Method and system for controlling dynamic blade tip clearance of axial flow fan
Through multiphysics coupling analysis and real-time monitoring, the dynamic deformation problem that was not considered in the design of the tip clearance of axial flow fans was solved, achieving safe and reliable minimization optimization and improving the performance and economy of the fans.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI SUFAN AUTOMOTIVE TECH CO LTD
- Filing Date
- 2026-01-28
- Publication Date
- 2026-05-08
AI Technical Summary
Existing tip clearance design methods for axial flow fans fail to fully consider the radial deformation, temperature changes, and dynamic deformation of the impeller under vibration during high-speed rotation, resulting in performance loss and safety hazards. Traditional methods are too conservative or complex and expensive active control technologies are not applicable.
By constructing a multiphysics coupling analysis model, taking into account factors such as centrifugal force, temperature, vibration, and manufacturing tolerances, the minimum safe clearance between the impeller and the frame is accurately calculated to guide the design of the fan to avoid interference. Multidisciplinary simulation tools are used to quantify the influence of each factor, and sensors are placed at key locations for real-time monitoring.
It achieves the minimization and optimization of blade tip clearance while ensuring safety, improves wind turbine efficiency and performance, reduces manufacturing costs, adapts to design requirements of different operating conditions and materials, and provides reliable safety assurance.
Smart Images
Figure CN121997664A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of fluid machinery design and manufacturing technology, specifically to a method and system for controlling the tip clearance of an axial flow fan, and in particular, a method and system for precise design of dynamic tip clearance based on multi-physics coupling analysis. Background Technology
[0002] Axial flow fans, as core equipment widely used in ventilation, cooling, and air conditioning, directly impact system efficiency through their performance and reliability. Tip clearance (the radial distance between the tip of the impeller blades and the inner wall of the fan frame) is one of the key design parameters for axial flow fans. Theoretically, a smaller tip clearance can effectively reduce leakage losses, improve fan efficiency and output pressure, and reduce noise caused by tip vortices. However, excessively small tip clearance may cause interference between the impeller and the frame during fan operation, especially under complex conditions such as high temperature, high speed, and vibration, where the risk of such interference increases significantly.
[0003] Traditional blade tip clearance design methods mainly rely on empirical formulas and static analysis, typically based on geometric dimensions under static conditions at room temperature, simply considering machining tolerances and reserving a fixed clearance. This method has significant shortcomings: 1) It does not fully consider the radial deformation caused by centrifugal force when the impeller rotates at high speed; 2) It does not consider the dimensional changes caused by the thermal expansion of the impeller and frame materials at operating temperatures; 3) It does not systematically evaluate the dynamic deformation of the frame and support system under vibration; 4) It does not quantify the comprehensive impact of static deviations such as manufacturing tolerances and coaxiality errors.
[0004] In existing technologies, some precision rotating machinery (such as aero engines) employs active clearance control technology, but such systems are complex in structure and expensive, making them unsuitable for ordinary industrial fans. Most industrial fans still use conservative clearance designs, leading to performance losses. Patent CN20231056789.X discloses an impeller clearance design method that considers thermal deformation, but it only considers temperature as a single factor. Patent CN20221123456.7 relates to a fan impeller anti-collision and abrasion method, mainly preventing interference through monitoring and alarms, which is a post-event protection rather than a pre-event design optimization.
[0005] Therefore, there is an urgent need to develop a precise design method for blade tip clearance that comprehensively considers multiple physical field factors, so as to minimize and optimize blade tip clearance while ensuring safety and reliability, thereby improving the performance of the wind turbine. Summary of the Invention
[0006] The purpose of this application is to overcome the shortcomings of the prior art and provide a dynamic tip clearance control method and system for axial flow fans. By systematically analyzing the dynamic deformation behavior of the impeller and frame under the coupled effects of multiple physical fields such as centrifugal force, temperature, vibration, and manufacturing tolerances, the minimum safe clearance is accurately calculated to guide the design and manufacturing of the fan and achieve the minimization and optimization of tip clearance while avoiding operational interference.
