GB2608169A

GB2608169A - Portable combustion device

Info

Publication number: GB2608169A
Application number: GB2109121.0A
Authority: GB
Inventors: Michael Taphouse Jonathan
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-06-24
Filing date: 2021-06-24
Publication date: 2022-12-28
Anticipated expiration: 2041-06-24
Also published as: GB2608169B; GB202109121D0

Abstract

A portable combustion device 10 comprises a preferably conical housing 13 configured to contain solid fuel and having an air inlet section 16 and an air outlet sections 17, (18, Fig.2). A forcing device (22, Fig.2) such as a fan, is configured to force air into the housing via the air inlet section. The housing 13 and a filter 14 are mutually configured so that exhaust gases exiting the housing 13 will pass through the filter 14, which may be removable, and/or used to funnel fuel into the combustion chamber 12. The filter may be made from or coated with a catalytic material, or from other materials such as metal, glass, ceramic, carbon or be a mesh, foam or grid structure. The fan may be powered by a battery or external power source via connector 27, and the fan blades may be made of a heat reflective material. A heat shield (28, Fig.2) may be positioned between the combustion chamber and fan.

Description

Portable Combustion Device Held The present invention relates to a portable combustion device. More particularly, the present invention relates to a portable combustion device for efficient and safe combustion of fuel and reduced smoke emissions.

Background

Portable combustion devices are devices that can be used as a stove by persons to cook food and provide heat in situations such as travelling, camping, rescue or emergencies, and during power outages when larger, more permanent cooking and heating devices are unavailable or impractical. There exist a variety of fuels for these available devices, such as liquid fuels (for example, kerosene, petroleum and alcohol), gasses (for example, propane and butane) and biomass (for example, wood, dried dung, crops and peat).

With the exception of biomass, these fuels have to be purchased and stored in a bottle or canister and carried along with the combustion device. As the supply of gas and liquid fuels is limited by the size of the carried container, the device will have a limited combustion time before the fuel needs to be replenished. This is often problematic when travelling, camping, or in emergencies. In contrast, biomass is very often available in these situations and provides a more reliable fuel source.

Biomass stoves typically have drawbacks that make them inefficient, dirty or dangerous. A fire driven stove will often lack the oxygen needed for complete combustion, and as such will produce smoke and soot during the combustion process. In addition to dirtying pots and pans, this smoke can contain harmful and toxic products as a result of the incomplete combustion. These include carbon monoxide, soot particles and heavy metals. The smoke can also carry burning embers, which can start unnecessary wildfires, and this has resulted in the use of these devices being restricted in some areas.

Methods often employed for increasing a biomass stove's efficiency include passing the smoke through the combustion chamber multiple times, or to forcibly drive more airflow (and therefore oxygen) over the biomass during combustion to produce a smokeless stove. However, force-driven stoves can eject burning embers from the combustion chamber, which has the potential to ignite surrounding biomass. In addition, these designs can be complex and expensive, requiring the use of thermoelectric generators and battery chargers to power the fan. There can also be a tendency for the fan to overheat and fail, and some designs of this type are prone to inefficiencies in windy conditions. Designs of this type can also provide an inefficient burn during the initial warm up of the stove.

U34,730,597 discloses a biomass stove with a perforated inner combustion chamber and a continuous outer shell, in a concentric cylindrical configuration. The inner combustion chamber has holes to allow entry of additional combustion air There is an air gap between the two parts which transports and distributes a secondary combustion air into the fuel chamber The addition of the secondary air adds more oxygen to the combustion increasing the burn temperature and efficiency of the stove. The secondary airflow is fire driven; the convection from the elevated heat draws additional air through the combustion chamber US8,459,193 discloses a fire driven combustion device where the biomass fuel is subject to gasification and / or pyrolysis. The hot exhaust gas and smoke is pulled downwards through the fuel with minimum oxygen, this produces wood gasification. This wood gas is then controllably mixed with air (including oxygen) to produce combustion for heat and cooking. The combustion gases produced are unpressurised, and therefore this design is easily extinguished by external air turbulence (such as wind), resulting in a combustion device suitable for indoor use only.

