A low-pressure turbine guide brazing process multi-scale simulation optimization method

Abstract

The application discloses a low-pressure turbine guider brazing process multi-scale simulation optimization method, and divides a low-pressure turbine guider simulation analysis model into three scales: one is overall structure modeling, two is local blade modeling, and three is brazing seam modeling.The overall structure model is used for verifying the deformation and stress distribution law of the part in the existing brazing process; the local blade model is used for verifying the deformation and stress distribution law in different brazing processes; and the brazing seam model is used for studying the brazing material coating amount change and the brazing material flow state.The application proposes a multi-scale brazing simulation method, and uses a thermal force coupling added flow field simulation method to better restore the on-site brazing process, and improves the simulation accuracy.

Description

Technical Field

[0001] This invention relates to a multi-scale computer numerical simulation optimization method for the brazing process of low-pressure turbine guide vanes for aero-engines, belonging to the field of welding technology. Background Technology

[0002] In the traditional brazing process optimization design of low-pressure turbine guide vanes, it is still necessary to conduct long-term process parameter exploration experiments based on the structural characteristics of low-pressure turbine guide vanes. This relies heavily on the accumulation of a large amount of past experience, and the test cycle is long, the test consumables cost is high, and a lot of manpower and resources are required.

[0003] Computer numerical simulation has been widely used in welding analysis. Existing mature commercial finite element simulation software can reduce the cost of optimizing traditional welding processes and improve work efficiency through appropriate secondary development. However, existing computer numerical simulations of welding processes only focus on a single scale of the welding process, resulting in limited simulation accuracy and somewhat one-sided results.

[0004] Multiscale computer numerical simulation analyzes the same physical process from multiple dimensions, which can greatly improve the simulation accuracy. Summary of the Invention

[0005] This invention aims to provide a multi-scale simulation optimization method for the brazing process of low-pressure turbine guide vanes, which solves the problems of long cycle and high cost in traditional process design and improves the accuracy of simulation results.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A multi-scale simulation optimization method for the brazing process of a low-pressure turbine guide vane includes: Step 1: Simulation modeling of the low-pressure turbine guide vane, and dividing the simulation analysis model of the low-pressure turbine guide vane into three scales: The first step is to model the overall structure of the low-pressure turbine guide to obtain an overall model of the low-pressure turbine guide, which is used to verify the deformation and stress distribution of the low-pressure turbine guide in the current brazing process. The second step involves modeling a local blade of the low-pressure turbine guide vane to obtain a local blade model of the low-pressure turbine guide vane, which is used to verify the deformation and stress distribution laws during different brazing processes. The third step involves modeling the brazed weld seam to obtain a weld seam fluid model, which is used to study the changes in the amount of brazing filler metal coating and the flow state of the brazing filler metal. Step 2: Perform local refinement processing on the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model, wherein: The mesh of the overall model of the low-pressure turbine guide vane and the local blade model of the low-pressure turbine guide vane are locally refined in the thin-walled structure area. In the weld fluid model, the weld and brazing filler metal coating areas are locally densified; Step 3: Apply boundary conditions to the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model; Step 4, Obtain the material database: Use experimental methods, theoretical calculations and literature to obtain the parameters required for the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model; Step 5: Using the modeling method described above, construct the obtained brazing model, load the model of the part to be welded (i.e., load the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model respectively), simulate the welding process under different process parameters, and obtain simulation data, including: A thermo-mechanical coupling method is used for both the overall model and the local blade model of the low-pressure turbine guide vane. For the weld fluid model, a fluid simulation method is used; Step 6: Analyze the simulation results and select the optimal brazing fixture, optimal process parameters, and weld gap.

[0007] Alternatively, in step 1: The overall model of the low-pressure turbine guide vane adopts the standard model of the low-pressure turbine guide vane and includes all necessary accessory models required for its brazing process; Note: The standard model is the design drawing model; The local blade model of the low-pressure turbine guide vane adopts the standard model of the low-pressure turbine guide vane, and is a 1 / 20 to 1 / 2 equal division model of the standard model; Note: the standard model is the design drawing model, and the equal division model refers to the model of equal division on average, which is a common mesh generation method in finite element analysis.

