Patent Publication Number: US-11047243-B2

Title: Gas turbine blade

Description:
CROSS-REFERENCE(S) TO RELATED APPLICATIONS 
     This application claims priority to Korean Patent Application No. 10-2017-0000694, filed on Jan. 3, 2017 the disclosure of which is incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Exemplary embodiments of the present invention relate to a gas turbine blade capable of minimizing heat loss in a direction-changing portion, which allows the direction of cooling air flowing through a cooling passage formed in the turbine blade to be efficiently changed so as to enhance the cooling performance of the turbine blade while promoting the stable flow of the cooling air. 
     Description of the Related Art 
     In general, a variety of methods to increase the temperature at the inlet of a gas turbine have been proposed in order to enhance the performance of the gas turbine. However, the increase in temperatures at the inlet of the turbine enlarges the thermal load of a turbine blade, which eventually shortens its life. 
     In particular, due to the thermal load that is structurally generated in the turbine blade, the method of forcibly cooling the turbine blade by supplying a cooling fluid thereto is carried out. 
     This forced cooling method is a method of supplying a cooling fluid, which is discharged from a compressor of a turbine, to a blade through a passage within the blade, and of generating forced convection to cool the blade. In the cooling method using forced convection, an uneven profile is used to enhance cooling performance. The uneven profile is used to disturb the flow in the passage for an improvement in heat transfer. 
     A plurality of bar-shaped ribs are conventionally arranged in an inclined state in a cooling path within a blade for cooling thereof. However, cooling performance may vary depending on the angle of inclination of each of the ribs. 
     Especially, the cooling path formed in the blade is a U-shaped round curved pipe. Thus, when cooling air flows via the curved pipe, a vortex is formed in the curved pipe due to the drop in pressure or the separation of the cooling air, which may lead to a secondary flow. 
     Hence, the stable flow of cooling air may be disturbed according to the arrangement of the ribs at the position in which the flow direction of the cooling air is sharply changed in the curved pipe within the blade, additionally resulting in a reduction in cooling efficiency. Therefore, there is a need for measures to deal with them. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a gas turbine blade capable of having improved cooling efficiency by stably maintaining the flow of cooling air in a section in which the cooling air flowing along a cooling passage of the turbine blade flows via a direction-changing portion. 
     Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art to which the present invention pertains that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof. 
     In accordance with an aspect of the present invention, a gas turbine blade includes a plurality of cooling passages formed by a partition wall partitioning an internal region of the turbine blade, a direction-changing portion allowing for a change of direction of cooling air flowing along the cooling passages, a first rib unit having a plurality of unit ribs bent in the direction of the cooling air flowing along the cooling passages, a second rib unit having a plurality of unit ribs bent in the direction of the cooling air flowing via the direction-chaining portion, and a guide portion facing the direction-changing portion to guide the flow of the cooling air. 
     Each of the unit ribs of the first and second rib units may have a V shape. 
     The guide portion may include a first guide portion facing the direction-changing portion in the first rib unit, and a second guide portion facing the direction-changing portion to guide the flow direction of the cooling air, which passes through the first guide portion, to the second rib unit. 
     The first and second guide portions may have a shorter length than the constituent unit ribs of the first and second rib units. 
     When the first guide portion has a length of L1 and each of the constituent unit ribs of the first rib unit has a length of L, the length of L1 may be equal to a length of L/2 (L1=L/2). 
     When the second guide portion has a length of L2 and each of the constituent unit ribs of the second rib unit has a length of L, the length of L2 may be equal to a length of L/2 (L2=L/2). 
     The first and second guide portions may form an angle between 30° and 60° with an inner wall of the turbine blade. 
     The first and second guide portions may be disposed inside an end of the partition wall facing the direction-changing portion. 
     The first guide portion may consist of a plurality of first guide portions that face the direction-changing portion and are spaced apart from each other. 
     The second guide portion may consist of a plurality of second guide portions that face the direction-changing portion and are spaced apart from each other. 
     The first guide portion may have the same protruding height as or a lower protruding height than the constituent unit ribs of the first rib unit. 
     The first rib unit may have a reduced protruding height as it is close to the first guide portion. 
     The second guide portion may have the same protruding height as or a lower protruding height than the constituent unit ribs of the second rib unit. 
     The cooling passage in which the second rib unit is disposed may have a smaller width than the cooling passage in which the first rib unit is disposed. 
     The unit ribs of the second rib unit may have a reduced protruding height in the flow direction of the cooling air from the second guide portion. 
     The second rib unit may have relatively more unit ribs than the first rib unit. 
     The direction-changing portion may have an auxiliary rib to guide the flow of the cooling air passing through the first guide portion. 
     The auxiliary rib may have a curvature corresponding to the rounded curvature of the direction-changing portion. 
     The auxiliary rib may consist of a plurality of auxiliary ribs having different lengths. 
     The auxiliary rib may be spaced apart from an end of the partition wall. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view schematically illustrating a gas turbine according to an embodiment of the present invention; 
         FIG. 2  is a view illustrating an internal configuration of a gas turbine blade according to an embodiment of the present invention; 
         FIG. 3  is a view illustrating an internal configuration of a gas turbine blade according to another embodiment of the present invention; 
         FIG. 4  is a perspective view illustrating arrangement of a first rib unit and a first guide portion according to an embodiment of the present invention; 
         FIG. 5  is a perspective view illustrating arrangement of a second rib unit and a second guide portion according to an embodiment of the present invention; 
         FIGS. 6 and 7  are perspective views illustrating exemplary first and second guide portions according to an embodiment of the present invention; and 
         FIG. 8  is a view illustrating an auxiliary rib according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Throughout the disclosure, like reference numerals refer to like parts throughout the various figures and embodiments of the present invention. 
     Hereinafter, a gas turbine blade according to exemplary embodiments of the present invention will be described with reference to the accompanying drawings. 
     Referring to  FIGS. 1 to 3 , a gas turbine  10  includes a compressor  16 , a combustor  18 , and a turbine  11 . The gas turbine  10  mixes air compressed by the compressor  16  with fuel for combustion in the combustor  18  and the fuel is expanded by the turbine  11 . 
     The turbine  11  includes a rotor  15  that drives the compressor  16  and a fan, and the rotor  15  further includes a blade  100  and a vane  19 . 
     The blade  100  has an airfoil shape and a dovetail is formed at the lower side of the blade  100  as shown in  FIG. 1 . The turbine blade  100  has a plurality of cooling passages  120  formed by a partition wall  110  partitioning the internal region of the blade  100 . 
     The blade  100  includes a direction-changing portion  102  that allows a flow direction of cooling air flowing through the cooling passages  120  to be changed, a first rib unit  130  having a plurality of unit ribs  132  bent in the direction of the cooling air flowing through the cooling passages  120 , a second rib unit  140  that has a plurality of unit ribs  142  bent in the direction of the cooling air flowing through the direction-chaining portion  102 , and a guide portion  150  provided in a portion adjacent to the direction-changing portion  102  to guide the cooling air. 
     The blade  100  has a void space and the partition wall  110  partitioning the internal region thereof into a plurality of spaces. The partition wall  110  partitions the internal region by a predetermined width for the flow of cooling air. 
     The first and second rib units  130  and  140  are disposed in the cooling passages  120 , which is partitioned by the partition wall  110 , and they are repeatedly disposed according to the number of cooling passages. 
     For example, when the blade  100  has a plurality of cooling passages  120  therein, on the basis of the flow direction of the cooling air, the first rib unit  130  is disposed in position A, the second rib unit  140  is disposed in position B via the direction-changing portion  102 , and another rib unit of which bending direction is similar to the bending direction of the first rib  130  may be disposed in position C. 
     The cooling air, for example, serves to cool the blade  100  while flowing through the first and second rib units  130  and  140 . 
     In order to efficiently use the cooling air in the limited internal space, the first and second rib units  130  and  140  are provided in the cooling passages  120 . The first and second rib units  130  and  140  further include the unit ribs  132  and  142 , respectively, having, for example, a V-shape. 
     Referring to  FIGS. 1 to 3 , the unit ribs  132  and  142  may have different lengths depending on the width of the cooling passage  120  associated therewith, and each may have, for example, a length illustrated in the drawing. 
     The direction-changing portion  102  may have, for example, a U-shape. 
     When the unit ribs  132  and  142  have a V-shape, the unit ribs  132  and  142  may not be installed in the direction-changing portion  102  to improve heat transfer efficiency and maintain stable air flow. 
     For example, since the cooling air passes through the position A and then flows at a right angle toward the cooling passage in position B through the direction-changing portion  102 , the flow direction of the cooling air is sharply changed. Therefore, if the V-shaped unit rib is disposed in the direction-changing portion  102 , it may deteriorate the stable air flow there through. 
     The guide portion  150  including a first guide portion  152  and a second guide portion  154  is aimed at enhancing the cooling efficiency of the cooling air to eventually enhance the cooling efficiency of the turbine blade while obtaining the drop in pressure and the stable flow of the cooling air. 
     The guide portion  150  includes a first guide portion  152  and a second guide portion  154 . The first guide portion  152  is disposed near the direction-changing portion  102  in the first rib unit  130 , and the second guide portion  154  is disposed the direction-changing portion  102  to guide the flow direction of the cooling air, which passes through the first guide portion  152  to the second rib unit  140 . 
     The first guide portion  152  is positioned at an end portion of the partition wall  110 , which is adjacent to the direction-changing portion  102  and partitions between the first rib unit  130  and the second rib unit  140 . 
     The direction-changing portion  102  may be configured to be rounded outward from the inside of the blade  100  in a streamlined form. Although the direction-changing portion  102  is rounded as illustrated in the drawings, it is not limited thereto and may be modified into various curvatures and forms according to a flow trajectory of the cooling air. 
     The first and second guide portions  152  and  154  have a shorter length than the unit ribs  132  and  142  of the first and second rib units  130  and  140 , respectively, to prevent any disturbances of the cooling air flow. 
     In addition, the first and second guide portions  152  and  154  enables the cooling air to come into contact with an inner lower portion  103 , an upper surface (not shown), or a side surface  104  of the cooling passage, thereby increasing a contact surface area of the cooling air to enhance the cooling efficiency. Accordingly, the cooling air passes through the first and second guide portions  152  and  154  so as to stably flow toward the second rib unit  140 . 
     When cooling air serves to cool the blade  100  while flowing through the cooling passage  120 , the first and second guide portions  152  and  154  function as determining the flow direction of the cooling air. The drop position of the cooling air may include the inner lower portion  103 , upper surface (not shown), and the side surface  104  of the cooling passage  120 . 
     For example, although the drop position of the cooling air may be varied depending on the outward protruding height of each of the first and second guide portions  152  and  154  in the associated cooling passage  120 , the blade  100  can be cooled when the cooling air flows through the first and second guide portions  152  and  154  and then drop to the desired position. 
     However, since the direction-changing portion  102  may have a U-shape or semicircular shape in section, the flow direction of cooling air may be sharply changed. Therefore, the V-shaped unit ribs  132  and  142  may not be installed in the direction-changing portion  102 . 
     Since the first and second guide portions  152  and  154  have a bar shape as illustrated in  FIGS. 2 and 3 , most cooling air is guided to flow to the direction-changing portion  102 . Thus, the blade  100  can be effectively cooled due to the stable flow of the cooling air. 
     In addition, the first and second guide portions  152  and  154  are rectilinearly extending, instead of being bent, and have a shorter length than the unit ribs  132  and  142  to efficiently guide the flow of the cooling air. 
     Referring to  FIG. 2 or 4 and 5 , when the first guide portion  152  has a length of L1 and each of the unit ribs  132  of the first rib unit  130  has a length of L in an embodiment, the length of L1 is equal to a length of L/2 (L1=L/2). Here, the length of L/2 in the first rib unit  130  corresponds to a length from one end of the unit rib to the bent portion thereof. 
     The first guide portion  152  may have a half of the overall length of the unit rib  132 . In this case, since the first guide portion  152  is not bent, the cooling air may flow through the inner lower surface, upper surface, and the side surface  104  of the cooling passage associated with the first guide portion  152  when it flow to the direction-changing portion  102   
     Accordingly, the cooling efficiency of the blade  100  is not deteriorated due to the increase in contact surface area of the cooling air especially in the direction-changing portion  102 , resulting in the stable and effective cooling of the blade. 
     Referring to  FIG. 2 or 5 , when the second guide portion  154  has a length of L2 and each of the unit ribs  142  of the second rib unit  140  has a length of L in the present embodiment, the length of L2 is equal to a length of L/2 (L2=L/2). 
     For example, the second guide portion  154  may have a half of the overall length of the unit rib  142 . In this case, since the second guide portion  154  is not bent, the cooling air may come into stable contact with the inner lower or upper surface (not shown) and the side surface  104  of the associated cooling passage  120  when it flow toward the unit rib  142  adjacent to the second guide portion  154 . 
     Accordingly, the cooling efficiency of the blade  100  is not deteriorated due to the increase in contact surface area of the cooling air even after the cooling air passes through the direction-changing portion  102 , giving rise to the stable and effective cooling of the blade. 
     In an embodiment, the first and second guide portions  152  and  154  may form an angle between 30° and 60° with respect to the inner wall of the turbine blade  100 . Preferably, the first guide portion  152  may be obliquely disposed at an angle of 45°. This angle may be equal to an angle of inclination of the unit rib  132  adjacent to the first guide portion  152 . 
     The unit rib  132  may include a plurality of unit ribs in the cooling passage  120  associated with the unit rib  132  and is positioned adjacent to the first guide portion  152 . Therefore, the first guide portion  152  may have an angle of inclination similar or equal to that of the unit rib  132  to guide the stable flow of cooling air, allowing the cooling air to flow into a specific drop position. 
     Accordingly, heat exchange efficiency and the stable flow of the cooling air may be improved when the cooling air passes through the first guide portion  152  and the direction-changing portion  102 . 
     The first and second guide portions  152  and  154  are disposed in an end portion of the partition wall  110  facing the direction-changing portion  102 . The partition wall  110  does not extend to the direction-changing portion  102  but is maintained at a distance G spaced from the direction-changing portion  102 . 
     According to an embodiment of the present invention, the distance G is not limited to a specific value, but it may be defined as a distance spaced from the maximum position at which the direction-changing portion  102  is rounded outward. 
     The partition wall  110  partitions the cooling passage  120 . Thus, if the first and second guide portions  152  and  154  are disposed beyond the end of the partition wall  110 , the cooling air may be disturbed or may develop to a vortex in the portion. Therefore, the first and second guide portions  152  and  154  are disposed at the above-mentioned positions. 
     In an embodiment, the first guide portion  152  may include a plurality of first guide ribs, which are disposed in a portion close to the direction-changing portion  102  and are spaced apart from each other, as illustrated in  FIG. 3 . 
     When the first guide portion  152  includes a plurality of first guide portions, the first guide portions  152  may have the same length. Otherwise, the first guide portions  152  may have different lengths. The first guide portions  152  may become shorter as they are closer to the direction-changing portion  102 . 
     In the same manner, the second guide portion  154  may include a plurality of second guide ribs which are disposed in a portion close to the direction-changing portion  102  and are spaced apart from each other. 
     The second guide portion  154  may have one or more second guide portions so as to allow the cooling air to efficiently flow through the direction-changing portion  102 . When the second guide portion  154  includes a plurality of second guide portions, the second guide portions  154  may have the same length. Otherwise, the second guide portions  154  may have different lengths, such as being shortened as they are away from the direction-changing portion  102 . 
     The first and second guide portions  152  and  154  are responsible for guiding the cooling air to flow through the inner lower portion  103 , the upper surface, and the side surface  104  of the cooling passage  120 , thereby enhancing the cooling efficiency of the cooling air due to the increase in the contact surface area, i.e., heat exchange area. 
     Referring to  FIG. 4 , the first guide portion  152  may have the same protruding height as or a lower protruding height than the unit ribs  132  of the first rib unit  130 . 
     For example, when the first guide portion  152  has the lower protruding height than the unit rib  132 , the drop position of the cooling air may be shorter as compared to when the first guide portion  152  has the same protruding height as the unit rib  132 . 
     Accordingly, it is possible to easily adjust the drop position to a specific position when the cooling air flows to the direction-changing portion  102 , and it is possible to enhance the cooling efficiency through the increase in the contact surface area of the cooling air with the inner lower portion  103  or the upper surface (not shown) of the cooling passage  120 . 
     Referring to  FIG. 5 , the second guide portion  154  may have the same protruding height as or a lower protruding height than each of the constituent unit ribs  142  of the second rib unit  140 . 
     For example, when the second guide portion  154  has the lower protruding height than the unit rib  142 , the drop position of cooling air may become shorter as compared to when the second guide portion  154  has the same protruding height as the unit rib  142 . 
     Accordingly, it is possible to adjust the drop position to a specific position when the cooling air flows through the direction-changing portion  102 , and it is also possible to enhance the cooling efficiency due to the increase in contact surface area of the cooling air with the inner lower or upper surface (not shown) of the cooling passage  120 . 
     Referring to  FIG. 6 , the first rib unit ribs  132  may have shorter protruding heights as they are closer to the first guide portion  152 . Since cooling efficiency may be deteriorated due to the plurality of unit ribs  132  of the first rib unit  130  when the direction of cooling air is changed in the direction-changing portion  102 , it may be advantageous to enhance the cooling efficiency of the blade  100  by sufficiently performing heat exchange in the cooling passage  120 , in which the unit ribs  132  are arranged, before the cooling air flows to the direction-changing portion  102 . 
     The cooling passage in which the second rib unit  140  is disposed may have a smaller width than the cooling passage in which the first rib unit  130  is disposed. In this case, the unit ribs  142  of the second rib unit  140  may be configured such that the number of unit ribs of the second rib unit  140  is larger than that of unit ribs of the first rib unit  130 . 
     In the portion of the cooling passage in which a unit rib  142  is disposed, the cooling passage has a decreased area and the velocity of cooling air is changed, it may be preferable to arrange a plurality of unit ribs  142  in the above portion to improve heat exchange efficiency through an increase in area. 
     Accordingly, the cooling efficiency of the blade  100  is enhanced since heat exchange is stably performed regardless of the reduction in area of the cooling passage  120 . 
     Referring to  FIG. 7 , the protruding heights of the unit ribs  142  of the second rib unit  140  may have shorter protruding heights as they are closer to the second guide portion  154 . 
     The area of the cooling passage  120  in which the unit ribs  142  are disposed is reduced. Therefore, it is possible to improve heat exchange efficiency between cooling air and the inner lower and upper surfaces of the cooling passage  120  while the cooling air passes through the unit ribs  142 , resulting in the enhancement of the total cooling efficiency of the blade  100 . 
     The unit ribs  142  of the second rib unit  140  are disposed in a larger number than the unit ribs  132  of the first rib unit  130 . Therefore, the cooling efficiency of the blade is not deteriorated but the blade is stably cooled. The number of unit ribs  142  is not limited to a specific value, and may be modified into other numbers according to an embodiment of the present invention. 
     Referring to  FIG. 8 , the direction-changing portion  102  has an auxiliary rib  160  to allow the cooling air to efficiently pass through the first guide portion  152 . 
     The auxiliary rib  160  may have a curvature corresponding to the rounded curvature of the direction-changing portion  102  to promote the stable flow of cooling air. 
     The auxiliary rib  160  may include a plurality of auxiliary ribs disposed in the rounded portion of the direction-changing portion  102 , or may be disposed adjacent to the first guide portion  152  to guide the flow direction of the cooling air passing through the first guide portion  152 . 
     The auxiliary rib  160  may also be disposed adjacent to the second guide portion  154  to guide the direction of the cooling air flowing to the second guide portion  154  to a specific position. 
     Accordingly, the heat exchange and cooling air flow may be stably performed in the direction-changing portion  102  to enhance the total cooling efficiency of the blade  100 . 
     Also, the auxiliary rib  160  may consist of a plurality of auxiliary ribs that are spaced apart from the partition wall  110  and have different lengths. 
     For example, the auxiliary ribs  160  face the partition wall  110  and are spaced apart from each other in the downward direction, as shown in the drawing. 
     When the cooling air flows toward the direction-changing portion  102 , the direction of the cooling air may be changed to the second rib unit  140  having multiple unit ribs  142  by the auxiliary ribs  160 . 
     When the direction of cooling air is changed, the flow of the cooling air can be guided as much as possible by the unit ribs  132  and  142  in the blade  100  for enhancement of cooling efficiency. 
     To this end, the main flow of the cooling air is guided toward the second rib unit  140  by the direction-changing portion  102  and the auxiliary flow of cooling air is guided by the auxiliary ribs  160 , thereby achieving the stable cooling air flow. 
     Accordingly, the cooling air can be easily guided from position A to position C in the turbine blade  100  according to an embodiment of the present invention, and the cooling efficiency of the turbine blade  100  can be stably maintained. 
     As is apparent from the above description, the exemplary embodiments of the present invention can improve the stable flow of the cooling air within a turbine blade to thus enhance the cooling efficiency of the turbine blade. 
     The exemplary embodiments of the present invention can improve cooling efficiency at a position where the flow direction of cooling air is changed in the turbine blade. 
     The exemplary embodiments of the present invention can stably maintain the cooling efficiency of the turbine blade in all sections regardless of the internal structure of the turbine blade. 
     While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.