US1820939A

US1820939A - Combustion

Info

Publication number: US1820939A
Authority: US
Publication date: 1931-09-01
Anticipated expiration: 1948-09-01

Description

j Sept. 1,- 1931. G, H, GIBSON 1,820,939

COMBUSTION REGULATI 0N Filed Aug. 4, 1926 2 Sheets-She t 1 MASTER CON TIIOLLEA All? HEATER MA //Y CONTRO VROMETEF CONTROLLER.

INVENTOR 650264-- 6 6/5 50 ATTORNEY P 1931- v Q G. H. GIBSON 1,820,939

- COMBUSTION REGULATION Filed Aug. 4, 1926 2 Sheets-Sheet 2 A E CO/V TFOALE/K INVENTOR a o/rail! 670-50 ATTORNEY Patented Sept. 1 1931 UNITED STAT-ES PATENT'OFFIKIE'I CQMBUSTION REGULATION I Application filed August 4, 1926. Serial No. 126,954. 7

v 10 the fuel burned, the fuel-air ratio control with which the present invention is concerned, may

7 be correctly designated as an excess air control. v a

The invention is particularly useful in the 1 operation of powered coal burning boiler furnaces. In such furnaces the amount of air supplied to the combustion chamber in excess of that theoretically required by the momentary rate of fuel combustion may advantae geously be varied as the load and furnace temperature conditions vary. In burning powdered coal more excess air is ordinarily required to insure complete fuel combustion when the rate of combustion is relatively low, than when the rate of combustion is high. Generally speaking, the best thermal efliciency is obtainable when only so much excess air is supplied as is required to insure complete combustion of the fuel, but the extent to which the excess air can be reduced with advantage as the rate of combustion is increased, does not depend entirely on the thermal efliciency obtainable. 7 On the contrary,

with high rates of combustion it is usually as desirable to supply more excess air than would give maximum thermal efficiency in order to limit the. combustion chamber ternas of the supply of air, and my invention, in its more limited aspects, comprises improved means for regulating the rate of supply of powdered fuel to a furnace.

While the invention is especially useful in controlling combustion in powdered coal burning furnaces, and some of the features of the invention are restricted to use with such furnaces, other and more generat features of the invention-are not dependent on 0 the character of the fuel burned.

In lieu of, or in addition to an automatic control of the excess air ratio dependent on the combustion chamber temperature, 1n some cases I may make that ratio dependent on other factors such as the CO content of the flue gases, or the smoke content of the fiue gases. To this end I may employ a C0 measuring device of known type, or I may employ known means for determining the smoke content of flue gases from their light transmitting properties. The control of the excess air ratio in response to the smoke content of the gases is especially useful in the 7 case of oil burning furnaces wherein, in ordinary practice, the smoke content of the flue gases may be the factor limiting the extent to which the excess air ratio may be advantageously diminished.

The air-fuel ratio control which forms the 30 primary subject matter of the present invention, will ordinarily be incorporated in, or

added to a combustion regulating system, which is adapted to vary the general rate of combustion in accordance with changes in furnace load, or which is employed to automatically control other combustion coptrol factors.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed-to and forming a part of this specification. For a better understanding of the invention, however, its advantages and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which 'I'have illustrated and described preferred embodiments of my invention.

boo

Of the Fig. 1 is a diagrammatic representation of a powdered coal burning boiler furnace andcombustion regulating provisions therefor;

Fig. 2 is a sectional elevation of the fuel:-

feeding mechanism employed in Fig. 1;

Fig. 3 isv a section .on the line 3-.-3 of Fig. 2;

plpmg. The fuel burned in the combustion chamber A is supplied by one or more, usu-.

