GB2103289A

GB2103289A - Fluid modulation apparatus

Info

Publication number: GB2103289A
Application number: GB08215932A
Authority: GB
Inventors: John Theodore Moehring
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1981-08-07
Filing date: 1982-06-01
Publication date: 1983-02-16
Also published as: IT8222714A0; JPS5847927A; DE3228678A1; FR2511081A1

Abstract

The apparatus modulates uniformly the flow of fluid through a generally annular orifice 36, e.g. in the cooling air path of a gas turbine engine, and comprises a member 24 having the orifice 36 therethrough and a valve ring 38 movable axially to open and close the orifice. The valve ring 38 may be hinged by links 48 to extensions of member 24. Additional openings in member 24 permit a minimum flow of fluid when valve ring 38 is in the closed position abutting the member. <IMAGE>

Description

SPECIFICATION Fluid modulation apparatus This invention relates to flow modulation apparatus and particularly to a new and improved apparatus for providing uniform modulation about an annular orifice of the flow of fluid through the orifice.

The capability of modulating, or varying, the amount of fluid flowing through a structure can be very advantageous. For example, a gas turbine engine operates at high temperatures, and components, such as the turbine, within the engine must be cooled in order to maintain them within acceptable temperature limits. High pressure air bled from the engine compressor is normally used for such cooling.

However, most current engines employ fixed geometry cooling airflow systems. Such a fixed geometry cooling system is sized to supply a fixed proportion of high pressure air to the engine components at all engine power settings. The amount of cooling air supplied is that which is required at the highest engine power setting. At lower engine power settings, the temperature within the engine is correspondingly lower and less high pressure air is needed for cooling, yet the fixed geometry cooling system continues to supply the proportion of cooling air required at the highest power setting. The excess high pressure cooling air is wasted and engine efficiency is thereby decreased, since otherwise the air could have been supplied to the engine combustor and expanded through the turbine to produce work.Thus, a nonmodulating cooling air system can reduce engine efficiency and cannot exploit the full fuel savings potential over the operating power range.

Air modulation apparatus have been developed for use in engines to improve engine efficiency. When such a typical apparatus is employed to moduiate air flowing through an annular orifice within the cooling air circuit, however, the modulation about the annular orifice is nonuniform, that is, modulation is accomplished by blocking off arcuate segments of the orifice rather than the entire orifice. As a consequence, portions of the structure adjacent the unblocked segments of the orifice are cooled by the air flowing through the orifice more than the portions adjacent the blocked segments, resulting in thermal discontinuities and thermal stress.

Such thermal stress resulting from nonuniform modulation can lead to structural failure and shortened life.

Another difficulty encountered in employing modulation systems, particularly in gas turbine engines, involves the location of the modulation apparatus. Where the cooling air which is modulated is drawn from an internal flowpath, such as from an engine compressor, and transported through a cooling air flowpath inside of the engine, the modulation of the cooling air is difficult because of the inaccessibility of the cooling air flowpath. Furthermore, if it is desired to modify an existing unmodulated engine by adding a modulation apparatus to its internal cooling air flowpath, such modification may involve expensive redesign and rebuilding in order to accommodate the modulation apparatus.

Yet another problem encountered in modulation systems is reliability. If a modulation system were to fail in a closed position, serious overheating of engine components could result when engine power, and thus engine temperature, increases. Some current modulation systems include fail safe means which are built into the system actuator. Such fail-safe means provide overheat protection as long as the actuator is connected to the modulation valve. Under certain failure conditions, however, such as a disconnection of the actuator from the valve, fail-safe protection would be lost.

In view of the above-mentioned problems, it is therefore the object of the present invention to improve the efficiency of a gas turbine engine by incorporating therein an apparatus for modulating the amount of cooling air supplied to engine components in response to the need for such cooling air.

Another object of the present invention is to provide a modulation apparatus for modulating uniformly about an annular orifice the flow of cooling air through the orifice to thereby reduce thermal discontinuities in the structure adjacent the orifice.

