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This thesis addresses the experimental investigation of turbomachinery flows by means of particle image velocimetry (PIV). While PIV is an attractive investigation approach due to its non-intrusiveness and capability to offer whole-field velocity information, the geometrical complexity and unique operating conditions pose various challenges to implementing this technique in turbomachinery test rigs. The main objective of this thesis is to verify the feasibility and capability of PIV in turbomachinery-related applications and provide guidelines for the successful implementation of this measurement technique. The experimental test campaigns took place in three test facilities at the von Karman Institute for Fluid Dynamics: The L-12 low-speed wind tunnel equipped with an active turbulence grid, the S-1/C high-speed wind tunnel hosting a linear low-pressure turbine cascade, and the CT-3 short-duration high-speed rotating test rig fitted with a single high-pressure turbine stage.The measurement on the active turbulence grid presented the core capability of PIV combined with the fluorescent particle. The synthetic jet injected into the main flow from the grid was distinguished by seeding the fluorescent particle to the jet and a typical non-fluorescent oil particle to the rest.The PIV measurements on the transonic linear cascade in the S-1/C wind tunnel were carried out at Re_out,is= 70k – 120k, M_out,is = 0.70 - 0.95, matching the typical operating condition of low-pressure turbine stages employed in modern geared turbo-fan engines. The measurement on the upstream blade-to-blade (B2B) plane involved a parametric study on the data acquisition and processing settings, showing a high sensitivity of measured TI to the particle displacement. The measurement on the blade passage B2B plane demonstrated the performance of PIV in a transonic flow with high-velocity gradients and cross-validated RANS prediction and 5HP measurement results. The stereoscopic PIV measurement on the c, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

The motion of the free liquid surface inside a reservoir is called sloshing. Itis of large interest in different industrial fields such as satellite and spacecrafttrajectory control, automotive industry, nuclear engineering, buildingdesign, etc. The framework of propellant management on spacecraft is ofmain interest for this PhD thesis, even if its outcome can be applied to manyother fields concerned by sloshing.Being able to understand the behavior of the fluid in a reservoir subjectedto extreme environmental conditions means being able to predict its positionand topology inside the tank, for a given external and gravitationalacceleration and a determined thermodynamic condition. The predictionand control of this motion is far from being understood due to the differentparameters that play a role in the dynamic system such as the geometryof the container, the type of external excitation (shape, frequency contentand amplitude), the level of the liquid and finally the kind of liquid. In particular,the design of propulsion systems are affected by this phenomenon,still hampered by the unavailability of validated CFD models. Moreover theexisting experimental studies are mainly based on intrusive and local singlepoint measurement techniques, which give no information on the behaviorof the 3D liquid interface and on the velocity field inside the liquid phase.The main goal of this project has been to extend the experimental approachof liquid sloshing investigation in space propulsion, studying, developing andimproving non-intrusive measurement techniques for free surface behaviorand velocity characterization in the liquid phase. In particular, the free surfacebehavior have been studied by means of Laser Detection and Recordingtechnique (LeDaR), retrieving the profile of the interface over a line, andReference Image Topography technique (RIT), capturing the instantaneous3D interface shape. In addition, Particle Image Velocimetry (PIV) have beenused to measure the 2D velocity, Doctorat en Sciences de l'ingénieur et technologie, La thèse a également été publiée par le von Karman Institute for Fluid Dynamics, sous l'ISBN 978-2-87516-140-6, info:eu-repo/semantics/nonPublished

The Belgian nuclear research institute (SCK•CEN) is developing MYRRHA. MYRRHA is a flexible fastspectrum research reactor ,conceived as an accelerator driven system (ADS). It is designed to operate in sub-critical and critical modes, with a proton accelerator producing the neutron source by spallation. Theconfiguration of the primary loop is pool-type: the primary coolant and all the primary system components (coreand heat exchangers) are contained within the reactor vessel, while the secondary fluid is circulating in the heatexchangers. The primary coolant is Lead Bismuth Eutectic (LBE). The recent nuclear disaster of Fukushima in2011 changed the requirements for the design of new reactors, which should include the possibility to removethe residual decay heat through passive primary and secondary systems, i.e. natural convection (NC).Verifying that sufficient mass flow takes place between the core and the heat exchanger in passive decay heatremoval conditions (core power=11MW) is necessary to fulfill the safety requirement. Analyzing the naturalconvection flow before building the reactor is therefore the primary objective of this work. Furthermore, it is ofinterest to understand which factors contribute to enhance or decrease the primary coolant mass flow. Inparticular, stratification and pressure drops in the primary hydraulic loop are expected to play important roles.The secondary objective of the study was therefore to verify the influence of the loop geometry and of theplenum on the mass flow.The methodology chosen to address the primary objective of the study consisted in measuring the quantities ofinterest in a 1:5 scaled water model (MYRRHABELLE) of the reactor. In particular the simultaneousmeasurement of mass flow, velocity field and temperature in natural convection working conditions is requiredto fulfill the first objective. Facilities of increasing size and complexity were used to develop experimentalmethodology and techniques before carrying out the e, Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished

The purpose of the present research is to develop and apply an experi- mental technique for measuring the size of nanoparticles and nanodroplets in a flow environment. The developed non-intrusive, optical method is called Light Extinction Spectroscopy (LES) and it allows to determine the size of particles from measuring their light transmission spectrum on the Ultraviolet-Near-Infrared range. The most crucial part of the develop- ment work is to obtain a reliable data processing method, which is based on the regularized solution of an ill-conditioned inverse problem. The de- veloped method is first tested using synthetic data, which allows to deter- mine the measurement range and also the measurement errors caused by various sources. This is followed by performing laboratory experiments for validating the LES technique. Validation measurements using calibrated particles and a reference instrument shows that sizing errors are in the order of 5-10%. Afterwards, the technique is applied for characterizing the Brownian coagulation process of nanodroplets, where the growth rate of droplets is successfully measured and is found to agree with theoreti- cal expectations. Next, the LES technique is applied to coagulating solid particles, where the growth rate of these complex non-spherical objects is retrieved. Finally, a particle monolayer is deposited on an air-water inter- face and it is shown that the LES technique can retrieve the particle-water contact angle, which allows the characterization of nanoparticle wettabil- ity and the study of the related interesting physical phenomena., Doctorat en Sciences de l'ingénieur et technologie, info:eu-repo/semantics/nonPublished