Wide-adaptability rectifiable turbine after-machine casing airfoil and design method

Abstract

This invention provides a widely adaptable and rectifyable turbine rear casing blade profile and design method, relating to the field of gas turbine design technology. The blade profile includes: a leading-edge small circle, a trailing-edge small circle, and first, second, and third small circles sequentially located between them. The leading-edge small circle and the second small circle are connected by a first arc segment on the blade back side and blade head side, with the first small circle tangent to both and both arc segments tangent to the first small circle. The second and third small circles are connected by a straight segment on the blade back side and blade head side parallel to the engine axis. The third small circle and the trailing-edge small circle are connected by a second arc segment on the blade back side and blade head side, with these two arc segments symmetrical about the line connecting the centers of the third and trailing-edge small circles. The line connecting the centers of the leading-edge and second small circles forms an angle with the engine axis, and the center of the second small circle lies on a straight line perpendicular to the engine axis. This invention can rectify the large pre-swirl airflow at the turbine outlet to near the axial direction over a wide operating range, reducing flow losses and ensuring stable afterburning combustion.

Description

Technical Field

[0001] This invention relates to the field of gas turbine design technology, specifically to a widely adaptable and rectifiable turbine rear casing blade profile and design method. Background Technology

[0002] To broaden the operating envelope of aero-engines and gas turbines and improve overall efficiency, the design operating range of turbine components is becoming increasingly wider, leading to greater variations in turbine outlet aerodynamic performance parameters (such as airflow angle, Mach number, and total pressure) depending on the operating conditions. Traditional turbine rear casing blades typically employ symmetrical or near-symmetrical blade structures, primarily meeting the load-bearing and flow requirements at a single design point. However, under non-design conditions, especially those with large pre-swirl, in actual operation, when the turbine outlet airflow deviates significantly from the axial angle (e.g., 40°) or the Mach number is high (e.g., above 0.55), traditional rear casing blades are highly susceptible to inducing boundary layer thickening, airflow separation, and even vortex generation on the suction side. This significantly increases flow losses and prevents effective airflow rectification. Consequently, the flow field quality at the rear casing outlet deteriorates, resulting in uneven velocity distribution and increased pressure pulsation at the downstream afterburner inlet, causing ignition difficulties, unstable combustion, and even flameout, severely restricting the reliability and performance of the entire engine.

[0003] Therefore, there is an urgent need to provide a turbine rear casing blade profile and its design method that can adapt to a wide range of operating conditions, has good rectification capability and low flow loss. Summary of the Invention

[0004] In view of this, the embodiments of this specification provide a wide-adaptability rectified turbine rear casing blade profile and design method to solve the problem of unstable afterburning caused by the large axial deviation angle and high Mach number of the outlet airflow of the traditional turbine rear casing, reduce the flow loss of the turbine rear casing, and achieve the purpose of small-angle axial deflection exhaust of the outlet airflow of the rear casing under a wide range of operating conditions.

[0005] The embodiments in this specification provide the following technical solutions:

[0006] A wide-adaptability, rectifiable turbine rear casing blade profile, comprising: The leading edge small circle located at the leading edge of the turbine rear casing, the trailing edge small circle located at the trailing edge of the turbine rear casing, and the first small circle, the second small circle, and the third small circle located sequentially between the leading edge small circle and the trailing edge small circle; The leading edge small circle and the second small circle are connected by the first arc segment on the back side of the leaf and the first arc segment on the leaf basin side. The first small circle is tangent to both the leading edge small circle and the second small circle, and the first arc segment on the back side of the leaf and the first arc segment on the leaf basin side are both tangent to the first small circle. The second and third small circles are connected by a straight segment on the back side of the blade and a straight segment on the front side of the blade, both of which are parallel to the engine axis. The third small circle and the tail edge small circle are connected by the second arc segment on the back side of the leaf and the second arc segment on the leaf basin side; The line connecting the center of the leading small circle and the center of the second small circle forms an angle with the engine axis. ; The center of the second small circle lies on a straight line perpendicular to the engine axis; The second arc segment between the third small circle and the trailing small circle is symmetrical about the line connecting the center of the third small circle and the center of the trailing small circle.

[0007] Furthermore, the leading edge radius R of the leading edge small circle A The diameter is 2mm to 8mm; The second radius R of the second small circle B The third radius R of the third smaller circle C They are equal, and the second radius R B The diameter is 5mm to 30mm; The trailing radius R of the trailing small circle D The diameter is 1mm to 6mm; Inlet airflow angle The angle between the airflow and the frontal line of the blade. The angle is 50° to 80°. axial length between the center of the leading edge small circle and the center of the second small circle l 1 is 50~200mm; The axial distance between the center of the second small circle and the center of the third small circle l 2 is 5mm to 100mm; The axial distance between the center of the third small circle and the center of the trailing small circle. l 3 = y × R C , where the value of y ranges from 2 to 4; The axial half-length of the tail contour arc between the third small circle and the tail edge small circle l 4= l 3+z×R D Where z takes values ​​ranging from 0.3 to 0.8; The central angle corresponding to the line connecting the center of the first small circle and the center of the leading small circle is 0.5 ± 0.1, which is the proportion of the total central angle of the arc between the leading small circle and the second small circle.

