EP0631091A1 - Low NOx gas burner - Google Patents

Low NOx gas burner Download PDF

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Publication number
EP0631091A1
EP0631091A1 EP94401336A EP94401336A EP0631091A1 EP 0631091 A1 EP0631091 A1 EP 0631091A1 EP 94401336 A EP94401336 A EP 94401336A EP 94401336 A EP94401336 A EP 94401336A EP 0631091 A1 EP0631091 A1 EP 0631091A1
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EP
European Patent Office
Prior art keywords
holes
sheet
burner
tubular body
gas burner
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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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EP94401336A
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German (de)
French (fr)
Inventor
Jacques Bouix
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MTS SA
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MTS SA
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Publication of EP0631091A1 publication Critical patent/EP0631091A1/en
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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
    • F23D14/46—Details, e.g. noise reduction means
    • F23D14/48—Nozzles
    • F23D14/58—Nozzles characterised by the shape or arrangement of the outlet or outlets from the nozzle, e.g. of annular configuration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D2203/00—Gaseous fuel burners
    • F23D2203/10—Flame diffusing means
    • F23D2203/101—Flame diffusing means characterised by surface shape
    • F23D2203/1012—Flame diffusing means characterised by surface shape tubular

Definitions

  • the present invention relates to a gas burner of the type comprising a tubular body having a first end at least partially open for the admission of air and gaseous fuel into the internal space of the tubular body, a second closed end and a wall peripheral pierced with a multitude of through holes for the combustible gas mixture which burns on the outer peripheral surface of the tubular body, the peripheral wall of the tubular body being constituted by two perforated sheets, respectively inner and outer, held in contact with one another with the other, the inner sheet has holes which have a predetermined diameter, while the outer sheet has holes having a larger cross section than that of the holes in the inner sheet.
  • Gas burners of the above-mentioned type are well known. They are for example used in boilers models CECID HX135, HX175, ... HX495 marketed by the applicant.
  • the tubular body of these known burners is made with an inner perforated sheet of small thickness (of the order of 0.7 mm) having round perforations with a diameter of 0.8 mm, this latter dimension corresponding to the distance from safety necessary to avoid flashbacks inside the tubular body of the burner.
  • the distance between the round perforations is 1.5 mm, which determines, for the internal perforated sheet, a passage coefficient of 25% (ratio of the cumulative surface of the round perforations to the total surface of the internal perforated sheet) .
  • Perforated sheet outer of the tubular body of these known burners has a thickness of 1.5 mm and it is perforated with square holes arranged in a matrix in rows and columns.
  • the length of the rib of each square hole is 6 mm and the interval between two adjacent holes belonging to the same row or to the same column is 4 mm wide.
  • the external perforated sheet has a passage coefficient of the order of 36%, which gives, after assembly of the two internal and external perforated sheets, an overall passage coefficient of approximately 9%.
  • the present invention therefore aims to achieve this objective.
  • the burner according to the present invention is characterized in that the spacing of the holes in the outer sheet and their passage section are such that the assembly of the two perforated sheets of the burner has an overall coefficient of passage of gases through the glus equal to 7.8%.
  • the outer sheet has a thickness at least equal to 2 mm.
  • the holes in the outer sheet are preferably circular and preferably have a diameter at most equal to 6 mm.
  • the burner 1 represented in FIG. 1 is in the form of a tubular body, one end of which 3 is at least partially open for the admission of air and gaseous fuel and the opposite end of which is closed so gas-tight by a wall 4.
  • the end 3 of the tubular body is completely open, it could be closed by a wall having for example two intake ports, one for the primary combustion air and one for the gaseous fuel, or a single intake port for the air-gas mixture if the air and the gas have been mixed beforehand.
  • the peripheral wall 5 of the tubular body 2 is pierced with a multitude of holes through which the gaseous combustible mixture flows from the inside to the outside of the tubular body. In service, the gas mixture burns on the exterior surface or near the exterior surface of the peripheral wall 5 of the tubular body 2.
  • the peripheral wall 5 of the tubular body 2 is cylindrical, c that is, the tubular body has a circular cross section. Although such a circular shape is the most rational for the burner, the cross section of the tubular body 2 could have other shapes, for example elliptical or polygonal.