[0008] Alternatively, in step 2: The mesh of the overall model of the low-pressure turbine guide vane and the local blade model of the low-pressure turbine guide vane are locally refined in the thin-walled structure area, with the size being 1 / 10 to 1 / 5 of the maximum mesh size; In the weld fluid model, the weld and brazing filler metal coating areas are locally densified, with a size of 1 / 10 to 1 / 5 of the maximum mesh size.

[0009] Alternatively, in step 3: For the overall model of the low-pressure turbine guide: constrain the positions of the upper and lower clamp end faces; set the surface-to-surface contact type at the contact position between the part and the clamp, use hard contact for the normal direction of the contact attribute, use a penalty function for the tangential direction, and set the friction coefficient to 0.01 to 0.30; adopt radiation as the heat exchange method in the vacuum environment, with an emissivity of 0.1 to 0.8, which is given according to the parameters of the vacuum furnace. For the local blade model of the low-pressure turbine guide vane: constrain the positions of the upper and lower clamp end faces; set the surface-to-surface contact type at the contact positions between the part and the clamp, and the gap area of ​​the blade weld, with the contact attribute normal using hard contact, the tangential using a penalty function, and the friction coefficient of 0.01 to 0.30; the gaps in other non-weld areas use the Tie binding method; the vacuum environment heat exchange method adopts radiation, with an emissivity of 0.1 to 0.8, which is given according to the vacuum furnace parameters; For the weld fluid model: the weld filler metal flow includes the overall computational domain and its cross-section, the solid filler metal coating area, and the area to be welded.

[0010] Alternatively, in step 4: The parameters required for the overall model and the partial blade model of the low-pressure turbine guide vane include: density, elastic modulus, Poisson's ratio, yield strength, plastic strain, coefficient of thermal expansion, thermal conductivity, and specific heat capacity. The parameters required for the weld fluid model include: density, dynamic viscosity, specific heat capacity, wetting contact angle, and surface tension.

[0011] Alternatively, in step 5, the process parameters include the gap between the fixture and the part, the fixture material, the brazing temperature, the holding time, the assembly gap between the blade and the support plate, the size and uniformity of the weld gap, and the brazing filler coating.

[0012] As an alternative, in step 6, the welding simulation results are analyzed using a sequential study method. First, a simulation study is conducted on the overall model of the low-pressure turbine guide vane under existing processes to obtain the optimal brazing fixture. Then, the optimal brazing fixture is used to introduce a brazing simulation study on a local blade model of the low-pressure turbine guide vane to obtain the optimal brazing process parameters. Finally, the brazing gap is determined by the brazing filler metal flow simulation. Note: Here, "existing processes" refers to the existing / traditional processes for brazing the low-pressure turbine guide vane before the simulation analysis; "brazing gap filler metal flow simulation" refers to the entire simulation process, i.e., the display of simulation results.

[0013] This invention uses computer numerical simulation to simulate the brazing process of low-pressure turbine guide vanes, avoiding the disadvantages of long design cycles and high costs associated with traditional experimental process optimization.

[0014] This invention creatively proposes a multi-scale brazing simulation method (multi-scale computer numerical simulation analyzes the same brazing physical process from three dimensions: the overall low-pressure turbine guide vane, the local blades of the low-pressure turbine guide vane, and the weld seam). By using the thermo-coupling external flow field simulation method, the process of on-site brazing of the low-pressure turbine guide vane is well reproduced, thus improving the accuracy of the simulation. Attached Figure Description

[0015] Figure 1This is a roadmap illustrating the specific implementation of the numerical simulation optimization method for brazing process in this invention. Figure 2 In the diagram, (a) is the overall structural modeling diagram, (b) is the local blade modeling diagram, and (c) is the brazing weld modeling diagram. Detailed Implementation

