EP2343482A1 - Heating device equipped with fuel regulation - Google Patents

Abstract

The apparatus has a double wall provided with a controlled communication valves (11-14) located at different heights in a vertical section. Regulating units select an open or closed position for each valve according to smoke temperature measured by a temperature sensor (7) located at level of a smoke evacuation conduit (6) to adjust length of a smoke passing path (3) to minimize the smoke temperature while remaining above dew point of smokes. An independent claim is also included for a method for regulating a solid fuel heating apparatus.

Description

Object of the invention

The present invention relates to a heating apparatus, more particularly to a solid fuel domestic heating appliance, such as wood or coal, provided with a regulation that optimizes combustion and thereby maximizes the efficiency of the appliance.

Technological background and technical problem to be solved

Traditionally a wood or coal heater can operate in several gaits. Typically, there is for example a maximum pace, corresponding for example to P _max , an intermediate or average pace, corresponding to P _max / 2, a minimum pace corresponding to P _max / 4 and a pace of idling, corresponding to P _max / 8. P _max is the maximum power of the appliance which, for a wood stove, is typically between 5 and 15 kW. This classification is only given by way of example to allow the following illustration of the invention and to give orders of magnitude. It goes without saying that other intermediate steps and other power criteria are possible. The so-called "idle" pace, for a wood stove, is typically intended for night use. At bedtime, the user reloads the stove and sets the primary air valve on the minimum position. Upon awakening, the user reloads the stove into logs and opens the flapper up to fire.

c'est-à-dire, $$\mathrm{\eta }\mathrm{=}\mathrm{100}\mathrm{\%}\mathrm{-}{\mathrm{q}}_{\mathrm{1}}\mathrm{-}{\mathrm{q}}_{\mathrm{2}}\mathrm{-}{\mathrm{q}}_{\mathrm{3}}\mathrm{,}$$

où :

• q₁ = perte liée à la température des fumées (c'est-à-dire la chaleur qui s'échappe par la cheminée) ;
• q₂ = perte liée au rapport CO/CO₂ (prend en compte la qualité de la combustion) et pertes NO_x, C_xH_y (ces particules seront mesurées quand la prochaine norme européenne sera d'application, théoriquement en 2011) ; si la combustion est complète : q₂ = 0 ;
• q₃ = perte dans les cendres, constante et négligeable (environ 0, 5%) .

It is known that the efficiency η of a heating appliance, such as a wood-burning domestic appliance, is: $$\mathrm{\eta }\mathrm{=}\mathrm{100}\mathrm{\%}\mathrm{-}\mathrm{losses}\mathrm{,}$$

that is to say, $$\mathrm{\eta }\mathrm{=}\mathrm{100}\mathrm{\%}\mathrm{-}{\mathrm{q}}_{\mathrm{1}}\mathrm{-}{\mathrm{q}}_{\mathrm{2}}\mathrm{-}{\mathrm{<figure-callout\; id="3"\; label="q"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">q</figure-callout>}}_{\mathrm{3}}\mathrm{,}$$

or :

• q ₁ = loss due to flue gas temperature (that is, heat escaping through the chimney);
• q ₂ = loss on CO / CO ₂ ratio (taking into account the quality of combustion) and losses NO _x C _x H _y (these particles will be measured when the next European standard will apply, in theory in 2011); if the combustion is complete: q ₂ = 0;
• q ₃ = loss in ashes, constant and negligible (approximately 0, 5%).

To optimize the efficiency, it is necessary to minimize q ₁ and q ₂ , and more particularly q ₁ .

At maximum speed, the losses q ₁ are the highest and therefore the minimum efficiency, possibly lower than the nominal efficiency of the device, which is determined under very specific conditions.

Conversely, at slow speed, the smoke temperature is the lowest and the highest efficiency, but care must be taken to stay above the dew point of the fumes (60-70 ° C), otherwise condensation occurs with accumulation of soot.

The technical problem to be solved, in order to optimize the performance of the apparatus independently of the pace chosen, preferably automatically, is to reduce in a controlled manner the temperature of the smoke or combustion gases, especially at high speeds.

Heat recovery wood stoves are also known such that the evacuation of fumes from the heating body takes place along a maximized path, by a suitable design of the evacuation duct, possibly coupled with a sheath of the type convector (see for example document BE 903 620 A ).

Goals of the invention

The present invention aims to overcome the disadvantages of the state of the art.

