Silicon carbide porous combustion medium plate and silicon carbide porous medium burner

Abstract

This invention provides a silicon carbide porous combustion medium plate and a silicon carbide porous medium burner, relating to the field of porous medium combustion technology. The silicon carbide porous combustion medium plate has three-dimensional continuous pores, formed by a single or multiple triple-period minimal surface structures. The average curvature at each point on the triple-period minimal surface structure is zero, which can effectively reduce the concentration of thermal stress. The combustion medium plate prepared from silicon carbide slurry based on this structure has high compressive strength, which is beneficial to improving the service life of the silicon carbide porous combustion medium plate. The porous medium burner using this silicon carbide porous combustion medium plate utilizes its interconnected pores to promote uniform mixing of combustible gas and air. The combination of multiple triple-period minimal surface structures can specifically regulate the internal flow behavior of the mixed gas, thereby improving the thermal performance of the porous medium burner.

Description

Technical Field

[0001] This invention relates to the field of porous media combustion technology, specifically to a silicon carbide porous combustion media plate and a silicon carbide porous media burner. Background Technology

[0002] Porous media combustion technology is a novel combustion method that organizes the combustion process within porous materials. Its core lies in utilizing the high thermal conductivity, large specific surface area, and heat feedback effect of porous materials to achieve superadiabatic combustion. Since its initial report in the early 20th century, this technology achieved a breakthrough in the 1970s thanks to Weinberg's theory of "superadiabatic combustion." Its principle involves using the thermal circulation of porous media to feed the heat of combustion products back to the unburned mixture, thereby increasing the enthalpy and overcoming the temperature limitations of traditional combustion to achieve high efficiency and low emissions.

[0003] Compared with traditional free flame combustion, porous media combustion has the following significant advantages:

[0004] (1) High combustion efficiency: The thermal conduction and radiation effect of porous media preheats the unburned gas, increases the combustion rate, and the thermal efficiency can reach 80%~90%, with significant energy saving effect (traditional burners only about 30%).

[0005] (2) Low pollutant emissions: Through staged combustion and temperature homogenization, local high-temperature zones are suppressed, reducing NOx and CO generation, and the methane / air flammability limit can be as low as 0.1 equivalence ratio;

[0006] (3) Compact equipment: The high volumetric heat intensity reduces the burner volume by more than 50%, making it suitable for micro burners and industrial thermal equipment.

[0007] Porous ceramics, as core materials for combustion media, must meet requirements such as high temperature resistance (>1500℃), high porosity (70%~90%), low flow resistance, and excellent thermal shock resistance. Currently, porous ceramics used in combustion media are mainly divided into two categories: one is honeycomb structure ceramics with a porosity of 20%~60%, mostly obtained by extrusion molding, which has a regular structure but limited heat exchange efficiency; the other is random foam structure ceramics with a porosity of up to 70%~90%, mostly prepared by template replication method, whose open structure promotes gas turbulence, but has defects such as uneven pore distribution, stress concentration, low mechanical strength, and high flow resistance.

[0008] In the patent technology of application number CN114738990B, entitled "Gradual Porous Medium Material for Gas Water Heaters and its Preparation Method, Application and Gas Water Heater", a gradual three-dimensional spatial pore skeleton model for 3D printing is constructed, and then the gradual porous medium material for gas water heaters is prepared by combining 3D printing method. However, its pores are straight, the heat feedback is insufficient, and the surface power density is reduced by orders of magnitude; the porosity is too high, and the mechanical properties are poor; the straight edges are prone to stress concentration, and it is prone to cracking in cold and hot cycle applications. In the patent technology of application number CN214327577U, entitled "Porous Ceramics and Porous Medium Burners", the constructed porous ceramics have a multi-layer pore structure, and the pores of adjacent two layers of pore structure are interwoven and connected. Although the aforementioned patented technology constructs a three-dimensional porous ceramic structure and applies it to porous media combustion scenarios, the geometric structure it constructs is mainly a truss structure composed of nodes and ribs. Furthermore, the surface at the nodes where the ribs intersect has a large radius of curvature or abrupt curvature changes. Under complex working conditions such as high temperature and strong thermal shock, it is prone to local thermal stress concentration, which leads to cracking and affects service life.

[0009] In summary, the core materials of porous media burners in the current technology still face bottlenecks such as insufficient high temperature resistance, poor thermal shock resistance, and difficulty in balancing porosity and strength, which restrict the further development and application of porous media combustion technology towards higher temperatures and higher power densities. Summary of the Invention

[0010] According to embodiments of the present invention, a silicon carbide porous combustion medium plate and a silicon carbide porous medium burner are provided. This solution addresses the technical problem of cracking caused by localized thermal stress concentration in porous ceramic structures under complex operating conditions.

[0011] In a first aspect of the invention, a silicon carbide porous combustion medium plate is provided.

[0012] The silicon carbide porous combustion medium plate has one or more combinations of three-dimensional continuous Gyroid, Diamond, Schwarz, and iWP triple-periodic minimal surface structures, with smooth transitions between combinations of these structures. The silicon carbide porous combustion medium plate can achieve a dual-channel structure (thin-wall type) by thickening and solidifying the triple-periodic minimal surface structure, or a single-channel structure (rod type) by dividing the macroscopic space occupied by the plate into two independent subspaces and solidifying one of these subspaces. The silicon carbide porous combustion medium plate has a high specific surface area; the periodic pore structure provides low gas flow resistance, inducing micro-turbulence, accelerating the preheating process of the unburned mixture, enhancing radiation and thermal conductivity, and improving combustion efficiency and fuel adaptability.

