An S-shaped D-shaped deflecting vector nozzle with continuous centerline curvature and method

Abstract

A D-shaped deflected vector nozzle with continuous centerline curvature and method of the present invention belong to the technical field of aircraft; it includes a straight section of the nozzle and an S-bend section, which are smoothly connected; the outlet end of the S-bend section of the nozzle is successively connected with a D-shaped deflection section and a D-shaped outlet section, wherein the centerline curvatures of the straight section of the nozzle, the S-bend section and the D-shaped deflection section are continuous, and the surfaces of the three sections are smoothly first-order continuous; the D-shaped deflection section includes a deflection reserved section and a sliding section, and the sliding section is installed at the outlet end of the S-bend section of the nozzle through the deflection reserved section and can slide and expand along its centerline to realize the change of the vector deflection angle of the nozzle; the outlet of the sliding section is connected with the inlet of the D-shaped outlet section. By adopting the design of a D-shaped sliding cover for the S-bend nozzle, the present invention enables the S-bend nozzle to have the ability of large-angle vector actuation, and there is no problem of vector lag during large-angle vector actuation.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft, and particularly relates to an S-bend D-shaped deflected vector nozzle with continuous centerline curvature and a method thereof. Background Technique

[0002] With the urgent demand for short takeoff / vertical landing of carrier-based aircraft in maritime operations, the vector thrust nozzle, as a type of nozzle for aeroengines, helps to improve the vertical / short takeoff and maneuverability of fighter jets. Vector nozzles can be mainly divided into pneumatic vector nozzles and mechanical vector nozzles. Among them, the maximum deflection angle of pneumatic vector nozzles is limited, and it is difficult for the vector thrust deflection angle to reach 90°. Mechanical vector nozzles can be divided into binary vector, axisymmetric vector, three-bearing vector, D-shaped vector and other nozzle schemes. The deflection angles of binary vector and axisymmetric vector nozzles are limited and cannot achieve the effect of vertical deflection either. The three-bearing vector nozzle cannot provide lateral force / torque control in the conventional mode. The D-shaped nozzle can deflect the airflow vector angle up to 90°, but research shows that the vector deflection angle of the D-shaped nozzle designed abroad may lag behind the model deflection angle by about 20°.

[0003] The S-bend nozzle has a smoothly curved outlet channel shape, its layout is relatively compact, and at the same time, the offset from the engine outlet to the nozzle outlet can be adjusted. Since the curved pipe can effectively shield strong scattering / high-temperature components such as the internal turbine blades, struts, and mixers of the engine, it has good radar and infrared stealth performance. There has been some research on endowing the S-bend nozzle with thrust vector performance. In the prior art, a certain degree of thrust vector ability is achieved through mechanical adjustment of the outlet baffle. However, after deflection, the baffle forms a sharp corner with discontinuous curvature with the nozzle wall surface, resulting in a decrease in aerodynamic performance. At the same time, due to the limited deflection angle designed for the baffle, it is difficult to achieve a vector angle with an airflow deflection angle of 90°. Therefore, there is still a lack of a design method for an S-bend vector nozzle with a continuous centerline curvature of the nozzle structure. Summary of the Invention

[0004] Technical Problems to be Solved

[0005] In order to avoid the deficiencies of the prior art, the invention provides an S-bend D-shaped deflected vector nozzle with continuous centerline curvature. By introducing a high-order power function to control the change law of the centerline of the S-bend section, curvature matching is carried out with the circular arc centerline of the deflected section to achieve first-order continuity of the centerline. Make the upper side surface at the connection between the end section of the S-bend of the nozzle and the deflected section smooth and continuous, reduce the aerodynamic loss caused by discontinuous surface curvature, so as to achieve good aerodynamic performance of the vector nozzle. At the same time, a multi-section sliding cover is adopted to enable the vector deflection angle to reach 90°, and solve the problem of vector angle lag during large-angle deflection.

[0006] The technical solution of the present invention is: an S-shaped D-shaped deflection vector nozzle with continuous centerline curvature, including a nozzle straight section and an S-shaped section, which are smoothly connected; the outlet end of the S-shaped section of the nozzle is successively connected with a D-shaped deflection section and a D-shaped outlet section, wherein the centerline curvatures of the nozzle straight section, the S-shaped section, and the D-shaped deflection section are continuous, and the curved surfaces of the three sections are smoothly first-order continuous;

[0007] The D-shaped deflection section includes a deflection reserved section and a sliding section. The sliding section is installed at the outlet end of the S-shaped section of the nozzle through the deflection reserved section and can slide and expand along its centerline to realize the change of the vector deflection angle of the nozzle; the outlet of the sliding section is connected to the inlet of the D-shaped outlet section.

