Gas and oil burner

Abstract

Claims

Oct. 21 1924. GAS AND OIL BURNER Filed Avril 13, 1923 FIG. 3 ENVENTOR Patented @et. 2t, 1924. UNHED STATES PATENT @EFHQE. FREDERICK PFAHL, OF GLASSPORT, PENNSYLVANIA, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO S. SEVERANCE MFG. COMPANY, OF GLASSPORT, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA. GAS AND OIL BURNER. Application filed April 13, 1923. Serial No. 631,808. To all whom it may concern: Be it known that I, FREDERICK G. PFAHL, a citizen of the United States, and resident of Glassport, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Gas and Oil Burners; and I do hereby declare the following to be a full, clear, and exact description thereof. My invention relates to burners for hydrocarbon fuels and it has special reference to the type of burner in which either oil or gas may be employed as the fuel. One object of my invention is to provide a simple and effective burner wherein air at low pressure may be used when oil isbeing burned, as well as when gas is being burned. Another object of my invention is to provide a burner which may be permanently connected to sources ofgas and oil in such a way that the change from oil fuel to gas fuel may be made without the introduction of any extra or auxiliary parts, and without making any change in the pressure of the air supplied by the blower. A further object of my invention is to provide a burner having an air channel, an oil channel, and a separate gas channel, and in which the gas channel is utilized to supply air, in addition to the normal air su ply, when oil is employed as the fuel. Ot er objects of advantages of my invention will appear from the following description, taken in connection with the accompanying drawing, in which: Fig. 1 is a longitudinal central sectional view through a burner constructed in aceordance with my invention; Fig. 2 is an end view of the burner as seen from the left of Fig. 1; Fig. 3 is a transverse sectional view taken substantially on the line 3-3, Fig. 1; Fig. 4 is another transverse section taken substantially on the line 44 Fig. 1; and Fig. 5 is a side elevational view of a portion of a furnace equipped with a system of burners constructed and arranged according to my invention. Industries which are located in the natural-gas regions have commonly employed natural gas as the fuel for their furnaces and other heating appliances. Within recent years the supply of natural gas has been a fluctuating quantity, especially in cold weather, and it has been necessary to adopt some other type of fuel equipment as a substitute for the ordinary gas burners in times of gas shortage. Burners have been designed for utilizing either gas or oil. Such combination burners have usually been satisfactory when gas is available as the fuel, but when it is nec essary to substitute oil for gas it has been found that the ordinary low-pressure air, which is entirely sufficient for the gas, will not properly atomize the oil in the combination burners which have heretofore been designed. The reason for this is that a less volume of air is required for combustion of oil than is required for combustion of gas. When the normal air supply is throttled down to produce the requisite quantity of air for combustion with oil, there is a reduction not only in the volume of the air, but also in its velocity, and it has been found that this reduction in velocity deprives the air of the rending force necessary to disperse the oil in the form of a spray. Under conditions requiring comparatively low temperatures, where the air supply is cut down to the greatest extent, the air has not even sufficient force to carry the fuel into the furnace, and the result is that the oil drips againstthe outer wall of the furnace and runs down to the floor in streams, forming great pools. The combination burners heretofore employed have had separate inlets for the oil fuel and for the gaseous fuel, and a third inlet for the air. lVhen oil is used as the fulel the gas inlet has been shut off and left id e. According to my present invention I provide separate oil and gas inlets as in prior burners, but I make use of the gas inlet when oil is used as the fuel to furnish an auxiliary supply of air, under the normal pressure used with gas, the auxiliary air being so directed as to engage the'oil before its force is dissipated, thereby atomizing the oil throughly and assisting incarrying it forward into the furnace. In the specific construction herein shown, the burner includes a tubular easing, a central oil tube extending through the casing, and an intermediate tubular channel member which forms an annular space around the, oil tube and another annular space between itself and the outer casing. Air is admitted to the outer annular chamber, and either air or fuel gas is supplied to the intermediate annular chamber through suitable pipe connections. When oil. is used as -the fuel it is sup plied to the central fuel tube. At its forward end, this tube is enlarged .and is provided with one or more series of openings which extend inwardly and forwardly, placing the forward enlarged end of the oil tube in communication with the intermediate annular chamber of the burner. lVhen fuel oil is burned, air, under the normal pressure of the blower, is supplied to the intermediate annular chamber in addition to the lowerpressure air supplied to the outer chamber, and part of the auxiliary air passes through the openings just described and engages the oil with an atomizing action before it escapes from the burner. Other portions of the higher-pressure air admitted through the intermediate annular chamber are directed against the issuing oil in the form of a conically converging annular stream by means of a cap which surrounds the outer end of the intermediate annular channel member of the burner and which is provided with a central outlet. The front end of the outer casing is closed by means of another cap which is so shaped and spaced from the cap of the intermediate tube as to cause the air from the outer air chamber to form an inwardly converging cone which still further breaks up the fuel and helps to carry it forward. l/Vhen gas is used as the fuel the oil inlet is shut off by means of a suitable valve, the air supply is shut off from the intermediate annular chamber, and the fuel gas is admitted to the burner through this intermediate annular chamber. Air is supplied to the outer chamber of the burner in the same manner as when oil is burned, but a somewhat larger volume of air is required for burning gas than for burning oil. The air throttle is therefore arranged to deliver air at the proper volume for burning gas. That portion of the air which enters the outer air chamber of the burner is throttled down when oil is burned, but the auxiliary air is supplied at the normal blower pressure. In Figs. 1 t64 of the drawing, the numeral 2 indicates an outer tubular casing or body member having a lateral opening surrou'nded by an externally screw-threaded flange 3, to which may be applied a suitable connection for coupling the casing .to a source of air under pressure. The front end of the casing 2 is provided with external screw threads 4 by means of which a cap 5 is adjustably secured to the casing 2. The cap 5 has a conically converging portion 6 and a central discharge opening 7. At the rear end of the casing 2 is formed a circular flange 8 to which a corresponding flange 9 carried by an intermediate tubular member 10 is removably secured by means of bolts 11 and nuts 12, as shown on Fig. l. The intermediate tubular member 10 is enlarged at its rear end to form a closed chamber 13 having an internally screw threaded lateral outlet into which may be screwed a coupling 14 leading to a source of air under pressure, and also leading to a source of fuel gas. The front end of the tube 10 is provided with screw threads 15 for adjustably securing a cap 16 upon the front end of this tube. The cap 16 has a conically converging portion 17 and a dis charge opening 18 similar to the corresponding parts of the outer cap 5, and the caps 5 and 16 are so adjusted as to provide a small annular space between them. At its rear end, the intermediate tubular member 10 is provided with an internally screw threaded flange 20 by means of which a fuel tube 21 is secured in place at the central axis of the burner. This fuel tube has an enlargement 22 for limiting the rearward movement of the fuel tube with respect to the rear wall of the intermediate member 10, and a nut 23 is applied to the outer screw threaded portion of the fuel tube for the purpose of fixing the fuel tube in its adjusted position. The fuel tube 21 is somewhat reduced in diameter near its forward end, as shown at 24, and this reduced portion terminates in 'an enlarged head or nozzle 25 which is spaced somewhat from the inner surface of the cap 16. Two rows of openings 26 and 27 extend through the enlargement 25 and into an enlarged cavity 28' formed within the head 25. These openings are inclined forwardly as shown. One of the rows of perforations may be omitted, if desired. A needle valve 30 is applied to the rear end of the fuel tube 21 and communicates with a fuel supply pipe 31. A central channel 32 is formed axlally through the fuel tube 21 and communicates with the enlarged chamber 28. For the purpose of keeping the intermediate tube 10 in proper position within the casing 2. ribs 34 are formed on the inner surface of the casing 2 and extend inwardly and radially a sufficient distance to admit the tube 10 between them. It will be seen that the construction just described provides three concentric channels, which are the central bore 32 of the fuel tube, an intermediate channel 33 between the fuel tube and the intermediate tube 10, and an outer annular channel 34 between the intermediate tube 10 and the outer casing 2. The air connection 3 and the oil connect-ion 31 are to be connected permanently to sources of air and oil respectively. The connection 14 which