A cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet

Abstract

The present invention discloses a cross-sectional shape control method applied to a three-dimensional inward-rotating adjustable air inlet, which belongs to the field of aerodynamic design of air inlet surface, and comprises the following steps: step one: optimizing design of inward-rotating reference flow field; obtaining a preliminarily optimized inward-rotating reference flow field based on a given incoming flow design condition; step two: optimizing design of inward-rotating adjustable air inlet surface; given an air inlet inlet capture profile and an adjustable cross-sectional control constraint, an inward-rotating air inlet that meets the requirements is obtained by streamline tracking in the inward-rotating reference flow field in step one in combination with an optimization tool using an optimization algorithm; step three: surface adjustment design, performing surface adjustment design at a set rotation axis straight line on the basis of the inward-rotating air inlet generated in step two; the inward-rotating air inlet generated directly by streamline tracking in this scheme has the characteristic that the cross-sectional profile at the specified cross-section is approximately a straight line, which solves the problem in the prior art that the original streamline tracking profile needs to be changed to match the adjustable design.

Description

Technical Field

[0001] The present invention relates to the field of aerodynamic design of air inlet profiles, and in particular to a cross-sectional shape control method applied to a three-dimensional inward-rotating adjustable air inlet. Background Art

[0002] Compared to conventional dual-element inlets, inward-turning inlets offer advantages such as enhanced compression capability and a smaller wetted area. Therefore, adjustable inlet systems based on inward-turning inlets hold great promise for development. Since inward-turning inlets are typically constructed through streamline tracing in an inward-converging flow field, their compression profile is typically a curved surface with three-dimensional features.

[0003] In order to match the inward-turning air inlet with the adjustment mechanism, the profile at the transition of the adjustment surface is required to be as straight as possible. Existing measures include, on the one hand, meeting the constraints by designing the air inlet inlet profile or local modification, and on the other hand, using segmented streamline tracking technology and streamline gradient methods to make the predetermined rotation axis a straight line, or reconstructing the three-dimensional profile through spline curves to match the adjustable profile design.

[0004] However, this approach changes the compression profile at the front of the original inward-turning inlet adjustment at the design point, making it impossible to maintain the original flow field characteristics. Therefore, achieving adjustable design for the inward-turning inlet without changing the original profile is crucial to preserving the original flow field characteristics. Summary of the Invention

[0005] The purpose of the present invention is to provide a cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet in order to address the above-mentioned deficiencies, thereby realizing rotational variable geometry adjustment at a specified cross-section without changing the streamline tracking compression profile under the original high Mach design state, thereby helping to solve the problem of the incompatibility between the three-dimensional curved surface compression and geometric adjustment of the inward-rotating air inlet.

[0006] The present invention is achieved through the following solutions:

[0007] A cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet comprises the following steps:

[0008] Step 1: Optimization design of the internal rotation reference flow field: Based on the given incoming flow design conditions, a preliminary optimized internal rotation reference flow field is obtained;

[0009] Step 2: Optimize the inward-turning adjustable inlet profile. Given the inlet capture profile and adjustable cross-section control constraints, the optimization tool uses an optimization algorithm to track streamlines in the inward-turning reference flow field of step 1 to obtain an inward-turning inlet that meets the requirements.

[0010] Step 3: Surface adjustment design: Based on the inward-turning air intake duct generated in step 2, surface adjustment design is performed at the set rotation axis straight line.

[0011] In step one, a two-dimensional axisymmetric rotational characteristic line method is adopted; under the condition of given incoming flow parameters, the parameters of the generatrix of the rotating body are adjusted to adjust the reference flow field.

[0012] In step 1, the parameters of the revolution generatrix are as follows: the revolution generatrix abc is composed of a quadratic curve ab and a cubic curve bc. The design parameters include the coordinates of point a (x a ,r a ) and the inclination , the horizontal coordinate of point b (x b ) and the inclination , the coordinates of point c (x c ,r c ) and the inclination The design variables involved are expressed as formula x=(x1,x2,……,x8), where x1~x8 represent the 8 design variables of the rotating body busbar respectively. The 8 design variables are , , , , , , , , the busbar of the rotating body is obtained from the 8 design variables.

