Browsing by Subject "Combustion"
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Item A quantitative analysis of the flame produced by a gas-fueled propellant simulating burner including: soot field characterization, temperature diagnostic techniques, spectral analysis, heat flux, and aluminum particle combustion(Texas Tech University, 2007-05) Jackson, Matthew N.; Pantoya, Michelle; Berg, Jordan M.; Seshaiyer, Padmanabhan; Parameswaran, Siva; Levitas, ValeryThis study details the characterization and implementation of a burner devised to simulate solid propellant fires. The burner is designed with the ability to introduce particles (particularly aluminum) to a gas reactant flame. This work encompasses four different studies that both evaluate the performance of the burner as well as display its ability as a versatile test platform. First, the burner is used to create a high temperature, heavily sooting flame as the basis of the development of a virtual thermocouple model in a fire code at Sandia National Laboratories (VULCAN). Secondly, similar conditions are created to evaluate the effectiveness of dual-pump coherent anti-Stokes Raman scattering (CARS) measurements in heavily sooting flames. These thermometry measurements indicate the temperature profiles that exist in fuel rich conditions. Laser induced incandescence (LII) measurements map soot volume fractions and give insight into the reactant gas mixing in the flame structure. The third project evaluates the aluminized flame conditions produced by this burner based on temperature, heat flux, spectral emission, product species, and particle velocity. Using these results, flame performance is quantified in comparison to other known flames including hydrocarbon and propellant fires. Lastly, an aluminized flame is used to measure the burning rate of the particles. This work indicates the capability of the burner as test platform for Sandia’s ongoing effort to develop a comprehensive particulate combustion model, particularly in propellant fires. These studies accomplish two primary objectives: (1) characterization of a flame produced by a new and unique burner; and, (2) verification that the burner fulfills its design purpose of recreating small scale propellant flame conditions.Item Al/Fe203 energetic composites based on nanowire arrays(Texas Tech University, 2004-05) Thakar, Sameer GirishEnergetic materials consist of a mixture of oxidizer and fuel components, which when ignited release a large amount of energy due to an exothermic reaction. In this thesis, we demonstrate nanocomposite materials consisting of aluminum and iron oxide in close physical contact. The fabrication method is based on the use of nanoporous alumina membranes. These are aluminum oxide membranes consisting of cylindrical nanosized pores. Using such membranes, Fe nanowires are prepared by electrodeposition. The Fe wires are eventually oxidized to Fe oxide and a thin layer of aluminum film is deposited by means of thermal evaporation. In effect, Fe oxide nanowires act as oxidizer while Al film acts as fiiel in our nanocomposite. The complete fabrication process for the nanocomposite is described and the demonstration of ignition is discussed.Item An examination of possible reversible combustion at high temperatures and pressures for a reciprocating engine(2009-05-15) Patrawala, Kaushik TanvirConventional combustion processes are known to be highly irreversible processes. The potential to obtain useful work from the fuel is degraded during the combustion process. For example, for a reciprocating internal combustion engine, about 20% or more of the potential work from the fuel is destroyed during the combustion process. This potential work is known as availability (a thermodynamic property). The motivation for the current work was to develop a conceptual model of a set of processes related to reciprocating engines that would eliminate this destruction of availability. One conceptual model, proposed by Keenan, suggested that a preselected set of ?reactants? could be compressed (at constant composition) to a high temperature and pressure. At this high temperature and pressure, the ?reactants? would be in chemical equilibrium. At this point, the ?reactants? would be expanded back to the original volume. The expansion process would consist of a ?shifting? chemical equilibrium such that the composition during expansion would continue to change. At the end of the compression and expansion, net work would be available without destroying any of the work potential of the fuel. The purpose of the current work was to develop a quantitative model of this concept, and to use the model in a series of computations to examine the effects of temperature, pressure, and other parameters on the work production capability of the concept. The concept was studied for eight different fuels for various conditions. In general, the net work output increased as the temperature, pressure and compression ratio increased. For low compression temperatures and pressures, the concept resulted in a small amount of net work produced without destroying any fuel availability. For sufficiently high compression pressure and temperature (e.g., 10 MPa and 6000 K, respectively), however, the thermal efficiency was ~28% for isooctane and was ~40% for hydrogen and methane, for air as the oxidant, an equivalence ratio of 1.0, and a compression ratio of 18. Although the temperatures and pressures considered are well beyond practical