematic diagram illustrating the adjustment of the intermediate bearing position of the motor in the second step of the embodiment to ensure the required load value of the cross-sectional area between the two flange surfaces;

[0035] Figure 6 This is a schematic diagram illustrating the installation requirements for the coupling in the third step of the embodiment.

[0036] Figure 7 This is the jack-load curve from the third step of the embodiment;

[0037] Figure 8 This is a schematic diagram showing the misalignment of the front and rear ends of the coupling calculated in the third step of the embodiment and the requirements that it should meet.

[0038] Figure 9 This is the jack-load curve from the fourth step of the embodiment;

[0039] Figures 1-3 In the middle section: 1 is the output end of the low-speed machine crankshaft, 2 is the flange of the output end of the low-speed machine crankshaft, 3 is the front flange of the intermediate shaft, 4 is the intermediate shaft, 5 is the intermediate bearing, 6 is the rear flange of the intermediate shaft, 7 is the flexible coupling, 8 is the front flange of the output shaft, and 9 is the output shaft. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] The present invention provides a method for aligning a low-speed machine shaft system including a large flexible coupling. First, based on the overall shaft system arrangement (including bearing arrangement, such as...) Figure 1 As shown), design the deviation between the center of each bearing and the center of the shaft axis, and calculate the bearing stress in the final aligned state (Calculation 1) to ensure that the stress of each bearing meets the usage requirements. Then, ensuring that the deviation between the center of each bearing and the center of the shaft axis remains unchanged, eliminate the flexible couplings in the shaft system (such as...). Figure 2 As shown), the opening and displacement values ​​of the front and rear flange pairs of the flexible coupling (rear flange 6 of the intermediate shaft and front flange 8 of the output shaft) are calculated, as well as the load of each bearing in this state (Calculation 2).

[0042] First, connect the intermediate shaft and crankshaft at the flange pair (low-speed crankshaft output flange 2 and intermediate shaft front flange 3) with bolts. Install the intermediate bearing 5 on the intermediate shaft 4. Adjust the intermediate bearing 5 according to the deviation value between the center of the intermediate bearing 5 and the center of the shaft axis in calculation 1. Then measure the load of the intermediate bearing 5. At this time, the bearing load should be consistent with the intermediate bearing 5 load in calculation 2. Then you can proceed to the next step.

[0043] The second step is to adjust the position of the output shaft 9, leaving axial space for the flexible coupling between the intermediate shaft rear flange 6 and the output shaft front flange 8. Then, fix the laser alignment sensor 10 on the surfaces of the intermediate shaft rear flange 6 and the output shaft front flange 8, and set the laser alignment mode (see...). Figure 3 Adjust the position of the laser alignment instrument to ensure that the opening and displacement of the intermediate shaft rear flange 6 and the output shaft front flange 8 meet the opening and displacement values ​​of the front and rear flanges of the elastic coupling obtained in calculation 2.

[0044] The third step is to install the flexible coupling, connecting both ends of the flexible coupling to the rear flange 6 of the intermediate shaft and the front flange 8 of the output shaft with bolts. After completing the shaft system connection, measure the load on each bearing. The measured load on each bearing should be consistent with the load on each bearing in calculation 1, indicating that the shaft system alignment is complete.

[0045] The bearing stress conditions mentioned in Calculation 1 and the flange opening, displacement, and bearing load mentioned in Calculation 2 are all output results of the shaft alignment calculation. Shaft alignment calculation: The shaft system is considered as a continuous beam placed on multiple rigid hinge supports. The engineering mechanics theory for solving planar trusses can be used to solve for the reactions at each support and the bending moment, shear force, deflection, and rotation parameters at each specified section. Reasonable or optimal values ​​for these parameters are then obtained according to optimization theory. The entire calculation process is as follows:

[0046] 1) Establish a physical model for the alignment calculation of the entire shaft system (including bearings, supports, etc.);

[0047] 2) Determine the constraints (bearing allowable load limit, maximum shaft bending stress limit, maximum shaft bending angle limit, maximum coupling torque limit, etc.);

[0048] 3) Determine basic parameters such as the number of nodes, shaft diameter, span, concentrated force, and bearing position;

[0049] 4) Calculate the influencing parameters such as the moment of inertia of the cross section, uniformly distributed load, and buoyancy correction factor;

[0050] 5) Calculate the coefficients and constants of the variable to be determined;

[0051] 6) Calculate the bending moment, rotation angle, deflection, and support reaction force of each node when the shaft system is connected by a straight line;

[0052] 7) Calculate the bearing load influence number based on the relationship between bearing load and bearing displacement;

[0053] 8) Use the trial-and-error method to determine the reasonable displacement of the bearing;

[0054] 9) Calculate the bending moment, rotation angle, deflection, and support reaction force of the bearing in the hot state after displacement (if all the calculation results meet the constraint conditions, proceed to step 10; otherwise, return to step 8 and change the bearing displacement).

