US2592385A

US2592385A - Combustion control apparatus

Info

Publication number: US2592385A
Application number: US95654A
Authority: US
Inventors: David M Borden; Paul T Nims
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1949-05-27
Filing date: 1949-05-27
Publication date: 1952-04-08
Anticipated expiration: 1969-04-08

Description

APril 8, 1952 D. M. BORDEN ET AL 2,592,385

COMBUSTION CONTROL APPARATUS Filed May 2'7, 1949 3 Sheets-Sheet l um va C'plni'ra Z Bax BY 7% 444, 1M

FTTZFIVE/SZ P 8, 1952 D. M. BORDEN ETAL 2,592,385

COMBUSTION CONTROL APPARATUS Filed May 27, 1949 s Sheets-Sheet 2 April 1952 D. M. BORDEN ET AL COMBUSTION CONTROL APPARATUS 3 Sheets-Sheet 3 Filed May 27. 1949 TNVEN Patented Apr. 8, 1952 COMBUSTION CONTROL APPARATUS David. M. Borden, Huntington Woods, and Paul T. Nims, Detroit, Mich., assignors to Chrysler Corporation, Highland Park, Mioh., a corporation of Delaware Application May 27, 1949, Serial No. 95,654

18 Claims.

This invention relates to combustion regulating apparatus, particularly apparatus controlling the process of combustion in a burner of which the fuel supply is regulated according to predetermined rates dependent upon the temperature of the ener y gases discharged.

In burner devices for machines of which the combustion characteristic may be commonly referred to as the external type, certain problems arise which lead to complications not found in comparable equipment, for example, internal combustion engines. In internal combustion engines the leanness or richness of the fuel mixture is not critical to the point of eventually incapacitating the machinery in case of error since too rich a mixture merely incurs the result that unburnt fuel for which there is insu-fficient oxygen in the cylinders is merely discharged without apparent damage. On the other hand, in a burner such as involves an external combustion process the condition of too rich 2. mixture of fuel is attended by excessive temperatures which can rapidly cause the structure to deteriorate and be permanently damaged. If the mixture is leaned up too drastically, then the danger arises that the fire in the burner will be blown out and lost altogether. To meet this added problem in such combustion devices as the latter, designers in the field have turned to elements by means of which the combustion temperature may be sensed and the fuel flow corrected in time to prevent loss of the flame altogether in the burner as due to too lean a mixture or else excessively elevated temperatures such as may be due to an excessively rich mixture. A familiar technique among the known forms of controlling burners as to their combustion temperature is that of employing a metallic device such as a thermocouple for actually registering the temperature of combustion. Certain disadvantages, however, reside in the use of direct reading devices. For one thing, because of the poor response characteristics inherent in a system of temperature control dependent on the sensing of metal temperatures such a method has come to be considered generally impracticable particularly in the event of high temperatures existing in the burner. The sensing and control of combustion gas temperatures appears to be more advantageous than an attempt to control directly the temperature of the critical burner component. The combustion gas temperatures method appears more practical for high temperature application and moreover is not affected by the errors of radiation, conduction, and oxidization such as affect conventional gas temperaturesensing devices.

An object of the present invention resides in the provision of control apparatus not dependent upon a direct reading temperature device in the path of the combustion gases from a burner. According to this feature of the invention there is no need for continual calibration of any such thermocouple device exposed to the deteriorating effects of gases having an elevated temperature and moreover, the problems introduced owing to errors in radiation, conduction, and oxidization of a thermocouple are rendered inconsequential.

Another object of the invention resides in the provision of electrical apparatus which when calibrated and set, is free from operating errors continually introduced by sediment deposits and the like such as are attendant with counterpart types of control apparatus which involve calibration and adjustments for errors in valving.

A further object resides in the provision of electrical slider means of which the friction characteristic is a minimum such as may be readily operated by pressure and temperature-sensitive control devices with a minimum loss as to the actuating forces available.

Still another object is to provide a control apparatus from which a series of valves and restrictions may effectually be eliminated in order to prevent a cascading of errors and in which each sensing device varies more or less with its own error and not according to accumulative errors of the associated sensing elements.

A still further object resides in the provision of metering valve setting means in the form of a rapidly responsive electric motor adapted by a suitable amplifier to respond to small electrical signals.

A yet further object resides in the provision of control apparatus by means of which combustion temperatures can be effectively controlled by inferential means such as are not necessarily exposed to excessive heat efiects for which present day materials and their uses are not adequate.

Other objects and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

The instant invention takes advantage of certain fundamental relations which may be set up from a thermodynamic standpoint upon proper analysis of fuel combustion processes. As regards an isolated burner having a combustion zone it may be assumed first that the weight of the gases entering the combustion zone is substantially equal to the weight of the gases leaving that combustion zone. Of benefit in making a more complete analysis of the combustion process is the assumption of an upstream station No. 1 and a downstream station No. 2 on the respective sides of a combustion zone at which stations the quality of the gases may be conceived of in 3 terms of the generally accepted symbols set forth below:

Station No. l

sl tlTlAl Station No. 2

Combustion PnQPtZTZ Z zone W2V2 Upstream Downstream At the upstream side of the combustion zone, the static pressure (PS1), the total pressure (Pu) and the gas temperature (T1) are known. On the downstream side, the static pressure (PS2) and the total pressure (Pa) are known, while the gas temperature is unknown. The thermodynamic relationship between these known and unknown quantities may be established as follows. The notation to be used consists of:

A=cross sectional area c=specific heat at constant pressure g=acceleration of gravity J=mechanical equivalent of heat P=pressure T=temperature V=gas velocity W :gas Weight p=mass density of gas r=ratio of specific heats s=static t=total 1=upstream or cold point 2==downstream or hot point 1 1 P 51 32 E FIZTQ Substituting, since W1=W2 (approximately): K V1 z lzTn From (5) and (l):

o5 lea l Simplifying by using K5=(fi gf 1 lee l 4 An analysis of Equation 8 reveals that for the temperatures and pressures involved during the normal range of operation, the exponent may be reasonably accurately evaluated as a decimal constant and certain other quantities likewise evaluated. Then by holding the quantity temporarily constant, a plot of Ta as y along the Y axis on coordinate paper against the variable quantity as 9: along the X axis, yields a simple curve. Another reasonable operating value for quantity Changing the slope of the curves of the plots of Equation 9 is accomplished simply by multiplying the right side by slope constant K6, which when united with the constant K5 already in the equation, may be designated combined constant K.

Accordingly, for the practical range of values employed, the Equation 8 may be reduced to:

PB 9 rsczrsr,

and Th is easily measured (13) a2(Pt2 a2) where T2 and T1 represent respectively the total temperature at station 2 and the total temperature at station 1.

Relations derived from fundamental Equation 8, such as Equation 13 and other modifications, will be seen to be used to advantage in the instant invention. It is by means of these relations that the combustion temperature of the burner ,may beinferentially determined and'br'ought into conformity with the combustion temperature actually desired by the operator of the burner.

In the accompanying drawings in which like reference numerals are used to designate similar parts throughout, there are diagrammatically illustrated suitable mechanical embodiments for the purpose of disclosing the invention. The drawings, however, are for the purpose of illustration only and are not to be taken as limiting or restricting the invention since it will be apparent to those skilled in the art that various changes in the illustrated embodiments may be resorted to without in any way exceeding the scope of the invention.

In the drawings:

Figure 1 is a longitudinal sectional view of a fuel system to which the control apparatus of the instant invention has been applied;

Figure 2 is a schematic view of a control apparatus of Figure 1;

Figure 3 is a schematic view of a modified control apparatus; and

Figure 4 shows a further modification.

