Deflagration-Proof And Detonation-Proof Surface Combustion Gas Burner

Abstract

A flame-proof and explosion-proof surface combustion gas includes a burner body pierced with a series of orifices, each of which is extended by a rim, wherein the orifices are arranged in several rows of aligned orifices; and a gas distributor that includes a distributor body equipped with a plurality of longitudinal gas-distribution branches, each branch being pierced with a line of orifices bordered by a rim. The distributor body is positioned inside the burner body such that each orifice of the distributor body is coaxial with an orifice of the burner body, wherein when the burner body is coupled to an air supply source and the distributor body is coupled to a gas supply source, the air and the gas mix only at the rims of the burner body.

Description

FIELD OF THE INVENTION

[0001] This invention relates to a surface combustion gas burner, in particular a hydrogen burner. Such a burner is in particular intended to be used in domestic or industrial heating apparatuses, to heat a fluid circulating in an exchanger.PRIOR ART

[0002] There have been two main successive generations of gas burners, namely atmospheric burners and fan burners.

[0003] In atmospheric burners, the pressurized gas is emitted through a nozzle and causes a flow of air via a convergent-divergent device. Such a burner has the drawback of emitting polluting discharge into the atmosphere.

[0004] Among fan burners, air / gas premixture burners or “premix” burners allow total control of the premixing of gas and air (see for example the burner described in document WO2014006103). Polluting discharge is thus considerably reduced.

[0005] However, in the case of premix burners, combustion takes place at the outer surface of the burner. In order to avoid rapid ageing of the burner by exposing its jacket to reddening (which is the case if the flame comes too close to the surface of the jacket), the range of power variation of such a premix burner is in the order of 1 to 3, or even a maximum of 1 to 10, if the jacket is made of a material resistant to high temperatures or includes a specifically developed design such as the burner described in document WO2014006103.

[0006] Moreover, during the operation of this air / gas premix burner, the flow rate of the air and gas mixture must be varied so as to avoid the uprooting of the flame due to excessive flow and conversely, to avoid the flame returning into the burner due to the lack of a sufficient flow, thus causing a flashback.

[0007] Such a flashback can specifically lead to a deflagration, or even to a detonation.

[0008] For a given burner, the range of modulation of its power is therefore regulated by its maximum flow rate, which corresponds to an gas outlet speed less than the uprooting of the flame, and by its minimum flow rate, which corresponds to a gas outlet speed greater than the flashback speed.

[0009] In addition, these two extreme limits of the speed of the air and gas mixture are related to the propagation speed of the flame of the gas under consideration, in other words, to the kind of gas. Thus, one and the same air / gas premix burner will offer a different operating range as a function of the kind of gas used and its propagation speed.

[0010] By way of illustration, natural gas has an average propagation speed of 0.37 meters / second and hydrogen an average propagation speed in the order of 2.6 meters / second, i.e. nearly seven times faster.

[0011] Surface combustion burners of the prior art are therefore also not very suited to the use of hydrogen gas, if one wishes to be able to use such a burner over a wide range of power variations.

[0012] However, in order to comply with the environmental and ecological criteria, hydrogen could be a beneficial alternative as fuel for supplying these burners.SUMMARY OF THE INVENTION

[0013] One aim of the invention is therefore to make provision for a surface combustion burner which can operate in particular with hydrogen, while being reliable, i.e. avoiding the flashback phenomenon and the associated risks while also being able to be used over a wide range of power variations.

[0014] For this purpose, the invention relates to a deflagration-proof and detonation-proof surface combustion gas burner.

[0015] In accordance with the invention, this burner comprises a burner body made of metal or refractory material and a gas distributor, the burner body delimits an inner cavity connectable to an air supply source and has an outer face and an inner face, the burner body is perforated by a series of orifices, each of which is extended by a rim, which projects from this outer face and the central axis of which is normal to this outer face, these orifices being disposed in several rows of aligned orifices, the gas distributor comprises a distributor body which delimits a housing connectable to a gas supply source, the distributor body comprises a plurality of longitudinal gas distribution branches, each branch comprising two longitudinal walls, spaced apart from one another in such a way as to define between each other a longitudinal lamellar gas distribution space, which opens at its inner longitudinal end into said housing, the two walls of each branch meeting to form an outer longitudinal edge, a closed front end and a closed rear end of said branch, each branch is perforated by a series of orifices aligned along its outer longitudinal end, each orifice being bordered by a rim which projects over the outer face of said longitudinal edge and each orifice having a central axis normal to this outer face of said longitudinal edge, the distributor body is disposed in the inner cavity of the burner body so that each orifice of the distributor body is coaxial with an orifice of the burner body, the distributor body and the burner body are dimensioned so that the inner diameter D2 of an orifice of the burner body is greater than the outer diameter D1 of the apex of the rim of an orifice of the distributor body disposed facing this same orifice, so that there is a gap for the passage of air between the apex of the outer longitudinal edge of each branch and the inner face of the burner body, and so that the apex of the rim of each orifice is in immediate proximity to the inlet mouth of the orifice facing which it is placed, so that when the burner body is connected to an air supply source and the distributor body to a gas supply source, the air penetrates the burner body, circulates between the branches of the distributor body and in the gap and escapes from the burner through the rims of the burner body, while the gas penetrates the housing of the distributor body, circulates in the lamellar space of the branches then through the orifices and rims of this distributor body and finally through the rims of the burner body within which it meets the air and is mixed with this one.

[0016] Owing to these features of the invention, the gas and air circulate in the burner where the load losses are extremely small, through separate circuits, and are only mixed at the last moment inside the rims of the burner body. These rims thus constitute microchambers for mixing the gas and air and the combustion takes place at the surface, i.e. on exiting these rims, thus preventing any flashback.

[0017] Such a burner is therefore particularly suitable for use with hydrogen, a gas which has a high flame propagation speed, since flashback is prevented and therefore any risk of detonation or deflagration also.

[0018] In addition, the mixed volumes of gas and air are controlled and make it possible to obtain a wide modulation range.

[0019] According to other advantageous and non-limiting features of the invention, taken alone or in combination:

[0020] at least one rim of an orifice of the burner body and / or at least one rim of an orifice of the distributor body is toothed so as to have notches.

[0021] the burner body is formed from a cylindrical shell, shut off at its rear end by a back wall and the front end of which is equipped with a front wall flange connectable to the air supply source, the orifices of the burner body are fashioned in said shell so that the rows of orifices extend axially over this shell, the distributor body comprises a hollow cylinder which delimits said housing of this body, this housing being central and cylindrical, the longitudinal gas distribution branches extending radially around this cylinder, the distributor body is shut off at its rear end by a back wall and at its front end by a front flange, equipped with a central hole connectable to the gas supply source, the gas distributor comprises a gas pre-distribution device, which comprises a cylindrical body, equipped with an axial cylindrical central opening and several stages of radial channels, each radial channel extending from said central opening all the way to the outer surface of said cylindrical body, and this gas pre-distribution device is disposed coaxially inside the cylindrical housing of the distributor body, so that its central opening is facing the central hole of the flange and each of its radial channels opens into the lamellar space of a branch of the distributor body.

[0022] the cylindrical body of the gas pre-distribution device comprises several rear washers and one front washer, these rear and front washers each having a cylindrical central opening and two opposing flat faces, these central openings being of the same diameter, the front washer and the rear washers being assembled against one another so that their respective central openings are coaxial, the rear washers having on one of their flat faces a series of radial grooves which delimit, with the opposite face of a neighboring rear washer, said radial channels.

[0023] the gas pre-distribution device comprises a device for moving the gas entering into this gas pre-distribution device, to impart to this gas a helical motion when it circulates inside the central opening of the cylindrical body.

[0024] the device for moving the gas is a fixed propeller.

