Finite element calculation method for impeller front end clearance of high-temperature CO2 centrifugal compressor

Abstract

The invention discloses a finite element calculation method for the impeller front end clearance of a high-temperature CO2 centrifugal compressor, and relates to the technical field of centrifugal compressors. The method comprises the following steps: 1, creating a three-dimensional entity calculation model in UG-NX software, wherein the entity calculation model comprises a volute rear half part, a volute front half part, a bolt, a gasket, an air seal body, a centrifugal impeller, a rotating shaft and a sealing shaft sleeve; 2, importing the entity calculation model into finite element analysis software Workbench, and carrying out mesh refinement processing on a contact surface, a bolt and a gasket in the entity calculation model; the method breaks through a traditional experience-dependent design mode, converts fuzzy estimation of the impeller front-end clearance into accurate quantification through modeling-analysis-calculation-clearance determination full-process standardized design, fundamentally solves the problems of efficiency reduction caused by too large clearance under a high-temperature working condition, frictional wear caused by too small clearance and the like, and improves the working efficiency of the impeller front-end clearance. And the safety and the stability of equipment operation are obviously improved.

Description

Technical Field

[0001] This invention relates to the field of centrifugal compressor technology, and specifically to a finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor. Background Technology

[0002] In the design of CO2 centrifugal compressors, the impeller exhaust temperature was not high in the past, and the impeller front clearance setting relied on design parameters and experience.

[0003] However, when the impeller exhaust temperature is high, the system stability will decrease. If the above design method is still used, the impeller front clearance will be too large or too small. If the impeller front clearance is too large, it will lead to increased leakage and decreased efficiency. If the impeller front clearance is too small, it will cause the impeller to rub against the casing, resulting in vibration, noise and wear, which will affect the safety and operational stability of the equipment. Summary of the Invention

[0004] The purpose of this invention is to address the problem that relying on design parameters and experience to set the impeller front clearance in high-temperature CO2 centrifugal compressors leads to reduced efficiency and affects equipment safety and operational stability. Therefore, this invention provides a finite element method for calculating the impeller front clearance of a high-temperature CO2 centrifugal compressor.

[0005] The technical solution of this invention is: a finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor, comprising the following steps:

[0006] Step 1: Create a 3D solid calculation model in UG-NX software. The solid calculation model includes the rear half of the volute, the front half of the volute, bolts, gaskets, air seal, centrifugal impeller, rotating shaft, and sealing bushing.

[0007] Step 2: Import the solid calculation model into the finite element analysis software Workbench, and refine the mesh of the contact surfaces, bolts and gaskets in the solid calculation model;

[0008] Step 3: In the finite element analysis software Workbench, define the material, temperature heat transfer boundary, force boundary, contact, displacement boundary, load, and other settings of the solid calculation model according to the calculation requirements;

[0009] Step 4: Perform transient analysis settings for half-speed and design speed operating conditions;

[0010] Step 5: Submit the finite element calculation results;

[0011] Step 6: Set the impeller front clearance of the CO2 centrifugal compressor.

[0012] Furthermore, the materials used to define the entity computation model in step two include:

[0013] The density of each component material and its linear expansion coefficient, Young's modulus, Poisson's ratio, bulk modulus, shear modulus, and thermal conductivity at different temperatures are used to assign the defined materials to the corresponding solid calculation models.

[0014] Furthermore, the contact defined in step two for the entity computation model includes:

[0015] The rear half of the volute casing makes frictional contact with the gasket, defining the coefficient of friction.

[0016] The front half of the volute casing makes frictional contact with the gasket, defining the coefficient of friction.

[0017] Add binding contact between the bolt and the rear half of the volute;

[0018] Frictional contact is added between the bolt and the front half of the volute, and the coefficient of friction is defined.

[0019] Add binding contact between the gas seal body and the rear half of the volute;

[0020] Add binding contact between the centrifugal impeller, the rotating shaft, and the sealing bushing.

