US3096810A - Low pressure oil burner - Google Patents

Description

July 9, 1963 R. G. MARTZ 3,096,810

I .OW PRESSURE OIL. BURNER A rra/@NEM "July 9, 1963 Filed Feb. 24. 1960 R. G. MARTZ LOW PRESSURE OIL. BURNER 2 Sheets-Sheet 2 /A/vE/vrof' @oa-E@ G. /V/Aerz.

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United States Patent 3,096,810 LOW` PRESSURE OHL BUER Roger G. Martz, Lebanon, Ind., assigner to Stewart- Warner Corporation, Chicago, lll., a corporation of Virginia Filed Feb. 24, 196i), Ser. No. 16,751 2 Claims. (Cl. 153-28) This invention pertains to liquid fuel burners and more particularly to an improved method and means for controlling the ow of combustion air therefor.

It is an object of the invention to provide an improved liquid fuel burner which is extremely smooth, easy, and efficient in starting.

Another object is to provide a liquid fuel burner employ-ing supplementary or secondary Vair in which ignition of the burner is virtually instantaneous and quiet and uniformly so in contrast to the smoking and/ or explosions ordinarily accompanying starting of this type of burner.

Another object is to provide a liquid fuel burner of the above type in which the secondary air is automatically controlled in an economical and efficient manner.

Another and most important object is to reduce heat loss in the. heating plant with wh-ich the burner is employed when` Ithe burner is turned olf. This is accomplished by preventing the flow of cool `air through the burner and into the heating plant under the action of the draft when the burner is turned off.

`Other objects, advantages, and features of the invention will appear from the following description read in conjunction with the accompanying drawings in which:

FIG. l is a diagrammatic cross-sectional view of a liquid fuel burner employing the present invention;

FIG. 2 is a fragmentary top plan view of the actual btuner depicted in FIG. 1 and FIG. 3 is an enlarged fragmentary sectional view taken on line 3-3 of FIG. 2.

Referring to the drawings in detail and at the outset particularly to FIG. 1 thereof, fuel oil is delivered by gravity to the burner fromv a conventional supply tank (not shown) through a conduit 1 leading to the inlet side of a slow speed fuel metering pump 3. The fuel oil passes throughy a screen 4 and port S, controlled by a shutoff valve 6, into the interior of the metering pump. This pump is of the oscillating eccentric type in common use as avolumetric metering device delivering a positive volurne of fuel regardless of the viscosity thereof.

Briefiy,the working parts of the metering pump comprise a worm 9 `which rotates shaft 10 and a pair of oscillating eccentrics 13 thereon through worm gear 1i. The oscillating eccentrics operate a pair of pistons ll( through suitable linkage comprising eccentric rings 14, yokes 17, and clevises 18 connected to the respective parts by suitable pins as shown. By means of the eccentrics the pistons are moved in a combined reciprocatory and oscillatory manner. Intake and exhaust ports 21 and 22 oneachof the pistons 16 provide for the ilow of the oil through the cylinders 23 in a well known manner. It is therefore seen that a small quantity of fuel oil continually iiows from the metering valve regardless of its viscosity.

The oil is thus delivered through the conduit 26 to the fitting 27 and thence into a relatively high speed fuel and air mixing pump 29 ofthe eccentric type. The intake side ofthe latter pump also communicates with the atmosphere through the line 30 so that during each revolution of the pump rotor 31 a quantity of oil and a predetermined quantity of air is taken/into the chamber of the pump. The pump, therefore, functions to determine the fuel to air. ratio of the mixture delivered to the burner nozzle 38.