[0025] the shell of the burner body has a rear end, in that the back wall of the burner body comprises a solid disc equipped with a peripheral annular rim which is welded in a gastight manner to the rear end of the shell, in that said solid disc has a front face and is equipped with at least one locator pin which projects from this front face and in that said at least one locator pin is inserted between two neighboring branches of the body of the gas distributor.

[0026] the distributor body is formed from a metal sheet folded on itself to form the gas distribution branches.

[0027] the front and rear ends of each branch of the distributor body are closed by pinching and welding.

[0028] the gap for the passage of air has a height greater than or equal to 0.2 mm.

[0029] the ratio D2 / D1 of the inner diameter of an orifice of the burner body to the outer diameter of the apex of the rim of an orifice disposed facing this same orifice is between 1.2 and 4.

[0030] the gas is hydrogen.DESCRIPTION OF THE FIGURES

[0031] Other features, aims and advantages of the invention will become apparent from the following description, which is purely illustrative and non-limiting, and which must be read with reference to the appended drawings on which:

[0032] FIG. 1 is an exploded perspective view of the elements constituting a possible embodiment of the gas burner in accordance with the invention;

[0033] FIG. 2 is a perspective view of this same burner, the different elements of which are in the assembled position;

[0034] FIG. 3 is a perspective view of the gas distributor of the gas burner of FIG. 1;

[0035] FIG. 4 is an exploded perspective view of the different elements constituting the gas distributor of FIG. 3;

[0036] FIG. 5 is a longitudinal section view of the gas burner, taken along the section plane passing through the line V-V of FIG. 2;

[0037] FIG. 6 is a longitudinal section view of the orifices fashioned in the body of the burner and in the distributor, taken along the section plane passing through the line VI-VI of FIG. 7;

[0038] FIG. 7 is a magnified detail view of the body of the burner and of the distributor shown on FIG. 5.DETAILED DESCRIPTION OF THE INVENTION

[0039] In the remainder of the description, the surface combustion gas burner 1 in accordance with the invention is described as operating with a gas which is preferably hydrogen. However, it could also operate with another gas, for example natural gas, without however departing from the scope of the invention.

[0040] In the remainder of the description and claims, by convention, the term “front” denotes elements that are located or pointing toward the end of the burner through which the air is introduced into it (i.e. on the left on FIGS. 1 to 5) and the term “rear” denotes elements that are located or pointing in the opposite direction (i.e. on the right on FIGS. 1 to 5).

[0041] In general, the gas burner comprises a burner body 2 connectable to an air supply source and a gas distributor 5 connectable to a gas supply source.

[0042] According to a preferred (and therefore not exclusive) embodiment of the invention, which will now be described in more detail, the burner body 2 and the gas distributor 5 are of generally cylindrical shape.

[0043] On FIG. 1, it can be seen that the burner body 2 is shut off at its rear end 26 by a back wall 3 and is equipped at its front end 25 with a front wall flange 4, and that the gas distributor 5 is shut off at its rear end by a back wall 6 and is equipped at its front end with a front flange 7. These different elements will now be described.Burner Body 2

[0044] The burner body 2 is formed of a hollow cylindrical shell 200 extending around a central longitudinal axis X-X′, which also constitutes the central longitudinal axis of the burner 1. This shell 200 preferably consists of a thin metal sheet.

[0045] This body 2 delimits a cylindrical inner body 20.

[0046] Said shell is perforated by a plurality of orifices 21, each of which extends outward as a rim 22, (see in particular FIGS. 5 to 7). The rim 22 surrounds the periphery of the orifice 21. Each rim 22 projects over the outer face 23 of the body 2. Each orifice 21 and its rim 22 have a central axis Z1-Z′1 which is normal to this outer face 23 (see FIG. 6). The inner face of the shell is referenced 23′.

[0047] The rim 22 (and more particularly its free end 220) can advantageously be toothed so as to have notches 22′. These notches 22′ are used to create turbulences at the outlet of the body 2 and thus to reinforce the flame-holding effect and to avoid the uprooting of the flame.

[0048] The orifices 21 and the rims 22 are for example “punched holes”, obtained by stamping or punching of a flat metal sheet, which is then bent to form the cylindrical body 2 and both edges of which are welded.

[0049] These orifices 21 are circular or substantially circular and the rims 22 are cylindrical or substantially cylindrical.

[0050] Furthermore, the orifices 21 (and therefore the rims 22) are aligned so as to form several axial rows 24 of orifices. These rows 24 extend parallel to one another and also parallel to the central longitudinal axis X-X′ of the body 2. Furthermore, preferably, the different rows 24 are evenly distributed over the entire circumference of the burner body 2.

[0051] In a given row 24, the different orifices 21 can be evenly spaced apart from one another or contrariwise be grouped to form a pattern, for example grouped two-by-two as can be seen on the figures.Back Wall 3

[0052] The back wall 3 is composed of a solid disc 30, equipped with a peripheral annular rim 31. The diameter of this back wall 3 is adapted to the diameter of the burner body 2 (here to the shell 200), so that its peripheral rim 11 can be welded to the rear end 26 of the body 2, preferably inside this body 2, as can more clearly seen on the section of FIG. 5. The back wall 3 and the body 2 are thus welded in a gastight manner by a circular weld.

[0053] Furthermore, the back wall 3 is equipped with at least one locator pin 32, preferably three pins, which project from the front face 301 of the disc 30, in the direction of the inside of the cavity 20, when this back wall is assembled with the body 2. Their role will be detailed below.Front Wall Flange 4

[0054] As can be seen on FIG. 5, the front wall flange 4 is an annular element intended to be welded to the front end 25 of the burner body 2, to allow the connection of this body 2 to an air supply source (not shown on the figures), required for the combustion of the gas. The flange 4 for example comprises a ring 40 welded to the inside of this body 2 and which extends forward as a radial flange 41 for attaching the body 2.Gas Distributor 5

[0055] The gas distributor 5 has the function of distributing the gas, in particular hydrogen, as near as possible to the orifices 21 of the burner body 2 and also of distributing the air circulating in the body 2, as will be described in more detail further on.

[0056] The distributor 5 is intended to be inserted axially into the burner body 2.

[0057] As can be seen more clearly on FIGS. 1 and 3 to 5, the distributor 5 comprises a distributor body 50, the back wall 6 and the front flange 7.

[0058] The body 50 comprises a hollow cylinder 51, of central longitudinal axis X1-X′1. This axis X1-X′1 is coaxial with the axis X-X′ of the burner 1 when the distributor 5 is mounted in the body 2. The cylinder 51 is equipped with a plurality of radial branches 52, disposed in a star around the cylinder 51. The cylinder 51 delimits a cylindrical central housing 53. Each branch 52 extends both radially outward with respect to the central axis X1-X1′ and over the entire length of the cylinder 51.

[0059] As can be seen more clearly in FIG. 7, each branch 52 comprises two flat walls 54, 54′, parallel or substantially parallel to one another and spaced apart so as to fashion between themselves a lamellar space 55 which opens at its radially inner end into the cylindrical central housing 53. The two walls 54, 54′ meet one another, at their radially outer ends, by a joining area which defines the radially outer longitudinal edge 56 of each branch 52. This edge 56 is preferably of incurvated shape along its cross section, its concavity being turned toward the lamellar space 55.

[0060] Preferably, the body 50 is composed of a strip of metal sheet, bent to form the cylinder 51 and folded over on itself several times to form each branch 52 opening into the housing 53.

[0061] As can be seen on FIG. 3, each branch 52 is closed in a gas-tight manner at its front end 57 and at its rear end 57′, for example by pinching the two walls 54, 54′, then welding the edges of these walls to one another.

