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Accepted Manuscripts

BASIC VIEW  |  EXPANDED VIEW
research-article  
Alireza Sanaei, Yixin Ma and Ahmad Jamili
J. Energy Resour. Technol   doi: 10.1115/1.4040791
Gas and condensate production from nano-pore unconventional resources dramatically increased during the past decade. Transport properties and mechanisms deviate from their bulk behavior when the pore sizes in shale formations are in the order of nano-scale. This is due to the dominant effect of molecule-pore wall interactions comparing to molecule-molecule interactions in nano-pores. Therefore physics of multiphase flow in current commercial simulators should be altered to take into account the effect of pore size on both transport mechanisms and fluid properties. In this paper we analyze the effect of fluid confinement on phase behavior, fluid properties, and condensate banking around the hydraulic fracture where nano-pores perform as the dominate storage region and dispersed with pores with bulk behavior. Confinement effect is considered using modified critical properties in the phase behavior calculations. Using experimental results, an equation for estimating mean pore size is presented as a function of permeability and porosity. Pore size distribution of a shale sample is used to divide the reservoir into different regions. For each region, a specific permeability is assigned using the new developed correlation. Three different types of connectivity are considered between pores and its impact on production mechanisms is analyzed. Results of this study revealed that nano-pore confinement effect on phase behavior results in an increase in production while considering permeability variation with pore size has a negative contribution on hydrocarbon production. Connectivity type between different pore sizes has a significant effect and determines the dominant factor.
TOPICS: Physics, Fluids, Permeability, Reservoirs, Condensed matter, Multiphase flow, Fracture (Materials), Fracture (Process), Modeling, Nanoscale phenomena, Porosity, Storage, Shales
research-article  
Hanzade Haykiri-Acma and Serdar Yaman
J. Energy Resour. Technol   doi: 10.1115/1.4040792
This paper investigates the effectiveness of oxygen-enriched combustion process at low temperatures to avoid the unburnt carbon that remains in ash during conventional burning process. For this, thermal treatment of low quality fuels such as olive pomace and a Turkish lignite (Afsin-Elbistan) under oxygen-enriched conditions was tested in a tube furnace at temperatures between 400-700°C under O2/N2 mixtures containing O2 ratios in the range of 25-50 vol%. The calorific value and the unburnt carbon content of the residues from these tests were used to investigate the combined effects of temperature and O2 concentration on unusable part of fuels. Thermal reactivity of untreated parent samples and the residues obtained from oxygen-enriched combustion was also compared based on DTA (Differential Thermal Analysis) and DTG (Derivative Thermogravimetry) profiles. It was determined that oxygen-enriched conditions are able to remove the organic part of the fuels at low temperatures easily as O2 concentration increases and the oxygen-enriched conditions shifted complete burning temperature to lower values.
TOPICS: Combustion, Fuels, Carbon, Low temperature, Oxygen, Temperature, Thermal analysis, Furnaces, Thermogravimetry, Temperature effects
Technical Brief  
Yousef Haseli and Katherine Hornbostel
J. Energy Resour. Technol   doi: 10.1115/1.4040793
Maximum thermal efficiency is commonly assumed to correspond to minimum entropy generation. However, previous work has disproven this assumption for various power generation systems. In order to reconcile these two optimization approaches, 2nd law analysis is performed here in terms of specific entropy generation (SEG), defined as the total entropy generation per mole of fuel. An inverse relationship between thermal efficiency and SEG is derived here, and it is shown that maximum thermal efficiency always corresponds to minimum SEG for lean fuel/air mixtures. Furthermore, the maximum efficiency limit of conventional power plants is shown to differ from the Carnot efficiency. Finally, a modified second law efficiency is introduced, and it is shown that the exhaust combustion products are bounded by a theoretical minimum temperature.
