Abstract:
The invention relates generally to gas turbine engines used for electrical power generation. More specifically, embodiments of the present invention provide systems and ways for improving gas turbine engine reliability through an electric motor backup system for cooling features of the turbine section.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 62/293,887, filed on Feb. 11, 2016, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates generally to electrical power systems, including generating capacity of a gas turbine, and more specifically to systems and methods for providing an efficient and more reliable way of cooling engine components. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gas turbine engines are commonly used in land-based power plants for generating electricity. A representative simple cycle gas turbine engine  100  is shown in  FIG. 1 . These land-based power plants take atmospheric air into a compressor  101 , increase its pressure through a compression process, mix fuel with the compressed air and ignite the mixture to generate hot combustion gases through one or more combustors  102 , which drive a turbine  103  that is coupled to the compressor  101 . The mechanical work from the gas turbine engine  100  is used to drive a generator  104  for producing electricity. The exhaust from the gas turbine engine can be vented to the atmosphere or used for producing steam in a combined cycle operation. 
         [0004]    Current popular gas turbine engines typically take in ambient air at the engine inlet and raise its operating temperature and pressure from ambient conditions to approximately 700 deg. F. and 200-250 psi. This compressed air is then passed to one or more combustors where fuel is added and the fuel-air mixture is ignited, creating hot combustion gases having temperatures over 2000 deg. F. The hot combustion gases then pass through the turbine. In order to preserve the components in the turbine section that are exposed to these high temperatures, it is often times necessary to actively cool certain parts such as the stationary turbine vanes and rotating turbine blades. Cooling fluid such as air  105  from the compressor  101  is often directed to the turbine  103 , as shown in  FIG. 1 . However, removing air  105  from the compressor  101  reduces the amount of air which goes through the combustion process, thereby adversely affecting gas turbine engine efficiency. 
         [0005]    The assignee of the present invention has developed an auxiliary air compression process for use in gas turbine engines, known as TurboPHASE®, and is disclosed in co-pending U.S. patent application Ser. Nos. 14/350,469, 14/351,245, 14/329,340, and 14/329,433, each of which is hereby incorporated by reference. This auxiliary air compression process provides a system and method for improving the overall efficiency of a gas turbine engine through the addition of compressed air generated by a separately fueled air compression process. This air is directed to the combustion and turbine sections of the gas turbine engine. Furthermore, in co-pending U.S. patent application Ser. Nos. 14/972,403 and 62/201,031, the assignee of the present invention provides a way to utilize an auxiliary air compression system to aid in turbine cooling. 
         [0006]    While improvements have been made to the overall engine efficiency and to the turbine cooling, there is still a need to improve the overall reliability of the cooling system. 
       SUMMARY 
       [0007]    The present invention relates to systems and methods for improving the cooling of a turbine section of a gas turbine engine. In an embodiment of the present invention, a system for providing compressed air to a gas turbine engine is provided comprising a compressor, a combustion system, and a turbine fluidly connected, where a portion of the air from the compressor is used to cool components in the turbine, such as turbine blades and vanes. Also provided is an auxiliary air compression system having a fueled engine, an intercooled compressor, and a recuperator. An electric backup compression system is provided that is in fluid communication with the compressor and the turbine and includes an electrically-powered motor coupled to a backup compressor. In operation, compressed air from at least one of the auxiliary compression system and the electric backup compression system is directed into the turbine for cooling components of the turbine. 
         [0008]    In an alternate embodiment of the present invention, a method of providing cooling air to a turbine section of a gas turbine engine is provided where the method comprises operating the gas turbine engine to produce a supply of compressed air from a compressor of the gas turbine engine and operating an auxiliary compression system having a fueled engine, an intercooled compressor, and a recuperator to produce a first supply of pressurized air. An electric backup compression system is also operated comprising an electrically-powered motor coupled to a backup compressor to produce a second supply of pressurized air, where the second supply of pressurized air is formed from a portion of the compressed air from the compressor of the gas turbine engine. At least one of the first supply of pressurized air and the second supply of pressurized air is directed into the turbine section for cooling one or more components of the turbine. 
         [0009]    In yet another embodiment of the present invention, a method of providing cooling air to a turbine section of a gas turbine engine is provided. The method comprises operating the gas turbine engine compressor, combustor and turbine to produce a supply of compressed air from the engine compressor and directing a portion of the compressed air to an electronic backup compression system, where the electric backup compression system comprises an electrically-powered motor coupled to a backup compressor to produce a supply of pressurized air. The supply of pressurized air is directed into the turbine for cooling one or more components of the turbine. 
         [0010]    In yet another embodiment of the present invention, a method of providing cooling air to a turbine section of a gas turbine engine is disclosed. The method comprises operating the gas turbine engine to produce a supply of compressed air from the engine compressor and operating an auxiliary compression system comprising a fueled engine, an intercooled compressor, and a recuperator, to produce a supply of pressurized air. The supply of pressurized air is directed into the turbine for cooling one or more components of the turbine. 