values for the materials and designs of today, the general result of the study is that conditions can be identified to eliminate the combustion irreversibility.Item Analysis of power generation processes using petcoke(2009-05-15) Jayakumar, RamkumarPetroleum coke or petcoke, a refinery byproduct, has generally been considered as an unusable byproduct because of its high sulfur content. However energy industries now view petcoke as a potential feedstock for power generation because it has higher carbon content than other hydrocarbons like coal, biomass and sewage residue. This gives petcoke a great edge over other feedstocks to generate power. Models for the two most common processes for power generation, namely combustion and gasification, were developed using Aspen Plus steady state chemical process simulator. Overall plant layouts for both processes were developed by calculating the heat and mass balance of the unit operations. After conducting wide sensitivity analysis, results indicate that one ton of petcoke feedstock can generate up to 4 MW of net available power. Both processes have rates of return greater than 30%, although gasification offers a slightly more attractive opportunity than combustion.Item Characteristics of radially propagating smoldering combustion in a sawdust bed(2015-12) Bush, Robert H., III; Ellzey, Janet L.In this thesis, experimental work on smoldering of sawdust beds is presented and discussed. Extensive study has been done on wood burning cook stoves with an emphasis on performance characterization and optimization. Few studies, however, have focused on the smoldering process with the goal of understanding the propagation of the front and the production of emissions. In this study, photographs, temperature and emission measurements on smoldering sawdust clearly showed the evolution of the combustion process: an initial conversion of the raw sawdust to char followed by the conversion of char to ash. In general, the char front propagated symmetrically in the radial direction while the ash front was not symmetric, and typically followed paths where oxygen was most readily available. Further analysis was accomplished by observing the characteristics of the sawdust bed before transition to flaming occurred. Contrary to expected results, flaming did not occur as the air flow was increased, but rather once it was decreased, suggesting that flaming is determined by a balance between generation of volatiles and dilution by incoming air. Experiments with vitiated air, in which the oxygen content of air is diluted by adding nitrogen, were conducted to determine a limit at which combustion was no longer self-sustaining. Experiments showed that vitiated air with 7% oxygen in the supply air did not support self-sustaining combustion. Finally, a comparison between poplar and walnut was conducted to show the effect of wood species. Comparison of temperature, hydrocarbon, and carbon monoxide outputs identified characteristic differences between the poplar and walnut species.Item Combustion Assisted Gravity Drainage (CAGD): An In-Situ Combustion Method to Recover Heavy Oil and Bitumen from Geologic Formations using a Horizontal Injector/Producer Pair(2012-11-21) Rahnema, HamidCombustion assisted gravity drainage (CAGD) is an integrated horizontal well air injection process for recovery and upgrading of heavy oil and bitumen from tar sands. Short-distance air injection and direct mobilized oil production are the main features of this process that lead to stable sweep and high oil recovery. These characteristics identify the CAGD process as a high-potential oil recovery method either in primary production or as a follow-up process in reservoirs that have been partially depleted. The CAGD process combines the advantages of both gravity drainage and conventional in-situ combustion (ISC). A combustion chamber develops in a wide area in the reservoir around the horizontal injector and consists of flue gases, injected air, and mobilized oil. Gravity drainage is the main mechanism for mobilized oil production and extraction of flue gases from the reservoir. A 3D laboratory cell with dimensions of 0.62 m, 0.41 m, and 0.15 m was designed and constructed to study the CAGD process. The combustion cell was fitted with 48 thermocouples. A horizontal producer was placed near the base of the model and a parallel horizontal injector in the upper part at a distance of 0.13 m. Peace River heavy oil and Athabasca bitumen were used in these experiments. Experimental results showed that oil displacement occurs mainly by gravity drainage. Vigorous oxidation reactions were observed at the early stages near the heel of the injection well, where peak temperatures of about 550?C to 690?C were recorded. Produced oil from CAGD was upgraded by 6 and 2?API for Peace River heavy oil and Athabasca bitumen respectively. Steady O2 consumption for both oil samples confirmed the stability of the process. Experimental data showed that the distance between horizontal injection and production wells is very critical. Close vertical spacing has negative effect on the process as coke deposits plug the production well and stop the process prematurely. CAGD was also laboratory tested as a follow-up process. For this reason, air was injected through dual parallel wells in a mature steam chamber. Laboratory results showed that the process can effectively create self-sustained combustion front in the previously steam-operated porous media. A maximum