[0016] The present invention will be further described below with reference to specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0017] This invention proposes a multi-scale simulation optimization method for the brazing process of low-pressure turbine guide vanes, including... Step 1: Multi-scale modeling of low-pressure turbine guide brazing. The modeling method includes: The simulation analysis model of the low-pressure turbine guide vane is divided into three scales: the overall structural model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the brazed weld model of the low-pressure turbine guide vane. The overall structural model of the low-pressure turbine guide vane is used to verify the deformation and stress distribution of the parts during the current brazing process; the local blade model of the low-pressure turbine guide vane is used to verify the deformation and stress distribution during different brazing processes; and the brazed weld model is used to study the variation of the brazing filler metal coating amount and the flow state of the brazing filler metal.

[0018] The overall structural model and the partial blade model of the low-pressure turbine guide are both selected from the standard model of the low-pressure turbine guide (the design drawing model of the low-pressure turbine guide), and include all necessary accessory models required for its brazing process, such as fixtures, etc. The local blade model of the low-pressure turbine guide vane is selected from the standard model of the low-pressure turbine guide vane (the design drawing model of the low-pressure turbine guide vane), and the local blade model of the low-pressure turbine guide vane is a 1 / 20 to 1 / 2 equal division model of the standard model of the low-pressure turbine guide vane. To save computational resources, if necessary, the standard model of the low-pressure turbine guide (the design drawing model of the low-pressure turbine guide) is preprocessed with brazing simulation characteristics (physical properties of the part material, physical properties of the brazing filler metal such as temperature, specific heat, yield strength, coefficient of linear expansion, etc.) to form a simplified configuration.

[0019] The overall structure modeling, local blade modeling, and brazing weld modeling of the low-pressure turbine guide vane were all performed using CAD software such as UG and Solidworks for three-dimensional solid modeling.

[0020] Step 2: In the overall model, partial blade model, and weld fluid model of the low-pressure turbine guide vane, the mesh of the thin-walled structure in the overall model and partial blade model of the low-pressure turbine guide vane is locally refined, with a size of 1 / 10 to 1 / 5 of the maximum mesh size; the weld and brazing filler metal coating areas in the fluid model are locally refined, with a size of 1 / 10 to 1 / 5 of the maximum mesh size.

[0021] Step 3: Apply boundary conditions to the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model: (1) Overall model of low-pressure turbine guide: constrain the position of the upper and lower clamp end faces; set the surface contact type of the part and the clamp contact position, the contact attribute normal adopts hard contact, the tangential adopts penalty function, and the friction coefficient is 0.01~0.30; the vacuum environment heat exchange method adopts radiation form, the emissivity is 0.1~0.8, and the emissivity is given according to the vacuum furnace parameters; (2) Local blade model of low-pressure turbine guide: constrain the position of the upper and lower clamp end faces; set the surface contact type for the contact position between the part and the clamp and the gap area of ​​the blade weld, the contact attribute normal adopts hard contact, the tangential adopts penalty function, and the friction coefficient is 0.01~0.30; the gap of the remaining non-weld area (established to ensure mesh quality) adopts Tie binding method; the heat exchange method of vacuum environment adopts radiation form, the emissivity is 0.1~0.8, and the emissivity is given according to the vacuum furnace parameters; (3) The flow of filler metal in the weld includes the overall calculation domain and its cross-section, the solid filler metal coating area and the area to be welded (air domain).

[0022] Step 4: Obtain the material database: The parameters required for the overall structure of the guide vane and the local blade model include density, elastic modulus, Poisson's ratio, plastic parameters (yield strength, plastic strain), coefficient of thermal expansion, thermal conductivity and specific heat capacity; the brazed weld model includes density, dynamic viscosity, specific heat capacity, wetting contact angle, surface tension, etc.

[0023] Step 5: Construct the obtained brazing model using the above modeling method, load the model of the part to be welded, simulate the welding process with different process parameters, and obtain simulation data.