[0055] 10) Calculate the bending moment, rotation angle, deflection, and support reaction force of the bearing in the cold state after displacement;

[0056] 11) Calculate the reasonable opening and displacement values ​​of the connecting flanges between shaft segments.

[0057] Example: The specific application steps of the low-speed machine shaft alignment method using a large flexible coupling are as follows:

[0058] first step:

[0059] 1) The intermediate shaft is bolted to the crankshaft, and the intermediate bearing is installed;

[0060] 2) Adjust the clearance of the intermediate bearing to ensure that the intermediate bearing can withstand a load of about 7kN (since the bearing stiffness is only an estimated value, the following is for reference only: when the intermediate bearing is raised by about 0.15mm, the bearing is just in contact with the shaft; when the intermediate bearing is raised by about 0.17mm, the bearing can withstand a load of about 7kN).

[0061] 3) Measure the load on the main bearings MB2, MB3, MB4 and the intermediate bearing (node ​​nd2), and measure the crankshaft speed values;

[0062] 4) The calculated bearing loads, jack-up values ​​(see Table 1-1), and jack-load curves are shown in Table 1-1. Figure 4 ;

[0063] 5. Measure the shifting of each crank.

[0064] Table 1-1

[0065]

[0066] Step Two:

[0067] 1) The torque flange is connected to the motor shaft, with space reserved for the axial position of the coupling;

[0068] 2) Install laser alignment sensors on the rear flange face of the intermediate shaft and the front flange face of the torque flange. Use laser alignment to adjust the position of the intermediate bearing of the motor to ensure the load on the cross-sectional area between the two flange faces. Figure 5 Numerical requirements (gap & sag tolerance: ±0.05mm);

[0069] 3) Once the crack surface has been adjusted as required, the next step can be carried out.

[0070] Step 3:

[0071] 1) When installing the coupling, the following installation requirements must be met, see [link to installation instructions]. Figure 6 ;

[0072] 2) Measure the load of the main bearings MB2, MB3, MB4 and the intermediate bearing (node ​​nd2), measure the crankshaft speed, and measure the load of the front and rear bearings of the motor.

[0073] 3) The calculated bearing loads, jack-up values ​​(see Table 3-1), and jack-load curves are shown below. Figure 7 ;

[0074] Table 3-1

[0075]

[0076]

[0077] 4) If the shift value meets the requirements of Table 4-2 and the main bearing load is approved, then measure the angular misalignment (△Kw, mrad) and radial misalignment (△Kr, mm) on both sides of the coupling.

[0078] Table 4-2

[0079]

[0080] 5) The calculated misalignment of the front and rear ends of the coupling (see Table 4-3) and the requirements to be met are as follows: Figure 8 ;

[0081] Table 4-3

[0082]

[0083]

[0084] 6) If the misalignment at both ends of the coupling meets the requirements, the next step can be carried out after the data is approved.

[0085] Step 4:

[0086] 1) Oil supply to the motor bearings;

[0087] 2) After the motor bearings have stabilized, measure the load on the main bearings MB2, MB3, MB4 and the intermediate bearing (node ​​nd2), measure the crank swing value, and measure the load on the front and rear bearings of the motor.

[0088] 3) The calculated bearing loads, jack-load values, and jack-load curves are shown in the figure. Figure 9 ;

[0089] 4) If the shift value meets the requirements of Table 4-2 and the main bearing load is approved, then measure the angular misalignment (△Kw, mrad) and radial misalignment (△Kr, mm) on both sides of the coupling.

[0090] 5) The calculated misalignment of the front and rear ends of the coupling is shown in Table 4-4, and the requirements to be met are as follows: Figure 9 ;

[0091] Table 4-4

[0092]

[0093] 6) If the misalignment at both ends of the coupling meets the requirements, the alignment can be completed.

