Method for converting two-dimensional ice type of aircraft airfoil into three-dimensional ice type

Abstract

The invention belongs to the field of aviation icing research, and relates to a method for converting a two-dimensional ice form of an aircraft airfoil into a three-dimensional ice form. The method comprises the following steps: selecting an ice type with the maximum pneumatic influence from section ice types obtained by an icing wind tunnel test; performing ice type simplification on the selected ice type based on aerodynamic force similarity; and through methods of ice profile translation, bridging or curved surface filling and extrapolation extension, three-dimensional ice forms of different airfoils are generated from the simplified ice forms.

Description

Technical Field

[0001] The invention belongs to the field of aviation icing research and relates to a method for converting a two-dimensional ice type on an aircraft wing into a three-dimensional ice type. Background Art

[0002] According to the similarity criteria for wind tunnel tests on icing aircraft wing surfaces, ice wind tunnel tests usually use full-size wing component models or mixed scaled models with full-size wing leading edges for experimental research. Due to the size of the wind tunnel, only icing tests can be performed on part of the wing section. Ice type measurements in ice wind tunnel tests are usually carried out using the "hot knife method". During the measurement, a heated metal card is used to melt the ice on the measurement section, and then a plastic card is replaced with a coordinate paper to hand-draw the ice type outline to obtain a two-dimensional test ice type for the measurement section. A test piece usually has about three measurement sections. In summary, the ice type obtained from the ice wind tunnel test is only a two-dimensional ice type at different locations on a part of the wing surface. The study of the aerodynamic impact of icing on the aircraft wing surface requires converting the obtained two-dimensional ice type into a three-dimensional ice type covering the entire wing leading edge.

[0003] To ensure the authenticity of the three-dimensional ice type effect after conversion, the following issues need to be addressed during the ice type conversion process: (1) The two-dimensional ice type shape obtained from the ice wind tunnel test is irregular. Usually, the ice type needs to be simplified before conversion to reduce the difficulty of three-dimensional conversion of the ice type and subsequent simulation of the ice type model. Simplified ice type cannot change the aerodynamic effect of the original ice type; (2) The two-dimensional ice types obtained at different positions of the same test piece usually differ. In the ice type conversion, it is necessary to consider how to deal with the differences in ice types at different positions; (3) There are usually differences in chord length and thickness along the span direction of the wing surface. When freezing, the trajectory of water droplets and the impact area will differ, resulting in differences in ice types. In the ice type conversion, it is necessary to consider how to deal with the differences in ice types caused by changes in the wing surface shape. Summary of the invention

[0004] The purpose of the invention is to propose a method for converting a two-dimensional ice type on an aircraft wing into a three-dimensional ice type, so as to solve the problem of three-dimensional conversion of wind tunnel test results of icing on an aircraft wing.

[0005] Technical solution:

[0006] A method for converting a two-dimensional ice type on an aircraft wing into a three-dimensional ice type is proposed, comprising:

[0007] The ice type with the greatest aerodynamic impact is selected from the profile ice types obtained from the ice wind tunnel test;

[0008] Simplify the selected ice type based on aerodynamic similarity;

[0009] The simplified ice type is converted into three-dimensional ice types of different wing surfaces by means of ice type contour translation, bridging or surface filling, and extrapolation and extension.

[0010] Furthermore, the ice type with the greatest aerodynamic impact is selected from the profile ice types obtained from the ice wind tunnel test, including:

[0011] The ice type with the greatest impact on the aerodynamic characteristics of the aircraft is selected from multiple two-dimensional ice types of a component section as the basis for subsequent ice type conversion.

[0012] Furthermore, the ice type with the greatest impact on the aerodynamic characteristics of the aircraft is selected from multiple two-dimensional ice types of a certain component as a reference for subsequent ice type conversion, including:

[0013] Select the more obvious ice angle feature of each cross-sectional ice type, where the more obvious ice angle feature is the ice angle feature with the maximum projection height in the cross-sectional ice type itself;

[0014] All the more obvious ice angle features are aligned with the chord line to form a new section, and the most obvious ice angle feature is selected from the section. The section ice type corresponding to the most obvious ice angle feature is the ice type with the greatest aerodynamic impact;

[0015] If the ice type with the greatest aerodynamic impact cannot be selected, a two-dimensional ice type aerodynamic impact comparison calculation is performed to determine the ice type with the greatest impact;

[0016] For ice types with obvious ice angle characteristics, the ice type with the largest projection height of the icing angle in the lift direction is selected and determined as the ice type with the greatest aerodynamic impact. For cases where the ice angle characteristics are not obvious or the selected result is not unique, a two-dimensional ice type aerodynamic impact comparison calculation can be carried out to determine the ice type with the greatest impact.

