A TPMS structure micro-channel heat exchanger and a manufacturing method

Abstract

The application discloses a TPMS structure micro-channel heat exchanger and a manufacturing method, and belongs to the field of structural design and manufacturing of rocket engine heat exchangers. The heat exchanger core is a plurality of spiral flow channel structures adopting TPMS. The inlet side of a liquid oxygen inlet and outlet collector is connected with the inlet of the core spiral flow channel through a liquid oxygen partition plate, and the outlet side of the liquid oxygen inlet and outlet collector is connected with the outlet of the core spiral flow channel. A fuel gas inlet pipeline is connected with the inlet of the core spiral flow channel through a fuel gas partition plate, and a fuel gas outlet pipeline is connected with the outlet of the core spiral flow channel. The liquid oxygen partition plate and the fuel gas partition plate are each provided with a plurality of through holes, the through holes correspond to the spiral flow channels in the core one by one, and each through hole is connected with the inlet of one spiral flow channel in the core. The application adopts the TPMS spiral flow channel structure to increase the internal heat exchange area of the heat exchanger and improve the heating efficiency of the heat exchanger on fuel in the working process of the engine.

Description

Technical Field

[0001] This invention relates to a TPMS structure microchannel heat exchanger and its manufacturing method, belonging to the field of structural design and manufacturing of rocket engine heat exchangers. Background Technology

[0002] Reusable space transportation systems refer to space transportation systems capable of multiple trips between the Earth and space orbit, and reusable multiple times. They are characterized by "free access to space, on-demand return to Earth, and multiple reuses," making them ideal transportation tools for reducing space transportation costs and improving safety and reliability. Currently, countries worldwide are experiencing a surge in the development of combined-propellant reusable engines fueled by cryogenic liquid hydrogen and high-thrust reusable liquid rocket engines. For high-thrust reusable liquid rocket engines, highly reliable, lightweight, and easily maintainable high-compact heat exchangers are crucial for improving overall engine reliability. Liquid rocket engines typically use heat exchangers to heat the cryogenic medium to pressurize the rocket's propellant tanks. These typically employ a helical tube structure. However, helical tube heat exchangers have relatively low heat exchange capacity. As engine thrust increases, the demand for heat exchange also rises, making it increasingly difficult for traditional helical tube heat exchangers to meet the heat exchange requirements within a limited space. To meet the system's high heat exchange power requirements, the overall length of the helical tubes and the multi-layered helical tube layout significantly increase the structural complexity and overall weight. Meanwhile, the spiral tube heat exchanger has multiple welds, some of which must withstand the erosion of the combustion gases and the severe vibration loads of the engine, making them susceptible to failure and hindering its reusability. Considering the future development needs of reusable liquid oxygen-methane engines with greater thrust, the spiral tube heat exchanger cannot meet the requirements. Therefore, heat exchangers with high heat exchange capacity and small size and weight are the development direction for liquid rocket engine heat exchangers. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a TPMS structure microchannel heat exchanger and its manufacturing method. The TPMS spiral flow channel structure is adopted to increase the heat exchange area inside the heat exchanger and improve the heating efficiency of the heat exchanger for fuel during engine operation.

[0004] The technical solution of this invention is:

[0005] A TPMS structure microchannel heat exchanger includes a core, a shell, a gas inlet pipe, a gas outlet pipe, a liquid oxygen inlet pipe, a liquid oxygen outlet pipe, a liquid oxygen inlet and outlet collector, a liquid oxygen baffle, and a gas baffle.

[0006] The core is installed inside the outer shell, and the core has a multi-spiral flow channel structure using TPMS;

[0007] One end of the inlet side of the liquid oxygen inlet / outlet collector is connected to the liquid oxygen inlet pipeline, and the other end is connected to the inlet of multiple spiral flow channels of the core through a liquid oxygen baffle; one end of the outlet side of the liquid oxygen inlet / outlet collector is connected to the outlet of each spiral flow channel of the core, and the other end is connected to the liquid oxygen outlet pipeline.

[0008] The gas inlet pipe is connected to the inlet of multiple spiral channels of the core through a gas baffle, and the gas outlet pipe is connected to the outlet of each spiral channel of the core.

[0009] Both the liquid oxygen baffle and the gas baffle are provided with multiple through holes, which correspond one-to-one with the spiral flow channels in the core. Each through hole is connected to the inlet of a spiral flow channel in the core.

[0010] Furthermore, the liquid oxygen inlet and outlet collector is structured as a fan-shaped cross-section scanning array, which allows liquid oxygen to diffuse uniformly into the core.