temperature of 617?C was recorded, with cumulative oil recovery of 12% of original oil in place (OOIP). Post-experiment sand pack analysis indicated that in addition to sweeping the residual oil in the steam chamber, the combustion process created a hard coke shell around the boundaries. This hard shell isolated the steam chamber from the surrounding porous media and reduced the steam leakage. A thermal simulator was used for history matching the laboratory data while capturing the main production mechanisms. Numerical analysis showed very good agreement between predicted and experimental results in terms of fluid production rate, combustion temperature and produced gas composition. The validated simulation model was used to compare the performance of the CAGD process to other practiced thermal recovery methods like steam assistance gravity drainage (SAGD) and toe to heel air injection (THAI). Laboratory results showed that CAGD has the lowest cumulative energy-to-oil ratio while its oil production rate is comparable to SAGD.Item A computational fluid dynamics simulation model for flare analysis and control(2006) Castiñeira Areas, David; Edgar, Thomas F.Industrial flares are units designed to safely dispose of waste hydrocarbon gases from chemical and petrochemical plants by burning gases to carbon dioxide and steam, which are then released to the atmosphere. There is still great uncertainty about flare efficiency and the resultant gas emissions under different operating conditions. For this reason, environmental agencies have encouraged the development of predictive models for flare gas combustion systems, so effective control and mitigation strategies can be implemented. The principal focus of this dissertation is to develop mathematical models of industrial flares that predict the efficiency of these industrial combustion systems. For this purpose, a computational fluid dynamics (CFD) simulation model is implemented to analyze the effects of variables such as ambient wind velocity, gas heating value, and steam injection on flare combustion efficiency. Some advanced chemistry and turbulence submodels are also implemented to describe the complex flare flow phenomena. Simulation results show that flares may represent an important source of gas emissions due to inefficient operation at high crosswinds and large steam/fuel ratios. The predictive models presented in this work will allow for better estimation of the resulting gas emissions from industrial plants. Use of these simulation models will also yield economic savings for environmental studies compared to setting up expensive flare experiments. In addition, these predictive models allow for a detailed analysis of species concentration profiles and turbulent flow patterns within the flames, data which is not available experimentally. Furthermore, several instrumentation and control strategies for industrial flares are analyzed in this dissertation. A new approach for flare monitoring based on multivariate image analysis is proposed so that flare combustion efficiency can be measured in real-time.Item Controlling parameters of excess enthalpy combustion(2014-05) Belmont, Erica Lynn; Ellzey, Janet L.Excess enthalpy combustion utilizes heat recirculation, in which heat is transferred from hot products to cold reactants to effectively preheat the reactants, in order to achieve improved combustion performance through the extension of flammability limits and increased burning rate. This research examines the effect of key parameters in excess enthalpy combustion on combustion stability, fuel conversion, and product species production through experimental and numerical investigation. Operating condition parameters that are studied include inlet reactant equivalence ratio and inlet velocity, and reactor geometry parameters that are studied include reactor channel height and length. Premixed reactants, including gaseous and liquid fuels, are investigated at rich and lean conditions. The examination of liquid fuels and the ability of a reactor to support rich and lean combustion of both gaseous and liquid fuels is a significant demonstration of a reactor’s flexibility for practical applications. This research experimentally and numerically examines excess enthalpy combustion in a counter-flow reactor. First, the counter-flow reactor, previously used for thermal partial oxidation of gaseous hydrocarbon fuels, is used in experiments to reform a liquid hydrocarbon fuel, heptane, to syngas. The effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and product composition is explored. Second, lean combustion is demonstrated through experiments in the same counter-flow reactor previously used in reforming studies. The effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and pollutant concentrations in combustion products is studied. An analytical model, previously developed for rich combustion, is adapted to qualitatively predict the behavior of the counter-flow reactor in response to changes in lean operating conditions. Third, lean combustion in the counter-flow reactor is further studied by examining the combustion of increasingly complex gaseous and liquid fuels. Again, the effect of inlet operating conditions, including reactant equivalence ratio and inlet velocity, on combustion stability and pollutant concentrations in combustion products is studied. Fourth and finally, a computational scaling study examines the impact of counter-flow reactor channel geometry on combustion