Hydrofoil cavitating flow control structure

Abstract

A hydrofoil cavitating flow control structure includes a hydrofoil. A primary protuberant stripe is disposed in a middle position of a suction side of the hydrofoil, a plurality of symmetrically-distributed secondary protuberant stripes are disposed obliquely at both sides of the primary protuberant stripe, and the plurality of secondary protuberant stripes are uniformly and equidistantly distributed along the length direction of the primary protuberant stripe. By changing geometric parameters such as an included angle between the primary protuberant stripe and the second protuberant stripe, a ratio of cross section diameters and a distribution spacing of the second protuberant stripes along a chord length direction of the hydrofoil and the like, the shedding of cloud cavitation on a hydrofoil surface is effectively suppressed, and cavitation erosion and pressure pulsation generated by cavitation collapse is reduced, thus improving the operation efficiency and the service life of hydraulic machinery.

Claims

1. A hydrofoil cavitating flow control structure, comprising a hydrofoil, wherein a primary protuberant stripe is disposed in a middle position of a suction side of the hydrofoil, a plurality of symmetrically-distributed secondary protuberant stripes are disposed obliquely at both sides of the primary protuberant stripe, and the plurality of secondary protuberant stripes are uniformly and equidistantly distributed along a length direction of the primary protuberant stripe; the primary protuberant stripe is obtained from a protuberant part which is outside the hydrofoil and has a circular cross-section along an entire length of the primary protuberant stripe; a trajectory of the primary protuberant stripe is closely attached to the suction side of the hydrofoil, and a center of the circular cross-section of the primary protuberant stripe is located on the trajectory of the primary protuberant stripe; the secondary protuberant stripes are obtained from a protuberant part which is outside the hydrofoil and has a circular cross-section along an entire length of the secondary protuberant stripe; a trajectory of the secondary protuberant stripes is closely attached to the suction side of the hydrofoil, and a center of the circular cross-section of the secondary protuberant stripes is located on the trajectory of the secondary protuberant stripe.

2. The hydrofoil cavitating flow control structure of claim 1, wherein an included angle between the primary protuberant stripe and the secondary protuberant stripes is 27 to 32.

3. The hydrofoil cavitating flow control structure of claim 1, wherein a ratio D.sub.1/D.sub.2 of a diameter D.sub.1 of the circular cross-section of the primary protuberant stripe to a diameter D.sub.2 of the circular cross-section of the secondary protuberant stripes is in a range of 2 to 4.

4. The hydrofoil cavitating flow control structure of claim 1, wherein a distribution spacing S of the secondary protuberant stripes along a chord length direction of the hydrofoil is 0.04 C to 0.06 C, and C is a chord length of the hydrofoil.

5. The hydrofoil cavitating flow control structure of claim 1, wherein the entire length L.sub.1 of the primary protuberant stripe is 0.5 C to 0.9 C and the entire length L.sub.2 of the secondary protuberant stripes is 0.4 C to 0.8 C, and C is a chord length of the hydrofoil.

6. The hydrofoil cavitating flow control structure of claim 1, wherein the hydrofoil is a rotary impeller blade or stationary impeller blade of hydraulic machinery.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a structural schematic diagram of the disclosure.

(2) FIG. 2 is an enlarged structural schematic diagram of a part Ain FIG. 1.

(3) FIG. 3 is a top view of FIG. 1.

(4) FIG. 4 is an enlarged structural schematic diagram of a part B in FIG. 3.

(5) FIG. 5 is a comparison diagram of time-averaged cavitation circumstances with and without a hydrofoil cavitating flow control structure.

(6) FIG. 6 shows comparison of pressure standard deviations at 20 mm from a midplane on a hydrofoil surface.

(7) Numerals of the drawings are described as follows: 1. primary protuberant stripe, 2. secondary protuberant stripe, 3. hydrofoil, 4. hydrofoil leading edge, 5. hydrofoil trailing edge, 6. circular cross-section of the primary protuberant stripe, 7. scan trajectory of the primary protuberant stripe, 8. circular cross-section of secondary protuberant stripe, 9. scan trajectory of secondary protuberant stripe.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) The technical solution and specific embodiments of the disclosure will be clearly and fully described in combination with accompanying drawings in the disclosure.

(9) The disclosure comprises a primary protuberant stripe 1, secondary protuberant stripes 2, a hydrofoil 3, a hydrofoil leading edge 4, a hydrofoil trailing edge 5, a circular cross-section 6 of the primary protuberant stripe, a scan trajectory 7 of the primary protuberant stripe, a circular cross-section 8 of the secondary protuberant stripe, and a scan trajectory 9 of the secondary protuberant stripe. An embodiment of the disclosure provides a hydrofoil cavitating flow control structure, comprising the primary protuberant stripe 1 and the secondary protuberant stripes 2 distributed on a suction side of the hydrofoil 3.

