Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2011. / "June 2011." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 29). / The motivation behind this report was to develop a stronger understanding of pine needle combustion behavior in a semi-gasifier, in order to ultimately design an effective pine needle cook stove for people in the developing world. Pine needles are a cheap, energy-dense fuel source that can be harnessed for cooking purposes, but they are often physically or chemically altered prior to being used as a fuel. The challenge remains to develop a stove that uses unprocessed pine needles. Using principles of a semi-gasification biomass stove, this paper explores the combustion and burn characteristics of unprocessed pine needles by measuring the effects of temperature in a configured burner when altering primary and secondary airflow into the burner. Experiments showed that pine needles in a semi-gasifier combust in two regimes--one characterized by secondary combustion of volatiles released from the primary burn of raw pine needles, and another characterized by the smoldering of pine needle charcoal. Each regime needed unique balances between primary air and secondary airflow. The first regime required a relatively low primary airflow with a high secondary airflow, while the second regime needed a high primary airflow to maintain charring and low or no secondary airflow. The balance of airflow in the first regime was crucial in determining whether the volatiles combusted or were released as plumes of smoke. The findings of this report can be used as an initial benchmark and resource in the further development of an existing proof-of-concept prototype, which was built by the authors with a team of MIT students and affiliates and a community partner in Uttarakhand, India. / by Liane Jessica Fang and Caroline M. Hane-Weijman. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002. / Includes bibliographical references (p. 145-149). / Successful design and fabrication of structures and systems at the micro-scale requires a sound theoretical understanding and reliable experimental data on the mechanical behavior of materials at that scale. Generation of experimental data requires accurate, robust, reliable, versatile and yet simple micro-scale mechanical testing devices. This thesis describes the design, development and applications of materials testing technologies at the micro-scale. Using the rectilinear travel characteristics of compound flexures, two novel testing machines have been designed and built to conduct tension, bending and indentation tests in the force regime of 10 pN - 35 N and displacement regime of 20 nm - 6 mm. These machines have been used in measuring the mechanical properties of free-standing gold thin films, rolled metallic foils, elastomeric fibers and other materials. Numerical simulations of the mechanical behavior of gold thin films and rolled copper foils have been conducted and compared with experimental results. Microstructural investigations into deformation mechanisms of the free-standing gold thin films have also been conducted. / by Sauri Gudlavalleti. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006. / Includes bibliographical references. / This research involved the design and manufacture of a prototype for a hybrid bicycle system. The design called for a vehicle capable of being used in a mode where normal bicycle operation is possible while being reconfigurable into a cargo carrying configuration where both wheels are coaxial. The simplification of the process by which the device could change from one mode to the other and the robustness of the system as a whole were set as primary design criteria. This design would allow for the transportation of individuals and cargo under varying situations, including the evacuation of a wounded individual when in cargo mode. The success of the prototype proved the value of the concept and its possible applications in military, urban, and outdoor environments. Testing also showed that further research into refining the cargo transports driving dynamics and the manufacturing of the most critical components is merited. / by Andreas Pino ; in collaboration with Orlando Soto. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 272-297). / Since their invention in 1948 by Dennis Gabor, holograms have demonstrated to be important components of a variety of optical systems and their implementation in new fields and methods is expected to continue growing. Their ability to encode 3D optical fields on a 2D plane opened the possibility of novel applications for imaging and lithography. In the traditional form, holograms are produced by the interference of a reference and object waves recording the phase and amplitude of the complex field. The holographic process has been extended to include different recording materials and methods. The increasing demand for holographic-based systems is followed by a need for efficient optimization tools designed for maximizing the performance of the optical system. In this thesis, a variety of multi-domain optimization tools designed to improve the performance of holographic optical systems are proposed. These tools are designed to be robust, computationally efficient and sufficiently general to be applied when designing various holographic systems. All the major forms of holographic elements are studied: computer generated holograms, thin and thick conventional holograms, numerically simulated holograms and digital holograms. Novel holographic optical systems for imaging and lithography are proposed. In the case of lithography, a high-resolution system based on Fresnel domain computer generated holograms (CGHs) is presented. The holograms are numerically designed using a reduced complexity hybrid optimization algorithm (HOA) based on genetic algorithms (GAs) and the modified error reduction (MER) method. The algorithm is efficiently implemented on a graphic processing unit. Simulations as well as experimental results for CGHs fabricated using electron-beam lithography are presented. A method for extending the system's depth of focus is proposed. The HOA is extended for the design and optimization of multispectral CGHs applied for high efficiency solar concentration and spectral splitting. A second lithographic system based on optically recorded total internal reflection (TIR) holograms