ally a plurality of, nozzles G through which ablast of powdered coal carrying air is passed into the combustion chamber. Powderedfcoal is supplied to the nozzles C by a fuel feeder D, and the carrying stream of air into whichthe coal supplied by the feeder D is introduced, is supplied by a blower E connected to the nozzle, or nozzles G, by piping E. The main body of air forcombustion supplied to the combustion chamber A. is furnished by a fan or blower F'discharging .into the inlet of an air preheater F from a which the heated air is passed through a distributing conduit or conduits F to channels A formed, in the walls of the combustion chamberA'; and openingto the latter through suitably distributed ports A". The passage 20 of the air through the channels A serves to further heat the air, while at the same time desirably cooling the combustion chamber walls. The hot products of combustion escaping from-the boiler furnace through .the outlet A pass into the air preheater F through a conduit. F and pass away from theair heater through the stack connection F. Insofar as the boiler furnace and acces-' sories' already described are concerned, the

an construction shown in Fig. l embodies nothing'novel with me, but on the contrary is a typical example of the kind of boiler furnace installation with which the present invention may be used with advantage.

The combustion regulating system shown in Fig. 1 comprises means'for-maintaining a control force in the form of an electric current which flowsalong a conductor 3, and varies with the boiler load.. The control current is'suppliedfby'current supply mains '1'and'2, and "its strength determines the rates of air deliverand isthe primary .factordeterminin'g't e rate of fuel delivery by the fuel feeder D. As shown, the strength a5 the control current flowing along the. consuperheated steam outlet piping B of the Y ductor 3is dependent upon the amount of avariable resistance R in circuit the latter being adjusted by a master controller, in the form of a pressure device G, in automatic response to changes in the static steam pressure .in the superheated steam outlet piping B3. Insofar as thegeneral control of'the air and'fuel feeds referredto are concerned, the control force may be maintained and may control the air and fuel feeds in accordance with principles previously patented by me, but the control system shown in Fig. 1 diflt'ers from control systems heretofore known in the manner in which the controlling effect of the main control force is applied and modified to thereby desirably vary theexcess; air ratio as the conditions of operation vary. The device G, as shown, comprises a pressure chamber G to which the pressure in the boiler, or battery, of boilers controlled, is transmitted by a conduit B. A lever G hearing at one end against a fulcrum G, opposes the outward thrust of the pressure in the chamber G against a flexible wall G of the latter with a force which depends on two opposing forces, one of which is due to an adjustable weight Gr carried by the arm G and the other of which is due to the electromagnetic interaction between a coil 9 carried at the free end ofthe lever G,- and a pair of co-operating stationary coils g, the coils g and 9' being connected in series with one another in the circuit 3. The weight (5': is so proportioned and disposed as to balance the steam pressure in the chamber G when that pressure corresponds to the normal boiler steam pressure. Normally the-pressure in the chamber G'- is lower than the actual boiler steam pressure as a result of the drop in pressure or loss in headv which.v results from, and is a -measure of the rate of-steam flow through the header B The current flow through the coils g and g is adjusted by the balance in amanner now to be described, so that it normally acts on the lever Gr through the coils g and 'g' as required to hold the lever.

G in an intermediate position between a normally open pair of contacts H and a 11 normally open pair of contacts h.

When the upward thrust of the pressure acting against the underside of the wall G increases relatively to the magnetic interaction between the coils g and the coils g and the lever=G tilts in the counter-clockwise direction about'the fulcrum G, the contacts H are energized and the motor M is started into rotation in the direction to diminish the amount of resistance R in circuit, and the motor M thus continues to rotate until as a result of the decrease in the amount of resistance R in circuit the current flowing alongthe conductor 3 increases sufficiently to restore the lever G to its normal neutral position. Conversely, when the magnetic interaction between the coils g and g overbalances the action of the pressure against the underside of the wall Gr on the lever Gr and thelatter tilts in the" clockwise diiection the contacts k are 1 closed. The closure ofthe contacts k starts .the motor M into rotation in the direction In consequence the current flowing through the circuit 3 varies directly with the steam flow through the piping B when the boiler steam. pressure is at the normal value. On

