CA2208801C - A bleed apparatus for a gas turbine engine - Google Patents
A bleed apparatus for a gas turbine engine Download PDFInfo
- Publication number
- CA2208801C CA2208801C CA002208801A CA2208801A CA2208801C CA 2208801 C CA2208801 C CA 2208801C CA 002208801 A CA002208801 A CA 002208801A CA 2208801 A CA2208801 A CA 2208801A CA 2208801 C CA2208801 C CA 2208801C
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- CA
- Canada
- Prior art keywords
- bleed
- gas turbine
- turbine engine
- casing
- valve means
- 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 - Lifetime
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
- F02C9/00—Controlling gas-turbine plants; Controlling fuel supply in air- breathing jet-propulsion plants
- F02C9/16—Control of working fluid flow
- F02C9/18—Control of working fluid flow by bleeding, bypassing or acting on variable working fluid interconnections between turbines or compressors or their stages
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D17/00—Regulating or controlling by varying flow
- F01D17/10—Final actuators
- F01D17/105—Final actuators by passing part of the fluid
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/02—Surge control
- F04D27/0207—Surge control by bleeding, bypassing or recycling fluids
- F04D27/0215—Arrangements therefor, e.g. bleed or by-pass valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/02—Surge control
- F04D27/0207—Surge control by bleeding, bypassing or recycling fluids
- F04D27/023—Details or means for fluid extraction
Abstract
A bleed apparatus (34) for a gas turbine engine (10) is positioned in the duct (16) between a low pressure compressor (14) and an intermediate pressure compressor (18). The bleed apparatus (34) comprises a plurality of circumferentially spaced bleed apertures (38) and a plurality of pivoted (42) bleed doors (40) which move between a fully open position and a fully closed position. Each bleed door (40) has an independent actuator (44,46) and the actuators (44,46) operate to fully close or open the bleed doors (40) in unison. Each actuator (44,46) comprises a hydraulically operated piston (46) and a cylinder (44) which ensures uniform closing and sealing and the remaining bleed doors (40) operate if one seizes. The bleed apertures (38) have radially extending side walls (72,74) which control the bleed air. The first and second walls (72,74) prevent the bleed air flowing circumferentially from the bleed aperture (38) until the bleed doors (40) have opened a predetermined amount to provide a continuously increasing bleed area as the bleed doors (40) move towards the fully open position.
Description
_ CA 02208801 1997-06-24 A BLEED APPARATUS FOR A GAS TURBINE ENGINE
The present invention relates to bleed apparatus for gas turbine engines, particularly, but not exclusively, to bleed apparatus for industrial gas turbine engines.
In industrial gas turbine engines which comprise in flow series a low pressure compressor, a core engine and a low pressure turbine directly connected to an electrical generator it is a requirement that the low pressure turbine rotate at the same speed from zero to full power. This requirement has made it necessary to provide a bleed apparatus between the low pressure compressor and the core engine in order to bleed a large amount of air from the gas turbine engine during zero power and at power levels below a predetermined level.
It is known to provide bleed apparatus between a low pressure compressor and a core engine to bleed air from the gas turbine engine during power levels below a predetermined level. These bleed apparatus comprise a plurality of circumferentially spaced bleed apertures, each one of which has a bleed valve means to pivot between a first position in which the bleed apertures are closed and a second position in which the bleed apertures are fully open. Each bleed valve means is actuated by a respective bell crank, or lever, and the bell cranks, or levers, are operated by a unison ring which is mounted coaxially of the engine on a support ring.
The bell cranks are pivotally mounted on the support ring.
However, this arrangement may suffer from the problem of~one bleed valve means, or actuating means, seizing and disabling the entire system. Additionally deflections of the unison ring may necessitate the use of bearings between the support ring and the unison ring. There may be a requirement for springs between the unison ring and the bleed valve means to ensure that all bleed valve means close after one bleed valve means closes to guarantee uniform closure of all the bleed valve means.
Accordingly the present invention seeks to provide a bleed apparatus for a gas turbine engine which overcomes the above mentioned problems.
The present invention relates to bleed apparatus for gas turbine engines, particularly, but not exclusively, to bleed apparatus for industrial gas turbine engines.
In industrial gas turbine engines which comprise in flow series a low pressure compressor, a core engine and a low pressure turbine directly connected to an electrical generator it is a requirement that the low pressure turbine rotate at the same speed from zero to full power. This requirement has made it necessary to provide a bleed apparatus between the low pressure compressor and the core engine in order to bleed a large amount of air from the gas turbine engine during zero power and at power levels below a predetermined level.
It is known to provide bleed apparatus between a low pressure compressor and a core engine to bleed air from the gas turbine engine during power levels below a predetermined level. These bleed apparatus comprise a plurality of circumferentially spaced bleed apertures, each one of which has a bleed valve means to pivot between a first position in which the bleed apertures are closed and a second position in which the bleed apertures are fully open. Each bleed valve means is actuated by a respective bell crank, or lever, and the bell cranks, or levers, are operated by a unison ring which is mounted coaxially of the engine on a support ring.
The bell cranks are pivotally mounted on the support ring.
However, this arrangement may suffer from the problem of~one bleed valve means, or actuating means, seizing and disabling the entire system. Additionally deflections of the unison ring may necessitate the use of bearings between the support ring and the unison ring. There may be a requirement for springs between the unison ring and the bleed valve means to ensure that all bleed valve means close after one bleed valve means closes to guarantee uniform closure of all the bleed valve means.
