Variable-camber stator vane with shaft offset and slot inclination and its design method

Abstract

The present application provides a variable camber stator blade with shaft offset and gap inclination and its design method, belonging to the technical field of gas turbine engines. It includes a front-section blade, a rear-section blade and a blade shank. The rear-section blade and the blade shank are integrally formed. The center of the blade shank is located at the edge of the front end of the pressure surface side of the rear-section blade. The trailing edge of the front-section blade is set as a concave arc curve, and the leading edge of the rear-section blade is set as a convex arc curve. The concave arc curve and the convex arc curve are respectively arcs on the same concentric circle, and the blade shank and the center of the concentric circle are located at the same position. The axial length of the suction surface of the front-section blade is greater than the axial length of the pressure surface of the front-section blade, so that the concentric circle gap formed between the trailing edge of the front-section blade and the leading edge of the rear-section blade is inclined relative to the suction surface; and preloading is performed on the suction surface of the tail of the front-section blade. The solution of the present application reduces the airflow loss at large adjustment angles and improves the total pressure recovery coefficient of the variable camber stator.

Description

Technical Field

[0001] The present application relates to the technical field of gas turbine engines, and particularly relates to a variable camber stator blade with a shaft offset and a gap inclination and a design method thereof. Background Art

[0002] The next-generation variable cycle engine has put forward the requirement of an ultra-wide flow rate / pressure ratio adjustment range for the fan, that is, it is required that the fan can achieve different pressure ratio adjustments under the same flow rate condition, or different flow rate adjustments under the same pressure ratio condition. For a traditional fan, its characteristic curve is fixed at a fixed rotational speed, and the high-efficiency region formed at different rotational speeds is also very narrow, which far cannot meet the requirements of the variable cycle engine for a wide flow rate and a wide pressure ratio adjustment range.

[0003] The adjustable blade changes the flow direction of the rotor incoming flow and optimizes the intake angle, so as to expand the working range of the fan. The variable camber stator is a kind of adjustable blade. The conventional variable camber stator is divided into two sections. The front section remains fixed, and the rear section changes the air flow direction by rotating around the axis. Refer to Figure 1 .

[0004] Considering factors such as the cumulative error of the machining and assembly dimension chain, there must be a certain gap between the front and rear section blades of the variable camber stator. Due to the geometric discontinuity and the air flow leakage at the gap position, the total pressure recovery coefficient of the variable camber stator is reduced. Especially at a large adjustment angle, the geometric discontinuity and leakage between the front and rear section blades increase sharply, resulting in the degradation of the performance of the engine, such as the fuel consumption rate and the thrust. Summary of the Invention

[0005] In view of this, the embodiments of the present application provide a variable camber stator blade with a shaft offset and a gap inclination and a design method thereof, which at least partially solve the problem that when the variable camber stator is at a large adjustment angle in the prior art, due to the sharp increase in the geometric discontinuity and leakage between the front and rear section blades, the performance of the engine, such as the fuel consumption rate and the thrust, degrades.

[0006] In a first aspect, an embodiment of the present application provides a variable-camber stator vane with shaft offset and gap inclination, including a front-section vane, a rear-section vane, and a blade shank. The rear-section vane and the blade shank are integrally formed. The upper surfaces of the front-section vane and the rear-section vane are suction surfaces, and the lower surfaces of the front-section vane and the rear-section vane are pressure surfaces. The center of the blade shank is located at the edge of the front end of the rear-section vane on the pressure surface side. The trailing edge of the front-section vane is set as a concave arc curve, and the leading edge of the rear-section vane is set as a convex arc curve. The concave arc curve and the convex arc curve are respectively arcs on the same concentric circle, and the center of the blade shank and the center of the concentric circle are located at the same position; the axial length of the suction surface of the front-section vane is greater than the axial length of the pressure surface of the front-section vane, so that the concentric circle gap formed between the trailing edge of the front-section vane and the leading edge of the rear-section vane is inclined relative to the suction surface; preloading is performed on the suction surface at the tail of the front-section vane, so that the geometric profile of the suction surface at the tail of the front-section vane is deflected in advance.