TOPICS: Entropy, Combustion systems, Thermal efficiency, Fuels, Temperature, Combustion, Energy / power systems, Optimization, Power stations, Exhaust systems
research-article  
Xiaofei Sun, Yanyu Zhang, Jie Wu, Mengke Xie and Hang Hu
J. Energy Resour. Technol   doi: 10.1115/1.4040751
With the worldwide decline of conventional oil production, tremendous unconventional resources, such as low-permeability reservoirs, are becoming increasingly important. Cyclic water injection (CWI) as an oil recovery method has attracted increasing attention in the present environment of low oil prices. However, the optimal CWI strategy is dif?cult to determine for a mature oilfield due to the involvement of multiple wells with multiple operational parameters. Thus, our main focus in this paper is to present a novel and systematic approach to optimize CWI strategies by studying a typical low-permeability reservoir G21. To this end, a comprehensive method that combines the advantages of streamline simulation and fuzzy comprehensive evaluation was proposed to identify water channeling in the reservoir. Second, the reliability of the method was verified using tracer tests. Finally, a new hybrid optimization algorithm, the simulated annealing genetic algorithm (SAGA), coupled with a reservoir simulator was developed to determine an optimal CWI strategy for the low-permeability reservoir. The results show that the CWI technique is viable as a primary means in the present environment of low oil prices to improve waterflooding performance in low-permeability reservoirs. The oil recovery of the most efficient strategy increases by 6.81% compared to conventional waterflooding. The asymmetric CWI scheme is more efficient than the symmetric CWI scheme for the low-permeability reservoir.
research-article  
Qi Gao, Yuanfang Cheng, Chuanliang Yan, Long Jiang and Songcai Han
J. Energy Resour. Technol   doi: 10.1115/1.4040753
With the production of oil and gas from the reservoir for a long period of time, pore pressure will decline from the initial value to a lower level, which narrows the safety mud weight window and consequently makes it easier to generate the drilling induced fracture (DIF). In this paper, a new analytical model is proposed for predicting initiation pressure and corresponding initiation mode of DIF in the pressure depleted reservoir. The effect of pore pressure decline on stress field is considered. Formation around the borehole is divided into plastic zone and elastic zone according to the geomechanical parameters, and small deformation theory is adopted in both of the plastic zone and elastic zone. For plastic zone, the non-linear constitutive relationship is captured using equivalent stress and equivalent strain. In addition, excess pore pressure theory is introduced to describe the pore pressure change during the drilling process owing to the formation of mudcake on the borehole wall. Then, the stress and pore pressure distribution in these two zones and the radius of the plastic zone are obtained. Meanwhile, the theoretical formula of initiation pressure and the corresponding initiation mode of DIF are derived. The reliability of the new model is validated by comparing the obtained results with other published models and the field measured data.
research-article  
Hongwei Chen, Qihong Feng, Xianmin Zhang, Sen Wang, Wensheng Zhou and Fan Liu
J. Energy Resour. Technol   doi: 10.1115/1.4040754
Proper well placement can improve the oil recovery and economic benefits during oilfield development. Due to the nonlinear and complex properties of well placement optimization, an effective optimization algorithm is required. In this paper, cat swarm optimization (CSO) algorithm is applied to optimize well placement for maximum net present value (NPV). CSO algorithm, a heuristic algorithm that mimics the behavior of a swarm of cats, has characteristics of flexibility, fast convergence, and high robustness. Oilfield development constraints are taken into account during well placement optimization process. Rejection method, repair method, static penalization method, dynamic penalization method and adapt penalization method are respectively applied to handle well placement constraints and then the optimal constraint handling method is obtained. Besides, we compare the CSO algorithm optimization performance with genetic algorithm (GA) and differential evolution (DE) algorithm. With the selected constraint handling method, CSO, GA, and DE algorithms are applied to solve well placement optimization problem for a 2D conceptual model and a 3D semi-synthetic reservoir. Results demonstrate that CSO algorithm outperforms GA and DE algorithm. The proposed CSO algorithm can effectively solve the constrained well placement optimization problem with adapt penalization method.
