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Beatrice FRAGGE’s Thesis Defense

par Laurence Laffont - publié le

Beatrice FRAGGE’s thesis defense, intitled Allumage d’une chambre de combustion par retournement temporel micro-onde (Ignition of a Combustion Chamber by Microwave Time Reversal) will be taking place on Thursday, March 17th 2022 in Salle des Colloques (Building 3R2).

Pour des raisons liées aux restrictions sanitaires, les places seront limitées.
Un mail peut être envoyé directement à Beatrice pour obtenir le lien de visioconférence.

Jury :

Ana LACOSTE (Professor, LPSC/IN2P3, Grenoble), Rapporteur

Marc BELLENOUE (Professor, PPRIME, Poitiers), Rapporteur

Valérie VIGNERAS (Professor, INP Bordeaux), Reviewer

Éric FREYSZ (Research director, Bordeaux University), Reviewer

Jérôme SOKOLOFF (Senior Lecturer, Toulouse 3 University), Thesis Director

Olivier ROUZAUD (Senior researcher, ONERA Toulouse), Thesis co-director

Olivier PASCAL (Professor, Toulouse 3 University), Supervizor

Mikaël ORAIN (Senior Researcher, ONERA Fauga Mauzac), Supervizor

Franck Hervy (DGA ), Guest

Abstract :

During this thesis, we studied a new approach for an ignition device for air breathing engines based on a microwave system and time reversal. In the first part we describe the path from the spark plug to time reversal. It describes the basics of two-phase combustion as well as the history and the mechanics of time reversal and the interest in its use for this study. A replacement for the spark plug is intensely studied and we show the state of the art of the different approaches. The first step in our study was to show the capacity of a plasma, created by focused microwaves to ignite a liquid fuel. This step is described in part two of this manuscript, which treats the first experimental set-up, designed during this thesis. This study is done in a resonant cavity with initiators and a droplet stream. We explain the need of the approach for this set-up before presenting the results of ignition tests of ethanol and kerosene droplets. After the demonstration of kerosene ignition in the first part, we continue with time reversal (TR) in the third part of this manuscript. For the study of plasma ignition by TR in air at atmospheric pressure, we designed a second set-up, this time a multimodal cavity. This last part presents the design process of the cavity and the first TR tests with low power levels. After optimization of the TR we switch to tests on high power levels. We use again initiators, here SRRs, to increase the electric field density. The results show a successful ignition of a plasma with a sinusoidal signal and a TR signal. We finish this part with ignition tests of a kerosene spray by a conventional spark plug and the plasma created in the gap of the SRRs with the sinusoidal signal and the TR signal. During this thesis, two experimental set-ups have been designed and built from scratch.