High-precision wind tunnel nozzle profile design method based on spinning process coupling

Abstract

The invention discloses a high-precision wind tunnel nozzle profile design method, and belongs to the technical field of wind tunnel nozzle profile design based on a computer. The problems that in the prior art, a traditional wind tunnel nozzle molded surface design method is poor in process feasibility, and the number of molded surface correction iterations is large are solved. According to the method, modeling software is adopted to construct an initial profile mathematical model, geometric constraints are integrated, a wall thickness initial distribution model is established, and wall thickness distribution is optimized; s2, quantizing an objective function according to the constraint and the model parameters in the step S1, optimizing the objective function, and refining the constraint to obtain refined constraint conditions; and according to the wall thickness initial distribution model and the wall thickness parameters, design software is combined with the refined constraint conditions to carry out parametric modeling, a process feedback mechanism is constructed to carry out correction compensation on initial molded surface modeling, and high-precision wind tunnel nozzle molded surface design is completed. The pneumatic performance and the material utilization rate are effectively improved, and the method can be applied to high-precision pneumatic verification tests.

Description

Technical Field

[0001] This invention relates to a high-precision wind tunnel nozzle profile design method, and more particularly to a high-precision wind tunnel nozzle profile design method based on spinning process coupling, belonging to the field of computer-based wind tunnel nozzle profile design technology. Background Technology

[0002] In the field of defense science and technology industry, wind tunnel testing serves as a "ground benchmark" for verifying aerodynamic characteristics in major projects such as hypersonic vehicles and next-generation aero engines. The reliability of the data directly determines the engineering accuracy of equipment performance. Traditional wind tunnel nozzles mostly adopt segmented welding or integral forging processes. Segmented welding leads to geometric accuracy deviations at the joints (typical error ≥0.5mm), causing airflow disturbances; integral forging has a material utilization rate of less than 40% when machining large billets, and heat treatment is prone to residual stress deformation; complex surfaces are difficult to achieve high surface quality (Ra≤1.6μm) through machining. Traditional nozzle profile design only considers aerodynamic performance requirements (such as the characteristic line method and MOC method) and is not coupled with manufacturing process constraints, which leads to the following problems: (1) The theoretical profile curvature change point (such as the throat transition area) exceeds the limit of the spinning forming process (wrinkling occurs when the minimum curvature radius R < 0.3m); (2) The design-manufacturing iteration cycle is long, and the deviation between the measured profile and the theoretical value is ≥ 0.2mm; (3) The wall thickness distribution does not consider the flow characteristics of the spinning material, and the local thinning rate is > 20%.

[0003] In summary, a high-precision wind tunnel nozzle profile design method based on spinning process coupling is needed. Summary of the Invention

[0004] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0005] In view of this, in order to solve the problems of poor process feasibility and numerous iterations of profile correction in the traditional wind tunnel nozzle profile design method in the prior art, the present invention provides a high-precision wind tunnel nozzle profile design method based on spinning process coupling.

[0006] The technical solution is as follows: A high-precision wind tunnel nozzle profile design method based on spinning process coupling, comprising the following steps:

[0007] S1. Parametric modeling of the profile is performed using modeling software, that is, an initial mathematical model of the profile is constructed, geometric constraints are integrated, an initial wall thickness distribution model is established, and the wall thickness distribution is optimized.

[0008] S2. Based on the constraints of step S1 and the parameters of the initial surface mathematical model, quantify the objective function, optimize the objective function, refine the constraints, and obtain the refined constraint conditions.

[0009] S3. Based on the initial wall thickness distribution model and wall thickness parameters, parametric modeling is performed using design software combined with refined constraints. A process feedback mechanism is constructed to correct and compensate for the preliminary surface modeling, thus completing the high-precision wind tunnel nozzle surface design.