[0011] Furthermore, the thickness of the thin-walled structure of the core unit is 0.3mm to 0.5mm, and the unit size is 5mm to 10mm; the porosity of each core unit is not less than 0.7, and the surface-to-body ratio is not less than 3000mm. 2 / mm 3 .

[0012] Furthermore, the gas and liquid oxygen flow through different spiral channels and do not share the same spiral channels.

[0013] Furthermore, the liquid oxygen inlet pipeline, the liquid oxygen outlet pipeline, and the liquid oxygen inlet / outlet manifold are connected by flanges.

[0014] A method for manufacturing a TPMS structured microchannel heat exchanger includes:

[0015] The core structure is designed based on heat exchange requirements and printability requirements; the scanning parameters for printing are designed based on the core structure.

[0016] Add process chamfers and fillets at the contact points between the 3D model of the heat exchanger and the substrate to form the model to be processed;

[0017] Install the forming substrate in the SLM forming equipment and fill the forming cavity with inert gas; import the model to be processed into the SLM forming equipment, start forming according to the scanning parameters for printing, remove the formed heat exchanger part from the SLM forming equipment, and remove the substrate.

[0018] Furthermore, the scanning parameters for printing are: scanning power of 240W to 260W, scanning speed of 600mm / s to 900mm / s, and scanning spacing of 0.08mm to 0.1mm.

[0019] Furthermore, 316L powder with a particle size of 15μm to 38μm is used, and the powder is formed by layer-by-layer spreading and layer-by-layer melting and stacking.

[0020] Furthermore, the 3D model of the heat exchanger is processed.

[0021] Increase process allowances at the upper and lower end faces of the heat exchanger, etc.

[0022] The original output heat exchanger model is simplified by triangular facets.

[0023] For the simplified heat exchanger model, a self-forming structural solid support is added to the suspended position of the core and the liquid oxygen inlet and outlet collector, and a mesh and column support is added to the bottom of the core.

[0024] Further, the formed heat exchanger parts are removed from the SLM forming equipment, and residual powder in the flow channel is removed by ultrasonic vibration and compressed gas blowing. Stress-relief vacuum heat treatment is performed at a temperature of 810℃~850℃ and a holding time of 2 hours~4 hours. After the heat treatment, the substrate is removed by wire cutting.

[0025] The advantages of this invention compared to the prior art are:

[0026] (1) Compared with the original spiral tube heat exchanger, the present invention has a 3-fold increase in structural compactness, a 4-fold increase in heat exchange efficiency, and integrates 41 parts into 1 part. All 35 welds are eliminated, and the manufacturing cycle is shortened by more than 60%. It can improve the heating efficiency of the heat exchanger for fuel, thereby shortening the structural length of the engine, reducing the weight of the engine, and improving the efficiency of the engine.

[0027] (2) This invention uses a high-energy laser to melt loose powder layers, and forms three-dimensional parts with a certain density by layer-by-layer powder spreading and melting. Compared with traditional machining processes, selective laser melting (SLM) additive manufacturing technology can realize the manufacturing of complex thin-walled precision components with variable cross-sections and complex internal flow channels. It has the advantages of high forming accuracy, uniform channel wall thickness, strong product dimensional consistency, good internal quality, excellent mechanical properties, and easy integrated manufacturing.

[0028] (3) In the existing technology, the difficulties in the integrated additive manufacturing of TPMS heat exchangers are as follows: First, the printing process of TPMS thin-walled structures is not yet mature; second, the optimization design of the self-forming of the suspended surface of the closed inner cavity during integrated additive manufacturing; and third, the cleaning of powder in the complex cavity and the removal of supports after forming. In response to the above three difficulties, this invention explored the basic printing process parameters of the TPMS thin-walled structural feature components in the early stage. By designing a self-forming structure at the collector position to optimize the design of the integrated heat exchanger, the amount and difficulty of support removal were reduced. Attached Figure Description

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0030] Figure 1 This is a schematic diagram of a TPMS structure microchannel heat exchanger according to an embodiment of the present invention;

[0031] Figure 2 This is a structural diagram of a TPMS microchannel heat exchanger according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the flow of gas and liquid oxygen through the TPMS core in an embodiment of the present invention;

[0033] Figure 4 This is a schematic diagram of the spiral flow channel design of the TPMS core in an embodiment of the present invention. Detailed Implementation

