US1768901A - Method of and apparatus for controlling the combustion of oil in oil burners - Google Patents

Description

y 1, 1930. B. GREENFIELD 1,768,901

METHOD OF AND APPARATUS FOR CONTROLLING THE COMBUSTION OF OIL IN OIL BURNERS Filed July 12, 1921 2 Sheets-Sheet 1 July 1, 1930. B. GREENFIELD METHOD OF AND APPARATUS FOR CONTROLLING THE COMBUSTION OF OIL IN OIL BURNERS Filed July 12, 1921 V 2 Sheets-Sheet 2 l I l 1 1 i w llll II Ill 32 W mum/l WMM M oil in oil burners.

Patented July 1, 1930 unite; rnrss ,P-ATSEN o'FFicE BENJAMIN GREENFIELD, F BARTL'ESVILLE, OKLAHOMA, ASSIGNOR TO DOHER-TY RESEARCH COMPANY, OF NEW YORK, N. Y., A. CORPORATION OF DELAWARE METHOD OF AND APPARATUS FOR CONTROLLING THE COMBUSTION OF OIL IN OIL BURNERS Application filed Ju1y 12, 1921. Serial No. 484,141.

This invention relates vto a method and apparatus for controlling the combustion of The invention will be hereinafter described, by Way of example, as applied to a field boiler of thetype for drilling oil wells,

In the use of oil burnerslfor commercial purposes, as for example, in boilers, it is customary to maintain from to 60 pounds pressure per squareinch on'the oil burner header and to vary the rate of feed of the oil to the burner by adjustment of the burner regulating valve.

Gil feeding systems have, however, been devised in which the regulation of the feed of the oil is obtained by varying the pressure of the oil at the oil burner header from about 30 pounds to about 60 pounds per square inch. In certain of the last-mentioned systems thevariations in the pressure of the oil and, consequently, in the rate of feed of the oil, are'accomplished automatically. In both the hand-controlled and automatic systems in which the rate of feed of the oil is regulated by changing the pressure on the oil, a control valve is usually provided. at each oil burner for manually modifying the pressure regulation. Ihe pressure of oil as it issues from a burner is, of course, the same as that surrounding the burner, and the pressure prevailing about a burner is ordinarily atmospheric or. slightly below atmospheric. The drop in pressure due to oil passing through the oil burner itself is usually very small. The greater part of the drop in pressure from anamountvarying between 30 and'GOpounds to atmospheric is eifected at the regulating valve. I

As a consequence of the high pressure on the oil at the regulating valves of oil burners, the valve openings under normal conditions of operational-e small. Even in the case of a burner of large capacity in whichthereg: ulating valve presents a relatively large openwhen the burner is being operated atits maximum rate, the opening becomes small at the lower rates of combustion asthe fire is turned down. reason of the small size'of its opening, the burner regulating valve obstructs the movement throughkit ofthe foreign solid matter usually present in fuel oil, wlth the result that such matter accumulates on the supply side of the valve and seriously relatively low rates of flow is elongated and narrowas in the case of the usual globe valve or needle valve. In this position of adjust ment the valve acts as a strainer, stopping all foreign matter that cannot pass through the narrow slit.

Inasmuch as the rate of flow of oil through I an opening carries directly as its area and the area of the opening varies substantially as the square of what may be denominated its mean dimension, assuming that the length and breadth of the area are simultaneously increased or decreased, it follows that valves presenting small openings are very sensitive, it being understood that an equal change in its mean dimension will produce a much larger change in the area of a small opening than in that of a relatively large one. Accordingly, in the use of the present systems of feeding oil, a minute adjustment of the regulating valve produces a large change in the rate of flow of oil tothe burner. On this account it frequently happens in the use of oil-fired boilers that a small opening movement of the valve passes too much oil to the boiler and causes the stack of the boiler to smoke, and when the valve is turned toward closed position the flow of oil .is shut off so to boilers is that when a correct adjustment is finally obtained it will continue for av short interval only. During. this interval solid matter may accumulate at the valve and reduce the flow, or matter held back by the valve, during the adjustment =may work through the valve opening and allow an excess of oil to flow to the boiler.

A further disadvantage of oil feeding systems as at present constructed is that by their use an operator can obtain almost unlimited combustion capacities with resultant dam age to the heating appliance or to the process in which the heating appliance is being used. This source of trouble is aggravated by the necessity of making frequent adjustments of the regulating valve and the inability of the operator to determine the actual rate of oil flow.

A still further disadvantage in the useof present oil feeding systems is that since the actual rate of flow of oil to the oil burner can not be accurately controlled, it is impossible to regulate the *entilation of the burner so as to provide the amount of air needed for complete combustion of the (Hi without supplying a large excess of air.

It is an object of this invention to feed oil to a burner at a rate which can be readily and accurately determined and regulated.

A further object of the invention is to feed oil to a burner in a manner which will enable a desired rate of feed of the oil when once established to be retained unchanged without adj ustment of the flew-regulating means.

