EP3513123B1

EP3513123B1 - Premix gas burner

Info

Publication number: EP3513123B1
Application number: EP17761904.6A
Authority: EP
Inventors: Roelof BOER; Daniel HOLTROP; René VAN ZUTPHENT; Geert Folkers
Original assignee: Bekaert Combustion Technology BV
Current assignee: Bekaert Combustion Technology BV
Priority date: 2016-09-13
Filing date: 2017-09-11
Publication date: 2021-02-17
Anticipated expiration: 2037-09-11
Also published as: CN109716023A; CN109690190A; JP2019526776A; JP2019526777A; KR102368554B1; CN109690190B; CN109716023B; EP3513123A1; KR20190045211A; WO2018050310A1; EP3513122B1; WO2018050578A1; CN112050208A; EP3513122A1

Description

Technical Field

The invention relates to the field of premix gas burners, more particularly to surface stabilized premix gas burners comprising a woven wire mesh as burner deck.

Background Art

Surface stabilized premix gas burner having a woven wire mesh burner deck are known.
US5474443A discloses a premix gas burner with a hemispherical burner deck out of a woven wire mesh.
US2005/172915 shows a premix gas burner having a woven wire mesh combustion surface comprising rigidizing ribs.
EP2876369A1 discloses a gas burner for a boiler. The burner comprises a combustion membrane with a diffuser layer in the shape of a three-dimensional shell forming an outer combustion surface with at least one double-curvature region. The combustion surface comprises a first portion formed by a perforated metal sheet, and a second portion formed by a permeable fibre- or thread-based material.
US2014011143A discloses a gas boiler burner comprising a diffuser, suitable for diffusing premixed fuel gases in a combustion chamber. The diffuser comprises a diffuser central portion and two diffuser longitudinally peripheral portions. The two diffuser longitudinally peripheral portions are connected together through the central diffuser portion. The central diffuser portion extends longitudinally in a direction perpendicular to the flow of the fuel gases over a length I greater than zero and has transversal cross-sections shaped as a circumference arc having a uniform radius of curvature r. Each of the diffuser longitudinally peripheral portions are shaped as a portion of a sphere having radius r.
US2016040905A discloses a burner assembly comprising a diffuser plate and a plurality of burners. The burners are preferably defined in a unitary mesh structure, for example being stamped or pressed into mesh structure.

