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Item Open Access Performance and accuracy enhancements of radiative heat transfer modeling via Monte Carlo(Colorado State University. Libraries, 2002) Zeeb, Charles Nelson, authorTwo ways to reduce the computational requirements of radiative heat transfer Monte Carlo simulation are explored. First, an efficient algorithm for tracing particles in large, arbitrarily complex, planar geometries containing nonparticipating media is presented. For arbitrary triangles and/or convex planar quadrilaterals, an efficient intersection algorithm is discussed in detail. After surveying several techniques used in ray tracing to limit the number of surfaces tested, the method of Uniform Spatial Division (USD) is implemented. The efficiency of the intersection algorithm and USD are demonstrated by timing results. Second, improving the accuracy of the Monte Carlo results by applying reciprocity and closure is explored. Statistical theory is applied to the reciprocity estimation smoothing (RES) technique which combines reciprocity enforcement through estimation and closure enforcement through the technique of least-squares smoothing. By examining a large number of runs of two large geometries, several RES methods are compared to find the best method. The effects of the RES method on surfaces and individual results between surfaces are also explored. Estimates of the improvements caused by the RES method that can be calculated from the results of a single run are also derived.Item Open Access Experimental and CFD investigation of re-agent mixing in an SCR system(Colorado State University. Libraries, 2007) Ivaturi, Krishna, author; Olsen, Daniel B., advisor; Mitchell, Charles E., committee member; Meroney, Robert, committee memberNitrogen oxides (NOx) cause a gamut of problems such as harmful particulate matter, ground level ozone (smog) and acid rain. Currently, a significant capital is being invested researching new techniques to control NOx emissions. One of the best ways to breakdown NOx is the Selective Catalytic Reduction (SCR) after-treatment method. A reducing agent (re-agent) is injected into exhaust gases and passed through a catalyst that facilitates NOx breakdown into Nitrogen and Water. To ensure effective NOx conversion, there must be uniform mixing between re-agent and exhaust gas upstream of the catalyst blocks. The current thesis focuses on investigating the mixing quality for an SCR test system employed for a 2-stroke lean-bum natural gas engine. CFD investigations were conducted to simulate the physical flow process. The mixing quality for different injector locations and the effect of utilizing a downstream in-line mixer was investigated. The CFD simulations were compared to experimental results. To measure ammonia concentrations experimentally, a traversing probe was designed and built. Re-agent concentrations were measured at various locations on a plane slightly upstream of the catalyst substrate. Detailed discussion is presented on different cases of CFD analysis. Experiments were conducted for the best and worst case of mixing based on CFD computation. Results suggest that a mixer plays a vita1 role in improving the mixing.Item Open Access Plasma flow field measurements downstream of a hollow cathode(Colorado State University. Libraries, 2007) Farnell, Casey Coffman, author; Williams, John D., advisor; Wilbur, Paul J., advisorThe focus of the research described herein is to investigate and characterize the plasma produced downstream of a hollow cathode with the goal of identifying groups of ions and possible mechanisms of their formation within a plasma discharge that might cause erosion, especially with respect to the hollow cathode assembly. In space applications, hollow cathodes are used in electrostatic propulsion devices, especially in ion thrusters and Hall thrusters, to provide electrons to sustain the plasma discharge and neutralize the ion beam. This research is considered important based upon previous thruster life tests that have found erosion occurring on hollow cathode, keeper, and ion optics surfaces exposed to the discharge plasma. This erosion has the potential to limit the life of the thruster, especially during ambitious missions that require ultra long periods of thruster operation. Results are presented from two discharge chamber configurations that produced very different plasma environments. Four types of diagnostics are described that were used to probe the plasma including an emissive probe, a triple Langmuir probe, a remotely located electrostatic analyzer (ESA), and an ExB probe attached to the ESA. In addition, a simulation model was created that correlates the measurements from the direct and remotely located probes.Item Open Access Performance and lifetime simulation of ion thruster optics(Colorado State University. Libraries, 2007) Farnell, Cody Coffman, author; Williams, John D., advisor; Wilbur, Paul J., advisorA simulation code, ffx, was developed to study various aspects of ion thruster optics. Information concerning sheaths, impingement limits, perveance, electric potential, charge exchange, and sputtering is covered. Electron backstreaming and pit and groove wear are discussed in detail as two grid failure mechanisms. The code was used to study the effects of several parameters on grid performance and lifetime, including grid