Pumps – Processes
Reexamination Certificate
1999-09-24
2001-07-10
Thorpe, Timothy S. (Department: 3746)
Pumps
Processes
C417S367000, C417S406000, C415S176000, C415S178000
Reexamination Certificate
active
06257834
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and an arrangement for the indirect cooling of the flow in radial gaps formed between rotors and stators of turbomachines.
BACKGROUND OF THE INVENTION
To seal off rotating systems, non-contact seals, in particular labyrinth seals, are widespread in turbomachine construction. In the separating gap, through which flow occurs, between rotating and stationary parts, high friction power occurs as a result of the forming flow boundary layers. This leads to heating of the fluid in the separating gap and thus also to the heating of the components surrounding the separating gap. The high material temperatures result in a reduction in the service life of the corresponding components.
DE 195 48 852 A1 discloses a radial compressor of simple construction without a sealing geometry formed in the separating gap. In this case, too, the friction heat produced as a result of flow shearing layers at the rear wall of the compressor impeller causes heating of the compressor impeller and thus reduces its service life.
EP 0 518 027 B1 discloses air cooling for radial compressors with a sealing geometry on the rear side of the compressor impeller. To this end, an additional annular space is formed between the individual sealing elements the casing wall side of the radial compressor. A cold gas which has a higher pressure than the pressure prevailing at the outlet of the compressor impeller is directed into this annular space. The air supplied acts as impingement cooling. In the process, it divides in the sealing region and flows mainly radially inward as well as outward. This is intended to additionally achieve a blocking effect against the flow of hot compressor air through the separating gap from the outlet of the compressor impeller. However, the air blown in in this way causes an increase in thrust and additional friction losses in the flow boundary layers.
In addition to this direct cooling, DE 196 52 754 A1 also discloses indirect cooling of the rear wall of the compressor impeller or of the medium flowing through the separating gap. To this end, a feed and distributing device connected to the lubricating-oil system of the turbocharger is arranged on or in the casing part disposed at the rear wall and forming with the latter the separating gap. The oil used for the bearing lubrication serves as cooling medium, for which purpose the lubricating-oil circuit of the turbocharger is tapped. A disadvantage of this cooling is the relatively high oil demand and the heat quantity to be additionally dissipated by the oil cooler. This leads to an increased overall volume of the cooler. In addition, in the event of an accident with damage to the corresponding parts, there is an increased risk of deflagration.
U.S. Pat. No. 4,815,184 also discloses water cooling of the bearing housing of a turbocharger. However, this cooling serves to remove the carbonization risk of the lubricating oil remaining in the bearing housing of the turbocharger after shutdown of the latter. In contrast to the abovedescribed solutions of the prior art, the feeding of the cooling medium is not necessary during the continuous operation but rather when the turbocharger is shut off. This type of cooling of the bearing housing is therefore unable to provide any reference to indirect cooling of the flow in radial gaps formed between rotors and stators of turbomachines. In addition, this solution expressly does not deal with the cooling of the intermediate wall.
SUMMARY OF THE INVENTION
The invention attempts to avoid all these disadvantages. Its object is to provide a method of cooling the flow in radial gaps formed between rotors and stators of turbomachines, which method is improved with regard to its cooling effect. In addition, a simple, cost-effective and robust arrangement for realizing the method is to be specified.
According to the invention, this is achieved in that, in a method according to the preamble of claim
1
, water is used as cooling fluid for the stator part adjacent to the radial gap.
The water used as cooling medium has a somewhat higher density than the known lubricating oils as well as approximately twice as high a specific heat capacity. Since the heat flow to be dissipated via a cooling medium is in proportion to the product of density and specific heat capacity, a distinct advantage over oil cooling is obtained when using water. At the same mass flow and the same temperature of the water, a greater quantity of heat can thus be extracted from the medium flowing through the radial gap via the stator part to be cooled. The cooling effect on the regions of the rotor which are adjacent to the radial gap is therefore likewise greater. Conversely, to dissipate the same quantity of heat, a smaller mass flow of cooling water is required compared with the lubricating oil, as a result of which the feed and discharge device for the cooling medium may be of correspondingly smaller dimensions.
To this end, at least one recess is formed in the interior of the stator part adjacent to the radial gap or at least one cavity is arranged at the stator part. The recess or the cavity is connected to both a feed line and a discharge line for the cooling fluid. The cooling fluid is introduced or drawn off again via these lines. Depending on the rotor-side wall thickness, which is to be kept as small as possible, an improved cooling effect can be achieved by the guidance of the water directly adjacent to the radial gap in the interior of the stator part. If, however, instead of the recess in the stator part, the cavity described is formed at the stator part, simpler and more cost-effective manufacture can be realized with likewise good cooling effect.
In a system consisting of an internal combustion engine, a charge-air cooler and an exhaust-gas turbocharger, either fresh water from outside the system or advantageously water present in the system is used as cooling fluid. In the latter case, the cooling water located in a cooling-water circuit of the charge-air cooler is used for this purpose, and this cooling water is branched off upstream of the charge-air cooler. In this case, the fixed stator part is a casing part of a radial compressor, and this casing part defines the radial gap relative to the rotor, i.e. relative to the rotating compressor impeller of an exhaust-gas turbocharger.
Formed as a recess of the stator part is a tube integrally cast in the stator part, as a result of which a simple and robust cooling arrangement is obtained. As an alternative to this, at least one groove is arranged in the stator part, at least one tube which serves as recess being inserted and cast in each groove. Of course, a stator part having at least one corresponding integrally cast core, which is removed in order to form the recess, is far simpler in production.
An additional advantage is achieved by virtue of the fact that the cooling fluid, before the water cooling of the stator part adjacent to the radial gap, is used for the indirect cooling of the diffuser, receiving the main flow of the working medium downstream of the point at which the leakage flow is branched off, and of the diffuser plate delimiting the diffuser relative to the bearing housing. Effective cooling of the material of the turbomachine can thus also be achieved in this downstream region. In addition, the heat flow from the diffuser to the stator part adjacent to the radial gap is thus reduced.
In an especially advantageous manner, a second cooling fluid is used in addition to the water cooling and is directed into the radial gap, in which case air is preferably used. On account of the double cooling of the radial gap, the temperature of the rotor, which is subjected to high thermal loading, can be further reduced. To this end, at least one feed passage as well as a discharge device for the second cooling fluid are arranged at the radial gap.
By the feed of the second cooling fluid being partly or even completely shut off, the cooling effect can be adapted in a simple manner to the conditions to be expected during op
Bothien Michajlo
Bremer Joachim
Gieszauf Helmut
Greber Jurg
Muller Ulf Christian
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Gartenberg Ehud
Thorpe Timothy S.
LandOfFree
Method and arrangement for the indirect cooling of the flow... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and arrangement for the indirect cooling of the flow..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and arrangement for the indirect cooling of the flow... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2566360