External film laying method and fixed-wing aircraft

Abstract

The present application relates to a method for laying an external film and a fixed-wing aircraft, including: constructing a three-dimensional model of the surface of the fixed-wing aircraft; simulating the flow field of the fixed-wing aircraft in flight based on the three-dimensional model; spreading the area to be laid into a plane; discretizing the streamlines on the plane to obtain the linear fitting lines corresponding to the streamlines, and the angles between the tangents of the streamlines and the corresponding linear fitting lines are all less than or equal to a preset angle; identifying the paving surface of the plane based on the discretization results; selecting an external film, cutting the external film based on the size and shape of each paving surface to obtain external film patches corresponding to each paving surface; laying the external film patches to the outer surface of the fixed-wing aircraft. The present application can effectively reduce the surface friction resistance of the fixed-wing aircraft during flight, improve fuel efficiency, and achieve the purpose of energy conservation, emission reduction, and flight efficiency improvement.

Description

Technical Field

[0001] The present application relates to the field of aviation engineering technology, and in particular to a method for laying an external film and a fixed-wing aircraft. Background Art

[0002] With the rapid development of the global aviation industry, energy conservation and emission reduction have become one of the major challenges facing the aviation industry. Flight resistance is a key factor affecting aircraft fuel consumption and emissions, among which the surface friction resistance of fixed-wing aircraft (such as airplanes) accounts for a considerable part of the total resistance. Therefore, the development of technologies that can effectively reduce the surface friction resistance of aircraft is of great significance to improving the environmental protection and economy of air transportation. As a non-invasive and easy-to-implement solution, external film technology has received widespread attention in recent years and plays a vital role. It mainly plays a role in multiple protection of the outer surface of civil aircraft, used for commercial advertising, or scientifically and effectively reducing the surface friction resistance during flight.

[0003] However, how to scientifically and rationally design the paving plan for the external film to achieve the best drag reduction effect is still a problem that needs to be solved urgently. Summary of the invention

[0004] Based on this, it is necessary to address the above problems, and the present application provides a method for laying an external film and a fixed-wing aircraft.

[0005] In a first aspect, the present application provides a method for laying an external film, comprising:

[0006] Constructing a three-dimensional model of a surface of a fixed-wing aircraft, wherein the surface of the fixed-wing aircraft includes an area to be tiled;

[0007] Simulating the flow field of the fixed-wing aircraft in flight based on the three-dimensional model to analyze and obtain the airflow characteristics and streamline directions of different areas on the surface of the fixed-wing aircraft;

[0008] Spreading the area to be paved into a plane;

[0009] Discretize the streamlines on the plane to obtain linear fitting lines corresponding to the streamlines, wherein the angles between the tangents of the streamlines and the corresponding linear fitting lines are less than or equal to a preset angle;

[0010] The plane is identified as a paving surface based on the discretization processing result, including: if each streamline on the plane obtains a linear fitting line after the discretization processing, the plane is used as a paving surface; if each streamline on the plane obtains a plurality of linear fitting lines connected in sequence after the discretization processing, the connection point of two mutually connected linear fitting lines is used as a segmentation point, and the plurality of segmentation points are fitted along the arrangement direction of the plurality of streamlines to obtain a segmentation line; the plane is segmented based on the segmentation line to obtain a plurality of segmentation areas, each of which is a paving surface;

[0011] Selecting an external film, and cutting the external film based on the size and shape of each paving surface to obtain external film patches corresponding to each paving surface;

[0012] The outer film sticker is laid on the outer surface of the fixed-wing aircraft.

[0013] In the method for laying the external film of the present application, by discretizing the streamlines on the plane, a linear fitting line corresponding to the streamline can be obtained, ensuring that the angle between the tangent of the streamline and the corresponding linear fitting line is less than or equal to a preset angle, and the plane is identified for laying the external film based on the discretization result before laying the external film, so that efficient and accurate external film laying can be achieved on the outer surface of the fixed-wing aircraft, which can effectively reduce the surface friction resistance of the fixed-wing aircraft during flight, improve fuel efficiency, and achieve the purpose of energy conservation and emission reduction as well as improved flight efficiency.

[0014] In one embodiment, the front side of the external film has a microstructure; the external film selection includes:

[0015] Obtaining an average dimensionless boundary layer thickness of the fixed-wing aircraft;

[0016] According to the average dimensionless boundary layer thickness of the fixed-wing aircraft, the dimensionless height of the microstructure of the external film is obtained;

[0017] The height of the microstructure of the outer film is obtained based on the dimensionless height of the microstructure of the outer film.

