Method of additive manufacturing of an evaporation tube and evaporation tube

Abstract

This invention relates to an additive manufacturing method for an evaporator tube and the evaporator tube itself, belonging to the field of aero-engine combustion chamber technology. The method includes: establishing and reshaping a three-dimensional digital model of the evaporator tube; placing the tubular body at an angle of 15°–45° to the vertical direction, ensuring the overhanging area has an inclination angle ≥45°; adding a detachable support structure; setting the powder layer thickness, laser power, and scanning speed; performing selective laser melting for integral forming; stress-relief annealing; and precision machining the flange mounting surface and positioning holes, polishing to Ra≤3.2. The evaporator tube includes a tubular body and a flange, with a wall thickness of 0.8mm–1.2mm, and an internal concave curved section and a throttling sleeve. It is an integrally formed structure made of GH3625 powder through selective laser melting. The advantages of this invention are: it solves the problems of low yield and poor consistency in traditional welding, and improves combustion efficiency.

Description

Technical Field

[0001] This invention relates to an additive manufacturing method for an evaporator tube and the evaporator tube thereof, belonging to the field of aero-engine technology. Background Technology

[0002] Evaporator tube combustors are a mainstream technology for micro turbojet engines. Micro turbojet engines are characterized by their small size, light weight, simple structure, and low cost, and are widely used in military aviation and civilian model aircraft power units such as unmanned aerial vehicles and loitering munitions. Evaporator tube combustors use evaporator tubes instead of traditional swirlers and complex nozzles, offering advantages such as simple structure, lower manufacturing cost, and lower fuel supply pressure. The evaporator tube is the core component of the combustor. Its working principle is as follows: fuel is injected through the nozzle into the incandescent evaporator tube surrounded by high-temperature combustion gases, where it rapidly absorbs heat and evaporates into vapor. After initial mixing with a small amount of air, it is injected into the main combustion zone for efficient combustion. The structural form of the evaporator tube directly determines the fuel atomization and evaporation effect, and has a decisive influence on the combustion efficiency and the uniformity of the outlet temperature field of the combustor.

[0003] However, existing evaporator tube manufacturing technologies have many shortcomings. Structurally, traditional evaporator tubes are mostly uniformly thick, uniformly cross-section tubes welded to a support ring. Due to the limited length of the evaporator tube, the fuel residence time inside is short, resulting in incomplete fuel atomization and low combustion efficiency in the combustion chamber. In terms of manufacturing processes, the intake end of the evaporator tube and the support ring are typically welded using argon arc welding. Since the evaporator tube wall thickness is usually only about 1mm and has complex bends, traditional welding (such as argon arc welding) results in high heat input, easily leading to material property loss and deformation. Furthermore, post-weld stress is difficult to completely eliminate through heat treatment, significantly impacting product performance and quality. Welding multiple evaporator tubes one by one also easily leads to significant coaxiality deviations, resulting in a poor combustion chamber outlet temperature field. In addition, product quality is determined by the skill level of the welding personnel, resulting in low yield rates and inconsistent product quality.

[0004] With the development of additive manufacturing technology, Selective Laser Melting (SLM) technology has provided a new approach to the manufacturing of evaporator tubes. Based on the principle of layer-by-layer melting and deposition of metal powder, SLM technology can overcome the limitations of traditional subtractive manufacturing processes on structural machinability, achieving integrated forming of complex structures. Existing research shows that additive manufacturing technology can achieve integrated forming of the combustion chamber's inner and outer walls with the evaporator tube, reducing weight, decreasing overall dimensions, and improving overall performance. However, current technologies lack an integrated additive manufacturing method for the evaporator tube's own structure (including the tubular body and flange seat), and the forming process challenges of the evaporator tube's slender, thin-walled structure, internal fuel flow channels, and overhanging areas during additive manufacturing remain unresolved. Therefore, there is an urgent need to develop an additive manufacturing method capable of achieving high-precision, high-quality integrated forming of evaporator tubes. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides an additive manufacturing method for an evaporator tube and the evaporator tube thereof. The technical solution of this invention is as follows: An additive manufacturing method for an evaporator tube, the evaporator tube comprising a tubular body (101) and a flange seat (102) disposed at one end of the tubular body (101), wherein a fuel evaporation channel is formed inside the tubular body (101), characterized by comprising the following steps: Step S1: Establish a three-dimensional digital model of the evaporator pipe. The three-dimensional digital model includes the tubular body (101) and the flange seat (102) integrally formed with the tubular body (101). The flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model are modified. Step S2: Based on the structure of the tubular body (101) and the end face mounting features of the flange seat (102), determine the placement posture of the evaporator tube on the forming substrate, so that the length direction of the tubular body (101) extends along the vertical direction or at an angle of 15°-45° with the vertical direction, and the flange seat (102) is located at the lower end or upper end of the tubular body (101) to reduce the overhang length of the overhang area of ​​the outer wall of the tubular body (101) and the inner wall of the fuel evaporation channel, so that the tilt angle of each overhang area is greater than or equal to 45°; Step S3: According to the placement posture determined in step S2, add a detachable support structure to the overhanging bottom surface of the flange seat (102), the overhanging area of ​​the outer wall of the tubular body (101), and the overhanging surface of the inner wall of the fuel evaporation channel. The support structure is at least one of a conical support, a block support, or a grid support, and the connection interface between the support structure and the evaporation tube entity is set to be serrated or dotted. Step S4: Set the powder layer thickness to 0.02mm~0.05mm, set the laser scanning strategy to strip scanning or checkerboard scanning, slice and layer the three-dimensional digital model, plan the laser scanning path according to the geometric contour of each layer section, set the process parameter combination of laser power, scanning speed and scanning spacing, and generate a printing program that can be recognized by the selective laser melting equipment. Step S5: Using a selective laser melting device under an inert gas protective atmosphere, high-temperature alloy GH3625 powder is used as raw material. According to the printing program generated in step S4, the GH3625 powder is melted layer by layer by a high-energy laser beam, so that the tubular body (101), the flange seat (102) and the support structure are integrally formed to obtain an evaporator tube blank with the support structure; wherein, the outer curved surface of the tubular body (101), the fuel evaporation channel and the mounting structure of the flange seat (102) are manufactured simultaneously in the integral forming process; Step S6: Stress-relief annealing treatment, followed by removal of the support structure from the evaporator tube blank; Step S7: Perform finishing on the evaporator tube, including at least using a CNC machining center to cut the assembly surface and positioning hole of the flange seat (102) so that the dimensional accuracy, geometric tolerance and surface roughness of the assembly surface and the positioning hole meet the design requirements.

