A moving blade structure and a gas turbine

Abstract

This invention relates to the field of gas turbine technology, and provides a moving blade structure and a gas turbine. The moving blade structure includes at least: a moving blade body, the blade tip of which is provided with a groove for reducing the flow rate of leakage flow in the blade tip clearance; ribs, which divide the groove into several small, non-interconnected grooves, the small grooves being classified into type A, type B, and type C grooves along the axial direction of the moving blade body; a film cooling hole is provided upstream of the flow separation line formed by the vortex behind the rib in the type B groove; and / or, a film cooling hole is provided upstream of the flow separation line formed by the pressure side vortex in the type B groove. The moving blade structure provided by this invention changes the position of the film cooling hole, allowing the cool air to effectively cover the bottom of the groove, preventing the impact of the leakage flow in the blade tip clearance on the blade tip wall, avoiding direct erosion of the blade tip wall by high-temperature combustion gas, and thus extending the service life of the moving blade body.

Description

Technical Field

[0001] This invention relates to the field of gas turbine technology, and more specifically to a moving blade structure and a gas turbine. Background Technology

[0002] A gas turbine consists of several turbine stages. Each stage contains a varying number of stationary blades and a varying number of moving blades. The stationary and moving blades are radially surrounded by endwalls and a casing. The endwalls are divided into two parts: the endwall connected to the root of the stationary blade is called the stationary endwall, and the endwall connected to the root of the moving blade is called the moving endwall. The stationary blades, stationary endwalls, and casing remain stationary during gas turbine operation, while the moving blades and moving endwalls rotate. To prevent friction between the moving blades and the casing during operation, a radial clearance, called the tip clearance, exists between them. The pressure distribution on the pressure side and suction side of the blade tip differs, creating a significant pressure gradient. Driven by this pressure gradient, the high-temperature gas flows through the tip clearance, forming a tip clearance leakage flow. This tip clearance leakage flow does not perform work on the moving blades, resulting in tip leakage losses and wasting the high-temperature gas. To reduce tip clearance leakage flow, modern gas turbines commonly employ grooved tip structures. This structure, by incorporating side shoulders, alters the flow field characteristics within the tip clearance, significantly reducing the leakage flow. However, the use of grooved tips generates pressure-side vortices and scraping vortices within the tip clearance, increasing the thermal load on the tip wall. Arranging ribs within the tip grooves can effectively reduce the heat transfer coefficient of the tip wall. This is because the ribs within the tip grooves are perpendicular to the extension direction of the pressure-side vortices, inhibiting their formation and development. The pressure-side vortices are thus divided into smaller grooves within the tip, weakening their ability to entrain the tip leakage flow into these grooves. Simultaneously, the ribs prevent scraping vortices from entering the tip grooves. Based on these two effects, the impact of the tip clearance leakage flow on the tip wall is reduced.

[0003] However, since the blade tip wall is exposed to a high-temperature combustion gas environment, it also requires film cooling holes. For traditional grooved blade tips, film cooling holes are generally located at the flow separation line on the bottom of the groove, where the cool air can effectively cover the blade tip wall. However, when ribs are added to the blade tip groove, the flow structure within the blade tip clearance changes. The positions and shapes of the pressure-side vortices and scraping vortices are no longer the same, and the flow direction of the leakage flow in the blade tip clearance changes. Consequently, the previously arranged film cooling holes can no longer effectively provide cooling protection for the blade tip wall. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is that when ribs are added to the blade tip groove in the prior art, the flow structure in the blade tip gap changes, the position and shape of the pressure side vortex and scraping vortex are no longer the same, the flow direction of the leakage flow in the blade tip gap changes, and thus the previously arranged film cooling holes cannot effectively provide cooling protection for the blade tip wall, thereby providing a moving blade structure and a gas turbine.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] On one hand, the present invention provides a moving blade structure, comprising at least: a moving blade body, wherein the blade tip of the moving blade body is provided with a groove for reducing the leakage flow rate at the blade tip gap; ribs, wherein the ribs are equally spaced in the groove along the mid-arc direction of the blade tip, one end of each rib abuts against the pressure side shoulder wall of the blade tip, and the other end abuts against the suction side shoulder wall of the blade tip, thereby dividing the groove into several small grooves that are not interconnected with each other, wherein the small grooves are divided into type A grooves, type B grooves, and type C grooves along the axial direction of the moving blade body; a film cooling hole is provided upstream of the flow separation line formed by the vortex behind the rib in the type B groove, and the distance between the film cooling hole and the upstream rib and the suction side shoulder wall of the blade tip is equal; and / or, a film cooling hole is provided upstream of the flow separation line formed by the pressure side vortex in the type B groove, and the distance between the film cooling hole and the upstream rib and the pressure side shoulder wall of the blade tip is equal.