More particularly, the object of the invention is to optimize the combustion for each heating step.

The invention also aims to provide security to prevent tarring in the flues, which could lead to a build-up of soot and possibly a chimney fire.

The invention also aims to optimize combustion irrespective of the type or the height of the chimney, as well as in the case of variable atmospheric conditions.

Main characteristic elements of the invention

• une double paroi délimitant, à l'extérieur de la chambre de combustion, un second conduit d'évacuation des fumées, sis sur le parcours des fumées entre la chambre de combustion et ledit premier conduit et munie, dans une section verticale, d'une pluralité de clapets de communication commandés, situés à des hauteurs respectives différentes h1, h2, h3, h4, etc., le second conduit d'évacuation des fumées étant configuré, grâce à une ouverture de la double paroi dans sa partie basse, de manière à allonger le chemin parcouru par les fumées, dans une mesure qui dépend de la sélection du clapet d'entrée ouvert dans le second conduit, les autres clapets étant fermés ;
• des moyens de régulation configurés pour sélectionner, pour chacun desdits clapets, une position ouverte ou fermée, en fonction de la température des fumées mesurée par une sonde de température situé au niveau dudit premier conduit, de manière à ajuster la longueur du chemin parcouru par les fumées pour minimiser la température des fumées, tout en restant au-dessus de leur point de rosée.

A first object of the present invention relates to a solid fuel heater comprising a combustion chamber and a first flue gas duct, characterized in that the heater comprises:

• a double wall delimiting, outside the combustion chamber, a second flue gas discharge duct, located on the smoke path between the combustion chamber and said first duct and provided, in a vertical section, with a plurality of controlled communication valves, at different respective heights h1, h2, h3, h4, etc., the second flue gas duct being configured, thanks to an opening of the double wall in its lower part, so as to lengthen the path traveled by the flue gases, to a degree that depends on the selection of the open inlet flap in the second flue, the other flaps being closed;
• control means configured to select, for each of said valves, an open or closed position, as a function of the flue gas temperature measured by a temperature probe located at said first duct, so as to adjust the length of the path traveled by the fumes to minimize the temperature of the fumes, while remaining above their dew point.

• le premier conduit d'évacuation est une cheminée verticale ou un conduit horizontal ou de départ arrière ;
• la sonde de température est située à une certaine distance de l'extrémité de la cheminée débouchant à l'atmosphère ;
• la sonde de température est sise à environ 30 cm au-dessous du sommet de la cheminée ;
• la double paroi comprend, à chaque hauteur h1, h2, h3, h4, etc., deux clapets situés à proximité des deux parois latérales de la chambre de combustion ;
• l'appareil comprend en outre un clapet de tirage direct pour l'admission des fumées dans le premier conduit ;
• les moyens de régulation comprennent ladite sonde température, un microcontrôleur et un actionneur se présentant sous la forme d'un moteur pour l'ouverture et la fermeture de chaque clapet ;
• la régulation est une régulation en boucle ouverte ou fermée, de préférence de type PID ;
• un conduit de réchauffement d'air primaire ou secondaire aboutissant dans le haut de la chambre de combustion est disposé entre la chambre de combustion et le second conduit d'évacuation des fumées.

According to examples of embodiments, the heating apparatus according to the invention further comprises one or more of the following characteristics:

• the first exhaust duct is a vertical chimney or a horizontal duct or rear departure;
• the temperature probe is located at a distance from the end of the chimney opening to the atmosphere;
• the temperature probe is located approximately 30 cm below the top of the chimney;
• the double wall comprises, at each height h1, h2, h3, h4, etc., two valves located near the two side walls of the combustion chamber;
• the apparatus further comprises a direct draw valve for the admission of fumes into the first conduit;
• the regulating means comprise said temperature probe, a microcontroller and an actuator in the form of a motor for opening and closing each valve;
• the regulation is an open or closed loop regulation, preferably of the PID type;
• a primary or secondary air heating duct leading to the top of the combustion chamber is disposed between the combustion chamber and the second flue gas discharge duct.

• à une allure maximum de l'appareil, le clapet de hauteur la plus élevée h1 est ouvert et les autres clapets fermés ;
• à une allure intermédiaire de l'appareil, le clapet de hauteur la plus élevée h1 est fermé et au moins un clapet de hauteur inférieure h2, h3, h4, etc., est ouvert, les clapets restants étant fermés ;
• à une allure minimum de l'appareil ou au ralenti, tous les clapets sont fermés sauf le clapet de hauteur la plus faible ou bien tous les clapets sont fermés sauf le clapet de tirage direct, admettant directement les fumées dans le premier conduit.