[0024] Different process parameters include fixture parameters (gap between fixture and part, fixture material), brazing process parameters (brazing temperature, holding time, assembly gap between blade and support plate), and weld and brazing filler metal parameters (weld gap size, uniformity, and brazing filler metal coating).

[0025] The overall structure simulation and local blade brazing simulation utilize a thermo-mechanical coupling method, while the brazing filler metal flow simulation in the brazing weld gap employs a fluid simulation method.

[0026] The simulation results should focus on the residual stress results.

[0027] After analyzing the welding simulation results, the optimal process parameters were selected.

[0028] like Figure 1 As shown, the welding simulation results are analyzed using a sequential research method. First, the overall structure is simulated under the existing process to obtain the optimal brazing fixture design. Then, the optimal brazing fixture design is used to introduce local blade brazing simulation to obtain the optimal process parameters. Finally, the brazing gap is determined by the brazing filler metal flow simulation.

[0029] When studying and analyzing the simulation results, the above-mentioned sequential study method can be used to analyze the welding simulation results, or the study order of the three scales can be rearranged.

[0030] Example 1: Step 1: Select the standard model of the low-pressure turbine guide (the design drawing model of the low-pressure turbine guide), and establish a solid model of the overall structure of the low-pressure turbine guide based on the above standard configuration.

[0031] Step 1.1: Select the standard model of the low-pressure turbine guide.

[0032] Step 1.2: Based on the above standard model, create a solid model of the low-pressure turbine guide in UG, such as... Figure 2 (a)

[0033] Step 1.3: Preprocess the welding simulation characteristics to form a simplified model, reducing features with weak correlation to vacuum brazing simulation and highlighting features with strong correlation to vacuum brazing simulation. The simplified model includes the low-pressure turbine guide and the fixture.

[0034] Step 2: Perform finite element mesh generation on the solid model of the low-pressure turbine guide vane structure, forming several mesh elements for the solid model. Refine the mesh at the weld locations, setting the mesh size to 1 / 10 of the maximum mesh size. Step 3: Obtain the material database required for brazing simulation by using material property testing methods.

[0035] Step 4: Constrain the positions of the upper and lower fixture end faces; set the contact position between the part and the fixture to surface-to-surface contact type, with hard contact for the normal direction and penalty function for the tangential direction, and a friction coefficient of 0.15; use radiation for heat exchange in the vacuum environment, with an emissivity of 0.8; constrain the positions of the upper and lower fixture end faces, and set the gap between the fixture and the part to 0.3mm and 0.5mm, respectively, and compare the simulation results of the two. Step 5: Generate the temperature field load input for vacuum brazing simulation based on the actual vacuum furnace heating and cooling curves.

[0036] Step 6: Perform simulation using the thermo-mechanical coupling method, obtain simulation results, and select the optimal fixture clearance. The minimum peak value of the simulated residual stress is used as the criterion for the optimal fixture clearance.

[0037] Example 2: Step 1: Select the standard model of the low-pressure turbine guide (the design drawing model of the low-pressure turbine guide), and establish the solid model of the local blades of the low-pressure turbine guide according to the above standard configuration.

[0038] Step 1.1: Select the standard model of the low-pressure turbine guide.

[0039] Step 1.2: Based on the above standard model, establish the solid model of the low-pressure turbine guide in UG, as follows: Figure 2 (b)

[0040] Step 1.3: A simplified model is created by preprocessing the welding simulation characteristics, reducing features less relevant to vacuum brazing simulation and highlighting features more relevant to it. This simplified model includes the low-pressure turbine guide and the fixture.

[0041] Step 1.4: Divide the above model into 18 equal parts and take one part as the local blade model.

[0042] Step 2: Perform finite element mesh generation on the solid model of the local blade structure of the low-pressure turbine guide vane, forming several mesh elements of the solid model. Refine the mesh at the weld location, setting the mesh size to 1 / 10 of the maximum mesh size. Step 3: Obtain the material database required for brazing simulation by using material property testing methods.