[0007] Furthermore, an air film cooling hole is provided upstream of the flow separation line formed by the pressure-side vortex in the C-type groove, and the distance between the air film cooling hole and the pressure-side shoulder wall and the suction-side shoulder wall of the blade tip is equal.

[0008] Furthermore, each of the ribs is arranged perpendicular to the mid-arc line of the blade tip.

[0009] Furthermore, the width of the rib is 1%-3% of the height of the moving blade body.

[0010] Furthermore, the distance between the air film cooling hole in the type B groove and the upstream rib is 1%-3% of the height of the moving blade body.

[0011] Furthermore, the distance between the air film cooling hole in the C-shaped groove and the upstream rib is 1%-3% of the height of the moving blade body.

[0012] Furthermore, the ribs comprise four, which divide the groove into five smaller grooves, including one type A groove, two type B grooves, and two type C grooves.

[0013] Furthermore, each of the air film cooling holes is a circular hole, and the diameter of the air film cooling hole is 1%-3% of the height of the moving blade body.

[0014] Furthermore, the direction of the airflow ejected from each of the air film cooling holes is perpendicular to the bottom of the groove.

[0015] On the other hand, the present invention also provides a gas turbine, including the moving blade structure described in any of the above claims, and further including a casing; a gap is left between the blade tip of the moving blade body and the inner wall of the casing to form a blade tip gap.

[0016] The technical solution of this invention has the following advantages:

[0017] The moving blade structure provided by this invention divides the original groove into multiple small grooves by setting ribs. According to the flow change characteristics of the airflow in the blade tip gap, the position of the film cooling hole is changed so that the cold air can effectively cover the bottom of the groove, prevent the leakage flow in the blade tip gap from impacting the blade tip wall, avoid the direct erosion of the blade tip wall by high temperature gas, and help extend the service life of the moving blade body. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the moving blade structure in an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the B-type groove in the moving blade structure of an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the C-shaped groove in the moving blade structure of an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the blade tip gap flow in the moving blade structure of this invention embodiment;

[0023] Figure 5 for Figure 2 Schematic diagram of the internal flow field at mid-section A;

[0024] Figure 6 for Figure 2 Schematic diagram of the internal flow field at midsection B;

[0025] Figure 7 for Figure 3Schematic diagram of the internal flow field at mid-section C;

[0026] Figure 8 This is a cross-sectional view of the meridional plane of the blade cascade passage in a gas turbine according to an embodiment of the present invention.

[0027] 1. Moving blade body; 2. Rib; 3. Film cooling hole; 4. Type A groove; 5. Type B groove; 6. Type C groove; 7. Rear vortex of rib; 8. Pressure side angle vortex; 9. Casing; 10. Blade tip clearance; 11. Stationary blade; 12. Stationary blade end wall; 13. Moving blade end wall; 14. Pressure side shoulder wall; 15. Suction side shoulder wall. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0031] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] like Figure 1As shown, this embodiment provides a moving blade structure, including at least: a moving blade body 1, the blade tip of the moving blade body 1 is provided with a groove for reducing the leakage flow rate at the blade tip gap; ribs 2, the ribs 2 are equally spaced in the groove along the mid-arc direction of the blade tip, one end of each rib 2 abuts against the pressure side shoulder wall 14 of the blade tip, and the other end abuts against the suction side shoulder wall 15 of the blade tip, so as to divide the groove into several small grooves that are not interconnected with each other. The small grooves are divided into type A groove 4, type B groove 5 and type C groove 6 along the axial direction of the moving blade body 1; a film cooling hole 3 is provided upstream of the flow separation line formed by the rib vortex 7 in type B groove 5, and the distance between the film cooling hole 3 and the upstream rib 2 and the suction side shoulder wall 15 of the blade tip is equal; and / or, a film cooling hole 3 is provided upstream of the flow separation line formed by the pressure side angular vortex 8 in type B groove 5, and the distance between the film cooling hole 3 and the upstream rib 2 and the pressure side shoulder wall 14 of the blade tip is equal.

