EP2775209A1 - Oven - Google Patents

Abstract

The oven (1) has a combustion chamber (2) provided with a rear wall (3c) and two side walls, and an air channel (4) for supplying air into the combustion chamber. The air channel is arranged at the rear wall and/or one of the side walls and extended over widths of the rear wall and/or side wall such that air led by the air channel warms up by thermal radiation radiated from the combustion chamber. The rear wall and/or side walls form a thermal insulation layer for the air channel. The air flows along at a glass pane of an oven door (9). An independent claim is also included for a method for controlling an oven for heat generation.

Description

FIELD OF THE INVENTION

The present invention relates generally to furnaces for heat generation, and more particularly to a furnace for generating heat with a secondary air duct and a method of controlling such a furnace.

BACKGROUND OF THE INVENTION

There are generally known stoves for heat generation, which are particularly suitable for the combustion of wood, such as logs or pellets. Such ovens are typically also used in living quarters, e.g. set up in the form of a stove.

Since the installation area for such ovens is often limited, it is desirable that such ovens are built as compact as possible. This desire is contrary to the desire to incorporate more and more comfort features in such ovens, such as. A window air purge, flows along the secondary air on a glass of an oven door and thus reduces contamination of the glass by fire residues. In addition, there is a desire also in wood-burning stoves, which are placed like stoves in particular in living rooms, to optimize the combustion by appropriate control of the air supply and thus, for example, to reduce the particulate matter pollution and the emission of nitrogen oxides.

Typically, however, known wood stoves have only user-adjustable flaps or sliders to control the air supply, which is inefficient and cumbersome for the user. This typically means that such flaps or slide is not changed during the firing process in the wood stove, but they remain in one position. As a result, optimal combustion is not guaranteed.

From the publication EP 2 495 497 A2 For example, a heater with a manual supply air control device is known. The supply air control device has a primary air opening and a secondary air opening. With the secondary air opening, a secondary air channel is connected, which runs at a rear side of the heater and is designed as a separate channel. The width of the secondary air duct substantially corresponds to the width of the secondary air opening and is many times smaller than the width of the rear side of the heating device.

The object of the present invention is to provide an improved furnace for heat generation, in particular a wood-burning stove such as a log-burning stove or pellet stove, and an improved control method for an oven.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides a furnace for heat generation, in particular a wood-burning stove, such as a log-burning stove or pellet stove, in accordance with independent claim 1. In a second aspect, the present invention provides a method for controlling a furnace for heat generation, in particular a furnace according to the first aspect.

Further aspects and features of the present invention will become apparent from the dependent claims, the accompanying drawings and the following description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWING

• Fig. 1 ein Ausführungsbeispiel eines Holzofens in Übereinstimmung mit der vorliegenden Erfindung in einer vertikalen Querschnittsansicht veranschaulicht;
• Fig. 2 den Holzofen in einer dreidimensionalen Teilschnittansicht zeigt;
• Fig. 3 den Holzofen in einer weiteren dreidimensionalen Schnittansicht darstellt;
• Fig. 4 den Holzofen in einer dreidimensionalen horizontalen Schnittansicht darstellt; und
• Fig. 5 ein Verfahren zur Steuerung der Tertiärluftzufuhr des Holzofens der Fig. 1 bis 4 veranschaulicht.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which:

• Fig. 1 an embodiment of a wood stove in accordance with the present invention in a vertical cross-sectional view illustrates;
• Fig. 2 shows the wood stove in a three-dimensional partial sectional view;
• Fig. 3 the wood stove in another three-dimensional sectional view represents;
• Fig. 4 depicting the wood-burning oven in a three-dimensional horizontal sectional view; and
• Fig. 5 a method for controlling the tertiary air supply of the wood stove of Fig. 1 to 4 illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the Fig. 1 to 4 an embodiment of a wood oven 1 in accordance with the present invention is illustrated. Before a detailed description follows first general explanations to the embodiments and their advantages.

The embodiments relate to a furnace for heat generation, which is designed to burn a fuel in a combustion chamber. In principle, all types of fuels are considered, which are made of biomass, but also fuels such as gas, oil, lignite, wood or hard coal and the like.

In particular, the further description also relates, without the present invention being restricted thereto, to a wood-burning stove, such as e.g. a log wood stove or a pellet stove, which is designed, for example, as a wood-burning stove, tiled stove or the like, and can typically be set up in a living room.

In the exemplary embodiments, a furnace for heat generation, in particular a wood-burning stove, such as a logwood stove or pellet stove, comprises a combustion chamber with a rear wall and two side walls. Compared to the rear wall of the combustion chamber is typically closed with an oven door.