[0018] In one embodiment, the average dimensionless boundary layer thickness The formula is:

[0019]

[0020] is the dimensionless boundary layer thickness at the i-th position on the surface of the fixed-wing aircraft; n is the total number of dimensionless boundary layer thicknesses of the fixed-wing aircraft;

[0021] , where u i is the velocity of the boundary layer at the i-th location, t is the eddy viscosity coefficient, and v is the fluid dynamic viscosity coefficient; i is greater than or equal to 1 and less than or equal to n;

[0022] The dimensionless height of the microstructure of the external film The formula is:

[0023]

[0024] The formula for obtaining the height h of the microstructure of the outer film based on the dimensionless height of the microstructure of the outer film is:

[0025]

[0026] Where v is the fluid dynamic viscosity coefficient, is the wall friction velocity.

[0027] In one embodiment, the front side of the external film has a microstructure; the external film selection includes:

[0028] Dividing the fixed-wing aircraft into a nose area, a fuselage area, and a tail area;

[0029] Respectively obtaining the local average dimensionless boundary layer thickness of the nose region, the fuselage region, and the tail region;

[0030] According to the local average dimensionless boundary layer thickness of the nose region, the dimensionless height of the microstructure of the external film required in the nose region is obtained; according to the local average dimensionless boundary layer thickness of the fuselage region, the dimensionless height of the microstructure of the external film required in the fuselage region is obtained; based on the local average dimensionless boundary layer thickness of the tail region, the dimensionless height of the microstructure of the external film required in the tail region is obtained;

[0031] The height of the microstructure of each external film is obtained based on the dimensionless height of the microstructure of each external film.

[0032] In one embodiment, the local average dimensionless boundary layer thickness of the nose region, the fuselage region or the tail region is The formula is:

[0033]

[0034] is the dimensionless boundary layer thickness at the i-th location in the nose region, the fuselage region or the tail region; n is the total number of dimensionless boundary layer thicknesses in the nose region, the fuselage region or the tail region;

[0035] , where u i is the velocity of the boundary layer at the i-th location in the nose region, the fuselage region or the tail region, t is the eddy viscosity coefficient, v is the fluid dynamic viscosity coefficient; i is greater than or equal to 1 and less than or equal to n;

[0036] The dimensionless height of the microstructure of the external film required for the nose region, the fuselage region or the tail region The formula is:

[0037]

[0038] Based on the dimensionless height of the microstructure of the external film, the formula for obtaining the height h of the microstructure of the external film is:

[0039]

[0040] Where v is the fluid dynamic viscosity coefficient, is the wall friction velocity.

[0041] In one of the embodiments, constructing the three-dimensional model of the surface of the fixed-wing aircraft includes: acquiring geometric dimensions of the fixed-wing aircraft, and constructing the three-dimensional model of the surface of the fixed-wing aircraft based on the geometric dimensions;

[0042] The simulating the flow field condition of the fixed-wing aircraft in flight based on the three-dimensional model includes: obtaining flight performance parameters of the fixed-wing aircraft; and simulating the flow field condition of the fixed-wing aircraft in flight based on the flight performance parameters and the three-dimensional model.

[0043] In one embodiment, the front side of the external film has a plurality of microstructures arranged in multiple rows and columns; after the external film patches are paved on the outer surface of the fixed-wing aircraft, the downstream direction of the microstructure of each external film patch is the same as the extension direction of the linear fitting line in the paving surface.

[0044] In one of the embodiments, during the process of paving the outer film patch onto the outer surface of the fixed-wing aircraft, laser ranging and machine vision technology are used to monitor the accuracy of the paving position of the outer film patch, and the paving position of the outer film patch is adjusted when there is a deviation in the paving position.

[0045] In one embodiment, the preset angle is 1°~5°.

[0046] In a second aspect, the present application further provides a fixed-wing aircraft, the fixed-wing aircraft comprising:

[0047] Fixed-wing aircraft body;

[0048] The external film is applied to the outer surface of the fixed-wing aircraft body by using the external film application method described in the first aspect.