[0008] A design method for a widely adaptable and rectifyable turbine rear casing airfoil, comprising the following steps: Based on the incoming airflow angle range at the turbine outlet and the structural strength requirements of the blade leading edge, determine the position of the small leading edge circle and the corresponding leading edge radius R. A ; Based on the layout of the internal piping of the turbine rear casing and the requirements of the rear casing cooling and structural design, the second radius R is determined.B The position of the second small circle is determined based on the inlet airflow angle; Based on the geometric constraints between the leading edge small circle, the second small circle, and the first small circle, determine the position and the first radius R of the first small circle. E ; Based on the axial mounting space of the rear casing load-bearing frame and the second small circle, determine the position of the third small circle and the corresponding third radius R. C ; Based on the diffuser requirements of the turbine outlet airflow, the turbine outlet Mach number, and the structural design and manufacturing requirements of the third small circle and the rear casing, the position of the trailing edge small circle and the corresponding trailing edge radius R are determined. D ; The tail section outer contour is determined based on the required rear casing outlet airflow angle, wherein the tail section outer contour is symmetrical about the line connecting the centers of the third small circle and the tail edge small circle. Based on the leading edge circle, the first small circle, the second small circle, and the third small circle, construct the leaf back side profile line and the leaf basin side profile line; The turbine rear casing airfoil is determined by the blade back side profile, blade basin side profile, and tail outer contour line, and the number of blades in the airfoil is determined so that the rear casing simultaneously meets the support point requirements of the load-bearing frame.

[0009] Furthermore, based on the range of the incoming airflow angle at the turbine outlet and the structural strength requirements of the blade leading edge, the position of the small leading edge circle and the corresponding leading edge radius R are determined. A ,include: Obtain the minimum and maximum values ​​of the incoming airflow angle range at the turbine outlet, the maximum aerodynamic load and thermal stress that the leading edge small circle needs to withstand; The minimum value of the future airflow angle range is used as the design input reference for the leading edge wedge angle of the leading edge small circle, and the maximum value of the future airflow angle range is used as the upper limit of the adaptive airflow angle of the leading edge small circle. Calculate the minimum radius of curvature required for the leading edge small circle based on the maximum aerodynamic load and thermal stress. The smaller of the minimum radius of curvature and the preset minimum allowable radius for machining is used as the radius R. A Initial value; Based on the upper limit of the adaptive airflow angle, the leading edge radius R A The initial value is corrected. When the upper limit of the adaptive airflow angle is greater than the upper limit threshold of the airflow angle, the leading edge radius R is adjusted. A Increase the set increase ratio and use it as the leading edge radius R. A The final value; The geometric starting point of the leading edge profile of the turbine rear casing is taken as the center of the leading edge small circle.

[0010] Furthermore, based on the layout of the internal piping of the turbine rear casing and the requirements of the rear casing cooling and structural design, the second radius R is determined. BThe position of the second small circle is determined based on the inlet airflow angle, including: The line connecting the center of the leading small circle and the center of the second small circle forms an angle with the engine axis. The included angle is determined by the inlet airflow angle. ,in, The inlet airflow angle; axial length between the center of the leading edge small circle and the center of the second small circle l 1 is 50~200mm, and ; Obtain the maximum outer diameter D of the internal piping of the rear casing. max And based on the maximum outer diameter D max Determine the second radius R B , where R B ≥D max / 2+ Structural safety margin; Based on the position of the center of the small circle at the leading edge and the included angle axial length between the centers of the second small circle l 1 and second radius R B Calculate the coordinates of the center of the second small circle, and make the leading small circle tangent to the second small circle; Output the coordinates of the center of the second smaller circle and its second radius R. B .

[0011] Furthermore, based on the geometric constraints between the leading small circle, the second small circle, and the first small circle, the position and the first radius R of the first small circle are determined. E ,include: Obtain the minimum and maximum incoming flow angles at the turbine outlet, as well as the inlet Mach number; The leading edge wedge angle is set according to the minimum value of the incoming flow angle, the upper limit of the leading edge adaptive flow angle is set according to the maximum value of the incoming flow angle, and the thickness growth rate along the flow direction between the leading edge and the second small circle is determined according to the inlet Mach number. Using the leading edge wedge angle and the upper limit of the adaptive airflow angle as the first constraint, the curvature change gradient of the arc segment between the leading edge small circle and the second small circle is parametrically reconstructed. Using the thickness growth rate along the flow direction as the second constraint, through iterative correction, the central angle scaling factor and radius factor satisfying the first and second constraints are extracted. The central angle scaling factor is the proportion of the central angle corresponding to the line connecting the center of the first small circle and the center of the leading edge small circle to the total central angle of the arc segment between the leading edge small circle and the second small circle. The radius factor is the first radius R of the first small circle. E With the second radius R of the second smaller circle B The ratio; Using the tangency of the first small circle to both the leading small circle and the second small circle as a geometric constraint, and based on the central angle scaling factor and radius factor, the coordinates of the center of the first small circle and its corresponding first radius R are calculated according to the geometric constraints. E； Output the coordinates of the center of the first small circle and its first radius R. E .

[0012] Furthermore, based on the axial mounting space of the rear casing load-bearing frame and the second small circle, the position of the third small circle and the corresponding third radius R are determined. C ,include: The third radius R of the third small circle C Set to the radius R of the second smaller circle, which is equal to the radius of the second smaller circle. B ; Based on the axial positions of the front and rear mounting flange faces of the rear casing load-bearing frame and the bolt arrangement space required for flange connection, determine the axial distance between the center of the third small circle and the center of the second small circle. l 2. Position the second small circle inside the front mounting flange face and the third small circle inside the rear mounting flange face. Set the center of the third small circle, such that the line connecting the center of the third small circle and the center of the second small circle is parallel to the engine axis, and the axial distance between the centers of the third and second small circles is [missing information]. l 2; Output the coordinates of the center of the third smaller circle and its corresponding third radius R. C .

