Machining method for rocket engine mixer inlet fillet

Abstract

The invention relates to a machining method for an inlet fillet of a rocket engine mixer. The machining method comprises the steps that a mixer blank is turned after being subjected to heat treatment; the upper end and the lower end of the lathed semi-finished flow mixer are fixed, the fixed semi-finished flow mixer is installed on a machining center, and main body structure machining, including drilling and milling operation, of the semi-finished flow mixer is conducted; performing numerical control programming according to the shape and the size of the inlet fillet, re-parameterizing the curved surface of the inlet fillet, and processing the inlet fillet on a processing center; the flow mixer is taken down from the machining center to be trimmed by a bench worker; the flow mixer is installed on a numerical control lathe, final turning is carried out, and the overall size is corrected; the flow mixer is taken down from the numerical control lathe, bench worker finishing is conducted again, and the machined inlet fillet is finely ground and polished; and the processed flow mixer is cleaned. The problems that the consistency cannot be guaranteed and the efficiency is low due to the fact that the inlet fillet of the tangential hole of the flow mixer is manually polished are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of numerical control machining and relates to a method for machining the fillet of a rocket engine mixer inlet. Background Art

[0002] As one of the important parts of rocket engines, the mixer has been adopted by many types of rocket engines to suppress oscillating combustion. It plays a vital role in improving combustion efficiency and gas working capacity, and eliminating oscillation at the turbine inlet or thrust chamber gas path inlet. Therefore, the processing of the mixer is particularly important.

[0003] Currently, the processing of mixers has achieved CNC precision processing, but the inlet corners of the tangential holes are manually polished, which has low processing efficiency and cannot guarantee consistency. This will cause ablation or even cracks at the inlet corners after combustion, and the service life cannot be guaranteed. Summary of the Invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology and propose a method for processing the fillet of the inlet of a rocket engine mixer, so as to solve the problems in the existing technology that the fillet of the inlet of the tangential hole of the mixer is manually polished, the consistency cannot be guaranteed, and the efficiency is low.

[0005] The present invention solves the technical problem by providing a method for processing the fillet of a rocket engine mixer inlet, comprising the following steps:

[0006] Heat treating the mixer blank;

[0007] Turning heat-treated mixer blank;

[0008] Use the contoured pressing plate and base to fix the upper and lower ends of the machined semi-finished mixer, install the fixed semi-finished mixer on the machining center, and perform the main structure processing of the semi-finished mixer on the machining center, including drilling and milling operations;

[0009] After the main structure is machined on the machining center, CNC programming is performed based on the shape and size of the entry fillet, the entry fillet surface is re-parameterized, and the entry fillet is machined on the machining center;

[0010] Remove the mixer from the machining center and perform bench trimming to remove burrs and sharp edges generated during machining;

[0011] Install the mixer on a CNC lathe, perform final turning, and correct the overall dimensions;

[0012] The mixer is removed from the CNC lathe and trimmed again by benchwork, and the processed inlet fillet is finely ground and polished.

[0013] Furthermore, the turning of the heat-treated mixer blank includes rough turning, semi-finishing turning, finishing turning and correction.

[0014] Furthermore, in the rough turning process, a margin of 1.5 to 2 mm is reserved between the outer circle and the inner hole of the mixer blank;

[0015] In the semi-finishing machining, a margin of 0.2 to 0.4 mm is reserved between the outer circle and the inner hole of the mixer blank;

[0016] In the precision turning process, a margin of 0.03 to 0.06 mm is reserved between the outer circle and the inner hole of the mixer blank.

[0017] Furthermore, the re-parameterizing of the inlet fillet surface includes:

[0018] Input the spline curve C(u) of the mixer inlet fillet surface to be reparameterized;

[0019] Calculate new weights Get the reparameterized spline curve set {C k (u)}, where i is the number of control points selected by C(u) and k is the sequence number of the reparameterized spline curve;

[0020] The reparameterized spline curve set is used to construct the skin surface to obtain the surface u represents the position along one direction of the surface, and v represents the position along the other direction of the surface, which is perpendicular to the u parameter;

[0021] Check the re-parameterized skin surface to ensure that the error between the re-parameterized surface and the original surface is within 0.01mm;

[0022] The re-parameterized skin surface is applied to CNC machining, tool paths are generated, and actual machining is performed.

