CA1152471A - Fluid temperature control system - Google Patents
Fluid temperature control systemInfo
- Publication number
- CA1152471A CA1152471A CA000364717A CA364717A CA1152471A CA 1152471 A CA1152471 A CA 1152471A CA 000364717 A CA000364717 A CA 000364717A CA 364717 A CA364717 A CA 364717A CA 1152471 A CA1152471 A CA 1152471A
- Authority
- CA
- Canada
- Prior art keywords
- fluid
- servo
- servo fluid
- supply
- temperature
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/01—Control of temperature without auxiliary power
- G05D23/13—Control of temperature without auxiliary power by varying the mixing ratio of two fluids having different temperatures
- G05D23/138—Control of temperature without auxiliary power by varying the mixing ratio of two fluids having different temperatures for gases
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/185—Control of temperature with auxiliary non-electric power
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- Power Engineering (AREA)
- Control Of Temperature (AREA)
- Temperature-Responsive Valves (AREA)
- Superconductors And Manufacturing Methods Therefor (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Transition And Organic Metals Composition Catalysts For Addition Polymerization (AREA)
Abstract
FLUID TEMPERATURE CONTROL SYSTEM
ABSTRACT OF THE DISCLOSURE
Fluid temperature control system for providing a sup-ply fluid at a select temperature by warming or cooling a first fluid with a controlled flow of a second fluid. The control of the second fluid flow is achieved by a modula-tion valve adjustable in response to the pressure of a supply of servo fluid which is itself adjusted in response to the temperature of the supply fluid. The adjustment of the servo fluid pressue by the control system is such that the change in servo fluid pressure from a steady state condition is initially great, diminishing with time to a lesser, steady state value, thereby enhancing the transient response of the control system.
ABSTRACT OF THE DISCLOSURE
Fluid temperature control system for providing a sup-ply fluid at a select temperature by warming or cooling a first fluid with a controlled flow of a second fluid. The control of the second fluid flow is achieved by a modula-tion valve adjustable in response to the pressure of a supply of servo fluid which is itself adjusted in response to the temperature of the supply fluid. The adjustment of the servo fluid pressue by the control system is such that the change in servo fluid pressure from a steady state condition is initially great, diminishing with time to a lesser, steady state value, thereby enhancing the transient response of the control system.
Description
1152~7~
BACKGROUND OF THE INVENTION
Field of the Invention - This invention relates to -systems for providing a fluid of a select temperature by mixing of two fluids of differing temperatures or by dis-position of such fluids in mutual heat transfer relation-ship and more particularly to such a system for use in supplying bleed air of a particular temperature from a gas turbine engine.
Description of the Prior Art - It is well known to air-condition aircraft cabins and power various aircraft subsystems with air bled from the aircraft's propulsion system. In air-conditioning the cabin of a gas turbine engine powered aircraft, it has been the practice to sup-ply the cabin with air bled from the compressor section of the engine, such air being cooled to the desired tempera-ture by mixture or mutual heat transfer with cooler air supplied by the engine's fan. Inasmuch as differing engine operating conditions cause variations in the tem-perature of the compressor bleed air, systems which moni-tor the temperature of the bleed air and cool the bleed air with a controlled flow of cooler fan air are necessitated.
Such systems have in the past been of two general types.
The first type as exemplified by the systems disclosed in U. S. Patents Nos. 3,441,213 and 3,537,644 each assigned to the assignee of the present invention, generally com-prises a pneumatic temperature sensor controlling a pneu-matic fan air modulating or control valve. While such pneumatic temperature sensors exhibit fairly accurate steady state response, it has been found that the transient performance of such sensors could be improved upon. While ~15~4~1 certain fast-acting pneumatic or mechanical temperature sensing transducers have been proposed, the accuracy of such sensing devices has been found inadequate for air-craft cabin air-conditioning systems.
Other proposed fluid temperature control systems such as that shown in U. S. Patent No. 2,919,859 to Krueger employ electrical temperature sensors, and con-trols, and, while such systems may exhibit both adequate steady state accuracy and rapid transient response, they require the disposition of rather delicate electrical sensors and connectors in the hostile environmer.t of the gas turbine engine and therefore are subject to damage from heat and/or vibration resulting in poor system reliability.
It is therefore an object of the present invention to provide a fluid temperature control system which over-comes the deficiencies of the prior art.
It is another object of the present invention to pro-vide such a fluid temperature control system of enhanced steady state accuracy.
It i9 another object of the present invention to pro-vide a fluid temperature control system which responds rapidly to sudden changes in inlet fluid temperature.
It is another object of the present invention to provide a fluid temperature control system which employs no electrical components.
It is another object of the present invention to provide such a fluid temperature control system of en-hanced reliability.