[0006] In step S2, the angle between the length direction and the vertical direction of the tubular body (101) is 30°.

[0007] In step S4, the laser power is 200W to 400W, the scanning speed is 800mm / s to 1200mm / s, and the scanning interval is 0.08mm to 0.12mm.

[0008] The stress-relief annealing process in step S6 is carried out at a temperature of 1100℃ for 1.5h to 2h.

[0009] The finishing process in step S7 further includes abrasive flow polishing of the outer surface of the tubular body (101) and the inner wall of the fuel evaporation channel to make its surface roughness no greater than Ra3.2.

[0010] The tubular body (101) has at least one concave curved surface section along its length direction. The concave curved surface section is recessed towards the radial inner side of the tubular body (101) to form a reflux zone in the fuel evaporation channel. The fuel evaporation channel is also provided with a throttling sleeve, which is fixedly connected to the inner wall of the tubular body (101).

[0011] An evaporator tube, manufactured using the additive manufacturing method described above, comprises: A tubular body (101) has a fuel evaporation channel formed inside it. At least one concave curved section is provided along the length of the tubular body (101). The concave curved section is recessed radially inward to the tubular body (101) to form a reflux zone in the fuel evaporation channel. A throttling sleeve is also provided inside the fuel evaporation channel. The throttling sleeve is fixedly connected to the inner wall of the tubular body (101). A flange seat (102) is fixedly connected to one end of the tubular body (101). The flange seat (102) is provided with positioning holes and mounting surfaces for detachably installing the evaporator tube onto the support structure of the combustion chamber or the oil distribution ring. The tubular body (101) and the flange seat (102) are an integrally formed structure made of GH3625 powder layer by layer by selective laser melting. The density of the integrally formed structure is not less than 99.99%. The inlet of the fuel evaporation channel is connected to the fuel supply channel through the flange seat (102), and the outlet of the fuel evaporation channel leads to the combustion zone.

[0012] The dimensional tolerances of the positioning holes and assembly surfaces of the flange seat (102) are controlled within ±0.05mm, and the surface roughness of the outer surface of the tubular body (101) and the inner wall of the fuel evaporation channel is no greater than Ra3.2.

[0013] The evaporator tubes are multiple in number and are evenly arranged around the head of the flame tube of the combustion chamber. Each evaporator tube is connected to the oil distribution ring through its respective flange seat (102), and the tubular body (101) of each evaporator tube extends into the combustion chamber.

[0014] The advantages of this invention are: 1. This invention uses selective laser melting additive manufacturing technology to integrate the tubular body and flange seat into one piece, fundamentally replacing the traditional manufacturing mode. It eliminates the problems of material property loss, deformation and stress residue caused by welding heat input, so that product quality no longer depends on the level of manual welding, and greatly improves the yield rate and batch consistency.

[0015] 2. The complex curved surface of the tubular body, the fuel evaporation channel, the concave curved section and the throttling sleeve are manufactured simultaneously, eliminating the need for separate processing and subsequent welding assembly, thus simplifying the manufacturing process; at the same time, the flow channel can achieve a smooth transition, improving flow uniformity and enhancing combustion quality.

[0016] 3. By tilting the evaporation tubes on the forming substrate (the length of the tubular body forms an angle of 15° to 45° with the vertical direction), the tilt angle of the hanging area is ≥45° to achieve self-supporting forming, reducing the need for additional support structures; combined with the process parameters of 0.02mm to 0.05mm powder layer thickness, 200W to 400W laser power, and 800mm / s to 1200mm / s scanning speed, no collapse or deformation occurs during the forming process.

[0017] 4. First, stress-relief annealing at 1100℃ is used to eliminate residual stress generated by additive manufacturing. Then, the assembly surface and positioning holes of the flange seat are precision machined by CNC machining center to control the tolerance within ±0.05mm. Combined with abrasive flow polishing, the surface roughness is no greater than Ra3.2, fully ensuring assembly accuracy and smooth flow.

