Propeller system dynamics analysis method based on shell unit

Abstract

The invention discloses a propeller system dynamics analysis method based on a shell unit, and the method comprises the steps: firstly determining the geometric parameters and design conditions of a propeller according to the design task and working condition of an aviation aircraft; and blade chord length distribution and mounting angle distribution are calculated based on an aerodynamic load rule, and an NACA airfoil profile is selected to generate a three-dimensional geometric model. Then, grid division is carried out according to the model, the connection relation between blade nodes and units is established, and a quadrilateral eight-node shell unit grid is formed; a finite element model is established by adopting an isoparametric element theory, a stiffness matrix and a mass matrix are calculated, and then a kinetic equation of the propeller is established. The inherent frequency and vibration mode characteristics of the blade are obtained through modal analysis, and on the basis, aerodynamic loads are applied for dynamic response analysis. According to the method, the parameterized modeling process of the propeller from geometric modeling to kinetic analysis is realized, the aerodynamic coupling vibration characteristics of the blade can be efficiently evaluated, and the method has the advantages of high modeling precision, high analysis efficiency and high adaptability.

Description

Technical Field

[0001] This invention belongs to the field of aerospace engineering technology, specifically relating to a dynamic analysis method for a propeller system based on shell elements. Background Technology

[0002] Current methods for propeller dynamics analysis typically involve first establishing a three-dimensional model, then importing the model into finite element analysis software for dynamic analysis. For example, Niu Hongwei established a vibration model of a rotating blade in ANSYS software and performed modal analysis using the structural finite element method. He then studied the effects of aerodynamic and centrifugal loads on the blade's inherent characteristics using comparative analysis. Zhang Yongwang et al. established a dynamic model in ANSYS software to analyze the propeller's aerodynamic performance, obtaining the propeller's lift variation curve and pressure contour map of the blade, thus verifying the propeller's aerodynamic performance requirements. Wei Wuguo et al. established a three-dimensional finite element model of the propeller's overall structural vibration characteristics in ANSYS software, calculating its mode shapes and frequencies under common speed conditions with simultaneous centrifugal and aerodynamic loads.

[0003] The method of manually creating a 3D model and performing dynamic analysis in finite element software has high computational performance requirements, and if structural parameters need to be changed, the model needs to be manually created again, which cannot achieve rapid parameter optimization. Summary of the Invention

[0004] In order to solve the technical problems existing in the background art, the present invention aims to provide a dynamic analysis method for propeller systems based on shell units.

[0005] To solve the technical problem, the technical solution of the present invention is as follows:

[0006] A method for dynamic analysis of a propeller system based on shell elements, the method comprising:

[0007] Based on the design mission and operating conditions of the aircraft, determine the geometric parameters and design conditions of the propeller, and calculate the chord length distribution of the blades along the radial direction based on the geometric parameters.

[0008] Based on the design conditions and chord length distribution, the inflow angle and angle of attack are calculated, the radial installation angle distribution of the blade is determined, and the airfoil is selected and the blade profile coordinates are established based on the chord length distribution and installation angle distribution to generate a three-dimensional geometric model of the blade.

[0009] Mesh generation is performed based on the three-dimensional geometric model to establish the node coordinates and element connection relationships of the blade, forming a shell element finite element mesh. A shell element model is established based on isoparametric element theory, and the stiffness matrix and mass matrix of the blade are calculated. The dynamic equations are established using the stiffness matrix and mass matrix, and modal and dynamic response analyses are performed to obtain the dynamic characteristics of the blade.

[0010] Based on the established dynamic equations, assuming that the system damping is zero, the equations are transformed into a generalized eigenvalue problem. The Lanczos iterative method is used to solve for the system eigenvalues ​​and eigenvectors, obtain the natural frequencies and mode shapes of the propeller blades, and use them as the modal basis for subsequent aerodynamic coupling analysis.

[0011] Based on the obtained modal information, aerodynamic loads are applied to map the forces on the blades under specific working conditions to the external load vector. The Newmark numerical integration method is used to solve the dynamic equations in the time domain to obtain the displacement and acceleration responses of the blades under periodic or transient loads, thus realizing the analysis of the aerodynamic-structural coupled dynamic characteristics of the propeller.

[0012] Furthermore, based on the aforementioned geometric parameters, and according to the aerodynamic load distribution law and propulsion efficiency requirements, the chord length variation of the blade along the radial direction is calculated to obtain the blade chord length distribution curve.

[0013] Furthermore, using the aforementioned design conditions and chord length distribution as input, the inflow angle and angle of attack are calculated through aerodynamic geometry. Based on the change of the inflow angle along the radial direction, the torsional law of the blade is determined, enabling each blade element to operate at the design angle of attack, and outputting the installation angle variation curve of the blade along the radial direction.

