Combustion membrane for a gas burner

Abstract

A combustion membrane (14) for a gas burner (2) comprises a fabric (21) having two opposite fabric surfaces (19, 20) which form a combustion surface (19) exposed on the outer side (17) and an inner surface (20) facing an inner side (18), respectively, wherein the fabric (21) forms an interlacement of metal threads (22) comprising warp threads and weft threads transverse with respect to the warp threads, wherein: both fabric surfaces (19, 20) form high-relief ribs (23) formed by a main float thread (25), respectively, extending straddling exactly three underlying transverse threads, and wherein a side thread bridge (25), extending straddling exactly one underlying transverse thread, is formed on both longitudinal sides of each main float thread (25), so that the main float thread (25) and the two side thread bridges (25) delimit a cross thread configuration (25) formed by mutually parallel threads.

Claims

1. A combustion membrane (14) for a gas burner (2), said combustion membrane (14) having an inner side (18) to which a combustible gas (13) is conveyed and an outer side (17) on which combustion of the combustible gas (13) occurs after it has crossed the combustion membrane (14), said combustion membrane (14) comprising a fabric (21) having two opposite fabric surfaces (19, 20) which form a combustion surface (19) exposed on the outer side (17) and an inner surface (20) facing the inner side (18), respectively, wherein the fabric (21) forms an interlacement of metal threads (22) comprising warp threads and weft threads transverse with respect to the warp threads, wherein both fabric surfaces (19, 20) form high-relief ribs (23) alternating with low-relief sags (24), characterized in that: the ribs (23) are formed by a main float thread (25), respectively, extending straddling exactly three underlying transverse threads, and a side thread bridge (25), extending straddling exactly one underlying transverse thread, is formed on both longitudinal sides of each main float thread (25), directly adjacent and parallel thereto and located centrally with respect to the longitudinal extension thereof, so that the main float thread (25) and the two side thread bridges (25) delimit a cross thread configuration (25) formed by mutually parallel threads.

2. A combustion membrane (14) according to claim 1, wherein in the same cross thread configuration (25), the side thread bridges (25) are retracted with respect to the main float thread (25) which protrudes from the fabric (21).

3. A combustion membrane (14) according to claim 1 or 2, wherein on the combustion surface (19) and on the inner surface (20), said cross thread configurations (25) are formed with both weft metal threads (22) and warp metal threads (22).

4. A combustion membrane (14) according to any one of the preceding claims, wherein: A) a first plurality of the cross thread configurations (25) formed by warp threads is arranged grouped into first groups (25.1) of exactly two cross thread configurations (25) directly adjacent and aligned in a first diagonal direction (28.1) with respect to the weft (30) and warp (31) directions of the fabric (21), wherein between two said first groups (25.1) of cross configurations (25) aligned along said first diagonal direction (28.1), respectively, a first diagonal distance (26.1) is formed without cross configurations (25) aligned along the same first diagonal direction (28.1), wherein said first diagonal distance (26.1) is equal to a first diagonal extension (27.1) of the first group (25.1) of cross thread configurations (25), B) a second plurality of the cross thread configurations (25) formed by warp threads is arranged grouped into second groups (25.2) of exactly two cross thread configurations (25) directly adjacent and aligned in a second diagonal direction (28.2) with respect to the weft (30) and warp (31) directions of the fabric (21), transverse to the first diagonal direction (28.1), wherein between two said second groups (25.2) of cross configurations (25) aligned along said second diagonal direction (28.2), respectively, a second diagonal distance (26.2) is formed without cross configurations (25) aligned along the same second diagonal direction (28.2), wherein said second diagonal distance (26.2) is equal to a second diagonal extension (27.2) of the second group (25.2) of cross thread configurations (25), C) a third plurality of the cross thread configurations (25) formed by weft threads is arranged grouped into third groups (25.3) of exactly two cross thread configurations (25) directly adjacent and aligned in a third diagonal direction (28.3) with respect to the weft (30) and warp (31) directions of the fabric (21), wherein between two said third groups (25.3) of cross configurations (25) aligned along one said third diagonal direction (28.3), respectively, a third diagonal distance (26.3) is formed without cross configurations (25) aligned along the same third diagonal direction (28.3), wherein said third diagonal distance (26.3) is equal to a third diagonal extension (27.3) of the third group (25.3) of cross thread configurations (25), D) a fourth plurality of the cross thread configurations (25) formed by weft threads is arranged grouped into fourth groups (25.4) of exactly two cross thread configurations (25) directly adjacent and aligned in a fourth diagonal direction (28.4) with respect to the weft (30) and warp (31) directions of the fabric (21), transverse to the third diagonal direction (28.3), wherein between two said fourth groups (25.4) of cross configurations (25) aligned along said fourth diagonal direction (28.4), respectively, a fourth diagonal distance (26.4) is formed without cross configurations (25) aligned along the same fourth diagonal direction (28.4), wherein said fourth diagonal distance (26.4) is equal to a fourth diagonal extension (27.4) of the fourth group (25.4) of cross thread configurations (25).

