A method for constructing a fully parametric propeller model

Abstract

The present invention provides a method for constructing a fully parameterized propeller model, which specifically includes the following steps: S1: determining the parent propeller section airfoil corresponding to the propeller model to be constructed, and various radial parameters under different radial directions; S2: each radial parameter under different radial directions determined by S1 respectively constitutes an original parameter curve, and curve fitting is performed on each original parameter curve according to the F‑spline curve fitting principle to obtain a corresponding fitting parameter curve. In the curve fitting process, it is ensured that the variance of the fitting points of the final fitting parameter curve and the original parameter curve is the smallest; S3: using the fitting parameter curve corresponding to each radial parameter obtained in step S2 to realize the masked expression of the parametric surface along the radial direction to obtain a complete propeller model. The technical solution of the present invention solves the problem that the existing propeller blade model construction method requires manual three-dimensional modeling, which is cumbersome and error-prone.

Description

Technical Field

[0001] The present invention relates to the field of ship propulsion technology, and in particular to a method for constructing a fully parameterized propeller model. Background Art

[0002] The structure of the propeller blade model is relatively complex. When constructing the model, it is usually necessary to perform three-dimensional modeling manually, which is cumbersome and prone to errors, and requires a lot of time and effort. For example, Zhang Hongwei et al. proposed a program design method for calculating propeller type value point coordinates, and manually imported the data file through ProE software for solid modeling, but did not study the rapid modeling method after the type value points were imported into the software; Cheng Dong et al. conducted secondary development of UG / Grip, discussed the key technologies of propeller modeling, and created a three-dimensional propeller model; Wu Lihong et al. used MATLAB to calculate the spatial coordinate points of the propeller blades, and read the spatial coordinate points into ProE at one time, but needed to manually build a three-dimensional solid propeller; Liu Yongjie et al. used Excel to manually calculate the blade type value points, and used VB.NET language to write a program to import the type value point coordinate value data in Excel into CATIA to generate a type value point cloud map, but ultimately still needed to manually complete the establishment of the propeller three-dimensional model.

[0003] In existing research, there is no method of fully parametric modeling to perform integrated modeling of the propeller, so as to optimize the performance of the propeller. Summary of the invention

[0004] Based on the above technical problems that the existing propeller blade model construction method requires manual three-dimensional modeling, which is cumbersome and error-prone, a fully parametric propeller model construction method is provided, which uses a fully parametric modeling approach to integrate modeling of the propeller, thereby optimizing the performance of the propeller.

[0005] The technical means adopted by the present invention are as follows:

[0006] A method for constructing a fully parameterized propeller model comprises the following steps:

[0007] S1: Determine the parent propeller section airfoil corresponding to the propeller model to be constructed, as well as various radial parameters under different radial directions;

[0008] S2: Each radial parameter under different radial conditions determined by S1 constitutes an original parameter curve. According to the F-spline curve fitting principle, each original parameter curve is subjected to curve fitting to obtain a corresponding fitting parameter curve. During the curve fitting process, the variance of the fitting points between the final fitting parameter curve and the original parameter curve is ensured to be the smallest.

[0009] S3: Using the fitting parameter curves corresponding to the radial parameters obtained in step S2, a masked method expression of the parameterized surface along the radial direction is achieved to obtain a complete propeller model.

[0010] Further, radial parameters include chord length, thickness, crown, pitch, skew and pitch.

