WO2019201600A1

WO2019201600A1 - Premix gas burner

Info

Publication number: WO2019201600A1
Application number: PCT/EP2019/058362
Authority: WO
Inventors: Geertjan KOOITJE; Geert Folkers; Roelof BOER
Original assignee: Bekaert Combustion Technology B.V.
Priority date: 2018-04-19
Filing date: 2019-04-03
Publication date: 2019-10-24
Also published as: CN112567176B; EP3781866B1; EP3781866A1; CN112567176A

Abstract

The premix gas burner comprises a metal mounting plate (102), a mixing chamber (108) and a porous burner deck (110). 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 burner also comprises a plate structure (106) comprising a plurality of perforations (112). 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 rounded. The plate structure has along its length an elongated section (131) and two end caps (133). Each of the end caps is provided at an end of the elongated section. The plate structure is provided via cutting and folding of a metal plate into the convex shape of the plate structure. The elongated section of the plate structure comprises at least one groove (135) created by deep drawing. The at least one groove is provided on the crest line of the plate structure. The at least one groove is convex in the same direction as the plate structure. In each of the two end caps two edges (137) of the metal plate join parallel to the length direction of the elongated section in order to form the end caps.

Description

Premix gas burner

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.

[4] W02018/050578A1 discloses a premix gas burner comprising a metal mounting plate; a mixing chamber; a porous burner deck enclosing the mixing chamber and onto which combustion is stabilized after premix gas has flown from the mixing chamber through the porous burner deck; and a plate structure comprising 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 plate structure comprises a convex shape. The circumference of the porous burner deck has the shape of a rectangle of which the two short sides have been rounded. The plate structure has along its length an elongated section and two end caps, wherein each of the end caps is provided at an end of the elongated section.

[5] WO2018/050310A1 discloses a premix gas burner comprising a metal mounting plate, a burner deck and a metal plate structure. The metal mounting plate has a plain section for mounting the burner in a heating appliance. The burner deck comprises a woven wire mesh onto which the flames are stabilized when the burner is in use. At least part of the metal plate structure is perforated for the premix gas to flow through the perforations before the premix gas flows through the woven wire mesh. The metal mounting plate has an opening. The woven wire mesh is inserted through the opening of the metal mounting plate. The woven wire mesh is bent, such that a flange parallel with the plain section of the metal mounting plate is provided. The flange is held between the metal mounting plate and the metal plate structure such that play is present of the flange relative to the metal mounting plate and relative to the metal plate structure. Disclosure of Invention

[6] 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. In use of the burner, 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 plate structure comprises a convex shape. 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 has along its length an elongated section - preferably having constant cross section - and two end caps. Each of the end caps is provided at an end of the elongated section. The plate structure is provided via cutting and folding of a metal plate into the convex shape of the plate structure. The elongated section of the plate structure comprises at least one groove created by deep drawing. The at least one groove is provided on the crest line of the plate structure. The at least one groove is convex in the same direction as the plate structure. In each of the two end caps two edges of the metal plate join parallel to the length direction of the elongated section in order to form the end caps. Preferably, the plate structure is symmetrical with respect to the plane vertical to the plate structure at the crest line of the plate structure.

[7] The metal mounting plate, the porous burner deck and the plate structure are produced in separate manufacturing operations before these three parts are assembled into the burner. The deepdrawing operation in the manufacturing process of the plate structure - performed to make and shape the groove after cutting and folding the metal plate into the convex shape of the plate structure - allows to control that the two edges of the metal plate are positioned in a controlled way in the end cap. This way, slits in the end caps can be controlled in size. As a consequence, the invention provides a premix gas burner that can be manufactured to much better controlled dimensional tolerances. The benefit is that differences in functional operation of such premix gas burners is drastically reduced. Furthermore, control of the slit size in the end caps is important, as an excessive width of the slits could cause flashback of the flames.

