Matching Items (13)
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- All Subjects: Aerospace Engineering
- Creators: Dahm, Werner
Description
This thesis seeks to further explore off-design point operation of gas turbines and to examine the capabilities of GasTurb 12 as a tool for off-design analysis. It is a continuation of previous thesis work which initially explored the capabilities of GasTurb 12. The research is conducted in order to: 1) validate GasTurb 12 and, 2) predict off-design performance of the Garrett GTCP85-98D located at the Arizona State University Tempe campus. GasTurb 12 is validated as an off-design point tool by using the program to predict performance of an LM2500+ marine gas turbine. Haglind and Elmegaard (2009) published a paper detailing a second off-design point method and it includes the manufacturer's off-design point data for the LM2500+. GasTurb 12 is used to predict off-design point performance of the LM2500+ and compared to the manufacturer's data. The GasTurb 12 predictions show good correlation. Garrett has published specification data for the GTCP85-98D. This specification data is analyzed to determine the design point and to comment on off-design trends. Arizona State University GTCP85-98D off-design experimental data is evaluated. Trends presented in the data are commented on and explained. The trends match the expected behavior demonstrated in the specification data for the same gas turbine system. It was originally intended that a model of the GTCP85-98D be constructed in GasTurb 12 and used to predict off-design performance. The prediction would be compared to collected experimental data. This is not possible because the free version of GasTurb 12 used in this research does not have a module to model a single spool turboshaft. This module needs to be purchased for this analysis.
ContributorsMartinjako, Jeremy (Author) / Trimble, Steve (Thesis advisor) / Dahm, Werner (Committee member) / Middleton, James (Committee member) / Arizona State University (Publisher)
Created2014
Description
Two methods of improving the life and efficiency of the Pulsed Inductive Thruster
(PIT) have been investigated. The first is a trade study of available switches to
determine the best device to implement in the PIT design. The second is the design
of a coil to improve coupling between the accelerator coil and the plasma. Experiments
were done with both permanent and electromagnets to investigate the feasibility of
implementing a modified Halbach array within the PIT to promote better plasma
coupling and decrease the unused space within the thruster. This array proved to
promote more complete coupling on the edges of the coil where it had been weak in
previous studies. Numerical analysis was done to predict the performance of a PIT
that utilized each suggested switch type. This model utilized the Alfven velocity to
determine the critical mass and energy of these theoretical thrusters.
(PIT) have been investigated. The first is a trade study of available switches to
determine the best device to implement in the PIT design. The second is the design
of a coil to improve coupling between the accelerator coil and the plasma. Experiments
were done with both permanent and electromagnets to investigate the feasibility of
implementing a modified Halbach array within the PIT to promote better plasma
coupling and decrease the unused space within the thruster. This array proved to
promote more complete coupling on the edges of the coil where it had been weak in
previous studies. Numerical analysis was done to predict the performance of a PIT
that utilized each suggested switch type. This model utilized the Alfven velocity to
determine the critical mass and energy of these theoretical thrusters.
ContributorsRaines, Taylor (Author) / Takahashi, Timothy T (Thesis advisor) / White, Daniel B (Committee member) / Dahm, Werner (Committee member) / Arizona State University (Publisher)
Created2018
Description
In previous work, the effects of power extraction for onboard electrical equipment and flight control systems were studied to determine which turbine shaft (i.e. high power shaft vs low power shaft) is best suited for power extraction. This thesis will look into an alternative option, a three-spool design with a high-pressure turbine, low-pressure turbine, and a turbine dedicated to driving the fan. One of the three-spool turbines is designed to be a vaneless counter-rotating turbine. The off-design performance of this new design will be compared to the traditional two-spool design to determine if the additional spool is a practical alternative to current designs for high shaft horsepower extraction requirements. Upon analysis, this thesis has shown that a three-spool engine with a vaneless counter-rotating stage has worse performance characteristics than traditional two-spool designs for UAV systems.
ContributorsBurgett, Luke Michael (Author) / Takahashi, Timothy (Thesis advisor) / Dahm, Werner (Committee member) / Trimble, Steve (Committee member) / Arizona State University (Publisher)
Created2019
Description
This thesis encompasses research performed in the focus area of structural health monitoring. More specifically, this research focuses on high velocity impact testing of carbon fiber reinforced structures, especially plates, and evaluating the damage post-impact. To this end, various non-destructive evaluation techniques such as ultrasonic C-scan testing and flash thermography were utilized for post-impact analysis. MATLAB algorithms were written and refined for the localization and quantification of damage in plates using data from sensors such as piezoelectric and fiber Bragg gratings sensors. Throughout the thesis, the general plate theory and laminate plate theory, the operations and optimization of the gas gun, and the theory used for the damage localization algorithms will be discussed. Additional quantifiable results are to come in future semesters of experimentation, but this thesis outlines the framework upon which all the research will continue to advance.