5. A combustion membrane (14) according to claim 4, wherein a first orthogonal distance (29.1) between two said first neighboring diagonal directions (28.1), respectively, along which the first groups (25.1) of cross thread configurations (25) are arranged, is constant and equal to the first diagonal distance (26.1).

6. A combustion membrane (14) according to claim 4 or 5, wherein a second orthogonal distance (29.2) between two said second neighboring diagonal directions (28.2), respectively, along which the second groups (25.2) of cross thread configurations (25) are arranged, is constant and equal to the second diagonal distance (26.2).

7. A combustion membrane (14) according to claim 4 or 5 or 6, wherein a third orthogonal distance (29.3) between two said third neighboring diagonal directions (28.3), respectively, along which the third groups (25.3) of cross thread configurations (25) are arranged, is constant and equal to the third diagonal distance (26.3).

8. A combustion membrane (14) according to any one of claims 4 to 7, wherein a fourth orthogonal distance (29.4) between two said fourth neighboring diagonal directions (28.4), respectively, along which the fourth groups (25.4) of cross thread configurations (25) are arranged, is constant and equal to the fourth diagonal distance (26.4).

9. A combustion membrane (14) according to any one of claims 4 to 8, wherein the first (26.1), second (26.2), third (26.3), and fourth (26.4) diagonal distances are equal and constant.

10. A combustion membrane (14) according to any one of claims 4 to 9, wherein a fifth smaller orthogonal distance (29.1-3) between one of the first diagonal directions (28.1), along which the first groups (25.1) of cross thread configurations (25) are arranged, and one of the third diagonal directions (28.3), along which the third groups (25.3) of cross thread configurations (25) are arranged, is less than half the first orthogonal distance (29.1) and less than half the third orthogonal distance (29.3).

11. A combustion membrane (14) according to any one of claims 4 to 10, wherein a sixth smaller orthogonal distance (29.2-4) between one of the second diagonal directions (28.2), along which the second groups (25.2) of cross thread configurations (25) are arranged, and one of the fourth diagonal directions (28.4), along which the fourth groups (25.4) of cross thread configurations (25) are arranged, is less than half the second orthogonal distance (29.2) and less than half the fourth orthogonal distance (29.4).

12. A combustion membrane (14) according to any one of claims 4 to 11, wherein the first diagonal directions (28.1) and third diagonal directions (28.3) are parallel to one another, and the second diagonal directions (28.2) and fourth diagonal directions (28.4) are parallel to one another.

13. A combustion membrane (14) according to any one of claims 4 to 12, wherein both cross thread configurations (25) of each first group (25.1) are directly bordering to both cross thread configurations (25) of a respective third group (25.3), except for the edges of the fabric (21).

14. A combustion membrane (14) according to any one of claims 4 to 13, wherein both cross thread configurations (25) of each second group (25.2) are directly bordering to both cross thread configurations (25) of a respective fourth group (25.3), except for the edges of the fabric (21).

15. A combustion membrane (14) according to any one of the preceding claims, wherein the combustion surface (19) and the inner surface (20) both have the same weave structure, mutually turned by 90.

