GB1579829A

GB1579829A - Gas burners

Info

Publication number: GB1579829A
Application number: GB2241276A
Authority: GB
Original assignee: Geo Bray and Co Ltd
Current assignee: Geo Bray and Co Ltd
Priority date: 1977-07-29
Filing date: 1977-07-29
Publication date: 1980-11-26

Description

(54) IMPROVEMENTS IN AND RELATING TO GAS BURNERS (71) We, GEO. BRAY & COMPANY LIMITED, a British Company, of Leicester Place, Leeds, LS1 9BH, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a flamestrip for a gas burner and a gas burner incorporat ing such a flamestrip.

The present invention provides a gas burner flamestrip having a plurality of flame ports arranged in spaced parallel groups of rows transverse to the length of the flamestrip, each group comprising three rows of ports, the spacing between adjacent rows of ports in each group being less than the spacing between the closest two rows of ports of two adjacent groups, each port being substantially rectangular in form and the longitudinal axis of each port extending transversely to the length of the flamestrip; wherein the length of each port lies within the range of 3.0mm to 4.5mm, the length to width ratio of each port lies within the range of 3.0 to 5.625, the ratio of the length of each port to the distance between adjacent ports in each row lies within the range of 1.0 to 2.25, and the ratio of the length of each port to the spacing between adjacent rows of ports in each group lies within the range of 1.2 to 3.0.

A flamestrip constructed in accordance with the invention can, despite the fact that each flame port has a relatively large area, when incorporated in a gas burner as referred to in greater detail below, and when the burner is used with slow burning gases, for example natural gas, provide high port loadings and hence, if required, high heat outputs per unit area of the flame strip. High port loadings, which may be, for example, 30,000 to 45,000 Btu/sq inch, are possible, because the disposition of each flame port relative to its neighbours in a given group of ports is such that the flamestrip has excellent flame stability and resistance to flame lift.

Further, such port loadings can be achieved with up to 70% of the total air required for combustion being primary air, which results in relatively short flames on the flamestrip, because the flamestrip has excellent flame stability given not only by the large area of each flame port which reduces the pressure at each port and hence reduces the tendency for flame lift but also because of the disposition of each port relative to its neighbours.

The disposition of the flame ports one from another in each group is such that the flame on each individual port stabilises its neighbour and acts as a flame retention device.

The spacing between the two closest rows of ports in two adjacent groups of ports is wide enough to allow sufficient secondary air to reach the flames in each group and close enough to achieve the required heat output. Clearly to increase or decrease the heat output the said spacing is made smaller or larger respectively.

Further, because of the rectangular shape and size of the flame ports the flamestrip can have a relatively low resistance to passage of airborne dust or lint and, consequently, the risk of port blockage is reduced. This is a particularly important characteristic of the flamestrip especially when it is used in domestic appliances where such low resistance is a prerequisite.

Advantageously, further to minimise the resistance to passage of dust or lint, the thickness of the flamestrip should not be high and is preferably within the range of 0.4mm to 1.0mum and is preferably 0.5mm.

Advantageously, the flamestrip has at least two lines of additional flame ports extending along the length of the flamestrip, each additional port having a cross-sectional area which is small compared to the crosssectional area of each rectangular port. The additional burner ports serve to interconnect the groups of ports for transmitting the flame from one group of ports to an adjacent group of ports.

Preferably each additional port is circular in form.

Advantageously, a further port having a cross-sectional area which is small compared to the cross-sectional area of each rectangular port is arranged at each end of each row of rectangular ports. These further ports further restrict flame-lift at the rectangular ports.

Preferably, the strip is convex is transverse cross-section.

The present invention further provides a gas burner comprising a flamestrip constructed in accordance with the invention.

Preferably, the burner comprises a tubular chamber, the flamestrip constituting a wall of the chamber, gas inlet means being provided in the chamber for supplying a mixture of gas and air to the chamber.

Advantageously, a filter comprising a sheet of metallic gauze is detachably secured in, and so extends across the chamber that the gas and air mixture from the inlet means passes through the burner ports via the gauze. The gauze may be spaced from the flamestrip, for example, by at least Smm.

Although for many applications the rectangular shape and size of the flame ports will provide satisfactory insurance against port blockage the gauze sheet acts as a filter for the gas and air mixture and therefore reduces still further the dust and lint resistance of the burner flame ports. The gauze sheet must be detachable from the chamber, however, for periodic cleaning. The gauze sheet also serves to give better distribution of the gas and air mixture resulting in improved performance of the burner and reduction in flame noise.

