GB2281963A

GB2281963A - Gaseous fuel burners

Info

Publication number: GB2281963A
Application number: GB9319200A
Authority: GB
Inventors: Geoffrey John Edmund Brown; Benjamin Frank Gostelow; Frank Spruce
Original assignee: Stoves PLC
Current assignee: Stoves PLC
Priority date: 1993-09-16
Filing date: 1993-09-16
Publication date: 1995-03-22
Anticipated expiration: 2013-09-16
Also published as: GB2281963B; GB9319200D0

Abstract

A gaseous fuel burner comprises a chamber bounded by a burner plate 6 and a burner box, formed by a sheet metal body 2, with fuel leading into the chamber via a tube 12. The burner plate has a series of bosses formed round its periphery and each boss accommodates a flame port 18. Immediately adjacent flame ports are separated by a distance which minimises the risk of flames from one flame port impinging on those of adjacent ports but which is also sufficient to ensure cross ignition of fuel issuing from adjacent ports. Each boss comprises a flange pressed from the burner plate and has an inturned edge that bounds the flame port. Also, the inturned edge supports a mesh member consisting of two layers of mesh. <IMAGE>

Description

Improvements in and relating to Gaseous Fuel Burners.

This invention relates to gaseous fuel burners and has particular reference to gaseous fuel burners for domestic appliances, for example domestic gas cookers.

The combustion products released from gaseous fuel burners such as are used in domestic appliances include a number of undesirable gases including oxides of nitrogen now known as NOX gases and other compounds including formaldehyde. Although such undesirable gases and compounds are present in extremely small quantities they are now considered to be a health hazard especially in the home and also to be harmful to the environment. Consequently, effort is now being made to ensure that the emission of such undesirable combustion products is reduced to an absolute minimum.

It is an object of the present invention to provide a gaseous fuel burner whose combustion products, in use, contain an acceptably low level of NOX gases and other potentially dangerous chemicals.

According to the present invention a burner for burning a gaseous fuel mixture comprises a burner chamber, an inlet for the admission of mixture to the chamber, the chamber being bounded, at least in part, by a burner plate having a series of flame ports spaced apart by a distance sufficient to minimise the impingement of flames of adjacent ports and to allow cross ignition between adjacent ports.

The flame ports may be arranged in a row or they may be arranged in a closed loop adjacent the periphery of the burner plate.

The burner plate may be of a rectangular shape and in this case, the flame ports are positioned close to the sides of the plate. There may be additional flame ports at locations lying at the mid points of the sides of the burner plate and inwardly of the first-mentioned ports.

In one embodiment of the invention, the flame ports lie on bosses on the burner plate. The bosses may be formed in the burner plate and each may comprise a flange pressed from the plate and having an inturned edge that bounds the flame port.

The inturned edge may support a mesh member that may consist of two layers of mesh. The mesh member or the two layers may be supported on the inturned edge of the flange.

The mesh member or the two layers may be held in place in the boss by a retaining ring which may have a peripheral wall that is slotted at intervals, the parts of the wall between the slots being sprung outwardly to allow the ring to be retained in the boss.

Gaseous fuel mixture may be supplied to the burner through a tube that passes into the chamber and has an open end inside the chamber.

To improve the flow of gaseous mixture from the tube to the flame ports, a baffle may be fitted inside the chamber adjacent the open end of the tube.

In one form of the invention the chamber is bounded by the burner plate and a burner box secured to the plate. The burner box may have a raised portion that lies centrally of the burner box and into which the tube passes. In that case, the baffle extends into the raised portion.

Preferably, the burner is supplied with a gaseous mixture of a gaseous fuel and primary air under pressure.

By way of example only, a grill burner suitable for a domestic gas cooker will now be described in greater detail with reference to the accompanying drawings of which : Fig. 1 is a side elevation of the burner, Fig. 2 is a view of the burner from above, Fig. 3 is a section on the line III - III of Fig. 2, and, Fig. 4 is a section on an enlarged scale of a part of the burner.

The grill burner 1 shown in the drawings is of generally rectangular form when seen in plan as in Fig.2. The burner comprises a chamber bounded on one side by a sheet metal body 2 in the form of a shallow tray with an upper (as seen in Fig.

1 and 3) face 3 and a peripheral wall 4. The edge of wall 4 is out-turned to provide a flange 5 that is returned on itself to grip the edge of a burner plate 6 of stainless steel which provides another boundary of the chamber. The body 2 is upset over its central area to provide a raised portion 7 of approximately semi-cylindrical shape with a central recessed part 8.

Located internally of the body 2 and directly beneath the portion 7 is a metal baffle plate 9 that has a flange 10 by which it is fixed to the inside of face 3 of the body 2, and an upstanding wall 11 that is contoured to fit into the interior of the portion 7 as is shown in Fig. 1. The baffle plate 9 is located about halfway along the length of the burner, the wall 11 being spaced from and facing the open end of a burner tube 12 that extends into the portion 7 through a collar 13 formed in an end wall 14 of the portion 7. The opposite end wall 15 of portion 7 is inclined downwardly and at its lower end merges with the peripheral wall 4.

Also fixed to the upper surface of the body 2 are upstanding elongate brackets 16 that are located one on each side of the portion 7 and adjacent the side walls of the body 2. As can be seen from Fig. 1, the brackets extend along almost the entire length of the body 2 and each has outwardly projecting flanges 17 at its upper and lower edges. The lower ones of the flanges 17 are used to secure the brackets 16 to the face 3 of body 2. The brackets 16 are used to support the grill burner in a desired position in or above an oven or grill cavity of the cooker. Further details of possible locations for the grill burner are described in co pending UK Patent Application No. GB 9114956.7 (2257503A)..

