Parameter determination method for 90-degree bending flow guide molded surface

Abstract

The invention discloses a method for determining parameters of a 90-degree bending flow guide molded surface, which comprises the following steps of: determining a flow guide molded surface of an existing basic airfoil profile, and respectively dispersing an upper molded surface, a lower molded surface and a chord line of the basic airfoil profile into point sets; determining an angle needing to be rotated by each discrete point of the basic airfoil profile; determining a hyper-ellipse guide line control equation, dispersing the 1 / 4 hyper-ellipse guide line into a point set, and enabling the discrete points of the chord line of the basic airfoil profile to be in one-to-one correspondence with the discrete points of the 1 / 4 hyper-ellipse guide line, so as to obtain the rotation angles of the discrete points of the chord line of the basic airfoil profile; determining the rotation angles of the discrete points corresponding to the upper profile and the lower profile of the basic airfoil according to the rotation angles of the discrete points of the chord line of the basic airfoil; and determining the coordinate of each discrete point according to the determined rotation angle of each discrete point, and smoothly connecting each discrete point to obtain the 90-degree bending airfoil profile. Through parameterization control of the hyperelliptical guide line, parameterization adjustment of the long axis and the short axis is allowed, and diversified flow guide airfoil design is achieved.

Description

Technical Field

[0001] The invention relates to the field of aircraft design, and in particular to a method for determining parameters of a 90-degree bent flow guide profile. Background Art

[0002] Unmanned aerial vehicles are playing an important role in the civilian field. At present, most high-performance UAVs use tail propeller propulsion. As a key aerodynamic component of such aircraft, the air inlet must provide the engine with high-quality airflow of the required flow rate, and at the same time meet the constraints or restrictions from the aircraft's shape integration, structural layout, radar stealth, etc., so its design faces great challenges. In particular, its compact flow path layout characteristics of "horizontal air intake in the air inlet → vertical air intake in the volute → horizontal air intake in the engine" make the airflow undergo two 90-degree deflections before entering the engine core, which can easily induce significant separation flow and vortex flow, resulting in significant flow loss and outlet swirl on the engine inlet surface. Therefore, in the design of the air inlet of high-performance UAVs, arranging guide vanes at the bend is crucial to optimize the flow field quality and improve the aerodynamic performance of the engine inlet surface, and is a key technical measure to ensure the aerodynamic efficiency and stealth characteristics of the aircraft.

[0003] However, in the design of the double 90-degree bend air inlet of high-performance UAVs, the design of the guide vane faces a series of complex aerodynamic challenges. First, since the airflow is very likely to produce flow separation and vortexes when undergoing continuous 90-degree turns, the guide vane must be precisely designed to effectively guide the airflow and reduce these adverse phenomena, which is crucial to improving the total pressure recovery and swirl characteristics of the engine inlet surface. Secondly, the design of the guide vane must also consider how to minimize energy losses in areas where the airflow turns sharply to maintain high engine efficiency and performance. In addition, the aerodynamic characteristics of the air inlet of the UAV will change at different flight speeds and altitudes, so the design of the guide vane must be able to adapt to these changes to ensure good aerodynamic stability under various flight conditions. These combined factors pose challenges to the design of the guide vane in the double 90-degree bend air inlet. Summary of the invention

[0004] Purpose of the invention: In view of the above shortcomings, the present invention provides a method for determining the parameters of a 90-degree curved flow guide surface that improves the aerodynamic performance of the engine inlet surface. By precisely controlling the airflow to reduce flow separation and vortex, minimize energy loss, and adapt to the aerodynamic characteristics under different flight conditions, the flow field quality is optimized, the aerodynamic efficiency and stealth characteristics of the aircraft are ensured, and the complex aerodynamic challenges faced by the inlet flow in the existing design are met.

[0005] Technical solution: To solve the above problem, the present invention adopts a method for determining parameters of a 90-degree bent flow guide profile, comprising the following steps:

[0006] (1) determining the guide surface of the existing basic airfoil, including the upper surface and the lower surface, and discretizing the upper surface, the lower surface and the chord line of the basic airfoil into n points respectively;

[0007] (2) determining the angle that each discrete point of the basic airfoil needs to rotate; determining the super ellipse guide line control equation, discretizing the 1 / 4 super ellipse guide line into n points, aligning the endpoint of the basic airfoil chord line with the starting point of the 1 / 4 super ellipse guide line, and making the discrete points of the basic airfoil chord line correspond to the discrete points of the 1 / 4 super ellipse guide line one by one, obtaining the rotation angle of the discrete points of the basic airfoil chord line, and determining the rotation angle of the corresponding discrete points of the upper and lower surfaces of the basic airfoil according to the rotation angle of the discrete points of the basic airfoil chord line;

[0008] (3) The coordinates of each discrete point are determined according to the rotation angle of each discrete point, and each discrete point is smoothly connected to obtain a 90-degree bent airfoil.