16. A combustion membrane (14) according to any one of the preceding claims, wherein the fabric (21) is formed by a repetition in the weft direction (30) and in the warp direction (31) of a same 8-by-8 base weaving pattern: T,O,T,O,T,O,T,T O,T,O,O,O,T,O,T T,O,T,O,T,T,T,O O,T,O,T,O,T,O,O T,T,T,O,T,O,T,O O,T,O,T,O,O,O,T T,O,T,T,T,O,T,O O,O,O,T,O,T,O,T, wherein, viewed from one side of the fabric (21), the emerging and visible weft threads are indicated by T and the emerging and visible warp threads are indicated by O.

17. A combustion membrane (14) according to any one of the preceding claims, wherein the fabric (21) is supported by and in contact with a support layer (32) arranged on the inner side (18) of the combustion membrane (14).

18. A combustion membrane (14) according to any one of the preceding claims, wherein the fabric (21) has a weight by extension area in the range from 1.1 kg/m.sup.2 to 1.3 kg/m.sup.2, or of 1.20 kg/m.sup.2.

19. A gas burner (2) comprising a combustion membrane (14) according to any one of the preceding claims.

Description

[0027] In order to better understand the invention and appreciate the advantages thereof, a description is provided below of certain non-limiting exemplary embodiments, with reference to the accompanying drawings, in which:

[0028] FIG. 1 is a diagrammatic view of a gas combustion system, e.g., for a boiler, with a burner provided with a combustion membrane,

[0029] FIGS. 2 and 3 are perspective and section views of an exemplary burner, provided with a combustion membrane,

[0030] FIG. 3A is an enlarged, diagrammatic section view of a combustion membrane according to an embodiment of the invention,

[0031] FIGS. 4 and 5 are views of the two sides of a metal fabric of a combustion membrane according to an embodiment of the invention,

[0032] FIG. 6 shows a layout, i.e., a graphical representation of the weaving, of the metal thread fabric according to FIGS. 4, 5, with additional indication of particular weaving and structure features by means of crosses and diagonal lines,

[0033] FIG. 7 shows an enlarged layout, i.e., a graphic representation of the weaving, of a 8-by-8 base pattern of the metal fabric according to FIGS. 4, 5,

[0034] FIG. 8 shows an enlarged layout, i.e., a graphic representation of the weaving, of a 8-by-8 base pattern, similar to that in FIG. 7, but with different weft and warp direction,

[0035] FIG. 9 is a diagrammatic representation of some selected geometric features of the weaving structure of the metal fabric according to the embodiments. In particular, FIG. 9 does not show all the fabric structures continuously, to better highlight the individual geometric features and the distances between the various thread interlacement formations.

DETAILED DESCRIPTION OF THE COMBUSTION SYSTEM 1

[0036] With reference to FIG. 1, a gas combustion system 1, e.g., for a boiler, comprises: [0037] a burner 2 for producing heat by combustion of combustible gas and combustion air, [0038] a supply system 3 for supplying the combustible gas or gas combustible and combustion air mixture 13 to the burner 2, said supply system 3 comprising a gas control device 4 for controlling a flow of the combustible gas (e.g., an electrically controllable gas valve or gas conveying means or gas suction means) and, if provided, an air control device 5 (e.g., air conveying means or air suction means, an electric fan, a radial fan, an air valve or air gate valve) for controlling a flow of combustion air, [0039] an electric ignition device 6 for igniting the combustion, e.g., an ignition electrode adapted to generate a spark, [0040] possibly, an ionization sensor 7 arranged at a combustion area 8 of the burner 2 and adapted to provide an electrical ionization signal which varies as a function of a combustion condition of the burner 2, [0041] an electronic control unit 9 connected to the supply system 3, the ignition device 6 and the ionization sensor 7, the electronic control unit 9 having a combustion control module 10 adapted to control the ignition device 6 and the supply system 3 depending on an operating program and user commands and depending on the ionization signal,

Detailed Description of the Burner 2

[0042] According to an embodiment (FIGS. 2, 3), the gas burner 2 comprises: [0043] a support wall 11 forming one or more inlet passages 12 for the introduction (of the mixture) of combustible gas 13 (and combustion air) into the burner 2, [0044] a tubular combustion membrane 14, e.g., cylindrical, and coaxial with respect to a longitudinal axis 15 of the burner 2 and having a first end connected to the support wall 11 in flow communication with the inlet passage 12, a second end closed by a closing wall 16, and a perforation for the passage of the gas 13 or the gas-air mixture from inside the burner 2 to an outer side 17 of the combustion membrane 14 where the combustion occurs (combustion area 8).

