U.S. patent application number 11/051350 was filed with the patent office on 2005-08-18 for air/gas burner system.
This patent application is currently assigned to Sit-Bray Limited. Invention is credited to Hart, Edward, Lewis, Dennis.
Application Number | 20050181321 11/051350 |
Document ID | / |
Family ID | 34315456 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050181321 |
Kind Code |
A1 |
Hart, Edward ; et
al. |
August 18, 2005 |
Air/gas burner system
Abstract
A burner manifold for one or a series of burners including a
first chamber having at least one outlet leading to said one or
more burners and gas supply means arranged to introduce gas to mix
with the air. Air is introduced into the first chamber from a
second chamber, which is supplied with air under pressure via an
inlet and the first and second chambers are arranged to be in fluid
communication via a plurality of apertures.
Inventors: |
Hart, Edward; (Leeds,
GB) ; Lewis, Dennis; (Charlotte, NC) |
Correspondence
Address: |
WINSTEAD SECHREST & MINICK P.C.
PO BOX 50784
DALLAS
TX
75201
US
|
Assignee: |
Sit-Bray Limited
Leeds
GB
|
Family ID: |
34315456 |
Appl. No.: |
11/051350 |
Filed: |
February 4, 2005 |
Current U.S.
Class: |
431/278 ;
431/328 |
Current CPC
Class: |
F23D 14/045 20130101;
F23D 2900/00003 20130101; F23D 14/64 20130101; F23D 2900/14641
20130101 |
Class at
Publication: |
431/278 ;
431/328 |
International
Class: |
F23D 014/12; F23C
005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2004 |
GB |
0402619.1 |
Mar 10, 2004 |
GB |
0405359.1 |
Claims
1. A burner manifold for one or a series of burners, said manifold
apparatus comprising a first chamber having at least one outlet
leading to said one or more burners and into which air is
introduced from a second chamber, an inlet for the supply of air
under pressure into the second chamber, gas supply means arranged
to introduce gas to mix with the air, wherein said first and second
chambers are arranged to be in fluid communication via a plurality
of apertures.
2. A burner manifold according to claim 1, wherein the first and
second chambers are separated by a plate with the apertures
provided therein so as to control the flow of air from the second
chamber into the first chamber.
3. A burner manifold according to claim 2, wherein the plate is
perforated.
4. A burner manifold according to claim 2, wherein the plate forms
a wall of each of the first and second chambers.
5. A burner manifold according to claim 1, wherein the gas supply
means supplies gas into the first chamber such that mixing of the
air and gas occurs in said first chamber and the air/gas mixture is
supplied to the one or more burners.
6. A burner manifold according to claim 1, wherein the gas supply
means supplies gas into the vicinity of the one or more outlets
from the first chamber such that the gas mixes with the air upon
exit of the air from the first chamber so as to provide an air/gas
mixture to the one or more burners.
7. A burner manifold according to claim 6, wherein the first
chamber primarily contains air.
8. A burner manifold according to claim 1, including a third
chamber primarily containing gas as part of the gas supply
means.
9. A burner manifold according to claim 1, wherein the gas supply
means includes one or a series of ducts having an opening through
which gas is supplied.
10. A burner manifold according to claim 9, wherein one duct is
provided for each of the burners which are connected to the
manifold.
11. A burner manifold according to claim 1, wherein the gas supply
means injects gas tangentially to the air flow.
12. A burner manifold according to claim 1, wherein the air is
introduced into the second chamber via a fan unit.
13. A burner manifold according to claim 1, wherein substantially
all of the air passing through the burner is supplied by the fan
unit.
14. A burner manifold according to claim 1, wherein the one or more
outlets include a main aperture and one or more radial
apertures.
15. A burner manifold according to claim 1, wherein the manifold is
substantially sealed from the atmosphere.
16. A burner manifold according to claim 1, wherein the manifold
forms an elongate member and the first and second chambers extend
along the length of the manifold.