  • the tubular body 2 could have a frustoconical shape, the large base of the truncated cone on the end side 3 and the small base being formed by the end wall 4.
  • the peripheral wall 5 of the tubular body 2 is constituted by two perforated sheets, namely an inner sheet 6 and an outer sheet 7.
  • the sheets 6 and 7 are kept intimately in contact with each other for example by several welding points.
  • the thickness e1 of the inner sheet 6, the diameter ⁇ 1 of the holes 8 of this sheet and the distance l1 between the axes of the adjacent holes 8 may have values identical to those of the inner sheet of the known burner described in the preamble.
  • e1 can be between 0.3 and 0.8 mm, preferably equal to 0.7 mm
  • ⁇ 1 can be equal to 0.8 mm
  • l1 can be equal to 1.5 mm.
  • the inner sheet 6 has a natural coefficient of passage of 25%.
  • the section for the passage of the holes 9 in the external sheet 7 is chosen so as to be smaller than the section for the passage of the holes in the external sheet of the known burner described in the preamble.
  • the distance l2 between the axes of the adjacent holes 9 is chosen so as to be greater than the distance between the axes of the adjacent holes of the external sheet of the known burner.
  • the interval d2 between two adjacent holes 9 in the external sheet 7 is greater than the corresponding interval in the external sheet of the known burner. More specifically, the spacing d2 of the holes 9 in the outer sheet 7 and their passage section are chosen such that all of the two sheets 6 and 7 have an overall coefficient of passage at most equal to 7.8%.
  • the holes 9 are preferably circular and have a diameter ⁇ 2 at most equal to 6 mm and a center distance l2 of between 8 and 10 mm.
  • the holes 9 of the outer sheet 7 have a smaller section and that their spacing d2 is increased relative to the known burner, the number of holes 8 of the inner sheet 6 which are exposed by the holes 9 is therefore smaller than in the known burner.
  • the same value of the flow rate of the air-gas mixture as in the known burner for a given supply pressure of the air-gas mixture therefore to obtain the same nominal power of the burner , it is necessary to increase the dimensions of the external peripheral surface 5 of the burner in order to increase the number of holes 8 which will be uncovered by the holes 9. This can be obtained without difficulty by increasing the external diameter and / or the length of the tubular body 2 of the burner 1.
  • the outer sheet 7 preferably has a thickness e2 markedly greater than that e1 of the inner sheet 6.
  • the thickness e2 of the outer sheet 7 is equal to 3 mm. From the point of view of the cooling of the outer sheet 7 therefore also of the cooling of the flames and consequently from the point of view of the reduction of the NOx rate, it would be advantageous if the thickness e2 of the sheet 7 was the most great possible.
  • the thickness e2 must be limited for economic reasons (cost of the sheet and tools capable of perforating thick sheets) and for mechanical reasons (the thickness e2 of the sheet must be less than the diameter ⁇ 2 of the holes 9 ).
  • the thickness e2 of the sheet 7 will be between 2.5 and 3.5 mm.
  • the diameter ⁇ 2 of the holes 9 cannot be less than the thickness e2 of the sheet 7. Consequently, when a thick sheet is used for the sheet 7, for example a sheet of 3 mm thick, the diameter ⁇ 2 of the holes 9 may not be less than approximately 4 mm.
  • the Applicant has produced a burner with a nominal power of 375 kWh constructed as described above and having the dimensional characteristics indicated in the table below.
  • This table also indicates, for comparison, the dimensional characteristics of a burner known from same power, used in boilers of the HX375 type manufactured by the applicant.
  • the NOx rates produced respectively by the burner according to the invention and by the known burner operating at the nominal power of 375 kWh have also been indicated.
  • the burner of the present invention produces more than three times less NOx than the known burner.
  • each hole has its center placed in the center of a circle and the adjacent holes which surround the hole in question have their center located on said circle and are distributed regularly over this circle with a constant angular spacing of 60 °.
  • the holes 9 do not necessarily have all the same diameter and they can therefore have different diameters provided that the overall coefficient of passage of the gases from the burner remains at most equal to 7.8%

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Gas Burners (AREA)

Abstract

In this gas burner comprising a tubular body (2), the peripheral wall (5) of which consists of two perforated metal sheets (6, 7), internal and external respectively, which are held in contact with one another, the internal metal sheet (6) having holes which have a predetermined diameter while the external metal sheet (7) has holes which have a greater passage section than that of the holes of the internal metal sheet (6), and the spacing of the holes of the external metal sheet (7) and their passage section are such that the assembly of the two perforated metal sheets (6 and 7) of the burner (1) has an overall gas passage coefficient at most equal to 7.8%. <IMAGE>

