Parametric design method and device for aircraft engine nozzle

Abstract

The application discloses an aircraft engine nozzle parameter design method and device, and the method comprises the following steps: designing a circular inlet section and a peanut-shaped outlet section of an aircraft engine nozzle; determining the coordinates of each discrete node on the inlet section and the outlet section; calculating the geometric profile of each cross section of the main pipeline of the aircraft engine nozzle based on the curvature of each discrete node on the inlet section and the outlet section, a preset cross section curvature change expression and constraint conditions; correcting the geometric profile of each cross section to obtain the geometric profile of each cross section after correction; determining a target transition curve by using a preset transition curve equation and the area change law of each cross section; calculating the fourth area of each cross section and adjusting each cross section; designing a center line offset; and establishing a cylinder based on the center coordinates of the inlet section, a preset radius and a stretching length to generate the aircraft engine nozzle after the center line is penetrated, so that the consumption of human resources can be saved and the design efficiency can be improved.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and in particular to a method and apparatus for parametric design of aircraft engine nozzles. Background Technology

[0002] With the rapid development of various aerospace vehicles, fighter jets, rockets, and other aircraft, propulsion equipment has begun to face new development goals and higher requirements, demanding both lightweight and low power consumption, as well as high efficiency and large thrust. In the aerospace industry, parametric design technology has inherent advantages in improving the design cycle timeliness and flexibility of aircraft, thus its application areas are very wide.

[0003] Engine nozzle design is a crucial aspect of aircraft design. Parametric design of engine nozzles can significantly improve an aircraft's maneuverability, stability, and stealth capabilities, particularly in the design of hypersonic vehicles and unmanned aerial vehicles (UAVs). Globally, researchers widely employ parametric design strategies, precisely controlling key geometric properties of the nozzle—such as length, diameter, and expansion angle. The design principles are primarily based on fluid dynamics and aerodynamics, using the shape and size of the tail nozzle to regulate and optimize propellant airflow.

[0004] However, existing engine nozzle designs require a significant amount of human resources and time. Therefore, there is an urgent need for those skilled in the art to provide an efficient engine nozzle design that saves on human resources. Summary of the Invention

[0005] The purpose of this invention is to provide a parametric design method and apparatus for aircraft engine nozzles, which can solve the above-mentioned problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a parametric design method for aircraft engine nozzles, comprising:

[0008] Design the circular inlet cross section and the cashew-shaped outlet cross section of the aircraft engine nozzle, and discretize each node on the circular inlet cross section and the cashew-shaped outlet cross section;

[0009] Determine the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section;

[0010] Based on the curvature of each discrete node on the inlet section, the curvature of each discrete node on the cashew-shaped outlet section, and the preset expression for the curvature change of the friction section, the geometric profile of each friction section of the main duct of the aircraft engine nozzle is calculated according to the constraint conditions.

[0011] The calculated geometric profiles of each friction section are corrected to obtain the corrected geometric profiles of each friction section.

[0012] The target transition curve is determined by using a preset transition curve equation and the variation law of the area of ​​each cross section along the flow path; wherein, the target transition curve includes: a first fifth-order polynomial characterizing the first transition curvature from the inlet cross section to the intermediate cross section, and a second fifth-order polynomial characterizing the second transition curvature from the intermediate cross section to the cashew-shaped outlet cross section;

[0013] Based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section, calculate the fourth area of ​​each friction section;

[0014] The fourth area of ​​each friction section is adjusted using preset rules to determine each friction section after area adjustment;

[0015] The centerline is designed to be offset so that the inlet section, each of the friction sections and the outlet section transition smoothly and continuously along the centerline.

[0016] A cylinder is constructed based on the center coordinates of the inlet section, the preset radius, and the stretching length, and an aircraft engine nozzle is generated after the center tube is inserted.

[0017] Optionally, the steps of designing the circular inlet cross-section and cashew-shaped outlet cross-section of the aircraft engine nozzle, and discretizing the nodes on the inlet cross-section and the cashew-shaped outlet cross-section, include:

[0018] Determine the variable and unknown parameters of the cashew nut-shaped cross-section;

[0019] A set of equations for the shape parameters of the cashew-shaped cross section is constructed based on the aforementioned variable and unknown parameters; wherein, the set of equations for the shape parameters of the cashew-shaped cross section is a nonlinear set of equations.

[0020] The Newton-Raphson iteration method was used to calculate the system of equations for the shape parameters of the cashew-shaped cross-section, and the unknown parameters and variable parameters were obtained by solving the equations.

[0021] Based on the position parameters and variable parameters, an inlet cross section and a cashew-shaped outlet cross section are generated, and each node on the inlet cross section and the cashew-shaped outlet cross section is discretized.

[0022] Optionally, the step of determining the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section includes:

[0023] For the inlet cross section, the circumference of the inlet cross section is divided into N parts, and the angle between each arc segment and the positive horizontal axis is calculated.

[0024] For each arc segment, the chord length of the arc segment is determined based on the included angle corresponding to the arc segment and the radius of the circumference of the inlet section.

[0025] For each arc segment, the dimensionless arc length corresponding to the discrete node is determined based on the chord length of the arc segment, and the coordinates of the discrete node are determined based on the dimensionless arc length.

[0026] For the cashew-shaped outlet cross section, determine the straight segments and arc segments with different curvatures included on the cashew-shaped outlet cross section;

[0027] The curvature of each discrete point on the straight line segment is determined to be 0. For arc segments with different curvatures, the corresponding curvature calculation formula is matched according to the type of each arc segment.

[0028] Based on the curvature and arc length corresponding to each discrete point in the cashew-shaped outlet section, the coordinates of each discrete node in the cashew-shaped outlet section are determined.

[0029] Optionally, the step of correcting the calculated geometric profiles of each friction section to obtain the corrected geometric profiles of each friction section includes:

[0030] For each friction section, determine the initial point of the friction section;

[0031] Using a coordinate recursive method, starting from the initial point, the coordinates of the next point are calculated based on the arc length and the curvature of the current point, until all points along the transition section are obtained, thus obtaining the coordinates of all points;

[0032] The closure of the friction section is determined based on the curvature and arc length of all points along the section.

[0033] If the friction section is not closed, then determine the correction factor;

[0034] The geometry of the friction section is corrected based on the correction factor.

