Apparatus for burning liquid fuel

Application filed December 8, 1923. Serial No. 879,487.

This invention pertains in general to apparatus for burning liquid fuel, and more particularly to oil burners so called, for heating, and power plants adapted for both ³ industrial and domestic purposes.

My invention as herein illustrated is, however, particularly designed for house heating, as for. example, by installation in connection with a furnace, hot water heater, or boiler.

¹⁰ The primary object of the present invention is to provide simplified and improved apparatus of this character, which may be produced and installed at a comparatively low cost and will have a low operating and ¹⁵ maintenance cost and will be efficient and economical in its fuel consumption.

In furtherance of this general object, my invention contemplates the provision of apparatus embodying new principles of con²⁰ struction and operation, briefly described as follows:

I have provided a burner that is operated continuously as distinguished from those types which operate intermittently or pe²⁵ riodically. That is, certain types of oil burners are designed to operate only at such times and duration under the thermostatic control, as is necessary to maintain a given heat. During these periods of operation the fuel consumption is at a comparatively high rate. Furthermore, the repeated starting and stopping necessitates the provision of ignition means and an automatic control therefor. This intermittent operation with its sudden ⁵ and extreme change of temperature in the fire pot and consequent expansion and contraction thereof, sooner or later, invariably causes the fire pot to crack, requiring replacement; and when such apparatus is used for heating a boiler, the latter is subjected to severe strains by the high temperature and sudden changes. Also in most instances where the apparatus is intermittently oper_r ated, the liquid fuel is atomized, thus neces-^J sitating high fuel pressures, additional equipment and more power to operate the same. It follows that this periodic operation involves the provision of special mechanism of a more or less complicated nature for control⁵⁰ ling the fuel and air supply and the ignition means and for starting and stopping the apparatus. On the other hand, in a system such as I have devised, the apparatus operates continuously, producing such heat as is needed. For example, in the fall and spring when only ³³a small amount of heat is required, the fuel and air delivery will be regulated so that a comparatively small flame will be burned continuously. When greater heat is required, the fuel and air will be increased accordingly; ⁸⁰such delivery being increased or diminished at will by manual operation or automatically as by means of a gradual thermostatic control, so that only the necessary heat is produced.

However, an important consideration is that ⁰³I am able to burn a much lower flame and consume considerably less current for operation than is possible with apparatus of the kind which operates intermittently. One of the reasons for this is the novel method of ⁷⁰ and means for feeding the liquid fuel and air to the combustion chamber and of controlling the feed. My invention contemplates supplying fuel to the in-take of a centrifugal pump under a constant head as by gravity from a supply chamber in which the fuel is maintained at a predetermined level, raising the fuel by means of the pump to a head higher than the in-take of said pump, delivering the fuel from the outlet of said pump to an overflow point, the elevation of which is but slightly greater than the level of fuel in said chamber, and permitting the fuel to feed by gravity from said overflow point to a discharge point in proximity to the combustion chamber and in the presence of the air which is simultaneously delivered to the combustion chamber at a predetermined velocity. The fuel will be vaporized by contact with the fire pot or by any suitable means and mixed with the air, providing a combustible mixture. As a result, the fuel feed is positively controlled and but little power is required, as will be explained more fully hereinafter; and in the event that the pump stops, the feed of the fuel to the combustion chamber will cease, as distinguished from some systems wherein the fuel continues to feed to the combustion chamber after some casualty interrupts the normal operation.

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2,897,818 the float valve taken substantially on the line 9—9 of Fig. 1.

The following description is for purpose of clearness, under subject titles, viz: combustion chamber, air delivery nyeans, fuel delivery means, operating means, frame structure, safety provisions and general operation ; this in no way limiting the scope of the invention.

