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Full-Text Articles in Mechanical Engineering

Combustion Of Lunar Regolith Mixed With Energetic Additives: Thermodynamic Calculations And Experimental Studies, Francisco Alvarez Jan 2011

Combustion Of Lunar Regolith Mixed With Energetic Additives: Thermodynamic Calculations And Experimental Studies, Francisco Alvarez

Open Access Theses & Dissertations

The future of space exploration will require longer missions in order to better understand the conditions of near-Earth celestial objects, like the Moon or Mars. Future space missions will require the development of goods, such as propulsion fuel and structural materials, produced using the extraterrestrial resources available. The area that develops these technologies is called In-Situ Resource Utilization (ISRU). ISRU allows reducing the payload, and as a consequence reduces the energy consumption and cost of space travel. The production of structural materials on the Moon can be accomplished using Self-Propagating High-Temperature Synthesis (SHS). This work describes the combination of ISRU ...


Design And Cfd Optimization Of Methane Regenerative Cooled Rocket Nozzles, Christopher Linn Bradford Jan 2011

Design And Cfd Optimization Of Methane Regenerative Cooled Rocket Nozzles, Christopher Linn Bradford

Open Access Theses & Dissertations

Liquid rocket engines benefit in life cycle from the active regenerative cooling method which passes the fuel as the coolant through channels surrounding the combustion chamber. These channels are designed and optimized using structural considerations as well as heat transfer theory, then CFD simulations with the software FLUENT are performed for the final analysis. The difficulty in using methane as the fuel/coolant is addressed, and requires the use of the ideal gas numerical model in preliminary CFD simulations. Comparison to real gas numerical models is made, and results also given for one channel design. The techniques utilized herein allow ...


Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores Jan 2011

Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores

Open Access Theses & Dissertations

Most large scale rocket engines use a regeneratively cooled system to cool the rocket engine using either the rocket fuel or oxidizer. The use of liquid methane as a rocket fuel is an emerging technology proving to have several advantages over current rocket fuels. However, liquid methane is lacking the extensive research as a rocket fuel compared to highly used rocket fuels like liquid hydrogen. A heat transfer test rig was built with the goal to characterize the heat transfer characteristics of liquid methane as it passes through a heated channel. The development of the test rig underwent considerations designed ...


Experimental Study Of Thermoelectric Properties For Randomly Distributed Carbon Nanotubes And Silicon Carbide Nanoparticles, Onasis Garcia Jan 2011

Experimental Study Of Thermoelectric Properties For Randomly Distributed Carbon Nanotubes And Silicon Carbide Nanoparticles, Onasis Garcia

Open Access Theses & Dissertations

In this experimental study, the thermoelectric (TE) properties of carbon nanotubes (CNTs) and Silicon carbide (SiC) nanoparticles have been investigated. Nanoparticles were randomly disrtibuted on a non-conductive glass or quartz substrate. The carbon nanotubes used were single-walled and multi-walled type, consisting of approximately 60% semiconducting 40% metallic tubes. The experimental design is analogous to that of a thermocouple measurement, with the nanoparticle layers creating hot and cold joints with a dissimilar metal Alumel (Ni-Al). Voltage (mV), current (μA) and resistance (Ω) values were measured with respect to temperature (°C), and Seeback coefficient values were also calculated in parallel. Summarized results ...


Study Of Probabilistic Approach For Structural Health Assessment Of Aerospace Structures, Jose Antonio Garcia Jan 2011

Study Of Probabilistic Approach For Structural Health Assessment Of Aerospace Structures, Jose Antonio Garcia

Open Access Theses & Dissertations

Current practical approaches used in structural health assessment programs of aerospace structures involve performing a fracture mechanics analysis to verify the safe life of structural components. The analysis typically makes several conservative assumptions implemented by NASA fracture control standard practices for critical structural components. This well-established paradigm for fracture control follows a deterministic approach and, in some cases, the calculations may produce overly conservative remaining life estimates.

This thesis describes the results of a study to approach the health assessment challenge of several critical components using probabilistic methods. The probabilistic analysis takes the current deterministic model and identifies variables that ...


Investigation On Flame Characteristics Of Oxy-Fuel Combustion, Md R. Islam Jan 2011

Investigation On Flame Characteristics Of Oxy-Fuel Combustion, Md R. Islam

Open Access Theses & Dissertations

Oxy-fuel combustion is currently being considered by the U.S Department of Energy as a promising technology for efficient carbon capture. This technology could substantially reduce NOx and CO2 emissions. In addition, the implementation of oxy-fuel combustion technology in a power generation system could potentially reduce negative environmental impacts of fossil fuel use. It also encourages the use of reliable and domestic energy sources. The U.S. Department of Energy has made efforts to investigate the performance of a CO2 and H2O diluted oxy-fuel combustion system in a high-pressure combustor. In an effort to better understand and characterize the fundamental ...


A Combined X-Fem And Level Set Approach For Modeling Composite Material's Micro Structure, Himanshu Kumar Jan 2011

A Combined X-Fem And Level Set Approach For Modeling Composite Material's Micro Structure, Himanshu Kumar

Open Access Theses & Dissertations

Composite materials are usually made of fibers and binding matrix. It's always a challenge to model composite materials' microstructure through the traditional finite element method because construction of an approximation space which is discontinuous across a given line or surface will place strict restrictions on the FE mesh. The interfacing of fibers in composites' microstructure through the standard finite element method is irksome and tedious because the presence of fiber presents a discontinuity in the binding material. In this present work, the composite's microstructure is modeled through the combined approach of Level Set and Extended Finite Element Method ...


Evaluation Methods For Health Monitoring Of Aerospace Structure Rotary Joints, Sergio Armando Navarro Jan 2011

Evaluation Methods For Health Monitoring Of Aerospace Structure Rotary Joints, Sergio Armando Navarro

Open Access Theses & Dissertations

In September 2007, the excessive vibrations played a significant role in the station operation since one of the rotary joints, which provides the station electrical energy, presented an anomaly. The replacement of its bearing components and re-lubrication were necessary to reduce the problem. To avoid a new anomaly, the inspection of the rotary joints performance continues by using the accelerometers data. This thesis presents three new approaches to monitor the vibrations at the International Space Station based on Root-Mean-Square, kurtosis, and Approximate Entropy (ApEn). MATLAB functions and codes were necessary to implement the three monitoring techniques results from the provided ...


Improved Joining Method For Segmental Prestressed Structures, Ralph Warren Jensen Jan 2011

Improved Joining Method For Segmental Prestressed Structures, Ralph Warren Jensen

Open Access Theses & Dissertations

This dissertation addresses the need for more robust and materially efficient structures, specifically structures that absorb higher levels of energy, can self-erect and which have variable reaction capabilities. These structures can take much higher levels of strain and loading compared to current technologies in reinforced concrete and carbon fiber composites. These structures are made using a novel method of joining segmental elements. A great advantage with this segmental structural system is it's survivability under overloaded conditions. During an impact, or concentrated pressure load, the structure will wrap around the impact zone thereby widely distributing the contact stresses. This function ...


Synthesis, Microstructure And Thermal Analysis Of Gd2o3 - Hfo2 Coatings, Chandan Kumar Roy Jan 2011

Synthesis, Microstructure And Thermal Analysis Of Gd2o3 - Hfo2 Coatings, Chandan Kumar Roy

Open Access Theses & Dissertations

Thermal barrier coatings (TBCs) are critical for future gas turbines of advanced coal based power generation systems. The TBCs are protective layers of low thermal conductivity ceramic materials, which prevent the damage of components that are exposed to very high temperature of the hot gases. Due to increasing demand to improve the efficiency, it is necessary to find alternate TBC materials which can withstand higher temperature for longer period than state-of-art TBCs. The present study focuses on the Gd2O3 stabilized HfO2 (GSH) as a potential candidate for TBC. GSH materials were synthesized in bulk and coatings form. The Gd2O3 content ...


Experimental Investigation Of Magnesium/Regolith Combustion For In-Situ Production Of Materials On The Moon, Christopher White Jan 2011

Experimental Investigation Of Magnesium/Regolith Combustion For In-Situ Production Of Materials On The Moon, Christopher White

Open Access Theses & Dissertations

Future settlements on the Moon will require that strong, cost-effective structural materials be developed in whole or in part from locally available resources. Such materials can be created in-situ from the lunar regolith using self-propagating high-temperature synthesis (SHS). By mixing the lunar regolith with metal additives, such as aluminum or magnesium, a combustible mixture is formed which, when ignited, can reach temperatures high enough to allow combustion to be self-sustaining, sintering the lunar regolith without further energy input and without the need for atmospheric oxygen. The resulting products may be strong enough for some structural applications, such as radiation shielding ...


Experimental And Numerical Investigation Of The Effect Of Fuel Composition On Flame Stability On A Gas Turbine Combustor, Gilberto Corona Jan 2011

Experimental And Numerical Investigation Of The Effect Of Fuel Composition On Flame Stability On A Gas Turbine Combustor, Gilberto Corona

Open Access Theses & Dissertations

Gas turbines are used for power generation and aviation all over the world. Fossil fuels remain the main source of energy for the operation of gas turbines but the recent increase in environmental awareness has influenced government agencies to impose stringent limits on pollutant emissions from power generation plants. Pollutant emissions control is one of the major challenges for gas turbine designers. In this study, experimental methods and computational fluid dynamics (CFD) technologies are used to study the problems that arise when coal derived fuels are used in Gas Turbine Combustors.

Gas turbine designers need both experimental data and combustion ...


On Feasibility Of Reducing Metal Fuel Content And Operating Temperatures In Chemical Oxygen Generators, Allen Garcia Jan 2011

On Feasibility Of Reducing Metal Fuel Content And Operating Temperatures In Chemical Oxygen Generators, Allen Garcia

Open Access Theses & Dissertations

Chemical oxygen generators are widely used in aircraft, submarines, spacecraft, and other applications, problems such as combustion instabilities and a risk of fire may be present. For example, due to malfunction of an oxygen generator, fire occurred onboard the Mir Space Station in 1997. It is thus important to improve the process stability and fire safety of chemical oxygen generators. Chemical compositions for oxygen generators include an oxygen source such as sodium chlorate (NaClO3), a transition metal oxide as a catalyst, and a metal fuel to provide energy for self-sustaining combustion. Eliminating or decreasing the metal fuel would decrease the ...