Patent ID: 12189362

DETAILED DESCRIPTION

Before discussing the embodiments in any more detail, first an overview will be provided. Embodiments provide a technique for reliably producing a component of an abatement apparatus having predefined operating characteristics. A 3D model of the component is generated and characteristics of that component (such as properties of fluid flow into, out and/or through the component, structural, thermal, chemical and/or physical requirements of the component, and the like) are defined. These characteristics are used when meshing the 3D model to provide finite element representation of the component which incorporates those characteristics. In other words, when creating the finite element representation of the component, characteristics of the component can be specified in order to influence the extent to which each finite element is filled and by what. For example, the porosity of a surface of a region of the component can be controlled by controlling the number of filled faces of the finite elements making up that surface and/or by varying the thickness of the edges joining vertices of those faces. Likewise, the permeability of a region of the component can be controlled by varying the degree to which finite elements in that region are filled. Again, such filling can be achieved by varying the thickness of the edges joining vertices of the finite elements. Whole structural members can be formed by filling finite elements to define that structural member, such as a ceiling face, a rib or a flange and the like. It is possible to vary physical or chemical properties of different regions of the component by controlling the material used to fabricate the component. For example, highly conductive materials may be used in some regions and highly insulating materials in others. Likewise, mechanically strong materials may be used in some regions and less strong materials in others. This finite element representation can then be fabricated in order to produce the component.

The component is typically constructed from the finite element representation using additive manufacturing as the finite element representation provides modular building-blocks which are well-suited to such additive manufacturing techniques.

FIG.1is a flow chart showing the main steps of one embodiment. As will be apparent, although the steps are shown for ease of description as being sequential, many of the steps may be performed iteratively or in parallel, depending on the implementation used. The processing steps are typically performed by a computer (not shown) programmed to perform those steps. The fabrication is typically performed by an additive manufacturing apparatus (not shown) operating under the control of a computer (not shown).

3D Model Creation

At step S1, a 3D spatial model of a component of an abatement apparatus is created using a model processor running on the computer. It will be appreciated that a variety of different modelling techniques, representations or formats may be used to represent the component in 3D space. For example, surfaces, edges, vertices and/or points defining the shape of the component may be specified in the 3D spatial model. Schematic illustrations of illustrating such models are shown inFIGS.2A and2B. InFIG.2A, (1) illustrates non-porous sealing surfaces/edges; (2) illustrates a smooth inner surface; (3) illustrates an outer surface with selective porosity; (4) illustrates a compositional gradient with catalytic material buried in the structure and selective “binding” to minimise radiative heat transfer; (5) illustrates a solid; (6) illustrates a porous material; and (7) indicates a nozzle.FIG.2Bis bell-shaped and (8) indicates a graded porosity. The models may be of a part of an abatement apparatus such as a sleeve for a reaction chamber. The models may also be of a larger part which would normally be formed from separate components such as a combined reaction chamber and head assembly.

Meshing

At step S2, the 3D spatial model is meshed by a meshing processor using one or more different finite elements or cellular structures. Again, it will be appreciated that a variety of different techniques may be used to perform such meshing. The cellular structures are typically formed from polyhedrons having polygons joined at their edges. When meshing, more than one type of polyhedron may be used. Furthermore, the size of the polyhedrons used may be varied as required. The cellular structures may be selected based on those best-suited to the additive manufacturing technique to be used to fabricate the component.

When meshing, terminal constraints may be defined which may specify that the cellular structures are not permitted to extend beyond a surface or boundary of the 3D spatial model. In order to achieve this, the meshing processor may select combinations of different cellular structures and/or vary their size to achieve this. In some circumstances, the meshing processor may truncate or sub-divide the cellular structures to achieve those terminal constraints.

Once the meshing processor has filled the 3D spatial model with cellular structures then processing proceeds to step S3.

Characteristic Allocation

At step S3, characteristics for all or, more typically, a part of the component are allocated. For example, a porosity in a particular region may be defined or a porosity gradient across a region may be defined. Similarly, a permeability through a region or a permeability gradient through a region may be defined. Likewise, mechanical strength or thermal conductivity of regions may be defined. In some situations, the chemical properties or materials in a particular may be defined.

With these characteristics, the meshing processor determines the material required for each cellular structure, together with how that cellular structure is to be filled. For example, should low porosity be required in a region, then the cellular structures in that region can be filled and/or have the faces forming a surface of the component filled and/or have a greater thickness of the edges defining those cellular structures to reduce porosity in that region. Conversely, should higher porosity be required, then the cellular structures in that region can be unfilled and/or have the faces forming a surface of the component unfilled and/or have a reduced thickness of the edges defining those cellular structures to increase porosity in that region. A similar approach can be used for cellular structures within the body of the component to adjust permeability through the region of that body. Likewise, the thermal properties can be adjusted by selective filling of faces (or blinding) to adjust radiative heat transfer.

These techniques can be used to create solid structures within the component to provide, for example, sealing surfaces or edges, strengthening struts, connecting flanges, screw-threads, through-bores or other mechanical structures, as well as providing structures to provide the correct thermal properties or thermal paths for the component.

Where more than one material is available for forming the cellular structures, these materials may also be specified by the meshing processor to achieve those characteristics. Likewise, different materials may be specified to provide the correct chemical properties at different locations in the component.

At step S4, an optimized mesh is defined. Each cellular element in the optimized mesh is specified as being filled or not and, if filled, the extent of filling. Where different materials can be specified, each cellular element in the optimized defined to be formed from a specified material.

At step S5, the component is fabricated using an additive manufacturing technique such as, for example, 3D printing.

Embodiments provide a printed cylinder burner structure with controlled porosity and geometry such that the exit surface is smooth, the burner is robust, cleanable, washable and suitable for gas flow (methane/propane etc.). On the back side (where gas enters) there is a cellular structure which can be designed/tailored to give the desired gas flow. An inner blinded surface can be also included to control thermal conductivity and heat loss by radiation. A further design addition is to have solid areas (typically rings at the top and bottom/sealing surfaces) which can insert and seal directly to the plenum. With these design considerations the overall geometry of the structure can be changed whereby we can we have a bell shaped profile (like a rocket burner), or square or trapezoid shaped. Geometric features can be added to control the flow of gas i.e. make it turbulent or laminar where required. Another feature of the burner is to have a graded composition (material) whereby this can be used to control catalytic properties i.e. noble metals in the middle of the burner thickness or surface, for thermal and chemical reasons (ceramic or outside to metal on inside).

Embodiments provide features i.e. multi-functional layers, interface with plenum, which are not possible to make conventionally as they can't be cast or made from sheets. A key advantage is that the structure/geometry/composition (material density, lattice) and flow paths can be controlled. This means that burner nozzles can be placed where we please and the design iterated without cost implication/difficulty to have to re-cast/manufacture conventionally. In embodiments, algorithms are used for foam or cellular geometry/lattice structure. The designs can be customised for different applications i.e. output volumes, gas loading, etc based on requirements.

Embodiments provide tailored overall shape/geometry, custom size depending on application, multi-layer configuration, lattice/foam structure variations, outer skin porosity (geometrical shapes e.g. circular, triangular, hex mesh spacing grid positioning). The materials used—metallic, ceramic, polymer alloys—could all be varied. Nozzle configuration, positions and quantity can be varied. Internal features to shroud nozzles, direct flow and facilitate turbulent and laminar flow can be provided where required. Internal channels can be incorporated to extract/manage heat. Stiffening structure/ribs can be incorporated to give strength where required.

Embodiment provide a technique for 3D printing components of an abatement apparatus such as burner liners and induction heat susceptors. The technique can be used to produce a porous gas control element for use either as a foraminous burner or a susceptor for an induction heated abatement system.

The technique comprises: 1) Modelling the solid shape in a 3D computer aided design (CAD) environment, e.g. Catia; 2) Exporting the shape in a transferable format e.g. STEP file; 3) Importing into a meshing package that creates a reticulated foam replica of the solid shape; 4) Exporting the foam shape in a transferable format e.g. STEP file for 3D printing.

The meshing package would typically accept “high-level” parameters such as fibre thickness, porosity, pores per inch to create the basic structure. The mesh scheme (cubic, tetrahedral etc.) is selectable or one type favoured/optimised. The downstream termination would typically be continuous, i.e. not having dangling ends. Fully occluded areas of the upstream face would typically be defined as mounting surfaces for fitting into fixtures. Partial occlusion of the upstream face, by closing selected cell faces would typically be used to control the flow and hence firing rate of parts of the burner. Different zones may be defined as having different porosity.

Materials of interest for printing: Fe—Cr-AI-Y “fecralloy”, 314 Stainless Steel would be basic materials for burners. Higher-temperature materials such as 0Cr27AI7Mo2 or “ferromolybdenum” for induction heating.

In embodiments, the porous shape is loaded into a computational fluid dynamics (CFD) package, for example Star CCM+ and then to “mesh the mesh” in order to model the flow characteristics of the porous material. This would be particularly suited to understanding how the flow develops downstream of a selectively-occluded face. Likewise, modelling the back-face temperature under “real conditions” in a burner could be useful. Together, these pieces of information allow optimisation of the thickness of the porous layer, ultimately economising on material.

Embodiments provide a burner liner having one or more of: A smooth downstream surface; No dangling fibre ends; Robust, cleanable, washable; Suitable for a surface-firing rate range with residual oxygen; Back-face selectively-blinded to give controlled flow-rate/surface firing rate, also jointing or sealing surfaces top and bottom (for a cylindrical burner); Refinements to flow channels to produce a bell-mouth; Controlled back-face temperature through conductivity/opacity control; selective blinding in a regular pattern through the structure so as to achieve line-of-sight optical-blindness, thereby minimising radiative heat transfer.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.