[0007] This application provides a method for controlling the dynamic tip clearance of an axial flow fan, the method comprising the following steps: Step S1: Construct a multiphysics coupling analysis model of the impeller-frame system; the model includes at least: a radial deformation model of the impeller under centrifugal force and temperature load, a static manufacturing tolerance model of the impeller and frame, a coaxiality error model of the impeller support system, and a dynamic deformation model of the frame under vibration and temperature load; Step S2: Based on the multiphysics coupling analysis model, the maximum radial displacement ΔR_rotor of the impeller and the minimum radial displacement ΔR_housing of the inner circle of the frame are simulated and calculated to obtain the dynamic envelope range of the outer edge of the impeller and the dynamic envelope range of the inner edge of the frame under the design conditions. Step S3: Calculate the minimum safety clearance δ_min required between the impeller and the frame: δ_min = ΔR_rotor_max - ΔR_housing_min + K×σ_total, where ΔR_rotor_max is the maximum radial displacement of the outer edge of the impeller, ΔR_housing_min is the minimum radial displacement of the inner circle of the frame, σ_total is the total uncertainty of the system, and K is the safety factor; Step S4: Based on the calculated minimum safety clearance δ_min, guide the mechanical design of the wind turbine to ensure that the actual assembled blade tip clearance is greater than or equal to δ_min.
[0008] In some embodiments, in step S1, the radial deformation model of the impeller under centrifugal force and temperature load specifically includes: establishing a finite element model of the impeller, applying centrifugal force load and temperature field distribution load corresponding to the operating speed, and calculating the total radial displacement field after the superposition of radial thermal expansion deformation and centrifugal deformation of the impeller from the static cold state to the working state through thermal-structural coupling analysis.
[0009] In some embodiments, the temperature field distribution load is obtained based on computational fluid dynamics analysis, taking into account the combined effects of internal flow heat transfer and external ambient temperature.
[0010] In some embodiments, in step S1, the static manufacturing tolerance model of the impeller and the frame includes: the radial runout tolerance zone δ_rotor_machining of the outer circle after impeller machining and the radial runout tolerance zone δ_housing_machining of the inner circle after frame machining.
[0011] In some embodiments, in step S1, the coaxiality error model of the impeller support system includes: bearing clearance, bearing housing machining error, and dynamic coaxiality deviation δ_concentricity between the impeller center and the frame center caused by shaft deflection.
[0012] In some embodiments, in step S1, the dynamic deformation model of the frame under vibration and temperature loads includes: the radial deformation of the inner circle of the frame caused by the vibration excitation of the wind turbine operation and the temperature gradient, and the dynamic deformation amount δ_housing_vibration of the inner circle of the frame is evaluated by modal analysis and random vibration analysis.
[0013] In some embodiments, in step S2, the formula for calculating the maximum radial displacement of the impeller ΔR_rotor_max is: ΔR_rotor_max = ΔR_centrifugal + ΔR_thermal_rotor + δ_rotor_machining / 2 + δ_concentricity; where ΔR_centrifugal is the maximum radial deformation of the impeller caused by centrifugal force, and ΔR_thermal_rotor is the maximum radial thermal expansion of the impeller caused by temperature.
[0014] In some embodiments, in step S2, the formula for calculating the minimum radial displacement ΔR_housing of the inner circle of the frame is: ΔR_housing_min = ΔR_thermal_housing - δ_housing_machining / 2 - δ_housing_vibration - δ_concentricity; where ΔR_thermal_housing is the minimum radial thermal expansion of the inner circle of the frame caused by temperature.
[0015] In some embodiments, step S5 is further included: arranging temperature and vibration sensors at key locations of the wind turbine to monitor the temperature and vibration data of the impeller and frame in real time, and dynamically correcting the minimum safety clearance δ_min.
[0016] This application also provides a system for designing the clearance between the impeller and the frame of an axial flow fan, including: The multiphysics coupling analysis module is used to execute steps S1-S3 of the method described in any of the above items; The clearance optimization design module optimizes the structural design parameters of the impeller and frame based on the calculated minimum safe clearance δ_min. The real-time monitoring module is used to monitor the operating status of the wind turbine in real time and dynamically assess the safety of the blade tip clearance.
[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of this application. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 A flowchart illustrating a dynamic tip clearance control method for an axial flow fan according to this application is shown.
[0020] Figure 2 A flowchart illustrating another method for controlling the dynamic tip clearance of an axial flow fan according to this application is shown.