spacing, aperture diameter, and grid thickness. An evolutionary algorithm was used with the ffx code to design grid sets, utilizing net accelerating voltage and current density as primary input parameters. Validation of the ffx code was accomplished through comparison to other ion optics codes and to experimental data obtained from both gridlet and full thruster testing. Gridlet test comparisons included simulations of finite aperture grid sets. The NSTAR thruster was studied in detail with regard to lifetime. The methods used for accurate and efficient optics simulation are discussed, including the multigrid method for solving for electric potential.Item Open Access Extending the performance of net shape molded fiber reinforced polymer composite valves for use in internal combustion engines(Colorado State University. Libraries, 2007) Buckley, Richard Theodore, author; Stanglmaier, Rudolf, advisor; Radford, Donald, advisorFiber Reinforced Composite (FRC) materials offer the possibility of reduced mass and increased structural performance over conventional metals. When used in reciprocating components of internal combustion engines, this may enable increased power and mechanical efficiency. Previously published work on FRC engine valves has both shown structural and thermal limitations.Item Open Access Development and optimization of a stove-powered thermoelectric generator(Colorado State University. Libraries, 2008) Mastbergen, Dan, author; Willson, Bryan, advisorAlmost a third of the world's population still lacks access to electricity. Most of these people use biomass stoves for cooking which produce significant amounts of wasted thermal energy, but no electricity. Less than 1% of this energy in the form of electricity would be adequate for basic tasks such as lighting and communications. However, an affordable and reliable means of accomplishing this is currently nonexistent. The goal of this work is to develop a thermoelectric generator to convert a small amount of wasted heat into electricity. Although this concept has been around for decades, previous attempts have failed due to insufficient analysis of the system as a whole, leading to ineffective and costly designs. In this work, a complete design process is undertaken including concept generation, prototype testing, field testing, and redesign/optimization. Detailed component models are constructed and integrated to create a full system model. The model encompasses the stove operation, thermoelectric module, heat sinks, charging system and battery. A 3000 cycle endurance test was also conducted to evaluate the effects of operating temperature, module quality, and thermal interface quality on the generator's reliability, lifetime and cost effectiveness. The results from this testing are integrated into the system model to determine the lowest system cost in $/Watt over a five year period. Through this work the concept of a stove-based thermoelectric generator is shown to be technologically and economically feasible. In addition, a methodology is developed for optimizing the system for specific regional stove usage habits.Item Open Access Fiber delivery and diagnostics of laser spark ignition for natural gas engines(Colorado State University. Libraries, 2008) Joshi, Sachin, author; Yalin, Azer, advisor; Willson, Bryan, advisorLaser ignition via fiber optic delivery is challenging because of the need to deliver pulsed laser beam with relatively high energy and sufficient beam quality to refocus the light to the intensity required for creating spark. This dissertation presents work undertaken towards the development of a multiplexed fiber delivered laser ignition system for advanced lean-burn natural gas engines. It also describes the use of laser ignition system to perform in-cylinder optical diagnostics in gas engines. Key elements of the dissertation includes: (i) time resolved emission spectroscopy (TRES) of laser sparks in air to investigate the dependence of spark temperatures and electron number densities on ambient gas pressures, (ii) optical characterization of hollow core fibers, step-index silica fibers, photonic crystal fibers (PCFs) and fiber lasers, (iii) development and on-engine demonstration of a multiplexer to deliver the laser beam from a single laser source to two engine cylinders via optical fibers, and (iv) demonstration of simultaneous use of laser sparks for ignition and Laser Induced Breakdown Spectroscopy (LIBS) to measure in-cylinder equivalence ratios in a Cooperative Fuel Research (CFR) engine. For TRES of laser sparks, the ambient gas pressure is varied from 0.85 bar to 48.3 bar (high pressures to simulate elevated motored in-cylinder pressures at time of ignition in advanced gas engines). At later stages (~1μs) of spark evolution, spark temperatures become comparable at all pressures. Electron number densities increase initially with increasing ambient gas pressure but become comparable at pressures greater than ~20 bar. The effects of launch conditions and bending for 2-m long hollow core fibers are studied and an optimum launch f/# of ~55 is shown to form spark in atmospheric pressure air. Spark formation using the output of a pulsed fiber laser is shown and delivery of 0.55 mJ nanosecond pulses through PCFs is achieved. Successful multiplexed laser ignition of a CAT G3516C gas engine via hollow core fibers is shown. LIBS analysis