stability, temperature increase above adiabatic values, heat recirculation, and fuel and product species conversion efficiency.Item Determination of Optimal Process Flowrates and Reactor Design for Autothermal Hydrogen Production in a Heat-Integrated Ceramic Microchannel Network(2012-07-16) Damodharan, ShaliniThe present work aimed at designing a thermally efficient microreactor system coupling methanol steam reforming with methanol combustion for autothermal hydrogen production. A preliminary study was performed by analyzing three prototype reactor configurations to identify the optimal radial distribution pattern upon enhancing the reactor self-insulation. The annular heat integration pattern of Architecture C showed superior performance in providing efficient heat retention to the system with a 50 - 150 degrees C decrease in maximum external-surface temperature. Detailed work was performed using Architecture C configuration to optimize the catalyst placement in the microreactor network, and optimize reforming and combustion flows, using no third coolant line. The optimized combustion and reforming catalyst configuration prevented the hot-spot migration from the reactor midpoint and enabled stable reactor operation at all process flowrates studied. Best results were obtained at high reforming flowrates (1800 sccm) with an increase in combustion flowrate (300 sccm) with the net H2 yield of 53% and thermal efficiency of >80% from methanol with minimal insulation to the heatintegrated microchannel network. The use of the third bank of channels for recuperative heat exchange by four different reactor configurations was explored to further enhance the reactor performance; the maximum overall hydrogen yield was increased to 58% by preheating the reforming stream in the outer 16 heat retention channels. An initial 3-D COMSOL model of the 25-channeled heat-exchanger microreactor was developed to predict the reactor hotspot shape, location, optimum process flowrates and substrate thermal conductivity. This study indicated that low thermal conductivity materials (e.g. ceramics, glass) provides enhanced efficiencies than high conductivity materials (e.g. silicon, stainless steel), by maintaining substantial thermal gradients in the system through minimization of axial heat conduction. Final summary of the study included the determination of system energy density; a gravimetric energy density of 169.34 Wh/kg and a volumetric energy density of 506.02 Wh/l were achieved from brass architectures for 10 hrs operation, which is higher than the energy density of Li-Ion batteries (120 Wh/kg and 350 Wh/l). Overall, this research successfully established the optimal process flowrates and reactor design to enhance the potential of a thermally-efficient heat-exchanger microchannel network for autothermal hydrogen production in portable applications.Item Development of a multiple-pass Raman spectrometer for flame diagnostics(2013-05) KC, Utsav; Varghese, Philip L.A multiple-pass cell is developed and applied to enhance the Raman signal from methane-air flames for temperature measurements. Stable operation of the cell was demonstrated and studied in two alignment modes. In the ring mode, the beams are focused into a ring of ~ 3 mm diameter at the center of the cell, and spectra were recorded at low dispersion (0.26 nm/pixel). Temperature is calculated from the ratio of the intensity of Stokes to anti-Stokes signal from nitrogen. Temperature is also inferred from the shapes of the Stokes and anti-Stokes peaks in the spectrum. The uncertainty in the value of flame temperature in these measurements was ±50 K. The signal gain from 100 passes is a factor of 83. Signal to noise ratio (SNR) improved by a factor of 9.3 in room temperature air with an even higher factor in flames. The improvement in SNR depends on the acquisition time and is best for short acquisition times. In the two point mode, multi passing is achieved simultaneously with high spatial resolution as the laser is focused at two small regions separated by ~ 2 mm at the center of the cell. The probe regions are 300 [mu]m × 200 [mu]m. The vast improvement in the spatial resolution is achieved at the cost of a reduced number of passes and signal gain. The two point mode is operated with 25 passes at each point with a signal gain factor of ~20; the SNR gain depends on the data acquisition time. Spectra were recorded at high dispersion (~0.03 nm/pixel). Temperature is inferred from curve fitting to the high resolution Stokes spectrum of nitrogen in methane-air flames. The curve fit is based on very detailed simulation of Raman spectrum of nitrogen. The final model includes the angular dependence of Raman scattering, electrical and mechanical anharmonicity in the polarizability matrix elements, and the presence of a rare isotope of nitrogen in air. The uncertainty in the value of temperature in the least noisy data is ±9 K. The sources of uncertainty in temperature and their contribution to the total uncertainty are also identified.Item Direct numerical simulation and reaction path analysis of titania formation in flame synthesis(2012-08) Singh, Ravi Ishwar; Ezekoye, Ofodike A.; Raman, VenkatFlame-based synthesis is an attractive industrial process for the large scale generation of nanoparticles. In this aerosol process, a gasifi ed precursor is injected into a high-temperature turbulent flame, where oxidation followed by particle nucleation and other solid phase dynamics create