EP0701092A1 - Device for spreading a flame using COANDA effect and oven using this device - Google Patents

Device for spreading a flame using COANDA effect and oven using this device Download PDF

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Publication number
EP0701092A1
EP0701092A1 EP95401906A EP95401906A EP0701092A1 EP 0701092 A1 EP0701092 A1 EP 0701092A1 EP 95401906 A EP95401906 A EP 95401906A EP 95401906 A EP95401906 A EP 95401906A EP 0701092 A1 EP0701092 A1 EP 0701092A1
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EP
European Patent Office
Prior art keywords
jet
flame
oven
gas
main
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP95401906A
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German (de)
French (fr)
Inventor
Christian Larquet
Alain Villermet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Publication date
Application filed by Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Publication of EP0701092A1 publication Critical patent/EP0701092A1/en
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/32—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid using a mixture of gaseous fuel and pure oxygen or oxygen-enriched air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/20—Non-premix gas burners, i.e. in which gaseous fuel is mixed with combustion air on arrival at the combustion zone
    • F23D14/22—Non-premix gas burners, i.e. in which gaseous fuel is mixed with combustion air on arrival at the combustion zone with separate air and gas feed ducts, e.g. with ducts running parallel or crossing each other
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S239/00—Fluid sprinkling, spraying, and diffusing
    • Y10S239/07—Coanda

