High-temperature-resistant sealing structure and design method thereof

Abstract

The invention provides a high-temperature-resistant sealing structure and a design method thereof and relates to the technical field of structural design, the sealing structure is composed of functionally graded materials, and the design method comprises the following steps that S1, the dimension N and material components of the functionally graded materials are determined according to the working temperature field of the sealing structure; wherein N is equal to 1, 2 or 3; s2, the sealing structure is divided into a plurality of grid units; and S3, determining a target thermal expansion coefficient of each grid unit material, and designing different material ratios of each grid unit according to the target thermal expansion coefficient and the material characteristics. In the sealing process, under the influence of high temperature, high-temperature side deformation and low-temperature side deformation are coordinated and consistent, the sealing structure is not prone to cracking, the service life of the sealing structure is guaranteed, and the working reliability of turbine parts is improved.

Description

Technical Field

[0001] This invention relates to the field of structural design technology, specifically to a high-temperature resistant sealing structure and its design method. Background Technology

[0002] In aviation gas turbine engines, such as Figure 1 As shown, complex air system designs exist, and due to the gaps between components, airflow leakage is inevitable. To reduce leakage and improve engine efficiency, sealing structures are often designed in the flow channels to minimize gap leakage losses. Common turbine sealing materials and design methods include dynamic and static friction seals, contact seals, labyrinth seals, and mechanical lip seals.

[0003] With the increasing demands for thrust and efficiency in civil aviation engines, the total inlet temperature of engines is also rising, reaching 1978K under high-temperature takeoff conditions. Currently, the service temperature and performance of traditional high-temperature alloy materials for turbine stators are nearing their limits. In recent years, new turbine guide vane structures, represented by ceramic matrix composites (CMC), have emerged, such as... Figure 2 As shown in Figures 3, 4(a), 4(b), and 4(c).

[0004] Turbine guide vanes are components in the high-temperature turbine parts of a gas turbine engine that rectify the high-temperature, high-pressure gas upstream and output it downstream. The turbine guide vanes are mounted on the casing and together with the casing form the stator. Ceramic matrix composites (CMCs) are composite materials with a ceramic matrix and toughening materials. They mainly include carbon / silicon carbide, silicon carbide / silicon carbide, zirconium boride / silicon carbide, and other composites composed of different ceramic matrices and toughening materials. They feature high service temperature, good oxidation resistance and microcrack resistance, low density, and high strength and stiffness.

[0005] However, although this type of CMC guide vane structure can withstand higher temperatures, up to 1300℃, expansion margins are reserved between the structures during the design of high-temperature components, as shown in Figure 5(c), with a circumferential design gap 5. Especially since the CMC component and the surrounding metal components have significantly different coefficients of thermal expansion, sufficient gaps are often designed between them to avoid thermal mismatch problems. Sealing is a key design element to prevent uncontrolled leakage of cold air or backflow of combustion gases. Furthermore, because there is a design pressure difference between the guide vanes circumferentially and between the guide vanes and the internal metal conduit radially, cooling gas can leak radially from the cold air side 240 through the gap 5 into the hot air side 250 of the cavity, leading to unintended consequences.

[0006] Seals typically refer to sealing technologies used in turbomachinery (such as turbines and turbopumps) to prevent fluid (such as gas or liquid) leakage and the entry of external substances into the turbine, thereby maintaining equipment efficiency and preventing contamination. These seals may employ a dynamic and static ring structure, and are precisely designed and manufactured to ensure excellent sealing performance under high-speed rotation.

[0007] The general sealing structure adopts the following design: a strip-shaped sealing plate 16 is placed in the circumferential sealing groove 131 of the upper support to radially seal the cold air side 240 (cooling induced air) and the hot air side 250. A similar structure is a W-shaped bellows-type sealing ring 17, which is placed in the radial sealing groove 133 of the upper support to circumferentially seal the cold air side 240 (cooling induced air) and the hot air side 250.

[0008] Traditional sealing methods, such as labyrinth seals, require complex sealing structures to be machined or fabricated on the surface of the part. For blades made of new materials such as CMC, these complex features cannot be fabricated, making them unsuitable for sealing designs of CMC blades. Another type is slotted sealing. While this structure is simple—slots are cut into the surface of the part requiring sealing, and a metal sheet is used to design the sealing structure and seal the gaps—in CMC guide vane assemblies, this metal sheet can only operate normally at around 1100℃. It cannot withstand higher temperatures and is prone to oxidation and fracture, making it unsuitable for long-term service, thus presenting certain application difficulties.

[0009] Traditional sealing methods suffer from the following technical problems:

[0010] 1. In traditional slotted sealing methods, there is a gap between the size of the sealing plate and the installation size of the sealing groove. In actual use, leakage problems still exist. For example, there is a gap 52 between the sealing ring and the sealing groove as shown in Figure 4(c), and the first gap 54, the second gap 53, and the third gap 51 as shown in Figure 13(a), which leads to poor actual sealing effect.

[0011] Second, pure metal sealing sheets cannot withstand higher temperature requirements, and due to the isotropic thermal expansion of the material, they will generate high thermal stress in working environments with drastic temperature gradient changes, resulting in a shorter service life.

[0012] Third, metal sheet sealing plates with thermal barrier coatings solve the problem of pure metal sealing plates being unable to withstand high temperatures. However, when the thermal barrier coating material is used in conjunction with the metal substrate material, a serious thermal mismatch problem occurs under high temperatures. Specifically, the coefficient of thermal expansion of the thermal barrier coating material of the sealing plate is only about 1 / 3 of that of the metal substrate material. Under high-temperature operating conditions, such as... Figure 6As shown, the upper thermal barrier coating and the lower metal sealing plate substrate are heated at different temperatures and have different coefficients of thermal expansion α. ​​A certain expansion difference will be generated between the two (△L1≠△L2), causing the sealing plate metal material and the thermal barrier coating material to crack or peel off. Ultimately, this leads to premature oxidation and failure of the metal sealing plate, affecting the turbine's working efficiency.