[0021] Figure 3 A schematic diagram of the structure of an axial flow fan impeller and frame clearance design system according to this application is shown. Detailed Implementation
[0022] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0023] To enable those skilled in the art to better understand the solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0024] In the embodiments of this application, it should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.
[0025] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one…" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0026] In the description of the embodiments of this application, the words "example" or "for example" are used to indicate exemplification, illustration, or description. Any embodiment or design described as "example" or "for example" in the embodiments of this application is not to be construed as being more preferred or having more advantages than another embodiment or design. The use of the words "example" or "for example" is intended to present relative concepts in a clear manner.
[0027] In addition, "multiple" in the embodiments of this application refers to two or more. Therefore, "multiple" can also be understood as "at least two" in the embodiments of this application. "At least one" can be understood as one or more, such as one, two or more. For example, including at least one means including one, two or more and is not limited to which ones are included. For example, including at least one of A, B and C, then it can be A, B, C, A and B, A and C, B and C, or A and B and C.
[0028] It should be noted that in the embodiments of this application, "and / or" describes the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. In addition, the character " / ", unless otherwise specified, generally indicates that the associated objects before and after it are in an "or" relationship.
[0029] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.
[0030] This application provides a method for controlling the dynamic tip clearance of an axial flow fan, such as... Figure 1 As shown, the method includes: Step S1: Construct a multiphysics coupling analysis model of the impeller-frame system; the model includes at least: a radial deformation model of the impeller under centrifugal force and temperature load, a static manufacturing tolerance model of the impeller and frame, a coaxiality error model of the impeller support system, and a dynamic deformation model of the frame under vibration and temperature load; Step S2: Based on the multiphysics coupling analysis model, the maximum radial displacement ΔR_rotor of the impeller and the minimum radial displacement ΔR_housing of the inner circle of the frame are simulated and calculated to obtain the dynamic envelope range of the outer edge of the impeller and the dynamic envelope range of the inner edge of the frame under the design conditions. Step S3: Calculate the minimum safety clearance δ_min required between the impeller and the frame: δ_min = ΔR_rotor_max - ΔR_housing_min + K×σ_total, where ΔR_rotor_max is the maximum radial displacement of the outer edge of the impeller, ΔR_housing_min is the minimum radial displacement of the inner circle of the frame, σ_total is the total uncertainty of the system, and K is the safety factor; Step S4: Based on the calculated minimum safety clearance δ_min, guide the mechanical design of the wind turbine to ensure that the actual assembled blade tip clearance is greater than or equal to δ_min.
[0031] Traditional methods typically only consider machining tolerances or single thermal expansion. This application, for the first time, systematically models and couples five key influencing factors—centrifugal force, temperature field, mechanical vibration, manufacturing error, and assembly coaxiality—in a unified manner. This ensures that no risk factor that could lead to wear under real-world conditions is overlooked, fundamentally avoiding the design blind spot of "treating symptoms rather than the root cause," and achieving full coverage of factors affecting blade tip clearance.
[0032] In step S1, the radial deformation of the impeller under centrifugal force and temperature load is considered. The radial deformation model of the impeller under centrifugal force and temperature load specifically includes: establishing a finite element model of the impeller, applying centrifugal force load and temperature field distribution load corresponding to the operating speed, and calculating the total radial displacement field after the superposition of radial thermal expansion deformation and centrifugal deformation of the impeller from the static cold state to the working state through thermal-structural coupling analysis.