[0049] In the fixed-wing aircraft of the present application, since the outer surface is paved with an external film laid using the external film laying method as described in the first aspect, the surface friction resistance of the fixed-wing aircraft during flight can be effectively reduced, fuel efficiency can be improved, and the purpose of energy conservation and emission reduction and improved flight efficiency can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a flow chart of a method for laying an external film provided in one embodiment of the present application;

[0051] Figure 2 This is a schematic diagram of the curved surface A at the nose position of the fixed-wing aircraft after being spread into a plane in step S30 of the external film laying method provided in the present application;

[0052] Figure 3 This is a schematic diagram of discretizing the streamlines of a plane in step S40 of the method for laying an external film provided in the present application;

[0053] Figure 4 for Figure 2 Schematic diagram of the A8 plane after segmentation;

[0054] Figure 5 It is a schematic diagram of spreading the curved surface of the straight section of the middle section of the fuselage of a civil aircraft into a plane in one embodiment of the present application;

[0055] Figure 6 For the general Figure 5 Schematic diagram of the discretization of streamlines in the plane spread out in the figure;

[0056] Figure 7 This is a schematic diagram of spreading a curved surface at a bulge position of a civil aircraft fuselage into a flat surface in one embodiment of the present application;

[0057] Figure 8 For the general Figure 7 Schematic diagram of the discretization and segmentation of the C3 plane in .

[0058] Component number description: 10. Fixed-wing aircraft. DETAILED DESCRIPTION

[0059] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0061] In the description of the present application, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the methods or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0062] In one embodiment, see Figure 1 The present application provides a method for laying an external film, and the method for laying an external film may include:

[0063] S10: constructing a three-dimensional model of a surface of a fixed-wing aircraft, wherein the surface of the fixed-wing aircraft includes an area to be paved.

[0064] S20: simulating the flow field of the fixed-wing aircraft in flight based on the three-dimensional model to analyze and obtain the airflow characteristics and streamline directions of different areas on the surface of the fixed-wing aircraft.

[0065] S30: Spreading the area to be tiled into a plane.

[0066] S40: discretizing the streamlines on the plane to obtain linear fitting lines corresponding to the streamlines, wherein the angles between the tangents of the streamlines and the corresponding linear fitting lines are less than or equal to a preset angle.

[0067] S50: Based on the discretization processing result, the plane is identified as a paving surface, including: if each streamline on the plane obtains a linear fitting line after the discretization processing, then the plane is used as a paving surface; if each streamline on the plane obtains a plurality of sequentially connected linear fitting lines after the discretization processing, then the connection point of two mutually connected linear fitting lines is used as a segmentation point, and the plurality of segmentation points are fitted along the arrangement direction of the plurality of streamlines to obtain a segmentation line; based on the segmentation line, the plane is segmented to obtain a plurality of segmentation areas, and each of the segmentation areas is a paving surface.

[0068] S60: selecting an external film, and cutting the external film based on the size and shape of each paving surface to obtain external film patches corresponding to each paving surface.

[0069] S70: Laying the outer film sticker onto the outer surface of the fixed-wing aircraft.

[0070] In the method for laying the external film of the present application, by discretizing the streamlines on the plane, a linear fitting line corresponding to the streamline can be obtained, ensuring that the angle between the tangent of the streamline and the corresponding linear fitting line is less than or equal to a preset angle, and the plane is identified for laying the external film based on the discretization result before laying the external film, so that efficient and accurate external film laying can be achieved on the outer surface of the fixed-wing aircraft, which can effectively reduce the surface friction resistance of the fixed-wing aircraft during flight, improve fuel efficiency, and achieve the purpose of energy conservation and emission reduction as well as improved flight efficiency.

[0071] In step S10, refer to Figure 1 In step S10, a three-dimensional model of a surface of a fixed-wing aircraft is constructed, wherein the surface of the fixed-wing aircraft includes an area to be paved.

[0072] As an example, before constructing a three-dimensional model of the surface of a fixed-wing aircraft, the following steps may be included: obtaining the geometric dimensions and flight performance parameters of the fixed-wing aircraft. Specifically, any existing acquisition method may be used to obtain the geometric dimensions and flight performance parameters of the fixed-wing aircraft. For example, the geometric dimensions of the fixed-wing aircraft may be obtained by design drawings, referring to flight manuals, referring to maintenance manuals, or performing 3D mapping of the fixed-wing aircraft; the flight performance parameters of the fixed-wing aircraft may be obtained by referring to historical data records or referring to flight manuals.

[0073] As an example, the flight performance parameter may include, but is not limited to, at least one of a cruise altitude, a cruise speed, a cruise Mach number, and a cruise angle of attack.

[0074] As an example, the fixed-wing aircraft may include but is not limited to civil aircraft.

[0075] As an example, a three-dimensional model of the surface of the fixed-wing aircraft may be constructed based on the acquired geometric dimensions of the fixed-wing aircraft; specifically, any existing model construction method may be used to construct the three-dimensional model of the surface of the fixed-wing aircraft.

