U.S. patent application number 11/013479 was filed with the patent office on 2006-02-23 for cover member for a gas combustion heads, and gas burner comprising such a cover member.
This patent application is currently assigned to RIELLO S.p.A.. Invention is credited to Andrea Lovato, Giuseppe Toniato.
Application Number | 20060040224 11/013479 |
Document ID | / |
Family ID | 34486572 |
Filed Date | 2006-02-23 |
United States Patent
Application |
20060040224 |
Kind Code |
A1 |
Lovato; Andrea ; et
al. |
February 23, 2006 |
Cover member for a gas combustion heads, and gas burner comprising
such a cover member
Abstract
A cover member for gas combustion heads. The cover member has at
least one tubular base structure. And the tubular base structure is
formed by knitting at least one metal wire.
Inventors: |
Lovato; Andrea; (Terranegra
Legnago, IT) ; Toniato; Giuseppe; (Legnago,
IT) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
RIELLO S.p.A.
Legnago
IT
|
Family ID: |
34486572 |
Appl. No.: |
11/013479 |
Filed: |
December 17, 2004 |
Current U.S.
Class: |
431/90 ;
431/329 |
Current CPC
Class: |
F23D 14/74 20130101;
F23D 2900/00019 20130101; Y02P 70/62 20151101; D04B 1/225 20130101;
F23D 14/145 20130101; F23D 14/82 20130101; Y02P 70/635
20151101 |
Class at
Publication: |
431/090 ;
431/329 |
International
Class: |
F23N 1/02 20060101
F23N001/02; F23D 14/14 20060101 F23D014/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2003 |
EP |
03425807.9 |
Claims
1) A cover member (19a, 19b) for gas or vapourized liquid fuel
combustion heads (17); the cover member (19a, 19b) being
characterized by comprising at least one tubular base structure
(40), and each tubular base structure (40) being formed by means of
a first knitting operating using at least one metal wire (32).
2) A cover member (19a, 19b) as claimed in claim 1, characterized
in that said cover member (19a) is formed by means of a second
knitting operation using at least one tubular base structure (40)
formed by means of said first knitting operation.
3) A cover member (19a, 19b) as claimed in claim 1, characterized
in that said cover member (19b) is formed by means of a weaving
operation using at least one tubular base structure (40) formed by
means of said first knitting operation.
4) A cover member (19a, 19b) as claimed in claim 1, characterized
by being in the form of a seamless stocking.
5) A cover member (19a, 19b) as claimed in claim 1, characterized
in that said tubular base structure (40) has a diameter of 0.5 mm
to 4 mm.
6) A cover member (19a, 19b) as claimed in claim 5, characterized
in that said tubular base structure (40) is formed using at least
one wire (32) of 0.05 mm to 1 mm in diameter.
7) A cover member (19a, 19b) as claimed in claim 6, characterized
in that said wire (32) is formed by drawing
high-temperature-resistant materials, such as NiCr or FeCrAl
alloys.
8) A premix gas or vapourized liquid fuel burner (10),
characterized by comprising at least one cover member (19a, 19b) as
claimed in claim 1.
Description
[0001] The present invention relates to a metal cover member for
premix burner gas combustion heads.
[0002] The present invention also relates to a gas or vapourized
liquid fuel burner comprising such a cover member.
BACKGROUND OF THE INVENTION
[0003] As is known, in premix combustion heads, i.e. in which gas
and air are mixed upstream from the combustion region where the
flame is generated, the perforated metal combustion head from which
the inflammable mixture is emitted can be covered with a specially
constructed metal cover member.
[0004] Covering the combustion head with a metal cover member is
particularly advantageous by enhancing heat exchange by radiation,
while at the same time protecting the metal structure of the
combustion head underneath. High modulation ratios and
high-thermal-power premix applications can thus be achieved, which
would otherwise be impossible on account of the severe thermal
stress to which the combustion head is subjected.
[0005] The metal cover member also prevents the combustion head
underneath from overheating to the extent that hazardous backfiring
occurs.
[0006] Finally, the porosity of the metal cover member over the
combustion head improves distribution of the fuel gas/air mixture,
while at the same time reducing flame temperature and, hence,
nitric oxide emissions.
[0007] In premix radiant burners, known solutions employ
appropriately shaped woven or sintered cover members fitted to the
combustion heads.
[0008] In the case of a burner with a cylindrical perforated
combustion head, the woven or sintered cover member is folded to
fit completely over the cylindrical surface of the combustion head,
the free portions of the cover member are welded together, and the
cover member so formed is welded to the combustion head.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide a cover
member for gas burners, and a gas or vapourized liquid fuel burner
comprising such a cover member, which is improved with respect to
currently marketed types.