[0033] The moving blade structure provided in this embodiment divides the original groove into multiple small grooves by setting ribs 2. According to the flow characteristics of airflow changes in the blade tip gap 10, the position of the air film cooling hole 3 is changed so that the cold air can effectively cover the bottom of the groove, prevent the leakage flow in the blade tip gap from impacting the blade tip wall, avoid the direct erosion of the blade tip wall by high temperature gas, and help extend the service life of the moving blade body 1.

[0034] For example, the rib 2 includes four ribs, which divide the groove into five smaller grooves, including one type A groove 4, two type B grooves 5 and two type C grooves 6.

[0035] For example, each rib 2 is perpendicular to the mid-arc line of the blade tip. Preferably, the width of the rib 2 is 1%-3% of the height of the blade body 1, for example, the width of the rib 2 is 1% of the height of the blade body 1. For example, each film cooling hole 3 is a circular hole, and the diameter of the film cooling hole 3 is 1%-3% of the height of the blade body 1, for example, the diameter of the film cooling hole 3 is 1% of the height of the blade body 1. For example, the direction of the airflow ejected from each film cooling hole 3 is perpendicular to the bottom of the groove. For example, the distance between the film cooling hole 3 in the B-type groove 5 and the upstream rib 2 is 1%-3% of the height of the blade body 1, for example, the distance between the film cooling hole 3 in the B-type groove 5 and the upstream rib 2 is 2% of the height of the blade body 1.

[0036] In this design, a film cooling hole 3 is provided upstream of the flow separation line formed by the pressure-side vortex 8 within the C-groove 6, and the distance between the film cooling hole 3 and the pressure-side shoulder wall 14 and suction-side shoulder wall 15 at the blade tip is equal. Furthermore, the distance between the film cooling hole 3 within the C-groove 6 and the upstream rib 2 is 1%-3% of the height of the moving blade body 1, and the distance between the film cooling hole 3 within the C-groove 6 and the upstream rib 2 is 2% of the height of the moving blade body 1.

[0037] For example, there are six film cooling holes 3 distributed on the blade tip wall: no film cooling holes 3 are provided in type A groove 4, two film cooling holes 3 are provided in each type B groove 5, and one film cooling hole 3 is provided in each type C groove 6.

[0038] Among them, the shape of type A groove 4 is approximately triangular. The shape of type B groove 5 is approximately quadrilateral. The common feature of type A groove 4 and type B groove 5 is that the length and width of the groove are approximately equal. The shape of type C groove 6, which is closer to type B groove 5, is approximately quadrilateral; the shape of type C groove 6, which is farther from type B groove 5, is approximately triangular. Although the shapes of the two type C grooves 6 are different, the length of the two type C grooves 6 is much greater than their width. This characteristic causes the flow structure inside the two type C grooves 6 to be different from that of type B groove 5.

[0039] In this case, no obvious vortex is formed in the A-type groove 4. The leakage flow from the blade tip gap enters the A-type groove 4 from both sides of the pressure side shoulder wall 14 and the suction side shoulder wall 15. At this time, there is no high heat transfer area on the bottom surface of the A-type groove 4.

