FR2624255A1 - Air-gas burner with a very-stable inner-core flame, constituting the functional part of a torch nozzle - Google Patents

Abstract

The subject of the invention is an air-gas burner with a inner-core flame, comprising a one-piece body formed by an inlet tube 1 and a tubular part 3 housing the diffuser and the outwardly-open combustion chamber. By virtue of two identical flanges 7, 11 mounted on the shouldered central sleeve 5, the diffuser provides for a helical flow of the air-gas mixture which, upon entering the combustion chamber, generates the pilot flames 27 for the inner-core flame. In the path of this air-gas mixture, the space 24, lying between the two flanges, acts as an expansion chamber, while the incurvate radial tongues 6 of the said flanges act as deflectors. The large number of outlet holes of the diffuser, the nature and the velocity of the flow of the air-gas mixture make all the pilot flames extremely stable. Application: the equipping of conventional torch nozzles or of those with piezoelectric ignition.

Description

 The present invention relates to stard flame burners of fuel gas brazing torches whose air is the oxidizer. Dart flame aero-gas burners of the type described in the French patents BULGIN 1 383 936 and RIPPES 2 063 341 have been known for a very long time. In these burners, the piloting of the main flame called the darting flame is obtained by a belt of small flames called pilot flames which come from the orifices made in the side wall of the diffusers at the level of the mark 19 of the BULGIN patent and at the level of the marks 8, 9 of the RIPPES patent.

 On the one hand, these diffusers are costly to produce because they have one or two series of orifices, the drilling of which requires a fairly long machining time, and on the other hand, their effectiveness is not sufficient because the pilot flames from of these orifices distributed over one or two annular rows do not ensure total stability of the main flame.

 The burner according to the invention overcomes these drawbacks.

Excellent stability of the main flame consisting of a dart and a plume is obtained by a belt of pilot flames originating in a stream of air-gas mixture flowing helically at the outlet of a diffuser which is very simple does not have orifices on its side wall which means that its cost price is relatively low.

 The burner object of the invention which is either an extension of a mixing chamber or an assembly which can be connected in a known manner to a tube ensuring a more or less long connection with an independent mixing chamber, comprises a cylindrical diffuser placed at the base of the combustion chamber where it is held in position by an appropriate means acting on its front and rear flanges.

 internally along the direction of passage of the air-gas mixture, the burner has two concentric bores connected by a sectional section. The upstream bore of small diameter is used to bring the air gas mixture from the mixing chamber or the connecting tube to the diffuser which is housed in the downstream bore of larger diameter which houses the combustion chamber.

 The diffuser has a central sleeve whose internal section is identical to or less than that of the upstream bore while being concentric with it. Thus the transfer of the air-gas mixture from said upstream bore to the combustion chamber takes place on the one hand through the passage of the central sleeve and on the other hand through the orifices of the rear and front flanges after having passed through the frustoconical connection .

 The geometrical axes of the orifices of the rear and front flanges being all inclined at the same angle relative to the axis of the bores upstream and downstream of the burner, the flow of the air-gas mixture takes on the appearance of a helical flow at the level of the flange rear then crosses the inter-flange annular space in which it relaxes before emerging helically into the combustion chamber by leaving the orifices of the front flange. In this combustion chamber, the dart flame is born in the jet of air-gas mixture leaving the central sleeve of the diffuser while the pilot flames are born at the exit of the orifices of front panel.

 diffuser the short and very stable pilot flames are generated at the base of the dart flame, which they surround obliquely to give it excellent stability, coupled with exceptional resistance to blowing.

 One of the advantages of this aero-gas burner is that it allows the operator to work outdoors even in difficult atmospheric conditions.

 In what follows the invention is explained in detail using drawings representing only one embodiment given by way of nonlimiting example.

- Figure 1 shows a longitudinal section view of a burner according to the in
vention equipped with a diffuser including the orifices which can
read the helical flow of the air-gas mixture
as the pilot flames are located at the periphery
two flanges between turned radial tabs
outward and the inner wall of the burner body.

- Figure 2 shows a longitudinal section view of a burner according
the invention equipped with a diffuser whose orifices which
channel the helical flow of the air-gas mixture
feeding the pilot flames are located inside
laughing of two flanges between radial tabs
facing the axis of the burner and the external wall of the
central sleeve.

