An optimization design method for variable section rim thrusters based on section cylindrical coordinate changes

Abstract

The present invention provides a method for optimizing the design of a variable-section rim thruster based on changes in section cylindrical coordinates, comprising the following steps: obtaining the geometric characteristic parameters of a parent thruster; selecting the chord length and thickness of the blade and duct airfoil sections, as well as the position and number of the modified sections, as design parameters and determining the parameter variation range and minimum sample variance; obtaining a sample database using a low-variance sampling sequence based on the design parameters; selecting a sample and generating a blade by modifying the blade and duct section profile points according to the sample, and then combining them to generate a rim thruster model; and accurately obtaining the hydrodynamic performance of the rim thruster model corresponding to the sample using a finite element theory hydrodynamic performance calculation program. This design method can flexibly modify the structure of an existing rim thruster without being constrained by traditional design methods, thereby finding more suitable structural parameters and laying the foundation for the future development of suitable rim thruster design concepts and methods.

Description

Technical Field

[0001] The present invention relates to the field of shipbuilding and marine engineering, and in particular to an optimization design method for a variable-section rim propeller based on changes in section cylindrical coordinates. Background Art

[0002] In recent years, with the needs of naval defense construction and the development of maritime trade, the performance requirements for ship propulsion systems have become increasingly stringent. The disadvantages of traditional shaft-driven propulsion systems have become increasingly apparent, and they are no longer able to meet these requirements. For example, traditional shaft-driven propulsion systems have many components, complex structures, large cabin space occupation, high energy loss, difficulty in vibration and noise control, and high construction and maintenance costs. These shortcomings have led to a gradual shift in attention to more advanced shaftless propulsion systems.

[0003] Currently, there is no recognized and complete design concept and process for shaftless rim-driven propulsion. Existing rim-driven propulsion systems are all completed by making adaptive modifications to the design process of traditional propellers. The Chinese patent "A fully parametric rim-driven propulsion system design method, device and storage medium" (CN117429575A) discloses a fully parametric rim-driven propulsion system design method. However, this method is roughly the same as the traditional propeller design methods involved in the Chinese patent "Propeller database establishment method based on fully parametric design of Bezier curves" (CN116991826A) and the Chinese patent "A propeller blade parameterization and surface generation method based on B-splines" (CN115358024A). It is just that the traditional propeller design method has been adaptively modified to form the rim-driven propulsion system design method. Although the rim propeller is very similar to the traditional ducted propeller in appearance, the difference in flow field between the two and the difference in torque at the root of the blade caused by the load of the blade thrust make it unreasonable to completely copy the design method of the traditional propeller or make only slight adjustments to complete the design of the rim propeller. The current efficiency defects of the rim propeller are also largely related to the lack of reasonable design concepts and methods. In contrast, the present invention proposes a variable-section rim propeller optimization design method based on the change of section cylindrical coordinates. It can flexibly modify the structure of the existing rim propeller without being constrained by traditional design methods, find more suitable structural parameters, and lay the foundation for proposing suitable rim propeller design concepts and methods in the future. Summary of the Invention

[0004] The purpose of the present invention is to provide a variable-section rim thruster optimization design method based on the change of section cylindrical coordinates. This design method can flexibly modify the structure on the existing rim thruster, is not constrained by traditional design methods, and find more suitable structural parameters, laying the foundation for proposing suitable rim thruster design concepts and methods in the future.

[0005] The present invention is achieved in that:

[0006] The present invention provides a method for optimizing the design of a variable-section rim propeller based on changes in section cylindrical coordinates, which is characterized by comprising the following steps:

[0007] Step 1: Obtain the geometric characteristic parameters of the mother propeller; the parameters include the spatial coordinates of the shape value points on each radial blade section and the spatial coordinates of the contour shape value points on the duct section;

[0008] Step 2: Select the chord length, thickness, pitch of the blade and duct airfoil section, as well as the position and number of the changed sections as design parameters and determine the parameter variation range and minimum sample interval;

[0009] Step 3: Based on the design parameters, a sample database is obtained by using uniform stratified sampling, Halton sequence, Sobol sequence, and other algorithms that can uniformly sample the sample space;

[0010] Step 4: Select a sample and modify the blade section and duct section shape points according to the sample to generate a blade, and then combine them to generate a rim propeller model;

[0011] Step 5: Combine the finite element theory hydrodynamic performance calculation program to accurately obtain the hydrodynamic performance of the rim thruster model corresponding to the sample, providing a basis for optimizing the thruster performance;

[0012] Step 6: Repeat the above steps to find the N models with the best performance, and then resample near the N best model samples to obtain a new sample database with a smaller gap;

[0013] Step 7: Select samples in the new database and repeat the above steps until the final sample gap meets the requirements and export the final optimal sample and calculation results.

