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(11) | EP 1 813 864 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | High-power burner device |
| (57) A burner (1) to be supplied with a fuel comprises a diffuser (3) with a pattern of
openings (5) for the fuel to pass therethrough and be combusted, a fuel conduction
pathway (7) to the diffuser (3, 8), wherein the diffuser (3) comprises a plate-like
body (8) with two opposite diffusion surfaces (9, 10) facing the outside of the plate-like
body (8), such as to allow a combustion to take place on two opposite sides (17, 18)
of a same plate-like body (8).
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[0001] The present invention relates to a burner device for generating heat by means of the combustion of a fuel and oxidant mixture.
[0002] Burner devices are known to be provided with a diffuser, such as for a fuel-air premixed gas to be blown therethrough, which supplies a pattern of a plurality of flames for generating heat. The heat is then transferred by means of the hot combustion gases to a heat exchanger for heating a fluid, such as water, which is then piped to a utility, such as a heating system for an industrial process, for dwelling environments, and the like. These utilities require, particularly during production or heating peak periods, a large amount of heat, which requires high-power burner devices.
[0003] By means of prior art burner devices, combustion power can be changed by changing the fuel supply to the diffuser. This fuel supply, and accordingly the combustion power, can be only increased, however, to a limited extent, as flame stability problems occur at higher values, which affect the burner operation. To further increase the combustion power, the diffuser size thus requires to be also increased. This inevitably results in an undesired increase in the burner overall dimensions, which is often incompatible with the narrow space available for burner installation.
[0004] The object of the present invention is thus to provide a burner device having such characteristics as to increase the ratio of the burner combustion power to the overall dimensions thereof.
[0005] This and other objects are achieved by means of a burner that can be supplied by a fuel-air mixture, comprising:
- a diffuser with a pattern of openings for said mixture to pass therethrough and be burnt,
- a mixture conduction pathway to the diffuser,
[0006] By arranging a plate-like body with two opposite diffusion surfaces facing the outside of the plate-like body, two large-area flame fields can be obtained at an individual diffuser body of small thickness and bulk. This allows considerably increasing the total combustion area within a given volume, as this volume can be filled as desired by means of one or more plate-like bodies. By the term "fuel" is meant herein both a fuel-oxidant mixture, such as methane and air, and a fuel not premixed with an oxidant, such as methane or natural gas.
[0007] In order to better understand the invention and appreciate the advantages thereof, several exemplary non-limiting embodiments of the same will be described below, with reference to the annexed drawings, in which:
- Fig. 1 is a perspective view of a burner according to an embodiment of the invention;
- Fig. 2 is a perspective view of a detail of the burner in Fig. 1, as seen from an external side of the burner;
- Fig. 3 is a perspective view of the detail in Fig. 2, as seen from an internal side of the burner;
- Fig. 4 is a view of the detail in Fig. 2, as seen from the outside of the burner;
- Fig. 5 is a side view of the detail in Fig. 2;
- Fig. 6 is a view of the detail in Fig. 2 from the inside of the burner;
- Fig. 7 is a top view of the detail in Fig. 2;
- Fig. 8 is a sectional view of the burner shown in Fig. 1;
- Fig. 9 is a perspective view of a burner according to a further embodiment of the invention;
- Fig. 10 is a side view of the burner in Fig. 9;
- Fig. 11 is a sectional view of the burner in Fig. 9;
- Fig. 12 shows a detail of the burner in Fig. 9, as seen from the inside of the burner;
- Fig. 13 is a side view of the detail in Fig. 12;
- Fig. 14 is a view of the detail in Fig. 12 from the outside of the burner;
- Fig. 15 is a perspective view of a further detail of the burner in Fig. 9;
- Fig. 16 is a perspective view of a further detail of the burner in Fig. 9;
- Fig. 17 is a sectional view of a burner according to a further embodiment of the invention as obtained by means of the components shown in Fig. 12, 13, 14, 15, 16;
- Fig. 18A, 18B, 18C schematically show prior art burner solutions;
- Fig. 19A, 19B, 19C schematically show three embodiments of the burner according to the invention;
- Fig. 20 schematically shows a burner according to a further embodiment of the invention;
- Fig. 21 and 22 are sectional, schematic views of two further embodiments of the invention;
- Fig. 23 is a sectional, schematic view of a further embodiment of the invention;
- Fig. 24 is a sectional, schematic view of a still further embodiment of the invention.
[0008] With reference to the figures, a burner for generating heat by means of the combustion of generally a combustible gas or particularly a gas/air premix is generally designated with numeral 1. The burner 1 comprises a support structure 2 supporting a diffuser 3, and preferably though not necessarily, a distributor, particularly a distribution wall 4. The diffuser 3 defines a plurality of openings 5 for the fuel to pass therethrough and be combusted, which define the area in which the combustion takes place. The distribution wall 4, which is arranged upstream of the diffuser 3 (relative to the fuel flow), defines a plurality of openings 6 which are substantially evenly arranged and having a total passage area that is much lower than that of the diffuser 3 in order to allow the fuel or premix to be supplied to the diffuser 3 in an evenly distributed manner. The distributor 4 is usually arranged in a fuel conduction pathway 7 extending within the burner 1 from an external fuel source (not shown in the figures) to the diffuser 3.
[0009] According to the invention, the diffuser 3 comprises a plate-like body 8 with two opposite diffusion surfaces 9, 10 facing the outside of the plate-like body 8, such as to allow a combustion to take place on two opposite sides of the same plate-like body 8. The distance 11 between the two diffusion surfaces 9, 10 defines a thickness of the plate-like body 8 and the surface extension of each of the diffusion surfaces is greater than said thickness. Such "flattened" or "slender" shape of the plate-like body allows arranging a large combustion area (which is further doubled as combustion takes place on both opposite sides of the plate-like body) within a given volume.
[0010] In accordance with an embodiment, the plate-like body 8 has a substantially box-like hollow shape, with at least two opposite diffusion walls 12, 13, which form said diffusion surfaces 9, 10 on the outside thereof, and define a space 14 within the plate-like body 8 for fuel conduction. The plate-like body 8 defines, at a base side 15, one or more openings 16 for the fuel to flow in the conduction space 14, and advantageously, the conduction space is tapered away from said base side 15, i.e. said inlet opening 16 in the plate-like body 8. Due to the conduction space 14 tapering away from the fuel inlet opening 16, a gradual reduction in the flow section is obtained, which compensates the reduction in the overall flow rate of the fuel while moving away from this inlet opening 16 (which reduction is due to the fuel being diffused through the diffusion openings 5 arranged along the fuel conduction pathway). Due to this "geometric" compensation, the flow speed, and thus the fluid dynamic pressure of the fuel on the diffusion walls is substantially evenly distributed all over the combustion surface. Thereby, the requirement of providing a suitable distribution wall along each diffusion wall is avoided. According to a particularly advantageous embodiment, the fuel conduction space 14 is tapered in a substantially linear manner in order to compensate substantially even flow rate "drops" along the conduction pathway, and consequently, in order to allow providing a pattern of diffusion opening 5 that is substantially even, i.e. with a ratio of the passage area to the diffusion surface being substantially even, regardless of the distance from the inlet opening 16. This contributes to an even distribution of the combustion areas within the total combustion volume, and thus to an optimum use of the total space available.
[0011] As may be seen, for example, in the embodiments shown in Fig. 8, 11 and 13, the conduction space 14 extending from the fuel inlet opening 16 to the diffusion walls 12, 13, is advantageously not provided with further walls for distributing the fuel on the diffusion walls.
[0012] According to an alternative embodiment, such as shown in Fig. 23, a distribution wall 28 is arranged substantially parallel to the diffusion walls 12, 13.
[0013] In order to ensure a substantially even distribution of the fuel supply (for example an air-fuel premix) to the plate-like body 8, particularly when the latter has a high width extension, a drilled distribution wall 4 is advantageously placed at the base side 15 of the plate-like body 8, such that the openings 6 of the distribution wall 4 provide the inlet opening 16 for the fuel. Due to the generally thin or flattened shape of the plate-like body, the fuel main flow is parallel to the diffusion walls 12, 13. For an effective distribution of the fuel all over the width of the plate-like body 8, the distribution wall 4 is thus advantageously oriented crosswise to the opposite diffusion walls 12, 13, such as shown in Fig. 11 and 17.
[0014] In accordance with an embodiment (Fig. 1, 9, 19B), the plate-like body 8 develops across its width along a substantially annular or polygonal line, such as to form the wall of a globally tubular structure, such as a cylinder, a truncated cone, a cone, a polyhedron, a prism, or a parallelepiped, which results in that the opposite diffusion surfaces 9, 10 allow the combustion outside 17 and inside 18 the tubular structure.