The side and / or back wall of the furnace may be made of various materials typical of furnaces (e.g., sheet metal, cast iron, etc., as well as a cladding with firebricks or the like inside). The present invention is not limited to a particular material configuration of the back wall or the side wall.

In addition, the furnace includes a secondary air passage for supplying secondary air into the combustion chamber. The secondary air channel is disposed on the rear wall or on one of the side walls and extends across the width thereof, i. the width of the rear wall or the respective side wall to which it is arranged. The secondary air channel may preferably extend over the entire or almost entire width of the rear wall or side wall on which it is arranged, whereby almost the entire width is to be understood as meaning at least 75% of the entire width. Alternatively, the secondary air channel may extend over at least 50% of the entire width of the rear wall or side wall on which it is disposed. In some embodiments, there are also more than one secondary air channel and / or the secondary air channel is divided, and the secondary air channels then also preferably at least almost completely extend over at least one side wall or the rear wall.

The secondary air duct is designed such that the air guided through it through the heat radiation radiated from the combustion chamber is heated and the air present in the secondary air channel forms a heat insulation layer for the rear wall or the side wall on which the secondary air duct is arranged.

This allows the secondary air duct to perform two functions. He directs the secondary air into the combustion chamber and by the spatial extent over the (at least almost all) width of the rear wall or the side wall to which it is arranged, the (secondary) air in it forms a heat insulating layer, the rear wall or the side wall on which it is arranged, thermally insulated.

Due to the expansion of the secondary air channel across the (entire) width of the rear wall or side wall to which it is arranged, the secondary air channel may be flat, i. with a shallow depth, be formed. Accordingly, little space can have such an oven.

In some embodiments, in the furnace for generating heat, a portion of the secondary air passage is formed by the rear wall and the side wall to which it is disposed. This can save material, as, for example, sheets are needed essentially only for three sides of the secondary air duct and for an upper and lower end of the secondary air duct.

In some embodiments, the secondary air channel is at least partially made of a heat-insulating material and / or has inside a material that reflects heat radiation to enhance the heat-insulating effect of the air layer contained in the secondary air channel. In some embodiments, only one wall of the secondary air channel, which runs parallel to the rear wall or side wall of the combustion chamber, provided with a heat-insulating and / or heat radiation reflecting material.

The secondary air is directed in some embodiments from above into the combustion chamber to provide oxygen for the combustion of flue gases in the combustion chamber. The secondary air may also be used (partially) as a disc purging air, the secondary air flowing down a disc from an oven door from top to bottom and thereby flushing the disc.

According to a sibling aspect of the invention, the combustion chamber of the furnace for generating heat may additionally have a tertiary air supply through the air the secondary air duct is guided into the combustion chamber. The tertiary air can be used to further improve the mixing of flue gases with air (oxygen) in the combustion chamber. Accordingly, in some embodiments, the tertiary air opening is mounted at a height such that the tertiary air is supplied to a certain height of a flame in the combustion chamber, as would typically be expected.

The furnace for generating heat may additionally have a tertiary air supply device for controlling the supply of tertiary air into the combustion chamber. The tertiary air supply device may be configured to control the supply of the tertiary air in dependence on a combustion parameter and / or it is adapted to control the tertiary air supply by manual adjustment. The Tertiärluftzufuhreinrichtung can be electrically operated accordingly. It can have a lifting magnet and a pin with a plate section. The solenoid is operable to displace the stylus and thus the disc portion in the direction of the tertiary air port or away from the tertiary air port. The lifting magnet can move the pin with the plate section so far that the plate section closes the tertiary air opening (completely) and thus prevents the supply of tertiary air.

Some embodiments relate to a method for controlling a furnace for heat generation, in particular a furnace, as described above. The furnace includes a primary air supply, a secondary air supply and a tertiary air supply, also described above.

The method comprises detecting at least one parameter that is characteristic of a burning process in the combustion chamber of the furnace. The parameter may characterize the oxygen content, the carbon dioxide content or the carbon monoxide content in the flue gas produced by the firing process or a firing temperature. The detected parameter is analyzed and the tertiary air supply, and in some embodiments also the primary air supply and the secondary air supply, is controlled in dependence on the analysis result of the detected parameter. The detection of the parameter is carried out by appropriately designed means which are arranged, for example, in the combustion chamber or in a flue gas duct of the furnace.

Typically, in the analysis of the sensed parameter, it can be seen that the combustion is incomplete, and consequently, oxygen delivery through the tertiary air port may increase combustion quality. An incomplete combustion can be detected via a residual oxygen content in the flue gas and / or based on the carbon dioxide content and / or on the basis of the carbon monoxide content in the flue gas. In addition, based on a firing temperature, which is measured, for example, in the combustion chamber above the flame, be closed to the quality of combustion and as a measure, the supplied tertiary air can be increased or decreased.

