Characterization of semi-permeable films promotes the systematic selection of membranes and process design. When acquiring the diffusive and sorption properties of gas transport in non-porous membranes, the time lag method is considered the conventional method of characterization. The time lag method involves monitoring the transient accumulation of species due to permeation on a fixed volume present in a downstream reservoir. In the thesis at hand, an alternative approach to the time lag technique is proposed, termed as the short cut method. The short cut method appoints the use of a two reservoir system, where the species decay in the upstream face of the membrane is monitored, in combination with the accumulation on the downstream end. The early and short time determination of membrane properties is done by monitoring the inflow and outflow flux profiles, including their respective analytical formulas. The newly proposed method was revealed to have estimated the properties at 1/10 the required time it takes for the classical time lag method, which also includes a better abidance to the required boundary conditions. A novel design of the upstream reservoir, consisting of a reference and working volume, is revealed, which includes instructional use, and the mechanics involved with its operation. Transient pressure decay profiles are successfully obtained when the reference and working volumes consisted of only tubing. However when tanks were included in the volumes, large errors in the decay were observed, in particular due to a non-instantaneous equilibration of the pressure during the start up. This hypothesis was further re-enforced by examining different upstream tank-based configurations. iii In the end, a validated numerical model was constructed for the purpose of simulating the two reservoir gas permeation system. A modified form of the finite differences scheme is utilized, in order to account for a concentration-dependent diffusivity of penetrants within the membrane. Permeation behavior in a composite membrane system was disclosed, which provided a new perspective in analyzing the errors associated with the practical aspect of the system.

Following stringent mandates from environmental regulatory authorities worldwide, various steps are being implemented to ensure clean combustion with minimum emissions, including fuel dilution, mild combustion and additives. Due to the need to understand combustion characteristics in primary applications (engines and turbines) with minimum emissions, the laminar burning velocity of natural gas has been measured with CO2 dilution and a wide range of blends with higher hydrocarbons. And because it has improved anti-knock quality to reduce greenhouse gas emissions (GHGE), the demand for oxygenated gasoline is now worldwide, making a compelling case for determining combustion behavior of oxygenated gasoline doped with hydrogen, ozone and carbon monoxide. The first section of this dissertation discusses dilution of methane with CO2 at elevated pressures, providing insight into comparative laminar burning characteristics in a wide range of equivalence ratios, particularly significant at elevated initial pressure. Utilizing CHEMKIN, a detailed kinetic study has been performed that explains the varying dependence on dilution ratio controlled by initial pressure. The second phase of this work reports the laminar burning velocity measurement of commercial gasoline. A TPRFE surrogate was used here to investigate burning characteristics and to provide detailed kinetic analysis of gasoline doped with additives (hydrogen, carbon monoxide and ozone). A study was also made of the behavior of gasoline with these additives in practical applications like engine and turbines. For this purpose, laminar burning velocity was measured at elevated pressures and temperatures, by varying the concentrations of synthetic EGR, and followed by measuring turbulent burning velocity at two turbulent intensities.

