The present invention relates to an apparatus and method for the combustion of flammable liquids having high flash points, such as oils or fats of animal or plant origin.

There are growing concerns over the global continued use of fossil fuels. One possible alternative source of fuel is biofuel (fuel that is directly obtained from biological matter) . Such biofuels include oils derived from oil-bearing crops such as oil palm, soya beans, rapeseed, sunflowers and maize. These oils are typically of a high viscosity and a high flash point, making them difficult to burn. For example, the flash points of crude palm oil, rapeseed oil and sunflower oil are about 24O ⁰ C, 24O ⁰ C and 270 ⁰ C respectively.

Attempts have been made to provide apparatuses that burn oil having a high flash point. The Babington nozzle burner comprises a ball over which fuel oil is passed to create a thin film on the surface of the ball. Air is passed through a nozzle in the surface of the ball, therefore atomising the oil passing over the nozzle. The atomised oil will ignite, and a continuous flame may be produced if the region of the apparatus associated with the atomised oil is contained within a pipe. However, the unused fuel passing over the surface of the ball has to be collected and returned to a suitable container. US4155700 of Babington also describes a related fuel burner that relies on using spray heads to produce atomised oil that combusts when ignited. Such atomisation-based burners generally require pressurised gas to produce the atomised spray, which is inconvenient and

expensive (especially because an external power source is required to operate the actuator, such as an air compressor) . In addition, the length of the flame resulting from the momentum of the air varies considerably with the oil feed rate, making it difficult to produce a compact burner. A further known heater comprises a fuel source (in this case, an elevated container of oil) feeding oil to a burner that comprises a helical coil of copper tube with a fuel injector, in the form of a hole, in the tube at one end. A flame is emitted from the fuel injector into the space defined by the helical coil, and combustion may eventually become self-sustaining. However, in order for combustion to be self-sustaining, the oil in the coil has to be heated for a considerable time (10-15 minutes) after ignition by placing the burner in an oven in order to raise the temperature of the fuel oil sufficiently. Further fuel oil burners require the use of wicks in order to maintain a satisfactory amount of light or heat.

The present invention addresses some of the problems of the prior art.

In accordance with a first aspect of the present invention, there is provided a burner suitable for the combustion of fuel oils having a high flash point, the burner comprising a container for the containment of fuel oil and a burner head comprising an evaporation chamber for the heating of fuel oil therein, fluid communication for the transfer of fuel oil being permitted between the container and the evaporation chamber, said evaporation chamber being provided with at least one aperture for the egress of fuel oil for burning, wherein the evaporation chamber is configured such

that, in use, there is sufficient heating of the evaporation chamber from the flame so generated to support self- sustaining combustion of fuel oil.

This provides a burner that may carry on burning by ensuring that the evaporation chamber is heated hence maintaining the vapourisation of fuel therein.

The "flash point" of a fuel refers to the temperature at which vapour given off will ignite when a source of ignition is applied, such as a flame or electric heating element.

The term "fuel oils having a high flash point" is intended to include those oils having a flash point not less than 120°C. Such fuel oils may be derived from biological sources such as oil palm, soya beans, rapeseed, sunflowers and maize. It is believed that the burner of the present invention is unsuitable for the combustion of liquids having a very low flash point, such as petrol or diesel, because such fuels would prove to be an explosive hazard.

The burner may be configured so that, in use, the evaporation chamber is heated by said flame immediately after ignition of the fuel oil to produce sufficient heating of the evaporation chamber from the flame so generated immediately after ignition to support self-sustaining combustion of fuel oil.

Self-sustaining combustion may not be realised immediately after lighting or ignition of the fuel oil. It may be necessary to provide one or both of a heat source for

providing heat to the fuel oil in the evaporation chamber and an ignition source for lighting the fuel oil in order to heat the oil so that it becomes sufficiently hot so as to support self-sustaining combustion. The heat source may, for example, be an electrical heating element. The ignition source may be a source of flame; the flame would reignite the fuel oil in the event that a flame became extinguished and could also be used to heat the fuel oil in the evaporation chamber.

The burner may be arranged so that the flame, in use, is directed so as to heat part of (and preferably the majority of) the evaporation chamber.

The burner may be further arranged so that, in a normal operating position, the at least one aperture is beneath a majority of the evaporation chamber. This is a convenient geometry for facilitating the heating of a large proportion of the evaporation chamber by the flames emitted from the aperture (s) .

The burner may be configured so that, in use, the evaporation chamber (or part thereof) is directly heated by said flame. The direct heating by the flame may be sufficient so that immediately after ignition of the fuel oil to produce sufficient heating of the evaporation chamber from the flame so generated to support self-sustaining combustion of fuel oil. In this case, "directly" means that the flame is in intimate contact with the evaporation chamber. This aids the burner of the present invention to produce self-sustaining combustion, even in the absence of a secondary heat source (such as an oven) .

The burner head may be provided with a flame director, the flame director being arranged so that, in use, a flame emitted from the at least one aperture impinges on the flame director and is directed by the flame director towards or on to the evaporation chamber so as to heat the contents thereof.

The flame director increases the interaction between the flame and the evaporation chamber, thus increasing the vaporisation of fuel oil therein.

It is preferred that the evaporation chamber is provided with a plurality of mutually spaced apertures for the egress of fuel oil for burning. This allows for a distribution of flame to a larger area of the evaporation chamber. It is preferred that there are at least two, three or four apertures for the egress of fuel oil for burning. It is further preferred that there are at least six (and preferably at least eight) apertures for the egress of fuel oil for burning.

One or more of the apertures for the egress of fuel oil may be slit-shaped. Such an aperture may, in use, provide a flame over a large area of the evaporation chamber.

It is preferred that each of the apertures for the egress of fuel oil is associated with at least one, and preferably only one, flame director.

The evaporation chamber may comprise an evaporation chamber main body spaced relative to an aperture-providing portion.

The aperture providing portion comprises the at least one aperture for the egress of fuel for burning. In use, the flames emitted from the apertures impinge on the evaporation chamber main body. The aperture-providing portion is preferably spaced at a distance from the main body so that sufficient mixing of air and fuel takes place to produce a stable blue flame. If the aperture (s) is too close to the main body, then mixing of air and fuel is poor and a sooty, yellow flame is formed; such a flame may be of use when emitted from a lighting burner. It is preferred that, when the burner is in a normal operational orientation, the aperture-providing portion is below the evaporation chamber main body.

The spacing between the aperture-providing portion and the evaporation chamber main body may be from 50% to 250% (preferably from 75% to 200%, more preferably from 75% to 150% and further more preferably from 80% to 110%) of the height of the main body. The height is the dimension of the main body in a substantially vertical direction when the burner is placed on a horizontal surface in an orientation ready for use. For example, if the evaporation chamber main body has a frusto-conical shape, then the height is typically the dimension of the frusto-conical shape in a direction along the axis of the frusto-conical shape.

It has been found that such spacing between the aperture providing portion and the evaporation chamber facilitates the heating of the evaporation chamber main body by relatively hot parts of the flame; the region immediately above an aperture does not appear to contain a hot part of a flame. Therefore, it has been found that if the aperture

providing portion is too close to the evaporation chamber main body, then flames are not incident on the portions of the evaporation chamber main body closest to the aperture providing portion.

It is preferred that the evaporation chamber main body is substantially conical, frusto-conical in shape, or trumpet- shaped. Such a shape provides an effective burner geometry.

If the evaporation chamber main body is substantially conical or frusto-conical in shape, then it is preferred that the base of the cone or frusto-cone is above the apex when the burner is in a normal operational orientation. If the evaporation chamber main body is trumpet-shaped, then it is preferred that, when the burner is in a normal operational orientation, the evaporation chamber main body flares outwardly from a lower portion of the evaporation chamber main body to an upper portion of the evaporation chamber main body (for example, from the bottom to the top of the evaporation chamber main body) . The angle of flare may increase continuously from the lower portion to the upper portion.

