Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24B—DOMESTIC STOVES OR RANGES FOR SOLID FUELS; IMPLEMENTS FOR USE IN CONNECTION WITH STOVES OR RANGES
  • F24B1/00—Stoves or ranges
  • F24B1/18—Stoves with open fires, e.g. fireplaces
  • F24B1/185—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion
  • F24B1/189—Stoves with open fires, e.g. fireplaces with air-handling means, heat exchange means, or additional provisions for convection heating ; Controlling combustion characterised by air-handling means, i.e. of combustion-air, heated-air, or flue-gases, e.g. draught control dampers 
  • F24B1/19—Supplying combustion-air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24B—DOMESTIC STOVES OR RANGES FOR SOLID FUELS; IMPLEMENTS FOR USE IN CONNECTION WITH STOVES OR RANGES
  • F24B5/00—Combustion-air or flue-gas circulation in or around stoves or ranges
  • F24B5/02—Combustion-air or flue-gas circulation in or around stoves or ranges in or around stoves
  • F24B5/021—Combustion-air or flue-gas circulation in or around stoves or ranges in or around stoves combustion-air circulation

Definitions

• Combustion apparatus for solid fuel and a method of firing therein.
• the present invention relates to the technical field of combustion or firing apparatuses for solid fuel, e.g. wood, coal and briquettes. Particularly, but not exclusively, the invention relates to combustion apparatuses of such types as fire-places, stoves and the like. More specifically, the invention relates to an improved combustion apparatus for solid fuel and a new method of firing solid fuel therein.
• solid fuel e.g. wood, coal and briquettes.
• the invention relates to combustion apparatuses of such types as fire-places, stoves and the like. More specifically, the invention relates to an improved combustion apparatus for solid fuel and a new method of firing solid fuel therein.
• Combustion apparatuses of such types as open fire-places, door-fronted stoves and the like have become more and more usual in houses, leisure dwellings and flats, not in the least due to the heavily rising prices in recent years for the conventional energy sources oil and electricity.
• Door-fronted stoves have become a supplement to the conventional heating systems as reserve heating sources or for energy saving, but also as a congeniality factor.
• the heavy increase of such solid fuel-burning combustion apparatuses has caused air pollution problems, perhaps primarily in thickly populated areas. In many countries the authorities have therefore put strict requirements on flue gas discharges from such apparatuses and also on heating boilers, or are expected to make such requirements. In Sweden, for example, attention is concentrated on the tar content in the discharged flue gases, decrease in the tar content being sought for. With a lower tar content the content of the most important remaining pollutants also decreases.
• the traditional door-fronted stove comprises a hearth which may be closed by doors, through which fuel is also supplied.
• the doors, and possibly several of the side wails of the stove are often transparent so that the congeniality of an open fire will be felt.
• the stove may be insulated, provided with a heat accumulator, fan system, combustion air preheating etc. for increasing the heating efficiency.
• a chief object of the present invention is to improve the combustion in solid fuel-fired combustion apparatuses, particularly stoves and door-fronted stoves so that the amount of discharged pollutants is reduced in comparison with conventional such apparatuses with combustion air supplied from below.
• Another object of the invention Is to increase the efficiency in iring this type of combustion apparatuses.
• a salient feature of the combustion apparatus in accordance with the invention is that the combustion air is supplied to the fire from above/obliquely from above, in contradistinction to the conventional door-fronted stoves described hereinbefore, where combustion air is supplied from below.
• the combustion air is supplied in a controlled way via special supply ducts. After an initial heating-up period, the combustion chamber of the apparatus is kept substantially entirely closed off, so that the sole supply of air takes place via the special supply ducts.
• the air supply duct or ducts thus open out in the combustion chamber at least at a level, and preferably at several different levels, above the hearth, spreader devices directing the supplied air down towards the hearth, preferably in a turbulent flow directed substantially towards the center of the hearth.
• the spreader devices comprise preferably at least two substantially horizontal . spreader ducts situated at different heights and provided with a plurality of blowing apertures with coacting deflection plates, which direct the combustion air flowing out from the blowing apertures towards the hearth.
• the air supply continues by self induction.
• the flow rate depends, inter alia, on the firing temperature and the design of the combustion apparatus or hearth, and it is primarily regulated by varying the flow area and flow resistance of the supply ducts (as well as adjusting the flue damper associated with the apparatus). It is essential for the invention that this regulation is carried out so that there is a balance between the downwardly directed combustion air and the upwardly directed gases from the hearth.
• the flows will be self-balancing/self- reguiating during the course of combustion. For example, a smaller flame leads to a reduced intake of combustion air, which in turn gives the desired lesser degree of cooling from the combustion air.
• Fig. 1 is a schematic front view, partly sectioned, of a presently preferred embodiment, illustrating a combustion apparatus in accordance with the invention.
• Fig. 2 is a schematic side view of the apparatus in Fig. 1 during firing. Description of Preferred Embodiments
• the reference numeral 1 denotes the combustion chamber itself, there being a plinth 2 supporting the hearth, and the flue gases are led out via a lue or a flue connection 3.
• Fig. 2 the combustion apparatus is illustrated during firing solid fuel *, e.g. wood, coal or briquettes, which can be kept in place with the aid of a support 5. Flames from the fire are denoted by the numeral 6.
• the combustion chamber of the apparatus is suitably and conventionally surrounded with heat-insulating and/or heat accumulating mate ⁇ rial 7.
• the bottom of the hearth (on which the fuel is placed) is impervious, in contradistinction to conventional stoves with air supply from below.