[0043] Step 4: Constrain the positions of the upper and lower fixture end faces; set the contact position between the part and the fixture to surface-to-surface contact type, with hard contact for the normal direction and penalty function for the tangential direction, and a friction coefficient of 0.15; adopt radiation as the heat exchange method in the vacuum environment, with an emissivity of 0.8; constrain the positions of the upper and lower fixture end faces, and set the gap between the fixture and the part to 0.05mm.

[0044] Step 5: Generate the temperature field load input for vacuum brazing simulation based on the actual vacuum furnace heating and cooling curves. The process specifications specify holding times of 10 min and 30 min at the process temperature; compare the simulation results of the two. Step 6: Perform simulation using the thermo-mechanical coupling method, obtain simulation results, and select the optimal heat preservation time. The minimum peak value of the simulated residual stress is used as the criterion for the optimal heat preservation time.

[0045] Example 3: Step 1: Select the standard model of the low-pressure turbine guide (the design drawing model of the low-pressure turbine guide), and establish the brazing weld model of the low-pressure turbine guide according to the above standard configuration.

[0046] Step 1.1: Select the standard model of the low-pressure turbine guide.

[0047] Step 1.2: Create a solid model of the low-pressure turbine guide in UG based on the above standard model.

[0048] Step 1.3: Preprocess the welding simulation characteristics to form a simplified model, reduce features that are weakly related to vacuum brazing simulation, and highlight features that are strongly related to vacuum brazing simulation.

[0049] Step 1.4: Select the weld as the research object and model it, such as... Figure 2 (c)

[0050] Step 2: Perform finite element mesh generation on the solid model of the brazed weld structure of the low-pressure turbine guide vane, forming several mesh elements of the solid model. Refine the mesh at the weld location, setting the mesh size to 1 / 10 of the maximum mesh size. Step 3: Obtain the material database required for brazing simulation by using material property testing methods.

[0051] Step 4: By adjusting the wall temperature, heat exchange is achieved between the wall and the brazing filler metal, thus melting and solidifying the filler metal. The overall operating pressure of the computational domain is 0.04 Pa, corresponding to the pressure in the vacuum furnace during actual brazing. The initial fluid velocity is 0 m / s, and the inner and outer boundaries of the filler metal coating area (the inner boundary being the part where the filler metal contacts the sealing strip) are both non-slip wall boundaries. The upper and lower surface boundaries of the air domain are non-slip walls. To prevent excessive outflow of molten filler metal from the computational domain during filling, the air domain outlet also uses non-slip wall conditions and the same temperature control as the wall of the filler metal coating area. The weld gaps are set to 0.05 mm, 0.10 mm, and 0.15 mm, and the simulation results of the three are compared.

[0052] Step 5: Analyze the flow field using simulation methods, obtain the simulation results, and select the optimal weld gap. The minimum peak value of the optimal brazing filler metal coating result is used as the criterion for the optimal weld gap.

[0053] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes, characterized in that, include: Step 1: Simulation modeling of the low-pressure turbine guide vane, and dividing the simulation analysis model of the low-pressure turbine guide vane into three scales: The first step is to model the overall structure of the low-pressure turbine guide to obtain an overall model of the low-pressure turbine guide, which is used to verify the deformation and stress distribution of the low-pressure turbine guide in the current brazing process. The second step involves modeling a local blade of the low-pressure turbine guide vane to obtain a local blade model of the low-pressure turbine guide vane, which is used to verify the deformation and stress distribution laws during different brazing processes. The third step involves modeling the brazed weld seam to obtain a weld seam fluid model, which is used to study the changes in the amount of brazing filler metal coating and the flow state of the brazing filler metal. Step 2: Perform local refinement processing on the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model, wherein: The mesh of the overall model of the low-pressure turbine guide vane and the local blade model of the low-pressure turbine guide vane are locally refined in the thin-walled structure area. In the weld fluid model, the weld and brazing filler metal coating areas are locally densified; Step 3: Apply boundary conditions to the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model; Step 4, Obtain the material database: Use experimental methods, theoretical calculations and literature to obtain the parameters required for the overall model of the low-pressure turbine guide vane, the local blade model of the low-pressure turbine guide vane, and the weld fluid model; Step 5: Construct the obtained brazing model using the above modeling method, load the model of the part to be welded, simulate the welding process under different process parameters, and obtain simulation data, including: A thermo-mechanical coupling method is used for both the overall model and the local blade model of the low-pressure turbine guide vane. For the weld fluid model, a fluid simulation method is used; Step 6: Analyze the simulation results and select the optimal brazing fixture, optimal process parameters, and weld gap.

