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Full-Text Articles in Mechanical Engineering

Modeling Pyrolysis Of Large Coal Particles With Many Species, Jianqing Li Oct 2016

Modeling Pyrolysis Of Large Coal Particles With Many Species, Jianqing Li

Master's Theses (2009 -)

Coal currently supplies 40% of the world’s electricity needs, and is one of the most important energy sources. As the initial stage of coal combustion, pyrolysis is a thermal decomposition process which converts coal into light gases and tars, which are subsequently consumed in combustion reactions, as well as solid char. Recently there has been interest in using slow pyrolysis as a stand-alone process for the production of chemicals and fuels from large (mm-scale) coal particles. Simulations can be used to efficiently study the impact of pyrolysis conditions on gas, tar and char yields, as well as gas and tar …


Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte Oct 2016

Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte

Master's Theses (2009 -)

This thesis presents the study of fatigue crack propagation in a low carbon steel (ASTM A36) and two different weld metals (AWS A5.18 and AWS A5.28). Fatigue crack propagation data for each weld wire is of interest because of its use for predicting and analyzing service failures. Fatigue crack growth test specimens were developed and fabricated for the low carbon steel base metal and for each weld wire. Weld specimens were stress relieved prior to fatigue testing. Specimens were tested on a closed-loop servo hydraulic test machine at two different load ratios. Fatigue test data was collected to characterize both …


Analysis And Synthesis Of A Planar Reconfigurable Mechanism With A Variable Joint, Peter William Malak Jul 2016

Analysis And Synthesis Of A Planar Reconfigurable Mechanism With A Variable Joint, Peter William Malak

Master's Theses (2009 -)

Currently, there is a demand for mechanisms with variable topology that can perform multiple tasks with the least amount of actuators. These devices have the ability to provide numerous motion profiles within one device. In the following thesis, a specific planar reconfigurable mechanism with a kinematic reconfigurable joint was mathematically modeled. This mechanism functions as a RRRP mechanism in one configuration and as a RRRR in the other and is known as a RRRR-RRRP Mechanism. The kinematics and kinetics of the RRRR-RRRP Mechanism were analyzed with a Lagrangian approach. The models are simulated and verified using a trajectory planner and …


Application Of A Multi-Zone Model For The Prediction Of Species Concentrations In Rapid Compression Machine Experiments, David Wilson Apr 2016

Application Of A Multi-Zone Model For The Prediction Of Species Concentrations In Rapid Compression Machine Experiments, David Wilson

Master's Theses (2009 -)

Accurate chemical kinetic models, which predict species evolution and heat release rates in chemically reactive systems, are essential for further advancements in fuel and combustion technology. An experimental facility that is widely used for evaluating the accuracy of kinetic models is a rapid compression machine (RCM), which creates a well-defined reaction environment by compressing a reactive mixture inside a chamber. Generally, RCM experiments are conducted in order to obtain ignition delay data. However, chemical speciation data provides greater insight into reaction pathways, and is therefore a more rigorous benchmark for validating kinetic models. In order for a chemical kinetic model …


Ramifications Of Projectile Velocity On The Ballistic Dart Penetration Of Sand, Peter Anthony Sable Apr 2016

Ramifications Of Projectile Velocity On The Ballistic Dart Penetration Of Sand, Peter Anthony Sable

Master's Theses (2009 -)

With the advent of novel in-situ experimental measurement techniques, highly resolved quantitative observations of dynamic events within granular media can now be made. In particular, high speed imagery and digital analysis now allow for the ballistic behaviors of sand to be examined not only across a range of event velocities but across multiple length scales. In an attempt to further understand the dynamic behavior of granular media, these new experimental developments were implemented utilizing high speed photography coupled with piezo-electric stress gauges to observe visually accessible ballistic events of a dart penetrating Ottawa sand. Projectile velocities ranged from 100 to …


Modeling And Investigation Of Refrigeration System Performance With Two-Phase Fluid Injection In A Scroll Compressor, Rui Gu Apr 2016

Modeling And Investigation Of Refrigeration System Performance With Two-Phase Fluid Injection In A Scroll Compressor, Rui Gu

Master's Theses (2009 -)

Vapor compression cycles are widely used in heating, refrigerating and air-conditioning. A slight performance improvement in the components of a vapor compression cycle, such as the compressor, can play a significant role in saving energy use. However, the complexity and cost of these improvements can block their application in the market. Modifying the conventional cycle configuration can offer a less complex and less costly alternative approach. Economizing is a common modification for improving the performance of the refrigeration cycle, resulting in decreasing the work required to compress the gas per unit mass. Traditionally, economizing requires multi-stage compressors, the cost of …