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) alternating with low-relief sags (24), and the ribs (23) comprise: weft ribs (25) formed by weft threads and extending in the weft direction (26) arranged in weft rib sequences (2) aligned along weft directions (26) substantially straight and parallel to one another, and warp ribs (27) formed by warp threads and extending in the warp direction (28) and arranged in zigzag warp rib sequences (27), wherein all the warp threads participate in the formation of said warp ribs (27) in an alternating and repetitive manner along the extension thereof in the warp direction (28).

Claims

1. A combustion membrane for a gas burner, said combustion membrane having an inner side to which a combustible gas is conveyed and an outer side on which the combustion of the combustible gas occurs after it has crossed the combustion membrane, said combustion membrane comprising a fabric having two opposite fabric surfaces which form a combustion surface exposed on the outer side and an inner surface facing the inner side, respectively, wherein the fabric forms an interlacement of metal threads comprising warp threads and weft threads transverse with respect to the warp threads, wherein both fabric surfaces form high-relief ribs alternating with low-relief sags, wherein the ribs comprise: weft ribs formed by weft threads and extending in the weft direction, arranged in weft rib sequences aligned along weft directions substantially straight and parallel to one another, and warp ribs formed by warp threads and extending in the warp direction and arranged in zigzag warp rib sequences, wherein all the warp threads participate in the formation of said warp ribs in an alternating and repetitive manner along their extension in the warp direction.

2. A combustion membrane according to claim 1, wherein the weft ribs and warp ribs form continuous ribs, uninterrupted by said sags, and delimit the coffered or lacunar sags.

3. A combustion membrane according to claim 1, wherein the sags are delimited all around by quadrilateral, rectangular or parallelogram protruding frames formed by the weft ribs and the warp ribs.

4. A combustion membrane according to claim 1, wherein in a first one of the combustion surface and inner surface of the fabric: an apical ridge of the warp ribs is formed by a main warp float thread, respectively, extending straddling exactly six underlying transverse weft threads, on both longitudinal sides of each main warp float thread, directly adjacent and parallel thereto, a secondary warp float thread is formed, extending straddling exactly three underlying transverse weft threads, and on one longitudinal side of each of the two secondary warp float threads, facing away from the main warp float thread, a side warp bridge is formed, extending straddling exactly one underlying transverse weft thread, so that the main warp float thread, the two secondary warp float threads, and the two side warp bridges form a first warp thread configuration in the shape of a rhombus with a unilateral central elongation in the warp direction, wherein the first warp thread configuration is symmetrical with respect to a local longitudinal axis from the main warp float thread, but not symmetrical with respect to any axis oriented in the weft direction.

5. A combustion membrane according to claim 4, wherein the secondary warp float threads are retracted with respect to the most protruding main warp float thread, and the warp side bridges are retracted with respect to the secondary warp float threads, resulting in a transition from the warp rib to the sag.

6. A combustion membrane according to claim 4, wherein two consecutive first warp thread configurations, respectively, arranged along the same zigzag warp rib sequence, are mutually offset in the weft direction by the space occupied by a warp thread.

7. A combustion membrane according to claim 1, wherein in a first surface of the combustion surface and inner surface of the fabric: an apical ridge of the weft ribs is formed by a main weft float thread, respectively, extending straddling exactly five underlying transverse warp threads, and on both longitudinal sides of each main weft float thread, directly adjacent and parallel thereto, a secondary weft float thread is formed, extending straddling exactly three underlying transverse warp threads, and on a longitudinal side of each of the two secondary weft float threads, facing away from the main weft float thread, a side weft bridge is formed, extending straddling exactly one underlying transverse warp thread, an additional weft bridge (36) is formed next to one end of the main weft float thread, wherein the main weft float thread, the two secondary weft float threads, the two side weft bridges (36), and the additional weft bridge (36) together form a first weft thread configuration in the shape of a rectangle with the four sides inclined with respect to the weft and warp directions and with a unilateral leg extending from a corner of the first rectangular weft thread configuration in the warp direction, wherein the first weft thread configuration is not symmetrical with respect to any axis oriented in the warp direction and with respect to any axis oriented in the weft direction.

8. A combustion membrane according to claim 7, wherein the secondary weft float threads are retracted with respect to the most protruding main weft float thread, and the warp side bridges (36) are retracted with respect to the secondary weft float threads, resulting in a transition from the weft rib to the sag.

9. A combustion membrane according to claim 7, wherein two first weft thread configurations, respectively, consecutive in the warp direction, are mutually offset in the weft direction by the space occupied by a warp thread.