[0034] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0035] This invention proposes a TPMS (Transmission-Transfer-Maintenance System) microchannel heat exchanger. The heat exchanger structure is designed based on the overall requirements of the engine structure and performance simulation results. Figure 1 , Figure 2As shown, the system includes a TPMS core 1, an outer shell 2, a gas inlet 3, a gas outlet 4, a liquid oxygen inlet 5, a liquid oxygen outlet 6, a liquid oxygen inlet / outlet collector 7, a liquid oxygen baffle 8, and a gas baffle 9. The liquid oxygen baffle 8 is located on the outside of the TPMS core 1, while the gas inlet 3 and gas outlet 4 are located at the top and bottom. The liquid oxygen inlet / outlet 7 is located between the liquid oxygen inlet / outlet 5 and liquid oxygen outlet 6 and the TPMS core 1. The outer shell 2 is located outside the liquid oxygen inlet / outlet collector 7 and the TPMS core 1.

[0036] The TPMS core 1 adopts a spiral flow channel structure using TPMS. Based on heat exchange efficiency calculations and comprehensive considerations of printability, the core unit thin-wall structure is designed with a thickness of 0.3mm, a unit size of 8mm, a radial fill of 14, an axial fill of 12, a porosity of ≥0.7 for each unit, and a surface-to-body ratio of ≥3000mm. 2 / mm 3 .

[0037] Liquid oxygen inlet 5 and liquid oxygen outlet 6 are connected to core 1 via collector 7. Liquid oxygen enters the liquid oxygen inlet collector from the liquid oxygen inlet, then circulates through the liquid oxygen baffle into the core, and finally enters the liquid oxygen outlet collector, and is discharged from the liquid oxygen outlet. The path is as follows: Figure 2 As shown by the blue arrow, the gas enters from the gas inlet, passes through the gas baffle, enters the core, and then exits from the gas outlet, following the path shown. Figure 3 As indicated by the red arrows, the flanges at the liquid oxygen inlet and outlet are used to connect the liquid oxygen delivery pipeline. The other end of the flange is connected to the liquid oxygen inlet and outlet manifold, which is constructed using a fan-shaped cross-section scanning array to allow liquid oxygen to diffuse evenly into the internal core structure for subsequent heat exchange.

[0038] The TPMS core structure divides the space into two regions: the blue arrow represents the liquid oxygen region, and the red arrow represents the fuel gas region, as shown below. Figure 4 As shown in the diagram, the liquid oxygen baffle allows liquid oxygen to enter the blue liquid oxygen zone of the core structure while simultaneously blocking the gas flow passage within the core, preventing gas leakage from the liquid oxygen collector end. Conversely, the gas flow baffle allows gas to enter the red gas flow zone of the core structure while simultaneously blocking the liquid oxygen flow passage within the core, preventing liquid oxygen leakage from the gas inlet and outlet. The baffles restrict each zone to a single inlet and outlet, completing a closed loop in the overall heat exchange path.

[0039] The TPMS microchannel heat exchanger is manufactured using selective laser melting (SLM) technology. It employs 15-38μm 316L powder and, through process parameter control, achieves a 0.3mm thin-walled TPMS structure. The main process steps are:

[0040] 1) Determining Printing Parameters: Based on the structural characteristics of the model, the printing process for thin-walled microchannel structures was explored through preliminary process experiments. Based on the warpage observed during printing and metallographic analysis, the optimal scanning power was determined to be 260W, the scanning speed 900mm / s, and the scanning spacing 0.1mm. Under these optimal parameters, a 0.3mm TPMS thin-walled structure can be manufactured.

[0041] 2) Model Processing: Based on subsequent processing requirements, process allowances are added to the upper and lower end faces of the heat exchanger. The original heat exchanger model is simplified using triangular facets in Magics software. Self-forming structural solid supports are added to the suspended positions such as the lower end faces of core 1 and collector 7 on the optimized heat exchanger model. Mesh and columnar supports are added to the bottom of core 1 to reduce the risk of damage to the thin-walled structure of the core when the supports are removed, while ensuring forming quality.

[0042] 3) Process design: In order to prevent deformation and cracking at the root, a process chamfer and fillet of not less than R5 are added at the contact position between the model and the substrate to reduce the stress on the bonding surface.

[0043] 4) SLM molding: Install the molding substrate in the SLM molding equipment, fill the molding cavity with inert gas to make the oxygen content in the molding cavity less than 0.1%; import the processed model into the SLM molding equipment and start molding.

[0044] 5) Post-processing: Remove the formed microchannel heat exchanger parts from the SLM forming equipment and remove residual powder from the flow channels by ultrasonic vibration and compressed gas blowing; perform stress-relief vacuum heat treatment at 850℃ for 3 hours; remove the substrate by wire cutting; and complete the forming of the TPMS structure microchannel heat exchanger by removing the support and polishing the parts.