[0013] Furthermore, based on the diffusion requirements of the turbine outlet airflow, the turbine outlet Mach number, and the third small circle, the position of the trailing edge small circle and the corresponding trailing edge radius R are determined. D ,include: The target exit Mach number is determined based on the diffusion requirement of the turbine outlet airflow. The diffuser ratio is calculated based on the ratio of the turbine exit Mach number to the target exit Mach number. Assume the axial distance between the center of the trailing small circle and the center of the third small circle is... l 3. Determine the axial distance based on the diffusion ratio. l 3 and the third radius R C The ratio y, where the ratio y is positively correlated with the diffusion ratio; Move the center of the third small circle a distance along the engine axis. l 3 = y × R C This gives the axial position of the center of the small trailing circle; The center of the trailing edge circle is set on the line connecting the center of the third small circle and the center of the trailing edge circle, wherein the connecting line is parallel to the engine axis. The tail rim radius R is determined based on the minimum allowable wall thickness of the tail rim casting process. D ; Output the coordinates of the center of the trailing small circle and the corresponding trailing radius R. D .

[0014] Furthermore, based on the required rear casing outlet airflow angle, the tail section outer contour is determined, including: Obtain the contraction of the trailing edge and set the symmetrical half-length of the tail's outer contour. l 4 and the trailing edge radius R D The correlation coefficient z is negatively correlated with the contraction of the trailing edge; Using the line connecting the centers of the third small circle and the tail edge small circle as the axis of symmetry, construct an arc segment as the outer contour line of the tail. The center of the arc segment lies on the extension line of the third small circle passing through the axis of symmetry, and the axial distance from the point of tangency between the arc segment and the tail edge to the center of the third small circle is [missing information]. l 4, where the symmetrical half-length of the arc segment l 4= l 3+z × R D .

[0015] Furthermore, based on the leading edge circle, the first circle, the second circle, and the third circle, the leaf back lateral profile and the leaf base lateral profile are constructed, including: The blade back profile consists of a back arc segment that passes through the corresponding points on the blade back side of the leading edge small circle, the first small circle, and the second small circle in sequence, as well as a back straight segment that is tangent to the second small circle and the third small circle and parallel to the engine axis. The blade side profile consists of a blade arc segment that passes through the corresponding points on the blade side of the leading edge small circle, the first small circle, and the second small circle in sequence, as well as a blade straight line segment that is tangent to the second and third small circles and parallel to the engine axis. The corresponding point on the back of the leaf and the corresponding point on the leaf base are located on both sides of the same line connecting the centers of the small leading edge circle, the first small circle, and the second small circle, respectively.

[0016] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least: The turbine rear casing airfoil of this invention achieves efficient rectification and diffusion of the large pre-swirling airflow at the turbine outlet over a wide operating range, reducing flow losses, increasing the total pressure recovery coefficient, and bringing the outlet airflow close to the axial direction, thereby ensuring stable combustion with afterburner. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the airfoil of a widely adaptable and rectifiable turbine rear casing according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a typical flow field structure for a symmetrical rear casing blade profile in a conventional design. Figure 3 This is a schematic diagram of a typical flow field structure of the rear casing blade type according to an embodiment of the present invention; Figure 4 This is a comparison chart of the performance parameters of the turbine rear casing between the conventional solution and the embodiment of the present invention. Detailed Implementation

[0019] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] I. Structure of the turbine rear casing blades.

[0022] like Figure 1 As shown, this embodiment provides a widely adaptable and rectifiable turbine rear casing blade profile. For ease of description, the following geometric elements are defined: Leading edge small circle ( Figure 1 Circle A in the diagram): Located at the leading edge of the turbine rear casing, with a radius of R. A .

[0023] The first small circle ( Figure 1 Circle E): Located between the leading small circle and the second small circle, with radius R. E .

[0024] The second small circle ( Figure 1 Circle B in the diagram is located between the first and third smaller circles and has a radius of R. B .

[0025] The third small circle ( Figure 1 Circle C in the middle): Located between the second small circle and the tail edge small circle, with a radius of R. C .

[0026] Tail edge small circle ( Figure 1 Circle D in the diagram): located at the trailing edge of the turbine rear casing, with a radius of R. D .

[0027] The five small circles are connected as follows: The leading small circle (circle A) and the second small circle (circle B) are connected by the first circular arc segment. (Including the first arc segment on the back of the leaf and the first arc segment on the leaf basin) are connected, and the first small circle (circle E) is located on the first arc segment and is tangent to both circle A and circle B.

[0028] The second small circle (circle B) and the third small circle (circle C) are connected by a straight line segment. (Including the straight section on the back side of the blade and the straight section on the blade base) are connected, and this straight section is parallel to the engine axis.

[0029] The third small circle (circle C) and the trailing small circle (circle D) are separated by the second arc segment. (Including the second arc segment on the leaf underside and the second arc segment on the leaf base side) are connected, and the second arc segment is symmetrical about the line connecting the centers of circle C and circle D.

[0030] The angle between the line connecting the center of circle A and the center of circle B and the engine axis is α1, and the center of circle B is located on a straight line perpendicular to the engine axis.

