Structures and Methods for Forcing Coupling of Flow Fields of Adjacent Bladed Elements of Turbomachines, and Turbomachines Incorporating the Same

Abstract

Turbomachines having close-coupling flow guides (CCFGs) that are designed and configured to closely-couple flow fields of adjacent bladed elements. In some embodiments, the CCFGs may be located in regions extending between the adjacent bladed elements, described herein as coupling avoidance zones, where conventional turbomachine design would suggest no structure should be added. In yet other embodiments, CCFGs are located upstream and/or downstream of rows of blades coupled to the bladed elements, including overlapping one of more of the rows of blades, to improve flow coupling and machine performance. Methods of designing turbomachines to incorporate CCFGs are also provided.

What is claimed is: 
     
         1 . A method of designing a close-coupling flow guide (CCFG) for a turbomachine having first and second bladed elements and a design operating range, the method comprising:
 selecting at least one location proximate the first and second bladed elements for locating at least one CCFG; and   designing the at least one CCFG to have a configuration that increases aerodynamic feedback over the design operating range between a flow field of the first bladed element and a flow field of the second bladed element to thereby couple the flow fields of the first and second bladed elements and increase performance of the turbomachine.   
     
     
         2 . A method according to  claim 1 , wherein said selecting includes locating at least a portion of the CCFG downstream of the first bladed element, and said designing includes designing the CCFG to create a pressure field that influences at least one of a diffusion or work input of the upstream first bladed element to thereby improve machine performance. 
     
     
         3 . A method according to  claim 2 , wherein said selecting includes locating at least a portion of the CCFG in a coupling avoidance zone extending between the first and second bladed elements. 
     
     
         4 . A method according to  claim 3 , wherein the second bladed element comprises a plurality of second blades arranged and configured into a low solidity blade row and said designing comprises adding a contoured surface to a leading edge of each of the second blades, the contoured surfaces each having at least one leg extending into the coupling avoidance zone. 
     
     
         5 . A method according to  claim 3 , wherein said selecting includes locating a second CCFG downstream of said second bladed element and said designing includes configuring the second CCFG as at least one rib extending from a trailing edge of a blade of the second bladed element. 
     
     
         6 . A method according to  claim 1 , wherein the second bladed element includes a first low solidity blade row, and wherein said designing comprises adding a second tandem blade row having a lower blade count than, and positioned downstream of, said low solidity blade row, and configuring the tandem blade row to improve flow stability. 
     
     
         7 . A method according to  claim 1 , wherein the first bladed element has a plurality of first blades and a rotational axis and at least one of the plurality of first blades has a trailing edge located at a radius, r 2 , from said rotational axis, said designing includes locating a leading edge of the CCFG at a radius, r c , from said rotational axis, and wherein r c /r 2  is less than about 1.08. 
     
     
         8 . A method according to  claim 1 , wherein the first bladed element has at least one blade with a chord length, C, and a trailing edge, said designing includes locating a leading edge of the CCFG such that a distance between the leading edge and the trailing edge is less than about C/4. 
     
     
         9 . A method of designing a turbomachine having a first bladed element upstream of a second bladed element, the first bladed element having a plurality of first blades with trailing edges and the second bladed element having a plurality of second blades with leading edges, the method comprising:
 adding a first structure to the turbomachine at a location downstream of the first bladed element; and   configuring the first structure to have an aerodynamic feedback effect on a flow field of the first bladed element to thereby improve the performance of the turbomachine.   
     
     
         10 . A method according to  claim 9 , wherein said configuring includes configuring the first structure to improve at least one of a work transfer of the first bladed element or relative diffusion of flow in the first bladed element. 
     
     
         11 . A method according to  claim 9 , wherein the second bladed element comprises a diffuser having a hub and shroud surface and forming a diffuser passageway therebetween, the method further comprising increasing a distance between the hub and shroud surfaces to compensate for a reduction in diffuser passageway cross sectional flow area caused by the addition of the first structure to thereby minimize vane blockage caused by the addition of the first structure. 
     
     
         12 . A method according to  claim 9 , wherein said adding includes locating the first structure on at least one of the leading edges of the plurality of second blades to thereby reduce a vaneless space between the first and second bladed elements, and said configuring includes configuring the first structure to increase aerodynamic coupling between the first and second bladed elements when the turbomachine is operating at design operating conditions. 
     
     
         13 . A method according to  claim 12 , wherein the second bladed element is a low solidity diffuser, said configuring includes configuring the first structure as a contoured surface on at least one of the leading edges of the plurality of second blades. 
     
     
         14 . A method according to  claim 12 , wherein the first bladed element has a rotational axis and at least one of the trailing edges of the plurality of first blades is located at a radius, r 2 , from said rotational axis, said configuring including locating the at least one leading edge having the first structure at a radius, r c , from said rotational axis, wherein r c /r 2  is less than about 1.08. 
     
     
         15 . A method according to  claim 12 , wherein at least one of the plurality of first blades has a chord length, C, said configuring including locating the at least one leading edge having the first structure such that a distance between the leading edge and the trailing edge of the at least one of the plurality of first blades is less than about C/4. 
     
     
         16 . A method according to  claim 12 , wherein said configuring step includes configuring the first structure as a contoured surface having at least one leg, wherein the at least one leg extends upstream of the at least one leading edge and overlaps said plurality of first blades. 
     
     
         17 . A method according to  claim 12 , further comprising:
 adding a second structure upstream of the second bladed element and adjacent the first bladed element; and   configuring the second structure to influence the flow field in the first bladed element.   
     
     
         18 . A method according to  claim 17 , wherein said adding a second structure includes locating the second structure in at least one of a hub and a shroud surface between adjacent ones of the plurality of first blades, and said configuring includes configuring the second structure as a trough. 
     
     
         19 . A method according to  claim 17 , wherein said adding a second structure includes locating the second structure in at least one of a hub and a shroud surface between adjacent ones of the plurality of first blades, and said configuring includes configuring the second structure as a rib. 
     
     
         20 . A method according to  claim 17 , further comprising:
 adding a third structure downstream of the second bladed element; and   configuring the second structure to influence the flow field in the second bladed element.   
     
     
         21 . A method according to  claim 20 , wherein said adding includes adding a contoured surface to a trailing edge of at least one of said plurality of second blades. 
     
     
         22 . A method according to  claim 20 , wherein said adding includes adding a rib to a trailing edge of at least one of said plurality of second blades.