[0013] In view of this, the inventors of this application have designed a high-temperature resistant sealing structure and its design method in order to overcome the above-mentioned technical problems. Summary of the Invention

[0014] The technical problem to be solved by the present invention is to overcome the shortcomings of the traditional slotted sealing method in the prior art, where there is a gap between the size of the sealing sheet and the installation size of the sealing groove, and leakage still occurs in actual use; pure metal sealing sheets cannot withstand higher temperature requirements; and the defects of metal sheet sealing sheets with thermal barrier coatings are that they will have serious thermal mismatch problems under high temperature. The present invention provides a high-temperature resistant sealing structure and its design method.

[0015] The present invention solves the above-mentioned technical problems through the following technical solution:

[0016] This invention provides a high-temperature resistant sealing structure design method, characterized in that the designed sealing structure is composed of functionally graded materials. The design method includes the following steps: S1, determining the dimension N and material composition of the functionally graded material based on the operating temperature field of the sealing structure; wherein, N = 1, 2, 3; S2, dividing the sealing structure into multiple grid units; S3, determining the target thermal expansion coefficient of the material in each grid unit, and designing different material ratios for each grid unit based on the target thermal expansion coefficient and material properties.

[0017] According to one or more embodiments of the present invention, the functionally graded material has at least two components, including a first material and a second material; each grid cell of the sealing structure is composed solely of the first material, solely of the second material, or a mixture of the first and second materials.

[0018] According to one or more embodiments of the present invention, the first material is GH5188 or GH141; the second material is mullite, yttrium-stabilized zirconium oxide and mullite, barium strontium aluminum silicate, RE silicate, rare earth silicate doped with β-SiC nanocomposites, or rare earth silicate containing Al2O3.

[0019] According to one or more embodiments of the present invention, the sealing structure includes three directions: length, thickness, and width. In step S1: if, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along only one of the three directions (length, thickness, and width), while the other two directions remain unchanged, then the working temperature field is 1-dimensional, thereby determining that the functionally graded material has a dimension of 1; if, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along any two of the three directions (length, thickness, and width), while the other direction remains unchanged, then the working temperature field is 2-dimensional, thereby determining that the functionally graded material has a dimension of 2; if, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along all three directions (length, thickness, and width), then the working temperature field is 3-dimensional, thereby determining that the functionally graded material has a dimension of 3.

[0020] According to one or more embodiments of the present invention, if the dimension of the functionally graded material is 1, then in step S2, the sealing structure is divided into x grid units along one of the three directions of temperature change (length, thickness, and width) based on the sealing temperature difference; where x ≥ 2.

[0021] According to one or more embodiments of the present invention, if the dimension of the functionally graded material is 2, then in step S2, the sealing structure is divided into x*y grid units along two of the three directions of temperature change: length, thickness, and width, based on the sealing temperature difference; where x≥2, y≥2.

[0022] According to one or more embodiments of the present invention, if the functionally graded material has a dimension of 3, then in step S2, the sealing structure is divided into x*y*z grid units along the length direction, thickness direction, and width direction according to the sealing temperature difference; wherein, x≥2, y≥2, z≥2.

[0023] According to one or more embodiments of the present invention, step S3 includes the following steps: S 31 To ensure that the total elongation of the grid cells in each direction remains consistent for functionally graded materials, determine the target coefficient of thermal expansion for each grid cell material; S 32 The volume ratio of the first and second materials is designed to achieve the target coefficient of thermal expansion for each grid cell material.

[0024] The present invention also provides a high-temperature resistant sealing structure, characterized in that the high-temperature resistant sealing structure is designed using the high-temperature resistant sealing structure design method described above.

[0025] According to one or more embodiments of the present invention, the high-temperature resistant sealing structure is a strip-shaped sealing sheet.

[0026] According to one or more embodiments of the present invention, the high-temperature resistant sealing structure is a sealing sheet or sealing ring with a W-shaped, V-shaped, Z-shaped or U-shaped cross section.

[0027] According to one or more embodiments of the present invention, the sealing structure is manufactured by a spraying method or a 3D printing method.

[0028] According to one or more embodiments of the present invention, the high-temperature resistant sealing structure is disposed in a sealing groove, and a half-groove is provided on each side of the guide vane circumferential assembly gap, and the cross-sectional shape of each half-groove is trapezoidal.

[0029] According to one or more embodiments of the present invention, the high-temperature resistant sealing structure is disposed in a sealing groove, and leakage holes are provided on the upper and lower sides of the sealing groove.

[0030] The positive and progressive effects of this invention are as follows:

[0031] The high-temperature resistant sealing structure of this invention has at least the following advantages:

[0032] I. The high-temperature resistant sealing structure of this invention uses functionally graded materials, and the sealing sheet can be manufactured using methods such as spraying and 3D printing, making it easy to manufacture.

[0033] Second, through the three-dimensional gradient design of the sealing structure, the deformation of the high-temperature side and the low-temperature side of the sealing structure are coordinated and consistent during the sealing process under the influence of high temperature. The sealing structure is not prone to cracking, which ensures the working life of the sealing structure and improves the working reliability of the turbine components.

[0034] Third, the sealing groove structure in this invention can effectively reduce the temperature difference on both sides of the sealing sheet, thereby reducing the thermal deformation difference between each layer and improving the working life of the sealing sheet.

[0035] IV. The high-temperature resistant sealing structure of this invention typically contains a higher content of high-temperature materials on its high-temperature side, thus making the high-temperature side materials more heat-resistant. The low-temperature side contains a higher content of metallic materials, providing greater elasticity and achieving pre-tight sealing. Functionally graded materials can not only be prepared by mixing two raw materials, but the method of this invention can also be extended to designs using a mixture of multiple materials.

[0036] V. The present invention provides a sealing structure in the radial, circumferential or other directions, which can adopt U-shaped, V-shaped or W-shaped and other cross-sectional geometries. This structure utilizes the elastic characteristics of thin sheet metal material to provide a spring-like pre-tensioning effect and improve the sealing effect.

[0037] VI. The various features of the sealing structure of the present invention can be combined and designed as needed, and are applicable to sealing of various parts, thus possessing a certain degree of versatility. Attached Figure Description

[0038] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features, wherein:

[0039] Figure 1 This is a cross-sectional schematic diagram of a turbofan engine.

[0040] Figure 2 This is a schematic diagram of the turbine guide vane assembly.

