A molding method for axial flow fan blade structure of nuclear power plant

Abstract

This invention belongs to the field of axial flow fan technology, specifically relating to a method for designing the blade structure of an axial flow fan for nuclear power plants. The method involves selecting a basic model, scaling it up by an amplification factor x to obtain the target model, and introducing a Reynolds number correction factor K. Re And through the Reynolds number correction factor K Re Adjust the blade chord length of the target aircraft model to obtain the blade chord length parameter C. 新 ; through the Reynolds number correction factor K Re Adjust the blade installation angle of the target aircraft model to obtain the blade installation angle parameter β. 新 The blade is divided into n equal regions from the blade root to the blade tip, and an installation angle adjustment rule is established. The blade thickness of the target model is optimized by gradient to obtain the thickness distribution function t(r) along the spanwise direction of the blade. The blade structure of the target model is completed. This method can optimize the efficiency and service life of the scaled-up wind turbine and provide technical guidance for how to develop wind turbines of different sizes.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of axial flow fans, and particularly relates to a modeling method for an axial flow fan blade structure of a nuclear power station. BACKGROUND

[0002] The axial flow fan is widely applied to a ventilation and cooling system in a nuclear power station, and its core performance depends on the matching design of an impeller size and airflow. In the prior art, a model amplification method is often used for quickly developing fans of different sizes, but simple equal proportion scaling will cause problems such as Reynolds number difference and blade boundary layer separation. The fan obtained after equal proportion scaling has low actual working efficiency due to insufficient aerodynamic performance matching, and is difficult to meet the use requirements. At present, some people have conceived to optimize the working efficiency of the fan by adjusting the blade installation angle, but have not mentioned how to determine the angle to be adjusted in a certain rule or calculation manner. In actual use, it is found that the fan obtained after equal proportion scaling also has problems of stress concentration or fatigue fracture of the blade, which affects the service life of the fan and is difficult to meet the high requirements of the nuclear power station on safe and reliable operation. SUMMARY

[0003] In order to solve the problems in the prior art, the application provides a modeling method for an axial flow fan blade structure of a nuclear power station, which can optimize the efficiency and service life of the amplified fan, provides technical guidance for how to develop fans of different sizes, and meets the requirements of the nuclear power station on safe and reliable operation.

[0004] The specific technical scheme adopted by the application is:

[0005] A modeling method for an axial flow fan blade structure of a nuclear power station, which is characterized by comprising the following steps:

[0006] S1, selecting a basic model, amplifying the basic model with an impeller diameter D0 by a magnification factor x to obtain a target model with an impeller diameter D1;

[0007] S2, introducing a Reynolds number correction factor K Re , and adjusting the blade chord length of the target model by the Reynolds number correction factor K Re to obtain a blade chord length parameter C 新 ;

[0008] S3, adjusting the blade installation angle of the target model by the Reynolds number correction factor K Re to obtain a blade installation angle parameter β 新 , and equally dividing the blade from a blade root to a blade tip into n regions to establish an installation angle adjustment rule β(r);

[0009] S4, gradient optimizing the blade thickness of the target model to obtain a thickness distribution function t(r) of the blade along the span direction;

[0010] S5、according to the blade chord parameter C 新 , the blade installation angle parameter β 新 , the installation angle adjustment rule β(r) and the thickness distribution function t(r) complete the blade structure modeling of the target model.

[0011] The calculation formula of the Reynolds number correction factor is,

[0012] ,

[0013] Where Re 原 is the Reynolds number of the base model, and Re 新 is the Reynolds number of the target model.

[0014] The blade chord parameter C

[0015] C 新 =C 原 ×K Re ,

[0016] Where C 原 is the blade chord of the base model.

[0017] The blade installation angle parameter β

[0018] β 新 =β 原 +Δβ×(1-K Re ),

[0019] Where β 原 is the blade installation angle of the base model, and Δβ is the installation angle compensation.

[0020] The installation angle compensation Δβ

[0021] ,

[0022] Where n 新 is the impeller speed of the target fan, n 原 is the impeller speed of the base model, Q 新 is the air volume of the target fan, Q 原 is the air volume of the base model, the value range of k is 0.5-2.0, and the value range of m is 0.1-0.5.