[0040] like Figure 2 , Figure 4 , Figure 5 as well as Figure 6As shown, the tip clearance leakage flow in the B-type groove 5 is divided into two parts. One part of the tip clearance leakage flow enters the B-type groove 5 from the pressure side shoulder wall 14, and the other part enters the B-type groove 5 from the rib 2. Two vortices are formed in the B-type groove 5: one is the rib-back vortex 7, with the flow direction from the suction side of the B-type groove 5 to the pressure side; the other is the pressure side angular vortex 8, with the flow direction from the upstream rib 2 to the downstream rib 2. The two vortices are relatively short, cannot be fully developed, and have low rotational intensity, so they cannot drive the tip clearance leakage flow to produce a strong impact on the bottom surface of the B-type groove 5. However, the bottom of the B-type groove 5... The surface still has two flow separation lines formed by the vortex behind the rib 7 and the pressure-side angular vortex 8: one flow separation line is located downstream of the upstream rib 2, and this flow separation line is formed by the tip clearance leakage flow driven by the vortex behind the rib 7. The height and width of the vortex behind the rib 7 are equal, so the distance between the flow separation line and the upstream rib 2 is equal to the height of the rib 2; the other flow separation line is located downstream of the pressure-side shoulder wall 14, and this flow separation line is formed by the tip clearance leakage flow driven by the pressure-side angular vortex 8. Since the height and width of the pressure-side angular vortex 8 are equal, the distance between the flow separation line and the pressure-side shoulder wall 14 is equal to the height of the shoulder wall.

[0041] like Figure 3 , Figure 7 As shown, since the ribs 2 that serve as the channel wall of the C-type channel 6 are too short, there is no obvious distribution of the rib-back vortex 7 in the C-type channel 6, and the flow field structure in the C-type channel 6 is dominated by the pressure side angular vortex 8; at the same time, since the width of the C-type channel 6 is small, the space of the C-type channel 6 is completely filled by the pressure side angular vortex 8, and the tip clearance leakage flow cannot enter the interior of the C-type channel 6.

[0042] During operation, for a specific type B tank 5, two film cooling holes 3 are arranged inside, respectively on two flow separation lines on the bottom surface of type B tank 5. As shown in the flow field structure in section A: the film cooling holes 3 are located downstream of the pressure side shoulder wall 14 at the flow separation line position. After leaving the film cooling holes 3, the cooled air flows to both sides: part of the cooled air is drawn into the pressure side shoulder wall 14 by the pressure side vortex 8, and the other part of the cooled air flows towards the suction side shoulder wall 15 together with the tip clearance leakage flow. As shown in the flow field structure in section B: the film cooling holes 3 are located downstream of the rib 2 at the flow separation line position. After leaving the film cooling holes 3, the cooled air flows to both sides: part of the cooled air is drawn into the rib 2 upstream by the rib rear vortex 7, and the other part of the cooled air flows towards the rib 2 downstream together with the tip clearance leakage flow.

[0043] For a certain C-shaped tank 6, a film cooling hole 3 is arranged inside it, located in the middle of the bottom surface of the C-shaped tank 6. As shown in the flow field structure in section C: since the space inside the C-shaped tank 6 is completely occupied by the pressure side vortex 8, the cold air is directly entrained by the pressure side vortex 8 and cooled on the bottom surface of the C-shaped tank 6 after leaving the film cooling hole 3, so there is no need to arrange any other film cooling holes 3.

[0044] like Figure 8 As shown, another embodiment provides a gas turbine, including a casing 9. The gas turbine also includes several turbine stages, each turbine stage comprising a varying number of stationary blades 11 and a varying number of moving blade bodies 1. The stationary blades 11 and moving blade bodies 1 are radially surrounded by end walls and the casing 9. The end walls are divided into two parts: the end wall to which the root of the stationary blade 11 is connected is called the stationary blade end wall 12, and the end wall to which the root of the moving blade body 1 is connected is called the moving blade end wall 13. The stationary blades 11, the stationary blade end wall 12, and the casing 9 remain stationary during gas turbine operation, while the moving blade bodies 1 and the moving blade end wall 13 remain rotating. To avoid friction between the moving blade bodies 1 and the casing 9 during gas turbine operation, a radial clearance, called the blade tip clearance 10, exists between the moving blade bodies 1 and the casing 9. For example, the size of the blade tip clearance 10 can be 0.01 times the height of the moving blade body 1.

