EP0580500A1 - Gas burner - Google Patents

Abstract

The invention relates to a gas burner of the type which distributes through multiple nozzles the flames (8) produced by the combustion of a burnable gas under pressure in the air under pressure, said nozzles (5, 7) each being perforated in a wall (2) opposite the outlet of a hollow needle (1) fed by the gas under pressure (G), said outlet being at a spacing from said wall so as to reserve between them an annular passage (R), via which the air under pressure (A) is admitted, around the jet of gas emerging from the needle, into the nozzle concerned. This burner comprises, attached to the outer face of the perforated wall and superposed one against the other, at least two metal grilles (9) with small rectangular mesh openings which are inclined obliquely one on the other, each grille being passed through by small holes (10) opposite the nozzles. <IMAGE>

Description

The invention relates to gas burners of the type distributing through multiple nozzles the flames generated by the combustion of a combustible gas under pressure in the pressurized air, this gas being able for example to be at will one or the other of the following: natural gas, butane, propane.

Such burners are used, for example, in water heaters, bath heaters, domestic or industrial central heating boilers, stoves, etc.

The invention relates more specifically, among these burners those for which the nozzles are essentially constituted by orifices each perforated in a wall opposite the outlet of a hollow needle supplied by the pressurized gas, said outlet being slightly spaced from said wall so as to reserve between them an annular passage through which air under pressure is admitted, around the jet of gas leaving the needle, in the orifice concerned in the wall.

It is aimed more particularly still - because it is in their case that its application seems to offer the most interest, but not exclusively - among said burners, those for which the partition consists of two plates juxtaposed and perforated differently so such that the outer plate forms bridges cutting the axes of the needles and dividing the orifices into two halves or elementary orifices (see US Patent No. 4,887,963).

Burners of the kind in question have the advantage of making it possible to adjust the calorific power in a very wide range, for example between 2 and 40 kW thermal, in particular because of the possibility for the flames to catch on the bridges.

But in practice, it has been found that, from of a certain power, generally located towards the middle of the conceivable range, the operation of the burner was noisy, the catching of the flames on the perforated wall sometimes becoming unstable, in particular during regime changes.

The object of the invention is, above all, to remedy this drawback by ensuring for all regimes a secure and stable attachment of the flames and, consequently, silent operation of the burner.

To this end, the burners of the type in question according to the invention are essentially characterized in that they comprise, attached to the external face of the perforated wall and superimposed one against the other, at least two metal grids with small rectangular stitches, the directions of the constituent wires of each grid being inclined on the directions of the constituent wires of each other grid with angles different from 90 °, each grid being hollowed out, opposite the perforations in the wall, with slightly more holes smaller than these orifices, and each of the two dimensions of the meshes of each grid being less than half the diameter or equivalent of each hole.

• le nombre des grilles superposées est égal à 3 et les fils qui composent chaque grille sont inclinés sur les fils qui composent chaque grille contiguë d'angles égaux à 60°,
• chaque grille est constituée par des fils en acier inoxydable dont le diamètre est compris entre 0,15 et 0,20 mm, formant des mailles carrées dont le pas est de l'ordre de 0,40 à 0,50 mm, le diamètre de chaque trou évidé dans la grille étant de l'ordre de 2 mm,
• la cloison est constituée par deux plaques juxtaposées et perforées différemment de façon telle que la plaque extérieure forme des pontets coupant les axes des aiguilles et divisant les orifices en deux moitiés ou orifices élémentaires,
• les axes des deux relativement petits trous évidés dans les grilles superposées et correspondant aux deux orifices élémentaires d'une même paire d'orifices associée à une aiguille sont plus éloignés de l'axe de l'aiguille que les axes de ces deux orifices élémentaires,
• les orifices élémentaires présentent une section circulaire de diamètre 2,8 mm et sont séparés par des pontets larges de 1 mm et les trous évidés dans chaque grille présentent une section circulaire de diamètre 2 mm et sont séparés par une bande de grille large de 2,6 mm.

In preferred embodiments, use is also made of one and / or the other of the following arrangements:

• the number of superimposed grids is equal to 3 and the wires that make up each grid are inclined on the wires that make up each contiguous grid with angles equal to 60 °,
• each grid consists of stainless steel wires whose diameter is between 0.15 and 0.20 mm, forming square meshes whose pitch is of the order of 0.40 to 0.50 mm, the diameter of each hole hollowed out in the grid being of the order of 2 mm,
• the partition is constituted by two plates juxtaposed and perforated differently so that the outer plate forms bridges cutting the axes of the needles and dividing the orifices into two halves or elementary orifices,
• the axes of the two relatively small holes hollowed out in the superimposed grids and corresponding to the two elementary orifices of the same pair of orifices associated with a needle are more distant from the axis of the needle than the axes of these two elementary orifices,
• the elementary orifices have a circular section of diameter 2.8 mm and are separated by bridges 1 mm wide and the holes hollowed out in each grid have a circular section of diameter 2 mm and are separated by a strip of grid wide 2, 6 mm.