[0014] In some optional embodiments, in step 1, the blade section profile point is a point on the section where a cylinder with the rotation axis as the axis is tangent to the blade.

[0015] In some optional implementation schemes, in step 1, the spatial coordinates need to convert the spatial rectangular coordinates into coordinates on a cylindrical coordinate system, expressed as (r, θ, z).

[0016] In some optional embodiments, in step 3, the algorithm capable of uniformly sampling in the sample space is one of uniform stratified sampling, Halton sequence, and Sobol sequence.

[0017] In some optional embodiments, in step 4, the selected samples are all based on the guide edge as the baseline, and a sample is selected that increases the local chord length or local thickness of the radius section by x%, or increases the local chord length and local thickness or local pitch at the same time. The section coordinates are changed according to the sample, and the cylindrical coordinates of the section value point are changed every other section so that the chord length of the section increases by Y%. Then, the blade is generated based on the B-spline curve to change the blade section, and the duct is generated according to normal conditions. Then, a rim propeller model with a wavy concave-convex structure trailing edge is generated by combining the two. Wherein, X and Y are natural numbers, 0 <X<15,0<Y<15。

[0018] In some optional implementations, the modified cylindrical coordinates described in step 4 are modified to allow the blade to form a desired shape. The method for modifying the cylindrical coordinates is as follows:

[0019] Method for changing the local chord length of a radial section: Assume that the cylindrical coordinates of the point on the leading edge of the section are (r1, θ1, z1), and the cylindrical coordinates of the point on the trailing edge are (r2, θ2, z2). If the shape of the trailing edge of the blade is to be changed, then the point on the leading edge is used as the base point. After the chord length of the section is increased by x%, the cylindrical coordinates of the value points on the trailing edge can be calculated using the following formula:

[0020] r3=r2=r1

[0021] θ3=(θ2-θ1)×(1+x%)+θ1

[0022] z3=(z2-z1)×(1+x%)+z1

[0023] All other points remain unchanged. At this time, the leaf surface curve and leaf back curve are formed by connecting the various type value points based on the B-spline curve. The thickness remains unchanged and the section with the chord length at the edge protrudes by x% is obtained.

[0024] If you need to reduce the section chord length, just change the x in x% to a negative number;

[0025] If you need to change the blade into a concave-convex structure along the edge, you only need to modify it once at intervals of the same number of radius sections;

[0026] If the shape of the guide edge needs to be changed, the point on the edge is used as the base point. After the chord length of the section increases by x%, the cylindrical coordinates of the value point on the guide edge can be calculated by the following formula:

[0027] r3=r2=r1

[0028] θ3=(θ1-θ2)×(1+x%)+θ2

[0029] z3=(z1-z2)×(1+x%)+z2.

[0030] In some optional implementations, the modified cylindrical coordinates described in step 4 are modified to allow the blade to form a desired shape. The method for modifying the cylindrical coordinates is as follows:

[0031] Method for changing the local thickness of a radial section: The blade surface curve and the blade back curve of each section are composed of the same number of evenly distributed type value points. Assuming that the first point on the blade surface curve close to the leading edge is (r5, θ5, z5), and the first point on the blade back curve close to the leading edge is (r6, θ6, z6), then after the thickness increases by x%, the cylindrical coordinates of the first point on the blade surface curve close to the leading edge are:

[0032] r7=r5=r6

[0033] θ7=(θ5-θ6)×(1+0.5×x%)+θ6

[0034] z7=(z5-z6)×(1+0.5×x%)+z6

[0035] The cylindrical coordinates of the first point on the blade curve close to the guide edge are:

[0036] r8=r5=r6

[0037] θ8=(θ6-θ5)×(1+0.5×x%)+θ5

[0038] z8=(z6-z5)×(1+0.5×x%)+z5

[0039] Change the second point, the third point, and so on until all points on the section are changed. Then, based on the B-spline curve, connect the various value points to form the leaf surface curve and the leaf back curve. You can get a section with the leaf back curve and the leaf surface curve shifted back by 0.5 times x% based on the section centerline, thereby achieving a section with a leaf thickness increased by x%.

[0040] If the leaf surface curve is used as the basis, the value of each point on the leaf back curve can be increased by x% according to the above formula; if the leaf back curve is used as the basis, the value of each point on the leaf surface curve can be increased by x% according to the above formula.