~lS2471 SUMMARY OF TEIE INVENTION
These and other objects which will become more readily apparent from the following detailed description taken in connection with the accompanying drawings, are achieved by the fluid temperature control system of the present invention in which a first fluid is either warmed or cooled by a controlled flow of a second fluid to achieve an outlet fluid flow at a preselected temperature. The flow rate of the second fluid is controlled by a modulation or control valve set by an actuator responsive to the pressure of a supply or servo fluid. The temperature of the outlet fluid supplied by the system of the present invention is continuously monitored by a temperature sensing means oper-atively connected to means which continually adjusts the servo fluid pressure in response to the output of the temper-ature sensing means. The servo fluid pressure is adjusted such that the change of pressure from that of the prior steady stat~ condition is initially great, diminishing with time to a ~maller Qteady state value. This initial servo fluid pr~ssure change in xesponse to the temperature change detected by the temperature senqing means causes the modulation valve actuator to respond quickly to any transient fluid temperature fluctuations.
In accordance with a particular embodiment of the invention there is provided a system for controlling the fluid supply temperature of a first fluid flowing through a first duct by disposition of the first fluid in heat transfer relationship with a second fluid flowing through a second duct at a temperature different from that of the first fluid.
The system comprises a valve disposed in the second duct for regulating the flow of fluid therethrough and an actuator ~ 4 -11524~1 - operatively connected to the valve for the modulation thereof.
The actuator communicates with and is responsive to the pressure of a supply of servo fluid. The system further com-prises means for adjusting the pressure of the servo fluid in response to the supply temperature of the first fluid thereby effecting the operation of the actuator and the modulation of the valve. The means adjusts the servo fluid pressure such that the change of the servo fluid pressure from steady state diminishes with time from the initiation of the servo fluid pressure adjustment from an initial greater value to a subsequent lesser steady state value thereby enhancing the transient response of the control system.
In accordance with a further embodiment of the invention there is provided a system for controlling the fluid supply temperature of a first fluid flowing through a first duct by disposition of the first fluid in heat transfer xelationship with a second fluid flowing through a second duct. ~he system comprises a valve disposed in the second duct for regulating the flow of fluid therethrough and an actuator for modulating the valve in response to the pressure of a primary supply of servo fluid with which the actuator communicates. Means are provided for controlling fluid pressure in the primary servo fluid supply in response to the temperature of the first fluid thereby selectively activating the actuator. A secondary servo fluid supply communicates with the primary servo fluid supply through a flow restrictor whereby initial adjustments in fluid pressure in the primary servo fluid supply from a steady state condition are damped by delayed servo fluid pressure equalization between the primary and secondary supplies.
~- 4a -. ~
BRIEF DESCRIPTION OF THE DRAWINGS
. _ Figure 1 is a schematic illustration of the fluid temperature control system of the present invention.
Figure 2 is a plot of the time change in servo system fluid pressure for a sudden change in supply fluid temperature.
- 4b -~SZ47~
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, the fluid temperature control system of the present invention is shown generally at 10. The system controls the temperature of a first fluid flowing through a first duct 15 by either mixing that fluid with a second fluid at a different temperature flowing through a second duct 20 or by the disposition of the two fluids in mutual heat transfer relation to achieve the desired temperature in the resulting supply fluid flow-ing through a third duct 25. The system of the present invention is particularly useful for Rupplying air at a predetermined temperature for cabin air-conditioning and thermal anti-icing of a gas turbine engine powered air-craft. When so employed, the first fluid in first conduit 15 may comprise air, bled from the compressor section of the gas turbine engine, while second fluid flowing throùgh second conduit 20 may comprise cooler fan a~r, the two fluids channeled through a precooler or heat exchanger 27 at the intersection of ducts 15 and 20 wherein heat from the compressor bleed air is given up to the cooler fan air.
The resulting controlled temperature fluid exit~ the ap-paratu8 to the aircraft air supply sy~tems through duct 25.
However, it will be appreciated that the temperature con-trol system of the present invention is useful wherever it is desired to control the temperature of a first fluid by either mixing that fluid with a second fluid at a differ-ent temperature or disposing the two fluids in heat trans-fer relationship to one another.
Broadly, the present invention comprises a modulating 1~5i247J.
or throttle valve 30 operated by valve actuator 35 respon-sive to the pressure of a supply of servo fluid 40 which communicates with the actuator. For economy of construc-tion, the servo fluid may be obtained from a tap of one of ducts 15 or 20 by third duct 45. However, it will be appreciated that a separate source of servo fluid may be employed if so desired. The servo fluid pressure is ad-justed by means 50 responding to the output of tempera-ture responsive means 55 which continually senses the temperature of the bleed supply air. In the preferred embodiment, the temperature responsive means comprises a bimetallic element which changes length in response to exposure to varying temperatures. However, it will be understood that any of various other temperature sensors may be employed without departing from this invention. A
change in the temperature of the bleed air i8 therefore sensed by means 55 which actuates means S0 to adjust the ~ervo fluid pressure. The adjusted servo fluid pressure, i5 ~en~ed by actuator 35 responding to this adjusted pres~ure by actuation of valve 30 which adjusts the flow rate of fan air to mixing chamber or heat exchanger 27 thereby elevating or depressing the temperature of the compressor bleed air to the desired value.
