Master of Science in Mechanical Engineering (MSME), Wright State University, 2018, Mechanical Engineering

High-lift low-pressure turbine blades produce significant losses at the junction with the endwall. The losses are caused by several complex three-dimensional vortical flow structures, which interact with the blade suction surface boundary layer. This study investigates the unsteady characteristics of these endwall flow structures on a highly loaded research profile and the adjacent endwall using surface-mounted hot-film sensors. Experiments were conducted in a low-speed linear cascade wind tunnel. The front-loaded blade profile was subjected to three different inlet conditions, consisting of two turbulence levels, and three incoming boundary layer thicknesses. Multiple surface-mounted hot-film sensors were installed throughout the passage. This thesis progressed in three stages of research. The first verified that the hot-film sensors could be used to detect flow structures in the cascade. The second used the results from installed hot-films to examine the unsteady characteristics of vortices formed near the leading edge and the propagation of the passage vortex across the passage where it interacts with a corner separation along the suction surface. Simultaneous measurements from the hot-film sensors were analyzed for frequency spectra and time lag in order to provide new insight into the endwall flow dynamics. Finally, signatures from the hot-films were linked to specific flow phenomena through concurrent flow visualization. At each stage of the investigation, results were compared to the results of a numerical simulation.

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

Master of Science in Mechanical Engineering (MSME), Wright State University, 2016, Mechanical Engineering

Improvements in turbine design methods have resulted in the development of blade profiles with both high lift and good Reynolds lapse characteristics. An increase in aerodynamic loading of blades in the low pressure turbine section of aircraft gas turbine engines has the potential to reduce engine weight or increase power extraction. Increased blade loading means larger pressure gradients and increased secondary losses near the endwall. Prior work has emphasized the importance of reducing these losses if highly loaded blades are to be utilized. The present study analyzes the secondary flow field of the front-loaded low-pressure turbine blade designated L2F with and without blade profile contouring at the junction of the blade and endwall. The current work explores the loss production mechanisms inside the low pressure turbine cascade. Stereoscopic particle image velocimetry data, total pressure loss data and oil flow visualization are used to describe the secondary flow field. The flow is analyzed in terms of total pressure loss, vorticity, Q-Criterion, Reynolds' stresses, turbulence intensity and turbulence production. The flow description is then expanded upon using an Implicit Large Eddy Simulation of the flow field. The RANS momentum equations contain terms with static pressure derivatives. With some manipulation these equations can be rearranged to form an equation for the change in total pressure along a streamline as a function of velocity only. After simplifying for the flow field in question the equation can be interpreted as the total pressure transport along a streamline. A comparison of the total pressure transport calculated from the velocity components and the total pressure loss is presented and discussed. Peak values of total pressure transport overlap peak values of total pressure loss through and downstream of the passage suggesting that total pressure transport is a useful tool for localizing and predicting loss origins and loss development using (open full item for complete abstract)

Committee: Mitch Wolff Ph.D. (Advisor); Rolf Sondergaard Ph.D. (Committee Member); Rory Roberts Ph.D. (Committee Member) Subjects: Aerospace Engineering; Engineering

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Sciences (Engineering), Case Western Reserve University, 2020, EMC - Mechanical Engineering

A comparative analysis has been performed for vertical-axis wind turbines, including the straight, troposkien, and helical-bladed Darrieus configurations, to assess their aerodynamic efficiency and real-power performance. The experimentation process included numerical modeling, CAD design, 3D printing-fabrication, and wind tunnel testing of lab-scale prototypes with a maximum power point tracking (MPPT) control scheme under different wind velocities. Implementing a double multiple streamtube (DMST) model, aided in the delimitation of non-dimensional parameters, where the local Reynolds numbers are between Re_b = 32,000 and 190,000, finding the ideal solidity value to be ς < 1.7 for low tip-speed ratio conditions, λ < 2.5. The optimum rotor swept areas are S = 0.048 m2 and 0.093 m2 with a maximum rotational speed around ω ≅ 1100 RPMs. At the designed conditions, the best wind tunnel results are obtained from the troposkien configuration (T-v1), with a Cp_opt = 0.218 at λ_opt = 2.25, followed by the straight-bladed (SB-v2) with a Cp_opt = 0.118 at λ_opt = 1.31 and helical-bladed (H45-v3) with Cp_opt = 0.082 at λ_opt = 0.99. The implementation of a free-vortex wake (LLFVW) method demonstrated the artificial increases in Cp (13-17%) and TSR (4-6%) due to wind tunnel blockage ratios between BR = 18% and 26% with turbine curvature ratios c/R > 0.5. Nonetheless, the power predictions for the vortex model are not consistent with real experimental data varying around |∆Cp| ≥ 30%, while the DMST deviates on average by |∆Cp| ≥ 25%. As such, the best strategy for small-scale wind turbine experimentation resides on wind tunnel tests, whereas basic aerodynamic models are mainly taken as tools for parameter selection and wake-flow visualization in the downstream region.

Committee: Mario Garcia-Sanz Ph.D. (Committee Chair); Paul Barnhart Ph.D. (Committee Member); Robert Gao Ph.D. (Committee Member); Brian Maxwell Ph.D. (Committee Member) Subjects: Aerospace Engineering; Energy; Engineering; Fluid Dynamics; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2018, Aerospace Engineering

So-called wind-lens turbines offer the potential for improved energy efficiency and better suitability for urban and suburban environments compared to unshrouded or bare wind turbines. Wind-lenses, which are typically comprised of a diffuser shroud equipped with a flange, can enhance the wind velocity at the rotor plane due to the generation of a lower back pressure. This work comprises of two main studies which aim to develop fast and accurate simulation tools for the performance prediction and design of shrouded horizontal axis wind turbines. In the first study, a low-order theoretical model of ducted turbines is developed to establish a better understanding of the basic aerodynamics of shrouded wind turbines. Then a cost-effective CFD tool coupled with a multi-objective genetic algorithm is developed and employed to improve the performance of shrouded wind turbines. A low-order semi empirical model, which offers performance prediction for the power and thrust coefficients, is developed and applied to shrouded turbines. This 1D model is based on assumptions and approximations to calculate optimal power coefficients and power extraction, as well as augmentation ratios. It is revealed that the power enhancement is proportional to the mass stream rise produced by the nozzle diffuser-augmented wind turbine (NDAWT). Such mass flow rise can only be accomplished through two essential principles: an increase in the area ratios and/or by reducing the negative back pressure at the exit. The thrust coefficient for optimal power production of a conventional bare wind turbine is known to be 8/9, whereas the theoretical analysis of the NDAWT predicts an ideal thrust coefficient either lower or higher than 8/9 depending on the back-pressure coefficient at which the shrouded turbine operates. Computed performance expectations demonstrate a good agreement with numerical and experimental results, and it is demonstrated that much larger power coefficients than for traditional win (open full item for complete abstract)

Committee: Markus Rumpfkeil Ph.D. (Advisor); Kevin Hallinan Ph.D. (Committee Member); Andrew Chiasson Ph.D. (Committee Member); Youssef Raffoul Ph.D. (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1971, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1971, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1950, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1968, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science in Renewable and Clean Energy Engineering (MSRCE), Wright State University, 2023, Renewable and Clean Energy

In the past several years, the energy sector has experienced a rapid increase in renewable energy installations due to declining capital costs for wind turbines, solar panels, and batteries. Wind and solar electricity generation are intermittent in nature which must be considered in an economic analysis if a fair comparison is to be made between electricity supplied from renewables and electricity purchased from the grid. Energy storage reduces curtailment of wind and solar and minimizes electricity purchases from the grid by storing excess electricity and deploying the energy at times when demand exceeds the renewable energy supply. The objective of this work is to study the generation of electric power with wind turbines and solar panels coupled to either battery energy storage or hydrogen energy storage. So that logical conclusions can be drawn on the economic effectiveness of battery and hydrogen energy storage, four scenarios are analyzed: 1) purchasing all required electricity from the grid, 2) generating electricity with a combined wind and solar farm without energy storage, 3) generating electricity with a combined wind and solar farm with battery energy storage, and 4) generating electricity with a combined wind and solar farm with hydrogen energy storage. All four of these scenarios purchase electricity from the grid to meet demand that is not met by the renewable energy power plant. All scenarios are compared based on the lowest net present cost of supplying the specified electrical loads to serve 25,000 homes in Rio Vista, California over 25 years of operation. The detailed economics and electric power production of both wind and solar combined with energy storage for any size of wind facility, solar facility, battery facility, and hydrogen facility are analyzed with a MATLAB computer program developed for this work. The program contains technical and economic models of each of these systems working in different combinations. Current equipment c (open full item for complete abstract)

Committee: James Menart Ph.D. (Advisor); Hong Huang Ph.D. (Committee Member); Mitch Wolff Ph.D. (Committee Member) Subjects: Alternative Energy; Energy; Engineering

Master of Science, The Ohio State University, 2023, Aerospace Engineering

Over the last decades, research has shown that water applications serving small scales (small population) is causing major health problems due to water pollution. Those applications include home and hospital water supply line. In fact, water pollution is increasing year after the other due to the bad use of the resources available. However, in the United States, engineers are trying to benefit now from the renewable energy available, including hydropower, wind, and solar power. Small-scale hydropower has been the focus of engineers over the last years since generating power at that small-scales can be a solution for developing and rural areas all over the world where money access is not available. Turbine designs available in the market are typically larger and provide more power than the power required for small scales applications (about 200W needed). As a result, this paper seeks to solve the water pollution at small-scales applications by designing a pico-hydropower system that is able to provide enough power to run the water disinfection reactor. Water disinfection is done using UV LED lights that are healthier for humans and for the environment. This new emerging technology is still under review and will be more efficient by the upcoming years. The hydropower system designed is based on a new concept of using a centrifugal pump and reverse the flow path to generate energy instead of consuming energy. Two new methods were created to be able to predict the multistage pump performance when removing and adding stages along with predicting the turbine performance at different stages. The results show that the PAT technology is efficient in terms of generating energy that is enough to water disinfection at small scales application.