[0010] According to the present invention, there are provided a
cover member for gas combustion heads, and a gas burner comprising
such a cover member, as claimed in the accompanying independent
Claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Two non-limiting embodiments of the present invention will
be described by way of example with reference to the accompanying
drawings, in which:
[0012] FIG. 1 shows a layout of a premix gas burner featuring an
innovative cover member;
[0013] FIG. 2 shows an enlarged detail of the perforated combustion
head of the FIG. 1 burner fitted with the cover member which is the
main object of the present invention;
[0014] FIG. 3 shows a number of stitches of a tubular base
structure from which the cover member in FIGS. 1 and 2 is
formed;
[0015] FIG. 4 shows a tubular base structure made using at least
one drawn wire and knitted by means of a first knitting
operation;
[0016] FIG. 5 shows a cover member formed by means of a second
knitting operation using at least one tubular base structure formed
by means of the first knitting operation; the tubular base
structure is the one shown in FIGS. 3 and 4;
[0017] FIG. 6 shows an enlarged detail of the cover member in FIG.
5;
[0018] FIG. 7 shows a cover member formed by weaving a number of
tubular base structures as shown in FIGS. 3 and 4;
[0019] FIG. 8 shows an enlarged detail of the cover member in FIG.
7.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Number 10 in FIG. 1 indicates a premix gas burner featuring
an innovative cover member in accordance with the present
invention.
[0021] Burner 10 comprises a main body 11 supplied with fuel gas or
vapourized liquid fuel by a pipe 12. Fuel gas flow along pipe 12 is
controlled in the normal way by a pressure regulator 13 connected
to main body 11 by a conduit 14.
[0022] Pipe 12 terminates with a nozzle 15 at the end projecting
inside body 11.
[0023] A fan 16, integral with main body 11, provides for feeding
into main body 11 the amount of primary air required to burn the
gas, or vapourized liquid fuel, supplied by nozzle 15.
[0024] A substantially cylindrical, perforated metal combustion
head 17 projects from body 11.
[0025] As shown in FIG. 1, combustion head 17 is fixed at a first
end 17a, as stated, to main body 11, and is closed at a second end
17b by a cap 18.
[0026] As shown in FIGS. 1 and 2, the cylindrical outer surface 17c
of perforated metal combustion head 17 is covered with a cover
member 19b (FIGS. 7 and 8) in accordance with one embodiment of the
present invention.
[0027] As shown particularly in FIG. 2, combustion head 17 has a
number of openings 20 through which the fuel gas/air mixture flows
from body 11 and combustion head 17 outwards to where the mixture
is ignited to form the flame (not shown). As stated, the outer
surface 17c (FIGS. 1, 2) of combustion head 17 is fitted with cover
member 19b.
[0028] With reference to FIGS. 5 and 7, the cover member 19a (FIG.
5), 19b (FIG. 7) is formed by interlacing at least one tubular base
structure 40 shown by way of example in FIG. 4.
[0029] FIG. 3 shows a number of stitches 31a-31g of a tubular base
structure 40 (FIG. 4). Stitches 31a-31g are formed by knitting, by
means of a first knitting operation, at least one metal wire 32 on
a known knitting machine (not shown).
[0030] More specifically, as shown in FIG. 3, wire 32 is knitted
using a knitting method commonly used, for example, in the
manufacture of hosiery.
[0031] This method produces a tubular base structure 40, as shown
in FIG. 4, in which stitches 31a-31g are looped using a method also
commonly used in the knitting industry, and particularly in the
manufacture of nylon stockings.
[0032] Advantageously, though not necessarily, the tubular base
structure in FIG. 4 has a diameter of about 0.5 mm to 4 mm, and may
be compressed to facilitate subsequent processing.
[0033] Advantageously, though not necessarily, wire 32 from which
stitches 31a-31g are formed has a diameter of 0.05 mm to 1 mm.
[0034] Wire 32 is normally formed by drawing alloys resistant to
high temperature and corrosion, such as NiCr or FeCrAl.
[0035] The tubular base structure 40 (FIG. 4) described is much
lighter than stranded wire (not shown) used in conventional cover
members (not shown). A stranded wire, in fact, is formed by
combining a number of wires or fibres, and gives rise to a solid,
heavy structure.
[0036] The tubular base structure 40 in FIG. 4, on the other hand,
is characterized by being lightweight and extremely porous.
[0037] The porosity of cover member 19a (FIG. 5), 19b (FIG. 7) is a
fundamental parameter in combustion applications.
[0038] Porosity, in fact, affects nitric oxide emission values, and
reduces the load losses of combustion head 17; and adequate
porosity of cover member 19a, 19b also aids in preventing
backfiring.
[0039] The light weight of cover member 19a, 19b reduces thermal
inertia, which is an important factor in reducing the heating time
of the burner at start-up. In fact, the shorter the heating time
is, the more stable the flame will be. Also, when the burner is
turned off, faster cooling reduces thermal stress of combustion
head 17, thus reducing wear. The light weight of cover member 19a,
19b also means less material is required.
[0040] The number of needles (not shown) used to produce tubular
base structure 40 (FIG. 4) determines to some extent the elasticity
and porosity of the finished article.
[0041] The same knitting method used to produce tubular base
structure 40 may also be used to produce cover member 19a in FIGS.
5, 6.
[0042] In actual fact, the cover member 19a in FIG. 5, which
represents a first embodiment of the present invention, is formed
by means of a second knitting operation using at least one tubular
base structure 40 formed using the first knitting operation
described with reference to FIGS. 3 and 4.
[0043] Performing a second knitting operation using at least one
tubular base structure 40 advantageously produces a tubular cover
member 19a as shown in FIG. 5, and which can be fitted directly
onto the combustion head. In this case, no welding is required to
loop cover member 19a, thus simplifying manufacture and use of
cover member 19a.
[0044] In the second knitting operation, it is essential to control
the overall elasticity of cover member 19a and form a type of knit
which, once fitted on, permits thermal expansion of combustion head
17 during operation of burner 10.
[0045] Once fitted on, cover member 19a adheres to combustion head
17.
[0046] Though the solution proposed is particularly suitable for
cylindrical combustion heads 17, this does not exclude the
possibility of using cover member 19a on combustion heads of other
shapes or on flat structures.
[0047] When producing cover member 19a, it is important to avoid
ladders which, in service, are particularly hazardous by giving
rise to backfiring. Ladders may be avoided by using special knit
configurations known in literature.
[0048] The type of knit also determines the porosity of the final
structure.
[0049] In a second embodiment of the present invention shown in
FIGS. 7 and 8, as opposed to the second knitting operation
described with reference to FIGS. 5 and 6, tubular base structures
40 in FIG. 4 can be assembled by straightforward weaving on a frame
(not shown), and the finished article may be flat or tubular,
depending on the type of loom used.
[0050] One example of a cover member 19b of this type is shown in
FIGS. 7 and 8. The FIG. 8 detail shows the weft 50 and warp 51
configuration typical of a cover member 19b woven on a loom (not
shown).
[0051] More specifically, the weft 50 is defined by a number of
tubular base structures 40a, 40b, 40c, and the warp 51 by tubular
base structures 40d, 40e, 40f; and weft 50 and warp 51 are woven on
a frame (not shown).
[0052] Tubular base structures 40a-40f are all formed as described
with reference to FIGS. 3 and 4.
[0053] The elasticity achieved by weaving as in FIGS. 7 and 8 is
also ensured by the elasticity of tubular base structures
40a-40f.
[0054] Unlike cover member 19a in the first embodiment, however,
cover member 19b in the second embodiment poses no danger of
laddering.
[0055] Various types of weave can be used to obtain the desired
porosity.
[0056] Both the intrinsic characteristics of combustion head 17 and
knitting or weaving cover member 19a or 19b provide for achieving
the porosity and elasticity of cover member 19a, 19b required when
applied to premix burners 10.
[0057] More specifically, the porosity of cover member 19a, 19b
provides for generating the flame front inside and downstream from
cover member 19a, 19b (in the flow direction of the premixed
mixture), thus averting any danger of backfiring.
[0058] The elasticity of cover member 19a, 19b enables it to be
fitted on cold, and permits in-service thermal expansion of the
supporting combustion head 17.
[0059] Another advantage, as stated, of the cover member 19a, 19b
proposed is that it can be fitted onto perforated combustion head
17 and used with no need for welding to loop it, thus simplifying
production and use of the cover member.
[0060] Moreover, once fitted on, cover member 19a, 19b generally
adheres to perforated combustion head 17. In some applications,
however, it may prove useful to weld it to combustion head 17.
[0061] Advantageously, though not necessarily, the single wire 32
(FIG. 3) used to form tubular base structure 40 may be made of
high-temperature-resistant alloy, such as NiCr or FeCrAl.
* * * * *