[0031] In this embodiment, the preferred ranges for the radius and position parameters of each circle are as follows: Leading edge radius R A : 2mm~8mm (5mm preferred); Second radius R B With the third radius R C Equal, second radius R B With the third radius R C : 5mm~30mm (15mm preferred); Trailing edge radius R D : 1mm~6mm (4mm preferred); Inlet airflow angle Range (angle with the rear receiver datum): 50°~80°; The angle between the line connecting the center of the leading small circle and the center of the second small circle and the engine axis. : ; Axial distance between the center of circle A and the center of circle B l 1: 50mm~200mm (preferably 135mm); Axial distance between the center of circle B and the center of circle C l 2: 5mm~100mm (35mm is preferred); Axial distance between the center of circle C and the center of circle D l 3 = y × R C, where y is the diffuser length coefficient, which represents the relative length of the diffuser section (from the third small circle to the trailing edge), and the value of y ranges from 2 to 4 (preferably 2.33). l It is the total axial length of the rear support plate. l =Radius of the leading small circle A + l 1+ l 2+ l 3 + radius of the trailing small circle D; The tail outline is symmetrical and half-length l 4 (Axial half-length of the tail contour arc between circle C and circle D) = l 3+z×R D Where z is the tail profile half-length coefficient, which represents the axial extension length of the tail profile from the third small circle C to the tail edge small circle D. The value of z ranges from 0.3 to 0.8 (preferably 0.5). The central angle corresponding to the line connecting the center of the first small circle E and the center of the leading small circle A is given by the central angle proportionality coefficient λ. Total central angle of the arc proportion ( Figure 1 middle Central angle occupy Central angle The central angle scaling factor λ is 0.5 ± 0.1 (preferably 0.5).

[0032] The radius coefficient x of the first small circle E is used to characterize the size of the first small circle E relative to the leading small circle and the second small circle B, and satisfies the following... The value of x ranges from 0.5 to 0.8 (preferably 0.66).

[0033] II. Design method of turbine rear casing blade profile.

[0034] This embodiment also provides a design method for the above-mentioned blade shape, including the following steps.

[0035] Step 1. Determine the position and radius R of the leading edge small circle A. A .

[0036] Based on the incoming flow angle range at the turbine outlet and the structural strength requirements of the blade leading edge, determine the position and radius R of circle A. A The details are as follows: Obtain the minimum value α of the turbine outlet inlet angle of attack range. min and maximum value α max And the maximum aerodynamic load and thermal stress that the leading edge small circle needs to withstand.

[0037] Minimum value α minAs the design input for the leading edge wedge angle, the maximum value α max As an adaptation to the upper limit of the angle of attack.

[0038] The minimum radius of curvature required for the leading edge small circle is calculated based on the maximum aerodynamic load and thermal stress. Specifically, the minimum radius of curvature required for the leading edge small circle is calculated based on the maximum Mach number at the turbine exit, the incoming flow angle of attack range, and the airflow temperature. Through aerodynamic pressure distribution estimation and thermal-structural coupling analysis, the minimum radius of curvature under aerodynamic load constraints and the minimum radius of curvature under thermal stress constraints are obtained respectively. The larger of the two values ​​is then multiplied by the material safety factor (usually 1.2 to 1.5) to obtain the minimum radius of curvature required for the leading edge small circle.

[0039] The smaller of the minimum radius of curvature and the preset minimum allowable radius for machining is taken as R. A The initial value of .

[0040] The initial value is corrected based on the upper limit of the adaptive angle of attack: when the upper limit of the adaptive angle of attack is greater than 30° (the upper limit threshold of the angle of attack), R is adjusted. A Increase by 10% to 20% (the set increase ratio) and use it as the final value.

[0041] The geometric starting point of the leading edge profile of the turbine rear casing is taken as the center of circle A.

[0042] Step 2. Determine the position and radius R of the second small circle B. B .

[0043] Based on the angle of the turbine outlet airflow deviating from the axial direction and the layout requirements of the internal piping of the rear casing, the position and radius R of circle B are determined. B The details are as follows: Obtain the design inlet airflow angle (The angle between the airflow and the blade tip, ranging from 50° to 80°), calculate the angle between the line connecting the center of circle A and the center of circle B and the engine axis. .

[0044] Obtain the maximum outer diameter D of the internal piping of the rear casing. max and determine R B ≥D max / 2+ Structural safety margin.

[0045] Based on the center position and included angle of circle A axial distance between the center of circle A and the center of circle B l 1 and second radius R B Calculate the coordinates of the center of circle B so that circle A is tangent to circle B.

[0046] Step 3. Determine the position and radius R of the first small circle E. E .

[0047] Determine the position and radius R of circle E based on the geometric constraints between circles A and B and circle E. E This step aims to improve the aerodynamic performance of the rear casing support plate airfoil and suppress expansion flow losses by performing a refined forward optimization design on the leading edge region of the airfoil.

[0048] Obtain the minimum and maximum incoming airflow angle at the turbine outlet and the inlet Mach number.

[0049] The leading edge wedge angle is set based on the minimum value of the incoming airflow angle, the upper limit of the leading edge adaptive angle of attack is set based on the maximum value, and the thickness growth rate along the flow direction between the leading edge and circle B is determined based on the inlet Mach number.

[0050] Using the leading-edge wedge angle and the upper limit of the adaptive angle of attack as the first constraint, the curvature gradient of the arc segment between circle A and circle B is parametrically reconstructed. The thickness growth rate along the flow direction is used as the second constraint. Through iterative correction, the central angle scaling factor λ and the radius factor x that satisfy the first and second constraints are extracted. Specifically: using the leading-edge wedge angle and the upper limit of the adaptive angle of attack as the first constraint, the curvature gradient of the arc segment between circle A and circle B is parametrically reconstructed, i.e., the curvature distribution is parametrically configured using cubic splines to ensure that the curvature at the leading edge matches the leading-edge wedge angle, and the curvature integral satisfies the angle of attack adaptation requirement. Using the thickness growth rate along the flow direction as the second constraint, a thickness distribution function is defined, allowing the growth rate to gradually increase from zero to the target value (determined by the Mach number). The central angle scaling factor λ and the radius factor x are used as optimization variables. Through iterative correction (such as gradient descent or genetic algorithms), the curvature distribution is made continuous, and the thickness growth rate matches the target, ultimately extracting λ and x that satisfy the constraints.

