INWARDLY BURNING SURFACE STABILIZED GAS PREMIX BURNER

Abstract

The burner (100) comprises a cylindrical porous substrate (110); and an end cap (130) at a first end of the cylindrical porous substrate (110). The cylindrical porous substrate (110) is provided for flow of a premix of combustible gas and air from the outside of the cylindrical porous substrate (110) through the pores of the cylindrical porous substrate (110) to an interior cavity (140), for the combustible gas to be combusted on the inner surface of the cylindrical porous substrate (110) thereby generating hot gas. The burner has an opening (182) at the second end of the cylindrical porous substrate (110) to exit the hot flue gas out of the interior cavity (140). The cylindrical porous substrate (110) has a higher permeability section (170), located at the opening (182) at the second end. The higher permeability section (170) has a lower resistance to gas flow than other sections of the cylindrical porous substrate (110).

Claims

1-15. (canceled)

16. A burner comprising, a cylindrical porous substrate; an end cap at a first end of the cylindrical substrate; wherein the cylindrical porous substrate and the end cap enclose an interior cavity; wherein the cylindrical porous substrate is provided for flow of a premix of combustible gas and air from the outside of the cylindrical porous substrate through the pores of the cylindrical porous substrate to the interior cavity, for the combustible gas to be combusted on the inner surface of the cylindrical porous substrate thereby generating hot gas; wherein the burner has an opening at the second end of the cylindrical porous substrate, for allowing the hot gas to exit the interior cavity; wherein the cylindrical porous substrate has a higher permeability section, wherein the higher permeability section is located at the opening at the second end; and wherein the higher permeability section has a lower resistance to gas flow than other sections of the cylindrical porous substrate.

17. A burner as in claim 16, wherein the higher permeability section comprises or consists out of an annular section of the cylindrical porous substrate.

18. A burner as in claim 16, wherein the cylindrical porous substrate comprises a first porous substrate present over the full height of the cylindrical porous substrate; wherein outside the higher permeability section of the cylindrical porous substrate the inner side of the first porous substrate is covered with a second porous substrate; and wherein in the higher permeability section when the burner is in use combustion occurs on the inner surface of the first porous substrate.

19. Burner as in claim 16, wherein the cylindrical porous substrate comprises a first porous substrate; wherein the inner side of the first porous substrate is covered with a second porous substrate; wherein the second porous substrate is a woven, knitted or braided fabric comprising stainless steel fibers; and wherein the higher permeability section is provided by differences in the structure of the fabric compared to outside the higher permeability section.

20. Burner as in claim 18, wherein the second porous substrate is a textile fabric comprising yarns, and wherein the yarns comprise a plurality of metal fibers in the cross section of the yarns.

21. Burner as in claim 18, wherein the second porous substrate is a weft knitted fabric; and wherein the weft direction of the weft knitted fabric is provided in the circumferential direction of the cylindrical porous substrate.

22. Burner as in claim 18, wherein the second porous substrate is a weft knitted fabric; and wherein the weft direction of the weft knitted fabric is provided in the axial direction of the cylindrical porous substrate.

23. Burner as in claim 16; wherein the cylindrical porous substrate has a higher porosity in the higher permeability section than in other sections of the cylindrical porous substrate.

24. Burner as in claim 23, wherein the cylindrical porous substrate comprises or consists out of a perforated plate; and wherein in the higher permeability section, the higher porosity is provided by means of a higher number of perforations per unit of surface area and/or by larger perforations of a larger cross sectional area.

25. Burner as claim 16, wherein the burner comprises a flange at the second end of the cylindrical porous substrate, and wherein in use, hot flue gas exits the interior cavity via the central opening in the flange.

26. Burner as in claim 25, wherein the flange is attached to the cylindrical porous substrate at the inner side of the cylindrical porous substrate.

27. Burner as in claim 16, wherein the end cap comprises perforations for the passage of premix combustible gas and air through the end cap to the inside of the interior cavity, for the premix combustible gas to be combusted inside the interior cavity.

28. Burner as in claim 27, wherein the end cap comprises perforations in a first area around the centre point of the end cap; wherein the first area has a diameter of less than 60% of the diameter of the end cap; wherein the end cap comprises perforations in a second area, wherein the second area is located outside the area around the centre point of the end cap; with diameter more than 75% of the diameter of the end cap; and wherein the end cap is not perforated in the area between the first area and the second area.

29. Burner as in claim 16, wherein the end cap is connected onto the cylindrical porous substrate at the outer side of the cylindrical porous substrate.

30. Heating device for heating a fluid, wherein the heating device comprises at least two burners as in claim 16.

Description

BRIEF DESCRIPTION OF FIGURES IN THE DRAWINGS

[0031] FIG. 1 shows an example of a burner according to the invention.

[0032] FIGS. 2 and 3 show cross sections of burners according to the invention.

[0033] FIG. 4 shows an example of an end cap that can be used in burners according to the invention.

[0034] FIG. 5 shows a heating device according to the second aspect of the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

[0035] FIG. 1 shows an example of a burner 100 according to the invention.

[0036] FIG. 2 shows a section of the burner taken according to the plane 2-2 parallel with and through the central axis of the burner. The burner 100 comprises a cylindrical porous substrate 110; and an end cap 130 at a first end of the cylindrical substrate. The cylindrical porous substrate 110 and the end cap 130 enclose an interior cavity 140.

[0037] The end cap 130 of the exemplary burner 100 has perforations 132 for the passage of premix combustible gas and air through the end cap 130 to the inside of the interior cavity 140 for being combusted inside the interior cavity 140. The end cap 130 of the exemplary burner 100 is connected onto the porous substrate at the outer side of the porous substrate.

[0038] The cylindrical porous substrate 110 is provided for flow of a premix of combustible gas and air from the outside of the cylindrical porous substrate 110 through the pores of the cylindrical porous substrate to the interior cavity 140, for the combustible gas to be combusted on the inner surface of the cylindrical porous substrate thereby generating hot gas. The burner 100 has an opening 182 at the second end of the cylindrical porous substrate, for allowing the hot gas to exit the interior cavity. In the example shown, the burner 100 comprises a flange 180 at the second end. The opening 182 is provided in the flange 180. In the exemplary burner 100, the flange 180 is attached to the cylindrical porous substrate 110 at the inner side of the cylindrical porous substrate 110, by means of welding. The flange 180 can be used to mount a burner to a support structure.

[0039] The cylindrical porous substrate 110 of the exemplary burner 100 comprises a first porous substrate 112 present over the full height of the cylindrical porous substrate 110. Outside the higher permeability section 170 of the cylindrical porous substrate 110 the inner side of the first porous substrate 112 is covered with a second porous substrate 114. Due to fact that outside the higher permeability section 170 of the cylindrical porous substrate 110, premix gas and air needs to flow through the first porous substrate 112 and through the second porous substrate 114, the resistance to gas flow is higher and therefore, the gas permeability is lower. In the higher permeability section 170, combustion will occur on the inner surface of the first porous substrate 112. Outside the higher permeability section 170, combustion will occur on the inner surface of the second porous substrate 114. In the example, the higher permeability section consists out of annular section of the cylindrical porous substrate 110; however other shapes of the higher permeability sections are possible.

[0040] Preferred examples for the first porous substrate are a woven metal wire mesh or a perforated metal plate. Preferred example for the second porous substratethat can be combined with any of the first porous substratesis a textile fabric comprising yarns, wherein the yarns comprise a plurality of metal fibers in the cross section of the yarns. It is preferred when the textile fabric is soft welded onto the first porous substrate. A specific example for the second porous substrate is a weft knitted fabric out of yarns spun from FeCrAlloy fibers. As an example, the weft direction of the weft knitted fabric can be provided in the circumferential direction of the cylindrical porous substrate. As an alternative example, the weft direction of the weft knitted fabric can be provided in the axial direction of the cylindrical porous substrate.

[0041] FIG. 3 shows the section of an alternative burner 300 according to the invention. The burner 300 is to a large extent similar to the burner shown in FIGS. 1 and 2. Parts in FIG. 3 with the same reference numeral as in FIGS. 1 and 2 are identical as in the burner shown in FIGS. 1 and 2. The burner 300 in FIG. 3 differs from the burner shown in FIG. 2 in that the cylindrical porous substrate 316 is formed out of a perforated metal plate welded at its contact edge to form the cylindrical porous substrate 316. The perforated metal plate, and thus the cylindrical porous substrate, has a higher porosity in the higher permeability section 370 than in its other sections 374. In the example, the higher permeability section 370 is an annular section of the cylindrical porous substrate 316, at the second end of the cylindrical porous substrate 316. The perforations in the perforated metal plate can be circular perforations and/or slits. Preferably, circular perforations have a diameter of less than 0.9 mm, e.g. 0.8 mm. Slits preferably have a width of less than 0.6 mm; e.g. 0.5 mm. The higher porosity in the higher permeability section 370 is e.g. provided by means of a higher number of perforations (circular perforations and/or slits) than in the other sections 374 of the cylindrical porous substrate 316. The porosity in the higher permeability section 370 is e.g. 26%. Outside the higher permeability section, the porosity of the perforated metal plate is e.g. 15%. The perforated metal plate can also have a small section at the end cap, wherein the section has a porosity of e.g. 9%.

[0042] FIG. 4 shows an example of an end cap 430 that can be used in the invention. The end cap 430 has a diameter D. the end cap 430 comprises perforations 434 in a first area around the centre point of the end cap. The first area has a diameter D1 of less than 60% of the diameter of the end cap. The end cap 430 comprises perforations 436 in a second area. The second area is located outside the area around the centre point of the end cap; wherein the area has a diameter D2 of more than 75%. The end cap 430 is not perforated in the area between the first area and the second area. The perforations of in the first area and the perforations in the second area e.g. have a diameter of 0.8 mm.

[0043] FIG. 5 shows a heating device 500 for heating a fluid according to the second aspect of the invention. The heating device 500 comprises a number of burners 100 as in the first aspect of the invention. The burners 100 are linearly aligned in the heating device 500. The flanges 580 of the burners 500 are attached to a mounting plate 592. The burners are provided in a premixing chamber 594, which is provided with walls 596. A premix of combustible gas and air in fed (see arrow 598) into the premixing chamber 594 through one of the walls of the premixing chamber. Hot gas generated by combustion of the premix gas on the inner surface of the cylindrical porous substrate 510 flows from the interior cavity 140 of the burner 100 through opening 582 into a tube 590, via the combustion chamber 597 provided between the burners 100 and the tubes 590. Each of the burners is provided to exit hot gas through the opening at the second end of the burner into a specific tube of a tubular heat exchanger. The heating device can be a furnace air heater.