Turbine shaft seals are vulnerable to rubs caused by thermal distortion, mis-alignment and rotor dynamic vibration that are often not well understood. When seals rub as a machine is brought up to operating conditions performance is compromised due to increased seal leakage. Much effort has been extended in recent years to develop seals that mitigate those losses. This paper presents a seal design with segmented film riding runners capable of non-contacting seal operation during rotor transients. Operating differential seal pressure displaces seal leaves and attached runners toward the rotor surface until balanced by hydrostatic and hydrodynamic lift. Sufficient radial range of operation is provided to follow the rotor seal surface during transients while maintaining a small seal clearance. Seal design features and function will be described and illustrated along with analysis of forces and motions for a sample application. Planned modeling and testing will also be presented. This concept promises enhanced shaft sealing by combining a leaf seal structure that provides a large range of motion to avoid rubs during startup and shutdown with runner elements capable of generating hydrostatic and hydrodynamic lift forces to maintain shaft–seal separation during all rotor displacement transients. Improved turbine performance from small operating seal clearance and extended seal life without rubs are expected benefits of the Film Riding Pressure Actuated Leaf Seal (FRPALS).

The introduction of a ceramic gas turbine component in commercial power generation service will require significant effort. A careful assessment of the power plant performance benefit achievable from the use of ceramic components is necessary to rationalize the priority of this development compared to other alternatives. This paper overviews a study in which the performance benefit from ceramic components was evaluated for an MS9001FA gas turbine in a combined cycle power plant configuration. The study was performed with guidelines of maintaining constant compressor inlet airflow and turbine exit NOx emissions, effectively setting the combustion reaction zone temperature. Cooling flow estimates were calculated to maintain standard design life expectancy of all components. Monolithic silicon nitride ceramic was considered for application to the transition piece, stage one and two buckets, nozzles and shrouds. Performance benefit was calculated both for ceramic properties at 1093°C (2200°F) and for the more optimistic 1315°C (2400°F) oxidation limit of the ceramic. Hybrid ceramic-metal components were evaluated in the less optimistic case.

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The introduction of a ceramic gas turbine component in commercial power generation service will require significant effort. A careful assessment of the power plant performance benefit achievable from the use of ceramic components is necessary to rationalize the priority of this development compared to other alternatives. This paper overviews a study in which the performance benefit from ceramic components was evaluated for an MS9001FA gas turbine in a combined cycle power plant configuration. The study was performed with guidelines of maintaining constant compressor inlet airflow and turbine exit NOx emissions, effectively setting the combustion reaction zone temperature. Cooling flow estimates were calculated to maintain standard design life expectancy of all components. Monolithic silicon nitride ceramic was considered for application to the transition piece, stage one and two buckets, nozzles and shrouds. Performance benefit was calculated both for ceramic properties at 1093C (2200F) and for the more optimistic 1315C (2400F) oxidatian limit of the ceramic. Hybrid ceramic-metal components were evaluated in the less optimistic case.