[0076] In step S20, refer to Figure 1 In step S20, the flow field of the fixed-wing aircraft in flight is simulated based on the three-dimensional model to analyze and obtain the airflow characteristics and streamline directions of different areas on the surface of the fixed-wing aircraft.

[0077] As an example, computational fluid dynamics (CFD) may be used to simulate the flow field of the fixed-wing aircraft in flight, so as to analyze and obtain the airflow characteristics and streamline directions of different regions on the surface of the fixed-wing aircraft.

[0078] As an example, the flow field condition of the fixed-wing aircraft in flight state may be simulated based on the aircraft performance parameters and the three-dimensional model.

[0079] As an example, the airflow characteristics mainly include the velocity distribution on the surface of the fixed-wing aircraft.

[0080] In step S30, refer to Figure 1 S30 steps in Figure 2 , spread the area to be paved into a plane.

[0081] As an example, Figure 2 FIG. 1 is a schematic diagram of the curved surface A at the nose position of the fixed-wing aircraft 10 after being spread into a plane in step S30, wherein: Figure 2 Figure (a) is a schematic diagram of the nose of the fixed-wing aircraft 10. Figure 2 Figure (b) shows the Figure 2 (a) is a schematic diagram of the eight planes A1, A2, A3, A4, A5, A6, A7 and A8 obtained by spreading and dividing the A area in the figure. It should be noted that after spreading the A area, it can be divided into eight planes A1, A2, A3, A4, A5, A6, A7 and A8 based on experience. There are no specific restrictions on the division, so that the subsequent paving is the primary consideration.

[0082] In step S40, refer to Figure 1 S40 steps and Figure 3 , the streamlines on the plane are discretized to obtain linear fitting lines corresponding to the streamlines, and the angles between the tangents of the streamlines and the corresponding linear fitting lines are less than or equal to a preset angle.

[0083] As an example, first, the intersection of the streamline and the plane boundary is used as the tangent point to make the tangent of the streamline. The tangent point is the starting point of the discretization process. The tangent point is recorded as the first tangent point, and the corresponding tangent is recorded as the first tangent. Then the streamline is discretized to obtain a linear fitting line. At this time, the angle α between the linear fitting line and the first tangent is less than or equal to the preset angle; the linear fitting line will intersect with the streamline, and the intersection is used as the second tangent point to make the tangent. The tangent is recorded as the second tangent. The size of the angle between the second tangent and the linear fitting line is determined. If the angle between the second tangent and the linear fitting line is greater than the preset angle, the discretization process is adjusted so that the angle between the second tangent and the linear fitting line is equal to the preset angle. Then, the second tangent point is used as the new starting point of the discretization process, and the above discretization process steps are repeated to ensure that after the discretization process, the angle between the tangent of the streamline and the corresponding linear fitting line is less than or equal to the preset angle.

[0084] It should be noted that if the angle between the second tangent line and the linear fitting line is less than the preset angle, the discretization process is adjusted so that the intersection of the linear fitting line and the streamline is oriented in the direction of Figure 3 Move to the left of the plane, and promptly determine whether the angle between the tangent line and the linear fitting line when the new intersection point is used as the tangent point is less than the preset angle. If so, repeat the above steps until the intersection point of the linear fitting line and the streamline is the intersection point of the streamline and the other boundary of the plane. That is, at this time, the streamline in the plane has only one linear fitting line after discretization, and the angles between all the tangent lines of the streamline and the linear fitting line are less than or equal to the preset angle. At this time, the situation corresponds to Figure 6 The situation in .

[0085] As an example, the preset angle can be set according to actual needs. For example, the preset angle may range from 1° to 5°. In this embodiment, the preset angle is preferably 3°.

[0086] In step S50, refer to Figure 1 S50 steps in Figure 4 , Figure 6 and Figure 8 , based on the discretization processing result, the plane is identified as a paving surface, including: if each streamline on the plane obtains a linear fitting line after the discretization processing, then the plane is used as a paving surface; if each streamline on the plane obtains a plurality of linear fitting lines connected in sequence after the discretization processing, then the connection point of two mutually connected linear fitting lines is used as a segmentation point, and the plurality of segmentation points are fitted along the arrangement direction of the plurality of streamlines to obtain a segmentation line; based on the segmentation line, the plane is segmented to obtain a plurality of segmentation areas, and each of the segmentation areas is a paving surface.

