1. A hydrofoil cavitation flow control structure comprises a hydrofoil and is characterized in that a first-stage convex stripe is arranged in the middle of a suction surface of the hydrofoil, a plurality of second-stage convex stripes are symmetrically distributed on two sides of the first-stage convex stripe in an inclined mode, and the plurality of second-stage convex stripes are uniformly distributed at equal intervals along the length direction of the first-stage convex stripe.

2. The hydrofoil cavitation flow control structure according to claim 1, characterized in that: the first-stage convex stripes are obtained by scanning a first-stage convex stripe section circle along a first-stage convex stripe section circle scanning track to form a convex part positioned outside the hydrofoil; wherein, the scanning track of the first-level raised stripe section circle is tightly attached to the suction surface of the hydrofoil, and the center of the first-level raised stripe section circle is positioned on the scanning track of the first-level raised stripe section circle; the secondary convex stripe is obtained by scanning a convex part outside the hydrofoil, which is formed by scanning a secondary convex stripe section circle along a secondary convex stripe section circle scanning track; wherein, the scanning track of the second-level convex stripe section circle is tightly attached to the suction surface of the hydrofoil, and the circle center of the second-level convex stripe section circle is positioned on the scanning track of the second-level convex stripe section circle.

3. The hydrofoil cavitation flow control structure according to claim 1, characterized in that: the included angle beta between the first-level raised stripes and the second-level raised stripes is 27-32 degrees.

4. A hydrofoil cavitation flow control structure as claimed in claim 2, wherein: the diameter D of the cross section circle of the first-level raised stripe₁Diameter D of cross section circle of second-level convex stripe₂Ratio D between₁/D₂The range is 2-4.

5. The hydrofoil cavitation flow control structure according to claim 1, characterized in that: the interval distribution distance S of the secondary convex stripes along the chord length direction of the hydrofoil is 0.04-0.06C, wherein C is the chord length of the hydrofoil.

6. The hydrofoil cavitation flow control structure according to claim 1, characterized in that: the length L of the first-level raised stripe₁0.5-0.9C, length L of the secondary convex stripe₂Is 0.4-0.8C, wherein C is the chord length of the hydrofoil.

7. The hydrofoil cavitation flow control structure according to claim 1, characterized in that: the hydrofoils can be either rotating blades or stationary blades of a hydraulic machine.

Background

Cavitation is a complex phase change phenomenon that typically occurs at partial static pressures below the saturated vapor pressure within a liquid and plays a destructive role in many industrial applications. Cavitation is of great concern because of its frequent occurrence in hydraulic mechanical applications and its significant impact on vibration, noise, and cavitation performance. In addition, for rotating hydraulic machines such as water pumps, inducers and water turbines, the falling cloud cavitation often blocks the impeller flow channel, and further reduces the operating efficiency of the unit. Therefore, the cavitation suppression has an important role in improving the operation efficiency and the service life of the hydraulic machine. In contrast to cavitation flow active control structures, passive control structures are easy to implement in full scale devices because they do not require external energy supply. The passive control of the unsteady cloud cavitation has great application potential and implies great economic benefit. Therefore, it is extremely important to design different cavitation flow passive control structures.

Disclosure of Invention

Aiming at the problems, the invention provides a hydrofoil cavitation flow control structure to inhibit the falling of the cloud cavitation on the surface of the hydrofoil, reduce the cavitation erosion and pressure pulsation generated on the surface of the hydrofoil due to cavitation collapse and improve the hydraulic performance of the hydrofoil.

In order to achieve the purpose, the invention provides the following scheme:

the utility model provides a hydrofoil cavitation flow control structure, includes the hydrofoil, hydrofoil suction surface intermediate position is equipped with the protruding stripe of one-level, the protruding stripe both sides slope of one-level sets up many second grade convex stripes of symmetric distribution, many the second grade convex stripe is followed the protruding stripe length direction of one-level is equidistant evenly distributed.

Furthermore, the primary convex stripe is obtained by scanning a convex part which is formed by scanning a primary convex stripe section circle along a primary convex stripe section circle scanning track and is positioned outside the hydrofoil; wherein, the scanning track of the first-level raised stripe section circle is tightly attached to the suction surface of the hydrofoil, and the center of the first-level raised stripe section circle is positioned on the scanning track of the first-level raised stripe section circle; the secondary convex stripe is obtained by scanning a convex part outside the hydrofoil, which is formed by scanning a secondary convex stripe section circle along a secondary convex stripe section circle scanning track; wherein, the scanning track of the second-level convex stripe section circle is tightly attached to the suction surface of the hydrofoil, and the circle center of the second-level convex stripe section circle is positioned on the scanning track of the second-level convex stripe section circle.

Furthermore, the included angle beta between the first-level raised stripes and the second-level raised stripes is 27-32 degrees.

Further, the diameter D of the cross section circle of the primary convex stripe₁Diameter D of cross section circle of second-level convex stripe₂Ratio D between₁/D₂The range is 2-4.

Furthermore, the interval distribution distance S of the secondary convex stripes along the chord length direction of the hydrofoil is 0.04-0.06C, wherein C is the chord length of the hydrofoil.

Further, the length L of the primary raised stripe₁0.5-0.9C, length L of the secondary convex stripe₂Is 0.4-0.8C, wherein C is the chord length of the hydrofoil.

Further, the hydrofoil can be a rotating blade or a static blade of a hydraulic machine.

Compared with the prior art, the invention has the following beneficial technical effects:

when liquid flows from the leading edge of the hydrofoil to the trailing edge of the hydrofoil at the suction surface of the hydrofoil, the increase in liquid velocity causes a reduction in the local static pressure at the suction surface, which may result in sheet cavitation at the suction surface. When the cavitation of the sheet grows to a certain length, back jet flow appears at the tail part of the cavitation of the sheet. When the back jet moves to the vicinity of the leading edge of the hydrofoil, the cavitation interface of the slice is cut off, the slice is cavitated and shed to form cloud cavitation, and intense pressure pulsation and cavitation are caused. After the invention is adopted, the first-level raised stripes and the second-level raised stripes on the suction surface of the hydrofoil can obviously change the motion direction of the back jet flow and weaken the momentum intensity of the back jet flow, thereby effectively inhibiting the falling of cloud cavitation, reducing pressure pulsation and cavitation erosion, improving the efficiency of hydraulic machinery and prolonging the service life.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is an enlarged schematic view of portion A of FIG. 1;

FIG. 3 is a top view of FIG. 1;

FIG. 4 is an enlarged schematic view of portion B of FIG. 3;

FIG. 5 is a comparison graph of time-averaged cavitation without a hydrofoil cavitation flow control structure and with a cavitation flow control structure;

figure 6 is a comparison of the standard deviation of pressure at 20mm from the midplane on the surface of the hydrofoil.

In the figure, 1-first level raised stripe, 2-second level raised stripe, 3-hydrofoil, 4-hydrofoil front edge, 5-hydrofoil tail edge, 6-first level raised stripe section circle, 7-first level raised stripe section circle scanning track, 8-second level raised stripe section circle, and 9-second level raised stripe section circle scanning track.

Detailed Description

The technical solution and the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

The hydrofoil airfoil comprises a primary raised stripe 1, a secondary raised stripe 2, a hydrofoil 3, a hydrofoil front edge 4, a hydrofoil tail edge 5, a primary raised stripe section circle 6, a primary raised stripe section circle scanning track 7, a secondary raised stripe section circle 8 and a secondary raised stripe section circle scanning track 9. The embodiment provides a hydrofoil cavitation flow control structure, which comprises a first-stage raised stripe 1 and a second-stage raised stripe 2 distributed on the suction surface of a hydrofoil 3.

As shown in fig. 1 and 2, a scanning track 7 of a cross-sectional circle of the primary convex stripe is tightly attached to the suction surface of the hydrofoil 3, the center of the cross-sectional circle 6 of the primary convex stripe is located on the scanning track 7 of the cross-sectional circle of the primary convex stripe, and a convex part of the cross-sectional circle 6 of the primary convex stripe, which is obtained by scanning along the scanning track 7 of the cross-sectional circle of the primary convex stripe and located outside the hydrofoil 3, is the primary convex stripe 1; similarly, the scanning track 9 of the section circle of the secondary convex stripe is tightly attached to the suction surface of the hydrofoil 3, the center of the section circle 8 of the secondary convex stripe is located on the scanning track 9 of the section circle of the secondary convex stripe, and the convex part of the section circle 8 of the secondary convex stripe, which is located outside the hydrofoil 3 and is obtained by scanning along the scanning track 9 of the section circle of the secondary convex stripe, is the secondary convex stripe 2. In order to reduce the resistance of the ends of the primary raised stripes 1 and the secondary raised stripes 2 to the fluid, blunt-tipped treatment is adopted at the ends of the primary raised stripes 1 and the secondary raised stripes 2.

As shown in fig. 3 and 4, the secondary raised stripes 2 on both sides of the primary raised stripe 1 are distributed at intervals in a completely consistent manner, and the primary raised stripe 1 is located in the middle of the suction surface of the hydrofoil 3.

Example 1

The included angle beta between the first-level convex stripe 1 and the second-level convex stripe 2 is 27 degrees, and the diameter D of the section circle 6 of the first-level convex stripe is₁2.8mm, a second level raised stripe cross section circle 8 diameter D₂The interval distribution distance S of the secondary convex stripes 2 along the chord length direction of the hydrofoil 3 is 8mm, and the chord length C of the hydrofoil 3 is 150 mm. Length L of primary raised stripe 1₁Is 116.2 mm. Length L of secondary raised stripe 2₂Is 89.2 mm.

The feasibility of the present invention is illustrated by performing numerical simulations on the embodiments provided above, where fig. 5 (a) shows the cavitation-averaged behavior when the hydrofoil cavitation flow control structure provided in the embodiments is not installed, and fig. 5 (b) shows the cavitation-averaged behavior when the hydrofoil cavitation flow control structure provided in the embodiments is installed. Comparing (a) and (b) in fig. 5, it can be seen that the falling off of the cloud cavitation and the size of the cavitation can be significantly suppressed by adding the hydrofoil cavitation flow control structure provided in this embodiment. The numerical simulation result of the embodiment shows that the time-averaged cavitation volume can be compressed to 47.53% of the original volume after the hydrofoil cavitation flow control structure provided by the invention is adopted. Figure 6 is a comparison of the standard deviation of pressure at 20mm from the midplane on the surface of the hydrofoil. From this figure, it can be seen that the standard deviation of the pressure at the surface of the hydrofoil is significantly reduced after the installation of the cavitation flow control structure provided in this embodiment. This means that the cavitation flow control structure provided by this embodiment can be installed to significantly reduce pressure pulsations at the surface of the hydrofoil. In addition, the ratio of the lift coefficient to the drag coefficient (lift-drag ratio) of the hydrofoil is an important parameter for measuring hydrodynamic characteristics of the hydrofoil. Numerical simulation results show that after the hydrofoil cavitation flow control structure provided by the embodiment is adopted, the lift-drag ratio of the hydrofoil can be improved by 57%. This means that the hydrodynamic characteristics of the hydrofoil can be improved significantly while cavitation is suppressed by the present invention.

Example 2

The included angle beta between the first-level convex stripe 1 and the second-level convex stripe 2 is 32 degrees, and the diameter D of the section circle 6 of the first-level convex stripe is₁1.9mm, a second level raised stripe cross-section circle of 8 diameter D₂The interval distribution distance S of the secondary convex stripes 2 along the chord length direction of the hydrofoil 3 is 7.9mm, and the chord length C of the hydrofoil 3 is 150 mm. Length L of primary raised stripe 1₁Is 116.2 mm. Length L of secondary raised stripe 2₂Is 89.2 mm.

The feasibility of the present invention is illustrated by performing numerical simulations on the embodiments provided above, where fig. 5 (a) shows the cavitation conditions when the hydrofoil cavitation flow control structure is not installed, and fig. 5 (c) shows the cavitation conditions when the hydrofoil cavitation flow control structure provided in this example is installed. Comparing (a) and (c) in fig. 5, it can be seen that the falling off of the cloud cavitation can be significantly suppressed and the cavitation size can be suppressed after the hydrofoil cavitation flow control structure provided by the embodiment is added. The numerical simulation result of the embodiment shows that the time-averaged cavitation volume can be compressed to 45.28% of the original volume by adopting the hydrofoil cavitation flow control structure provided by the invention. Figure 6 is a comparison of the standard deviation of pressure at 20mm from the midplane on the surface of the hydrofoil. From this figure, it can be seen that the standard deviation of the pressure at the surface of the hydrofoil is significantly reduced after the installation of the cavitation flow control structure provided in this embodiment. This means that the cavitation flow control structure provided by this embodiment can be installed to significantly reduce pressure pulsations at the surface of the hydrofoil. In addition, the numerical simulation result shows that the lift-drag ratio of the hydrofoil can be improved by 38.73% after the hydrofoil cavitation flow control structure provided by the embodiment is adopted. This means that the hydrodynamic characteristics of the hydrofoil can be improved significantly while cavitation is suppressed by the present invention.

Example 3

The included angle beta between the first-level convex stripe 1 and the second-level convex stripe 2 is 29 degrees, and the diameter D of the section circle 6 of the first-level convex stripe is₁3.5mm, a second level raised stripe cross section circle 8 diameter D₂The interval distribution distance S of the secondary convex stripes 2 along the chord length direction of the hydrofoil 3 is 7.2mm, and the chord length C of the hydrofoil 3 is 150 mm. Length L of primary raised stripe 1₁Is 116.2 mm. Of secondary raised stripes 2Length L₂Is 89.2 mm.

The feasibility of the present invention is illustrated by performing numerical simulations on the embodiments provided above, where fig. 5 (a) shows the cavitation conditions when the hydrofoil cavitation flow control structure is not installed, and fig. 5 (d) shows the cavitation conditions when the hydrofoil cavitation flow control structure provided in this example is installed. Comparing (a) and (d) in fig. 5, it can be seen that the falling off of the cloud cavitation and the size of the cavitation can be significantly suppressed by adding the hydrofoil cavitation flow control structure provided in this embodiment. The numerical simulation result of the embodiment shows that the time-averaged cavitation volume can be compressed to 50.43% of the original volume after the hydrofoil cavitation flow control structure provided by the invention is adopted. Figure 6 is a comparison of the standard deviation of pressure at 20mm from the midplane on the surface of the hydrofoil. From this figure, it can be seen that the standard deviation of the pressure at the surface of the hydrofoil is significantly reduced after the installation of the cavitation flow control structure provided in this embodiment. This means that the cavitation flow control structure provided by this embodiment can be installed to significantly reduce pressure pulsations at the surface of the hydrofoil. In addition, the numerical simulation result shows that the lift-drag ratio of the hydrofoil can be improved by 33.4% after the hydrofoil cavitation flow control structure provided by the embodiment is adopted. This means that the hydrodynamic characteristics of the hydrofoil can be improved significantly while cavitation is suppressed by the present invention.

Example 4

The included angle beta between the first-level convex stripe 1 and the second-level convex stripe 2 is 32 degrees, and the diameter D of the section circle 6 of the first-level convex stripe is₁3.0mm, a second level raised stripe cross section circle 8 diameter D₂The interval distribution distance S of the secondary convex stripes 2 along the chord length direction of the hydrofoil 3 is 7.6mm, and the chord length C of the hydrofoil 3 is 150 mm. Length L of primary raised stripe 1₁Is 116.2 mm. Length L of secondary raised stripe 2₂Is 89.2 mm.

The feasibility of the present invention is illustrated by performing numerical simulations on the embodiments provided above, where fig. 5 (a) shows the cavitation conditions when the hydrofoil cavitation flow control structure is not installed, and fig. 5 (e) shows the cavitation conditions when the hydrofoil cavitation flow control structure provided in this example is installed. Comparing (a) and (e) in fig. 5, it can be seen that the falling off of the cloud cavitation can be significantly suppressed and the cavitation size can be suppressed after the hydrofoil cavitation flow control structure provided by this embodiment is added. The numerical simulation result of the embodiment shows that the time-averaged cavitation volume can be compressed to 47.21% of the original volume by adopting the hydrofoil cavitation flow control structure provided by the invention. Figure 6 is a comparison of the standard deviation of pressure at 20mm from the midplane on the surface of the hydrofoil. From this figure, it can be seen that the standard deviation of the pressure at the surface of the hydrofoil is significantly reduced after the installation of the cavitation flow control structure provided in this embodiment. This means that the cavitation flow control structure provided by this embodiment can be installed to significantly reduce pressure pulsations at the surface of the hydrofoil. In addition, the numerical simulation result shows that the lift-drag ratio of the hydrofoil can be improved by 45.71% after the hydrofoil cavitation flow control structure provided by the embodiment is adopted. This means that the hydrodynamic characteristics of the hydrofoil can be improved significantly while cavitation is suppressed by the present invention.

The foregoing examples are provided for illustration and description of the invention only and are not intended to limit the invention to the scope of the described examples. Furthermore, it will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that many variations and modifications may be made in accordance with the teachings of the present invention, all of which fall within the scope of the invention as claimed.