[0009] Furthermore, the 90-degree bent airfoil obtained by smoothly connecting each discrete point in step (3) is stretched and scaled to obtain the parameters of the guide surface of the scaled 90-degree bent airfoil. The scaled 90-degree bent airfoil is placed in the bending part of the air inlet, with the leading edge of the 90-degree bent airfoil facing the incoming flow direction, the trailing edge being in the same direction as the airflow direction and directing the airflow to the bending direction. After placement, the 90-degree bent airfoil is trimmed where it exceeds the air inlet wall so that it fits the air inlet wall, and the final design parameters of the 90-degree bent airfoil are obtained.

[0010] Furthermore, the control equation of the super ellipse guide line is:

[0011]

[0012] Among them, x is the horizontal coordinate of the super ellipse guide line, y is the vertical coordinate of the super ellipse guide line, a is the major axis of the super ellipse, b is the minor axis of the super ellipse, m is the shape control parameter, and t is the independent variable.

[0013] Furthermore, the basic airfoil adopts a NACA6412 model airfoil.

[0014] Furthermore, the coordinates of each discrete point are determined according to the rotation angle of each discrete point:

[0015]

[0016] Among them, the original coordinates of the i-th discrete point are (x i ,y i ), the rotation angle of the i-th discrete point is α i , the coordinates of the i-th discrete point after rotation are (x i ',yi ').

[0017] The present invention also adopts an air intake duct, including the air intake duct and a guide plate installed at the bending position of the air intake duct, and the profile of the guide plate is determined by the parameter determination method of the 90-degree bending guide profile mentioned above.

[0018] The present invention also adopts a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor implements the steps of the above method when executing the computer program.

[0019] The present invention also adopts a computer-readable storage medium on which a computer program is stored, characterized in that the computer program implements the steps of the above method when executed by a processor.

[0020] Beneficial effects: Compared with the prior art, the significant advantage of the present invention is that through the parametric control of the super-elliptical guide line, the major axis and the minor axis can be parametrically adjusted to achieve a variety of guide airfoil designs. Its basic profile is not restricted and any airfoil can be used. The designed airfoil can precisely control the airflow to reduce flow separation and vortex, minimize energy loss, and adapt to the aerodynamic characteristics under different flight conditions, thereby optimizing the flow field quality, improving the aerodynamic performance of the engine inlet surface, and ensuring the aerodynamic efficiency and stealth characteristics of the aircraft, so as to cope with the complex aerodynamic challenges faced by the inlet flow in the existing design. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the NACA6412 airfoil used in the present invention.

[0022] Figure 2 Schematic diagram of a 1 / 4 superelliptic curve under different major axes in the present invention.

[0023] Figure 3 It is a schematic diagram of a 1 / 4 superelliptic curve under different shape control parameters in the present invention.

[0024] Figure 4 It is a schematic diagram of the correspondence between the discrete points of the basic airfoil chord line and the discrete points of the 1 / 4 super ellipse guide line in the present invention.

[0025] Figure 5 It is a schematic diagram of the deformation process of the basic wing according to the 1 / 4 super ellipse guide line in the present invention.

[0026] Figure 6 Schematic diagram of the flow guide surface generated by using different major axis 1 / 4 super ellipses in the present invention.

[0027] Figure 7 Schematic diagram of the flow guide surface generated by using 1 / 4 super ellipse with different shape control parameters in the present invention.

[0028] Figure 8 This is a cross-sectional view of the guide plate of the present invention installed on the air inlet duct.

[0029] Fig. 9 The figure is a schematic diagram of the overall structure of the guide plate installed on the air inlet duct in the present invention. DETAILED DESCRIPTION

[0030] A method for determining parameters of a 90-degree curved flow guide profile in this embodiment specifically includes the following steps:

[0031] (1) Determine the original airfoil. In this embodiment, NACA6412 is used as the basic airfoil, and its upper and lower surfaces are discretized into n points, such as Figure 1 As shown in the figure, the chord length l of NACA6412 is 1, and the chord length l is discretized into n points.

[0032] (2) Determine the angle that each discrete point of the basic airfoil needs to rotate.

[0033] (2.1) Figure 2 , 3 As shown, the control equation of the super ellipse guide line is determined, and the 1 / 4 super ellipse guide line is discretized into n points. The control equation is:

[0034]

[0035] Among them, the major axis and minor axis of the superellipse are determined by a and b, where equation a 2 +b 2 = 1, the straight-line distance between the two end points of the 1 / 4 superellipse is determined to be 1. At the same time, one degree of freedom is reserved to achieve parametric control of the major axis and the minor axis. Figure 2 As shown in Figure 1, different parameters a generate different superellipse lines. Control parameter m to achieve different superellipse lines. For different curves generated, please refer to Figure 3 .

