CA2340831A1 - Liquid-fuel leaktight heating appliance - Google Patents

Abstract

An open-flued, liquid-fuel, leaktight, low-power individual domestic heating appliance (1), in which means for removing the burnt gases derived from the combustion, and also means for feeding in oxidant gas (air), are mounted directly on an external structure (5), such as an outside wall, which may be a bearing wall, or the roof of a dwelling or a room to be heated, without connection to a chimney, comprises a burner pot (4) containing a catalyst (15), preferably made of refractory steel, which stabilizes the flame and which has a nominal heat output of between 50 % and 100 %, and preferably between 75 % and 100 %, of the said output of a conventional burner of the same dimensions connected to the chimney of a dwelling.

Description

LIQUID-FUEL LEAKTIGHT HEATING APPLIANCE
Subject of the invention The present invention relates to the field of liquid-fuel leaktight heating appliances, in particular heating appliances fired by fuel oil (domestic fuel).
In particular, the invention relates to a small-power individual heating appliance or cooker, which is balanced and open-flued for heat exchange with the ambient air, without an intermediate and by radiation through a partition limiting the combustion chamber, which comprises a heat-producing oil-fired burner.
Technological background and state of the art A large number of old houses have unsuitable chimneys, which do not permit an efficient draw which is suited to the heating appliances currently manufactured and which, according to the European standards, require outputs of greater than 80 %.
Thus, in order to ensure a minimal combustion output, it is necessary for the chimneys of buildings, in particular of dwellings, to have a draw which is sufficient, but not too strong or possibly opening into a katabatic wind zone.
In addition, a large number of modern dwellings do not have a chimney and/or are based on the use of expensive electric heating systems.
Often, consumers wish to add a heating system for occasional use, in particular a fuel-oil stove.
Consequently, there is a need for liquid-fuel heating appliances which may be adapted to bearing structures external to the dwelling to be heated, in particular to the outside walls, while at the same time allowing a satisfactory "draw" of the burnt gases derived from the combustion.

