Design method for fir-tree-shaped tenon of turbine blade

Abstract

The invention provides a design method for a fir-tree-shaped tenon of a turbine blade. The design method comprises the following steps of building a structure parameter system, determining an initial parameter range, building a stress calculation model and optimizing multi-target parameters. According to the turbine fir tree-shaped tenon structure design method, turbine fir tree-shaped tenon structure design parameters are established, on the basis of the turbine fir tree-shaped tenon structure design parameters, the extrusion stress and the shear stress of the tenon meshing face are calculated, the turbine fir tree-shaped tenon structure design can be rapidly completed under the limiting condition, the stress of the turbine fir tree-shaped tenon structure design can be evaluated, and a set of proper structure parameters are selected.

Description

Technical Field

[0001] This invention relates to a design method for a fir tree-shaped tenon for turbine blades, belonging to the field of aero-engine and gas turbine technology. Background Technology

[0002] The turbine blade tenon reliably fixes the blade to the disk, ensuring that each characteristic section of the blade body is at the height section given by the aerodynamic design, and transmits the rotational mechanical work to the disk and shaft, and drives the fan to ensure that the engine can continuously perform work.

[0003] In existing technologies, turbine blades generally use fir tree-shaped tenons to reduce throat stress. However, current tenon designs lack a systematic parameter correlation model, requiring repeated adjustments to structural parameters (such as wedge angle α, pressure angle β, number of teeth k, etc.) to meet strength requirements, resulting in long design cycles and low efficiency. Secondly, the calculation of compressive stress and shear stress on the tenon meshing surface is not explicitly expressed with structural parameters, making it impossible to quickly assess the feasibility of multiple sets of parameters in the preliminary design stage. For example, Chinese patent CN118428002A discloses a design method for a simulated tree-shaped tenon connection, the core technology of which is to adjust the size of the simulated part to equivalent real structural stress state, which is an experimental verification technology and is fundamentally different from the forward parameterized design method of this application.

[0004] In summary, there is currently no similar technique that achieves rapid multi-objective optimization by establishing parametric relationship expressions. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a design for a fir tree-shaped tenon for turbine blades.

[0006] The present invention is achieved through the following technical solutions.

[0007] The present invention provides a design method for a fir tree-shaped tenon for turbine blades, comprising the following steps: ① Establish a structural parameter system: Define the key structural parameters of the tenon, including the tenon wedge angle α, the normal pressure angle of the tenon meshing surface β, the angle between the tenon meshing surface and the non-meshing surface γ, the pitch L of the first tenon tooth, and the tooth pitch. , Tenon span distance The total number of tenons is k, and the axial length of the tenons is... Width of the tenon meshing surface ; ② Determine the initial parameter range: Determine the reference section height of the tenon based on the height of the hot flow channel in the aerodynamic design, and initially select L according to the principle of equal division of the chord width between the wheel disk tenon and the blade tenon; Select the angle parameter range based on the structural parameters of the mature engine turbine fir tree tenon: 30°≤α≤45°, 35°≤β≤50°, 50°≤γ≤60°; Under the constraints of L and α, select k, and increase the rounding R of the tenon meshing surface and the non-meshing surface. ③ Establish a stress calculation model: Based on the structural parameters and centrifugal force, obtain the compressive stress and shear stress on the tenon meshing surface. The calculation formulas for compressive stress and shear stress are as follows: Where m is the blade mass, and r is the height of the centroid. Rotational speed; ④ Multi-objective parameter optimization: Under the premise of meeting the design standards of extrusion stress and shear stress, multiple sets of candidate structural parameter combinations are generated. Then, taking into account rotor weight reduction and blade resonance point, and based on reducing the height of the tenon reference plane and reducing the rim mass, a set of structural parameters that balances rotor lightweighting and vibration safety is selected from the candidate structural parameters.

[0008] In step ②, k = 4~6.

[0009] In step ③, when calculating the compressive stress and shear stress, all the symmetrical working surfaces of the tenons are subjected to uniform stress, and the axial length direction of the tenons is subjected to uniform stress.

[0010] The beneficial effects of this invention are as follows: It establishes a design parameter for a turbine fir tree-shaped tenon structure, and based on this, calculates the compressive stress and shear stress on the tenon meshing surface. It can quickly complete the structural design of the turbine fir tree-shaped tenon under limited conditions, evaluate its stress, and select a more suitable set of structural parameters. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of the turbine fir tree-shaped tenon of the present invention; Figure 2 This is a diagram illustrating the structural parameters of the turbine fir tree-shaped tenon of the present invention. Detailed Implementation