[0023] In step S3, the blade is equally divided into n regions from the blade root to the blade tip, R is the impeller radius, r is the radius of a certain region, and the installation angle adjustment rule of each region is

[0024] ,

[0025] Where β 根The blade root installation angle of the target model, β 根 The blade root installation angle of the target model, β 尖 The blade tip installation angle of the target model, β 尖 The blade tip installation angle of the target model, β

[0026] The blade tip installation angle of the target model, β

[0027] ,

[0028] Wherein, t 根 The blade root thickness of the target model impeller, t 尖 The blade tip thickness of the target model impeller, t 根 =(1.1-1.4)t 原 ; t 尖 = (0.8-0.96)t 原 , t 原 The blade thickness of the base model at the corresponding radial position.

[0029] The beneficial effects of the present application are:

[0030] The present application improves the aerodynamic efficiency of large-size fans, especially the energy conversion rate under high pressure difference conditions, by scaling up the size of the base model in proportion, dynamically adjusting the blade installation angle and designing the gradient after the blade, enhances the structural strength of the blade, avoids the risk of stress concentration or fatigue fracture caused by scaling up the model, and also expands the applicable working condition range to adapt to different industrial scenarios with different air volume and pressure requirements.

[0031] The method of the present application provides technical guidance on how to quickly develop fans of different sizes, enabling staff to quickly obtain the blade structure modeling of the scaled-up fan, engineers do not need to repeatedly calculate, and the development cycle of large-size fans is shortened, the design risk is reduced, and reliable technical support is provided for the large-scale and precise development of nuclear power station axial flow fans. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The front view of the impeller;

[0033] Figure 2 The front view of the impeller;

[0034] Figure 3 The blade wrap angle nonlinear distribution diagram;

[0035] Figure 4 The blade installation angle nonlinear distribution diagram;

[0036] Figure 5 The blade thickness gradient distribution diagram;

[0037] In the drawing, 1, hub, 2, blade. DETAILED DESCRIPTION

[0038] The application will be further described below in combination with the drawing and specific embodiments:

[0039] In specific embodiments, the application relates to a modeling method for the blade structure of an axial flow fan in a nuclear power plant, which is characterized by comprising the following steps:

[0040] S1, selecting a basic model, enlarging the basic model with a wheel diameter D0 by a coefficient x to obtain a target model with a wheel diameter D1, in this embodiment, the basic model is No. 12 model which is enlarged to No. 13.3 target model by x proportion, the wheel diameter D0 of the basic model is 1.2 m, and the wheel diameter D1 of the target model is 1.33 m; then x is D1 / D0=1.108.

[0041] S2, introducing a Reynolds number correction factor K Re The calculation formula of the Reynolds number correction factor K Re is

[0042] ,

[0043] The blade chord length parameter C

[0044] of the target model is obtained by adjusting the blade chord length of the target model through the Reynolds number correction factor 新 =C 原 ×K Re ,

[0045] wherein Re 原 is the Reynolds number of the basic model,

[0046] Re 原 =ρV0D0 / μ;

[0047] Re 新 is the Reynolds number of the target model,

[0048] Re 新 =ρV1D1 / μ;

[0049] C 原 is the blade chord length of the basic model;

[0050] The chord length is a core parameter affecting the air flow capturing capacity and boundary layer development of the blade, and by adjusting the chord length, the influence of the Reynolds number change on the boundary layer can be compensated to ensure that the aerodynamic efficiency of the target model matches that of the basic model.

[0051] S3, the blade installation angle parameter

[0052] of the target model is obtained by adjusting the blade installation angle of the target model through the Reynolds number correction factor 新= beta 原 + delta beta x (1 - k Re ),

[0053] wherein beta 原 is the blade installation angle of the base model, and delta beta is the installation angle compensation amount;

[0054] The installation angle compensation amount delta beta is usually determined based on the impeller rotating speed (n) and the operating condition (such as the air volume Q) and is dynamically determined in the following manner:

[0055] A rotating speed-condition-delta beta mapping table or an empirical formula is established based on the test data or CFD simulation results of the base model;

[0056] It can be preliminarily estimated by the following formula:

[0057]

[0058] wherein n 新 is the impeller rotating speed of the target fan, n 原 is the impeller rotating speed of the base model, Q 新 is the air volume of the target fan, Q 原 is the air volume of the base model, and the value range of k is 0.5-2.0, and the value range of m is 0.1-0.5.