[0013] In step 1, a multi-objective optimization design is performed with the weighted variance D(Ma) of the flow field after the shock wave is reflected by the inward-rotating reference flow field and the total pressure recovery coefficient σ as the targets. The weighted variance of the Mach number represents the uniformity of the flow field, and the statistical weighting method is based on the mass flow rate, as shown in the following formula:

[0014]

[0015] Where, subscript i=1,2..., n is the grid unit number of the reference flow field reflection shock wave position unit, is the mass flow rate through the grid cell, is the total mass flow rate, is the average Mach number weighted by mass flow rate.

[0016] In step 1, the design variables of the reference flow field need to meet the geometric constraints, where the ab segment affects the leading edge shock wave, the intensity of the leading edge shock wave is directly related to the total pressure loss, and the expansion of the airflow after point b needs to be avoided. Need to be greater than the inclination The design parameters are all floated by 20% in each direction in the initial state to determine the floating range V. During the optimization process, it is also necessary to ensure that the pressure rise ratio of the reference flow field after the shock wave is reflected is not less than 90% of the original flow field. The optimization problem is summarized as follows:

[0017]

[0018] Where: and There are two optimization objective functions; and Respectively represent the average pressure at the outlet of the benchmark flow field before and after optimization; V n is the floating range set of each coordinate point; after preliminary optimization, an inward-rotating reference flow field with a relatively high total pressure recovery coefficient and good flow field uniformity is obtained.

[0019] In step 1, the optimization is performed based on the multi-science optimization platform Isight, and a multi-island genetic algorithm is used for multi-objective optimization. The population size is set to 10, the number of islands is 10, the evolutionary generations are 10, and the crossover rate is 0.9. The Pareto optimization theory is introduced to seek the optimal solution set of the Pareto frontier for multi-objective optimization problems.

[0020] The free stream Mach number is 6 Ma, the static pressure is 2511.18 Pa, and the static temperature is 221.649 K.

[0021] In step 2, the projection line of the inward-turned air inlet capture profile is designed as a rectangle A1B1C1D1, where the side is B1C1 and the upper surface edge is A1B1. The design variables include the capture inlet profile length L and width H.

[0022] In step 2, specifically, B1C1 is the projection profile of the inward-turning inlet leading edge line BC on the projection surface, BMF and CNG are both wall streamlines generated in the current inward-turning reference flow field, and a certain section is designated to intersect the streamlines BMF and CNG at M and N, respectively. MN is the pre-set reference line that serves as the rotation axis of the adjustment surface.

[0023] The existing streamline PQ passing through any point P on the leading edge line BC flows to the specified section, and the distance between it and the straight line MN is recorded as Therefore, the mean square error MSE ( ) is small enough, the intersection line of the profile at the specified section is considered to be approximately a straight line; since the compression profile of the middle section of the inward-turning inlet is mainly affected by the horizontal coordinate xb of point b in the reference flow field and the inclination angle Therefore, it is also included in the secondary optimization, and the design parameter fluctuation is 10% to determine the floating range U; at the same time, the intake duct capture area is required to be no less than 90% of the initial area; the optimization model is defined as follows:

[0024]

[0025] Where: and are two optimization objective functions. The weighted variance of the Mach number is used as the optimization objective function again in this optimization to ensure that the change of the reference flow field during the secondary optimization process will not have a significant impact on the airflow uniformity. and R represent the radius of the central body and the maximum radius of the flow field, respectively; and Respectively represent the inward flow capture area of ​​the inward turning inlet before and after optimization; and Represents the horizontal coordinate xb and inclination of point b respectively ;

[0026] The same method is used to optimize the upper surface of the air intake duct.

[0027] In step three, specifically, the inward-turning air inlet configuration whose side profile at the specified cross section is approximately a straight line obtained in step two is rotated at the set rotation axis on the side to achieve adjustment; similarly, after optimizing the upper surface of the air inlet in step two, the inward-turning air inlet configuration whose upper surface profile at the specified cross section is approximately a straight line is obtained, and the upper surface is rotated at the rotation axis to achieve adjustment.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. This solution directly generates an inward-turning air inlet through streamline tracing, resulting in a cross-sectional profile that is approximately a straight line at the specified cross-section. This solves the problem of existing technologies requiring the original streamline tracing profile to be modified to match the adjustable design. The original inward-turning air inlet streamline tracing profile largely retains and inherits the characteristics of the original reference flow field. This method provides a way to solve the problem of incompatibility between three-dimensional surface compression and geometric adjustment of the inward-turning air inlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of determining the wall curve and the leading edge shock wave of the axisymmetric inner curved cone in the prior art;