In the case of liquid-fuel heating appliances, in particular systems fired by fuel oil, petroleum or vegetable oil, combustion brings about the formation of a certain number of aromatic compounds, if the draw is excessive or if the stove is poorly designed or poorly regulated, along with the formation and possibly the deposition of dust and soot, if the draw is insufficient or following poor combustion.
Such problems do not arise with gas-fired heating appliances, given that the products resulting from the combustion are carbon dioxide and water vapour. In a blue-flame gas appliance, whether it is either leaktight with an air drain or connected to a chimney, it is the injection of the gas into an atmospheric burner venturi which serves as the "motor" for drawing in the oxidant gas (air).
In heat-producing liquid-fuel appliances, the draw of the chimney is thus of fundamental importance and is the source of all the problems of the installation.
The reason for this is that it is the chimney which entrains the oxidant air through the injectors of a burner pot and an insufficient draw leads to a production of soot, while too strong a draw leads to the destruction of the catalyst and to the production of CO gas at low flame.
Thus, balanced-flued leaktight heating appliances are known per se for gas fuel and for a number of fuel oil-fired boilers. Oil-fired heating appliances are also well known as connected on a conventional chimney with a draw comprised between 1.3 and 2.3 mm water column, i. e. between 13 and 23 ~ 5 Pa.
Document EP-A-0 171 504 discloses a water heater comprising a cylindrical water tank under which is a combustion chamber comprising a gas-fired burner or a liquid-fuel burner. A double wall is mounted around the tank to allow the intake of fresh air into the combustion chamber. This double wall is extended in the form of a concentric double nozzle. The inner nozzle is connected to the combustion chamber and allows the burnt gases to be removed, while the space between the inner nozzle and the outer nozzle allows the inlet of combustion air into the double wall mentioned above.
This device cannot be used as an individual appliance for heating ambient air, given the low output which would result from the presence of a heat exchange, first towards the heated water and then from this heated water to the combustion air circulating in the double wall. The inner nozzle for removing the burnt gases, passing through the middle of the reservoir, also favours stabilization of the draw, which is not the case in a conventional heating appliance in which the combustion chamber is of a larger size. In addition, the combustion air does not arrive into the chamber via calibrated orifices, as needs to be the case in an appliance with equilibrated evacuation of the burnt gases.
Document EP-A-0 190 394 discloses a device which has a nozzle for removing the burnt gases, surrounded by a second nozzle which is concentric to the first nozzle. The common axis of the two nozzles is inclined at an angle of about 4° relative to the horizontal, rising towards the exterior. This device is intended to be incorporated into a cutting made in an outside wall and to be connected on the internal side to a gas-fired or liquid-fuel heating installation. The fresh combustion air enters the device by passing into the space between the two nozzles.
In addition, a device in which a starter burner is combined with a porous component to allow the stabilized surface combustion of liquid fuel with the oxidant gas is known, according to document WO-A-97/49 952. The porous body consists of special steel or of ceramic and may be coated with materials which increase the available area or which are catalytic.
Aims of the invention The present invention is directed towards providing a stabilized-flame heating appliance of leaktight type based on the use of a liquid fuel, which does not require the systems for removing the gases to be connected to a chimney.
The present invention is directed towards providing such a heating appliance which is characterized by an efficient output, which does not give rise to any risks of unsafety for the consumer and which does not require ventilation of the room to be heated.
Brief description of the figures FIGURE 1 diagrammatically shows a perspective view of a liquid-fuel leaktight heating appliance according to the present invention.
FIGURE 2 is a view in detail corresponding to FIGURE 1 for the combustion chamber, the means for feeding in oxidant gas and the means for removing the burnt gases from the heating appliance according to the invention.
FIGURE 3 diagrammatically shows a view in cross section of the double nozzle mounted on an external bearing structure, for feeding in oxidant gas and removing the burnt gases.
FIGURE 4 diagrammatically shows an elevated view of a burner pot equipped with a catalyst according to the invention.

