US 3241595 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
March 22, 1966 F. GILBERT FLAME DETECTOR coomue MEANS 5 Sheets-Sheet 1 Filed April 22, 1963 MEIL INVENTOR L.YMAN F GILBERT W ATTORNEY March 22, 1966 L. F. GILBERT FLAME DETECTOR COOLING MEANS 5 Sheets-Sheet 2 Filed April 22, 1963 MMI 1 F'IGJO INVENTOR L.YMAN F. GILBERT BY M ATTORNEY March 22, 1966 F. GILBERT 3,241,595
FLAME DETECTOR COOLING MEANS Filed April 22, 1963 5 Sheets-Sheet 3 FIG-6 INVENTOR LYMAN F'. GILBERT BY ATTORNEY March 22, 1966 L. F. GILBERT FLAME DETECTOR COOLING MEANS 5 Sheets-Sheet 4 Filed April 22, 1963 FIG 7 ATTORNEY March 22, 1966 L. F. GILBERT FLAME DETECTOR COOLING MEANS Filed April 22, 1963 5 Sheets-Sheet 5 //Z fZ/wace INVENTOR LYMAN F'. G I LBERT' ATTORNEY United States Patent M 3,241,595 FLAME DETECTQR COOLING MEANS v Lyman F. Gilbert, Somers, Conn, assignor to Combustion Engineering, lino, Windsor, Conn, a corporation of Delaware Filed Apr. 22, 1963, Ser. No. 274,611 19 Claims. (Cl. 158-28) This invention relates to flame scanners or detectors and particularly to cooling means for the same.
An object of this invention is an improved means for cooling a flame detector subject to being heated by the flame it is detecting.
A further object is a detector cooling system using a small amount of air that may be supplied from the furnace normal air sources so that no additional or special air source is necessary.
A further object is means for providing direct contact air cooling for the detector.
Further and other objects will be apparent from the following specification and the attached drawings in which:
FIG. 1 is a side view partly in section of a flame detector incorporating the present invention;
FIG. 2 is a detailed sectional view showing the detector element, its supporting tube and the air cooling path;
FIG. 3 is an end view of the structure of FIG. 2;
FIG. 4 is a modification of the structure of FIG. 2;
FIG. 5 is a partial sectional view showing a modified air inlet;
FIG. 6 is a vertical section of burners incorporating a detector;
FIG. 7 is a liragmentary horizontal section of the burner and igniter;
FIG. 8 is a schematic showing of the air supply system;
FIG. 9 is an enlarged view of a portion of the system of FIG. 8 including a schematic showing of the emergency cooling; and
FIG. 10 is a furnace end view of an oil burner nozzle with the detector installed.
A flame detector in order to function must be positioned so that it can scan or see the flame or fire-ball whose presence or absence it is to detect. When so positioned the detector element which may comprise a glass envelope enclosing a space in which detector electrodes are positioned, is subject to radiation from the flame which it is detecting and which may have a temperature of 2500 F. The heat produced by such radiation would soon destroy the detector element unless such heat can be rapidly dissipated. It is an object therefore of this invention to rapidly dissipate such radiant heat from the detector element by passing cooling air in direct contact with and over the detector element to carry away such radiant heat and return it to the furance with a minimum of expended energy and equipment.
Reference may be made to Armacost Patent 2,697,422 issued December 21, 1954 for Boiler Furnace for a detailed showing and description of a furnace with which the detector may be used and FIGS. 6 and 10 show the detector mechanism installed in such a furnace in position for flame scanning. The flame scanner indicated generally at 10 is shown in FIG. 1 mounted in a nozzle tip 12. The scanner comprises a tubular supporting member indicated generally at 14 and comprising a rigid support member 16 secured in a suitable manner such as by welding in the nozzle tip 12 to one side thereof. Secured to the rigid metallic portion 16 in any suitable manner as by clamps 18 is a flexible metallic sleeve 20 which in turn is connected by a suitable means such as clamps 22 to a rigid metal pipe 24 which is secured by any suitable means such as welding 26 to the shell 28 Patented Mar. 22, 1966 of the air duct supplying air to the burner. Secured on the outer end of pipe 24, as by threads, is a casting 30 having a chamber 32 communicating with the interior of the tubular member 14 and having an air inlet 34 for directing air from a suitable source of supply to the interior of the tubular member 14. If desired, an aspirator 36 having outlets 37 supplied with comparatively high pressure air through the inlet 38 may be provided under certain conditions to prevent flame or hot gases from feeding back from the furnace through the tubular member 14.
