Variable geometry turbine vane assembly coupled with a non-axisymmetric endwall structure and method of shaping

Abstract

The application discloses a variable geometry turbine guide vane assembly coupled with a non-axisymmetric end wall structure and a molding method. The variable geometry turbine guide vane assembly comprises a hub, a casing, a plurality of rotating shafts and a plurality of guide vanes. The hub and the casing jointly enclose an annular flow channel. The rotating shafts are equidistantly arranged in the annular flow channel in the circumferential direction and extend along the radial direction of the annular flow channel. The guide vanes are rotatably arranged on the rotating shafts. There are gaps between the upper ends of the guide vanes and the casing and between the lower ends of the guide vanes and the hub. The area on the outer side of the hub opposite to the guide vanes and / or the area on the inner side of the casing opposite to the guide vanes is provided with a continuous concave-convex structure. The maximum convex height of the concave-convex structure is lower than the height of the gap, and the maximum concave height is lower than the wall thickness of the component. The reduction of the surface pressure difference on both sides of the guide vanes can reduce the leakage flow loss at the upper and lower end walls of the guide vanes, reduce the passage vortex intensity, reduce the secondary flow loss of the flow channel and improve the efficiency of the variable geometry turbine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of variable geometry turbine of aero-engine / gas turbine, and particularly relates to a variable geometry turbine guide vane assembly coupled with a non-axially symmetric end wall structure and a modeling method. BACKGROUND

[0002] The characteristics and development trend of future war require the next generation of fighters to be able to perform subsonic and supersonic flight tasks according to actual combat tasks. As the power device of the fighter, it requires its engine to have the dual requirements of high unit thrust and low fuel consumption, and the concept of variable cycle engine (VCE) emerges as the times require. The turbine of the variable cycle engine plays an important role in adjusting the flow, controlling the thrust and adjusting the working point of the engine, and is an important part of the variable cycle engine. The variable cycle engine requires the turbine components to improve the change of the flow rate during the engine working process and then change the turbine power, which means that the flow passage geometry and size of the core section of the engine need to be adjusted to realize the change of the turbine flow.

[0003] In order to obtain the ability of adjusting the flow, controlling the thrust and adjusting the working point of the engine which the traditional fixed geometry turbine does not have, the throat area of the variable geometry turbine must be adjustable. For the variable geometry turbine based on the adjustable installation angle of the guide vane, the adjustable throat area is realized by changing the installation angle of the guide vane (guide vane rotation), which requires the installation of rotating shafts at the upper and lower ends of the turbine guide vane and the reservation of gaps at the upper and lower end walls of the guide vane. However, such a structure will cause complex leakage flow at the upper and lower gaps of the variable geometry turbine guide vane and additional leakage flow loss. At the same time, the leakage flow will greatly deteriorate the turbine end area flow field environment and increase the additional end area secondary flow loss. In order to further apply the variable geometry turbine technology and improve the variable working condition performance of the engine, the cycle benefit obtained by the variable geometry turbine must not be offset by too much turbine efficiency reduction caused by the structure modification, and the design point efficiency must be approximately unchanged. As known, the turbine guide vane end area secondary flow loss and the end area leakage flow loss are the main components of the total turbine loss, so effectively controlling the additional loss caused by the structural modification of the variable geometry turbine is the key to the success of the variable geometry turbine design.

[0004] Flow control technology has received widespread attention and development in recent years. Flow control refers to achieving greater mainstream flow benefits, or even altering the mainstream flow state, at the cost of relatively small flow modifications or losses, to organize the flow field and improve turbine performance. Flow control can be divided into passive flow control and active flow control. Due to safety and ease of use considerations, research on turbine flow control has primarily focused on passive control methods. Many scholars have proposed excellent passive control techniques, such as non-axisymmetric endwalls, leading-edge trimming, blade fenders, and blade bending, to control leakage and secondary flow losses in the turbine end region. However, current research focuses on traditional fixed-geometry turbines, and research on control strategies for end region flow losses in variable-geometry turbines, which have significant development potential, is largely lacking.

[0005] This invention discloses a variable geometry turbine guide vane configuration based on a non-axisymmetric endwall design. This configuration can not only effectively reduce the pressure difference between the suction surface and the pressure surface of the guide vane, thereby suppressing the intensity of the channel vortex in the end region and reducing the secondary flow loss in the end region, but also meet the requirements for the rotation of the variable geometry turbine guide vane based on the adjustable guide vane installation angle. Furthermore, it can meet the requirement that the control method can improve the flow characteristics under different guide vane openings. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a variable geometry turbine guide vane configuration based on a non-axisymmetric endwall design. This configuration not only effectively reduces the pressure difference between the suction and pressure surfaces of the guide vane, thereby suppressing the intensity of the channel vortex in the end region and reducing secondary flow losses in the end region, but also meets the requirements for rotating the variable geometry turbine guide vane based on an adjustable guide vane installation angle. Furthermore, it meets the requirement that this control method can improve flow characteristics under different guide vane openings.