[0041] Figure 3(a) is a schematic diagram of a typical CMC guide vane structure.

[0042] Figure 3(b) is a schematic diagram of the strip-shaped sealing sheet.

[0043] Figure 3(c) is an enlarged schematic diagram of part C in Figure 3(a).

[0044] Figure 4(a) is a schematic diagram of the assembly of a typical CMC guide vane structure.

[0045] Figure 4(b) is an enlarged AA cross-sectional view of Figure 4(a).

[0046] Figure 4(c) is an enlarged BB cross-sectional view of Figure 4(a).

[0047] Figure 5(a) is a cross-sectional schematic diagram of the three guide vane structure.

[0048] Figure 5(b) is an enlarged schematic diagram of part D in Figure 5(a).

[0049] Figure 5(c) is an enlarged schematic diagram of part E in Figure 5(a).

[0050] Figure 6 This is a schematic diagram of a metal sheet sealing strip with a thermal barrier coating.

[0051] Figure 7 This is a schematic diagram of a two-layer functionally graded material sealing sheet structure in the high-temperature resistant sealing structure of the present invention.

[0052] Figure 8 This is a schematic diagram of a multilayer functionally graded material sealing sheet structure in the high-temperature resistant sealing structure of the present invention.

[0053] Figure 9 This is a schematic diagram of a 2D functionally graded material sealing sheet structure in the high-temperature resistant sealing structure of this invention.

[0054] Figure 10This is a schematic diagram of a 3D functionally graded material sealing sheet structure in the high-temperature resistant sealing structure of this invention.

[0055] Figure 11(a) is a schematic diagram of a fully annular W-shaped sealing ring in the high-temperature resistant sealing structure of the present invention.

[0056] Figure 11(b) is a schematic diagram of an open W-type sealing ring in the high-temperature resistant sealing structure of the present invention.

[0057] Figure 11(c) is a schematic diagram of the installation of a W-type sealing ring in the high-temperature resistant sealing structure of the present invention.

[0058] Figure 12(a) is a schematic diagram of the assembly of the W-shaped strip sealing sheet in the high-temperature resistant sealing structure of the present invention.

[0059] Figure 12(b) is a schematic diagram of the W-shaped strip sealing sheet in the high-temperature resistant sealing structure of the present invention.

[0060] Figure 12(c) is a schematic diagram of the V-shaped strip sealing sheet in the high-temperature resistant sealing structure of the present invention.

[0061] Figure 13(a) is a schematic diagram of the traditional strip sealing plate and sealing groove.

[0062] Figure 13(b) is a schematic diagram of the nozzle-shaped sealing groove in the high-temperature resistant sealing structure of the present invention. Detailed Implementation

[0063] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0064] Embodiments of the invention will now be described in detail with reference to the accompanying drawings. Preferred embodiments of the invention will now be described in detail, examples of which are illustrated in the drawings. Wherever possible, the same reference numerals will be used in all the drawings to denote the same or similar parts. Furthermore, although the terminology used herein is selected from commonly known and used terminology, some terms mentioned in this specification may have been chosen by the applicant at his or her discretion, and their detailed meanings are explained in the relevant sections of the description herein. Moreover, the invention should be understood not only by the actual terms used, but also by the meaning implied by each term.

[0065] like Figure 1 As shown, this is a cross-section of a typical turbofan engine. Its main components include a nacelle 100, a fan 200, a compressor 300, a combustion chamber 400, and a turbine 500. The turbine 500 contains a certain number of guide vanes, forming a guide vane assembly 50, which is used to regulate the upstream airflow.

[0066] like Figure 2 The image shown is a schematic diagram of a turbine guide vane assembly. Figure 2 It includes a guide vane assembly 50, an engine shaft L1, a CMC guide vane 12, an upper support 13, a lower support plate 14, and a connecting rod 15.

[0067] like Figures 3(a) to 3(c) The diagram shows a typical CMC guide vane structure, including a cooling air inlet 132, an upper support 13, a circumferential sealing groove 131 on the upper support, a leakage hole 134, a strip-shaped sealing plate 16, a W-shaped sealing ring 17, an upper edge plate 121 of the CMC guide vane, a blade body 122, a lower edge plate 123 of the CMC guide vane, an air guide pipe 124, a lower support plate 14, an air outlet 142 on the lower support plate, a connecting rod body 151, and a connecting rod bolt 152.

[0068] like Figures 4(a) to 4(c) The figure shows the assembly and cross-sectional structure of a typical CMC guide vane, including the cooling air inlet 132, the leakage hole 134, the strip-shaped sealing plate 16, and the lower air collection chamber.

[0069] 1100, strip-shaped sealing plate 18, W-shaped sealing ring 17, upper support 13, upper edge plate of CMC guide vane 121, gap between sealing ring and sealing groove 52.

[0070] like Figures 5(a) to 5(c) The figure shows a cross-sectional view of a three-part guide vane structure, including a left guide vane 210, a right guide vane 220, a circumferential assembly gap 230 for the guide vanes, a cooling air chamber 600, an upper cavity 700, a flow channel cavity 800, a guide air chamber 900, a lower air collection chamber 1100, an air outlet 142 on the lower support plate, a radial sealing groove 133 on the upper support, a W-shaped sealing ring 17, a strip-shaped sealing plate 16, and a circumferential sealing groove 131 on the upper support.

[0071] like Figure 6 The diagram shows a metal sheet sealing strip with a thermal barrier coating. The outer side of the upper layer is the cold air side 240, and the outer side of the lower layer is the hot air side 250. The length direction is L' and the thickness direction is h'. The thickness of the upper thermal barrier coating material is △h1, and the thickness of the lower metal substrate material is △h2. △L1 is the thermal elongation of the thermal barrier coating material under heat, and △L2 is the thermal elongation of the metal substrate material under heat. The two materials are heated at different temperatures and have different coefficients of thermal expansion, which will result in a thermal deformation difference △L1≠△L2.

[0072] This invention provides a high-temperature resistant sealing structure design method. The designed sealing structure is composed of functionally graded materials, and the design method includes the following steps:

[0073] Step S1: Determine the dimension N and material composition of the functionally graded material based on the working temperature field of the sealing structure; where N = 1, 2, 3;

[0074] Step S2: Divide the sealing structure into multiple mesh elements;

[0075] Step S3: Determine the target thermal expansion coefficient of the material for each grid cell, and design different material ratios for each grid cell based on the target thermal expansion coefficient and material properties.

[0076] In a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, the functionally graded material has at least two components, including a first material and a second material;

[0077] Each grid cell of the sealing structure is composed of a first material alone, or a second material alone, or a mixture of the first and second materials.

[0078] It should be noted that the components of the functionally graded material are not limited to the first material and the second material, but can also be designed by mixing two or more materials.

[0079] Functionally graded materials are a new type of composite material composed of two or more materials with a continuous gradient in composition and structure. They are developed to meet the needs of high-tech fields such as modern aerospace industry and to ensure that they can work normally under extreme environments.

[0080] As a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, the first material is GH5188 or GH141; the second material is mullite, yttrium oxide stabilized zirconium oxide and mullite, barium strontium aluminum silicate, RE silicate, rare earth silicate doped with β-SiC nanocomposite, or rare earth silicate containing Al2O3.

[0081] It should be noted that the first material is usually a metallic material, which can provide more metallic elasticity. Specifically, high-temperature alloys such as GH5188 and GH141 can be used. The second material is usually a high-temperature material that can withstand higher temperatures. The second material is preferably a ceramic material, specifically mullite, YSZ (yttrium-stabilized zirconium oxide) combined with mullite, BSAS (barium-strontium aluminum silicates), RE silicates, rare earth silicates doped with β-SiC nanocomposites, and rare earth silicates containing Al2O3 can be used.

[0082] The high-temperature side typically contains a higher content of high-temperature materials, thus making it more heat-resistant. The low-temperature side contains a higher content of metallic materials, providing greater elasticity and enabling pre-tight sealing. Functionally graded materials can not only be prepared by mixing two raw materials, but the method of this invention can also be extended to the design of multiple material mixtures.

[0083] As a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, the sealing structure includes three directions: length direction, thickness direction, and width direction. In step S1:

[0084] If, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes in only one of the three directions—length, thickness, and width—while the other two directions remain unchanged, then the working temperature field is 1-dimensional, thereby determining that the dimension of the functionally graded material is 1.

[0085] If, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along any two of the three directions of length, thickness, and width, while the other direction remains unchanged, then the working temperature field is 2-dimensional, thereby determining that the dimension of the functionally graded material is 2.

[0086] If, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along three of the three directions: length, thickness, and width, then the working temperature field is 3-dimensional, thereby determining that the dimension of the functionally graded material is 3.

[0087] like Figure 7 and Figure 8 As shown, in a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, if the dimension of the functionally graded material is 1, then in step S2, the sealing structure is divided into x grid units along one of the three directions of temperature change (length direction, thickness direction, and width direction) according to the sealing temperature difference; where x≥2.

[0088] like Figure 7 The diagram shows a two-layer functionally graded material sealing sheet structure, which is divided into two grid units. The upper layer is a first material A, and the lower layer is a second material B. The outer side of the upper layer is the cold gas side 240°, and the outer side of the lower layer is the hot gas side 250°. The length direction is L', and the thickness direction is h'. The temperature remains constant along the length direction L', but varies along the thickness direction h'. The thickness of A is Δh1, and the thickness of B is Δh2. ΔL1 is the thermal elongation of A, and ΔL2 is the thermal elongation of B. The deformation of both is consistent, ΔL1 = ΔL2.

[0089] like Figure 8 The diagram shows a multilayer functionally graded material sealing sheet structure. The upper outer layer is the cold gas side (240°), and the lower outer layer is the hot gas side (250°), with a thickness of h'. ​​The middle layer is divided into multiple layers, i.e., the sealing structure is divided into n grid units, each with a thickness of Δh1, Δh2, Δh3, ..., Δh'. n The neutral planes of each layer are located at positions h1, h2, h3, ..., h n .

[0090] like Figure 9As shown, in a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, if the dimension of the functionally graded material is 2, then in step S2, the sealing structure is divided into x*y grid units along two of the three directions of temperature change: length, thickness, and width, based on the sealing temperature difference; where x≥2, y≥2.

[0091] Figure 9 This is a 2D functionally graded material (FJT) sealing sheet structure, composed of 6 grid cells. The upper outer layer is the cold gas side (240°C), and the lower outer layer is the hot gas side (250°C). The operating temperature field varies simultaneously along the length direction L' and the direction h'. The sealing structure is divided into 2*3=6 grid cells, and the operating temperatures of the 6 grid cells are T0, ... 11 T 12 T 13 T 21 T 22 T 23 △L1 is the total elongation of the upper layer due to heat, and △L2 is the total elongation of the lower layer due to heat. The deformation of the two is consistent: △L1 = △L2.

[0092] As a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, if the dimension of the functionally graded material is 3, then in step S2, the sealing structure is divided into x*y*z grid units along the length direction, thickness direction and width direction according to the sealing temperature difference; where x≥2, y≥2, z≥2.

[0093] Figure 10 This is a 3D functionally graded material sealing sheet structure, composed of 12 grid cells. The upper outer layer is the cold gas side (240°C), and the lower outer layer is the hot gas side (250°C). The operating temperature field varies along the thickness direction (h'), length direction (L'), and width direction (W'). The sealing structure is divided into 2*3*2 = 12 grid cells, and the operating temperatures of the 12 grid cells are T0, ... 111 T 121 T 131 T 211 T 221 T 231 T 112 T 122 T 132 T 212 T 222 T 232 , △L 11 , △L 12 ΔL is the total elongation of the upper layer due to heat. 21 , △L 22 The total elongation of the lower layer due to heat is ΔL, and all deformations are consistent. 11 =△L 12=△L 21 =△L 22 .

[0094] In a preferred embodiment of the high-temperature resistant sealing structure design method of the present invention, step S3 includes the following steps:

[0095] Step S 31 To ensure that the total elongation of the grid cells in each direction of the functionally graded material remains consistent, the target coefficient of thermal expansion of each grid cell material is determined.

[0096] Step S 32 The volume ratio of the first and second materials is designed to achieve the target coefficient of thermal expansion for each grid cell material.

[0097] The principle of the high-temperature resistant sealing structure design method provided by this invention is as follows:

[0098] The design method of one-dimensional graded functionally graded materials is illustrated using the strip-shaped sealing sheet 16 in Figure 3(a). The specific sealing sheet material structure is as follows: Figure 7 As shown, assuming the sealing sheet consists of only two layers of materials A and B (in reality, it can be a mixture of multiple materials), A represents the first material, which is usually a metallic material that provides greater metallic elasticity. Specifically, high-temperature alloys such as GH5188 and GH141 can be used. B represents the second material, which is usually a high-temperature material capable of withstanding higher temperatures. Specifically, materials such as mullite, YSZ (yttrium-stabilized zirconium oxide) combined with mullite, BSAS (barium-strontium aluminum silicates), RE silicates, rare-earth silicates doped with β-SiC nanocomposites, and rare-earth silicates containing Al2O3 can be used. The initial sealing sheet length is L, with length, thickness, and width directions L', h', and W' respectively. The sealing temperature difference (T) on a certain outer side... hot -T cold Under these conditions, the temperature remains constant along the length L' direction but varies along the thickness h' direction. The upper layer A has a thickness of Δh1, and the lower layer B has a thickness of Δh2. The outer surface of the upper layer is the cold air side at 240°C, with a temperature of T. cold The lower outer surface is the hot air side, 250°C, with a temperature of T. hot The temperature of the upper layer is T1, and the temperature of the lower layer is T2. The expansion and elongation of the upper layer after heating is ΔL1, and that of the lower layer is ΔL2. The coefficient of thermal expansion of the upper layer is α1, and that of the lower layer is α2. According to thermoelasticity, the following is true:

[0099] ΔL1=(T1-T ref )×α1×L (1)

[0100] ΔL2=(T2-Tref )×α2×L (2)

[0101] Among them, T ref The reference temperature for testing the coefficient of thermal expansion of the materials is a constant. To ensure that the elongation of the two materials remains consistent, i.e., ΔL1 = ΔL2, we can obtain...

[0102]

[0103] Therefore, the thermal expansion coefficients α1 and α2 of the two materials can be determined by the temperature T experienced by the two materials. ref Generally much smaller than T, that is:

[0104] αT=C (4)

[0105] Where C is a constant, which can be freely determined within a certain range.

[0106] This sealing sheet is a one-dimensional functionally graded material, and its coefficient of thermal expansion α can be determined by the volume ratio of the two materials A and B, R = V. A / V B If we can control this, then the design method F for functionally graded materials can be determined by the coefficient of thermal expansion α:

[0107] F(R,h)=α(h) (5)

[0108] The operating temperature of the aforementioned sealing plate is actually one-dimensional, varying only with the thickness direction h. This temperature field T can be given by the engine heat transfer design, and is expressed here as:

[0109] T=f(h) (6)

[0110] According to equations (4), (5), and (6) above, it can be seen that at a certain actual external sealing temperature difference (T) hot -T cold Under the condition of unidirectional temperature change in one dimension, the design method F of this one-dimensional functionally graded material can be accurately designed based on the temperature field T of the sealing sheet. The specific method is as follows:

[0111] F·T=C (7)

[0112] Among them, the temperature field T of the sealing plate is given by the engine heat transfer design, and C is a constant that can be freely determined within a certain range.

[0113] Furthermore, the above method can be seen as a special case of continuous layers, such as... Figure 8 As shown, multi-layer gradient materials can actually be designed, based on the sealing temperature difference (T). hot -T cold By discretizing the thickness of the sealing sheet into multiple layers, it is possible to determine the thickness based on the neutral plane h. nThe value maps the temperature field T of the sealing sheet to each layer, thus obtaining the temperature T experienced by each layer of material. n :

[0114] T n =f(h) n (8)

[0115] Similarly, the coefficient of thermal expansion α of each functionally graded material layer n It can be determined by the volume ratio of two materials A and B, R = V. A / V B Therefore, for this sealing sheet, the material design method F along the thickness direction h' can be derived from α. n Determined as:

[0116] F(R,h)=α(h) (9)

[0117] Similarly, it can be obtained that under the condition of a unidirectional change in the temperature field T of a certain 1D sealing sheet, the design method F of the 1D functionally graded material can be accurately designed based on the 1D temperature field T. The specific method is as follows:

[0118] F·T=C (10)

[0119] Among them, the temperature field T of the sealing plate is given by the engine heat transfer design, and C is a constant that can be freely determined within a certain range.

[0120] Furthermore, such as Figure 9 As shown, the operating temperature field T of the sealing strip varies not only along the thickness direction h', but also along the length direction L', i.e., the temperature field is two-dimensional. This temperature field can be given by the engine heat transfer design, and is expressed here as:

[0121] T=f(h,L) (11)

[0122] The sealing sheet can be designed by discretizing it into uniform 2D grid cells (each grid cell has the same length in the same direction). Let's assume it's divided into 6 grid cells, with each grid cell operating at a temperature of T. 11 T 21 T 12 T 21 T 22 T 23 To ensure that the expansion of each grid cell remains consistent, the coefficient of thermal expansion α of the material in each grid cell can be determined by the volume ratio of the two materials A and B, R = V. A / V B If we design it this way, then the 2D functional graded material design method F can be determined by α as follows:

[0123] F(R,h,L)=α(h,L) (12)

[0124] Similarly, it can be obtained that under a certain 2D sealing temperature field T, the design method F of the 2D functionally graded material can be accurately designed based on the 2D temperature field T. The specific method can also be expressed as:

[0125] F·T=C (13)

[0126] Among them, the temperature field T of the sealing plate is given by the engine heat transfer design, and C is a constant that can be freely determined within a certain range.

[0127] Furthermore, such as Figure 10 As shown, the operating temperature field T of the sealing strip varies along the thickness direction h', length direction L', and width direction W', meaning the temperature field is 3-dimensional. This temperature field can be given by the engine heat transfer design, and is expressed here as:

[0128] T = f(h, L, W) (14)

[0129] The sealing sheet can be designed by discretizing it into uniform 3D grid cells (each grid cell has the same length in the same direction). Let's assume it's divided into 12 grid cells, with each grid cell operating at a temperature of T. 111 T 121 T 131 T 211 T 221 T 231 T 112 T 122 T 132 T 212 T 222 T 232 To ensure that the expansion of each grid cell remains consistent, the coefficient of thermal expansion α of the material in each grid cell can be determined by the volume ratio R = V of the two materials A and B. A / V B If we design it this way, then the 3D functionally graded material design method F can be determined by α as follows:

[0130] F(R,h,L,W)=α(h,L,W) (15)

[0131] Similarly, it can be obtained that under a certain 3D sealing temperature field T, the design method F of the 3D functionally graded material can be accurately designed based on the 3D temperature field T. The specific method can also be expressed as:

[0132] F·T=C (16)

[0133] Among them, the temperature field T of the sealing plate is given by the engine heat transfer design, and C is a constant that can be freely determined within a certain range.

[0134] Furthermore, the above method can be used to design a mixture of two or more materials, with similar design ideas and methods.

[0135] The present invention provides a high-temperature resistant sealing structure design method. By designing a three-dimensional gradient for the sealing structure, the deformation on the high-temperature side and the low-temperature side are coordinated and consistent during the sealing process under the influence of high temperature. This makes the sealing structure less prone to cracking, ensuring its service life and improving the working reliability of turbine components.

[0136] The present invention also provides a high-temperature resistant sealing structure, which is designed using the high-temperature resistant sealing structure design method described above.

[0137] As a preferred embodiment of the high-temperature resistant sealing structure of the present invention, the high-temperature resistant sealing structure is a strip-shaped sealing sheet.

[0138] like Figures 11(a) to 12(c) As a preferred embodiment of the high-temperature resistant sealing structure of the present invention, the high-temperature resistant sealing structure is a sealing sheet or sealing ring with a W-shaped, V-shaped, Z-shaped or U-shaped cross section.

[0139] Preferably, the sealing ring can be a corrugated type sealing ring.

[0140] Figure 11(a) shows a full-ring W-type sealing ring, Figure 11(b) shows an open W-type sealing ring, and Figure 11(c) shows an installation diagram of a W-type sealing ring. The figures include a cooling air inlet 132, a radial sealing groove 133 on the upper support, a W-type sealing ring 17, an upper support 13, and an upper edge plate 121 of the CMC guide vane.

[0141] Figure 12(a) shows the assembly structure of a W-type strip sealing sheet, Figure 12(b) shows the structure of a W-type strip sealing sheet, and Figure 12(c) shows the structure of a V-type strip sealing sheet.

[0142] As shown in Figure 11(a), the sealing structure in the radial direction can adopt the form of a W-shaped sealing ring. Due to the elasticity of the metal material, this structure can provide a spring-like preload effect. During engine operation, as shown in Figure 11(c), when cold air enters the W-shaped bellows sealing ring 17 from the opening 132, it remains in a radially fitted state under the pressing action of the upper bracket 13 and the upper edge plate 121 of the CMC guide vane, ensuring that the bleed air cannot leak into the hot air side 250, thus improving the sealing effect.

[0143] The second type of sealing strip has a W-shaped or V-shaped cross section, as shown in Figure 12(a). Through the sealing grooves at both ends, the W-shaped sealing strip can generate a preload force F. This type of sealing strip can seal in the circumferential direction.

[0144] Preferably, the cross-section of the sealing sheet or sealing ring can also be V-shaped, Z-shaped, U-shaped, or other shapes.

[0145] The aforementioned functionally graded material design for sealing sheets or sealing rings, including W-shaped and V-shaped cross-section designs, can be combined to create complex cross-section sealing sheets or sealing rings of functionally graded materials according to design requirements. Preferably, the sealing sheets or sealing rings can be manufactured by methods such as spraying or 3D printing.

[0146] As a preferred embodiment of the high-temperature resistant sealing structure of the present invention, the sealing structure is manufactured by spraying or 3D printing.

[0147] As shown in Figure 13(b), in a preferred embodiment of the high-temperature resistant sealing structure of the present invention, the high-temperature resistant sealing structure is disposed in the sealing groove, and a half-groove is provided on each side of the guide vane circumferential assembly gap 230, and the cross-sectional shape of each half-groove is trapezoidal.

[0148] Figure 13(a) is a schematic diagram of the structure of a conventional strip sealing plate and sealing groove. Figure 13(b) is the structure of the sealing groove in this invention, which is a nozzle-shaped sealing groove. The figure includes an upper outer side 240 (cold air side), a lower outer side 250 (hot air side), a first gap 54, a second gap 53, a third gap 51 between the sealing plate and the sealing groove, a guide vane circumferential assembly gap 230, a strip sealing plate 16, and an upper support circumferential sealing groove 131.

[0149] As can be seen from the above formulas (1), (2) and (3), in addition to the design expansion coefficient mentioned above, which can make the deformation of each layer of material uniform, the thermal deformation difference of each layer can also be reduced by changing the temperature difference between the upper and lower sides of the sealing sheet. That is, the deformation of the sealing sheet can be made uniform by reducing the temperature difference between the upper and lower sides. As shown in Figure 13(a), the sealing groove 131 is usually designed to be straight. Since the installation fit cannot be completely leak-proof, the actual leakage process is as follows: when the cooling induced gas enters from the gap 5, it flows along the first gap 54, the second gap 53 and the third gap 51 between the sealing sheet and the sealing groove on both sides, and finally leaks into the hot gas side 250.

[0150] Therefore, the present invention proposes a nozzle-type sealing groove in the form of Figure 13(b). Since the gap 51 is a design with a gradually decreasing cross-section, the air velocity will increase when the air flows through it, thus improving the cooling effect and achieving the effect of reducing the temperature difference between the upper and lower sides.

[0151] like Figures 3(a) to 4(c) As shown, in a preferred embodiment of the high-temperature resistant sealing structure of the present invention, the high-temperature resistant sealing structure is disposed in a sealing groove, and leakage holes 134 are provided on the upper and lower sides of the sealing groove.

[0152] Due to design tolerances and assembly effects, some leakage will still occur in the sealing groove, as shown by gap 52 in Figure 4(c) and the first gap 54, second gap 53, and third gap 51 in Figure 13(a). To reduce the temperature difference between the two sides of the sealing sheet, this invention proposes an active leakage design, as shown in Figure 4(c). A leakage hole 134 is designed in the sealing groove. This feature can effectively guide the airflow to leak from this point, making the leaked gas more concentrated and blowing towards the lower side of the sealing sheet, thereby reducing the temperature difference on the upper side, reducing the thermal deformation difference between the layers, and improving the service life of the sealing sheet.

[0153] The high-temperature resistant sealing structure of the present invention is provided in the following specific embodiments:

[0154] Example 1

[0155] like Figure 10 As shown, this embodiment provides a strip-shaped sealing sheet. This strip-shaped sealing sheet is applicable to 1D, 2D, and 3D temperature fields, corresponding to 1D, 2D, and 3D functionally graded materials. Here, we specifically describe the most complex 3D functionally graded sealing sheet design method of this embodiment. The 1D and 2D design methods are similar.

[0156] Assuming the operating temperature field T of the strip seal varies along the thickness direction h', length direction L', and width direction W', i.e., the temperature field is 3-dimensional, this temperature field can be given by the engine heat transfer design, and is expressed here as:

[0157] T = f(h, L, W) (17)

[0158] The strip sealing sheet can be discretized into 3D mesh elements for design. Let's assume it's divided into 12 mesh elements, with the material temperature of each mesh element being T. 111 T 121 T 131 T 211 T 221 T 231 T 112 T 122 T 132 T 212 T 222 T 232 To ensure consistent material expansion across all grid cells, the coefficient of thermal expansion α of the functionally graded material in each grid cell can be determined by the volume ratio of materials A and B, R = V. A / V B To design (which can actually be done by mixing multiple materials), here is one design method:

[0159]

[0160] Where, α A Let α be the coefficient of thermal expansion of material A. B Let be the coefficient of thermal expansion of material B. Assuming that material A has a greater thermal expansion property than material B, it can be deduced from the above that the coefficient of thermal expansion α of the new material formed by mixing materials A and B is α. A and α B In between:

[0161] α B ≤α≤α A (19) Therefore, the 3D functional graded material design method F can be determined by α as follows:

[0162] F(R,h,L,W)=α(h,L,W) (20)

[0163] Similarly, under a certain 3D sealing sheet operating temperature field T, the design method F of the 3D functionally graded material can be accurately designed based on the 3D temperature field T. The specific method can also be expressed as:

[0164] F·T=C (21)

[0165] The temperature field T of the sealing plate is given by the engine heat transfer design, and C is a constant that can be freely determined within a certain range. Here, a method for determining C is given.

[0166] As can be seen from formula (4), the product of the thermal expansion coefficient α and the temperature T experienced by the material remains unchanged.

[0167] The temperature field T of the sealing plate is known, and the maximum temperature is assumed to be T. max Then C can be designed as:

[0168] C = α B ·T max (twenty two)

[0169] The C design is explained in detail below:

[0170] Assume the operating temperature of the grid cells is T = λT max Therefore, it is easy to obtain:

[0171]

[0172] From the above formulas (4) and (21), it can be seen that the material expansion coefficient α of any mesh element follows the following formula:

[0173] α·T=α·λT max =C=α B ·T max (twenty four)

[0174] Then the coefficient of thermal expansion α of any mesh element material is:

[0175]

[0176] From formulas (23) and (25), we can obtain:

[0177]

[0178] Since both formula (19) and formula (25) must be satisfied simultaneously, therefore:

[0179]

[0180] That is, the design must satisfy the following relationship:

[0181]

[0182] Therefore, the selection of the first material A and the second material B must satisfy the following: the ratio of the expansion rates of the first material A and the second material B needs to be greater than the ratio of the maximum temperature to the minimum temperature in the working temperature field of the sealing sheet, which is easy to achieve. Therefore, the design of formula (22) is reasonable.

[0183] Example 2

[0184] This embodiment discloses a sealing plate with a W-shaped cross section, as shown in Figure 12(a). Through the sealing grooves at both ends, the W-shaped sealing plate can generate a preload force F.

[0185] In some alternative methods, as shown in Figure 12(c), the cross-section of the sealing strip can also be V-shaped, Z-shaped, U-shaped, etc. This type of sealing strip can seal in the circumferential direction. Similar scenarios can be seen in the sealing strip 18 in Figure 4(a) and the strip sealing strip 16 in Figure 4(b).

[0186] In some alternative options, a sealing ring with the cross-sectional shape of the sealing strip as described above is provided, as shown in Figure 11. This sealing ring is a W-shaped corrugated tube sealing structure with a W-shaped cross-section. Figure 11(a) shows a fully annular structure. The annular shape can be designed to match the sealing surface. For example, in Figure 3, the outline of the air duct 124 is teardrop-shaped, so the W-shaped corrugated tube sealing ring 17 is also a teardrop-shaped fully annular structure. It is easy to imagine that, as shown in Figure 11(b), an open-type ring structure can also be used. This type of sealing strip can seal radially, as exemplified by the W-shaped corrugated tube sealing ring 17 in Figure 4(b), which provides one such application scenario.

[0187] Example 3

[0188] As shown in Figure 13(b), this embodiment provides a sealing groove in the form of a trapezoidal nozzle. The sealing groove has a semi-groove on each side of the guide vane circumferential assembly gap 230. Each semi-groove has a trapezoidal cross-sectional shape. Because the third gap 51 has a gradually decreasing cross-section design, the airflow velocity increases when it flows through, thus improving the cooling effect and reducing the temperature difference between the upper and lower sides. In some alternative configurations, the cross-section can also be various arc-shaped nozzle forms.

[0189] Example 4

[0190] This embodiment provides an active leakage sealing groove, as shown in Figure 4(c). The sealing groove is designed with leakage holes 134, which effectively guide airflow to leak from these holes, allowing the leaked gas to be more concentrated and blown towards the lower side of the sealing sheet. This reduces the temperature difference on the upper side, thereby reducing the thermal deformation difference between layers and improving the service life of the sealing sheet. In this embodiment, there are three leakage holes 134, and the shape of the leakage holes 134 is square. In some optional embodiments, a greater number of leakage holes 134 can be included, and the shape of the leakage holes 134 can also be other than square.

[0191] Preferably, the sealing sheet or sealing ring and sealing groove can be designed and used in combination to form a better sealing effect. The sealing sheet or sealing ring and sealing groove can be promoted using the above ideas and methods (formula (20)) and then designed and prepared.

[0192] In summary, the high-temperature resistant sealing structure and its design method of the present invention have the following advantages:

[0193] I. The high-temperature resistant sealing structure of this invention uses functionally graded materials, and the sealing sheet can be manufactured using methods such as spraying and 3D printing, making it easy to manufacture.

[0194] Second, through the three-dimensional gradient design of the sealing structure, the deformation of the high-temperature side and the low-temperature side of the sealing structure are coordinated and consistent during the sealing process under the influence of high temperature. The sealing structure is not prone to cracking, which ensures the working life of the sealing structure and improves the working reliability of the turbine components.

[0195] Third, the sealing groove structure in this invention can effectively reduce the temperature difference on both sides of the sealing sheet, thereby reducing the thermal deformation difference between each layer and improving the working life of the sealing sheet.

[0196] IV. The high-temperature resistant sealing structure of this invention typically contains a higher content of high-temperature materials on its high-temperature side, thus making the high-temperature side materials more heat-resistant. The low-temperature side contains a higher content of metallic materials, providing greater elasticity and achieving pre-tight sealing. Functionally graded materials can not only be prepared by mixing two raw materials, but the method of this invention can also be extended to designs using a mixture of multiple materials.

[0197] V. The present invention provides a sealing structure in the radial, circumferential or other directions, which can adopt U-shaped, V-shaped or W-shaped and other cross-sectional geometries. This structure utilizes the elastic characteristics of thin sheet metal material to provide a spring-like pre-tensioning effect and improve the sealing effect.

[0198] VI. The various features of the sealing structure of the present invention can be combined and designed as needed, and are applicable to sealing of various parts, thus possessing a certain degree of versatility.

[0199] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A high-temperature resistant sealing structure design method, characterized in that, The designed sealing structure is composed of functionally graded materials, and the design method includes the following steps: S1. Determine the dimension N and material composition of the functionally graded material based on the working temperature field of the sealing structure; where N = 1, 2, 3; S2. Divide the sealed structure into multiple grid units; S3. Determine the target thermal expansion coefficient of the material for each grid cell, and design different material ratios for each grid cell based on the target thermal expansion coefficient and material properties.

2. The high-temperature resistant sealing structure design method as described in claim 1, characterized in that, The functionally graded material has at least two components, including a first material and a second material. Each grid cell of the sealing structure is composed of a first material alone, or a second material alone, or a mixture of the first and second materials.

3. The high-temperature resistant sealing structure design method as described in claim 2, characterized in that, The first material is GH5188 or GH141; the second material is mullite, yttrium-stabilized zirconium oxide and mullite, barium strontium aluminum silicate, RE silicate, rare earth silicate doped with β-SiC nanocomposite, or rare earth silicate containing Al2O3.

4. The high-temperature resistant sealing structure design method as described in claim 2, characterized in that, The sealing structure includes three directions: length direction, thickness direction, and width direction. In step S1: If, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes in only one of the three directions—length, thickness, and width—while the other two directions remain unchanged, then the working temperature field is 1-dimensional, thereby determining that the dimension of the functionally graded material is 1. If, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along any two of the three directions of length, thickness, and width, while the other direction remains unchanged, then the working temperature field is 2-dimensional, thereby determining that the dimension of the functionally graded material is 2. If, under the sealing temperature difference, the temperature in the working temperature field of the sealing structure changes along three of the three directions: length, thickness, and width, then the working temperature field is 3-dimensional, thereby determining that the dimension of the functionally graded material is 3.

5. The high-temperature resistant sealing structure design method as described in claim 4, characterized in that, If the functionally graded material has a dimension of 1, then in step S2, the sealing structure is divided into x grid units along one of the three directions of temperature change (length, thickness, and width) based on the sealing temperature difference; where x ≥ 2.

6. The high-temperature resistant sealing structure design method as described in claim 4, characterized in that, If the functionally graded material has a dimension of 2, then in step S2, the sealing structure is divided into x*y grid units along two of the three directions of temperature change: length, thickness, and width, based on the sealing temperature difference; where x≥2, y≥2.

7. The high-temperature resistant sealing structure design method as described in claim 4, characterized in that, If the functionally graded material has a dimension of 3, then in step S2, the sealing structure is divided into x*y*z grid units along the length, thickness and width directions according to the sealing temperature difference; where x≥2, y≥2, z≥2.

8. The high-temperature resistant sealing structure design method as described in claim 4, characterized in that, Step S3 includes the following steps: S 31 To ensure that the total elongation of the grid cells in each direction of the functionally graded material remains consistent, the target coefficient of thermal expansion of each grid cell material is determined. S 32 The volume ratio of the first and second materials is designed to achieve the target coefficient of thermal expansion for each grid cell material.

9. A high-temperature resistant sealing structure, characterized in that, The high-temperature resistant sealing structure is designed using the high-temperature resistant sealing structure design method as described in any one of claims 1-8.

10. The high-temperature resistant sealing structure as described in claim 9, characterized in that, The high-temperature resistant sealing structure is a strip-shaped sealing sheet.

11. The high-temperature resistant sealing structure as described in claim 9, characterized in that, The high-temperature resistant sealing structure is a sealing plate or sealing ring with a W-shaped, V-shaped, Z-shaped or U-shaped cross section.

12. The high-temperature resistant sealing structure as described in claim 10 or 11, characterized in that, The sealing structure is manufactured by spraying or 3D printing.

13. The high-temperature resistant sealing structure as described in claim 10 or 11, characterized in that, The high-temperature resistant sealing structure is set in the sealing groove, and a half-groove is set on each side of the guide vane circumferential assembly gap. The cross-sectional shape of each half-groove is trapezoidal.

14. The high-temperature resistant sealing structure as described in claim 10 or 11, characterized in that, The high-temperature resistant sealing structure is installed in the sealing groove, and leakage holes are provided on the upper and lower sides of the sealing groove.

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