[0035] Optionally, the step of adjusting the fourth area of ​​each friction section using preset rules and determining the adjusted area of ​​each friction section includes:

[0036] For each of the friction sections, the friction section is divided into multiple triangles; wherein, the vertex of each triangle is located at the center point of the friction section, and the other two sides are respectively set along the outline of the friction section;

[0037] The fifth area is obtained by summing the faces of all the triangles in the cross section along the path;

[0038] Calculate the area ratio of the fourth area to the fifth area of ​​the friction section;

[0039] The target transition curve of the friction section is adjusted according to the area ratio, and the adjusted area of ​​the friction section is calculated based on the adjusted target transition curve.

[0040] This invention also provides a parametric design apparatus for aircraft engine nozzles, comprising:

[0041] A discretization module is used to design the circular inlet section and cashew-shaped outlet section of the aircraft engine nozzle, and to discretize each node on the circular inlet section and the cashew-shaped outlet section.

[0042] The determination module is used to determine the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section;

[0043] The geometry profile determination module is used to calculate the geometry profile of each section along the main duct of the aircraft engine nozzle based on the curvature corresponding to each discrete node on the inlet section, the curvature corresponding to each discrete node on the cashew-shaped outlet section, and the preset curvature change expression of the section along the duct, according to the constraint conditions.

[0044] The correction module is used to correct the geometric profiles of each friction section obtained from the calculation, so as to obtain the corrected geometric profiles of each friction section.

[0045] The transition curve determination module is used to determine the target transition curve by using a preset transition curve equation and the area change law of each cross section along the process; wherein, the target transition curve includes: a first fifth-order polynomial characterizing the first transition curvature from the inlet section to the intermediate cross section, and a second fifth-order polynomial characterizing the second transition curvature from the intermediate cross section to the cashew-shaped outlet section;

[0046] The first area calculation module is used to calculate the fourth area of ​​each friction section based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section.

[0047] The adjustment module is used to adjust the fourth area of ​​each of the friction sections using preset rules, and to determine each friction section after area adjustment;

[0048] The centerline design module is used to design the centerline offset so that the inlet section, each of the friction sections and the outlet section transition continuously and smoothly along the centerline.

[0049] The tube-through design module is used to create a cylinder based on the center coordinates of the inlet section, the preset radius, and the stretching length, and to generate the aircraft engine nozzle after the center tube is inserted.

[0050] Optionally, the discretization module includes:

[0051] The first submodule is used to determine the variable and unknown parameters of the cashew nut-shaped cross section;

[0052] The second submodule is used to construct a set of cashew cross-sectional shape parameter equations based on the variable parameters and unknown parameters; wherein, the set of cashew cross-sectional shape parameter equations is a nonlinear set of equations.

[0053] The third submodule is used to calculate the set of equations for the shape parameters of the cashew-shaped cross-section using Newton's iteration method, and to solve for the unknown parameters and variable parameters.

[0054] The fourth submodule is used to generate the inlet cross section and the cashew-shaped outlet cross section based on the position parameters and variable parameters, and to discretize each node on the inlet cross section and the cashew-shaped outlet cross section.

[0055] Optionally, the determining module is specifically used for:

[0056] For the inlet cross section, the circumference of the inlet cross section is divided into N parts, and the angle between each arc segment and the positive horizontal axis is calculated.

[0057] For each arc segment, the chord length of the arc segment is determined based on the included angle corresponding to the arc segment and the radius of the circumference of the inlet section.

[0058] For each arc segment, the dimensionless arc length corresponding to the discrete node is determined based on the chord length of the arc segment, and the coordinates of the discrete node are determined based on the dimensionless arc length.

[0059] For the cashew-shaped outlet cross section, determine the straight segments and arc segments with different curvatures included on the cashew-shaped outlet cross section;

[0060] The curvature of each discrete point on the straight line segment is determined to be 0. For arc segments with different curvatures, the corresponding curvature calculation formula is matched according to the type of each arc segment.

[0061] Based on the curvature and arc length corresponding to each discrete point in the cashew-shaped outlet section, the coordinates of each discrete node in the cashew-shaped outlet section are determined.

[0062] Optionally, the correction module is specifically used for:

[0063] For each friction section, determine the initial point of the friction section;

[0064] Using a coordinate recursive method, starting from the initial point, the coordinates of the next point are calculated based on the arc length and the curvature of the current point, until all points along the transition section are obtained, thus obtaining the coordinates of all points;

[0065] The closure of the friction section is determined based on the curvature and arc length of all points along the friction section.

[0066] If the friction section is not closed, then determine the correction factor;

[0067] The geometry of the friction section is corrected based on the correction factor.

[0068] Optionally, the adjustment module includes:

[0069] The fifth submodule is used to divide each of the friction sections into multiple triangles; wherein the vertex of each triangle is located at the center point of the friction section, and the other two sides are respectively set along the outline of the friction section.

[0070] The sixth submodule is used to sum the faces of all triangles in the cross section along the path to obtain the fifth area;

[0071] The seventh submodule is used to calculate the area ratio of the fourth area to the fifth area of ​​the friction section;

[0072] The eighth submodule is used to adjust the target transition curve of the friction section according to the area ratio, and to calculate the adjusted area of ​​the friction section according to the adjusted target transition curve.

[0073] The parametric design scheme for aircraft engine nozzles provided in this invention designs the circular inlet section and cashew-shaped outlet section of the aircraft engine nozzle, and discretizes each node on the circular inlet section and the cashew-shaped outlet section; determines the coordinates of each discrete node on the inlet section and the cashew-shaped outlet section; calculates the geometric profiles of each friction section of the main duct of the aircraft engine nozzle based on the curvatures corresponding to each discrete node on the inlet section, the curvatures corresponding to each discrete node on the cashew-shaped outlet section, and a preset expression for the curvature change along the friction section, according to constraints; and corrects the calculated geometric profiles of each friction section to obtain the corrected profile. The geometric profiles of each friction section are determined; the target transition curve is determined using a preset transition curve equation and the area variation law of each friction section; based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section, the fourth area of ​​each friction section is calculated; the fourth area of ​​each friction section is adjusted using preset rules to determine the friction sections after area adjustment; a centerline offset is designed to ensure a continuous and smooth transition along the centerline for the inlet section, each friction section, and the outlet section; a cylinder is established based on the center coordinates of the inlet section, a preset radius, and an extension length to generate the aircraft engine nozzle after the center tube is inserted. This scheme achieves two advantages: firstly, it reduces the amount of manual work for engineers and shortens the design cycle; work that previously took two weeks can now be completed in minutes; secondly, because it is implemented using software, all calculations are performed by a computer, ensuring the accuracy of the calculation results and reducing design errors. Attached Figure Description

[0074] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0075] Figure 1 This is a flowchart illustrating a parametric design method for an aircraft engine nozzle according to an embodiment of this application.