[0062] Finally, the radially outer longitudinal edge 56 of each branch 52 is perforated by a plurality of orifices 58, each of them extending by a rim 59, (see FIGS. 6 and 7). The rim 59 surrounds the periphery of the orifice 58. Each rim 59 projects outward, from the radially outer face 560 of the edge 56. Each orifice 58 and its rim 59 have a central axis Z2-Z′2, which is normal to the outer face 560.

[0063] The rim 59 can advantageously be toothed so as to have notches 59′ making it possible to create turbulences on exiting the rim 59 and thus improve the air / gas mixture which penetrates the orifice 21 and then the rim 22.

[0064] The orifices 58 and rims 59 are for example “punched holes”, obtained by stamping a metal sheet. These orifices 58 are circular or substantially circular and the rims 59 are cylindrical or substantially cylindrical.

[0065] The distributor body 50 comprises at the most as many branches 52 as there are rows 24 of orifices 21 in the burner body 2. There can be fewer branches 52 than there are rows 24 of orifices and in this case, only air will exit the rows 24 of orifices. Preferably, there are as many branches 52 as there are rows 24 of orifices.

[0066] The orifices 58 (and therefore the rims 59) are axially aligned along the longitudinal edge 56. Moreover, on each longitudinal edge 56 of each branch 52, there are as many orifices 58 as there are orifices 21 in one row 24 of the burner body 2. On a given longitudinal edge 56, the different orifices 58 can be evenly spaced apart from one another or contrariwise be grouped into groups of several orifices, so as to form a pattern, for example grouped two-by-two, as can be seen on the figures.

[0067] The back wall 6 is a disc, the outer diameter of which is equal to that of the inner diameter of the cylindrical central housing 53, and it is welded in a gas-tight manner to the cylinder 51, so as to shut off said housing 53.

[0068] The front flange 7 makes it possible to connect the distributor body 50 to a pressurized gas (hydrogen) supply source (not shown on the figures).

[0069] The front flange 7 preferably comprises a disc 70 perforated by a central hole 71. The outer diameter of the disc 70 is equal to the inner diameter of the cylindrical central housing 53 and this disc 70 is welded at its periphery to the front end of the cylinder 51, in a gastight manner, as can be seen on FIG. 3. This disc 70 extends forward as a tube 72, of longitudinal axis X-X′, which allows the connection of the front flange 7 to the gas supply source (not shown on the figures).Assembly

[0070] The distributor 5 is inserted axially inside the cylindrical cavity 20 of the burner body 2, to which the back wall 3 has been welded beforehand, then the front wall flange 4 is itself welded to the burner body 2.

[0071] In this assembled position, it can be seen that the locator pins 32 are each positioned between two neighboring branches 52 and that they thus prevent any rotation of the distributor 5 around the longitudinal axis X-X′, with respect to the burner body 2.

[0072] The assembly of the distributor 5 and of the body 2 is also done so that each orifice 58 (and therefore its rim 59) is coaxial with an orifice 21 and its rim 22 of the burner body 2, (see on FIG. 6 the alignment of the axes Z1-Z′1 and Z2-Z′2).Dimensions

[0073] As can be seen on FIG. 6, the outer diameter D1 of the apex 590 of each rim 59 of the distributor 50 is less than the inner diameter D2 of the orifice 21 of the burner body 2 facing which it is disposed.

[0074] Furthermore, the height H1 between the apex 590 of each rim 59 (i.e. its most radially outward end) and the inner face 23′ of the shell 2 is as small as possible so that the apex 590 is in immediate proximity to the inlet mouth 210 of the orifice 21. Thus, the rim 59 constitutes a gas micro-injector which opens virtually into the orifice 21, and the air / gas mixing is done in the rim 22. The height H1 corresponds to the axial insertion clearance of the body 50 of the distributor 5 in the body 2, when these two elements are cylindrical. Preferably, H1 is less than or equal to 0.1 mm.

[0075] The distributor body 50 and the burner body 2 are dimensioned so that there is a gap 27 for the passage of air between the apex 561 of the longitudinal edge 56 of each branch 52 and the inner face 23′ of the shell 2.

[0076] Preferably, the height H2 between the apex 561 of the edge 56 of each branch 52 and the inner face 23′ of the shell is greater than or equal to 0.2 mm.

[0077] Preferably, the height H3 between the apex of the free end 220 of a rim 22 of the burner body 2 and the inner face 23′ of the body 2 is between 0.8 and 2 mm.

[0078] According to other embodiments not shown on the figures, the burner body 2 and the gas distributor 5 could have shapes other than cylindrical.

[0079] The burner body 2 can for example comprise only a portion of its surface acting as a combustion surface and in which the orifices 21 equipped with rims 22 as previously described are perforated. Such a combustion surface can for example be flat or slightly bent or V-shaped.

[0080] In this case, the shape of the distributor body 50 is adapted accordingly so that it can be inserted into the cavity 20 of the body 2. The body 50 still comprises the branches 52 perforated by orifices 58 equipped with rims 59, as described above, but these branches are not radial.

[0081] Finally, the features previously described on the subject of the relative positioning of the orifices 21 and 58 and of the dimensions would be the same.

[0082] In the special case in which the burner body 2 and the gas distributor 5 are cylindrical, the gas burner 1 then further comprises a gas pre-distribution device 8 and preferably a device 9 for moving the gas entering the device 8.Gas Pre-Distribution Device 8

[0083] In the embodiment shown, particularly on FIGS. 1 and 4, the gas pre-distribution device 8 comprises a series of annular washers 80, assembled against one another, as well as one front washer 81 (see FIGS. 1 and 4).

[0084] Each annular washer 80 has a cylindrical central opening 800, a flat front face 801, an opposing flat rear face 802 and a cylindrical lateral face 803.

[0085] Provision is made on each annular washer 80, for example here on the front face 801, for a series of straight grooves 804, dug into the thickness of the washer and which each extend radially from the central opening 800 until they open onto the face 803. On each washer 80, there are as many grooves 804 as there are branches 52 in the distributor 5.

[0086] When the different washers 80 are pressed flat against one another, the rear face 802 of one comes into contact with the front face 801 of the neighboring washer and this rear face 802 forms channels 805 with the different grooves 804 (see FIGS. 1, 5 and 7). These channels 805 have mouths 806 which open onto the lateral face 803. Several successive stages 807 of radial channels 805 are thus obtained.

[0087] The front washer 81 comprises a cylindrical central opening 810, a flat front face 811, and an opposing flat rear face 812.

[0088] The openings 800 and 810 are coaxial and of the same diameter.

[0089] As can be seen more clearly on the section of FIG. 4, an annular shoulder 814 is formed inside the central opening 810, so that this opening 810 has a rear portion 815, the inner diameter of which is the same as that of the diameter of the openings 800 and a front portion 816, the inner diameter of which is greater than that of the rear portion 815, so as to fashion at this front portion 816 a housing 817 for receiving the device 9 (which is preferably a propeller).

[0090] The annular shoulder 814 thus makes it possible to axially lock the propeller 9 toward the rear.

[0091] When the front washer 81 is pressed flat against the immediately neighboring washer 80, its rear face 812 comes into contact with the front face 801 of this washer and also delimits radial channels 805 with the grooves 804. It would also be possible to make provision for the grooves 804 on the rear face 802.

[0092] The different washers 80 and the front washer 81 are assembled against one another and the gas pre-distribution device 8 thus formed is inserted axially and housed inside the housing 53 of the distributor 5, so that the rear face 802 of the last washer 80 comes into contact with the back wall 6 and so that the front face 811 of the front washer 81 is in contact with the disc 70. For this purpose, the outer diameter of the different washers 80 and 81 is equal, within the insertion clearance, to the inner diameter of the cylinder 51.