[0023] Further, calculate the new weight factor Get the reparameterized spline curve set {C k (u)}, specifically:

[0024] C(u) is a cross-sectional curve defined on u∈[a,b]. The reparameterized spline curve is obtained as follows:

[0025] Basis function {N i,p (u)} is an n-order Bernstein polynomial, ω i is the weight factor, {P i} is a control point and remains unchanged before and after reparameterization, then u∈[a,b];

[0026] Suppose \(u = f(s)\) is a scalar function defined on \(s\in[c,d]\). For \(s\in[c,d]\), let \(\mu(u)=\gamma u+\delta\), then where \(p\) is the degree of the cross - sectional curve \(C(u)\), \(u\) i+j is the knot of the curve \(C(u)\) to be re - parameterized, \(u\in[a,b]\) is the parameter before re - parameterization, \(s\in[c,d]\) is the parameter after re - parameterization, and \(\delta,\beta,\gamma,\alpha\) are all polynomial coefficients;

[0027] Then the re - parameterized curve is

[0028] Perform the above re - parameterization operation on each cross - sectional curve \(C(u)\) to be re - parameterized, and obtain the set of re - parameterized spline curves \(\{C\) k (u)\}(k = 0,1,\cdots,K)\), where \(K\) is the total number of spline curves.

[0029] Furthermore, use the set of re - parameterized spline curves to construct a skin surface. Specifically:

[0030] The set of spline curves \(\{C\) k (u)\} has a unified degree \(p\) and knot vector \(U\) in the \(u\) - direction. Select the degree \(q\) in the \(v\) - direction, \(q < K\), and determine the knot vector \(V=\{v\) i} and the parameter are obtained by taking the average through \(v\) i , that is k = 1,2,\cdots,K - 1; where \(P\) i,k is the control point, \(d\) i is \(P\) i,0 , \(\cdots\), \(P\) i,K 's total chord length;

[0031] Then, according to the parameter and the knot vector \(V\), perform \(n + 1\) - order curve interpolation on the control points of the cross - sectional curve to obtain the control points of the skin surface

[0032] Furthermore, obtain the skin surface where \(N\) i,p , \(N\) j,q are the \(n\) - th basis function in the \(u\) - direction and the \(m\) - th basis function in the \(v\) - direction respectively.

[0033] Furthermore, if the error between the surface generated after re - parameterization and the original surface is more than \(0.01\mathrm{mm}\), it is necessary to re - perform the operations of parameterized spline curves and constructing the skin surface until the error between the generated surface and the original surface is within \(0.01\).

[0034] Furthermore, when generating the tool path, the controlled cutting parameters include: the tool axis angle must not interfere or overcut; the tool path is in a spiral pattern along the chamfer of the hole mouth to prevent uneven allowances from causing tool breakage and surface roughness that does not meet the requirements; the step distance during rough machining is 0.1~0.2mm, and the step distance during fine machining is 0.02~0.04mm.

[0035] Furthermore, the machining center is a four-axis machining center or a five-axis machining center.

[0036] Furthermore, the method further includes the following steps:

[0037] Clean the processed mixer to remove the oil, chips and impurities remaining during the processing;

[0038] The cleaned mixer is subjected to quality inspection, including inspection of dimensional accuracy, surface quality, and geometric shape, and the mixers that pass the inspection are packaged.

[0039] The beneficial effects of the present invention compared with the prior art are:

[0040] The present invention ensures that the position of each part is accurate during the processing by cooperating with tooling on a four-axis or five-axis machining center, thereby improving the dimensional accuracy and shape consistency of the entry fillet; through CNC programming and re-parameterized surfaces, the tool path and cutting parameters can be accurately controlled to further improve the processing accuracy, so that the processed entry fillet better meets the design requirements, reduces the dimensional deviation and shape irregularity caused by manual polishing, and at the same time can reduce the problems of uneven cutting force and reduced tool path quality, thereby improving the processing speed and feed rate, and further shortening the processing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a flow chart of a method for processing fillet of a rocket engine mixer inlet according to the present invention;

[0042] Figure 2 This is a schematic diagram of the overall structure during machining in the machining center;

[0043] Figure 3 Schematic diagram of the overall structure of the mixer;