FIGURES 5.a to 5.c show a top view of three embodiments of the reaction ring of a burner pot belonging to a heating appliance according to the invention.
Summary of the invention The present invention relates to an open-flued, leaktight, low-power individual domestic heating appliance, which is fired by liquid fuel (that is to say a heating appliance fired by fuel oil or domestic fuel, petroleum, vegetable oil, etc.), in which the means for removing the burnt gases derived from the combustion of this liquid fuel, and also means for feeding in oxidant gas (air) are mounted directly on an external structure, such as an outside wall, which may be a bearing wall, or the outer roof, relative to the room or dwelling to be heated and without requiring connection to a chimney.
The expression "leaktight heating appliance" means a heating appliance which does not require means for feeding in oxidant gas from the inside of the dwelling or room to be heated, the leaktight heating appliance optionally being protected from the atmosphere of the dwelling or room to be heated via a double wall which ensures total leaktightness.
Preferably, the invention concerns a heat-producing oil-fired burner in installation conditions corresponding to D-vent, balanced flue or air drain, with a depression reduced to a value comprised between 1/2 and 1/3 of the chimney value, i.e. between 4 and 12 ~ 2 Pa, and for oxidant gas (air) heated through an intake which is concentric with the burnt gases exhaust.
According to the invention, the heating appliance comprises a burner pot containing a catalyst, preferably made of refractory steel, which stabilizes the f lame and which has a nominal heat output equal to at least 50%, and preferably at least 75 %, of the said output of a conventional burner of the same dimensions connected to the chimney of a dwelling.
Advantageously, the burner pot has calibrated oxidant-gas (air) injectors whose overall cross section is increased by a factor of about the square root of 3 compared with the said injectors of a conventional burner of the same dimensions connected to a chimney.
The motive power of the oxidant gas is provided by the temperature difference due to oil combustion.
According to one preferred embodiment of the invention, the means for feeding in oxidant gas (air) mounted on an external bearing structure comprise a double nozzle consisting of two nested cylinders, an inner cylinder allowing the burnt gases derived from the combustion to be removed, and the ring portion between the inner cylinder and an outer cylinder allowing oxidant gas (air) to be fed into the heating appliance. The end of the double nozzle on the external bearing structure is preferably covered with an air drain.
Advantageously, the end of the inner cylindrical tube projects out relative to the bearing structure and relative to the end of the outer cylinder.
A first embodiment of the invention which is particularly preferred comprises a burner, the diameter of which is preferably 10 inches, and including a reaction ring of frustoconical share. which preferably at an angle of 45° ~ 5° relative to the axis of the burner, with a first plurality of equidistant holes, the diameter of which is preferably 5.7 mm, arranged in a circle, and a second plurality of holes, the diameter of which is preferably 2.8 mm, arranged 7 _ essentially in a circle, which are in greater number, preferably 50 % more, and on a radius which is greater than that of the first plurality of holes.
A second embodiment of the invention which is particularly preferred comprises a burner, the diameter of which is preferably 10 inches, and including a reaction ring of frustoconical shape, which is preferably at an angle of 45° ~ 5° relative to the axis of the burner, with a first plurality of equidistant holes arranged in a circle on a first radius, the said holes being in the form of a series of holes with a first diameter, which is preferably 6 mm, alternating with a second series of holes, of a smaller second diameter, which is preferably 5.7 mm, a second plurality of holes, the diameter of which is preferably 2.3 mm, arranged in a circle on a second radius which is greater than the first radius, and a third plurality of holes, the diameter of which is preferably 4 mm, arranged in a circle on a third radius which is greater than the second radius.
Description of a preferred embodiment of the invention The liquid-fuel heating appliance bearing the general reference numeral 1 in the attached Figures 1 to 3 comprises a combustion chamber 3, in which the oxidant air is entrained through a heat-producing burner pot 4.
The heating appliance 1 is designed such that the injection of air into this burner pot 4 is within a combustion ratio of about from 1 to 3, preferably from 1 to 4, compared with a liquid-fuel heating appliance connected conventionally to a chimney.
The heating appliance of the invention is also advantageously provided with a catalyst 15 made of refractory steel to stabilize the flame in the said heat-producing burner 4.
This catalyst stabilizes the combustion in the low-flame and intermediate blue-flame regimes, that is to say in a cracking of the hydrocarbons ranging predominantly towards CO rather than C (particulate carbon). It also cools the flame by infra-red emission, thereby reducing the degree of oxidation of the nitrogen in the air to NOX. What is more, this heats the base of the evaporator, thereby reducing the residence time of the liquid hydrocarbons that are the most difficult to vaporize and hence reducing the fouling by polymerization of these hydrocarbons into a hard black lustrous crust.
Preferably, the means for removing the burnt gases derived from the combustion, and the means for feeding in oxidant gas (air), mounted directly on the external bearing structure S, such as an outside wall, consist of a double nozzle for introducing the oxidant gases and removing the burnt gases derived from the combustion. This double nozzle, which is a component that is optionally bent as shown in FIGURE 3, advantageously consists of two cylinders 6, 7, preferably nested one into the other (or optionally parallel to each other). The inner cylinder 6 allows the removal of the burnt gases derived from the combustion and the annular space between the inner cylinder 6 and the outer cylinder 7 allows the oxidant gas (air) intended for combustion to be fed in.
The end part of this cylindrical structure is advantageously covered with an air drain 8 fixed to the external bearing structure 5, thus making it possible to prevent the formation of disturbances and turbulence possibly caused by wind blowing towards the said bearing structure 5.

