Burner

Abstract

The invention relates to a gaseous-fuel burner (10) having a longitudinal axis (L), in particular for a kiln for firing ceramic articles, the burner (10) comprising a tubular body (12) formed of at least one annular wall and intended to be connected to means (34) for supplying a gas flow, the tubular body (12) housing a central duct (22) that delimits, together with the annular wall of the tubular body (12), an annular channel (25) surrounding the central duct (22), the burner (10) comprising a first flow circuit for the flow of at least part of the gas flow from the supply means (34) to a central channel (23) having a longitudinal axis (L) and delimited by the central duct (22) and, separately from the first flow circuit, a second flow circuit for the flow of at least part of the gas flow from the supply means (34) to the annular channel (25), wherein the tubular body (12) comprises a radially inner annular outlet surface (19) having a convex curved profile along the longitudinal axis (L).

Description

DESCRIPTION TITLE: BURNER Technical field of the invention

[0001] The present invention relates to a burner intended for use in a tunnel kiln for firing ceramic products such as roofing tiles. Previous Art

[0002] Document FR2963086B1 is known to exist, concerning an improvement to a gaseous fuel burner, particularly suited for ceramic industry kilns, notably continuous-fire tunnel kilns. These burners, often called "tuyeres" or "foils," mix combustion air and fuel gas near the burner nozzle, called the "nose," and combustion occurs primarily within the firing chamber.

[0003] The main problem addressed in this document is controlling the position of the combustion zone within the cooking chamber. To ensure even cooking of the products, it is necessary to adjust this position. Existing solutions, such as varying the air and gas supply pressures or modifying the geometry of the burner nozzles, have drawbacks such as altering the burner power or requiring burner disassembly.

[0004] To this end, a burner with a distribution device located at the burner nozzle was proposed, allowing combustion air to be distributed to two injection zones with different aerodynamic characteristics: a high-velocity central zone and a peripheral diffusion zone. This device is divided into several radial sectors and includes a rotating shutter that allows certain sectors to be covered to distribute combustion air between the injection zones, thus adjusting the flame position within the cooking chamber without significantly affecting the air or fuel gas supply conditions.

[0005] The main features of this document include: a distribution system divided into radial sectors, with radial partitions separating the sectors, two injection zones: a central high-speed zone and a peripheral diffusion zone, a rotating shutter to mask certain areas and adjust the distribution of combustion air, a burner body consisting of concentric tubes for the transfer of air and gas.

[0006] The applications of this burner mainly concern the equipment of tunnel kilns in the ceramic industry, allowing to improve the homogeneity of the temperature and reduce the overall energy consumption of the kilns.

[0007] Also known from US patent 5110285 is a liquid fuel burner in which a change in the direction of the flame emanating from the burner is desired, for example, in the case of scrap metal smelting. In this case, a change in the flame direction is sought to directly supply heat to the unmelted scrap metal, rather than waiting for conduction and convection currents to supply heat to the unmelted scrap metal from the combustion zone where the flame is directed. To this end, a diverting fluid is introduced into a fluidic cavity comprising, from upstream to downstream, taking into account the flow of a fluid jet, a constricted zone and an enlarged zone.The introduction of the deflection fluid is carried out in a direction substantially perpendicular to the longitudinal axis of the fluidic cavity and slightly upstream or just at the transition from the constricted flow zone to the enlarged flow zone for an effective change of direction of the fluid jet and, ultimately, a deflection of the flame from its normally axial position, aligned with the burner, in one direction or another, depending on the positioning of the deflection fluid injection point.

[0008] However, these types of burners do not allow for a sufficiently diffuse 360° diffusion of the combustion flame around the burner outlet.

[0009] The invention aims to remedy these drawbacks in a simple, reliable and inexpensive way. Presentation of the invention

[0010] A gaseous fuel burner with a longitudinal axis is thus proposed, in particular for a kiln for firing ceramic articles, comprising a tubular body intended to be connected to means for supplying gas flow, said tubular body housing a circumferential gas flow distributor having first sectors and second sectors connected at the inlet to said means for supplying gas flow, the first sectors opening at the outlet into a central channel with a longitudinal axis and the second sectors opening at the outlet into an annular channel surrounding the central channel, in which the tubular body includes a radially internal annular outlet surface having a convex curved profile along the longitudinal axis.