In particular regard to Figure 1 of the drawings, the control box In constructed according to the principles of the instant invention is shown applied to a controlled combustion system. A manual setting lever I8 is provided on box It to afford a means of setting the selected operating temperature for the combustion system. Into one side of control box [0 are fed signals from a sensitive device going to form a set comprised of a temperature responsive element 22, a total pressure responsive element 24, and a static pressure responsive element 26. ditional set of sensing elements is provided for the control box, which is comprised of a total pressure responsive element 32 and a static pressure responsive element 34. The foregoing sets of sensitive elements are adapted to be mounted in conjunction with a burner having a means 42 forming an inlet passage for the air or other combustion-supporting medium introduced into the burner. A structural member 44 serves to provide a passage for the flow of the energy laden products of combustion of the burner being discharged from the combustion zone. The combustion-supporting medium is led through the inlet 42 along the inside of the walls 46 of the outer tube of the burner. Inwardly spaced from walls are walls 48 formed by a series of frustoconical elements 58, which are positioned to constitute an inner tube for the burner. Suitable brackets and clips 5| and 53 serve to position the frustoconical elements 50 against displacement within the burner. The air from the chamber between the respective outer and inner tubes is led through the spaces between the frustoconical elements and directed inside the inner tube in a direction toward the closed end 52 thereof. Arranged through suitable openings in wall 52 are respectively a spray nozzle 54 served by a fuel inlet line 55 and an igniter 56 energized by a conductor 51. The fuel may ordinarily be introduced into the inner tube in a suitable spray pattern by nozzle 54 and ignited by the device 56 to burn in the presence of the turbulent air flow within the inner tube. The products resulting from the combustion are led from the burner in an energy laden state through the discharge outlet 44.

Control box l0 may be powered from a supply generally indicated at 66 from which it derives energy that is translated into a fuel control signal and passed along a cable l9. Suitable valv- An ading at 70 provides for fuel control to be exerted by the control box over the atomizing nozzle just described. The valving mechanism is provided with a metering orifice 12 which establishes communication between a chamber 14 leading from the fuel supply line of the nozzle, to the bypass chamber 16. Valving I5 is adapted to be positioned within the metering orifice 12 by means of a member 11 on which it is carried and to which is connected a rack 18. The control signals emitted from the control box through cable I9 may be fed into a motor of which the rotor 82 carries a shaft 86 therewith. A pinion 88 carried by the rotor and shaft 88 meshes with the rack 18 to position metering valving (5. A suitable ground at 84 may be provided for motor 80. The main fuel pump 90 is adapted to receive fuel from the line 96 and introduces this fuel under pressure into the supply line 55 for atomizing nozzle 54. The bypass of pump 90 is arranged to be controlled by the metering motor 80 such that the quantity of fuel actually available for introduction into the burner may be accurately controlled. Intake line 96 for pump 90 is itself supplied from flow structure 92 provided with fuel by a line 98. Transfer pump 94 serves the line 98 and is provided with a bypass valve 59 for regulating the operation thereof.

During normal operation of the combustion system just described, a controlled supply of fuel is introduced into the inner tube 48 of the burner and there broken into small particles readily consumed in the mixture of burning energy gases. The temperature and the pressures of the incoming relatively cooler air is registered by the sensing set 20 and communicated to control box [0. The energy gases passing along discharge 44 may be expected to have a characteristic highly elevated temperature. Therefore only the static pressure and total pressure of the energy gases is conveniently registered by means of the sensing set 39 and communicated to the control box l0. These data afforded by the sensing sets are sufficient of themselves to provide the control box with sufficient information to regulate the temperature of combustion accurately by means of the metering control which the control box effectively exercises over metering valve 15.

In Figure 2 is schematically shown a system designed to control the nozzle box temperature T2 by action based on the values of the other variables of Equation 13. The voltage level at point E7 is a continuous indication of temperature at the nozzle box.

This control system is unusual in that the required multiplication, division, and subtraction are accomplished automatically by electromechanical means. The results of the computation, represented by voltage level E7, is communicated to the operators temperature setting lever 18 and assembly to establish a balanced circuit. When, however, the lever I8 is moved to call for a temperature at the nozzle box different from that indicated by voltage level E1, an unbalance is created which is transmitted in modified electrical form as a signal to amplifier means and to fuel metering motor 85. The motor 80 then varies the flow of fuel supplied to the burner to accord with the nozzle box temperature demanded and eventually a balance is struck again in the system. An examination of the detailed operation of the balancing circuits is reserved to a later portion of the instant discussion.

In particular regard to the calculating means, the basic circuit is a positionable means in the form of a potentiometer connected to give an output voltage which is proportional to the product of the input voltage and slider position. If each slider is positioned by one of the pressures or temperatures in Equation 13 then the electrical circuit will perform the necessary computation. The arrangement uses amplifier tubes in the cathode follower circuit to make the currents in the various potentiometers less dependent on one another.

The calculating means Ii may conveniently be divided into three operating portions I2, It, and I6. At the input side of portion i2, is a conductor I02 leading from the power supply 60, in series with a potentiometer I9 2. The slider of the potentiometer is carried by a bar I06 pivoted at I93. The positioning means for the bar includes a rod Iii attached to the free end of a temperature bellows IE2 which expands or contracts in accordance with temperature changes sensed by the remote temperature bulb or capsule 22. Bulb 22 is arranged on one end of a sealed conduit communicating with bellows H2 and disposed in the inlet air passage of the burner. Since the slider of the potentiometer varies its position with the temperature of the inlet air and taps mi from level E'o at H32 a voltage proportional to the temperature, the voltage level E1 at point lilfivmay be related properly to the temperature by the following equation:

(14) E1=T1Eo The cathode follower circuit H4 is used to impress the voltage E1 onto potentiometer I It without adding a current drain to potentiometer I04. The slider of the potentiometer H6 is mounted in a similar fashion on bar i it pivoted at I20, to take a position in respect to the static pressure PS2 of the hot gases. Tapped off at point I25 of vacuum bellows unit I25, the voltage E2 may be expressed in equation form as:

(15) E2=Ps2El As such, the voltage E2 is transmitted to operating portion it. I

In regard to portion I 43, the voltage E2 is transmitted by conductor I28 to the slider on bar I38 pivoted at I 32. The bar swings along the potentiometer dividing it into an upper segment I34 and a lower segment I36. The lower segment E35 is connected to the paralleled low resistor I33 and high resistance primary winding I40. Bar I moves in response to the static inlet pressure PS1 through the agency of vacuum bellows unit 54 3. Hence the pressure i n is represented by the value of the electrical resistance offered by segment I36. For all practical purposes, the current carried by segment its is all directed through the low resistor I38 of resistance value R1. The voltage drops across these resistors may be expressed in equation relationship as follows:

1 E R1 (16) z i1+ i The value of R1 is purposely chosen low relative to resistance PS1 such that equation may be transposed and reduced as:

F I i z' R132 11: 3 P81+R1 P81 3 The high resistance coil I w is the primary winding of a transformer I45 Whose ratio is predetermined as The secondary M8 is connected to conductor I50 whose potential E4 bears this relation to the input voltage E32 Conductor 1 53 is connected to a cathode follower circuit it? in such a manner as to renderthe output of transformer I46 at zero.

The voltage E4 is impressed through potentiometer terminal 55 onto potentiometer I56. The slider bar W8 is pivoted at Ito to provide a tapped off potential E5. The value of E5 depends on the position of the slider, set in proportion to the difierential in pressure afforded by Pm over s2; that is to say, the velocity pressure at station 2. As the pressure in the lower bellows iiii rises relative to that of the upper or PS2 bellows I85, the voltage E5 approaches the impressed voltage at its, El. In other words:

This adjusted voltage, is transferred over to operating portion M.