[0013] Furthermore, the silicon carbide porous combustion medium plate has a pore size range of 3~12 mm, with a uniform pore size, or a non-linear gradient pore size along the thickness direction of the plate from the inlet end to the outlet end, with a pore size gradient change rate of 0.1~1 mm / mm; the silicon carbide porous combustion medium plate has a porosity range of 70%~90%, with a uniform porosity, or a gradient porosity that gradually changes from the inlet end to the outlet end along the thickness direction of the plate, with a porosity gradient change rate ≤2% / mm.

[0014] The thickness of the silicon carbide porous combustion medium plate, which is thickened by a triple-period minimal curved surface structure, is constrained by pore size and porosity and does not need to be listed separately.

[0015] Furthermore, the silicon carbide porous combustion medium plate is made of reaction-sintered silicon carbide, and the silicon carbide solid content is greater than 75 wt%.

[0016] Furthermore, the silicon carbide porous combustion medium plate has a compressive strength ≥10 MPa when the average porosity is 80%.

[0017] In a second aspect of the present invention, a method for preparing a porous silicon carbide combustion medium plate is provided. The method specifically includes the following steps:

[0018] (1) Prepare a slurry containing silicon carbide;

[0019] (2) Use 3D design software to design a geometric model with one or more combinations of Gyroid, Diamond, Schwarz, iWP triple period minimal surface structures, and output it as an STL or OBJ format file to the 3D printer.

[0020] Among them, the 3D design software can be selected from 3DMAX, SolidWorks, Rhinoceros, nTopology, Cinema4D, Blender, etc.

[0021] (3) 3D printing: Using a DLP or SLA 3D printer, the slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. After printing, it is cleaned and dried to obtain a porous silicon carbide green body.

[0022] (4) Pyrolysis: The porous silicon carbide green body in step (3) is pyrolyzed at 600℃~900℃ under vacuum or inert gas protection for 1~10 h to obtain a porous silicon carbide preform.

[0023] (5) Sintering: The porous silicon carbide preform in step (4) is sintered under vacuum at 1450℃~2000℃ to achieve densification. The holding time is 0.5h~5h to obtain a porous silicon carbide medium plate.

[0024] In the above method, a porous silicon carbide combustion medium plate preform is printed by 3D printing. The 3D printing technology prints layer by layer, and can print complex porous silicon carbide green blanks with triple periodic minimal curved surface structures according to the designed documents.

[0025] Using the silicon carbide porous media plate described in the first aspect above as a core component, a silicon carbide porous media burner can be fabricated.

[0026] Furthermore, in step (3), during DLP printing, the printing layer thickness is 20~100 μm and the exposure intensity is 40 mW / cm²~60 mW / cm²; during SLA 3D printing, the printing layer thickness is 20~100 μm and the laser power is 500~3000 mW. Preferably, using a DLP 3D printer can improve printing efficiency.

[0027] Furthermore, the formula for the Gyroid surface is cos(x)⋅sin(y) + cos(y)⋅sin(z) + cos(z)⋅sin(x) = a; the formula for the Diamond surface is: sin(x)⋅sin(y)⋅sin(z) + sin(x)⋅cos(y)⋅cos(z) + cos(x)⋅sin(y)⋅cos(z) + cos(x)⋅sin(y)⋅cos(z) + cos(x)⋅cos(y)⋅cos(z) + cos(x)⋅cos(y)⋅cos(z)⋅co ... x)⋅cos(y)⋅sin(z)=a; the Schwarz surface formula is: cos(2πx)+cos(2πy)+cos(2πz)=a; the iWP surface formula is: cos(2πx)+cos(2πy)+cos(2πz)+cos(2πx)cos(2πy)cos(2πz)=a, where a is a constant related to the lattice size.

[0028] Further, the slurry in step (1) includes the following raw materials by mass parts: 30-80 parts of silicon carbide powder, 10-50 parts of carbon source, 20-80 parts of photosensitive resin, as well as photoinitiator, dispersant, leveling agent and anti-settling agent;

[0029] By mass fraction, silicon carbide powder, carbon source, photosensitive resin, photoinitiator, dispersant, leveling agent, anti-settling agent and other raw materials are fully ball-milled and mixed for 1 to 12 hours to obtain a high solids content silicon carbide ceramic slurry that can be used for photocuring 3D printing.

[0030] The photoinitiator is added at 1% to 5% of the total mass of the photosensitive resin, the dispersant is added at 0.5% to 3% of the mass of the silicon carbide powder, the leveling agent is added at 0.5% to 2% of the mass of the silicon carbide powder, and the anti-settling agent is added at 0.5% to 2% of the mass of the silicon carbide powder.

[0031] The silicon carbide ceramic slurry formulation provided by this invention can be used for photopolymerization 3D printing. It features high solids content, good anti-settling properties, suitable viscosity, uniform curing, and excellent printing stability. Its volumetric solids content is ≥45%, and its viscosity is less than 8 Pa·s (@30 s). -1 ).

[0032] Furthermore, the median diameter D of the silicon carbide powder 50 = 5~20 μm.

