Power plants – Combustion products used as motive fluid – Multiple fluid-operated motors
Reexamination Certificate
2000-10-23
2001-10-09
Casaregola, Louis J. (Department: 3746)
Power plants
Combustion products used as motive fluid
Multiple fluid-operated motors
C060S039780, C415S114000
Reexamination Certificate
active
06298657
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a combined cycle power generation plant including a gas turbine plant and a steam turbine plant.
2. Description of the Prior Art
A combined cycle power generation plant is a power generation system including a gas turbine plant and a steam turbine plant. A high temperature thermal energy is utilized by the gas turbine, and a low temperature thermal energy is utilized by the stream turbine. Thus, the thermal energy is recovered and effectively used.
In such a combined cycle power generation plant, research and development thereof has been done with emphasis on how much the high temperature thermal energy can be increased for enhancing the thermal efficiency of the combined cycle power generation plant.
However, there must be provided a cooling system for cooling the gas turbine after the high temperature thermal energy has been utilized. Air has been used as a cooling medium in this cooling system.
However, when air is used as the cooling medium, even if the high temperature thermal energy is attained, there are problems which prevent the thermal efficiency from being enhanced. These problems include a power loss at an air compressor used for elevating pressure of air which is used for cooling the gas turbine. These problems also include lowering of the mean temperature of a gas flowing in passages in the gas turbine, when the gas is mixed with the air which is used for cooling the gas turbine. This lowering of the mean temperature results in a lowering of energy contained in the gas.
In order to resolve these problems and to enhance the thermal efficiency, a cooling system using the stream s the cooling medium, in place of air, has been disclosed.
Japanese laid-open patent No. Hei 05(1993)-163960 discloses an idea to employ steam as the cooling medium of the gas turbine, but various problems exist therewith which must be resolved.
Japanese laid-open patent No. Hei 05(1993)-163960 discloses only a basic idea of using steam as the cooling medium. In this regard, steam is supplied into a hot gas turbine from a certain steam source and flows through portions to be cooled. Then, the steam is led into a recovery portion after it has cooled the gas turbine. However, no mention is made of particular consideration of problems such as pressure loss of the steam during cooling of the gas turbine.
That is, steam cooling is still in a stage of trial and error, wherein no satisfactory solution to the aforementioned problems has been realized.
The prior remains a basic idea, as mentioned above, wherein cooling steam passages are formed in series so as to communicate with one another along an entire portion of the gas turbine to be cooled, i.e. a stationary system or a rotating system.
That is, the stationary system to be cooled is constructed such that the cooling steam flows in series through a first stage stationary blade and then a second stage stationary blade. The steam becomes heated as it flows through these blades, and then it flows to a recovery portion.
In such a construction, there is caused a large pressure loss at the stationary system to be cooled, and accordingly, various restrictions are placed on the upstream side and the downstream side of the stationary system, which make designing and manufacturing more restrictive. Also, operation of the gas turbine is restricted, and plant efficiency is reduced. That is, if pressure of the steam is reduced when it is recovered, after cooling of the stationary system, output from the steam turbine is accordingly reduced, which results in lowering of plant efficiency.
On the other hand, if a predetermined pressure is to be obtained continuously at the steam turbine, with this pressure loss being considered in advance, a control valve having a capacity larger than is necessary must be provided. This means an increase of cost in designing and manufacturing, as well as employment of an impractically large control valve.
SUMMARY OF THE INVENTION
In view of the mentioned problems in the prior art it is an object of the present invention to provide a combined cycle power generation plant in which pressure loss is prevented from becoming large at the gas turbine to be cooled, and a cooling steam is recovered efficiently.
In order to attain this object, the present invention provides a combined cycle power generation plant including a gas turbine plant, a steam turbine plant, a waste heat recovery boiler using waste heat from a gas turbine of the gas turbine plant for generating steam for driving a steam turbine of the steam turbine plant, a steam system using steam for cooling the gas turbine, and a recovery system for recovering superheated steam from the gas turbine. There is provided at the gas turbine independent parallel cooling steam passages. Because the cooling steam passages are arranged in parallel, locations at which pressure loss of the cooling steam can occur are dispersed, whereby an aggregate of all the pressure losses can be reduced.
In one embodiment, the present invention provides a combined cycle power generation plant as mentioned above, wherein the parallel cooling steam passages consist of a cooling steam passage of a first stage stationary blade, and a cooling steam passage of a second stage stationary blade. Specifically, the stationary blades are provided with mutually independent cooling steam passages which are between the first stage stationary blade and the second stage stationary blade, whereby the pressure loss at the cooling steam passages is dispersed, and hence an aggregate of all the pressure losses can be reduced.
Also in this embodiment, the present invention provides a combined cycle power generation plant as mentioned above, wherein the parallel cooling steam passages consist of a cooling steam passage of a first stage moving blade, and a cooling steam passage of a second stage moving blade. Specifically, the moving blades are provided with mutually independent cooling steam passages which are between the first stage moving blade and the second stage moving blade, whereby the pressure loss at the cooling steam passages is dispersed, and hence an aggregate of all the pressure losses can be reduced.
In a second embodiment, the present invention provides a combined cycle power generation plant as mentioned above, wherein the parallel cooling steam passages consist of a plurality of mutually independent and parallel cooling steam passage systems, with each system comprising a plurality of stationary blades or moving blades sectioned with respect to one another in the same stage. Thus, the pressure loss at the cooling steam passages is dispersed, and hence an aggregate of all the pressure losses can be reduced.
REFERENCES:
patent: 4424668 (1984-01-01), Mukherjee
patent: 4571935 (1986-02-01), Rice
patent: 5340274 (1994-08-01), Cunha
patent: 5412937 (1995-05-01), Tomlinson et al.
patent: 5758487 (1998-06-01), Salt et al.
patent: 062 932 A1 (1982-10-01), None
patent: 764 767 A2 (1997-03-01), None
patent: 63-40244 (1988-08-01), None
patent: 8-270408 (1996-10-01), None
Fukuizumi Yasushi
Ichiryu Taku
Kataoka Masahito
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