Department: Aeronautical and Astronautical Engineering ![[clear]](close-x.png "Remove this limiter")
40 matches in the database.
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1.
Al-Qadi, Ibraheem M. A.
Three-dimensional numerical simulation of a supersonic under-expanded rectangular jet.
Degree: PhD, Aeronautical and Astronautical Engineering, 2003, Ohio State University
► A three-dimensional numerical simulation of the unsteady flow in an under-expanded supersonic…
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▼ A three-dimensional numerical simulation of the unsteady flow in an under-expanded supersonic rectangular jet has been conducted for the purpose of investigating and analyzing the production and propagation of jet noise. The compressible three-dimensional Navier-Stokes equations are solved using high-order spatial and temporal differencing schemes. The solution method applies linear and nonlinear filtering schemes to produce oscillation-free shocks and discontinuities while minimizing dissipation effects in smooth regions. The solution method also applies nonreflecting boundary conditions to minimize reflections. Characteristic boundary conditions are implemented at the upstream and far-field boundaries and an absorbing buffer zone is added at the outflow boundary. OpenMP shared- memory model was utilized to parallelize the simulation and good parallel performance was achieved. The code was used to conduct a time dependent numerical simulation of an under-expanded supersonic rectangular jet. A comprehensive database of the simulation was generated. The results of the simulation were validated against experimental measurements and show very good agreement. The simulation is shown to resolve critical unsteady flow features of the jet such as vortex shedding, shock-cell structure, shock shear-layer interaction, flapping, and axis-switching. Visualization of the unsteady flow and analysis of the turbulent flow-field shows that the location of axis-switching is immediately downstream of the fourth shock. It is also observed that the location of the dominant screech source is at the third shock. Two-point space-time correlations demonstrate that the convection velocities in the jet shear layer are highly modulated by the presence of shock waves. Spectral analysis show that the simulation predicts, with good accuracy, screech modes frequencies, wavelengths, phase, and amplitudes. Analysis inside the jet shear layer and in the acoustic near-field reveal exact correspondence in frequency and phase between the inner and the outer parts of the screech loop. The simulation also predicts the complex pattern of the near acoustic field associated with screech. The current simulation represents the first successful three- dimensional numerical simulation of an under-expanded supersonic rectangular jet. It also represents a significant contribution towards accurate prediction of noise production and far-field radiation in supersonic jets. The computational tools developed in this study can be used to investigate a wide range of problems related to unsteady flows and aeroacoustics. A three-dimensional numerical simulation of the unsteady flow in an under-expanded supersonic rectangular jet has been conducted for the purpose of investigating and analyzing the production and propagation of jet noise. The compressible three-dimensional Navier-Stokes equations are solved using high-order spatial and temporal differencing schemes. The solution method applies linear and nonlinear filtering schemes to produce oscillation-free shocks and discontinuities while minimizing dissipation effects in smooth regions. The solution method also applies nonreflecting boundary conditions to minimize reflections. Characteristic boundary conditions are implemented at the upstream and far-field boundaries and an absorbing buffer zone is added at the outflow boundary. OpenMP shared- memory model was utilized to parallelize the simulation and good parallel performance was achieved. The code was used to conduct a time dependent numerical simulation of an under-expanded supersonic rectangular jet. A comprehensive database of the simulation was generated. The results of the simulation were validated against experimental measurements and show very good agreement. The simulation is shown to resolve critical unsteady flow features of the jet such as vortex shedding, shock-cell structure, shock shear-layer interaction, flapping, and axis-switching. Visualization of the unsteady flow and analysis of the turbulent flow-field shows that the location of axis-switching is immediately downstream of the fourth shock. It is also observed that the location of the dominant screech source is at the third shock. Two-point space-time correlations demonstrate that the convection velocities in the jet shear layer are highly modulated by the presence of shock waves. Spectral analysis show that the simulation predicts, with good accuracy, screech modes frequencies, wavelengths, phase, and amplitudes. Analysis inside the jet shear layer and in the acoustic near-field reveal exact correspondence in frequency and phase between the inner and the outer parts of the screech loop. The simulation also predicts the complex pattern of the near acoustic field associated with screech. The current simulation represents the first successful three- dimensional numerical simulation of an under-expanded supersonic rectangular jet. It also represents a significant contribution towards accurate prediction of noise production and far-field radiation in supersonic jets. The computational tools developed in this study can be used to investigate a wide range of problems related to unsteady flows and aeroacoustics.
Advisors/Committee Members: Scott, James.
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2.
Barrows, Sean Thomas.
TURBO Turbulence Model Validation with Recommendations to Tip-Gap Modeling.
Degree: MS, Aeronautical and Astronautical Engineering, 2008, Ohio State University
► Two new turbulence models have been implemented in the turbomachinery flow simulation…
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▼ Two new turbulence models have been implemented in the turbomachinery flow simulation code TURBO. This paper focuses on the validation and implementation of the shear stress transportation (SST) model and the detached eddy simulation (DES) model. The models are validated against experimental data as well as results from the current two-equation, low Reynolds number, K-E model. Validation is conducted on a circular cylinder and the NASA transonic compressor rotor, Rotor 35. Cp and St predictions are examined for the cylinder while operating range and performance figures are examined for Rotor 35.Upon validation, the models are examined for robust performance with regards to the tip-gap modeling of Rotor 35. Currently TURBO standard grids utilize a periodic loss-less tip region. Grid spacing near this region is explored by introducing clustering at the blade tip. A vena-contracta approach and griding of the tip-gap region are also explored.
Advisors/Committee Members: Chen, Jen-Ping.
Subjects: Engineering; Fluid dynamics
Keywords: TURBO; CFD; tip-gap modeling; computational fluid dynamics; turbulence modeling
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3.
Bennett, David W.
Numerical investigation of compressible vortices using the quasi-cylindrical approximation.
Degree: PhD, Aeronautical and Astronautical Engineering, 2007, Ohio State University
► To obtain a better understanding of compressible vortex dynamics, a numerical investigation…
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▼ To obtain a better understanding of compressible vortex dynamics, a numerical investigation of laminar, compressible vortices was conducted using the quasi-cylindrical approximation. The goal was to determine if the phenomena of vortex breakdown would occur. Vortex breakdown is an important and unsolved problem in the field of fluid dynamics. The results show that two possible flow regimes can occur for a potential vortex with a constant edge axial velocity. The first is a vortex that decays in a manner similar to the incompressible vortices examined by Batchelor. The centerline axial velocity decay is driven by the edge axial velocity. Far downstream, the axial velocity profile is nearly constant with the tangential and radial velocities approaching zero. The second flow regime occurs when the edge axial velocity is sufficiently small and vortex breakdown occurs. For a given Mach number, the critical value of edge axial velocity for breakdown was determined. For a set value of the edge axial velocity, the stream wise distance to obtain vortex breakdown was a strong function of the Mach number. As the Mach number increased, the distance to vortex breakdown was decreased.
Advisors/Committee Members: Bodonyi, Richard.
Subjects: Engineering, Aerospace
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4.
Bloxham, Matthew Jon.
A Global Approach to Turbomachinery Flow Control: Loss Reduction using Endwall Suction and Midspan Vortex Generator Jet Blowing.
Degree: PhD, Aeronautical and Astronautical Engineering, 2010, Ohio State University
► A flow control scheme using endwall suction and vortex generator jet (VGJ)…
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▼ A flow control scheme using endwall suction and vortex generator jet (VGJ) blowing was employed to reduce the turbine passage losses associated with the endwall flow field and midspan separation. Unsteady midspan control at low Re had a significant impact on the wake total pressure losses, decreasing the area-average losses by 54%. The addition of leading edge endwall suction resulted in an area-average total pressure loss reduction of 57%. The minimal additional gains achieved with leading edge endwall suction showed that the horseshoe vortex was a secondary contributor to endwall loss production (primary contributor- passage vortex). A similar flow control strategy was employed with an emphasis on passage vortex (PV) control. During the design, a theoretical model was used that predicted the trajectory of the passage vortex. The model required inviscid results obtained from two-dimensional CFD. It was used in the design of two flow control approaches, the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control on the endwall below the passage vortex trajectory. The redirection approach attempted to alter the trajectory of the PV by removing boundary layer fluid through judiciously placed suction holes. Suction hole positions were chosen using a potential flow model that emphasized the alignment of the endwall flow field with inviscid streamlines. Model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade comprised of the highly-loaded L1A blade profile. Detailed wake total pressure losses were measured, while matching the suction and VGJ massflow rates, for the removal and redirection approaches at ReCx=25000 and blowing ratio, B, of 2. When compared with the no control results, the addition of steady VGJs and endwall suction reduced the wake losses by 69% (removal approach) and 68% (redirection approach). The majority of the total pressure loss reduction resulted from the spanwise VGJs, while the suction schemes provided modest additional reductions (<2%). At ReCx=50000, the endwall control effectiveness was assessed for a range of suction rates without midspan VGJs. Area-average total pressure loss reductions of up to 28% were measured in the wake at ReCx=50000, B=0, with applied endwall suction employed using the removal scheme (compared to no suction at ReCx=50000). At which point, the total pressure loss core was almost completely eliminated. PIV showed that the endwall suction changed the location of the PV eliminating its influence on the suction surface of the turbine blade. Suction with the removal approach removed the corner vortex (CV) increasing the available span by more than 10%. The redirection approach was less effective at higher suction rates due to the continual presence of the CV. A system analysis was performed that compared the power needed to operate the flow control system to the power gained by the system. The power gains were assessed by comparing the change in lift and wake total pressure losses with and without flow control. The resultant power ratio showed that only 23% of the total power gained was needed to operate the flow control system for an L1A rotor at ReCx=50000, B=2.
Advisors/Committee Members: Bons, Jeffrey.
Subjects: Engineering
Keywords: turbomachinery; vortex generator jet; flow control; turbine; gas turbine; horseshoe vortex; passage vortex; corner vortex; separation
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5.
Bruzzese, John Reed.
Development Of An Electric Discharge Oxygen-Iodine Laser And Modelling Of Low-Temperature M=4 Flow Deceleration By Magnetohydrodynamic Interaction.
Degree: MS, Aeronautical and Astronautical Engineering, 2008, Ohio State University
► The present work addresses performance optimization of a small-scale, electric discharge excited,…
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▼ The present work addresses performance optimization of a small-scale, electric discharge excited, gasdynamic oxygen iodine laser (DOIL). For this, (i) nitric oxide has been added to the laser mixture, and (ii) iodine vapor was dissociated in an auxiliary electric discharge prior to its injection into the laser flow. The addition of NO has a significant effect on the laser performance, increasing small signal gain in the supersonic laser cavity from 0.05 %/cm to 0.08 %/cm. On the other hand, although large iodine dissociation fractions in the laser cavity have been achieved using an auxiliary discharge (up to 50%), only modest increase in gain was detected. The DOIL laser apparatus has been scaled up, with the main electric discharge volume increased by a factor of four and the flow rate through the laser doubled. The scaled-up laser has been tested using a nanosecond pulser / DC sustainer discharge or a capacitively coupled radio frequency discharge (CCRF) sustained at powers up to 2.7 kW and 4.5 kW, respectively. In both these cases, single-delta oxygen yield of up to 3-4% has been measured. Small signal gain up to 0.116 %/cm has been measured in the laser cavity while using the CCRF discharge to generate singlet delta oxygen. Numerical modeling of magnetohydrodynamic deceleration of a low-temperature M=4 flow was conducted using a three-dimensional compressible Navier-Stokes flow code. The results are in good agreement with recent experiments conducted at Ohio State, where flow deceleration by up to 2% has been demonstrated.
Advisors/Committee Members: Adamovich, Igor.
Subjects: Engineering
Keywords: DOIL; e-COIL; MHD; Magnetohydrodynamic; CFD; Laser; singlet delta oxygen
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6.
Claypool, Ian Randolph.
A theoretical and numerical study of the use of grid embedded axial magnetic fields to reduce charge exchange ion induced grid erosion in electrostatic ion thrusters.
Degree: PhD, Aeronautical and Astronautical Engineering, 2007, Ohio State University
► Decay of ion thruster grids due to impact by charge exchange ions…
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▼ Decay of ion thruster grids due to impact by charge exchange ions is the main life limiting factor in ion propulsion systems. Any system which can reduce the number or energy of ions impacting the grids will add to the life expectancy at current power levels. One possible technique for reducing damage from charge exchange ions would involve the incorporation in the grids of axial aligned embedded magnetic fields. These fields, generated by currents running around the grid apertures would form mini magnetic nozzles guiding beam ions through the aperture while diverting charge exchange ions from directly impacting the grids. A simple computational simulation of the environment within a single set of ion thruster grids has been created for use in evaluating the response of single charge exchange ions to many different grid geometries and field arrangements. This effort involved the development of the ionLite code which simulates the grid geometries, fields, and ion beam charge distribution while allowing individual charge exchange ions to be created at any point and their trajectories and eventual fates to be determined. Using this code the use of auxiliary magnetic fields was examined. This analysis shows that energy transfer to a simulated accelerator grid from charge exchange ions can be reduced by approximately 20%, but only at vary large magnitude magnetic field strengths (order of 100 T). It was found that for the configurations investigated the optimum performance resulted when the applied magnetic field was just enough to cause the particle Larmor radius to be approximately equal to the grid aperture radius. The use of lower mass propellants such as Neon or Helium allow for this benefit at fields on the order of 20 T. The potential impact of the embedded magnetic fields is shown to be very sensitive to grid geometry, and therefore it is probable that a different configuration could provide even greater reduction in kinetic energy transfer at moderate field levels.
Advisors/Committee Members: York, Thomas M.
Subjects: Engineering, Aerospace
Keywords: Ion Propulsion, Charge Exchange Ions, Ion Thruster Grid Erosion, Charged Particle Simulations, Particle in Cell Code
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7.
Cramer, Klaron Nathanael.
Design, Construction, and Preliminary Validation of the Turbine Reacting Flow Rig.
Degree: MS, Aeronautical and Astronautical Engineering, 2009, Ohio State University
► This thesis presents the design, construction and partial operation of the Turbine…
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▼ This thesis presents the design, construction and partial operation of the Turbine Reacting Flow Rig (TuRFR), which is a high temperature turbine vane test facility at The Ohio State University’s Aeronautical and Astronautical Research Laboratory. It is capable of producing combustor temperatures up to 2200°F and is rated for normal operation at pressures of 30 psig. The facility matches real engine flow parameters such as Mach number, gas temperature, density ratio, pattern factor, and turbulence level. It is designed to test industry hardware and has a modular design to allow for various turbine vane shapes and sizes. It consists of a steel base (for flow conditioning and supporting of the burner), natural gas burner (for elevating the gas temperature), spool piece (for viewing burner during operation), cone (for accelerating the flow), equilibration tube (for allowing entrained seed particles to reach thermal and kinematic equilibrium), transition piece (for sealing with the equilibration tube and transitioning from a circular to rectangular cross section), view section (for optical access to the turbine vanes), and vane holder (for securely holding the turbine vane in place during experiments). It is capable of providing film cooling air at a density ratio of 2.8, with plans to upgrade the heating system for lower density ratios. To date, the facility has been tested at mass flowrates up to 2.6 lbm/s, which is adequate mass flow to fill four 1st stage high pressure vane passages from a modern high bypass aero-engine at a representative inlet Mach number of 0.25 and gas temperature of 2200°F.
Advisors/Committee Members: Bons, Jeffrey.
Subjects: Aerospace materials; Engineering
Keywords: turbine; reacting flow; facility; deposition
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8.
Gero, Ryan Micah.
Low-Impact and Damped State Feedback Control of a Solar Sail on an Optimal Non-Keplerian Planet-Centered Orbit.
Degree: MS, Aeronautical and Astronautical Engineering, 2009, Ohio State University
► Consider the most fundamental difference between a solar sail and conventional spacecraft:…
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▼ Consider the most fundamental difference between a solar sail and conventional spacecraft: propellant. In order to effect propulsion, solar sails receive a constant supply of massless photons to reflect while conventional spacecraft must carry a limited supply of fuel. At first glance, solar sails are infinitely more efficient than conventional spacecraft simply because of this fact. However, while certainly an advantage to solar sailing, propellant consumption is not the proper metric for spacecraft comparison or the only appealing facet of the solar sail.It can be shown by a reasonable and straightforward analysis that solar sails have the potential to out-perform conventional spacecraft on the basis of effective specific impulse, a parameter that incorporates launch and payload masses as well as total mission duration via an adaptation of the illustrious rocket equation. Pair an aggressive specific impulse with the orbital possibilities that arise when solar sail performance is at a level capable of producing spacecraft accelerations the same order of magnitude as local solar or planetary gravitational acceleration, and the engineer finds significantly fewer constraints limiting the design of future space missions. Imagine a spacecraft for which a Lagrange equilibrium point becomes a large surface, rather than a singular location, on which it is able to remain at rest. Picture a space vehicle hovering high above an ecliptic plane or perhaps racing along some other non-Keplerian orbit taking measurements and relaying signals from positions previously untenable. Solar sails can do all of these things, and it is the intent of this body of work to generate a proof of concept for one of the most attainable and pertinent capabilities unique to solar sails mentioned thus far. In the pages that follow it will be shown that a solar sail is inherently stable for some of the optimal non-Keplerian family of planet-centered orbits, and can be stabilized by straightforward control schemes for the rest. Beginning from scratch with a radiation pressure model, gain parameters were developed for low-impact and damped state feedback control via sail pitch attitude variation. Optimal orbits are attainable, as these trajectories were designed to minimize the required spacecraft acceleration and thus lower the solar sail performance requirement. Planet-centered orbits are pertinent, since a solar sail must inevitably begin its journey by escaping from the planet Earth and most of NASA’s recent efforts in space are geared towards the exploration of nearby planets and their moons. Uniqueness stems from the specification of the non-Keplerian family of orbits, since solar sails are capable of sustaining them whereas modern conventional spacecraft are not. In today’s day and age, with payload miniaturization and the ability to manufacture extremely light weight reflective materials, solar sailing has the potential to become reality within the next five to ten years. The concepts highlighted in this thesis have a significant probability of being among the first demonstrated capabilities of solar sail spacecraft once they take flight.
Advisors/Committee Members: Freuler, Richard.
Subjects: Astrophysics; Engineering
Keywords: solar sail; optimal non-Keplerian planet-centered orbit; solar sail control; damped state feedback control; astrophysics
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9.
Gompertz, Kyle Adler.
Separation Flow Control with Vortex Generator Jets Employed in an Aft-Loaded Low-Pressure Turbine Cascade with Simulated Upstream Wakes.
Degree: MS, Aeronautical and Astronautical Engineering, 2009, Ohio State University
► Detailed pressure and velocity measurements were acquired at Rec = 20,000 with…
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▼ Detailed pressure and velocity measurements were acquired at Rec = 20,000 with 3% inlet free stream turbulence intensity to study the effects of position, phase and forcing frequency of vortex generator jets employed on an aft-loaded low-pressure turbine blade in the presence of impinging wakes. The L1A blade has a design Zweifel coefficient of 1.34 and a suction peak at 58% axial chord, making it an aft-loaded pressure distribution. At this Reynolds number, the blade exhibits a non-reattaching separation region beginning at 60% axial chord under steady flow conditions without upstream wakes. Wakes shed by an upstream vane row are simulated with a moving row of cylindrical bars at a flow coefficient of 0.91. Impinging wakes thin the separation zone and delay separation by triggering transition in the separated shear layer, although the flow does not reattach. Instead, at sufficiently high forcing frequencies, a new time-mean separated shear layer position is established which begins at approximately 72%Cx. Reductions in area-averaged wake total pressure loss of more than 75% were documented. One objective of this study was to compare pulsed flow control using two rows of discrete vortex generator jets (VGJs). The VGJs are located at 59%Cx, approximately the peak Cp location, and at 72%Cx. Effective separation control was achieved at both locations. In both cases, wake total pressure loss decreased 35% from the wake only level and the shape of the Cp distribution indicates that the cascade recovers its high Reynolds number (attached flow) performance. The most effective separation control was achieved when actuating at 59%Cx where the VGJ disturbance dominates the dynamics of the separated shear layer, with the wake disturbance assuming a secondary role only. On the other hand, when actuating at 72%Cx, the efficacy of VGJ actuation is derived from the relative mean shear layer position and jet penetration. When the pulsed jet actuation (25% duty cycle) was initiated at the 72%Cx location, synchronization with the wake passing frequency (8.7Hz) was critical to produce the most effective separation control. A 20% improvement in effectiveness over the wake-only level was obtained by aligning the jet actuation between wake events. A range of blowing ratios was investigated at both locations to maximize separation reduction with minimal mass flow. The optimal control parameter set for VGJ actuation at 72%Cx does not represent a reduction in required mass flow compared to the optimal parameter set for actuation at 59%Cx. Differences in the fundamental physics of the jet interaction with the separated shear layer are discussed and implications for the application of flow control in a full engine demonstrator are reviewed. Evidence suggests that flow control using VGJs will be effective in the highly unsteady LPT environment of an operating gas turbine, provided the VGJ location and amplitude are adapted for the specific blade profile.
Advisors/Committee Members: Bons, Jeffrey.
Subjects: Aerospace materials; Engineering; Fluid dynamics; Mechanical engineering
Keywords: flow control, vortex generator jets, negative jet, low pressure turbine aerodynamics, simulating wakes
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10.
Haldeman, Charles W.
An experimental investigation of clocking effects on turbine aerodynamics using a modern 3-D one and one-half stage high pressure turbine for code verification and flow model development.
Degree: PhD, Aeronautical and Astronautical Engineering, 2003, Ohio State University
► This research uses a modern 1 and 1/2 stage high-pressure (HP) turbine…
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▼ This research uses a modern 1 and 1/2 stage high-pressure (HP) turbine operating at the proper design corrected speed, pressure ratio, and gas to metal temperature ratio to generate a detailed data set containing aerodynamic, heat-transfer and aero-performance information. The data was generated using the Ohio State University Gas Turbine Laboratory Turbine Test Facility (TTF), which is a short-duration shock tunnel facility. The research program utilizes an uncooled turbine stage for which all three airfoils are heavily instrumented at multiple spans and on the HPV and LPV endwalls and HPB platform and tips. Heat-flux and pressure data are obtained using the traditional shock-tube and blowdown facility operational modes. Detailed examination show that the aerodynamic (pressure) data obtained in the blowdown mode is the same as obtained in the shock-tube mode when the corrected conditions are matched. Various experimental conditions and configurations were performed, including LPV clocking positions, off-design corrected speed conditions, pressure ratio changes, and Reynolds number changes. The main research for this dissertation is concentrated on the LPV clocking experiments, where the LPV was clocked relative to the HPV at several different passage locations and at different Reynolds numbers. Various methods were used to evaluate the effect of clocking on both the aeroperformance (efficiency) and aerodynamics (pressure loading) on the LPV, including time-resolved measurements, time-averaged measurements and stage performance measurements. A general improvement in overall efficiency of approximately 2% is demonstrated and could be observed using a variety of independent methods. Maximum efficiency is obtained when the time-average pressures are highest on the LPV, and the time-resolved data both in the time domain and frequency domain show the least amount of variation. The gain in aeroperformance is obtained by integrating over the entire airfoil as the three-dimensional effects on the LPV surface are significant. This research uses a modern 1 and 1/2 stage high-pressure (HP) turbine operating at the proper design corrected speed, pressure ratio, and gas to metal temperature ratio to generate a detailed data set containing aerodynamic, heat-transfer and aero-performance information. The data was generated using the Ohio State University Gas Turbine Laboratory Turbine Test Facility (TTF), which is a short-duration shock tunnel facility. The research program utilizes an uncooled turbine stage for which all three airfoils are heavily instrumented at multiple spans and on the HPV and LPV endwalls and HPB platform and tips. Heat-flux and pressure data are obtained using the traditional shock-tube and blowdown facility operational modes. Detailed examination show that the aerodynamic (pressure) data obtained in the blowdown mode is the same as obtained in the shock-tube mode when the corrected conditions are matched. Various experimental conditions and configurations were performed, including LPV clocking positions, off-design corrected speed conditions, pressure ratio changes, and Reynolds number changes. The main research for this dissertation is concentrated on the LPV clocking experiments, where the LPV was clocked relative to the HPV at several different passage locations and at different Reynolds numbers. Various methods were used to evaluate the effect of clocking on both the aeroperformance (efficiency) and aerodynamics (pressure loading) on the LPV, including time-resolved measurements, time-averaged measurements and stage performance measurements. A general improvement in overall efficiency of approximately 2% is demonstrated and could be observed using a variety of independent methods. Maximum efficiency is obtained when the time-average pressures are highest on the LPV, and the time-resolved data both in the time domain and frequency domain show the least amount of variation. The gain in aeroperformance is obtained by integrating over the entire airfoil as the three-dimensional effects on the LPV surface are significant.
Advisors/Committee Members: Dunn, Michael G.
Subjects: Engineering, Aerospace
Keywords: Short-duration experiements; high pressure turbine; clocking; pressure measurements; heat-flux measurements
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11.
Hollis, Rebecca M.
The Effects of Localized Blade Endwall Suction on Surface Heat Transfer.
Degree: MS, Aeronautical and Astronautical Engineering, 2009, Ohio State University
► Two methods of flow control were designed to mitigate the effects of…
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▼ Two methods of flow control were designed to mitigate the effects of the horseshoe vortex structure (HV) at an airfoil/endwall junction. An experimental study was conducted in a low-speed wind tunnel to quantify the effects of localized boundary layer removal on surface heat transfer. A transient infrared technique was used to measure theconvective heat transfer values along the surrounding surface. Particle image velocimetry was used to collect the time-mean velocity vectors of the flow field adjacent to the endwall along three planes of interest. Boundary layer suction was applied through a thin slot, in the leading edge of the airfoil at two heights. The first height, referred to as Method 1, was immediately along the endwall, the second height, Method 2, was located at ~1/3 of the approaching boundary layer height. Five suction rates were tested, 0%, 6.5%, 11%, 15% and 20% of the boundary layer mass flow was removed at a constant rate. Both methods reduced the effects of the HV with increasing suction on the symmetry, 0.5-D and 1-D planes. Method 2 performed better at reducing the surface heat transfer but Method 1 outperformed Method 2 aerodynamically by completely removing the HV structure when the 11% suction rate was applied. This method however produced other adverse effects such as high surface shear stress and localized areas of high heat transfer near the slot edges at high suction rates.
Advisors/Committee Members: Bons, Jeffrey P.
Subjects: Fluid dynamics
Keywords: horseshoe vortex; flow control; boundary layer removal; heat transfer
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12.
Hong, Soonyoung.
An effective data mining approach for structure damage indentification.
Degree: PhD, Aeronautical and Astronautical Engineering, 2007, Ohio State University
► An efficient, neural network based, online nondestructive structural damage identification procedure is…
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▼ An efficient, neural network based, online nondestructive structural damage identification procedure is developed for determining the damage characteristics (the damage locations and the corresponding severity) from dynamic measurements in near real-time. The procedure utilizes unique data processing techniques to track the most useful modal information based on modal strain energy and to calculate the associated data based on principal component analysis for further processing in a neural network based identification scheme. With two unique features, this approach is significantly different from currently available damage identification procedures for real-time structural integrity monitoring/diagnostics. First, the most sensitive mode for the specific damage is selected in an automatic process which increases the accuracy of damage identification and decreases time spent on neural network training. Second, the approach creates unique data that extracts core characteristics from modal information for a number of different damage cases; and consequently, the accuracy of the damage identification improves significantly. This approach can be operated online providing real time structural damage identification. The method is tested for simulated damage cases, including situations of single and multiple damage in the closely-spaced frequencies of Kabe's model. The philosophy behind the proposed research is to provide a means to online and nondestructively predict the degradation of a structure's integrity (i.e. damage location and the corresponding severity, strength loss).
Advisors/Committee Members: Shen, Mo-How Herman.
Keywords: Structure Health Monitoring; Vibration Based Damage Identification; Principal Component Analysis; Modal Strain Energy
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13.
Huang, Hsun-Hsuan.
Controller Design for Stability and Rollover Prevention of Multi-body Ground Vehicles with Uncertain Dynamics and Faults.
Degree: PhD, Aeronautical and Astronautical Engineering, 2009, Ohio State University
► Rollover prevention is a fundamental and significant issue for vehicle safety research.…
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▼ Rollover prevention is a fundamental and significant issue for vehicle safety research. Passenger and commercial vehicles with a relatively high center of gravity are especially prone to rollover. Rollover is a threat especially for military vehicles, which operate in severe operational environments and maneuvers. Additional assistance from active anti-rollover control systems can mitigate the deficiency in human capability. Furthermore, the ant-rollover control systems have to accommodate perturbations in the rollover parameters (e.g., speed and road adhesion coefficient) and external disturbances (such as adverse weather and terrain conditions) and have to be fault-tolerant in order to enhance rollover prevention. Thus, with rollover prevention of military multi-body ground vehicles as the objective of this research, in this dissertation, we first propose a novel control system analysis and design technique by extending the popular Linear Quadratic Regulator (LQR) control design method specializing it for the ‘control coupled output regulation’ problem. Specifically, in this rollover prevention problem, a ‘unified rollover index’ is proposed, which captures both the roll dynamics and lateral dynamics, explicitly into the optimization procedure of the LQR framework, which results in a performance index with a coupled term in state and control variables. Thus, the proposed rollover prevention technique effectively incorporates the physical nature of the vehicle dynamics into the problem formulation resulting in significantly improved performance. Moreover, the proposed technique allows us to compare different controller configurations and select the most efficient controller structure in terms of both control effort as well as cost. It is shown that because of the inherent coupling the system has, sometimes it is possible that a well designed single controller (actuator) can result in better performance than multiple controllers (actuators) with improper design. The proposed methodology is illustrated with two applications in the vehicle dynamics area. In the first application, an active steering control system is designed which shows the improved roll over prevention capability of the proposed design compared to the existing designs in the literature. The second application considers a more complicated tractor semi-trailer vehicle and shows how a single active anti-roll bar system at the trailer unit gives better performance than multiple-axle actuators at tractor and trailer together with the double lane change maneuver as the external disturbance. Next the issue of robust control design to handle uncertainties in the vehicle dynamics parameters as well as component faults. Based on the theory of ‘Linear interval parameter matrix families’, a single robust full state feedback control gain is designed by a convex combination of the control gains designed for finite points (vertices) of the uncertain parameter space. The uncertainty in the forward speed of the vehicle and the road adhesion coefficient are considered I the he proposed robust controller design. The results show the efficacy of the proposed robust controller under the assumed perturbations. Therefore, the proposed techniques not only prevent rollover of multi-body ground vehicles with controllers of reduced control effort (which means actuator and power savings) but also guarantee the stability and performance for vehicles with uncertain dynamics and faults.
Advisors/Committee Members: Yedavalli, Rama K.
Subjects: Engineering; Mechanical engineering
Keywords: rollover prevention, rollover index, LQR design, coupling effect, robust control, uncertain dynamics, faults, linear interval parameter matrix families
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14.
Janiszewska, Jolanta M.
Three dimensional aerodynamics of a simple wing in oscillation including effects of vortex generators.
Degree: PhD, Aeronautical and Astronautical Engineering, 2004, Ohio State University
► A comprehensive experimental program has been conducted on a LS(1)-0421MOD airfoil model…
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▼ A comprehensive experimental program has been conducted on a LS(1)-0421MOD airfoil model in the 3'x5' OSU subsonic wind tunnel. Surface pressure distributions were obtained for 2D baseline and 3D configurations under clean and surface grit conditions. Several vortex generator configurations were evaluated. The data were taken for steady state and unsteady conditions. The steady state data included angles of attack from 0 to 30 degrees and Reynolds numbers of 1.0 million. The unsteady conditions were simulated using a face cam that provided a sinusoidal angle of attack variation with 10 degrees amplitude for three frequencies of 0.6 and 1.8 Hz at mean angles of attack of 8, 14 and 20 degrees. Surface pressure data were obtained from six spanwise stations, which were integrated to local coefficients. The maximum 2D lift coefficient obtained for the 1.0 million Reynolds number was 1.58 at 14.4 degrees angle of attack. For the 3D case the maximum lift coefficient at the wall was 1.58 at 19.5 degrees and at the tip was 1.20 at 18.3 degrees. The results showed that the application of the grit roughness reduces the maximum lift coefficients in all configurations by as much as 50%. The Flat and Curled vortex generators increased the maximum lift coefficient for both the 3D tip and wall stations, up to 1.6 and 1.92, respectively. The application of the vortex generators shifted the stall angle of attack by approximately 30%. A gritted model with the vortex generators saw an increase in both the maximum lift and stall angle of attack by approximately 25% in comparison to grit only. The unsteady maximum lift coefficients were always higher than those for the steady state up to 60% and showed, generally, large hysteresis loops. The hysteresis loops were smaller for the 3D wing configuration due to the tip vortex influence, therefore smallest hysteresis loops occurred at the tip. The Flat and Curled vortex generators removed the hysteresis loops for all frequencies at 14 degrees mean angle and significantly reduced the minimum value of the pitching moment and the pressure drag at stall.
Advisors/Committee Members: Gregorek, Gerald.
Subjects: Engineering, Aerospace
Keywords: three dimensional; wing; unsteady; oscillating; vortex generators; grit
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15.
Johnson, Benjamin P.
Observed Flow Characteristics of Rotating Stall Inception and its Prevention Using Discrete Tip Injection in the NASA Stage 35 Axial Compressor with New Analysis Methods.
Degree: MS, Aeronautical and Astronautical Engineering, 2008, Ohio State University
► In order to further our understanding of the effects of tip injection…
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▼ In order to further our understanding of the effects of tip injection in preventing rotating stall, a number of computational cases were run which modeled stall inception in the NASA compressor Stage 35. The flow solver TURBO, written and developed by Dr. Jen-Ping Chen, was used and new post-processing analysis methods were implemented in these cases. These include the investigation of three-dimensional disturbance (zero axial velocity) pockets, diffusion factor analyses, angle of attack analyses, and negative axial velocity volume measurements. The utilization of these methods led to a number of observations. The first was that the three-dimensional disturbances were first formed in the mid-span of the rotor passages and then migrated to the tip region. Secondly, in both the stable and unstable cases, the disturbances travelled at 100% rotor speed around the annulus upon their inception. The third observation made was that, in stalling cases, the disturbances would eventually occupy the entire breadth of a rotor passage in the vicinity of the tip. Upon this occurrence, the disturbance would begin to propagate upstream of the leading edge of the rotor blade. It would then migrate around the rotor leading edge, merging with the disturbances in the adjacent passages while slowing to approximately 50% rotor speed. The diffusion factor and angle of attack analyses proved less conclusive than had been hoped in providing a definitive, quantitative indication of the inevitability of stall. The original hope was that one or both of these parameters would prove to be a reliable, definitive indicator of the inevitable onset of stall at a given throttle. The diffusion factor analysis provided a means to indicate qualitative differences between different cases, i.e. indicating whether one case is more likely to stall than another. The angle of attack analysis, for the most part, seemed to accurately reflect the actual flow conditions - high angles of attack were recorded for blades which exhibited leading-edge flow separation. Two cases were chosen to represent a stable and stalling case. The results of the stable case indicate that the tip injectors maintain stability in the compressor by preventing the formation of disturbances which occupy the full breadth of a given rotor passage. As the disturbances migrated toward the tip, the injectors would wash them away. To maintain stable operation, some disturbances required passage through the influence of only one injector, while in other cases passage through multiple injectors was required. The results of the unsteady case indicate that if the amount of injection is insufficient, the subsequent merging and growth of the disturbances blocks a significant portion of the rotor face and prevents sufficient mass flow from getting through, resulting in rotating stall.
Advisors/Committee Members: Chen, Jen-Ping.
Subjects: Engineering
Keywords: Rotating Stall; Axial Compressor; NASA Stage 35
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18.
Krumanaker, Matthew Lee.
Aerodynamics and Heat Transfer for a Modern Stage and One-Half Turbine.
Degree: MS, Aeronautical and Astronautical Engineering, 2003, Ohio State University
► This paper describes measurements obtained for a state of the art one…
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▼ This paper describes measurements obtained for a state of the art one and one-half stage turbine with emphasis on the experimental results. As part of the experimental effort, the position of the HPT vane was clocked relative to the downstream LPT vane to determine the influence of vane clocking on the unsteady pressure loadings on the LPT vane and the HPT blade. In addition, the axial location of the HPT vane relative to the HPT blade was changed to investigate the combined influence of vane/blade spacing and clocking on the unsteady pressure loading. In recent years, other investigators have also examined clocking and vane/blade spacing (but not within the same data set) using different turbine stages and those works will be put into perspective with this work. Time-averaged and time-accurate surface pressure will be presented for several spanwise locations on the vanes and blade. Results were obtained at four different clocking positions for the HPT vane and for two different vane/blade axial spacings at three (of the four) clock positions. This thesis also describes the heat transfer results for a measurement program utilizing the same state of the art one and one-half stage transonic turbine. Both aerodynamic data (surface pressure data) and heat transfer data were obtained at the 50% span location on the HPT vane, HPT blade, and LPT vane. The heat flux data are normalized and presented as time-averaged Stanton numbers and compared to flat plate correlations. Time accurate Stanton numbers are also presented for selected locations on the HPT blade and on the blade outer air seal.
Advisors/Committee Members: Dunn, Michael G.
Subjects: Engineering, Aerospace
Keywords: Gas Turbine Heat Transfer and Aerodynamics
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19.
Luk, Daniel H.
Steady Heat Transfer Predictions For A Highly Loaded Single Stage Turbine With Flat Tip.
Degree: MS, Aeronautical and Astronautical Engineering, 2008, Ohio State University
► This thesis presents steady computational predictions for a single stage (2-blade-row), highly…
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▼ This thesis presents steady computational predictions for a single stage (2-blade-row), highly loaded, turbine. Computational predictions and experimental measurements of heat flux are compared for both the stator vane and the rotor blade with a flat tip. Comparisons for both blade rows are presented at three different spanwise locations as well as on the hub and casing endwalls and rotor tip. The experimental measurements were taken from earlier experiments conducted at the Ohio State University Gas Turbine Laboratory Test Facility. The computational predictions were achieved using TURBO. This CFD code is a 3D, Reynolds-Averaged Navier-Stokes (RANS), computational fluid dynamics code capable of handling unsteady flows. The CFD solutions were steady and computed as two separate computations. First, the stator vane simulation was performed using known inlet and exit boundary conditions. Then, inlet boundary conditions for the rotor blade simulation were taken from radial exit profiles of the steady stator vane solution and exit boundary conditions for the rotor blade was taken from previous CFD solutions which involved a 3-blade row simulation. The CFD heat transfer predictions compared well with the stator vane experimental values. The CFD heat flux prediction comparisons with the experimental measurements for the rotor blade were only fair. The largest percent error between the computation and the experimental measurements was 25%. The predictions for the hub of the rotor blade had good agreement with the experimental data. Most of the predictions were within the tight scatter of experimental data. The CFD heat transfer prediction for the rotor tip had good agreement with previous computational predictions but only fair agreement with experimental data. The rotor tip predictions for heat transfer were on average 15.5% greater than the experimental measurements. The rotor blade casing surface heat transfer results are presented in this thesis, however there were no other data for the results to be compared to. Detailed analysis and discussion over the CFD predictions and results are contained in this thesis.
Advisors/Committee Members: Chen, Dr. Jen-Ping.
Subjects: Engineering
Keywords: TURBO; CFD; heat transfer; predictions; steady state; stator; rotor
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21.
Marriott, Darin William.
Magnetoplasmadynamic thruster behavior at the hundred megawatt level.
Degree: PhD, Aeronautical and Astronautical Engineering, 2003, Ohio State University
► Characteristic measurements were made of a hundred megawatt modified helium inverse pinch…
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▼ Characteristic measurements were made of a hundred megawatt modified helium inverse pinch switch and compared against numerical modeling and theoretically expected behavior. Thruster voltage was measured for currents between three and three hundred kilo amps and for mass flow rates between 0.96 and 40 grams per second. From that, characteristic voltage, power, and resistance curves were generated. Electron temperature measurements made inside the plasma flow were found to be between three and thirty electron volts. General expected behavior, such as decreasing resistance with increasing mass flow rate, were confirmed. The quasi steady assumption was studied between 1.5 and 1.7 milliseconds and found to be appropriate. A theoretical model, based on normal MPD thrust behavior, was used to estimate fall voltages and pumping coefficients. An empirical model for thruster voltage was then created to estimate the behavior of voltage as a function of the similarity parameter. The two models were then put together and found to be self consistent with the experimental data. Total temperatures, specific impulses, and efficiencies for assumed isentropic nozzle expansion were then calculated.
Advisors/Committee Members: Gregorek, Gerald.
Subjects: Engineering, Aerospace
Keywords: MPD Thruster; Gigawatt; Pulseline
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22.
Mikellides, Yiangos George.
Theoretical modeling and optimization of ablation-fed pulsed plasma thrusters.
Degree: PhD, Aeronautical and Astronautical Engineering, 1999, Ohio State University
► Theoretical modeling of ablation-fed, pulsed plasma thrusters (PPTs) with the MACH2 code…
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▼ Theoretical modeling of ablation-fed, pulsed plasma thrusters (PPTs) with the MACH2 code has shown that after repeated pulsed operation, the total expelled mass is due to ablation during the discharge and solid decomposition that persists long after the pulse. The latter mass does not considerably contribute to the impulse-bit thus degrading thruster performance. For the rectangular PPT geometry, optimizing current waveforms in combination with channel widths are presented, that utilize all decomposed mass, electromagnetically. These waveforms are characterized by short rise times (<1 µsec) and prolonged decays (>25 µsec). Simplified modeling based on steady-state, one-dimensional flow reveals that the mass flow rate varies linearly with the square of the magnetic field and that the downstream flow speed is driven towards the Alfven wave speed when the magnetic pressure is much greater than the gasdynamic pressure. The model has been confirmed by MACH2. The mass flow requirement for such magnetosonic flow in turn, determines the surface temperature of the solid.Numerical simulations of coaxial geometries show that, compared with the rectangular, annular and linear pinch configurations, only an arrangement which operates an inverse-pinch discharge offers the convenience of axisymmetry for better correlation between theory and experiment, and operation at relatively high magnetic fields with propellant temperatures below the decomposition limit. Design guidelines for an inverse pinch thruster are provided. The inverse-pinch discharge produced by a non-reversing, waveform that rises to 18 kAmps in 0.625 μsec and decays in 6 μsec, in a lcm-(propellant) radius thruster, is found to prevent solid decomposition while still providing ablated mass for accelaration. At these lower magnetic field levels (~0.4 T, maximum) it is found that thermal effects are driving the surface temperature of the solid, during the latter times of current decay.
Advisors/Committee Members: Turchi, Peter J.
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26.
Park, Jungwan.
Characteristic behavior of a side branch in a dendritic crystal growth.
Degree: PhD, Aeronautical and Astronautical Engineering, 2007, Ohio State University
► This study investigates the characteristic behavior of disturbances on the interface of…
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▼ This study investigates the characteristic behavior of disturbances on the interface of a needle crystal, Ivantsove parabola, based on an asymptotic analysis as well as a numerical study. Focusing on tip growth and width behavior, we examine anisotropy in surface energy, initial strength of the disturbances. It is found that a tip grows as ftip = exp(Ct) close to the tip region and ftip exp(Ct1/2) at far field and wave-length, λo, does not show large variation to different initial conditions so that the width of a disturbance behaves as Δy∼y1/2λo. This constant wave-length, λo, suggests that the possibility of the existence of an attractor in λo. An evolution of finger competition between two disturbances with different initial strengths is investigated to understand the selection mechanism.
Advisors/Committee Members: Foster, Michael R.
Subjects: Engineering, Aerospace
Keywords: dendrite, crystal growth, side branch, surface tension, anisotropy, finger competition, wave length.
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27.
Pluim, Jonathon Douglas.
DESIGN OF A HIGH FIDELITY WAKE SIMULATOR FOR RESEARCH USING LINEAR CASCADES.
Degree: MS, Aeronautical and Astronautical Engineering, 2009, Ohio State University
► Owing to the extensive use of wake generators in the study of…
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▼ Owing to the extensive use of wake generators in the study of turbine and compressor airfoils in linear cascades, a study was undertaken to determine the most accurate model for the wakes generated by upstream blade rows. Velocity (PIV) measurements were taken to compare wake properties of several bluff bodies with different cross sections to the wake of an ultra high lift low pressure turbine profile (L1A). These measurements were taken at two Reynolds numbers, a low and a high one, to simulate a separated and attached wake, respectively, for both the blade and two of the shape configurations. The L1A turbine blade profile was determined to shed a wake typical of high lift turbine blade profiles. It is shown that the wake of the turbine blade is highly dependent on Reynolds number. In order to make an appropriate comparison, all bluff body data were extracted along a plane parallel to the equivalent inlet plane of a rotor stage in the stationary frame of reference. It was found that no single rod shape matched all of the blade wake characteristics. From the shapes used in this study, a 30° isosceles wedge placed 6 diameters upstream of the cascade inlet in the axial direction and skewed 15° from the rod relative flow was found to yield the closest match for the low Re case due to the asymmetry in the velocity and Reynolds shear stresses in this wake compared with the wake of the low pressure turbine blade. The same configuration placed 10 diameters upstream yielded the best comparison to a higher Re, more attached L1A wake. The boundary layer response of the L1A to the wake shed from a cylindrical wake was compared to the response from a wedge shaped wake skewed 15° to the rod relative flow. A hot-film anemometer was placed on a blade follower device to determine velocity, rms, and intermittency data. It was found that the wake shed from the wedge acts to suppress the separation more than the wake from a cylinder placed the same distance upstream from the cascade leading edge. The shear layer and point of transition occur further downstream on the blade surface when using a wedge shaped rod and the calm zone has a greater duration.
Advisors/Committee Members: Bons, Jeffrey.
Keywords: Wake Simulation, Low pressure turbine, wake generator
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29.
Scharlemann, Carsten A.
Investigation of thrust mechanisms in a water fed pulsed plasma thruster.
Degree: PhD, Aeronautical and Astronautical Engineering, 2003, Ohio State University
► Analytic models predict the possibility of extending the range of performance parameters…
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▼ Analytic models predict the possibility of extending the range of performance parameters of Pulsed Plasma Thrusters (PPT) by using propellants other than the traditionally used Teflon. A theoretical and experimental effort was initiated at The Ohio State University to investigate the use of alternative propellants for PPT. Analytical and numerical calculations (MACH2) indeed indicate a significant broadening of the obtainable range of specific impulse and thrust-to-power ratios when alternative propellants such as lithium or water are utilized. Consequently, in an effort to investigate changes in physical phenomena and thruster performance experimentally, a hybrid thruster was designed and built, facilitating the use of alternatively water or Teflon. The thruster design includes a unique water propellant feed system, allowing the supply of the water propellant without detrimentally affecting the inherent simplicity of the PPT system. ii The thruster operation and performance was investigated by several different diagnostic methods, including current and voltage measurements, Langmuir probes, and magnetic field probes. Furthermore, impact pressure measurements in the plume of the thruster allowed new insight into the plume structure and the accurate evaluation of impulse bits. Employment of the diagnostic methods for Teflon and water propellant enabled the unambigous identification of propellant related effects such as reduced electron temperature and higher exhaust velocites in the case of water propellant. The electromagnetic nature of the water thruster was clearly identified. For 30 J discharge energy, the water thruster requires only 5% of the mass bit of a Teflon thruster to produce an impulse bit 30% of the magnitude of the Teflon thruster, suggesting greatly increased propellant efficiencies. In agreement with the plasma diagnostic results, a specific impulse for the water thruster of up to 8000 s and efficiencies of up to 16% were evaluated.
Advisors/Committee Members: York, Thomas M.
Subjects: Engineering, Aerospace
Keywords: Electric Propulsion; Pulsed Plasma Thruster; Water; Teflon; Plasma diagnostic; Langmuir probe; Magnetic field probe; Pressure probe; Space propulsion; Analyitic model; MACH2
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30.
Seidt, Jeremy Daniel.
Development of a novel vibration based high cycle fatigue test method.
Degree: MS, Aeronautical and Astronautical Engineering, 2001, Ohio State University
► A new vibration based test method for evaluating fatigue properties of aeroengine…
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▼ A new vibration based test method for evaluating fatigue properties of aeroengine materials has been developed. In this method, fatigue energy is accumulated on a base-excited, cantilevered plate specimen at high frequency resonant modes such as the two-stripe mode. This method allows for great versatility in the ability to conduct multiaxial stress high cycle fatigue tests.The test method has been developed at The Ohio State University and the Propulsion (PRT) and Material (MLLN) Directorates of the Air Force Research Laboratory (AFRL). Extensive pre-fatigue test FEA analysis and testing was performed to gainunderstanding of the test equipment and the dynamic behavior of various test specimens. The fatigue tests were performed on steel plate specimens on a 6,000 lb electrodynamic shaker at the Turbine Engine Fatigue Facility (PRT). Fatigue test data for steel was acquired by use of the step test method at fully reversed cyclic loading at high frequency modes. The fully reversed fatigue data point of a Goodman diagram has been constructed and compared to data found in the literature.The optimal design problem of minimizing the ratio of maximum stress in the clamped edge of the plate to the maximum stress in the free edge of the plate has been analyzed. The sequential quadratic programming (SQP) optimization program, VMCON was linked to a finite element code named DPLATE which is capable of analyzing the free and forced vibration of flat plates to accomplish this task. An optimal solution was achieved via VMCON/DPLATE search processes in various case geometries with the design variable, the ratio of the length of the free edge to the length of the clamped edge. Plate specimen geometry was determined for which fretting fatigue and eventual failure at the clamped edge of the plate was no longer a major concern.
Advisors/Committee Members: Shen, M.-H. Herman.
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