FLEXTURBINE will lead to innovations able to enter into service before the end of this decade underpinning the overall ambition of the consortium to deliver solutions enabling flexible operation of thermal power plants and thus a more flexible electricity grid. This desired grid flexibility will not be possible by optimising power distribution on the grid alone. It will also need technical developments of the plants themselves to allow highly flexible operation.

 

Technology Readiness Levels of the FLEXTURBINE technologies

 

Therefore, the FLEXTURBINE objectives are:

  • To predict the off-design partial load operating regimes at which flutter can occur and, at these conditions, to assess the relevant blade design parameters influencing the dynamic  behaviour. The simulation of these aerodynamic conditions remains a challenge as they present strong non-linear phenomena (shock waves and wide zones of detached flow).
  • To predict the occurrence of flutter on the extended turbomachinery operating range through a dedicated experimental campaign on a scaled-down test turbine especially at very low volume flow conditions at which the non-synchronous aerodynamic excitation can occur and lead to high dynamic loading on the exhaust blades. This aspect will make a step beyond the typical flutter experimental campaigns usually dedicated to design operating conditions.
  • To calibrate and validate the flutter predictive models at the most severe operating conditions especially where current computational tools have not yet been used to predict flutter occurrence.
  • To develop best practices for flutter assessment focusing on the optimal blade design parameters including the use of stiffness and damping elements. Such best practices will be extended to these more severe operating conditions.
  • To develop flutter-free design criteria to be applied in the design of new longer exhaust blades for achieving high ST performance and simultaneously ensuring wider ST operation ranges (with regard to flutter and thus preventing any potential machinery failures). These flutter-free design criteria will be exploited in designing future high performance ST blade rows.
  • To deepen the understanding of displacement mechanisms in transient turbo machines and quantify the effect of interaction of all seals in the secondary flow system on performance, coolant flow supply and effectiveness of transient and cyclic operation
  • To identify new design needs for each individual seal in the sealing system to allow for highly flexible operation taking into account frequent fast and short-notice cyclic load changes without compromising on lifetime and performance
  • To quantify the effect of fast thermal cycles associated with load changes on the growth of seal gaps and clearances and on wear, the effect of relative movements caused by cyclic thermal loads on static interface seals between the gas turbine combustor and the turbine within their operational environment and develop new design criteria
  • To develop novel turbine seals and bearings to address the thermal and structural hazards of flexible operations to be qualified as a medium term solution (i.e. implemented within 3 years after the end of project)
  • To develop novel self-adaptive seals being able to track the dynamic behaviour associated with fast and frequent load changes
  • To develop novel fluid-film bearing technologies in order to optimise bearing tribology for low friction loss while meeting the increasing dynamical demands on bearings due to slender rotor designs and flexible operation. The aim is to achieve an efficiency increase of up to 0.10 % in utility steam turbines by reducing the mechanical losses at the bearings.
  • To develop novel seals with greatly reduced wear and leakage flows (80 % less) for 0.5 point efficiency increase.
  • To increase endurance of seal and bearing systems without considerable loss of effectiveness in order to reduce maintenance intervals and costs.
  • Overall, to improve quantification of the impact of cyclic operation in order to improve component lifetime management.
  • To provide the basis for increasing cyclic life usage in turbine discs and blade roots by possibly up to a quarter by specialised long term fatigue testing and lifing model validation.
  • To reduce conservatism in fatigue life models for high mean stress fatigue and combined cycle fatigue in gas turbine blade aerofoils and thereby provide less restrictions on turbine blade dynamic behaviour over the engine speed range or allow engines to cycle more frequently.
  • To reduce conservatism and provide an improved physical basis for cyclic lifetime predictions for steam turbine rotors that will allow faster ramp-ups and higher cyclic life statements
  • To improve confidence in hot gas path component lifing statements and potentially increased cyclic capability of gas turbine combustor parts and turbine tip seals through the development of a high temperature/high pressure cyclic test rig for life model validation under near engine test conditions.
  • To increase the cyclic life statements for large gas turbine buckets in the turbine hot gas paths by testing and improved understanding of the effects of material grain defects on fatigue life.
  • To enable selected critical components which currently pace the overhaul schedule to sustain increased cycling and potentially greater cyclic damage over a given operating period, avoid premature and costly parts replacement and thereby minimising any increase in overall life cycle costs arising from more flexible operation.
  • To prolong the point of life expiry of critical high value components and moderate the pressure on the sourcing and/or recovery of high value elements which go to make up the alloys used in these components.

Results

  • FLEXTURBINE expects to deliver the following (technical) results:

  • Improved aero-mechanical stability of large aspect ratio turbine blades
    • Improved design of flutter-free blades
    • Allowing turbines to support fast start-ups and the load ramps required
    • Improvement of the steam turbine performance
  • Improved seal and bearing design
    • Increase in efficiency by 0.5 points by better understanding the displacement mechanism in transient turbo machinery operating conditions
    • Lower secondary flows (leakages between combustor and turbine could either be translated by a reduced NOx level (-15% for 1% leakage reduction) or an increase in Hot
    • Gas Temperature (+10 K) leading to an additional improved efficiency of 0.2 points
    • Increasing the equivalent operating hours between service intervals by 30% to 50%
  • Improved fatigue life time method
    • Improved life time method development program
    • Improved failure prediction to immediately reduce maintenance cost through more flexible service intervals and maintenance scheduling

Thanks to the results of FLEXTURBINE, the European turbine OEMs will be able to build power plants capable of better complying with the requirements of a safer and greener power production strategy allowing the final utilities to operate without risks of any forced outage of the plants. Moreover, FLEXTURBINE will provide new and cost-effective solutions for highly flexible new and existing power plants.

FLEXTURBINE technologies will be compatible with existing infrastructure without impeding CCS (Carbon Capture & Storage) readiness.

FLEXTURBINE will improve the innovation capacity and integration of new knowledge, as FLEXTURBINE innovations will be part of the next generation turbine design, targeting an entry into service by 2020.

Finally, FLEXTURBINE will give competitive advantages to the European industry in multiple views:

  • Improved bearing design is estimated to result in power loss reduction potential for a utility CCPP steam turbine as high as 200 kW, which, at evaluation factors of 800-1500€/kW, can equal up to 300 000 € business benefit and an estimated increase of plant efficiency of 0.1%.
  • Improved seal design for flexible operation will result in reduced wear and leakage flows at key locations by up to 80% with an associated efficiency increase of 0.5 points. 
  • Extended lifecycles of power generating units support the grid stability with the impact of less outages and less stand-still. Higher lifecycles of parts mean less resources are required to produce replacement parts. This reduces costs of operation and hence, costs of energy production.
  • Reduced leakages increase power units efficiency, and hence, result in lower fuel consumption in the power generating industry and finally less costs for the energy consumers.

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