Abstract:
A method for assembling a gas turbine engine assembly that includes mounting a gas turbine engine including an inlet and an exhaust within a module that includes an inlet area, an exhaust area, and an engine area extending therebetween, such that the gas turbine engine is housed within the module, coupling a first deflector within the module engine area such that when cooling air is channeled past the deflector, the deflector induces a substantially helically-shaped cooling air flowpath around a periphery of the gas turbine engine, and coupling an exhaust duct to an outlet of the module exhaust area.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for cooling gas turbine engines.  
         [0002]     Gas turbine engines are used as a power source within a variety of applications. To protect the engine from the environment, and to shield a surrounding structure from the gas turbine engine, the gas turbine engine may be mounted within an enclosure that includes an inlet area, an exhaust area, and an engine area that extends between the inlet area and the exhaust area. The enclosure provides a physical structure to contain any engine fires that may ignite, and may include an apparatus to facilitate extinguishing fires within the enclosure. For example, the apparatus may release agents into the enclosure to distinguish the flames, or alternatively, the enclosure may include an apparatus to restrict air from entering the enclosure, thus preventing airflow from fueling the fire.  
         [0003]     Because engines generally require continuous airflow for operation, within at least some known modules, the module inlet area includes a duct to route ambient air from outside the module to the engine, and the module exhaust area includes a duct to channel exhaust gases produced during operation of the engine from the module. During operation, heat is constantly generated by the gas turbine engine and various auxiliary equipment. Accordingly, cooling air is also channeled to the interior of the enclosure to facilitate cooling the gas turbine engine and other auxiliary equipment to within reasonable operating parameters. More specifically, at least one known gas turbine engine enclosure includes a fan configured to channel air from a forward end of the enclosure, through the enclosure, and outward through an exhaust duct coupled to an aft end of the enclosure.  
         [0004]     However, channeling cooling air axially through the enclosure may generate a non-symmetric cooling airflow with respect to the gas turbine engine. The non-symmetric cooling airflow may cause an upper half of the gas turbine engine casing to receive a greater quantity of cooling air than a lower half of the gas turbine engine casing. Accordingly, non-symmetric thermal gradients may result within the gas turbine engine casing and cause a non-symmetric mechanical distortion of the casing, and eventually blade tips and/or seals may rub against an interior surface of the casing. Specifically, as the blade tip clearance increases, the gas turbine engine performance is reduced and an exhaust an gas temperatures (EGT) margin is reduced.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     In one aspect, a method of assembling a gas turbine engine is provided. The method includes coupling a first deflector within the module engine area such that when cooling air is channeled past the deflector, the deflector induces a substantially helically-shaped cooling air flowpath around a periphery of the gas turbine engine, and coupling an exhaust duct to an outlet of the module exhaust area.  
         [0006]     In another aspect, a cooling system for a gas turbine engine is provided. The cooling system includes a first deflector coupled within a module, and a first supply fan configured to channel cooling air through the first deflector such that a substantially helically-shaped cooling air flowpath is generated around the gas turbine engine.  
         [0007]     In a further aspect, a gas turbine engine assembly is provided. The gas turbine engine assembly includes a cooling system that includes a first deflector coupled within a module, and a first supply fan configured to channel cooling air through the first deflector such that a substantially helically-shaped cooling air flowpath is generated around the gas turbine engine. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic illustration of an exemplary gas turbine engine;  
         [0009]      FIG. 2  is side view of an exemplary gas turbine module assembly that includes the gas turbine engine shown in  FIG. 1 ;  
         [0010]      FIG. 3  is an end view of the gas turbine engine module assembly shown in  FIG. 2  viewed along view  3 - 3 ; and  
         [0011]      FIG. 4  is a top view of the gas turbine engine module assembly shown in  FIG. 2  viewed along view  4 - 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]      FIG. 1  is a schematic illustration of a gas turbine engine  10  including an engine inlet  22 , at least one compressor  12 , a combustor  16 , a high pressure turbine  18 , a low pressure turbine  20 , and an exhaust nozzle  24  connected serially. In the exemplary embodiment, engine  10  is an LM2500 engine commercially available from General Electric Company, Cincinnati, Ohio. Compressor  12  and turbine  18  are coupled by a first shaft  26 , and turbine  20  and a driven load  28  are coupled by a second shaft  30 .  
         [0013]     In operation, air flows into engine inlet  22 , through compressor  12  in a direction that is substantially parallel to a central axis  34  extending through engine  10 . The compressed air is then delivered to combustor  16  where it is mixed with fuel and ignited. Airflow from combustor  16  drives rotating turbines  18  and  20  and exits gas turbine engine  10  through exhaust nozzle  24 .  
         [0014]      FIG. 2  is side view of an exemplary gas turbine engine assembly  50 .  FIG. 3  is an end view of gas turbine engine assembly  50  shown in  FIG. 2  viewed along view  3 - 3 .  FIG. 4  is a top view of gas turbine engine assembly  50  shown in  FIG. 2  viewed along view  4 - 4 .  
         [0015]     Gas turbine engine assembly  50  includes a module  60  that may be used with a gas turbine engine similar to engine  10  (shown in  FIG. 1 ). Module  60  includes an module inlet area  62 , a module exhaust area  64 , and a module engine area  66  that extends between module inlet and exhaust areas  62  and  64 , respectively.  
         [0016]     Module engine area  66  extends between module inlet area  62  and module exhaust area  64 . Module engine area  66  defines a cavity  70  sized to receive engine  10  therein. Engine  10  is mounted within module engine area cavity  70  such that engine inlet  22  (shown in  FIG. 1 ) is adjacent module inlet area  62 , and engine exhaust nozzle  24  (shown in  FIG. 1 ) is adjacent module exhaust area  64 . In the exemplary embodiment, module inlet area  62  and module exhaust area  64  extend substantially perpendicularly from module engine area  66 .  
         [0017]     Gas turbine engine assembly  50  includes a module inlet duct  80  coupled in flow communication with module inlet area  62 , and a module exhaust duct  82  coupled in flow communication with module exhaust area  64 . Gas turbine engine assembly  50  also includes a module cooling system  100 . In the exemplary embodiment, module cooling system  100  includes a first supply fan assembly  102  and a second supply fan assembly  104  that are both coupled within module inlet duct  80 . In an alternative embodiment, gas turbine engine assembly  50  only includes either fan assembly  102  or fan assembly  104 . In the exemplary embodiment, at least one of first and second supply fan assemblies  102  and  104  is energized to channel air through module inlet duct  80  and into module engine area  66 .  
         [0018]     Cooling system  100  also includes a cooling system exhaust duct  106  that is coupled in flow communication with module engine area  66 . Specifically, in the exemplary embodiment, module inlet duct  80  is coupled to module engine area  66  for supplying cooling air to module engine area  66  for external cooling of engine  10 . Spent cooling air is then discharged from module engine area  66  through cooling system exhaust duct  106  after cooling engine  10 . More specifically, module engine area  66  is partitioned from module inlet area  62  such that airflow channeled through module inlet duct  80  is directed only through module engine area  66  for cooling engine  10 .  
         [0019]     In the exemplary embodiment, cooling system  100  also includes a first deflector  110  and a second deflector  112 . First and second deflectors  110  and  112  are each coupled within module engine area  66  and each is formed with a radius of curvature  120  that is substantially similar to an external radius of curvature  122  of gas turbine engine  10 .  
         [0020]     In the exemplary embodiment, at least a portion  130  of first deflector  110  is positioned adjacent an end  132  of second deflector  112  such that a flow channel  134  is defined between first and second deflectors  110  and  112 , respectively. More specifically, flow channel  134  is defined between a radially outer surface  136  of first deflector  110  and a radially inner surface  138  of second deflector  112 .  
         [0021]     In the exemplary embodiment, cooling system  100  also includes at least one booster fan assembly  150  coupled within module engine area  66 . More specifically, in the exemplary embodiment, cooling system  100  includes a first booster fan assembly  152 , a second booster fan assembly  154 , and a third booster fan assembly  156 . At least one of first booster ban assembly  152 , second booster fan assembly  154 , and/or third booster fan assembly  156  is oriented within module engine area  66  at a tangential angle  158  measured with respect to centerline axis of rotation  34 , such that cooling air discharged from at least one of first booster ban assembly  152 , second booster fan assembly  154 , and/or third booster fan assembly  156  is discharged at an angle  158  that has a tangential component relative to engine axis of rotation  34 .  
         [0022]     Although, in the exemplary embodiment, cooling system  100  is illustrated as including three booster fan assemblies,  152 ,  154 , and  156 , it should be realized that cooling system  100  can have any quantity of booster fan assemblies. For example, cooling system  100  can include a single booster fan assembly  150 , two booster fan assemblies  150 , or more than three booster fan assemblies  150  without departing from the scope of the method and apparatus described herein.  
         [0023]     During operation, air channeled through module inlet duct  80  to module engine area  66  facilitates cooling gas turbine engine  10 . More specifically, at least one of supply fans  102  and/or  104  is energized to facilitate increasing a velocity of cooling air  160  channeled into module engine area  66 . In the exemplary embodiment, at least a portion of the cooling air directed towards module engine area  66  is channeled through flow channel  134 . The orientation of deflectors  110  and  112  to each other and within module engine area  66  facilitates generating a substantially helically-shaped cooling air flowpath  162  around a periphery  164  of gas turbine engine  10 . More specifically, cooling air discharged from supply fan assemblies  102  and/or  104  is initially channeled into module engine area  66  in a substantially linear flowpath. As the flow enters flowpath  162 , the orientation of deflectors  110  and  112  to each other and within module engine area  66  turns the direction of the flowpath and causes a substantially circular air flowpath to be generated. Accordingly, cooling air flowpath  162  includes an axial component and a helical component such that the cooling air  160  is channeled in a substantially helical, or swirling, fashion around gas turbine engine periphery  164 . The helical flowpath facilitates enhancing cooling of the periphery  164  circumferentially about gas turbine engine  10 .  
         [0024]     Moreover, as the substantially helical flowpath  162  is generated about gas turbine engine  10 , the velocity of such air  160  may be reduced. Accordingly, at least one of booster fans  152 ,  154 , and/or  156  is energized to facilitate increasing the velocity of cooling air  160  within module engine area  66 . More specifically, as an operating temperature within engine area  66  increases, at least one booster fan  152 ,  154 , and/or  156  is energized to facilitate maintaining helical flowpath  162  of cooling air  160  about gas turbine engine  10 . Moreover, increasing the velocity of cooling air  160  facilitates increasing the cooling capacity of cooling air  160 , thus reducing the operating temperature of gas turbine engine  10 . Cooling air  160  is then discharged through cooling system exhaust duct  106 .  
         [0025]     The above-described gas turbine engine module assembly is cost-effective and highly reliable. The engine module assembly includes a cooling system that facilitates generating a substantially helical air flowpath circumferentially around the gas turbine engine. More specifically, a pair of deflectors impart a swirling motion to the cooling air such that the cooling air revolves at least once about a circumference of the gas turbine engine. At least one booster fan is used to facilitate increasing the velocity of the cooling air and maintaining the helical flowpath axially around the outer periphery of the gas turbine engine. Accordingly, the gas turbine engine is circumferentially exposed to cooling air at approximately the same velocity and temperature. The cooling system described herein facilitates maintaining a uniform thermal environment around and along the gas turbine engine, thus out-of-round distortion and backbone bending of the gas turbine engine which are caused by thermal gradients are facilitated to be reduced. Accordingly, thermal gradients are reduced and clearances within the gas turbine engine are maintained.  
         [0026]     Exemplary embodiments of gas turbine assemblies are described above in detail. The assemblies are not limited to the specific embodiments described herein, but rather, components of each assembly may be utilized independently and separately from other components described herein. Specifically, the cooling system described herein can also be used in combination with other gas turbine engine assemblies.  
         [0027]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.