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Description
Image processing in canals, rivers and other bodies of water has been a very important concern. This research using Image Processing was performed to obtain a photographic evidence of the data of the site which helps in monitoring the conditions of the water body and the surroundings. Images are captured using a digital camera and the images are stored onto a datalogger, these images are retrieved using a cellular/ satellite modem. A MATLAB program was designed to obtain the level of water by just entering the file name into to the program, a curve fit model was created to determine the contrast parameters. The contrast parameters were obtained using the data obtained from the gray scale image mainly the mean and variance of the intensity values. The enhanced images are used to determine the level of water by taking pixel intensity plots along the region of interest. The level of water obtained is accurate to less than 2% of the actual level of water observed from the image. High speed imaging in micro channels have various application in industrial field, medical field etc. In medical field it is tested by using blood samples. The experimental procedure proposed determines the flow duration and the defects observed in these channel using a fluid introduced into the micro channel the fluid being water based dye and whole milk. The viscosity of the fluid shows different types of flow patterns and defects in the micro channel. The defects observed vary from a small effect to the flow pattern to an extreme defect in the channel such as obstruction of flow or deformation in the channel. The sample needs to be further analyzed by SEM to get a better insight on the defects.
ContributorsShasedhara, Abhijeet Bangalore (Author) / Lee, Taewoo (Thesis advisor) / Huang, Huei-Ping (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2011
Description
A new method of adaptive mesh generation for the computation of fluid flows is investigated. The method utilizes gradients of the flow solution to adapt the size and stretching of elements or volumes in the computational mesh as is commonly done in the conventional Hessian approach. However, in the new method, higher-order gradients are used in place of the Hessian. The method is applied to the finite element solution of the incompressible Navier-Stokes equations on model problems. Results indicate that a significant efficiency benefit is realized.
ContributorsShortridge, Randall (Author) / Chen, Kang Ping (Thesis advisor) / Herrmann, Marcus (Thesis advisor) / Wells, Valana (Committee member) / Huang, Huei-Ping (Committee member) / Mittelmann, Hans (Committee member) / Arizona State University (Publisher)
Created2011
Description
Processed pyro-gel contains castor oil with solid component of boehmite (Al-OOH). The pyro-gel is synthesized by heat to convert boehmite to gamma-Al2O3 and to a certain extent alpha-Al2O3 nano-particles and castor oil into carbon residue. The effect of heat on pyro-gel is analyzed in a series of experiments using two burning chambers with the initial temperature as the main factor. The obtained temperature distribution profiles are studied and it is observed that the gel behaves very close to the theoretical prediction under heat. The carbon residue with Al2O3 is then processed for twelve hours and then analyzed to obtain the pore distribution of the Al2O3 nano-particles and the relation between the pore volume and the pre-heat temperature is analyzed. The obtained pore distribution shows the pore volume of Al2O3 nano-particles has direct relation to the pre-heat temperature. The experimental process involving the cylindrical reactor is simulated by using a finite rate chemistry eddy-dissipation model in a non-premixed and a porous mesh. The temperature distribution profile of the processed gel for both the meshes is obtained and a comparison is done with the data obtained in the experimental analysis. The temperature distribution obtained from the simulations show they follow a very similar profile to the temperature distribution obtained from experimental analysis, thus confirming the accuracy of both the models. The variation in numerical values between the experimental and simulation analysis is discussed. A physical model is proposed to determine the pore formation based on the temperature distribution obtained from experimental analysis and simulation.
ContributorsSagi, Varun (Author) / Lee, Taewoo (Thesis advisor) / Phelan, Patrick (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2010
Description
Derived from the necessity to increase testing capabilities of hybrid rocket motor (HRM) propulsion systems for Daedalus Astronautics at Arizona State University, a small-scale motor and test stand were designed and developed to characterize all components of the system. The motor is designed for simple integration and setup, such that both the forward-end enclosure and end cap can be easily removed for rapid integration of components during testing. Each of the components of the motor is removable allowing for a broad range of testing capabilities. While examining injectors and their potential it is thought ideal to obtain the highest regression rates and overall motor performance possible. The oxidizer and fuel are N2O and hydroxyl-terminated polybutadiene (HTPB), respectively, due to previous experience and simplicity. The injector designs, selected for the same reasons, are designed such that they vary only in the swirl angle. This system provides the platform for characterizing the effects of varying said swirl angle on HRM performance.