[0014] Furthermore, the chord length distribution and installation angle distribution are input, and the appropriate NACA airfoil family is selected as the blade profile. The coordinates of the upper and lower surfaces and the mid-arc line of the airfoil are generated according to the airfoil definition equation. The actual size is scaled according to the chord length, and combined with the radial relative thickness variation law, a complete cross-sectional geometric model of the blade from the root to the tip is formed, and the three-dimensional coordinate data of each radial section of the blade are obtained.

[0015] Furthermore, based on the aforementioned three-dimensional geometric model, the number of chordal mesh divisions is set according to the structural analysis accuracy requirements. With radial division number Generate in the radial direction Each leaf element section is divided in the chord direction. Each node is assigned a number of nodes. The 3D coordinates, mid-arc normal, and tangential direction of each node are calculated, and a local coordinate system is established. After the node data is completed, an 8-node quadrilateral shell element mesh is generated based on the node connection relationship, and the node and element data are output.

[0016] Furthermore, the node and element data are input, and the coordinate mapping equation and displacement interpolation function of the 8-node shell element are established based on the isoparametric element method. Through the strain-displacement relationship and stress-strain relationship, the stiffness matrix and mass matrix of the shell element are derived using the principle of virtual work. The shape function matrix is ​​defined by the nodal displacement and geometric coordinates, and the element stiffness matrix and mass matrix of the propeller blade are output.

[0017] Furthermore, using the stiffness matrix and mass matrix as inputs, and combining the blade material parameters and boundary conditions, the dynamic control equations of the propeller blade are established. By introducing the Rayleigh damping matrix, structural modal analysis and dynamic response analysis are completed, and the dynamic characteristics of the blade, namely the blade's natural frequency, mode shape distribution, and dynamic characteristics, are obtained.

[0018] Furthermore, the geometric parameters include: propeller diameter, hub radius, number of blades, design rotational speed and flight speed, target thrust and design thrust.

[0019] Furthermore, the node and unit data includes: node coordinates, local coordinate system, thickness information, and unit connection relationships.

[0020] A dynamic analysis system for a propeller system based on shell elements, the system comprising:

[0021] Design parameter confirmation module: Based on the aircraft's design task book and operating conditions, determine the basic design parameters of the propeller and obtain the overall geometric boundary parameters and design operating conditions of the propeller.

[0022] Blade chord length distribution calculation module: Based on the geometric boundary parameters, according to the aerodynamic load distribution law and propulsion efficiency requirements, calculate the chord length variation of the blade along the radial direction to obtain the blade chord length distribution curve;

[0023] Blade installation angle calculation module: Taking the design conditions and chord length distribution as input, it calculates the inflow angle and angle of attack through aerodynamic geometry. Based on the change of the inflow angle along the radial direction, it determines the torsional law of the blade, so that each blade element works at the design angle of attack, and outputs the installation angle change curve of the blade along the radial direction.

[0024] Airfoil selection and profile generation module: Input the chord length distribution and installation angle distribution, select the appropriate NACA airfoil family as the blade profile, generate the coordinates of the upper and lower surfaces and the mid-arc line of the airfoil according to the airfoil definition equation, scale the actual size according to the chord length, and combine the radial relative thickness variation law to form a complete cross-sectional geometric model of the blade from the root to the tip, and obtain the three-dimensional coordinate data of each radial section of the blade.

[0025] Mesh generation module: Based on the aforementioned 3D coordinate data, sets the number of chordal mesh divisions according to the structural analysis accuracy requirements. With radial division number Generate in the radial direction Each leaf element section is divided in the chord direction. Each node is assigned a number of nodes. The 3D coordinates, mid-arc normal, and tangential direction of each node are calculated, and a local coordinate system is established. After the node data is completed, a quadrilateral 8-node shell element mesh is generated based on the node connection relationship, and the node and element data are output.

[0026] Finite element model establishment module: Input the node and element data, establish the coordinate mapping equation and displacement interpolation function of the 8-node shell element based on the isoparametric element method, derive the shell element stiffness matrix and mass matrix by means of strain-displacement relationship and stress-strain relationship, and use the principle of virtual work. The shape function matrix is ​​defined by the node displacement and geometric coordinates, and outputs the element stiffness matrix and mass matrix of the propeller blade.

[0027] Dynamics Analysis Module: Using the stiffness matrix and mass matrix as input, combined with blade material parameters and boundary conditions, the dynamic control equations of the propeller blade are established. By introducing the Rayleigh damping matrix, structural modal analysis and dynamic response analysis are completed to obtain the blade's natural frequency, mode shape distribution and dynamic characteristics.