A detector element shown in more detail in FIGS. 2, 3 and 4 is enclosed within a tube 40 which is telescoped within the rigid element 16 and centered by any suitable means such as ribs 42. The outboard end of the tube 40 has positioned therein a bushing 44 (FIG. 2) to which is attached a flexible conduit 46 enclosing electrical conductors 48 and terminating in a rigid section 50 which is threaded into a casting 52 having a flange member 54 by means of which it may be removably secured to the outer end of the casting 30 as by bolts 56. The electrical conductors 48 are threaded through the pipe 50 and through the chamber 58 in the casting 52 and lead to a terminal 60 from which suitable connections may be made to the remainder of the detector electrical circuit. An air inlet connection 62 is provided in the casting 52 leading into the chamber 58 and the interior of the rigid member 50, flexible member 46 and the tube 40 to supply a stream of coo-ling air through the tube 40 and out the open end 64 thereof.
A quartz window 66 (FIG. 2) is centered in the tube 40 by pins 68 and in the passageway through the center of the tube through which the detector sees the flame and prevented from outward movement by pins: 70 secured in the tube 40. A wire 72 bent into generally triangular shape is fitted within the tube 40 and is pressed against the underside of the glass by means to be explained later. To hold the quartz window in position a sleeve 74 of corrugated or extended surface heat transmitting or conducting material is inserted in the tube 40 and expands so as to contact the interior surface of the tube 40 and the exterior surface of detector 76 with the corrugations running lengthwise of the tube.
The detector element shown generally at 76 has light sensitive electrodes 78 supported in a space enclosed by a transparent glass envelope 8t and supported in a base or socket 82 through which the leads 48 may be connected to the electrodes 78 in any desired manner as by connecting the leads 48 to prongs 83 on the base or socket which in turn are connected to the electrodes. The pins 85 supporting the detector 76 and connected with the electrodes 78 may be imbedded in the base 82 and connected with the prongs 83 or may be removably inserted in mating receptacles in the socket 82 electrically connected with prongs 83. Washers S6 and 38 are positioned on opposite sides of a flange 84 formed on the base or socket @2. A spring 94) having one end positioned by the bushing 44 presses on the washer 86 and provides a resilient positioning means and support tor the detector element 76. The spring 90 thus urges the washer 86, the base 82, the washer 88, the corrugated or extended surface heat conductor 74, the triangular member 72 and the quartz glass window 66 outwardly against the pins 70 and positions the entire assembly within the tube 40. The bushing 44 is held in the tube 40 by screws 92- and removal of the screws permits removal of the entire assembly or any port-ion thereof up to and including the quartz window.
Air entering the tube 40 from the flexible member 46 is received in chamber 94 in the tube 40. From chamber 94 the air passes through a central passage 96 in the base 82 and is directed outwardly to the annular passage formed between the detector element glass envelope 80 and the inside of tube 40 and thence outwardly past the circumference of the quartz window 66. The corrugated or extended surfiace member 74 acts as a heat sink to absorb heat from the detector element 76. The corrugated surface supplies a large wind swept area for removal of this heat. The air passing over and in direct contact with the glass envelope 8t of the detector element 76 also serves to rapidly remove heat from the detector element. A washer 98 is supported downstream from the window 66 between the pins 7t) and 1% and has an inside diameter or aperture sized so as to direct the air stream issuing from the open end of the tube 40 in a substantially cylindrical or parallel sided annulus. This air stream in the form of a cylindrical annulus has very little outward divergence, perhaps 10 degrees, and has suflicient energy to deflect any particles that might otherwise tend to enter the end of the tube 49 and contact the quartz window.
Under certain conditions it is desirable to restrict the scanning angle and under those conditions a collimating tube 102 may be substituted for the washer 98 and provide an extension beyond the open end of the tube 44) and which will serve both as a means for reducing the scanning angle and providing additional protection for the window 66.
In a furnace of the type shown in the Armacost patent and which is used as an example to illustrate and describe the present invention air under pressure for the burners 104, the igniters 106 and for sealing air may be supplied from a central source such as fan 108.