[0093] In this assembly position, which appears more clearly on FIG. 5, it can be seen that the disc 70 interacts with the housing 817 to axially lock the fixed propeller 9 toward the front. This is therefore maintained between the front flange 7 and the washer 81.

[0094] The different washers 80 and 81 are positioned angularly with respect to the longitudinal axis X-X′, so that their respective grooves 804 are superimposed and the outer mouths 806 of the channels 805 form axial alignments 82, as can be seen on FIG. 1. For this purpose, poka-yokes can be provided on the different washers 80 and 81 to assemble them correctly. An alignment 82 is schematically represented by a dotted line on FIG. 1.

[0095] Furthermore, the washers 80 and 81 are inserted into the housing 53, so that each outer mouth 806 of a radial channel 805 opens directly onto a lamellar space 55. In other words, each alignment 82 is located facing a branch 52.

[0096] According to a simplified variant embodiment, not shown on the figures, the gas pre-distribution device 8 can also be formed from a single solid cylindrical body instead and in place of the different washers 80, 81. Such a solid cylindrical body has an axial cylindrical central opening corresponding to the set of central openings 800 and 810 and a plurality of radial channels 805 opening firstly into this central opening and secondly onto the outer surface 803 of the cylindrical body level with the mouths 806. These different channels 805 are distributed across different stages 807 and make it possible to supply the branches 52 of the distributor body with gas. Finally, such a single cylindrical body also has, at the front end of its central opening, a housing 817 to receive the propeller 9.

[0097] Note that it is not necessary to have as many stages 807 of channels as there are orifices 58 (or rims 59) on a branch 52. By way of purely illustrative example, there are thus seven stages 807 of radial channels for fourteen rims 59 on each branch 52 in the exemplary embodiment shown on the drawings.

[0098] As can be seen on FIG. 4, the fixed propeller 9 comprises a central disc 91 from which extend a plurality of blades 92. The blades 92 are oriented with a setting angle, which makes it possible to deflect the incoming gas to give it a helical motion inside the central openings 800 and 810.Materials

[0099] The burner body 2, the back walls 3 and 6, the flanges 4 and 7, the gas distributor 5, the gas pre-distribution device 8 and the propeller 9 are advantageously made of metal, particularly made of stainless steel, the device 8 being however able to be made of aluminum or made of composite material. The burner body 2 could also be made of refractory material.Operation

[0100] The tube 72 is connected to a pressurized gas supply source, preferably hydrogen. Moreover, the front flange 4 is connected to an air supply source, also pressurized.

[0101] The trajectory of the air inside the gas burner 1 will now be described. This trajectory is symbolized by arrows referenced as “a” with an index number.

[0102] The air penetrates the annular space around the tube 72 (arrows a1 in FIG. 5), then divides into layers of air inside the spaces 520 formed between the branches 52 (arrows a2). The air is then radially directed outward along the walls 54 or 54′ (arrows a3 on FIG. 7) and also along an axial direction between the apex 561 of the edge 56 and the inner face 23′ of the shell (arrows a4 on FIG. 6). Finally, the air escapes through the rims 22 (arrows a5 on FIG. 6).

[0103] The trajectory of the gas inside the gas burner 1 will now be described. This trajectory is symbolized by the arrows referenced as “g” with an index number.

[0104] The gas penetrates the tube 72 (arrow g1 on FIG. 5) and is then driven in a helical motion (arrow g2 on FIG. 5) by the fixed propeller 9. In the special case where the gas is hydrogen, and thus an extremely volatile gas, this makes it possible to ideally distribute the hydrogen on its entry into all the channels 805.

[0105] The gas is thus inserted into the different channels 805 (arrows g3 on FIGS. 5 and 7) then exits from them inside the lamellar space 55 (arrows g4 on FIGS. 5 and 7). The gas having been previously distributed in the different channels 805, each lamellar space 55 is supplied with gas homogeneously over its entire axial length.

[0106] The gas then exits through the orifices 58 and rims 59 of the distributor 5 (arrows g5 on FIG. 6), then penetrates the orifices 21 and the rims 22 (arrows g6 on FIG. 6) where it is then mixed with air. It is therefore only inside these rims 22 that the air / gas mixing and the combustion takes place on exiting the rims 22, so with no risk of flashback in the spaces 520, or in the radial branches 52.

[0107] The gas burner in accordance with the invention can thus operate with hydrogen, although this gas is extremely volatile, while offering a range of power modulation of at least 1 to 10, with no risk of flashback and therefore with no risk of deflagration or detonation.

[0108] Finally, the measurements taken have made it possible to demonstrate that the combustion with hydrogen is done with an air lambda of 1.3 to 2 and a Nox emission level of 0.5 to 3 ppm.

[0109] In the embodiments in which the pre-distribution device 8 is not present, the gas exiting the tube 72 directly penetrates the housing 53.

Examples

Embodiment Construction

[0039]In the remainder of the description, the surface combustion gas burner 1 in accordance with the invention is described as operating with a gas which is preferably hydrogen. However, it could also operate with another gas, for example natural gas, without however departing from the scope of the invention.

[0040]In the remainder of the description and claims, by convention, the term “front” denotes elements that are located or pointing toward the end of the burner through which the air is introduced into it (i.e. on the left on FIGS. 1 to 5) and the term “rear” denotes elements that are located or pointing in the opposite direction (i.e. on the right on FIGS. 1 to 5).

[0041]In general, the gas burner comprises a burner body 2 connectable to an air supply source and a gas distributor 5 connectable to a gas supply source.

[0042]According to a preferred (and therefore not exclusive) embodiment of the invention, which will now be described in more detail, the burner body 2 and the gas ...

FIELD OF THE INVENTION

[0001] This invention relates to a surface combustion gas burner, in particular a hydrogen burner. Such a burner is in particular intended to be used in domestic or industrial heating apparatuses, to heat a fluid circulating in an exchanger.PRIOR ART

[0002] There have been two main successive generations of gas burners, namely atmospheric burners and fan burners.

[0003] In atmospheric burners, the pressurized gas is emitted through a nozzle and causes a flow of air via a convergent-divergent device. Such a burner has the drawback of emitting polluting discharge into the atmosphere.

[0004] Among fan burners, air / gas premixture burners or “premix” burners allow total control of the premixing of gas and air (see for example the burner described in document WO2014006103). Polluting discharge is thus considerably reduced.

[0005] However, in the case of premix burners, combustion takes place at the outer surface of the burner. In order to avoid rapid ageing of the burner by exposing its jacket to reddening (which is the case if the flame comes too close to the surface of the jacket), the range of power variation of such a premix burner is in the order of 1 to 3, or even a maximum of 1 to 10, if the jacket is made of a material resistant to high temperatures or includes a specifically developed design such as the burner described in document WO2014006103.

[0006] Moreover, during the operation of this air / gas premix burner, the flow rate of the air and gas mixture must be varied so as to avoid the uprooting of the flame due to excessive flow and conversely, to avoid the flame returning into the burner due to the lack of a sufficient flow, thus causing a flashback.

[0007] Such a flashback can specifically lead to a deflagration, or even to a detonation.

[0008] For a given burner, the range of modulation of its power is therefore regulated by its maximum flow rate, which corresponds to an gas outlet speed less than the uprooting of the flame, and by its minimum flow rate, which corresponds to a gas outlet speed greater than the flashback speed.

[0009] In addition, these two extreme limits of the speed of the air and gas mixture are related to the propagation speed of the flame of the gas under consideration, in other words, to the kind of gas. Thus, one and the same air / gas premix burner will offer a different operating range as a function of the kind of gas used and its propagation speed.

[0010] By way of illustration, natural gas has an average propagation speed of 0.37 meters / second and hydrogen an average propagation speed in the order of 2.6 meters / second, i.e. nearly seven times faster.