Committee: Clarissa Belloni (Advisor); Natalie Hull (Committee Member); Randal Mathison (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2020, Mechanical Engineering

The simulations and experiments outlined are designed to explore the effect of existing turbulent dispersion models in predicting particle deposition characteristics at higher temperatures. The continuous phase solution was obtained from using a Reynolds-Averaged Navier Stokes (RANS) turbulence model and the turbulent dispersion was modeled using a Continuous Random Walk (CRW) model. Euler-Maruyama scheme was implemented to solve the non-dimensional Langevin equation to model the stochastic nature of the equation appropriately. Previous studies have shown that the particle deposition characteristics depend greatly on the time step of integration. With the Euler-Maruyama scheme, the CFD results were shown to be less sensitive to the time step of integration and with decrease in time step more stable results were obtained. Direct comparison with the Discrete Random Walk (DRW) model shows that DRW fails to predict flow fluctuations seen by particles in the diffusion-impaction regime. Previous studies of this phenomenon were all performed at ambient conditions. The CRW model was shown to predict impact velocities reasonably well, when the chosen time step of integrations is such that the stochastic and damping term are comparable in magnitude. Presented here are pipe-flow experiments conducted in the High Temperature Deposition Facility (HTDF) with a mean jet velocity of 150 m/s – 200 m/s with exit centerline temperature of 1525K to assess the capability of CRW in predicting particle deposition characteristics at high temperatures. The flow temperature was chosen in such a way that the temperature inside the pipe at any point is higher than the melting point of dust used, so that an `all stick' condition can be used to model particle-wall interactions. The derivation and the effect of the drift correction and the stochastic terms in the normalized Langevin equation were discussed in detail. Simulations were performed trying to reproduce experimental results with and (open full item for complete abstract)

Committee: Jeffrey Bons Dr. (Advisor); Lian Duan Dr. (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2020, Mechanical Engineering

In order to keep turbine blade surface temperature below melting point in gas turbine engines, internal passages in blades must be used to route cooler air through the blade. Design optimization of cooling passages necessitates an understanding of heat transfer patterns to minimize cooling mass flow. This project compares two approximations used to determine the heat transfer rate inside cooling channels in both computational and experimental investigations. The two approximations used in this project are constant surface temperature and transient heating. In an operating engine, the accuracy of both these conditions are not guaranteed. During steady state operation, the blade can cycle through many different flow paths which will impart different temperatures across the surface, and at no time will a blade be under completely uniform temperature except for the starting cycle. However, to make measurements of heat transfer easier, the two assumptions mentioned beforehand are utilized extensively. The constant surface temperature method uses a heater attached to the back of a thin copper plate to hold the surface temperature at a constant value in air flow. In the transient full-field method, thermochromic liquid crystals, which change colors with temperature, are applied to flat plate and turbulated geometries to capture the change in wall temperature during heating and cooling processes. Heat transfer rates are then derived from the transient temperature data using a semi-infinite solid model. The constant temperature approach is better established than the transient method and produces significantly higher Nusselt numbers, but the transient method provides better spatial resolution. A numerical conjugate heat transfer model is used to further investigate the discrepancy between the methods. The experimental geometry is replicated for both methods to gain an understanding of the fluid dynamics in each setup and how they differ.

Committee: Randall Mathison Ph.D (Advisor); Michael Dunn Ph.D (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Electrical and Computer Engineering

Electric power grids are currently undergoing a major transition from large centralized power stations to distributed generation in which small and flexible facilities produce power closer to where it is needed. This move towards a decentralized delivery of energy is driven by a combination of economic, technological and environmental factors. In recent years, the cost of renewable energy in the form wind turbines and solar PV has dropped dramatically due to advances in manufacturing and material science, leading to their rapid deployment across the US. To supplement the intermittent nature of wind and solar energy, there is a growing need for small, highly controllable sources such as natural gas turbines. With the fracking boom in the US, there is currently abundant natural gas to use for this purpose. The resulting proliferation of many small energy producers creates technical problems such as voltage and frequency control that can be addressed with battery storage, whose cost is also dropping. These factors are leading to a move away from large energy production facilities that require too much initial investment. Also, a distributed supply is more efficient and reliable. The threat of global climate change is creating pressure to increase the integration of distributed generation and information technology is now capable of managing a greater number of energy producers, utilizing a vast supply of information to predict supplies and demand and to determine optimal dispatching of energy. The move towards a higher percentage of renewable energy creates many interesting technical issues, many of which are due to the lack of control over the renewable resources. Energy dispatching between multiple sources, some controllable and some not, and multiple loads leads to a need for dispatching strategies that maximize the percentage of the load that is met with renewable energy. A growing aspect of this energy dispatch is a stream of information about energy demand, w (open full item for complete abstract)

Committee: Malcolm Daniels Dr. (Advisor) Subjects: Electrical Engineering; Energy; Mechanical Engineering