Frictional Damper Experiences for Reliable, Flexible GTCC Operations
Authors: Shrivastava Rishabh , Kayser Andreas , Siewert Christian , Costamagna Raoul , Tusche Johannes , Szwedowicz Jaroslaw 
Published: August 2024

Growing demand for cleaner and sustainable energy resulted in substantial transformation within the energy landscape. To compensate for fluctuations of renewables in the power grid, turbines need to operate more flexible between idle and base-load operation mode as well as in peaking cycles if required. Thus, along with numerous advantages of renewable energy, there are technical challenges that need to be addressed for consistent power supply and stable grid.

The gas turbine (GT) plays a crucial role in overcoming above challenges by operating efficiently and reliably under part-load conditions. Additionally, the GT must show abilities for quick starts and shutdowns to act as a peaker unit, along with that steam turbine should also be capable of part load operation especially for combine cycle power plants. The peaking and part load cycles mainly affect the Low cycle fatigue (LCF) and High Cycle Fatigue (HCF).

To prevent rotating equipment from HCF failures the frictional damper technology is extensively used for reducing vibration amplitudes. For over 45 years Siemens Energy relies on this dissipation technology applied to gas and steam turbines. For the turn-down engine operation demanded by the power market, the frictional dampers in rotating blades of steam and gas turbines are crucial designed components assuring HCF safety of Gas Turbine Combined Cycle (GTCC) power plants. Moreover, the under-platform damper (UPD) has the additional function to improve sealing performance of hot GT components. The dissipation and sealing design functions in a single component are based on the multi-disciplinary solution for failure-free HCF blade operations under varying operating conditions like load points and rotor speeds.

Frictional dampers called midspan damping elements are applied to industrial steam turbines, which will be discussed briefly in this paper, too. This existing technology has been successfully scaled up for the low-pressure (LP) last stage of a large steam turbine. The numerical prediction of the LP steam turbine stage with the midspan damping elements agreed very well with the measured test data.

For the GT operating between no-load and full-load, Siemens Energy has developed an advanced, validated engineering process and vibration analysis tools for reliable prediction of the GT blade frequencies and resonance responses by incorporating various uncertainties. In this paper, the validation results for the 2nd and 3rd stages of the modern GT are presented. The presented results of tip timing measurements show explicitly a significant increase of blade vibrations under the no load and part-load operations in comparison with that measured for the full-load operation. This higher response of part-load operations is suppressed effectively below the allowable vibration limit. For these non-linear blade dynamics, an in-house tool predicts in very good agreement the overall damping of the blade assembly, what is discussed in the paper. Strain gauge measurements of the vibration response at several blades are in a good agreement with the numerical results.

This entire study concludes that the frictional damper technology is the crucial design element of rotating equipment for peaking and flexible operations of each GTCC. The presented results of the frictional dissipation techniques meet the market requirement for Reliability, Availability, Maintainability, and Safety (RAMS) of GTCC flexibility of interest of end users.