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Particle characterization is important to the aerospace field because particle ingestion in propulsion engines can lead to catastrophic failures. It has been shown laser based methodologies can determine size and concentration of spherical particles by using light extinction. However, when one moves to increasingly complex shapes one must take into consideration not only light extinction but multi angle light scattering. Cylindrical particles scatter light in a way that can be quantified by electromagnetic wave theory. This scattering distribution is directly related to the cylinders diameter and material properties, as well as the wavelength of the incident light. This project designed and implemented a rig that measures the scattering distribution of single static cylindrical particles. It was shown that the scattering distribution for cylinders can be measured and compared to computational expected values, especially in the forward scattering region. Future work in measuring the scattering distribution of increasingly complex geometries and in flow conditions is proposed. / Master of Engineering

Master of Science / Particulate ingestion has been an ongoing issue in the aviation industry as aircraft are required to operate in hostile environments. Ingesting particulates such as sand or dust can erode and damage engine components. This damage will affect the life cycle of parts and compromise the safety of the aircraft. This issue is very costly and dangerous. In order to combat these issues, a particle sensor with the ability to monitor in-stream particulate size, shape, and mass flow rate is necessary. Our team with the Advanced Propulsion and Power Laboratory developed a non-intrusive optical sensor that is able to characterize non-spherical particles. This sensor has been used in various applications through the years; however, most recently, the sensor has been demonstrated at the Virginia Tech M250 engine inlet. This was the first time that the sensor was directly attached to an engine's inlet and subjected to engine conditions. For this validation, highly erosive, coarse quartz was used. Utilizing laser and cameras, the sensor is able to deduce the particles' average shape and size distributions. From those measurements, the mass flow rate of the particle can be calculated. The works provided in the thesis show that particle ingestion rates can be measured to an acceptably high accuracy. In contrast, refinement of the processing techniques can provide spatially resolved measurements of particle characteristics as well.

The content in the dissertation is divided into two main categories: (1) micro-particle characterization techniques based on elastic light scattering, and (2) ultra-compact on-chip plasmonic light concentration and its applications. For category (1), I developed two techniques, one is in vitro and the other is in the scenario of flow cytometry. I investigated theoretically and experimentally the spectra of scattered light from spherical dielectric particles at certain fixed angles, and demonstrate the linearity between the peak positions in the Fourier domain and the diameter of the particle. Based on this discovery, I demonstrate an efficient and accurate technique for in-vitro micro-particle sizing. Moreover, I theoretically analyzed the far-field elastic scattering signals from micro-particles passing through a flow cytometer with tightly focused incident beams, and established an algorithm to extract size information from the detected signals with higher accuracy than that in conventional flow cytometry systems. For category (2), I proposed an on-chip plasmonic nanofocusing technique whose unit device is a plasmonic triangle-shaped nanotaper mounted upon a dielectric optical waveguide. This structure provides highly efficient and robust light concentration into the tip of the nanotaper. Near-field measurements were performed to thoroughly investigate a fabricated sample and prove the concept. I also proposed theoretically a novel concept named phase-induced local-field configuration with logic behaviors, whose actuators are composite devices built on units of single on-chip plasmonic light concentrators mentioned above.

The first aim of this work was to integrate, validate, and document, a digital particle image quantification (Flow-IQ) software package developed in conjunction with and supported by Aeroprobe Corporation. The system is tailored towards experimental fluid mechanics applications. The second aim of this work was to test the performance of DPIV algorithms in wall shear flows, and to test the performance of several particle sizing algorithms for use in spray sizing and average diameter calculation. Several particle sizing algorithms which assume a circular particle profile were tested with DPIV data on spray atomization, including three point Guassian, four point Gaussian, and least squares algorithms. A novel elliptical diameter estimation scheme was developed which does not limit the measurement to circular patterns. The elliptic estimator developed in this work is able to estimate the diameter of a particle with an elliptic shape, and assumes that the particle is axisymmetric about the x or y axis. Two elliptical schemes, the true and averaged elliptical estimators, were developed and compared to the traditional three point Gaussian diameter estimator using theoretical models. If elliptical particles are theoretically used, the elliptical sizing schemes perform drastically better than the traditional scheme, which is limited to diameter measurements in the x-direction. The error of the traditional method in determining the volume of an elliptical particle increases dramatically with the eccentricity. Monte Carlo Simulations were also used to characterize the error associated with wall shear measurements using DPIV. Couette flow artificial images were generated with various shear rates at the wall. DPIV analysis was performed on these images using PIV algorithms developed by other researchers, including the traditional multigrid method, a dynamically-adaptive DPIV scheme, and a control set with no discrete window offset. The error at the wall was calculated for each data set. The dynamically adaptive scheme was found to estimate the velocity near the wall with less error than the no discrete window offset and traditional multigrid algorithms. The shear rate was found to be the main factor in the error in the velocity measurement. In wall shear velocity measurement, the mean (bias) error was an order of magnitude greater than the RMS (random) error. A least squares scheme was used to correct for this bias error with favorable results. The major contribution of this effort stems from providing a novel elliptical particle sizing scheme for use in DPIV, and quantifies the error associated with wall shear measurements using several DPIV algorithms. A test bed and comprehensive user's manual for Flow-IQ v2.2 was also developed in this work. / Master of Science

La métrologie des nanoparticules est devenue un enjeu scientifique et industriel capital pour pouvoir contrôler les caractéristiques des nano-objets (taille, densité, etc.) dans les procédés industriels tant pour la qualité des produits fabriqués que pour la protection des personnes et de l’environnement. Il est important, par conséquent, de trouver des méthodes de caractérisation innovantes et simples à mettre en oeuvre. L’objectif de ce travail de recherche fût de développer et d’optimiser des solutions pour caractériser des nanoparticules en voie sèche à l’aide d’un plasma (favorisant la désagglomération de l’échantillon de poudres à étudier). La présence de nanoparticules modifiant sensiblement les caractéristiques électriques du plasma, nous avons, dans un premier temps, développé un diagnostic basé sur la caractérisation électrique de la décharge et du plasma. Cette méthode nous renseignant sur la taille et la densité moyenne des nanoparticules. Puis, dans un second temps, nous avons développé un diagnostic basé sur la diffusion multi-angle de la lumière laser, nous permettant d’obtenir, là aussi, la taille et la densité moyenne des nanoparticules présent dans le plasma mais également leur indice de réfraction. Nous nous sommes, enfin, intéressés à la sédimentation assistée par plasma permettant d’obtenir la distribution en taille des nanoparticules, en l’optimisant. La corrélation de ces trois diagnostics nous donne, donc, un diagnostic efficace et fiable permettant la caractérisation en taille, en densité et en propriétés optiques des nanoparticules piégées dans le plasma. / Dust nanoparticles metrology has become a major scientific and industrial issue in order to control the characteristics of nano-objects (size, density, etc.). For industrial interests it concerns processes control and monitoring, manufactured products quality, human being and environment protection. It is therefore, crucial to find innovative methods of characterization and easy to implement and to handle. The objective of this research program was to develop and optimize solutions for characterizing nanoparticles in dry process and environment using a plasma (promoting disagglomeration of the studied powders). The presence of nanoparticles substantially altering the electrical characteristics of the plasma, we have, at first, developed a diagnostic based on the electrical characteristics of the discharge and the plasma. This method allows the determination the average nanoparticles size and concentration trapped in the plasma gas phase. Then, in a second step, we developed a diagnostic based on multi-angle laser light scattering, allowing us to get the size and the average density of the nanoparticles in the plasma, but also their refractive index. We finally focused our interest on the optimization of the plasma-assisted sedimentation of nanoparticles to obtain their size distribution especially for particles having sizes below 10 nm. The correlation of these three diagnostics gives us, so an efficient and reliable diagnostic for the global characterization in terms of size, density and optical properties of nanoparticles trapped in the plasma.

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

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As environmental awareness raises the expectations to reduce emission of modern diesel engines are growing as well. Fuel diversity and the advanced injector systems requires even more attention on an ever existing problem which is called nozzle hole fouling. Recent literature and observations at Scania indicate the phenomena is connected to fuel filter plugging caused by metal carboxyl contaminants through the formation of “soft particles”. This report begins with a literature review about the nature of agglomerates in biodiesel. Followed by the evaluation of six particle sizing equipment. This include one ensemble technique based on Brownian motion, namely dynamic light scattering. The remaining five techniques are single particle counters, including a high speed camera system, light blocking system, Nano tracking analysis and two different approaches using light microscope. To characterise the structure and chemical components of the particles SEM, EDX, FT-IR and ICP-OES were used. From the above mentioned methods optical microscopy was chosen to be the best method to evaluate the particle distribution. The main reasons for this is the ability to measure particles in the solution in the desired size range and the possibility to couple it with a Raman spectrometer, providing possibilities for future studies. Besides finding the best technique to measure the particles, a secondary result is the negation of Zinc-neodecanoate creating particles in the fuel. It opposes the assumption made in the literature about filter blocking, and it finds the need for deeper understanding of the nature of soft particles.