US1684079A - Liquid-fuel burner and control mechanism therefor - Google Patents

Description

Sept. 11, 1928.

R. E. WHITE LIQUID FUEL BURNER AND CONTROL MECHANISM THEREFOR Filed Dec. 14. 1921 2 Sheets-Sheet 1 M ,flttornag;

Sept. 11, 1928.

R. E. WHITE LIQUID FUEL BURNER AND CONTROL MECHANISM THEREFOR Filed Dec. 14- 1921 I 2 Sheets-Sheet 2 Patented Sept. 11, 19 28.

UNITED STATES 1,684,079 PATENT OFFICE.

1. WHITE, OF CHICAGO, ILLINOIS, ASSIGNOR T0 TUBAL BOILER COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

LIQUID-FUEL BURNER AND CONTROL MECHANISM THEREFOR.

Application filed December 14, 1921. Serial No. 522,350.

The present invention relates to a liquid fuel burner and control mechanism therefor. The present burner has been developed with the ultimate object of supplying a reliable and efiicient liquid fuel burner for the boilers of self-propelled vehicles, such as steam automobiles, trucks, tractors, etc. It will be apparent, however. as the description proceeds, that the burner has a much wider field of utility, having particular application Where nicety of control under varying boiler loads is desirable. It will further be apparent that certain of the important features of the invention are not strictly confined to liquid fuel burners, and accordingly the appended claims have been drawn to cover these features as employed in connection with burners generally for different kinds of fuel, of which pulverized coal is a typical example.

The atomizing type of liquid fuel burner has such pronounced advantages over the vaporizing type of burner for steam vehicle practice that it is now becoming the prevalent type in this field. However, there are certain inherent difliculties in the atomizing burner which have heretofore retarded its development, particularly where control is an essential factor. One of these difiiculties is the necessity of maintaining at all times during the burner operation a blast of air of suflicient velocity and volume to properly atomize the fuel. The difiiculty becomes apparent when it is attempted to control such a burner by reducing the volume and velocity of the atomizing blast of air. If such air blast is reduced to a point where there is not suflicient velocity to break up and atomize the fuel the fuel enters the combustion chamber in large globules or in unbroken liquid form, with the consequent productlon of a smoky fire, the deposition of soot on the boiler tubes, and like. difficulties resulting from the burning of an improperly composed mixture. If the air conduit or nozzle is made sufliciently small so that adequate velocity ls maintained at the lowest rate of firing the nozzle or conduit chokes the air supply when an increased volume of air is supplied for a higher rate of firing.

Another difliculty in the atomizing burner results from the attempt to control the air blast by controlling the speed of the blower or "ther blast creating means. In the majority of instances these blowers are only eflicient at a definite speed for which they are designed. If this speed is reduced materially. thelr efiiciency drops off at a much higher rate. wlth the result that an unreliable control of the air blast is obtained, and with a considerable loss of power.

VVith the View to overcoming the above dlfliculties, it is one of the principal objects of my invention to divide the air supply into two separate blasts, one a primary or atomizmg blast for atomizing the fuel, and the other a supplementary blast which cooperates with the primary or atomizing blast of air for controlling the rate of firing. The primary or atomizing blast of air is always maintained, during the operation of the burner, at.a relatlvely high velocity in order to effectively atomize the fuel fed thereto. It is one of the incidents in the control of the burner to regulate the quantity of liquid fuel supplied through a relatively wide range, but the velocity of this atomizing blast of air is sufiicient to effectively atomize at all times all of the liquid fuel fed to it. The volume of air supplied by this atomizing blast is proportioned to produce the proper volume of mixture for firing the boiler at a fraction of its maximum rate; in the present instance this fraction is in the neighborhood of one third, which is, of course, merely exemplary. When a higher rate of firing is desired, the supplementary air blast comes into play and increases the volume of mixture to any extent desired. It is also one of the objects of the invention to provide improved means for controlling the volume of liquid fuel fed to the burner in accordance with the selective feed of air to the burner from one or both of said air blasts.

Another particular object of the invention is to provide means which will control the volume of air supplied to the burner without substantially varying the speed of the air blast creating mechanism. The power for creatingthese air blasts may be derived from an electric motor, a steam rotor, etc., which, as a result of the present control system. may be run continuously at its most eflicient speed during all periods of the burner operation. The control system for the present burner preferably embodies means for shutting off the operation of such power device entirely when the boiler pressure becomes excessive. so that the control of such power device is preferably secured by intermittent operation rather than by speed variation.