[0041] In some optional implementations, the modified cylindrical coordinates described in step 4 are modified to allow the blade to form a desired shape. The method for modifying the cylindrical coordinates is as follows:

[0042] Method for changing the local pitch of a radial section: Assume that the cylindrical coordinates of the point on the guide edge of the section are (r1, θ1, z1), and the cylindrical coordinates of the point on the trailing edge are (r2, θ2, z2), then the pitch of the section P = (z1-z2) / (θ1-θ2)×2π. From this formula, it can be seen that the pitch of the section will not be changed after the steps of changing the chord length and thickness of the section are executed; if the point on the guide edge is used as the base point, the coordinates of any other point are (r x ,θ x ,z x ), then the cylindrical coordinates of the point after the pitch of the section increases by x% can be calculated by the following formula:

[0043] r y =r1=r x

[0044] θ y =θ x

[0045] z y =(z x -z1)×(1+x%)+z1

[0046] By changing all points except the base point on the entire section in sequence using the above formula, and then connecting the various type value points based on the B-spline curve to form the blade surface curve and the blade back curve, you can get a section based on the guide edge with a pitch increased by x%;

[0047] If the following edge is used as the basis, it is only necessary to replace the coordinates of the point on the following edge before modification with (r1, θ1, z1) in the above formula, and each point of the section can be changed with the above formula to achieve it; if the blade centerline is used as the basis, it is only necessary to replace the coordinates of the point on the blade centerline on the section with (r1, θ1, z1) in the above formula, and each point of the section can be changed with the above formula to achieve it.

[0048] In some optional implementations, the modified cylindrical coordinates described in step 4 are modified to allow the blade to form a desired shape. The method for modifying the cylindrical coordinates is as follows:

[0049] Method to change the local chord length and thickness of a radial section at the same time: If the point on the guide edge is used as the base point, assuming that the cylindrical coordinates of the point on the guide edge are (r1, θ1, z1), and the coordinates of any other point are (r x ,θ x ,z x ), then the cylindrical coordinates of the point after the thickness and chord length increase by x% are:

[0050] r y =r 1 =r x

[0051] θ y=(θ x -θ1)×(1+x%)+θ1

[0052] z y =(z x -z1)×(1+x%)+z1

[0053] Use the above formula to sequentially modify all points on the entire section except the base point, and then connect the various value points based on the B-spline curve to form the blade surface curve and the blade back curve, so that the section with the leading edge as the basis and the blade thickness and chord length increased by x% can be obtained; if the basis is the trailing edge, then it is only necessary to replace the coordinates of the point on the trailing edge before the modification with (r1, θ1, z1) in the above formula, and each point of the section can be modified with the above formula to achieve this; if the basis is the blade centerline, then it is only necessary to replace the coordinates of the point on the blade centerline on the section with (r1, θ1, z1) in the above formula, and each point of the section can be modified with the above formula to achieve this;

[0054] If you want to change the pitch at the same time, you only need to perform the above pitch change steps again because the pitch of the section will not be changed after the steps of changing the chord length and thickness are executed.

[0055] In some optional implementation schemes, the modified converted cylindrical coordinates described in step 4 are modified to allow the catheter to form a desired shape. The method for modifying the catheter coordinates is as follows: the catheter is formed by rotating the catheter cross section and generally has only one shape value point of the cross-section contour. However, a wavy leading edge or trailing edge structure cannot be formed by rotating a single cross-section. Therefore, the entire catheter needs to be differentiated and multiple cross-sections are used to complete the catheter modeling.

[0056] The method of modifying the blade shape and the duct shape described in step 4 is completed by the Python program. After the coordinate database is established, a program is compiled according to the above formula. If you want to get the required blades and ducts, you can use the program to directly calculate the spatial rectangular coordinates of all the modified shape points, and then import these spatial rectangular coordinates into the modeling to get the required model.

[0057] The beneficial effects of the present invention are:

[0058] 1. The existing rim propeller design refers to the design method of traditional propellers, so the cross-sectional shapes of the designed rim propeller blades at different radii are the same. Even if there is a rim propeller with partially variable cross-sectional shapes, it will seriously increase the design difficulty, and there are only two different cross-sectional shapes at most. The present invention can easily change the cross-sectional shape, and the change is one cross-sectional shape at a time, so it is easy to obtain a rim propeller with variable cross-sectional shapes or even different cross-sectional shapes at each radius.

[0059] 2. The wavy bionic structure imitating the whale fin has been studied on hydrofoils and traditional propellers, but the existing research only considered the wavelength and amplitude of the wavy bionic structure. In essence, it is to change the chord length and thickness of a blade section at the same time, as well as the interval between the modified sections. Therefore, the research results are not ideal. The present invention can change the chord length or thickness of a blade section independently, so it has greater research prospects and can obtain more ideal results.

