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Master Thesis

Optimisation d'aubes de turbomachines : minimisation de la réponse vibratoire à la suite de contacts avec le carter

Abstract : One of the strategies used in recent years to improve turbomachines' overall efficiency is the reduction of radial clearances between rotating and static components. However, as this clearance reduces, the probability of structural contacts between blade-tips and the surrounding casings increases; to a point that such events are now anticipated in non-accidental configurations. For that reason, contact interactions must now be accounted for as early as the design stage of bladed components. However, contact is a highly non-linear phenomenon and, to this day, no relevant criterion exists to discriminate blades according to their sensitivity to contact events. In a recent study, it was found that a redesigned blade, featuring significant improvements with respect to its vibratory response following contacts, essentially differed from the original blade with respect to its clearance consumption (which characterizes the evolution of blade/casing clearance as the blade vibrates over its first free-vibration modes). From this observation, it was decided to carry out a thorough investigation on the possible relation between clearance consumption and the non-linear vibratory response following contacts. This master's thesis presents an automated structural optimization procedure of a blade design using an objective-function related to the blade’s clearance consumption. The optimization variables used are the geometrical parameters stemming from the blade model created for this study. It relies on a derivative free optimization software (NOMAD) using the mesh adaptive direct search algorithm. The presented optimization procedure is applied on several existing blades from the literature. The procedure yields blades featuring lower clearance consumption. Initial and final blades shapes are then analyzed by means of an in-house numerical tool dedicated to the simulation of rotor/stator interactions. An in-depth comparison of numerical results underlines that the amplitudes of vibration following contacts are significantly lowered for the final blade . Overall, it is evidenced that the blades' sensitivity to contact has been lowered as certain critical speeds vanish for the final blade shapes.
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https://dumas.ccsd.cnrs.fr/dumas-01737838
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Submitted on : Monday, March 19, 2018 - 10:34:59 PM
Last modification on : Tuesday, March 20, 2018 - 1:30:05 PM

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  • HAL Id : dumas-01737838, version 1

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Julien Lainé. Optimisation d'aubes de turbomachines : minimisation de la réponse vibratoire à la suite de contacts avec le carter. Génie mécanique [physics.class-ph]. 2017. ⟨dumas-01737838⟩

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