Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2011. / Aromatic polyamides (PAs) are widely used as high-performance polymers in technical applications due to their unique combination of outstanding thermal, optical, mechanical and chemical properties. Although PAs are mostly utilized where strength or heat resistance is of primary concern, they also find use in other important applications such as in NOMEX membranes for desalination of brackish water or seawater. PAs do however have some disadvantages such as high melting points, high glass transition temperatures (Tg) and a limited solubility in most organic solvents, which makes their processing difficult. Polyureas (PUs) are generally known for their excellent thermal stability and high chemical resistance due to the presence of thermally stable bonds of aromatic or heterocyclic ring systems along their backbone. Both polymer systems are poorly researched when it comes to the introduction of furan units into the chains. The same is valid for cases where two or more different diacids or diamines are incorporated. The aim of this study was therefore to investigate the influence of furan units in the polymer chains and the change in properties if the composition of starting materials is varied further.

The experimental investigation in this work concerns the compression-ignition (CI) engine combustion process both in normal operation and dual-fuel operation. There is a bulk of literature reporting thermal efficiencies, brake specific fuel consumption (BSFC) and emissions under single and dual fueling conditions in CI engines. Most of the studies lack the full implications of changing load (power output) and speed on these performance indicators. The studies are either restricted to various loads/powers at one engine speed (neglecting the effect of engine speed) or one or two load/power conditions at various speeds (neglecting load variations). There is a scarcity of full engine maps in the open literature (these are the full contours of thermal efficiency or BSFC plotted throughout the power versus speed range of the engine, or the torque versus speed range of the engine). This thesis provides performance and emissions maps for a CI engine using two different fuels (diesel and rapeseed methyl ester used as single fuels) and two gaseous fuels (natural gas and hydrogen) used with two different pilot fuels (diesel and rapeseed methyl ester ) under what is termed dual fueling mode. A novel approach is used to present the performance and emissions over the entire engines operational range. The results are presented as iso- contours of thermal efficiency, volumetric efficiency and brake specific NOX, specific HC and specific CO2 on a power-speed graph throughout the operating range of the engine. Many studies conclude that the emissions, particularly NOX during dual fueling are expected to form in the spatial region around the pilot spray. This region is expected to be subjected to high localised temperatures as the equivalence ratio is close to stoichiometric, thus maximising heat release from combustion. The effect of changing the pilot fuel quantity on performance and emissions is rarely reported. This study addresses this scarcity in the literature and investigates the effect of changing the pilot fuel quantity and type on various combustion and emission parameters. Diesel and rapeseed methyl ester (RME) have been used as pilot fuels for both the natural gas as well as hydrogen and three different pilot fuel settings have been employed for each of the gaseous fuels. The effect of using a different pilot fuel quantity to achieve the same brake mean effective pressure (BMEP) for the two gaseous fuels has been analysed and compared. This thesis also includes a chapter on the computational modeling of the engine esmissions. This study uses combinations of different spray and combustion models to predict in-cylinder pressure, rate of heat release and emissions. The approach employs two combustion models: Unsteady Flamelet Model (UFM) with PDF method and Finite Rate Chemistry (FRC) with stiff chemistry solver implemented through In-Situ Adaptive Tabulation (ISAT) algorithm. Two spray models used includeWAVE and Kelvin Helmohltz Rayleigh Taylor (KHRT) spray models. The UFM coupled with KHRT spray model has been used to predict NOX, CO and CO2 emissions. The model captures the emissions trends well. In-cylinder contours of O2, NO and mass average temperature have also been presented. A chemical mechanism of n-heptane with 29 species and 52 reactions has been used.