[0045] The burner 2 in FIG. 3 further features a tubular silencing accessory (without reference numeral), which is optional and could be reduced in size or completely eliminated.

[0046] According to a further embodiment (not shown), the combustion membrane 14 can be substantially flat, e.g., planar or curved or convex, or however of non-tubular or non-cylindrical shape, and having a peripheral edge connected to the support wall 11 in flow communication with the inlet passage 12, as well as a perforation for the passage of the gas 13 or the gas-air mixture from inside burner 2 to an outer side 17 of the combustion membrane 14 where the combustion occurs (combustion area 8).

[0047] According to an embodiment, in the burner 2, upstream of the combustion membrane 14 (with reference to the flow direction of the combustible gas 13) and spaced apart therefrom, a perforated distributor wall can be positioned in order to distribute the combustible gas 13 in a desired manner towards the combustion membrane 14.

Detailed Description of the Combustion Membrane 14

[0048] The combustion membrane 14 has an inner side 18 to which a combustible gas 13 is conveyed and an outer side 17 on which the combustion of the combustible gas 13 occurs after it has crossed the combustion membrane 14, said combustion membrane 14 comprising a fabric 21 having two opposite fabric surfaces 19, 20, which form a combustion surface 19 exposed on the outer side 17 and an inner surface 20 facing the inner side 18, respectively, where the fabric 21 forms an interlacement of metal threads 22 comprising warp threads and weft threads transverse with respect to the warp threads, said fabric 21 being made on a loom (unlike meshes which are to be considered excluded from the definition of fabric).

[0049] The fabric 21 is advantageously supported by and in contact with a support layer 32, e.g., a perforated sheet metal or metal mesh support, arranged on the inner side 18 of the combustion membrane 14 and forming part of the combustion membrane 14 itself or forming only a support structure for the combustion membrane 14.

[0050] Thus, the combustion membrane 14 can be a single-layer structure (including only the fabric 21) or a multilayer structure (containing at least the fabric 21 and the support layer 32 (FIGS. 3, 3A).

Description of Surface Profile Features of the Fabric 21

[0051] According to an aspect of the invention, both fabric surfaces 19, 20 form high-relief ribs 23 alternating with low-relief sags 24, and both ribs 23 and sags 24 have an extension, in at least one (weft or warp) direction in the plane of the fabric 21, smaller than or equal to the space occupied by three consecutive warp threads in the weft direction 30 and smaller than or equal to the space occupied by three consecutive weft threads in the warp direction 31.

[0052] According to a preferred embodiment, the ribs 23, seen from one of the fabric surfaces 19, 20, are formed by a main float 25 (i.e., a passage of one weft thread over several consecutive warp threads, or a passage of one warp thread over several consecutive weft threads), respectively, extending straddling exactly three underlying transverse threads.

[0053] A side thread bridge 25, extending straddling exactly one underlying transverse thread, is formed on both longitudinal sides of each main float thread 25, directly adjacent and parallel thereto and located centrally with respect to the longitudinal extension thereof, so that the main float 25 and the two side thread bridges 25 delimit a cross thread configuration 25 formed by mutually parallel threads (and possibly fibers). In this context, the term parallel means all in the same warp or weft direction. In FIGS. 4 and 5, some of these cross thread configurations 25 are highlighted by a frame of white lines superimposed on the image of the metal fabric. In FIGS. 6 and 7, the cross thread configurations 25 are visible as a black cross formed by five black squares and as a white cross formed by five white squares.