[0028] Modal characteristic analysis module: Based on the established dynamic equations, assuming that the system damping is zero, the equations are transformed into a generalized eigenvalue problem. The Lanczos iterative method is used to solve for the system eigenvalues ​​and eigenvectors, obtain the natural frequencies and mode shapes of the propeller blades, and serve as the modal basis for subsequent aerodynamic coupling analysis.

[0029] Aerodynamic coupling response analysis module: Based on the obtained modal information, aerodynamic loads are applied to map the forces on the blades under specific working conditions to the external load vector. The Newmark numerical integration method is used to solve the dynamic equations in the time domain to obtain the displacement and acceleration responses of the blades under periodic or transient loads, thereby realizing the analysis of the aerodynamic-structural coupling dynamic characteristics of the propeller.

[0030] Compared with the prior art, the advantages of the present invention are as follows:

[0031] High-efficiency modeling: Enables fully automated parametric modeling of propellers, from geometric parameters to finite element models, significantly shortening the analysis cycle.

[0032] High-precision calculation: Based on the isoparametric element theory, a shell element model is established, which can accurately reflect the mechanical and aerodynamic characteristics of the blade.

[0033] Strong comprehensive analysis capability: Combining modal analysis and aerodynamic coupling response analysis, it achieves full-domain dynamic evaluation from inherent characteristics to external load response.

[0034] Wide applicability: It can be adapted to different propeller shapes, airfoils and material parameters to meet the design and optimization needs of various aviation propulsion systems.

[0035] Highly innovative: By using a parametric shell element modeling method, structural analysis and aerodynamic performance evaluation are integrated, improving the level of intelligence in propeller design. Attached Figure Description

[0036] Figure 1 Airfoil upper and lower edge coordinate definition diagram;

[0037] Figure 2 1. Model diagram of blade shell unit;

[0038] Figure 3 1. Natural frequencies and mode shapes of the propeller rotor arm under certain conditions;

[0039] Figure 4 The effect of blade thickness on blade tip dynamics is shown in the graph. Detailed Implementation

[0040] The specific implementation of the present invention is described below with reference to embodiments:

[0041] It should be noted that the structures, proportions, sizes, etc. shown in this specification are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0042] Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0043] Example 1:

[0044] In an exemplary embodiment, this invention proposes detailed steps for a shell element-based propeller system dynamics analysis method. This method takes propeller geometry and aerodynamic parameters as input, and follows a complete process: geometric modeling → aerodynamic distribution calculation → airfoil generation → mesh generation → finite element modeling → dynamic equation establishment → modal analysis → aerodynamic coupling response analysis. This forms an automated, parametric design path from parameters to a finite element model. Compared with traditional 3D modeling methods, this method has advantages such as directly generating shell element models from parameter input, high calculation accuracy, and high analysis efficiency, significantly improving the engineering application efficiency of propeller dynamics simulation. Specifically, it includes the following steps:

[0045] 1) Determine the propeller diameter, hub radius, number of blades, etc., according to the operating conditions required by the aircraft.

[0046] 2) The blade chord length varies radially, and its relative chord length is determined by formula (1).

[0047] (1)

[0048] 3) The blade installation angle is the angle between the blade element profile chord and the plane of rotation; the angle of attack is the angle between the blade element profile chord and the direction of the relative airflow velocity; and the inflow angle is the angle between the geometrically combined velocity and the plane of rotation. The inflow angle is calculated using formula (2).

[0049] (2)

[0050] Leaf angle of attack:

[0051] (3)

[0052] Under normal operating conditions, the airfoil has a positive angle of attack. To ensure that the entire propeller blade element operates at a favorable angle of attack, the blades must be twisted radially. Since the airflow angle varies along the radial direction, the blade element installation angle also varies along the blade radius. Common angles of attack range from 5° to 25°. Because the airflow angle is relatively large, this design uses a fixed angle of attack of 6° to simplify the structure.

[0053] 4) Select the NACA (National Advisory Committee on Aeronautics) airfoil. The coordinate definition of the airfoil is as follows: Figure 1 As shown.

[0054] like Figure 1 As shown, the curves of the upper and lower surfaces of the airfoil are represented by the relative coordinates of chords. The function representation of, i.e. and Here Also string length relative value Similarly, the arc of the airfoil is also represented by a function of the relative coordinates of the chord, i.e. Therefore, the thickness of the airfoil ,thickness For chord length The relative value is It is usually expressed as a percentage; relative curvature is It is usually expressed as a percentage. The line connecting the point on the middle arc to the origin and... The included angle of the axis.

[0055] Therefore, it can be concluded that the curves of the upper and lower surfaces of the airfoil are related to... , , The parametric equation is shown in formula (4).

