Door with a built-in burner for a heating appliance

0001The present invention relates to an integrated burner door, thermally insulated, for heater.

0002It is particularly applicable to heating appliances consisting of a tube or set of tubes, come (s) by a fluid to be heated-for example of the water- and the wall is exposed to combustion gases generated by the burner.

0003This "gate" is a wall which is removable so as to allow the aircraft maintenance, in particular periodic cleaning of the burner. It is set by example with a series of peripheral screws fixed perimeter frame) from the front of the unit. Such a door is described by document<patcit id="pcit0001" dnum="DE8800650W1"><text>DE 88 00 650 W1</text></patcit>

0004The burner is fixed in the central part of the door, on its inner face, so that it is positioned in the interior of the device, close to (or more) pipe (s) when the door is closed . The outer face of the door is connected to a cuff for supplying a combustible gaseous mixture (fuel gas / air or fuel / air), and the transfer of this mixture to the burner is done through an appropriate opening in the door. Generally the feed gas mixture in the cuff is using a fan.

0005Conventionally, the area of ​​the internal face of the door which surrounds the burner is furnished with a heat-resistant material and thermally insulating, for example a ceramic plate base material, the door itself being metal, usually cast aluminum.

0006With the unit in operation, the temperature of the gas from the burner has a value, an indication, is generally between 950 and 1000 ° C. Despite the presence of this insulating lining, the temperature of the external face of the door may reach a temperature between 120 and 180 ° C.

0007This reduces heat radiation in no small measure the overall performance of the device; thus, for a circular door, with a diameter of 220 mm, the energy loss can be of the order of 150 Wh, ie 540 kJ (depending on the burner output system).

0008In addition, the fact that the outer face of the door is brought to a relatively high temperature, there arises a risk of burns to people who may come into contact with the door, in particular for the operator in charge of maintenance and of camera settings.

0009A first object of the invention is to provide a door significantly reducing loss, improving therefore the performance of the device.

0010A second objective of the invention is to provide a single gate structure, lightweight, easy to manufacture, inexpensive and amenable to automated mass production.

0011A third objective of the invention is to provide a door whose design improves the quality of combustion of the burner.

0012A fourth object of the invention is to improve safety by preventing the risk of burns.

0013The invention therefore relates to an integrated burner door heater, and this door is provided on its inner side with a gas burner and on its outer face with a feed system of a combustible gas mixture the burner; it is adapted to be engaged in the framing of a wall of the device, and to be secured to the frame removably.

0014According to the invention, this door comprises a pair of metal sheets secured to each other at their periphery, the outer sheet having in its central region an inlet opening for the supply of said gaseous mixture while the sheet inner present in its central region an outlet opening, coaxial with said inlet opening, to which is fixed the burner, these two sheets being spaced from each other, leaving between them a space inside which is fixedly mounted a deflector plate, the latter having the shape of a disc whose diameter is substantially larger than that of said inlet and outlet openings of said door, and being mounted centered on the axis of these openings and perpendicular thereto, this deflector plate being composed of two closely spaced parallel plates, fixed to each other at their periphery, said deflector plate being so shaped and dimensioned that the mixed gas stream enters the camera by said inlet opening is deflected outwardly of the deflector plate, in bypasses the peripheral edge of the outside to the inside, and then flows on its inner face, to come out through said outlet opening and into the burner .

0015Thanks to this arrangement, the gas mixture current enters the camera follow a zigzag path; these cold streams lick in the first instance the inner face of the outer sheet and the outer face of the deflector plate, which acts as a heat shield and the internal face of the latter before reaching the combustion surface of the burner.

0016The outer sheet which is exposed to ambient air remains cold or warm, according to the objective. Furthermore, preheating the mixture prior to the burner improves the combustion quality and performance of the device.