[0054] According to a preferred embodiment, where the fabric 21 is made according to the layout setting shown in FIGS. 6 and 7. In the same cross thread configuration 25, the side thread bridges 25 are retracted with respect to the main float thread 25 which instead protrudes from the fabric 21 towards the observer's side.

[0055] Said cross thread configurations 25 with both weft metal threads 22 and warp metal threads 22 are formed on the same side 17 or 18, and on each of the inner side 18 and outer side 17 (or, in other words, on the combustion surface 19 and/or on the inner surface 20), as is clearly visible from the black and white cross configurations in FIGS. 6, 7.

Cross Configurations of Warp Threads

[0056] According to an embodiment, a first part of the cross thread configurations 25 formed by warp threads is arranged grouped into first groups 25.1 of (exactly) two cross thread configurations 25 directly adjacent and aligned in (at least) a first diagonal direction (or parallel directions) 28.1 with respect to the weft and warp directions of the fabric 21.

[0057] Between two first groups 25.1 of cross configurations 25 aligned along the same first diagonal direction 28.1, respectively, a first diagonal distance 26.1 is formed (with no cross configurations 25 aligned along the same first diagonal direction 28.1) equal to a first diagonal extension 27.1 of the first group 25.1 of cross thread configurations 25.

[0058] According to an embodiment, a second part of the cross thread configurations 25 formed by warp threads is arranged grouped into second groups 25.2 of (exactly) two cross thread configurations 25 directly adjacent and aligned in (at least) a second diagonal direction (or parallel directions) 28.2 with respect to the weft and warp directions of the fabric 21, transverse to the first diagonal direction 28.1.

[0059] Between two second groups 25.2 of cross configurations 25 aligned along the same second diagonal direction 28.2, a second diagonal distance 26.2 is formed (with no cross configurations 25 aligned along the same second diagonal direction 28.2), respectively, equal to a second diagonal extension 27.2 of the second group 25.2 of cross thread configurations 25

Cross Configurations of Weft Threads

[0060] According to an embodiment, a third part of the cross thread configurations 25 formed by weft threads is arranged grouped into third groups 25.3 of (exactly) two cross thread configurations 25 directly adjacent and aligned in (at least) a third diagonal direction (or parallel directions) 28.3 with respect to the weft and warp directions of the fabric 21.

[0061] Between two third groups 25.3 of cross configurations 25 aligned along a same third diagonal direction 28.3, a third diagonal distance 26.3 is formed (with no cross configurations 25 aligned along the same third diagonal direction 28.3), respectively, equal to a third diagonal extension 27.3 of the third group 25.3 of cross thread configurations 25.

[0062] According to an embodiment, a fourth part of the cross thread configurations 25 formed by weft threads is arranged grouped into fourth groups 25.4 of (exactly) two cross thread configurations 25 directly adjacent and aligned in (at least) a fourth diagonal direction (or parallel directions) 28.4 with respect to the weft and warp directions of the fabric 21, transverse to the third diagonal direction 28.3.

[0063] Between two fourth groups 25.4 of cross configurations 25 aligned along the same fourth diagonal direction 28.4, a fourth diagonal distance 26.4 is formed (with no cross configurations 25 aligned along the same fourth diagonal direction 28.4), respectively, equal to a fourth diagonal extension 27.4 of the fourth group 25.4 of cross thread configurations 25

Description of Exemplary Embodiments of the Fabric 21

[0064] According to an embodiment, a first orthogonal distance 29.1 between two first neighboring diagonal directions 28.1, respectively, along which the first groups 25.1 of cross thread configurations 25 are arranged, is constant and preferably equal to the first diagonal distance 26.1.

[0065] According to an embodiment, a second orthogonal distance 29.2 between two second neighboring diagonal directions 28.2, respectively, along which the second groups 25.2 of cross thread configurations 25 are arranged, is constant and preferably equal to the second diagonal distance 26.2.

[0066] According to an embodiment, a third orthogonal distance 29.3 between two third neighboring diagonal directions 28.3, respectively, along which the third groups 25.3 of cross thread configurations 25 are arranged, is constant and preferably equal to the third diagonal distance 26.3.

