US2102153A - Ignition apparatus for closed-sys - Google Patents

Description

J. W. HAYS Dec. 14, 1937;

- IGNITION APPARATUS FOR CLOSED SYSTEM FLUENT COMBUSTIBLE BURNERS Filed March 18, 1933 INVENTOR WITNE Patented Dec. 14, 1937 UNITED STATES IGNITION APPARATUS FOR CLQSED-SYS- TEM FLUENT: CODIBUSTIBLE BURNERS Joseph Hays, Tulsa, Okla.

paratus for heater systems using mixtures of air and fuels, such as gas, liquid, vapor or powdered fuel, and is particularly suitable for use with 5 heaters of the fiameless combustion type.

Flameless combustion heaters, also known as catalytic combustion and surface combustion heaters, operate on the principle that when a combustible mixture of fuel and oxygen is contacted With a mass of materialheated to incandescence, the mixture will burn without flame on the surface of the incandescent mass.

Such heaters are known in the art but have never heretofore been commercially practical because of the fact that they are unsafe in operation. Due to the manner in which the mixture of the fuel and air is fed to the combustion zone, there has been a tendency in the prior heaters to flash-back and back fire, thereby causing explosions in the heater and in the fuel feeding system.

In my co-pending application, Serial No. 653,468, filed January 25, 1933, I have disclosed a construction which overcomes the dangers of explosions in surface combustion typesof heaters.

Difiiculties have been encountered in igniting the mixture of fuel and oxygen in the prior sur.- face combustion heaters. There are several causes for the failure of known type'of igniting devices to operate satisfactorily in these systems. The first of these is that the gases and fuel in a relatively cool condition are injected at high velocities into the combustion chamber and zone of combustion. Suchhigh velocities tend to cool below a temperature at which fuel can be ignited, igniters of the hot wire type situated in the path of flow of the fuel mixture.

A second cause of failure of igniters of both the heated wire and spark type is that, if located within the combustion chamber, they are also so situated with respect to the refractory material upon which fiameless combustion takes place, that heat radiations fuse and render them inoperative.

An object of the present invention is to produce an ignition construction which will be situated out of the path of how of the fuel and combustion supporting gas, so that it will not be cooled by the passage of the elements making up the combustible mixture.

A further object of the invention is to introduce an ignition system into the heater in sucha position that it is out of the path of radiations from the combustible mixture and shielded by additional refractory material, so that heat 1933, Serial No. 661,627

radiations cannot strike directly upon the ignition element.

The objects of the invention have been achieved by situating the ignition element in a recess or housing opening into but not within the combustion chamber. The housing is preferably located closely adjacent the surface of the refractory material on which combustion of the, fuel takes place. The housing preferably is located between the combustion zone and the fuel and combustion-supporting gas inlets of the system, so that as the fuel mixture is mixed at the surface of the refractory, excitation of the ignition device will cause the fuel to ignite initially at the surface of the refractory. The housing for the igniting device preferably extends from the heating chamber through a water jacket surrounding the heating chamber, so that the ignition system is cooled by circulation of water through the water jacket while the heating system is operating.

The igniting element is protected from radiations from the refractory mass in the combustion zone by a layer of additional refractory material of lower heat conductivity placed adjacent to and covering the opening between the housing and the combustion chamber. This refractory of lower heat conductivity is cooled somewhat on the fuel inlet side by the incoming fuel and combustion-supporting gas mixture. Because of its lower conductivity, the refractory layer does not permit the conduction of heat transmitted by radiation from the incandescent refractory to the adjacent side of this refractory layer.

I have also provided means for allowing a portion of the mixture of. fuel to pass through the housing of the igniting device to outer air, in 7 order that positive contact may be had between 'the'ignition device and the fuel mixture. The purpose of this construction is to avoid possible formation of a pocket of non-combustible gas or vapor around the igniting device which would prevent ignition of the fuel mixture.

For a better understanding of the present invention, reference may be had to the accompanying drawing, in which Figure 1 discloses a section of a surface combustion type of heater partly broken away with a typical embodiment of my igniting device therein also-shown in the section.

One embodiment of my heating device is shown as applied to a heating system of the type disclosed in my co-pending application Serial No. 653,468, which 7 may consist of a combustion chamber or combustion tube CT, packed with pieces of a refractory material Re upon the surfaces and in the interstices of which surface combustion takes place. The combustion chamber CT is enclosed in a jacket J, retaining a fluid Fd between the jacket and the combustion tube CT for cooling both the combustion chamber and heating the fluid. Fuel and a combustible gas may be injected into the combustion tube CT and onto the surface of the refractory Re, by means of injection nozzles and combustion-supporting gas injection orifices, which may be suitably of the type disclosed in my co-pencling application Serial No. 653,468.

Projecting through and mounted in the walls of combustion tube CT and water jacket J is a housing or jacketing nipple WJ of any suitable material which may be fixed in the jacket and tube. The housing WJ is so disposed that it will be completely surrounded by the fluid in jacket J and cooled thereby during the operation of the device. Threaded into the nipple WJ is a plug Pg preferably made of some refractory material, such as the porcelain used in jackets of spark plugs containing a centrally located porcelain insulating tube PI, through which extend two conductors CW and CW connected to any suitable source of electrical energy. Bridging the inner ends of the connecting wires CW and CW is a wire HW preferably made of platinum which may be heated or excited by the passage of electric current therethrough. The porcelain insulating tube PI is of such a length that the hot wire HW will be situated externally of but adjacent to the combustion tube or chamber CT and therefore out of the direct path of the fuel and combustion-supporting gas injected into or onto the refractory Refrom the injecting nozzles. In initiating combustion of the combustible fuel mixture, electric current is passed through the hot wire, heating it to a point where the fuel mixture will be ignited and caused to burn, thereby heating the refractory mass Re to incandescence.