[0008] A further technical solution of the present invention is: the inlet of the S-shaped section of the nozzle is the outlet of the straight section, and the outlet is a D-shaped control section, which serves as the inlet of the D-shaped deflection section. The area of the nozzle in this section gradually converges along the flow direction of the working medium, and the centerline deflects upward according to the change law of the power function. The working medium of the engine increases in speed in this section and deflects upward along the centerline, and its deflection angle is equal to the angle of the reserved deflection section.

[0009] A further technical solution of the present invention is: the deflection reserved section is obtained by rotating the D-shaped control section at the outlet of the S-shaped section by θ angles around its bottom line segment as the axis.

[0010] A further technical solution of the present invention is: the sliding section includes multiple D-shaped sliding covers. The radial section of the D-shaped sliding cover is D-shaped, and its profile is obtained by rotating θ angles around its bottom line segment as the axis;

[0011] The bottoms of the multiple D-shaped sliding covers are successively coaxially hinged to the bottom of the deflection reserved section and can slide and retract around the hinge axis into the deflection reserved section or slide and expand into a 90-degree spherical surface.

[0012] A further technical solution of the present invention is: the cross-sectional shape of the D-shaped deflection section is a "D" shape with rounded corners, that is, the sharp corners with discontinuous curvatures on both sides of the semicircle of the main body are connected by arcs with continuous curvatures. The inverted arc is tangent to the semi-arc, and the inverted arc is also tangent to the semi-circle line segment.

[0013] A further technical solution of the present invention is: the reserved angle θ of the deflection reserved section is between 10° and 60°.

[0014] A further technical solution of the present invention is: the radial section of the D-shaped outlet section of the nozzle is D-shaped, and the cross-sectional area from the inlet to the outlet shows a converging change; or its cross-section first increases and then decreases to form a convergent-divergent vector nozzle.

[0015] A further technical solution of the present invention is that the fillet radius r of the D-shaped control section of the S-bend D-shaped deflecting vector nozzle and the semi-circular arc radius R satisfy r ≤ 0.5R. When r = 0.5R, this section is circular.

[0016] A further technical solution of the present invention is that the straight section of the nozzle is a cylindrical channel with a specified length and equal diameter. Its inlet is the outlet of the engine turbine, its diameter is the same as the diameter of the engine turbine outlet, its outlet is the inlet of the S-bend section, and the straight section of the nozzle can rotate around the end face of the turbine outlet. The engine working medium moves axially in this section.

[0017] A design method for an S-bend D-shaped deflecting vector nozzle with continuous centerline curvature is as follows:

[0018] Step 1: Determine the areas of the inlet section, D-shaped control section, and outlet section of the nozzle;

[0019] Step 2: Determine the semi-circle - fillet radius ratio A of the D-shaped control section r ;

[0020] Step 3: Calculate the semi-circular radius R and fillet radius r of the D-shaped control section;

[0021] Based on Step 1 and Step 2, the area S and radius ratio A of the D-shaped control section are determined r , and the semi-circular radius R and fillet radius r are obtained through numerical integration and iteration;

[0022] Step 4: Calculate the arc length and curvature distribution of the D-shaped control section;

[0023] The D-shaped control section is an axisymmetric structure, and both symmetric sides include a straight section, a chamfered arc section, and a semi-circular arc section; according to the Pythagorean theorem and the arc length formula, the following expressions can be obtained

[0024]

[0025] In the formula, R is the curvature radius of the semi-circular arc section, r is the curvature radius of the chamfered arc section, a0, a1, and a2 are the lengths of the straight section, chamfered arc section, and semi-circular arc section respectively, α is the angle between the radius line passing through the upper end point of the chamfered arc section and the straight section, and β is the central angle of the chamfered arc section;

[0026] The curvature k(s) expression of the D-shaped control section is obtained

[0027]

[0028] Step 5: Calculate the curvature and area of each cross-section along the S-bend section;

[0029] For the j-th section among the total j0 equally spaced intermediate sections of the nozzle, the cross-section area and curvature distribution are respectively expressed as

[0030] A j = A in + c1(j)[A out - A in

[0031] k j (s) = k in (s)+ c2(j)[k out (s)- k in (s)]