Yet another object of the present invention is to provide a cooling air modulation apparatus which can be readily and inexpensively incorporated into an existing unmodulated engine.

Still another object of the present invention is to provide a cooling air modulation apparatus having fail-safe means which is inherently self-operable independently of the actuator means.

The present invention comprises an apparatus for modulating uniformly about a generally annular orifice the flow of a fluid through the orifice. The apparatus comprises a member having a generally annular orifice therethrough, a positionable valve ring which in a closed position abuts the member and covers the orifice, and which in an open position is spaced apart from the member and orifice and thereby permits a flow of fluid through the orifice, and actuating means for positioning the valve ring.

In a particular embodiment of the invention there are also included openings through the member to provide a minimum flow of fluid when the valve ring is closed. Fail-safe means can also be included for positioning the valve ring to an open position in the event of predetermined conditions.

This invention will be better understood from the following description taken in conjuction with the accompanying drawings, wherein: Figure 1 is a cross-sectional view of the upper half of a portion of a gas turbine engine incorporating features of the present invention.

Figure 2 is an enlarged view of the valve ring arrangement shown in cross section in Fig. 1.

Figure 3 is a top view of the valve ring arrangement taken along line 3-3 of Fig. 2.

Figure 4 is a rear view of the valve ring arrangement taken along line 4-4 of Fig. 2.

Turning now to a consideration of the drawing, and in particular to Fig. 1, there is shown a portion of the upper half of a gas turbine engine incorporating a configuration of the present invention.

Fig. 1 shows an annular combustor 10.

Radially outward of the combustor 10 is an annular outer conduit 1 2 and radially inward of the combustor 10 is an annular inner conduit 14. By "radially" is meant in a direction generally perpendicular to the engine longitudinal axis, depicted by the dashed line 1 5. A portion of the high pressure air exiting the engine compressor (not shown) flows into the combustor 10 wherein it is mixed with fuel and burned. Most of the remainder of the high pressure air flows through the outer and inner conduits 1 2 and 14, respectively, and is employed for cooling the combustor walls and other engine components.

One arrangement for cooling engine components, such as the turbine (not shown) located downstream of the combustor 10, is to divert some of the high pressure air from the inner conduit 14 through a hole 1 6 in the combustor inner casing 1 8. That high pressure air then flows through a cooling air passage 20 to the component to be cooled. The cooling air passage 20 can be defined in any appropriate manner. For example, in Fig. 1, the portion of the cooling air passage shown is defined by a first compartment 22, bounded by the combustor inner casing 18 and the pressure seal 24, a second compartment 26, bounded by the nozzle support 28, seat support 30 and the pressure seal 24, and a third compartment 32, bounded by the seal 33 and the seal support 30.The cooling air passage 20 is further defined by additional compartments (not shown) ieading to the component to be cooled. The first compartment 22, second compartment 26, third compartment 32 and additional compartments are each in fluid communication with its adjacent compartments through a plurality of holes or orifices such that the high pressure cooling air can flow through the compartments to the engine components to be cooled. For example, the combustor inner casing 1 8 and the seal support 30 each includes holes 16 and 34, respectively, therein, while the pressure seal 24, which is preferably annular, includes a generally annular orifice 36 therethrough. The annular orifice 36 as shown in Fig. 4 is configured as comprising a plurality of circumferentially spaced apertures 37 which collectively define the annular orifice 36.The annular orifice 36 could alternatively comprise a single continuous orifice or it could comprise a plurality of apertures 37 having shapes different from that shown in Fig. 4. Although for purposes of simplification and clarity reference will hereinafter be made simply to a "generally annular orifice 36," it is to be understood that such an orifice could comprise any of the above-described configurations. Additionally, since the annular orifice 36 could be located in any suitable member within the cooling air passage 20 other than the pressure seal 24 as well, hereinafter the orifice 36 will simply be described as being included in a "member 24." The present invention comprises an apparatus for modulating uniformly about a generally annular orifice, such as the orifice 36, the flow of fluid, such as high pressure cooling air, through the orifice.Modulation of the amount of cooling air through the orifice 36 permits varying of the amount of cooling air flowing through the cooling air passage 20 to engine components. At low or medium power settings when engine components require less cooling, the cooling airflow can be modulated at the orifice 36 to supply only the amount of cooling air needed. Thus, the excess high pressure air not needed for cooling at low or medium power settings, which in an unmodulated engine would have been wasted high pressure air, is, in an engine incorporating the present invention, available to be supplied to the combustor. As a result, the compressor need not work as hard and engine efficiency is improved.Although this invention will be described in terms of its modulating high pressure cooling air, it is to be understood that it can also be successfully employed to modulate any other fluid and in environments other than cooling air passages.

