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Full-Text Articles in Engineering
Solid Amine-Boranes As High Performance Hypergolic Hybrid Rocket Fuels, Mark A. Pfeil
Solid Amine-Boranes As High Performance Hypergolic Hybrid Rocket Fuels, Mark A. Pfeil
Open Access Dissertations
Hypergolic hybrid rockets have the potential of providing systems that are simple, reliable, have high performance, and allow for energy management. Such a propulsion system can be applied to fields that need a single tactical motor with flexible mission requirements of either high speed to target or extended loitering. They also provide the possibility for alternative fast response dynamic altitude control systems if ignition delays are sufficiently short. ^ Amines are the traditional fuel of choice when selecting a hypergolic combination as these tend to react readily with both nitric acid and dinitrogen tertroxide based oxidizers. It has been found …
Trajectory Design In The Spatial Circular Restricted Three-Body Problem Exploiting Higher-Dimensional Poincare Maps, Amanda F. Haapala
Trajectory Design In The Spatial Circular Restricted Three-Body Problem Exploiting Higher-Dimensional Poincare Maps, Amanda F. Haapala
Open Access Dissertations
In this investigation, the role of higher-dimensional Poincaré maps in facilitating trajectory design is explored for a variety of applications. To begin, existing strategies to implement Poincaré maps for trajectory design applications in the spatial CR3BP are evaluated. New applications for these strategies are explored, including an analysis of the natural motion of Jupiter-family comets that experience temporary capture about Jupiter, and the search for periodic orbits in the vicinity of the primary bodies in the spatial problem. Because current strategies to represent higher-dimensional maps, generally, lead to a loss of information, new approaches to represent all information contained in …
Crossflow Instability And Transition On A Circular Cone At Angle Of Attack In A Mach-6 Quiet Tunnel, Christopher A. C Ward
Crossflow Instability And Transition On A Circular Cone At Angle Of Attack In A Mach-6 Quiet Tunnel, Christopher A. C Ward
Open Access Dissertations
To investigate the effect of roughness on the stationary crossflow vortices, roughness elements 2 inches from the nosetip were created in a Torlon insert section of a 7-deg half-angle cone at 6-deg angle of attack in the Boeing/AFOSR Mach-6 Quiet Tunnel. Roughness elements with depths and diameters on the order of 500 microns were found to have a significant effect on the generation of the stationary vortices and the location of crossflow-induced transition under quiet flow. Crossflow-induced transition was measured under fully quiet flow. The controlled roughness elements also appeared to dominate the generation of the vortices, overwhelming the effect …
Coupled Fluid-Thermal Analysis Of Low-Pressure Sublimation And Condensation With Application To Freeze-Drying, Arnab Ganguly
Coupled Fluid-Thermal Analysis Of Low-Pressure Sublimation And Condensation With Application To Freeze-Drying, Arnab Ganguly
Open Access Dissertations
Freeze-drying is a low-pressure, low-temperature condensation pumping process widely used in the manufacture of bio-pharmaceuticals for removal of solvents by sublimation. The goal of the process is to provide a stable dosage form by removing the solvent in such a way that the sensitive molecular structure of the active substance is least disturbed. The vacuum environment presents unique challenges for understanding and controlling heat and mass transfer in the process. As a result, the design of equipment and associated processes has been largely empirical, slow and inefficient.^ A comprehensive simulation framework to predict both, process and equipment performance is critical …
Analysis Of The Interaction Of Two Parallel Surface Cracks, Jeeyeon Hahn
Analysis Of The Interaction Of Two Parallel Surface Cracks, Jeeyeon Hahn
Open Access Dissertations
The objective of this research is to analyze and predict the interaction of surface cracks that occur in parallel planes. Multiple cracks may form in aging aircraft that forms at stress concentrations such as fastener holes and notched components by stress corrosion and fatigue cracking. The lifetime of the structures are significantly affected by the interaction between these cracks. Depending on relative positions and orientations of neighboring cracks, local stress fields and crack driving forces can be affected by the presence of adjacent cracks. Even small subcritical cracks may rapidly grow to a size that will cause failure in service …
Applications Of Femtosecond Coherent Anti-Stokes Raman Scattering In Combustion, Claresta Nicole Dennis
Applications Of Femtosecond Coherent Anti-Stokes Raman Scattering In Combustion, Claresta Nicole Dennis
Open Access Dissertations
The dissertation deals with the further development of chirped-probe-pulse femtosecond coherent anti-Stokes Raman spectroscopy (CPP fs-CARS) for applications of gas phase thermometry and extension to methane concentration measurements. The main effort has been to assess the usefulness and robustness of the technique in turbulent combustors of practical interest. A primary aim has been to evaluate the use of CPP fs-CARS for vibrational N2 thermometry in a highly turbulent environment. It has been suggested that due to the laser beam temporal overlap required for fs-CARS signal generation, the technique would be unsuccessful due to beam propagation retardation effects from density …
Investigation Of Condensed And Early Stage Gas Phase Hypergolic Reactions, Jacob Daniel Dennis
Investigation Of Condensed And Early Stage Gas Phase Hypergolic Reactions, Jacob Daniel Dennis
Open Access Dissertations
Traditional hypergolic propellant combinations, such as those used on the space shuttle orbital maneuvering system first flown in 1981, feature hydrazine based fuels and nitrogen tetroxide (NTO) based oxidizers. Despite the long history of hypergolic propellant implementation, the processes that govern hypergolic ignition are not well understood. In order to achieve ignition, condensed phase fuel and oxidizer must undergo simultaneous physical mixing and chemical reaction. This process generates heat, intermediate condensed phase species, and gas phase species, which then may continue to react and generate more heat until ignition is achieved. The process is not well understood because condensed and …
Measurements Of Entropy-Layer Instabilities Over Cone-Ogive-Cylinders At Mach 6, Roger T Greenwood
Measurements Of Entropy-Layer Instabilities Over Cone-Ogive-Cylinders At Mach 6, Roger T Greenwood
Open Access Dissertations
Predicting the onset of boundary layer transition is critical in hypersonic flight. To improve transition prediction methods, it is necessary to understand the underlying instability mechanisms that cause transition. Entropy-layer instabilities are of particular interest in the design of blunt reentry vehicles and other blunt supersonic and hypersonic vehicles. Entropy-layer instabilities from outside the boundary layer may enter the boundary layer and have a significant effect on transition. There is little experimental data for entropy-layer instabilities. ^ Experimental measurements of what appear to be entropy-layer instabilities have been made in the Boeing/AFOSR Mach-6 Quiet Tunnel (BAM6QT) using surface pressure transducers …
Measurement Of Combustion Response To Transverse Modes At High Pressure, Matthew Kenneth Wierman
Measurement Of Combustion Response To Transverse Modes At High Pressure, Matthew Kenneth Wierman
Open Access Dissertations
A two dimensional transverse combustor capable of producing and modulating an unstable flowfield was tested at Purdue. The combustor used an array of coaxial ox-centered shear injector elements. The oxidizer posts were able to be discretely changed in length between tests to investigate different post resonance conditions. A single Study element was placed in the middle of the driven unsteady flowfield so its response could be measured using pressure measurement and high speed imagery. This approach was supported by past testing of the longitudinal Continuously Variable Resonance Combustor and past transverse chambers. Mean flow rates and pressures were fixed across …