Patent Application
20100232935
The invention relates to an air bleed in a compressor with variable guide vanes and a guide vane arrangement.
In a conventional gas turbine engine a compressor is used for pressurising ambient air which is mixed with fuel in a combustor, ignited and burned. Energy is extracted from the hot combustion gas by passing it through a turbine. The rotatable sections of an engine typically comprise annular arrays of compressor or turbine rotor blades, the blades normally being intersected with annular arrays of static aerodynamic guide vanes (also called stator vanes). Each set of rotor blades and guide vanes is referred to as a stage. The guide vanes ensure the gas impinges on the rotor at the correct angle.
The first stages of a compressor may be equipped with variable guide vanes that are pivotable about spindles to adapt the stagger during operation of the compressor. The guide vanes are connected to a lever which is pivotably attached to a unison actuator ring mounted around the periphery of the compressor casing. By moving the unison actuator ring the stagger of the guide vanes is altered.
During the start-up of an engine the position of a variable guide vane row is altered and the compressor intake is closed in such a way that the mass flow is restricted. The position of the variable guide vane row is dynamically altered. Flow instabilities during the starting or accelerating of the compressor can be reduced and/or overcome.
In compressors with highly loaded stages (e.g. few stages for a given pressure ratio) it is practice to use several rows of variable guide vanes at the front end of the compressor. The vanes are gradually closed as the load is decreased.
Not all of the compressed air is used for combustion. A part of the air may be used in many other different ways, like de-icing at the compressor entry, or turbine blade cooling. Therefore, compressed air is taken from within the engine, in or after the compressor stage(s), depending on the application, and before the fuel is injected in the burners. This compressed air is called bleed air.
In compressors, variable guide vanes may mechanically interfere with air bleeds arranged in the proximity of the variable guide vanes and the delivery requirements for bleed air are not met.
Furthermore, if air is bled through holes in the casing, outside the rotor blades a large sealed chamber incorporating the whole of the variable guide vane mechanism including the actuator has to be fitted onto the compressor casing. The temperature inside would be above the normal operating temperature of (at least) electric actuators. This chamber would also restrict access for inspection and maintenance of the guide vane mechanism:
U.S. Pat. No. 7,131,815 B2 refers to the problem of ice formation on variable and static inlet guide vanes and describes a vane with a spindle; the spindle is configured to engage in operation with a support such that the vane pivots about the spindle. The vane is further provided with an electrically operable heater which is communicable with an electrical supply via an electrical connection node located in the spindle.
The patent application JP2002195196 shows a configuration with bleed holes between vanes in a cascade of a axial compressor.
In US2006/0182623 is disclosed a bleed arrangement based of angled holes outside the rotor blade tips of a compressor.
U.S. Pat. No. 6,588,195:
This patent describes a bleed valve exhausting into a bleed duct.
U.S. Pat. No. 7,090,462 shows an arrangement with an external bleed chamber connected to a slot downstream of a vane row.
U.S. Pat. No. 5,517,817 describes a variable guide vane of a power turbine comprising a supply hole of air through the centre line of the vane. See
In the U.S. Pat. No. 4,861,228 is shown a variable guide vane of a power turbine comprising a supply hole of air through the centre line of the vane.
In the U.S. Pat. No. 4,834,634 a sliding vane rotary compressor with a partial passage through the driveshaft is shown.
U.S. Pat. No. 4,576,547 shows an air passage through a fixed vane in a compressor.
In EP1609999A2 a variable guide vane of a compressor is shown comprising a supply hole of air provided partially through a hollow spindle used primarily to pivot the vane.
EP1536146A2 and U.S. Pat. No. 4,155,680 show alternatives how to pass bleed air from the air path of the compressor.
It is an objective of the invention to provide an improved guide vane and an improved guide vane arrangement with an air bleed not being mechanically interfered by the variable guide vane as a function of the stagger of the variable guide vane.
This objective is achieved by the claims. The dependent claims describe advantageous developments and modifications of the invention.
An inventive guide vane for a compressor comprises an airfoil and a base plate for mounting the guide vane to a compressor casing. The base plate includes an air duct appropriate for bleeding air, i.e. to guide air from the compressor flow path through the air duct.
It is preferable that the inventive guide vane comprises a spindle connected to the base plate and facing away from the airfoil to allow the vane to pivot about the spindle. It is furthermore preferable that the air duct extends from the base plate through the spindle.
It is advantageous to have at least one inlet opening of the air duct arranged in the base plate of the guide vane.
For an intermittent flow, it is preferable to have only one inlet opening arranged in the base plate as the pressure difference between the aerofoil pressure and suction surfaces may cause recirculation through the passageway between the two surfaces.