[0021] Furthermore, the temperature heat transfer boundary defined in step two for the solid computational model includes:

[0022] Temperature heat transfer boundary of the front half inlet shaft section of the volute;

[0023] The heat transfer boundary of the inlet to outlet arc section of the volute.

[0024] Temperature heat transfer boundary of diffuser in the rear half and front half of volute.

[0025] Heat transfer boundary at the outlet temperature of the rear half and front half of the volute.

[0026] Temperature heat transfer boundary of the arc section from the inlet to the outlet of the centrifugal impeller;

[0027] Temperature heat transfer boundary on the back of the centrifugal impeller;

[0028] Temperature heat transfer boundary of rotating shaft and sealing bushing.

[0029] Furthermore, the displacement boundaries, force boundaries, and loads defined in step two for the solid calculation model include:

[0030] The rotating shaft and sealing bushing constrain axial and rotational displacement to zero.

[0031] The rear half of the volute is constrained to have zero axial and rotational displacement.

[0032] Operating speed of centrifugal impeller, rotating shaft and sealing bushing;

[0033] Pressure boundary of the arc section from the inlet to the outlet of the centrifugal impeller;

[0034] Centrifugal impeller back pressure boundary;

[0035] Bolt tightening force boundary.

[0036] Furthermore, the transient analysis settings for the half-speed operating condition in step four include:

[0037] Set the calculation end time T1, the number of calculation steps N1, the calculation step time T2, and the half rotation speed R1.

[0038] Furthermore, the transient analysis settings for the design conditions in step four include:

[0039] Set the calculation end time T2, the number of calculation steps N2, the calculation step time T4, and the design rotational speed R2.

[0040] Furthermore, the submission of finite element calculation results in step five includes:

[0041] Transient analysis finite element calculation results under half-speed operation: extract the total calculation time T3, the axial displacement of the front end of the centrifugal impeller S1, and the axial displacement of the front half of the volute S2;

[0042] The transient analysis finite element calculation results under the design conditions are as follows: the total calculation time T4, the axial displacement of the centrifugal impeller front end S3, and the axial displacement of the front half of the volute front end S4 are extracted.

[0043] Furthermore, the calculation is considered complete when both the transient analysis finite element calculation results for the half-speed condition and the transient analysis finite element calculation results for the design condition reach a steady state; otherwise, step five is repeated until the calculation results reach a steady state.

[0044] Furthermore, the step six step of setting the impeller front clearance of the CO2 centrifugal compressor includes:

[0045] The axial displacement S at the front end of the centrifugal impeller 1、 The axial displacement S2 at the front end of the volute and the axial displacement S3 at the front end of the centrifugal impeller are compared, and the larger value is set as L1.

[0046] Given a safety margin L2 for the impeller front clearance;

[0047] The impeller front clearance of the CO2 centrifugal compressor is then set to L1+L2.

[0048] Compared with the prior art, the present invention has the following advantages:

[0049] 1. The finite element method for calculating the impeller front clearance of a high-temperature CO2 centrifugal compressor provided by this invention breaks away from the traditional experience-based design model. Through a standardized design process of modeling, analysis, calculation, and clearance determination, the impeller front clearance is transformed from fuzzy estimation to precise quantification. This fundamentally solves the problems of efficiency reduction caused by excessive clearance under high-temperature conditions and friction and wear caused by excessive clearance, significantly improving the safety and stability of equipment operation. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0051] In the diagram: 1. Rear half of the volute; 2. Front half of the volute; 3. Bolt; 4. Gasket; 5. Air seal; 6. Centrifugal impeller; 7. Sealing bushing. Detailed Implementation

[0052] Specific implementation method one: Combining Figure 1 This embodiment describes the following steps:

[0053] Step 1: Create a three-dimensional solid calculation model in UG-NX software. The solid calculation model includes the rear half of the volute 1, the front half of the volute 2, the bolt 3, the gasket 4, the air seal 5, the centrifugal impeller 6, the rotating shaft and the sealing bushing 7.

