Infrared radiation emitter

Abstract

The invention relates to a gas-heated infrared radiation emitter (1), comprising a burner plate (8) the burner plate serving as a combustion surface, and a radiating screen (12) positioned on the side of the combustion surface of the burner plate. The radiating screen (12) is formed by a mesh material or material with open pores, and has an inner face oriented towards the combustion surface side of the burner plate. The inner surface of the screen comprises at least a first portion (16) and a second portion (18) offset from one another in relation to the combustion surface, such that the distance between the combustion surface and the first portion (16) is less than the distance between the combustion surface and the second portion (18).

Description

Technical Field

[0001] The present invention relates to the field of infrared radiation emitters, and in particular gas-heated emitters. Prior art

[0002] It is known to use a screen in gas-heated infrared radiation emitters. Such screens, positioned opposite a burner plate, generally a perforated ceramic plate on which the gas is burned, are intended to be heated by the combustion of the gas in order to emit infrared radiation, while allowing the circulation through them of the gases once burned.

[0003] Such screens can thus be formed by metal rods mounted parallel to each other, in the same plane, at a distance from each other. Alternatively, such screens can be formed by a set of metal wires intertwined, or woven, between them.

[0004] Transmitters with such screens have been known for a long time and offer stable and optimized operation, allowing good efficiency to be achieved while limiting operating anomalies.

[0005] There are also screens formed from foamed materials, or open-pore materials.

[0006] It is also known to use a mesh material to form the screen of a gas-heated infrared radiation emitter. Such mesh materials can be referred to as lattice-structured materials, or even as lattice-structured materials. Such materials have, in particular, a geometric spatial organization. Thus, the structure of such materials corresponds to the repetition, in the three spatial directions, of the same elementary geometric pattern (mesh or cell), preferably in three dimensions. In particular, such materials may have a structure forming the edges of the patterns (or meshes or cells) repeated in a three-dimensional network.

[0007] Such mesh materials have recently proven to be of interest for replacing traditional screens for infrared radiation emitters, particularly due to their efficiency. An infrared radiation emitter comprising such a mesh material as a screen is described in particular in document WO 2017 / 156440.

[0008] However, the operation of such screens differs from traditional screens, so that it is not always possible to obtain stability and operating time of the emitter with a screen made of mesh material that are as high as those obtained with an emitter with a traditional screen. Thus, it has been observed that with such emitters with a screen made of mesh material, the flame of the emitter could remain lit with more difficulty than with emitters with a traditional screen. In other words, it appeared that the flame could be made to go out more easily or more frequently with a screen made of mesh material than with an emitter with a traditional screen.

[0009] WO 2012 / 084561 relates to a gas-fired infrared radiation emitter that comprises a burner plate acting as a combustion surface and a radiant shield positioned on the combustion side of the burner plate. The radiant shield is embossed, thereby establishing locally different distances between the burner plate and the radiant shield. US 2014 / 116424 and JP 2002 / 267115 disclose other gas-fired infrared radiation emitters. Statement of the invention

[0010] The present invention aims to solve the various technical problems stated above. The present invention thus aims to propose a gas-heated infrared radiation emitter, having an operating stability comparable to traditional emitters, and an efficiency superior to that of traditional emitters. In particular, the present invention thus aims to propose a gas-heated infrared radiation emitter with a screen made of mesh material having improved operating stability, in particular during ignition.

[0011] Thus, according to one aspect, there is provided a gas-fired infrared radiation emitter, comprising a burner plate, said burner plate serving as a combustion surface, and a radiating screen positioned on the combustion surface side of said burner plate. Said radiating screen is formed by a mesh or open-pore material, and has an inner face oriented on the combustion surface side of the burner plate. The inner surface of the screen comprises at least a first portion and a second portion offset from each other relative to the combustion surface, such that the distance between the combustion surface and the first portion is less than the distance between the combustion surface and the second portion.

[0012] It was indeed observed by the applicant that the operating stability of the mesh screen emitter, particularly during ignition, increased when the distance between the burner plate and the screen increased. Thus, by positioning the screen directly on the surface of the burner plate, as illustrated in WO 2017 / 156440, the emitter may be difficult to ignite because the flame is caused to detach from the surface of the burner plate and go out. However, the distance of the mesh screen from the burner plate also leads to a decrease in the efficiency of the emitter, which may lead to similar performance to that of emitters with a traditional screen.

[0013] The emitter according to the present invention thus makes it possible to improve the operating stability of the emitter, in particular during ignition, thanks to the second portion of the internal surface of the screen which is located at a distance from the burner plate, while maintaining a higher infrared radiation efficiency than that of emitters with a traditional screen, thanks to the first portion of the internal surface of the screen which remains in the immediate vicinity of the burner plate. In particular, the applicant has found that it is sufficient to keep a distance between the screen made of mesh material and the burner plate, only on a portion of the internal surface of the screen, to maintain the flame on the burner plate.Indeed, the applicant observed that the flame could, when lighting an emitter according to the present invention, detach itself mainly at the burner plate area located opposite the first portion of the screen, but not at the burner plate area located opposite the second portion of the screen, so that the flame still present on the burner plate area located opposite the second portion of the screen could then relight the flame on the rest of the burner plate. Thus, thanks to the emitter according to the present invention, it becomes possible to obtain an area of ​​the burner plate at which the flame remains attached and can relight the flame on the rest of the plate if the latter were to go out.The burner plate area opposite the second portion of the screen also acts as a pilot light for the transmitter, allowing it to be fully re-ignited when it partially goes out.

[0014] Importantly, the applicant observed that the efficiency of the emitter could remain as high as that of an emitter as described in WO 2017 / 156440, even with the second screen portion distant from the burner plate.

[0015] Preferably, the difference in distance between the combustion surface and the first and second portions is between 0.5 mm and 10 mm, preferably between 1 mm and 5 mm.

[0016] Such distances allow both to maintain the flame of the emitter, in particular during ignition, while presenting a high efficiency.

[0017] According to the invention, the screen also has an external face opposite the internal face, the external face being substantially flat and parallel to the two offset portions of the internal face so that the thickness of the screen at the first portion is greater than the thickness of the screen at the second portion.

[0018] Preferably, the internal face of the screen is formed by the absence or removal, at the level of the second portion, of one or more meshes.

[0019] The screen made of mesh material comprising a structure resulting from the repetition, in the three directions of space, of the same elementary geometric pattern, it is sufficient, to obtain the second portion of internal surface located set back from the first portion of internal surface, to delete or remove one or more elementary patterns from the structure of the mesh material, for example a layer of several elementary patterns on the side, the layer having a thickness of between 1 and 5 elementary patterns.

[0020] Preferably, the second portion of the screen is arranged substantially opposite the center of the burner plate, for example opposite the center of a ceramic plate, preferably perforated.

[0021] The second portion of the shield is intended to be located opposite the hottest area of ​​the burner plate. This is because the hottest areas of the burner plates may be subject to damage first, so by providing the second portion of the shield opposite such normally hotter areas of the burner plate, it becomes possible to limit the temperature thereof and thus increase its service life.

[0022] Preferably, the emitter comprises two burner plates mounted side by side, for example two ceramic plates, preferably perforated, and the screen comprises two second portions located substantially opposite the center of each of the burner plates.

[0023] Here again, the second portions of screen are provided opposite the hottest areas, that is to say opposite the center of each of the burner plates, in order to increase the lifespan of the emitter.

[0024] Alternatively, the second portion of the screen is disposed opposite a peripheral portion of the burner plate, or each of the burner plates, for example on a peripheral portion of the inner surface of the screen such as a corner or along an edge of the inner surface of the screen.

[0025] Preferably, the screen forms edges of a plurality of geometric meshes assembled into a three-dimensional network.

