Abstract. Turbine start-up transients are induced by the wicket gates opening sequence and generate high amplitude stress cycles. These stress cycles have a detrimental effect leading to faster crack growth in the runner blades. Using a series of direct measurements taken on a prototype runner in order to find the optimal start-up parameters exposes both the runner and the instrumentation to a series of successive damaging transient events during the optimization process. To solve this, finding sensors strongly correlated to strain gauges and whose signals can be easily obtained to identify a model to predict the strain, instead of directly measuring it, would reduce the risk, cost and downtime associated with a measurement campaign. This paper shows that turbine shaft torsion measurements is highly correlated to the strain at a runner blade hotspot, and we demonstrate that the ARMAX model can be used to represent the dynamic system in order to minimize the strain on blades.

The thermal impedance of a tow-plaster material is determined from the thermal electrical analogy in the dynamic frequency regime. The thermophysical characteristics magnitudes of the material, thermal conductivity and coefficient of thermal diffusivity are relating to shunt and series resistances determined from the results of the study of representations of Nyquist and Bode plots. The study applied to the composite tow-plaster showed it can be used as a good thermal insulator.

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The aim of this study is to characterize thermal insulating local material, kapok, from a study in 3 dimensions in Cartesian coordinate and in dynamic frequency regime. From a study a 3 dimensional the heat transfer through a material made of wool kapok (thermal conductivity: λ = 0.035 W/m/K; density: ρ = 12.35 kg/m 3 ; thermal diffusivity: α = 17, 1.10-7 m 2 /s) is presented. The evolution curves of temperature versus convective heat transfer coefficient have helped highlight the importance of pulse excitation and the depth in the material. The thermal impedance is studied from representations of Nyquist and Bode diagrams allowing characterizing the thermal behavior from thermistors. The evolution of the thermal impedance with the thermal capacity of the material is presented.

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