Master of Sciences (Engineering), Case Western Reserve University, 2014, EMC - Mechanical Engineering

To better understand the behavior of wind turbines placed in an urban environment, a study was performed to characterize the wind availability and performance of a 100-kilowatt Northern Power Systems wind turbine installed at Case Western Reserve University. It was found that the annual average wind speed was 4.0m/s, generating net energy of 67MWh at a rate of 8.0kW. It was also found that the winds rarely reach the required 15m/s for the turbine to output at its rated capacity. The winds that do reach 15m/s or faster exist only in short gusts, prevalently during the Winter 2011 and Spring 2012 months. Additionally, in studying the turbine performance, it was found that the turbine has a maximum efficiency of 65-70% relative to the Betz Limit, at a wind speed of approximately 6.75m/s.

Committee: Iwan Alexander (Advisor); Jaikrishnan Kadambi (Committee Chair); Paul Barnhart (Committee Member) Subjects: Aerospace Engineering; Energy; Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2010, Aeronautical and Astronautical Engineering

A new turbine research facility at The Ohio State University Aeronautical and Astronautical Research Lab has been constructed. The purpose of this facility is to re-create deposits on the surface of actual aero-engine Nozzle Guide Vane (NGV) hardware in an environment similar to what the hardware was designed for. This new facility is called the Turbine Reacting Flow Rig (TuRFR). The TuRFR provides air at temperatures up to 1200 °C and at inlet Mach numbers comparable to those found in an actual turbine (~0.1). Several validation studies have been undertaken which prove the capabilities of the TuRFR. These studies show that the temperature entering the NGV cascade is uniform, and they demonstrate the capability to provide film cooling air to the NGV cascade at flow rates and density ratios comparable to the NGV design. Deposition patterns have also been created on the surface of actual NGV hardware. Deposition was created at different flow temperatures, and it was found that deposition levels decrease with decreasing gas temperature. Also, film cooling levels were varied from 0% film cooling to 4% film cooling. It was found that with increased rates of film cooling deposition decreased. With the TuRFR capabilities demonstrated, research on the effects of deposition on the aerodynamic performance of the NGV hardware was conducted. Integrated non-dimensional total pressure loss values were calculated in an exit Rec range of 0.2x106 to 1.7x106 for a deposit roughened NGV cascade and a smooth cascade. The data suggests that deposition causes increased losses across the NGV cascade and possibly earlier transition. The data also suggests a possible region of separated flow in the NGV cascade which disappears at higher exit Reynolds numbers. These results are similar to those found in the literature.

Committee: Jeffrey Bons PhD (Advisor); James Gregory PhD (Committee Member); Ali Ameri PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2023, Aero/Astro Engineering

The feasibility of an active flow control enabled variable area turbine was explored. Pressurized air was ejected from the nozzle guide vanes to reduce the effective choke area, and mass flow rate through, the turbine inlet. A set of experimental and computational studies were conducted with varying actuator types and parameters to determine their effectiveness and develop models of the flow physics. Preliminary results from a simple quasi-1D converging-diverging nozzle, with an injection flow slot upstream of the throat, showed a 2.2:1 ratio between throttled mass flow rate and injected mass flow rate at a constant nozzle pressure ratio. The penetration of the injection flow and corresponding reduction in the primary flow streamtube were successfully visualized using a shadowgraph technique. Building on this success, a representative single passage nozzle guide vane transonic flowpath was constructed to demonstrate feasibility beyond the quasi-1D converging-diverging nozzle. Both secondary slot blowing from the vane pressure surface and vane suction surface just upstream of the passage throat again successfully reduced primary flow. In addition, fluidic vortex generators were used on the adjacent suction surface to reduce total pressure loss along the midspan and further throttle the primary flow. Computational fluid dynamics simulations were used to explore the effects of a variety of parameters on the flow blockage and actuator effectiveness. Simplified models were developed to describe the relationships of various factors impacting flow blockage, turning angle, and total pressure loss. Finally, the active flow control systems were simulated at engine relevant pressures and temperatures and found to have only a minimal drop in total pressure recovery and effectiveness, which could be predicted by the simplified blockage model.