[0056] (4)

[0057] The NACA airfoil was proposed by NASA after extensive and systematic research on airfoils. NACA comprises many series, each with different thickness and camber distributions, resulting in excellent aerodynamic performance. The thickness distribution formula for the NACA airfoil family is:

[0058] (5)

[0059] The mid-arc is a parabola consisting of two segments that are tangent at the highest point:

[0060] (6)

[0061] in, For the thickness of the airfoil, Let be the ordinate of the highest point of the middle arc. Let x be the x-coordinate of the highest point of the middle arc. Given... , and The value can then be used to obtain an airfoil family.

[0062] NACA airfoils are expressed using either four or five digits. In four-digit airfoil families, the first digit represents the percentage of the chord length. The second digit is a tenth of the chord length, representing... The last two digits represent the percentage of the chord length. Multiplying the obtained relative airfoil coordinates by the chord length will magnify them to the true airfoil coordinates. For example, NACA 4406 represents an airfoil family where the ordinate of the highest point of the mid-curve is 4%, the abscissa of the highest point of the mid-curve is 40%, and the thickness is 6%. Basic information such as the airfoil's thickness, camber, and the location of maximum camber can be obtained from the airfoil number.

[0063] Any cross section of the blade Maximum thickness at The thickness of the blade is called its thickness. Generally, the blade thickness decreases monotonically along the radial direction from the root to the tip. The ratio of the blade thickness to the blade chord length is called the relative thickness of the blade. To improve propeller efficiency, thinner blades are typically used, but this results in poorer aerodynamic characteristics in the stall region. The relative thickness of the metal blade tip is usually set at 4% to 7%. The approximate curve for the relative thickness of the blades in this design is as follows:

[0064] (7)

[0065] 5) After determining the structural parameters of the blades, such as Figure 2 As shown, the blade is modeled using shell elements. First, the mesh density of the blade shell elements is determined and set as nx and ny, where nx is the number of elements in the chord direction and ny is the number of elements in the radial direction.

[0066] There are ny elements in the radial direction, which means there are ny+1 blade element sections. A uniform mesh is used, and the blade element sections are calculated at equal intervals from the blade root to the blade tip. Within each blade element section, nx elements are divided along the chord length, resulting in nx+1 points at equal intervals along the chord length. The coordinates of each point lie on the mid-arc line connecting the midpoints of the upper and lower surfaces of the blade element section. Each point on the blade element section is numbered, and the thickness of each point within the blade element section is calculated to provide parameters for building the finite element model. To ensure accurate representation of the blade's dynamic characteristics, the mesh density can be slightly higher. For each node, the normal to the mid-arc line and the tangent plane of the mid-arc line need to be calculated. A local coordinate system is established using the normal and the tangent plane for subsequent shell element creation. After numbering the nodes and recording the 3D coordinates, local coordinate system, and thickness of each node, the nodes are connected to form several quadrilateral elements, which are then numbered. The eight node numbers corresponding to each element are also recorded.

[0067] 6) After completing the mesh generation, the finite element model of the blade is established using the following shell element theory.

[0068] For an 8-node shell element, the coordinate equations of any point within the element are defined using the isoparametric element method.

[0069] (8)

[0070] The definition rule for this formula is as follows: Assuming the shell elements have the same displacement in the thickness direction, the coordinate problem is actually a planar problem. Therefore, we first define an 8-node isoparametric element in the plane, where the coordinate variables of the parent element are... Thus, the plane is obtained Coordinates. Regarding the thickness direction, The thickness of the surface at each node, The coordinates are in the parent element. Since the thickness direction is simply defined, the mapping between the parent element and the child element is linear.

[0071] For an 8-node shell element, the displacement of any point within the element can be obtained through shape function interpolation:

[0072] (9)

[0073] The first term on the right-hand side of the equation represents the displacement values ​​of each node. Applying the isoparametric element method to these values ​​yields the displacement of any node within the shell element on the shell's mid-plane. The right-hand side of the equation represents the influence of the shell element's thickness and the rotational degrees of freedom of the nodes within the element on the displacement of any point within the shell element. Indicates the angular displacement of the node. The matrix defines the direction of the influence of the rotational angular displacement of a node on the node displacement.

[0074] The strain-displacement relationship of the 8-node shell element can be obtained using formula (9).

[0075] (10)

[0076] The stress-strain relationship is as follows:

[0077] (11)

[0078] Based on the principle of virtual work, the stiffness matrix expression for an N-node shell element is derived as follows:

[0079] (12)

[0080] The mass matrix expression for an N-node shell element is:

[0081] (13)

[0082] Among them, the shape function matrix is ​​the matrix expression of the displacement-node coordinate relationship, as shown in formula (14).

