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research-article  
Valery L. Okulov, Robert Mikkelsen, Jens N. N⊘rkær S⊘rensen, Igor V. Naumov and Mikhail Tsoy
J. Energy Resour. Technol   doi: 10.1115/1.4036250
In the current experiments, two identical wind turbine models were placed in uniform flow conditions in a water flume. The initial flow in the flume was subject to a very low turbulence level, limiting the influence of external disturbances on the development of the inherent wake instability. Both rotors are three-bladed and designed using blade element/lifting line (BE/LL) optimum theory at a tip speed ratio, ?, of 5 with a constant design lift coefficient along the span, CL= 0.8. Measurements of the rotor characteristics were conducted by strain sensors installed in the rotor mounting. The resulting power capacity has been studied and analyzed at different rotor positions and a range of tip speed ratios from 2 to 8 and a simple algebraic relationship between the velocity deficit in the wake of the front turbine and the power of the second turbine was found, when both rotors have the coaxial position.
TOPICS: Rotors, Wind turbines, Turbines, Flow (Dynamics), Wakes, Flumes, Design, Turbulence, Blades, Strain sensors, Water, Algebra
research-article  
Mohamed Mahmoud
J. Energy Resour. Technol   doi: 10.1115/1.4036251
Sandstone rocks integrity and consolidation are highly affected by the type and the strength of the stimulation fluids. Strong acids such as HF/HCl impair the rock consolidation. The reduction in the sandstone rock consolidation will trigger the sand production. Sand causes erosion of downhole and surface equipment especially when it is produced with high gas flow rates. In this study gentle stimulation fluids for sandstone that consists of chelating agents and catalyst were proposed. The chelating agents are DTPA and EDTA. The change in the mechanical properties of sandstone rocks (Bandera and Berea) was evaluated. The possibility of the formation damage after using seawater based chelating agents was investigated and compared to HF/HCl mud acid. Coreflooding experiments were conducted to evaluate the effect of these fluids on the rock integrity. Computed Tomography (CT) scanner was used to assess the formation damage. Different models were used to predict the sand production possibility after the stimulation with chelating agent/catalyst and this was compared to the HF/HCl mud acid. The results showed that the permeability of sandstone core increased after acidizing. The reduction in CT number after acidizing confirmed that no formation damage occurred. Rock mechanics evaluation showed no major changes occurred in the rock moduli and no sands production was observed. The model results showed that using chelating gents to stimulate Berea and Bandera sandstone cores did not cause sand production. Applying the same models for cores stimulated by HF/HCl acids indicated high possibility of sand production.
TOPICS: Sands, Reservoirs, Rocks, Damage, Fluids, Catalysts, Computerized tomography, Permeability, Gas flow, Mechanical properties, Erosion, Rock mechanics, Seawater
research-article  
Jeffrey T. Hwang, Alex J. Nord and William F. Northrop
J. Energy Resour. Technol   doi: 10.1115/1.4036252
Aftermarket dual-fuel injection systems using a variety of different fumigants have been proposed as alternatives to expensive aftertreatment to control NOX emissions from legacy diesel engines. However, our previous work has shown that available add-on systems using hydrous ethanol as the fumigant achieve only minor benefits in emissions without re-calibration of the diesel fuel injection strategy. This study experimentally re-evaluates a novel aftermarket dual-fuel port fuel injection system used in our previous work, with the addition of higher flow injectors to increase the fumigant energy fraction (FEF), defined as the ratio of energy provided by the hydrous ethanol on a lower heating value basis to overall fuel energy. Results of this study confirm our earlier findings that as FEF increases, NO emissions decrease, while NO2 and unburned ethanol emissions increase, leading to no change in overall NOX. Peak cylinder pressure and apparent rates of heat release are not strongly dependent on FEF, indicating that in-cylinder NO formation rates by the Zel'dovich mechanism remains the same. Through single zone modeling, we show the feasibility of in-cylinder NO conversion to NO2 aided by unburned ethanol. The modeling results indicate that NO to NO2 conversion occurs during the early expansion stroke where bulk gases have temperature in the range of 1150 - 1250K. This work conclusively proves that aftermarket dual fuel systems for fixed calibration diesel engines cannot reduce NOX emissions without lowering peak temperature during diffusive combustion responsible for forming NO in the first place.
