GB2250339A - Gas burner - Google Patents

Abstract

In a gas-fired appliance noxious fume levels are reduced to an acceptable level by directing secondary air into close, intimate contact with the gas burner surfaces and gas flames to cool the former and reduce the height of the latter by speeding burning. This is achieved, for example by using a slotted plate 16 in combination with burner blades 13 of a gas burner to define around the burner blades slots 18 through which secondary air flows, or is caused to flow, into intimate contact with the burner blades surfaces and gas flames, and possibly intermingling contact with the latter. The slotted plate 16 may be planar or corrugated (Fig 3, not shown) or replaced by bars closely adjacent the burner blades. The slots may have castellated edges to increase air flow adjacent the gas ports. (20) (Fig 4, not shown). <IMAGE>

Description

GAS-FIRED APPLIANCES This invention relates to gas-fired appliances and especially to gas burners therefor.

Existing gas burners, during operation, give off noxious fumes of nitrogen oxide and nitrogen dioxide within the range of 250 to 270 parts per million (p.p.m.) for example.

This is undesirable and unacceptable and will soon be illegal in that this range will far exceed the upper limit of the proposed European Standard, which upper limit, it is believed, will be 140 p.p.m. or thereabouts.

The undesirable noxious fumes result from the chemical interaction of nitrogen in the combustion air (primary and secondary) and the gas supplied to the gas burner and the flame front present during combustion, the hot metal of the gas burner acting as a catalyst.

It is an object of the present invention to provide a gas burner where the noxious fume level (p.p.m.) is at least substantially reduced, preferably to a level below the proposed, and eventually set, European Standard.

According to the present invention this is achieved by constraining or directing secondary air supplied to the gas burner into close intimate contact with, and possibly over, the gas burner surface and any generated gas flame.

As a result this supplied secondary air acts to cool the gas burner, and produces much more rapid combustion in consequence of which flame height (flame front) is reduced and the p.p.m. value is significantly reduced to 80 to 90 p.p.m. for example.

Also according to the invention there is provided a gas burner incorporating means for constraining and/or directing secondary air supplied to the gas burner into close and intimate contact with, and possibly over, the gas burner surface and any generated gas flame.

According to the present invention one specific solution provides that the secondary air flow is controlled and directed by a grid surrounding the gas burner, the grid and gas burner defining therebetween a narrow passage through which the secondary air must pass.

As a result the close and intimate contact between the flow of secondary air and gas burner and any generated gas flame is achieved with the consequent attainment of the aforesaid low and acceptable p.p.m. level of noxious fumes.

Preferably the gas burner is a single injector, multi-bladed gas burner although it will be appreciated that a multiple multi-bladed injector may replace the single injector. Preferably the secondary air flow controlling grid is a plate having multiple slots therein (one for each burner blade) with each burner blade and slot cooperating to define a narrow flow passage for the secondary air.

The plate may be of flat or planar construction, or it may be of V-corrugated configuration.

In the former case, the secondary air interfaces with the burner blade(s) and the gas flames.

In the latter case, the secondary air is positively directed against the burner blade(s) and into the gas flames.

It is to be understood that the slotted plate may be any suitable configuration permitting such secondary air directional control.

The secondary air control grid may alternatively be defined by bars (planar or directionally-configured) laid alongside but spaced from the burner blades to define the secondary air outlet flow passages.

The slots defined between the plate or bars and the burner blades may be parallel sided or may be of castellated configuration to provide increased secondary air flow adjacent the gas ports of the burner blade(s).

This is achieved by castellating the edges of the slots in the plate or the edges of the bars, The slotted plate may be a part of the gas burner or a part of a gas-fired appliance into which the gas burner is incorporated.

The secondary air may be supplied by natural aspiration, suction or blowing, or combinations thereof.

The term "burner blade" used herein and in the claims is to be construed and including a burner bar or other member from which gas egresses for combustion.

A reduction in the noxious fume level, to an acceptable value, may be achieved by controlling and directing the secondary air flow around and over only one or some of the blades of the gas burner (provided more than one burner is provided) and the present invention includes this arrangement within its scope.

The combustible gas supplied to the gas burner may be any of the kind usable with gas-fired appliances.

Further according to the present invention there is provided a gas-fired appliance having a gas burner and a means associated with the latter for controlling and directing secondary air flow into close and intimate contact with, and possibly over, the, or each, or some, of the burner blade(s) of the gas burner and any generated gas flame.

The control means is preferably a slotted plate but may be bars.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing, in which: Fig. 1 is a diagrammatic perspective view of a gas burner assembly according to the present invention; Fig. 2 is a detail transverse sectional view of the relationship between a burner blade and the secondary air flow control plate or grid.

Fig. 3 is a detail transverse sectional view of a modified burner blade/control plate arrangement; and Fig. 4 is a fragmentary plan view of another modified burner blade/ control plate arrangement.

