Structure for improving aerodynamic efficiency of low-pressure turbine blade and working method thereof

Abstract

A turbine blade structure for improving aerodynamic efficiency of low-pressure turbine blades, including: a suction side, a pressure side, multiple dimples and a blade body. The suction side is an outer convex side of the blade body. The pressure side is an inner concave side of the blade body. The dimples are arranged on the suction side in pairs. Each dimple forms an inclination angle β with an air flow. The air flow includes a first fluid and a second fluid, and the energy of the first fluid is lower than that of the second fluid. Each dimple sucks the first fluid at a first end when the air flow passes a surface of the blade body, and allows the first fluid to spirally flow along an inclined direction in each dimple to form a spiral vortex, and discharge the first fluid through a second end.

Claims

1. A turbine blade structure, comprising: a suction side; a pressure side; a plurality of dimples; and a blade body; wherein the suction side is an outer convex side of the blade body; and the pressure side is an inner concave side of the blade body; the plurality of dimples are arranged on the suction side in pairs in a V-shaped manner; and each of the plurality of dimples forms an inclination angle β with an air flow; the air flow comprises a first fluid and a second fluid, and an energy of the first fluid is lower than that of the second fluid; each of the plurality of dimples is configured to suck the first fluid at a first end when the air flow passes a surface of the blade body, and allow the first fluid to spirally flow along an inclined direction in each of the plurality of dimples to form a spiral vortex, and discharge the first fluid through a second end; a spiral direction of the spiral vortex inside each of the plurality of dimples is consistent with a direction of a main flow above the suction side; the plurality of dimples are arranged at an area on the suction side where flow separation occurs, wherein the area is located at 50-90% of a chord length of the blade body from a leading edge; each of the plurality of dimples comprises an upstream section, a downstream section and a middle section; the upstream section is a hemispherical surface with a diameter of D.sub.2; the downstream section is a hemispherical surface with a diameter of D.sub.1; and D.sub.1 is greater than or equal to D.sub.2; the middle section is a cylindrical or conical surface to achieve smooth transition between the upstream section and the downstream section; and from an end of the middle section connected with the upstream section to an end of the middle section connected with the downstream section, a diameter of the middle section remains the same or increases; the inclination angle β is 0-90°; a narrowness of each of the plurality of dimples is calculated by L/D.sub.1, wherein L is a distance between a center of the upstream section and a center of the downstream section; and a value of the L/D.sub.1 is 1-10; a first depth ratio of each of the plurality of dimples is calculated by h.sub.1/D.sub.1, wherein h.sub.1 is a depth of the upstream section; a second depth ratio of each of the plurality of dimples is calculated by h.sub.2/D.sub.2, wherein h.sub.2 is a depth of the downstream section; and the first depth ratio and the second depth ratio are both 0-0.2; and the downstream section and the upstream section of each of the plurality of dimples are respectively provided with an edge fillet.

2. A working method of the turbine blade structure of claim 1, comprising: generating a spiral vortex through the turbine blade structure; and subjecting an air flow to attachment at the downstream section of each of the plurality of dimples to delay flow separation on the suction side.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will be described in detail below with reference to the embodiments and accompanying drawings to make objects, features and advantages of the present disclosure clearer.

(2) FIG. 1 schematically depicts an overall structure of a turbine blade structure according to an embodiment of the present disclosure; and

(3) FIG. 2 is a sectional view of the turbine blade structure according to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) The present disclosure will be described below in detail with reference to the embodiments. It is apparent that the embodiments are merely illustrative and are not intended to limit the disclosure. It should be noted that any variations and improvements made by those of ordinary skilled in the art without departing from the spirit of the disclosure shall fall within the scope of the disclosure defined by the appended claims.

(5) As shown in FIGS. 1-2, a turbine blade structure includes a suction side 10, a pressure side 11, multiple dimples 20 and a blade body. The suction side 10 is an outer convex side of the blade body. The pressure side 11 is an inner concave side of the blade body. The dimples 20 are arranged on the suction side 10 in pairs. Each of the dimples 20 forms an inclination angle β with an air flow. The air flow includes a first fluid and a second fluid, and an energy of the first fluid is lower than that of the second fluid. Each of the dimples 20 is configured to suck the first fluid when the air flow passes through a surface of the blade body, and allow the first fluid to spirally flow along an inclined direction in each of the dimples 20 to form a spiral vortex, and discharge the first fluid through a second end. When the air flow passes through the dimples 20 on the suction side 10, due to a reduction of shear stress of the suction side 10, the fluid above the suction side 10 is accelerated and attached to a suction surface downstream the dimples 20, increasing the flow energy of the downstream boundary layer. In addition, a spiral direction of the spiral vortex inside each of dimples 20 is consistent with a direction of a main flow above the suction side. The spiral vortex brings the main flow near to the suction side, thus increasing a flow kinetic energy near the suction side and promoting a flow transition near the suction side.