[0033] Furthermore, the carbon source includes one or more of phenolic resin, diamond, carbon black, cellulose, and chopped carbon fibers, wherein the median diameter D of phenolic resin, diamond, carbon black, and cellulose is... 50 = 0.5~5 μm, short-cut carbon fiber length 1~5 μm;

[0034] The photosensitive resin includes one or more of the following: ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, epoxidized soybean oil acrylate, aliphatic polyurethane acrylate, modified polyurethane acrylate, aromatic polyurethane acrylate, bisphenol A epoxy acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylated triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated neopentyl glycol diacrylate, dipropylene glycol diacrylate, cyclotrimethylolpropane methyl acetal acrylate, isobornyl acrylate, hydroxyethyl acrylate, and hydroxyethyl methacrylate.

[0035] The photoinitiator includes one or more of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-isopropylthioxanthone, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, and bis(1-(2,4-difluorophenyl)-3-pyrrolithium)titanium oxide;

[0036] The dispersant includes one or more of BYK-108, BYK-180, KOS163, KOS110, KOS2400, 17000, and K-271;

[0037] The leveling agent includes one or more of BYK-323, BYK-333, BYK-354, H421, LS3003, DH-4072, AKN-1181, and AKN-1035;

[0038] The anti-settling agent includes one or more of KMT-4542, DH-6900, BYK-410, K-635, and AKN-7020.

[0039] Because silicon carbide powder has a much higher UV absorbance than oxide ceramic powder, silicon carbide ceramic slurries typically used for 3D printing often have a median diameter (D). 50 Silicon carbide particles ≥30 μm are used to enhance the curing depth of the slurry under UV irradiation. However, the addition of large-particle silicon carbide can easily lead to problems such as rapid slurry settling, unstable printing, high residual silicon content after sintering, and low mechanical properties, making it difficult for the product to meet the combustion performance requirements of porous media. Therefore, it is necessary to develop a photopolymerization 3D printing silicon carbide ceramic slurry using small-particle silicon carbide as the basic raw material. At the same time, by adding an additional carbon source, the content of secondary silicon carbide generated by the silicon-carbon reaction during the reaction sintering process can be increased, reducing the residual silicon in the microstructure and improving the mechanical and thermal properties of the final product.

[0040] In a third aspect of the invention, a silicon carbide porous media burner is provided, comprising a silicon carbide porous combustion media plate obtained by the preparation method described in the second aspect above.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] This invention provides a silicon carbide porous combustion medium plate and a porous medium burner. The silicon carbide porous combustion medium plate features a triple-periodic minimal curved surface structure, enabling precise control of porosity from 70% to 90%. The pore size gradient can be designed to reduce gas flow resistance (pressure drop reduction of 30% to 50%), avoiding the flow dead zones caused by the random pore structure of traditional foam ceramics, and significantly improving gas permeability. Simultaneously, the high specific surface area of ​​the triple-periodic minimal curved surface structure (increased internal surface area per unit volume by 40% to 60%) enhances radiative and conductive heat transfer, accelerates the preheating process of the unburned mixture, results in a more uniform combustion temperature distribution, suppresses localized high-temperature zones, reduces NOx formation, and the periodic pore structure induces micro-turbulence in the gas, prolonging the residence time of combustible gases in the combustion zone, widening the lean-burn limit (e.g., the flammability equivalence ratio of methane / air mixtures can be as low as 0.05), and improving combustion efficiency and fuel adaptability. Furthermore, the silicon carbide slurry formulation developed in this study features high solid content, good anti-settling properties, suitable slurry viscosity, uniform curing, and excellent printing stability. The addition of an extra carbon source addresses the shortcomings of low solid content in silicon carbide 3D printing slurries and insufficient mechanical properties in reaction-sintered silicon carbide ceramic products. Utilizing the smooth transition and uniform stress distribution of the triple-period minimal curved surface structure, the compressive strength of the prepared combustion medium plate is further enhanced, increasing it by 2-3 times compared to traditional foam ceramics, thus solving the industry pain point of "difficulty in balancing high porosity and high strength." The isotropic characteristics can uniformly disperse thermal stress, and combined with the high thermal conductivity of silicon carbide, significantly improve thermal shock resistance, preventing structural cracking and collapse under high-temperature conditions and extending the burner's service life.

[0043] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0044] The above and other features, advantages, and aspects of the various embodiments of the present invention will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0045] Figure 1 This is the geometric model of the Gyroid curved surface structure uniform pore size silicon carbide porous combustion medium plate provided in Embodiment 1 of the present invention;

[0046] Figure 2 This is a schematic diagram of the smallest unit of the Gyroid surface structure provided in Embodiment 1 of the present invention;

[0047] Figure 3This is the geometric model of the Gyroid surface structure gradient porosity silicon carbide porous combustion medium plate provided in Embodiment 2 of the present invention;

[0048] Figure 4 This is the geometric model of the Gyroid surface structure gradient pore size silicon carbide porous combustion medium plate provided in Embodiment 3 of the present invention;

[0049] Figure 5 This is the geometric model of the diamond-shaped silicon carbide porous combustion medium plate with uniform pore size provided in Embodiment 4 of the present invention.

[0050] Figure 6 This is the geometric model of the Schwarz surface structure uniform pore size silicon carbide porous combustion medium plate provided in Embodiment 5 of the present invention;

[0051] Figure 7 This is the geometric model of the uniform pore size silicon carbide porous combustion medium plate with Gyroid-Schwarz surface composite smooth transition structure provided in Embodiment 6 of the present invention.