[0032] Wherein, A in and A out are the inlet and outlet areas respectively, and k in (s) and k out (s) are the curvature change laws of each point at the inlet and outlet sections respectively. c i (j) is the control law of the curve boundary condition;

[0033] Step Six: Calculate the control law of the center line of the S-bend section;

[0034]

[0035] Step Seven: Calculate the parameters of the deflection reserved section and the sliding hood;

[0036] The deflection reserved section is obtained by rotating the D-shaped control section at the outlet of the S-bend section by an angle θ around its bottom line segment, and the geometric shape of each sliding hood is obtained by rotating by an angle θ around its bottom line segment, but the sum of the angles of each sliding hood is restricted by the maximum rotation angle.

[0037] Advantageous Effects

[0038] The advantageous effects of the present invention are as follows: By designing the S-bend nozzle with a D-shaped sliding hood, the S-bend nozzle has the ability of large-angle vector actuation, and there is no problem of vector lag during large-angle vector actuation. As can be seen from Figure 5 , for the same preferred embodiment, under the condition of large-angle deflection, the vector lead angle of the nozzle under different pressure ratios is positive, indicating that there is no problem of vector lag. By introducing a high-order power function to control the change law of the center line of the S-bend section and matching the center line curvature of the end section of the S-bend of the nozzle with that of the D-shaped deflection section, the curvature of the center line of each section of the nozzle and the upper side surface of the nozzle is ensured to be continuous, so that the S-bend D-shaped nozzle has good aerodynamic performance. As can be seen from Figure 6 , for the same preferred embodiment, under the condition of small-angle deflection, due to the first-order continuity design of the curved surface, the pressure ratio of the nozzle is greater than 0.99 under a wide range of pressure ratios; under the condition of large-angle deflection, the aerodynamic performance with a thrust coefficient above 0.96 can also be achieved.

[0039] ​Preferably, the reserved angle ( Figure 3 denoted as θ in Figure 3 should be between 10° and 60°. When the reserved angle is too small, the number of D-shaped sliding hood segments is too large, which is not conducive to the control of the deflection angle. When the reserved angle is too large, the deflection angle of the S-bend is too large, resulting in poor aerodynamic performance or too large offset, making it impossible to be reasonably installed on the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 FIG. 1 is a schematic external view of the S-bend D-shaped vector nozzle of the present invention in the non-deflection state.

[0041] Figure 2 FIG. 2 is a schematic external view of the S-bend D-shaped vector nozzle of the present invention with a deflection angle of 90°.

[0042] Figure 3 FIG. 3 is a left view and a schematic diagram of the center line of the S-bend D-shaped vector nozzle of the present invention in the non-deflection state.

[0043] Figure 4 FIG. 4 is a schematic diagram of the geometric parameters of the D-shaped control section of the S-bend D-shaped vector nozzle of the present invention.

[0044] Figure 5 FIG. 5 is a graph showing the variation law of the vector lead angle of the S-bend D-shaped vector nozzle of the present invention at different deflection angles and different pressure ratios.

[0045] Figure 6 FIG. 6 is a graph showing the variation law of the thrust coefficient of the S-bend D-shaped vector nozzle of the present invention at different deflection angles and different pressure ratios.

[0046] Figure 7 FIG. 7 is a three-dimensional model diagram of a preferred embodiment of the S-bend D-shaped vector nozzle of the present invention before and after deflection.

[0047] Description of reference numerals: 1. straight section at the nozzle inlet, 11. center line of the straight section at the nozzle inlet, 2. S-bend section of the nozzle, 21. center line of the S-bend section of the nozzle, 3. reserved deflection section of the nozzle, 4. D-shaped sliding hood of the nozzle, 34. center line of the reserved deflection section and the sliding hood of the nozzle, 5. D-shaped outlet section of the nozzle, 51. center line of the D-shaped convergent section of the nozzle, 6. D-shaped control section of the nozzle, 61. straight section of the D-shaped control section, 62. rounded section of the D-shaped control section, 63. semi-circular arc section of the D-shaped control section. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0049] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0050] Referring to Figures 1-3 As shown, a D-shaped deflecting vector nozzle with continuous centerline curvature in this embodiment includes a straight section 1 of the nozzle and an S-bend section 2, which are smoothly connected; the outlet end of the S-bend section 2 of the nozzle is sequentially connected with a D-shaped deflecting section and a D-shaped outlet section 5, wherein the centerline curvatures of the straight section 1 of the nozzle, the S-bend section 2, and the D-shaped deflecting section are continuous, and the curved surfaces of the three sections are smoothly first-order continuous;

[0051] The D-shaped deflecting section includes a deflecting reserved section 3 and a sliding section. The sliding section is installed at the outlet end of the S-bend section 2 of the nozzle through the deflecting reserved section and can slide and expand along its centerline to realize the change of the vector deflection angle of the nozzle; the outlet of the sliding section is connected to the inlet of the D-shaped outlet section 5.

[0052] Furthermore, the straight section 1 of the nozzle is a cylindrical channel with a specified length and an unchanged diameter. Its inlet is the outlet of the engine turbine, and its diameter is the same as that of the engine turbine outlet. Its outlet is the inlet of the S-bend section. The straight section of the nozzle can rotate around the end face of the turbine outlet, and the engine working medium moves axially in this section.

[0053] Furthermore, the inlet of the S-bend section of the nozzle is the outlet of the straight section, and the outlet is the inlet of the D-shaped deflecting section. The area of the nozzle in this section gradually converges along the flow direction of the working medium, and the centerline deflects upward according to the variation law of the power function. The engine working medium increases in speed and deflects upward along the centerline in this section, and its deflection angle is equal to the angle of the reserved deflecting section.

[0054] Furthermore, the inlet of the D-shaped deflecting section of the nozzle is the outlet of the S-bend section, and the outlet is the inlet of the D-shaped outlet section. This section consists of a deflecting reserved section and multiple deflectable D-shaped sliding covers. The sliding covers can be retracted into the deflecting reserved section, so there may be a small gap between the sliding covers.

[0055] Furthermore, in the parametric design, the cross-sectional shapes of the deflecting reserved section and the D-shaped sliding cover are the same, both being D-shaped. The D-shaped sliding cover can be obtained by rotating and sweeping the D-shaped cross-section around the lower side rotation axis of the wall surface.

[0056] Furthermore, the reserved angle of the deflecting reserved section (Figure 3 The angle (denoted as θ in the figure) should be between 10° and 60°. When the reserved angle is too small, the number of D-shaped sliding hood segments is too large, which is not conducive to the control of the deflection angle. When the reserved angle is too large, the deflection angle of the S-bend is too large, resulting in poor aerodynamic performance or too large an offset, making it impossible to be reasonably installed on the aircraft.

[0057] Furthermore, the cross-sectional shape of the D-shaped deflection section is a "D" shape with rounded corners, that is, the sharp corners with discontinuous curvature on both sides of the semi-circular shape of the main body are connected by arcs with continuous curvature. The inverted arc is tangent to the semi-circular arc, and the inverted arc is also tangent to the semi-circular line segment.

[0058] Furthermore, the inlet of the D-shaped outlet section of the nozzle is the outlet of the S-bend section, and the outlet is the outlet of the S-bend D-shaped nozzle. The cross-sectional shape of this section is still a "D" shape, but the cross-sectional area can be changed according to the variation law according to the design requirements.

[0059] Furthermore, the radius r of the rounded corner of the D-shaped control section and the radius R of the semi-circular arc should satisfy the relationship r ≤ 0.5R. When r = 0.5R, the cross-section is circular, and when r > 0.5R, the cross-section cannot be described by geometric parameters.

[0060] A main design method for an S-bend D-shaped deflection vector nozzle with continuous centerline curvature includes the following steps:

[0061] Step 1: Determine the areas of the nozzle inlet section, D-shaped control section, and outlet section

[0062] Determine the nozzle inlet area according to the diameter of the engine turbine outlet end face, determine the area ratio between the inlet and outlet according to the design conditions of the nozzle, and then determine the area ratio between the D-shaped control section and the outlet section according to the convergence section angle constraint (such as the convergence angle is less than 12°). The areas of the nozzle inlet section, D-shaped control section, and outlet section have been determined.

[0063] Step 2: Determine the semi-circle-rounded corner radius ratio A of the D-shaped control section r

[0064] It can be determined according to the constraint that the radius r of the rounded corner of the D-shaped control section and the radius R of the semi-circular arc satisfy r ≤ 0.5R.

[0065] Step 3: Calculate the semi-circular radius R and rounded corner radius r of the D-shaped control section

[0066] According to Step 1 and Step 2, the area S and radius ratio A of the D-shaped control section are determined r , and the semi-circular radius R and rounded corner radius r are obtained through numerical integration and iteration.