(6) The dimples 20 are arranged at an area on the suction side where flow separation occurs, where the area is located at 50-90% of a chord length of the blade body from a leading edge. Each dimple 20 includes an upstream section 21, a downstream section 23 and a middle section 25. The upstream section 21 is a hemispherical surface with a diameter of D.sub.2. The downstream section 23 is a hemispherical surface with a diameter of D.sub.1. D.sub.1 is greater than or equal to D.sub.2. The middle section 25 is a cylindrical or conical surface to achieve smooth transition between the upstream section and the downstream section. From an end of the middle section 25 connected with the upstream section 21 to an end of the middle section connected with the downstream section 23, a diameter of the middle section 25 increases. The inclination angle β is 0-90° .

(7) A narrowness of each of the dimples 20 is calculated by L/D.sub.1, where L is a distance between a center of the upstream section 21 and a center of the downstream section 23. A value of the L/D.sub.1 is 1-10.

(8) A first depth ratio of the dimples 20 is calculated by h.sub.1/D.sub.1, where h.sub.1 is a depth of the upstream section 21. A second depth ratio of the dimples 20 is calculated by h.sub.2/D.sub.2, where h.sub.2 is a depth of the downstream section 23. The first depth ratio and the second depth ratio are both 0-0.2.

(9) In an embodiment, the dimples 20 are arranged after 50% of the chord length of the blade body;

(10) In an embodiment, the inclination angle β is 30-60° .

(11) In an embodiment, the value of the L/D.sub.1 is greater than 3 for a better concave effect.

(12) In an embodiment, the first depth ratio and the second depth ratio are both 0.05-0.2 for a better effect. A depth ratio of each of the dimples 20 is varied. A depth of each of the dimples becomes shallower from the downstream section to the upstream section. The downstream section is bigger and deeper, and the first depth ratio is 0-0.2. The upstream section is shallower, and the second depth ratio is 0-0.2.

(13) The turbine blade structure provided herein can eliminate or reduce the flow separation at the suction side when operating under a low Reynolds number condition, improving an aerodynamic performance of the high-load low-pressure turbine, avoiding additional aerodynamic loss under a high Reynolds number condition, and rendering a wilder turbine blade operating range. The air flow on the surface of the blade body interacts with the inclined dimples, such that the first fluid near the suction side allows to spirally flow inside the downstream section 23 of each of the dimples 20, and then is discharged through an end of the upstream section 21. Regarding the turbine blade structure provided herein, the spiral vortex can be discharged constantly, and the second fluid is subjected to attachment at a rear suction side, which provides significant flow control superiority over other blades in which vortices reside in the dimples.

(14) In an embodiment, the diameter of the downstream section 23 is twice the diameter of the upstream section 21.

(15) In an embodiment, the downstream section 23 and the upstream section 21 are respectively provided with an edge fillet to reduce flow loss of the air flow after attachment at a trailing edge of each of the dimples, and to discharge the spiral vortex from the dimples.

(16) In an embodiment, the dimples 20 are arranged in a V-shaped manner with a top end towards an air flow upstream or downstream.

(17) Provided herein is a working method of the above-mentioned turbine blade structure. The spiral vortex is generated through the turbine blade structure. The air flow is subjected to attachment at the downstream section 23 of each of the dimples 20 to delay flow separation on the suction side 10 for drag reduction.

(18) Due to the variation of Reynolds number and air flow parameters, the flow separation occurs at different areas. When the Reynolds number is low, the flow separation occurs near an upstream surface of the blade body. When the Reynolds number is high, the flow separation occurs near a downstream surface of the blade body. By means of the inclined dimples, variation of area for flow separation can be adapted, realizing a wider effective working range for suppressing the flow separation.

(19) The inclined dimples on the suction side reduce the influence of the downstream flow separation or adverse pressure gradient over the turbine blade on the upstream flow, causing less flow separation at the upstream section of each of the dimples, and facilitating drag reduction.

(20) The spiral vortex can be generated inside the dimples 20, which reduces shear force of an external main flow and guides external high-energy fluid to the surface of the blade, improving kinetic energy of the fluid near the surface. A spiral direction of the vortex is consistent with a direction of the external main flow to reduce shear stress, so as to accelerate the external main flow near the surface.

(21) By means of the bigger and deeper downstream section 23 of each of the dimples 20, more downstream low-energy fluids near the suction side are guided into the dimples 20, leading to a stronger interaction between the high-speed main flow and the dimples above the suction side, and making a stronger spiral vortex inside the dimples 20.

(22) By means of the narrower and shallower upstream section 21 of each of the dimples 20, the flow separation reduces, the spiral vortex can flow out from the upstream section 21 and be carried by upstream high-energy fluid. Under a high Reynolds number condition, the upstream section 21 of each of the dimples 20 avoids to introduce additional flow losses when the flow separation does not occur in the upstream section 21 of each of the dimples 20, making a wilder aerodynamic drag reduction range of turbine.

(23) As used herein, terms “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner” and “outer” refer to orientational or positional relationship shown in the drawings, which are merely for better description of the present disclosure instead of indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, these terms should not be construed as a limitation to the present disclosure.

(24) Described above are only some embodiments of the present disclosure, which are not intended to limit the disclosure. Any variations and modifications made by those of ordinary skilled in the art without departing from the spirit of the disclosure should fall within the scope of the disclosure defined by the appended claims.