Definitions

  • the invention relates to a device for spreading a flame by the Coanda effect.
  • Heating nozzles are known, for example, comprising a central tube which delivers a combustible gas and an annular tube, surrounding the central tube, which delivers an oxidizing gas. It is known to place a cone-shaped obstacle in the flow of the jet of combustible gas in order to widen it. The annular jet of oxidizing gas is entrained by the combustible gas, which forms an enlarged flame.
  • the present invention relates to a flame spreading device which achieves this result.
  • Another advantage of this device is that it gives very good stability to the spread flame.
  • the spread flame obtained follows the curved surface perfectly, which makes it possible to obtain a very flat flame and therefore an excellent distribution of the heat which it produces.
  • the section of the main nozzle and the section of the secondary nozzle can naturally take a wide variety of forms.
  • the main nozzle has a circular section
  • the secondary nozzle of annular section, surrounds the main nozzle
  • the main nozzle is rectangular, at least one secondary nozzle delivering a tangential secondary jet to one of the sides of the rectangle formed by the section of the main nozzle.
  • the main nozzle can also have other very diverse shapes, for example square, polygonal, polygonal with rounded angles, ellipsoidal or ovoid, etc.
  • combustible gases for example methane or propane or any hydrocarbon.
  • the oxidizing gas is preferably oxygen, but it can also be air.
  • the invention also relates to an oven comprising walls delimiting an enclosure and heating means.
  • Ovens are already known comprising a refractory wall heated by a flame.
  • the refractory wall then heats the interior atmosphere of the furnace and the charge contained in the furnace.
  • flame spreading devices are used.
  • the main jet is substantially perpendicular to a wall of the oven, and the curved surface deflects the jet substantially by 90 ° so that the flame flows tangentially to a wall of the oven.
  • This embodiment makes it possible to widen the flame which becomes completely flat and to heat the refractory wall of the furnace. This gives a very good heat diffusion.
  • This embodiment is advantageously applied to small ovens in which the flame must not reach the charge to be heated.
  • ovens are also known in which it is desired to obtain a fine flame. We can in this case wish that the flame remains parallel to the surface of the bath and has a thickness as constant as possible in order to ensure a regular and homogeneous heating of the bath.
  • the zone substantially perpendicular to the wall of the furnace is arranged horizontally.
  • the zone substantially perpendicular to the wall of the furnace is arranged vertically.
  • the Coanda effect is a known phenomenon in which a jet flow remains attached to a tangent surface on which it flows.
  • the jet remains attached to the tangent surface even if the latter gradually deviates from its initial direction by a certain angle.
  • Figure 3 illustrates the principle of a flame spreading device according to the invention.
  • the device comprises a main nozzle 4 capable of delivering a gas, for example a combustible gas.
  • a gas for example a combustible gas.
  • the end of the nozzle 4 is located in a hole formed in a thick wall.
  • the main jet whose flow is shown diagrammatically by the arrows 6, opens in parallel to a curved wall 10 formed by the thick wall.
  • the secondary nozzle 8 consists of the space between the main nozzle 4 and the curved surface 10.
  • the secondary jet 12 for example of oxidizing gas, flows tangentially to the walls 10 at the outlet of the secondary nozzle 8.
  • L 'space between the outside of the main nozzle 4 and the wall 10 has a substantially constant section and of small dimension, for example 0.3 mm.
  • the secondary jet 12 When the secondary jet 12 is alone, it flows tangentially to the wall 10 by the Coanda effect. This wall is curved and gradually widens until it forms an angle of 90 ° relative to the axis of the main and secondary nozzles.
  • the secondary jet also called parietal jet because it flows along the wall 10, produces a strong depression in the central zone where the main nozzle 4 opens.
  • the parietal jet When the two jets, namely the main jet and the secondary jet (or parietal jet) flow simultaneously, the parietal jet whose flow speed is significantly higher than that of the main jet, sucks the latter. The two jets mix and the resulting jet flows horizontally.
  • the depression created by the Coanda effect at the heart of the parietal jet in the area of curvature is such that the entire main jet is driven by the parietal jet to follow the wall 10.
  • the equilibrium of the spread jet is perfectly stable in a range of relative speed of the parietal jet compared to the main jet and it is not possible to upset this balance.
  • the flow of primary gas for example combustible, mixes rapidly with the flow of secondary gas, for example oxidizing gas, to form a combustible mixture which gives rise to the flame.
  • secondary gas for example oxidizing gas
  • FIG. 1 a sectional view of an oven of the prior art, designated by the general reference 20.
  • This oven has an outer wall 11 of steel and an inner wall 22 lined with bricks of refractory material.
  • a hearth 24 is disposed on the bottom 26 of the oven.
  • the oven 20 includes heating means 30 which deliver a flame 32. It is known to use flame enlargement devices in order to obtain a flame as large and flat as possible so as to distribute the heat of this flame and to heat the part 28 in a homogeneous manner. This result cannot be easily achieved with the flame spreading devices currently known.
  • FIG. 4 shows heating means which equip an oven according to the present invention.
  • These heating means are constituted by a tube 4, of circular section, which constitutes a main nozzle.
  • the tube 4 is surrounded by a tube 7 also of circular section.
  • This tube 7 is connected to an O-ring piece 9.
  • the end of the tube 4 opens substantially in the middle of the thickness of the piece 9.
  • the piece 9 is inserted into the roof of the oven at the position of the heating means 30 shown on Figure 1. It has the curved surface 10.
  • the external wall of the furnace is constituted by a steel sheet 11 internally lined with refractory bricks 22.
  • the main nozzle 4 delivers a jet of combustible gas.
  • Comburan gas is brought into the annular space 8 between the tube 4 and the tube 7.
  • An annular passage of small thickness is between the outer surface of the part 9 and the outer diameter of the tube 4.
  • the typical value of this space is between 0.2 mm and 1 mm, but can take other values. This makes it possible to give the secondary jet a much higher flow speed than that of the main jet 6.
  • a pipe 34 in which a refrigerating fluid such as water circulates ensures the cooling of the part 9.
  • the part to be heated 28 is not touched by the flames because the latter flow along the wall. This characteristic is advantageous in particular in the case of an oven of small dimensions.
  • An oven was produced, the walls of which were lined with refractory material and had circular main nozzles 20 mm in diameter.
  • the annular space between the outside of the main nozzle and the tangent wall of the part 9 was 0.3 mm.
  • the power developed by each flame was of the order of 4.2 W.
  • FIG. 5 shows an alternative embodiment of the heating means fitted to an oven according to the invention.
  • the main nozzle and the secondary nozzle have a circular section
  • the main nozzle is constituted by a box 35 of elongated rectangular section.
  • a plate 37 delimits with the wall of the box 35 which faces it a space which makes it possible to supply the secondary gas, whether it is combustible gas or oxidizing gas.
  • the part 9 instead of having a toroidal shape, is of elongated rectilinear shape. It delimits a slot which extends parallel to the length of the oven.
  • the operation of this device is identical. Its advantage lies in the fact that it makes it possible to obtain a flame of great width, for example a flame which occupies most of the length of the oven. This provides better heat distribution over the length of the oven than a series of spaced heating nozzles.
  • FIG. 7 a third alternative embodiment of this device.
  • the main nozzle 35 has a square section and the part 9 also has a square section which is rounded at its four corners.
  • This variant makes it possible to obtain four flames, namely one flame per side. It goes without saying that a large number of other forms could be imagined.
  • FIG. 2 shows a second type of oven of the prior art, designated by the reference 40. It has walls formed of refractory bricks 22. This oven contains a charge 42. Heating nozzles 44 are provided for each side of oven 40.
  • the flames 46 produced by the nozzles 44 be parallel to the level of the charge 42 in order to heat it regularly.
  • the flames 46 release hydroxyl radicals which oxidize the charge 42 when they are too close to it. A fine flame, the distance to the surface of the bath is constant, avoids this drawback.
  • FIG 8 shows a vertical sectional view of heating means fitted to an oven according to the present invention.
  • These heating means comprise a box 35 of elongated rectangular section identical to the boxes shown in Figures 5 and 6.
  • a sheet metal housing 50 connects an outer wall of the box 35 to the wall of the oven.
  • a supply duct 52 transports a secondary gas 12 to the secondary nozzle constituted by a narrow width slot provided between an outer wall of the box 35 and the curved surface of the part 9.
  • the main jet 6 and the secondary jet 12 mix and follow the wall of the room 9. Note also the presence of the pipes intended for the optional circulation of a cooling fluid such as water.
  • the part 9 ends with a horizontal surface 54 perpendicular to the vertical wall 22 of the oven. In this way, the flame 56 is detached from the part 9 and enters the furnace horizontally, that is to say parallel to the surface of the glass bath 42.
  • the flame 56 does not flare and remains fine, even at a relatively large distance from the wall 22 of the oven. This characteristic is particularly interesting because it is thus possible to arrange the flame so that it is relatively close to the surface of the charge without, however, touching it.
  • FIG. 9 a third embodiment of a heating device for an oven.
  • the heating means are identical to those which have been described with reference to FIG. 8, but the orientation of the part 9 is different.
  • the reference 22a designates the upper part of the oven and the reference 22b the lower part of this oven. It can therefore be seen that the planar surface of the part 9 is arranged in a vertical plane instead of a horizontal plane according to FIG. 8.
  • the outlet section of the box 35 constituting the main nozzle is also arranged in a vertical plane. As a result the thin flame 56 is also.
  • a device such as that which is shown in FIG. 9 can be used in an oven of the type shown in FIG. 2.
  • the height of the piece 9 should not be very large. Indeed, it is desirable that the flame 56 remains relatively close to the free surface of the glass bath 42. This is the reason why will have a series of heating devices identical to that shown in Figure 9 along the length of the oven to heat the load.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Furnace Details (AREA)

Abstract

The flame spreader consists of main and secondary nozzles (35, 8) delivering jets of fuel gas and oxidant, and a curved surface (9) situated at a tangent to the secondary gas jet to turn it by the Coanda effect which draws the fuel gas jet and mixes it with the oxidant gas to form the flame. The main nozzle can be circular in section, with the secondary one surrounding it, or else rectangular in section, with the secondary nozzle delivering the oxidant gas at a tangent to one side of the rectangle. The fuel gas delivered by the main nozzle is methane or propane, and the oxidant gas is oxygen or air.

Description

L'invention concerne un dispositif d'étalement d'une flamme par effet Coanda.The invention relates to a device for spreading a flame by the Coanda effect.

Dans de nombreux domaines, en particulier l'industrie, on utilise la chaleur d'une flamme obtenue par le mélange et la combustion d'un gaz combustible et d'un gaz comburant. Afin de répartir la chaleur de la flamme, des dispositifs d'étalement de flamme ont déjà été imaginés.In many fields, in particular industry, use is made of the heat of a flame obtained by the mixing and combustion of a combustible gas and an oxidizing gas. In order to distribute the heat of the flame, flame spreading devices have already been devised.