ContributorsMccrea, John Patrick (Author) / Chattopadhyay, Aditi (Thesis director) / Borkowski, Luke (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Department of Military Science (Contributor)
Created2015-05
Description
Advanced aerospace materials, including fiber reinforced polymer and ceramic matrix composites, are increasingly being used in critical and demanding applications, challenging the current damage prediction, detection, and quantification methodologies. Multiscale computational models offer key advantages over traditional analysis techniques and can provide the necessary capabilities for the development of a comprehensive virtual structural health monitoring (SHM) framework. Virtual SHM has the potential to drastically improve the design and analysis of aerospace components through coupling the complementary capabilities of models able to predict the initiation and propagation of damage under a wide range of loading and environmental scenarios, simulate interrogation methods for damage detection and quantification, and assess the health of a structure. A major component of the virtual SHM framework involves having micromechanics-based multiscale composite models that can provide the elastic, inelastic, and damage behavior of composite material systems under mechanical and thermal loading conditions and in the presence of microstructural complexity and variability. Quantification of the role geometric and architectural variability in the composite microstructure plays in the local and global composite behavior is essential to the development of appropriate scale-dependent unit cells and boundary conditions for the multiscale model. Once the composite behavior is predicted and variability effects assessed, wave-based SHM simulation models serve to provide knowledge on the probability of detection and characterization accuracy of damage present in the composite. The research presented in this dissertation provides the foundation for a comprehensive SHM framework for advanced aerospace materials. The developed models enhance the prediction of damage formation as a result of ceramic matrix composite processing, improve the understanding of the effects of architectural and geometric variability in polymer matrix composites, and provide an accurate and computational efficient modeling scheme for simulating guided wave excitation, propagation, interaction with damage, and sensing in a range of materials. The methodologies presented in this research represent substantial progress toward the development of an accurate and generalized virtual SHM framework.
ContributorsBorkowski, Luke (Author) / Chattopadhyay, Aditi (Thesis advisor) / Liu, Yongming (Committee member) / Mignolet, Marc (Committee member) / Papandreou-Suppappola, Antonia (Committee member) / Rajadas, John (Committee member) / Arizona State University (Publisher)
Created2015
Description
The aerospike nozzle belongs to the class of altitude compensating nozzles making it a strong candidate for Space Shuttle Main Engines. Owing to their higher efficiency compared to conventional bell nozzles, the aerospike nozzles are being studied extensively and are being used for many Single State to Orbit (SSTO) designs. A rocket engine nozzle with altitude compensation, such as the aerospike, consumes less fuel than a rocket engine with a bell nozzle. Aerospike nozzles are huge and are often difficult to construct and have to be truncated in order to make them feasible for application in a rocket propulsion system. Consequently, truncation of the aerospike leads to pressure loss under the base, which in-turn decreases the overall thrust produced by the rocket nozzle. To overcome this loss, a technique called base bleed is implemented in which a secondary jet is made to flow through the base of the truncated portion. This thesis uses dynamic pressure contour plots to find out the ideal base bleed mass flow rate to avoid base recirculation in 10 %, 20 % and 30 % truncated aerospike nozzles.
ContributorsNagarajan, Venkatraman (Author) / White, Daniel B (Thesis advisor) / Dahm, Werner (Thesis advisor) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2017
Description
Advanced fibrous composite materials exhibit outstanding thermomechanical performance under extreme environments, which make them ideal for structural components that are used in a wide range of aerospace, nuclear, and defense applications. The integrity and residual useful life of these components, however, are strongly influenced by their inherent material flaws and defects resulting from the complex fabrication processes. These defects exist across multiple length scales and govern several scale-dependent inelastic deformation mechanisms of each of the constituents as well as their composite damage anisotropy. Tailoring structural components for optimal performance requires addressing the knowledge gap regarding the microstructural material morphology that governs the structural scale damage and failure response. Therefore, there is a need for a high-fidelity multiscale modeling framework and scale-specific in-situ experimental characterization that can capture complex inelastic mechanisms, including damage initiation and propagation across multiple length scales. This dissertation presents a novel multiscale computational framework that accounts for experimental information pertinent to microstructure morphology and architectural variabilities to investigate the response of ceramic matrix composites (CMCs) with manufacturing-induced defects. First, a three-dimensional orthotropic viscoplasticity creep formulation is developed to capture the complex temperature- and time-dependent constituent load transfer mechanisms in different CMC material systems. The framework also accounts for a reformulated fracture mechanics-informed matrix damage model and the Curtin progressive fiber damage model to capture the complex scale-dependent damage and failure mechanisms through crack kinetics and porosity growth. Next, in-situ experiments using digital image correlation (DIC) are performed to capture the damage and failure mechanisms in CMCs and to validate the high-fidelity modeling results.
