US3327758A

US3327758A - Flame detecting means

Info

Publication number: US3327758A
Application number: US95764A
Authority: US
Inventors: Cleall Alfred
Original assignee: Babcock and Wilcox Ltd
Current assignee: Babcock International Ltd
Priority date: 1960-01-07
Filing date: 1961-01-04
Publication date: 1967-06-27
Anticipated expiration: 1984-06-27
Also published as: GB932298A

Description

June 27, 1967 Filed Jan. 4, 1961 PHOTO- ELECTRIC CELL A- CLEALL FLAME DETECTING MEANS 4 Sheets-Sheet 1 Is? STAGE 2 I36 AMPLIFIER 24 TARY COCK 2 d STAG I74 /2MPL|F|EER 70 DRIVE MOTOR SUPPLY PUMP IN !/E N TOR Alfred F. Cleall A TTOR/VE Y June 27, 1967 CLEALL 3,327,758

FLAME DETECTING MEANS Filed Jan. 4, 1961 4 Sheets-Sheet 2 J lA/VE/VTOR 74 Alfred F. Cleall June 27, 1967 A. CLEALL FLAME DETECTING MEANS 4 Sheets-Sheet 3 Filed Jan. 4, 1961 u o o INVENTOR. Alfred F. Cleall ATTORNEY A. CLEALL 4 Sheets-Sheet 4 ifi //VVEA/TOR Alfred F. Cleall A TTORNE Y FLAME DETECTING MEANS June 27, 1967 Filed Jan. 4. 1961 QB -65: MSEQ United States Patent i 3,327,758 FLAME DETECTING MEANS Alfred Cleall, London, England, assignor to Babcock & Wilcox, Limited, London, England, a corporation of Great Britain Filed Jan. 4, 1961, Ser. No. 95,764 Claims priority, application Great Britain, Jan. 7, 1960, 605/60 The portion of the term of the patent subsequent to Feb. 8, 1983, has been disclaimed 6 Claims. (Cl. 158--28) This invention relates to apparatus adapted to distinguish between the presence of flame due to combustion of liquid fuel discharged from a burner and the absence of the flame. In known devices of the kind utilizing means responsive to flame radiation, the difficulty arises, when a combustion space is supplied with fuel by a plurality of burners, that the flames from different burners may be adjacent and may even intermingle, with the result that discrimination between the different flames becomes difficult and the flame failure device applied to one burner may not operate upon failure of the flame at the burner if there is a flame from an adjacent burner.

An object of the invention is the provision of apparatus capable of distinguishing the flame from an associated burner from the flame or flames from another burner or other burners.

Apparatus adapted to distinguish between the presence of flame due to combustion of liquid fuel discharge from a burner and the absence of the flame, according to the present invention includes modulating means, adapted by varying the pressure of fluid supplied to the burner tip for discharge therefrom, to modulate the flame at predetermined frequency, radiation responsive means subject to radiation from the flame and detecting means sub ject to the output from the radiation responsive means and adapted by responding to a frequency determined by the frequency of flame modulation to distinguish between the presence and the absence of flame from the burner.

The invention will now be described, by way of example, with reference to the accompanying partly diagrammatic drawings, in which:

FIGURE 1 shows a pressure atomizing oil fuel burner provided with a flame failure detecting circuit and rotary plug cock valve in the oil fuel supply line;

d FIIGURE 2 shows the rotary plug cock in greater etai FIGURE 3 is a cross-section of the rotary plug cock taken on the line III-III of FIGURE 2;

FIGURE 4 shows a diagram of the flame failure circuit arranged to detect a signal emitted from the burner flame; and

FIGURE 5 shows a steam atomizing oil fuel burner provided with a pressure relief duct connected to a rotary plug cock and a flame failure detecting circuit.

Referring to FIGURES 1, 2 and 3, the pressure atomizing burner includes a barrel 2 mounted on a tail piece 4 and provided with a sprayer head 6 held in place by a cap nut 8. The barrel 2 extends through a coupling 10 carrying a coupling yoke 12 for securing the tail piece 4 to the coupling 10, and a carrier tube 14 which supports an impeller plate 16 located adjacent the sprayer head 6. A fuel oil inlet 18 in the coupling 10 is connected by a duct 20 to a chamber 22 in the tail piece 4 connecting with the barrel 2.