On connaît par exemple des buses de chauffage comportant un tube central qui délivre un gaz combustible et un tube annulaire, entourant le tube central, qui délivre un gaz comburant. Il est connu de placer un obstacle en forme de cône dans l'écoulement du jet de gaz combustible afin de l'élargir. Le jet annulaire de gaz comburant est entraîné par le gaz combustible, ce qui forme une flamme élargie.Heating nozzles are known, for example, comprising a central tube which delivers a combustible gas and an annular tube, surrounding the central tube, which delivers an oxidizing gas. It is known to place a cone-shaped obstacle in the flow of the jet of combustible gas in order to widen it. The annular jet of oxidizing gas is entrained by the combustible gas, which forms an enlarged flame.

Il est également connu de placer une pièce métallique en forme d'entonnoir renversé à la sortie de la buse du jet de gaz comburant. Ceci oblige la flamme à suivre cette pièce et donc à s'élargir. Toutefois, le transfert de chaleur de la flamme vers la pièce métallique est très important. Cette solution est donc très difficile à mettre en oeuvre.It is also known to place a metal part in the form of an inverted funnel at the outlet of the nozzle of the oxidizing gas jet. This forces the flame to follow this part and therefore to widen. However, the transfer of heat from the flame to the metal part is very important. This solution is therefore very difficult to implement.

Cependant, l'ensemble des dispositifs d'élargissement de flamme actuellement connus ne permettent pas d'obtenir une flamme plane, c'est-à-dire une flamme très élargie dont la hauteur est très faible.However, all of the flame extender devices currently known do not make it possible to obtain a planar flame, that is to say a very enlarged flame whose height is very small.

La présente invention a pour objet un dispositif d'étalement de flamme qui permet d'atteindre ce résultat.The present invention relates to a flame spreading device which achieves this result.

A cet effet, le dispositif selon l'invention comporte :

  • au moins une buse principale délivrant un jet de gaz combustible ou de gaz comburant ;
  • au moins une buse secondaire délivrant un jet de gaz comburant ou de gaz combustible qui s'écoule autour du jet principal et qui possède une épaisseur sensiblement constante ;
  • au moins une surface courbe disposée tangentiellement au jet de gaz secondaire afin de le dévier par effet Coanda, d'aspirer le jet de gaz principal et de mélanger le jet de gaz secondaire et le jet de gaz principal pour former une flamme.
To this end, the device according to the invention comprises:
  • at least one main nozzle delivering a jet of combustible gas or oxidizing gas;
  • at least one secondary nozzle delivering a jet of oxidizing gas or combustible gas which flows around the main jet and which has a substantially constant thickness;
  • at least one curved surface disposed tangentially to the secondary gas jet in order to deflect it by Coanda effect, to suck up the main gas jet and to mix the secondary gas jet and the main gas jet to form a flame.

Grâce à ce dispositif on obtient un excellent mélange du gaz combustible et du gaz comburant en raison de la différence de vitesse entre les deux jets et de l'écoulement turbulent qui en résulte.Thanks to this device, an excellent mixture of combustible gas and oxidizing gas is obtained due to the difference in speed between the two jets and the turbulent flow which results therefrom.

Un autre avantage de ce dispositif est qu'il confère une très bonne stabilité à la flamme étalée.Another advantage of this device is that it gives very good stability to the spread flame.

De plus, la flamme étalée obtenue suit parfaitement la surface courbe, ce qui permet d'obtenir une flamme très plate et donc une excellente répartition de la chaleur qu'elle produit.In addition, the spread flame obtained follows the curved surface perfectly, which makes it possible to obtain a very flat flame and therefore an excellent distribution of the heat which it produces.

La section de la buse principale et la section de la buse secondaire peuvent naturellement prendre des formes très variées.The section of the main nozzle and the section of the secondary nozzle can naturally take a wide variety of forms.

Dans une forme de réalisation courante la buse principale présente une section circulaire, et la buse secondaire, de section annulaire, entoure la buse principale.In a common embodiment, the main nozzle has a circular section, and the secondary nozzle, of annular section, surrounds the main nozzle.

Selon une autre réalisation courante, la buse principale est de forme rectangulaire, au moins une buse secondaire délivrant un jet secondaire tangentiel à l'un des côtés du rectangle formé par la section de la buse principale. La buse principale peut également avoir d'autres formes très diverses, par exemple carrée, polygonale, polygonale à angles arrondis, ellipsoïdale ou ovoïde, etc...According to another common embodiment, the main nozzle is rectangular, at least one secondary nozzle delivering a tangential secondary jet to one of the sides of the rectangle formed by the section of the main nozzle. The main nozzle can also have other very diverse shapes, for example square, polygonal, polygonal with rounded angles, ellipsoidal or ovoid, etc.

Divers gaz combustibles peuvent être utilisés, par exemple le méthane ou le propane ou tout hydrocarbure.Various combustible gases can be used, for example methane or propane or any hydrocarbon.

Le gaz comburant est de préférence de l'oxygène, mais ce peut être également de l'air.The oxidizing gas is preferably oxygen, but it can also be air.

L'invention concerne également un four comportant des parois délimitant une enceinte et des moyens de chauffage.The invention also relates to an oven comprising walls delimiting an enclosure and heating means.

On connaît déjà des fours comportant une paroi réfractaire chauffée par une flamme. La paroi réfractaire chauffe ensuite l'atmosphère intérieure du four et la charge contenue dans le four. Afin d'assurer une meilleure répartition possible de la chaleur, on utilise des dispositifs d'élargissement de flamme.Ovens are already known comprising a refractory wall heated by a flame. The refractory wall then heats the interior atmosphere of the furnace and the charge contained in the furnace. To ensure the best possible distribution of heat, flame spreading devices are used.

Cependant, ces dispositifs ne permettent d'obtenir une flamme parfaitement plane.However, these devices do not allow a perfectly flat flame to be obtained.

