Combustion has been used for a long time as a means of energy extraction. However, in the recent years there has been further increase in air pollution, through pollutants such as nitrogen oxides, acid rain etc. To solve this problem, there is a need to reduce carbon and nitrogen oxides through lean burning, fuel dilution and usage of bi-product fuel gases. A numerical analysis has been carried out to investigate the effectiveness of several reduced mechanisms, in terms of computational time and accuracy. The cases were tested for the combustion of hydrocarbons diluted with hydrogen, syngas, and bi-product fuel in a cylindrical combustor. The simulations were carried out using the ANSYS Fluent 19.1. By solving the conservations equations, several global reduced mechanisms (2-5-10 steps) were obtained. The reduced mechanisms were used in the simulations for a 2D cylindrical tube with dimensions of 40 cm in length and 2.0 cm diameter. The mesh of the model included a proper fine quad mesh, within the first 7 cm of the tube and around the walls. By developing a proper boundary layer, several simulations were performed on hydrocarbon/air and syngas blends to visualize the flame characteristics. To validate the results “PREMIX and CHEMKIN” codes were used to calculate 1D premixed flame based on the temperature, composition of burned and unburned gas mixtures. Numerical calculations were carried for several hydrocarbons by changing the equivalence ratios (lean to rich) and adding small amounts of hydrogen into the fuel blends. The changes in temperature, radical formation, burning velocities and the reduction in NOx and CO2 emissions were observed. The results compared to experimental data to study the changes. Once the results were within acceptable range, different fuels compositions were used for the premixed combustion through adding H2/CO/CO2 by volume and changing the equivalence ratios and preheat temperatures, in the fuel blends. The results on flame temperature, shape, burning velocity and concentrations of radicals and emissions were observed. The flame speed was calculated by finding the surface area of the flame, through the mass fractions of fuel components and products conversions that were simulated through the tube. The area method was applied to determine the flame speed. It was determined that the reduced mechanisms provided results within an acceptable range. The variation of the inlet velocity had neglectable effects on the burning velocity. The highest temperatures were obtained in lean conditions (0.5-0.9) equivalence ratio and highest flame speed was obtained for Blast Furnace Gas (BFG) at elevated preheat temperature and methane-hydrogen fuels blends in the combustor. The results included; reduction in CO2 and NOx emissions, expansion of the flammable limit, under the condition of having the same laminar flow. The usage of diluted natural gases, syngas and bi-product gases provides a step in solving environmental problems and providing efficient energy.

Acoustic radiation efficiency is defined as the ratio of sound power radiated to the surface vibration power of a piston with equivalent surface area. It has been shown that the radiation efficiency is maximized and may exceed unity when the structural and acoustic wavelengths are approximately equal. The frequency at which this occurs is called the critical frequency and can be shifted with structural modifications. This has proven to be an effective way to reduce noise. The standard radiation efficiency measurement is comprised of an intensity scan for sound power measurement and accelerometer array for spatially averaged vibration determination. This method is difficult to apply to lightweight structures, complicated geometries, and when acoustic sources are in close proximity to one another. Recently, robust particle velocity sensors have been developed. Combined with a small microphone in the same instrument, particle velocity and sound pressure can be measured simultaneously and at the same location. This permits radiation efficiency to be measured using a non-contact approach with a single sensor. A suggested practice for measuring radiation efficiency has been developed and validated with several examples including two flat plates of different thickness, an oil pan, and components on a running small engine.

Space vehicles, while entering the planetary atmosphere, experience high loads of heat. Ablative materials are commonly used for a thermal protection system, which undergo mass removal mechanisms to counter the heat rates. Spallation is one of the ablative processes, which is characterized by the ejection of solid particles from the material into the flow. Numerical codes that are used in designing the heat shields ignore this phenomenon. Hence, to evaluate the effectiveness of spallation phenomenon, a numerical model is developed to compute the dynamics and chemistry of the particles. The code is one-way coupled to a CFD code that models high enthalpy flow field around a lightweight ablative material. A parametric study is carried out to examine the variations in trajectories with respect to ejection parameters. Numerical results are presented for argon and air flow fields, and their effect on the particle behavior is studied. The spallation code is loosely coupled with the CFD code to evaluate the impact of a particle on the flow field, and a numerical study is conducted.

The effective radiative conductivity of fibrous material is an important part of the evaluation of the thermal performance of fibrous insulators. To better evaluate this material property, a three-dimensional direct simulation model which calculates the effective radiative conductivity of fibrous material is proposed. Two different geometries are used in this analysis. The simplified model assumes that the fibers are in a cylindrical shape and does not require identically-sized fibers or a symmetric configuration. Using a geometry with properties resembling those of a fibrous insulator, a numerical calculation of the geometric configuration factor is carried out. The results show the dependency of thermal conductivity on temperature as well as the orientation of the fibers. The calculated conductivity values are also used in the continuum heat equation, and the results are compared to the ones obtained using the direct simulation approach, showing a good agreement. In continue, the simulated model is replaced by a realistic geometry obtained from X-ray micro-tomography. To study the radiative heat transfer mechanism of fibrous carbon, three-dimensional direct simulation modeling is performed. A polygonal mesh computed from tomography is used to study the effect of pore geometry on the overall radiative heat transfer performance of fibrous insulators. An robust procedure is presented for numerical calculation of the geometric configuration factor to study energy-exchange processes among small surface areas of the polygonal mesh. The methodology presented here can be applied to obtain accurate values of the effective conductivity, thereby increasing the fidelity in heat transfer analysis.

Change in papillary muscle motion as a result of left ventricular (LV) remodeling after posterolateral myocardial infarction is thought to contribute to ischemic mitral regurgitation. A finite element (FE) model of the LV was created from magnetic resonance images acquired immediately before myocardial infarction and 8 weeks later in a cohort of 12 sheep. Severity of mitral regurgitation was rated by two-dimensional echocardiography and regurgitant volume was estimated using MRI. Of the cohort, 6 animals (DC) received hydrogel injection therapy shown to limit ventricular remodeling after myocardial infarction while the control group (MI) received a similar pattern of saline injections. LV pressure was determined by direct invasive measurement and volume was estimated from MRI. FE models of the LV for each animal included both healthy and infarct tissue regions as well as a simulated hydrogel injection pattern for the DC group. Constitutive model material parameters for each region in the FE model were assigned based on results from previous research. Invasive LV pressure measurements at end diastole and end systole were used as boundary conditions to drive model simulations for each animal. Passive stiffness (C) and active material parameter (Tmax) were adjusted to match MRI estimations of LV volume at end systole and end diastole. Nodal positions of the chordae tendineae (CT) were determined by measurements obtained from the excised heart of each animal at the terminal timepoint. Changes in CT nodal displacements between end systole and end diastole at 0 and 8-week timepoints were used to investigate the potential contribution of changes in papillary muscle motion to the progression of ischemic mitral regurgitation after myocardial infarction. Nodal displacements were broken down into radial, circumferential, and longitudinal components relative to the anatomy of the individual animal model. Model results highlighted an outward radial movement in the infarct region after 8 weeks in untreated animals, while radial direction of motion observed in the treated animal group was preserved relative to baseline. Circumferential displacement decreased in the remote region in the untreated animal group after 8 weeks but was preserved relative to baseline in the treated animal group. MRI estimates of regurgitant volume increased significantly in the untreated animal group after 8 weeks but did not increase in the treated group. The results of this analysis suggest that hydrogel injection treatment may serve to limit changes in papillary muscle motion and severity of mitral regurgitation after posterolateral myocardial infarction.

An instrumented unmanned aerial vehicle (UAV) was developed and employed to observe the full range of turbulent motions that exist within the inertial subrange of atmospheric surface layer turbulence. The UAV was host to a suite of pressure, temperature, humidity, and wind sensors which provide the necessary data to calculate the variety of turbulent statistics that characterize the flow. Flight experiments were performed with this aircraft, consisting of a large square pattern at an altitude of 100 m above ground level. In order to capture the largest turbulent scales it was necessary to maximize the size of the square pattern. The smallest turbulent scales, on the other hand, were measured through the use of a fast response constant temperature hot wire anemometer. The results demonstrates that the UAV system is capable of directly measuring the full inertial subrange of the atmospheric surface layer with high resolution and allowing for the turbulence dissipation rate to be calculated directly.

Carbon Fiber Reinforced Polymers (CFRP) are a class of advanced materials widely used in versatile applications including aerospace and automotive industries due to their exceptional physical and mechanical properties. Owing to the heterogenous nature of the composites, it is often a challenging task to machine them unlike metals. Drilling in particular, the most commonly used process for component assembly is critical especially in the aerospace sector which demands parts of highest quality and surface integrity. Conventionally, all composites are machined under dry conditions. While there are drawbacks related to dry drilling, for example, poor surface roughness, there is a need to develop processes which yield good quality parts. This thesis investigates the machining performance when drilling CFRP under cryogenic, MQL and hybrid (CryoMQL) modes and comparing with dry drilling in terms of the machining forces, delamination, diameter error and surface integrity assessment including surface roughness, hardness and sub-surface damage analysis. Additionally, the effect of varying the feed rate on the machining performance is examined. From the study, it is concluded that drilling using coolant/ lubricant outperforms dry drilling by producing better quality parts. Also, varying the feed rate proved to be advantageous over drilling at constant feed.

NiTiHf shape memory alloys have been receiving considerable attention for high temperature and high strength applications since they could have transformation temperatures above 100 °C, shape memory effect under high stress (above 500 MPa) and superelasticity at high temperatures. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf alloys have some drawbacks such as low ductility and high work hardening in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. Shape memory properties and microstructure of four Ni-rich NiTiHf alloys (Ni50.3Ti29.7Hf20, Ni50.7Ti29.3Hf20, Ni51.2Ti28.8Hf20, and Ni52Ti28Hf20 (at. %)) were systematically characterized in the furnace cooled condition. H-phase precipitates were formed during furnace cooling in compositions with greater than 50.3Ni and the driving force for nucleation increased with Ni content. Alloy strength increased while recoverable strain decreased with increasing Ni content due to changes in precipitate characteristics. The effects of the heat treatments on the transformation characteristics and microstructure of the Ni-rich NiTiHf shape memory alloys have been investigated. Transformation temperatures are found to be highly annealing temperature dependent. Generation of nanosize precipitates (~20 nm in size) after three hours aging at 450 °C and 550 °C improved the strength of the material, resulting in a near perfect dimensional stability under high stress levels (> 1500 MPa) with a work output of 20–30 J cm– 3. Superelastic behavior with 4% recoverable strain was demonstrated at low and high temperatures where stress could reach to a maximum value of more than 2 GPa after three hours aging at 450 and 550 °C for alloys with Ni great than 50.3 at. %. Shape memory properties of polycrystalline Ni50.3Ti29.7Hf20 alloys were studied via thermal cycling under stress and isothermal stress cycling experiments in tension. Recoverable strain of ~5% was observed for the as-extruded samples while it was decreased to ~4% after aging due to the formation of precipitates. The aged alloys demonstrated near perfect shape memory effect under high tensile stress level of 700 MPa and perfect superelasticity at high temperatures up to 230 °C. Finally, the tensioncompression asymmetry observed in NiTiHf where recoverable tensile strain was higher than compressive strain. The shape memory properties of solutionized and aged Ni-rich Ni50.3Ti29.7Hf20 single crystals were investigated along the [001], [011], and [111] orientations in compression. [001]-oriented single crystals showed high dimensional stability under stress levels as high as 1500 MPa in both the solutionized and aged conditions, but with transformation strains of less than 2%. Perfect superelasticity with recoverable strain of more than 4% was observed for solutionized and 550 °C-3h aged single crystals along the [011] and [111] orientations, and general superelastic behavior was observed over a wide temperature range. The calculated transformation strains were higher than the experimentally observed strains since the calculated strains could not capture the formation of martensite plates with (001) compound twins.

