A method for fabricating scoop-shaped film pores in turbine blades using femtosecond laser

Abstract

This invention relates to the field of laser processing technology, specifically to a method for fabricating a scoop-shaped film cooling hole in a turbine blade using a femtosecond laser. The method includes the following steps: S1. Parametrically modeling the scoop-shaped film cooling hole; S2. Laser filling and scanning to process the scoop opening portion of the scoop-shaped film cooling hole; S3. Laser spiral scanning to process the oblique hole portion of the scoop-shaped film cooling hole; S4. Performing quality inspection on the completed scoop-shaped film cooling hole. This invention enables high-quality forming of a type of scoop-shaped film cooling hole in turbine blades, significantly reducing processing errors and defects, improving the aerodynamic performance, cooling efficiency, and structural strength of the turbine blade, thereby enhancing the operational reliability and service life of the turbine blade.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, and in particular to a method for preparing scoop-shaped air film pores in turbine blades using femtosecond lasers. Background Technology

[0002] Aero engines are the "crown jewel" of industry, and turbines are the components with the heaviest thermal and mechanical loads. Turbine blades operate in particularly harsh environments, enduring the impact of high-temperature, high-pressure combustion gases during the engine cycle. Their manufacturing technology is considered a key technology for modern aero engines. With the continuous improvement of gas turbine engine power, thermal efficiency, thrust-to-weight ratio, and other performance characteristics, turbine inlet temperatures have risen significantly, far exceeding the limit operating temperature of turbine blade materials. This has led to the development of film cooling (FSL) technology to raise the upper limit of usable temperatures. FSL involves distributing N rows of cooling film holes along the blade height. The cooling airflow ejected from these holes forms a film on the blade surface, blocking the high-temperature combustion gases and thus improving the high-temperature resistance of the blade material. Statistics show that turbine inlet temperatures rise by an average of 25K per year, with approximately 15K attributed to advancements in cooling technology. Over the past three to four decades, turbine inlet temperatures have increased by approximately 450K. 70% of this increase is due to the efficient cooling design of turbine working blades and turbine guide vanes, while the remaining 30% is attributable to improvements in high-temperature alloys and casting processes.

[0003] Film cooling technology is a representative and important structural improvement that has greatly enhanced engine performance. In recent years, in order to achieve higher cooling efficiency, many advanced gas turbine engines have adopted scoop-shaped non-circular film cooling holes with diffuser sections, which has also placed higher demands on film cooling hole processing technology.

[0004] Chinese patent CN106735657A discloses a method for processing film holes in double-layer turbine blades of aero-engines, which can combine electrical discharge machining and electrochemical machining to remove the remelted layer generated during the processing of film holes; Chinese patent CN102861956B discloses a method for processing film holes in aero-engine turbine blades without remelted layer, which uses the same simple electrode with a hollow circular cross section to process both the circular holes and the scoop-shaped orifices of the film holes, reducing the difficulty of electrode manufacturing, shortening the manufacturing cycle of the formed electrode, and saving costs.

[0005] Currently, existing technologies for fabricating scoop-shaped film cooling holes primarily employ electrical discharge machining (EDM) and traditional laser processes. However, these methods suffer from insufficient geometric precision and poor surface quality. Furthermore, current techniques struggle to fabricate scoop-shaped film cooling holes with smooth, curved surfaces. This negatively impacts the aerodynamic performance, cooling efficiency, and structural strength of turbine blades. Therefore, seeking a more efficient fabrication method for scoop-shaped film cooling holes has significant engineering value and importance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing scoop-shaped film cooling holes for turbine blades using femtosecond lasers and its application. This method can achieve high-quality processing of scoop-shaped film cooling holes for turbine blades, improve existing turbine blade film cooling technology, and thus enhance the working performance of gas turbine engines.

[0007] This invention provides a method for fabricating scoop-shaped film pores in turbine blades using femtosecond lasers, comprising the following steps:

[0008] S1. Parametric modeling of the sieve-shaped air film vent;

[0009] S2. Femtosecond laser filling scanning is used to process the hopper-shaped air film aperture portion;

[0010] S3. Femtosecond laser spiral scanning is used to process the oblique hole portion of the scoop-shaped air film aperture;

[0011] S4. Perform processing quality inspection on the completed sieve-shaped air film holes.