A still further object of the invention is to control the ventilation of an oil burner so that at all rates of feed of oil, the amount of air admitted to the burner will be suflicient for complete combustion of the oil but will not be in any considerable excess over the amountrequired for complete combustion.

In the fulfillment of these objects in accordance with the invention, the flow of oil to the burner is controlled by a low pressure drop or differential across an orifice, and the rate of flow of oil to the burner is regulated by varying the pressure drop across the orifice between zero and a desired maximum. The pressure drop across the orifice in most installations is, preferably, limited to an amount not substantially exceeding one pound per square inch, and the orifice is made of relatively large size so that all foreign solid matter usually to be found in fuel oil may pass through it without obstruction. Preferably, the orifice is circular and the part which contains the orifice is so formed that the size of the orifice cannot be changed without substitution of parts, thereby obviating all danger of the size of the orifice being unduly restricted or increased by the operator.

In accordance with a further feature of the invention, the differential pressure across the orifice is controlled through the agency of a gaseous fluid, and the feeding of the oil is, preferably, accomplished in such a way that oil is fed to the burner only when there is a greater gaseous fluid pressure on the supply side of the orifice than on its delivery side. Obv1ously,var1ous gaseous fluids may be used without departing from the principles of the invention, but when the invention is applied to steam boilers, it is preferable, for the sake of convenience, to utilize steam withdrawn from the boiler.

A further feature of the invention resides in simultaneously varying the rate of feed of oil to the burner and regulating the ventilation of the burner so that the amount of air admitted to the burner is always substantially that required for complete combustion of the oil. Various other features of the invention pertain to the utilization of steam or other gaseous fluid for varying and limiting the rate of feed of the oil, atomizing the oil, regulating the ventilation of theburner, and reducing the feed of oil to a boiler when the pressure of the steam in the boiler tends to exceed a pro-determined degree.

Still other objects and features of the invention will appear as the description proceeds and will be pointed out in the appended claims.

In the drawings which show a preferred embodiment of the invention:

Fig. 1 is a view in side elevation of an oil- [ired boiler equipped with combustion controlling apparatus illustrative of the invention.

Fig. 2 is a view of the boiler in end elevation looking from the right in Fig. 1.

Fig. 3 is a sectional View in elevation of the device for regulating the feed of the oil.

F ig. 4 is a detail view of the orifice chamber.

Fig. 5 is a sectional elevation of the relief valve in the low pressure line for controlling the ventilation of the boiler and the feed of the oil to the boiler; and

Fig. 6 is a like view of the pressure regulator.

In the practice of the method of this invention forcontrolling the combustion of oilin oil burners, the oil is caused to flow through an orifice of relatively large size such as to enable all matter ordinarily )resent in fuel oil to pass freely through it, and alow pressure drop or differential usually less than one pound per square inch, which is apm-oximate 1y equivalent to 30 inches of oil, is utilized to produce flow of oil through the orifice to the burner. The size of the orifice in individual installations is preferably constant, and the control of the flow of oil to the burner is erfected by varying the pressure differential across the orifice between zero and an amount which for most installations does not exceed one pound per square inch. A gaseous fluid is, preferably, employed to produce the pressure drop across the orifice, and the oil is caused to flow through the orifice under a head corresponding to the difference in gaseous fluid pressures on the oil supply side of the orifice and on its delivery side. The gaseousfluid may conveniently be used for atom- I ried out by apparatus of varying forms.

izing the oil in the burner, and in such a case, the fluid is employed for controlling the feed of oil to the burner at a pressure less than the atomizing pressure.

The ventilation of the burner is also controlled by the pressure of the gaseous fluid in such a manner that the amount of air supplied to the burner will always be sufficient for the complete combustion of the oil without substantial excess. The rate of feed of oil to the burner is limited to a desired maximum by limiting the pressure differential across the orifice. This is in turn effected by sul jeoting the delivery side of the orifice .to at mospheric pressure and limiting the pressure of the gaseous fluid on the oil at the supply side of the orifice. The gaseous fluid, preferably, controls the ventilation of the burner under a pressure substantially equal to the pressure imposed on the oil. Various kinds of gaseous fluids may be used without departing from the principles of the invention. In the application of the 111Vc11 tion to steam boilers, however, the gaseous fluid pressure for regulating the feed of the oil and the ventilation of the burner is, preferably, obtained through the agency of steam withdrawn from the boiler. Moreover, when the invention is used in connectionwith steam boilers, the feed of oil to the boiler furnace is reduced whenever the pressure of the steam in the boiler tends to exceed a predetermined degree. I V g The apparatus shown in theaccompanying drawings constitutes a convenient and sati factory means wherebythemethod of this invention may be putinto practice. It is recognized, however, that the method may be c.- cordi-ngly, the apparatus herein disclosed is to be considered as illustrative only of means by which the method may be applied in a commercial way.

In the illustrated construction, a field boiler 10 of the type used'for drilling oil wells is provided with a sub-furnace 12 in which is placed an oil burner 14. As shown, the oil burner 14 comprises a cylindrical chamber in which is fitted a core 16 having a single opening 18 for oil and a plurality of openings 20 below the opening 18 for conducting an atomiain fluid into close contact with the oil. The arrangement of the openings 20 is such as to form the atomizing fluid into a fan-like layer upon which the oillfalls as it issues from the opening '18. The oil burner 14 does not require further description inasmuch as it is of a type well known to the trade and constitutes per se no part'of the present invention.

