WO2006079157A1

WO2006079157A1 - Kebab machine

Info

Publication number: WO2006079157A1
Application number: PCT/AU2006/000075
Authority: WO
Inventors: Ali Basaraner
Original assignee: International Fast Food Systems Pty Ltd
Priority date: 2005-01-25
Filing date: 2006-01-23
Publication date: 2006-08-03

Abstract

A vertical burner array includes two or more burners (10, 11), with an intermediate plate (16) between the burners. A slot (17) permits additional air to be drawn between the burners from the rear of the burners. The face (11) of the burners can be tilted.

Description

Kebab Machine

Technical Field

[01] This invention relates to burners for combustion heating systems, and addresses the problem of oxygen starvation in the case where two or more burners are stacked one above the other. In such an arrangement, the efficiency of burners above the lowest burner may be impaired because the burners are deprived of sufficient oxygen.

Background of the Invention

[02] The invention will be described with reference to fuel burner arrangements for kebab cookers. Such cookers are usually designed to cook food on a rotisserie. In most cases the rotisserie has a vertical axis. However, in the context of a rotisserie, reference in this specification to vertical should be understood to refer to the axial direction of the rotisserie. The invention is applicable to cases where the axis is tilted at an angle to the vertical, depending on whether the burners are stacked so that there is at least partial deprivation of oxygen from the higher burners due to the combustion products from the lower burners. The burners are supported on a frame which is usually made of stainless steel or some other suitable material.

[03] It is desirable to be able to control both the location of the heat source relative to the food being heated, and the intensity of the heat source at various heights. To this end, a substantially vertical array of heater elements is used to enable a vertical gradation of heating. The food is rotated in front of a substantially vertical heater. The burners have a radiating surface which is heated by the burning fuel. The food is heated by radiation from the burners. The burners are usually stacked close together with a small distance separating them to provide a substantially continuous and even heating surface. The space between the burners is usually closed by a stainless steel plate which may also serve as part of a frame to support the burners. Disclosure of the Invention

[04] This invention is directed, to a stack of fuel burning heaters, such as gas heaters.

[05] The invention provides an arrangement of two or more fuel burners in which at least one upper burner is stacked above a bottom burner, wherein each burner has a radiator element which presents a radiation surface; each burner has a combustion region at which the fuel is burnt; the combustion region being located so that the heat from the burnt fuel heats the radiation element; an air passage is provided at or near the base of each upper burner above the bottom burner to admit uncombusted air to facilitate combustion of the fuel in the or each upper burner.

[06] The term "upper burner" refers to a burner at any level above the lowest burner.

[07] The radiator element can include perforations which permit the passage of an air fuel mixture for combustion.

[08] The arrangement can include a deflection vane at or near the base of each upper burner to direct burnt gases away from the upper burner.

[09] The radiator element can be tilted at an angle.

[ 10] The radiator element can be tilted at an angle which presents an overhanging surface.

[11] The radiator element can be tilted at an angle between 3 and 15 degrees.

[12] The radiator element can be tilted at an angle of 7.5 degrees.

[13] The radiator can be substantially planar. [ 14] The radiator can be concave.

[15] The burner can include a mixing chamber in which air is mixed with the fdel.

[ 16] The air/fuel ratio in the mixing chamber can be controllable.

[17] The burner arrangement can include a first choke means to control the amount of air entering the mixing chamber.

[18] The burner arrangement can include a second choke means to control the amount of air passing through the air passage

Brief Description of the Drawings

[19] Figure 1 is a schematic diagram illustrating a stack of three gas burners.

[20] Fig. 2 shows an array of burners according to an embodiment of the invention.

[21] Figure 3 illustrates an array of burners with a deflection vane.

[22] Figure 4 illustrates the air passage with a choke arrangement.

[23] Figure 5 shows an alternative embodiment including a deflection vane.

[24] Figure 6 shows a pressure/movement servo.

[25] Figure 7 shows a further embodiment of the invention.

Description of the Invention

[26] The arrangement of Figure 1 shows a vertical stack of three burners. [27] Each burner includes a pre-mixing chamber 10 in the form of a box. The box is enclosed on all sides except for the front face which is closed by a perforated radiator 11. The individual burners are joined by a plate 16.