[8] Preferably, the depth of the at least one groove is more than 0.3 mm; preferably more than 0.5 mm, preferably less than 1 mm; and preferably less than 1.5 mm. Such embodiments provide better controlled dimensional tolerances between the edges of the metal plate in the end caps.

[9] Preferably, the plate structure comprises open ended slits, one in each of the two end caps. Each of the open ended slits ends at one of the short sides of the circumference of the porous burner deck. The open ended slits are provided in the end caps between the two edges of the metal plate that join parallel to the length direction of the elongated section. Each of the open ended slits is parallel with the length direction of the circumference of the porous burner deck. Preferably, the width of the slit is less than 0.6 mm, more preferably less than 0.5 mm, even more preferably less than 0.4 mm.

[10] Preferably, the elongated section of the plate structures comprises at least two grooves created by deep drawing. The at least two grooves are provided on the crest line of the plate structure. The at least two grooves are convex in the same direction as the plate structure. The at least two grooves are provided in-line with each other.

[1 1] Preferably, the metal mounting plate has a plain section for mounting the burner in a heating appliance.

[12] Preferably, 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.

[13] 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 plate structure is inserted in the burner through the opening in the metal mounting plate, after the porous burner deck has been inserted through the opening in the metal mounting plate.

[14] In preferred embodiments, 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.

[15] 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 in their cross section a plurality of metal fibers.

[16] 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.

[17] Preferably, the metal mounting plate surrounds the complete porous burner deck.

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

circumference. More preferably the flange of the porous burner deck is along the circumference of the porous burner deck split in a plurality of flange segments. Even more preferred, the flange is only provided to the porous burner deck along the long sides of the rectangular circumference of the porous burner deck: it is meant that the porous burner deck does not comprise flanges along the two - preferably continuously - rounded short sides of the rectangular circumference of the porous burner deck. The bend angle providing the flange of the porous burner deck is preferably at least 90°.

[19] Preferably, the flange of the porous burner deck is held between the metal mounting plate and the plate structure. More preferably the flange of the porous burner deck is held between the metal mounting plate and the plate structure such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

[20] Preferably, the plate structure is firmly attached to the metal mounting plate. It is meant that there is no play between the plate structure and the metal mounting plate. More preferably, the plate structure is firmly attached to the metal mounting plate only along the long sides of the rectangular cross section of the burner deck. In more preferred embodiments, the plate structure is firmly attached to the metal mounting plate by clamping. In other more preferred embodiments, the plate structure is firmly attached to the metal mounting plate by welds.

[21] Preferably, the metal mounting plate comprises a plurality of lips. More preferably lips are only provided along the long sides of the rectangular circumference of the porous burner deck. The lips are folded over in order to clamp the plate structure firmly to the metal mounting plate; preferably in such way that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

[22] Preferably, a flange is provided on the plate structure. More preferably, the flange of the plate structure is along the circumference of the plate structure split in a plurality of flange segments. The flange of the porous burner deck is held between the metal mounting plate and the flange of the plate structure. Preferably the flange of the porous burner deck is held between the metal mounting plate and the flange of the plate structure such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

[23] Preferably, the metal mounting plate comprises upstanding ridges providing supporting elements onto which the plate structure is clamped by the metal mounting plate. More preferably, the upstanding ridges of the metal mounting plate fit into notches in the flange of the porous burner deck; such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

[24] Embodiments wherein the porous burner deck - e.g. via its flange - is held with play between the metal mounting plate and the plate structure have the benefit that the burner deck can expand when hot when the burner is in use. The benefit of such embodiments is that a burner with long lifetime is provided.

[25] It has surprisingly been found that the lifetime is even longer in embodiments wherein the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure, but wherein the porous burner deck has no flange at the short sides of the rectangular circumference of the rectangular shape of the porous burner deck.

Furthermore, assembly of the burner is facilitated in such embodiments.

[26] 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 perforations are positioned at a distance from the porous burner deck. [27] 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

[28] 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 view on the burner along II - II of figure 2.

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 before assembly in the burner.