Ce problème est résolu, selon la présente invention, par le fait que les moyens de chauffage qui équipent le four sont constitués par :

  • au moins une buse principale délivrant un jet de gaz combustible ou de gaz comburant ;
  • au moins une buse secondaire délivrant un jet de gaz comburant ou gaz combustible qui s'écoule autour du jet principal et qui possède une épaisseur sensiblement constante ;
  • au moins une surface courbe disposée tangentiellement au jet de gaz secondaire afin de le dévier par effet Coanda, d'aspirer le jet de gaz principal et de mélanger le jet de gaz secondaire et le jet de gaz principal pour former une flamme.
This problem is solved, according to the present invention, by the fact that the heating means which equip the oven consist of:
  • at least one main nozzle delivering a jet of combustible gas or oxidizing gas;
  • at least one secondary nozzle delivering a jet of oxidizing gas or combustible gas which flows around the main jet and which has a substantially constant thickness;
  • at least one curved surface disposed tangentially to the secondary gas jet in order to deflect it by Coanda effect, to suck up the main gas jet and to mix the secondary gas jet and the main gas jet to form a flame.

Dans un mode de réalisation du four, le jet principal est sensiblement perpendiculaire à une paroi du four, et la surface courbe dévie le jet sensiblement de 90° de manière à ce que la flamme s'écoule tangentiellement à une paroi du four.In one embodiment of the oven, the main jet is substantially perpendicular to a wall of the oven, and the curved surface deflects the jet substantially by 90 ° so that the flame flows tangentially to a wall of the oven.

Ce mode de réalisation permet d'élargir la flamme qui devient totalement plate et de chauffer la paroi réfractaire du four. On obtient ainsi une très bonne diffusion de la chaleur. Ce mode de réalisation s'applique de manière avantageuse aux fours de petites dimensions dans lesquels la flamme ne doit pas atteindre la charge à chauffer.This embodiment makes it possible to widen the flame which becomes completely flat and to heat the refractory wall of the furnace. This gives a very good heat diffusion. This embodiment is advantageously applied to small ovens in which the flame must not reach the charge to be heated.

On connaît également d'autres types de fours dans lesquels on souhaite obtenir une flamme fine. Nous pouvons dans ce cas désirer que la flamme reste parallèle à la surface du bain et ait une épaisseur aussi constante que possible afin d'assurer un chauffage régulier et homogène du bain.Other types of ovens are also known in which it is desired to obtain a fine flame. We can in this case wish that the flame remains parallel to the surface of the bath and has a thickness as constant as possible in order to ensure a regular and homogeneous heating of the bath.

Ce problème est résolu conformément à la présente invention par le fait que la surface courbe se termine par une zone sensiblement perpendiculaire à la paroi du four de manière à obtenir une flamme perpendiculaire à cette paroi.This problem is solved in accordance with the present invention by the fact that the curved surface ends in an area substantially perpendicular to the wall of the furnace so as to obtain a flame perpendicular to this wall.

Grâce à cette caractéristique on obtient une flamme fine dont on peut contrôler l'orientation. On obtient ainsi une flamme fine dont la distance à une charge peut être maintenue constante.Thanks to this characteristic, a fine flame is obtained, the orientation of which can be controlled. A fine flame is thus obtained, the distance to a charge of which can be kept constant.

Dans un mode de réalisation la zone sensiblement perpendiculaire à la paroi du four est disposée horizontalement.In one embodiment, the zone substantially perpendicular to the wall of the furnace is arranged horizontally.

Dans un autre mode de réalisation, la zone sensiblement perpendiculaire à la paroi du four est disposée verticalement.In another embodiment, the zone substantially perpendicular to the wall of the furnace is arranged vertically.

D'autres caractéristiques et avantages de la présente invention apparaîtront encore à la lecture de la description détaillée qui va suivre pour la compréhension de laquelle on se reportera aux dessins annexés dans lesquels :

  • La figure 1 est une vue en coupe d'un four de type connu ;
  • la figure 2 est une vue en coupe d'un autre four de type connu ;
  • la figure 3 est une vue schématique en coupe qui illustre le fonctionnement d'un dispositif d'étalement de flamme conforme à l'invention ;
  • la figure 4 est une vue en perspective d'un dispositif d'étalement de flamme conforme à l'invention comportant des buses principale et secondaire de section circulaire ;
  • la figure 5 est une vue en perspective d'un dispositif d'étalement de flamme conforme à l'invention comportant des buses principale et secondaire de section rectangulaire avec un jet secondaire unique ;
  • la figure 6 est une vue en perspective d'un dispositif identique à celui de la figure 5, mais comportant deux jets secondaires ;
  • la figure 7 est une vue en perspective d'un dispositif d'étalement de flamme conforme à l'invention comportant une buse principale de section carrée ;
  • la figure 8 est une vue en coupe partielle d'un mode de réalisation d'un four conforme à l'invention ;
  • la figure 9 est une vue en coupe partielle d'un autre mode de réalisation d'un four conforme à l'invention.
Other characteristics and advantages of the present invention will become apparent on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:
  • Figure 1 is a sectional view of a known type of oven;
  • Figure 2 is a sectional view of another oven of known type;
  • Figure 3 is a schematic sectional view illustrating the operation of a flame spreading device according to the invention;
  • Figure 4 is a perspective view of a flame spreading device according to the invention comprising main and secondary nozzles of circular section;
  • Figure 5 is a perspective view of a flame spreading device according to the invention comprising main and secondary nozzles of rectangular section with a single secondary jet;
  • Figure 6 is a perspective view of a device identical to that of Figure 5, but comprising two secondary jets;
  • Figure 7 is a perspective view of a flame spreading device according to the invention comprising a main nozzle of square section;
  • Figure 8 is a partial sectional view of an embodiment of an oven according to the invention;
  • Figure 9 is a partial sectional view of another embodiment of an oven according to the invention.