A rotary plug cock 24, interposed in the fuel oil supply line between a supply pump 26 and the fuel oil inlet 18 adjacent the coupling 10 includes a spindle 28 having an enlarged frusto-conical portion 30 fitting Within a corresponding bore 32 in a valve body 34 and located by two roller bearings 36, 38. Two further roller Patented June 27, 1967

ice bearings

44, 56 restrain axial movement of the spindle 28 and respectively abut an end plate 40 bolted to the lower end 42 of the valve body 34 and an obscurating plate 46 positioned between a shoulder 48 formed on the upper end 50 of the valve body 34 and a spindle housing 54 bolted to the valve body 34. A rotating seal 58 encircling the spindle 28 is biased against a fixed sealing member 60, bolted to the spindle housing 54, by a spring 62 bearing against a collar 64 fixed to the spindle 28 by a grub screw 66. A casing 68 is mounted on the valve body 34 and extends towards an electric motor 70 having a driving shaft 72 connected to the spindle 28.

A tapped inlet 74 to the valve body 34 terminates in a slot 76 of rectangular cross-section and four similar, equiangularly spaced slots 78 formed in the frusto-conical portion 30 of the spindle 28 terminate in a central bore 80. The end plate 40 is provided with a drilled and tapped outlet 82, so that, upon energizing the electric motor 70 to rotate the spindle 28 when any of the slots 78 are in alignment with the slot 76, the inlet 74 is connected with the outlet 82.

Referring to FIGURE 4, the component values being by way of example, the detecting circuit includes a transformer coupled to a main supply of 250 volts 50 cycles per second and provided with 6.3 volt tappings X-X and Y-Y for heater and warning light circuits. A double diode valve 102 such as the type E240, provides a 220 volt full wave rectified output across two 8

microfarad condensers

104, 106 arranged in parallel across a choke 108. A rectifier 110 is connected to the transformer 100 and is arranged to give a half wave rectified negative voltage applied to a filter circuit consisting of two 8

micro-farad condensers

116, 118 and 330 kilo-ohm resistance 120. Two 250 kilo-ohm resistances 112, 114 are connected across the filter circuit. A .24 volt negative tapping 122 from the resistance 112 is connected, through a 22 kilo-ohm resistance 124, to provide direct current supply to a photo-transistor 126, such as the germanium transistor type OCP71, which is focused on the flame from the burner. The emitter and base of the phototransistor 126 are respectively grounded through a 2.2 kilo-ohm resistance 128 and a 417 kilo-ohm resistance 130, whilst the collector is connected, through a 0.25 micro-farad condenser 132, to the core of a co-axial cable 134, the sheath of which also is grounded, connecting with a first stage amplifying circuit 136.

The first stage amplifying circuit 136 includes a common grounding point 138 to which the sheath of the coaxial cable 134 is connected. An adjustable gain tapping 142 on a 100 kilo-ohm resistance connects through a 0.25 micro-farad condenser 144 and a 212 kilo-ohm resistance 146 to the control grid of a pentode valve 150, such as the type E1 86. Intermediate the condenser 144 and resistance 146 a connection is made to the grounding point 138 through a one meg-ohm resistance 152. The suppressor grid of the pentode 150 is connected to the cathode which in turn is connected to the grounding point 138 through a 1000 micro-farad condenser 154 and a resistance 156 arranged in parallel. An 8 micro-farad condenser 158 is connected across the pentode 150 from intermediate a 200 kilo-ohm resistance 160 and a 50 kiloohm resistance 162 connected in series, the resistance 160 being connected to the anode, to the grounding point 138. The screen grid of the pentode 150 is connected through a 1.5 meg-ohm resistance 164 to the anode load side of the first stage amplifier 136 and through an 8 micro-fared condenser 166 to earth. The output from the pentode 150 is passed through a filter circuit including a 0.5 micro-farad condenser 168,- a 2 meg-ohm resistance 170 and a 820 kilo-ohm, resistance 172 so that the output from the first stage amplifier 136 consists of an amplified pulsating signal from the photo-transistor 126, which signal is fed to a second stage amplifier 174 including a negative feed back loop having a sharp cut-off filter circuit 176.