[0026] Preferably, the screen forms a network of cubic meshes.

[0027] Preferably, the screen comprises silicon carbide, preferably infiltrated with silicon.

[0028] Silicon carbide provides good resistance to high temperatures while maintaining, unlike many ceramics, high thermal conductivity. This therefore allows for a uniform screen temperature, but also avoids hot spots on the combustion support.

[0029] Preferably, the first portion and the second portion are substantially flat and parallel to each other.

[0030] The use of substantially flat portions allows for better control of the behavior of the flame at each of said portions.

[0031] Preferably, the screen is distant from the burner plate, for example at least 1 mm, and preferably at least 2 mm. Brief description of the drawings

[0032] [ Fig. 1 ] There figure 1 is a partial perspective section of an infrared radiation emitter with a screen according to the prior art, [ Fig. 2 ] There figure 2 is a schematic perspective representation of a first embodiment of a screen according to the invention for an infrared radiation transmitter, [ Fig. 3 ] There figure 3 is a schematic representation of a cross-section of the screen shown in the figure 2 , [ Fig. 4 ] There figure 4 is a schematic representation of a cross-section of an infrared radiation emitter equipped with the screen shown in figure 2 , [ Fig. 5 ] There Figure 5 is a schematic representation of a cross-section of a second embodiment of the screen according to the invention, [ Fig. 6 ] There figure 6 is a schematic representation of a cross-section of an infrared radiation emitter equipped with the screen shown in Figure 5 , And [ Fig. 7 ] There figure 7is a schematic perspective representation of a third embodiment of a screen according to the invention for an infrared radiation transmitter. Description of the embodiments

[0033] There figure 1 represents a gas-heated infrared radiation emitter 1, comprising a screen 2 according to the prior art, for example in the form of a metal grid or braided metal wires.

[0034] The transmitter 1 comprises a frame 4 with a supply inlet 6 for the gases to be burned, and a burner plate 8 arranged opposite the internal surface of the screen 2. The frame 4 and the burner plate 8 delimit an interior chamber into which the gases entering through the supply inlet 6 are conveyed.

[0035] The burner plate 8 may be, for example, a perforated ceramic plate whose perforations are intended to allow the gases present in the inner chamber of the emitter 1 to escape. Upon exiting the perforations, the gases are then burned on the outer surface 10, or combustion surface, of the burner plate 8 when there is a flame, and then heat the screen 2 arranged opposite the outer surface 10.

[0036] In particular, as illustrated in the figure 1 , the burner plate 8 may comprise a notched or grooved external surface 10. Thus, the burner plate 8 may have, at the external surface 10, different levels of combustion surface, for example two. The external surface 10 may for example comprise parallel grooves arranged obliquely over the entire surface of the burner plate 8.

[0037] Such burner plates 8 with several levels of combustion surface are described in particular in document WO 2010 / 003904.

[0038] There figure 2 schematically illustrates the general shape of a screen according to the present invention. The screen is formed by a mesh or open-pore material, and may comprise silicon carbide, preferably infiltrated with silicon. Thus, the screen may be formed by a material having a structure resulting from the repetition, in the three spatial directions, of the same elementary geometric pattern, as schematically illustrated in the figures 3 to 6 , or may be formed from a foamed material. A screen made of mesh material is notably described in WO 2017 / 156440.

[0039] In both cases, the surface of the mesh material is considered, in the remainder of the description, to be the (fictitious) plane in which the end edges or end vertices of the mesh material are located. Thus, the lower surface of the material will correspond to the plane in which the lower end edges or lower end vertices of the mesh material are located.

[0040] There figure 2 therefore illustrates the geometric shape of a screen according to the present invention, by representing its contours by planes. More precisely, the figure 2 illustrates a screen whose surface intended to face the burner plate, i.e. the internal surface, is shown.

