US2852642A

US2852642A - Thermal responsive device

Info

Publication number: US2852642A
Application number: US632746A
Authority: US
Inventors: Robert M Cromwell
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1957-01-07
Filing date: 1957-01-07
Publication date: 1958-09-16
Anticipated expiration: 1975-09-16

Description

Sept 16, 1958 R. M. CROMWELL THERMAL RESPONSIVE DEVICE 2 Sheets-Sheet 1 Filed Jan. 7, 1957 RCROMWELL INVEN TOR. m

BY 3W QQQMW A T HORNE KY Sept. 16, 1958 R. M. CROMWELL 2,852,542

THERMAL RESPONSIVE DEVICE Filed Jan. 7, 1957 2 Sheets-Sheet 2 R. CROMWE L L INVENTOR.

A TTORNEVS United States Patent THERMAL RESPONSIVE DEVICE Robert M. Cromwell, Deal-born, Mich., assignor to Ford Motor Company, Dearborn, Mich, a corporation of Delaware Application January 7, 1957, Serial No. 632,746

Claims. (Cl. 200-140) This invention relates to a thermal responsive mechanism and more particularly to a high temperature mechanism for use in the control system of a gas turbine or the like.

An object is to provide a thermal responsive device for accurate operation over a wide range of temperatures.

Another object is to provide a mechanism which is designed to be actuated by vapor pressure at a predetermined temperature.

A further object is to provide a simple, rugged temperature actuated device for use at extreme temperatures in which the more delicate components are not subjected to the temperatures which actuate the device.

Still another object is to provide a high temperature mechanism for use in the combustor section of a gas turbine to control the operation of the torch igniter.

These and other objects will become apparent upon reading the following specifications and drawings wherein:

Figure 1 is a partly schematic representation of the combustor portion of a turbine utilizing my invention and Figure 2 is an enlarged section of the control means of Figure 1.

The combustor assembly shown in Figure 1 comprises a tubular outer casing and a perforated flame tube 11 having a fuel nozzle 12 and primary air swirlers 13 at its forward end coaxially mounted within this casing. Nozzle 12 is disposed within a hollow strut 14 which serves to support the flame tube in position and to protect the fuel inlet line 15. The forward end 16 of casing 10 communicates with the compressor (not shown) and the discharge end 17 of the casing communicates with the compressor turbine. A torch igniter of the conventional type is shown generally at 18, is mounted on the outer surface of the casing 10 and has an electrically heated igniter element (not shown) shrouded by a shield 19 which extends into the combustor. A normally closed thermally operated control 20 is also mounted in the casing adjacent to the discharge end and is electrically connected in series with said ignitor and the electrical power supply (not shown).

Reference should now be had to Figure 2 in order to understand the operation of the control element 20 which embodies the principles of the instant invention. It comprises an upper housing 21, a plate 22 releasably secured thereto and a base plate 23. A flanged adapter 24 having a central depression or bowl 25 is secured to the base plate by bolts 26 and is mounted on the outer wall of casing 10 by bolts 27. However, base plate 23 is thermally insulated from the flanged adapter, and the casing 10 by the insulation shown at 29 and 30 and insulation 28 between the base plate and the adapter which insulation also fills bowl 25. A cylindrical probe supporting member 31 having a shoulder portion 32 resting upon base plate 23 and a central portion 33 fits within a suitable bore in base plate 23 and abuts insulation 28 to prevent undue jarring of the device and minimize convection heating of the interior of housing 21; seal 34 aids in these functions. The probe 35 is essentially a thin tube closed at 2,852,642 Patented Sept. 16, 1958 one end which extends into the interior of the combustor assembly and is securely attached to member 31 at its opposite end as by welding shown at 36. It extends into the flame tube down stream of nozzle 12 Where the secondary air mixes with the hot combustion gases thereby assuring that the temperature measured is lower and more uniform than the temperature at the nozzle 13. The probe is an extremely small diameter tube to minimize heat losses along its length and to maintain low values of heat transfer lag across its walls so that the temperature within the probe will quickly follow the variations in the ambient temperature. A material such as mercury or sodium partly fills the probe 'as shown at 52. This material volatilizes upon being heated so that when the temperature within the combustion assembly reaches a point at which the flame therein becomes selfsustaining, the vapor formed exerts sufficient pressure to actuate the control 20 in the manner described herein below. Depending upon the design of the combustor, a relatively low temperature volatilizing material such as mercury or a high temperature material such as sodium may be used. A sealing ring 37 is seated at the bottom of bowl portion in 25 and supports a pressure diaphragm 38 which is firmly seated against this ring by an upper spacer ring 39 which is urged against the diaphragm by a nut 40 which is threaded into the upper portion of 31. Thus a space is provided below the diaphragm which is fluidly connected to the interior of the probe 35 whereby the diaphragm may be flexed when the vapor pressure of the material within tube 35 reaches a certain value.