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

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

Mode(s) for Carrying Out the Invention

[29] Figures 1 - 7 show in combination an 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 view on the burner along II - II of figure 2. 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 before its assembly in the burner. 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.

[30] The premix gas burner comprises a metal mounting plate 102, a mixing chamber 108, a porous burner deck 110 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. The plate structure 106 is inserted through the opening of the metal mounting plate after the woven wire mesh burner deck has been inserted through the opening of the metal mounting plate.

[31] 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 has along its length an elongated section 131 and two end caps 133. Each of the end caps is provided at an end of the elongated section. The plate structure is provided via cutting and folding a metal plate, followed by a deep drawing operation to form groove 135. The elongated section of the plate structure comprises at least one groove 135 created by deep drawing after cutting and folding the metal plate. The groove 135 is provided on the crest line of the plate structure. The groove is convex in the same direction as the plate structure. In the exemplary burner, the depth of the groove 135 is 0.7 mm. In each of the two end caps two edges 137 of the metal plate join parallel to the length direction of the elongated section in order to form the end caps. The plate structure is symmetrical with respect to the plane vertical to the plate structure at the crest line of the plate structure.

[32] Figure 6 shows the flat metal plate structure 104 after cutting it from a metal plate and before folding it. Figure 7 shows the shaped plate structure 106 after folding it and after the deep drawing operation to form groove 135. Figure 7 shows the shaped plate structure as it is assembled in the burner of figure 1.

[33] 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. The open ended slits 1 14 are provided in the end caps between the two edges 137 of the metal plate that join parallel to the length direction of the elongated section. 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, the open ended slit has a width of 0.2 mm.

[34] 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.

[35] The porous burner deck is bent such that a flange - split is a plurality of flange segments 122 - is formed at its circumference, see e.g. figure 4. Notches 124 are provided between the flange segments 122. The bent angle providing the flange of the porous burner deck is more than 90°. The flange 122 is held in the burner between the metal mounting plate and the plate structure. In the exemplary burner, flange segments on the porous burner deck are only provided along the long sides of the rectangular circumference of the porous burner deck. No flange is provided on the porous burner deck along the short sides of the rectangular circumference of the porous burner deck.

[36] In the exemplary burner, the flange of the porous burner deck is held between the metal mounting plate and the plate structure; such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

[37] The metal mounting plate comprises a plurality of lips 1 16. In the exemplary burner lips are only provided along the long sides of the rectangular circumference of the porous burner deck. The lips are folded over in order to clamp the plate structure firmly to the metal mounting plate. Figure 5 shows the metal mounting plate, with the lips 1 16, before assembly in the burner. The lips 1 16 are folded towards the inside of the burner during assembly of the burner.

[38] 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 notches split the flange in a plurality of flange segments along the circumference of the plate structure. The notches 1 18 in the flange 120 of the plate structure are positioned around the lips 1 16 in the metal mounting plate. This way, the plate structure is correctly positioned in the burner.

[39] The metal mounting plate comprises upstanding ridges 126 providing supporting

elements onto which the plate structure is clamped by the metal mounting plate, more specifically by the folded lips of the metal mounting plate. The lips 1 16 clamp the flange segments of the plate structure onto the upstanding ridges 126; this way the plate structure is firmly clamped onto the metal mounting plate. The arrangement is such that only clamping (only lips folded over to act as clamps) is provided along the long sides of the rectangular cross section (with continuously rounded short sides) of the porous burner deck. Such arrangement facilitates the manufacturing operation.

[40] The upstanding ridges 126 of the metal mounting plate fit into notches 124 in the flange of the porous burner deck. The height of the upstanding 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 on the other hand. This way, the burner deck can efficiently cope with thermal expansion and contraction.