Advantageously, to facilitate attachment and/or detachment in or from the chamber, the chamber is provided with two opposed axially extending grooves or ribs for slidably receiving opposed edge portions of the gauze sheet.

The gauze sheet may comprise woven or perforated metal having apertures each of which is smaller in area than the area of each rectangular flame port. The total open area of the gauze sheet is determined by the conditions in which the burner is operating but usually it will be at least 46% of the total surface area.

A flamestrip and a gas burner incorporating the flamestrip both constructed in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawing, in which: Fig. 1 is partly broken away perspective view of the burner, Fig. 1 (a) shows a detail of the burner shown in Fig. 1, Fig. 2 is an end view of the burner of Fig. 1 with parts removed, Fig. 3 is a plan view of part of the flamestrip incorporated in the burner shown in Fig. 1, and Fig. 3(a) is an enlarged view of part of the flamestrip shown in Fig. 3.

Referring to the accompanying drawings, the burner has an elongate tubular metal body 1 closed by end plates 2 and 3. The body consists of a channel-section lower part 4 and a U-section upper part 5 which are secured together by forming a mechanical joint 6 at their marginal edge portions and, if necessary, welding those portions together. The upper part 5 of the body 1 has a wall 7, which is convex in section, forming a flamestrip.

The end plate 3 which is welded or brazed to the body supports the inlet portion of a mixing or venturi tube 8. A hood-like structure 9 having an aperture 10 for receiving a gas injector (not shown) is welded or brazed to the plate 3. The structure 9 has a side and bottom opening 11 through which air is entrained by gas injection from the injector in to the venturi 8 so that a gas and air mixture enters the chamber 12 defined by the tubular body 1.

The side walls parts of the upper portion 5 of the body are each formed with a longitudinal rib 13. The end plate 2 and its sealing gasket 2a is detachably secured to the body 1 by screws 14 which are received in a bridge member 15 secured to the body.

When the end plate 2 is removed a gauze filter sheet 16 can be inserted into the chamber 12 by sliding it lengthwise along the ribs 13. As shown in Fig. 1 the gauze sheet 16 extends between the two end plates 2 and 3. A stiffening plate 17 is provided on one end of the sheet 16 to improve handling and to facilitate entry and insertion of the sheet into the chamber 12. The plate 17 also assists in preventing flame lift on those ports 18 in the group 18 closest to the end plate 2. The gauze sheet 16 is spaced from the wall 7 as is more clearly seen in Fig. 2, which is an end view of the burner with the plate 3 removed.

As shown in more detail in Figs. 3 and 3a, the wall 7 is provided, by piercing or otherwise, with several spaced groups of parallel transverse rows of rectangular flame ports 18, each group having three parallel rows of ports. A series of circular ladder ports 19 are provided in the wall 7 and are arranged in two parallel rows which extend along the length of the burner between each group of rectangular ports. Further, small stabilising ports 20 are provided in the wall 7 and arranged at each end of each row of rectangular ports.

When the gas and air mixture enters the chamber 12 the mixture passes to the flame ports 18, 19 and 20 via the gauze sheet 16.

The ports 18 in each group are sufficiently close together so that when any port in that group is ignited it will ignite and serve to stabilise its neighbours. Stabilisation is improved by flames formed on the ports 20. Ports 19 interconnect the groups of ports 18 and constitute a ladder burner serving to ignite the ports 18 in one group after ignition of the ports 18 in an adjacent group.

The ratio of the transverse extent of each group of ports 18 to the distance between the two closest rows of ports 18 in two adjacent groups is so chosen that the said distance is large enough to allow secondary aeration of the flames formed at the ports 18 and small enough to allow the burner to operate with high heat outputs.

Because of the rectangular configuration of the ports 18 the resistance to airborne lint or dust is relatively low. The gauze 16 also acts as a filter for the lint or dust.

Further, the gauze sheet 16 can be removed for cleaning and replacement by detaching end plate 2.

The gauze sheet is formed of woven or perforated metal having apertures, the area of each aperture being less than the area of each port 20. Because the gauze sheet provides more uniform distribution of the gas and air mixture passing to the ports 18 the operation of the burner is improved and flame noise is reduced.

The burner is especially suited for operation with slow burning gas such as natural gas and can be operated at a range of pressures by adjusting the injector size.

Usually the pressure range would be between 100 and 150mm water gauge.