         [0011]    In another embodiment of the present invention, a system for providing compressed air to cool gas turbine engine components is provided comprising a compressor, a combustion system, and a turbine fluidly connected, where a portion of the air produced by the compressor is used to cool components in the turbine. The system also includes a plurality of auxiliary compression systems in selective fluid communication with the components in the turbine, each system comprising a fueled engine, an intercooled compressor, and a recuperator and capable of producing compressed air providing a backup supply of cooling air to the components in the turbine. 
         [0012]    In yet another embodiment of the present invention, a system is provided for cooling gas turbine engine components. The system comprises an auxiliary compression system comprising a fueled engine, an intercooled compressor, and a recuperator. An electric backup compression system is also provided comprising an electrically-powered motor coupled to a backup compressor. The auxiliary compression system provides a primary source of cooling air to the gas turbine engine components and the electric backup compression system provides a secondary source of cooling air in the event the auxiliary compression system is not available. 
         [0013]    One aspect of the present invention relates to a system and method for allowing a gas turbine engine to continue operating at full power when an auxiliary compression system stops operating. 
         [0014]    Another aspect of the present invention relates to systems and methods for an all-electric system to be used in place of the separately fueled auxiliary compression system for air injection. 
         [0015]    Another aspect of the present invention relates to a method and system for an all-electric way of taking gas turbine compressor discharge air in a mixing process to add heat to the air being delivered from the electric-driven intercooled air compressor. 
         [0016]    Other advantages, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure and the combination of parts will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0017]    The present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0018]      FIG. 1  is a schematic drawing of a gas turbine engine in accordance with the prior art. 
           [0019]      FIG. 2  is a schematic drawing of an auxiliary compression system and an electric backup compression system in accordance with an embodiment of the present invention. 
           [0020]      FIG. 3  is a schematic drawing of a gas turbine engine having an electric backup compression system in accordance with an embodiment of the present invention. 
           [0021]      FIG. 4  is a schematic drawing of a series of auxiliary compression systems in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Embodiments of the present invention are described below with respect to  FIGS. 2-4 . Referring initially to  FIG. 2 , a gas turbine engine  200  is provided comprising a compressor  201 , a combustion system  202 , and a turbine  203  in fluid communication. The compressor  201  takes in ambient air and compresses it, through a multi-stage compression process, to a higher temperature and pressure and passes the compressed air to the combustion system  202 . A portion of the compressed air  210  is directed from the compressor discharge for purposes of cooling components in the turbine  203 . 
         [0023]    The compressed air  210  is passed to an electric backup compression system  220  that is also in fluid communication with the turbine  203 . The electric backup compression system  220  comprises a motor  222  powered by an electrical supply  224 . The motor  222  provides shaft power to turn the backup compressor  226 . This electric backup compression system  220  takes compressed air  210  from the engine compressor  201 , or an engine compressor discharge at the exit of compressor  201 , and further compresses the air to a higher operating pressure. Depending on the temperature and pressure requirements for the cooling air  231  being supplied to the turbine  203 , the compressed air may pass through a cooler  228 , to cool the air to a lower temperature. However, care must be used when cooling the air temperature of air from the backup compressor in order to ensure the temperature is not lowered to the point of causing cracking in turbine parts due to thermal shock. Compressed air  230 , also referred to as a second supply of pressurized air, then passes through a valve  232 , which controls flow to the turbine  203 . 
         [0024]    The electric backup compression system  220  can be used alone as a way to further compress cooling air, as shown in  FIG. 3 , or can be used in the event of trouble or availability issues with an auxiliary air compression system  250 , as shown in  FIG. 2 . Referring back to  FIG. 2 , the electric backup compression system  220  operates in conjunction with or as a separate unit to the auxiliary air compression system  250 . The auxiliary air compression system  250  comprises a reciprocating engine  252 , which takes in fuel  254  and ambient air  256  and generates power in the form of torque on a shaft, and provides shaft power to turn a multistage intercooled compressor  258 . The compressor  258  draws in ambient air  260  and compresses the air to form warm compressed air  262 . 
         [0025]    The auxiliary air compression system  250  also comprises a recuperator  264 , which receives exhaust  266  from the reciprocating engine  252  and the warm compressed air  262  from the compressor  258 . As the compressed air  262  passes through the recuperator  264 , the compressed air  262  is heated by the exhaust  266  from the reciprocating engine  252 . As a result, a supply of hot compressed air  268 , also referred herein as a first supply of pressurized air, exits from the recuperator  264 . The remaining exhaust  270 , which is now cooler due to it being used as a heating source, is routed to the atmosphere or to the gas turbine exhaust. 
         [0026]    The electric backup compression system  220  can be sized to continuously supply a portion of the cooling air where the portion of the cooling air represents a fraction of the capacity of the electric driven system. By doing this, the electric backup compression system  220  can operate continuously to minimize any lag time in the event all of, or a portion of, the auxiliary compression system  250  goes offline. 