Oil is conducted to the burner 14 by a pipe 22 which communicates with the burner sub stantially in line with the opening 18. The pipe 22 extends through the front wall of the sub-furnace 12 and is connected at its outer a strainer to prevent the passage of large forelgn ob ects of a kind not ordinarily present in fuel oil.

The flow-regulating devlce 26 comprlses a member 32 provided with an orlfice or re stricted opening 34, and means for creating a low drop in pressure across the orlfice tov cause oil to flow through it to the burner 14.

in the present exemplification of the invent on, the pressure of a gaseous fluid is utilized to regulate the flow of oil through the orifice 34. Consequently, it is desirable, in

order to cause the rate of flow of oil through the orifice to be influenced by the least possible number of variable factors and thereby enable the rate of flow of the oil to be regulated with the greatest possible accuracy, that the pressure on the oil as it enters the flow-controlling device 26 shall have no eff feet on the pressure at the orifice 34. Manifestly, if oil is supplied to the device 26 by a pump, the pressure on the oil as it enters thedevice will vary with the speed of the pump and the head of oil in the pipe 28, and

if oil is supplied to the device 26 by gravity alone, the pressure on the oil will still vary in accordance with the level ofthe oil in the ultimate source of supply. To the end that the rate of flow of oil through the orifice 34 may be entirely unafii'ected by the pressure of the oil asit enters the device 26,

the flow-controlling device includes a trap or chamber 36 located on the supply side of the orifice 34 and provided with means for maintaining the oil in the trap at a fixed level. As shown, such means comprises a valve 38 (Fig. 3) arranged to control the inflow of oil to the chamber 36 from the pipe 28 and. connected by suitable linkage 40 to a float 42. The arrangement of these parts is such that when the oil tends to rise above the fixed level, the float 42is raised and moves the valve 38 toward closed position, whereas when the oil tends to recede below the fixed level, the float 42 falls andmoves the valve 38 toward open position.

The trap 36is formed at one side near its bottom with a projecting portion '44 in which i pipe 46 and on its delivery side with the orifice chamber 48. As shown, the orifice memher is in the form of a plate threaded into the orifice chamber48 adjacent to the pipe 1 46, and theorifice 34 is of the type commonly called an orifice, in thin plate. It is eviis of a type such that the introduction of an atomizing fluid into it produces no suction in the oil pipes 22 and 24. In order to insure against the creation of any suction 1n the pipes 22 and 24 and the orifice chamber 48,

the chamber is is formed at its sides with two large openings 52. The openings 52 are preferably threaded to allow them to be closed by screw plugs 53 when necessary to prevent the entrance of dust into the chamber 48.

Inasmuch as the orifice chamber 48 is open to the atmosphere, the pressure on the deliveryside of the orifice is substantially constant. Consequently, the rate of flow of oil through the orifice 34 may be cont-rolled by gaseous fluid pressure imposed on the oil in the trap 36. In order to enable a low pressure drop to be readily obtained across the orifice 34 and to enable the pressure drop to be readily reducedsubstantially to zero thus substantially suspending the flow of oil to the burner 14. the oil in the trap 36 is preferably maintained at the level of the orifice 34. With this construction, oil is caused to flow through the orifice only when there is a greater gaseous fluid pressure on the oil in the trap 36 than on the delivery side of the orifice 34, or, in other words, only when the pressure of the gaseous fluid in the trap 36 is greater than atmospheric pressure. Consequently, if the gaseous fluid pressure in the trap 36 is reduced to atmospheric, the flow of oil to the burner 14 through the orifice 34 is discontinued.

The use of a low pressure drop for producing flow of oil through the orifice 34 is of particular importance in field boilers since it enables oil to be fed to a boiler from a field tank by gravity. The pipe 28 of the illustrated installation is designed to receive oil from a field tank without the use of a pump. The expense and trouble which are avoided in this way are very considerable.

Means is preferably provided for enabling a small quantity of oil to be supplied to the burner 14 at any time regardless of pressure conditions in the trap 36. A convenient embodiment of such means consists of a pilot pipe 54 interposed between the oil trap 36 and the pipe 22 and provided with a valve 55.

In the illustrated construction, the gaseous fluid which controls the feed of the oil is conducted to the trap 36 from a stand-pipe 56 connected to the top of the trap by a pipe 58 (Fig. 2). A second pipe 60 leads from the trap 36 below the oil level to the stand-pipe 56. With this construction, it is evident that the oil level in the stand-pipe 56 will be the same as that in the trap 36. In order to en able the oil level to be observed by the operator, a gauge glass 62 is connected to the stand-pipe above and below the oil level by pipes 64 and 66 respectively. A second gauge glass 68 communicates at its lower end with the'stand-pipe 56 below the oil level and is open to the atmosphere at its upper end The stand-pipe 56 may also be provided at its bottom with a pet-cock 70.