(10) As shown in FIGS. 1 and 2, the scan trajectory 7 of the primary protuberant stripe is closely attached to a suction side of the hydrofoil 3, and a center of the circular cross-section 6 of the primary protuberant stripe is located on the scan trajectory 7 of the primary protuberant stripe. A protuberant part which is outside the hydrofoil 3 and formed by scanning the circular cross-section 6 of the primary protuberant stripe along the scan trajectory 7 of the primary protuberant stripe is the primary protuberant stripe 1. Likewise, the scan trajectory 9 of the secondary protuberant stripe is closely attached to the suction side of the hydrofoil 3, and a center of the circular cross-section 8 of the secondary protuberant stripe is located on the scan trajectory 9 of the secondary protuberant stripe. A protuberant part which is outside the hydrofoil 3 and formed by scanning the circular cross-section 8 of the secondary protuberant stripe along the scan trajectory 9 of the secondary protuberant stripe is the secondary protuberant stripe 2. In order to reduce a drag force generated by ends of the primary protuberant stripe 1 and the secondary protuberant stripe 2 for a fluid, passivated tips are adopted for the ends of the primary protuberant stripe 1 and the secondary protuberant stripe 2.

(11) As shown in FIGS. 3 and 4, the secondary protuberant stripes 2 on both sides of the primary protuberant stripe 1 are arranged in a same spaced distribution manner, and the primary protuberant stripe 1 is located in a middle position of the suction side of the hydrofoil 3.

Embodiment 1

(12) An included angle between the primary protuberant stripe 1 and the secondary protuberant stripe 2 is 27. The circular cross-section 6 of the primary protuberant stripe has a diameter D.sub.1 of 2.8 mm and the circular cross-section 8 of secondary protuberant stripe has a diameter D.sub.2 of 0.8 mm. A distribution spacing S of the secondary protuberant stripes 2 along a chord length direction of the hydrofoil 3 is 8 mm, where a chord length C of the hydrofoil 3 is 150 mm. A length L.sub.1 of the primary protuberant stripe 1 is 116.2 mm and a length L.sub.2 of the secondary protuberant stripe 2 is 89.2 mm.

(13) The feasibility of the disclosure is described by performing numerical simulation on the above specific embodiment. (a) of FIG. 5 shows time-averaged cavitation circumstance without a hydrofoil cavitating flow control structure provided by the specific embodiment and (b) of FIG. 5 shows time-averaged cavitation circumstance with a hydrofoil cavitating flow control structure provided by the specific embodiment. It can be seen from the comparison of (a) and (b) of FIG. 5 that the embodiment with the hydrofoil cavitating flow control structure can not only significantly suppress the shedding of cloud cavitation but also suppress the size of the cavitation. The numerical simulation results of the present embodiment show that, with the hydrofoil cavitating flow control structure provided by the disclosure, the time-averaged cavitation volume can be reduced to 47.53% of the original. FIG. 6 shows comparison of pressure standard deviations at 20 mm from a midplane on a hydrofoil surface. It can be found from the drawing that, with the cavitating flow control structure provided by the present embodiment, the pressure standard deviation of the hydrofoil surface is significantly reduced. That is, the mounting of the cavitating flow control structure provided by the present embodiment can reduce the pressure pulsation of the hydrofoil surface. Furthermore, a ratio of a lift coefficient to a drag coefficient of the hydrofoil (a lift-to-drag ratio) is an important parameter for determining the hydrodynamic properties of the hydrofoil. The numerical simulation results show that, with the hydrofoil cavitating flow control structure provided by the present embodiment, the lift-to-drag ratio of the hydrofoil can be increased by 57%, which indicates that the disclosure can improve the hydrodynamic properties of the hydrofoil while suppressing cavitation.

Embodiment 2

(14) The included angle between the primary protuberant stripe 1 and the secondary protuberant stripe 2 is 32. The circular cross-section 6 of the primary protuberant stripe has a diameter D.sub.1 of 1.9 mm and the circular cross-section 8 of secondary protuberant stripe has a diameter D.sub.2 of 0.8 mm. The distribution spacing S of the secondary protuberant stripes 2 along the chord length direction of the hydrofoil 3 is 7.9 mm, where the chord length C of the hydrofoil 3 is 150 mm. The length L.sub.1 of the primary protuberant stripe 1 is 116.2 mm and the length L.sub.2 of the secondary protuberant stripe 2 is 89.2 mm.

(15) The feasibility of the disclosure is described by performing numerical simulation on the above specific embodiment. (a) of FIG. 5 shows time-averaged cavitation circumstance without a hydrofoil cavitating flow control structure provided by the specific embodiment and (c) of FIG. 5 shows time-averaged cavitation circumstance with a hydrofoil cavitating flow control structure provided by the specific embodiment. It can be seen from the comparison of (a) and (c) of FIG. 5 that the embodiment with the hydrofoil cavitating flow control structure can not only significantly suppress the shedding of cloud cavitation but also suppress the size of the cavitation. The numerical simulation results of the present embodiment show that, with the hydrofoil cavitating flow control structure provided by the disclosure, the time-averaged cavitation volume can be reduced to 45.28% of the original. FIG. 6 shows comparison of pressure standard deviations at 20 mm from a midplane on a hydrofoil surface. It can be found from the drawing that, with the cavitating flow control structure provided by the present embodiment, the pressure standard deviation of the hydrofoil surface is significantly reduced. That is, the mounting of the cavitating flow control structure provided by the present embodiment can reduce the pressure pulsation of the hydrofoil surface. Furthermore, the numerical simulation results show that, with the cavitating flow control structure provided by the present embodiment, the lift-to-drag ratio of the hydrofoil can be increased by 38.73%, which indicates that the disclosure can improve the hydrodynamic properties of the hydrofoil while suppressing cavitation.

