A method for precise configuration of integrally formed rounding of a ship propeller rotor blade root

Abstract

The present application relates to a kind of ship propeller rotor blade root rounding integrated forming accurate configuration method, comprising the following steps: drawing the profile line of the maximum thickness of different radius airfoil of ship propeller rotor, create rounding boundary line, measure the extension distance of each radius on rounding boundary line relative to maximum thickness profile line;Tangent is made at any point on original airfoil and makes the vertical line of outward extension perpendicular to the tangent, new point is taken at the position of vertical line distance tangent point distance d, new point taken is the point on new airfoil including rounding boundary;Original airfoil is repeated above process from leading edge to trailing edge, and new airfoil including rounding boundary is obtained;Blade three-dimensional reconstruction.The transition of ship propeller rotor blade root and hub is not smooth enough, the configuration of blade root rounding is difficult to accurately, the accurate definition of blade root rounding type surface can be realized, and rounding and blade surface can be integrated, the smooth transition is realized, and the occurrence of stress concentration can be reduced.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding and marine engineering, and in particular to a precise configuration method for integrally rounding the root of a marine propulsion rotor. Background Technology

[0002] Marine propulsion rotors, including propellers, pump-jet impellers, and waterjet propulsion impellers, often have their blade root configuration overlooked. This is partly because the blade root configuration requires a smooth transition between the blade surface and the rounded root, a complex spatial surface connection issue. Secondly, before the emphasis on refined design, the blade root position had a relatively small impact on propulsion performance, often using filler for a rough transition, with the surface shape largely dependent on the experience of the manufacturing workers. Finally, current major classification society regulations do not mandate specific blade root configurations. For example, the DNV (Det Norske Veritas) regulations only require that the local stress at the blade root not exceed 1.2 times the nominal allowable stress. Alternatively, for rounded blade roots of equal radius, the regulations only require that the rounding radius not be less than 0.75 times the design thickness of the blade root.

[0003] Recently, the rotor blade root configuration of marine propellers has received increasing attention, primarily driven by several factors. Firstly, there have been propeller blade root fracture incidents where the lack of precise design specifications for the blade root configuration has led to uncertainty regarding liability. Secondly, the increasing orders for polar vessels have led to a corresponding increase in demand for ice-class propellers. Ice-class propellers frequently collide with ice during operation, thus designers place greater emphasis on blade strength. The blade root, connecting the blades and the hub, is the area of ​​greatest bending stress, hence its increased importance. Traditional experience-based blade root packing configurations, which may result in uneven transitions and stress concentration, are becoming increasingly unsuitable for the design and manufacture of ice-class propellers. Figure 1 .

[0004] Precisely configuring the blade root of a marine propeller rotor presents significant challenges. Firstly, a smooth transition between the blade surface and the rounded blade root is crucial. Since the intersection line of the blade surface and the hub surface is a complex spatial curve with varying slopes at different locations, and different curvatures on either side of the same location, achieving a smooth transition between the two surfaces constitutes a complex spatial mathematics problem. Furthermore, the cylindrical cross-section of the marine propeller rotor blade root is an airfoil that is thicker in the middle and tapered at both ends. (See...) Figure 2 When subjected to bending stress, the maximum stress occurs at the location with the greatest thickness in the middle of the chord (because this location is furthest from the neutral axis in the cross-section). Therefore, to make the stress distribution at the root more uniform, the blade root rounding needs to be made into a variable radius type, with the goal of making the rounding radius relatively large in the middle of the chord and relatively small at both ends. This further increases the difficulty of the blade root rounding configuration. Summary of the Invention

[0005] To address the issues of insufficient smoothness in the transition between the rotor blade root and the rotor hub, and the difficulty in achieving precise blade root rounding, a method for integrally forming a precise blade root rounding configuration for marine propeller rotors is proposed. This method is based on rigorous mathematical definitions. By increasing the area of ​​the rounding and integrating it into a standard two-dimensional planar airfoil, and then performing a mathematical transformation of the planar airfoil from two-dimensional to three-dimensional space, a smooth transition between the blade surface and the blade root rounding is achieved, along with a precise configuration of the blade root surface.

[0006] The technical solution of this invention is as follows:

[0007] A method for precisely shaping the root rounding of a marine propulsion rotor blade in one piece includes the following steps:

[0008] Step 1: Determining the root rounded boundary: Draw the outline of the maximum thickness of the airfoil of different radii of the marine propeller rotor. Create a rounded boundary line between the maximum thickness outline and the hub boundary line. The rounded boundary line is tangent to the maximum thickness line and the hub boundary line. Measure the extension distance of the rounded boundary line relative to the maximum thickness outline on each radius.