[0087] As an example, in step S50, the paving surface identification of the plane based on the discretization processing result may include the following steps: if each streamline on the plane obtains a linear fitting straight line after the discretization processing, the plane is used as the paving surface, such as Figure 6 As shown; if each streamline on the plane is subjected to the discretization process to obtain a plurality of linear fitting lines connected in sequence, then the connection point of two mutually connected linear fitting lines is used as a segmentation point, and the plurality of segmentation points are fitted along the arrangement direction of the plurality of streamlines to obtain a plurality of segmentation lines; the plane is segmented based on each of the segmentation lines to obtain a plurality of segmentation areas, such as Figure 4 and Figure 8 As shown; each of the divided areas is a paved surface.

[0088] As an example, the multiple segmented areas after segmentation can be multiple segmented areas of different sizes; the multiple segmented areas can be numbered in order so that each segmented area has a serial number arranged in order, for example, the multiple segmented areas can be numbered from front to back in the order from the front to the back of the fixed-wing aircraft. Of course, the multiple paving surfaces can also be numbered separately so that each paving surface has its own serial number. It should be noted that the serial number of the paving surface and the serial number of the segmented area need to be different to facilitate distinction and avoid confusion.

[0089] As an example, Figure 4 for Figure 2 The schematic diagram of the A8 plane after segmentation is shown in Figure 1. Figure 4 It can be seen that the A8 area can be divided into six areas: A8-1, A8-2, A8-3, A8-4, A8-5 and A8-6. Figure 4 The curve with an arrow in the middle is the streamline of the plane.

[0090] As an example, in step S60, see Figure 1 In step S60, an external film is selected, and the external film is cut based on the size and shape of each of the paving surfaces to obtain external film patches corresponding to each of the paving surfaces.

[0091] In one example, the front side of the external film has a microstructure. The fixed-wing aircraft can be taken as a whole, and the providing of the external film includes the following steps: obtaining the average dimensionless boundary layer thickness of the fixed-wing aircraft; obtaining the dimensionless height of the microstructure of the external film according to the average dimensionless boundary layer thickness of the fixed-wing aircraft; and obtaining the height of the microstructure of the external film based on the dimensionless height of the microstructure of the external film.

[0092] As an example, the dimensionless boundary layer thickness of the fixed-wing aircraft is The formula can be:

[0093]

[0094] is the dimensionless boundary layer thickness at the ith location on the surface of the fixed-wing aircraft; and n is the total number of dimensionless boundary layer thicknesses of the fixed-wing aircraft.

[0095] , where u i is the velocity of the boundary layer at the i-th location, t is the eddy viscosity coefficient, v is the fluid dynamic viscosity coefficient; i is greater than or equal to 1 and less than or equal to n.

[0096] The dimensionless height of the microstructure of the external film The formula can be:

[0097]

[0098] The formula for obtaining the height h of the microstructure of the outer film based on the dimensionless height of the microstructure of the outer film can be:

[0099]

[0100] Where v is the fluid dynamic viscosity coefficient, is the wall friction velocity.

[0101] It should be noted that the dimensionless height of the microstructure of the external film is There can be 3, and you can choose any dimensionless height Substitute the height h of the microstructure of the external film into the formula to obtain the height h of the microstructure of the external film; you can also use the three dimensionless heights The heights h of the microstructures of the three outer films were respectively substituted into the formulas for the height h of the microstructures of the outer films, and then the best height h was selected through testing and verification.

[0102] In another example, the front side of the external film has a microstructure. In order to make the height of the microstructure of the external film more accurately match different areas of the fixed-wing aircraft, the fixed-wing aircraft can be divided first; in this case, the external film selection includes: dividing the fixed-wing aircraft into a nose area, a fuselage area and a tail area; obtaining the local average dimensionless boundary layer thickness of the nose area, the fuselage area and the tail area respectively; obtaining the dimensionless height of the microstructure of the external film required for the nose area according to the local average dimensionless boundary layer thickness of the nose area; obtaining the dimensionless height of the microstructure of the external film required for the fuselage area according to the local average dimensionless boundary layer thickness of the fuselage area; obtaining the dimensionless height of the microstructure of the external film required for the tail area based on the local average dimensionless boundary layer thickness of the tail area; obtaining the height of the microstructure of each external film based on the dimensionless height of the microstructure of each external film.