US3,868,943 discloses a portable forced air camping stove, that includes a blower assembly consisting of an electrically powered fan. The fan removes the need for a flue or chimney to move air through the combustion chamber; instead the fan drives the airflow through the biomass increasing the combustion efficiency. Additional secondary burn air is added again through the employment of a perforated inner combustion cylinder.

GB2,125,160 discloses a cooking stove having a combustion chamber into which air for combustion is drawn from outside the chamber by either, natural convection, or by a hand operated air pump, or both.

US9,219,213 discloses a portable forced air stove for efficient combustion with a fan is electrically powered by a rechargeable power source and a thermoelectric element provides power to the fan and to the rechargeable power source.

US8,851,062 discloses a forced air biomass stove for more efficient combustion, where a fan is electrically powered by a rechargeable power source and a thermoelectric element providing power for the fan and the rechargeable power source is located on the outside of the main housing to remove the risk of heat damage to the electrical components. This however increases the overall size and reduces portability of the device.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

Summary

It is an object of the present invention to provide a portable combustion device which goes some way to overcoming the above mentioned disadvantages or which at least provides the public or industry with a useful choice.

The term "comprising" as used in this specification and indicative independent claims means "consisting at least in part of". Wien interpreting each statement in this specification and indicative independent claims that includes the term "comprising", features other than that or those prefaced by the term may also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

As used herein the term "and/or" means "and" or "or", or both.

As used herein "(s)" following a noun means the plural and/or singular forms of the noun.

Accordingly, in a first aspect the present invention may broadly be said to consist in a portable combustion device, comprising: a housing configured to in use to contain fuel and having an air inlet section and an air outlet section; a forcing means configured to force air into the housing via the air inlet section; a filter, the housing and filter mutually configured so that air exiting the housing will pass through the filter.

In an embodiment, the housing is configured so that the air inlet section is at or towards the bottom of the housing in use, and the air outlet section is above the inlet section.

In an embodiment, the housing comprises an outer shell and an inner combustion chamber, a space formed between the inner surface of the outer shell and the outer surface of the combustion chamber, the space configured to that a minor portion of air forced into the housing will pass through the space rather than the interior of the combustion chamber.

In an embodiment, the forcing means comprises a fan.

In an embodiment, the portable combustion device further comprises a battery, the battery configured to provide power to the fan in use.

In an embodiment, the portable combustion device further comprises a cable, the cable configured to connect between the fan and an external power source so as to provide power to the fan in use.

In an embodiment, the fan is positioned substantially adjacent to the inlet section. In an embodiment, the blades of the fan are formed from a heat reflective material.

In an embodiment, the portable combustion device further comprises a heat shield or shields positioned between the combustion chamber and the fan and configured to reduce heat radiation from the combustion chamber to the fan.

In an embodiment, the filter has a conical shape In an embodiment, the filter is configured so as to funnel fuel into the combustion chamber during refuelling.

In an embodiment, the filter is configured to be removable to allow additional fuel to be added to the housing.

In an embodiment, the filter is constructed from one or more of: a woven mesh; welded mesh; a foam; a felt; a grid structure.

In an embodiment, the filter is constructed from at least one of: metal-glass ceramic; carbon.

In an embodiment, the material used to form the filter has catalytic properties.

In an embodiment, the filter is coated with a material that has catalytic properties.

In an embodiment, the filter is configured to baffle the interior of the housing from external air turbulence.

In an embodiment, the portable combustion device further comprises a filter lid configured to connect with the housing to direct exhaust gases from the housing through the filter.

In an embodiment, the filter lid comprises a cooking vessel.

With respect to the above description then, it is to be realised that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Brief description of the figures

Further aspects of the invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings which show an embodiment of the device by way of example, and in which: Figure 1 shows a perspective view from above and to one side of a first embodiment of a portable combustion device according to the invention, with an emissions filter suitable for cooking.

Figure 2 shows a cross-sectional view from one side of the portable combustion device of figure 1, showing internal detail of the combustion device.

Figure 3 shows a cross-sectional view from one side of the portable combustion device of figures 1 and 2, from the same angle as figure 2, showing detail of the device in operation.