In the operating portion It, connection I53 energized at the level of E5, is carried by the end of slider bar Ilii which is pivoted at it?) and positioned in accordance with the Value of the velocity pressure at station 1. The positioning mechanism includes a difierential rod H2 controlled downwardly by the excess in pressure rise of the total pressure Pu, transmitted to pressure bellows I'M, over static pressure P51, in bellows I15. The potentiometer for slider bar He is inverted in the manner of the potentiometer for bar I33, explained above. The potential E's supplied to line I32 may be expressed by the following relation in which symbol R2 refers to the resistance ofiered by low resistor i842 Since R2 is relatively low, Equation 21 can be simplified in the fashion of Equation 17.

Equations l4, 15, 19, and 20 results in an Equation 25 like the fundamental control equation number 13:

82 H an This potential is fed from the computing section II of control box I6 into the fuel motor controlling section [3.

As previously stated, the tube in each cathode follower circuit serves the purpose of tapping oif voltages from the preceding potentiometer without taking current of consequence out of the slider of that potentiometer. Thus the follower circuit cannot by its own variances introduce an error in the calculation process of the preceding potentiometer. Otherwise, the error in the first potentiometer I64 of the group would represent a cascading of variables in the succeeding potentiometers, II6, I34, etc., and be nowhere near to allowable. Practically, it may be found desirable to install a cathode tube, similar to H4 and I52, between the operating portions I2 and I4, and another between portions I4 and I6. The purpose in the one case would be to make the operation of potentiometer II6 entirely independent of potentiometer I36; in the other case, potentiometer I56 would be made less dependent on potentiometer I86.

As to the controlling section I3, as a unit it operates to balance up the voltage level of E as against that level in terms of temperature setting, called for and instituted by the manually set lever I8. In equation form the relation may be expressed:

Wi=rate of fuel flow,

t=time, and

K y=constant for fuel system.

The mode of operation is a devious one whereby section I3 actuates the fuel metering motor 86 to change the rate of fuel flow and consequently the downstream temperature T2. The voltage level at E7 then changes to balance out the temperature setting, Tsct, called for.

Potentiometer I98 is bridged across supply lines I94 and I95 so as to be in series with a calibration resistor I96. Temperature setting lever I8, grounded by the pivot I99 and its line 266 is mounted to slide along the potentiometer I98. Line I92, at the voltage level of E7, connects with the lever I8 and ground line 266 through a resistor 262. Any unbalance in the system is reflected by suitable signal owing to voltage drop or rise over this resistor 202 to ground line 266.

For providing D. C. power to the audio amplifier tube 226 and phase discriminator tubes 236 and 246, conventional means may be provided such as rectifier tube 256. The above tubes have a common terminal for their grounded heaters denoted by the character F and may be connected thereby, in parallel, to one terminal of the secondary winding 266 of transformer 266, similarly marked F. The plates of the rectifier tube 266 may be connected to the transformer 266 at the terminals of secondary winding 268 seen to be grounded by center tap 269. On the cathode side of tube 256 is a filter 252 which delivers a steady D. C. supply to audio amplifier tube 226.

During balanced condition of the system, that is when the voltage E7 at line I92 is at the level of ground line 266 or ground level, the grid in amplifier tube 226 is uncharged and the tube conducts uninterruptedly. Associated with the plate circuit of tube 226 by a coupling condenser 22I in line 222 are grids of phase discriminator tubes 236 and 246. These grids are grounded through a suitable resistance at point 223. During steady state conditions these grids accordingly will have neutral charges and will allow the discriminator tubes 236 and 246 to conduct steadily. The cathodes of these discriminator tubes are grounded at 223 and 243 respectively, the plate connections are led to the end terminals of secondary winding 262 in transformer 266, each plate lead going to the opposite end respectively. Winding 262 is provided with a center tap 263 which is led over to field coil 86 grounded at 8'! and condenser 88 in parallel, also grounded. This field coil is located in fuel metering motor 86 which comprises a rotor 82 and another field winding or coil 84 disposed in a 96 relation to the field coil before mentioned. The motor is of two-phase type and is actuated by these two coils. Field coil 84 is energized by power source 66 which also energizes the primary winding 26I of the transformer 266. However, the interposition of condenser 85 in series with the coil 84 causes a phase shift as between the voltages over these respective coils 84 and 26I such that the voltage of winding 84 leads the voltage of coil 26I by an angle The phase relation of coils 26I and 262 is essentially the same. Hence the variance between the phase angles of the voltage of coil 262 and winding 84 is of the same order as As has been stated above, the charge on the grids of the discriminator tubes normally is neutral. These tubes under this condition normally conduct alternately, that is, tube 236 will conduct for half the cycle through the upper half of coil 262 through motor winding 86 and then tube 246 conducts for the second half of the cycle through the lower half of coil 262 through the center tap to the winding 86. The condenser 88 serves in a flywheel capacity and tends to maintain an unwavering direct current fiow through winding 86 with the result that a steady flux is maintained in the field. Within the influence of coil 84 an alternating flux is maintained and the two fluxes do not provide any field which actuates the fuel metering motor rotor 82. As to operation of the system of the embodiment of Fig. 2, the first indication of unbalanced activity will be that voltage E7 in line I92 will attain a level alternately above and below the ground level maintained in line 266. Let it be assumed that the instantaneous charge on the grid of tube 226 during the unbalanced state will be positive at the same instant that the top terminal of coil 262 goes positive. Conduction in tube 226 is decreased and the input plate of condenser 22I goes less negative with the result that the grids of tubes 236 and 246 go positive. Since the upper terminal of coil 262 is positive, the upper tube 236 is the one which will conduct for this half cycle at a stimulated production due to the change in the charge on the grid. Accordingly, the coil 66 has the effect of an increased field. During the next half cycle, however, the charge on the grid of amplifier tube 226 goes negative with the result that during this second half of the cycle when tube 246 conducts, the grid of tube 246 goes negative to the end that tube 246 conducts only a fraction of its steady state output. Hence, the flux in winding 86 dies down appreciably with the effect that the field of winding 86 has a pulsing action. As has been stated, the

voltages actuating windings

84 and 66 are disposed at an angle to one another and the windings themselves physically are disposed at an angle of Their fields tend to cooperate yielding a resultant which imparts a rotating field to fuel motor 86. The more the grid charges are, relatively speaking, the greater the vector quantity of the resultant is, such that motor speed depends upon the amount of unbalance in the system. On the other hand, if the unbalance in the system over resistor 202 is in the other direction the instantaneous charge on the grid in the amplifier 220 will be negative at the same time that the upper terminal of coil 262 is itself positive. Under such condition the tube 240 will conduct at a more stimulated pace while the conduction of tube 238 will be retarded. The field produced by winding 86 will be growing and dying in an exact opposite relation to what it was during the first situation considered. Hence the rotating field will take the opposite direction and the fuel motor will rotate in an opposite direction. The shaft rotation then may be said to correspond in direction and magnitude with the temperature error. Of significance in the overall operation is this last mentioned fact that the greater is the unbalance created in the system the greater is the field created and collapsed in winding 86 and the stronger is the fuel motor response.

The embodiment shown in Figure 3 is arranged to operate from a modified control equation. This modification is accomplished by substituting directly in Equation 8 some actual values met over the normal range of operation, the remaining terms reducing to:

The equipment used is essentially the same as for the first embodiment, depending upon the same variables as formerly except employing them in a slightly diiferent manner. The layout of Figure 1 again applies.

The device of Figure 3 is different in some marked respects however. The sole source of power relied on by the control box and the metering equipment is of D. C. nature. The fuel metering motor is D. C. as well. Any alternating current required in the net is self-converted within the system by an oscillator incorporated therein. All the vacuum tubes and the fuel control motor have the same direct current power source in common. Metering motor Bil may be provided with two motor windings of which one, when selectively energized, will cause motor rotation in one direction whereas the other when selectively energized will cause motor 80' to rotate in the other direction.

The control box It may be comprised of a computing section H and a controlling section l3. Both sections may be furnished a supply of alternating current by transformer 460. Supply line 392 to the computing section is maintained as potential E which is alternately above and below the ground level at a value determined by the relative position of the grounded slide wire bar 18' relative to its potentiometer 398.