         [0027]    Referring back to  FIG. 3 , the electric backup compression system  220  is capable of supplying all of the cooling requirements to the turbine  203 . Although only a single electric backup compression system  220  is depicted, it may be advantageous to utilize multiple electric backup compression systems in order to provide redundancy to the cooling system. 
         [0028]    Referring back to  FIG. 2 , the valve  232  regulates the flow of compressed air for cooling in the turbine  203 . That is, the valve  232  is adjustable and can restrict the compressed air to that of the first supply of pressurized air  268  from the auxiliary air compression system  250  or a second supply of pressurized air  230  from the electric backup compression system  220 , or a combination of the first supply of pressurized air  268  and the second supply of pressurized air  230  to form the cooling air  231  for cooling components in the turbine  203 , such as turbine vanes or turbine blades. 
         [0029]    As one skilled in the art can appreciate, it is beneficial to be able to control the temperature of the hot compressed air  268 . This control is accomplished by a compressed air bypass or an exhaust bypass around the recuperator  264 , both of which are not depicted for clarity purposes. 
         [0030]    Depending on the pressure ratio of the backup compressor  226 , it may be advantageous to pull the compressed air for the electric backup compression system  220  from a location other than a compressor discharge plenum, such as an upstream stage in the compressor  201 . If air is withdrawn from an earlier stage of the compressor  201 , then the cooler  228  may be eliminated from the electric backup compression system  220  because the air entering the system will be cooler than air taken from the compressor discharge plenum. Furthermore, utilizing a backup compressor  226  having more than one stage of compression, such as an intercooled compressor, is another way of reducing the compressor exit temperature by intercooling one or more stages. 
         [0031]    One of the main aspects of cooling turbine components through an auxiliary supply system, as disclosed herein, is that the present invention provides cooling air at a pressure higher than the compressor discharge pressure of the engine  200 , allowing for more efficient cooling and advanced cooling schemes to be used, resulting in a reduced amount of cooling air required. Using less air for cooling increases the amount of air going through the combustion process, which translates into improved engine efficiency. Furthermore, by lowering the operating temperatures of hot gas path turbine parts, operating life of the turbine parts can be extended. 
         [0032]    Referring now to  FIG. 4 , a system  400  for providing compressed air to cool gas turbine engine components is depicted. The system  400  comprises a gas turbine engine having a compressor  401 , a combustor  402 , and turbine  403  fluidly connected where a portion of the air  405  from the compressor  401  is used to cool components in the turbine  403 . Shaft power from the gas turbine engine drives a generator  404 . A plurality of auxiliary compression systems  420  are in selective fluid communication with the gas turbine engine at least one of the auxiliary compression system  420  comprises a fueled engine  422 , an intercooled compressor  424 , and a recuperator  426 . The auxiliary compression systems  420  depicted in  FIG. 4  are in accordance with the auxiliary air compression system discussed above, and as shown in  FIG. 2 . While the cooling air  405  for the components of turbine  403  is taken from the compressor  401 , the compressed air  430  produced by auxiliary compression systems  420  provides a backup supply of cooling air to the components in turbine  403 . The flow of compressed air  430  from the auxiliary compression systems  420  to turbine  403  is regulated by a valve  440 . 
         [0033]    As used herein, the term “fueled engine” means a heat engine, such as a piston driven or rotary (e.g. Wankel) internal combustion engine (e.g. gasoline engine, diesel engine, natural gas fired engine, or similar fuels, or a combination of such fuels) or a gas turbine, that produces work by combusting a fuel with air to heat a working fluid which then drives blades or the like. The shaft of the engine turns a multi-stage auxiliary compressor which compresses the air, thereby heating the air. Depending on the configuration of the separate compressed air source, the compressor of the backup compression system may be an intercooled compressor, where the air is cooled between each stage of the compressor, thereby allowing for further compression of the air over more typical compression systems. According to one embodiment, the auxiliary compressor is a multistage compressor having at least one upstream compression stage and at least one downstream compression stage fluidly downstream of the upstream compression stage, and the step of operating the fueled engine to drive the auxiliary compressor to produce compressed air from the auxiliary compressor includes the step of cooling the compressed air exiting the upstream compression stage before delivering it to the downstream compression stage. Preferably, the apparatus further comprises an intercooler heat exchanger fluidly connected to at least one of the stage inlets and at least one of the stage outlets to cool the compressed air exiting the at least one of the stage outlets prior to delivering the compressed air to the at least one of the stage inlets downstream thereof. 
         [0034]    As those skilled in the art will readily appreciate, each of the embodiments of the present invention may also include flow control valves, backflow prevention valves, and shut-off valves as required to insure that the flow of air, auxiliary compressed air, and compressor discharge air flow only in the directions described herein. While the particular systems, components, methods, and devices described herein and described in detail are fully capable of attaining the above-described objects and advantages of the invention, it is to be understood that these are but embodiments of the invention and are thus representative of the subject matter which is broadly contemplated by the present invention. The scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims. It will be appreciated that modifications and variations of the invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.