Combustion – Porous – capillary – particulate or sievelike flame holder,... – Means supplying fuel for passage through the flame holding...
Patent
1998-10-08
2000-05-23
Lazarus, Ira S.
Combustion
Porous, capillary, particulate or sievelike flame holder,...
Means supplying fuel for passage through the flame holding...
F23D 1414
Patent
active
060659637
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a conical surface burner with a non-sintered, fabric-type metal fibre structure as burner membrane. This fibre structure can be knitted, knotted, braided or woven.
Conventional burners with prismatic or cylindrical surfaces have the disadvantage during use that at the end of the burner (in the direction of the gas flow) a gas pressure builds up which is higher than the average gas pressure in the combustion chamber. As a consequence, a flaring flame is frequently observed at this end. These conventional burners thus are often not capable of producing homogeneous combustion over the entire surface of the burner without the installation of pressure distribution elements, which result in an extra pressure drop and are considerably more labourintensive to manufacture.
The use of sintered metal fibre webs as burner membranes in surface burners is known from patent EP 0157432. The problems of non-uniform gas flow over the membrane surface associated with this type of membrane were partially solved by providing the sintered porous metal fibre plate with a regular pattern of openings, as described in WO 93/18342 of the applicant. The problem of obstructed thermal expansion remained, however, since the membrane plates should be able to expand in all directions and then contract, in accordance with the heating and cooling cycles. The plates often possess a considerable surface area, however, and are mounted in a fixed peripheral frame, so that the thermal expansion cannot take place unobstructedly. During use, this leads to uncontrollable deformation phenomena.
In contrast to the conventional sintered membranes, a non-sintered (for example, knitted) membrane is highly deformable, so that the problems resulting from the thermal expansion of the membrane are avoided, even in burners with a large surface area. Moreover, the knitted metal fibre membranes are capable of producing homogenous combustion, both in the radiation mode and in the blue-flame mode.
Furthermore, as a result of the very open knitted structure, no filter is required for the gas mixture which is to be burned. Additionally, the chance of flame resonance is very small, with the consequence that the disturbing whistling sounds are avoided. The knitted membranes also offer the advantage that the time required for warming up and cooling down (response time) is extremely short, so that a very great amount of variation in heat flux can be realized in a very short time span (in the order of seconds). Hence, the change-over from one burning mode to another takes place very smoothly. The quick response is very beneficial from the standpoint of safety.
It is an object of the invention to provide a surface burner in which the change of pressure of the gas/air mixture flowing through the gas supply chamber is uniform and the flaring of the flames at the end of the burner is greatly diminished in comparison to many conventional burners. To this end, the burner membrane has a cone-shaped surface, whether truncated or not, and is composed of non-sintered metal fibres. This burner enables to obtain homogeneous combustion over the entire surface of the burner, without any particular fittings or partitions being required in the chamber, which would considerably increase the pressure drop in the flow through the burner. Depending on the dimensions of the burner and the heat flux in question, the pressure drop in the flow through a burner according to the invention is generally two to three times lower than the pressure drop in the flow through the known conventional burners.
More specifically, the invention provides a surface burner for gas comprising a gas supply chamber enclosed by a burner membrane at its gas outlet side and a coupling element to connect it with the gas supply means, in which the surface of the membrane is conically shaped, and in which the membrane is fixed to a support net at the gas supply side of the membrane. The burner membrane consists of a non-sintered fabrictype structure made of stainless steel fibres having an equi
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Patent Abstracts of Japan, vol. 096, No. 006, Jun. 28, 1996 & JP 08 028824 A (Rinnai Corp; Others: 01), Feb. 2, 1996, see abstract.
Dewaegheneire Gabriel
Marrecau Willy
Vansteenkiste Philip
Clarke Sara
Lazarus Ira S.
N.V. Acotech S.A.
N.V. Bekaert S.A.
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