EP1582815B1

EP1582815B1 - Stove in particular for pellets or granular solid fuel

Info

Publication number: EP1582815B1
Application number: EP05005537A
Authority: EP
Inventors: Vagn Hvam Pedersen
Original assignee: Hwam AS
Current assignee: Hwam AS
Priority date: 2004-03-17
Filing date: 2005-03-15
Publication date: 2011-05-11
Anticipated expiration: 2025-03-15
Also published as: EP1582815A1; ATE509237T1; DK1582815T3

Abstract

A stove (2), particularly for combusting pelletised or granular fuel, including a combustion chamber (10) with a fireplace or a combustion zone (28), a feeding aperture (36) for primary combustion air arranged thereunder, a feeding aperture (42) for secondary combustion air arranged above the fireplace (10), and a feeding aperture for tertiary combustion air supplied over the combustion chamber and conducted downwards along the inner side of a glass pane (50) of a front door (52) for the stove (2), which behind the combustion chamber (10) includes a fuel hopper (18) with an inclining bottom plate (20), that the burning stove (2) includes a filling opening (26) for fuel in a sidewall, and that between the fuel hopper (18) and the fireplace or the combustion zone (28) there is provided a slotted firing opening (24). By means of simple measures is hereby provided a burning stove with a fuel magazine from which the fuel may be supplied successively through a slot-formed firing opening for achieving a continuous underburning of pelletised or granular fuel.

Description

Field of the Invention

The present invention concerns a stove, particular for combusting pelletised or granular solid fuel and of the kind specified in the preamble of claim 1.

Background of the Invention

Over time, wood-burning stoves have gone through an evolution, starting with open fireplaces to detached closed stoves. This development has almost always occurred as a reaction to consumer patterns and social conditions. The development of detached wood-burning stoves had a renaissance during the oil crisis in the seventies, and has since been established as a practical and comfortable solution for providing alternative heating of the living-quarters.
The demands of the future to stoves are more of architectural nature, where the stove is more regarded as a furniture and decoration of the habitation with a possibility of experiencing human instincts around the fire: the heat, the smell, the sound of fire. The comfort associated with using wood-burning stoves and fireplaces requires, however, application of new technological means for operating stove or fireplace and controlling combustion in the stove or fireplace.
This need may be fulfilled in that some modern wood-burning stoves may be used as closed stoves with closed door with glass pane as well as an open fireplace with open door into the combustion chamber, and by using the newest technology for data collection and processing combustion data as well as combustion control, fulfilling the need for combining open and closed fireplace with maximum comfort and optimal combustion.
Due to safety and environmental considerations, standards for wood-burning stoves have been made, which are also for ensuring the quality of stoves offered on the market. These standards contain e.g. rules for erecting wood-burning stoves in order to prevent ignition of surrounding material, e.g. walls or furniture. Furthermore, these standards include guidelines for emission of carbon monoxide at the combustion of solid fuel. The emission of carbon monoxide from the stove is closely related to the emission of environmentally harmful, particularly carcinogenic substances, why it is desirable with a controlled combustion in the stove.
By manually operated wood-burning stoves, most often an optimal combustion does not occur. This is due to various factors. After ignition, the user possibly desires rapid heat production without regard to possible environmental load. Or the user is not acquainted with the effect of supplying primary and secondary air during the combustion.
In a stove for solid fuel, the combustion is controlled by regulating the primary air and the secondary air. The primary air is the air supplied to the fuel directly and which controls the combustion of the fuel. The secondary air is supplied over the fuel for enhancing the combustion of the flue gases. The latter aspect is important for sake of the environment.
By igniting the stove, there is a great need for primary air, while secondary air is preferably avoided. During combustion, secondary air is added for preventing too large emission of uncombusted flue gas, while feeding of primary air is reduced. An optimal combustion thus requires regulation of the amount of supplied primary air and secondary air in dependence of the combustion process.
US-A-5 285 738 discloses a pellet burning heating device designed to operate at a combustion efficiency of about 90-98 %, and to emit exhaust gases having a carbon monoxide concentration, by volume of about 0.04 % or less, which device does not incorporate a fan system for introducing combustion air into, or extracting exhaust gases from, the stove. High combustion efficiency and clean burning are accomplished by providing a plurality of apertures in the burn pot of the device having a predetermined size, number, and placement. The heating device also includes an aperture which provides a wash of relatively cool air to the inside surface of the window in order to reduce carbon deposits. A shaker located in the bum pot provides a heat sink which helps to increase the efficiency of the heating device.

