Patent Application
20120315131
This application claims priority of European Patent Office application No. 11169109.3 EP filed Jun. 8, 2011. All of the applications are incorporated by reference herein in their entirety.
The invention refers to an axial turbocompressor having an annular compressor passage which is arranged concentrically around a rotational axis, is delimited radially on the outside by a passage wall and in which rotor blades, which can be assembled to form a ring, are arranged in a rotatably mounted manner around the rotational axis, wherein the free-ending tips of the rotor blades lie opposite the passage wall in each case, forming a gap, and the passage wall, in the axial section of the tips, has at least partially a wall structuring (also known as casing treatment) and wherein a bleed opening of a bleed passage is provided in the passage wall for the tapping of a medium flowing in the compressor passage.
The afore-described arrangement is known from GB 2 158 879 A, for example. The casing treatment is provided on the casing-side passage wall above an upstream-disposed rotor blade row and the bleed point for the tapped air is located at a rotor blade row which is disposed downstream thereof. In the bleed passage, provision is made, moreover, for a valve in order to tap different volumes of compressor air in dependence upon the operating state. Both measures enable a degree of control of the operation of the compressor for high pressure ratios without undesirable compressor phenomena, such as surging or separation phenomena, resulting in the process. It is disadvantageous, however, that the aforesaid design has proved to be unsatisfactory for a partial load operation of a gas turbine.
The object of the invention is therefore the provision of an axial turbocompressor in which the operating range is further improved by a more efficient avoidance of undesirable compressor phenomena.
A further object of the invention is the provision of a gas turbine with an axial turbocompressor according to the invention which avoids impermissibly high emissions particularly during partial load operation.
The object forming the basis of the invention is achieved with an axial turbocompressor according to the features of the claims. Advantageous developments and embodiments are disclosed in the dependent claims in each case.
According to the invention it is intended to locate the bleed opening in the wall structuring. Therefore, not only is the simultaneous use of a casing treatment and the tapping of compressor air inside an axial turbocompressor proposed, but the combination is also put into effect locally, specifically in the region of a single rotor blade row of the axial turbocompressor. A backing up of the compressed air and an aerodynamically unfavorably high pressure ratio, associated therewith, in the subsequent compressor stages can therefore be avoided, which in the main avoids the occurrence of the undesirable compressor phenomena. As a result of the combination according to the invention, the surge limit of the compressor stage in question can be adjusted in a particularly simple manner and in dependence upon the operating state. This, when the axial turbocompressor is used in a stationary gas turbine, enables a particularly low partial-load operation without the emissions limits being exceeded in the process. When being used in a gas turbine, a correspondingly small air volume for the partial load can be directed into the combustion chamber, specifically by the tapping of compressor air, as a result of which the CO emissions are minimized. Therefore, air is extracted from the compressor in a specific manner so that no unwanted fluidic effects occur, as can happen in the case of conventional blow-off valves. Moreover, the tapping of air which is provided in the casing treatment also assists the effect of the wall structuring itself so that the casing treatment can be formed in a more space-saving manner than a casing treatment without bleed openings located therein.
According to a first advantageous development, the wall structuring is variable in its extent and/or form and as a result the bleed opening can be at least partially uncovered. This embodiment enables, in a simple construction, three operating states of the axial turbocompressor in all:
The axial turbocompressor is operated without casing treatment and without bleed of compressor air, preferably at full load,
The axial turbocompressor is operated only with casing treatment, but also without the tapping of compressor air, preferably at high partial load, and
The axial turbocompressor is operated with casing treatment with simultaneous tapping of compressor air, preferably at low partial load.
Consequently, the casing treatment, which is adjustable in its extent or form, does not serve solely for adjusting the wall structuring but at the same time also serves as an actuating element for engaging or disengaging the bleed of compressor air. This also enables a particularly space-saving construction.
