Ignition sequence and electrode tip geometry for oil-fired furnace

Abstract

The ignition sequence of a conventional oil-fired furnace is altered to achieve significant fuel economy. In response to a thermostatic call for heat, a short two to five second delay interval ensues during which the ignition electrode pair are energized to cause an arc which associates with the nozzle surface to burn off unburned fuel debris and, in effect, clean the nozzle, electrode tips and warm the spark. At the termination of this short interval, the oil pump and air blower are energized to achieve combustion of oil mist and air within an association ignition chamber.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

BACKGROUND

A typical oil-fired furnace is configured with a combustion chamber which confronts an oil ejecting nozzle. That nozzle is operationally associated with an oil pump and squirrel cage fan driven in common by a burner motor. Oil under pressure is caused to atomize or become a fine mist as it exits the orifice of the nozzle. Simultaneously with burner motor startup, two electrodes are energized, for example, at 10,000 volts, to create an arc or spark function to ignite the misted oil. A photocell is employed to monitor for such ignition for thirty seconds. Where no ignition occurs within that interval, the system is locked out and must be manually reset to attempt a restart.

The tips of the two ignition electrodes generally are mounted under a specification geometry. In this regard, they are spaced apart ⅛ inch symmetrically above the nozzle orifice while being spaced above it ½ inch and forwardly of it ⅛ inch.

The simultaneous energization of the burner motor and electrodes is in response to a thermostat call for heat made to a primary control or relay box. Simultaneous electrical drive to the electrodes is provided from an ignition transformer typically mounted adjacent the primary control. Oil supplied to the oil pump is from a storage tank and supply line containing a shutoff valve and oil filter.

Before a heating season commences, these furnaces are serviced. Typically encountered will be a build-up of insufficiently ignited or un-ignited fuel debris disposed over the front of the nozzle and electrodes. That build-up can be a cause of high fuel consumption and/or insufficient heat. A standard procedure accordingly is to replace the nozzle. Additionally, the specified geometry for the electrode tips is checked and adjustment made where required.

SUMMARY

The present disclosure is addressed to an oil-fired furnace system and method for its operation. Prior to oil pressure and fan air startup in response to a thermostat call for heat, a short, two to five second delay is interposed while the ignition components of the system are activated. During this short delay interval, an arc is generated between the tips of an electrode pair. That arc extends about the forward portion of a nozzle which otherwise would be expressing oil to burn off any unburned fuel debris, cleaning electrode tip and warming the ignition spark. To enhance this automatic cleansing feature, the otherwise standard tip geometry of the ignition electrode pair is altered. In this regard, the electrode tips are arranged further apart laterally; closer to the nozzle vertically; and closer thereto horizontally. However, the fuel ignition function of the electrode tips is not impaired inasmuch as fan driven air, which is provided with nozzle ejected oil mist, functions to blow the pre-existing electrode generated arc into the path of oil mist. Accordingly, ignition of this oil mist and combustion air combination is realized.

The overall result of the system and method at hand is the preservation of burner system nozzles and the realization of a quite substantial fuel economy. Such significant advantage is realized with the addition of a time delay component and minor adjustment of the tip geometry of the system electrode function.

The discourse at hand provides a method for operating an oil-fired furnace incorporating a nozzle, a motor driven fan and oil pump, and electrode pair extending to mutually spaced tips, and a controller responsive to a thermostat call for heat to commence an ignition sequence, comprising the steps:

(a) providing the electrodes with a tip geometry effective when energized to burn off unburned fuel at the nozzle;

(b) responding at the controller to a thermostat call for heat to energize the electrode pair; and

(c) then energizing the motor driven oil pump and fan only after a delay effective to permit the energized electrode pair to burn off unburned fuel from the nozzle.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

The invention, accordingly, comprises the system and method possessing the construction, combination of elements, arrangement of parts and steps, which are exemplified in the following detailed disclosure.

For a fuller understanding of the nature and objects of the invention, reference should had to the following detailed description taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of the burner components and combustion chamber of an oil-fired furnace;

FIG. 2 is a flowchart describing the ignition sequence of a conventional oil-fired burner;

FIG. 3 is a schematic front view of the nozzle and electrode pair components of a conventional oil-fired burner;

FIG. 4 is a schematic front view showing the tip geometry of the electrodes and nozzle as reconfigured in accordance of the present teachings;

FIG. 5 is a flowchart illustrating the revised ignition sequence of the present system and method;

FIG. 6 is a schematic block diagram of the present control system;

FIG. 7 is a schematic top view of a nozzle and electrode pair according to the present teachings showing an arc as it is used to remove unburned fuel debris from the surface of a nozzle; and

FIG. 8 is a reproduction of FIG. 7 but showing the effect of fan-blown air on an ignition arc.

