Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1998-12-23
2001-05-15
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C415S114000
Reexamination Certificate
active
06230483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steam cooled type gas turbine in which steam is used as a gas turbine cooling medium.
2. Description of the Prior Art
As one example of a prior art gas turbine cooling structure, cooling of an air cooled type stationary blade will be outlined with reference to FIG.
4
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In a gas turbine having a system to cool a high temperature portion using air as a cooling medium, cooling air is led from a stationary blade outer shroud side as shown by arrows a. A portion of the air so led flows in the blade for cooling of an inner surface thereof and then flows out of holes provided in the blade to flow along the blade surface for cooling thereof as shown by arrows b, and is discharged in a combustion gas passage as shown by arrows e.
A remaining portion of the air does not flow out of the holes provided in the blade but is led into a stationary blade inner shroud for cooling of the inner shroud and a blade lower portion and then flows as shown by arrow c to be discharged into the combustion gas passage.
In the above, in order to prevent the air so led as shown by arrows a from leaking directly into the combustion gas passage before it performs its original duty to cool the blade portion and the blade lower portion, there are provided seals d at contact surfaces between the blade and the outer shroud and between the blade and the inner shroud.
As mentioned above, in the air cooled type gas turbine, after the air as cooling medium has cooled the structural body of the stationary blade, shrouds, etc., it is discharged into the combustion gas passage without being recovered, hence there is less thermal efficiency in this system.
Thus, as part of a recent tendency to obtain a better system in thermal efficiency, a steam cooled type gas turbine has been disclosed as another prior art example in which steam is used as the cooling medium in place of air.
As to this prior art example, although illustration is omitted, steam as a cooling medium is supplied into portions to be cooled of the gas turbine, including the structural body of the stationary blade, shrouds, etc., and the steam which has been heated through cooling of the cooled portions is recovered so that the heat of the steam is utilized effectively and enhancement of the thermal efficiency can be attained.
In this steam cooled system, however, in order to ensure recovery of the heat obtained in the cooled portions, there is needed an accurate and strong construction of cooling passages in which the steam does not leak, not only into the combustion gas passage, but also along the way of steam flow passages.
Hence, in the steam cooled system, construction thereof is preferably such that steam supply ports and recovery ports are lessened to the extent possible, and stationary blades of a first stage, second stage and subsequent stages are supplied with the cooling steam for cooling thereof through a single steam passage, and then the steam is recovered.
SUMMARY OF THE INVENTION
Based on such a view point, it is an object of the present invention to provide a steam cooled type gas turbine comprising a steam chamber unit having a compact structure by which a cooling steam can be appropriately supplied, used for cooling and recovered.
In order to achieve the object, the present invention provides a steam cooled type gas turbine characterized in comprising a steam chamber unit which is formed in one unit having therein a steam supply passage for leading thereinto a cooling steam, a steam connection passage for leading therethrough the cooling steam which has cooled a front stage to a subsequent stage, and a steam recovery passage for recovering therethrough the cooling steam which has cooled a plurality of the stages. The unit further has a heat insulating structural member for insulation of heat from a moving blade and a stationary blade supporting portion, both provided in an inner circumferential surface portion in a turbine radial direction of the steam chamber unit.
According to this invention, the steam chamber unit is formed in one unit integrally having therein three passages including the steam supply passage, the steam connection passage and the steam recovery passage, as well as having the heat insulating structural member and the stationary blade supporting portion. The process of supply and recovery of the cooling steam and cooling by the cooling steam of the stationary blade cooled portion can thereby be appropriately done by a compact structure so that the stationary blade is cooled effectively and a highly economical and reliable gas turbine can be obtained.
Also, the present invention provides a steam cooled type gas turbine as mentioned above, characterized in that a consecutive cooling passage is formed by the steam supply passage, steam connection passage the and the steam recovery passage, each being connected to a stationary blade cooling steam passage via a branch pipe having an opening to open to the respective steam passages.
According to this invention, the steam supply passage, steam connection passage and steam recovery passage for leading therethrough the cooling steam are connected to the stationary blade cooling steam passage provided in the stationary blade via the branch pipe, whereby a single consecutive cooling steam passage having a compact structure is completed and the process of supply and recovery of the cooling steam and cooling by the cooling steam can be done appropriately by that single consecutive passage, and a highly economical and reliable gas turbine can be obtained.
Further, the present invention provides a steam cooled type gas turbine as mentioned above, characterized in that the branch pipe is formed in a hollow bolt-like member having a threaded portion and is fixed to a fitting portion in the steam chamber unit via the threaded portion.
According to this invention, the branch pipe for connecting the steam supply passage, steam connection passage and steam recovery passage to the stationary blade cooling steam passage is formed in the bolt-like member, and this bolt-like member is fixed to the steam chamber unit via the threaded portion, whereby the entire construction of the passages is made in a further compact form and a highly economical and reliable gas turbine can be obtained.
Also, the present invention provides a steam cooled type gas turbine as mentioned above, characterized in that the branch pipe is formed in a hollow pipe-like member having a flange at its top portion and is fixed to a fitting portion in an outer circumferential surface portion in the turbine radial direction of the steam chamber unit via the flange.
According to this invention, the branch pipe for connecting the steam supply passage, steam connection passage and steam recovery passage to the stationary blade cooling steam passage is formed in the pipe-like member having the flange, instead of the bolt-like member, and this pipe-like member is fixed to the steam chamber unit via the flange, whereby the entire construction of the passages is made in a likewise compact form and a highly economical and reliable gas turbine can be obtained.
Furthermore, the present invention provides a steam cooled type gas turbine as mentioned in any one of the above inventions, characterized in that there are provided a steam supply pipe connected to the steam supply passage for supplying therethrough the cooling steam into a portion of a combustor to be cooled and a steam recovery pipe connected to the steam connection passage for recovering therethrough the cooling steam from the portion of the combustor to be cooled.
According to this invention, in a case where the cooling of the gas turbine is to be made not only for the stationary blade but also for the combustor, the portion of the combustor to be cooled is connected to the steam supply passage in the steam chamber unit via the steam supply pipe and to the steam connection passage in the steam chamber unit via the steam recovery pipe so that, not only the stationary blade, but also the
Endo Tadayoshi
Sakon Toshio
Casaregola Louis J.
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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