. vftween the tubes of the boiler.

Viewed in another aspect, the invention may be considered as embodying two burners or two mixture producing devices, one of.

which is operable alone to maintain a certain relatively low rate of firing. and the other of which is operable conjointly therewith for increasing the rate of firing.

Referring now to the accompanying drawings wherein I have illustrated a preferred embodiment of my invention for the purpose of acquainting those skilled in the art how to construct and use the same:

Figure 1 is a plan view of the burner apparatus;

Fig. 2 is a fragmentary side view, partly in section, and illustrating the control mechanism diagrammatically;

Fig. 3 is a view similar to Fig. 2 illustrating a. completely automatic control system;

Figure 4 is an elevational view of the refractory diaphragm; and

Eigure 5 is a sectional view of the pilot.

Referring to Figure 1, the combustion chamber or fire box 5 is defined in a refractory setting 6 which is disposed under the boiler B, according to any conventional practice. The burner is designated 7 in its entirety, and is disposed close to one side of the setting for a tangential discharge through the passageway 8 into the circular combustion chamber 5. This tangential injection of a high velocity mixture into a circular combustion chamber produces a rotating flame path which rises helically up be- By thus revolving the products of combustion and helically wrapping the flame upon itself, a maximum extent of flame space and a maximum combustion interval can be obtained from a very confined combustion area. The advantages of this are well known; the long flame space and the extended combustion interval insuring complete combustion of the mixture before the same strikes the relatively cold tubes of the boiler.

The burner 7 is housed in a circular casing 11 having a flange 12 which is secured to the outside of the setting 6. A hub or flange 13 supports the nozzle from which the mixture is discharged. For protecting the housing 11 the interior thereof is lined with a ring 14 of heat refractory material. The mixture is directed through a generally tapering opening 15 in a heat refractory diaphragm 16 which is set in a recess in the refractory setting 6. The area anterior or to the front of the diaphragm 16 constitutes a regenerative chamber 17 which has as its function to complete the vaporization of the whole fuel charge. The parts are preferably so proportioned that the velocity of the mixture discharged through this chamber and through the opening 15 tends to create a slight vacuum in the chamber 17. Re-circulating o enings 18 are provided in the lower circum erence of the diaphragm 16, and these openings align with grooves 19 in the refractory setting and with angular passages 21 in the insulating ring 14. The relative pressures prevailing on opposite sides of the diaphragm 16 induce a circulation through the openings 18 in the direction indicated, whereby products of combustion flow into the regenerative chamber 17 and enter the mixture stream, effectively vaporizing the whole fuel charge therein. The heat of the carbon monoxide generated in this chamber 17 vaporizes such fuel particles as are not completely atomized and secures the vaporization of the entire fuel charge.

Mounted in the hub or flange 13 is an air conduit 22 which supplies the supplementary blast of air to the burner. A compound nozzle in the form of a single casting 23 is mounted within the end of the conduit 22, this nozzle comprising an inner Venturi tube 24 and an outer nozzle passageway 25. The inner Venturi tube 24 is supported in the outer tube by spider arms 26, and extending through one of these spider arms is a fuel feeding passageway 27 which discharges substantially at the throat of the Venturi tube 24. The atomizing blast of air is fed to the inner Venturi 24 through a conduit 28 which fits over the projecting end of the inner Venturi tube and which enters the supplementary air conduit 22 diagonally, as shown in Figure 1. The air conduit 22 leads to the outlet of a blower 31, and the air conduit 28 extends to the discharge outlet of a separate blower 32. The two blowers are mounted at opposite ends of a power-unit 33, which may be a steam rotor, an electric motor, or other suitable power means. In the preferred embodiment shown, this power unit is illustrated as being an electric motor owing to its greater facility of control, this motor being operated from a storage battery carried in the vehicle. As illustrative of a typical relation of blowers, an installation which has operated satisfactorily employed a blower 31 of proper design for creating an air blast of substantially one ounce pressure or a velocity of approximately 50 feet per second, and a blower 32 was employed which would produce a blast of substantially four ounces pressure or a velocity of approximately 100 feet per second. It is noteworthy that the above pressure of the atomizing blast is relatively low as compared with pressures which have heretofore been necessary for the complete vaporization of the fuel oil or kerosene. This is because in the majority of prior constructions the breaking up of the fuel was performed entirely mechanically by the high velocity of the air blast. In the present embodiment the final gasification of the fuel is performed partly mechanically and partly by heat. The application of heat occurs in the regenerative chamber 17 where a quantity of incompletely burned mixture is circulated up into the entering mixture stream and by its relatively high temperature completes the vaporization of these fuel particles which have not been broken up by atomization. For proper com bustion this final vaporization should occur before ignition of the mixture and such action as attained in the present construction. By thus using heat to assist in the final gasification of the fuel a lower velocity and pressure of air in the atomizing blast suffices, and consequently less power is required for the operation of the blowers.