[0044] Figure 4 Before and after reparameterization of the inlet fillet surface;

[0045] Figure 5 Schematic diagram of the measurement position of the inlet fillet surface. DETAILED DESCRIPTION

[0046] The present invention proposes a method for processing the fillet of a rocket engine mixer inlet, such as Figure 1 As shown, the following steps are included:

[0047] S1. heat treating the mixer blank;

[0048] S2, clamping the heat-treated mixer blank on a CNC lathe, and lathing the heat-treated mixer blank;

[0049] S3. Fix the upper and lower ends of the machined semi-finished mixer using a contoured pressing plate and a base, install the fixed semi-finished mixer on a machining center, and perform main structure machining of the semi-finished mixer on the machining center, including drilling and milling operations;

[0050] S4. After the main structure is processed by the machining center, CNC programming is performed based on the shape and size of the inlet fillet, the inlet fillet surface is re-parameterized, and the inlet fillet is processed on the machining center;

[0051] S5. Remove the mixer from the machining center and perform bench trimming to remove burrs and sharp edges generated during the machining process;

[0052] S6. Install the mixer on a CNC lathe for final machining and correction of overall dimensions.

[0053] S7. Remove the mixer from the CNC lathe, perform bench trimming again, and finely grind and polish the processed inlet fillet;

[0054] S8. Clean the processed mixer to remove the oil, chips and impurities remaining in the processing process, perform quality inspection on the cleaned mixer, and package the mixers that pass the inspection.

[0055] The present invention will be further described below with reference to the accompanying drawings and examples.

[0056] Example 1

[0057] refer to Figures 2 to 4 , the processing method of this embodiment includes the following steps:

[0058] S1. Heat treatment is performed on the mixer blank to improve the mechanical properties of the material, such as hardness, strength and toughness. The specific heat treatment process is selected according to the characteristics and requirements of the material, including quenching, tempering, annealing, etc.

[0059] S2. Turning the heat-treated mixer blank, including rough turning, semi-finishing turning, finishing turning and correction;

[0060] S201, the first turning process, rough turning; remove most of the allowance, lay the foundation for subsequent processing, determine the approximate shape and size of the part, and leave a processing allowance of 1.5 to 2 mm;

[0061] S202, the second turning process, semi-finishing turning process; further improve the shape and inner hole dimensional accuracy and surface quality of the parts, reduce the machining allowance to 0.2-0.4mm, and prepare for subsequent finishing process;

[0062] S203, the third turning process, for finishing turning; accurately control the size and shape of the parts, and reserve a margin of 0.03 to 0.06 mm between the outer circle and the inner hole of the mixer blank to ensure that the accuracy of the outer circle diameter meets the design requirements and improve the surface finish;

[0063] S204, the fourth turning process, is the final finishing and correction process; fine-tuning is performed on the parts’ dimensions and surface quality, and all dimensions are checked and ensured to meet the design tolerance requirements.

[0064] S3, use the contoured pressing plate and base to fix the upper and lower ends of the semi-finished mixer after machining, such as Figure 2 As shown; the fixed mixer semi-finished product is installed on the machining center, and the main structure of the mixer semi-finished product is processed on the machining center, including drilling and milling operations.

[0065] S4. After the main structure is processed by the machining center, CNC programming is performed according to the shape and size of the inlet fillet, and the inlet fillet surface is re-parameterized. The inlet fillet is processed on the machining center, such as Figure 3 .

[0066] In this embodiment, a MIKRON HPM 600U HD five-axis machining center is used as the machining center. CNC programming is performed according to the shape and size of the entry fillet, and the entry fillet surface is re-parameterized for entry fillet processing on the machining center. Taking into account machining difficulties such as uneven stock distribution, surface irregularities, and undercuts, cutting parameters such as the tool axis angle, tool path, and cutting depth are strictly controlled to ensure machining quality and efficiency. Close attention is paid to tool wear and workpiece deformation during machining, and timely adjustments are made.

[0067] To reparameterize the inlet fillet surface:

[0068] S401, inputting a spline curve C(u) of the fillet surface of the mixer inlet to be re-parameterized;

[0069] S402, calculate new weight factor Get the reparameterized spline curve set {C k (u)}, where i is the number of control points selected by C(u) and k is the sequence number of the re-parameterized spline curve.

[0070] New weight factor and spline curve set {C k(u) is calculated as follows:

[0071] C(u) is a cross-sectional curve defined on u ∈ [a, b]. The reparameterized spline curve is obtained as follows:

[0072] The basis function {N i,p (u)} is an n-degree Bernstein polynomial, ω i is the weight factor, {P i} are the control points and remain unchanged before and after reparameterization. Then u ∈ [a, b];

[0073] Assume u = f(s) is a scalar function defined on s ∈ [c, d]. s ∈ [c, d]. Let μ(u) = γu + δ. Then where p is the degree of the cross-sectional curve C(u), u i+j is the knot of the curve C(u) to be reparameterized, u ∈ [a, b] is the parameter before reparameterization, s ∈ [c, d] is the parameter after reparameterization, and δ, β, γ, α are all polynomial coefficients. In this embodiment, δ, β, γ, α are taken as 3.2, 2, 1.5, and 3.5 respectively.

[0074] Then the reparameterized curve is

[0075] Perform the above reparameterization operation on each cross-sectional curve C(u) to be reparameterized to obtain the reparameterized spline curve set {C k (u)}(k = 0, 1,..., K), where K is the total number of spline curves.

[0076] S403. Use the reparameterized spline curve set to construct a skin surface to obtain the surface u represents the position along one direction of the surface, and v is the position along another direction of the surface, perpendicular to the u parameter. The skin surface construction method is as follows:

[0077] The spline curve set {C k (u)} has a unified degree p and knot vector U in the u direction. Select the degree q in the v direction, q < K, and determine the knot vector V = {v i} and the parameter are obtained by taking the average of v i , that is k = 1, 2,..., K - 1; where P i,k is the control point, d i is P i,0 ,..., P i,K 's total chord length;

[0078] Then according to the parameters The control points of the skin surface can be obtained by performing n+1 curve interpolation on the control points of the cross-section curve and the node vector V.

[0079] Then we get the skin surface where N i,p 、N j,q They are the nth-order basis function in the u direction and the mth-order basis function in the v direction respectively.

[0080] S404: Check the re-parameterized skin surface to ensure that the error between the re-parameterized surface and the original surface is within 0.01 mm. If the error between the re-parameterized surface and the original surface is greater than 0.01 mm, re-parameterize the spline curve and construct the skin surface until the error between the re-parameterized surface and the original surface is within 0.01.

[0081] S405. Apply the re-parameterized skin surface to CNC machining, generate tool paths, and perform actual machining.

[0082] When generating the tool path, the controlled cutting parameters include: the tool axis angle must not interfere or overcut; the tool path is in a spiral pattern along the chamfer of the hole to prevent uneven allowances from causing tool breakage and surface roughness that does not meet the requirements; the step distance during rough machining is 0.1~0.2mm, and the step distance during fine machining is 0.02~0.04mm.

[0083] S5. Remove the mixer from the machining center and perform bench trimming to remove burrs and sharp edges generated during the machining process;

[0084] S6. Install the mixer on a CNC lathe for final machining and correction of overall dimensions.

[0085] S7. Remove the mixer from the CNC lathe, perform bench trimming again, and finely grind and polish the processed inlet fillet;

[0086] S8. Clean the finished mixer to remove any residual oil, chips, and impurities from the process using appropriate cleaning methods, such as solvent cleaning or ultrasonic cleaning. Perform a comprehensive quality inspection of the cleaned mixer, including dimensional accuracy, surface quality, and geometric shape. Use measuring tools and testing equipment to ensure the mixer meets design requirements and quality standards. Inspect and package the mixer to protect it from damage during transportation and storage.

[0087] Example 2

[0088] The material of the mixer to be processed in this embodiment is a high-temperature alloy, and the processing steps are as follows:

[0089] S1. Preparation before processing the fillet of the mixer inlet: The material of the mixer to be processed is high-temperature alloy. First, heat treatment is performed to reduce work hardening and improve cutting performance. Special processing tooling is made to ensure the stability and precision of the mixer during the processing.

