Constraints of Parametrically Defined Guide Vanes for a High-Head Francis Turbine

Filip Stojkovski,Zoran Markov,Igor Iliev,Marija Lazarevikj,Ole Gunnar Dahlhaug

doi:10.3390/en14092667

Filip Stojkovski, Zoran Markov + Show 3 more

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https://doi.org/10.3390/en14092667

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Abstract

This paper is focused on the guide vane cascade as one of the most crucial stationary sub-systems of the hydraulic turbine, which needs to provide efficient inflow hydraulic conditions to the runner. The guide vanes direct the flow from the spiral casing and the stay vanes towards the runner, regulating the desired discharge. A parametric design tool with normalized geometrical constraints was created in MATLAB, suitable for generating guide vane cascade geometries for Francis turbines. The goal is to determine the limits of these constraints, which will lead to future faster prediction of initial guide vane configurations in the turbine optimal operating region. Several geometries are developed using preliminary design data of the turbine and are investigated using CFD simulations close to the best efficiency point (BEP) of the turbine. This research is part of the Horizon-2020—HydroFlex project led by the Norwegian University of Science and Technology (NTNU), focusing on the development of a flexible hydropower generation.

Highlights

Hydropower, as a part of the family of renewable energy sources, is an active engineering and scientific field which focuses on optimization of the entire energy transformation process so as to attain more efficient, flexible, and reliable electricity generation
The guide vane configurations are developed according to the turbine design point, i.e., the best efficiency point
An approach for further optimization of the guide vane design for highhead Francis turbines has been presented, by developing several geometries within a design space pre-described by the Francis-99 turbine model from the Waterpower Laboratory at NTNU

Summary

Introduction

Hydropower, as a part of the family of renewable energy sources, is an active engineering and scientific field which focuses on optimization of the entire energy transformation process so as to attain more efficient, flexible, and reliable electricity generation. Increased electricity demands for balancing and, sometimes, temptingly high profit margins for off-design operation have pushed hydroturbines to their structural limits. The turbines are being operated at unfavorable loads, which has raised concerns and challenged the existing design philosophy. The critical requirements for modern turbines are high efficiency and stability over the wide operating range. Increasing flexibility in energy production from hydropower plants is a task demanded by the hydropower sector in Europe and worldwide, especially in off-design operation conditions of the turbines. The turbines need to operate with more start–stop cycles and high ramping rates. Variable-speed operation of Francis turbines is seen as an alternative solution to achieve high ramping rates and more efficient energy production in off-design operating conditions [1,2,3]

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