[0076] Figure 2 This is a schematic diagram of a cashew nut-shaped cross-section;

[0077] Figure 3 This is a schematic diagram of the cashew nut-shaped cross-section parameter settings;

[0078] Figure 4 These are schematic diagrams of the inlet and outlet cross sections;

[0079] Figure 5 This is a schematic diagram illustrating the principle of curvature calculation;

[0080] Figure 6 It is C J Schematic diagram of the function curve;

[0081] Figure 7 This is a schematic diagram of the verification calculation along the friction section;

[0082] Figure 8 This is a diagram illustrating the principle of "rapid first, then slow" (y'').

[0083] Figure 9 This is a diagram illustrating the principle of "gradual acceleration followed by rapid acceleration" (y'').

[0084] Figure 10 This is a diagram illustrating the relative urgency of the situation.

[0085] Figure 11 This is a diagram illustrating the cumulative area of ​​a triangle;

[0086] Figure 12 This is a schematic diagram showing the offset along the center line;

[0087] Figure 13 This is a schematic diagram of the parametric waist-shaped section layout of the main pipeline;

[0088] Figure 14 This generates a solid model of the center tube.

[0089] Figure 15 This is a structural block diagram illustrating an aircraft engine nozzle parametric design device according to an embodiment of this application. Detailed Implementation

[0090] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0091] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0092] The purpose of this invention is to achieve parameterized control of the nozzle, realize automatic nozzle generation, and provide a model basis for optimized design. The parameterized design scheme for aircraft engine nozzles provided by this invention mainly includes the following steps: cashew-shaped cross-section calculation, main duct parameterized calculation, central through-pipe and support plate design, and nozzle model generation.

[0093] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0094] The parametric design scheme for aircraft engine nozzles provided in this application will be described in detail below with reference to the accompanying drawings, through specific embodiments and application scenarios.

[0095] As attached Figure 1 As shown, the parameterized design method for aircraft engine nozzles in this application includes the following steps:

[0096] Step 101: Design the circular inlet section and cashew-shaped outlet section of the aircraft engine nozzle, and discretize each node on the circular inlet section and cashew-shaped outlet section.

[0097] Step 101 is the calculation process for the cashew-shaped cross-section. In an optional embodiment, designing the circular inlet cross-section and cashew-shaped outlet cross-section of the aircraft engine nozzle, and discretizing the nodes on the inlet and cashew-shaped outlet cross-sections, may include the following sub-steps:

[0098] Sub-step 1: Determine the variable and unknown parameters of the cashew nut-shaped cross-section.

[0099] Appendix Figure 2 This is a schematic diagram of a cashew nut-shaped cross-section. Figure 2 The parameters are marked with various variable and unknown parameters. The cashew nut shape parameter settings are as follows: Figure 3 As shown, the parameters include variable parameters and unknown parameters. The variable parameters include area, aspect ratio, L and R1, ensuring that each parameter is within the practically feasible range. The unknown parameters include R2, R3 and θ.

[0100] Sub-step 2: Construct a set of shape parameter equations for the cashew nut-shaped cross-section based on each variable and unknown parameter.

[0101] The equations for the shape parameters of the cashew nut-shaped cross-section are nonlinear. The specific equations for the shape parameters of the cashew nut-shaped cross-section are as follows:

[0102] 1 / 2 area: S = S1 + S2 + S3 + S4 - S5

[0103] Aspect Ratio:

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] Sub-step 3: Use the Newton-Raphson iteration method to calculate the equations of the cashew cross-section shape parameters, and solve for the unknown parameters and variable parameters.

[0113] In practical implementation, a series of nonlinear equations are constructed based on the cashew nut-shaped surface features. To solve this complex system of equations, the classic Newton-Raphson iteration method is used as the computational engine. The essence of this method lies in its ability to utilize the derivative information of the function at a certain point, i.e., the gradient or Jacobian matrix, to transform the original nonlinear problem into a series of solvable linear subproblems, thereby gradually approximating the true solution. Initial value selection: The initial input values ​​of the variable parameters area, aspect ratio, L and R1, and R3 are determined as the starting point for iteration, and R2, R3, and θ are solved.

[0114] Sub-step 4: Based on the position parameters and variable parameters, generate the inlet cross section and the cashew-shaped outlet cross section, and discretize each node on the inlet cross section and the cashew-shaped outlet cross section.

[0115] Figure 4 This is a schematic diagram of the inlet and outlet cross-sections. Figure 4 The left-middle image is a schematic diagram of the outlet cross-section. Figure 4 The right-middle figure is a schematic diagram of the inlet cross-section.

[0116] In practical implementation, the key parameters controlling the positioning of each part of the cashew nut-shaped surface—a, b, c, d—can be accurately solved using Newton's iteration method. The cross-section is discretized into points. To ensure a smooth transition with the inlet circle at the interface, the number of nodes in parts a and b can be kept strictly consistent with that in parts c and d, thus achieving coordinate transformation and surface continuity.

[0117] After completing the cashew-shaped cross-section calculation, the main pipeline is parametrically calculated. The parametric calculation of the main pipeline includes the following steps: obtaining the inlet and outlet cross-section parameters, calculating the friction section, verifying and correcting the friction section, scaling the area of ​​each friction section, and designing the centerline offset, as shown in steps 102 to 108.

[0118] Step 102: Determine the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section.

[0119] This step involves obtaining the parameters of the inlet and outlet sections, primarily by acquiring the coordinates of discrete points on the inlet and outlet sections.

[0120] In one alternative embodiment, determining the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section may include the following sub-steps:

[0121] Sub-step 1: For the inlet section, divide the circumference of the inlet section into N parts, and calculate the angle between each arc segment and the positive horizontal axis.

[0122] Sub-step 2: For each arc segment, determine the chord length of the arc segment based on the included angle corresponding to the arc segment and the radius of the circumference of the inlet cross section.

[0123] Sub-step 3: For each arc segment, determine the dimensionless arc length corresponding to the discrete node based on the chord length of the arc segment, and determine the coordinates of the discrete node based on the dimensionless arc length.

