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Title: A Multi-Species Single-LED Hazardous Gas Sensor for Commercial Space Applications.
Creator: Parupalli, Akshita, Vasu Sumathi, Subith, Ahmed, Kareem, Chow, Louis, University of Central Florida
Abstract / Description: In the interest of furthering both commercial and government-funded opportunities for deep space exploration, the safety of life and equipment onboard must be absolutely certain. In this regard, the presence of any hazardous gases or combustion events onboard space vehicles must be quickly characterized and detected. Several hazardous gases of interest have absorption features in the mid-infrared range and can be detected with an infrared light source, via the principles of absorption...
Show moreIn the interest of furthering both commercial and government-funded opportunities for deep space exploration, the safety of life and equipment onboard must be absolutely certain. In this regard, the presence of any hazardous gases or combustion events onboard space vehicles must be quickly characterized and detected. Several hazardous gases of interest have absorption features in the mid-infrared range and can be detected with an infrared light source, via the principles of absorption spectroscopy. A non-dispersive infrared (NDIR) sensor that follows these principles has been developed to utilize light-emitting diodes (LEDs) for gas detection and quantification. LEDs contain a particular advantage in this situation because they have low power requirements, are robust and easily adaptable, and they are cheaper than existing laser-based systems. The design has successfully performed several laboratory, environmental chamber, and high-altitude balloon flight tests. The main purpose of these various tests was to place the sensor in challenging environments, examine the effects on sensor performance, and adjust accordingly.The current sensor design utilizes a single 4.2?m LED and a rotating diffraction grating to detect both carbon dioxide (CO2) and nitrous oxide (N2O) within a single scan. These measurements were further validated using two distributed feedback quantum cascade lasers (QCL) centered at 4.25?m and 4.58?m. The sensor collected data on a wavelength range of 4117nm to 4592nm. Mixtures containing the concentrations of the two species of interest varying from 0.2% to 0.8% were analyzed. The integrated absorbance data was calculated for each species and compared with theoretical predictions. The results show that the data follows the expected behavior and correlates better at lower concentrations. Subsequent work on this sensor will focus on increasing the quantity of identifiable gases and on further testing in hazardous environments.
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Date Issued: 2019
Identifier: CFE0007898, ucf:52752
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007898

Title: Investigation of Heat Transfer Enhancement Within a Concentric Annulus.
Creator: Hanhold, Alexander, Kapat, Jayanta, Ahmed, Kareem, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Effective heat exchange is key for many energy applications including heat exchangers, heat extraction from heat source, and heat rejection to ambient thermal sink. This study focuses on the investigation for a specific heat exchange configuration, namely heat removal within a concentric annular passage using helical turbulators and jet impingement. Numerical testing was used to see how the different geometric parameters affect the heat transfer and pressure drop within the annulus by using...
Show moreEffective heat exchange is key for many energy applications including heat exchangers, heat extraction from heat source, and heat rejection to ambient thermal sink. This study focuses on the investigation for a specific heat exchange configuration, namely heat removal within a concentric annular passage using helical turbulators and jet impingement. Numerical testing was used to see how the different geometric parameters affect the heat transfer and pressure drop within the annulus by using helicoil turbulators. A vast range of designs were studied by changing the turbulator shape, pitch, and blockage ratio while maintaining a constant Reynolds number of 25,000. CFD was performed in STARCCM+ using the realizable ?-? turbulence model. Results show that turbulence and heat transfer increase with a higher blockage ratio and smaller pitch but the pressure drop is subsequently increased as well. The square turbulator promoted higher heat transfer compared to the circle turbulator but the pressure drop was significantly increased when the helix angle was greater than 20(&)deg; and blockage ratio greater than 0.48.Experimental and numerical efforts were used to find the heat transfer due to impingement jets on the target surface. Multiple flows as a function of jet Reynolds number ranging from 16,000-33,000 were tested for two geometries. Temperature Sensitive Paint (TSP) was utilized to observe local heat transfer. It was observed that jet degradation occurs after the 6th row of stream-wise impingement jets for both cases experimentally and it was difficult to numerically capture the effect of the cross flow from previous jets but managed to follow the same trend. The numerical results showed that they can be used with good agreement to predict the surface averaged Nusselt number to be within the 12% uncertainty found from experimental efforts. Geometry B was determined to perform better in terms of heat transfer as opposed to Geometry A with the same pressure loss.
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Date Issued: 2017
Identifier: CFE0007286, ucf:52155
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007286

Title: Influence of Transverse Slot Jet on Premixed Flame Acceleration.
Creator: Tarrant, Dylan, Ahmed, Kareem, Bhattacharya, Samik, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: This work aims to identify the key flow parameters that influence flame acceleration in a semi-confined square channel. A transverse fluidic jet was used as an active flow blockage mechanism and to introduce turbulence into the propagating flame. Three experimental parameters were used to examine the relative influence of (1) mixture reactivity defined here as system equivalence ratio (SER), (2) jet mixture composition (JMC), and the momentum ratio (MR) on the acceleration of laminar premixed...
Show moreThis work aims to identify the key flow parameters that influence flame acceleration in a semi-confined square channel. A transverse fluidic jet was used as an active flow blockage mechanism and to introduce turbulence into the propagating flame. Three experimental parameters were used to examine the relative influence of (1) mixture reactivity defined here as system equivalence ratio (SER), (2) jet mixture composition (JMC), and the momentum ratio (MR) on the acceleration of laminar premixed methane flame. High-speed PIV and schlieren photography were utilized to characterize the instantaneous flow-field conditions throughout the flame-jet interaction. Using these diagnostic techniques, flame front positions and local velocity vector fields have been spatially and temporally resolved. Changes in flame properties including flame structure, velocity, and vorticity were tracked as a function of time. Stoichiometric equivalence ratios were more effective in the production of vorticity and the promotion of flame acceleration. The stoichiometric condition accelerated the flame to the highest final flame velocity of the three parameters examined. Different compositions of the jet mixture demonstrated that the flame acceleration is primarily affected by the jet turbulence and not on the reactivity of the jet compositions. Out of the three parameters examined, the momentum ratio parameter had the least amount of influence on the flow field and flame acceleration. The increase of 33 % in the momentum ratio had negligible effect in the final flame front velocity and implies that the jet turbulence is the main driving mechanism for flame acceleration.
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Date Issued: 2018
Identifier: CFE0007255, ucf:52186
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007255