[0007] According to a specific implementation manner of the embodiment of the present application, the deviation between the center of the blade shank and the edge of the front end of the rear-section vane on the pressure surface side is set to ±0.5 mm.

[0008] According to a specific implementation manner of the embodiment of the present application, the radius of the blade shank is set to 3 - 6 mm.

[0009] According to a specific implementation manner of the embodiment of the present application, the deflection angle range of the geometric profile of the suction surface at the tail of the front-section vane is set to 5° - 10°.

[0010] In a second aspect, an embodiment of the present application further provides a design method for a variable-camber stator vane with shaft offset and gap inclination as described in any one of the embodiments of the first aspect. The method includes:

[0011] According to the proportion of the axial length of the pressure surface of the front-section vane in the axial length of the entire vane, the front-section vane and the rear-section vane are segmented, and the segmentation point s is determined;

[0012] According to the segmentation point s, the angle alfi at the segmentation point s, and the radius Rf of the concave arc curve at the trailing edge of the front-section vane, the center point c of the concentric circle is determined. The angle alfi is the included angle between the air inlet side of the concentric circle gap and the x-axis;

[0013] According to the radius Rf of the concave arc curve at the trailing edge of the front-section vane and the width of the concentric circle gap, the radius Rb of the convex arc curve and the radius Rc of the middle arc of the concentric circle gap are determined. According to the radius Rf, the radius Rb, the radius Rc, and the center point c, the construction of the concentric circle of the front-section vane profile, the concentric circle of the rear-section vane profile, and the blade shank is completed;

[0014] According to the concentric circle gap outlet side angle alfo and the center point c, truncate the front-stage blade type concentric circles and the rear-stage blade type concentric circles, and at the truncation points, use tangent lines to intersect with the blade suction surface to obtain the complete front-stage blades, rear-stage blades and the concentric circle gap arranged obliquely;

[0015] Rotate the rear-stage blades to obtain the suction surface fitting line;

[0016] According to the suction surface fitting line, obtain the angle distribution curve of the suction surface fitting line and the x-axis;

[0017] Smooth the non-smooth area of the angle distribution curve to obtain the smoothed angle distribution curve;

[0018] According to the smoothed angle distribution curve, obtain the suction surface profile with preloading at the tail suction surface of the front-stage blades.

[0019] According to a specific implementation manner of the embodiment of the present application, the obtaining the suction surface profile with preloading at the tail suction surface of the front-stage blades according to the smoothed angle distribution curve includes:

[0020] Use the integral formula for the smoothed angle distribution curve to calculate the suction surface profile of the front-stage blades to obtain the suction surface profile of the front-stage blades;

[0021] Use the front-stage blade type concentric circles to cut the suction surface profile of the front-stage blades to obtain the suction surface profile with preloading at the tail suction surface of the front-stage blades.

[0022] According to a specific implementation manner of the embodiment of the present application, the integral formula is:

[0023] ,

[0024] where x a ≤x g ≤x e , x b =x e ; x a is the abscissa of the starting point a of the suction surface profile fitting of the front-stage blades, y a is the ordinate of the starting point a of the suction surface profile fitting of the front-stage blades, x g is the abscissa of any point on the suction surface of the front-stage blades, y g is the ordinate of any point on the suction surface of the front-stage blades, beta is the angle between the suction surface fitting line on the smoothed angle distribution curve and the x-axis, x e is the abscissa of the end point e of the suction surface profile of the front-stage blades before preloading, x b is the abscissa of the end point b of the suction surface profile of the front-stage blades after preloading.

[0025] According to a specific implementation manner of an embodiment of the present application, the value of the concentric circle gap outlet side angle alfo is less than 15°.

[0026] According to a specific implementation manner of an embodiment of the present application, the proportion range of the axial length of the front blade pressure surface in the axial length of the entire blade is 0.3 - 0.5.