[0124] After determining the discrete coordinates of the inlet and outlet sections, the parameters of the inlet and outlet sections are determined, such as... Figure 4 As shown, the inlet parameter is a circle, therefore the inlet parameter satisfies the following condition: the curvature of all points on the inlet profile is equal. Discretizing the circle involves dividing the circumference into multiple small segments, each representing a small arc segment. These arc segments can then be approximated by straight line segments (chord lengths). Each such straight line segment is called ssi, which is the straight-line distance between two points. An angle θi is also introduced, representing the angle between this line segment and the positive horizontal axis. A schematic diagram of the curvature calculation principle is shown below. Figure 5 As shown.

[0125] Specifically, you can find the SSI by following these steps:

[0126] Determine θi: This is the angle between line segment ssi and the positive horizontal axis. It can be determined by measuring the central angle. If the circle is divided evenly, then θi is equal to 360 degrees divided by the number of segments.

[0127] To find ssi using θi and radius R: Since ssi is actually a chord, we can calculate it using the sine or cosine law. However, in this case, a more direct approach is to use the cosine theorem, since θi and R are known. According to the cosine theorem:

[0128]

[0129] The dimensionless arc lengths corresponding to each discrete node are as follows:

[0130]

[0131] Where, x i y i Let i be the coordinates of node i.

[0132] Sub-step 4: For the cashew-shaped outlet section, determine the straight segments and arc segments with different curvatures contained on the cashew-shaped outlet section.

[0133] Sub-step 5: Determine that the curvature of each discrete point on the straight line segment is 0. For arc segments with different curvatures, match the corresponding curvature calculation formula according to the type of each arc segment.

[0134] The exit section has a shape comprising arc segments with varying curvatures and straight segments, the latter having zero curvature. For any point on the curve, the curvature k is defined as the ratio of the absolute value of the rate of change of the tangent direction at that point to the rate of change of the arc length of the curve.

[0135] Specifically, if y=f(x) is the equation of a curve, then the curvature k at x=x0 is given by the following formula:

[0136]

[0137] For a curve in parametric form, where x = x(t) and y = y(t), the curvature κ is given by the following equation:

[0138]

[0139] In the above formula, the single dot at the top represents the first derivative with respect to the parameter t, and the double dot represents the second derivative.

[0140] Sub-step 6: Determine the coordinates of each discrete node in the cashew-shaped outlet section based on the curvature and arc length corresponding to each discrete point in the cashew-shaped outlet section.

[0141] Step 103: Based on the curvature of each discrete node on the inlet section, the curvature of each discrete node on the cashew-shaped outlet section, and the preset curvature change expression of the friction section, calculate the geometric profile of each friction section of the main duct of the aircraft engine nozzle according to the constraints.

[0142] This step outlines the relevant procedures for calculating friction section.

[0143] The variation law of the cross-sectional profile along the bending pipe is based on a polynomial curve of curvature variation. The expression for the curvature variation of the cross-section along the bending pipe is:

[0144]

[0145] C J =

[0146] i is a point on each cross-section profile, i = 1, 2, 3...I, where I is the number of points on the cross-section profile; J is the number of friction sections, J = 1, 2, 3...J, where J is the number of friction sections; C J C is a function that controls the curvature transition. J Schematic diagram of function curve, s i The arc length at each point corresponding to the profile cross section. Let the curvature of the inlet external flow channel cross-section be the curvature corresponding to point i. Let i be the curvature of the exit section profile at point i. Let be the curvature of the i-th transition section profile corresponding to point i. Based on the distribution of curvature k along the arc length for each section determined above, the geometric profile of each section can be calculated. The coefficients of the fifth-order polynomial can be changed to adjust the rate of change of the section curvature.

[0147] Constraints:

[0148] 1. The slope at both ends of the curve is 0, ensuring that the curvature of the cross-section near the inlet is close to Kin, and the curvature of the cross-section near the outlet is close to Kout.

[0149] 2. At the starting point C0=0, at the ending point C J =1, which yields two valid equations.

[0150]

[0151] The curvature of each section can be controlled by adjusting a3, b3, c3, d3, and e3 using the above equations.

[0152] Step 104: Correct the calculated geometric profiles of each friction section to obtain the corrected geometric profiles of each friction section.

[0153] This step outlines the calculation process for verifying and correcting the friction section. A schematic diagram of the friction section verification calculation is shown below. Figure 7 As shown.

[0154] The process of correcting the calculated geometric profiles of each friction section to obtain the corrected geometric profiles can include the following sub-steps:

[0155] Sub-step 1: For each friction section, determine the initial point of the friction section;

[0156] Sub-step 2: Using coordinate recursion, starting from the initial point, calculate the coordinates of the next point based on the arc length and the curvature of the current point, until all points along the friction section are reached, and the coordinates of all points are obtained;

[0157] Sub-step 3: Determine the closure of the friction section based on the curvature and arc length of all points along the section;

[0158] Sub-step 4: If the friction section is not closed, determine the correction factor; based on the correction factor, correct the geometry of the friction section.

[0159] Total arc length estimation: The total arc length is calculated by accumulating the lengths of each chord segment.

[0160] Initial point setting: Assume the starting point is located at the origin, i.e., coordinates (x1, y1) = (0, 0), which is the starting point for calculation.

[0161] Coordinate recursion: Starting from the second point, using the arc length SSi and the curvature kj(si) of the current point, calculate the coordinates of the next point. This is determined by the following equation. Starting from the third point, this process is repeated until all points on the transition section have been calculated.

[0162]

[0163] Closure judgment and correction

[0164] Closure test: Ensuring the closure of the graph is crucial during calculation. To do this, the cumulative product of curvature and arc length at all discrete coordinate points is calculated. Theoretically, if the graph is closed, this cumulative value should equal π (considering potential small errors). If the cumulative value does not equal π, then... The value π indicates that the figure is not yet completely closed. To correct this, the product of curvature kj(si) and arc length SSi, kj(si) * SSi, can be adjusted by multiplying it by an appropriate correction factor to gradually approximate the value of π. This correction factor can be found through iterative iteration until the figure reaches a closed state.

[0165] Step 105: Determine the target transition curve by using the preset transition curve equation and the variation law of the cross-sectional area along the process.

[0166] The target transition curves include: a first fifth-order polynomial representing the first transition curvature from the inlet section to the intermediate friction section, and a second fifth-order polynomial representing the second transition curvature from the intermediate friction section to the cashew-shaped outlet section.

[0167] Steps 105 to 107 describe the friction-cross-sectional area scaling process. When designing curved pipes, the change in cross-sectional area along the friction path is a critical factor, affecting not only fluid dynamics but also structural stability and efficiency. Using a fifth-order polynomial as the transition curve is an effective method for precisely controlling this change. The following is a detailed explanation of this process, including how to define the transition curve, calculate the cross-sectional area, and make necessary area ratio adjustments.