[0060] 3. The present invention also provides a method for changing the pitch. When the present invention designs a variable-section rim propeller with good performance, if the pitch needs to be changed due to changes in working conditions, the pitch of the variable-section rim propeller can be directly changed to adapt to the new working conditions.

[0061] 4. The original rim thruster design method is too much based on the design method of traditional thrusters, so the efficiency is not as good as that of traditional thrusters. The present invention has extremely high flexibility, which can make the rim thruster design free from the constraints of traditional design methods and find more suitable structural parameters, laying the foundation for proposing suitable rim thruster design concepts and methods in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0063] Figure 1 A schematic diagram of a process flow provided by an embodiment of the present invention.

[0064] Figure 2 Schematic diagram of the distribution of 50 samples provided in this embodiment of the present invention.

[0065] Figure 3 A sample of increasing the local chord length of a radius section by 10% provided by an embodiment of the present invention, and a schematic diagram of the original section and the changed section after the section coordinates are changed according to the sample.

[0066] Figure 4 A sample with a 10% local thickness of a radius section provided by an embodiment of the present invention, and a schematic diagram of the original section and the changed section after the section coordinates are changed according to the sample.

[0067] Figure 5 A sample with a 10% local thickness of a radius section provided by an embodiment of the present invention, and a schematic diagram of the original section and the changed section after the section coordinates are changed according to the sample.

[0068] Figure 6A comparison diagram of the initial rim thruster provided in an embodiment of the present invention and the optimized rim thruster model with a wavy concave-convex trailing edge. DETAILED DESCRIPTION

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0070] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0071] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0072] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0073] Furthermore, terms such as "horizontal," "vertical," and "overhanging" do not necessarily imply that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0074] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0075] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0076] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0077] This embodiment provides a variable section rim thruster optimization design method based on section cylindrical coordinate changes, including: Figure 1 The following steps are shown:

[0078] Step 1: Choose a rim propeller as the master model, extract its surface type value points, extract the number of sections of the type value points and the type value of each section. The number of points determines the size of the sample space.

[0079] Obtaining geometric characteristic parameters of the mother propeller; the parameters include the spatial coordinates of the shape value points on each radius blade section and the spatial coordinates of the contour shape value points on the duct section;

[0080] The blade section value point is a point on the section surface where the cylinder with the rotation axis as the axis is tangent to the blade;

[0081] The spatial coordinates need to be converted from spatial rectangular coordinates to coordinates on a cylindrical coordinate system, expressed as (r, θ, z);

[0082] In this example, the section interval is 0.1r, and 20 points are evenly selected on each section, with 10 points on the back and the front of the leaf respectively;

[0083] Step 2: Select the chord length, thickness, pitch of the blade and duct airfoil section, as well as the position and number of the changed sections as design parameters and determine the parameter variation range and minimum sample interval;

[0084] Step 3: Based on the design parameters, the Sobel algorithm is used to sample and obtain the sample database (preliminary sampling). The sample distribution of the 50 samples is as follows: Figure 2 As shown;

[0085] Step 4: Select a sample and change the blade section and duct section value points according to the sample. The three examples in this example all use the guide edge as the baseline:

[0086] (1) Select a sample with a 10% local chord length of the radius section, and change the section coordinates according to the sample to the original section and the changed section as follows: Figure 3 As shown;

[0087] (2) Select a sample with a 10% local thickness increase in the radius section, and change the section coordinates of the sample to the original section and the changed section as shown in the following example. Figure 4 As shown;

[0088] (3) Select a sample that increases the local thickness and chord length of the radius section by 10%, and change the section coordinates of the original section and the changed section according to the sample. Figure 5 As shown;

[0089] Continue with the first example, change the cylindrical coordinates of the section value point every other section so that the chord length of the section increases by 10%, and then generate the blade based on the changed blade section based on the B-spline curve. The duct is generated according to normal conditions, and then combined to generate a rim propeller model with a wavy concave-convex structure trailing edge. The original rim propeller and the generated rim propeller model with a wavy concave-convex structure trailing edge are shown as follows: Figure 6 As shown;

[0090] In the above technical solution, the modified cylindrical coordinates described in step 4 are modified to allow the blade to form the desired shape. The method for modifying the cylindrical coordinates is as follows:

[0091] (1) Method for changing the local chord length of a radial section: Assume that the cylindrical coordinates of the point on the leading edge of the section are (r1, θ1, z1), and the cylindrical coordinates of the point on the trailing edge are (r2, θ2, z2). If the shape of the trailing edge of the blade is to be changed, the point on the leading edge is used as the base point (fixed point). After the chord length of the section is increased by x%, the cylindrical coordinates of the value points on the trailing edge can be calculated by the following formula:

[0092] r3=r2=r1

[0093] θ3=(θ2-θ1)×(1+x%)+θ1

[0094] z3=(z2-z1)×(1+x%)+z1

[0095] All other points remain unchanged. At this time, the leaf surface curve and the leaf back curve are formed by connecting the various type value points based on the B-spline curve, and a section with unchanged thickness and only the chord length protruding by x% at the edge can be obtained.

