A method for calculating self-adaptive adjustment of axial force of a single-stage centrifuge head

Abstract

This invention discloses a calculation method for adaptive adjustment of axial force in a single-stage centrifuge head, belonging to the field of centrifugal compressor technology. The method first establishes a parametric simulation model including the impeller, diffuser, impeller back, labyrinth seal, and impeller back opening flow channel, setting the impeller back opening diameter as an adjustable variable. Through CFD simulation, the forces F1 on the impeller cover surface, F2 on the impeller back bottom surface, and the axial forces of the impeller hub and impeller back are calculated under different opening diameters. The optimal opening size is determined with the goal of the total absolute value of the axial force being less than 10N. Then, points are uniformly sampled along the meridional plane on the impeller cover surface and the impeller back bottom surface. Through simulation calibration, the sum of forces F3 and F4 at the measuring points is made to tend towards equilibrium. Finally, force sensors are set at the measuring point locations, and the size of the impeller back opening is adaptively adjusted based on the relationship between F3 and F4, achieving real-time dynamic balance of axial force. This invention eliminates the need for a balance disc or double-suction impeller, has a simple structure, is suitable for high-pressure, low-flow operating conditions, and can keep the axial force close to zero, significantly reducing bearing load and improving the operational stability and service life of the single-stage centrifuge head.

Description

Technical Field

[0001] This invention relates to the field of centrifugal compressor technology, specifically to a simulation calculation and adaptive adjustment method for axial force balance in a single-stage centrifugal compressor head. Background Technology

[0002] During high-speed operation, the uneven gas pressure distribution on both sides of a single-stage centrifuge head creates a significant pressure difference between the impeller cover and the impeller back. This pressure difference directly acts on the impeller, generating an axial force. When the axial force is too large or its direction changes frequently, it continuously exerts additional load on the motor bearings, accelerating bearing wear. In severe cases, this can lead to bearing damage, excessive equipment vibration, or even shutdown, affecting the operational stability and service life of the centrifuge head.

[0003] In existing technologies, two main methods are used to balance the axial force of centrifugal impellers: one is to add a balance disc structure, which uses the pressure difference on both sides of the balance disc to offset part of the axial force. However, this method has a complex structure, large gas leakage, and extremely high requirements for machining and assembly precision. It also cannot achieve real-time dynamic adjustment according to changes in working conditions, and the balancing effect is limited. The other method is to use a double-suction impeller structure, which offsets the axial force by symmetrical air intake on both sides of the impeller. However, the double-suction impeller has a complex overall structure, occupies a large space, and has limited aerodynamic design. It cannot be applied to high-pressure, low-flow working conditions and has poor versatility.

[0004] In practical engineering applications, it is known in the industry that opening a vent hole behind the labyrinth seal on the impeller back of a single-stage centrifuge head can affect the pressure distribution on the impeller back by changing the flow area of ​​the vent hole, thereby adjusting the magnitude and direction of the axial force. However, existing solutions can only roughly determine the opening size based on experience or static simulation, and cannot adaptively adjust the vent hole size according to real-time operating conditions. This makes it difficult to ensure that the impeller maintains an ideal state with near-zero axial force under varying operating conditions, pressures, and flow rates, and still results in problems such as high bearing load and insufficient operational stability. Summary of the Invention

[0005] The main technical problem to be solved by the present invention is to provide a method that can guide the design of openings through simulation calculations and realize the real-time adaptive adjustment of axial force, so as to solve the defects of existing technologies such as complex structure, poor versatility and inability to dynamically balance axial force.

[0006] To address the aforementioned technical problems, this invention provides a method for calculating the adaptive adjustment axial force of a single-stage centrifuge head, comprising the following steps:

[0007] S1. Establish a simulation model of the centrifugal impeller flow channel, including the impeller, diffuser, impeller back, labyrinth seal and impeller back opening flow channel, and set the impeller back opening diameter as an adjustable variable;

[0008] S2. Mesh the simulation model and mark the wheel cover surface, wheel hub surface, wheel back surface and wheel back bottom surface areas respectively to extract the force data of each area;

[0009] S3. Import the simulation model into CFD software for aerodynamic simulation calculation, record the total force F1 on the wheel cover surface, the total force F2 on the bottom surface of the wheel back, the axial force of the wheel hub and the axial force of the wheel back under different wheel back opening diameters, and obtain the relationship between the total axial force and the opening diameter.

[0010] S4. Based on the simulation results, with the goal of the absolute value of the total axial force being less than the set threshold, determine the optimal diameter of the wheel back opening so that the axial force is close to zero.

[0011] S5. Measure the area of ​​the wheel cover surface and the area of ​​the bottom surface of the wheel back. Take points evenly along the meridian plane on the wheel cover surface and the bottom surface of the wheel back, and calculate the total force F3 on the points taken on the wheel cover surface and the total force F4 on the points taken on the bottom surface of the wheel back.