Alternatively, the base of the cone or frusto-cone may be below the apex when the burner is in a normal operational orientation. If "the evaporation chamber main body is trumpet-shaped, when the burner is in a normal operational orientation, the evaporation chamber main body may flare outwardly from an upper portion of the evaporation chamber main body to a lower portion of the evaporation chamber main body (for example, from the top to the bottom of the evaporation chamber main body) . The angle of flare may

increase continuously from the upper portion to the lower portion.

A substantial part of the evaporation chamber (such as the evaporation chamber main body, if the evaporation chamber comprises mutually-spaced evaporation chamber main body and aperture-providing portion) may be trumpet-shaped, cylindrical, conical or truncated conical (for example, frusto-conical) in shape (preferably trumpet-shaped, conical or frusto-conical) . Such a substantial part may be heated by the flames emanating from the aperture (s) being incident upon the substantial part. The evaporation chamber may comprise a conduit formed into a desired shape (such as cylindrical, conical, trumpet-shaped, truncated conical or flat spiral) .

The cone angle at the apex of a conical or frusto-conical part of the evaporation chamber may typically be from 75 to 120 degrees.

If the evaporation chamber comprises a conduit, such a conduit is preferably made of a thermally conductive material, such as a metal. It is preferred that the thermally conductive material has a melting point of at least HOO ⁰ C. Examples of such conductive materials include stainless steel and Ni:Cr alloys, such as Ni:Cr 80:20. It is preferred that said thermally conductive material is resistant to the formation of soot thereon i.e. resistant to the build-up of carbon deposits on the metal. Examples of such materials include Ni: Cr alloys. Stainless steel has proved to be susceptible to soot deposition which may cause

closure of the aperture (s). The conductive material is preferably oxidation-resistant up to HOO ⁰ C.

It is preferred that the conduit is thin-walled, having a wall-thickness of no more than 0.8mm, and preferably having a wall-thickness of from 0.2mm to 0.5mm.

If the evaporation chamber comprises a trumpet-shaped, conical or frusto-conical portion (such as when the evaporation chamber comprises an evaporation chamber main body that is trumpet-shaped, conical or frusto-conical in shape) , then at least one of the apertures may be provided so that, in use, flames are emitted at an angle to the axis of the trumpet-shaped, conical or frusto-conical portion (i.e. the flames are not parallel to the axis). It is preferred that the angle between said axis and said flames is from 10° to 50°, preferably from 10° to 40°, and more preferably from 15° to 30°. If the evaporation chamber comprises a conical or frusto-conical portion, it is preferred that the angle between the flame and the axis of the cone or frusto-cone is less than half the cone angle of the cone or frusto-cone. This facilitates effective heating of the cone or frusto-cone by permitting flames to be incident on the sides of an evaporation chamber, with the flames then being directed upwards along the sides of the evaporation chamber.

This may be achieved by forming bores in the evaporation chamber at appropriate angles.

If the evaporation chamber comprises a trumpet-shaped, conical or frusto-conical portion, then at least one of the

apertures may be provided so that the axis of the bore providing the at least one of the apertures is at an angle to the axis of the trumpet-shaped, conical or frusto-conical portion (i.e. the flames are not parallel to the axis of the trumpet-shaped, conical or frusto-conical portion) . It is preferred that the angle between the axis of the bore and the axis of the trumpet-shaped, conical or frusto-conical portion is from 10° to 50°, preferably from 10° to 40°, and more preferably from 15° to 30°. If the evaporation chamber comprises a conical or frusto-conical portion, it is preferred that the angle between the axis of the bore and the axis of the cone or frusto-cone is less than half the cone angle of the cone or frusto-cone. This facilitates effective heating of the cone or frusto-cone by permitting flames to be incident on the sides of an evaporation chamber, with the flames then being directed upwards along the sides of the evaporation chamber.

The burner may further be provided with a heat sink member for placement in proximity to the evaporation chamber or part thereof. The heat sink member is typically made of a thermally conductive material and, in use, is heated by the flames emitted by the burner. Although the applicant does not wish to be bound by the correctness or otherwise of this theory, it is anticipated that the heat sink absorbs and emits heat, and that this emission of heat in proximity to the evaporation chamber helps heat the evaporation chamber, thus aiding evaporation of fuel in the evaporation and thus improving combustion. The heat sink member may comprise perforations to allow passage of air therethrough. The presence of perforations aids combustion. The heat sink member may have a shape corresponding to that of the

evaporation chamber or part thereof. For example, if the evaporation chamber comprises an evaporation chamber main body and an aperture-providing portion, the shape of the heat sink member may correspond to that of the evaporation chamber main body. For example, the heat sink member may be frusto-conical; this is of particular benefit when the evaporation chamber is provided with a frusto-conical portion. It is preferred that the heat sink comprises a mesh; this facilitates simple manufacture and provides perforations for the passage of air therethrough.

It is preferred that, if the evaporation chamber comprises a conduit, then the conduit is formed into an evaporation chamber at least part of which has a trumpet-shape or a truncated conical shape, preferably a truncated conical shape. Such a shape, when used in conjunction with a flame director, produces an effective heater. The length of the conduit forming the truncated conical shape may be about 400 to 1000 times the internal diameter of the conduit.

It has been found that the degree of evaporation of fuel oil is determined, amongst other things, by the volume of the evaporation chamber and the size of the aperture or apertures from which the fuel oil is emitted for combustion. For a given volume of evaporation chamber, a smaller aperture will result in a higher pressure build-up in the evaporation chamber which will generally produce a blue- yellow flame better disposed for heating. A larger aperture will result in a lower pressure build-up in the evaporation chamber which will generally produce a yellow flame better disposed for lighting. The relationship between aperture area and evaporation chamber volume can conveniently be

related to each other by considering the relative ratios of the surface areas of the evaporation chamber and the aperture .

It is particularly preferred that the ratio of the surface area of the evaporation chamber which, in use, may be exposed to flame from fuel oil burnt by the burner, to the total surface area of all of the apertures of the burner from which such flame or flames may emanate is from 2000:1 to 6000:1, more preferably from 3000:1 to 4500:1. Such burners have been found to produce superior heating burners .

It is further preferred that the ratio of the surface area of the evaporation chamber which, in use, may be exposed to flame from fuel oil burnt by the burner, to the total surface area of all of the apertures of the burner from which such flame or flames may emanate is from 500:1 to 1500:1. This is especially beneficial in the production of good lighting burners that burn with a strong yellow flame.

The surface area of the evaporation chamber which, in use, may be exposed to flame from fuel oil burnt by the burner may be provided by one or more outer surfaces of the evaporation chamber. For example, said surface may be provided by an outer surface or surfaces of the main body of an evaporation chamber main body, if the evaporation chamber comprises an evaporation chamber main body and an aperture- providing portion.

For example, if the burner comprises an evaporation chamber main body provided by a conduit formed into a conical or frusto-conical shape, then the surface area of the

evaporation chamber exposed to flame may be half the surface area of the portion of conduit forming the conical or frusto-conical portion.

An evaporation chamber comprising a conduit formed into a substantially flat spiral has been found to produce an excellent light source. In this case, it is preferred that, in use (i.e. when the burner is in a normal operational orientation) , the at least one aperture for the egress of fuel oil is located below the flat spiral. This evaporation chamber therefore provides an evaporation chamber main body (in the form of a substantially flat spiral) and an aperture-providing portion, the aperture-providing portion being located below the evaporation chamber main body when the burner is in a normal operational orientation. The length of the conduit forming the flat spiral may be about 100 to 200 times the internal diameter of the conduit. Such an arrangement is especially beneficial in the production of lighting burners.

The evaporation chamber may comprise a trumpet-shaped, conical or truncated conical body defining a trumpet-shaped, conical or truncated conical volume therein. This is an alternative arrangement to an evaporation chamber formed by a conduit.

It is preferred that, if the evaporation chamber (or part thereof) has a conical or truncated conical shape, then, in use, the apex of said conical or truncated conical shape is below its base. In this case, at least one aperture for the egress of fuel oil may be located towards the apex of the cone or truncated conical shape. It is preferred that each

aperture is located towards the apex of the cone or truncated conical shape. If the evaporation chamber (or part thereof) is trumpet-shaped, then it is preferred that, when the burner is in a normal operational orientation, the evaporation chamber main body flares outwardly from a lower portion of the evaporation chamber main body to an upper portion of the evaporation chamber main body (for example, from the bottom to the top of the evaporation chamber main body) . The angle of flare may increase continuously from the lower portion to the upper portion. It is preferred that each aperture is located at or towards the bottom of the evaporation chamber.