Title: Ignition Studies of Oxy-Syngas/CO2 Mixtures Using Shock Tube for Cleaner Combustion Engines.
Creator: Barak, Samuel, Vasu Sumathi, Subith, Kapat, Jayanta, Ahmed, Kareem, University of Central Florida
Abstract / Description: In this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2 cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% - 85% by volume...
Show moreIn this study, syngas combustion was investigated behind reflected shock waves in order to gain insight into the behavior of ignition delay times and effects of the CO2 dilution. Pressure and light emissions time-histories measurements were taken at a 2 cm axial location away from the end wall. High-speed visualization of the experiments from the end wall was also conducted. Oxy-syngas mixtures that were tested in the shock tube were diluted with CO2 fractions ranging from 60% - 85% by volume. A 10% fuel concentration was consistently used throughout the experiments. This study looked at the effects of changing the equivalence ratios (?), between 0.33, 0.5, and 1.0 as well as changing the fuel ratio (?), hydrogen to carbon monoxide, from 0.25, 1.0 and 4.0. The study was performed at 1.61-1.77 atm and a temperature range of 1006-1162K. The high-speed imaging was performed through a quartz end wall with a Phantom V710 camera operated at 67,065 frames per second. From the experiments, when increasing the equivalence ratio, it resulted in a longer ignition delay time. In addition, when increasing the fuel ratio, a lower ignition delay time was observed. These trends are generally expected with this combustion reaction system. The high-speed imaging showed non-homogeneous combustion in the system, however, most of the light emissions were outside the visible light range where the camera is designed for. The results were compared to predictions of two combustion chemical kinetic mechanisms: GRI v3.0 and AramcoMech v2.0 mechanisms. In general, both mechanisms did not accurately predict the experimental data. The results showed that current models are inaccurate in predicting CO2 diluted environments for syngas combustion.
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Date Issued: 2018
Identifier: CFE0006974, ucf:52909
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006974

Title: Shock Tube Investigations of Novel Combustion Environments Towards a Carbon-Neutral Future.
Creator: Barak, Samuel, Vasu Sumathi, Subith, Kapat, Jayanta, Ahmed, Kareem, University of Central Florida
Abstract / Description: Supercritical carbon dioxide (sCO2) cycles are being investigated for the future of power generation. These cycles will contribute to a carbon-neutral future to combat the effects of climate change. These direct-fired closed cycles will produce power without adding significant pollutants to the atmosphere. For these cycles to be efficient, they will need to operate at significantly higher pressures (e.g., 300 atm for Allam Cycle) than existing systems (typically less than 40 atm). There is...
Show moreSupercritical carbon dioxide (sCO2) cycles are being investigated for the future of power generation. These cycles will contribute to a carbon-neutral future to combat the effects of climate change. These direct-fired closed cycles will produce power without adding significant pollutants to the atmosphere. For these cycles to be efficient, they will need to operate at significantly higher pressures (e.g., 300 atm for Allam Cycle) than existing systems (typically less than 40 atm). There is limited knowledge on combustion at these pressures or at the high dilution of carbon dioxide. Nominal fuel choices for gas turbines include natural gas and syngas (mixture of CO and H2). Shock tubes study these problems in order to understand the fundamentals and solve various challenges. Shock tube experiments have been studied by the author in the sCO2 regime for various fuels including natural gas, methane and syngas. Using the shock tube to take measurements, pressure and light emissions time-histories measurements were taken at a 2-cm axial location away from the end wall. Experiments for syngas at lower pressure utilized high-speed imaging through the end wall to investigate the effects of bifurcation. It was found that carbon dioxide created unique interactions with the shock tube compared to tradition bath gasses such as argon. The experimental results were compared to predictions from leading chemical kinetic mechanisms. In general, mechanisms can predict the experimental data for methane and other hydrocarbon fuels; however, the models overpredict for syngas mixtures. Reaction pathway analysis was evaluated to determine where the models need improvements. A new shock tube has been designed and built to operate up to 1000 atm pressures for future high-pressure experiments. Details of this new facility are included in this work. The experiments in this work are necessary for mechanism development to design an efficient combustor operate these cycles.
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Date Issued: 2019
Identifier: CFE0007781, ucf:52359
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007781

