Description

Technical Field

[1] The invention relates to the field of premix gas burners, more particularly to surface stabilized premix gas burners comprising a porous burner deck onto which the flames are stabilized.

Background Art

[2] Premix gas burners of which the circumference of the porous burner deck has the shape of a rectangle of which the two short sides are continuously rounded find application in a broad range of boilers and heating appliances.

[3] WO2015/000869 A1 discloses a premix gas burner wherein the circumference of the porous burner deck has the shape of a rectangle of which the two short sides are continuously rounded. The burner comprises a metal mounting plate, a mixing chamber, a porous burner deck and a distributor. The porous burner deck encloses the mixing chamber. Combustion of premix gas occurs on the porous burner deck after premix gas has flown from the mixing chamber through the porous burner deck. A distributor is provided in the mixing chamber for flow of the premix gas through the perforations of the distributor before the premix gas flows through the porous burner deck.

Disclosure of Invention

[4] The first aspect of the invention is a premix gas burner comprising a metal mounting plate, a mixing chamber, a porous burner deck and a plate structure. The porous burner deck encloses the mixing chamber. Combustion is stabilized on the porous burner deck after premix gas has flown from the mixing chamber through the porous burner deck. The plate structure comprises a plurality of perforations. The plate structure is provided in the mixing chamber for flow of premix gas through the perforations of the plate structure before the premix gas flows through the porous burner deck. The circumference of the porous burner deck has the shape of a rectangle of which the two short sides have been - preferably continuously - rounded. The plate structure is provided via cutting and folding of a metal plate. The plate structure is attached to the metal mounting plate only along the long sides of the rectangular circumference of the porous burner deck.

[5] Attaching the plate structure to the metal mounting plate only along the long sides of the rectangular circumference of the porous burner deck has shown to provide surprising benefits as the burner can be more easily assembled.

[6] A further surprising benefit is that the burner deck can better cope with the thermal stresses, resulting in a longer lifetime of the burner deck; and thus, of the burner. This surprising benefit is to a larger extent present in embodiments where the porous burner deck is not attached to the metal mounting plate nor to the plate structure, but held in the burner with play possible between the porous burner deck on the one hand and the metal mounting plate and the plate structure on the other hand.

Preferably, the metal mounting plate surrounds the complete burner deck.

In a preferred embodiment, the porous burner deck is provided in a convex shape; more preferably the porous burner deck is provided in a convex shape over the full surface of the porous burner deck provided for stabilizing the flames.

Preferably, the porous burner deck has a double curved surface. Where a surface is at a point on it double curved, there is at that point no direction in which the radius of curvature at that point is infinite. As an example, a cylindrical burner is a burner that has a single curved surface, not a double curved surface.

Preferably, the metal mounting plate comprises an opening. The porous burner deck is inserted through the opening of the metal mounting plate. More preferably, the opening is at the center of the metal mounting plate.

In a preferred embodiment, the porous burner deck is a woven metal wire mesh.

Preferably, the woven wire mesh has a thickness between 0.6 and 1 .3 mm. As an example, a woven wire mesh of 0.9 mm thickness can be advantageously used in the invention.

In a preferred embodiment, the porous burner deck is provided by a woven, knitted or braided fabric comprising metal fibers. More preferably, the porous burner deck is provided by a woven, knitted or braided fabric comprising yarns. The yarns comprise a plurality of metal fibers in their cross section.

Preferably, in the assembly of the burner, the plate structure is deformed and allowed to recover such that in the burner elastic forces of the plate structure ensure that the plate structure is positioned against supporting elements of the metal mounting plate.

Supporting elements are only provided along the two long sides of the rectangular shape of the porous burner deck.

In a preferred embodiment, the metal plate structure is welded onto the metal mounting plate at or around supporting elements.

In a preferred embodiment, the metal plate structure is mechanically attached onto the metal mounting plate at or around the supporting elements. The mechanical attachment can e.g. be performed by means of clamping, crimping, riveting, or via other mechanical means.

In a preferred embodiment, the plate structure comprises at its circumference a plurality of notches. The metal mounting plate comprises upstanding ridges providing supporting elements. In the burner the notches of the plate structure hit the upstanding ridges of the metal mounting plate. In the assembly of the burner, the plate structure is deformed and allowed to recover such that in the burner elastic forces of the plate structure ensure that the plate structure is positioned against the upstanding ridges of the metal mounting plate. More preferably, the upstanding ridges are only provided along the two long sides of the rectangular circumference of the burner deck; and notches are only provided on the plate structure along the two long sides of the rectangular circumference of the burner deck.

Preferably, the porous burner deck is bent such that a flange is formed at its

circumference. In a more preferred embodiment, the flange is along the circumference of the porous burner deck split in a plurality of flange segments.

In embodiments wherein the porous burner deck is bent such that a flange is formed at the circumference of the porous burner deck, the bend angle providing the flange of the porous burner deck is preferably at least 90°.

In preferred embodiments wherein the porous burner deck is bent such that a flange is formed at the circumference of the porous burner deck, the flange is only provided along the full circumference of the porous burner deck.