[0103] As an example, the local average dimensionless boundary layer thickness of the nose region, the fuselage region or the tail region is The formula is the same as:

[0104]

[0105] is the dimensionless boundary layer thickness at the i-th location in the nose region, the fuselage region, or the tail region; and n is the total number of dimensionless boundary layer thicknesses in the nose region, the fuselage region, or the tail region. is the local average dimensionless boundary layer thickness in the nose region, is the dimensionless boundary layer thickness at the i-th location in the nose region, and n is the total number of dimensionless boundary layer thicknesses in the nose region; is the local average dimensionless boundary layer thickness in the fuselage region, is the dimensionless boundary layer thickness at the ith location in the fuselage region, and n is the total number of dimensionless boundary layer thicknesses in the fuselage region; is the local average dimensionless boundary layer thickness in the tail region, is the dimensionless boundary layer thickness at the i-th location in the tail region, and n is the total number of dimensionless boundary layer thicknesses in the tail region.

[0106] , where u i is the velocity of the i-th boundary layer in the nose region, the fuselage region or the tail region, t is the eddy viscosity coefficient, v is the fluid dynamic viscosity coefficient; i is greater than or equal to 1 and less than or equal to n. When u is the dimensionless boundary layer thickness at the i-th location in the nose region, iis the velocity of the boundary layer at the i-th position in the nose region; is the dimensionless boundary layer thickness at the i-th location in the fuselage region, u i is the velocity of the i-th boundary layer in the fuselage region; When u is the dimensionless boundary layer thickness at the i-th location in the tail region, i is the velocity of the i-th boundary layer in the tail region.

[0107] The dimensionless height of the microstructure of the external film required for the nose region, the fuselage region or the tail region The formula is:

[0108]

[0109] Based on the dimensionless height of the microstructure of the external film, the formula for obtaining the height h of the microstructure of the external film is:

[0110]

[0111] Where v is the fluid dynamic viscosity coefficient, is the wall friction velocity.

[0112] It should be noted that the dimensionless height of the microstructure of the external film is There can be 3, and you can choose any dimensionless height Substitute the height h of the microstructure of the external film into the formula to obtain the height h of the microstructure of the external film; you can also use the three dimensionless heights The heights h of the microstructures of the three outer films were respectively substituted into the formulas for the height h of the microstructures of the outer films, and then the best height h was selected through testing and verification.

[0113] If the height of the microstructure of the outer film is too high, the boundary layer development will increase, resulting in an increase in surface friction resistance during flight; if the height of the microstructure of the outer film is too small, the microstructure cannot affect the boundary layer flow and cannot reduce the surface friction resistance. In the present application, by selecting the height of the microstructure of the outer film by the above method, the surface friction resistance of the fixed-wing aircraft during flight can be effectively reduced, fuel efficiency can be improved, and the purpose of energy conservation, emission reduction and improved flight efficiency can be achieved.

[0114] As an example, in the process of cutting the external film based on the size and shape of each paving surface, it is necessary to ensure that the external film blocks obtained after cutting are consistent with the shape and size of the paving surface to be paved, so as to ensure that the paving surface can be completely covered after paving.

[0115] In step S70, refer to Figure 1In step S70, the outer film sticker is applied to the outer surface of the fixed-wing aircraft.

[0116] As an example, the outer film patch may be laid on the outer surface of the fixed-wing aircraft with the aid of a laying device, or may be laid on the outer surface of the fixed-wing aircraft manually.

[0117] As an example, the front side of the external film has a plurality of microstructures arranged in multiple rows and columns, that is, the front side of each external film patch has a plurality of microstructures arranged in multiple rows and columns; after the external film patch is paved on the outer surface of the fixed-wing aircraft, the downstream direction of the microstructure of each external film patch is the same as the extension direction of the linear fitting line in the paving surface. The downstream direction of the microstructure of the external film patch can be the row direction of the plurality of microstructures arranged in multiple rows and columns, that is, the arrangement direction of the plurality of microstructures in the same row.

[0118] If the downstream direction of the microstructure of the outer film patch is relatively large with the angle between the linear fitting line and the tangent of the streamline, for example, greater than 5°, the drag reduction capability of the outer film will be weakened, and even with the increase of the angle, the surface friction resistance will increase during flight. Therefore, in the present application, after the outer film patch is paved on the outer surface of the fixed-wing aircraft, the downstream direction of the microstructure of each outer film patch is limited to be the same as the extension direction of the linear fitting line in the paving surface, so that the outer film can have the best drag reduction effect.

[0119] It should be noted that, during the paving process, each of the outer film stickers is paved on the surface of the paving surface having a shape and size corresponding thereto.