[0041] As illustrated in the figure 2, the screen 12 according to the present invention does not have a flat internal surface, but on the contrary comprises an internal surface 14 with a first main portion 16 and at least one second portion 18 arranged set back relative to the first portion 16. In the example illustrated in the figures 2 to 4 , the screen 12 thus comprises two second portions 18.

[0042] More precisely, the surface of the second portions 18 is offset relative to the surface of the first portion 16, and is located below the surface of the first portion 16. The screen 12 thus has a geometric shape in which the internal surface 14 comprises two hollows or recesses.

[0043] The second portions 18 are flat, like the first portion 16, and are parallel to the first portion 16.

[0044] There figure 3 illustrates a section of the screen 12 shown schematically on the figure 2 . As can be seen on the figure 3, the screen 12 has a flat external surface 20 which is opposite and parallel to the internal surface 14. The screen 12 then has a thickness which is greater at the level of the first portion 16 than at the level of the second portions 18. Thus, the difference in thickness of the screen 12 between the first portion 16 and the second portions 18 of the internal surface 14 can be between 0.5 mm and 10 mm, preferably between 1 mm and 5 mm.

[0045] Such a difference in thickness may correspond to a multiple of the thickness of an elementary geometric element of the mesh material. Thus, to produce the second portions 18, it may be sufficient not to form or to remove one or more layers of elementary geometric elements of the mesh material, in order to obtain second portions 18 with a flat surface parallel to the first portion 16.

[0046] There figure 4represents an infrared radiation transmitter 1 comprising a screen 12 as illustrated in Figures 2 and 3 . The transmitter 1 comprises in particular a frame 4 and a combustion surface. However, in the example illustrated in figure 4 , the combustion surface of the emitter 1 is formed by two burner plates 8a, 8b arranged adjacently to form a continuous combustion surface.

[0047] As shown in the figure 4 , the screen 12 is arranged opposite the burner plates 8a, 8b, with the internal surface 14 facing the combustion surface. The screen 12 is not arranged directly on the burner plates 8a, 8b, but at a distance, for example the first portion 16 may be located at least 1 mm from the burner plates 8a, 8b, preferably at least 2 mm. Indeed, the proximity of the screen 12 may lead, in use, to “detaching” the flame from the combustion surface and therefore to extinguishing the emitter 1, in particular during ignition.

[0048] In order to limit such a problem, the screen 12 comprises the second portions 18 which, as they are arranged set back from the first portion 16, are even further away from the burner plates 8a, 8b. It then becomes easier and simpler to maintain the flame on the combustion surface at least at the level of the second portions 18. Thus, when the flame goes out from the combustion surface located opposite the first portion 16 of the screen, it can be rekindled by the flame still present on the combustion surface located opposite the second portion 18. The second portion 18 therefore makes it possible to maintain the operation of the transmitter 1, in particular upon ignition.

[0049] However, and in order to maintain a high efficiency of the emitter 1 which is, in the prior art, obtained with a screen made of mesh material positioned as close as possible to the combustion surface, the second portions 18 are provided with reduced dimensions. Thus, the total surface area of ​​the second portions 18 may be between 1% and 70% of the total surface area of ​​the internal surface, preferably between 5% and 50% and more preferably between 10% and 30%.

[0050] Furthermore, the second portions 18 may be provided opposite the hottest surface of the burner plates 8a, 8b, i.e. opposite the center of the burner plates 8a, 8b. Indeed, the hottest surfaces of the burner plates are the surfaces which deteriorate most quickly and which are most likely, over time, to prevent the proper functioning of the emitter. Thus, by providing the second portions 18 opposite the hottest areas of the burner plates 8a, 8b, it becomes possible to extend the service life of the emitter.

[0051] Alternatively, the second portions 18 may be provided opposite a peripheral portion of the burner plates 8a, 8b, for example in a peripheral portion of the internal surface 14 of the screen.