10. A combustion membrane according to claim 7, wherein: at segments of the zigzag warp rib sequence having the same first orientation, the first weft thread configurations also all have the same primary orientation, while at segments of the zig-zag warp rib sequence having the same second orientation different from the first orientation, the first weft thread configurations all have the same secondary orientation either different or overturned with respect to the primary orientation.

11. A combustion membrane according to claim 1, wherein between two of the weft ribs and the warp ribs, respectively, checkerboard interlacing regions of the weft threads and the warp threads forming the sags are formed.

12. A combustion membrane according to claim 1, wherein the combustion surface and the inner surface both have the same structure of ribs and sags.

13. A combustion membrane according to claim 1, wherein: the positions of the weft ribs of the combustion surface are offset in the warp direction with respect to the positions of the weft ribs of the inner surface by half the distance between two adjacent weft rib sequences on the same side of the fabric, and the positions of the warp ribs of the combustion surface are offset in the weft direction with respect to the positions of the warp ribs of the inner surface by half the distance between two adjacent warp rib sequences on the same side of the fabric, the weft rib sequences and the warp rib sequences of the inner surface intersect at the sags of the combustion surface and vice versa.

14. A combustion membrane according to claim 1, wherein the fabric is formed by a repetition in the weft direction and in the warp direction of the same 8 (weft direction)-by-96 (warp direction) base weaving pattern as follows and as defined by the layout in FIG. 7: OTOTTTTT TOTOTTTO OOOTOTOT OOOOTOTO OOOTOTOT TOTOTTTO TOTOTTTT OTOTOTTT TOOOTOTO OOOOOTOT TOOOTOTO OTOTOTTT TTOTOTTT TOTOTOTT OTOOOTOT TOOOOOTO OTOOOTOT TOTOTOTT TTTOTOTT TTOTOTOT TOTOOOTO OTOOOOOT TOTOOOTO TTOTOTOT TTTTOTOT TTTOTOTO OTOTOOOT TOTOOOOO OTOTOOOT TTTOTOTO TTTTTOTO OTTTOTOT TOTOTOOO OTOTOOOO TOTOTOOO OTTTOTOT OTTTTTOT TOTTTOTO OTOTOTOO OOTOTOOO OTOTOTOO TOTTTOTO TOTTTTTO OTOTTTOT OOTOTOTO OOOTOTOO OOTOTOTO OTOTTTOT OTTTTTOT TOTTTOTO OTOTOTOO OOTOTOOO OTOTOTOO TOTTTOTO TTTTTOTO OTTTOTOT TOTOTOOO OTOTOOOO TOTOTOOO OTTTOTOT TTTTOTOT TTTOTOTO OTOTOOOT TOTOOOOO OTOTOOOT TTTOTOTO TTTOTOTT TTOTOTOT TOTOOOTO OTOOOOOT TOTOOOTO TTOTOTOT TTOTOTTT TOTOTOTT OTOOOTOT TOOOOOTO OTOOOTOT TOTOTOTT TOTOTTTT OTOTOTTT TOOOTOTO OOOOOTOT TOOOTOTO OTOTOTTT OTOTTTTT TOTOTTTO OOOTOTOT OOOOTOTO OOOTOTOT TOTOTTTO TOTTTTTO OTOTTTOT OOTOTOTO OOOTOTOO OOTOTOTO OTOTTTOT wherein, viewed from one side of the fabric, the emerging and visible weft threads are indicated by T and the emerging and visible warp threads are indicated by O.

15. A combustion membrane according to claim 1, wherein the fabric is supported by and in contact with a support layer arranged on the inner side of the combustion membrane.

16. A gas burner comprising a combustion membrane according to claim 1.

Description

[0028] 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:

[0029] FIG. 1 is a diagrammatic view of a gas combustion system, e.g., for a boiler, with a burner provided with a combustion membrane,

[0030] FIGS. 2 and 3 are perspective and section views of an exemplary burner, provided with a combustion membrane,

[0031] FIG. 3A is an enlarged, diagrammatic section view of a combustion membrane according to an embodiment of the invention,

[0032] FIG. 4A is a view of one side of a metal fabric of a combustion membrane according to an embodiment of the invention, which highlights a characteristic zigzag pattern of high-relief formations made from warp threads,

[0033] FIG. 4B shows an enlarged detail of the metal fabric in FIG. 4A,

[0034] FIG. 5A is a view of an opposite side of the same metal fabric in FIG. 4A, which also highlights a characteristic zigzag pattern of high-relief formations made from warp threads,

[0035] FIG. 5B shows an enlarged detail of the metal fabric in FIG. 5A,

[0036] FIG. 6A and 6B show enlarged parts of a layout, i.e., a graphic representation of the weaving, of the metal fabric according to FIGS. 4A, 5A,

[0037] FIG. 7 shows an overall layout, i.e., a graphic representation of the weaving, of a 8 (in the weft direction)-by-96 (in the warp direction) base pattern.