The evaporation chamber may be provided with a means for closing at least one of the apertures. The means for closing at least one of the apertures may be used to partially or fully close the aperture and may comprise a movable collar, The collar may be provided with bores therethrough. Each bore may be associated with an aperture for the egress of fuel oil. The collar may also act as a flame director. The size of the aperture, coupled with the volume of the evaporation chamber, dictates the degree of vapourisation of the fuel oil in the evaporation chamber. Reducing aperture size decreases the flow therefrom of fuel oil, increasing the residence time within the evaporation chamber and therefore increases the degree of vaporisation of fuel oil prior to burning.

A flame director, if present, may comprise a thermally- insulating material, such as ceramic material.

A flame director, if present, may be in the shape of a truncated cone; this is particularly advantageous if the evaporation chamber (or part thereof) is in the shape of a cone or truncated cone. In this case, it is preferred that the flame director extends around at least part of the outer surface of the evaporation chamber (or part thereof) . The part of the evaporation chamber referred to above may be an evaporation chamber main body, if the evaporation chamber comprises an evaporation chamber main body spaced from an aperture-providing portion. Alternatively, the flame director may comprise a hollow cylinder. In this case, at least part (and preferably most and more preferably substantially all) of the evaporation chamber may be disposed within the cavity formed by the hollow cylinder.

Flame directors are particularly advantageous in producing burners that may act as heaters that burn with an intense orange-blue flame. The blue flame is indicative of more complete combustion of the fuel oil (as opposed to a yellow flame which is indicative of incomplete combustion) .

The evaporation chamber may comprise a deformable or moveable element that is deformable or movable under the influence of a change in pressure in the evaporation chamber so as to change the effective volume of the chamber. This helps to maintain a more constant supply of fuel to the apertures for burning, and thus helps maintain a more constant flame. This is particularly useful when a burner is operating as a heating burner. For example, when there is an increase in pressure in the evaporation chamber (say, when fuel oil is being efficiently converted to vapour in the evaporation chamber) , the deformable or movable element may

deform or move so as to increase the effective volume of the evaporation chamber. This increase in volume will act to maintain a constant pressure in the evaporation chamber. This may be desirable because increased pressure in the evaporation chamber may inhibit flow of fuel from the container to the evaporation chamber, which can lead to a flame flickering and becoming unstable.

Alternatively, the element may comprise a sheet of substantially inelastic material that is movable under the influence of a change in pressure in the evaporation chamber. For example, the element may comprise a sheet of inelastic metal material that may "bulge" outwards (relative to the evaporation chamber) under the influence of increased pressure in the evaporation chamber and may return inwards to its original form under the influence of decreased pressure in the evaporation chamber.

It is preferred that a substantial part of the evaporation chamber is conical or truncated conical in shape and that the deformable or movable element (such as a sheet of substantially inelastic material) is provided at the base of the cone or truncated cone. The base of the cone is the widest portion of the cone, not that portion of the cone that is, in use, lowest or closest to the ground. It is preferred that the evaporation chamber comprises a conical or truncated conical body defining a conical or truncated conical volume therein. This is an alternative arrangement to an evaporation chamber formed by a conduit.

The burner may be provided with a pilot light chamber for forming a pilot light. The pilot light may assist in the

lighting of the fuel emitted from the aperture (s) provided in the evaporation chamber. The pilot light chamber is, in use, provided with a flammable material. The pilot light chamber may be in fluid communication with the container so that fuel oil may be provided to the pilot light chamber. The pilot light chamber may be in the form of a conduit. This provides a convenient form of pilot light chamber. The pilot light chamber may be provided with one or more pilot light apertures for egress of fuel oil therefrom. The fuel oil emitted therefrom may be lit to form a pilot light. The pilot light chamber may be arranged so that a flame emitted from the one or more pilot light apertures heats at least a portion of the pilot light chamber so as to encourage evaporation of fuel oil in the pilot light chamber. This improves the stability and intensity of the pilot light flame .

The pilot light chamber may comprise a pilot light chamber main body and a pilot light chamber aperture-providing portion, the pilot light chamber main body being spaced relative to the pilot light chamber aperture-providing portion. It is preferred that, when the burner is in a normal operational orientation, the pilot light chamber main body is above the pilot light chamber aperture-providing portion The pilot light chamber may be of the same geometry as the evaporation chamber of the burner head e.g. conical or frusto-conical . At least part of the pilot light chamber (such as the pilot light chamber main body) is preferably conical or frusto-conical. It is preferred that, when the burner is in a normal operational orientation, the base of the conical or frusto-conical part of the pilot light chamber is below the apex.

A pilot light formed by the pilot light chamber may be used to help heat the evaporation chamber so that combustion of fuel in the burner head becomes self-sustaining.

The pilot light chamber may be provided by a fuel oil collector arranged for the collection of liquid fuel oil emitted from the at least one aperture provided in the evaporation chamber, wherein, in use, said fuel oil may be ignited so as to form a stable pilot light. The fuel oil collector may be in the form of a dish. When the burner is in operating position, the fuel oil collector may be located below the at least one aperture of the evaporation chamber. Liquid oil emitted from the at least one aperture of the evaporation chamber would then fall into the fuel oil collector where it could be burned.

The burner may be provided with a one-way valve arranged to resist backflow of fuel from the burner head to the container. It is believed that the valve helps maintain a stable flame by confining the pressure build-up to the evaporation chamber therefore inhibiting the interruption of the flow of fuel into the evaporation chamber.. Furthermore, the valve may preferably be placed proximate (in terms of the flow path of fuel) to the burner head.

The container may be provided with a quantity of a fuel oil having a high flash, point. The fuel oil may have a flash point of at least 120 ⁰ C, or preferably at least 200 ⁰ C, or more preferably at least 250 ⁰ C.

1

The container may, in use, be located above the evaporation chamber so that fuel oil may be transmitted by gravity from the container to the evaporation chamber.

The container may be pressurised or capable of delivering fuel oil at a positive pressure.

The container may comprise a receptacle for the containment of fuel oil, the receptacle being compressible in use, and a compressor for exerting force on the compressible receptacle so that, in use, fuel oil may be urged from the receptacle to the evaporation chamber. Such a receptacle may not be compressible when not in use, for example, if the receptacle is sealed prior to use. The receptacle may be compressible along a longitudinal axis. The receptacle may be compressible along substantially its whole length. Compressibility during use may be achieved, for example, by providing a series of alternate ridges and troughs spaced along the length of the receptacle. Such ridges and troughs may advantageously extend circumferentially around the receptacle.

Alternatively, the receptacle may comprise a flexible bag, such as a bag made from plastics material.

The compressor may comprise two mutually spaced compression surfaces, the receptacle being located between said surfaces, the spacing of which may be varied so as to vary the compression force on the receptacle. This allows the user to control the rate of flow of the oil from the receptacle, and thus the rate of fuel use and flame intensity. It is preferred that the spacing of said

compression surfaces may be fixed at any of a plurality of different values, for example, by providing the compressor with a screw thread.

In order to vary the spacing of the compression surfaces, the compressor may comprise a two-part housing with which the receptacle is associated, and preferably housed within. Each parts of the housing may be provided with a formation that engages with a corresponding formation on the other part of the housing, such as a screw thread. Alternatively, the first part of the housing may be provided with a projection that is locatable in a plurality of apertures provided in the second part of the housing.

The compressor may be provided with a bias means that, in use, is capable of exerting a compressive force on the receptacle. The bias means may be a compression spring, such as a helical coil spring. If the compressor comprises a two- part housing, then the bias means may be located between the housing and the compressible receptacle.

