Apparatus and process for forming an air cooled turbine airfoil with a cooling air channel and discharge slot in a thin wall
A ceramic core used to cast and cooling circuit in a thin wall turbine airfoil, where the ceramic core includes a row of metering and impingement forming pieces that discharge into a radial plenum, followed by a row of pedestals and a row of diffusion channels that then flow into a single discharge slot. The ceramic core has bumpers of both sides to position the core in a wax mold. The metering and impingement holes are offset from the cooling passage in the airfoil wall so that impingement of the hot surface of the wall occurs.
1. A ceramic core for use in forming a cooling passage in a thin wall of an air cooled turbine airfoil, the ceramic core comprising:
a radial extending plenum forming section;
a plurality of metering and impingement forming pieces connected to the radial extending plenum;
a plurality of pedestal forming pieces downstream in a cooling flow direction from the plenum forming section;
a plurality of diffusion forming pieces downstream from the plurality of pedestal forming pieces;
a discharge forming slot section downstream from the plurality of diffusion forming pieces;
a plurality of bumpers to position the ceramic core within a wax mold;
the ceramic core forms a cooling passage in a thin wall airfoil with multiple metering and impingement holes followed by pedestal cooling and diffusion and then discharge from a single slot; and,
the metering and impingement forming pieces are offset at 90 degrees from the pedestal and diffusion forming pieces such that impingement will occur against an inside surface of the thin wall formed by the ceramic core.
2. The ceramic core of claim 1 , and further comprising:
the metering and impingement forming pieces each have convex shaped ends.
3. The ceramic core of claim 1 , and further comprising:
a positioning bumper on the ceramic core on an opposite side from the metering and impingement forming piece that functions to position the ceramic core between two walls.
4. An air cooled turbine stator vane comprising:
a thin airfoil wall with one side exposed to a hot gas stream and an opposite side forming a cooling air supply cavity;
a row of metering and impingement holes formed in the thin wall and opening into the cooling air supply cavity, the row of metering and impingement holes directing impingement cooling air against an inside surface of the thin airfoil wall;
a radial extending plenum downstream from the metering and impingement holes;
a row of pedestals in a cooling air passage formed within the thin wall and downstream from the metering and impingement holes;
a row of diffusion channels downstream from the row of pedestals; and,
a single cooling air discharge slot downstream from the diffusion channels.
5. The air cooled turbine stator vane of claim 4 , and further comprising:
the row of metering and impingement holes open into the radial extending plenum such that impingement cooling of the side of the airfoil exposed to the hot gas stream occurs.
6. The air cooled turbine stator vane of claim 4 , and further comprising:
the metering and impingement holes and the plenum and the pedestals and the diffusion channels and the discharge slot are cast within the thin airfoil wall by a ceramic core.
7. The air cooled turbine stator vane of claim 4 , and further comprising:
the thin airfoil wall includes a row of discharge slots; and,
each discharge slot is connected to a cooling channel having metering and impingement holes followed by a plenum and pedestals and diffusion channels that flow into the discharge slot.
8. An air cooled turbine airfoil comprising:
an airfoil wall with one side exposed to a hot gas stream and an opposite side forming a cooling air supply cavity;
a row of metering and impingement holes formed in the airfoil wall and opening into the cooling air supply cavity, the row of metering and impingement holes directing impingement cooling air against an inside surface of the thin airfoil wall;
a radial extending plenum downstream from the metering and impingement holes;
a row of pedestals in a cooling air passage formed within the airfoil wall and downstream from the metering and impingement holes;
a row of diffusion channels downstream from the row of pedestals;
a single cooling air discharge slot downstream from the diffusion channels; and,
a flow passage from the diffusion channels into the discharge slot produces no additional metering of the flow such that a coat down of a TBC can be applied without masking that will not produce an additional metering of the cooling air flowing into the discharge slot.