US3123027A

US3123027A - Apparatus and method of flame or combustion rate

Info

Publication number: US3123027A
Authority: US
Publication date: 1964-03-03
Anticipated expiration: 1981-03-03

Description

March 3, 1964 w. L. LIVINGSTON 3,123,027

APPARATUS AND METHOD OF FLAME 0R COMBUSTION RATE DETECTION IN A COMBUSTION CHAMBER Original Filed Nov. 3, 1958 s Sheets-Sheet 1 l2 A|R\ FUEL [0 kg 20 J 26 28 I ATMOSPHERIGfi 0 PRESSURE g -025 L 3: a -+0.25 3 05 All Q I H005 -o.7s--o.5 o uni- 5 ,r l

Ii FIG 8 El; 'IE El? LL] 0 IL} INVENTOR. 2 WILLIAM L. LIVINGSTON AGENT March 1954 w. L. LIVINGSTON 3,123,027

APPARATUS AND METHOD OF FLAME OR COMBUSTION RATE DETECTION IN A COMBUSTION CHAMBER Original Filed Nov. 3, 1958 3 Sheets-Sheet 2 I25 INVENTOR I25 WILLIAM L. LIVINGSTON /24 AGENT I11 III FIG. 9

March 3, 1964 w. L. LIVINGSTON 3,123,027

APPARATUS AND METHOD OF FLAME OR COMBUSTION RATE 7 DETECTION IN A COMBUSTION CHAMBER Original Filed Nov. 3, 1958 5 Sheets-Sheet 3 FRICTION LOSS FIG. 7

In 2 6 05 sans's 8d cums T IN VEN TOR.

WILLIAM L. LIVINGSTON AGENT United States Patent 3,123,927 APPARATUS AND METHGD 0F FLANiE 0R COM- BUSTEQN RATE DETECTION IN A COMBUSTION CHAR/BER William L. Livingston, Bloomfield, Conn, assignor to Combustion Engineering, inc, New York, N.Y., a corporation of Delaware Continuation of appiication Ser. No. 771,375, Nov. 3, 3358. This application .lune 19, 1962, Ser. No. 205,483 Claims. (Cl. 11023) The present application is a continuation of an original application Serial No. 771,375 filed in the name of William L. Livingston on November 3, 1958, now abandoned.

The invention relates to combustion sensing and indicating apparatus and method as employed in connection with a combustion chamber, and is more particularly concerned with an indicating method and system for sensing difference in combustion rate such as detecting the absence or presence of combustion or flame in the chamber and transmitting this information to a signal or other indicating device located at a control point remote from the combustion chamber.

My invention can readily be employed in connection with a wide variety of combustion chambers or furnaces. it especially finds important and useful application as indicating means for reporting differences in combustion rate or for detecting the presence of flame in furnaces of steam generators, and in igniter apparatus employed in connection therewith.

Such igniter apparatus usually takes the form of an auxiliary burner also called pilot or igniter torch, using oil or gas to ignite other fuel streams such as pulverized cofi delivered into a furnace as by means of tilting burners or the like. One such igniter torch and the manner in which it generally operates is disclosed in US. Patent 2,622,669 issued to V. Z. Caracristi on December 23, 1952. As described in this patent the fuel and air mixture delivered to the pilot torch is ignited by means of a spark plug, and it is very important that the operator be informed whether or not ignition of the fuel in the torch has actually taken place and whether or not a pilot flame has been produced and is ready to light the ignitable mixture of fuel and air which is about to issue from the main burners. Because of the danger of explosion it is absolutely necessary that the fuel is only then discharged into the furnace when and after the pilot torches are positiveiy lit.

As soon as ignition has taken place of the main burner fuel and the un t is in operation, the flame of the igniter torch is extinguished. However, to guarantee safe operation of the steam generator furnace at all loads, and especially at reduced loads, it is required that each burner i equipped with a device which will immediately indicate black-outs or the loss of flame of a main burner. Failure of the burner to maintain ignition is apt to occur when the burner is made to operate at low capacity, as during reduced load operation. T o forestall possible explosion of the unburned fuel and air mixture, such blacr-out or ignition failure must immediately be followed by a shutting ofi of the fuel and air supply to the burner. Such actions should of course be automatic and should preferably be free of any possibility of human failure.

In addition to the difliculties experienced in translating a burner black-out signal into fuel and air shut-off action, it is primarily the degree of reliability of presentday flame sensing devices which leaves much to be desired. Failure of these devices to report loss of flame have in fact been the cause of at least one recent furnace explosion.

Various means have heretofore been employed to give indication of such presence of flame. One device comprises a thermocouple, also called pilot generator, installed in the wall of the pilot torch or in the wall of the furnace near each burner. The thermocouple in conjunction with a relay system indicates presence of flame by activating a signal at the control board when the temperature in the pilot torch or near the burner has risen above the ignition temperature. Another device used for flame indication consists in a so-called fire-eye, making use of a lead sulphide cell being sensitive to the presence of a flame. These devices require very complicated electric and electronic circuitry including numerous relays, which equipment when being exposed to the rugged use and environment of a steam power plant, breaks down quite frequently and requires costly maintenance, replacement and repair. Furthermore, the reliability of the pilot generator and fire-eye device is impaired by accumulations of ash and slag on the surfaces and parts of the sensing element thereof, which of necessity are exposed to the intense heat within the nozzle or the furnace and which are frequently decomposed by this heat.