DETAILED DESCRIPTION

In the discourse to follow, a conventional oil-fired furnace system is described along with a discussion of the conventional and specified ignition sequence and electrode tip geometry is set forth. Then, the advantageous electrode tip geometry and ignition sequence is set forth which improves fuel burning efficiency to a significant extent.

Referring to FIG. 1, the pertinent portions of an oil-fired furnace system are represented in general at 10. System 10 shows portions of a furnace housing 12 and a combustion chamber 14 disposed therein. The oil burner operatively associated with housing 12 and combustion chamber 14 is represented in general at 16. Burner 16 operates in conjunction with one or more thermostats symbolically represented at 18. Thermostat 18 is electrically and operationally associated with the burner 16 as represented at cable 20. Cable 20 extends to a primary control or controller 22 which performs in conjunction with a relay box 24 attached above it. When thermostat 18 calls for heat, primary control 22 and associated relay box 24 actuates or turns on a burner motor 26. Motor 26 is configured to simultaneously or in common drive a squirrel cage type fan within fan housing 28 as well as an oil pump 30. Oil pump 30 pumps oil from an oil supply source (not shown) which provides oil through an oil supply line 32 which typically incorporates a shutoff valve (not shown) and an oil filter 34. Filtered oil is directed to the pump 30 via line or conduit 36. While the fan blows air into the combustion chamber 14, the pump 30 draws oil from the noted storage tank and then expresses it out the orifice of a nozzle 38. Nozzle 38 forms a fine mist or atomization of the oil that mixes with blower air entering the combustion chamber 14 in somewhat standardized systems, with the actuation of motor 26. Controller 22 and associated relays 24 energize an ignition transformer 42 which functions to boost household voltage from 120 volts (USA) to 10,000 volts which are sent to paired electrodes represented generally at 44, across which a spark or arc is caused to be generated, which ignites the oil-air mixture represented symbolically and in general at 46. Combustion gases exit through a stack at the back of the furnace (not shown). In the event of a misfire, a light-sensing photoelectric cell shuts down the system until a reset button on the relay box is pressed. System 10 additionally is illustrated incorporating a delay circuit 48 electrically associated with the controller 22 as represented at cable 50.

Referring to FIG. 2, the ignition sequence heretofore utilized in connection with controllers as at 22 is set forth in flowchart fashion. In the figure, block 60 indicates that a call for heat has been made by a thermostat as at 18. Then, as represented at arrow 62 and block 64, the controller as described at 22 is enabled. Upon such enablement, as represented at arrow 66 and block 68, the ignition components are energized, for example, as represented in conjunction with ignition transformer 24. Simultaneously, as represented at arrow 70 and block 72, a photocell functions to commence monitoring for ignition for an interval of thirty seconds. Again simultaneously, as represented at arrow 74 and block 76, a motor as at 26 is started or energized which functions to drive the combustion blower or fan 28 and the fuel pump or oil pump 30. As represented at arrow 78 and block 80, at the termination of the noted thirty seconds of monitoring, a determination is made as to whether ignition is present. In the event that it is not, then as represented at arrow 82 and block 84, the system is locked out and may be reactivated by the user by actuating a reset button or switch. This reset function is represented at arrow 86, block 88 and loop arrow 90. Loop arrow 90 is seen to extend to arrow 66.

Returning to the query posed at block 80, where ignition is present within the thirty second monitoring interval, then as represented at arrow 92 and block 94, combustion is continued while the call for heat by thermostat 18 remains.

In conjunction with the prior art or standardized ignition sequence represented in FIG. 2, servicing personnel are called upon to assure that the tip geometry of the electrode pair 44 is within specification. In this regard, referring to FIG. 3, a nozzle is represented generally at 100 having a forward surface 102 and a centrally disposed orifice 104 through which oil in the form of a mist is expelled. Associated in igniting relationship with the nozzle 100 is an electrode pair represented generally at 106 having somewhat pointed tips 108 and 110. Servicing personnel are called upon to assure that tips 108 and 110 are spaced apart ⅛ inch and are spaced above orifice 104, ½ inch. Additionally, assurance is made that tips 108 and 110 are spaced forwardly of forward surface 102, ⅛ inch. With this tip geometry, in accordance with standard procedure, an arc is cause to occur between tips 108 and 110 while simultaneously, oil is expelled from orifice 104 and blown air or combustion air is directed through the arrangement. With such geometry and with the ignition sequence described in connection with FIG. 2, for a given heating season, unburned fuel will accumulate at nozzle surface 102 as well as a tapered region extending rearwardly therefrom as shown at 112. Because of this buildup of unburned oil debris, nozzles as at 100 typically are replaced at or before the end of a heating season.

