The demand for low cost, high efficiency and clean burning gas turbine has increased in past years to meet consumer demands and governmental emission policies. The direct relationship between the production of NOx, temperature, and residence time has shown difficulty in obtaining higher efficiency without elevating emission level. Modern Dry Low NOx (DLN) combustors are reaching their limits for effectively operating at low NOx levels. As such, research for further improvements in current combustors has increased in recent years. The work in this dissertation further investigates axial stage combustion, one of the novel technologies aiming to reach desirable firing temperatures and emission levels. Real time gas turbine can operate at elevated pressures, making it difficult to scale the results in literature to operational load conditions. Multiple studies were conducted to isolate the effects of the various parameters on the reacting jet. The current work experimentally investigated premixed reacting jets in vitiated crossflow under various pressure, mixture composition and stoichiometric conditions to further understand their influence on flame characteristics and emission. Recent literature investigating jet in crossflow, conduct the experiments at ambient conditions. The goal of this work was to provide more insight in the jet in crossflow interaction at relevant operating conditions found in a gas turbine. The first part of this work focus on understanding the influence of pressure on the jet in crossflow mechanism as well as and the effect on NOx levels. Jet conditions such equivalence ratio and momentum flux ratios were held constant throughout the study with the pressure of the system ranging from 1atm to 5atm. The flow structure and flame stabilization of the jets at different pressures were characterized using particle image velocimetry (PIV) and CH* chemiluminescence. The results of this study demonstrated variation in jet trajectory, flame stabilization and NOx level, demonstrating the underpredictions of studies at atmospheric conditions. The second part of this work studied the influence of the axial jet mixture composition by introducing diluents such as CO2 and N2. Flame stabilization and NOx emission are driven by both the fluid dynamics and chemical kinetics of the system. By adding diluents to the axial jet, the chemical kinetics are altered allowing for further investigation on the relationship between the axial jet chemical kinetics, flame stabilization and NOx emissions. CH* chemiluminescence was utilized to analyze the flame behavior such as liftoff height, flame attachment, and dispersion as a result to the addition of diluents. Emissions were obtained to study the direct relationship between emissions and axial jet composition. The results of this work demonstrate the important effect of pressure and axial jet composition on the flame dynamics and emissions of reacting jets in crossflow.

Cavity stabilized flames are one of the primary methods of flame holding being researched for use in supersonic combustion ramjets (scramjets). In order to hold a flame in the supersonic freestream using a cavity, the cavity itself must first be ignited and a stable flame formed within. A fueled cavity in a supersonic crossflow was ignited via a pulse detonator (PD) producing detonation waves that were then decoupled to produce varying degrees of shock-flame separation at the exit of the PD tube. This decoupling allowed for observation of the cavity ignition mechanism, and the key parameters required for successful cavity ignition were identified. Measurements were made using high-frame-rate OH Planar Laser-Induced Fluorescence (PLIF) and schlieren and chemiluminescence imaging. It was shown that the entrainment of high-temperature intermediate species into the forward region of the cavity, immediately behind the step, is the principal criterion for cavity ignition. Both coupled and slightly decoupled detonation cases induced significant OH shedding into the step region, leading to ignition and flame stabilization within the cavity. At conditions where OH shedding into the step region did not occur, cavity ignition was not observed. In coupled and slightly decoupled cases, there is more shedding of OH behind the step due to the greater disturbances created in the flowfield. As the degree of detonation decoupling increases, there is less shedding of OH and therefore a lower likelihood of ignition. Additionally, the time required for cavity combustion to reach its steady-state condition varied with the degree of decoupling of the detonation. Coupled detonation cases were shown to be more disruptive to the cavity and thus required more time to reach steady state than the decoupled cases.

With rapidly increasing computational power, modeling and simulation of complex systems is gradually becoming the norm for evaluating and predicting performance. This research focuses on modeling and simulating thermodynamic behavior of condensers within Combined Cycle Power Plants. This is particularly useful for power generation companies as this allows a wide range of operating conditions to be simulated and characterized without risking damage or the need to shut down the power plant, all of which results in losing revenue in the process. Moreover, being able to observe the thermodynamic evolution of the system provides useful insight into efficiency and response to perturbation. To this end, a dynamic model of a condenser is developed using Siemens Power Plant Automation T3000 (SPPA-T3000), Siemens' proprietary plant monitoring software. The model is simulated using the geometry and specifications of a reference condenser provided by Siemens Energy Inc., along with operating conditions and multiple data sets for model validation. The condenser is modeled using lumped control volumes coupled by heat and mass transfer. Based on extensive literature survey, the model incorporates accurate and time-varying formulations of derived thermodynamic quantities and other heat transfer and fluid flow related coefficients, such as heat capacities, dynamic viscosity, thermal conductivity, and heat transfer coefficients, ensuring the simulation's validity over a wide range of operating conditions. The model is capable of predicting and simulating both phase changes from steam to liquid water (condensation) and liquid water to steam (evaporation). The latter occurs, over short durations, when the condensate experiences low pressure above it. A switching mechanism is implemented to transition between different modes of operation and model the process of temperature change and mass transfer in each mode. The resulting simulation values for temperature and pressure agree with those provided by Siemens Energy Inc. for different operating conditions.