In connection with some types of burners and in furnaces where a plurality of these burners is employed, it has heretofore been necessary, because of the nature of the sensing devices used, to place a sensing device adjacent each burner. In case of loss of fire on one burner the fuel and air mixture flowing to this burner is shut ofli. This detrimentally effects the air-fuel ratio of the mixture being delivered to the remaining burners, thereby greatly increasing the possibility of the entire furnace to lose ignition and causing a complete shut down of the steam generator. Such interruption of service is undesirable because it increases maintenance cost and decreases stability of operation and availability of the unit.

My inventive improvement as herein disclosed overcomes or greatly diminishes the above difficulties through the employment of a superior indicating system. The functioning of my system is based on reliable pressure differences received by a pressure diflerential switch from the combustion chamber in question, such as a pilot torch nozzle or an entire furnace, for indicating the presence or absence of combustion or flame Within said combustion chamber. This is accomplished by positive and dependable means and with practically no delay in action.

It is accordingly a primary object of my invention to provide in connection with a combustion chamber an improved and reliable flame or combustion indicating sysitem, one important feature thereof being a sensing elernent which is not subject to or exposed to the radiant heat in the combustion chamber.

Another and more specific object of my invention is to increase the dependability, ruggedness and useful life of a flame or combustion indicating system used in connection with the ignition torch and/ or in connection with the combustion zone of a steam generating furnace.

A further object of my invention is to provide a dependable system and method for indicating at a remote point of control, differences in combustion rate or intensity occurring in a combustion chamber at different elevations or zones thereof.

An additional object of my invention is to provide a flame sensing system, the sensing element of which is independent of individual burners and has a sensing range which extends over the entire combustion zone or furnace.

Other and further objects of the invention will become apparent to those skilled in the art as the description hereof proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired as hereinafter more particularly set forth in the following detailed description of illustrative embodiments, said embodiments being shown by the accompanying drawings wherein:

FIG. 1 is a diagrammatic illustration of a combustion chamber equipped with the herein disclosed pressure sensing device for flame indication;

FIG. 2 is a diagrammatic illustration of a steam generator having a furnace equipped with my improved flame indicating system, including a schematic diagram illustrating how the various components of my flame indicating system are interconnected for coordinating cooperation;

FIG. 3 is a diagrammatic cross-sectional plan View of a furnace equipped with tangentially firing corner burners, and showing the associated igniters or pilot torches in relation therewith;

PEG. 4 is an enlarged plan section through the lower right side corner of the furnace shown in FIG. 3, through the partially shown burner and side igniter torch associated therewith;

FIG. 5 is an elevational section taken on line 55 of PEG. 4 of a pilot torch and a schematic diagram illustrating how the various components of my flame indi cating system are interconnected for coordinating cooperation;

FIG. 6 is an end view of the igniter nozzle as viewed from line 6-5 of FIG. 5;

FIGS. 7 and 8 are graphic illustrations of the pressure differences existing between two selected points in a combustion chamber, under conditions when the flame is lit or combustion takes place and when the flame is extinguished; with the graph of FIG. 7 more specifically pertaining to the igniter shown in FIG. 5 and the graph of PEG. 8 to the vertical furnace of FIG. 2;

FIG. 9 is a diagrammatic illustration of a furnace chamber bein equipped with the herein disclosed inventive device for indicating at a remote control station the relative differences in combustion rate or intensity occurring at various elevations or zones of the furnace chamber.

The Inventive Basic Device Referring now to FIG. 1, an elongated combustion chamber it) is bounded by walls 12. Fuel in a gaseous, liquid or pulverized form enters the chamber 14 as by Way of nozzle 14 and after mixing with air entering by way of slot 1 is ignited as by device 17 and burns at least partially within said chamber 1 3. The generated combustion gases leave the chamber via outlet 18. A pressure differential responsive device 20 is operatively connected to two

openings

22 and 24 provided in the wall 12 of chamber lb, such connection being effected by conduits 25 and 23 respectively. Device 2t accordingly maintains static pressure communication with the interior of chamber iii. The opening 22 is located adjacent the fuel and air inlet end and the opening 24 adjacent the combustion gas outlet end of chamber 10.

If combustion is absent in chamber Zltl and the effect of air flow is neglected, the static pressure P, measured at 22 is found to be the same as the static pressure Q measured at 24-. The pressure differential responsive device 263 accordingly records a diflerential pressure of zero. However, as soon as the fuel and air mixture is ignited and combustion is taking place within chamber lit the static pressure P observed at the fuel inlet end rises and the static pressure Q observed at the gas outlet end drops, so that a positive pressure differential P-Q is almost instantly indicated by instrument 20. It is this phenomenon of change in pressure differential between a state of combustion and a state of noncombustion which is being made use of in my herein disclosed novel flame and combustion indicating system.

The Environment Although my inventive control system can be employed in connect on with many diflerent combustion chambers or furnaces and burning all types of fuel, only two important applications thereof will now be described. Such description is intended to be illustrative only of two out of many possible applications, and is not to be interpreted as being restricted to the use thereof in the steam boiler furnace or in the pilot torch organization herein described.