As shown schematically in FIG. 8 this air is lead through air heaters 110 where it suffers a pressure drop and then through burners 104 where it suffers a further pressure drop then through the furnace 112 and out the stack 1141. A bypass 116 is taken from the output of the fan 108 before it passes through the air heaters and is led to the igniters 106 and to sealing air chambers. When operating under normal load the fan 1% may supply a pressure of 40 inches of water and the air heaters and burners may reduce this pressure by say 16 inches of water. Allowing for a six inch water pressure drop through the bypass 1 16 leaves say a ten inch differential across and between igniter air chest 118 and the furnace 112. As cooling air requirements for the above described detector are satisfied with 4 to 5 inches of water pressure and 2 to 4 cubic feet per minute flow through the tube 40 and 17 cubic feet per minute flow through the tubular member 14 the entire air supply for the cooling requirements for the detector may be bled out of the air chest 118 through line 119 without adversely affecting the operation of the igniter or the sealing air. In fact, because of this small pressure and flow requirements for cooling and because the normal pressure and flow requirements of the furnace are so large in comparison thereto; the air for the cooling of the flame detector may be bled from substantially any convenient source around the boiler without materially adversely affecting that source.
Under low load conditions, where the air flow through the burners or required by the burners is small, the pressure drop through the air heaters and the burners may not be suflicient to provide the substantially 3 inches of water presure required by the igniter and the sealing air. In the event that the differential pressure between the furnace and the air chest .118 should drop to 3 inches of water a switch 120 actuated by the reduced differential pressure will activate a booster fan 122 to bring the pressure in the air chest 118 up to a pressure in excess of 3 inches of Water greater than that in the furnace. As the cooling air supply for the flame detector is, in the illustrative embodiment, taken from the air chest 113 it will continue to be supplied with sufiicient cooling air even under the low load conditions of the furnace without any auxiliary equipment being required. In the event of failure of the booster fan 122 and the reduction of the air pressure in the air chest 118 below that at which the switch is actuated a differential pressure actuated switch (not shown) similar to switch 120 is utilized to open a valve 124 connected with the normal high pressure compressed air lines at the boiler to temporarily supply working air to an aspirator 125 to augment the necessary cooling air until the fault can be located and remedied. Again because of the small flow requirements for this cooling system the normal compressed air supply for sootblowing and burner tilting, etc. can be tapped and bled without the necessity of supplying a large storage capacity or additional equipment and still not adversely affect the normal operation of the compressed air supply.
The flame detector circuit which is utilized in the illustrative embodiment is that disclosed and claimed in Gilbert application Serial No. 235,098 filed November 2, 1962 for Flame Detector. The internal cooling i.e. along the wires and around the connections and over the exterior surface of the detector 76 is possible because of this circuit in which a short circuit between the electrical conductors 48 or electrical leakage will not cause a false signal but will merely reduce the amplitude of the pulse signal, complete shorting reducing the flame output signal to zero. Reference may be made to the above-identified Gilbert application for further details of this circuit.
The rigid support member 16 has a ring stop or inwardly directed flange 127 secured adjacent the open end thereof which will act as a stop and positioning means for the tube 40 carrying the detector. The inner air conducting means contains some compressible element such as the conduit 46 which may be compressed by bringing the flange member 54- into contact with the end of casting 3i and securing it in place. Compression of this compressible member will force and resiliently urge the tube 40 against the ring 127 and hold it in place and block the flow of air between said member 16 and said tube 40.
The end of tube 41 between the washer 98 and the open end of the tube, is provided with holes 129 which provide air exit means for the air flowing from inside of tubular member 14 and outside of the conduit 46 between member 16 and tube 40 and regulate the pressure drop through tubular member 14. This air will mix with the substantially cylindrical air stream issuing from the end of tube 40, through the aperture in the washer 93, and assist in providing a high energy air stream which will insulate the window 66, and in the absence of the window, the detector element 76 from flying particles in the furnace. The ring 127 in addition to providing a stop for the tube 40 acts as a guide for the air issuing from the open end of the rigid member 16.
