EP0635677B1 - Flameholder plate for gas burner, method of manufacturing same and burner comprising such plate - Google Patents

Description

The invention relates to a plate flame attachment, usable in particular on gas mixture burners.

We already know plates of this type, level of which we seek to substantially stabilize the flames produced, so as to favor their development without too much fluctuation in the combustion. Other expressions still designate these plates, such as "flame hanging plates" or "combustion grates" (see for example document JP-A-58-205012).

They are made of various materials, such than ceramic or metal, and are usually drilled orifices of suitable size and distribution for allow the passage of gases and their combustion. They are arranged in the gas burner between the distribution and combustion, which they separate.

Among the drawbacks which have been observed on such plates in the burners of the prior art, it may be noted:
first of all, the stabilization of the flames by these plates which is not always satisfactory. We then try to improve this stability somewhat, for example by adapting the trajectory of the mixing jets, or even by providing an additional grid or gas distribution screen inside the distribution chamber; this leads in particular to additional costs and makes the installations more complex. However, this instability of the flames can also generate malfunctions such as possible return of flames inside the distribution chamber, or even excessive production of harmful gases. In addition, the very structure of the existing plates often makes it difficult to significantly modulate the power of the burner.

Such pierced plates still pose problems related to their mounting because they are in fact often made up of several thin plates which must be stacked on top of each other in the burner. That poses adjustment problems between plates and armature a high installation cost.

The object of the invention is to resolve these difficulties thanks to a flame attachment plate improved, notably allowing stabilization efficient and good distribution of the flames over its entire surface, with formation of a flame front substantially uniform, further promoting risk reduction back from flames.

Other advantages of the invention lie in the structure or texture of the hanging plate of flame which, installed in a gas burner, allows particularly during operation, modulation consequent of the power which can itself be important. In addition, the plate according to the invention drives a relatively low pressure drop of around 35 to 50 Pa and promotes limitation of the quantities of gas emitted harmful (oxides of carbon, nitrogen, ...).

The proposed solution consists of a plate with passages crossing it for traffic at through it gases to be burned, the plate of the invention is characterizing in that the wire network (s) looks like a tube flattened knitted fabric comprising one or more sections.

As can be seen, the invention allows in particular, by its structure or texture in yarn (s) to intertwined parts, a passage substantially uniformly gas distributed over the entire surface of the plate, with even spread of the flame created, making it possible in practice (for example in the case of installations heating), advantageously reduce the spacing between the flame attachment zone and the heat exchanger heat often associated with the burner, since the front of flame may be of relatively low height.

In addition, the easy implementation of the net or interlacing consisting of the parts of knitted threads, allows the production of plates easily adaptable to variable forms of burners, at low cost.

The invention also relates to a burner of the general gas mixture type, comprising a distribution supplied with combustion air and gas fuel, communicating with a combustion chamber, with interposition between them of the plate according to the invention.

The plate of the invention can be used in particular for domestic burners, such as, for example, blown air, total premix and blue flame, making possible in particular a large modulation in power, which can, for example, go from '' about 3 to 33 kilowatts, or a power modulation of 1: 11, with a pfd which can range from 225 to 2500 kw / cm ² , approximately.

• on met en forme un réseau d'au moins un fil à parties entrelacées, pour qu'il présente la forme générale d'une plaque, ledit fil résistant à des températures de l'ordre de 1000°C à 1200°C environ,
• et on comprime ce réseau de telle manière que le réseau comprimé conserve, entre ses parties de fil, les passages prévus pour la circulation des gaz.

The invention also relates to a method of manufacturing such a plate, in which:

• a network of at least one wire with interlaced parts is shaped, so that it has the general shape of a plate, said wire withstanding temperatures of the order of about 1000 ° C. to 1200 ° C.,
• and this network is compressed so that the compressed network retains, between its parts of wire, the passages provided for the circulation of gases.

• les figures 1 et 10 montrent, en perspective, deux exemples d'une plaque d'accrochage de flamme conforme à l'invention ;
• la figure 2 montre schématiquement en perspective, un exemple de réalisation de l'ouvrage tricoté à partir duquel peut être obtenue la plaque des figures 1 et 10 ;
• la figure 3 montre un détail de réalisation de l'ouvrage tricoté de la figure 2, à l'endroit du repère III de cette figure ;
• la figure 4 illustre, à plus grande échelle, une possible réalisation de l'entrelacs du réseau ;
• les figures 5 et 6 présentent, en perspective, deux étapes d'un principe possible de réalisation de la plaque de la figure 1, à partir de l'ouvrage tricoté de la figure 2 ;
• la figure 7 présente, toujours en perspective, un autre principe possible de mise en oeuvre de l'ouvrage tricoté ;
• la figure 8 montre, en perspective, une variante supplémentaire de mise en oeuvre de l'ouvrage tricoté ; et
• la figure 9 présente, en coupe verticale médiane, une utilisation possible de la plaque de l'invention, sur un brûleur à mélange de gaz (chauffe-eau par exemple).

Other characteristics and advantages of the invention will appear from the description which follows, given with reference to the appended drawings given solely by way of examples, and in which:

• Figures 1 and 10 show, in perspective, two examples of a flame attachment plate according to the invention;
• Figure 2 shows schematically in perspective, an embodiment of the knitted work from which the plate of Figures 1 and 10 can be obtained;
• Figure 3 shows a detail of the knitted work of Figure 2, at the location of the reference III of this figure;
• FIG. 4 illustrates, on a larger scale, a possible embodiment of the network interlacing;
• Figures 5 and 6 show, in perspective, two steps of a possible principle of realization of the plate of Figure 1, from the knitted work of Figure 2;
• Figure 7 shows, still in perspective, another possible principle of implementation of the knitted work;
• Figure 8 shows, in perspective, an additional variant of implementation of the knitted work; and
• Figure 9 shows, in median vertical section, a possible use of the plate of the invention, on a gas mixture burner (water heater for example).

Referring to Figures 1 and 10, we see a flame attachment plate for mixture burner gas, according to the invention, identified as a whole by reference 1. Preferably substantially planar, this distribution plate or sieve can be shaped by example with a substantially circular section (Figure 1) or rectangular parallelepiped (figure 10), with dimensions adapted to those of the associated burner.

In FIG. 4 in particular, it can be seen that the plate includes, in its constitution, a network 2 of wire (s) flexible (s) 12, with intertwined or entangled parts, providing between them passages 27 or channels passing through the plate for the circulation through it of gases. he appears that the entanglement of the parts of wire (s) of the network, when it is in a compressed state, likewise that the shape, size and position of the passage of gases within the plate, are random and depend on the effort that will have been exerted on the network to compress it.

This network of wire (s) or interlacing 2 presents itself here as a knitted work 10 consisting of at least one thread flexible. In this case, this knitted work is made in one single wire 12 extending continuously between its ends free 12a and 12b (Figure 2). This wire can be made in a ductile metallic material which is easily knitted, such as, for example, two-tenths "304L" stainless steel millimeter in diameter. In any event, the material used to make the plate should preferably keep its characteristics (mechanical in particular) up to high temperatures, around 1000 ° C to 1200 ° C.

From Figures 3 and 4, we see that the wire 12 is sort of "knitted", like knitting a sock, so as to constitute the work 10, which advantageously have the form of a tube. We could however, consider using other crossing modes or known braiding.

In FIG. 3, the diagram is illustrated way in which loops 19 in "Ω" (OMEGA) of wire 12 can be intertwined, delimiting meshes 14, of suitable dimensions. These meshes (corresponding to passages 27 above) being advantageously relatively initially loose, the mesh produced can be easily distorted in different directions at the start of the shaping of the plate.

Figure 4 shows more precisely the interlacing of the sections or parts 15 of the wire, which overlap each other, presenting areas interlacing as referenced in 17, these sections forming "upper" loops 19a which pass through the loops below them 19b, thus delimiting the passages 27. For the clarity of the representation, we have represented these passages of the knitted work in a state relatively loose, these same passages being found distributed throughout the network structure in the state tablet according to shape, size and function layout compression forces exerted.

Now let’s also look at Figures 5 and 6, to describe a first possibility of shaping of the knitted work to obtain the plate sought.

As illustrated in Figure 5, here we started from a knitted work 10 in the form of a cylindrical tube (Figure 2), deformable and compressible. This tube is first of all flattened or flattened along two fold lines 16, 18, both substantially parallel to the longitudinal axis 20 of this tube, the knitted work then having the general shape of a strip 21 of double thickness . (One could however also conceive of making the plate from a work knitted in a single thickness strip). The strip obtained is then wound on itself, from one of its ends 21a. In FIG. 6, it can be seen that the roll 22 formed, of axis 25 substantially perpendicular to the longitudinal axis 46 of the strip, is advantageously produced by tightening the strip well when it is wound on itself. This winding 22 is then compressed substantially uniformly along its axis 25, in the direction of the arrows F _a and F ' _a , and possibly in the case where this compression along the axis 25 is insufficient, also perpendicularly to this axis 25 in the direction of the arrows Fr, until the compressed network constituting the desired plate is obtained such as that of FIG. 1, which compressed network preserves between its parts of wire (s) the passages, although deformed, intended for the circulation of gases . Preferably, the axial compression will first be applied, then, if necessary, the radial compression. It will be noted that here the compression is therefore carried out substantially parallel and perpendicular to the surface of the plate thus formed. The plate, whose orifices 27 for the passage of gases will thus be randomly distributed over its entire surface, will in particular allow effective self-stabilization of the flame.