changes in the boiler steam pressure, the current varies to compensate for such changes. This mode of regulating the current flowing through the circuit 3 is an advantageous one, but as already indicated, the present i11 vention in its more general aspects is not dependent onthe precise character or mode of operation of the master controller G. 1' represents an adjustable resistance shown about the coils g and g by which the constant, so to speak. of the controller G may be adjusted to vary the ratio between the boiler load and rate of combustion, or to adjust the apparatus to the flow resistance of the piping B The blowers E and F are driven by electric motors E and F at the speeds required to make the rate of air delivery of each blower vary in proportion with chan es in the control current flowing through t e circuit 3. For this purpose the motor E is provided with an electromagnetic flow balance controller EA comprising means for opposing the differential fluid pressure in the pipes e and e which is a measure of the rate of flow of air delivered by the blower E against an electromagnetic force which is proportional to the s uare of the strength of the electric current owing in the circuit 3. On a change of one of these 'forces relative to the other the controller EA varies the shunt field current of the motor E as required to restore the balance. Branch conductors 4 and 5 from'the supply conductors 1 and 2 furnish the armature currents required for energizing the motor E and the field current is furnished by the conductors 4, andv the

branches

51 and 52 from the conductor 5, said branches being connected through the? ad-.

justable resistance (not shown) of the con troller EA. The said resistance may be associated with the motor E and controlled by the motor D and is controlled by the controller I as hereinafter described.

The controller FA may be similar in construction and operation to the controller EA and serves to vary the current supplied to the motor F from the corresponding branch supply conductors 4 and 5 as required to maintainthe predetermined relation between the strength of current flow through the circuit 3 and the rate of air delivery by the blower F. The controllers EA and FA each may be similar to the balance G and its motor M, except that the single chamber G of the balance is replaced by two chambers connected to the pipes e and e in the controllers EA and FA. The latter need not be further illustrated or described herein, however, as various types'of controllers suitable for the purpose are known, one suitable type being shown, for example, in Fig. 7 of my Patent No. 1,167,343, granted January 4:, 1916.

In the apparatus shown in Fig. 1, the rate at which fuel is passed into the combustion chamber A through the nozzle or nozzles C depends primarily on the speed of the motor D which, as shown in Fig. 2, rotates the feed screw D employed to feed coal from a supply hopper traversed at the bottom by the feed screw D into the feeder outlet chamber D through which the coal is discharged into the pipe E The speed of the fuel feeder motor D is made primarly dependent on the strength of the current flowing through the circuit 3 by a controller I, but the speed of the motor D is varied to vary the excess air ratio, by passing more or less of the control current through a by-pass about the fuel control mechanism. eludes conductors 8 and 9, contacts L and M and the portion of the resistance R between the contacts L and M In Fig. 1 means are provided which tend to increase and decrease the amount of the resistance R in the by-pass as the control current increases and decreases, and tend to decrease orin crease the amount of the resistance R in the by-pass accordingly as the combustion chamber temperature measured by a thermo-coupleP rises or falls.

The means shown for increasing the resistance R in the by-passas the control current increases comprises a solenoid L in series with the circuit 3, and a magnetic core L drawn into the solenoid by the current flow through the latter, to the position at which the pull of the solenoid L on the core L is balanced by a tension spring L connected to the core and opposing the movement of the latterinto the solenoid. The contact L is connected tothe core L and slides along in contact with the resistance It as the current in the circuit 3 increases and On this account, I provide a stop L limiting the movement of the core L into the solenoid L beyond the position to which it is moved when the load increases to a certain value well be' ow the maximum load which may be carried. v

The means illustrated for adjusting the contact M as the combustion chamber temperature varies comprises a motor MA hav-' ing a threaded spindle passing through a nut-like portion of the contact M The motor MA is controlled by a pyrometer controller 0 which operates to move a contact 0 into engagement with a terminal of the motor M when the combustion chamber temperature to whichthe thermo-couple P responds rises above a predetermined value.