It may be desirable to heat the two blasts of air to a certain extent, and to this end the supplementary air conduit 22 is provided with an exhaust steam jacket 35, and the atomizing blast conduit 28 is provided with a similar jacket 36. The manner of circulating the exhaust steam through these jackets will be obvious to one skilled in the art. The heat thus imparted to the air blasts also assists in the vaporization of the fuel.

Referring now to the semi-automatic control system for this burner, it will be noted from Fig. 2 that the circuit for the motor 33, extendin through the wires 37 and 38, is interrupte by a suitable switching unit 39, which is preferably of a snap type for quick make and break. The position of this switch is controlled by boiler pressure acting through the pipe line 41 upon a diaphragm 42 of a pressure responsive element 43. This diaphragm has operative connection with the movable switch element through the rod 44, a spring 45 normally tending to raise the diaphragm and close the switch 39. This pressure responsive device is set to operate at the maximum pressure at which the boiler is to operate, and upon attaining this pressure the device automatically cuts off the electric motor 33 so that all further firing of the boiler is interrupted. A manual control switch 46 is preferably inserted in the circuit 3738 to turn the system on or off.

The shaft 34 of the electric motor is extended beyond one of the blowers to have operative connection with a. fuel pump 47. For simplicity, this fuelpuinp. is preferably a positive pressure gear pump having its inlet supplied with fuel from the supply tank 48 through the supply pipe 49. The outlet ipe 51 communicates through a T connection 52 with a primary fuel supply pipe 53 and a supplementary fuel supply pipe 54. These two supply pipesagain merge into a common pipe 55 whlch discharges into the fuel feeding passageway 27 opening into the inner Venturi tube 24. Anterior to their common point of connection with the pipe 55 the two supply pipes 53 and 54 are provided with separate regulating valves 56 and 57, by which the respective rates of fuel discharge through the pipes 53 and 54 may be balanced or regulated with the primary and supplementary blasts of air. The fuel pump 47 is designed to deliver fuel at a rate equal to or slightly in excess of the maximum require ments of the burner, and when the fuel discharge is restricted a suitable relief for the excess fuel discharged from the pump 47 is necessary. This is provided in the form of a relief valve 58 which has connection at 59 in the su ply pipe 51, and which has a return pipe 61 ischarging the excess fuel back to the supply tank 48. A suitable ball valve 62 held to its seat by an adjustable spring 63 performs the above relief function. Interposed in the supplementary fuel supply pipe 54 is a suitable valve 64 which is manually operable to shut off the fuel flow through the pipe 54, and which may be desi ned to meter the fuel flow therethrough. e movable element of the valve has connection through the operating arm 65 with a link or rod 66 which extends up to an accessible point-in the drivers compartment, such as to a suitable control member on the steering column or on the dash. The lower end of the control rod 66 has pivotal connection through a link with the operating arm 67 of a throttle valve 68 which is pivoted in the supplementary air conduit 22 upon a transverse shaft 69. The arm 67 is preferably slotted as indicated at and the lower end of the link 7 O is adapted to be adjustably clamped at any desired point in the slot 80. This permits of convenient adjustment of the angular timing between the valves 64 and 68.

Upon initiating the operation of the burner the mixture is ignited from a pilot light which is supplied with fuel through the pilot burner tube 72 entering through the lower part of the main burner housing 7. The pilot tube 72 extends beyond the diaphragm 16 through a slot 73 in the lower periphery of the diaphragm. This pilot burner is illustrated in detail in Figure 5 and comprises a vaporizing tube 86 which projects into the regenerative chamber 17 above the pilot 'burner tube 72. The fuel which is normally supplied to the main burner may be employed in this pilot burner, or a more volatile fuel such as gasolene may be employed. The f nel enters the vaporizing tube 86 through a. supply tube 87 which enters the closed front end of the vaporizing tube and discharges adjacent the closed rear end of said tube. The vaporizing tube 86 is highly heated and the liquid fuel flashes into vapor in flowing back along the bottom of the tube to the outlet which is located at the closed front end of the vaporizing tube. This outlet is through a passage 89 extendin down through a block. 88 mounted on the on of the vaporizing tube. A nozzle 91 is carried on the block 88 and communicates with the passage 89 'to 'd-ischarge the heated fuel va or into the open front end of the burner tu e 72. The injection of this fuel vapor induces a flow of air through the Venturi mouth 92, which is preferably flanged at its lower edge as indicated at 93 for forming a pocket for the accumulation of a limited volume of liquid fuel. The burning of such accumulation of fuel in this pocket serves to heat the nozzle 9], block 88 and vaporizing tube 86 for the purposes of starting. The intermediate port-ion of the burner tube 72 is provided with a plurality of slots or holes 94 in its upper periphery in position for heating the vaporizing tube 86. The end of the burner tube beyond the diaphragm 16 is provided with a diagonally arranged series of slots or holes 95 for igniting the main mixture stream. It should be noted that the heat rising from the flames emitted from the slots 94, beneficially acts on the main mixture stream passing through the regenerative chamber 17 by assisting in the vaporizing action above described.

The atomizing blast of air discharged through the conduit 28 and the primary volume of fuel discharged through the pipe 53 combine to produce a certain volume of mixture of a predetermined proportion for combustion when the boiler load is comparatively light. This mixture may be of just suflicient volume to meet the demands of the boiler when operating at light loads analogously to an idling mixture in the case of an internal combustion engine; or this mixture may be of sufficient volume to supply all the ordinary demands of the engine. This is a matter of design determinable only by the requirements of the articular installation. In either event, w en a greater volume of mixture is desired for meeting ordinary or overload demands on the boiler, the control rod 66 is depressed and the supplementary volumes of air and fuel admitted through the respective conduits 22 and 54. This immediately increases the volume of mixture to the desired extent, the proportion of this increased volume of mixture being determined bythe relative settings of the valves 56 and 57 and of connection between the link 70 and arm 67. It will be apparent that by raising or lowering the control rod 66 this added increment of mixture may be decreased or increased as desired. Referring to the arrangement of the nozzles or tubes 24 and 25 it will be seen that this supplementary volume of air is directed by the nozzle 25 angularly into the blast of mixture from the inner Venturi tube. This on hances the breaking up of the fuel particles and insures an intimate commingling of the two blasts. It will also be noted that the two tubes or nozzles exert a mutual aspirating effeet on each other. By thus supplying this supplementary volume of air to the burner through a separate conduit a sufiiciently high velocity is maintained in the inner venturi to atomize the fuel at low rates of firing without choking the supplementary volume of 8.11

which is necessary to be admitted for increased rates of firing.

In Fig. 3 I have shown a control system wherein the feeding and regulation of this added increment of mixture is performed aureaches a predetermined 'maximum. When the boiler pressure reaches a predetermined point slightly below this maximum pressure, at which point it is desirable to reduce the rate of firing, this boiler pressure acts through a pipe line 75 upon the diaphragm 76 of a pressure responsive element 77. This diaphragm, operating through a rod 78, controls a valve 79 in a valve housing 81 interposed in the supplementary fuel supply pipe 54. The rise and fall of the valve 79 in response to the flexure of the diaphragm 76 regulates the flow of fuel through the supplementary supply pipe 54 in an obvious manner. For e purpose of automatically opening the throttle valve 68 in accordance with the quantity of fuel flowing through the supplementary fuel supply pipe 54, a'cylinder 83 is interposed in this supply pipe. A. piston 84 is adapted for reciprocation in this cylinder and has connection with the control rod 66' which extends upwardly from the throttle arm 67 and enters the closed lower end of the cylinder 83 through a boss 85;; Any leakage of fuel past the piston 84 is conducted by way of a pipe 86 to the fire box, so that the cylinder'will not become clogged by the trapping of fuel below the piston and so that no loss of fuel can occur. A compression spring 87 in the lower closed end of the cylinder 83 normally tends to raise the piston 84 andclose the throttle valve 68.

In the operation of this arrangement, the lowering of the boiler pressure will allow the valve 79 to be raised, thereby initiating a fl ow of fuel through the supplementary fuel p1 54, or increasing the rate of a flow y existing in this pipe. This fuel will discharge into the Venturi throat, as in the previous embodiment and will also, through the medium of the piston 84, open the throttle valve 68 to permit or increase the flow of supplementary air through the conduit 22. The extent of opening of the throttle valve 68 will be determined by the rate of flow through the pipe 54, which will exert a greater or less pressure on the piston The pressure responsive element 7 7 which controls the admission of this added increment of mixture is preferably set to operate. between a range of pressures slightly below that at which the pressure responsive element 43 18 set. For example, in a typical high pressure installation, the pressure r nslve element 77 could be set to operate at tween and 425 pounds and the pressure respons ve element 43 could be set to operate at between 425 and 450 pounds. Thus, if the boiler pressure tends to fall below the minimum setting the. valve T9 will initiate or increase the low of supplementary air for the purpose of bringing the boiler pressure back to its predetermined range, and. if the pressure tends to exceed the maximum setting the operation of the pressure responsive element 4?, will interrupt the running of the motor 323. In between these two limits the pressure responsive. element 77 may be made to maintain a substantially constant pressure under all ordinary conditions by regulating the volume of fuel discharged through the pipe 54.

Although I have described my invention with reference to a particular embodiment as required by the statutes, I do not intend thereby to limit the invention to any of the details herein described, as it is evident that numerous modifications will at once be apparent to those skilled in the art. and I desire that all such modifications shall be considered as coming within the scope of the present invention I claim:

1. In a liquid fuel burner, the combination of a. mixing chamber, means for supplying liquid fuel thereto. a primary air passageway for supplying the requisite "olume of air to said mixing chamber for supporting combustion d illillg' a relatively low stage of firing, a '0ll lill' air passageway for supplying a supplementary volume of air to said mixing chamber during an advanced stage of firing, a throttle controlling the air flow through said secondary air passageway, valve means for supplementing the supply of liquid fuel to said inixing'chamber. and actuating means ro-operating with said throttle and said valve means. A

'3. In a liquid fuel burner, the combination of a mixing chamber, means for supplying liquid fuel thereto, a primary air passageway for supplying the requisite volume of air to said mixing chamber for supporting complete combustion during a relatively low rate of firing, a secondary air passageway for supplementing the volume of air during an'advanced rate of firing, blower mechanism connected to said passageways, a throttle con-- trolling said secondary air passageway, a fuel valve for increasing the supply of liquid fuel to said mixing chamber, means for simultaneously operating said fuel valve and said throttle, and igniting means located substantially posterior to the point of admixture between said liquid fuel and said supplementary air supply.

In combination, a burner, fuel feeding means, a first air conduit connected to said burner, a blower supplying a substantially constant volume of air to said first air conduit, a second air conduit connected torsaid burner, a blower for supplying air thereto, means for controlling the discharge of air through said second air conduit, and valve means co-operating with said latter controlling means for controlling the discharge of fuel from said fuel feeding means.

4. In combination, a burner, an atomizing air conduit discharging thereto, a supplementary air conduit discharging to said burner. a valve interposed in one of said conduits. fuel feeding means discharging to said burner, a fuel passageway connected thereto, a valve in said passageway, means for shunting fuel to'said fuel feeding means around said valve. and control mechanisms connected to both of said valves.

.3. In combination, a burner, a boileradapted to be heated thereby. means for feeding fuel to said burner, primary and secondary air conduits discharging to said burner, blower mechanism for supplying air to said conduits. control means responsive to con ditions in said boiler for controlling the operation of said blower mechanism, a valve in said secondary air conduit, a fuel valve controlling the fuel supply, and control means for controlling said valves.

- In witness whereof, I hereunto subscribe my name this 26th day of November, 1921. RAYMOND E. WHITE.

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