[0011] This document also relates to a gaseous burner with a longitudinal axis, in particular for a kiln for firing ceramic articles, comprising a tubular body formed of at least one annular wall and intended to be connected to means for supplying gas flow, said tubular body housing a central conduit delimiting, with the annular wall of the tubular body, an annular channel surrounding said central conduit, said burner comprising a first flow circuit of at least a part of said gas flow from said means for supplying to a central channel with a longitudinal axis and delimited by the central conduit and, separate from said first flow circuit, a second flow circuit of at least a part of said gas flow from said means for supplying to said annular channel, in which the tubular body comprises a radially internal annular outlet surface having a convex curved profile along the longitudinal axis.

[0012] In this eventuality, said burner may include a flow distributor configured to include at least said first flow circuit, and possibly also said second flow circuit.

[0013] The flow distributor can then consist of a circumferential gas flow distributor comprising first sectors and second sectors intended to be connected at the inlet to said gas flow supply means, the first sectors opening at the outlet into a central channel with a longitudinal axis and the second sectors opening at the outlet into an annular channel surrounding the central channel, in which the tubular body comprises a radially internal annular outlet surface having a convex curved profile along the longitudinal axis.

[0014] It is therefore proposed to create a surface with a convex, curved profile that allows for the formation of a combustion flame extending 360° around the burner outlet and substantially radially to the longitudinal axis. This shape produces a Coanda effect, which attracts or binds the gas mixture to the convex surface. Thus, as the gas mixture flows through the annular channel, it escapes in a direction perpendicular to the longitudinal axis, thereby increasing the diffusion of the combustion flame within the tunnel furnace housing such a burner.

[0015] This convex, curved profile can be tangent to a plane perpendicular to the longitudinal axis, this plane passing through the distal free end of the tubular body. This configuration further improves the attachment of the gas mixture exiting the annular channel.

[0016] The downstream end of the central conduit may extend, at least in part, radially opposite, with respect to the longitudinal axis, from said radially internal annular outlet surface having a convex curved profile along the longitudinal axis, for a local narrowing of the flow section of the annular channel and an improvement of the Coanda effect.

[0017] The annular channel includes an annular gyrator arranged between an inlet and an outlet of the annular channel. More specifically, the annular gyrator can be positioned upstream of the annular channel, allowing the gas mixture to be gyrated well before its outlet, thereby increasing the Coanda effect due to the presence of the convex surface at the outlet of the tubular body. The addition of a gyrator creates a helical flow within the annular channel, achieving the Coanda effect while maintaining a reduced longitudinal dimension and curvature of the convex surface. In this way, the overall size of this portion is reduced compared to a configuration without a gyrator. The gyration effect increases the distance traveled by the gas flow along the convex surface, facilitating its attachment to it.

[0018] The annular canal may have a convergent section over at least part of its longitudinal extent. Preferably, the annular canal converges all the way to its exit.

[0019] In this scenario, the convex curved profile can also be tangent at the junction between said curved profile and the converging section. Ideally, then, there is a double tangency of said convex curved profile: firstly, with the plane perpendicular to the longitudinal axis passing through the end of the tubular body, and secondly, with the converging section.

[0020] In a preferred embodiment, the annular canal could have a substantially constant cross-section from the canal's inlet to its outlet, thus better maintaining the gyration effect and consequently the desired Coanda effect. The cross-section could still be divergent.

[0021] The downstream end of the central channel opens upstream of the downstream end of the tube body. In one embodiment, the downstream end of the channel could be aligned longitudinally with the downstream end of the tube body. In practice, the downstream end of the tube body will be tangent to the inner surface of the tunnel furnace on which the burner is mounted so that the gas flow spreads well over the inner surface of the furnace, while minimizing turbulence.

[0022] The burner may include, or be connected to, gas supply means, which may include a combustible gas supply duct opening into a cavity formed upstream of the circumferential distributor. The formation of an air / gaseous fuel mixing cavity upstream of the circumferential distributor allows for better mixing of the two components, facilitating their ignition in a tunnel furnace.

[0023] According to another feature, a rotating ring is arranged upstream of the circumferential distributor, the ring being shaped to partially and / or totally prohibit the flow of gas streams in said first and second sectors.

