Patent Application
20050239006
The present invention relates generally to an improved burner system and method for providing multiple stages of fuel. More particularly, the present invention relates to a multi-stage burner.
Gas fired hot air furnaces have long been used to heat spaces in both residential and commercial setting. Most conventional gas fired furnaces include a plurality of heat exchangers spaced apart to allow air flow therebetween. The heat exchangers define an internal flow path for hot combustion gases supplied by burners. Heat transferred through the heat exchangers may be used to effect heating of a particular area. The furnace works by sending hot combustion gases through the heat exchangers and blowing room air over the heat exchangers so as to heat the air from the furnace into the area to be heated.
In order to control the air temperature of the hot air exiting the furnace and into the room, you control the temperature of the heat exchangers. This is typically done by controlling the hot combustion gases flowing through the heat exchanger. An increase or decrease in the combustion gases can be affected by controlling the combustion flame exiting the burner. A known burner arrangement is shown and described in U.S. patent application Ser. No. 10/299,479, filed Nov. 19, 2002, entitled “One Shot Heat Exchanger Burner”. This application is incorporated by reference herein for all purposes.
As schematically shown in
It may be appreciated that regulation or modulation of the fuel air mixture entering the burner can control the flame and thereby the temperature of the heat exchangers. It has been found that using burners of the type shown in
To reduce such frequent cycling, the prior art has also seen the use of multiple burners in a single furnace. Multiple burners allow cycling among one or more burners so as to increase the modulation. However, the use of multiple burners in a single furnace is not a cost effective solution. Also, even in multiple burner situations, frequent on/off cycling results in heat exchangers seeing both hot and cold temperatures. When a heated heat exchanger cools, it forms undesirable condensation within the internal cavity of the heat exchanger. Any contaminants in the air, when condensed, can form acids which reduce the life of the heat exchanger.
It is, therefore, desirable to provide a fuel fired furnace which allows increased modulation without known undesirable effects and without the need to employ multiple burners in a single furnace.
The present invention provides an apparatus and a method for providing multiple stages of fuel. The apparatus includes a burner for production of a flame at a face of the burner; wherein the burner has a plurality of longitudinally adjacent burner chambers opening to the burner face. Also included are a plurality of heat exchangers positioned across the face of the burner to receive the flame. A divider is placed in the burner for dividing the burner chambers into a first section and a second section, wherein the second section includes the plurality of burner chambers being greater in number than the first section. Additionally, a first fuel supply line supplies fuel to the first section of the burner chambers and a second fuel supply line supplies fuel to the second section of the burner chambers, wherein the first supply line supplying fuel to the first section is independent of the supply line of the fuel to the second section by the second supply line. Further, an igniter is positioned at the burner face for igniting the fuel supplied by the first supply line to the first section of the chambers at the face.
In its method aspect, the present invention provides multiple stages of fuel to a furnace. A burner is divided into a first and second section. Air temperature is monitored to determine heating needs and fuel is supplied to at least one section of the burner independent of the supply to said other section. The fuel at the supplied section is ignited. The other or both sections may also be ignited depending upon the heating needs.
Referring to
The burner 20 includes a face 21 where the flame is produced. The burner 20 also includes plurality of longitudinally adjacent burner chambers 30 having one side of the openings at the face 21 and the other side of the openings connected to venturi tubes 24 and 25. The burner 20 is designed in such a manner that it preferably splits into two separate sections 20a and 20b with a divider 29. The divider 29 divides the burner 20 in such a manner that section 20a includes ⅔ of the total number of chambers in the burner 20 and section 20b includes ⅓ of the total number of chambers in the burner 20. Therefore, section 20 is able to hold and provide a ⅔ capacity of the gas and chamber 20b is able to hold and provide ⅓ capacity of the gas. Each of the sections of the burner 20a and 20b operate independent of each other as will be described in greater detail below.
A modulator 28 regulates the quantity of fuel being supplied to the burner sections 20a and 20b via the venture tubes 24 and 25 respectively. Venturi tube 24 acts as a fuel gas supply line for supplying fuel to the first section 20a and the venturi tube 25 is a fuel gas supply line for supplying fuel to the second section 20b.