[0012] Furthermore, step S1 includes the following sub-steps:

[0013] S101. Establish a model for the formation of a scoop-shaped air film pore, and define the geometric parameters of the scoop-shaped air film pore in a parameterized manner;

[0014] S102. The scoop-shaped irregular film air hole is obtained by forming the model and the Boolean operation of the turbine blade component.

[0015] Preferably, in step S101, the parameterized definition of the geometric parameters of the scoop-shaped air film pore includes the parameterized definition of the geometric feature quantities and formation relationships of the scoop-shaped air film pore, and some of the geometric feature quantities satisfy the following relationship:

[0016]

[0017] B = L1 × tanβ + D

[0018] Wherein, α is the principal tilt angle, β is the forward tilt angle, γ is the opening angle, D is the diameter of the oblique hole, L2 is the length of the oblique hole, L1 is the length of the scoop-shaped opening model, A is the half-length of the mapping surface, B is the height of the mapping surface, and R is the chamfer of the mapping surface. α and L2 are quantities that need to be parameterized during modeling. Therefore, the geometric configuration of the scoop-shaped film air hole can be easily changed based on theoretical calculations of aerodynamics, cooling efficiency, and strength. The theoretical calculations of these three factors are considerations when designing irregularly shaped film air holes, and the geometric model of the irregular hole will be modified according to changes in the scheme and actual application effects. This patent provides a processing method for such irregularly shaped film air holes, and the provided model is a parameterized model that can be flexibly modified based on theoretical calculations in engineering to reduce the workload of remodeling.

[0019] Furthermore, step S2 includes the following sub-steps:

[0020] S201. Slice the model of the scoop-shaped air film pore along the axis of the inclined hole;

[0021] S202. Perform graphic filling on each slice of the sieve opening section, determine the processing path of laser filling scan, and generate processing code;

[0022] S203. Perform femtosecond laser filling scanning ablation trial processing on each slice of the sieve opening to obtain the relationship between processing parameters, ablation depth, and ablation surface quality, thereby determining the optimal processing parameters that can obtain a suitable ablation depth and good surface quality.

[0023] S204. Adjust the workpiece to the positioning coordinates ① according to the design angle and hole position, and perform laser focus compensation according to the design model of the scoop mouth to obtain the machining coordinates ②;

[0024] S205. Set the optimal processing parameters obtained in step S203 and perform processing of the scoop-shaped air film pore expansion port.

[0025] Preferably, in step S201, the slice of the scoop mouth part model of the scoop-shaped air film pore is a closed slice, and the thickness of the closed slice should be ≤0.1mm, so that the processed scoop mouth curved surface can be smoothly transitioned.

[0026] Preferably, in step S202, the graphic fill of each slice of the sieve opening is a "bow" shaped fill, and the line spacing of the fill is ≤0.01mm, so that the processed sieve opening achieves a smaller surface roughness.

[0027] Preferably, in step S203, the main processing parameters adjusted are: average laser output power (W), which represents the energy of the laser per unit area; scanning speed (V), which represents the moving speed in the plane during laser scanning; number of scans (T), which represents the number of scans during each layer scanning process; and single-layer scanning focal point downward displacement (H), which represents the distance the laser focal point moves downward after each layer scanning is completed.

[0028] Furthermore, step S3 includes the following sub-steps:

[0029] S301. Perform focal length measurement, obtain machining coordinates ③ by focal compensation, and focus the laser focus on the bottom of the hopper opening;

[0030] S302. Femtosecond laser rotary cutting for rough machining of the oblique hole portion of the hopper-shaped air film aperture;

[0031] S303. Femtosecond laser rotary cutting is used to precisely process the oblique hole portion of the hopper-shaped air film aperture.

[0032] Preferably, in step S302, when the femtosecond rotary cutter rough processes the oblique hole portion of the scoop-shaped air film hole, a variable radius spiral scanning method is used to quickly process a round hole with good roundness and no taper.