[0027] According to a specific implementation manner of an embodiment of the present application, the range of the angle alfi at the splitting point s is 80° - 90°.

[0028] Beneficial effects:

[0029] The variable-camber stator blade with a shaft offset and a gap inclination and its design method in the embodiment of the present application, by means of a variable-camber stator rotation shaft offset, a preloading at the tail of the front blade suction surface, and a concentric circle inclined gap, maintain the size of the gap between the front and rear blades unchanged during blade adjustment, leaving a margin for errors such as machining and assembly dimension chain accumulation. While ensuring the structural feasibility, it greatly reduces the airflow loss under a large adjustment angle and improves the total pressure recovery coefficient of the variable-camber stator. Description of the drawings

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 Structural schematic diagram of a variable-camber stator blade of the prior art;

[0032] Figure 2 Structural schematic diagram of a variable-camber stator blade according to an embodiment of the present invention;

[0033] Figure 3 Schematic diagram of a variable-camber stator blade after rotation according to an embodiment of the present invention;

[0034] Figure 4 Schematic diagram for confirming the splitting point according to an embodiment of the present invention;

[0035] Figure 5 Schematic diagram for constructing concentric circles of front and rear blades according to an embodiment of the present invention;

[0036] Figure 6 Schematic diagram for constructing a concentric circle gap according to an embodiment of the present invention;

[0037] Figure 7Schematic diagram of fitting the suction surface profile after rotation of variable camber stator blades according to an embodiment of the present invention;

[0038] Figure 8 Schematic diagram of the angle distribution between the suction surface of variable camber stator blades and the horizontal direction according to an embodiment of the present invention;

[0039] Figure 9 Schematic diagram of the suction surface profile distribution formed after integration according to an embodiment of the present invention;

[0040] Figure 10 Schematic diagram of the trimmed suction surface profile according to an embodiment of the present invention;

[0041] Figure 11 Schematic diagram of the angle distribution between the suction surface of another variable camber stator blade and the horizontal direction according to an embodiment of the present invention;

[0042] Figure 12 Comparison diagram of the flow field calculation results when the rear-stage blades are in the non-adjusted state of variable camber stator blades according to an embodiment of the present invention. (a) is the flow field calculation result of using the blades of the prior art, and (b) is the flow field calculation result of using the blades of the present application;

[0043] Figure 13 Comparison diagram of the flow field calculation results when the rear-stage blades are adjusted by 38° according to an embodiment of the present invention. (a) is the flow field calculation result of using the blades of the prior art, and (b) is the flow field calculation result of using the blades of the present application;

[0044] Figure 14 Diagram of the gap between the front and rear stage blades of variable camber stator blades according to an embodiment of the present invention. (a) shows the rear-stage blade adjustment angle of 0°, and (b) shows the rear-stage blade adjustment angle of 38°.

[0045] Figure 15 Comparison diagram of the intersection angle between the midline of the gap and the suction surface profile when the rear-stage blades are adjusted by 38°. (a) shows the use of the blades of the prior art, and (b) shows the use of the blades of the present application.

[0046] In the figure: 101, front-stage blade; 102, rear-stage blade; 103, blade root; A, trailing edge of the front-stage blade; B, suction surface at the tail of the front-stage blade; C, leading edge of the rear-stage blade. Detailed implementation mode

[0047] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0048] The following describes the embodiments of the present application through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all embodiments. The present application can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0049] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present application, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. Additionally, this device and / or this method can be implemented using other structures and / or functionality in addition to one or more of the aspects described herein.