[0033] For example, in the finite element model of the impeller, a precise geometric model of the impeller (including blades and hub) is created using 3D CAD software (such as SolidWorks). The model is then imported into finite element analysis software (such as ANSYS Workbench), and a suitable element type (such as SOLID186) is selected for mesh generation, ensuring mesh refinement in key areas such as blade tips and hub edges. Under centrifugal load, a rotational speed of 1500 rpm (157.08 rad / s) around the axis is applied in the structural analysis module. Under temperature field load, computational fluid dynamics (CFD) analysis is performed first. Using CFD software such as Fluent, a fluid domain model containing the flow channel of the axial flow fan is established, setting inlet boundary conditions (e.g., ambient temperature 25°C, velocity inlet), outlet boundary conditions (pressure outlet), wall conditions, etc., and performing steady-state flow field-temperature field coupling calculations. The simulation yields a steady-state temperature distribution cloud map of each impeller component under design operating conditions. Figure 2 As shown, the impeller temperature field exhibits a non-uniform distribution, with higher temperatures at the blade tips and leading edges (approximately T_rotor_max = 65°C) and lower temperatures at the hub center (approximately 40°C). In the thermo-structural coupled solution, the temperature field obtained from CFD calculations is used as a volume load and mapped onto the finite element model of the impeller. Simultaneously, the centrifugal force load is maintained. A sequential coupled thermo-structural analysis is performed: first, the thermal strain caused by the temperature field is calculated, then the elastic strain caused by the centrifugal force is calculated, and finally, the total displacement field is obtained by superposition. The analysis results show that the maximum combined radial displacement of the impeller occurs at the blade tips, and its value consists of two parts: ΔR_centrifugal (centrifugal deformation) = 0.22 mm, and ΔR_thermal_rotor (thermal expansion) = 0.92 mm.
[0034] High-fidelity CAE simulations (FEA, CFD) can accurately calculate the specific deformation of the impeller under centrifugal force and non-uniform temperature fields (e.g., 0.22 mm + 0.92 mm in the example), rather than relying on coarse empirical coefficients. The deformation of the frame is also quantified through modal and random vibration analysis (e.g., 0.03 mm).
[0035] The temperature field distribution load is obtained based on computational fluid dynamics analysis, taking into account the combined effects of internal flow heat transfer and external ambient temperature.
[0036] In step S1, the static manufacturing tolerance model of the impeller and the frame includes: the radial runout tolerance zone δ_rotor_machining of the outer circle after impeller machining and the radial runout tolerance zone δ_housing_machining of the inner circle after frame machining.
[0037] This model quantifies the geometric uncertainties introduced by manufacturing precision during cold and static states. Based on the company's internal control standards and the GB / T 1800 series tolerance standards, the tolerances for the key dimensions of the fan are determined. For example, when the impeller rotates, the maximum radial offset of its outer circle profile relative to the theoretical axis is ±0.06 mm, and the radial runout tolerance zone of the impeller outer circle is δ_rotor_machining = 0.12 mm; the maximum radial offset of the frame inner circle profile relative to the theoretical center is ±0.05 mm, and the radial runout tolerance zone of the frame inner circle is δ_housing_machining = 0.10 mm.
[0038] In step S1, the coaxiality error model of the impeller support system includes: bearing clearance, bearing housing machining error, and dynamic coaxiality deviation δ_concentricity between the impeller center and the frame center caused by shaft deflection.
[0039] This model describes the dynamic offset between the impeller's rotation center and the theoretical center of the frame during operation. For example, regarding bearing clearance, a deep groove ball bearing with a radial clearance of 0.02 mm is selected; regarding bearing housing machining and installation errors, the concentricity error of the bearing housing bore is estimated at 0.03 mm; regarding shaft deflection, under the impeller's gravity and aerodynamic loads, the shaft undergoes slight bending, resulting in an impeller center offset of approximately 0.01 mm. Considering all these factors, the dynamic coaxiality deviation between the impeller and the frame is conservatively estimated as: δ_concentricity = 0.02 + 0.03 + 0.01 = 0.06 mm. This error will affect the envelope range of both the impeller and the frame.
[0040] In step S1, the dynamic deformation model of the frame under vibration and temperature loads includes: the radial deformation of the inner circle of the frame caused by the vibration excitation of the wind turbine operation and the temperature gradient, and the dynamic deformation amount δ_housing_vibration of the inner circle of the frame is evaluated by modal analysis and random vibration analysis.