[0011] Surface combustion burners of the prior art are therefore also not very suited to the use of hydrogen gas, if one wishes to be able to use such a burner over a wide range of power variations.

[0012] However, in order to comply with the environmental and ecological criteria, hydrogen could be a beneficial alternative as fuel for supplying these burners.SUMMARY OF THE INVENTION

[0013] One aim of the invention is therefore to make provision for a surface combustion burner which can operate in particular with hydrogen, while being reliable, i.e. avoiding the flashback phenomenon and the associated risks while also being able to be used over a wide range of power variations.

[0014] For this purpose, the invention relates to a deflagration-proof and detonation-proof surface combustion gas burner.

[0015] In accordance with the invention, this burner comprises a burner body made of metal or refractory material and a gas distributor, the burner body delimits an inner cavity connectable to an air supply source and has an outer face and an inner face, the burner body is perforated by a series of orifices, each of which is extended by a rim, which projects from this outer face and the central axis of which is normal to this outer face, these orifices being disposed in several rows of aligned orifices, the gas distributor comprises a distributor body which delimits a housing connectable to a gas supply source, the distributor body comprises a plurality of longitudinal gas distribution branches, each branch comprising two longitudinal walls, spaced apart from one another in such a way as to define between each other a longitudinal lamellar gas distribution space, which opens at its inner longitudinal end into said housing, the two walls of each branch meeting to form an outer longitudinal edge, a closed front end and a closed rear end of said branch, each branch is perforated by a series of orifices aligned along its outer longitudinal end, each orifice being bordered by a rim which projects over the outer face of said longitudinal edge and each orifice having a central axis normal to this outer face of said longitudinal edge, the distributor body is disposed in the inner cavity of the burner body so that each orifice of the distributor body is coaxial with an orifice of the burner body, the distributor body and the burner body are dimensioned so that the inner diameter D2 of an orifice of the burner body is greater than the outer diameter D1 of the apex of the rim of an orifice of the distributor body disposed facing this same orifice, so that there is a gap for the passage of air between the apex of the outer longitudinal edge of each branch and the inner face of the burner body, and so that the apex of the rim of each orifice is in immediate proximity to the inlet mouth of the orifice facing which it is placed, so that when the burner body is connected to an air supply source and the distributor body to a gas supply source, the air penetrates the burner body, circulates between the branches of the distributor body and in the gap and escapes from the burner through the rims of the burner body, while the gas penetrates the housing of the distributor body, circulates in the lamellar space of the branches then through the orifices and rims of this distributor body and finally through the rims of the burner body within which it meets the air and is mixed with this one.

[0016] Owing to these features of the invention, the gas and air circulate in the burner where the load losses are extremely small, through separate circuits, and are only mixed at the last moment inside the rims of the burner body. These rims thus constitute microchambers for mixing the gas and air and the combustion takes place at the surface, i.e. on exiting these rims, thus preventing any flashback.

[0017] Such a burner is therefore particularly suitable for use with hydrogen, a gas which has a high flame propagation speed, since flashback is prevented and therefore any risk of detonation or deflagration also.

[0018] In addition, the mixed volumes of gas and air are controlled and make it possible to obtain a wide modulation range.

[0019] According to other advantageous and non-limiting features of the invention, taken alone or in combination:

[0020] at least one rim of an orifice of the burner body and / or at least one rim of an orifice of the distributor body is toothed so as to have notches.

[0021] the burner body is formed from a cylindrical shell, shut off at its rear end by a back wall and the front end of which is equipped with a front wall flange connectable to the air supply source, the orifices of the burner body are fashioned in said shell so that the rows of orifices extend axially over this shell, the distributor body comprises a hollow cylinder which delimits said housing of this body, this housing being central and cylindrical, the longitudinal gas distribution branches extending radially around this cylinder, the distributor body is shut off at its rear end by a back wall and at its front end by a front flange, equipped with a central hole connectable to the gas supply source, the gas distributor comprises a gas pre-distribution device, which comprises a cylindrical body, equipped with an axial cylindrical central opening and several stages of radial channels, each radial channel extending from said central opening all the way to the outer surface of said cylindrical body, and this gas pre-distribution device is disposed coaxially inside the cylindrical housing of the distributor body, so that its central opening is facing the central hole of the flange and each of its radial channels opens into the lamellar space of a branch of the distributor body.

[0022] the cylindrical body of the gas pre-distribution device comprises several rear washers and one front washer, these rear and front washers each having a cylindrical central opening and two opposing flat faces, these central openings being of the same diameter, the front washer and the rear washers being assembled against one another so that their respective central openings are coaxial, the rear washers having on one of their flat faces a series of radial grooves which delimit, with the opposite face of a neighboring rear washer, said radial channels.

[0023] the gas pre-distribution device comprises a device for moving the gas entering into this gas pre-distribution device, to impart to this gas a helical motion when it circulates inside the central opening of the cylindrical body.

[0024] the device for moving the gas is a fixed propeller.

[0025] the shell of the burner body has a rear end, in that the back wall of the burner body comprises a solid disc equipped with a peripheral annular rim which is welded in a gastight manner to the rear end of the shell, in that said solid disc has a front face and is equipped with at least one locator pin which projects from this front face and in that said at least one locator pin is inserted between two neighboring branches of the body of the gas distributor.

[0026] the distributor body is formed from a metal sheet folded on itself to form the gas distribution branches.

[0027] the front and rear ends of each branch of the distributor body are closed by pinching and welding.

[0028] the gap for the passage of air has a height greater than or equal to 0.2 mm.

[0029] the ratio D2 / D1 of the inner diameter of an orifice of the burner body to the outer diameter of the apex of the rim of an orifice disposed facing this same orifice is between 1.2 and 4.

[0030] the gas is hydrogen.DESCRIPTION OF THE FIGURES

[0031] Other features, aims and advantages of the invention will become apparent from the following description, which is purely illustrative and non-limiting, and which must be read with reference to the appended drawings on which:

[0032] FIG. 1 is an exploded perspective view of the elements constituting a possible embodiment of the gas burner in accordance with the invention;

[0033] FIG. 2 is a perspective view of this same burner, the different elements of which are in the assembled position;

[0034] FIG. 3 is a perspective view of the gas distributor of the gas burner of FIG. 1;

[0035] FIG. 4 is an exploded perspective view of the different elements constituting the gas distributor of FIG. 3;

[0036] FIG. 5 is a longitudinal section view of the gas burner, taken along the section plane passing through the line V-V of FIG. 2;

[0037] FIG. 6 is a longitudinal section view of the orifices fashioned in the body of the burner and in the distributor, taken along the section plane passing through the line VI-VI of FIG. 7;

[0038] FIG. 7 is a magnified detail view of the body of the burner and of the distributor shown on FIG. 5.DETAILED DESCRIPTION OF THE INVENTION

[0039] In the remainder of the description, the surface combustion gas burner 1 in accordance with the invention is described as operating with a gas which is preferably hydrogen. However, it could also operate with another gas, for example natural gas, without however departing from the scope of the invention.

[0040] In the remainder of the description and claims, by convention, the term “front” denotes elements that are located or pointing toward the end of the burner through which the air is introduced into it (i.e. on the left on FIGS. 1 to 5) and the term “rear” denotes elements that are located or pointing in the opposite direction (i.e. on the right on FIGS. 1 to 5).

[0041] In general, the gas burner comprises a burner body 2 connectable to an air supply source and a gas distributor 5 connectable to a gas supply source.

[0042] According to a preferred (and therefore not exclusive) embodiment of the invention, which will now be described in more detail, the burner body 2 and the gas distributor 5 are of generally cylindrical shape.

[0043] On FIG. 1, it can be seen that the burner body 2 is shut off at its rear end 26 by a back wall 3 and is equipped at its front end 25 with a front wall flange 4, and that the gas distributor 5 is shut off at its rear end by a back wall 6 and is equipped at its front end with a front flange 7. These different elements will now be described.Burner Body 2

[0044] The burner body 2 is formed of a hollow cylindrical shell 200 extending around a central longitudinal axis X-X′, which also constitutes the central longitudinal axis of the burner 1. This shell 200 preferably consists of a thin metal sheet.

[0045] This body 2 delimits a cylindrical inner body 20.

[0046] Said shell is perforated by a plurality of orifices 21, each of which extends outward as a rim 22, (see in particular FIGS. 5 to 7). The rim 22 surrounds the periphery of the orifice 21. Each rim 22 projects over the outer face 23 of the body 2. Each orifice 21 and its rim 22 have a central axis Z1-Z′1 which is normal to this outer face 23 (see FIG. 6). The inner face of the shell is referenced 23′.

[0047] The rim 22 (and more particularly its free end 220) can advantageously be toothed so as to have notches 22′. These notches 22′ are used to create turbulences at the outlet of the body 2 and thus to reinforce the flame-holding effect and to avoid the uprooting of the flame.

[0048] The orifices 21 and the rims 22 are for example “punched holes”, obtained by stamping or punching of a flat metal sheet, which is then bent to form the cylindrical body 2 and both edges of which are welded.

[0049] These orifices 21 are circular or substantially circular and the rims 22 are cylindrical or substantially cylindrical.

[0050] Furthermore, the orifices 21 (and therefore the rims 22) are aligned so as to form several axial rows 24 of orifices. These rows 24 extend parallel to one another and also parallel to the central longitudinal axis X-X′ of the body 2. Furthermore, preferably, the different rows 24 are evenly distributed over the entire circumference of the burner body 2.

[0051] In a given row 24, the different orifices 21 can be evenly spaced apart from one another or contrariwise be grouped to form a pattern, for example grouped two-by-two as can be seen on the figures.Back Wall 3

[0052] The back wall 3 is composed of a solid disc 30, equipped with a peripheral annular rim 31. The diameter of this back wall 3 is adapted to the diameter of the burner body 2 (here to the shell 200), so that its peripheral rim 11 can be welded to the rear end 26 of the body 2, preferably inside this body 2, as can more clearly seen on the section of FIG. 5. The back wall 3 and the body 2 are thus welded in a gastight manner by a circular weld.

[0053] Furthermore, the back wall 3 is equipped with at least one locator pin 32, preferably three pins, which project from the front face 301 of the disc 30, in the direction of the inside of the cavity 20, when this back wall is assembled with the body 2. Their role will be detailed below.Front Wall Flange 4

[0054] As can be seen on FIG. 5, the front wall flange 4 is an annular element intended to be welded to the front end 25 of the burner body 2, to allow the connection of this body 2 to an air supply source (not shown on the figures), required for the combustion of the gas. The flange 4 for example comprises a ring 40 welded to the inside of this body 2 and which extends forward as a radial flange 41 for attaching the body 2.Gas Distributor 5

[0055] The gas distributor 5 has the function of distributing the gas, in particular hydrogen, as near as possible to the orifices 21 of the burner body 2 and also of distributing the air circulating in the body 2, as will be described in more detail further on.

[0056] The distributor 5 is intended to be inserted axially into the burner body 2.

[0057] As can be seen more clearly on FIGS. 1 and 3 to 5, the distributor 5 comprises a distributor body 50, the back wall 6 and the front flange 7.

[0058] The body 50 comprises a hollow cylinder 51, of central longitudinal axis X1-X′1. This axis X1-X′1 is coaxial with the axis X-X′ of the burner 1 when the distributor 5 is mounted in the body 2. The cylinder 51 is equipped with a plurality of radial branches 52, disposed in a star around the cylinder 51. The cylinder 51 delimits a cylindrical central housing 53. Each branch 52 extends both radially outward with respect to the central axis X1-X1′ and over the entire length of the cylinder 51.

[0059] As can be seen more clearly in FIG. 7, each branch 52 comprises two flat walls 54, 54′, parallel or substantially parallel to one another and spaced apart so as to fashion between themselves a lamellar space 55 which opens at its radially inner end into the cylindrical central housing 53. The two walls 54, 54′ meet one another, at their radially outer ends, by a joining area which defines the radially outer longitudinal edge 56 of each branch 52. This edge 56 is preferably of incurvated shape along its cross section, its concavity being turned toward the lamellar space 55.

[0060] Preferably, the body 50 is composed of a strip of metal sheet, bent to form the cylinder 51 and folded over on itself several times to form each branch 52 opening into the housing 53.

[0061] As can be seen on FIG. 3, each branch 52 is closed in a gas-tight manner at its front end 57 and at its rear end 57′, for example by pinching the two walls 54, 54′, then welding the edges of these walls to one another.

[0062] Finally, the radially outer longitudinal edge 56 of each branch 52 is perforated by a plurality of orifices 58, each of them extending by a rim 59, (see FIGS. 6 and 7). The rim 59 surrounds the periphery of the orifice 58. Each rim 59 projects outward, from the radially outer face 560 of the edge 56. Each orifice 58 and its rim 59 have a central axis Z2-Z′2, which is normal to the outer face 560.

[0063] The rim 59 can advantageously be toothed so as to have notches 59′ making it possible to create turbulences on exiting the rim 59 and thus improve the air / gas mixture which penetrates the orifice 21 and then the rim 22.

[0064] The orifices 58 and rims 59 are for example “punched holes”, obtained by stamping a metal sheet. These orifices 58 are circular or substantially circular and the rims 59 are cylindrical or substantially cylindrical.

[0065] The distributor body 50 comprises at the most as many branches 52 as there are rows 24 of orifices 21 in the burner body 2. There can be fewer branches 52 than there are rows 24 of orifices and in this case, only air will exit the rows 24 of orifices. Preferably, there are as many branches 52 as there are rows 24 of orifices.

[0066] The orifices 58 (and therefore the rims 59) are axially aligned along the longitudinal edge 56. Moreover, on each longitudinal edge 56 of each branch 52, there are as many orifices 58 as there are orifices 21 in one row 24 of the burner body 2. On a given longitudinal edge 56, the different orifices 58 can be evenly spaced apart from one another or contrariwise be grouped into groups of several orifices, so as to form a pattern, for example grouped two-by-two, as can be seen on the figures.

[0067] The back wall 6 is a disc, the outer diameter of which is equal to that of the inner diameter of the cylindrical central housing 53, and it is welded in a gas-tight manner to the cylinder 51, so as to shut off said housing 53.

[0068] The front flange 7 makes it possible to connect the distributor body 50 to a pressurized gas (hydrogen) supply source (not shown on the figures).

[0069] The front flange 7 preferably comprises a disc 70 perforated by a central hole 71. The outer diameter of the disc 70 is equal to the inner diameter of the cylindrical central housing 53 and this disc 70 is welded at its periphery to the front end of the cylinder 51, in a gastight manner, as can be seen on FIG. 3. This disc 70 extends forward as a tube 72, of longitudinal axis X-X′, which allows the connection of the front flange 7 to the gas supply source (not shown on the figures).Assembly

[0070] The distributor 5 is inserted axially inside the cylindrical cavity 20 of the burner body 2, to which the back wall 3 has been welded beforehand, then the front wall flange 4 is itself welded to the burner body 2.

[0071] In this assembled position, it can be seen that the locator pins 32 are each positioned between two neighboring branches 52 and that they thus prevent any rotation of the distributor 5 around the longitudinal axis X-X′, with respect to the burner body 2.