[0067] According to an embodiment, a fourth orthogonal distance 29.4 between two fourth neighboring diagonal directions 28.4, respectively, along which the fourth groups 25.4 of cross thread configurations 25 are arranged, is constant and preferably equal to the fourth diagonal distance 26.4.

[0068] Advantageously, the first 26.1, second 26.2, third 26.3, and fourth 26.4 diagonal distances are equal and constant.

[0069] According to an embodiment, a fifth smaller orthogonal distance 29.1-3 between one of the first diagonal directions 28.1, along which the first groups 25.1 of cross thread configurations 25 are arranged, and one of the third diagonal directions 28.3, along which the third groups 25.3 of cross thread configurations 25 are arranged, is less than half the first orthogonal distance 29.1 and less than half the third orthogonal distance 29.3.

[0070] According to an embodiment, a sixth smaller orthogonal distance 29.2-4 between one of the second diagonal directions 28.2, along which the second groups 25.2 of cross thread configurations 25 are arranged, and one of the fourth diagonal directions 28.4, along which the fourth groups 25.4 of cross thread configurations 25 are arranged, is less than half the second orthogonal distance 29.2 and less than half the fourth orthogonal distance 29.4.

[0071] The first 28.1 and third 28.3 diagonal directions are parallel to each other, and the second 28.2 and fourth 28.4 diagonal directions are parallel to each other.

[0072] According to an embodiment, both cross thread configurations 25 of each first group 25.1 are directly adjacent to both cross thread configurations 25 of a respective third group 25.3 (except for the edges of the fabric 21, along which the weaving pattern ends).

[0073] Similarly, both cross thread configurations 25 of each second group 25.2 are directly adjacent to both cross thread configurations 25 of a respective fourth group 25.3 (except for the edges of the fabric 21, along which the weaving pattern ends).

[0074] According to a preferred embodiment, the combustion surface 19 and the inner surface 20 both have the same weaving structure (described above), mutually turned by 90.

[0075] Again according to a preferred embodiment, the fabric 21 is formed by a repetition in the weft direction 30 and warp direction 31 of the same 8-by-8 base weaving pattern, where the weft threads are indicated by T and the warp threads are indicated by O, as follows, and as shown in FIG. 7: [0076] T,O,T,O,T,O,T,T [0077] O,T,O,O,O,T,O,T [0078] T,O,T,O,T,T,T,O [0079] O,T,O,T,O,T,O,O [0080] T,T,T,O,T,O,T,O [0081] O,T,O,T,O,O,O,T [0082] T,O,T,T,T,O,T,O [0083] O,O,O,T,O,T,O,T.

[0084] By virtue of the structure of the fabric 21 described, the metal fabric 21 of the combustion membrane 14 achieves a technical effect of discrete, repetitive spacer in a manner that reconciles the need for structural uniformity, thickness and permeability, to achieve the goal of flame uniformity, with the need for volume and void spaces and the alternating presence and absence of metal fibers, to achieve the goal of reduced weight per area for the same thermal insulation properties of the combustion membrane 14.

[0085] This obviates the overheating of the combustion membrane 14, improves the thermal insulation of the combustion membrane 14, reduces the risk of flame detachment, and improves the distribution of flow speed of the gas 13 through the combustion membrane 14.

Description of the Metal Thread 22

[0086] According to an embodiment, the metal threads 22 comprise bundles of metal fibers, e.g., unspun, or bundles of (preferably) parallel or interlaced or spun metal fibers, e.g., of the long fiber filament or short fiber filament type.

[0087] The metal threads 22 can be at least or only initially bonded by means of a binder, e.g., a water-soluble or non-soluble bonding thread, e.g., made of PVA or polyester, or by means of a water-soluble or non-soluble bonding adhesive, e.g., made of polymer.

[0088] Advantageously, the weight of the fabric 21 is less than the weight classified as heavy fabric or coarse fabric but with features such that it competes with the range of heavy or coarse fabrics because of its high properties of flame uniformity, thermal insulation capacity, and durability, while having a relatively low weight (and, therefore, material cost), advantageously about 1.2 kg/m.sup.2, for example in the range of 1.1 kg/m.sup.2 to 1.3 kg/m.sup.2.