[0018] 5. The multiple evaporator tubes made using this invention are evenly arranged around the head of the combustion chamber flame tube. Each evaporator tube is detachably connected to the oil distribution ring via a flange seat, which not only ensures the coaxiality of the installation and improves the uniformity of the outlet temperature field, but also facilitates the independent maintenance and replacement of a single evaporator tube. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the main structure of the present invention.

[0020] Figure 2 yes Figure 1 AA sectional view. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer as a result. However, these embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0022] See Figure 1 and Figure 2 This invention relates to an additive manufacturing method for an evaporator tube, the evaporator tube comprising a tubular body 101 and a flange seat 102 disposed at one end of the tubular body 101, wherein a fuel evaporation channel is formed inside the tubular body 101, the method comprising the following steps: Step S1: Establish a three-dimensional digital model of the evaporator tube. The three-dimensional digital model includes the tubular body 101 and the flange seat 102 integrally formed with the tubular body 101. The flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model are modified. By modifying the flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model, the printability of the part is optimized from the source, avoiding the collapse of the overhang area due to lack of support during the forming process, while ensuring the structural stability and dimensional accuracy of the thin-walled area during the printing process.

[0023] Step S2: Based on the structure of the tubular body 101 and the end face mounting characteristics of the flange seat 102, determine the placement posture of the evaporator tube on the forming substrate, so that the length direction of the tubular body 101 extends along the vertical direction or at an angle of 15°-45° with the vertical direction, and the flange seat 102 is located at the lower or upper end of the tubular body 101, so as to reduce the overhang length of the overhanging area of ​​the outer wall of the tubular body 101 and the inner wall of the fuel evaporation channel, and make the inclination angle of each overhanging area greater than or equal to 45°; determine the placement posture of the evaporator tube on the forming substrate, so that the length direction of the tubular body is at an angle of 15°-45° with the vertical direction, and the inclination angle of each overhanging area is ≥45°, thus realizing the self-supporting forming of the inner wall of the fuel evaporation channel under the condition of no physical support, significantly reducing the amount of support structure added, reducing material consumption and post-processing difficulty.

[0024] Step S3: Based on the placement posture determined in step S2, add detachable support structures to the suspended bottom surface of the flange seat 102, the suspended area of ​​the outer wall of the tubular body 101, and the suspended surface of the inner wall of the fuel evaporation channel. The support structure is at least one of a conical support, a block support, or a grid support, and the connection interface between the support structure and the evaporation tube entity is set to be serrated or dot-matrix. By adding conical supports, block supports, or grid supports to the suspended bottom surface of the flange seat, the suspended area of ​​the outer wall of the tube body, and the suspended surface of the inner wall of the fuel evaporation channel, and setting the connection interface to be serrated or dot-matrix, the stability of the suspended structure during the forming process is ensured, deformation and collapse are prevented, and the mechanical removal of the support structure is facilitated, reducing damage to the surface of the evaporation tube entity.

[0025] Step S4: Set the powder layer thickness to 0.02mm~0.05mm, set the laser scanning strategy to strip scanning or checkerboard scanning, slice and layer the three-dimensional digital model, plan the laser scanning path according to the geometric contour of each layer section, set the process parameter combination of laser power, scanning speed and scanning spacing, and generate a printing program that can be recognized by the selective laser melting equipment; by setting the powder layer thickness to 0.02mm~0.05mm and cooperating with strip scanning or checkerboard scanning strategy, combined with the optimized combination of laser power, scanning speed and scanning spacing, high-precision forming of thin-walled structures with a wall thickness of 0.8mm~1.2mm is achieved, effectively controlling the accumulation of thermal stress and avoiding warping deformation of thin-walled areas during the layer-by-layer deposition process.

[0026] Step S5: Using a selective laser melting device under an inert gas protective atmosphere, high-temperature alloy GH3625 powder is used as raw material. Following the printing program generated in step S4, a high-energy laser beam scans and melts the GH3625 powder layer by layer, integrating the tubular body 101, the flange seat 102, and the support structure to obtain an evaporator tube blank with the support structure. The outer curved surface of the tubular body 101, the fuel evaporation channel, and the mounting structure of the flange seat 102 are simultaneously manufactured during this integrated forming process. Using a selective laser melting device with GH3625 powder as raw material, the tubular body, flange seat, and support structure are integrated into one unit. The outer curved surface of the tubular body, the fuel evaporation channel, and the mounting structure of the flange seat are manufactured simultaneously, eliminating the need for separate processing and subsequent welding assembly. This fundamentally solves the problems of low yield, poor consistency, and performance degradation in the heat-affected zone caused by traditional welding processes.

[0027] Step S6: Stress-relief annealing treatment, followed by removal of the support structure on the evaporator tube blank; by removing the support structure and then performing stress-relief annealing treatment at 1100℃ for 1.5h to 2h, the thermal stress and residual stress generated during the layer-by-layer melting and rapid cooling process of additive manufacturing are effectively eliminated, preventing deformation and cracking of the evaporator tube during subsequent finishing and use, and ensuring the dimensional stability of the parts.

[0028] Step S7: Perform precision machining on the evaporator tube, including at least using a CNC machining center to cut the assembly surface and positioning hole of the flange seat 102, so that the dimensional accuracy, geometric tolerance and surface roughness of the assembly surface and the positioning hole meet the design requirements.