Disclosure of Invention

The first aspect of the invention is a premix gas burner according to claim 1.
The woven wire mesh burner deck of surface stabilized premix gas burners warms up when the burner is in use. The woven wire mesh burner deck needs to be able to cope with the stresses induced by the thermal expansion associated with the high temperature when the burner is in use and by the shrinkage when the burner is not in use. If this is not the case, early mechanical failure of the burner deck will occur. Thanks to the provision of the tab or tabs at the circumference of the woven wire mesh burner - tab or tabs which are inserted through openings in the metal plate structure - an amount of movement of the woven wire mesh relative to the metal plate structure is possible when the woven wire mesh expands when warming up or shrinks when cooling down. The certain amount of movement of the woven wire mesh relative to the metal plate structure is possible as the tab or tabs are not mechanically nor physically (e.g. by means of welds) bonded onto the metal plate structure. Therefore surprisingly, the premix gas burner of the invention has shown to be very well suited to withstand thermal expansion and shrinkage, resulting in a long lifetime of the premix gas burner.
Preferred tabs have a substantially rectangular shape. Preferred tabs have a width between 4 and 20 mm; more preferred between 6 and 12 mm. Preferred tabs have a height between 1 to 12 mm; more preferably between 3 and 6 mm.
Preferred tabs have a largest width between 4 and 20 mm; more preferably between 6 and 12 mm. Preferred tabs have a largest height between 3 and 6 mm.
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.
Preferably, at least one tab is bent such that an included angle less than 180° is provided between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening. Preferably all tabs are bent such that an included angle less than 180° is provided between the tab through the opening and the section of the woven wire mesh at the other side of the opening. More preferably, the included angle is less than 150°, even more preferably less than 120°. Preferably, the included angle is more than 30°, even more preferably more than 60°, even more preferably more than 90°. Embodiments wherein at least one tab is bent ensure that the woven wire mesh is better held in place in applications where the burner is used with the burner deck facing downwards; and contribute to the realization of a longer lifetime of the burner deck and the burner.
In a preferred embodiment, the burner deck is provided in a convex shape. It is meant that when the burner is in operation, the flames of the burner are anchored onto the convex side of the burner deck. More preferably, the full surface of the burner deck is provided in a convex shape; meant is that when the burner is in operation, the full surface of the burner deck at the side of which the flames are anchored has a convex shape.
In a preferred embodiment, the woven wire mesh does not comprise ribs nor embossments.
In a preferred embodiment, the woven wire mesh comprises ribs and/or embossments.
In embodiments in which the circumference of the burner deck has the shape of a rectangle of which the two short sides have been - preferably continuously - rounded, preferably tabs are only provided along the two long sides of the rectangular shape of the circumference of the burner deck. Meant is that no tabs are provided along the - possibly continuously - rounded short sides. Burners according to this embodiment are even better suited for long lifetime use, as the absence of tabs along the short sides allows better thermal expansion of the woven wire mesh in its length direction.
In a preferred embodiment, the metal plate structure comprises a groove. The width of the groove is larger than the thickness of the woven wire mesh. At least part of the - and preferably the complete - circumferential edge of the woven wire mesh is positioned in the groove. Preferably, at least part the openings - and preferably all openings - are provided in the groove (and preferably at the bottom of the groove). Such embodiments synergistically add to provide a burner with a long life time. As the width of the groove is wider than the thickness of the woven wire mesh, a certain amount of movement of the woven wire mesh relative to the metal plate structure is provided. Furthermore, such embodiments have an additional benefit, in that less risk of flame flashback via the edges of the woven wire mesh exists.
Preferably, the depth of the groove is at least 1 mm, more preferably at least 2 mm. Preferably, the width of the groove is at least 0.1 mm larger than the thickness of the woven wire mesh. More preferably the width of the groove is at least 0.3 mm larger than the thickness of the woven wire mesh. Preferably, the width of the groove is less than 0.8 mm larger than the thickness of the woven wire mesh. Such embodiments provide burners that have a long lifetime; as such burners are very well suited to cope with the thermal stresses on the woven wire mesh burner deck in use of the burner.
Preferably, the depth of the groove is a least three times the difference between the width of the groove and the thickness of the woven wire mesh. Such embodiments provide burners that have a long lifetime; as such burners are even better suited to cope with the thermal stresses on the woven wire mesh burner deck in use of the burner.
In embodiments wherein the metal plate structure comprises a groove and wherein the circumference of the burner deck has the shape of a rectangle but with the two short sides - preferably continuously - rounded; preferably the width of the groove is larger in the two - preferably continuously - rounded short sides than along the two long sides of the rectangular shape of the circumference of the burner deck. Burners according to this embodiment are even better suited for long lifetime use, as the absence of tabs along the short sides in combination with the wider groove at the short side allows better thermal expansion of the woven wire mesh in length direction.
In preferred embodiments wherein the metal structure comprises a groove, spread along the full circumference of the burner deck a number of slits are provided in the plate structure at the bottom of the groove. The circumferential edge of the woven wire mesh comprises a number of tabs spread along the complete circumferential edge of the woven wire mesh; and each tab is inserted through a slit. Such embodiments provide further improvement with respect to the lifetime of the burner.
Preferred premix gas burners comprise a perforated plate segments through which the premix gas flows before the premix gas flows through the woven wire mesh. The perforated plate segment is provided to distribute the premix gas more evenly over the surface of the burner deck; and therefore, contributes to the prolonged lifetime of the burner. More preferably, all zones of the perforated plate segment provided with perforations are provided at a distance of at least 1 mm from the woven wire mesh; and preferably at a distance of less than 3 mm. Such embodiments contribute to the ability to produce burners that have a long lifetime.
In preferred burners comprising a perforated plate segment through which the premix gas flows before the premix gas flows through the woven wire mesh, the metal plate structure comprises a first metal plate for mounting the burner in a heating appliance and a second metal plate comprising the perforated plate segment. In such embodiments wherein the metal plate structure comprises a groove, preferably one side of the groove is provided by the first metal plate; and the other side of the groove is provided by the second metal plate.
In preferred burners comprising a perforated plate segment through which the premix gas flows before the premix gas flows through the woven wire mesh, the metal plate structure comprises a metal plate. The metal plate comprises sections for mounting the burner in a heating appliance as well as the perforated plate segment. In such embodiments wherein the metal plate structure comprises a groove, preferably the groove is provided by shaping the metal plate; e.g. by means of deep drawing of the metal plate.
In an example, there is provided 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

Figures 1 and 2 show a premix gas burner according to the invention.
Figures 3, 4 and 5 show cross sections of premix gas burners according to the invention.
Figure 6 illustrates the included angle between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening.