L'effet Coanda est un phénomène connu dans lequel un écoulement en jet reste attaché à une surface tangente sur laquelle il s'écoule. Le jet reste attaché à la surface tangente même si celle-ci s'écarte progressivement de sa direction initiale d'un certain angle. Cet effet sera expliqué en référence à la figure 3 qui illustre le principe d'un dispositif d'étalement de flamme conforme à l'invention.The Coanda effect is a known phenomenon in which a jet flow remains attached to a tangent surface on which it flows. The jet remains attached to the tangent surface even if the latter gradually deviates from its initial direction by a certain angle. This effect will be explained with reference to Figure 3 which illustrates the principle of a flame spreading device according to the invention.

Le dispositif comporte une buse principale 4 apte à délivrer un gaz, par exemple un gaz combustible. L'extrémité de la buse 4 est située dans un trou formé dans une paroi épaisse. Le jet principal, dont l'écoulement est schématisé par les flèches 6, débouche parallèlement à une paroi courbe 10 formée par la paroi épaisse.The device comprises a main nozzle 4 capable of delivering a gas, for example a combustible gas. The end of the nozzle 4 is located in a hole formed in a thick wall. The main jet, whose flow is shown diagrammatically by the arrows 6, opens in parallel to a curved wall 10 formed by the thick wall.

La buse secondaire 8 est constituée par l'espace compris entre la buse principale 4 et la surface courbe 10. Le jet secondaire 12, par exemple de gaz comburant, s'écoule tangentiellement aux parois 10 à la sortie de la buse secondaire 8. L'espace compris entre l'extérieur de la buse principale 4 et la paroi 10 présente une section sensiblement constante et de faible dimension, par exemple 0,3 mm.The secondary nozzle 8 consists of the space between the main nozzle 4 and the curved surface 10. The secondary jet 12, for example of oxidizing gas, flows tangentially to the walls 10 at the outlet of the secondary nozzle 8. L 'space between the outside of the main nozzle 4 and the wall 10 has a substantially constant section and of small dimension, for example 0.3 mm.

Lorsque le jet principal est seul, il sort de la buse principale verticalement (selon l'orientation de la figure 3).When the main jet is alone, it leaves the main nozzle vertically (according to the orientation of Figure 3).

Lorsque le jet secondaire 12 est seul, il s'écoule tangentiellement à la paroi 10 par effet Coanda . Cette paroi est courbe et s'évase progressivement jusqu'à former un angle de 90° par rapport à l'axe des buses principale et secondaire. Le jet secondaire, également appelé jet pariétal parce qu'il s'écoule le long de la paroi 10, produit une forte dépression dans la zone centrale où débouche la buse principale 4.When the secondary jet 12 is alone, it flows tangentially to the wall 10 by the Coanda effect. This wall is curved and gradually widens until it forms an angle of 90 ° relative to the axis of the main and secondary nozzles. The secondary jet, also called parietal jet because it flows along the wall 10, produces a strong depression in the central zone where the main nozzle 4 opens.

Lorsque les deux jets, à savoir le jet principal et le jet secondaire (ou jet pariétal) s'écoulent simultanément, le jet pariétal dont la vitesse d'écoulement est nettement supérieure à celle du jet principal, aspire ce dernier. Les deux jets se mélangent et le jet résultant s'écoule horizontalement. La dépression créée par effet Coanda au coeur du jet pariétal dans la zone de courbure est telle que l'ensemble du jet principal est entraîné par le jet pariétal pour suivre la paroi 10. L'équilibre du jet étalé est parfaitement stable dans un domaine de vitesse relative du jet pariétal par rapport au jet principal et il n'est pas possible de rompre cet équilibre.When the two jets, namely the main jet and the secondary jet (or parietal jet) flow simultaneously, the parietal jet whose flow speed is significantly higher than that of the main jet, sucks the latter. The two jets mix and the resulting jet flows horizontally. The depression created by the Coanda effect at the heart of the parietal jet in the area of curvature is such that the entire main jet is driven by the parietal jet to follow the wall 10. The equilibrium of the spread jet is perfectly stable in a range of relative speed of the parietal jet compared to the main jet and it is not possible to upset this balance.

L'écoulement de gaz primaire, par exemple combustible, se mélange rapidement avec l'écoulement de gaz secondaire, par exemple de gaz comburant, pour former un mélange combustible qui donne naissance à la flamme.The flow of primary gas, for example combustible, mixes rapidly with the flow of secondary gas, for example oxidizing gas, to form a combustible mixture which gives rise to the flame.

On a représenté sur la figure 1 une vue en coupe d'un four de l'art antérieur, désigné par la référence générale 20. Ce four comporte une paroi extérieure 11 d'acier et une paroi intérieure 22 garnie de briques de matériau réfractaire. Une sole 24 est disposée sur le fond 26 du four. Une pièce métallique à chauffer 28, par exemple un lingot d'acier, repose sur la sole 24.There is shown in Figure 1 a sectional view of an oven of the prior art, designated by the general reference 20. This oven has an outer wall 11 of steel and an inner wall 22 lined with bricks of refractory material. A hearth 24 is disposed on the bottom 26 of the oven. A metal piece to be heated 28, for example a steel ingot, rests on the floor 24.

A sa partie supérieure le four 20 comporte des moyens de chauffage 30 qui délivrent une flamme 32. Il est connu d'utiliser des dispositifs d'élargissement de flamme afin d'obtenir une flamme aussi large et plate que possible de manière à répartir la chaleur de cette flamme et à chauffer la pièce 28 de manière homogène.Ce résultat ne peut être atteint aisément avec les dispositifs d'élargissement de flammes actuellement connus.At its upper part the oven 20 includes heating means 30 which deliver a flame 32. It is known to use flame enlargement devices in order to obtain a flame as large and flat as possible so as to distribute the heat of this flame and to heat the part 28 in a homogeneous manner. This result cannot be easily achieved with the flame spreading devices currently known.

On a représenté sur la figure 4 des moyens de chauffage qui équipent un four conforme à la présente invention.FIG. 4 shows heating means which equip an oven according to the present invention.

