BE1018339A3 - SYSTEM OF AIR SUPPLY AND EXHAUST OF BURNED GASES. - Google Patents

Abstract

The invention relates to a system for supplying air and for exhausting burnt gases for a closed hearth, comprising: - an air supply circuit comprising a forced circulation device, and - a gas evacuation circuit burned. Said supply and evavuation circuits are in contact on one or more common sections 6 to exchange heat between the air and the flue gases, and said forced circulation device 18,30 of the air supply circuit is located upstream of at least a portion of a common section 6 heat exchanger.

Description

"Air supply and exhaust gas system"

The present invention relates to a system for supplying air and exhaust gas burned for closed fireplaces.

In the combustion systems of the state of the art, regenerative devices are known for recovering heat from combustion gases in order to preheat the combustion air and thus to improve the efficiency of the combustion system. There are known, for example so-called suction tubes, comprising a central channel for the evacuation of combustion gases and a peripheral channel for the supply of combustion air. Such suction tubes may optionally be provided with an insulation, as illustrated for example in the document EP 1369642, in order to limit heat losses.

Such supply and extraction ducts can operate by simple convection. However, in this case, their effectiveness decreases with the length of the ducts, especially if they include bends. Thus, from a certain length, forced circulation means become necessary to ensure a satisfactory supply and evacuation.

Document DE 3539311 discloses a heating device associated with a suction tube. The hot combustion gases are discharged via the central channel, while the combustion air passes through the peripheral channel, into which this air is preheated before entering the combustion chamber. To activate the suction of the fumes and thus the admission of fresh air into the combustion chamber, the free end of the central channel is provided with an exhaust fan.

CA 2260524 discloses a device for introducing a stream of fresh air from the bottom of a flue or chimney. Alternatively, the chimney comprises a jacketed pipe so as to define a central channel for discharging fumes and a peripheral channel for supplying preheated fresh air to the combustion chamber, as well as in the chimney. Fresh air is propelled into the chimney via a fan. This fan is a fan sucking the air to blow it into the chimney.

Document EP 0 013 700 discloses a device for evacuating burnt gases and fresh air intake for gas-tight heaters comprising two concentric ducts, the inner duct being intended for evacuation of flue gases. , while the outer peripheral duct conducts fresh air to the heater. The inner duct is associated with a profiled exhaust hood and an exhaust fan.

The admission of air into the combustion chamber is therefore always obtained by the suction of the combustion gases. This does not allow a precise adjustment of the admitted combustion air volume, a setting which is advantageous for controlling the temperature and appearance of the combustion flame, as well as the amount of fuel burned.

The document US Pat. No. 4,262,608 describes a system for supplying air and for evacuating burnt gases, comprising an air supply circuit comprising a forced circulation device, and a flue gas evacuation circuit, said circuits for supply and discharge being in contact on one or more common sections to exchange heat between the air and the flue gases. In particular, this system of the state of the art comprises a fan downstream of a peripheral channel of a suction pipe for pushing the combustion air supplied by said peripheral channel to a combustion chamber via a simple pipe, and an extractor sucking fumes upstream of the central channel of the suction pipe to blow them in said central channel. The fan thus acts on a preheated combustion air, while the extractor acts on hot combustion gases.

This system of the state of the art is however intended to be installed on a boiler. The flue gases therefore arrive at the extractor after passing through a heating block, that is to say a gas-liquid heat exchanger in the boiler. Neither their temperature nor, consequently, that of the preheated air, will be more very high.

Closed hearth, however, means hearths, stoves, inserts or cassettes, solid fuel or gas, having a combustion chamber substantially closed but not comprising a gas-liquid heat exchanger. In such closed fireplaces the heat of combustion is mainly released by radiation and / or air convection, and not by heat exchange with a liquid circuit. In such a closed hearth, the flue gases are normally discharged at a temperature substantially higher than in a boiler. The device for supplying air and exhaust gas burned in US 4,262,608 thus has several disadvantages for use in a closed fireplace.

Firstly, the high temperatures of the flue gas and combustion air preheated by these flue gases in the suction tube could damage the fan, the extractor, and their actuating motor.

In addition, while boilers are normally installed in low-traffic areas, closed fireplaces are often decorative and are normally installed in well-frequented rooms. The noise generated by the fan, the extractor, and their actuation motor placed near the fireplace will be much more inconvenient.

Thus, all these devices of the state of the art do not provide optimal heat exchange between the combustion air and the flue gases of a closed fireplace.

The present invention aims to overcome these disadvantages by placing said forced circulation device of the air supply circuit upstream of at least a portion of a common heat exchanger section.