[0029] The assembly surface and positioning holes of the flange seat are precision machined by CNC machining center to control the dimensional tolerance within ±0.1mm. Combined with abrasive flow polishing, the surface roughness of the outer surface of the tubular body and the inner wall of the fuel evaporation channel is no greater than Ra3.2. This fully ensures the assembly accuracy of the flange seat with the combustion chamber support structure or fuel distribution ring and the smoothness of the flow channel, thus improving the overall performance of the evaporation tube.

[0030] In step S2, the angle between the length direction and the vertical direction of the tubular body 101 is 30°.

[0031] In step S4, the laser power is 200W to 400W, the scanning speed is 800mm / s to 1200mm / s, and the scanning interval is 0.08mm to 0.12mm.

[0032] The stress-relief annealing process in step S6 is carried out at a temperature of 1100℃ for 1.5h to 2h.

[0033] The finishing process in step S7 further includes abrasive flow polishing of the outer surface of the tubular body 101 and the inner wall of the fuel evaporation channel to achieve a surface roughness of no more than Ra3.2. Abrasive flow polishing of the outer surface of the tubular body 101 and the inner wall of the fuel evaporation channel to achieve a surface roughness of no more than Ra3.2 effectively reduces the flow resistance of the inner wall of the fuel evaporation channel, reduces the adhesion and residue of fuel and fuel-air mixture in the flow channel, makes fuel flow smoother and atomization evaporation more uniform, and at the same time, the smooth outer surface reduces the adhesion and corrosion of high-temperature combustion gases to the pipe wall, extending the service life of the evaporation pipe.

[0034] The tubular body 101 has at least one concave curved section along its length. This concave curved section is recessed radially inwards towards the tubular body 101 to form a reflux zone within the fuel evaporation channel. A throttling sleeve is also provided inside the fuel evaporation channel, and the throttling sleeve is fixedly connected to the inner wall of the tubular body 101. Simultaneously, the concave curved section along the length of the tubular body 101 forms a reflux zone within the fuel evaporation channel. Combined with the throttling sleeve to reduce the airflow velocity, the two work synergistically to extend the mixing time and path of fuel vapor and air, resulting in more uniform fuel-air mixing, thereby significantly improving combustion efficiency and achieving stable combustion.

[0035] The present invention also relates to an evaporation tube manufactured using the aforementioned additive manufacturing method, the evaporation tube comprising: A tubular body 101 has a fuel evaporation channel formed inside it. At least one concave curved section is provided along the length of the tubular body 101. The concave curved section is recessed radially inward to form a reflux zone in the fuel evaporation channel. A throttling sleeve is also provided inside the fuel evaporation channel. The throttling sleeve is fixedly connected to the inner wall of the tubular body 101. Flange seat 102 is fixedly connected to one end of the tubular body 101. The flange seat 102 is provided with positioning holes and mounting surfaces for detachably installing the evaporator tube onto the support structure of the combustion chamber or the oil distribution ring. The tubular body 101 and the flange seat 102 are integrally formed by selective laser melting and layer-by-layer deposition of GH3625 powder. The density of the integrally formed structure is not less than 99.99%. The inlet of the fuel evaporation channel is connected to the fuel supply channel through the flange seat 102, and the outlet of the fuel evaporation channel leads to the combustion zone.

[0036] The concave curved section forms a reflux zone within the fuel evaporation channel, which works in conjunction with the throttling sleeve to reduce airflow velocity, extend the mixing time and path of fuel vapor and air, and make the fuel-air mixture more uniform, thereby achieving efficient and stable combustion.

[0037] The main body 101 and the flange seat 102 are integrally formed by selective laser melting and layer-by-layer deposition of GH3625 powder, with a density of not less than 99%. No welding connection is required, which fundamentally eliminates the weld defects, heat-affected zone performance degradation and residual stress problems of traditional welded structures. At the same time, the positioning holes and assembly surfaces on the flange seat 102 enable precise and detachable installation with the combustion chamber support structure or oil distribution ring, which not only ensures the coaxiality of multiple evaporator tubes when arranged circumferentially, but also facilitates the independent maintenance and replacement of individual evaporator tubes.

[0038] The dimensional tolerances of the positioning holes and assembly surfaces of the flange seat 102 are controlled within ±0.1mm, and the surface roughness of the outer surface of the tubular body 101 and the inner wall of the fuel evaporation channel is no greater than Ra3.2.

[0039] The evaporator tubes are multiple in number and are evenly arranged around the head of the flame tube in the combustion chamber. Each evaporator tube is connected to the oil distribution ring through its respective flange seat 102, and the tubular body 101 of each evaporator tube extends into the combustion chamber.

[0040] Example 1: This example provides an additive manufacturing method for an evaporator tube. The evaporator tube includes a tubular body 101 and a flange seat 102 disposed at one end of the tubular body 101. A fuel evaporation channel is formed inside the tubular body 101. The wall thickness of the tubular body 101 is 1.0 mm. The tubular body 101 has a concave curved surface section along its length direction. The concave curved surface section is recessed radially inward of the tubular body 101. A throttling sleeve is also provided inside the fuel evaporation channel. The throttling sleeve is fixedly connected to the inner wall of the tubular body 101.