Description

La présente invention concerne un brûleur à gaz du type comprenant un corps tubulaire ayant une première extrémité au moins partiellement ouverte pour l'admission de l'air et du combustible gazeux dans l'espace interne du corps tubulaire, une seconde extrémité fermée et une paroi périphérique percée d'une multitude de trous de passage pour le mélange combustible gazeux qui brûle à la surface périphérique extérieure du corps tubulaire, la paroi périphérique du corps tubulaire étant constituée par deux tôles perforées, respectivement intérieure et extérieure, maintenues en contact l'une avec l'autre, la tôle intérieure présentant des trous qui ont un diamètre prédéterminé, tandis que la tôle extérieure présente des trous ayant une section de passage plus grande que celle des trous de la tôle intérieure.The present invention relates to a gas burner of the type comprising a tubular body having a first end at least partially open for the admission of air and gaseous fuel into the internal space of the tubular body, a second closed end and a wall peripheral pierced with a multitude of through holes for the combustible gas mixture which burns on the outer peripheral surface of the tubular body, the peripheral wall of the tubular body being constituted by two perforated sheets, respectively inner and outer, held in contact with one another with the other, the inner sheet has holes which have a predetermined diameter, while the outer sheet has holes having a larger cross section than that of the holes in the inner sheet.

Les brûleurs à gaz du type sus-indiqué sont bien connus. Ils sont par exemple utilisés dans les chaudières modèles C.E.C.I.D. HX135, HX175,... HX495 commercialisées par la demanderesse. Le corps tubulaire de ces brûleurs connus est réalisé avec une tôle perforée intérieure de faible épaisseur (de l'ordre de 0,7 mm) ayant des perforations rondes d'un diamètre de 0,8 mm, cette dernière dimension correspondant à la distance de sécurité nécessaire pour éviter les retours de flamme vers l'intérieur du corps tubulaire du brûleur. L'entraxe entre les perforations rondes est de 1,5 mm, ce qui détermine, pour la tôle perforée intérieure, un coefficient de passage de 25% (rapport de la surface cumulée des perforations rondes à la surface totale de la tôle perforée intérieure). La tôle perforée extérieure du corps tubulaire de ces brûleurs connus a une épaisseur de 1,5 mm et elle est perforée de trous carrés disposés de façon matricielle en rangées et en colonnes. La longueur du côte de chaque trou carré est de 6 mm et l'intervalle entre deux trous adjacents appartenant à une même rangée ou à une même colonne a une largeur de 4 mm. Dans ces conditions, la tôle perforée extérieure a un coefficient de passage de l'ordre de 36%, ce qui donne, après assemblage des deux tôles perforées intérieure et extérieure, un coefficient global de passage d'environ 9%.Gas burners of the above-mentioned type are well known. They are for example used in boilers models CECID HX135, HX175, ... HX495 marketed by the applicant. The tubular body of these known burners is made with an inner perforated sheet of small thickness (of the order of 0.7 mm) having round perforations with a diameter of 0.8 mm, this latter dimension corresponding to the distance from safety necessary to avoid flashbacks inside the tubular body of the burner. The distance between the round perforations is 1.5 mm, which determines, for the internal perforated sheet, a passage coefficient of 25% (ratio of the cumulative surface of the round perforations to the total surface of the internal perforated sheet) . Perforated sheet outer of the tubular body of these known burners has a thickness of 1.5 mm and it is perforated with square holes arranged in a matrix in rows and columns. The length of the rib of each square hole is 6 mm and the interval between two adjacent holes belonging to the same row or to the same column is 4 mm wide. Under these conditions, the external perforated sheet has a passage coefficient of the order of 36%, which gives, after assembly of the two internal and external perforated sheets, an overall passage coefficient of approximately 9%.

Bien que les brûleurs connus décrits ci-dessus aient donné jusqu'ici entièrement satisfaction, devant l'importance que prennent aujourd'hui les facteurs intervenant sur la qualité de l'environnement ainsi que sur la durée de vie des appareils, il s'est avéré utile d'améliorer les brûleurs du type sus-indiqué à ces deux égards et en particulier en ce qui concerne la réduction du taux de NOx produit par le brûleur.Although the known burners described above have been entirely satisfactory up to now, given the importance which today takes on the factors influencing the quality of the environment as well as the life of the appliances, it has proved useful to improve the burners of the type indicated above in these two respects and in particular with regard to the reduction of the level of NOx produced by the burner.

La présente invention a donc pour but d'atteindre cet objectif.The present invention therefore aims to achieve this objective.