A mechanical linkage comprising a first lever 41 pivotally mounted at 42 and a second lever 43 pivotally mounted at 44 amplifies the motion of the diaphragm and transmits it to a switch S-l secure in a bracket 49 which is in turn rigidly connected to the threaded member 50 adjustably mounted in plate 22. The levers are connected to respond to the motion of diaphragm 38 by means of a follower or push rod 45 having a lower anvil portion 46 which rests against the upper surface of diaphragm 38. This rod tits in an appropriate hole in lever 41 and has a collar 54 against which this lever operates. A central slit is cut in lever 43 to form an arm which is bent at an angle of about ninety degrees to the plane of the main portion of this lever as shown at 47. An externally adjustable screw 48 in housing 21 operates against this arm tending to move it clockwise when the screw is moved to the right thereby urging levers 41 and 43 downwardly to increase the force exerted by anvil 46 against diaphragm 38 in opposition to the gas pressure exerted by the vapor formed below the diaphragm, this provides an effective method of biasing the diaphragm and therefore a method of varying the combustor temperature at which control 20 operates.

Operation The air from the compressor flows through inlet 16 of the combustor assembly where it divides. A portion of the air flows through primary air swirlers 13 and is mixed with the fuel spray from nozzle 12; the remainder of the air flows in the annular space between the casing and the flame tube. Of this latter air some flows into the flame tube 11 to aid in combustion and also to dilute the hot combustion gases to a temperature that is low enough for use in the turbine while the remainder forms a jacket of relatively cool air surrounding the flame tube. Of course, this jacket air ultimately mixes with the gas as it passes through exit 17 to the turbine.

The torch igniter which may be a glow plug or a spark plug serves to ignite the air fuel mixture in the flame tube and is turned on immediately upon starting the engine. When the temperature within the combustor reaches a value at which the flame becomes self sustaining the torch igniter is no longer needed and is automatically turned off by control 20 in the following manner: The material in the probe tube 35 .vaporizes to form a gas which fills the tube and the space below diaphragm 38. Upon continueddieating,this gas exerts snnic'i'nt'prssure on the' diaphragm to eyercs se'tae bias exerted by anvil 46 on the upper surface of the diaphragm and urges said diaphragm upward thereby actuating push rod '45. Levers 41 and 43, in turn, multipl'y'the motion imp arted to the push rod andthe free' e nd of lever'43 acts against micro switch S-1 which peasthe circuit between input terminal 51 which is connected to a power supply (not shown) and the output terminal 52 which is connected to the glow plug 18. a j j One advantage inherent in this control is that the sensitive diaphragm and the switch s l are not subjected to extremes in temperatureso that there is no danger of damage due to thermal shock, Only the temperature'pro be and the material within it are subjected to the temperature to be measured, the switch andthe diaphragm remain at relatively constant temperatures so'that their operation remains constant regardless of the temperatures encountered in the combustor. j