[0051] Using the tangency of circle E to both circles A and B as a geometric constraint, the coordinates of the center and the radius R of circle E are calculated based on the central angle scaling factor and the radius factor. E .

[0052] Step 4. Determine the position and radius R of the third small circle C. C .

[0053] Based on the axial mounting space of the rear casing load-bearing frame and circle B, determine the position and radius R of circle C. C .

[0054] R C Set to equal R B .

[0055] Based on the axial positions of the front and rear mounting flange faces of the rear casing load-bearing frame and the bolt arrangement space required for the flange connection, determine the axial distance between the center of circle C and the center of circle B. l 2. Position circle B inside the front mounting flange face and circle C inside the rear mounting flange face.

[0056] Set the center of circle C such that the line connecting it to the center of circle B is parallel to the engine axis, with an axial distance of [missing information]. l 2.

[0057] Step 5. Determine the position and radius R of the trailing edge circle D. D .

[0058] Based on the diffusion requirements of the turbine outlet airflow, the turbine outlet Mach number, and circle C, determine the position and radius R of circle D. D .

[0059] Based on the diffusion requirement, the target export Mach number is determined.

[0060] The diffuser ratio is calculated based on the ratio of the turbine exit Mach number to the target exit Mach number.

[0061] Let the axial distance between the center of circle D and the center of circle C be... l 3. Determine the ratio y based on the diffusion ratio. l 3 / R C The ratio y is positively correlated with the diffusion ratio. Specifically, within the range of y from 2 to 4, the larger the diffusion ratio, the larger the value of y (for example, when the diffusion ratio is 1.5, y is 2.33).

[0062] Move the center of circle C along the engine axis by a distance l 3 = y × R C This gives us the axial position of the center of circle D.

[0063] The center of circle D is set on the line connecting the center of circle C and the center of circle D, and this line is parallel to the engine axis.

[0064] R is determined based on the minimum allowable wall thickness of the tail-edge casting process. D (Usually a smaller value is taken, such as 4mm).

[0065] Step 6. Construct the leaf back side profile and leaf basin side profile.

[0066] Based on circles A, E, B, and C, construct the leaf dorsal lateral profile and leaf pelt lateral profile (see...). Figure 1 ): Leaf back profile: formed by corresponding points on the leaf back side passing through circles A, E, and B in sequence ( Figure 1 The back arc segment of A1, E1, B1) And the straight line segment on the back side that is tangent to circles B and C and parallel to the engine axis. constitute.

[0067] Leaf-pot side profile: consisting of corresponding points on the leaf-pot side of circles A, E, and B in sequence ( Figure 1 The basin arc segment of A2, E2, B2) And the straight section on the side of the cone that is tangent to circles B and C and parallel to the engine axis. constitute.

[0068] The corresponding point on the underside of the leaf and the corresponding point on the leaf base are located on opposite sides of the same line connecting the centers of circles A, E, and B, respectively.

[0069] Points A1 and A2 are the intersections of the line passing through radius O1A and circle A, points E1 and E2 are the intersections of the line passing through radius O1E and circle E, and points B1 and B2 are the intersections of the line passing through radius O1B and circle B.

[0070] Circles B and C have the same radius, and the line connecting them is parallel to the engine axis. , The endpoints are the intersection points of the straight lines passing through the centers of circles B and C and perpendicular to the engine axis, and are tangent to circles B and C.

[0071] Step 7: Determine the outer contour line of the tail.

[0072] Determine the tail section outline based on the required rear casing outlet airflow angle. and The outer contour line is symmetrical about the line connecting the centers of circles C and D.

[0073] Obtain the target value of the required rear casing outlet airflow angle.

[0074] Set the tail outline to be symmetrical half length l 4 and R D The coefficient z is related to the trailing edge wake loss of the rear casing (i.e., the shrinkage of the trailing edge).

[0075] The contraction of the trailing edge refers to the degree of "narrowing" of the trailing profile of the turbine rear casing blade (the arc segment from the third small circle C to the trailing edge small circle D) in its axial projection. Specifically, it is defined as the ratio of the blade thickness at trailing edge small circle D to the blade thickness at the third small circle C, or a quantitative indicator of the deviation between the exit airflow angle and the design target. In this invention, the contraction is directly related to the axial half-length coefficient z of the trailing profile arc: the larger the z value, the gentler the trailing profile (smaller contraction), the more balanced the airflow pressure at the trailing edge, and the lower the wake loss; the smaller the z value, the steeper the trailing profile (larger contraction), and the easier it is for the exit airflow angle to deflect. Preferably, the contraction is negatively correlated with the target value of the rear casing exit airflow angle, i.e., the smaller the required exit airflow angle, the greater the contraction, and the correspondingly larger the z value (within the range of 0.3 to 0.8). This parameter is used to optimize diffusion and mixing in the trailing edge region, reducing wake loss.

[0076] Using the line connecting the centers of circles C and D as the axis of symmetry, construct an arc segment as the outer contour line of the tail. The center O2 of the circle lies on the extension of the axis of symmetry, and the symmetrical half-length of the arc segment... l 4= l 3+z×R D .

[0077] Step 8. Determine the number of leaves.