DETAILED DESCRIPTION OF THE COMBUSTION SYSTEM 1

[0038] With reference to FIG. 1, a gas combustion system 1, e.g., for a boiler, comprises: [0039] a burner 2 for producing heat by combustion of combustible gas and combustion air, [0040] 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, [0041] an electric ignition device 6 for igniting the combustion, e.g., an ignition electrode adapted to generate a spark, [0042] 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, [0043] 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

[0044] According to an embodiment (FIGS. 2, 3), the gas burner 2 comprises: [0045] 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, [0046] 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).

[0047] 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.

[0048] 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).

[0049] 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

[0050] 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).

[0051] 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.

[0052] 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

[0053] According to an embodiment, both fabric surfaces 19, 20 form high-relief ribs 23 alternating with low-relief sags 24, where the ribs 23 comprise: [0054] weft ribs 25 formed by weft threads and extending and arranged in weft rib sequences 25 aligned along weft directions 26 substantially straight and parallel to one another, and [0055] warp ribs 27 formed by warp threads and extending in the warp direction 28 and arranged in zigzag warp rib sequences 27 (along imaginary lines), where all the warp threads participate in the formation of said warp ribs 27 in an alternating and repetitive manner along the extension thereof in the warp direction 28.

[0056] By virtue of the participation of all warp threads in the formation of the warp ribs, it is possible to uniform the warp thread length per length unit of the fabric, and thus reduce differential metal thread tensions and optimize the weaving process of the fabric 21.

[0057] By virtue of the arrangement of the warp ribs 27 in zigzag sequences, as opposed to diagonal continuous sequences, undesired structural and functional anisotropy effects of the fabric 21 are avoided, in particular the diagonal parallelogram warping tendency of the fabric 21 is obviated.

[0058] According to an embodiment, the weft ribs 25 and the warp ribs 27 form continuous ribs, uninterrupted by said sags 24, and delimit the coffered or lacunar sags 24. In other words, the sags (cavities) 24 are delimited all around by quadrilateral, rectangular or parallelogram protruding frames, formed by the weft ribs 25 and by the warp ribs 27.

DESCRIPTION OF WARP RIBS 27 (FIRST SURFACE OF THE FABRIC 21)

[0059] According to an embodiment, an apical ridge of the warp ribs 27, in one (first) of the fabric surfaces 19, 20, is formed by a main warp float 29 (i.e., a passage of a warp thread over several consecutive weft threads), respectively, extending straddling exactly six underlying transverse (weft) threads.

[0060] On both longitudinal sides of each main warp float 29, directly adjacent and parallel thereto, a secondary warp float 29 is formed, extending straddling exactly three underlying transverse (weft) threads, and on the longitudinal side of each of the two secondary warp floats 29, facing away from the main warp float 29, a warp side bridge 29 extending straddling exactly one underlying transverse (weft) thread is formed, so that the main warp float 29, the two warp secondary floats 29 and the two warp side bridges 29 form a first warp thread configuration 33 in the shape of a rhombus with a unilateral central elongation 34 in the warp direction 28 (by exactly the space occupied by one underlying transverse (weft) thread).

[0061] The first warp thread configuration 33 is symmetrical with respect to a local longitudinal axis 35 from the main warp float thread 29, but not symmetrical with respect to any axis oriented in the weft direction 26.

[0062] The secondary warp float threads 29 are retracted with respect to the (most protruding) main warp float thread 29, and the warp side bridges 29 are retracted with respect to the secondary warp float threads 29, resulting in a transition from the warp rib 27 to the sag 24.

[0063] Two consecutive first warp thread configurations 33, respectively, arranged along the same zigzag warp rib sequence 27, are mutually offset in the weft direction 26 by the space of a warp thread.