[0050] It also needs to be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. The diagrams only show the components related to the present application, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and proportion of each component in its actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0051] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0052] In a first aspect, referring to Figure 2 and Figure 3, an embodiment of the present application provides a variable-camber stator vane with shaft offset and gap inclination, including a front-section vane 101, a rear-section vane 102, and a blade shank 103. The rear-section vane 102 and the blade shank 103 are integrally formed. The upper surfaces of the front-section vane 101 and the rear-section vane 102 are suction surfaces, and the lower surfaces of the front-section vane 101 and the rear-section vane 102 are pressure surfaces. The center of the blade shank 103 is located at the edge of the front end pressure surface side of the rear-section vane. The trailing edge A of the front-section vane is set as a concave circular arc curve, and the leading edge (C) of the rear-section vane is set as a convex circular arc curve. The concave circular arc curve and the convex circular arc curve are respectively arcs on the same concentric circle, and the center of the blade shank 103 and the center of the concentric circle are located at the same position; the axial length of the suction surface of the front-section vane is greater than the axial length of the pressure surface of the front-section vane, so that the concentric circle gap formed between the trailing edge A of the front-section vane and the leading edge (C) of the rear-section vane is inclined relative to the suction surface; preloading is performed on the trailing suction surface B of the front-section vane, so that the geometric profile of the trailing suction surface B of the front-section vane deflects in advance.

[0053] In this embodiment, by means of variable-camber stator rotation shaft offset, preloading of the trailing suction surface of the front-section vane, and concentric circle inclined gap, the airflow loss at a large adjustment angle is greatly reduced, and the total pressure recovery coefficient of the variable-camber stator is improved. Specifically, by adjusting the position of the blade shank 103, the rotation shaft of the variable-camber stator is offset from the inside of the vane to the outside of the vane, increasing the smoothness of the first derivative of the geometric profiles of the suction surfaces of the front and rear sections of the vane after the rear-section vane 102 rotates (representing the angle between the suction surface and the axis); through preloading of the trailing part of the front-section vane (the geometric profile at position B deflects in advance), the smoothness of the first derivative of the geometric profiles of the suction surfaces of the front and rear sections of the vane after the rear-section vane 102 rotates is further increased; the gap between the front and rear sections of the vane is a concentric circle, and the angle at which the center line of the gap (the central arc of the gap) intersects the suction surface profile is greatly reduced, that is, the concentric circle gap is inclined relative to the suction surface, which also increases the smoothness of the first derivative of the geometric profiles of the suction surfaces of the front and rear sections of the vane after the rear-section vane 102 rotates, thereby reducing the airflow loss at a large adjustment angle and improving the total pressure recovery coefficient of the variable-camber stator.

[0054] In one embodiment, the deviation between the center of the blade shank 103 and the edge of the front end pressure surface side of the rear-section vane is set to ±0.5 mm.

[0055] In one embodiment, the radius of the blade shank 103 is set to 3 - 6 mm.

[0056] In one embodiment, the deflection angle range of the geometric profile of the trailing suction surface B of the front-section vane is set to 5° - 10°.

[0057] Second aspect, embodiments of the present application further provide a design method for a variable camber stator vane with shaft offset and gap inclination as described in any embodiment of the first aspect. The method includes:

[0058] Step 1: Divide the front-section blade 101 and the rear-section blade 102 according to the ratio of the axial length of the pressure surface of the front-section blade to the axial length of the entire blade, and determine the division point s. The coordinates of the division point s are (x s , y s ), and the division of the front and rear-section blades 102 is completed. Among them, the axial length of the pressure surface of the front-section blade is L1, and the axial length of the entire blade is L2, then the ratio a1 = L1 / L2. Refer to Figure 4 ;

[0059] Step 2: Determine the center point c of the concentric circles according to the division point s, the angle alfi at the division point s, and the radius Rf of the concave circular arc curve of the trailing edge A of the front-section blade. The angle alfi is the included angle between the air inlet side of the concentric circle gap and the x-axis. Refer to Figure 5 , and the coordinates of point c are (x c , y c ), where:

[0060] x c = x s + Rf * sin(alfi),

[0061] y c = y s - Rf * cos(alfi);