[0067] Step 4: Calculate the arc length and curvature distribution of the D-shaped control section

[0068] According toFigure 4 It can be seen that the D-shaped control section is symmetric about the dashed axis of symmetry. Therefore, only the geometric parameters of the right half are calculated. The right arc is composed of a straight line segment 61, a chamfered arc 62, and a semi-circular arc 63. According to the Pythagorean theorem and the arc length formula, the following expressions can be obtained

[0069]

[0070] In the formula, R is the radius of curvature of the semi-circular arc 63, r is the radius of curvature of the chamfered arc 62, a0, a1, and a2 are the lengths of the 61, 62, and 63 segments respectively, and α and β are Figure 4 the angles formed by the dashed lines shown

[0071] Furthermore, it can be further deduced from the similarity criterion that

[0072]

[0073] Furthermore, by substituting α and β into Equation (3), the arc lengths of each segment can be obtained

[0074] Furthermore, the expression of the curvature k(s) of the D-shaped control section can be obtained

[0075]

[0076] Step 5: Calculate the curvature and area of each cross-section along the S-bend section

[0077] For the j-th cross-section among the j0 equally spaced intermediate cross-sections of the nozzle, the cross-sectional area and curvature distribution can be expressed as

[0078] A j = A in + c1(j)[A out - A in (4)

[0079] k j (s) = k in (s) + c2(j)[k out (s) - k in (s)] (5)

[0080] In the formula, A in , A out are the inlet and outlet areas respectively, k in (s), k out (s) are the curvature change laws of each point at the inlet and outlet cross-sections respectively. c i (j) can be one of the following control laws or other control laws that satisfy the curve boundary conditions not listed

[0081]

[0082] Step Six: Calculate the control law of the center line of the S-bend section

[0083] Consider that the center line of the L1 section satisfies the following relational expression

[0084]

[0085] Furthermore, construct the equation y = Ax γ (A≠0, γ>1) and substitute it into Equation (9) to obtain Therefore, the center line control equation is obtained

[0086]

[0087] Step Seven: Calculate the parameters of the deflection reserve section, the sliding hood, and the convergence section

[0088] The deflection reserve section is obtained by rotating the D-shaped control section at the outlet of the S-bend section by an angle θ around its bottom line segment, as Figure 4 shown. The geometric shape of each section of the sliding hood is also obtained by rotating by an angle θ around its bottom line segment, but the sum of the angles of each section of the sliding hood is restricted by the maximum rotation angle. The parameters of the convergence section are jointly determined by the area ratio and the length of the convergence section.

[0089] So far, the design of an S-bend D-shaped vector nozzle with continuous center line curvature is completed. After setting and calculating the above parameters, the three-dimensional models before and after deflection in a preferred embodiment are as Figure 7 shown.

[0090] The above embodiments are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. For example:

[0091] 1. In this example, the area of the convergence section decreases along the way. However, according to the design conditions and application ranges of the nozzle, the area of this section can also increase first and then decrease along the way to form a convergent-divergent vector nozzle;

[0092] 2. The main control section of the vector nozzle in this example is a D shape with rounded corners. However, when the control section of the nozzle is a geometric shape with rounded corners or other forms of continuous curvature, such as a triangle, a rectangle, or a trapezoid, a vector nozzle of this shape can also be generated according to the parametric design method in the present invention.

[0093] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principle and purpose of the present invention.

Claims

1. An S-bend D-shaped thrust vectoring nozzle with continuous centerline curvature, comprising a straight section of the nozzle and an S-bend section, which are smoothly connected; characterized in that: The outlet end of the S-bend section of the nozzle is successively connected with a D-shaped deflection section and a D-shaped outlet section, wherein the centerline curvatures of the straight section, the S-bend section, and the D-shaped deflection section of the nozzle are continuous, and the curved surfaces of the three sections are smooth and reach first-order continuity; The D-shaped deflection section includes a deflection reserved section and a sliding section. The sliding section is installed at the outlet end of the S-bend section of the nozzle through the deflection reserved section and can slide and expand along its centerline to realize the change of the vector deflection angle of the nozzle. The outlet of the sliding section is connected to the inlet of the D-shaped outlet section; The inlet of the S-bend section of the nozzle is the outlet of the straight section, and the outlet is a D-shaped control section, which serves as the inlet of the D-shaped deflection section. The area of the nozzle in this section gradually converges along the flow direction of the working medium, and the centerline deflects upward according to the variation law of the power function. The engine working medium increases in speed and deflects upward along the centerline in this section, and its deflection angle is equal to the angle of the reserved deflection section; The sliding section includes multiple D-shaped sliding covers. The radial cross-section of the D-shaped sliding cover is D-shaped, and its profile is obtained by rotating around the bottom line segment as the axis. The bottoms of the multiple D-shaped sliding covers are coaxially hinged to the bottom of the deflection reserved section in sequence, and can slide and retract into the deflection reserved section around the hinge axis, or slide and expand into a 90-degree spherical surface. The fillet radius of the D-shaped control section of the S-shaped D-shaped deflection vector nozzle and the semi-circular arc radius satisfy , when this section is circular.