[0015] According to another embodiment (Fig. 19C), the plate-like body 8 develops across its width along a curved line, such as coiled, spiralled, or zigzag-shaped line, such as to form the wall of a three-dimensional open-profile structure, such as in the form of a labyrinth.
[0016] According to a still further embodiment (Fig. 20), the plate-like body 8 branches off across its width according to a reticular or grid-like pattern, such as to form the wall of an alveolar structure and said opposite diffusion surfaces 9, 10 allow combustion to occur within the individual cells and outside this alveolar structure.
[0017] Advantageously, the plate-like body 8 comprises a plurality of diffuser elements 19 and the diffusion walls 12, 13 are formed in or by these diffuser elements 19. In order to avoid problems connected to the thermal expansion of the opposite diffusion walls 12, 13, the diffuser elements 19 are separated from each other by one or more expansion joints 20, which allow deformations and mutual displacements of the diffuser elements 19 to a certain extent, or alternatively, these diffuser elements 19 are provided with such a shape as to result being locally deformable or collapsible (in a controlled manner and to a certain extent which does not impair their diffusion function) following expansions of their opposite diffusion walls 12, 13 in the case where the global expansions of either the individual diffuser elements 19 or the whole plate-like body 8 are prevented, for example by the support structure 2.
[0018] To allow said thermal expansion of the diffusion walls 12, 13 without increasing the overall dimensions of the individual diffuser element 19 and without developing excessive stress due to a prevented thermal expansion, it has proved particularly advantageous that the diffuser elements are generally formed as a thinned-wall open profile. This allows the diffusion walls to escape the thermal expansion stress by means of bend or local buckling.
[0019] In order to control the shape and restrain the level of local deformation of the diffusion walls 12, 13, the diffuser elements 19 are advantageously provided with a substantially box-like shape with two opposite main walls being the opposite diffusion walls 12, 13, along with side walls 21 that are intended to form joining regions with corresponding side walls 21 of adjacent diffuser elements 19. In order to conciliate the apparently contradictory requirements for a box-like shape on the one hand, and a thinned wall open profile on the other hand, the diffuser element 19 preferably has a tubular or box-like shaped body, with at least one continuous slot 22, such as to obtain the thinned wall open profile as mentioned above.
[0020] Advantageously, the slot 22 is formed in one of the opposite diffusion walls 12, 13 of the diffuser element 19.
[0021] In the embodiment such as shown in Fig. 2 to 6, the diffuser element 19 has an elongated shape and the slot 22 at least approximatively extends in the longitudinal direction of the diffuser element 19. This allows a well-controllable local deformation of the diffuser element 19, which allows the same to escape the thermal stress due to being crosswise fitted relative to the longitudinal extension of the diffuser element 19.
[0022] The diffuser element 19 is advantageously formed as one piece from a sheet-metal or plate-like semifinished product that has been previously drilled at the diffusion walls 12, 13.
[0023] In order to obtain the tapering of the conduction space 14 of the plate-like body 8, the individual diffuser elements 19 making up this plate-like body also comprise a box-like body having a base side 23 with a fuel inlet opening and that internally defines a fuel conduction space, which is tapered away from the base side 23. Similarly to what has been discussed with reference to the plate-like body 8, the individual diffuser elements 19 making up the same have a substantially triangular or trapezoid shape in the longitudinal section thereof, such as to provide a linear tapering of the fuel conduction space 14.
[0024] In accordance with an embodiment (Fig. 1, 8, 9, 11, 17), the base side 15 of the plate-like body 8 is supported by the support structure 2 of the burner 1, which comprises one or more openings for supplying the fuel to the plate-like body 8.
[0025] Advantageously, the plate-like body 8 is connected to the support structure 2 by means of an interference coupling, preferably by means of a snap fitting connection (Fig. 11, 17) .
[0026] In accordance with the embodiments as shown in Fig. 11 and 17, the support structure 2 forms a seat 24 (in the specific case, an annular seat) for an interference connection with the base side 15 of the plate-like body 8 (in the specific case, the plate-like body 8 forms the circumferential wall of an internally cylindrical and externally truncated cone-shaped tubular structure) and the seat 24 is, in turn, formed by the distribution wall 4 of the burner 1.