[0120] As an example, during the process of paving the outer film patch to the outer surface of the fixed-wing aircraft, laser ranging and machine vision technology can be used to monitor the accuracy of the paving position of the outer film patch, and the paving position of the outer film patch can be adjusted when there is a deviation in the paving position.

[0121] In one embodiment, see Figure 5 Taking the analysis of the curved surface of the straight section in the middle section of the fuselage of a civil aircraft as an example, the partial structural diagram of the civil aircraft is shown in Figure 5 As shown in Figure (a) in the figure; when this part is unfolded, its shape is close to a rectangle, as shown in Figure 5 Plane B1 in (b) of the figure. According to CFD simulation calculation, the streamlines in the plane B1 area are as follows Figure 6 As shown, Figure 6The arrowed lines in the figure are streamlines, and the angles between the tangents of the streamlines and the linear fitting lines after discretization are all less than 3°. Therefore, plane B1 does not need to be divided into regions according to the streamline angles. It is only necessary to cut the external film according to the size of plane B1 and then lay it. After laying, the downstream direction of the microstructure of the external film is the same as the extension direction of the linear fitting line.

[0122] In one embodiment, see Figure 7 Taking the analysis of the curved surface of the bulge part of the fuselage of a civil aircraft as an example, the schematic diagram of part of the structure of the civil aircraft is as follows: Figure 7 As shown in Figure (a) in the figure; due to the complex curved surface of the fuselage bulge, it is divided into six planes C1-C6 after unfolding. According to CFD simulation calculation, the streamlines in plane C3 are as follows Figure 8 As shown by the arrowed curve in the figure, the tangent angle of the streamline changes dramatically and also changes significantly along the span direction. In order to make the angle between the tangent of the streamline and the linear fitting line after discretization less than 3°, the plane C3 needs to be divided into 4 irregular segmented areas according to the streamline angle. The external film is cut according to the size of the segmented area. After paving, the downstream direction of the microstructure of the external film is the same as the extension direction of the linear fitting line of the paving surface where the external film is located.

[0123] The paving method of the external film of the present application has the following beneficial effects:

[0124] 1. Significant drag reduction: Through the precisely designed external film laying solution, the surface friction resistance of civil aircraft during flight is effectively reduced, thereby improving fuel efficiency.

[0125] 2. Environmentally friendly: reducing fuel consumption and directly reducing carbon emissions, which is in line with the green development trend of the global aviation industry.

[0126] 3. Economical and efficient: The installation and maintenance cost of the external film is low, and it has a higher cost-effectiveness than other drag reduction measures.

[0127] 4. Strong adaptability: This method is applicable to various types of civil aircraft and can be customized according to specific models.

[0128] In one embodiment, the present application further provides a fixed-wing aircraft, which may include: a fixed-wing aircraft body; an external film, wherein the external film is made of Figures 1 to 8 The method for laying the external film described in the corresponding embodiment is to lay the film on the outer surface of the fixed-wing aircraft body.

[0129] In the fixed-wing aircraft of the present application, since the outer surface is paved with a Figures 1 to 8The external film laid by the method for laying the external film described in the corresponding embodiment can effectively reduce the surface friction resistance of the fixed-wing aircraft during flight, improve fuel efficiency, and achieve the purpose of energy conservation and emission reduction and improved flight efficiency.

[0130] As an example, the fixed-wing aircraft may include but is not limited to civil aircraft.

[0131] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0132] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for laying an external film, characterized in that: include: Constructing a three-dimensional model of a surface of a fixed-wing aircraft, wherein the surface of the fixed-wing aircraft includes an area to be tiled; Simulating the flow field of the fixed-wing aircraft in flight based on the three-dimensional model to analyze and obtain the airflow characteristics and streamline directions of different areas on the surface of the fixed-wing aircraft; Spreading the area to be paved into a plane; Discretize the streamlines on the plane to obtain linear fitting lines corresponding to the streamlines, wherein the angles between the tangents of the streamlines and the corresponding linear fitting lines are less than or equal to a preset angle; The plane is identified as a paving surface based on the discretization processing result, including: if each streamline on the plane obtains a linear fitting line after the discretization processing, the plane is used as a paving surface; if each streamline on the plane obtains a plurality of linear fitting lines connected in sequence after the discretization processing, the connection point of two mutually connected linear fitting lines is used as a segmentation point, and the plurality of segmentation points are fitted along the arrangement direction of the plurality of streamlines to obtain a segmentation line; the plane is segmented based on the segmentation line to obtain a plurality of segmentation areas, each of which is a paving surface; Selecting an external film, and cutting the external film based on the size and shape of each paving surface to obtain external film patches corresponding to each paving surface; The outer film sticker is laid on the outer surface of the fixed-wing aircraft.