The burner may comprise a plurality of burner heads. At least two of the plurality of burner heads may be provided with a common fuel source (that is, fuel oil may be provided from one container or canister) . A burner with more than one burner head may be provided with a reservoir in the fluid path between the container and said burner heads. The reservoir permits the use of only one conduit from the container to the reservoir, rather than providing a conduit directly from the container to each burner head. The plurality of burners may form an array, such as a linear or circular array. One or more such arrays may be used as a

cooking stove or lighting source, depending on the nature of the burner. For example, a heater may comprise two arrays, each associated with different containers of fuel oil. In this case, it is preferred that the two arrays are concentrically arranged.

In accordance with the present invention, there is provided a heater comprising a burner in accordance with the present invention. The heater may be a water heater, the water heater further comprising a heat exchanger arranged such that, in use, heat from said burner provides heat to the heat exchanger. The water heater preferably comprises a plurality of heat exchangers, each heat exchanger being associated with a burner. It is further preferred that each burner is associated with only one heat exchanger. The heat exchangers may be arranged in series . The water would then be heated each time it passed through a heat exchanger.

In accordance with the present invention there is provided a lamp comprising a burner in accordance with the present invention. The lamp may further comprise a shield to protect the flame so produced in use from the effects of wind.

Further in accordance with the present invention, there is provided a stove comprising a burner in accordance with the present invention. The stove may additionally comprise a platform for the support of cooking receptacles during cooking. The stove may comprise a first array of burners in accordance with the present invention. Alternatively or additionally, the stove may comprise a burner in accordance with the present invention, the burner comprising a first array of burner heads. This allows one fuel source to supply

fuel to more than one burner head. The stove may further comprise a second array of burners in accordance with the present invention. Alternatively or additionally, the stove may comprise a second burner in accordance with the present invention, the second burner comprising a second array of burner heads. The burners or burner heads of the first array may be arranged in a generally circular manner, and the burners or burner heads of the second array may be arranged in a generally circular manner, preferably concentric with the first array.

A second aspect of the present invention provides a burner head suitable for use as the burner head of the burner according to the first aspect of the present invention.

A third aspect of the present invention provides a method of generating heat and/or light comprising;

(i) providing a burner comprising a source of fuel oil having a high flash point and an evaporation chamber provided with an aperture therein for the egress of fuel oil therefrom

(ii) urging fuel oil into the evaporation chamber and out of the aperture

(iii) igniting the fuel oil emitted from the aperture, wherein the evaporation chamber is configured such that there is sufficient heating of the evaporation chamber from the flame so generated to support self-sustaining combustion of said fuel oil.

"High flash point" is understood to mean a flash point of at least 120°C. Preferably the flash point of the fuel oil is at least 15O ⁰ C, more preferably at least 200 ⁰ C, and further

more preferably at least 25O ⁰ C. Preferably, the flash point of the fuel oil is up to 450 "C and more preferably up to 400°C.

The burner used in the method of the third aspect of the present invention may comprise the burner in accordance with the first aspect of the present invention, and hence may comprise those features of the burner described with reference to the burner of the first aspect of the present invention.

The fuel oil preferably comprises a vegetable oil, such as rape seed oil or palm oil.

The fuel oil may comprise one or more of a perfuming agent, an insect repellent and a flame-colouring agent.

A fourth aspect of the present invention provides a container for the controllable delivery of fuel oil to a burner, the container comprising a receptacle for the containment of fuel oil, the receptacle being compressible in use, the container comprising an outlet for the egress of fuel oil and a compressor for exerting force on the compressible receptacle so that, in use, fuel oil may be urged from the receptacle to the evaporation chamber, wherein the compressor comprises two mutually spaced compression surfaces, the receptacle being located between said surfaces, the spacing of which may be varied so as to vary the compression force on the receptacle, and fixable in any one of a plurality of different spacings .

The container of the fourth aspect of the present invention may comprise those features of the container described with reference to the burner of the first aspect of the present invention.

The present invention is now described by way of example only by reference to the following figures of which: Figure 1 is a sectional view of a burner according to a first example of an embodiment of the present invention; Figure IA is a cross-sectional view of the burner head taken along line AA of Figure 1;

Figure 2 is a cut-away view of an alternative burner head for use in a burner of the present invention; Figure 2A is a plan view of the burner head of Figure 2; Figure 2B is a view of a further alternative burner head for use in a burner of the present invention;

Figure 3 is a side-on view of a further alternative burner head for use in a burner of the present invention; Figure 3A is a plan view of the burner head of Figure 3; Figure 4 is a plan view of a heating device comprising an array of the burner heads of Figures 1 and IA arranged to produce a high capacity burner;

Figure 4A is a sectional view taken along line BB of Figure 4, showing the fuel supply lines to the burner heads; Figure 5 is a schematic diagram showing a heat exchanger comprising several burners in accordance with the present invention;

Figure 5A is a section taken along line CC of Figure 5 and depicts a suitable layout of a heat conducting pipe for use in the heat exchanger of Figure 5;

Figure 6 is a plan view of a burner in accordance with the present invention comprising a plurality of burner heads;

Figure 7 shows a plan view of a cooking stove comprising a burner in accordance with the present invention, the burner comprising a plurality of burner heads;

Figure 7A is a sectional view taken along line DD of Figure 7 and shows the arrangement used to supply fuel to the burner heads;

Figure 8a is a plan view of a further alternative burner head for use in a burner of the present invention;

Figure 8b is a side view of the burner head of Figure 8a; Figure 9a is a plan view of a further alternative burner head for use in a burner of the present invention;

Figure 9b is a side view of the burner head of Figure 9a;

Figure 10a is a plan view of a further alternative burner head for use in a burner of the present invention; Figure 10b is a side view of the burner head of Figure 10a;

Figure 11 is a side view of part of a further alternative burner comprising an alternative pilot light arrangement; and

Figure 12 shows several alternative evaporation chamber main bodies of a trumpet shape that may be used in the burner of the present invention.

Figure 1 shows a burner in accordance with a first example of an embodiment of the present invention, the burner 1 comprising a container 2 for the containment of fuel oil 7 and a burner head 20 comprising an evaporation chamber 3 for the heating of fuel, oil therein, wherein fluid communication is permitted for the transfer of fuel oil between the container 2 and the evaporation chamber 3, said evaporation chamber 3 being provided with at least one aperture 4 for ' the egress of fuel oil for burning, wherein the evaporation chamber is configured such that, in use, after an initial

warming-up period of about 1 or 2 minutes, there is sufficient heating of the evaporation chamber from the flame so generated to support self-sustaining combustion of fuel oil. The evaporation chamber 3 comprises a metal cone 22 provided with a cover 21 that defines the volume of the evaporation chamber and prevents unwanted loss of fuel oil therefrom. The evaporation chamber 3 is provided with four apertures (one of which is labelled "4") spaced around the evaporation chamber 3 as shown in Figures 1 and IA to permit egress of fuel oil from the evaporation chamber 3. The metal cone 22 is provided with a screw thread (not shown) that allows the attachment and removal of the evaporation chamber onto, and from, conduit 5 that carries fuel oil to the evaporation chamber 3. The burner head 20 comprises a flame director 16 in the form of a frusto-conical skirt that extends circumferentially around the (lower) portion of the metal cone 22 that comprises apertures 4. In use, oil is supplied from container 6 to the evaporation chamber 3 via conduit 5. The oil is emitted from apertures 4 in the lower part of the metal cone 22 out of the evaporation chamber 3. An external ignition source, such as a match, or electrical heating element is placed adjacent or near to one or more of the apertures 4 to heat the evaporation chamber 3 and to cause the fuel oil to ignite. The flames so emitted from the apertures 4 are initially directed outwards from the metal cone 22 but impinge on the flame director 16 which is arranged to direct the flame towards and around the metal cone 22. In this manner, the flame generated by the burning of the fuel oil is directed towards and around the evaporation chamber 3. This causes evaporation of the fuel oil in the evaporation chamber 3 and thus increases the ease with which the fuel oil burns. The whole combustion process

is self-sustaining, after the initial warming-up period, and there is thereafter no need to provide a second heat source to heat the oil. During the warming-up period, an additional heat source such as the flame from a match has to be applied to the evaporation chamber because, in the absence of such a secondary heart source the fuel oil emitted from the apertures 4 will not stay lit. The secondary heat source reignites fuel oil emitted from the apertures 4 and serves to heat the evaporation chamber, thus increasing evaporation of oil within the chamber. After a certain period, the degree of evaporation in the evaporation chamber and the heat generated by the flame will be sufficient to give self- sustaining combustion, and the secondary heat source may be removed.