[0168] In actual implementation, the process of determining the target transition curve can be as follows:

[0169] (1) Determine the preset transition curve equation:

[0170] The change in cross-sectional area along the friction section of a curved pipe is divided into two parts: from the inlet section to the intermediate section, and from the intermediate section to the outlet section. The change in cross-sectional area along the friction section of the curved pipe follows a transitional pattern based on a fifth-order polynomial curve. By changing the coefficients of the fifth-order polynomial, the rate of change in cross-sectional area can be adjusted.

[0171] Transition curvature from inlet section to intermediate section:

[0172] Transition curvature from intermediate section to exit section: y2=

[0173] The distance between two adjacent sections is denoted as x (in the determination coefficient section); a1, b1, c1, d1, e1, a2, b2, c2, d2, and e2 are control parameters.

[0174] (2) Determining coefficients:

[0175] To determine the patterns of urgent followed by less urgent, less urgent followed by urgent, or equally urgent and less urgent, the calculation formula above needs to be simplified. We can observe its derivative, because the derivative represents the slope of the function (i.e., the steepness of the curve). The "steepness" or "gentleness" of a curve can be measured by the absolute value of its derivative: a large value means steep, and a small value means gentle. To make a curve "steep at first and then gentle," we need the derivative to decrease from a large value to a small value. Conversely, to make a curve "gentle at first and then steep," we need the derivative to increase from a small value to a large value. A curve with "equal steepness and gentleness" will have several places where the absolute values ​​of the derivative are approximately equal.

[0176] The transformation of the fifth-degree polynomial is as follows:

[0177] First derivative

[0178] Second derivative

[0179] The steepness of a curve can be analyzed by observing the sign of its second derivative. Specifically...

[0180] When y'' > 0, the first derivative y' increases, which means that the rate of change of the function y is increasing, i.e., the function is accelerating.

[0181] When y'' < 0, the first derivative y' is decreasing, which means that the rate of change of the function y is decreasing, that is, the function is decelerating.

[0182] To address the scenario of initial rapid growth followed by a gradual slowdown, we can try making the coefficients of higher-order terms larger than those of lower-order terms. This way, when x is small, the higher-order terms have a greater impact on the function value, resulting in a steeper curve; as x increases, the influence of the lower-order terms gradually becomes apparent, and the curve becomes flatter. Choosing a, b, c, d, and e as 0.4, 0.3, 0.2, 0.08, and 0.02 respectively, we can see that the second derivative gradually changes from positive to negative, indicating that the function initially accelerates and then begins to decelerate.

[0183] For situations involving a "slow start followed by a rapid finish," the second derivative needs to change from negative to positive. For example, if a < 0 and other coefficients cause y'' to change from negative to positive, the effect of deceleration followed by acceleration can be achieved. This is because when a < 0, as x increases... The term will also govern the sign change of y'', but in the opposite direction. Choose a set of parameters -0.4, -0.3, 0.2, 0.08, 0.02, and check if they produce the expected effect. From Figure 8-10 We can see that the second derivative gradually changes from a negative value to a positive value, indicating that the function initially decelerates during growth and then accelerates during growth.

[0184] Finally, regarding the case of "equal urgency," this typically occurs when the second derivative is close to zero or fluctuates little within a certain interval. For example, if a is close to zero, then higher-order terms contribute less to y'', and other terms, such as... , , This will dominate the change of y'', making its change relatively gradual. Let's choose a set of coefficients: 0.01, 0.01, 0.2, 0.4, 0.4, to make the absolute value of the first derivative as consistent as possible across the entire interval. From Figure 8-10 It can be seen that the second derivative is close to a constant throughout the entire interval, which indicates that the rate of change of the function remains basically consistent, without significant acceleration or deceleration.

[0185] Step 106: Based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section, calculate the fourth area of ​​each friction section.

[0186] The formula for calculating the area from the inlet section to the intermediate section is as follows:

[0187]

[0188] Calculation of the area from the intermediate section to the outlet section:

[0189]

[0190] A in A is the area of ​​the inlet cross-section of the bent pipe; m A is the area of ​​the cross-section along the middle of the bent pipe; out Let A be the area of ​​the cross-section at the outlet of the curved pipe. Based on the selected cross-sectional area variation curve, calculate the cross-sectional area A, i.e., the fourth area, of the curved pipe at the friction section.

[0191] Step 107: Adjust the fourth area of ​​each friction section using preset rules to determine the friction section after area adjustment.

[0192] In one optional embodiment, the fourth area of ​​each friction section is adjusted using preset rules, and the method for determining each friction section after area adjustment may include the following sub-steps:

[0193] Sub-step 1: For each friction section, divide the friction section into multiple triangles.

[0194] In this configuration, the vertex of each triangle is located at the center point of the friction section, and the other two sides are set along the outline of the friction section.

[0195] Sub-step 2: Add up the faces of all triangles along the cross section to obtain the fifth area;

[0196] Profile coordinate discretization: Using the recursive method from the previous step, the profile coordinates of the j-th transition section (i.e., the friction section) are obtained. To calculate the area Aj,now of this section, the closed shape needs to be discretized into multiple small triangles, and then the triangle faces are accumulated. One vertex of each small triangle is located at the center point of the section, and the other two sides are along the profile of the section, forming a small triangle with the chord length as its base. For each triangle, its area can be calculated using Heron's formula or a direct geometric method. By accumulating the faces of all these small triangles, the total area Aj,now of the section can be obtained. A schematic diagram of the triangle area accumulation is shown below. Figure 11 As shown.

[0197] Sub-step 3: Calculate the area ratio of the fourth area to the fifth area of ​​the friction section;

[0198] By comparing the cross-sectional area Aj predicted by the transition curve with the actual area Aj calculated through graphical discretization, we can obtain the area ratio ARj. The specific calculation formula is as follows:

[0199]

[0200] Sub-step 4: Adjust the target transition curve of the friction section according to the area ratio, and calculate the adjusted area of ​​the friction section according to the adjusted target transition curve.

[0201] This step involves adjusting and optimizing the cross-sectional area along the friction path: If ARj deviates significantly from 1, it indicates a difference between the theoretical and actual areas. This could be due to inaccuracies in the transition curve or approximation errors during the discretization process. In this case, consider adjusting the coefficients of the fifth-order polynomial and recalculating the target transition curve used for calculating the friction path area until ARj approaches 1, ensuring consistency between the theoretical and actual cross-sectional areas.