17. A burner manifold according to claim 1, wherein the burner
comprises a flamestrip which extends substantially along a side of
the manifold.
18. A burner manifold according to claim 1, wherein the one or more
burners comprise a flamestrip which extends from a side of the
manifold.
19. A burner system, said system comprising a manifold to which is
connected one or a series of burners, said manifold incorporating
gas supply means for introducing gas to each burner via one or more
outlets in the manifold, and at least one chamber into which air is
introduced via at least one air inlet, wherein substantially all of
the air supplied to said one or more burners is introduced from
externally of the manifold under pressure into said chamber.
20. A burner system according to claim 19, including a first
chamber into which air is introduced from a second chamber.
21. A burner system according to claim 20, wherein air is
introduced into the first chamber from the second chamber via a
plurality of apertures.
22. A burner system according to claim 20, wherein the gas supply
means introduces gas downstream of the second chamber.
23. A burner system according to claim 19, wherein the air is
supplied under pressure to the manifold by a fan unit.
24. A burner system according to claim 19, wherein between 120-135%
of the air required for combustion is supplied to the manifold.
25. A method of premixing air and gas prior to combustion
comprising the steps of: providing a manifold including two or more
chambers; introducing air into one chamber under pressure from
externally of the manifold; introducing air into a further chamber
from said one chamber via a plurality of apertures; introducing gas
into the air flow downstream of said one chamber via one or more
gas supply means; passing said air and gas through one or more
outlets in the manifold.
26-28. (canceled)
Description
FIELD OF THE INVENTION
[0001] The invention to which this application relates is a system
for allowing the controlled and efficient introduction of air and
gas into a burner for the air and gas mixture to be burned to
provide a heating effect.
BACKGROUND OF THE INVENTION
[0002] Under traditional means gas flows through a tubular steel
manifold to a controlled brass orifice to regulate the quantity of
gas injected into a burner. Changes in gas pressure affect the
volume of primary air being induced into the burner. Therefore, any
loss in gas pressure translates to a reduction in air entering the
burner under atmospheric conditions. Typically, atmospheric burners
operate between 50-70% primary aeration with NOx emission of
approximately 200-250 ppm.
[0003] The apparatus typically comprises a manifold into which air
is introduced and, in relation to said manifold, there are provided
one or a series of gas inlets for introducing gas into or through
the manifold. Connected to the manifold, are one or a series of
burners, the same located with respect to the manifold such that
the gas and air is introduced into the burners as a mixture of
desired gas/air quantities for ignition and burning through the
burners. A preferred form of burner is described within the
applicant's patent U.S. Pat. No. 6,461,152.
[0004] Typically, a plurality of burners are provided, each with an
open end connected to the manifold, at spaced locations along the
manifold, which is typically in a linear form. The provision of
manifolds of this type to provide a gas and air mixture which is
subsequently burned on the burners is known.
[0005] One patent, namely U.S. Pat. No. 6,461,152 describes a
system for hypo stoichiometric burners whereby there is provided a
manifold which is open to atmosphere so as to allow air to enter
the manifold and a series of gas inlets are provided with respect
to the manifold so that gas also enters the same. Further air is
introduced with a volume of approximately 1-30% of additional air
via a fan unit which introduces the additional air in a pressurised
manner into the manifold in addition to the air which is able to
enter the manifold from atmosphere. The gas and air are then
allowed to leave the manifold in a direction towards the burners
passing through a Venturi tube, which is a well known feature in
burner assemblies. The mixing of the gas and air occurs within the
Venturi tube prior to entering the burner. While it is claimed that
this provides an efficient manner of providing an air and gas
mixture, it has been found to be impractical in that in order to
operate successfully, the pressure of the gas is required to be at
a relatively high level and, furthermore, of a uniform flow rate so
as to ensure that the required gas and air mixture ratio occurs
every time. However, in certain areas such as, for example, certain
States in the USA, it is found that the gas supply pressure is
relatively low which can cause problems in the operation and,
furthermore, that there can be relatively large fluctuations in the
gas pressure over time which can also cause problems in the
operation. These problems, in turn, mean that the burning
efficiency is poor and emissions can be too high such that emission
limit requirements can be exceeded therefore meaning that the
burners cannot be used.
[0006] Global awareness of harmful emissions has lead to
legislation to control and reduce emissions of gas appliances
particularly in the European Community countries and USA. Pre-mix
burners offer the benefits of low Co (carbon monoxide) and NOx
(nitric oxide).
[0007] However the market direction calls for more compact heating
units at lower production cost with an increased output yet with
lower Co and NOx emission. These factors cause conflict for the
appliance designer.
[0008] A further problem which is experienced is that the gas and
air mixture is not efficiently supplied to each of the burners such
that, for example, one burner may receive a higher proportion of
gas in the gas and air mixture than other burners connected to the
manifold at different locations with respect to the manifold.
Indeed, what typically happens is that the burner which is at the
furthest end of the manifold from the additional air inlet,
receives a larger percentage of air in the gas and air mixture
compared to the other burners. Similarly this problem can be
attributed to other burner arrangements wherein varying amounts of
the mixture with differing proportions of air and gas are supplied
to different areas of one or more burner plates, resulting in
inconsistent temperature distributions during use.
[0009] The aim of the present invention is to provide a burner
manifold system which allows a uniform supply of the gas and air
mixture, particularly for super stoichiometric combustion and also
to provide a more predictable operation of the same such that the
required emission levels can be met.
SUMMARY OF THE INVENTION
[0010] In a first aspect of the invention, there is provided a
burner manifold for one or a series of burners, said manifold
including a first chamber having at least one outlet leading to
said one or more burners and into which air is introduced from a
second chamber, an inlet for the supply of air under pressure into
the second chamber, and gas supply means arranged to introduce gas
to mix with the air, wherein said first and second chambers are
arranged to be in fluid communication via a plurality of
apertures.
[0011] According to a preferred embodiment, the gas supply means
introduces gas downstream of the second chamber. Typically, in the
vicinity of the outlet or outlets from the manifold, mixing of the
air and gas occurs such that an air/gas mixture is supplied to the
burner.
[0012] Typically, the shape of the outlet is selected so as to
control the air/gas mixture which is supplied to the burner. In one
embodiment, the burner may be connected directly to the manifold or
each can be connected via a tube which links the burner to the
manifold and along which the air/gas mixture passes to the
burner.
[0013] In one embodiment, the air is introduced into the second
chamber of the manifold via a fan unit with the air inlet located
at one end of the said manifold. The manifold is not open to
atmosphere and therefore all, or substantially all, of the air
which is utilised in the manifold is supplied under pressure from
the fan unit. Thus the fan unit is provided to supply required air,
typically 120%-135% of the required air. This therefore ensures
that efficient supply of air is provided and the manifold is not
required to induce air from the atmosphere or by any other means.
As a result, lower NOx emissions are achievable with the capability
to increase loading to the burner hence resulting in lower cost
combustion.
[0014] Typically, the manifold first and second chambers are
separated by a plate which passes along the length of the manifold
and defines one of the walls of the said first and second chambers.
The plate has apertures provided therein to allow the passage of
air from the second chamber into the first chamber. The plate may
be perforated and the size, shape and pattern of the apertures on
the plate can be selected to suit particular manifold design
requirements. The provision of the plate with the apertures,
ensures that air is supplied more uniformly along the length of the
manifold such that each of the burners receive, at their location,
the required quantity of air which mixes with the gas which is
introduced at that location. Typically, a gas supply means is
provided for each of the burners which are connected to the
manifold.
[0015] In one embodiment, one of the burners may be supplied with
an air/gas mixture which is richer in gas than the other burners so
as to ensure that that burner will ignite more readily when
attempting to ignite the burners.
[0016] To assist a homogeneous gas/air mixture, more than one
radial outlet may be used and, furthermore the arrangement which
will be described herein, allows gas to be injected tangentially to
the air flow.
[0017] Typically the system as herein described, is for use with
premix burners being supplied with air at approximately 120% to
135% of the required air for operation i.e. including excess air,
to allow super stoichiometric combustion.
[0018] In a second aspect of the invention there is provided a
burner manifold system, said manifold system incorporating a
manifold to which is connected one or a series of burners, said
manifold incorporating gas supply means, for introducing gas to a
burner via an outlet in the manifold, a first chamber into which
air is introduced from a second chamber wherein substantially all
of the air supplied to said one or more burners is introduced from
externally of the manifold under pressure into the second chamber
via at least one air inlet.
[0019] In one embodiment some gas may be present in the first
chamber so as to allow mixing to occur, as the gas and air leave
the outlet apertures in the manifold towards the burner. The
provision of the apertures provide control for the gas and air as
the mixture enters the burner and also offer a means to assist
timely, smooth, ignition.
[0020] Typically, the system can operate at low gas pressure such
as below 7.5 mbars and is not reliant upon high gas pressure, above
7.5 mbars to induce aeration atmospherically.
[0021] In a third aspect of the present invention there is provided
a method of premixing air and gas prior to combustion comprising
the steps of, providing a manifold including two or more chambers,
introducing air into one chamber under pressure from externally of
the manifold, introducing air into a further chamber from said one
chamber via a plurality of apertures, introducing gas into the air
flow downstream of said one chamber via gas supply means, passing
said air and gas through one or more outlets in the manifold.
[0022] Typically the gas and air passes through the outlets in the
manifold to a burner or burners which are connected directly to the
manifold.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The foregoing summary as well as the following detailed
description of the preferred embodiment of the invention will be
better understood when read in conjunction with the appended
drawings. It should be understood, however, that the invention is
not limited to the precise arrangements and instrumentalities shown
herein. The components in the drawings are not necessarily to
scale, emphasis instead being placed upon clearly illustrating the
principles of the present invention. Moreover, in the drawings,
like reference numerals designate corresponding parts throughout
the several views.
[0024] The invention may take physical form in certain parts and
arrangement of parts. For a more complete understanding of the
present invention, and the advantages thereof, reference is now
made to the following descriptions taken in conjunction with the
accompanying drawings, in which
[0025] FIGS. 1a to 1g illustrate a first embodiment of the
invention in various views;
[0026] FIG. 2 illustrates a more detailed view of the gas manifold
with a front plate removed; and
[0027] FIG. 3 illustrates the air/gas system in accordance with one
embodiment of the invention.
[0028] FIG. 4 shows a plan view of a manifold according to a second
embodiment of the present invention.
[0029] FIG. 5 shows a cross section of the manifold of FIG. 4 taken
through the plane B-B.
[0030] FIG. 6 shows a cross-section of the manifold of FIG. 4,
taken through the plane A-A.
[0031] FIG. 7 shows a part cut away perspective view of the
manifold of FIG. 4.
[0032] FIG. 8 shows a perspective view of the manifold of FIG. 4
with the burner removed.
[0033] FIG. 9 shows a perspective view of the manifold of FIG. 4
with the burner attached.
DETAILED DESCRIPTION OF THE INVENTION
[0034] Although the invention has been described with reference to
specific embodiments, these descriptions are not meant to be
construed in a limiting sense. Various modifications of the
disclosed embodiments, as well as alternative embodiments of the
invention will become apparent to persons skilled in the art upon
reference to the description of the invention. It should be
appreciated by those skilled in the art that the conception and the
specific embodiment disclosed may be readily utilized as a basis
for modifying or designing other structures for carrying out the
same purposes of the present invention. It should also be realized
by those skilled in the art that such equivalent constructions do
not depart from the spirit and scope of the invention as set forth
in the appended claims.
[0035] It is therefore, contemplated that the claims will cover any
such modifications or embodiments that fall within the true scope
of the invention.
[0036] Each of the embodiments described below provide for a
manifold with two or more chambers disposed so as to allow control
of the pressurised air flow in order to achieve the required
distribution of the air/gas mixture for supply to one or more
burners.
[0037] Referring firstly to FIGS. 1a to 1g, there are illustrated
various views of the gas/air manifold in accordance with the
invention. In this embodiment, the manifold 2 is linear and
elongate in shape and has a series of air/gas supply outlet
apertures 4 and, although not shown, at each outlet aperture 4
there is provided a burner such that the air and gas leave each
outlet 4 as indicated in the general direction of arrow 6 in FIG.
1a to enter the burners. The manifold has a front plate 8 in which
the outlet apertures 4 are formed and protruding through the outlet
apertures 4 are the ends of the gas supply means in the form of
ducts 10, which act as gas injection means 10. However it should be
appreciated that the injection means need not protrude through the
apertures 4 and may instead be provided with openings for the
injection of gas which are substantially flush with the outlet
apertures 4 or else retracted from the outlet apertures 4.
[0038] The manifold also has a top plate 12, end plates 14 and 16,
a base plate 18 and rear wall 20 so as to form an elongate box with
an air 28 and gas 36 inlet disposed at one end.
[0039] FIG. 1e illustrates a cross sectional view along line A-A
and shows the interior of the manifold. FIG. 1g shows part of the
interior of the manifold with the front plate 8 having been
removed.
[0040] The interior of the manifold comprises a first chamber 22, a
second chamber 24 and a third chamber 26. Each of the first, second
and third chambers run along the length of the manifold. The first
and second chambers 22, 24 are provided to receive air which is
introduced into the second chamber 24 via the inlet 28 through
which the air is blown under pressure by a fan unit, not shown. The
air then passes along the chamber 24 and as it does so, it comes up
against the plate 30 which separates the first and second chambers.
Reference should also be made at this point to FIG. 2 which
illustrates the view of FIG. 1g in greater detail and shows how the
plate 30 has a series of apertures provided along the length
thereof, said apertures provided to allow air to pass from the
second chamber 24 into the first chamber 22.
[0041] The apertures 32 are provided in a pattern to suit
particular usage requirements and in this case, there are provided
a plurality of clusters of apertures 34 spaced as shown in more
detail in FIG. 2. Air passes through these apertures into the
second chamber 24 and it is found that, by altering the shape, size
and numbers of apertures 32, a uniform airflow can be achieved into
the chamber 22 along the entire length of the manifold. This allows
for a substantially equal distribution of air to each of the outlet
apertures 4 disposed along the length of the manifold 2.
[0042] The third chamber 26 is connected to receive a gas supply at
pressure via the gas supply inlet 36. The chamber 26 is isolated
from chamber 24 such that chamber 26 contains substantially no air
and the chamber 24 contains substantially no gas. The gas passes
through the injection means 10 and, although, in this embodiment,
the injection means are shown to pass through the chamber 22, it is
possible that in certain arrangements, the injection means may stop
at the will of the chamber 22. The gas injection means 10 passes
through the outlet apertures 4 in the front plate 8. A certain
amount of the gas may pass into the chamber 22 which is mostly
filled with air; however this is found not to be a problem. The air
passes through the outlet apertures 4 around the space left between
the outer wall of the front plate 8 and the gas injectors 10.
[0043] The particular shape of the apertures 4 with respect to the
provision of the gas injection means can be designed so as to
provide an optimum mixture of the gas and air. The gas and air then
passes as indicated by arrow 6 in FIG. 1a away from the manifold
either directly into the burners or via tubes which connects the
apertures 4 to the burner. In each case, the mixing of the gas and
air occurs efficiently and uniformly along the length of the
manifold.
[0044] It will be appreciated that by providing a manifold system
as shown which is sealed from the surrounding atmosphere, the fan
can control the amount of air being supplied for combustion. Thus
one or more burners can be attached directly to the manifold
without the need to entrain air from the surrounding environment.
In addition burners can be oriented as required by provision of
tubing (not shown) connecting the burners to the manifold.
[0045] FIG. 3 illustrates the manifold with burners connected
thereto and illustrates, via the arrows 38, the air supply
direction and arrows 40 which show the gas supply, and the mixing
of the air/gas which occurs.
[0046] Turning now to FIGS. 4 to 9 which relate to a second
embodiment of the present invention, there is illustrated a burner
manifold arrangement which differs from the first embodiment in the
arrangement of the gas injectors and the alignment of the
burner.
[0047] The assembly of FIG. 4 is similar to the first embodiment in
that it includes an inlet 104 through which gas enters under
pressure into the chamber 106 which passes along the length of the
assembly. At spaced intervals along the chamber 106 are provided
orifices in the form of injector ducts 108 which project forwardly
as shown in FIGS. 2 and 3. There is also provided an inlet 114
which allows the entry of air under pressure into chamber 116 which
passes along the length of the assembly. Connecting this chamber
116 to the chamber 118 is a plate 120 which has a series of
apertures which allows the air to pass from the chamber 116 into
the chamber 118.
[0048] However in this embodiment, the injectors 108 stop short of
the front plate 122 and the outlet apertures 124 are offset from
the injectors 108 in order to promote mixing within the chamber
118. The air inside the chamber 118 and gas from the injectors 108
mix and pass through the plate 122 into the housing 130 via the
series of apertures 124 at spaced intervals along the length
thereof. In this example, the apertures 124 are shown as having a
relatively large size and large pitch. However it should be
appreciated that in other embodiments of the invention a larger
number of smaller holes with a smaller pitch can be provided to
allow the passage of the gas air mixture. The gas and air therefore
are introduced into the housing 130 which passes along the length
of the assembly.
[0049] The housing 130 includes a side wall 128 which is formed as
a flame strip and in which are provided a series of apertures in a
particular configuration and designed to suit particular burning
requirements. The flamestrip can be formed of any suitable
materials such as, for example, Stainless Steel, woven ceramic,
sintered metal. FIG. 4 shows a portion 131, of the flame strip,
with the remainder of the flame strip omitted for ease of
reference. The air and gas mixture then passes through the flame
strip and is ignited to allow flames to be generated from the flame
strip.
[0050] The arrangement of this embodiment promotes mixing of the
air/gas prior to passing through the outlets 124 and is thus
particularly suited to an arrangement whereby a single burner is
provided along the length of the manifold since it provides for
even distribution of a substantially homogeneous mixture onto the
length of the flamestrip 128. It will be noted that this
arrangement provides a flamestrip 128 that is substantially lateral
to the flow entering the housing 130 through outlets 124, when
compared to the longitudinal arrangement of the burners in the
previous embodiment. That is to say that the burner in this
embodiment runs along the length of the manifold, whereas the
previous burners extended away from the manifold.
[0051] This second embodiment is beneficial in that a manifold and
burner can be provided as a complete module and so any number of
burners can be provided for a given application without the need to
provide a predefined number of burners as with the arrangement of
the first embodiment.
[0052] FIGS. 7 to 9 illustrate the separate components of the
second embodiment. FIG. 7 illustrates the rear of the assembly and
shows the chamber 118 with plate 120 with apertures (not shown) and
the injectors 108 from the gas chamber passing thereinto. It should
however be appreciated that the injectors 108 may not be required
and in certain embodiments, the gas can simply be allowed to leave
the chamber 106 to mix with the air in the chamber 118 prior to
passing through the apertures 124 in the plate 122 as shown in FIG.
8. The air and gas mixture therefore passes through these apertures
124 and into the housing 130 defined by the component added to the
same as shown in FIG. 9 with the flame strip 128 allowing the
passage of air and gas mixture therethrough to be ignited 132 as
indicated.
[0053] The manifold and burner assemblies as herein described
provide an efficient gas air mixture which allows excess air
(approximately 120-135%) for the super stoichiometric combustion
and lower NOx emissions.
* * * * *