_ g _ This air drain 8 is designed and arranged on the external bearing structure 5 so as to allow the end 9 of the inner cylindrical tube 6 to project out relative to the external bearing structure 5, but also to project out relative to the end 10 of the outer cylinder 7, as illustrated in FIGURE 3.
The heating appliance also comprises a device 12 for introducing liquid fuel, dispersed by natural gravitation or introduced into the combustion chamber 3 by any injection device or like, the heating appliance comprising a flow regulator 11, optionally fitted with an overflow safety 13.
The combustion power of the heating appliance of the invention is adjusted by the user as a function of the position of a control lever or of a thermostatic actuator.
The oxidant air is in drained into the burner pot 4 through a series of calibrated perforations 14 by means of the draw of the devices for removing the burnt fuel gases, more specifically by means of the difference in weight between a column of unit cross section of oxidant air and a column of unit cross section of burnt gases derived from the combustion.
This configuration also allows an efficient draw of the burnt gases derived from the combustion.
As the oxidant gas (inlet air) heats up in the annular portion between the outer cylinder 7 and the inner cylinder 6, on contact with the burnt gases derived from the combustion and leaving via the inner cylinder 6, the difference in pressure between the upstream and downstream of the air injector in the burner pot 4 is about 1/3 of that found in an appliance with a conventional chimney in which the column of inlet air is at ambient temperature.

