Aurélien Quarroz’s Master’s thesis
In a Pelton turbine, the distributor plays a vital role: it distributes the water from the penstock to the various nozzles that feed the runner. The quality of the flow through this component affects both the hydraulic losses and the quality of the jets striking the buckets.
In the field of small-scale hydraulics, two main architectures can be used. The so-called distribution systems 90° are made up of standard elbows, T-pieces and pipes, and have the advantage of being relatively simple and inexpensive to manufacture. The manifolds spiral, which are more compact and sophisticated, are designed to improve flow quality; however, they are more complex and costly to manufacture. Until now, the actual benefit of this second option has been difficult to quantify for turbines ranging from a few hundred kilowatts to a few megawatts.
The work of Aurélien Quarroz, produced in collaboration with Jacquier-Luisier, was therefore aimed at carrying out a numerical comparison of these two architectures and identifying ways to improve the spiral distributor developed by the company.
The numerical model has also been designed parametrically so that the injector orifices can be modified and various operating conditions analysed using a single calculation configuration.
CFD as a design tool for small-scale hydropower
Beyond a comparison of two geometries, this work primarily provides a a numerical methodology for analysing and improving low-power Pelton turbine distributors.
It shows that performance cannot be assessed solely on the basis of pressure drops: the structure of secondary flows and their influence on the jets must also be taken into account. Helicity therefore emerges as a relevant indicator to guide the development of future distributor geometries.
This work thus gives Jacquier-Luisier a better understanding of the hydraulic behaviour of his spiral distributor and provides a solid basis for continuing to optimise it and propose solutions tailored to the specific constraints of small-scale hydropower.