- Figure 3 shows a side view of the burner diffuser of the
.figure 1 with a diagram of the dart flame and
pilot flames showing their respective position by
compared to the downstream part of the burner body seen in section.

- Figure 4 shows a front view of a diffuser flange,
the orifices which channel the helical flow of the
air-gas mixture feeding the pilot flames are
located at the periphery between the curved radial tabs
vee.

- Figure 5 shows a side view of the burner diffuser of the
Figure 2 with a diagram of the dart flame and
pilot flames showing their respective position by
compared to the downstream part of the burner body seen in section.

- Figure 6 shows a front view of a diffuser flange,
the orifices which channel the helical flow of the
air-gas mixture feeding the pilot flames are
located inside between the tower radial tabs
born towards the center.

Referring to FIG. 1, it can be seen that the aero-gas burner with a dart flame comprises a monobloc body formed by an intake tube (l) internally connected by a truncated cone (2) to a tubular part (3) larger diameter in which a combustion chamber (4) open to the outside follows a diffuser ensuring two outlet sections for the air-gas mixture coming from a mixing chamber or a connecting tube on which the burner must be fitted by screwing or by any other means. The outlet section of the air-gas mixture supplying the main flame is provided by the passage section of the central sleeve (5) while that supplying the pilot flames is provided by the passages existing between the tabs (6) of the rear flanges and front of the diffuser.

 Depending on the size of the burners, the passages between the tongues of the front and rear flanges are adjacent either to the downstream bore of the burner body, or to the side wall of the central sleeve.

The diffuser still consists of a central sleeve and two flanges but according to the first embodiment shown in Figure 1, the flanges (7), (11) which are hooped on the shoulders (8), (10) cut at each end of the central sleeve are integral with the latter and remain separated from each other by the non-turned length of the side wall (9) of said sleeve. This diffuser is held in position in the burner body by an external crimp (12).

 According to the second embodiment shown in Figure 2, the flanges (13) (15) with internal tabs (18) are mounted symmetrically on the ends of the smooth central sleeve (14) by elastic deformation of said tabs. As in the first embodiment, the front (15) and rear (13) flanges are identical, but their mounting on the smooth sleeve does not allow them to impose a precise spacing, they are separated from one another by a cylindrical spacer (20) of the same diameter which isolates the annular expansion chamber (21) from the burner body. Maintaining in position in the downstream bore (16) of this diffuser with its spacer is obtained by a reinforcement ring ( 17) introduced under stress into the combustion chamber (19) to increase the thickness of the burner body without increasing the outside diameter.

 FIGS. 3 and 4 show that the rear and front flanges of the first diffuser model are metal crowns (22) provided with radial tongues (6) directed outwards, slightly curved and strongly inclined relative to the plane of the crown, so that the geometric axes of the passages (23) existing between said tongues are all inclined at the same angle relative to the axis of the burner.

Due to their special shape, these tabs act as deflectors placed on either side of the expansion chamber (24) of the air gas mixture feeding the pilot flames. Thus at the entrance to this chamber the rear flange (11) generates a vortex flow while at the entrance to the combustion chamber the front flange (7) transforms this partially relaxed vortex into a helical flow. In other words the part of the air-gas mixture which diverges in the sectional flaring (25) of the burner body is transformed into a helical flow by leaving the expansion chamber (24) between the deflectors that are the tongues integral with the crown. metal (22) hooped on the shoulder (8) of the central sleeve.

 FIGS. 5 and 6 show that the rear and front flanges of the second diffuser model are metal crowns (26) provided with radial tongues (18) directed inwards, slightly curved and strongly inclined relative to the plane of the crown, so that the geometric axes of the passages (28) existing between said tongues are all inclined at the same angle relative to the axis of the burner. As in the first model, the helical flow of the air-gas mixture feeding the flames piloting is created by the curved radial tongues (18) of the front flange acting as deflectors with respect to the part of the air-gas mixture which has diverged in the section flaring (30) and which has partially relaxed in the expansion chamber (21) after entering it undergoing rolling in the oblique passages (29) existing between the tabs of the rear flange (13) and the central sleeve (14).

 Referring to Figures 3 and 5 showing the schematic shapes of the pilot flames (27) and the plume (32) surrounding the stinger (31) we see that in these two embodiments the internal wall of the combustion chamber maintains the pilot flames (27) in a hollow cylinder in the thickness of which they describe helices emerging in the axis of the air-gas mixture jets leaving the orifices (23) (28) of the front flange. The dart flame burning in the extension of the central sleeve, its base is perfectly surrounded by the pilot flames along the entire length of the combustion chamber plus a slight overshoot outside. It is only stable if the pilot flames are themselves stable.