2. The method for laying an external film according to claim 1, characterized in that: The front side of the external film has a microstructure; the external film selection includes: Obtaining an average dimensionless boundary layer thickness of the fixed-wing aircraft; According to the average dimensionless boundary layer thickness of the fixed-wing aircraft, the dimensionless height of the microstructure of the external film is obtained; The height of the microstructure of the outer film is obtained based on the dimensionless height of the microstructure of the outer film.

3. The method for laying an external film according to claim 2, characterized in that: The average dimensionless boundary layer thickness The formula is: is the dimensionless boundary layer thickness at the i-th position on the surface of the fixed-wing aircraft; n is the total number of dimensionless boundary layer thicknesses of the fixed-wing aircraft; , where u i is the velocity of the boundary layer at the i-th location, t is the eddy viscosity coefficient, and v is the fluid dynamic viscosity coefficient; i is greater than or equal to 1 and less than or equal to n; The dimensionless height of the microstructure of the external film The formula is: The formula for obtaining the height h of the microstructure of the outer film based on the dimensionless height of the microstructure of the outer film is: Where v is the fluid dynamic viscosity coefficient, is the wall friction velocity.

4. The method for laying an external film according to claim 1, characterized in that: The front side of the outer film has a microstructure; the outer film selection includes: Dividing the fixed-wing aircraft into a nose area, a fuselage area, and a tail area; Respectively obtaining the local average dimensionless boundary layer thickness of the nose region, the fuselage region, and the tail region; According to the local average dimensionless boundary layer thickness of the nose region, the dimensionless height of the microstructure of the external film required in the nose region is obtained; according to the local average dimensionless boundary layer thickness of the fuselage region, the dimensionless height of the microstructure of the external film required in the fuselage region is obtained; based on the local average dimensionless boundary layer thickness of the tail region, the dimensionless height of the microstructure of the external film required in the tail region is obtained; The height of the microstructure of each external film is obtained based on the dimensionless height of the microstructure of each external film.

5. The method for laying an external film according to claim 4, characterized in that: The local average dimensionless boundary layer thickness of the nose region, the fuselage region or the tail region The formula is: is the dimensionless boundary layer thickness at the i-th location in the nose region, the fuselage region or the tail region; n is the total number of dimensionless boundary layer thicknesses in the nose region, the fuselage region or the tail region; , where u i is the velocity of the boundary layer at the i-th location in the nose region, the fuselage region or the tail region, t is the eddy viscosity coefficient, v is the fluid dynamic viscosity coefficient; i is greater than or equal to 1 and less than or equal to n; The dimensionless height of the microstructure of the external film required for the nose region, the fuselage region or the tail region The formula is: Based on the dimensionless height of the microstructure of the external film, the formula for obtaining the height h of the microstructure of the external film is: Where v is the fluid dynamic viscosity coefficient, is the wall friction velocity.

6. The method for laying an external film according to claim 1, characterized in that: The constructing of the three-dimensional model of the surface of the fixed-wing aircraft comprises: acquiring geometric dimensions of the fixed-wing aircraft, and constructing the three-dimensional model of the surface of the fixed-wing aircraft based on the geometric dimensions; The simulating the flow field condition of the fixed-wing aircraft in flight based on the three-dimensional model includes: obtaining flight performance parameters of the fixed-wing aircraft; and simulating the flow field condition of the fixed-wing aircraft in flight based on the flight performance parameters and the three-dimensional model.

7. The method for laying an external film according to claim 1, characterized in that: The front side of the external film has a plurality of microstructures arranged in multiple rows and columns; after the external film patches are paved on the outer surface of the fixed-wing aircraft, the downstream direction of the microstructure of each external film patch is the same as the extension direction of the linear fitting line in the paving surface.

8. The method for laying an external film according to claim 1, characterized in that: During the process of paving the outer film patch to the outer surface of the fixed-wing aircraft, laser ranging and machine vision technology are used to monitor the accuracy of the paving position of the outer film patch, and the paving position of the outer film patch is adjusted when there is a deviation in the paving position.

9. The method for laying an external film according to any one of claims 1 to 8, characterized in that: The preset angle is 1°~5°.

10. A fixed-wing aircraft, characterized in that: include: Fixed-wing aircraft body; The external film is paved on the outer surface of the fixed-wing aircraft body by using the external film paving method according to any one of claims 1 to 9.

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