Since the gauge glass 68 and the orifice chamber 48 are both open to the atmosphere, the height of oil in the glass 68 indicates the pressure differential or drop across the orifice 34. The glass 68 is calibrated so as to enable the pressure differential to be measured. In order to measure the rate of flow of oil directly, the gauge glass. 68 must be calibrated to correspond with the size of the orifice 34. If, for any reason, the size of the orifice should be changed, a new gaugeglass 68 would have to be substituted for the one previously in use. If the gauge glass 68 is calibrated to indicate the pressure differential only, the rate of flow of oil in any installation can be readily computed from the indicated differential and the known size of the orifice 34.

In actual installations which have been operated very successfully, an orifice 34 of onequarter inch diameter and a pressure drop across the orifice of .65 pounds of oil have been employed in firing a 250 horse power boiler at 125% of its rated capacity. In these installations the fuel oil used was Kansas crude having a specific gravity of about 34 Baum. The size of the orifice 34 is decreased in firing boilers of smaller capacity, but by using a low pressure differential, the size of the orifice for boilers of all capacities may be made large enough to permit all foreign solid matter usually present in fuel oil to pass freely through it. In this connection it is to be noted that oils ordinarily used commercially for fuel purposes contain a considerable amount of solid matter which it is impractical to remove from the oil by filtration or otherwise. Such matter usually consists of partieles of dirt, etc. If the strainer 30 were, designed to remove such particles from the oil, it would be quickly clogged by a large accumulation of matter. For this reason the strainer 30 is designed to remove from. the oil only objects of considerable size. Such objects are not usually present in fuel oil, and the strainer may therefore be used for a long time without cleaning.

Theaccuracy with which the rate of feed of oil to a burner can be controlled and regulated depends in great measure on the number of variable factors afiecting the feed of the oil. In the use of this invention, the number of such variable factors is reduced to a .minimum. The size of the orifice 84 cannot be changed Without substitution of one plate .32 foranother. Such a substitution is generally not made after an installation is complete and cannot be made without interrupting the operation of the burner. Moreover, when one orifice plate is substituted for another, the substitution is not effected as a temporary adjustment but with a view topermanency, as, for example, when the capacity of the burner is changedk The status of the orifice 34 as a fixed rather than a variable factor in controlling the rate of flow of oil to the burner is further established by the fact that the orifice is always made of sufficient size so that it will interpose no obstruction to the passage through it of foreign solid matter suchas isordinarily present in fuel oil. Thisprevents solid matter from restricting either temporarily or permanently the actual size of the opening available for the passage of oil. As already indicated the 5 rate of flow of oil througlilthe orifice is entirelyuninfluenced bychange in the pressure on the oil in the pipe 28. The creation of a pressure drop across the orifice 34 involves two factors one of which, namely, thepressure on the delivery side of the orifice is substantially constant. Consequently, the only variable factor afiecting the rate of flow of oil to the burner 14 is the pressure of thegaseous fluid on the oil inthe trap 36. This invention not only enables the rate of flow of oil to the burner 14 to be controlled and regulated with great accuracy, but it also enables the rate of flow of oil to be very accurately determined by reference to the gauge glass 68.

Where a gaseous fluid under a pressure either greater or less than atmospheric pressure is conveniently availableflt is preferred to utilize such fluid at one'side of the orifice and atmospheric pressure on the other side of the orifice for producing and regulating the flow of oil through the orifice. It is recognized, however, that certain of the principles of the invention involving the use of alarge orifice and a low-pressure drop across the orifice, can be applied in a commercial way with other means forinducing adrop in pressure across the orifice. For example, varying gaseous fluid pressures may beem'ployed on both sides of the orifice, and'when a gaseous fluid is not readily availablethe dropin pressure across the orifice maybe varied by-vary ing the head of the liquid oil. on the orifice.

In the latter event, however, the pressure of the oil at the orifice-should be so controlled as to be'independent of the pressure at which the oil is supplied to the flow-controlling mechanism.

The pressure of the gaseous fluid in the trap 36 may be varied manually or automatically within the scope of theinvention. In the illustrated construction, a mixture of steam and air is employed as thegaseous fluid and the pressure of the gaseous fluid is controlled automatically. To this end, steam is withdrawn from the boiler 10 by a conduit including a pet-cock 72, valve 74, strainer 76,,

pressure regulator 78, pressure gauge 80, orifice nipple 82, and blow-cock 84. The steam isreduced to a pre-determined pressure by the pressure regulator 78, and its pressure is further reduced by passing through the orifice nipple 82. The conduit 7 0 communicates on the outlet side of the nipgauge glass 68 may be mounted on the trap The pressure regulator 78 isset to -reduce the steam to the pressure best adapted for atomizing the oil in theburner 14, and a coni necting pipe 88 leads from the conduit 70 intermediate between the pressure regulator 78 and the orifice nipple 82 to the burner. The

pressure regulator 7 8 is of known construction and does not require detailed description. As seen in Fig. 6, steam passes through the regulator from left to right and is governed by a valve90. The valve is connected to a diaphragm 92, the under side of which is subjected to the pressure of the steam on the outlet side of the valve. If the pressure of the steam on the outlet side of the regulator tends to exceed that for which the regulator is set, the diaphragm 92 is forced upwardly against the, tension of a spring 94 thus causing the valve 90 to move toward closed position. If, on the other hand, the pressure of the steam tends to fall below that for which the-regulator is set, the spring 94 moves thevalve 90 toward open position.

As hereinbefore indicated one of the features of the invention contemplates that the rateof flow of oilto the burner v 14 shall be reduced whenever the pressure of the steam boilein Asshown, the device 96 is located at one end of the low pressure line 86 and comprises a casing formed to provide an inlet chamber 98 and an outlet chamber 100,

trolled by the pressure ofthe steam in the the latter being open to the atmosphere. The I flow of fluid through the device96 is normally prevented by a valve 102 maintained in closed position by a lever 104 and weight 106. The device 96 is formed at its upper end witha chamber 108 containing a dia phragm 110 connected to the valve 102. The chamber 108 above the diaphragm 110 is closed to the admission of air and has connected to it a pipe 112 leading from the conduit 7 on the inlet side of the pressure regulator 78. The pipe 112 conducts steam to the chamber 108 of the pressure relief device 96 substantially at boiler pressure. Consequently, if the pressure of the steam in the boiler tends to exceed that for which the device 96 is set, the valve 102 of the device is opened, thus relieving the pressure in the low pressure line 86 and reducing the feed of oil to the boiler.

The rate of supply of air for supporting the combustion of the oil fed to the boiler is controlled by a damper 118 in the stack or flue 120 of the boiler in such a manner that whatever the rate of feed of oil to the boiler may be, air is admitted to the boiler in sufficient quantity to support the combustion of the oil but without any considerable excess. As shown, the damper 118 is fixed on a rotatable shaft 122, provided at one end with a pulley 124 over which passes a cable. 126. The cable 126 is attached at one end to a small weight 128 and at its other end to an actuator arranged to move vertically in accordance with the pressure in the low pressure line 86.

The actuator may have various forms. In

the illustrated construction, however, it is in the form of an inverted bell 130 closed at its 8 upper end and having its open lower end im such that when the damper is closed, the bell 130 isin its lowermost position, and the crank arm 136 extends horizontally from the shaft 122 in a direction such as to cause the weight 138 to swing downwardly as the bell 130 is raised. From the foregoing it will be understoodthat the weight 138 tends in the closed position of-the damper to raise the bell 130. As the bell 130 is raised the moment of the weight 138 tending to lift the bell gradually decreases so that the gas pressure necessary to further elevate the bell increases as the bell attains the higher positions of its movement. 7

By reference to the well known equation for determining the rate of flow of liquid through an orifice, Q=c adm, in which Q represents the quantity or rateof flow, a,

the area of the orifice, g, the gravity co-efiicient, h, the pressure drop across the orifice and c, a co-efiicient based on the shape of the orifice, it will be understood that the rate of flow of oil through the orifice 34 varies in accordance with the square root of the pressure in the low pressure line 86.

For convenience in explaining the principle of operation of the damper 118, the factors affecting the action of the damper may be symbolized as follows:

VV=the mass of the weight 138,

X=the net weight of the bell 130, that is, the weight of the bell minus the weight of the striker 142 and weight 128;

R=the moment arm of the bell 130 and Weight 136 in inches;

a=the transverse area of the bell in square inches; v

P=the gas pressure in the bell in inches of water;

A=the transverse area of the stack 120 at the damper;

D the area of the damper; and

=the angle made by the arm 136 and the damper 118 with the horizontal plane through the damper axis.

The moments of the weight 138 and the bell 130 when the arm 136 is in horizontal position and the damper 118 closed are usually made substantially equal so that when there is'atmospheric pressure only in the bell 130, the weight 138, damper 118, and bell 130 are in equilibrium. Accordingly W It=X R, and when the length of the arm 136 equals the radius of the wheel124e, W and X are also made substantially equal.

One cubic inch of water weighs .036127 lbs. Accordingly, for any position of the damper 118 between wide open and closed positions,

WR Cos =XR .036127 aPRor X036127 a P W mentioned equation the area of the damper opening is-ascertained to be equal to Experiments appear to indicate that the rate of flow of airthrough the boiler 10 varies substantially in direct proportion to the area of the opening defined by the stack damper, and that the amount of air supplied to the furnaces will be properly proportioned to the rate of feed of the oil, when the area of the damper opening varies in about the same ratio as the rate of feed of oil to the boiler furnace.

When the damper 118 is moved from closed position a comparatively large angular movement of the damperproducesu only a small increase in area, of thedamper opening. Consequently, if the damper 118 were caused to move angularly in direct proportion to the pressure in the bell 180, the boiler would be properly ventilated only when the pressure in the bell 130 approximated themaximum pressure required to cause the damper 118 to be fully opened. At all lower pressures the boiler would be badly under-ventilated. By causing the area of the damper opening to vary in proportion to-the pressure in the bell 130, the rate offiow of air through the boiler furnace is caused to vary in a ratio which quite closely approximates the variations in the rate of flow of oil to the burner 14:.