Research, pilot scale and field developments of In-Situ Combustion (ISC) for enhanced oil recovery (EOR) in shallow, low pressure, heavy oil reservoirs intensified between the first and the second oil crisis from 1973 to 1981. A decline of interest in EOR followed the collapse of the oil prices in 1986. Renewed interest on in-situ combustion EOR research in the late 1980’s and beginning of the 1990’s was expanded and focused on high pressure medium and light oil reservoirs. The applicability of air injection in deep high pressure light petroleum reservoirs was established by research work of Greaves et al. in 1987 & 1988, Yannimaras et al. in 1991 and Ramey et a l in 1992. Accelerating rate calorimeter (ARC) tests were used to screen the applicability of various types of light oil reservoirs for in-situ combustion EOR by Yannimaras and Tiffin in 1994. The most successful light oil air injection project in the 1990s in the Medicine Pole Hills Unit, Williston Basin, N. Dakota started in 1987 and was reported by Kumar, Fassihi & Yannimaras, in 1994. Low temperature oxidation of light North Sea petroleum was studied at the University of Bath. A high-pressure combustion tube laboratory system was built at Bath University to evaluate performance of medium and light petroleum in-situ combustion processes. Gravity effects and the impact of horizontal wells in Forced Flow In-Situ Combustion Drainage Assisted by Gravity (FFISCDAG) were studied with three-dimensional combustion experiments. In this study, the university of Bath combustion tube experiments have been simulated and history matched. The tube experiments were up-scaled and field simulation studies were performed. A generic PVT characterization scheme based on 5 hydrocarbon pseudo-components was used, which was validated for light Australian and medium ‘Clair’ oil. A generic chemical reaction characterization scheme was used, which was validated for light Australian and medium ‘Clair’ oil. Advanced PVT and chemical reaction characterizations have been recommended for future work with more powerful hardware platforms. Extensive front track and flame extinction studies were performed to evaluate the performance of currently available non-iso-thermal simulators and to appraise their necessity in air injection processes. Comparative ISC field scale numerical simulation studies of Clair medium oil and light Australian petroleum were based on up-scaled combustion tube experimental results. These studies showed higher than expected hydrocarbon recovery in alternative EOR processes for both pre and post water flood implementation of ISC. Further in this study field scale numerical simulation studies revealed high incremental hydrocarbon recovery was possible by gravity assisted forced flow. The applicability of light oil ISC to gas condensate and sour petroleum reservoirs has been examined in this study with promising results. Light petroleum ISC implemented by a modified water flood including oxidants such as H2O2 and NH4NO3 are expected to widen the applicability of ISC processes in medium and light petroleum reservoirs, especially water flooded North Sea reservoirs.

L’objectif de la thèse est le développement d'une stratégie pour quantifier expérimentalement le bruit indirect et le séparer du bruit direct, puisque le bruit direct et indirect co-existent dans la plupart des applications. La configuration retenue pour l'étude est un banc expérimental avec une tuyère et la stratégie proposée a pour l’objectif de mesurer les fonctions de transfert de la tuyère. Le premier chapitre définit les fonctions de transfert de la tuyère utilisée dans l'étude comme référence pour la validation de la stratégie. Le deuxième chapitre présente une configuration originale qui génère simultanément le bruit direct et indirect sans introduire la combustion. Le troisième chapitre détaille les méthodes pour évaluer les ondes acoustiques et d'entropie à partir des mesures de température et de pression. Le quatrième chapitre termine la première partie de la thèse en décrivant la stratégie avant de la tester avec les signaux expérimentaux et numériques de haute fidélité. La deuxième partie se concentre sur l'utilisation de la stratégie dans les simulations à grandes échelles d'un brûleur à combustion turbulente. Les simulations sont validées par des données expérimentales tandis que les signaux sont traités à quantifier le bruit direct et indirect de combustion dans la chambre. / The objective of the thesis is the development of a practical strategy to quantify experimentally indirect noise and to discriminate it from direct noise as they co-exist in most practical conditions. The configuration retained for the study is a test bench with a nozzle and the proposed the strategy relies on nozzle transfer functions. The first chapter defines the nozzle transfer functions used in the study as references for the validation of the strategy. The second chapter introduces an original setup that generates simultaneously direct and indirect noise without handling combustion. The third chapter details the methods to evaluate the acoustic and entropy waves from raw temperature and pressure signals. The fourth chapter closes the first part of the study by describing the strategy then testing it on high-fidelity simulation and experimental signals. The second part focuses on the use of the strategy in Large Eddy Simulations of a turbulent combustion test bench. Simulations are validated by experimental data then raw signals are processed to quantify the direct and indirect noise sources as well as the direct and indirect noise contributions.