[0059] The blade installation angle parameter beta 新 is the global installation angle adjustment reference value of the blade and is used to compensate the aerodynamic performance deviation caused by the change of the Reynolds number.

[0060] The installation angle directly determines the angle of attack of the airflow entering the blade, and the installation angle is increased by the Reynolds number correction factor, so that the airflow separation is reduced, and the turning efficiency of the blade to the airflow is ensured.

[0061] The blade is equally divided into 5 regions along the radial direction from the blade root to the blade tip, and r / R is 0.2, 0.4, 0.6, 0.8 and 1 respectively, wherein R is the impeller radius, and r is the radius of a certain region;

[0062] An installation angle adjustment rule is established, and the installation angle adjustment rule of each region (r / R) is

[0063] ,

[0064] wherein beta 根 is the blade root installation angle of the target model, the difference between beta 根 and the blade root installation angle of the base model is 2°-3°, the anti-separation ability is enhanced, beta 尖 is the blade tip installation angle of the target model, the difference between the blade tip installation angle of the base model and beta 尖 is 1°-1.5°, and the wake vortex shedding is inhibited; and specific beta 根The difference between the blade root installation angle of the basic model and the difference between the blade tip installation angle of the basic model and β 尖 The difference can be further verified and determined through CFD simulation and test.

[0065] The blades are adjusted globally, and then secondarily optimized according to the radial position, so as to further optimize the aerodynamic load and flow separation at different radial positions, so that the airflow of the impeller at the full radial position is in the high-efficiency working interval, the working condition requirements of large flow and high pressure of the nuclear power station fan are met, and the stability of the operation efficiency is further improved; and the blade structure strength can be effectively enhanced, and stress concentration can be avoided.

[0066] S4, gradient optimization is performed on the blade thickness of the target model to obtain a thickness distribution function of the blade along the span direction (radial direction)

[0067] ,

[0068] Where t 根 is the blade root thickness of the impeller of the target model, t 尖 is the blade tip thickness of the impeller of the target model; in this embodiment, the magnification is 1.108, t 根 =1.3t 原 , t 尖 =0.9t 原 , the thickened blade root can significantly improve the bending strength and avoid stress concentration, and the thinned blade tip can make the airflow disturbance at the blade tip more smooth, reduce the inertial load, and reduce noise and vortex loss; t 原 is the blade thickness of the basic model at the corresponding radial position (r / R).

[0069] S5, according to the blade chord length parameter C 新 , the blade installation angle parameter β 新 , the installation angle adjustment rule β (r) and the thickness distribution function t (r), wherein β (r) and β 新 are the main variable parameters, and other parameters such as C 新 , t (r) and the like can also be fine-tuned, CFD (computational fluid dynamics) and FEA (finite element analysis) coupling simulation is adopted, the aerodynamic efficiency η, the noise level L p , and the maximum stress σ max of the basic model are taken as the optimization objectives, the optimal parameter combination is determined through genetic algorithm iteration for 20-30 rounds, the blade structure modeling of the target model is completed, and the structure of the impeller of the target model is as shown in Figure 1 , Figure 2 If the basic model does not have corresponding aerodynamic efficiency η, noise level L p , and maximum stress σmax data, the industry standards or design requirements can be referred to.

[0070] The roles of each optimization objective are as follows:

[0071] Pneumatic efficiency η (maximization): Ensure the energy conversion rate of the fan under high pressure difference conditions;

[0072] Maximum stress σ max (minimization): Avoid blade stress concentration or fatigue fracture, improve service life;

[0073] Noise level L p (minimization): Reduce fan operation noise to meet the environmental requirements of nuclear power plants.