[0031] Figure 2 It is a schematic diagram of determining the leading edge shock wave dependent area in the prior art;

[0032] Figure 3 It is a schematic diagram of determining the reference flow field area in the prior art;

[0033] Figure 4 It is a schematic diagram of determining the isentropic main compression zone in the prior art;

[0034] Figure 5 This is a schematic diagram of determining the lip mouth reflected shock wave dependent area and corresponding streamlines in the prior art;

[0035] Figure 6 It is a schematic diagram of determining the stable area and the corresponding streamline in the prior art;

[0036] Figure 7 This is a schematic diagram of the standard flow field outlet of the original air inlet in the prior art;

[0037] Figure 8 This is a schematic diagram of the design principle of the internal rotation reference flow field in the present invention;

[0038] Figure 9 It is a schematic diagram of the capture inlet profile design in the present invention;

[0039] Figure 10 This is a schematic diagram of the side streamline control principle of the air inlet in the present invention;

[0040] Figure 11 This is the side-adjustable configuration of the inward-turning air inlet in the present invention;

[0041] Figure 12 This is a schematic diagram of the side adjustment of the inward-turned air intake duct in the present invention;

[0042] Figure 13 The upper surface of the inward-turning air inlet duct of the present invention is adjustable;

[0043] Figure 14 Schematic diagram of the adjustment of the upper surface of the inward-turning air inlet duct in the present invention;

[0044] Figure numerals: 15, inlet lip plane; 16, inlet outlet plane; 21, rotating body generatrix; 22, center body; 23, inlet capture profile; 24, inward shock wave; 25, projection surface; 26, upper surface; 27, side; 28, designated section; 29, incoming flow; 210, rotation axis; 211, reflected shock wave. DETAILED DESCRIPTION

[0045] All features disclosed in this specification, or all steps in the disclosed methods or processes, except mutually exclusive features and / or steps, can be combined in any manner.

[0046] Any feature disclosed in this specification (including any appended claims and abstract), unless otherwise stated, may be replaced by other equivalent or similar features. In other words, unless otherwise stated, each feature is only an example of a series of equivalent or similar features.

[0047] In the description of the present invention, it should be understood that the terms "up", "down", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are 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 predetermined direction, be constructed and operated in a predetermined direction, and therefore cannot be understood as a limitation on the present invention.

[0048] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features being referred to. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of such features.

[0049] This embodiment first describes the existing method for solving the inward-rotating reference flow field using the rotating characteristic line method, referring to the patent application No. 201910325410.6, which discloses an integrated design method for an inward-rotating waverider forebody air inlet for a supersonic aircraft. The rotating characteristic line theory is applied to design and solve the axisymmetric reference flow field of the inward-rotating waverider forebody air inlet, wherein the wall curve and the axisymmetric inner curved surface cone leading edge shock wave are first determined, and a three-dimensional rectangular coordinate system oxrz is first constructed. The three-dimensional rectangular coordinate system oxrz is established with the inward-rotating waverider forebody air inlet as the center, the central symmetry plane of the inward-rotating waverider forebody air inlet is the xor plane, the direction of the airflow in the air inlet is the x direction, and the direction perpendicular to the xor plane is the z direction, as shown in FIG. Figure 1 As shown, in the xor coordinate system, let A ' B ' C2 ' is the wall curve, where A ' B ' is a quadratic curve, B ' C2 ' For a cubic curve, given A ' The coordinates of the point (x A＇ ,r A＇ ) and the slope k A' 、B ' Point horizontal coordinate x B' and the slope k B' , and C2 ' The coordinates of the point (x C＇ ,r C＇ ) and the slope k C＇ , A ' 、B ' The parameters given by the point can form three equations to solve the quadratic curve A ' B ' , and then calculate the coordinates of point B' (x B＇ ,r B＇ ), combined with the known B ' 、C2 'The parameters given by the points form four equations to solve the cubic curve B ' C2 ' , and then uniquely determine the wall curve A ' B ' C2 ' Then, the rotation characteristic line theory is applied to solve the axisymmetric reference flow field of the inward-rotating forebody inlet. Under the zero-angle-of-attack design flow condition (M0>1), the axisymmetric inner curved cone leading edge shock wave A is generated. ' R ' , where point R ' It is the imaginary point of the shock wave at the leading edge of the axisymmetric inner curved cone close to the symmetry axis;