Committee: Jeffrey Bons (Advisor); Datta Gaitonde (Committee Member); Randall Mathison (Committee Member) Subjects: Aerospace Engineering

Master of Science, The Ohio State University, 2020, Aero/Astro Engineering

This thesis covers the intensive research effort to elucidate the role of elevated temperature in deposition. Several experimental campaigns were conducted in this pursuit. The testing explored high temperature deposition with 0-10 micron Arizona Road Dust (ARD) with the intent of creating a yield strength model that included temperature effects and could be incorporated into the existing OSU deposition model. Experimental work was first conducted in the impulse kiln facility where small amounts of the test dust were placed on ceramic targets and rapidly exposed to temperatures between 1200K and 1500K. Trends in the packing factor confirmed the existence of two threshold values (1350K and 1425K) that could be linked to strength characteristics of the dust when exposed to high temperatures. Using the information obtained from the kiln experiments, HTDF testing was conducted between 1325K and 1525K. Exit temperatures were set at 25K intervals in this region with a constant jet velocity of 150 m/s. The capture efficiency data showed this trend with temperature and indicated a softening temperature and melting temperature of 1362K and 1512K respectively. With these critical values in hand, the Ohio State University Molten Model was created to modify yield strength with particle velocity and temperature. The model was tested using CFD and showed a good capability for capturing particle temperature effects in deposition from an impinging particle-laden jet. A subsequent test campaign was conducted to explore the effect of varying surface temperature on deposition. Hastelloy coupons with Thermal Barrier Coatings (TBCs) were subjected to a constant jet at 1600K jet and 200 m/s while being cooled via a backside impingement jet. Surface temperatures between 1455K and 1125K were impacted with 0-10 micron ARD while an IR camera monitored the surface. Coupons with higher coolant flowrates (lower surface temperature) saw significantly lower deposition rates than the higher surf (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Randall Mathison Dr. (Committee Member) Subjects: Aerospace Engineering

Master of Science in Mechanical Engineering (MSME), Wright State University, 2019, Mechanical Engineering

A primary source of periodic unsteadiness in low-pressure turbines is the wakes shed from upstream blade rows due to the relative motion between adjacent stators and rotors. These periodic perturbations can affect boundary layer transition, secondary flow, and loss generation. In particular, for high-lift front-loaded blades, the secondary flowfield is characterized by strong three-dimensional vortical structures. It is important to understand how these flow features respond to periodic disturbances. A novel approach was taken to generate periodic unsteadiness which captures some of the physics of turbomachinery wakes. Using stationary pneumatic devices, pulsed jets were used to generate disturbances characterized by velocity deficit, elevated turbulence, and spanwise vorticity. Prior to application in a turbine flow environment, the concept was explored in a small developmental wind tunnel using a single device. The disturbance flowfield for different input settings was measured using hot-film anemometry and Particle Image Velocimetry. Insight was also garnered on how to improve later design iterations. With an array of devices installed upstream of a linear cascade of high-lift front-loaded turbine blades, settings were found which produced similar disturbances at varying frequencies that periodically impinged upon the leading-edge region. These settings were used to conduct an in-passage secondary flow study using high-speed Stereoscopic Particle Image Velocimetry. Results demonstrated the application of the periodic unsteadiness generator but found minor changes to the passage vortex. The vortex rotational strength decreased, and migration increased with increased perturbation frequency. Fourier analyses found the PV to be responsive at the actuation frequency with phase-locked ensemble-averaged data revealing that the disturbance periodically caused the PV to lose rotational strength. However, at the tested discrete frequencies, the vortex did not become locked (open full item for complete abstract)

Committee: Mitch Wolff Ph.D. (Advisor); Rolf Sondergaard Ph.D. (Committee Member); Christopher Marks Ph.D. (Committee Member) Subjects: Aerospace Engineering; Engineering; Experiments; Fluid Dynamics; Mechanical Engineering

Master of Science in Mechanical Engineering, Cleveland State University, 2013, Fenn College of Engineering