It is never desirable that a stack damper be made to fit a stack tightly because of the danger of the accumulation of explosive gases. In the use of thisinvention the existence of a considerableareaof leakage between thedamper 118 when in closed position and i the stack causes the ratios of the ventilation and the rate of flow of oil to approach each other more closely than if there Were no leakage, If the leakage area about the damper 118 when in closed position is 25% of the transverse area of the stack ,at the damper,

and the installation is set to attain maximum combustion capacity at-a pressure of 18 inches of water, the ventilation ,of the boiler would be theoretically correct at 33% of combustion capacity and a pressure of 2 inches under such conditions is actually; slightly f over-ventilated, due it is thought, tothe effect of increasing flue-gas temperature with increased rates of combustion andalso to the fact that the law of flow of gases past the stack damper is not exactly the same as the law governing flow of fluids through an orifice in thin plate)? r i It has-been determined in a number ofcommercial installations that by the use. of this invention, the ventilation of a burnermay be accurately proportioned to the rate of feed of oil to the burner, as evidenced by a constant percentage of CO in the exhaust gases, between combustion rates of and 100%. I It is not ordinarily of commercial importance to regulate the ventilation of a burner in strict accordance with the rate of flow of oil to the burner at rates of combustion less than 25%; of maximum.

In actual practice the weight138 and the degree of opening of the damper 118 may be made greater or less according as the draft, intensity which governs the velocity of flow of gases through. the stack is small or-large. This adjustment to compensate for varying draft intensities is made possible by the fact that the area of the damper opening is automatically kept in direct proportion to the pressure in the bell 130 irrespective of the weight of the parts 138 and 130. It is contemplated, however, that, inthe use of the invention, the draft intensity will also be regulated in the usual manner as, for example,by secondary dampers or openings at the inlet to the boiler furnace. g

If the boiler 10 were operated at a heavy load it would be possible for oil to be fed to the burner 14 in'excess of the safe combus tion capacity of the boiler without generating sufficient pressure in the boiler to operate the relief device 96. It is desirable that the rate of flow of oil to the burner shall be limited to the safe-combustion capacity of the boiler regardless of thelo'ad on theboiler. To this end the low pressure line 86 is provided with an upstanding portion 139 which is open to theatmosphere. The flow of fluid through the portion 139 is controlled by a butterfly valve 140 whichis normally closed, but is arranged to be opened Whenever the pressure in the low pressure line 86 tends to exceed a pre-deter-mined maximum. Manifestly, since the rate of flow of. the oil depends on the pressure in the line 86, the relief of such' pressure at a pre-determined mamimum de gree limits the rate of flow of oil to the boiler furnace.

In order to relieve the pressure in the low pressure line 86 when the rate of feed of the oil tends to exceedthe maximum rate desired, the valve 140 in theupstanding portion 139 of the pressure line 86 is operatively connected to a lever 141 having an opening in one end through which the cable 126 passes. The. cable 126 carries a Weight or striker 142 positioned so asto engage the end of the lever 141 and thereby open the valve 140 when the damper 118 attains the most widely opened position for which it is adjusted. The striker 142 may be located in various positions on the cable 126 in accordance as the maximum degree of opening of the damper 118 is changed. The valve 140 is returned to closed position by a weighted plunger 144 connected to the other end of the lever 141. The plunger 144 is preferably enclosed in a dash-pot so as to dampen the movements 01 the valve 140. The weight 128 is of a size sufficient only to properly control the cable 126 and striker 142.

The flow of steam through the nipple 82 induces flow of air into the low pressure line 86 through the aspirator 84. The air'reduces the amount of steam required to be supplied to the line '86 not only directly by taking the place of steam that would otherwise be required to produce the necessary pressure but also indirectly by reducing condensation of the steam in the low pressure line 86, oil trap 36, and bell 130. The reduction in the condensation of the steam arises from the fact that a mixture of steam and air has a much lower temperature than pure steam at the same pressure.

The low pressure line 86 is preferably pro vided at its low point with a pet-cock 146 (Fig. 2) which is left open continuously to allow the escape of water formed by condensation of steam in the line. The amount of steam and air which issues from the petcock is negligible. The pet-cock 72 may be opened to permit the escape of water from p the high pressure conduit 70.

It is first decided what the maximum gaseous fluid pressure on the oil in the trap 36 shall be. Then the mass of the weight 138 and the net weight of the bell 130 are calculated from the equation COS wer??? @P In this computation X andW are assumed to be equal and they are so calculated as to cause the damper to be opened at an angle of 7 or 80 degrees to the horizontal at the maximum burner pressure. The cross-sectional area of the bell, denoted by a, in commercial installations is about 60 square inches.

Although in the above calculations the weights X and W have been assumed to be.

feet of making the weight X greater than the weight l/V is to cause the opening of the damper to be delayed with respect to the development of pressure in the oil trap 36 and the low pressure line 86 and to cause the damper to close a short time before the pressure in the bell 180 is reduced to atmospheric. The weight of the bell 130 is sufficiently close to the weight 138 to enable the weights X and 1V to be calculated from the above equation with sufi'icient accuracy to satisfy all practical requirements.

In the use of the illustrated apparatus, assuming the boiler to be cold, the valve in, the pilot pipe 54 is first opened to allow oil to flow to the burner 14. When steam has been generated in the boiler, the valve. 55 is nearly or fully closed, and the valve 74 in the conduit is opened to allow steam to pass into the low pressure line 86. The pressure regulator 78 is set to cause steam to be delivered from it at a desired pressure which is indicated by the gauge 80. The pressure of the steam is further reduced by the orifice nipple 82 and air is admitted through the asp'irator 84 to form a mixture of steam and air. Steam at the pressure determined by the pressure regulator 78 is conducted to the burner 14 to atomize the oil, and the size of the orifice in the nipple 82 is so proportioned to the pressure of the steam as it issues from the regulator 7 8 that the mixture of steam and air in the low pressure pipe 86 may develop a pressure greater than that necessary to cause oil to be fed at the maximum rate. The pressure which maybe developed in the low pressure pipe 86 is, however, limited by the size of the orifice in the nipple 82 to a degree such that it may quickly be reduced to the required extent in the event that the steam pressure in the boiler tends to become excessive or the pressure in the low pressure line 86 tends to exceed that necessary to cause oil to be fed to the. burner at the desired maximum rate. The valve 102 of the pressure relief device 96 is operated to reduce the pressure in the low pressure line quickly in case the pressure of the steam in the boiler tends to exceed the degree determined by the relief device. The striker 142 on the cable 126, is, however, generally moved very slowly in response to like movements of the bell 130. Consequently, the

valve 140 is not moved abruptly but is gently urged toward open position by the weight of the striker resting on the lever 141. The plunger 144, and the dash-pot also tends to impart a gentle action to the valve 140. The result of the above described action of the valve 140 is to cause the conditions which control the operation of the boiler to be maintained substantially constant when the boiler is being operated at or near'the full capacity of the burner 14.

The operation of the boiler may be quickly discontinued by closing either the valve 74 the high pressure conduit 70 or the valve "29. in the oil supply pipe 28 or both. When the operation of the boiler is stopped by closing the valve 745, the pressure ofthe steamv and air. in the low pressure line 86 and oil trap, 36 is quickly relieved by the emission of steam and air through the aspirator 84. Inasmuch as the pressure in the line 86 is always very small, the relief of thepressure when V the valve 74 is closed is practically instantaneous. In case the operation of a field boiler a burner in the furnace comprising an oil containing chamber, a' member on the delivery side of the chamber provided with an orifice through which theoil is fed, means for maintaining the outlet side of the orifice under atmospheric pressure,:means for producing a superatmospheric pressure in sa1d oil chamber to feed Oll through the orifice, means for maintamlng'the oil in the 011 chamber constantly at the level of the ori- V fice, and a direct gravity run between said orifice and said burner. I i 2.- Inan apparatus of the class described, a

boiler, an oil burner for heating said boiler,

and means for feeding oil to said burner comprising a supply chamber, connectlons bee tween said chamber and said burner including a restricted opening of uniform area, connections between said boiler and said chamber including a reducing valve, a restricted opening of constant area intermediate said reducing valve and said chamber, and means for automatically ventingthe pressure in said second mentionedconnection and chamber.

3. In an apparatus of the class described,

a field boiler, afurnace for the boiler provided with a burner, andmeans for feeding oil to the burner comprising a member provided with anorifice through which the oil is fed, an oil containing chamber on the supply side of the orifice, means for maintaining the oil in the chamber substantially at the level of the orifice, means for subjectingthe delivery side of the orifice to atmospheric pressure, and means for imposing a gaseous fluid pressure slightly greater than atmospheric on the oil in said chamber to produce flow of oil through the orifice, said orifice being of sufficiently large size so as to enable an adequate supply of fuel oil to be delivered to said boiler with a gaseous fluid pressure in said chamber of 30 inches of oilso that oil may be fed by gravity from a field tank to the chamber.

4. Inan apparatus of the class described, an oil burner, and means for feeding oil to the burner comprising an oil trap, a hollow vmember associated with the trap, an orifice plate arranged to communicate on its supply side with the hollow member, a chamber communicating with said plate on its delivery side, means for exerting pressure not substantially exceeding one poundper square" inch on the oilin the trap, and meansfor conducting oil under atmospheric pressure from the delivery sideof the orifice to the burner;

i '5. In an apparatus of the class described," an oil burner, and means for feeding oil to the burner comprisingan oil trap, means for mamtalning the oil in the trap at a predetermined level, a pipe communicating with the trap below the level of the liquid in the trap and extending upwardly, a chamber en-v closingjthe upper end of the pipe andopen v to the atmosphere, an orifice plate mounted in substantially the same horizontal plane as the level of liquid in the trap and arranged to communicate .on its supply side with the plpe and on its delivery sidewith the chamber, means for conducting oil by gravity from the delivery side of the orifice to the burner, and means for imposing gaseous" pressure greater than atmospheric on the 011m the trap to produce flow of oil to the burner.

6. 'Inan apparatus of the class described,

aboiler, means for feeding oil to the furnace of saidboiler, mechanism for controlling the V ventilationof the furnace, a fluid pressure line for controllingfthe feed of the oil to the furnace and for operating said mechanism,

means for conducting steam from the boiler tofthe fluid pressure 11118, and a pressure regulator and a constant area orifice member for controlling the passage of steam from the boiler to the pressure line. Y

' 7, In an apparatus of the class described,

a boiler, means for feeding oil to the furnace of saldboller, mechamsm for controlling the iventilation of the furnace, a fluid pressure line for controlling the feed of oil to the furnace and for operating said mechanism, a

pipe for. conducting steam from the boiler to the pressure line, and .an aspirator in said pipe for causing air to be drawn into the pipe in order to dllute the steam and thus reduce condensation of steam in the feeding means and in said mechanism. 7 V a j 8. In an apparatus of the class described, a

boiler, means for feedingoilto the furnace of-said boiler comprising a member provided 7 with an orifice, a conduit for conducting l steam from the boiler tothe feeding means on the supply side of the orifice so asto impose greater pressure on the oil at the supply sideof the orifice than on the delivery side [said aspirator being constructed to cause air 'to be drawn into said conduit by flow of steam through the conduit when the valve is open and to permit flow of air and steam outwardly from the conduit when the valve is closed so as quickly to reduce the pressure in the feeding means to atmospheric.

9. In anapparatus of the class described,

.a boiler, means for feeding oil to the furnace of said boiler, echanism for controlling the ventilation of the furnace, a lineof piping for conducting steam from the boiler, a pressure regulator in said piping, an orifice member on the outlet side of the regulator, a connection between the piping and the furnace for conducting steam to the furnace to atomize the oil, said connection communicating with the piping between the pressure regulator and the orifice member, and means connected with the piping on the outlet side of the orifice member for transmitting steam at ,low pressure to the feeding means andsaid mechanism.

10. In an apparatus of the class described,

a boiler, means for feeding oil to the furnace of said boiler, a line of piping for conducting steam fronithe boiler, a pressure regulator in said piping, an orifice member on the outlet side of the regulator, a connection between the piping and the furnacefor conducting steam to the furnaceto atomize the oil, said connection communicatingwith the piping between the pressure regulatorand the orifice member, and a connection betweenthe piping on the outlet side of theorifice member and the feeding means for transmitting I steam at low pressure to the feeding means.-

11. The method of controlling combustion in oil-fired boiler furnaceswhich consists in withdrawing steam from the boiler, reducing the steam to a pre-determined pressure, uti-' lizing steam at such pressure for atomizing the oil in the boiler furnace, reducing the steam to a still lower pressure, andutilizing steam at the last-mentioned pressure for controlling the feed of oil to the'furnace.

12. The method of controlling combustion in a furnace for which oil isatomized by a fluid which consists in supplying the atomizin g fluid at a constant pressure, and utilizing a portion of the atomizing fluid at a varying pressure lower than the atomizing pressure for controlling the feed of oil to the burner.

13. The method of controlling combustion in oil-fired boiler furnaces which-consists in withdrawing steam, from the boiler, reducing the steam to a 'pre-determmed pressure,

utilizing the steam at such pressure for atomizing the oil in the furnace, further reducing the pressure of the steam, and utilizing the steam at the last-mentioned pressure for controlling the ventilation of the furnace.

14c. The method of controlling combustion in oil-fired boilers which consists in withdrawing steam from the boiler, reducing the steam to a pre-determined pressure, utilizing steam at such pressure for atomizing the oil, further reducing the pressure of the steam, utilizing the steam at the last-mentioned pressure for controlling the ventilation of the boiler and the feed of the oil, and utilizdrawing steam from the boiler, reducing the steam to a predetermined low pressure which remains substantially constant regardless of changes in pressure of the steam in the boiler, utilizing a stilllower fluid pressure derived from said constant pressure for controlling "feed of oil to the boiler furnace, and releasi the oil feed control pressure whenever the pressure of the steam in the boiler tends to increase beyond a predetermined amount.

16. A method of controlling combustion in boiler furnaces comprising establishing a stream of elastic fluid flowing continuously during periods of normal steam pressure in the boiler to be controlled, developing a rela tively low super-atmospheric pressure by means of said stream and utilizing such pressure to control the flow of fuel to the boiler furnace, and governing the rate of flow of fuel to the furnace by gradually opening said stream to the atmosphere to a greater or less extent in accordance with Variations of the steam pressure of the boiler.

17. In an apparatus of the class described, a boiler, pressure controlled means for feeding oil to the furnace of the boiler, means for conducting steam from the. boiler to the feeding means and separate means for relieving:

pressure of the steam in the boiler tends to exceed a predetermined amount. i

In testimony whereof I aflix my signature.

BENJAMIN GREENFIELD.

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