Title: Heat Transfer, Friction, and Turbulent Analysis on Single Ribbed-Wall Square Channel.
Creator: Vergos, Christopher, Kapat, Jayanta, Vasu Sumathi, Subith, Ahmed, Kareem, University of Central Florida
Abstract / Description: An experimental investigation of heat transfer and friction behavior for a fully developed flow in a non-rotating square channel was conducted under a wide range of Reynolds numbers from 6,000 to 180,000. The rig used in this study was a single ribbed wall variant of Ahmed et al.'s [ 1 ] rig from which results of this rig were compared. Ahmed et al.'s rig was a replica of Han et al.'s square channel [ 2 ] used to validate their work, and expand the Reynolds number range for both heat transfer...
Show moreAn experimental investigation of heat transfer and friction behavior for a fully developed flow in a non-rotating square channel was conducted under a wide range of Reynolds numbers from 6,000 to 180,000. The rig used in this study was a single ribbed wall variant of Ahmed et al.'s [ 1 ] rig from which results of this rig were compared. Ahmed et al.'s rig was a replica of Han et al.'s square channel [ 2 ] used to validate their work, and expand the Reynolds number range for both heat transfer and friction data. The test section was 22 hydraulic diameters (Dh) long, and made of four aluminum plates. One rib roughened bottom wall, and three smooth walls bounded the flow. Glued brass ribs oriented at 45(&)deg; to the flow direction, with a ratio of rib height to channel hydraulic diameter (e/Dh) and a ratio of pitch to rib height (p/e) of 0.063 and 10, respectively, lined the bottom wall. A 20Dh long acrylic channel with a continuation of the test section's interior was attached at the inlet of the test section to confirm the fully developed flow. Heat transfer tests were conducted in a Reynolds number range of 20,000 to 150,000. During these tests, the four walls were held under isothermal conditions. Wall-averaged, and module-averaged Nusselt values were calculated from the log-mean temperature differences between the plate surface temperature and calculated, by energy balance, fluid bulk temperature. Streamwise Nusselt values become constant at an x/Dh of 8 within the tested Reynolds number range. Wall averaged Nusselt values were determined after x/Dh=8, and scaled by the Dittus-Boelter correlation, Nuo, for smooth ducts to yield a Nusselt augmentation value (Nu/Nuo). Non-heated friction tests were conducted from a Reynolds number range of 6,000 to 180,000. Pressure drop along the channel was recorded, and channel-averaged Darcy-Weisbach friction factor was calculated within the range of Reynolds number tested. Scaling the friction factor by the smooth-wall Blasius correlation, fo, gave the friction augmentation (f/fo). The thermal performance, a modified ratio of the Nusselt and friction augmentation used by Han et al. [ 2 ], was then calculated to evaluate the bottom-line performance of the rig. It was found that the Nusselt augmentation approached a constant value of 1.4 after a Reynolds number of 60,000 while friction augmentation continued to increase in a linear fashion past that point. This caused the overall thermal performance to decline as Reynolds number increased up to a certain point. Further studies were conducted in an all acrylic, non-heated variant of the rig to study the fluid flow in the streamwise direction on, and between two ribs in the fully developed region of the channel. Single-wire hot-wire anemometry characterized velocity magnitude profiles with great detail, as well as turbulence intensity for Reynolds numbers ranging from 5,000 to 50,000. As the Reynolds number increased the reattachment point between two ribs remained about stationary while the turbulence intensity receded to the trailing surface of the upstream rib, and dissipated as it traveled. At low Reynolds numbers, between 5,000 and 10,000, the velocity and turbulence intensity streamwise profiles seemed to form two distinct flow regions, indicating that the flow over the upstream rib never completely attached between the two ribs. Integral length-scales were also derived from the autocorrelation function using the most turbulent signal acquired at each Reynolds number. It was found that there is a linear trend between Reynolds number and the integral length-scale at the most turbulent points in the flow. For example, at Re=50,000 the most the length scale found just past the first rib was on the order of two times the height of the rib. Rivir et al. [ 30 ] found in a similar case that at Re = 45,000, it was 1.5 times the rib height. Several factors could influence the value of this integral length-scale, but the fact that their scale is on the order of what was obtained in this case gives some level of confidence in the value.
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Date Issued: 2017
Identifier: CFE0007138, ucf:52318
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007138

Title: Ellipsometric Measurements of Alternative Fuels.
Creator: Nash, Leigh, Vasu Sumathi, Subith, Kapat, Jayanta, Ahmed, Kareem, University of Central Florida
Abstract / Description: Alternative jet fuels will be important in the future to ensure cleaner burning, reliable, and reasonably priced air transportation. One important property that must meet certification standards is the fuel's thermal stability, or its ability to withstand heating before breaking down. Jet fuels are used as engine coolants, and thermally unstable fuels can form deposits in the fuel delivery systems, leading to a loss of fuel flow. In the past, the thermal stability of a fuel was rated using a...
Show moreAlternative jet fuels will be important in the future to ensure cleaner burning, reliable, and reasonably priced air transportation. One important property that must meet certification standards is the fuel's thermal stability, or its ability to withstand heating before breaking down. Jet fuels are used as engine coolants, and thermally unstable fuels can form deposits in the fuel delivery systems, leading to a loss of fuel flow. In the past, the thermal stability of a fuel was rated using a color standard method. The color of the deposit left on a metal tube that had been heated and exposed to a test fuel were matched with a color standard to rate the level of deposition, and thus the fuel's thermal stability. Ellipsometry, which is an optical technique that uses changes in a beam of light's polarization after it reflects off a sample to determine the thickness of any film on that sample, has recently been implemented to improve the thermal stability characterization standard.Various aspects of the ellipsometric method have been investigated in this work. In addition, several thermal stability studies were carried out. The effect of increasing temperature on the thermal stability of Sasol Iso-Paraffinic Kerosene, Jet A, JP-8, and Gevo jet fuel have been analyzed, and the effect of varying levels of the additive naphthalene in Sasol IPK has also been investigated. Various theoretical optical models have been evaluated for their ability to predict deposit thickness. Finally, attempts to validate these measurements were made using scanning electron microscopy, ellipsometric tube rating, interferometric tube rating, and reference tubes. The analysis carried out in this work was used to make recommendations for improving the thermal stability test standard.
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Date Issued: 2017
Identifier: CFE0007130, ucf:52323
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007130

Title: Mechanisms of Flame Extinction for Bluff Body Stabilized Flames with Influences of Pressure Gradient Tailoring.
Creator: Morales, Anthony, Ahmed, Kareem, Bhattacharya, Samik, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Flame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NOx emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic...
Show moreFlame extinction continues to hinder the performance of combustion technologies used in propulsion systems and power generating turbomachinery. Within these applications, there is a crucial need to improve energy output while minimizing harmful environmental impacts. Lean combustion helps attain these goals by minimizing fuel costs and reducing NOx emissions. However, operating at lean conditions increases the likelihood of flame extinction; the flame becomes more susceptible to hydrodynamic instabilities which can induce global blowout and termination of the combustion process. The work in this thesis is focused on identifying the mechanisms of flame extinction and controlling these mechanisms via pressure gradient tailoring. This is accomplished within a premixed blow-down combustion facility utilizing a bluff body flame stabilizer where flame extinction is induced by removing the flow of fuel into the reactant mixture. CH* chemiluminescence imaging and high-speed particle imaging velocimetry (PIV) are used to determine the flame boundary and resolve the reacting flow field, respectively. The mechanisms of flame extinction are attributed to the changing vorticity dynamics within the flow field as the equivalence ratio is reduced, which will directly influence the strain rate experienced by the flame. To influence these vorticity dynamics, the test section walls are manipulated to alter the downstream pressure gradients. It is determined that increasing the magnitude of the downstream pressure gradient increases the growth of the strain rate and vorticity experienced by the flame.
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Date Issued: 2018
Identifier: CFE0007229, ucf:52240
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007229

Title: Investigation of oxy-fuel combustion behind reflected shockwaves.
Creator: Pryor, Owen, Vasu Sumathi, Subith, Kapat, Jayanta, Kassab, Alain, University of Central Florida
Abstract / Description: Supercritical carbon dioxide has brought about new questions on the chemical kinetics of several small hydrocarbon fuels and the effects of carbon dioxide as the primary diluent on the different fuels. This report presents work on the ignition delay times and several species time-histories of methane, ethylene and syngas over a range of conditions. All experiments were conducted behind reflected shock waves using two different shock tubes. The ignition delay times were measured using a GaP...
Show moreSupercritical carbon dioxide has brought about new questions on the chemical kinetics of several small hydrocarbon fuels and the effects of carbon dioxide as the primary diluent on the different fuels. This report presents work on the ignition delay times and several species time-histories of methane, ethylene and syngas over a range of conditions. All experiments were conducted behind reflected shock waves using two different shock tubes. The ignition delay times were measured using a GaP photodetector to measure the emission of light. The species time-histories were measured using single laser spectroscopy. The effect of CO2 as a diluent on the fluid dynamics of the system were also examined using high-speed camera images. It was determined that the ignition delay times and fuel time-histories were able to be accurately predicted by mechanisms in the literature for pressures up to 30 atm but the literature mechanisms were unable to predict the carbon monoxide time-histories beyond qualitative trends for the various fuels. It was also determined that the carbon monoxide had a string effect on the fluid dynamics of the experiments resulting in a significantly smaller chemical reaction zone. Experiments were also performed to examine the effects of water as a diluent with a ratio up to 66% of the total diluent on the ignition delay times. Using the experimental data, a global kinetic mechanism was created for methane and syngas to predict the ignition delay times and the carbon monoxide time-histories for pressures up to 300 atm.
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Date Issued: 2018
Identifier: CFE0007236, ucf:52216
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007236

Title: Numerical Simulation of Non-Premixed and Premixed Axial Stage Combustor at High Pressure.
Creator: Worbington, Tyler, Ahmed, Kareem, Bhattacharya, Samik, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Axial-staged combustors represent an important concept that can be applied to reduce NOx emissions throughout a gas turbine engine. There are four main CFD models presented in this study that describe a highly turbulent jet-in-crossflow (JIC) simulation of partially premixed and non-premixed jets with a constant chamber pressure of 5 atm absolute. The equivalence ratio of the partially premixed jet was held constant at rich conditions with a ?_jet of 4 while the main stage varied from ?_1 and...
Show moreAxial-staged combustors represent an important concept that can be applied to reduce NOx emissions throughout a gas turbine engine. There are four main CFD models presented in this study that describe a highly turbulent jet-in-crossflow (JIC) simulation of partially premixed and non-premixed jets with a constant chamber pressure of 5 atm absolute. The equivalence ratio of the partially premixed jet was held constant at rich conditions with a ?_jet of 4 while the main stage varied from ?_1 and ?_2 of 0.575 and 0.73 with an average headend temperature of 1415K and 1545K, respectively. Chemistry was reduced by tabulation of eight main species using the equilibrium calculation of the software Chemkin. The centerline temperatures entering the JIC stage were measured experimentally and used as the starting point of a radial temperature profile that follows a parabolic trend. Comparison between the uniform and radial temperature profiles showed that the latter had a higher penetration depth into the vitiated crossflow due to a direct relationship between temperature and velocity. To capture the combustion process, Flamelet Generated Manifold (FGM) model was used. The progress variable source uses Turbulent Flame Speed Closure (TFC) to calculate flame propagation and position. There are two distinct flame positions of stability, the windward and leeward sides of the jet. The leeward flame positions for the two equivalence ratios showed that the richer condition sits closer to the jet due to the hotter equilibrium temperature; while the windward flame position is shifted upstream for the leaner case due to more availability of oxygen. The total temperature rise for ?_1 = 0.575 and ?_2 = 0.73 are ?T = 239 K and 186 K, respectively. The non-premixed simulations used a Steady Laminar Flamelet (SLF) approach with a headend equivalence ratio of ?_non = 0.6 and a detailed prediction of CH4 usage, CO production, and temperature increase throughout the jet-in-crossflow domain. Methane was shown to be consumed at a high amount, at almost 90% conversion with a temperature rise of ?T = 149 K. The heat release is below the calculated equilibrium ?T with the main reason pointed out that a significant amount of CH4 is only partially oxidized to CO due to limited oxygen availability with a fuel only configuration. Realizable K-Epsilon, SST K-Omega ?-Re?, and Reynolds Stress Transport (RST) turbulence models were used and compared. RST turbulence model showed to over predict the penetration depths and dissipation of the jet in the downstream domain when compared to literature and experimental data.
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Date Issued: 2019
Identifier: CFE0007880, ucf:52772
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007880

Title: Surface Measurements and Predictions of Full-Coverage Film Cooling.
Creator: Natsui, Gregory, Kapat, Jayanta, Raghavan, Seetha, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Full-coverage film cooling is investigated both experimentally and numerically. First,surface measurements local of adiabatic film cooling eeffectiveness and heat transfer augmentation for four different arrays are described. Reported next is a comparison between two very common turbulence models, Realizable k-epsilon and SST k-omega, and their ability to predict local film cooling effectiveness throughout a full-coverage array.The objective of the experimental study is the quantification of...
Show moreFull-coverage film cooling is investigated both experimentally and numerically. First,surface measurements local of adiabatic film cooling eeffectiveness and heat transfer augmentation for four different arrays are described. Reported next is a comparison between two very common turbulence models, Realizable k-epsilon and SST k-omega, and their ability to predict local film cooling effectiveness throughout a full-coverage array.The objective of the experimental study is the quantification of local heat transferaugmentation and adiabatic film cooling effectiveness for four surfaces cooled by large, both in hole count and in non-dimensional spacing, arrays of film cooling holes. The four arrays are of two different hole-to-hole spacings (P=D = X=D = 14.5; 19.8) and two different hole inclination angles (alpha = 30°; 45°), with cylindrical holes compounded relative to the flow(beta = 45°) and arranged in a staggered configuration. Arrays of up to 30 rows are tested so that the superposition effect of the coolant film can be studied. In addition, shortened arrays of up to 20 rows of coolant holes are also tested so that the decay of the coolant film following injection can be studied.Levels of laterally averaged effectiveness reach values as high as η = 0.5, and are not yet at the asymptotic limit even after 20 - 30 rows of injection for all cases studied. Levels of heat transfer augmentation asymptotically approach values of h=h0 ≈ 1.35 rather quickly, only after 10 rows. It is conjectured that the heat transfer augmentation levels off very quickly due to the boundary layer reaching an equilibrium in which the perturbation from additional film rows has reached a balance with the damping effect resulting from viscosity. The levels of laterally averaged adiabatic film cooling effectiveness far exceeding eta = 0.5 aremuch higher than expected. The heat transfer augmentation levels off quickly as opposed tothe film effectiveness which continues to rise (although asymptotically) at large row numbers. This ensures that an increased row count represents coolant well spent.The numerical predictions are carried out in order to test the ability of the two mostcommon turbulence models to properly predict full-coverage film cooling. The two models chosen, Realizable k-epsilon (RKE) and Shear Stress Transport k-omega (SSTKW), areboth two-equation models coupled with Reynolds Averaged governing equations which makeseveral gross physical assumptions and require several empirical values. Hence, the modelsare not expected to provide perfect results. However, very good average values are seen tobe obtained through these simple models. Using RKE in order to model full-coverage filmcooling will yield results with 30% less error than selecting SSTKW.
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Date Issued: 2012
Identifier: CFE0004580, ucf:49221
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004580

Title: Optimization of Ocean Thermal Energy Conversion Power Plants.
Creator: Rizea, Steven, Ilie, Marcel, Bai, Yuanli, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: A proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select...
Show moreA proprietary Ocean Thermal Energy Conversion (OTEC) modeling tool, the Makai OTEC Thermodynamic and Economic Model (MOTEM), is leveraged to evaluate the accuracy of finite-time thermodynamic OTEC optimization methods. MOTEM is a full OTEC system simulator capable of evaluating the effects of variation in heat exchanger operating temperatures and seawater flow rates. The evaluation is based on a comparison of the net power output of an OTEC plant with a fixed configuration. Select optimization methods from the literature are shown to produce between 93% and 99% of the maximum possible amount of power, depending on the selection of heat exchanger performance curves. OTEC optimization is found to be dependent on the performance characteristics of the evaporator and condenser used in the plant. Optimization algorithms in the literature do not take heat exchanger performance variation into account, which causes a discrepancy between their predictions and those calculated with MOTEM. A new characteristic metric of OTEC optimization, the ratio of evaporator and condenser overall heat transfer coefficients, is found. The heat transfer ratio is constant for all plant configurations in which the seawater flow rate is optimized for any particular evaporator and condenser operating temperatures. The existence of this ratio implies that a solution for the ideal heat exchanger operating temperatures could be computed based on the ratio of heat exchanger performance curves, and additional research is recommended.
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Date Issued: 2012
Identifier: CFE0004430, ucf:49343
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004430

Title: Dynamics of a Perfectly Premixed Jet Flame Exhibiting Self-Excited High-Frequency, Transverse Thermoacoustic Instabilities.
Creator: Tran, Lucky, Kapat, Jayanta, Kassab, Alain, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: This work is an investigation of the behavior of a premixed turbulent jet flame in a cylindrical dump combustor. The degeneracy of the simple configuration in this study lends itself for a detailed study of inherent mechanisms of a self-excited thermoacoustic instability in isolation from system coupling effects, enabling detailed numerical simulations to be carried out to supplement experimental findings. Tests were done at a nominal pressure of 8 bar and inlet temperature around 450 ?C....
Show moreThis work is an investigation of the behavior of a premixed turbulent jet flame in a cylindrical dump combustor. The degeneracy of the simple configuration in this study lends itself for a detailed study of inherent mechanisms of a self-excited thermoacoustic instability in isolation from system coupling effects, enabling detailed numerical simulations to be carried out to supplement experimental findings. Tests were done at a nominal pressure of 8 bar and inlet temperature around 450 ?C. Self-excited large eddy simulations were also carried out in OpenFOAM, using a b-? flame-wrinkling model to model the combustion process. Eigenfrequency analysis in COMSOL was also done to support and explain the findings from both the numerical simulations and trends observed in the experiments. Measurements from high frequency pressure transducers were analyzed to determine the frequencies of the excited modes in the rig test and compared to the spectra from the LES simulation. The time-resolved fields from the LES simulation were phase-averaged to deduce the acoustic-flame interactions. Despite the (axis)symmetry in this configuration, the non-axisymmetric 1T and 1T1L modes were (simultaneously) excited. Two distinct behaviors are noted for the dynamic flame behavior. In the downstream region, the flame motion is well described by a bulk kinematic displacement as a result of the interaction of the flame front with the local acoustic perturbation. In the upstream region, near the combustor dump plane, large-scale wrinkles are observed in the flame front that have characteristics of a convective wave. The current findings provide additional evidence supporting and further establishing the theory of inherent acoustic-flame interactions as an excitation mechanism (distinct from acoustically-induced hydrodynamic oscillations) for high-frequency, transverse thermoacoustic instabilities.
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Date Issued: 2019
Identifier: CFE0007542, ucf:52616
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007542