A cascode valve 177, such as the type 1'2AX7, shown as upper and lower valves 178 and 180, receives the input signal on theg rid of the upper valve 178, the anode thereof being connected to the grid of a triode valve 182, such as one half of a twin triode of the type 12AU7, the other half not being utilized, and through a 200 kiloohm resistance 184 to the 220 volt supply. The cathode of the triode 182 is connected to a negative feed back cincuit in which the output is taken through a 0.25 microfarad condenser 186, connections being made to earth through a cathode bias resistance 188 and a 1 meg-ohm grid resistance 190, to the sharp cut-off filter 176 arranged as a twin-T network with two 0.5

micro-farad condensers

192, 194 and a 4.5 kilo-ohm resistance 196 in the first T and two 10.5 kilo-ohm resistance 198, 200 and a one micro-farad condenser 202 in the second T. The component values of the twin-T network in the present example are such that it will attenuate signals having a frequency of 32 cycles per second, the frequency of flame modulation in the present instance.

The output from the sharp cut-off filter 176 is fed to the grid of the lower valve 180 of the cascode 177 and, being out of phase, suppresses all signals other than that to which the sharp cut-off filter circuit 176 is tuned, thereby permitting a greatly increased output from the upper valve 178 at the predetermined frequency. The greatly increased output signal from the cascode is coupled through the triode 182 to the control grid of a pentode valve 206, such as the type 6CH6, through a 0.25 micro-farad condenser 204. Intermediate the condenser 204 and the control grid, a variable tapping is made through a 1 meg-ohm resistance 208, to the resistance 114 to provide a negative bias.

The pentode 206 operates as a power amplifier the anode of which is connected through a relay 210R having a shunt two micro-farad condenser 212, to the anode load supply of 220 volts, the screen grid of which is connected direct to the anode load supply and the suppressor grid and cathode of which are connected together and to earth. The relay 210R operates a spring loaded two-way switch 2108 in the YY tapping from the transformer 100 biassed towards a contact 214 connected with a red indicating light 216. Upon the pentode 206 conducting, relay 210R is energized to move the switch 2108 into contact with the contact 218 connected with a green indicating light 220.

In operation, fuel oil supplied at a suitable pressure from the pump 26 to the rotary plug cock 24 passes, when the spindle 28 is rotating and one of the slots 78 comes into alignment with the slotv76, to the barrel 2 through the inlet 18, the duct 20 and the chamber 22 and is discharged as a spray, which is ignited, from the sprayer head 6, Since the electric motor 70 rotates at constant speed, for example 480 r.p.m., the inlet 76 will be connected with the outlet 82 at a predetermined frequency, in the example given, 32 times per second, so that with the rotary plug cock 24 positioned as indicated in FIGURE 1, the fuel oil supply from the pump 26 to the burner will be interrupted at the predetermined frequency thereby producing a periodic variation in the luminosity in the flame having the predetermined frequency, in this instance, of 32 cycles per second.

The periodic variation in the luminosity of the flame produces a periodic variation in the output from the photo-transistor 126', which may be considered as a periodically fluctuating voltage superimposed upon a random fluctuating voltage, the result of light from other luminous sources falling on the photo-transistor 126. The output is fed through the coaxial cable 134 to the first stage amplifying circuit 136. The output signal from the first stage amplifying circuit is fed into the second stage amplifying circuit 174 through the cascode 177 to the sharp cut-off filter circuit 176. The cascode, as mentioned previously conducts a substantially greater current when receiving a signal having decreased negative feed back from the sharp cut-off filter circuit 176 than when a higher value of negative feed back is applied. The frequency attenuated by the sharp cut-off filter 176 corresponds to the periodic variation in luminosity imposed upon the burner flame, When the cascode 177 conducts the said substantially increased current the relay 210R is energized to close the switch 2108 so that the green indicating light 220 is lit. Should the predetermined frequency not be present in the signal transmitted from the photo-transistor 126 then the negative feed back signal from the sharp cut-off filter circuit 176 will prevent the cascode 177 from conducting an appreciable current, the relay 210R will not be energized and the red indicating light 216 will be lit indicating failure of the flame with which the photo-transistor 126 is associated.