Accordingly the present invention seeks to provide a bleed apparatus for a gas turbine engine which overcomes the above mentioned problems.
Accordingly the present invention provides a gas turbine engine comprising in flow series a low pressure compressor, a core engine, and a low pressure turbine, the low pressure turbine being arranged to drive the low pressure compressor, the core engine comprising in flow series at least one compressor, combustion means and at least one turbine, the at least one turbine being arranged to drive the at least one compressor, a duct connecting the outlet of the low pressure compressor and the inlet of the at least one compressor of the core engine, the duct being defined by a casing, a bleed apparatus for bleeding air from the duct, the bleed apparatus comprising a plurality of circumferentially spaced bleed apertures extending through the casing, a plurality of bleed valve means arranged to selectively move between a first position in which the bleed apertures are closed and a second position in which the bleed apertures are fully open to allow a bleed flow from the low pressure compressor, and a plurality of independent actuating means, each independent actuating means is arranged to independently actuate one of the plurality of bleed valve means, the actuating means being arranged to actuate the plurality of bleed valve means in unison, the independent actuating means comprising ram means.
Preferably the core engine comprises in flow series an intermediate pressure compressor, a high pressure compressor, combustion means, a high pressure turbine and an intermediate pressure turbine, the intermediate pressure turbine being arranged to drive the intermediate pressure compressor, the high pressure turbine being arranged to drive the high pressure compressor.
The low pressure turbine may be arranged to drive a load.
Preferably the load is an electrical generator, a pump or a drive shaft.
Preferably each actuator means comprises a piston and cylinder. Preferably there are means to supplied fluid to the cylinders to move the pistons. Preferably there are means to supply fluid is a supply of hydraulic fluid.
Preferably the cylinders are mounted on a support ring, the support ring is mounted coaxially on the gas turbine engine.
Preferably the core engine comprises in flow series an intermediate pressure compressor, a high pressure compressor, combustion means, a high pressure turbine and an intermediate pressure turbine, the intermediate pressure turbine being arranged to drive the intermediate pressure compressor, the high pressure turbine being arranged to drive the high pressure compressor.
The low pressure turbine may be arranged to drive a load.
Preferably the load is an electrical generator, a pump or a drive shaft.
Preferably each actuator means comprises a piston and cylinder. Preferably there are means to supplied fluid to the cylinders to move the pistons. Preferably there are means to supply fluid is a supply of hydraulic fluid.
Preferably the cylinders are mounted on a support ring, the support ring is mounted coaxially on the gas turbine engine.
Preferably the bleed valve means are pivotally mounted onto the casing. Preferably each piston is pivotally connected to the respective bleed valve means.
Preferably each bleed aperture has a first side wall and a second side wall extending radially outwardly from the casing at the circumferentially spaced sides of each bleed aperture, each bleed valve means being pivotally mounted by a pivot extending between the respective first side wall and second side wall.
Preferably the first and second side walls extend the full axial length of the bleed aperture and extend a predetermined distance radially outwardly from the casing whereby the first and second walls prevent the bleed flow flowing circumferentially from the bleed aperture until the bleed valve means have opened a predetermined amount to provide a continuously increasing bleed area as the bleed valve means move towards the second position.
Preferably each bleed valve means comprises a first member and a second member, the first member is pivotally mounted onto the casing, the first member is arranged to carry the second member, the second member has an inner surface, the casing has an inner surface and an outer surface, the first member is arranged to abut the outer surface of the casing in the first position, the second member is arranged to fit in the bleed aperture and the inner surface thereof is arranged to lie flush with inner surface of the casing when in the first position.
Preferably a seal is located between the first member and the second member, the second member has a periphery, the seal extends around the periphery of the second member such that the seal abuts the outer surface of the casing around the respective bleed aperture in the first position. Preferably the seal is P
shaped in cross-section. Preferably the seal comprises rubber enclosed in a fabric.
Preferably the outer surface of the casing has chamfered edges around the respective bleed aperture.
Preferably the bleed valve means have upstream ends, the bleed valve means are pivotally mounted to the casing at their upstream ends.
Preferably each bleed aperture has a first side wall and a second side wall extending radially outwardly from the casing at the circumferentially spaced sides of each bleed aperture, each bleed valve means being pivotally mounted by a pivot extending between the respective first side wall and second side wall.
Preferably the first and second side walls extend the full axial length of the bleed aperture and extend a predetermined distance radially outwardly from the casing whereby the first and second walls prevent the bleed flow flowing circumferentially from the bleed aperture until the bleed valve means have opened a predetermined amount to provide a continuously increasing bleed area as the bleed valve means move towards the second position.
Preferably each bleed valve means comprises a first member and a second member, the first member is pivotally mounted onto the casing, the first member is arranged to carry the second member, the second member has an inner surface, the casing has an inner surface and an outer surface, the first member is arranged to abut the outer surface of the casing in the first position, the second member is arranged to fit in the bleed aperture and the inner surface thereof is arranged to lie flush with inner surface of the casing when in the first position.
Preferably a seal is located between the first member and the second member, the second member has a periphery, the seal extends around the periphery of the second member such that the seal abuts the outer surface of the casing around the respective bleed aperture in the first position. Preferably the seal is P
shaped in cross-section. Preferably the seal comprises rubber enclosed in a fabric.
Preferably the outer surface of the casing has chamfered edges around the respective bleed aperture.
Preferably the bleed valve means have upstream ends, the bleed valve means are pivotally mounted to the casing at their upstream ends.