The conventionally specified tip geometry represented at FIG. 3 is altered with the present teaching. Looking to FIG. 4, a nozzle is represented in general at 120. As before, the nozzle 120 includes a forward surface 122 incorporating a symmetrically disposed orifice 124 through which oil under pressure and in mist form is expressed. A tapered region is represented at 126 and an electrode pair is represented generally at 128. The tips 130 and 132 of electrode pair 128 are seen to be mutually spaced apart a distance of ¼ inch as contrasted to ⅛ inch described in connection with FIG. 3. Additionally, the tips 130 and 132 are seen to be spaced ¼ inch above orifice 124 as opposed to ½ inch as described in conjunction with the prior art of FIG. 3. Further, the tips 130 and 132 are spaced forwardly of forward surface 122 about 1/16 inch. In this regard, in the course of development of the instant system and method a nickel coin was used for deriving this forward spacing. The tip geometry represented in FIG. 4 contributes to the function of burning off unburned fuel at nozzle 120, cleaning electrode tip and warming the ignition sparks.

Referring to FIG. 5, a flowchart is represented showing an ignition sequence which further contributes to this function of burning off otherwise unburned fuel debris which collects at the nozzle. Looking to that figure, block 140 calls for the provision of an electrode geometry (tip) effective to burn off unburned fuel debris from the nozzle. That tip geometry has been discussed immediately above in connection with FIG. 4. Next, as represented at arrow 142 and block 144, a thermostat as at 18 will have called for heat. In response to this call, as represented at arrow 146 and block 148 a controller as at 22 is enabled and, as represented at arrow 150 and block 152, the controller 22 energizes the ignition, for example, energizing the ignition transformer 42. Simultaneously, as represented at arrow 154 and block 156, a photocell monitoring for ignition interval commences. As before, that interval typically is thirty seconds. With the commencement of energization of the ignition system at the electrode pair, as represented at arrow 158 and block 160, a delay is commenced while the arc between the electrode tips continues to be created. The delay is selected to effect a burning off of any unburned fuel debris, cleaning electrode tips and warming the spark which may have collected upon the nozzle. In this regard, a typical delay will be about two to five seconds. Accordingly, as represented at arrow 162 and block 164 a determination is made as to whether the delay is completed, for example, at four seconds. In the event that it is not completed, then as represented at loop arrow 166 the delay will continue. At the termination of the fuel cleansing delay, for example, at four seconds, as represented at arrow 168 and block 170 a conventional ignition sequence continues with the starting of motor 26 which will, in turn, cause the driving of fan 28 and fuel pump 30 to derive a mist of oil to be driven into the combustion chamber 14. As is apparent, the thirty second monitoring for ignition will have continued beyond the delay of four seconds. Accordingly, as represented at arrow 172 and block 174, the controller determines whether ignition is present within this thirty second envelope of time. In the event that it is not present within that thirty seconds, then as represented at arrow 176 and block 178, the burner system is locked out and cannot be reset until a user actuates a reset button or switch. Accordingly, as represented at arrow 180 and block 182 with the actuation of a reset switch, as represented at arrow 184 leading to arrow 150, the ignition features creating an arc are reactivated.

Turning to FIG. 6, the control components of the instant system are illustrated in block diagrammatic fashion. In the figure, the primary controller function is represented at block 190 which receives 120 volts of household power as represented at arrow 192. Controller 190 responds to a call for heat from a thermostat as represented at block 194 and arrow 196. A photocell is used to detect the presence or absence of ignition of the misted oil. That photocell is represented at block 198 and its input to controller 190 is represented at arrow 200. Controller 190 responds to the input of thermostat 194 to activate or energize the ignition circuit represented by the electrodes 128 in FIG. 4, such response being represented at arrow 202 and block 204. It may be recalled that the fuel pump and fan functions are not actuated at this juncture in the startup to provide heat. The arc generated by the igniter is used during a short delay of two to five seconds to clear the nozzle of unburned fuel debris cleaning electrode tips and warming the spark. This two to five second delay is represented in the figure at arrow 206 and time delay block 208. Such time delays are commercially available, for example, one being marketed as a model AK05-120 by Aerotronics, Inc. of Cazenovia, N.Y. 13035. Following this short delay as represented at arrow 210 and block 212, the fuel pump and fan motor is actuated. It further may be recalled that the photocell 198 will monitor for the development of actual ignition of the fuel mist for a thirty second interval. Should that thirty second interval expire without the presence of ignition then the system will be shut down.