[0012] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0013] like Figure 1 and 2 As shown, a design method for a fir tree-shaped tenon for turbine blades includes the following steps: ① Establish a structural parameter system: Define the key structural parameters of the tenon, including the tenon wedge angle α, the normal pressure angle of the tenon meshing surface β, the angle between the tenon meshing surface and the non-meshing surface γ, the pitch L of the first tenon tooth, and the tooth pitch. , Tenon span distance The total number of tenons is k, and the axial length of the tenons is... Width of the tenon meshing surface ; ② Determine the initial parameter range: Based on the height of the hot flow channel in the aerodynamic design, determine the reference section height of the tenon. Initially select L according to the principle of evenly dividing the chord width between the wheel disk tenon and the blade tenon. Select the angle parameter range based on the structural parameters of the mature engine turbine fir tree tenon: 30°≤α≤45°, 35°≤β≤50°, 50°≤γ≤60°. Under the constraints of L and α, select k, and increase the rounded radius R of the tenon meshing and non-meshing surfaces (this needs to be considered simultaneously). ); ③ Establish a stress calculation model: Based on the structural parameters and centrifugal force, obtain the compressive stress and shear stress on the tenon meshing surface. The calculation formulas for compressive stress and shear stress are as follows: Where m is the blade mass, and r is the height of the centroid. Rotational speed; Preferably, in the preliminary design stage, the tenon quality is estimated based on 8% to 15% of the quality of the leaves above the root extension section, and then iterated once.

[0014] Preferred, The axial chord length of the blade root, given by aerodynamics, can be slightly less than the axial chord length of the blade root to avoid excessive radial stress due to the rounded transition between the lower edge plate and the tenon. The circumferential width of the root extension section is determined based on the axial length of the tenon and the centrifugal force of the blade body and blade crown (if any), satisfying the radial stress criterion for the root extension section.

[0015] ④ Multi-objective parameter optimization: Under the premise of meeting the design standards of extrusion stress and shear stress, multiple sets of candidate structural parameter combinations are generated. Then, taking into account rotor weight reduction and blade resonance point, and based on reducing the height of the tenon reference plane and reducing the rim mass, a set of structural parameters that balances rotor lightweighting and vibration safety is selected from the candidate structural parameters.

[0016] Furthermore, reducing the height of the tenon reference plane increases the radial height of the blade, causing a rapid decrease in the blade's static frequency. This leads to an increase in potential resonance points between the overtone lines of the rotational speed and the blade's lower-order frequencies (first-order bending, first-order chord, first-order torsion, second-order bending) on ​​the blade's Campbell's diagram, making it difficult to control blade vibration. Therefore, the difficulty of designing the impeller and blade vibration must be comprehensively considered during the selection of structural parameters.

[0017] In step ②, to reduce stress concentration at the throat of the tenon, it is preferable to select a tenon structure with 2 to 3 pairs of tenons, i.e., k=4 to 6.

[0018] In step ③, when calculating the compressive stress and shear stress, all symmetrical working surfaces of the tenons are subjected to uniform force, and the axial length direction of the tenons is subjected to uniform force (for common working points, the axial center of gravity and circumferential center of gravity of the blade are controlled to balance the bending moment in the two directions, and the symmetry of the tenon sides, the taper along the tensile direction of the tenon and the deviation from the design state in the circumferential direction are controlled by machining, and finally, a certain margin is reserved to ensure reliable operation).

Claims

1. A design method for a fir tree-shaped tenon for turbine blades, characterized in that: Includes the following steps: ① Establish a structural parameter system: Define the key structural parameters of the tenon, including the tenon wedge angle α, the normal pressure angle of the tenon meshing surface β, the angle between the tenon meshing surface and the non-meshing surface γ, the pitch L of the first tenon tooth, and the tooth pitch. , Tenon span distance The total number of tenons is k, and the axial length of the tenons is... Width of the tenon meshing surface ; ② Determine the initial parameter range: Determine the reference section height of the tenon based on the height of the hot flow channel in the aerodynamic design, and initially select L according to the principle of equal division of the chord width between the wheel disk tenon and the blade tenon; Select the angle parameter range based on the structural parameters of the mature engine turbine fir tree tenon: 30°≤α≤45°, 35°≤β≤50°, 50°≤γ≤60°; Under the constraints of L and α, select k, and increase the rounding R of the tenon meshing surface and the non-meshing surface. ③ Establish a stress calculation model: Based on the structural parameters and centrifugal force, obtain the compressive stress and shear stress on the tenon meshing surface. The calculation formulas for compressive stress and shear stress are as follows: Where m is the blade mass, and r is the height of the centroid. Rotational speed; ④ Multi-objective parameter optimization: Under the premise of meeting the design standards of extrusion stress and shear stress, multiple sets of candidate structural parameter combinations are generated. Then, taking into account rotor weight reduction and blade resonance point, and based on reducing the height of the tenon reference plane and reducing the rim mass, a set of structural parameters that balances rotor lightweighting and vibration safety is selected from the candidate structural parameters.

2. The design method for the turbine blade fir tree-shaped tenon as described in claim 1, characterized in that: In step ②, k = 4~6.

3. The design method for the turbine blade fir tree-shaped tenon as described in claim 1, characterized in that: In step ③, when calculating the compressive stress and shear stress, all the symmetrical working surfaces of the tenons are subjected to uniform stress, and the axial length direction of the tenons is subjected to uniform stress.

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