The gas-fired appliance (Figs. 1 and 2) is, for example, a gas boiler having a front vertical plate 10 mounting centrally of its lower edge a gas burner 11 comprising a single gas injector 12 which, on top thereof, mounts spaced parallel burner blades 13. The burner blades 13 have upper parted surfaces 14 for gas egress and combustion purposes.

The burner blades 13 are parallel with the front vertical plate 10 and the injector 12 and the burner blades 13 are enclosed within a vertically-open box structure 15 through which the secondary air for the gas burner 11 freely flows without restriction by natural aspiration, suction or blowing or combinations thereof.

With this arrangement an unacceptable level of noxious fumes is created, as aforesaid, due to the secondary air flow rapidly sweeping past the burner blades 13 and pulling or lengthening the generated flames.

According to the present invention the level of noxious fumes is reduced to an acceptable level by controlling and directing the secondary air flow around and over the burner blades 13 and gas flames.

One means of achieving this is to close the vertically-open box structure 15 around the burner blades 13 by a slotted plate 16, there being a slot 17 in the plate 16 for each burner blade 13 closely circumscribing same to define around the burner blade a narrow passage 18 through which the secondary air can flow in close and intimate contact around, and possibly over, the burner blade 13 thereby cooling same while simultaneously shortening the generated gas flames to produce a more rapid combustion of the gas. As a consequence of these factors noxious fume level (p.p.m.) is significantly reduced - to a more than acceptable level.

The slotted plate 16 has at its front edge an upstanding flange 19 to permit it to be fastened, e.g. bolted, to the vertical front plate 10.

The secondary air flow is indicated at A and the gas and primary air flow at G.

The slotted plate 16 may form part of the gas injector/burner blade assembly 12, 13.

Instead of a slotted plate 16 the passages 18 may be defined or created by bars lying alongside but spaced from the burner blades 13.

Referring now to Fig. 3 the plate 16A instead of being of planar configuration as shown at 16 in Figs. 1 and 2 is of V-corrugated crosssection to be defined with the burner blades 13A inclined or angled secondary air directional slots 18A.

This ensures that secondary air is positively delivered into the flame and over the top of the burner blades 13A as opposed to intimate inter-facial contact therewith.

It will be manifest that if bars are used these will be of V-crosssection.

In Fig. 4, there is shown one way of ensuring increased secondary air presence and flow at each gas port 20 of a burner blade 13B and this is to increase the width of the gap 18B at these particular regions 18C.

A simple and effective way of doing this is to castellate the edges of the slots of the control plate 16B, or to castellate the edges of the bars.

The modifications of Figs. 3 and 4 may be employed separately or in combination.

It is to be noted that if bars are used to define the secondary air control grid they may instead of being of planar or V configuration be round bars, i.e. circular cross-section.

Claims (19)

1. A method of reducing the noxious fume level in a gas burner, the method of comprising the step of delivering secondary air into close intimate contact with at least the gas burning surfaces of the gas burner and gas flames generated by the latter.

2. A method as claimed in claim 1, comprising the step of directing the secondary air into gas flames generated by the gas burner.

3. A method as claimed in claim 1 or 2 comprising the step of increasing the quantity of secondary air delivered in the region of each gas flame location of the gas burner.

4. A method of reducing the noxious fume level in a gas burner, substantially as hereinbefore described with reference to the accompanying drawings.

5. A gas burner incorporating means for constraining and/or directing secondary air into close intimate contact with at least the gas burning surfaces of the gas burner and gas flames generated thereby.

6. A gas burner as claimed in claim 5 comprising a blade burner surrounded by a surface defining with the latter a narrow passage or an air gap surrounding the blade burner and through which the secondary air is delivered.

7. A gas burner as claimed in claim 6 comprising a plurality of blade burners, preferably disposed in spaced parallel array, surrounded by a grid which defines with each blade burner a surrounding narrow passage or air gap.

8. A gas burner as claimed in claim 7 in which the grid is constituted by a slotted plate, there being one slot for each burner.

9. A gas burner as claimed in claim 7, in which the grid is constituted by spaced bars with a burner blade between adjacent bars.

10. A gas burner as claimed in claim 8 or 9 in which the slotted plate or bars are of planar configuration or round configuration.

11. A gas burner as claimed in claim 8 or 9 in which the slotted plate is of V-corrugated or similar configuration in cross-section.

12. A gas burner as claimed in claim 9 or 10 in which the bars are of V-cross-section or similar.

13. A gas burner as claimed in any one of claims 8 to 12 in which the narrow passage or air gap is of increased width in the region of each gas port of the burner blade.

14. A gas burner as claimed in claim 13 in which the burner blade edge of each plate slot or bar is of castellated construction.

15. A gas burner as claimed in any one of claims 7 to 14 in which the grid is integral with, or connected to, the gas burner.

16. A gas burner, substantially as hereinbefore described with reference to the accompanying drawings.

17. A gas-fired appliance incorporating a gas burner as claimed in any one of claims 5 to 16.

18. A gas-fired appliance as claimed in claim 17 in which the grid is part of the appliance.

19. A gas-fired appliance as claimed in claim 17 or 18 in the form of a hot water boiler.