[0052] THE figures 5 And 6illustrate a second embodiment of the invention. In this second embodiment, the emitter comprises only one burner plate 8. In this case, only a second portion 18 is provided in the screen 12, and is arranged opposite the center of the burner plate 8. Alternatively, the second portion 18 may also be arranged opposite a peripheral portion of the burner plate 8, for example on a peripheral portion of the internal surface of the screen such as a corner or an edge of the internal surface of the screen.

[0053] There figure 7 illustrates a third embodiment of the invention. More specifically, the figure 7 illustrates a screen whose surface intended to face the burner plate, i.e. the internal surface, is shown.

[0054] As illustrated in the figure 7, the screen 12' according to the third embodiment of the invention does not have a flat internal surface, but on the contrary comprises an internal surface 14 with a first main portion 16 and a second portion 18' arranged set back relative to the first portion 16. In the example illustrated in the figure 7 , the screen 12' thus comprises a single second portion 18'. In particular, the second portion 18' is positioned on the periphery of the internal surface 14, in this case in a corner.

[0055] More specifically, the surface of the second portion 18' is offset relative to the surface of the first portion 16, and is located below the surface of the first portion 16. The screen 12' thus has a geometric shape in which the internal surface 14 has a hollow or recess on the periphery. The screen 12' is illustrated with a single second portion 18' but can obviously comprise several, arranged at the corners and / or edges of the internal surface 14.

[0056] The second portion 18' may be planar, like the first portion 16, and may be parallel to the first portion 16.

[0057] Thus, thanks to the specific shape of the screen according to the present invention, it becomes possible to combine the efficiency of mesh or open-pore materials while maintaining the operating stability of traditional screen emitters. In particular, it becomes possible to keep a screen close to the burner plate, while ensuring operating stability, particularly during ignition.

Claims

1. A gas-heated infrared radiation emitter (1) comprising a burner plate (8), said burner plate (8) serving as a combustion surface, and a radiating screen (12) positioned on the combustion surface side of said burner plate (8), said radiating screen (12) being formed by a mesh material or material with open pores, and having an inner face (14) oriented towards the combustion surface side of the burner plate (8), the inner surface (14) of the screen comprising at least a first portion (16) and a second portion (18) offset from one another in relation to the combustion surface, such that the distance between the combustion surface and the first portion (16) is less than the distance between the combustion surface and the second portion (18) characterised in that the screen (12) also has an outer face (20) opposite the inner face (14), the outer face (20) being substantially planar and parallel to the two offset portions (16, 18) of the inner face (14) such that the thickness of the screen (12) in the first portion (16) is greater than the thickness of the screen (12) in the second portion (18).

2. The emitter (1) according to the preceding claims, wherein the difference in distance between the combustion surface and the first and second portions (16, 18) is between 0.5 mm and 10 mm, preferably between 1 mm and 5 mm.

3. The emitter (1) according to any one of the preceding claims, wherein the inner face (14) of the screen is formed by the absence or by removal, in the second portion (18), of one or more mesh elements.

4. The emitter (1) according to any one of the preceding claims, wherein the second portion (18) of the screen is arranged substantially facing the centre of the burner plate (8), for example facing the centre of a, preferably perforated, ceramic plate.

5. The emitter (1) according to any one of claims 1 to 3, wherein the second portion (18) of the screen is arranged facing a peripheral part of the burner plate (8), for example on a peripheral part of the inner surface (14) of the screen, such as a corner or along an edge of the inner surface (14) of the screen.

6. The emitter (1) according to any one of the preceding claims, wherein the screen (12) forms edges of a plurality of geometric mesh elements assembled in a three-dimensional network.

7. The emitter (1) according to any one of the preceding claims, wherein the screen (12) comprises silicon carbide, preferably infiltrated with silicon.

8. The emitter (1) according to any one of the preceding claims, wherein the first portion (16) of the screen (12) is at a distance from the burner plate (8), for example at least 1 mm, and preferably at least 2 mm.

Images