Abstract:
A combustion turbine is disclosed having a single shaft compressor that includes a low pressure side and a high pressure side. The compressor operation is optimized by inter-cooling within the compressor. In particular, a compressed fluid is extracted from a selected stage and the extracted fluid is cooled and returned to a selected stage within the compressor. The compressor inter-cooling improves engine performance and cycle performance, as measured by an increase in power or a decrease in heat rate for the same power.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention is directed generally to combustion turbines, and more particularly to combustion turbines having a single compressor, wherein compressed fluid, such as air, is extracted from one or more selected stages within the compressor, the extracted compressed fluid is cooled and returned to one or more selected stage within the compressor. 
       BACKGROUND 
       [0002]    Combustion turbines are generally employed in power generation plants. Typically, combustion turbines include three main components: a compressor for compressing a fluid, such as air; a combustor for mixing the compressed fluid with fuel and igniting the mixture; and a turbine for producing power. These components are generally configured in series and are sealed to form a gas-tight system. 
         [0003]    The compressor and turbine components typically contain many rows of opposing airfoil-shaped blades that are grouped in stages. In the compressor component, the stages typically include a row of rotating blades (rotors) followed by a row of stationary blades (stators), as viewed from a direction of fluid flow from an inlet side to an outlet side. In the turbine component, the stages typically include a row of stationary blades (vanes) followed by a row of rotating blades (blades), as viewed in a direction of fluid flow from an inlet side to an outlet side. The combustor component is located between the compressor component and the turbine component. The combustor component generally operates at high temperatures, which may exceed 2,500 degrees Fahrenheit. 
         [0004]    The stages within the compressor component and the turbine component are configured in series and each contributes to a pressure rise in the compressor component and a pressure drop in the turbine component. The rotating blade rows are coupled to a shaft that runs through the compressor component to the turbine component. The stationary blade rows are typically coupled to an interior periphery of the corresponding compressor and turbine components. 
         [0005]    The compressor component is configured to include a funnel-shaped structure or annulus that reduces a volume available to an air mass that travels from the inlet side to the outlet side. The compressor component receives ambient air at the inlet side. The blades within the compressor component transfer mechanical energy into the flow through aerodynamic lift and force the air mass through the annulus. The blade and vane airfoils diffuse the fluid flow to higher pressures thus compressing and heating the air mass. The compressor component ejects the compressed air mass into the combustor component. In the combustor component, fuel is injected into the compressed air stream and ignited. The burning fuel causes the fuel/compressed air mass mixture to rise significantly in temperature. The heated flow travels through the turbine where it expands back toward ambient conditions. The turbine component is configured to include a reverse funnel-shaped structure that increases a volume available to an air mass that travels from the inlet side to the outlet side. The air mass travels through the turbine and, again, aerodynamic lift causes the turbine blades to spin, allowing the airfoils to extract mechanical energy from the fluid flow. The air mass expands as it pushes through the turbine component. The turbine blades spin the shaft coupled thereto. One or more shafts run between the turbine component and the compressor component. As a result, the spinning shaft drives both the compressor blades and a generator, or other load of the combustion turbine. 
         [0006]    While advances have been made in increasing the efficiency of combustion turbines, a need still exists for increasing engine performance and cycle performance of combustion turbines. Conventional systems have relied on multiple series connected compressors and/or multiple series connected turbine sections to increase efficiency. However, these conventional systems include several drawbacks. 
       SUMMARY OF THE INVENTION 
       [0007]    Various aspects of the invention overcome at least some of these and other drawbacks of existing systems. According to one embodiment of the invention, a compressor is provided for a combustion turbine that include a low pressure structure having a plurality of stages and a high pressure structure having a plurality of stages, wherein the low pressure structure and the high pressure structure are coupled to the same shaft. The low pressure structure and the high pressure structure are enclosed in a compressor structure. An intercooler is fluidly coupled to the compressor structure, with the intercooler being positioned between the low pressure structure and the high pressure structure. The intercooler includes an inlet that extracts fluid from at least one stage within the low pressure structure and an outlet that returns cooled fluid to at least one stage within the high pressure structure. The intercooler may include a heat exchanger, among other coolers. 
