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Accepted Manuscripts

BASIC VIEW  |  EXPANDED VIEW
research-article  
Mohammed Al Dushaishi, Runar Nygaard and Daniel S. Stutts
J. Energy Resour. Technol   doi: 10.1115/1.4037682
Excessive drill stem vibration while rotary drilling of oil and gas wells causes damages to drill bits and bottom hole assemblies. In attempt to mitigate drill stem vibrations, theoretical modeling of drill stem dynamics are used to predict severe vibration conditions. To construct the model, decisions have to be made on which beam theory to use, how to implement forces acting on the drill stem, and the geometry of the drill stem. The objective of this paper is to emphasize the effect of these assumptions on drill stem vibration behavior under different, yet realistic, drilling conditions. The nonlinear equations of motion were obtained using Hamilton's principle and discretized using the finite element method. The finite element formulations were verified with uncoupled analytical models. A parametric study showed that increasing the weight on bit and the drill pipe length clearly decreases the drill stem frequencies. How- ever, extending the drill collar length does not reveal a clear trend in the resulting lateral vibration frequency behavior. At normal operating conditions with low operating rotational speed, less than 80 RPM, the nonlinear Euler-Bernoulli and Timoshenko models give comparable results. At higher rotational speeds models deliver different outcomes. Considering only the bottom hole assembly overestimates the drill stem critical operating speed, thus the entire drill stem has to be considered to determine the critical RPM values to be avoided.
research-article  
Ling Zhou, Lingjie Zhang, Weidong Shi, Ramesh Agarwal and Wei Li
J. Energy Resour. Technol   doi: 10.1115/1.4037685
A coupled computational fluid dynamics (CFD)/discrete element method (DEM) is used to simulate the gas-solid two-phase flow in a laboratory scale spouted fluidized bed. Transient experimental results in the spouted fluidized bed are obtained in a special test rig using the high-speed imaging technique. The computational domain of the quasi-3D spouted fluidized bed is simulated using the commercial CFD flow solver ANSYS-Fluent. Hydrodynamic flow field is computed by solving the incompressible continuity and Navier-Stokes equations, while the motion of the solid particles is modeled by the Newtonian equations of motion. Thus, an Eulerian-Lagrangian approach is used to couple the hydrodynamics with the particle dynamics. The bed height, bubble shape, and static pressure are compared between the simulation and the experiment. At the initial stage of fluidization, the simulation results are in very good agreement with the experimental results; the bed height and the bubble shape are almost identical. However, the bubble diameter and the height of the bed are slightly smaller than in the experimental measurements near the stage of bubble breakup. The simulation results with their experimental validation demonstrate that the CFD/DEM coupled method can be successfully used to simulate the transient gas-solid flow behavior in a fluidized bed which is not possible to simulate accurately using the granular approach of purely Euler simulation.
research-article  
Avinash Kumar Agarwal, Suresh Gadekar and Akhilendra P. Singh
J. Energy Resour. Technol   doi: 10.1115/1.4037686
In-cylinder flows in IC engines have always been a focus of study, in order to gain better understanding of fuel-air mixing process and combustion optimization. Different conventional experimental techniques such as hot wire anemometry (HWA), laser Doppler anemometry (LDA) and numerical simulations have been grossly inadequate for complete understanding of the complex 3-D flows inside the engine cylinder. In this experimental study, tomographic PIV was applied in a four-valve, single-cylinder optical research engine, with an objective of investigating the in-cylinder flow evolution during intake and compression strokes in an engine cycle. The motion of these tracer particles was captured using two cameras from different viewing angles. These two directional projections of flow-field were used to reconstruct the 3-D flow-field of the measurement volume (36 x 25 x 8 mm3), using MART algorithm. Results indicated that the in-cylinder flows are dependent on the piston position and spatial location inside the engine cylinder. The randomness of air-flow fields during the intake stroke was very high, which became more homogeneous during the compression stroke. The flows were found to be highly dependent on Z plane location inside the engine. During the intake stroke, flows were highly turbulent throughout the engine cylinder and velocities vectors were observed in all directions. However, during the compression stroke, flow velocities were higher near the injector and they reduced closer to the valves.