- 1~ -Modification of the burner pot 4 according to the invention thus makes it possible to maintain an efficient combustion.
In this case, the kinetic energy available for the injection is of the order of 1/3 of that which is available in a conventional system connected to a chimney.
The energy is proportional to the square of the speed and to the density (1/3 pv2) . Consequently, it is necessary to inject the same volume of oxidant gas (inlet air) per unit of time (if it is assumed that the density has barely changed), the injection speed of the leaktight appliance is of the order of 1/~3 of that which is found in a conventional heating appliance.
Consequently, the burner pot 4 of the heating appliance of the invention is modified so that the overall cross section of all the injectors of the burner pot is increased by a ratio equal to about ~3, that is to say about 1.7, relative to a comparable conventional appliance, in particular one which is comparable with regard to its dimensions, with connection to a chimney.
If it is considered that the flow rate of oxidant air is more or less equal to that of a conventional appliance, the speed is necessarily modified and, by modifying the burner pot according to the invention, an equilibrium is observed which allows an efficient combustion. This prevents destabilization of the flame, as well as the formation of combustion derivatives which may result in the formation of dust and the deposition of soot. In order to satisfy the abovementioned mathematical conditions, the burner pot 4 of the invention has been modified by forming a distribution of perforations of different sizes, such as large perforations next to small perforations, optionally alternately, or a succession of alternating small perforations in the lowest stage of the burner pot 4.
This alternation of large and small holes in the same stage of the burner enlarges the diameter of the combustion disc. The reaction cones arising from the large holes, or respectively from the small holes, end their combustion closer to, or respectively further from, the centre of the stage. The reaction area is thus increased without creating excessive pressure drops caused by turbulence in the overall dynamics of the combustion, which is important in a context of reduced draw.
The abovementioned mathematical data are designed for a reference of 8 feet in height of a leaktight heating appliance.
However, the characteristics of the leaktight heating appliance of the invention may be adapted to other conditions by a person skilled in the art, on the basis of the teaching of the present description.
The leaktight heating device of the invention is also characterized by a high output, ensuring a low production of CO gas, in particular less than the limits of the European and Canadian standards (European standard EN1 and Canadian standard B140.3).
An example of a liquid-fuel burner which may be used in the context of the invention is disclosed in American patent US-A-6 015 287 and shown in FIGURE 4.
This burner contains a central catalytic component comprising an assembly of knives arranged concentrically about a vertical axis.
According to one particularly preferred embodiment of the invention, the final reaction stage of the burner, that is to say the ring 16, is treated to increase the reaction area before the combustion products escape along the vertical axis of the burner with harmful unburnt materials, if the combustion is incomplete, and with nitrogen oxides (NOX) if the combustion is too long and at too high a temperature, that is to say close to the stoichiometry.
The ring may itself be made according to several embodiments.
FIGURE 5.a shows a top view of the ring before drawing in a cone frustum at an angle of 45° ~ 5°
relative to the axis, the cone frustum stopping at the tangent circumference to the inside of the large holes (reference numeral 16 in FIGURE 4} . The flame is in the form of a very attractive and very supple skirt of small cups, which is resistant to sudden surges of the 15 draw, formed by an alternation of blue spokes arising from small holes 21. The blue spokes from the combustion of CO in excess air and the bright yellow spokes from the combustion of particulate carbon C
under slightly sub-stoichiometric conditions, which 20 come together at the centre on the axis of the burner (and of the skirt of fire) make it possible simultaneously to reduce the emissions of NOX and of CO, which is noteworthy. This situation of blue spokes in excess air alternating with yellow spokes lacking air has the effect of making the degrees of oxygenation of the combustion locally heterogeneous while at the same time keeping the overall level close to stoichiometry. This result is obtained by pinching the flame "aerolically" by means of large holes 20 inside the ring and small intercalating holes 21 slightly more to the outside. This flame of very high aesthetic appeal and combustion qualities is, however, highly laminar and the reaction exchanges are mild. Under the poorest draw conditions, for example with a 3 m double-walled nozzle, a nominal heat output reduced to about 3/4 of that of a standard burner of the same diameter on a standard single-wall chimney is permitted.
FIGURE 5.b shows a top view drawn under the same conditions as that of FIGURE 5.a. In this case, a destruction of the appearance of a skirt with blue/yellow cups allows a nominal heat output equal to that of a standard burner of similar diameter. It also allows the superposition of a grille covered with false coals or false wood (ceramic fibre, light refractory concrete, etc.) made of refractory material. The large holes 22A play the same role as the holes 20 in FIGURE
5.a. The holes 22B, on which are mounted smaller holes 23, draw the flame locally upwards while inducing a strong accelerating turbulence of the combustion phenomena without reducing the overall pressure drops, but, on the other hand, while increasing the flame pressure in the outermost zone and the zone most upstream of the coronal flame, which activates the draw of the oxidant air. The skirt with blue/yellow laminar cups is replaced here by a lens of small, lively, intense concentric flames with erratic local behaviour, essentially a flame which is much closer to that of spray burners, without having the drawback of their noise. In this case, the rate of combustion over the trajectory which runs from the ring to the axis is overall of the order of 4/3 of its value in the appearance of a skirt of cups (FIGURE 5.a). Finally, the holes 24 act as "inter-lighters" and "flame anchors" between the groups 22A and 22B.
FIGURE 5.c gives an example which is intermediate between the above two cases, adapted here to a burner 6" in diameter rather than 10" in diameter, in the same overall configuration as in FIGURE 4.
If it is desired to retain a smooth skirt of conventional appearance, the heat outputs permitted are even less than those of a skirt with blue/yellow cups (50% to 70 % of a conventional burner of the same diameter). The output may be improved by attaching N
tubes (N = 3, 4, 5, etc.) or profiled holes. The result then all the more resembles the first two cases above the more N increases.
Decreasing the minimum output may be obtained by positioning a second low-flame ring under the existing ring, between the first and the second stage of injector holes. This second low-flame ring advantageously has holes, to allow a certain level of permeability between the upstream parts of the two stages thus defined.
Overall, in an air-drain stove of this type, the loading parts of the circuit are adjusted by closing a baffle plate more or less tightly. This adjustment is made once and for all by the manufacturer as a function of the vertical and horizontal lengths of the double-walled nozzle.
Direct and optimized exchange is performed through the design of a specific combustion chamber combined to a research linking appearance and technique, so that all active partitions directly transfer the energy produced in the room or dwelling. This direct transfer of heat to the room to be heated permits to maintain appliance efficiency at the different rates from minimum to maximum, with the following advantages .
- greater active surface temperature and thus greater thermal comfort or improved cooking ;
- wind and internal depression insensitivity for the new leaktight dwellings with controlled air replacement ;
- absence of any fuel oil odor emission in the dwelling ;
- improved flame appearance.