[0083] For a node with 5 displacements, the shape function is:

[0084] (14)

[0085] 7) Based on the structural parameters of the propeller blade, complete the 8-node shell element mesh generation of the blade, and obtain the mass matrix and stiffness matrix of the blade shell element model through shell element theory, and establish the following dynamic equations.

[0086] (15)

[0087] After inputting the stiffness matrix and mass matrix, and calculating the Rayleigh damping matrix, dynamic analysis can be performed on the blade shell element model, such as... Figure 3 As shown.

[0088] 8) The process of solving for the frequency and mode shape is as follows:

[0089] Assuming zero damping, the equations of motion can be derived by assuming harmonics. Transform into:

[0090] (16)

[0091] This is the generalized eigenvalue problem, which requires the following:

[0092] (17)

[0093] The Lanczos iterative method can be used to obtain eigenvalues ​​and eigenvectors. By visualizing the values ​​of each eigenvector, the mode shapes can be obtained.

[0094] 9) To analyze the aerodynamic characteristics, first obtain the forces acting on the blade under specific working conditions, map the forces onto the F vector in the dynamic equation, and use the Nermark method to solve formula (15).

[0095] By inputting a sinusoidal excitation, the displacement response at the blade tip can be obtained. By changing the blade parameters, the influence of the blade parameters on the blade tip dynamic response can be observed. Figure 4 As shown.

[0096] Example 2:

[0097] This invention provides a shell-element-based propeller system dynamics analysis system, which can be used to implement the aforementioned shell-element-based propeller system dynamics analysis method, specifically including:

[0098] Design parameter confirmation module: Based on the aircraft's design task book and operating conditions, determine the basic design parameters of the propeller and obtain the overall geometric boundary parameters and design operating conditions of the propeller.

[0099] Blade chord length distribution calculation module: Based on the geometric boundary parameters, according to the aerodynamic load distribution law and propulsion efficiency requirements, calculate the chord length variation of the blade along the radial direction to obtain the blade chord length distribution curve;

[0100] Blade installation angle calculation module: Taking the design conditions and chord length distribution as input, it calculates the inflow angle and angle of attack through aerodynamic geometry. Based on the change of the inflow angle along the radial direction, it determines the torsional law of the blade, so that each blade element works at the design angle of attack, and outputs the installation angle change curve of the blade along the radial direction.

[0101] Airfoil selection and profile generation module: Input the chord length distribution and installation angle distribution, select the appropriate NACA airfoil family as the blade profile, generate the coordinates of the upper and lower surfaces and the mid-arc line of the airfoil according to the airfoil definition equation, scale the actual size according to the chord length, and combine the radial relative thickness variation law to form a complete cross-sectional geometric model of the blade from the root to the tip, and obtain the three-dimensional coordinate data of each radial section of the blade.

[0102] Mesh generation module: Based on the aforementioned 3D coordinate data, sets the number of chordal mesh divisions according to the structural analysis accuracy requirements. With radial division number Generate in the radial direction Each leaf element section is divided in the chord direction. Each node is assigned a number of nodes. The 3D coordinates, mid-arc normal, and tangential direction of each node are calculated, and a local coordinate system is established. After the node data is completed, a quadrilateral 8-node shell element mesh is generated based on the node connection relationship, and the node and element data are output.

[0103] Finite element model establishment module: Input the node and element data, establish the coordinate mapping equation and displacement interpolation function of the 8-node shell element based on the isoparametric element method, derive the shell element stiffness matrix and mass matrix by means of strain-displacement relationship and stress-strain relationship, and use the principle of virtual work. The shape function matrix is ​​defined by the node displacement and geometric coordinates, and outputs the element stiffness matrix and mass matrix of the propeller blade.

[0104] Dynamics Analysis Module: Using the stiffness matrix and mass matrix as input, combined with blade material parameters and boundary conditions, the dynamic control equations of the propeller blade are established. By introducing the Rayleigh damping matrix, structural modal analysis and dynamic response analysis are completed to obtain the blade's natural frequency, mode shape distribution and dynamic characteristics.

[0105] Modal characteristic analysis module: Based on the established dynamic equations, assuming that the system damping is zero, the equations are transformed into a generalized eigenvalue problem. The Lanczos iterative method is used to solve for the system eigenvalues ​​and eigenvectors, obtain the natural frequencies and mode shapes of the propeller blades, and serve as the modal basis for subsequent aerodynamic coupling analysis.

[0106] Aerodynamic coupling response analysis module: Based on the obtained modal information, aerodynamic loads are applied to map the forces on the blades under specific working conditions to the external load vector. The Newmark numerical integration method is used to solve the dynamic equations in the time domain to obtain the displacement and acceleration responses of the blades under periodic or transient loads, thereby realizing the analysis of the aerodynamic-structural coupling dynamic characteristics of the propeller.

