Patent Publication Number: US-2016237904-A1

Title: Systems and methods for controlling an inlet air temperature of an intercooled gas turbine engine

Description:
TECHNICAL FIELD 
     The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to systems and methods for controlling an inlet air temperature of an intercooled gas turbine engine. 
     BACKGROUND OF THE INVENTION 
     Generally, an intercooled gas turbine engine may include a high pressure compressor for compressing an incoming flow of air, a combustor for mixing the compressed flow of air with a pressurized flow of fuel and igniting the mixture to create a flow of combustion gases, and a high pressure turbine for producing mechanical work as the flow of combustion gases passes therethrough. The high pressure compressor, the combustor, and the high pressure turbine may collectively be referred to as the “core engine.” In some applications, an intercooled gas turbine engine also may include a low pressure compressor, which alternatively may be referred to as a “booster,” for supplying compressed air to the high pressure compressor for further compression therein. 
     It is well known that the operating characteristics of a gas turbine engine may be affected by the ambient temperature of the operating environment, which determines the temperature of the incoming flow of air supplied to the core engine. In particular, when the ambient temperature is relatively low, the core engine may operate to output a high shaft horse power (SHP) while the core engine temperature is maintained at an acceptable level. However, when the ambient temperature is relatively high, the core engine temperature may reach an unacceptably high level if a high SHP is being delivered. 
     To satisfy a demand for outputting a high SHP even when the ambient temperature is relatively high, a cooling system may be utilized, particularly on hotter days, to cool the incoming flow of air supplied to the core engine. In this manner, the cooling system may increase the range of ambient temperature in which the gas turbine engine may deliver maximum power while operating within emissions limits. As an example, the cooling system may include an intercooler for cooling air received from the low pressure compressor and supplying the cooled air to the high pressure compressor. Intercooled gas turbine engines may benefit from a power increase across all ambient temperatures. Some intercooled gas turbine engines may not include any means for controlling the temperature of the cooled air, and thus a certain variation in the cooled air temperature may be inevitable as the ambient temperature changes. 
     Other intercooled gas turbine engines may control the temperature of the cooled air supplied to the core engine by manipulating the temperature of the cooling fluid, such as water, entering the intercooler. Although this indirect control method may be effective in some applications, it presents certain undesirable drawbacks. For example, manipulation of the cooling fluid entry temperature may require significant recirculation of hot fluid back through the inlet of the intercooler to increase the product air temperature when required. Additionally, the amount of recirculation required for fast start-up may increase the cost of the intercooler system. Furthermore, indirectly controlling the cooled air temperature by manipulating the cooling fluid entry temperature is an inherently slow control method due to the lag time between cooled air temperature measurement, cooling fluid temperature change, intercooler equilibrium, and cooled air temperature change. 
     There is thus a desire for improved systems and methods for controlling an inlet air temperature of an intercooled gas turbine engine. Such improved systems and methods may provide fast, accurate, and low-cost control of the temperature of the cooled air supplied to the core engine. In particular, as compared to existing systems and methods involving manipulation of the temperature of the cooling fluid entering the intercooler, such improved systems and methods may reduce product cost as well as start-up times. 
     SUMMARY OF THE INVENTION 
     The present application and the resultant patent provide an intercooled gas turbine engine. The intercooled gas turbine engine may include a low pressure compressor configured to produce a compressed flow of air, an intercooler, a low pressure compressor configured to produce a compressed flow of air, a high pressure compressor, a second air line positioned between the intercooler and the high pressure compressor and configured to direct the first portion of the compressed flow of air toward the high pressure compressor, and a bypass air line positioned between the low pressure compressor and the high pressure compressor and configured to direct a second portion of the compressed flow of air to the second air line. 
     The present application and the resultant patent also provide a method of controlling a temperature of an incoming flow of air supplied to a core engine of an intercooled gas turbine engine. The method may include the steps of producing a compressed flow of air with a low pressure compressor, directing a first portion of the compressed flow of air to an intercooler for cooling therein, bypassing a second portion of the compressed flow of air around the intercooler, mixing the first portion of the compressed flow of air and the second portion of the compressed flow of air downstream of the intercooler to form the incoming flow of air, and directing the incoming flow of air to the core engine. 