The present invention also provides a gas turbine engine comprising in flow series a low pressure compressor, a core engine, and a low pressure turbine, the low pressure turbine being arranged to drive the low pressure compressor, the core engine comprising in flow series at least one compressor, combustion means and at least one turbine, the at least one turbine being arranged to drive the at least one compressor, a duct connecting the outlet of the low pressure compressor and the inlet of the at least one compressor of the core engine, the duct being defined by a casing, a bleed apparatus for bleeding air from the duct, the bleed apparatus comprising a plurality of circumferentially spaced bleed apertures extending through the casing, a plurality of bleed valve means arranged to selectively move between a first position in which the bleed apertures are fully open to allow a bleed flow from the low pressure compressor, actuating means to actuate the bleed valve means in unison, each bleed aperture has a first side wall and a second side wall extending radially outwardly from the casing at the circumferentially spaced sides of each bleed aperture, the first and second side walls extend the full axial length of the bleed apertures and extend a predetermined distance radially outwardly from the casing whereby the first and second walls prevent the bleed flow flowing circumferentially from the bleed aperture until the bleed valve means have opened a predetermined amount to provide a continuously increasing bleed area as the bleed valve means move towards the second position.
Preferably there is a plurality of independent actuating means, each independent actuating means is arranged to independently actuate one of the plurality of bleed valve means, the actuating means being arranged to actuate the plurality of bleed valve means in unison, the independent actuating means comprising ram means.
Preferably each bleed valve means is pivotally mounted by a pivot extending between the respective first side wall and second side wall.
The present invention will be more fully described by 5 way of example with reference to the accompanying drawings, in which:
Figure 1 is a partially cut away view of an industrial gas turbine engine showing a bleed apparatus according to t~:e present invention.
Figure 2 is an enlarged view in the direction of arrow A
in figure 1 showing the bleed apparatus.
Figure 3 is a further enlarged view of one of the bleed valve means and independent actuating means shown in figure 2.
Figure 4 is a cross-sectional view on line B-B of figure 3, and Figure 5 is a cross-sectional view on line C-C of figure 3.
An industrial gas turbine engine 10, shown in figure 1, comprises in axial flow series an inlet 12, a low pressure compressor 14, an inter compressor duct 16, an intermediate pressure compressor 18, a high pressure compressor 20, combustion means 22, a high pressure turbine 24, an intermediate pressure turbine 26, a low pressure turbine 28 and an exhaust 30. The high pressure turbine 24 is arranged to drive the high pressure compressor 20 via a shaft (not shown), the intermediate pressure turbine 26 is arranged to drive the intermediate pressure compressor 18 via a shaft (not shown) and the low pressure turbine 28 is arranged to drive the low pressure compressor 14 via a shaft (not shown).
Also the low pressure turbine 28 is arranged to drive an electrical generator 32 via a shaft 31. However, the low pressure turbine 28 may be arranged to provide drive for other purposes, for example a pump or a drive shaft of a ship etc. The intermediate pressure compressor 18, the high pressure compressor 20, the combustion means 22, the high pressure turbine 24, and the intermediate pressure turbine 26 form a core engine. The operation of the gas turbine engine 10 is quite conventional, and will not be discussed further.
Preferably there is a plurality of independent actuating means, each independent actuating means is arranged to independently actuate one of the plurality of bleed valve means, the actuating means being arranged to actuate the plurality of bleed valve means in unison, the independent actuating means comprising ram means.
Preferably each bleed valve means is pivotally mounted by a pivot extending between the respective first side wall and second side wall.
The present invention will be more fully described by 5 way of example with reference to the accompanying drawings, in which:
Figure 1 is a partially cut away view of an industrial gas turbine engine showing a bleed apparatus according to t~:e present invention.
Figure 2 is an enlarged view in the direction of arrow A
in figure 1 showing the bleed apparatus.
Figure 3 is a further enlarged view of one of the bleed valve means and independent actuating means shown in figure 2.
Figure 4 is a cross-sectional view on line B-B of figure 3, and Figure 5 is a cross-sectional view on line C-C of figure 3.
An industrial gas turbine engine 10, shown in figure 1, comprises in axial flow series an inlet 12, a low pressure compressor 14, an inter compressor duct 16, an intermediate pressure compressor 18, a high pressure compressor 20, combustion means 22, a high pressure turbine 24, an intermediate pressure turbine 26, a low pressure turbine 28 and an exhaust 30. The high pressure turbine 24 is arranged to drive the high pressure compressor 20 via a shaft (not shown), the intermediate pressure turbine 26 is arranged to drive the intermediate pressure compressor 18 via a shaft (not shown) and the low pressure turbine 28 is arranged to drive the low pressure compressor 14 via a shaft (not shown).
Also the low pressure turbine 28 is arranged to drive an electrical generator 32 via a shaft 31. However, the low pressure turbine 28 may be arranged to provide drive for other purposes, for example a pump or a drive shaft of a ship etc. The intermediate pressure compressor 18, the high pressure compressor 20, the combustion means 22, the high pressure turbine 24, and the intermediate pressure turbine 26 form a core engine. The operation of the gas turbine engine 10 is quite conventional, and will not be discussed further.
