Thesis (M.P.H.)--University of Adelaide, Dept. of Community Medicine, 1992. / Includes bibliographical references (leaves 73-80).

Diss--Universität Bayreuth.

Zugl.: Bayreuth, Univ., Diss., 2007

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Kerry A. Kinney. Vita. Includes bibliographical references.

Thesis (PH.D.)--Michigan State University. Mechanical Engineering, 2008. / Title from PDF t.p. (viewed on Aug. 28, 2009) Includes bibliographical references. Also issued in print.

Zugl.: Darmstadt, Techn. Univ., Diss., 2009

Universiẗat, Diss., 2004--München.

This work is an extension to the spray model of Watkins and Jones (2010). In their model, the spray is characterized by evaluating the three moments Q_2, Q_3 and Q_4 of general gamma number size distribution from their transport equations. The sub-models of drop drag, drop break-up and drop collisions were simulated in terms of gamma distributions. The model is considered as non-vaporising and compared with cases which have low ambient gas temperature and also is strict to a particular set of sub-models for drop drag and break up which they are applicable to produce integrable functions. In this work the model is adjusted to allow a variety of sub-models to be implemented. Three models (TAB, ETAB, DDB) are considered for drop breakup which have been basically introduced to be used with the Droplet Discrete Method (DDM) approach. So in order to implement these models with the model of Watkins and Jones the source terms of the breakup are calculated by grouping the droplets in each cell into parcels which contain a certain number of droplets with similar physical properties (size, velocity, temperature ...). The source terms of each parcel are calculated and multiplied by the number of droplets in these parcels and a numerical integration is then used to obtain the resultant effect of the drop breakup in each cell. The number of drops in each cell is determined from the gamma size distribution. Also three hybrid breakup models (KH-RT, Turb-KH-RT, Turb-TAB) which include two distinct steps: primary and secondary break up model are implemented. The Kelvin- Helmholtz (KH) and the turbulence induced breakup (Turb) models were used to predict the primary break up of the intact liquid core of a liquid jet while the secondary break up is modelled using the TAB model and competition between the KH and the RT models. Both models are allowed to work simultaneously. However it is assumed that if the disintegration occurs due to the RT the KH break up does not occur. In case of drag sub-model, a dynamic drag model is introduced which accounts for the effects of drop distortion and oscillation due to the effects of high relative velocity between the liquid and the surrounding gas. In this model the drag coefficient is empirically related to the magnitude of the drop deformation. The magnitude of drop deformation was calculated by using the TAB model. In this work, the effects of mass and heat transfer on the spray are modelled. An additional equation for the energy of the liquid is solved. The mass transfer rate is evaluated using the model of Godsave (1953) and Spalding (1953) while the Faeth correlation (1983) is used to model heat transfer between the two phases. For all equations of heat and mass transfer between phases, the drop Nusselt and Sherwood number are calculated by using the correlation of Ranz and Marshall. In this model also the liquid surface-average temperature T_l2 which is calculated by Watkins (2007) is used to determine the heat and mass transfer between phases instead of liquid volume-average temperature. It was derived by assuming a parabolic temperature profile within individual drops. All the equations are treated in Eulerian framework using the finite volume method. The model has been applied to a wide range of sprays and compared to a number of experiments with different operating conditions including high liquid injection pressure and high ambient gas density and temperature. A reasonable agreement is found by the ETAB model with most of the data while the TAB and the DDB models continually underestimate the penetration and drop sizes of the spray. The hybrid breakup models perform well and show better agreement with the available experimental data than the single breakup models. In term of high temperature cases, the model correctly captures the effect of evaporation on the different spray properties especially with hybrid break up model.

Le but de cette thèse de doctorat état d’analyser la possibilité de la métallisation des couches des polymères à l’aide de la méthode de pulvérisation avec du gaz froid sous une basse pression. Deux substrats thermoplastiques et cinq poudres métalliques ont été étudiés. Les substrats étaient le polycarbonate amorphe et le polyamide 6 semicristalin. La poudre était : sphérique, globulaire, dendrique cuivre, aluminium et étain. Le processus de déposition s'est avéré beaucoup plus complexe que dans le cas du substrat de métal. Les problèmes étaient, entre autres : faible dureté du substrat, comportement fragile dans les basses températures, l'amollissement thermique dans des températures très basses. Le travail a commencé avec un calcul de la vitesse dans une basse pression du processus de pulvérisation a froid. La vitesse calculée pour toutes les poudres sauf l'étain étaient au-dessous de la vitesse critique pour les paramètres acceptables en ce qui concerne la déposition des polymères. Les premières épreuves ont confirmé que la déformation des particules de poudre n'était pas suffisante. Dans le cas de cuivre, il était impossible d'obtenir le revêtement. En plus, la force de liaison était très faible - les revêtements étaient delaminés spontanément. Deux mesures ont été entreprises pour améliorer les résultats : réduire la vitesse critique de la poudre et insérer des couches intermédiaires. Avec ces deux moyens, il a été possible d'obtenir les revêtements en cuivre et alluminium sur PA6 et PC. En s'appuyant sur l'étude, des conditions optimales pour la déposition de revêtement ont été choisies pour la caractérisation. La caractérisation des revêtements a inclu : l'analyse structurelle avec le microscope à la lumière et électronique à balayage, mesure d'adhésion, mesures du module d'Young, résistivité électrique, mesures de micro-dureté, mesures de coefficient de dilatation thermique, mesures de contenu d'oxygène et la simulation FEM pour étudier le mécanisme de déposition. / The aim of this Phd thesis was to analyze the possibility of metallization of polymers surface using a Low-Pressure Cold Gas spraying method. Two polymers substrate: polyamide 6 (Pa 6) and polycarbonate (PC) were investigated. The coatings were deposited using: tin, aluminium and copper powders. Within the framework of this work powders particles velocity and temperature was calculated during spraying process. The obtained particle velocity was compared to the critical velocity to select initial spraying conditions. Direct spraying on polymers substrate brought acceptable properties only for tin powder. Aluminium coatings delaminated spontaneously after spraying process. In case of copper powder deposition of continuous layer was impossible. Next, the influence of powder morphology, heat treatment of the feedstock material and the use of interlayers on the deposition process was investigated. Consequently, aluminium and copper coatings were obtained on both polymers. For a set of received coatings (Sn, Al, Cu) microstructure was observed and the results of adhesion, resistivity, micro-hardness, Young's modulus, and oxygen content in powders and coatings measurements were given. The bonding mechanism of the powder particles with substrate material was investigated using simulation of impact of copper and tin particle on polyamide substrate in Abaqus program. The simulation results were compared to experimental results. The dissertation was summed up with conclusion and possibilities of further research. / Celem niniejszej rozprawy doktorskiej była analiza możliwości metalizacji powierzchni tworzyw sztucznych za pomocą metody niskociśnieniowego natryskiwania zimnym gazem (z ang. Low-Pressure Cold Spraying – LPCS). Jako podłoże zastosowano dwa polimery: poliamid 6 (PA 6) i poliwęglan (PC). Powłoki zostały wykonane z użyciem proszków: cyny, aluminium i miedzi. W ramach pracy obliczono prędkość oraz temperatura cząstek proszku podczas procesu natryskiwania. Na podstawie porównania otrzymanych wyników prędkości cząstek proszku do prędkości krytycznej dobrano wstępne parametry procesu. W przypadku bezpośredniego natryskiwania na tworzywo jedynie powłoki cynowe charakteryzowały się akceptowalnym właściwościami. Powłoki aluminiowe miały tendencje do samoistnego odspajania. W przypadku prób nanoszenia proszku miedzi nie udało się uzyskać ciągłej warstwy. W dalszej kolejności zbadano wpływ morfologii i obróbki cieplnej proszku oraz zastosowania międzywarstw na proces formowania powłoki, co pozwoliło na uzyskanie powłok aluminiowych i miedzianych na powierzchni obydwu tworzyw sztucznych.Dla kompletu uzyskanych powłok (Sn, Al, Cu) przedstawiono zdjęcia mikrostruktury oraz wyniki pomiarów wyniki pomiarów przyczepności, rezystywności, mikrotwardości,modułu Younga, zawartości tlenu w proszku i powłoce. Mechanizm wiązania cząstek proszku z materiałem podłoża przeanalizowano za pomocą symulacji uderzenia cząstek miedzi i cyny w podłoże poliamidowe w programie Abaqus. Wyniki z symulacji zostały porównane do rezultatów eksperymentalnych. Całość pracy podsumowano wnioskami oraz przedstawiono możliwości dalszych badań.

The continuing tightening of emission regulations has encouraged extensive research into fuel spray vaporising and combustion. This thesis is an investigation into the effect that the cylinder boundaries have upon the quantity and composition of the unburnt hydrocarbons present in the exhaust gas and particulate matter. To determine the cylinder boundaries' effect on the exhaust hydrocarbon content a series of engine tests was completed. The engine used for these experiments was a modem four cylinder turbo charged direct injection diesel engine, operated at five steady state test points. The test consisted of two standard engine builds to determine the accuracy of measurement and to supply a base point for comparison. The second test used standard pistons with modified oil control rings to increase the oil film thickness. The final test used pistons with the top ring moved nearer the top of the piston by 5.5 mm to reduce the top land crevice volume by ?55%.The composition of the particulate soluble organic fraction (SOF) for the test using the low tangential load oil control piston ring was shown to have a greater fuel content than for other tests, showing that adsorption of the fuel in the lubricating oil contributes to the particulate. The reduction of the top ring crevice volume produced similar quantities of particulate SOF but it consisted of generally lighter hydrocarbon species. The effects of these changes were replicated in a mathematical model which calculated the in cylinder values for fuel, soot, temperature and hydrocarbons. The model also simulated the oxidation of hydrocarbons at the cylinder boundary and consisted of 3 primary zones; the combustion chamber, crevice volume and oil film. This research shows that careful design of engine components can influence the quantity and composition of the particulates exhaust gas and allow the reduction of regulated components.