[0072] The assembly of the distributor 5 and of the body 2 is also done so that each orifice 58 (and therefore its rim 59) is coaxial with an orifice 21 and its rim 22 of the burner body 2, (see on FIG. 6 the alignment of the axes Z1-Z′1 and Z2-Z′2).Dimensions

[0073] As can be seen on FIG. 6, the outer diameter D1 of the apex 590 of each rim 59 of the distributor 50 is less than the inner diameter D2 of the orifice 21 of the burner body 2 facing which it is disposed.

[0074] Furthermore, the height H1 between the apex 590 of each rim 59 (i.e. its most radially outward end) and the inner face 23′ of the shell 2 is as small as possible so that the apex 590 is in immediate proximity to the inlet mouth 210 of the orifice 21. Thus, the rim 59 constitutes a gas micro-injector which opens virtually into the orifice 21, and the air / gas mixing is done in the rim 22. The height H1 corresponds to the axial insertion clearance of the body 50 of the distributor 5 in the body 2, when these two elements are cylindrical. Preferably, H1 is less than or equal to 0.1 mm.

[0075] The distributor body 50 and the burner body 2 are dimensioned so that there is a gap 27 for the passage of air between the apex 561 of the longitudinal edge 56 of each branch 52 and the inner face 23′ of the shell 2.

[0076] Preferably, the height H2 between the apex 561 of the edge 56 of each branch 52 and the inner face 23′ of the shell is greater than or equal to 0.2 mm.

[0077] Preferably, the height H3 between the apex of the free end 220 of a rim 22 of the burner body 2 and the inner face 23′ of the body 2 is between 0.8 and 2 mm.

[0078] According to other embodiments not shown on the figures, the burner body 2 and the gas distributor 5 could have shapes other than cylindrical.

[0079] The burner body 2 can for example comprise only a portion of its surface acting as a combustion surface and in which the orifices 21 equipped with rims 22 as previously described are perforated. Such a combustion surface can for example be flat or slightly bent or V-shaped.

[0080] In this case, the shape of the distributor body 50 is adapted accordingly so that it can be inserted into the cavity 20 of the body 2. The body 50 still comprises the branches 52 perforated by orifices 58 equipped with rims 59, as described above, but these branches are not radial.

[0081] Finally, the features previously described on the subject of the relative positioning of the orifices 21 and 58 and of the dimensions would be the same.

[0082] In the special case in which the burner body 2 and the gas distributor 5 are cylindrical, the gas burner 1 then further comprises a gas pre-distribution device 8 and preferably a device 9 for moving the gas entering the device 8.Gas Pre-Distribution Device 8

[0083] In the embodiment shown, particularly on FIGS. 1 and 4, the gas pre-distribution device 8 comprises a series of annular washers 80, assembled against one another, as well as one front washer 81 (see FIGS. 1 and 4).

[0084] Each annular washer 80 has a cylindrical central opening 800, a flat front face 801, an opposing flat rear face 802 and a cylindrical lateral face 803.

[0085] Provision is made on each annular washer 80, for example here on the front face 801, for a series of straight grooves 804, dug into the thickness of the washer and which each extend radially from the central opening 800 until they open onto the face 803. On each washer 80, there are as many grooves 804 as there are branches 52 in the distributor 5.

[0086] When the different washers 80 are pressed flat against one another, the rear face 802 of one comes into contact with the front face 801 of the neighboring washer and this rear face 802 forms channels 805 with the different grooves 804 (see FIGS. 1, 5 and 7). These channels 805 have mouths 806 which open onto the lateral face 803. Several successive stages 807 of radial channels 805 are thus obtained.

[0087] The front washer 81 comprises a cylindrical central opening 810, a flat front face 811, and an opposing flat rear face 812.

[0088] The openings 800 and 810 are coaxial and of the same diameter.

[0089] As can be seen more clearly on the section of FIG. 4, an annular shoulder 814 is formed inside the central opening 810, so that this opening 810 has a rear portion 815, the inner diameter of which is the same as that of the diameter of the openings 800 and a front portion 816, the inner diameter of which is greater than that of the rear portion 815, so as to fashion at this front portion 816 a housing 817 for receiving the device 9 (which is preferably a propeller).

[0090] The annular shoulder 814 thus makes it possible to axially lock the propeller 9 toward the rear.

[0091] When the front washer 81 is pressed flat against the immediately neighboring washer 80, its rear face 812 comes into contact with the front face 801 of this washer and also delimits radial channels 805 with the grooves 804. It would also be possible to make provision for the grooves 804 on the rear face 802.

[0092] The different washers 80 and the front washer 81 are assembled against one another and the gas pre-distribution device 8 thus formed is inserted axially and housed inside the housing 53 of the distributor 5, so that the rear face 802 of the last washer 80 comes into contact with the back wall 6 and so that the front face 811 of the front washer 81 is in contact with the disc 70. For this purpose, the outer diameter of the different washers 80 and 81 is equal, within the insertion clearance, to the inner diameter of the cylinder 51.

[0093] In this assembly position, which appears more clearly on FIG. 5, it can be seen that the disc 70 interacts with the housing 817 to axially lock the fixed propeller 9 toward the front. This is therefore maintained between the front flange 7 and the washer 81.

[0094] The different washers 80 and 81 are positioned angularly with respect to the longitudinal axis X-X′, so that their respective grooves 804 are superimposed and the outer mouths 806 of the channels 805 form axial alignments 82, as can be seen on FIG. 1. For this purpose, poka-yokes can be provided on the different washers 80 and 81 to assemble them correctly. An alignment 82 is schematically represented by a dotted line on FIG. 1.

[0095] Furthermore, the washers 80 and 81 are inserted into the housing 53, so that each outer mouth 806 of a radial channel 805 opens directly onto a lamellar space 55. In other words, each alignment 82 is located facing a branch 52.

[0096] According to a simplified variant embodiment, not shown on the figures, the gas pre-distribution device 8 can also be formed from a single solid cylindrical body instead and in place of the different washers 80, 81. Such a solid cylindrical body has an axial cylindrical central opening corresponding to the set of central openings 800 and 810 and a plurality of radial channels 805 opening firstly into this central opening and secondly onto the outer surface 803 of the cylindrical body level with the mouths 806. These different channels 805 are distributed across different stages 807 and make it possible to supply the branches 52 of the distributor body with gas. Finally, such a single cylindrical body also has, at the front end of its central opening, a housing 817 to receive the propeller 9.

[0097] Note that it is not necessary to have as many stages 807 of channels as there are orifices 58 (or rims 59) on a branch 52. By way of purely illustrative example, there are thus seven stages 807 of radial channels for fourteen rims 59 on each branch 52 in the exemplary embodiment shown on the drawings.

[0098] As can be seen on FIG. 4, the fixed propeller 9 comprises a central disc 91 from which extend a plurality of blades 92. The blades 92 are oriented with a setting angle, which makes it possible to deflect the incoming gas to give it a helical motion inside the central openings 800 and 810.Materials

[0099] The burner body 2, the back walls 3 and 6, the flanges 4 and 7, the gas distributor 5, the gas pre-distribution device 8 and the propeller 9 are advantageously made of metal, particularly made of stainless steel, the device 8 being however able to be made of aluminum or made of composite material. The burner body 2 could also be made of refractory material.Operation

[0100] The tube 72 is connected to a pressurized gas supply source, preferably hydrogen. Moreover, the front flange 4 is connected to an air supply source, also pressurized.

[0101] The trajectory of the air inside the gas burner 1 will now be described. This trajectory is symbolized by arrows referenced as “a” with an index number.

[0102] The air penetrates the annular space around the tube 72 (arrows a1 in FIG. 5), then divides into layers of air inside the spaces 520 formed between the branches 52 (arrows a2). The air is then radially directed outward along the walls 54 or 54′ (arrows a3 on FIG. 7) and also along an axial direction between the apex 561 of the edge 56 and the inner face 23′ of the shell (arrows a4 on FIG. 6). Finally, the air escapes through the rims 22 (arrows a5 on FIG. 6).

