Combustion – Mixer and flame holder
Reexamination Certificate
2000-03-29
2001-09-25
Price, Carl D. (Department: 3743)
Combustion
Mixer and flame holder
C239S432000, C239S553300
Reexamination Certificate
active
06293786
ABSTRACT:
The invention concerns a burner with Venturi tube, provided with flow distributing elements.
In the burner equipped with Venturi tube, the fuel is fed at a certain pressure and speed to the mouth of the Venturi tube, causing the aspiration of a certain quantity of air, the so-called primary air, which is mixed to the fuel at the inside of the Venturi tube and, after leaving the tube, is distributed to the slots of the burner diffuser.
The distribution of the mixture air-fuel to the slots of the burner diffuser is usually not uniform, thus generating a non-uniform flame and causing both the flame to be detached from some areas of the diffuser, even in normal operating conditions, and the flame to be flattened on the surface of some areas of the diffuser, which causes overheating of said surface.
In addition, the Venturi tube is fixed to the diffuser at one end, for example by means of welding, whilst the other end remains free. Therefore, the Venturi tube acts as a beam fixed at one end, bending owing to its own weight and being subject to a danger of permanent strains, caused, for example, by impacts or by temperature variations to which the burner is subject during operation. The bending of the Venturi tube aggravates the non uniformity of the distribution of the mixture to the slots of the diffuser.
It is known from DE-2350846 a burner fed with a flow of an air-fuel mixture, comprising a Venturi tube arranged at the inside of a burner body provided with apertures through which said flow passes, said Venturi tube being supported to said body at one of its ends and being further supported two rows of baffles distributed through the whole length of the burner. The baffles are capable of generating vortices in the flow of air-fuel mixture flowing out of the Venturi tube in order to prevent solid impurities contained in the air-fuel mixture from reaching the apertures of the burner body. The above mentioned baffles avoid bending of the Venturi tube but the formation of the vortices in the flow of air-fuel mixture due to the presence of the baffles is detrimental to a uniform distribution of the air-fuel mixture to the apertures of the burner body.
U.S. Pat. No. 3,353,583 discloses a radiant burner fed with a flow of an air-fuel mixture, comprising a Venturi tube arranged at the inside of a burner body provided with an elongated aperture through which said flow passes, said aperture being covered by combustion sustaining screen assembly, said Venturi tube being supported to said body at one of its ends and being further supported by a curved baffle having an end which is aligned with a portion of the outlet of the Venturi tube and interferes with the flow of the air-fuel mixture in order to divide the flow into two streams directed to different portions of said elongated aperture. The baffle interferes with the flow of air-fuel mixture in the region of the outlet of the Venturi tube, when the speed of the mixture is relatively high, which implies a considerable turbulence in the flow of the mixture being generated, which increases the resistance of the burner and makes difficult to obtain a uniform distribution of the mixture through the elongated aperture.
EP-A-0 217 470 discloses a burner for gas boilers fed with a flow of an air-fuel mixture, comprising a Venturi tube arranged at the inside of a burner body provided with apertures through which said flow passes, said Venturi tube being supported to said body at one of its ends whilst the other end remains free. The burner is provided with a partition extending in an axial direction and provided in a region remote from said apertures with an opening, said partition being further provided with a deflector which diverts the air-fuel mixture flowing or the Venturi tube in the direction of the opening in the partition. The deflector and the partition reduces the turbulence of the air-flow mixture flowing out of the venturi tube and improve the uniformity of distribution of the mixture to the apertures of the burner body. However the Venturi tube, which is supported only at one end, is subjected to bending stresses which reduce the life of the burner.
This invention intends to eliminate the above mentioned drawbacks. According to the invention there is provided a burner comprising a tubular burner body, a Venturi tube arranged at the inside of said burner body and supplying a flow of air-fuel mixture to the inside of said bruner body provided with apertures through which said flow passes and generates a flame, one end of said Venturi tube being fixed to said burner body, additional support and centring means provided with control means for controlling the distribution of said flow of air-fuel mixture to said apertures, said support and centring means having a substantially flat shape, characterized in that said control means comprises openings defined in said support and centring means.
REFERENCES:
patent: 1507791 (1924-09-01), Packer
patent: 2533104 (1950-12-01), Golden et al.
patent: 3185204 (1965-05-01), Loeb et al.
patent: 3353583 (1967-11-01), Silhavy
patent: 4413976 (1983-11-01), Sherer
patent: 4927355 (1990-05-01), Haire et al.
patent: 2350846-A (1974-04-01), None
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patent: 1577719-A (1969-08-01), None
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patent: 2266585-A (1993-11-01), None
Fogliani Giuseppe
Lasagni Feliciano
Price Carl D.
Reising, Ethington, Barnes, Kisselle, Learman & McCulloch, P.C
Worgas Bruciatori S.r.l.
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