[0078] Determine the number of blades in the airfoil (preferably no more than 20, for example, 16) so that the rear casing simultaneously meets the support point requirements of the load-bearing frame.

[0079] Specifically, the number of blades N is determined. The turbine rear casing, acting as a load-bearing frame, requires a circumferentially distributed support plate (i.e., blades) whose number matches the number of support points on the load-bearing frame. Specifically, the number of circumferential support points on the load-bearing frame between the front and rear mounting flanges of the rear casing is typically given by the overall machine design (e.g., 8-20). To ensure the blades function both aerodynamic rectification and structural support, the number of blades N is set equal to the number of support points, and N is controlled to be no greater than 20 blades (e.g., N=16), thus meeting the installation strength and stiffness requirements of the load-bearing frame without adding additional support components.

[0080] like Figure 1 As shown, in one embodiment of the present invention, the following turbine rear casing can be designed according to the above design method: 16 support blades, R... A =5,R B =R C =15, R D =4, =65°, =12.5°, / =0.5, =135, =35, =34.95, =36.95, x=0.66, y=2.33, z=0.5, at this time the radius R of the arc lines on the rear casing basin side and back side where the leading edge small circle, the first small circle, and the second small circle are tangent. ss =254、R PS =456, the radius R of the arc between the third small circle and the trailing small circle. H =65, the turbine rear casing maintains good flow characteristics within the range of inlet airflow angle deviation from the axial direction not exceeding 40° and Mach number not exceeding 0.55.

[0081] like Figure 2 As shown, when the angle between the inlet airflow and the engine axis reaches 35°, a large separation vortex is formed on the blade back side of the rear casing, and when the outlet airflow angle of the rear casing deviates from the axial direction by 25°, the flow separation leads to significant flow losses. Figure 3As shown, when the inlet airflow reaches 35° with the engine axis, the leading edge of the rear casing plays a good guiding role. The airflow flows smoothly along the arc on the back side of the basin constructed by the first small circle, the second small circle, and the third small circle. It diffuses evenly in the trailing edge region without forming obvious flow separation. The outlet airflow angle deviates from the axis by 7°, the flow separation loss is small, and the airflow is close to the axial exhaust. The inlet airflow is rectified from a 35° deviation from the axis to a 7° deviation, achieving a good flow rectification effect.

[0082] like Figure 4 As shown, the performance parameters of the rear casing in this embodiment are compared with those of a conventional configuration. The horizontal axis represents the rear casing inlet airflow angle (unit: °, angle with the axis), the vertical axis of the upper half represents the rear casing total pressure recovery coefficient (the ratio of the rear casing outlet total pressure to the inlet total pressure), and the vertical axis of the lower half represents the rear casing outlet airflow angle (unit: °, angle with the axis). Figure 4 As can be seen, with the increase of the inlet airflow angle, the inlet airflow deviates more from the axial direction, the total pressure recovery coefficient of the conventional rear casing scheme gradually decreases, and the outlet airflow angle of the rear casing gradually increases. When the inlet airflow angle is greater than 20°, the outlet airflow angle exceeds 22°, exceeding the design requirement of an outlet airflow angle ≤ 15°. As the inlet airflow angle of the rear casing increases from 0° to 40°, the total pressure recovery coefficient of this invention first increases and then decreases, with a minimum value of 0.967. The outlet airflow angle of the rear casing is always less than 15°, meeting the design requirements and exhibiting good overall performance.

[0083] Beneficial effects of the embodiments of the present invention: The embodiments of the present invention employ a blade profile design method combining circular arcs and straight lines, along with dual-parameter control of the central angle proportionality coefficient λ and the radius coefficient x. This enables the blade profile to maintain stable aerodynamic performance within a wide range, including an inlet airflow angle deviating from the axial direction by 0° to 40° and a Mach number not exceeding 0.55. This effectively suppresses flow separation and achieves reliable rectification of the large pre-swirling airflow at the turbine outlet.

[0084] By finely controlling the gradient of airfoil curvature and the thickness expansion rate along the friction, the strong adverse pressure gradient in the suction surface region is weakened, constraining the boundary layer separation range and scale, and suppressing unsteady flow losses such as secondary flow and vortex structures. Under harsh conditions of an inlet airflow angle of 40° and a Mach number of 0.55, the total pressure recovery coefficient of the aft casing can reach over 0.967, and the outlet airflow angle is controlled within 10° to 15° of the axial deviation, which is significantly better than conventional aft casing designs.

[0085] The airfoil of this invention not only achieves rectification and diffusion functions but also serves as a support for the rear casing load-bearing frame. By rationally setting the radius of the second small circle (to meet the internal piping layout) and the position of the third small circle (to match the load-bearing frame mounting flange), the number of components is reduced, the structural integration and compactness are improved, and the overall weight of the machine is reduced.

[0086] The blade's outer contour is entirely composed of arcs and straight line segments, without complex freeform surfaces. Furthermore, the tail contour adopts a symmetrical arc design, which reduces the manufacturing precision requirements for the tail edge, making it easier to cast, machine, and inspect. This helps reduce manufacturing costs and increase the yield.

[0087] The design method provided in this embodiment of the invention clarifies each geometric parameter (leading edge radius, included angle α0, axial distance). l 1. The determination basis and design logic of ratios y and z, central angle proportionality coefficient λ, radius coefficient x, etc. are driven by actual engineering constraints such as aerodynamic load, thermal stress, pipeline layout, load-bearing frame installation space, diffusion requirements, and outlet airflow angle. This ensures that the design process has a clear causal relationship and repeatability, making it easier for engineering technicians to implement.