The invention includes, apart from these main provisions, certain other provisions which are preferably used at the same time and which will be more explicitly discussed below.

In what follows, a preferred embodiment of the invention will be described with reference to the accompanying drawing, of course in a non-limiting manner.

Figure 1 of this drawing shows an enlarged partial axial section along I-I, Figure 2, a gas burner established in accordance with the invention.

Figure 2 shows this burner in partial plan view.

Figure 3 shows on an even larger scale than Figure 1 a portion of the plan view of Figure 2 with cutaways showing the different superimposed grids.

• une pluralité d'aiguilles creuses parallèles 1 toutes alimentées en gaz combustible sous pression et débouchant toutes dans un même plan P,
• une paroi plane 2 perpendiculaire aux axes des aiguilles 1 et composée de deux plaques 3 et 4 juxtaposées et perforées, paroi délimitant en partie un boîtier (non représenté) qui enveloppe les aiguilles 1 et dans lequel est admis de l'air sous pression.

In a manner known per se from the publication indicated above, the burner considered here comprises:

• a plurality of parallel hollow needles 1 all supplied with pressurized combustible gas and all opening into the same plane P,
• a flat wall 2 perpendicular to the axes of the needles 1 and composed of two juxtaposed and perforated plates 3 and 4, wall partly defining a housing (not shown) which envelops the needles 1 and into which air under pressure is admitted.

• des paires d'orifices élémentaires circulaires 5 évidés dans la plaque extérieure 3 et séparés par des pontets 6,
• et des lumières allongées 7 évidées dans la plaque interne 4 et dont le contour correspond à celui de l'ensemble formé par deux orifices 5 et par le pontet 6 qui les sépare.

The perforations of the wall 2 are here respectively:

• pairs of circular elementary orifices 5 hollowed out in the outer plate 3 and separated by bridges 6,
• and elongated lights 7 hollowed out in the internal plate 4 and whose outline corresponds to that of the assembly formed by two orifices 5 and by the bridge 6 which separates them.

Each trigger guard 6 is centered on the axis of a needle 1.

The inner face of the internal plate 4 is spaced from the plane P by a distance D sufficient for an annular passage R to be created around the outlet of each needle 1 allowing a stream of oxidizing air A to be admitted, around the jet of gas G coming from said needle, in the perforations opposite the wall 2.

The operation of the burner thus described is as follows.

The two pressurized streams of gas G and air A are admitted simultaneously through the needle 1 and the passage R in the direction of the recesses 5 and 7 and the bridges 6.

The impacts of the central gas jets G against said bridges 6 have the consequence of deflecting these jets transversely, forcing them to mix with air A and it is the intimate mixture of these two gaseous components which is ignited as soon as it leaves the orifices 5 to form the flames 8.

To further improve this operation by ensuring excellent attachment of said flames 8 to the wall 1 for all regimes, and even for those corresponding at the maximum calorific powers and therefore at the maximum gas and air flow rates, in accordance with the invention, a plurality of superimposed grids 9 made up of very fine wires forming very small meshes are reported on the external face of the external plate 3 , perforated grids to the right of the orifices 5 by holes 10 smaller than these orifices.

The number of superimposed grids could be equal to 2, the wires which make up each grid then being inclined by 45 ° on the wires making up the other grid.

In the preferred embodiment illustrated, the number of superimposed grids is equal to 3 and the constituent wires of each of these three grids, designated respectively by the references 9₁, 9₂ and 9₃, are then inclined by 60 ° on the wires making up each contiguous grids.

The small meshes of each grid are rectangular and preferably square.

In FIG. 3, three sections of the external face of the burner have been represented, corresponding respectively, from the left, to the superposition of the three grids, to the superposition of only two grids, one grid being removed, and to the presence of one grid only, the other two grids being deleted.

In this FIG. 3, the two holes 10 of the same pair corresponding to the two holes 5 constituting the nozzle of the same flame 8 have been shown respectively in the left-hand section corresponding to the actual embodiment and in the middle section.

The constituent wire of each grid must of course be made of a refractory material.

It has a small diameter, this diameter being in particular of the order of 0.1 to 0.2 mm.

The mesh pitches of each grid are advantageously of the order of 0.4 to 0.5 mm.

A typical example is as follows: the wires are made of stainless steel and have a diameter of 0.17 mm, the meshes are square and their pitch is equal to 0.45 mm.