For continuous flow, it is advantageous, when the air duct comprises one or more inlet openings arranged in the base plate, the inlet openings being arranged on opposite sides of the airfoil. The risk of having air flowing from the pressure side to the suction side when using bleed holes on both sides of the aerofoil which are in communication can be avoided by using a restrictor in the whole located on the high-pressure side or simply by differential inlet opening sizes.
It is advantageous to combine at least two inventive guide vanes to build a guide vane arrangement for an axial flow compressor.
Preferably, the guide vanes are circumferentially arranged about a longitudinal axis of the compressor and extend radially. The spindles of the guide vanes allow for pivotably mounting the guide vanes for rotation about their longitudinal axis in a stator structure of the axial flow compressor, the stator structure being surrounded by an actuator ring. Levers, circumferentially arranged about the longitudinal axis of the compressor, extend from the actuator ring to respective spindles of guide vanes.
It is particularly advantageous to gather the thereby obtained bleed air with an air duct extension connected to the spindle ends of the at least two guide vanes and to guide the bleed air to a bleed manifold.
For variable guide vanes with only small movements the air duct extension preferably is a flexible hose arranged at a radially outer end of the spindle. The flexible hose easily copes with small torsions and can be connected directly to a bleed manifold or air ducting.
For variable guide vanes with larger movements a more elaborate air duct extension is necessary.
It could be advantageous to impose a hose adaptor on the end of the spindle to connect the hose to the spindle. It is therefore advantageous to have a flatted recess arranged in the outer surface of the hose adaptor to allow for retaining the hose adaptor by a simple yoke attached to the casing in its position, i.e. to keep the hose adaptor from rotating or slipping off the spindle.
To prevent air loss off the air duct while still allowing for a rotational movement of the spindle it is preferable to have a seal arranged between the spindle and the hose adaptor.
For large movements of the guide vane another advantageous alternative is to use a combined vane drive lever and duct, to transport the bleed air from the spindle to a bleed manifold which could be a hollow actuator ring. To pipeline the bleed air from the spindle to the lever and from the lever to the bleed manifold hollow articulated joints can be used allowing for free rotation of the variable guide vane spindle in the lever and free rotation of the lever at the actuator ring connection.
Here, it is advantageous when the spindle extends through a first end of the lever.
It is also advantageous when the flow communication between the spindle and the lever is established through at least one opening in the spindle.
Preferably, seals arranged between the spindle and the lever allow for a rotational movement of the spindle while preventing air loss off the cavity.
It is advantageous to use the inventive guide vane arrangement as variable inlet guide vane arrangement in a gas turbine engine compressor.
By extracting the air from the gas path through the spindle of the variable guide vane and ducting the air to an external manifold the bleed can be located anywhere among the rows of variable guide vanes.
Compared to conventional guide vane arrangements only a few new components are required, such as cavities in the guide vane spindle, arm/lever and actuator ring, which in turn can be connected to air ducting in the or adjacent to the skid through a flexible hose.
Air with the right pressure and temperature for the application can be obtained without any preparations saving cost and increasing performance of the gas turbine.
The cavities in the vanes could also be used for borescope/fibrescope access to inspect adjacent rotor blades, injection of fluids for cleaning or of corrosion inhibitors for long term storage.
The invention will now be further described with reference to the accompanying drawings in which:
In the drawings like references identify like or equivalent parts.
Illustrated in
With reference to
A lever 5 connects the spindle 4 of the guide vane 2 to an actuator ring 6. Movements of the actuator ring 6 alter the stagger of the guide vanes 2. The compressor casing/outer portion of the stator structure is not shown.
A flexible conduit, i.e. a hose 11, is arranged as air duct extension 12 at one end of the spindle 4 of the inventive guide vane 2. The hose 11 connects the spindle 4 to a bleed manifold 13 or an air ducting and is most suitable for guide vane applications with small movements of the guide vane 2.
The alternative embodiment shown in
Unlike in the previous embodiment, the air duct 9 of the guide vane 2 in
A similar sealing arrangement is found for the connection between the lever 5 and the actuator ring 6 to establish flow communication between the cavity 14 in the lever 5 and the bleed manifold 13 in the actuator ring 6, allowing for a rotational movement of the lever 5 at the actuator ring connection while preventing air loss off the cavity 14. Arrows show the way of the bleed air 18 through the guide vane arrangement 17.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07021944.9 | Nov 2007 | EP | regional |
This application is the U.S. National Stage of International Application No. PCT/EP2008/063436, filed Oct. 8, 2008 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 07021944.9 DE filed Nov. 12, 2007. All of the applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP08/63436 | 10/8/2008 | WO | 00 | 5/5/2010 |