[0027] In order to be capable of further increasing the combustion area relative to the bulk of the burner, a further diffuser 25 is advantageously provided to be arranged in the support structure 2 within a space being defined by the plate-like body 8 (for example, within the cylindrical or truncated-cone shaped structure as shown in Fig. 1 and 9) and oriented crosswise relative to the latter. Advantageously, the further diffuser 25 is also connected to the support structure 2 by means of an interference coupling, preferably by means of a snap fitting connection (Fig. 11, 17).
[0028] In the case where the plate-like body 8 consists of a plurality of diffuser elements 19 in the form of elongated beams, the latter are advantageously arranged adjacent to each other and supported by means of an individual end (base side 23) in the support structure 2 of the burner. Due to the division of the plate-like body 8 into a plurality of diffuser elements 19 it is further possible to provide the plate-like body 8 with complex shapes, such as curved or branched, which can be hardly obtained by means of a single-piece plate-like body.
[0029] In accordance with a further embodiment (Fig. 21, 22), the opposite diffusion walls 12, 13 forming the opposite diffusion surfaces 9, 10 of the plate-like body 8 are, in turn, formed with a double wall and each diffusion wall with double wall comprises a first diffusion wall 26 for a stable flame combustion of the fuel within a first flow rate range and a second diffusion wall 27 for a stable flame combustion of the fuel within a second flow rate range other than the first flow rate range, wherein the first diffusion wall 26 and the second diffusion wall 27 are preferably parallel and sequentially arranged in the fuel conduction pathway through the diffusion wall with double walls.
[0030] Due to the sequential arrangement of several diffusion walls which allow for the formation of a stable flame within different flow rate ranges, one can obtain a stable flame combustion within a much greater overall range than the optimum range of each individual diffusion wall, and consequently, a very high modulation (ratio of the minimum combustion power to the maximum combustion power).
[0031] The opposite diffusion walls 12, 13, and preferably the whole plate-like body 8 or the whole diffuser elements 19 are made of drilled sheet-metal made of high-thermal resistance metal material, or alternatively, of porous or drilled ceramic material, or metal or ceramic fibers, such as permeable metal mesh. In view of the current fabrication cost of the materials listed above, the greatest advantage in terms of combustion power at the same cost and overall dimensions is obtained using high-temperature resistant drilled steel sheet.
1. A burner (1) to be supplied with a fuel, comprising:
- a diffuser (3) with a pattern of openings (5) for the fuel to pass therethrough and be combusted,
- a fuel conduction pathway (7) to the diffuser (3, 8),
characterized in that the diffuser (3) comprises a plate-like body (8) with two opposite diffusion surfaces (9, 10) facing the outside of the plate-like body (8), such as to allow a combustion to take place on two opposite sides (17, 18) of a same plate-like body (8).2. The burner (1) according to claim 1, wherein the distance (11) between the two diffusion
surfaces (9, 10) is lower than the width or height extension of each of the diffusion
surfaces (9, 10).
3. The burner (1) according to any preceding claim, wherein said plate-like body (8)
has a substantially box-like shape with at least two opposite diffusion walls (12,
13) which provide said opposite diffusion surfaces (9, 10) and define a fuel conduction
space (14) within the plate-like body (8).
4. The burner (1) according to the preceding claim, wherein the plate-like body (8) defines,
at a base side (15) thereof, one or more openings (6, 16) for the fuel to flow in
the conduction space (14) and the fuel conduction space (14) is tapered away from
said base side (15) of the plate-like body (8).
5. The burner (1) according to the preceding claim, wherein said fuel conduction space
(14) is tapered in a substantially linear manner.
6. The burner (1) according to claim 4 or 5, wherein the conduction space (14) downstream
the inlet opening (6, 16) for the fuel to the diffusion walls is not provided with
further walls for distributing the fuel to the diffusion walls (12, 13).
7. The burner (1) according to claim 4, 5 or 6, comprising a drilled distribution wall
(4) arranged at the base side (15) of the plate-like body (8) such as to provide said
inlet opening (16, 6) for the fuel.
8. The burner (1) according to the preceding claim, wherein said distribution wall (4)
is crosswise-oriented relative to the two opposite diffusion walls (12, 13) of the
plate-like body (8).