[0011] Furthermore, step S2 specifically includes the following steps:

[0012] S21: For a certain original parameter curve, select the first and last points as the reference points of the fitting curve, the first point represents the starting point of the first F-spline curve, and the last point represents the end point of the second F-spline curve;

[0013] S22: intercepting n fitting points from the head point to the tail point on the original parameter curve to fit the original parameter curve, each of the intercepted points can be used as the end point of the first F-spline curve and the starting point of the second F-spline curve, and the two F-spline curves corresponding to each point are fitted into an intermediate fitting curve, and finally n intermediate fitting curves are obtained;

[0014] S23: Calculate the variance of n fitting points intercepted from each intermediate fitting curve and n fitting points intercepted from the original parameter curve, and take the intermediate fitting curve with the smallest variance as the final fitting parameter curve. The variance calculation formula is as follows:

[0015] s 2 =[(x 1 -x) 2 +...(x n -x) 2 ] / n

[0016] Among them, s 2 represents the variance, x 1 ....x n represents the value of each fitting point, and x represents x 1 ....x n The average value of , n represents the number of fitting points.

[0017] Furthermore, step S22 extracts 50 fitting points from the head point to the tail point on the original parameter curve for curve fitting.

[0018] Furthermore, step S3 is implemented using the Curve Engine function of CAESES.

[0019] Furthermore, the propeller model obtained by S3 can be visualized through CAESES.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The fully parametric propeller model construction method provided by the present invention realizes the parametric modeling of the propeller based on the F-spline curve fitting principle programming, fits the radial parameter distribution of the propeller with an F-spline curve respectively, and adds the restriction condition of minimum variance of the fitting points during curve fitting, which greatly reduces the error between the fitting curve and the original curve; according to the fitted propeller radial parameter curve, the shape of the mother propeller can be accurately described, and the smoothness of the propeller geometric shape in the generated sample space is guaranteed.

[0022] Based on the above reasons, the present invention can be widely promoted in the fields of wings, rudder blades, impellers and pump blades in the fields of aviation, aerospace, navigation and industrial energy and power. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 This is a comparison chart between the original chord length parameter curve (chord) and the chord length fitting parameter curve chord_fit.

[0025] Figure 2 It is a comparison chart between the original skew parameter curve (skew) and the skew fitting parameter curve skew_fit.

[0026] Figure 3 Schematic diagram of six fitting parameter curves. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use.

[0028] Example 1

[0029] The present invention provides a method for constructing a fully parameterized propeller model, which specifically comprises the following steps:

[0030] S1: Determine the parent propeller section airfoil corresponding to the propeller model to be constructed, as well as various radial parameters at different radial directions, that is, radial parameters at different radii of the propeller;

[0031] S2: Each radial parameter under different radial conditions determined by S1 constitutes an original parameter curve. According to the F-spline curve fitting principle, each original parameter curve is subjected to curve fitting to obtain a corresponding fitting parameter curve. During the curve fitting process, the variance of the fitting points between the final fitting parameter curve and the original parameter curve is ensured to be the smallest.

[0032] S3: Using the fitting parameter curves corresponding to the radial parameters obtained in step S2, a masked method expression of the parameterized surface along the radial direction is achieved to obtain a complete propeller model.

[0033] The present invention utilizes fewer control variables to accurately fit the curve and the idea of ​​minimizing the variance of the fitting points, which greatly reduces the error between the fitting parameter curve and the original parameter curve; the F-Spline curve is used to express the characteristic parameters of the propeller blade parameters, which can clearly express the distribution of the propeller chord length, thickness, camber, pitch, and pitch parameters, and at the same time, a smoother distribution curve is generated after changing the parameters. The propeller generated in this way can maintain good smoothness;

[0034] like Figure 1-2 As shown, it can be seen that the fitting parameter curve obtained by the method of the present invention has a small error with the original parameter curve, and can accurately describe the shape of the propeller and is smooth.

[0035] Furthermore, different types of propellers correspond to different two-dimensional airfoil profiles and different radial parameters, such as Figure 3 As shown, the radial parameters of the present invention include chord, thickness, camber, rake, skew, and pitch.

