An aircraft propeller blade and its aerodynamic, noise and stiffness comprehensive design method

Abstract

The present application provides an aircraft propeller blade and a comprehensive aerodynamic, noise and stiffness design method thereof, which belongs to the field of aircraft blade design. The method comprises: determining initial parameters of the propeller blade, including geometric parameters, material parameters and operating parameters of the blade; performing propeller aerodynamic performance calculation based on the initial parameters to obtain the aerodynamic performance of the blade under multiple operating conditions; performing nonlinear deformation calculation of the blade to obtain the deformed blade shape; performing iterative calculation of the aerodynamic performance of the blade under multiple operating conditions and the deformed blade shape to make them converge; calculating the noise at different propeller blade passing frequencies based on the frequency domain noise method; performing global optimization with geometric parameters and radial stiffness distribution as design variables and aerodynamics and noise under different operating conditions as optimization targets to obtain comprehensively optimized blade geometric parameters; drawing the shape of the blade based on the comprehensively optimized geometric parameters to obtain the comprehensively optimized blade shape.

Description

Technical Field

[0001] The present application belongs to the technical field of aircraft blade design, and in particular relates to an aircraft propeller blade and a comprehensive design method for its aerodynamics, noise and stiffness. Background Art

[0002] The propeller is the earliest power unit of the aircraft. Due to its low fuel consumption rate and high flight efficiency, it is still one of the most important aircraft power units today. Although propeller aircraft have many advantages, they also have serious noise problems. For a long time, the low-noise design of aircraft propellers has mostly adopted the coupling analysis and optimization method of aerodynamics and noise, and the numerical simulation method based on finite elements is used to ensure aerodynamic performance while reducing noise as much as possible. These methods are suitable for the detailed design stage of the propeller, which only considers aerodynamics and noise, but not structural strength, which makes the propeller design too conservative. The existing numerical method based on finite elements has too low design efficiency and cannot meet the needs of rapid iterative design of aircraft propellers. If the rapid prediction of propeller aerodynamics and noise can be achieved, and the structural deformation can be accurately analyzed based on stiffness, a multidisciplinary optimization design method suitable for the preliminary design stage of the propeller can be formed, which can further improve the low-noise design level of the propeller.

[0003] Therefore, a technology or solution is needed to achieve the above purpose. Summary of the invention

[0004] The purpose of the present application is to provide an aircraft propeller blade and a comprehensive design method for its aerodynamics, noise and stiffness, so as to solve or alleviate at least one problem in the background technology.

[0005] On the one hand, the technical solution of the present application is: a method for comprehensive design of aerodynamics, noise and stiffness of aircraft propeller blades, comprising:

[0006] Determining initial parameters of the propeller blade, wherein the initial parameters include geometric parameters, material parameters and operating condition parameters of the blade;

[0007] Calculating the propeller aerodynamic performance based on the initial parameters of the propeller blades to obtain the aerodynamic performance of the blades under multiple working conditions;

[0008] Carry out nonlinear deformation calculation of the blade to obtain the shape of the blade after deformation;

[0009] Carry out iterative calculation of the aerodynamic performance of the blades under multiple working conditions and the deformed blade shape, make them converge, and complete the aerodynamic and deformation coupling calculation of the propeller blades;

[0010] The noise at different propeller blade passing frequencies is calculated based on the frequency domain noise method;

[0011] The multi-objective optimization design is carried out by integrating the calculation methods of aerodynamics, deformation and noise. The geometric parameters and radial stiffness distribution are used as design variables, and the aerodynamics and noise under different working conditions are used as optimization targets for global optimization. The geometric parameters of the blades after comprehensive optimization are obtained.

[0012] The shape of the blade is drawn based on the comprehensively optimized geometric parameters, thereby obtaining the comprehensively optimized blade shape.

[0013] In a preferred embodiment of the present application, the geometric parameters include blade twist angle, chord length, side bend, sweep, thickness and radial distribution of the airfoil.

[0014] In a preferred embodiment of the present application, the material parameters include blade torsional stiffness, torsional center and elastic modulus.

[0015] In a preferred embodiment of the present application, the propeller aerodynamic performance calculation is carried out based on the vortex grid method and the method considering the airflow separation tail vortex, and the process includes:

[0016] According to the determined initial parameters of the blade, the radial grid number, chord-wise grid number, tail vortex calculation length and angle interval of the tail vortex calculation required for the aerodynamic performance calculation are set;

[0017] The blade is discretized into an attached vortex and a trailing vortex on the blade surface. The induced velocity is expressed by the vorticity. The induced velocity on the blade surface must satisfy the physical surface boundary conditions, and then the induced velocity of the vortex ring is obtained. At the same time, the force exerted on each vortex ring is obtained by the Kutta-Joukowski relationship, and the drag coefficient and lift coefficient of the compressible airfoil are considered to obtain the aerodynamic performance of the propeller blade.

[0018] In a preferred embodiment of the present application, the aerodynamic performance includes aerodynamic force distribution on the blade surface, total thrust and efficiency.

[0019] In a preferred embodiment of the present application, the nonlinear deformation calculation of the blade is carried out based on the transfer matrix, and the process includes:

[0020] The blade is simplified into a spatially pre-distorted cantilever rod structure, and the spatially pre-distorted cantilever rod is discretized into N-segment structures along the axial direction. The elastic modulus and torsion center of the material in each segment remain unchanged. It is represented by a straight line before deformation, and its bending and sweeping characteristics are represented by the transfer matrix relationship of the local unit coordinate vectors of adjacent straight lines.

[0021] Assuming that the material of the cantilever rod is adiabatic elastic and satisfies the Bernoulli-Euler beam, Saint-Venant torsion and that the axis of the rod passes through the shear center of the cross section, the relationship between the deformation and the force in each discrete segment is determined, and then the relationship between the transfer matrix after deformation and the force is clarified;

[0022] The shape of the deformed blade is obtained using the obtained aerodynamic force distribution and transfer matrix acting on the blade surface.

[0023] In a preferred embodiment of the present application, global optimization is performed based on a genetic algorithm combined with spline curve fitting.

[0024] On the other hand, the technical solution provided by the present application is: an aircraft propeller blade, wherein the propeller blade is obtained by any of the above-mentioned aircraft propeller blade aerodynamic, noise and stiffness comprehensive design methods.

[0025] The aircraft propeller blades and their aerodynamic, noise and stiffness comprehensive design provided in this application have controllable design variables, fully utilizing the advantages of the fast speed of the analytical method, and avoiding the aerodynamic and noise estimation deviations caused by the traditional method that cannot consider structural deformation, providing a more effective means for the optimization design of propeller blades in the preliminary design stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0027] Figure 1 This is a schematic diagram of the comprehensive optimization design process of aircraft propeller blades in this application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0029] In order to overcome the problem in the prior art that aircraft propeller blades usually only consider aerodynamics and noise, which makes the propeller design too conservative and the design efficiency too low to meet the needs of rapid iterative design of aircraft propellers, the present application proposes a comprehensive design method for aerodynamics, noise and stiffness of aircraft propeller blades.

[0030] like Figure 1 As shown, the present application provides a method for comprehensive design of aerodynamics, noise and stiffness of aircraft propeller blades, the method comprising the following steps:

[0031] S10, determining initial parameters of the propeller blades, wherein the initial parameters include geometric parameters, material parameters, operating condition parameters, etc.

[0032] In some embodiments of the present application, the propeller blades may be manufactured using composite laminates. The propeller blades using composite laminates are usually subjected to compression and / or shear loads.

[0033] By extracting the geometric features of the propeller blades, the geometric parameters of the blades can be obtained, including the blade twist angle, chord length, side bend, sweep, thickness and radial distribution of the airfoil, so that the blade radius, hub ratio, advance speed ratio, etc. can be determined.

[0034] According to the composite laminate used in the propeller blade, the material parameters of the composite laminate distributed along the radial direction can be obtained, including the blade torsional stiffness, torsional center and elastic modulus.

[0035] The operating parameters of the propeller blades, such as rotation speed, lift coefficient, drag coefficient, etc., can be determined based on the aircraft operating conditions.

[0036] S20, based on the initial parameters of the propeller blades, a rapid prediction of the propeller aerodynamic performance is carried out to obtain the aerodynamic performance of the blades under multiple working conditions.

[0037] In this application, the aerodynamic performance of the blades under multiple working conditions is quickly calculated based on the lifting surface method. The process includes:

[0038] S21, according to the determined initial parameters such as the blade installation angle and the rotation speed, the radial grid number, the chord-wise grid number, the tail vortex calculation length and the angular interval of the tail vortex calculation required for the aerodynamic performance calculation are set.

[0039] S22, the aerodynamic performance is calculated by using the vortex grid method that can realize the rapid evaluation of the propeller aerodynamic performance and the method considering the airflow separation tail vortex, that is, the blade is discretized into the attached vortex and the tail vortex on the blade surface, and the induced velocity is expressed by the vorticity. The induced velocity on the blade surface must meet the surface boundary conditions, and then the induced velocity of the vortex ring is obtained; at the same time, the force on each vortex ring is obtained by the Kutta-Joukowski relationship, and the airfoil drag coefficient C with compressibility is considered d and lift coefficient C L , and then the aerodynamic performance of the propeller can be obtained, which includes physical quantities such as aerodynamic force distribution on the blade surface, total thrust and efficiency.

[0040] S30, performing a fast calculation of the nonlinear deformation of the blade to obtain a deformed shape of the blade.

[0041] In this application, the nonlinear deformation of the blade is quickly calculated based on the transfer matrix, and the process includes:

[0042] S31, simplify the blade into a spatially pre-distorted cantilever rod structure, discretize the spatially pre-distorted cantilever rod into N segments along the axial direction, the elastic modulus and torsion center of the material in each segment remain unchanged, and can be represented by a straight line before deformation, and its bending and sweeping characteristics are represented by the transfer matrix relationship of the local unit coordinate vectors of adjacent straight lines;

[0043] S32, assuming that the material of the cantilever rod is adiabatic elastic and satisfies the Bernoulli-Euler beam, Saint-Venant torsion and that the axis of the rod passes through the shear center of the cross section, thereby determining the relationship between the deformation and the force in each discrete segment, and further clarifying the relationship between the transfer matrix after deformation and the force;

[0044] S33, using the aerodynamic force distribution and transfer matrix acting on the blade surface obtained in step S20, the shape of the deformed blade is obtained.

[0045] S40, performing coupled iterative calculation according to the aerodynamic performance obtained in step S20 and the deformation of the propeller blade under the aerodynamic force obtained in step S30, so as to achieve convergence.

[0046] Since the aerodynamic force distribution on the blade surface changes after the blade is deformed, it is necessary to consider the coupling characteristics between the aerodynamic and structural deformation. The present application couples the aerodynamic performance of step S20 and the blade deformation of step S30 for iterative calculation until convergence, thereby completing the aerodynamic and deformation coupling calculation of the propeller blade.

[0047] S50, based on the frequency domain noise method, quickly predicts the noise at different propeller blade passing frequencies, and realizes rapid calculation of propeller aerodynamic noise.

[0048] In this application, according to the Hanson frequency domain noise calculation method, after obtaining the blade shape and discrete aerodynamic force distribution on the blade surface when the propeller is running, the noise in the near field and far field of the propeller, at different azimuth angles, and at different blade passing frequencies can be obtained.

[0049] S60, a multi-objective optimization design is carried out by integrating the rapid calculation methods of aerodynamics, deformation and noise. The geometric parameters and radial stiffness distribution of the blades are used as design variables, and the aerodynamics and noise under different working conditions are used as optimization targets. The optimization algorithm is used for global optimization to obtain the design variables after comprehensive optimization.

[0050] In step S60 of the present application, in the process of multi-objective optimization design of aircraft propellers under different working conditions, aerodynamics, deformation and noise are comprehensively considered, and the design variables include blade twist angle, chord length, lateral bend, sweep, thickness and radial distribution of geometric parameters of airfoil and radial stiffness distribution. Since the variation space of stiffness is large in blade structure design, the present application also sets stiffness as one of the design variables. In addition, in the present application, aerodynamics and noise under different working conditions are optimized as multiple optimization targets, for example, noise under take-off conditions is the main target and aerodynamic efficiency is the secondary target, and aerodynamic efficiency under cruise conditions is the main target and noise is the secondary target. The unification of optimization targets is achieved by giving coefficients of different physical quantities under different working conditions.

[0051] In the present application, a genetic algorithm is selected and combined with spline curve fitting as an optimization algorithm, which can not only obtain the advantages of global optimization of the genetic algorithm, but also avoid the distorted structure caused by sudden changes in the design variables of the propeller along the radial direction.

[0052] S70, drawing a blade shape based on the comprehensively optimized geometric parameters, thereby obtaining a comprehensively optimized blade shape.

[0053] The aerodynamic, noise and stiffness comprehensive design method of aircraft propeller blades provided in the present application adopts the unsteady vortex grid method and combines the tail vortex separation prediction model to quickly evaluate the propeller aerodynamic force distribution under different working conditions, analyzes the single-frequency noise under different blade passing frequencies based on the frequency domain acoustic analogy theory, and uses the transfer matrix method to quickly evaluate the stiffness-based blade deformation, and performs low-noise optimization design based on genetic algorithms and multi-objective optimization methods. This method has controllable design variables, fully utilizes the advantages of the fast speed of analytical methods, and avoids the aerodynamic and noise estimation deviations caused by the inability of traditional methods to consider structural deformation, providing a more effective means for the optimization design of propeller blades in the preliminary design stage.

[0054] Finally, the present application also provides an aircraft propeller blade, which is designed using the above-mentioned aerodynamic, noise and stiffness comprehensive design method for aircraft propeller blades.

[0055] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for comprehensive design of aerodynamics, noise and stiffness of aircraft propeller blades, characterized in that: include: Determining initial parameters of the propeller blade, wherein the initial parameters include geometric parameters, material parameters and operating condition parameters of the blade; Calculating the propeller aerodynamic performance based on the initial parameters of the propeller blades to obtain the aerodynamic performance of the blades under multiple working conditions; The nonlinear deformation calculation of the blade is carried out based on the transfer matrix to obtain the shape of the deformed blade. The process includes: simplifying the blade into a spatially pre-twisted cantilever rod structure, discretizing the spatially pre-twisted cantilever rod into N-segment structures along the axial direction, and the elastic modulus and torsion center of the material in each segment remain unchanged. It is represented by a straight line before deformation, and its bending and sweeping characteristics are represented by the transfer matrix relationship of the local unit coordinate vectors of adjacent straight lines; assuming that the material of the cantilever rod is adiabatic elastic and satisfies the Bernoulli-Euler beam and Saint-Venant torsion parallel rod, the axis passes through the shear center of the cross section, thereby determining the relationship between the deformation and the force in each discrete segment, and then clarifying the relationship between the transfer matrix and the force after deformation; using the obtained aerodynamic force distribution and transfer matrix acting on the blade surface to obtain the shape of the deformed blade; Carry out iterative calculation of the aerodynamic performance of the blades under multiple working conditions and the deformed blade shape, make them converge, and complete the aerodynamic and deformation coupling calculation of the propeller blades; The noise at different propeller blade passing frequencies is calculated based on the frequency domain noise method; The multi-objective optimization design is carried out by integrating the calculation methods of aerodynamics, deformation and noise. The geometric parameters and radial stiffness distribution are used as design variables, and the aerodynamics and noise under different working conditions are used as optimization targets for global optimization. The geometric parameters of the blades after comprehensive optimization are obtained. The shape of the blade is drawn based on the comprehensively optimized geometric parameters, thereby obtaining the comprehensively optimized blade shape.

2. The aircraft propeller blade aerodynamic, noise and stiffness comprehensive design method according to claim 1, characterized in that: The geometric parameters include blade twist angle, chord length, side bend, sweep, thickness and radial distribution of the airfoil.

3. The aircraft propeller blade aerodynamic, noise and stiffness comprehensive design method according to claim 1, characterized in that: The material parameters include blade torsional stiffness, torsional center and elastic modulus.

4. The method for comprehensive design of aerodynamics, noise and stiffness of aircraft propeller blades according to any one of claims 1 to 3, characterized in that: The propeller aerodynamic performance calculation is carried out based on the vortex grid method and the method considering the airflow separation trailing vortex. The process includes: According to the determined initial parameters of the blade, the radial grid number, chord-wise grid number, tail vortex calculation length and angle interval of the tail vortex calculation required for the aerodynamic performance calculation are set; The blade is discretized into the attached vortex and the trailing vortex on the blade surface, and the induced velocity is expressed by the vorticity. The induced velocity on the blade surface must satisfy the physical surface boundary conditions, and then the induced velocity of the vortex ring is obtained. At the same time, the force exerted on each vortex ring is obtained by the Kutta-Joukowski relationship, and the drag coefficient and lift coefficient of the compressible airfoil are considered, and then the aerodynamic performance of the propeller blade is obtained.

5. The aircraft propeller blade aerodynamic, noise and stiffness comprehensive design method according to claim 4, characterized in that: The aerodynamic performance includes the aerodynamic force distribution on the blade surface, total thrust and efficiency.

6. The aircraft propeller blade aerodynamic, noise and stiffness comprehensive design method according to claim 5, characterized in that: Global optimization based on genetic algorithm combined with spline curve fitting.

7. An aircraft propeller blade, characterized in that: The propeller blade is obtained by the aircraft propeller blade aerodynamics, noise and stiffness comprehensive design method as described in any one of claims 1 to 6.

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