[0007] According to one aspect of the present invention, a variable geometry turbine guide vane assembly with coupled non-axisymmetric endwall structure is provided, comprising:

[0008] Wheel hub;

[0009] The casing, together with the hub, forms an annular flow channel;

[0010] Multiple rotating shafts are arranged at equal intervals in the circumferential direction within the annular flow channel, and the rotating shafts extend radially along the annular flow channel; and

[0011] Multiple guide vanes are rotatably mounted on the rotating shaft, and there are gaps between the upper end of the guide vane and the casing, and between the lower end of the guide vane and the hub.

[0012] The area on the outer side of the hub opposite to the guide vane and / or the area on the inner side of the casing opposite to the guide vane is provided with a continuous concave-convex structure, the maximum convex height of the concave-convex structure is lower than the height of the gap, and the maximum concave height of the concave-convex structure is lower than the wall thickness of the component.

[0013] According to some embodiments of the present application, the ratio of the height of the gap to the height of the guide vane along the axis of the rotating shaft is 4.5%.

[0014] According to some embodiments of the present application, the rotating shaft is arranged at a distance of 20% of the axial chord length from the leading edge point of the guide vane, and the center of the rotating shaft is located on the mean camber line of the guide vane.

[0015] According to some embodiments of the present application, the ratio of the diameter of the rotating shaft to the height of the guide vane along the axis of the rotating shaft is 4%.

[0016] According to some embodiments of the present application, a guide vane flow passage is formed between two adjacent guide vanes, the part of the guide vane flow passage in contact with the hub is a first non-axially symmetric end wall profile A1, the part of the lower end surface of the guide vane in contact with the hub during rotation is a second non-axially symmetric end wall profile B1, the part of the guide vane flow passage in contact with the casing is a third non-axially symmetric end wall profile A2, and the part of the lower end surface of the guide vane in contact with the casing during rotation is a fourth non-axially symmetric end wall profile B2, wherein the starting position of the first non-axially symmetric end wall profile A1 and the third non-axially symmetric end wall profile A2 is arranged at a distance of 0%-30% of the axial chord length from the leading edge point of the guide vane, and the end of the second non-axially symmetric end wall profile B1 and the fourth non-axially symmetric end wall profile B2 is arranged at a distance of 0%-30% of the axial chord length from the trailing edge point of the guide vane.

[0017] According to some embodiments of the present application, the working medium of the variable geometry turbine guide vane assembly is air, nitrogen, oxygen, carbon dioxide, natural gas, ammonia, freon or water vapor.

[0018] According to some embodiments of the present application, the type of the variable geometry turbine includes a radial type, a mixed flow type, a single stage or a multi-stage structure.

[0019] According to some embodiments of the present application, the variable geometry turbine guide vane assembly coupled with the non-axially symmetric end wall structure is also provided with a profiling method, which is used to profile the variable geometry turbine guide vane assembly as described above, and includes the following steps:

[0020] Obtaining original parameter information of an original variable geometry turbine, and performing fluid dynamics calculation on the original parameter information to obtain original aerodynamic performance;

[0021] Introducing a non-axially symmetric end wall profile on the basis of the original variable geometry turbine.

[0022] adjusting parameters of the non-axisymmetric end wall structure;

[0023] a variable geometry turbine coupled with the non-axisymmetric end wall;

[0024] performing a fluid dynamics calculation on the coupled variable geometry turbine to obtain aerodynamic performance of the reshaped variable geometry turbine;

[0025] rotating the guide vanes within a preset range of installation angles, judging whether the aerodynamic performance of the reshaped variable geometry turbine under different guide vane opening conditions is higher than the original aerodynamic performance, if yes, inputting as a modified variable geometry turbine, if no, returning to adjusting parameters of the non-axisymmetric end wall structure.

[0026] According to some embodiments of the present application, introducing the non-axisymmetric end wall structure on the basis of the original variable geometry turbine comprises: using any one of the following methods to construct the non-axisymmetric end wall of the guide vane assembly of the original variable geometry turbine, including point displacement method, middle arc line rotation method, symmetric and asymmetric function superposition method, symmetric and asymmetric function superposition method and third-order Fourier function method.

[0027] According to some embodiments of the present application, the installation angle of the guide vane is reduced to negative, the installation angle of the guide vane is increased to negative, and the rotation range of the guide vane includes -α1~α2, wherein the specific values of α1 and α2 are obtained by reverse calculation based on the thrust variation range of the variable cycle engine.