Valve 30 may be of any known varieties of flow con-trol valves depending of course on the nature of the fluid controlled thereby. In the preferred embodiment, where for example the valve is employed to control the flow rate of fan air, valve 30 is preferably of the butterfly variety, the plate or valve element being connected to actuator 35 by means of any suitable linkage 60.
1~5~71 Likewise, actuator 35 may be of any of a number of known varieties depending on the nature of the actuated valve and the type of ser~o fluid employed therewith.
As shown, the actuator comprises a housing 65 enclosing a diaphragm piston 70 biased toward the upper end of servo fluid chamber 75 by spring 80. A connecting rod 85 connects the piston to linkage 60 and valve 30. In operation, the spring urges the diaphragm piston in a valve opening direction, the piston being urged in an opposite direction to close valve 30 in response to servo fluid pressure in chamber 75.
Means 50 for adjusting the servo fluid pressure in response to an input from temperature sensing means 55 comprises a fixed orifice 91 in duct 45 and an orifice or port 90 in the end of branch line 95 in communication with conduit 45. The effective area of port 90 is adjusted between totally open and totally closed conditions in response to the temperature of engine bleed air in conduit 15 by means of a closure member or flapper 100 fixed to or integrally comprising a lever 105 pivotally connected to a stationary mount at 110. The end of lever 105 op-posite that which adjoins flapper 100 is connected to a counterbalance spring 115 fîxedly mounted to a stationary surface 120 at 125. Thus, it will be seen that the spring 115 . disposed between lever 105 and fixed mount 125 i8 compressed, maintaining the equilibrium of the lever and flapper in conjunction with spring 116 when the flapper is exposed to positive servo fluid pressure through port 90. Spring 116 transmits a driving force to the lever, from bimetallic element 55 connected to the spring by way of bellcrank 130 pivotally connected to tempexature xe-sponsive means 55 at one end thereof and at the other end thereof to shaft 135 which is in turn connected to spring 11~ at an end thereof opposite that connected to lever 105.
It will be seen then, that the fluid temperature con-trol system of the present invention describes a single feedback loop control circuit wherein bimetallic element 55 when actuated by an error in air temperature within duct 25 changes length transmitting a signal to lever 105 via bellcrank 130, shaft 135 and spring 116. This signal results in a force change on the lever thereby causing the flapper to ad~ust the effective area of port 90 until a balancing pressure force change on the lever is produced.
This adjustment in servo fluid pressure within duct 45 and actuator chamber 75 activates actuator 35 which reposi-tions valve 30. This repositioning, adjus~ the flow rate of fluid through duct 20 to correct the sen~ed temperature error within duct 15.
It will be appreciated that the ~ignal provided by a mechanical temperature ~ensor such as bimetallic element 55 or an equivalent pneumatic temperature actuator lags in time the temperature variation which causes the sensor to initiate such a ~ignal. ~o compen~ate for such a time lag, the temperature control system of the present inven-tion is provided with a chamber or secondary servo fluid supply 140 in fluid communication with branch 95 of servo fluid duct 45 through a flow restrictor or orifice 145.
One wall of chamber 140 comprises a diaphragm 150 which is connected to lever 105 by link 155. In steady state, ~5;~
the fluid communication of chamber 140 with duct 45 ef-fects an equalization of servo fluid pressure within those members. However, the restrictive properties of orifice 145 and the compressibility imparted to chamber 140 by diaphragm 150 cause equalization of servo fluid pressures in duct 45 and chamber 140 to lag an adjustment of servo fluid pressure in actuator chamber 75 when spring 116 is compressed by a change in sensed temperature.
Referring to Figs. 1 and 2 it will be seen that a change in force applied to lever 105 by spring 116 at time tl, in response to a step error in compressor bleed air temperature initially causes the flapper to open thereby causing an immediate drop in servo fluid pressure in duct 45 and actuator chamber 75 from Pl to P2. As the servo fluid pressure in chamber 75 decreases, a pressure dif-ferential is formed across orifice 145, causing servo fluid flow from chamber 140, through orifice 145 thereby decreasing the pressure in chamber 140. This causes the control lever to gradually reclose the flapper 100 thereby increasing the pressure in chamber 75 and duct 40 to P3.