         [0008]    According to one embodiment of the invention, the compressor intercooler may be configured to maintain a pressure drop equal to or less than 5 pounds per square inch. According to another embodiment of the invention, the compressor intercooler may be configured to extract from the compressor substantially all of the total compressor air flow. According to another embodiment of the invention, the compressor intercooler may be configured to extract from the compressor up to 20% by volume of the total compressor air flow. According to one embodiment of the invention, the compressor intercooler may introduce the cooled fluid into the compressor at a temperature that is at least 25% cooler than the fluid extracted from the compressor. The compressor intercooler provides the compressor with higher performance by reducing the work needed to run the compressor. 
         [0009]    According to another embodiment of the invention, a combustion turbine includes a compressor, combustor and turbine that are configured in series and include a singe shaft coupling the compressor and turbine. The compressor includes a low pressure structure having a plurality of stages and a high pressure structure having a plurality of stages, wherein the low pressure structure and the high pressure structure are coupled to the same shaft. The low pressure structure and the high pressure structure are enclosed in a compressor structure. An intercooler is fluidly coupled to the compressor structure, with the intercooler being positioned between the low pressure structure and the high pressure structure. The intercooler includes an inlet that extracts fluid from at least one stage within the low pressure structure and an outlet that returns cooled fluid to at least one stage within the high pressure structure. The intercooler may include a heat exchanger, among other coolers. 
         [0010]    These and other embodiments are described in more detail below. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention. 
           [0012]      FIG. 1  illustrates a combustion turbine according to one embodiment of the invention. 
           [0013]      FIG. 2  illustrates an Enthalpy/Temperature v. Entropy graph according to one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    While specific embodiments of the invention are discussed herein and are illustrated in the drawings appended hereto, the invention encompasses a broader spectrum than the specific subject matter described and illustrated. As would be appreciated by those skilled in the art, the embodiments described herein provide but a few examples of the broad scope of the invention. There is no intention to limit the scope of the invention only to the embodiments described. 
         [0015]    According to one embodiment of the invention illustrated in  FIG. 1 , a gas turbine  10  or internal combustion (IC) engine is provided. According to one embodiment of the invention, the gas turbine  10  may employ a continuous combustion process. The gas turbine  10  may include a compressor  12  having a low pressure side  5  including a structure  1  having a plurality of stages, a high pressure side  6  including structures  2 , 3 , 4  having a plurality of stages and a compressor intercooler  14  that is fluidly coupled between the low pressure side  5  and the high pressure side  6 . According to one embodiment of the invention, the low pressure side  5  may include at least six stages. According to one embodiment of the invention, the high pressure side  6  may include at least nine stages. According to another embodiment of the invention, the low pressure side  5  may include less than ten stages. According to one embodiment of the invention, the high pressure side  6  may include less than ten stages. One of ordinary skill in the art will readily appreciate that any number of stage may be employed in the low pressure side  5  and/or the high pressure side  6 . 
         [0016]    According to one embodiment of the invention, the compressor  12  may include a single shaft that is coupled to components of the low pressure side  5  and to components of the high pressure side  6  of compressor  12 . Structures  1 - 4  perform the function of compressing the fluid that passes through compressor  12 . According to one embodiment of the invention, a bleed line  8  may be provided after the low pressure side  5  side of compressor  12  to supply cooling fluid to a rear of the turbine  18 . According to one embodiment of the invention, a bleed line  10  may be provided between structures  2  and  3  to supply cooling fluid to a mid-stage of the turbine  18 . According to one embodiment of the invention, a bleed line  18  may be provided after the structure  4  to supply cooling fluid to a front of the turbine  18 . 
