Bionic blade structure for inhibiting water wing cavitation

Abstract

The present application relates to the field of fluid machinery, and particularly relates to a bionic blade structure for inhibiting water wing cavitation, wherein the water wing blade comprises a basic airfoil and two convex structures arranged in parallel along the width direction of the basic airfoil and located at the leading edge of the basic airfoil, and the suction surface of the water wing blade is provided with an L-shaped groove arranged along the width direction thereof; the convex structure and the L-shaped groove structure are complementary in terms of cavitation inhibition effect, the wave crest of the convex structure plays a role in inhibiting the generation of cavitation, and the L-shaped groove structure breaks the continuity of the development of attached cavitation; the novel bionic water wing blade not only shortens the cavity length of the wave trough section of the leading edge of the water wing blade, but also significantly reduces the total cavitation volume; the present application is also a passive control method for cavitation, does not require additional energy input, and is helpful to enhancing the performance stability and efficiency of the fluid machinery to a certain extent.

Description

Technical Field

[0001] The present invention relates to the technical field of fluid machinery, and in particular to a bionic blade structure for suppressing cavitation of hydrofoils. Background Art

[0002] Cavitation has always been a major issue in the field of fluid machinery research. It is a typical and unavoidable unstable and complex turbulent phenomenon. Cavitation occurs when the local pressure inside the liquid is lower than the saturation pressure of water vapor at this temperature. It generally occurs in the phase change process inside the liquid or at the solid-liquid interface, and includes four processes: the generation, development, shedding, and collapse of cavitation bubbles. The hazards of cavitation are mainly reflected in the following aspects: the generation of cavitation will affect the efficiency of fluid machinery, the rupture of cavitation bubbles will cause vibration, impact, and noise, and will also produce changes in local pressure, aggravating cavitation erosion on the surface of the object and causing structural fatigue damage. Suppressing the generation and development of cavitation, and accelerating the shedding and collapse of cavitation are the main research directions at present. As one of the most critical and important components of fluid machinery, hydrofoils directly affect its performance. It is very important to suppress hydrofoil cavitation.

[0003] There are many studies on cavitation suppression methods, but most of them are changes to a single structure, or require additional energy input. Although they can suppress cavitation to a certain extent, they will also reduce the performance of hydraulic machinery. In addition, there is still room for improvement in the suppression effect, and further improvement is necessary. Summary of the Invention

[0004] The purpose of the present invention is to provide a bionic blade structure for suppressing hydrofoil cavitation. The combination of the leading edge protrusion structure and the L-shaped groove structure achieves the superposition of the advantages of the two structures and realizes complementarity in the cavitation suppression effect. The bionic leading edge protrusion structure induces counter-rotating vortex pairs at the leading edge of the hydrofoil, thereby deflecting the water flow. In the trough area, the fluid momentum is increased and the pressure is reduced, which limits the initial cavitation to the trough area and suppresses the development of crest cavitation. The L-shaped groove structure breaks up the development of attached cavitation and hinders the concave jet to a certain extent. It accelerates cavitation shedding, produces more small-scale cavities, and reduces the maximum length of the attached cavity. The new bionic hydrofoil blade has a good effect on suppressing hydrofoil cavitation, so as to solve the defects raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A bionic blade structure for suppressing hydrofoil cavitation, the hydrofoil blade comprising a basic airfoil and two raised structures arranged in parallel on the leading edge of the basic airfoil along the width direction of the basic airfoil, the suction surface of the hydrofoil blade being provided with an L-shaped groove arranged along the width direction thereof.

[0007] As a preferred technical solution, the projections of the two raised structures along the thickness direction of the hydrofoil blade are sinusoidal.

[0008] As a preferred technical solution, the chord length of the basic airfoil is C, the wavelength of the sine curve where the projection is located is B, the amplitude of the sine curve where the projection is located is A, B=0.15C, A=0.04C.

[0009] As a preferred technical solution, the L-shaped groove is provided with a first bevel and a second bevel perpendicular to each other, the first bevel is close to the leading edge of the hydrofoil blade, and the angle between the first bevel and the chord length direction of the hydrofoil blade is α, α=82°.

[0010] As a preferred technical solution, the vertical distance between the first oblique cut surface and the suction surface of the hydrofoil blade and the second oblique cut surface is H, and H=0.005C.

[0011] As a preferred technical solution, the distance between the leading edge of the basic airfoil and the L-shaped groove along the chord length direction is X, where X=0.3C.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] The raised structure and the L-shaped groove structure complement each other in terms of cavitation suppression effect. The crest of the raised structure suppresses cavitation, while the L-shaped groove structure prevents the development of attached cavitation. It not only shortens the cavity length of the trough section of the leading edge of the hydrofoil blade, significantly reduces the total cavitation volume, but also enhances the performance of the hydraulic machinery to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of a traditional hydrofoil blade;

[0015] Figure 2 It is a schematic diagram of the structure of the new bionic hydrofoil blade;

[0016] Figure 3 yes Figure 2 A side view schematic diagram of

[0017] Figure 4 yes Figure 2 Schematic top view of

[0018] Figure 5 yes Figure 2 A schematic cross-sectional view of the middle L-shaped groove;

[0019] Figure 6 1 is a comparison diagram of the hydraulic characteristics of the traditional hydrofoil blade and the new bionic hydrofoil blade model in this embodiment;

[0020] Figure 7is a distribution diagram of cavitation volume fraction of the traditional hydrofoil blade and the novel bionic hydrofoil blade model in this embodiment;

[0021] Figure 8 This is a diagram of the cavitation evolution of the traditional hydrofoil blade and the new bionic hydrofoil blade model in this embodiment.

[0022] In the figure: 1-hydrofoil blade; 2-basic airfoil; 3-raised structure; 4-L-shaped groove; 5-first oblique section; 6-second oblique section. DETAILED DESCRIPTION

[0023] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Figure 1 It is a structure of a traditional hydrofoil blade (model Clark-Y). Compared with the hydrofoil blade 1 of this embodiment, the leading edge of the traditional hydrofoil blade does not have the protruding structure 3.

[0025] like Figures 2 to 5 The hydrofoil blade 1 of this embodiment is shown. The hydrofoil blade 1 includes a basic airfoil 2 and two raised structures 3 arranged side by side on the leading edge of the basic airfoil 2 along the width direction of the basic airfoil 2. The structure of the basic airfoil 2 is the same as that of a traditional hydrofoil blade. The maximum thickness of the hydrofoil blade 1 at the raised structure 3 is greater than the maximum thickness of the hydrofoil blade 1 at the basic airfoil 2.

[0026] In this embodiment, the projections of the two raised structures 3 along the thickness direction of the hydrofoil blade 1 are sinusoidal. Specifically, the chord length of the basic airfoil 2 is C, C = 70 mm, the wavelength of the sinusoidal curve where the projections are located is B, and the amplitude of the sinusoidal curve where the projections are located is A, B = 0.15C, A = 0.04C.

[0027] In addition, the suction surface of the hydrofoil blade 1 is provided with an L-shaped groove 4 arranged along its width. The L-shaped groove 4 has a first beveled surface 5 and a second beveled surface 6, which are perpendicular to each other. The first beveled surface 5 is close to the leading edge of the hydrofoil blade 1, and the second beveled surface 6 is close to the trailing edge of the hydrofoil blade 1. The end of the first beveled surface 5 away from the second beveled surface 6 is inclined toward the leading edge of the hydrofoil blade 1. The specific parameters of the L-shaped groove 4 are: the angle between the first beveled surface 5 and the chord length direction of the hydrofoil blade 1 is α, α = 82°; the vertical distance between the first beveled surface 5 from the suction surface of the hydrofoil blade 1 and the second beveled surface 6 is H, H = 0.005°; the distance between the leading edge of the basic airfoil profile 2 and the L-shaped groove 4 along the chord length is X, X = 0.3°.

[0028] Conduct simulation experiments:

[0029] In an example of this embodiment, a cavitation performance budget of a novel bionic hydrofoil blade 1 is performed; specifically, ANSYS Fluent software based on the finite volume method is used to perform a numerical simulation of the cavitation performance of the novel bionic hydrofoil blade 1 and the basic hydrofoil 2 to verify the effectiveness of this embodiment.

[0030] Figure 6 This is a comparison chart of the hydraulic characteristics of the traditional hydrofoil blade and the hydrofoil blade 1 model of this embodiment, including cavitation volume, lift coefficient, drag coefficient, and lift-to-drag ratio. Among them, BH represents the traditional hydrofoil blade, S&JH0.3 ​​represents the hydrofoil blade 1 of this embodiment;

[0031] Table 1 Time average values ​​of characteristic parameters of two hydrofoil models

[0032]

[0033] As shown in Table 1, represents the average lift coefficient, represents the rate of change of the average lift coefficient, represents the average drag coefficient, represents the average drag coefficient change rate, represents the average lift-to-drag ratio, represents the average lift-to-drag ratio change rate, represents the average cavitation volume, represents the average cavitation volume change rate. Compared with the conventional BH airfoil, the new bionic hydrofoil J&H0.3 has a reduced average drag coefficient of 2.2, while its average lift coefficient and lift-to-drag ratio increase by 0.396% and 2.6%, respectively. The average cavitation volume of the new bionic hydrofoil is reduced by 51.54%. This demonstrates that the new bionic hydrofoil effectively suppresses cavitation and, to a certain extent, contributes to enhancing the performance stability and efficiency of fluid machinery.

[0034] Figure 7 3-T represents the trough position at the raised structure 3 of the hydrofoil blade 1 of the present embodiment.

[0035] Figure 8 3 are cavitation evolution diagrams of the traditional hydrofoil blade and the hydrofoil blade 1 model of this embodiment, where BH represents the traditional hydrofoil blade and S&JH0.3 ​​represents the hydrofoil blade 1 of this embodiment.

[0036] like Figure 7As shown in Figure 8, under the dual effects of the leading edge protrusion and L-shaped groove structure, cavitation on the leading edge of the S&JH0.3 ​​hydrofoil is also confined to the wave trough area, with almost no cavitation at the wave crest. Sheet cavitation is broken up by the biomimetic microstructure, and the maximum length of attached cavitation on the S&JH0.3 ​​is reduced. The two biomimetic structures in the S&JH0.3 ​​have a certain complementary effect, respectively inhibiting the generation and development of cavitation and promoting cavitation collapse to a certain extent.

[0037] The raised structure 3 and the L-shaped groove 4 structure of the hydrofoil blade 1 of this embodiment complement each other in terms of cavitation suppression effect. The crest of the raised structure 3 suppresses cavitation, and the L-shaped groove 4 structure prevents the development of attached cavitation, which not only shortens the cavity length of the trough section of the leading edge of the hydrofoil blade 1, but also significantly reduces the total cavitation volume, thereby improving the stability and efficiency of the hydraulic machinery to a certain extent.

[0038] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A bionic blade structure for suppressing hydrofoil cavitation, characterized by: The invention comprises a hydrofoil blade (1), wherein the hydrofoil blade (1) comprises a basic airfoil (2) and two raised structures (3) arranged in parallel on the leading edge of the basic airfoil (2) along the width direction of the basic airfoil (2); the suction surface of the hydrofoil blade (1) is provided with an L-shaped groove (4) arranged along the width direction; the projections of the two raised structures (3) along the thickness direction of the hydrofoil blade (1) are in the shape of a sine curve; the L-shaped groove (4) is provided with a first oblique cut surface (5) and a second oblique cut surface (6) perpendicular to each other, the first oblique cut surface (5) being close to the leading edge of the hydrofoil blade (1), and the angle between the first oblique cut surface (5) and the chord length direction of the hydrofoil blade (1) is α, and α=82°.

2. A bionic blade structure for suppressing hydrofoil cavitation according to claim 1, characterized in that include: The chord length of the basic airfoil (2) is C, the wavelength of the sine curve where the projection is located is B, and the amplitude of the sine curve where the projection is located is A, B=0.15C, and A=0.04C.

3. The bionic blade structure for suppressing hydrofoil cavitation according to claim 1, characterized in that include: The vertical distance between the first oblique cut surface (5) and the suction surface of the hydrofoil blade (1) and the second oblique cut surface (6) is H, where H=0.005C.

4. The bionic blade structure for suppressing hydrofoil cavitation according to claim 1, characterized in that include: The distance between the leading edge of the basic airfoil (2) and the L-shaped groove (4) along the chord length direction is X, where X=0.3C.

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