TOPICS: Flow (Dynamics), Internal combustion engines, Cylinders, Engine cylinders, Engines, Compression, Valves, Chaos, Optimization, Pistons, Laser Doppler anemometry, Air flow, Wire, Optical research, Algorithms, Ejectors, Combustion, Particulate matter, Fuels, Turbulence, Computer simulation, Cycles
research-article  
Xidong Du, Min Gu, Shuo Duan and Xuefu Xian
J. Energy Resour. Technol   doi: 10.1115/1.4037687
The effects of CO2 injection pressure (PCO2) on CO2 dispersion and the mechanism of CO2-CH4 displacement in shale were studied. Results indicate that Coats-Smith dispersion-capacitance model can give a reasonable simulated result to the effluent composition curves of CO2 under different PCO2. The shapes of CO2 breakthrough curves become more asymmetrical with increasing PCO2. Higher PCO2 causes early breakthrough of CO2 and hence reduces the recovery of CH4 at CO2 breakthrough (Rpipeline-CH4). The competitive adsorption of CO2-CH4 is strengthened and the ultimate CH4 recovery (Rultimate-CH4) is enhanced at higher PCO2. Lower PCO2 is conductive to gaining higher Rpipeline-CH4. With the increase of PCO2, dispersion coefficient (Kd) increases nearly exponentially. Larger Kd leads to the lower Rpipeline-CH4 and longer transition zone. The flowing fraction (F) in pore space decreases linearly with injection pressure. The stagnant region is the place where competitive adsorption takes place. Majority of injected CO2 diffuses into stagnant region to replace in-place CH4 under higher PCO2, resulting in larger Rultimate-CH4. The mass transfer coefficient (Km) between the flowing and stagnant regions rises with PCO2 increases. By improving Km, CO2 molecules diffuse easily into micropores, causing the smaller F and higher Rultimate-CH4. In addition, CO2 diffusion provides major contribution to CO2 dispersion at lower PCO2, and at higher PCO2 mechanical mixing of CO2-CH4 offers predominant contribution to CO2 dispersion. Larger mechanical mixing accelerates the mixing of CO2-CH4 and is harmful to Rpipeline-CH4 at higher PCO2.
research-article  
Omid Askari
J. Energy Resour. Technol   doi: 10.1115/1.4037688
Chemical composition and thermodynamics properties of different thermal plasmas are calculated in a wide range of temperatures and pressures. The calculation is performed in dissociation and ionization temperature ranges using statistical thermodynamic modeling. The thermodynamic properties are being considered in this study are enthalpy, entropy, Gibbs free energy, specific heat at constant pressure, specific heat ratio, speed of sound, mean molar mass, and degree of ionization. The calculations have been done for seven pure plasmas such as hydrogen, helium, carbon, nitrogen, oxygen, neon and argon. In this study, the Debye-Hukel cutoff criterion in conjunction with the Griem's self-consistent model are applied for terminating the electronic partition function series and to calculate the reduction of the ionization potential. The Rydberg and Ritz extrapolation laws have been used for energy levels which are not observed in tabulated data. Two different methods called complete chemical equilibrium and progressive methods are presented to find the composition of available species. The calculated pure plasma properties are then presented as functions of temperature and pressure, in terms of a new set of thermodynamically self-consistent correlations for efficient use in CFD simulations. The results have been shown excellent agreement with literature. The results from pure plasmas are then used as a reliable reference source to calculate the thermodynamic properties of any arbitrary plasma mixtures having elemental atoms of H, He, C, N, O, Ne and Ar in their chemical structure. This alternative method is only valid for high temperature thermal plasmas.
TOPICS: Pressure, Temperature, Plasmas (Ionized gases), Specific heat, Ionization, Speed of sound, Simulation, Entropy, Energy levels (Quantum mechanics), Thermodynamics, Atoms, Equilibrium (Physics), Gibbs' free energy, Ionization energy, Carbon, Computational fluid dynamics, Engineering simulation, Modeling, Enthalpy, Helium, Hydrogen, Nitrogen, Oxygen, High temperature
Technical Brief  
Yinghao Ma, Kaigui Xie, Jizhe Dong, Heng-Ming Tai and Bo Hu
J. Energy Resour. Technol   doi: 10.1115/1.4037536
Bundled wind-thermal generation system (BWTGS) is an effective way to utilize remote large-scale wind power. The optimal generation maintenance schedule for BWTGS is not only helpful to improve the system reliability level, but also useful to enhance the system economic efficiency and extend the lifetime of components. This paper presents a model to optimize the generation maintenance schedule for BWTGS. The probabilistic production simulation technique is employed to calculate the system costs, and a sequential probabilistic method is utilized to capture the sequential and stochastic nature of wind power. A hybrid optimization algorithm based on the simulated annealing and multi-population parallel genetic algorithm is developed to solve the proposed model. Case studies demonstrate the effectiveness of this proposed model. Effects of the reliability deterioration of thermal generating units and the pattern of BWTGS transmission power are also investigated.
TOPICS: Maintenance, Wind, Wind power, Reliability, Simulation, Genetic algorithms, Optimization algorithms, Simulated annealing
research-article  
Howard Njoku, Onyemaechi Valentine Ekechukwu and Samuel O. Onyegegbu
J. Energy Resour. Technol   doi: 10.1115/1.4037535
This paper investigates the nature of entropy generation in stratified sensible thermal energy stores (SSTES) during charging using a dimensionless axisymmetric numerical model of an SSTES. Time-varying dimensionless entropy generation rates and the cumulative entropy generation in SSTES were determined from finite volume computations. The aspect ratios, AR, Peclet numbers, Pe_D, and Richardson numbers, Ri, for the stores considered were within the ranges 1 <= AR <= 4, 5 x 10^3 <= Pe_D <= 100 x 10^3, and 10 <= Ri <= 10^4, respectively. Using the Bejan number, Be, the total entropy generation was shown to be almost entirely due to thermal effects in the SSTES. The Bejan number is practically unity for most of the SSTES' charging duration. The contributions of radial thermal gradients to the thermal entropy generation were further shown to be largely negligible in comparison to the contributions of axial thermal gradients, except at low Ri. Entropy generation numbers, N_s, in the SSTES were also computed and found to increase with decreasing AR and Pe_D, and with increasing Ri. Pe_D was found to have the most significant influence on N_s. Based on this axisymmetric analyses of time-varying entropy generation in STESS, estimates have been obtained of (1) the relative significance of radial effects on entropy generation within SSTES, and (2) the relative significance of viscous shear entropy generation mechanisms within SSTES.
TOPICS: Entropy, Temperature gradient, Computer simulation, Thermal energy, Shear (Mechanics), Temperature effects, Computation
research-article  
Dokhani Vahid, Yu Mengjiao, Gao Chao and Bloys James
J. Energy Resour. Technol   doi: 10.1115/1.4037480
Routine measurement of hydraulic diffusivity of ultra-low permeability rocks, such as shale, is a prolonged process. This study explores the effects of sorptive characteristic of porous medium on hydraulic diffusivities of shale rocks. The examined rock types include Mancos Shale, Catoosa Shale, Eagle Ford Shale, and core samples from Gulf of Mexico. Firstly, the adsorption isotherms of the selected shale rocks were obtained. Then, the hydraulic properties of the selected shale rocks were determined using Shale/Fluid Interaction Testing Cell, which employs Pore Pressure Transmission technique (PPT). The experimental results show that the moisture content of shale is correlated with water activity using a multilayer adsorption theory. It is found that the adsorption isotherms of various shale formations can be scaled using their respective cation exchange capacity into a single adsorption curve. Analyzing the transient pore pressure response in the downstream side of shale sample allows calculating the transport coefficients of shale samples. Hydraulic properties of shales are obtained by matching the pore pressure history with 1-D coupled fluid flow model. The experimental results indicate that sorptive properties can be inversely related to the hydraulic diffusivity of shale rocks. It is found that with an increase in the magnitude of sorption potential of shale, the hydraulic diffusivity decreases. This study is useful for shale characterization and provides a correlation, which can have various applications including, but not limited to, wellbore stability prediction during well planning.
TOPICS: Sorption, Shales, Rocks, Pressure, Stability, Fluid dynamics, Fluids, Permeability, Porous materials, Transients (Dynamics), Water, Gulf of Mexico, Testing
research-article  
Zhenkun Sang, Zemin Bo, Xing Liu and Yiwu Weng
J. Energy Resour. Technol   doi: 10.1115/1.4037481
In order to eliminate pollution from ultra low calorific value gas (ULCVG) of methane and realize energy recovery simultaneously, a novel reactor with the function of regenerator and catalytic combustion named rotary regenerator type catalytic combustion reactor is studied. The reactor walls which store and reject heat alternatively can preheat the ULCVG temperature to the ignition temperature of methane, then catalytic combustion occurs rapidly. Periodical rotation of the reactor can maintain the stability of catalytic combustion. According to the feature of the reactor such as rotator and catalytic combustion, considering the coupled heat exchange boundary condition, the characteristic of this reactor was calculated and analyzed with the help of computational fluid dynamics (CFD). The results show that the ULCVG can be oxidized as a primary fuel, with the methane conversation rate above 91%, and the feasibility of this reactor is proved in theory. The reactor can continuously generate high temperature gas(1035 K-1200 K) which can be used by the heat consumption unit (HCU) such as turbine, boiler and SOFC service etc. In state I (or II) the outlet gas and flue temperature was increased by approximately linear law. This rule is useful to evaluate the performance of this reactor. Periodical rotation not only supports high temperature zone which is useful to catalytic combustion, but also avoids catalyst high temperature deactivation.
TOPICS: Combustion, Heat, Temperature, Methane, High temperature, Computational fluid dynamics, Rotation, Stability, Fuels, Flues, Boilers, Energy recovery, Solid oxide fuel cells, Turbines, Boundary-value problems, Catalysts, Ignition, Pollution
research-article  
DING Hao, HE Ren and DENG Xiaoxi
J. Energy Resour. Technol   doi: 10.1115/1.4037482
In order to solve the issues of onboard refueling vapor evaporation existing in the Hybrid Electric Vehicle(HEV), two different devices, Fuel Vapor-containment System(FVS) and Vapor Reducing Fuel Tank System(VRFTS), are researched and compared to find that the FVS has an advantage on the fuel vapor recovery. The general refueling progress of the FVS has been studied in detail and divided into two different stages, the decompression stage and the refueling stage. Then the two different stages' mathematical models have been developed based on the binary diffusion theory and time-variation diffusion theory, and simulated using MATLAB to calculate the evaporative emission with regard to time. Finally, The experiments about the decompression emissions and refueling emissions have been conducted respectively. It is found that the results of tests and calculation are in good agreement by contrast the test and simulation.
TOPICS: Vapors, Modeling, Hybrid electric vehicles, Emissions, Diffusion (Physics), Fuels, Simulation, Evaporation, Matlab, Fuel storage, Containment
research-article  
Zhenjian Liu, Zhenyu Zhang, Yiyu Lu, Sing Ki Choi and Xiaoqian Liu
J. Energy Resour. Technol   doi: 10.1115/1.4037483
Sorption hysteresis characterization of CH4 and CO2 on lignite, bituminous coal and anthracite were studied to improve the understanding of the interaction between gas molecules and different ranks of coal and further improve the precision of the adsorption methods in characterizing pore structure at low pressure. Pore structure of three ranks of coal was firstly investigated with scanning electron microscopy (SEM) and techniques of Nitrogen (N2) adsorption. Then CH4 and CO2 sorption isotherms were measured using the gravimetric method at 288, 308 and 328 K. The N2 sorption isotherms show that a wide distribution of pore size existed in three coal samples, and with the process of coalification the specific surface area firstly decreased and then increased, while the pore size of coal monotonically decreased. This is confirmed by SEM observation. The measured sorption isotherms were then decomposed into simultaneously-running adsorption and absorption branches based on the assumption that the former is totally reversible and the later completely irreversible. The reconstructed adsorption branches can be well described by both Langmuir model and Dubinin-Radushkevich (D-R) equation. The absorption, which represents the sorption hysteresis portion, increased with pressure, but decreased with temperature. The absorbed amount of gas increased with pressure, but the absorption of CO2 increased concavely with gas pressure while CH4 followed an upward exponential function. Also, the absorption varied with coal rank, following a U-shaped function. This study can provide new insights to CH4 and CO2 sorption hysteresis on coal and other organic geomaterial.
TOPICS: Pressure, Sorption, Coal, Carbon dioxide, Methane, Absorption, Nitrogen, Scanning electron microscopy, Temperature
research-article  
Xiaoyan Meng and Daoyong (Tony) Yang
J. Energy Resour. Technol   doi: 10.1115/1.4037374
Mathematical formulations have been proposed and verified to determine dynamic dispersion coefficients for solutes flowing in a circular tube with fully-developed laminar flow under different source conditions. Both the moment analysis method and the Green’s function are used to derive mathematical formulations, while the three-dimensional (3D) random walk particle tracking (RWPT) algorithm in a Cartesian coordinate system has been modified to describe solute flow behaviour. The newly proposed formulations have been verified to determine dynamic dispersion coefficients of solutes by achieving an excellent agreement with both the RWPT results and analytical solutions. The differences among transverse average concentration using the Taylor model with and without dynamic dispersion coefficient and center-of-mass velocity are significant at early times but indistinguishable when dimensionless time (tD ) approaches 0.5. Furthermore, compared to solutes flowing in a 3D circular tube, dispersion coefficients of solutes flowing in a two-dimensional (2D) parallel-plate fracture are always larger for a uniform planar source; however, this is not always true for a point source. Solute dispersion in porous media represented by the tube-bundle model is greatly affected by pore size distribution and increases as standard deviation of pore size distribution (σ) increases across the full-time scale.
TOPICS: Flow (Dynamics), Porous materials, Particulate matter, Laminar flow, Center of mass, Fracture (Materials), Algorithms, Fracture (Process)
research-article  
Gerald G. Kleinstein
J. Energy Resour. Technol   doi: 10.1115/1.4037375
The motion of a fluid in a defined domain is called thermodynamically admissible if it satisfies the global system of the principles of continuum mechanics and the principle of entropy; or, its equivalent differential system, consisting of a system of differential equations and jump conditions. In an earlier publication, we have shown that he motion of a three dimensional rigid body in an irrotational viscous and heat conducting fluid violates the entropy jump condition, referred to as the Clausius-Duhem jump condition. Such a motion is thermodynamically inadmissible and could not persist. In a more recent publication we have demonstrated that, if the fluid-solid interface is isentropic, boundary conditions at the material interface, such as the no-slip condition and the continuity of the temperature follow directly from the Clausius-Duhem jump condition. It is the purpose of this analysis to extend this methodology for the derivation of boundary conditions at isentropic material interfaces to non-isentropic material interfaces. We show that, if the boundary conditions at the fluid-solid interface are a-priori selected to satisfy the Clausius-Duhem jump condition, the resulting motion, as described by the solution of the Navier-Stokes equations - whether the interface is isentropic or non isentropic - is thermodynamically admissible.
TOPICS: Fluids, Boundary-value problems, Entropy, Continuum mechanics, Navier-Stokes equations, Differential equations, Heat, Temperature
research-article  
Guangying Yu, Omid Askari and Hameed Metghalchi
J. Energy Resour. Technol   doi: 10.1115/1.4037376
A numerical study has been carried out to investigate the impact of adding syngas into JP-8 fuel. A new chemical mechanism has been assembled from existing mechanism of JP-8 and Syngas and has been examined by comparing with experimental data from literatures. The mechanism was then applied to Cantera zero-dimension constant internal energy and constant volume model and 1-D freely propagating flame model to calculate the ignition delay time and laminar burning speed respectively. The simulations were carried out over a large range of temperature (700 K to 1000 K), blending ratio (0% to 20% Syngas) and H2/CO ratio (10/90 to 50/50). Simulation results showed that blending syngas with JP-8 will slightly increase the ignition delay time and laminar burning speed.
TOPICS: Combustion, Syngas, Ignition delay, Temperature, Flames, Simulation results, Fuels, Dimensions, Simulation, Internal energy (Physics), Engineering simulation
research-article  
Ali Lesan, Seyed Ehsan Eshraghi, Abbas Bahroudi, Mohammad R. Rasaei and Hossein Rahami
J. Energy Resour. Technol   doi: 10.1115/1.4037368
To have an acceptable accuracy for water flooding projects, proper history matching is an important tool. Capacitance-Resistance-Model (CRM) simulates water flooding performance based on two tuning parameters of time constant and connectivity. Main advantages of CRM are its simplicity and fastness; furthermore, it needs only some field-available inputs like injection and production flow rates. CRM is reliable if producers receive the injection rate signal; in other words, duration of history matching must be enough so that the rate signal of injection be sensed in producers. It is a shortcoming of CRM that the results might not be accurate as a result of short history. In the common CRM, time constant is considered to be a static parameter (constant number) during the history of simulation. However, time constant is a time-dependent function that depends on the reservoir nature. In this paper, a new model has been developed so as to it decreases model dependency on the history matching length by shifting time axis. This new definition adds a rate shift constant to the model mathematics. Moreover, a new model is considering dynamic time constants. This new model is called Dynamic Capacitance-Resistance Model (DCRM). Two reservoir models have been simulated to analyze the performance of DCRM, and, as a results, it is found that the static time constant is an erroneous assumption. Finally, the accuracy of the results have been improved since the degree of freedom of the CRM increased in the new version.
TOPICS: Capacitance, Reservoirs, Floods, Signals, Water, Mathematics, Simulation, Degrees of freedom, Flow (Dynamics)
research-article  
Marcin Szega and Piotr Zymelka
J. Energy Resour. Technol   doi: 10.1115/1.4037369
The paper present the approach of thermo-economic analysis of centralized cold generation in trigeneration system integrated with steam-powered absorption chillers. The analysis was conducted for real back-pressure combined heat and power (CHP) unit BC-50 and single-effect absorption refrigerators using water and lithium bromide as the working fluids. It has been assumed that the heating medium supplied to the chiller generator is technological steam from the existing steam bleeding. Mathematical simulation models of cogeneration and trigeneration systems have been developed with the commercial program for power plant simulation EBSILON®Professional. System effects of heat and electricity cogeneration and cogeneration with additional cold production have been calculated. The effect of trigeneration has been assessed quantitatively by the coefficient of the increasing the cogeneration effects, which has been calculated as a fraction of ratio of chemical energy savings of fuels to the demand for heat by the consumers in the cases of trigeneration and cogeneration. The paper includes also analysis of economic effectiveness of a trigeneration system with absorption chillers for cold agent production. The results of economic calculations show that an acceptable payback period of approximately thirteen years for a CHP and absorption system may be achieved, which is equal to the half of assumed operating time of the system. The carry out sensitivity analysis shows that the most important impact on profitability is the selling price of cold and the purchase of fuel – hard coal.
TOPICS: Heat, Absorption, Combined heat and power, Economic analysis, Steam, Fuels, Pressure, Fluids, Chemical energy, Simulation, Coal, Power stations, Thermoeconomics, Water, Heating, Generators, Lithium, Profitability, Sensitivity analysis, Simulation models
research-article  
Vishal V Patil and Ranjit S Patil
J. Energy Resour. Technol   doi: 10.1115/1.4037372
Research focused in the present paper to evaluate the combustion, performance, and emission characteristics of refined biodiesel (refined biofuel) such as sunflower oil methyl ester (SOME) with the partial addition of n-butanol (butanol) in it. Various characteristics of butanol-SOME blends with varying volume percentage of butanol such as 5, 10, 15, and 20 in butanol-SOME blends were compared with the characteristics of neat SOME (100%) and neat diesel (100%). It is investigated that with an increase in butanol content from 5% to 20% in butanol-SOME blends at full load condition, brake specific fuel consumption and NOx emissions were increased by 11% and 43% respectively while brake thermal efficiency was decreased by 8%. At full load condition, for all the selected fuels HC emissions were found to be negligible i.e less than 0.12 g/kW-hr.CO emissions at full load condition for the four butanol-SOME blends were observed to be four to six times more than observed CO emissions in case of neat SOME and neat diesel. Various characteristics of all the selected fuels were compared in order to finalize the promising alternate sustainable renewable fuel. Thus study reports the solution for increase in demand and price of shortly diminishing conventional diesel fuel which is widely used for power generation and also to reduce the serious issues concerned with environmental pollution due to usage of neat diesel.