[0036] (2.2) Figure 4 As shown, the endpoint of the basic airfoil chord is coincident with the starting point of the 1 / 4 super ellipse guide line, and the discrete points of the basic airfoil chord are matched one by one with the discrete points of the 1 / 4 super ellipse guide line to obtain the rotation angle of the discrete points of the basic airfoil chord.

[0037] (2.3) Figure 5 As shown, the rotation angles of the corresponding discrete points of the upper and lower surfaces of the basic airfoil are determined according to the rotation angles of the discrete points of the basic airfoil chord. Taking the basic airfoil NACA6412 in this embodiment as an example, the angle required to rotate the i-th discrete point is α i .

[0038] (3) Determine the coordinates of each discrete point according to the rotation angle of each discrete point, and smoothly connect each discrete point to obtain a 90-degree bent airfoil. The original coordinates of the i-th discrete point of the basic airfoil NACA6412 are (x i ,y i )The rotated coordinates (x i ',y i ')for:

[0039]

[0040] (4) According to the steps (1) to (3) above, guide surfaces with different parameters are generated as required, and the generated airfoil is stretched and scaled accordingly according to the size of the inlet to form the guide surface required in the inlet. The guide surfaces formed by different parameters a and different parameters m are as follows: Figure 6 and Figure 7 shown.

[0041] (5) The formed guide surface is placed at the bend of the aircraft air inlet for assembly. The assembly method is that the leading edge of the guide surface airfoil faces the incoming flow direction, and the trailing edge is in the same direction as the airflow and guides the airflow to the bending direction. After assembly, the part of the guide surface protruding from the air inlet wall is trimmed to make it fit with the air inlet wall, and the final design parameters of the 90-degree bent airfoil are obtained. The final assembly effect is shown in Figure 1. Figure 8 and Fig. 9 shown.

Claims

1. A method for determining parameters of a 90-degree bend flow-guiding surface, characterized in that: The following steps are involved: (1) determining the guide surface of the existing basic airfoil, including the upper surface and the lower surface, and discretizing the upper surface, the lower surface and the chord line of the basic airfoil into n points respectively; (2) Determine the angle that each discrete point of the basic airfoil needs to rotate; Determine the control equation of the super ellipse guide line, discretize the 1 / 4 super ellipse guide line into n points, make the endpoint of the basic airfoil chord line coincide with the starting point of the 1 / 4 super ellipse guide line, and make the discrete points of the basic airfoil chord line correspond to the discrete points of the 1 / 4 super ellipse guide line one by one, obtain the rotation angle of the discrete points of the basic airfoil chord line, and determine the rotation angle of the corresponding discrete points of the upper and lower surfaces of the basic airfoil according to the rotation angle of the discrete points of the basic airfoil chord line; (3) The coordinates of each discrete point are determined according to the rotation angle of each discrete point, and each discrete point is smoothly connected to obtain a 90-degree bent airfoil.

2. The method for determining parameters of a 90-degree bending flow-guiding profile according to claim 1, characterized in that: The 90-degree bent airfoil obtained by smoothly connecting each discrete point in step (3) is stretched and scaled to obtain the parameters of the guide surface of the scaled 90-degree bent airfoil.

3. According to the parameter determination method of the 90-degree bent guide surface described in claim 2, the scaled 90-degree bent airfoil is placed in the bending part of the air inlet, the leading edge of the 90-degree bent airfoil faces the incoming flow direction, the trailing edge is in the same direction as the airflow and guides the airflow to the bending direction, and after placement, the part of the 90-degree bent airfoil that exceeds the wall of the air inlet is trimmed to make it fit with the wall of the air inlet, so as to obtain the final design parameters of the 90-degree bent airfoil.

4. The method for determining parameters of a 90-degree bending flow-guiding profile according to claim 1, characterized in that: The control equation of the super ellipse guide line is: Among them, x is the horizontal coordinate of the super ellipse guide line, y is the vertical coordinate of the super ellipse guide line, a is the major axis of the super ellipse, b is the minor axis of the super ellipse, m is the shape control parameter, and t is the independent variable.

5. The method for determining parameters of a 90-degree bending flow-guiding profile according to claim 1, characterized in that: The basic airfoil adopts the NACA6412 model airfoil.

6. The method for determining parameters of a 90-degree bending flow-guiding profile according to claim 1, characterized in that: The coordinates of each discrete point are determined according to the rotation angle of each discrete point: Among them, the original coordinates of the i-th discrete point are (x i ,y i ), the rotation angle of the i-th discrete point is α i , the coordinates of the i-th discrete point after rotation are (x i ',y i ').

7. An air intake duct, characterized in that: It comprises an air inlet and a guide plate installed at the bending part of the air inlet, wherein the profile of the guide plate is determined by the parameter determination method of the 90-degree bending guide profile described in any one of claims 1-6.

8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

Images