[0062] Step 3: Determine the radius Rb of the convex circular arc curve and the radius Rc of the middle arc line of the concentric circle gap according to the radius Rf of the concave circular arc curve of the trailing edge A of the front-section blade and the width of the concentric circle gap. Complete the construction of the front-section blade concentric circle, the rear-section blade concentric circle, and the blade handle 103 according to the radius Rf, the radius Rb, the radius Rc, and the center point c. Among them, Rf = Rb + 0.8, Rc = (Rf + Rb) * 0.5. In this embodiment, the width of the concentric circle gap is set to 0.8 mm;

[0063] Step 4: Truncate the front-section blade concentric circle and the rear-section blade concentric circle according to the air outlet side angle alfo of the concentric circle gap and the center point c, and make them intersect with the suction surface of the blade at the truncation point with a tangent line to obtain the complete front-section blade 101, the rear-section blade 102, and the inclined concentric circle gap. Refer to Figure 6 ;

[0064] Step 5: Rotate the rear-section blade 102 to obtain the suction surface fitting line L1. Specifically, refer to Figure 7, with the concentric circle center point c as the rotation axis, rotate the rear-stage blade 102 according to the use angle alf (the value of alf is generally 15° - 45°. If this variable-camber stator is used in the rear fan of a variable cycle engine, the alf angle value is 40°), and fit the suction surface. Analyze the distribution of the angle beta between the suction surface fitting line L1 and the x-axis. The definition of beta is as follows: beta = atan(dy / dx), where x and y are the coordinate values of the points on the suction surface fitting line;

[0065] Step 6: Obtain the angle distribution curve between the suction surface fitting line L1 and the x-axis according to the suction surface fitting line L1;

[0066] Step 7: Smooth the non-smooth area of the angle distribution curve to obtain the smoothed angle distribution curve. Refer to Figure 8 , in the figure, the angle distribution curve before preloading is the angle distribution curve between the suction surface fitting line L1 and the x-axis, and the given suction surface angle distribution curve after preloading is the smoothed angle distribution curve;

[0067] Step 8: Obtain the suction surface profile with preloading for the suction surface B at the tail of the front-stage blade according to the smoothed angle distribution curve.

[0068] Further, the obtaining of the suction surface profile with preloading for the suction surface B at the tail of the front-stage blade according to the smoothed angle distribution curve includes:

[0069] Calculate the suction surface profile of the front-stage blade using the integral formula for the smoothed angle distribution curve to obtain the suction surface profile of the front-stage blade. Refer to the ab curve in Figure 9 . The ab curve is the profile obtained by integration after preloading, and the ae curve is the profile before preloading (i.e., the profile before smoothing);

[0070] Use the concentric circles of the front-stage blade profile to cut the suction surface profile of the front-stage blade to obtain the suction surface profile with preloading for the suction surface B at the tail of the front-stage blade. Refer to Figure 10 .

[0071] Further, the integral formula is:

[0072] ,

[0073] In the formula, x a ≤ x g ≤ x e , x b = x e ; x a is the abscissa of the starting point a of the suction surface profile fitting of the front-stage blade, y a is the ordinate of the starting point a of the suction surface profile fitting of the front-stage blade, x gis the abscissa of any point on the suction surface of the front-stage blade, y g is the ordinate of any point on the suction surface of the front-stage blade, beta is the angle between the suction surface fitting line on the angle distribution fairing curve and the x-axis, x e is the abscissa of the end point e of the suction surface profile of the front-stage blade before preloading, x b is the abscissa of the end point b of the suction surface profile of the front-stage blade after preloading.

[0074] Furthermore, the value of the concentric circle gap outlet side angle alfo is less than 15°. In this embodiment, the concentric circle gap outlet side angle is limited, which can reduce the loss after the outlet gap air flow is mixed with the mainstream.

[0075] Furthermore, the axial length of the pressure surface of the front-stage blade ranges from 0.3 to 0.5 of the axial length of the entire blade.

[0076] Furthermore, the range of the angle alfi at the splitting point s is 80° - 90°.