[0050] Solve the leading edge shock wave dependent area, such as Figure 2 As shown, in the xor coordinate system, its dependent area is A ' -B ' -D ' , first on the wall curve A ' B ' C2 ' Select point B on ' , from point B ' The starting right-moving Mach line and the leading edge shock wave A of the axisymmetric inner curved cone ' R ' Intersect at point D ' , will pass through point D ' The cross section of the inlet lip plane 15 is used as the reference flow field, and it is necessary to iteratively calculate the point D ' location.

[0051] Solve the reference flow field area, such as Figure 3 As shown, in the xor coordinate system, its area is B ' -C1 ' -D ' First, using the theory of rotating characteristic lines, the right-moving Mach line B ' D ' and wall curve A ' B ' C2 ' Curve segment B on ' C2 ' , solve through D ' The left-moving Mach line of point A and the wall curve A ' B ' C2 ' Intersect at point C1 ' , and solve the right-moving Mach line B ' D ' 、Left-moving Mach line D ' C1 ' and curve B ' C1 'The flow field of the enclosed area.

[0052] Solve for the isentropic main compression region, such as Figure 4 As shown, in the xor coordinate system, its area is B ' -C ' -D ' , with point D ' As the starting point of the lip reflected shock wave, the flow direction angle distribution behind the reflected shock wave is given as shown in formula (1). The position and shape of the lip reflected shock wave are solved by using the estimation-correction iterative method until the lip reflected shock wave is consistent with the curve B. ' C1 ' Intersect at shoulder point C ' Finally, the oblique shock wave theory is used to solve the flow parameter distribution behind the wave. ' D ' 、lip mouth reflected shock wave D ' C ' and wall curve B ' C ' Enclosed area B ' -C ' -D ' The main compression zone of isentropic compression between shock waves, which is the reference flow field of the inlet, is referred to as the isentropic main compression zone B. ' -C ' -D ' .

[0053] ,2 =θ D＇C＇,2(x) ,x∈[x D＇ ,x C＇ ] (1)

[0054] in, ,2 It is the lip-mouth reflected shock wave D ' C ' Flow direction angular distribution behind the wave.

[0055] Solve the reflected shock wave dependent area, such as Figure 5 As shown, in the xor coordinate system, this area is C ' -D ' -E ' and streamline is D ' E ' ;

[0056] The solid lines with arrows represent streamlines, and the dotted lines are Mach lines. Using the streamline point unit process of the rotating characteristic line theory, the shock wave D is reflected by the lip. ' C ' The position coordinates and post-wave flow parameters are used to solve the lip reflection shock wave dependence area C ' -D' -E ' , until it passes point D ' The streamline passes through point C ' The left-moving Mach line intersects at point E ' , we get streamline D ' E ' .

[0057] Solve for the stable region, such as Figure 6 As shown, the area is C ' -E ' -F ' -G ' and streamline E ' F ' , the stable area of ​​the inlet reference flow field and the solution streamline E ' F ' First, the shoulder point C ' The wall curve C on the right ' G ' The wall inclination angle distribution and Mach number distribution on the curve are given by equations and equations. Given the wall inclination angle distribution is equivalent to giving the curve C ' G ' It should be noted that the wall curve C ' G ' At shoulder point C ' The wall inclination angle at the lip must be consistent with the local airflow direction angle (i.e., the lip reflection shock wave D ' C ' At point C ' The direction angle of the airflow behind the wave at the lip is coincident to ensure that the lip reflects the shock wave D ' C ' There is no reflection at the shoulder point C', which achieves the effect of wave elimination. Then, using the streamline point unit process of the rotational characteristic line theory, the left-moving Mach line C ' E ' The position coordinates and flow parameters, wall curve C ' G ' And the flow parameter distribution on the curve, solve the stable area C of the inlet duct reference flow field ' -E ' -F ' -G ' , until it passes point E ' The streamlines passing through G ' The left characteristic line intersects at point F ' , and we get the streamline E ' F ' .