Referring now also to
In the arrangement being described with respect to
Attached to upper wall 20c of burner housing 20 and projecting outwardly therefrom is a venturi tube 24. The venturi tube 24 is, in one particular arrangement, as shown in
Referring again to
In one embodiment of the present invention in operation, a three stage heating system is disclosed. In the first stage, under computer control modulation gas valve 28, fuel is supplied through valve 27 to venturi tube 25, where a quantity of air is also introduced. The supplied fuel and air mixture are drawn into the burner section 20b as a result of the suction pressure produced by an induction draft fan (not shown) which is connected to the exhaust ports of the heat exchangers 22. The air/fuel mixture drawn through the burner face 21 is ignited by igniter 23 causing combustion of the air/fuel mixture in the chambers of section 20b. As a result, only ⅓ section of the burner 20 i.e. only section 20b lights at high fire causing the heat gases to be forced preferably into the associated heat exchangers. At this stage, the burner is modulated between 50 to 100% of the ⅓ capacity of burner section 20b. The air temperature of the burner 20 is preferably monitored by a computer (not shown) for heating the temperature of heat exchanges 22 so as to monitor exiting air temperature at a controlled set point temperature. The temperature is controlled or regulated by modulating the gas valve/pressure into venturi tube 25. If more heat is needed to meet set point temperature, valve 28 is opened to allow an additional flow of fuel. If still more heat is needed to meet set point temperature, valve 26 is opened in the second stage. The fuel flows into the venture tube 24 and is mixed with air. The air/fuel mixture is drawn into the chamber of burner section 20a, which picks up the flame from the burner section 20b. The gas pressure is maximum during this interval to assure flame carry over to the burner section 20a, which occupies ⅔ of the burner capacity. In this second stage, the burner is modulated between 50% to 100% of the ⅔ capacity of the burner section 20b. The heat gas from the chambers 30 of burner chamber 20a is forced into the heat exchangers 22. At this time, the burner 20 is running at full capacity with gas being provided by chambers 30 of both sections 20a and 20b. However, if only ⅔ capacity of the gas is required, burner section 20b can be turned off by the valve 27. A period of 20 second delay is required to assure flame carry over prior to disabling the burner section 20b.
In another case scenario, while the burner section 20a remains active, when the heating set point is satisfied, there may preferably be no need to keep the burner section 20a (of ⅔ capacity) active. At this point, valve 27 is opened. Again, the gas pressure is maximum at this interval to assure flame carry over from burner section 20a to 20b. Both burner sections 20a and 20b remain enabled and the burner 20 is running at full capacity for about twenty seconds. After the twenty second cycle interval, valve 26 is closed, thereby disabling the burner chamber 20a.
The third stage of the heating system occurs when both valves 26 and 27 are opened and both the burner sections 20a and 20b are providing gas to the heat exchangers 22. This case scenario occurs when 100% capacity of the ⅔ section of burner 20a is not enough to heat the heat exchanger 22. In this third stage, burner 20 is modulated to 50 to 100% of the 3/3 or full capacity of the burner 20.
Therefore, you can now control the heat at the heat exchangers 22 by modulating the temperature of the combustion gas into the heat exchanger 22. This method is unique in that each burner is only modulated to 50% of capacity while maintaining gas thermal efficiencies. You can use ⅓, ⅔ or 3/3 capacities of a single split burner to provide 6:1 gas modulation as shown in Table 1 herein below.
It should now be appreciated that the single split burner design arrangement, as described herein, provides significant advantages over the conventional multiple burner configurations. For example, an increased modulation can be obtained utilizing only one single burner. Also, cost savings may be realized as a result of the elimination of the gas manifold used in the multiple burner arrangement as well as a reduction in the number of independent burners. In addition, the single burner replaces multiple orifices with a single orifice that more effectively meters the proper amount of combustible air/gas mixture flowing through the burner face. Furthermore, the undesirable condensation is greatly reduced due to less cycling between hot/cold in heat exchangers.
Having described the preferred embodiments herein, it should now be appreciated that variations may be made thereto without departing from the contemplated scope of the invention. Accordingly, the preferred embodiments described herein are deemed illustrative rather than limiting, the true scope of the invention being set forth in the claims appended hereto.
