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Rotating instability in the vaneless diffuser of a radial flow pump

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Journal of Thermal Science 2008年第4期17卷 368-374页

作者： A.Dazin O.Coutier-delgosha P.Dupont S.Coudert G.Caignaert G.Bois laboratoire de mécanique de Lille(UmR CNRS 8107) Arts et Métiers ParisTech laboratoire de mécanique de Lille Ecole Centrale de Lille laboratoire de mécanique de Lille CNRS

The paper refers to the behavior of a vaneless diffuser of a radial flow pump in partial flow operating conditions. Some experimental data have been obtained using 2D/2C PIV and unsteady pressure measurements within the diffuser, in various operating conditions. The experimental results at the lower flow rate are compared with two-dimensional numerical calculations.

关键词： Vaneless diffuser Radial flow pump Instability Particle Image Velocimetry pressure measurements 2D calculations.

Numerical study of the performance of multistage Scaba 6SRGT impellers for the agitation of yield stress fluids in cylindrical tanks

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Journal of Hydrodynamics 2015年第3期27卷 436-442页

作者： AmeUR Houari BOUZIT mohamed GHeNAIm Abdellah laboratoire de mécanique appliquée Faculté de Génie MécaniqueUSTO-MB Institut de Technologie Université Ibn Khaldoun INSA de Strasbourg-24 Bd de la Victoire-67084 Strasbourg-France

The 3-D flow fields and power consumption in a vessel stirred by multistage Scaba 6SRGT impeller have been investiga- ted. The Xanthan gum solutions in water were used, which have a shear thinning behavior with yield stress. This study was carried out with the help of a CFD package （CFX 13.0, Ansys Inc.） which is based on the finite volume method to solve the momentum equations. The effects of stirring rate, fluid rheology, impeller number, impeller location and vessel size on the performance of such stirred system are presented. To validate the CFD model, our predicted results have been compared with other literature data and a satisfactory agreement has been found.

关键词： Scaba 6SRGT impeller multistage agitator yield stress fluid stirred tank power consumption

Topological Studies of Three-dimensional Flows in a High pressure Compressor Stator Blade Row without and with Boundary Layer Aspiration

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Chinese Journal of Aeronautics 2011年第5期24卷 541-549页

作者： Ankit SACHdeVA Francis LeBOeUF laboratoire de mécanique des Fluides et d'Acoustique Ecole Centrale de Lyon

This paper presents a numerical study of the flow topologies of three-dimensional （3D） flows in a high pressure compressor stator blade row without and with boundary layer aspiration on the hub wall. The stator blade is representative of the first stage operating under transonic inlet conditions and the blade design encourages development of highly complex 3D flows. The blade has a small tip clearance. The computational fluid dynamics （CFD） studies show progressive increase of hub corner stall with the increase in incidence. Aspiration is implemented on the hub wall via a slot in the comer between the hub wall and the suction surface. The CFD studies show aspiration to be sensitive to the suction flow rate; lower rate leads to very complex flow struc- tures and increased level of losses whereas higher rate renders aspiration effective for control of hub comer separation. The flow topologies are studied by trace of skin friction lines on the walls. The nature of flow can be explained by the topological rules of closed separation. Furthermore, a deeper analysis is done for a particular case with advanced criterion to test the non-degeneracy of critical points in the flow field.

关键词： high pressure compressor flow topologies three-dimensional flows boundary layer aspiration tip clearance

STUDY OF THRee-DImeNSIONAL SePARATION OF BOUNDARY LAYeR OVeR BLUNT BODIeS

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Journal of Hydrodynamics 2009年第1期21卷 100-107页

作者： ATmANI R. BRImA A. ASKOVIC R. laboratoire de mécanique des fluides Université de ValenciennesAulnoy lez Valenciennes 59326 France Département de mécanique Université de BiskraBiskra 07000 Algérie

In the case of three-dimensional flows, the separation can be defined in more than one way. Discussions about three-dimensional boundary layer separation in the literature have found a rational extension of the zero skin friction. Attempts have been made to establish the identity of “separation lines”. Among definitions, these may be found：（1） envelopes of limiting streamlines, （2） lines dividing flow which has come from different regions, （3） lines of singularities （problems of topology）, （4） lines on which some component of the skin friction vanishes. each of these is valid under certain conditions, but none is universally valid. In the present work, we use the definition （4）, i.e. at low incidence of a blunt body the separation line is identified as the zero of the meridian skin friction component （Wang 1975）. So the separation line on a flattened spheroid （6：3：1） at 6° of incidence is calculated, as well as experimentally determined by using the electrochemical method, which allows to follow the evolution of the parietal velocity gradient.