"It is apparent that it is possible to adjust the temperature at which the switch will open by three methods: The first involves changing the material in the tube 35; for example, if sodium is used the temperature at which the switch will be opened is in the neighborhood of 1800 F., while' if mercury is used, the switch will operate at about 1000 F. For more convenient and rapid change over it is desirable to remove the subassembly comprising member 31, temperature probe 35 and the diaphragm as aun it and substitute another such subassembly in which the probe contains'a different material. A second method is by adjusting the position of screw 50 and thereby altering the position of S1 with respect to the lever arm The third method is by adjusting screw 48 so as to increase or decrease the bias on the diaphragm. The last two named methods are limited by the fact that at a certain temperature all the material in the tube will be volatilized and will be in equilibrium with the'vapbr that condenses in the upper insulated'cooler portion of tube 35 and refluxes down theItube. This will be the point above which an increase ihtemperature in the flame tube will not appreciably increase the pressure acting on'the diaphragm and the diaphragm will'rnove no further. J

This method of controlling the operation of the torch igniter is'es se'ntially without hysteresis; it will turn oif ah'd 'on at the same temperature (providing the adjustment of the shutoff control is riot changed) throughout repeated cycling. In fact, the only hysteresis in the control ariseslfrom that inherent in 8-1. j i

The probe 35 need not be a straight tube but may be coiledinto a spiral'if a greater volume of volatilizable material is required. In the event that it is desired to present a minimum of obstructions to the how path within the flame tube the probe may be mounted along a supporting strut of the flame tube and is, of course, held away frorn' the strut by insulators so that the probe is not effected by the strut which may act as a heat reservoir and tend to increase the heat lag time of the probe.

Although Idiave described the thermally responsive device in combination with the combustor assembly of a turbine it to be understood that the invention is by no means so limited. For example, at relatively constant pressures, this device could be employed at extremely low temperatures using propane, methane or even Dry Ice or liquid oxygen as the material contained within the tube. This extremely rugged and versatile device could be used in any temp erature range where extremely accurateresponse and a minimum of hysteresis is desired.

It will be understood that the invention is not to be limited to the exact construction shown and described, but that varipps' changes and modifications may be made with out departing from the spirit and scope of the invention, as defined in the appended claims.

I claim:

1. A temperature responsive means comprising; a casing having an apertured end, control means Within the casing remote from said apertured end, support means removably fitted within said apertured end, said support means having a bowl portion and a bore communicating therewith, a hollow probe'depending from said support and rigidly secured within said bore whereby the interior of ksaidpztcb: is in fluid communication with the bowl portion of said support means, a material within .said probe adapted to vaporize at a selected temperature, a pressure"sensitive diaphragm sealingly disposed within said bowl so that the obverse surface of said diaphragm is acted upon by the pressure of the vapor formed within said probe to flex said diaphragm when the temperature within the probe reaches a predetermined value, follower means abutting the reverse sutfambf said diaphragm for mo'tidn' therjewith, first lever pivotally mouiited within said casing and operatively connected to said follower means, a second lever pivotally mounted within said easiagoperaave y' eonne'cted to said control means and ,adaptedto be actuated by said first lever, an arm integral 'wi th said second lever, externally adjustable means mounted in said casing and adapted to operate on said arm whereby the pressure exerted by said follower on said diaphgralgim be selectively varied.

' 2. A thermalrespo nsive device comprising a housing, an adaptens ecured to said honsin g and having a bowl portion, a layer of insulating material positioned between said housin g' and said'iadhpter, said bowl portion also beiiighlled 'withinsulatiiig'material, a hollow temperature sensing elemehtextendihg from the interior of said o sin thl 'qi s h ev q nsul ma ia n itionedbetween the housing and the adapter, through the insulating material positioned 'in said bowl portion of the adap'ter'and through said bowl portion, a material positioned within said hollow temperature sensing element forming a gas at'a selected temperature, a pressure op ra le dia h a m Po t oned ithin sai housing having one side in fluid "communication with the interior of said hollow temperature sensing element so that the gas formed bysaidm'aterial at the selected temperature flexes said pressure operable diaphragm; a follower within said hon rig having'one end operatiyely connected to said diaphr jt g i, Control means operatiyely connected to said f j 11owrwaae yita fleirure of said diaphragm actuat'es said control 'means. l V

