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In high-pressure gas turbines which use a contra-rotating low-pressure turbine, the geometry of the inlet guide vane of the low-pressure component induces a reflected shock wave impacting the blade. Constant exposure to these shock waves degrades turbine performance and increases cycle fatigue leading to failure. Approaches to shock wave mitigation have resulted in the use of a large number of downstream low-pressure turbine vanes which ensure no resonance occurs upstream. The additional vanes, weight, and added costs result in a less than ideal solution.
Air Force scientists have created a new design to eliminate shock waves in the turbine with the use of jets of compressor bleed air in the contra-rotating unit. The high-pressure side of the downstream vane is fitted with holes that allow jets of compressor bleed air to penetrate the boundary layer and induce a net velocity component across the main flow direction in the near-wall region. A moving shock wave generates a small velocity component in the direction of travel. By inducing a velocity component equal and opposite to that produced by the moving shock in the near-wall region of the low-pressure turbine vane, the incident shock can be canceled, which eliminates the shock reflection that would otherwise travel back upstream to impact the rotating blade row.
This approach is similar to steady film cooling, but the jet velocities are designed to cancel the incident shock from the upstream vane row instead of providing heat-transfer management as in the case of film cooling.
- Enables a lighter, lower-cost, low-pressure turbine vane row
- Can be used to reduce unsteady interactions in all commercial gas turbine engines (land, sea, and air applications) with vaned contra-rotating geometries
- Businesses can license US patent 8,739,508 for commercial uses
- TechLink provides expert licensing assistance at no charge
- Potential for collaboration with Air Force researchers