Abstract:
A portion of cooling air for cooling the turbine section of a gas turbine engine is tapped and passed through a heat exchanger. The portion of the cooling air is cooled in the heat exchanger, and the heat taken out of the portion of the cooling air is utilized to generate electricity.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a ground-based turbine for generating electricity, wherein cooling air for the turbine sections is cooled in a generator and electricity is generated from the cooling step. 
         [0002]    Ground based turbine systems are known and are utilized to generate electricity. Gas turbine engines generally include a compressor section compressing air and delivering the air into a combustion section at which it is mixed with fuel. The fuel and the air are combusted, and the products of this combustion are passed downstream over turbine rotors to drive the turbine rotors. The turbine rotors become quite hot, as the products of combustion are hot. Thus, it is known in the gas turbine industry to circulate cooling air through the turbine sections. 
         [0003]    One main application for gas turbine engines are aviation-based uses. In such uses, the engines are cycled on and off relatively quickly (on the order of hours). One other application for gas turbine engines is the generation of electricity in ground-based uses. Such applications typically require the gas turbine engines to be operating for more constant and longer periods of time. Thus, ground-based turbine sections are subject to different challenges than air-based turbine sections. In particular, ground-based turbine sections are subject to creep life and oxidation limits. 
         [0004]    It is known to cool various fluids, and utilize the cooling of those fluids to generate electricity. As an example, UTC-Power has a system known as the Pure Cycle®, which cools a fluid, and utilizes the energy captured from cooling the fluid to generate electricity. 
       SUMMARY OF THE INVENTION 
       [0005]    A gas turbine engine taps cooling air to be utilized in the turbine section. This cooling air is passed through a vapor cycle driven generator, and generates additional electricity while it is cooled. The cooled cooling air is re-introduced into the turbine section. 
         [0006]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic view of a ground-based gas turbine engine incorporating a vapor cycle driven generator for cooling air. 
           [0008]      FIG. 2  schematically shows an example vapor cycle driven generator. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]      FIG. 1  shows a gas turbine engine  20  which is utilized in ground-based application. As known, air is compressed in compressor sections  22 . This air is delivered downstream into a combustion section  26  where it is mixed with fuel and combusted. The products of combustion pass downstream over rotors  29  in turbine section  28 , which are driven to rotate and power a shaft  30 . As shown schematically, this shaft  30  drives compressor sections  22 . As also shown, either the shaft  30  or a separate shaft driven by another turbine section drives a generator  41  for creating electricity for various uses  40 . While one type ground-based electricity generation system is shown schematically, this application would extend to any type of generator for generating electricity utilizing a gas turbine engine. While a ground-based gas turbine engine for generating electricity is discussed, the invention can extend to other gas turbine engine applications. 
         [0010]    As mentioned above, the turbine sections  28  are subject to high temperature from the products of combustion. Thus, it is typical to circulate a cooling fluid through the turbine section  28 . A cooling fluid includes a portion of the air compressed by the compressor section  22 , and may be delivered into a path  70  leading downstream toward the turbine section  28 . While the cooling air in section  70  is cooler than the products of combustion, it is also heated relative to the ambient environment due to its compression in the compressor section  22 . The present invention taps a portion of the cooling air from a discharge chamber  24  downstream of the compressor section  22  through a tap line or flow path  32  leading to a boost pump  34 . This air is then delivered into a heat exchanger  36 , where it is cooled by a vapor cycle driven generator  38 . The cooling of the air creates electricity in the vapor cycle driven generator  38 , and this electricity is delivered downstream to a use  140 . The use  140  may be the same as the downstream use  40  of the generator  41 , or may be some other auxiliary use. In one embodiment, less than 20%, and more narrowly 4-10% of the total cooling air is circulated through the heat exchanger, while the remainder is delivered directly into the combustion section. Downstream of the heat exchanger  36 , the air passes back through lines  42  and  44  to perform its cooling functions. 
         [0011]      FIG. 2  shows one example vapor cycle driven generator  38 . The vapor cycle driven generator  38  includes the heat exchanger  36  and the cooling air passing from the gas turbine engine  20  through the heat exchanger  36 . A second fluid circulates through the heat exchanger  36 , to cool the cooling air. This fluid passes into a line  52 . The fluid in line  52  may be a refrigerant, or any other appropriate fluid that has good heat transfer characteristics. The fluid in line  52  has been elevated in pressure and heat by cooling the cooling air in the heat exchanger  36 . This fluid now passes into a turbine section  54  that generates additional electricity in the generator  56 . The fluid downstream of the turbine  54  passes through another heat exchanger  58 , then to a pump  50 , and back to the heat exchanger  36 . Essentially, heat exchanger  36  functions as an evaporator and heat exchanger  58  functions as a condenser. A cooling tower  60  may circulated another fluid, such as cold water, through the heat exchanger  58  to cool the refrigerant prior to its being directed back to the heat exchanger  36 . 
         [0012]    The system as shown in  FIG. 2  is generally known in the prior art as the Pure Cycle® system, and is available from UTC-Power of South Windsor, Conn. However, this system has never been utilized in combination with a gas turbine engine to cool cooling air, and extract additional electricity from that cooling air. 
         [0013]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.