What is great about the pump / turbine the ALPHEUS project is developing?
The counter-rotating pump-turbine under development in ALPHEUS is of axial type, which is more suitable for low-head applications. It has no guide vanes, but instead there are two counter-rotating runners that interact to give the best possible conditions at all time. In order to find a fish friendly configuration for the ALPHEUS project, a low rotation speed machine was considered as a latent solution. That is why a positive displacement machine such as the lobe pump-turbine was considered a potential option for low-head applications.
As the difference in elevation of the water levels at each side of the power plant changes, at the same time as the need of electric power varies, the rotational speeds of each of the runners can be set individually to meet the needs under the present conditions at optimal efficiency. The runner blades are designed to work efficiently with flow in both directions, either pumping water to the elevated reservoir or extracting energy from the flow in pump mode. It is based on a concept that is used in marine applications, and experiences, materials and components from those applications can be used also in the application of the developed pump-turbine in sea-water conditions.
Plus, unlike dynamic pumps, a PD machines can maintain nearly constant flow rate and efficiency regardless of significant changes in pressure.
What tools do you use to design the pump / turbine?
The design is developed using a set of numerical tools. ADT has designed and optimized the initial model scale prototype of both the shaft driven and rim driven contra rotating propeller RPT for the ALPHEUS project. ADTs inhouse software TURBOdesign Suite served as the design tool for the design and optimization of the initial prototype. Meanline design is performed using ADT’s TURBOdesign Pre software. The blade design is carried out using TURBOdesign1 which is a unique software utilizing a 3D inverse design methodology.
Design evaluation is performed using CFD analysis, Ansys Turbogrid was used for meshing and Ansys CFX was used as the solver. The optimization method of the model scale prototype involved a Design of Experiments method for the shaft driven RPT.
A workflow is created in Ansys Workbench to obtain a design matrix with various design variations are generated and CFD evaluation results of each design. Blade designs are generated using TURBOdesign 1 which is integrated with Ansys Workbench through ADT’s TURBOdesign Link Workbench software. A surrogate model based approximation of the generated data and optimization using Multi-objective Genetic Algorithm was performed using Dassault Systemes Isight software. Final optimized designs are generated using TURBOdesign 1, based on the design parameter values obtained as a result of optimization and evaluated in CFD.
For the rim driven design, optimization is performed based on manual design iterations involving blade designs using TURBOdesign 1 followed by CFD analysis using Ansys CFX. FEA analysis of the various designs are performed using Ansys Workbench.
How will the design be implemented in the lab and in real life?
The machine will be manufactured in lab-scale, for tests of a wide range of operating conditions at Chalmers. The experimental results will be used to validate the numerical results at NTNU, so that the numerical results can be trusted for investigations that are not feasible in the lab. Up-scaling to prototype scale will be done numerically, yielding results that are to be expected in real life application of the machine. The outcome of the project will give important input to future manufacturers of counter-rotating pump-turbines for low-head sea-water applications. It shall inspire manufactures and encourage them to invest in this new energy storage solution.
ABOUT THE AUTHORS
Professor Håkan Nilsson, Chalmers University of Technology, has been doing research on CFD for hydropower applications since 1997, together with 7 PhD students, 5 post-docs, and a number of master thesis students. In the APLHEUS project, he is mainly responsible for numerical studies of transient operation of the novel counter-rotating pump-turbine concepts, together with PhD student Jonathan Fahlbeck.
Pål-Tore Storli is an Associate Professor at the Waterpower laboratory at the Norwegian University of Science and Technology. He is the leader of Workpackage 2 – Turbine Design, and directly involved in the part concerning the Positive Displacement machine that’s being investigated for energy storage applications.
Luiz Henrique Accorsi Gans holds a double degree in Mechanical Engineering. With 5 years of previous experiences in CAE (CFD and FEA), Luiz is now a PhD candidate at the Norwegian University of Science and Technology and is part of the Work Package 2 – Turbine Design on the ALPHEUS project. He is responsible for the CFD simulations and design optimization of Positive Displacement RPT.
Professor Mehrdad Zangeneh is founder and managing director of Advanced Design Technology and Professor of Thermofluids at University College London. His research interests cover development of computational design methods based on 3D Inverse Design and automatic optimization to a variety of turbomachinery applications. He is also involved in WP 2 – Turbine Design.
Melvin Joseph is working as a Turbomachinery Design Engineer in ADT’s engineering team. He designs different kinds of turbomachinery as part of consultancy projects for various customers worldwide. He started his career in turbomachinery design after post-graduation in Aerospace Propulsion specialization in 2014. For ALPHEUS project, he is involved in the hydraulic design and optimization of model axial CR RPT (Task 2.1) and upscaling to full scale prototype (Task 2.4) as part of WP2 (Turbine design).