In this way, the forced circulation device acts on the combustion air at a temperature closer to ambient temperature. In this way it is possible to ensure good reliability of the device without having to take expensive and expensive thermal protection or cooling measures. In addition, because of the higher density of this cooler air, the efficiency of the forced circulation device is higher. The regulation of the air flow is also facilitated. Finally, since the forced circulation device is upstream of at least a portion of the common heat exchanger section on the air supply circuit, it may be located at a greater distance from the insert insert type hearth. The apparent noise in the vicinity of the closed hearth can thus be reduced without recourse to the same complex and expensive soundproofing means.

Preferably, the system may further comprise a control unit of at least said forced circulation device connected to a flow sensor. Such a device thus makes it possible to ensure a suitable flow rate of air in the combustion air supply circuit or in a portion thereof, for example as a function of the need for air necessary for combustion. It also allows a good heat exchange or air heating. Normally, flow is defined as mass flow.

However, the volume flow could be used alternately.

Other sensors are possible, for example to check the content of CO, CO2, etc. · flue gas. The control device can for example in case of poor combustion (too much CO) to control the forced circulation device to bring more air into the closed fireplace.

. Preferably, said at least a portion of a common heat exchanger section located downstream of the forced circulation device may have a length of at least two meters, preferably at least three meters. In this way it is ensured that the preheating of the combustion air is carried out mainly downstream of the forced circulation device.

Preferably, said common heat exchanger section may be a suction tube comprising a central channel for exhausting burnt gases and a peripheral channel for supplying combustion air. In this way, the efficient heat exchange between the flue gas and the combustion air is easily and efficiently provided. In addition, such a suction tube can easily be adapted to a closed hearth, and can also easily give him a path with one or more elbows. However, said common heat exchanger section may alternatively have a different arrangement of the supply and discharge channels, for example a side-by-side arrangement.

More preferably, said forced circulation device may comprise at least one nozzle opening into said peripheral channel. Even more advantageously, said nozzle may be oblique with respect to said peripheral channel. Thus, it also imparts a helical movement to the combustion air, so as to increase the heat exchange between the flue gases in the central channel and the combustion air in the peripheral channel.

In a particular embodiment, the forced circulation device may be at least partially integrated in said peripheral channel, so as to reduce the size of the system.

Advantageously, the forced circulation device may comprise at least one fan, which allows a control of the flow rate by controlling the operating speed of the fan. For example, this fan could be a centrifugal fan.

Advantageously, the forced circulation device may comprise at least one ejector. This or these ejectors eject a small amount of air at high speed to blow or propel a larger amount of air. The efficiency of the forced circulation device can thus be improved.

Advantageously, the air supply circuit and / or the exhaust gas evacuation circuit may comprise one or more ducts of circular section, but they may also be of different section, such as a square section, a rectangular section. , a hexagonal section, etc. according to the necessities.

The present invention also relates to a method for regulating the flow of combustion air in a system for supplying air and exhausting burnt gases according to the invention, in which the forced circulation device is controlled to maintain a substantially constant air flow. More preferably, said substantially constant air flow is pre-selected. Thus, the length of the air supply system and exhaust gas can be varied by keeping the same forced circulation device and flow.

The present invention also relates to a closed hearth having a substantially closed combustion chamber connected to a system for supplying air and exhausting burnt gases according to the invention, wherein the combustion chamber comprises at least one burner gas connected to a fuel gas supply circuit with a flow regulator. Preferably,

The features and details of the invention will become apparent from the following detailed description in which reference is made to the accompanying drawings.

In these drawings, - Figure 1 is a schematic view of a closed hearth according to one embodiment of the invention, partially in section, - Figure 2 is a sectional view along line II-II of Figure 1 FIG. 3 is a perspective view of an oblique fin-shaped deflector; FIG. 4 is a schematic view of a closed hearth according to another embodiment of the invention; FIG. a schematic view of a fan used in the installation of FIG. 5; FIG. 6 is a diagrammatic view of a detail of an air supply and exhaust gas evacuation system according to another embodiment embodiment of the invention, and - Figure 8 is a schematic view of a detail of a system for supplying air and exhaust gas burned according to yet another embodiment of the invention.