Figure 4 shows a cross-sectional view from one side of the portable combustion device of figures 1 to 3, from the same angle as figures 2 and 3, showing the device being refuelled.

Figure 5 shows a perspective view from above and to one side of a second embodiment of a portable combustion device according to the invention.

Figure 6 shows a cross-sectional view from one side of the portable combustion device of figure 5, showing internal detail of the combustion device.

Detailed Description

Embodiments of the invention, and variations thereof, will now be described in detail with reference to the figures.

An embodiment of a portable combustion device is shown in figures 1 to 4, as portable biomass stove 10. The stove 10 comprises a cylindrical outer housing 13, with a cylindrical combustion chamber 12 formed within an upper portion of the cylindrical outer housing 13. A filter 14 surrounds and closes the generally open top end 15 of the cylindrical outer housing 13. The top rim of the outer housing acts as a cooking surface to support a pot or similar in use. However, in variations, the filter 14 also acts as a cooking surface.

The upper portion of the outer housing 13 provides a support structure for a cooking vessel and includes a plurality of holes 25 to still allow egress of filtered exhaust gases. The lower portion of the outer housing 13 includes an air inlet 16 that runs circumferentially around the lower part of the outer housing 13, the inlet allowing ambient air to be drawn into the combustion chamber 12. Primary air outlets 18 are formed in the lower portion of the combustion chamber 2, and a plurality of secondary air outlets 17 are formed in the upper portion of the combustion chamber 12.

A cylindrical stove base 26 is disposed at the lower end or base of the device, spaced from the upper housing by the fan positioning plate 19. This spacing creates a gap that allows ambient air to be drawn into the housing by the fan 22. The ambient air has a cooling effect on the stove base 26 ensuring the outer surface is sufficiently cool in operation to be safe to the touch. An electrical connecting socket 27 protrudes through the lower cylindrical base 26. This provides an external power connection, to provide power to the fan 22.

The cylindrical housing 13 surrounds the inner cylindrical combustion chamber 12, forming an annular space 21 between the walls of the housing and chamber. The combustion chamber 12 comprises a substantially cylindrical vessel having a plurality of primary air outlets 18 formed in the upper part of the wall of the cylinder, and a plurality of secondary air outlets 17 formed in a lower part of the wall of the cylinder. The upper end edge of the combustion container 12 is contiguous with the inside of the outer housing 13, maintaining the annular space 21 and supporting the combustion chamber 12. Air passing through the annular space 21 is pre-heated by radiant heat from the combustion chamber 12 before entering the combustion chamber 12 through the upper secondary air outlets 17.

The fan positioning plate 19 comprises a corrugated cylindrical vessel having apertures to allow air to flow through into the combustion chamber 2. An electric fan 22 is positioned adjacent to the apertures in the fan positioning plate 19. The fan 22 comprises a central brushless motor 24, and an impeller formed from outwardly radiating blades 23. The blades 23 are in this embodiment formed from a heat reflective material such as aluminium. This assists with shielding the electronic components from heat radiated by the combustion chamber Reflective heat shields 28, which in the preferred embodiment are sheets of reflective aluminium foil, are disposed between the closed end of the combustion chamber and the fan 22 thereby reducing heat radiation from the combustion chamber to the fan 22 and protecting the fan 22 from heat damage in operation.

A filter 14 comprising a fine wire mesh is supported by the inner edge of an annular plate 33, the outer edge is contiguous with the upper end edge of the combustion chamber 12, the filter is cone shaped to funnel fuel towards the opening in the annular plate 33 to assist in refuelling the stove.

An electrical connecting socket 27 for an external power connection protrudes through the lower cylindrical base 26 of the stove and is electrically connected to the fan 22. In alternative variations an electrical cable and plug protrude through the base 26 for connecting to an external power source or battery to the fan.

The intended airflow is illustrated in the cross-sectional view of figure 3. VVhen the fan is turned on, air (shown by arrows 51) is drawn into the stove through opening 16 at the bottom edge of the cylindrical housing 13. The air passes through the apertures in the fan positioning plate 19 (this part of the process shown by arrows 53), where it is accelerated by the rotating outwardly radiating blades 23. A proportion of the pressurised air is forced into the combustion chamber 12 through the lower air outlets 18 providing primary air for the combustion. Unburned gases and smoke (shown by arrows 54) are pushed upwards. Pressurised air (shown by arrows 55) enters the combustion chamber through the upper air outlets 17 to mix with the unburned gases and smoke, and provides adequate additional oxygen so that complete combustion takes place. A filter lid 45 (which in this embodiment is a cooking vessel) is supported by the upper portion of the outer housing 13 and directs exhaust gases 56 through the filter 14 and then through openings 25 to allow the egress of filtered exhaust gases.

The pressurised air and the baffle effect of the mesh filter provides a stable cooking environment in windy conditions, the filter is heated by the passing exhaust and this heat is radiated back into the cooking vessel for improved cooking efficiency.

Figure 4 illustrates the intended refuelling process. A lid 45 of the filter 14 is removed from the stove 10 to create an opening 15 for additional fuel 31 to enter the combustion chamber 12 through annular aperture 33 in the filter 14. Any additional fuel 31 that misses the aperture is collected by the funnel shaped filter 14 and deflected through the annular aperture (as shown by arrow 60) and into the combustion chamber 12.

A second embodiment of the portable biomass stove 110 is shown in figures Sand 6. The stove comprises a cylindrical combustion chamber formed within an upper portion of a cylindrical outer housing 113 and enclosed by a filter 114 surrounding an otherwise generally open top end 115 that is configured for use as a cooking surface. The upper portion of the outer housing 113 is configured as a support structure for the cooking vessel and includes a plurality of holes 125 configured to allow the egress of filtered exhaust gases. The lower portion of the outer housing 113 includes an air inlet 116 for ingress of ambient air, which is drawn into the combustion chamber 112 by fan 122. A cylindrical stove base 126 is disposed at the lower end thereof the device, distanced from the upper housing by the fan positioning plate 119 to allow the ingress of ambient air drawn by the fan 122. The ambient air has a cooling effect on the stove base 126 ensuring the outer surface is sufficiently cool in operation to be safe to the touch. An electrical connecting socket 127 for an external power connection protrudes through the lower cylindrical base 126 to power the fan 122 and in this embodiment re-charge the internal battery 40.

Figure 6 illustrates the internal arrangements of a second embodiment of the biomass stove 110. The cylindrical housing 113 surrounds the inner cylindrical combustion chamber 112, forming an annular space 121 between the vertical walls. The combustion chamber 112 comprises a vessel with a plurality of upper secondary air outlets 117 and a plurality of lower primary air outlets 118 formed in the walls of the cylinder. The upper end edge of the combustion container 112 is contiguous with the inside of the outer housing 113 maintaining the annular space 121 and supporting the combustion chamber 112. Air passing through the annular space 121 is pre-heated by radiant heat from the combustion chamber 112 before entering the combustion chamber 112 through the upper secondary air outlets 117.

A fan positioning plate 119 comprises a corrugated cylindrical vessel having apertures to allow air through into the combustion chamber 112. An electric fan 122 is positioned adjacent to the apertures, the fan 122 comprising a central brushless motor 124, with an impeller formed from outwardly radiating blades 123 formed int his embodiment from a heat reflective material such as aluminium, to further shield the electronic components from heat radiated by the combustion chamber.

Reflective heat shields 128, formed from sheets of reflective aluminium foil, are disposed between the closed end of the combustion chamber 112 and the fan 122 thereby reducing heat radiation from the combustion chamber to the fan 122 and protecting the fan 122 from heat damage in operation.

An electrical connecting socket 127 for an external power connection protrudes through the lower cylindrical base 126 of the stove and is electrically connected to the fan 122 and an option of an internal rechargeable battery 140.

A filter 114, constructed from a fine wire mesh, is supported by the inner edge of annular plate 133. The outer edge of the plate contiguous with the upper end edge of the combustion chamber 112 which supports the filter 114 is dome-shaped to fully enclose the opening in the annular plate 33 so as to filter all emissions from the combustion chamber 112.

In this embodiment, the filter 114 is constructed of and/or coated with a catalytic material, the catalyst being a combination of one or more precious metals, including the following: platinum, palladium, rhodium and cerium. The catalyst chemically lowers the combustion temperature of smoke, thereby allowing more smoke to burn, resulting in higher efficiency and cleaner exhaust. Carbon and/or activated carbon may also be used as a material for the filter 114, where the material absorbs the compounds in the exhaust, such as volatile hydrocarbons, carbon monoxide, and other contaminants, in addition to filtering the larger particles through entrapment.

The materials used for the filter 114 may be constructed in various ways, including, but not limited to a honeycomb structure, woven mesh, welded mesh, felt, or foam; in all instances the constructed pore sizes are small enough to trap the relatively large embers and particles exiting from the combustion chamber 112.

The filter 114 may be configured to funnel fuel into the combustion chamber by taking a conical form, such as in the first embodiment shown in figures 1 to 4, with the upper outer diameter being greater than the smaller lower diameter When constructed with materials of high thermal uptake (such as metals) the efficiency of the stove is increased as the filter absorbs heat from the exhaust and radiates it back towards the supported cooking utensil; additionally the filter provides a partial barrier which buffers external winds and air turbulence further increasing efficiency in these conditions when compared to that of the stove without said filter

Claims

Claims 1. A portable combustion device, comprising: a housing configured to in use to contain fuel and having an air inlet section and an air outlet section; a forcing means configured to force air into the housing via the air inlet section; a filter, the housing and filter mutually configured so that air exiting the housing will pass through the filter.
2. A portable combustion device as claimed in claim 1 wherein the housing is configured so that the air inlet section is at or towards the bottom of the housing in use, and the air outlet section is above the inlet section.
3. A portable combustion device as claimed in claim 1 or claim 2 wherein the housing comprises an outer shell and an inner combustion chamber, a space formed between the inner surface of the outer shell and the outer surface of the combustion chamber, the space configured to that a minor portion of air forced into the housing will pass through the space rather than the interior of the combustion chamber
4. A portable combustion device as claimed in any one of claims 1 to 3 wherein the forcing means comprises a fan.
5. A portable combustion device as claimed in claim 4 further comprising a battery, the battery configured to provide power to the fan in use.
6. A portable combustion device as claimed in claim 4 further comprising a cable, the cable configured to connect between the fan and an external power source so as to provide power to the fan in use.
7. A portable combustion device as claimed in any one of claims 4 to 6 wherein the fan is positioned substantially adjacent to the inlet section.
8 A portable combustion device as claimed in any one of claims 4 to 7 wherein the blades of the fan are formed from a heat reflective material.
9. A portable combustion device as claimed in any one of claims 4 to 8 further comprising a heat shield or shields positioned between the combustion chamber and the fan and configured to reduce heat radiation from the combustion chamber to the fan.
10. A portable combustion device as claimed in any one of claims 1 to 9 wherein the filter has a conical shape
11. A portable combustion device as claimed in claim 10 wherein the filter is configured so as to funnel fuel into the combustion chamber during refuelling.
12. A portable combustion device as claimed in anyone of claims 1 to 9 wherein the filter is configured to be removable to allow additional fuel to be added to the housing.
13. A portable combustion device as claimed in any one of claims 1 to 12 wherein the filter is constructed from one or more of: a woven mesh; welded mesh a foam; a felt; a grid structure.
14. A portable combustion device as claimed in any one of claims 1 to 13 wherein the filter is constructed from at least one of: metal; glass; ceramic; carbon.
15. A portable combustion device as claimed in any one of claims 1 to 14 wherein the material used to form the filter has catalytic properties.
16. A portable combustion device as claimed in any one of claims 1 to 14 wherein the filter is coated with a material that has catalytic properties.
17. A portable combustion device as claimed in any one of claims 1 to 16 wherein the filter is configured to baffle the interior of the housing from external air turbulence.
18. A portable combustion device as claimed in any one of claims 1 to 17 further comprising a filter lid configured to connect with the housing to direct exhaust gases from the housing through the filter.
19. A portable combustion device as claimed in claim wherein the filter lid comprises a cooking vessel.