[0052] Figure 8 This is a physical image of the silicon carbide porous combustion medium plate provided in Embodiment 3 of the present invention;

[0053] Figure 9 This is a physical image of the silicon carbide porous media burner provided in Embodiment 4 of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0056] Example 1

[0057] A silicon carbide porous combustion medium plate and a porous medium burner are disclosed, wherein the silicon carbide porous combustion medium plate has a single Gyroid structure.

[0058] (1) Preparation of printing slurry: All raw materials are ball-milled and mixed evenly for 6 hours according to the following slurry formula to prepare slurry. The properties of the prepared slurry are: solid content 48 vol%, viscosity 4.5 Pa·s @30s⁻¹;

[0059] Slurry formulation (by weight):

[0060] Silicon carbide powder (D50=8μm): 65 parts

[0061] Phenolic resin (carbon source, D50=2μm): 20 parts

[0062] Aliphatic polyurethane acrylate (photosensitive resin): 15 parts

[0063] Propylene oxide neopentyl glycol diacrylate (photosensitive resin): 20 parts

[0064] Phenylated bis(2,4,6-trimethylbenzoyl)phosphine oxide (photoinitiator): 1 part (2.9% of the photosensitive resin mass)

[0065] BYK-180 dispersant: 1.2 parts (1.8% of silicon carbide powder)

[0066] BYK-333 leveling agent: 0.8 parts (1.2% of silicon carbide powder)

[0067] KMT-4542 anti-settling agent: 1.3 parts (accounting for 2% of silicon carbide powder).

[0068] (2) Triple-period minimal surface structure model: A triple-period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate is as follows: Figure 1 As shown, it consists of a uniform Gyroid structure, as Figure 2 As shown, the right small image is a pure Gyroid surface structure, which is thickened and solidified to obtain a dual-channel structure (thin-wall type, left small image).

[0069] Gyroid surface formula: cos(x)⋅sin(y)+cos(y)⋅sin(z)+cos(z)⋅sin(x)=a (where a=5).

[0070] (3) 3D printing: Using a DLP 3D printer, the ceramic slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. The printing process parameters are set as follows: ultraviolet light wavelength 405 nm, exposure intensity 50 mW / cm², printing layer thickness 0.025 mm, and single layer exposure time 30 s. After the printing is completed, it is cleaned and dried with isopropanol to obtain a porous silicon carbide green body.

[0071] (4) The porous silicon carbide green body in step (3) is thermally degreased at 800 °C under the protection of high-purity argon (Ar) for 3 h to obtain the porous silicon carbide preform.

[0072] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 1700 °C to achieve densification. The holding time is 2 h to obtain a porous silicon carbide medium plate. SiC phase content: 78 wt%.

[0073] Gyroid structural parameters:

[0074] Pore ​​size: uniform 5 mm; Porosity: uniform 80%;

[0075] Dimensions: Flat plate 120 mm × 80 mm × 5 mm (thickness direction is gas flow direction);

[0076] Strength: Compressive strength 12 MPa (measured value).

[0077] (6) Combustion performance test:

[0078] Surface power density: 1200 kW / m 2 ;

[0079] Emission targets: NOx = 3.8 mg / Nm³ at an equivalence ratio φ = 0.7 @ 1300 ℃;

[0080] Thermal shock cycling: No cracking after ≥2500 cycles of hot and cold cycling at ΔT=1300 ℃.

[0081] Example 2

[0082] A silicon carbide porous combustion medium plate and a porous medium burner are disclosed, wherein the silicon carbide porous combustion medium plate has a single Gyroid structure.

[0083] (1) Preparation of printing slurry: All raw materials are ball-milled and mixed evenly for 4 hours according to the following slurry formula to prepare slurry. The properties of the prepared slurry are: solid content 48 vol%, viscosity 6.2 Pa·s @30 s⁻¹;

[0084] Slurry formulation (by weight):

[0085] Silicon carbide powder (D 50 =12 μm): 60 copies

[0086] Short-cut carbon fiber (3 μm) + carbon black (2 μm): 25 parts (3:2)

[0087] Epoxidized soybean oil acrylate + 1,6-hexanediol diacrylate: 40 parts (1:1)

[0088] 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide: 1.5 parts

[0089] KOS110 dispersant: 1.5 parts

[0090] DH-4072 leveling agent: 1.0 part.

[0091] (2) Triple-period minimal surface structure model: A triple-period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate is as follows: Figure 3 As shown, it consists of a single Gyroid structure, which is a pure Gyroid surface structure. The solid part is a dual-channel structure (thin-wall type) obtained by thickening and solidifying the Gyroid surface.

[0092] Gyroid surface formula: cos(x)⋅sin(y)+cos(y)⋅sin(z)+cos(z)⋅sin(x)=a (where a=7).

[0093] (3) 3D printing: Using an SLA 3D printer, the ceramic slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. The printing process parameters are set as follows: SLA printing, ultraviolet light wavelength 405 nm, light source power 1 W, printing layer thickness 0.025 mm, scanning rate (8 m / s). After the printing is completed, it is cleaned and dried with isopropanol to obtain a porous silicon carbide green body.

[0094] (4) The porous silicon carbide green blank in step (3) is thermally degreased at 750 °C under vacuum conditions and kept at the temperature for 4 h to obtain a porous silicon carbide preform.

[0095] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 1600 °C to achieve densification. The holding time is 1 h to obtain a porous silicon carbide medium plate. SiC phase content: 79 wt%.