A cet effet, le brûleur selon la présente invention est caractérisé en ce que l'espacement des trous de la tôle extérieure et leur section de passage sont tels que l'ensemble des deux tôles perforées du brûleur ait un coefficient global de passage des gaz au glus égal à 7,8%.To this end, the burner according to the present invention is characterized in that the spacing of the holes in the outer sheet and their passage section are such that the assembly of the two perforated sheets of the burner has an overall coefficient of passage of gases through the glus equal to 7.8%.

De préférence, la tôle extérieure a une épaisseur au moins égale à 2 mm. En outre, les trous de la tôle extérieure sont de preférence circulaires et ont de préférence un diamètre au plus égal à 6 mm.Preferably, the outer sheet has a thickness at least equal to 2 mm. In addition, the holes in the outer sheet are preferably circular and preferably have a diameter at most equal to 6 mm.

D'autres caractéristiques et avantages de la présente invention ressortiront mieux au cours de la description qui va suivre d'une forme d'exécution du brûleur de la présente invention, donnée en référence aux dessins annexés sur lesquels :

  • la figure 1 est une vue en perspective d'un brûleur conforme à la présente invention.
  • La figure 2 est une vue en coupe verticale suivant la ligne II-II de la figure 1, montrant, à plus grande échelle, une partie des deux tôles assemblées formant le corps du brûleur.
Other characteristics and advantages of the present invention will emerge more clearly during the description which follows of an embodiment of the burner of the present invention, given with reference to the appended drawings in which:
  • Figure 1 is a perspective view of a burner according to the present invention.
  • Figure 2 is a vertical sectional view along line II-II of Figure 1, showing, on a larger scale, part of the two assembled sheets forming the body of the burner.

Le brûleur 1 représenté dans la figure 1 se présente sous la forme d'un corps tubulaire, dont une extrémité 3 est au moins partiellement ouverte pour l'admission de l'air et du combustible gazeux et dont l'extrémité opposée est obturée de manière étanche au gaz par une paroi 4. Bien que dans la forme de réalisation représentée dans la figure 1, l'extrémité 3 du corps tubulaire soit complètement ouverte, elle pourrait être fermée par une paroi ayant par exemple deux orifices d'admission, un pour l'air primaire de combustion et un pour le combustible gazeux, ou un unique orifice d'admission pour le mélange air-gaz si l'air et le gaz ont été mélangés au préalable.The burner 1 represented in FIG. 1 is in the form of a tubular body, one end of which 3 is at least partially open for the admission of air and gaseous fuel and the opposite end of which is closed so gas-tight by a wall 4. Although in the embodiment shown in Figure 1, the end 3 of the tubular body is completely open, it could be closed by a wall having for example two intake ports, one for the primary combustion air and one for the gaseous fuel, or a single intake port for the air-gas mixture if the air and the gas have been mixed beforehand.

Comme montré dans la figure 1, la paroi périphérique 5 du corps tubulaire 2 est percée d'une multitude de trous à travers lesquels le mélange combustible gazeux s'écoule de l'intérieur vers l'extérieur du corps tubulaire. En service, le mélange gazeux brûle à la surface extérieure ou près de la surface extérieure de la paroi périphérique 5 du corps tubulaire 2. Dans le mode de réalisation représenté dans la figure 1, la paroi périphérique 5 du corps tubulaire 2 est cylindrique, c'est-à-dire que le corps tubulaire a une section transversale circulaire. Bien qu'un telle forme circulaire soit la plus rationnelle pour le brûleur, la section transversale du corps tubulaire 2 pourrait avoir d'autres formes par exemple elliptique ou polygonale. En outre, au lieu d'être cylindrique, le corps tubulaire 2 pourrait avoir une forme tronconique, la grande base du tronc de cône se trouvant du côté de l'extrémité 3 et la petite base étant formée par la paroi d'extrémité 4.As shown in Figure 1, the peripheral wall 5 of the tubular body 2 is pierced with a multitude of holes through which the gaseous combustible mixture flows from the inside to the outside of the tubular body. In service, the gas mixture burns on the exterior surface or near the exterior surface of the peripheral wall 5 of the tubular body 2. In the embodiment shown in FIG. 1, the peripheral wall 5 of the tubular body 2 is cylindrical, c that is, the tubular body has a circular cross section. Although such a circular shape is the most rational for the burner, the cross section of the tubular body 2 could have other shapes, for example elliptical or polygonal. In addition, instead of being cylindrical, the tubular body 2 could have a frustoconical shape, the large base of the truncated cone on the end side 3 and the small base being formed by the end wall 4.