This energizes the motor MA through a branch conductor-4 connecting the contact O to the supply conductor 1, and a corresponding'branch 5 from the supply conductor 2 permanently connected to one terminal of the motor MA. When so energized the motor rotates in the direction to decrease the amount ofresistance R in the by-pass, and

thereby increase the excess air ratio. When the combustion chamber temperature to which the thermocouple P responds falls below a predetermined value, the-pyrometer 'controller 0 moves the contact 0 into engagement with the terminal 11 of the motor I MA, and thereby energizes said motor through said terminal 11 and the terminal of the motor MA connected by the conductor 5 to supply conductor 2. When thus energized, the motor MA rotates in the direction to increase the resistance R in the by-pass and thereby decrease the excess air ratio. The p ometer controller 0 need not be fur-' ther i lustrated' or described herein, as such controllers are well known and in common use, one form of pyrometer controller suitable for the purpose being shown in the 1 "patent of Leeds No. 1,332,182, granted February 24, 1920. v .1

The controller I which directly controls the fuel feed motor D, tends to maintain the latter in operation at a speed proportional to-the fraction of 'the control current'not bypassed about the controller I. In the forin 1 shown in Fig. 1, the controller I comprises parts I, I 1, 1 ,2, 2'', H and h identical res tively with the parts G, G G G, g, g, f and h of the controller G. The controller v I difiers from the controllerG, however, in

that the controller I includes nothing an alogous to the weight (1: and. the magnetic interaction of the coils i and z" opposes, and the flexible wall I on the lever I. a v

the feed screw 1) impinges.

The pressure acting against the flexible wall I of the contoller I is proportional to the square of speed of the motor 1). For this purpose a small blower K is driven by the motor D, at a speed proportional to the speed of the motor D, the blower K having control mechanism comprising a reversible v motor MB which may be identical with the motor MA, and which is caused to run in one direction or the other accordingly as the lever I closes the associated contacts H or h. When the pressure in the chamber I rises relative to the strength of current flow through the coils i and z", the contacts -H are closed and the motor MB then rotatesin the direction to move the contact nut M on the threaded motor spindle so as to decrease the amount of resistancev R in the shunt field circuit including the

conductors

51 and 52 from the conductor 5 which with the conductor t supplies both armature and field current, thereby decreasing the speed of the motor D. Conversely, on a relative decrease in the pressure in the chamber I which causes the lever I to close the associated contacts h, the motor MB turns in the direction to increase the amount of resistance R in circuit,

and thereby speed up the motor D.

The rate at which powdered coal is de livered by a feeder like the feeder D, is not strictly proportioned to the speed of the feed screw of the feeder. On the contrary,

changes in the extent to which the coal is aerated, variations in the moisture content of the coal, and even changes in atmospheric humidity may make significant difi'erences in the amount of coal delivered with a given speed of rotation of the feed screw D Furthermore, the rate at which coal is delivered the feed screw is interfered with, of course, i

by any packing of the coal in the hopper from which the coal is discharged by the feed screw.

In accordance with the present invention" I provide means for making the actual rate of fuel feed, rather than the speed of. the

feed screw D proportional to the part of thecontrol current pass ng through the coils.

i and z" of the controller I. This I accomplish" by the use of a mechanism measuring the actual rate of coal delivery by the feed screw D. The particularmechsnism shown for this purpose comprises an impact plate D against which the coal dropping away from As shown, guides D are provided to drive allof the coal falling away from the feed screw into-impingement with the plate D, .1,

the plate. The plate is carried at one end of a horizontal lever D whichis pivotally supported at-D.

The impingement of the falling coal against the plate D subjects the lever D to a clockwise torque normally balanced by an electromagnetic force proportional to the control'current, or rather to.the portion of that current flowing through the coils i and 2". As shown, this magnetic force action is due to a vertically disposed polarized magnet or core D", the ends of which extend into stationary solenoid coils D which are connected in series with the coils z' and i of the controller I, and, like the latter, are included in the branch of the circuit 3 in multiple with the bypass conductors 8 and 9 and the. variable resistance R. The two coils D are so wound that the current flow through each acts on the core I) in a direction tending to turn the lever D in the counter clockwise direction. This tendency of the coils D and core D to turn the lever D opposes, and

normally balances, the tendency of the fall- ,ing coal impinging against the plate D to 'turn the levers in the clockwise direction.

With a polarized or fully saturated core D".

the torque to which the lever D is subjected by the current flow through the coils D is proportional to the strength of the electric current flowing through those coils. In con sequence, if the rate at which coal impinges against the plate D is just sufficient to balance the torque due to the interaction of the coils D and core D the lever D will remain in a neutral position. The clockwise torque impressed on the'plate D varies, of course, with the. amount of coal falling, and it is to be noted that any slowing down of the falling coal particles by the air,

through-which they fall does not afiect the situation since the force then transmitted by 1 the coal to the air, is transmitted by the air to the plate D.

The control provisions for the motor D previously described tend to make the speed of the motor D proportional to the portion of the control current passing through the coils i and z" of the controller I. If, for such reasons as have already been mentioned, the rate at which fuel is delivered is not maintained proportional to the speed of the motor D the lever D tilts in one direction or the clockwise direction, the valve D throttles the bleeder outlet. This increases the pressure transmitted by the pipe K from the blower K to the pressure chamber I of the controller I, and the controller I then operates to decrease the speed of the motor D. Conversely, when the rate of fuel feed is relatively low, the lever D tilts in the counter-clockwise direction and moves the valve l) to increase the effective area of the bleeder outlet; In consequence the pressure then transmitted to the pressure chamber 1 is diminished, and the speed of the motor D is correspondingly increased. In order to dampen any tendency of the arm D to oscillate it is connected to a plunger D which moves in an air dash pot D. A variable resistance shunt R permits of an adjustment of the contant, so to speak. of the lever B, which is useful for various purposes as to compensate for changes in the- B. t. u. value of the coal.

The piping E connecting the outlet of the blower E to the nozzle or nozzles C is open at its upper side to the chamber D for a corresponding portion of the length of the piping. To prevent disturbances in the air pressure in the chamber 1) by the air flow through the pipe E, I provide a rotating gate D geared to, and driven by the motor D for transferring the coal reaching the bottom of the chamber D to the piping E while at the same time substantially preventing air flow between the chamber D and. the piping E 7 Fromthe foregoing it will be apparent that the apparatus shown in Figs. 1, 2 and 3 normally operates to maintain a control current in the circuit 3 which varies in response to changes in the boiler load in the manner in which the general rate of combus' tion should vary in response to load changes.

The controllers EA and FA operate to make the supplies of primary and secondary air furnished by the blowers E and F, respectively, proportional at all times to the strength of the control current. 'With suitable combustion chamber temperature conditions the rate of .fuel feed will vary with the boiler load, and the excess air ratio will consequently remain constant, throughout an upper load range above the load value at which the contact L is moved against the stop L In this upper load range,however, the excess air ratio will ordinarily be increased as the load increases because with load increases the combustion chamber tem perature tends to rise, and the thermocouple P and controller 0 operate as previously described to decrease and increase the rate of fuel feed and thereby increase and decrease, respectively, the excess air ratio as required to maintain an approximately constant combustion chambertemperature. During a lower load range in which contact L is not in engagement with the stop L, the solenoid L and associated parts tend to decrease the excess air ratio as the loadincreases. In this lower portion of the load range, control of the excess air ratio is not'ordinarily required to prevent overheating of the GOIIlbllitlOIl chamber walls but is required to insure complete combustion on the one hand, and the avoidance on the other hand of excess air in amount to objectionably decrease the thermal efliciency of the unit. 1 Generally speak ing, in the operation of a furnace, and particularly in the operation of a furnace burning fuel in suspension in air, whether that fuel be powdered coal, gas or oil, combus-" tion conditions improve and less excess air is required for complete combustion as the rate of combustion increases. This is due to the fact that as the rate of combustion in creases better mixing of the fuel and air is ordinarily obtained, and alio because an in-' crease in combustion chamber temperature accelerates the combustion of the fuel.

\Vith the apparatus shown in Figs. 1, 2, and 3, the desired excess air control is secured by modifying the rate of fuel supply. The same general character of excess air control can I by modifying the rate of fuel supply or by' also be secured by modifying the rate of air supply rather than the rate of fuel supply, and superficially considered, thelast mentioned mode of excess air control mayseem to be the only logical one. In practice, however, with the general type of control apparatus shown in Figs. 1, 2, and 3, and with the range in excess air required in the'control of a boiler furnace of the'type illustrated in Fig. 1, it is, generally speaking, immaterial whether the exce:s air control is secured modifying the rate of air supply. Inthe apparatus shown in the excess aincontrol is obtained by'modifyin the rate of air supply by apparatus whiai, in this respect, differs from that shown in Figs. 1, 2 and 3 substantially only in that in Fig. 4, the by-pass including the resistance R extends about the portion of the circuit 3 including the instrumentalities regulating the volume'of draft, instead of about the instrumentalities regulating the fuel feed. p

In Fig. 4 I have illustrated the use of the present invention in controlling combustion in a boiler furnace AA in which the combustion chamber A has all or a large portion of its walls lined by suitably disposed tubes 13*", B, and B forming'a part of the water circulating system of the boiler and exertirtiig such a combustion chamber wall cooling e ect that the combustionchamber temperature may safely be materially higher than with the type of boiler furnace shown in Fig.

. 1. In the'formshown in"Fig. 4, theexcess air ratio is primarily dependenton the C0 content of the flue gases, and means are provided for varying the excess air ratio as reenergizes the norma Fig. 4 now'to be described,

quired .to increase the CO content of. the flue gases as the load increases.-

' In the formshownin Fig. 4, the primary air carrying the powdered coal supplied'by the feeder D is discharged into a so-called cyclone air and fuel mixerCA which also receives air unmixed with coal from the blower E. through a branch pipe E. Thefuel and air mixture passes from the mixer GA to the upper portion of the chamber A through distributed branch supply-pipes C 3. The heat ing gases pass from the combustion chamber downward acrossthe tubes E into a chamber BA containing the superheater tubes B, whichchamber may also contain feed water preheating tubes. From the top of the chamber BA the heating gases pass'into an air preheater F. The latter, 'as shown, has its air inlet F open to the atmosphere, and has its air outlet connected by piping F to the combustion chamber A. In'Fig; 4 the volume of secondary air passing through the preshown in Fig. 1. Itcomprises a main control circuit 3, the current flow through which is regulated by a master controller G which may be identical with the controller G of Fig. 1,

and like the latter is directly responsive to the pressure in the superheater outlet piping B. The controller ea may be identical in construction and operation with the controller EA first described. The motor D is controlled by a controller IA which might be identical with the controller I first described,

' but as diagrammatically illustrated diflers in that the lever I of the controller IA, corre-v sponding to the lever I of the controller I, is pivotallysupported between its ends, and instead of bearing against the flexible wall of a pressure chamber carries a hell I dipping into a sealing liquid held in a chamber I"- open at its top to the atmosphere. The pipe K from the blower K opens into the space beneath the hell I. The tilting of the lever 1 out of its neutral position brings thelever IA into engagement with upper and lower contacts HAand ha, respectively, and thereby energizes a motor MB to increase or decrease the amount of resistance R in the energizing uiredto make cireuit of the motor ED, as v v the speed of that motor'such ,t attire rate of fuel discharged by. the feeder D will 'bemaintained in a constant ratio with the strength of the control current flowing through the circuit 3. I j v i The controllers E A, ea, and IA are all connected in series in the control circuit 3, but