Ces moyens de chauffage sont constitués par un tube 4, de section circulaire, qui constitue une buse principale. Le tube 4 est entouré par un tube 7 également de section circulaire. Ce tube 7 est raccordé à une pièce torique 9. L'extrémité du tube 4 débouche sensiblement au milieu de l'épaisseur de la pièce 9. La pièce 9 est insérée dans la voûte du four à la position des moyens de chauffage 30 représentés sur la figure 1. Elle comporte la surface courbe 10.These heating means are constituted by a tube 4, of circular section, which constitutes a main nozzle. The tube 4 is surrounded by a tube 7 also of circular section. This tube 7 is connected to an O-ring piece 9. The end of the tube 4 opens substantially in the middle of the thickness of the piece 9. The piece 9 is inserted into the roof of the oven at the position of the heating means 30 shown on Figure 1. It has the curved surface 10.

La paroi extérieure du four est constituée par une tôle d'acier 11 garnie intérieurement par les briques réfractaires 22.The external wall of the furnace is constituted by a steel sheet 11 internally lined with refractory bricks 22.

La buse principale 4 délivre un jet de gaz combustible.The main nozzle 4 delivers a jet of combustible gas.

Un gaz comburan est amené dans l'espace annulaire 8 compris entre le tube 4 et le tube 7.Comburan gas is brought into the annular space 8 between the tube 4 and the tube 7.

Un passage annulaire de faible épaisseur est compris entre la surface extérieure de la pièce 9 et le diamètre extérieur du tube 4. La valeur typique de cet espace est comprise entre 0,2 mm et 1 mm, mais peut prendre d'autres valeurs. Ceci permet de donner au jet secondaire une vitesse d'écoulement beaucoup plus importante que celle du jet principal 6.An annular passage of small thickness is between the outer surface of the part 9 and the outer diameter of the tube 4. The typical value of this space is between 0.2 mm and 1 mm, but can take other values. This makes it possible to give the secondary jet a much higher flow speed than that of the main jet 6.

Une canalisation 34 dans laquelle circule un fluide de réfrigération tel que de l'eau assure le refroidissement de la pièce 9.A pipe 34 in which a refrigerating fluid such as water circulates ensures the cooling of the part 9.

Le fonctionnement de ces moyens de chauffage est identique à ce qui a été expliqué en référence à la figure 3. En d'autres termes, la flamme qui résulte du mélange du gaz combustible 6 et du gaz comburant 12 suit la surface courbe de la pièce 9 puis s'écoule le long des briques réfractaires 22, sensiblement parallèlement à ces dernières. Dans ces conditions la flamme chauffe essentiellement les briques réfractaires qui assurent ensuite une répartition de la chaleur par rayonnement.Il sera donc possible d'obtenir un chauffage très homogène d'une charge telle que la pièce 28.The operation of these heating means is identical to what has been explained with reference to FIG. 3. In other words, the flame which results from the mixture of the combustible gas 6 and the oxidizing gas 12 follows the curved surface of the part. 9 then flows along the refractory bricks 22, substantially parallel to the latter. Under these conditions, the flame essentially heats the refractory bricks which then distribute the heat by radiation. It will therefore be possible to obtain very homogeneous heating of a charge such as part 28.

Il n'est pas indispensable que le gaz combustible s'écoule par la buse principale et le gaz comburant par la buse secondaire. Un résultat identique serait obtenu en délivrant le gaz comburant au moyen du tube 4 constituant la buse principale et en amenant le gaz combustible dans l'espace annulaire compris entre le tube 4 et le tube 7.It is not essential that the combustible gas flows through the main nozzle and the oxidant gas through the secondary nozzle. An identical result would be obtained by delivering the oxidizing gas by means of the tube 4 constituting the main nozzle and by bringing the combustible gas into the annular space comprised between the tube 4 and the tube 7.

La pièce à chauffer 28 n'est pas touchée par les flammes parce que ces dernières s'écoulent le long de la paroi. Cette caractéristique est avantageuse en particulier dans le cas d'un four de petites dimensions.The part to be heated 28 is not touched by the flames because the latter flow along the wall. This characteristic is advantageous in particular in the case of an oven of small dimensions.

On a réalisé un four dont les parois garnies de matériau réfractaire comportaient des buses principales circulaires de 20 mm de diamètre. L'espace annulaire compris entre l'extérieur de la buse principale et la paroi tangente de la pièce 9 était de 0,3 mm. Une flamme, réalisée par un débit de propane de 2,5 l/min pour chaque buse a été complètement étalée pour un débit d'air supérieur à 40 l/min. La puissance développée par chaque flamme était de l'ordre de 4,2 W.An oven was produced, the walls of which were lined with refractory material and had circular main nozzles 20 mm in diameter. The annular space between the outside of the main nozzle and the tangent wall of the part 9 was 0.3 mm. A flame, produced by a propane flow of 2.5 l / min for each nozzle, was completely spread for an air flow greater than 40 l / min. The power developed by each flame was of the order of 4.2 W.

On a représenté sur la figure 5 une variante de réalisation des moyens de chauffage équipant un four conforme à l'invention.FIG. 5 shows an alternative embodiment of the heating means fitted to an oven according to the invention.

Alors que sur la figure 4 la buse principale et la buse secondaire présentent une section circulaire, dans le cas du mode de réalisation de la figure 5 la buse principale est constituée par un caisson 35 de section rectangulaire allongée. Une plaque 37 délimite avec la paroi du caisson 35 qui lui fait face un espace qui permet d'amener le gaz secondaire, qu'il s'agisse du gaz combustible ou du gaz comburant.While in FIG. 4 the main nozzle and the secondary nozzle have a circular section, in the case of the embodiment of FIG. 5 the main nozzle is constituted by a box 35 of elongated rectangular section. A plate 37 delimits with the wall of the box 35 which faces it a space which makes it possible to supply the secondary gas, whether it is combustible gas or oxidizing gas.

