A centrifugal blade having a spanwise parabolic thickness distribution and a design method

Abstract

This invention provides a centrifugal blade with a spanwise parabolic thickness distribution. The blade is mounted on a centrifugal compressor impeller, which includes a main blade and a splitter blade. The spanwise thickness distribution control function of the main blade is as follows: by changing the spanwise thickness distribution of the centrifugal blade, the blade thickness near the blade tip is reduced, enhancing the blade leading edge's adaptability to supersonic airflow, weakening shock wave losses at the transonic impeller inlet, achieving a larger gas flow rate with the same inlet area, reducing blade weight, lowering centrifugal stress at the blade root, enhancing aerodynamic performance and structural strength within the compressor, and thus improving the impeller's aerodynamic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine technology, specifically relating to a centrifugal impeller blade with spanwise parabolic thickness and its design method. Background Technology

[0002] In the field of small and medium-sized aero-engines, centrifugal compressors have a series of advantages, including high single-stage pressure ratio, fewer parts, compact structure, and high reliability, and have been widely used. With increasingly higher performance requirements for aero-engines, the pressure ratio requirements for compressors are becoming increasingly stringent. However, there are certain limitations to the design of high pressure ratios. In aerodynamic design, a high pressure ratio results in an excessively high relative Mach number at the inlet blade tip of the centrifugal compressor, typically leading to supersonic airflow. The presence of supersonic airflow introduces shock wave losses, and the interaction between the shock wave and the boundary layer exacerbates impeller inlet losses, reducing impeller efficiency. In structural design, a high pressure ratio results in a high linear velocity at the trailing edge of the centrifugal impeller, leading to high centrifugal stress at the blade root. If this stress exceeds the allowable stress of the material, it can cause blade breakage.

[0003] Existing centrifugal compressor blades are mostly linearly stacked in the spanwise direction. The stress problem at the blade root is mainly solved by increasing the blade thickness. However, this approach also increases the blade thickness at other locations, reducing the aerodynamic performance of the impeller and the intake flow rate.

[0004] Therefore, there is a need to provide an impeller blade that can be used in small and medium-sized aero-engine centrifugal compressors with high pressure ratio, high flow rate, and high specific speed. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to enhance the adaptability of the blade leading edge to supersonic airflow by altering the spanwise thickness distribution of the centrifugal blades, thereby reducing the blade thickness near the blade tip and weakening the shock wave loss at the transonic impeller inlet. Simultaneously, it achieves a larger gas flow rate with the same inlet area, reduces blade weight, and lowers centrifugal stress at the blade root. This enhances both the aerodynamic performance and structural strength of the compressor. It is particularly suitable for centrifugal compressors in small and medium-sized aero-engines and gas turbines with high pressure ratios, high flow rates, and high specific speeds.

[0006] To achieve the above objectives, the present invention provides a centrifugal blade with a spanwise parabolic thickness distribution. The blade is mounted on a centrifugal compressor impeller, which includes multiple pairs of blade groups evenly spaced and intersecting along the impeller's circumference. Each pair of blade groups includes a main blade and a branch blade. The main blade and the branch blade have the same shape but different lengths, with the branch blade's length being 60%-70% of the main blade's length.

[0007] The control function for the distribution of the spanwise thickness of the main blade is:

[0008]

[0009] Among them, V span Indicates the thickness of the leaf at different heights;

[0010] The span indicates the relative position of the blade along its span.

[0011] V s Indicates the thickness of the leaf blade at the leaf tip;

[0012] V h Indicates the thickness of the leaf blade at the leaf base;

[0013] Ln() is a logarithmic function;

[0014] M represents the relative position of the impeller flow direction;

[0015] A(M) is the blade thickness distribution control coefficient.

[0016] The centrifugal impeller blade with spanwise parabolic thickness provided by the present invention also has the feature that the blade thickness has different thickness distribution control functions at different axial positions on the meridional plane, and the number of thickness distribution control functions is not less than 2.

[0017] The centrifugal impeller blade with spanwise parabolic thickness provided by the present invention also has the following feature: the number of thickness distribution control functions is 3, located at the leading edge of the blade, 50% of the meridional plane, and the trailing edge of the blade, respectively.

[0018] Another object of the present invention is to provide a design method for a centrifugal impeller blade having a spanwise parabolic thickness as described in any of the preceding claims, the method comprising:

[0019] Using the centrifugal engine impeller axis as the abscissa and the blade thickness as the ordinate, thickness distribution curves at the blade root and blade tip positions are constructed.

[0020] Select the blade thickness distribution control coefficient under different impeller flow direction positions, and complete the definition of the curve function for different flow direction positions;

[0021] The thickness distribution of the blade at different blade spans is calculated based on the distribution function of the blade span thickness.

[0022] Based on the thickness distribution of the blades at different spanwise directions, the impeller thickness is corrected to obtain a three-dimensional configuration of centrifugal blades with a spanwise parabolic thickness distribution.