Referring now to the FIGS. 2 and 3, there are shown in diagrammatic form an elevational section and a plan cross section through a combustion chamber 10, here specifically designated as furnace chamber 3% of a steam generator. Four main burners 32 are arranged in the four corners of the chamber 3% for discharging streams of fuel and air for burning in directions tangential to an imaginary firing circle 34. A so-called side igniter or pilot torch 36 (see FIG. 3) is positioned adjacent each burner 32 for igniting the fuel issuing therefrom at the proper time. These side igniters or pilot torches 36 are associated with burners 32 in the manner illustratively shown in FIG. 4 in an enlar ed scale. The walls of furnace 30, as shown in FIG. 2, are generally lined with water carrying and steam generating tubes 38.

The combustion gases rising in the furnace 30 enter a horizontal gas outlet passage containing superheater 42, which may be followed by a vertical down-draft gas passage (not shown) in which additional heat absorb ing surfaces may be disposed such as an economizer and an air heater (not shown).

The Flame Sensing Apparatus as Applied to Igniter Torch 36 An important application of my flame sensing apparatus and method is illustrated in FIGS. 4 and 5.

The illustrative igniter torch 36 shown is adapted to burn oil. However, the novel control and indication facilities of the present invention also can be used with igniter torches which are fired by fuels other than oil such as gas, for example. The igniter torch 36 is mounted adjacent main burner nozzle 32 and comprises a mounting plate 46, torch head 48, torch nozzle 5%), spark plug 51, an atomizer 52, the interior of nozzle 5%? representing combustion chamber lit. The mounting plate 46 supporting the igniter torch 35 is bolted onto the furnace casing 54, the mounting plate 46 being shielded against heat by insulation 47. Nozzle 54) is suspended from the mounting plate 46 by means of bracket 55. One end 56 of the nozzle is round, and, as here shown, the other end is flared in one direction and contracted at right angles thereto to form along narrow opening 57 through which a sheet of flame 58 issues. may be used to ignite another fuel stream 59, FIG. 4, issuing from an adjacent main burner 32, which maybe tilted to direct the fuel stream 59 upwardly or downwardly or to any intermediate position. shape of the pilot torch nozzle 5'0 assures adequate flame distribution at all tilt positions of the adjacent main burner 32.

The pilot torch head 48 comprises a body portion forming an internal chamber 6%), open toward the nozzle 50 and having openings for receiving spark plug 51 and atomizer 52. The pilot torch head 48 is also provided with peripherally disposed air inlet vanes 62 to impart to V ply tube 65. The resultant air and oil mixture is dis charged into chamber 60 and ignited by the spark formed between electrode 66 of the spark plug 51 and the beveled face 67 of the torch head 48. The rotating secondary Such a flaring nozzle The flaring air entering through vanes 62 promotes a desirable mixing action and minimizes harmful fly ash settlement, while the burning mixture is flowing through nozzle 50 and issuing from opening 57 in a hot luminous flame.

Flame Indicating Functions T 0 Be Achieved in Connection With Igniter Torch In commercial installations of boiler furnaces of the high capacity type diagrammed in FIG. 2 it is desirable to organize the main furnace burners such as 32 for complete control and supervision in part by an operator located at a centralized control point remote from the furnace, and in remaining part by automatic apparatus similarly located. In furtherance of this objective each of the main burners 32 is equipped with its individual igniter torch 36.

The problem then is, while an operator is enabled at a centralized control point remote from the furnace to bring torches 36 into action at the furnace when it is desired to light up their associated main burners 32, to receive back from each torch a reliable indication that ignition of the fuel in the torch has been actually obtained. For reasons of safety it is absolutely essential that such indication be received before a fuel and air mixture is discharged into the furnace through the main burners 32.

Utilized to accomplish this particular function is a pressure differential responsive device 2%) in the form of switch 68, FIG. 5, installed in a control box 69. This switch comprises two pressure chambers 76 and 71 separated by a diaphragm 72, and a rod 73 one end thereof being fixedly attached to diaphragm 72 and the other end organized to open or close electric contact switch 74 and contact switch 75 by means of bar 76. An adjuster 77, including spring 78 serves to keep contacts 74 closed when the pressure in chamber 71 fails to exceed by a predetermined amount the pressure existing in chamber 76. Chamber 70 is connected by way of conduit 79 to a pressure tap 89 secured in opening 24 located in the wall of nozzle 59 adjacent the outlet end thereof, and chamber 71 is connected by way of conduit 81 to a pressure tap 82 secured in opening 22 located in the torch head 48 near the fuel inlet end of the pilot torch. Therefore the pressure prevailing in chamber 76) corresponds to the static pressure existing in the vicinity of the opening 2 at the gas outlet of the torch, and the pressure prevailing in chamber 71 corresponds to the static pressure existing near the opening 22 or at the fuel inlet of the torch.

