FR2563611A1 - SOLDER BURNER WITH BALANCED SECONDARY AIR SUPPLY - Google Patents

Abstract

1. A burner with vanes of the kind comprising an opening (3) in the wall (1) of a combustion chamber, a nozzle (4) for injection of a combustible substance through the opening and an assembly (5, 6) for distribution of secondary air of combustion comprising a plurality of deflecting vanes (5) disposed annularly around the nozzle so as to make the combustion air flow together with the combustible substance in a helical trajectory, the secondary air of combustion being injected transversely towards the vanes (5) from a plurality of at least two injectors (7) regularly distributed around the said nozzle, characterized in that to allow a supply of secondary air of combustion without an air box, the injectors and the vanes are disposed immediately behind the wall (1) of the combustion chamber (2) and in that the axial deviation of this secondary air of combustion (before its meeting with the combustible substance) is controlled by means of a circular flange (6) movable along the nozzle and presenting openings crossed by the vanes.

Description

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  The present invention relates to burners, sometimes referred to as

  "turbulent burners", in which a fluid fuel, such as pulverized coal suspended in a primary air stream, is introduced into a furnace by means of a nozzle and in which secondary air, necessary for fuel combustion, is put

  rotating around the end of the nozzle by means of flaps de-

  fliers commonly called "ventelles". The invention relates more

  precisely the way in which the secondary air is brought to the fans.

such.

  A burner of the aforementioned type is described in particular in the

vet FR-2.054.741.

  In a conventional manner, as specified in particular the aforementioned patent, the secondary air is distributed through the louvers from a wind box surrounding the nozzle. Characteristics

  of the helical flow of secondary air are usually adjusted

  or by varying the cross section of the secondary air through the lamellae by acting on the axial gap existing between the transverse walls. who determine this

passage section.

  It is also important, for safety reasons, that one can monitor the combustion flame, in particular to detect its possible extinction. For this purpose, it is advantageous to use

  sensors, for example ultraviolet ray cells, which

  preferably be oriented towards the flame in a

  parallel to the nozzle so as to avoid that, in the case for example of a fireplace equipped with several burners, the sensor associated with

  a burner may be sensitive to the flame of a nearby burner.

  In practice, the wind box through which the secondary air is distributed has a large footprint along the nozzle. It is indeed unanimously accepted that a large volume wind box is a sine qua non condition without which a homogeneous distribution of secondary air through louvers can not be obtained. It is admitted, in a very general way, that a good distribution of secondary air requires a passage

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  in a kind of expansion chamber in which the secondary air can be homogenized in pressure. As we know, a regular distribution of secondary air is essential for

  have a flame well aligned with the nozzle and to ensure

  complete combustion of the fuel. Irregularities in the distribution of secondary air induce air defects or excess air in certain parts of the flame, which prevents combustion being complete. A small axial space and a regular distribution of secondary air are therefore commonly considered as requirements

  between which a compromise must be defined according to needs.

  The axial size of the aforementioned wind boxes, which can reach

  the order of magnitude of their diameter, proves to be very

  especially a great length of linkage for the orientation

  louvers or the setting of the section for the passage of secondary air

  between them. It also requires, for monitoring

  of the flame, sensors that are quite powerful and therefore quite expensive:

  for the reasons stated above, they are arranged opposite the flame with respect to the wind box and must be capable of

  detect the flame at a very low angle of observation.

  The present invention aims to overcome these drawbacks.

  by providing secondary air distribution

  than in the case of a wind box, yet with a

  axial reduction as small as possible, thereby simplifying the structure of the control elements charged to adjust the characteristics of the air flow through the louvers, and also allowing the use of simple and inexpensive sensors arranged axially low

  distance from the flame to be monitored.

  The invention thus proposes a vane burner of the kind

  having a lumen in the wall of a fireplace, a nozzle for

  jection of a fuel through light, and a set of dis-

  combustion air intake comprising a plurality of louvers de-

  flectrices arranged in a ring around the nozzle, in the vicinity of the furnace lumen, in order to conflate the combustion air with the fuel in a helical path, characterized in that the combustion air is injected transversely to the the louvelles from

  a plurality of at least two injectors regularly distributed over

turn of said nozzle.

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  It should be noted that the solution recommended by the invention goes against the previously received idea that implied that no multiplication of the number of injectors could afford to ensure a distribution of secondary air as good only with a wind box. The Applicant has nevertheless been able to note, in a very surprising way, that a very good result, substantially comparable to that obtained with a wind box, could be achieved with only two

  injectors diametrically opposed. It is understood that this mid value

  nimal of "two" is preferred since it corresponds to the structure

simpler.