[0036] Furthermore, step S2 specifically includes the following steps:

[0037] S21: For a certain original parameter curve, select the first and last points as the reference points of the fitting curve, the first point represents the starting point of the first F-spline curve, and the last point represents the end point of the second F-spline curve;

[0038] S22: intercepting n fitting points from the head point to the tail point on the original parameter curve to fit the original parameter curve, each of the intercepted points can be used as the end point of the first F-spline curve and the starting point of the second F-spline curve, and the two F-spline curves corresponding to each point are fitted into an intermediate fitting curve, and finally n intermediate fitting curves are obtained;

[0039] S23: Calculate the variance of n fitting points intercepted from each intermediate fitting curve and n fitting points intercepted from the original parameter curve, and take the intermediate fitting curve with the smallest variance as the final fitting parameter curve. The variance calculation formula is as follows:

[0040] s 2 =[(x 1 -x) 2 +...(x n -x) 2 ] / n

[0041] Among them, s 2 represents the variance, x 1 ....x n represents the value of each fitting point, and x represents x 1 ....x n The average value of , n represents the number of fitting points.

[0042] Furthermore, step S22 extracts 50 fitting points from the head point to the tail point on the original parameter curve for curve fitting.

[0043] Furthermore, step S3 is implemented using the Curve Engine function of CAESES.

[0044] Furthermore, the propeller model obtained by S3 can be visualized through CAESES.

[0045] The present invention relates to the field of ship propulsion. When optimizing the performance of a propeller, it is necessary to establish a sufficient sample space for optimization calculation, that is, to achieve full parametric modeling of the parent propeller. The modeling method provided by the present invention can be integrated with secondary development programming on CAESES. Under the premise that the radial parameters of the propeller model to be constructed are known, the full parametric propeller modeling can be completed by running the program. There is no need to manually complete the establishment of the propeller three-dimensional model, and the relationship between the geometric characteristics of the propeller and the propeller performance can be better established.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a fully parameterized propeller model, characterized in that: The specific steps include: S1: Determine the parent propeller section airfoil corresponding to the propeller model to be constructed, as well as various radial parameters under different radial directions; S2: Each radial parameter under different radial conditions determined by S1 constitutes an original parameter curve. According to the F-spline curve fitting principle, each original parameter curve is subjected to curve fitting to obtain a corresponding fitting parameter curve. During the curve fitting process, the variance of the fitting points between the final fitting parameter curve and the original parameter curve is ensured to be the smallest. Step S2 specifically includes the following steps: S21: For a certain original parameter curve, select the first and last points as the reference points of the fitting curve, the first point represents the starting point of the first F-spline curve, and the last point represents the end point of the second F-spline curve; S22: intercepting n fitting points from the head point to the tail point on the original parameter curve to fit the original parameter curve, each of the intercepted points can be used as the end point of the first F-spline curve and the starting point of the second F-spline curve, and the two F-spline curves corresponding to each point are fitted into an intermediate fitting curve, and finally n intermediate fitting curves are obtained; S23: Calculate the variance of n fitting points intercepted from each intermediate fitting curve and n fitting points intercepted from the original parameter curve, and take the intermediate fitting curve with the smallest variance as the final fitting parameter curve. The variance calculation formula is as follows: s 2 =[(x1-x) 2 +...(x n -x) 2 ] / n Among them, s 2 represents the variance, x1....x n Represents the value of each fitting point, x represents x1....x n The average value of , n represents the number of fitting points; S3: Using the fitting parameter curves corresponding to the radial parameters obtained in step S2, a masked method expression of the parameterized surface along the radial direction is achieved to obtain a complete propeller model.

2. The method for constructing a fully parameterized propeller model according to claim 1, characterized in that: Radial parameters include chord length, thickness, crown, trim, skew and pitch.

3. The method for constructing a fully parameterized propeller model according to claim 1, characterized in that: In step S22, 50 fitting points are intercepted from the head point to the tail point on the original parameter curve for curve fitting.

4. The method for constructing a fully parameterized propeller model according to claim 1, characterized in that: Step S3 is implemented using the Curve Engine function of CAESES.

5. The method for constructing a fully parameterized propeller model according to claim 4, characterized in that: The propeller model obtained by S3 can be visualized using CAESES.

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