It will be noted that the compression forces being exercised from the edge of the network, this should cause the formation of a density and porosity plate variables from the center of the plate to its periphery.

Another possibility of achieving this plate is shown in Figure 7, for example to obtain the plate in the form of a substantially quadrilateral in Figure 10. In this case, we can still start from the flattened tubular strip 21 which is then folded on itself to form at least one fold line 32.

Preferably and as illustrated, the strip is folded several times on itself in a stacking direction of the folds 45 in the manner of an accordion, constituting a series of folds of which only the upper fold has been referenced at 42 , the folds can be arranged substantially parallel to the plane 30 of the plate thus formed. This fold 40 is then compressed, being advantageously subjected to a first compression substantially along the stacking axis 45 of the folds in the direction of the arrows F _a and F ' _a , then if desired a second compression, substantially perpendicular to this same axis 45, in the direction of the arrows F _l .

According to an alternative embodiment of the plate 1 as illustrated in FIG. 8, one could also provide that it is constituted by a stack 40a of sections 42a precut from the strip 21, all of dimensions substantially equal, this stack then being compressed substantially parallel, and incidentally, perpendicular to the stacking axis 45a of these sections.

Preferably, the parts or sections 42a of the stacked strip, will be oriented substantially parallel to the plane 30 of the plate, the axis 45a being then substantially perpendicular to this plane.

It is clear that the dimensions of the structure knitted 10, as well as roll 22 of folding 40, or the stack 40a, will be adapted so that, after compression, the dimensions of the plate correspond substantially to that of the associated burner. As example, to obtain a flame attachment plate, circular in shape, you can start from a height roller about 30 mm and about 150 mm in diameter, made up by a tight winding of the strip on itself, this roller is then subjected to a pressure substantially axial (Fa, Fa ') to reduce the height of the plate to about 15 mm. Finally, a metal band (not shown) can keep the plate at its around. The compressions of the shaped work, in view of obtaining the plate according to the invention, can be produced using a small known type press.

It is clear that the mode of implementation shape of the knitted item (winding, folding, stacking of sections ...) is not decisive for the final shape flame attachment plate. We could perfectly conceive of making a plate 1 according to the invention, of substantially quadrilateral shape (Figure 10) by compressing a roller 22 as illustrated in Figure 6; the compressive forces then being suitably adapted to obtain the desired contour of the plate. If necessary, we could also without difficulty making a plate other than flat (for example curled or arched).

Referring now to Figure 9, we sees shown a plate 1, mounted in a burner of known type, referenced as a whole in 80, as by example a domestic air blower, premixed total and blue flame.

This burner 80 essentially comprises a distribution chamber 81, which has the general shape of a box in truncated cone, substantially in section circular, connected at its most rear side narrow 81a with separate supply lines 83, 84 in combustion air and combustible gas respectively. This distribution chamber 81 is delimited transversely, on its front face, by the plate flame attachment 1. In this case, this plate is present in the form of a substantially circular disc, mounted in a hoop 90 whose dimensions are adapted to those of the burner to which it is attached by all means known to those skilled in the art, the plate being arranged substantially perpendicular to the axis 86 of the chamber 81 so as to separate the latter from the combustion 82. In this figure, the letters AV and AR allow to locate the sides "front" and "rear" of the burner, with reference to the circulation of the fuel mixture, in the burner, as shown by arrows 87, 87 'and 88. As seen on the figure, the fuel gas supply line 84 meets the air supply duct 83 just in upstream of the distribution chamber (at 85). Of course, here we plan to install a fan upstream of the duct 83 (pressurized air supply).

As illustrated, the ignition of the burner is provided by an electrode 97 suitably insulated and supplied with high voltage, by a power cable not shown, ignition taking place by sparks or electric arc between the tip 97a of the electrode and, by example, the wall next to the plate (if the latter is metallic) or the wall of the combustion, or even the grid 1 itself.

For example, the screened structure or plate 1 in stainless steel reference "304L" may have a diameter of about 130 mm and a thickness about 15 mm to be installed in a burner servant of which the distribution chamber is made up a truncated cone about 95 mm high. We have found that during operation the maximum pressure drop created by the combustion head 1 is relatively small, of the order of 50 Pa, the maximum temperature at the output 1a of the plate 1 at the stoichiometry being 750 ° C; moreover, there was no noise pollution notable. It will be noted that the plate according to the invention can as well be mounted on gas premix burners only on burners without premix.