[0017] Furthermore, the selected ice type is simplified based on aerodynamic similarity, including:

[0018] From the coordinate points of the reference contour, select the characteristic coordinate points reflecting the extreme shape and characteristic shape and the contour coordinate points between a small number of characteristic points, ignore the coordinate points of the shape details in the non-extreme area, and use spline curves to draw simplified ice models to smooth the local pits and rough shapes of the original ice model to meet the requirements of aircraft simulation ice model manufacturing;

[0019] Carry out aerodynamic impact assessment before and after simplification of two-dimensional ice type, and determine whether the simplification of ice type is feasible based on the principle of aerodynamic equivalence. If not feasible, retain the coordinate points of some shape details in non-extreme areas to obtain a new simplified ice type, and conduct aerodynamic impact assessment again until simplification is feasible.

[0020] Furthermore, the characteristic coordinate points reflecting the extreme shape and the characteristic shape are the coordinate points of the upper / lower icing limits and the coordinate points of the upper / lower ice angle shape.

[0021] Furthermore, the simplified ice type is converted into three-dimensional ice types of different airfoils by translating, bridging or filling in curved surfaces, and extending the ice type contour, including:

[0022] The wingtip is selected for ice type simplification, and the leading edge line of the tail is used as a guide line for translation and adjustment of the upper ice angle to obtain the ice type contours at both ends of the wing surface. The ice type contours at both ends of the wing surface are bridged to obtain the three-dimensional ice type of the entire wingspan.

[0023] Furthermore, the simplified ice type is converted into three-dimensional ice types of different airfoils by translating, bridging or filling in curved surfaces, and extending the ice type contour, including:

[0024] For the wing, the wingtip and wing root are selected for ice type simplification. The closed curve filling method is used to generate the upper wing surface three-dimensional ice type surface, the windward surface three-dimensional ice type surface and the lower wing surface three-dimensional ice type surface in blocks based on the ice type contour lines at both ends, the upper / lower wing surface icing limit connection lines, the upper / lower ice angle connection lines and other characteristic lines. Then, the interpolation and extension method is used to generate the wing leading edge ice type outside the ice type contour lines.

[0025] Beneficial Effects

[0026] The three-dimensional ice shape generated by this method has a simple contour, low processing difficulty, and realistic aerodynamic impact, and can be applied to the study and verification of the aerodynamic impact of aircraft icing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of ice shape screening for the same measurement profile;

[0028] Figure 2 It is a schematic diagram of ice shape screening for the same component with different measurement profiles;

[0029] Figure 3 It is a simplified schematic diagram of ice shape;

[0030] Figure 4 It is a schematic diagram of the three-dimensional ice type transformation on the tail wing surface;

[0031] Figure 5 It is a schematic diagram of the three-dimensional ice type transformation on the wing surface. DETAILED DESCRIPTION

[0032] The present invention proposes a method for converting a two-dimensional ice type of an aircraft wing surface into a three-dimensional ice type. The ice type with the greatest aerodynamic impact is selected from the cross-sectional ice types obtained from the ice wind tunnel test, the selected ice type is simplified based on the aerodynamic similarity, and then the three-dimensional ice types of different wing surfaces are generated by translating the ice type contour, bridging or surface filling, and extrapolating and extending. The method comprises the following steps:

[0033] (1) Ice type screening. The ice type with the greatest impact on the aerodynamic characteristics of the aircraft is selected from multiple two-dimensional ice types of a component section as the basis for subsequent ice type conversion: For ice types with more obvious ice angle characteristics, the ice type with the largest projection height of the icing angle in the lift direction can be selected and determined as the ice type with the greatest aerodynamic impact. For cases where the ice angle characteristics are not obvious or the selection result is not unique, a two-dimensional ice type aerodynamic impact comparison calculation can be carried out to determine the ice type with the greatest impact.

[0034] (2) Ice type simplification. From the coordinate points that characterize the original ice type contour, select the characteristic coordinate points (upper / lower icing limits, upper / lower ice angle contour) that reflect the extreme shape and characteristic shape, as well as the contour coordinate points between a small number of characteristic points, ignore the coordinate points of the shape details in the non-extreme area, and use spline curves to draw simplified ice types to smooth the local pits and rough shapes of the original ice type to meet the requirements of aircraft simulation ice type manufacturing. Carry out aerodynamic impact assessment before and after simplification of the two-dimensional ice type, and determine whether the ice type simplification is feasible based on the principle of equivalent aerodynamic forces.

[0035] (3) Three-dimensional ice type conversion of tail wing surface. The three-dimensional conversion of ice type of tail wing surface is obtained by iso-section stretching method. The two-dimensional ice type of the wing tip is selected and simplified, and the leading edge line of the tail wing is used as the guide line for translation and equal upper ice angle height adjustment to obtain the ice type contours at both ends of the wing surface. The ice type contours at both ends of the wing surface are bridged to obtain the three-dimensional ice type of the entire wingspan. Because the water droplet collection rate at the wing tip is higher than that at the wing root, the icing at the wing tip is more severe than that at the wing root. The ice type effect of the three-dimensional conversion using the ice type at the wing tip is relatively severe. However, due to the small span of the tail wing, the deviation of this treatment method is acceptable.

[0036] (4) Three-dimensional ice type conversion of wing surface. The three-dimensional ice type conversion of wing surface is obtained by using different ice type profile interpolation methods. The two-dimensional ice type of the wing tip and wing root is selected and simplified. The ice type contour lines at both ends, the upper / lower wing surface icing limit connection line, the upper / lower ice angle connection line and other characteristic lines are used. The closed curve filling method is used to generate the upper wing surface three-dimensional ice type surface, the windward surface three-dimensional ice type surface and the lower wing surface three-dimensional ice type surface in blocks. Then, the extrapolation extension method is used to generate the wing leading edge ice type outside the ice type contour line.

[0037] Example 1

[0038] The present invention proposes a method for converting a two-dimensional ice type of an aircraft wing into a three-dimensional ice type. Based on a plurality of known two-dimensional ice type contours of an aircraft wing, a full-span three-dimensional ice type is generated through ice type screening, ice type simplification and three-dimensional ice type conversion. The specific implementation steps of the method are as follows:

[0039] Step 1: Place the two-dimensional ice types of the same measurement section and the same type of ice formation on a test piece together in a way that they are aligned with the airfoil contour, compare the projection heights of the ice angles of each ice type in the lift direction, and select the ice type with the maximum projection height as the selected ice type for the measurement section, such as Figure 1 As shown; determine the selected ice type of other measurement sections by the same method; put the selected ice types of each section together in a way that the leading edge point and the chord line of the airfoil are aligned, compare the projection height of the ice angle of each ice type in the lift direction, and select the ice type with the maximum projection height as the selected ice type of the measurement component, as shown in Figure 2 shown.

[0040] Step 2: Simplify the ice type selected in step 1, use the spline curve drawing method, select the characteristic coordinate points that reflect the extreme shape and characteristic shape (upper / lower icing limit, upper / lower ice angle shape) and the contour coordinate points between a small number of characteristic points, ignore the coordinate points of the shape details in the non-limit area, and form a simplified ice type, such as Figure 3 As shown; carry out aerodynamic calculations of airfoil plus original ice type / simplified ice type, and determine the appropriate simplified ice type based on the equivalence of aerodynamic forces before and after ice type simplification.

[0041] Step 3: For wing surfaces with a smaller span, such as the tail, mark the upper ice angle extreme point P0 on the simplified ice type contour line L0 determined in step 2, use the leading edge line of the wing as a guide line, translate the ice type contour line L0 and the ice angle extreme point P0 to the two ends of the icing area of ​​the wing surface, and make fine adjustments in the direction of the chord line of the wing surface, so that the heights of the ice angle extreme points P1 and P2 at both ends to the wing surface are the same as P0, forming ice types L1 and L2 at both ends of the wing surface, and generate a three-dimensional ice type between L1 and L2 by bridging, and process the gap and intersection between the three-dimensional ice type and the wing surface by extrapolation, extension, and shearing. Figure 4 shown.

[0042] Step 4: For wing surfaces with a larger span, such as wings, determine simplified ice types L1 and L2 at the wing tip and wing root respectively according to step 2. According to the upper and lower wing surface icing limit points and the upper and lower ice angle maximum thickness points of ice types L1 and L2, connect the upper wing surface icing limit line L3, the lower wing surface icing limit line L4, the upper ice angle line L5, and the lower ice angle line L6. Select ice types L1, L2 and lines L3 and L5 to generate a three-dimensional ice type surface for the upper wing surface using the closed curve filling method. Select ice types L1, L2 and lines L5 and L6 to generate a three-dimensional ice type surface for the windward surface using the closed curve filling method. Select ice types L1, L2 and lines L6 and L4 to generate a three-dimensional ice type surface for the lower wing surface using the closed curve filling method. Then use the extrapolation and extension method to extrapolate the three surfaces obtained above to the two ends of the wing surface to obtain the three-dimensional ice type of the entire wing leading edge. Figure 5 shown.