[0041] Includes the following steps: Step S1: Establish a three-dimensional digital model of the evaporator pipe. The three-dimensional digital model includes the tubular body 101 and the flange seat 102 integrally formed with the tubular body 101. The flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model are modified. Step S2: Based on the structure of the tubular body 101 and the end face mounting features of the flange seat 102, determine the placement posture of the evaporation tube on the forming substrate, so that the length direction of the tubular body 101 extends at a 30° angle with the vertical direction, and the flange seat 102 is located at the lower end of the tubular body 101, and the inclination angle of each hanging area is greater than or equal to 45°. Step S3: According to the placement posture determined in step S2, add a detachable support structure to the suspended bottom surface of the flange seat 102, the suspended area of ​​the outer wall of the tubular body 101, and the suspended surface of the inner wall of the fuel evaporation channel. The support structure is a conical support, and the connection interface between the support structure and the evaporation tube entity is set to be sawtooth-shaped. Step S4: Set the powder layer thickness to 0.03mm, set the laser scanning strategy to strip scanning, slice the three-dimensional digital model into layers, plan the laser scanning path according to the geometric contour of each layer section, set the laser power to 280W, the scanning speed to 1000mm / s, and the scanning interval to 0.10mm, and generate a printing program that can be recognized by the selected area laser melting equipment. Step S5: Using a selective laser melting device, under an inert gas protective atmosphere, high-temperature alloy GH3625 powder is used as raw material. According to the printing program generated in step S4, the GH3625 powder is melted layer by layer by a high-energy laser beam, so that the tubular body 101, the flange seat 102 and the support structure are integrally formed to obtain an evaporator tube blank with the support structure. Step S6: Remove the support structure on the evaporator tube blank, and perform stress-relieving annealing on the evaporator tube after removing the support structure. The annealing temperature is 1100℃ and the holding time is 1.8h. Step S7: Perform precision machining on the evaporator tube. Use a CNC machining center to cut the assembly surface and positioning hole of the flange seat 102 to control the dimensional tolerance of the assembly surface and the positioning hole within ±0.1mm. Perform abrasive flow polishing on the outer surface of the tubular body 101 and the inner wall of the fuel evaporation channel to make its surface roughness no greater than Ra3.2.

[0042] The evaporator tube manufactured in this embodiment has a tubular body 101 and a flange seat 102 that are integrally formed by selective laser melting and layer-by-layer deposition of GH3625 powder, with a density of not less than 99%. The inlet of the fuel evaporation channel is connected to the fuel supply channel through the flange seat 102, and the outlet of the fuel evaporation channel leads to the combustion zone. The flange seat 102 is provided with positioning holes and mounting surfaces for detachably installing the evaporator tube onto the support structure of the combustion chamber or the fuel distribution ring.

[0043] Example 2: This example provides an additive manufacturing method for an evaporator tube. The evaporator tube includes a tubular body 101 and a flange seat 102 disposed at one end of the tubular body 101. A fuel evaporation channel is formed inside the tubular body 101. The wall thickness of the tubular body 101 is 0.8 mm. The tubular body 101 has two concave curved surface sections along its length direction. Each concave curved surface section is recessed radially inward towards the tubular body 101. A throttling sleeve is also provided inside the fuel evaporation channel. The throttling sleeve is fixedly connected to the inner wall of the tubular body 101.

[0044] Includes the following steps: Step S1: Establish a three-dimensional digital model of the evaporator pipe. The three-dimensional digital model includes the tubular body 101 and the flange seat 102 integrally formed with the tubular body 101. The flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model are modified. Step S2: Based on the structure of the tubular body 101 and the end face mounting features of the flange seat 102, determine the placement posture of the evaporation tube on the forming substrate, so that the length direction of the tubular body 101 extends in the vertical direction, and the flange seat 102 is located at the upper end of the tubular body 101, and the inclination angle of each hanging area is greater than or equal to 45°. Step S3: According to the placement posture determined in step S2, add a detachable support structure to the suspended bottom surface of the flange seat 102, the suspended area of ​​the outer wall of the tubular body 101, and the suspended surface of the inner wall of the fuel evaporation channel. The support structure is a block support, and the connection interface between the support structure and the evaporation tube entity is set to be a dot matrix. Step S4: Set the powder layer thickness to 0.02mm, set the laser scanning strategy to checkerboard scanning, slice and layer the three-dimensional digital model, and plan the laser scanning path according to the geometric contour of each layer section. Set the laser power to 200W, the scanning speed to 800mm / s, and the scanning interval to 0.08mm to generate a printing program that can be recognized by the selected area laser melting equipment. Step S5: Using a selective laser melting device, under an inert gas protective atmosphere, high-temperature alloy GH3625 powder is used as raw material. According to the printing program generated in step S4, the GH3625 powder is melted layer by layer by a high-energy laser beam, so that the tubular body 101, the flange seat 102 and the support structure are integrally formed to obtain an evaporator tube blank with the support structure. Step S6: Remove the support structure on the evaporator tube blank, and perform stress-relieving annealing on the evaporator tube after removing the support structure. The annealing temperature is 1100℃ and the holding time is 2h. Step S7: Perform precision machining on the evaporator tube. Use a CNC machining center to cut the assembly surface and positioning hole of the flange seat 102 to control the dimensional tolerance of the assembly surface and the positioning hole within ±0.05mm. Perform abrasive flow polishing on the outer surface of the tubular body 101 and the inner wall of the fuel evaporation channel to make its surface roughness no greater than Ra3.2.