Line 362 is connected to the terminal of a potentiometer 3% whose other terminal is served by return 3%. This potentiometer is the first of a series of positionable potentiometers, including am and 33, each of which is in parallel with the circuit of the slider of the respective preceding potentiometer. Every time a voltage is tapped off by one of these sliders, a step such as multiplication for instance, in the computation is performed. The mechanics involved are essentially as set for in regard to the first embodiment described.

Slider bar 3% may be mounted on a pivot 301 and is adapted to communicate the voltage tapped off, by means of connection 308, to conductor 313. The voltage level in conductor M3, E1, may be expressed as: a=gfa where K1 is a correction factor for the system. Also: 31 E,=E, (173P.1- 149.21%

Equation 31 is transformed into a reality owing to the ratio of areas selected to be exposed in the bellows 322 and bellows 324. From an upstream station number 1, the static pressure registered by tube 26' may be transmitted to the outside surface of bellows 32 6. The total pressure Pu is communicated to the inside of this bellows from Pitot tube 2d. The inside of the top of bellows 324 however, is partially blanked oil to pressure Pu by a vacuum bellows 322 to the extent that the ratio of effective areas exposed to the actuating pressures are in the ratio of 173 to 149.2 for the top outside and top inside respectively. The net force acting in rod 320 depends then on the quantity (173Ps1-1492Pt1) Slider bar M8 is pivoted at 3H! and connected at 326 to conductor 328.

Another subtraction transpires at positionable potentiometer 334 which is actuated by the pressure differential between Ptz and PS2, or inversely to the velocity pressure at an upstream station number 2, whichever way is more suitable for the reader to look upon the situation. Slider bar 358 is pivoted at 359 and there connected to conductor 366. A correction factor is necessary to be introduced at this computation, and the following equation relating the level at 366, E3, to the level at 328, E2 may be derived:

Potentiometer 3'16, next in the circuit, is of different design from the previous instruments. It is not only inverted as connected, but also constructed to have a cubic taper winding. The static pressure signal from tube 26 operates to yield inversel to the cube of its own value, the voltage E4 in conductor 3%. It may be accordingly stated that:

Slider bar 3ft is pivoted at connection 368.

To complete the circuit between conductor 3M and return line 3&3 are two resistors in series,

315 and 22. The resistance oifered at 375 is of high value R3. The resistor 22', a temperature sensitive type located in the air inlet of the burner substantially as is the thermometer bulb of Figure 1, offers relatively low resistance which varies directly with the total temperature at station number 1. The voltage E5 at tap 318 between these resistors may be related to E; as follows:

Yet Tm is only a negligible fraction of R3 and the A substitution in Equation 36 of values derived in Equations 30, 31, 32, and 33, yields:

The resulting voltage E5, representing the temperature T2 (that is the total temperature at station 2) of Equation 29, is used to provide the charge on the grid in section 422 of amplifier tube 420 through the medium of conductor 392.

Within the control box I6 is an oscillator tube 450 of the push pull type. This oscillator tube is powered from the D. C. power source 60' and serves to control the polarity of transformer 466 according to the relative algebraic sign of the charges on the grids 452 and 454. The primary winding 456 of the transformer creates a field of alternating polarity. Secondary windings 412 and 462 power respectively the computing portion H and the controlling portion I3 of the control box. Tapped across secondar winding 412 is a potentiometer similar to that illustrated in the embodiment of Figure 2, in series with a calibration rheostat 396. The slide wire bar I8 is grounded. The cathode of the amplifier tube 422 of the controlling unit [3 is at the ground level with the slide wire 406. When the voltage E in lead 392 is at ground level, that is, the charge is neutral, this tube 422 conducts. The plate in the side 424 of tube 420 is led suitably to the power source 60' through a resistor. Associated with this plate circuit is a line 426 containing a condenser 42! which is led to a resistor grounded at 423 in parallel with a line 453 leading to the center tap in secondary winding 462 of transformer 466. The terminals of coil 462 are led one to the grid of phase discriminator tube 430 and the other to the grid of phase discriminator tube 440. The plates of these latter mentioned tubes are led to a relay circuit comprising coils 43l, 432, 44!, 442, and relays 436 and 446. interposed in this coil circuit are two condensers 434 and 444 which will be described later. These solenoid coils are set up in opposed relation and when one overcomes the other, these coils serve to close relays 43S and 446 as the case may be which throw onto the line motor 80, grounded at 81'. This motor is an ordinary direct current machine and revolves in a direction depending upon which of its field coils, either 84' or 86, happens to be energized. The relay and motor are conventional. As to the connections between the circuits of the amplifier tube and the discriminator tube during steady state condition the center tap 463 of secondary winding 462 is uncharged and the grids of tubes 43!] and 446 alternately go positive-negative, then negative-positive.

14 The effect will be that tube 436 will conduct for half a cycle and then tube 446 will conduct for the next half cycle. Consider the half cycle when tube 436 is conducted during the steady state condition. A field will be created in coil 43! and also in coil 432, the former tending to close relay contact 436 and the latter tending to open relay contact 446. The condenser 434 serves in the flywheel eiiect to maintain a fairly steady field intensity through these two coils under consideration even during the half cycle when tube 430 is not conducting. On the other hand, during the next half cycle when tube 440 conducts, the solenoid coil 44! is energized which tends to open relay 436. Simultaneously coil 442 is energized which tends to close relay contact 446. A condenser 444 in this circuit likewise tends to provide constant flux through the two pertinent windings. The output of the tubes is the same during this situation because their capacities have been predetermined to be the same and the coils tend to counteract the effect of one another and let the relay contacts remain unafiected. Accordingly, the motor 86 is idle. As to the active operation of the embodiment of Figure 3 the first change to be noted will be that voltage E5 in conductor 392 will go either above or below ground level and begin to carry an alternating charge. This condition will, of course, be brought about by movement of the said lever 48' calling for more fuel and accordingly causing the voltage E5 to be at variance with the ground. For a practical illustration of the mechanics involved, let it be assumed. that the instantaneous charge on the grid of tube 422 is positive. This tube begins to conduct at an accelerated pace and causes less activity in tube 424 which conducts, by virtue of the condenser coupling with the tube 422, in a decreasing fashion with lowered output. The charge on the output side of condenser 42| .becomes less positive and accordingly by means of line 426 the potential at center tap 463 rises above ground level. If the instantaneous polarity of secondary winding 462 happens at this time to be positive at terminal 466 and negative at terminal 468, the voltage level will be at point 463 actually more positively charged than when it was charged during existence of the normal ground level potential of the center tap. At all times that the terminal 466 is positive, tube 436 is the discriminator tube which is conducting, and the added potential to the grid will cause tube 436 to conduct even more with the result that the field in the coils 43! and 432 begins to strengthen. At this same time when center tap 462 becomes positive the potential at terminal 468 becomes less negative than it was and during the next half cycle will be less positive than what it is during the normal steady state condition. The result is that during this second half cycle when tube 446 is conducting, the coils 44! and 442 will be producing less of a flux density and their field Will be altogether overcome by the stronger fields 43! and 432. Relay contacts 436 accordingly, will close, relay contacts 443 will be enforcedly held open, and the motor winding appropriately selectively energized will cause motor 8 1' to revolve in one direction. The alternate condition which could have been chosen would be that when the grid in amplifier tube 422 goes positive the terminal at 468 happens to he the positive terminal. Under such circumstances an opposite efifect will be experienced and the field coils actuated by discriminator tube 443 will dominate, causing relay 436 to open and the contact 446 to close thereby selectively energizing the alternate winding for so effecting the motor 89 that it rotates in the opposite direction. The motor 80', it will be recalled, operates through the means of a rack and pinion to alter the fuel flow to the burner. Any change in fuel fiow will bring about a change in the voltage level at E5, which represents the temperature at station 2 and the system will be brought back into balanced condition.