[28] Gas enters the pre-mixing chamber 10 via pipe 12, and air is drawn in through opening 13. The gas enters the box under pressure, and air from opening 13 is entrained with the gas to form a pre-combustion mixture. The pre-combustion mixture escapes through the perforations 14 and is initially ignited, by, for example, pilot burner 15 in front of the radiator 11. Once alight, the combustion should be self-sustaining until the gas supply is turned off. The pre-combustion mixture is chosen to prevent the mixture within the mixing chamber igniting and blowing back to the gas pipe 12.

[29] An efficient combustion mixture is formed when the pre-combustion mixture from the mixing chamber mixes with the external air after passing through the perforations 14, and this can be ignited by the pilot flame 15.

[30] The burning gases heat the radiator element 11 to radiant temperature.

[31] We have found that, while the bottom burner works efficiently, combustion at each higher burner in the stack is not always satisfactory. We attribute this to the fact that the hot post-combustion gases, 1 in Figure 1, rising from the lower burners are oxygen depleted, so that there is insufficient oxygen available at the higher burners in the stack to obtain optimal combustion when lower burners are operating. The rising combustion products act to prevent unburnt air from reaching the pre-combustion mixture emerging from the perforations in the radiation element. Thus there is effectively a convection current of burnt gas flowing across the face of the upper radiation elements, providing a less than optimal air/fuel mixture for combustion at the combustion zones of the upper burners.

[32] Accordingly, this invention makes additional oxygen available at the combustion zones of the upper burners by providing an air path to introduce unburnt air to the face of the or each upper burner. We do this in a first embodiment by providing an airway between the burners.

[33] The airway can provide air access between the back and the front of the burners.

[34] In a further embodiment, the orientation of the burners is adjusted so that, while they form an upright stack, each burner is tilted individually. This tilting can help to provide space for an airway from the front to the back of the burners. It also provides a gap between the rising combustion products from the lower burners, and the air drawn through the air passage 17 is drawn into this space, from where it can be drawn up by convection to mix with the pre-combustion mixture emerging through the perforations 14 in the radiator element 11.

[35] Figure 2 shows an embodiment of the invention in which an air passage in the form of aperture 17 in the plate 16 joining the burners is provided to permit air to pass between the front and the back of the burner. The air is drawn through the aperture by the convection of the combusted gases at the front of the radiators. This provides a supply of additional oxygen to the gases emerging via the perforations in the upper radiators.

[36] A further feature shown in Figure 2 is the tilting of the individual burners.

We have found that by tilting the burners, the plate 16 can be formed in an inverted "L" shape, the air passage 17 can be formed in the transverse portion of the "L". The exact angle of the "L" is not critical and it can vary between acute and obtuse, so the transverse portion is not required to be exactly horizontal. In the embodiment shown in Figure 2, the angle is shown as being acute, and the transverse portion is shown as horizontal.

[37] A shown in Figure 4, the air passage 17 may consist of an array of holes dimensioned to provide optimal airflow at the designed burning rate. [38] In a further embodiment, a deflection vane is provided between burners to deflect combusted gases away from the face of the radiator above. This vane may take the form of a deflection plate angled away from the plane of the burner faces.

[39] In a further embodiment shown in Figure 3, a deflection vane 18 has been added. This has the effect of deflecting the combustion products 19 from the lower burners away from the face of the upper burners. The deflection vane provides a gap between the face of the upper burner and the rising combustion products from the lower burner. This may facilitate the access between the fresh air drawn up through the air passage 17 and the pre-combustion air/gas mixture passing through the perforations in the radiation element.

[40] As shown in Figure 5, the deflection vane may be used with an arrangement as shown in Figure 1, with the air passage 17 provided in the vertical plate 16.

[41] In the exploded view of a further embodiment shown in Figure 4, choke means have been added to provide a means of controlling the amount of air drawn through the air passage. In operation, the choke plate 20 is adjacent to the part of plate 16 carrying the air passages 17. The choke 19 is constrained, e.g., by tabs 23, to move in the direction of arrow 21 and has apertures 22 which can be moved to fully open the air passages 17 or to partially or completely close these air passages.