Title: Mid-Infrared Absorption Spectrometer for Multi-Species Detection Using LEDs for Space Applications: Development and Flight Testing.
Creator: Villar, Michael, Vasu Sumathi, Subith, Chow, Louis, Partridge, William, University of Central Florida
Abstract / Description: As commercial space travel expands, the need for specialized instrumentation to ensure the safety of crew and cargo becomes increasingly necessary. Both the Federal Aviation Administration (FAA) and pioneers in the space tourism industry have expressed an interest in a robust, low cost, and low power consumption sensor to measure atmospheric composition aboard spacecraft. To achieve this goal a time-resolved NDIR absorption sensor that measures transient levels of gaseous carbon dioxide (CO2)...
Show moreAs commercial space travel expands, the need for specialized instrumentation to ensure the safety of crew and cargo becomes increasingly necessary. Both the Federal Aviation Administration (FAA) and pioneers in the space tourism industry have expressed an interest in a robust, low cost, and low power consumption sensor to measure atmospheric composition aboard spacecraft. To achieve this goal a time-resolved NDIR absorption sensor that measures transient levels of gaseous carbon dioxide (CO2) and carbon monoxide (CO) was developed. The developed sensor has a wide range of applications applicable to the growing needs of industry, from monitoring CO and CO2 levels for crew cabin safety to early detection of gas leaks, fires, or other atmospheric altering events. A proof of concept, lab-bench dependent sensor has been previously developed to begin to target the needs of this industry. This thesis discusses the expansion and evolution from this previous lab-bench dependent design into a portable, autonomous, and remote sensor that is able to withstand the harsh environmental conditions required for its intended operation in near space. The sensor incorporates compact high-efficiency LEDs that transmit in the 3-5?m wavelength range. These LEDs are further centered at 4.2?m and 4.7?m by the use of narrow band-pass filters to measure the spectral absorbance features of CO2 and CO respectively. Active and passive thermal management of all components is achieved via thermal electric coolers (TEC) and thermal sinks to enable sensor temperature control in applicable low convection environments. To accomplish the needs for a stand-alone sensor, remote and autonomous operation is achieved via the inclusion of a real-time embedded controller with configurable FPGA/IO modules that autonomously handle thermal management, LED operation, and signal data acquisition/storage. Initial instrument validation was completed by utilizing a thermal vacuum chamber with a testable temperature and pressure range from standard temperature and pressure (STP) down to -22(&)deg;F and 8mbar. Variable measurements of CO/CO2/N2 gas mixtures were supplied via mass flow controllers to the sensor's gas cell in order to determine various key metrics of sensor operation. The culmination of the sensor's operational validation was via its flight aboard a NASA funded Louisiana State University (LSU) high-altitude balloon. This flight reached an altitude of 123,546ft with ambient temperatures and static pressures ranging from 910mbar and 53(&)deg;F at ground level to .68mbar and -54(&)deg;F at float altitude. A total mission time of 18h:09m:30s was reached with a total float time of 15h:08m:54s. Successful sensor operation was achieved throughout the entire mission which demonstrates the applicability, adaptability, and relevance of the technologies discussed here for space applications.
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Date Issued: 2017
Identifier: CFE0006671, ucf:51238
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006671

Title: Combustion of 1,3-Butadiene behind Reflected Shocks.
Creator: Lopez, Joseph, Vasu Sumathi, Subith, Orlovskaya, Nina, Kassab, Alain, University of Central Florida
Abstract / Description: The chemical kinetics of 1,3-butadiene (1,3-C4H6) are important because 1,3-butadiene is a major intermediate during the combustion of real fuels. However, there is only limited information on the chemical kinetics of 1,3-butadiene combustion, which has applications in several combustion schemes that are currently being developed, including spark-assisted homogeneous charge compression ignition and fuel reformate exhaust gas recirculation.In the present work, the ignition delay times of 1,3...
Show moreThe chemical kinetics of 1,3-butadiene (1,3-C4H6) are important because 1,3-butadiene is a major intermediate during the combustion of real fuels. However, there is only limited information on the chemical kinetics of 1,3-butadiene combustion, which has applications in several combustion schemes that are currently being developed, including spark-assisted homogeneous charge compression ignition and fuel reformate exhaust gas recirculation.In the present work, the ignition delay times of 1,3-butadiene mixtures has been investigated using pressure data. Oxidation of 1,3-butadiene/oxygen mixtures diluted in argon or nitrogen at equivalence ratios (?) of 0.3 behind reflected shock waves has been studied at temperatures ranging from 1100 to 1300K and at pressures ranging from 1 to 2atm. Reaction progress was monitored by recording concentration time-histories of 1,3-butadiene and OH* radical at a location 2cm from the end wall of a 13.4m long shock tube with an inner diameter of 14cm. 1,3-Butadiene concentration time-histories were measured by absorption spectroscopy at 10.5?m from the P14 line of a tunable CO2 gas laser. OH* production was measured by recording emission around 306.5nm with a pre-amplified gallium phosphide detector and a bandpass filter. Ignition delay times were also determined from the OH* concentration time-histories. The measured concentration time-histories and ignition delay times were compared with two chemical kinetics models. The measured time-histories and ignition delay times provide targets for the refinement of chemical kinetic models at the studied conditions.
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Date Issued: 2017
Identifier: CFE0006618, ucf:51276
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006618

Title: Planar Laser Induced Fluorescence Experiments and Modeling Study of Jets in Crossflow at Various Injection Angles.
Creator: Thompson, Luke, Vasu Sumathi, Subith, Kassab, Alain, Kapat, Jayanta, University of Central Florida
Abstract / Description: Planar Laser Induced Fluorescence (PLIF) with acetone seeding was applied to measure the scalar fields of an axisymmetric freejet and an inclined jet-in-crossflow as applicable to film cooling. From the scalar fields, jet-mixing and trajectory characteristics were obtained. In order to validate the technique, the canonical example of a nonreacting freejet of Reynolds Numbers 900-9000 was investigated. Desired structural characteristics were observed and showed strong agreement with...
Show morePlanar Laser Induced Fluorescence (PLIF) with acetone seeding was applied to measure the scalar fields of an axisymmetric freejet and an inclined jet-in-crossflow as applicable to film cooling. From the scalar fields, jet-mixing and trajectory characteristics were obtained. In order to validate the technique, the canonical example of a nonreacting freejet of Reynolds Numbers 900-9000 was investigated. Desired structural characteristics were observed and showed strong agreement with computational modeling. After validating the technique with the axisymmetric jet, the jet-in-crossflow was tested with various velocity ratios and jet injection angles. Results indicated the degree of wall separation for different injection angles and demonstrate both the time-averaged trajectories as well as select near-wall concentration results for varying jet momentum fluxes. Consistent with literature findings, the orthogonal jet trajectory for varying blowing ratios collapsed when scaled by the jet-to-freestream velocity ratio and hole diameter, rd. Similar collapsing was demonstrated in the case of a non-orthogonal jet. Computational Fluid Dynamic (CFD) simulations using the OpenFOAM software was used to compare predictions with select experimental cases, and yielded reasonable agreement. Insight into the importance and structure of the counter rotating vortex pair and general flow field turbulence was highlighted by cross validation between CFD and experimental results.
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Date Issued: 2015
Identifier: CFE0006057, ucf:50992
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006057

Title: The safe removal of frozen air from the annulus of a liquid hydrogen storage tank.
Creator: Krenn, Angela, Bhattacharya, Aniket, Youngquist, Robert, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Large Liquid Hydrogen (LH2) storage tanks are vital infrastructure for NASA. Eventually, air may leak into the evacuated and perlite filled annular region of these tanks. Although the vacuum level is monitored in this region, the extremely cold temperature causes all but the helium and neon constituents of air to freeze. A small, often unnoticeable pressure rise is the result. As the leak persists, the quantity of frozen air increases, as does the thermal conductivity of the insulation system...
Show moreLarge Liquid Hydrogen (LH2) storage tanks are vital infrastructure for NASA. Eventually, air may leak into the evacuated and perlite filled annular region of these tanks. Although the vacuum level is monitored in this region, the extremely cold temperature causes all but the helium and neon constituents of air to freeze. A small, often unnoticeable pressure rise is the result. As the leak persists, the quantity of frozen air increases, as does the thermal conductivity of the insulation system. Consequently, a notable increase in commodity boiloff is often the first indicator of an air leak. Severe damage can then result from normal draining of the tank. The warming air will sublimate which will cause a pressure rise in the annulus. When the pressure increases above the triple point, the frozen air will begin to melt and migrate downward. Collection of liquid air on the carbon steel outer shell may chill it below its ductility range, resulting in fracture. In order to avoid a structural failure, as described above, a method for the safe removal of frozen air is needed. Two potential methods for air removal are evaluated here. The first method discussed is the connection of a vacuum pump to the annulus which provides pumping in parallel with drainage of LH2. The goal is to keep the annular pressure below the triple point so that the air continues to sublimate, thus eliminating the threat that liquefaction poses. The second method discussed is the application of heat to the bottom of the outer tank during tank drain. Though liquefaction in the annular space will occur, the goal of the heater design is to keep the outer shell above the embrittlement temperature, so that cracking will not occur.In order to evaluate these methods, it is first necessary to characterize some the physical properties and changes that take place in the system. A thermal model of the storage tank was created in SINDA/FLUINT (C(&)R Technologies, 2014) to identify locations where air can freeze. This model shows the volume that is capable of freezing air under varying conditions. It is also necessary to characterize the changes in thermal conductivity of perlite which has nitrogen frozen into its interstitial spaces. The details and results of an experiment designed for that purpose is outlined. All data, including operational data from existing LH2 tanks, is compiled and a physics-based evaluation of the two proposed air removal techniques is performed.Due to small pumping capacities at low pressure and the large quantity of air inside the annulus, the pumping option is not deemed feasible. It would take many years to remove a significant amount of air by pumping while maintaining the annular pressure below the necessary triple point. Application of heating devices is a feasible option. For a specific case, it is shown that approximately 105 kilowatts of power would be required to vaporize the air in the annulus and keep the temperature of the outer tank wall above the freezing point of water. Several engineering solutions to accomplish this are also discussed. There are many unknowns and complexities in addressing the problem of safely removing frozen air from the annulus of an LH2 storage sphere. The work that follows utilized: research, modeling, experimentation, analysis, and data from existing tanks to arrive at possible solutions to the problem. Heating solutions may be implemented immediately and could result in significant savings to the user.
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Date Issued: 2015
Identifier: CFE0005969, ucf:50766
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005969

Title: Multi-Row Film Cooling Boundary Layers.
Creator: Natsui, Gregory, Kapat, Jayanta, Raghavan, Seetha, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: High fidelity measurements are necessary to validate existing and future turbulence models for the purpose of producing the next generation of more efficient gas turbines. The objective of the present study is to conduct several different measurements of multi-row film cooling arrays in order to better understand the physics involved with injection of coolant through multiple rows of discrete holes into a flat plate turbulent boundary layer. Adiabatic effectiveness distributions are measured...
Show moreHigh fidelity measurements are necessary to validate existing and future turbulence models for the purpose of producing the next generation of more efficient gas turbines. The objective of the present study is to conduct several different measurements of multi-row film cooling arrays in order to better understand the physics involved with injection of coolant through multiple rows of discrete holes into a flat plate turbulent boundary layer. Adiabatic effectiveness distributions are measured for several multi-row film cooling geometries. The geometries are designed with two different hole spacings and two different hole types to yield four total geometries. One of the four geometries tested for adiabatic effectiveness was selected for flowfield measurements. The wall and flowfield are studied with several testing techniques, including: particle image velocimetry, hot wire anemometry, pressure sensitive paint and discrete gas sampling.
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Date Issued: 2015
Identifier: CFE0005982, ucf:50776
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005982

Title: Heat Transfer and Pressure Measurements from Jet Array Impingement onto a Large Radius Curved Surface.
Creator: Harrington, John, Kapat, Jayanta, Ahmed, Kareem, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: This study investigates the heat transfer and pressure drop characteristics of jet array impingement in two distinct parts. In the first part, the performance of a uniform array of jets on both a flat and a large radius curved target surface are compared. This comparison was done at average jet Reynolds number ranging from 55,000 to 125,000. In the second part, the characteristics of a non-uniform array of jets, more typical of geometries used in actual gas turbine combustors, are...
Show moreThis study investigates the heat transfer and pressure drop characteristics of jet array impingement in two distinct parts. In the first part, the performance of a uniform array of jets on both a flat and a large radius curved target surface are compared. This comparison was done at average jet Reynolds number ranging from 55,000 to 125,000. In the second part, the characteristics of a non-uniform array of jets, more typical of geometries used in actual gas turbine combustors, are investigated, including the effects of the removal of downstream rows and the placement of rib features onto the target surface. The non-uniform configurations studied have varying hole diameters and geometric spacing for spatial tuning of the heat transfer behavior. First row jet Reynolds numbers ranging from 50,000 to 160,000 are reported. For all configurations, spent air is drawn out in a single direction which is tangential to the target plate curvature. A steady-state measurement technique utilizing temperature sensitive paint (TSP) was used on the target surface to obtain heat transfer coefficients, while pressure taps placed on the sidewall and jet plate were used to evaluate the pressure and flow distribution in the impingement channel. Alongside the experimental work, CFD simulations were performed utilizing the v^2-f eddy viscosity turbulence model. The results from the uniform array impingement onto a curved surface comparison show that the large radius curvature of the current geometry has little to no effect on the flow distribution and heat transfer of the array.The non-uniform array results illustrate the applicability of tuning a jet impingement array using varying jet diameters and spacing. However, there are some difficulties in obtaining streamwise pitch resolved heat transfer predictions for non-uniform arrays as current open literature correlations for uniform arrays are shown to be not applicable. The computational results from this study show that simulations can be used to obtain initial predictions, with streamwise pitch averaged Nu values found to be within 20% of experimental results. The use of ribs downstream in place of several jet rows was shown to yield similar heat transfer results at lower pressure drop levels.
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Date Issued: 2016
Identifier: CFE0006317, ucf:51547
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006317

Title: Investigation of Real Gas Effects on Centrifugal Compressor Analytical Methods for Supercritical CO2 Power Cycles.
Creator: Blanchette, Lauren, Kapat, Jayanta, Kassab, Alain, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: As supercritical carbon dioxide (sCO2) power cycles have shown potential to be the next generation power cycle, an immense amount of research has gone into developing this system. One of the setbacks facing development and optimization of this cycle is the unknown in current design and analysis methods ability to accurately model turbomachinery working with sCO2. Due to the desired inlet conditions to the compressor close proximity to the critical point, accurate design and analysis of this...
Show moreAs supercritical carbon dioxide (sCO2) power cycles have shown potential to be the next generation power cycle, an immense amount of research has gone into developing this system. One of the setbacks facing development and optimization of this cycle is the unknown in current design and analysis methods ability to accurately model turbomachinery working with sCO2. Due to the desired inlet conditions to the compressor close proximity to the critical point, accurate design and analysis of this power cycle component is one of the main concerns. The present study provides aerodynamic analysis of a centrifugal compressor impeller blade with sCO2 as the working fluid through a comparative study between three dimensional (3D) computational fluid dynamics (CFD) and a one dimensional (1D) mean line analyses. The main centrifugal compressor in reference to a 100 MW sCO2 closed loop Recuperated Recompression Brayton cycle is investigated. Through the use of conventional loss correlations for centrifugal compressors found in the literature, and geometrical parameters developed through a past mean line design, losses were calculated for the specified compressor impeller. The aerodynamic performance is then predicted through the 1D analysis. Furthermore, the boundary conditions for the CFD analysis were derived through the mean line analysis of the centrifugal compressor to carry out the 3D study of the sCO2 impeller blade. As the Span and Wagner equation of state has been proven to be the most accurate when working in the vicinity of the critical point, this real gas equation of state was implemented in both analyses. Consequently, a better understanding was developed on best practices for modeling a real gas sCO2 centrifugal compressor along with the limitations that currently exist when utilizing commercial CFD solvers. Furthermore, the resulting performance and aerodynamic behavior from the 1D analysis were compared with the predicted conclusions from the CFD analysis. Past literature studies on sCO2 compressor analysis methodology have been focused on small scale power cycles. This work served as the first comparison of 1D and 3D analysis methodology for large scale sCO2 centrifugal compressors. The lack of commercial CFD codes able to model phase change within sCO2 turbomachinery and the possible breach of flow properties into the saturation region at the leading edge of the impeller blade creates a limit to the operating conditions that can be simulated within these analysis tools. Further, the rapid expansion rate within this region has been predicted to cause non-equilibrium condensation leading the fluid to a metastable vapor state. Due to the complexity of two phase models, a proposed methodology to model sCO2 compressors as single phase is to represent metastable properties through the extrapolation of equilibrium properties onto the liquid domain up until the spinodal limit. This equation of state definition with metastable properties was used to model a 3D converging-diverging nozzle due to the similar flow dynamics occurring when compared to a compressor blade channel. The equation of state was implemented through a temperature and pressure dependent property table amended with metastable properties using the NIST REFPROP Database. Modeling was performed for inlet conditions with varied closeness to the fluid's critical point. Investigation on the accuracy of utilizing this table to define sCO2 properties with respect to its resolution was executed. Through this, it was determined that the resulting interpolation error was highly influenced on the closeness to the critical point. Additionally, the effect on the capable modeling operating region when utilizing the metastable real gas property table through single phase modeling was examined.
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Date Issued: 2016
Identifier: CFE0006442, ucf:51466
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006442

Combustion (9)	+ -
combustion (5)	+ -
heat transfer (5)	+ -
Film Cooling (4)	+ -
carbon dioxide (4)	+ -

Heat Transfer (3)	+ -
Premixed Combustion (3)	+ -
film cooling (3)	+ -
power generation (3)	+ -
supercritical carbon dioxide (3)	+ -
Experimental (2)	+ -
Gas Turbine (2)	+ -
Ignition Delay Time (2)	+ -
Large Eddy Simulations (2)	+ -
Lean (2)	+ -
Methane (2)	+ -
Modeling (2)	+ -
NDIR (2)	+ -
Particle Image Velocimetry (2)	+ -
Shock tube (2)	+ -
bifurcation (2)	+ -
biofuels (2)	+ -
carbon monoxide (2)	+ -
computational fluid dynamics (2)	+ -
design (2)	+ -
energy (2)	+ -
gas turbine (2)	+ -
gas turbines (2)	+ -
heat exchanger (2)	+ -
hydrogen (2)	+ -

University of Central Florida (48)	+ -
Vasu Sumathi, Subith (48)	+ -
Kapat, Jayanta (31)	+ -
Kassab, Alain (18)	+ -
Ahmed, Kareem (15)	+ -

Chow, Louis (5)	+ -
Orlovskaya, Nina (5)	+ -
Bhattacharya, Samik (4)	+ -
Raghavan, Seetha (3)	+ -
Barak, Samuel (2)	+ -
Gordon, Ali (2)	+ -
Ilie, Marcel (2)	+ -
Kauffman, Jeffrey (2)	+ -
Martin, Scott (2)	+ -
Natsui, Gregory (2)	+ -
Peale, Robert (2)	+ -
Pryor, Owen (2)	+ -
Shivamoggi, Bhimsen (2)	+ -
Terracciano, Anthony (2)	+ -
Tran, Lucky (2)	+ -
Almansour, Bader (1)	+ -
Bai, Yuanli (1)	+ -
Barari, Ghazal (1)	+ -
Bhattacharya, Aniket (1)	+ -
Blanchette, Lauren (1)	+ -
Canon, Ornan (1)	+ -
Chen, Ruey-Hung (1)	+ -
Claretti, Roberto (1)	+ -
Cooper, David (1)	+ -
Das, Tuhin (1)	+ -

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