Embodiment 3

(16) The included angle between the primary protuberant stripe 1 and the secondary protuberant stripe 2 is 29. The circular cross-section 6 of the primary protuberant stripe has a diameter D.sub.1 of 3.5 mm and the circular cross-section 8 of secondary protuberant stripe has a diameter D.sub.2 of 0.9 mm. The distribution spacing S of the secondary protuberant stripes 2 along the chord length direction of the hydrofoil 3 is 7.2 mm, where the chord length C of the hydrofoil 3 is 150 mm. The length L.sub.1 of the primary protuberant stripe 1 is 116.2 mm and the length L.sub.2 of the secondary protuberant stripe 2 is 89.2 mm.

(17) The feasibility of the disclosure is described by performing numerical simulation on the above specific embodiment. (a) of FIG. 5 shows time-averaged cavitation circumstance without a hydrofoil cavitating flow control structure provided by the specific embodiment and (d) of FIG. 5 shows time-averaged cavitation circumstance with a hydrofoil cavitating flow control structure provided by the specific embodiment. It can be seen from the comparison of (a) and (d) of FIG. 5 that the embodiment with the hydrofoil cavitating flow control structure can not only significantly suppress the shedding of cloud cavitation but also suppress the size of the cavitation. The numerical simulation results of the present embodiment show that, with the hydrofoil cavitating flow control structure provided by the disclosure, the time-averaged cavitation volume can be reduced to 50.43% of the original. FIG. 6 shows comparison of pressure standard deviations at 20 mm from a midplane on a hydrofoil surface. It can be found from the drawing that, with the cavitating flow control structure provided by the present embodiment, the pressure standard deviation of the hydrofoil surface is significantly reduced. That is, the mounting of the cavitating flow control structure provided by the present embodiment can reduce the pressure pulsation of the hydrofoil surface. Furthermore, the numerical simulation results show that, with the cavitating flow control structure provided by the present embodiment, the lift-to-drag ratio of the hydrofoil can be increased by 33.4%, which indicates that the disclosure can improve the hydrodynamic properties of the hydrofoil while suppressing cavitation.

Embodiment 4

(18) The included angle between the primary protuberant stripe 1 and the secondary protuberant stripe 2 is 32. The circular cross-section 6 of the primary protuberant stripe has a diameter D.sub.1 of 3.0 mm and the circular cross-section 8 of secondary protuberant stripe has a diameter D.sub.2 of 0.9 mm. The distribution spacing S of the secondary protuberant stripes 2 along the chord length direction of the hydrofoil 3 is 7.6 mm, where the chord length C of the hydrofoil 3 is 150 mm. The length L.sub.1 of the primary protuberant stripe 1 is 116.2 mm and the length L.sub.2 of the secondary protuberant stripe 2 is 89.2 mm.

(19) The feasibility of the disclosure is described by performing numerical simulation on the above specific embodiment. (a) of FIG. 5 shows time-averaged cavitation circumstance without a hydrofoil cavitating flow control structure provided by the specific embodiment and (e) of FIG. 5 shows time-averaged cavitation circumstance with a hydrofoil cavitating flow control structure provided by the specific embodiment. It can be seen from the comparison of (a) and (e) of FIG. 5 that the embodiment with the hydrofoil cavitating flow control structure can not only significantly suppress the shedding of cloud cavitation but also suppress the size of the cavitation. The numerical simulation results of the present embodiment show that, with the hydrofoil cavitating flow control structure provided by the disclosure, the time-averaged cavitation volume can be reduced to 47.21% of the original. FIG. 6 shows comparison of pressure standard deviations at 20 mm from a midplane on a hydrofoil surface. It can be found from the drawing that, with the cavitating flow control structure provided by the present embodiment, the pressure standard deviation of the hydrofoil surface is significantly reduced. That is, the mounting of the cavitating flow control structure provided by the present embodiment can reduce the pressure pulsation of the hydrofoil surface. Furthermore, the numerical simulation results show that, with the hydrofoil cavitating flow control structure provided by the present embodiment, the lift-to-drag ratio of the hydrofoil can be increased by 45.71%, which indicates that the disclosure can improve the hydrodynamic properties of the hydrofoil while suppressing cavitation.

(20) The above embodiments are used only to illustrate and describe the disclosure and not intended to limit the disclosure to the scope of the described embodiments. Those skilled in the art can understand that the disclosure is not limited to the above embodiments and more variations and changes can be made under the teaching of the disclosure. These variations and changes shall all fall within the scope of protection of the disclosure.