[0023] The design method provided by this invention also has the following feature: the thickness of the blade gradually increases from the leading edge, reaches its maximum thickness at a position of 30%-50% of the blade flow direction, and then gradually decreases to the trailing edge of the blade.

[0024] The design method provided by this invention also has the feature that the value of the control function A(M) is between 0 and 1.

[0025] The design method provided by this invention also has the following feature: the value of span is interpolated between 0 and 1; when it is 0, V... span V is the thickness of the leaf root; when taken as 1, V span This refers to the thickness at the blade tip.

[0026] Beneficial effects

[0027] The centrifugal impeller blade with spanwise parabolic thickness provided by this invention reduces the blade thickness near the blade tip by changing the spanwise thickness distribution of the centrifugal blade, thereby enhancing the blade leading edge's adaptability to supersonic airflow, reducing shock wave losses at the transonic impeller inlet, achieving a larger gas flow rate with the same inlet area, reducing blade weight, lowering centrifugal stress at the blade root, enhancing the aerodynamic performance and structural strength within the compressor, and ultimately improving the impeller's aerodynamic efficiency.

[0028] The design method for centrifugal impeller blades with a spanwise parabolic thickness distribution provided by this invention fully considers the different thickness requirements of the blades along the spanwise direction. Through the nonlinear thickness distribution of the blades, the strength requirements of the blade root and the aerodynamic requirements of the blade tip are met. The centrifugal impeller designed by this method has high aerodynamic efficiency. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a three-dimensional centrifugal impeller structure with a spanwise parabolic thickness distribution provided in an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of the meridional plane of a three-dimensional centrifugal impeller with a spanwise parabolic thickness distribution provided in an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of the cross-section of a centrifugal impeller blade with a spanwise parabolic thickness;

[0032] Figure 4 This is a schematic diagram of the spanwise parabolic thickness distribution in an embodiment of the present invention.

[0033] Wherein, 100: main blade; 200: branch blade; 1: leading edge of blade; 2: trailing edge of blade; 3: apex of blade; 4: root of blade. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent changes or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the protection scope of the present invention.

[0035] In the description of the embodiments of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention.

[0036] Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art will understand the specific meaning of these terms in this invention based on the specific circumstances.

[0038] The relevant technical terms used in the technical solution provided in this application are as follows:

[0039] Centrifugal compressor: A compressor, also known as an air compressor, is a type of rotating machinery used to compress air. A centrifugal compressor is also called a radial compressor, meaning that gas enters axially and exits radially after compression. A centrifugal compressor generally consists of an inlet duct, impeller, diffuser, and volute.

[0040] Impeller: Composed of a disk and blades, the airflow flows along the channel formed by the disk, casing, and blades, and in this process, the mechanical work absorbed by the rotating impeller is converted into pressure (potential energy) and velocity (kinetic energy). The working impeller is the most important component of the compressor, and its quality has a decisive influence on the characteristics of the compressor.

[0041] Blades: In a compressor, blades perform work on airflow and guide its direction. The design of a compressor mainly involves designing the shape of the blades, including inlet and outlet structural parameters, as well as angle and thickness distribution.

[0042] Impeller meridional plane: This is a plane passing through the impeller axis, formed by rotating each point around the axis to the same axial plane, with coordinates r and z.

[0043] Leaf span: that is, the direction of leaf height, such as Figure 2 The direction from the leaf root to the leaf tip is the leaf spread direction, r direction.

[0044] Blade flow direction: from inlet to outlet.

[0045] Leading edge of the blade: the blade inlet.

[0046] Blade trailing edge: Blade exit.

[0047] Blade axis: z-direction.

[0048] Leaf tip: the top of the leaf.

[0049] Leaf root: the base of the leaf.

[0050] Leaf tip: The top of the leading edge of the leaf.

[0051] Specific speed: The dimensionless type number of the impeller.

[0052] This invention provides a centrifugal blade with a spanwise parabolic thickness distribution. The blade is mounted on a centrifugal compressor impeller. The centrifugal compressor impeller includes multiple pairs of blade groups evenly spaced and intersecting along the impeller circumference. Each pair of blade groups includes a main blade 100 and a branch blade 200. The main blade 100 and the branch blade 200 have the same shape but different lengths. The length of the branch blade 200 is 60%-70% of the length of the main blade 100.

[0053] The control function for the spanwise thickness distribution of the main blade 100 is:

[0054]

[0055] Among them, V span Indicates the thickness of the leaf at different heights;

[0056] The span indicates the relative position of the blade along its span.

[0057] V s This indicates the leaf thickness at the top 3 of the leaf;

[0058] V h This indicates the leaf thickness at point 4 of the leaf base;

[0059] Ln() is a logarithmic function;

[0060] M represents the relative position of the impeller flow direction;

[0061] A(M) is the blade thickness distribution control coefficient. In some embodiments, the blade thickness has different thickness distribution control functions at different axial positions on the meridional plane, and the number of thickness distribution control functions is not less than 2.