It will -be understood that by varying the number of slots 78 in the frusto-conical portion 30 of the spindle 28, say from one to five, five different predetermined frequencies of periodic variation in the luminosity of the flame may be obtained and that this number of frequencies may be increased by the use of different, predetermined, speeds of rotation. By altering the component values of the twin-T network of the sharp cutoff filter circuit 176, other filter circuits rejecting other predetermined frequencies may be obtained so that it is possible to discriminate between adjacent burners the luminosity of the flames of which are varied at different frequencies, the flame failure circuits associated with the different burners being tuned to the respective frequencies.

It will be understood that alternative means may be provided for inducing the periodic variations in the fuel oil supply pressure at the burner head. Thus in an embodiment (not shown) a motor driven piston or diaphragm is reciprocated in a chamber by means of a cam driven by a constant speed electric motor, the chamber being connected to the oil supply adjacent the inlet to the burner so that the pressure at the burner head is at periodic intervals increased above the fuel oil supply pressure.

Whilst the rotary plug cock is illustrated in FIGURE 1 positioned in the oil supply line, since such positioning will involve an overall reduction in oil supply pressure at the burner head, it is desirable or necessary in some installations to avoid such reduction. As an alternative, the rotary plug cock may be fitted in a pressure relieving duct arranged to bleed fuel oil from the burner supply line at periodic intervals.

Referring to FIGURE 5 of the drawings a steam atomizing burner includes, mounted on a tail piece 222, an inner steam tube 224 provided with a nozzle 226 and an outer oil tube 228 provided with a sprayer plate 230 held in place by a cap nut 232. A coupling 234 is provided with a coupling yoke 236-, for securing the tail piece 222 to the coupling 234 and a carrier tube 238 which supports an impeller plate 240 located adjacent the sprayer plate 230.

A steam inlet 242 in the coupling 234 is connected by a duct 246 to a chamber 248 in the tail piece 222 connecting with the inner tube 224, whilst the fuel oil inlet 250 is connected by a duct 252 to a chamber 254'in the tail piece 222 connecting with the outer tube 228. A pressure relief duct 2545 leads from the chamber 254 to a rotary plug cock, such as that described in connection with FIGURES 2 and 3, which connects with the inlet side of a supply pump 26.

In operation, fuel oil is supplied, at a suitable pres-' sure, from the pump 26 to the inlet 250 and passes through the duct 252 and chamber 254 to the outer tube 228 to be discharged as a spray which is atomized by steam supplied through the inner tube 224, from the sprayer plate 230, the atomized spray being ignited. As before, the electric motor 70 driving a rotary plug cock 24 rotates at a constant speed, so that at given intervals of time the chamber 254 is connected with the inlet side of the pump 26 thereby causing a drop in the pressure exerted on the fuel oil in the chamber 254 and thus in the instantaneous change in the rate of flow of the oil at the sprayer plate 230. As described in connection with FIGURE 1, the periodic variation in the rate of flow causes a periodic variation in the luminosity of the flame which is detected by the detecting circuit described in connection with FIGURE 4.

While in accordance with the provision of the statutes I have illustrated and described herein the best form and mode of operation of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. In combination, a combustion chamber, a plurality of burners each discharging a flame into said combustion chamber with the flame from each burner exposed to radiation from at least one other burner, means supplying fuel to said burners, means associated with each of said burners for distinguishing the presence or absence of their respective flames in the presence of flame due to the combustion of fuel from one or more other of said burners, each of said distinguishing means including a modulating means imparting pulses to the radiation of its respective burner flame at a predetermined frequency other than that of said other burners, radiation responsive means operably associated with said burners and oriented to sight the radiation of said flames to produce a fluctuating output signal corresponding to the frequency of the radiation of each of said flames, and means responsive to said radiation responsive means for detecting the fluctuating output signal corresponding to the frequency of the radiation of a given flame from the output signals corresponding to the radiation of said other flames to distinguish between the presence and absence of said given flame, said modulating means comprising a motor having its shaft penetrating the fuel line, and a valve fixed to said shaft for rotation therewith and operable to at least partially obstruct said fuel supply line at constant intervals during rotation of said shaft.