[0074] The specific steps are as follows:

[0075] S5-1, obtain parameters and set genetic algorithm

[0076] Obtain parameters:

[0077] Since the value range of k is 0.5-2.0 and the value range of m is 0.1-0.5, based on this, set a reasonable search range for Δβ, Δβ as the main variable; Obtain blade chord length parameters C 新 , thickness distribution function t(r) and other parameters from the basic model.

[0078] Genetic algorithm settings:

[0079] Population size: According to the complexity of the problem, usually set 50-100 individuals (each individual represents a Δβ value);

[0080] Encode Δβ as a binary string or real number;

[0081] Randomly generate an initial population within the search range of Δβ.

[0082] S5-2, CFD / FEA coupling simulation evaluates each individual

[0083] For each individual in the population (that is, each Δβ value), perform the following coupling simulation:

[0084] S5-2a, geometric model construction:

[0085] Calculate β 新 = β 原 + Δβ × (1 - K Re ) using the current Δβ.

[0086] Combine the blade chord length C 新 , thickness distribution function t(r) and installation angle adjustment rule β(r) to generate a three-dimensional geometric model of the target model blade (such as through CAD software).

[0087] S5-2b, CFD simulation (aerodynamic performance analysis):

[0088] Structured or unstructured meshing for blade passage domain, ensuring near-wall grid refinement to capture boundary layer;

[0089] Setting inlet wind speed, pressure, turbulence model (e.g. k-ε or SST model), based on target model's operating conditions (air volume Q 新 , rotational speed n 新 );

[0090] Using CFD software ANSYS Fluent to simulate the flow field, calculating:

[0091] Aerodynamic efficiency η: calculated based on input power and output wind pressure / air volume.

[0092] Noise level L p : estimated by acoustic analogy models (e.g. FW-H equation) to estimate far-field noise;

[0093] Obtaining blade surface pressure distribution, velocity field, aerodynamic efficiency η and noise level L p .

[0094] S5-2c, FEA simulation (structural strength analysis):

[0095] Importing the pressure distribution obtained from CFD calculation as aerodynamic load into the FEA model for load mapping;

[0096] Solid meshing for blade structure, focusing on blade root and tip regions;

[0097] Fixing the hub connection, applying centrifugal force (based on rotational speed n 新 ) and aerodynamic load;

[0098] Using FEA software ANSYS Mechanical for static force analysis, calculating:

[0099] Stress distribution: especially the maximum stress σ max (which is usually located in the blade root or stress concentration area);

[0100] Evaluating the safety of the blade.

[0101] S5-2d, objective function calculation:

[0102] Extracting η, σ max and L p values from simulation;

[0103] Constructing a comprehensive objective function (fitness function), for example using the weighted sum method:

[0104] Fitness = w1·η− w2·σ max − w3·L p

[0105] where the weight coefficients w1, w2, w3 are adjusted according to design requirements (e.g. nuclear power plants emphasize safety more, giving σ max a higher weight).

[0106] S5-3, Genetic Algorithm Optimization Loop

[0107] S5-3a, Fitness Evaluation: Calculate the fitness value of each individual in the population (based on the results of Step 2).

[0108] S5-3b, Selection Operation: Use methods such as roulette wheel selection, tournament selection, etc., to select individuals with high fitness as parents.

[0109] S5-3c, Crossover Operation: Perform crossover (such as single-point crossover) on the selected parent individuals to generate offspring individuals. The crossover probability is usually set to 0.7-0.9.

[0110] S5-3d, Mutation Operation: Randomly mutate (such as small changes Δβ value) the offspring individuals to maintain population diversity. The mutation probability is usually set to 0.01-0.1.

[0111] S5-3e, New Generation Population: Replace the old population with the offspring individuals to form a new generation.

[0112] S5-3f, Iteration Check: Repeat Steps S5-2 and S5-3 for 20-30 iterations until the fitness converges (change less than threshold) or reaches the maximum number of iterations.

[0113] S5-4: Optimal Solution Determination and Verification

[0114] Output Optimal Δβ: Select the individual with the highest fitness from the final population as the optimal installation angle compensation Δβ.

[0115] Verification: Perform final CFD / FEA simulation on the blade shape corresponding to the optimal Δβ to confirm that the efficiency is improved by ≥8% and the maximum stress is reduced by ≥15%.