In order to render the action of the hot wire HW in igniting the fuel mixture more certain, provisions are made for allowing a small portion of the fuel mixture to pass around the hot wire I-IW, through the housing WJ and out of the plug Pa. The purpose of this construction is to avoid an accumulation or pocket of non-combustible gas in the housing WJ which would prevent ignition of the fuel mixture in the combustion chamber. A suitable construction for allowing the mixture to pass by the heated wire HW and to the open air may consist of a screw-threaded plug P9 engaged in a threaded aperture in the igniter plug Pg. The plug P9 may be removed and replaced as desired, and is preferably replaced after ignition of the fuel mixture hastaken place.

In order to screen or shield the hot wire from radiations from the refractory Re, during combustion of the fuel mixture on the surface of the refractory, I have placed a layer of relatively low heat conductive refractory Ref such as for example, fused magnesia in line with the housing WJ In addition to its shielding function, the refractory Ref also will maintain a zone of lower temperature adjacent the hot wire HW because of the cooling effect that the mixture of fuel impinging upon the surface of the refractory Ref from the injecting nozzles and passing along the channels MF between the refractory elements will have.

It will thus be seen that I have produced an igniting device which is positive in its operation and which will have extended life over long periods of operation of the heating system, due to the fact that it Will not be destroyed or rendered ineffective by excessive heating.

It will further be understood that there can be many variations in the specific construction of my heating unit without varying from the inventive concept thereof and therefore the embodiment disclosed should be considered as illustrative only and not as limiting the scope of the following claims.

I claim:

1. A heater, adapted to burn a fluent explosive mixture, comprising a combustion chamber, a refractory catalyst in said combustion chamber, means for supplying an explosive mixture to said combustion chamber, a recessed housing opening into said combustion chamber, a Vent from said housing to the outside air, a movable stopper in said vent, and a hot wire igniting element in said housing.

2. A heater comprising a combustion chamber, a refractory catalyst in said combustion chamber, a housing continuously open for passage of air and gas from or into said combustion chamber, a heating element in said housing, a refractory material of low conductivity in said combustion chamber opposite said heating element, means of producing a fluent combustible mixture and of causing same to flow into said combustion chamber against said refractory material and over said catalysts and means for raising the temperature of the heating element to the igniting point of the said combustible mixture, together with means for diverting a portion of the mixture and causing same to flow over said heating element and escape to the outside air.

3. A heater comprising a combustion chamber packed with a refractory catalyst, a packing of refractory material of low heat conductivity at the entrance to said combustion chamber, an igniting device adjacent to said refractory material, and means for causing streams of air and gas to be mixed by impingement upon said refractory material, together with means for diverting a portion of the mixed stream and causing same to flow over said igniting device and escape to the outside air.

4. A heater comprising a combustion chamber packed with a refractory catalyst, a packing of refractory material of low heat conductivity positioned adjacent the fuel admission opening thereto, an igniting device adjacent to said refractory material of low heat conductivity and located in a housing opening toward said combustion chamber, an outlet through said housing to the open air, means for causing streams of gas and air to mix by impingement upon said refractory material of low heat conductivity and to flow in part over said igniting device.

5. In a heater having a combustion chamber, an apertured refractory mass in said chamber and means for introducing fuel and combustionsupporting gas into said chamber for impingement and mixing on the surface of said mass; the combination of means for igniting the fuel, a housing for said igniting means opening into said chamber adjacent the surface of the refractory mass and supporting said igniting means in a position exteriorly of the chamber, a vent in said housing for allowing passage of fuel and gas from said chamber through and out of said housing, and means for exciting said igniting means to initially ignite fuel in said housing.

6. In a heater having a combustion chamber, an apertured mass of refractory material therein, and means for introducing fuel and combustion-supporting gas into said chamber for combustion on surfaces of the refractory material; the combination of means for igniting the fuel, a housing for said igniting means opening into said chamber between said mass of refractory material and said fuel introducing means, and supporting said igniting means exteriorly of said chamber, a vent in said housing for allowing passage of said fuel and gas from said chamber through said housing, means for exciting said igniting means to initially ignite fuel in said housing, and a layer of refractory material of lower heat conductivity than the refractory mass disposed in front of the housing for reducing the temperature in the housing during combustion of the fuel in said chamber.

7. In a heater having a combustion chamber containing an apertured mass of refractory material and means for injecting fuel and combustion-supporti'ng gas under pressure into said chamber and against a surface of said refractory mass to form a combustible mixture; the combination of means for igniting said combustible mixture comprising a housing opening into said chamber adjacent said refractory mass surface, a vent in said housing spaced from the chamber, allowing part of said mixture to pass from said chamber through the housing and to the outer air, a heating unit in said housing between the chamber and said vent, and means for energizing said heating unit to ignite the mixture in said housing.

8. In a heater having a combustion chamber containing a mass of apertured refractory material, and means for injecting fuel and combustion-supporting gas under pressure into said chamber and against a surface of said refractory material to form a combustible mixture; the combination of a housing opening into said chamber adjacent said surface of said refractory material, a vent spaced from said chamber in said housing, allowing part of the mixture to pass from said chamber through said housing and to the outer air, igniting means in said housing between said chamber and said vent and means for exciting said igniting means toignite the mixture in said housing.

JOSEPH W. HAYS.

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