Th~s~ it will be appreciated that upon a step change in spring force 116 the initial signal presRure change in duct 45 (a Pa) is proportional to the product of the change in loading on lever 105 from actuation of the bimetallic element and the inverse of the surface area of that por-tion of the flapper in registry with port 90. However in a steady state conditi,on, the change in servo fluid pres-sure ( ~Pb) from the previous steady state condition is significantly less, being proportional to the product of the force change on the lever and the inverse of the sum of the flapper and diaphragm areas. The system of the 115~471 present invention operates similarly, i.e., yielding a large initial servo pressure change followed by a gradually decreasing pressure change when the flapper is operated to close off port 90 for closing control valve 30.
Therefore, though valve actuator 35 requires a par-ticular steady state servo fluid pressure drop to (~ Pb) to adjust the valve 30 to effect a particular steady state temperature change in duct 15, the initial pressure (~ Pa) drop seen by valve actuator 35 is much higher than that steady state drop. Therefore, the actuator piston will be moved initially beyond that point effecting a steady state adjustment of valve 30 and will then approach the steady state point as the pressures within branch 95 and chamber 140 equalize. Thus it will be appreciated that this rapid and extensive actuation of valve 30 compen-sates to a degree for the inherent delay in the actuation of valve 30 in response to a temperature change detected by bimetallic member 55. This "lead" compensating char-acteristic of the system of the present invention, is par-ticularly beneficial when the system is called upon to adju8t the fan airflow in response to compressor bleed air temperature variations of short duration. Such "slugs"
of compressor bleed air would, in prior art mechanical or pneumatic systems, be dealt with by a gradual position-ing of the fan air control valve in response to a gradual increase in pressure change within the servo fluid duct.
Thus, such a slug could completely traverse duct 15 be-tween cooler 25 and the aircraft supply system before the system responds to the temperature change. However, with the present invention, such a short term discontinuity is ~5~71 met by a rapid and extensive adjustment of valve 30 thereby effectively altering the flow of fan bleed air to compensate for the varying temperature slug of compressor bleed air.
While in the preferred embodiment, a chamber 140 is provided to effect a continuous decrease in the change in pressure of the servo fluid, it will be understood that various other means of effecting such decrease in servo pressure change with time may be employed. By way of example, a separate supply of servo fluid adapted to bleed into duct 45 upon actuation of flapper 100 may be employed. It will be understood by those skilled in the art that various other modifications may be made to the embodiment shown in the drawings without departing from the invention and it is intended by the appended claims to cover such modifications as fall within the true spirit and scope of this invention.
BACKGROUND OF THE INVENTION
Field of the Invention - This invention relates to -systems for providing a fluid of a select temperature by mixing of two fluids of differing temperatures or by dis-position of such fluids in mutual heat transfer relation-ship and more particularly to such a system for use in supplying bleed air of a particular temperature from a gas turbine engine.
Description of the Prior Art - It is well known to air-condition aircraft cabins and power various aircraft subsystems with air bled from the aircraft's propulsion system. In air-conditioning the cabin of a gas turbine engine powered aircraft, it has been the practice to sup-ply the cabin with air bled from the compressor section of the engine, such air being cooled to the desired tempera-ture by mixture or mutual heat transfer with cooler air supplied by the engine's fan. Inasmuch as differing engine operating conditions cause variations in the tem-perature of the compressor bleed air, systems which moni-tor the temperature of the bleed air and cool the bleed air with a controlled flow of cooler fan air are necessitated.
Such systems have in the past been of two general types.
The first type as exemplified by the systems disclosed in U. S. Patents Nos. 3,441,213 and 3,537,644 each assigned to the assignee of the present invention, generally com-prises a pneumatic temperature sensor controlling a pneu-matic fan air modulating or control valve. While such pneumatic temperature sensors exhibit fairly accurate steady state response, it has been found that the transient performance of such sensors could be improved upon. While ~15~4~1 certain fast-acting pneumatic or mechanical temperature sensing transducers have been proposed, the accuracy of such sensing devices has been found inadequate for air-craft cabin air-conditioning systems.
Other proposed fluid temperature control systems such as that shown in U. S. Patent No. 2,919,859 to Krueger employ electrical temperature sensors, and con-trols, and, while such systems may exhibit both adequate steady state accuracy and rapid transient response, they require the disposition of rather delicate electrical sensors and connectors in the hostile environmer.t of the gas turbine engine and therefore are subject to damage from heat and/or vibration resulting in poor system reliability.
It is therefore an object of the present invention to provide a fluid temperature control system which over-comes the deficiencies of the prior art.
It is another object of the present invention to pro-vide such a fluid temperature control system of enhanced steady state accuracy.
It i9 another object of the present invention to pro-vide a fluid temperature control system which responds rapidly to sudden changes in inlet fluid temperature.
It is another object of the present invention to provide a fluid temperature control system which employs no electrical components.
It is another object of the present invention to provide such a fluid temperature control system of en-hanced reliability.