[0045] The evaporator tube manufactured in this embodiment has a tubular body 101 and a flange seat 102 that are integrally formed by selective laser melting and layer-by-layer deposition of GH3625 powder, with a density of not less than 99%. The inlet of the fuel evaporation channel is connected to the fuel supply channel through the flange seat 102, and the outlet of the fuel evaporation channel leads to the combustion zone. The flange seat 102 is provided with positioning holes and mounting surfaces for detachably installing the evaporator tube onto the support structure of the combustion chamber or the fuel distribution ring.

[0046] Example 3: This example provides an additive manufacturing method for an evaporator tube. The evaporator tube includes a tubular body 101 and a flange seat 102 disposed at one end of the tubular body 101. A fuel evaporation channel is formed inside the tubular body 101. The wall thickness of the tubular body 101 is 1.2 mm. The tubular body 101 has a concave curved surface section along its length direction. The concave curved surface section is recessed radially inward of the tubular body 101. A throttling sleeve is also provided inside the fuel evaporation channel. The throttling sleeve is fixedly connected to the inner wall of the tubular body 101.

[0047] Includes the following steps: Step S1: Establish a three-dimensional digital model of the evaporator pipe. The three-dimensional digital model includes the tubular body 101 and the flange seat 102 integrally formed with the tubular body 101. The flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model are modified. Step S2: Based on the structure of the tubular body 101 and the end face mounting features of the flange seat 102, determine the placement posture of the evaporation tube on the forming substrate, so that the length direction of the tubular body 101 extends at a 45° angle with the vertical direction, and the flange seat 102 is located at the lower end of the tubular body 101, so that the inclination angle of each hanging area is greater than or equal to 45°. Step S3: According to the placement posture determined in step S2, add a detachable support structure to the suspended bottom surface of the flange seat 102, the suspended area of ​​the outer wall of the tubular body 101, and the suspended surface of the inner wall of the fuel evaporation channel. The support structure is a grid support, and the connection interface between the support structure and the evaporation tube entity is set to be sawtooth-shaped. Step S4: Set the powder layer thickness to 0.05mm, set the laser scanning strategy to strip scanning, slice the three-dimensional digital model into layers, and plan the laser scanning path according to the geometric contour of each layer section. Set the laser power to 400W, the scanning speed to 1200mm / s, and the scanning interval to 0.12mm to generate a printing program that can be recognized by the selected area laser melting equipment. Step S5: Using a selective laser melting device, under an inert gas protective atmosphere, high-temperature alloy GH3625 powder is used as raw material. According to the printing program generated in step S4, the GH3625 powder is melted layer by layer by a high-energy laser beam, so that the tubular body 101, the flange seat 102 and the support structure are integrally formed to obtain an evaporator tube blank with the support structure. Step S6: Remove the support structure on the evaporator tube blank, and perform stress-relieving annealing on the evaporator tube after removing the support structure. The annealing temperature is 1100℃ and the holding time is 1.5h. Step S7: Perform precision machining on the evaporator tube. Use a CNC machining center to cut the assembly surface and positioning hole of the flange seat 102 to control the dimensional tolerance of the assembly surface and the positioning hole within ±0.1mm. Perform abrasive flow polishing on the outer surface of the tubular body 101 and the inner wall of the fuel evaporation channel to make its surface roughness no greater than Ra3.2.

[0048] The evaporator tube manufactured in this embodiment has a tubular body 101 and a flange seat 102 that are integrally formed by selective laser melting and layer-by-layer deposition of GH3625 powder, with a density of not less than 99.99%. The inlet of the fuel evaporation channel is connected to the fuel supply channel through the flange seat 102, and the outlet of the fuel evaporation channel leads to the combustion zone. The flange seat 102 is provided with positioning holes and mounting surfaces for detachably installing the evaporator tube onto the support structure of the combustion chamber or the fuel distribution ring.

[0049] To verify the technical effect of the present invention, the following experimental group and control group were set up for comparative experiments.

[0050] I. Experimental Grouping Experimental group: Evaporation tubes were prepared using the method described in Example 1 of this invention, with a total of 100 tubes prepared. The GH3625 powder particle size ranged from 15μm to 53μm. The SLM equipment was a German EOS M290 model. The process parameters were: laser power 280W, scanning speed 1000mm / s, scanning spacing 0.10mm, powder layer thickness 0.03mm, and a strip scanning strategy. Post-treatment: Stress-relief annealing at 500℃ for 1.8h, followed by abrasive flow polishing until Ra≤3.2.

[0051] Control Group 1 (Traditional Welding Group): Evaporator tubes were prepared using traditional processes, i.e., the tubular body and flange were machined separately and then assembled by argon arc welding. The tubular body was made of GH3625 high-temperature alloy tubing (1.0mm wall thickness), and the flange was a GH3625 forging. Welding parameters: TIG welding, current 120A, voltage 11V, argon flow rate 18L / min. Post-weld stress relief treatment was performed at 900℃. A total of 100 tubes were prepared.

[0052] Control Group 2 (Additive Manufacturing Without Optimization): Evaporation tubes were fabricated using SLM additive manufacturing technology, with the tubular body and flange seat integrally formed, but the optimized process parameters and placement strategy of this invention were not adopted. Specifically: the tubular body was placed horizontally on the forming substrate (the length direction was at a 90° angle to the vertical direction), and the tilt angle of the overhanging area was not controlled; the laser power was 180W, the scanning speed was 600mm / s, the scanning spacing was 0.09mm, and the powder layer thickness was 0.03mm; no abrasive flow polishing treatment was performed. A total of 100 tubes were fabricated.