From the fuel and air mixing pump 29 the mixture of Mice fuel oil and air is delivered under pressure through the conduits 35, 36 'and 37 to the nozzle 38 for discharge into the combination chamber of the heating plant with which the burner is used. A percolating chamber` 40 Vis provided between the lines 35 and 36 which chamber causes an agitation or percolation of the oil and air mixture thereby maintaining the oil in aproperly dispersed and uniform mixture with :the air. A cushioning chamber 42 connects with the percolating chamber so as to provide a body of air under pressure upon which the slightly pulsating pressure of the fuel oil and air in line 35 can act so as to be made uniform and provide even burning of the mixture at lthe nozzle end..

Line 44 is connected to the upper end of thercushioning charnber by fitting 46 and leads therefrom to a cylinder 45 provided 'above the metering pump 3. The fitting 46 connecting line 44 has a sm-all orifice (not shown) which has a relatively high flow resistance through which the pressure in the cushioning chamber bleeds or passes in a relatively slow manner to the cylinder I45. The size of the orifice is selected to allowv the full pressure of the cushioning chamber to reach the cylinder 45 in` from three to five seconds.

A piston 49 is positioned within the cylinder 45, normally being urged downwardly by a compression spring 50. A shaft 53 connects the piston -to one end of a beam or lever 55 pivotally supported on post 56 extending from the top of the metering pump casing. The opposite end of the lever 55 is connected by means of shaft 59 to the shutoff valve 6. The shaft is suitably sealed by diaphragm 60 to retain the fuel within the metering pump 3.

lt is therefore seen `that within a relatively short time after the burner is turned on, and the fuel metering and mixing pumps begin to operate. the shutoff valve 6 ofthe metering pump opens. It is likewise understood that shortly after the burner is turned off, the `air pressure in chamber 42 passes through percolaitor 40 to reduce the air pressure in cylinder 45. The shutoif valve 6 then automatically closes through the action of the spring 50.

A sump 63 is provided between conduits 36 and 37 to collect the liquid fuel as it drains back through the slightly inclined conduit 37 when the burner is turned off. A tube 64 is positioned within the sump so as to allow aspiration of the collected fuel through the end 65 into the conduit 37 uponr starting of the burner.

The nozzle 38 is 'of a form known in the art having an inner plug element 69 and a series of passages (not shown) extending around the plug member for atomization of the liquid fuel and air mixture. A blower 71 is provided within housing 72 for the supply of supplementary or secondary 'air around the nozzle,38 for complete combustion of the ignited mixture of fuel oil and air- The secondary air passes through a blast tube` 74 which terminates at the discharge end in a hood 73 for direction of the secondary air around the ignited mixture.

A pair of horizontally disposed electrodes 75only one of which can be seen, is positioned above the nozzle for ignitionof the air and oil mixture in the usual manner. Control of the ignition circuit may be effected in any conventionaly manner forming no part of thepresent invention.

The electrodes are supported within aporcelain insulator member 76 received in a holder element 77. The latter element is` provided with swirl tins 79 f-or thepassage `of secondary air within and around a forward shellmembei 81 in a whirling pattern. Members 'i7 and 8l are in turn received Within ia flame controller member 84 having a plurality of supporting tins 85 and 86 adapted to spin the air` passing outwardly of the flame controller in the oppositedirection to that flowing around the members 77 and 81. The flame controller member is adapted to be moved longitudinally for changing the lamount of secondary air passing between the same and hood at the front thereof. In this manner the characteristics of the flame can be accurately controlled in accordance with presently lknown practice.

The blower shaft 90, fuel and air mixing pump shaft 91, and the worm shaft of the fuel metering pump at 9 are operated by a common source of power, as by motor 92 (see FIG. 2). Actually these shafts are coaxial and at least partly common inasmuch as FIG. l is a diagrammatic showing. The coaxial driven arrangement is clear from FIG. 2 which shows the actual arrangement of the parts.