La pièce 9, au lieu de présenter une forme torique, est de forme rectiligne allongée. Elle délimite une fente qui s'étend parallèlement à la longueur du four. Le fonctionnement de ce dispositif est identique. Son avantage réside dans le fait qu'il permet d'obtenir une flamme de grande largeur, par exemple une flamme qui occupe la plus grande partie de la longueur du four. Ceci permet d'obtenir une meilleure répartition de la chaleur sur la longueur du four qu'une série de buses de chauffage espacées.The part 9, instead of having a toroidal shape, is of elongated rectilinear shape. It delimits a slot which extends parallel to the length of the oven. The operation of this device is identical. Its advantage lies in the fact that it makes it possible to obtain a flame of great width, for example a flame which occupies most of the length of the oven. This provides better heat distribution over the length of the oven than a series of spaced heating nozzles.

On a représenté sur la figure 6 une variante de réalisation du dispositif de la figure 5. Cette variante se distingue par le fait qu'un jet secondaire est prévu de chacun des grands côtés du caisson 35.There is shown in Figure 6 an alternative embodiment of the device of Figure 5. This variant is distinguished by the fact that a secondary jet is provided on each of the long sides of the box 35.

Enfin, on a représenté sur la figure 7 une troisième variante de réalisation de ce dispositif. La buse principale 35 comporte une section carrée et la pièce 9 présente également une section carrée qui est arrondie à ses quatre coins. Cette variante permet d'obtenir quatre flammes, à savoir une flamme par côté. Il va de soi qu'un grand nombre d'autres formes pourrait être imaginé.Finally, there is shown in Figure 7 a third alternative embodiment of this device. The main nozzle 35 has a square section and the part 9 also has a square section which is rounded at its four corners. This variant makes it possible to obtain four flames, namely one flame per side. It goes without saying that a large number of other forms could be imagined.

On a représenté sur la figure 2 un second type de four de l'art antérieur, désigné par la référence 40. Il comporte des parois formées de briques réfractaires 22. Ce four contient une charge 42. Des buses de chauffage 44 sont prévues de chaque côté du four 40.FIG. 2 shows a second type of oven of the prior art, designated by the reference 40. It has walls formed of refractory bricks 22. This oven contains a charge 42. Heating nozzles 44 are provided for each side of oven 40.

On souhaite que les flammes 46 produites par les buses 44 soient parallèles au niveau de la charge 42 afin de la chauffer régulièrement. En outre, il a été constaté que les flammes 46 libèrent des radicaux hydroxyle qui oxydent la charge 42 lorsqu'elles en sont trop proches. Une flamme fine, dont la distance à la surface du bain est constante, permet d'éviter cet inconvénient.It is desired that the flames 46 produced by the nozzles 44 be parallel to the level of the charge 42 in order to heat it regularly. In addition, it has been found that the flames 46 release hydroxyl radicals which oxidize the charge 42 when they are too close to it. A fine flame, the distance to the surface of the bath is constant, avoids this drawback.

La figure 8 représente une vue en coupe verticale de moyens de chauffage équipant un four conforme à la présente invention. Ces moyens de chauffage comportent un caisson 35 de section rectangulaire allongée identique aux caissons représentés sur les figures 5 et 6. Un carter de tôle 50 relie une paroi extérieure du caisson 35 à la paroi du four. Un conduit d'amenée 52 transporte un gaz secondaire 12 jusqu'à la buse secondaire constituée par une fente de faible largeur prévue entre une paroi extérieure du caisson 35 et la surface courbe de la pièce 9. Le jet principal 6 et le jet secondaire 12 se mélangent et suivent la paroi de la pièce 9. On notera également la présence des canalisations destinées à la circulation facultative d'un fluide de refroidissement tel que l'eau.Figure 8 shows a vertical sectional view of heating means fitted to an oven according to the present invention. These heating means comprise a box 35 of elongated rectangular section identical to the boxes shown in Figures 5 and 6. A sheet metal housing 50 connects an outer wall of the box 35 to the wall of the oven. A supply duct 52 transports a secondary gas 12 to the secondary nozzle constituted by a narrow width slot provided between an outer wall of the box 35 and the curved surface of the part 9. The main jet 6 and the secondary jet 12 mix and follow the wall of the room 9. Note also the presence of the pipes intended for the optional circulation of a cooling fluid such as water.

La pièce 9 se termine par une surface horizontale 54 perpendiculaire à la paroi verticale 22 du four. De la sorte, la flamme 56 se détache de la pièce 9 et pénètre dans le four horizontalement, c'est-à-dire parallèlement à la surface du bain de verre 42.The part 9 ends with a horizontal surface 54 perpendicular to the vertical wall 22 of the oven. In this way, the flame 56 is detached from the part 9 and enters the furnace horizontally, that is to say parallel to the surface of the glass bath 42.

En outre, il a été constaté que la flamme 56 ne s'évase pas et reste fine, même à une distance relativement importante de la paroi 22 du four. Cette caractéristique est particulièrement intéressante parce que l'on peut ainsi disposer la flamme de manière qu'elle soit relativement proche de la surface de la charge sans cependant la toucher.In addition, it has been found that the flame 56 does not flare and remains fine, even at a relatively large distance from the wall 22 of the oven. This characteristic is particularly interesting because it is thus possible to arrange the flame so that it is relatively close to the surface of the charge without, however, touching it.

On a représenté sur la figure 9 un troisième mode de réalisation d'un dispositif de chauffage pour un four.On retrouve la paroi 11 de tôle extérieure du four et les briques réfractaires 22 qui garnissent cette paroi. Les moyens de chauffage sont identiques à ceux qui ont été décrits en référence à la figure 8, mais l'orientation de la pièce 9 est différente.
La référence 22a désigne la partie haute du four et la référence 22b la partie basse de ce four. On constate donc que la surface plane de la pièce 9 est disposée selon un plan vertical au lieu d'un plan horizontal selon la figure 8. La section de sortie du caisson 35 constituant la buse principale est également disposé selon un plan vertical. Par suite la flamme mince 56 l'est également. Un dispositif tel que celui qui est représenté sur la figure 9 peut être utilisé dans un four du type représenté sur la figure 2.There is shown in Figure 9 a third embodiment of a heating device for an oven. We find the wall 11 of the outer sheet of the oven and the refractory bricks 22 which line this wall. The heating means are identical to those which have been described with reference to FIG. 8, but the orientation of the part 9 is different.
The reference 22a designates the upper part of the oven and the reference 22b the lower part of this oven. It can therefore be seen that the planar surface of the part 9 is arranged in a vertical plane instead of a horizontal plane according to FIG. 8. The outlet section of the box 35 constituting the main nozzle is also arranged in a vertical plane. As a result the thin flame 56 is also. A device such as that which is shown in FIG. 9 can be used in an oven of the type shown in FIG. 2.