The cover 21 is made of a substantially inelastic deformable material (in this case, metal) that may be deformed under the influence of a change in pressure in the evaporation chamber 3, said deformation changing the effective volume of the chamber 3. For example, for any given quantity of fuel oil, if the degree of evaporation in the evaporation chamber 3 is increased, then the volume of given quantity of fuel oil is increased. In the absence of a deformable cover, this expansion will increase the pressure of fuel oil vapour being emitted from the apertures 4 but will also inhibit ingress of fuel oil into the evaporation chamber 3 from the conduit 5. This will lead to poor delivery of fuel oil to the evaporation chamber 3, leading to a flame that has a tendency to vary in intensity over time. The cover 21 is deformable and so helps mitigate against this problem. When the degree of evaporation in the evaporation chamber (and consequently the pressure) is high, the deformable cover 21

is blown outwards, away from the metal cone 22. This increases the volume of the evaporation chamber 3, thus reducing the back-pressure effect that may prevent fuel oil from entering the evaporation chamber 3 from the conduit 5.

The flame director 16 is part of a component that is provided with a screw thread that mates with a corresponding screw thread provided on one end of the conduit 5. Rotation of the component on the conduit's screw thread causes the flame director 16 to be moved towards or away from the metal cone 22. The flame director 16 may be moved into contact with the metal cone 22, thus effectively preventing emission of fuel oil from the evaporation chamber 3, and therefore turning-off the burner 1.

The surface area of the curved (conical) surface of metal cone 22 that forms the evaporation chamber 3 is about 80000 times greater than the surface area of each aperture 4. The surface are of the curved (conical) surface of the cone (i.e. that which may be exposed to flames emanating from the apertures 4) is about 20000 times greater than the total surface area of the four apertures 4. The small aperture size (for the given size of evaporation chamber 3) results in a burner that, when lit, will generate a relatively high oil vapour pressure at the apertures 4, the oil burning with an intense orange-blue flame. This was found to be an effective burner, but it was found that effectiveness could be increased by increasing the size of the apertures. For example, in a further embodiment, the total surface area of the apertures 4 is larger such that the surface area of the metal cone 22 that is, in use, exposed to flames is about 5000 times the total surface area of the apertures 4. This

produces a more efficient burner than previously described. The flame is blue, indicating more complete combustion, and is more intense than the orange-blue flame generated when using smaller apertures.

Those skilled in the art should realise that the fuel oil may be supplied to the burner head in any manner. For example, it is conventional to locate the fuel oil container above the burner head so that fuel oil is delivered to the burner head under the influence of gravity. Such an arrangement may be inconvenient, cumbersome and unsafe.

In the present example of an embodiment of the burner in accordance with the present invention, the fuel oil is supplied to the burner head 20 by virtue of a container 2 comprising a receptacle β for the containment of fuel oil, the receptacle being compressible in use, and a compressor for exerting force on the compressible receptacle so that, in use, fuel oil may be urged from the receptacle to the evaporation chamber. The compressor comprises upper 9 and lower 10 sections of a housing, each section being provided with matching screw threads 15a and 15b respectively that allow the separation of surface 23 and surface 24 to be altered. The compressible receptacle 6 is in the form of a plastic canister provided with a series of alternate troughs 12 and ridges 13. The troughs and ridges allow the canister to be compressed. The compressor further comprises a compression spring 8 positioned between the lower section 10 of the housing and the plastic canister and arranged so as to exert a compressive force on the plastic canister. The plastic canister is provided with a neck 11 into which may be inserted conduit 5 to allow passage of fuel oil to the

burner head 20. In use, the plastic canister which is at least partially filled with fuel oil is placed on top of compression spring 8 which itself abuts onto surface 24 in the lower section 10 of the housing. The upper section 9 of the housing is then placed on top of the plastic canister and screwed onto the top of the lower section 10 of the housing so that the canister abuts against surface 23. Conduit 5 is inserted into neck 11 to allow flow of fuel oil to the burner head 20. The upper section 9 of the housing is then rotated relative to the lower section 10 so as to decrease the distance between surface 23 and surface 24 which dictates the space to be occupied by the compression spring 8 and the plastic canister. This compresses the compression spring, increasing the force on the compressible receptacle 6. This causes compression of the plastic canister and causes fuel oil to flow out of the receptacle, through the conduit 5 and into the evaporation chamber 3. An ignition source placed in the vicinity of the apertures 4 will cause the fuel oil to light and stay lit as described above. The flow rate of fuel oil from the apertures may be altered by turning the two sections 9, 10 of housing so as to alter the distance between surface 23 and surface 24 and thus alter the force on the compression spring 8. For example, the burner may be turned off by turning the two sections 9, 10 of housing to decrease the force on the compression spring 8, which in turn decreases the force acting on the plastic canister, thus reducing the supply of fuel oil to the burner head 20. Altering the flow rate of fuel from the apertures will obviously have an effect on the size of the flame generated (and thus the amount of heat and light produced) .

The size of the apertures 4 dictates, inter alia, the pressure that builds up inside the evaporation chamber 3. For a given volume of evaporation chamber, small apertures result in a high pressure build up, resulting in biofuel vapour escaping from the apertures in the form of turbulent jets. Upon ignition, these vapour jets form intense blue and orange flames that are suitable for heating.

For a given size of aperture 4, the volume of evaporation chamber 3 also dictates the sort of flame that will be discharged from apertures 4. Large evaporation chambers aid the complete vapourisation of fuel oil, leading to more complete combustion of the fuel, generating a flame that is intense and suitable for heating.

Decreasing the size of the evaporation chamber and increasing the size of the apertures reduces the degree of vapourisation of the fuel oil before combustion, leading to incomplete combustion, which generates a yellow flame that is suitable for lighting.

The container of Figure 1 may be replaced by other containers, for example, a hand pressurised pump such as those used to spray liquids over garden plants (e.g. pressure sprayers provided by Hozelock, UK) .

Figures 2 and 2A show another example of a burner head 30 of a burner in accordance with the present invention. The burner head 30 comprises an evaporation chamber 33 in the form of tube formed into a conical spiral, a large proportion of which is located in the interior of a hollow ceramic cylinder that forms a flame director 36. The

evaporation chamber 33 is provided with two apertures 34 located towards the bottom of the spiral. The apertures 34 are provided by drilling bores through the walls of the tube, the bores being angled so that, in use, the body of the flame will come into contact with a large surface area of the evaporation chamber. In use, fuel oil is supplied from a container as described with reference to Figure 1 via conduit 5 into the evaporation chamber 33. Fuel is emitted through apertures 34 for burning. On ignition, the flames so produced rise and heat the evaporation chamber to encourage vaporisation of fuel oil within the evaporation chamber 33. The cylindrical flame director 36 assists in keeping the flame in the vicinity of the evaporation chamber 33 and thus increases the thermal contact between the flame and the evaporation chamber 33, ensuring that the fuel oil will burn in a self-sustainable manner after the fuel has been ignited. Note that the internal bore of the tube that forms the evaporation chamber is large compared to that of the conduit 5 used to supply the fuel to the evaporation chamber 33. This gives the evaporation chamber 33 a relatively high volume. The relatively high volume of the evaporation chamber 33 and the relatively small size of the apertures 34 enable the burner to produce an intense orange-blue flame that is of use in heating.

The tube used in the burner of Figures 2 and 2A is copper tube with an internal diameter of 2mm. The length of tube that effectively forms the evaporation chamber 3 is about 300mm, giving an evaporation chamber 33 with a volume of about 1000mm ³ and a surface area of about 1900mm ² . The geometry of the evaporation chamber is such that the surface area of the evaporation chamber that may be exposed to flame

emanating from the apertures is about a half of the total surface area of the evaporation chamber i.e. about 950mm ² . The diameter of each of the apertures 34 is about 0.1mm, the ratio of the area of an aperture to the area of the evaporation chamber 33 that may be exposed to flames being of the order of 1:120,000. The evaporation chamber is provided with four apertures 34 and hence the ratio of the total area of the four apertures to the surface area of the evaporation chamber 33 that may be exposed to flames is of the order of 1:30000. The small aperture size (for the given size of evaporation chamber 33) results in a burner that, when lit, will generate a relatively high pressure at the apertures 34, the fuel oil vapour burning with an intense orange-blue flame. The flame was, however, prone to flicker and the generation of smoke, indicating that combustion was incomplete. It is believed that the small apertures produced relatively small flames that could not provide sufficient heat to ensure full vaporisation of fuel oil in the evaporation chamber.

A further alternative embodiment of the present invention is now described with reference to Figures 2 and 2A. The evaporation chamber 33 may be provided with eight (as opposed to two) apertures for the egress of fuel oil, each aperture having a diameter of about 0.4mm. A one-way valve may be placed in the fluid path between the evaporation chamber 33 and the fuel container. This valve prohibits back-flow of fuel into the container which can cause a drop in pressure in the evaporation chamber, which leads to poor flame characteristics. The tube forming the evaporation chamber 33 may be Nichrome alloy, having an internal diameter of 2mm and a wall thickness of 0.5mm. The length of

tube that effectively forms the part of the evaporation chamber that is, in use, exposed to flames generated by the burning fuel oil, is about 850mm, giving an evaporation chamber with a volume of about 2600mm ³ and an external surface area of about 7800mm ² . The surface area of the evaporation chamber that is, in use, exposed to flames is about 3900mm ² .

This may be calculated as follows: the total surface area of the evaporation chamber formed by the cylindrical tube is

(πdl) , where d is the external diameter of the tube and 1 is the length; in this case, the total surface area of the evaporation chamber is about 7800mm ² . The geometry of the evaporation chamber is such that about half of the external surface of the evaporation chamber is exposed to flames during use of the burner, and hence the surface area of the evaporation chamber that is, in use, exposed to flames is about 3900mm ² .

Each of the eight apertures has a surface area of πr ² , where r is the radius of the aperture. In this case, r=0.2mm; the surface area of each aperture is about 0.12mm ² ; the total surface area of the eight apertures is therefore about lmm ² .

The surface area of the evaporation chamber that is, in use, exposed to flames is about 3900 times greater than the total surface area of the eight apertures. Such an arrangement provides an effective burner. It should be noted that when the burner is operating normally (i.e. after the initial start-up phase) , the flames emitted from the apertures extend above the top of the conical portion of the evaporation chamber.

Figure 2B shows a further embodiment of a burner head of a burner in accordance with the present invention. Rather than being part of a spiral configuration as is shown in Figures 2 and 2A, the portion 38 of evaporation chamber 33 comprising apertures 34 in the burner head of Figure 2B extend downwards in a substantially vertical manner. Again, the apertures 34 would be provided by drilling bores through the walls of the tube, the bores being angled so that, in use, the body of the flame will come into contact with a large surface area of the evaporation chamber. Furthermore, a fuel oil collector 39 is provided below the apertures 34. This collects liquid fuel oil emitted from the apertures 34. This liquid fuel oil may be lit, when the heater is cold, to form a pilot light. The pilot light may be used (optionally with the assistance of a further heat source, such as an electrical heating element) to heat the evaporation chamber during the warming-up period until full self-sustaining combustion can be maintained. The ratio of the surface area of the evaporation chamber to the surface area of one of the apertures 34 is about 240,000:1.

In a further embodiment, the total surface area of the apertures is larger than described above in relation to Figure 2B such that the surface area of the evaporation chamber that is, in use, exposed to flames is about 4000 times the total surface area of the apertures. This produces an efficient burner.

Figures 3 and 3A show another example of a burner head 40 of a burner in accordance with the present invention. The burner head 40 comprises an evaporation chamber 43 in the

form of a flat spiral with a downwardly extending appendage 45. The appendage 45 is substantially of a J shape, with an aperture 44 provided on the upper surface of an upturned end section 46. In use, fuel oil is supplied from a container as described with reference to Figure 1 via conduit 5 into the evaporation chamber 43. Fuel is emitted through aperture 44 for burning. On ignition, the flames so produced rise and heat the evaporation chamber to encourage vaporisation of fuel oil within the evaporation chamber. This ensures that the fuel oil will burn in a self-sustainable manner after the fuel has been ignited. Note that, in contrast to the burner head 30 of Figures 2 and 2A, the internal bore of the tube that forms the evaporation chamber 43 is the same size as the conduit 5 used to supply the fuel to the evaporation chamber 43 (0.5mm internal bore). This gives the evaporation chamber 33 a relatively low volume and low surface area. Furthermore, the aperture 44 is relatively large, having a diameter corresponding to the bore of the conduit. The relatively large size of the aperture 44 (for a given size of evaporation chamber) enables the burner to produce a yellow flame that is of use in lighting. The diameter of the flat spiral arrangement of the evaporation chamber 33 at its largest point is typically 5-lOmm, and aperture 44 is located about 5-10mm below evaporation chamber 43 in the operating position. The ratio of the surface area of the evaporation chamber 33 to the surface area of the aperture 44 is about 650:1.

A further example of a burner in accordance with the present invention is shown in Figures 4 and 4A. The burner 50 comprises an array of burner heads 20a-j being supported by support plate 51. Each burner head 20a-j is essentially the

same as the burner head described with reference to Figures 1 and IA. Only one of the burner heads 20a is labelled to show the components described with reference to Figures 1 and IA. Each burner head 20a-j is supplied by a conduit (shown as 55a-e in Figure 4A) extending into a communal fuel reservoir 52 which in turn is fed by a fuel supply arrangement as described with reference to Figures 1 and IA. The use of the communal fuel reservoir overcomes the need for each burner head 20a-j to be supplied with an individual fuel supply container or arrangement as described with reference to Figures 1 and IA. The support plate 51 provides support for the burner heads 20a-j and is shaped to provide cylindrical shields shown as 5βa-e in Figure 4A. These shields help prevent flames from being extinguished by wind and help contain flames in the vicinity of the evaporation chambers of the individual burner heads 20a-j and thus aid the self-sustaining nature of the combustion process. An external ignition source would be required to light each of the individual burners 20a-j, and this may conveniently be provided by a match flame or an electrical heating element.

Several of the burners described with reference to Figures 4 and 4A may be incorporated into a hot water heater suitable for domestic or industrial water heating as shown in Figure 5. The arrows indicate the direction of water flow in the water heater. Each burner 50a-c is associated with a respective heat exchanger 60a-c. Water passes through heat exchanger 60a and is subject to any heating provided by burner 50a. The water then passes to heat exchanger 60b and is subject to any heating provided by burner 50b, and then passes to heat exchanger 60c where it is subjected to heating provided by burner 50c before being used or stored.

In this manner, the temperature of the water may be altered by controlling the burners 50a-c. Each heat exchanger βOa-c comprises a winding metal tube having an arrangement as shown in Figure 5A.

Alternative burner arrangements are possible such as that shown in Figure 6. Several burner heads 70a-f are arranged in a circular manner in a support plate 71. Each burner head 70a-f corresponds to the burner head 20 described with reference to Figures 1 and IA. Support plate 71 is shaped to provide a shield (not shown) for each burner head 70a-f, the shields being the same as those described with reference to Figures 4 and 4A.

A further alternative burner arrangement is shown in Figures 7 and 7A. Burner heads 80a-h are formed in a first circular array 82 around a second circular array 83 of burner heads 8Oi-I, the burner heads 8Oa-I corresponding to the burner head 20 described with reference to Figures 1 and IA and being supported by support plate 81. Support plate 81 is shaped to provide a shield (not shown) for each burner head 8Oa-I, the shields being the same as those described with reference to Figures 4 and 4A. The burner heads of the first 82 and second 83 circular arrays are connected to first 84 and second 85 sources of fuel oil respectively. The provision of separate sources of fuel oil means that the burner heads of the first 82 and second 83 circular arrays are operable separately from each other. Lighting of the second array 83 would result in a low heat, the first array 82 would result in a medium heat and both the first 82 and second 83 arrays would result in a high heat.