[0058] δ C＇G＇ =δ C＇G＇ (x),x∈[x C＇,x G＇ ]

[0059] M C＇G＇ =M C＇G＇ (x),x∈[x C＇ ,x G＇ ]

[0060] Among them, δ C＇G＇ and M C＇G＇ Curve C ' G ' The wall inclination angle and Mach number distribution.

[0061] in, Figure 6 Given the inlet outlet plane 16 and the shoulder point C ' The distance x along the x direction C＇K＇ , exit point K ' , L ' Located at the inlet exit plane. C＇K＇ , which is defined as:

[0062] The original inlet duct reference flow field outlet is as follows Figure 7 Shown is an inner diameter r F＇ , outer diameter r G＇ Now make an equivalent circle with a diameter of d1 as the equivalent outlet of the inlet reference flow field, let x C＇K＇ =0.5d1.

[0063] Example 1

[0064] The present invention provides a technical solution:

[0065] like Figures 8 to 14 As shown, a cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet is provided; the method comprises the following steps:

[0066] S1: Optimization design of reference flow field: Based on the given inflow 29 design conditions, the preliminarily optimized inward-rotating reference flow field is obtained;

[0067] This embodiment is based on the existing reference flow field design and adopts the two-dimensional axisymmetric rotation characteristic line method; under the condition of given incoming flow 29 parameters, the reference flow field can be adjusted by adjusting the parameters of the rotating body generatrix 21abc, such as Figure 8 The rotating body busbar 21abc is composed of a quadratic curve ab and a cubic curve bc. The design parameters include the coordinates of point a (x a ,r a ) and the inclination , the horizontal coordinate of point b (x b ) and the inclination , the coordinates of point c (x c ,r c) and the inclination The design variables involved in this implementation case can be expressed as a formula, where x=(x1,x2,……,x8)represents the eight design variables of the rotary busbar 21 ( , , , , , , , ), the eight design variables can be used to determine the rotating body's busbar 21. The main design parameters of the internal rotation reference flow field include: free stream 29 Mach number 6 Ma, static pressure 2511.18 Pa, and static temperature 221.649 K.

[0068] In this implementation case, a multi-objective optimization design is performed with the Mach number weighted variance D(Ma) and the total pressure recovery coefficient σ of the flow field after the reflected shock wave 211 in the inward-rotating reference flow field as the targets. The weighted variance of the Mach number can characterize the uniformity of the flow field, and the statistical weighting method is based on the mass flow rate, as shown in Equation (2).

[0069]

[0070] Where, subscript i=1,2..., n is the grid unit number of the reference flow field reflected shock wave 211 position unit, is the mass flow rate through the grid cell, is the total mass flow rate, is the average Mach number weighted by mass flow rate.

[0071] The design variables of the benchmark flow field need to meet certain geometric constraints. The ab section mainly affects the leading edge shock wave. The intensity of the leading edge shock wave is directly related to the total pressure loss. At the same time, it is necessary to avoid the expansion of the airflow after point b. Need to be greater than the inclination The design parameters are all initially set with a 20% float in all directions to determine the float range V. During the optimization process, it is also necessary to ensure that the pressure rise ratio of the reference flow field after the reflected shock wave 211 is no less than 90% of the original flow field. The optimization problem is summarized in Equation (3).

[0072]

[0073] Where: and There are two optimization objective functions; and Respectively represent the average pressure at the outlet of the benchmark flow field before and after optimization; V n A collection of floating ranges for each coordinate point.

[0074] After preliminary optimization, an inward-rotating reference flow field with a relatively high total pressure recovery coefficient and good flow field uniformity was obtained.

[0075] This example uses the multi-objective optimization platform Isight, employing a multi-island genetic algorithm (MIGA) for multi-objective optimization. The population size is set to 10, the number of islands is 10, the number of evolutionary generations is 10, and the crossover rate is 0.9. Pareto optimization theory is introduced to identify the optimal solution set on the Pareto frontier for multi-objective optimization (MO). This implementation example illustrates one of these optimal solutions.

[0076] S2: Optimization design of the inward-turning adjustable inlet profile. Given the inlet inlet capture profile 23 and the adjustable cross-section control constraints, the optimization tool uses the optimization algorithm to track streamlines in the inward-turning reference flow field in step 1 to obtain an inward-turning inlet that meets the requirements.

