CN102536327B - Pneumatic and structural feature considered three-dimensional geometric structure of fan blade of aircraft engine - Google Patents

Abstract

The invention discloses a three-dimensional geometric structure of a large fan connotation blade of a civil aeroengine taking into account both aerodynamic and structural features. In the traditionally designed large fan root, the rear section of the blade shape has a relatively large bend angle, and the suction surface of the trailing edge forms a relatively small acute angle with the hub. Low-energy gas accumulates in this corner area, causing a large flow loss, and the suction surface and the hub are relatively small. The angle is not conducive to the structural modeling of the root section of the blade. The present invention mainly optimizes the change of the metal angle at the exit metal angle of the base element blade shape along the blade height of the connotation blade of the large fan (the part within 20% of the blade height of the large fan blade), and fits the distribution curve of the metal angle at the exit of the connotation blade and the trailing edge line in A projected curve on a plane perpendicular to the axis. After three-dimensional CFD verification, the invention can effectively reduce the flow separation in the angular area formed by the suction surface of the fan trailing edge and the hub, improve the efficiency of the fan connotation, and provide a good inlet condition for the booster stage, and the root blade is opposite to the hub The near verticality also facilitates the installation of the blades on the disc.

Description

A three-dimensional geometric structure of aeroengine fan blades considering both aerodynamic and structural features

technical field

The invention relates to a three-dimensional geometric structure of connotative blades of a large fan of a civil aeroengine taking into account both aerodynamic and structural features, and belongs to the technical field of impellers of turbomachinery axial flow compressors.

Background technique

In the large fan of a civil aeroengine, the flow parameters change drastically along the radial direction due to the relatively small hub. The traditional design idea is to adopt the law of power distribution along the blade height, thinking that this can minimize the radial mixing of the flow and reduce the flow loss. Due to the large difference in root tip tangential velocity of large fans, in order to ensure equal power from the root to the tip of the rim, it is necessary to have a relatively large twist of the basic element of the fan’s inner blade. acute angle. However, studies have shown that the design of equal power distribution cannot minimize the radial mixing of the flow. In terms of aerodynamics, low-energy gas accumulates in the corner area formed by the suction surface of the trailing edge and the hub, and the loss of flow separation is very large. At the same time, the inner outlet of the fan The high Mach number increases the difficulty and risk of supercharging stage design; in terms of structure, the small angle between the suction surface and the hub is not conducive to the structural shape of the root section, which makes it difficult to install the blade on the wheel , it is possible to generate excessive stress in the root section.

With the development of design and three-dimensional numerical simulation technology, modern aero-engine large fans adopt full three-dimensional design methods, break through some traditional design concepts, and carry out blade modeling according to the actual flow situation, so that the blade geometry is more in line with the flow requirements, improve the flow, reduce the Small loss, while taking into account the structural features, to facilitate the installation of the blades and avoid excessive stress.

Contents of the invention

The purpose of the present invention is to provide a three-dimensional geometric structure of the connotative blade of a large fan of a civil aeroengine taking into account both aerodynamic and structural features, as shown in FIG. 1 . When designing the large fan 1, the present invention adjusts the design parameters such as the added work and lagging angle of the connotation part blade 2 (the part within 120% of the blade height of the large fan blade), and optimizes the outlet metal angle β _2k of the connotation blade 2 along the span direction. distribution, the optimized connotation blade trailing edge curve 3 is obtained, and it can be seen that the connotation blade trailing edge suction surface 5 is closer to vertical to the hub line 10 . The purpose of the design is to control the flow separation in the angular area formed by the suction surface at the root of the fan and the hub, improve the efficiency of the fan, improve the inlet conditions of the internal booster stage, and at the same time facilitate the structural shape of the fan root section and facilitate the blade on the wheel disk. Install.

In order to realize the above-mentioned purpose of the invention, the technical solution of the present invention mainly includes the following points:

A three-dimensional geometric structure of the connotation blade of a large fan of a civil aeroengine taking into account both aerodynamic and structural features, wherein the connotation blade refers to the part of the blade height of 0-20% of the blade of the large fan, and is characterized in that:

1. The outlet metal angle of the connotation blade 2 satisfies the following conditions: the outlet metal angle of the connotation blade 2 (the part within 20% of the leaf height of the large fan blade) primitive blade shape β _2k (as shown in Figure 2, the middle arc Tangent and axis at trailing edge point The included angle, clockwise is positive) The distribution along the spread can be described by a cubic polynomial

y=79.804x ³ +70.411x ² +33.222x-8.62

Among them, x is the percentage of relative spread height, y is the outlet metal angle of the corresponding leaf height primitive blade shape, the unit is degree (°), and the tolerance range of outlet metal angle is ±0.2°. The outlet metal angle with such a spanwise distribution reduces the vane angle of the inner blade, reduces the amount of work done, and effectively controls the flow separation of the suction surface of the root.

2. At the same time, the connotative blade trailing edge line satisfies the following condition: the projection of the connotative blade trailing edge line 3 on the XOY plane perpendicular to the axial direction can be fitted into a cubic polynomial curve. As shown in Figure 3, ω is the direction of impeller rotation, and the point where the blade trailing edge line 3 intersects the hub line 10 is defined as the coordinate origin (0,0), and the coordinate axis is the opposite direction of the origin tangent velocity, Pointing to the direction of increasing radius along the radial direction, the x and y coordinate values are respectively dimensionless, and the dimensionless scales are the absolute lengths from the hub line 10 to the connotative blade trailing edge line 3 in the x and y directions. Under the definition of the above coordinate system, the projection curve fitting formula of the trailing edge line on the XOY plane is:

Wherein, the tolerance range of y is ±0.03.