conducted at equivalence ratios from 0.6 to 0.95 in the CFR engine show a linear variation and linear correlation (R2 > 0.99) of line intensity ratio (Hα/O777 and Hα/Ntot) with equivalence ratio.Item Open Access A biomechanical analysis of venous tissue in its normal, post-phlebitic, and genetically altered conditions(Colorado State University. Libraries, 2009) McGilvray, Kirk Cameron, author; Puttlitz, Christian M., advisorThe incidence of vein disease is very high, affecting more than 2% of the hospitalized patients in the United States; a number that is expected to increase. Post phlebitic veins, the result of chronic deep vein thrombosis, is considered to be one of the most important venous disease pathologies. Unfortunately, little information is currently available on the biomechanical effects of thrombus resolution in the deep veins. The aim of this research was to characterize the biomechanical response of both healthy and diseased venous tissue using a murine model. It was hypothesized that biomechanical response parameters derived from healthy and diseased tissue would give insight into the resultant clinical complications observed in patients following thrombus resolution. Biomechanical analysis revealed that statistically significant deleterious changes in vein wall compliance were observed following thrombus resolution. Data also revealed that matrix metallopeptidase 9 expression has a statistically significant effect on the biomechanical response of the tissue. These results indicate that clinical complications following deep venous thrombosis manifest from significant decreases in the compliance of the vein wall. Finite element analyses were also performed. Biomechanical data served as input material parameters for modeling. Finite element modeling was used to evaluate the response of the inferior vena cava under physiologic loads. The results indicate that peak stresses are generated in the circumferential direction of loading during luminal pressurization. Decreased dilatation was observed following thrombus resolution. The data indicates that deep venous thrombosis lead to increased vein wall stress in correlation with decreased luminal distensability.Item Open Access Interaction space abstractions: design methodologies and tools for autonomous robot design and modeling(Colorado State University. Libraries, 2009) Kaiser, Carl L., author; Troxell, Wade O., advisorCurrent abstractions, design methodologies, and design tools are useful but inadequate for modern mobile robot design. By viewing robotics systems as an interactive and reactive agent and environment combination, and focusing on the interactions between the two, particularly those interactions that result in task accomplishment, one arrives at the interaction space abstraction. The role of abstractions, formalisms and models are discussed, with emphasis on several specific abstractions used for robotics as well as the strengths and shortcomings of each. The role of design methodologies is also discussed, again with emphasis on several currently used in robotics. Finally, design tools and the use thereof are briefly discussed. The concept of interaction spaces as an abstraction and a formalism is developed specifically for use in robot design. Types of elements within this formalism are developed, defined, and described. A formal nomenclature is introduced for these elements based on Simulink blocks. This nomenclature is used for descriptive models and the Simulink blocks are used for predictive models. The interaction space abstraction is combined with the concept of exploration-based design to create a design methodology specifically adapted for use in descriptive modeling of autonomous robots. This process is initially developed around a simple wall-following robot, then is expanded around a multi-agent foraging system and an urban search and rescue robot model, each of which demonstrates different aspects and capabilities of interaction space modeling as a design methodology. A design tool based on iterative simulation is developed. The three specific examples above are used to perform quantitative simulation and the results are discussed with emphasis on determination and quantification of factors necessary for task accomplishment. These simulations are used to illustrate how to explore the design space and evaluate trade offs between design parameters in a system.Item Open Access Development of a hyaluronan-polyethylene copolymer for use in articular cartilage repair(Colorado State University. Libraries, 2009) Oldinski, Rachael, author; James, Susan P., advisorArticular cartilage is the connective tissue which covers the ends of long bones, providing a lubricious, hydrodynamic surface for articulation and energy dissipation. Articular cartilage has a limited ability to repair itself; once the native tissue has become damaged, either from injury or disease (e.g., arthritis), it is irreversible and the tissue will degrade with time resulting in joint pain. The goal of this research was to develop a permanent (i.e., non biodegradable/bioerodible) bioactive material and assess its applicability for articular cartilage repair and/or replacement. Utilizing two constituents, polyethylene (the 'gold standard' bearing material for total joint replacements) and hyaluronan (HA, a native component of articular cartilage), a hyaluronan-polyethylene graft copolymer (HA-co-HDPE) was developed. The novel HA- co-HDPE material was successfully synthesized using an interfacial polymerization reaction in a non-aqueous environment. Although the material has limited melt-processability, it is more processable than HA and was successfully compression molded into samples for physical, mechanical and in vitro biological characterization (e.g., swell ratio, dynamic mechanical analysis). HA-co-HDPE exploits the strength, rigidity and melt-processability associated with HDPE, and achieves increased osteogenic potential by incorporating the highly hydrophilic biopolymer HA. In conclusion, the swelling, mechanical and degradation properties of the copolymer can be custom-optimized for biomedical applications by tailoring chemical or physical crosslinking strategies and varying the amount and molecular weights of HA and HDPE incorporated into the copolymer.Item Open Access Characterization of gaseous and particulate emissions from combustion of algae based methyl ester biodiesel(Colorado State University. Libraries, 2009) Fisher, Bethany, author; Marchese, Anthony John, 1967-, advisor; Olsen, Daniel B., committee member; Volckens, John, committee memberThe advantages to using biodiesel in place of petroleum diesel are also accompanied by disadvantages. Biodiesel is usually made from crops that are also used to produce food. The land and water use impacts would be profound if current biodiesel feedstocks were used to displace a significant portion of current global petroleum diesel consumption. Oil-producing algae is a favorable alternative to the more common biodiesel feedstocks (soy, canola, etc.) because it does not compete with food sources, does not require arable land to grow and has the potential to produce significantly more oil per area per year than any other oil crops. However, the fatty acid composition of the oil produced by algal species currently under consideration for fuel production differs from that of the more common vegetable oils in that it often includes high quantities of long chain and highly unsaturated fatty acids. When transesterified into fatty acid methyl esters (FAME) biodiesel, the unique fatty acid composition could have a substantial impact on emissions such as Nitrogen Oxides (NOx) and particulate matter (PM). Accordingly, the goal of this study was to examine the effect of the chemical structure of algal methyl esters on pollutant emissions from a diesel engine operating on algae-based FAME biodiesel. Tests were performed on a 2.4 L, 39 kW John Deere 4024T, off-road diesel engine meeting USEPA Tier 2 emissions regulations. The engine was fitted with a unique, low-volume fuel system that enabled emissions tests to be conducted with small specialty fuel samples. Tests were performed on 9 different fuel blends at 2 different engine loading conditions. Exhaust gas measurements were made using a 5-gas emissions analysis system that includes chemiluminescence measurement of NOx, flame ionization detection of total hydrocarbons, paramagnetic detection of oxygen and non-dispersive infrared detection of CO and CO2. Particulate matter was characterized using an Aerosol Mass Spectrometer (AMS), which is capable of direct measurement of particle composition. The PM size distributions (between 10 to 1000 nm) were measured using a Sequential Mobility Particle Sizer. Total PM mass emissions were measured using gravimetric analysis of Teflon filters and the ratio of elemental carbon to organic was measured using thermo-optical analysis of quartz filters. Experiments were performed with ultra-low sulfur diesel, soy biodiesel (both pure biodiesel, B100, and a blend of 20% biodiesel and 80% diesel, B20), canola biodiesel (B20 and B100), and two synthetic algal methyl ester formulations (B20 and B100 for each). Combustion of algal methyl esters resulted in decreased NOx relative to both canola and soy biodiesel and ULSD, in contrast to previous research that examined the effect of fatty acid saturation and chain length on NOx emissions. A correlation was found between NOx emissions and premixed burn fraction, which provides an explanation for these results. Emissions of formaldehyde and organic PM were found to be slightly elevated with the two algal fuels in comparison with the traditional feedstocks. Particle size distribution, total PM mass, total hydrocarbons, CO and acetaldehyde emissions were similar between the different types of biodiesel.Item Open Access On the energy sources of Mozambican households and the demand-supply curves for domestic electricity in the northern electrical grid in Mozambique(Colorado State University. Libraries, 2009) Arthur, Maria de Fatima Serra Ribeiro, author; Willson, Bryan D., advisor; Bond, Craig A., advisor; Duff, William S., committee member; Troxell, Wade O., committee member; Kling, Robert W., committee memberThe development of electrical infrastructure to supply rural households is considered economically unfeasible because of the high cost of capital investment required to expand the distribution grids. Although domestic electricity consumption in many developing regions is small when compared to the requirements of some emerging agroindustries, the social benefits are significant, such that many donor agencies agree to finance grid extensions based on poorly projected social benefits of electrification. However, there is evidence that households with electrical connections do not increase their electricity consumption above the bare minimum, allegedly because electricity is more expensive and possibly because of insufficient funds to invest in electrical appliances. The controversy is then whether or not electrification can support household development (and poverty alleviation) and vice-versa, can domestic consumption support the costs of electrification investments. The current work is composed of a theoretical model and two empirical models, developed in order to answer the following specific questions: 1) To what extent the ownership of assets is determinant to the adoption of high-grade energy sources in the domestic settings of poor families? 