The present invention relates to a burner with a diffuser resistant to high operating temperatures, in particular to a premix burner.
In the burners subject to high operating temperatures, such as for example the premix burners, the high thermal stresses can easily causes deformation and mechanical stresses on the diffuser of the burner, which may cause the diffuser to break. This drawback occurs with any form of diffuser of the burner, but has been shown to be particularly serious in burners with flat diffusers. In order to remedy the above drawback, it has been proposed to use special materials for making the diffuser of the burner, for example a metal mesh or a ceramic material. However, this results in a significant increase in the cost of the burner in the event of use of the metal mesh and significant fragility of the diffuser in the event of use of a ceramic material.
It has also been proposed to divide the diffuser of the burner to reduce mechanical stresses arising from temperature variations during burner operation. Burners of this type are known from patent applications M02003A000180 and M02004A000031, in the name of the same applicant.
In these patent applications burners are disclosed wherein the diffuser of the burner is divided into a plurality of diffuser elements that are adjacent to one another, that are free to expand in at least one direction.
The burners disclosed in the aforementioned patent applications satisfactorily solve the problem of reducing the mechanical stresses generated by the temperature variations to which the diffuser is subjected during operation of the burner and by temperature differences between the various zones of the diffuser; nevertheless, said burners are complex to make and are relatively expensive.
The present invention aims at providing burners of the aforementioned type with divided diffusers that are simpler and cheaper to make.
According to the present invention a burner is provided that is suppliable with a mixture of air and fuel, comprising a burner body provided with a diffuser on which openings are made for the passage and subsequent combustion of said mixture, said diffuser being divided into a plurality of diffuser elements that are adjacent to one another, characterised in that said diffuser elements are fixed to a support and distribution element provided with first mechanical coupling means for coupling with said diffuser elements and with openings for distributing said mixture to said diffuser elements.
Owing to the invention, the construction and assembly of the burner is significantly simplified, in as much as a same element acts as a support for the diffuser elements and as a distributor of the mixture to the diffuser elements and it is therefore no longer necessary to provide a distributing element for each diffuser element. Furthermore, fixing the diffuser elements to said support and distribution element is very simple and rapid to achieve, thus reducing considerably burner assembly time.
Further advantages and features of the invention will be shown by the disclosure that follows that is given merely by way of non-limitative example with reference to the attached drawings, in which:
The diffuser elements 2 are fitted next to one another on a support and distribution element 11, that may have the form of a flat quadrangular plate, as shown in
The plate 11, with the diffuser elements 2 that are fixed to it, constituting the diffuser 1 of the burner, can be fixed to a support frame, with a shape corresponding to the shape of the plate 11, which will be disclosed below.
The diffuser elements 2 can be made of metal, ceramic material or of any other material resistant to the operating temperatures of the burner. The upper face 3 of the diffuser elements 2, rather than being provided with the openings 7, 8, 9, can be made of porous material with pore dimensions sufficient to ensure the passage of the mixture of air and fuel without excessive load losses.
The burner is completed by an upper base and by a lower base that are not shown, in one of which a hole is made for connecting a pipe supplying the mixture of air and fuel.
The support and distribution element 14 may as an alternative have a cylindrical shape, in which the diffuser elements 2 will preferably have a slightly arched shape, in such a way as to define as a whole a diffuser 1 with a substantially cylindrical shape.
In FIGS. 10 to 17 further versions of the support and distribution element in a burner according to the invention are shown.
In
The support and distribution element 14a furthermore has two L-shaped side faces 16, 17 connected to a pair of opposite sides of the upper face 15, to constitute two support feet for the support and distribution element, suitable for example for facilitating the coupling with a support frame and/or adjusting the height of the diffuser of the burner inside a combustion chamber, by varying for example the height H of the side faces 16, 17. In the support and distribution element 14a the rows of slits 12 and the rows of holes 13 are arranged perpendicular to the pair of sides to which the side faces 16 and 17 are connected. In FIGS. 12 to 14 another version of a support and distribution element 14b according to the invention is shown, which differs from the support and distribution element 14a inasmuch as the rows of slits 12 and the rows of holes 13 are parallel to the pair of sides to which the side faces 16 and 17 are connected. A burner according to the invention can be made with a support and distribution element 14a, 14b, with the respective diffuser elements 2 fixed thereto (
Alternatively, a burner according to the invention can be made with a plurality of support and distribution elements 14a, 14b that are placed near one another and fitted in a containing frame, with the respective diffuser elements 2 fixed to each support and distribution element 14a, 14b.
In
The rows of slits 12 and the rows of holes 13 made in the upper face 15 of the support and distribution elements 14a, 14b, 14c can also be arranged tilted in relation to the sides of said upper face 15.
The upper face 15 of the support and distribution elements 14a, 14b, 14c, similarly to the plate 11, may be flat and quadrangular in shape, but also have a polygonal, circular, oval shape and have a convex surface.
