Open AccessOperation Cycle Concept for the fatigue life prediction of Francis runners
Author(s) -
Florian von Locquenghien,
Benjamin Leibing,
Andreas Greck
Publication year - 2019
Publication title -
iop conference series. earth and environmental science
Language(s) - English
Resource type - Journals
eISSN - 1755-1307
pISSN - 1755-1315
DOI - 10.1088/1755-1315/405/1/012008
Subject(s) - transient (computer programming) , strain gauge , amplitude , gauge (firearms) , stress (linguistics) , steady state (chemistry) , constant (computer programming) , signal (programming language) , fatigue testing , event (particle physics) , structural engineering , computer science , control theory (sociology) , mechanics , engineering , materials science , physics , artificial intelligence , linguistics , philosophy , chemistry , quantum mechanics , metallurgy , programming language , operating system , control (management)
A Francis runner is exposed to various loading conditions of steady and transient nature that need to be considered in a fatigue life assessment. Steady state conditions (e.g. Speed No Load, Full Load) have a constant stress amplitude pattern and therefore it is best practice to calculate a fatigue damage rate that can be multiplied by the operation time to determine fatigue damage values. Transient conditions (e.g. Start, Stop, Load Rejection) are characterized by time dependent mean stress and stress amplitudes. Traditionally, strain gauge signals are Rainflow counted and the results are evaluated using SN-curves for each separate event. With this approach, major fatigue damage driving events across operating conditions might be missed. With the introduction of the Operation Cycle Concept, the strain gauge signal is regarded from Standstill to Load to Standstill as one cycle. The influence of this approach compared to the traditional one is presented based on strain gauge measurements of Francis runners. Operating conditions with potential for optimization are identified. This knowledge is especially important for machines that are faced to flexible operation, including numerous Start-ups and Shut-downs.