The present invention is a three-dimensional geometric structure of the connotation blade of a large fan of a civil aeroengine taking into account both aerodynamic and structural features. The separation of the flow in the corner area formed by the suction surface of the trailing edge and the hub improves the efficiency of the fan, reduces the Mach number of the inner outlet of the fan, improves the inlet conditions of the booster stage, and is also beneficial to the structural shape of the root extension section. Taking into account the aerodynamic performance and structural requirements of the fan. After computational fluid dynamics (CFD) numerical calculations, the performance of the fan is good, and the fan efficiency at the design point reaches 93.17%, especially the intrinsic efficiency of the fan reaches 96.27%.

Description of drawings

Fig. 1 shows the schematic diagram of three-dimensional geometric modeling of the fan blade of the present invention

Fig. 2 shows the blade shape schematic diagram of the connotation blade of the fan of the present invention at 0%, 10%, and 20% spanwise blade height sections

Fig. 3 shows the schematic diagram of the projection curve of the connotation blade trailing edge line of the fan of the present invention on a plane perpendicular to the axial direction

The specific labels and symbols in the figure are as follows:

1: large fan blade; 2: fan inner blade (within 20% leaf height); 3: inner blade trailing edge line; 4: pressure surface; 5: suction surface; 6: 0% leaf height section blade shape; 7: 10 % blade height profile; 8: 20% blade height profile; 9: 0% blade height profile arc; 10: hub line

β _2k : Exit metal angle (the tangent and axial direction of the middle arc 9 at the point of the trailing edge angle, clockwise is positive)

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the drawings and embodiments.

A three-dimensional geometric structure of the connotation blade of a large fan of a civil aeroengine taking into account both aerodynamic and structural features, wherein the connotation blade refers to the part of the blade height of 0-20% of the blade of the large fan, and is characterized in that:

1. The outlet metal angle β _2k of the connotation blade 2 primitive airfoil (as shown in Figure 2, the tangent and axial direction of the middle arc at the trailing edge point The included angle, clockwise is positive) The distribution along the spread can be described by a cubic polynomial

y=79.804x ³ +70.411x ² +33.222x-8.62

Among them, x is the percentage of the relative spread height, y is the outlet metal angle of the corresponding leaf height primitive blade shape, the unit is degree (°), and the tolerance range of the outlet metal angle is ±0.05°. The outlet metal angle with such a spanwise distribution reduces the vane angle of the inner blade, reduces the amount of work done, and effectively controls the flow separation of the suction surface of the root.

2. Connotation The projection of the blade trailing edge line 3 on the XOY plane perpendicular to the axial direction can be fitted into a cubic polynomial curve. As shown in Figure 3, ω is the rotation direction of the fan, and the point where the blade trailing edge line 3 intersects the hub line 10 is defined as the coordinate origin (0,0), and the coordinate axis is the opposite direction of the origin tangent velocity, Pointing to the direction of increasing radius along the radial direction, the x and y coordinate values are respectively dimensionless, and the dimensionless scales are the absolute lengths of the blade trailing edge line 3 in the x and y directions of the connotation of the hub line 10 to 20% of the blade height. Under the definition of the above coordinate system, the projection curve fitting formula of the trailing edge line on the XOY plane is:

Wherein, the tolerance range of y is ±0.03.

In summary, according to the radial distribution law of the outlet metal angle of the inner blade of the fan, and satisfying the projection curve equation of the trailing edge line on the axial plane relative to the coordinate system, a three-dimensional geometric feature of the inner blade of the fan can be obtained, which can Effectively control the flow separation in the inner corner area of the fan, improve the efficiency of the fan, reduce the Mach number at the inlet of the supercharging stage, and at the same time facilitate the structural shape of the root section of the fan blade.

Claims (1)

1. A civil aeroengine large fan connotation blade three-dimensional geometric structure taking into account both aerodynamic and structural features, wherein the connotation blade refers to the 0-20% blade height part of the large fan blade, characterized in that: (1) The outlet metal angle of the connotation blade satisfies the following conditions: the distribution of the outlet metal angle β _2k along the span height of the connotation blade primitive blade shape can be described by a cubic polynomial: y=79.804x ³ +70.411x ² +33.222x-8.62, Among them, x is the percentage of relative spread height, y is the outlet metal angle of the corresponding leaf height primitive blade shape, the unit is °, the tolerance range of the outlet metal angle is ±0.2°; β _2k : outlet metal angle, defined as the middle arc Tangent and axis at trailing edge point The included angle is positive clockwise; (2) At the same time, the connotative blade trailing edge line satisfies the following conditions: the projection of the connotative blade trailing edge line on the XOY plane perpendicular to the axis can be fitted into a cubic polynomial curve, defining the connotative blade trailing edge line and The point where the hub lines intersect is the coordinate origin (0,0), ω is the impeller rotation direction, and the coordinate axis is the opposite direction of the origin tangent velocity, Pointing to the direction of increasing radius along the radial direction, the x and y coordinate values are respectively dimensionless, and the dimensionless scales are the absolute lengths of the connotative blade trailing edge line in the x and y directions; under the definition of the above coordinate system, the trailing edge line The projection curve fitting formula on the XOY plane is: Wherein, the tolerance range of y is ±0.03.