IIt has been the experience in low pressure burners of the present type for the liquid fuel to drain back in the lines, in this case into sump 63, when the burner is turned off. Upon starting the burner, this fuel and the fuel from the pump 29 is ejected from the nozzle 38 into a relatively cool combustion chamber having a lean fuel air mixture therein. The electrodes 75 do not produce suflicient heat to ignite this mixture particularly since the natural draft from the chimney rushing past the electrodes cools the electrodes. Eventually and some times only after a large mass `of fuel has collected in the combustion chamber land a rich fuel-air mixture is attained, ignition will, of course, take place. Where the previously mentioned ejected fuel is merely incompletely burned producing smoke and soot, or where the fuel has been ejected in a nonignited condition, ignition of this large mass of fuel and air mixture will produce ra violent explosion in the combustion chamber heard throughout a house or building, and even therebeyond. This explosion is very objectionable to the occupants of a home `or building besides producing the soot which lines the inside of the combustion chamber and reduces its efliciency.

Another very objectionable feature of presently known burners lof this type is that vwhen the burner is turned oif and not operating, the natural draft of the chimney to 'which the heating plant is connected draws in cool air through the secondar-y air channel of the burner and into fthe heating plant and up the chimney. This very substan-tial and constant supply of cool air greatly reduces the inside temperature of the heating unit on the off cycle, rapidly cooling the same. Besides subjecting the parts of the combustion chamber to relatively great and rapid changes in temperatures and to `the alternate heating and cooling of the same which is undesirable, great efficiency of the heating plant is lost occasioned by the additional heat necessary tto bring the plant up to the operating temperature from Ia cool condition each time it is operated.

The present invention is adapted to eliminate both of these major diiculties in a very simple, reliable and inexpensive manner.

In accordance with the present invention an air regulator housing 94 is provided for the intake of air within the blower or main housing 72. The regulator housing is provided with a single inlet opening 95 of rectangular form. This housing has a lbore 96 on one side and a plate member 97 on the other side having a bore 98 in coaxial relation with the bore 96. Mounted within the bores are a pair of coaxial shaft elements 98 and 99. A rectangular damper 101 is supported in end slots in these `shaft elements, being suitably retained in position by screws.

The damper 101 is formed with upwardly and downwardly turned edges 102 and 103 for substantially tight sealing engagement with the spaced parallel inside surfaces 104 and 105 of the air regulator housing inthe closed damper position shown in full `lines in FIG. 2. A tension spring 107 is mounted between the damper and regulator housing, being attached through suitable openings in each of the latter. This spring is so attached to Ithe damper as to normally move the same from the closed position to an Aopen position. Bead chain 110 is attached to the damper at the opposite side `of Athe line of pivot thereof by means of connector 112 extending through an opening in the damper. This chain extends from Ithe damper to a pulley 115 over which the chain passes. The pulley is supported on a structure extending from the top of the fuel metering pump 3. The chain is further attached by suitable means to the lever 55 above the metering pump.

The plate 97 on the side of Ithe air regulator housing is provided -with an inturned ange portion 123. An adjusting screw extends through a threaded opening in this flange, being adapted to be moved upwardly and downwardly and locked in any desired position by means of the lock nu-t 126. This screw constitutes a stop for limiting the opening movement of the air damper 101, as clearly seen in FIG. 3. It is pointed out in this connection that proper adjustment of Ithe ysecondary |air is of major importance in obtaining complete and proper cornbustion of lthe fuel discharged from the nozzle. The adjusting screw provides very lfine and accurate adjustment of the amount of secondary air allowed 'to flow through the burner during normal operation thereof, for the most eicient `combustion of the fuel.

In accordance lwith the present invention, the bead chain 110 is in a taut condition when the outer end 128 of the lever 55 and the piston 49 are in a down position. It is also noted that :this condition of the chain produces a closed position of the damper 101. Upon upward movement of lthe piston 49 and end 128 of the lever 55 the chain will slacken and allow the spring 107 to move the damper into an open position against the stop member 125.