~lS2471 SUMMARY OF TEIE INVENTION
These and other objects which will become more readily apparent from the following detailed description taken in connection with the accompanying drawings, are achieved by the fluid temperature control system of the present invention in which a first fluid is either warmed or cooled by a controlled flow of a second fluid to achieve an outlet fluid flow at a preselected temperature. The flow rate of the second fluid is controlled by a modulation or control valve set by an actuator responsive to the pressure of a supply or servo fluid. The temperature of the outlet fluid supplied by the system of the present invention is continuously monitored by a temperature sensing means oper-atively connected to means which continually adjusts the servo fluid pressure in response to the output of the temper-ature sensing means. The servo fluid pressure is adjusted such that the change of pressure from that of the prior steady stat~ condition is initially great, diminishing with time to a ~maller Qteady state value. This initial servo fluid pr~ssure change in xesponse to the temperature change detected by the temperature senqing means causes the modulation valve actuator to respond quickly to any transient fluid temperature fluctuations.
In accordance with a particular embodiment of the invention there is provided a system for controlling the fluid supply temperature of a first fluid flowing through a first duct by disposition of the first fluid in heat transfer relationship with a second fluid flowing through a second duct at a temperature different from that of the first fluid.
The system comprises a valve disposed in the second duct for regulating the flow of fluid therethrough and an actuator ~ 4 -11524~1 - operatively connected to the valve for the modulation thereof.
The actuator communicates with and is responsive to the pressure of a supply of servo fluid. The system further com-prises means for adjusting the pressure of the servo fluid in response to the supply temperature of the first fluid thereby effecting the operation of the actuator and the modulation of the valve. The means adjusts the servo fluid pressure such that the change of the servo fluid pressure from steady state diminishes with time from the initiation of the servo fluid pressure adjustment from an initial greater value to a subsequent lesser steady state value thereby enhancing the transient response of the control system.
In accordance with a further embodiment of the invention there is provided a system for controlling the fluid supply temperature of a first fluid flowing through a first duct by disposition of the first fluid in heat transfer xelationship with a second fluid flowing through a second duct. ~he system comprises a valve disposed in the second duct for regulating the flow of fluid therethrough and an actuator for modulating the valve in response to the pressure of a primary supply of servo fluid with which the actuator communicates. Means are provided for controlling fluid pressure in the primary servo fluid supply in response to the temperature of the first fluid thereby selectively activating the actuator. A secondary servo fluid supply communicates with the primary servo fluid supply through a flow restrictor whereby initial adjustments in fluid pressure in the primary servo fluid supply from a steady state condition are damped by delayed servo fluid pressure equalization between the primary and secondary supplies.
~- 4a -. ~
BRIEF DESCRIPTION OF THE DRAWINGS
. _ Figure 1 is a schematic illustration of the fluid temperature control system of the present invention.
Figure 2 is a plot of the time change in servo system fluid pressure for a sudden change in supply fluid temperature.
- 4b -~SZ47~
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, the fluid temperature control system of the present invention is shown generally at 10. The system controls the temperature of a first fluid flowing through a first duct 15 by either mixing that fluid with a second fluid at a different temperature flowing through a second duct 20 or by the disposition of the two fluids in mutual heat transfer relation to achieve the desired temperature in the resulting supply fluid flow-ing through a third duct 25. The system of the present invention is particularly useful for Rupplying air at a predetermined temperature for cabin air-conditioning and thermal anti-icing of a gas turbine engine powered air-craft. When so employed, the first fluid in first conduit 15 may comprise air, bled from the compressor section of the gas turbine engine, while second fluid flowing throùgh second conduit 20 may comprise cooler fan a~r, the two fluids channeled through a precooler or heat exchanger 27 at the intersection of ducts 15 and 20 wherein heat from the compressor bleed air is given up to the cooler fan air.
The resulting controlled temperature fluid exit~ the ap-paratu8 to the aircraft air supply sy~tems through duct 25.
However, it will be appreciated that the temperature con-trol system of the present invention is useful wherever it is desired to control the temperature of a first fluid by either mixing that fluid with a second fluid at a differ-ent temperature or disposing the two fluids in heat trans-fer relationship to one another.
Broadly, the present invention comprises a modulating 1~5i247J.
or throttle valve 30 operated by valve actuator 35 respon-sive to the pressure of a supply of servo fluid 40 which communicates with the actuator. For economy of construc-tion, the servo fluid may be obtained from a tap of one of ducts 15 or 20 by third duct 45. However, it will be appreciated that a separate source of servo fluid may be employed if so desired. The servo fluid pressure is ad-justed by means 50 responding to the output of tempera-ture responsive means 55 which continually senses the temperature of the bleed supply air. In the preferred embodiment, the temperature responsive means comprises a bimetallic element which changes length in response to exposure to varying temperatures. However, it will be understood that any of various other temperature sensors may be employed without departing from this invention. A
change in the temperature of the bleed air i8 therefore sensed by means 55 which actuates means S0 to adjust the ~ervo fluid pressure. The adjusted servo fluid pressure, i5 ~en~ed by actuator 35 responding to this adjusted pres~ure by actuation of valve 30 which adjusts the flow rate of fan air to mixing chamber or heat exchanger 27 thereby elevating or depressing the temperature of the compressor bleed air to the desired value.