[0088] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical solutions, and technical solutions in this invention can be freely combined and used.

Claims

1. A widely adaptable and rectifiable turbine rear casing blade profile, characterized in that, include: The small leading edge circle located at the leading edge of the turbine rear casing, the small trailing edge circle located at the trailing edge of the turbine rear casing, and the first, second, and third small circles located sequentially between the small leading edge circle and the small trailing edge circle; The leading edge small circle and the second small circle are connected by a first arc segment on the leaf back side and a first arc segment on the leaf basin side. The first small circle is tangent to both the leading edge small circle and the second small circle, and the first arc segment on the leaf back side and the first arc segment on the leaf basin side are both tangent to the first small circle. The second small circle and the third small circle are connected by a straight segment on the back side of the blade and a straight segment on the front side of the blade, both of which are parallel to the engine axis. The third small circle and the tail edge small circle are connected by the second arc segment on the leaf back side and the second arc segment on the leaf basin side; The center of the second small circle is located on a straight line perpendicular to the engine axis; The second arc segment between the third small circle and the trailing edge small circle is symmetrical about the line connecting the center of the third small circle and the center of the trailing edge small circle.

2. The turbine rear casing blade profile according to claim 1, characterized in that, The leading edge radius R of the leading edge small circle A The diameter is 2mm to 8mm; The second radius R of the second small circle B With the third radius R of the third small circle C They are equal, and the second radius R B The diameter is 5mm to 30mm; The trailing radius R of the trailing small circle D The diameter is 1mm to 6mm; Inlet airflow angle The angle between the airflow and the frontal line of the blade. The angle is 50° to 80°. The axial length between the center of the leading edge small circle and the center of the second small circle. l 1 is 50~200mm; The axial distance between the center of the second small circle and the center of the third small circle l 2 is 5mm to 100mm; The axial distance between the center of the third small circle and the center of the trailing edge small circle l 3 = y × R C , where the value of y ranges from 2 to 4; The axial half-length of the tail contour arc between the third small circle and the tail edge small circle l 4= l 3+z×R D Where z takes values ​​ranging from 0.3 to 0.8; The central angle corresponding to the line connecting the center of the first small circle and the center of the leading edge small circle is 0.5 ± 0.1, which is the proportion of the total central angle of the arc between the leading edge small circle and the second small circle.

3. A design method for a widely adaptable and rectifyable turbine rear casing airfoil, said design method being used to design the turbine rear casing airfoil according to any one of claims 1 to 2, characterized in that, Includes the following steps: Based on the incoming airflow angle range at the turbine outlet and the structural strength requirements of the blade leading edge, the position of the small leading edge circle and the corresponding leading edge radius R are determined. A ; Based on the layout of the internal piping of the turbine rear casing and the requirements of the rear casing cooling and structural design, the second radius R is determined. B The position of the second small circle is determined based on the inlet airflow angle; Based on the geometric constraints between the leading edge small circle and the second small circle and the first small circle, determine the position of the first small circle and its first radius R. E ; Based on the axial mounting space of the rear casing load-bearing frame and the second small circle, determine the position of the third small circle and the corresponding third radius R. C ; Based on the diffuser requirements of the turbine outlet airflow, the turbine outlet Mach number, and the structural design and manufacturing requirements of the third small circle and the rear casing, the position of the trailing edge small circle and the corresponding trailing edge radius R are determined. D ; The tail section outer contour is determined according to the required rear casing outlet airflow angle, wherein the tail section outer contour is symmetrical about the line connecting the centers of the third small circle and the tail edge small circle. Based on the leading edge circle, the first small circle, the second small circle, and the third small circle, construct the leaf back side profile and the leaf basin side profile; The turbine rear casing blade profile is determined by the blade back side profile, the blade base side profile, and the tail outer contour line, and the number of blades in the blade profile is determined so that the rear casing simultaneously meets the support point requirements of the load-bearing frame.

4. The design method according to claim 3, characterized in that, Based on the incoming airflow angle range at the turbine outlet and the structural strength requirements of the blade leading edge, the position of the small leading edge circle and the corresponding leading edge radius R are determined. A ,include: Obtain the minimum and maximum values ​​of the incoming airflow angle range at the turbine outlet, and the maximum aerodynamic load and thermal stress that the leading edge circle needs to withstand; The minimum value of the incoming airflow angle range is used as the design input reference for the leading edge wedge angle of the leading edge small circle, and the maximum value of the incoming airflow angle range is used as the upper limit of the adaptive airflow angle of the leading edge small circle. Calculate the minimum radius of curvature required for the leading edge small circle based on the maximum aerodynamic load and thermal stress; The smaller value between the minimum radius of curvature and the preset minimum allowable radius for machining is taken as the radius R. A Initial value; Based on the upper limit of the adaptive airflow angle, the leading edge radius R A The initial value is corrected. When the upper limit of the adaptive airflow angle is greater than the upper limit threshold of the airflow angle, the leading edge radius R is adjusted. A Increase the set increase ratio and use it as the leading edge radius R. A The final value; The geometric starting point of the leading edge profile of the turbine rear casing is taken as the center of the small leading edge circle.