Claims

1. A method of aligning a low speed shafting comprising a large elastic coupling, characterized in that: First, based on the overall shaft system layout, the deviation between the center of each bearing and the center of the shaft axis is designed, and the bearing stress in the final aligned state is calculated to ensure that the stress of each bearing meets the usage requirements. Then, ensuring that the deviation between the center of each bearing and the center of the shaft axis remains unchanged, the flexible coupling in the shaft system is removed, and the opening value and displacement value of the flanges before and after the flexible coupling, as well as the load on each bearing in this state, are calculated. The specific steps of this low-speed machine shaft system alignment method are as follows: The first step is to bolt the intermediate shaft and crankshaft together at the flange. Then, install the intermediate bearing on the intermediate shaft and adjust it according to the calculated deviation between the center of the intermediate bearing and the center of the shaft axis. After that, measure the load on the intermediate bearing. The measured load on each bearing should be consistent with the load on each bearing in the bearing force situation calculated in the final alignment state of the entire shaft system. This indicates that the shaft system alignment is complete. The second step is to adjust the position of the output shaft. A space is reserved between the rear flange of the intermediate shaft and the front flange of the output shaft for the axial position of the flexible coupling. A laser alignment sensor is fixed on the surfaces of the rear flange of the intermediate shaft and the front flange of the output shaft. The laser alignment sensor is set to the correct mode, and the beam position is adjusted so that the opening and displacement of the rear flange of the intermediate shaft and the front flange of the output shaft satisfy the opening and displacement values ​​of the front and rear flanges of the flexible coupling obtained in the calculation of canceling the flexible coupling in the shaft system. The specific method for calculating the opening and displacement values ​​of the front and rear flanges of the flexible coupling, and the load on each bearing in this state, is as follows: The shaft system is considered as a continuous beam placed on multiple rigid hinge supports. The engineering mechanics theory for solving planar rod systems can be used to solve for the reaction forces on each support and the bending moment, shear force, deflection, and rotation parameters on each specified section. The reasonable or optimal values ​​of the above parameters are then obtained according to the optimization theory. The third step is to install the flexible coupling, and bolt the two ends of the flexible coupling to the rear flange of the intermediate shaft and the front flange of the output shaft. The entire calculation process is as follows: 1) Establish a physical model for the centering calculation of the entire shaft system; 2) Determine the constraints; 3) Determine the basic parameters such as the number of nodes, shaft diameter, span, concentrated force, and bearing position; 4) Calculate the parameters affecting the cross-sectional moment of inertia, uniformly distributed load, and buoyancy correction factor; 5) Calculate the coefficients and constants of the variable to be determined; 6) Calculate the bending moment, rotation angle, deflection, and support reaction force at each node when the shaft system is connected by a straight line; 7) Calculate the bearing load influence number based on the relationship between bearing load and bearing displacement; 8) Use the trial-and-error method to determine the reasonable displacement of the bearing; 9) Calculate the bending moment, rotation angle, deflection, and support reaction force of the bearing in its hot state after displacement; 10) Calculate the bending moment, rotation angle, deflection, and support reaction force of the bearing in the cold state after displacement; 11) Calculate the reasonable opening and displacement values ​​of the connecting flanges between shaft segments.

2. The low speed shafting alignment method incorporating a large elastic coupling of claim 1, wherein: In the first step, the intermediate bearing load should be consistent with the intermediate bearing load calculated in the case of canceling the flexible coupling in the shaft system before proceeding to the next step.

3. The method for aligning a low-speed machine shaft system including a large flexible coupling according to claim 1, characterized in that: In the third step, after completing the shaft system connection, the load on each bearing is measured.

4. The method for aligning a low-speed machine shaft system including a large flexible coupling according to claim 1, characterized in that: Based on the overall shaft system layout, design the deviation between the center of each bearing and the center of the shaft axis, calculate the bearing stress in the final aligned state, and ensure that the stress of each bearing meets the usage requirements.

5. The method for aligning a low-speed machine shaft system including a large flexible coupling according to claim 1, characterized in that: In step 2) above, the constraints include bearing allowable load limit, maximum shaft bending stress limit, maximum shaft bending angle limit, and maximum coupling torque limit.

6. The method for aligning a low-speed machine shaft system including a large flexible coupling according to claim 1, characterized in that: In step 9) above, if all the calculation results meet the constraints, proceed to step 10); otherwise, return to step 8) to change the bearing displacement.

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