[0090] S2, turning stage: First turning: Rough turning is performed to remove most of the excess and lay the foundation for subsequent processing. During the turning process, pay attention to controlling the cutting parameters to avoid excessive cutting force that may cause deformation of the workpiece;

[0091] Second turning: semi-finishing turning is performed to further improve the dimensional accuracy and surface quality of the parts. At this time, the machining allowance is reduced, and the cutting speed and feed rate can be appropriately increased;

[0092] The third turning process: finishing turning, precisely controlling the size and shape of the parts. The accuracy of key dimensions is required to be controlled within ±0.01mm, and the surface roughness reaches Ra1.6μm;

[0093] The fourth turning process: final finishing and correction to ensure that all dimensions meet the design tolerance requirements. The surface of the part is polished to improve the surface finish.

[0094] S3, machining center processing stage:

[0095] Perform other parts processing on the machining center, such as drilling, milling and other operations, to complete the main structure processing of the part;

[0096] Input the spline curve C(u) of the mixer inlet fillet surface to be reparameterized;

[0097] Calculate new weights Get the reparameterized spline curve set {C k (u)};

[0098] Skin surface construction: Use skinning algorithm to perform mask construction on the reparameterized spline curve set;

[0099] Check and smooth the re-parameterized surface to ensure that the parameterization is within the parameter domain;

[0100] S4, machining center processing entrance fillet:

[0101] CNC programming is performed based on the re-parameterized surface, and fixed contour milling is used to select the surface as the driving body to generate high-quality tool paths.

[0102] Perform entry radius processing and strictly control cutting parameters to ensure processing quality and efficiency. During processing, pay close attention to tool wear and workpiece deformation and make timely adjustments.

[0103] S5, fitter stage:

[0104] Preliminary benchwork operations: remove burrs and sharp edges generated during machining, and grind and polish the surface of parts.

[0105] Finishing bench operation: Finely grind and polish the processed entrance fillet to ensure the surface quality of the fillet is smooth and flawless.

[0106] S6. Inspection and acceptance:

[0107] Adopt three R specifications: R1.25, R1.5 and R1.75. Figure 5 The position is determined, and each inner and outer arc is tested; the test results show that the R gauge with a size of 1.5 fits well, while the R gauges of R1.25 and R1.75 do not fit well and there are gaps, indicating that the arc meets the requirements of R1.2 to R1.8 and is close to R1.5.

[0108] Carry out comprehensive inspection on the dimensional accuracy, surface quality, geometric shape and other aspects of the parts to ensure that the parts meet the design requirements and quality standards.

[0109] Example 3

[0110] The material of the mixer to be processed in this embodiment is stainless steel, and the processing steps are as follows:

[0111] S1. Preparation before processing the fillet of the mixer inlet: The material of the mixer to be processed is stainless steel. Appropriate heat treatment is carried out to improve the processing performance of the material, and high-precision processing tooling is made to ensure the stability and accuracy of the mixer during the processing.

[0112] S2, turning stage: First turning: Rough turning to remove most of the excess. Use a larger cutting depth and feed rate to improve processing efficiency.

[0113] Second turning: semi-finishing turning, reducing machining allowance, improving dimensional accuracy and surface quality. The cutting speed can be increased appropriately to obtain better surface finish.

[0114] The third turning process: Finish turning, precisely controlling the size and shape of the parts. The accuracy of key dimensions is required to be controlled within ±0.005mm, and the surface roughness reaches Ra1.6μm.

[0115] The fourth turning process: final finishing and correction to ensure that all dimensions meet the design tolerance requirements. The surface of the part is finely polished to improve the surface quality.

[0116] S3, machining center processing stage:

[0117] Other parts are processed on the machining center, such as milling, drilling and other operations, to complete the main structure processing of the part.

[0118] Input the spline curve C(u) of the mixer inlet fillet surface to be reparameterized;

[0119] Calculate new weights Get the reparameterized spline curve set;

[0120] Skin surface construction: Use skinning algorithm to perform mask construction on the reparameterized spline curve set;

[0121] Check and smooth the re-parameterized surface to ensure that the parameterization is within the parameter domain;

[0122] S4, machining center processing entrance fillet:

[0123] CNC programming is performed based on the re-parameterized surface, and the surface is selected as the driving body using fixed contour milling to generate high-quality tool paths.