         [0017]    According to one embodiment of the invention, the compressor intercooler  14  may include a heat exchanger or other intercooler that extracts the compressed fluid, such as air or other compressed fluid, from the gas turbine  10  at one or more selected stages within the compressor  12 . According to another embodiment of the invention, the compressor intercooler  14  cools the compressed fluid using a cooling fluid, such atmospheric air, water, or other cooling fluid and reintroduces the cooled compressed fluid into the gas turbine  10  at one or more selected stages within the compressor  12 . According to one embodiment of the invention, the compressor intercooler  14  may extract the compressed fluid after a sixth stage of the compressor  12  and may reintroduce the cooled compressed fluid before the seventh stage of the compressor  12 . According to another embodiment of the invention, the compressor intercooler  14  may extract the compressed fluid after a low pressure side  5  of the compressor  12  and may reintroduce the cooled compressed fluid before the high pressure side  6  of the compressor  12 . According to one embodiment of the invention, the compressed fluid may be extracted from the compressor  12  after approximately  50 % completion of the compression process. One of ordinary skill in the art will readily appreciate that the compressor intercooler  14  may extract the compressed fluid from any stage of the compressor  12  and may reintroduce the compressed fluid into any stage of the compressor  12 . 
         [0018]    According to one embodiment of the invention, the compressor intercooler  14  returns the cooled compressed fluid to one or more stages of the compressor  12  that are located at a same stage and/or at a closer stage to the outlet side of the compressor  12 , compared to the one or more stages of the compressor  12  from which the compressed fluid is extracted. According to one embodiment of the invention, the compressor intercooler  14  may cool the extracted fluid by approximately 200 degrees Fahrenheit before reintroducing the cooled fluid into the compressor  12 . According to another embodiment of the invention, the compressor intercooler  14  may introduce the cooled fluid into the compressor  12  at a temperature that is at least 40% cooler than the extracted fluid. According to another embodiment of the invention, the compressor intercooler  14  may introduce the cooled fluid into the compressor  12  at a temperature that is at least 25% cooler than the extracted fluid. One of ordinary skill in the art will readily appreciate that other amounts of cooling may be provided by the compressor intercooler  14 . 
         [0019]    According to one embodiment of the invention, the compressor intercooler  14  may be configured to maintain a pressure drop equal to or less than approximately 5 pounds per square inch (psi). According to one embodiment of the invention, the compressor intercooler  14  may be configured to maintain a pressure drop equal to or less than approximately 3.5 psi. One of ordinary skill in the art will readily appreciate that other amounts of pressure drop may be designed into the intercooler  14 . Intercooler pressure losses may be mitigated by decelerating the extracted flow to lower velocities with an exit diffuser, thereby reducing the dynamic losses in intercooler components, such as piping and the heat exchanger. According to another embodiment of the invention, one or more stages of the compressor  12  that are located downstream of the return stage (e.g., closer to the outlet side of the compressor  12 ) may be designed to compensate for any pressure drop that is introduced by intercooler  14 . 
         [0020]    According to one embodiment of the invention, the compressor intercooler  14  may be configured to extract substantially all of the compressor air flow from the compressor  12 , without causing an adverse pressure drop in the compressor  12 . According to another embodiment of the invention, the compressor intercooler  14  may be configured to extract up to approximately 80% by volume of the total compressor air flow from the compressor  12 , without causing an adverse pressure drop in the compressor  12 . According to another embodiment of the invention, the compressor intercooler  14  may be configured to extract up to approximately 40% by volume of the total compressor air flow from the compressor  12 , without causing an adverse pressure drop in the compressor  12 . According to yet another embodiment of the invention, the compressor intercooler  14  may be configured to extract up to approximately 20% by volume of the total compressor air flow from the compressor  12 , without causing an adverse pressure drop in the compressor  12 . According to one embodiment of the invention, the configuration of down stream blades may be designed to compensate for a reduced mass flow rate. One of ordinary skill in the art will readily appreciate that other volumes of compressed air flow may be extracted from the compressor  12  without causing an adverse pressure drop in the compressor  12 . 