Claims

1. A method for converting a two-dimensional ice type on an aircraft wing into a three-dimensional ice type, characterized in that: include: The ice type with the greatest aerodynamic impact is selected from the profile ice types obtained from the ice wind tunnel test; Simplify the selected ice type based on aerodynamic similarity; The simplified ice type is converted into three-dimensional ice types of different wing surfaces by means of ice type contour translation, bridging or surface filling, and extrapolation and extension.

2. The method according to claim 1, characterized in that The ice type with the greatest aerodynamic impact is selected from the profile ice types obtained from the ice wind tunnel test, including: The ice type with the greatest impact on the aerodynamic characteristics of the aircraft is selected from multiple two-dimensional ice types of a component section as the basis for subsequent ice type conversion.

3. The method according to claim 2, characterized in that The ice type with the greatest impact on the aerodynamic characteristics of the aircraft is selected from multiple 2D ice types of a component as the basis for subsequent ice type conversion, including: Select the more obvious ice angle feature of each cross-sectional ice type, where the more obvious ice angle feature is the ice angle feature with the maximum projection height in the cross-sectional ice type itself; All the more obvious ice angle features are aligned with the chord line to form a new section, and the most obvious ice angle feature is selected from the section. The section ice type corresponding to the most obvious ice angle feature is the ice type with the greatest aerodynamic impact; If the ice type with the greatest aerodynamic impact cannot be selected, a two-dimensional ice type aerodynamic impact comparison calculation is performed to determine the ice type with the greatest impact; For ice types with obvious ice angle characteristics, the ice type with the largest projection height of the icing angle in the lift direction is selected and determined as the ice type with the greatest aerodynamic impact. For cases where the ice angle characteristics are not obvious or the selected result is not unique, a two-dimensional ice type aerodynamic impact comparison calculation can be carried out to determine the ice type with the greatest impact.

4. The method according to claim 3, characterized in that The selected ice type is simplified based on aerodynamic similarity, including: From the coordinate points of the reference contour, select the characteristic coordinate points reflecting the extreme shape and characteristic shape and the contour coordinate points between a small number of characteristic points, ignore the coordinate points of the shape details in the non-extreme area, and use spline curves to draw simplified ice models to smooth the local pits and rough shapes of the original ice model to meet the requirements of aircraft simulation ice model manufacturing; Carry out aerodynamic impact assessment before and after simplification of two-dimensional ice type, and determine whether the simplification of ice type is feasible based on the principle of aerodynamic equivalence. If not feasible, retain the coordinate points of some shape details in non-extreme areas to obtain a new simplified ice type, and conduct aerodynamic impact assessment again until simplification is feasible.

5. The method according to claim 4, characterized in that The characteristic coordinate points reflecting the extreme shape and characteristic shape are the coordinate points of the upper / lower icing limit and the coordinate points of the upper / lower ice angle shape.

6. The method according to claim 5, characterized in that By translating the ice shape contour, bridging or surface filling, and extrapolating and extending, the simplified ice shape is converted into three-dimensional ice shapes of different airfoils, including: The wingtip is selected for ice type simplification, and the leading edge line of the tail is used as a guide line for translation and adjustment of the upper ice angle to obtain the ice type contours at both ends of the wing surface. The ice type contours at both ends of the wing surface are bridged to obtain the three-dimensional ice type of the entire wingspan.

7. The method according to claim 5, characterized in that By translating the ice shape contour, bridging or surface filling, and extrapolating and extending, the simplified ice shape is converted into three-dimensional ice shapes of different airfoils, including: For the wing, the wingtip and wing root are selected for ice type simplification. The closed curve filling method is used to generate the upper wing surface three-dimensional ice type surface, the windward surface three-dimensional ice type surface and the lower wing surface three-dimensional ice type surface in blocks based on the ice type contour lines at both ends, the upper / lower wing surface icing limit connection lines, the upper / lower ice angle connection lines and other characteristic lines. Then, the interpolation and extension method is used to generate the wing leading edge ice type outside the ice type contour lines.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

Images