[0103] The trajectory of the gas inside the gas burner 1 will now be described. This trajectory is symbolized by the arrows referenced as “g” with an index number.

[0104] The gas penetrates the tube 72 (arrow g1 on FIG. 5) and is then driven in a helical motion (arrow g2 on FIG. 5) by the fixed propeller 9. In the special case where the gas is hydrogen, and thus an extremely volatile gas, this makes it possible to ideally distribute the hydrogen on its entry into all the channels 805.

[0105] The gas is thus inserted into the different channels 805 (arrows g3 on FIGS. 5 and 7) then exits from them inside the lamellar space 55 (arrows g4 on FIGS. 5 and 7). The gas having been previously distributed in the different channels 805, each lamellar space 55 is supplied with gas homogeneously over its entire axial length.

[0106] The gas then exits through the orifices 58 and rims 59 of the distributor 5 (arrows g5 on FIG. 6), then penetrates the orifices 21 and the rims 22 (arrows g6 on FIG. 6) where it is then mixed with air. It is therefore only inside these rims 22 that the air / gas mixing and the combustion takes place on exiting the rims 22, so with no risk of flashback in the spaces 520, or in the radial branches 52.

[0107] The gas burner in accordance with the invention can thus operate with hydrogen, although this gas is extremely volatile, while offering a range of power modulation of at least 1 to 10, with no risk of flashback and therefore with no risk of deflagration or detonation.

[0108] Finally, the measurements taken have made it possible to demonstrate that the combustion with hydrogen is done with an air lambda of 1.3 to 2 and a Nox emission level of 0.5 to 3 ppm.

[0109] In the embodiments in which the pre-distribution device 8 is not present, the gas exiting the tube 72 directly penetrates the housing 53.

Examples

Embodiment Construction

[0039]In the remainder of the description, the surface combustion gas burner 1 in accordance with the invention is described as operating with a gas which is preferably hydrogen. However, it could also operate with another gas, for example natural gas, without however departing from the scope of the invention.

[0040]In the remainder of the description and claims, by convention, the term “front” denotes elements that are located or pointing toward the end of the burner through which the air is introduced into it (i.e. on the left on FIGS. 1 to 5) and the term “rear” denotes elements that are located or pointing in the opposite direction (i.e. on the right on FIGS. 1 to 5).

[0041]In general, the gas burner comprises a burner body 2 connectable to an air supply source and a gas distributor 5 connectable to a gas supply source.

[0042]According to a preferred (and therefore not exclusive) embodiment of the invention, which will now be described in more detail, the burner body 2 and the gas ...

Claims

1. A deflagration-proof and detonation-proof surface combustion gas burner comprises a burner body comprising metal or refractory material; and a gas distributor,wherein the burner body delimits an inner cavity connectable to an air supply source and has an outer face and an inner face,wherein the burner body is perforated by a series of orifices, each of the orifices being extended by a rim, which projects from the outer face and a central axis of the orifice is normal to the outer face, the orifices being disposed in several rows of aligned orifices,wherein the gas distributor comprises a distributor body which delimits a housing connectable to a gas supply source,wherein the distributor body comprises a plurality of longitudinal gas distribution branches, each branch comprising two longitudinal walls, spaced apart from one another to define between each other a longitudinal lamellar gas distribution space, the longitudinal lamellar gas distribution space comprising an inner longitudinal end which opens into the housing, the two walls of each branch meeting to form an outer longitudinal edge, a closed front end and a closed rear end of the branch,wherein each branch is perforated by a series of orifices aligned along the outer longitudinal edge, each orifice of a branch being bordered by a rim which projects over an outer face of the longitudinal edge and each orifice having a central axis normal to the outer face of the longitudinal edge,wherein the distributor body is disposed in the inner cavity of the burner body so that each orifice of the distributor body is coaxial with one orifice of the burner body,and wherein the distributor body and the burner body are dimensioned so that an inner diameter of one of the orifices of the burner body is greater than an outer diameter (D1) of an apex of the rim of one of the orifices of the distributor body disposed facing the same orifice of the burner body, so that there is a gap for the passage of air between an apex of the outer longitudinal edge of each branch of the distributor body and the inner face of the burner body, and so that the apex of the rim of each orifice of the distributor body is in immediate proximity to an inlet mouth of the orifice of the burner body facing which it is placed, such that when the burner body is connected to an air supply source and the distributor body to a gas supply source, the air penetrates the burner body, circulates between the branches of the distributor body and in the gap and escapes from the burner through the rims of the burner body, while the gas penetrates the housing of the distributor body, circulates in the lamellar space of the branches, through the orifices and rims of the distributor body, and through the rims of the burner body within which it meets the air and is mixed.

2. The gas burner of in claim 1, wherein at least one rim of one orifice of the burner body and / or at least one rim of one orifice of the distributor body is toothed so as to have notches.

3. The gas burner of claim 1, wherein the burner body is formed from a cylindrical shell, wherein the cylindrical shell comprises a rear end shut off by a back wall and a front end equipped with a front wall flange connectable to the air supply source,wherein the orifices of the burner body are fashioned in the shell so that the rows of orifices extend axially over the shell,wherein the distributor body comprises a hollow cylinder which delimits the housing of the distributor body, the housing of the distributor body being central and cylindrical,wherein the longitudinal gas distribution branches extend radially around the hollow cylinder,wherein the distributor body comprises a rear end shut off by a back wall and a front end shut off by a front flange, equipped with a central hole connectable to the gas supply source,wherein the gas distributor comprises a gas pre-distribution device, which comprises a cylindrical body, equipped with an axial cylindrical central opening and several stages of radial channels, each radial channel extending from the central opening all the way to an outer surface of the cylindrical body,and wherein the gas pre-distribution device is disposed coaxially inside the cylindrical housing of the distributor body, so that the central opening of the cylindrical body is facing the central hole of the front flange and each of the radial channels opens into the lamellar gas distribution space of a branch of the distributor body.

4. The gas burner of claim 3, wherein the cylindrical body of the gas pre-distribution device comprises several rear washers and one front washer the rear washers and the front washer each having one cylindrical central opening and two opposing flat faces, the cylindrical central openings being of the same diameter, the front washer and the rear washers being assembled against one another so that their respective central openings are coaxial, the rear washers having on one of their flat faces a series of radial grooves which delimit, with the opposite flat face of a neighboring rear washer, the radial channels.

5. The gas burner of claim 3, wherein the gas pre-distribution device comprises a device for moving the gas entering into the gas pre-distribution device, to impart to the gas a helical motion when the gas circulates inside the central opening of the cylindrical body.

6. The gas burner of claim 5, wherein the device for moving the gas is a fixed propeller.

7. The gas burner of claim 3, wherein the shell of the burner body has a rear end, wherein the back wall of the burner body comprises a solid disc equipped with a peripheral annular rim which is welded in a gastight manner to the rear end of the shell, wherein the solid disc has a front face and is equipped with at least one locator pin which projects from the front face and wherein the at least one locator pin is inserted between two neighboring branches of the body of the gas distributor.

8. The gas burner of claim 1, wherein the distributor body is formed from a metal sheet folded on itself to form the gas distribution branches.

9. The gas burner of claim 8, wherein the front end and the rear end of each branch of the distributor body are closed by pinching and welding.

10. The gas burner of claim 1, wherein the gap for the passage of air has a height greater than or equal to 0.2 mm.

11. The gas burner of claim 1, wherein the ratio D2 / D1 of the inner diameter (D2) of an orifice of the burner body to the outer diameter (D1) of the apex of the rim of an orifice of the distributor body disposed facing this same orifice of the burner body is between 1.2 and 4.

12. The gas burner of claim 1, wherein the gas is hydrogen.

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