[0077] Next, the suction surfaces after rotation of the variable camber stator blade of the prior art and the new variable camber stator blade in the embodiment of the present application are respectively fitted, and the angle distribution between the fitted suction surface and the axis is analyzed. The results are as Figure 11 shown. When the axial relative position ranges from 0.288 to 0.379, the angle change of the suction surface of the variable camber stator blade of the prior art is 42.7°, and the angle change of the new variable camber stator blade of the present application is 22.0°. When the axial relative position of the variable camber stator blade of the present application ranges from 0.288 to 0.379, the angle change is reduced by 48.5%. Therefore, the data shows that for the variable camber stator blade of the present application, after the rotation adjustment of the rear-stage blade 102, the smoothness of the first-order derivative of the geometric profile of the suction surfaces of the front and rear-stage blades (representing the angle between the suction surface and the axis) is greatly improved.

[0078] Furthermore, the starting performance is analyzed. When in the non-adjustment state of 0°, the total pressure recovery coefficients of the new variable camber stator blade of the present application and the variable camber stator blade of the prior art are both 0.9967. When the adjustment angle is 38°, the total pressure recovery coefficient of the new variable camber stator blade of the present application is 3.9% higher than that of the variable camber stator blade of the prior art. The detailed results are shown in Table 1. This is because the angle change of the variable camber stator blade of the present application from 0.288 to 0.379 in the axial direction is reduced by 48.5%, eliminating the separation of the air flow in this area. The calculation results are shown in Figure 12 and Figure 13 .

[0079] Table 1 Comparison of Aerodynamic Calculation Results

[0080]

[0081] In addition, the inclined concentric circle gaps of the present application ensure that the gap size between the front and rear blades remains unchanged during adjustment, leaving a margin for errors such as machining and assembly dimension chain accumulation, and ensuring the feasibility of the structure (as Figure 14 shown). After the concentric circle gaps are inclined, the included angle at the intersection of the midline of the gap and the suction surface profile decreases by 26°, reducing the included angle between the leakage flow and the mainstream (as Figure 15 shown), and weakening the loss of the leakage flow.

[0082] In the embodiment provided by the present invention, (1) by adjusting the position of the blade stalk 103, the rotation axis of the variable camber stator is offset from the inside of the blade to the outside of the blade, increasing the smoothness of the first-order derivative of the geometric profile of the suction surfaces of the front and rear blades after the rear blade 102 rotates (representing the included angle between the suction surface and the axial direction);

[0083] (2) By preloading the tail of the front blade, the smoothness of the first-order derivative of the geometric profile of the suction surfaces of the front and rear blades after the rear blade 102 rotates is further increased;

[0084] (3) The gaps between the front and rear blades are concentric circles, and the included angle between the outlet of the midline of the gap and the suction surface profile is greatly inclined;

[0085] Through the structural settings in the above three forms, the gap size between the front and rear blades is maintained unchanged during blade adjustment, leaving a margin for errors such as machining and assembly dimension chain accumulation. While ensuring the structural feasibility, the air flow loss under a large adjustment angle is greatly reduced, and the total pressure recovery coefficient of the variable camber stator is improved.

[0086] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A variable-camber stator blade with an offset shaft and inclined gap, characterized in that: The invention comprises a front blade (101), a rear blade (102) and a petiole (103), wherein the rear blade (102) and the petiole (103) are integrally formed, the upper surfaces of the front blade (101) and the rear blade (102) are suction surfaces, the lower surfaces of the front blade (101) and the rear blade (102) are pressure surfaces, the center of the petiole (103) is located at the edge of the pressure surface side of the front end of the rear blade, the trailing edge (A) of the front blade is set to be an inwardly concave arc curve, and the leading edge (C) of the rear blade is set to be an outwardly convex arc curve. The concave arc curve and the convex arc curve are arcs on concentric circles, respectively, and the center of the petiole (103) and the center of the concentric circle are located at the same position; the axial length of the suction surface of the front blade is greater than the axial length of the pressure surface of the front blade, so that the concentric circle gap formed between the trailing edge (A) of the front blade and the leading edge (C) of the rear blade is inclined relative to the suction surface; and the suction surface (B) at the rear of the front blade is preloaded so that the geometric profile of the suction surface (B) at the rear of the front blade is deflected in advance.