[0045] The microchannel heat exchanger core designed in this invention adopts a TPMS structure design, which increases the effective heat exchange area per unit space and improves the heat exchanger's heat exchange efficiency. The manufacturing process features the use of laser selective melting forming technology to achieve integrated forming of the internal TPMS structure and the outer shell. The self-forming structure optimizes the overall manufacturing of the collector, improving manufacturing reliability and shortening the manufacturing cycle.

[0046] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A TPMS structure microchannel heat exchanger, characterized in that, It includes a core, outer shell, gas inlet pipe, gas outlet pipe, liquid oxygen inlet pipe, liquid oxygen outlet pipe, liquid oxygen inlet and outlet collector, liquid oxygen baffle, and gas baffle; The core is installed inside the outer shell, and the core has a multi-spiral flow channel structure using TPMS; One end of the inlet side of the liquid oxygen inlet / outlet collector is connected to the liquid oxygen inlet pipeline, and the other end is connected to the inlet of multiple spiral flow channels of the core through a liquid oxygen baffle; one end of the outlet side of the liquid oxygen inlet / outlet collector is connected to the outlet of each spiral flow channel of the core, and the other end is connected to the liquid oxygen outlet pipeline. The gas inlet pipe is connected to the inlet of multiple spiral channels of the core through a gas baffle, and the gas outlet pipe is connected to the outlet of each spiral channel of the core. Both the liquid oxygen baffle and the gas baffle are provided with multiple through holes, which correspond one-to-one with the spiral flow channels in the core. Each through hole is connected to the inlet of a spiral flow channel in the core.

2. The TPMS structure microchannel heat exchanger according to claim 1, characterized in that, The liquid oxygen inlet and outlet collector is structured as a fan-shaped cross-section scanning array, which allows liquid oxygen to diffuse uniformly into the core.

3. A TPMS structure microchannel heat exchanger according to claim 1, characterized in that, The core unit has a thin-walled structure with a thickness of 0.3mm to 0.5mm and a unit size of 5mm to 10mm; the porosity of each core unit is not less than 0.7, and the surface-to-body ratio is not less than 3000mm. 2 / mm 3 .

4. A TPMS structure microchannel heat exchanger according to claim 1, characterized in that, The fuel gas and liquid oxygen flow through different spiral channels and do not share the same spiral channels.

5. A TPMS structure microchannel heat exchanger according to claim 1, characterized in that, The liquid oxygen inlet pipeline, liquid oxygen outlet pipeline, and liquid oxygen inlet / outlet manifold are connected by flanges.

6. A method for manufacturing a TPMS structured microchannel heat exchanger as described in claim 1, characterized in that, include: The core structure is designed based on heat exchange requirements and printability requirements; Based on the core structure, design the scanning parameters for printing; Add process chamfers and fillets at the contact points between the 3D model of the heat exchanger and the substrate to form the model to be processed; The forming substrate is installed in the SLM forming equipment, and the forming cavity is filled with inert gas; The model to be processed is imported into the SLM forming equipment. The forming process begins according to the scanning parameters for printing. The formed heat exchanger part is then removed from the SLM forming equipment, and the substrate is removed.

7. The method for manufacturing a TPMS structured microchannel heat exchanger according to claim 6, characterized in that, The scanning parameters for printing are: scanning power of 240W to 260W, scanning speed of 600mm / s to 900mm / s, and scanning spacing of 0.08mm to 0.1mm.

8. The method for manufacturing a TPMS structured microchannel heat exchanger according to claim 6, characterized in that, The 316L powder with a particle size of 15μm to 38μm is used for shaping by layer-by-layer powder spreading and layer-by-layer melting and stacking.

9. The method for manufacturing a TPMS structured microchannel heat exchanger according to claim 6, characterized in that, Process the 3D model of the heat exchanger. Increase process allowances at the upper and lower end faces of the heat exchanger, etc. The original output heat exchanger model is simplified by triangular facets. For the simplified heat exchanger model, a self-forming structural solid support is added to the suspended position of the core and the liquid oxygen inlet and outlet collector, and a mesh and column support is added to the bottom of the core.

10. The method for manufacturing a TPMS structured microchannel heat exchanger according to claim 6, characterized in that, After forming, the heat exchanger parts are removed from the SLM forming equipment, and residual powder in the flow channel is removed by ultrasonic vibration and compressed gas blowing. Stress-relief vacuum heat treatment is performed at a temperature of 810℃~850℃ for 2 hours to 4 hours. After heat treatment, the substrate is removed by wire cutting.

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