[0024] The combustible gas supply conduit is centered on the rotating ring, which ensures a balanced distribution of the gas flow in the distributor cavities, and is used as a rotational drive device for positioning the rotary distributor.

[0025] The circumferential distributor, the annular gyrator and the central channel can be formed from a single piece, for example by casting or additive manufacturing.

[0026] The tubular body may include an annular wall element comprising a first wall element separated from a second wall element by a radial annular shoulder designed to receive the annular gyrator, the second wall element having a convex curved surface. The annular shoulder allows for precise positioning of the gyrator within the tubular body and also for precise positioning of the downstream end of the central channel relative to the burner's tubular body outlet. The annular shoulder also allows for centering of the distributor, the gyrator, and the central channel within the tubular body. Brief description of the figures [Fig. 1] Figure 1 represents a burner according to a variant of the invention; [Fig. 2] Figure 2 represents two component parts of the burner according to a variant of the invention; [Fig. 3] Figure 3 represents the burner of Figure 1, the rotary gas mixture distributor being in a first position in Figure 3A allowing the passage of the mixture only outside the central conduit, in the annular channel, and the rotary gas mixture distributor being in a second position in Figure 3B allowing the passage of the gas mixture simultaneously outside in the central channel and in the annular channel. Detailed description of the invention

[0027] Reference is now made to Figure 1, which represents a burner 10 with longitudinal axis L according to a preferred embodiment of the invention, and also to Figures 2 and 3. In such an embodiment, said gaseous fuel burner 10, intended in particular for a kiln for firing ceramic articles, comprises a tubular body 12 intended to be connected to gas flow supply means 34, said tubular body 12 housing a circumferential gas flow distributor 20 comprising first sectors S1 and second sectors S2 connected at the inlet to said gas flow supply means 34, the first sectors S1 opening at the outlet into a central channel 23 with longitudinal axis L and the second sectors S2 opening at the outlet into an annular channel 25 surrounding the central channel 23, in which the tubular body 12 comprises a radially internal annular outlet surface 19 having a convex curved profile along the longitudinal axis L.As will be described in more detail below, said convex curved profile may be tangent to a plane perpendicular P to the longitudinal axis, said plane passing through the distal free end of the tubular body 12. Furthermore, the annular canal 25 may include an annular gyrator 28 arranged between an inlet and an outlet of the annular canal. Said annular canal 25 may have a convergent section over at least part of its longitudinal extent, and preferably, it converges all the way to its outlet.

[0028] Figure 2 illustrates a possible embodiment of the burner 10 in two separate parts 10a, 10b assembled one inside the other, in particular part 10b being engaged inside part 10a along the same longitudinal axis L. Figure 3 represents two possible positions for the gas flow through the burner 10. The terms internal and external are used with reference to the longitudinal axis L of the burner 10. The terms upstream and downstream are used with reference to the flow of a gas stream in the burner 10 along the longitudinal axis L between a first end E1 and a second end E2 of the burner 10. The first end E1 corresponds to an inlet of a gas to be burned and the second end E2 corresponds to an outlet of the burner 10 of an air / gas mixture.

[0029] The burner 10 comprises a tubular body 12 which may be formed from a first annular wall 12a extending into a second annular wall 12b. The first wall 12a may have a constant thickness and be cylindrical with a circular cross-section. The second annular wall 12b may have a cylindrical external surface with a straight cross-section, the diameter of which may be smaller than the external diameter of the first annular wall 12a. In this way, it is possible to reduce the overall size of the tubular body 12 at the level of the second annular wall 12b, this second annular wall 12b being intended to be mounted within a wall such as the vault 14 of a baking oven. The radially internal surface 16 of the second annular wall 12b converges along the longitudinal direction L in a first direction L1 oriented from the first end E1 to the second end E2 of the burner 10. The radially internal surface 16 may also have a constant cross-section.

[0030] An internal radial annular shoulder 18 is formed at the junction of the first annular wall 12a and the second annular wall 12b. In other words, a radial annular shoulder 18 is formed at the junction of a radially internal annular surface of the first annular wall 12a and a second radially internal surface of the second annular wall 12b. Generally, the tubular body 12 may include an internal radial annular shoulder 18; the tubular body 12 may, for example, comprise a single annular wall, which has the same external diameter.

