Catalyst combustion device

Details Catalyst combustion device Catalyst combustion device

2000-09-25

2002-05-28

Yeung, James C. (Department: 3743)

Combustion

Process of combustion or burner operation

In a porous body or bed, e.g., surface combustion, etc.

C431S268000, C431S328000, C431S170000

Reexamination Certificate

active

06394789

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a catalytic combustion apparatus for combustion of gaseous fuel or liquid fuel.
BACKGROUND OF THE INVENTION
An existing catalytic combustion apparatus is of a configuration as illustrated in
FIG. 29
, for example. In the diagram, numeral
1
is a gas tank for storing liquefied petroleum gas such as butane, propane, and the like. Fuel gas contained inside the gas tank
1
is ejected from a gas nozzle
3
passing through a gas passage
2
. The gas ejected from the gas nozzle
3
draws in air through an air intake
4
by the effect of gas flow ejection and is mixed with air in a mixing chamber
5
, and is then supplied to a combustion chamber
6
. There being a catalytic body
7
inside the combustion chamber
6
, the mixed gas burns by the catalytic action as it passes an internal passage
7
′ of the catalytic body
7
and generates combustion heat. An ignition device
8
is provided opposite the mixed gas entrance of the combustion chamber
6
. When starting the apparatus, the mixed gas is ignited by a spark generated by a spark plug
9
provided on the tip of the ignition device
8
. The catalytic body
7
is heated by a flame formed downstream of the catalytic body
7
. When the temperature of the catalytic body
7
reaches the active temperature, catalytic combustion starts to take place on the surface of the catalytic body
7
, the supply of the mixed gas to the flame is stopped, and the flame disappears. Under this condition, the mixed gas supplied to the combustion chamber
6
undergoes catalytic combustion over the entire catalytic body
7
, and the combustion gas is exhausted from an exhaust port
10
.
Such a catalytic combustion apparatus is being used in portable irons and warming devices.
However, as such existing catalytic combustion apparatus suffers several problems when trying to make it smaller and thinner for better portability, there was a limit in the improvement of portability.
To be more specific, an existing catalytic body
7
is generally a cylindrical honeycomb made of ceramic or metal supporting a catalyst. As its diameter is roughly determined by the amount of combustion, the height of the burner cannot be made smaller than this diameter. Furthermore, when the catalytic body
7
is made unreasonably small, it will present a problem of not being able to obtain a predetermined heating value as the combustion characteristic is lowered.
Additionally, as existing catalytic combustion apparatuses are configured in a straight line by directly coupling a mixing chamber
5
and a catalytic body
7
, the total length of the burner tends to be large. Though the combustion chamber
5
may be bent in order to make the length shorter, such configuration will suffer non-uniform distribution of the mixed gas flow velocity and will result in non-uniform combustion on the catalytic body
7
, thereby presenting fundamental difficulty in making the size smaller. Also, when the catalytic body
7
is formed into the shape of a thin plate, the velocity of flow of the mixed gas becomes high when a flame for the purpose of firing is formed on the downstream side of the catalytic body
7
, and the flame is formed apart from the catalytic body
7
, thereby either delaying or stopping transition to catalytic combustion. Downsizing will also suffer a problem of causing a higher watt density, leading to an excessive increase in the catalyst temperature thereby shortening the life of the catalyst.
The present inventors had already developed a thin type catalytic combustion system in which the height of the burner was made low by disposing a catalytic body formed in the shape of a flat plate with its planar area greater than the area of the side, and providing a gas passage on the catalytic body to allow flow of mixed gas in the lateral direction. However, in manufacturing a low-profile burner, difficulties were faced in the method of fabrication. To be more specific, when employing a structure in which a nozzle, a catalytic body, etc., are mounted onto a mother component in which a mixing chamber, a combustion chamber, etc., have been formed into a single piece by aluminum die casting, for example, there was a limit in making the mother component thinner in which the mixing chamber and the combustion chamber had been integrally formed into a single piece from the standpoint of the thickness of molding, etc., to say nothing of the difficulty in securing precision.
SUMMARY OF THE INVENTION
The present invention addresses the above described issues of the prior art. It is an object of the present invention to make a smaller and thinner burner by making the height and length smaller while securing ignitability thereby to provide a catalytic combustion apparatus which is superior in durability and portability.
A description will now be given of exemplary embodiments of the present invention for achieving the above objective.
A first exemplary embodiment of the present invention comprises a combustor, a fuel tank, a valve, and an ignition device, wherein the combustor further comprises a gas nozzle, an air intake/ejector, a mixing chamber, a firing chamber, an ignition plug, a combustion chamber, a catalyst for combustion (first catalyst) housed in the combustion chamber, and an exhaust port. The mixing chamber is a straight cylindrical passage, a cylindrical firing chamber of which an opening on its side communicating with the combustion chamber is provided in parallel to the mixing chamber, a burner port is disposed on the boundary of the mixing chamber and the firing chamber, and the burner port comprises a catalytic net (second catalyst). With this structure, it is made possible to form a flame on the upstream side of the catalyst for combustion, and heat the catalyst for combustion to a catalytic combustion enabling temperature with the heat of the flame thus causing catalytic combustion on the catalytic net, too, whereby the flame spontaneously disappears allowing the catalyst for combustion to commence catalytic combustion, and suggesting that catalytic combustion can be performed without fail even when the combustion chamber is configured with a low profile. Furthermore, as the combustion takes place on both the catalytic net and the catalyst for combustion, the temperature rise of the catalyst for combustion is kept small and the life is lengthened. As a result, the thickness of the catalytic body can be made smaller without sacrificing the igniting characteristics and durability, thereby allowing the burner height to be made smaller and providing a smaller and thinner catalytic combustion apparatus.
A second exemplary embodiment is configured such that, in a catalytic combustion apparatus as described in the first exemplary embodiment, the combustion on the catalytic net, is adjusted to half of the entire combustion thereby to quickly extinguish the flame to allow smooth transition to catalytic combustion as well as to halve the combustion on the catalytic net thus lengthening the life of both the catalytic net and the catalyst for combustion.
A third exemplary embodiment of the present invention comprises a combustor, a fuel tank, a valve, and an ignition device, wherein the combustor further comprises a gas nozzle, an air intake/ejector, an air intake, a mixing chamber, a firing chamber, a burner port provided in the firing chamber, an ignition plug, a combustion chamber, a catalyst for combustion housed in the combustion chamber, and an exhaust port. An intake-air shutter is provided on the air intake which is operable by a temperature detecting means provided in the vicinity of the combustion chamber. With this arrangement, the ratio of combustion on the catalytic net can be lowered by making the velocity of the fuel air mixed gas passing through the catalytic net greater by increasing the air-to-fuel ratio after transition to catalytic combustion, thereby to secure the life of the catalytic net. Also, by increasing the air-to-fuel ratio, the temperature of the catalyst for combustion is lowered and the durabili

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