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DESCRIPTION

Technical field

The object of the present invention is an end apparatus for a burner and a burner.

In particular, the end apparatus for a burner that is the object of the present invention is adapted to be applied to burners that have to be installed in a combustion chamber, particularly on boilers for generating hot water or steam, diathermic oil boilers, kilns, dryers, etc ...but can also be applied to air duct solutions. Generally, the burners can be supplied with combustion gas or diesel or mixtures (gas and diesel or gas and naphtha or yet another mixture that is not expressly indicated here).

Background of the invention

The burners generally comprise a fan or a supply conduit for supplying the comburent, a supply conduit for supplying the fuel and a combustion head, i.e. the front part of the burner adapted to generate and support the flame, optimising mixing of the fuel and the comburent and maintaining stability thereof during operation.

Currently, various conformations are known for end apparatuses for blown air burners that generally have in common the presence of an outer tubular body and an inner tubular body supplying the gas, fixed to the body of the burner and ending in the front part with a distributor of the gas. In other words, the two tubular bodies are coaxial and the comburent air is supplied therebetween.

The end apparatus comprises the combustion head that has in the zone adapted to generate the flame a diffuser that is usually of discoid or truncated conical shape. The diffuser is normally provided with uniformly distributed passage holes or gaps that enable the comburent air to pass into the mixing zone with the fuel and the flame to be ignited and maintained.

Substantially, the diffuser retains the flame near the end part of the combustion head to enable the flame to be supported.

The outer tubular casing conveys, with the cylindrical body thereof, the comburent air blown by the fan of the burner.

Disadvantageously, the technical solutions described above often do not enable the burners to so contain the emissions as to maintain the emissions below current emission limits for NOx (nitrogen oxides) specified by recent regulations that set increasingly strict limits (also below 15 ppm) for burners for domestic and industrial use.

Objects of the present invention

In this situation, the object of the present invention is to make an end apparatus for a burner and a burner that obviate the aforementioned drawbacks.

A particular object of the present invention is to make an end apparatus for a burner and a burner that enables NOx emissions to be reduced.

An object of the present invention is moreover to make an end apparatus for a burner and a burner without the use of techniques for recirculating burnt fumes to the flue that are expensive and often involve a reduction in efficiency (and consequently dispensed power) of the machine.

A still further object of the present invention is to make an end apparatus for a burner and a burner that enable NOx emissions to be reduced without however increasing the value of other polluting substances (like for example carbon monoxide), on the contrary maintaining other polluting substances as low as possible.

A yet further object of the invention is to make an end apparatus that can maintain the advantages set out above but with significant adjusting elasticity of the fuel/comburent mixture (range of extended excess air approximately comprised between 1 .05 <A< 1 .35).

The objects indicated are substantially attained by an end apparatus for a burner and a burner according to what is described in the appended claims.

Brief description of the figures

Further characteristics and the advantages of the present invention will appear more clearly from the detailed description of some preferred, but not exclusive, embodiments illustrated in the appended drawings, wherein:

- figures 1 -3 are perspective views according to respective angles of an end apparatus for a burner according to one possible embodiment of the present invention;

- figures 4-5 are partially broken perspective views according to respective angles of the end apparatus for a burner of figures 1 -3;

- figure 6 is a section view of the end apparatus for a burner of figures 1 -3;

- figure 7 is an exploded view of the end apparatus for a burner of figures 1 -3;

- figure 8 is a perspective view of a burner according to one possible embodiment of the present invention;

- figure 9 is a schematic representation of a software simulation of the distribution of the temperature generated inside a container (e.g. boiler) to which the burner according to the present invention is applied in one operating step thereof;

- figure 10 is a schematic representation of a software simulation of the distribution of the speed of the flows generated inside a container (e.g. boiler) to which the burner according to the present invention is applied in one operating step thereof.

Description of one or more preferred embodiments according to the present invention

With reference to the appended drawings, the reference number 1 has been used to generally designate an end apparatus for a burner, which will be referred to here as apparatus 1 for the sake of descriptive simplicity.

The apparatus 1 comprises a combustion head 2 connectable to supply means for supplying a fuel 101 and having at least one inlet opening 3, adapted to enable a fuel to enter, and a plurality of outlet openings 4 adapted to enable an outflow of fuel.

It should be noted that between the fuel inlet and the inlet opening 3 a butterfly adjusting valve can be housed (not shown in the drawings).

For example, the fuel supplied by the supplying means for supplying a fuel 101 can be natural gas or other gaseous fuels, like LPG, biogas, hydrogen or mixtures with variable H2 content.

The apparatus 1 further comprises a comburent supply conduit 5 configured to convey a comburent to the combustion head 2 and extending between a comburent introduction opening 6 of the comburent and an emission opening 7 thereof along a main extension direction “X”.

