Active Flow Control system FOR improving HYDRaulic turbine performances at off-design Operation

Project Information

AFC4Hydro

Grant agreement ID: 814958

DOI

10.3030/814958

Project closed

EC signature date 15 May 2019

Start date 1 June 2019

End date 30 November 2023

Funded under

• SOCIETAL CHALLENGES - Secure, clean and efficient energy

Total cost

€ 4 711 589,25

EU contribution

€ 4 711 589,25

Coordinated by

UNIVERSITAT POLITECNICA DE CATALUNYA
Spain

Periodic Reporting for period 3 - AFC4Hydro (Active Flow Control system FOR improving HYDRaulic turbine performances at off-design Operation)

Reporting period: 2021-12-01 to 2023-11-30

Summary of the context and overall objectives of the project

AFC4HYDRO main objective has been to design and validate an Active Flow Control (AFC) system in actual hydraulic turbines that permits to operate at extreme off-design conditions and sustain more transients. For that, a consortium of two universities, Universitat Politècnica de Catalunya (UPC) in Spain and Luleå University of Technology (LTU) in Sweden, two of the Europe’s largest renewable energy producers, Vattenfall in Sweden and Statkraft in Norway, a Small and medium-sized enterprise, Flow Design Bureau (FDB) in Norway, and the Porjus Hydropower Center in Sweden, was created.

This innovative and affordable AFC solution, allowing an improvement of existing hydraulic turbines, has been validated at small scale in a model turbine and at large scale in three prototypes: i) one 10 MW Kaplan turbine located in Porjus (Sweden), and its homologous reduced scale model installed at the Vattenfall Research and Development Center in Älvkarleby (Sweden), ii) one 200 MW Francis turbine located in Oksla (Norway) and, iii) one 25 MW Francis turbine located in Svorka (Norway).

Different technologies have been combined to reduce the unsteady pressure loads exerted on the runners of Francis and Kaplan hydraulic turbines induced by the draft tube flow using: (1) protrusion of rods in radial direction (IPM system); and (2) injection of variable speed water jets with different orientation angles (ICM system). A structural health monitoring system (SHM system) has been developed to evaluate the effects of the IPM and ICM on the dynamic response of the runner, the shaft line, the generator, the bearings, the waterways and the supporting structures using on-board and off-board sensors. These measurements have been used to assess the suitability of a Controller to find the best actuation strategies in real-time operation to reduce pressure fluctuations, structural loads and induced vibrations. An AFC system tailored for full-scale prototypes has been tested against demanding off-design conditions such as speed-no-load (SNL), part load (PL) and load ramping where special attention has been be given to mitigate the powerful and dangerous flow instability provoked by the vortex rope breakdown.

With AFC4Hydro, existing turbines will extend their operating range beyond the stablished safety limits at PL, will face more operation at SNL and will be submitted to more frequent load transients with less wear and tear than before. Consequently, the application of this technology will reduce the maintenance and operating costs, improve performance, facilitate the integration of hydropower in the European energy system, increase the renewable power system flexibility, favour the circular economy and reduce the negative effects of the climate change.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The development of IPM started in a down-scale test rig at LTU to characterize the hydraulic behavior of a Kaplan runner mapping the appearance of a rotating vortex rope (RVR) at PL. Various IPM configurations were simulated numerically with Computer Fluid Dynamics (CFD) and experimentally tested demonstrating that the pressure induced pulsations could be significantly reduced and, in some cases, completely mitigated. Then, the IPM was designed using CFD for the model turbine. Again, the mitigation of the pressure pulsations was confirmed. Finally, CFD was also used to design the IPM at Porjus and Oksla prototypes. The measurements confirmed a significant mitigation of the RVR pressure pulsations at all operating conditions.

The development of the ICM started by reviewing the experience with the 1st generation ICM commercialized by FDB to improve the protruding nozzle exit with the capability of changing orientation in two planes of rotation. The new ICM designs for down-scale and model turbines were manufactured and assembled. The ICM performance was tested at the model turbine. For the Porjus and Svorka prototypes, the final nozzles were designed with a pressure rating of about 25 bar and the benefit of adjusting nozzle injection direction was demonstrated for various flow conditions. Moreover, the chosen sealing solutions adopted to overcome the low relative pressures of about 1 bar at the injection points were also validated.

For the SHM, a test rig was built at the UPC lab for developing experimental and numerical techniques to predict the structure dynamic response. Acquisition routines and online post processing tools were developed for on-board and off-board sensors. Innovative fiber optic sensors were also used. The suitability of the SHM to measure the effects of the ICM and IPM systems on the induced vibrations at the model turbine and its corresponding prototype was confirmed. The modal responses of all the turbines were simulated numerically and measured experimentally. Finally, a simplified version of the SHM for prototypes was successfully designed and tested both at Oksla (with the IPM) and Svorka (with the ICM).

The development of the Controller started with the IPM at the LTU down-scale test rig and with the SHM at the UPC test rig. The communication between the ICM, IPM, SHM and Controller was tested and the complete AFC system was implemented in the model turbine. The tests indicated that the mitigation of the pressure pulsations was possible for different ICM and IPM parameters depending on the operating condition. Then, experiments on three prototypes were performed but, unfortunately, it was not feasible to validate the complete AFC system due to severe time constraints arising from turbine-related issues and safety requirements. Nevertheless, the results obtained were encouraging, underscoring its potential.

The project website (www.afc4hydro.eu) and social networks have been running with news and blog posts. Four newsletters and three videos were published. The project has been presented in international events and the results have been disseminated through magazines, popular science articles, open access articles and conferences. Two partners are promoting the standardization of the AFC technologies in the EIC committees. The possibility of registering patents is also being considered. And a final open workshop was organized for the stakeholders.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The following points present the progress beyond the state of the art:
• A novel technique has been developed and validated applying protrusions in the water conduits (IPM) to manipulate flow structures with the effect of mitigating pressure pulsations at prototype level.
• Innovations based on a first-generation of flow control solutions (ICM) for prototypes including novel features that allow more degrees of freedom have been validated thus expanding the turbine operating range.
• Fiber optics sensors have been successfully used to monitor structural responses (SHM) in a model turbine.

The increase of flexibility of hydro power production that can be achieved with the project results leads to a series of positive impacts from both an economic and environmental perspective:
• Increased power production by exploiting local minimum flow requirements.
• Increased lifespan.
• Avoiding a full refurbishment by just retrofitting an existing plant to adopt a new production scheme.
• Increasing the available flexibility of power production, enabling the addition of new renewable energy such as wind and solar power.

AFC4Hydro simple logo

AFC4Hydro complete logo

Outline of the AFC4Hydro concept with the subsystems