Claims

1. Premix gas burner comprising,

- a metal mounting plate (102);

- a mixing chamber (108);

- a porous burner deck (1 10) enclosing the mixing chamber and onto which combustion is stabilized after premix gas has flown from the mixing chamber through the porous burner deck; and

- a plate structure (106) comprising a plurality of perforations (1 12), wherein 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;

wherein the plate structure comprises a convex shape;

wherein the circumference of the porous burner deck has the shape of a rectangle of which the two short sides have been rounded;

wherein the plate structure has along its length an elongated section (131 ) and two end caps (133), wherein each of the end caps is provided at an end of the elongated section;

characterized in that the plate structure is provided via cutting and folding of a metal plate into the convex shape of the plate structure;

wherein the elongated section of the plate structure comprises at least one groove (135) created by deep drawing, wherein the at least one groove is provided on the crest line of the plate structure; and wherein the at least one groove is convex in the same direction as the plate structure;

wherein in each of the two end caps two edges (137) of the metal plate join parallel to the length direction of the elongated section in order to form the end caps.

2. Premix gas burner as in claim 1 , wherein the depth of the at least one groove (135) is more than 0.3 mm; preferably more than 0.5 mm; preferably less than 1 mm; and preferably less than 1.5 mm.

3. Premix gas burner as in any of the preceding claims, wherein the plate structure comprises open ended slits (1 14); wherein each of the open end slits ends at one of the short sides of the circumference of the porous burner deck;

wherein the open ended slits are provided in the end caps between the two edges of the metal plate that join parallel to the length direction of the elongated section; and

wherein each of the open ended slits is parallel with the length direction of the circumference of the porous burner deck.

4. Premix gas burner as in any of the preceding claims, wherein the elongated section of the plate structures comprises at least two grooves created by deep drawing, wherein the at least two grooves are provided on the crest line of the plate structure, wherein the at least two grooves are convex in the same direction as the plate structure and wherein the at least two grooves are provided in-line with each other.

5. Premix gas burner as in any of the preceding claims, wherein the porous burner deck (1 10) is provided in a convex shape; preferably wherein the porous burner deck is provided in a convex shape over the full surface of the porous burner deck provided for stabilizing the flames.

6. Premix gas burner as in any of the preceding claims,

wherein the metal mounting plate comprises an opening;

wherein the porous burner deck is inserted through the opening of the metal mounting plate.

7. Premix gas burner as in any of the preceding claims;

wherein the porous burner deck is a woven metal wire mesh; or

wherein the porous burner deck is provided by a woven, knitted or braided fabric comprising metal fibers.

8. Premix gas burner as in any of the preceding claims,

wherein the porous burner deck is bent such that a flange (122) is formed at its circumference; preferably wherein the flange of the porous burner deck is along the circumference of the porous burner deck split in a plurality of flange segments (122).

9. Premix gas burner as in claim 8; wherein the flange of the porous burner deck is only provided along the long sides of the rectangular circumference of the porous burner deck.

10. Premix gas burner as in claims 8 or 9;

wherein the flange (122) of the porous burner deck is held between the metal mounting plate and the plate structure; preferably such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

1 1. Premix gas burner as in any of the claims 8 - 10;

wherein the metal mounting plate comprises a plurality of lips (1 16) - preferably only along the long sides of the rectangular circumference of the porous burner deck -;

wherein the lips are folded over in order to clamp the plate structure firmly to the metal mounting plate;

preferably such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

12. Premix gas burner as in any of the claims 8 - 1 1 ;

wherein a flange (120) is provided on the plate structure - preferably wherein the flange of the plate structure is along the circumference of the plate structure split in a plurality of flange segments -;

wherein the flange of the porous burner deck (122) is held between the metal mounting plate and the flange (120) of the plate structure;

13. Premix gas burner as in any of the preceding claims;

wherein the metal mounting plate comprises upstanding ridges (126) providing supporting elements onto which the plate structure is clamped by the metal mounting plate.

14. Premix gas burner as in any of the preceding claims 8 - 12 and as in claim 13;

wherein the upstanding ridges (126) of the metal mounting plate fit into notches (118) in the flange of the porous burner deck; such that the flange of the porous burner deck is held with play between the metal mounting plate and the plate structure.

15. Condensing boiler comprising a premix gas burner as in any of the preceding claims.