The canister may be discarded after use or recharged with fuel oil for subsequent use, depending on whether the compression of the canister is reversible. The compressible receptacle may take a form other than a plastic canister. For example, the canister may be made from metal.

Alternatively, the compressible receptacle may comprise a bag made of plasties material.

It was observed during operation of the burners of Figures 2, 2a and 2b that the region immediately above an aperture was "cold" in that the flame was not developed in that region. It therefore proved to be beneficial to increase the spacing between the aperture-providing portion of the evaporation chamber and the portion of the evaporation chamber heated by the flames. The burners of Figures 8 to 11 show such an increased spacing and further improved performance .

Figures 8a and 8b show another example of a burner head 100 of a burner in accordance with the present invention. The burner head 100 comprises an evaporation chamber 103 comprising an evaporation chamber main body 103a and an aperture-providing portion 103b, the aperture providing portion 103b being spaced apart from the main body 103a. The evaporation chamber 103 is formed from a tube of Ni: Cr alloy, with a wall thickness of 0.5mm and an internal diameter of 2mm. The evaporation chamber main body 103a is conical in shape, with the apex of the cone above the base.

The diameter of the base of the truncated cone is about 35mm. The height of the truncated cone is about 20mm. The

distance between the base of the cone and the aperture providing portion 103b is about 15mm.

The aperture providing portion 103b is substantially annular in shape and is provided with five apertures (each of about 0.4mm diameter), two of which are labelled 104. The apertures 104 are provided by drilling bores through the walls of the tube, the bores being angled so that, in use, the body of the flame will come into contact with a large surface area of the evaporation chamber. The spacing between adjacent apertures 104 is about 10mm. The cone angle (labelled "θ" in Figure 8b) at the projected apex of the truncated cone is 80°. The axis of the cone is shown as a broken line.

In use, fuel oil is supplied from a container as described with reference to Figure 1 via conduit 105 into the evaporation chamber 103. Fuel is emitted through apertures 104 for burning. On ignition, the flames so produced rise and heat the evaporation chamber to encourage vaporisation of fuel oil within the evaporation chamber 103.

The conduit 105 is provided with a one-way valve 106 for resisting backflow of fuel from the burner head to the fuel container. Such backflow occurs as a result of a build-up of vapour pressure in the evaporation chamber. This helps maintain a stable flame which flickers less than in the absence of the valve.

Figures 9a and 9b show another example of a burner head 110 of a burner in accordance with the present invention. The burner head 110 comprises an evaporation chamber 113

comprising an evaporation chamber main body 113a and an aperture-providing portion 113b, the aperture providing portion 113b being spaced apart from the main body 113a. The evaporation chamber 113 is formed from a tube of Ni: Cr alloy, with a wall thickness of 0.5mm and an internal diameter of 2mm. The evaporation chamber main body 113a is frusto-conical in shape, with the apex of the cone being located below the base. The cone angle (analogous to "θ" shown in Figure 8b) is 100°.

The burner is further provided with a heat sink member 117 comprising a metal mesh formed in a frusto-conical shape. The heat sink member is, in use, located close to the evaporation chamber main body 113a.

The aperture providing portion 113b is substantially annular in shape and is provided with eight apertures, two of which are labelled 114. The apertures 114 are each of 0.4mm diameter and are provided by drilling bores through the walls of the tube, the bores being angled so that, in use, the body of the flame will come into contact with a large surface area of the evaporation chamber.

In use, fuel oil is supplied from a container as described with reference to Figure 1 via conduit 115 into the evaporation chamber 113. Fuel is emitted through apertures 114 for burning. On ignition, the flames so produced rise and heat the evaporation chamber main body 113a to encourage vaporisation of fuel oil within the evaporation chamber 113. The bores through the conduit forming apertures 114 are angled at about 20-30 degrees to the axis of the cone so that flames emanating from the apertures are incident on the

lower part of the evaporation chamber main body, and are directed up the sides of the evaporation chamber main body. This provides a convenient geometry for heating the fuel oil. The flames also heat the heat sink member 117. A better quality flame is produced when the heat sink member is in position compared to when the heat sink member is absent. The heat sink member 117 is seen to become very hot and glow red. It is believed that the radiation of heat from the heat sink member 117 provides heat to the evaporation chamber main body 113a and that this assists in confining heat to the vicinity of the evaporation chamber therefore improving the combustion process. This has the effect of providing a flame that is less subject to flickering than in the absence of the heat sink member 117. The heat sink member 117 is particularly of use when the flames are not optimally incident on the main body of the evaporation chamber. This may occur, for example, if the apertures have not been formed at the optimal angle in the tube.

The conduit 115 is provided with a one-way valve 116 as described in relation to Figures 8a and 8b.

The distance between an aperture 114 and the closest part 113c of the evaporation chamber main body 113a is about the height of the evaporation chamber main body 113a. This has proved to be an effective burner head geometry.

Figures 10a and 10b show another example of a burner head 120 of a burner in accordance with the present invention. The burner head 120 comprises an evaporation chamber 123 comprising an evaporation chamber main body 123a and an aperture-providing portion 123b, the aperture providing

portion 123b being spaced apart from the main body 123a. The evaporation chamber 123 is formed from a tube of Ni: Cr alloy, with a wall thickness of 0.5mm and an internal diameter of 2mm. The evaporation chamber main body 123a is frusto-conical in shape, with the apex of the cone being located below the base. The burner is further provided with a heat sink member 127 comprising a metal mesh formed in a frusto-conical shape. The heat sink member is, in use, located close to the evaporation chamber main body 123a.

The aperture providing portion 123b is a substantially vertical portion of tube is provided with eight apertures, one of which is labelled 124. The apertures 124 are provided by drilling bores of about 0.4mm diameter through the walls of the tube, the bores being angled so that, in use, the body of the flame will come into contact with a large surface area of the evaporation chamber main body 123a.

The burner head is further provided with a fuel oil collector 129 for providing a pilot light.

In use, fuel oil is supplied from a container as described with reference to Figure 1 via conduit 125 into the evaporation chamber 123. Fuel is emitted through apertures 124 for burning. Initially, the evaporation chamber 123 is cold and the fuel oil is emitted from the apertures 124 as liquid fuel oil. This liquid falls into the fuel oil collector 129. The pilot light may be used (optionally with the assistance of a further heat source, such as an electrical heating element) to heat the evaporation chamber during the warming-up period until full self-sustaining combustion can be maintained.

On ignition of fuel oil at the apertures, the flames so produced rise and heat the evaporation chamber main body 123a to encourage vaporisation of fuel oil within the evaporation chamber 123, essentially as described with reference to the burner head of Figures 9A and 9B. The flames also heat the heat sink member 127. A better quality flame is produced when the heat sink member is in position compared to when the heat sink member is absent. The heat sink member 127 is seen to become very hot and glow red. It is believed that the radiation of heat from the heat sink member 127 provides heat to the evaporation chamber main body 123a and that this assists in providing a flame that is less subject to flickering than in the absence of the heat sink member 127. The heat sink member 127 is particularly of use when the flames are not optimally incident on the main body of the evaporation chamber. This may occur, for example, if the apertures have not been formed at the optimal angle in the tube.

The conduit 125 is provided with a one-way valve 126 as described in relation to Figures 8a and 8b.

The distance between an aperture 124 and the closest part 123c of the evaporation chamber main body 123a is about the height of the evaporation chamber main body 123a. This has proved to be an effective burner head geometry.

Figure 11 shows an alternative burner in accordance with the present invention. The burner shown generally by reference numeral 300 comprises a burner head 110 having the features as described above with reference to Figures 8a and 8b. The

features bearing reference numerals are the same as those features having the same reference numerals in Figures 8a and 8b. The burner 300 further comprises a pilot light chamber 203 comprising a pilot light chamber main body 203a in the form of a cone and a pilot light chamber aperture- providing portion 203b. The pilot light chamber aperture- providing portion 203b is provided with 4 apertures for the egress of fuel oil for burning. The pilot light chamber aperture-providing portion 203b is located approximately 13mm below the pilot light chamber main body 203a. The height of the pilot light chamber main body 203a is about 7mm. The pilot light chamber is formed from a Ni : Cr conduit. The base of the cone is about 21mm in diameter. A conduit 205 is provided to facilitate fluid communication with a container of fuel oil so that fuel oil may be supplied to the pilot light chamber.

The pilot light chamber 203 is located close to the aperture-providing portion 113b of the evaporation chamber 113a of the burner head 110.

The operation of the burner of Figure 11 will now be described. Oil is supplied to the pilot light chamber and the chamber is lit using a match. The flames emanating from the apertures 204 are incident upon (and heat) the pilot light chamber main body 203b. This causes evaporation of fuel oil in the pilot light chamber, which leads to the fuel oil being more readily burned and an increase in flame size. The flame rises approximately through the centre of the conical pilot light chamber main body 203a and heats the aperture providing portion 113b of the evaporation chamber 113a of the burner head 110.

Fuel oil is then supplied to the evaporation chamber 113a of the burner head. This flame from the pilot light encourages evaporation of fuel oil in the evaporation chamber 113a of the burner head 110, making the fuel oil emitted at the apertures 114 easier to light. Once the burner head is sufficiently well-lit, the supply of fuel oil to the pilot light chamber 203 may be terminated.

Those skilled in the art will realise that Figure 11 is not to scale; the burner head 110 is larger than the pilot light chamber 203.

In each of the burners shown in Figures 8 to 11 the surface area of the evaporation chamber main body that is, in use, exposed to flame is about 4000 times greater than the total surface area of the apertures.

Figures 8, 9, 10 and 11 demonstrated burners comprising evaporation chamber main bodies, each main body having a substantially conical or frusto-conical shape. Figure 12 shows three evaporation chamber main bodies (denoted "B" in each case), each having a trumpet shape. Each main body has a lower portion (denoted ^Nλ L") that, when the burner is in a normal operational position, is below an upper portion

(denoted "U") . The axis of each evaporation chamber main body is denoted by a broken line labelled "A". The evaporation chamber main body flares outwardly in a direction from the lower portion of the evaporation chamber main body to the upper portion of the evaporation chamber main body. The angle of flare may increase continuously from

the lower portion of the evaporation chamber main body to the upper portion of the evaporation chamber main body.

In the case of the burners of Figures 8, 9, 10 and 11, this may be determined in a manner similar to that described above in relation to Figure 2. The length of the conduit forming the evaporation chamber main body is known, and the surface area of the evaporation -chamber main body can therefore be calculated. The surface area of the evaporation chamber is (πdl) , where d is the external diameter of the conduit forming the evaporation chamber main body and 1 is its length. The geometry of the evaporation chamber main body is such that the surface area of the evaporation chamber main body that may, in use, be contacted by the flames produced at the apertures is one-half of the surface area of the evaporation chamber main body. The total surface area of the apertures is known and hence it is simple to calculate the ratio between the surface area of the evaporation chamber main body exposed to flame and the total area of the apertures for the egress of fuel oil.

Experiments have shown that it is particularly preferred for the surface area of the evaporation chamber main body that may be, in use, exposed to flame to be from 2000 to 6000 times greater than the total surface area of the apertures. Such a relationship between the surface area of the evaporation chamber main body exposed to flame and the total area of the apertures for the egress of fuel oil has proved to be particularly effective in producing efficient burners.

Burner Conduit Conduit

Example external internal Aperture

Number Burner diameter diameter 1 Number of size Work

Type (mm) (mm) (mm) apertures (mm) RATIO ?

A 9 2.5 2.0 1020 8 0.4 3984 Y

B 9 3.0 2.0 710 8 0.4 3328 Y

C 10 3.0 2.0 830 8 0.4 3891 Y

D 10 3.0 2.0 770 8 0.5 2310 Y

E 10 3.0 2.0 770 5 0.5 3696 Y

F 9 3.0 2.0 690 8 0.3 5750 Y

G 9 3.0 2.0 830 6 0.4 5188 Y

H 9 3.0 2.0 830 8 0.6 1729 N

I 9 3.0 2.0 690 6 0.4 4313 Y

J 9 3.0 2.0 1667 8 0.6 3473 Y

K 8 1.6 0.8 163 3 0.2 4347 Y

L 8 3.1 2.0 316 5 0.4 2449 Y

M 8 3.1 2.0 180 5 0.2 5580 Y

N 8 3.1 2.0 180 5 0.3 2480 Y

Table 1 Burners A to N were produced with the parameters mentioned above and tested to determine their effectiveness. Referring to Table 1, Burner Type indicates the burner arrangement that was used; "8" indicates the burner of Figures 8a and 8b, "9" indicates the burner of Figures 9a and 9b and "10" indicates the burner arrangement of Figures 10a and 10b. "1" indicates the length of conduit that is used to make the evaporation chamber main body. The number of apertures indicates the number of apertures in the aperture providing portion. "Aperture size" indicates the diameter of each of the apertures. "RATIO" indicates the ratio of the surface area of the evaporation chamber main body that may be exposed to flames emanating from the apertures to the total surface area of the apertures. In this case, the surface area of the evaporation chamber main body that may be exposed to flames emanating from the apertures is one-half the total surface area of the evaporation chamber main body i.e. (^ πdl) , where "d" is the external diameter of the

conduit and 1 is as defined above. The total surface area of the apertures is (nπr ² ) , where "n" is the number of apertures and "r" is. the radius of each aperture. In the "Work?" column, "Y" indicates that the burner in question worked well and "N" ^' indicates that the burner did not work well.

All of the burners indicated above performed well (i.e. produced an intense blue flame with little flicker after the initial start-up phase) apart from burner H which produced an orange-blue flame prone to flicker. The "ratio" as calculated above for this burner was 1729. It was noticeable that the "ratio" for the other burners was higher (at least about 2300) and that these other burners functioned well.

The spacing between the aperture-providing portion and the evaporation chamber main body for each burner was sufficient to allow flames to be fully developed at the lowest portion of the evaporation chamber main body.

The internal diameter of the conduit forming the evaporation chamber in Figure 9 was varied form 0.5mm to 3mm to determine whether such variation affected the preferred ratio of the surface area of the evaporation chamber main body exposed to flame to the total area of the apertures for the egress of fuel oil. No noticeable variation is preferred ratio was found.

If the surface area of the evaporation chamber main body that may be, in use, exposed to flame is less than 2000 times greater than the total surface area of the apertures, then the flame produced has poor characteristics, at least

for heating. This is believed to be because there is insufficient vapour pressure build-up in the evaporation chamber. It is further believed that such reduced pressure reduces mixing of air with the vapour-liquid mixture when the vapour-liquid mixture is emitted from the apertures. Consequently, the heat generated by burning is non-optimal for self-sustaining combustion of the fuel oil.

If the surface area of the evaporation chamber main body that may be, in use, exposed to flame is greater than 6000 times greater than the total surface area of the apertures, then the flame produced can have poor characteristics. The flames produced give insufficient heat output, leading to poor evaporation of fuel oil in the evaporation chamber. This may lead to the formation of an intermittent smoky, yellow flame.

As mentioned above in relation to the burner of Figures 2 and 2A, for many burner configurations, it is possible to calculate the surface area of the evaporation chamber which, in use, may be exposed to flame from fuel oil burnt by the burner. Likewise, for the burner of figure 1, it is simple to calculate the surface area of the conical evaporation chamber 22 that may be, in use, exposed to flames from the burning fuel oil. Hence, the surface area that is, in use, exposed to flames from the burning fuel oil is the surface area of the outer curved surface of the cone.

Furthermore, it is possible to determine the surface area that is, in use, exposed to flames from the burning fuel oil by observing the burner in operation. In order to do this, the burner should be operated to obtain the maximum flame

output. This usually involves waiting until after the initial start-up phase when flames may be yellow and/or small. The oil used should preferably be sunflower oil or rapeseed oil. The burner should be operated in a room at ambient temperature with no draughts. The user will be able to observe those surfaces of the evaporation chamber that are exposed to the flame. The ratio of the surface area of the evaporation chamber that is, in use, heated by flames emitted from the apertures to the total surface area of the apertures may then be calculated.