Bionic blade structure for inhibiting hydrofoil cavitation

Abstract

The invention relates to the field of fluid machinery, in particular to a bionic blade structure for restraining hydrofoil cavitation, a hydrofoil blade comprises a basic wing section and two protruding structures arranged on the front edge of the basic wing section side by side in the width direction of the basic wing section, and an L-shaped groove formed in the width direction of the suction surface of the hydrofoil blade is formed in the suction surface of the hydrofoil blade; according to the novel bionic hydrofoil blade, the convex structure and the L-shaped groove structure are complementary in the aspect of cavitation suppression effect, the wave crest of the convex structure plays a role in suppressing cavitation, the L-shaped groove structure breaks the continuity of attachment cavitation development, and the novel bionic hydrofoil blade not only shortens the cavity length of the cross section of the wave trough at the front edge of the hydrofoil blade, but also remarkably reduces the total volume of cavitation; the method is also a cavitation passive control method, does not need extra energy input, and contributes to enhancing the performance stability and efficiency of the fluid machinery to a certain extent.

Description

Technical Field

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

[0002] Cavitation has always been a major issue in the field of fluid machinery research. It is a typical and inevitable unstable complex turbulence 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, including the generation, development, shedding and collapse of cavitation bubbles. The hazards of cavitation are mainly reflected in: the generation of cavitation will affect the efficiency of fluid machinery, the rupture of cavitation bubbles will cause vibration, impact, noise, and will also cause changes in local pressure, aggravating cavitation on the surface of the object and causing structural fatigue damage. Inhibiting 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, the hydrofoil directly affects its performance. It is very important to inhibit the cavitation of the hydrofoil.

[0003] There are many studies on cavitation suppression methods, but most of them are single structural changes, 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 cavitation of hydrofoils. The combination of the leading edge protrusion structure and the L-shaped groove structure achieves the advantages of the two structures, and complements each other 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. The cavitation shedding is accelerated, more small-scale cavities are generated, and the maximum length of the attached cavity is reduced. The new bionic hydrofoil blade has a good effect on suppressing hydrofoil cavitation, so as to solve the defects mentioned 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 at the leading edge of the basic airfoil along the width direction of the basic airfoil, the suction surface of the hydrofoil blade is provided with an L-shaped groove arranged along its width direction.

[0007] As a preferred technical solution, the projections of the two protruding structures along the thickness direction of the hydrofoil blade are in the shape of a sine curve.

[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 beveled surface from the suction surface of the hydrofoil blade and the second beveled 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 convex structure and the L-shaped groove structure complement each other in terms of cavitation suppression effect. The crest of the convex 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 reducing 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 A top view schematic diagram of

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

[0019] Figure 6 is a comparison diagram of hydraulic characteristics of a traditional hydrofoil blade and a novel 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 It is a cavitation evolution diagram 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-convex structure; 4-L-shaped groove; 5-first bevel section; 6-second bevel section. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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 has no protruding structure 3.

[0025] like Figures 2 to 5 The hydrofoil blade 1 of the present embodiment is shown, and the hydrofoil blade 1 includes a basic airfoil 2 and two raised structures 3 arranged in parallel at 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, and 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 projection is located is B, and the amplitude of the sinusoidal curve where the projection is 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 direction, and the L-shaped groove 4 is provided with a first chamfer 5 and a second chamfer 6 which are perpendicular to each other, the first chamfer 5 is close to the leading edge of the hydrofoil blade 1, the second chamfer 6 is close to the trailing edge of the hydrofoil blade 1, and the end of the first chamfer 5 away from the second chamfer 6 is inclined toward the leading edge of the hydrofoil blade 1. The specific parameters of the L-shaped groove 4 are that the angle between the first chamfer 5 and the chord length direction of the hydrofoil blade 1 is α, α = 82°; the vertical distance between the first chamfer 5 from the suction surface of the hydrofoil blade 1 and the second chamfer 6 is H, H = 0.005C; the distance between the leading edge of the basic airfoil 2 and the L-shaped groove 4 along the chord length direction is X, X = 0.3C.

[0028] Conduct simulation experiments:

[0029] In an example of the present 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 numerical simulations of the cavitation performance of the novel bionic hydrofoil blade 1 and the basic hydrofoil 2 to verify the effectiveness of the present 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, is 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 traditional airfoil BH, the average drag coefficient of the new bionic hydrofoil J&H0.3 is reduced by 2.2, and the average lift coefficient and lift-to-drag ratio are increased by 0.396% and 2.6% respectively; the average cavitation volume of the new bionic hydrofoil is reduced by 51.54%. This shows that the new bionic hydrofoil has a good effect on suppressing cavitation and helps to enhance the performance stability and efficiency of fluid machinery to a certain extent.

[0034] Figure 7 It is a distribution diagram of the cavitation volume fraction of the traditional hydrofoil blade and the hydrofoil blade 1 model of the present embodiment, wherein Vf is the cavitation volume fraction, BH is the traditional hydrofoil blade, S&JH0.3-P represents the peak position at the raised structure 3 of the hydrofoil blade 1 of the present embodiment, and S&JH0.3-T represents the trough position at the raised structure 3 of the hydrofoil blade 1 of the present embodiment.

[0035] Figure 8 It is the cavitation evolution diagram of the traditional hydrofoil blade and the hydrofoil blade 1 model of this embodiment, wherein 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 the L-shaped groove structure, the cavitation at the leading edge of the hydrofoil of S&JH0.3 ​​is also limited to the trough area, there is almost no cavitation at the wave crest, the sheet cavitation is broken at the bionic microstructure, and the maximum length of the attached cavitation of S&JH0.3 ​​is reduced. The two bionic structures in S&JH0.3 ​​have a certain complementary effect, which respectively inhibits the generation and development of cavitation and promotes the collapse of cavitation 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 wave 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 by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A bionic blade structure for inhibiting cavitation of a hydrofoil, characterized in that include: The hydrofoil blade (1) comprises a basic airfoil (2) and two raised structures (3) arranged in parallel at 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 thereof.

2. A bionic blade structure for inhibiting hydrofoil cavitation according to claim 1, characterized in that include: The projections of the two protruding structures (3) along the thickness direction of the hydrofoil blade (1) are in the shape of a sine curve.

3. A bionic blade structure for suppressing hydrofoil cavitation as claimed in claim 2, 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, the amplitude of the sine curve where the projection is located is A, B=0.15C, A=0.04C.

4. A bionic blade structure for suppressing hydrofoil cavitation as claimed in claim 3, characterized in that include: The L-shaped groove (4) is provided with 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 angle between the first beveled surface (5) and the chord length direction of the hydrofoil blade (1) is α, α=82°.

5. A bionic blade structure for suppressing hydrofoil cavitation as claimed in claim 4, characterized in that include: The vertical distance between the first beveled surface (5) and the suction surface of the hydrofoil blade (1) and the second beveled surface (6) is H, where H=0.005C.

6. A bionic blade structure for suppressing hydrofoil cavitation according to claim 5, 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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