Inwardly firing premix gas burner

Abstract

A premix gas burner comprises a main body, a porous wall, a distribution chamber delimited by the main body and by the porous wall, and an entrance in the main body for introducing a premix of combustible gas and air into the distribution chamber. The main body comprises a cylindrical shape. The porous wall comprises a first porous wall segment and a second porous wall segment. The first porous wall segment and the second porous wall segment both comprise pores for the premix gas to flow from the distribution chamber through the pores, for combustion of the premix gas outside the distribution chamber. The first porous wall segment comprises or consists out of a shaped segment. The shaped segment is directed to the inside of the distribution chamber, such that when the burner is in use premix gas flows from the distribution chamber through the pores of the shaped segment to the inside of the shaped segment. The second porous wall segment comprises an annular porous wall segment. The annular porous wall segment is provided at the base of the shaped segment. The base of the shaped element is provided at the side of the shaped element opposite to the location of the entrance in the main body.

Claims

1. Premix gas burner, comprising a main body; wherein the main body comprises a cylindrical shape; a porous wall; a distribution chamber delimited by the main body and by the porous wall, an entrance in the main body for introducing a premix of combustible gas and air into the distribution chamber; wherein the porous wall comprises a first porous wall segment and a second porous wall segment; wherein the first porous wall segment and the second porous wall segment both comprise pores for the premix gas to flow from the distribution chamber through the pores for combustion of the premix gas outside the distribution chamber; wherein the first porous wall segment comprises or consists out of a shaped segment, wherein the shaped segment is directed to the inside of the distribution chamber, such that when the burner is in use premix gas flows from the distribution chamber through the pores of shaped segment to the inside of the shaped segment; wherein the second porous wall segment comprises an annular porous wall segment; wherein the annular porous wall segment is provided at the base of the shaped segment; wherein the base of the shaped element is provided at the side of the shaped element opposite to the location of the entrance in the main body.

2. Premix gas burner as in claim 1, wherein the shaped segment comprises or consists out of a conical or frusto-conical shape.

3. Premix gas burner as in claim 1, wherein the annular porous wall segment comprises or consists out of a flat annular porous wall segment.

4. Premix gas burner as in claim 1, wherein the annular porous wall segment is not flat.

5. Premix gas burner as in claim 1, wherein the annular porous wall segment comprises or consists out of a segment with frusto-conical shape.

6. Premix gas burner as in claim 2, wherein the annular porous wall segment comprises or consists out of a segment with frusto-conical shape, and wherein the annular porous wall segment comprises or consists out of a segment with frusto-conical shape with cone angle larger than or equal to the largest cone angle of the segment with conical or frusto-conical shape of the first porous wall segment.

7. Premix gas burner as in claim 1, wherein the annular porous wall segment comprises a perforated plate, a woven wire mesh or an expanded metal sheet.

8. Premix gas burner as in claim 7, wherein the annular porous wall segment comprises a woven, knitted or braided burner deck comprising metal fibers, covering the perforated plate, woven wire mesh or expanded metal sheet; and wherein the woven, knitted or braided burner deck is provided for anchoring flames onto the annular porous wall segment.

9. Premix gas burner as in claim 7, wherein the gas permeable area of the perforated plate, woven wire mesh or expanded metal sheet of the annular porous wall segment is less than 7% of its total area.

10. Premix gas burner as in claim 1, wherein the shaped segment of the first porous wall segment comprises a perforated plate, a woven wire mesh or an expanded metal sheet shaped into shape of the shaped element; and wherein the perforated plate, woven wire mesh or expanded metal sheet of the shaped segment of the first porous wall segment is covered at the inner side of the shaped segment by a woven, knitted or braided burner deck comprising metal fibers.

11. Premix gas burner as in claim 10, wherein the annular porous wall segment comprises a perforated plate, a woven wire mesh or an expanded metal sheet; and wherein the relative gas permeable area of the perforated plate, woven wire mesh or expanded metal sheet of the shaped segment of the first porous wall segment is higher than the relative gas permeable area of the perforated plate, woven wire mesh or expanded metal sheet of the annular porous wall segment.

12. Premix gas burner as in claim 1, wherein the shaped element widens in the direction away from the entrance in the main body.

13. Premix gas burner as in claim 1, wherein the cylindrical shape of the main body comprises a perforated section; wherein the perforated section is covered by a woven, knitted or braided burner deck comprising metal fibers; and wherein the woven, knitted or braided burner deck provides an extended burner deck for anchoring of flames when the burner is in use.

14. Premix gas combustion system, comprising a combustion chamber having lateral walls; and a premix gas burner as in claim 1, wherein the premix gas burner is provided at a first longitudinal end of the combustion chamber; wherein the second longitudinal end of the combustion chamber is closed by a wall; wherein the combustion chamber is provided for the combustion of the premix gas after the premix gas has flown from the distribution chamber through the pores of the porous wall; and wherein an exit for combustion gas is provided in the combustion chamber at the first longitudinal end of the combustion chamber.