Valve 30 may be of any known varieties of flow con-trol valves depending of course on the nature of the fluid controlled thereby. In the preferred embodiment, where for example the valve is employed to control the flow rate of fan air, valve 30 is preferably of the butterfly variety, the plate or valve element being connected to actuator 35 by means of any suitable linkage 60.
1~5~71 Likewise, actuator 35 may be of any of a number of known varieties depending on the nature of the actuated valve and the type of ser~o fluid employed therewith.
As shown, the actuator comprises a housing 65 enclosing a diaphragm piston 70 biased toward the upper end of servo fluid chamber 75 by spring 80. A connecting rod 85 connects the piston to linkage 60 and valve 30. In operation, the spring urges the diaphragm piston in a valve opening direction, the piston being urged in an opposite direction to close valve 30 in response to servo fluid pressure in chamber 75.
Means 50 for adjusting the servo fluid pressure in response to an input from temperature sensing means 55 comprises a fixed orifice 91 in duct 45 and an orifice or port 90 in the end of branch line 95 in communication with conduit 45. The effective area of port 90 is adjusted between totally open and totally closed conditions in response to the temperature of engine bleed air in conduit 15 by means of a closure member or flapper 100 fixed to or integrally comprising a lever 105 pivotally connected to a stationary mount at 110. The end of lever 105 op-posite that which adjoins flapper 100 is connected to a counterbalance spring 115 fîxedly mounted to a stationary surface 120 at 125. Thus, it will be seen that the spring 115 . disposed between lever 105 and fixed mount 125 i8 compressed, maintaining the equilibrium of the lever and flapper in conjunction with spring 116 when the flapper is exposed to positive servo fluid pressure through port 90. Spring 116 transmits a driving force to the lever, from bimetallic element 55 connected to the spring by way of bellcrank 130 pivotally connected to tempexature xe-sponsive means 55 at one end thereof and at the other end thereof to shaft 135 which is in turn connected to spring 11~ at an end thereof opposite that connected to lever 105.
It will be seen then, that the fluid temperature con-trol system of the present invention describes a single feedback loop control circuit wherein bimetallic element 55 when actuated by an error in air temperature within duct 25 changes length transmitting a signal to lever 105 via bellcrank 130, shaft 135 and spring 116. This signal results in a force change on the lever thereby causing the flapper to ad~ust the effective area of port 90 until a balancing pressure force change on the lever is produced.
This adjustment in servo fluid pressure within duct 45 and actuator chamber 75 activates actuator 35 which reposi-tions valve 30. This repositioning, adjus~ the flow rate of fluid through duct 20 to correct the sen~ed temperature error within duct 15.
It will be appreciated that the ~ignal provided by a mechanical temperature ~ensor such as bimetallic element 55 or an equivalent pneumatic temperature actuator lags in time the temperature variation which causes the sensor to initiate such a ~ignal. ~o compen~ate for such a time lag, the temperature control system of the present inven-tion is provided with a chamber or secondary servo fluid supply 140 in fluid communication with branch 95 of servo fluid duct 45 through a flow restrictor or orifice 145.
One wall of chamber 140 comprises a diaphragm 150 which is connected to lever 105 by link 155. In steady state, ~5;~
the fluid communication of chamber 140 with duct 45 ef-fects an equalization of servo fluid pressure within those members. However, the restrictive properties of orifice 145 and the compressibility imparted to chamber 140 by diaphragm 150 cause equalization of servo fluid pressures in duct 45 and chamber 140 to lag an adjustment of servo fluid pressure in actuator chamber 75 when spring 116 is compressed by a change in sensed temperature.
Referring to Figs. 1 and 2 it will be seen that a change in force applied to lever 105 by spring 116 at time tl, in response to a step error in compressor bleed air temperature initially causes the flapper to open thereby causing an immediate drop in servo fluid pressure in duct 45 and actuator chamber 75 from Pl to P2. As the servo fluid pressure in chamber 75 decreases, a pressure dif-ferential is formed across orifice 145, causing servo fluid flow from chamber 140, through orifice 145 thereby decreasing the pressure in chamber 140. This causes the control lever to gradually reclose the flapper 100 thereby increasing the pressure in chamber 75 and duct 40 to P3.