[0009] Step 2, Blade Root Airfoil Correction: Draw a tangent line at any point on the original airfoil, and then draw a perpendicular line extending outward from that tangent line through that point. Take a new point on the perpendicular line at a distance d from the tangent point. This new point is the point on the new airfoil containing the rounded boundary. Repeat the above process from the leading edge to the trailing edge of the original airfoil to obtain the new airfoil containing the rounded boundary. After correction, the planar airfoil at the blade root can be represented using two-dimensional coordinates.

[0010] Step 3, Blade 3D Reconstruction: After completing the rounding correction of the blade root airfoil according to the steps in Step 1 and Step 2, replace the original airfoil with the corrected airfoil within the blade root area, and reconstruct the blade's 3D configuration. The two-dimensional coordinates are converted from planar two-dimensional to spatial three-dimensional coordinates, which enables precise control of the rounded surface of the blade root through precise coordinates.

[0011] Preferably, the maximum thickness contour line in step one is the theoretical contour at the blade root position, and rounding is required in actual processing.

[0012] Preferably, the range of the blade root in step one refers to the number of radii of the blade root that need to be rounded near the blade hub.

[0013] Preferably, the rounded boundary line in step one is not strictly limited; it can be an arc or a smoothly transitioned spline curve.

[0014] Preferably, the distance d from each point in step two to the outward extension is different, and is represented by d1, d2...di respectively, in order to meet the requirement of variable radius for leaf root rounding.

[0015] Furthermore, for variable radius blade root rounding, the extension distance di varies with the chord length position and is a function with the chord length position as the independent variable. Its distribution law is consistent with the distribution of the original airfoil thickness with the chord length. It is obtained by multiplying the distribution function of the original airfoil thickness and the chord length by ti after normalization, where ti is the extension distance of the rounded boundary line on the corresponding radius relative to the maximum thickness profile line.

[0016] Furthermore, if a rounding with equal radii is required, simply set d1 = d2 = ... di.

[0017] Furthermore, if we use the function T(x) to represent the distribution law of the thickness after the original airfoil's maximum value is normalized with the chord length, where x is the chord length position; then di = T(x) × ti, where ti is the extension distance of the rounded boundary line on the corresponding radius relative to the maximum thickness profile line.

[0018] Preferably, the modified blade root planar airfoil can be represented by coordinates (x0, y0), where x0 represents the chord length position of a certain point on the airfoil profile, and y0 represents the height value at a certain chord length position. In the airfoil plane, the lead edge point of the airfoil is taken as the origin of the coordinate system, and the direction of the lead edge to the trailing edge is the x-axis direction.

[0019] Preferably, the three-dimensional reconstruction of the blade in step three is a mathematical transformation process from a two-dimensional planar airfoil to a real three-dimensional blade, which includes the following steps in sequence: planar airfoil (x0, y0), pitch transformation (x1, y1, z1), skew transformation (x2, y2, z2), longitudinal skew transformation (x3, y3, z3), winding onto a cylindrical surface (x4, y5, z5), and the real blade.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention patent enables the precise definition of the rounded surface of the blade root, and the rounding and the blade surface can be integrated to achieve a smooth transition, which can reduce the occurrence of stress concentration. It is very practical for marine propulsion rotors, such as high-ice-class propellers, which have very high requirements for strength performance. Attached Figure Description

[0022] Figure 1 The transition between leaf roots in the background technology is not smooth;

[0023] Figure 2 Background art: Rotor airfoil diagram of a marine propulsion unit;

[0024] Figure 3This is a diagram showing the maximum thickness of the rotor blade root of the marine propulsion unit of the present invention.

[0025] Figure 4 A diagram is created for the rounded boundary lines of this invention;

[0026] Figure 5 This is a modified airfoil diagram of the blade root of the present invention;

[0027] Figure 6 This is a coordinate representation diagram of the modified airfoil of the present invention;

[0028] Figure 7 This diagram illustrates the transformation process from a planar airfoil to a real blade according to the present invention.

[0029] Figure 8 The following is a comparison of the implementation effects of the present invention (left column: leaf root without rounding; middle column: traditional leaf root filler with rounding; right column: the present invention patent with rounding). Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] To achieve the precise configuration of the rotor blade root of a marine propulsion unit, the following steps will be followed: 1. Determining the rounded boundary of the root; 2. Correcting the blade root airfoil; 3. Reconstructing the three-dimensional shape of the blade. These steps will be described in detail below.