As provision must be made for removing the detector assembly including the casting 52, the conduit 46, the tube as and their associated members while the furnace is in operation and as the pressure inside the furnace is, in a pressure furnace system, higher than atmospheric pressure provision must be made for preventing flames and hot gases from flowing out through the tubular member 14 during and while the tube 40 is being removed. During the removal operation air under pressure is continuously supplied through the air inlet 62 which includes a flexible member such as a hose 63 and high pressure air is sup plied through the inlet 38 and the aspirator 36 having outlets 37 to maintain a pressure at the outer end of tube 24 slightly larger than the pressure in the furnace. In a forced draft or suction type of furnace where the furnace is at a pressure less than atmospheric the separate supply through inlet 62 may be omitted as shown in FIG. 5 and the entire air supply both for the external and internal cooling of the tube 40 and the air stream external and internal to the conduit id may be supplied through the air inlet 3 by providing holes 126 connecting the chambers 58 and 32 thus permitting air from the chamber 32 to flow through the orifices 126 and into pipe 50 and conduit 46. As the pressure in the furnace is less than atmospheric the detector assembly may be removed through the tubular member 14 without danger of the flame coming out through the tube.
It is to be understood that the invention is not limited to .the specific embodiment herein illustrated and described but may be used in other ways without departure from its spirit and that various changes can be made which would come within the scope of the invention which is limited only by the appended claims.
1. A flame detector comprising a tube open at both ends, means directing a stream of air along the exterior of said tube for cooling the tube exterior, a detector ele ment comprising detector members encased in a transparent sealed enclosure in said tube, a corrugated heat transmitting shield between said enclosure and the inner walls of said tube, a passageway through said tube including a center portion for transmitting light to said detector and an annular portion defined by said enclosure and said shield and means for connecting said passageway, including said center portion, with a source of cooling gas.
2. A flame detector comprising a tube open at one end, a detector element in said tube and forming with said tube an annular passageway in said tube, a window between said element and said open end and spaced from the walls of said tube with the window periphery forming, with the tube, an extension of said passageway, means forming an opening in said tube adjacent said open end larger than said window and directing cooling gases passing across said window periphery and out said open end as a substantially cylindrical annulus extension of the annulus formed by said passageway and means for connecting said tube with a source of cooling gas.
3. A flame detector comprising a tube open at one end, means for cooling the tube exterior, a detector element, comprising detector members encased in a transparent sealed enclosure, and a base enclosing electrical leads for said members, and supporting said members in said enclosure in said tube, and substantially filling said tube cross section except for an annular passageway in said tube defined by said enclosure wall and the inner walls of said tube and means including a passageway through said base for connecting said annular passageway with a source of cooling gas, and an extended surface heat conductor open at both ends in said annular passageway and dividing said annular passageway into longitudinally extending passageways and contacting both said enclosure and the inner walls of said tube.
4. A flame detector comprising a tube open at one end, a detector element in said tube and forming with said tube an annular passageway in said tube, a window between said element and said open end exposed to air flow through said tube and spaced from the walls of said tube with the window periphery forming with said tube an extension of said passageway, means protecting said window from moving objects including means directing cooling air out the open end of said tube in a substantially parallel sided annular stream and means for connecting said tube with a source of cooling air.
5. A detector as claimed in claim 4 in which said directing means includes a tubular extension beyond the end of said tube and window.
6. A flame detector comprising a .tubular casing having an open end and a tube having an open end and enclosing a light sensitive flame detector element and having a central passageway for transmitting light to said element and removably retained in said tubular casing and substantially closing said open end of said casing, means adjacent the other end of said casing for connecting the inside of said casing with a source of pressure air and supplying a stream of cooling air inside said casing and out of contact with said element, means for discharging only said air from said casing adjacent said open end of said casing and means for directing cooling air from a supply independent of said stream to the inside of said tube and through said passageway in direct contact with said element and out the open end of said tube.
7. A flame detector as claimed in claim 6 in which said directing means includes separate means connecting the other end of said .tube with said supply independent of said means connecting said casing with said source.
8. A flame detector comprising a light sensitive flame detector element, a tube open at one end surrounding said element, means closing the other end of said tube except for a conduit extending from said other end of said tube, means for connecting said conduit with a. source of air pressure for forcing a first stream of air through said conduit, into said .tube and around and in direct contact with said element and out said open end for direct air cooling of said element, a tubular casing open at one end, means for releasably retaining said tube and conduit in said casing with the open end of said tube terminating adjacent the open end of said casing, means for connecting said casing with a source of air pressure for forcing a second stream of air through said casing outside of said tube and conduit and out the open end of said casing for cooling said casing, tube and conduit, said tube and conduit completely separating said air streams between said respective connecting means and said respective open ends.