The flamestrip (formed by the wall 7) and burner described and illustrated hereinbefore can be modified in a number of ways.

Thus, the flamestrip may be separately formed from the remainder of the burner body 1 and suitably attached thereto, for example by welding. The flame strip need not be curved and can take various shapes -- for example it could be flat or polygonal in form.

The lower portion 4 of the body 1 may be U-shaped and the upper part 5 flat or both parts may be U-shaped. The lower part 4 may be shaped to support the venturi or mixing tube 8. Further, the two parts 4 and 5 an be replaced by a single sheet folded into tubular form, opposed marginal edge portions of the sheet being secured together, for example, by deformation to form a mechanical joint -- and/or by welding; the seam being formed, preferably, at the base of the burner body.

One of the side and bottom openings 11 can be closed off.

For many applications the burner will operate satisfactorily without the stabilising ports 20.

Finally, it is possible, especially when the burner is fitted in a region where the air conditions are relatively clean, to dispense with the gauze sheet 16.

The rectangular ports 18 described above have a length, A, of 3.00 mm to 4.5 mm and preferably 4.0 mm, and a width, B, of 0.8 mm to 1.0 mm and preferably 0.9 mm.

The spacing C between the ports 18 in each row of each ports is 2.0 mm to 3.00 mm and preferably 2.5 mm. The spacing D between adjacent rows of ports 18 in each group of ports is 1.5 mm to 2.5 mm and preferably 2.00 mm.

The ratio of the transverse extent of each row of ports to the spacing between the two closest rows of ports 18 in two adjacent groups is between 2.0 and 3.0, and is preferably 2.16.

The spacing between the gauze filter sheet and the wall 7 is about 5 mm at its edge portions and about 8 mm at its centre portion.

WHAT WE CLAIM IS: 1. A gas burner flamestrip having a plurality of flame ports arranged in spaced parallel groups of rows transverse to the length of the flamestrip, each group comprising three rows of ports, the spacing between adjacent rows of ports in each group being less than the spacing between the closest two rows of ports of two adjacent groups, each port being substantially rectangular in form and the longitudinal axis of each port extending transversely to the length of the flamestrip; wherein the length of each port lies within the range of 3.0 millimetres to 4.5 millimetres, the length to width ratio of each port lies within a range of 3.0 to 5.625, the ratio of the length of each port to the distance between adjacent ports in each row lies within the range 1.0 to 2.25, and the ratio of the length of each port to the distance between adjacent rows of ports in each group lies within the range of 1.2 to 3.0.

2. A flamestrip as claimed in claim 1, in which the thickness of the flamestrip is within the range of 0.4 millimetres to 1.0 millimetres.

3. A flamestrip as claimed in claim 2, in which the thickness of the flamestrip is 0.5 millimetres.

4. A flamestrip as claimed in any one of claims 1 to 3, in which the flamestrip has at least two lines of additional flame ports

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Claims

**WARNING** start of CLMS field may overlap end of DESC **.

ports 20 are provided in the wall 7 and arranged at each end of each row of rectangular ports.

When the gas and air mixture enters the chamber 12 the mixture passes to the flame ports 18, 19 and 20 via the gauze sheet 16.

The ports 18 in each group are sufficiently close together so that when any port in that group is ignited it will ignite and serve to stabilise its neighbours. Stabilisation is improved by flames formed on the ports 20. Ports 19 interconnect the groups of ports 18 and constitute a ladder burner serving to ignite the ports 18 in one group after ignition of the ports 18 in an adjacent group.

The ratio of the transverse extent of each group of ports 18 to the distance between the two closest rows of ports 18 in two adjacent groups is so chosen that the said distance is large enough to allow secondary aeration of the flames formed at the ports 18 and small enough to allow the burner to operate with high heat outputs.

Because of the rectangular configuration of the ports 18 the resistance to airborne lint or dust is relatively low. The gauze 16 also acts as a filter for the lint or dust.

Further, the gauze sheet 16 can be removed for cleaning and replacement by detaching end plate 2.

The gauze sheet is formed of woven or perforated metal having apertures, the area of each aperture being less than the area of each port 20. Because the gauze sheet provides more uniform distribution of the gas and air mixture passing to the ports 18 the operation of the burner is improved and flame noise is reduced.

The burner is especially suited for operation with slow burning gas such as natural gas and can be operated at a range of pressures by adjusting the injector size.

Usually the pressure range would be between 100 and 150mm water gauge.