[0041] For example, a finite element model of the wind turbine frame (casing) is established. Under temperature load, the temperature field of the inner wall surface of the frame obtained from CFD analysis, with an average temperature rise of approximately 20°C (ΔT_housing_avg = 20°C), is applied as the load. The average radial increment of the inner circle of the frame due to thermal expansion is calculated to be ΔR_thermal_housing_avg = 0.24 mm. Considering material inhomogeneity and constraint inhomogeneity, the minimum radial increment occurs at the local stiffener constraint, ΔR_thermal_housing_min = 0.20 mm. In vibration load analysis, modal analysis is performed. First, constrained modal analysis is conducted on the frame to obtain its first few natural frequencies. The analysis shows that the first natural frequency of the frame is 320 Hz, which is much higher than the impeller passing frequency (number of blades × rotational frequency, assumed to be 10 × 25Hz = 250Hz) and the rotational frequency (25Hz), avoiding the risk of resonance. Random vibration analysis is then performed on the frame based on the measured or estimated vibration power spectral density (PSD) of the wind turbine. The analysis results show that under the excitation of vibration, the inner circle of the frame will generate dynamic radial deformation oscillation, and its maximum amplitude (3σ value, that is, 99.73% probability of not exceeding this value) is δ_housing_vibration = 0.03 mm.
[0042] In step S2, the dynamic envelope range is calculated based on multiphysics coupling analysis. Through simulation calculations, the dynamic envelope range of the impeller outer edge (ΔR_rotor_max) and the dynamic envelope range of the frame inner edge (ΔR_housing_min) under the design conditions are determined. The formula for calculating the maximum radial displacement of the impeller, ΔR_rotor_max, is as follows: ΔR_rotor_max = ΔR_centrifugal + ΔR_thermal_rotor + δ_rotor_machining / 2 + δ_concentricity; Where ΔR_centrifugal is the maximum radial deformation of the impeller caused by centrifugal force, and ΔR_thermal_rotor is the maximum radial thermal expansion of the impeller caused by temperature.
[0043] For example, if all factors that cause the impeller outer edge to move outward are taken as maximum values and superimposed in the same direction, ΔR_rotor_max = ΔR_centrifugal + ΔR_thermal_rotor + (δ_rotor_machining / 2) + δ_concentricity = 0.22 mm + 0.92 mm + 0.06 mm + 0.06 mm = 1.26 mm. This means that, starting from the theoretical cold-state design position, the impeller outer edge may move outward by a maximum of 1.26 m during operation.
[0044] According to the formula, it provides clear guidance on how to synthesize the calculation results of each sub-model (ΔR_centrifugal, δ_rotor_machining, etc.) under the most dangerous working conditions, so as to obtain scientific and quantitative dynamic envelope boundaries (ΔR_rotor_max and ΔR_housing_min).
[0045] In step S2, the formula for calculating the minimum radial displacement ΔR_housing of the inner circle of the frame is: ΔR_housing_min = ΔR_thermal_housing - δ_housing_machining / 2 - δ_housing_vibration - δ_concentricity; Where ΔR_thermal_housing is the minimum radial thermal expansion of the inner circle of the frame caused by temperature.
[0046] For example, by summing the most unfavorable values of all factors that cause the inner edge of the frame to move inward (or counteract its outward expansion), ΔR_housing_min = ΔR_thermal_housing_min - (δ_housing_machining / 2) - δ_housing_vibration - δ_concentricity = 0.20 mm - 0.05 mm - 0.03 mm - 0.06 mm = 0.06 mm. This means that, calculated from the theoretical cold-state design inner diameter position, the minimum possible position of the inner edge of the frame during operation is only 0.06 mm outward, and even under the influence of certain factors, it may tend to contract inward relative to its theoretical thermal expansion center.
[0047] In step S3, based on the calculation results of step S2, the minimum safety clearance δ_min required between the impeller and the frame is determined: δ_min = ΔR_rotor_max - ΔR_housing_min + K×σ_total. Where σ_total is the total uncertainty of the system (a combination of uncertainties in manufacturing measurements, material parameters, boundary conditions, etc.), and K is the safety factor (usually 1.2-2.0).
[0048] The total uncertainty of the system, σ_total, is the root mean square value of each uncertainty, including manufacturing measurement uncertainty, material parameter uncertainty, and boundary condition uncertainty.
[0049] The safety factor K ranges from 1.2 to 2.0, and the specific value is determined based on the safety level of the wind turbine application.