ContributorsSummers, Matt H (Author) / Lee, Taewoo (Thesis advisor) / Chen, Kangping (Committee member) / Wells, Valana (Committee member) / Arizona State University (Publisher)
Created2013
Description
Modern day gas turbine designers face the problem of hot mainstream gas ingestion into rotor-stator disk cavities. To counter this ingestion, seals are installed on the rotor and stator disk rims and purge air, bled off from the compressor, is injected into the cavities. It is desirable to reduce the supply of purge air as this decreases the net power output as well as efficiency of the gas turbine. Since the purge air influences the disk cavity flow field and effectively the amount of ingestion, the aim of this work was to study the cavity velocity field experimentally using Particle Image Velocimetry (PIV). Experiments were carried out in a model single-stage axial flow turbine set-up that featured blades as well as vanes, with purge air supplied at the hub of the rotor-stator disk cavity. Along with the rotor and stator rim seals, an inner labyrinth seal was provided which split the disk cavity into a rim cavity and an inner cavity. First, static gage pressure distribution was measured to ensure that nominally steady flow conditions had been achieved. The PIV experiments were then performed to map the velocity field on the radial-tangential plane within the rim cavity at four axial locations. Instantaneous velocity maps obtained by PIV were analyzed sector-by-sector to understand the rim cavity flow field. It was observed that the tangential velocity dominated the cavity flow at low purge air flow rate, its dominance decreasing with increase in the purge air flow rate. Radially inboard of the rim cavity, negative radial velocity near the stator surface and positive radial velocity near the rotor surface indicated the presence of a recirculation region in the cavity whose radial extent increased with increase in the purge air flow rate. Qualitative flow streamline patterns are plotted within the rim cavity for different experimental conditions by combining the PIV map information with ingestion measurements within the cavity as reported in Thiagarajan (2013).
ContributorsPathak, Parag (Author) / Roy, Ramendra P (Thesis advisor) / Calhoun, Ronald (Committee member) / Lee, Taewoo (Committee member) / Arizona State University (Publisher)
Created2013
Description
ABSTRACT The heat recovery steam generator (HRSG) is a key component of Combined Cycle Power Plants (CCPP). The exhaust (flue gas) from the CCPP gas turbine flows through the HRSG − this gas typically contains a high concentration of NO and cannot be discharged directly to the atmosphere because of environmental restrictions. In the HRSG, one method of reducing the flue gas NO concentration is to inject ammonia into the gas at a plane upstream of the Selective Catalytic Reduction (SCR) unit through an injection grid (AIG); the SCR is where the NO is reduced to N2 and H2O. The amount and spatial distribution of the injected ammonia are key considerations for NO reduction while using the minimum possible amount of ammonia. This work had three objectives. First, a flow network model of the Ammonia Flow Control Unit (AFCU) was to be developed to calculate the quantity of ammonia released into the flue gas from each AIG perforation. Second, CFD simulation of the flue gas flow was to be performed to obtain the velocity, temperature, and species concentration fields in the gas upstream and downstream of the SCR. Finally, performance characteristics of the ammonia injection system were to be evaluated. All three objectives were reached. The AFCU was modeled using JAVA - with a graphical user interface provided for the user. The commercial software Fluent was used for CFD simulation. To evaluate the efficacy of the ammonia injection system in reducing the flue gas NO concentration, the twelve butterfly valves in the AFCU ammonia delivery piping (risers) were throttled by various degrees in the model and the NO concentration distribution computed for each operational scenario. When the valves were kept fully open, it was found that it led to a more uniform reduction in NO concentration compared to throttling the valves such that the riser flows were equal. Additionally, the SCR catalyst was consumed somewhat more uniformly, and ammonia slip (ammonia not consumed in reaction) was found lower. The ammonia use could be decreased by 10 percent while maintaining the NO concentration limit in the flue gas exhausting into the atmosphere.
