IE46024B1 - Improvements relating to burner assemblies - Google Patents

Description

The present invention comprises improvements relating to burner assemblies.

British Patent Specification No. 1,156,918 describes a pressure jet oil burner assembly for a space heating apparatus. Gas burner assemblies are equally known for such a purpose.

The present invention aims to provide a dual fuel burner assembly for a space heating apparatus for burning alternatively either oil or gas, simply upon the action of changing over a switch.

According to the present invention such a burner assembly comprises a burner chamber which houses a pilot gas burner, an oil fuel feed means, a main gas burner and ignition means and which presents a burner chamber mouth, the burner chamber having first air inlet means to allow passage to the burner chamber of combustion air for discharge from the burner chamber mouth along with fuel fed through the oil fuel feed means, or the main gas burner, the pilot gas burner comprising a pilot tube surrounding the oil fuel feed means and defining therewith an annular pilot gas passage having an annular mouth, and second air inlet means to allow passage into said pilot gas passage of combustion air, the main gas burner comprising an annular gas passage having an annular mouth surrounding said pilot gas passage mouth.

The pilot gas burner may incorperate an air swirler in said pilot gas passage downstream of said air inlet means to said passage. - 2 46024 Also a bluff body maybe provided in said pilot gas passage downstream of the air swirler for further stabilising the pilot flame.

Feasibly, the bluff body might be relied upon exclusively to stabilise the pilot flame at the mouth of the pilot gas passage, the air swirler being omitted in this case.

A specific embodiment of the present invention will now be described, by way of example, and not by way of limitation, with reference to the accompanying drawings in which:Fig. 1 is a cross-sectional elevation of a dual fuel burner assembly according to the present invention, Fig. 2 is a top view of the assembly shown in Pig. 1, Fig. 3 is an underneath view of the assembly shown in Fig. 1, and Fig. 4 shows the burner assembly installed in a space heating apparatus.

With reference to the accompanying drawings, the dual fuel burner assembly which is about to be described is intended to be positioned in a voluto chamber such as the volute chamber 1 described in British Patent Specification No. 1,156,918, and indicated at 1 in Fig. 4 hereof, in replacement for the sub-assembly carried by, and including, the burner base plate 13 described in that specification and indicated at 13 in Figs. 1,2,3 and 4 hereof. Thus, in Fig. 4 hereof, reference numerals 21, 23 and 28 indicate respectively the dished face plate 21, the throat opening 23 and the flame tube 28 described in - 3 46924 British Patent Specification No. 1,156,918.

The dual fuel burner assembly comprises a burner chamber 10 which is generally cylindrical and which is positioned with its cylindrical axis co-axial with the volute chamber. The chamber 10 houses an oil fuel feed means 11 incorporating a spray nozzle at its upper end in Fig. 1 and as seen in Fig. 2 and ignition means comprising a pair of spaced electrode rings surrounding the nozzle adjacent but downstream of its mouth. One of the rings being mounted on the fuel feed means and forming a nozzle shroud.

As shown in Fig. 4, the burner chamber extends at its lower end through an opening in the base end wall of the volute chamber, the base plate 13 being secured to such wall by set screws entered through key hole slots 50 in the base plate. The upper end of the burner chamber 10 is frusto-conical and is smoothly narrowed to present a circular burner chamber mouth 16 concentric with the cylindrical axis of the combustion chamber the mouth 16 being located below the level of a large diameter opening 17 in the top end wall 18 of the volute chamber.

Vaned or otherwise formed louvres or inlets 19 or like means in the cylindrical wall 20 of the burner chamber between the burner chamber and the volute chamber are arranged to allow passage of combustion air from the volute chamber to the burner chamber and to impart to such air a swirling motion as indicated at CS contra-rotational to the swirling motion of air in the volute chamber.

The dished plate 21 has a flat annular plate portion or diaphragm 22 which seats onto the volute - 4 4 6‘ 0 2 4 chamber top wall 18 and is suitably removably fixed > ί thereto. The diaphragm has welded thereto depending ί throat means comprising a frusto-conical shield the t I upper, smaller diameter end of which defines the throat ί opening 23 hereinbefore referred to. The throat means registers with the opening 17 so that the shield is ί spaced above the top of the combustion chamber 10 to S define an annular passage which is generally of frusto- s f conical form and which constitutes the volute chamber ! ( mouth 25 which surrounds the burner chamber mouth 16 | Ϊ at about the same level. These mouths lead into the | common throat opening 23. The plate 21 may present at j its upper edge an annular flange (not shown) for suitable | fixing around an opening in the bottom of a combustion | or heat exchanger chamber, in particular, of a space I heating apparatus. The flame tube 28 seats into the plate 21. The tube is of cylindrical form and has an inturned flange for fixing onto the diaphragm 22. A ring of holes (not shown) is formed in the diaphragm 22 j of the face plate in register with the opening 17 in the j’ t top wall of the volute chamber and located radially i outwardly around the common throat opening 23, so that a ί proportion of air issues through such holes from the volute chamber.

The oil fuel nozzle lies along the main cylindrical axis of the burner co-axial with the burner chamber 10 and the burner chamber mouth 16. The burner chamber mouth 16 is disposed co-axially with the volute chamber mouth, the throat opening, the ring of holes therearound, and the flame tube. - 5 >16024 In. operation, using oil fuel, the oil fuel is delivered, under pressure through the oil fuel feed means 11 to the nozzle mouth and the nozzle is designed to impart to the oil fuel a rotary motion in the opposite sense to the air motion in the volute chamber and in the same sense as the air motion in the burner chamber, the oil fuel being sprayed through the burner chamber mouth 16 and thence the throat opening 23. Air is supplied under fan pressure into the volute chamber which imparts to the air a swirling motion about the cylindrical wall 20 of the burner chamber 10. A fraction of this air is taken into the burner chamber 10 through the inlets 19 with a contra-swirling motion, and discharges through the burner chamber mouth 16 and thence the throat opening 23, mixing with the fuel spray. The remainder of the swirling air from the volute chamber discharges through the frusto-conical mouth 25 exteriorly around the contra-swirling air and fuel discharging from the burner mouth 16 and thus through the throat opening 23.

The arrangement ensures a uniform main swirl motion in and from the volute chamber co-axial with the burner axis. The flow of air past the electrode 12 is restricted so that ignition is facilitated. At the same time a proper air flow rate and degree of swirl is maintained to ensure the best oil fuel combustion performance.

The air issuing from the ring of holes around the throat opening forms an air cushion radially constraining the flame and preventing it spreading laterally in the region of flame discharge from the - 6 4 6 0 2 4 throat opening of the burner. The flame tube 28 which surrounds the ring of holes and such air curtain supports this effect. r To enable the burner to burn gas instead of oil, the burner is adapted to establish a gas pilot flame for igniting a main gas burner. In order not to break up the swirling pattern of the primary oil fuel combustion air in the chamber 10, which is so important for the proper combustion of oil fuel in the burner, the gas pilot burner is located at the centre of the burner base plate 13 and concentrically about the oil fuel feed means 11. The gas pilot burner comprises a cylindricallyshaped pilot tube 51 surrounding the oil fuel feed means 11. Pilot gas is fed to the bottom of the gas pilot tube via an inlet pipe 52 and combustion air is likewise fed to the bottom of the tube via a radial air intake duct 54 communicating with one of the inlets 19. The duct 54 directs primary combustion air from that inlet into the bottom of the pilot gas tube, the combustion air then passing along the tube to its mouth 56 which is annulai· and which lies somewhat below the level of the top of the oil fuel nozzle. The duct 54 extends from its associated inlet 19 rearwardly of the mouth 16 (from which the swirl vane is omitted in this case) to the bottom of the pilot gas tube, the duct traversing a main gas burner passage 66.

To rotate the pilot air in the pilot gas tube and stabilise the pilot gas flame, a pilot air swirler 58 is provided in the tube, carried by the oil fuel feed means 11, part way up the tube. Downstream of the pilot air swirler and also carried by the oil fuel feed means 11 - 7 46024 is a bluff body in the form of a radial flange 60 which extends outwardly from the oil fuel feed means towards the inside of the wall of the pilot gas tube so as to define therewith only a narrow annular gap for the passage of swirling air and pilot gas towards the mouth 56 of the pilot gas tube. The action of the swirling air and pilot gas combines with that of the flange 60 to stabilise the pilot flame at the mouth of the pilot gas tube irrespective of pressure fluctuations in the supply of pilot gas to ensure that the pilot flame is properly positioned to ignite fuel gas emanating from a main gas burner 64. The annular gas passage 66 of the main gas burner 64 is disposed below the burner base plate 13 concentrically about the oil fuel feed means 11. The passage 66 leads upwardly to an annular main gas outlet 69 positioned in the bottom of the burner chamber 10 around the inside of its cylindrical wall 20 and below the level of the combustion air inlet means 19. Gas is supplied Into the passage 66 via a main gas inlet 70 and the gas is distributed uniformly to the outlet 69 in the passage.

The gas flows into the bottom of the chamber 10 through the outlet 69 and out through the chamber mouth 16 where it is ignited by the pilot burner flame.

The electrodes 12 define an annular spark gap positioned in the mouth 16 and over the mouth of the gas pilot tube.

An ultra-violet flame detector 72 is provided, see Fig. 4, suitable for detecting both an oil fuel and a gas fuel flame. This is positioned low down on the side wall of the volute casing and sighted upwardly at an angle - 8 4 6 0 2 4 so as to view” the flame through the mouth 25 of the volute casing.

The flame detector may be common to electrical control equipment of any known or convenient construction for alternatively establishing the combustion of oil fuel or gas fuel in the burner upon the changeover of a two position electrical switch when a start switch is in a closed position.

Whilst a dual fuel burner has been specifically 10 described in a space heater environment using a prescribed volute chamber to supply combustion air to the burner with a swirling motion about the burner chamber 10, it is to be understood that the invention extends to dual fuel burners generally and that a dual fuel burner in accordance with the present invention may be employed with any I suitable primary and secondary combustion air supply means to provide a swirling airstream about the inlets 19 in the burner chamber wall.

Claims (13)

1. CLAIMS:1. A dual fuel burner assembly for a space heating apparatus for burning alternatively either oil or gas comprising a burner chamber which houses a pilot gas burner, an oil fuel feed means, a main gas burner 5 and ignition means and which presents a burner chamber mouth, the burner chamber having first air inlet means to allow passage to the burner chamber of combustion air for discharge from the burner chamber mouth along with fuel fed through the oil fuel feed means, or the main gas io burner, the pilot gas burner comprising a pilot tube surrounding the oil fuel feed means and defining therewith an annular pilot gas passage having an annular mouth, and second air inlet means to allow passage into said pilot qas passage of combustion air, the main gas burner comprising 15 an annular gas passage having an annular mouth surrounding said pilot gas passage mouth.

2. A burner assembly as claimed in claim 1 in which the pilot gas burner incorporates an air swirler in said pilot gas passage downstream of said second air inlet 20 means

3. A burner assembly as claimed in claim 2 in which a bluff body is provided in said pilot gas » passage downstream of the air swirler.

4. A burner assembly as claimed in claim 1 25 in which the pilot gas burner incorporates a bluff body in said pilot gas passage downstream of said second air inlet means.

5. A burner assembly as claimed in any preceding claim in which the burner chamber is cylindrical 30 and said burner chamber mouth is circular and is centred - 10 a o u a it on the cylindrical axis of the burner chamber.

6. A burner assembly as claimed in claim 5 in which said first air inlet means comprises air inlet openings in the cylindrical wall of the burner 5 chamber.

7. A burner assembly as claimed in claim 6 in which said air inlet openings have vanes to impart swirl to combustion air entering said burner chamber about the cylindrical axis thereof. io

8. A burner assembly as claimed in claim 5, 6 or 7 in which the oil fuel feed means comprises an oil spray nozzle disposed co-axially with the burner chamber.

9. A burner assembly as claimed in claim 8 in which the pilot tube is cylindrically shaped and is 15 disposed concentrically about the oil spray nozzle.

10. A burner assembly as claimed in any preceding claim in which said second said air inlet means comprises an air intake duct opening from outside said burner chamber and leading into said pilot gas passage, 2o the duct traversing the annular gas passage.

11. A burner assembly as claimed in claims 6 and 10 in which the air intake duct communicates with an air inlet opening in the cylindrical wall of the burner chamber, the air intake duct extending from said 25 opening radially inwardly with respect to the cylindrical axis of the burner chamber and rearwardly with respect to the burner chamber mouth.

12. A dual fuel burner assembly for a space heating apparatus for burning alternatively either oil 30 . or gas substantially as hereinbefore described with 4 6 0 2 4 reference to, and as shown in, the accompanying drawings.

13. Space heating apparatus substantially as hereinbefore described with reference to Fig. 4 of 5 the accompanying drawings.