[0054] Step 2: Import the solid calculation model into the finite element analysis software Workbench, and refine the mesh of the contact surface, bolt 3 and gasket 4 in the solid calculation model;

[0055] Step 3: In the finite element analysis software Workbench, define the material, temperature heat transfer boundary, force boundary, contact, displacement boundary, load, and other settings of the solid calculation model according to the calculation requirements;

[0056] Step 4: Perform transient analysis settings for half-speed and design speed operating conditions;

[0057] Step 5: Submit the finite element calculation results;

[0058] Step 6: Set the impeller front clearance of the CO2 centrifugal compressor.

[0059] Taking the final stage impeller of a megawatt-class CO2 centrifugal compressor as an example, the design operating conditions have an inlet total temperature of 207.99℃, an inlet total pressure of 16195.40 kPa, an outlet total temperature of 243.51℃, and an outlet total pressure of 21497.58 kPa; the half-speed warm-up operating conditions have an inlet total temperature of 126.00℃, an inlet total pressure of 7600.00 kPa, an outlet total temperature of 132.00℃, and an outlet total pressure of 7795.00 kPa.

[0060] The finite element method for calculating the impeller front clearance of the CO2 centrifugal compressor in this embodiment breaks away from the traditional experience-based design model. Through a standardized design process of modeling, analysis, calculation, and clearance determination, the impeller front clearance is transformed from fuzzy estimation to precise quantification. This fundamentally solves the problems of efficiency reduction caused by excessive clearance under high-temperature conditions and friction and wear caused by excessive clearance, significantly improving the safety and stability of equipment operation.

[0061] Specific Implementation Method Two: Combining Figure 1 This embodiment differs from specific embodiment one in that the materials used to define the entity computation model in step two include:

[0062] The density of each component material and its coefficient of linear expansion, Young's modulus, Poisson's ratio, bulk modulus, shear modulus, and thermal conductivity at different temperatures are used to assign the predefined materials to the corresponding solid calculation models. Other components and connections are the same as in Specific Implementation Method 1.

[0063] Specific implementation method three: Combining Figure 1 This embodiment differs from specific embodiment one in that the contact in step two, which defines the entity computation model, includes:

[0064] Frictional contact is added between the rear half 1 of the volute and the gasket 4, defining the coefficient of friction;

[0065] Frictional contact is added between the front half 2 of the volute and the gasket 4, defining the coefficient of friction;

[0066] Bolt 3 is added to the rear half of the volute housing for binding contact;

[0067] Bolt 3 is brought into frictional contact with the front half 2 of the volute, and the coefficient of friction is defined.

[0068] Add binding contact between the gas seal body 5 and the rear half of the volute 1;

[0069] The centrifugal impeller 6 is connected to the rotating shaft and sealing sleeve 7 through a binding contact. Other components and connections are the same as in Specific Embodiment 1.

[0070] Specific implementation method four: Combination Figure 1 This embodiment differs from specific embodiment one in that the temperature heat transfer boundary of the solid computation model defined in step two includes:

[0071] Temperature heat transfer boundary of the front half of the volute shaft section at the two inlets;

[0072] The heat transfer boundary of the inlet-outlet arc section of the front half of the volute;

[0073] 1. Rear half of the volute, 2. Diffuser temperature heat transfer boundary.

[0074] Heat transfer boundary at the outlet temperature of the rear half of the volute and the front half of the volute.

[0075] The heat transfer boundary of the arc section from the inlet to the outlet of the centrifugal impeller 6;

[0076] Centrifugal impeller 6: Temperature transfer boundary on the back of the impeller;

[0077] The rotating shaft and sealing bushing 7 form the temperature heat exchange boundary. Other components and connections are the same as in Specific Embodiment 1.