• les trous 5 circulaires avaient chacun un diamètre de 2,8 mm et étaient séparés par un pontet 6 large de 1 mm,
• quant aux trous 10 perforés dans chaque grille, ils étaient également circulaires, présentaient un diamètre de 2 mm et étaient séparés par une bande de grille large de 2,6 mm.

In one embodiment which gave satisfactory results, the other dimensions relating to the perforations of the burner were as follows:

• the circular holes 5 each had a diameter of 2.8 mm and were separated by a bridge 6 wide by 1 mm,
• as for the holes 10 perforated in each grid, they were also circular, had a diameter of 2 mm and were separated by a strip of grid wide by 2.6 mm.

If we therefore consider a projection on the plane P, the circles corresponding to the holes 10 are tangent internally to the circles corresponding to the orifices 5: in other words, the relatively "small" holes 10 hollowed out in the grids are eccentric relative to the orifices 5 larger, the axes of said holes 10 being more distant from the axis X of needle 1 than the axes of said orifices 5, as clearly visible in FIG. 3. This eccentricity has an advantage which will be explained below.

When the grids 9₁, 9₂ and 9₃ are perforated to form the holes 10, the constituent wires of these grids are cut and the different cut ends of these wires delimit around each hole 10 crowns of sharp "points" oriented in multiples directions.

Experience shows that the presence of these spikes, which are very quickly heated and even brought to red when the flames are lit, has the effect of very effectively retaining the bases of these flames by preventing them from taking off, even for flow rates. of the air-gas mixture.

This gives excellent burner stability, which results in silent operation of the latter at all speeds.

The eccentricity described above with respect to the embodiment illustrated in FIGS. 1 and 3 has the following advantage: the distribution of the "tips" of cut wire which project inwards from the channels defined by the axial extensions of the orifices 5 towards the outside of the burner is all the more dense the closer one gets to the axis X of the needle 1, that is to say to the central portion of the gas stream to be ignited.

This preferred distribution of said attachment points towards said central portion promotes the effectiveness of this attachment, for a given diameter of the orifices 5 and therefore for a given flow rate of the combustible gas.

As a result of which, and whatever the embodiment adopted, there is finally a burner whose constitution, operation and advantages result sufficiently from the above.

As goes without saying, and as it already follows from the foregoing, the invention is in no way limited to those of its modes of application and embodiments, which have been more especially envisaged; on the contrary, it embraces all its variants.

Claims (6)

Gas burner of the type distributing through multiple nozzles the flames (8) generated by the combustion of a combustible gas under pressure in the pressurized air, said nozzles being essentially constituted by orifices each perforated in a wall (2) opposite the outlet of a hollow needle (1) supplied by the pressurized gas (G), said outlet being slightly spaced from said wall so as to reserve between them an annular passage (R) through which the air under pressure (A) is admitted, around the jet of gas leaving the needle, into the orifice concerned in the wall, characterized in that it comprises, attached to the external face of the perforated wall (2) and superimposed on it one against the other, at least two metal grids (9) with small rectangular meshes, the directions of the contiguous wires of each grid being inclined to the directions of the constituent wires of each other grid of angles different from 90 °, each e grid being hollowed out, opposite the orifices (5) perforated in the wall, holes (10) slightly smaller than these orifices, and each of the two dimensions of the meshes of each grid being less than half the diameter or equivalent of each hole. Gas burner according to claim 1, characterized in that the number of superimposed grids (9) is equal to 3 and in that the wires which make up each grid are inclined on the wires which make up each contiguous grid with angles equal to 60 °. Gas burner according to any one of the preceding claims, characterized in that each grid (9) is constituted by stainless steel wires whose diameter is between 0.15 and 0.20 mm, forming square meshes whose pitch is of the order of 0.40 to 0.50 mm, the diameter of each hole (10) hollowed out in the grid being of the order of 2 mm. Gas burner according to any one of the preceding claims, characterized in that the partition consists of two plates (3,4) juxtaposed and perforated differently so that the outer plate (3) forms bridges (6) cutting the axes of the needles (1) and dividing the orifices into two halves or elementary orifices (5). Gas burner according to claim 4, characterized in that the axes of the two relatively small holes (10) hollowed out in the superimposed grids and corresponding to the two elementary orifices (5) of the same pair of orifices associated with a needle (1 ) are more distant from the axis of the needle than the axes of these two elementary orifices. Gas burner according to claim 5, characterized in that the elementary orifices (5) have a circular section with a diameter of 2.8 mm and are separated by bridges (6) 1 mm wide and in that the holes (10) hollowed out in each grid (9) have a circular section of diameter 2 mm and are separated by a grid strip (11) 2.6 mm wide.

Images