A second subject of the invention relates to a method of regulating a heating apparatus as described above, characterized in that, in operation, said regulation means are implemented so that:

• at a maximum speed of the apparatus, the highest height valve h1 is open and the other valves closed;
• at an intermediate speed of the apparatus, the highest height valve h1 is closed and at least one valve of lower height h2, h3, h4, etc., is open, the remaining valves being closed;
• at a minimum speed of the apparatus or at idle speed, all the valves are closed except for the valve of the lowest height or all the valves are closed except the direct draft valve, admitting directly the fumes in the first conduit.

Brief description of the figures

The figure 1 is a perspective view in section, right and back, of an exemplary embodiment of the regulated heating apparatus according to the present invention.

The figure 2 represents a right and sectional view of the device of the figure 1 .

The figure 3 schematically represents a perspective view of the back of the camera the figure 1 .

The figure 4 schematically represents a view from the right and in section of the apparatus of the figure 1 , with the smoke path shown at maximum speed.

Description of preferred embodiments of the invention

The principle implemented in the invention is to reduce the smoke temperature precisely by extending the path traveled by the fumes between the combustion chamber and the entry into the chimney. Indeed, this elongation of path traveled allows greater expansion of gas and / or better heat exchange with the walls, so the cooling of fumes. According to the invention, it is desired to constantly adapt the path traveled by the fumes at different speeds of the heater, so as to optimize the performance of it, regardless of the pace adopted.

According to the invention, it is proposed for this purpose a heating device, as shown on the figures 1 and 2 , in which the combustion chamber 1 is provided with a double wall 2A which can communicate with the combustion chamber by means of a plurality of valves, for example at least four in number of valves 11, 12, 13, 14 located at different heights h1, h2, h3 and h4, such as h1>h2>h3> h4. For the skilled person, it is understood that any damper system or damper suitable for controlling the draft of a heater may be used in the context of the present invention. The invention is advantageously implemented automatically by means of an open or closed loop regulation, comprising a temperature sensor (7) located in the upper part of the chimney (8, figure 3 ) and an actuator (not shown) which opens or closes the various valves above according to the value measured for the flue gas temperatures and the set temperature. Each valve is secured to a small motor that is controlled by wire connection or radio frequency.

It is then appropriate to apply the method of the invention by examining separately the different paces.

Maximum pace

The flue gas temperature being the highest at this rate, as indicated above, the flap 11 located at the height h1 is opened in order to circulate the combustion gases 3 over a significant distance, namely 2x + a + h. ( figure 3 ), to be able to cool them and thus obtain a better yield. The valves 12, 13 and 14 remain closed (as on the figure 2 ). However, care must be taken not to cool the fumes below the dew point (approximately 65 ° C). It will be noted that, since the height h of the chimneys is not constant, it is necessary to provide for the positioning of the flue gas temperature sensor at the top of the chimney 6, for example at 30 cm below the vertex 8. This positioning of the This sensor makes the invention compatible with any chimney height and allows for varying atmospheric conditions.

The figure 4 shows the path traveled by the fumes in the case of the maximum pace (valve 11 open). The fumes escape to the atmosphere by backward passage 4 or above 4A (towards the chimney).

The "labyrinth" path of the fumes can be obtained by any simple means of construction known to those skilled in the art, for example by means of an "L" folded sheet revealing an orifice 2B in the lower part. stove.

Average pace

As the flue gas temperature is lower than the maximum, there will be a risk of condensation if the path for flue gas cooling remains the same as at maximum speed. It is necessary to shorten their path by controlling the opening and closing of the aforementioned valves. Specifically, when we go from the maximum pace to the average pace and the flue gas temperature measured at the top of the chimney approaches the dew point, an instruction is sent to close the valve 11 and open the valve 12 (the valves 13 and 14 remaining closed), which will decrease the cooling distance of y (that is to say passing from 2x + a + h to 2x + a + hy, figure 3 ). The flue gas temperature will then increase to a value further from the dew point.

Minimum pace and slow motion

At these speeds, the temperature of the fumes again likely to approach (or fall below) the dew point, the valve 13 (14, etc.) will be open (valves 11, 12 closed) to further reduce the distance traveled by the fumes and increase the smoke temperature, and so on. If that's not enough, a direct draft damper 5 directly admitting the flue gases into the chimney, which is normally closed at other speeds, will be open at the last end, away from the dew point.

In the case of high efficiency heating appliances with preheated air, for example of the Woodbox ^® type (patent EP 1 563 228 B1 ), the "double wall" of the apparatus according to the present invention becomes a triple wall, which exchanges heat with the heating channel of the incoming air, which is also heated by the combustion chamber. This sandwiching of the heating channel between two hot walls makes it possible to increase in this case the inlet temperature of the air preheated in the combustion chamber and to reduce the losses q ₂ , because the combustion is improved when it is powered by preheated air. However, the losses q ₁ can also increase, which must be readjusted by means of the regulation according to the invention.

Still in the case of Woodbox ^® type appliances equipped with an upper cooking plate, it was noted that the upper double heating jacket constituted an insulating element which made cooking difficult. The apparatus according to the invention restores the cooking possibilities insofar as the cooking plate can now be in contact with the hot flue exhaust duct.

Simulations have shown that, for a temperature of about 80 ° C at the outlet of the chimney and with an air preheated to 300 ° C, or even 350 ° C, one obtains, for a wood stove with high efficiency regulated by according to the invention, a yield of 85-90% and a CO / CO ₂ ratio of the order of 0.1%, which is in conformity with most of the standards or ecolabels in force in view of to increase the performance and reduce the pollution of heating appliances (eg "Green Flame" label in France, Austria, etc.).

Claims (10)

Solid fuel heating apparatus comprising a combustion chamber (1) and a first flue gas duct (6), characterized in that the heating apparatus comprises: - a double wall (2A) delimiting, outside the combustion chamber, a second flue gas discharge duct (2), located on the flue gas path between the combustion chamber (1) and said first duct ( 6) and provided, in a vertical section, with a plurality of controlled communication valves (11, 12, 13, 14, etc.), at respective different heights h1, h2, h3, h4, etc., the the second flue gas duct (2) being configured, thanks to an opening (2B) of the double wall (2A) in its lower part, so as to lengthen the path traveled by the flue gases, to a degree that depends on the selecting the inlet valve open in the second conduit (2), the other valves being closed; - Control means configured to select, for each of said valves (11, 12, 13, 14, etc.), an open or closed position, depending on the flue gas temperature measured by a temperature sensor (7) located at level of said first conduit (6), so as to adjust the length of the path traveled by the fumes (3) to minimize the temperature of the fumes, while remaining above their dew point. Heating apparatus according to claim 1, characterized in that the first discharge duct (6) is a vertical chimney or a horizontal duct or rear outlet. Heating apparatus according to claim 2, characterized in that the temperature sensor (7) is located at a distance from the end of the chimney (8) opening into the atmosphere. Heating apparatus according to claim 3, characterized in that the temperature sensor (7) is located approximately 30 cm below the top of the chimney (8). Heating apparatus according to claim 1, characterized in that the double wall (2A) comprises, at each height h1, h2, h3, h4, etc., two valves (11, 12, 13, 14, etc.) located at proximity of the two side walls of the combustion chamber (1). Heating apparatus according to claim 1, characterized in that it further comprises a direct draft valve (5) for the admission of fumes into the first duct (6). Heating apparatus according to claim 1, characterized in that the regulating means comprise said temperature probe (7), a microcontroller and an actuator in the form of a motor for opening and closing each valve. Heating apparatus according to claim 7, characterized in that the control is an open or closed loop control, preferably of the PID type. Heating apparatus according to claim 1, characterized in that a primary or secondary air heating duct (9) terminating in the top (10) of the combustion chamber (1) is arranged between the combustion chamber (1). ) and the second flue gas duct (2). A method of regulating a heating apparatus according to claim 1, characterized in that , in operation, said regulating means are implemented so that: at a maximum speed of the apparatus, the highest-height valve (11) h1 is open and the other valves (12, 13, 14, etc.) closed; at an intermediate speed of the apparatus, the highest-height valve (11) h1 is closed and at least one lower-height valve h2, h3, h4, etc. is open, the remaining flaps being closed; - at a minimum speed of the apparatus or at idle speed, all valves are closed except for the lowest height valve or all valves (11, 12, 13, 14, etc.) are closed except the flap valve Direct (5), directly admitting the fumes in the first conduit (6).

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