[0012] S6. Adjust the dimensions of the sampling section to keep the ratio of F3 to F4 within the error range, which is considered as the wheel cover surface and the back of the wheel being subjected to balanced forces.

[0013] S7. Set a force sensor at the sampling point and use the relationship between F3 and F4 as the criterion to adaptively adjust the size of the wheel back opening so that the axial force is always kept in the range close to zero.

[0014] In a preferred embodiment: In step S1, the wheel back opening is located on the rear side of the labyrinth seal, and the gas is depressurized by the labyrinth seal before entering the wheel back opening.

[0015] In a preferred embodiment: In step S1, the diameter of the wheel back opening is defined as a variable by an equation in the modeling software to achieve parameterized adjustment of the opening size.

[0016] In a preferred embodiment: In step S3, a k-ε two-equation model is used for simulation calculation, with mass flow rate as the inlet boundary and pressure as the outlet boundary, and the energy equation is activated.

[0017] In a preferred embodiment: In step S3, the total axial force is the difference between the hub axial force and the wheel back axial force, and the threshold is set to an absolute value of less than 10N.

[0018] In a preferred embodiment: In step S4, the diameter of the wheel back opening is adjusted using linear optimization logic: when the axial force of the wheel hub is greater than the axial force of the wheel back, the opening diameter is reduced; when the axial force of the wheel hub is less than the axial force of the wheel back, the opening diameter is increased.

[0019] In a preferred embodiment: In step S5, the same number of measuring points are taken on the wheel cover surface and the bottom surface of the wheel back along the meridional plane, and the measuring points are columnar boss structures.

[0020] In a preferred embodiment: the cross-sectional dimensions of the measuring point boss are adjusted according to the ratio of F1 / F2 and the area ratio of the wheel cover surface and the bottom surface of the wheel back, so that the error of the ratio of F3 to F4 is less than 2%.

[0021] In a preferred embodiment: In step S7, when F3 > F4, the wheel back opening is reduced, and when F3 < F4, the wheel back opening is increased until F3 and F4 tend to be equal.

[0022] In a preferred embodiment, the size of the wheel back opening can be adjusted by a force sensor in conjunction with an electronically controlled actuator, or by a mechanical adaptive structure.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] 1. The optimal wheel back opening size is accurately determined through simulation calculation, replacing traditional experience-based design, resulting in higher axial force balance accuracy;

[0025] 2. Real-time feedback from the force measurement points on the wheel cover and wheel back is adopted to achieve adaptive adjustment of the vent size, which can keep the axial force close to zero under varying working conditions;

[0026] 3. No need to add a balance disc or use a double suction impeller; simple structure, low leakage, and low processing cost.

[0027] 4. It is applicable to high-pressure, low-flow conditions, with a wider range of applications and greater versatility;

[0028] 5. Real-time dynamic adjustment effectively reduces bearing load and significantly improves the operational stability and service life of the centrifuge head. Attached Figure Description

[0029] Figure 1. Schematic diagram of centrifugal impeller flow channel model;

[0030] Figure 2. Schematic diagram of the impeller model with the back opening variable defined by equations;

[0031] Figure 3. Schematic diagram of impeller grid and partition of each region;

[0032] Figure 4. Simulated pressure cloud diagram of the impeller;

[0033] Figure 5. Schematic diagram of the impeller flow channel model with points taken from the bottom surface of the wheel cover and wheel back;

[0034] Figure 6. Schematic diagram of the force calculation surface after point selection.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Impeller, 2. Diffuser, 3. Wheel back, 4. Labyrinth seal, 5. Wheel back vent, 6. Wheel cover surface, 7. Wheel hub surface, 8. Wheel back surface, 9. Wheel back bottom surface. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0038] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0040] In the description of this embodiment, the terms "upper," "lower," "right," and "left," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0041] This embodiment discloses in detail a method for calculating the adaptive adjustment of axial force in a single-stage centrifuge head. Through modeling, parameterized variable setting, mesh generation, CFD simulation, data fitting, measurement point calibration, and adaptive adjustment, it achieves accurate calculation of the wheel back opening size and real-time control of axial force, which is applicable to the axial force balance design and control of various single-stage centrifuge heads.

[0042] Referring to Figures 1 to 6, this embodiment first establishes a complete centrifugal impeller flow channel model in SolidWorks software. This model includes the impeller 1, diffuser 2, impeller back 3, labyrinth seal 4, impeller back vent 5, and far-field flow domain. The labyrinth seal 4 must be positioned upstream of the impeller back vent 5, ensuring that gas is depressurized before entering the impeller back vent 5, preventing direct leakage of high-pressure gas and maintaining high aerodynamic efficiency while adjusting axial force. After the model is established, equation variables are added in the software, setting the opening diameter of the impeller back vent 5 as an adjustable variable. Modifying the equation values ​​directly changes the opening size, achieving parametric-driven modeling and providing a basis for rapid modification in subsequent simulation calculations.