L’allumage constitue une phase critique dans de nombreuses applications de combustion et plus particulièrement dans celles qui sont liées à la propulsion aéronautique et spatiale. Un des défis actuels a été de développer des simulations aux grandes échelles de ce phénomène transitoire dans des configurations réalistes comme celles trouvées dans les moteurs aéronautiques. A cet égard, le travail pionnier de Boileau et al. (2008)a indiqué que des calculs complets de ce processus pouvaient être réalisés dans des géométries complètes de chambre de combustion annulaire et que ces calculs pouvaient fournir des informations de première main sur le processus d’allumage circulaire. Il était toutefois important devoir si la simulation pouvait reproduiredes données expérimentales bien contrôlées.Ceci est accompli dans le présent travail qui utilise un dispositif expérimental nouveau désigné sous le nom de MICCA.La thèse décrit l’ensemble des données recueillies au cours d’essais systématiques sur MICCA, la méthode de calcul aux grandes échelles et sa validation dans une configuration de brûleur simplifiée, les résultats de simulations aux grandes échelles du processus d’allumage circulaire, une analyse détaillée des résultats numériques et enfin une modélisation simplifiée du processus d’allumage fondée sur des équations de bilan macroscopiques. / Ignition constitutes a critical phase in many combustion applications and specifically those related to aerospace propulsion. One of the current challenges has been to develop large eddy simulations of this transient phenomenon in realistic configurations like those found in aeroengines.In this respect, the pioneering work of Boileau et a. (2008) indicated that complete calculations of this process in a full annular combustor geometry could be carried out and that they provided first hand information on the light-round process.It was however important to see if the simulation can match well controlled experimental data. This is accomplished in the present work which uses a novel experimental device named MICCA. The thesis describes the experimental set of data,the calculation methodology and its validation in a single burner configuration,results of large eddy simulation of the full light round process, a detailed analysis of the numerical results and an attempt to build a simplified model of the process based on macroscopic balance equations.

Le bruit de combustion est devenu un contributeur de plus en plus important dans le bruit total de moteur d'avion. Ce bruit global a deux composantes: Le bruit direct et le bruit indirect. Le premier est issu des fluctuations de dégagement de chaleur dans la flamme elle-même. Le deuxième a pour origine les inhomogénéités de température dans les gaz brûlés. L'objectif de ce travail est la conception d'un banc de combustion sous pression avec une flamme pauvre, prémélangée swirlée dont les paramètres d'injection permettront d'obtenir des grandes quantités de bruit indirect.Il est nécessaire de caractériser ce banc et d'établir quelle est la part du bruit direct et de l'indirect afin d'identifier les sources de ces contributions. Pour cette caractérisation il est nécessaire d'utiliser différents diagnostics, de prendre en compte la résolution temporelle. Ces diagnostics à haute cadence permettent de caractériser les champs de vitesse et les dynamiques de flamme, les instabilités de combustion dans le système et ainsi évaluer les contributions du bruit direct et indirect. / Combustion noise has become an increasing contributor of overall aircraft engine noise. It consists of two major parts, direct and indirect combustion noise. The former is generated by the heat release fluctuations of the flame itself. The latter is generated by the temperature inhomogeneities in the burnt gases, which are accelerated in the turbine stages or nozzle following the combustion chamber.The aim of this work is to design and build a pressurized lean swirling combustor test bench, in order to quantify the two contributions.The combustor is thus supposed to generate high quantities of indirect combustion noise. The second aim is then to determine the contributions of direct and indirect combustion noise quantitatively and to gain insight about the sources of the two contributions. These analyses are conducted by different high-speed diagnostics, which were worked on during this work. These diagnostics allow to characterize the flow fields and flame dynamics, to put forward the combustion instability in the system and finally to quantify the direct and indirect combustion noise contributions.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaf 93. / by Ronald Alan Dictor. / M.S.