Magnetic Shape Memory Alloys (MSMAs) have the unique ability to change their shape within a magnetic field, or in the presence of stress and a change in temperature. MSMAs have been widely investigated in the past decade due to their ability to demonstrate large magnetic field induced strain and higher frequency response than conventional shape memory alloys (SMAs). NiMn-based alloys are the workhorse of metamagnetic shape memory alloys since they are able to exhibit magnetic field induced phase transformation. In these alloys, martensite and austenite phases have different magnetization behavior, such as the parent phase can be ferromagnetic and martensite phase can be weakly magnetic. The magnetization difference between the transforming phases creates Zeeman energy, which is the main source for magnetic field induced phase transformation, is unlimited with applied field and orientation independent. Thus, metamagnetic shape memory alloys can be employed in polycrystalline form and provide higher actuation stress than conventional MSMAs. High actuation stress levels and frequencies in metamagnetic shape memory alloys are promising for magnetic actuation applications. Effects of heat treatments and cooling rates on the transformation temperatures, magnetization response and shape memory behavior under compressive stress were explored in Ni45Mn36.5Co5In13.5 [100] oriented single crystalline alloys to obtain high transformation temperatures, large magnetization difference, and low hysteresis behavior. It was found that transformation temperatures increase with higher heat treatment temperatures and decrease drastically at lower cooling rates. Temperature hysteresis decreased with increasing heat treatment temperatures. It was revealed that transformation temperatures, hysteresis, and magnetization response can be tailored by heat treatments via modifying interatomic order. Magnetic and mechanical results of NiMn-based metamagnetic alloys in single and polycrystalline forms as functions of composition, stress, temperature and magnetic field (up to 9 Tesla) were revealed through thermal-cycling under stress and magnetic field; stress-cycling as functions of temperature and magnetic field; and magnetic-field-cycling under stress at several temperatures experiments. Single crystalline samples of NiMnCoIn showed recoverable strain of 1.5 % due to magnetic field induced reversible phase transformation under constant stress and strain of 3.7 % by magnetic field induced recovery after variant reorientation of martensite. The magnetic field effect on the superelasticity and shape memory effects were also explored in selected orientations of [100], [110] and [111]. Fe-based ferromagnetic shape memory alloys have received considerable attention due to their better workability, strength, and lower cost compared with commercial NiTi based SMAs. The shape memory properties of a ferrous single crystalline alloy, FeNiCoAlNb, were investigated along the [100] orientation by thermal cycling under constant stress and superelasticity tests in both tension and compression. Aging was used to form nano-size precipitates to demonstrate shape memory behavior and tailor the shape memory properties. It was found that after proper heat treatments, [001] oriented FeNiCoAlNb showed a compressive strain of 15%, low temperature dependent superelastic behavior, high compression-tension asymmetry, and high compressive strength (~3GPa). The orientation dependence of the mechanical properties of FeNiCoAlNb single crystals were investigated along the [100], [110], [012] and [113] orientations. In addition, martensite phase showed higher magnetization than austenite phase as opposed to NiMn-based metamagnetic shape memory alloys. This magnetization difference is promising because it can allow magnetic field induced forward transformation. Ferrous alloys have great potential for high strength, temperature independent, and large scale actuator applications.

Packed bed reactors with counter-current, gas-liquid flows have been considered to be applicable in CO2 capture systems for post-combustion processing from fossil-fueled power production units. However, the hydrodynamics within the packing used in these reactors under counter-current flow has not been assessed to provide insight into design and operational parameters that may impact reactor and reaction efficiencies. Hence, experimental testing of a laboratory-scale spherical ball, packed bed with two-phase flow was accomplished and then a meso-scale 3D CFD model was developed to numerically simulate the conditions and outcomes of the experimental tests. Also, the hydrodynamics of two-phase flow in a packed bed with structured packing were simulated using a meso-scale, 3D CFD model and then validated using empirical models. The CFD model successfully characterized the hydrodynamics inside the packing, with a focus on parameters such as the wetted surface areas, gas-liquid interactions, liquid distributions, pressure drops, liquid holdups, film thicknesses and flow regimes. The simulation results clearly demonstrated the development of and changes in liquid distributions, wetted areas and film thicknesses under various gas and liquid flow rates. Gas and liquid interactions were observed to occur at the interface of the gas and liquid through liquid entrainment and droplet formation, and it became more dominant as the Reynolds numbers increased. Liquid film thicknesses in the structured packing were much thinner than in the spherical ball packing, and increased with increasing liquid flow rates. Gas flow rates had no significant effect on film thicknesses. Film flow and trickle flow regimes were found in both the spherical ball and structured packing. A macro-scale, porous model was also developed which was less computationally intensive than the meso-scale, 3D CFD model. The macro-scale model was used to study the spherical ball packing and to modify its closure equations. It was found that the Ergun equation, typically used in the porous model, was not suitable for multi-phase flow. Hence, it was modified by replacing porosity with the actual pore volume within the liquid phase; this modification successfully accounted for liquid holdup which was predicted via a proposed equation.