U.S. patent application number 12/739027 was filed with the patent office on 2010-12-16 for burner, specifically a premix gas burner.
This patent application is currently assigned to SIT LA PRECISA S.P.A.. Invention is credited to Loris Barduca, Maurizio Beghi, Nicola Lollo, Simone Masiero, Danilo Pulzato, Gianfranco Scribano.
Application Number | 20100316967 12/739027 |
Document ID | / |
Family ID | 40314833 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100316967 |
Kind Code |
A1 |
Scribano; Gianfranco ; et
al. |
December 16, 2010 |
BURNER, SPECIFICALLY A PREMIX GAS BURNER
Abstract
What is described is a burner, specifically for gas fuels with
premixing, comprising a burner body designed to be housed in a
combustion chamber of a heating apparatus, the burner body being
provided with a burner head on which an air and gas mixture
supplied to the combustion chamber is burnt, in which the burner
head has a surface profile in the form of a dome-shaped spherical
segment, the height of the dome being less than half of the
diameter of the sphere to which the segment belongs.
Inventors: |
Scribano; Gianfranco;
(Noventa Padovana, IT) ; Beghi; Maurizio; (Schio,
IT) ; Lollo; Nicola; (Padova, IT) ; Masiero;
Simone; (Bovolenta, IT) ; Pulzato; Danilo;
(Albignasego, IT) ; Barduca; Loris; (Massanzago,
IT) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
UNITED PLAZA, 30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
SIT LA PRECISA S.P.A.
Padova
IT
|
Family ID: |
40314833 |
Appl. No.: |
12/739027 |
Filed: |
October 31, 2008 |
PCT Filed: |
October 31, 2008 |
PCT NO: |
PCT/EP2008/064788 |
371 Date: |
April 21, 2010 |
Current U.S.
Class: |
431/329 |
Current CPC
Class: |
F23D 14/14 20130101;
F23D 2203/102 20130101; F23D 2203/1015 20130101 |
Class at
Publication: |
431/329 |
International
Class: |
F23D 14/14 20060101
F23D014/14 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2007 |
IT |
PD2007A000363 |
Claims
1. A burner, specifically for gas fuels with premixing, comprising
a burner body (2) housed in a combustion chamber (4) of a heating
apparatus, said burner body (2) comprising a burner head (3) on
which an air and gas mixture supplied to the combustion chamber (4)
is burnt, wherein said burner head (3) has a surface profile (3a)
in the form of a dome-shaped spherical segment, a height (H) of
said dome being less than half of a diameter (D) of the sphere to
which said segment belongs.
2. A burner according to claim 1, in which the height (H) of said
dome-shaped spherical segment is less than half a base diameter
(D1) of said dome.
3. A burner according to claim 1, in which said burner head (3) is
made from metallic material.
4. A burner according to claim 3, in which said burner head (3) is
made from perforated sheet metal.
5. A burner according to claim 1, in which said burner head (3) is
made in the form of a metallic grid or mesh.
6. A burner according to claim 1, in which said burner head (3) is
made from fibre.
7. A burner according to claim 1, comprising a fastener for
fastening the burner head (3) to a support flange (8) of said head,
said fastener comprising at least one seat (16) on said flange (8)
shaped in the form of a pocket and at least one portion of a
perimetric base edge (10) of the dome, said seat (16) being
engageable by said portion of dome with the possibility of limited
relative sliding, thus locking the head (3) to the flange (8) while
allowing the free expansion of the head (3), particularly its
thermal expansion, relative to the seat (16).
8. A burner according to claim 7, in which said pocket-shaped seat
(16) extends circumferentially along the flange (8) in a continuous
way without any interruption.
9. A burner according to claim 7, in which said seat (16) is formed
jointly by two corresponding distinct and separate portions (8a,
8b) of said flange (8) which can be fastened together while
maintaining a distance between them, in such a way that the pocket
of said seat (16) is formed as a result of their locking
together.
10. A burner according to claim 7, in which said seat (16) has, in
a diametric cross section, a predominant longitudinal extension in
a direction which cuts the principal axis of the dome.
11. A burner according to claim 10, in which the depth of said
pocket-shaped seat (16) is chosen so as to allow the edge (10) of
the head (3) engaged in said seat (16) to slide freely, at least
along the said direction of longitudinal extension.
12. A burner according to claim 1, in which a device is provided to
guide the air and gas mixture towards the burner head (3), said
device comprising a wall (12) positioned inside the dome, and
spaced apart from the inner surface of said dome, the flow of said
air and gas mixture being guided between said surface of the head
(3) and said wall (12), towards the burner head, said wall being
positioned coaxially with the head (3) and having a curved profile
with its convexity facing the burner head (3).