This project involves study of 2-Blade and 3-Blade Savonius vertical wind turbines positioned at different orientations. For a 2-Blade turbine the orientations considered were 0 degree, 45 degree, 90 degree and 135 degree in reference to the direction of the prevailing wind and for the 3-Blade turbine the orientations taken into account were 0 degree, 30 degree, 60 degree and 90 degree in reference to the direction of the prevailing wind. The basic aim of this thesis was to study how the two designs are different from each other and which design produces more power when applied with constant wind velocity of 10mps. Computational Fluid Dynamics (CFD) analyses were conducted for every case to find out the torque and power generated by the turbines for each orientation. To ensure the accuracy of the results, CFD techniques were applied using Gambit 2.2.30 and Fluent 6.2.16. All cases were run using “transition-SST” flow model and the faces were meshed using `Quadrilateral Pave' meshing scheme. The turbine was also tested for varying wind velocities of 5mps, 20mps, and 30mps for a constant orientation of turbine. The results were later compared and graphs were created for easy comparison of power and torque generated by turbines at different velocities. Maximum change in pressure occurs when 2-Blade turbine in perpendicular to direction of wind flow direction i.e. at 90 degree and when 3-Blade turbine is at 60 degree orientation. The 2-Blade Turbine generates higher value of torque (215.28 N) as compared to 3-Blade turbine, generating torque of value 110.92 N for any given constant wind velocity; 30mps in this case. This information can help the designer of the system to select the proper wind turbine considering the efficiency and stability along with other factors.

Committee: Majid Rashidi PhD (Committee Chair); Rama Gorla PhD (Committee Member); Asuquo Ebiana PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2010, EECS - System and Control Engineering

Currently, environmental and economic concerns have pressed the power generation industry to develop more efficient and clean ways of generating electricity power. Facing such environmental and economic pressures, advanced control technology plays key role for both fossil fueled power plants and renewable energy systems. In this work, nonlinear control problems are studied for a boiler-turbine unit and wind turbine systems. Advanced control is crucial for safe and efficient operations of power plants, especially in the presence of fast and large load changes. We study the control problems of load changes for a 160MW boiler-turbine unit. Two schemes are proposed to effectively control the boiler-turbine unit that has various constraints on the system states, outputs, control input and rate of control signals. By taking advantage of the nonlinearities of the boiler-turbine unit, we design a nonlinear state feedback controller. With a careful selection of the controller gains, the states and control inputs can be guaranteed to be within the required physical constraints. To further incorporate the constraints on the system outputs as well as control-input rates into feedback design, we utilize the moving horizon control strategy. The nonminimum phase behavior can be compensated by using a relatively long but computationally-affordable horizon length. The simulations of two control methods demonstrate the well-controlled performances of the boiler-turbine unit under large and fast load changes. Modeling and variable speed control strategies for wind turbines are studied in order to capture maximum wind power. Wind turbines are modeled as two-mass drive-train system. Based on the obtained wind turbine models, variable speed control schemes are investigated for region 2. We designed nonlinear tracking controllers to achieve asymptotic tracking control for given rotor speed reference signals so as to yield maximum wind power capture. Due to the difficulty of torsional angl (open full item for complete abstract)

Committee: Wei Lin DSc (Advisor); Kenneth Loparo PhD (Committee Member); Mario Garcia-Sanz PhD (Committee Member); Vincenzo Liberatore PhD (Committee Member) Subjects: Electrical Engineering

Master of Science, The Ohio State University, 2013, Mechanical Engineering

Commercially available CMCs, or ceramic matrix composites, provide several benefits over metal blades including weight and increased temperature capability, which may save performance by significant reduction of the cooling flow bled from the compressor. The turbine inlet temperature has consistently increased over the past 70-years. Materials like CMC are typically used in areas such as the LPT, or low-pressure turbine, where reliability at high-temperatures beyond the capability of metal blades will be needed as the desire for higher performance capability increases. As part of a co-operative research program between GE Aviation and the OSU Gas Turbine Laboratory, the response of a CMC stage 1 LPT blade has been compared with the response of a comparable metal blade using the OSU GTL large spin pit facility, LSPF as the test vehicle. Load cell mounted on the casing wall, strain gages mounted on the airfoils, and other instrumentation is used to assess blade tip rub interactions with the stationary casing. The intent is to measure the dynamic response of both the CMC and the metal blades with the turbine disk operating at design speed and with representative incursion rates and depths. This thesis will explore these responses and compare the CMC results to typical metal blades to assess the operability of CMC blades during and after a tip rub. There are currently many papers being published related to the performance of ceramic matrix composites as this material seems to have the ability to cover both the high stresses and high temperatures of the ever complex engine environment. There are papers dealing with combustor liners, nozzles, casings, as well as blades. This thesis will focus on the mechanical behavior of the blade when operating at tight clearances ultimately resulting in a tip rub event. In summary, the tip rub event has been evaluated in this thesis showing a distinct comparison between the CMC blade and the conventional metal turbine blade. Shoe (open full item for complete abstract)

Committee: Michael Dunn (Advisor); Mohammad Samimy (Committee Member) Subjects: Aerospace Engineering; Materials Science

Doctor of Philosophy (Ph.D.), University of Dayton, 2023, Aerospace Engineering

Turbomachinery components, such as the low pressure turbine, are highly complex rotating machines, therefore, conducting fundamental fluid mechanics studies in them is exceedingly difficult. For this reason, testing is generally completed in facilities such as linear cascades, like the one present in the Low Speed Wind Tunnel Facility at AFRL, which typically utilize a low freestream turbulence intensity, when in reality, the freestream turbulence intensity in a full, rotating low pressure turbine is likely much higher. Slightly elevating the freestream turbulence intensity (e.g., 3%) typically improves the Reynolds-lapse characteristics of a blade profile by affecting the transition process, reducing the detrimental effects of laminar boundary layer separation, and shifting the knee in the loss curve. Front loaded blades are more resistant to separation, however, they can experience high losses in the endwall region due to the complex vortical structures present. Therefore, a better understanding whether high levels of freestream turbulence intensity will increase the overall losses generated in the passage is important. An intial study with a jet based active grid was completed on the L2F blade. Based of the insight gained from that study, a new mechanical agitator based active grid was implemented into a linear cascade of L3FHW-LS blades in order to more effectively study how elevated FSTI impacts the endwall flow behavior and loss production. Coefficient of pressure measurements, three planes of SPIV, two additional planes of flow visualization, and three planes of total pressure loss measurements were collected. Impacts of incoming turbulence on the endwall losses as well as the endwall flow structures were assessed.

Committee: Markus Rumpfkeil (Advisor); Christopher Marks (Committee Member); Sidaard Gunasekaran (Committee Member); John Clark (Committee Member) Subjects: Aerospace Engineering

Master of Science in Engineering, Youngstown State University, 2021, Department of Mechanical, Industrial and Manufacturing Engineering

The TJT-3000 on the campus of Youngstown State University is like one of many micro turbine engines used in UAV and other large RC aircraft. This project aims to analyze and propose improvements to the combustion chamber of micro turbine engines using the TJT-3000 as a baseline. These improvements would include an overall increase in the combustion chamber without heavily increasing the overall temperature reaching the turbine inlet. To analyze these criteria, the feasibility of using a handheld Creaform scanner for the purpose of scanning small turbine engine components is tested. The scanner was found to be viable, but a finer resolution was desirable as the scanned data from these scanned components would be refined and turned in to CFD capable models. The created CFD models in this project required a considerable amount of post processing to prepare. With a baseline model to compare to experimental data of the turbine engine, hypothesized geometric changes were applied to the turbine engine where the impact of each change would be considered and summarized. Based on the CFD models and literature review it was found that the geometric changes of the combustion chamber should be focused on improving the flow rate through the engine without extinguishing the produced flame while as much of the initial relatively cold flow coming from the compressor should be directed towards the back of the combustion chamber to cool the turbine inlet. Restricting the amount of flow through the combustion chamber leads to a higher pressure drop and an increase in combustion efficiency at the cost of unmanageable chamber wall temperatures, while geometry modifications that force flow through the inner most sections of the combustion chamber first will increase the cooling of the turbine stator inlet with a manageable increase in combustion chamber wall temperatures.

Committee: Stefan Moldovan PhD (Advisor); Hazel Marie PhD (Committee Member); Kyosung Choo PhD (Committee Member) Subjects: Aerospace Engineering; Design; Energy; Mechanical Engineering

Master of Science in Mechanical Engineering (MSME), Wright State University, 2019, Mechanical Engineering

The low-pressure turbine is an important component of a gas turbine engine, powering the low-pressure spool which provides the bulk of the thrust in medium- and high-bypass engines. It is also a significant fraction of the engine weight and complexity as it can comprise up to a third of the total engine weight. One way to drastically reduce the weight of the low-pressure turbine is to utilize high lift blades. To advance high-lift technology, the Air Force Research Laboratory (AFRL) designed the L2F blade profile, which was implemented in the linear cascade at AFRL/RQT's low speed wind tunnel facility. The L2F blade has very high lift and an excellent midspan performance, however, it was previously demonstrated to generate significant losses in the endwall region. These losses are primarily driven by the complex time-dependent three-dimensional vortical structures present in the region of the junction of the blade and the endwall, dominated by the Passage Vortex (PV). Aerodynamic flow control is one way to mitigate these losses. Previously, a pulsed endwall blowing system was implemented in the endwall region of the L2F blade which produced a loss reduction. This loss reduction was dependent on the pulsing frequency. In this research, the vortical structures for the baseline flow were characterized with respect to time. The time dependent behavior of the passage vortex motion, location, and strength were found for each pulsing frequency to determine a relationship with total pressure loss reduction. The flow through the passage of the tunnel was characterized with respect to time using high-speed stereoscopic particle image velocimetry. The flow for each test condition was characterized using Q-criterion to determine the strength of the passage vortex and its time dependent behavior. It was found that the passage vortex loses and gains strength in an unsteady manner at time scales between 1.9 < ΔT+ < 6.7. The largest total pressure loss reduction was found to corres (open full item for complete abstract)

Committee: Mitch Wolff Ph.D. (Advisor); Christopher R. Marks Ph.D. (Committee Member); Rolf Sondergaard Ph.D., P.E. (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2019, Mechanical Engineering

Aerodynamic losses due to tip leakage in a High Pressure Turbine (HPT) rotor setting are analyzed using the commercial CFD software Star-CCM+. The compressible RANS equations were solved over unstructured polyhedral grids of 11 to 17 million cells, with turbulence resolved using the k-w SST model. A study of 3 blade tip/casing configurations at tip clearances between 0% and 4% of blade span is performed, with resulting mass-flow Reynolds #'s of 2.4-2.7 million and levels of reaction of 0.13-0.17. A flat-tip blade experienced a linear correlation between tip clearance and efficiency. The same blade with recessed casing was more efficient for small clearances, but large shear losses were seen to nullify this advantage at high clearances. A shrouded blade was more efficient than both at all clearances, displaying asymptotic behavior at high clearances. Various pressure and velocity monitoring techniques are employed to evaluate leakage flow and loss. Location and strength of leakage vortices are discussed, as these are closely tied with efficiency. A parametric study was performed on the shroud geometry, examining seal angle, number of seals, seal wear, and shroud axial gap. Efficiencies were compared between each study point at clearances of 2% and 4% of blade span. Total pressure loss was tracked across the blade and split between the main flow path and tip gap to distinguish between Profile and Internal Gap Shear losses. Axial gap was seen to have the greatest impact on efficiency, as a narrower gap acts as additional tip flow blockage and increases efficiency. At lower clearances, seal wear produced a negative impact as well.

Committee: Jeffrey Bons Dr. (Advisor); Randall Mathison Dr. (Committee Member); Ali Ameri Dr. (Committee Member); Robert Boyle (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science in Renewable and Clean Energy Engineering (MSRCE), Wright State University, 2017, Renewable and Clean Energy

People understand and have seen that renewable energy has many advantages over conventional energy sources. Because of these advantages, more and more emphasis has been given to generating electrical energy with renewable sources. Among the many renewable and conventional ways currently available for a society to generate electrical power, wind turbines are one of the cheapest ways of doing this. The main objective of this thesis work is to develop a computer program that assesses the wind resource at a given location, designs a wind turbine rotor for optimum power capture for one wind speed, and analyzes the performance of this designed rotor over a range of wind speeds. A key output of this computer program is the energy that a wind turbine can produce over a one year period, at a given location. Many other results are produced by this newly developed computer program as well. This computer program allows for three different air foil types to be used on a single blade. Using more than one airfoil type along a single blade is necessary for good performance of larger diameter wind turbines. While the computer model developed for this thesis work is applicable to any location, any elevation, and any time period; results are produced for only one location and one hub height. The location studied is Eaton, Ohio and the hub height is 70 meters above the ground. Plots and single numbers that describe the Eaton wind resource are presented. A 20-meter radius wind turbine rotor is designed using three NREL S-series airfoils along the length of each blade of a three-bladed wind turbine rotor. For the root section of the blade a S818 airfoil is used, for the primary section of the blade a S816 airfoil is used, and for the tip section of the blade a S817 airfoil is used. A couple of design parameters are surveyed along with one operational parameter.

Committee: James A. Menart Ph.D. (Advisor); Hong Huang Ph.D. (Committee Member); Zifeng Yang Ph.D. (Committee Member) Subjects: Alternative Energy; Mechanical Engineering; Mechanics

Doctor of Philosophy, The Ohio State University, 2016, Mechanical Engineering

An experiment was performed at The Ohio State University Gas Turbine Laboratory for a film-cooled high-pressure turbine stage operating at design-corrected conditions, with variable rotor and aft purge cooling flow rates. Several distinct experimental programs are combined into one experiment and their results are presented. Pressure and temperature measurements in the internal cooling passages that feed the airfoil film cooling are used as boundary conditions in a model that calculates cooling flow rates and blowing ratio out of each individual film cooling hole. The cooling holes on the suction side choke at even the lowest levels of film cooling, ejecting more than twice the coolant as the holes on the pressure side. However, the blowing ratios are very close due to the freestream massflux on the suction side also being almost twice as great. The highest local blowing ratios actually occur close to the airfoil stagnation point as a result of the low freestream massflux conditions. The choking of suction side cooling holes also results in the majority of any additional coolant added to the blade flowing out through the leading edge and pressure side rows. A second focus of this dissertation is the heat transfer on the rotor airfoil, which features uncooled blades and blades with three different shapes of film cooling hole: cylindrical, diffusing fan shape, and a new advanced shape. Shaped cooling holes have previously shown immense promise on simpler geometries, but experimental results for a rotating turbine have not previously been published in the open literature. Significant improvement from the uncooled case is observed for all shapes of cooling holes, but the improvement from the round to more advanced shapes is seen to be relatively minor. The reduction in relative effectiveness is likely due to the engine-representative secondary flow field interfering with the cooling flow mechanics in the freestream, and may also be caused by shocks and other compr (open full item for complete abstract)

Committee: Randall Mathison (Advisor); Michael Dunn (Committee Member); Sandip Mazumder (Committee Member); Jeffrey Bons (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Master of Science in Engineering, Youngstown State University, 2010, Department of Civil/Environmental and Chemical Engineering

The siting of modern wind turbines to generate electricity requires accurate wind flow data over at least an annual weather cycle for optimum selection of both the wind turbine and its installed height, as well as for predicting the expected annual energy production at the site. Since wind energy is a relatively new industry in North America, detailed annualized data are often not available, especially in rural areas, except for a single prediction of the average annual wind speed that is modeled by interpolating weather data from sensors that may be located several miles from the intended wind turbine site. This has led to several user disappointments when the actual energy obtained from a wind turbine was less than predicted. In response, the present study focused on the development of a more realistic predictive model of power generation based on actual wind patterns at the site. Data on wind flow and energy output were obtained from an installation of three industrial-sized wind turbines at a local K-12 school. Minute-by-minute wind data were sorted and aggregated to provide the model input. The empirical model developed predicted energy output within 4.1% of that observed over a period of 78 days; that is, an estimate of 13,875 kWh versus 14,470 kWh actually produced. A simpler model applicable to lower wind speeds (up to a “Moderate Breeze” of 7.5 m/s) was also developed that yielded a good energy output estimate of 11.5 kWh versus the full model's estimate of 11.7 kWh for an actual day's wind conditions.

Committee: Scott Martin PhD (Advisor); Javed Alam PhD (Committee Member); Salvatore Pansino PhD (Committee Member) Subjects: Area Planning and Development; Civil Engineering; Energy; Environmental Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2007, Mechanical Engineering