Indiana University-Purdue University Indianapolis (IUPUI) / A chemically reactive turbulent traversing hot-jet issued from a pre-chamber to a relatively long combustion chamber is experimentally investigated. The long combustion chamber represents a single channel of a wave rotor constant-volume combustor. The issued jet ignites the fuel-air mixture in the combustion chamber. Fuel-air mixtures are prepared with different hydrocarbon fuels of different reactivity, namely, methane, propane, methane-hydrogen blend, methane-propane blend and methane-argon blend. The jet acts as a rapid, distributed and moving source of ignition, traversing across one end of the long combustion chamber entrance, induces complex flow structures such as a train of counter rotating vortices that enhance turbulent mixing. In general, a stationary hot-jet ignition process lack these structures due to absence of the traversing motion. The ignition delay of the fuels and fuel blends are measured in order to obtain insights about constant-volume pressure-gain combustion process initiated by a moving source of ignition and also to glean useful data about design and operation of a wave rotor combustor. Reactive hot-jets are useful to ignite fuel-air mixtures in internal combustion engines and novel wave rotor combustors. A reactive hot-jet or puff of gas issued from a suitably designed pre-chamber can act as rapid, distributed and less polluting ignition source in internal combustion engines. Each cylinder of the engine is provided with its own pre-chamber. A wave rotor combustor has an array of circumferentially arranged channels on a rotating drum. Each channel acts as a constant-volume combustor and produces high pressure combustion products. Implementation of hot-jet igniter in a wave rotor combustor offers utilization of available high temperature and high pressure reactive combustion products residing in each of the wave rotor channels as a distributed source of ignition for other channels, thus requiring no special pre-chamber in ultimate implementation. Such reactive products or partially combusted and radical-laden gases can be issued from one or more channels to ignite the fuel-air mixture residing in another channel. Due to the rotation of the rotor channels, the issued hot-jet would have relative motion with respect to one end of the channels and traverse across it. This thesis aims to investigate the effects of jet traverse time experimentally on ignition delay along with other important factors that affect the hot-jet ignition process such as fuel reactivity, fuel-air mixture preparation quality and stratification and equivalence ratio. In this study, the traversing motion of the hot-jet at one end of the main combustion chamber is implemented by keeping the main combustion chamber stationary and rotating a pre-chamber at speeds of 400 RPM, 800 RPM and 1200 RPM. The rotational speeds correspond to jet traverse times of 16.9 ms, 8.4 ms and 5.6 ms respectively. The fuel-air mixture inside the channel is at room temperature and pressure initially and its equivalence ratio is varied from 0.4 to 1.3. The cylindrical pre-chamber is initially filled with a 50%-50% methane-hydrogen blend fuel and air mixture at room pressure and temperature and at an equivalence ratio of 1.1. These conditions were chosen based on prior evidence of ignition rapidity with the jet properties. The hot-jet is issued by rupturing a thin diaphragm isolating the chambers. Using high frequency dynamic pressure transducer pressure histories, the diaphragm rupture moment and onset of ignition is measured. Pressure traces from two transducers are employed to measure the initial rupture shock speed and ignition delay. Schlieren images recorded by a high speed camera are used to identify ignition moment and validate the measured ignition delay times. Ignition delay is defined as time interval from the rupture moment to onset of ignition of fuel-air mixture in the main combustion chamber. The ignition system is designed to produce diaphragm rupture at almost exactly the moment when jet traverse begins. Ignition delay times are measured for methane, propane, methane-hydrogen blends, methane-propane blend and methane-argon blend. The equivalence ratio of the fuel-air mixtures varied from 0.4 to 1.3 in steps of 0.1 for stationary-hot jet ignition experiments and in steps of 0.3 for traversing hot-jet ignition experiments. Hot-jet ignition delay of fuel-air mixtures, for both stationary hot-jet ignition process and traversing hot-jet ignition process, generally increased with increasing equivalence ratio. For stationary hot-jet ignition delay, the minimum ignition delay occurs between Ф = 0.4 to Ф = 0.6 for the tested fuel-air mixtures. Both stationary and traversing hot-jet ignition delay depended on fuel reactivity. In particular, the shortest ignition delay times were observed for a fuel blend containing hydrogen. Among pure fuels propane exhibited slightly shorter ignition delay times, on average, compared to pure methane fuel. The addition of argon to pure methane, intended to control fuel density and buoyancy, increased the ignition delay. The traversing hot-jet ignition delay generally increased with increasing jet traverse times. To explain the variations in the measured hot-jet ignition delay and investigate qualitatively the effect of buoyancy on flame propagation and mixture stratification, the fuel-air mixture inside the main combustion chamber was ignited using a spark plug to generate a propagating laminar flame. The laminar flame propagated within the flammable regions of the channel in ways that sensitively reveal variations in local fuel-air mixture equivalence ratio. Flame luminosity images from a high speed camera and schlieren images revealed the fuel-air mixture being highly stratified depending on the density difference between the fuel and air and provided mixing time (0 s, 10s ,30s for most fuels). The lack of buoyancy-driven spreading caused the fuel to remain in the vicinity of the fuel injector resulting in significant longitudinal stratification of the fuel-air mixture. Lighter fuels stratified to the top of the chambers and heavier fuel stratified to the bottom of the chamber. Increasing the mixing time, which is defined as the time interval from end of fuel injection into the chamber to the triggering of the spark plug, improved the buoyancy-driven spreading and extended the flammable region as evidenced by the schlieren and flame luminosity images. The maximum pressure developed in the combustor for the three ignition processes, namely, stationary hot-jet ignition, traversing hot-jet ignition and spark ignition process in laminar flame propagation experiments were compared. Stationary hot-jet ignition process generally exhibited the highest pressure being developed in the chamber. Variations in heat loss, fuel-air mixture leakage and mass addition mechanisms reduced the maximum pressure for spark ignition and traversing hot-jet ignition process.