2. The variable camber stator blade with shaft offset and slot inclination according to claim 1, characterized in that: The deviation between the center of the petiole (103) and the edge on the pressure surface side of the front end of the rear blade is set to ±0.5 mm.

3. The variable camber stator blade with shaft offset and slot inclination according to claim 1, characterized in that: The radius of the petiole (103) is set to 3-6 mm.

4. The variable camber stator blade with shaft offset and slot inclination according to claim 1, characterized in that: The angle range of the geometric profile deflection of the suction surface (B) at the tail of the front blade is set to 5°-10°.

5. A design method for a variable-camber stator blade with a shaft offset and a slot tilt as claimed in any one of claims 1 to 4, characterized in that: The method comprises: The front blade (101) and the rear blade (102) are segmented according to the proportion of the axial length of the pressure surface of the front blade to the axial length of the entire blade, and a segmentation point s is determined; The center point c of the concentric circle is determined according to the segmentation point s, the angle alfi at the segmentation point s, and the radius Rf of the concave arc curve of the trailing edge (A) of the front blade. The angle alfi is the angle between the air inlet side of the concentric circle gap and the x-axis. According to the radius Rf of the concave arc curve of the trailing edge (A) of the front blade and the width of the concentric circle gap, the radius Rb of the convex arc curve and the radius Rc of the middle arc line of the concentric circle gap are determined, and according to the radius Rf, the radius Rb, the radius Rc and the center point c, the front blade concentric circle, the rear blade concentric circle and the petiole (103) are constructed; According to the air outlet angle alfo of the concentric circle gap and the center point c, the front blade concentric circle and the rear blade concentric circle are cut off, and a tangent straight line is used to intersect the suction surface of the blade at the cutoff point to obtain a complete front blade (101), a rear blade (102) and an inclined concentric circle gap; Rotating the rear blade (102) to obtain a suction surface fitting line; According to the suction surface fitting line, a distribution curve of the angle between the suction surface fitting line and the x-axis is obtained; The non-smooth area of ​​the angle distribution curve is smoothed to obtain the angle distribution smooth curve; According to the angle distribution smoothing curve, the suction surface profile (B) of the tail of the front blade with preload is obtained.

6. The design method according to claim 5, characterized in that: The method of obtaining the suction surface profile of the tail of the front blade (B) with a preload according to the angle distribution smoothing curve includes: The angle distribution smoothing curve is used to calculate the suction surface profile of the front blade using an integral formula to obtain the suction surface profile of the front blade; The suction surface profile of the front blade is cut using the concentric circle of the front blade profile to obtain the suction surface profile of the tail of the front blade (B) with preload.

7. The design method according to claim 6, characterized in that: The integral formula is: ， In the formula, x a ≤x g ≤x e , x b =x e ;x a is the horizontal coordinate of the starting point a of the front blade suction surface profile fitting, y a is the ordinate of the starting point a of the front blade suction surface profile fitting, x g is the horizontal coordinate of any point on the suction surface of the front blade, y g is the ordinate of any point on the suction surface of the front blade, beta is the angle between the suction surface fitting line on the angle distribution smoothing curve and the x-axis, x e is the abscissa of the end point e of the suction surface profile of the front blade before preloading, x b It is the abscissa of the end point b of the suction surface profile of the front blade after preloading.

8. The design method according to claim 5, characterized in that: The value of the concentric circle gap air outlet side angle alfo is less than 15°.

9. The design method according to claim 5, characterized in that: The axial length of the pressure surface of the front blade accounts for 0.3-0.5 of the axial length of the entire blade.

10. The design method according to claim 5, characterized in that: The angle alfi at the dividing point s ranges from 80° to 90°.

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