[0045] In practical implementation and application, due to differences in gas turbine models, the shape of the turbine blade tip varies to some extent, and the geometric design of the film cooling hole 3 in this application cannot be blindly followed. When laying the film cooling hole 3 in the blade tip groove, it is first necessary to determine the ratio of the groove's length to its width: when the groove's width and length are approximately the same, the design of type B groove 5 in this application can be adopted; while when the groove's width is much smaller than its length, the design of type C groove 6 in this application can be adopted.

[0046] In summary, the blade structure and gas turbine of this application, with four ribs 2 equidistantly arranged perpendicular to the tip arc within the blade tip groove, alters the flow field structure within the blade tip clearance 10. The pressure-side angular vortex 8 is divided into smaller grooves and cannot fully develop; simultaneously, the vortex 7 behind the rib is blocked by the ribs 2 from entering the groove and thus has little impact on the blade wall. Therefore, no obvious flow separation line is formed on the bottom surface of the blade tip groove.

[0047] In the moving blade structure and gas turbine of this application, the cold air in the B-type tank 5 flows to both sides after exiting the film cooling hole 3, which can provide a more complete cold air coverage effect on the bottom surface of the B-type tank 5, thereby improving the cooling efficiency.

[0048] In the moving blade structure and gas turbine of this application, the cooling gas in the C-type groove 6, after flowing out of the gas film cooling hole 3, entrains and covers the pressure side angle vortex 8 onto the bottom surface of the C-type groove 6, thereby improving the cooling efficiency.

[0049] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A moving blade structure, characterized in that, At least including: The blade body has a groove at its tip to reduce the leakage flow rate at the blade tip gap. Ribs are evenly spaced in the groove along the mid-arc direction of the blade tip. One end of each rib abuts against the pressure side shoulder wall of the blade tip, and the other end abuts against the suction side shoulder wall of the blade tip, so as to divide the groove into several small grooves that are not connected to each other. The small grooves are divided into type A groove, type B groove and type C groove along the axial direction of the moving blade body. An air film cooling hole is provided upstream of the flow separation line formed by the vortex behind the rib in the B-type groove, and the distance between the air film cooling hole and the upstream rib and the suction side shoulder wall of the blade tip is equal. An air film cooling hole is provided upstream of the flow separation line formed by the pressure side vortex in the B-type groove, and the distance between the air film cooling hole and the upstream rib and the pressure side shoulder wall of the blade tip is equal. An air film cooling hole is provided upstream of the flow separation line formed by the pressure side vortex in the C-type groove, and the distance between the air film cooling hole and the pressure side shoulder wall and the suction side shoulder wall of the blade tip is equal.

2. The moving blade structure according to claim 1, characterized in that, Each of the ribs is positioned perpendicular to the mid-arc line of the blade tip.

3. The moving blade structure according to claim 1, characterized in that, The width of the rib is 1%-3% of the height of the moving blade body.

4. The moving blade structure according to claim 1, characterized in that, The distance between the air film cooling hole in the B-type groove and the upstream rib is 1%-3% of the height of the moving blade body.

5. The moving blade structure according to claim 1, characterized in that, The distance between the air film cooling hole in the C-shaped groove and the upstream rib is 1%-3% of the height of the moving blade body.

6. The moving blade structure according to any one of claims 1-5, characterized in that, The ribs comprise four ribs, which divide the groove into five smaller grooves, including one type A groove, two type B grooves, and two type C grooves.

7. The moving blade structure according to claim 6, characterized in that, Each of the aforementioned film cooling holes is a circular hole, and the diameter of the film cooling hole is 1%-3% of the height of the moving blade body.

8. The moving blade structure according to claim 7, characterized in that, The direction of the airflow ejected from each of the air film cooling holes is perpendicular to the bottom of the groove.

9. A gas turbine, characterized in that, The blade structure included in any one of claims 1 to 8 further includes a casing; A gap is left between the blade tip of the moving blade body and the inner wall of the casing to form a blade tip gap.

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