Toutefois la hauteur de la pièce 9 ne doit pas être très importante. En effet, il est souhaitable que la flamme 56 reste relativement proche de la surface libre du bain de verre 42. C'est la raison pour laquelle on disposera une série de dispositifs de chauffage identiques à celui qui est représenté sur la figure 9 selon la longueur du four afin de chauffer la charge.However, the height of the piece 9 should not be very large. Indeed, it is desirable that the flame 56 remains relatively close to the free surface of the glass bath 42. This is the reason why will have a series of heating devices identical to that shown in Figure 9 along the length of the oven to heat the load.

Claims (11)

Dispositif d'étalement d'une flamme caractérisé en ce qu'il comporte au moins une buse principale (4, 35) délivrant un jet de gaz combustible ou de gaz comburant (6), au moins une buse secondaire (8) délivrant un jet de gaz comburant ou de gaz combustible (12) qui s'écoule autour du jet principal et qui possède une épaisseur sensiblement constante, et au moins une surface courbe (9) disposée tangentiellement au jet de gaz secondaire afin de le dévier par effet Coanda, d'aspirer le jet de gaz principal (6) et de mélanger le gaz du jet secondaire (12) et le gaz du jet principal (6) pour former une flamme.Flame spreading device characterized in that it comprises at least one main nozzle (4, 35) delivering a jet of combustible gas or of oxidizing gas (6), at least one secondary nozzle (8) delivering a jet oxidant gas or combustible gas (12) which flows around the main jet and which has a substantially constant thickness, and at least one curved surface (9) arranged tangentially to the secondary gas jet in order to deflect it by Coanda effect, sucking the main gas jet (6) and mixing the gas of the secondary jet (12) and the gas of the main jet (6) to form a flame. Dispositif selon la revendication 1, caractérisé en ce que la buse principale (4) présente une section circulaire, et que la buse secondaire (8), de section annulaire, entoure la buse principale.Device according to claim 1, characterized in that the main nozzle (4) has a circular section, and that the secondary nozzle (8), of annular section, surrounds the main nozzle. Dispositif selon la revendication 1, caractérisé en ce que la buse principale (4) présente une section de forme rectangulaire, au moins une buse secondaire (35) délivrant un jet secondaire (12) tangentiel à l'un des côtés du rectangle formé par la buse principale (35).Device according to claim 1, characterized in that the main nozzle (4) has a rectangular section, at least one secondary nozzle (35) delivering a secondary jet (12) tangential to one of the sides of the rectangle formed by the main nozzle (35). Dispositif selon la revendication 1, caractérisé en ce que la buse principale présente une section de forme polygonale.Device according to claim 1, characterized in that the main nozzle has a polygonal section. Dispositif selon l'une quelconque des revendications 1 à 4 caractérisé en ce que le gaz combustible est le méthane ou le propane.Device according to any one of Claims 1 to 4, characterized in that the combustible gas is methane or propane. Dispositif selon l'une quelconque des revendications 1 à 5 caractérisé en ce que le gaz comburant est l'oxygène ou l'air.Device according to any one of Claims 1 to 5, characterized in that the oxidizing gas is oxygen or air. Four selon l'une quelconque des revendications 1 à 6, comportant des parois (22) délimitant une enceinte et des moyens de chauffage, caractérisé en ce que les moyens de chauffage sont constitués par un dispositif d'étalement de flamme selon l'une quelconque des revendications 1 à 6.Oven according to any one of claims 1 to 6, comprising walls (22) delimiting an enclosure and heating means, characterized in that the heating means consist of a device flame spreading according to any one of claims 1 to 6. Four selon la revendication 7, caractérisé en ce que le jet principal est sensiblement perpendiculaire à une paroi (22) du four et en ce que la surface courbe (9) dévie le jet (6) sensiblement de 90° de manière à ce que la flamme s'écoule tangentiellement à une paroi du four.Oven according to claim 7, characterized in that the main jet is substantially perpendicular to a wall (22) of the oven and in that the curved surface (9) deflects the jet (6) substantially by 90 ° so that the flame flows tangentially to a wall of the furnace. Four selon la revendication 7, caractérisé en ce que la surface courbe (9) se termine par une zone (54) sensiblement perpendiculaire à une paroi (22) du four de manière à obtenir une flamme (56) perpendiculaire à cette paroi.Oven according to claim 7, characterized in that the curved surface (9) ends in a zone (54) substantially perpendicular to a wall (22) of the oven so as to obtain a flame (56) perpendicular to this wall. Four selon la revendication 9, caractérisé en ce que la zone (54) sensiblement perpendiculaire à une paroi (22) du four est disposée horizontalement.Oven according to claim 9, characterized in that the zone (54) substantially perpendicular to a wall (22) of the oven is arranged horizontally. Four selon la revendication 9, caractérisé en ce que la zone (54) sensiblement perpendiculaire à une paroi (22) du four est disposée verticalement.Oven according to claim 9, characterized in that the zone (54) substantially perpendicular to a wall (22) of the oven is arranged vertically.
EP95401906A 1994-09-07 1995-08-17 Device for spreading a flame using COANDA effect and oven using this device Withdrawn EP0701092A1 (en)

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FR9410704A FR2724217B1 (en) 1994-09-07 1994-09-07 DEVICE FOR SPREADING A FLAME BY COANDA EFFECT AND OVEN COMPRISING THIS DEVICE
FR9410704 1994-09-07

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Title
PATENT ABSTRACTS OF JAPAN vol. 13, no. 204 (M - 825) 15 May 1989 (1989-05-15) *

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US5658141A (en) 1997-08-19
JPH08178230A (en) 1996-07-12
FR2724217B1 (en) 1996-10-25
FR2724217A1 (en) 1996-03-08

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