Matching Items (25)

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A Modeling System to Understand the Design and Performance of a Two Spool Gas Turbine Engine

Description

The purpose of my Honors Thesis was to generate a tool that could be implemented by Aerospace students at Arizona State University. This tool was created using MatLab which is

The purpose of my Honors Thesis was to generate a tool that could be implemented by Aerospace students at Arizona State University. This tool was created using MatLab which is the current program students are using. The modeling system that was generated goes step-by-step through the flow of a two spool gas turbine engine. The code was then compared to an ideal case engine with predictable values. It was found to have less than a 3 percent error for these parameters, which included optimal net work produced, optimal overall pressure ratio, and maximum pressure ratio. The modeling system was then run through a parametric analysis. In the first case, the bypass ratio was set to 0 and the freestream Mach number was set to 0. The second case was with a bypass ratio of 0 and fresstream Mach number of 0.85. The third case was with a bypass ratio of 5 and freestream Mach number of 0. The fourth case was with a bypass ratio of 5 and fresstream Mach number of 0.85. Each of these cases was run at various overall pressure ratios and maximum Temperatures of 1500 K, 1600 K and 1700 K. The results modeled the behavior that was expected. As the freestream Mach number was increased, the thrust decreased and the thrust specific fuel consumption increased, corresponding to an increase in total pressure at the combustor inlet. It was also found that the thrust was increased and the thrust specific fuel consumption decreased as the bypass ratio was increased. These results also make sense as there is less airflow passing through the engine core. Finally the engine was compared to two real engines. Both of which are General Electric G6 series engines. For the 80C2A3 engine, the percent difference between thrust and thrust specific fuel consumption was less than five percent. For the 50B, the thrust was below a two percent difference, but the thrust specific fuel consumption clearly provided inaccurate results. This could be caused by the lack of inputs provided by General Electric. The amount of fuel injected is largely dependent on the maximum temperature which is not available to the public. Overall, the code produces comparable results to real engines and can display how isolating and modifying a certain parameter effects engine performance.

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Created

Date Created
  • 2015-05

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Characterization of ingestion through the rim seal of rotor-stator disk cavity in a subscale single-stage axial turbine

Description

In order to achieve higher gas turbine efficiency, the main gas temperature at turbine inlet has been steadily increased from approximately 900°C to about 1500°C over the last few decades.

In order to achieve higher gas turbine efficiency, the main gas temperature at turbine inlet has been steadily increased from approximately 900°C to about 1500°C over the last few decades. This temperature is higher than the maximum acceptable temperature for turbine internals. The hot main gas may get ingested into the space between rotor and stator, the rotor-stator disk cavity in a stage because of the pressure differential between main gas annulus and the disk cavity. To reduce this ingestion, the disk cavity is equipped with a rim seal; additionally, secondary (purge) air is supplied to the cavity. Since the purge air is typically bled off the compressor discharge, this reducing the overall gas turbine efficiency, much research has been carried out to estimate the minimum purge flow necessary (cw,min) for complete sealing of disk cavities.

In this work, experiments have been performed in a subscale single-stage axial turbine featuring vanes, blades and an axially-overlapping radial-clearance seal at the disk cavity rim. The turbine stage is also equipped with a labyrinth seal radially inboard. The stage geometry and the experimental conditions were such that the ingestion into the disk cavity was driven by the pressure asymmetry in the main gas annulus. In the experiments, time-averaged static pressure was measured at several locations in the main annulus and in the disk cavity; the pressure differential between a location on the vane platform close to lip (this being the rim seal part on the stator) and a location in the 'seal region' in the cavity is considered to be the driving potential for both ingestion and egress. Time-averaged volumetric concentration of the tracer gas (CO2) in the purge air supplied was measured at multiple radial locations on the stator surface. The pressure and ingestion data were then used to calculate the ingestion and egress discharge coefficients for a range of purge flow rates, employing a simple orifice model of the rim seal. For the experiments performed, the egress discharge coefficient increased and the ingestion discharge coefficient decreased with the purge air flow rate. A method for estimation of cw,min is also proposed.

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Created

Date Created
  • 2014

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Modeling and characterization of ammonia injection and catalytic reduction in Kyrene Unit-7 HRSG

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

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.