La pollution atmosphérique est une problématique urbaine majeure, avec des concentrations de polluants dépassant fréquemment les seuils de recommandations pour la santé. Les véhicules participent fortement à la pollution atmosphérique malgré l’intégration de systèmes de dépollution dans leur ligne d’échappement. L’objectif de ce travail de recherche était de caractériser les émissions primaires à l’échappement des véhicules ainsi que leur évolution physique en champ proche pour mieux comprendre la contribution des émissions primaires liées au trafic à la pollution atmosphérique urbaine. L’évolution des émissions a été étudiée dans une chambre de simulation atmosphérique qui a permis de simuler des conditions atmosphériques contrôlées.La première partie de ce travail était centrée sur les mesures d’émissions à l’échappement des véhicules récents qui sont ou seront majoritaires dans le parc automobile français dans les prochaines années. Pour cela, un échantillon de véhicules regroupant les principales technologies de dépollution commercialisées a été testé. Les gaz d’échappement émis par les véhicules ont été analysés lors de tests sur un banc à rouleau suivant différentes conditions de conduites. Les polluants soumis aux réglementations Européennes ont été mesurés, ainsi que certains composés non-réglementés par les normes Européennes mais dont la dangerosité a été mise en évidence par la communauté scientifique.La deuxième partie de ce travail se concentre sur l’évolution en champ proche des polluants particulaires dans les heures qui suivent leur rejet dans l’atmosphère. L’effet de la dilution soudaine des gaz en sortie de pot d’échappement a été étudié en utilisant une méthodologie innovante de prélèvement directement à l’échappement. Ensuite l’évolution des particules dans les premières heures après leur rejet a été étudiée dans une chambre de simulation atmosphérique de 8 m3, construite spécifiquement dans le cadre de cette thèse pour être couplé au banc à rouleau. / Air pollution is a major urban issue, with pollutant concentrations frequently exceeding health recommendations. Vehicles are highly involved in air pollution despite the integration of pollution control systems. The objective of this research is to characterise the primary exhaust emissions of vehicles and their physical evolution in the near field to better understand the impact of primary emissions related to traffic on urban air pollution. Emissions evolution was studied in an atmospheric simulation chamber with controlled atmospheric conditions. The first part of this work aims to determine the exhaust emissions of recent vehicles that are or will be major in the French car fleet in the coming years. A sample of vehicles grouping the main commercialised depollution technologies was tested on a chassis dynamometer according to different driving conditions and the emissions from their exhaust gas were analysed. The pollutants subject to European regulations were taken into account, as well as compounds not regulated by European standards but whose toxicity has been highlighted by the scientific community.The second part of this work focuses on the near-field evolution of particulate pollutants in the hours following their release into the atmosphere. The effect of the abrupt gas dilution at the end of the exhaust has been studied using an innovative sampling methodology directly at the exhaust of the vehicles. Then the evolution of the particles in the first hours after their rejection was studied in an atmospheric simulation chamber of 8 m3, built specifically within the framework of this thesis to be coupled with the dynamometer.