[0032] 1. Determining the rounded boundary at the root

[0033] like Figure 3 This is the profile of the maximum thickness of airfoils with different radii on marine propeller rotors. For example, the maximum thickness of 0.25R (where R is the radius of the marine propeller rotor) represents the maximum thickness of the airfoil with that radius. This diagram can be obtained from the blade profile value table. (The profile value table is a file generated during the rotor design process to define the outer surface of the rotor, including two-dimensional coordinates of profiles with different radii, as well as parameters such as skew, pitch, etc., that guide the transformation of these two-dimensional coordinates; however, the two-dimensional coordinates here do not include rounding.)

[0034] for Figure 3 The maximum thickness contour line drawn in the diagram represents the theoretical contour at the blade root; actual machining requires additional rounding. The scope of the blade root is not precisely defined, but generally refers to the radii of the radius at which the blade root rounding needs to be applied near the hub. For example... Figure 4Create a rounded boundary line between the maximum thickness profile and the hub boundary line. The rounded boundary line is not strictly limited; it can be an arc or a smoothly transitioning spline curve. The design principle is to ensure tangency to both the maximum thickness line and the hub boundary line. After designing the rounded boundary line, the extension distance of the rounded boundary line relative to the maximum thickness profile line at each radius can be measured, such as... Figure 4 In this context, t1, t2, t3, and t4 represent the extension distances of 0.35R, 0.3R, 0.25R, and 0.2R, respectively.

[0035] 2. Correction of blade root airfoil

[0036] In the first step, the rounded boundary lines were created, and the extension distances t1, t2, t3, and t4 of the rounded boundary lines relative to the maximum thickness profile line on several radii at the blade root were obtained. Next, the airfoils at the blade root will be modified based on these extension distances. Marine propulsion rotors are generally obtained by transforming two-dimensional airfoils on a plane into three-dimensional airfoils. Therefore, the original planar airfoils at the blade root will be modified here to form new airfoils that include rounded boundaries.

[0037] Airfoil modification process comments Figure 5 . Figure 5 The dashed line represents the original airfoil with a certain radius at the blade root. A tangent is drawn at any point on the original airfoil. A perpendicular line is then drawn from this point outwards from the tangent (operating within the plane of the original airfoil). A new point is selected at a distance *d* from the tangent point on this perpendicular line. This new point is the point on the new airfoil containing the rounded boundary. Repeating this process from the leading edge to the trailing edge of the original airfoil yields a new airfoil containing the rounded boundary. Here, the outward extension distance *d* is different for each point, denoted by *d1*, *d2*, ..., *di*, to satisfy the requirement of variable radius rounding at the blade root (variable radius means that the radius of the rounding differs at different chord length positions; the radius of the rounding is a function of the chord length position, and the specific way it changes with the chord length position can vary, but the extension distance *d* of the rounding at different chord length positions is consistent with the variation of the airfoil thickness with the chord length). If a uniform radius rounding is required, simply set *d1* = *d2* = ..., *di*.

[0038] For variable radius blade root rounding, the extension distance *di* varies with the chord length position, acting as a function with the chord length position as the independent variable. For example, we can assume that the variation of *di* for variable radius rounding follows the same pattern as the variation of thickness with the chord length. Its distribution pattern is consistent with the original airfoil thickness distribution with the chord length, obtained by normalizing the original airfoil thickness and chord length distribution function and multiplying it by *ti*. If we let *T(x)* represent the distribution pattern of the original airfoil thickness with the chord length after normalization of the maximum value, where *x* is the chord length position, then *di* = *T(x)* × *ti*, where *ti* is as follows... Figure 4The figure shows the extension distance of the rounded boundary line relative to the maximum thickness profile line on the corresponding radius. After correction, the planar airfoil at the blade root can be represented by coordinates (x0, y0), where x0 represents the chord length position at a certain point on the airfoil section, and y0 represents the height value at that chord length position. The xy coordinate system is shown in [reference needed]. Figure 6 In the airfoil plane, the origin of the coordinate system is the leading edge point of the airfoil, and the direction of the leading edge to the trailing edge is the x-axis direction.

[0039] 3. Three-dimensional reconstruction of the blade

[0040] After completing the rounding correction of the blade root airfoil according to steps one and two, replace the original airfoil with the corrected airfoil within the blade root area, and re-design the three-dimensional configuration of the blade. There is a fixed procedure for blade three-dimensional configuration, which can be found in books such as "Principles of Naval Architecture." The procedure is as follows: Figure 7 The airfoil at the blade root passes through... Figure 7 After the transformation, its coordinates are converted from two-dimensional plane coordinates to three-dimensional space coordinates, which can be represented as (x4, y4, z4). This allows for precise control of the rounded surface of the blade root through precise coordinates.