Comme montré dans la figure 1 et comme cela est encore mieux visible dans la figure 2, la paroi périphérique 5 du corps tubulaire 2 est constituée par deux tôles perforées, à savoir une tôle intérieure 6 et une tôle extérieure 7. Les tôles 6 et 7 sont maintenues intimement en contact l'une avec l'autre par exemple par plusieurs points de soudure. L'épaisseur e₁ de la tôle intérieure 6, le diamètre φ₁ des trous 8 de cette tôle et la distance l₁ entre les axes des trous 8 adjacents peuvent avoir des valeurs identiques à celles de la tôle intérieure du brûleur connu décrit en préambule. Par exemple, e₁ peut être compris entre 0,3 et 0,8 mm, de préférence égal à 0,7 mm, φ₁ peut être égal à 0,8 mm et l₁ peut être égal à 1,5 mm. Dans ces conditions, la tôle intérieure 6 a un coefficient propre de passage de 25%.As shown in FIG. 1 and as is even more visible in FIG. 2, the peripheral wall 5 of the tubular body 2 is constituted by two perforated sheets, namely an inner sheet 6 and an outer sheet 7. The sheets 6 and 7 are kept intimately in contact with each other for example by several welding points. The thickness e₁ of the inner sheet 6, the diameter φ₁ of the holes 8 of this sheet and the distance l₁ between the axes of the adjacent holes 8 may have values identical to those of the inner sheet of the known burner described in the preamble. For example, e₁ can be between 0.3 and 0.8 mm, preferably equal to 0.7 mm, φ₁ can be equal to 0.8 mm and l₁ can be equal to 1.5 mm. Under these conditions, the inner sheet 6 has a natural coefficient of passage of 25%.

Dans le brûleur selon l'invention, la section de passage des trous 9 de la tôle extérieure 7 est choisie de manière à être plus petite que la section de passage des trous de la tôle extérieure du brûleur connu décrit en préambule. En outre, la distance l₂ entre les axes des trous 9 adjacents est choisie de manière à être plus grande que la distance entre les axes des trous adjacents de la tôle extérieure du brûleur connu. Dans ces conditions, l'intervalle d₂ entre deux trous 9 adjacents de la tôle extérieure 7 est plus grand que l'intervalle correspondant dans la tôle extérieure du brûleur connu. Plus précisément, l'espacement d₂ des trous 9 de la tôle extérieure 7 et leur section de passage sont choisis de telle façon que l'ensemble des deux tôles 6 et 7 ait un coefficient global de passage au plus égal à 7,8%. Les trous 9 sont de préférence circulaires et ont un diamètre φ₂ au plus égal à 6 mm et un entraxe l₂ compris entre 8 et 10 mm.In the burner according to the invention, the section for the passage of the holes 9 in the external sheet 7 is chosen so as to be smaller than the section for the passage of the holes in the external sheet of the known burner described in the preamble. In addition, the distance l₂ between the axes of the adjacent holes 9 is chosen so as to be greater than the distance between the axes of the adjacent holes of the external sheet of the known burner. Under these conditions, the interval d₂ between two adjacent holes 9 in the external sheet 7 is greater than the corresponding interval in the external sheet of the known burner. More specifically, the spacing d₂ of the holes 9 in the outer sheet 7 and their passage section are chosen such that all of the two sheets 6 and 7 have an overall coefficient of passage at most equal to 7.8%. The holes 9 are preferably circular and have a diameter φ₂ at most equal to 6 mm and a center distance l₂ of between 8 and 10 mm.

Les essais effectués par la Demanderesse avec des brûleurs réalisés comme décrits ci-dessus ont montré que les taux de NOx produit par les brûleurs sont nettement inférieurs à ceux des brûleurs connus décrits en préambule. Ceci peut s'expliquer de la manière suivante. Etant donné que l'espacement d₂ entre les trous 9 est plus grand que dans le brûleur connu, la tôle extérieure 7 présente une plus grande surface de contact avec la tôle intérieure 6 qui est refroidie par le mélange air-gaz entrant dans le brûleur. En conséquence, la tôle extérieure 7 est elle-même mieux refroidie que dans le brûleur connu, ce qui a pour effet d'abaisser la température des flammes qui sont produites par le brûleur et qui sont en contact avec le bord des trous 9. Or, comme on le sait, l'abaissement de la température des flammes est un facteur permettant d'abaisser le taux de NOx d'un brûleur.The tests carried out by the Applicant with burners carried out as described above have shown that the NOx levels produced by the burners are much lower than those of the known burners described in the preamble. This can be explained as follows. Since the spacing d₂ between the holes 9 is greater than in the known burner, the outer sheet 7 has a larger contact surface with the inner sheet 6 which is cooled by the air-gas mixture entering the burner. Consequently, the outer sheet 7 is itself better cooled than in the known burner, which has the effect of lowering the temperature of the flames which are produced by the burner and which are in contact with the edge of the holes 9. Or As we know, lowering the flame temperature is a factor in lowering the NOx level of a burner.

Par contre, du fait que les trous 9 de la tôle extérieure 7 ont une plus petite section et que leur espacement d₂ est augmenté par rapport au brûleur connu, le nombre des trous 8 de la tôle intérieure 6 qui sont découverts par les trous 9 est par conséquent plus petit que dans le brûleur connu. Pour obtenir à travers les trous 8 du brûleur de la présente invention la même valeur de débit du mélange air-gaz que dans le brûleur connu pour une pression d'alimentation donnée du mélange air-gaz, donc pour obtenir la même puissance nominale du brûleur, il faut augmenter les dimensions de la surface périphérique extérieure 5 du brûleur afin d'augmenter le nombre de trous 8 qui seront découverts par les trous 9. Ceci peut être obtenu sans difficulté en augmentant le diamètre extérieur et/ou la longueur du corps tubulaire 2 du brûleur 1. Une telle augmentation du diamètre extérieur et/ou de la longueur du corps tubulaire 2 ne pose pas de problème majeur étant donné que la chambre de combustion des chaudières est habituellement largement dimensionnée et qu'elle peut donc accepter une telle augmentation des dimensions du brûleur 1. L'agrandissement de la surface de la paroi périphérique 5 du corps tubulaire 2 contribue également à un meilleur refroidissement de la tôle extérieure 7, donc aussi des flammes, ce qui, là encore, permet d'abaisser le taux de NOx.By cons, because the holes 9 of the outer sheet 7 have a smaller section and that their spacing d₂ is increased relative to the known burner, the number of holes 8 of the inner sheet 6 which are exposed by the holes 9 is therefore smaller than in the known burner. To obtain, through the holes 8 of the burner of the present invention, the same value of the flow rate of the air-gas mixture as in the known burner for a given supply pressure of the air-gas mixture, therefore to obtain the same nominal power of the burner , it is necessary to increase the dimensions of the external peripheral surface 5 of the burner in order to increase the number of holes 8 which will be uncovered by the holes 9. This can be obtained without difficulty by increasing the external diameter and / or the length of the tubular body 2 of the burner 1. Such an increase in the outside diameter and / or in the length of the tubular body 2 does not pose any major problem since the combustion chamber of the boilers is usually largely dimensioned and that it can therefore accept such an increase in the dimensions of the burner 1. The enlargement of the surface of the peripheral wall 5 of the tubular body 2 also contributes to better cooling of the outer sheet 7, therefore also of the flames, which, here again, makes it possible to lower the NOx level.

En outre, dans le brûleur 1 de la présente invention, la tôle extérieure 7 a de préférence une épaisseur e₂ nettement plus grande que celle e₁ de la tôle intérieure 6. De préférence, l'épaisseur e₂ de la tôle extérieure 7 est égale à 3 mm. Du point de vue du refroidissement de la tôle extérieure 7 donc aussi du refroidissement des flammes et par conséquent du point de vue de la réduction du taux de NOx, il y aurait intérêt à ce que l'épaisseur e₂ de la tôle 7 soit la plus grande possible. Toutefois, l'épaisseur e₂ doit être limitée pour des raisons économiques (coût de la tôle et des outillages capables de perforer des tôles épaisses) et pour des raisons mécaniques (l'épaisseur e₂ de la tôle doit être inférieure au diamètre φ₂ des trous 9). En conséquence, en pratique, l'épaisseur e₂ de la tôle 7 sera comprise entre 2,5 et 3,5 mm. Pour les raisons mécaniques évoquées ci-dessus, le diamètre φ₂ des trous 9 ne peut être inférieur à l'épaisseur e₂ de la tôle 7. En conséquence, lorsqu'on utilise une tôle épaisse pour la tôle 7, par exemple une tôle de 3 mm d'épaisseur, le diamètre φ₂ des trous 9 ne pourra être inférieur à environ 4 mm.In addition, in the burner 1 of the present invention, the outer sheet 7 preferably has a thickness e₂ markedly greater than that e₁ of the inner sheet 6. Preferably, the thickness e₂ of the outer sheet 7 is equal to 3 mm. From the point of view of the cooling of the outer sheet 7 therefore also of the cooling of the flames and consequently from the point of view of the reduction of the NOx rate, it would be advantageous if the thickness e₂ of the sheet 7 was the most great possible. However, the thickness e₂ must be limited for economic reasons (cost of the sheet and tools capable of perforating thick sheets) and for mechanical reasons (the thickness e₂ of the sheet must be less than the diameter φ₂ of the holes 9 ). Consequently, in practice, the thickness e₂ of the sheet 7 will be between 2.5 and 3.5 mm. For the mechanical reasons mentioned above, the diameter φ₂ of the holes 9 cannot be less than the thickness e₂ of the sheet 7. Consequently, when a thick sheet is used for the sheet 7, for example a sheet of 3 mm thick, the diameter φ₂ of the holes 9 may not be less than approximately 4 mm.