The burner plate 6 has, adjacent its periphery, a series of spaced flame ports 18, further flames ports 19 being formed at four locations disposed at the mid points of the four sides of the burner plate and inwardly of the adjacent row of flame ports 18. The flames ports 18 and 19 lie on the outer faces of bosses that project downwardly (as viewed in Figs. 1 and 3) from the plane of the burner plate 6, The bosses are formed by pressing out flanges 20 from the plate 6. The bosses are all identical. Each flange 20 has an inturned edge 21 that surrounds the actual flame port. As can be seen clearly in Fig. 4, each flange forms a housing that accommodates an outer mesh disc 22 of stainless steel, an inner mesh disc 23 also of stainless steel and a retaining ring 24.Those components seat on the inturned edge 21, the mesh discs being held in position by the retaining ring 24 which has a peripheral wall 25 slotted at intervals as at 26 and an inturned edge 27. The wall 25 between the slots 26 is sprung outwardly and is pressed into the boss and is held therein by contact with the flange 20.

The size and number of flame ports is selected to provide a desired heat output from the burner. The flame ports are spaced apart by distances sufficient to minimise the possibility of the flame from one port impinging on the flames from adjacent ports but also sufficient to allow cross ignition of gaseous fuel issuing from adjacent ports.

The flame ports are of larger size than is conventional in grill burners and they operate at a higher temperature and this is thought to reduce the emission of NOX gases.

The arrangement of the flame ports is also such that, because radiant heat from each port is emitted from each port in a divergent pattern, an even spread of heat in a horizontal plane is obtained from the grill burner at a distance of about 100mm from the ports.

The burner is supplied with a mixture of gaseous fuel, for example natural gas, and air for combustion, referred to herein as primary air, via tube 12 suitable flow control means, for example a gas tap, being provided.

Gaseous fuel mixture emerging from the open end of tube 12 impinges on wall 10 of the baffle 9 and is spread thereby to be distributed equally amongst the flame ports.

In addition, the burner will be fitted with an ignition device, for example an piezo-electric igniter or an electrically energised ignition coil. The ignition device is positioned close to one of the flame ports so that gaseous fuel mixture issuing from the latter will be ignited readily and, because of the spacing of the flame ports, flames from the one port will ignite fuel issuing from the immediately adjacent ports and so on. Conveniently, the ignition device will be energised when the gas tap is operated to an "on" position.

Preferably, the primary air is supplied under pressure to a mixing chamber to which the gaseous fuel is also fed.

The mixing chamber is part of or is joined to the tube 11.

Details of arrangements for supplying primary air under pressure are given in UK Patent Application No. GB 9317612.9.

It will be understood that the invention may be incorporated in burners other that grill burners. For example, a burner suitable for use in the oven of a gas cooker may have a number, for example three, of flame ports arranged in a line. In that case, each flame port will be operating at a much higher temperature in order to give a required total heat output from the burner and so the inner and outer meshes positioned in each port will be of a material able to withstand such higher temperatures, for example a mesh of silicon fibres may be used as could a mesh of fibres of some other ceramic material.

Claims

Claims.

1. A burner for burning a gaseous fuel mixture the burner comprising a burner chamber, an inlet for the admission of fuel mixture to the chamber, the chamber being defined, at least in part, by a burner plate having a series of flame ports spaced apart by a distance sufficient to minimise the impingement of flames of adjacent ports and to allow cross ignition between adjacent burners.

2. A burner as claimed in claim 1 in which the flame ports are arranged in a row.

3. A burner as claimed in claim 1 in which the flame ports are arranged in a close loop adjacent the periphery of the burner plate.

4. A burner as claimed in claim 3 in which the burner plate is rectangular, the flame ports being arranged adjacent the sides of the rectangle, and in which there are additional flame ports at locations lying at the mid points of the sides of the burner plate and inwardly of the firstmentioned ports.

5. A burner as claimed in claim 2, 3 or 4 in which each flame port lies on a boss on the burner plate.

6. A burner as claimed in claim 5 in which the boss is formed in the burner plate.

7. A burner as claimed in claim 6 in which the boss comprises a flange pressed from the burner plate and having an inturned edge that bounds the flame port.

8. A burner as claimed in claim 7 in which the inturned edge supports a mesh member of a heat resistant material.

9. A burner as claimed in claim 8 in which the mesh member comprises two layers of mesh.

10. A burner as claimed in claim 8 or 9 in which the member is, or the layers are, held in the boss by a retaining ring.

11. A burner as claimed in claim 10 in which the retaining ring has a peripheral wall slotted at intervals, the parts of the wall between the slots being sprung outwardly to alow the ring to be retained in the boss.

12. A burner as claimed in any one of the preceding claims and further comprising a tube passing into the chamber for supplying gaseous fuel mixture thereto, the tube having an open end inside the chamber.

13. A burner as claimed in claim 12 in which there is a fuel mixture baffle located within the chamber adjacent the open end of the tube.

14. A burner as claimed in claim 12 or 13 in which the chamber is bounded by the burner plate and a burner box secured to the plate, the burner box having a raised portion that lies centrally of the burner box and into which the tube passes.

15. A burner as claimed in claim 14 in which the baffle extends into the raised portion.

16. A burner installation comprising a burner as claimed in any one of the preceding claims, a source of air under pressure joined to a mixing chamber, a gaseous fuel supply pipe connected to the mixing chamber, an outlet pipe from the mixing chamber leading to the burner for conveying gaseous fuel mixture to the burner.

17. A burner for burning a gaseous fuel mixture substantially as herein described with reference to and as illustrated by Figs. 1 to 4 of the accompanying drawings.