communicates with the intermediate channel 33 is intended to be connected both to a source of air and to a source of fuel gas, so that either air or gas may be supplied to the channel 33 without any change in the system except the proper operation of the valves. Such an arrangement is shown somewhat diagrammatically on Fig. 5, which shows at 40 a. portion of a furnace which is to be heated by means of a battery of burners, three of which are indicated at 41. The oil inlet pipes 31 of these burners are all connected to a pipe 42 which is connected to a source of oil supply and is provided with a valve 43 by means of which the oil may be shut off from all of the burners. Air is supplied to the burners 41 through a header pipe 44 which is provided with a control valve 44 and which is connected by means of branch pipes 45 to the large inlet flanges 3 of the burners, for delivering air into the outer annular air channels 34 of the burners. Gas is supplied to the inlet pipes 14 of the several burners 41 from a header pipe 46 leading from a suitable source of gas supply and provided with a valve 47. The gas header 46 is connected by means of branch pipes 48 and suitable couplings to the inlet pipes 14 of the burners. The air header 44 and the gas header 46 are connected by means of a pipe 49 which is provided with a valve 50 and connects with the header 46 on the side of the gas valve 47 toward the burners. The pipe 49 is used to supply auxiliary air to the burners, and is connected to the air header 44 outside of the valve 44 in order that the auxiliary air may be unthrottled when the main air pressure is cut down by the valve 44 if used with oil fuel. When the burner system just described is to be used with gas as the fuel, the oil valve 43 and the auxiliary air valve 50 are closed and the gas valve 47 is opened. Gas then enters each burner through the inlet pipe 14, traverses the annular channel 33 and issues from the opening l8 in the cap 17, where it is mixed with air which has entered the outer channel 34 and which is discharged through the opening 7 in the outer cap 6. When oil is to be used as the fuel, the gas valve 47 is closed and the oil valve 43 is opened. The auxilia airvalve 50 is also opened to supply air rom the header 44 to the header 46 which is now utilized to supply auxiliary air through the pipes 48 to the inlet pipes 14 of the burner, and thence to the annular channels'33 which now become auxiliary air channels instead of gas channels. The main air valve 44 may be closed somewhat in order to reduce the volume of the air to the quantity which is proper for combustion with oil. When the system is operating in this manner some of the unthrottled auxiliary air traversing the'channel 38 passes through the openings 26 and 27 and strikes the oil which is issuing from the oil channel 32, thus atomizing the -oil to some extent before it issues from the oil tube. The atomization is completed by the converging annular streams of air which issue both from the channel 33 and from the outer, channel 34. The auxiliary air supply through the channel 33 has sufiicient force to insure that the oil will be carried into the furnace. without changing or replacing any of the. parts of the burner or its attachments. It is a principal advantage of the system herein shown and described that the gas chamber is utilized to furnish auxiliary air for burning oil instead of being merely used for burnin gas only, as in prior burnerslof this general type, with the very convenient additional feature that it will burn gas just as efficiently as though it were designed for that purpose alone. A further advantage of this system is that it permits oil to be burned with air under much lower pressure than has heretofore been considered possible. It has generally been considered that pressures of not less than 1 pounds per square inch are necessary for atomizing fuel oil, and this has led to the development of mechanical atomizers, the principle of which is to'force the liquid fuel through small apertures under high pressure, and to direct the small streams against a deflecting Wall with sufiicient impact to scatter it into fine particles. The weakness of this atomizing method as applied to oil fuel, is that much dirt and other foreign matter is constantlyheld in suspension in the oil and tends to clog the small openings, which requires frequent interruptions for cleaning. I have found that my present invention enables oil fuel to be burned satisfactorily with only ten ounces of air pressure and without the use of atomizing openin s that are so small as to become clogged rea ily. i l iary parts for either fuel. reduce believe that this burner is the simplest device so far designed which is complete within itself for either oil or gas fuel and does not require the introduction of any auxil- Cn the other hand, no part of the burner can be dispensed with in making a change from one fuel to the other. Even the oil tube plays a part in burning gas, to keep the flow of gas