Object of the Invention

On this background, the purpose of the invention is to provide a new and improved burning stove of the kind mentioned in the introduction, and which has substantial advantages in use compared with the known wood-burning stoves.

Brief Description of the Invention

The burning stove according to the invention is characterised in that the burning stove includes a filling opening for fuel in a sidewall, that between the fuel hopper and the fireplace or the combustion zone there is provided a slotted firing opening, that an upper transverse top edge of the inclining bottom plate is pivotally suspended in the vicinity of a back side of the stove, and that a lower transverse edge part of the bottom plate is connected with an activating mechanism for moving the inclined bottom plate of the fuel hopper. By means of simple measures is hereby provided a burning stove with a fuel magazine from which the fuel may be supplied successively through a slot-formed firing opening for achieving continuous downdraught combustion of pellets or granular fuel. Such a vibrating or tilting function has the purpose of vibrating the fuel downwards against the bottom of the fuel hopper in case that the fuel cannot slide downwards by itself.
The stove according to the invention may furthermore be designed so that the combustion chamber is designed with a tilting bottom plate which by movement or vibration enables emptying ashes down into an underlying ash pan, which bottom plate is designed so that fuel or ember layer cannot slide down into the ash pan.
In a particularly simple way, the stove according to the invention may be designed so that the activation mechanism is common to the inclining bottom plate in the fuel hopper and the tilting bottom plate in the combustion chamber. By this combined function it becomes possible to vibrate the fuel down the inclining bottom plate and further out into the fireplace for distributing the fuel evenly in the transversely positioned combustion zone.
The stove according to the invention may furthermore advantageously be designed so that predominantly over the entire width of the combustion chamber between a front side of the tilting bottom plate and a fixed bottom plate part there is provided a slot for feeding primary combustion air.
With the purpose of further optimising the combustion of gases, the stove according to the invention may advantageously be designed so that in a lower part of the combustion chamber there is designed a mixing chamber by means of a transverse outwards/upwards ceramic element disposed with spacing in front of the fireplace or the combustion zone, and a further ceramic element extending inwards from a top side edge of the previously mentioned ceramic element, the ceramic elements extending mainly in the whole width of the combustion chamber.
It may furthermore be very advantageous that the stove according to the invention is designed so that a transverse slot for feeding secondary combustion air is provided in the first mentioned ceramic element, which slot is extending predominantly horizontally and predominantly in the entire width of the mixing chamber.
Appropriately, the stove according to the invention is designed so that secondary and tertiary combustion air is fed into the surrounding casing of the stove through a common air intake, from where the tertiary combustion air is conducted upwards through one or more riser pipes to a transverse distribution channel disposed over the front door with a downwards/outwards inclining guide surface, so that the tertiary combustion air is fed downwards and predominantly along the entire width of the glass pane of the front door and from there horizontally into the combustion chamber.

Brief Description of the Drawing

The invention is explained in the following in more detail with reference to the drawing, on which:

Fig. 1: shows a plane view of an embodiment of a stove according to the invention, shown from its front side;
Fig. 2: shows a sectional view through a stove, cf. Fig. 1 and cf. the sectional line II- II in Fig. 1;
Fig. 3: shows a plane view of the stove in Fig. 1, seen from its right side;
Fig. 4: shows a sectional view through the stove cf. Fig. 1 and cf. the sectional line IV-IV in Fig. 3;
Fig. 5: shows a plane view of the stove shown in Fig. 1, as seen from its right side;
Fig. 6: a sectional view through the stove, cf. Fig. 1 and cf. the sectional line VI-VI in Fig. 5;
Fig. 7: shows a perspective view, partly in section, of the embodiment of the stove according to the invention shown in Fig. 1.

Detailed Description of the Invention

The stove 2 shown in Figs. 1 - 7 is designed as a convection oven with an outer jacket 4 spaced from the stove itself and with an upper section 6 designed as a water heater 8 heated by the flue gas that passes from a combustion chamber 10 through vertical flue ducts 12 which extend through the water heater 8, a fact most clearly seen in Figs. 2, 4 and 7. The flue ducts 12 debouch into an upper flue gas chamber 14 which is connected to a not shown chimney, so that the stove 2 operates with low pressure only provided by the chimney.
The combustion chamber 10 has relatively small depth, as the combustion chamber 10 is limited at the rear by a ceramic lining or rear wall 16 which also forms a front wall in a fuel hopper 18. This is designed with an inclining rear wall 20 which at a back side of the stove 2 is pivotally suspended along an upper back side edge 22, so that the inclining rear wall 20 of the fuel hopper 18 may be moved or vibrated with the intention of ensuring an optimal movement of the fuel downwards against a transverse slot-formed firing opening 24, in case the fuel does not move downwards against the firing opening 24 by itself.
The fuel hopper 18 is supplied with pellets or granulated fuel 25 through a door 26 in the right side of the stove, which door 26 is most clearly seen in Figs. 3 and 5. The door 26 is designed with an external recessed handle 27, so that it does not take up external space on the side concerned on the stove 2.
The fuel hopper or magazine 18 is dimensioned to accommodate about 18 - 20 kg fuel, by way of example wood pellets, corresponding to a time of operation of the stove 20 of about 22-24 hours. In order to facilitate secure feeding of fuel through the door 26, this is hinged along a lower side edge. The pelletised or granulated fuel is expected delivered in apportioned packings, by way of example plastic bags, with a volume corresponding to the capacity of the fuel hopper 18.
In order to avoid risk of back-burning from the fireplace, the user's guide for the stove 2 should contain a clear instruction about the door 26 to the fuel hopper 18 not to be opened when the stove is in operation.
Opposite the firing opening 24, most clearly shown in Fig. 4, is arranged a transverse fireplace or combustion zone 28 which is delimited at the front by a forward/upwards extending inclining ceramic element 30, from the upper edge of which a second ceramic element 32 is extending largely horizontally inwards towards the ceramic back wall 16, so that a mixing chamber 33 is formed, and so that the fireplace or the combustion zone 28 are almost entirely enclosed by ceramic material, excepting a fixed transverse bottom plate 34 of steel or cast iron extending rearwards from the lower edge of the ceramic element 30.
Opposite the fixed bottom plate 34 there is provided a relatively narrow transverse slot 36 with a width of about 5 mm between the fixed bottom plate 34 and a transverse movable bottom plate 38 which is connected to a vibrating mechanism, so that the movable bottom plate 38 can be vibrated with the intention of allowing ashes to pass through the slot 36 and down into an ash pan 40 - in such a way that ember layer or not combusted fuel is not allowed to be carried down into the ash pan 40. The movable bottom plate 38 may advantageously be connected with the inclining back wall 20 of the fuel hopper 18, so that the movable bottom plate 38 and the inclining rear wall 20 of the fuel magazine 18 may be vibrated simultaneously by means of a common vibration mechanism which is operated from the front side of the stove by means of a handle 41.
For maintaining the combustion in the fireplace or the combustion zone 28, primary combustion air is fed from the ash pan up through the slot 36 directly under the fireplace or combustion zone 28, while primary combustion air is supplied into the mixing chamber 33 through a transverse slotted nozzle 42 in the inclining ceramic element 30 so that an optimal combustion of the combustible flue gases is ensured for forming a flame curtain in the whole width of the combustion chamber 10 in front of its ceramic rear wall 16.
The secondary tertiary combustion air is sucked in from the cavity under the surrounding jacket 4, and the secondary combustion air is fed, as mentioned above, to the mixing chamber 33 through the slotted nozzle 42, while the tertiary combustion air is led upwards through a vertical riser pipe 44 and distributed by means of a transverse duct 46 with a downwards/outwards directed guiding surface 48 in a way known per se downwards along the inner side of a glass pane 50 of a front door 52 of the stove 2, from where the tertiary combustion air is sucked inwards into the combustion chamber 10 and contributes to maintaining optimal combustion of the combustible flue gases up along the rear wall 16 of the combustion chamber, so that the flue gas combustion may be viewed through the glass pane 50 before the flue gases reach the flue ducts 12 of the upper section 6 and disappear out through the chimney.
The supply of combustion air (primary, secondary and tertiary) is controlled by means of known automatics, which by way of example are described in DK patent 166 637 , that is determined by the actual flue gas temperature. By using downdraught principle and feeding of tertiary combustion air, it becomes possible to utilise the high efficiency of the downdraught principle by an even flue gas production at a high temperature for achieving a visible flue gas combustion as known from traditional burning of wood.