Combustion chamber

The combustion chamber or fire pot designated generally by 11, may be supported by any suitable means and in co-operative relation with any apparatus to be heated. In the present illustration of my invention, the fire pot is supported on the grate bars 12 of a furnace 13, such as is used for house heating. In this instance, the fire pot is of such size that it may be in inserted through the fire door opening 14 and simply placed on the grate bars, the fire pot having ribs 15 and 16 on its bottom for maintaining it in a level position. The fire pot is characterized by a bottom wall 17, which inclines downwardly at both sides to a trough 18 located at the center and parallel with the plane in which the air and fuel is delivered to the combustion chamber. The sides of the combustion chamber are defined or bounded by an arcuate wall 19 at each side of said center, these walls converging upwardly from the bottom wall 17 and providing a constricted open top 21. Liquid fuel and air are delivered into the combustion chamber, as will be explained more fully hereinafter through a throat 22, the bottom of which is substantially co-planar with the bottom wall of the fire pot and which has a fuel channel or trough 23 along its center, this being a continuation of the trough 18 above referred to. In this instance, said throat has an upstanding elbow providing an inlet opening 24 for connection with an air delivery pipe which will be later described. The side walls of the fire pot are shaped to provide an inwardly reaching ridge 25 disposed diametrically opposite from the throat 22, reaching from top to bottom of the combustion chamber and following the vertical inclination of its side walls. It will be here noted that each side wall 19 is substantially involute, the curvature of which is greatest at the ridge 25.

The functioning of the fire pot is briefly as j₂o follows: Air will be delivered at a predeter-. mined velocity through the inlet opening 24 and the throat 22 into the combustion chamber by means described hereinafter, and liquid fuel will be delivered by gravity into the 125 trough 18 at the entrance to the combustion chamber, as also will be described hereinafter. The liquid fuel flows along said trough 18 and is confined thereby to a definite

Another feature of my invention is that in a system of the character described, I am enabled to employ a comparatively small electric motor for driving the blower and pump, with a commensurate low current consumption, this being due mainly to the fact that the air and oil are delivered at low pressures and the pump friction is reduced to a minimum, as hereinafter described. And because there are no static heads to overcome · in either the air or fuel lines, but only frictional resistances, it follows that the amounts of air and oil delivered by this apparatus, and consequently the resultant heat, are proportional to the speed of rotation of the motor. Control of the motor speed, therefore, by any suitable means governs the operation of the apparatus and gives a variable heat which may be easily and accurately controlled. However, it should be understood that my invention is not limited to the use of a variable speed motor, as the motor speed might be constant and the fuel and air be varied as will be explained hereinafter.

Other features covered in a divisional application Serial No. 70,754, filed November 23,1925, are found in the construction of the centrifugal fuel pump and the method of supplying fuel thereto and of delivering it to the combustion chamber, the omission of a pump stuffing box and the method of burning fuel leakage therefrom, as well as the provision of safety devices for shutting off the fuel supply in the event that the flame should for any reason be extinguished, and the provision of a novel structure for adjustably supporting the several devices.

Other objects and attendant advantages will be appreciated by those skilled in this art as the invention becomes better understood by reference to the following description when considered in connection with the accompanying drawings, in which—

Figure 1 is a side elevation partly in section, of a liquid fuel burner embodying my invention;

Fig. 2 is a vertical section taken substantially on the line 2—2 of Fig. 1, , with the blower also in vertical section;

Fig. 3 is an enlarged fragmentary section through the centrifugal fuel pump taken substantially on the line 3—3 of Fig. 1;

Fig.4 i s a vertical section through the cen«5 trifugal pump taken substantially on the line 4—4 of Fig. 3;

Fig. 5 is an enlarged top view of the fire pot;

Fig. 6 is a horizontal section through the to fire pot on the same enlarged scale, taken substantially on the line 6—6 of Fig. 1;

Fig. 7 is an end view of the fire pot;

. Fig. 8 is a vertical sectional view of the fire pot taken on the line 8—8 of Fig. 6; and _____„______________________..___________

Fig. 9 is a vertical sectional view through channel so as to insure equal distribution of 130

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1,897,318 vapor on both sides of the combustion chamber. Assuming that the fire pot is heated, the liquid fuel will be vaporized by contact with the heated bottom thereof, the vaporization ⁵ occurring in the presence of the incoming air and providing a combustible mixture. Combustion occurs practically instantaneously, and the burning mixture impinges on the ridge 25 and is divided thereby into opposite ¹⁰ currents or flames which follow the wall 19 and are caused thereby to whirl or-rotate in the combustion chamber as indicated by the arrows in Fig. 6. The inclined side walls of the combustion chamber cause the flames to 15 be directed downwardly so as to hug the bottom as long as possible and to be thrown together as they reach the throat opening. These flames by reason of the curvature of the side walls 19 and of being thrown to20 gether against the incoming current delivered through the throat will be caused to rotate as above mentioned. The horizontal cross-section of the combustion chamber and the cross section of the throat are so propor25 tioned that the air currents produced thereby and resulting in two oppositely whirling or rotating flames will burn with a bright clean flame and will leave no dead spaces in the combustion chamber for the formation 30 of unburned carbon caused by incomplete combustion. These proportions also insure the maintenance of a low flame when operating at a low speed as will be explained hereinafter, without the flame blowing out. It 35 should be understood that the apparatus of this invention is not limited to use with this special fire pot nor any other open top pot but is adapted for use with other types of fire pots open at the side, front or otherwise.

⁴⁰ Air delivery means

Air is delivered by suitable means to the inlet opening 24 of the throat 22 for mixture in predetermined proportions with the liquid 45 fuel for providing the desired combustible mixture in the fire pot. I prefer to deliver this air by means of a centrifugal blower or fan, designated generally by 26 having an air inlet opening 27 and a delivery opening 28, 50 the latter of which is connected by a slightly inclined pipe section 29, an elbow 31, and a vertical pipe section 32, with the inlet opening 24 of the fire pot structure- above described. It will be manifest that by varying 55 the speed of the impeller 33, the amount of air, that is, the cubic, feet per hour delivered to the combustion chamber may be varied. While in the present instance the air delivery pipe passes through the fire door opening 60 14, it should be understood that this condition in the design is imposed by reason of the application of my improvements to a furnace changed over to oil burning, and that wdiere the conditions and requirements differ from 65 the present, the air delivery pipe or line may be otherwise suitably arranged between the blower and the fire pot.

Fuel delivery means

This apparatus is designed to burn oil of 70 a low grade, the present embodiment being intended to burn oil having a specific gravity not higher than 30 degrees Baume, commercially known as gas oil. A suitable oil supply tank 34 is supported at such height from 75 the floor that the oil will flow by gravity to the fire pot. My invention contemplates, however, interposing in the oil supply line, devices for delivering a predetermined and uniform quantity of oil to the burner per 80 hour, and means whereby this feed of oil may be varied and regulated so as to burn a steady low flame, or to increase the feed gradually to the maximum for correspondingly increasing the flame and heat produc- 85 tion.

To this end I employ a small centrifugal pump to which oil is fed to the intake side at a uniform low pressure by gravity from a chamber in which a predetermined level is 90 maintained by a float controlled valve, in turn fed by gravity from the service tank 34. As shown in Fig. 1, the oil flows from said tank through a suitable strainer 35 and pipe line 36 to the float valve designated generally by 95 37. This valve may be of any .suitable or preferred construction, and at present I have shown one of conventional design for maintaining the oil at a constant level at all loads. This comprises a float 38 in the chamber 39 100 adapted to actuate through connections 41, a needle valve 42 for maintainng the oil in the chamber 39 at a predetermined level, said chamber being fed through the pipe connection 36, and such feed being controlled by 105 the needle valve 42 as will be obvious. Oil from the chamber 39 flows through a pipe con- ‘ nection 43 to the inlet side of a centrifugal pump designated generally by 44, the float valve being supported above the pump so as 110 to insure the desired constant flow thereto.

The centrifugal pump, best shown in Figs. 3 and 4, comprises a casing 45 having an inlet side 46 to which the pipe 43 connects, and an outlet opening 47 connected to a delivery pipe 115 line, designated generally by 48, and a blade impeller 49 carried by a shaft 51 journaled in the bearing portion 52 of the casing. The impeller shaft will be constantly driven in a clockwise direction viewing Fig. 4, by means 120 described hereinafter, thereby raising the pressure of the oil to a comparatively low pressure head in proportion to the square of the speed. The oil escapes from the outlet side of the pump through an adjusting valve 125 53 in the oil delivery line 48 to an overflow point 54, the elevation of which is from oneeighth to one-fourth of an inch above the constant level of the oil in the float chamber 39. The escape of oil through the valve 53 is pro- 130

1,887,318 portional to the square root of the head at the outlet or discharge side of the pump, and consequently proportional to the pump speed. The oil overflows at the point 54 into a pipe ⁵ 55 and flows by gravity to a discharge point 56 approximately at the juncture of the throat 22 and the combustion chamber. It will be observed that the oil delivery line at the point 54 is open to the air pressure in the air de¹⁰ livery pipe 29 through means of an upstanding L 57 or the equivalent facing into the air stream so as to scoop air into the vertical pipe 55. This air pressure prevents the oil from overflowing and running down on the out¹⁵ side of the pipe 55 and insures a constant feed of oil through said pipe as well as minimizing danger of oil adhering to the inside walls of the pipe 55 and possibly clogging the same. If the oil delivery pipe line were closed as at ²⁰ the point 54, a siphon action would result which would destroy the proper proportion of the fuel and air delivery sought. In order to insure against vaporization of oil in the pipe 55 it is supported in the center of the air ⁵ pipe 32 and the throat 22 by means of a spider bracket 58, so as to be substantially out of contact with the heated walls of said pipe and the fire pot throat.