• the apparatus is, of course, conventionally provided with draught doors (not shown) through which fuel is also supplied.
• the combustion apparatus is provided with inlet ducts 8a, 8b, 8c for the supply of combustion air, these ducts leading the air to substantially horizontal blowing ducts 9a, 9b, 9c, situated at different levels in the combustion chamber 1, all above the hearth.
• the flow of supplied combustion air is denoted on the drawings by arrowed full lines, while the flow from the hot gases from the fire are schematically denoted by arrowed dashed lines.
• the blowing or spreader ducts 9a, 9b, 9c are provided with blowing apertures 10a, 10b, 10c in the form of slits or, preferably a plurality of separate holes distributed along the respective duct.
• the blowing apertures 10a, 10b, 10c coact with deflection plates 11a, l ib, lie directing the air flow from the respective aperture downward towards the fire, preferably substantially towards its centre.
• the central duct 8b leads air only to the first spreader or blowing duct 9a, while the outer supply ducts 8a and 8c divide their flow between the ducts 9b and 9c (and possibly also 9a).
• the two undermost ducts 9a and 9b are illustrated as extending across the entire combustion chamber 1, while the upper duct 9c is illustrated as being divided into two smaller ducts 9c.
• a further air supply duct 9d is also illustrated in the Figures, with its corresponding deflection plate lOd, both situated above the blowing duct 9c.
• Figure 2 also depicts a guide plate 12.
• the combustion apparatus is finally equipped with a regulatable, schematically illustrated damper 13 and a flame catcher I*.
• a combustion apparatus in accordance with the invention When a combustion apparatus in accordance with the invention is installed, it is first adjusted so that a balanced flow of downwardly directed combustion air (arrowed full lines) and upwardly directed flue gases (arrowed dashed lines) is obtained, primarily by adjusting the flow area and flow resistance in the ducts or the conduits for supplying combustion air to the combustion chamber.
• the inlet openings of the risers 8a-8c can be suitably obstructed to obtain this effect.
• the damper 13 is also adjusted to suit the installation in question, primarily with regard to the draught properties of the flue used. If so desired, and to advantage, an extended flow path for the flue gases may be arranged in connection with the damper 13 for increasing the post combustion zone. It has been found to be particularly advantagenous to allow the flue gases to pass the rear side of the air inlet unit in heat-exchanging contact with it for further preheating the combustion air, as illustrated by the arrowed dashed line P in Fig. 2. Combustion will be more effective and the flue gas temperature higher, due to the preheating of the combustion air and the extended path of the flue gases.
• the combustion apparatus thus installed is operated and functions in the following manner. Firing is started in a conventional manner, and the draught door is closed when the fire has got well under way, i.e. when the apparatus has got a sufficiently high temperature to function as a self-inducting pump for taking in combustion air via the risers 8a-8c.
• the combustion air flows according to the arrowed full lines in the drawing, and from the lower spreader duct 9a there is a strong flow of air towards the centre of the fire, which then gets a very high temperature at its centre (e.g. in the order of magnitude of 1000°C). This results in that the smoke is drawn in towards the centre, resulting in that surrounding wood gets a poor supply of oxygen and combustible gases are formed.
• combustion takes place in four combustion zones A, B, C and D, where the zone D may be regarded as a post combustion zone without extra oxygen supply.
• combustion zones may also be designated as whirl zones. Combustion will be practically complete and free from soot. Measurements that have been carried out show that in firing with wood in a door-fronted stove designed in accordance with the drawing Figures there are only obtained tar contents in the order of magnitude 10-15 mg/kJ and below, i.e. only approximately a tenth of the values for stoves with conventional air supply under the hearth.
• the efficiency of the combustion apparatus can be improved further by providing the flame catcher 1*, which is situated at a level in the combustion chamber such that it is in contact with the flames 6, suitably between the spreader ducts 11a and lib.
• the flame catcher 1 is made from perforated plate, netting, grating or the like, which allows air and flue gases to pass through and which breaks up the flames into many small flames, thus increasing the utilizable oxygenation surface.
• the flame catcher 14 also functions as an ash barrier. It is particularly preferred, as in the illustrated embodiment, to combine the upper spreader duct 9c and its associated deflection plate l ie with the guide plate 12 and one or more reflector plates 15.
• the guide plate 12 guides the flue gases to the combustion zone C and the reflector plate/plates 15 also function as heat reflectors by reflecting heat to the combustion zone C.
• the air flow from the blowing apertures lOd also serves as a flame brake.
• the flow from the different spreader ducts can be varied within the scope of the invention, inter alia with respect to their number and placing, the number, size and placing of the blowing apertures, etc. In general it is preferred to have the heaviest flow from the lowest spreader duct (9a).
• the combustion apparatus in accordance with the invention can be manufactured as an entire unit, but it may also be implemented as a special insert for building into existing fireplaces or stoves.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Solid-Fuel Combustion (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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ID=20354770

Family Applications (1)

Country Status (6)

Cited By (4)

Families Citing this family (1)

Citations (1)

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• 1984
  • 1984-02-16 SE SE8400836A patent/SE8400836L/ not_active Application Discontinuation
• 1985
  • 1985-02-15 DE DE8585901118T patent/DE3571496D1/de not_active Expired
  • 1985-02-15 EP EP85901118A patent/EP0204704B1/en not_active Expired
  • 1985-02-15 WO PCT/SE1985/000077 patent/WO1985003762A1/en active IP Right Grant
  • 1985-10-16 NO NO854103A patent/NO854103L/no unknown
• 1986
  • 1986-08-13 FI FI863279A patent/FI84856C/fi not_active IP Right Cessation

Patent Citations (1)

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