[0028] The variable geometry turbine guide vane assembly coupled with the non-axisymmetric end wall structure of the embodiments of the present application changes the existing axisymmetric geometry structure of the end wall of the variable geometry turbine, so that the non-axisymmetric curved surface with local concave-convex structure is formed, thereby forming the non-axisymmetric end wall, changing the flow area of each flow channel, and reducing the pressure difference between the pressure surface on one side of each flow channel and the suction surface on the other side by optimizing the non-axisymmetric end wall structure. The reduction of the pressure difference on both sides of the guide vane surface can effectively reduce the leakage flow at the upper and lower end regions of the guide vane, and can also delay the formation and development of the passage vortex and reduce the passage vortex intensity by affecting the secondary flow velocity distribution, thereby ultimately reducing the secondary flow loss of the flow passage. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The stator domain schematic diagram of the variable geometry turbine guide vane assembly coupled with the non-axisymmetric end wall structure of the embodiments of the present application is schematically shown;

[0030] Figure 2 is Figure 1 The partition schematic diagram of the introduction area when the variable geometry turbine guide vane assembly is introduced into the hub is shown;

[0031] Figure 3is Figure 1 Fig. 1 is a schematic diagram of the overall structure of a variable geometry turbine vane assembly;

[0032] Figure 4 Fig. 2 is a schematic diagram of a control point construction method in a point displacement method in a modeling method;

[0033] Figure 5 Fig. 3 is a schematic diagram of a Bezier curve controlling an axial control line in a modeling method;

[0034] Figure 6 Fig. 4 is a schematic diagram of a sinusoidal curve controlling a circumferential control line in a modeling method;

[0035] Figure 7 Fig. 5 is a schematic diagram of an introduced non-axisymmetric endwall structure optimization process;

[0036] Figure 8 Fig. 6 is a three-dimensional schematic diagram of a certain variable geometry turbine vane to which a non-axisymmetric endwall structure is added;

[0037] Figure 9 Fig. 7 is a concave-convex distribution nephogram of the A1 region on the hub surface to which a non-axisymmetric endwall is added;

[0038] Figure 10 Fig. 8 is a blade surface pressure distribution curve at 5% blade height;

[0039] Figure 11 Fig. 9 is a distribution curve of the total pressure loss coefficient of a cross section at 40% Cx downstream of the blade trailing edge;

[0040] Figure 12 Fig. 10 is a nephogram of the total pressure loss coefficient of a cross section at 40% Cx downstream of the blade trailing edge.

[0041] In the above figures, the meanings of the reference signs are as follows:

[0042] 1 - vane;

[0043] 2 - rotating shaft;

[0044] 3 - vane leading edge line;

[0045] 4 - vane trailing edge connecting line;

[0046] 5 - hub;

[0047] 6 - casing;

[0048] 7 - vane lower end surface leading edge point; 7* - adjacent vane lower end surface leading edge point; 7_0, 7_1, 7_2 are vane lower end surface leading edge points at different installation angles of the variable geometry turbine vane;

[0049] 8 - lower end surface trailing edge point of the guide vane; 8* - adjacent lower end surface trailing edge point of the guide vane; 8_0, 8_1, 8_2 are lower end surface trailing edge points of the guide vane at different installation angles of the variable geometry turbine;

[0050] 9 - pressure surface of the guide vane blade;

[0051] 10 - suction surface of the guide vane blade;

[0052] 11 - circumferential control line;

[0053] 12 - axial control line; and

[0054] 13 - control point. DETAILED DESCRIPTION

[0055] In order to make the objects, technical solutions, and advantages of the present application clearer, the following will further describe the present application with reference to the embodiments and the accompanying drawings.

[0056] It is to be understood, however, that the description is merely exemplary and explanatory in nature, and is not intended to limit the scope of the present application. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to one skilled in the art that one or more embodiments can be practiced without these specific details. In other instances, well-known methods have not been described in detail in order to avoid unnecessarily obscuring the concepts of the present application.

[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present application. As used herein, the term "includes" indicates the presence of the features, steps, operations, etc. but does not exclude the presence or addition of one or more other features.

[0058] In the case where expressions such as "at least one of A, B, and C, etc." are used, it generally should be interpreted to include any of one, all, etc. of the items enumerated (e.g., "a system having at least one of A, B, and C" should be interpreted to include a system having A alone, a system having B alone, a system having C alone, a system having both A and B together, a system having both A and C together, a system having both B and C together, and / or a system having all of A, B, and C together, etc.). In the case where expressions such as "at least one of A, B, or C, etc." are used, it generally should be interpreted to include any of one, all, etc. of the items enumerated (e.g., "a system having at least one of A, B, or C" should be interpreted to include a system having A alone, a system having B alone, a system having C alone, a system having both A and B together, a system having both A and C together, a system having both B and C together, and / or a system having all of A, B, and C together, etc.).

[0059] All terms used herein, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein are to be interpreted as having a meaning that is consistent with the context of the specification, and should not be interpreted in an idealized or overly formal way.

[0060] Figure 1 A schematic diagram of a stator region of a variable geometry turbine vane assembly coupled with a non-axisymmetric endwall structure is shown; Figure 2 is Figure 1 A schematic diagram of a partition of an introduction area of the variable geometry turbine vane assembly shown when introducing the hub is shown; Figure 3 is Figure 1 A schematic diagram of an overall structure of the variable geometry turbine vane assembly shown.