3. thermal responsiye device comprising, a housing, an adapterfsfecu'r'edtosaid housing 'and having a 'bewl portion pb sitioned' therein, a layer of thermal insulat ingiiiaterial' positioned between said housing and said adapter; said bowl pbrtioii of said adapter also being filled with thermal insulating material, means filled with atemperature sensitive material extending from the interior of said housing throughthe layer of thermal insulating" material pesitioned between the housing and the adapter, through the insulating material positioned in the' h o'wl portion of'the 'adapter'and through th e'end wallof said bowl portion, pressure operable means positioned within" said housing and being in communication with [the meansfilled .witha temperature sensitive material so that'said pressure operable means is actuated by the temperature sensitive material at a selected temperature control'means positioned within said housing and motion amplifying means positioned in said housing in contact with the pressure operable means and said control means whereby said control 'means will be actuated by said pressure operablerneans through said motion amplifying means at said selected temperature.

A thermal responsive device comprising a housing, an adapter secured to said housing and having a bowl portion positioned therein, a layer of thermal insulating e als! were P ti es said toss n and sa l as rt said bowl portion of said adapter also being filled with thermal insulating material, a hollow temperature sensing element extending from the interior of said housing through the layer of insulating material positioned between the housing and the adapter, through the insulating material positioned in said bowl portion of the adapter and through the end wall of said bowl portion, a temperature sensitive .material positioned said hollow temperature sensing element forming a gas at a selected temperature, a pressure operable diaphragm positioned within said housing having one side in fluid communication with the interior of said hollow temperature sensing element so that the gas formed by said material at the selected temperatul'e flexes said pressure operable diaphragm, a follower within said housing having one end connected to said pressure operable diaphragm, a first lever pivotally mounted within said housing and operatively connected to the other end of said follower, a second lever pivotally mounted within said housing and engaging said first lever, a control means mounted in said housing, said second lever being operatively connected to said control means so that the flexure of said pressure operable diaphragm actuates said control means, an arm integral with said second lever and extending at substantially a right angle therefrom, externally adjustable means mounted in said casing and engaging said arm whereby the pressure exerted by said follower on said diaphragm may be selectively varied.

5. A thermal responsive device comprising a housing, an adapter secured to said housing and having a bowl portion, a layer of insulating material positioned between said housing and said adapter, said bowl portion also being filled with insulating material, a supporting member positioned within said housing and having one end abutting said layer of thermal insulating material positioned between said housing and said adapter, said supporting member having a first bore extending from the end abutting the layer of thermal insulating material to a point intermediate the ends of said supporting memher, a second bore of larger diameter than the first bore extending from the other end of said supporting member to said point intermediate the ends of the supporting memher, a sealing ring positioned in the bottom of said second bore, a flexible diaphragm supported by said sealing ring, a spacer ring positioned over said flexible diaphragm and a nut threaded into said second bore for urging said spacer ring into engagement with said flexible diaphragm, a hollow temperature sensing element aflixed in said first bore in said supporting member and extending through said layer of insulating material positioned between said housing and said adapter, through the insulating material in said bowl portion and through the end wall in said bowl portion, said hollow temperature sensing element being filled with a temperature sensitive material which is in communication with said flexible diaphragm so that said flexible diaphragm is flexed by said temperature sensitive material at a selected temperature, a follower within said housing having one end operably connected to said diaphragm, control means operably connected to said follower whereby the flexure of said diaphragm actuates said control means.

References Cited in the file of this patent UNITED STATES PATENTS 1,024,079 Jennings Apr. 23, 1912 2,496,502 Steensma Feb. 7, 1950 2,536,831 Allan Ian. 2, 1951 2,748,225 Kautz May 29, 1956 2,773,147 Judson Dec. 4, 1956