Mode(s) for Carrying Out the Invention

Figures 1 and 2 show a premix gas burner according to the first aspect of the invention. Figure 1 shows the burner at the side of the burner deck where the combustion occurs, whereas figure 2 shows the burner from the side from which premix gas is supplied. The premix gas burner comprises a metal plate structure 105 for mounting the premix gas burner in a heating appliance, a burner deck 110 and a groove 115 (not visible in figure 1, the groove can be observed from its bottom in figure 2) in the metal plate structure 105. The burner deck 110 consists out of a woven wire mesh on the outer surface of which premix gas is combusted after the premix gas has flown through the woven wire mesh. In the example, the burner deck is provided in a convex shape over the full surface of the burner deck. In the exemplary burner, the woven wire mesh does not comprise ribs or embossments. The circumference of the burner deck of the exemplary burner has the shape of a rectangle of which the two short sides have been continuously rounded; other circumferential shapes of the burner deck are possible however.
The width of the groove 115 is larger than the thickness of the woven wire mesh. A number of openings 120 are provided in the bottom of the groove 115. The openings can e.g. take the form of slits at the bottom of the groove. The circumferential edge of the woven wire mesh is positioned in the groove 115. The circumferential edge of the woven wire mesh comprises a number of tabs 125; each tab is inserted through an opening in the bottom of the groove. In the example, tabs are only provided along the two long sides of the rectangular shape of the circumference of the burner deck. In the example, the width of the groove is larger in the two continuously rounded short sides than along the two long sides of the rectangular shape of the circumference of the burner deck.
In preferred burners, the tabs are bent (not shown in figure 2, but is illustrated in figure 6) with respect to the surface of the burner deck, such that the woven wire mesh is better held in the premix gas burner.
As is visible in figure 2 which shows the burner from the side from which premix gas is supplied, the exemplary burner comprises a perforated plate 130 through which the premix gas flows before the premix gas flows through the woven wire mesh.
Figures 3, 4 and 5 show cross sections of three different executions of burners according to the first aspect of the invention.
Figure 3 shows a cross section 300 according to plane A1-A1 of figure 1 of the exemplary burner shown in figures 1 and 2. The metal plate structure 305 comprises a metal plate comprising sections 307 for mounting the burner in a heating appliance as well as the perforated plate segment 330. The metal plate structure (one metal plate) 305 is shaped by punching and deep drawing. The metal plate 305 comprises a groove 315, with openings 320. The circumferential edge of the woven wire mesh 310 is positioned in the groove 315. The tabs 325 at the circumferential edge of the woven wire mesh 310 are inserted through openings 320 in the bottom of the groove 315 (the cross section shown in figure 3 crosses through tabs at both sides of the burner). Preferably, all zones of the perforated plate segment 330 provided with perforations are provided at a distance of at least 1 mm from the woven wire mesh 310; and preferably at a distance of less than 3 mm. As an example, the depth D of the groove is 2 mm and the width W of the groove 1.5 and the thickness of the woven wire mesh is 0.9 mm. Preferably, the tabs are bent (not shown in figure 3) - more preferably to the inside of the burner - such that an included angle less than 180° - and preferably less than 150° - is created between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening.
Figure 4 shows a cross section 400 of a burner according to an alternative embodiment of the invention. The metal plate structure 405 comprises a metal plate. The metal plate comprises sections 407 for mounting the burner in a heating appliance as well as the perforated plate segment 430. Premix gas flows through the perforations of the perforated plate segment 430 before the premix flows through the woven wire mesh burner deck 410 to be combusted at the other side of the woven wire mesh burner deck 410. The metal plate structure (one metal plate) 405 is shaped by punching and deep drawing. The metal plate 405 comprises openings 420, but no groove. The tabs 425 at the circumferential edge of the woven wire mesh 410 are inserted through the openings (the cross section shown in figure 4 crosses through tabs at both sides of the burner). Preferably, all zones of the perforated plate segment 430 provided with perforations are provided at a distance of at least 1 mm from the woven wire mesh 410; and preferably at a distance of less than 3 mm. Preferably, the tabs are bent (not shown in figure 4) - more preferably to the inside of the burner - such that an included angle less than 180° - and preferably less than 150° - is created between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening.
Figure 5 shows a cross section 500 of a burner according to an alternative embodiment of the invention. The metal plate structure 505 comprises a first metal plate 507 for mounting the burner in a heating appliance and a second metal plate 530 comprising the perforated plate segment. Premix gas flows through the perforated plate segment before the premix gas flows through the woven wire mesh burner deck 510 to be combusted at the other side of the woven wire mesh burner deck 510. A groove 515 is provided in the metal plate structure 505. One side of the groove 515 is provided by the first metal plate 507; and the other side of the groove is provided by the second metal plate 510. The circumferential edge of the woven wire mesh 510 is positioned in the groove 515. The tabs 525 at the circumferential edge of the woven wire mesh 510 are inserted through openings 520 in the bottom of the groove 515 (the cross section shown in figure 5 crosses through tabs at both sides of the burner). As an example, the depth of the groove is 2 mm and the width of the groove 1.5 mm and the thickness of the woven wire mesh is 0.9 mm. Preferably, the tabs are bent (not shown in figure 5) - more preferably to the inside of the burner - such that an included angle less than 180° - and preferably less than 150° - is created between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening.
Figure 6 illustrates the included angle between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening. Figure 6 shows part of an inventive burner. Figure 6 shows part of the metal plate structure 605 for mounting the burner, part of the perforated metal plate 630, the groove 615, part of the woven wire mesh 610 and a tab 625 inserted through an opening in the bottom of the groove. Figure 6 illustrates how the tab is preferably bent such that an included angle alpha (α) is created between the tab 615 inserted through the opening and the section of the woven wire mesh 610 at the other side of the opening. Preferably, the included angle is less than 150°. In the example the tab is bent to the inside of the burner.

Claims

Premix gas burner comprising
- a metal plate structure (105) for mounting the premix gas burner in a heating appliance; and

- a burner deck (110), wherein the burner deck comprises a woven wire mesh on the outer surface of which premix gas is combusted after the premix gas has flown through the woven wire mesh; wherein one or more than one opening (120) is provided in the metal plate structure;
wherein the woven wire mesh comprises a circumferential edge;
characterized in that the circumferential edge of the woven wire mesh comprises at least one tab (125);
wherein each at least one tab is inserted through an opening in the metal plate structure.
Premix gas burner as in claim 1, wherein at least one tab; and preferably all tabs; is bent such that an included angle less than 180° - and preferably less than 150° - is provided between the tab inserted through the opening and the section of the woven wire mesh at the other side of the opening.
Premix gas burner as in any of the preceding claims, wherein the burner deck is provided in a convex shape; preferably wherein the burner deck is provided in a convex shape over the full surface of the burner deck.
Premix gas burner as in any of the preceding claims, wherein the circumference of the burner deck has the shape of a rectangle of which the two short sides have been - preferably continuously - rounded.
Premix gas burner as in claim 4, wherein tabs are only provided along the two long sides of the rectangular shape of the circumference of the burner deck.
Premix gas burner as in any of the preceding claims,
wherein the metal plate structure comprises a groove (115);
wherein the width of the groove is larger than the thickness of the woven wire mesh;
wherein at least part of the - and preferably the complete - circumferential edge of the woven wire mesh is positioned in the groove; and
wherein at least part of the openings - and preferably all openings - are provided in the groove.
Premix gas burner as in claim 6, wherein the width of the groove is at least 0.1 mm larger than the thickness of the woven wire mesh.
Premix gas burner as in any of the claims 6 or 7;
wherein the circumference of the burner deck has the shape of a rectangle but with the two short sides rounded;
and wherein the width of the groove is larger in the two rounded short sides than along the two long sides of the rectangular shape of the circumference of the burner deck.
Premix gas burner as in any of the preceding claims, wherein the burner comprises a perforated plate segment (330) through which the premix gas flows before the premix gas flows through the woven wire mesh.
Premix gas burner as in claim 9, wherein all zones of the perforated plate segment provided with perforations are provided at a distance of at least 1 mm from the woven wire mesh; and preferably at a distance of less than 3 mm from the woven wire mesh.
Premix gas burner as in claims 9 or 10; wherein the metal plate structure comprises a first metal plate for mounting the burner in a heating appliance; and a second metal plate comprising the perforated plate segment.
Premix gas burner as in claim 11; and as in any of the claims 6 to 8; wherein one side of the groove is provided by the first metal plate; and the other side of the groove is provided by the second metal plate.
Premix gas burner as in claims 9 or 10, wherein the metal plate structure comprises a metal plate; wherein the metal plate comprises sections for mounting the burner in a heating appliance as well as the perforated plate segment.
Premix gas burner as in claim 13; and as in any of the claims 6 to 8, wherein the groove is provided by shaping the metal plate.