Showing papers in "Journal of Energy Resources Technology-transactions of The Asme in 2017"

High Pressure Shock Tube Ignition Delay Time Measurements During Oxy-Methane Combustion With High Levels of CO2 Dilution

Abstract: For this study, ignition delay times and methane species time-histories were measured for methane/O2 mixtures in a high CO2 diluted environment using shock tube and laser absorption spectroscopy. The experiments were performed between 1300 K and 2000 K at pressures between 6 and 31 atm. The test mixtures were at an equivalence ratio of 1 with CH4 mole fractions ranging from 3.5% -5% and up to 85% CO2 with a bath of argon gas as necessary. The ignition delay times and methane time histories were measured using pressure, emission, and laser diagnostics. Predictive ability of two literature kinetic mechanisms (GRI 3.0 and ARAMCO Mech 1.3) was tested against current data. In general, both mechanisms performed reasonably well against measured ignition delay time data. The methane time-histories showed good agreement with the mechanisms for most of the conditions measured. A correlation for ignition delay time was created taking into the different parameters showing that the ignition activation energy for the fuel to be 49.64 kcal/mol. Through a sensitivity analysis, CO2 is shown to slow the overall reaction rate and increase the ignition delay time. To the best of our knowledge, we present the first shock tube data during ignition of methane/CO2/O2more » under these conditions. In conclusion, current data provides crucial validation data needed for development of future kinetic mechanisms.« less

Effects From Complex Terrain on Wind-Turbine Performance

Abstract: In this work, experimental measurements are made to study wind turbines over complex terrains and in presence of the atmospheric boundary layer. Thrust and power coefficients for single and multipl ...

Theoretical Prediction of Laminar Burning Speed and Ignition Delay Time of Gas-to-Liquid Fuel

Abstract: Gas-to-liquid (GTL), an alternative synthetic jet fuel derived from natural gas through Fischer–Tropsch (F–T) process, has gained significant attention due to its cleaner combustion characteristics when compared to conventional counterparts. The effect of chemical composition on key performance aspects such as ignition delay, laminar burning speed, and emission characteristics has been experimentally studied. However, the development of chemical mechanism to predict those parameters for GTL fuel is still in its early stage. The GTL aviation fuel from Syntroleum Corporation, S-8, is used in this study. For theoretical predictions, a mixture of 32% iso-octane, 25% n-decane, and 43% n-dodecane by volume is considered as the surrogate for S-8 fuel. In this work, a detailed kinetics model (DKM) has been developed based on the chemical mechanisms reported for the GTL fuel. The DKM is employed in a constant internal energy and constant volume reactor to predict the ignition delay times for GTL over a wide range of temperatures, pressures, and equivalence ratios. The ignition delay times predicted using DKM are validated with those reported in the literature. Furthermore, the steady onedimensional premixed flame code from CANTERA is used in conjunction with the chemical mechanisms to predict the laminar burning speeds for GTL fuel over a wide range of operating conditions. Comparison of ignition delay and laminar burning speed shows that the Ranzi et al. mechanism has a better agreement with the available experimental data, and therefore is used for further evaluation in this study. [DOI: 10.1115/1.4033984]

Auto-Ignition Characteristics Study of Gas-to-Liquid Fuel at High Pressures and Low Temperatures

Abstract: Onset of auto-ignition of premixed gas-to-liquid (GTL)/air mixture has been determined at high pressures and low temperatures over a wide range of equivalence ratios. The GTL fuel used in this study was provided by Air Force Research Laboratory (AFRL), designated by Syntroleum S-8, which is derived from natural gas via the Fischer–Tropsch (F–T) process. A blend of 32% iso-octane, 25% n-decane, and 43% n-dodecane is employed as the surrogates of GTL fuel for chemical kinetics study. A spherical chamber, which can withstand high pressures up to 400 atm and can be heated up to 500 K, was used to collect pressure rise data, due to combustion, to determine the onset of autoignition. A gas chromatograph (GC) system working in conjunction with specialized heated lines was used to verify the filling process. A liquid supply manifold was used to allow the fuel to enter and evaporate in a temperature-controlled portion of the manifold using two cartridge heaters. An accurate high-temperature pressure transducer was used to measure the partial pressure of the vaporized fuel. Pressure rise due to combustion process was collected using a high-speed pressure sensor and was stored in a local desktop via a data acquisition system. Measurements for the onset of auto-ignition were done in the spherical chamber for different equivalence ratios of 0.8–1.2 and different initial pressures of 8.6, 10, and 12 atm at initial temperature of 450 K. Critical pressures and temperatures of GTL/air mixture at which auto-ignition takes place have been identified by detecting aggressive oscillation of pressure data during the spontaneous combustion process throughout the unburned gas mixture. To interpret the auto-ignition conditions effectively, several available chemical kinetics mechanisms were used in modeling autoignition of GTL/air mixtures. For low-temperature mixtures, it was shown that autoignition of GTL fuel is a strong function of unburned gas temperature, and propensity of auto-ignition was increased as initial temperature and pressure increased. [DOI: 10.1115/1.4033983]

Emergence of Delamination Fractures Around the Casing and Its Stability

Abstract: Casing support and zonal isolation are principal objectives in cementing the wells; however the later objective always raises the most concern particularly when there is a potential for formation fluid migration into the cement sheath. Wellbore integrity is highly dependent upon the integrity of the interfacial bond between the cement and the formation as well as the bonding between casing and cement. A closer look at the common cement strength test data, performed routinely in the labs, reveals complicated behavior that cannot be simply modeled using a single parameter (i.e. the interfacial strength).In this work we used a cohesive interface constitutive equation to model the behavior of cement interfaces. Comprehensive analysis of microannulus formation is presented by utilizing an axisymmetric poroelastic finite element model enriched with cohesive interfaces to simulate initiation of the failure zone and possible broaching of the failure zone along the wellbore to shallower zones. Using this model, we demonstrated that it is possible to use data from routine tests, such as the push-out test, to determine not only the shear strength but also normal fracture energy and the stiffness of the cement-formation interface. Cohesive interface properties are calibrated such that simulated test results match with the measured response of the specimens. In the next step, we used these parameters to anticipate well-cement behavior for the field-scale problem. A sensitivity analysis is provided at the end of the part to show the role of each parameter in initiation and development of the failure zone. Interestingly, the shear strength, which is commonly measured from push-out tests are not the only parameter determining the size of the fracture. Other parameters derived in this approach such as normal strength show equal influence on initiation and propagation of the failure zone. The proposed approach provides a tool for a more accurate prediction of cement integrity in the subsurface conditions to quantify the risk of wellbore integrity issues.