DESCRIPTION OF WEFT RIBS 25 (FIRST SURFACE OF THE FABRIC 21)

[0064] According to a embodiment, an apical ridge of the weft ribs 25, in one of the fabric surfaces 19, 20 (preferably the same first fabric surface to which the foregoing description of warp ribs 27 refers), is formed by a main weft float 36 (i.e., a passage of one weft thread over several consecutive warp threads), respectively, extending straddling exactly five underlying transverse (warp) threads.

[0065] On both longitudinal sides of each main weft float thread 36, directly adjacent and parallel thereto, a secondary weft float thread 36 is formed, extending straddling exactly three underlying transverse (warp) threads, and on a longitudinal side of each of the two secondary weft float threads 36, facing away from the main weft float thread 36, a side weft bridge 36 is formed, extending straddling exactly one underlying transverse warp thread. Furthermore, an additional weft bridge 36 is formed next to one end of the main weft float thread 36.

[0066] The main weft float thread 36, the two secondary weft float threads 36, the two side weft bridges 36, and the additional weft bridge 36 together form a first weft thread configuration 37 in the shape of a rectangle with the four sides inclined with respect to the weft 26 and warp 28 directions and with a unilateral leg extending from a corner of the first rectangular weft thread configuration 37 in the warp direction 28 (by exactly the space occupied by two adjacent weft threads).

[0067] The first weft thread configuration 37 is not symmetrical with respect to any axis oriented in the warp direction 28 and with respect to any axis oriented in the weft direction 26.

[0068] The secondary weft float threads 36 are retracted with respect to the (most protruding) main weft float thread 36, and the weft side bridges 36 are retracted with respect to the secondary weft float threads 36, resulting in a transition from the weft rib 25 to the sag 24.

[0069] Two consecutive first weft thread configurations 37, respectively, in the warp direction 28 are mutually offset in the weft direction 26 by the space of a warp thread.

[0070] Furthermore, at segments of the zigzag warp rib sequence 27 having the same first orientation, the first weft thread configurations 37 also all have the same primary orientation, while at segments of the zigzag warp rib sequence 27 having the same second orientation different from the first orientation, the first weft thread configurations 37 all have the same secondary orientation different from or overturned with respect to the primary orientation (FIGS. 6A, 6B).

[0071] Between two of the first warp thread configurations 33 and first weft thread configurations 37, respectively, or between two of the weft ribs 25 and warp ribs 27, respectively, checkerboard interlacing regions of the weft threads and the warp threads (always on the same first fabric surface) forming the sags 24 are formed.

[0072] According to a preferred embodiment, the combustion surface 19 and the inner surface 20 both have the same structure of ribs and sags.

[0073] According to a preferred embodiment, [0074] the positions of the weft ribs 25 of the combustion surface 19 are offset in the warp direction 28 with respect to the positions of the weft ribs 25 of the inner surface 20 by half the distance between two adjacent weft rib sequences 25 on the same side of the fabric 21, and [0075] the positions of the warp ribs 27 of the combustion surface 19 are offset in the weft direction 26 with respect to the positions of the warp ribs 27 of the inner surface 20 by half the distance between two adjacent warp rib sequences 27 on the same side of the fabric 21.

[0076] The weft rib sequences 25 and the warp rib sequences 27 of the inner surface 20 thus intersect at the sags 24 of the combustion surface 19 and vice versa.

[0077] This gives the fabric 21 a bilateral, very uniform coffered surface structure and a higher thickness and volume than the prior technique, thus increasing thermal insulation with the same weight/area and minimizing the inevitable anisotropy of the structural and permeability properties of the combustion membrane 14.