With the revised electrode tip geometry described in connection with FIG. 4, during the initial two to five second delay the arc extending between the tips of the electrode pair will extend about the nozzle. Turning to FIG. 7, a nozzle is again represented in general at 220. Nozzle 220 is shown having an orifice 222, a forward surface 224 and a tapered region 226. The associated electrodes are represented in general at 228 and 230 having tips arranged with the geometry of FIG. 4 respectively at 232 and 234. As a consequence, an arc is evoked which moves about the surface of tapered region 226 and forward region 224. Such an arc is represented in the figure at dashed line 236. Observing a demonstrator of the instant system, it appears that from time to time the arc extends into the nozzle itself. Notwithstanding the arc structuring, it is observed that any unburned fuel or like debris is cleansed from the nozzle end, also cleaning electrode tips and warming ignition spark.

With such relocation of the arc, one may question if the arc is in position to carry out an effective ignition of the oil mist and air combination occurring about two to five seconds from the initial arc development. Turning to FIG. 8, the condition of nozzle 220, electrodes 228 and 230 at the termination of the two to five second delay interval is schematically represented. In the figure, combustion is represented generally at 240 in conjunction with fan driven air as represented at arrow 242. The force of this fan driven air represented at 242 will move the arc to a generally bow-shaped forward orientation as represented in dashed line fashion at 244. With this orientation as represented at dashed line 244, the arc is positioned to cause ignition of the misted oil and air combination.

Experimentation with the instant system and method has revealed that for a typical home installation, over a heating system, for example, in the Midwest region of the United States, a homeowner will realize a fuel oil savings of at least about 60 to 100 gallons of oil. With current fuel oil prices at about $3.00 or more per gallon, employment of the instant method will result in significant economic benefit.

Since certain changes may be made to the above described method and system without departing from the scope of the invention herein involved, it is intended that all matter contained in the description thereof or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. The method for operating an oil-fired furnace incorporating a nozzle, a motor-driven fan, an oil pump, an electrode pair extending to mutually spaced tips, and a controllable response to a thermostat call for heat to commence an ignition sequence, comprising the steps:

(a) providing said electrodes with a tip geometry effective when energized to burn off unburned fuel debris at the nozzle;

(b) responding at said controller to a said thermostat call for heat to energize said electrode pair; and

(c) then energizing said motor driven oil pump and fan only after a delay effective to permit the energized electrode pair to burn off unburned fuel debris from the nozzle.

2. The method of claim 1 in which:

step (a) provides the electrode tip geometry such that, at least during said step (c), delay an arc is caused to pass about the surface of the nozzle between the tips.

3. The method of claim 1 in which:

step (a) provides the electrode tip geometry as mutually spacing the tips about ¼ inch apart.

4. The method of claim 1 in which:

step (a) provides the electrode tip geometry as spacing each tip about ¼ inch above the orifice of the nozzle.

5. The method of claim 1 further comprising the steps:

(d) simultaneously with step (b) commencing to monitor for the presence of fuel ignition for an ignition monitoring interval; and

(e) subsequent to step (c) at the termination of the monitoring interval and in the absence of fuel combustion, terminating steps (b) through (d).

6. The method of claim 1 in which:

step (c) energizes said motor driven oil pump and fan following a said delay of about 2 to 5 seconds.

7. An oil-fired furnace system, comprising:

a combustion chamber;

a nozzle having an orifice for expelling oil mist into the combustion chamber;

an electrode pair having a tip geometry effective, when energized to burn off unburned fuel debris at the nozzle;

a fan assembly actuable to blow air into the combustion chamber;

an oil pump actuable to pump fuel oil from a source through the nozzle surface;

a controller assembly including one or more relays actuable to simultaneously energize the fan assembly and oil pump, an ignition transformer circuit energizable to effect creation of an arc between the electrode tips, and a delay circuit actuable to effect a delay output following a delay interval, said controller assembly being responsive to a thermostat call for heat to energize said ignition transformer circuit and simultaneously actuate said delay circuit and responsive to said delay output following a delay interval effective to cause said electrode pair to burn off unburned fuel debris at the nozzle, to simultaneously actuate said fan assembly and said oil pump.

8. The system of claim 7 in which:

said electrode pair tip geometry is configured such that, at least during the delay interval, an arc is caused to pass about the surface of the nozzle.

9. The system of claim 7 in which:

said electrode pair tip geometry is configured to mutually space the tips about ¼ inch apart.

10. The system of claim 7 in which:

said electrode pair tip geometry is configured to space each said tip about ¼ inch above the nozzle orifice.

11. The system of claim 7 in which:

said delay circuit delay interval is about 2 to 5 seconds.

12. The system of claim 7 in which:

said electrode tip geometry is configured to space each tip about 1/16 inch forwardly from the forward surface of the nozzle.