[0031] According to this document, the downstream end of the tubular body 12 comprises a radially internal annular surface 19 having a convex curved profile along the longitudinal axis. This convex curved surface is therefore formed at the outlet end of the tubular body 12.

[0032] In a particular embodiment, the convex curved profile is tangent to a plane P perpendicular to the longitudinal axis, this plane passing through the distal free end of the tubular body 12. The radius of the convex surface can be between 3 and 8 mm. In the event that the radially internal surface 16 of the second annular wall 12b converges along the longitudinal direction L in the direction L1, the convex curved profile 19 can also be tangent at the junction between said curved profile 19 and the converging section 16. Ideally, then, there is a double tangency of said convex curved profile 19, on the one hand with the plane perpendicular P to the longitudinal axis passing through the end of the tubular body 12, and on the other hand with the converging section 16.

[0033] Figure 2 represents the first part 10a forming the tubular body 12 and the second part 10b intended to be inserted into the tubular body 12 so as to form the structural part of the burner.

[0034] This second component 10b comprises a circumferential distributor 20 connected downstream to a central conduit 22 defining a central channel 23 with longitudinal axis L. The circumferential distributor 20 comprises first truncated conical angular sectors S1 and second truncated conical angular sectors S2, preferably arranged alternately around the longitudinal axis L. The sectors S1 and S2 are circumferentially delimited by partitions. The first sectors S1 form a first fluid flow circuit distinct from a second fluid flow circuit formed by the second sectors S2. Each of the first sectors S1 comprises an upstream inlet, in particular two, preferably opposite each other with respect to the longitudinal axis L (Figure 3). Each of the second sectors S2 comprises an upstream inlet.The upstream inlets, in particular the two of them, are preferably opposite each other with respect to the longitudinal axis L (Figure 3). In Figure 3B, we observe that sectors S1 and S2 are arranged alternately around the longitudinal axis. Circumferentially over 180°, we obtain the following pattern: one sector S1, one sector S2, and one solid sector. While in the example shown there are only two sectors S1 and two sectors S2, there could be four sectors S1 and four sectors S2, for example, with sectors S1 and S2 arranged alternately circumferentially with each other.

[0035] When the second part 10b is mounted in the first part 10a, the central duct 22, together with the second annular wall 12b, forms an annular channel 25. A gyrator 28 is mounted at the outlet of the first and second sectors S1, S2 and comprises a plurality of partitions 30 that allow the air exiting the gyrator to be given a helical angle. The partitions 30 are thus oriented obliquely with respect to the longitudinal axis and all in the same direction.

[0036] As shown in Figure 3A, a ring 32 is rotatably mounted around the longitudinal axis at the upstream end of the circumferential distributor. It comprises a plurality of openings 24, 26 positioned to permit the flow of gas into at least one of the first sectors S1 and the second sectors S2.

[0037] As shown in Figure 1, means 34 for supplying a gas stream, such as a combustible gas, are provided and include a conduit 34 coaxial with the longitudinal axis L. This conduit 34 includes orifices 36 opening radially to the longitudinal axis L into a cavity formed upstream of the rotating ring 32. The burner 10 includes air supply means 38 formed at an end opposite the outlet end E2 of the burner 10. More specifically, the air supply means 38 include an annular channel surrounding the fuel gas supply means 34. The air and gas mix upstream of the rotating ring 32 and therefore upstream of the circumferential distributor, which allows for better air / gas mixing.

[0038] The openings 24 and 26 are positioned around the longitudinal axis L such that, in a first position shown in Figure 3A, the ring 32 allows the air / gas mixture to pass only outside the central conduit 22, i.e., into the annular channel 25. In this position, the air / gas mixture flows through the openings 24 of the ring and into the second sectors S2, then through the gyrator, and finally into the annular channel 25. In a second position shown in Figure 3B, the ring 32 allows the air / gas mixture to pass simultaneously into the central channel 23 and the annular channel 25. In the first position of the ring illustrated in Figure 3A, a radial flame is generated along the arrows F1 by the addition of a convex curved surface 19, creating a Coanda effect.In the second position of the ring 32, the gas and air mixture flows into the annular channel 25 to generate a radial flame along the arrows F1 as previously mentioned, and also flows into the central conduit 22 to generate a vertical flame along the arrow F2. As previously indicated, a gyrator 38 is preferably added, which allows for the formation of a helical flow in the annular channel 25, resulting in a convex annular surface 19 with reduced longitudinal dimensions and a similarly reduced curvature.