In addition, in some embodiments, the tertiary air supply may be controlled in response to a combustion duration of combustion in the combustion chamber and the sensed parameter is characteristic of the combustion duration. Typically, combustion, especially of wood, such as logs or pellets, has different firing phases occurring at different times (e.g., a firing phase and a stable firing phase). Depending on the firing phase, it may be favorable to supply more, less or no tertiary air. In some embodiments, the control of the tertiary air supply takes place as a function of the burning time and the associated burning phase.

Thus, in some embodiments, combustion may be optimized by controlling the supply of primary, secondary, and tertiary air.

Some embodiments relate to a furnace controller for controlling a furnace for generating heat as described above, wherein the controller is adapted to carry out the method described above. Such a controller may include a microprocessor and a (working) memory in which a control program is stored, which causes the microprocessor to perform the corresponding method steps. Thresholds for the analysis of the detected parameters can also be stored in the memory. For example, a detected parameter may be compared in the analysis of the detected parameter with an associated stored threshold value. For example, if the detected parameter is above the threshold value, then tertiary air is supplied; if it is below, no tertiary air is supplied. Similarly, the supply of primary air and / or secondary air can be controlled. In other exemplary embodiments, the analysis of the detected parameter also includes, for example, a time profile of the detected parameter or other more complex analysis methods.

Coming back to the Fig. 1 to 4 These illustrate an embodiment of a wood stove 1, which is adapted for the combustion of firewood.

The wood stove 1 has an oven door 9, which is partially formed by means of a glass sheet, and two side walls 3a and 3b (s. Fig. 3 and 4 ) and a rear wall 3 c, which together define a combustion chamber 2. To set up the wood stove 1 has a stand 17 which is connected to the combustion chamber 2 and a bottom plate 18.

On the rear wall 3 c, a secondary air duct 4 is attached, which extends over the entire width of the rear wall 3 c. The secondary air channel 4 directs air from an air supply control device 10, which is arranged below the combustion chamber 2, past the rear wall 3c upwards. At the upper end of the secondary air duct 4, a secondary air duct 6 is arranged, which directs the secondary air from the secondary air duct 3c through an upper opening 25 and via a guide plate 21 to the inner side 22 in the upper region of the oven door 9. The secondary air duct 6 extends obliquely in an upper region of the combustion chamber 2 and connects the upper end of the secondary air duct 4 with the guide plate 21.

The secondary air duct 4 has a rear wall 5, which runs essentially parallel to the rear wall 3c of the combustion chamber 2, two side walls and one upper and one end. Accordingly, the secondary air duct 4 is closed except for an opening to the air supply control device 10 and an opening 20 to the secondary air duct 6 and so far forms a sealed cavity 15 is guided in the secondary air.

In the present embodiment, the secondary air channel 4 is arranged directly on the rear wall 3c, so that a wall of the secondary air channel 4 is formed by the rear wall 3c. In other embodiments, the secondary air duct may also have an object wall.

The secondary air guided through the secondary air passage 4 is heated due to the heat radiation radiated from the back wall 3c of the combustion chamber 2, at the same time the secondary air in the secondary air passage 4 forms a heat insulating layer and insulates the back wall 3c of the combustion chamber 2 from heat loss curb.

Although the secondary air is heated on its way through the secondary air duct 4 and the secondary air duct 6, it is typically still colder than the mixture of air and flue gas in the combustion chamber 2 after this heating, so it falls down on the inside 22 of the oven door in the combustion chamber 2 and in this way rinses the disc of the oven door 9. The flue gases that arise during combustion in the combustion chamber 2 are discharged through a flue gas connection 19 on the top of the wood stove 1.

The secondary air is, as already indicated above, introduced via an air supply control device 10 in the secondary air channel 4. The air supply control device 10 has a supply air connection 11 via the supply air 12 flows into the air supply control device 10. The supply air 12 may be fresh air from outside the site of the wood stove 1 and / or removed from the ambient air of the wood stove 1. Depending on the setting, the air supply control device 10 distributes the supply air 12 to a primary air opening 13 and a secondary air opening 14. From the primary air opening 13, the primary air flows through an area below the combustion chamber and then through a grate 16 which is arranged at the bottom of the combustion chamber 2. The secondary air flows through the secondary air opening 14 into the secondary air channel 4. For the distribution of the supply air 12 to the primary air opening 13 and the secondary air opening 14, the air supply control device 10 has a primary air flap 23 (FIG. Fig. 3 ) and a secondary air damper 24 (FIG. Fig. 3 ). Depending on the position of the primary air flap 23 or the secondary air flap 24, more or less primary air / secondary air passes through the primary air opening 13 or the secondary air opening 14.

