The demand for flexible part load operation of stationary gas turbines challenges the design for sufficient efficiencies and life times. Both can be addressed by the secondary air system. The here applied concept modulates cooling air supply in off-design. Basically, a reduction of cooling air yields higher efficiency but minor component life.

This paper presents investigations on such concepts, aiming for trade-offs between fuel burn and turbine blade life. The considered lifing mechanisms are creep, which is dominant in rotor blades, and oxidation, which is dominant in stator vanes. In addition, the effects on emissions from the combustion are outlined.

The reference gas turbine is a literature based, generic gas turbine in the 300MW power output segment. Regarding cooling air control, the focus is on the first two stages of the four stage turbine.

All simulations are performed by application of component zooming with an appropriate in-house tool: A previously introduced coupled model of the reference gas turbine essentially connects gas turbine performance with a secondary air system network model. This coupled model is now extended with blade life evaluation and emission models.

The results contain the trade-offs for a set of operating points at base and part load. Also shown are sensitivities of secondary air supply control to cooling layers and hot gas ingestion at rim seals. Finally, the trades mark the promising potential of this concept from a technical point of view.


Trade-Off Assessments for Part Load Controlled Cooling Air in Stationary Gas Turbines

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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