Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991. / Includes bibliographical references. / by Norman Lewis Fortenberry. / Sc.D.

Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (leaf 84). / by Amy B. Smith. / Mech.E.

Thesis (B.S. and M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1994. / Includes bibliographical references (leaves 141-142). / The New Products Program (NPP) is a joint venture between the Massachusetts Institute of Technology (MIT) and industrial sponsors. The aims of the program are the advancement of engineering education and the development of new commercial products. This particular project was sponsored by Becton Dickinson, a Fortune 500 biomedical company, to develop a next generation QBC blood analyzer. This thesis documents the mechanical design of the machine as well as the development process used by the MIT student team. The traditional roles of industry and academia in developing new products are being redefined by projects like the BD-NPP. / by Andrés Pieczanski. / B.S.and M.S.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995. / Includes bibliographical references (leaf 54). / by Herbert L. Singleton, Jr. / B.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 99). / This paper continues the work of M. Akilian and A. Husseini on developing a noncontact glass slumping/shaping process. The shift from vertical slumping to horizontal slumping is implemented and various technologies required for the horizontal slumping process are developed. In the horizontal slumping process, a thin sheet of glass is placed in between two horizontal ceramic air bearings with a bearing to glass gap of about 50 pm, and the assembly is heated up to 600*C. The glass is unconstrained in the horizontal plane and must be positioned without any solid contact. Specifically, the technologies developed are: an optical distance sensor for positioning of the glass, glass position control via air bearing fluid shear force and tilt of device, and device mechanisms for operation in 600*C. Glass was slumped horizontally with bearing-to-glass gaps of >50 [mu]m, 36±2.5 pm, and 30.5±2.5 [mu]m. The best flatness achieved was 6.7/3.6+0.5 [mu]m for front/back of the glass sheet, with a gap of 36+2.5 [mu]pm. It was discovered that 600*C is hotter than necessary and that 550*C is still too hot for optimal slumping conditions. In addition, an important shift is made from using an oven, which heats the entire device, to using in-line pipe heaters, which supply heated air. This allows for much quicker heating and cooling times, which decreases slumping time to less than 30 minutes (10 minutes heating, 5 minutes slumping, 10 minutes cooling). / by Edward Sung. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 119-125). / A need exists for small, robust, and efficient cryocoolers operating in the 25-100 K range; however, while technological advances have enabled the development of such machines, a greater understanding of the losses affecting their performance is needed to make informed design tradeoffs. This thesis takes steps to provide this understanding by examining several losses in the context of a multi-stage cryocooler being developed by MIT and Advanced Mechanical Technologies, Inc. Based on a modular Collins-type design, this cryocooler will use computer-controlled floating piston expanders to simultaneously provide 20 and 100 Watts of cooling at 25 and 100 K, respectively. The contributions in this thesis can be divided into two broad categories. The first is concerned with the systems-level efficiency of the cryocooler, and addresses a significant inefficiency caused by an inherent cooler-to-load temperature mismatch. By using an alternative cryocooler configuration with multiple expanders in series, the overall efficiency may be increased by an estimated 24%. A simple memorizable heuristic was also found to estimate the magnitude of the mismatch loss in a given stage of the cryocooler: the fractional increase in operating power is approximately the base-10 logarithm of the pressure ratio divided by twice the number of series expanders, assuming a monatomic working fluid. The second area of research focused on the design of the cryocooler's unique floating piston expanders. A variety of losses affect the performance of these expanders; these range from the obvious to the obscure (e.g., the enhanced "shuttle" heat transfer that arises from reciprocating piston motion) and often favor conflicting design choices. Eleven such losses are discussed along with both existing literature and a new analysis of fluid flow and heat transfer in the piston-cylinder gap. A numerical model incorporating six of these losses was used to gain considerable insight into the design tradeoffs involved in expander design and provide preliminary support for the multi-expander designs discussed earlier. The simulations also challenged a previous design guideline for the piston's stroke length and, unexpectedly, revealed that imperfect expansion and compression can yield a net increase in expander efficiency due to the importance of shuttle heat transfer. / by Martin Alan Segado. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 101-107). / Membrane-based reverse osmosis (RO), which accounts for over 40% of the current worldwide desalination capacity, is limited by the solution-diffusion mode of water transport through a tortuous polymeric active layer. Alternatively, simulations suggest that introducing rigid sub-nanometer pores into the active layer could substantially increase the water permeability and achieve perfect salt rejection. In this thesis, we synthesized MFI (Mobil Five) zeolites that have uniform, well-defined pores of ~~ 5.5 Å and experimentally investigated the transport across these sub-nanometer pores. This porous structure serves as a model framework to experimentally investigate water and salt transport and can be used to suggest the potential performance of such microporous active layers in RO-based desalination. We first developed an experimental methodology that combined vapor sorption analysis with high-pressure infiltration to probe both the role of crystal size and internal surface chemistry on the transport properties. For purely siliceous MFI zeolites, upwards of 100 MPa was required to saturate the porous network to the framework capacity of 35 water molecules per unit cell. However, by introducing hydrophilic (i.e, acidic) defects within the structure, this infiltration pressure was reduced by five orders of magnitude (to ~~ 1 kPa). While increasing the defect density increased the amount of water within the pores at typical RO pressures (~~ 5 - 6 MPa), the diffusivity of this infiltrated water within the more defective zeolites was 1 - 2 orders of magnitude lower than that of the water within the purely siliceous MFI zeolite. This decreased diffusivity, which was attributed to the strong attraction of water to the hydrophilic defect sites, resulted in ~~ 10x decrease in the estimated permeability. We subsequently microfabricated sub-micron thick zeolite-based membranes to investigate transport limited to the zeolite crystals. By quantifying the water flux generated by a concentration gradient (i.e., forward osmosis), the flux across the more hydrophobic MFI zeolites was ~~ 8 - 10x higher than that across the more hydrophilic MFI zeolites. Additionally, although a small amount of meso/macro-sized defects existed in the membranes, no salt transport (within experimental uncertainty) was detected across the zeolite pores, which demonstrated that the pores of MFI zeolites were capable of selectively transporting water and rejecting hydrated salt ions. Collectively, this work presents an improved fundamental understanding of the transport of water that is confined within the sub-nanometer pore structure of zeolites. The insights gained demonstrate the potential of size-selective membranes in water desalination and offers approaches toward improving the performance of future RO membranes. / by Thomas Humplik. / Ph. D.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 78-92). / This thesis investigates a mainstream metal 3-D printing technique (i.e., direct metal laser sintering of stainless steel {SS} 316L) and two relatively new metal additive manufacturing methods (i.e., lost-wax casting of sterling silver using stereolithography-printed wax masters, and binder inkjet printing of SS 316L) for the fabrication, using tens-of-microns sized voxels, of freeform, finely featured, mesoscaled metal structures part of compact systems. Characterization of the 3-D printing methods includes the assessment of dimensional accuracy and in-plane minimum feature size, measurement of vacuum outgassing and porosity, and estimation of thermal and electrical properties of the printed parts. The data demonstrate that binder inkjet printing of SS 316L has associated the smallest in-plane offset, out-of-plane offset, and eccentricity of nominally symmetric features, while showing ultra-high-vacuum compatibility and intrinsic electrical and thermal properties close to those of bulk metal. Characterization of binder inkjet-printed SS 316L MEMS cantilevers shows repeatable micron-level linear actuation and a near-isotropic Young's modulus of the printed material close to the bulk value. Also, current-voltage characteristics in air of binder inkjet-printed SS 316L MEMS corona discharge ionizers with high aspect-ratio tips are presented. In addition, high-resolution microscopy of binder inkjet-printed SS 316L electrodes part of a novel, compact, multi-electrode harmonized Kingdon mass trap estimates at -15 ptm the maximum height difference between the printed part and the digital model. / by Zhumei Sun. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 90-93). / The realization of a standalone microrobotic platform has thus far been elusive due to size, weight, and power constraints. Recently, a novel microhydraulic electrowetting actuator (MEA) has been developed at MIT Lincoln Laboratory, enabling powerful, efficient, and scalable actuation. The MEA's use of efficient (17 > 65%), low-voltage electrowetting (<25 V) and high power density favorably positions the actuator for applications in microrobotics, which includes systems on the centimeter-scale and below. In this thesis, I present the design of a miniature robotic "squid" which features the MEA as the driving component. The system was inspired by cephalopod paralarvae, which predominantly rely on jet propulsion in their early stages of development. The squid robot can produce thrust by diaphragm pump-like operation, in either single-acting or double-acting modes. Since the actuator is a critical component, further modeling and analysis on the MEA is first presented and confirmed by experiments. After demonstrating actuator reliability, the design and fabrication of the squid are presented, from component-level considerations to system assembly procedures. High-resolution 3D printing methods are exploited to fabricate monolithic, multi-material structures and to develop passive flap check valves for gauging the pumping capability of MEA. The pump characteristics are modeled and tested, achieving flow rates of up to 1.79 mL/min. A finalized robotic squid design is predicted to swim at a velocity of 3 cm/s, which is comparable to that of young squid. Suggestions are made for the continued development of the mini-robotic squid. It is hoped that the squid design presented herein will serve as a precursor to more advanced, standalone microrobotic systems, which may find use in medicine and defense-related applications. / by Kevin Dehan Meng. / S.M.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015. / Numbering for pages 3-4 duplicated. Cataloged from PDF version of thesis. / Includes bibliographical references (pages 183-195). / conventional reserves has led to a boom in the use of hydraulic fracturing to recover oil and gas in North America. Among the most significant challenges associated with hydraulic fracturing is water resource management, as large quantities of water are both consumed and produced by the process. The management of produced water, the stream of water associated with a producing well, is particularly challenging as it can be hypersaline, with salinities as high as nine times seawater. Typical disposal strategies for produced water, such as deep well injection, can be unfeasible in many unconventional resource settings as a result of regulatory, environmental, and/or economic barriers. Consequently, on-site treatment and reuse-a part of which is desalination-has emerged as a strategy in many unconventional formations. However, although desalination systems are well understood in oceanographic and brackish groundwater contexts, their performance and design at significantly higher salinities is less well explored. In this thesis, this gap is addressed from the perspective of two major themes: energy consumption and scale formation, as these can be two of the most significant costs associated with operating high-salinity produced water desalination systems. Samples of produced water were obtained from three major formations, the Marcellus in Pennsylvania, the Permian in Texas, and the Maritimes in Nova Scotia, and abstracted to design-case samples for each location. A thermodynamic framework for analyzing high salinity desalination systems was developed, and traditional and emerging desalination technologies were modeled to assess the energetic performance of treating these high-salinity waters. A novel thermodynamic parameter, known as the equipartition factor, was developed and applied to several high-salinity desalination systems to understand the limits of energy efficiency under reasonable economic constraints. For emerging systems, novel hybridizations were analyzed which show the potential for improved performance. A model for predicting scale formation was developed and used to benchmark current pre-treatment practices. An improved pretreatment process was proposed that has the potential to cut chemical costs, significantly. Ultimately, the results of the thesis show that traditional seawater desalination rules of thumb do not apply: minimum and actual energy requirements of hypersaline desalination systems exceed their seawater counterparts by an order of magnitude, evaporative desalination systems are more efficient at high salinities than lower salinities, the scale-defined operating envelope can differ from formation to formation, and optimized, targeted pretreatment strategies have the potential to greatly reduce the cost of treatment. It is hoped that the results of this thesis will better inform future high-salinity desalination system development as well as current industrial practice. / by Gregory P. Thiel. / Ph. D.