ContributorsAdulkar, Sajesh (Author) / Roy, Ramendra (Thesis advisor) / Lee, Taewoo (Thesis advisor) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2011
Description
This thesis examines themodeling, analysis, and control system design issues for scramjet powered hypersonic vehicles. A nonlinear three degrees of freedom longitudinal model which includes aero-propulsion-elasticity effects was used for all analyses. This model is based upon classical compressible flow and Euler-Bernouli structural concepts. Higher fidelity computational fluid dynamics and finite element methods are needed for more precise intermediate and final evaluations. The methods presented within this thesis were shown to be useful for guiding initial control relevant design. The model was used to examine the vehicle's static and dynamic characteristics over the vehicle's trimmable region. The vehicle has significant longitudinal coupling between the fuel equivalency ratio (FER) and the flight path angle (FPA). For control system design, a two-input two-output plant (FER - elevator to speed-FPA) with 11 states (including 3 flexible modes) was used. Velocity, FPA, and pitch were assumed to be available for feedback. Aerodynamic heat modeling and design for the assumed TPS was incorporated to original Bolender's model to study the change in static and dynamic properties. De-centralized control stability, feasibility and limitations issues were dealt with the change in TPS elasticity, mass and physical dimension. The impact of elasticity due to TPS mass, TPS physical dimension as well as prolonged heating was also analyzed to understand performance limitations of de-centralized control designed for nominal model.
ContributorsKhatri, Jaidev (Author) / Rodriguez, Armando Antonio (Thesis advisor) / Tsakalis, Konstantinos (Committee member) / Wells, Valana (Committee member) / Arizona State University (Publisher)
Created2011
Description
Efficient performance of gas turbines depends, among several parameters, on the mainstream gas entry temperature. At the same time, transport of this high temperature gas into the rotor-stator cavities of turbine stages affects the durability of rotor disks. This transport is usually countered by installing seals on the rotor and stator disk rims and by pressurizing the cavities by injecting air (purge gas) bled from the compressor discharge. The configuration of the rim seals influences the magnitude of main gas ingestion as well as the interaction of the purge gas with the main gas. The latter has aerodynamic and hub endwall heat transfer implications in the main gas path. In the present work, experiments were performed on model single-stage and 1.5-stage axial-flow turbines. The turbines featured vanes, blades, and rim seals on both the rotor and stator disks. Three different rim seal geometries, viz., axially overlapping radial clearance rim seals for the single-stage turbine cavity and the 1.5-stage turbine aft cavity, and a rim seal with angular clearance for the single-stage turbine cavity were studied. In the single-stage turbine, an inner seal radially inboard in the cavity was also provided; this effectively divided the disk cavity into a rim cavity and an inner cavity. For the aft rotor-stator cavity of the 1.5-stage turbine, a labyrinth seal was provided radially inboard, again creating a rim cavity and an inner cavity. Measurement results of time-average main gas ingestion into the cavities using tracer gas (CO2), and ensemble-averaged trajectories of the purge gas flowing out through the rim seal gap into the main gas path using particle image velocimetry are presented. For both turbines, significant ingestion occurred only in the rim cavity. The inner cavity was almost completely sealed by the inner seal, at all purge gas flow rates for the single-stage turbine and at the higher purge gas flow rates for 1.5-stage turbine. Purge gas egress trajectory was found to depend on main gas and purge gas flow rates, the rim seal configuration, and the azimuthal location of the trajectory mapping plane with respect to the vanes.