[0078] According to a preferred embodiment, the fabric 21 is formed by a repetition in the weft direction 26 and in the warp direction 28 of the same 8 (weft direction)-by-96 (warp direction) base weaving pattern, in which the weft threads are denoted by T and the warp threads are denoted by O, as follows, and as shown in FIG. 7 (in case of transcription inconsistency, the graphical representation of the paper layout in FIG. 7 prevails): [0079] OTOTTTTT [0080] TOTOTTTO [0081] OOOTOTOT [0082] OOOOTOTO [0083] OOOTOTOT [0084] TOTOTTTO [0085] TOTOTTTT [0086] OTOTOTTT [0087] TOOOTOTO [0088] OOOOOTOT [0089] TOOOTOTO [0090] OTOTOTTT [0091] TTOTOTTT [0092] TOTOTOTT [0093] OTOOOTOT [0094] TOOOOOTO [0095] OTOOOTOT [0096] TOTOTOTT [0097] TTTOTOTT [0098] TTOTOTOT [0099] TOTOOOTO [0100] OTOOOOOT [0101] TOTOOOTO [0102] TTOTOTOT [0103] TTTTOTOT [0104] TTTOTOTO [0105] OTOTOOOT [0106] TOTOOOOO [0107] OTOTOOOT [0108] TTTOTOTO [0109] TTTTTOTO [0110] OTTTOTOT [0111] TOTOTOOO [0112] OTOTOOOO [0113] TOTOTOOO [0114] OTTTOTOT [0115] OTTTTTOT [0116] TOTTTOTO [0117] OTOTOTOO [0118] OOTOTOOO [0119] OTOTOTOO [0120] TOTTTOTO [0121] TOTTTTTO [0122] OTOTTTOT [0123] OOTOTOTO [0124] OOOTOTOO [0125] OOTOTOTO [0126] OTOTTTOT [0127] OTTTTTOT [0128] TOTTTOTO [0129] OTOTOTOO [0130] OOTOTOOO [0131] OTOTOTOO [0132] TOTTTOTO [0133] TTTTTOTO [0134] OTTTOTOT [0135] TOTOTOOO [0136] OTOTOOOO [0137] TOTOTOOO [0138] OTTTOTOT [0139] TTTTOTOT [0140] TTTOTOTO [0141] OTOTOOOT [0142] TOTOOOOO [0143] OTOTOOOT [0144] TTTOTOTO [0145] TTTOTOTT [0146] TTOTOTOT [0147] TOTOOOTO [0148] OTOOOOOT [0149] TOTOOOTO [0150] TTOTOTOT [0151] TTOTOTTT [0152] TOTOTOTT [0153] OTOOOTOT [0154] TOOOOOTO [0155] OTOOOTOT [0156] TOTOTOTT [0157] TOTOTTTT [0158] OTOTOTTT [0159] TOOOTOTO [0160] OOOOOTOT [0161] TOOOTOTO [0162] OTOTOTTT [0163] OTOTTTTT [0164] TOTOTTTO [0165] OOOTOTOT [0166] OOOOTOTO [0167] OOOTOTOT [0168] TOTOTTTO [0169] TOTTTTTO [0170] OTOTTTOT [0171] OOTOTOTO [0172] OOOTOTOO [0173] OOTOTOTO [0174] OTOTTTOT

[0175] By virtue of the structure of the described fabric 21, the metal fabric 21 of the combustion membrane 14 reduces the warp metal thread breaks and reduces the mechanical property anisotropy, and still achieves the desired technical effect of uniformity of structure, thickness, and permeability to achieve the goal of flame uniformity and thermal insulation of the combustion membrane 14.

DESCRIPTION OF THE METAL THREAD 22

[0176] 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.

[0177] 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.

[0178] Advantageously, the fabric 21 is a heavy or coarse fabric, i.e., a fabric with a weight per fabric area either equal to or greater than 1.3 kg/m.sup.2 or in the range from 1.3 kg/m.sup.2 to 1.6 kg/m.sup.2.

[0179] 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.

[0180] 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.

[0181] Big fibers and big threads allow economical and industrially advantageous manufacture of coarse fabrics that are not excessively impermeable.

[0182] 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.

[0183] 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

[0184] 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.

[0185] 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 micrometers, spun, e.g., 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

[0186] combustion system 1 [0187] burner 2 [0188] supply system 3 [0189] gas control device 4 [0190] air control device 5 [0191] ignition device 6 [0192] ionization sensor 7 [0193] combustion area 8 [0194] electronic control unit 9 [0195] combustion control module 10 [0196] support wall 11 [0197] inlet passages 12 [0198] combustible gas 13 [0199] combustion membrane 14 [0200] longitudinal axis 15 [0201] closing wall 16 [0202] outer side 17 [0203] inner side 18 [0204] combustion surface 19 [0205] inner surface 20 [0206] fabric 21 [0207] metal threads 22 [0208] ribs 23 [0209] sags 24 [0210] weft ribs 25 [0211] weft rib sequences 25 [0212] weft direction 26 [0213] warp ribs 27 [0214] warp rib sequences 27 [0215] warp direction 28 [0216] main warp float 29 [0217] secondary warp floats 29 [0218] warp side bridge 29 [0219] support layer 32 [0220] first warp thread configuration 33 [0221] unilateral central elongation 34 [0222] local longitudinal axis 35 from the main warp float 29 [0223] main weft float 36 [0224] secondary weft float 36 [0225] weft side bridges 36 [0226] additional weft bridge 36 [0227] first weft thread configuration 37