[0043] The centrifugal impeller model with completed parameter settings was imported into the mesh generation software. Independent parts were created for key areas such as the impeller cover surface (6), hub surface (7), impeller back surface (8), impeller back bottom surface (9), diffuser (2), and blade walls, and these parts were named and labeled to accurately extract the force data of each wall surface during CFD simulation. After mesh generation, the mesh file was imported into the CFD simulation software, and the standard k-ε two-equation model was used for calculation. The fluid medium was set to ambient temperature and pressure air, the energy equation was enabled, the inlet boundary was set to a mass flow rate inlet, and the outlet boundary was set to a pressure outlet. Iterative calculations were performed after pre-simulation processing.

[0044] In this embodiment, simulation calculations are performed for multiple sets of different opening diameters. The diameters of the vent holes 5 on the wheel back are set sequentially to 35mm, 34mm, 33mm, 32mm, 31mm, 30mm, 29.9mm, 29.85mm, 29.8mm, 29.7mm, 29.65mm, 29.6mm, 29.5mm, 29.45mm, 29.4mm, 29mm, 28mm, 27mm, 26mm, and 25mm. After each set of simulation calculations is completed, the axial force of the wheel hub, the axial force of the wheel back, the total axial force, the total force F1 on the wheel cover surface, and the total force F2 on the bottom surface of the wheel back are extracted and recorded, and the ratio of F1 / F2 is calculated. Simulation data shows that as the diameter of the wheel arch opening gradually decreases, the wheel arch pressure gradually increases, and the wheel arch axial force increases accordingly. The total axial force gradually decreases from a positive value and then turns negative. When the opening diameter is too large, the wheel arch pressure is low, and the total axial force is large; when the opening diameter is too small, the wheel arch pressure is high, and the total axial force increases in the opposite direction. See the table below:

[0045]

[0046] Based on simulation data, linear optimization logic was used for judgment. The judgment rules were set as follows: when the total axial force is greater than 10N, the force on the hub side is considered too large, and the diameter of the wheel back opening is reduced; when the total axial force is less than -10N, the force on the wheel back side is considered too large, and the diameter of the wheel back opening is increased; when the absolute value of the total axial force is less than 10N, the axial force balance requirement is met. After multiple iterative calculations, when the diameter of the wheel back opening is 29.65mm, the total axial force drops to 8N, which is less than the set threshold of 10N, meeting the design goal of axial force approaching zero. At this time, the corresponding F1 / F2 ratio is 1.1932, and the larger the opening diameter, the larger the F1 / F2 ratio, and the smaller the opening diameter, the smaller the F1 / F2 ratio.

[0047] After determining the optimal opening diameter, the areas of the wheel cover surface 6 and the bottom surface 9 of the wheel back were measured using the surface evaluation function in SolidWorks. The measured area of ​​the wheel cover surface was 59145 mm², and the area of ​​the bottom surface of the wheel back was 37139 mm². Based on the ratio F1 / F2=1.1932 under the optimal model, the force ratio per unit area was calculated as: (1.1932 / 59145) / (1 / 37139)=0.749. Subsequently, seven measuring points were evenly selected along the meridional wheel cover line on the wheel cover surface 6. Each measuring point was set as a 1mm×1mm×1mm cube boss with a cross-section of 1mm×1mm and perpendicular to the wheel cover surface. At the same time, seven measuring points were evenly selected along the meridional plane on the bottom surface 9 of the wheel back. Each measuring point was set as a 1mm×1mm×0.749mm cuboid boss with a cross-section of 1mm×0.749mm.

[0048] A new simulation model with measuring point bosses was established using the above-described point selection method. The previous CFD simulation parameters and boundary conditions were used for calculation. The total force on the seven measuring point bosses on the wheel cover surface was extracted and denoted as F3, and the total force on the seven measuring point bosses on the bottom surface of the wheel arch was extracted and denoted as F4. The initial calculation yielded F3 / F4 = 1.05. Based on this proportional deviation, the cross-sectional size of the measuring point bosses on the wheel cover surface was reduced to 1 / 1.05mm × 1mm. Simulation calculations were performed again, and the values ​​of F3 and F4 were recorded. The measuring point size was iteratively adjusted repeatedly until the deviation of F3 / F4 was less than 2%. At this point, it was determined that the force on the measuring points on the wheel cover surface was approximately equal to the force on the measuring points on the bottom surface of the wheel arch, thus completing the force calibration.