[0039] The angular openings 24, 26 may present an angular sector shape.

[0040] It is understood that the circumferential distributor, the central conduit, and the gyrator are advantageously formed from a single piece, for example by additive manufacturing, which simplifies the production of this complex component. However, the various elements mentioned above could be assembled from individual parts or manufactured in any other way.

[0041] As can be seen in Figure 1, the downstream end of the central conduit and therefore of the central channel can open upstream of the downstream end of the tubular body.

[0042] Although the invention has been described above by means of a particular embodiment of a burner 1 implementing a circumferential distributor 20 comprising sectors S1, S2, the invention is not limited to such a configuration.

[0043] Thus, more generally, the invention also relates to a gaseous fuel burner 10 with longitudinal axis L, in particular for a kiln firing ceramic articles, comprising a tubular body 12, formed of an annular wall, and intended to be connected to gas supply means 34, said tubular body 12 housing a central conduit 22 delimiting, with the annular wall of the tubular body 12, an annular channel 25 surrounding said central conduit 22, said burner 10 comprising: - a first flow circuit of at least a part of said gas flow from said supply means 34 to a central channel 23 with longitudinal axis L and delimited by the central conduit 22 and, - distinct from said first flow circuit, a second flow circuit of at least a part of said gas flow from said supply means 34 to said annular channel 25, - the tubular body 12 comprising a radially internal annular outlet surface 19 having a convex curved profile along the longitudinal axis L.

[0044] Such a burner is defined in particular in claim 1 below.

[0045] It is particularly advantageous for the downstream end of the central conduit 22 to extend, at least partially, radially opposite, with respect to the longitudinal axis L, the radially internal annular outlet surface 19 having a convex curved profile along the longitudinal axis. Such a geometric arrangement defines, between the downstream end of the central conduit 22 and the annular surface 19, a local narrowing of the flow cross-section of the annular channel 25, forming a minimum cross-section of this channel 25. For a given flow rate of gaseous fluid and for a given temperature, the mixture circulating in the annular channel 25 is thus accelerated at this minimum cross-section, so as to reach a flow velocity substantially ideal for implementing the Coanda effect on the convex surface 19.The increase in speed and the resulting local pressure drop in the vicinity of surface 19 promote the adhesion of the gas jet to this surface and the progressive deflection of the flow along said radially internal annular surface 19, which contributes to the formation of a substantially annular combustion flame extending 360° around the burner outlet.

[0046] In the preferred embodiment of the burner 10 of the invention described above in connection with the attached Figures 1 to 3, the burner 10 comprises a flow distributor housed in the tubular body 12 and shaped to include the first flow circuit to the central channel 23 and the second flow circuit to the annular channel 25. In this example, the flow distributor consists of a circumferential distributor 20 of gas flow having first sectors S1 (forming the first flow circuit of the fluid) and second sectors S2 (forming the second flow circuit of the fluid) intended to be connected at the inlet to the gas flow supply means 34, each sector defining a portion of the first flow circuit or the second flow circuit.The first sectors S1 are arranged so as to open out into the central channel 23, while the second sectors S2 are arranged so as to open out into the annular channel 25 surrounding the central channel 23. The rotating ring 32 allows the supply of these sectors to be selected, at least partially, and thus the gas flow to be distributed between the central channel 23 and the annular channel 25.

[0047] In other embodiments not shown, the first and second flow circuits, which distribute the gas flow from the feed means 34 to the central channel 23 and the annular channel 25 respectively, may be implemented differently. These first and second flow circuits may, in particular, be integrated within a flow distributor arranged in the tubular body 12 between the gas flow feed means 34 and the central channel 23 and the annular channel 25, respectively. By way of example, the burner 10 may include two separate coaxial or parallel air / gas mixture feed ducts connected upstream to said feed means 34, with an inner duct preferentially opening into the central channel 23 and an outer duct preferentially opening into the annular channel 25.Flow control devices, such as adjustable valves or obturators, can be arranged on each of these supply conduits so as to adjust the proportion of gas flow directed towards the central channel 23 and that directed towards the annular channel 25, thus defining respectively the first flow circuit and the second flow circuit.