[42] hi a further embodiment, the choke 20 may be designed to have two positions, a first position when operating on a first fuel, and a second position when operating on a second fuel having different combustion characteristics &om the first fuel.

[43] Additionally, the choke may be adjusted to take account of variations in gas pressure. A servo-mechanism can be provided to control the position of the choke in response to the variations in gas pressure. Figure 6 shows a pressure/movement servo 31 having a pressure sensor pipe 32 and a movement armature 33. The servo causes the armature to move in response to changes in pressure. The servo may be programmed to give a desired pressure/movement transfer characteristic. The programming can also take account of the combustion characteristics of the fuel. For example, the fuel may be coal gas or natural gas, which have different combustion characteristics.

[44] In another embodiment, air is supplied to the combustion zone via an air duct and a fan. Figure 7 shows an array of burners with fan forced air supplied to the combustion zone of the upper burners. In Figure 7, a fan, 71 is arranged to force air into a cowling 72 which is connected to duct 73. The air is delivered to air box 74 and emitted through an aperture shown as slot 75.

Claims

The claims defining the invention

1. An arrangement of two or more fuel burners in which at least one upper burner is stacked above a bottom burner, wherein each burner has a combustion region at which the fuel is burnt; an air passage is provided at or near the base the combustion region of each upper burner to admit uncombusted air to facilitate combustion of the fuel in the. or each upper burner.

2. An arrangement as claimed in claim 1 , wherein the air passage permits air from the part of the burner away from the combustion region to access the combustion region.

3. An arrangement as claimed in claim 1 or claim 2, wherein the burner includes a radiator element, and wherein the radiator element includes perforations which permit the passage of an air /fuel mixture to the combustion region for combustion.

4. An arrangement as claimed in any one of claims 1 to 3, including a deflection vane at or near the base of each upper burner combustion zone to direct burnt gasses away from the upper burner combustion zone.

5. An arrangement as claimed in any one of claims 1 to 4, wherein the radiator element is tilted at an angle to the vertical.

6. An arrangement as claimed in claim 5, wherein the radiator element is tilted at an angle which presents an overhanging surface.

7. An arrangement as claimed in claim 5 or claim 6, wherein the radiator element is tilted at an angle between 3 and 15 degrees.

8. An arrangement as claimed in claim 5, wherein the radiator element is tilted at an angle of 7.5 degrees.

9. An arrangement as claimed in any one of claims 1 to 8, wherein the radiator element is substantially planar.

10. An arrangement as claimed in any one of claims 1 to 8, wherein the radiator element is concave.

11. An arrangement as claimed in any one of claims 1 to 10, wherein the burner includes a mixing chamber in which air is mixed with the fuel.

12. An arrangement as claimed in claim 11 , wherein air/fuel ratio in the mixing chamber can be controllable.

13. An arrangement as claimed in any one of claims 1 to 12, including a first choke means to control the amount of air entering the mixing chamber.

14. An arrangement as claimed in any one of claims 1 to 13, including a second choke means to control the amount of air passing through the air passage.

15. An arrangement as claimed in claim 13, including a first pressure/movement servo to control the first choke.

16. An arrangement as claimed in claim 14 or 15, including a second pressure/movement servo to control the second choke.

17. A method of improving the combustion of the upper burners of a stack of burners in which each burner has a combustion zone, the method including entraining air at the base of the combustion zone of each burner above the lowest burner.

18. A method as claimed in claim 17, including tilting the combustion zone of each upper burner.

19. A method as claimed in claim 17 or claim 18, including the step of deflecting the combustion products away from the combustion zone of each upper burner.

20. A method as claimed in any one of claims 17 to 19, including the step of adjusting the flow of air into the burner in response to one or more characteristics of the gas.

21. A fuel burner stack arrangement substantially as herein described with reference to the accompanying drawings.

22. A method of improving combustion in a burner stack substantially as herein described with reference to the accompanying drawings.