13. A burner according to claim 12, in which said wall (12) is
formed by a shaped sheet of metal.
14. A burner according to claim 12, in which a deflector element
(14) is provided between said wall (12) and the head (3) to divert
the flow of the combustible mixture.
15. A burner according to claim 14, in which said deflector element
(14) extends coaxially with the head, (3) and is spaced apart from
said wall (12).
16. A burner according to claim 14, in which said deflector element
(14) extends radially from said flange (8) and runs
circumferentially inside the dome of the burner head (3).
17. A burner according to claim 12, in which a distributor element
(11) is provided between said wall (12) and the head (3), for
supplying the flow of the combustible mixture towards the head
(3).
18. A burner according to claim 17, in which said distributor
element (11) extends coaxially with the head (3), and is spaced
apart from it.
19. A burner according to claim 17, in which said distributor
element (11) has a plate-like shape with a curved profile, having
its convexity facing the burner head (3).
20. A burner according to claim 19, in which said distributor
element (11) comprises a plurality of through holes for
distributing the mixture over the surface of the burner head
(3).
21. A burner according to claim 20, in which said distributor
element (11) and said guide wall (12) form a guide passage whose
annular section, in the direction of the flow, decreases towards
the principal axis of the dome.
Description
TECHNICAL FIELD
[0001] The present invention relates to a burner and specifically
to a premix gas burner having the characteristics described in the
preamble of claim 1 which is the principal claim.
TECHNOLOGICAL BACKGROUND
[0002] In this specific technical field, there is a known way of
making a premix gas burner whose burner head is intended to be
housed in a combustion chamber in a position facing a heat
exchanger which, when contacted by the combustion products of the
burner, heats the fluid passing through it. Typically, the burner
is connected to a shutter or similar element for sealing the
combustion chamber. In a first known kind of burner of the
aforesaid type, the burner head of the burner is made in a
cylindrical shape which can extend into a combustion chamber, which
is also of cylindrical shape, the cylinders preferably being
coaxial with each other. In this configuration, the cylindrical
shell of the burner head faces the coils of the exchanger in the
annular space of the chamber which is substantially delimited by
the overall dimensions of the cylindrical burner. One of the major
problems encountered in the production of burners of the aforesaid
type arises from the fact that, during the operation of the heating
apparatus, the burner is subjected to a state of stress due to
thermal deformation generated by the thermal expansion of the
material from which it is made. These states of stress may
adversely affect the strength of the material, and in some more
severe cases may even cause the fracture of the material. In this
context, the burner head area is one of the more critical areas of
the burner. The shutter is also typically designed with a diameter
greater than that of the combustion chamber. In this case, a
further problem is that of reducing the heat losses through the
annular space of the shutter which is not occupied by the
connection to the burner, this problem generally being tackled by
providing this area with a covering of insulating material which
reduces the onset of corrosion in the shutter, as well as providing
thermal insulation.
[0003] In an attempt to make the best use of the available surface
in the shutter, burners with flat circular burner heads have also
been proposed in the prior art. Although it does not allow the
flames to face the coils of the exchanger, this configuration
enables the use of insulation on the shutter to be reduced or even
eliminated, but it has some limitations. A first limitation is that
the burner head does not have a preferred direction of expansion. A
second limitation is that the available cross section for the
burner head is limited in size by the cross section of the
cylindrical combustion chamber.
[0004] In a further known type of burner, the burner head is
hemispherical, and more specifically its diameter is equal to the
diameter of the cylindrical combustion chamber. In this
configuration, the flames at the base of the hemispherical head are
very close to the coils of the exchanger, causing possible damage
or premature wear due to the closeness of the flame front, unless
the dimensions of the burner are reduced (i.e. by reducing the base
diameter of the hemisphere with respect to the diameter of the
cylindrical combustion chamber). Furthermore, this shape occupies a
considerable volume in the combustion chamber, which is greater
than that of an equivalent cylindrical shape.
[0005] As regards the fixing of the burner, the burner head is
typically designed to be fixed by a connecting flange to the
structure of the shutter. The system for fastening the burner head
to the flange may include, for example, a welded joint. In other
known systems, the burner head is fastened to the burner flange by
bending over pins or by fixing with screw means. The aforesaid
systems have the limitation of opposing the expansion of the burner
head as a result of the locking action, thus causing the appearance
of states of stress of thermal origin, which may adversely affect
the burner head itself.