FIG. 1 shows a closed hearth type "cassette" comprising: - a combustion chamber 1 substantially closed, said chamber 1 being in this embodiment surrounded by a casing 2 adapted to allow the passage of air 3 in the envelope along one or outer walls of the combustion chamber 1 or in contact with the combustion chamber 1, and also comprising a gas burner 4A supplied by a fuel gas supply circuit 4 also comprising a flow regulator 4B, said envelope 2 also having one or more openings 5 for the passage of air towards the combustion chamber 1, a duct 6 of the concentric suction tube type comprising two concentric ducts 6A, 6B, namely a central duct 6A connected to the combustion chamber 1 so as to serve to evacuate the smoke or combustion gas, and an outer duct 6B defining a peripheral channel 7 connected to the casing 2 to bring air at the combustion chamber 1, the top of the duct 6 being advantageously provided with a perforated cap 8 with inclined flaps to prevent the entry of rain into the channel 7, and a distributor 9 to control the evacuation fumes out of the central channel 6A, two flat 10,11 shaped rings extending in the peripheral channel 7 between the outer wall of the central duct 6A and the inner wall of the peripheral duct 7B, so as to divide the peripheral channel 7 defined between the ducts 6A and 6B in three portions, namely an upper portion 7A extended by the suction cap 8, a lower portion 7B connected to the casing 2, and an intermediate portion 7C which is sealed relative to the portions 7A, 7B, the upper portion having in the vicinity of the level of the flat 10 an exit window 12 (just above the flat 10), while the lower portion 78 has an inlet window 13 in the vicinity of u level of the plate 11 (just below the plate 11), - a housing 14 removably mounted on the conduit 6, this housing having a channel 15 extending between an inlet opening 16 and an outlet nozzle 17, the inlet opening being intended to be facing the window 12, while the outlet nozzle 17 is intended to face the window 13, said housing 14 thus serving to put the upper portion 7A in communication with the lower portion 7B of the peripheral channel 7, - a fan 18 located in a portion of the channel 15 of the housing 14, said fan being rotated by a motor 19, said fan 18 being adapted to suck the air from the upper portion 7A to blow it into the lower portion 7B through the nozzle 17, - a first series of oblique fin-shaped deflectors 20 located at a distance of about 10 to 30 cm downstream of the nozzle 17, said fins being arranged to induce a helical movement to the air circulating in the lower portion 7B or in a portion thereof; - a second series of fins 21 spaced from the first set of fins 20 to induce again a helical movement to the air circulating in a portion of the lower portion 7B, the intermediate portion 7C of the channel 7 has an opening 21 located opposite a door 22 closing an access window inside the inner conduit 6, a plug 23 blocking the opening 21, - a control unit 24 adapted to control the fuel gas flow controller 4B, and the rotation of the motor 19 and its rotational speed, said control unit 24 being connected by wired connection and / or wireless, for receiving signals from one or more flow sensors 25. Sensors other than the flow sensor 25, such as temperature, pressure, velocity, and other sensors, such as e valve actuators placed in the air supply, flue gas discharge or fuel gas supply circuits could also be connected to the control unit 24.

In this way, the portions 7A, 7B of the peripheral channel 7 and the channel 15 form a combustion air supply circuit to the combustion chamber 1, while the central channel or duct 6A forms a discharge circuit of combustion gas from the combustion chamber 1.

In a possible embodiment the plates 10, 11 would only partially close the passage section of the peripheral channel so as to form an air passage between the portions 7A and 7B which is parallel to the channel 15 of the housing 14.

Figure 2 is a top view of the series of fins 20. These fins extend between the inner conduit 6A and 1p outer conduit 6B. These fins are advantageously welded to said ducts and are advantageously made of a heat conductive material.

The fins 20 (see FIG. 3) are profiled to generate a substantially helical air movement in the peripheral channel.

However, in an alternative embodiment, the peripheral channel 7 may also be devoid of fins, such that the air stream is not helical, but substantially parallel to the axis of the duct 6.

The conduit 6B may be provided with a thermal insulation.

FIG. 4 is a schematic view of an installation according to an embodiment of the invention which is similar to that shown in FIG. 1, except that the fan housing has been replaced by a series of four small fans 30, integrated in the peripheral channel 7B, and whose axis of rotation is inclined relative to the axial axis of the duct 6. One of these fans 30 is illustrated in Figure 5.

Instead of using inclined fans, it is also possible to use turbines placed parallel to the axis of the duct 6, but whose output is associated with an inclined nozzle or a deflector.

FIG. 6 is a schematic view of a part of an installation according to another embodiment of the invention which is also similar to that shown in FIG. 1, except that the fan 18 is located at the top duct 6B, the combustion air entering the fan 18 via a single duct 31.

FIG. 7 is a schematic view of part of an installation according to another embodiment of the invention which is also similar to the previous ones, except that the ducts 6A, 6B are not concentric, but placed side by side, the duct 6A thus serving to supply air, and the duct 6B to the evacuation of combustion gas.

In operation, the combustion chamber 1 of the closed hearth of FIG. 1 is supplied with combustion air by the combustion air supply circuit formed by the portions 7A, 7B of the peripheral channel 7, the channel 15, and the fan 18 of the channel 15, and combustion air by the fuel gas supply circuit 4 via the flow regulator 4B and the burner 4A. An air / fuel mixture is thus formed in the combustion chamber 1 to be burned. The flue gases are then discharged through line 6A.

The control unit 24 controls the flow regulator 4B of the fuel gas supply circuit 4. A user can thus adjust the intensity of the flame through the control unit 24 by increasing and decreasing the flow rate of the gas. through this control unit 24 and the flow controller 4B. This control unit 24 also governs the speed of rotation of the motor 19 of the fan 18 according to signals from the flow sensor 25, so as to maintain a substantially constant air flow rate, and this independently of the resistance to the flow of water. air of the combustion air supply circuit. The control unit 24 regulates the level of the air flow so as to maintain a substantially constant air / fuel ratio in the combustion chamber 1. In this way the two flow rates are regulated together.

Although the present invention has been described with reference to a specific exemplary embodiment, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. For example, the closed fireplace could be a solid fuel fireplace (coal, coke or wood). In this case, the airflow would remain adjustable, even if the fuel flow would not be adjustable. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims (17)

An air supply and flue gas exhaust system for a closed hearth, comprising: an air supply circuit having a forced circulation device (18,30), and a gas exhaust system burned, said supply and discharge circuits being in contact on one or more common sections (6) for exchanging heat between the air and the flue gases, and the system being characterized in that said forced circulation device (18,30) of the air supply circuit is located upstream of at least a portion of a common section (6) heat exchanger. The closed combustion flue gas supply and exhaust system according to claim 1, comprising a control unit (24) of at least one of the forced circulation device (18, 30) connected to a flow sensor (25). An air supply and flue gas exhaust system for a closed firebox as claimed in any one of the preceding claims, wherein said at least a portion of a common heat exchanger section (6) located downstream of the device forced circulation has a length of at least two meters, preferably at least three meters. 4.The closed furnace flue gas supply and exhaust system according to any one of the preceding claims, wherein said at least one common heat exchanger section (6) is a suction tube having a central channel ( 6A) for exhausting burnt gases and a peripheral channel (7) for supplying combustion air. 5.A closed air combustion and exhaust gas supply system according to claim 4, wherein said forced circulation device (18) comprises at least one nozzle (17) opening into said peripheral channel (7). ). 6. A closed combustion air supply and exhaust gas discharge system according to claim 5, wherein said nozzle (17) is oblique with respect to said peripheral channel (7). An air supply and flue gas exhaust system for a closed fireplace according to any one of claims 4 to 6, wherein the forced circulation device (30) is at least partially integrated in said peripheral channel (7). ). An enclosed air supply and exhaust gas exhaust system according to any one of the preceding claims, wherein the forced circulation device (18, 30) comprises at least one fan. An enclosed air supply and exhaust gas exhaust system as claimed in any one of the preceding claims, wherein the forced circulation device comprises at least one ejector. The closed combustion flue gas supply and exhaust system according to any one of the preceding claims, wherein the air supply circuit and / or the flue gas exhaust circuit comprise a or more conduits (6A, 6B) of circular section. A method of controlling combustion air flow rate in an air supply and flue gas exhaust system according to any one of the preceding claims, wherein the forced circulation device (18, 30) is controlled for maintain a substantially constant air flow. The control method of claim 11, wherein said substantially constant airflow is previously selected. Closed hearth having a substantially closed combustion chamber (1) connected to an air supply and exhaust gas discharge system according to any of claims 1-10, wherein the combustion chamber (1) comprises at least one gas burner (4A) connected to a fuel gas supply circuit (4) with a flow regulator (4B). The closed hearth of claim 13, wherein said flow controller (4B) and said forced circulation device (18,30) are connected to a common control unit (24). A combustion control method in a closed hearth according to claim 16 or 14, wherein the forced circulation device (18,30) and the flow regulator (4B) of the fuel gas supply circuit (4) are controlled to maintain a substantially constant air / fuel ratio. 16. The control method according to claim 15, wherein the forced ventilation device (18,30) and the flow regulator (4B) of the fuel gas supply circuit (4) are controlled to maintain air flow rates. and substantially constant fuel gas. The regulating method of claim 16, wherein said substantially constant rates are pre-selected.