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Flexible Fossil Power Plants for the Future Energy Market through new and advanced Turbine Technologies

Periodic Reporting for period 2 - FLEXTURBINE (Flexible Fossil Power Plants for the Future Energy Market through new and advanced Turbine Technologies)

Reporting period: 2017-07-01 to 2019-03-31

Despite the increasing share of renewable energy, the amount of electric power which can be supplied to the grid depends on the time of the day and weather conditions. A conventional fleet of thermal power plants is needed to compensate for these fluctuations before large scale energy storage technologies will be mature and economically viable. For a strong expansion of renewables, this fleet has to operate flexibly at competitive cost. Current power plants cannot fill this role immediately without impeding their efficiency, safety of operation and engine lifetime. New technologies need to be introduced to balance demand peaks with renewable output fluctuations at minimal fuel consumption and emissions. FLEXTURBINE is the first step in a medium to long term technology roadmap addressing future and existing power plants and consists of new solutions for extended operating ranges to predict and control flutter, improved sealing and bearing designs to increase turbine lifetime and efficiency, and an improved lifecycle management and safety of operation through better control and prediction of life consumption of critical parts to improve competitive costs.
A newly developed flutter prediction software tool addressing the non-linear dynamic interaction between blades and unsteady flow in off-design operation was validated, confirming the tool’s availability to correctly assess flutter behaviour. A newly designed last stage moving blade was validated employing a T10MW test turbine at strong off-design operating conditions pointing out its flutter resistant design. The use of an innovative snubber interlocking solution improved the aerodynamic damping stability of the component. The geometry of the snubber and its optimised radial position was verified and design criteria was validated. These latter can be applied to design new longer exhaust blades and guarantee their flutter-free behaviour.
Regarding innovative bearings, a PEEK-lined radial bearing applicable in utility turbo-generators was successfully tested. The bearing allows to reduce friction loss, wear during start-up and shutdown, and to face the challenge of future tin shortage. Regarding seals development, a split self-adaptive seal for power generation gas turbines was successfully developed and matured. For steam turbines experiencing high rotor vibrations in flexible operation, novel integral squeeze film damper bearings were developed and are ready to be applied to any steam turbine with a potential to reduce dangerous rotor vibration by one order of magnitude. Felt-metal was found as new material and qualified for steam turbine inter-stage seals. New manufacturing technology was developed for its application. A significant improvement of the turbine operational safety is obtained by the application of the felt-metal seal, the product is fully certified and ready to be applied in the real engine. A coupled design system to take into account transient operation of the gas turbine was obtained. The programme suite consists of flow and thermal solvers developed that has been validated by real engine test data. With the aid of the design process an improved re-design of the test engine could be achieved and demonstrated by the test results.
FLEXTURBINE research significantly contributed to the reduction of conservatism in life prediction methods in components, such as ST rotors, GT blades and discs, GT blade airfols and GT blades at the trailing edge root. For the steam turbine rotor, a comprehensive material test programme was carried out which has allowed mathematical models of material behaviour to be fitted. Advanced thermo-mechanical fatigue lifing model was applied for rotor life prediction, its results were verified in a test campaign. This will allow shortening of steam turbine ramp-up time and increase of number of turbine startups. Further, the benefit of introducing a compressive residual stress to the surface of turbine blade roots and turbine disc design features was investigated as well as the influence of complex load cycles on the fatigue behaviour of turbine disc features was investigated. FLEXTURBINE research allowed the development of a life model capable of predicting crack initiation and propagation of René80 at high temperature, and X5CrNiCuNb16-4 at room temperature, in regimes of LCF-HCF superposition. Fatigue testing of trailing edge feature of large gas turbine blades showed the possibility to extending the allowable number of cycles during GT service.
FLEXTURBINE has developed an engine and plant simulation tool that considers electricity markets and allows to model the reference power plant with newly developed components and technologies implemented. The tool can calculate the improved optimal dispatch and changes in the dispatch due to flexibility technologies. The main output of the simulation is a list of events. From this event list the total profit increase, total fuel consumption and CO2 emissions decrease, the capacity factor and the energy produced as well as the number of turbine starts and the number of low load events can be calculated. This allows a benefit assessment of eac
The flutter-free steam turbine last stage moving blades allow turbines to operate safely in off-design conditions or at minimal loads. It is ready for application in the real engine. Innovative seals and bearing concepts show clear advantages compared to state-of-the-art components in terms of robustness and durability and their application will lead to lower secondary flows, optimised coolant flows and thus optimised operation. Felt-metal has been found and qualified as new material for steam turbine seals. The initially envisaged efficiency increase by 0.5 points has been reached. Long term fatigue testing and lifing model validation on GT blade and discs have shown that shot peened components are capable for 2.5 times longer cyclic life than state-of-the-art gas turbine blade and discs. Regarding large GT blades, the results of the experimental campaign highlighted that it is possible to increase the design life in terms of number of start-ups and shutdowns by up to 50%, thus allowing more flexible GT operating conditions. For ST rotors, the FLEXTURBINE life prediction method has been developed. Considering same start-up times and number of cycles, newly developed life prediction method gives 60% life margin compared to current state-of-the-art method enabling shortening ramp-up times and increasing number of cycles. In addition to this, the whole engine model developed within FLEXTURBINE can serve as standard process and benchmark for further investigations concerning operational flexibility of power plants. The model developed can be used to better understand the needs of the power plant operator/utilities and guide the research and development process of new technologies. FLEXTURBINE technologies open a cost-effective opportunity to upgrade the current plant infrastructure and increase flexibility by enabling the retrofit of existing thermal plants without impeding their CCS readiness. FLEXTURBINE significantly contributes to the social target of low-carbon-energy by the enhancement of health and quality of life, sustainability, job creation, education and cost efficiency.