[0061] According to an embodiment of an aspect of the present application, a variable geometry turbine vane assembly coupled with a non-axisymmetric endwall structure is provided, as shown in Figures 1 to 3 includes vanes 1, rotating shafts 2, a hub 5, and a casing 6. The casing 6 and the hub 5 together enclose an annular flow passage. A plurality of rotating shafts 2 are arranged equidistantly in the circumferential direction in the annular flow passage, and extend in the radial direction of the annular flow passage. A plurality of vanes 1 are rotatably arranged on the rotating shafts 2, and gaps exist between the upper ends of the vanes 1 and the casing 6 and between the lower ends of the vanes 1 and the hub 5; wherein a continuous concave-convex structure is arranged on the region of the outer side of the hub 5 opposite to the vanes 1 and / or on the region of the inner side of the casing 6 opposite to the vanes 1, the maximum convex height t of the concave-convex structure is lower than the height τ of the gap, and the maximum concave height a of the concave-convex structure is lower than the wall thickness of the component (the hub 5 or the casing 6) on which the concave-convex structure is arranged.

[0062] In the present embodiment, the axisymmetric geometry of the existing variable geometry turbine endwall is changed to a non-axisymmetric surface with a local concave-convex structure, thereby forming a non-axisymmetric endwall, changing the flow area of each flow passage, and reducing the pressure difference between the pressure surface on one side and the suction surface on the other side of each flow passage by optimizing the non-axisymmetric endwall structure. The reduction of the pressure difference on both sides of the blade surface of the vane 1 can effectively reduce the leakage flow at the upper and lower end regions of the vane 1, and can also delay the formation and development of passage vortices and reduce the intensity of passage vortices by affecting the secondary flow velocity distribution, thereby ultimately reducing the secondary flow loss of the flow passage.

[0063] According to some embodiments of the present application, the ratio of the height τ of the gap to the height H of the vane in the axial direction of the rotating shaft is 4.5%.

[0064] According to some embodiments of the present application, the rotating shaft is arranged at an axial chord length (h) of 20% from the leading edge point of the vane, and the center of the rotating shaft is located on the mean camber line of the vane.

[0065] According to some embodiments of the present application, the ratio of the diameter of the rotating shaft to the height of the guide vane along the axis of the rotating shaft is 4%.

[0066] According to some embodiments of the present application, a guide vane flow channel is formed between two adjacent guide vanes, the part of the guide vane flow channel in contact with the hub is a first non-axisymmetric end wall profile A1 (the area enclosed by 7-7*-8*-8-7), the part of the lower end surface of the guide vane in contact with the hub during rotation is a second non-axisymmetric end wall profile B1 (the area enclosed by 7_1-8_2-8_1-7_2-7_1), the part of the guide vane flow channel in contact with the casing is a third non-axisymmetric end wall profile A2 (refer to A1, not shown in the figure), the part of the lower end surface of the guide vane 1 in contact with the casing during rotation is a fourth non-axisymmetric end wall profile B2 (refer to B1, not shown in the figure), wherein the starting position of the first non-axisymmetric end wall profile A1 and the third non-axisymmetric end wall profile A2 is set at 0%-30% of the axial chord length before the leading edge point of the guide vane, and the end of the second non-axisymmetric end wall profile B1 and the fourth non-axisymmetric end wall profile B2 is set at 0%-30% of the axial chord length after the trailing edge point of the guide vane.

[0067] According to some embodiments of the present application, the working medium of the variable geometry turbine guide vane assembly is air, nitrogen, oxygen, carbon dioxide, natural gas, ammonia, freon or water vapor.

[0068] According to some embodiments of the present application, the type of variable geometry turbine includes radial, mixed flow, single stage or multi-stage structure.

[0069] Figure 7 is a schematic diagram of the optimization process of the introduced non-axisymmetric end wall structure of the variable geometry turbine guide vane assembly coupled with the non-axisymmetric end wall structure.

[0070] According to embodiments of another aspect of the present application, a modeling method of a variable geometry turbine guide vane assembly coupled with a non-axisymmetric end wall structure is also provided, for modeling a variable geometry turbine guide vane assembly as described above, as shown, comprising the steps of: Figure 7

[0071] obtaining original parameter information of the original variable geometry turbine, and performing computational fluid dynamics (CFD) calculation on the original parameter information to obtain original aerodynamic performance;

[0072] introducing a non-axisymmetric end wall structure on the basis of the original variable geometry turbine;

[0073] adjusting the parameters of the non-axisymmetric end wall structure;

[0074] coupling the non-axisymmetric end wall variable geometry turbine;

[0075] ​The aerodynamic performance of the variable geometry turbine after coupling is calculated to obtain the aerodynamic performance of the variable geometry turbine after shaping;

[0076] The guide vane is rotated within a preset range of installation angle, and it is judged whether the aerodynamic performance of the variable geometry turbine after shaping under different guide vane opening conditions is higher than the original aerodynamic performance, if yes, the variable geometry turbine after shaping is input, if not, the parameter of the non-axisymmetric end wall structure is returned to be adjusted.

[0077] According to some embodiments of the present application, the installation angle of the guide vane of the original variable geometry turbine and the variable geometry turbine coupled with the asymmetric end wall is respectively rotated within a preset range, and the aerodynamic performance is compared, and optionally, the installation angle of the guide vane is rotated by a certain angle, for example, 0.1°, 0.2°, 0.3°, 0.4°, …, 1°, 1.5°, 2°, …, etc.

[0078] According to some embodiments of the present application, if the aerodynamic performance of the variable geometry turbine coupled with the asymmetric end wall under each installation angle condition is higher than the aerodynamic performance of the original variable geometry turbine, the parameter of the variable geometry turbine coupled with the asymmetric end wall is output as the result; if the aerodynamic performance of the variable geometry turbine coupled with the asymmetric end wall under each installation angle condition cannot satisfy the condition of being higher than the aerodynamic performance of the original variable geometry turbine, the parameter of the non-axisymmetric end wall structure is returned to be iteratively adjusted until the condition is satisfied.

[0079] According to some embodiments of the present application, if the aerodynamic performance of the variable geometry turbine coupled with the asymmetric end wall under more than 90% of the installation angle conditions is higher than the aerodynamic performance of the original variable geometry turbine, the parameter of the variable geometry turbine coupled with the asymmetric end wall is output as the result; if the aerodynamic performance of the variable geometry turbine coupled with the asymmetric end wall under more than 90% of the installation angle conditions cannot satisfy the condition of being higher than the aerodynamic performance of the original variable geometry turbine, the parameter of the non-axisymmetric end wall structure is returned to be iteratively adjusted until the condition is satisfied. Optionally, the condition can also be adjusted according to actual needs, for example, 80%, 85%, 95%, etc.

[0080] According to some embodiments of the present application, any one of the point displacement method, the middle arc line rotation method, the symmetric and asymmetric function superposition method, the symmetric and asymmetric function superposition method and the third order Fourier function method is used to construct the non-axisymmetric end wall of the variable geometry turbine guide vane assembly.

[0081] According to some embodiments of the present application, the point displacement method is used for shaping, which includes steps S1-S4.

[0082] Figure 4 It is a point displacement control point construction method schematic diagram of the shaping method of the variable geometry turbine guide vane assembly coupled with the non-axisymmetric end wall structure.

[0083] Step S1 includes: as shown inFigure 4 As shown in the figure, control points in the non-axisymmetric end wall to be shaped are obtained by the intersection of axial control lines and circumferential control lines, the circumferential control lines are curves obtained by tangency of the meridional passage surface and the casing or the hub, and the axial control lines are obtained by translating the camber line of the guide vane profile by a preset circumferential angle.

[0084] Figure 5 The figure is a schematic diagram of a Bezier curve controlling the axial control line of a shaping method of a variable geometry turbine guide vane assembly coupled with a non-axisymmetric end wall structure.

[0085] Optionally, as Figure 5 shown, the Bezier curve is applicable to control the axial control line.

[0086] Figure 6 The figure is a schematic diagram of a sinusoidal curve controlling the circumferential control line of a shaping method of a variable geometry turbine guide vane assembly coupled with a non-axisymmetric end wall structure.

[0087] Step S2 includes: as Figure 6 shown, a sinusoidal function is used to construct the circumferential profile of the non-axisymmetric end wall to be shaped, including:

[0088]

[0089] Wherein, C(y) represents the circumferential amplitude, A(x) is an axial amplitude control function representing the concave-convex degree of the axial profile, x represents the axial coordinate position of the control point, y represents the circumferential coordinate position of the control point, and t represents the distance between the camber lines of adjacent two turbine blades.

[0090] Step S3 includes: using the differential pressure method based on the end region static pressure distribution to construct the axial profile of the non-axisymmetric end wall to be shaped, including:

[0091]

[0092] ΔP = max(P PS -P SS ) (3)

[0093] Wherein, R is an amplitude control coefficient, ΔP is the maximum value of the end region pressure difference at each axial position, P PS is the static pressure near the end wall of the blade pressure surface, and P SS is the static pressure near the end wall of the blade suction surface.

[0094] Step S4 includes: repeating steps S1-S3 for partition shaping for each end wall surface in which the non-axisymmetric end wall structure needs to be introduced.

[0095] According to some embodiments of the present application, the installation angle of the guide vane is reduced to be negative, the installation angle of the guide vane is increased to be negative, and the rotation range of the guide vane includes -α1~α2, wherein the specific values of α1 and α2 are obtained by reverse calculation based on the thrust variation range of the variable cycle engine.

[0096] According to some embodiments of the present application, the adjustable installation angle of the guide vane makes the structure of the variable geometry turbine guide vane unique, which increases the leakage flow loss at the upper and lower end regions of the guide vane and increases the end region secondary flow loss compared with the conventional turbine, but due to the stationary position of the guide vane, the non-axisymmetric end wall is used to suppress the guide vane tip leakage flow. Therefore, the non-axisymmetric end wall structure is introduced into the variable geometry turbine to reduce the end region secondary flow loss while reducing the rotatable guide vane end region leakage flow loss.

[0097] According to some embodiments of the present application, as Figure 2 The hub surface and the casing surface where the non-axisymmetric end wall needs to be introduced are divided into four parts, which are defined as: the part of the guide vane passage contacting the hub is the non-axisymmetric end wall modeling surface A1, the part of the lower end surface of the rotating guide vane contacting the hub during rotation is the non-axisymmetric end wall modeling surface B1; the part of the guide vane passage contacting the casing is the non-axisymmetric end wall modeling surface A2, and the part of the lower end surface of the rotating guide vane contacting the casing during rotation is the non-axisymmetric end wall modeling surface B2. When modeling B1 and B2 regions, the maximum height of the protruding part of the non-axisymmetric structure needs to be considered to be smaller than the reserved gap at the guide vane tip, and when modeling A2 and B2 regions, the maximum height of the concave part of the non-axisymmetric structure needs to be considered to be smaller than the wall thickness of the casing wall surface; since the reaction degree in the guide vane passage of the turbine changes obviously in the blade height direction, the non-axisymmetric end wall structures at the casing and the hub need to be modeled respectively.

[0098] The technical solutions of the present application are further described below in conjunction with specific embodiments, and it should be understood that the specific embodiments are only for better understanding of the technical solutions of the present application by those skilled in the art, and should not be regarded as improper limitation on the protection scope of the present application.

[0099] In this embodiment, the high-load low-pressure turbine cascade designed by a certain research institute is taken as the research object, the structure is first modified (i.e. the rotating shaft is added by reserving the gap at the upper and lower end walls of the blade), then the non-axisymmetric end wall structure is introduced into the hub wall surface and the casing wall surface, the modified cascade is as Figure 8 shown, and finally the numerical simulation is performed to study the change of the turbine aerodynamic performance after introducing the non-axisymmetric end wall structure.

[0100] As Figure 1As shown, when the variable geometry turbine retrofit is performed, the guide vane 1 upper and lower end wall is reserved τ = 4.5% H gap, the rotating shaft 2 is arranged at a distance of 20% axial chord length Cx from the blade leading edge point, the center of the rotating shaft 2 is located on the blade mean camber line, and the diameter of the rotating shaft 2 is set as D = 4% H. The guide vane installation angle under the turbine design condition is taken as the research condition, and the non-axisymmetric structure is introduced at the upper and lower end region positions of the turbine.

[0101] In the embodiment, the "point displacement" method is used to construct the concave-convex structure of the non-axisymmetric end wall, which needs to discretize the control surface, and the concave-convex structure of the end wall is changed by assigning the radial height of each control point one by one; as shown in the figure, Figure 4 As shown, the control points are obtained by the intersection of the axial control lines and the circumferential control lines, in the embodiment, the four circumferential control lines are the curves obtained by the tangency of the meridional flow passage surface and the casing or the hub, and the ten axial control lines are the curves obtained by the translation of the mean camber line of the guide vane profile by a certain circumferential angle, the intersection of the control lines in two directions obtains 40 control points to realize the concave-convex control of the non-axisymmetric end wall geometry. The control profile of the control point circumferential distribution in the embodiment is shown in the figure, Figure 6 As shown, the geometric convex curvature of the end wall near the blade cascade pressure surface side 9 can accelerate the flow and reduce the local static pressure; the wall surface concave curvature can delay the flow and increase the local static pressure. A large number of numerical calculation results show that the circumferential static pressure distribution in the turbine cascade is similar to the sine function distribution, therefore, the circumferential (y direction) profile of the end wall is constructed by using the sine function, and the control function equation is as follows:

[0102]

[0103] Wherein, C(y) represents the circumferential amplitude, A(x) is the axial amplitude control function representing the concave-convex degree of the axial profile, x represents the axial coordinate position of the control point, y represents the circumferential coordinate position of the control point, and t is the distance between adjacent two turbine blade mean camber lines.

[0104] According to some embodiments of the present application, the "pressure difference method" based on the end region static pressure distribution is used to realize the control of the axial profile. The end wall profile amplitude at each discrete axial position is determined by formula (2), wherein R is the amplitude control coefficient, and ΔP is the maximum value of the end region pressure difference at each axial position (formula (3)). Figure 5 As shown, the Bezier curve connects each discrete control point, and the radial height of each two control points in front and back is 0 to ensure the first-order continuity of the non-axisymmetric end wall and the inlet and outlet end wall geometry.

[0105]

[0106] ΔP = max (P PS -P SS ) (3)

[0107] wherein R is an amplitude control coefficient, ΔP is the maximum value of the pressure difference of the end region at each axial position, P PS is the pressure side pressure at each axial position, SS is the suction side pressure at each axial position.

[0108] The amplitude control coefficient R is set to 3.85 mm. Figure 9 A two-dimensional view of the non-axisymmetric end wall is shown, clearly showing the concave-convex conditions of each position of the end wall.

[0109] According to some embodiments of the present application, the numerical calculation uses a commercial software CFX in Ansys 2021. The Reynolds time-averaged Navier-Stokes (RANS) method coupled with the Gamma-Theta transition model is used, the turbulence model is selected as the SST k-ω model, and the convection term is a high-precision discrete difference format. The numerical simulation gives the size and direction of the inlet velocity at Re = 100000, and the turbulence intensity of the inlet flow is set to 3%, and the outlet pressure is set to atmospheric pressure. Since the relevant numerical calculation results have proved the symmetry of the flow field, this embodiment only carries out numerical calculation on the flow field of the semi-leaf height of the variable geometry turbine, and sets the blade surface and the lower interface as adiabatic no-slip boundary, and sets the upper interface of the calculation domain as a free flow interface. The present application uses the outlet total pressure loss coefficient λ to verify the influence of the non-axisymmetric end wall on the aerodynamic performance of the variable geometry turbine. The total pressure loss coefficient λ is defined as follows:

[0110]

[0111] wherein in the formula, Po,i represents the average total pressure of the mass flow at the inlet of the flow field, Po,loc represents the local total pressure in the flow field, Po,plane1 represents the average total pressure of the mass flow at Plane1 section, and Ps,plane1 represents the average static pressure of the mass flow at Plane1 section. The axial distance of Plane1 section from the blade tail edge is 0.4Cx.

[0112] The numerical calculation results are shown in Figures 10 to 12 , and Figure 10 the pressure distribution curves of the blade surface at 5% blade height before and after adding the non-axisymmetric end wall structure are shown in the figure. After adding the non-axisymmetric end wall structure, the pressure difference between the suction surface and the pressure surface of the blade at 5% blade height is reduced, which means that the transverse pressure gradient in the guide vane passage is reduced. Because the transverse pressure gradient is the main driving force of the end region secondary flow loss and the tip leakage flow loss, the reduction of the transverse pressure gradient in the guide vane passage means the reduction of the end region secondary flow loss and the tip leakage flow loss. Figure 11 and Figure 12The total pressure loss coefficient distribution curves and cloud maps at the section 40% of the axial chord length downstream of the blade trailing edge are shown in the drawings, and the total pressure loss coefficient in the guide vane passage is obviously reduced after adding the non-axisymmetric end wall structure. Table 1 shows the leakage flow at the turbine hub gap and the average total pressure loss coefficient of the mass flow at the Plane1 section before and after adding the non-axisymmetric end wall structure, and it can be seen that the leakage flow at the turbine hub gap is reduced by 8.41% and the average total pressure loss coefficient of the mass flow at the Plane1 section is reduced by 11.66% after introducing the non-axisymmetric end wall structure.

[0113] Table 1

[0114]

[0115] The control technology for controlling the flow loss of the variable geometry turbine end area through the non-axisymmetric end wall structure comprises the following steps: changing the axisymmetric geometric structure of the existing variable geometry turbine end wall, replacing it with a non-axisymmetric curved surface with local concave-convex structure, thereby forming a non-axisymmetric end wall, changing the flow area of each flow channel, and reducing the pressure difference between the pressure surface on one side of each flow channel and the suction surface on the other side by optimizing the non-axisymmetric end wall structure. The reduction of the pressure difference on both sides of the guide vane surface can effectively reduce the leakage flow at the upper and lower end areas of the guide vane, and on the other hand, it can delay the formation and development of the passage vortex by affecting the secondary flow velocity distribution, reduce the passage vortex intensity, and finally realize the reduction of the secondary flow loss of the flow passage.

[0116] The effectiveness of the present application is fully and effectively proved through the above-mentioned embodiments. Those skilled in the art can understand that the present application includes but is not limited to the contents described in the drawings and the above detailed embodiments. Although the present application has been described in relation to the presently preferred embodiments thereof, it is to be understood that the application is not limited to the disclosed embodiments, and any modification not deviating from the functional and structural principles of the present application shall be included in the scope of the claims.

[0117] Up to now, the embodiments of the present application have been described in detail in combination with the drawings. It should be noted that the implementation modes not shown or described in the drawings or the text of the specification are the modes known by those skilled in the art, and are not described in detail. In addition, the definition of each component described above is not limited to the various specific structures, shapes or modes mentioned in the embodiments, and those skilled in the art can make simple changes or replacements.

[0118] It is also to be understood that the numerical parameters set forth in the specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present application. At the very least, each numerical parameter should be construed in light of the

[0119] Those skilled in the art will appreciate that the features recited in the various embodiments and / or claims of the present application can be combined or / and integrated in a variety of ways, even if such combinations or integrations are not expressly disclosed in the present application. In particular, the features recited in the various embodiments and / or claims of the present application can be combined and / or integrated in a variety of ways without departing from the spirit and teachings of the present application. All such combinations and / or integrations are within the scope of the present application.

[0120] The above-described embodiments of the present application have been further described in detail to explain the purposes, technical solutions and beneficial effects of the present application. It should be understood that the above-described embodiments are merely specific embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A variable geometry turbine vane assembly coupled to a non-axially symmetric endwall structure, characterized by, The application relates to a variable-geometry turbine vane assembly, comprising: a hub; a casing, which cooperates with the hub to form an annular flow channel; a plurality of rotating shafts, which are arranged equidistantly in the circumferential direction in the annular flow channel and extend along the radial direction of the annular flow channel; and a plurality of vanes, which are arranged rotatably on the rotating shafts, and gaps exist between the upper ends of the vanes and the casing and between the lower ends of the vanes and the hub. The outer side of the hub and the inner side of the casing are provided with continuous concave-convex structures, the maximum convex height of the concave-convex structures is lower than the height of the gaps, and the maximum concave height of the concave-convex structures is lower than the wall thickness of the components. The continuous concave-convex structures are constructed by a point displacement method and comprise the following steps: obtaining control points in a non-axially symmetric end wall to be shaped, the control points are obtained by the intersection of an axial control line and a circumferential control line, the circumferential control line is a curve obtained by the tangency of a meridian flow channel surface and the casing or the hub, and the axial control line is obtained by the translation of a camber line of a vane profile by a preset circumferential angle; constructing a circumferential profile line of the non-axially symmetric end wall to be shaped by using a sine function, which comprises: constructing an axial profile line of the non-axially symmetric end wall to be shaped by using a differential pressure method based on the static pressure distribution in an end region, which comprises: shaping the outer side of the hub and the inner side of the casing by using the above steps. The height ratio of the gaps to the height of the vanes along the axis direction of the rotating shafts is 4.5%. The rotating shafts are arranged at a distance of 20% of the axial chord length from the leading edge points of the vanes, and the centers of the rotating shafts are located on the camber lines of the vanes. The diameter ratio of the rotating shafts to the height of the vanes along the axis direction of the rotating shafts is 4%. Two adjacent vanes form a vane flow channel, the part of the vane flow channel in contact with the hub is a first non-axially symmetric end wall shaping surface A1, the part of the lower end surface of the vane in contact with the hub during rotation is a second non-axially symmetric end wall shaping surface B1, the part of the vane flow channel in contact with the casing is a third non-axially symmetric end wall shaping surface A2, and the part of the lower end surface of the vane in contact with the casing during rotation is a fourth non-axially symmetric end wall shaping surface B2, wherein the starting positions of the first non-axially symmetric end wall shaping surface A1 and the third non-axially symmetric end wall shaping surface A2 are arranged at a distance of 0%-30% of the axial chord length before the leading edge points of the vanes, and the ending positions of the second non-axially symmetric end wall shaping surface B1 and the fourth non-axially symmetric end wall shaping surface B2 are arranged at a distance of 0%-30% of the axial chord length after the trailing edge points of the vanes. The working medium of the variable-geometry turbine vane assembly is air, nitrogen, oxygen, carbon dioxide, natural gas, ammonia, freon or water vapor. The variable-geometry turbine can be of the radial type, mixed-flow type, single-stage type or multi-stage type. The method for shaping the variable-geometry turbine vane assembly comprises the following steps: obtaining original parameter information of an original variable-geometry turbine, performing fluid dynamics calculation on the original parameter information to obtain original aerodynamic performance; introducing a non-axially symmetric end wall configuration on the basis of the original variable-geometry turbine; adjusting the parameters of the non-axially symmetric end wall structure; ； wherein, represents the circumferential amplitude, A(x) is an axial amplitude control function representing the concave-convex degree of the axial profile, x represents the axial coordinate position of the control point, y represents the circumferential coordinate position of the control point, and t represents the distance of the arc line in the adjacent two turbine blades. ​ ； ； wherein R is an amplitude control coefficient, ΔP is the maximum value of the pressure difference in the end region at each axial position, P PS is the static pressure near the end wall on the pressure side of the blade SS is the static pressure near the end wall on the suction side of the blade; ​ 2. The variable geometry turbine vane assembly of claim 1, wherein, ​ 3. The variable geometry turbine vane assembly of claim 1, wherein, ​ 4. The variable geometry turbine vane assembly of claim 1, wherein, ​ 5. The variable geometry turbine vane assembly of claim 1, wherein, ​ 6. The variable geometry turbine vane assembly of claim 1, wherein, ​ 7. The variable geometry turbine vane assembly of claim 1, wherein, ​ 8. A method of profiling a variable geometry turbine vane assembly coupled to a non-axially symmetric endwall structure, characterized by, ​ ​ ​ ​ Variable geometry turbine coupled with non-axisymmetric end wall Performing fluid dynamics calculation on the coupled variable geometry turbine to obtain aerodynamic performance of the shaped variable geometry turbine Rotating the guide vane within a preset range of installation angle, judging whether the aerodynamic performance of the shaped variable geometry turbine at different guide vane opening conditions is higher than the original aerodynamic performance, if yes, inputting as the modified variable geometry turbine, if no, returning to adjust the parameters of the non-axisymmetric end wall structure.

9. The molding method according to claim 8, wherein Introducing the non-axisymmetric end wall configuration on the basis of the original variable geometry turbine includes: Using any one of the point displacement method, the middle arc line rotation method, the symmetric and asymmetric function superposition method, the symmetric and asymmetric function superposition method and the third order Fourier function method to construct the non-axisymmetric end wall of the guide vane assembly of the original variable geometry turbine respectively.

10. The molding method according to claim 8, wherein The installation angle of the guide vane is reduced to negative, the installation angle of the guide vane is increased to negative, and the rotation range of the guide vane includes -α1~α2, wherein the specific values of α1 and α2 are obtained by reverse calculation through the thrust variation range of the variable cycle engine.

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