is studied. A comparative analysis between scalar and (cont.) vector diffraction theories for the modeling and simulation of the system is performed. / A complete numerical model of the system is conducted including the photoresist response and first order models for shrinkage of the holographic emulsion. A novel block-stitching algorithm is introduced for the calculation of large diffraction patterns that allows overcoming current computational limitations of memory and processing time. The numerical model is implemented for optimizing the system's performance as well as redesigning the mask to account for potential fabrication errors. The simulation results are compared to experimentally measured data. In the case of imaging, a segmented aperture thin imager based on holographically corrected gradient index lenses (GRIN) is proposed. The compound system is constrained to a maximum thickness of 5mm and utilizes an optically recorded hologram for correcting high-order optical aberrations of the GRIN lens array. The imager is analyzed using system and information theories. A multi-domain optimization approach is implemented based on GAs for maximizing the system's channel capacity and hence improving the information extraction or encoding process. A decoding or reconstruction strategy is implemented using the superresolution algorithm. Experimental results for the optimization of the hologram's recording process and the tomographic measurement of the system's space-variant point spread function are presented. A second imaging system for the measurement of complex fluid flows by tracking micron sized particles using digital holography is studied. A stochastic theoretical model based on a stability metric similar to the channel capacity for a Gaussian channel is presented and used to optimize the system. The theoretical model is first derived for the extreme case of point source particles using Rayleigh scattering and scalar diffraction theory formulations. The model is then extended to account for particles of variable sizes using Mie theory for the scattering of homogeneous dielectric spherical particles. The influence and statistics of the particle density dependent cross-talk noise are studied. Simulation and experimental results for finding the optimum particle density based on the stability metric are presented. For all the studied systems, a sensitivity analysis is performed to predict and assist in the correction of potential fabrication or calibration errors. / by José Antonio Domínguez-Caballero. / Ph.D.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 32-33). / The DARPA Robotic Challenge (DRC) required the development of user interface, perception, and planning and control modules for a robotic humanoid. This paper focuses on the planning and control component for the manipulation qualification task of the virtual section of the DRC. Nonlinear algorithms were employed for the planning systems, such as the grasp optimization system and the robot state trajectory computation system. However, for closed-loop control, a linear proportional-derivative (PD) joint position controller was used. The nonlinear algorithms used for the planning systems may be improved, but their current functionality allows the successful completion of the manipulation qualification task. Also, even though PD controllers seem appropriate for the closed-loop control, PID controllers might yield a higher level of accuracy if tuned properly. In conclusion, a linear controller appears sufficient for certain control of the highly nonlinear ATLAS humanoid robot and Sandia hand as long as accurate optimization and planning systems complement such control. / by Cecilia G. Cantu. / S.B.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001. / Includes bibliographical references (leaves 93-96). / by Carolyn Phillips. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 133-135). / An experimental study was performed to assess the feasibility of performing methane (CH4) partial oxidation (POX) in two internal combustion engines: one equipped to perform spark-ignition (the "spark-ignited engine"), and the other containing a catalyst in the engine cylinder (the "catalytic engine"). The exhaust gases were rich in hydrogen- (H 2) and carbon monoxide- (CO), and could be used as synthesis gas ("syngas") for the synthesis of liquid fuels such as methanol. Conventional syngas production techniques are only economical on a large scale and cannot be transported to hard-to-reach gas sources, where gas-to-liquids (GTL) would have the biggest impact on the transportability of that gas. Engines could be deployed at these locations to produce syngas on a small scale and at low cost, as they benefit from the economies of mass production that have been achieved through advanced manufacturing techniques. We call this type of engine an "engine reformer". This thesis contrasts the results of performing methane POX in two different engine reformers, using atmospheric air as the oxidizer. One of four cylinders in a Yanmar 4TNV84T marine diesel generator was converted to ignite methane POX mixtures using a spark plug. Intake temperatures > 350 °C were required to minimize misfire. Exhaust H2 to CO ratios of 1.4 were achieved with methane-air equivalence ratios (0m) up to 2.0, while ratios of > 2.0 were achieved with hydrocarbon-air equivalence ratios (PHc) up to 2.8 with the assistance of hydrogen (H 2) and ethane (C 2H6). High equivalence ratios °PHC > 2.2 showed reduced CH4 conversion efficiency, therefore PHC = 2.2 (with H2 produced a good tradeoff between syngas quality and CH4 conversion. A single-cylinder Lister-Petter TRl diesel generator was used to perform methane POX using a palladium (Pd) washcoat catalyst deposited on a Fecralloy® disk. With > 150 °C intake temperatures, exhaust H2 to CO ratios of 1.0 were achieved with methane-air equivalence ratios (PM = 4.0 with varying amounts of CO2 to simultaneously perform methane dry reforming. Spark-ignition appeared to provide higher reliability, though tests will continue to be performed on the catalytic engine to optimize performance. A larger engine of a similar design to the spark-ignited Yanmar will be deployed at a demonstration plant in North Carolina to produce syngas at higher flow rates, and will be integrated with a liquids synthesis reactor to produce methanol. / by Emmanuel G. Lim. / S.M.

Thesis: M. Eng. in Manufacturing, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 68-69). / This thesis develops and describes the product architecture for a LED based detector for liquid chromatography systems. The product architecture development is discussed using a customized methodology, incorporating elements from different views on product architecture development. The market scope and segmentation for such a device was studied and the effect of technologies for such a device on the product architecture was reviewed. The architecture of the product is described at 2 different levels. The first level is the concept design phase which links functional elements to physical components. The second level contains the grouping of components into sub-systems of the product. Design Structure Matrices for the key interactions at the sub-system level were created. These serve to elucidate the key interactions between the chunks for the detailed designers. Finally, the implications of the developed architecture are discussed. One configuration of the developed architecture was selected for detailed design. The optical and mechanical design for this configuration was carried out by separate MIT students. / by Saksham Saxena. / M. Eng. in Manufacturing

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 224-229). / A number of CO₂ capture-enabled power generation technologies have been proposed to address the negative environmental impact of CO₂ emission. An important barrier to adopting these technologies is the associated energy and economic penalties. Chemical-looping (CLC) is an oxycombustion technology that can significantly lower such penalties, utilizing a redox process to eliminate the need for an air separation unit and enable better energy integration. Conventional CLC employs two separate reactors, with metal oxide particles circulating pneumatically in-between, leading to significant irreversibility associated with reactor temperature difference. A rotary reactor, on the other hand, maintains near-thermal equilibrium between the two stages by thermally coupling channels undergoing oxidation and reduction. In this thesis, a multiscale analysis for assessing the integration of the rotary CLC reactor technology in power generation systems is presented. This approach employs a sequence of models that successively increase the resolution of the rotary reactor representation, ranging from interacting thermal reservoirs to higher fidelity quasi-steady state models, in order to assess the efficiency potential and perform a robust optimization of the integrated system. Analytical thermodynamic availability and ideal cycles are used to demonstrate the positive impact of reactor thermal coupling on system efficiency. Next, detailed process flow-sheet models in which the rotary reactor is modeled as a set of interacting equilibrium reactors are used to validate the analytical model results, identify best cycle configurations and perform preliminary parametric analysis for between the reactor and the system while maintaining computational efficiency, an intermediate fidelity model is developed, retaining finite rate surface kinetics and internal heat transfer within the reactor. This model is integrated with a detailed system model and used for optimization, parametric analysis and characterization of the relative techno-economic performance of different oxygen carrier options for thermal plants integrated with the rotary CLC reactor. Results show that thermal coupling in the redox process increases the efficiency by up to 2% points for combined, recuperative and hybrid cycles. The studies also show that the thermal efficiency is a function of the reactor purge steam demand, which depends on the reactivity of the oxygen carrier. While purge steam constitutes a monotonic parasitic loss for the combined cycle, for recuperative and hybrid cycles, it raises the efficiency as long as the steam demand is less than a threshold value. This relationship between reactivity and system efficiency provides a useful selection criteria for the oxygen carrier material. Optimization results based on efficiency and levelized cost of electricity (LCOE) identify nickel-based oxygen carriers as the most suitable for the rotary reactor because its high reactivity ensures low steam demand and reactor cost. Compared to nickel, maximum efficiency and minimum LCOE are respectively 7% lower and 40% higher for a copper-based system; iron-based systems have 4% higher maximum efficiency and 7% higher minimum LCOE. This study also showed that optimal efficiency generally has an inverse profile to that for the optimized LCOE. / by Chukwunwike Ogbonnia Iloeje. / Ph. D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1932. / MICROFICHE COPY AVAILABLE IN ENGINEERING. / by Thomas H. Jenkins and Edwin B. Powell, Jr. / B.S.