[0049] After calibration, force sensors are installed at measuring points on the wheel cover and the bottom surface of the wheel back. The sensor signals are then connected to the centrifuge head control system, forming a closed-loop adaptive adjustment structure. During actual impeller operation, the sensors collect the force signals F3 and F4 in real time: when F3 > F4, the control system determines that the axial force on the hub side is too large, drives the actuator to reduce the opening area of ​​the wheel back vent 5, and increases the wheel back pressure to increase the wheel back axial force until F3 and F4 are equal again; when F3 < F4, the control system determines that the axial force on the wheel back side is too large, drives the actuator to increase the opening area of ​​the wheel back vent 5, and decreases the wheel back pressure to reduce the wheel back axial force until F3 and F4 are balanced again. Through this real-time adaptive adjustment, the total axial force of the impeller is always kept below 10N, continuously approaching zero.

[0050] This embodiment accurately determines the optimal wheel back opening size through simulation calculation. Combined with measuring point calibration and force sensor closed-loop adjustment, it can achieve axial force adaptive balance without the need for a balance disc or double suction impeller structure. It has a simple structure, sensitive adjustment, and high balance accuracy. It can be applied to complex working conditions such as high pressure and low flow rate, effectively reducing motor bearing load and significantly improving the operating stability and service life of single-stage centrifuge head.

[0051] The above is only one specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be deemed as infringing the protection scope of the present invention.

Claims

1. A method for calculating the adaptive adjustment axial force of a single-stage centrifuge head, characterized in that, Includes the following steps: S1. Establish a simulation model of the centrifugal impeller flow channel, including the impeller, diffuser, impeller back, labyrinth seal and impeller back opening flow channel, and set the impeller back opening diameter as an adjustable variable; S2. Mesh the simulation model and mark the wheel cover surface, wheel hub surface, wheel back surface and wheel back bottom surface areas respectively to extract the force data of each area; S3. Import the simulation model into CFD software for aerodynamic simulation calculation, record the total force F1 on the wheel cover surface, the total force F2 on the bottom surface of the wheel back, the axial force of the wheel hub and the axial force on the wheel back under different wheel back opening diameters, and obtain the relationship between the total axial force and the opening diameter. S4. Based on the simulation results, with the goal of the absolute value of the total axial force being less than the set threshold, determine the optimal diameter of the wheel back opening so that the axial force is close to zero. S5. Measure the area of ​​the wheel cover surface and the area of ​​the bottom surface of the wheel back. Take points evenly along the meridian plane on the wheel cover surface and the bottom surface of the wheel back, and calculate the total force F3 on the points taken on the wheel cover surface and the total force F4 on the points taken on the bottom surface of the wheel back. S6. Adjust the dimensions of the sampling section to keep the ratio of F3 to F4 within the error range, which is considered as the wheel cover surface and the back of the wheel being subjected to balanced forces. S7. Set a force sensor at the sampling point and use the relationship between F3 and F4 as the criterion to adaptively adjust the size of the wheel back opening so that the axial force is always kept in the range close to zero.

2. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S1, the wheel back opening is located behind the labyrinth seal, and the gas is depressurized by the labyrinth seal before entering the wheel back opening.

3. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S1, the diameter of the wheel back opening is defined as a variable by an equation in the modeling software, thereby achieving parameterized adjustment of the opening size.

4. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S3, the k-ε two-equation model is used for simulation calculation, with mass flow rate as the inlet boundary and pressure as the outlet boundary, and the energy equation is activated.

5. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S3, the total axial force is the difference between the axial force of the wheel hub and the axial force of the wheel back, and the threshold is set to an absolute value of less than 10N.

6. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S4, the diameter of the wheel back opening is adjusted using linear optimization logic: when the axial force of the wheel hub is greater than the axial force of the wheel back, the opening diameter is reduced; when the axial force of the wheel hub is less than the axial force of the wheel back, the opening diameter is increased.

7. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S5, the same number of measuring points are taken on both the wheel cover surface and the bottom surface of the wheel back along the meridian plane. The measuring points are columnar boss structures.

8. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 7, characterized in that: Based on the ratio of F1 / F2 and the area ratio of the wheel cover surface and the bottom surface of the wheel back, adjust the cross-sectional dimensions of the measuring point boss so that the error of the ratio of F3 to F4 is less than 2%.

9. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: In step S7, when F3 > F4, the wheel back opening is reduced, and when F3 < F4, the wheel back opening is increased until F3 and F4 tend to be equal.

10. The method for calculating the adaptive adjustment axial force of a single-stage centrifuge head according to claim 1, characterized in that: The size of the wheel back opening can be adjusted by a force sensor in conjunction with an electronically controlled actuator, or by a mechanical adaptive structure.

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