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Created

Date Created
  • 2011

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Experimental study of the flow field in a model 1.5-stage gas turbine rotor-stator disk cavity

Description

A major concern in the operation of present-day gas turbine engines is the ingestion of hot mainstream gas into rotor-stator disk cavities of the high-pressure turbine stages. Although the engines

A major concern in the operation of present-day gas turbine engines is the ingestion of hot mainstream gas into rotor-stator disk cavities of the high-pressure turbine stages. Although the engines require high gas temperature at turbine entry for good performance efficiency, the ingested gas shortens the lives of the cavity internals, particularly that of the rotor disks. Steps such as installing seals at the disk rims and injecting purge (secondary) air bled from the compressor discharge into the cavities are implemented to reduce the gas ingestion. Although there are advantages to the above-mentioned steps, the performance of a gas turbine engine is diminished by the purge air bleed-off. This then requires that the cavity sealing function be achieved with as low a purge air supply rate as possible. This, in turn, renders imperative an in-depth understanding of the pressure and velocity fields in the main gas path and within the disk cavities. In this work, experiments were carried out in a model 1.5-stage (stator-rotor-stator) axial air turbine to study the ingestion of main air into the aft, rotor-stator, disk cavity. The cavity featured rotor and stator rim seals with radial clearance and axial overlap and an inner labyrinth seal. First, time-average static pressure distribution was measured in the main gas path upstream and downstream of the rotor as well as in the cavity to ensure that a nominally steady run condition had been achieved. Main gas ingestion was determined by measuring the concentration distribution of tracer gas (CO2) in the cavity. To map the cavity fluid velocity field, particle image velocimetry was employed. Results are reported for two main air flow rates, two rotor speeds, and four purge air flow rates.

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Created

Date Created
  • 2010

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Numerical simulation of environmental flow over buildings for renewable energy application

Description

For the increasing concerns of influence on environment by fossil-electricity generation, application of renewable energy becomes one of the most focused issues in society. Based on the limitation on urban

For the increasing concerns of influence on environment by fossil-electricity generation, application of renewable energy becomes one of the most focused issues in society. Based on the limitation on urban environment, wind turbines, which can be mounted on rooftop or between buildings, are regarded as a feasible way for wind energy generation. This study presents wind flow simulations in a large-scale environment with certain dimension buildings. Different inlet velocity boundary conditions are tested firstly, and the non-uniform inlet boundary condition shows better agreement with realistic situation. Turbulence intensity is set to be 10% for comparison consistency. The k-epsilon turbulence model is regarded as a better simulation for this certain condition. After that, three different structures, which include single building, pristine double building and modified circular gap double building systems, are tested in this environment condition. The result shows 18.8% velocity increasing on the top of single building system. Pristine double building systems are tested with 4 different gap distances, and building with 10 meters gap achieved the best velocity condition, which 32.8% velocity increasing and 11.8% improvement comparing to single building system, respectively. But the location of maximum velocity moves to the gap and the maximum velocity on the rooftop of double building system is approximately 5.1% lower than single building system. Based on previous study, modified circular gap double building system is created with 10 meters gap. Comparing result with single building system, modified circular gap system achieves higher improvement for wind flow, whose improvement of velocity increasing in the gap and on the rooftop of building are 47.1% and 3.0%, respectively. As a result, the modified circular gap double building can be regarded as a high efficiency system of environmental wind flow over buildings for renewable energy system.

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Created

Date Created
  • 2015

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A Computational Protocol for Spray Flows Using the Quadratic Formula as the Primary Atomization Module

Description

Computability of spray flows is an important issue, from both fundamental and practical perspectives. Spray flows have important applications in fuel injection, agriculture, medical devices, and industrial processes such as

Computability of spray flows is an important issue, from both fundamental and practical perspectives. Spray flows have important applications in fuel injection, agriculture, medical devices, and industrial processes such as spray cooling. For this reason, many efforts have been devoted to experimental, computational and some theoretical aspects of spray flows. In particular, primary atomization, the process of bulk liquid transitioning to small droplets, is a central and probably the most difficult aspect of spray flows. This thesis discusses developed methods, results, and needed improvements in the modeling of primary atomization using a predictive Sauter Mean Diameter (SMD) formula. Primary atomization for round injectors and simplex atomizers is modeled using a three-step procedure. For each spray geometry, a volume-of-fluid simulation is run to resolve the trajectory of the intact liquid core. Atomization criterion is applied to the volume-of-fluid velocity field to determine atomization sites. Local droplet size is predicted at the atomization sites using the quadratic formula for Sauter Mean Diameter. Droplets with the computed drop size are injected from the atomization sites and are tracked as point-particles. A User Defined Memory (UDM) code is employed to compute steady-state Sauter Mean Diameter statistics at locations corresponding to experimental interrogation locations. The resulting Sauter Mean Diameter, droplet trajectory, and droplet velocity are compared against experimental data to validate the computational protocol. This protocol can be implemented on coarse-grid, time-averaged simulations of spray flows, and produces convincing results when compared with experimental data for pressure-atomized sprays with and without swirl. This approach is general and can be adapted in any spray geometry for complete and efficient computations of spray flows.