Thesis. 1976. Mech.E.--Massachusetts Institute of Technology. Dept. of Mechanical Engineering. / Microfiche copy available in Archives and Engineering. / Includes bibliographical references. / by Marcos G. Ortiz Molina. / Mech.E.

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The mixture preparation process in a Direct Injection Spark Ignition (DISI) engine has a strong influence on the processes that follow it, including combustion and the formation of pollutant emissions. The formation of particulate matter during DISI engine combustion is a complex phenomenon that has proven difficult to predict. Vehicle tailpipe emissions are subject to increasingly stringent particulate matter emissions worldwide; in Europe, particulate number emission limits came into force in 2014 and these will become an order of magnitude stricter in 2017. The choice of injection strategy can play an important role in reducing the source of these emissions during combustion, which are chiefly caused by rich mixture combustion. This in turn occurs due to mixture inhomogeneity and combustion around liquid films and liquid droplets. This thesis outlines work undertaken to improve understanding of gasoline mixture preparation processes, simulation of droplet evaporation, flash boiling, spray evaporation and spray penetration, and experimental investigation of fuel sprays in an optical spray chamber and an optical engine. Assessments of the suitability of different sub-models for spray simulation were needed, in order to capture enough of the spray physics and fuel behaviour to aid correct prediction of spray evaporation, mixture homogeneity and fuel impingement by Computational Fluid Dynamics (CFD) packages. Phenomena have been explored on the individual droplet scale, including non-ideal behaviour of fuel mixtures, models for droplet heating/cooling during spray evaporation, the behaviour of superheated droplets under flash boiling conditions and multi-component fuel evaporation formulations. Detailed droplet evaporation routines have been created in MATLAB and single droplet studies performed under a range of conditions encountered in a DISI engine cylinder. From these results, recommendations have been made regarding the required complexity of droplet models for accurate predictions, at various fuel injection conditions. It was found necessary to model the non-ideal vapour-liquid equilibrium of ethanol-containing model gasoline fuels, for ethanol content of 10% by volume and above, and to include models for a non-uniform droplet temperature model across most fuels and in-cylinder conditions studied. In addition, the effect of finite liquid species mixing in the fuel droplet was deemed to be important to consider for non-ideal fuel mixtures. Sub-models for droplet evaporation, incorporating non-ideal fuel behaviour, have been created for an OpenFOAM Lagrangian Particle Tracking spray CFD solver. Results from these runs confirm that trends observed at a single droplet level are typically apparent at the spray scale. It was then possible to predict the effects that different evaporation modelling approaches had on spray penetration, which is important when assessing the extent of fuel spray impingement. Including a model for the non-uniform temperature distribution inside the droplet (finite thermal conductivity) was found not to influence the overall spray behaviour as much as expected, due to the competing effects of droplet break-up, droplet collisions and gas phase cooling. Numerical predictions have been compared with findings from spray imaging investigations in a purpose-built continuous flow, atmospheric pressure spray chamber, and with findings from optical engine experiments. In addition, adiabatic flash calculations have been performed to predict the degree of flash evaporation expected under flash boiling conditions, to help to interpret the results from flash boiling spray experiments. Various images from fuel spray experiments that represent different engine conditions have been taken and analysed for axial penetration, fuel impingement, structure and evaporation rate. These have helped to understand how a certain spray might lead to conditions where increased particulate emissions are likely. The fuels used during these tests were model gasoline fuels, containing 15% methanol by volume. This type of mixture represented fuel commercially available in some markets and was chosen to investigate the effects of a highly non-ideal and volatile fuel under both superheated and sub-cooled spray conditions. It was found that, as the degree of superheat was increased, the spray collapse tended to intensify, leading eventually to increased liquid penetration, a greater degree of spray impingement and a stratification of fuel towards the cylinder centre. Optical engine experiments have been performed using an early injection strategy for homogeneous operation, at 0.5 bar inlet plenum pressure, for various fuel temperatures and injection timings. Particulate number measurements were taken from the exhaust, and were found to be highest when the fuel was hottest and at typical early injection timings. Retarding or advancing the injection was found to reduce the particulate number count.