2. The S-shaped D-shaped deflection vector nozzle with continuous centerline curvature according to claim 1, characterized in that: The deflection reserved section is obtained by rotating the D-shaped control section at the outlet of the S-shaped section around its bottom line segment as the axis. Angle acquisition.

3. The S-shaped D-shaped deflection vector nozzle with continuous centerline curvature according to claim 2, wherein: The reserved angle of the deflection reserved section is between 10° and 60°.

4. The S-shaped D-shaped deflection vector nozzle with continuous centerline curvature according to claim 1, characterized in that: The cross-sectional shape of the D-shaped deflection section is a "D" shape with rounded corners, that is, the sharp corners with discontinuous curvatures on both sides of the main body's semi-circle are connected by arcs with continuous curvatures. The inverted arc is tangent to the semi-arc, and the inverted arc is also tangent to the semi-circle segment.

5. The S-shaped D-shaped deflection vector nozzle with continuous centerline curvature according to claim 1, characterized in that: The radial cross-section of the D-shaped outlet section of the nozzle is D-shaped, and the cross-sectional area from the inlet to the outlet shows a converging change; or its cross-section first increases and then decreases to form a convergent-divergent vector nozzle.

6. The S-shaped D-shaped deflection vector nozzle with continuous centerline curvature according to claim 1, characterized in that: The straight section of the nozzle is a cylindrical channel with a specified length and equal diameter. Its inlet is the outlet of the engine turbine, and its diameter is the same as that of the engine turbine outlet. Its outlet is the inlet of the S-bend section. The straight section of the nozzle can rotate around the end face of the turbine outlet, and the engine working medium moves axially in this section.

7. A design method for an S-shaped D-shaped deflection vector nozzle with continuous centerline curvature according to any one of claims 1-6, characterized in that The specific steps are as follows: Step 1: Determine the areas of the inlet section, the D-shaped control section, and the outlet section of the nozzle; Step 2: Determine the semi-circle - fillet radius ratio of the D-shaped control section ; Step 3: Calculate the semi-circle radius R and the rounded corner radius r of the D-shaped control section; The area S and radius ratio of the D-shaped control section are determined according to Step 1 and Step 2 , and the semi-circle radius and fillet radius are obtained through numerical integration and iteration; Step 4: Calculate the arc length and curvature distribution of the D-shaped control section; The D-shaped control section is an axisymmetric structure, and both symmetric sides include a straight section, a chamfered arc section, and a semi-arc section. The following expressions can be obtained according to the Pythagorean theorem and the arc length formula In the formula, is the radius of curvature of the semi-circular arc segment, is the radius of curvature of the chamfered arc segment, , , are the lengths of the straight line segment, the chamfered arc segment, and the semi-circular arc segment respectively, is the angle between the radius line passing through the upper endpoint of the chamfered arc segment and the straight line segment, is the central angle of the chamfered arc segment; Obtain the curvature of the D-shaped control section Expression ； Step 5: Calculate the curvatures and areas of each cross-section along the S-bend section; For the nozzle with a total of equidistant intermediate cross-sections, for the th cross-section, the cross-sectional area and curvature distribution are respectively expressed as In the formula, and are the inlet and outlet areas respectively, and are the curvature change laws of each point at the inlet and outlet cross-sections respectively; is the control law of the curve boundary condition; Step 6: Calculate the centerline control law of the S-bend section; ； Step 7: Calculate the parameters of the deflection reserved section and the sliding cover; The deflection reserved section is obtained by rotating the D-shaped control section at the outlet of the S-bend section around its bottom line segment by an angle. The geometric shape of each sliding cover is obtained by rotating by an angle, but the sum of the angles of each sliding cover is restricted by the maximum rotation angle.

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