TOPICS: Fuel systems, Diesel engines, Ethanol, Nitrogen oxides, Emissions, Fuels, Cylinders, Modeling, Calibration, Temperature, Combustion, Gases, Pressure, Flow (Dynamics), Heat, Ejectors, Diesel, Heating
research-article  
Marlon Cadrazco, John R. Agudelo, Luz Y. Orozco and Verónica Estrada
J. Energy Resour. Technol   doi: 10.1115/1.4036253
This work evaluated the genotoxic potential of the soluble organic material (SOM) extracted from the particulate matter (PM) emitted by an automotive diesel engine. The engine was modified to operate with a home-made multipoint-port injection system to substitute 10% of ultra-low-sulfur diesel (ULSD) fuel in energy basis by hydrous ethanol (h-Et) or n-butanol (n-Bu) injected into the manifold during the intake stroke. A low engine load mode named M4 (43 Nm at 2410 min-1) and a medium-load mode M2 (95 Nm at 2410 min-1) were selected from the vehicle homologation cycle. PM was collected with a stainless steel filter located 1.5 m downstream the exhaust manifold. The SOM of the PM was extracted to evaluate the genotoxic activity on human lymphocytes using the Comet assay. Results indicated that independently of the mode, the SOM coming from alcohols led more genotoxicity than ULSD, following the order h-Et > n-Bu > ULSD. The low engine load operation exhibited much more DNA damage than mode M2, especially the PM produced by hydrous ethanol port-injection. Although further research is still necessary, these findings suggest that the biology activity of the SOM coming from alcohols PM could be a barrier for the implementation of alcohol port-injection technology.
TOPICS: Particulate matter, Gates (Closures), Diesel, Ethanol, Engines, Stress, Fuels, Diesel engines, Vehicles, Cycles, Filters, Manifolds, Stainless steel, Sulfur, DNA, Biology, Damage, Exhaust manifolds
research-article  
Owen Pryor, Samuel Barak, Joseph Lopez, Erik Ninnemann, Batikan Koroglu, Leigh Nash and Subith Vasu
J. Energy Resour. Technol   doi: 10.1115/1.4036254
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/O2 under these conditions. Current data provides crucial validation data needed for development of future kinetic mechanisms.
TOPICS: Combustion, Carbon dioxide, Methane, Shock tubes, Ignition delay, Ignition, Lasers, Fuels, Absorption spectroscopy, Sensitivity analysis, Pressure, Emissions
research-article  
Syeda Humaira Tasnim
J. Energy Resour. Technol   doi: 10.1115/1.4036053
Growing evidence suggests that research must be done to develop energy efficient systems and clean energy conversion technologies to combat the limited sources of fossil fuel, its high price, and its adverse effects on environment. Thermoacoustic is a clean energy conversion technology that uses the conversion of sound to thermal energy and vice versa for the design of heat engines and refrigerators. However, the efficient conversion of sound to thermal energy demands research on altering fluid, operational, and geometric parameters. The present study is a contribution to improve the efficiency of thermoacoustic devices by introducing a novel stack design. This novel stack consists of alternative conducting and insulating materials or heterogeneous materials. The author examined the performance of 8 different types of heterogeneous stacks (combination 1 to 8) that are only a fraction of the displacement amplitude long and consisted of alternating Aluminum and Corning Celcor or Reticulated Vitreous Carbon (RVC) foam materials. From the thermal field measurements, the author found that combination 8 performs better (12% more temperature difference at the stack ends) than all the other combinations. One interesting feature obtained from these experiments is that combination 7 produces the minimum temperature at the cold end (17% less than other combinations). The thermal performance of the heterogeneous stack is compared to that of the traditional homogeneous stack. Based on the study, the newly proposed stack design provides better cooling performance than a traditionally designed stack.