Th~s~ it will be appreciated that upon a step change in spring force 116 the initial signal presRure change in duct 45 (a Pa) is proportional to the product of the change in loading on lever 105 from actuation of the bimetallic element and the inverse of the surface area of that por-tion of the flapper in registry with port 90. However in a steady state conditi,on, the change in servo fluid pres-sure ( ~Pb) from the previous steady state condition is significantly less, being proportional to the product of the force change on the lever and the inverse of the sum of the flapper and diaphragm areas. The system of the 115~471 present invention operates similarly, i.e., yielding a large initial servo pressure change followed by a gradually decreasing pressure change when the flapper is operated to close off port 90 for closing control valve 30.
Therefore, though valve actuator 35 requires a par-ticular steady state servo fluid pressure drop to (~ Pb) to adjust the valve 30 to effect a particular steady state temperature change in duct 15, the initial pressure (~ Pa) drop seen by valve actuator 35 is much higher than that steady state drop. Therefore, the actuator piston will be moved initially beyond that point effecting a steady state adjustment of valve 30 and will then approach the steady state point as the pressures within branch 95 and chamber 140 equalize. Thus it will be appreciated that this rapid and extensive actuation of valve 30 compen-sates to a degree for the inherent delay in the actuation of valve 30 in response to a temperature change detected by bimetallic member 55. This "lead" compensating char-acteristic of the system of the present invention, is par-ticularly beneficial when the system is called upon to adju8t the fan airflow in response to compressor bleed air temperature variations of short duration. Such "slugs"
of compressor bleed air would, in prior art mechanical or pneumatic systems, be dealt with by a gradual position-ing of the fan air control valve in response to a gradual increase in pressure change within the servo fluid duct.
Thus, such a slug could completely traverse duct 15 be-tween cooler 25 and the aircraft supply system before the system responds to the temperature change. However, with the present invention, such a short term discontinuity is ~5~71 met by a rapid and extensive adjustment of valve 30 thereby effectively altering the flow of fan bleed air to compensate for the varying temperature slug of compressor bleed air.
While in the preferred embodiment, a chamber 140 is provided to effect a continuous decrease in the change in pressure of the servo fluid, it will be understood that various other means of effecting such decrease in servo pressure change with time may be employed. By way of example, a separate supply of servo fluid adapted to bleed into duct 45 upon actuation of flapper 100 may be employed. It will be understood by those skilled in the art that various other modifications may be made to the embodiment shown in the drawings without departing from the invention and it is intended by the appended claims to cover such modifications as fall within the true spirit and scope of this invention.
Claims (12)
1. A system for controlling the fluid supply tem-perature of a first fluid flowing through a first duct by disposition of said first fluid in heat transfer relation-ship with a second fluid flowing through a second duct at a temperature different from that of said first fluid, said system comprising a valve disposed in said second duct for regulating the flow of fluid therethrough, an actuator operatively connected to said valve for the modulation thereof, said actuator communicating with and being responsive to the pressure of a supply of servo fluid, said system further comprising means for adjusting the pressure of said servo fluid in response to the sup-ply temperature of said first fluid thereby effecting the operation of said actuator and the modulation of said valve, said means adjusting said servo fluid pressure such that the change of said servo fluid pressure from steady state diminishes with time from the initiation of said servo fluid pressure adjustment from an initial greater value to a subsequent lesser steady state value thereby enhancing the transient response of said control system.
2. A temperature control system according to claim 1 wherein said servo fluid pressure adjusting means com-prises a port in said servo fluid supply, closure means for selectively adjusting the effective area of said port thereby adjusting said servo fluid supply pressure in re-sponse to a signal from temperature responsive means dis-posed in said first duct, and a chamber in fluid communi-cation with said servo fluid supply, said closure means being connected to said chamber and said chamber communicating with said servo fluid supply such that said closure means effects a transitory adjustment in supply servo fluid pressure followed by a corresponding change in said chamber servo fluid pressure, compensating for said supply servo fluid pressure adjustment, and effect-ing a diminution of said supply servo fluid pressure adjustment.
3. A temperature control system according to claim 2 wherein said servo fluid supply comprises a third duct communicating with one of said first and second ducts whereby said servo fluid comprises one of said first and second fluids.
4. A temperature control system according to claim 2 wherein said servo fluid supply communicates with said chamber through a flow restrictor and wherein said closure member comprises a pivotable lever, a first por-tion of which is selectively disposed in area adjusting relation to said outlet port and a second portion of which is connected to a diaphragm, said diaphragm compris-ing a wall portion of said chamber whereby a servo fluid pressure change within said chamber effects a correspond-ing change in loading of said lever for maintenance of an adjusted steady state servo fluid pressure.
5. A temperature control system according to claim 4 wherein said temperature responsive means comprises a bimetallic member, said lever being driven from a third portion thereof by said bimetallic member and being pivot-able about a location thereon between said third portion and one of said first and second portions.
6. A temperature control means according to claim 5 and further including a counterbalance spring engaging said lever at said third portion thereof, said spring maintaining the equilibrium of said lever against loading of said lever by said bimetallic members and said servo fluid pressure.