[0096] Gyroid structural parameters:

[0097] Pore ​​size: uniform 7 mm; Porosity: continuous gradient variation of 70%~85% along the thickness direction, with an average of 77.5%, and a porosity gradient variation rate of 0.83% / mm, that is, the porosity changes by 0.83% for every 1 mm increase in thickness.

[0098] Dimensions: Flat plate 120 mm × 80 mm × 18 mm (thickness direction is gas flow direction);

[0099] Strength: Compressive strength 10.8 MPa (measured value).

[0100] (6) Combustion performance test:

[0101] Surface power density: 1000 kW / m 2 ;

[0102] Emission targets: NOx = 2.5 mg / Nm³ at an equivalence ratio φ = 0.9 @ 1000 ℃;

[0103] Thermal shock cycling: No cracking after ≥5000 cycles of hot and cold cycling at ΔT=1000 ℃.

[0104] Example 3

[0105] A silicon carbide porous combustion medium plate and a porous medium burner are disclosed, wherein the silicon carbide porous combustion medium plate has a single Gyroid structure.

[0106] (1) Preparation of printing paste: All raw materials are ball-milled and mixed evenly for 2 hours according to the following paste formula to prepare paste. The properties of the prepared paste are: solid content 52 vol%, viscosity 3.0 Pa·s @30 s⁻¹;

[0107] Slurry formulation (by weight):

[0108] Silicon carbide powder (D 50 =8 μm): 70 copies

[0109] Diamond (D) 50 =0.8 μm): 15 copies

[0110] Modified polyurethane acrylate: 15 parts (low viscosity)

[0111] Trimethylolpropane ethoxytriacrylate: 15 parts

[0112] 2-Isopropylthioxanthone: 1.8 parts

[0113] BYK-108 dispersant: 1.0 part

[0114] H421 leveling agent: 1.0 part

[0115] AKN-7020 anti-settling agent: 1.2 parts.

[0116] (2) Triple-period minimal surface structure model: A triple-period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate is as follows: Figure 4As shown, it consists of a single Gyroid structure. The solid part is divided into two independent subspaces by the Gyroid surface. One of the spaces is taken and solidified to obtain a single-channel structure (rod type).

[0117] The formula for a curved surface is: cos(x)⋅sin(y)+cos(y)⋅sin(z)+cos(z)⋅sin(x)=a (where a=8~10).

[0118] (3) 3D printing: Using a DLP 3D printer, the ceramic slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. The printing process parameters are set as follows: ultraviolet light wavelength 405 nm, exposure intensity 45 mW / cm², printing layer thickness 0.025 mm, and single layer exposure time 40 s. After the printing is completed, it is cleaned and dried with isopropanol to obtain a porous silicon carbide green body.

[0119] (4) The porous silicon carbide green blank in step (3) is thermally degreased at 700 °C under nitrogen (N2) protection for 8 h to obtain the porous silicon carbide preform.

[0120] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 1750 °C to achieve densification. The holding time is 1 h to obtain a porous silicon carbide medium plate. SiC phase content: 83 wt%.

[0121] Figure 8 This is a photograph of the silicon carbide ceramic plate porous media burner prepared in this embodiment.

[0122] Gyroid structural parameters:

[0123] Pore ​​size: continuously varying in gradient from 8 to 10 mm along the thickness direction, with a pore size gradient rate of 0.11 mm / mm; Porosity: uniform 70%;

[0124] Dimensions: Flat plate 120 mm × 80 mm × 18 mm (thickness direction is gas flow direction);

[0125] Strength: Compressive strength 14 MPa (measured value).

[0126] (6) Combustion performance test:

[0127] Surface power density: 1500 kW / m 2

[0128] Emission targets: NOx = 6.5 mg / Nm³ at an equivalence ratio φ = 0.8 @ 1300 ℃.

[0129] Thermal shock cycling: No cracking after ≥3000 cycles of hot and cold cycling at ΔT=1250℃.

[0130] Example 4

[0131] A silicon carbide porous combustion medium plate and a porous medium burner, wherein the silicon carbide porous combustion medium plate has a single Diamond structure.

[0132] (1) Preparation of printing slurry: All raw materials are ball-milled and mixed evenly for 12 hours according to the following slurry formula to prepare slurry. The properties of the prepared slurry are: solid content 46 vol%, viscosity 5.2 Pa·s @30 s⁻¹;

[0133] Slurry formulation (by weight):

[0134] Silicon carbide powder (D 50 =15 μm): 55 copies

[0135] Phenolic resin (5 μm) + cellulose (microcrystals, 2 μm): 30 parts (2:1)

[0136] Bisphenol A epoxy acrylate: 10 parts

[0137] Cyclotrimethylolpropane methyl acetal acrylate: 30 parts

[0138] Phenylacetylbis(2,4,6-trimethylbenzoyl)phosphine oxide: 2.5 parts

[0139] KOS2400 dispersant: 2.0 parts

[0140] DH-4072 leveling agent: 1.0 part.

[0141] (2) Triple-period minimal surface structure model: A triple-period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate is as follows: Figure 5 As shown, it consists of a single Diamond surface structure, and the solid part is a dual-channel structure (thin-wall type) obtained by thickening and solidifying the Diamond surface.

[0142] Diamond surface formula: sin(x)⋅sin(y)⋅sin(z)+sin(x)⋅cos(y)⋅cos(z)+cos(x)⋅sin(y)⋅cos(z)+cos(x)⋅cos(y)⋅sin(z)=a (where a=9).

[0143] (3) 3D printing: Using a DLP 3D printer, the ceramic slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. The printing process parameters are set as follows: ultraviolet light wavelength 405 nm, exposure intensity 60 mW / cm², printing layer thickness 0.030 mm, and single layer exposure time 25 s. After the printing is completed, it is cleaned and dried with isopropanol to obtain a porous silicon carbide green body.

[0144] (4) The porous silicon carbide green body in step (3) is thermally degreased at 900 °C under nitrogen (N2) protection for 1 h to obtain the porous silicon carbide preform.

[0145] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 2000 °C to achieve densification. The holding time is 0.5 h to obtain a porous silicon carbide medium plate. SiC phase content: 79 wt%.

[0146] Figure 9 This is a photograph of the silicon carbide ceramic plate porous media burner prepared in this embodiment.

[0147] Diamond surface structure parameters:

[0148] Pore ​​size: uniform 9 mm; Porosity: uniform 75%;

[0149] Dimensions: Flat plate 120 mm × 80 mm × 18 mm (thickness direction is gas flow direction);

[0150] Strength: Compressive strength 10.2 MPa (measured value).

[0151] (6) Combustion performance test:

[0152] Surface power density: 1200 kW / m 2

[0153] Emission targets: NOx = 4.5 mg / Nm³ at an equivalence ratio φ = 0.8 @ 1100 ℃;

[0154] Thermal shock cycling: It can withstand ≥4000 cycles of hot and cold cycling at ΔT=1100℃ without cracking. And its continuous operating life is >500 hours (without structural failure).

[0155] Example 5

[0156] A silicon carbide porous combustion medium plate and a porous medium burner, wherein the silicon carbide porous combustion medium plate has a single Schwarz structure.

[0157] (1) Preparation of printing paste: All raw materials are ball-milled and mixed evenly for 3 hours according to the following paste formula to prepare paste. The properties of the prepared paste are: solid content 54 vol%, viscosity 7.9 Pa·s @30 s⁻¹;

[0158] Slurry formulation (by weight):

[0159] Silicon carbide powder (D50=8 μm): 80 parts

[0160] Cellulose (microcrystals, 1 μm): 50 parts

[0161] Aliphatic polyurethane acrylate: 20 parts

[0162] Isoborneol acrylate: 60 parts

[0163] Bis(1-(2,4-difluorophenyl)-3-pyrrolithyl)dicenoctanetane: 2.0 parts

[0164] K-271 dispersant: 2.6 parts

[0165] LS3003 leveling agent: 1.0 part

[0166] BYK-410 antisettling agent: 1.0 part.

[0167] (2) Triple-period minimal surface structure model: A triple-period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate is as follows: Figure 6 As shown, it consists of a single Schwarz surface structure, and the solid part is a dual-channel structure (thin-wall type) obtained by thickening and solidifying the Schwarz surface.

[0168] Schwarz surface formula: cos(2πx)+cos(2πy)+cos(2πz)=a (where a=12).

[0169] (3) 3D printing: Using a DLP 3D printer, the ceramic slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. The printing process parameters are set as follows: ultraviolet light wavelength 405 nm, exposure intensity 50 mW / cm², printing layer thickness 0.020 mm, and single layer exposure time 20 s. After the printing is completed, it is cleaned and dried with isopropanol to obtain a porous silicon carbide green body.

[0170] (4) The porous silicon carbide green body in step (3) is thermally degreased at 800 °C under the protection of high-purity argon (Ar) for 1 h to obtain the porous silicon carbide preform.

[0171] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 1720 °C to achieve densification. The holding time is 2 h to obtain a porous silicon carbide medium plate. SiC phase content: 79 wt%.

[0172] Schwarz structural parameters:

[0173] Pore ​​size: uniform 12 mm; Porosity: uniform 90%;

[0174] Dimensions: Flat plate 120 mm × 80 mm × 18 mm (thickness direction is gas flow direction);

[0175] Strength: Compressive strength 11.2 MPa (measured value).

[0176] (6) Combustion performance test:

[0177] Surface power density: 1100 kW / m 2

[0178] Emission targets: NOx = 5.5 mg / Nm³ at an equivalence ratio φ = 0.9 @ 1000 ℃.

[0179] Thermal shock cycling: No cracking after ≥3000 cycles of hot and cold cycling at ΔT=1000 ℃.

[0180] Example 6

[0181] A silicon carbide porous combustion medium plate and a porous medium burner are disclosed, wherein the silicon carbide porous combustion medium plate has a Gyroid-Schwarz composite smooth transition structure.

[0182] (1) Preparation of printing slurry: All raw materials are ball-milled and mixed evenly for 12 hours according to the following slurry formula to prepare slurry. The properties of the prepared slurry are: solid content 46 vol%, viscosity 3.6 Pa·s @30 s⁻¹;

[0183] Slurry formulation (by weight):

[0184] Silicon carbide powder (D 50 =5 μm): 80 copies

[0185] Carbon black (D) 50 =1 μm): 10 portions

[0186] Polyethylene glycol (600) dimethacrylate: 30 parts

[0187] 1,6-Hexanediol diacrylate: 30 parts

[0188] 2,4,6-Trimethylbenzoyl-di(p-tolyl)phosphine oxide: 1.2 parts

[0189] KOS163 dispersant: 1.0 part

[0190] BYK-323 leveling agent: 1.0 part

[0191] KMT-4542 antisettling agent: 1.0 part.

[0192] (2) Triple-period minimal surface structure model: A triple-period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate is as follows: Figure 7 As shown, it consists of a smooth transition from the inlet Gyroid to the outlet Schwarz composite. The solid part is formed by thickening and solidifying the Gyroid and Schwarz curved surfaces to obtain a dual-channel structure (thin-wall type).

[0193] Gyroid surface formula: cos(x)⋅sin(y)+cos(y)⋅sin(z)+cos(z)⋅sin(x)=a

[0194] Schwarz surface formula: cos(2πx)+cos(2πy)+cos(2πz)=a (where a=10).

[0195] (3) 3D printing: Using a DLP 3D printer, the ceramic slurry in step (1) is used as raw material, and the triple period minimal surface structure model generated in step (2) is photopolymerized and 3D printed. The printing process parameters are set as follows: ultraviolet light wavelength 405 nm, exposure intensity 50 mW / cm², printing layer thickness 0.035 mm, and single layer exposure time 30 s. After the printing is completed, it is cleaned and dried with isopropanol to obtain a porous silicon carbide green body.

[0196] (4) The porous silicon carbide green body in step (3) is thermally degreased at 600 °C under nitrogen (N2) protection for 5 h to obtain the porous silicon carbide preform.

[0197] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 1450 °C to achieve densification. The holding time is 2 h to obtain a porous silicon carbide medium plate. SiC phase content: 75 wt%.

[0198] Gyroid-Schwarz structural parameters:

[0199] Pore ​​size: uniform 10 mm; Porosity: uniform 80%

[0200] Dimensions: Flat plate 120 mm × 80 mm × 30 mm (thickness direction is gas flow direction);

[0201] Strength: Compressive strength 10.6 MPa (measured value).

[0202] (6) Combustion performance test:

[0203] Surface power density: 1100 kW / m 2

[0204] Emission targets: NOx = 3.0 mg / Nm³ at an equivalence ratio φ = 0.9 @ 1000 ℃.

[0205] Thermal shock cycling: No cracking after ≥3000 cycles of hot and cold cycling at ΔT=1000 ℃.

[0206] Example 7

[0207] A silicon carbide porous combustion medium plate and a porous medium burner, wherein the silicon carbide porous combustion medium plate has a single iWP structure.

[0208] (1) Preparation of printing slurry: All raw materials are ball-milled and mixed evenly for 2 hours according to the following slurry formula to prepare slurry. The properties of the prepared slurry are: solid content 54 vol%, viscosity 7.9 Pa·s @30 s⁻¹;

[0209] Slurry formulation (by mass parts): Same as Example 5.

[0210] (2) Triple period minimal surface structure model: The triple period minimal surface structure model was designed using 3D design software, exported in STL format, and imported into the 3D printer. The geometric model of the silicon carbide porous combustion medium plate consists of a single iWP surface structure. The solid part is obtained by thickening the iWP surface to form a dual-channel structure (thin-wall type).

[0211] iWP surface formula: cos(2πx)+cos(2πy)+cos(2πz)+cos(2πx)cos(2πy)cos(2πz)=a

[0212] (Where a=12).

[0213] (3) 3D printing: Same as Example 5.

[0214] (4) The porous silicon carbide green body in step (3) is thermally degreased at 850 °C under the protection of high-purity argon (Ar) for 4 h to obtain the porous silicon carbide preform.

[0215] (5) The porous silicon carbide preform in step (4) is sintered under vacuum at 1550 °C to achieve densification. The holding time is 3 h to obtain a porous silicon carbide medium plate. SiC phase content: 79 wt%.

[0216] iWP structural parameters:

[0217] Pore ​​size: uniform 12 mm; Porosity: uniform 90%;

[0218] Dimensions: Flat plate 120 mm × 80 mm × 18 mm (thickness direction is gas flow direction);

[0219] Strength: Compressive strength 16.9 MPa (measured value).

[0220] (6) Combustion performance test:

[0221] Surface power density: 1200 kW / m 2

[0222] Emission targets: NOx = 12.3 mg / Nm³ at an equivalence ratio φ = 0.8 @ 1000 ℃.

[0223] Thermal shock cycling: No cracking after ≥1200 cycles of hot and cold cycling at ΔT=1000 ℃.

[0224] Comparative Example 1

[0225] A random foamed alumina flat plate:

[0226] Alumina flat plates were prepared by the replication foam method: polyurethane foam was impregnated with alumina slurry, dried, and then sintered at 1650℃ for 2 h.

[0227] Its structural type is: random foam structure; pore size: average 5 mm; porosity: uniform 80%;

[0228] Dimensions: 120 mm × 80 mm × 18 mm

[0229] Strength: Compressive strength 2.8 MPa (measured value)

[0230] Combustion performance test: Surface power density can reach 750 kW / m² 2 The average NOx concentration is 36 ppm, and the service life under thermal cycling at an operating temperature of 1200℃ is less than 200 cycles.

[0231] Compared with the embodiments of the present invention, the material is alumina, which has low thermal conductivity, insufficient heat feedback, and reduced surface power density; the mechanical properties of alumina are worse than those of silicon carbide; the random foam structure has high flow resistance; the pore structure is uneven, which easily leads to thermal stress concentration and poor panel life.

[0232] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0233] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A silicon carbide porous combustion medium plate, characterized in that, The silicon carbide porous combustion medium plate includes a single-channel structure or a dual-channel structure; the dual-channel structure is a thickened, solidified triple-periodic minimal surface structure; the single-channel structure includes two independent subspaces formed by the triple-periodic minimal surface structure, and one of the subspaces is a solidified single channel; the triple-periodic minimal surface structure includes one or more three-dimensional continuous triple-periodic minimal surfaces; the pore size of the silicon carbide porous combustion medium plate ranges from 3 to 12 mm, with uniform pore size, or a nonlinear gradient pore size along the plate thickness direction from the inlet end to the outlet end, with a pore size gradient change rate of 0.1 to 1 mm / mm; the porosity of the silicon carbide porous combustion medium plate ranges from 70% to 90%, with uniform porosity, or a gradient porosity that gradually changes from the inlet end to the outlet end along the plate thickness direction, with a porosity gradient change rate ≤ 2% / mm.

2. The silicon carbide porous combustion medium plate according to claim 1, characterized in that, The silicon carbide porous combustion medium plate is made of reaction-sintered silicon carbide, with a silicon carbide solid content greater than 75 wt%.

3. The method for preparing the silicon carbide porous combustion medium plate according to any one of claims 1 to 2, characterized in that, Specifically, the following steps are included: (1) Prepare a slurry containing silicon carbide; (2) Design a geometric model having one or more three-dimensional continuous triple periodic minimal surface structures; the geometric model includes one or more combinations of Gyroid, Diamond, Schwarz, and iWP triple periodic minimal surface structures; (3) 3D printing: Using a DLP or SLA 3D printer, the slurry in step (1) is used as raw material, and the geometric model generated in step (2) is photopolymerized and 3D printed. After printing, the model is cleaned and dried to obtain a porous silicon carbide green body. (4) Pyrolysis: The porous silicon carbide green body in step (3) is pyrolyzed at 600℃~900℃ under vacuum or inert gas protection for 1~10 h to obtain a porous silicon carbide preform. (5) Sintering: The porous silicon carbide preform in step (4) is sintered under vacuum at 1450℃~2000℃ to achieve densification, and the holding time is 0.5h~5h.

4. The preparation method according to claim 3, characterized in that, The formula for the Gyroid surface is: cos(x)·sin(y)+cos(y)·sin(z)+cos(z)·sin(x)=a The formula for the Diamond surface is: sin(x)·sin(y)·sin(z)+sin(x)·cos(y)·cos(z)+cos(x)·sin(y)·cos(z)+cos(x)·cos(y)·sin(z)=a The Schwarz surface formula is as follows: cos(2πx)+cos(2πy)+cos(2πz)=a The iWP surface formula is: cos(2πx)+cos(2πy)+cos(2πz)+cos(2πx)cos(2πy)cos(2πz)=a Where a is a constant related to the lattice size.

5. The preparation method according to claim 3, characterized in that, Step (1) The slurry includes the following raw materials by mass parts: 30-80 parts of silicon carbide powder, 10-50 parts of carbon source, 20-80 parts of photosensitive resin, as well as photoinitiator, dispersant, leveling agent and anti-settling agent; The photoinitiator is added at 1% to 5% of the total mass of the photosensitive resin, the dispersant is added at 0.5% to 3% of the mass of the silicon carbide powder, the leveling agent is added at 0.5% to 2% of the mass of the silicon carbide powder, and the anti-settling agent is added at 0.5% to 2% of the mass of the silicon carbide powder.

6. The preparation method according to claim 5, characterized in that, The median diameter D of the silicon carbide powder 50 = 5~20μm.

7. The preparation method according to claim 5, characterized in that, The carbon source includes one or more of phenolic resin, diamond, carbon black, cellulose, and chopped carbon fibers, wherein the median diameter D of phenolic resin, diamond, carbon black, and cellulose is... 50 =0.5~5 μm, short-cut carbon fiber length 1~5 μm; The photosensitive resin includes one or more of the following: ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, epoxidized soybean oil acrylate, aliphatic polyurethane acrylate, modified polyurethane acrylate, aromatic polyurethane acrylate, bisphenol A epoxy acrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane ethoxylated triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated neopentyl glycol diacrylate, dipropylene glycol diacrylate, cyclotrimethylolpropane methyl acetal acrylate, isobornyl acrylate, hydroxyethyl acrylate, and hydroxyethyl methacrylate. The photoinitiator includes one or more of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-isopropylthioxanthone, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, and bis(1-(2,4-difluorophenyl)-3-pyrrolithium)titanium oxide; The dispersant includes one or more of BYK-108, BYK-180, KOS163, KOS110, KOS2400, 17000, and K-271; The leveling agent includes one or more of BYK-323, BYK-333, BYK-354, H421, LS3003, DH-4072, AKN-1181, and AKN-1035; The anti-settling agent includes one or more of KMT-4542, DH-6900, BYK-410, K-635, and AKN-7020.

8. The preparation method according to claim 3, characterized in that, For DLP printing, the printing layer thickness is 20~100μm and the exposure intensity is 40 mW / cm²~60 mW / cm²; for SLA 3D printing, the printing layer thickness is 20~100μm and the laser power is 500~3000 mW.

9. A silicon carbide porous media burner, characterized in that, The plate comprises a silicon carbide porous combustion medium obtained by the preparation method according to any one of claims 3 to 8.

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