ContributorsBalasubramanian, Jagdish Harihara (Author) / Roy, Ramendra P (Thesis advisor) / Lee, Taewoo (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2010
Description
An understanding of aerodynamics is crucial for automobile performance and efficiency. There are many types of “add-on” aerodynamic devices for cars including wings, splitters, and vortex generators. While these have been studied extensively, rear spoilers have not, and their effects are not as widely known. A Computational Fluid Dynamics (CFD) and wind tunnel study was performed to study the effects of spoilers on vehicle aerodynamics and performance. Vehicle aerodynamics is geometry dependent, meaning what applies to one car may or may not apply on another. So, the Scion FRS was chosen as the test vehicle because it is has the “classic” sports car configuration with a long hood, short rear, and 2+2 passenger cabin while also being widely sold with a plethora of aftermarket aerodynamic modifications available. Due to computing and licensing restrictions, only a 2D CFD simulation was performed in ANSYS Fluent 19.1. A surface model of the centerline of the car was created in SolidWorks and imported into ANSYS, where the domain was created. A mesh convergence study was run to determine the optimum mesh size, and Realizable k-epsilon was the chosen physics model. The wind tunnel lacked equipment to record quantifiable data, so the wind tunnel was utilized for flow visualization on a 1/24 scale car model to compare with the CFD.
0° spoilers reduced the wake area behind the car, decreasing pressure drag but also decreasing underbody flow, causing a reduction in drag and downforce. Angled spoilers increased the wake area behind the car, increasing pressure drag but also increasing underbody flow, causing an increase in drag and downforce. Longer spoilers increased these effects compared to shorter spoilers, and short spoilers at different angles did not create significantly different effects. 0° spoilers would be best suited for cases that prioritize fuel economy or straight-line acceleration and speed due to the drag reduction, while angled spoilers would be best suited for cars requiring downforce. The angle and length of spoiler would depend on the downforce needed, which is dependent on the track.
0° spoilers reduced the wake area behind the car, decreasing pressure drag but also decreasing underbody flow, causing a reduction in drag and downforce. Angled spoilers increased the wake area behind the car, increasing pressure drag but also increasing underbody flow, causing an increase in drag and downforce. Longer spoilers increased these effects compared to shorter spoilers, and short spoilers at different angles did not create significantly different effects. 0° spoilers would be best suited for cases that prioritize fuel economy or straight-line acceleration and speed due to the drag reduction, while angled spoilers would be best suited for cars requiring downforce. The angle and length of spoiler would depend on the downforce needed, which is dependent on the track.
ContributorsNie, Alexander (Author) / Wells, Valana (Thesis director) / Huang, Huei-Ping (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-12
Description
Ingestion of high temperature mainstream gas into the rotor-stator cavities of a gas turbine is one of the major problems faced by the turbine designers. The ingested gas heats up rotor disks and induces higher thermal stresses on them, giving rise to durability concern. Ingestion is usually reduced by installing seals on the rotor and stator rims and by purging the disk cavity by secondary air bled from the compressor discharge. The geometry of the rim seals and the secondary air flow rate, together, influence the amount of gas that gets ingested into the cavities. Since the amount of secondary air bled off has a negative effect on the gas turbine thermal efficiency, one goal is to use the least possible amount of secondary air. This requires a good understanding of the flow and ingestion fields within a disk cavity. In the present study, the mainstream gas ingestion phenomenon has been experimentally studied in a model single-stage axial flow gas turbine. The turbine stage featured vanes and blades, and rim seals on both the rotor and stator. Additionally, the disk cavity contained a labyrinth seal radially inboard which effectively divided the cavity into a rim cavity and an inner cavity. Time-average static pressure measurements were obtained at various radial positions within the disk cavity, and in the mainstream gas path at three axial locations at the outer shroud spread circumferentially over two vane pitches. The time-average static pressure in the main gas path exhibited a periodic asymmetry following the vane pitch whose amplitude diminished with increasing distance from the vane trailing edge. The static pressure distribution increased with the secondary air flow rate within the inner cavity but was found to be almost independent of it in the rim cavity. Tracer gas (CO2) concentration measurements were conducted to determine the sealing effectiveness of the rim seals against main gas ingestion. For the rim cavity, the sealing effectiveness increased with the secondary air flow rate. Within the inner cavity however, this trend reversed -this may have been due to the presence of rotating low-pressure flow structures inboard of the labyrinth seal.
ContributorsThiagarajan, Jayanth kumar (Author) / Roy, Ramendra P (Thesis advisor) / Lee, Taewoo (Committee member) / Mignolet, Marc (Committee member) / Arizona State University (Publisher)
Created2013