7. A system for controlling the fluid supply tempera-ture of a first fluid flowing through a first duct by dis-position of said first fluid in heat transfer relationship with a second fluid flowing through a second duct, said system comprising a valve disposed in said second duct for regulating the flow of fluid therethrough, an ac-tuator for modulating said valve in response to the pres-sure of a primary supply of servo fluid with which said actuator communicates, means for controlling fluid pres-sure in said primary servo fluid supply in response to the temperature of said first fluid thereby selectively activating said actuator and a secondary servo fluid sup-ply communicating with said primary servo fluid supply through a flow restrictor whereby initial adjustments in fluid pressure in said primary servo fluid supply from a steady state condition are damped by delayed servo fluid pressure equalization between said primary and secondary supplies.
8. A system according to claim 7 wherein said means for controlling the pressure of said servo fluid comprises a port in said primary servo fluid supply and a closure member adapted to selectively adjust the ef-fective area of said port in response to said first fluid temperature thereby adjusting said supply servo fluid pressure and wherein said secondary servo fluid supply comprises a chamber opening into said primary servo fluid supply, said chamber at a wall portion thereof being con-nected to said closure member such that servo fluid pres-sure change within said chamber effects a corresponding change in loading of said lever for maintenance of an ad-justed steady state servo fluid pressure.
9. A temperature responsive control system accord-ing to claim 8 wherein said primary servo fluid supply comprises a third duct communicating with one of said first and second ducts whereby said servo fluid comprises one of said first and second fluids.
10. A temperature responsive control system accord-ing to claim 8 wherein said primary servo fluid supply com-municates with said chamber through a flow restriction and wherein said closure member comprises a pivotable lever, a first portion of which is selectively disposed in area adjusting relation to said outlet port and a second por-tion of which is connected to said chamber at a diaphragm comprising a portion of said chamber wall whereby servo fluid pressure change in said chamber effects a corre-sponding change in loading of said lever for maintenance of an adjusted steady state servo fluid pressure.
11. A temperature responsive control system accord-ing to claim 10 wherein said first fluid temperature is detected by a bimetallic member, said lever being pivot-ally driven from a third portion thereof by said bimetal-lic member, about a location on said lever between said third portion and one of said first and second portions.
12. A temperature responsive control means accord-ing to claim 11 and further including a counterbalance spring engaging said lever at said third portion thereof, said spring maintaining the equilibrium of said lever against forces applied thereto by said bimetallic member and said servo fluid pressure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9697079A | 1979-11-23 | 1979-11-23 | |
| US096,970 | 1979-11-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1152471A true CA1152471A (en) | 1983-08-23 |
Family
ID=22260017
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000364717A Expired CA1152471A (en) | 1979-11-23 | 1980-11-14 | Fluid temperature control system |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5694409A (en) |
| CA (1) | CA1152471A (en) |
| DE (1) | DE3044124A1 (en) |
| FR (1) | FR2470408A1 (en) |
| GB (1) | GB2065330B (en) |
| IL (1) | IL61519A (en) |
| IT (1) | IT1134399B (en) |
| NO (1) | NO153470C (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2919859A (en) * | 1956-09-04 | 1960-01-05 | Rudolph E Krueger | Temperature control system |
| US3441213A (en) * | 1968-01-23 | 1969-04-29 | United Aircraft Corp | Pneumatic air temperature control system |
| US3537644A (en) * | 1968-08-12 | 1970-11-03 | United Aircraft Corp | Combined pressure and temperature regulator |
-
1980
- 1980-11-14 CA CA000364717A patent/CA1152471A/en not_active Expired
- 1980-11-18 GB GB8036992A patent/GB2065330B/en not_active Expired
- 1980-11-19 IL IL61519A patent/IL61519A/en unknown
- 1980-11-21 FR FR8024727A patent/FR2470408A1/en active Granted
- 1980-11-21 IT IT26145/80A patent/IT1134399B/en active
- 1980-11-21 NO NO803517A patent/NO153470C/en unknown
- 1980-11-24 DE DE19803044124 patent/DE3044124A1/en not_active Ceased
- 1980-11-25 JP JP16576980A patent/JPS5694409A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| NO803517L (en) | 1981-05-25 |
| JPS5694409A (en) | 1981-07-30 |
| GB2065330B (en) | 1983-07-06 |
| NO153470C (en) | 1986-04-02 |
| IL61519A (en) | 1985-05-31 |
| FR2470408A1 (en) | 1981-05-29 |
| IT1134399B (en) | 1986-08-13 |
| GB2065330A (en) | 1981-06-24 |
| IT8026145A0 (en) | 1980-11-21 |
| FR2470408B1 (en) | 1983-12-09 |
| JPH0147694B2 (en) | 1989-10-16 |
| NO153470B (en) | 1985-12-16 |
| DE3044124A1 (en) | 1981-06-04 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |