Showing papers in "Journal of Energy Resources Technology-transactions of The Asme in 2015"

Computational Fluid Dynamics Simulation of Gasoline Compression Ignition

Abstract: Gasoline compression ignition (GCI) is a low temperature combustion (LTC) concept that has been gaining increasing interest over the recent years owing to its potential to achieve diesel-like thermal efficiencies with significantly reduced engine-out nitrogen oxides (NOx) and soot emissions compared to diesel engines. In this work, closed-cycle computational fluid dynamics (CFD) simulations are performed of this combustion mode using a sector mesh in an effort to understand effects of model settings on simulation results. One goal of this work is to provide recommendations for grid resolution, combustion model, chemical kinetic mechanism, and turbulence model to accurately capture experimental combustion characteristics. Grid resolutions ranging from 0.7 mm to 0.1 mm minimum cell sizes were evaluated in conjunction with both Reynolds averaged Navier–Stokes (RANS) and large eddy simulation (LES) based turbulence models. Solution of chemical kinetics using the multizone approach is evaluated against the detailed approach of solving chemistry in every cell. The relatively small primary reference fuel (PRF) mechanism (48 species) used in this study is also evaluated against a larger 312-species gasoline mechanism. Based on these studies, the following model settings are chosen keeping in mind both accuracy and computation costs—0.175 mm minimum cell size grid, RANS turbulence model, 48-species PRF mechanism, and multizone chemistry solution with bin limits of 5 K in temperature and 0.05 in equivalence ratio. With these settings, the performance of the CFD model is evaluated against experimental results corresponding to a low load start of injection (SOI) timing sweep. The model is then exercised to investigate the effect of SOI on combustion phasing with constant intake valve closing (IVC) conditions and fueling over a range of SOI timings to isolate the impact of SOI on charge preparation and ignition. Simulation results indicate that there is an optimum SOI timing, in this case −30 deg aTDC (after top dead center), which results in the most stable combustion. Advancing injection with respect to this point leads to significant fuel mass burning in the colder squish region, leading to retarded phasing and ultimately misfire for SOI timings earlier than −42 deg aTDC. On the other hand, retarding injection beyond this optimum timing results in reduced residence time available for gasoline ignition kinetics, and also leads to retarded phasing, with misfire at SOI timings later than −15 deg aTDC.

Application of Real-Time Field Data to Optimize Drilling Hydraulics Using Neural Network Approach

Abstract: Real-time drilling optimization improves drilling performance by providing early warnings in operation Mud hydraulics is a key aspect of drilling that can be optimized by access to real-time data. Different from the investigated references, reliable prediction of pump pressure provides an early warning of circulation problems, washout, lost circulation, underground blowout, and kicks. This will help the driller to make necessary corrections to mitigate potential problems. In this study, an artificial neural network (ANN) model to predict hydraulics was implemented through the fitting tool of matlab. Following the determination of the optimum model, the sensitivity analysis of input parameters on the created model was investigated by using forward regression method. Next, the remaining data from the selected well samples was applied for simulation to verify the quality of the developed model. The novelty is this paper is validation of computer models with actual field data collected from an operator in LA. The simulation result was promising as compared with collected field data. This model can accurately predict pump pressure versus depth in analogous formations. The result of this work shows the potential of the approach developed in this work based on NN models for predicting real-time drilling hydraulics.

Efficient Wind Energy Conversion: Evolution to Modern Design

Abstract: The vast dimensions of the renewable energy field have drawn diverse approaches, resources, and results for a long time. The continual changing behaviors and cycles of renewable energy have encouraged novel developments over the years with most commonly used approaches being three blade designs mounted on a rotor and are commonly used to harvest onshore and offshore wind energy. The renewable energy field is extremely dynamic and perplexing, thus creating a heavy interest in discovering the most economical, efficient, and reliable method to harvest renewable wind energy. Producing energy through the wind is well proven and widely used method with current activities focused on improving efficiency, performance, and reliability. A major challenge of wind energy is that it is available only when and where winds prevail. The electricity produced must be used instantly or stored for use in times when none to limited winds exist. The developments of blades have been based on the aircraft propeller design but extended over a larger area to capture much energy from the wind. This paper provides some basic guidelines on the optimum design staring from the historical design, recent developments, and opportunities. Some challenges on trends are discussed with novel ideas of some future wind energy harvesting designs for enhanced applications at greater efficiency.

Measurement of Laminar Burning Speeds and Investigation of Flame Stability of Acetylene (C2H2)/Air Mixtures

Abstract: Laminar burning speeds and flame structures of spherically expanding flames of mixtures of acetylene (C2H2) with air have been investigated over a wide range of equivalence ratios, temperatures, and pressures. Experiments have been conducted in a constant volume cylindrical vessel with two large end windows. The vessel was installed in a shadowgraph system equipped with a high speed CMOS camera, capable of taking pictures up to 40,000 frames per second. Shadowgraphy was used to study flame structures and transition from smooth to cellular flames during flame propagation. Pressure measurements have been done using a pressure transducer during the combustion process. Laminar burning speeds were measured using a thermodynamic model employing the dynamic pressure rise during the flame propagation. Burning speeds were measured for temperature range of 300–590 K and pressure range of 0.5–3.3 atm, and the range of equivalence ratios covered from 0.6 to 2. The measured values of burning speeds compared well with existing data and extended for a wider range of temperatures. Burning speed measurements have only been reported for smooth and laminar flames. [DOI: 10.1115/1.4028363]

Offshore Wind Foundation Design: Some Key Issues

Abstract: Despite the growth of the offshore wind industry, there are currently doubts relating to the design of wind facilities in the sea. This paper expounds current, already identified structural uncertainties: problems for soil characterization and transition piece (TP) design. This document also introduces new doubts or issues to be researched in the near future in this field (wave theory, scour process, wave load actions, scale difficulty, etc.), not as yet identified due to the scarce experience in the offshore wind industry. With this in mind, technical offshore wind standards related to foundation design have been reviewed.

On Icing and Icing Mitigation of Wind Turbine Blades in Cold Climate

Abstract: A review on icing physics, ice detection, anti-icing and de-icing techniques for wind turbines in cold climate has been performed. Typical physical properties of atmospheric icing and the corresponding meteorological parameters are presented. For computational modeling of ice accretion on turbine blades, the LEWINT code was adopted to simulate ice accretion on an aerofoil for a 2 MW wind turbine. Ice sensors and the basic requirements for ice detection on large blades are described. Besides, this paper presents the main passive and active ice mitigation techniques and their advantages and disadvantages. Scope of future work is suggested as wind turbine blades scale up.

Advances in Horizontal Axis Wind Turbine Blade Designs: Introduction of Slots and Tubercle

Abstract: Despite being harvested thousands of years ago, wind energy was neglected during the industrial revolution because of the strong dependence on fossil fuels. However, after the alarming decrease in the fossil fuels reserves, many have drawn their attentions back to a renewable energy technology, especially the wind energy. This paper presents some of the new designs that are being tested, including slotted blades and tubercles design models. The experimental results are used to validate the numerical studies that are being conducted parallel to the experiments for better understanding and more detailed results. The new slotted blade design produced more power compared to the straight blade for lower wind speeds, while the tubercle blades showed better power performance in severe wind conditions and a more steady behavior under unsteady and higher wind velocities.

Full Fluid–Solid Cohesive Finite-Element Model to Simulate Near Wellbore Fractures

Abstract: This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.

Numerical Shape Optimization of a Wind Turbine Blades Using Artificial Bee Colony Algorithm

Abstract: Use of wind turbines is rapidly growing because of environmental impacts and daily increase in energy cost. Therefore, improving the wind turbines' characteristics is an important issue in this regard. This study has two objectives: one is investigating the aerodynamic performance of wind turbine blades and the other is developing an efficient approach for shape optimization of blades. The numerical solver of flow field was validated by phase VI rotor as a case study. First, flow field around the wind turbine blades was simulated using computational flow dynamics (CFD) and blade element momentum (BEM) methods, then obtained results were validated by available experimental data to show an appropriate conformity. Then for yielding the optimal answer, a shape optimization algorithm was used based on artificial bee colony (ABC) coupled by artificial neural networks (ANNs) as an approximate model. Effect of most important parameters in wind turbine, such as twist angle, chord line, and pitch angle, was changed till achieving the best performance. The flow characteristics of optimized and initial geometries were compared. The results of global optimization showed a value of 8.58% increase for output power. By using pitch power regulate, the maximum power was shifted to higher wind speed and results in a steady power for all work points.

Pressure Profile in Annulus: Solids Play a Significant Role

Abstract: This paper looks into the effects of solids on the wellbore pressure profile under different conditions An extensive number of experiments were conducted on a 90-ft-long, 45 in 8 in full-scale flow loop to simulate field conditions The flow configurations are analyzed A solid–liquid two-phase flow configuration map is proposed Significant difference is found between the pressure profile with solids and without solids in the wellbore The results of this study show how the pressure profile in the wellbore varies when solids present in the annulus, which may have important applications in drilling operations [DOI: 101115/14030845]

Feasibility of Using More Geothermal Energy to Generate Electricity

Abstract: Human population is ever-increasing and, thus, demand for energy is escalating. Consequently, seeking clean methods of producing electricity is a most crucial endeavor at this time. The shrinking reserves of oil have added urgency to the matter as well. One other recognized source of renewable energy besides wind, water, and solar (WWS) is geothermal energy, which has been proven to be useful in baseload power generation, a significant advantage over WWS. As compared to fossil fuels, geothermal energy is not subjected to the supply and cost fluctuations of which fuel is at risk. To date, there have been a number of innovative procedures explored to use geothermal energy to produce electricity. A relatively innovative yet not uncommon method has been to use hot solid rocks to heat water and pump the superheated water to use in power plants. These rocks are generally underground and at higher temperatures due to their proximity to volcanoes or natural geothermal vents. The water goes deeper down into the earth's crust to become superheated by the rocks, and then is pumped out to power turbines, and subsequently returned into the ground to repeat the process. In Krafla, Iceland, during their Icelandic Deep Drilling Project (IDDP) in 2009, a borehole was accidentally dug into the magma at 2100 m. The temperature of this magma was about 900–1000 °C. A steel casing with perforations on the flat side was cemented into the well bottom. This design was to slow the heat flow, and superheated steam was made for the following two years till July 2012. The steam reached temperatures of 450 °C and was at high pressures. Krafla was the world's first magma-enhanced geothermal system (EGS) to generate electricity. This paper will explore the feasibility of using geothermal power plant methods as a sustainable source of clean energy. Geothermal energy has tremendous potential if the right methods can be found to tap that potential, as well as if the cost may be brought down by innovation and demand. In addition, an innovative method, which already exists in some form, is proposed in the current review to harness more geothermal energy for use.

Experimental Study of Low Concentration Sand Transport in Multiphase Air–Water Horizontal Pipelines

Abstract: The ultimate goal of this work is to determine the minimum flow rates necessary for effective transport of sand in a pipeline carrying multiphase flow. In order to achieve this goal, an experimental study is performed in a horizontal pipeline using water and air as carrier fluids. In this study, successful transport of sand is defined as the minimum flow rates of water and air at which all sand grains continue to move along in the pipe. The obtained data cover a wide range of liquid and gas flow rates including stratified and intermittent flow regimes. The effect of physical parameters such as sand size, sand shape, and sand concentration is experimentally investigated in 0.05 and 0.1 m internal diameter pipes. The comparisons of the obtained data with previous studies show good agreement. It is concluded that the minimum flow rates required to continuously move the sand increases with increasing sand size in the range examined and particle shape does not significantly affect sand transport. Additionally, the data show the minimum required flow rates increase by increasing sand concentration for the low concentrations considered, and this effect should be taken into account in the modeling of multiphase sand transport.

An Experimental Investigation of Reactivity-Controlled Compression Ignition Combustion in a Single-Cylinder Diesel Engine Using Hydrous Ethanol

Abstract: Dual-fuel reactivity-controlled compression ignition (RCCI) combustion using port injection of a less reactive fuel and early-cycle direct injection (DI) of a more reactive fuel has been shown to yield both high thermal efficiency and low NOX and soot emissions over a wide engine operating range. Conventional and alternative fuels such as gasoline, natural gas, and E85 as the lower reactivity fuel in RCCI have been studied by many researchers; however, published experimental investigations of hydrous ethanol use in RCCI are scarce. Making greater use of hydrous ethanol in internal combustion engines has the potential to dramatically improve the economics and life cycle carbon dioxide emissions of using bioethanol. In this work, an experimental investigation was conducted using 150 proof hydrous ethanol as the low reactivity fuel and commercially available diesel as the high reactivity fuel in an RCCI combustion mode at various load conditions. A modified single-cylinder diesel engine was used for the experiments. Based on previous studies on RCCI combustion by other researchers, early-cycle split-injection strategy of diesel fuel was used to create an in-cylinder fuel reactivity distribution to maintain high thermal efficiency and low NOX and soot emissions. At each load condition, timing and mass fraction of the first diesel injection was held constant, while timing of the second diesel injection was swept over a range where stable combustion could be maintained. Since hydrous ethanol is highly resistant to auto-ignition and has large heat of vaporization, intake air heating was needed to obtain stable operations of the engine. The study shows that 150 proof hydrous ethanol can be used as the low reactivity fuel in RCCI through 8.6 bar indicated mean effective pressure (IMEP) and with ethanol energy fraction up to 75% while achieving simultaneously low levels of NOX and soot emissions. With increasing engine load, less intake heating is needed and exhaust gas recirculation (EGR) is required to maintain low NOX emissions.

Analysis of Hydraulic Fracturing and Reservoir Performance in Enhanced Geothermal Systems

Abstract: Analyses of fracturing and thermal performance of fractured reservoirs in engineered geothermal system (EGS) are extended from a depth of 5 km to 10 km, and models for flow and heat transfer in EGS are improved. Effects of the geofluid flow direction choice, distance between fractures, fracture width, permeability, radius, and number of fractures, on reservoir heat drawdown time are computed. The number of fractures and fracture radius for desired reservoir thermal drawdown rates are recommended. A simplified model for reservoir hydraulic fracturing energy consumption is developed, indicating it to be 51.8–99.6 MJ per m fracture for depths of 5–10 km. [DOI: 10.1115/1.4030111]

Micro-Emulsion Phase Behavior of a Cationic Surfactant at Intermediate Interfacial Tension in Sandstone and Carbonate Rocks

Abstract: Based on the conventional approach, the trapped oil in rock pores can be easily displaced when a Winsor type (III) micro-emulsion is formed in the reservoir during surfactant flooding. On the other hand, the Winsor type (III) involves three phase flow of water, oil, and micro-emulsion that causes considerable oil phase trapping and surfactant retention. This work presents an experimental study on the effect of micro-emulsion phase behavior during surfactant flooding in sandstone and carbonate core samples. In this study, after accomplishing salinity scan of a cationic surfactant (C16–N(CH3)3Br), the effects of Winsor (I), Winsor (III) and Winsor (II) on oil recovery factor, differential pressure drop, relative permeability, and relative permeability ratio were investigated extensively. To carry out a comparative study, homogeneous and similar sandstone and carbonate rocks were selected and the effects of wettability alteration and dynamic surfactant adsorption were studied on them. The results of oil recovery factor in both rock types showed that Winsor (I) and Winsor (III) are preferred compared to Winsor (II) phase behavior. In addition, comparison of normalized relative permeability ratio at high water saturations revealed that Winsor (I) has more appropriate oil and water relative permeability than Winsor (II). The results presented in this paper demonstrate that optimum salinity which results in higher recovery factor and better oil displacement may occur at salinities out of Winsor (III) range. Therefore, the best way to specify optimum salinity is to perform core flood experiments at several salinities, which cover all phase behaviors of Winsor (I), Winsor (III), and Winsor (II).

Realtime Rate of Penetration Optimization Using the Shuffled Frog Leaping Algorithm

Abstract: The increasing complexities of wellbore geometry imply an increasing well cost. It has become more important than ever to achieve an increased rate of penetration (ROP) and, thus, reduced cost per foot. To achieve maximum ROP, an optimization of drilling parameters is required as the well is drilled. While there are different optimization techniques, there is no acceptable universal mathematical model that achieves maximum ROP accurately. Usually, conventional mathematical optimization techniques fail to accurately predict optimal parameters owing to the complex nature of downhole conditions. To account for these uncertainties, evolutionary-based algorithms can be used instead of mathematical optimizations. To arrive at the optimum drilling parameters efficiently and quickly, the metaheuristic evolutionary algorithm, called the “shuffled frog leaping algorithm,” (SFLA) is used in this paper. It is a type of rising swarm-intelligence optimizer that can optimize additional objectives, such as minimizing hydromechanical specific energy. In this paper, realtime gamma ray data are used to compute values of rock strength and bit–tooth wear. Variables used are weight on bit (WOB), bit rotation (N), and flow rate (Q). Each variable represents a frog. The value of each frog is derived based on the ROP models used individually or simultaneously through iteration. This optimizer lets each frog (WOB, N, and Q) jump to the best value (ROP) automatically, thus arriving at the near optimal solution. The method is also efficient in computing optimum drilling parameters for different formations in real time. The paper presents field examples to predict and estimate the parameters and compares them to the actual realtime data.

Optimum Performance Improvements of the Combined Cycle Based on an Intercooler–Reheated Gas Turbine

Abstract: The performance enhancements and modeling of the gas turbine (GT), together with the combined cycle gas turbine (CCGT) power plant, are described in this study. The thermal analysis has proposed intercooler–reheated-GT (IHGT) configuration of the CCGT system, as well as the development of a simulation code and integrated model for exploiting the CCGT power plants performance, using the MATLAB code. The validation of a heavy-duty CCGT power plants performance is done through real power plants, namely, MARAFIQ CCGT plants in Saudi Arabia with satisfactory results. The results from this simulation show that the higher thermal efficiency of 56% MW, while high power output of 1640 MW, occurred in IHGT combined cycle plants (IHGTCC), having an optimal turbine inlet temperature about 1900 K. Furthermore, the CCGT system proposed in the study has improved power output by 94%. The results of optimization show that the IHGTCC has optimum power of 1860 MW and thermal efficiency of 59%. Therefore, the ambient temperatures and operation conditions of the CCGT strongly affect their performance. The optimum level of power and efficiency is seen at high turbine inlet temperatures and isentropic turbine efficiency. Thus, it can be understood that the models developed in this study are useful tools for estimating the CCGT power plant’s performance