ExempleExample

La Demanderesse a réalisé un brûleur d'une puissance nominale de 375 kWh construit comme décrit ci-dessus et ayant les caractéristiques dimensionnelles indiquées dans le tableau ci-dessous. Dans ce tableau, on a également indiqué, à titre de comparaison, les caractéristiques dimensionnelles d'un brûleur connu de même puissance, utilisé dans les chaudières du type HX375 fabriquées par la demanderesse. Enfin, dans le bas du tableau on a également indiqué les taux de NOx produits respectivement par le brûleur selon l'invention et par le brûleur connu fonctionnant à la puissance nominale de 375 kWh. Comme on peut le voir, le brûleur de la présente invention produit plus de trois fois moins de NOx que le brûleur connu.

Figure imgb0001
The Applicant has produced a burner with a nominal power of 375 kWh constructed as described above and having the dimensional characteristics indicated in the table below. This table also indicates, for comparison, the dimensional characteristics of a burner known from same power, used in boilers of the HX375 type manufactured by the applicant. Finally, at the bottom of the table, the NOx rates produced respectively by the burner according to the invention and by the known burner operating at the nominal power of 375 kWh have also been indicated. As can be seen, the burner of the present invention produces more than three times less NOx than the known burner.
Figure imgb0001

Il va de soi que les valeurs indiquées dans le tableau ci-dessus pourront varier selon la valeur de la puissance nominale pour laquelle le brûleur est conçu. Il est du reste bien entendu que la forme d'exécution de l'invention qui a été décrite ci-dessus a été donnée à titre d'exemple purement indicatif et nullement limitatif, et que de nombreuses modifications peuvent être apportées par l'homme de l'art sans pour autant sortir du cadre de l'invention. C'est ainsi notamment qu'au lieu d'être disposés en rangées et en colonnes selon l'arrangement montré sur la figure 1, les trous 8, 9 d'au moins l'une des deux tôles perforées 6, 7 peuvent être disposés autrement, par exemple de manière à ce que chaque trou soit équidistant de tous les trous adjacents qui l'entourent. Dans ce cas, chaque trou a son centre placé au centre d'un cercle et les trous adjacents qui entourent le trou considéré ont leur centre situé sur ledit cercle et sont répartis régulièrement sur ce cercle avec un espacement angulaire constant de 60°. En outre, les trous 9 n'ont pas nécessairement tous le même diamètre et ils peuvent donc avoir des diamètres différents sous réserve que le coefficient global de passage des gaz du brûleur reste au plus égal à 7,8%It goes without saying that the values indicated in the table above may vary depending on the value of the nominal power for which the burner is designed. It is moreover of course understood that the embodiment of the invention which has been described above has been given by way of purely indicative and in no way limiting example, and that numerous modifications can be made by the person skilled in the art. art without departing from the scope of the invention. Thus in particular that instead of being arranged in rows and columns according to the arrangement shown in Figure 1, the holes 8, 9 of at least one of the two perforated sheets 6, 7 can be arranged otherwise, for example so that each hole is equidistant from all the adjacent holes which surround it. In this case, each hole has its center placed in the center of a circle and the adjacent holes which surround the hole in question have their center located on said circle and are distributed regularly over this circle with a constant angular spacing of 60 °. In addition, the holes 9 do not necessarily have all the same diameter and they can therefore have different diameters provided that the overall coefficient of passage of the gases from the burner remains at most equal to 7.8%

Claims (5)