' the portion of the circuit 3 containing the pass.

controllers EA and ea which collectively regulate the combustion airsupplied to the combustion chamber A", is in multiple with a by- The latter includes

conductors

80 and 90, a resistance R, and a contact M adjusted. by the rotation in one direction or the other of themotor MA. When the motor-MA of Fig. 4, turns in the direction to decrease the amount of resistance R in the by-pass circuit, the excess air ratio is diminished, and the latter is increased by the rotation of the motor MA is the direction to increase the amount of resistance R in the by-pass circuit.

I In Fig. 4, the motor MAis operated to increase and decrease the excess air ratio as required to maintain a C content in flue gases which varies with the load. This result is secured by the use of a C0 meter Qoperating in conjunction with a solenoid L and'associat-ed parts including a contact L adjusted by the solenoid L as the strength of thecurincrease the resistance R incircuit.

increases theex'cess air ratio, and thereby rerent flowing through the circuit3 varies just as the contact L of Fig. 1 is adjusted. The CO meter comprises a stem Q which carries a pair of spaced apart contacts Q and Q and which ismove'd to the left or to the right,

as the CO content in a fluegas sample passing to the controller Q through a pipe, Q 9 increases or diminishes- As CO2 metersiof various forms suitable foruse in the manner described are well known and'in common rise, further illustration or description of the con- .troller Q is unnecessary.

the corresponding furnace load. Then the contact Q engages the contact L, the motor MA is set into operation in the directio il hto 1s duces the CO content ofthe flue gases. Conv'ersely. when the CO content in the flue gases falls below the predetermined. amount for the then load,=themeter Q moves the contact Q into engagement with the contact L and thereby. energizes the motor MA in the direction to reduce the amount of resistance R in thezby-pass' circuit, thereby decreaslngthe excess air ratio and increasing the CO content in the furnace gases. 7

In lieu of the CO meter employedln Fig.

4, I may employ an oxygenmeter or a com- 7 bustible gas constituent meter,each of which maybe of 'known type. An oxygen meter should be arranged to-decrease and-increase theexcess air ratio as the oxygen in the flue gases increases and decreases, while the com--' bustible gas meter should increase and decrease the excess air ratio as the combustible gas in the flue gases increases and decreases.

lYhile in accordance with the provisions of the statutes, I have illustrated and described the best forms of embodiment of my invention now 'known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is v 1. .In a boiler furnace combustion control system, the combination with means for creating a control force varying in a predetermined manner with changes in the boiler load, of a fuel feeder, means actuated by and responsive to the rate of fuel delivery by said feeder, and control means for the fuel feeder jointly responsive to the action of said second mentioned means and to saidcontrol force for making the rate at which fuel is delivered proportional. to said control force.

2. In a powdered coal burning furnace, the

combination with a fuel feeder, of control mechanism "therefor comprising means for mainta ning a control force Independent of the o eration of said feeder, and means actuated I y and responsive to the rate atwhich .fuel is discha-rged'by the feeder and to said control force for maintaining said rate proportional tosaid force.

3. In a boiler furnace combustion control system, the combination with afuel feeder, of means controlling the operation of said feeder tending to operate it at a speed varying in a predetermined manner with changes in the boiler load, and means actuated by and responsive to the rate at which fuel is delivered by said feeder for adjusting said control means.

4. In a boiler furnace-combustion control system, the combination of fuel feeding means, draft regulating means, means responsive to the volume of draft, means re sponsive to the rate of fuel feed, and controlling means responsiveto a condition of boiler lozpd and to the action of the third and fourth mentioned means and tending normally to maintain a predetermined proportion between the rate of fuel feed and the volume of draft and thereby maintain a constant ex cess air ratio, and cooperating means responsive to the combustion chamber temperature for increasing the ratio of draft relative to,

the rate of fuel feed as the furnace chamber temperature increases.

5. In a boiler combustion control system, means for creating a control force comprising a balance. means for subjecting the balance to a pressure which is less than the boiler steam pressure by an amount which is a function of the steam-outflow fronrthe boiler, means for subjecting said balance to a constant opposing force sufficient to neutralize the action on the balance-of the first mentioned force when the latter is equal to-the normal boiler stea'in pressure, means for subjecting said balance to a force created by said control-force and acting on said balance inthe same direction as the first menm-tioned pressure, and a regulator actuated by said balance to increase and decrease said control force'accordiugly as said constant force overbalances or under-balances the action on the balance of the first mentioned 5 pressure and said constant force. j

6. ,In a boiler combustion control. system,

' means for creating an-electric control current comprising a balance, means for subjecting the balance to a pressure-which is less than the boiler steam pressure by an amount which ism, function of the steam outflow from the boiler, means for subjecting said balance to a constant opposing force sufficient to neutralize the action on the balance of the first mentioned force when the latter is equal to the normalboiler steam pressure, means for subjecting said balance to anfelec tro-magnetic force created by said control current and acting on said balance in the same direction as the first mentioned force, and a current regulator actuated by said balance to increase and decrease said control current accordingly as said constant force j overbalances or underba-lances the joint action on the balance of the other two forces.

f7Q In a boiler furnace control system, the

combination with a boiler and a pipe to which steam generated in the boiler is delivered, of a balance including a pressure chamber hava flexible wall, means connecting said chamber to said pipe at a point'at which the pressure is appreciably less than that in the boiler when steam is flowing through said pipe, a memberopposing the outward move-' forcebalancing the action of the pressure in said chamber when that pressure is-equal to the normal boiler steam pressure desired, means for subjecting said member to a control'force acting on the member in the same direction as the pressure in said chamber, and areg'ula tor actuated by the movements of said member away from a neutral position for increasing and decreasing said control force as required to return said member to said neutral position, and combustion regulating' means controlled by the strength of said control force. f .8. In aboilerfurnace control system, thecombination with a boiler and a pipe to which steam generated in the boiler is delivered, of a balance including a pressure chamber having a flexible wall, means connecting said chamber to said pipe at a point which is at 65 a distance from the boiler, a member opposment of said flexible-wall with a constant ing the outward movement of said flexible boilersteam pressure desired, a coil carried by said member, .a cooperating stationary coil, means for passing a current through said coils and thereby subjecting said member to an electro-maguetic force acting on the mem- .r ber inthe same direction as the pressure in said chamber,- and a. current regulator actu- I ated by movements of said memberout of a normal position for increasing and {decreasing said current as required to return said member to said normal position, and combustion regulating means controlled by the strength of said current.

9.- In a boiler furnace combustion regulating system, the combination with means responsive to the boiler load for normally supplying fuel and air for combustion at predetermined rates dependent on the boiler 'load, of means responsive to the combustion chamber temperature for varying one of said rates and thereby yarying the excess air ratio in a maimer minimizing variations in said temperature.

10. In aboiler furnace combustion'control system, the combination with means for creating a control force varying in a predetermined manner with changes in the boiler load, of a fuel feeder, control means for the latter jointly responsive to the rate at which fuel is delivered by said feeder and to said control force for making-the rate at which fuel is delivered proportional to said control force, and means responsive to the furnace combustion chamber temperature. for modifying the rate at which fuel is fed in predetermined accordance with changes in said temperature.

Signed atPhiladelphia, in the county of Philadelphia and State of Pennsylvania, this second day of August, A. D. 1926.

'. GEORGE H. GIBSON.