Patent ID: 6179565
Filing Date: 2001-01-30
Classification: B22C,F01D,F05D,Y02T

Abstract:
For an axial flow rotary machine having an axis A and a turbine section which includes an annular flowpath for working medium gases disposed about the axis A, an airfoil having an opening which adapts the airfoil to be in flow communication with a source of cooling fluid under operative conditions, the airfoil having a leading edge region and a trailing edge region, the airfoil having an inner portion, an outer portion, and a mid-span portion that extends from the inner portion to the outer portion, the airfoil having a suction wall extending chordwisely and spanwisely about one side of the airfoil from the leading edge region to the trailing edge region and having a suction wall lip disposed in the trailing edge region, the airfoil having a pressure wall extending chordwisely and spanwisely about the opposite side of the airfoil and from the leading edge region to the trailing edge region, the pressure wall being spaced laterally from the suction wall leaving a cavity for cooling fluid therebetween in flow communication with said opening and a flowpath for cooling fluid which extends through the trailing edge region past the suction wall lip, the pressure wall including a pressure wall lip which is axially upstream of the suction wall lip, and wherein the suction wall lip and pressure wall lip define a trailing edge disposed in the trailing edge region, which comprises:an internal passage for the flowpath for cooling fluid which extends spanwisely and is in flow communication with the opening for cooling fluid;a plurality of structural heat transfer members in the mid span portion of the airfoil that extend laterally to join the suction wall to the pressure wall, the three rearmost of said members being comprised ofa single rib which extends spanwisely in the trailing edge region and laterally from the suction wall to the pressure wall, the rib having a plurality of orifices extending therethrough which are spaced spanwisely leaving rib material extending therebetween and spaced laterally from the walls leaving rib material extending therebetween;a single array of pedestals which is spaced chordwisely from the rib leaving a first chordwisely extending supply passage for cooling fluid therebetween, the array extending spanwisely in the airfoil, each pedestal extending from the pressure wall to the suction wall to join the walls together, each pedestal being spaced spanwisely from the adjacent pedestal leaving an opening therebetween which extends chordwisely between the pedestals and from the suction wall to the pressure wall;an array of flow dividers which is spaced chordwisely from the pedestals leaving a second chordwisely extending supply passage therebetween, each flow divider having an upstream portion which extends from the pressure wall to the suction wall, each divider including a flow divider leading edge;, anda first converging sidewall and a second converging sidewall, the converging sidewalls forming a pair of sidewalls, each of the pair of converging sidewalls extending to a point downstream of the pressure wall lip to form a cutback portion for each divider that is not covered by the pressure wall, the cutback portion adapting the airfoil to expose the cutback portion and the dividers to the flow path for hot working medium gases under operative conditions, the pair of converging sidewalls converging in the downstream direction such that spanwisely facing sidewalls of adjacent dividers diverge to define a diffusing section having diffusion channels between adjacent dividers;wherein the diffusing section extends from upstream of the pressure wall lip to downstream of the pressure lip;wherein the flowpath for cooling fluid extends axially through the orifices of the rib, and rearwardly toward the trailing edge along the chordwisely extending first supply passage, impinges on the pedestals which are facing the orifices in the chordwise direction, extends through the openings between each pair of pedestals and impinges on the leading edge of the flow divider and extends through the diffusing section of the flow dividers for convectively cooling the interior of the platform and for film cooling the suction wall trailing edge of the airfoil;wherein part of the trailing edge region has an upstream zone which includes the rib and which extends from the rib to the diffusing section in the array of flow dividers and each of said heat transfer members in the upstream zone has a hydraulic diameter for the flow path which is less than the hydraulic diameter of the heat transfer feature immediately upstream and the decrease in hydraulic diameters accelerates the flow of cooling fluid as it moves rearwardly to enhance convective heat transfer and decrease the difference in velocity between the exiting flow of cooling fluid and the working medium gases;wherein during the casting process and handling of the core for the airfoil, support for the trailing edge region of the core is provided by core material disposed spanwisely between the array of adjacent pedestals to form the pedestal openings and core material disposed chordwisely and spanwisely between the array of flow dividers to form the channels; and, wherein during handling and processing of the airfoil after casting and during operative conditions, the impingement rib and the flow dividers cooperate with the pressure wall and suction wall to form a box-like structure for strengthening the trailing edge region of the airfoil and the pedestals reinforce the box-like structure by being disposed chordwisely between the rib and the array of flow dividers.