However, as stated above because the low pressure turbine 28 drives the electrical generator 32 it is a requirement that the low pressure turbine 28, low pressure compressor 14 and shaft 31 rotate at the same speed throughout the full power range of the gas turbine engine 10. This makes it necessary to provide a bleed apparatus 34 in the inter compressor duct 16 to bleed air from between the low pressure compressor 14 and the intermediate pressure compressor 18 below predetermined power levels. For example for a 50MW industrial gas turbine engine this would necessitate bleeding of air at power levels below about 40MW, and at certain condition up to 50% of the air leaving the low pressure compressor 14 may be bleed air.
The bleed apparatus 34, as shown more clearly in figures 2 to 5, comprises a plurality of, for example eighteen, equi-circumferentially spaced apertures 38 in a casing 36 which defines the outer surface of the inter compressor duct 16. The inter compressor duct 16 connects the outlet of the low pressure compressor 14 and the inlet of the intermediate pressure compressor 18. There are a plurality of bleed valve means, bleed doors 40, one for each bleed aperture 38. The bleed doors 40 have an upstream end 41 and a downstream end 43 and axially extending side edges 45 and 47. The bleed doors 40 are pivotally mounted at their upstream ends 41 to the casing 36 by a pivot 42. Each bleed door 40 is provided with its own independent actuator 44, 46 and each actuator comprises a cylinder 44 and a piston 46. The cylinders 44 are supplied with fluid, either hydraulic fluid or pneumatic fluid, to move the pistons 46 to vary the position of the bleed doors 40. Each actuator 44, 46 is arranged centrally and substantially perpendicularly to the respective bleed door 40 to ensure uniform sealing of the bleed doors 40 around the bleed apertures 38.
Each bleed door 40 comprises a first member 48 and a second member 50, as show more clearly in figures 4 and 5. The first member 48 is pivotally mounted onto the casing 36 by the pivot 42 and the first member 48 is arranged to carry the second member 50 by means of four threaded studs 52 extending from the second member 50 which pass through corresponding apertures 54 in the first member 48 and by four nuts 55 which are threaded onto the studs 52. The second member 50 has a contoured inner surface 51 to match the inner surface of the casing 36. The outer surface of the second member 50 and the inner surface of the first member 48 are substantially planar.
Each bleed door 40 has a pair of circumferentially spaced lugs 56 and 58 which extend outwardly from the first member 48 and the corresponding piston 46 is attached to the lugs 56 and 58 by a pivot arrangement in which a bolt 60 passes through coaxial apertures in the lugs 56 and 58 and also through an aperture in the end of the piston 46 and a nut 62 is located on the threaded end of the bolt 60. The piston 46 is free to slide axially along the bolt 60 to some extent to avoid binding and to reduce side loads on the actuator 44,46.
Each bleed door 40 has a hinge 64 which fits around the pivot 42 and which is secured to the first member 48 by threaded studs 66 which extend outwardly from the first member 48 and pass through apertures in the hinge 64 and nuts 67 which are threaded onto the studs 66. The hinge 64 is U-shaped and flexes in operation to allow the bleed door 40 to seat properly around the bleed aperture 38 to prevent leakage.
Each first member 48 is designed such that it has axial and circumferential dimensions greater than those of the corresponding bleed aperture 38 such that the periphery of the first member 48 will abut the outer surface of the casing 36 around the bleed aperture 38. Each second member 50 is designed such that it has axial and circumferential dimensions slightly smaller than those of the corresponding bleed aperture 38 such that the second member 50 will fit in the bleed aperture 38.
Each bleed door 40 is provided with a seal 68 which is located between the first member 48 and the second member 50.
The seal 68 extends beyond the periphery of the second member 50 but under the periphery of the first member 48. The seal 68 is secured to the first member 48 by four retainers (not g shown) and twelve screws (not shown) and nuts 69,70. The seal 68 is P shaped in cross-section and comprises rubber enclosed in a fabric, for example rubber enclosed in nylon fabric. It may also be necessary to provide silicone sealant to seal any small leaks.
Each bleed aperture 38 has circumferentially spaced side edges 37 and 39 and all the edges of each bleed aperture are chamfered at the outer surface of the casing 36. Each bleed aperture 38 has a first side wall 72 and a second side wall 74 extending radially outwardly from the casing 36 and spaced circumferentially from its axially extending side edges 37 and 39. Each bleed door 40 is pivotally mounted by the pivot 42 which extends between the respective first side wall 72 and the second side wall 74. The first and second side walls 72 and 74 are secured to the casing by bolts 76 and 78 respectively.
The cylinder 44 of each actuator 44, 46 is mounted onto a support ring 80 by means of brackets 82 and 84 which are secured to the support ring by bolts 86 and 88 respectively. Each cylinder 44 is rotably mounted on the respective brackets 82 and 84 by support pins 87 and 89 which locate in bushes 91 and 93 in the brackets 82 and 84 to allow the cylinder to pivot slightly as the piston 46 moves in the cylinder 44.
Each cylinder 44 defines a first chamber 98 and a second chamber 100 at opposite sides of the respective piston 46. The first chamber 98 of each actuator 44, 46 is supplied with fluid by a manifold 90 and one of a plurality of pipes 94 and fluid is bled from the chamber 100 of each actuator 44, 46 by a manifold 92 and one of a plurality of pipes 96. A servo valve (not shown) varies the pressure difference between the fluid in the manifolds 90 and 92 to move the pistons 46 in unison in the cylinders 44 so as to vary the position of the bleed doors 40 in unison.