Claims

A burning stove (2), in particular for combusting pellets or granular fuel, including a combustion chamber (10) with a fireplace or a combustion zone (28), a feeding aperture (36) for primary combustion air arranged thereunder, a feeding aperture (42) for secondary combustion air arranged above the fireplace, a feeding aperture (52) for tertiary combustion air supplied over the combustion chamber (10) and conducted downwards along the inner side of a glass pane (50) of a front door (52) for the stove (2), and that the stove includes a fuel hopper (18) with an inclining bottom plate (20) behind the combustion chamber (10), characterised in that the burning stove (2) includes a filling opening (26) for fuel in a sidewall, that between the fuel hopper (18) and the fireplace or the combustion zone (28) there is provided a slotted firing opening (24), that an upper transverse top edge (22) of the inclining bottom plate (20) is pivotally suspended in the vicinity of a back side of the stove (2), and that a lower transverse edge part of the bottom plate (20) is connected with an activating mechanism for moving the inclined bottom plate (20) of the fuel hopper (18).
Stove (2) according to claim 1, characterised in that said combustion chamber (10) is designed with a tilting bottom plate (38) which by movement or vibration enables emptying ashes down into an underlying ash pan (40), which bottom plate (38) is designed so that fuel or ember layer cannot slide down into the ash pan (40).
Stove (2) according to claims 1 - 2, characterised in that the activation mechanism is common to the inclining bottom plate (20) of the fuel hopper and said tilting bottom plate (38) in the combustion chamber (10).
Stove (2) according to claims 1 - 3, characterised in that predominantly over the entire width of the combustion chamber (10) between a front side of said tilting bottom plate (38) and a fixed bottom plate part (34) there is provided a slot (36) for feeding primary combustion air.
Stove (2) according to claims 1, characterised in that in a lower part of the combustion chamber (10) there is designed a mixing chamber by means of a transverse outwards/upwards ceramic element (30) disposed with spacing in front of the fireplace or the combustion zone (28), and a further ceramic element (32) extending inwards from a top side edge of the previously mentioned ceramic element (30), the ceramic elements (30, 32) extending mainly in the whole width of the combustion chamber (10).
Stove (2) according to claim 5, characterised in that a transverse slot (42) for feeding secondary combustion air is provided in the first mentioned ceramic element (30), which slot is extending predominantly horizontally and predominantly in the entire width of the mixing chamber (10).
Stove (2) according to claim 1, characterised in that secondary and tertiary combustion air is fed into the surrounding casing of the stove (2) through a common air intake, from where the tertiary combustion air is conducted upwards through one or more riser pipes (44) to a transverse distribution channel (46) disposed over the front door (52) with a downwards/outwards inclining guide surface (48), so that the tertiary combustion air is fed downwards and predominantly along the entire width of the glass pane (50) of the front door (52) and from there horizontally into the combustion chamber (10).