divid- 10 ed into separate diffused streams in order to accomplish the most intimate possible mixture between the gas and the air before they are delivered to the furnace. It will be understood that steam may 1 be used as the atomizing fluid instead of air, ples of my invention may be carried out with various other apparatus within the scope of the appended .claims. I claim as my invention: 1. Combustion apparatus comprising a burner having se arate channels for liquid fuel, gaseous fuel and air, and means for supplying auxiliary air through said gaseous fuel channel when said burner is used to burn liquid fuel, and means for utilizing said auxiliary air to assist in atomizing the liquid fuel. 2. Combustion apparatus comprising a burner having separate channels for liquid fuel, gaseous fuel and air, and a main air supply, means for permanently connecting said gaseous fuel channel to sources 'of fuel gas and auxiliary air, and valves for controlling the flow of air and gas in said'gaseous fuel channel and for controlling the relative pressures of said main and auxiliary air. 3. Combustion apparatus comprising a burner having a central liquid. fuel tube, an annular channel surrounding said fuel tube, 60 means for supplying either gaseous fuel or air to said annular channel, and means for utilizing a portion of said air to assist in atomizing said fuel. 4. Combustion apparatus comprising a burner having a central liquid fuel tube, an annular chamber surrounding said fuel tube, means for supplying either gaseous fuel or air to said annular chamber, an outer annular air chamber surrounding said firstnamed annular chamber, and means for supplying air to said outer chamber, the air supply to said first-named chamber being utilized only when liquid fuel is admitted to the burner. 5. Combustion apparatus comprising a burner having separate channels for liquid fuel, gaseous fuel and air, pipes for supplying liquid fuel, gaseous fuel and air to said channels respectively, a pipe connecting said air pipe and said gaseous fuel pipe, a valve in said last named pipe, and a valve in said gaseous fuel pipe for, cutting 05 the supply of gas from said pipe when said pipe is placed in communication with said air pipe. 6. Combustion apparatus comprising a plurality of burners each having separate channels for liquid fuel, gaseous fuel and air, header pipes having branches connected to said channels and means for causing said gas header to supply auxiliary air to said burners, the said means comprising a valve in said gas header, a pipe connecting said air header and said gas header on the side .of said valve toward said burners, and a valve in said last named pipe, for restricting flow of air t-herethrough. I 7. Combustion apparatus comprising a plurality of burners, each having separate channels for liquid fuel, gaseous fuel and air, header pipes having branches connected to said channels, and means for causing said gas header to deliver auxiliary air to said burners under higher pressure than the air supply, the said means comprising a valve in said gas header, a pipe connecting said air header and said gas header on the side of said valve toward said burners, a valve in said pipe, and a valve in said air header on the side of said pipe toward said burners, for restricting the flow of air therethrough. 8. A burner comprising a casing having an annular air chamber therein, a central fuel tube, and an intermediate annular chamber between said fuel tube and said air chamber, means for supplying either gas fuel or air into said intermediate annular chamber, and means for employing the air to assist in the combustion of fuel supplied through said tube. 9'. A burner comprising a hollow casing having an outwardly extending flange at its rear end, external screw threads at its front end, and a lateral air inlet. an intermediate tube having an external flange removably attached to the said flange on said outer casing, said intermediate tube extending forward through said outer casing and having external screw threads formed at its outer end. a central fuel tube extending through said intermediate tube and spaced therefrom, said fuel tube having a screw-threaded rear portion extending through a screw-threaded opening in the closed rear end of said intermediate tube, and caps applied to the screw threaded end of said outer casing and said intermediate tube, the said caps having conically converging portions and registering central openings. 10: Combustion apparatus comprising a burner having a liquid fuel tube, a main air supply pass e, a gaseous fuel supply passage, means or controllin the flow ofgasvetting a portion of the main air to said second-named passage when liquid fuel is being supplied. In testimony whereof I, the said F RED eous fuel, means for restrlcting the flow of ERICK G-PFA'HL, have hereunto set my hand. air through said main pass e, and means in advance of said last-nam means for. di- FREDERICK G. PFAHL.

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