[0202] Step 108: Design the centerline offset to ensure a smooth and continuous transition along the centerline between the inlet section, each friction section, and the outlet section.

[0203] This step involves centerline offset design, as shown in the schematic diagram along the centerline offset. Figure 12 As shown. Specifically, it includes the following parts:

[0204] Part 1: Determining the Equation of the Centerline Curve

[0205] (1) Selection of curve equation

[0206] The centerline is a complex quadratic curve, and the expression for the curve is:

[0207] Here, x and y are the horizontal and vertical coordinates in the spatial coordinate system, respectively, while b, c, d, and e are coefficients to be determined.

[0208] (2) Boundary conditions:

[0209] The inlet and outlet points of the pipeline must lie on this curve. Let the coordinates of these two points be (x1, y1) and (x2, y2) respectively, then we can obtain two equations:

[0210]

[0211]

[0212] (3) Tangential condition

[0213] Furthermore, the directions of the pipeline inlet and outlet provide additional constraints. The angle between the inlet and the horizontal direction is 4 degrees, meaning the slope of the curve at the inlet is tan(4), and the angle between the outlet and the horizontal direction is 60 degrees, so the slope should be tan(60). Therefore, we can write the derivative equations of the curve at the inlet and outlet:

[0214]

[0215]

[0216] Where y'(x) represents the derivative of the curve at point x, that is, the slope of the curve.

[0217] Part Two: Solving for Curve Parameters

[0218] Solving the system of equations: The four equations in the first part are two boundary condition equations and two tangential condition equations. By solving the system of equations simultaneously and using Gaussian elimination, the values ​​of b, c, d, and e can be obtained, thus determining the specific shape of the centerline.

[0219] Part Three: Section Position Adjustment

[0220] Translation operation: The starting point of each intermediate section needs to be translated to the selected centerline. This means that for each section, the distance from its starting point to the centerline needs to be calculated, and then the entire section needs to be moved the corresponding distance in that direction to ensure that the starting point falls exactly on the centerline.

[0221] Rotation Operation: Next, based on the slope of the centerline at each starting point, rotate the cross-section so that it is perpendicular to the centerline. If the slope is m, the rotation angle α can be calculated using α = arctan(m). If the design requires maintaining a certain angle θ between the cross-section and the tangent direction of the centerline, the actual rotation angle should be α + θ or α − θ, depending on the sign of θ.

[0222] After translation and rotation adjustments, the position and orientation of all sections need to be checked again to ensure they meet design requirements, including their relationship to the centerline and the continuity and smooth transition between adjacent sections.

[0223] After completing the parametric calculations for the main duct, the center-through-pipe design is performed, ultimately generating the aircraft engine nozzle after the center-through-pipe. A schematic diagram of the parametric waist-shaped cross-section layout of the main duct is shown below. Figure 13 As shown.

[0224] Step 109: Based on the center coordinates of the inlet section, the preset radius and the stretching length, a cylinder is established to generate the aircraft engine nozzle after the center tube is inserted.

[0225] In actual implementation, the coordinates of the center of the inlet section are obtained, the radius is set, the stretching length is specified, a cylinder is constructed, and then Boolean operations are performed to obtain the result. Figure 14 The solid model shown is the generated central tube after the tube is inserted.

[0226] The parametric design method for aircraft engine nozzles provided in this application involves designing the circular inlet section and cashew-shaped outlet section of the aircraft engine nozzle, and discretizing each node on the circular inlet section and the cashew-shaped outlet section; determining the coordinates of each discrete node on the inlet section and the cashew-shaped outlet section; calculating the geometric profiles of each friction section of the main duct of the aircraft engine nozzle based on the curvatures corresponding to each discrete node on the inlet section, the curvatures corresponding to each discrete node on the cashew-shaped outlet section, and a preset expression for the curvature change along the friction section, according to constraints; and correcting the calculated geometric profiles of each friction section to obtain the corrected profiles. The geometric profiles of each friction section are determined; the target transition curve is determined using a preset transition curve equation and the area variation law of each friction section; based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section, the fourth area of ​​each friction section is calculated; the fourth area of ​​each friction section is adjusted using preset rules to determine the friction sections with area adjustment; a centerline offset is designed to ensure a continuous and smooth transition along the centerline for the inlet section, each friction section, and the outlet section; a cylinder is established based on the center coordinates of the inlet section, a preset radius, and an extension length to generate the aircraft engine nozzle after the center tube is inserted. This method offers two advantages: firstly, it reduces the amount of manual work for engineers and shortens the design cycle; work that previously took two weeks can now be completed in minutes; secondly, because it is software-based, all calculations are performed by a computer, ensuring the accuracy of the calculation results and reducing design errors.

[0227] Figure 15 The structural block diagram of the aircraft engine nozzle parametric design device according to the embodiments of this application is shown.

[0228] The aircraft engine nozzle parametric design device according to this application includes the following functional modules:

[0229] Discretization module 1501 is used to design the circular inlet section and cashew-shaped outlet section of the aircraft engine nozzle, and to discretize each node on the circular inlet section and the cashew-shaped outlet section.

[0230] The determining module 1502 is used to determine the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section;

[0231] The geometry profile determination module 1503 is used to calculate the geometry profile of each section along the main duct of the aircraft engine nozzle based on the curvature corresponding to each discrete node on the inlet section, the curvature corresponding to each discrete node on the cashew-shaped outlet section, and the preset curvature change expression of the section along the duct, according to the constraint conditions.

[0232] The correction module 1504 is used to correct the geometric profiles of each friction section obtained from the calculation, so as to obtain the corrected geometric profiles of each friction section.

[0233] The transition curve determination module 1505 is used to determine the target transition curve by using a preset transition curve equation and the area change law of each cross section along the process; wherein, the target transition curve includes: a first fifth-order polynomial characterizing the first transition curvature from the inlet section to the intermediate cross section, and a second fifth-order polynomial characterizing the second transition curvature from the intermediate cross section to the cashew-shaped outlet section.

[0234] The first area calculation module 1506 is used to calculate the fourth area of ​​each friction section based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section.

[0235] The adjustment module 1507 is used to adjust the fourth area of ​​each of the friction sections using preset rules, and to determine each friction section after area adjustment.

[0236] The centerline design module 1508 is used to design the centerline offset so that the inlet section, each of the friction sections and the outlet section transition continuously and smoothly along the centerline.