[0033] Preferably, in step S303, when the femtosecond rotary cutting is used to finely process the oblique hole portion of the scoop-shaped air film hole, a scanning method with a fixed radius spiral is used for rapid processing, thereby removing hole wall defects and thermal damage generated in step S302 and achieving good hole wall surface quality.

[0034] Preferably, in steps S204 and S301, when adjusting the workpiece posture and acquiring coordinates, a precision five-axis moving platform equipped with a high-precision laser rangefinder is used, with a repeatability accuracy of ≤10μm.

[0035] Furthermore, step S4 includes the following sub-steps:

[0036] S401. Perform geometric accuracy inspection on the processed scoop-shaped air film holes;

[0037] S402. Perform surface integrity testing on the processed hopper-shaped air film pores.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The present invention designs a parameterized model of a scoop-shaped air film orifice, thereby enabling convenient modification of the geometric configuration of the scoop-shaped air film orifice based on theoretical calculations of aerodynamics, cooling efficiency and strength.

[0040] (2) The present invention improves the previous straight-edge scoop-shaped air film hole. The designed curved scoop-shaped air film hole can achieve better aerodynamic performance and energy efficiency, and can reduce the structural strength loss caused by stress concentration around the hole.

[0041] (3) The invention achieves high-quality processing of a turbine blade hopper-shaped film air hole through femtosecond laser processing technology optimization such as focus compensation, scanning path planning and parameter adjustment, significantly reducing processing errors and defects, and providing valuable reference for the processing of other types of irregular film air holes in the pre-research.

[0042] (4) This invention promotes the existing turbine blade film cooling technology by optimizing the model design and improving the processing quality of the scoop-shaped film cooling hole, thereby improving the operational reliability and service life of the turbine blade. Attached Figure Description

[0043] Figure 1 This is a flowchart of a method for preparing scoop-shaped film pores in turbine blades using femtosecond laser.

[0044] Figure 2 This is a schematic diagram of the formation model of a sieve-shaped air film pore, where Ⅰ is the sieve opening and Ⅱ is the oblique hole.

[0045] Figure 3 This is a schematic diagram of the geometric parameters of a model for the formation of a scoop-shaped air film pore.

[0046] Figure 4 This is a schematic diagram of a parametric model of a scoop-shaped air film pore.

[0047] Figure 5 This is a schematic diagram of a sieve-shaped air film pore.

[0048] Figure 6 This is a schematic diagram of the laser filling scanning path for a sieve-shaped air film vent. The left side shows the graphic filling of a slice of the sieve-shaped air film vent, and the right side is a magnified schematic diagram of a portion of the scanning path.

[0049] Figure 7 This is a schematic diagram of a femtosecond laser processing focus compensation method for a scoop-shaped air film aperture.

[0050] Figure 8 This is a schematic diagram of a femtosecond laser rotary cutting method for oblique holes in a scoop-shaped air film aperture, where (a) is a schematic diagram of rough rotary cutting and (b) is a schematic diagram of fine rotary cutting.

[0051] Figure 9 This is a photograph of a sieve-shaped air film aperture obtained by femtosecond laser processing.

[0052] Figure 10It is a three-dimensional contour map of the sieve opening portion of a sieve-shaped air film aperture obtained by femtosecond laser processing.

[0053] Figure 11 This is a photograph of the oblique hole portion of a scoop-shaped air film aperture obtained by femtosecond laser processing. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] Figure 1 This is a flowchart of a method for fabricating hopper-shaped air film holes in turbine blades using femtosecond lasers, with reference to the specific geometric configuration of the irregular holes.

[0057] This embodiment provides a method for preparing scoop-shaped film pores in turbine blades using femtosecond lasers, including the following steps:

[0058] S1. Parametric modeling of the sieve-shaped air film vent;

[0059] S2. Femtosecond laser filling scanning is used to process the hopper-shaped air film aperture portion;

[0060] S3. Femtosecond laser spiral scanning is used to process the oblique hole portion of the scoop-shaped air film aperture;

[0061] S4. Perform processing quality inspection on the completed sieve-shaped air film holes.