[0053] II. Evaluation Indicators and Methods (1) Yield: The percentage of products that meet the design dimensional tolerance requirements (critical dimension deviation ≤ ±0.1mm), have no macroscopic cracks, and have no collapse deformation after forming each component.

[0054] (2) Density: The density of each component was tested using the Archimedes displacement method.

[0055] (3) Surface roughness: The surface roughness Ra value of the inner wall of the fuel evaporation channel was tested using a roughness tester.

[0056] (4) Tensile strength: The tensile strength of each component was tested at room temperature in accordance with GB / T 228.1 standard.

[0057] (5) Combustion efficiency: Each group of evaporator tubes was assembled in the combustion chamber of the same type of 55 kg turbojet engine (8 tubes were assembled in each group and evenly arranged around the head of the flame tube). The combustion efficiency was tested under the same operating conditions (inlet air temperature 450℃, fuel supply pressure 0.3MPa, fuel-air ratio 0.025).

[0058] III. Experimental Results Yield 96% 62% 71% Density 99.99% Approximately 98% in the weld zone and approximately 99.5% in the base metal zone. 98.6% Inner wall surface roughness Ra 2.8μm 6.5μm (welded inner wall) 11.2μm tensile strength 965 MPa The weld zone pressure is approximately 650 MPa. 912 MPa Combustion efficiency 94.2% 86.5% 89.8% IV. Results Analysis 1. Yield: The yield rate of the experimental group reached 96%, higher than that of control group 1 (62%) and control group 2 (71%). Control group 1, due to the large heat input of argon arc welding, was prone to thermal deformation and weld defects in its thin-walled tubes (1.0mm wall thickness) during welding, and the coaxiality deviation was large when welding multiple evaporation tubes one by one. Control group 2, because it did not adopt the optimized placement posture of this invention (horizontal placement resulted in a tilt angle of the overhanging area far less than 45°), experienced collapse and deformation of the thin-walled structure during SLM forming due to a lack of effective self-support. The experimental group effectively ensured the forming stability of the thin-walled structure by placing the tubular main body at an angle of 15° to 45° with the vertical direction, achieving a tilt angle of ≥45° in the overhanging area, and combining this with precise control of the powder layer thickness of 0.02mm to 0.05mm.

[0059] 2. Density: The experimental group achieved a density of 99.99%, comparable to the base material region of control group 1. However, the weld region of control group 1 had a density of only about 98%. GH3625 alloy is prone to cracking during welding, and the heat-affected zone of the weld leads to a loss of material properties. The density of control group 2 was 98.6%, which did not reach the density level of this invention.

[0060] 3. Surface roughness: After abrasive flow polishing, the inner wall roughness Ra of the experimental group was 2.8 μm, significantly lower than that of control group 1 (6.5 μm) and control group 2 (11.2 μm). Control group 2, lacking abrasive flow polishing, exhibited unmelted powder particles and a step effect on the surface of the SLM-formed part, resulting in higher roughness. The smooth inner wall effectively reduced flow resistance within the fuel evaporation channel, minimizing fuel and fuel-air mixture adhesion and residue, leading to smoother fuel flow and more uniform atomization and evaporation.

[0061] 4. Mechanical properties: The tensile strength of the experimental group reached 965 MPa, comparable to that of the base metal region of control group 1, but significantly higher than the approximately 650 MPa of the weld region of control group 1. The mechanical properties of control group 1 were significantly reduced due to grain coarsening and precipitate aggregation in the weld region of the GH3625 alloy caused by welding heat input. The tensile strength of control group 2 was 912 MPa, higher than that of the weld region of control group 1, but still lower than that of the experimental group.

[0062] 5. Combustion efficiency: The combustion efficiency of the experimental group reached 94.2%, significantly higher than that of control group 1 (86.5%) and control group 2 (89.8%). This is attributed to the high density of the evaporator tube in the experimental group, which ensured excellent heat conduction performance, allowing the fuel to absorb heat and evaporate rapidly; the reflux zone formed by the concave curved section, in conjunction with the throttling sleeve, extended the mixing time of fuel vapor and air; and the smooth inner wall surface reduced flow resistance, making the fuel-air mixture more uniform.

[0063] The experimental results above demonstrate that, compared to traditional argon arc welding manufacturing processes, this invention achieves integrated forming of the evaporator tube tubular body and flange seat through SLM additive manufacturing technology, fundamentally solving problems such as low yield, degradation of mechanical properties in the weld zone, poor surface quality, and low combustion efficiency caused by welding processes. Compared to unoptimized SLM additive manufacturing processes, this invention significantly improves yield, density, surface quality, and mechanical properties by optimizing the placement posture (the length direction of the tubular body forms an angle of 15°-45° with the vertical direction, and the tilt angle of the overhanging area is ≥45° to achieve self-supporting forming), finely controlling process parameters (powder layer thickness 0.02mm~0.05mm, laser power 200W~400W, scanning speed 800mm / s~1200mm / s), and adding abrasive flow polishing post-treatment, thereby greatly improving the combustion efficiency of the turbojet engine combustion chamber.