nanoparticles. Precursor oxidation, which ultimately leads to nucleation, is strongly influenced by the turbulent flame dynamics. Here, direct numerical simulation (DNS) of a canonical homogeneous flow is used to understand the interaction between a methane/air flame and titanium tetrachloride oxidation to titania. Detailed chemical kinetics is used to describe the combustion and precursor oxidation processes. Results show that the initial precursor decomposition is heavily influenced by the gas phase temperature field. However, temperature insensitivity of subsequent reactions in the precursor oxidation pathway slow down conversion to the titania. Consequently, titania formation occurs at much longer time scales compared to that of hydrocarbon oxidation. Further, only a fraction of the precursor is converted to titania, and a signi cant amount of partially-oxidized precursor species are formed. Introducing the precursor in the oxidizer stream as opposed to the fuel stream has only a minimal impact on the oxidation dynamics. In order to understand modeling issues, the DNS results are compared with the laminar flamelet model. It is shown that the flamelet assumption qualitatively reproduces the oxidation structure. Further, reduced oxygen concentration in the near-flame location critically a ffects titania formation. The DNS results also show that titania forms on the lean and rich sides of the flame. A reaction path analysis (RPA) is conducted. The results illustrate the di ffering reaction pathways of the detailed chemical mechanism depending on the composition of the mixture. The RPA results corroborate with the DNS results that titania formation is maximized at two mixture fraction values, one on the lean side of the flame, and one on the rich side.Item Effect of Co-Firing Torrefied Woody Biomass with Coal in a 30 kWt Downfired Burner(2014-04-25) Thanapal, Siva SMesquite and juniper can be beneficially utilized for gasification and combustion applications. Torrefaction has been considered to be one of the thermal pretreatment options to improve the chemical (e.g. heat content) and physical (e.g. grindability) properties of raw biomass. A simple three component parallel reaction model (TCM) was formulated to study the effect of heating rate, temperature, residence time and type of biomass on torrefaction process. Typically inert environment (e.g. N_(2), He, Ar) is maintained to prevent oxidation of biomass during torrefaction. A novel method for utilization of carbon dioxide as the pretreatment medium for woody biomass has been investigated in the current study. Both raw and the torrefied biomass (TB) were pyrolyzed using TGA under N_(2). The TB fuels were also fired with coal in a 30 kWt downfired burner to study the NOx emission. In addition, tests were also done using raw biomass (RB) (mesquite and juniper) blended with coal and compared with results obtained from cofiring TB with coal. A zero dimensional model has been developed to predict the combustion performance of cofired fuels. The results are as follows. TGA studies yielded global kinetics based on maximum volatile release (MVR) method. TCM predicts higher loss of hemicellulose upon torrefaction when compared to the other components, cellulose and lignin resulting in improved heat values of TB. Comparable mass loss at lower temperatures, improved grindability, and improved fuel properties were observed upon using CO_(2) as the torrefaction medium. Co-firing 10% by mass of raw mesquite with coal reduced the NOx emission from 420 ppm to 280 ppm for an Equivalence ratio (ER) of 0.9. Further cofiring TB with coal reduced the NOx emission by 10% when compared to base case NOx emission from combustion of pure PRB coal. NOx emission decreased with increase in equivalence ratio. In addition, a term used in the biological literature, respiratory quotient (RQ), is applied to fossil and biomass fuels to rank the potential of fuels to produce carbon dioxide during oxidation process. Lesser the value of ?RQ? of a fuel, lower the global warming potential.Item Effect of heterogeneous catalyst during combustion of diesel fuel(Texas Tech University, 1999-05) Arefeen, QuamrulWith the increase in number of vehicles using diesel engines, the contributions to environmental pollution made by diesel engines is also on the rise. Carbon monoxide, oxides of nitrogen and sulfur, hydrocarbons, and particulates are currently regulated as harmful emissions from diesel engines. Recent technologies to control harmful engine emissions have been almost exclusively directed towards gasoline engines. It is generally held that fuel quality will have to play an important role with all Internal Combustion (IC) engines to meet future stringent regulations. The objective of the present study was to determine the effects of heterogeneous catalyst on combustion. Micron sized solid catalyst, suspended in a specific organic peroxide, has been found to promote better combustion by modifying kinetics and changing the thermodynamic pathways of the reactions. The catalyst reduces emissions without dramatically changing the properties of the fuel. The characteristic parameters of a baseline fuel, and the same fuel with the additive, were analyzed. The dosage of additive used was found to be compatible with commercial diesel fuel. Diesel vehicles were driven unloaded atnormal road conditions during the experiments. Exhaust emissions were measured when the trucks were at static conditions and the engine running on idle and at 2000 rpm. The gaseous components in the exhaust, O2, CO2, CO, NO, NO2, NOx, SO2, and CxHy were monitored. Particulates were trapped on a pre-weighed glass filter. Some of the filters were sent to an Independent laboratory for microscopic and elemental analysis of the collected debris. Zinc oxide/peroxide suspended in tert-butyl hydro peroxide were used as the heterogeneous fuel catalyst. This combination increased the cetane rating of a commercial diesel fuel from 45 to a level of 70 depending on treatment ratio. A treatment ratio of one ounce of the additive per 5 gallons of diesel fuel increased cetane number by an average of 5 points. Road mileage with the additive increased by an average of more than 10%. Gaseous and particulate emissions were reduced by more than 20%. Engine wear decreased due to increased lubricity of the fuel. A decrease in flash point of the diesel fuel may make the additive more suitable for cold weather operations.Item Efficiency Improvements with Low Heat Rejection Concepts Applied to Low Temperature Combustion(2014-06-25) Penny, MichaelWith increasingly stringent governmental regulations on engine emissions such as oxides of nitrogen (NO_(X)) and particulate matter (PM), there is a strong motivation to decrease the production and release of these harmful substances from internal combustion engines. Simultaneously, there are on-going efforts to increase fuel efficiency to curb usage of natural resources and emission of carbon. In general, improvements in one of these areas comes at the cost of the other; however, the results of a previous computational study have indicated that emissions can be decreased while simultaneously increasing efficiency through the application of low heat rejection (LHR) techniques to low temperature combustion (LTC). The goal of this study is to experimentally confirm these findings using a light duty, multi-cylinder diesel engine. LTC is realized through high levels of exhaust gas recirculation (EGR) and retarded injection timings while different degrees of LHR are achieved by means of higher coolant temperatures which should serve to decrease the temperature gradients across the cylinder walls. An energy balance is conducted on the engine to ensure the validity of the efficiency findings. By applying LHR techniques to LTC operation, the undesirable side effects of LTC were found to be mitigated. Specifically, the emissions of carbon monoxide (CO) and unburned hydrocarbons (HC) were reduced and the loss in engine efficiency was also diminished. NO_(X) and PM emissions did increase but they remained at acceptably low levels. In addition, the results of the energy balance substantiated these trends by properly accounting for the bulk of the input energy. While the full potential of improvements in LTC were not explored due to current engine limitations, these results point to the viability of further research into LHR-LTC concepts.Item Experimental investigation of film cooling and thermal barrier coatings on a gas turbine vane with conjugate heat transfer effects(2013-05) Kistenmacher, David Alan; Bogard, David G.In the United States, natural gas turbine generators account for approximately 7% of the total primary energy consumed. A one percent increase in gas turbine efficiency could result in savings of approximately 30 million dollars for operators and, subsequently, electricity end-users. The efficiency of a gas turbine engine is tied directly to the temperature at which the products of combustion enter the first stage, high-pressure turbine. The maximum operating temperature of the turbine components’ materials is the major limiting factor in increasing the turbine inlet temperature. In fact, current turbine inlet temperatures regularly exceed the melting temperature of the turbine vanes through advanced vane cooling techniques. These cooling techniques include vane surface film cooling, internal vane cooling, and the addition of a thermal barrier coating (TBC) to the exterior of the turbine vane. Typically, the performance of vane cooling techniques is evaluated using the adiabatic film effectiveness. However, the adiabatic film effectiveness, by definition, does not consider conjugate heat transfer effects. In order to evaluate the performance of internal vane cooling and a TBC it is necessary to consider conjugate heat transfer effects. The goal of this study was to provide insight into the conjugate heat transfer behavior of actual turbine vanes and various vane cooling techniques through experimental and analytical modeling in the pursuit of higher turbine inlet temperatures resulting in higher overall turbine efficiencies. The primary focus of this study was to experimentally characterize the combined effects of a TBC and film cooling. Vane model experiments were performed using a 10x scaled first stage inlet guide vane model that was designed using the Matched Biot Method to properly scale both the geometrical and thermal properties of an actual turbine vane. Two different TBC thicknesses were evaluated in this study. Along with the TBCs, six different film cooling configurations were evaluated which included pressure side round holes with a showerhead, round holes only, craters, a novel trench design called the modified trench, an ideal trench, and a realistic trench that takes manufacturing abilities into account. These film cooling geometries were created within the TBC layer. Each of the vane configurations was evaluated by monitoring