5. The design method according to claim 3, characterized in that, Based on the layout of the internal piping of the turbine rear casing and the requirements of the rear casing cooling and structural design, the second radius R is determined. B The position of the second small circle is determined based on the inlet airflow angle, including: The line connecting the center of the leading small circle and the center of the second small circle forms an angle with the engine axis. The included angle is determined by the inlet airflow angle. ,in, The inlet airflow angle; axial length between the center of the leading edge small circle and the center of the second small circle l 1 is 50~200mm, and ; Obtain the maximum outer diameter D of the internal piping of the rear casing. max And according to the maximum outer diameter D max Determine the second radius R B , where R B ≥D max / 2+ Structural safety margin; Based on the center position and included angle of the small leading edge circle axial length between the centers of the second small circle l 1 and the second radius R B The coordinates of the center of the second small circle are calculated, and the leading edge small circle is made tangent to the second small circle. Output the coordinates of the center of the second small circle and the second radius R. B .

6. The design method according to claim 3, characterized in that, Based on the geometric constraints between the leading edge small circle and the second small circle and the first small circle, determine the position of the first small circle and its first radius R. E ,include: Obtain the minimum and maximum incoming flow angles at the turbine outlet, as well as the inlet Mach number; The leading edge wedge angle is set according to the minimum value of the incoming airflow angle, the upper limit of the leading edge adaptive airflow angle is set according to the maximum value of the incoming airflow angle, and the thickness growth rate along the flow direction between the leading edge and the second small circle is determined according to the inlet Mach number. Using the leading edge wedge angle and the upper limit of the adaptive airflow angle as the first constraint, the curvature change gradient of the arc segment between the leading edge small circle and the second small circle is parametrically reconstructed. Using the thickness growth rate along the flow direction as the second constraint, through iterative correction, the central angle ratio coefficient and radius coefficient satisfying the first and second constraints are extracted. The central angle ratio coefficient is the proportion of the central angle corresponding to the line connecting the center of the first small circle and the center of the leading edge small circle to the total central angle of the arc segment between the leading edge small circle and the second small circle. The radius coefficient is the first radius R of the first small circle. E With the second radius R of the second small circle B The ratio; Using the tangency of the first small circle to both the leading small circle and the second small circle as a geometric constraint, and based on the central angle proportionality coefficient and the radius coefficient, the center coordinates and the corresponding first radius R of the first small circle are calculated according to the geometric constraint. E； Output the coordinates of the center of the first small circle and the first radius R. E .

7. The design method according to claim 3, characterized in that, Based on the axial mounting space of the rear casing load-bearing frame and the second small circle, determine the position of the third small circle and the corresponding third radius R. C ,include: The third radius R of the third small circle C Set to be equal to the radius R of the second smaller circle. B ; Based on the axial positions of the front and rear mounting flange faces of the rear casing load-bearing frame and the bolt arrangement space required for flange connection, determine the axial distance between the center of the third small circle and the center of the second small circle. l 2. The second small circle is located inside the front mounting flange surface and the third small circle is located inside the rear mounting flange surface. The center of the third small circle is set such that the line connecting the center of the third small circle and the center of the second small circle is parallel to the engine axis, and the axial distance between the center of the third small circle and the center of the second small circle is [missing information]. l 2; Output the coordinates of the center of the third small circle and the corresponding third radius R. C .

8. The design method according to claim 3, characterized in that, Based on the diffusion requirements of the turbine outlet airflow, the turbine outlet Mach number, and the third small circle, the position of the trailing edge small circle and the corresponding trailing edge radius R are determined. D ,include: The target exit Mach number is determined based on the diffusion requirement of the turbine outlet airflow. The diffuser ratio is calculated based on the ratio of the turbine outlet Mach number to the target outlet Mach number. Assume the axial distance between the center of the trailing edge small circle and the center of the third small circle is... l 3. Determine the axial distance based on the diffusion ratio. l 3 and the third radius R C The ratio y, wherein the ratio y is positively correlated with the diffusion ratio; Move the center of the third small circle a distance along the engine axis. l 3 = y × R C The axial position of the center of the small trailing edge circle is obtained; The center of the trailing edge small circle is set on the line connecting the center of the third small circle and the center of the trailing edge small circle, wherein the connecting line is parallel to the engine axis. The tail rim radius R is determined based on the minimum allowable wall thickness of the tail rim casting process. D ; Output the coordinates of the center of the small trailing edge circle and the corresponding trailing edge radius R. D .

9. The design method according to claim 3, characterized in that, Determine the tail section outline based on the required rear casing outlet airflow angle, including: Obtain the contraction degree of the trailing edge and set the symmetrical half-length of the outer contour line of the tail. l 4 and the trailing edge radius R D The relationship coefficient z is such that the relationship coefficient z is negatively correlated with the contraction of the trailing edge; Using the line connecting the centers of the third small circle and the tail edge small circle as the axis of symmetry, an arc segment is constructed and serves as the outer contour line of the tail. The center of the arc segment lies on the extension line of the third small circle passing through the axis of symmetry, and the axial distance from the point of tangency with the tail edge to the center of the third small circle is [missing information]. l 4, wherein the symmetrical half-length of the arc segment l 4= l 3+z × R D .

10. The design method according to claim 3, characterized in that, Based on the leading edge circle, the first small circle, the second small circle, and the third small circle, the leaf back side profile and the leaf base side profile are constructed, including: The blade back profile is composed of a back arc segment that passes through the corresponding points on the blade back side of the leading edge small circle, the first small circle and the second small circle in sequence, and a back straight line segment that is tangent to the second small circle and the third small circle and parallel to the engine axis. The blade basin side profile is composed of a basin arc segment that passes through the corresponding points on the blade basin side of the leading edge small circle, the first small circle and the second small circle in sequence, and a basin side straight line segment that is tangent to the second small circle and the third small circle and parallel to the engine axis. The corresponding point on the back of the leaf and the corresponding point on the leaf base are located on both sides of the same line connecting the centers of the leading edge circle, the first small circle, and the second small circle, respectively.

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