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An additive manufacturing method for an evaporator tube, the evaporator tube comprising a tubular body (101) and a flange seat (102) disposed at one end of the tubular body (101), wherein a fuel evaporation channel is formed inside the tubular body (101), characterized in that, Includes the following steps: Step S1: Establish a three-dimensional digital model of the evaporator pipe. The three-dimensional digital model includes the tubular body (101) and the flange seat (102) integrally formed with the tubular body (101). The flow path and overhang area of ​​the fuel evaporation channel in the three-dimensional digital model are modified. Step S2: Based on the structure of the tubular body (101) and the end face mounting features of the flange seat (102), determine the placement posture of the evaporator tube on the forming substrate, so that the length direction of the tubular body (101) extends along the vertical direction or at an angle of 15°-45° with the vertical direction, and the flange seat (102) is located at the lower end or upper end of the tubular body (101) to reduce the overhang length of the overhang area of ​​the outer wall of the tubular body (101) and the inner wall of the fuel evaporation channel, so that the tilt angle of each overhang area is greater than or equal to 45°; Step S3: According to the placement posture determined in step S2, add a detachable support structure to the overhanging bottom surface of the flange seat (102), the overhanging area of ​​the outer wall of the tubular body (101), and the overhanging surface of the inner wall of the fuel evaporation channel. The support structure is at least one of a conical support, a block support, or a grid support, and the connection interface between the support structure and the evaporation tube entity is set to be serrated or dotted. Step S4: Set the powder layer thickness to 0.02mm~0.05mm, set the laser scanning strategy to strip scanning or checkerboard scanning, slice and layer the three-dimensional digital model, plan the laser scanning path according to the geometric contour of each layer section, set the process parameter combination of laser power, scanning speed and scanning spacing, and generate a printing program that can be recognized by the selective laser melting equipment. Step S5: Using a selective laser melting device under an inert gas protective atmosphere, high-temperature alloy GH3625 powder is used as raw material. According to the printing program generated in step S4, the GH3625 powder is melted layer by layer by a high-energy laser beam, so that the tubular body (101), the flange seat (102) and the support structure are integrally formed to obtain an evaporator tube blank with the support structure; wherein, the outer curved surface of the tubular body (101), the fuel evaporation channel and the mounting structure of the flange seat (102) are manufactured simultaneously in the integral forming process; Step S6: Stress-relief annealing treatment, followed by removal of the support structure from the evaporator tube blank; Step S7: Perform finishing on the evaporator tube, including at least using a CNC machining center to cut the assembly surface and positioning hole of the flange seat (102) so that the dimensional accuracy, geometric tolerance and surface roughness of the assembly surface and the positioning hole meet the design requirements.

2. The additive manufacturing method for the evaporator tube according to claim 1, characterized in that, In step S2, the angle between the length direction and the vertical direction of the tubular body (101) is 30°.

3. The additive manufacturing method for the evaporator tube according to claim 1, characterized in that, In step S4, the laser power is 200W to 400W, the scanning speed is 800mm / s to 1200mm / s, and the scanning interval is 0.08mm to 0.12mm.

4. The additive manufacturing method for the evaporator tube according to claim 1, characterized in that, The stress-relief annealing process in step S6 is carried out at a temperature of 1100℃ for 1.5h to 2h.

5. The additive manufacturing method for the evaporator tube according to claim 1, characterized in that, The finishing process in step S7 further includes abrasive flow polishing of the outer surface of the tubular body (101) and the inner wall of the fuel evaporation channel to make its surface roughness no greater than Ra3.

2.

6. The additive manufacturing method for the evaporator tube according to any one of claims 1 to 5, characterized in that, The tubular body (101) has at least one concave curved surface section along its length direction. The concave curved surface section is recessed towards the radial inner side of the tubular body (101) to form a reflux zone in the fuel evaporation channel. The fuel evaporation channel is also provided with a throttling sleeve, which is fixedly connected to the inner wall of the tubular body (101).

7. An evaporation tube, characterized in that, The evaporation tube is manufactured using the additive manufacturing method according to any one of claims 1 to 6, and comprises: A tubular body (101) has a fuel evaporation channel formed inside it. At least one concave curved section is provided along the length of the tubular body (101). The concave curved section is recessed radially inward to the tubular body (101) to form a reflux zone in the fuel evaporation channel. A throttling sleeve is also provided inside the fuel evaporation channel. The throttling sleeve is fixedly connected to the inner wall of the tubular body (101). A flange seat (102) is fixedly connected to one end of the tubular body (101). The flange seat (102) is provided with positioning holes and mounting surfaces for detachably installing the evaporator tube onto the support structure of the combustion chamber or the oil distribution ring. The tubular body (101) and the flange seat (102) are an integrally formed structure made of GH3625 powder layer by layer by selective laser melting. The density of the integrally formed structure is not less than 99.99%. The inlet of the fuel evaporation channel is connected to the fuel supply channel through the flange seat (102), and the outlet of the fuel evaporation channel leads to the combustion zone.

8. The evaporation tube according to claim 7, characterized in that, The dimensional tolerances of the positioning holes and assembly surfaces of the flange seat (102) are controlled within ±0.05mm, and the surface roughness of the outer surface of the tubular body (101) and the inner wall of the fuel evaporation channel is no greater than Ra3.

2.

9. The evaporator tube according to claim 7 or 8, characterized in that, The evaporator tubes are multiple in number and are evenly arranged around the head of the flame tube of the combustion chamber. Each evaporator tube is connected to the oil distribution ring through its respective flange seat (102), and the tubular body (101) of each evaporator tube extends into the combustion chamber.

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