[0237] The tube-through design module 1509 is used to create a cylinder based on the center coordinates of the inlet section, the preset radius and the stretching length, and generate the aircraft engine nozzle after the center tube is inserted.

[0238] Optionally, the discretization module includes:

[0239] The first submodule is used to determine the variable and unknown parameters of the cashew nut-shaped cross section;

[0240] The second submodule is used to construct a set of cashew cross-sectional shape parameter equations based on the variable parameters and unknown parameters; wherein, the set of cashew cross-sectional shape parameter equations is a nonlinear set of equations.

[0241] The third submodule is used to calculate the set of equations for the shape parameters of the cashew-shaped cross-section using Newton's iteration method, and to solve for the unknown parameters and variable parameters.

[0242] The fourth submodule is used to generate the inlet cross section and the cashew-shaped outlet cross section based on the position parameters and variable parameters, and to discretize each node on the inlet cross section and the cashew-shaped outlet cross section.

[0243] Optionally, the determining module is specifically used for:

[0244] For the inlet cross section, the circumference of the inlet cross section is divided into N parts, and the angle between each arc segment and the positive horizontal axis is calculated.

[0245] For each arc segment, the chord length of the arc segment is determined based on the included angle corresponding to the arc segment and the radius of the circumference of the inlet section.

[0246] For each arc segment, the dimensionless arc length corresponding to the discrete node is determined based on the chord length of the arc segment, and the coordinates of the discrete node are determined based on the dimensionless arc length.

[0247] For the cashew-shaped outlet cross section, determine the straight segments and arc segments with different curvatures included on the cashew-shaped outlet cross section;

[0248] The curvature of each discrete point on the straight line segment is determined to be 0. For arc segments with different curvatures, the corresponding curvature calculation formula is matched according to the type of each arc segment.

[0249] Based on the curvature and arc length corresponding to each discrete point in the cashew-shaped outlet section, the coordinates of each discrete node in the cashew-shaped outlet section are determined.

[0250] Optionally, the correction module is specifically used for:

[0251] For each friction section, determine the initial point of the friction section;

[0252] Using a coordinate recursive method, starting from the initial point, the coordinates of the next point are calculated based on the arc length and the curvature of the current point, until all points along the transition section are obtained, thus obtaining the coordinates of all points;

[0253] The closure of the friction section is determined based on the curvature and arc length of all points along the friction section.

[0254] If the friction section is not closed, then determine the correction factor;

[0255] The geometry of the friction section is corrected based on the correction factor.

[0256] Optionally, the adjustment module includes:

[0257] The fifth submodule is used to divide each of the friction sections into multiple triangles; wherein the vertex of each triangle is located at the center point of the friction section, and the other two sides are respectively set along the outline of the friction section.

[0258] The sixth submodule is used to sum the faces of all triangles in the cross section along the path to obtain the fifth area;

[0259] The seventh submodule is used to calculate the area ratio of the fourth area to the fifth area of ​​the friction section;

[0260] The eighth submodule is used to adjust the target transition curve of the friction section according to the area ratio, and to calculate the adjusted area of ​​the friction section according to the adjusted target transition curve.

[0261] The parametric design device for aircraft engine nozzles provided in this application has two advantages. First, it can reduce the amount of manual work for engineers and shorten the design cycle; what used to take two weeks can now be completed in minutes. Second, because it is implemented in software and all calculations are performed by a computer, the accuracy of the calculation results can be ensured, thereby reducing design errors.

[0262] The embodiments provided in this application Figure 15 The aircraft engine nozzle parametric design device shown can achieve Figure 1 The various processes implemented in the method implementation examples will not be described again here to avoid repetition.

[0263] This application also provides an electronic device, which includes a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus.

[0264] The memory is used to store computer programs; the processor is used to execute the programs stored in the memory to implement the parameterized design process of the aircraft engine nozzle in the above embodiments.

[0265] The communication bus mentioned above can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc. The communication interface is used for communication between the aforementioned terminal and other devices.

[0266] The memory may include random access memory (RAM) or non-volatile memory, such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0267] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0268] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0269] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A parametric design method for aircraft engine nozzles, characterized in that, include: Design the circular inlet cross section and the cashew-shaped outlet cross section of the aircraft engine nozzle, and discretize each node on the circular inlet cross section and the cashew-shaped outlet cross section; Determine the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section; Based on the curvature of each discrete node on the inlet section, the curvature of each discrete node on the cashew-shaped outlet section, and the preset expression for the curvature change of the friction section, the geometric profile of each friction section of the main duct of the aircraft engine nozzle is calculated according to the constraint conditions. The calculated geometric profiles of each friction section are corrected to obtain the corrected geometric profiles of each friction section. The target transition curve is determined by using a preset transition curve equation and the variation law of the area of ​​each cross section along the flow path; wherein, the target transition curve includes: a first fifth-order polynomial characterizing the first transition curvature from the inlet cross section to the intermediate cross section, and a second fifth-order polynomial characterizing the second transition curvature from the intermediate cross section to the cashew-shaped outlet cross section; Based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section, calculate the fourth area of ​​each friction section; The fourth area of ​​each friction section is adjusted using preset rules to determine each friction section after area adjustment; The centerline is designed to be offset so that the inlet section, each of the friction sections and the outlet section transition smoothly and continuously along the centerline. A cylinder is constructed based on the center coordinates of the inlet section, the preset radius, and the stretching length, and an aircraft engine nozzle is generated after the center tube is inserted.

2. The method according to claim 1, characterized in that, The steps of designing the circular inlet cross-section and cashew-shaped outlet cross-section of an aircraft engine nozzle, and discretizing the nodes on the inlet cross-section and the cashew-shaped outlet cross-section, include: Determine the variable and unknown parameters of the cashew nut-shaped cross-section; A set of equations for the shape parameters of the cashew-shaped cross section is constructed based on the aforementioned variable and unknown parameters; wherein, the set of equations for the shape parameters of the cashew-shaped cross section is a nonlinear set of equations. The Newton-Raphson iteration method was used to calculate the system of equations for the shape parameters of the cashew-shaped cross-section, and the unknown parameters and variable parameters were obtained by solving the equations. Based on the position parameters and variable parameters, an inlet cross section and a cashew-shaped outlet cross section are generated, and each node on the inlet cross section and the cashew-shaped outlet cross section is discretized.