[0010] Furthermore, step S1 includes the following steps:

[0011] S11. Based on aerodynamic performance, construct an initial surface mathematical model including the inlet section, throat, and expansion section according to the method of characteristics;

[0012] In S11, the initial surface mathematical model is established as follows:

[0013] The axial Mach number distribution function is defined using the improved Sivells method of characteristics;

[0014] The axial Mach number distribution function is expressed as:

[0015]

[0016] in, The initial Mach number at the entrance. Here, is the amplitude of the Mach number change, and k is the kurtosis parameter. For feature location parameters, This refers to the axial position of the nozzle;

[0017] Establish the correlation between nozzle length and surface curvature, and complete the initial surface mathematical model construction;

[0018] Relationship between nozzle length and surface curvature Represented as:

[0019]

[0020] in, Let x be the cross-sectional area at the axial position x of the nozzle. This is the critical cross-sectional area. , These are the first and second derivatives of the cross-sectional area with respect to the axial coordinates, respectively.

[0021] S12. Integrated geometric constraints, namely, setting embedded spinning process geometric limit constraints and surface slope change rate to achieve curvature continuity;

[0022] In S12, the geometric limit constraint of the embedded spinning process is expressed as: minimum radius of curvature. ; Rate of change of slope of profile ; NURBS curves are used for parametric discretization, control points are defined, and curvature continuity is achieved through weight adjustment;

[0023] S13. Based on the flow characteristics of spun materials, establish an initial wall thickness distribution model and optimize the wall thickness distribution;

[0024] In S13, the initial wall thickness distribution model Represented as:

[0025]

[0026] in, Where L is the initial inlet wall thickness and L is the total nozzle length. Control point intervals;

[0027] The spinning process was simulated using finite element analysis, with constraints on the local thinning rate and dynamic adjustment of the wall thickness gradient in the expansion section.

[0028] Furthermore, step S2 includes the following steps:

[0029] S21. Quantify the objective function, that is, define the aerodynamic performance objective, the process feasibility objective, and the structural strength objective;

[0030] In S21, the aerodynamic performance target Represented as:

[0031]

[0032] in, Let be the discrete points of the exit section. The Mach number at that location, For the target Mach number, The total number of discrete points;

[0033] Process feasibility objectives Represented as: ;

[0034] Structural strength target Represented as: , This refers to the change in wall thickness during the spinning process;

[0035] S22. Use the NSGA-II algorithm to optimize the objective, optimize the algorithm parameters, and obtain the population size, crossover probability, and number of iterations;

[0036] S23. Further refine the constraints of the profile design to obtain the refined constraint conditions. The constraints of the profile design include setting the radius of curvature, thinning rate, exit Mach number in the hard constraints, and the surface roughness and spinning force in the soft constraints.

[0037] Furthermore, step S3 includes the following steps:

[0038] S31. Collaborative platform architecture, integrating toolchain;

[0039] In step S31, design software is used for parametric modeling, CFD simulation, and FEA simulation, and the algorithm library is optimized.

[0040] S32. Based on the initial wall thickness distribution model and wall thickness parameters output in step S1, generate an automated iterative logic initial design;

[0041] In S32, during performance verification, the outlet Mach number distribution and the target Mach number matching the inlet total pressure and outlet static pressure in the boundary conditions are obtained through CFD simulation calculation.

[0042] During process verification, spinning was simulated using FEA simulation to output stress distribution and thinning rate;

[0043] Finally, the initial wall thickness distribution model was corrected through iterative modification. Based on the simulation results of performance verification and process verification, the control point coordinates and wall thickness parameters are dynamically adjusted using an optimization algorithm until the preset convergence conditions are met.

[0044] S33. Construct a process feedback mechanism, establish a spinning test database, record the forming force-springback relationship of different materials, reverse the surface compensation amount, and complete the high-precision wind tunnel nozzle surface design.

[0045] The beneficial effects of this invention are as follows: This invention significantly improves design-manufacturing synergy, reduces the number of trial productions from 6–8 times to 1–2 times, shortens the design cycle from 3 months to 18 days, optimizes design efficiency, and improves the uniformity of the exit Mach number by 40%, i.e., improves aerodynamic performance. The geometric accuracy error of the profile is <0.1mm, effectively avoiding defects such as spinning wrinkling and excessive thinning, and improving material utilization. It is suitable for high-precision aerodynamic verification scenarios such as hypersonic wind tunnels and aero-engine testing. Attached Figure Description

[0046] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0047] Figure 1This is a flowchart illustrating a high-precision wind tunnel nozzle profile design method based on spinning process coupling.