When the pilot torch 3-5 is out of operation, the static pressure at the fuel inlet (chamber as and at the flame outlet end 57 are practically of the same magnitude, if friction losses are neglected. However, when the torch is lighted and a flame is burning, a substantially higher pressure exists at the fuel in et end opening 22 or cham ber 71 than at the flame discharge end, or chamber 7%. When this pressure difference attains a predetermined value to overcome the tension of spring 78 the contacts 74 will open and the contacts 75 will close. Closing of contacts 75 energizes an electric circuit 34 and actuates a signal device such as a green light bulb 85. Closing of contacts 74 energizes electric circuit 86 and actuates a signal device such as red light bulb 87.

Signal devices

85 and 87 are located at a central control point and serve to indicate to the operator whether or not a flame is issuing into the furnace from pilot torch 36, in a manner which will now be described.

Assuming, for example, that the excess of static pressure measured at opening 22 over that measured at opening 24, when the pilot torch is lighted is established by tests to be 2 inch VLG. Then the adjuster 77 may be set, so that an excess of pressure of 1 /2 inch W.G. in chamber 71 over that existing in chamber 743 will open switch contacts 74 and close switch contacts 75.

This is graphically illustrated in FIG. 7, where are shown three sets of pressure conditions. The first set indicates the pressures, a and b, respectively, prevailing at

openings

22 and 24 when the flame is lit; and the second set indicates the pressures c and d, respectively, when the flame is extinguished. A friction loss of 0.25 is assumed to exist due to air flow through the nozzle 59. The third set of pressure readings A and B indicates the controlling pressure differential (1.5 inch W.G.) at which the pressure switch 68 is set to act. Thus as the pressure difference drops from the 2 inch W.G. value (flame lit) to the 0.25 inch W.G. value (flame out) it passes through the 1.5 inch WG. value at which switch 68 is set for atcion.

This means that when the torch is out of operation and without a flame the contacts of switch 743 will be closed and a red bulb $7 will light up warning the operator that the torch 36 is not in readiness to ignite any fuel that may be discharged into the furnace by way of main burner 32. However, as soon as ignition has been established in the pilot torch nozzle the contacts of switch 74 will open extinguishing red light 87 and switch 75 will close lighting up green bulb 85. This will be an indication to the operator that a flame is issuing from nozzle 59 and that it is safe to discharge fuel through the main burners 32 into the furnace. If, for some reason, the flame in nozzle 5% should be extinguished, then the pressure differential between pressure taps Sit and 82 will drop below 2 inch W.G. causing contacts 75 to open and switch 74 to close, and green light 85 to go out and red light 87 to light up.

Flame Indicating Functions T 0 Be Achieved in Connection With Furnace 30 During normal operation of the furnace 3f the pilot igniters 36 associated with main burners 32 are generally extinguished. Under certain conditions of low load operation or when low grade fuel is burned the possibility exists of losing total ignition in the furnace. As earlier pointed out herein such loss of flame is dangerous because of the explosive nature of the unburned comminuted fuel mixed with heated air that is entering the furnace. In such an event the feeding of the fuel must be immediately stopped and the furnace must be scavenged of unburned fuel before the burners can again be lighted.

My flame indicating method and system as herein disclosed, because of its simplicity and reliability, is exceptionally well adapted to function both in warning the operator, such as by an alarm bell or the like, that the fire has gone out, and/ or in automatically shutting off the fuel fed to the main burners in case ignition is lost in the furnace. How this is accomplished will now be described.

The burners 32 of the steam boiler as diagrammatically illustrated in PEG. 2, are supplied with comminuted fuel from a source not shown via

fuel pipes

88 and 99. An automatically operated fuel valve 92 is installed in pipe 9% and serves to shut off the flow of fuel to the burners 32 when desired. Although one single valve is here shown to control the fuel flow to all burners of a tangentially fired furnace 3%, such showing is considered merely representative, and my inventive flame indication system an fuel flow control can with equal benefit be applied to furnaces employing other types of burners and firing. Such furnaces may discharge fuel from a row of burners disposed in one or two walls or in the roof thereof. In these cases it may be advantageous to provide each individual burner with a flame indication system and fuel flow control in the same manner as herein described and illustrated in FIG. 2.

Two pressure connections 93 and @4 are provided in the wall of the furnace 3%, one 93 in connection with opening 22 below or at the burner elevation, and the other 94 in connection with opening 24 in the upper part of the furnace. The relative location of these pressure connections is not critical except that the lower connection 93 should preferably be located in the fuel discharge zone and the upper pressure connection 94 in a zone where combustion of the fuel has been well established or is partially completed. These connections 93 and 94 serve the purpose of obtaining relative indications of the static pressure prevailing in the furnace in the vicinity of

respective openings

22 and 24. The values obtained may be positive or negative. A furnace operating under suction will give negative values. However, whether positive or negative values are obtained is relatively unimportant, since it is the pressure differential between pressure points 93 and 594 or

openings

22 and 24 which is being utilized in my herein disclosed system of flame indication.

In an upright furnace chamber, such as that diagramrncd in FIG. 2 where the combustion gases flow in a vertical direction, the chimney er ect of these hot gases must be taken into consideration in the evaluation of the pressure difierential between connection 93 and 94. This holds true regardless of whether the fuel is ignited in the lower portion of the furnace, the gases flowing upwardly and leaving by way of a top gas outlet, or is ignited in the upper portion of the furnace, the gases flowing downwardly and leaving by way of a bottom gas outlet.