In operation at high power, for example at power levels greater than 40MW for a 50MW gas turbine engine, the servo valve sets the pressure difference between the fluid in the manifolds 90 and 92 such that the pistons 46 move in the cylinders 44 so as to push the bleed doors 40 to a first position in which the bleed apertures 38 are closed by the bleed doors 40 to prevent a bleed flow from the low pressure compressor 14. At zero power and idle the servo valve sets the pressure difference between the fluid in the manifolds 90 and 92 such that the pistons 46 move in the cylinders 44 so as to pull the bleed doors 40 to the second position in which the bleed apertures 38 are fully open to allow maximum, in this example 500, bleed flow from the low pressure compressor 14. At low power, for example at power levels less than 40MW
for a 50MW gas turbine engine and greater than zero power, the servo valve sets the pressure difference between the fluid in the manifolds 90 and 92 such that the pistons 46 move in the cylinders 44 so as to pull the bleed doors 40 to a position between the first position and the second position such that the bleed apertures 38 are partially open by the bleed doors 40 to allow a bleed flow between zero and 50%
from the low pressure compressor 14.
The first member 48 is arranged such that its periphery abuts the outer surface of the casing 36 around the bleed aperture 38 when the bleed door 40 is in the first position.
The second member 50 is arranged to fit in the bleed aperture 38 and the inner surface 51 is arranged to lie flush with the inner surface of the casing 36 when the bleed door 40 is in the first position. The seal 68 is arranged to abut the outer surface of the casing 36 around the respective bleed aperture 38, in particular on the chamfered edges of the bleed apertures 38, when the bleed door 40 is in the first position.
The first and second side walls 72 and 74 extend the full axial length of each bleed aperture 38 and extend a predetermined distance radially outwardly from the casing 36 whereby the first and second walls 72 and 74 prevent the bleed air flowing circumferentially from the bleed aperture 38 until the bleed doors 40 have opened a predetermined amount to provide a continuously increasing bleed area as the bleed doors 40 move from the first position towards the second position. When the bleed doors 40 have opened beyond the predetermined amount the bleed air is able to flow circumferentially from the bleed apertures 38. The circumferential dimension of each first member 48 is substantially the same but only slightly smaller than the circumferential dimension between the corresponding first and 5 second side walls 72 and 74 to minimise leakage of bleed air therebetween while the bleed door 40 moves from the first position to the predetermined position.
The periphery of the second member 50 of the bleed doors 40 are tapered and are given a radius to provide a smooth l0 transition for the air as it passes over the closed bleed doors 40. The tapered periphery of the second member 50 of the bleed doors 40 also provides cavities for the P seals to deform into when the bleed doors 40 are closed to minimise damage to the P seals.
I5 The servo valve is operated by an engine management system which schedules the amount of bower reaui rPr3 from rt,A
gas turbine engine 10.
The advantages of this arrangement are that the direct piston force on the bleed door 40 ensures proper sealing of the bleed aperture 38 by the bleed door 40, in particular the P cross-section seal 68 seats properly on the chamfered edges of the bleed aperture 38. Also the use of the piston and cylinder actuators and fluid provides a uniform force on each of the bleed doors 40 to ensure that all the bleed doors 40 close together. Additionally if one of the bleed doors 40 or actuator 44,46 seizes the remaining bleed doors 40 will operate to open or close the remaining bleed doors 40. If there is a loss of fluid then all the bleed doors 40 will open to provide a failsafe feature. The side walls 72 and 74 provide a gradual increase in flow area as the bleed doors 40 are opened.
The first and second members 48 and 50 of the bleed doors 40 are preferably made from materials with low density so as to decrease the response time of the bleed doors 40, i . a . the time for the bleed doors 40 to open or close . For example the second member 50 is cast from aluminium and the first member is cast from stainless steel.
Although the description has referred to a core engine comprising an intermediate pressure compressor, a high pressure compressor, combustor means, a high pressure turbine and an intermediate pressure turbine it is possible for the core engine to comprise a high pressure compressor, combustor means, and a high pressure turbine. Although the descriptior_ has referred to actuators comprising a cylinder and piston arrangement supplied with hydraulic or pneumatic fluid, which are fluid driven rams, it is possible to use other types of ram arrangements for example electrically driven rams.
The bleed apparatus 34, as shown more clearly in figures 2 to 5, comprises a plurality of, for example eighteen, equi-circumferentially spaced apertures 38 in a casing 36 which defines the outer surface of the inter compressor duct 16. The inter compressor duct 16 connects the outlet of the low pressure compressor 14 and the inlet of the intermediate pressure compressor 18. There are a plurality of bleed valve means, bleed doors 40, one for each bleed aperture 38. The bleed doors 40 have an upstream end 41 and a downstream end 43 and axially extending side edges 45 and 47. The bleed doors 40 are pivotally mounted at their upstream ends 41 to the casing 36 by a pivot 42. Each bleed door 40 is provided with its own independent actuator 44, 46 and each actuator comprises a cylinder 44 and a piston 46. The cylinders 44 are supplied with fluid, either hydraulic fluid or pneumatic fluid, to move the pistons 46 to vary the position of the bleed doors 40. Each actuator 44, 46 is arranged centrally and substantially perpendicularly to the respective bleed door 40 to ensure uniform sealing of the bleed doors 40 around the bleed apertures 38.
Each bleed door 40 comprises a first member 48 and a second member 50, as show more clearly in figures 4 and 5. The first member 48 is pivotally mounted onto the casing 36 by the pivot 42 and the first member 48 is arranged to carry the second member 50 by means of four threaded studs 52 extending from the second member 50 which pass through corresponding apertures 54 in the first member 48 and by four nuts 55 which are threaded onto the studs 52. The second member 50 has a contoured inner surface 51 to match the inner surface of the casing 36. The outer surface of the second member 50 and the inner surface of the first member 48 are substantially planar.