[0062] In some embodiments, the thickness distribution control function is three in number, located at the leading edge 1 of the blade, 50% of the meridional plane, and the trailing edge 2 of the blade.

[0063] In some embodiments, a method for designing centrifugal impeller blades with spanwise parabolic thickness as described in any of the foregoing claims is provided, the method comprising:

[0064] Using the impeller axis as the x-axis and blade thickness as the y-axis, a thickness distribution curve V is constructed at position 4 of the impeller blade root. h And the thickness distribution curve V at position 3 of the blade tip s ;

[0065] Select the control coefficient A(M) for the blade thickness distribution at different impeller flow directions, and define the curve function for different flow directions; the control coefficient A(M) is shown in the table below:

[0066] Flow to location M% Control factor A(M) 0％ 0.08 50％ 0.1 100％ 0.5

[0067] The thickness distribution of the blade at different blade spans is calculated based on the distribution function of the blade span thickness.

[0068] Based on the thickness distribution of the blades at different spanwise directions, the impeller thickness is corrected to obtain a three-dimensional configuration of centrifugal blades with a spanwise parabolic thickness distribution.

[0069] In the above embodiments, the initial centrifugal impeller blades are used as a basis for shaping, and the thickness distribution function of the blade spanwise at different axial positions is adjusted to reduce the blade thickness, thereby enhancing the centrifugal impeller tip's adaptability to supersonic airflow and reducing shock wave and secondary flow losses. Simultaneously, the centrifugal stress at the blade root is reduced, meeting different blade strength requirements along the airflow direction and forming a nonlinearly controllable blade thickness distribution characteristic.

[0070] In some embodiments, the thickness of the leaf at the leaf root and leaf tip gradually increases from the leading edge 1 of the leaf, reaching its maximum thickness at a position of 30%-50% of the leaf flow direction, and then gradually decreases to the trailing edge 2 of the leaf.

[0071] In some embodiments, the control function A(M) takes a value between 0 and 1.

[0072] In some embodiments, the value of span is interpolated between 0 and 1; when it is 0, V... span V is the thickness of the leaf root; when taken as 1, V span This refers to the thickness at the blade tip.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A centrifugal blade having a spanwise parabolic thickness distribution, said blade being mounted on a centrifugal compressor impeller, characterized in that, The centrifugal compressor impeller includes multiple pairs of blade groups evenly spaced and intersecting along the circumference of the impeller. Each pair of blade groups includes a main blade and a splitter blade. The main blade and the splitter blade have the same shape but different lengths. The length of the splitter blade is 60%-70% of the length of the main blade. The control function for the distribution of the spanwise thickness of the main blade is: in, Indicates the thickness of the leaf at different heights; The span indicates the relative position of the blade along its span. Indicates the thickness of the leaf blade at the leaf tip; Indicates the thickness of the leaf blade at the leaf base; Ln() is a logarithmic function; M represents the relative position of the impeller flow direction; A(M) is the blade thickness distribution control coefficient.

2. The centrifugal impeller blade with a spanwise parabolic thickness according to claim 1, characterized in that, The blade thickness has different thickness distribution control functions at different axial positions on the meridional plane, and the number of thickness distribution control functions is not less than 2.

3. The centrifugal impeller blade with a spanwise parabolic thickness according to claim 2, characterized in that, The thickness distribution control function has three functions, located at the leading edge of the blade, 50% of the meridional plane, and the trailing edge of the blade.

4. A design method for a centrifugal impeller blade with a spanwise parabolic thickness as described in any one of claims 1-3, characterized in that, The method includes: Using the centrifugal compressor impeller axis as the abscissa and the blade thickness as the ordinate, thickness distribution curves at the blade root and blade tip positions are constructed. Select the blade thickness distribution control coefficient under different impeller flow direction positions, and complete the definition of the curve function for different flow direction positions; The thickness distribution of the blade at different blade spans is calculated based on the distribution function of the blade span thickness. The impeller thickness is corrected based on the thickness distribution of the blades at different spanwise directions to obtain a three-dimensional configuration of centrifugal blades with a spanwise parabolic thickness distribution.

5. The design method according to claim 4, characterized in that, The thickness of the leaf at the leaf root and leaf tip positions gradually increases from the leading edge, reaching its maximum thickness at the 30%-50% position of the leaf flow direction, and then gradually decreases to the trailing edge of the leaf.

6. The design method according to claim 4, characterized in that, The value of the blade thickness distribution control coefficient A(M) in the control function is between 0 and 1.

7. The design method according to claim 4, characterized in that, The value of span is interpolated between 0 and 1. When it is 0, The thickness of the leaf root; when taken as 1, This refers to the thickness at the blade tip.

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