a variety of temperatures, including the temperature of the exterior vane wall and the exterior surface of the TBC. This study found that the presence of a TBC decreased the sensitivity of the thermal barrier coating and vane wall interface temperature to changes in film coolant flow rates and changes in film cooling geometry. Therefore, research into improved film cooling geometries may not be valuable when a TBC is incorporated. This study also developed an analytical model which was used to predict the performance of the TBCs as a design tool. The analytical prediction model provided reasonable agreement with experimental data when using baseline data from an experiment with another TBC. However, the analytical prediction model performed poorly when predicting a TBC’s performance using baseline data collected from an experiment without a TBC.Item Experimental Study of In Situ Combustion with Decalin and Metallic Catalyst(2011-02-22) Mateshov, DaurenUsing a hydrogen donor and a catalyst for upgrading and increasing oil recovery during in situ combustion is a known and proven technique. Based on research conducted on this process, it is clear that widespread practice in industry is the usage of tetralin as a hydrogen donor. The objective of the study is to find a cheaper hydrogen donor with better or the same upgrading performance. Decalin (C10H18) is used in this research as a hydrogen donor. The experiments have been carried out using field oil and water saturations, field porosity and crushed core for porous medium. Four in situ combustion runs were performed with Gulf of Mexico heavy oil, and three of them were successful. The first run was a control run without any additives to create a base for comparison. The next two runs were made with premixed decalin (5 percent by oil weight) and organometallic catalyst (750 ppm). The following conditions were kept constant during all experimental runs: air injection rate at 3.1 L/min and combustion tube outlet pressure at 300 psig. Analysis of the performance of decalin as a hydrogen donor in in-situ combustion included comparison of results with an experiment where tetralin was used. Data from experiments of Palmer (Palmer-Ikuku, 2009) was used for this purpose, where the same oil, catalyst and conditions were used. Results of experiments using decalin showed better quality of produced oil, higher recovery factor, faster combustion front movement and higher temperatures of oxidation. API gravity of oil in a run with decalin is higher by 4 points compared to a base run and increased 5 points compared to original oil. Oil production increased by 7 percent of OOIP in comparison with base run and was 2 percent higher than the experiment with tetralin. The time required for the combustion front to reach bottom flange decreased 1.6 times compared to the base run. The experiments showed that decalin and organometallic catalysts perform successfully in in situ combustion, and decalin is a worthy replacement for tetralin.Item Experimental Techniques for the Study of Liquid Monopropellant Combustion(2012-07-16) Warren, WilliamPropellants based on hydroxylammonium nitrate (HAN) have shown promise as a hydrazine replacement because of their comparably low toxicity, low vapor pressure, high specific impulse and high density. Herein, the recent history of advanced monopropellant research is explored, and new experimental techniques are presented to investigate the combustion behavior of a potential hydrazine replacement propellant. Nitromethane, a widely available monopropellant with a recent resurgence in research, is utilized in the current study as a proof of concept for the newly designed equipment and as a step towards investigating more-advanced, HAN-based monopropellants. A strand bomb facility capable of supporting testing at up to 340 atm was employed, and experiments were performed between 28 atm and 130 atm. Burning rate data for nitromethane are calculated from experiments and a power correlation is established as r(mm/s) = 0.33[P(MPa)]^1.02. A comparison with available literature reveals this correlation to be very much in agreement to other studies of nitromethane. Other physical characteristics of nitromethane combustion are presented. Updates to the facility and new methods to examine the combustion of liquid propellant are described in detail. Special focus is given to procedures and safety information.Item Hydrodynamical analysis of nanometric aluminum/teflon deflagrations(2008-05) Stacy, Shawn Christopher; Pantoya, Michelle; Levitas, Valery; Weeks, Brandon L.The hydrodynamics of deflagrations from reactive materials (RM) submerged underwater can be studied using a modified aquarium test. Normally loose powder RM will disperse after being submerged in water. Introducing hydrophobic materials such as Teflon into the reactant matrix, enables a barrier against permeation of water into the reactants. Also, ignition via resistance heating can be difficult underwater because significant energy is lost by convection off the wire into the water. Nano-Al particles require significantly less energy for ignition than their micron scale counterparts such that underwater ignition via resistance heating can be achieved. The objective of this study is to examine the reaction hydrodynamics from a submerged nano Al-Teflon mixture as a function of mixture composition and bulk density. Submerged Aluminum/Teflon mixtures were ignited and the ensuing reaction was recorded with a high