Indiana University-Purdue University Indianapolis (IUPUI) / Investigations of a constant-volume combustor ignited by a penetrating transient jet (a puff) of hot reactive gas have been conducted in order to provide vital data for designing wave rotor combustors. In a wave rotor combustor, a cylindrical drum with an array of channels arranged around the axis spins at a high rpm to generate high-temperature and high-pressure product gas. The hot-gas jet ignition method has been employed to initiate combustion in the channels. This study aims at experimentally investigating the ignition delay time of a premixed combustible mixture in a rectangular, constant-volume chamber, representing one channel of the wave rotor drum. The ignition process may be influenced by the multiple factors: the equivalence ratio, temperature, and the composition of the fuel mixture, the temperature and composition of the jet gas, and the peak mass flow rate of the jet (which depends on diaphragm rupture pressure). In this study, the main mixture is at room temperature. The jet composition and temperature are determined by its source in a pre-chamber with a hydrogen-methane mixture with an equivalent ratio of 1.1, and a fuel mixture ratio of 50:50 (CH4:H2 by volume). The rupture pressure of a diaphragm in the pre-chamber, which is related to the mass flow rate and temperature of the hot jet, can be controlled by varying the number of indentations in the diaphragm. The main chamber composition is varied, with the use of four equivalence ratios (1.0, 0.8, 0.6, and 0.4) and two fuel mixture ratios (50:50, and 30:70 of CH4:H2 by volume). The sudden start of the jet upon rupture of the diaphragm causes a shock wave that precedes the jet and travels along the channel and back after reflection. The shock strength has an important role in fast ignition since the pressure and the temperature are increased after the shock. The reflected shock pressure was examined in order to check the variation of the shock strength. However, it is revealed that the shock strength becomes attenuated compared with the theoretical pressure of the reflected shock. The gap between theoretical and measured pressures increases with the increase of the Mach number of the initial shock. Ignition delay times are obtained using pressure records from two dynamic pressure transducers installed on the main chamber, as well as high-speed videography using flame incandescence and Schileren imaging. The ignition delay time is defined in this research as the time interval from the diaphragm rupture moment to the ignition moment of the air/fuel mixture in the main chamber. Previous researchers used the averaged ignition delay time because the diaphragm rupture moment is elusive considering the structure of the chamber. In this research, the diaphragm rupture moment is estimated based on the initial shock speed and the longitudinal length of the main chamber, and validated with the high-speed video images such that the error between the estimation time and the measured time is within 0.5%. Ignition delay times decrease with an increase in the amount of hydrogen in the fuel mixture, the amount of mass of the hot-jet gases from the pre-chamber, and with a decrease in the equivalence ratio. A Schlieren system has been established to visualize the characteristics of the shock wave, and the flame front. Schlieren photography shows the density gradient of a subject with sharp contrast, including steep density gradients, such as the flame edge and the shock wave. The flame propagation, gas oscillation, and the shock wave speed are measured using the Schlieren system. An image processing code using MATLAB has been developed for measuring the flame front movement from Schlieren images. The trend of the maximum pressure in the main chamber with respect to the equivalence ratio and the fuel mixture ratio describes that the equivalence ratio 0.8 shows the highest maximum pressure, and the fuel ratio 50:50 condition reveals lower maximum pressure in the main chamber than the 30:70 condition. After the combustion occurs, the frequency of the pressure oscillation by the traversing pressure wave increases compared to the frequency before ignition, showing a similar trend with the maximum pressure in the chamber. The frequency is the fastest at the equivalence ratio of 0.8, and the slowest at a ratio of 0.4. The fuel ratio 30:70 cases show slightly faster frequencies than 50:50 cases. Two different combustion behaviors, fast and slow combustion, are observed, and respective characteristics are discussed. The frequency of the flame front oscillation well matches with that of the pressure oscillation, and it seems that the pressure waves drive the flame fronts considering the pressure oscillation frequency is somewhat faster. Lastly, a feedback mechanism between the shock and the flame is suggested to explain the fast combustion in a constant volume chamber with the shock-flame interactions.