9. A flame detector as claimed in claim 8 in which said conduit encloses electrical conductors leading to said element.
10. In combination with a furnace having a normal combustion air supply means including an air chest and means for maintaining the air pressure in said chest above a predetermined minimum, said chest having a standby separate compressed air supply, a flame scanner including a detector element and means for directing a stream of cooling air along and in direct contact with said element, means connecting said air chest directly with said stream directing means, and pressure actuated valve means connecting said directing means with said compressed air supply when the pressure in said chest falls below said minimum.
11. A flame detector as claimed in claim 8 in which said casing is fixed in an opening in a furnace and said element, said tube, said conduit and said means for connecting said conduit with a source of air pressure are removable as a unit from said tubular fixed casing while air is flowing through said conduit and tube.
12. In combination with a furnace having a movable burner secured in a furnace wall, a flame scanner adapted to be mounted on said movable burner cfor movement therewith, comprising a tubular support secured to said burn-er and including a flexible conduit, a. tubular member including a flexible conduit telescoped with said support and detector mechanism supported in said member, said tubular member adapted to be inserted through said support while secured .to said burner and means for removably securing said member in said support and means for forcing separate streams of cooling air through said tubular support and said tubular member.
13. A flame scanner, comprising a tubular support having an open end, a tubular member having an open end, telescoped with and spaced from said support and defining an annular air passage therebetween, detector mechanism supported in said member, means urging said tubular member axially of said tubular support, an inwardly directed flange member defining an air exit opening for said member and positioning said member axially of said support and blocking one end of said annular passage, air exit means, for said annular passage, in said tubular member adjacent the open end thereof connecting the blocked end of said annular passage with the open end of said member and means for forcing a stream of cooling air through said tubular support and a separate stream of cooling air through said tubular member said streams being combined adjacent said air exit means.
14. In combination with a furnace having a normal combustion air supply means, a duct connecting said supply with said furnace and including an air heater and a burner in said duct, an air chest connected with said supply by a conduit bypassing said air heater and burner, means maintaining the air pressure in said chest above a predetermined minimum including pressure boosting means connected with said conduit for boosting the pressure in said chest, a flame scanner including a detector element and means for directing a stream of cooling air along and in direct contact with said element, means connecting said chest directly with said stream directing means and pressure actuated means activating said boosting means when the pressure in said chest falls below said minimum.
15. A combination as claimed in claim 10 including air conducting means connecting said supply means and said chest and in which the means for maintaining the air pressure in said chest includes pressure boosting means in said air conducting means between said supply means and said chest and means responsive to the pressure difference between said furnace and said chest for controlling operation of said pressure boosting means.
16. A flame detector as claimed in claim 11 including means for maintaining said second stream with said conduit and tube removed from said casing.
17. A flame detector as claimed in claim 8 in combination with a furnace having a normal combustion air supply means including an air chest and means for maintaining the air pressure in said chest above a predetermined minimum and providing both said sources of air pressure for said first and second streams of air.
18. A flame detector as claimed in claim 17 in which said detector element comprises energy sensitive members encased in a transparent sealed enclosure in direct contact with said first stream and the cooling requirements of said element are satisfied with said first stream of air between two and four cubic feet per minute and said second stream approximately seventeen cubic feet per minute.
19. A flame detector for detecting the presence and absence of a flame, comprising a detector element having electrical connections, a tube open at one end and surrounding said element, a conduit connected with the other end of said tube and enclosing wires connected with said element, said wires and elements forming part of a fail-safe electrical circuitin which complete shorting of the wires or connections will indicate absence of a flame by reducing the flame output signal to zero, means connecting said conduit with a source of air pressure and forcing a stream of air through said conduit in contact with said wires and into said tube around and in direct contact with said element and said electrical connections for direct air cooling of said element.
References Cited by the Examiner UNITED STATES PATENTS 1,945,652 2/1934 Martin.
2,054,382 9/1936 Larsen et al. 158-28 2,462,395 2/1949 Heiman 126-106 2,481,040 9/1949 RothWell et a1. 15828 2,493,078 1/1950 Mead.
2,592,847 4/1952 Babicz 15828 FOREIGN PATENTS 717,860 11/1954 Great Britain.
JAMES W. WESTHAVER, Primary Examiner.