Film-cooled turbine blade for a turbomachine
A turbine blade for a turbomachine has an outer wall which delimits an inner cavity. Cooling fluid flows in the inner cavity. A through duct is arranged in the outer wall through which the cooling fluid flows from the inner cavity to an outside of the turbine blade. The through duct is inclined with respect to a trailing edge of the turbine blade, wherein a marginal portion of an entrance of the through duct is designed on an upstream side to be sharp-edged in relation to other marginal portions of the entrance such that a separation zone of a cooling fluid flow is formed in the through duct. A pair of swirls builds up in the through duct, wherein velocity vectors of the cooling fluid flow between the swirl centers point toward a downstream side of the through duct.
1. A turbine blade for a turbomachine, comprising:
an outer wall which delimits an inner cavity of the turbine blade, wherein cooling fluid is provided in the inner cavity for film-cooling of the turbine blade,
at least one through duct arranged in the outer wall, wherein the cooling fluid flows through the at least one through duct from the inner cavity to an outside of the turbine blade so as to form a cooling film on an outer face of the outer wall,
wherein the at least one through duct is inclined with respect to a trailing edge of the turbine blade,
wherein a marginal portion of an entrance of the at least one through duct is designed to be sharp-edged on an upstream side in relation to other marginal portions of the entrance such that a separation zone of a cooling fluid flow is formed in the at least one through duct,
wherein the separation zone induces a centric transverse flow of the cooling fluid which is directed toward a side of the at least one through duct which lies opposite the separation zone,
wherein a pair of contra-directional vortices develops in the at least one through duct such that velocity vectors of the cooling fluid flow between vortex centers point toward a downstream side of the at least one through duct, and
a clearance provided on an inner face of the outer wall in which the at least one through duct is arranged,
wherein the clearance is hat-shaped such that the clearance includes a clearance inlet margin that is rounded,
wherein the clearance has a downstream rear side in which the entrance is formed and the entrance is inclined with respect to an axis of the at least one through duct such that the marginal portion of the entrance of the at least one through duct is designed on the upstream side to be more sharp-edged than an opposite marginal portion of the entrance.
2. The turbine blade as claimed in claim 1 , wherein the rear side of the clearance is arranged essentially perpendicularly to the inner face of the outer wall or at an inclination with respect to the trailing edge of the turbine blade.
3. The turbine blade as claimed in claim 1 , wherein the clearance is of round shape at an inlet margin such that the cooling fluid flows into the clearance free of separation.
4. The turbine blade as claimed in claim 1 , wherein the clearance is a groove, and wherein a plurality of through ducts leads into the groove.