Combustion – Mixer and flame holder
Reexamination Certificate
2003-01-21
2004-09-07
Yeung, James C. (Department: 3749)
Combustion
Mixer and flame holder
C431S278000, C431S285000, C431S328000, C126S09200C
Reexamination Certificate
active
06786717
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combustion apparatus, and more particularly relates to a combustion apparatus adapted for use with a hot-water supply system, a boiler or the like.
2. Related Art
The “thick and thin fuel combustion” method known in the art is designed to burn a fuel gas in its thin state. At least one main flame formed by burning a thin gas and at least one auxiliary flame formed by burning a thick gas will be jetted in juxtaposition to each other in this prior art system. In detail, such a thin gas for forming the main flame is composed a volume of the gas premixed with an amount of air whose volume is about 1.6 times as much as the theoretical amount of air for said gas. A thick gas for forming the auxiliary flame contains a lesser amount of air.
In the thick and thin fuel combustion method, the fuel gas is burned with such an excess of air so that flame temperature is kept relatively lower to produce a less amount of nitrogen oxides. Thus, some types of current house-held water heater are constructed using such burners of the thick and thin fuel combustion system.
Examples of thick and thin fuel combustion apparatuses widely used heretofore are disclosed in the Japanese Patent Laying-Open Gazettes No. 10-238719 and No. 10-47614.
In the apparatus shown in the Gazette No. 10-238719, two fuel-air mixtures of different concentrations are prepared outside a burner body and fed thereto through respective burner ports. This system requires an external gas concentration regulator, which will render the apparatus more complicated in structure. One of the gas-air mixtures will be jetted at a very low rate through one of the burner ports whose opening area is so small that it is difficult to manufacture the apparatus and to precisely regulate the rate of jetted fuel-air mixtures.
In another thick and thin fuel combustion apparatus shown in the Gazette No. 10-47614, air is mixed internally thereof with a fuel gas fed through a fuel nozzle. This apparatus that does not need any external regulator for controlling the concentration of fuel-air mixture will be made simpler in structure.
However, these prior art combustion apparatuses have their principal parts manufactured each by combining metal plates one with another, which have been pressed or otherwise processed to have corrugations or the like. The pressing of metal plates can not ensure a satisfactory preciseness in dimension of said parts, often failing to provide an airtight mutual consolidation of their lateral sides. Consequently, a considerable quantity of gas mixture flowing in between two metal plates is likely to leak sideways through crevices present between the metal plates forming a fuel feed passage. In such an event, concentration and jet rate of fuel gas would suffer from fluctuation, resulting in an unstable combustion thereof.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide an improved combustion apparatus that will stabilize combustion of a fuel gas.
In order to achieve this object, the present invention has made the following improvements.
From a first aspect, the present invention provides a combustion apparatus that comprises at least one main burner port for jetting and burning a thin fuel gas mixture, and at least one auxiliary burner port for jetting and burning a thick fuel gas mixture. This apparatus further comprises an air intake for introduction of air or the thin gas mixture, and a fuel intake for introduction of air and the thick gas mixture, in addition to a thin gas passage and a thick gas passage. The air intake communicates with the thin gas passage for supplying the main burner port with the gas, and the fuel intake communicates with the thick gas passage for supplying the auxiliary burner port with the gas. Characteristically in the apparatus of the invention, the thick gas passage surrounds in part a portion of the thin gas passage, and the portion of this passage has at least one supplementary gas openings formed therein. A controlled amount of the thick gas mixture flowing through the thick gas passage will enter the thin gas passage through the said supplementary gas ope nings.
The main burner port cooperates with the auxiliary burner port that jets high-concentration gas rather than the gas jetted from the main burner port. Thus, there will be established a condition for thick and thin fuel combustion such that a flame formed out of the main flame is stabilized by another flame formed out of the auxiliary burner port.
As noted above, the thick gas passage in the present invention surrounds a portion of the thin gas passage, and the portion of this passage has the supplementary gas opening formed therein. By virtue of this structure, a controlled amount of the thick gas mixture will enter the thin gas passage through which a highly thin gas mixture, or almost the air itself, is flowing. The fraction of fuel gas mixture will be stirred within the thin gas mixture or air so as to spread uniformly through-out it, spontaneously, smoothly and instantly when it flows into the thin gas passage. Thus, the gas mixture being jetted out from the main burner port will be homogenized in concentration of gas, thereby stabilizing the main flame. Incomplete combustion can now be almost avoided when starting operation of this apparatus, thus diminishing the amount of ecologically harmful exhaust gas.
From a further aspect, and also in order to achieve the object mentioned above, the present invention provides a combustion apparatus that comprises at least one main burner port for jetting and burning a thin fuel gas mixture, and at least one auxiliary burner port for jetting and burning a thick fuel gas mixture. This apparatus further comprises an air intake for introduction of air or the thin gas mixture, and a fuel intake for introduction of air and the thick gas mixture, in addition to a thin gas passage and a thick gas passage. The thin gas passage for supplying the main burner port with the gas communicates the air intake with the main burner port, and the thick gas passage for supplying the auxiliary burner port with the gas communicates the fuel intake with the auxiliary burner port. Characteristically in the apparatus of the invention, it comprises a blending station for intermixing the air with the thick gas mixture delivered from the fuel intake. Further, the thick gas passage has an enlarged or expanded section and a constricted section, with the former section directly continuing to the auxiliary burner port so as to supply it with the thick gas mixture. The constricted section of the thick gas passage intervenes between the blending station and the enlarged or expanded section. Thus, a part of the gaseous fuel flows from the blending station into the thin gas passage in order to form the thin gas mixture blown out through the main burner port. The remainder of the gaseous fuel will pass through the blending station and advance through the constricted section so as to remain as the thick gas mixture until blown out of auxiliary burner port.
Also in this apparatus provided herein from the further aspect, the main burner port cooperates with the auxiliary burner port that jets the fuel-air mixture richer in the fuel than the gas jetted from the main burner port. Thus, here is also established a condition for thick and thin fuel combustion such that a flame formed out of the main flame is stabilized by another flame formed out of the auxiliary burner port.
The thin and thick gas passages formed in the apparatus will feed respective gas mixtures to the respective burner ports. The gaseous fuel having entered the apparatus through the fuel intake is then mixed with the air within the blending station, before diverged into the thin and thick gas passages.
The remainder of air-fuel mixture will be agitated well when it passes through the constricted section of a reduced cross-sectional area, before advancing into the enlarged section of the thick gas passage. The gas mixture being blown from the au
Akiyama Takashi
Hasegawa Takashi
Hata Hidenori
Iguchi Masahiro
Kameyama Shuji
Noritz Corporation
Wood Phillips Katz Clark & Mortimer
Yeung James C.
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