[0062] Step S1 includes the following sub-steps:

[0063] S101. Establish a model for the formation of a scoop-shaped air film pore, and define the geometric parameters of the scoop-shaped air film pore in a parameterized manner;

[0064] S102. The scoop-shaped irregular film air hole is obtained by forming the model and the Boolean operation of the turbine blade component.

[0065] In step S101, the scoop-shaped air film pore formation model is as follows: Figure 2 As shown, it is divided into a sieve-shaped opening section (Ⅰ) and an oblique hole section (Ⅱ), and the geometric parameters forming the model are as follows. Figure 3As shown. Define the geometric features: principal tilt angle (α) is 30°, forward tilt angle (β) is 15°, opening angle (γ) is 10°, oblique hole diameter (D) is 0.4mm, oblique hole length (L2) is 10mm, scoop mouth forming model length (L1) is 10mm, half length of the mapping surface (A), height of the mapping surface (B), and chamfer of the mapping surface (R) is 0.2mm. Then the half length of the mapping surface (A) and the height of the mapping surface (B) are:

[0066]

[0067] B=L1×tanβ+D=10×tan15°+0.4=3.08mm

[0068] In step S102, the parameterized model of a sieve-shaped air film pore obtained after Boolean operation is as follows: Figure 4 As shown.

[0069] Step S2 includes the following sub-steps:

[0070] S201. Slice the model of the scoop-shaped air film vent along the axis of the inclined hole. A schematic diagram of the slice is shown below. Figure 5 As shown;

[0071] S202. Fill in the graphic for each slice of the sieve opening section separately (e.g., Figure 6 (As shown), determine the processing path for laser filling scanning and generate processing code;

[0072] S203. Femtosecond laser filling scanning ablation was performed on each slice of the scoop section to determine the relationship between processing parameters, ablation depth, and ablation surface quality. The optimal processing parameters for obtaining suitable ablation depth and good surface quality were then determined: laser power density (W) of 6W, scanning speed (V) of 3000mm / min, number of scans (T) of 5, and focal point shift (H) of 0.01mm per scan.

[0073] S204. Adjust the workpiece to the positioning coordinates ① according to the design angle and hole position. Perform laser focus compensation based on the design model of the hopper opening to obtain the machining coordinates ②. The focus compensation method used is as follows: Figure 7 As shown;

[0074] S205. Set the optimal processing parameters obtained in step S203 and perform processing on the expansion opening of the hopper-shaped air film orifice. A physical image of the processed hopper opening is shown below. Figure 9 As shown, its three-dimensional contour map is as follows: Figure 10 As shown, the processed winnowing basket has a regular shape, smooth walls without burrs, and no obvious ablation.

[0075] In step S201, the slicing of the sloping mouth part model of the sloping air film hole is a closed slice with a thickness of 0.1 mm, so that the processed sloping mouth curved surface can be smoothly transitioned. The schematic diagram of the slice is shown in the figure.

[0076] In step S202, the pattern fill for each slice of the sieve opening is a "bow" shape, with a line spacing of 0.01 mm, thus achieving a low surface roughness for the processed sieve opening. A schematic diagram of the local "bow" shape fill and scanning is shown below. Figure 6 As shown.

[0077] In step S203, the processing parameters adjusted include: average laser output power (W), scanning speed (V), number of scans (T), and focal point shift in a single scan (H).

[0078] Step S3 includes the following sub-steps:

[0079] S301. Perform focal length measurement and focus compensation to obtain machining coordinates ③, so that the laser focus is on the bottom of the hopper opening. The focus compensation method used is as follows: Figure 7 As shown;

[0080] S302. Femtosecond laser rotary cutting rough machining of the oblique hole portion of the hopper-shaped air film aperture. A schematic diagram of the rotary cutting rough machining is shown below. Figure 8 As shown in (a);

[0081] S303. Femtosecond laser rotary cutting for precision machining of the oblique hole portion of a hopper-shaped air film aperture. A schematic diagram of the rotary cutting precision machining process is shown below. Figure 8 As shown in (b).

[0082] In step S302, when the femtosecond rotary cutter roughs the oblique hole portion of the scoop-shaped air film hole, a variable radius spiral scanning method is used to quickly process a round hole with good roundness and no taper.