Advantageously, the combustion head 2 can have a passage conduit 1000 defining an inlet 1001 and an outlet 1002 through which a flow of comburent “C” can flow.

Further, the apparatus 1 can comprise flame ignition means 8, the means being adapted to promote the ignition of the mixture and usable both for the fuel supplied by the supplying means 101 , and for the fuel supplied by the further supply conduit 17 (e.g. diesel) which will be discussed subsequently. According to one possible embodiment of the present invention and as illustrated in the appended figures, the combustion head 2 is at least partially inserted into the supply conduit 5, at the emission opening 7, so as to define a passage gap 9 between the combustion head 2 and the supply conduit 5 for the flow of comburent “C”.

In other words, the flow of comburent “C” can comprise a component passing through the outlet 1002 and/or a component passing through the passage gap 9.

Advantageously, the combustion head 2 can be movable (both in one direction and the opposite direction) relative to the supply conduit 5 along a movement direction parallel to, preferably coincident with, the main extension direction “X” so as to permit adjustment of the dimensions of the passage gap 9 and thus, of the speed of the flow of comburent “C”.

In this manner, the apparatus 1 enables the conformation of the flame to be modified and the extension of the flame to be varied along a direction prevalently parallel to the main extension direction “X”.

In other words, the relative movement between the combustion head 2 and the supply conduit 5 enables the shape of the flame to be varied.

Advantageously, further, the supply conduit 5 can have an end portion 10 defining a convergent profile near the emission opening 7.

In particular, the end portion 10 determines the convergence of the flow of comburent “C” to the centre of the head, promoting the flame detachment from the surface thereof, apart from the retaining surface 22 that will be disclosed below.

In greater detail, the end portion 10 interacting with the combustion head 2 (as will be described in greater detail below) conveys the flow of comburent "C" such that the flame extends and is sustained at a greater distance from the end part of the combustion head 2 relative to prior art apparatuses.

Advantageously, the combustion head 2 comprises a plurality of outer openings 11 configured to emit a first flow of fuel “F1 ” outside the flow of comburent "C".

In particular, the outer openings 1 1 are arranged outside the passage gap 9 according to a direction that is radial to the main extension direction “X”. The fuel introduced from the openings 1 1 preferably follows the direction “X”.

In other words, the outer openings 1 1 are arranged outside the supply conduit 5.

Preferably, the outer openings 1 1 are arranged on the perimeter of the supply conduit 5.

Still more preferably, the outer openings 11 are distributed uniformly on the perimeter of the end portion 10 of the supply conduit 5. Further, the combustion head 2 comprises a plurality of inner openings 12 arranged at and/or inside the passage gap 9 according to a direction that is radial to the main extension direction “X”.

In particular, the inner openings 12 are adapted to introduce a second flow of fuel “F2’, F2”” inside the flow of a comburent "C".

The presence of the first flow of fuel “F1 ” and of the second flow of fuel “F2’, F2”” that join in the flow of comburent in different positions enable the flame to be developed in different zones. In detail, the first flow of fuel “F1 ” promotes “delayed” mixing that is achieved forwards in the combustion chamber in direction “X”, owing to the fact that it introduces the comburent by means of relatively big sections (by way of purely non-limiting example, sections having a diameter equal to 15 millimetres) in a zone lacking comburent. The second flow of fuel “F2””, owing to the shaped nozzles thereof and with a profile substantially parallel to the end portion 10, tends to diffuse the gas in a rear/radial zone through a recirculating effect with flow reversal.

The second flow “F2”’ facilitates the retention of the flame by promoting fast mixing with the comburent “C” in a low pressure zone that is substantially arranged at the connecting surface 22 that will be described in greater detail below.

According to one possible embodiment and as illustrated in the appended figures, the combustion head 2 can comprise a central body 13 extending between a first end 14, defining the inlet opening 3, and a second end 15, distal from the inlet opening 3, along an extension direction “E”.

In particular, the extension direction “E” can be parallel to, preferably coincident with, the main extension direction “X”.

The central body 13 can be at least partially inserted into the supply conduit 5.

Further, the second end 15 can define with the supply conduit 5 at least partially the passage gap 9.

Preferably, the second end 15 can define with the end portion 10 of the supply conduit 5 at least partially the passage gap 9.

Advantageously, the central body 13 can have an extension that is substantially axially symmetric relative to the extension direction “E”.

In this manner, the central body 13 can define with the supply conduit 5 a passage gap 9 having a conformation that is at least partially annular that confers stability and uniformity on the flow of comburent "C" and, thus, on the flame.