[0089] Advantageously, the metal thread 22 is a yarn of weight per length in the range from 0.8 g/m to 1.4 g/m, advantageously from 0.9 g/m to 1.1 g/m, e.g., 1 g/m.

[0090] Advantageously, the metal thread 22 consists of fibers with a diameter in the range from 30 micrometers to 50 micrometers, e.g., about 40 micrometers.

[0091] Big fibers and big threads allow economical and industrially advantageous manufacture of coarse fabrics that are not excessively impermeable.

[0092] According to an embodiment, the material of the metal threads 22 or metal fibers can be, for example, a ferritic steel, or a FeCrAl alloy, e.g., doped with Yttrium, Hafnium, Zirconium.

[0093] The metal thread 22 can be, for example, a Y-, Hf-, Zr-doped FeCrAl alloy yarn, weighing 1 g/m and consisting of fibers having a diameter of 40 micrometers, unspun, possibly crimped (wavy), retained by means of a binding thread, possibly made of PVA or polyester, and having, for example, the following doped composition:

TABLE-US-00001 C Mn Si Al Cu Cr Y Hf Zr P S Ti N Ni Fe Min. 5.5 19 0.03 0.05 0.03 rest or 0.03 Max. 0.04 0.4 0.5 6.5 0.03 22 0.03 0.03 0.5 0.02 0.3

[0094] According to a further embodiment, the material of the metal threads or metal fibers can be, for example, a ferritic steel, or a FeCrAl alloy, e.g., additionally containing Yttrium, Hafnium, Zirconium.

[0095] The metal thread can be, for example, a Y-, Hf-, Zr-doped FeCrAl alloy yarn, weighing 1 g/m and consisting of fibers with a diameter of 40 micrometer, spun, for example with 30 to 150 twists per meter, possibly with fiber ends protruding divergently from the yarn (hairy yarn), with fibers shorter than the yarn, e.g., with fiber lengths in the range of 7 cm to 30 cm, not necessarily but possibly restrained by means of a binding thread, possibly made of PVA or polyester, and having, for example, the same doped composition as shown in the table above.

REFERENCE NUMERALS IN THE DESCRIPTION AND DRAWINGS

[0096] combustion system 1 [0097] burner 2 [0098] supply system 3 [0099] gas control device 4 [0100] air control device 5 [0101] ignition device 6 [0102] ionization sensor 7 [0103] combustion area 8 [0104] electronic control unit 9 [0105] combustion control module 10 [0106] support wall 11 [0107] inlet passages 12 [0108] combustible gas 13 [0109] combustion membrane 14 [0110] longitudinal axis 15 [0111] closing wall 16 [0112] outer side 17 [0113] inner side 18 [0114] combustion surface 19 [0115] inner surface 20 [0116] fabric 21 [0117] metal threads 22 [0118] ribs 23 [0119] sags 24 [0120] main float 25 [0121] side thread bridge 25 [0122] cross thread configuration 25 [0123] first groups of cross configurations 25.1 [0124] second groups of cross configurations 25.2 [0125] third groups of cross configurations 25.3 [0126] fourth groups of cross configurations 25.4 [0127] first diagonal distance 26.1 [0128] second diagonal distance 26.2 [0129] third diagonal distance 26.3 [0130] fourth diagonal distance 26.4 [0131] first diagonal extension 27.1 [0132] second diagonal extension 27.2 [0133] third diagonal extension 27.3 [0134] fourth diagonal extension 27.4 [0135] first diagonal direction 28.1 [0136] second diagonal direction 28.2 [0137] third diagonal direction 28.3 [0138] fourth diagonal direction 28.4 [0139] first orthogonal distance 29.1 [0140] second orthogonal distance 29.2 [0141] third orthogonal distance 29.3 [0142] fourth orthogonal distance 29.4 [0143] fifth orthogonal distance 29.1-3 [0144] sixth orthogonal distance 29.2-4 [0145] weft direction 30 [0146] warp direction 31 [0147] support layer 32