The flamestrip (formed by the wall 7) and burner described and illustrated hereinbefore can be modified in a number of ways.

Thus, the flamestrip may be separately formed from the remainder of the burner body 1 and suitably attached thereto, for example by welding. The flame strip need not be curved and can take various shapes -- for example it could be flat or polygonal in form.

The lower portion 4 of the body 1 may be U-shaped and the upper part 5 flat or both parts may be U-shaped. The lower part

4 may be shaped to support the venturi or mixing tube 8. Further, the two parts 4 and 5 an be replaced by a single sheet folded into tubular form, opposed marginal edge portions of the sheet being secured together, for example, by deformation to form a mechanical joint -- and/or by welding; the seam being formed, preferably, at the base of the burner body.

One of the side and bottom openings 11 can be closed off.

For many applications the burner will operate satisfactorily without the stabilising ports 20.

Finally, it is possible, especially when the burner is fitted in a region where the air conditions are relatively clean, to dispense with the gauze sheet 16.

The rectangular ports 18 described above have a length, A, of 3.00 mm to 4.5 mm and preferably 4.0 mm, and a width, B, of 0.8 mm to 1.0 mm and preferably 0.9 mm.

The spacing C between the ports 18 in each row of each ports is 2.0 mm to 3.00 mm and preferably 2.5 mm. The spacing D between adjacent rows of ports 18 in each group of ports is 1.5 mm to 2.5 mm and preferably 2.00 mm.

The ratio of the transverse extent of each row of ports to the spacing between the two closest rows of ports 18 in two adjacent groups is between 2.0 and 3.0, and is preferably 2.16.

The spacing between the gauze filter sheet and the wall 7 is about 5 mm at its edge portions and about 8 mm at its centre portion.

WHAT WE CLAIM IS: 1. A gas burner flamestrip having a plurality of flame ports arranged in spaced parallel groups of rows transverse to the length of the flamestrip, each group comprising three rows of ports, the spacing between adjacent rows of ports in each group being less than the spacing between the closest two rows of ports of two adjacent groups, each port being substantially rectangular in form and the longitudinal axis of each port extending transversely to the length of the flamestrip; wherein the length of each port lies within the range of 3.0 millimetres to 4.5 millimetres, the length to width ratio of each port lies within a range of 3.0 to 5.625, the ratio of the length of each port to the distance between adjacent ports in each row lies within the range 1.0 to 2.25, and the ratio of the length of each port to the distance between adjacent rows of ports in each group lies within the range of 1.2 to 3.0.
2. A flamestrip as claimed in claim 1, in which the thickness of the flamestrip is within the range of 0.4 millimetres to 1.0 millimetres.
3. A flamestrip as claimed in claim 2, in which the thickness of the flamestrip is 0.5 millimetres.
4. A flamestrip as claimed in any one of claims 1 to 3, in which the flamestrip has at least two lines of additional flame ports

extending along the length of the flamestrip, each additional port having a cross-sectional area which is small compared to the crosssectional area of each rectangular port.
5. A flamestrip as claimed in claim 4, in which each additional port is circular in form.
6. A flamestrip as claimed in any one of claims 1 to 5, in which a further port having a cross-sectional area which is small compared to the cross-sectional area of each rectangular port is arranged at each end of each row of rectangular ports.
7. A flamestrip as claimed in any one of claims 1 to 6, in which the strip is convex in transverse cross-section.
8. A flamestrip substantially as hereinbefore described, with reference to and as illustrated by the accompanying drawings.
9. A gas burner comprising a flamestrip as claimed in any one of claims 1 to 8.
10. A burner as claimed in claim 9, in which the burner comprises a tubular chamber, the flamestrip constituting a wall of the chamber, and a gas inlet means being provided in the chamber for supplying a mixture of gas and air to the chamber.
11. A gas burner as claimed in claim 10, in which a filter comprising a sheet of metallic gauze is detachably secured in, and so extends across the chamber that the gas and air mixture from the inlet means passes through the burner ports via the gauze.
12. A gas burner as claimed in claim 11, in which the gauze is spaced from the flamestrip by at least 5 millimetres.
13. A gas burner as claimed in claim 11 or claim 12, in which the chamber is provided with two opposed axially extending grooves or ribs for slidably receiving opposed edge portions of the gauze sheet.
14. A gas burner as claimed in any one of claims 11 to 13, in which the gauze sheet comprises woven or perforated metal having apertures, each of which is smaller in area than the area of each rectangular flame port.
15. A gas burner substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.