EP0106761B2 - Plate with honeycombed radiating face for a radiant burner - Google Patents

Abstract

PCT No. PCT/FR83/00205 Sec. 371 Date Jun. 5, 1984 Sec. 102(e) Date Jun. 5, 1984 PCT Filed Oct. 11, 1983 PCT Pub. No. WO84/01613 PCT Pub. Date Apr. 26, 1984.The alveoli of a plate having an alveolar radiating face are provided in the front face of the plate according to a family of patterns regularly distributed in rows, generally different, rows of holes, all the holes existing in the plate opening out totally or partially and in all regular distribution conditions of staggered, checkered or offset holes in the rows, into corresponding alveoli each containing a central hole; the base of the alveoli has an hexagonal or quadrilateral shape, regular or irregular, and the alveoli may have depth profiles which correspond to revolution volumes or facet volumes.

Description

The present invention relates to a wafer with a honeycombed radiant face for a radiant burner.

In general, plates for radiant burners have rows of holes passing through them and serving to channel the fuel-oxidant mixture from the rear face of the plate to the radiating face. To increase the radiating power of the wafer, it has already been envisaged in the prior art to form, in the front face of the wafer, cavities or cells grouping several holes. Indeed, a hole which has been truncated before opening into the front face of the wafer distributes the flame which it produces so that it heats the surrounding surfaces of the cavity or cell. Such arrangements were known for example from the subject of Belgian patent No 710536 which had a somewhat irregular arrangement of the holes, then from that of French patent No 1 570 721 which had the advantage of a regular arrangement .

However, in the wafers known by this latter patent, the cells formed leave a number of holes between them which do not thus participate in the increase in the radiating power of the wafer.

The object of the invention is to remedy the aforementioned drawbacks, and others, of known embodiments, by means of a plate with a dimpled front face for a radiant burner, formed of a ceramic material, comprising rows of holes. passage of oxidant-fuel mixture, and in which it is possible to provide cells regularly distributed in rows and involving all the holes existing in the wafer.

Maximum heat transfer is thus obtained between the flames and the wafer by increasing the contact surface with the material of the wafer, all the combustion products sweeping the walls of the cells.

This results in a rise in temperature of these walls and, consequently, for equal power consumption, a significant increase in the radiated power, therefore in the radiation efficiency.

In addition, a reduction in conduction losses towards the rear of the wafer is obtained, the quantity of material existing between two adjacent cells being reduced to a minimum and also the emisivity being increased thanks to the particularly pronounced relief of the radiating face of the brochure.

• Etant donné une plaquette comportant plusieurs rangées de trous qui sont répartis conformément à un quinconçage comme cela sera précisé par la suite, il faut d'abord définir la répartition des bases des alvéoles sur la face frontale de la plaquette par rapport à ces rangées. On choisit un trou quelconque d'une rangée : on considère six trous voisins de ce trou quelconque, et à partir du centre de ce trou quelconque, on trace des vecteurs joignant ce centre aux centres des trous voisins. On obtient ainsi six vecteurs caractérisés par leur direction, leur sens et leur longueur. La figure formée par les segments joignant les extrémités desdits vecteurs définit ce qu'on appellera dans la suite la base théorique d'alvéole ; cette figure a une forme d'hexagone. Dans cette figure, si on considère un vecteur donné, il existe toujours, par rapport à ce vecteur, un vecteur placé à droite, un vecteur placé à gauche et un vecteur placé à l'opposé, qui sera appelé dans la suite "vecteur contraire".

To solve the problem in accordance with the present invention, the following geometrical considerations are used:

• Given a plate comprising several rows of holes which are distributed in accordance with a quinconcing as will be specified below, it is first necessary to define the distribution of the bases of the cells on the front face of the plate with respect to these rows. We choose an arbitrary hole in a row: we consider six holes neighboring this arbitrary hole, and starting from the center of this arbitrary hole, we draw vectors joining this center to the centers of the neighboring holes. Six vectors are thus obtained, characterized by their direction, their direction and their length. The figure formed by the segments joining the ends of said vectors defines what will be called hereinafter the theoretical cell base; this figure has a hexagon shape. In this figure, if we consider a given vector, there always exists, compared to this vector, a vector placed on the right, a vector placed on the left and a vector placed on the opposite, which will be called hereinafter "opposite vector ".

Thus, the invention relates to a plate for a radiant burner, as defined in claim 1.

• - on définit une base théorique d'alvéole en traçant à partir du centre d'un trou donné six vecteurs joignant ce centre aux centres des six trous voisins choisis et en joignant les extrémités de ces six vecteurs ainsi choisis, à chacun desquels sont toujours associés un vecteur de droite, un vecteur de gauche et un vecteur contraire,
• - on trace à partir de l'extrémité de chacun de ces vecteurs choisis, un vecteur de même longueur orienté en sens inverse à leur vecteur contraire associé,
• - on trace, à partir de l'extrémité de chacun de ces nouveaux vecteurs, soit chaque fois un vecteur identique à leur vecteur de droite associé, soit chaque fois un vecteur identique à leur vecteur de gauche associé, les points correspondant aux extrémités des vecteurs cités en dernier définissant, dans chacune des deux possibilités ainsi créées, les centres des bases théoriques des alvéoles adjacents à celui de départ, semblables et de même orientation, cette orientation étant définie par celle de la plus grande diagonale passant par le centre de l'alvéole, et
• - en opérant ensuite de proche en proche, on détermine l'un des deux motifs de répartition régulière d'alvéoles selon le choix de l'une ou l'autre des deux possibilités.

Thus, in the plate according to the invention, with a dimpled front face for a radiant burner, formed of a ceramic material and comprising rows of holes for passage of oxidizer-fuel mixture, the dimples are formed in the radiating front face of the plate. according to a family of patterns of regular distribution in rows, generally different from the rows of holes, all the holes existing in the plate each open in whole or in part in the corresponding cells each containing a central hole, and the family of patterns of regular distribution of cells in the radiating face of the wafer is determined as follows:

• - we define a theoretical cell base by drawing from the center of a given hole six vectors joining this center to the centers of the six chosen neighboring holes and joining the ends of these six vectors thus chosen, to each of which are always associated a right vector, a left vector and an opposite vector,
• - a vector of the same length oriented in the opposite direction to their associated opposite vector is drawn from the end of each of these chosen vectors,
• - we trace, from the end of each of these new vectors, either each time a vector identical to their associated right vector, or each time a vector identical to their associated left vector, the points corresponding to the ends of the vectors cited last defining, in each of the two possibilities thus created, the centers of the theoretical bases of the alveoli adjacent to that of departure, similar and of the same orientation, this orientation being defined by that of the largest diagonal passing through the center of the cell, and
• - then operating step by step, one of the two distribution patterns is determined. regular alveoli according to the choice of one or the other of the two possibilities.

• - la base théorique des alvéoles a une forme d'hexagone régulier ;
• - la base réelle des alvéoles est définie par un polygone semblable à celui de la base théorique, ledit polygone devant couper ou contenir chacun des trous dont les centres sont situés sur le pourtour de la base théorique d'alvéole ;
• - en profondeur, chaque alvéole a un profil cylindrique, conique, hémisphérique ou un autre volume de révolution ;
• - chaque alvéole a en profondeur un profil à facettes ;
• - chaque alvéole a en profondeur un profil constitué par un ou plusieurs volumes de révolution complets ou tronqués, par exemple un profil cylindroconique ;
• - l'angle au sommet du fond d'alvéole, partant du centre du trou central dudit alvéole, est compris entre environ 30 et 180⁰ ;
• - les orifices ménagés dans la plaquette sont de préférence cylindriques et ont un diamètre compris entre environ 0,4 et 5 mm ;
• - la profondeur des alvéoles est comprise entre 0,5 mm et 3/5 de l'épaisseur de plaquette ;
• - le diamètre équivalent de la base théorique de l'alvéole est défini par la somme des diamètres de deux trous voisins et de l'épaisseur de matière entre ces deux trous ;
• - pour reculer la limite de rentrée de combustion par augmentation de la vitesse d'écoulement du mélange combustible-comburant, on bouche un ou plusieurs orifices de chaque alvéole.

According to other features of the invention:

• - the theoretical basis of the alveoli has a regular hexagon shape;
• - The actual base of the cells is defined by a polygon similar to that of the theoretical base, said polygon having to cut or contain each of the holes whose centers are located around the periphery of the theoretical cell base;
• - in depth, each cell has a cylindrical, conical, hemispherical profile or another volume of revolution;
• - each cell has a deep faceted profile;
• - Each cell has a depth profile consisting of one or more complete or truncated volumes of revolution, for example a cylindroconical profile;
• - The angle at the top of the cell bottom, starting from the center of the central hole of said cell, is between approximately 30 and 180 ⁰ ;
• the orifices made in the wafer are preferably cylindrical and have a diameter of between approximately 0.4 and 5 mm;
• - the depth of the cells is between 0.5 mm and 3/5 of the thickness of the insert;
• - The equivalent diameter of the theoretical base of the cell is defined by the sum of the diameters of two neighboring holes and the thickness of material between these two holes;
• - To reduce the combustion re-entry limit by increasing the flow speed of the fuel-oxidant mixture, one or more orifices of each cell are plugged.

• - la fig. 1 est une vue en plan partielle de la face rayonnante d'une plaquette de brûleur radiant, mettant en évidence le processus de détermination des motifs de distribution régulière des alvéoles théoriques dans la plaquette,
• - la fig. 2 montre les répartitions d'alvéoles théoriques que l'on peut obtenir dans le cas d'un quinconçage équilatéral des trous des rangées,
• - les fig. 3 et 4 montrent, pour une même disposition des rangées de trous et une même base théorique d'alvéole, deux motifs d'alvéoles hexagonaux réels qu'il est possible d'obtenir conformément à la présente invention,
• - les fig. 5 et 6 représentent deux coupes transversales de plaquettes des figures 3 et4, faites respectivement suivant les lignes X-X et Y-Y de façon à montrer le profil en profondeur des alvéoles, et
• - les fig. 7A à 7E sont des coupes transversales de plaquettes montrant différents profils en profondeur des alvéoles.

Other advantages and characteristics of the invention will be highlighted in the following description given by way of nonlimiting example, with reference to the appended drawings in which:

• - fig. 1 is a partial plan view of the radiating face of a radiant burner plate, highlighting the process of determining the patterns of regular distribution of the theoretical cells in the plate,
• - fig. 2 shows the theoretical cell distributions that can be obtained in the case of equilateral quinconcing of the holes in the rows,
• - fig. 3 and 4 show, for the same arrangement of the rows of holes and the same theoretical cell base, two real hexagonal cell patterns which it is possible to obtain in accordance with the present invention,
• - fig. 5 and 6 represent two transverse sections of plates of FIGS. 3 and 4, made respectively along lines XX and YY so as to show the profile in depth of the cells, and
• - fig. 7A to 7E are cross sections of platelets showing different depth profiles of the cells.

In Figure 1, there is shown, in plan view, part of a plate for radiant burner having several rows of holes designated by T and we have highlighted the geometric processes which allow to obtain the patterns of regular distribution cells in the radiating face of the wafer according to the present invention.

For a given hole, such as the one whose center is designated by O, we can consider that there are six neighboring holes whose centers are respectively designated by A, B, C, D, E and F. To define the positions well relative to the holes, we draw, from the center O of the given hole of the vectors connecting this center to the centers of the neighboring holes, which gives the vectors,,,, and

The cells to be provided in the wafer are defined by their theoretical base, that is to say their geometric base, and their depth profile. The actual shape of the cells is then determined from the theoretical profile, taking into account the conditions of implementation, such as the technological conditions of machining, molding and other shaping.

In the exemplary embodiment of FIG. 1, the extreme points of the six vectors are connected together, which gives the theoretical base of the cell a shape of an AV hexagon as indicated in FIG. 1.

We will now describe how the different patterns of cell distribution are obtained.

We start from a given vector p _A. For this vector ^p _A , there is, in all cases, a vector on the right, a vector on the left and a vector placed opposite, which is called the vector against the given vector.

qui est parallèle de même longueur, et de sens opposé au vecteur contraire . Puis, à partir du point A₁, on trace un vecteur

qui est parallèle, de même longueur et de même sens que le vecteur de droite . Le point 0₁ ainsi obtenu est le centre de la base théorique d'un alvéole AV₁.From the end A of the vector o _A , we draw a vector

which is parallel with the same length, and opposite direction to the opposite vector. Then, starting from point A ₁ , we draw a vector

which is parallel, of the same length and in the same direction as the vector on the right. The point 0 ₁ thus obtained is the center of the theoretical base of a cell AV ₁ .

By operating in the same way for the five other vectors starting from the point O, one finally obtains for a central theoretical base AV six bases neighboring theory and, then working step by step, we obtain in the whole of the front plate of the wafer a pattern of distribution of cells which involves all the holes each emerging in whole or in part in a cell and which can be established for any pattern of distribution of said holes, that is to say for any pattern of hardware, or grid, or any offset.

The distribution pattern corresponding to point 0 ₁ is not unique. Indeed, from point A ₁ , we can draw a parallel vector, of the same length and in the same direction as the vector on the left, which gives the vector

This point O ′ _i constitutes the center of a theoretical base of a cell, designated by AV ′ ₁ in FIG. 1 and which corresponds to another pattern of distribution of hexagonal cells.

In FIG. 2, the patterns of distribution of cells which can be obtained are shown, for a distribution of holes corresponding to an equilateral quinconcing in which cells are obtained in the form of a regular hexagon. We designated by AV1 to AV ₇ , and by solid lines, the cells of the type obtained from the right vector and by AV ' _i to AV' ₄ , and by dashed lines, the cells of the patterns obtained. from the vector on the left.

Once we have determined the theoretical patterns of cells, we must define their real shapes and we then involve thermal and technological considerations. The inserts according to the invention are manufactured by pressure molding and it is obvious that the distribution and the shape of the cells have an influence on the manufacturing process since they condition the production of the corresponding parts of the mold, which must have the efficiency and optimal reliability while being as low a cost price as possible.

We will give in the following some examples of embodiment of the plate according to the invention. Thus, as seen in Figs. 3 and 4 corresponding to a distribution of the holes with equilateral quixing in which there is for the real base of the cell a regular hexagon shape, the pattern in FIG. 3 is obtained by the plot involving the vector on the left while the pattern in FIG. 4 is obtained by the plot involving the vector on the right. A comparison of FIGS. 3 and 4 with FIG. 2, which gives the distribution patterns of the theoretical bases of cells in the same case, shows that the real hexagons have been slightly turned around their centers relative to the theoretical hexagons, this angular offset being justified by machining considerations. In the example in question, the cells have a depth profile which is highlighted in FIGS. 5 and 6, FIG. 5 being a cross section taken along the line X-X of FIG. 3 while fig. 6 is a cross section taken along the line Y-Y of FIG. 4. Each cell is thus delimited, from the base in the shape of a regular hexagon, by curved facets starting from the sides of the hexagon and ending at a bottom defined by a plane located at a distance H from the front face of plate, the intersections of the facets with said bottom plane defining small hexagons, visible in FIGS. 3 and 4 and respectively circumscribed to the central holes of the cells, visible in T1, in FIGS. 3, 4,5,6.

• - usinage dans la masse par fraisage ou par électro-érosion par exemple,
• - moulage en cire perdue d'éléments dont la forme positive correspond au profil négatif des alvéoles et fixation de ces éléments dans une plaque de poinçon, un peu à la façon des ailettes de turbines.

To form these faceted cells, a mold punch must be produced provided with projecting parts corresponding to said cells. There are different solutions for making such a punch, including:

• - machining in the mass by milling or by electro-erosion for example,
• - molding in lost wax of elements whose positive shape corresponds to the negative profile of the cells and fixing of these elements in a punch plate, a little like the blades of turbines.

In the example considered, the form milling process was adopted and, to allow the cutter to pass, the solution consisting of angularly shifting the basic hexagons of the cells was adopted.

In FIGS. 7A to 7E, some examples of depth profiles have been indicated which it is possible to adopt for the cells, in particular a hemispherical profile, a truncated conical profile, a stepped cylindrical profile and a simple cylindrical profile. It is possible to envisage other profiles, for example profiles of surfaces of revolution such as paraboloids or composite profiles such as cylindro-conical.

Different parameters can be used to determine the depth profile. In particular, the angle at the top of the bottom of the cell, starting from the center of the central hole of said cell, is between approximately 30 and 180 °. The depth of the cells should preferably be between 0.5 mm and 3/5 of the thickness of the insert. Also, the orifices provided in the wafer are preferably cylindrical and have a diameter of between approximately 0.4 and 5 mm. The equivalent diameter of the theoretical cell base is defined by the sum of the diameters of two neighboring holes and the thickness of material between these two holes.

In addition, it should be noted that, in order to increase the speed of flow of the fuel-oxidant mixture in the holes and thus reduce the limit of re-entry of combustion, it is possible to plug one or more orifices in each cell.

Claims (4)

1. Plate for radiant burner, formed from a ceramic material and provided with holes for the passage of oxidant/fuel mixture corresponding to respective ducts passing through the plate, in which the said holes for the passage of oxidant/fuel mixture, which are formed regularly in the plate, are arranged in a totally homogeneous configuration in parallel rows arranged as staggered rows, the spacing between any two adjacent passage holes always being the same, having a honeycomb system (AV, AV₁) in the form of regular hexagons hollowed out of the combustion face of the said plate, each honeycomb cell having a central passage hole (T_i) and six peripheral passage holes each connected geometrically to the central passage hole by radius vectors

this plate being characterized in that each passage hole is located at least partly in a honeycomb cell, and the honeycomb cells are distributed such that each honeycomb cell is deduced by translation from another in accordance with a vector (₁ ) corresponding to the geometric sum of a vector equal to the geometric double of a radius vector (OA ) and the immediately neighbouring radius vector to its right or left ( ), of the other honeycomb cell, the honeycomb cells are pivoted by a predetermined angle about the central passage hole with respect to the hexagon resulting from connecting to one another outside points of the said radius vectors connecting the central passage hole to the peripheral passage holes, and each peripheral passage hole straddles an external edge of the hexagon formed by the honeycomb cell.

2. Plate according to Claim 1, characterized in that at least one passage hole in each honeycomb cell is closed off.

3. Plate according to Claim 1, characterized in that, at least on part of its depth, each honeycomb cell has the profile of a surface of revolution.

4. Plate according to Claim 1, characterized in that each honeycomb cell has a faceted profile.

Images