The present invention relates to a catalytic combustion apparatus for combustion of gaseous fuel or liquid fuel.
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 7xe2x80x2 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.
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 durability is improved.
A fourth exemplary embodiment is a catalytic combustion apparatus as described in the first exemplary embodiment comprising 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. A quantity-of-flow adjustable means is provided between the valve and the combustor so that the adjustable range of the amount of combustion can be widened in a manner such that when the quantity of gas flow is reduced by adjusting the quantity-of-flow adjustable means, combustion will take place on the combustion net only, and when the quantity of gas flow is increased, combustion will take place on both the catalytic net and the catalyst for combustion.
A fifth exemplary embodiment is an invention as described in the first exemplary embodiment comprising a combustor, a fuel tank, a valve, and an ignition device, in which the combustor further comprises a gas nozzle, an air intake/ejector, an air intake, a mixing chamber, a firing chamber, an ignition plug, a combustion chamber, a catalyst for combustion housed in the combustion chamber, and an exhaust port. The mixing chamber is a straight cylindrical passage, a cylindrical firing chamber a side opening of which communicating with the combustion chamber is provided in parallel to the mixing chamber, a burner port is provided on the boundary between the mixing chamber and the firing chamber, the burner port is configured with a catalytic net, and the mixing chamber and a part of the catalytic net are made to come into contact with each other so that the heat of the catalytic net can be conducted to the combustor through the wall of the mixing chamber, thereby suppressing the temperature rise of the catalytic net and securing the life of the catalytic net.
A sixth exemplary embodiment is one in which the catalytic net of the fifth exemplary embodiment is formed in the shape of a square letter C so that its two sides come into contact with the wall of the mixing chamber thereby to remove dispersion of the area of contact between the mixing chamber and the catalytic net during assembly work and to obtain stable characteristics.
A seventh exemplary embodiment is a catalytic combustion apparatus as described in the fifth exemplary embodiment, in which the catalytic net is formed in the shape of an open square so that its three sides come into contact with the wall of the mixing chamber. As it is made easy to maintain the shape of the catalytic net, dispersion of the area of contact between the mixing chamber and the catalytic net during assembly work can be removed, and stable characteristics can be obtained.
An eighth exemplary embodiment is a catalytic combustion apparatus, in which the ignition plug is disposed in the end of the firing chamber where the density of combustion gas becomes high thereby to assure firing and allow reduction in size and thickness.
A ninth exemplary embodiment is a catalytic combustion apparatus, in which a part of the catalyst for combustion is disposed in such a way that it projects into the firing chamber thereby to increase the speed of transition to catalytic combustion by increasing the rate of temperature rise of the catalyst for combustion and allow reduction in size and thickness.
A tenth exemplary embodiment is a catalytic combustion apparatus, in which the air intake/ejector is provided with a quantity-of-flow adjustable means for varying the quantity of intake air thereby to improve combustion characteristics during catalytic combustion by increasing the ratio of excess air upon transition to catalytic combustion and allow reduction in size and thickness.
An eleventh exemplary embodiment is a catalytic combustion apparatus, in which the valve comprises a solenoid valve and a control apparatus, and the control apparatus controls the solenoid valve in a manner such that the control apparatus temporarily closes the solenoid valve after an ignition device has operated and subsequently opens it again thereby to assure smooth transition to catalytic combustion and allow reduction in size and thickness.
A twelfth exemplary embodiment is a catalytic combustion apparatus, in which the valve is provided with a quantity-of-flow adjustable means for adjusting the quantity of intake air, and the quantity-of-flow adjustable means is fully opened to allow the ignition device to ignite, and throttles back the quantity of supply of fuel gas after ignition thereby to assure stable ignition and transition to catalytic combustion and to allow reduction in size and thickness.
A thirteenth exemplary embodiment is a catalytic combustion apparatus, in which the valve comprises a solenoid valve and a control apparatus, and the control apparatus controls the solenoid valve to be temporarily closed based on a signal from a temperature detecting means disposed in the combustion chamber thereby to assure ignition and stable transition to catalytic combustion and to allow reduction in size and thickness.
A fourteenth exemplary embodiment is a catalytic combustion apparatus, in which the exhaust port is disposed on the combustor in such a manner that it will not overlap the combustion chamber and will come to a position opposite the direction of ejection of mixed gas into the mixing chamber thereby to allow uniform catalytic combustion through uniform passage of the mixed gas through the catalyst for combustion and reduction in size and thickness.
A fifteenth exemplary embodiment is a catalytic combustion apparatus, in which a burner port area adjustable means provided on the combustor is operable with a signal from a temperature detecting means provided in the vicinity of the burner port thereby to allow instantaneous transition to catalytic combustion by reducing the open area of the burner port upon reaching a catalytic combustion enabling temperature.
A sixteenth exemplary embodiment is a catalytic combustion apparatus, in which the catalyst for combustion is affixed to the combustion chamber with a space between itself and the inner wall of the combustion chamber thereby to reduce the quantity of transfer of the heat generated by the catalyst for combustion to the combustor and to keep the temperature of the outer wall low even when the apparatus is downsized to obtain user-friendliness.
A seventeenth exemplary embodiment is a catalytic combustion apparatus, in which the catalyst for combustion is provided with a thickness adjustable means for adjusting thickness thereby enabling adjustment of the quantity of heat transfer to the combustor in order to obtain a wide temperature control range.
An eighteenth exemplary embodiment is a catalytic combustion apparatus, in which a catalytic body formed into the shape of a flat plate of which the area of the planar surface is greater than the area of the side is disposed inside the combustion chamber and a gas passage to allow flow of mixed gas in the lateral direction is provided on the catalytic body, thereby making the burner height low and providing a small sized and thin catalytic combustion apparatus.
A nineteenth exemplary embodiment is a catalytic combustion apparatus, in which a straight cylindrical gas passage communicating with the outlet of the mixing chamber is provided and the inlet of the combustion chamber is made to communicate with a side of the gas passage so that the mixing chamber and the catalytic body are disposed in parallel to each other thereby to shorten the burner length to obtain a compact design.
A twentieth exemplary embodiment is a catalytic combustion apparatus, in which the length of the straight cylindrical gas passage is made longer than the width of the inlet of the combustion chamber and the inlet of the combustion chamber is disposed inside the straight cylindrical gas passage thereby to allow more uniform mixing of fuel gas and air and to uniformly supply the mixed gas to the catalytic body.
A twenty-first exemplary embodiment is a catalytic combustion apparatus, in which a gas flow resistant body is provided in the outlet of the mixing chamber to reduce the velocity of mixed gas flow thereby to slow down the velocity of the mixed gas flow inside the straight cylindrical gas passage and to uniformly supply the mixed gas to the catalytic body.
A twenty-second exemplary embodiment is a catalytic combustion apparatus, in which a gas rectifier is provided in the inlet of the combustion chamber to rectify the flow of mixed gas thereby to rectify the mixed gas that comes out from the straight cylindrical gas passage and to uniformly supply the mixed gas to the catalytic body.
A twenty-third exemplary embodiment is a catalytic combustion apparatus, in which the catalytic body supports a catalyst on a corrugated carrier made by folding a thin metal sheet into the shape of continuous waves thereby to provide a catalytic body which is simple in shape, simple to continuously. process, and superior in mass producibility.
A twenty-fourth exemplary embodiment is a catalytic combustion apparatus, in which the catalytic body supports a catalyst on a multilayer carrier fabricated by alternately stacking a corrugated sheet made by folding a thin metal sheet into the shape of continuous waves and a flat thin metal sheet thereby to secure high combustion efficiency even when the amount of combustion is increased.
A twenty-fifth exemplary embodiment is a catalytic combustion apparatus comprising a nozzle for ejecting a fuel gas, a mixing chamber for making a mixed gas by mixing the fuel gas ejected from the nozzle and air, and a combustion chamber having a catalytic body inside it for burning the mixed gas, in which the combustion chamber is comprised of discrete components which can be divided into the mixing chamber, nozzle, and catalytic body, thereby to provide a small and thin catalytic combustion apparatus with a low burner height.
A twenty-sixth exemplary embodiment is a catalytic combustion apparatus, in which the combustion chamber comprises a plurality of components divided by a plane approximately in parallel with the direction of ejection from the nozzle thereby to lower the height of the combustion chamber.
A twenty-seventh exemplary embodiment is a catalytic combustion apparatus, in which a subassembly integrating the combustion chamber and the nozzle is secured by sandwiching a plurality of components that comprise the combustion chamber thereby to downsize the mixing chamber and the nozzle.
A twenty-eighth exemplary embodiment is a catalytic combustion apparatus, in which a temperature detecting means for detecting the temperature of the combustion chamber and a control unit for controlling the quantity of ejection of the fuel gas based on the output of the temperature detecting means are provided. The temperature detecting means is secured by a plurality of components that comprise the combustion chamber thereby to simplify the structure of affixing the temperature detecting means to the combustion chamber, downsize the combustion chamber, as well as to assure securing of the temperature detecting means by sandwiching it with the combustion chamber.