At very high altitudes the Reynolds number flow through the low pressure turbine section of the gas turbine engine can drop below 25,000. At these low Reynolds numbers the flow is laminar and extremely susceptible to separation which can lead to increased losses and reduced lift. Small jets of air injected through the suction surface of the airfoil, called Vortex Generator Jets (VGJs), have been shown successful in suppressing separation and maintaining attached flow. Pulsing of these jets has been shown to be as effective as steady jets while reducing the amount of mass flow needed. An experiment using Particle Image Velocimetry (PIV) was set up to study the interaction of the VGJ flow with the main flow. A cascade of Pratt and Whitney Pack-B turbine blades were mounted in the test section of a low speed wind tunnel at Wright Patterson Air Force Base. On the middle six blades were rows of 1mm VGJ holes. The VGJ holes were oriented with a 30o pitch angle and 90o skew angle. The pitch angle is the angle the jet makes with the surface of the turbine blade while the skew angle is the angle the jet makes with the cross-flow. Blowing ratios, a ratio of the jet velocity to the cross-flow velocity, of 0.5, 1, and 2 were examined. These three blowing ratios were selected because they represent when the cross-flow momentum dominates the fluid interaction (B=0.5); when the momentums of the jet flow and cross-flow are equal (B=1); and when the momentum of the jet flow dominates the interaction. Blowing ratios of 0.5 and 1 were studied for pulsing frequencies of 10Hz and 0.4Hz while the blow ratio of 2 was studied only with 10Hz pulsing. A duty cycle of 50% was used for both pulsing frequencies. The two pulsing frequencies allowed data to be taken to show how the pulsed VGJ maintains attached flow (10Hz) and how the pulsed VGJ suppresses the separation bubble (0.4Hz). Results show that jets interacting with separated flow are able to suppress the separation bubble almost immedi (open full item for complete abstract)

Committee: Mitch Wolff (Advisor) Subjects:

Doctor of Philosophy, The Ohio State University, 2010, Aeronautical and Astronautical Engineering

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 los (open full item for complete abstract)

Committee: Jeffrey Bons PhD (Advisor); James Gregory PhD (Committee Member); Jen-Ping Chen PhD (Committee Member); Mohammad Samimy PhD (Committee Member) Subjects: Engineering

Master of Sciences (Engineering), Case Western Reserve University, 2010, EMC - Fluid and Thermal Engineering

In this study, a code ‘Wind Farm Optimization using a Genetic Algorithm' (referred as WFOG) is developed in MATLAB for optimizing the placement of wind turbines in large wind farms to minimize the cost per unit power produced from the wind farm. A genetic algorithm is employed for the optimization. WFOG is validated using the results from previous studies. The grid spacing (distance between two nodes where a wind turbine can be placed) is reduced to 1/40 wind turbine rotor diameter as compared to 5 rotor diameter in previous studies. Results are obtained for three different wind regimes: Constant wind speed and fixed wind direction, constant wind speed and variable wind direction, and variable wind speed and variable wind direction. Cost per unit power is reduced by 11.7 % for Case 1, 11.8 % for Case 2, and 15.9 % for Case 3 for results obtained using WFOG. The advantages/benefits of a refined grid spacing of 1/40 rotor diameter (1 m) are evident and are discussed.

Committee: J. Iwan D. Alexander PhD (Committee Chair); Alexis R. Abramson PhD (Committee Member); Jaikrishnan R. Kadambi PhD (Committee Member); Joseph M. Prahl PhD (Committee Member) Subjects: Energy; Mechanical Engineering

Master of Science in Mechanical Engineering, University of Toledo, 2012, Mechanical Engineering

This thesis examines the effects of surface ice sheets on an offshore wind turbine. First, the main ice load cases are presented, and methods used to calculate the loads from each of these cases are explained. These load cases consist of loads from moving ice sheets, loads from non-moving ice sheets, and loads from agglomerated masses of ice, called ice ridges. Next, the data required to conduct the load calculations are presented from sources applicable to an offshore site in Lake Erie, which is the location of interest in this work. The load calculation methods were implemented into a wind turbine simulation software package, and simulations were run subjecting an offshore wind turbine to extreme ice loads combined with a large representative wind load. Results from these simulations are presented, which show the relative magnitude of the effects of the ice loads compared to the magnitude of the effects of the wind load. It was found that the effects on the foundation due to extreme ice loads can be much larger than the effects caused by a large representative wind load. Also presented in this work is an examination of how the ice loads would influence the design of an offshore wind turbine foundation (i.e. how much bigger should the foundation be to support the ice loads). The simulation results presented in this study indicate that the surface ice sheet loads can be much larger than the wind loads and could be the driving parameter of the design of offshore wind turbine foundations in areas where ice can occur.

Committee: Abdollah Afjeh Dr. (Committee Co-Chair); Sorin Cioc Dr. (Committee Co-Chair); Efstratios Nikolaidis Dr. (Committee Member) Subjects: Mechanical Engineering

Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects: