[0001] This invention relates to a flame screen arranged as a flame arresting burner assembly
for use with the combustion of a gaseous fuel.
[0002] In a combustion process for a gaseous or liquid fuel, the leading edge of the flame
is usually referred to as a flame front. It is often required to control the flame
front in a combustion process, for example to prevent the flame igniting a combustible
surrounding atmosphere, or to prevent a so-called "light-back" where the flame front
moves in an uncontrolled way backwards into the fuel feed pipe. For example, it is
known to use a simple gauze as in a traditional miner's lamp to isolate the flame
front from a possibly hazardous gas laden surrounding atmosphere. Such a gauze is
a simple and low cost solution both as a flame arrester and a flame trap, but also
a gauze can serve as a burning surface for the actual combustion process itself. A
simple gas ring has perforations for the exit of the combustible mixture of gas and
air and these perforations act in essentially the same way as a fine gauze and so
serve as a flame arresting screen.
[0003] The size and the depth of the openings in flame arresting screens have a significant
effect upon the performance of such screens. The actual shape and physical arrangement
of the openings are particularly important when considering burner design. Special
characteristics such as flame shape, flame stability, turn-down ratio, ignitability,
flame temperature and flame speed all may depend upon the flame screen design.
[0004] The requirements for a flame trap are generally less arduous than those needed for
a flame screen. Flame traps are commonly fitted in a pipeline feeding a combustible
fuel mixture to a process. The prime object of a flame trap is to prevent light-back
which may occur when the flame moves in an uncontrolled way backwards into the feed
pipe with the possible danger of travelling back to and igniting the bulk fuel storage
system. The main requirements of a flame trap is to be capable of stopping a flame
from passing in the reverse direction with the minimum possible impediment to the
flow of fuel in the forward direction.
[0005] Modern requirements for burners adapted for use with hydrocarbon fuels include very
high combustion efficiency, whilst maintaining a very low volumes of undesirable by-products
such as carbon monoxide and oxides of nitrogen (NOx). Thorough pre-mixing of the fuel
with the required amount of oxygen with little or no take up of oxygen from the combustion
space is a good basis to burn hydrocarbons cleanly and completely. In order to control
the flame front of such burners, an efficient flame screen is needed not only to maintain
the performance but also for safety reasons. When burning pure hydrogen or gas mixtures
containing high ratios of hydrogen, it has been found that particularly small apertures
are needed for safe and consistent operation of such burners.
[0006] The use of very small apertures in a flame screen has several negative effects. Clearly
there will be a greater pressure loss across the screen that will in most cases require
a larger delivery system at a higher pressure, leading to increased cost. A further
significant disadvantage is that the range of flame shapes and patterns that can be
obtained may cause difficulties in some applications over the ability to control the
undesirable production of CO and NOx.
[0007] Instead of having very small apertures or a woven wire gauze in a screen, it is known
to use fine fibres in knitted, woven or randomly strewn or packed forms. The purpose
of a fibrous flame screen of this kind can be as a cost reduction measure because
such a screen requires less engineering exactitude to install and operate.
[0008] Compared to very fine drilled or woven wire screens, a fibrous screen makes it possible
to have a large flow area of even smaller but more numerous openings. Also, because
the fine fibres may easily glow when heated by a gas flame, a fibrous screen may serve
as a simple infra red heat emitter to aid heat transfer.
[0009] A major disadvantage of a fibre based screen is that it tends to become blocked readily
with small airborne particles such as dust and pollen, due not only to the fine openings
but also the indirect pathways within such materials. Most applications using fibrous
flame screens require fine filtration of the gas and air mixture leading to increased
costs in materials and maintenance.
[0010] It is known that the flame screens described above function by causing a temperature
loss in a flame attempting to return into the fuel and oxygen mixture; the reduced
temperature and aperture will thus prevent the flame passing through the screen. The
screen will be cooled by the action of the cold combustible gas mixture passing therethrough,
when operated in the correct direction. It therefore follows that an alternative to
reducing the size of the openings could be to increase the depth of each opening,
by increasing the thickness of the screen, to allow a longer path for an effective
heat exchange to take place. This has been achieved simply by laminating pressed metal
strips by either stacking or winding them into a sandwich that allows gas passages
to be created, for example between flat layers and corrugated layers. This technique
can produce long narrow passages that form the basis of many flame arresters and traps
manufactured today.
[0011] A design as just described is not so useful as a burner screen. Due to the need to
press intricate shapes, often in difficult materials such as stainless steel, the
layers need to be of thin material. In addition, this technique often also relies
upon the component parts being sprung or friction fitted together and because pressed
metal is particularly prone to changing shape with temperature, reliability in use
can be low. The consequence is the arrangement has limited use as a burner flame screen,
as the assembled components require a sturdy mount and also a very durable arrangement
to contain the gas and air mixture prior to that mixture exiting the screen.
[0012] According to this invention, there is provided a multi-layer flame screen burner
assembly comprising first and second outer layers, at least one flame layer having
a plurality of fingers defined by slots provided in the flame layer, the slots opening
along one edge of the flame layer, and at least one gas distribution layer overlying
the flame layer and defining an aperture which overlies the slots between the fingers
of the adjacent flame layer, the flame layer and overlying gas distribution layer
together being disposed between the outer layers, and the burner assembly having at
least one port for the admission of combustible gas to the aperture of the gas distribution
layer, whereby gas supplied to the port is fed through the aperture to the slots between
the fingers of the flame layer.
[0013] In one arrangement of this invention, the burner assembly has one flame layer, one
gas distribution layer disposed on one side of the flame layer, and a pair of outer
layers, one outer layer being disposed on the side of the gas distribution layer remote
from the flame layer and the other outer layer being disposed on the side of the flame
layer remote from the gas distribution layer. In such a case, the outer layer disposed
on the gas distribution layer may be provided with a port for the supply of gas to
the aperture of the gas distribution layer.
[0014] In an alternate arrangement, the burner assembly has one flame layer, a pair of gas
distribution layers disposed one to each side of the flame layer, and a pair of outer
layers disposed on the sides of the gas distribution layers remote from the flame
layer. In this case, only one of the outer layers need be provided with a port for
the supply of gas, and gas is fed to the aperture of the gas distribution layer remote
from that outer layer through an opening in the flame layer between that gas distribution
layer and the outer layer having the port.
[0015] In a preferred embodiment, there are two flame layers, a gas distribution layer disposed
between the flame layers, and a pair of outer layers disposed on the sides of the
flame layers remote from the gas distribution layer. In this arrangement, only one
of the outer layers is provided with a port for the supply of gas, and gas is fed
to the aperture of the gas distribution layer between the flame layers through an
opening in the flame layer between that gas distribution layer and the outer layer
having the port. In yet another arrangement, there is arranged between the outer layers
a plurality of flame and gas distribution layers alternately disposed, the apertures
in the gas distribution layers communicating with the gas supply port through openings
in the flame layers.
[0016] Instead of an outer layer having a port for a gas supply pipe to feed gas to the
or each gas distribution layer, the or each gas distribution layer may have an edge
opposed to the edges producing the flame front and the aperture in the or each gas
distribution layer opens through that opposed edge. Then, there may be provided a
gas supply pipe fitted to the burner to be in communication with the or each aperture
opening through that opposed edge thereby to supply gas to the slots between the fingers
in the or each flame plate. For example, the gas supply pipe may have a cut-out region
inter-fitting with the assembly of layers to be in communication the or each aperture
opening through that opposed edge.
[0017] In an alternative arrangement, the burner assembly is located in a plenum chamber
with the edges of the layers which produce the flame front exposed though a face of
the chamber, and there being a gas supply pipe in communication with the interior
of the chamber thereby the supply gas to the burner. A bezel may be fitter to the
face of the chamber through which the burner assembly is exposed, thereby to seal
the burner assembly to the plenum chamber.
[0018] In any of the above arrangements of this invention, the layers may be substantially
planar - and typically formed from metal plates, such as of stainless steel. In the
alternative, the layers are formed into a three-dimensional shape, such as a substantially
cylindrical shape with the slots extending substantially parallel to the axis of the
cylindrical shape. The outer encircling wall could have any of a wide variety of transverse
cross-sectional shapes but preferably is of substantially cylindrical shape of circular
cross-section. In this case, the outer layers, flame layers and gas distribution layers
are preferably in the form of closely inter-fitting cylinders.
[0019] Other features and advantages of flame screen burner assemblies of this invention
will become apparent from the following description of preferred embodiments, referring
to the drawings as necessary, and also from the appended claims.
[0020] By way of example only, certain specific embodiments of flame screen burner assemblies
will now be described in detail, reference being made to the accompanying drawings,
in which:
Figure 1 is an exploded view of a planar embodiment of flame arresting burner assembly
constructed and arranged in accordance with the invention;
Figures 2A to 2D show alternative flame plates for use in an embodiment of burner
assembly of this invention;
Figure 3 shows yet another flame plate for use in a further embodiment of a burner
assembly;
Figures 4A to 4D show alternative gas distribution plates for use in embodiments of
burner assembly, Figure 4D also showing two possible further edge profiles;
Figures 5A and 5B show two planar gas distribution plates and one planar flame plate
assembled together for use with a pair of cover plates (not shown) to form an embodiment
of burner assembly;
Figures 6A and 6B show two alternative planar gas distribution plates and one alternative
planar flame plate assembled together for use with a pair of cover plates (not shown)
to form another embodiment of burner assembly, similar to that of Figure 1;
Figure 7 shows the plates used in a further embodiment of burner assembly of this
invention, having a circular form;
Figure 8 shows the plates used in yet another embodiment of burner assembly of this
invention, having a generally rectangular form;
Figure 9 is an exploded view of a cylindrical embodiment of flame arresting burner
assembly constructed and arranged in accordance with the invention;
Figure 10A is an end view on the assembled burner of Figure 9 and Figure 10B is a
detailed view on an enlarged scale on a portion of the periphery of the burner as
shown in Figure 10A; and
[0021] Figures 1A to 11C and 11D show two alternative gas supply arrangements for a burner
of this invention.
[0022] Figure 1 shows the first embodiment of flame arresting burner assembly in the form
of a plurality of planar plates assembled together, for the combustion of a gas. The
burner assembly comprises a pair of cover plates 10,11 each of generally rectangular
form of essentially identical external shape and size. Each plate has a rectangular
extension 12,13 formed from a corresponding edge of each plate and cover plate 11
has a port 14 formed in the extension 13 for the admission of combustible gas to the
burner assembly, as will be described below. Provided between those cover plates 10,11
are two flame plates 15 and also one gas distribution plate 16 disposed between the
flame plates, the flame plates and gas distribution plates also being of the same
external shape and size as the cover plates 10,11. Though shown in exploded in Figure
1, the completed burner assembly has the five plates assembled together in a multi-layer
sandwich arrangement.
[0023] Each flame plate 15 has an opening 17 formed in a rectangular extension 18 to the
plate, the opening and extension corresponding to those of cover plate 11. Each flame
plate also defines four fingers 19 by way of slots 20 formed through the plate, the
slots opening through edge 21 of the plate opposed to the edge of the plate having
extension 18. The fingers 19 and slots 20 are both of generally rectangular shape
such that the gaps between the fingers are of constant width.
[0024] The gas distribution plate 16 also has a rectangular extension 22 provided with an
aperture 23 having a first part 24 corresponding to the opening 17 of the flame plate
and the port 14 of cover plate 11, and a second part 25 of generally rectangular shape
and extending across the gas distribution plate, the second part 25 communicating
with the first part through a narrow channel 26. A gas supply pipe 27 is connected
to the cover plate 11 in register with the port 14 such that when all of the plates
are assembled together, the gas is supplied to the first part 24 of the aperture 23
in the gas distribution plate and from there is fed into the second part 25 of that
aperture and thence into the slots 20 of the flame plates, all as shown by the arrows
in Figure 1.
[0025] All of the plates described above are made of relatively thin sheet metal, such as
stainless steel. The plates may be made for example by a stamping operation and are
assembled together to form the complete burner. Appropriate fixings are provided to
hold the plates clamped together. For example, the plates could be held together by
way of rivets, spiral pins or other fasteners, or could be welded together. For some
burners a combination of fasteners may be employed, such as spiral pins and welding
at different locations around the burner.
[0026] Referring now to Figures 2A to 2D, there are shown four different configurations
for flame plates suitable for use in a slightly different configuration of burner
assembly from that described in Figure 1. Flame plate 30 shown in Figure 2A has four
fingers 31 with simple rectilinear slots 32 between the fingers, the overall configuration
of the plate being substantially quadrilateral but otherwise the arrangement of the
fingers is essentially as shown in Figure 1. Each slot 32 opens along edge 33 of the
plate 30 but is closed by the plate at the other end 34 of the slot. The dimensions
of the fingers and of the slots may be selected to give the required flame pattern.
[0027] Flame plate 35 shown in Figure 2B has slots 36 the width of which increases in the
direction towards edge 37 of the plate. This configuration of each slot reduces the
gas velocity therein, to aid stability of the flame. Conversely flame plate 38 (Figure
2C) has slots which narrow towards edge 39. This configuration may be used to maintain
gas velocity, when this is required. Flame plate 40 (Figure 2D) is similar to plate
30 but the free ends 41 of the fingers 42 are formed with teeth or serrations 43.
These serve to extend the flame base and the particular shape and dimensions of these
serve to create the required flame profile and effect. It has also been found that
the teeth or serrations projecting from the finger ends 41 into the flame base increase
the electrical conductivity of the flame to earth, thus greatly improving the reliability
of a flame sensing system which may be used with the burner.
[0028] Figure 3 shows yet another flame plate 45 having an external shape and size similar
to the flame plates 15 of the assembly of Figure 1. Thus, this flame plate 45 has
an extension 18 provided with an opening 17 as with flame plate 15, as well as fingers
19 and slots 20. The flame plate of Figure 3 differs from that of Figure 1 in that
the fingers 19 have side edges which are configured to provide slots having a labyrinthine
path for the gas passing along the slots. This is achieved by providing each finger
with projections 46 directed towards the corresponding edge of the adjacent finger.
It is found that this configuration is particularly suitable for use with certain
gases which require additional chilling by the flame screen to prevent light-back.
This is especially so for hydrogen when fully pre-mixed with oxygen in stoichiometric
proportions. By providing a labyrinthine path in this way, a greater chilling effect
can be achieved. In addition, the projections 46 may serve as a baffle to prevent
a loud exit noise when shutting down a gas burner that has failed to maintain the
required gas/air ratio at turn-off.
[0029] Gas distribution plate 48 (Figure 4A) is of substantially quadrilateral shape, the
overall dimensions of which correspond to those of the flame plates of Figures 2A
to 2D. The distribution plate 48 has a rectangular aperture 49 extending partway across
the plate and disposed such that when the distribution plate overlies flame plate
30 with the edges in alignment, the aperture 49 overlies the slots 32 adjacent the
other ends 34 thereof. The size and shape of the aperture 49 may be selected in order
to produce a required flame pattern.
[0030] Gas distribution plate 50 (Figure 4B) is similar to distribution plate 48 except
that the plate has an extension 51 from one edge and a generally T-shaped aperture
52, including a part disposed in the extension 51. Thus, this plate is suitable for
use in a burner generally as shown in Figure 1 and the aperture 52 allows the fuel
gas to be fed to the slots of the flame plate at a location spaced from the other
ends of the slots; this may give a more uniform distribution of gas. When a plurality
of flame plates as shown in Figure 3 and gas distribution plates as shown in Figure
4B are assembled together the part of the aperture within the extension may form a
common conduit to allow the supply of gas to each flame plate.
[0031] Gas distribution plate 53 (Figure 4C) is similar to plate 50 except that edge 54
of the aperture 55 is profiled to assist the chosen distribution of gas to the slots
of the chosen flame plate, between the fingers thereof. The edge 54 selectively directs
the combustible gas and air mixture towards the sides of the plate and reduces the
gas flow to the central slot. Adjustment of the profile allows a wide choice of flame
patterns.
[0032] Gas distribution plate 56 (Figure 4D) is similar to plate 53 but includes extra apertures
57,58 adjacent the free ends of the fingers of a chosen flame plate. Selection of
appropriate shapes and dimensions for these extra apertures (which need not be as
shown in Figure 4D) allows a precise flame pattern to be achieved. Also illustrated
with plate 56 is a profiled edge 59 which will overlie the free ends of the fingers
of the chosen flame plate. The profiled edge 59 is designed to extend the burning
surface, thereby to create additional flame stability. Adjacent the profiled edge
of plate 56 are shown two possible other profiled edges which could be used instead
at the edge of plate 56. The profile of that edge 59 may be a combination of curves
or angles selected to create the required effect. It has also been found that such
a profiled edge increases the electrical conductivity to earth of the flame, greatly
to improve the reliability of flame sensing systems.
[0033] Figures 5A and 5B show a stacking configuration for two gas distribution plates 48
and one flame plate 30, to be used in conjunction with two simple rectangular cover
plates (not shown) one of which has a port for the introduction of combustible gas
to the burner assembly.
[0034] Figures 6A and 6B show a stacking configuration similar to that of Figures 5A and
5B but using gas distribution plates similar to those of Figure 1 and two flame plates
also similar to those of Figure 1. As compared to the burner of Figure 1, which has
two flame plates 15 and one gas distribution plate 16, the assembly of Figures 6A
and 6B has two gas distribution plates 16 and one flame plate 15.
[0035] The burners of Figures 5A, 5B and Figures 6A,6B are completed by two cover plates
(not shown) arranged to overlie the gas distribution plates. At least one of those
cover plates, but possibly both, includes a gas/air supply port in register with aperture
23 in the distribution plates. In the case of the assembly of Figures 6A and 6B, both
the flame plate and the gas distribution plate have aligned extensions with openings
therein, to allow the flow of gas between the two distribution plates, through the
opening in the extension of the flame plate. In other respects, and when assembled
with two cover plates, the arrangement is essentially the same as Figures 5A and 5B.
[0036] The above-described embodiments are of planar configuration but may be arranged in
circular, rectangular or similar formats. Figure 7 shows a configuration having two
circular (in plan) cover plates 61,62, a circular flame plate 63 and at least one
circular gas distribution plate 64 with a central opening 65. Cover plate 61 has a
gas supply port 66 in communication with the central opening 65 of the gas distribution
plate 64, in order that combustible gas may be supplied to the slots 67 between the
plurality of generally radially extending fingers 68 of the flame plate 63.
[0037] Figure 8 shows a configuration similar to that of Figure 7 but having a generally
rectangular overall shape. Thus, there is a pair of cover plates 70,71, cover plate
70 having a gas supply port 72. Flame plate 73 has a plurality of fingers 74 extending
outwardly from a hollow central region with slots 75 between the fingers. A gas distribution
plate 76 has an external profile matching that of the outer ends of the fingers 74
and a central aperture 77 for feeding combustible gas to the slots between the fingers.
[0038] The burner assemblies of Figures 7 and 8 are examples of possible burner assemblies
but almost any configuration of flame shape may be achieved by providing flame and
distribution plates with appropriate shapes. The flame pattern, length, depth and
intensity may be determined by the shape of each cut-out slot and finger of the flame
plate, as described above. The examples of Figures 7 and 8 will fire through a full
360 angular degrees. Other angles may be selected depending upon the slot and finger
pattern.
[0039] With all of the above described burner assemblies, different numbers of flame plates
and gas distribution plates may be employed. For example, one such burner assembly
has two cover plates, five gas distribution plates and six flame plates arranged alternately,
in an overlying manner and secured together to provide a high output burner.
[0040] Figures 9 and 10 show a cylindrical embodiment of burner assembly using the same
principles as those of the previous embodiments which are of a planar configuration.
This cylindrical burner assembly 79 has inner and outer cylindrical cover rings 80,81,
the inner cover ring 80 having a port 82 for the supply of combustible gas to the
assembly. The burner assembly also has two cylindrical gas distribution rings 83,84
and two cylindrical flame rings 85,86. The diameters of the rings 80 and 81, and 83
to 86 are such that all six rings interfit closely with ring 80 innermost and ring
81 outermost and the gas distribution rings and flame rings arranged alternately.
Figure 10A is an isometric view of the overall assembly with the rings interfitted
as described, and Figure 10B is an end view on the overall assembly.
[0041] The inner gas distribution ring 83 has a first circumferentially-extending aperture
87 which includes an offset region 88 in register with the port 82 when assembled
with the inner cover ring, and two further aligned circumferentially-extending apertures
89,90. Outer gas distribution ring 84 also has a first circumferentially-extending
aperture 91 with an offset region 92 corresponding to that of the ring 83, and further
circumferentially-extending apertures 93. Each of the flame rings 85,86 has a plurality
of fingers 94 extending parallel to the axis of the assembly, with slots 95 formed
between those fingers.
[0042] A gas supply pipe (not shown) is connected internally of the inner cover plate 80
to the port 82, for feeding combustible gas to the apertures 87 to 93 of the two gas
distribution rings, such that the gas is fed to the slots 95 between the fingers 94
of the flame rings, for combustion at the outer ends of the slots in the same manner
as has been described above in relation to the planar embodiments of Figures 1 to
8.
[0043] Though the cylindrical inner cover plate 80 is shown as having a gas port 82 to which
a gas supply pipe (not shown) may be connected, it would be possible to provide two
circular end plates on the inner cover plate 80 thereby to form a chamber within the
cylindrical inner cover plate, and to furnish a gas port in one of those circular
end plates, for the connection thereto of a gas supply pipe. With such an arrangement,
it may be possible to omit the cylindrical inner cover plate; in this case the end
plates must be welded at least to the innermost cylindrical gas distribution ring
83. Further, as with the planar burners, different numbers of inter-fitting cylindrical
flame and gas distribution plates may be arranged alternately between the cylindrical
inner and outer cover plates, in order to achieve the required burning profile.
[0044] With all of the above described embodiments, combustible gas is supplied to the burner
through a port in one of the cover plates, though for a burner having a large number
of flame and gas distribution plates, it would be possible to have corresponding ports
in the opposed cover plates and a pair of gas supply pipes connected to the two ports.
Figures 11A to 11C and 11D show two alternative arrangements, where gas is supplied
to the burner assembly other than through a port in at least one of the cover plates.
In these Figures, parts having essentially the same function as those of the previous
embodiments are given the same reference characters; these parts will not be described
again here.
[0045] Figures 11A to 11C show a burner substantially as has been described above with reference
to Figure 1, except that two similar planar cover plates are used neither of which
is provided with a gas supply port. Instead, the extensions 12,13,18 and 22 of the
plates are formed as slots opening on the edges of the extensions furthest from the
major areas of the plates. Gas is supplied to the assembly through a gas supply pipe
97 of square cross-section and having a cut-out region 98 of such a shape and size
that the slots of the extensions of the burner plates will inter-fit snugly therewith,
as shown in Figures 11B. Once fitted together (Figure 11 C), the pipe is welded in
position to provide a gas-tight seal around the cut-out region 98. It will be appreciated
that in this assembly, gas is fed from the pipe 97 to the slots 20 between the fingers
19 of the flame plates 15 by entering the channel 26 and then the second part 25 of
the aperture 23 in the gas distribution plate. In all other respects, the burner of
Figures 11A to 11C performs as has been described above with reference to at least
Figure 1.
[0046] Figure 11D shows an alternative gas supply arrangement for the burner of Figures
11A and 11B. Instead of the supply pipe 97, the burner is housed within a generally
rectangular plenum chamber 100 defined by opposed side walls 101, opposed top and
bottom walls 102 and a rear wall (not visible in Figure 11 D). Combustible gas is
supplied to the interior of the chamber 100 by a gas supply pipe 103 provided in a
wall of the chamber; two alternative locations for the gas supply pipe are shown but
in practice it is envisaged that only one such pipe need be provided. Once the burner
has been installed in the chamber, it is secured in position by a bezel 104 which
fits closely to the side, top and bottom walls of the chamber and also to the burner.
Typically, the bezel will be welded to the burner and also to the plenum chamber walls,
to give a gas-tight seal. In all other respects, the burner of Figure 11D performs
as has been described above with reference Figures 11 Ato 11C.
[0047] Advantages which may be obtained with various embodiments of the flame screen burner
assemblies of this invention, for the combustion of fuel gas may include the following:
- 1) Improved performance due to improved cooling of the gases. The gas passes through
openings that are of a flat section in a thicker material which allows mostly laminar
gas flow and also more surface contact with the screen. It is possible to extend the
gas path in order to obtain several more benefits such as a compact design for use
with difficult gases such as hydrogen and also control of exit noise which may occur
on a failure of the gas/air ratio, on shutdown.
- 2) An opportunity for easily changing the opening area of the flame plates. This may
be obtained by way of a continuous tapering or a stepped reduction in the width of
each slot to maintain gas velocity or, when inverted, flame stability.
- 3) The gas distribution plates and flame plates may be suitably profiled at the flame
front. This profiling can be a continuous zig-zag, scalloping or other pattern to
change the size and shape of the plate at the base of the flame, thereby to change
the ignition, ionisation and flame stability or other characteristics of the flame.
- 4) The design does not require the component parts to be bent in the course of manufacture
or even to be flexible. The components may be produced in materials which cannot be
used with other burner designs but which offer advantages due to heat, gas and chemical
resistance. These materials may be metallic or non-metallic, coated or uncoated.
- 5) Burners may be designed and constructed in many different shapes such as linear,
circular or rectangular. Moreover, combinations of these different shapes may be manufactured.
- 6) The tooling and set-up costs for these burners is economical and uncomplicated,
for most of the possible variations in design.
- 7) The burners have lower maintenance requirements due to the strength of construction
and the high resistance to blockage by foreign particles.
1. A multi-layer flame screen burner assembly comprising first and second outer layers
(10,11), at least one flame layer (15) having a plurality of fingers (19) defined
by slots (20) provided in the flame layer, the slots (20) opening along one edge of
the flame layer, and at least one gas distribution layer (16) overlying the flame
layer (15) and defining an aperture (23) which overlies the slots (20) between the
fingers (19) of the adjacent flame layer (15), the flame layer and overlying gas distribution
layer together being disposed between the outer layers (10,11), and the burner assembly
having at least one port (14) for the admission of combustible gas to the aperture
(23) of the gas distribution layer (16), whereby gas supplied to the port is fed through
the aperture to the slots between the fingers of the flame layer.
2. A burner assembly as claimed in claim 1, wherein there are at least three alternately
arranged layers (15,16) between the outer layers (10,11).
3. A burner assembly as claimed in claim 1 or claim 2, wherein the port (14) for the
supply of gas to the burner is provided in an outer layer (11), the port being in
communication with the aperture (23) in the or each gas distribution layer between
the outer layers.
4. A burner assembly as claimed in claim 1 and in which there is a multiplicity of flame
and gas distribution layers (15,16), wherein the layers between the outer layers (10,11)
have openings (17,24) therein in register with each other, and for each gas distribution
layer (16) the aperture (23) therein has first and second parts (24,25) in communication
with each other.
5. A burner assembly as claimed in any of the preceding claims, wherein the slots (32)
in the or each flame layer (30) are substantially parallel-sided.
6. A burner assembly as claimed in any of claims 1 to 4, wherein the slots (36) in the
or each flame layer (35 or 38) taper from one end to the other, either towards the
inner ends of the slots or towards the outer ends of the slots.
7. A burner assembly as claimed in any of the preceding claims, wherein the fingers (19)
to each side of a slot (20) are provided with projections (46) directed towards the
adjacent finger whereby a labyrinthine path for the gas flow is defined by the projections.
8. A burner assembly as claimed in any of the preceding claims, wherein the free ends
of the fingers (42) have a non-linear profile (43) in order to modify the flame front
produced by the burner assembly.
9. A burner assembly as claimed in any of the preceding claims, wherein the edge of the
or each distribution plate (56) adjacent the free ends of the fingers has a non-linear
profile (59) in order to modify the flame front produced by the burner assembly.
10. A burner assembly as claimed in any of the preceding claims, wherein the aperture
(49) in the or each gas distribution layer (16) is generally rectangular and overlies
the slots between the fingers of an, adjacent flame layer, at or adjacent the inner
ends of the slots.
11. A burner assembly as claimed in any of the preceding claims, wherein the layers (10,11,15,16)
are substantially planar.
12. A burner assembly as claimed in any of the preceding claims, wherein the or each gas
distribution layer (16) has an edge opposed to the edges of the layers producing the
flame front and the aperture (23) in the or each gas distribution layer opens through
said opposed edge, and there is provided a gas supply pipe (97) fitted to the burner
in communication with the or each aperture opening through said opposed edge thereby
to supply gas to the slots between the fingers in the or each flame plate.
13. A burner assembly as claimed in any of the preceding claims, wherein the burner assembly
is located in a plenum chamber (100) with the edges of the layers which produce the
flame front exposed though a face of the chamber, and there being a gas supply pipe
(103) in communication with the interior of the chamber thereby the supply gas to
the burner.
14. A burner assembly as claimed in any of claims 1 to 10, wherein the layers (80,81 and
83 to 86) are formed into a three-dimensional shape.
15. A burner assembly as claimed in claim 14, wherein the three-dimensional shape is substantially
cylindrical, the outer layers (80,81), flame layers (85,86) and gas distribution layers
(83,84) being in the form of inter-fitting cylinders with the slots (95) in the or
each flame layer (85,86) extending substantially parallel to the axis of the cylindrical
shape.