[0048] Regardless of the embodiment considered, the gas flow directed into the annular channel 25, upon exiting the burner 10, flows along the radially internal annular surface 19, which has a convex curved profile along the longitudinal axis L. This results in the gas flow being attached to this surface by the Coanda effect, which can be further enhanced by the presence of the annular gyrator 28 and, where applicable, by a convergence of the annular channel 25. The result is the formation of a combustion flame extending 360° around the burner outlet and substantially radially to the longitudinal axis L. When the first flow circuit also feeds the central channel 23, an axial flame can also be generated downstream of the central conduit 22.

[0049] Of course, the various features described in this description and in the claims can be combined in various configurations, provided they are not incompatible, to constitute other embodiments of the burner within the scope of the invention.

[0050] The burner described in this document is suitable for use in tunnel kilns where the charge to be fired is moving. It is also suitable for use in kilns where the charge to be fired is static.

Claims

DEMANDS 1. A gas-fueled burner (10) with a longitudinal axis (L), in particular for a kiln firing ceramic articles, comprising a tubular body (12) formed of at least one annular wall and intended to be connected to gas supply means (34), said tubular body (12) housing a central conduit (22) delimiting, with the annular wall of the tubular body (12), an annular channel (25) surrounding said central conduit (22), said burner (10) comprising a first flow circuit of at least a part of said gas flow from said supply means (34) to a central channel (23) with a longitudinal axis (L) and delimited by the central conduit (22) and, separate from said first flow circuit, a second flow circuit of at least a part of said gas flow from said supply means (34) to said annular channel (25),wherein the tubular body (12) comprises a radially internal annular outlet surface (19) having a convex curved profile along the longitudinal axis (L).

2. Burner (10) according to claim 1, wherein said convex curved profile is tangent to a plane perpendicular (P) to the longitudinal axis, said plane passing through the distal free end of the tubular body (12).

3. Burner (10) according to claim 1 or 2, wherein the annular channel (25) comprises an annular gyrator (28) arranged between an inlet and an outlet of the annular channel (25).

4. Burner (10) according to any one of claims 1 to 3, wherein the annular channel (25) has a convergent cross-section over at least a portion of its longitudinal extent.

5. Burner (10) according to claim 4, in which the annular channel converges (25) until its exit.

6. Burner (10) according to any one of claims 1 to 5, wherein the downstream end of the central channel (23) opens upstream of the downstream end of the tubular body (12).

7. Burner (10) according to any one of claims 1 to 6, wherein said burner (10) comprises a flow distributor shaped to include at least said first flow circuit.

8. Burner (10) according to any one of claims 1 to 7, wherein said flow distributor is configured to include said second circuit.

9. Burner (10) according to claim 7 or 8, wherein the gas flow distributor is a circumferential gas flow distributor (20) comprising first sectors (S1) and second sectors (S2) intended to be connected at the inlet to said gas flow supply means (34), the first sectors (S1) opening at the outlet into a central channel (23) with longitudinal axis (L) and the second sectors (S2) opening at the outlet into the annular channel (25) surrounding the central channel (23).

10. Burner (10) according to claim 9, comprising gas flow supply means (34) comprising a combustible gas supply conduit (34) opening into a cavity formed upstream of the circumferential distributor (20).

11. Burner (10) according to claim 9 or claim 10, wherein a rotating ring (32) is arranged upstream of the circumferential distributor (20), the ring (32) being shaped to permit the flow of gas stream into at least one of said first sectors (S1) and said second sectors (S2).

12. Burner (10) according to claims 11, in which the combustible gas supply conduit (34) is centered on the rotating ring (32).

13. Burner (10) according to any one of claims 9 to 12, wherein the circumferential distributor (20), the annular gyrator (28) and the central channel (23) are formed in one piece, for example by casting or additive manufacturing.

14. Burner (10) according to any one of claims 3 to 13, in which the tubular body (12) comprises an annular wall element having a first wall element (12a) separated from a second wall element (12b) by a radial annular shoulder (18) intended to receive the annular gyrator (28), the second wall element (12b) having the convex curved surface (19).

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