2. The multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes according to claim 1, characterized in that, In step 1: The overall model of the low-pressure turbine guide is based on the standard model of the low-pressure turbine guide and includes all necessary accessory models required for its brazing process. The partial blade model of the low-pressure turbine guide vane adopts the standard model of the low-pressure turbine guide vane, and is a model that is 1 / 20 to 1 / 2 of the standard model.

3. The multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes according to claim 1, characterized in that, In step 2: The mesh of the overall model of the low-pressure turbine guide vane and the local blade model of the low-pressure turbine guide vane are locally refined in the thin-walled structure area, with the size being 1 / 10 to 1 / 5 of the maximum mesh size; In the weld fluid model, the weld and brazing filler metal coating areas are locally densified, with a size of 1 / 10 to 1 / 5 of the maximum mesh size.

4. The multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes according to claim 1, characterized in that, In step 3: For the overall model of the low-pressure turbine guide: constrain the positions of the upper and lower clamp end faces; set the surface-to-surface contact type at the contact position between the part and the clamp, use hard contact for the normal direction of the contact attribute, use a penalty function for the tangential direction, and set the friction coefficient to 0.01 to 0.30; use radiation as the heat exchange method in the vacuum environment, with an emissivity of 0.1 to 0.8, which is given according to the parameters of the vacuum furnace. For the local blade model of the low-pressure turbine guide vane: constrain the positions of the upper and lower clamp end faces; set the surface-to-surface contact type at the contact positions between the part and the clamp, and the gap area of ​​the blade weld, with the contact attribute normal using hard contact, the tangential using a penalty function, and the friction coefficient of 0.01 to 0.30; the gaps in other non-weld areas use the Tie binding method; the vacuum environment heat exchange method adopts radiation, with an emissivity of 0.1 to 0.8, which is given according to the vacuum furnace parameters; For the weld fluid model: the weld filler metal flow includes the overall computational domain and its cross-section, the solid filler metal coating area, and the area to be welded.

5. The multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes according to claim 1, characterized in that, In step 4: The parameters required for the overall model and the partial blade model of the low-pressure turbine guide vane include: density, elastic modulus, Poisson's ratio, yield strength, plastic strain, coefficient of thermal expansion, thermal conductivity, and specific heat capacity. The parameters required for the weld fluid model include: density, dynamic viscosity, specific heat capacity, wetting contact angle, and surface tension.

6. The multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes according to claim 1, characterized in that: In step 5, the process parameters include the gap between the fixture and the part, the fixture material, the brazing temperature, the holding time, the assembly gap between the blade and the support plate, the size and uniformity of the weld gap, and the brazing filler coating.

7. The multi-scale simulation optimization method for brazing process of low-pressure turbine guide vanes according to claim 1, characterized in that: In step 6, the welding simulation results are analyzed using a sequential research method. First, the overall model of the low-pressure turbine guide vane is simulated under the existing process to obtain the optimal brazing fixture. Then, the optimal brazing fixture is used to introduce the brazing simulation study of the local blade model of the low-pressure turbine guide vane to obtain the optimal brazing process parameters. Finally, the brazing gap is determined by the brazing filler metal flow simulation.

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