DESCRIPTION OF THE INVENTION
[0006] The fundamental problem tackled by the invention is that of
providing a burner, and specifically a premix gas burner, whose
structural and functional design is such that the limitations of
the aforementioned prior art can be overcome. This problem is
resolved by the invention by means of a burner made in accordance
with the following claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Other features and advantages of the invention will become
clear from the following detailed description of some preferred
examples of embodiment thereof, illustrated, for the purposes of
guidance and in a non-limiting way, with reference to the appended
drawings, in which:
[0008] FIG. 1 is a perspective view of a burner made according to
the invention;
[0009] FIG. 2 is a view in side elevation of the burner of FIG. 1,
housed in a combustion chamber which is only partially
illustrated;
[0010] FIG. 3 is a partial schematic view of a detail of the burner
of the preceding figures;
[0011] FIG. 4 is a perspective view in partial section of a further
detail of the preceding figures;
[0012] FIG. 5 is a view in partial section of a detail of FIG.
4;
[0013] FIGS. 6 to 8 are schematic views, in partial section, of
different embodiments of the invention.
PREFERRED EMBODIMENTS OF THE INVENTION
[0014] With reference to FIGS. 1 to 3 initially, the number 1
indicates the whole of a burner, specifically a burner for
combustible gas of the premixed type, made according to the present
invention.
[0015] The burner comprises a burner body 2 with a burner head 3
where the air and gas mixture supplied to the burner is burnt, with
the aid of a fan device (not shown) for example.
[0016] The burner is designed to be housed in a combustion chamber
4, which is shown only schematically, of a heating apparatus (not
shown), in which a heat exchanger 5 is also housed, the exchanger
being provided with a tube bundle 6 in which a working fluid
circulates and is heated by means of the burner. The burner body 2
is fixed to a shutter element 7 which is provided to seal the
combustion chamber and which is removably connected to a static
structure of the chamber. The number 8 indicates a connecting
flange for fixing the burner body to the shutter, as will be
described clearly below.
[0017] According to a principal feature of the invention, the
burner head 3 has a surface profile 3a shaped in the form of a
domelike segment of a sphere, as is also shown clearly in FIGS. 2
and 3. More specifically, given that H indicates the height of the
spherical segment, D indicates the diameter of the sphere to which
the dome belongs, and D1 indicates the base diameter of the dome,
as shown in FIG. 3, it is specified that the height H is
conveniently chosen to be less than half of the diameter D, and
that H is preferably less than half of the base diameter D1 of the
dome.
[0018] It is to be understood that the dome shape can also be
produced from similar solid shapes with curved profiles, for
example as an ellipsoidal dome instead of a spherical dome.
[0019] Also identified on the dome are a vertex 9, at the
intersection with the principal axis of axial symmetry X, and a
circumferential edge 10 at the base of the dome.
[0020] It should be noted that, in the positioning of the burner in
the combustion chamber, the base diameter D1 of the dome is chosen
to have a value suitably smaller than the diameter of the
combustion chamber, indicated by D2 in FIG. 2.
[0021] The spherical dome head 3 can be made from metallic
material, from perforated sheet metal for example, or in the form
of a metal grid or mesh. In a further alternative, the head 3 can
be made from fibre, particularly from metallic fibre. Because of
the dome shape of the burner head 3, the flames only face the coils
of the tube bundle 6, while a suitable surface 3a of the head is
provided and the volume occupied by the chamber 4 is markedly
smaller than that which would be occupied by a hemispherical head
having a diameter D.
[0022] A distributor element 11 is also provided under the burner
head 3, inside the dome, this element being conveniently made in
the form of a platelike element provided with a plurality of
through holes, through which the combustible mixture is supplied
towards the burner head. The distributor element 11 is preferably
made from suitably shaped perforated sheet metal which is located
coaxially with the head, with respect to the principal axis X, and
which has a convex profile (in the form of a spherical or
elliptical dome, for example) whose convexity faces the concave
part of the dome, as shown schematically in FIG. 5.
[0023] The number 12 indicates an additional guide wall positioned
below the head 3 and the distributor 11, this wall preferably being
coaxial with the head and having a convex profile facing the head.
The wall 12, conveniently made in the form of a sheet having a
suitable profile (in the shape of a spherical or elliptical dome,
for example), has a base edge 12a which is spaced apart radially
from the head and from the flange 8, thus delimiting an annular
section 12b for the passage of the mixture supplied to the
burner.
[0024] The distributor element 11 is also positioned with respect
to the wall 12 so as to form, as shown in the axial sectional view
of FIG. 6, a kind of guide passage 13 whose cross section decreases
towards the axis X. This configuration makes it possible to guide
the mixture at substantially constant pressure over the whole
surface profile of the burner head 3.
[0025] In a variant embodiment, shown in FIG. 6, it is possible to
provide, as an alternative to the distributor element 11, a
deflector element 14, positioned at the mouth of the annular
section 12b, under the head 3, in the area of the passage 13 having
the greatest cross section. More specifically, the deflector 14 can
be made from shaped sheet metal which may or may not be perforated
and which extends in an annular way, either continuously or
discontinuously, from the flange 8, coaxially with the axis X, as
shown in FIG. 7. Additionally, the flange part 8b can conveniently
be made in one piece with the deflector 14. The principal function
of the deflector element 14 is that of diverting the flow of
combustible mixture supplied by the fan and guiding it into the
passage 13 formed between the head 3 and the wall 12.
[0026] Additionally, by the suitable shaping of the distributor 11
or of the deflector 14, or by a specified positioning of the
perforations passing through these components, a low-velocity area
15, which is especially stable, is created on the burner head 3. In
FIGS. 5 and 6, the area 15 is mainly located in the annular space
formed by the base portion of the deflector or of the distributor
in which there is a substantial change of curvature of the profile
of the component concerned.
[0027] These specific conditions allow the flame to be ignited and
made visible on the burner head. This is because, as a result of
the aforesaid properties, relative to the shaping and perforation
provided in the distributor or deflector, a pressure drop is
created in the area 15 as a result of the pressure losses which are
greater than in the rest of the head. The area 15 of the burner,
where the velocity is low and the flame stability is greater, can
cover a limited portion of the burner head 3, and can, for example,
be located in an annular outer ring of the head with a suitable
radial width.
[0028] The configurations of FIGS. 5 and 6, in which the guide wall
12 is provided, are particularly applicable to cases in which, in
order to achieve compactness, it is necessary to reduce the overall
space, and in which it is therefore helpful to adopt efficient
configurations where the volumes available for the fluid are
reduced, in order to achieve a good distribution of the mixture at
the burner head. The wall 12 can thus be used in these applications
to delimit the guide passage 13.
[0029] However, in cases in which it is unnecessary to reduce the
volumes available to the fluid, or where large volumes are
provided, there is no need for a guide passage, since the volume is
sufficient in itself to provide a low-velocity chamber. In this
application, therefore, no guide wall is provided, as in the case
shown in FIG. 7.
[0030] Fastening means and counter-means are provided to fix the
burner head 3 to the flange 8. These means comprise a pocket-shaped
seat 16 in the flange 8 which can be engaged by the edge 10 of the
dome that forms the burner head. The pocket-shaped seat 16 is
designed to be engaged by the circumferential edge of the dome
while allowing limited relative sliding, to enable the head to be
locked to the flange, while permitting the free expansion of the
head due to thermal deformations developed during operation, thus
preventing the creation of states of stress between the head and
the flange.
[0031] More specifically, the pocket-shaped seat 16 extends
circumferentially at an axial end of the flange opposite the end at
which the flange is fixed to the shutter. The seat extends
continuously, without any interruption, in a configuration coaxial
with the burner head 3. Said seat is also preferably formed jointly
by a pair of corresponding portions 8a and 8b of the flange, which
are separate and distinct, and which can be fastened to each other
and to the shutter by screw means. As shown in FIG. 5, the portion
8b is conveniently made in one piece with the distributor element
11.
[0032] The portions 8a and 8b are positioned coaxially with each
other, and at a distance from each other, in such a way that
corresponding surfaces of said portions which face each other
combine to delimit the annular space of the seat 16 which can
receive the edge 10 of the dome.
[0033] With reference to FIG. 5, the (diametric) cross section of
the pocket-shaped seat 16 has its main direction of longitudinal
extension cutting the principal axis X, in such a way that the edge
10 of the dome can remain engaged by insertion into the pocket. The
depth of the pocket 16, in the aforesaid direction of its main
longitudinal extension, is chosen so as to allow the edge of the
dome engaged in the seat to slide freely relative to the seat,
without substantial interface, thus facilitating the free expansion
of the head while also maintaining the locking action on the
flange.
[0034] Clearly, alternative shapes of the pocket-shaped seat are
possible, provided that it meets the requirement of fixing the head
while allowing it to expand freely, at least to a limited extent.
FIG. 8 shows schematically one such variant embodiment, in which
the flange 8 is bent over along one of its axial edges to form the
aforesaid pocket shape 16.
[0035] Thus the invention resolves the initial problem and yields
the stated advantages over the known solutions.
[0036] A further advantage lies in the overall reduction of the
manufacturing costs which can be achieved with the invention, by
comparison with the known solutions, together with the greater ease
of assembly of the burner, and the greater compactness which can be
obtained according to the claimed features.
[0037] It is also advantageously possible to change an apparatus
from a given power rating to a reduced power configuration (even to
a ratio of 1 to 4 between the power ratings concerned), simply by
replacing the burner head while leaving the rest of the burner
structure unaltered.
* * * * *