0017According to other possible advantageous characteristics, but not limiting of the invention:<ul><li>said inlet and outlet openings are circular</li><li>said baffle plate has, on the portion of the peripheral edge of its inner face, studs or bosses by means of which this face is applied and fixed against the external face of said inner panel, by this point-like contact areas, that would not bother passing the gaseous mixture, while limiting heat transmission to the inner sheet to the deflector plate;</li><li>said deflector plate is provided with a thermal insulator interposed between said sheets, said insulator consisting of a neutral gas such as nitrogen for example, or in a solid material, for example made of ceramic;</li><li>constitutive inner panel said deflector plate has a raised central portion which allows its elastic deformation and enables it to absorb the stresses generated by the expansion and contraction associated with temperature changes, as the unit is running or is stopped</li><li>the outer sheet constituting said baffle plate has a central portion nipple-shaped tip which faces the inlet opening, this stud promoting radial flow distribution of the gas mixture entering said inlet opening;</li><li>said burner is flat, its combustion surface being perpendicular to the axis of said openings;</li><li>said burner is slightly domed, the combustion surface being convex and centered on the axis of said openings;</li><li>said burner is annular, its cylindrical combustion surface being centered on the axis of said openings;</li><li>the area of ​​the inner panel surrounding the outlet opening is lined, on its internal face, a heat-resistant material and thermally insulating, such as a ceramic or ceramic-based material; </li><li>the door is provided on its inside with a peripheral seal adapted to be pressed against the outer face of a flange integral with said wall frame;</li><li>the supply system of the combustible gas mixture comprises a sleeve mounted at the inlet opening of said outer sheet, and attached thereto;</li><li>the door is equipped with an electric fan motor which is secured to said outer sheet and is adapted to draw the gas mixture through said inlet opening and discharging it to the burner;</li><li>said motor fan is of the centrifugal type and has a series of rotating blades which are accommodated in a wall of said outer panel recess, which acts as a casing, and extend close to the external face of the deflector plate;</li><li>one hand, the stator of said motor fan is positioned inside of said outer sheet inlet opening, and, on the other hand, the feed system of the combustible gaseous mixture comprises an annular manifold mounted at said inlet opening and secured to the outer sheet, thereby surrounding the stator of said motor fan, this collector being supplied with gaseous fuel via a conduit and its wall being pierced with a plurality of radial openings through which the gaseous fuel is circulated in the annular gap separating the stator from the edge of the inlet opening, to be then drawn by said rotating blades, together with ambient air (oxidant) that is sucked by the same annular gap.</li></ul>

0018Other characteristics and advantages of the invention will appear on reading the following description of various possible embodiments of the invention.

0019This description is made with reference to the accompanying drawings in which:<ul><li>the <figref idrefs="f0001">figure 1</figref> is a front view, in axial section, of a heating appliance with a door which is the subject of a first embodiment of the invention, wherein the integrated burner to the door is flat;</li><li>the <figref idrefs="f0002">2</figref> represents the same door in perspective, also cut off;</li><li>the <figref idrefs="f0003">3</figref> is a view analogous to that of <figref idrefs="f0001">figure 1</figref>Showing a second embodiment of the invention, wherein the integrated burner to the holder is cylindrical; </li><li>the <figref idrefs="f0004">4</figref> is a view analogous to that of <figref idrefs="f0001">figure 1</figref>, Showing a third embodiment of the invention, wherein the door is equipped with a motor-driven fan;</li><li>the <figref idrefs="f0005">5</figref> represents the same door in perspective, also cut off;</li><li>the <figref idrefs="f0006">6</figref> is a perspective view, cut, showing an alternative embodiment of the invention, wherein the deflector plate fitted to the door has a projecting portion;</li><li>the <figref idrefs="f0007">7</figref> is a perspective view showing the inner panel and the baffle plate of the door shown in <figref idrefs="f0006">6</figref>.</li></ul>

0020On the <figref idrefs="f0001">figures 1</figref>, <figref idrefs="f0003">3</figref>, <figref idrefs="f0004">4</figref> and <figref idrefs="f0006">6</figref>, Circulation of the gas streams was visualized by arrows, the apparatus being considered in operation.

0021The same numbers and reference letters have been used in a good clear goal in order to designate identical or similar elements of the various embodiments shown.

0022On the <figref idrefs="f0001">figures 1</figref> and <figref idrefs="f0002">2</figref>, Reference numeral 1 designates the door integrated burner 2, which is the subject of the invention.

0023The latter can adapt to different types of heaters.