The foregoing apparatus gives a positively ⁰ controlled delivery of oil to the combustion chamber, the feed being proportional to the speed of the impeller.

It will be further observed that by maintaining a low head of oil by means of the ⁵ centrifugal pump from which head the oil feeds through a restricted regulating orifice to an overflow point and thence by gravity to the combustion chamber, the feed will be continuous and uniform in amount rather than ⁴⁰ intermittent or in gulps and will cease when the motor stops.

In order to further insure a uniform feed of oil, I have provided the standpipe 59, in which the oil is arranged to rise in propor⁴⁶ tion to the speed of operation of the pump, a substantially uniform head of oil being ordinarily maintained in said pipe so that the oil is delivered in a steady stream into the fire pot. I also guard against a condi⁵⁰ tion which would tend to prevent the uniform feeding of oil, by providing means for preventing any air from being delivered by the pump. In experimenting, I have found that the churning of oil by the rapid revolu⁵⁵ tion of the impeller causes the formation of small bubbles of air or gas, some of which will escape through the pump’s outlet and rise in the standpipe 59 which is open to the atmosphere. Also some of the bubbles gather ⁶⁰ at the center of the impeller casing; and to remove the latter bubbles the shaft 51 is drilled axially as at 61, to a point intermediate the end of the bearing 52, at which point this axial hole is intersected by a diametrical ⁶⁵ hole 62, and the latter by a groove 63 turned in the periphery of the shaft. Air accumulating at the center of the impeller casing will pass through such holes and escape through a standpipe 64 which is in communication with the peripheral groove 63. ⁷⁰

Inasmuch as I have aimed in this invention. to reduce pressures and resistances to a minimum in order to reduce the electric current consumption required for operating the centrifugal pump, without however, impair- ⁷® ing accuracy and reliability of control and regulation, I have also reduced the pump shaft friction to a minimum by making the pump without a stuffing box. The impeller shaft is fitted in its bearings with a small ⁸⁰clearance which allows only a few drops of oil leakage per minute. This leaking oil may be conveyed to any receptacle, but I prefer to conduct it to the bottom of the charging throat of the fire pot so that it may be mixed ⁸⁵with the main oil supply and be vaporized and burned therewith. As shown in Figs. 1, 2 and 3, this leaking oil is conveyed through a drain pipe 66 having a horizontal portion 6(5' leading to a point beneath the fire pot, ⁹⁰and a riser portion 66 entering the bottom of the throat 22.

Operating means 95 The centrifugal blower and centrifugal oil pump are both preferably driven by a single electric motor 67. As shown in Fig. 2, this motor is interposed between and directly connected to the blower and pump. For ]₀₀convenience in assembling and so as not to require extreme accuracy in aligning these devices, I fix the blower shaft directly to the motor and provide a flexible connection, through means of a coil compression spring 105 68, to the impeller shaft 51. It will thus be seen that inasmuch as the blower and pump are directly connected by the motor and there are no static heads or resistances in the oil and air lines than frictional to overcome, no the amounts of air and oil delivered to the fire pot will be proportional to the speed of rotation of the motor.

The motor speed may be regulated in any suitable manner, as for example, by a speed 115 regulator in the form either of a rheostat or an adjustable transformer, the latter being diagrammatically shown in the present instance, and indicated by 69. This speed regulator in turn may be controlled either no by hand or automatically as by means of a thermostatic control, well known in this art.

A constant speed motor may be used in place of a variable speed motor, and in this event, a suitable means such as a butterfly ⁴²⁵valve 70 will be employed for regulating the air delivery. In such case, both the valves 53 and 70 would have to be adjusted in proportion when increasing or decreasing the fuel feed. 3⁰

1,897,318 ϊη view of the little power required to operate the blower and pump continuously, a comparatively small electric motor may be used and the electric current consumption will be correspondingly small.

Frame structure

I prefer to mount the blower, motor, pump and float valve in co-operative relation on a frame 71 in turn supported on a plurality of legs or posts 72 with capacity for vertical adjustment thereon, so that the pump and blower may be positioned at the desired elevation. At present the posts 72 are fixed to a base 73, and set screws 74 are used for adjustably securing the frame 71 on the posts. Suitable pads are provided on the frame 71 for. supporting the blower, motor and pump in substantially co-axial relation. The float valve is attached to a bracket 75 vertically adjustable upon and with respect to the frame 71, set screws 76 serving to secure the bracket 75 in any adjusted position.

The purpose of the foregoing adjustments is obviously to position the pump at the desired level below the overflow point 54 of the oil feed and to position the float valve so that its constant level is about one-eighth of an inch or more below said overflow point and sufficiently above the pump inlet as to insure gravity feed thereto.

Safety provisions

Means is provided for automatically stopping the delivery of oil to the centrifugal pump 44 in the event that the flame in the combustion chamber should, for any reason be extinguished, and in such event the fire pot will obviously be cooled rapidly by the delivery of air and oil until vaporization ceases. The oil delivered to the fire pot will then rise therein, and this rising level will overflow into a receptacle, which will be actuated by the weight of the fuel to shut off the oil supply at the float valve. At present, this overflow is obtained through a pipe 77, which rises from the pipe 66' to a level above the bottom of the fire pot and has a downturned overflow end 78 adapted to discharge into a suitable receptacle or bucket 79. This bucket is suspended from one end of a lever 81 pivotally mounted at 82 on the upper end of the bracket 75, the lever being positioned over the upper end of the needle valve 42 as shown in Figs. 1 and 9, and normally held in this inoperative position by a counter-balancing weight 83. When the level of the oil rises in the fire pot and overflows through the overflow pipe 77—78, the bucket 79 will be filled sufficiently to overcome the weight 83 and depress the lever 81, thereby closing the needle valve and stopping delivery of oil to the chamber 39, and consequently to the centrifugal pump. Should the float 38 for any reason sink in its chamber, or fail to properly function in maintaining the desired level therein, the oil level would rise in said chamber and overflow through the pipe 84 to the bucket 79, thereby shutting off the oil supply 70 in the manner j ust described. After the burner has been stopped by the trip bucket due to the oil level rising in the combustion chamber, the standing oil in said chamber may be drained by removing a plug 80 before start- 75 ing the burner. It is not necessary, however, to do this before starting, as the oil in the combustion chamber will be burned but with a longer flame and not as efficiently as with only the regulated feed of oil. 80

General operation

When starting the burner, the fire pot will be preheated by any suitable means, so that when the oil feed is started by opening the 85 valve 53, it will be vaporized by contact with the heated pot as described above, and will be ignited by such heating means. In a burner such as disclosed herein, especially adapted for house heating, I operate the motor at vari- 90 able speeds between what I term a “low load” at 300 R. P. M. and “high load” at between 2300 and 2400 R. P. M. Under the low load the centrifugal pump will deliver approximately one-fourth of a gallon of oil per 95 hour and at the high load two gallons per hour. The blower delivers approximately 330 and 2640 cubic feet of air per hour at the low and high loads, respectively. These figures are, of course, merely illustrative of one 100 practical example of the operation of my invention and show relatively the economies in fuel consumption. In the event that a thermostatic control is used for stepping the speeds of the motor up or down accordingly 105 as a greater or less heat is required to maintain a given temperature in the room or rooms to be heated, the motor will never be stopped but its speed will be gradually increased or diminished, as may be done with standard con- no trols of this kind on the market.

When starting the burner the valve 53 will be adjusted until the oil delivery is in the proper proportion to the air delivery and produces the desired combustible mixture. 115 After once setting the valve the amounts of air and oil delivered are proportional to the speed of the motor as described above.

In an emergency such as caused by complete failure of the electric power or inability 120 to secure oil the apparatus herein described may be easily removed from the furnace; and due to the fact that the grate bars have not been removed when installing the burner, the furnace is ready for immediate use with the 125 usual fuels.

It is believed that the foregoing conveys a clear understanding of the objects and principles of my invention, and it should be understood that when putting these into 130 β 1,897.318 practice, various changes might be made in the construction and arrangement of the necessary parts and devices without departing from the spirit and scope of the invents tion as expressed in the appended claims, in which.—