9. The burner (1) according to any preceding claim, wherein said plate-like body (8)
develops along its width along a substantially annular line such as to form the wall
of a globally tubular structure, such as cylindrical, truncated cone-, or cone-shaped,
and said opposite diffusion surfaces (9, 10) allow for combustion both outside (17)
and inside (18) the globally tubular structure.
10. The burner (1) according to any preceding claim, wherein said plate-like body (8)
develops along its width according to a substantially polygonal line such as to form
the wall of a globally tubular structure, such as a polyhedron, prism, or parallelepiped,
and said opposite diffusion surfaces (9, 10) allow combustion both outside (17) and
inside (18) the globally tubular structure.
11. The burner (1) according to any preceding claim, wherein said plate-like body (8)
develops along its width along a curved line, such as a coiled, spiralled, or zigzag-shaped
line, such as to form the wall of a three-dimensional open-profile structure, for
example in the form of a labyrinth.
12. The burner (1) according to any preceding claim, wherein said plate-like body (8)
branches off along its width according to a reticular or grid-like pattern, such as
to form the wall of an alveolar structure (Fig. 20) and said opposite diffusion surfaces
(9, 10) allow combustion to take place both inside and outside this alveolar structure.
13. The burner (1) according to any preceding claim, wherein said plate-like body (8)
comprises a plurality of diffuser elements (19) and said opposite diffusion walls
(12, 13) are formed in or by said diffuser elements (19).
14. The burner (1) according to the preceding claim, wherein said diffuser elements (19)
are separated from each other by means of one or more expansion joints (20) that allow
deformations and mutual displacements of the diffuser elements (19) to a certain extent.
15. The burner (1) according to claim 13 or 14, wherein said diffuser elements (19) have
such a shape as to be locally deformable or collapsible following dilatations of their
opposite diffusion walls (12, 13) in the case where the global dilatations of the
diffuser elements (19) are prevented.
16. The burner (1) according to one of claims 12 to 15, wherein said diffuser elements
(19) comprise a substantially box-like body having a base side (23) at the fuel inlet
opening (16) and which internally defines a fuel conduction space tapering away from
said base side (23).
17. The burner (1) according to the preceding claim, wherein said diffuser element (19)
has a substantially triangular or trapezoid shape in the longitudinal section thereof,
such as to provide a linear tapering of said fuel conduction space.
18. The burner (1) according to any preceding claim, wherein the opposite diffusion walls
(12, 13) forming the opposite diffusion surfaces (9, 10) of the plate-like body (8)
are, in turn, formed with a double wall, wherein said diffusion wall (12; 13) with
double wall comprises:
- a first diffusion wall (26) for a stable flame combustion of the fuel within a first flow rate range,
- a second diffusion wall (27) for a stable combustion flame of the fuel within a second flow rate range other than the first flow rate range, wherein said first diffusion wall (26) and said second diffusion wall (27) are arranged sequentially in the conduction pathway (7).
19. The burner (1) according to any preceding claim, wherein the base side (15) of the
plate-like body (8) can be connected to a support structure (2) of the burner (1),
said support structure (2) comprising fuel supply means being arranged at the base
side (15) of the plate-like body (8).
20. The burner (1) according to the preceding claim, wherein the plate-like body (8) is
connected to the support structure (2) by means of an interference connection, such
as by means of snap-fit connection.
21. The burner (1) according to claim 19 or 20, wherein the support structure (2) forms
a seat (24) for connection to the plate-like body (8) and said seat is formed by a
distributor (4) for an even distribution of the fuel flow.
22. The burner (1) according to one of claims 19 to 21, comprising a further diffuser
(25) that is arranged in said support structure (2) within a space defined by a wall
formed by said plate-like body (8).
23. The burner (1) according to any preceding claim, wherein the further diffuser (25)
is connected to the support structure (2) by means of an interference connection,
such as by means of snap-fit connection.
24. The burner (1) according to any preceding claim, wherein said diffusion walls (12,
13) comprise diffusion walls made of perforated sheet metal.
25. The burner (1) according to any preceding claim, wherein said diffusion walls (12,
13) comprise diffusion walls made of perforated or porous ceramic material.
26. The burner (1) according to any preceding claim, wherein said diffusion walls (12,
13) comprise diffusion walls made of permeable metal mesh.
27. The burner (1) according to any preceding claim, wherein said diffusion walls (12,
13) comprise diffusion walls made of metal or ceramic fibers.