Session: 41-05 Small, vertical and new concept turbines

Submission Number: 177647

Analysis and Quantification of the Jet Flow Distortion Inside and Outside of the
Pelton Turbine Nozzle 

It has been demonstrated by experimental investigations and theoretical simulations that the jet exiting a Pelton turbine's distributor is affected by secondary flows. These are generated by curves or bifurcations in the penstock and by the torpedo assembly within the distributor itself. This leads to two main issues: on one hand, the secondary flows reduce the overall kinetic energy available in the jet for the Pelton wheel's buckets. These circumferential flows constitute a direct loss, detracting from the total kinetic energy that can be converted.

On the other hand, these same circumferential velocities also induce a variation in the jet's shape, generating a displacement of the jet's centreline with respect to the spear axis. Quantifying these secondary flows and the jet's displacement is therefore important for the design of the turbine buckets, enabling them to capture the maximum incoming energy.

This study, based on the available literature, aims to analyse the effect of the inlet penstock's curvature and the torpedo's presence on the jet's form and intensity. Specifically, the flow behaviour inside and outside a real-world distributor from a Pelton hydroelectric plant was simulated using the multiphase code FINE™/Marine by Cadence, under a specified geodetic head. A metric expressing the magnitude of the circumferential kinetic energy relative to the axial energy was calculated for several jet sections (both internal and external to the distributor) and for various load conditions based on the spear's position. The eccentricity of the jet from its theoretical axis was also assessed.

The study has yielded important quantitative information for manufacturers, who can now account for the penalties arising from upstream pipe curvature and the presence of the torpedo during the design stage.

Presenting Author: Antonio Peretto Dept. of Industrial Engineering - University of Bolgogna

Presenting Author Biography: Antonio Peretto graduated in Nuclear Engineering at Università di Bologna.
Teaching fellow (assistant professor) from 1998, and full professor from 2001. He is now Full professor at the Department of Mechanical Engineering (DIEM) – School of Engineering - Università di Bologna.
He hold many courses on thermo-fluid machines with particular emphasis on energy conversion systems and combined heat and power. Since 1998 he teaches “Fluid machines” and “Combined heat and power”.
The main research activities are:
- Fuel energy systems: advanced gas turbines, off-design operation, ambient influence on performance, alternative fuels
- Combined heat and power: new technologies and operating strategies, economic aspects and regulations, environmental problems
- Fuel cells: experimental analysis for stand-alone and/or cogenerative applications
He participates and coordinates many research projects, also experimental, with many national and international companies.
Member of:
- PhD Board at University of Bologna,
- America Society of Mechanical Engineer (ASME),
- Italian thermo technical association (ATI),
He has been Chair of ASME Industrial and Cogeneration Committee, Session Organizer, Chair and Reviewer in the Industrial and Cogeneration Committee of the ASME International Gas Turbine Institute (IGTI).
Authors of 4 educational books and about 70 scientific papers; three of them awarded as “Best paper” from the IGTI.

Authors:

Salvatore Acerra Dept. of Industrial Engineering - University of Bologna
Francesco Peracchini NSI SRL
Antonio Peretto Dept. of Industrial Engineering - University of Bolgogna
Luca Ratto NSI SRL