0024On the illustrated embodiments, it is easy -to example- as a heat exchanger to condensation of the kind produced by the GIANNONI FRANCE under the name "ISOTHERMIC" (registered trademark).

0025This type of exchanger has two helical tube bundles mounted coaxially inside a gas-tight envelope, separated by a partition made of thermally insulating material. The tubes are crossed by the fluid to be heated, water for example. They have a flattened oval section and the gap between turns is calibrated and narrow. The burner is located inside one of the beams, said primary, and the hot gases from the burner pass through these gaps from the inside to the outside, with a high coefficient of heat exchange. They then bypass the insulating partition and pass through the interstices of the other beam, said secondary, in the opposite direction (from outside inward), before being discharged from the casing through a conduit or an appropriate cuff .

0026Such a device is well known, will not be described in detail below in order not to unnecessarily burden the present description.

0027However, if necessary, the reader is referred to the following patent documents, which relate to an exchanger of this type: <patcit id="pcit0002" dnum="EP0678186B"><text>EP-B-0678186</text></patcit> (See in particular Figure 18) <patcit id="pcit0003" dnum="WO200403621A1"><text>WO 2004 / 03621A1</text></patcit> (<figref idrefs="f0001">figures 1</figref> and <figref idrefs="f0005">5</figref>) and <patcit id="pcit0004" dnum="WO2004097311A1"><text>WO 2004 / 097311A1</text></patcit> (see <figref idrefs="f0001 f0002">figures 1-2</figref>).

0028The door 1 is fixed in the frame 61 of the front wall of an AC heater whose shell 6 has a side wall 60 and a bottom wall 62 having an exhaust sleeve 620 for connection to a conduit (not shown) for evacuating the burnt gases. This shell 6 contains a tubular helical coil of stainless steel 7, a flattened and oval section, of axis X-X '. It consists of a primary beam 70 and secondary beam 71, separated by an insulating disk 600. This is a heat exchanger with condensation, of the same type as those described in the aforementioned documents, adapted to heating water or any other fluid that is circulated through coil 7.

0029The door 1 has a generally circular form, centered on the axis XX 'and has peripheral fastening members (not shown) for mounting it removably on the front of the device, for example using four ears arranged at 90 °, and screwed to the facade.

0030Door 1 includes a pair of thin wall thickness, the outer one 10, the other internal 11. These walls are made of stainless steel cut and deep-drawn.

0031They are fixed to each other at their periphery by crimping and / or welding; this peripheral flange 100 has an annular recess, facing the interior which receives a seal 101 adapted to be pressed, when the door is closed, against a bearing flange 72 fixed in the frame 61 and contact by its internal face against the first turn of the winding 7.

0032The stamping of the outer sheet 10 is such that it has a convexity directed outwards, of which the central zone is formed with a circular opening 102 centered on X-X '. The wall bordering the opening has a profile adapted to the assembly and tight fixing -for example by means of screws or by soudage- a sleeve 5 (shown in phantom) for supplying the combustible gas mixture into the apparatus via a suitable conduit 50.

0033The stamping of the inner panel 11 is such that it has a convexity directed towards the inside, whose central area is pierced with a circular opening 103 centered on X-X '. This opening is bordered by an annular mouth to which is fixed the burner 2. The latter has the shape of a cylindrical cup of low height, the annular portion 20 is fitted and retained by clamping (press fitting) and / or by some welding spots on said mouth, while its flat bottom 21 is perforated, forming the combustion surface. In the illustrated embodiment, the burner has a composite structure comprising a pressed perforated inner sheet and a fibrous and porous outer wall allowing good adhesion of the flame.

0034Different structures (single-walled or double-walled in particular) and various forms of burner may be provided.

0035Thus, the bottom 21 by combustion surface office could be slightly curved, with its convexity facing the interior of the apparatus, and its center of curvature centered on X-X '. The curved shape allows good absorb expansion phenomena, the combustion surface can deform naturally to take a bend more or less pronounced depending on this expansion.

0036Given these forms stamped "hollow", a free space is available between the two sheets 10 and 11.

0037In this space accommodates a discoid plate 3 thin, centered on XX '. Its diameter is substantially larger than that of the openings 102 and 103; it is however slightly less than that of said free space.

0038The plate 3 consists of two thin walls 30, 31, for example made of stainless steel, fixed to each other at their periphery 300 in a sealed manner, for example by crimping and / or welding. The outer sheet 30 is flat; the inner panel 31 has an annular main area also planar, parallel to the sheet 30, and a central zone 310 slightly convex, with convexity turned towards the inside (side burner).

0039Between the walls 30 and 31 is encapsulated insulating material 32, for example an inert gas such as nitrogen or a solid material based on ceramic. Its function is to limit the transfer of heat between the two walls.

0040The inner wall 31 is provided at its periphery with a plurality of bosses, such as dished 311, uniformly distributed (eg six bosses 60 ° angle) by means of which it is fixed to the sheet 11.

0041This binding is achieved for example by welding, in areas of restricted area, point-like, to reduce the transfer of heat between the two walls 11 and 31, and also not to oppose the passage of gas between these last. These bosses are thus also act as spacers.

0042The door 1 comprises, inside, an annular gasket 4 in heat-insulating material, and heat-resistant, for example ceramic or ceramic based material. This lining is fitted axially with its central opening on the cylindrical portion 20 of the burner 2 and is retained against the inner face of the wall 11 by an inner flange of suitable shape 720 of the supporting collar 72. Thus, the annular packing 4 covers the periphery wall 11 of the burner up to the level of the coil 7, constituting a heat shield in relation to the hot gases from the burner present inside of the primary beam of the exchanger.

0043The burner having been ignited by means of an appropriate ignition system (not shown), and the fuel air / gaseous fuel mixture being fed into the cuff 5 via the conduit 50, the device operates in the manner explained above after.

0044The gas stream that enters the device through the opening 102 (arrows F), meeting the flat wall 30 of the plate 3 facing it, and is split into a multitude of gas streams that are deflected at right angles and flowing radially from the axis XX 'outwardly of the disc, to the peripheral edge 300 (arrows G), while licking the wall 30; arrived beyond the edge 300, they bypass the latter (arrows H) and flow in opposite directions, towards the axis XX ', towards the outlet opening 103, this time licking the wall 31 (arrows I) to finally enter the interior of the burner 2.

0045Combustion, visualized by darts d, generates gases burned hot (arrows J), the temperature is of the order of 950 to 1000 ° C;

0046These gases pass through the gaps between turns of the primary beam 70 radially from the inside outwards, emerge thereof (arrows K), is channeled inside the shell 6, enter the interstices between the turns of the beam secondary 71 (arrows L), pass through radially from the outside inwards, emerge thereof (arrows M), and are discharged through the cuff 620 (arrows N).

0047the fluid flowing inside the winding is first preheated in the secondary beam 71, and then heated in the primary beam 70, as is well known.

0048When the device is in operation, the inner sheet 31 of the baffle plate 3 is at a temperature substantially higher than the outer sheet 30. In addition, this temperature ranges from relatively significantly and frequently during commissioning phases road and stopping the device.

0049This results in successive expansions and retractions of said wall higher than the outer wall, a source of mechanical stresses term could affect the peripheral bonding of the two walls. However, this risk is eliminated by the presence of the central bulging 310 which can deform elastically in a reversible manner, by absorbing these stresses, so that they do not affect the level of the peripheral flange 300 junction.

0050Thanks to the presence of the baffle plate 3, the heat loss of the outwardly apparatus are extremely low.

0051Indeed, firstly, only a small part of the heat released by the plate 11 is transmitted to the plate 3 and on the other hand, almost all of the heat from the front is recovered by the gas mixture returning , licking the hot walls during its zigzag trajectory. Moreover, this preheating improves the quality of combustion.

0052Indication, if the gas mixture supplied by the cuff 5 is at a temperature in the range 20 to 25 ° C, the temperature of the outer wall 10 of the door is of the order of 25 to 30 ° C , significantly lower therefore the temperature at which would reach the outer wall of a traditional door, which temperature corresponds to the outside temperature of the wall 11 if it was not cooled by the incoming gas mixture, namely between 120 and 180 ° C.

0053Scalding of an operator is thus excluded.

0054The <figref idrefs="f0003">3</figref> refers to an embodiment of the door 1 which differs from the preceding only with the type of burner built into the door.

0055This is a cylindrical burner 2 ', of axis X-X', closed by a flat bottom 20 'and the input of which has a collar-shaped flange 21' that surrounds the central aperture 103 of the inner sheet 11 and is secured thereto, for example by welding at several points.

0056The operation of the apparatus is similar to that previously described.

0057The <figref idrefs="f0004">figures 4</figref> and <figref idrefs="f0005">5</figref> relate to an embodiment of the door 1 which differs from that of <figref idrefs="f0001">figures 1</figref> and <figref idrefs="f0002">2</figref> in that an electric motor fan 8 of the centrifugal type, centered on the axis XX, is integrated in the door.

0058This comprises an annular stator 80 which is secured to the outer sheet 10 by means of suitable fastening tabs, not shown.

0059It comprises a series of blades 82 carried by a rotatable disc 83 which is fixed to its rotor 81 using screw 810. These blades are housed in a circular recess, suitably shaped, formed in the wall of the outer panel 10 , which thus housing office for them.

0060The blade-carrying disc 83 extends in a general plane perpendicular to the axis XX 'and close to the external face of the deflector plate 3. The blades 82 are fixed to the external face of the disc 83.

0061The stator 80 of the motor fan is positioned with clearance (annular space) inside the inlet opening 102 of the outer sheet 10. This opening has the shape of a mouth surrounded by an annular manifold 9 (approximate ring) centered on the axis XX '. This collector can be attached to or forming part of the sheet 10.

0062The collector 9 is connected to a duct 91 for supplying a gaseous oxidant, such as butane or propane, for example. Its inner annular wall and / or that it surrounds the mouth is pierced with a plurality of apertures 90 regularly distributed at its periphery, for diffusing the gaseous oxidant in the form of jets in the annular gap surrounding the stator .

0063In operation, the rotor is rotated, the oxidant gas passes into the duct 91 (arrow C), arrives in the annular manifold 9 (arrows D), exits through the orifices 90 and is sucked into the interior of the apparatus 82 by the blades in motion (arrows F). The latter also draw in ambient air (fuel) which is taken from the outside (arrows E) and pass in the same annular gap, mixing gas from the orifices 90.

0064It is therefore a combustible gas pre-mixture which is forced inside of the door 1 by the motor fan 8.

0065It follows a similar path to that already described above with reference to <figref idrefs="f0001">figure 1</figref> (Arrows G, H and I), finally entering the flat burner 2 after passing the baffle plate 3.

0066According to the embodiment, the gas flows out of the inlet opening 102 does not strictly speaking lick the outside of the plate 3. However the effect is similar. The tray 3 acts as a heat shield; as it is not in contact with the rotary disc 83, there is no heat transfer between these two elements, which puts the motor-fan free of temperature increases.

0067It is of course possible to equip a motor fan of such a door provided with a cylindrical burner like the <figref idrefs="f0003">3</figref>.

0068The <figref idrefs="f0006">figures 6</figref> and <figref idrefs="f0007">7</figref> refer to an alternative embodiment of the door 1, which differs from the preceding by the shape of the outer plate of the deflector plate. The latter is then referenced 3 '.

0069This outer sheet, referenced 30 ', has an annular main area plane, parallel to the inner area 31 and a central sheet 301' projecting, pin-like, the tip of which is turned towards the inlet opening 102 of the gate 1.

0070This form is obtained for example by stamping.

0071The pin 301 'improves the radial distribution of incoming air flow, as shown by the arrows <b>P.</b>

0072In addition, this reduces the losses of load relative to a flat surface.

0073Thanks to this particular shape of the central area 301 ', the fan causing the combustible air / gaseous fuel, in the cuff 5, less strain and may rotate less fast to obtain the same flow.

0074The <figref idrefs="f0007">7</figref> lets see the deflector plate 3 'is not necessarily a strictly circular shape, but it can present its periphery notches 33 of various shapes adapted to the passage of various components such as the ignition electrodes or ionization, for example.

0075Although it is not shown, it can be the same for the baffle plate 3 described above.