[0048] Figure 2 This is a schematic flowchart of an embodiment of a high-precision wind tunnel nozzle profile design method based on spinning process coupling;

[0049] Figure 3 A structural schematic diagram for the surface design. Detailed Implementation

[0050] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0051] refer to Figures 1-3 This embodiment describes a high-precision wind tunnel nozzle profile design method based on spinning process coupling, specifically including the following steps:

[0052] S1. Parametric modeling of the profile is performed using modeling software, that is, an initial mathematical model of the profile is constructed, geometric constraints are integrated, an initial wall thickness distribution model is established, and the wall thickness distribution is optimized.

[0053] S2. Based on the constraints of step S1 and the initial surface mathematical model parameters, such as the target Mach number of 6, the inlet size of 255mm, the outlet size of 350mm, and the length of 1800mm for an axisymmetric nozzle, quantify the objective function, such as the inlet wall thickness of 15mm and the initial wall thickness gradient coefficient of 0.05. Use the NSGA-II algorithm to optimize the objective function and refine the constraints to obtain the refined constraint conditions.

[0054] S3. Input the wall thickness distribution parameters and surface control point coordinates obtained in step S2 into the parametric CAD system to generate an initial three-dimensional nozzle blank model. Import the three-dimensional model into a finite element analysis module such as Workbench, automatically execute the spinning process simulation, extract the local wall thickness reduction rate and stress distribution in the simulation results. When the thinning rate of any region exceeds the threshold or the stress exceeds the material yield limit, the feedback logic automatically adjusts the initial wall thickness parameters or surface curvature of the corresponding region and drives the CAD model to update. This iterative process continues until all process and strength constraints are met. Finally, a precise surface data model that can be directly used for CNC spinning machine programming is output, completing the high-precision wind tunnel nozzle surface design.

[0055] Furthermore, step S1 includes the following steps:

[0056] S11. Based on aerodynamic performance, construct an initial surface mathematical model including the inlet section, throat, and expansion section according to the method of characteristics;

[0057] In S11, the initial surface mathematical model is established as follows:

[0058] The axial Mach number distribution function is defined using the improved Sivells method of characteristics;

[0059] The axial Mach number distribution function is expressed as:

[0060]

[0061] in, This is the initial Mach number at the entrance (usually taken as 0.3~0.5). The value represents the Mach number variation amplitude (determined based on the target Mach number at the exit), and k is the distribution steepness parameter (controlling the smoothness of the throat transition; a value of 5-10 is recommended). These are the characteristic location parameters (axial coordinates of the throat center). This refers to the axial position of the nozzle;

[0062] Establish the correlation between nozzle length and surface curvature, and complete the initial surface mathematical model construction;

[0063] Relationship between nozzle length and surface curvature Represented as:

[0064]

[0065] in, Let x be the cross-sectional area at the axial position x of the nozzle. This is the critical cross-sectional area (minimum cross-sectional area of ​​the throat). , These are the first and second derivatives of the cross-sectional area with respect to the axial coordinates, respectively, to ensure the curvature continuity of the throat and the expansion segment (avoiding abrupt changes in the first derivative).

[0066] S12. Integrated geometric constraints, namely, setting embedded spinning process geometric limit constraints and surface slope change rate to achieve curvature continuity;

[0067] In S12, the geometric limit constraint of the embedded spinning process is expressed as: minimum radius of curvature. (For commonly used materials such as stainless steel, to avoid wrinkling during spinning); Surface slope change rate (Ensure smooth feeding of the spinning wheel); use NURBS curves for parametric discretization, define at least 15 control points (refine to one control point every 0.01m in the throat region), and achieve curvature continuity (second derivative continuity) through weight adjustment.

[0068] S13. Based on the flow characteristics of spun materials (taking S31608 stainless steel as an example), establish an initial wall thickness distribution model and optimize the wall thickness distribution;

[0069] In S13, the initial wall thickness distribution model Represented as:

[0070]

[0071] in, Where L is the initial inlet wall thickness and L is the total nozzle length. For control point intervals, =0.05m (the throat region is densified to q=0.01m);

[0072] The spinning process was simulated using finite element analysis (FEA), with a constrained local thinning rate of <20% (i.e., Dynamically adjust the wall thickness gradient of the expansion segment (recommended gradient value) ).

[0073] Furthermore, step S2 includes the following steps:

[0074] S21. Quantify the objective function, that is, define the aerodynamic performance objective, the process feasibility objective, and the structural strength objective;

[0075] In S21, the aerodynamic performance target Represented as:

[0076]

[0077] in, Let i be the Mach number at discrete point i on the exit section. For the target Mach number, The total number of discrete points;

[0078] Process feasibility objectives Represented as: (The deviation between the radius of curvature and the process limit,) (For feasibility)

[0079] Structural strength target Represented as: (Thinning rate deviation, (For feasibility) This refers to the change in wall thickness during the spinning process;

[0080] S22. Use the NSGA-II algorithm to optimize the objective, optimize the algorithm parameters, and obtain the population size, crossover probability, and number of iterations;

[0081] In S22, the population size is 50~80; the crossover probability is 0.8~0.9, the mutation probability is 0.01~0.05; and the number of iterations is 50~100 (based on the convergence of the objective function).

[0082] S23. Further refine the constraints of the profile design to obtain the refined constraint conditions. The constraints of the profile design include setting the radius of curvature, thinning rate, exit Mach number in hard constraints, and the surface roughness and spinning force in soft constraints.

[0083] In S23, the refined constraint condition is expressed as: the radius of curvature in the hard constraint. Thinning rate Export Mach number (Can be adjusted according to requirements), surface roughness of soft-constrained medium-sized surfaces Spin forming force ≤500kN.

[0084] Furthermore, step S3 includes the following steps:

[0085] S31. Collaborative platform architecture, integrating toolchain;

[0086] In S31, design software is used for parametric modeling (via CATIA / NX), CFD simulation (via Fluent, using the k-ωSST turbulence model), and FEA simulation (Abaqus, explicit dynamic analysis of the spinning process), and an optimization algorithm library (MATLAB Multi-Objective Optimization Toolbox) is used.

[0087] S32. Based on the initial wall thickness distribution model and wall thickness parameters output in step S1, generate an automated iterative logic initial design;

[0088] In S32, during performance verification, the outlet Mach number distribution (mesh size ≥ 5 million) and the inlet total pressure in the boundary conditions are obtained through CFD simulation calculations. Match the target Mach number with the outlet static pressure;

[0089] During process verification, FEA simulation was used to simulate spinning (spindle speed 50~100r / min, feed speed 5~10mm / s) and output stress distribution and thinning rate.

[0090] Finally, the initial wall thickness distribution model was corrected through iterative modification. Based on simulation results from performance and process verification, optimization algorithms (such as linear regression, neural networks, and Naive Bayes) are used to dynamically adjust the control point coordinates and wall thickness parameters until the preset convergence conditions are met; , , );

[0091] S33. Construct a process feedback mechanism, establish a spinning test database, record the forming force-springback relationship of different materials (such as S31608 stainless steel), reverse the profile compensation amount, and complete the high-precision wind tunnel nozzle profile design (typical compensation value: throat area + 0.05mm, expansion section end + 0.03mm).

[0092] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A high-precision wind tunnel nozzle profile design method based on spinning process coupling, characterized in that, Includes the following steps: S1. Parametric modeling of the profile is performed using modeling software, that is, an initial mathematical model of the profile is constructed, geometric constraints are integrated, an initial wall thickness distribution model is established, and the wall thickness distribution is optimized. S2. Based on the constraints of step S1 and the parameters of the initial surface mathematical model, quantify the objective function, optimize the objective function, refine the constraints, and obtain the refined constraint conditions. S3. Based on the initial wall thickness distribution model and wall thickness parameters, parametric modeling is performed using design software combined with refined constraints. A process feedback mechanism is constructed to correct and compensate for the preliminary surface modeling, thus completing the high-precision wind tunnel nozzle surface design.

2. The high-precision wind tunnel nozzle profile design method based on spinning process coupling according to claim 1, characterized in that, S1 includes the following steps: S11. Based on aerodynamic performance, construct an initial surface mathematical model including the inlet section, throat, and expansion section according to the method of characteristics; In S11, the initial surface mathematical model is established as follows: The axial Mach number distribution function is defined using the improved Sivells method of characteristics; The axial Mach number distribution function is expressed as: in, The initial Mach number at the entrance. Here, is the amplitude of the Mach number change, and k is the kurtosis parameter. For feature location parameters, This refers to the axial position of the nozzle; Establish the correlation between nozzle length and surface curvature, and complete the initial surface mathematical model construction; Relationship between nozzle length and surface curvature Represented as: in, Let x be the cross-sectional area at the axial position x of the nozzle. This is the critical cross-sectional area. , These are the first and second derivatives of the cross-sectional area with respect to the axial coordinates, respectively. S12. Integrated geometric constraints, namely, setting embedded spinning process geometric limit constraints and surface slope change rate to achieve curvature continuity; In S12, the geometric limit constraint of the embedded spinning process is expressed as: minimum radius of curvature. ; Rate of change of slope of profile ; NURBS curves are used for parametric discretization, control points are defined, and curvature continuity is achieved through weight adjustment; S13. Based on the flow characteristics of spun materials, establish an initial wall thickness distribution model and optimize the wall thickness distribution; In S13, the initial wall thickness distribution model Represented as: in, Where L is the initial inlet wall thickness and L is the total nozzle length. Control point intervals; The spinning process was simulated using finite element analysis, with constraints on the local thinning rate and dynamic adjustment of the wall thickness gradient in the expansion section.

3. The high-precision wind tunnel nozzle profile design method based on spinning process coupling according to claim 2, characterized in that, S2 includes the following steps: S21. Quantify the objective function, that is, define the aerodynamic performance objective, the process feasibility objective, and the structural strength objective; In S21, the aerodynamic performance target Represented as: in, Let be the discrete points of the exit section. The Mach number at that location, For the target Mach number, The total number of discrete points; Process feasibility objectives Represented as: ; Structural strength target Represented as: , This refers to the change in wall thickness during the spinning process; S22. Use the NSGA-II algorithm to optimize the objective, optimize the algorithm parameters, and obtain the population size, crossover probability, and number of iterations; S23. Further refine the constraints of the profile design to obtain the refined constraint conditions. The constraints of the profile design include setting the radius of curvature, thinning rate, exit Mach number in the hard constraints, and the surface roughness and spinning force in the soft constraints.

4. The high-precision wind tunnel nozzle profile design method based on spinning process coupling according to claim 3, characterized in that, S3 includes the following steps: S31. Collaborative platform architecture, integrating toolchain; In step S31, design software is used for parametric modeling, CFD simulation, and FEA simulation, and the algorithm library is optimized. S32. Based on the initial wall thickness distribution model and wall thickness parameters output in step S1, generate an automated iterative logic initial design; In S32, during performance verification, the outlet Mach number distribution and the target Mach number matching the inlet total pressure and outlet static pressure in the boundary conditions are obtained through CFD simulation calculation. During process verification, spinning was simulated using FEA simulation to output stress distribution and thinning rate; Finally, the initial wall thickness distribution model was corrected through iterative modification. Based on the simulation results of performance verification and process verification, the control point coordinates and wall thickness parameters are dynamically adjusted using an optimization algorithm until the preset convergence conditions are met. S33. Construct a process feedback mechanism, establish a spinning test database, record the forming force-springback relationship of different materials, reverse the surface compensation amount, and complete the high-precision wind tunnel nozzle surface design.

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