[0050] For example, the net space between the two boundaries calculated by the dynamic envelope is the theoretical minimum clearance required to avoid interference: 1.26 mm - 0.06 mm = 1.20 mm. To address model uncertainties, a safety margin is introduced. In the evaluation of the total system uncertainty σ_total, the batch dispersion (±5%) of material properties (such as elastic modulus and coefficient of thermal expansion), CFD boundary condition approximation, measurement errors, etc., are comprehensively considered. Through Monte Carlo simulation or engineering experience evaluation, σ_total = 0.08 mm is selected. In the selection of the safety factor K, given the extremely high requirements of data centers for the reliability of fan operation, a higher safety factor K = 1.8 is selected. The final calculation of the minimum safety clearance δ_min is: δ_min = (ΔR_rotor_max - ΔR_housing_min) + K × σ_total = 1.20 mm + 1.8 × 0.08 mm = 1.344 mm. To ensure that no rubbing occurs under all expected operating conditions and uncertainties, the tip clearance must be no less than 1.344 mm.
[0051] In step S4, the calculated minimum safety clearance δ_min is used as the design input to guide the mechanical design of the wind turbine and ensure that the actual assembled blade tip clearance is greater than or equal to δ_min.
[0052] For example, the initial empirical clearance is 1.5 mm, which provides a relatively large safety margin (1.5 - 1.344 = 0.156 mm). The design team can optimize accordingly.
[0053] Option A (Performance Priority): Tighten the nominal design clearance to 1.35 mm. This is 0.15 mm less than the original design, and is expected to reduce tip leakage loss and improve fan efficiency by about 1-2%, while still within the safety margin (1.35 > 1.344).
[0054] Option B (Cost / Tolerance Optimization): Maintain the 1.4 mm design clearance, but use the calculation results of δ_min to back-calculate and relax non-critical tolerances. For example, the dimensional tolerances of non-mating surfaces of the frame can be relaxed by one grade, thereby reducing machining costs. This embodies the tolerance allocation concept described in claim 14.
[0055] The manufacturing process documents and assembly instructions clearly define 1.35 mm (or 1.4 mm) as a critical control dimension, and specify its measurement method and inspection frequency to ensure that the actual cold assembly clearance δ_actual ≥ 1.35 mm for each fan leaving the factory.
[0056] Based on the above precise calculations, under the premise of ensuring safety, the excessive safety margin left by traditional experience (such as the original 1.5mm in the embodiment) can be scientifically reduced (optimized to 1.35mm), directly improving the aerodynamic efficiency of the fan, reducing leakage loss and noise.
[0057] like Figure 2 As shown, the method further includes step S5: arranging temperature and vibration sensors at key locations of the wind turbine to monitor the temperature and vibration data of the impeller and frame in real time, and dynamically correcting the minimum safety clearance δ_min.
[0058] In step S5, when the actual gap between the impeller and the frame is detected to be close to δ_min, the fan control system automatically adjusts the operating parameters or issues a warning signal.
[0059] For example, a non-contact infrared temperature sensor is installed on a stationary component near the impeller hub to monitor the average impeller temperature in real time; a vibration acceleration sensor is installed near the frame bearing housing to monitor the operating vibration level. A simplified real-time clearance prediction model is built into the wind turbine control system. This model uses the monitored temperature and vibration data as input, combined with the deformation laws in S1 (such as the coefficient of thermal expansion and vibration response transfer function), to estimate the current dynamic tip clearance δ_current in real time. Early warning and intervention are implemented, with a warning threshold δ_warning = 1.4 mm and an emergency threshold δ_alarm = 1.36 mm. When δ_current ≤ δ_warning, the control system issues a warning signal on the monitoring interface to alert maintenance personnel; when δ_current ≤ δ_alarm, a high risk is identified. The control system can automatically execute intervention strategies, such as gradually reducing the wind turbine speed to reduce centrifugal deformation and heat load, increasing the clearance until the dangerous state is over. Simultaneously, an audible and visual alarm is triggered.
[0060] This ensures that the final design clearance is neither overly conservative nor overly aggressive. It provides a quantifiable and traceable safety guarantee, proving that the wind turbine remains safe even under the worst operating conditions with the greatest uncertainty, greatly enhancing the product's reliability and market competitiveness.
[0061] Based on the above analysis, the following optimization measures can be further taken: For example, material optimization, using carbon fiber composite materials instead of aluminum alloy for the impeller to significantly reduce thermal deformation; structural optimization, employing a symmetrical reinforcing rib design for the frame to improve rigidity and reduce vibration deformation; tolerance optimization, reallocating manufacturing tolerances to balance processing costs and performance; and coating application, applying a wear-resistant coating to the inner wall of the frame to allow for a smaller initial clearance design. Using the method of this application, the minimum tip clearance can be scientifically determined while ensuring operational safety, achieving the optimal design of the fan performance.