Thus in a furnace of the type shown in FIG. 2 when in operation, i.e., when fuel is burned therein, the static pressure at point 94 may generally be maintained at a negative value of 0.5 inch W .G., whereas the furnace zone at point 93 would be under greater suction due to the stack effect of the heated gases. The pressure at 93 accordingly may be, for instance, l.O inch W.G., this value depending on the height of the furnace chamber, the temperature and velocity of the gases.

When total loss of ignition occurs in the furnace and the flame is extinguished the static pressure at 93 rises, for example to ).25 inch W.G., with the static pressure at point 94 kept at a normal value of 0.5 inch VG. by automatic control of the induced draft fan. Thus it is seen that a drop in pressure differential between point 93 (which corresponds to P of FIG. 1) and point 94 (which corresponds to Q of FIG. 1), in indicative of loss of ignition in the furnace chamber 39.

These conditions are graphically illustrated in FIG. 8 where, as in FIG. 7, are shown three sets of pressure conditions. The first set indicates the pressures e and 1, respectively, prevailing at pressure connections 93 (opening 22) and 94 (opening 24) when the flame is lit; and the second set g and h, respectively, when the flame is out. The pressure differential between e and f of 0.5 inch W.G. is arbitrarily here given a negative value because it falls below the pressure line of 0.5 inch W.G. which is the negative pressure generally maintained at the top outlet of the furnace. in distinction thereto the pressure differential between points g and h of +0.25 inch W .G. is given a positive value because it falls above said i).5 inch W.G. pressure line.

The change in pressure differential upon loss of fire, when transmitted to a pressure differential switch 95 functioning as the pressure differential responsive device 2%, actuates magnetically operated fuel valve 92 to shut off the flow of fuel to burners 32, and at the same time trips an alarm device 97 to inform the operator of the loss of tire in the furnace.

To accomplish these functions chamber 1% of pressure switch 95 is connected to pressure point ddby way of conduit 99, and chamber 98 is connected to pressure point 93 by way of conduit M1. The diaphragm 1G2 separating chambers 93 and 142% carries an extension rod P33, the free end of which is organized to open or close electric contact switches 1nd and Th5 by means of connecting bar 1%. The closing of switch 1 3-4 energizes a circuit generally designated 1&7, thereby actuating an indication device as by lighting a green bulb M3. The closing of switch M55 energizes a circuit generally designated 109, thereby setting olf an alarm device 97, and at the same time energizes a circuit 11.1 causing fuel valve 92 to close by action of the solenoid ll Valve 92 is shown as normally being held in the open position by a spring 112. Energization of circuit 116 causes plunger '8 of solenoid 111 to enter the winding thereof thus overcoming the pull of spring 1512 and closing valve 92.

Pressure diifcrential switch is normally biased by spring 113, the tension thereof being controlled by adjuster 114, to keep contacts 105 closed and contacts 104 open. As soon as the excess pressure in chamber over that prevailing in chamber 93 exceeds the tension of spring 113 contacts Hi5 will open and contacts 104 will close thereby energizing circuit 107 and lighting green bulb Hi8, which will stay lit as lont as the pressure in chamber 98 does not rise above a predetermined value. This indicates to the operator that combustion in the furnace is proceeding without interruption.

In practice the most suitable pressure differential that determines the tension of spring 113 or the setting of adjuster 114 is obtained by tests conducted at the time when the unit is first put into operation. Thus the largest pressure diflerential between point Q3 and 94, i.e., the lowest static pressure at point 3 with respect to point 94, would be observed when the unit is operating at maximum capacity and the highest static pressure when the unit is operating at its lowest capacity. Since a still higher presure at point 93 is obtained when the fire is totally extinguished, a pressure differential value may be chosen for the setting of adjuster 114 which lies between the pressure differential obtained when the flame is out but the furnace is still hot, and the value obtained when the furnace is operating at the lowest permissible capacity.

Thus returning to the earlier mentioned practical example as illustrated in PEG. 8, it was assumed that the pressure differential between points 94 and 93 or between chambers 1% and 98 has a value of 0.5 inch W.G. when the burners 32 are burning a suflicient amount of fuel to operate the unit at its lowest capacity, and the said pressure differential drops to +0.25 inch W.G. when loss of total ignition occurs in the furnace. Under these assumed conditions therefore the adjuster 117 controlling the tension of spring 113 must be so set that the electric contact switch res will open and contact switch will close during the time when the higher pressure differential between points 93 and 94, drops from a value of 0.5 inch W.G. to a value of +0.25 inch W.G. or a total of 0.75 inch W.G. For instance, spring 113 would be set under certain operating conditions to trip at a pressure differential of 0.1 inch W.G. This is shown by the third set of pressure readings C and D in FIG. 8 indicati ing the controlling pressure difierential of 0.1 inch W.G. at which the pressure switch 95 is set to act. Thus as soon as loss of ignition in the furnace occurs and the pressure differential drops from 0.5 inch W.G. (flame lit) to +0.25 inch W.G. (flame out), switch 1% will:

Visual Indication of Relative Combustion Rates To Be Achieved Referring now to FIG. 9, showing the furnace 311} in greatly simplified form, fuel and air for combustion is fed to furnace 3b via burners 32, the gases leaving by way of furnace outlet 40. According to the invention furnace chamber 34? is equipped with a combustion sensmg system including an indicator or multiple pressure gauge 116 for registering the relative static pressures prevailing at various elevations or zones in furnace chamber 3%. For this purpose there are provided in the wall of the furnace at successive elevations a series of openings. 117 through 123 for receiving pressure taps, each tap in turn being operatively connected to one of a corresponding series of pressure gauges 124 to 13% inclusive, conveniently assembled in indicator 116 for easy comparison.

in accordance with the herein disclosed invention the relative static pressure differential between two pressure 9. taps, spacedly located in direction of gas flow in the furnace Wall, affords a measure of the relative combustion rate or combustion intensity existing in the zone be tween the said two points. This is diagrammatically illustrated by gauge 116, affording a visual indication of the varying combustion intensities throughout the height of the furnace by registering the static pressures prevailing at successive elevations in the furnace, with the lowermost pressure tap 123 showing the highest suction in gauge 1'39, and the highest pressure tap 117 showing the lowest suction in gauge 124.

Thus, for example, the location or elevation of the flame in the furnace chamber can be determined with comparative ease and certainty at a control station remote from the furnace. Also the relative rate of combustion at different locations in the furnace can be ascertained from the relative distance between static pressure readings. For instance, as illustratively shown in FIG. 9, the combustion rate in the zone between pressure taps 117 and 118 would be considerably smaller and less intense than that existing in the zone between pressure taps 122 and 123 as indicated by the smaller pressure differential between suction readings of

gauges

124 and 125 when compared with the larger differential shown between readings of gauges 12? and 134 These and similar readings, of course, are obtained only While a fire is burning in .the furnace chamber 30. If ignition should be lost and combustion cease, the picture presented by indicator 116 will immediately and radically change. In such an emergency the suction readings of gauges 125 through 130 will drop to the value of, or go even beyond the value of, the reading shown by gauge 124 which records the static pressure generally maintained in the top of the furnace. This drop is indicated by dotted line 132.

' While I have shown in FIG. 9 the pressure conditions that are generally encountered in a vertical furnace operating under subatmosphen'c pressure, it must be understood that these conditions .may change when my invention is applied to a horizontal furnace or to a furnace fired from the top, or to a furnace operating under a static pressure higher than atmospheric. Although the operating conditions of these various furnace types may be different the basic concept upon which my invention is founded remains the same. This concept may be defined as a recognition and realization of the fact that the absence or presence as well as the degree or intensity of combustion taking place in any given combustion zone of a furnace chamber is immediately and with fair accuracy reflected in the static pressure differential observed between a point upstream and a point downstream of said zone, in the gasflow sense. This concept has been made use of in devising the herein disclosed system and method of flame or combustion indication observable and acting at a control point remote from the furnace chamber, and offering the important advantage of possessing a sensing element which is not subject to the heat of the furnace nor to accumulations of slag or ashes, as are other similar devices. My flame and combustion indicating system and method is therefore far superior to other systems as used heretofore, because of the simplicity in construction, ruggedness in service and dependability in operation which it affords.

While illustrative embodiments of this invention have been shown and described, it will be understood that changes in construction, combination and arrangement of parts may be made Without departing from the spirit and scope of the invention as claimed.

What I claim is:

1. In a steam generating furnace having means for detecting the loss of flame in a burner apparatus appended thereto and being provided with a chamber comprising a fuel receiving and ignition zone and a fuel burning zone downstream therefrom, and having means to provide a gaseous mixture of fuel and air to said fuel receiving and ignition zone, said chamber located to discharge into said furnace; the combination of the means subject to a first static pressure existing inside said chamber within said fuel receiving and ignition zone for indicating said first pressure exteriorly of said chamber; means subject to a second static pressure prevailing in said fuel burning zone and for indicating said second static pressure exteriorly of said chamber; means for determining variations in the differential between said first static pressure and said second static pressure; a control device for responding to operating conditions of said burner apparatus; means for operating said device; and means governed by said pressure differential variations for causing said control device to respond when said pressure differential drops to a predetermined value, whereby loss of flame within said chamber is readily detected, such detection being independent of and unaffected by ambient static pressure conditions existing exteriorly of the fuel and air inlet end as well as exteriorly of the flame discharge end of said chamber.

2. In a steam generating furnace having means for detecting the loss of flame in a burner apparatus appended thereto and being provided with a chamber having a fuel and air inlet and a fuel burning zone downstream therefrom, and having means to provide a gaseous mixture of fuel and air by Way of said fuel and air inlet, said chamber located to discharge into said furnace; the combination of means subject to a first static pressure existing inside said chamber adjacent the fuel and air inlet thereof and for indicating said first pressure exteriorly of said chamber; means subject to a second static pressure existing in the interior of said chamber adjacent the flame discharge end thereof and for indicating said second static pressure exteriorly of said chamber; means for determining variations in the differential between said first static pressure and said second static pressure; an alarm device including means for activating said alarm device; and means governed by said pressure differential variations for causing said alarm to respond when said pressure differential drops to a predetermined value, whereby loss of flame within said chamber is readily detected, such detection being independent of and unafiected by ambient static pressure conditions existing exterioriy of the fuel and air inlet end as well as exteriorly of the flame discharge end of said chamber.