speed camera and a pressure transducer. The resulting bubble shape, size, and pressure histories along with the burn time and rate allow the analysis and comparison of different fuel/oxidizer compositions and powder packing densities. Results show that as the density of the powder decreases the reaction transitions from a slow jet of multiple bubbles to quick single bubble. One observation is that as the percentage of aluminum increases the bubble radius also increases even though there is less of the gas producing Teflon in the mixture. This could imply that the excess aluminum is reacting with water.Item Large-Eddy simulation of gas turbine combustors using Flamelet Manifold methods(2015-12) Lietz, Christopher Fernandez; Clemens, Noel T.; Raman, Venkat; Ezekoye, Ofodike A; Goldstein, David B; Varghese, Philip LThe main objective of this work was to develop a large-eddy simulation (LES) based computational tool for application to both premixed and non- premixed combustion of low-Mach number flows in gas turbines. In the recent past, LES methodology has emerged as a viable tool for modeling turbulent combustion. LES is particularly well-suited for the compu- tation of large scale mixing, which provides a firm starting point for the small scale models which describe the reaction processes. Even models developed in the context of Reynolds averaged Navier-Stokes (RANS) exhibit superior results in the LES framework. Although LES is a widespread topic of research, in industrial applications it is often seen as a less attractive option than RANS, which is computationally inexpensive and often returns sufficiently accurate results. However, there are many commonly encountered problems for which RANS is unsuitable. This work is geared towards such instances, with a solver developed for use in unsteady reacting flows on unstructured grids. The work is divided into two sections. First, a robust CFD solver for a generalized incompressible, reacting flow configuration is developed. The computational algorithm, which com- bines elements of the low-Mach number approximation and pressure projection methods with other techniques, is described. Coupled to the flow solver is a combustion model based on the flamelet progress variable approach (FPVA), adapted to current applications. Modifications which promote stability and accuracy in the context of unstructured meshes are also implemented. Second, the LES methodology is used to study three specific problems. The first is a channel geometry with a lean premixed hydrogen mixture, in which the unsteady flashback phenomenon is induced. DNS run in tandem is used for establishing the validity of the LES. The second problem is a swirling gas turbine combustor, which extends the channel flashback study to a more practical application with stratified premixed methane and hydrogen/methane mixtures. Experimental results are used for comparison. Finally, the third problem tests the solver’s abilities further, using a more complex fuel JP-8, Lagrangian fuel droplets, and a complicated geometry. In this last configu- ration, experimental results validate early simulations while later simulations examine the physics of reacting sprays under high centripetal loading.Item Mercury emission behavior during isolated coal particle combustion(2009-05-15) Puchakayala, Madhu BabuOf all the trace elements emitted during coal combustion, mercury is most problematic. Mercury from the atmosphere enters into oceanic and terrestrial waters. Part of the inorganic Hg in water is converted into organic Hg (CH3Hg), which is toxic and bioaccumulates in human and animal tissue. The largest source of human-caused mercury air emissions in the U.S is from combustion coal, a dominant fuel used for power generation. The Hg emitted from plants primarily occurs in two forms: elemental Hg and oxidized Hg (Hg2+). The coal chlorine content and ash composition, gas temperature, residence time and presence of different gases will decide the speciation of Hg into Hg0 and Hg2+. For Wyoming coal the concentrations of mercury and chlorine in coal are 120ppb and 140ppb. In order to understand the basic process of formulation of HgCl2 and Hg0 a numerical model is developed in the current work to simulate in the detail i) heating ii) transient pyrolysis of coal and evolution of mercury and chlorine, iii) gas phase oxidation iv) reaction chemistry of Hg and v) heterogeneous oxidation of carbon during isolated coal particle combustion. The model assumes that mercury and chlorine are released as a part of volatiles in the form of elemental mercury and HCl. Homogenous reaction are implemented for the oxidation of mercury. Heterogeneous Hg reactions are ignored. The model investigates the effect of different parameters on the extent of mercury oxidation; particle size, ambient temperature, volatile matter, blending coal with high chlorine coal and feedlot biomass etc,. Mercury oxidation is increased when the coal is blended with feedlot biomass and high chlorine coal and Hg % conversion to HgCl2 increased from 10% to 90% when 20% FB is blended with coal. The ambient temperature has a negative effect on mercury oxidation, an increase in ambient temperature resulted in a decrease in the mercury oxidation. The percentage of oxidized mercury increases from 9% to 50% when the chlorine concentration is increased from 100ppm to 1000ppm. When the temperature is decreased from 1950 K to 950 K, the percentage of mercury oxidized increased from 3% to 27%.