[0062] Analysis shows that thermal deformation accounts for the largest proportion. If the impeller material is changed from aluminum alloy to carbon fiber composite material, its coefficient of thermal expansion can be reduced by an order of magnitude. Assuming that ΔR_thermal_rotor decreases from 0.92 mm to 0.10 mm, ΔR_rotor_max can be significantly reduced, which in turn significantly reduces the calculated value of δ_min, allowing for smaller clearances and greater potential for performance improvement.
[0063] The frame vibration deformation δ_housing_vibration mainly stems from insufficient local stiffness. Optimizing the arrangement of symmetrical stiffeners on the outer wall of the frame, as verified by finite element analysis, can raise its first natural frequency to above 400Hz and reduce δ_housing_vibration to 0.015 mm, thus contributing a smaller δ_min.
[0064] During the design phase, a 0.15 mm thick wear-resistant coating (such as a ceramic-based coating) is planned to be sprayed onto the inner wall of the frame. When calculating δ_min, this coating thickness can be taken into account as an additional safety buffer, meaning the actual gap in the metal frame can be smaller. Even in the event of extreme transient impact wear, the coating will wear first, providing protection for core components and buying time for the control system to intervene.
[0065] This application also provides a design system 300 for the clearance between the impeller and the frame of an axial flow fan, such as... Figure 3 As shown, the system includes: a multiphysics coupling analysis module 310, used to execute steps S1-S3 in any of the methods described above; a clearance optimization design module 320, which optimizes the structural design parameters of the impeller and frame based on the calculated minimum safe clearance δ_min; and a real-time monitoring module 330, used to monitor the wind turbine's operating status in real time and dynamically evaluate the tip clearance safety. The system also includes a tolerance allocation module, which uses the δ_min calculation results to deduce a reasonable allocation scheme for the manufacturing tolerances of the impeller and the frame.
[0066] This application also provides an axial flow fan, which uses the method described above to determine the minimum safe clearance between the impeller and the frame, and manufactures and assembles the fan according to this clearance. In this axial flow fan, the actual assembly clearance between the impeller and the frame satisfies: δ_actual ≥ δ_min, where δ_min is the minimum safe clearance calculated using the above method. The impeller is made of a composite material or titanium alloy with a low coefficient of thermal expansion to reduce radial deformation caused by temperature. A wear-resistant coating is applied to the inner side of the frame, and the thickness of the wear-resistant coating is included in the calculation of the minimum safe clearance δ_min. The frame structure adopts a symmetrical stiffening rib design to improve frame rigidity and reduce vibration deformation.
[0067] This application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of any of the methods described above.
[0068] Compared with the prior art, the present invention has the following significant advantages: 1. Comprehensiveness: For the first time, the system systematically considers the coupled effects of multiple physical field factors such as centrifugal force, temperature, vibration, manufacturing tolerance, and coaxiality error.
[0069] 2. Accuracy: The specific impact of each factor is quantitatively assessed through multidisciplinary simulation tools, avoiding the blindness and conservatism of empirical design.
[0070] 3. Safety: Safety factor and uncertainty analysis are introduced to ensure that the impeller and frame will not interfere even under the worst working conditions.
[0071] 4. Economic efficiency: Minimizing the tip clearance while ensuring safety improves the efficiency and performance of the fan, while reducing manufacturing costs through tolerance allocation optimization.
[0072] 5. Adaptability: The method is applicable to the design of axial flow fans with different materials, structures and working conditions, and has wide applicability.
[0073] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Although this application has disclosed preferred embodiments as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.