1.- Brûleur à gaz comprenant un corps tubulaire (2) ayant une première extrémité (3) au moins partiellement ouverte pour l'admission de l'air et du combustible gazeux dans l'espace interne du corps tubulaire, une seconde extrémité (4) fermée et une paroi périphérique (5) percée d'une multitude de trous de passage pour le mélange combustible gazeux qui brûle à la surface périphérique extérieure du corps tubulaire, la paroi périphérique (5) du corps tubulaire (2) étant constituée par deux tôles perforées (6,7), respectivement intérieure et extérieure, maintenues en contact l'une avec l'autre, la tôle intérieure (6) présentant des trous (8) qui ont un diamètre prédéterminé, tandis que la tôle extérieure (7) présente des trous (9) ayant une section de passage plus grande que celle des trous (8) de la tôle intérieure (6), caractérisé en ce que l'espacement (d₂) des trous (9) de la tôle extérieure (7) et leur section de passage sont tels que l'ensemble des deux tôles perforées (6 et 7) du brûleur (1) ait un coefficient global de passage des gaz au plus égal à 7,8 %. 1.- Gas burner comprising a tubular body (2) having a first end (3) at least partially open for the admission of air and gaseous fuel into the internal space of the tubular body, a second end (4 ) closed and a peripheral wall (5) pierced with a multitude of passage holes for the gaseous combustible mixture which burns on the external peripheral surface of the tubular body, the peripheral wall (5) of the tubular body (2) being constituted by two perforated sheets (6,7), respectively inside and outside, kept in contact with each other, the inside sheet (6) having holes (8) which have a predetermined diameter, while the outside sheet (7) has holes (9) having a larger cross-section than that of the holes (8) in the inner sheet (6), characterized in that the spacing (d₂) of the holes (9) in the outer sheet (7) and their passage section are such that the whole ble of the two perforated sheets (6 and 7) of the burner (1) has an overall coefficient of gas passage at most equal to 7.8%. 2.- Brûleur à gaz selon la revendication 1, caractérisé en ce que la tôle extérieure (7) a une épaisseur au moins égale à 2 mm. 2.- gas burner according to claim 1, characterized in that the outer sheet (7) has a thickness at least equal to 2 mm. 3.- Brûleur à gaz selon la revendication 2, caractérisé en ce que l'épaisseur de la tôle extérieure (7) est égale à 3 mm. 3.- Gas burner according to claim 2, characterized in that the thickness of the outer sheet (7) is equal to 3 mm. 4.- Brûleur à gaz selon l'une quelconque des revendications 1 à 3, caractérisé en ce que les trous (9) de la tôle extérieure (7) sont circulaires et ont un diamètre (φ₂) au plus égal à 6 mm. 4.- gas burner according to any one of claims 1 to 3, characterized in that the holes (9) of the outer sheet (7) are circular and have a diameter (φ₂) at most equal to 6 mm. 5.- Brûleur à gaz selon la revendication 4, caractérisé en ce que les trous (9) ont un diamètre de 5,5 mm et une distance de centre à centre de 10 mm. 5.- Gas burner according to claim 4, characterized in that the holes (9) have a diameter of 5.5 mm and a distance from center to center of 10 mm.
EP94401336A 1993-06-21 1994-06-15 Low NOx gas burner Withdrawn EP0631091A1 (en)

Applications Claiming Priority (2)

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FR9307463 1993-06-21
FR9307463A FR2706986B1 (en) 1993-06-21 1993-06-21

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EP0631091A1 true EP0631091A1 (en) 1994-12-28

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2037175B1 (en) 2007-09-12 2016-11-23 Polidoro S.p.A. Premixed burner
EP3910237A3 (en) * 2020-05-12 2022-02-23 Vaillant GmbH Burner assembly and distribution plate
IT202100011888A1 (en) * 2021-05-10 2022-11-10 Beckett Thermal Solutions S R L Combustion membrane for a gas burner

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1955163A1 (en) * 1969-06-14 1971-05-13 Schwank Gmbh Infra red source

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1955163A1 (en) * 1969-06-14 1971-05-13 Schwank Gmbh Infra red source

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2037175B1 (en) 2007-09-12 2016-11-23 Polidoro S.p.A. Premixed burner
EP3910237A3 (en) * 2020-05-12 2022-02-23 Vaillant GmbH Burner assembly and distribution plate
IT202100011888A1 (en) * 2021-05-10 2022-11-10 Beckett Thermal Solutions S R L Combustion membrane for a gas burner
EP4089328A1 (en) * 2021-05-10 2022-11-16 Beckett Thermal Solutions S.R.L. A combustion membrane for a gas burner

Also Published As

Publication number Publication date
FR2706986B1 (en) 1995-09-01
FR2706986A1 (en) 1994-12-30

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