The stability of the flame front at the outlet of a burner always results from a balance between the flow speed of the mixture and the flame propagation speed which depends on the nature of the gas, the air / gas ratio , the temperature, the dimensions of the orifice and the flow regime. The burner object of the present invention being supplied by an air-gas mixture at room temperature whose air / gas ratio is fixed by the air inlets of the torch to which it fits, the stability of all the pilot flames is mainly due to - a large number of outlet openings of the diffuser adapted to the diameter
of the combustion chamber and which are regularly distributed over the
metal crown of the front flange between the emerging tabs
either at the inner circumference when they are -orien-
tees towards the central sleeve, that is to say at the periphery when they
are facing the outside of the diffuser.

- a low flow speed of the air-gas mixture resulting from its
rolling in the orifices of the flanges and its passage in the
relaxation room.

- a helical flow of the air-gas mixture generated by the inclined and curved tongues which are regularly distributed circularly at the rate of one every 30 to 45 degrees.

In addition to the stability imparted to the dart flame by the pilot flames, it is possible to improve the fineness of the contour of the dart (31) by the longitudinal addition in the intake tube (1) of a thin partition. or two diametrically crossing at right angles to ensure a perfectly laminar flow of the air-gas mixture to enter the central sleeve (5)
The brazing torches using these stard flame burners surrounded by short and stable pilot flames have markedly improved performance.

 The burners according to the invention are perfectly suitable for equipping torch lances and more particularly for those provided with a piezoelectric ignition.

Claims (9)

 1) Aero-gas burner with a stard flame comprising a tubular part (3) internally connected by a truncated cone (2) to an intake tube (1) to form a monobloc body which provided with means for connection to a mixing chamber or to a connecting tube houses within its tubular part a diffuser and a combustion chamber open to the outside, characterized in that the diffuser ensures a helical flow of the air-gas mixture supplying the pilot flames ( 27) of the dart flame.  2) Aero-gas burner with stard flame according to claim 1 characterized in that the helical flow of the air-gas mixture supplying the pilot flames is created by curved radial tongues (6) acting as deflectors integral with a crown metal (22) constituting the front flange (7) of the diffuser.  3) Aero-gas burner with stard flame according to claim 1 characterized in that the diffuser comprises an annular chamber (21) formed by the space surrounding the central sleeve (14) between the front and rear flanges which ensures the relaxation of the mixture after rolling, in the passages (29) existing between the rear flange (13) and the central sleeve.  4) Aero-gas burner with stard flame according to any one of the preceding claims, characterized in that the front and rear flanges mounted on the central sleeve are identical and are separated from each other either by a cylindrical spacer (20 ) of the same outside diameter, either by the non-turned part of the central sleeve (5).  5) Aero-gas burner with stard flame according to claim 1 or claim 2 characterized in that the curved radial tongues ensuring the helical flow of the air-gas mixture feeding the pilot flames are regularly distributed on the metal crown of which they emerge either at the inner circumference when they are oriented towards the central sleeve, or at the periphery when they are turned towards the outside of the diffuser.  6) Aero-gas burner with stard flame according to any one of the preceding claims, characterized in that, depending on the position of the tongues relative to the metal crown, the front and rear flanges are mounted symmetrically on the ends of the central sleeve, either by elastic deformation tongues (18) on said sleeve (14) or by hooping metal crowns (22) on the external shoulders (8) (10) of the ends of the central sleeve (5).  7) Aero-gas burner with stard flame according to claim 1 or claim 3 characterized in that the supply of air-gas mixture to the expansion chamber (24) is ensured by a sectional flaring (25) from the inside of the burner body at the connection of the intake tube to the larger diameter tubular part housing the diffuser and the combustion chamber (4).  8) Aero-gas burner with stard flame according to claim 1 characterized in that the diffuser is held in position in the body of said burner either by an external crimp (12) or by a ring (17) of internal reinforcement of the thickness of the body introduced under stress into the combustion chamber (19).  9) Aero-gas burner with stard flame according to claim 1 characterized in that longitudinally the intake tubR (1) can be provided with a thin diametrical partition or two intersecting to ensure a perfectly laminar flow of the air-mixture gas to enter the central sleeve (5).