Another advantage is that a oxidant gas feeding, close to stoichiometry and regulated by a thermal regulator such as a structure modified bimetallic strip or by an output lever position, maximizes the output at the intermediate regimes.
At last, a regulation performed through a by-pass in the burner circuit stabilizes the minimal regimes, even in high wind conditions. The burner becomes thus insensitive to wind variations.

Claims (9)

1. Open-flued, liquid-fuel, leaktight, low-power individual domestic heating appliance (1), in which means for removing the burnt gases derived from the combustion, and also means for feeding in oxidant gas (air), are mounted directly on an external structure (5), such as an outside wall, which may be a bearing wall, or the roof of a dwelling or room to be heated, without connection to a chimney, characterized in that it comprises a burner pot (4) containing a catalyst (15), preferably made of refractory steel, which stabilizes the flame, and in that it has a nominal heat output of between 50 % and 100 %, and preferably between 75 % and 100 %, of the said output of a conventional burner of the same dimensions connected to the chimney of a dwelling.

2. Leaktight heating appliance according to Claim 1, characterized in that the burner pot (4) has calibrated oxidant-gas (air) injectors (14) whose overall cross section is increased by a factor of about the square root of 3 compared with the said injectors of a conventional burner of the same dimensions connected to a chimney.

3. Leaktight heating appliance according to Claim 1, characterized in that it contains a burner circuit presenting a depression reduced to a value comprised between 1/2 and 1/3 of the chimney conventional burner value, preferably comprised between 4 and 12 ~ 2 Pa.

4. Leaktight heating appliance according to Claim 1, characterized in that the means for removing the burnt gases derived from the combustion, and also the means for feeding in oxidant gas (air) mounted on an external bearing structure (5) comprise a double nozzle consisting of two nested cylinders (6,7), the inner cylinder (6) allowing the burnt gases derived from the combustion to be removed, and the ring portion between the inner cylinder (6) and the outer cylinder (7) allowing oxidant gas (air) to be fed into the heating appliance (1).

5. Leaktight heating appliance according to Claim 4, characterized in that the end (9, 10) of the double nozzle on the external bearing structure is covered with an air drain (8).

6. Heating appliance according to Claim 5, characterized in that the end (9) of the inner cylindrical tube (6) projects out relative to the bearing structure (5) and relative to the end (10) of the outer cylinder (7).

7. Heating appliance according to any one of the preceding claims, characterized in that the burner (4), the diameter of which is preferably 10 inches, includes a reaction ring (16) of frustoconical shape, which is preferably at an angle of 45° ~ 5° relative to the axis of the burner, comprising a first plurality of equidistant holes (20), the diameter of which is preferably 5.7 mm, arranged in a circle, and a second plurality of holes (21), the diameter of which is preferably 2.8 mm, arranged essentially in a circle, which are in greater number, preferably 100 o more, and on a radius which is greater than that of the first plurality of holes (20).

8. Heating appliance according to any one of Claims 1 to 6, characterized in that the burner (4), the diameter of which is preferably 10 inches, includes a reaction ring (16) of frustoconical shape, which is preferably at an angle of 45° ~ 5° relative to the axis of the burner, comprising a first plurality of equidistant holes (22A, 22B) arranged in a circle on a first radius, the said holes being in the form of a series of holes (22A) of a first diameter, which is preferably 6 mm, alternating with a second series of holes (22B), of a smaller second diameter, which is preferably 5.7 mm, a second plurality of holes (24), the diameter of which is preferably 2.3 mm, arranged in a circle on a second radius which is greater than the first radius, and a third plurality of holes (23), the diameter of which is preferably 4 mm, arranged in a circle on a third radius which is greater than the second radius.

9. Heating appliance according to any one of the preceding claims, characterized in that the liquid fuels are chosen from the group consisting of fuel oil or domestic fuel, petroleum and vegetable oil.