  Other objects, features and advantages of the invention

  from the description which follows, given by way of non-limiting example

  with reference to the accompanying drawings in which: - Figure 1 is a schematic longitudinal sectional view of a vent burner according to the invention - Figure 2 is a cross-sectional view along the line II-II of Figure Fig. 3 is a diagram showing the pressure zones by washing of the nozzle of a conventional burner, and Fig. 4 is a similar diagram showing the zones of

  pressure in front of the nozzle of a burner according to the invention.

  The burner shown by way of example in FIGS. 1 and 2 essentially comprises a wall 1 of a firebox 2 in which is

  an opening or a lumen 3. A nozzle 4 is arranged on the outside.

  the nozzle is directed in a direction X-X 'perpendicular to the wall 1. This nozzle is intended to inject through the light 3 a fluid fuel such as pulverized coal suspended in

  a primary gas, air most often.

  The wall 1 carries axially projecting, opposite the hearth 2, moon

  plurality of deflector flaps or louvers 5 arranged in a ring

  turn of the end 4A of the nozzle. These louvers are inclined at the same predetermined angle, for example 60, relative to the planes

Fictitious diameters cutting them.

  Along the nozzle 4 slides a flange 6 having

  openings through which the lamellae pass through. 5. The flange is axially

  by means not shown, so as to adequately vary the characteristics of the secondary air helical flow AS. It is advantageously deflected axially before its

  confluence with the fluid fuel.

  According to the invention, the secondary air is injected towards the yen

  such by a plurality of injectors 7 regularly distributed around the nozzle. In the example shown, these injectors are in number

  of two and are diametrically opposed.

  The flange 6 is movable axially between the wall 1 of the hearth

  and a transverse wall slightly offset with respect to said wall 1.

  The injectors 7 inject the secondary air substantially radially

between these walls.

  The injectors must be crossed by secondary air flows identical in flow and pressure. They are preferably

  fed from the same source through two parallel ducts

  the the. The equilibrium of flows and pressures is ensured for example by a rotating shutter disposed in at least one of said

  ducts. Alternatively, a diaphragm can be used.

  Figures 3 and 4 allow to appreciate the performance of a burner according to the invention compared to those of a burner having only one injector without wind box. In these figures are curves of equal pressure recorded under identical operating conditions: same flow rate and same secondary air temperature, at the same distance from the

  home. In fact, these curves were determined in the absence of

fluid.

  The pressures associated with each of these curves are given

  in arbitrary units. There are two zones inside and outside

  dull low pressure (sometimes called recirculation zones) from

  and another of a generally annular zone of greater pressure.

  It can be seen in FIG. 3 that the pressures are distributed very irregularly in the annular zone mentioned above. We aknowledge

  more precisely, the presence of areas of high pressure in the form of

  which are arranged substantially opposite the air inlet. Due to these crescent zones, there are strong pressure gradients around the axis of the nozzle which induce asymmetry of a flame, after fuel injection, and therefore incomplete combustion.

of the last.

  On the other hand, it can be seen in FIG. 4 that the use of two opposite injectors allows a clear improvement in the distribution of the pressures around the axis of the nozzle, which is favorable for obtaining good flame and good fuel combustion. It has been observed that the quality of the symmetry of the pressures highlighted in FIG. 4 is substantially as high as

  the implementation of traditional wind boxes.

  It goes without saying that the foregoing description has not been proposed

  as an illustrative example and that many variants can

  be proposed both in particular in the particular structure of

  such as in the secondary airflow adjustment mode, that

  in the number of injectors, without departing from the scope of the invention.

  The nature of the fuel does not matter. The injectors are, alternatively,

  inclined parallel to the axis of the nozzle.

Claims (4)

  1. Vent burner of the kind having a lumen in the wall of a fireplace, a nozzle for injecting a fuel at   through light, and a set of air distribution of com   nozzle comprising a plurality of baffle plates arranged in a ring around the nozzle, in the vicinity of the hearth lumen, for the purpose of causing the combustion air to fuse with the fuel in a helical path, characterized in that the air of combustion is injected transversally to the lamellae (5) from a plurality of at   at least two injectors (7) regularly distributed around said nozzle.   2. Burner according to claim 1, characterized in that its secondary air distribution assembly comprises two injectors diametrically opposed.   Burner according to claim 1 or 2, characterized in that   that the injectors are oriented radially.   4. Burner according to any one of claims 1 to 3,   characterized in that the injectors (7) are fed by the same secondary air source through bypass ducts, one of which   at least part comprises flow control and pressure control members.