Claims
1. A method for controlling the dynamic tip clearance of an axial flow fan, characterized in that, Includes the following steps: Step S1: Construct a multiphysics coupling analysis model of the impeller-frame system; the model includes at least: a radial deformation model of the impeller under centrifugal force and temperature load, a static manufacturing tolerance model of the impeller and frame, a coaxiality error model of the impeller support system, and a dynamic deformation model of the frame under vibration and temperature load; Step S2: Based on the multiphysics coupling analysis model, the maximum radial displacement ΔR_rotor of the impeller and the minimum radial displacement ΔR_housing of the inner circle of the frame are simulated and calculated to obtain the dynamic envelope range of the outer edge of the impeller and the dynamic envelope range of the inner edge of the frame under the design conditions. Step S3: Calculate the minimum safety clearance δ_min required between the impeller and the frame: δ_min = ΔR_rotor_max -ΔR_housing_min + K×σ_total, where ΔR_rotor_max is the maximum radial displacement of the outer edge of the impeller, ΔR_housing_min is the minimum radial displacement of the inner circle of the frame, σ_total is the total uncertainty of the system, and K is the safety factor; Step S4: Based on the calculated minimum safety clearance δ_min, guide the mechanical design of the wind turbine to ensure that the actual assembled blade tip clearance is greater than or equal to δ_min.
2. The dynamic tip clearance control method for axial flow fans according to claim 1, characterized in that, In step S1, the radial deformation model of the impeller under centrifugal force and temperature load specifically includes: A finite element model of the impeller is established, and centrifugal force load and temperature field distribution load corresponding to the operating speed are applied. The total radial displacement field after the superposition of radial thermal expansion deformation and centrifugal deformation of the impeller from the static cold state to the working state is calculated through thermal-structural coupling analysis.
3. The dynamic tip clearance control method for axial flow fans according to claim 2, characterized in that, The temperature field distribution load is obtained based on computational fluid dynamics analysis, taking into account the combined effects of internal flow heat transfer and external ambient temperature.
4. The method for controlling the dynamic tip clearance of an axial flow fan according to claim 1, characterized in that, In step S1, the static manufacturing tolerance model of the impeller and frame includes: The radial runout tolerance zone of the outer circle of the impeller after machining, δ_rotor_machining, and the radial runout tolerance zone of the inner circle of the frame after machining, δ_housing_machining.
5. The dynamic tip clearance control method for axial flow fans according to claim 1, characterized in that, In step S1, the coaxiality error model of the impeller support system includes: The dynamic coaxiality deviation δ_concentricity between the impeller center and the frame center is caused by bearing clearance, bearing housing machining error, and shaft deflection.
6. The method for controlling the dynamic tip clearance of an axial flow fan according to claim 1, characterized in that, In step S1, the dynamic deformation model of the frame under vibration and temperature loads includes: The frame is subjected to vibration excitation from the wind turbine and temperature gradient, resulting in radial deformation of the inner circle of the frame. The dynamic deformation δ_housing_vibration of the inner circle of the frame is evaluated through modal analysis and random vibration analysis.
7. The method for controlling the dynamic tip clearance of an axial flow fan according to claim 1, characterized in that, In step S2, the formula for calculating the maximum radial displacement ΔR_rotor_max of the impeller is: ΔR_rotor_max = ΔR_centrifugal + ΔR_thermal_rotor + δ_rotor_machining / 2+ δ_concentricity; Where ΔR_centrifugal is the maximum radial deformation of the impeller caused by centrifugal force, and ΔR_thermal_rotor is the maximum radial thermal expansion of the impeller caused by temperature.
8. The method for controlling the dynamic tip clearance of an axial flow fan according to claim 1, characterized in that, In step S2, the formula for calculating the minimum radial displacement ΔR_housing of the inner circle of the frame is: ΔR_housing_min = ΔR_thermal_housing - δ_housing_machining / 2 - δ_housing_vibration - δ_concentricity; Where ΔR_thermal_housing is the minimum radial thermal expansion of the inner circle of the frame caused by temperature.
9. The method according to claim 1, characterized in that, It also includes step S5: placing temperature and vibration sensors at key locations of the wind turbine to monitor the temperature and vibration data of the impeller and frame in real time, and dynamically correcting the minimum safety clearance δ_min.
10. A system for designing the clearance between the impeller and frame of an axial flow fan, characterized in that, include: Multiphysics coupling analysis module, used to execute steps S1-S3 of the method according to any one of claims 1-9; The clearance optimization design module optimizes the structural design parameters of the impeller and frame based on the calculated minimum safe clearance δ_min. The real-time monitoring module is used to monitor the operating status of the wind turbine in real time and dynamically assess the safety of the blade tip clearance.