research-article  
Jianguo Wang, Daihong Gu, Wei Guo, Haijie Zhang and Daoyong Yang
J. Energy Resour. Technol   doi: 10.1115/1.4040755
By correcting both the positive and negative ?logR separation resulting from the resistivity in organic-deficient shales, the traditional ?logR correlation is modified, validated, and applied to determine the total organic carbon (TOC) content in shale formations. The TOC content is determined once the Fisher distribution, which represents the significance of each model, and Student's t-distribution, which denotes the significance of every variable in the models, have achieved values equal to or higher than their respective threshold values at a confidence level of 95%. Using a total of 45 sets of logging measurements, the newly proposed correlation is found to be able to reproduce the measured TOC values with a root mean-squared absolute difference (RMSAD) of 0.30 wt% and root mean-squared relative difference (RMSRD) of 23.8%, respectively. Uranium concentration other than interval transit time and resistivity is found to be the key for determining the TOC content in organic-richness shale without other radioactive minerals. By combining the DGR reading, the traditional ?logR technique has now been improved and extended for the negative ?logR separation resulting from the resistivity in organic-deficient shale higher than that in organic-rich shale.
research-article  
Chetankumar Patel, Joonsik Hwang, Krishn Chandra, Rashmi A. Agarwal, Choongsik Bae, Tarun Gupta and Dr. Avinash Kumar Agarwal
J. Energy Resour. Technol   doi: 10.1115/1.4040579
In this experimental study, spray and combustion characterization inside the single cylinder optical engine were done by varying fuel injection pressures (40, 80 and 120 MPa). Karanja, Jatropha and Waste cooking oil biodiesels were utilized as test fuels and results were compared with conventional diesel. There was no significant difference observed in spray tip penetration amongst the test fuels. However, spray angle were found to be slightly wider for biodiesels. Mineral diesel showed relatively shorter injection delay than biodiesels at fuel injection pressure of 40 and 80 MPa. Jatropha and Karanja biodiesels showed higher flame luminosity at all fuel injection pressures, while waste cooking oil biodiesel showed lower flame luminosity, especially at higher fuel injection pressure of 80 and 120 MPa due to comparatively lower fuel viscosity amongst biodiesels. Flame spatial fluctuation (FSF) and flame non-homogeneity (FNH) were higher for biodiesels at lower fuel injection pressure of 40 MPa. Karanja and Jatropha biodiesels also showed higher FSF and FNH at higher injection pressures, while Waste cooking oil biodiesel showed lower FSF and FNH at higher fuel injection pressures.
TOPICS: Engines, Sprays, Cylinders, Combustion, Fuels, Flames, Pressure, Diesel, Biodiesel, Minerals, Viscosity, Delays
research-article  
Nikhil Sharma, Rashmi A. Agarwal and Dr. Avinash Kumar Agarwal
J. Energy Resour. Technol   doi: 10.1115/1.4040580
Direct injection spark ignition (DISI) or gasoline direct injection (GDI) engines are superior in terms of relatively higher thermal efficiency and power output compared to multipoint port fuel injection (MPFI) engines and direct injection (DI) diesel engines. In this study, a 500 cc single cylinder GDI engine was operated. Three gasohol blends (15% (v/v) ethanol/ methanol/ butanol with 85% (v/v) gasoline) were chosen for this experimental study and were characterized to determine important fuel properties. For particulate investigations, exhaust particles were collected on a quartz filter paper using a partial flow dilution tunnel. Comparative investigations for particle mass emissions, trace metal concentrations, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) analyses and High-resolution transmission electron microscopy (HR-TEM) imaging of the particulate samples collected for all test fuels and different engine loads were performed. For majority of the cases, gasohols showed relatively lower trace metal concentration in particulates compared to gasoline. HR-TEM images showed that higher engine loads and presence of oxygen in the test fuels increased soot reactivity. Multi-core shells like structures were visible in the HR-TEM images due to growth in nuclei, and rapid soot formation due to relatively higher temperature and pressure environment in the engine combustion chamber. Attention is being given by researchers to reduce particle emissions from GDI engine; however there is a vast research gap for such investigations related to gasohol fuelled GDI engines. This paper critically assesses and highlights morphological characteristics of gasohol fuelled GDI engine.
TOPICS: Metals, Particulate matter, Soot, Gasohol, Direct injection spark ignition engines, Engines, Fuels, Gasoline, Emissions, Stress, Fourier transform infrared spectroscopy, Resolution (Optics), Combustion chambers, Cylinders, Diesel engines, Ethanol, Exhaust systems, Filters, Ignition, Oxygen, Quartz, Shells, Pressure, Flow (Dynamics), Temperature, Transmission electron microscopy, Tunnels, Imaging, Methanol, Raman spectroscopy, Thermal efficiency
research-article  
Ladislav Veselý, K.R.V. Manikantachari, Subith Vasu, Jayanta Kapat, Vaclav Dostal and Scott Martin
J. Energy Resour. Technol   doi: 10.1115/1.4040581
The development of new power generation technologies is gaining increased attention. The supercritical carbon dioxide (S-CO2) cycle is one such technology, which has relatively high efficiency, compactness, and potentially could provide complete carbon capture. The S-CO2 cycle technology is adaptable for almost all of the existing heat sources such as solar, geothermal, fossil, nuclear power plants, and waste heat recovery systems. However, it is known that, optimal combinations of: operating conditions, equipment, working fuid, and cycle layout determine the maximum achievable efficiency of a cycle. Within an S-CO2 cycle the compression device is of critical importance as it is operating near the critical point of CO2. However, near the critical point, the thermo-physical properties of CO2 are highly sensitive to changes of pressure and temperature. Therefore, the conditions of CO2 at the compressor inlet are critical in the design of such cycles. Also, the impurity species diluted within the S-CO2 will cause deviation from an ideal S-CO2 cycle as these impurities will change the thermodynamic properties of the working fluid. Accordingly the current work examines the effects of different impurity compositions, considering binary mixtures of CO2 and: He, CO, O2, N2, H2, CH4, or H2S; on various S-CO2 cycle components. The second part of the study focuses on the calculation of the basic cycles and component efficiencies. The results of this study will provide guidance and defines the optimal composition of mixtures for compressors and coolers.
TOPICS: Compressors, Cycles, Supercritical carbon dioxide, Carbon dioxide, Compression, Methane, Nuclear power stations, Carbon capture and storage, Coolers, Heat recovery, Geothermal engineering, Design, Energy generation, Solar energy, Pressure, Heat, Temperature, Fluids
Review Article  
Dr. Avinash Kumar Agarwal, Sungwook Park, Atul Dhar, Chang Sik Lee, Suhan Park, Tarun Gupta and Neeraj Gupta
J. Energy Resour. Technol   doi: 10.1115/1.4040584
Biodiesel has emerged as a suitable alternative to mineral diesel in compression-ignition (CI) engines, in order to ensure global energy security and to reduce engine out emissions in near future. Biodiesel derived from various feedstocks available worldwide fits well in the current fuel supply arrangement for transport sector. However, biodiesel as an alternative transportation fuel has been extensively investigated because of differences in its important fuel properties compared with baseline mineral diesel. Since fuel properties greatly influence spray development, combustion and emission formation in IC engines, a number of experimental and computational studies on biodiesel usage in CI engines have been performed to determine its brake thermal efficiency (BTE), gaseous emissions, durability, etc., by various researchers using variety of engines and feedstocks. In present study, a critical review of the effect of biodiesel's fuel properties on engine performance, emissions and combustion characteristics in existing diesel engines vis-a-vis conventional diesel has been undertaken. In addition, the progress and advances of numerical modeling involving biodiesel is also reviewed to determine effect of fuel properties on spray evolution and development of reaction mechanisms for combustion simulation. Fuel properties are discussed in two categories: physical, and chemical properties, which are key parameters affecting spray and combustion processes. Subsequent sections review spray, combustion, emissions and performance characteristics of biodiesels under various engine operation conditions.
TOPICS: Engines, Combustion, Sprays, Emissions, Biodiesel, Fuels, Diesel, Diesel engines, Minerals, Feedstock, Simulation, Chemical properties, Durability, Internal combustion engines, Computer simulation, Transportation systems, Compression, Thermal efficiency, Brakes, Security, Ignition, Performance characterization
research-article  
Alexander Studniorz, Daniel Wolf, Andreas Christidis and George Tsatsaronis
J. Energy Resour. Technol   doi: 10.1115/1.4040527
The global demand for wireless, mobile communication and data services has grown significantly in the recent years. Consequently, electrical energy consumption to provide these services has increased. The principal contributors to this electricity demand are approximately 7 million telecommunication base stations (TBS) worldwide. They act as access points for mobile networks and have typical electrical loads of 2 3 kW. Whereas for most of the TBS the electricity is supplied by the grid, approximately 15 % are located in remote areas or regions with poor grid accessibility, where diesel generators (DG) supply the required electricity. Based on a dynamic simulation model built in Matlab/Simulink, the application of a latent heat storage (LHS) using phase change material (PCM) in existing off grid TBS has been analysed. The LHS unit has been modelled as an air based storage with phase change temperatures between 20 30 °C with the PCM being macro encapsulated in slabs. This paper demonstrates the potential to reduce the primary energy consumption in off grid TBS through the following methods: optimization of the operating point of the diesel generators and of the air conditioning unit operation schedule as well as utilization of photovoltaic energy.
TOPICS: Storage, Telecommunications, Diesel generators, Energy consumption, Latent heat, Matlab, Simulation models, Temperature, Air conditioning, Slabs, Stress, Phase change materials, Optimization
research-article  
Primoz Poredos, Boris Vidrih, Andrej Kitanovski and Alojz Poredos
J. Energy Resour. Technol   doi: 10.1115/1.4040102
This paper presents the results of a thermo-economic, primary-energy-factor and CO2-equivalent (CO2 (eq)), emissions-sensitivity analysis for the preparation of sanitary hot water (SHW) in 4th-generation district-heating systems. The annual required additional heat for the SHW provided by a local heating unit, based on an air-to-water heat pump, a natural-gas boiler and an electrical resistance heater, was determined using a TRNSYS simulation. Additionally, the seasonal performance factor of the heat pump under consideration was determined. The study considered three possible supply temperatures, i.e., 35, 40 and 45 °C. The results show that a local heating unit based on an air-to-water heat pump is the most efficient in terms of the consumed primary energy and CO2 (eq) emissions. This unit is also the second best in terms of thermo-economic performance. The unit based on a natural-gas boiler is much more appropriate than an electrical resistance heater unit in terms of both the primary energy factor and the CO2 (eq) emission factors for an electricity generation mix that has values higher than the average for the EU-28. The heat generated by this natural-gas unit is also cheaper than the heat produced by an electrical resistance heater based on the average price for electricity in the EU-28.
TOPICS: Central heating, Thermoeconomics, Water, Heating, Emissions, Carbon dioxide, Heat pumps, Electrical resistance, Heat, Natural gas, Boilers, Temperature, Simulation, Hot water, Electric power generation
research-article  
John Dooher, Marco Castaldi and Dean Modroukas
J. Energy Resour. Technol   doi: 10.1115/1.4040526
The program involves the application of a compact and modular gasification concept, termed a tunable catalytic gasifier (TCG) to produce syngas from coal, biomass, and waste slurries. The TCG employs a pressurized entrained flow reactor wherein the external wall surfaces are catalytically heated using a portion of the produced syngas. In addition, slurry is introduced into the reactor via a twin fluid atomizer to more efficiently promote syngas yields. The TCG is ideally suited for producing energy from coal, biomass and MSW because it uses an external catalytic combustion chamber to drive the steam-driven gasification reactions at 1000 C, providing for a variety of gasification feedstocks and low contamination in the exit gases. The TCG can be fed by a hydrothermal treatment reactor (HTR) for biomass and waste feedstocks, which employs well-developed hydrothermal processing technology using the addition of heat and water to provide a uniform slurry product. A clean syngas is produced at high cold gas efficiency (80%) and the fuel gas is cleaner than that produced in current technologies. The TCG can operate over a wide range of positive pressures (up to 30 bars) that provides process control to vary the output (tunable) to match end-use needs or feedstock rate. The system produces minimal emissions and operates at significantly higher efficiency and lower energy requirements than pyrolysis, plasma gasification, and carbonization systems. Test results and model simulations are presented on a single tube system and analyses of a variety of configurations presented.
TOPICS: Biomass, Coal, Syngas, Fuel gasification, Slurries, Feedstock, Simulation, Municipal solid wastes, Plasmas (Ionized gases), Combustion chambers, Contamination, Flow (Dynamics), Heat, Fluids, Gases, Gaseous fuels, Process control, Engineering simulation, Pyrolysis, Steam, Water, Emissions
research-article  
Miangzhang Pan, Haiqiao Wei and Dengquan Feng
J. Energy Resour. Technol   doi: 10.1115/1.4040528
Exhaust gas recirculation (EGR) gained prominence as a significant method to control port fuel injection (PFI) engine knock caused by high compression ratio and high intake pressure. In this paper, the effect of EGR on knock intensity were investigated under various conditions which included different compression ratios (9:1; 10:1; 11:1), intake pressures (1.0bar; 1.2bar; 1.4bar) and intake temperatures (20°C; 40°C; 60°C). The torque output being a crucial variant was also considered. The results showed that EGR effectively reduced the maximum amplitude of pressure oscillations (MAPO) and knock intensity factor (KI20). More significant knock resistance benefited from EGR was observed under higher compression ratio, intake pressure and intake temperature. The output torque of the engine reached a peak value with a suitable EGR ratio which also controlled the intensity of knock under different conditions.
TOPICS: Spark-ignition engine, Exhaust gas recirculation, Gasoline, Compression, Pressure, Temperature, Torque, Engines, Oscillations, Fuels
research-article  
Mohsen Emami, Hamidreza Shahbazian and Bengt Sunden
J. Energy Resour. Technol   doi: 10.1115/1.4040532
Combustion of CH4 in an industrial gas turbine combustor and NO and CO formation/emission are simulated. The objectives are to investigate influence of combustive parameters and varying the percentage of distributed air flow rate in burning, recirculation and dilution zones on reactive flow characteristics, NOx and CO emissions. The governing equations of mass, momentum, energy, turbulence quantities RNG (k-e), mixture fraction are solved by the finite volume method. The formation and emission of NOx is simulated in a post-processing fashion, as the pollutant concentration is low compared to the main combustion species. Focus is on different physical mechanisms of NOx formation. The thermal-NOx and prompt-NOx mechanisms are considered for modelling the NOx source term in the transport equation. Results show that in a gas-fuelled combustor, the thermal NOx is the dominating mechanism for NOx formation. The simulations provids insight into the correlation between the maximum combustor temperature, exhaust average temperatures and the thermal NO concentration. The exhaust temperature and NOx concentration decrease while the excess air factor increases. As the combustion air temperature increases, the combustor temperature increases and the thermal NOx concentration increases dramatically. Furthermore, results demonstrate that the NO concentration at the combustor exit is maximum for a swirl angle of 55° and a gradual rise in the NOx concentration is detected as the combustion fuel temperature increases. In addition, results demonstrate that the air distribution at laboratory conditions is optimal while the mass fractions of NO and CO are minimum.
TOPICS: Combustion, Industrial gases, Combustion chambers, Air flow, Turbines, Nitrogen oxides, Emissions, Temperature, Exhaust systems, Finite volume methods, Methane, Pollution, Chemically reactive flow, Simulation, Engineering simulation, Modeling, Fuels, Turbulence, Kinetic energy
research-article  
Jiazheng Qin, Shiqing Cheng, Youwei He, Yang Wang, Dong Feng, Zhonglin Yang, Dingyi Li and Haiyang Yu
J. Energy Resour. Technol   doi: 10.1115/1.4040533
Nowadays, estimation of rate performance of multi-fractured horizontal well (MFHW) has attracted great attention. This paper presents a mathematical model of MFHW with considering segmented fracture (SF) for better evaluation of fracture and reservoir properties. Each SF consists of two parts: fracture segment with high conductivity (FSHC) and fracture segment with low conductivity (FSLC) in segmented fracture model (SFM). Employing the Source function and Green's function, Newman's product method, Duhamel principle, Stehfest inversion algorithm and Laplace transform, production solution of MFHW can be obtained using SFM. Since total production rate is mostly contributed from FSHC rather than FSLC, ignoring this phenomenon may lead to obvious erroneous in parameter interpretation. Thus, clear distinctions can be found between CFM (previous model) and SFM on compound type curves. By using decline curve analysis (DCA), the influences of sensitive parameters (e.g. dimensionless half-length, dimensionless production rate, conductivity and distance between SF) on compound type curves are analyzed. The results of sensitivity analysis explore the possibility of parameter estimation during history matching.