     The present application and the resultant patent further provide an intercooled gas turbine engine. The intercooled gas turbine engine may include a low pressure compressor configured to produce a compressed flow of air, an intercooler, a low pressure compressor configured to produce a compressed flow of air, a high pressure compressor, a second air line positioned between the intercooler and the high pressure compressor and configured to direct the first portion of the compressed flow of air toward the high pressure compressor, a bypass air line positioned between the low pressure compressor and the high pressure compressor and configured to direct a second portion of the compressed flow of air to the second air line, a combustor in communication with the high pressure compressor, and a high pressure turbine in communication with the combustor. 
     These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a known gas turbine engine including a low pressure compressor, an intercooler, a high pressure compressor, a combustor, a high pressure turbine, and a low pressure turbine. 
         FIG. 2  is a schematic diagram of a gas turbine engine as may be described herein, the gas turbine engine including a low pressure compressor, an intercooler, an air bypass line, a high pressure compressor, a combustor, a high pressure turbine, and a low pressure turbine. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a schematic diagram of a known gas turbine engine  100 . The gas turbine engine  100  may include a high pressure compressor  104  for compressing an incoming flow of air  108  received via an air inlet  110  of the high pressure compressor  104 . The incoming flow of air  108  may be supplied to the high pressure compressor  104  via an air inlet line  112  extending to the air inlet  110 . The high pressure compressor  104  produces a compressed flow of air  114  (at a high pressure), which may be delivered to a combustor  118  of the gas turbine engine  100 . The combustor  118  mixes the compressed flow of air  114  with a pressurized flow of fuel  120  and ignites the mixture to create a flow of combustion gases  122 . Although only a single combustor  118  is shown, the gas turbine engine  100  may include any number of combustors  118 , which may be arranged in an annular array about a longitudinal axis of the gas turbine engine  100 . The gas turbine engine  100  also may include a high pressure turbine  126  that receives the flow of combustion gases  122  from the combustor  118 . The flow of combustion gases  122  drives the high pressure turbine  126  so as to produce mechanical work, which may drive the high pressure compressor  104  via a first shaft or high pressure rotor  128 . The mechanical work produced by the high pressure turbine  126  also may drive an external load (not shown), such as an electrical generator and the like, via the high pressure rotor  128 . The high pressure compressor  104 , the combustor  118 , and the high pressure turbine  126  may collectively form a core engine  130  of the gas turbine engine  100 , and the air inlet  110  of the high pressure compressor  104  may be the air inlet of the core engine  130 . 
     As is shown in  FIG. 1 , the gas turbine engine  100  also may include a low pressure compressor  132  for producing a compressed flow of air  134  (at a low pressure), which may be delivered from an air outlet  136  of the low pressure compressor  132  to an intercooler  138  of the gas turbine engine  100 . The compressed flow of air  134  may be delivered from the low pressure compressor  132  via an air outlet line  140  extending from the air outlet  136  of the low pressure compressor  132  to an air inlet  142  of the intercooler  138 . The compressed flow of air  134  passes through the intercooler  140  from the air inlet  142  to an air outlet  144  thereof. A flow of cooling fluid  146  also passes through the intercooler  138  from a cooling fluid inlet  148  to a cooling fluid outlet  150  thereof. When passing through the intercooler  138 , the compressed flow of air  134  and the flow of cooling fluid  146  are in heat transfer communication with one another. In this manner, the compressed flow of air  134  is cooled via the intercooler  138  and then supplied to the core engine  130  as the incoming flow of air  108 . 
     The gas turbine engine  100  also may include a low pressure turbine  152  that receives the flow of combustion gases  122  from the high pressure turbine  126 . The flow of combustion gases  122  drives the low pressure turbine  152  so as to produce mechanical work, which may drive the low pressure compressor  132  via a second shaft or low pressure rotor  154 . The mechanical work produced by the low pressure turbine  152  also may drive an external load (not shown), such as an electrical generator and the like, via the low pressure rotor  154 . Other configurations of the gas turbine engine  100  may be used, and the gas turbine engine  100  may include other components. 
     In some configurations, the gas turbine engine  100  may include one or more additional inline turbines that receive the flow of combustion gases  122 . For example, an additional turbine  156  may be included downstream of and in communication with the turbine  152 , as is shown via dashed lines, to receive the flow of combustion gases  122  therefrom. In this manner, the turbine  152  may be an “intermediate pressure turbine,” and the turbine  156  may be a “low pressure turbine.” It will be understood that the terminology for the turbines may be determined based on the relative positioning of the additional inline turbines. The intermediate pressure turbine  152  may drive the low pressure compressor  132  via the low pressure rotor  154 , and the low pressure turbine  156  may drive an external load, such as an electrical generator and the like, via a third shaft or load rotor  158 . Still other inline turbines may be used, according to other configurations of the gas turbine engine  100 . 
     During operation of the gas turbine engine  100 , the temperature of the incoming flow of air  108  entering the air inlet of the core engine  130  (i.e., the air inlet  110  of the high pressure compressor  104 ) may vary as the ambient temperature of the operating environment changes. Alternatively, the temperature of the incoming flow of air  108  may be controlled by manipulating the temperature of the flow of cooling fluid  146  entering the intercooler  138 , which affects the degree of cooling provided by the intercooler  138 . Although this indirect control method may be effective in some applications, it presents certain undesirable drawbacks, as described above. 
     The gas turbine engine  100  may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine  100  may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine  100  may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. 
       FIG. 2  shows a schematic diagram of a gas turbine engine  200  as may be described herein. The gas turbine engine  200  generally may be configured in a manner similar to the gas turbine engine  100 , although certain differences in structure and function may be described herein below. As is shown, the gas turbine engine  200  may include the high pressure compressor  104 , the combustor  118 , and the high pressure turbine  126 , which collectively form the core engine  130 . The gas turbine engine  200  also may include the low pressure compressor  132 , the intercooler  138 , and the low pressure turbine  152 . In some configurations, as described above, the turbine  152  may be an intermediate pressure turbine, and the gas turbine engine  200  may further include the low pressure turbine  156 . These components generally may function in manner similar to that described above with respect to the gas turbine engine  100 . 
     The gas turbine engine  200  may include the air outlet line  140  extending from the low pressure compressor  132  to the intercooler  138  and configured to direct a first portion of the compressed flow of air  134  to the intercooler  138  for cooling. The gas turbine engine  200  also may include a bypass air line  204 , which alternatively may be referred to as an “intercooler bypass air line.” The bypass air line  204  may be positioned between the low pressure compressor  132  and the high pressure compressor  104  and configured to direct a second portion of the compressed flow of air  134 , which also may be referred to as a “flow of bypass air,” to the air inlet line  112  without passing through the intercooler  138 . In other words, the second portion of the compressed flow of air  134  bypasses the intercooler  138  and thus is not cooled. 
     In some embodiments, as is shown, the bypass air line  204  may extend from the air outlet  136  of the low pressure compressor  132  to an intermediate portion of the air inlet line  112  (downstream of the air outlet  144  of the intercooler  138  and upstream of the air inlet  110  of the high pressure compressor  104 ). In other embodiments, the bypass air line  206  may extend from an intermediate portion of the air outlet line  140  (downstream of the air outlet  136  of the low pressure compressor  132  and upstream of the air inlet  142  of the intercooler  138 ) to an intermediate portion of the air inlet line  112  (downstream of the air outlet  144  of the intercooler  138  and upstream of the air inlet  110  of the high pressure compressor  104 ), as is shown via a dashed line. Either way, the uncooled second portion of the compressed flow of air  134  joins the cooled first portion of the compressed flow of air  134  to form the incoming flow of air  108  supplied to the core engine  130 . 
     As is shown, the gas turbine engine  200  also may include one or more valves  208  positioned on or along the bypass air line  204  and configured to control the second portion of the compressed flow of air  134 . In particular, the one or more valves  208  may be selectively adjustable between an open position and a closed position, thereby providing variable control of the volumetric flow rate of the second portion of the compressed flow of air  134  passing through the bypass air line  204 . 