By way of illustration, we have compared the quantities of harmful gases emitted on the same burner (of the type of that in FIG. 9) using either a "mesh" plate, according to the invention, or a conventional ceramic plate. The results, expressed in mg / kWh, specify the quantities of carbon oxides (CO), nitrogen (NO _x ) and hydrocarbons (C _n H _m ) formed for different operating powers (P) and for different factors d 'air (n). CERAMIC PLATE (A) PLATE ACCORDING TO INVENTION (B) P (kW) not Co NOx C _n H _m not Co NO _x C _n H _m 31.4 (for A ) 1.00 476 332 0 1.02 10 320 0 1.05 25 337 1 1.22 0 95 0 1.15 0 163 0 1.30 0 66 0 32.9 (for B ) 1.23 0 104 0 1.34 0 43 0 1.29 0 65 0 1.40 0 29 0 11.9 1.02 7400 171 0 1.02 30 181 0 1.06 164 240 0 1.06 2 193 0 1.12 7 137 0 1.12 0 150 0 1.20 2 94 0 1.20 0 92 0 1.26 15 85 3 1.28 0 83 0 1.37 124 44 30 1.47 29 63 24 3.3 1.02 6250 33 3 1.08 346 25 0 1.04 470 36 4 1.12 51 21 4 1.14 17 28 3 1.25 13 15 0 1.26 37 22 5 1.41 5 27 9 1.40 204 15 48 1.58 225 8 2324 1.58 675 10 2450 1.73 650 6 3940

Claims (10)

1. Flameholder plate (1) for a gas burner for a mixture of gases comprising at least one flexible metal wire (12) defining a compressed mesh network (2) permitting the flow of gas through it, characterised in that the mesh (2) of wire(s) (12) is a flattened knitted tube (10) comprising one or several sections.
2. Plate according to Claim 1, characterised in that the (each) tube section (10) comprises a single wire (12).
3. Flameholder plate according to either of Claims 1 to 2, characterised in that it is constituted by a roll (22) formed by rolling the strip (21), constituted by the said flattened tube (10), the axis (25) of the roll being substantially perpendicular to the longitudinal axis (46) of the strip (21).
4. Flameholder plate according to either of Claims 1 to 2, characterised in that it is constituted by a stack (40a) of several sections (42a) of the strip (21) which is constituted by the said flattened tube (10) following a given direction (45a) of stacking of the sections (42a).
5. Flameholder plate according to either of Claims 1 to 2, characterised in that it is constituted by a set of folds (40) of the strip (21) which is constituted by the said flattened tube (10), following a given direction (45) of stacking of the folds.
6. Gas burner for a mixture of gases comprising a distribution chamber (81) supplied with combustion air and with combustible gas and communicating with a combustion chamber (82), with a flameholder plate (1) according to any of the preceding claims positioned between them.
7. A method of manufacturing a flameholder plate (1) for a burner for a mixture of gases comprising at least one flexible metal wire (12) defining a compressed mesh network (2) permitting the flow of gas across it, characterised in that:

   there is provided a mesh (2) of wire(s) with interlaced parts defining a knitted tube (10) composed of at least one flexible metal wire (12) resistant to temperatures of the order of approximately 1000°C to 1200°C,

   the said knitted tube (10) is flattened along fold lines (16 and 18) substantially parallel to its longitudinal axis (20) in order to obtain a flat mesh (2),

   this flattened mesh (2) is shaped so as to give the general shape of a plate (1),

   and the mesh (2) thus shaped is compressed in such a way that, in a compressed state, it permits the flow of gas across it.
8. Method according to Claim 7, characterised in that in order to shape the said mesh (2), the strip (21) which is constituted by the said flattened tube (10) is wound on itself, the roll (22) thus formed being compressed substantially along its axis (25) and/or substantially perpendicular with respect to this axis (25).
9. Method according to Claim 7, characterised in that in order to shape the said mesh (2), the strip (21) which is constituted by the said flattened tube (10), is folded back on itself at least once, following a given direction (45) of stacking of the folds, the stack (40) thus obtained being compressed following a (some) direction(s) substantially parallel and/or perpendicular to the said direction (45) of stacking of the folds.
10. Method according to Claim 7, characterised in that in order to shape the said mesh (2), the strip (21) which is constituted by the said flattened tube (10), is cut into sections (42a) which sections are stacked on one another along a given direction (45a) of stacking of the sections, the stack (40a) thus obtained being compressed along a (some) direction(s) substantially parallel and/or perpendicular to the said direction (45a) of stacking of the sections.

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