TOPICS: Heat, Temperature, Cooling, Fluids, Aluminum, Thermal energy, Heat engines, Foamed materials, Thermoacoustic devices, Carbon, Design, Stack design, Displacement, Fossil fuels, Insulation, Renewable energy, Warfare
Technical Brief  
Lei CHEN, Peng SONG, Wuqiang LONG, Liyan FENG, Jing ZHANG and Yang WANG
J. Energy Resour. Technol   doi: 10.1115/1.4035427
Experimental research has been performed on a single cylinder naturally aspirated spark ignition engine that was modified to operate with coal-bed gas fuel to investigate methods of improving the stability of operation and lean burn limit. Various fuel compositions, with methane concentrations from 30% to 100% and CO2 volumetric fractions from 0 to 0.7, were employed to simulate coal-bed methane. Hydrogen was then used to improve the operational stability and lean burn limit. The results show that a stable operating range of the engine was obtained with most of the fuel compositions. In addition to operating beyond the lean burn limit, unstable operation with COVIMEP>10% only occurred at the lean burn limit with a CO2 volumetric fraction of 0.7 at each equivalence ratio. The lean burn limit was significantly reduced from the equivalence ratio of 0.6 to 0.4 by adding hydrogen. Stable operation with COVIMEP<5% at an equivalence ratio of 0.4 was also obtained with some high hydrogen concentration conditions. Hydrogen addition induced the reduction of both CO and THC emissions at all the tested equivalence ratios, especially with equivalence ratios of 0.4 and 0.6. However, a high CO2 volumetric fraction will lead to unstable operation, which worsens CO and THC emissions. Hydrogen addition improves the operation stability and enlarges the lean burn limit of coal-bed gas engines, and this addition could have a significant practical impact on the improvement and application of coal-bed gas engine technology.
TOPICS: Stability, Coal, Spark-ignition engine, Hydrogen, Carbon dioxide, Methane, Fuels, Engines, Emissions, Gas engines, Gaseous fuels, Cylinders
research-article  
Arild Saasen, Songxiong Ding, Per Amund Amundsen and Kristoffer Tellefsen
J. Energy Resour. Technol   doi: 10.1115/1.4033304
Materials such as added clays, weight materials, drill solids and metalic wear products in the drilling fluid are known to distort the geomagnetic field at the location of the Measurement While Drilling (MWD) tool magnetometers that are used to measure the direction of well path. This distortion contributes to substantial errors in determination of azimuth while drilling deviated wells. These errors may result in missing the target of a long deviated 12 ¼” section in the range of 1-200m; representing a significant cost to be mitigated. The error becomes even more pronounced if drilling occurs in arctic regions close to the magnetic North Pole ( or South Pole). The effect on the magnetometer readings is obviously linked to the kinds and amounts of magnetic materials in the drilling fluid. The problem has recently been studied by laboratory experiments and analyses of downhole survey data. A series of experiments has been carried out to understand how some drilling fluid additives relate to the magnetic distortion. Experiments with free iron ions show that presence of iron ions does not contribute to magnetic distortion; while experiments with bentonite-based fluids show a strong effect of bentonite on magnetic shielding. Albeit earlier measurements showing a strong dependency of the content of organophilic clay, clean laboratory prepared oil-based drilling fluids show no increased shielding when adding organophilic hectorite clays. The anticipated difference between these two cases is outlined in the paper. When eroded steel from an offshore drilling site is added into the oil-based drilling fluid, it is found that these swarf and steel fines significantly increase the magnetic shielding of the drilling fluid. The paper outlines how the drilling direction may be distorted by the presence of these additives and contaminants and how this relates to the rheological properties of the drilling fluid.
TOPICS: Fluids, Drilling, Rheology, Errors, Iron, Magnetic shielding, Steel, Ions, Magnetometers, Poles (Building), Drills (Tools), Solids, Wells, Weight (Mass), Wear, Scrap metals, Underwater drilling, Magnetic materials, Arctic region

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