FIGS. 18 to 23 show an embodiment of a support and containing frame 21, with which the support and distribution elements 11, 14a, 14b, 14c can be coupled, with the relative diffuser elements 2, to assemble a burner according to the invention.
The frame 21 is a composable frame 21, consisting of two pairs of frame elements 22, 22a; 23, 23a that are assemblable together. Each element 22, 22a of the first pair of frame elements consists of a substantially rectangular flat element 24 a longitudinal edge 25 of which is folded back into a squashed “S” shape, with an upper part 25a having a height a and a lower part 25b having a height b<a.
Each element 23, 23a of the second pair of frame elements also consists of a flat element 26, a longitudinal edge 27 of which is folded back into a non-squashed “S” shape, with an upper part 27a having a height c and a lower part 27b having a height d.
The height c of the upper part 27a of the longitudinal edge 27 is less than the height a of the upper part 25a of the longitudinal edge 25 and the height d of the lower part 27b of the longitudinal edge 27 is greater than the height b of the lower part 25b of the longitudinal edge 25.
The frame elements 22, 22a, 23, 23a are coupled together to form a quadrangular frame, as shown in
FIGS. 24 to 29 illustrate the assembly of a support and distribution plate according to the invention, for example a plate of the type shown in
Two opposite edges 11a of the plate 11 are inserted inside the upper parts 25a of the longitudinal edges 25, folded into the shape of a squashed “S”, of the elements 23, 23a, of the frame 21, as shown in
When the frame elements are fixed together by crushing, the edges 11a, 11b of the plate 11 remain immobilised in the respective squashed frame elements.
The plate 11 shown in FIGS. 24 to 29 has a slightly convex shape, but the same assembly can be achieved with a flat plate 11, or with a plate 14a, 14b, 14c.
FIGS. 30 to 33 show another diffuser version 28, associable with a frame 21 like the one shown in
The diffuser 28 consists of a plurality of diffuser elements 29 arranged parallel to one another and connected together along the longer sides by elastic-hinge connecting means 30.
The elastic-hinge connecting means 30 are used to absorb the heat expansion generated by the temperature variations to which the diffuser 28 is subjected during burner operation, thus enabling a reduction of the mechanical stresses due to said heat expansion and an increase in the working life of the diffuser 28.
The diffuser 28 may be provided with appendages similar to the appendages 10 of the previously disclosed diffuser elements 2 for coupling with a support and distribution plate 11, 14a, 14b, 14c.
FIGS. 34 to 37 show a further embodiment of a support and distribution element 31 according to the invention, which has an upper face 32 in which a plurality of rows of slits 12 is made for fixing diffuser elements 31; between pairs of rows of adjacent slits 12 rows of holes 13 are made for distribution to the respective diffuser element 2 of the mixture of air and fuel supplied to the burner. Both the rows of slits 12 and the rows of holes 13 are arranged parallel to a pair of opposite sides of said upper face 15.
The support and distribution element 31 furthermore has two side faces 33, 34 connected to a pair of opposite sides of the upper face 32. The side faces 33, 34 are each provided with a recess 35, 36 that extends over the entire length of the respective side face 33, 34. The recesses 35, 36 are suitable for facilitating, for example, coupling with a support frame and/or enabling easy coupling of the support and distribution element 31 with a combustion chamber or a heat exchanger.
The upper face 32 of the support and distribution element 31, similarly to the plate 11 and to the upper face 15 of the support and distribution elements 14a, 14b, 14c, may be flat and quadrangular in shape but may also have a polygonal, circular, oval shape and have a convex surface.
The diffuser elements 2 can be assembled on the support and distribution elements 11, 14a, 14b, 14c, 31, not only in configurations shown in
The diffuser elements 2 of each group are parallel to one another whereas the diffuser elements 2 of the central group are oriented in a direction substantially perpendicular to the diffuser elements 2 of the other two groups.
The slits 12 and the holes 13 on the support and distribution element must be arranged in such a way as to correspond to the arrangement of the diffuser elements 31.
As already said, any other arrangement configuration of the diffuser elements 2 is possible, by distributing in a corresponding manner the slits 12 and the holes 13, the configuration of the diffuser elements 2 thus being adaptable, for example, to the features of the heat exchanger of a boiler in which a burner according to the invention is installed.
Similarly, with reference to the versions of the support and distribution element illustrated in FIGS. 42 to 45, fixing of the support and distribution element 37, 42 to a heat exchanger or to a combustion chamber occurs by coupling of the recesses 41 or protrusions 43 with corresponding protrusions or recesses made on the walls of the heat exchanger or of the combustion chamber.
In the practical embodiment, the materials, the dimensions and the constructional details may be different from those indicated but be technically equivalent without thereby falling outside the legal scope of the present invention.
Number | Date | Country | Kind |
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MO2004 A 000277 | Oct 2004 | IT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/10897 | 10/10/2005 | WO | 12/19/2006 |