3. The method according to claim 1, characterized in that, The steps for determining the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section include: For the inlet cross section, the circumference of the inlet cross section is divided into N parts, and the angle between each arc segment and the positive horizontal axis is calculated. For each arc segment, the chord length of the arc segment is determined based on the included angle corresponding to the arc segment and the radius of the circumference of the inlet section. For each arc segment, the dimensionless arc length corresponding to the discrete node is determined based on the chord length of the arc segment, and the coordinates of the discrete node are determined based on the dimensionless arc length. For the cashew-shaped outlet cross section, determine the straight segments and arc segments with different curvatures included on the cashew-shaped outlet cross section; The curvature of each discrete point on the straight line segment is determined to be 0. For arc segments with different curvatures, the corresponding curvature calculation formula is matched according to the type of each arc segment. Based on the curvature and arc length corresponding to each discrete point in the cashew-shaped outlet section, the coordinates of each discrete node in the cashew-shaped outlet section are determined.

4. The method according to claim 1, characterized in that, The steps of correcting the calculated geometric profiles of each friction section to obtain the corrected geometric profiles of each friction section include: For each friction section, determine the initial point of the friction section; Using a coordinate recursive method, starting from the initial point, the coordinates of the next point are calculated based on the arc length and the curvature of the current point, until all points along the transition section are obtained, thus obtaining the coordinates of all points; The closure of the friction section is determined based on the curvature and arc length of all points along the friction section. If the friction section is not closed, then determine the correction factor; The geometry of the friction section is corrected based on the correction factor.

5. The method according to claim 1, characterized in that, The step of adjusting the fourth area of ​​each friction section using preset rules and determining the adjusted area of ​​each friction section includes: For each of the friction sections, the friction section is divided into multiple triangles; wherein, the vertex of each triangle is located at the center point of the friction section, and the other two sides are respectively set along the outline of the friction section; The fifth area is obtained by summing the faces of all the triangles in the cross section along the path; Calculate the area ratio of the fourth area to the fifth area of ​​the friction section; The target transition curve of the friction section is adjusted according to the area ratio, and the adjusted area of ​​the friction section is calculated based on the adjusted target transition curve.

6. A parametric design device for aircraft engine nozzles, characterized in that, include: A discretization module is used to design the circular inlet section and cashew-shaped outlet section of the aircraft engine nozzle, and to discretize each node on the circular inlet section and the cashew-shaped outlet section. The determination module is used to determine the coordinates of each discrete node on the inlet section and the coordinates of each discrete node on the cashew-shaped outlet section; The geometry profile determination module is used to calculate the geometry profile of each section along the main duct of the aircraft engine nozzle based on the curvature corresponding to each discrete node on the inlet section, the curvature corresponding to each discrete node on the cashew-shaped outlet section, and the preset curvature change expression of the section along the duct, according to the constraint conditions. The correction module is used to correct the geometric profiles of each friction section obtained from the calculation, so as to obtain the corrected geometric profiles of each friction section. The transition curve determination module is used to determine the target transition curve by using a preset transition curve equation and the variation law of the area of ​​each cross section along the transition; wherein, the target transition curve includes: a first fifth-order polynomial characterizing the first transition curvature from the inlet cross section to the intermediate cross section, and a second fifth-order polynomial characterizing the second transition curvature from the intermediate cross section to the cashew-shaped outlet cross section; The first area calculation module is used to calculate the fourth area of ​​each friction section based on the target transition curve, the first area of ​​the inlet section, the second area of ​​the outlet section, and the third area of ​​the intermediate friction section. The adjustment module is used to adjust the fourth area of ​​each of the friction sections using preset rules, and to determine each friction section after area adjustment; The centerline design module is used to design the centerline offset so that the inlet section, each of the friction sections and the outlet section transition continuously and smoothly along the centerline. The tube-through design module is used to create a cylinder based on the center coordinates of the inlet section, the preset radius, and the stretching length, and to generate the aircraft engine nozzle after the center tube is inserted.

7. The apparatus according to claim 6, characterized in that, The discretization module includes: The first submodule is used to determine the variable and unknown parameters of the cashew nut-shaped cross section; The second submodule is used to construct a set of cashew cross-sectional shape parameter equations based on the variable parameters and unknown parameters; wherein, the set of cashew cross-sectional shape parameter equations is a nonlinear set of equations. The third submodule is used to calculate the set of equations for the shape parameters of the cashew-shaped cross-section using Newton's iteration method, and to solve for the unknown parameters and variable parameters. The fourth submodule is used to generate the inlet cross section and the cashew-shaped outlet cross section based on the position parameters and variable parameters, and to discretize each node on the inlet cross section and the cashew-shaped outlet cross section.

8. The apparatus according to claim 6, characterized in that, The determining module is specifically used for: For the inlet cross section, the circumference of the inlet cross section is divided into N parts, and the angle between each arc segment and the positive horizontal axis is calculated. For each arc segment, the chord length of the arc segment is determined based on the included angle corresponding to the arc segment and the radius of the circumference of the inlet section. For each arc segment, the dimensionless arc length corresponding to the discrete node is determined based on the chord length of the arc segment, and the coordinates of the discrete node are determined based on the dimensionless arc length. For the cashew-shaped outlet cross section, determine the straight segments and arc segments with different curvatures included on the cashew-shaped outlet cross section; The curvature of each discrete point on the straight line segment is determined to be 0. For arc segments with different curvatures, the corresponding curvature calculation formula is matched according to the type of each arc segment. Based on the curvature and arc length corresponding to each discrete point in the cashew-shaped outlet section, the coordinates of each discrete node in the cashew-shaped outlet section are determined.

9. The apparatus according to claim 6, characterized in that, The correction module is specifically used for: For each friction section, determine the initial point of the friction section; Using a coordinate recursive method, starting from the initial point, the coordinates of the next point are calculated based on the arc length and the curvature of the current point, until all points along the transition section are obtained, thus obtaining the coordinates of all points; The closure of the friction section is determined based on the curvature and arc length of all points along the friction section. If the friction section is not closed, then determine the correction factor; The geometry of the friction section is corrected based on the correction factor.

10. The apparatus according to claim 6, characterized in that, The adjustment module includes: The fifth submodule is used to divide each of the friction sections into multiple triangles; wherein the vertex of each triangle is located at the center point of the friction section, and the other two sides are respectively set along the outline of the friction section. The sixth submodule is used to sum the faces of all triangles in the cross section along the path to obtain the fifth area; The seventh submodule is used to calculate the area ratio of the fourth area to the fifth area of ​​the friction section; The eighth submodule is used to adjust the target transition curve of the friction section according to the area ratio, and to calculate the adjusted area of ​​the friction section according to the adjusted target transition curve.

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