15. Method for operating a premix gas burner as in claim 1, wherein the burner operates at a capacity of more than 200 kW; and/or wherein the surface load of the shaped segment is more than 50 kW/dm.sup.2.

16. Premix gas burner as in claim 1, wherein the annular porous wall segment comprises a perforated plate; wherein the shaped segment of the first porous wall segment comprises a woven wire mesh shaped into shape of the shaped element; wherein the woven wire mesh of the shaped segment of the first porous wall segment is covered at the inner side of the shaped segment by a woven, knitted or braided burner deck comprising metal fibers.

17. Premix gas burner as in claim 16, wherein the relative gas permeable area of the woven wire mesh of the shaped segment of the first porous wall segment is higher than the relative gas permeable area of the perforated plate of the annular porous wall segment.

18. Premix gas burner as in claim 16, wherein the annular porous wall segment comprises a woven, knitted or braided burner deck comprising metal fibers covering the perforated plate; and wherein the woven, knitted or braided burner deck is provided for anchoring flames onto the annular porous wall segment.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a premix gas combustion system according to the invention.

(2) FIG. 2 shows a premix gas burner according to the invention.

(3) FIG. 3 shows another example of a premix gas burner according to the invention.

MODE(S) FOR CARRYING OUT THE INVENTION

(4) FIG. 1 shows a premix gas combustion system 100 according to the invention. The system 100 comprises a cylindrical combustion chamber 110 having lateral walls 112 and a premix gas burner 120 as in the first aspect of the invention. The premix gas burner 120 is provided at a first longitudinal end of the combustion chamber 110. The second longitudinal end 114 of the combustion chamber is closed by a wall.

(5) The premix gas burner 120 comprises a cylindrical main body 122, a porous wall 124, 126, a distribution chamber 140 delimited by the main body and by the porous wall, and an entrance 150 in the main body for introducing a premix of combustible gas and air into the distribution chamber. The porous wall comprises a first porous wall segment 124 and a second porous wall segment 126.

(6) The first porous wall segment 124 is provided by a segment with frusto-conical shape 124. The frusto-conical shape is directed to the inside of the distribution chamber; such that when the burner is in use premix gas flows from the distribution chamber through the pores of the frusto-conical shape segment to the inside of the frusto-conical shape segment. The closing section 123 of the frusto-conical shape is impermeable to premix gas. The conical part of the frusto-conical shape has an angle α (the cone angle), which can e.g. be 70°. The segment with frusto-conical shape 124 comprises a perforated plate 142 shaped into conical shape; as an example 36% of the surface of the perforated plate 142 is permeable to premix gas. The perforated plate 142 is covered at the inner side of the frusto-conical shape by a knitted burner deck 144 comprising yarns. The yarns comprise a plurality of metal fibers in their cross section. Alternatively, the perforated plate can e.g. be covered at the inner side of the frusto-conical shape by a braided or woven burner deck comprising metal fibers.

(7) The second porous wall segment is provided by a flat annular porous wall segment 126 provided at the base of the segment with conical shape. In the example in FIG. 1, the flat annular porous wall segment comprises a perforated plate 130, the gas permeable area of the perforated plate is less than 7% of its total area; e.g. 5% of its total area is permeable to gas. The perforated plate 130, covered by a knitted fabric 132 comprising metal fibers acts as burner deck. The knitted burner deck is provided for anchoring the flames 160 onto the flat annular porous wall segment.

(8) The combustion chamber is provided for the combustion of the premix gas after the premix gas has flown from the distribution chamber through the pores of the porous wall. Flames 160 are formed on the surface of the first porous wall segment and on the surface of the second porous wall segment. An exit 116 for combustion gas is provided in the combustion chamber at the first longitudinal end of the combustion chamber. The flow of the flue gas created by the combustion is schematically shown by flow lines 190.

(9) The premix gas burner can comprise an ignition electrode (not shown in FIG. 1) positioned such that ignition of the burner occurs on the flat annular porous wall segment provided at the base of the segment with conical shape.

(10) The premix gas burner can comprise an ionization electrode (not shown in FIG. 1) for flame sensing and/or for combustion control. The ionization electrode is preferably positioned such that ionization current is determined or measured at the flat annular porous wall segment provided at the base of the segment with conical shape.

(11) Examples of dimensions (with reference to FIG. 1) of premix gas burners according to the invention and their nominal capacity are given in table I.

(12) TABLE-US-00001 TABLE I Dimensions of examples according to FIG. 1 of premix gas burners Diameter Diameter Cone Height Diameter Capacity D.sub.2 D.sub.1 angle α H D.sub.3 (kW) (mm) (mm) (°) (mm) (mm) 500 200 168 68 125 24 700 245 200 71 140 24 1000 300 235 68 175 24 1400 350 285 71 200 24 3500 480 415 73 280 24

(13) Such burner according to the invention has been tested at different surface load of the burner deck. The burner functioned well at a surface load of the burner deck 100 kW/dm.sup.2 as well as at a surface load of the burner deck 2 kW/dm.sup.2, evidencing the large modulation range of the burner.