[0124] Perform entry radius processing and strictly control cutting parameters to ensure processing quality and efficiency. During the processing, monitor tool wear and workpiece deformation in real time and adjust processing parameters in a timely manner.

[0125] S5. Bench stage: preliminary bench operations: remove burrs and sharp edges generated during the processing, and perform preliminary grinding and polishing on the surface of the parts.

[0126] Finishing bench operation: Finely grind and polish the processed entrance fillet to ensure the surface quality of the fillet is smooth and flawless.

[0127] S6, Inspection and acceptance: Use R1.25, R1.5, R1.75 three R gauges, according to Figure 5 The position is determined and each inner and outer arc is tested. The test results show that the R gauge with a size of 1.5 fits well, while the R gauges of R1.25 and R1.75 do not fit well and there are gaps, which means that the arc meets the requirements of R1.2 to R1.8 and is close to R1.5.

[0128] Carry out comprehensive inspection on the dimensional accuracy, surface quality, geometric shape and other aspects of the parts to ensure that the parts meet the design requirements and quality standards.

[0129] refer to Figure 4; Isoparametric lines before and after re-parameterization (10 isoparametric lines in the u direction were extracted); the error between the re-parameterized surface and the original surface (number of analysis points: u×v=200×50) is less than 0.002mm; it proves that the accuracy of the re-parameterized surface can fully meet the subsequent processing; when the surface is selected as the driving body using fixed contour milling based on UG, the generated tool path quality is better, and thus the processing quality is also better.

[0130] Reparameterized Surface Error Analysis Table

[0131]

[0132]

[0133] After CNC programming and R gauge testing, it meets the design drawing requirements and has better surface quality, indicating that the method of precision CNC machining of the mixer inlet fillet by re-parameterizing the inlet fillet surface + CNC programming is feasible and has been verified by test runs. At the same time, the machining efficiency has been increased by 1 times, and the consistency has been better guaranteed, providing a strong guarantee for suppressing combustion vibration.

[0134] Taking into account cost and the minimal cutting force required during the inlet rounding process, this invention utilizes a simpler tooling design, avoiding overly complex and expensive tooling. This improves processing efficiency and consistency, reduces scrap and rework, and thus lowers production costs. Furthermore, the automated process reduces reliance on manual labor, lowering labor costs.

[0135] Precise machining accuracy and consistency make the inlet fillet of the mixer smoother and more uniform, reducing the resistance and energy loss of fluid flow, and improving the performance and efficiency of the mixer; avoiding surface defects and damage that may be caused by manual polishing, improving the surface quality and appearance of the product, and enhancing the reliability and service life of the product.

[0136] CNC machining and automated process flows have high stability and repeatability, which facilitates production management and quality control. Standardized machining processes can be achieved through programming and parameter settings, reducing the impact of human factors on machining quality. The use of R-gauge testing can promptly detect and correct problems in the machining process to ensure that product quality meets requirements.

[0137] In summary, the mixer inlet fillet processing method of the present invention has many beneficial effects such as improving processing accuracy and consistency, improving processing efficiency, reducing costs, improving product quality and reliability, and facilitating production management and quality control, providing an efficient and reliable solution for the production and manufacturing of mixers.

[0138] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

[0139] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for processing the fillet of a rocket engine mixer inlet, characterized in that: The following steps are involved: Heat treating the mixer blank; Turning heat-treated mixer blank; Use the contoured pressing plate and base to fix the upper and lower ends of the machined semi-finished mixer, install the fixed semi-finished mixer on the machining center, and perform the main structure processing of the semi-finished mixer on the machining center, including drilling and milling operations; After the main structure is machined on the machining center, CNC programming is performed based on the shape and size of the entry fillet, the entry fillet surface is re-parameterized, and the entry fillet is machined on the machining center; Remove the mixer from the machining center and perform bench trimming to remove burrs and sharp edges generated during machining; Install the mixer on a CNC lathe, perform final turning, and correct the overall dimensions; The mixer is removed from the CNC lathe and trimmed again by benchwork, and the processed inlet fillet is finely ground and polished.

2. The method for processing the fillet of a rocket engine mixer inlet according to claim 1, characterized in that: The turning of the heat-treated mixer blank includes rough turning, semi-finishing turning, finishing turning and correction.