Considering the operation of the device, it is therefore apparent that lwhen the operating pressure produced by the mixing pump 29 builds up in the cushioning chamber 42 and passes through line 44 into the cylinder 45 the piston 49 and lever 55 will be moved, thus opening the shutoif valve 6 and at the same time the damper 101. As has been previously pointed out, because of the flow resistance in the fitting 46 and in :the line 44 the air pressure takes awhile to build up in the cylinder 4'5, usually from three to ve seconds. Inasmuch as the damper 101 is operatively connected to the piston and lever, there will be a `delayed or rela-tively slow opening of the damper over the initial period of burner operation.

The damper 101 will therefore be in a closed position when the burner is turned on. Consequently there will be no secondary air rushing past the end of the nozzle 38 at this time. It has been found that by preventing movement of secondary air the initial amount of fuel ejected from the nozzle will immediately fully ignite. This is because of a hotter spark produced by the electrodes without being deflected by the rush of air therepast and because of the lack of the secondary air which would otherwise blow past the ejected fuel and prevent ignition or proper ignition. In this Way the smoking and production of soot and violent explosions are eliminated.

With the fuel valve `6 closed only a limited quantity of fuell can Abe discharged from meter 3, the quantity available generally being determined when the pressure capacity of the meter equalizes the vacuum built up in meter 3. However, the available fuel from meter 3 is supplemented by the fuel in percolator 40 and that laspirated from sump 63. Consequently, immediately after starting the burner, pump 29 delivers a combustible mixture of fuel and primary air -to nozzle 3S. Since the damper 101 is closed the hotter electrodes immediately ignite the mixture ejected from nozzle 38 to Support ignition.

By the time the available fuel from meter 3 and the fuel in the sump 63 has burned, the air pressure in cylinder 45 has built up sufficiently to open fuel valve 6. This replenishes the fuel meter 3 and per-mits sustained Ifuel flow from pump 29 to nozzle 38. Simultaneously with the fuel valve 6 opening, the damper 101 also opens to permit a gradually increasing quantity of secondary air flow past nozzle 33. This delayed admittance of second-ary air past the nozzle produces an extremely smooth and quiet burner starting. Beca-use of the ignition of the primary fuel `and air supply from meter 3, pump 29 and the sump 63, the ignition is almost instantaneous upon turning on of the burner and is continuous without the usual false or interrupted starting with the accompanying smoking and/or explosions previously noted.

Of equal importance to the smooth and quiet starting of the burner is the automatic closing of the damper 101 shortly after the burner is tur-ned off. The pressure of the compressed air in chamber 4Z, line 44 and cylinder 45 is dissipated either by bleeding through percolator 40 or by leakage. Spring S0 thus closes the damper 101 which totally prevents the drawing in of cool air through the burner and into the hot combustion chamber when the burner is off, thus to cool the plant and incur the great :loss of heat previously noted. It is understood that the ow resistance of the nozzle 38 is small as compared to the flow resistance of the fitting 46 and the line 44. Thus the air and oil mixture in the peroolator 40 is almost instantaneously discharged through the nozzle 38 as the pump 29 is stopped, while the air in cylinder 45 passes through the high ow resistance fitting and line to delay actuation of the damper 101 with respect to the operation of the pump. It has been found by tests that fully 5% of the heating fuel can be saved by the use of the present invention. It is quite evident that such a saving is important especially over a long period of time. This together with the total elimination Yof the rough explosive starting heretofore generally present in the industry for low pressure burners represents a desirable contribution to the art.

Although a particular embodiment and use of the invention has been illustrated and described, it is not desired to be so limited. The -appended claims should therefore be liberally construed in the overall light of the inventive concepts.