In preferred embodiments wherein the porous burner deck is bent such that a flange is formed at the circumference of the porous burner deck, the flange is only provided along the long sides of the rectangular circumference of the porous burner deck only. It means that no such flange is provided along the short sides of the rectangular circumference of the porous burner deck.

In preferred embodiments wherein the porous burner deck is bent such that a flange is formed at its circumference, the flange is held in the burner between the metal mounting plate and the plate structure.

In a preferred embodiment, the flange of the porous burner deck is held between the metal mounting plate and the plate structure such that along the full flange play is present between the flange on the one hand; and the metal mounting plate and the plate structure on the other hand. The metal mounting plate and the plate structure are attached to each other, by welding or by a mechanical joining technique. Different welding techniques can be used, e.g. capacitor discharge welding, TIG welding or laser welding.

In a preferred embodiment, the flange is attached into the burner by welds onto the metal mounting plate or onto the plate structure or onto both the metal mounting plate and the plate structure. The welds attaching the flange into the burner are only provided along the long sides of the rectangular circumference of the burner deck. Different welding techniques can be used, e.g. capacitor discharge welding, TIG welding or laser welding. Preferably, the plate structure comprises an open ended slit ending at each of the two short sides of the circumference of the porous burner deck. Each of the open ended slits ending at the two short sides is parallel with the length direction of the circumference of the porous burner deck. Burners according to such embodiments are easier to produce because of the ease of production and shaping of the plate structure.

Preferably, all zones of the plate structure provided with perforations are provided at a distance from the porous burner deck. It is meant that no perforation makes contact with the porous burner deck, but that the perforation is positioned at a distance from the porous burner deck. [26] The second aspect of the invention is a condensing boiler comprising a premix gas burner as in any embodiment of the first aspect of the invention. Preferably, the condensing boiler comprises a cast aluminium heat exchanger.

Brief Description of Figures in the Drawings

[27] Figure 1 shows a top view of a gas premix burner according to the invention.

Figure 2 shows a bottom view of the burner of figure 1.

Figure 3 shows a cross section of figure 2 along II - II.

Figure 4 shows the woven wire mesh forming the porous burner deck of the burner of figure 1.

Figure 5 shows the metal mounting plate of the burner of figure 1.

Figure 6 shows the plate structure of the burner of figure 1 before it is shaped.

Figure 7 shows the shaped plate structure as included in the burner of figure 1.

Figure 8 shows the plate structure of another burner of the invention before it is shaped.

Figure 9 shows the shaped plate structure derived from the plate structure shown in figure 8.

Figure 10 shows the metal mounting plate used in combination with the shaped plate structure of figure 9.

Figure 1 1 shows a cross section of the premix gas burner according to the invention made with the metal mounting plate of figure 10 and with the shaped plate structure of figure 9.

Mode(s) for Carrying Out the Invention

[28] Figures 1 - 7 show in combination a first example of a gas premix burner according to the invention. Figure 1 shows a top view 100 of a gas premix burner according to the invention. Figure 2 shows a bottom view 200 of the burner of figure 1 . Figure 3 shows a cross section 300 of figure 2 along II - II. Figure 4 shows the woven wire mesh forming the porous burner deck of the burner of figure 1. Figure 5 shows the metal mounting plate 102 of the burner of figure 1. Figure 6 shows the plate structure 104 of the burner of figure 1 before it is shaped. Figure 7 shows the shaped plate structure 106 as included in the burner of figure 1.

[29] The premix gas burner comprises a metal mounting plate 102, a mixing chamber 108, a porous burner deck 1 10 and a plate structure 106. In the exemplary burner, the porous burner deck is a woven metal wire mesh, e.g. 0.9 mm thick. The circumference of the porous burner deck has the shape of a rectangle of which the two short sides have been continuously rounded. The metal mounting plate comprises an opening. The woven wire mesh burner deck is inserted through the opening of the metal mounting plate.

[30] The plate structure 106 comprises a plurality of perforations 1 12; and is provided in the mixing chamber for flow of premix gas through the perforations of the plate structure before the premix gas flows through the porous burner deck. The plate structure is provided via cutting and folding a metal plate. Figure 6 shows the flat metal plate structure 104 after cutting and before folding it. Figure 7 shows the shaped plate structure 106 after folding it, meaning as included in the burner of figure 1. The plate structure comprises an open ended slit 1 14 ending at each of the two short sides of the circumference of the porous burner deck. Each of the open ended slits ending at the two short sides is parallel with the length direction of the circumference of the porous burner deck. The two open ended slits are a consequence of way the plate structure is produced, by folding the flat structure of figure 6 into the shaped structure of figure 7. In the exemplary burner, all zones of the plate structure provided with perforations 1 12 are provided at a distance from the porous burner deck.

