FR2658268A1 - GAS BURNER WITH LOW NITROUS CONTENT. - Google Patents

Abstract

The burner is of the type comprising a Venturi tube (2) extended by a divergent duct (5). The perforated plate (6) fixed to the outlet of this duct (5) is made of a material with a very low heat transmission coefficient, so that the transmission of combustion heat to the duct (5) is avoided. and that it is thus possible to guarantee combustion of the hyperstichiometric type, both during ignition and in normal operation.

Description

The subject of the present invention is a low-grade gas burner

into nitrous products.

  Burners have been known for a long time which comprise a Venturi tube inside which the oxidizing gas is introduced and which is extended by a divergent duct at the outlet of which is provided a surface pierced with suitably arranged and profiled perforations This surface acts as a combustion head for the burner since

  it is at this level that combustion takes place.

  When with such a structure the mixture of oxidant gas and combustible gas passes through the head under the combustion conditions, the

  temperature of said mixture is thus increased.

  Simultaneously there is an increase in the specific volume of the

  mixture, as well as an increase in its speed in terms of perfo-

  rations of the aforementioned surface, because the mass of the mixture remains

obviously constant.

  Under these conditions, an increase in resistance is obtained.

  with the passage of the mixture, which increase is of course proportion-

nel squared speed.

  Burners of this type are specially intended to operate in a so-called "hyperstechiometric" regime, that is to say with an excess of combustion air. This is a condition for obtaining combustion products with low NO x content.

  Currently these burners use platelets, perfo-

  transversely to allow the flow of the gas mixture; these plates are made of a thermally conductive material, so that the heat is thus transmitted to the conduits through which the gas mixture passes. To overcome this drawback, fans must be used which cause notable drawbacks with regard to regulation as a function of the flow rate of the gas mixture; alternatively we must very significantly reduce the power per unit

surface area of the burner.

  By thus obstructing the passage of the air emitted by the Venturi, it results in the elimination of excess air, so that if during the start-up the burner emits combustion products

  with a low N Ox content, the same cannot be said when the apparatus

reil works on his diet.

  The object of the present invention is to produce a burner of the type described above capable of giving good results in that

  which concerns the emission of nitrous products as well during the

mage than normal.

  This object is obtained according to the invention by having, at the outlet of the divergent conduit and over the entire transverse surface of this outlet, a plate made of a material with very low coefficient of heat transmission, said plate being of course pierced a series of transverse perforations to allow

the flow of the gas mixture.

  Particularly advantageously, the aforementioned brochure is

made of ceramic felt.

  With such a structure, it can be seen that the heat released by the combustion propagates very little towards the interior, so that the channels which the gas mixture passes through are not heated. As a result, the excess air is maintained, combustion remains

  hyperstechiometric type and The desired result is obtained.

  The attached drawing, given by way of example, will allow better understanding

  take the invention, the characteristics it presents and the advantages

  stages it is likely to provide: Fig 1 is a side view of a series of established burners

according to the invention.

  Fig 2 is a plan view of these burners.

  Fig 3 is a cross section on an enlarged scale showing

  the plate used at each burner.

  In fig 1 and 2 it was assumed that the invention was applied to

  burners 1 which have a Venturi tube 2 inside which

  mixes the gas from nozzle 3 with the combustion air drawn into the outside environment. In the illustrated structure, which is also well known in practice, a series of burners is provided, all of which are supplied by a manifold. single gas referenced 4 Downstream

  a divergent duct 5 is mounted on each Venturi tube.

  In accordance with the fundamental characteristic of the invention, at the outlet of each of the divergent conduits 5 is fixed a

  plate 6 made of a material with a very low trans-

  heat mission, for example ceramic felt; in this place

  quette 6 is provided a series of perforations 7 suitably profi-

  lées and arranged to allow the flow of the gas mixture.

  Thanks to this particular structure, heat does not spread

  from the outer surface of each plate towards the interior

  so that the ducts are kept at a sufficient temperature

  drastically low to obtain the advantages previously indicated.

  It should also be understood that the above description has not

  given as an example and does not limit the area

  ne of the invention from which one would not leave by replacing the details of execution described by all other equivalents.

Claims (2)

R E V E N D I C A T I 0 N S CLAIMS   1 Gas burner with low nitrous content, of the com-   taking a Venturi tube (2) which is extended by a divergent conduit (5), characterized in that the outlet of this conduit (5) is equipped, over its entire cross section, with a plate (6) made of a material very low heat transfer coefficient and breakthrough   a series of transverse perforations (7) to allow drainage gaseous mixture.   2 Burner according to claim 1, characterized in that the   plate (6) is made of ceramic felt.