[0096] To reduce the chord length of a section, simply make the x in x% negative. To change the blade's edge to a concave-convex structure, simply modify the section once every equal number of radius intervals. These two implementation methods apply to all subsequent steps and will not be further explained.

[0097] If the shape of the leading edge needs to be changed, the point on the leading edge is used as the base point (fixed point). After the chord length of the section increases by x%, the cylindrical coordinates of the value point on the leading edge can be calculated by the following formula:

[0098] r3=r2=r1

[0099] θ3=(θ1-θ2)×(1+x%)+θ2

[0100] z3=(z1-z2)×(1+x%)+z2

[0101] (2) Method for changing the local thickness of a radial section: The blade surface curve and the blade back curve of each section are composed of the same number of uniformly distributed shape value points. Assuming that the first point on the blade surface curve close to the leading edge is (r5, θ5, z5), and the first point on the blade back curve close to the leading edge is (r6, θ6, z6), then after the thickness increases by x%, the cylindrical coordinates of the first point on the blade surface curve close to the leading edge are:

[0102] r7=r5=r6

[0103] θ7=(θ5-θ6)×(1+0.5×x%)+θ6

[0104] z7=(z5-z6)×(1+0.5×x%)+z6

[0105] The cylindrical coordinates of the first point on the blade curve close to the guide edge are:

[0106] r8=r5=r6

[0107] θ8=(θ6-θ5)×(1+0.5×x%)+θ5

[0108] z8=(z6-z5)×(1+0.5×x%)+z5

[0109] By sequentially changing the second point, the third point, and so on, until all points on the entire section have been modified, and then connecting the various value points using a B-spline curve to form the leaf surface curve and the leaf back curve, you can obtain a section with a leaf thickness increased by x% by shifting the leaf back curve and the leaf surface curve backward by 0.5 times the leaf centerline (the fixed line) as the basis. If the leaf surface curve is the fixed line, then each point on the leaf back curve can be increased by x% according to the above formula; if the leaf back curve is the fixed line, then each point on the leaf surface curve can be increased by x% according to the above formula.

[0110] (3) Method for changing the local pitch of a radial section: Assume that the cylindrical coordinates of the point on the leading edge of the section are (r1, θ1, z1), and the cylindrical coordinates of the point on the trailing edge are (r2, θ2, z2), then the pitch of the section P = (z1-z2) / (θ1-θ2)×2π. From this formula, it can be seen that the pitch of the section will not be changed after the steps of changing the chord length and thickness of the section are executed. If the point on the leading edge is used as the base point (fixed point), the coordinates of any other point are (r x ,θ x ,z x ), then the cylindrical coordinates of the point after the pitch of the section increases by x% can be calculated by the following formula:

[0111] r y =r1=r x

[0112] θ y =θ x

[0113] z y =(z x -z1)×(1+x%)+z1

[0114] By sequentially modifying all points on the entire section except the base point using the above formula, and then connecting the various value points using a B-spline curve to form the blade surface curve and blade back curve, you can obtain a section with the leading edge as the basis (fixed line) and the pitch increased by x%. If the basis is the trailing edge (fixed line), simply replace the coordinates of the point on the trailing edge before modification in the above formula (r1, θ1, z1), and modify each point of the section according to the above formula to achieve this. If the basis is the blade centerline (different from the section centerline, the point on the blade centerline on the section is the midpoint of the line connecting the point on the leading edge and the point on the trailing edge on the section) (fixed line), simply replace the coordinates of the point on the blade centerline on the section in the above formula (r1, θ1, z1), and modify each point of the section according to the above formula to achieve this.

[0115] (4) Method for simultaneously changing the local chord length and thickness of a radial section: If the point on the guide edge is used as the base point, assuming that the cylindrical coordinates of the point on the guide edge are (r1, θ1, z1), and the coordinates of any other point are (r x ,θ x ,z x ), then the cylindrical coordinates of the point after the thickness and chord length increase by x% are:

[0116] r y =r1=r x

[0117] θ y =(θ x -θ1)×(1+x%)+θ1

[0118] z y =(z x -z1)×(1+x%)+z1

[0119] By sequentially modifying all points on the entire section except the base point using the above formula, and then connecting the various type value points using B-spline curves to form the blade surface curve and blade back curve, a section with the leading edge as the basis (fixed line) and the blade thickness and chord length increased by x% can be obtained. If the following edge is the basis (fixed line), simply replace the coordinates of the point on the following edge before the modification with (r1, θ1, z1) in the above formula, and modify each point of the section using the above formula to achieve this. If the blade centerline (different from the section centerline, the point on the blade centerline on the section is the midpoint of the line connecting the point on the leading edge and the point on the following edge on the section) is the basis (fixed line), simply replace the coordinates of the point on the blade centerline on the section with (r1, θ1, z1) in the above formula, and modify each point of the section using the above formula to achieve this.

[0120] If you want to change the pitch at the same time, you only need to perform the above pitch change steps again because the pitch of the section will not be changed after the steps of changing the chord length and thickness are executed.

[0121] Modify the converted cylindrical coordinates as described in step 4 to allow the catheter to form the desired shape. The method for modifying the catheter coordinates is as follows: The catheter is formed by rotating the catheter cross section and generally has only one shape value point of the cross section contour. However, the wavy leading edge or trailing edge structure cannot be formed by rotating a single cross section. Therefore, the entire catheter needs to be differentiated and multiple cross sections are used to complete the catheter modeling.

[0122] (1) Method of obtaining coordinates of other sections by differential catheter: Assuming that the cylindrical coordinates of a point on the catheter section coinciding with the x-axis are (r9, 0, z9), then the coordinates of the corresponding point on the next section are (r9, Δθ, z9), where Δθ is the angle between the two sections. In principle, the smaller the angle, the better. However, the smaller the angle, the more sections there are and the more complex it is. Therefore, the specific size depends on your needs.

[0123] (2) Method for changing the local length of a catheter section: If the leading edge of the catheter is taken as the baseline, assuming that the cylindrical coordinates of the point on the leading edge are (r 10 ,θ 10 ,z 10 ), the coordinates of the point on the trailing edge are (r 11 ,θ 11 ,z 11 ), then the cylindrical coordinates of the point on the trailing edge after the length increases by x% are (r 11 ,θ 11 ,(z 11 -z 10 )×(1+x%)+z 10 Because the inner and outer curves of the duct section are parallel for a long section, I modified all the points behind the parallel region. I modified the section again, then generated the surface to create a duct model with a wavy trailing edge.

[0124] If the trailing edge of the catheter is taken as the baseline, the cylindrical coordinates of the point on the leading edge after the length increases by x% after modification are (r 10 ,θ 10 ,(z 10 -z 11 )×(1+x%)+z 11 ), other modifications are the same as above.

[0125] (3) Method for changing the local thickness of a catheter section: If the inner side of the catheter is taken as the baseline, assuming that the cylindrical coordinates of the point on the inner side of the two points with the same z axis are (r 12 ,θ 12 ,z 12 ), the coordinates of the point on the outside are (r 13 ,θ 13 ,z 12 ), then the cylindrical coordinates of the point on the outside after the thickness increases by x% are ((r 13 -r 12 )×(1+x%)+r 12 ,θ 13 ,z 12 ), modify all the shape value points in the same way to increase the section thickness by x%, and modify the section again at intervals. After generating the surface, a catheter model with a wavy thickness can be obtained.

[0126] If the outer side of the catheter is taken as the baseline, the cylindrical coordinates of the point on the inner side after the thickness increases by x% after modification are ((r 12 -r 13 )×(1+x%)+r 13 ,θ 12 ,z 12 ), other situations are the same as above.

[0127] If the centerline of the catheter is used as the baseline, the cylindrical coordinates of the point on the inner side after the thickness increases by x% are ((r12-r13)×(1+0.5×x%)+r13,θ12,z12), and the cylindrical coordinates of the point on the outer side are ((r 13 -r 12 )×(1+0.5×x%)+r 12 ,θ 13 ,z 12 ), other situations are the same as above.

[0128] Method for simultaneously changing the local thickness and length of a catheter section: the above two steps do not conflict with each other. By completing the above two steps at the same time, the local thickness and length of a catheter section can be changed at the same time.

[0129] Step 5: Combine the finite element theory hydrodynamic performance calculation program to efficiently and accurately obtain the cavitation performance, hydrodynamic performance, noise performance, and vibration performance of the propeller corresponding to the sample;

[0130] Step 6: Repeat the above steps to find several models with better performance, and then resample near the samples of the better models to obtain a new sample database with a smaller gap;

[0131] Step 7: Select samples in the new database and repeat the above steps until the final sample gap meets the requirements and export the final optimal sample and calculation results.

[0132] Step 7: Select samples in the new database and repeat the above steps until the final sample gap meets the requirements and export the final optimal sample and calculation results.

[0133] Finally, multiple rim-thruster models with optimal individual or overall performance were obtained, and the effects of these parameter changes on the various performance characteristics of the rim-thruster were analyzed, laying the foundation for future design concepts and methods for suitable rim-thrusters. Among them, the model with higher hydrodynamic performance, i.e., higher efficiency and optimal vibration performance, can directly replace the original model in all applications where rim-thrusters can be used, thereby saving energy, improving comfort, and reducing the chance of rim-thruster damage. The model with the optimal cavitation performance is suitable for high-speed vessels, where the blades are more prone to cavitation, which generates noise and damages the blades. The model with the optimal noise performance is suitable for submarines, reducing the chance of detection.

[0134] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A variable section rim propeller optimization design method based on section cylindrical coordinate changes, characterized in that: The steps include: Step 1: Obtain the geometric characteristic parameters of the mother propeller; the parameters include the spatial coordinates of the shape value points on each radial blade section and the spatial coordinates of the contour shape value points on the duct section; Step 2: Select the chord length, thickness, pitch of the blade and duct airfoil section, as well as the position and number of the changed sections as design parameters and determine the parameter variation range and minimum sample interval; Step 3: Based on the design parameters, a sample database is obtained by sampling using an algorithm that can uniformly sample in the sample space; Step 4: Select a sample and modify the blade section and duct section shape points according to the sample to generate a blade, and then combine them to generate a rim propeller model; Step 5: Combine the finite element theory hydrodynamic performance calculation program to accurately obtain the hydrodynamic performance of the rim thruster model corresponding to the sample, providing a basis for optimizing the thruster performance; Step 6: Repeat steps 4 and 5 to find the N models with the best performance. Then, resample near the N best model samples to obtain a new sample database with a smaller gap. Step 7: Select samples in the new database and repeat the above steps until the final sample gap meets the requirements and export the final optimal sample and calculation results.

2. The optimization design method of a variable section rim propeller based on the change of section cylindrical coordinates according to claim 1 is characterized in that: In step 1, the blade section value point is a point on the section where the cylinder with the rotation axis as the axis is tangent to the blade.

3. The optimization design method of a variable section rim propeller based on the change of section cylindrical coordinates according to claim 1 or 2, characterized in that: In step 1, the spatial coordinates need to be converted from spatial rectangular coordinates to coordinates on a cylindrical coordinate system, expressed as (r, θ, z).

4. The optimization design method of a variable section rim propeller based on the change of section cylindrical coordinates according to claim 1 or 2, characterized in that: In step 3, the algorithm capable of uniformly sampling in the sample space is one of uniform stratified sampling, Halton sequence, and Sobol sequence.

5. The method for optimizing the design of a variable-section rim propeller based on changes in section cylindrical coordinates according to claim 1 or 2, characterized in that: In step 4, the selected samples are based on the guide edge and a section with increasing radius is selected. x % Local chord length or local thickness or increase local chord length and local thickness at the same time, and change the section coordinates according to the samples, and change the section value point cylindrical coordinates every other section so that the chord length of the section increases y %, then based on the B-spline curve to change the blade section to generate the blade, the duct is generated according to the normal conditions, and then combined to generate a rim propeller model with a wavy concave and convex structure trailing edge, where, x 、 y is a natural number, 0< x <15, 0< y <15.

6. The method for optimizing the design of a variable-section rim propeller based on the change of section cylindrical coordinates according to claim 5, characterized in that: In step 4, modify the converted cylindrical coordinates to make the propeller form the shape you need. The method to modify the cylindrical coordinates is as follows: Method to change the local chord length of a radial section: Assume that the cylindrical coordinates of the point on the leading edge of the section are (r1, θ1, z1), and the cylindrical coordinates of the point on the trailing edge are (r2, θ2, z2). If you want to change the shape of the blade trailing edge, then take the point on the leading edge as the base point, and the chord length of the section will increase. x %The cylindrical coordinates of the points on the edge can be calculated using the following formula: r3=r2=r1 θ3=(θ2-θ1)×(1+ x %)+θ1 z3=(z2-z1)×(1+ x %)+z1 All other points remain unchanged. At this time, the leaf surface curve and leaf back curve are formed by connecting the various type value points based on the B-spline curve. The thickness remains unchanged, and only the chord length at the edge is convex. x % of the cut surface; If you need to reduce the chord length of the section, you only need to x % x Just change it to a negative number; If you need to change the blade into a concave-convex structure along the edge, you only need to modify it once at intervals of the same number of radius sections; If the shape of the guide edge needs to be changed, the point on the edge is used as the base point, and the chord length of the section is increased. x The cylindrical coordinates of the type value points on the trailing edge can be calculated using the following formula: r3=r2=r1 θ3=(θ1-θ2)×(1+ x %)+θ2 z3=(z1-z2)×(1+ x %)+z2.