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Created

Date Created
  • 2020

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Numerical Modeling of Cake Formation and Permeate Flux Decline in Membrane Filtration Using OpenFOAM

Description

Membrane filtration is an important technology in industry. In the past few decades, equations have been developed from experimental results to predict cake formation and permeate flux decline in the

Membrane filtration is an important technology in industry. In the past few decades, equations have been developed from experimental results to predict cake formation and permeate flux decline in the membrane filtration process. In the current work, the block of particles on membrane surface is achieved by setting surface flux on membrane surface zero. This approach is implemented for both microfiltration and nanofiltration using OpenFOAM. Moreover, a new method to deal with cake resistance for nanofiltration is introduced. Cake resistance is applied to both cake and membrane. To validate the new techniques, results of crossflow microfiltration are compared to theoretical results and results of two crossflow nanofiltration cases are compared to experimental data. In addition, the new techniques are applied to dead end filtration to observe the different structure of the cake and explore the effect of resistance on velocity profile.

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Date Created
  • 2018

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Non-invasive methods to detect underground leaks

Description

Water is one of, if not the most valuable natural resource but extremely challenging to manage. According to old research in the field, many Water Distribution Systems (WDSs) around the

Water is one of, if not the most valuable natural resource but extremely challenging to manage. According to old research in the field, many Water Distribution Systems (WDSs) around the world lose above 40 percent of clean water pumped into the distribution system because of unfortune leaks before the water gets anywhere from the fresh water resources. By reducing the amount of water leaked, distribution system managers can reduce the amount of money, resources, and energy wasted on finding and repairing the leaks, and then producing and pumping water, increase system reliability and more easily satisfy present and future needs of all consumers. But having access to this information pre-amatively and sufficiently can be complex and time taking. For large companies like SRP who are moving tonnes of water from various water bodies around phoenix area, it is even more crucial to efficiently locate and characterize the leaks. And phoenix being a busy city, it is not easy to go start digging everywhere, whenever a loss in pressure is reported at the destination.

Keeping this in mind, non-invasive methods to geo-physically work on it needs attention. There is a lot of potential in this field of work to even help with environmental crisis as this helps in places where water theft is big and is conducted through leaks in the distribution system. Methods like Acoustic sensing and ground penetrating radars have shown good results, and the work done in this thesis helps us realise the limitations and extents to which they can be used in the phoenix are.

The concrete pipes used by SRP are would not be able to generate enough acoustic signals to be affectively picked up by a hydrophone at the opening, so the GPR would be helpful in finding the initial location of the leak, as the water around the leak would make the sand wet and hence show a clear difference on the GPR. After that the frequency spectrum can be checked around that point which would show difference from another where we know a leak is not present.

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Created

Date Created
  • 2019

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Detailed validation assessment of turbine stage disc cavity rotating flows

Description

The subject of this thesis is concerned with the amount of cooling air assigned to seal high pressure turbine rim cavities which is critical for performance as well as component

The subject of this thesis is concerned with the amount of cooling air assigned to seal high pressure turbine rim cavities which is critical for performance as well as component life. Insufficient air leads to excessive hot annulus gas ingestion and its penetration deep into the cavity compromising disc life. Excessive purge air, adversely affects performance. Experiments on a rotating turbine stage rig which included a rotor-stator forward disc cavity were performed at Arizona State University. The turbine rig has 22 vanes and 28 blades, while the rim cavity is composed of a single-tooth rim lab seal and a rim platform overlap seal. Time-averaged static pressures were measured in the gas path and the cavity, while mainstream gas ingestion into the cavity was determined by measuring the concentration distribution of tracer gas (carbon dioxide). Additionally, particle image velocimetry (PIV) was used to measure fluid velocity inside the rim cavity between the lab seal and the overlap. The data from the experiments were compared to an 360-degree unsteady RANS (URANS) CFD simulations. Although not able to match the time-averaged test data satisfactorily, the CFD simulations brought to light the unsteadiness present in the flow during the experiment which the slower response data did not fully capture. To interrogate the validity of URANS simulations in capturing complex rotating flow physics, the scope of this work also included to validating the CFD tool by comparing its predictions against experimental LDV data in a closed rotor-stator cavity. The enclosed cavity has a stationary shroud, a rotating hub, and mass flow does not enter or exit the system. A full 360 degree numerical simulation was performed comparing Fluent LES, with URANS turbulence models. Results from these investigations point to URANS state of art under-predicting closed cavity tangential velocity by 32% to 43%, and open rim cavity effectiveness by 50% compared to test data. The goal of this thesis is to assess the validity of URANS turbulence models in more complex rotating flows, compare accuracy with LES simulations, suggest CFD settings to better simulate turbine stage mainstream/disc cavity interaction with ingestion, and recommend experimentation techniques.

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Created

Date Created
  • 2016

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Experimental study of main gas ingestion and purge gas egress flow in model gas turbine stages

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

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.

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Agent

Created

Date Created
  • 2010