The aforesaid embodiment can be realized in a particularly simple manner with regard to construction if the wall structuring is variable in its extent and/or form by means of a movable insert and the bleed opening is located in a sidewall of the recess which accommodates the insert. The insert can be formed as a plug which can be displaced along the recess. Depending upon the position of the plug, either the recess is completely closed (for the first operating state), the recess is only partially closed with the bleed openings still closed (for the second operating state), or the recess and the bleed opening are open (for the third operating state). In this respect, solely by displacement of the plug along its recess, which accommodates it, switching back and forth between the three aforesaid operating states can be carried out in a simple and reliable manner.
The bleed passage can be expediently connected on the flow discharge side to a blow-off air system and/or cooling-air system.
It is also expedient to arrange a plurality of bleed openings per rotor blade ring. In this case, the medium flowing in the compressor passage—in most cases air—can be evenly bled off from this, as seen over the circumference of the axial turbocompressor. A gas turbine particularly advantageously has an axial turbocompressor of the previously described type of construction, according to the invention, as a result of which the gas turbine can be operated at low partial load particularly with low emissions.
Further advantages, features and characteristics of the invention are explained in more detail based on preferred exemplary embodiments in the drawing. Expedient embodiments result from advantageous combinations of features of the depicted devices according to the invention. In the drawing:
The axial turbocompressor 18 comprises an annularly designed compressor passage 25 with compressor stages, consisting of rotor blade rings and stator blade rings, arranged in series therein in a cascadic manner. The rotor blades 27, which are arranged on the rotor 14, lie opposite an outer passage wall 42 of the compressor passage 25 by their free-ending blade airfoil tips 29. The compressor passage 25, via a compressor exit diffuser 36, opens into a plenum 38. Inside the plenum, the annular combustion chamber 20 is provided with its combustion space 28 which communicates with an annular hot gas passage 30 of the turbine unit 24. According to the depicted exemplary embodiment, four turbine stages 32, connected in series, are arranged in the turbine unit 24. A generator or a driven machine (not shown in either case) is connected to the rotor 14.
During operation of the gas turbine 10, the axial turbocompressor 18 inducts ambient air 34, as medium to be compressed, through the inlet duct 16 and compresses this air. The compressed air is directed through the compressor exit diffuser 36 into the plenum 38, from whence it flows into the burners 22. Via the burners 22, fuel also makes its way into the combustion space 28. There, the fuel, with the addition of the compressed air, is combusted to form a hot gas M. The hot gas M then flows into the hot gas passage 30 where it expands, performing work on the turbine blades of the turbine unit 24. The energy released in the meantime is absorbed by the rotor 14 and on the one hand is used for driving the axial turbocompressor 18 and, on the other hand, for driving a driven machine or electric generator.
During operation of the gas turbine 10, and therefore during operation of the axial turbocompressor 18, conditions and aerodynamic phenomena may occur, however, which partially limit the operation. In order to avoid the occurrence of these conditions and phenomena, at least one wall structuring is provided in the passage wall 42. This wall structuring is not shown in
In a position of the insert 48 which is shown according to
According to a third embodiment, which is shown in
In all, with the present invention, an axial turbocompressor 18 or a gas turbine 10 is proposed, having an annular compressor passage 25 which is arranged concentrically around a rotational axis 12, is delimited radially on the outside by a passage wall 42, and in which rotor blades 27, which can be assembled to form a ring, are arranged in a rotatably mounted manner around the rotational axis 12. In this case, the free-ending tips 29 of the rotor blades 27 lie opposite the passage wall 42 in each case, forming a gap, wherein in the passage wall 42 itself provision is at least partially made in the axial section of the tips 29 for a wall structuring 44. In order to further improve the operating performance of the axial turbocompressor 18, provision is made for a bleed opening 52 of a bleed passage 50 for the tapping and discharging of air flowing in the compressor passage 25, which bleed opening is located in the wall structuring 44 according to the invention.
While specific embodiments have been described in detail, those with ordinary skill in the art will appreciate that various modifications and alternative to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims, and any and all equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| EP11169109 | Jun 2011 | EP | regional |