3. In a steam generating furnace having means for detecting the loss of flame in an igniter apparatus appended thereto and being provided with a chamber having a fuel and air inlet and a fuel burning zone downstream therefrom, and having means to provide a gaseous mixture of fuel and air by way of said fuel and air inlet, said chamber located to discharge into said furnace; the combination of means subject to a first static pressure existing inside said chamber adjacent the fuel and air inlet thereof and for indicating said first pressure exteriorly of said chamber; means subject to a second static pressure existing in the interior of said chamber adjacent the flame discharge end thereof and for indicating said second static pressure exteriorly of said chamber; a pressure switch subject to variations of the differential between said first static pressure and said second static pressure for indicating Variations of said differential at a point remote from said chamber; a signal device including means for activating said signal device; and means governed by the action of said pressure switch for causing said signal device to be activated when said pressure differential has attained a predetermined high value found to be indicative of combustion within said chamber, the accuracy of said activation being independent of and unaffected by ambient static pressure conditions existing exteriorly of the fuel and air inlet end as well as exteriorly of the flame discharge end of said chamber.

4. In a vapor generating furnace having means for detecting the loss of flame in a burner apparatus appended thereto and being provided with a combustion chamber comprising a fuel receiving and ignition zone and a fuel burning zone downstream therefrom, and having means to provide a gaseous mixture of fuel and air to said fuel receiving and ignition zone, said chamber located to discharge into said furnace; the combination of means to sense a differential of static pressure existing in the interior of said chamber between a point adjacent said fuel receiving and ignition zone and a point located remotely therefrom in the direction of combustion gas travel and Within the burning zone of said combustion chamber, and to indicate said pressure differential at a point outside of said combustion chamber; an alarm device including means for transmitting impulses from said pressure differential sensing means to said alarm device; and means governed by said pressure differential for ctivating said alarm device when said pressure differential attains a value of a magnitude indicative of combustion taking place within said combustion chamber, whereby presence of flame Within said chamber is readily detected, such detection being independent of and unaffected by ambient static pressure conditions existing exteriorly of the fuel and air inlet end as well as exteriorly of the flame discharge end of said chamber.

5. In the operation of a steam boiler having a furnace chamber fired with a mixture of air and finely divided fuel suspended in air, said mixture being discharged into said chamber by way of a burner and forming an explosive mixture prior to ignition thereof, said chamber being subject to an interior static pressure variable with respect to atmospheric pressure and having an igniter torch including an igniter torch housing for discharging a flame into said furnace chamber from said housing to ignite said mixture, the method of detecting the presence of said igniter flame issuing from said housing, comprising thesteps of obtaining a first static pressure reading at a first point within said housing, obtaining a second static pressure reading in the combustion zone Within said housing at a second point spaced downstream from said first point in the flame travel sense, dhferentiating said first pressure reading against said second pressure reading to obtain a pressure differential, determining the said pressure differential in the absence of flame and in the presence of flame, and utilizing these determined pressure differentials in a control device responding to a flameon condition or a flame-off condition which is independent of and unaffected by the atmospheric static pressure prevailing outside of said chamber and the static pressure prevailing inside of said chamber.

6. In a furnace for burning fuel suspended in air and provided with means to receive both fuel and air in a fuel receiving zone and to burn said fuel in a fuel burning zone, said furnace having water cooled walls for the generation of steam and having a furnace outlet remote from said fuel receiving zone to discharge the gaseous products of combustion; the combination of a series of successive openings provided in the water cooled wall of said furnace at locations in the fuel burning zone and spaced from each other generally in the gas flow sense; means for obtaining through said openings impulses of the static pressure prevailing in said furnace at said locations, said fuel burning zone being an unobstructed flow passageway, with the pressure differential between any two of said openings constituting a direct indication of the rate of combustion prevailing in the furnace zone portion between the said two openings, and said indication being unaffected by any other factors; and means to convert said impulses into an intelligent display indicating the relative combustion rates prevailing in the furnace zone portions between said openings.

7. In a furnace for burning fuel suspended in air and adapted to receive both fuel and air in a fuel receiving zone and to burn said fuel in a fuel burning zone, said furnace having water cooled walls for the generation of steam and having a furnace outlet remote from said fuel receiving zone for discharging the gaseous products of combustion; the combination of a series of successive openings provided in the water cooled wall of said furfrom each other generally in the gas flow sense; pressure taps inserted into said openings for obtaining readings of the static pressure prevailing in each furnace zone surrounding one of said openings, said fuel burning zone being an unobstructed flow passageway, with the pressure differential between any two of said readings constituting a direct indication of the combustion intensity prevailing in the furnace portion between the two openings from which the said two readings are taken, and said indication being unaffected by any other factors; a multi-reading pressure gauge adapted for recording said various static pressure readings side by side in the same succes sive order in which the corresponding pressure taps. are located in the furnace wall; and means for transmitting said static pressure readings to said multi-reading pressure gauge; whereby a composite picture is obtained of the relative combustion intensities prevailing in the furnace zones between said openings. 7 i