3. The method for processing the fillet of the inlet of a rocket engine flow mixer according to claim 2, characterized in that: During the rough turning process, a 1.5-2mm margin is reserved between the outer circle and the inner hole of the mixer blank; In the semi-finishing machining, a margin of 0.2 to 0.4 mm is reserved between the outer circle and the inner hole of the mixer blank; In the precision turning process, a margin of 0.03 to 0.06 mm is reserved between the outer circle and the inner hole of the mixer blank.

4. The method for processing the fillet of a rocket engine mixer inlet according to claim 1, characterized in that: The re-parameterizing of the inlet fillet surface comprises: Input the spline curve C(u) of the mixer inlet fillet surface to be reparameterized; Calculate new weights Get the reparameterized spline curve set {C k (u)}, where i is the number of control points selected by C(u) and k is the sequence number of the reparameterized spline curve; The reparameterized spline curve set is used to construct the skin surface to obtain the surface u represents the position along one direction of the surface, and v represents the position along the other direction of the surface, which is perpendicular to the u parameter; Check the re-parameterized skin surface to ensure that the error between the re-parameterized surface and the original surface is within 0.01mm; The re-parameterized skin surface is applied to CNC machining, tool paths are generated, and actual machining is performed.

5. The method for processing the fillet of the inlet of a rocket engine flow mixer according to claim 4, characterized in that: Calculate new weights Get the reparameterized spline curve set {C k (u)}, specifically: C(u) is a cross-sectional curve defined on u∈[a,b]. The reparameterized spline curve is obtained as follows: Basis function {N i,p (u)} is an n-order Bernstein polynomial, ω i is the weight factor, {P i } is a control point and remains unchanged before and after reparameterization, then Assume that u = f(s) is a scalar function defined on s∈[c,d], s∈[c,d], let μ(u)=γu+δ, then Where p is the degree of the cross-sectional curve C(u), u i+j are the nodes of the curve C(u) to be reparameterized, u∈[a,b] are the parameters before reparameterization, s∈[c,d] are the parameters after reparameterization, and δ, β, γ, and α are all polynomial coefficients; The reparameterized curve is The above reparameterization operation is performed on each cross-section curve C(u) to be reparameterized, and the reparameterized spline curve set {C k (u)}(k=0,1,…,K), K is the total number of spline curves.

6. The method for processing the fillet of the inlet of a rocket engine flow mixer according to claim 5, characterized in that: The skin surface is constructed using the reparameterized spline curve set, specifically: The spline curve set {C k (u)} has a uniform degree p and knot vector U in the u - direction. The degree q is selected in the v - direction, where q < K, and the knot vector V = {v i} and the parameter are obtained by the method of taking the average in the v i direction, that is where P i,k ris the control point, d i is the total chord length of P i,0 , …, P i,K . Then according to the parameters Perform n+1 curve interpolation on the control points of the cross-section curve with the node vector V to obtain the control points of the skin surface Then we get the skin surface where N i,p 、N j,q They are the nth-order basis function in the u direction and the mth-order basis function in the v direction respectively.

7. The method for processing the fillet of the inlet of a rocket engine flow mixer according to claim 6, characterized in that: If the error between the generated surface after re-parameterization and the original surface is more than 0.01mm, it is necessary to re-parameterize the spline curve and construct the skin surface until the error between the generated surface and the original surface is within 0.

01.

8. The method for processing the fillet of the inlet of a rocket engine flow mixer according to claim 6, characterized in that: When generating the tool path, the controlled cutting parameters include: the tool axis angle must not interfere or overcut; the tool path is in a spiral pattern along the chamfer of the hole to prevent uneven allowances from causing tool breakage and surface roughness that does not meet the requirements; the step distance during rough machining is 0.1~0.2mm, and the step distance during fine machining is 0.02~0.04mm.

9. The method for processing the fillet of a rocket engine flow mixer inlet according to claim 1, characterized in that: The machining center is a four-axis machining center or a five-axis machining center.

10. The method for processing the fillet of a rocket engine mixer inlet according to claim 1, characterized in that: The following steps are also included: Clean the processed mixer to remove the oil, chips and impurities remaining during the processing; The cleaned mixer is subjected to quality inspection, including inspection of dimensional accuracy, surface quality, and geometric shape, and the mixers that pass the inspection are packaged.

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