2) What is the price of electricity that sustains the supply costs and still promotes increased energy consumption in Mozambican households? To answer these questions the study formulated an inter-temporal utility maximization problem by which households can determine the limits of investment for energy consumption and for income generation that is required to evolve out of poverty in a sustainable manner. Next, the study calculated the elasticities of demand for the various domestic sources used by Mozambican households, surveyed in 2002/3 at the national level, enabling the construction of demand curves for these sources. The study also derived empirical loss equations for the northern transmission electrical grid (Linha Centro-Norte, LCN) in Mozambique, and constructed the supply curves for the distribution networks connected to the substations of the system. Based on the household data, the likelihood of adopting electricity as a domestic source was analyzed and results show that wealth is a major determining factor, confirming the findings of the theoretical and empirical household models. Finally, the study constructed the supply and demand plots, from which the sustainable price of electricity supplied to domestic consumers can be estimated and welfare evaluations made. Results indicate that households can evolve consuming electricity if credit for investment is made available and the income base is enlarged. Furthermore, it is demonstrated that current electricity prices are within budget of households and that electricity is competitive with biomass sources and kerosene in the domestic setting.Item Open Access A simulation method and laboratory brake friction dynamometer for tribology studies(Colorado State University. Libraries, 2009) Nivala, Peter Thompson, author; Radford, Donald W., advisor; Sakurai, Hiroshi, committee member; Heyliger, Paul Roy, 1958-, committee memberTwo of the most important parameters of brake system design are the frictional and wear capabilities of the rotor and pad materials. These parameters must meet minimum design requirements in an effort to enhance friction and reduce wear to improve the performance and life of brake system components. The frictional and wear performance of the rotor and pad materials can be assessed through laboratory brake dynamometer testing and evaluation. In the current study, a wear testing simulation and an inertia laboratory brake dynamometer were developed to resolve differences in wear rates of brake materials. Dynamometer testing was conducted to verify the logic of the simulation and the functionality of the dynamometer by measuring wear rates of brake rotor material samples, some of which were subjected to cryogenic heat treatment to modify their wear rates, at varying brake application pressures. Dynamometer testing established that the wear simulation and inertia laboratory brake dynamometer developed during the current study could function together as a suitable tribological experimental apparatus. Specifically, dynamometer testing demonstrated the ability of the experimental apparatus to resolve differences in wear rates of brake materials due to variations in brake application pressure at relatively short test durations; however, dynamometer test results did not show conclusive evidence to suggest an advantage in subjecting the rotor materials used in the current study to cryogenic treatment to lower the rotor or pad wear rates.Item Open Access Laser ignition for internal combustion engines via fiber optic delivery(Colorado State University. Libraries, 2009) DeFoort, Morgan, author; Yalin, Azer, advisor; Willson, Bryan, advisorIn the effort to reduce emissions and improve the efficiency of Otto cycle engines, the ignition system is often a limiting factor. Many "high energy" ignition systems have been developed, but almost all of these are based on traditional electric arc spark plugs. Laser ignition represents a fundamentally different approach to igniting gas mixtures and opens the door to improvements in fuel-lean engine operation and high-pressure combustion environments. Yet the promise of laser ignition remains unexploited, as practical systems have not been developed. In this contribution, we work towards the goal of developing a practical laser ignition system for stationary natural gas engines. Specifically, we focus on fiber optic delivery of the laser beam to the engine, thereby making a significant advance relative to past open-air (free-space) configurations. A combination of modeling and experimentation has been used to develop the needed fiber optic delivery systems, culminating in the first demonstration of fiber-optically delivered laser ignition on an engine.Item Open Access Computational modeling of the lower cervical spine: facet cartilage distribution and disc replacement(Colorado State University. Libraries, 2009) Womack, Wesley J., author; Puttlitz, Christian, advisorAnterior cervical fusion has been the standard treatment following anterior cervical discectomy and provides sufficient short-term symptomatic relief, but growing evidence suggests that fusion contributes to adjacent-segment degeneration. Motion-sparing disc replacement implants are believed to reduce adjacent-segment degeneration by preserving motion at the treated level. Such implants have been shown to maintain the mobility of the intact spine, but the effects on load transfer between the anterior and posterior elements remain poorly understood. In order to investigate the effects of disc replacement on load transfer in the lower cervical spine, a finite element model was generated using cadaver-based Computed Tomography (CT) imagery. The thickness distribution of the cartilage on the articular facets was measured experimentally, and material properties were taken from the literature. Mesh resolution was varied in order to establish model convergence, and cadaveric testing was undertaken to validate model predictions. The validated model was altered to include a disc replacement prosthesis at the C4/C5 level. The effect of disc-replacement on range of motion, antero-posterior load distribution, total contact forces in the facets, as well as the distribution of contact pressure on the facets were examined, and the effect of different facet cartilage thickness models on load sharing and contact pressure distribution predictions were examined. Model predictions indicate that the properly-sized implant retains the mobility, load sharing, and contact force magnitude and distribution of the intact case. Mobility, load sharing, nuclear pressures, and contact pressures at the adjacent motion segments were not strongly affected by the presence of the implant, indicating that disc replacement may not be a significant cause of post-operative adjacent-level degeneration. Variation in articular cartilage distribution did not substantially affect mobility, contact forces, or load sharing. However, mean and peak contact pressure, contact area, and center of pressure predictions were strongly affected by the cartilage distribution used in the model. These results indicate that oversimplification of the cartilage thickness distribution will negatively affect the ability of the model to predict facet contact pressures, and thus subsequent cartilage degeneration.Item Open Access Understanding the effects and infrastrcuture needs of plug-in electric vehicle (PEV) charging(Colorado State University. Libraries, 2010) Davis, Barbara Morgan, author; Bradley, Thomas H., advisor; Keske, Catherine M., committee member; Zimmerle, Daniel, committee memberPlug-in electric vehicles (PEV) are any vehicle that uses electricity to propel the vehicle, potentially in combination with other fuels like gasoline, diesel or hydrogen. PEV offer the benefits of reduced dependence on foreign oil and decreased greenhouse gas emissions. While the benefits are numerous for this new technology, the drawbacks are not fully understood. The largest concern for the utility company is to understand the necessary infrastructure requirements to minimize their impacts on the electric grid. This study focuses on the infrastructure needs and effects and how to best control PEV charging. The results of these analyses show the fundamental disconnect between the consumer and the utility company.Item Open Access Large bore natural gas engine performance improvements and combustion stabilization through reformed natural gas precombustion chamber fueling(Colorado State University. Libraries, 2010) Ruter, Matthew D., author; Olsen, Daniel B., advisor; De Miranda, Michael A., committee member; Marchese, Anthony John, 1967-, committee memberLean combustion is a standard approach used to reduce NOx emissions in large bore natural gas engines. However, at lean operating points, combustion instabilities and misfires give rise to high total hydrocarbon (THC) and carbon monoxide (CO) emissions. To counteract this effect, pre-combustion chamber (PCC) technology is employed to allow engine operation at an overall lean equivalence ratio while mitigating the rise of THC and CO caused by combustion instability and partial and complete misfires. A PCC is a small chamber, typically 1-2% of the clearance volume. A separate fuel line supplies gaseous fuel to the PCC and a standard spark plug ignites the slightly rich mixture (1.1 < Φ < 1.2) in the PCC. The ignited PCC mixture enters the main combustion chamber as a high energy flame jet, igniting the lean mixture in the main chamber. Typically, natural gas fuels both the main cylinder and the PCC. In the current work reported herein, a mixture of reformed natural gas (syngas) and natural gas fuels the PCC. Syngas is a broad term that refers to a synthetic gaseous fuel. In this case, syngas specifically denotes a mixture of hydrogen, carbon monoxide, nitrogen, and methane generated in a natural gas reformer. Syngas has a faster flame speed and a wider equivalence ratio range of operation. Fueling the PCC with syngas reduces combustion instabilities and misfires. This extends the overall engine lean limit, enabling further NOx reductions. Research results presented are aimed at quantifying the benefits of syngas PCC fueling. A model is developed to predict the equivalence ratio in the PCC for different mixtures and flow rates of PCC fuel. An electronic injection valve is used to supply the PCC with syngas. The delivery pressure, injection timing, and flow rates are varied to optimize PCC equivalence ratio. The two syngas mixtures evaluated contain the same ratio of hydrogen to carbon monoxide but different levels of nitrogen diluent. The syngas with the higher nitrogen content is denoted syngas 1 while syngas 2 specifies the lower nitrogen content syngas. Experimental results are presented for 80% syngas / 20% natural gas mixtures for each syngas PCC fueling scenario at 18" Hg intake manifold pressure. 80% syngas 1 / 20% natural gas PCC fueling resulted in an 18% reduction in NOx emission compared to natural gas fueling. Supplying the PCC with 80% syngas 2 / 20% natural gas improves combustion stability by 16% compared to natural gas PCC fueling. Increasing the intake manifold pressure to 22" Hg for 80% syngas 2 / 20% natural gas fueling provides an emission comparison at an equivalent combustion stability operating point. Comparing equivalent combustion stability operating points between syngas 2 and natural gas shows a 40% reduction in NOx emissions when fueling the PCC with 80% syngas 2 / 20% natural gas mixture compared to natural gas fueling. Experimental results are presented for varying PCC fuel mixtures of syngas 2 and natural gas at 18" Hg intake manifold pressure. Results show dramatic increases in combustion stability are realized for high syngas 2 mixtures (greater than 80% syngas 2). Reducing intake manifold boost for natural gas PCC fueling to 8.5" Hg produces equivalent main cylinder combustion stability compared to 100% syngas 2 PCC fueling at 18" Hg intake manifold pressure. NOx emission increases by 780% for natural gas PCC fueling at the equivalent combustion stability operating point compared to syngas 2 PCC fueling at 18" Hg intake manifold pressure.Item Open Access Development of a novel endoprosthesis for canine limb-sparing using a finite element approach(Colorado State University. Libraries, 2010) Shetye, Snehal, author; Puttlitz, Christian Matthew, advisor; James, Susan P., committee member; Santoni, Brandon G., committee member; Heyliger, Paul Roy, 1958-, committee memberOsteosarcoma is the most prevalent bone tumor in the canine population and the distal radius is the most commonly affected site. To date, amputation has been the preferred treatment option among veterinarians for distal radius osteosarcoma. However, with the advent of better chemotherapy protocols and the subsequent increasing survival rates, interest has now turned towards saving the legs of dogs with osteosarcoma. The current endoprosthesis used for limb-sparing is associated with a high failure rate, and hence, the design of a novel endoprosthesis is warranted. To aid in the development of a new endoprosthesis for canine limb-sparing a finite element model of the canine forelimb was generated. Accurate mechanical properties of soft tissues are essential to build a reliable finite element model. Since no data exists regarding the mechanical properties of canine carpal ligaments, six primary stabilizing ligaments of the canine carpus were identified and their mechanical properties were investigated by uniaxial testing in a materials testing machine. Convergence and validation are two crucial steps in the development of a finite element model. Convergence was investigated by generating three models with increasing mesh resolution. For the purposes of validation, eight intact canine forelimbs were tested in a materials testing machine. The limbs were instrumented to record bone strains and relative displacements. The acquired data were used to validate the canine forelimb model. The current endoprosthesis was evaluated to determine the mechanical underpinnings of clinical failures associated with these implants using the canine forelimb finite element model. The implant failure locations predicted by the model were similar to those observed clinically. The use of a locking plate in place of the current non-locking plate was also investigated. Several stress redistribution strategies were also examined. A novel modular design was developed in collaboration with the Colorado State University's Veterinary Teaching Hospital oncology surgeons. The design was extensively evaluated with the use of the validated and converged finite element of the canine antebrachium. The design was modified and improved based on the results. Significant stress reduction was achieved within the proximal radial screws and the distal metacarpal screws. Off-axis loading of the construct was also eliminated. The final design was approved for prototype development, biomechanical testing and cadaveric evaluation.Item Open Access Investigation of superturbocharger performance improvements through steady state engine simulation(Colorado State University. Libraries, 2010) Whitley, Kevin Lee, author; Olsen, Daniel B., advisor; Bradley, Thomas H., committee member; Zimmerle, Daniel John, committee member; Labadie, John W., committee memberAn integrated supercharger/turbocharger (SuperTurbo) is a device that combines the advantages of a supercharging, turbocharging and turbocompounding while eliminating some of their individual disadvantages. High boost, turbocompounding, and advanced controls are important strategies in meeting impending fuel economy requirements. High boost increases engine power output while many losses remain constant, producing an overall efficiency gain. Turbocompounding increases engine efficiency by capturing excess exhaust turbine power at high speed and torque. Supercharging increases low speed high torque operating performance. Steady state performance gains of a Superturbocharger equipped engine are investigated using engine simulation software. The engine simulation software uses a 1-D wave flow assumption to model the engine's unsteady flow behavior through one dimensional pipes. With these pipes connected to other engine components the overall performance of the engine can be modeled. GT-Power was chosen to run the simulations due to an already correlated engine model being available. This software is used to 'tune' an existing stock engine model to approximate stock engine data over the full speed and torque range. The SuperTurbo is added to the model and simulations are performed over the full engine speed and torque range for direct comparison with the stock engine. The model results show turbocompounding to be most effective at high speeds and torques in the area above 10 bar BMEP in the 3000 - 4000 RPM range and above 5 bar BMEP in the 500 - 6000 RPM range. In addition to turbocompounding there are fuel savings due to the reduced use of the compressor when it is not needed. With the stock configuration there is boost pressure created by compressor power that is then restricted by the throttle in the 2500 RPM range in the 8-12 bar BMEP range on up to 6000 RPM in the 2-10 bar BMEP range. The control of compressor speed to produce no boost at these locations improves efficiency by not wasting energy creating boost that is not needed.Item Open Access Increased understanding of hybrid vehicle design through modeling, simulation, and optimization(Colorado State University. Libraries, 2010) Geller, Benjamin M. (Benjamin Michael), author; Bradley, Thomas H., advisor; Kirkpatrick, Allan Thomson, committee member; Keske, Catherine M., committee memberVehicle design is constantly changing and improving due to the technologically driven nature of the automotive industry, particularly in the hybridization and electrification of vehicle drive trains. Through enhanced design vehicle level design constraints can result in the fulfillment of system level design objectives. These constraints may include improved vehicle fuel economy, all electric range, and component costs which can affect system objectives of increased national energy independence, reduced vehicle and societal emissions, and reduced life-cycle costs. In parallel, as computational power increases the ability to accurately represent systems through analytical models improves. This allows for systems engineering which is commonly quicker and less resource consuming than physical testing. As a systems engineering technique, optimization has shown to obtain superior solutions systematically, in opposition to trial-and-error designs of the past. Through the combination of vehicle models, computer numerical simulation, and optimization, overall vehicle systems design can greatly improve. This study defines a connection between the system level objectives for advanced vehicle design and the component- and vehicle-level design process using a multi-level design and simulation modeling environment. The methods and information pathways for vehicle system models are presented and applied to dynamic simulation. Differing vehicle architecture simulations are subjected to a selection of proven optimization algorithms and design objectives such that the performance of the algorithms and vehicle-specific design information and sensitivity is obtained. The necessity of global search optimization and aggregate objective functions are confirmed through exploration of the complex hybrid vehicle design space. Whether the chosen design space is limited to available components or expanded to academic areas, studies can be performed for numerous design objectives and constraints. The combination of design criteria into quantifiable objective functions allows for direct optimization comparison based on any number of design goals. Integrating well-defined objective functions into high performing global optimization search methods provides increased probability of obtaining solutions which represent the most germane designs. Additionally, key interactions between different components in the vehicular system can easily be identified such that ideal directions for gain relative to minimal cost can be achieved. Often times vehicular design processes require lower order representations or consist of time and resource consuming iterations. Through the formulation presented in this study, more details, objectives, and methods become available for comparing advanced vehicles across architectures. The main techniques used for setting up the models, simulations and optimizations are discussed along with results of test runs based on chosen vehicle objectives. Utility for the vehicular design efforts are presented through comparisons of available simulation and future areas of research are suggested.