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Modélisation, analyse et contrôle des compresseurs centrifuges contra-rotatifs : Aérodynamique Numérique et Expérimentale

Abstract : Nowadays, Centrifugal Compressors (CCs) are widely used in the automotive, naval, space and other industries and whose design and performance limits are quite known and well documented although the design codes of the latter are kept usually in secret from the literature and not easily accessible. It is with a view to improving CCs not only their standard limits, namely choke and stall, but also their optimization, that this thesis is introduced. Indeed, the first part of this thesis consists in developing several ultra-fast tools (compared to CFD) of direct or inverse design, performance analysis and optimization of CCs using a 0D/1D method (Meanline-approach) as well as those of the Quasi-3D type. These tools are validated on several CCs geometries available in the literature. TThus, they are grouped together in a code named C3Design.In the second part of the thesis, a first study of design, realization and analysis of the numerically and experimentally of the performances of a Contrarotating Centrifugal Compressor (CCCR) is proposed to the scientific community. Indeed, it is known that counter-rotating turbomachines have certain advantages over conventional machines with single rotor. However, no studies on either the design or the performance analysis of CCCR exist in the literature. Thus, four CCCRs are designed by an adaptation of C3Design to CCCRs and analyzed initially by the CFD in order to highlight not only their advantages over CCs, but also their limits at low and high mass flow rate (stable limit and that of blocking). Numerical results showed that CCCRs can achieve better performance in terms of efficiency and pressure rise compared to their CCs counterparts maintaining similar sizes. However, due to the strong counter-rotation of the flow present at the inlet of the downstream impeller (RR), CCCRs tend to have a lower choke margin than CCs and a roughly smaller or equal stall margin.In addition, by adjusting the additional degree of freedom of the CCCRs (speed ratio between the upstream rotor (FR) and the downstream one (RR)), the limits can be pushed back significantly: increasing the speed ratio makes it possible to widen the blocage margin and at the same time reduce the stall margin (increase the effect of the incidence at RR leading edge) and vice versa.Furthermore, two criteria for the limits on the stall and choke by a 0D approach were identified and validated numerically and experimentally.In order to consolidate and validate the numerical results concerning the first three CCCRs designed and simulated, the fourth CCCR is manufactured and tested in the LIFSE (Laboratory of Engineering of Fluids and Energy Systems), thus an experimental bench is realized for this fourth configuration. The experimental results obtained made it possible to validate not only C3Design code and the CFD but also the conclusions already drawn numerically for the CCCRs as well as the 0D criteria on stability at low mass flow rate and chocking at high mass flow rate. In addition, the speed modulation control is carried out experimentally at very low mass flow rate negligible compared to the nominal one to avoid stall instabilities by employing the counter-rotating and co-rotating mode where in the latter, the two upstream and downstream rotors rotate in the same direction which made it possible to enlarge the mass flow range of 58% toward low mass flow rate regions. Because of this additional degree of freedom, it is possible to control the local area of maximum efficiency toward high or low mass flow rate depending on the user wish.
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Submitted on : Wednesday, May 25, 2022 - 11:17:15 AM
Last modification on : Wednesday, September 28, 2022 - 5:57:00 AM

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  • HAL Id : tel-03678151, version 1

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Cheikh Brahim Abed. Modélisation, analyse et contrôle des compresseurs centrifuges contra-rotatifs : Aérodynamique Numérique et Expérimentale. Génie mécanique [physics.class-ph]. HESAM Université; Université Mohammed V (Rabat). Faculté des sciences, 2021. Français. ⟨NNT : 2021HESAE028⟩. ⟨tel-03678151⟩

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