         [0021]    According to one embodiment of the invention, the compressor  12  includes an outlet that provides a compressed air flow to combustor  17 . According to one embodiment of the invention, the compressed air flow may have an exit temperature of several hundred degrees Fahrenheit at the outlet to compressor  12 . According to another embodiment of the invention, the compressed air flow may have an exit temperature of several hundred degrees Fahrenheit at the outlet to compressor  12 . According to another embodiment of the invention, the compressed air flow may have an exit temperature of approximately 500 degrees Fahrenheit or higher at the outlet to compressor  12 . According to another embodiment of the invention, the compressed air flow may have an exit temperature of approximately 750 degrees Fahrenheit or higher at the outlet to compressor  12 . 
         [0022]    According to one embodiment of the invention, the combustor  17  receives the compressed air flow and injects fuel  16  into the compressed air flow. The compressed air flow/fuel mixture is ignited to increase the air mass temperature to over 2000 degrees Fahrenheit. According to one embodiment of the invention, the air flow/fuel mixture is ignited on a continuous basis. 
         [0023]    According to one embodiment of the invention, the heated and compressed air exits the combustor  17  and expands into the turbine  18 , thereby reducing the pressure and temperature of the compressed air and increasing the volume of the compressed air. The airflow through the turbine  18  spins blades that are connected to the shaft  15  through aerodynamic lift. A portion of the shaft power produced by the turbine  18  is used to run the compressor  12  and another portion of the shaft power may be delivered to an electric generator or other load. Remaining thermal energy may be extracted from the exhaust flow by a separate power turbine that in turn is connected to an electric generator or other load. 
         [0024]      FIG. 2  illustrates an open Brayton cycle graph plotted in terms of Enthalpy/Temperature vs. Entropy for the system illustrated in  FIG. 1 . The curve Po 1  is a constant pressure curve for ambient pressures. The curve Po 1 ′ is a constant pressure curve for intermediate pressure along the compression process. The curve Po 2  is a constant pressure curve for pressures at the compressor outlet and turbine inlet. 
         [0025]    According to one embodiment of the invention, point A corresponds to ambient pressure and temperature conditions at the inlet to the compressor  12 . According to one embodiment of the invention, point Aa corresponds to intermediate pressure and intermediate temperature conditions at an inlet of intercooler  14 . According to one embodiment of the invention, point Ab corresponds to intermediate pressure and intermediate temperature conditions at an outlet of intercooler  14 . According to one embodiment of the invention, point Bb corresponds to elevated pressure and elevated temperature conditions at the outlet of compressor  12  having a benefit of fluid cooling introduced by the intercooler  14 . In particular, the compressor intercooler  14  reduces the compressor  12  discharge temperature compared to point B, which corresponds to elevated pressure and further elevated temperature conditions at the outlet of compressor  12  without the benefit of fluid cooling by the intercooler  14 . 
         [0026]    According to one embodiment of the invention, point C corresponds to elevated pressure and elevated temperature conditions at the inlet of turbine  18 . According to one embodiment of the invention, point D corresponds to ambient pressure and elevated temperature conditions at the outlet of turbine  18 . 
         [0027]    Due to the addition of the area defined by box  20  onto area defined by box  22 , the overall area defined by boxes  20  and  22  is increased when compared to the area defined by box  22  alone. Box  20  signifies the effect of the compressor intercooler  14  on the compressor  12 . In particular, the compressor intercooler  14  provides the compressor  12  with higher performance by reducing an amount of work needed to run the compressor  12 . The increased overall area contributed by box  20  translates to higher performance of the gas turbine  10 . 
         [0028]    According to one embodiment of the invention, the compressor intercooler  14  provides improved engine performance and improved cycle performance. According to one embodiment of the invention, the compressor intercooler  14  provides the gas turbine  10  with a power output improvement of between 20 Mega Watts to 30 Mega Watts. 
         [0029]    The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.