     The gas turbine engine  200  further may include a fluid mixer  212  configured to mix or blend the cooled first portion of the compressed flow of air  134  and the uncooled second portion of the compressed flow of air  134  to form the incoming flow of air  108  supplied to the core engine  130 . In particular, the fluid mixer  212  may be configured to substantially mix the cooled first portion of the compressed flow of air  134  and the uncooled second portion of the compressed flow of air  134  prior to entry into the core engine  130 . In some embodiments, as is shown, the fluid mixer  212  may be positioned at an intersection of the bypass air line  204  and the air inlet line  112 . In other embodiments, the fluid mixer  212  may be positioned downstream of the intersection of the bypass air line  204  and the air inlet line  112 . Preferably, the fluid mixer  212  may be spaced a sufficient distance apart from the air inlet  110  of the high pressure compressor  104  to ensure a substantially uniform temperature distribution in the incoming flow of air  108  prior to entry into the core engine  130 . 
     As is shown, the gas turbine engine  200  also may include a temperature sensor  216  configured to measure the temperature of the incoming flow of air  108  supplied to the core engine  130 . The temperature sensor  216  may be positioned downstream of the intersection of the bypass air line  204  and the air inlet line  112 . According to embodiments including the fluid mixer  212 , the temperature sensor  216  may be positioned downstream of the fluid mixer  212 . Preferably, the temperature sensor  216  may be spaced a sufficient distance apart from the fluid mixer  212  to ensure a substantially uniform temperature distribution in the incoming flow of air  108  prior to measurement of the temperature of the incoming flow of air  108 . In some embodiments, the temperature sensor  216  may be positioned at or immediately upstream of the air inlet  110  of the high pressure compressor  104 . 
     The gas turbine engine  200  further may include a controller  220  in operable communication with the one or more valves  208  and the temperature sensor  216 , as is shown. The controller  220  may be operable to control the temperature of the incoming flow of air  108  supplied to the core engine  130 . In particular, the controller  220  may be operable to adjust the state of the one or more valves  208  to a fully open position, a fully closed position, or one of a number of partially open positions, based on the temperature of the incoming flow of air  108  measured by the temperature sensor  216 . Ultimately, the controller  220  may be operable to maintain the temperature of the incoming flow of air  108  at a desired level or within a desired range. In this manner, the controller  220  may be operable to prevent the core engine temperature from reaching an unacceptably high level. 
     During operation of the gas turbine engine  200 , the controller  220  may continuously monitor the temperature of the incoming flow of air  108  as measured by the temperature sensor  216 . If the temperature of the incoming flow of air  108  falls below a desired level or range, the controller  220  may cause the one or more valves  208  (or at least one of the valves  208 , if multiple valves  208  are present) to move toward or to the open position, thereby increasing the volumetric flow rate of the uncooled second portion of the compressed flow of air  134  passing through the bypass air line  204 . In this manner, the temperature of the incoming flow of air  108  may be increased to the desired level or within the desired range. Conversely, if the temperature of the incoming flow of air  108  rises above a desired level or range, the controller  220  may cause the one or more valves  208  (or at least one of the valves  208 , if multiple valves  208  are present) to move toward or to the closed position, thereby decreasing the volumetric flow rate of the uncooled second portion of the compressed flow of air  134  passing through the bypass air line  204 . In this manner, the temperature of the incoming flow of air  108  may be decreased to the desired level or within the desired range. Ultimately, the controller  220  may operate to directly control the temperature of the incoming flow of air  108  supplied to the core engine  130 . 
     The gas turbine engine  200  and related methods described herein thus provide improved systems and methods for controlling an inlet air temperature of an intercooled gas turbine engine. As described above, the gas turbine engine  200  may include the bypass air line  204 , which may be utilized in conjunction with the one or more valves  208 , the temperature sensor  216 , and the controller  220  to provide fast, accurate, and low-cost control of the temperature of the flow of incoming air  108  supplied to the core engine  130 . In particular, as compared to existing systems and methods involving manipulation of the temperature of the flow of cooling fluid  146  entering the intercooler  138 , the gas turbine engine  200  and related methods reduce product cost as well as start-up times. 
     It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.