[0041] The mathematical transformation process of the blade from a two-dimensional planar airfoil to a three-dimensional real blade can be found in the chapter on ship propulsion in "Principles of Ships"; for example... Figure 7 As shown, the process sequentially includes: planar airfoil (x0, y0) - pitch transformation (x1, y1, z1) - skew transformation (x2, y2, z2) - longitudinal skew transformation (x3, y3, z3) - winding onto a cylindrical surface (x4, y5, z5) - actual blade.

[0042] Example: Specific embodiments and effects of this invention patent can be found in the following examples. Figure 8 The left column in the image shows rounded fillers without leaf roots, the middle column shows the rounded filler effect achieved by traditional methods based on worker experience, and the right column shows the rounded fillers achieved using the method of this patent. Figure 8 As can be seen, without rounding at the blade root, the contact area between the blade and the hub is small, the transition is abrupt, and it is not conducive to uniform stress distribution. The middle column shows blade root rounding based on experience, with obvious broken lines at the transition to the blade surface, which may lead to stress concentration, and the control of the root surface is not precise enough. The right column shows blade root rounding generated by the method of this patent, which is integrated with the blade surface, without broken lines, and can achieve precise definition and control of the blade root surface. Figure 8 The left image shows the shape of the leaf root without rounding, the middle image shows the traditional rounding with discontinuous dividing lines, and the right image shows the rounding created by the method of this patent, which is smoothly integrated with the outer surface of the rotor and has no dividing lines.

[0043] This invention achieves a precise configuration of the leaf root rounding by integrating the leaf root rounding into the leaf root airfoil, and ensures the smoothness of the rounded surface and the blade surface.

[0044] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A method for precisely shaping a marine propeller rotor blade root by integral rounding, characterized in that... Includes the following steps: Step 1: Determining the root rounded boundary: Draw the outline of the maximum thickness of the airfoil of different radii of the marine propeller rotor. Create a rounded boundary line between the maximum thickness outline and the hub boundary line. The rounded boundary line is tangent to the maximum thickness line and the hub boundary line. Measure the extension distance of the rounded boundary line relative to the maximum thickness outline on each radius. Step 2, Blade Root Airfoil Correction: Draw a tangent line at any point on the original airfoil, and then draw a perpendicular line extending outward from that tangent line through that point. Take a new point on the perpendicular line at a distance d from the tangent point. This new point is the point on the new airfoil containing the rounded boundary. Repeat the above process from the leading edge to the trailing edge of the original airfoil to obtain the new airfoil containing the rounded boundary. After correction, the planar airfoil at the blade root can be represented using two-dimensional coordinates. Step 3, Blade 3D Reconstruction: After completing the rounding correction of the blade root airfoil according to the steps in Step 1 and Step 2, replace the original airfoil with the corrected airfoil within the blade root area, and reconstruct the blade's 3D configuration. The two-dimensional coordinates are converted from planar two-dimensional to spatial three-dimensional coordinates, which enables precise control of the rounded surface of the blade root through precise coordinates. In step two, the outward extension distance d from each point is different, denoted by d1, d2…di respectively, to satisfy the requirement of variable radius leaf root rounding; for variable radius leaf root rounding, if a function… This represents the distribution of the thickness as a function of the chord length after the normalization of the original airfoil's maximum value. Let the chord length be the position; then ,in It is the extension distance of the rounded boundary line on the corresponding radius relative to the maximum thickness profile line.

2. The precise configuration method for integrally rounding the root of a marine propeller rotor blade according to claim 1, characterized in that, The rounded boundary line in step one is either a circular arc or a spline curve with a smooth transition.

3. The precise configuration method for integrally rounding the root of a marine propeller rotor blade according to claim 1, characterized in that, The modified plane airfoil at the blade root can be represented using coordinates as follows: Here, x0 represents the chord length position of a certain point on the airfoil section, and y0 represents the height value at a certain chord length position. In the airfoil plane, the lead edge point of the airfoil is taken as the origin of the coordinate system, and the direction of the lead edge to the follow edge is the x-axis direction.

4. The precise configuration method for integrally rounding the root of a marine propeller rotor blade according to claim 1, characterized in that, Step 3, the three-dimensional reconstruction of the blade, is a mathematical transformation process from a two-dimensional planar airfoil to a real three-dimensional blade. It includes the following steps: planar airfoil (x0, y0), pitch transformation (x1, y1, z1), skew transformation (x2, y2, z2), longitudinal skew transformation (x3, y3, z3), winding onto a cylindrical surface (x4, y4, z4), and the real blade.

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