In regard to Figure 4, a modification is shown for the embodiment of Figure 3 just described whereby in place of a temperature sensitive resistor there is used a thermometer bulb 22". This thermometer bulb located in the inlet air passage as was the thermometer bulb of Figure 1 and mounted on one end of a sealed conduit, causes by means of pressure changes the actuation of a potentiometer and varies the tapped-off voltage in direct relation to the temperature measured, that is, the higher the temperature, the higher the voltage tapped off. The mode of operation for such thermometers was discussed in detail in connection with the first embodiment shown and operates in the same fashion as the instant thermometer capsule or bulb arrangement.

In order that the current drawn by each successive potentiometer in the embodiments of Figures 3 and 4 does not seriously introduce an error into its preceding potentiometer, it may be found advantageous to arrange the resistances in proportion to one another such that the current flowing in the conductor energized at the voltage E is of the order of one ampere, for instance, whereas the current flowing in the conductor energized at voltage E1 of the order of one-tenth ampere whereas the current in the conductor energized at the voltage E2 is of the order of one-hundredth of an ampere and so on. It is also contemplated that in certain instances the potentiometers be formed of varying resistors which will readily compensate for the additional current carried by it for the succeeding potentiometers.

The embodiments just described have certain features in common with one another. The positionable members comprising the rack and pinion, motor shaft, and motor rotor are adapted accurately to adjust the valving in the restricted fuel path which ultimately determines the rate of flow of fuel allowed for consumption by the burner. So long as the drive into the initial section of the amplifier device remains at the zero or ground level the disposition of the valving remains unchanged. Fluctuations in the flow pressures of the intake air and discharge gases as well as fluctuations in the intake air temperature are compensated for by the control apparatus which properly re-positions the valving in the fuel flow control. While temperature sensitive means are used, such means only contribute to the determination of the discharge temperature and paradoxically enough, are located in the inlet air passages. If the quality of fuel used is changed such that the heat output per unit quantity is changed, the instant control apparatus senses the discharge temperature change and self-compensates the fuel flow rate. Moisture content of the air supplied may be changed whereupon automatic compensation is eifected. Thus changes in the actual quality of the fuel and air supplied do not necessitate a recalibration of the instant device since the thermal level is automatically controlled by compensated fuel rate of flow, Inasmuch as the variables just mentioned have been interrelated by well known and fundamental thermodynamic laws the combustion temperature will be automatically maintained at a constant value by an inferential method. Once, however, is the manually operable slider changed as to its position so as to vary the input voltage to the control apparatus, then the resultin electrical signal arising out of the condition that the voltage equilibrium of the system has been changed into an unmatched state is impressed upon the amplifier and causes the fuel metering motor to readjust the position of the valving and change the combustion temperature by an appropriate amount. So soon as the combustion temperature changes, then according to the control equation the various temperatures and pressures are registered whereby the positionable potentiometer sliders are operated to match the new voltage setting inaugurated by the manually operable temperature setting lever. The control equations of the embodiments of the invention described as has been pointed out, involve the same variables except in a slightly diiferent fashion. These expressions, however, have been interrelated with the control apparatus so as to yield a suitable electrical signal to which the amplifier is responsive and to bring the system back into a state of equilibrium. For any assigned combustion temperature, the Tsct is equalled by the actual T2 on the downstream side of the burner owing to the automatic positioning tendency of the potentiometers. That is to say, so long as the respective expressions set forth yield constant values:

the actual temperature maintained equals the discharge temperature desired. In the first embodiment the fuel control motor was controlled in response to demands of the amplifier by means of one variable winding for which the energization could be controlled to varying degrees. In the second and third embodiments shown the metering motor was controlled by two windings which were selectively energized by the amplifier in an alternative fashion. That is to say, when the one winding was energized the other winding was deenergized altogether.

By way of further summary, it may be said that the last embodiment shown diiiered from the second embodiment in the manner by which intake air temperature was employed to vary the matching voltages in the electrical system of the control apparatus.

It will thus be seen that there has been disclosed suitable apparatus for determining coinbustion temperatures which is not subject to the poor response characteristics of a thermocouple or other metal temperature-sensing device and that an apparatus has been disclosed which is further not effected by the errors of radiation, conduction, and oxidization.

While suitable physical embodiments for the purpose of disclosing the invention has been illustrated in the accompanying drawings and hereinafter described, it is to be understood that the invention is not limited to the particular embodiments so illustrated and described but that such changes in the size, shape, and arrangements of the various parts and their particular functionszmay:berexertedtoasuchaas will-occur to thosesskilled intheart.

The invention "now "having been described so that othersrskilled inthe art may clearly understand the same, the claims are set forth to follow. By the :term air used therein is meant any suitable combustion-supporting medium and by fuel is meantany liquid, gaseous, crushed-or powderedfuel appropriatefor use in burners.

We claim:

v1. In a regulative combustion system inferentially determinative-of combustion temperatures irrespective of the initial quality of the fluids supplied and characterized by a burner, means providing a path for the flowjof air to the burner, meansproviding a path for the flow of energy gases discharged from the burner, means providing a path for'the flow of. fuel to the burner, and a metering element adjustable'to vary the rate of flow of fuel to the burner: the combination comprising a voltage divider including an indicator element adjustable to positions indicative of specific discharge temperatures-of the energy gases, pluralized voltage divider means, :a bridge circuit including said voltage divider and said voltage divider means, said voltagedivider means comprising first, second, third, fourth, andfifth voltage dividers, each including an adjustable contact and being coupled with one another in predetermined sequence ina manner such that a majority of the dividers are each coupled across the rtion of the preceding divider selected by its contact and at least one divider is coupled across a fixed length of the preceding divider, said first voltage divider including a contact adjustablein accordance with the temperature of the .air flowing to the burner effective to adjust the bridge circuit, said second voltage divider including a contact adjustable-in accordanc with the force differential created by the static and total pressures of the air flowing to the burner acting predeterminedly .in opposition tooneanother and eii'ective .to adjust the bridge circuit, saidthird voltage divider including a contact adjustable in accordance with the force difierential createdby the static and totalpressures of the energy gas from the burner acting predeten minedly in opposition to one another andefiective to adjust the bridge circuit, said fourth voltage divider including a contactadjustable in accordance with the static pressure .01 the air flowing to the'burner effective to adjust the bridge circuit, and said fifth voltage divider includinga contact adjustable in accordance with the static pressure of the energy gas from the burner effective to adjust the bridge circuit, and means responsive to the value of unbalance potential existing in the bridge circuit for adjusting an adjustable element above-named.

2.In a regulativecombustion system inferentially determinative of combustion temperatures irrespective of the initial quality .of .the fluids supplied and characterized'by a burner, means providing a path 'for'the'fiow chair to the burner. means providing "a path'i'or'the flow of energy gases discharged from the burner, means, providing-a path fortheflow ofjiuel tothe burner, and a metering element adjustable to vary the 'rate of flow of fuel to the burner: the combination com-prising a voltage divider including an in-' dicator element adjustable to positions indicative of specific discharge temperatures of the energy gases, pluraiizedvoltage divider'means',-a bridge circuit including ;.said voltage divider and ;said

voltagedivider means. saidvoltaae:dividermeans comprising first, second, third, Iourth, and :flfth volt ge dividers, each including an adjustable contact and being coupled with one anotherin predetermined sequence ina manner such that armajority of the dividers are each coupled across the portion of the preceding divider selected by its contact and at least'one divider iscoupled across a fixed length of Jthepreceding divider, said first voltage divider including a contact ad-- justable in accordance with the temperatureof the airflowing to the burner effectiveto adjust the bridge circuit, said second voltage divider including a contact adjustable in accordance with the force difierential created'by .the static and total pressures of the air flowing to theburner acting predeterminedly in oppositionito-ione another and efi'ective to adjust the bridge circuit, said third voltage divider including a contact adjustable in accordance with the force difierential created by the static and totalpressures of the energy gas from the burner acting predeterminedly in opposition to one'another and efiective to adjust the bridge circuit, said fourth voltage divider including a contact adjustable in .accordance with the static pressure of the air flowing to the burner effective to adjust the bridge circuit, and said fifth voltage divider including acontact adjustable in accordance with the static pressure of the energy gas from the burner'effective to adjust the bridgecircuit, and mean responsive to the value oi unbalance potential existing in the bridge circuit for adjusting an adjustable element above-named.

3. In .a regulative combustionsysteminferentially determinative of combustion temperatures irrespective of the initial qualityof the fluids supplied and characterized by a, burner, means providing a path for the flow of air to thezburner, means providing a path for th-eflowof energy gases discharged from-theburner, means providing a path for the flow offucl to the burner, and a metering element adjustable to vary-the rate of flow of fuel to the burner: the combination comprising a voltage divider including ,an indicator elementadjustable topositions indicative of specific discharge temperaturesof the energy gases, pluralized. voltage divider means, a bridgecircuit including saidvoltagedivider and said voltage divider means, said voltage divider means comprising first, second,andthirdvoltagc dividers, each including an adjustable contact and being coupled with one anotherin predetermined sequence in a mannersuch that :-a majorityof the dividers are each coupledacrossthe portion of the preceding divider selected'by its contact,.said first-voltage dividerincluding a contact adjustable in accordance with thetemperature of the air flcwingto the burner effective to adjust the bridge circuit,-.said second voltage-db vider including a contact adjustable in accordance with the force differential created .by the static and total pressureso'f the :air flowing-to the burner acting predeterminedly in oppOsit-ion to one another and effective to adjust the bridge circuit, and-said third voltage divider including a contact adjustable in accordance with the force differential created by thevstatic and'totai pressures of the energy gas from, the burner tacting predeterminedly in opposition-toone another and "effective -to adjust the bridge circuit-and means responsiveto the val-ue-o'tunbalande p tential existing in the bridge-circuit vfor adjusting an adjustable element above-named.

4. In a combustion apparatus-for aifueiriired burner system "characterized by fuel and iflhfine 19 lets, an energy gas discharge, and a fuel flow controlling mechanism having an adjustable element, the combination with voltage divider means including an adjustable element settable to adjusted positions indicative of changed combustion temperatures established in the burner system, pluralized voltage divider means, bridge circuit means including both divider means aforesaid, and means responsive to unbalance potentials in the bridge circuit to adjust the appropriate adjustable element above-mentioned, said pluralized divider means having at least first, second and third voltage dividers including first, second, and third adjustable contacts respective ly interrelated electrically in sequence such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact, of actuating means for adjusting said first, second, and third adjustable contacts consistlng of means responsive to inlet air static, pressure (P51) means responsive to inlet air total pressure (Pm) means responsive to inlet air temperature (T1), means responsive to energy gas v total pressure (Pm), and means responsive to energy gas static pressure (PS2), said actuating means being precalibrated for effecting the above-described adjustments whereby the value of the established combustion temperature in the burner system is yielded by the expression:

Pd m- 02) P tl" sl) 5. In a combustion apparatus for a fuel fired burner system characterized by fuel and air inlets, an energy gas discharge, and a fuel flow controlling mechanism having an adjustable element, the combination with voltage divider means including an adjustable element settable to adjusted positions indicative of changed combustion temperatures established in the burner system, pluralized voltage divider means, bridge circuit means including both divider means aforesaid, and means responsive to unbalance potentials in the bridge circuit to adjust the appropriate adjustable element above-mentioned, said pluralized divider means having at least first, second and third voltage dividers including first, second, and third adjustable contacts respectively, interrelated electrically in sequence such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact, of actuating means for adjusting said first, second, and third adjustable contacts consisting of means responsive to inlet air static, pressure (Psl), means responsive to inlet air total pressure (Pu), means responsive to inlet air temperature (T1), means responsive to energy gas total pressure (Pm) and means responsive to energy gas static pressure (PS2), said actuating means being precalibrated for effecting the above-described adjustments whereby the value of the established combustion temperature in the burner system is yielded by the expression:

let i P a ut= 1 51 z1] 42- 12] 6. Means for automatically controlling the rotative position of a fuel metering motor in an operating combustion system characterized by a burner supplied with the metered fuel and having means providing for a supply of intake air and for discharge of the energy gases, said fuel metering motor having a plurality of windings energizable to position the motor; said means comprising means including an amplifier device 20 responsive to electrical signals for controlling the energization of at least one of said windings to change the respective metering rate position of the motor, and means including an electrical system in a state of voltage balance comprising operator operated voltage divider means for changing the voltage level to be maintained in the system to adifferent level thereby introducing a state of unbalance in the system, and pluralized voltage divider means connected to said operator operated divider means for matching the new voltage level and restoring balance to the system, said pluralized divider means beingadapted to emit signals to the amplifier device for appropriately changing the metering rate to a different rate only so long as unbalance exists in the system and having first, second, third, fourth, and fifth voltage dividers electrically interrelated in-a predetermined sequence such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact and at least one divider is coupled across a fixed length of the pre ceding divider, said first voltage divider including an element adjustable in accordance with the temperature of the intake air to the burner, said second voltage divider including an element adjustable in accordance with an existing force differential created by static and total pressures of the intake air acting in opposition to one another according to a predetermined relationship, said third voltage dividerincluding an element adjustable in accordance with an existing force differential created by static and total pressures of the energy gas acting in opposition to one another according to a predetermined relationship, said fourth voltage divider including an element adjustable in accordance with one of the static and total pressures of the intake air to the burner, and said fifth voltage divider in-- cluding an element adjustable in accordance with one of the static and total pressures of the energy gas from the burner.

' 7. Means for automatically controlling the rotative position of a fuel metering motor in an operating combustion system characterized, by a burner supplied with the metered fuel, said fuel metering motor having a plurality of windings energizable to position the motor; said means comprising means including an amplifier device responsive to electrical signals for controlling the energization of at least one of said windings to change the respective metering rate position of the motor, and means including an electrical system in a state of voltage balance comprising operator operated voltage divider means for changing the voltage level to be maintained in the system to a different level thereby introducing a state of unbalance in the system, and pluralized voltage divider means connected to said operator operated divider means for matching the new voltage level and restoring balance to the system, said pluralized divider means being adapted to emit signals to the amplifier device for passages across a fixed length of the preceding divider, said first voltage divider including an element adjustable in accordance with the temperature of the intake air to the burner, said second voltage divider including an element adjustable in accordance with an existing force diiferential created by staticand total pressures of the intake air acting in opposition to one another according to a predetermined relationship, said third'voltage divider including an element ad.- justable in accordance with an existing force difierential created by static and total pressures of the energy gas acting in opposition to oneanother according to "a predetermined relationship, said fourth voltage divider including'an element adjustable in accordance with one of the static and total pressures of the intake air to the burner, and said fifth voltage divider including an element adjustable in accordance with one oi the static and total pressures of the energy gas from the burner.

8. Means for automatically controlling the rotative position of a fuel metering motor in an operating combustion system characterized by a burner supplied with the metered fuel and having means providing for a supply of intake air and for discharge of the energy gases, said fuel metering motor having a plurality of windings energizable to position the motor; said means comprising means including an amplifier device responsive to electrical signals for controlling the 'energization of said windings to change the respective metering rate position of the motor, and means including an electrical system in a state of voltage balance comprising operator operated voltage divider means for changing the voltage level to be maintained in the system to a different level thereby introducing a state of unbalance in the system, and pluralized voltage divider means connected to said operator operated divider means'for matching the new voltage level and restoring balance to the system, said pluralized divider means being adapted to emit signals to the amplifier device for effecting a variance in the overall character of the energization maintained on a certain winding to cause appropriate change in the metering rate to a difierent rate only so long as unbalance eX- ists in the system and having a plurality of voltage dividers electrically interrelated in sequence such that a majority of the dividers are each. coupled across the portion of the preceding divider selected by its contact and at least one divider is coupled across a fixed length of the preceding divider, said plurality comprising a first voltage divider including an element adjustable in accordance with the temperature of the intake air to the burner, a second voltage divider including an element adjustable in accordance with an existing force differential created by static and total pressures of the intake air acting in opposition to one another according to a predetermined relationshipyand a third voltage divider including an element adjustable in accordance with an existing force differential created by static and total pressures of the energy gas acting in opposition to one another according to a predetermined relationship.

9. Means-forautomatically controlling the rotative position of a fuel metering motor in an operating combustion system characterized by a burner supplied with the metered fuel and having meanssprovidingfor a supply of intake airand for discharge oflthe: energy gasespsaid fuel metering motor having a plurality of windings energizable to position the motor; said'means comprising means including an amplifier device responsive to electrical signals for controlling th energizetion of said windings to change the respective metering rate position of the motor, and means including an .electricalsystem in a state of *volt age balance comprising operator operated'voltage divider means for changing the voltage level to be maintained in the. system to a different level thereby introducing a state of unbalance in the system, and pluralizedvoltage divider means connected to the operator operated divider means for matching the new voltage level and-restoring balance to the system, said pluralizedtvoltage divider means being adapted to emit signals to the amplifier device for efiecting-a variance-in the'overall character of the energization main!- tained on a certain windingto cause appropriate change in the metering rate to a different rate only so long as unbalance exists in the system and having first, second, third, fourth, and fifth volt-' age dividers electrically interrelated in a-predetermined sequence such that a majority of the di-' viders are each coupled across the portion of the preceding divider selected by its contact andat least one divideris coupled across a fixed portion of'the preceding divider, said first voltage divider including an element adjustable in accordance with the temperature of the intake air to the burner, said second voltage divider including an element adjustable in accordance with the magnitu'de'of the velocity pressure of the intake air, said third voltage divider including an element adjustable in accordance with the magnitude-of the velocity pressure of the energy gas, said fourth voltage divider including an element adjustable in accordance with the first power 'of the static pressure of the intake air to the burner, and said fifth voltage divider including an element adjustable in accordance with the first power of the static pressure of the energy gas from the burner.

'10. Means for automatically controlling themtative' position of a fuel metering motorin an operating combustion system characterized by a burner supplied with the metered fuel and having means providing for a supply of intake air and for discharge of the energy gases, said fuelmetering motor having a plurality of windings energizable to position the motor; said means comprising means including an amplifier device responsive to electrical signals for controlling the energization of at least one of said windingsto change the respective metering rate position of the motor, and means including an electrical system in a state of voltage balance comprising operator operated voltage divider means for changing the voltage level to be maintained in the system to a difi'erent level thereby "introducing a state of unbalance in the system, and pluralized voltage divider means connected to the operator operated divider means formatching the new voltage level and restoring balance to the system, said pluralized divider means being adapted to emit signals to the amplifier device for appropriately changing the metering rate to a difierent rate only so long as unbalance exists in the system and having a plurality of voltage dividers electrically interrelated in sequence such that a majority of the dividers are each coupled across the portion ofthe preceding divider selected by its contact and at least one divider'is coupled'across a fixed length of the prece.dingdivider, said plurality *comprisinga first voltage divider including an element adjustable in accordance with the temperature of the intake air to the burner, a second voltage divider including an element adjustable in accordance with an existing force differential created by static and total pressures of the intake air acting in opposition to one another according to a predetermined relationship, and a third voltage divider including an element adjustable in accordance with an existing force difierential created by static and total pressures of the energy gas acting in opposition to one another according to a predetermined relationship. 7

I 11. In a regulated combustion system characterized by a burner, a supply of fuel for eventual introduction into the burner, means forming a restricted fuel fiow path for use in varying the flow rate of the fuel allowed to be introduced into the burner, means forming a path for the flow of air to the burner, and means forming a path for the flow of the products of combustion discharged by the burner: the combination with positionable members, valving in the restricted fuel path connected for movement with one of the positionable members, a voltage divider means adapted for graduation in terms of combustion temperature and including one of said positionable members having positions indicative of graduated temperature, pluralized voltage divider means, a bridge circuit including both divider means aforesaid, and means responsive to unbalance potential existing in the bridge circuit to position one said positionable member, said pluralized voltage divider means comprising first, second, third, fourth, and fifth voltage dividers including first, second, third, fourth, and fifth adjustable elements respectively, said voltage dividers being interrelated electrically in a sequence in a manner such that a majority of the dividers are each coupled across the efiective portion of the preceding divider selected by its adjustable element and at least one divider is coupled across some portion of the preceding divider unadjusted by its adjustable element, of means for adjusting the respective adjustable elements of the abovenamed voltage dividers including means responsive to the flow of air, to the burner, means responsive to the temperature of the air to the burner, and means responsive to the flow of products of combustion discharged by the burner, the above described responsive means being for a given combustion temperature interrelated and arranged at all times as to satisfy the following expression:

where T1=temperature of air to the burner Ps1=static pressure of the air to the burner Pu=total pressure of the air to the burner Piz==static pressure of the products of combustion Pzz=total pressure of the products of combustion 12. In a regulated combustion system characterized by a burner, a supply of fuel for eventual introduction into the burner, means forming a restricted fuel flow path for use in varying the flow rate of the fuel allowed to be introduced into the burner, means forming a path for the flow of air to the burner, and means forming a path for the flow of the products of combustion discharged by the burner: the combination with positionable members, valving in the restricted fuel path connected for movement with one of the 24 positionable members, a voltage divider mean adapted for graduation in terms of combustion temperature and including one of said positionable ,members having positions indicative of graduated temperature, pluralized voltage divider means, a bridge circuit including both divider means aforesaid, and means responsive to unbalance potential existing in the bridge circuit to position one said positionable member, said pluralized voltage divider means comprising first, second, third, fourth, and fifth voltage dividers including first, second, third, fourth, and fifth adjustable elements respectively, said voltage dividers being interrelated electrically in a sequence in a manner such that a majority of the dividers are each coupled across the effective portion of the preceding divider selected by its adjustable element and at least one divider is coupled across some portion of the preceding divider unadjusted by its adjustable element, of means for adjusting the respective adjustable elements of the abovenamed voltage dividers including means responsive to the flow of air, to the burner, means responsive to the temperature of the air to the burner, and means responsive to the flow of products of combustion discharged by the burner, the above described responsive means being for a given combustion temperature interrelated and arranged at all times as to satisfy the following expression:

where Ti=temperature of air to the burner Ps1=static pressure of the air to the burner Pn=total pressure of the air to the burner Psz=static pressure of the products of combustion Prz=total pressure of the products of combustion 13. Means for automatically controlling the rotative position of a fuel metering motor in an operating combustion system characterized by a burner supplied with the metered fuel and having means providing for a supply of intake air and for discharge of the energy gases, said fuel metering motor having a plurality of windings energizable to position the motor; said means comprising means including an amplifier device responsive to electrical signals for controlling the energization of at least one of said windings to change the respective metering rate position of the motor, and means including an electrical system in a state of voltage balance comprising operator operated voltage divider means for changing the voltage level to be maintained in the system to a different level thereby introducing a state of unbalance in the system, and pluralized divider means for matching the new voltage level and restoring balance to the system, said positionable means being adapted to emit signals to the amplifier device for appropriately changing the metering rate to a different rate only so long as unbalance exists in the system and having first, second, and third voltage dividers electrically interrelated in a predetermined sequence such that at least a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact, said first divider including a contact adjustable in accordance with the temperature of the intake air to the burner, said second divider including a contact adjustable in accordance with an existing force differential created by the static and total pressures of the intake air acting in opposition to one am other. accordingto a predetermined relationship, andsaid third divider including a'contact, adjustable-in accordance withan existing force differential created by the static and total pressures of the energy gas acting in opposition to one another according to a predetermined relationship.

14. A systemrfor controlling the rate of fuel flow to the combustion zone of a burner, theresulting combustion temperature of which is to be maintained uniformly at predetermined values by adjustment of fuel flow without recourse to the basis of actual measurement of combustion temperatures but rather in accordance with the respective magnitudes of other variable quantities involved in the combustion process, said burner having an adjustable fuel control: comprising, a plurality of voltage dividers each in: cluding an adjustable contact and being interrelated consecutively with one another in a manner such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact and at least one divider is coupled across a fixed length of the preceding divider, means for adjusting the contact of a first of said divider plurality in accordance with variations of a first of said other variable quantities, means for adjusting the contact of a second of said divider plurality in accordance with variations of a second of said other variable quantities, means for adjusting the contact of a third of said divider plurality in accordance with variations of a third of said other variable quantities, means for adjusting the contact of a fourth of said divider plurality in accordance with variations of a fourth of said other variable quantities, means for adjusting the contact of a fifth of said divider plurality in accordance with variations of a fifth ofsaid other variable quantities, a sixth voltage divider including a contact settable to a position representative of the combustion temperature in; the burner, a bridge circuit including said sixth voltagedivider and said divider plurality, and means responsive to an unbalance of said bridge circuit for adjusting the fuel flow control of the burners.

15. A system for controlling the rate of fuel flow to the combustion zone of a burner, the resulting combustion temperature of which is to be maintained uniformly at predetermined values by adjustment of fuel flow without recourse to the basis of actual measurement of combustion temperatures but rather in accordance with the respective magnitudes of other variable quantities involved in the combustion process, said burner having an adjustable fuel control: comprising, a plurality of voltage dividers each including an adjustable contact and being interrelated consecutively with one another in a manner such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact and at least one divider is coupled across a fixed length of the preceding divider, contact adjusting means for the divider plurality including means for adjusting the contact of a first of said divider pluralityin accordance with variations of a first of said other variable quantities, means for adjusting the contact of a second of said divider plurality in accordance wtih variations of a pressure-diiferential aiforded by said other variable quantities, and means for adjusting the contact of a third of said divider plurality in accordance with variations of a pressure-differential afiorded by said other variable quantities, a fourth voltage divider including a, contact settable to a position repre: sentative of the combustion temperature in the: burner, a bridge. circuit including said fourth. voltage divider and said divider plurality, and means responsive to an unbalance of said bridge circuit for adjusting the fuel flow control of the, burner;

16. A system for controlling the rate of fuel flow to the combustion zone of a burner, there, sulting combustion temperature of which is to, be maintained uniformly at predetermined values by adjustment of fuel flow without recourse to the basis of actual measurement of combustion temperatures but rather in accordance withthe respective magnitudes of other variable quantities involved in the combustion process, said burner having an adjustable fuel control: comprising, a plurality of voltage dividers cachineluding an adjustable contact and being inter! related consecutively with one another in a man-- ner such that a majority of the dividers are each. coupled across the portion of the preceding divider selected by its contact and at least one.

divider is coupled across a fixed length of the preceding divider, contact adjusting means for the divider plurality including means for adjusting the contact of a first of said divider plurality in accordance with variations of a first of said other variable quantities, means for adjusting the contact of a second of said divider plurality in accordance with variations of a second of said other variable quantities and means for adjusting the contact of a third of said divider plurality in accordance with variations of a third of said other variable quantities, a fourth voltage divider including a contact settable to a position representative of the combustion temperature in the burner, a bridge circuit including said fourth voltage divider and said divider plurality, and means responsive to an unbalance of said bridge circuit for adjusting the fuel flow control of the burner.

1'7. In a regulative combustion system inferentially determinative of combustion temperatures irrespective of the initial quality of the fluids supplied and characterized by a burner, means providing a path for the flow of air to the burner, means providing a path for the flow of energy gases discharged from the burner, means providing a path for the flow of fuel to the burner, and a metering element adjustable to vary the rate of flow of fuel to the burner: the combination comprising a voltage divider including an indicator element adjustable to positions indicative of specific discharge temperatures of the energy gases, pluralized voltage divider means, a bridge circuit including said voltage divider and said voltage divider means, said voltage divider means comprising first, second, and third voltage dividers each having coupling means to couple it in the divider means with the other dividers in predetermined sequence in a manner such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact, said coupling means comprising grid controlled means between at least two said adjacent voltage dividers and having the control grid thereof controlled by the preceding one of the two said adjacent voltage dividers and providing an anode-cathode path included in series with the successive one of the two said adjacent voltage dividers for controlling the energization of the latter in controlled dependence upon said control grid, said first voltage divider including an adjustable member adjusted in accordance with the temperature of the air flowing to the burner efiective to adjust the bridge circuit, said second voltage divider including a contact adjustable in accordance with the force difierential created by the static and total pressures of the air flowing to the burner acting predeterminedly in opposition to one another and effective to adjust the bridge circuit, and said third voltage divider including a contact adjustable in accordance with the force differential created by the static and total pressures of the energy gas from the burner acting predeterminedly in opposition to one another and effective to adjust the bridge circuit, and means responsive to the value of unbalanced potential existing in the bridge circuit for adjusting an adjustable element above-named.

18. Means for automatically controlling the rotative position of a fuel metering motor in an operating combustion system characterized by a burner supplied with the metered fuel, said fuel metering motor having a plurality of windings energizable to position the motor; said means comprising means including an amplifier device responsive to electrical signals for controlling the energization of at least one of said windings to change the respective metering rate position of the motor, and means including an electrical system in a state of voltage balance comprising operator operated voltage divider means for changing the voltage level to be maintained in the system to a different level thereby introducing a state of unbalance in the system, and pluralized voltage divider means connected to said operator operated divider means for matching the new voltage level and restoring balance to the system, said pluralized divider means being adapted to emit signals to the amplifier device for effecting-energization of at least one of said motor windings to change appropriately the metering rate to a difierent rate only so long as unbalance exists in the system and having first, second, third, fourth, and fifth voltage dividers having coupling means electrically interrelating them in a predetermined sequence such that a majority of the dividers are each coupled across the portion of the preceding divider selected by its contact and at least one divider is coupled across a fixed length of the preceding divider, said coupling means comprising grid controlled means between at least two said adjacent voltage dividers and having the control grid thereof controlled by the preceding one of the two said adjacent voltage dividers and providing an anodecathode path included in series with the successive one of the two said adjacent voltage dividers for controlling the energization of the latter in controlled dependence upon said con trol grid, said first voltage divider including an element adjustable in accordance with the tem perature of the intake air to the burner, said second voltage divider including an element adjustable in accordance with an existing force differential created by static and total pressures of the intake air acting in opposition to one another according to a predetermined relationship, said third voltage divider including an element adjustable in accordance with an existing force differential created by static and total pressures of the energy gas acting in opposition to one another according to a predetermined relationship, said fourth voltage divider including an element adjustable in accordance with one of the static and total pressures of the intake air to the burner. and said fifth voltage divider including an element adjustable in accordance with one of the static and total pressures of the energy gas from the burner.

DAVID M. BQRDEN. PAUL T. NIMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,455,633 Lundgard May 15, 1923 1,576,754 McLean Mar. 16, 1926 1,680,026 McLean -Aug. 7, 1928 2,323,180 Junkins June 29, 1943 2,337,851 Junkins Dec. 28, 1943 2,414,314 Machlet Jan. 14, 1947