TOPICS: Diesel engines, Ester, Emissions, Diesel, Fuels, Stress, Brakes, Thermal efficiency, Combustion, Biodiesel, Energy generation, Sustainability, Biofuel, Pollution, Nitrogen oxides, Fuel consumption
research-article  
YunFei Yan, Shuai Feng, Li Zhang, Lixian Li, Lei Zhang and Zhongqing Yang
J. Energy Resour. Technol   doi: 10.1115/1.4037373
Catalytic effects of metal oxides on combustion characteristics of inferior coal, sludge and their mixture were investigated by thermogravimetric analysis. Combustion and thermal dynamic characteristics including ignition temperatures, apparent activation energy and frequency factors of inferior coal, sludge and their mixture were observed. The catalytic effects and mechanism of combustion were discussed. Results showed that TG and DTG curves of coal and sludge shifted to lower temperature side, the weight losses increased and the ignition performance was improved with the addition of metal oxides CaO, Al2O3 and K2O. The combustion dynamics analysis showed that the apparent activation energy of co-combustion of coal blending sludge decreased by 11-20% and the frequency factors increased by 20-30%. The minimum apparent activation energy and the maximum frequency factors were obtained in the presence of K2O, indicating that the catalytic effect of K2O was most significant.
TOPICS: Combustion, Coal, Ignition, Temperature, Metals, Weight (Mass), Dynamics (Mechanics), Co-firing
research-article  
Flah Aymen
J. Energy Resour. Technol   doi: 10.1115/1.4037352
Controlling the charging power system in an electrical vehicle, presents a serious challenge for the engineer in order to find the best solution that guarantee the system effectiveness and performance. Related to this objective, this paper is presented to offer an intelligent power management algorithm, which guarantees the best process of power extraction and injection, respectively, from an electrical generator linked to an internal combustion engine to a system of batteries via a direct current to alternative current power converter. This intelligent process was based on the fuzzy technology and the system tuning is made after a various test. Obtaining the necessary power in the exact moment and in the specific condition, that presents the goal of the presented algorithm. For obtaining the best instruction from the present intelligent process, the State of Charge of the Battery, the measured output voltage from the battery and the acceleration decision of the user, are used as a real's input parameters for having a real statue of the electrical vehicle. This new process will be an asset to the highway electrical vehicle for optimizing the power consumption. To evaluate the algorithm performance MATLAB/SIMULINK is used and a simulation results are presented and discussed.
TOPICS: Electric vehicles, Algorithms, Batteries, Internal combustion engines, Power systems (Machinery), Engineers, Energy consumption, Power converters, Generators, Highways, Matlab, Simulation results
research-article  
G. Robello Samuel
J. Energy Resour. Technol   doi: 10.1115/1.4037351
Casing integrity management is crucial, especially in wells experiencing severe casing wall degradation. It is highly desirable to predict the threshold pressure for degraded casing burst and collapse strength and to design the casing strings considering these wear effects. Knowledge of stress distribution in worn casing helps predict where a casing failure occurs first. In industrial practice, a common method is to estimate the reduction of the casing burst strength in worn casing using API burst strength equation with a linear reduction in the remaining wall thickness or wear percentage equivalent to a "uniform-worn" casing model. This study focuses on building a rigorous engineering model for burst strength degradation prediction based on "crescent shape" casing wear. This model calculates the hoop strength directly, including the local bending in the thinner portion of the "crescent-worn" casing. This paper has developed a mathematical model to calculate the hoop strength of worn out casing with force and moment balance equations. This study finds the calculation of reduced strength using the linear wear model to be overly conservative because it only focuses on the stress at the thinnest portion of the worn casing. The stress predicted in this paper is similar to the results obtained from the finite element method (FEM), which validates equations and results obtained from this paper. The developed model is generic and can apply to casings, risers, and tubings.
TOPICS: Wear, Stress, Finite element methods, Risers (Casting), Stress concentration, Design, Collapse, Failure, Pipeline risers, Shapes, Wall thickness, Diluents, American Petroleum Institute, Wells, String, Engineering models, Pressure

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