Referring now to Fig. 2, which is an en- larged view of a portion of Fig. 1, the present invention comprises a member 24 which includes a generally annular orifice 36 therethrough, a positionable valve ring 38 and actuating means for the valve ring.

The member 24 is a stationary structure which can be attached, as by bolting, to any other stationary structure, such as to the combustor inner casing 1 8. Preferably, the member 24 also includes openings 40 therethrough which are always open, being disposed such that when the valve ring 38 is in a closed position, as will be described hereinafter, the openings 40 enable a minimum flow of cooling air through the member 24 and thus through the cooling passage 20.

Alternatively, the opening 40 could be located elsewhere, such as, for example, in the valve ring 38 itself.

The positionable, preferably one piece, valve ring 38 is arranged such that when it is in a closed position, it abuts the member 24 and covers the orifice 36, thereby blocking the flow of cooling air through the orifice 36.

When the valve ring 38 is in an open position, it is spaced apart from the member 24 and thereby permits a flow of cooling air through the orifice 36. The amount of cooling air which flows through the orifice 36 when th.e valve ring 38 is in the open position is dependent upon the dimensions of the orifice 36 and is predetermined by the degree of cooling required at high engine power settings. The valve ring 38 can also be positioned to any intermediate position, as it is in Fig. 2, between the open and closed position when an intermediate amount of cooling air is required.

As can best be seen in Fig. 2, the face of the valve ring 38 which abuts the member 24 adjacent the orifice 36 is sized radially such that it completely covers the orifice 36 when in the closed position. The valve ring 38 is also sized circumferentially so as to correspond to the annular shape of the orifice 36.

A primary advantage of the present invention is that it permits uniform modulation about the annular orifice 36 of the cooling air flowing through the orifice. By "uniform modulation" is meant that substantially the entire orifice circumferentially is blocked off when the valve ring 38 is closed and substantially the entire orifice circumferentially is uncovered and is equally spaced from the face of the valve ring 38 when the valve ring is in an intermediate or an open position. Such uniform modulation substantially reduces the thermal stress problems encountered in previous nonuniform modulation systems in which arcuate segments of an annular orifice were blocked off while other segments were not.

Such prior art arrangements resulted in some of the portions of the structure adjacent the orifice being cooled by the air flowing through the orifice more than other portions, causing thermal discontinuities and thermal stress.

Uniform modulation of the cooling air is accomplished by axially translating the entire valve ring 38 away from or toward the orifice 36 between the closed and open position. By "axially" is meant in a direction parallel to the engine longitudinal axis 1 5.

One arrangement for permitting the axial translation, and thus opening and closing, of the valve ring 38 is shown in Figs. 2 and 3.

The valve ring 38 includes generally axially extending flanges 44 which may be, but are not necessarily, circumferentially continuous around the valve ring 38. The member 24 also includes generally axially extending flanges 46 which likewise may be, but are not necessarily, circumferentially continuous around the member 24. A plurality of links 48 connect the valve ring 38 with the member 24. Preferably, one end of each link 48 is connected with the flanges 44 of the valve ring 38 and the other end of each link 48 is connected with the flanges 46 of the member 24. The connection between each of the links 48 and the flanges 44 and 46 can be accomplished with pins 50 and 52, respectively, inserted through holes in the links and flanges, one end of each pin including an enlarged head portion.The arrangement shown in Fig. 2 provides positive capture of the pins 50 and 52 as well as of the links 48 to prevent them from becoming dislodged into the cooling flowpath. As can be seen in Fig.

2, the flanges 46 extending from the member 24 prevent radial movement of the pins 50 in the valve ring 38. A keeper ring 54 can be attached to the member 24 such that it extends over the head portion of the pin 52 to thereby retain the pin.

When the member 24 includes flanges 46 and a keeper ring 54 extending therefrom, the flanges and keeper rings include holes 56 and 58, respectively, therethrough such that the cooling air flowing through the orifice 36 can continue to flow into the second compartment 26 and thus through the cooling air passage 20.

As can best be seen in Figs. 3 and 4, the links 48 are arranged such that when rotational movement relative to the member 24 is imparted to the valve ring 38, the links cause the valve ring 38 also to move axially away from or toward the member 24 and the orifice 36.

The present invention includes actuating means for positioning the valve ring 38. Preferably, the actuation means effects rotational movement of the valve ring 38 relative to the member 24, thereby permitting the arrangement of links 48 to also effect axial movement of the valve ring, as described earlier. Numerous arrangements of actuation means can be successfully employed with the present invention. The actuation means to be described hereinafter, however, is particularly advantageous when it is desired to locate the actuator portion of the actuation means at a distance from the valve ring 38. For example, it may be desirable to locate the actuator portion outside of the cooling air passage 20 in order to reduce blockage of the flow of high pressure cooling air through the cooling air passage.Further, it may be desirable to locate the actuator portion on the engine exterior, adjacent associated control components and piping for ease of maintenance and periodic inspection.

As can be seen in Fig. 1, the actuating means includes an actuator 60 and at least one connecting arm for connecting the actuator 60 to the valve ring 38. More specifically, in the configuration shown in Fig. 1, the output rod 62 of the actuator 60 is connected to a first connecting arm 64 and the connecting arm 64 is connected to one end of a first bellcrank 66. The first bellcrank 66 is connected at a pivot point 68 to a bracket 70 and transforms the generally radial motion of the first connecting arm 64 into generally axial motion of the second connecting arm 72, to which the first bell crank 66 is connected at its other end. As can be seen in Fig.

1, 2 and 3, the second connecting arm 72 is connected to one end of a second bellcrank 74. The second bellcrank 74, which is mounted at a pivot point 76 to a bracket 78, includes another end which extends through the orifice 36 and which is connected to the valve ring 38. If desired and as is shown in Fig. 3, a spherical ball bearing 80 can be employed to connect the second bellcrank 74 to the valve ring 38. The generally axial motion of the second connecting arm 72 is transformed by the second bellcrank 74 into rotational motion imparted to the valve ring 38, thereby, through the arrangement of links 48, causing the valve ring 38 to move axially between the open and closed positions.

A particular advantage of the present invention is that it can be readily incorporated into an existing unmodulated engine. As can be seen in Figs. 1 and 2, the brackets 70 and 78 which support the bellcranks 66 and 74, respectively, are bolted to the engine structure at locations where the bolts 79 and 81 are already employed for other purposes. Likewise, the keeper ring 54 and the member 24, which supports the valve ring 38 and links 48, are bolted to the engine structure using the bolt 81. Further the actuator 60 can be mounted on a hollow strut 83 at the downstream end of the compressor, while the output rod 62 and the first connecting arm 64 can be disposed so as to extend through the hollow strut 83. Thus, only relatively minor changes are required to the structure of an unmodulated engine in order to retrofit it to accept the present invention.Of course, in the case of a newly designed engine, the present invention can be included as an integral part of the design.

The actuator 60 of the actuation means can be any type actuator which imparts the desired motion through the connecting arms to the valve ring 38. For example, the actuator 60 shown in Fig. 1 is a pneumatically operated actuator which receives high pressure air from any available source, such as from the engine compressor. The actuator 60 includes a translatable piston 82 from which the output rod 62 extends. Preferably, the piston 82 is double faced and the actuator 60 includes an extend pressure port 84 and a retract pressure port 86 for supplying high pressure air to their respective faces of the piston 82.

Such an arrangement comprises a vibrationreducing pressure port arrangement because, with an appropriate valve, a difference in air pressure is exerted across the piston 82 at all times. As a result, the piston 82, output rod 62, first and second connecting arms 62 and 74, first and second bellcranks 66 and 74 and the valve ring 38 are positively loaded at all times. The positive loading reduces dithering or relative vibratory motion between components and therefore reduces wear and prolongs component life.

The present invention can include one or a plurality of actuators and associated sets of connecting arms and bellcranks. A plurality of actuators may be desirable to assure proper rotational motion of larger valve rings 38.

Furthermore, for example, and as was indicated earlier, it may be desirable that the actuator means be arranged as is shown in Fig. 1, whereby the actuator 60 is disposed outside of the cooling air passage 20. Such an arrangement reduces interference with the cooling air flowing through the cooling air passage 20 as well as simplifying installation of the present invention. Also, mounting actuators on the engine exterior adjacent associated control components and actuator piping is desirable for ease of maintenance and inspection access.

Preferably, the actuating means is configured to position the valve ring 38 in response to predetermined conditions. Such a predetermined condition could be, for example, turbine inlet temperature of the engine.

When the turbine inlet temperature is high, the turbine requires a greater amount of cooling air and the actuator 60, therefore, positions the valve ring 38 toward the open position. When the turbine inlet temperature is lower, the turbine requires less cooling air and the actuator 60 positions the valve ring 38 towards the closed position.

Such predetermined conditions can be received as an input signal by a controller 88.

Based on that input, the controller causes the actuator 60 to position the valve ring 38.

When the actuator 60 is pneumatically operated as is shown in Fig. 1, the controller 88 sends a signal to the valve 90 to supply the appropriate amount of high pressure air to the extend pressure port 84 and the retract pressure port 86.

The actuating means can include safety features. For example, it can include valve ring position verification means to monitor and annunciate the position of the actuator 60 and thus of the valve ring 38. One arrangement for the verification means is shown in Fig. 1 and comprises a signal valve spool 92 affixed on an integral moving stem extension 94 of the output rod 62 of the piston 82.

High pressure air is supplied through an orifice 96 to an inlet port 98 by means of a supply line 99. The high pressure air flows through the interior of the actuator 60 around the signal valve spool 92 and exits through a vent 1 00. Between the orifice 96 and the inlet port 98 is a pressure sensor 102 which senses the back pressure in the supply line 99. The back pressure in the supply line 99 will vary based upon how much of the inlet port 98 is covered by the signal valve spool 92, which in turn indicates the position of the signal valve spool and thus the position of the valve ring 38. The pressure sensor 102 then sends its pressure information as a feedback input to the controller 88 and, if desired, to an annunciator for position verification.

.The present invention preferably incorporates fail-safe means whereby the valve link 38 is positioned to an open position in the event of predetermined conditions to thereby prevent overheating of engine components.

The configuration shown in Figs. 1 and 2 discloses one example of such fail-safe means.

The fail-safe means shown comprises the arrangement of the valve ring 38 with respect to the member 24 and the orifice 36. Specifically, the valve ring 38 is disposed on the downstream side of the orifice 36, that is, the side of the orifice 36 from which the high pressure cooling air exits the orifice 36, and it is connected directly to the links 48 which enable the valve ring to move axially. If a predetermined condition occurs, such as loss of high pressure air to the actuator 60 causing actuator failure, or a disconnection of the actuator 60 or the connecting arms 64 or 72 from the valve ring 38, the natural pressure differential across the valve ring 38 and the connecting arrangement between the valve ring and the links 48 are such that the high pressure air flowing through the orifice will blow the valve ring 38 to an open position.

Thus, the fail-safe means is preferably inherent in this embodiment and is thereby operable to open the valve ring 38 independently of the actuation means.

It is to be understood that this invention is not limited to the particular embodiment disclosed, and it is intended to cover all modifications coming within the true spirit and scope of this invention as claimed.

Claims

1. An apparatus for modulating uniformly about a generally annular orifice the flow of fluid through said orifice comprising: a) a member including said generally annular orifice therethrough; b) a positionable valve ring arranged for, when in a closed position, abutting said member and covering said orifices, thereby blocking a flow of fluid through said orifice and, when in an open position, being spaced apart from said member and from said orifice for thereby permitting a flow of fluid through said orifice; and c) actuating means for positioning said valve ring.

2. The apparatus of claim 1 wherein said member further includes openings therethrough for enabling a minimum flow of fluid through said member when said valve ring is in a closed position.

3. The apparatus of claim 2 further comprising fail-safe means for positioning said valve ring to an open position in the event of predetermined condition.

4. The apparatus of claim 3 wherein said valve ring is connected with said member through a plurality of links, said links being arranged whereby rotational movement of said valve ring relative to said member effects through said links axial movement of said valve ring between said open and said closed positions.

5. The apparatus of claim 4 wherein said actuating means is configured to selectively rotate said valve ring and thereby effect axial movement thereof between said open and closed positions.

6. The apparatus of claim 5 wherein said actuating means is configured to position said valve ring in response to predetermined conditions.

7. In a gas turbine engine including a cooling air passage therein for supplying cooling air to engine components, a portion of said cooling air passage being defined by a generally annular orifice, an apparatus for modulating uniformly about said orifice the flow of cooling air through said orifice comprising:: a) a member including said generally annular orifice therethrough; b) a positionable valve ring connected with said member through a plurality of links, said valve ring and said links being arranged whereby when in a closed position, said valve ring abuts said member and completely covers said orifice thereby blocking the flow of said air through said orifice and whereby rotational movement of said valve ring relative to said member effects through said links axial movement of said valve ring between said closed position and an open position, said valve ring when in said open position being spaced apart from said member and said orifice for thereby permitting said flow of air through said orifice; and c) actuating means for effecting rotational movement of and thereby positioning said valve ring, said actuating means including at least one actuator and at least one connecting arm for connecting each said actuator to said valve ring.

8. The apparatus of claim 7 further comprising fail-safe means for positioning said valve ring to said open position in the event of predetermined conditions.

9. The apparatus of claim 8 wherein said member includes openings therethrough for enabling a minimum flow of said air through said cooling air passage when said valve ring is in a closed position.

10. The apparatus of claim 9 wherein said actuation means is arranged whereby said actuator is disposed outside of said cooling air passage.

11. The apparatus of claim 10 wherein said actuator is pneumatically operated.

1 2. The apparatus of claim 11 wherein said actuator includes a translatable, doublefaced piston therein, motion of said piston being transmitted to said connecting arm, and wherein said actuator further includes a vibration-reducing pressure port arrangement comprising an extend pressure port and a retract pressure port for supplying air pressure difference across said piston at all times.

1 3. The apparatus of claim 10 wherein said actuating means includes at least one bellcrank having one of its end connected with said connecting arm and the other end connected with said valve ring for imparting rotational motion to said valve ring from said connecting arm.

14. The apparatus of claim 1 3 wherein said actuation means includes a plurality of actuators and connecting arms.

1 5. The apparatus of claim 14 wherein each said bellcrank is connected with said valve ring through a spherical ball bearing.

16. The apparatus of claim 7 further comprising valve ring position verification means.

1 7. The apparatus of claim 8 wherein said fail-safe means comprises the disposition of said valve ring on the downstream side of said orifice and the connection of said valve ring to said links whereby in the event of predetermined failure of said actuating means, an air pressure differential across said valve ring positions said valve ring to an open position.

1 8. The apparatus of claim 10 wherein each of said links is connected with said member through a pin inserted through holes in said member and said link, said pins having an enlarged head portion and wherein said member includes a keeper ring attachable thereto for abutting said head portion of and thereby retaining in place each of said pins.

1 9. Flow modulating apparatus substantially as hereinbefore described with reference to and as illustrated in the drawings.

20. A gas turbine substantially as hereinbefore described with reference to and as illustrated in the drawings.