The dissertation also presents an exhaustive experimental investigation into the effects of temperature and manufacturing-induced defects on toughened epoxy adhesives and hybrid composite-metallic bonded joints. Nondestructive evaluation techniques are utilized to characterize the inherent defects morphology of the bulk adhesives and bonded interface. This is followed by quasi-static tensile tests conducted at extreme hot and cold temperature conditions. The damage mechanisms and failure modes are investigated using in-situ DIC and a high-resolution camera. The information from the morphology characterization studies is used to reconstruct high-fidelity geometries of the test specimens for finite element analysis.
ContributorsKhafagy, Khaled Hassan Abdo (Author) / Chattopadhyay, Aditi (Thesis advisor) / Fard, Masoud Y. (Committee member) / Milcarek, Ryan (Committee member) / Stoumbos, Tom (Committee member) / Borkowski, Luke (Committee member) / Arizona State University (Publisher)
Created2022
Description
This thesis describes the extension of an aircraft-style time-step integrating mission performance simulation to address aero-spaceplane design challenges. The result is a computationally lean program compatible with current Multi-Disciplinary Optimization schemes to assist in the conceptual design of hypersonic vehicles. To do this the starting aircraft style “Mission Code” required enhancements to the typical point-mass simulation for high altitude and high Mach flight. Stability parameters and the rigid-body modes of Short-Period and Dutch-Roll are tracked to understand time-domain limits to aerodynamic control, along with monitoring the Lateral Control Departure Parameter to ensure that the aircraft is not prone to spin. Additionally, experience has shown that for high Mach Number flight designers must consider aerothermodynamic effects early in the vehicle design process, and thus, an engineering level aerothermodynamic model is included. Comparisons to North American X-15 flight test datasets demonstrate the validity of this method in that application, and trade studies conducted show the utility of this application.
ContributorsGriffin, Jack Aidan (Author) / Takahashi, Timothy (Thesis advisor) / Dahm, Werner (Committee member) / Rodi, Patrick (Committee member) / Arizona State University (Publisher)
Created2022
Description
This thesis investigates the configurations needed to demonstrate positive lateraldirectional controllability across the flight envelope of a hypersonic vehicle. Itexamines the NASA Space Shuttle Orbiter as a baseline reference configuration, as it
was a successful hypersonic vehicle. However, the Orbiter had limited high-speed
maneuvering capability; it relied on reaction-control jets to augment controllability
due to a strong tendency for its aerodynamics to “control couple.” It was seen that
many problems associated with the control of the hypersonic Orbiter are due to its
slender configuration. This work relies upon the Evolved-Bihrle-Weissman chart as
an accurate indicator of lateral-directional stability and controllability. The also
explores variant configurations of larger wing tip verticals to explore what
configuration changes are needed to reduce dependence on reaction controls.
ContributorsHoopes, Connor Smith (Author) / Takahashi, Timothy (Thesis advisor) / Dahm, Werner (Committee member) / Perez, Ruben (Committee member) / Arizona State University (Publisher)
Created2023
Description
This thesis aims to determine how finite wing aerodynamic loads change in proximity to the ground. In this study, the primary design tool is an inviscid panel method code, VORLAX.
The validation tool is a commercial volume grid CFD package, ANSYS FLUENT. I use VORLAX
to simulate wings with different incidences and aspect ratios to look at how ground effect
impacts spanwise loading and incipient flow separation. Then the results were compared to
widely published equations such as McCormick, Torenbeek, and Hoerner & Borst. Because I
found that these “famous” equations function best only for specific conditions, I propose a
new empirical equation to estimate ground effect lift as a function of aspect ratio and
incidence. Using Stratford’s method to predict signs of flow separation in the inviscid
solutions, I found that variations in the height above the ground were not significant enough
to change the stall angle of low aspect ratio wings. I did find early signs of flow separation
with increasing aspect ratio. I observe significant changes in spanwise loading when in
ground effect; as I narrow the gap, the transverse loading builds higher near the center of the
wing. These effects were more apparent in wings with smaller aspect ratio; higher aspect
ratio wings experience a higher loading gradient near the tips in proximity to the ground. I
found that high aspect ratio wings have a smaller stall angle compared to that of lower
aspect ratio wings; these trends are consistent between the potential flow solution and the
volume grid CFD viscous solution.
ContributorsValenzuela, Jose Vanir (Author) / Takahashi, Timothy (Thesis advisor) / Dahm, Werner (Committee member) / Huang, Huei-Ping (Committee member) / Arizona State University (Publisher)
Created2024