Each bleed door 40 has a pair of circumferentially spaced lugs 56 and 58 which extend outwardly from the first member 48 and the corresponding piston 46 is attached to the lugs 56 and 58 by a pivot arrangement in which a bolt 60 passes through coaxial apertures in the lugs 56 and 58 and also through an aperture in the end of the piston 46 and a nut 62 is located on the threaded end of the bolt 60. The piston 46 is free to slide axially along the bolt 60 to some extent to avoid binding and to reduce side loads on the actuator 44,46.
Each bleed door 40 has a hinge 64 which fits around the pivot 42 and which is secured to the first member 48 by threaded studs 66 which extend outwardly from the first member 48 and pass through apertures in the hinge 64 and nuts 67 which are threaded onto the studs 66. The hinge 64 is U-shaped and flexes in operation to allow the bleed door 40 to seat properly around the bleed aperture 38 to prevent leakage.
Each first member 48 is designed such that it has axial and circumferential dimensions greater than those of the corresponding bleed aperture 38 such that the periphery of the first member 48 will abut the outer surface of the casing 36 around the bleed aperture 38. Each second member 50 is designed such that it has axial and circumferential dimensions slightly smaller than those of the corresponding bleed aperture 38 such that the second member 50 will fit in the bleed aperture 38.
Each bleed door 40 is provided with a seal 68 which is located between the first member 48 and the second member 50.
The seal 68 extends beyond the periphery of the second member 50 but under the periphery of the first member 48. The seal 68 is secured to the first member 48 by four retainers (not g shown) and twelve screws (not shown) and nuts 69,70. The seal 68 is P shaped in cross-section and comprises rubber enclosed in a fabric, for example rubber enclosed in nylon fabric. It may also be necessary to provide silicone sealant to seal any small leaks.
Each bleed aperture 38 has circumferentially spaced side edges 37 and 39 and all the edges of each bleed aperture are chamfered at the outer surface of the casing 36. Each bleed aperture 38 has a first side wall 72 and a second side wall 74 extending radially outwardly from the casing 36 and spaced circumferentially from its axially extending side edges 37 and 39. Each bleed door 40 is pivotally mounted by the pivot 42 which extends between the respective first side wall 72 and the second side wall 74. The first and second side walls 72 and 74 are secured to the casing by bolts 76 and 78 respectively.
The cylinder 44 of each actuator 44, 46 is mounted onto a support ring 80 by means of brackets 82 and 84 which are secured to the support ring by bolts 86 and 88 respectively. Each cylinder 44 is rotably mounted on the respective brackets 82 and 84 by support pins 87 and 89 which locate in bushes 91 and 93 in the brackets 82 and 84 to allow the cylinder to pivot slightly as the piston 46 moves in the cylinder 44.
Each cylinder 44 defines a first chamber 98 and a second chamber 100 at opposite sides of the respective piston 46. The first chamber 98 of each actuator 44, 46 is supplied with fluid by a manifold 90 and one of a plurality of pipes 94 and fluid is bled from the chamber 100 of each actuator 44, 46 by a manifold 92 and one of a plurality of pipes 96. A servo valve (not shown) varies the pressure difference between the fluid in the manifolds 90 and 92 to move the pistons 46 in unison in the cylinders 44 so as to vary the position of the bleed doors 40 in unison.
In operation at high power, for example at power levels greater than 40MW for a 50MW gas turbine engine, the servo valve sets the pressure difference between the fluid in the manifolds 90 and 92 such that the pistons 46 move in the cylinders 44 so as to push the bleed doors 40 to a first position in which the bleed apertures 38 are closed by the bleed doors 40 to prevent a bleed flow from the low pressure compressor 14. At zero power and idle the servo valve sets the pressure difference between the fluid in the manifolds 90 and 92 such that the pistons 46 move in the cylinders 44 so as to pull the bleed doors 40 to the second position in which the bleed apertures 38 are fully open to allow maximum, in this example 500, bleed flow from the low pressure compressor 14. At low power, for example at power levels less than 40MW
for a 50MW gas turbine engine and greater than zero power, the servo valve sets the pressure difference between the fluid in the manifolds 90 and 92 such that the pistons 46 move in the cylinders 44 so as to pull the bleed doors 40 to a position between the first position and the second position such that the bleed apertures 38 are partially open by the bleed doors 40 to allow a bleed flow between zero and 50%
from the low pressure compressor 14.
The first member 48 is arranged such that its periphery abuts the outer surface of the casing 36 around the bleed aperture 38 when the bleed door 40 is in the first position.
The second member 50 is arranged to fit in the bleed aperture 38 and the inner surface 51 is arranged to lie flush with the inner surface of the casing 36 when the bleed door 40 is in the first position. The seal 68 is arranged to abut the outer surface of the casing 36 around the respective bleed aperture 38, in particular on the chamfered edges of the bleed apertures 38, when the bleed door 40 is in the first position.