2. In combination with a com-bustion chamber, a plurality of burners each discharging a flame into said combustion chamber with the flame from each burner exposed to radiation from at least one other burner, a fuel line for supplying fuel to each of said burners, means associated with each of said burners for distinguishing the preesnce or absence of their respective flames in the presence of flame due to the combustion of fuel from one or more other of said burners, each of said distinguishing means including a modulating means imparting pulses to the radiation of its respective burner flame at a predetermined frequency other than that of said other burners, radiation responsive means operably associated with said burners and oriented to sight the radiation of said flames to produce a fluctuating output signal corresponding to the frequency of the radiation of each of said flames, and means responsive to said radiation responsive means for detecting the fluctuating output signal corresponding to the frequency of the radiation of a given flame from the output signals corresponding to the radiation of said other flames to distinguish between the presence and absence of said given flame, said modulating means comprising a valve in said fuel line for varying the rate of fuel flow to said burner, and means for continuously closing and opening said valve at said predetermined frequency.

3. The invention as claimed in claim 2 wherein said valve is a rotary valve, and said closing and opening means comprises an electric motor arranged to run at a constant speed.

4. The invention as defined in claim 3 wherein said rotary valve includes a rotatable spindle having a hollow portion connected with the outlet from said valve, said hollow portion having one or more slots arranged to connect with the inlet to the valve so that upon rotation of said spindle the inlet is repeatedly connected with and disconnected from the outlet.

5. The apparatus as defined in claim 2 wherein said valve is connected into the liquid fuel supply duct adjacent the fuel inlet to the flame producing means.

6. In combination with a combustion chamber, a plurality of burners each discharging a flame into said combustion chamber with the flame from each burner exposed to radiation from at least one other burner, a fuel line for supplying fuel to each of said burners, means associated with each of said burners for distinguishing the presence or absence of their respective flames in the presence of flame due to the combustion of fuel from one or more other of said burners, each of said distinguishing means including a modulating means imparting pulses to the radiation of its respective burner flame at a predetermined frequency other than that of said other burners, radiation responsive means operably associated with said burners and oriented to sight the radiation of said flames to produce a fluctuating output signal corresponding to the frequency of the radiation of each of said flames, and means responsive to said radiation responsive means for detecting the fluctuating output signal corresponding to the frequency of the radiation of a given flame from the output signals corresponding to the radiation of said other flames to distinguish between the presence and absence of said given flame, said modulating means comprising a by-pass valve constructed and arranged to by-pass a fraction of the fuel available for discharge from the burner, and means for continuously opening and closing said valve at said predetermined frequency.

References Cited UNITED STATES PATENTS 1,718,999 7/1929 Case. 2,032,588 3/1936 Miller. 2,304,641 12/1942 Jones l5828 2,408,589 10/ 1946 Wells. 2,481,620 9/1949 Rosenthal 15 877 2,506,672 5/1950 Kell et a1. 2,512,743 6/1950 Hansell. 2,532,554 12/1950 Joeck. 2,692,962 10/ 1954 Thomson 158-28 X 2,748,846 6/ 1956 Smith et a1 158-28 X 2,749,447 6/1956 Smith 158-28 X 2,771,942 11/1956 Miller l58-28 2,831,666 4/ 1958 Compton. 2,907,382 10/ 1959 McIlvaine 1584 2,949,900 8/ 1960 Bodine. 3,055,416 9/ 1962 Marshall 158-28 3,233,650 2/1966 Cleall.

FOREIGN PATENTS 596,945 4/1960 Canada.

JAMES W. WESTHAVER, Primary Examiner. PERCY PATRICK, Examiner.