[0077] Considering that a regular air intake capture inlet facilitates matching with the aircraft's forebody, the projection of the inward-turning air intake capture profile was designed as a rectangle during the initial design phase of this embodiment. Design variables included the capture profile length L and width H. The rectangular inlet facilitates multi-module design and allows streamline tracing to clearly distinguish the upper surface 26 and side surfaces 27.

[0078] It is worth noting that the inward-turned air inlet side 27 generated by streamline tracing is usually more distorted than the upper surface 26. Therefore, this embodiment optimizes the air inlet side 27. When the side B1C1 is a straight line, it is easier to obtain a relatively flat compression surface. In the actual design process, C1D1 can be adjusted as needed to change the shape of the capture port; and the same method in this embodiment can be used to optimize the upper surface 26 of the air inlet.

[0079] like Figure 9 B1C1 is the projection profile of the inward-turning inlet leading edge line BC on the projection surface 25. BMF and CNG are both wall streamlines generated in the current inward-turning reference flow field. A specific section is designated to intersect streamlines BMF and CNG at M and N, respectively. MN is a pre-set reference line that can serve as the adjustment surface rotation axis 210. The existing streamline PQ passing through any point P on the leading edge line BC flows to the designated section 28 (which can be set as needed). The distance between it and the line MN is recorded as Therefore, the mean square error MSE ( ) is small enough, then the intersection line of the profile at the specified section 28 can be considered to be approximately a straight line. Since the compression profile of the middle section of the inward-turned inlet duct is mainly affected by the horizontal coordinate xb of point b and the inclination angle Therefore, it is also included in the secondary optimization, but this time the design parameter is floated by 10% to determine the floating range U. At the same time, the inlet capture area is required to be no less than 90% of the initial area. The optimization model can be defined as Equation (4).

[0080]

[0081] Where: and are two optimization objective functions. The weighted variance of the Mach number is used as the optimization objective function again in this optimization to ensure that the change of the reference flow field during the secondary optimization process will not have a significant impact on the airflow uniformity. and R represent the radius of the center body 22 and the maximum radius of the flow field, respectively; and They represent the capture area of ​​the inward turning inlet flow 29 before and after optimization respectively; and Represents the horizontal coordinate xb and inclination of point b respectively .

[0082] S3: Surface adjustment design: Based on the inner-rotating air intake duct generated in step 2, surface adjustment design is performed at the set rotation axis 210 line;

[0083] This embodiment optimizes the side 27 of the air inlet, and finally obtains an inward-turning air inlet configuration in which the line of the side 27 at the designated section 28 is approximately a straight line, which can facilitate the rotation of the side 27 at the rotation axis 210 to achieve adjustable Figure 11 、 Figure 12 ,exist Figure 11 ABCD is the capture line of the inward-turning air inlet; similarly, by optimizing the upper surface 26 of the air inlet, an inward-turning air inlet configuration can be obtained in which the line of the upper surface 26 at the specified section 28 is approximately a straight line, which can facilitate the upper surface 26 to rotate at the rotation axis 210 to achieve adjustable Figure 13 、 Figure 14 ,exist Figure 13 ABCD in the middle is the inward-turned air inlet capture line.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling the cross-sectional shape of a three-dimensional inward-rotating adjustable air inlet, characterized by: The following steps are involved: Step 1: Optimization design of the internal rotation reference flow field; Based on the given incoming flow design conditions, the preliminarily optimized inward-rotating reference flow field is obtained; In step 1, a two-dimensional axisymmetric rotational characteristic line method is used; Under the condition of given incoming flow parameters, the parameters of the rotating body's generatrix are adjusted to adjust the reference flow field; In step 1, the parameters of the revolution generatrix are as follows: the revolution generatrix abc is composed of a quadratic curve ab and a cubic curve bc. The design parameters include the coordinates of point a (x a ,r a ) and the inclination , the horizontal coordinate of point b (x b ) and the inclination , the coordinates of point c (x c ,r c ) and the inclination The design variables involved are expressed as formula x=(x1,x2,……,x8), where x1~x8 represent the 8 design variables of the rotating body busbar respectively. The 8 design variables are , , , , , , , , the busbar of the rotating body is obtained from the 8 design variables; In step 1, a multi-objective optimization design is performed with the Mach number weighted variance D(Ma) and the total pressure recovery coefficient σ of the flow field after the reflected shock wave of the inward-rotating reference flow field as the targets; In step 1, the design variables of the reference flow field need to meet the geometric constraints, where the ab segment affects the leading edge shock wave, the intensity of the leading edge shock wave is directly related to the total pressure loss, and the expansion of the airflow after point b needs to be avoided. Need to be greater than the inclination The design parameters are all floated by 20% in each direction in the initial state to determine the floating range V; during the optimization process, it is also necessary to ensure that the pressure rise ratio of the reference flow field after the shock wave is reflected is not less than 90% of the original flow field; Step 2: Optimize the inward-turning adjustable inlet profile. Given the inlet capture profile and adjustable cross-section control constraints, the optimization tool uses an optimization algorithm to track streamlines in the inward-turning reference flow field of step 1 to obtain an inward-turning inlet that meets the requirements. In step 2, the projection line of the inward-turned air inlet capture profile is designed as a rectangle A1B1C1D1, where the side is B1C1 and the top surface is A1B1. The design variables include the capture inlet profile length L and width H. In step 2, specifically, B1C1 is the projection profile of the inward-turning inlet leading edge line BC on the projection surface, BMF and CNG are both wall streamlines generated in the current inward-turning reference flow field, and a certain section is designated to intersect the streamlines BMF and CNG at M and N, respectively. MN is the pre-set reference line that serves as the rotation axis of the adjustment surface. The existing streamline PQ passing through any point P on the leading edge line BC flows to the specified section, and the distance between it and the straight line MN is recorded as ; Since the compression profile of the middle section of the inward-turned inlet is mainly affected by the horizontal coordinate xb of point b in the reference flow field and the inclination angle Therefore, it is also included in the secondary optimization, and the design parameter floats by 10% to determine the floating range U; at the same time, the inlet capture area is required to be no less than 90% of the initial area; Step 3: Surface adjustment design: Based on the inward-turning air intake duct generated in step 2, surface adjustment design is performed at the set rotation axis straight line.

2. The cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet according to claim 1, characterized in that: In step 1, the weighted variance of the Mach number characterizes the uniformity of the flow field. The statistical weighting method is based on the mass flow rate, as shown in the following formula: Where, subscript i=1,2..., n is the grid unit number of the reference flow field reflection shock wave position unit, is the mass flow rate through the grid cell, is the total mass flow rate, is the average Mach number weighted by mass flow rate.

3. The cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet according to claim 2, characterized in that: In step 1, the optimization problem is summarized as follows; Where: and There are two optimization objective functions; and Respectively represent the average pressure at the outlet of the benchmark flow field before and after optimization; V n is the floating range set of each coordinate point; after preliminary optimization, an inward-rotating reference flow field with a relatively high total pressure recovery coefficient and good flow field uniformity is obtained.

4. The cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet according to claim 3, characterized in that: In step 1, the optimization is performed based on the multi-science optimization platform Isight, and a multi-island genetic algorithm is used for multi-objective optimization. The population size is set to 10, the number of islands is 10, the evolutionary generations are 10, and the crossover rate is 0.

9. The Pareto optimization theory is introduced to seek the optimal solution set of the Pareto frontier for multi-objective optimization problems.

5. The cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet according to claim 4, characterized in that: The free stream Mach number is 6 Ma, the static pressure is 2511.18 Pa, and the static temperature is 221.649 K.

6. The cross-sectional shape control method for a three-dimensional inward-rotating adjustable air inlet according to claim 5, characterized in that: In step 2, the optimization model is defined as follows: Where: and There are two optimization objective functions; and R represent the radius of the central body and the maximum radius of the flow field, respectively; and Respectively represent the inward flow capture area of ​​the inward turning inlet before and after optimization; and Represents the horizontal coordinate xb and inclination of point b respectively ; The same method is used to optimize the upper surface of the air intake duct.

7. A method for controlling the cross-sectional shape of a three-dimensional inward-rotating adjustable air inlet according to any one of claims 1 to 6, characterized in that: In step three, specifically, the inward-turning air inlet configuration whose side profile at the specified cross section is approximately a straight line obtained in step two is rotated at the set rotation axis on the side to achieve adjustment; similarly, after optimizing the upper surface of the air inlet in step two, the inward-turning air inlet configuration whose upper surface profile at the specified cross section is approximately a straight line is obtained, and the upper surface is rotated at the rotation axis to achieve adjustment.

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