TOPICS: Wells, Fracture (Materials), Fracture (Process), Thermal conductivity, Atomic force microscopy, Electrical conductivity, Reservoirs, Algorithms, Laplace transforms, Parameter estimation, Sensitivity analysis
research-article  
Dave Osborne and Dan Eyre
J. Energy Resour. Technol   doi: 10.1115/1.4040379
Integration of a supply chain involves the design, planning, execution, control and monitoring of delivery chain activities for creating net value. This includes, building appropriate infrastructure, leveraging logistics, synchronizing supply with demand and continually measuring/monitoring performance. The combination of advanced mining and beneficiation technologies and power plant improvement processes when integrated within a "whole-of-supply chain" promises great potential for creating step-changes in the way that coal is delivered to its end user. When the supply chain involves a direct mine-to-power plant, the benefits may initially seem limited, but the adoption of a value-in-use model to determine costs incurred along the chain can show how changes in mining, beneficiation and supply impact on power plant performance and, ultimately, total-supply chain costs. Uniper Technologies' proprietary Fuel Evaluation Tool as described in the paper is an expert value-in-use model, which combined with coal beneficiation modelling and expertise from Somerset International can show the potential improvements achievable by adopting a "whole-of-supply-chain" approach.
TOPICS: Chain, Coal, Power stations, Ore dressing, Supply chains, Mining, Fuels, Logistics, Design, Modeling
research-article  
Haojie Li, Yangrong Chen, YunFei Yan, Cheng Hu, Hu Fan and Shuai Feng
J. Energy Resour. Technol   doi: 10.1115/1.4040191
In consideration of high heat transfer efficiency and stable combustion, a new type of micro planar combustor for micro-TPV (micro-thermophotovoltaic) system is proposed, in which the heat transfer is enhanced by staggered cylindrical array. The numerical study results indicate that the temperature of radiation wall of cylindrical-array combustor is higher and more uniform comparing with the conventional-channel combustor, the application of cylindrical-array make the effective radiation of the combustor increase 34.55% and reach to 35.98w. Moreover, with inlet velocity increase from 4m/s to 16m/s, the cylindrical-array combustor shows the better stability of combustion, which the position of the flame moves 4.8mm in the cylindrical-array combustor and 9.1mm in the conventional-channel combustor. However, the 0.5-4.5 equivalence ratio range for stable combustion is slightly narrower than 0.4-6.0 in the conventional-channel combustor. To extend the equivalence ratio range, one row of cylindrical array was cancelled and the distribution length of cylindrical array was reduced to 10mm, After this improvement, the equivalence ratio range is extended to 0.3-5.5, the negative effect on the flame stability of the cylindrical array is basically eliminated.
TOPICS: Heat transfer, Combustion chambers, Combustion, Radiation (Physics), Stability, Flames, Temperature
research-article  
Esmaeel Khanmirza, Reza Madoliat and Ali Pourfard
J. Energy Resour. Technol   doi: 10.1115/1.4040073
Compressor stations in natural gas networks should perform such that time-varying demands of customers are fulfilled while all of the system constraints are satisfied. Power consumption of compressor stations impose the most operational cost to a gas network so their optimal performance will lead to significant money saving. In this paper, the gas network transient optimization problem is addressed. The objective function is the sum of the compressor's power consumption that should be minimized where compressor speeds and the value status are decision variables . This objective function is nonlinear which is subjected to nonlinear and combinatorial constraints including both discrete and continuous variables. To handle this challenging optimization problem a novel approach based on using two different structure intelligent algorithms, namely the particle swarm optimization (PSO) and cultural algorithm (CA) are utilized to find the optimum of the decision variables. This approach removes the necessity of finding an explicit expression for the power consumption of compressors as a function of decision variables as well as calculation of objective function derivatives . The objective function and constraints are evaluated in the transient condition by a fully implicit finite difference numerical method. The proposed approach is applied on a real gas network where simulation results confirm its accuracy and efficiency.
TOPICS: Transients (Dynamics), Algorithms, Natural gas, Optimization, Compressors, Energy consumption, Particle swarm optimization, Simulation results, Numerical analysis

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