As is best illustrated in figure 3, in the assembly of the burner, the plate structure is deformed and allowed to recover such that in the burner elastic forces of the plate structure ensure that the plate structure is positioned against supporting elements 1 16 of the metal mounting plate. Supporting elements are only provided along the two long sides of the rectangular shape of the porous burner deck. No supporting elements are provided along the two rounded short sides of the rectangular shape of the porous burner deck. The plate structure comprises at its circumference a plurality of notches 1 18 provided in a flange 120 at the circumference of the plate structure. The metal mounting plate comprises upstanding ridges 1 16 forming the supporting elements. Notches and ridges are only provided along the long sides of the rectangular (with continuously rounded short sides) circumference of the burner deck. In the gas premix burner notches of the plate structure are positioned against the upstanding ridges of the metal mounting plate. This way, the plate structure is correctly positioned in the burner, controlling the sizes of the open ended slits 1 14. This is best shown in figure 3.

The porous burner deck is bent such that a flange - split is a plurality of flange segments 122- is formed at its circumference. The bend angle providing the flange of the porous burner deck is more than 90°. The flange is held in the burner between the metal mounting plate and the plate structure (see figure 2). The openings 124 in between the flange segments 122 are positioned around second ridges 126 of the metal mounting plate. The height of the second ridges 126 determines the space between the metal mounting plate and the metal plate structure. This distance is selected to be larger than the thickness of the woven wire mesh burner deck, such that the flange segments are present between the metal mounting plate and the metal plate structure such that play is present between the flange segments on the one hand; and the metal mounting plate and the plate structure at the other hand. This way, the burner deck can efficiently cope with thermal expansion and contraction.

In the exemplary burner, flange segments are only provided along the long sides of the rectangular circumference of the porous burner deck. No flange is provided along the short sides of the rectangular circumference of the porous burner deck. The metal mounting plate and the plate structure are attached to each other, by means of welds at or around the notches and the ridges. Different welding techniques can be used, e.g. capacitor discharge welding, TIG welding or laser welding. As notches and ridges are only provided along the long sides of the rectangular (with continuously rounded short sides) of the burner deck, the plate structure is attached - by means of welds - to the metal mounting plate only along the long sides of the rectangular circumference of the porous burner deck.

Figures 8 - 1 1 illustrate in combination a second example of premix gas burner according to the invention. Figure 8 shows the plate structure of another burner of the invention before it is shaped. Figure 9 shows the shaped plate structure derived from the plate structure shown in figure 8. Figure 10 shows the metal mounting plate used in combination with the shaped plate structure of figure 9. Figure 1 1 shows a cross section of the premix gas burner according to the invention made with the metal mounting plate of figure 10 and with the shaped plate structure of figure 9. The burner deck 1 10 of figure 4 is used in the second exemplary burner.

The premix gas burner comprises a metal mounting plate 802, a mixing chamber 808, a porous burner deck 810 and a plate structure 806. The circumference of the porous burner deck has the shape of a rectangle of which the two short sides have been continuously rounded. The metal mounting plate comprises an opening. The woven wire mesh burner deck is inserted through the opening of the metal mounting plate.

The plate structure 806 comprises a plurality of perforations 812. The plate structure is provided via cutting and folding a metal plate, figure 8 shows the flat metal plate structure 804 after cutting and before folding it. Figure 9 shows the shaped plate structure 806 after folding it, meaning as included in the burner. The plate structure comprises an open ended slit 814 ending at each of the two short sides of the circumference of the porous burner deck. Each of the open ended slits ending at the two short sides is parallel with the length direction of the circumference of the porous burner deck. The two open ended slits are a consequence of way the plate structure is produced, by folding the flat structure of figure 8 into the shaped structure of figure 9.

In the exemplary burner, all zones of the plate structure provided with perforations 812 are provided at a distance from the porous burner deck.

As is best illustrated in figure 1 1 , in the assembly of the burner, the plate structure is deformed and allowed to recover such that in the burner elastic forces of the plate structure ensure that the plate structure is positioned against supporting elements (formed by upstanding ridges) 816 of the metal mounting plate. Supporting elements are only provided along the two long sides of the rectangular shape of the porous burner deck. No supporting elements are provided along the two rounded short sides of the rectangular shape of the porous burner deck. The plate structure comprises at its circumference a plurality of notches 818 provided in a flange 820 at the circumference of the plate structure. In the gas premix burner notches of the plate structure are positioned against the upstanding ridges of the metal mounting plate. This way, the plate structure is correctly positioned in the burner, controlling the sizes of the open ended slits 814. This is shown in figure 1 1.

The porous burner deck is bent such that a flange - split in a plurality of flange segments 822- is formed at its circumference. The bend angle providing the flange of the porous burner deck is more than 90°. The flange is held in the burner between the metal mounting plate and the plate structure. The openings 824 in between the flange segments 122 are positioned around the ridges 816 of the metal mounting plate.

The flange segments are positioned without play between the metal mounting plate and the metal plate structure. The flange segments are attached into the burner by welds onto the metal mounting plate and onto the plate structure or onto both the metal mounting plate and the plate structure. Welds are only made along the long sides of the rectangular (with continuously rounded short sides) circumference of the burner deck. Different welding techniques can be used.