The first and second side walls 72 and 74 extend the full axial length of each bleed aperture 38 and extend a predetermined distance radially outwardly from the casing 36 whereby the first and second walls 72 and 74 prevent the bleed air flowing circumferentially from the bleed aperture 38 until the bleed doors 40 have opened a predetermined amount to provide a continuously increasing bleed area as the bleed doors 40 move from the first position towards the second position. When the bleed doors 40 have opened beyond the predetermined amount the bleed air is able to flow circumferentially from the bleed apertures 38. The circumferential dimension of each first member 48 is substantially the same but only slightly smaller than the circumferential dimension between the corresponding first and 5 second side walls 72 and 74 to minimise leakage of bleed air therebetween while the bleed door 40 moves from the first position to the predetermined position.
The periphery of the second member 50 of the bleed doors 40 are tapered and are given a radius to provide a smooth l0 transition for the air as it passes over the closed bleed doors 40. The tapered periphery of the second member 50 of the bleed doors 40 also provides cavities for the P seals to deform into when the bleed doors 40 are closed to minimise damage to the P seals.
I5 The servo valve is operated by an engine management system which schedules the amount of bower reaui rPr3 from rt,A
gas turbine engine 10.
The advantages of this arrangement are that the direct piston force on the bleed door 40 ensures proper sealing of the bleed aperture 38 by the bleed door 40, in particular the P cross-section seal 68 seats properly on the chamfered edges of the bleed aperture 38. Also the use of the piston and cylinder actuators and fluid provides a uniform force on each of the bleed doors 40 to ensure that all the bleed doors 40 close together. Additionally if one of the bleed doors 40 or actuator 44,46 seizes the remaining bleed doors 40 will operate to open or close the remaining bleed doors 40. If there is a loss of fluid then all the bleed doors 40 will open to provide a failsafe feature. The side walls 72 and 74 provide a gradual increase in flow area as the bleed doors 40 are opened.
The first and second members 48 and 50 of the bleed doors 40 are preferably made from materials with low density so as to decrease the response time of the bleed doors 40, i . a . the time for the bleed doors 40 to open or close . For example the second member 50 is cast from aluminium and the first member is cast from stainless steel.
Although the description has referred to a core engine comprising an intermediate pressure compressor, a high pressure compressor, combustor means, a high pressure turbine and an intermediate pressure turbine it is possible for the core engine to comprise a high pressure compressor, combustor means, and a high pressure turbine. Although the descriptior_ has referred to actuators comprising a cylinder and piston arrangement supplied with hydraulic or pneumatic fluid, which are fluid driven rams, it is possible to use other types of ram arrangements for example electrically driven rams.
Claims (22)
1. A gas turbine engine comprising in flow series a low pressure compressor, a core engine, and a low pressure turbine, the low pressure turbine being arranged to drive the low pressure compressor, the core engine comprising in flow series at least one compressor, combustion means and at least one turbine, the at lease one turbine being arranged to drive the at least one compressor, a duct connecting the outlet of the low pressure compressor and the inlet of the at least one compressor of the core engine, the duct being defined by a casing, a bleed apparatus for bleeding air from the duct, the bleed apparatus comprising a plurality of circumferentially spaced bleed apertures extending through the casing, a plurality of bleed valve means arranged to selectively move between a first position in which the bleed apertures are closed and a second position in which the bleed apertures are fully open to allow a bleed flow from the low pressure compressor, and a plurality of independent actuating means, each independent actuating means is arranged to independently actuate one of the plurality of bleed valve means, the actuating means being arranged to actuate the plurality of bleed valve means in unison, the independent actuating means comprising ram means.
2. A gas turbine engine as claimed in claim 1 wherein the core engine comprises in flow series an intermediate pressure compressor, a high pressure compressor, combustion means, a high pressure turbine and an intermediate pressure turbine, the intermediate pressure turbine being arranged to drive the intermediate pressure compressor, the high pressure turbine being arranged to drive the high pressure compressor.
3. A gas turbine engine as claimed in claim 1 or claim 2 wherein the low pressure turbine is arranged to drive a load.
4. A gas turbine engine as claimed in claim 3 wherein the load is an electrical generator, a pump or a drive shaft.
5. A gas turbine engine as claimed in any of claims 1 to 4 wherein each actuator means comprises a piston and cylinder.
6. A gas turbine engine as claimed in claim 5 wherein there are means to supply fluid to the cylinders to move the pistons.
7. A gas turbine engine as claimed in claim 6 wherein the means to supply fluid is a supply of hydraulic fluid.
8. A gas turbine engine as claimed in any of claims 1 to 7 wherein the bleed valve means are pivotally mounted onto the casing.
9. A gas turbine engine as claimed in claim 8 wherein each bleed aperture has a first side wall and a second side wall extending radially outwardly from the casing at the circumferentially spaced sides of each bleed aperture, each bleed valve means being pivotally mounted by a pivot extending between the respective first side wall and second side wall.
10. A gas turbine engine as claimed in claim 9 wherein the first and second side walls extend the full axial length of the bleed aperture and extend a predetermined distance radially outwardly from the casing whereby the first and second walls prevent the bleed flow flowing circumferentially from the bleed aperture until the bleed valve means have opened a predetermined amount to provide a continuously increasing bleed area as the bleed valve means move towards the second position.
11. A gas turbine engine as claimed in claim 8, claim 9 or claim 10 wherein each bleed valve means comprises a first member and a second member, the first member is pivotally mounted onto the casing, the first member is arranged to carry the second member, the second member has an inner surface, the casing has an inner surface and an outer surface, the first member is arranged to abut the outer surface of the casing in the first position, the second member is arranged to fit in the bleed aperture and the inner surface thereof is arranged to lie flush with the inner surface of the casing when in the first position.
12. A gas turbine engine as claimed in claim 11 wherein a seal is located between the first member and the second member, the second member has a periphery, the seal extends around the periphery of the second member such that the seal abuts the outer surface of the casing around the respective bleed aperture in the first position.
13. A gas turbine engine as claimed in claim 12 wherein the seal is P shaped in cross-section.
14. A gas turbine engine as claimed in claim 13 wherein the seal comprises rubber enclosed in a fabric.
15. A gas turbine engine as claimed in claim 13 or claim 14 wherein the outer surface of the casing has chamfered edges around the respective bleed aperture.
16. A gas turbine engine as claimed in any of claims 8 to 15 wherein the bleed valve means have upstream ends, the bleed valve means are pivotally mounted to the casing at their upstream ends.
17. A gas turbine engine as claimed in claim 5 wherein the cylinders are mounted on a support ring, the support ring is mounted coaxially on the gas turbine engine.
18. A gas turbine engine as claimed in claim 5 wherein each piston is pivotally connected to the respective bleed valve means.
19. A gas turbine engine as claimed in claim 17 wherein each cylinder is pivotally mounted on the support ring.
20. A gas turbine engine comprising in flow series a low pressure compressor, a core engine, and a low pressure turbine, the low pressure turbine being arranged to drive the low pressure compressor, the core engine comprising in flow series at least one compressor, combustion means and at least one turbine, the at least on turbine being arranged to drive the at least one compressor, a duct connecting the outlet of the low pressure compressor and the inlet of the at least one compressor of the core engine, the duct being defined by a casing, a bleed apparatus for bleeding air from the duct, the bleed apparatus comprising a plurality of circumferentially spaced bleed apertures extending through the casing, a plurality of bleed valve means arranged to selectively move between a first position in which the bleed apertures are closed and a second position in which the bleed apertures are fully open to allow a bleed flow from the low pressure compressor, actuating means to actuate the bleed valve means in unison, each bleed aperture has a first side wall and a second side wall extending radially outwardly from the casing at the circumferentially spaced sides of each bleed aperture, the first and second side walls extend the full axial length of the bleed aperture and extend a predetermined distance radially outwardly from the casing whereby the first and second walls prevent the bleed flow flowing circumferentially from the bleed aperture until the bleed valve means have opened a predetermined amount to provide a continuously increasing bleed area as the bleed valve means move towards the second position.
21. A gas turbine engine as claimed in claim 20 wherein there is a plurality of independent actuating means, each independent actuating means is arranged to independently actuate one of the plurality of bleed valve means, the actuating means being arranged to actuate the plurality of bleed valve means in unison, the independent actuating means comprising ram means.
22. A gas turbine engine as claimed in claim 20 wherein each bleed valve means is pivotally mounted by a pivot extending between the respective first side wall and second side wall.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002208801A CA2208801C (en) | 1997-06-24 | 1997-06-24 | A bleed apparatus for a gas turbine engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002208801A CA2208801C (en) | 1997-06-24 | 1997-06-24 | A bleed apparatus for a gas turbine engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2208801A1 CA2208801A1 (en) | 1998-12-24 |
| CA2208801C true CA2208801C (en) | 2005-12-06 |
Family
ID=4160949
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002208801A Expired - Lifetime CA2208801C (en) | 1997-06-24 | 1997-06-24 | A bleed apparatus for a gas turbine engine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2208801C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3139365A1 (en) * | 2022-09-05 | 2024-03-08 | Safran Aircraft Engines | DISCHARGE VALVE WITH INTRUSIVE DOOR |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2443982B (en) * | 2006-01-20 | 2011-06-22 | Rolls Royce Power Eng | Bleed off valve system |
| FR2932855B1 (en) * | 2008-06-18 | 2014-04-11 | Snecma | <p> AIR DISCHARGE SYSTEM FOR AERONAUTICAL TURBOMACHINE COMPRESSOR </ p> |
| FR2982904B1 (en) * | 2011-11-18 | 2015-01-30 | Snecma | CARTER HUB FOR AN AIRCRAFT AIRCRAFT COMPRISING MEANS FOR CONTROLLING IMPROVED DISCHARGE VALVES |
| FR3082562B1 (en) * | 2018-06-19 | 2020-06-12 | Safran Aircraft Engines | DISCHARGE DOOR CONTROL RING FOR AN AIRCRAFT TURBOMACHINE AND TURBOMACHINE COMPRISING SAME |
| FR3083577B1 (en) * | 2018-07-06 | 2021-05-07 | Safran Aircraft Engines | TURBOMACHINE FOR AIRCRAFT CONTAINING A PLURALITY OF VARIABLE DISCHARGE VALVES AND CONTROL PROCEDURE |
| FR3083832B1 (en) * | 2018-07-10 | 2020-06-19 | Safran Aircraft Engines | DISCHARGE VALVE FOR TAKING FLUID FLOWING FROM A TURBOMACHINE VEIN |
| CN111058946A (en) * | 2019-12-05 | 2020-04-24 | 中国航发四川燃气涡轮研究院 | Compressor bypass air entraining device and system |
-
1997
- 1997-06-24 CA CA002208801A patent/CA2208801C/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3139365A1 (en) * | 2022-09-05 | 2024-03-08 | Safran Aircraft Engines | DISCHARGE VALVE WITH INTRUSIVE DOOR |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2208801A1 (en) | 1998-12-24 |
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| MKEX | Expiry |
Effective date: 20170627 |