(14) FIG. 2 shows a premix gas burner 220 according to the invention. The premix gas burner 220 comprises a cylindrical main body 222, a porous wall 224, 226, a distribution chamber 240 delimited by the main body and by the porous wall, and an entrance 250 in the main body for introducing a premix of combustible gas and air into the distribution chamber. The porous wall comprises a first porous wall segment 224 and a second porous wall segment 226.

(15) The first porous wall segment 224 is provided by a segment with frusto-conical shape 224. The frusto-conical shape is directed to the inside of the distribution chamber 240; such that when the burner is in use premix gas flows from the distribution chamber through the pores of the frusto-conical shape segment to the inside of the frusto-conical shape segment. The closing section 223 of the frusto-conical shape is impermeable to premix gas. The conical part of the frusto-conical shape has an angle α (the cone angle), which can e.g. be 70°. The segment with frusto-conical shape 224 comprises a perforated plate 242 shaped into conical shape. The perforated plate 242 is covered at the inner side of the frusto-conical shape by a knitted burner deck 244 comprising metal fibers. Alternatively, the perforated plate can e.g. be covered at the inner side of the frusto-conical shape by a braided or woven burner deck comprising metal fibers.

(16) The second porous wall segment is provided at the base of the segment with conical shape; the second porous wall segment consists out of an annular segment. The annular segment is a segment 226 with frusto-conical shape with cone angle β larger than the largest cone angle α of the segment with conical shape of the first porous wall segment. The angle β is e.g. 130° whereas the angle α is e.g. 70°. In the example in FIG. 2, the annular porous wall segment comprises a perforated plate 230. The gas permeable area of the perforated plate is less than 7% of its total area. The perforated plate 230 is covered by a knitted fabric 232 comprising metal fibers acting as burner deck. The knitted burner deck is provided for anchoring the flames (not shown in FIG. 2) onto the annular porous wall segment when the burner is in use.

(17) In the example of FIG. 2, the relative gas permeable area of the perforated plate of the segment with conical shape of the first porous wall segment is higher than the relative gas permeable area of the perforated plate of the annular porous wall segment.

(18) FIG. 3 shows a premix gas burner 320 according to the invention. The premix gas burner 320 comprises a cylindrical main body 322, a porous wall 324, 326, a distribution chamber 340 delimited by the main body and by the porous wall, and an entrance 350 in the main body for introducing a premix of combustible gas and air into the distribution chamber. The porous wall comprises a first porous wall segment 324 and a second porous wall segment 326.

(19) The first porous wall segment 324 is provided by a segment with frusto-conical shape 324. The frusto-conical shape is directed to the inside of the distribution chamber 340; such that when the burner is in use premix gas flows from the distribution chamber through the pores of the frusto-conical shape segment to the inside of the frusto-conical shape segment. The closing section 323 of the frusto-conical shape is impermeable to premix gas. The conical part of the frusto-conical shape has an angle α (the cone angle), which can e.g. be 70°. The segment with frusto-conical shape 324 comprises a perforated plate 342 shaped into conical shape. The perforated plate 342 is covered at the inner side of the frusto-conical shape by a knitted burner deck 344 comprising metal fibers.

(20) The second porous wall segment is provided at the base of the segment with conical shape. The second porous wall segment consists out of an annular segment. The annular segment is a segment 326 with frusto-conical shape with cone angle β larger than the largest cone angle α of the segment with conical shape of the first porous wall segment. The angle β is e.g. 130° whereas the angle α is e.g. 70°. In the example in FIG. 3, the annular porous wall segment comprises a perforated plate 330. The gas permeable area of the perforated plate is less than 7% of its total area. The perforated plate 330 is covered by a knitted fabric 332 comprising metal fibers acting as burner deck. The knitted burner deck is provided for anchoring the flames (not shown in FIG. 3) onto the annular porous wall segment when the burner is in use.

(21) The cylindrical main body 322 comprises a perforated section 362 along the full circumference of the cylindrical main body. The perforated section is covered by a knitted burner deck 364 comprising metal fibers. This knitted burner deck 364 provides an extended burner deck for anchoring of flames when the burner is in use. The perforated section 362 neighbours the annular porous wall segment 326, such that a continuous burner deck is provided on the burner. The extended burner deck provided by the knitted burner deck 364 provides a very convenient location for the installation for an ignition pen to ignite the complete burner, or for the installation of an ionization pen to monitor combustion on the burner.

(22) In the example of FIG. 3, the relative gas permeable area of the perforated plate of the segment with conical shape of the first porous wall segment is higher than the relative gas permeable area of the perforated plate of the annular porous wall segment; and the relative gas permeable area of the perforated section of the cylindrical shape of the main body is higher than the relative gas permeable area of the perforated plate of the annular porous wall segment.