According to one possible embodiment and as illustrated in the appended figures, the central body 13 can have a housing 16 that is adapted to receive in a reversibly inserted manner a supply conduit 17 for supplying a fuel.

In particular, the housing 16 can extend between the first end 14 and the second end 15 parallel to the extension direction “E”.

According to one possible embodiment of the present invention, the conduit passage conduit 1000 and the central body 13 are operationally connected so as to define a prolongation of the housing 16. In this manner, the housing 16 can extend substantially between the inlet 1001 of the passage conduit 1000 and the second end 15 of the central body 13.

The further supply conduit 17 can enable the supply of a fuel that is different from the one supplied by the supply conduit 5, for example diesel or fuel oil, ensuring great operating flexibility for the apparatus 1 .

Further, the apparatus 1 can comprise at least one switch-on conduit 18 in fluid communication with the supply conduit 5 and passing through the central body 13 adapted to insert the aforesaid flame ignition means 8 according to one possible embodiment of the present invention.

In this case, flame ignition means 8 can exit suitable switch-on openings 18a of the switch-on conduit 18.

According to some possible embodiments not illustrated in the appended figures, these switch-on openings 18a can have different positioning along the extension direction “E” without the inventive concept at the basis of the present invention being altered.

For example, the switch-on openings 18a can be arranged upstream of the plurality of outflow holes 20b that will be described in greater detail below. Advantageously, the second end 15 of the central body 13 can have a convergent portion 19, for example truncated conically shaped, along the extension direction “E” and defining with the supply conduit at least partially the passage gap 9.

This shaping promotes the detachment of the flame from the second end 15, contributing to move the second end 15 away from the combustion head 2 and at the same time ensuring, also owing to the particular divergent geometry of the profile 21 , a zone of minimum flame retention on the retaining surface 22.

The convergent portion 19 can have a plurality of outflow holes 20a adapted to introduce at least partially the second flow ”F2”’ of fuel inside the flow of a comburent "C".

In other words, the central body 13 can have a plurality of outflow holes 20a, 20b for introducing at least partially the second flow “F2”’ of fuel in the flow of a comburent "C".

In particular, the aforesaid plurality of outflow holes 20a defines at least partially the inner openings 12.

Purely by way of non-limiting example, the plurality of outflow holes 20a, 20b can have a diameter equal to 2.5 millimetres.

The convergent 19 and divergent 21 portions, together with the plurality of outflow holes 20a, 20b contribute to limiting the turbulent formation of components in the flow of comburent "C" and concomitant with the introduction of the second flow of fuel ”F2”’ inside the flow of comburent "C". Optimum mixing between fuel and comburent in this stage occurs near the surface 22, thus ensuring increased stability of the flame in this zone and thus ensuring reliability, safety and operating elasticity for the burner during the operating step. This elasticity characteristic enables operation with very extensive A factors (in which A indicates the excess air coefficient).

This stability, permitted by the flame anchoring zone at the retaining surface 22, enables the flame to be maintained distant from the combustion head 2 and the need for the diffuser (the aforesaid disc or truncated conical element) in the end zone of the combustion head 2 to be overcome.

In other words, the apparatus 1 can be devoid of the traditional flame retention diffuser.

Further, the absence of the diffuser enables the generation of turbulent zones to be avoided that result in great mixing, enabling the flame to be moved further away from the combustion head 2 and diffusing the flame homogeneously in the volume of the combustion chamber. The reduction of the specific thermal load (W/m3) and the reduction of the temperature of the flame near the head 2 favour a great reduction of the emissions of thermal NOx.

Further, this effect enables the influence of thermal stress factors to be reduced, permitting an improvement to the life of the components and the possible application of less noble and expensive materials.

According to one possible embodiment and as illustrated in the appended drawings, the second end 15 can have at least one divergent portion 21 along the extension direction “E”.

In particular, the divergent portion 21 can be arranged at least partially inside the convergent portion 19.

Advantageously, the further supply conduit 17 can be at least partially insertable from the inlet 1001 as far as inside the divergent portion 21 , permitting dispensing of the further fuel at the zone of the combustion head 2 adapted to the generation of the flame.

The divergent geometry of the profile 21 enables the cone of the spray of the atomizer to be followed, preferably at a solid spray angle comprised between 50° and 70°, ensuring an optimal flame extension of the secondary fuel. Also in this case, the principle of partial flame detachment with partial retention near the retaining surface 22 enables NOx emissions to be kept very small.

Further, this insertion enables the overall operating dimensions to be reduced that are induced by the presence of the further supply conduit 17. As illustrated in the appended drawings, the plurality of outflow holes 20b can be obtained at least partially on the divergent portion 21 to introduce at least partially the second flow of fuel ”F2”’ inside the flow of a comburent “C”.

According to one possible embodiment of the present invention that is not illustrated in the appended figures, the plurality of outflow holes 20a, 20b can be provided only on the divergent portion 21 without altering the inventive concept underlying the present invention.

It is emphasised that the outflow holes 20a are made on the convergent portion 19. Preferably, both the pluralities of outflow holes 20a, 20b as illustrated in appended figures are present.

Alternatively, only the plurality of outflow holes 20b and not the outflow holes 20a can be present.

Further, the second end 13 has at least one retaining surface 22 (previously mentioned) adapted to connect the divergent portion 21 and the convergent portion 19.

In particular, the retaining surface 22 can be perpendicular to the extension direction “E”.

Advantageously, the retaining surface 22 can be at least partially lobeshaped.

As illustrated in the appended drawings, the aforesaid flame ignition means 8 can be arranged at least partially inside the divergent portion 21 so as to promote the generation of the flame near the retaining surface 22.

According to one possible embodiment of the present invention and as illustrated in the appended drawings, the combustion head 2 comprises a plurality of outflow conduits 23 branching off from the first end of the central body 13.

Further, the plurality of outflow conduits 23 extends at least partially along a direction parallel to the extension direction “E”.

In particular, the plurality of outflow conduits 23 defines at least partially the aforesaid plurality of outer openings 1 1 . Preferably, the combustion head 2 can comprise at least one inner nozzle 24, still more preferably a plurality of inner nozzles 24, arranged inside the supply conduit 5 according to a direction that is radial to the main extension direction “X”.

In other words, the at least one inner nozzle 24 can be interposed between the central body 13 and the supply conduit 5 and, preferably, inside the end portion 10 and the passage gap 9.

In particular, the inner nozzles 24 define a part of said plurality of inner openings 12.

According to one possible embodiment of the present invention, the inner nozzles 24 can have a diameter equal to about 16 millimetres.

Further, the at least one inner nozzle 24 can have different conformations, for example, circular, oval elliptic or the like without altering the inventive concept underlying the present invention.

Advantageously, the at least one inner nozzle 24 can have an extension axis tilted relative to the extension direction “E”.

In this manner, the inner nozzle 24 limits the turbulent formation of components inside the flow of comburent "C" and/or the second flow “F2”” promoting the introduction of the second flow “F2”” along a direction substantially parallel to the surface of the convergent portion 19 and 10.

Preferably, the combustion head 2 comprises a plurality of inner nozzles 24 having an extension that is transverse to the extension direction “E” such that the second flow “F2”” is at least partially convergent along the extension direction “E”.

Preferably, the combustion head 2 further comprises a plurality of outer nozzles 25 in fluid communication with the inlet opening 3.

In particular, the outer nozzles 25 can be arranged outside the supply conduit 5 according to a direction that is radial to the main extension direction “X”.

Specifically, the outer nozzles 25 can define at least partially the plurality of outer openings 1 1 . Advantageously, the outer nozzles 25 can have an extension substantially parallel to the main extension direction “X” such as to emit the aforesaid first flow “F1 ” of fuel outside the flow of comburent "C".

In this manner, the first flow “F1 ” contributes to delaying mixing by enabling the flame to be moved away from the end part of the combustion head 2 according to what has been set out previously.

According to one possible embodiment and as illustrated in the appended drawings, the outer nozzles 25 can be arranged perimetrically to the supply conduit and near the emission opening 7.

Preferably, the inner nozzles and/or the outer nozzles can be an end portion of a respective outflow conduit 23.

According to a further aspect, the present invention refers to a burner 100 comprising an apparatus 1 according to what has been previously disclosed and suction means 102 configured to suck at least one quantity of comburent from an environment outside the burner 100 and to move the quantity from the introduction opening 6 to the emission opening 7.

Further, the burner can comprise supplying means for supplying a fuel 101 adapted to supply a fuel to the combustion head 2.

It is thus observed that the present invention achieves the proposed objects by making an end apparatus for a burner able to reduce NOx emissions owing to the presence of a plurality of outer openings arranged outside the passage gap of the flow of comburent and a plurality of inner openings arranged at and/or inside the passage gap of the comburent operationally connected to move the flame away from the end part of the combustion head.

Advantageously, the combustion head 2 works by promoting a diffusing extension of a flame that is thus as homogeneous as possible inside the hearth. This is ensured by progressive combustion and is possible according to the particular conformation of the combustion head 2, in function of the geometry of the convergent portion 19, of the end portion 10 and of the position and the dimension of the nozzles 24, 25 and of the outflow holes 20a, 20b. Owing to this principle, a generally more uniform temperature is ensured with concentrated peaks of value lower than a traditional combustion head in which there is a more localized concentration of flame in the same thermal load conditions [W/m3].