7. The method for optimizing the design of a variable-section rim propeller based on changes in section cylindrical coordinates according to claim 5, characterized in that: In step 4, modify the converted cylindrical coordinates to make the propeller form the shape you need. The method to modify the cylindrical coordinates is as follows: Method for changing the local thickness of a radial section: The leaf curve and the back curve of each section are composed of the same number of evenly distributed shape value points. Assume that the first point on the leaf curve close to the guide edge is (r5, θ5, z5), and the first point on the back curve close to the guide edge is (r6, θ6, z6). Then the thickness increases x %The cylindrical coordinates of the first point on the rear blade curve close to the guide edge are: r7=r5=r6 θ7=(θ5-θ6)×(1+0.5× x %)+θ6 z7=(z5-z6)×(1+0.5× x %)+z6 The cylindrical coordinates of the first point on the blade curve close to the guide edge are: r8=r5=r6 θ8=(θ6-θ5)×(1+0.5× x %)+θ5 z8=(z6-z5)×(1+0.5× x %)+z5 Change the second point, the third point, etc. in sequence until all points on the section are changed, and then connect the various value points based on the B-spline curve to form the leaf surface curve and the leaf back curve. You can get the leaf back curve and the leaf surface curve with the section midline as the basis, and the leaf back curve and the leaf surface curve are shifted 0.5 times respectively. x % thereby increasing leaf thickness x % of the cut surface; If the leaf surface curve is used as the basis, then each point on the leaf back curve only needs to be increased by the above formula. x % can be achieved; if the leaf back curve is used as the basis, then each point on the leaf surface curve only needs to be increased by the above formula x % can be achieved.

8. The method for optimizing the design of a variable-section rim propeller based on the change of section cylindrical coordinates according to claim 4, characterized in that: In step 4, modify the converted cylindrical coordinates to make the propeller form the shape you need. The method to modify the cylindrical coordinates is as follows: Method to change the local chord length and thickness of a radial section at the same time: If the point on the guide edge is used as the base point, assuming that the cylindrical coordinates of the point on the guide edge are (r1, θ1, z1), and the coordinates of any other point are (r x ,θ x ,z x ), the thickness and chord length increase x %Then the cylindrical coordinates of this point are: r y =r1=r x i y =(θ x -θ1)×(1+ x %)+θ1 With y =(of x -z1)×(1+ x %)+z1 Use the above formula to change all points on the entire section except the base point in sequence, and then connect the various value points based on the B-spline curve to form the leaf surface curve and the leaf back curve, so that the leaf thickness and chord length increase at the same time based on the guide edge. x % of the tangent plane; if the following edge is used as the basis, then the coordinates of the point on the following edge before modification only need to be replaced by (r1,θ1,z1) in the above formula, and each point of the tangent plane can be modified according to the above formula; if the blade centerline is used as the basis, then the coordinates of the point on the blade centerline on the tangent plane only need to be replaced by (r1,θ1,z1) in the above formula, and each point of the tangent plane can be modified according to the above formula; If you want to change the pitch at the same time, you only need to perform the above pitch change steps again because the pitch of the section will not be changed after the steps of changing the chord length and thickness are executed.

9. The method for optimizing the design of a variable-section rim propeller based on the change of section cylindrical coordinates according to claim 8, characterized in that: Step 4: Modify the converted cylindrical coordinates to make the catheter form the desired shape. The method for modifying the catheter coordinates is as follows: the catheter is formed by rotating the catheter cross section, and generally has only one shape value point of the cross section contour. However, the wavy leading edge or trailing edge structure cannot be formed by rotating a single cross section. Therefore, the entire catheter needs to be differentiated and multiple cross sections are used to complete the catheter modeling.

10. The method for optimizing the design of a variable-section rim propeller based on changes in section cylindrical coordinates according to claim 9, characterized in that: In step 4, the method of modifying the blade shape and the duct shape is completed by the Python program. After the coordinate database is established, a program is compiled according to the above formula. If you want to get the required changed blade, you can use the program to directly calculate the spatial rectangular coordinates of all the modified shape points, and then import these spatial rectangular coordinates into the modeling to get the required model.

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