[0083] In step S303, when the femtosecond rotary cutting is used to finely process the oblique hole portion of the scoop-shaped air film hole, a scanning method with a fixed radius spiral is used for rapid processing, thereby removing hole wall defects and thermal damage generated in step S302 and achieving good hole wall surface quality.

[0084] In steps S204 and S301, when adjusting the workpiece posture and acquiring coordinates, a precision five-axis moving platform equipped with a high-precision laser rangefinder is used, with a repeatability accuracy of 10μm.

[0085] Step S4 includes the following sub-steps:

[0086] S401. Perform geometric accuracy inspection on the processed scoop-shaped air film holes;

[0087] S402. Perform surface integrity testing on the processed hopper-shaped air film pores.

[0088] The final image of the machined oblique hole is shown below. Figure 11 As shown, the geometric dimensions of the inclined hole meet the standards, the inner wall is smooth, and there is no obvious ablation.

[0089] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A method of femtosecond laser fabrication of a turbine vane bucket type film hole, characterized by, The method comprises the following steps: S1. Parameterized modeling of the dustpan-shaped film hole; S2. Femtosecond laser filling scanning processing of the dustpan-shaped film hole; S3. Femtosecond laser spiral scanning processing of the inclined hole part of the dustpan-shaped film hole; S4. Processing quality detection of the processed dustpan-shaped film hole; The S1 comprises the following steps: S101. Establishing a dustpan-shaped film hole forming model, and parameterizing and defining the geometric parameters of the dustpan-shaped film hole; S102. Obtaining the dustpan-shaped film hole through Boolean operation of the forming model and the turbine blade component; In S101, the parameterized definition of the geometric parameters of the dustpan-shaped film hole comprises parameterized definition of geometric characteristic quantities and forming relationships of the dustpan-shaped film hole, and part of the geometric characteristic quantities satisfy the following relationship: B = L1 * tan β + D; Wherein, β is the rake angle, γ is the opening angle, D is the inclined hole diameter, L1 is the dustpan mouth forming model length, A is the mapping surface half length, B is the mapping surface height, and R is the mapping surface chamfer; The S2 comprises the following steps: S201. Slicing the dustpan-shaped film hole along the inclined hole axis direction; S202. Graphically filling each layer of the dustpan-shaped film hole, determining the processing path of the laser filling scanning, and generating the processing code; S203. Femtosecond laser filling scanning ablation trial processing of each layer of the dustpan-shaped film hole, obtaining the relationship between the processing parameters and the ablation depth and the ablation surface quality, and determining the optimal processing parameters that can obtain the appropriate ablation depth and good surface quality; S204. Adjusting the workpiece to the positioning coordinate ① according to the design angle and the hole forming position, and performing laser focal point compensation according to the design model of the dustpan-shaped film hole to obtain the processing coordinate ②; S205. Setting the optimal processing parameters obtained in step S203, and implementing the processing of the dustpan-shaped film hole; In S201, the slicing of the dustpan-shaped film hole is closed slicing, and the thickness of the closed slicing is ≤0.1mm; In S202, when graphically filling each layer of the dustpan-shaped film hole, the line spacing of the graphically filling is ≤0.01mm; The S3 comprises the following steps: S301. Focal length measurement, focal point compensation to obtain the processing coordinate ③, and focusing the laser focal point on the bottom of the dustpan-shaped film hole; S302. Femtosecond laser spiral cutting rough machining of the inclined hole part of the dustpan-shaped film hole; S303. Femtosecond laser spiral cutting fine machining of the inclined hole part of the dustpan-shaped film hole; In S302, when the femtosecond laser spiral cutting rough machining of the inclined hole part of the dustpan-shaped film hole, a variable radius spiral scanning mode is adopted; In S303, when the femtosecond laser spiral cutting fine machining of the inclined hole part of the dustpan-shaped film hole, a fixed radius spiral scanning mode is adopted for rapid processing; The step S4 comprises the following steps: S401. Geometric precision detection of the processed dustpan-shaped film hole; S402. Surface integrity detection of the processed dustpan-shaped film hole.

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