Indiana University-Purdue University Indianapolis (IUPUI) / This study contributes to a better working knowledge of the equipment being used in a well-established combustion lab. In particular, several constant-volume combustion properties (e.g., time ignition delay, flame propagation, and more) are examined to deduce any buoyancy effects between fuel and air mixtures and to develop a method aimed at minimizing such effects. This study was conducted on an apparatus designed to model the phenomena occurring within a single channel of a wave rotor combustor, which consists of a rotating cylindrical pre-chamber and a fixed rectangular main combustion chamber. Pressure sensors monitor the internal pressures within the both chambers at all times, and two slow-motion videography techniques visually capture combustion phenomena occurring within the main chamber. A new recirculation pump system has been implemented to mitigate stratification within the chamber and produce more precise, reliable results. The apparatus was used in several types of experiments that involved the combustion of various hydrocarbon fuels in the main chamber, including methane, 50%-50% methane-hydrogen, hydrogen, propane, and 46.4%-56.3% methane-argon. Additionally, combustion products created in the pre-chamber from a 1.1 equivalence ratio reaction between 50%-50% methane-hydrogen and air were utilized in the issuing pre-chamber jet for all hot jet ignition tests. In the first set of experiments, a spark plug ignition source was used to study how combustion events travel through the main chamber after different mixing methods were utilized – specifically no mixing, diffusive mixing, and pump circulation mixing. The study reaffirmed that stratification between fuel-air mixtures occurs in the main chamber through the presence of asymmetrical flame front propagation. Allowing time for mixing, however, resulted in more symmetric flame fronts, broader pressure peaks, and reduced combustion time in the channel. While 30 seconds of diffusion helped, it was found that 30 seconds of pumping (at a rate of 30 pumps per 10 seconds) was the most effective method at reducing stratification effects in the system. Next, stationary hot jet ignition experiments were conducted to compare the time between jet injection and main chamber combustion and the speed of the resulting shockwaves between cases with no mixing and 30 seconds of pump mixing. Results continued to show an improvement with the pump cases; ignition delay times were typically shorter, and shock speeds stayed around the same, if not increased slightly. These properties are vital when studying and developing wave rotor combustors, and therefore, reducing stratification (specifically by means of a recirculation system) should be considered a crucial step in laboratory models such as this one. Lastly, experiments between a fueled main chamber and rotating pre-chamber helped evaluate the leakage rate of the traversing hot jet ignition experimental setup paired with the new pump system. In its current form, major leaks are inevitable when attempting traversing jet experiments, especially with the pump’s suction action drawing sudden large plumes of outside air into the main chamber. To minimize leaks, gaps between the pre-chamber and main chamber should be reduced, and the contact surface between the two chambers should be more evenly distributed. Also, the pump system should only be operated as long as needed to evenly distribute the fuel-air mixture, which approximately happens when the main chamber’s total volume has been circulated through the system one time. Therefore, a new pump system with half of the original system’s volume was developed in order to decrease the pumping time and lower the risk of leaks.

Expansive or swelling soils, exist in many part of the world, show excessive volume changes with increasing water content. As a result of this volume increase, expansive soils apply vertical and lateral pressures to the structures located or buried in these regions. Many researchs have been carried out on vertical swelling pressures helping to the engineers to design structures withstanding on these stresses. However, lateral swell behaviour of swelling soils have not been fully understood yet. Structures such as / basement walls, water tanks, canals, tunnels, underground conduits and swimming pools which will be built in expansive soils have to be designed to overcome the lateral swelling pressures as well as the other lateral pressures exerted by the soil. For this aim accurate and reliable methods are needed to predict the magnitude of lateral swelling pressures of expansive soils and to understand the lateral swelling behaviour of expansive soils. In this experimental study, the lateral swelling behaviour of an highly expansive clay is investigated using a modified thin wall oedometer which was developed in the METU Civil Engineering Department Soil Mechanics Laboratory earlier. Statically compacted samples were used in constant volume swell (CVS) tests to measure the magnitude of the lateral and vertical swelling pressures. To study the relationship between the lateral and vertical sweeling pressures, they were measured simultaneously. The samples having different initial water contents and different initial dry densities were used to study the effects of these variables on the vertical and the lateral swelling pressures. It is observed that both lateral and vertical pressures increases with increasing initial dry density and they decrease with increasing initial water content. Swell pressure ratio, the ratio of lateral swelling pressure to the vertical one, is increasing with increasing initial water content. Time needed to obtain the magnitude of maximum lateral and vertical pressures decreases with increasing initial water content and increases with increasing initial dry density.