[0116] As Figures 3-5 , the blade installation angle refers to the angle between the blade airfoil chord line and the rotation plane, mainly affecting the angle of attack; the blade wrap angle refers to the overall bending of the blade in the rotation direction, mainly affecting the shape of the flow passage and the airflow path; the blade thickness refers to the normal distance of the blade airfoil at a specific radial position (r / R) perpendicular to the arc line, i.e. the vertical thickness of the blade airfoil profile line, and the thickness distribution affects the shape of the flow passage and the diffuser degree, thereby affecting the airflow separation, efficiency and stable working range, and the thickness is the most critical factor to resist centrifugal force and aerodynamic load, directly affecting the stress level and life of the blade.

[0117] Through fan performance test, the performance of the fan directly enlarged in equal proportion and the fan obtained through the method of the application is compared, and the fan obtained through the method of the application has an efficiency increase of greater than or equal to 8% and a maximum stress decrease of greater than or equal to 15%.

Claims

1. A method for designing the blade structure of an axial flow fan in a nuclear power plant, characterized in that, Includes the following steps: S1. Select the base model and multiply the base model with the magnification factor by the impeller diameter D0 to obtain the target model with impeller diameter D1. S2. Introducing the Reynolds number correction factor K Re And through the Reynolds number correction factor K Re Adjust the blade chord length of the target aircraft model to obtain the blade chord length parameter C. 新 ; S3, via Reynolds number correction factor K Re Adjust the blade installation angle of the target aircraft model to obtain the blade installation angle parameter β. 新 And divide the leaf blade into n equal regions from leaf root to leaf tip, and establish the installation angle adjustment rule β(r); S4. Perform gradient optimization on the blade thickness of the target model to obtain the blade thickness distribution function t(r) along the spanwise direction. S5. Based on the blade chord length parameter C 新 Blade installation angle parameter β 新 The blade structure design of the target aircraft model is completed by using the installation angle adjustment rule β(r) and the thickness distribution function t(r).

2. The method for designing the blade structure of an axial flow fan in a nuclear power plant according to claim 1, characterized in that: The formula for calculating the Reynolds number correction factor is as follows: ， Where Re 原 Reynolds number of the basic model, Re 新 The Reynolds number of the target aircraft model.

3. The method for designing the blade structure of an axial flow fan in a nuclear power plant according to claim 1, characterized in that: The blade chord length parameters of the target model C 新 =C 原 ×K Re , Where C 原 The blade chord length of the basic model.

4. The method for designing the blade structure of an axial flow fan in a nuclear power plant according to claim 1, characterized in that: The blade installation angle parameters of the target model b 新 =b 原 +Δβ×(1-K Re ) Where, β 原 The blade installation angle is the basic model, and Δβ is the installation angle compensation amount.

5. The method for designing the blade structure of an axial flow fan in a nuclear power plant according to claim 4, characterized in that: The installation angle compensation amount ， Where, n 新 Let n be the impeller speed of the target fan. 原 The impeller speed of the basic model, Q 新 Q represents the air volume of the target fan. 原 For the basic model's airflow, the value of k ranges from 0.5 to 2.0, and the value of m ranges from 0.1 to 0.

5.

6. The method for designing the blade structure of an axial flow fan in a nuclear power plant according to claim 1, characterized in that: In step S3, the blade is divided into n equal regions from the blade root to the blade tip, where R is the impeller radius and r is the radius of a certain region. The installation angle adjustment rules for each region are as follows. ， Where, β 根 β is the blade root mounting angle for the target aircraft model. 根 The blade root installation angle is greater than that of the basic model, β 尖 For the blade tip installation angle of the target aircraft model, β 尖 Smaller than the blade tip installation angle of the basic model.

7. The method for designing the blade structure of an axial flow fan in a nuclear power plant according to claim 1, characterized in that: The blade thickness distribution function along the span of the target aircraft model. ， Among them, t 根 For the impeller root thickness of the target model, t 尖 For the tip thickness of the impeller of the target model, t 根 = (1.1-1.4)t 原 ;t 尖 = (0.8-0.96)t 原 , t 原 This refers to the blade thickness at the corresponding radial position of the base model.

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