8. In a fuel burning and steam generating apparatus having a furnace chamber adapted to receive fuel suspended in air in a fuel receiving zone and to burn said fuel in a fuel burning zone prior to discharge of the products of combustion through a furnace outlet, said furnace chamber having water cooled walls for the generation of steam, the method of indicating the rate of combustion in a series of furnace zones successively disposed in the gas flow sense in the burning zone between and including said fuel receiving zone and said furnace chamber outlet, each zone having an opening in the wall of the furnace chamber for receiving a pressure tap; comprising the steps of obtaining an individual static pressure indication from each of said furnace zones via the respective pressure taps, said furnace zones forming an unobstructed flow passage- Way, with the pressure differential between any two of said furnace zones constituting a direct indication of the rate of combustion prevailing in the furnace zone between the said two respective pressure taps, and said indication being unaffected by any other factors; translating said static pressure indications into visual impression receiving means at a control station separated from said furnace chamber; and relating said impressions with each other in the successive order of said furnace zones to obtain a composite of the relative combustion rates prevailing in' said series of successively disposed furnace zones. 7

9. In a furnace for burning fuel suspended in air an provided with means to receive both fuel and air in a fuel receiving zone and to burn said fuel in a fuel burning zone, said furnace having an uprightly elongated shape and being provided with a furnace outlet remote from said fuel receiving zone to discharge the gaseous products of combustion; the combination of a plurality of successive openings provided in the wall of said furnace at locations spaced from each other generally in the gas flow sense;

means for obtaining through said openings impulses of the static pressure prevailing in said furnace at said locations,

with the pressure differential between any two of saidv openings constituting a direct indication of the rate of combustion prevailing in the furnace zone between any two of the said openings, and said indication being unaffected by any other factors; and means for responding to said impulses to indicate the combustion rates prevailing in the furnace zone portions surrounding said openings.

10. In the operation of a steam boiler having a furnace chamber fired with a mixture of air and finely divided fuel suspended in air, said mixture being ischarged into said chamber by way of a burner and forming an explosive mixture prior to ignition thereof, said chamber being subject to an interior static pressure variable with respect to atmospheric pressure and having means for igniting said' mixture and producing a flame, the method of detecting the presence of said flame within said chamber, comprising the steps of obtaining a first static pressure reading within said chamber and ahead of the normal point or origin of said flame in the flame travel sense, obtaining a second static pressure reading in the combustion zone Within said chamber and beyond the normal point of origin of said flame in the flame travel sense, differentiating said first pressure reading against said second pressure reading to obtain a pressure differential, obtaining the said pressure differential in the absence of flame and in the presence of flame, and utilizing these obtained pressure differentials in an impulse receiving means, whereby a flame-on condition or a flame-01f condition is determined in a manner which is totally independent of and unaffected by the atmospheric References Cited in the file of this patent UNITED STATES PATENTS 1,630,977 Smoot May 31, 1927 14 Roucka Nov. 22, Johnson Mar. 23, Turner Aug. 8, Hourvitz Apr. 17, Caracristi et a1. Dec. 23, Cumming Dec. 7, Perchonok Apr. 3, St. Clair June 17, Lewis et a1 Nov. 10,

FOREIGN PATENTS France Mar. 18, Germany Jan. 13,

Claims

1. IN A STEAM GENERATING FURNACE HAVING MEANS FOR DETECTING THE LOSS OF FLAME IN A BURNER APPARATUS APPENDED THERETO AND BEING PROVIDED WITH A CHAMBER COMPRISING A FUEL RECEIVING AND IGNITION ZONE AND A FUEL BURNING ZONE DOWNSTREAM THEREFROM, AND HAVING MEANS TO PROVIDE A GASEOUS MIXTURE OF FUEL AND AIR TO SAID FUEL RECEIVING AND IGNITION ZONE, SAID CHAMBER LOCATED TO DISCHARGE INTO SAID FURNACE; THE COMBINATION OF THE MEANS SUBJECT TO A FIRST STATIC PRESSURE EXISTING INSIDE SAID CHAMBER WITHIN SAID FUEL RECEIVING AND IGNITION ZONE FOR INDICATING SAID FIRST PRESSURE EXTERIORLY OF SAID CHAMBER; MEANS SUBJECT TO A SECOND STATIC PRESSURE PREVAILING IN SAID FUEL BURNING ZONE AND FOR INDICATING SAID SECOND STATIC PRESSURE EXTERIORLY OF SAID CHAMBER; MEANS FOR DETERMINING VARIATIONS IN THE DIFFERENTIAL BETWEEN SAID FIRST STATIC PRESSURE AND SAID SECOND STATIC PRESSURE; A CONTROL DEVICE FOR RESPONDING TO OPERATING CONDITIONS OF SAID BURNER APPARATUS; MEANS FOR OPERATING SAID DEVICE; AND MEANS GOVERNED BY SAID PRESSURE DIFFERENTIAL VARIATIONS FOR CAUSING SAID CONTROL DEVICE TO RESPOND WHEN SAID PRESSURE DIFFERENTIAL DROPS TO A PREDETERMINED