关键词： three-dimensional flows separation boundary layers blunt bodies

Doppler Global Velocimeter-development and Validation with measurements in a Round Free Jet

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Journal of Thermal Science 2009年第1期18卷 74-84页

作者： X.Ottavy S.Goguey J.Berthiau I.Trébinjac laboratoire de mécanique des Fluides et d’Acoustique(LmFA)

Doppler global velocimetry （DGV） has already been shown to be an interesting technique capable of measuring the three components of velocity in a plane. A 1-component DGV system is currently under development at the LmFA, using a stabilized continuous wave （CW） argon ion laser for ermssion, lne receiver Ieatures only one camera for both signal and reference images and incorporates a deF1 system to adjust the incident laser light frequency and its transmission coefficient on the iodine cell absorption line. A description of the whole system is presented and a validation with measurements of axial velocities at several positions in a round free jet is proposed.

关键词： laser anemometry Doppler shift iodine vapor absorption line filter deFI system image processing.

Serrated Flow model for metallic Glasses under Compressive Loading

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Acta metallurgica Sinica(english Letters) 2013年第5期26卷 503-508页

作者： m.A.Yousfi K.Hajlaoui Z.Tourki A.R.Yavari laboratoire de mcanique de Sousse LMS ENISo Universit de Sousse SImaP-LTPCm Institut National Polytechnique de Grenoble

A rheological model is proposed that incorporates the serrated flow nature of metallic glasses. It involves the process of the nucleation, propagation and the arrest of a shear bands in the samples subjected to compressive deformation at room temperature. Numerical resolution of the constitutive equations resulting from the model is compared with the stress-strain curve obtained from in-situ nano-compression test in Sem of Zrbased metallic glass. Parametric identification method was applied and enabled us to release the physical parameters of the model. The obtained results showed that the model is adequately valid to describe the experimental data and the almost adjustable model parameters are physically meaningful and comparable to literature.

关键词： metallic glasses Shear bands Serrated flow Rheological modelling Nanocrystallization

modal decomposition for the Analysis of the Rotor-stator Interactions in multi-stage Compressors

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Journal of Thermal Science 2012年第3期21卷 276-285页

作者： N.Courtiade X.Ottavy N.Gourdain laboratoire de mécanique des Fluides et d'Acoustique Ecole Centrale de Lyon CeRFACS CFD Team

A modal analysis method of the rotor-stator interactions in multistage compressors has been developed by LmFA. This method, based on a double modal decomposition of the flow over space and time, has been applied to nu- merical and experimental results of the high-speed 3Y2-stage compressor CReATe based at LmFA, Lyon-France. It reveals the presence of a very strong rotor-stator interaction which completely drives the flow at casing behind all the rotors. This modal analysis method applied to an unsteady RANS simulation permits to calculate the en- ergy of the rotor-stator interactions and to plot energetic meridian maps to explain experimental results and to analyze the interaction in the whole machine.

关键词： rotor-stator interactions modal analysis multistage compressors numerical and experimental results

Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction

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Chinese Physics B 2016年第1期25卷 480-488页

作者：李志新曹庆杰 Léger Alain School of Astronautics Harbin Institute of Technology laboratoire de mécanique et d'Acoustique CNRS

We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous （SD） oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography.

关键词： self-excited smooth and discontinuous (SD) oscillator multiple stick regions friction-inducedasymmetry stick-slip chaos

detailed Analysis of the Flow in the Inducer of a Transonic Centrifugal Compressor

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Journal of Thermal Science 2012年第1期21卷 1-12页

作者： Nicolas Buffaz Isabelle Trébinjac laboratoire de mécanique des Fluides et d'Acoustique ecole Centrale de Lyon 36 av. Guy de Collongue

Numerical and experimental investigations were conducted in a transonic centrifugal compressor stage composed of a backswept splittered unshrouded impeller and a vaned diffuser. A detailed analysis of the flow in the inducer (i.e. the entry zone of the impeller between the main blade leading edge and the splitter blade leading edge) is proposed from choke to surge. Steady and unsteady simulations were performed using the code elsA, which uses a multi-domain approach on structured meshes and solves the compressible RANS equations, associated with a two-equation turbulence model k-l in the rotating frame of reference. The 1mW LmFA-eCL test rig was used for carrying out the tests in the compressor stage. Unsteady pressure measurements up to 150 kHz and Laser Doppler Anemometry measurements were performed in the inducer. A good agreement is obtained between the experimental and numerical data even if an over dissipation is noticed in the numerical results. The change in flow pattern from choke to surge is mainly due to a change in the tip leakage flow trajectory which straightens, leading to a flow blockage of an individual passage near shroud. A spectral analysis shows that only the blade passing frequency and its harmonics compose the various spectra obtained from choke to surge.

关键词： transonic centrifugal compressor inducer unsteady pressure measurements