What is claimed is:

1. In a low pressure oil burner, the combination comprising a tube, a nozzle extending Within the tube, pressure producing means operable intermittently for the supply of cil and air mixture to the nozzle for intermittent ow therethrough, means for supplying secondary air to the tube including inlet means, normally closed closure means for substantially preventing admission of the secondary air through the inlet means, iuid pressure operated means operatively connected to the closure means effective for opening actuation thereof for admitting secondary air through the inlet means, and means forming a single continuous communicating path between the exhaust side of the .pressure producing means and the pressure operated means yoper-able to pressurize the latter upon operation of the former to open said closure means, and to vent the latter upon termination of the former to permit closing of the closure means, said communicating path means having a ilow resistance substantially greater than the tlow resistance of the nozzle and sufficiently high to delay in the order of a few seconds equalization of pressures in the exhaust side of the pressure producing mea-ns and the pressure operated means for delaying correspondingly the opening or closing of the closure means relative to the operation of the pressure producing means.

2. In a low pressure oil burner the combination comprising a tube, a nozzle extending within the tube, pressure producing means connected in series with the nozzle upstream therefrom, said pressure producing means being operable intermittently for the supply of oil and air mixture to the nozzle for intermittent ow therethrough, means Ifor supplying secondary air to the tube including inlet means, closure means for substantially preventing admission of the secondary air through the inlet means, means :normally biasing the closure means to the position closing the inlet means, fluid pressure operated means operatively connected to the closure means, said pressure operated means being operable upon full pressurization thereof to open the closure means against the biasing means and being operable upon discharge of pressure therein to permit the biasing means to close the closure means, and means including a single xed communicating path between the exhaust side of the pressure producing means and the pressure operated means operable to pressurize the latter responsive to operation of the fromer and to vent the latter upon te-rmination of the former, said communicating path having a higher flow resistance than the flow resistance of the nozzle and of such high ilow resistance operable to delay for -atleast a few seconds equalization of pressures in the exhaust side of the pressure producing means and the pressure operated means for delaying correspondingly the opening or closing of the closure means relative to operation of the pressure producing means.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. IN A LOW PRESSURE OIL BURNER, THE COMBINATION COMPRISING A TUBE, A NOZZLE EXTENDING WITHIN THE TUBE, PRESSURE PRODUCING MEANS OPERABLE INTERMITTENLY FOR THE SUPPLY OF OIL AND AIR MIXTURE TO THE NOZZLE FOR INTERMITTENT FLOW THERETHROUGH, MEANS FOR SUPPLYING SECONDARY AIR TO THE TUBE INCLUDING INLET MEANS, NORMALLY CLOSED CLOSURE MEANS FOR SUBSTANTIALLY PREVENTING ADMISSION OF THE SECONDARY AIR THROUGH THE INLET MEANS, FLUID PRESSURE OPERATED MEANS OPERATIVELY CONNECTED TO THE CLOSURE MEANS EFFECTIVE FOR OPENING ACTUATION THEREOF FOR ADMITTING SECONDARY AIR THROUGH THE INLET MEANS, AND MEANS FORMING A SINGLE CONTINUOUS COMMUNICATING PATH BETWEEN THE EXHAUST SIDE OF THE PRESSURE PRODUCING MEANS AND THE PRESSURE OPERATED MEANS OPERABLE TO PRESSURIZE THE LATTER UPON OPERATION OF THE FORMER TO OPEN SAID CLOSURE MEANS, AND TO VENT THE LATTER UPON TERMINATION OF THE FORMER TO PERMIT CLOSING OF THE CLOSURE MEANS, SAID COMMUNICATING PATH MEANS HAVING A FLOW RESISTANCE SUBSTANTIALLY GREATER THAN THE FLOW RESISTANCE OF THE NOZZLE AND SUFFICIENTLY HIGH TO DELAY IN THE ORDER OF A FEW SECONDS EQUALIZATION OF PRESSURES IN THE EXHAUST SIDE OF THE PRESSURE PRODUCING MEANS AND THE PRESSURE OPERATED MEANS FOR DELAYING CORRESPONDINGLY THE OPENING OR CLOSING OF THE CLOSURE MEANS RELATIVE TO THE OPERATION OF THE PRESSURE PRODUCING MEANS.

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