[0107] Example 3:

[0108] This embodiment provides a terminal device, which includes a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used in the operation of a shell-based propeller system dynamics analysis method, including the following steps:

[0109] S1: Based on the aircraft's design specifications and operating conditions, determine the basic design parameters of the propeller and obtain the overall geometric boundary parameters and design operating conditions of the propeller.

[0110] S2: Based on the geometric boundary parameters, according to the aerodynamic load distribution law and propulsion efficiency requirements, calculate the chord length variation of the blade along the radial direction to obtain the blade chord length distribution curve;

[0111] S3: Using the design conditions and chord length distribution as input, calculate the inflow angle and angle of attack through aerodynamic geometry. Based on the change of the inflow angle along the radial direction, determine the torsional law of the blade, so that each blade element works at the design angle of attack, and output the installation angle change curve of the blade along the radial direction.

[0112] S4: Input the chord length distribution and installation angle distribution, select the appropriate NACA airfoil family as the blade profile, generate the coordinates of the upper and lower surfaces and the mid-arc line of the airfoil according to the airfoil definition equation, scale the actual size according to the chord length, and combine the radial relative thickness variation law to form a complete cross-sectional geometric model of the blade from the root to the tip, and obtain the three-dimensional coordinate data of each radial section of the blade.

[0113] S5: Based on the aforementioned three-dimensional coordinate data, determine the number of chordal mesh divisions according to the structural analysis accuracy requirements. With radial division number Generate in the radial direction Each leaf element section is divided in the chord direction. Each node is assigned a number of nodes. The 3D coordinates, mid-arc normal, and tangential direction of each node are calculated, and a local coordinate system is established. After the node data is completed, a quadrilateral 8-node shell element mesh is generated based on the node connection relationship, and the node and element data are output.

[0114] S6: Input the node and element data, establish the coordinate mapping equation and displacement interpolation function of the 8-node shell element based on the isoparametric element method, derive the shell element stiffness matrix and mass matrix by means of strain-displacement relationship and stress-strain relationship, and use the principle of virtual work. The shape function matrix is ​​defined by the node displacement and geometric coordinates, and output the element stiffness matrix and mass matrix of the propeller blade.

[0115] S7: Using the stiffness matrix and mass matrix as input, and combining the blade material parameters and boundary conditions, establish the dynamic control equations of the propeller blade. By introducing the Rayleigh damping matrix, complete the structural modal analysis and dynamic response analysis to obtain the blade's natural frequency, mode shape distribution, and dynamic characteristics.

[0116] S8: Based on the established dynamic equations, assuming that the system damping is zero, the equations are transformed into a generalized eigenvalue problem. The Lanczos iterative method is used to solve for the system eigenvalues ​​and eigenvectors, obtain the natural frequencies and mode shapes of the propeller blades, and use them as the modal basis for subsequent aerodynamic coupling analysis.

[0117] S9: Based on the obtained modal information, aerodynamic loads are applied to map the forces on the blades under specific working conditions to the external load vector. The Newmark numerical integration method is used to solve the dynamic equations in the time domain to obtain the displacement and acceleration responses of the blades under periodic or transient loads, thereby realizing the analysis of the aerodynamic-structural coupled dynamic characteristics of the propeller.

[0118] Example 4:

[0119] This embodiment provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and extended storage media supported by the terminal device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device.

[0120] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the above embodiments regarding a method for dynamic analysis of a shell-based propeller system; one or more instructions in the computer-readable storage medium are loaded and executed by the processor to perform the following steps:

[0121] S1: Based on the aircraft's design specifications and operating conditions, determine the basic design parameters of the propeller and obtain the overall geometric boundary parameters and design operating conditions of the propeller.

[0122] S2: Based on the geometric boundary parameters, according to the aerodynamic load distribution law and propulsion efficiency requirements, calculate the chord length variation of the blade along the radial direction to obtain the blade chord length distribution curve;

[0123] S3: Using the design conditions and chord length distribution as input, calculate the inflow angle and angle of attack through aerodynamic geometry. Based on the change of the inflow angle along the radial direction, determine the torsional law of the blade, so that each blade element works at the design angle of attack, and output the installation angle change curve of the blade along the radial direction.

[0124] S4: Input the chord length distribution and installation angle distribution, select the appropriate NACA airfoil family as the blade profile, generate the coordinates of the upper and lower surfaces and the mid-arc line of the airfoil according to the airfoil definition equation, scale the actual size according to the chord length, and combine the radial relative thickness variation law to form a complete cross-sectional geometric model of the blade from the root to the tip, and obtain the three-dimensional coordinate data of each radial section of the blade.

[0125] S5: Based on the aforementioned three-dimensional coordinate data, determine the number of chordal mesh divisions according to the structural analysis accuracy requirements. With radial division number Generate in the radial direction Each leaf element section is divided in the chord direction. Each node is assigned a number of nodes. The 3D coordinates, mid-arc normal, and tangential direction of each node are calculated, and a local coordinate system is established. After the node data is completed, a quadrilateral 8-node shell element mesh is generated based on the node connection relationship, and the node and element data are output.

[0126] S6: Input the node and element data, establish the coordinate mapping equation and displacement interpolation function of the 8-node shell element based on the isoparametric element method, derive the shell element stiffness matrix and mass matrix by means of strain-displacement relationship and stress-strain relationship, and use the principle of virtual work. The shape function matrix is ​​defined by the node displacement and geometric coordinates, and output the element stiffness matrix and mass matrix of the propeller blade.

[0127] S7: Using the stiffness matrix and mass matrix as input, and combining the blade material parameters and boundary conditions, establish the dynamic control equations of the propeller blade. By introducing the Rayleigh damping matrix, complete the structural modal analysis and dynamic response analysis to obtain the blade's natural frequency, mode shape distribution, and dynamic characteristics.

[0128] S8: Based on the established dynamic equations, assuming that the system damping is zero, the equations are transformed into a generalized eigenvalue problem. The Lanczos iterative method is used to solve for the system eigenvalues ​​and eigenvectors, obtain the natural frequencies and mode shapes of the propeller blades, and use them as the modal basis for subsequent aerodynamic coupling analysis.

[0129] S9: Based on the obtained modal information, aerodynamic loads are applied to map the forces on the blades under specific working conditions to the external load vector. The Newmark numerical integration method is used to solve the dynamic equations in the time domain to obtain the displacement and acceleration responses of the blades under periodic or transient loads, thereby realizing the analysis of the aerodynamic-structural coupled dynamic characteristics of the propeller.

[0130] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0131] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0132] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0133] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0134] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0135] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. A method of propeller system dynamics analysis based on shell elements, characterized by, The propeller system dynamics analysis method comprises: According to the design task and working condition of the aircraft, the geometric parameters and design conditions of the propeller are determined, and the chord length distribution of the blade along the radial direction is calculated based on the geometric parameters; According to the design condition and chord length distribution, the inflow angle and angle of attack are calculated, the installation angle distribution of the blade along the radial direction is determined, the airfoil is selected according to the chord length distribution and installation angle distribution, the blade profile coordinate is established, the three-dimensional geometric model of the blade is generated; Based on the three-dimensional geometric model, the node coordinates and element connection relationship of the blade are established, and the shell element finite element grid is formed; based on the isoparametric element theory, the shell element model is established, the stiffness matrix and mass matrix of the blade are calculated; the stiffness matrix and mass matrix are used to establish the dynamic equation, and the modal and dynamic response analysis is carried out, and the dynamic characteristics of the blade are obtained; Based on the established dynamic equation, it is assumed that the system damping is zero, the equation is converted into a generalized eigenvalue problem, the Lanczos iteration method is used to solve the system eigenvalue and eigenvector, the natural frequency and each order mode shape of the propeller blade are obtained, and they are used as the modal basis for subsequent aerodynamic coupling analysis; Based on the obtained modal information, the aerodynamic load is applied, the stress of the blade under a specific working condition is mapped into an external load vector, the Newmark numerical integration method is used to solve the dynamic equation in time domain, the displacement and acceleration response of the blade under the action of periodic or transient load is obtained, and the analysis of the aerodynamic-structure coupling dynamics characteristics of the propeller is realized.

2. The propeller system dynamics analysis method of claim 1, wherein, Based on the geometric parameters, the chord length change of the blade along the radial direction is calculated according to the aerodynamic load distribution law and the demand of propelling efficiency, and the chord length distribution curve of the blade is obtained.

3. The propeller system dynamics analysis method of claim 1, wherein, The design condition and chord length distribution are input, the inflow angle and angle of attack are calculated through aerodynamic geometric relationship, the twist law of the blade is determined according to the change of the inflow angle along the radial direction, each element works at the design angle of attack, and the installation angle change curve of the blade along the radial direction is output.

4. The propeller system dynamics analysis method of claim 1, wherein, The chord length distribution and installation angle distribution are input, the NACA airfoil family is selected as the blade profile, the upper and lower surface and camber line coordinates of the airfoil are generated according to the airfoil definition equation, the actual size is scaled according to the chord length, and the complete profile geometric model of the blade from the root to the tip is formed combined with the relative thickness change law along the radial direction, and the three-dimensional coordinate data of each radial section of the blade is obtained.

5. The propeller system dynamics analysis method according to claim 1, wherein, Based on the three-dimensional geometric model, according to the structure analysis accuracy requirement, set the chordwise grid division number With radial division number ; Radial direction generates Blade element section, chordwise direction is divided Node, calculate the three-dimensional coordinates, mean arc line normal and tangential direction of each node, and establish a local coordinate system. After the node data is completed, generate quadrilateral 8-node shell element grid according to the node connection relationship, output node and element data.

6. The propeller system dynamics analysis method according to claim 1, wherein, The node and element data are input, the coordinate mapping equation and displacement interpolation function of the 8-node shell element are established based on the isoparametric element method, the stiffness matrix and mass matrix of the shell element are derived by using the virtual work principle through the strain-displacement relationship and stress-strain relationship, the shape function matrix is defined by the node displacement and geometric coordinates, and the element stiffness matrix and mass matrix of the propeller blade are output.

7. The propeller system dynamics analysis method according to claim 1, wherein, The stiffness matrix and mass matrix are input, combined with the material parameters and boundary conditions of the blade, the dynamic control equation of the propeller blade is established, the modal analysis and dynamic response analysis are completed by introducing the Rayleigh damping matrix, and the dynamic characteristics of the blade, i.e. the natural frequency, mode shape distribution and dynamic characteristics of the blade are obtained.

8. The propeller system dynamics analysis method of claim 1, wherein, The geometric parameters include: propeller diameter, hub radius, number of blades, design rotational speed and flight speed, target thrust, and design drag.

9. The propeller system dynamics analysis method according to claim 5 or 6, wherein, The node and element data include: node coordinates, local coordinate system, thickness information, and element connection relationship.

10. A shell element based propeller system dynamics analysis system, characterized by, The system comprises: A design parameter confirmation module: according to the design task book and working conditions of the aircraft, the basic design parameters of the propeller are determined, and the overall geometric boundary parameters and design working conditions of the propeller are obtained; A blade chord length distribution calculation module: based on the geometric boundary parameters, the chord length change of the blade along the radial direction is calculated according to the aerodynamic load distribution law and the demand of propulsive efficiency, and the chord length distribution curve of the blade is obtained; A blade installation angle calculation module: taking the design working condition and chord length distribution as input, the inflow angle and angle of attack are calculated through aerodynamic geometry relationship, the twist law of the blade is determined according to the change of the inflow angle along the radial direction, each blade element works at the design angle of attack, and the installation angle change curve of the blade along the radial direction is output; A profile selection and section generation module: input the chord length distribution and installation angle distribution, select the NACA airfoil family as the blade profile, generate the upper and lower surface and camber line coordinates of the airfoil according to the airfoil definition equation, scale the actual size according to the chord length, and combine the relative thickness change law along the radial direction to form the complete profile geometric model of the blade from the root to the tip, and obtain the three-dimensional coordinate data of each radial section of the blade; The grid generation module: based on the three-dimensional coordinate data, according to the structure analysis accuracy requirement, set the chordal grid division number With radial division number ; Radial direction generates A blade element section, chordal direction is divided Node, calculate the three-dimensional coordinates, mean arc line normal and tangential direction of each node, and establish a local coordinate system, after the node data is completed, generate quadrilateral 8-node shell element grid according to the node connection relationship, output node and element data; A finite element model establishment module: input the node and element data, establish the coordinate mapping equation and displacement interpolation function of the 8-node shell element based on the isoparametric element method, derive the stiffness matrix and mass matrix of the shell element by using the virtual work principle through the strain-displacement relationship and stress-strain relationship, and the shape function matrix is defined by the node displacement and geometric coordinates, and the element stiffness matrix and mass matrix of the propeller blade are output; A dynamics analysis module: taking the stiffness matrix and mass matrix as input, combining the blade material parameters and boundary conditions, establishing the dynamics control equation of the propeller blade, completing the modal analysis and dynamic response analysis by introducing the Rayleigh damping matrix, and obtaining the natural frequency, mode shape distribution and dynamic characteristics of the blade; A modal characteristic analysis module: based on the established dynamics equation, assuming that the system damping is zero, converting the equation into a generalized eigenvalue problem, solving the system eigenvalue and eigenvector by using the Lanczos iteration method, obtaining the natural frequency and each order mode shape of the propeller blade, and taking the mode shape as the modal basis for subsequent aerodynamic coupling analysis; An aerodynamic coupling response analysis module: based on the obtained modal information, applying aerodynamic load, mapping the stress of the blade under a specific working condition to the external load vector, solving the dynamics equation in time domain by using the Newmark numerical integration method, obtaining the displacement and acceleration response of the blade under the action of periodic or transient load, and realizing the analysis of the aerodynamic-structure coupling dynamics characteristics of the propeller.

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