[0078] Specific Implementation Method Five: Combining Figure 1 This embodiment differs from specific embodiment one in that the displacement boundaries, force boundaries, and loads of the solid calculation model defined in step two include:

[0079] The rotating shaft and sealing bushing 7 constrain axial and rotational displacement to 0 points;

[0080] The rear half of the volute is constrained to have zero axial and rotational displacements.

[0081] Operating speed of centrifugal impeller 6, rotating shaft and sealing bushing 7;

[0082] Pressure boundary of the arc section from the inlet to the outlet of centrifugal impeller 6;

[0083] Centrifugal impeller 6 Impeller back pressure boundary;

[0084] Bolt 3 tightening force boundary. Other components and connection relationships are the same as in specific implementation method one.

[0085] Specific Implementation Method Six: Combination Figure 1 This embodiment differs from specific embodiment one in that the transient analysis settings for the half-speed condition in step four include:

[0086] Set the calculation end time T1, calculation steps N1, calculation step time T2, and half rotation speed R1. Other components and connections are the same as in Specific Implementation Method 1.

[0087] Specific implementation method seven: Combining Figure 1 This embodiment differs from specific embodiment one in that the transient analysis settings for the design conditions in step four include:

[0088] Set the calculation end time T2, the number of calculation steps N2, the calculation step time T4, and the design rotational speed R2. Other components and connections are the same as in Specific Implementation Method 1.

[0089] Specific implementation method eight: Combination Figure 1This embodiment differs from specific embodiment one in that the submission of finite element calculation results in step five includes:

[0090] Transient analysis finite element calculation results under half-speed operation: extract the total calculation time T3, the axial displacement of the front end of centrifugal impeller 6 S1, and the axial displacement of the front end of the front half of the volute 2 S2;

[0091] The transient analysis finite element calculation results under the design conditions are as follows: the total calculation time T4, the axial displacement of the front end of the centrifugal impeller 6 S3, and the axial displacement of the front end of the volute 2 S4 are extracted. Other components and connections are the same as in Specific Implementation Method 1.

[0092] Specific Implementation Method Nine: Combining Figure 1 This embodiment differs from specific embodiment eight in that the calculation is considered complete when both the transient finite element analysis results for the half-speed condition and the transient finite element analysis results for the design condition reach a steady state; otherwise, step five is repeated until the calculation results reach a steady state. Other components and connections are the same as in specific embodiment eight.

[0093] Specific Implementation Method Ten: Combining Figure 1 This embodiment differs from specific embodiment eight in that the clearance at the front end of the CO2 centrifugal compressor impeller in step six includes:

[0094] Compare the axial displacement S1 at the front end of centrifugal impeller 6, the axial displacement S2 at the front end of the volute front half 2, and the axial displacement S3 at the front end of centrifugal impeller 6, and take the larger value as L1.

[0095] Given a safety margin L2 for the impeller front clearance;

[0096] The impeller front clearance of the CO2 centrifugal compressor is set to L1+L2. Other components and connections are the same as in specific implementation method eight.

[0097] The scope of this invention is not limited to the above-described embodiments; a combination of one or more specific embodiments can also achieve the purpose of the invention.

Claims

1. A finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor, characterized in that, Includes the following steps: Step 1: Create a three-dimensional solid calculation model in UG-NX software. The solid calculation model includes the rear half of the volute (1), the front half of the volute (2), bolts (3), gaskets (4), air seal (5), centrifugal impeller (6), rotating shaft and sealing bushing (7); Step 2: Import the solid calculation model into the finite element analysis software Workbench, and refine the mesh of the contact surface, bolt (3) and gasket (4) in the solid calculation model; Step 3: In the finite element analysis software Workbench, define the material, temperature heat transfer boundary, force boundary, contact, displacement boundary, load, and other settings of the solid calculation model according to the calculation requirements; Step 4: Perform transient analysis settings for half-speed and design speed operating conditions; Step 5: Submit the finite element calculation results; Step 6: Set the impeller front clearance of the CO2 centrifugal compressor.

2. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 1, characterized in that, The materials used to define the entity computation model in step two include: The density of each component material and its linear expansion coefficient, Young's modulus, Poisson's ratio, bulk modulus, shear modulus, and thermal conductivity at different temperatures are used to assign the defined materials to the corresponding solid calculation models.

3. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 1, characterized in that, The contact defined in step two for the entity computation model includes: Frictional contact is added between the rear half (1) of the volute and the gasket (4), and the coefficient of friction is defined; Frictional contact is added between the front half (2) of the volute and the gasket (4), and the coefficient of friction is defined; Bolt (3) is added to the rear half (1) of the volute for binding contact; Add frictional contact between bolt (3) and the front half (2) of the volute, and define the coefficient of friction; Add binding contact between the gas seal body (5) and the rear half of the volute (1); The centrifugal impeller (6) is made into binding contact with the rotating shaft and the sealing bushing (7).

4. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 1, characterized in that, The temperature heat transfer boundary defined in step two of the solid computation model includes: (2) Temperature heat transfer boundary of the inlet shaft section of the front half of the volute; (2) Temperature heat transfer boundary of the inlet to outlet arc section of the front half of the volute; Temperature heat transfer boundary of diffuser in the rear half (1) and front half (2) of volute; Heat transfer boundary of outlet temperature of the rear half (1) and front half (2) of the volute; The heat transfer boundary of the arc section from the inlet to the outlet of the centrifugal impeller (6); Centrifugal impeller (6) back heat transfer boundary; Rotating shaft and sealing bushing (7) Temperature heat exchange boundary.

5. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 1, characterized in that, The displacement boundaries, force boundaries, and loads defined in step two for the solid calculation model include: The rotating shaft and sealing bushing (7) constrain the axial and rotational displacement to 0 points; The rear half of the volute (1) constrains the axial and rotational displacements to point 0; Operating speed of centrifugal impeller (6), rotating shaft and sealing bushing (7); Pressure boundary of the arc section from the inlet to the outlet of the centrifugal impeller (6); Centrifugal impeller (6) Impeller back pressure boundary; Bolt (3) Tightening force boundary.

6. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 1, characterized in that, The transient analysis settings for the half-speed operating condition in step four include: Set the calculation end time T1, the number of calculation steps N1, the calculation step time T2, and the half rotation speed R1.

7. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 6, characterized in that, The transient analysis settings for the design conditions in step four include: Set the calculation end time T2, the number of calculation steps N2, the calculation step time T4, and the design rotational speed R2.

8. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 1, characterized in that, The finite element calculation results submitted in step five include: The transient analysis finite element calculation results under half-speed operation: extract the total calculation time T3, the axial displacement of the front end of the centrifugal impeller (6) S1, and the axial displacement of the front end of the front half of the volute (2) S2. The results of the transient analysis finite element calculation under the design conditions are as follows: the total calculation time T4, the axial displacement of the front end of the centrifugal impeller (6) S3, and the axial displacement of the front end of the front half of the volute (2) S4 are extracted.

9. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 8, characterized in that, The calculation is considered complete when both the transient analysis finite element calculation results for the half-speed condition and the transient analysis finite element calculation results for the design condition reach a steady state. Otherwise, repeat step five until the calculation results reach a steady state.

10. The finite element method for calculating the impeller front end clearance of a high-temperature CO2 centrifugal compressor according to claim 8, characterized in that, The step six step of setting the impeller front clearance of the CO2 centrifugal compressor includes: Compare the axial displacement S1 at the front end of the centrifugal impeller (6), the axial displacement S2 at the front end of the volute (2), and the axial displacement S3 at the front end of the centrifugal impeller (6), and take the larger value as L1. Given a safety margin L2 for the impeller front clearance; The impeller front clearance of the CO2 centrifugal compressor is then set to L1+L2.

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