Thermal Barrier Coatings have been extensively used to protect and insulate the metallic components in turbine engines from extreme environments to achieve higher turbine inlet temperatures, resulting in an increase in combined engine cycle efficiency, lowering NOx emissions and fuel consumption. Additionally, as the major failure mechanisms determining lifetime are thermally activated during engine operation, uncertainty in temperature measurements affects lifetime prediction. Early detection of Thermal Barrier Coatings spallation symptoms, associated with local delamination induced temperature changes, can reduce forced engine outages. Further improvements are envisioned with the development of more reliable measurement techniques. For this purpose, Phosphor Thermometry has been considered a promising method for precision monitoring of turbine blade coatings that contain embedded phosphor dopants. In this work, a modified four-flux Kubelka-Munk model for luminescent rare-earth doped Thermal Barrier Coating configurations supported the design and the fabrication of viable sensing coatings for potential industrial implementation. Phosphor Thermometry instrumentation was developed with the objective of expanding capabilities of the technique, using a synchronized acquisition method on sensing coatings. Experiments on an innovative Erbium-Europium co-doped Yttria-Stabilized Zirconia coating have demonstrated the effectiveness of this advanced Phosphor Thermometry instrument with enhanced sensitivity and extended temperature range. Delamination progression monitoring was achieved for the first time using a Thermal Barrier Coating configuration subjected to indentation that includes a thin luminescent layer deposited on the surface and associating the multi-layer configuration with a predictive model that evaluates the advancement of the degradation of the coatings. To further ensure the integrity of the phosphor doped coatings, synchrotron X-ray diffraction was performed to characterize the specific residual strains and thermal expansion of the materials, determining mechanical robustness and compatibility with state-of-the-art Thermal Barrier Coatings. The outcomes of this work pave the way for in-situ temperature measurements on phosphor-doped turbine blade coatings with increased performance and accuracy.

The CubeSat standard originated in 1999. It was a joint development led by Dr. Jordi Puig-Suari of California State Polytechnic University San Luis Obispo and Professor Robert Twiggs of Stanford University. The engineering challenges that have come from this picosatellite class have created incredible educational opportunities for engineering students throughout the world. Since the challenges of engineering a CubeSat abound the designers are always looking at novel and even revolutionary solutions to each one. One of those opportunities is in thermal subsystem design, implementation and characterization. A potential solution for CubeSats is adaptive component usage. This thesis is the written catalogue of my study of adaptive component utilization to solve the thermal management problem inherent in picosatellites. Inside the limited design space of a picosatellite’s electrical, mechanical and software subsystems active spacecraft thermal control often is a necessary forfeiture. This does not preclude CubeSat teams from addressing the thermal aspect of spacecraft design. To the contrary it forces them down a different route to ensuring the spacecraft is verified to meet appropriate environmental constraints. Most CubeSat teams, Cal Poly included, use punishing qualification testing, robust system design and a restricted spacecraft operational lifespan ensure their system will operate through all of the environments it will encounter during launch, separation, spacecraft activation and on until the end of operations. The testing, engineering and modeling I performed were to answer the hypothesis, can a standard* 1-U CubeSat utilize existing hardware and software to improve its thermal condition and operational lifetime? This hypothesis assumes thermal control or situational improvement would have to be gained without the addition of thermal control surfaces, active heaters, heat pipes or louvers and no additional flight software. Ground control software and operation alterations were explicitly not included in these assumptions. The thesis began with defining the many unknowns that existed in the material properties. This required: research into the methods required, specialized measurement hardware to be obtained and set-up, controlled measurements to be taken and thorough testing procedures to be developed. Once the unknowns were better defined the thesis required a detailed satellite thermal analysis by multiple methods along with both thermal vacuum chamber simulation trials and finally on-orbit testing. Based on the research, modeling and testing performed and results obtained through this study, yes, a standard* 1-U CubeSat utilizing existing hardware and software can improve its thermal condition and operational lifetime. As is shown in Section 3.0 and discussed in detail in Section 4.0, utilizing only the onboard electronics and existing flight software the orbital temperature delta that components are experiencing can be reduced by up to 35.8%. Further analyses in section 4.0 use the temperature data to show that by lowering the temperature deltas the satellite does in fact have the capability to both improve its lifetime and certain key subsystem performance parameters.

No description available.

This thesis investigates thermoforming of thin-ply thermoplastic composites via in-situ heating for in-space manufacturing applications. The proposed composite concept is based on combining conductive carbon nanotube (CNT) films and high-temperature thermoplastic matrix. The CNT film is made of randomly aligned carbon nanotubes, which possesses outstanding electrical, thermal, and mechanical properties. When combined with polymer matrix, it becomes a multifunctional composite structure. The thermoplastic chosen is polyether ether ketone (PEEK), which is a semicrystalline high-performance thermoplastic that has exceptional physical and mechanical properties at high temperatures. The composite structure studied is consists of a layer of CNT film sandwiched between two thin films of PEEK. The CNT acts as an in-situ conductive heater when a voltage difference is applied, and a mechanical reinforcement. The PEEK polymer impregnated with reinforcement fibers and CNT is capable of reforming by repeating the thermoforming process. The focus of this study is on developing and characterizing the manufacturing process suitable for in-space manufacturing, where CNT/PEEK can be treated as a composite prepreg capable of being reformed into different shapes on demand via thermoforming. The thermoforming of thin-ply composite structures is achieved solely via in-situ electrical heating.

No description available.

No description available.

The purpose of this research was to design and modify a combustor to study the combustion of aviation fuels and air at elevated pressures within the experimental facility. The fuels of interest are to be heated, atomized, and injected into the facility, where they are ignited in the recirculation zone of a bluff body flame holder. A converging nozzle is attached at the exit of the facility. The ignition of the fuel/air mixture chokes the flow at the nozzle exit, creating interior pressures up to 5atm. This increased temperature and pressure better represent conditions within combustors used in typical jet engines or gas turbines. A series of tests was completed, varying the pressure and equivalence ratio by adjusting the mass flow rates of the air and fuel into the facility. Several fuels including JP-8 and JP-5 have been successfully ignited for this experiment over the full range of desired pressures.