When studying pressure-gain combustion and wave rotor combustors, it is vital that any experimental model accurately reflect the real world conditions/applications being studied; this not only confirms previous computational and analytical work, but also provides new insights into how these concepts and devices work in real life. However, mixture stratification can have a noticeable effect on multiple combustion properties, including flame propagation, pressure, ignition time delay, and more, and this is especially true in constant-volume combustion chambers. Because it is beneficial to model wave rotor systems using constant-volume combustors such as what is employed in the IUPUI Combustion and Propulsion Research Laboratory, these stratification effects much be taken into account and reduced if possible. This study sought to find an effective method to reduce stratification in a rectangular constant-volume combustion chamber by means of manual recirculation pump. Spark-ignited flames were first produced in the chamber itself and studied using schlieren and color videography techniques as well as quantitative pressure histories. After determining the pump's effectiveness in reducing stratification, it was next employed when a hot jet of combustion products from a separate combustion chamber was used as an ignition source instead of the spark plug - a process typically employed in real wave rotor combustors. Lastly, the pump was used to study the leakage from the system for future test cases in order to offer further recommendations on how to effectively use the recirculation system. This process found that key properties significant to wave rotor development, such as time ignition delay, were affected by these stratification effects in past studies that did not account for this detail. As such, the pump has been permanently incorporated into the wave rotor model, as stratification is a vital. Additionally, significant fuel leakage is possible during rotational pre-chamber cases, and this should be address before proceeding with such experiments in the future. To combat this, the pump system has been reduced in volume, and suggestions have been provided on how to better seal the main rectangular chamber in the future.

No description available.

La propagation de flammes turbulentes dans des milieux réactifs inhomogènes concerne un grand nombre d’applications pratiques, y compris celles qui reposent sur des cycles de combustion à volume constant. Les hétérogénéités de composition (richesse, température,dilution par des gaz brûlés, etc.) sont issues de plusieurs facteurs distincts tels que la dispersion du spray de gouttelettes de combustible et son évaporation, la topologie de l’écoulement ainsi que la présence éventuelle de gaz brûlés résiduels issus du cycle précédent. La structure des flammes partiellement prémélangées qui en résultent est significativement plus complexe que celles des flammes plus classiques de diffusion ou de prémélange. L’objectif de ce travail de thèse est donc de contribuer à l’amélioration de leur connaissance, en s’appuyant sur la génération et l’analyse de base de données de simulations numériques directes ou DNS (Direct Numerical Simulation). Celles-ci sont conduites avec le code de calcul Asphodele qui est basé sur l’approximation de faible nombre de Mach. Le combustible de référence retenu est l’iso-octane.La base de données est structurée suivant cinq paramètres qui permettent de caractériser l’écoulement turbulent ainsi que l’hétérogénéité de composition du milieu réactif. Dans un premier temps, des configurations bidimensionnelles ont été considérées en raison du coût élevé induit par la description détaillée de la cinétique chimique. L’étude des ces différents cas de calcul a permis de mettre en lumière plusieurs mécanismes fondamentaux de propagation dans les milieux hétérogènes en composition. Une réduction significative des coûts de calcula pu ensuite être obtenue grâce au développement d’un modèle chimique simplifié optimisé.Son utilisation a permis d’étendre les analyses à de / The propagation of turbulent flames in non-homogeneous reactive mixtures of reactants concerns a large number of practical applications, including those based on constant volume combustion cycles. The composition heterogeneities (equivalence ratio, temperature, dilution by burnt gases, etc.) result from several distinct factors such as the dispersion of the spray of fuel droplets and its evaporation, the flow field topology as well as the possible presence of residual burnt gases issued from the previous cycle. The resulting partially premixed flames structure is significantly more complex than the one of more conventional diffusion or premixed flames.The aim of this thesis work is therefore to contribute to the improvement of their understanding, by proceeding to the generation and analysis of a new set of direct numerical simulations (DNS) databases. The present computations are performed with the low-Mach number DNS solver Asphodele. The database is structured according to five parameters that characterize the turbulent flow as well as the composition heterogeneity of the reactive mixture. First, because of the high numerical costs induced by the detailed description of chemical kinetics, two-dimensional configurations were considered. The study of these various simulations highlights several fundamental mechanisms of flame propagation in heterogeneous mixtures. Then, a significant computational cost saving has been achieved through the development of an optimized simplified chemistry model. The use of the latter allowed to overcome the major bottleneck of high CPU costs related to chemical kinetics description and thus to extend the analysis to three-dimensional configurations. Some of the conclusions obtained previously were reinforced.