The wood burning stove 1 also has a tertiary air supply formed by a tertiary air opening 7 in the back wall 3c. The tertiary air opening 7 is arranged so that secondary air from the secondary air passage 4 can flow through the tertiary air opening 7 into the combustion chamber 2 and forms a small tertiary air passage connecting the combustion chamber 2 and the secondary air passage 3 with each other. For controlling the amount of tertiary air supplied into the combustion chamber 2, a tertiary air supply device 8 is provided, which comprises a lifting magnet, which in turn can move a pin 8a with a plate section 8b attached thereto.

The plate portion 8b has a diameter larger than the diameter of the tertiary air opening 7, so that the tertiary air opening 7 is closed when the plate portion 8b abuts against it.

As already stated above, the tertiary air serves to improve the combustion in the combustion chamber 2, by flue gases with tertiary air and the oxygen contained therein be mixed.

The tertiary air supply is controlled by a control of the tertiary air supply device 8 in accordance with the optimization of combustion taking place in the combustion chamber 2 (the control itself is not shown in the figures).

A method for controlling the supply of the tertiary air of the wood stove 1 is in Fig. 5 illustrated.

In a first step 30, at least one parameter is detected which is characteristic of a burning process in the combustion chamber of the furnace. As already stated, such a parameter characterizes, for example, the oxygen content, the carbon dioxide content or the carbon monoxide content in the flue gas produced by the combustion process or a firing temperature. The parameter is detected by a corresponding means (e.g., a lambda probe in the flue gas port or the like).

In a next step 31, the detected parameter is analyzed. The analysis may, for example, include a comparison with a threshold, as has already been explained above.

Depending on the result of the analysis of the detected parameter, in a next step 32, the tertiary air supply is controlled by setting the solenoid 8a of the tertiary air supply 8 to a position that causes more or less or no tertiary air to flow through the tertiary air port 7.

In some embodiments, not only the supply of the tertiary air, but also the supply of the primary air and / or secondary air is controlled via control of the air supply control device 10 depending on the analysis result of the detected parameter.

Claims (10)

Furnace for heat generation, in particular wood-burning stove, such as log burning stove or pellet stove, comprising: a combustion chamber (2) having a rear wall (3c) and two side walls (3a, 3b); and a secondary air duct (4) for supplying secondary air into the combustion chamber (2), wherein the secondary air channel (4) on the rear wall (3 c) or on one of the side walls (3 a, 3 b) is arranged and over the width of the rear wall (3 c) or the side wall (3a, 3b) extends, so that the air guided through the secondary air duct (4) is heated by the heat radiation radiated from the combustion chamber (2) and the air present in the secondary air duct (4) forms a heat insulation layer for the rear wall (3c) resp the side wall (3a, 3b) forms. A heat generation furnace according to claim 1, wherein a portion of the secondary air passage (5) is formed by the rear wall (3c) and the side wall (3a, 3b), respectively. Oven for generating heat according to one of the preceding claims, wherein the combustion chamber (3c) additionally a Tertiärluftzufuhr (7) by the air from the secondary air duct (5) in the combustion chamber (3c) is guided. A heat generation furnace according to claim 3, further comprising tertiary air supply means (8) for controlling the supply of tertiary air through the tertiary air supply (7). A heat generation furnace according to claim 4, wherein the tertiary air supply means (8) is arranged to control the supply of the tertiary air in response to a combustion parameter. A heat generation furnace according to one of claims 4 or 5, wherein said tertiary air supply means (8) is electrically operable A heat generation furnace according to any one of claims 4 to 6, wherein said tertiary air supply means (8) comprises a solenoid and a pin (8a) having a cup portion (8b). Method for controlling a furnace for heat generation, in particular one A furnace according to any one of claims 1 to 6, wherein the furnace has a primary air supply, a secondary air supply and a tertiary air supply, the method comprising the steps of: Detecting (30) at least one parameter characteristic of a burning process in the combustion chamber (2) of the furnace (1), Analyzing (31) the detected parameter, and Controlling (32) the tertiary air supply in dependence on the analysis result of the detected parameter. The method of claim 8, wherein the parameter characterizes the oxygen content, the carbon dioxide content or the carbon monoxide content in the flue gas produced by the firing process or a firing temperature. The method of claim 8 or 9, wherein the parameter characterizes a burning time of a combustion in the combustion chamber and the control of the tertiary air supply takes place as a function of the burning time.

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