Frontiers in Energy

ISSN 2095-1701

ISSN 2095-1698(Online)

CN 11-6017/TK

Postal Subscription Code 80-972

2018 Impact Factor: 1.701

   Online First

Administered by

, Volume 6 Issue 1

For Selected: View Abstracts Toggle Thumbnails
FEATURE ARTICLE
Ultrafast solid-liquid-vapor phase change of a thin gold film irradiated by femtosecond laser pulses and pulse trains
Jing HUANG, Yuwen ZHANG, J. K. CHEN, Mo YANG
Front Energ. 2012, 6 (1): 1-11.  
https://doi.org/10.1007/s11708-012-0179-9

Abstract   HTML   PDF (335KB)

Effects of different parameters on the melting, vaporization and resolidification processes of thin gold film irradiated by femtosecond pulses and pulse train were systematically studied. The classical two-temperature model was adopted to depict the non-equilibrium heat transfer in electrons and lattice. The melting and resolidification processes, which was characterized by the solid-liquid interfacial velocity, as well as elevated melting temperature and depressed solidification temperature, was obtained by considering the interfacial energy balance and nucleation dynamics. Vaporization process which leads to ablation was described by tracking the location of liquid-vapor interface with an iterative procedure based on energy balance and gas kinetics law. The parameters in discussion included film thickness, laser fluence, pulse duration, pulse number, repetition rate, pulse train number, etc. Their effects on the maximum lattice temperature, melting depth and ablation depth were discussed based on the simulation results.

References | Related Articles | Metrics
RESEARCH ARTICLE
Economic analysis of a hybrid solar-fuel cell power delivery system using tuned genetic algorithm
Trina SOM, Niladri CHAKRABORTY
Front Energ. 2012, 6 (1): 12-20.  
https://doi.org/10.1007/s11708-012-0172-3

Abstract   HTML   PDF (165KB)

An economic evaluation of a network of distributed energy resources (DERs) comprising a microgrid structure of power delivery system in an Indian scenario has been made. The mathematical analysis is based on the application of tuned genetic algorithm (TGA). The analyses for optimal power operation pertaining to minimum cost have been made for two cases in Indian power delivery system. The first case deals with the consumers’ individual optimal operation of DERs, while in the second one, consumers altogether form a microgrid with the optimal supply of power from DERs. The total annual costs for these two cases are found to be economically competitive and encouraging. A reduction of approximately 5.7% in the annual cost has been obtained in the case of microgid system than that in the separately operating consumers’ system for a small locality of India. It is observed that the application of TGA results in a reduction of the minimum cost depicting an improved outcome in terms of energy economy.

Figures and Tables | References | Related Articles | Metrics
Numerical simulation and analysis of periodically oscillating pressure characteristics of inviscid flow in a rolling pipe
Yan GU, Yonglin JU
Front Energ. 2012, 6 (1): 21-28.  
https://doi.org/10.1007/s11708-012-0173-2

Abstract   HTML   PDF (287KB)

Floating liquefied natural gas (LNG) plants are gaining increasing attention in offshore energy exploitation. The effects of the periodically oscillatory motion on the fluid flow in all processes on the offshore plant are very complicated and require detailed thermodynamic and hydrodynamic analyses. In this paper, numerical simulations are conducted by computational fluid dynamics (CFD) code combined with user defined function (UDF) in order to understand the periodically oscillating pressure characteristics of inviscid flow in the rolling pipe. The computational model of the circular pipe flow is established with the excitated rolling motion, at the excitated frequencies of 1–4 rad/s, and the excitated amplitudes of 3°–15°, respectively. The influences of flow velocities and excitated conditions on pressure characteristics, including mean pressure, frequency and amplitude are systematically investigated. It is found that the pressure fluctuation of the inviscid flow remains almost constant at different flow velocities. The amplitude of the pressure fluctuation increases with the increasing of the excitated amplitude, and decreases with the increasing of the excitated frequency. It is also found that the period of the pressure fluctuation varies with the excitated frequency. Furthermore, theoretical analyses of the flow in the rolling circular pipe are conducted and the results are found in qualitative agreement with the numerical simulations.

References | Related Articles | Metrics
Development of oxide dispersion strengthened ferritic steels with and without aluminum
Jae Hoon LEE
Front Energ. 2012, 6 (1): 29-34.  
https://doi.org/10.1007/s11708-012-0178-x

Abstract   HTML   PDF (318KB)

Pure Fe, Cr, Al, Ti elemental powders and pre-alloyed Y2O3 powder were processed by high energy mechanical milling. The compositions of the mixed powders are designed as Fe-18Cr-0.2Ti-0.35Y2O3 and Fe-18Cr-5Al-0.2Ti-0.35Y2O3 in weight percent. The as-milled powders were consolidated by hot extrusion at 1423 K. The dispersed oxide particles were identified to be titania+ yttria for Al-free oxide dispersion strengthened (ODS) steel and alumina+ yttria for Al-added ODS steel, respectively. The ultimate tensile strength of Al-free ODS steel was higher than that of Al-added ODS steel over the temperature range of 298–973 K, because of the difference in number density and size of thermally stable oxide particles dispersed in both steel matrices. The strength in the longitudinal direction was lower than that in the transverse direction, probably due to anisotropy of the microstructure with elongated grains in the hot-extrusion direction for the 18%Cr-ODS steels with and without 5%Al.

Figures and Tables | References | Related Articles | Metrics
Modeling and control of photovoltaic energy conversion connected to the grid
Rebei NAJET, Ben Ghanem BELGACEM, Hasnaoui OTHMAN
Front Energ. 2012, 6 (1): 35-46.  
https://doi.org/10.1007/s11708-012-0169-y

Abstract   HTML   PDF (475KB)

This paper presents modeling and control of a photovoltaic generator (PVG) connected to the grid. The parameters of the PVG have been identified in previous work (series and parallel resistance, reverse saturation current and thermal voltage) using Newton-Raphston and the gradient algorithm. The electrical energy from a PVG is transferred to the grid via two static converters (DC/DC and DC/AC). The objective of the proposed control strategy is to maximize energy captured from the PVG. The adapted control law for extracting maximum power from the PVG is based on the incremental conductance algorithm. The developed algorithm has the capability of searching the maximum photovoltaic power under variable irradiation and temperature. To control the DC/AC inverter, an intelligent system based on two structures is constructed: a current source control structure and a voltage source control structure. The system has been validated by numerical simulation using data obtained from the PVG installed in the laboratory research (INSAT, Tunisia).

Figures and Tables | References | Related Articles | Metrics
Intelligent algorithm for optimal meter placement and bus voltage estimation in ring main distribution system
L. RAMESH, N. CHAKRABORTY, S. P. CHOWDHURY
Front Energ. 2012, 6 (1): 47-56.  
https://doi.org/10.1007/s11708-011-0159-5

Abstract   HTML   PDF (410KB)

The advancement in power distribution system poses a great challenge to power engineering researchers on how to best monitor and estimate the state of the distribution network. This paper is executed in two stage processes. The first stage is to identify the optimal location for installation of monitoring instrument with minimal investment cost. The second stage is to estimate the bus voltage magnitude, where real time measurement is conducted and measured through identified meter location which is more essential for decision making in distribution supervisory control and data acquisition system (DSCADA). The hybrid intelligent technique is applied to execute the above two algorithms. The algorithms are tested with institute of electrical and electronics engineers (IEEE) and Tamil Nadu electricity board (TNEB) benchmark systems. The simulated results proves that the swarm tuned artificial neural network (ANN) estimator is best suited for accurate estimation of voltage with different noise levels.

Figures and Tables | References | Related Articles | Metrics
Structural modeling of a typical gas turbine system
Naresh YADAV, Irshad Ahmad KHAN, Sandeep GROVER
Front Energ. 2012, 6 (1): 57-79.  
https://doi.org/10.1007/s11708-011-0164-8

Abstract   HTML   PDF (883KB)

This paper presents an approach for the structural modeling and analysis of a typical gas turbine system. This approach has been applied to the systems and subsystems, which are integral parts of a typical gas turbine system. Since a gas turbine system performance is measured in terms of fluid flow energy transformations across its various assemblies and subassemblies, the performance of such subsystems affects the overall performance of the gas turbine system. An attempt has been made to correlate the associativity of such subsystems contributing to overall gas turbine system functional evaluation using graph theoretic approach. The characteristic equations at the system level as well as subsystem level have been developed on the basis of associativity of various factors affecting their performance. A permanent function has been proposed for the functional model of a gas turbine system, which further leads to selection, identification and optimal evaluation of gas turbine systems.

Figures and Tables | References | Related Articles | Metrics
Spray characteristics and controlling mechanism of fuel containing CO2
Zhen HUANG, Jin XIAO, Xinqi QIAO, Gaozhi JIANG, Yiming SHAO, Seiichi SHIGA, Yasuhiro DAISHO
Front Energ. 2012, 6 (1): 80-88.  
https://doi.org/10.1007/s11708-012-0180-3

Abstract   HTML   PDF (667KB)

This paper presents studies of spray characteristics and controlling mechanism of fuel containing CO2. Using diesel fuel containing CO2 gas, experiments were conducted on diesel hole-type nozzles and simple nozzles. The steady spray and transient spray characteristics were observed and measured by instantaneous shadowgraphy, high-speed photography, phase Doppler anemometry (PDA) and LDSA respectively. The effects of CO2 concentration in the fuel, the injection pressure, the nozzle L/D ratio, surrounding gas pressure and temperature on the atomization behavior and spray pattern were evaluated. The results show that the injection of fuel containing CO2 can greatly improve the atomization and produce a parabolic-shaped spray; and the CO2 gas concentration, surrounding gas pressure, temperature and nozzle configuration have dominant influences on spray characteristics of the fuel containing CO2. New insight into the controlling mechanism of atomization of the fuel containing CO2 was provided.

Figures and Tables | References | Related Articles | Metrics
A novel light fluctuation spectrum method for in-line particle sizing
Shouxuan QIN, Xiaoshu CAI, Li MA
Front Energ. 2012, 6 (1): 89-97.  
https://doi.org/10.1007/s11708-012-0176-z

Abstract   HTML   PDF (506KB)

This paper discusses two problems in in-line particle sizing when using light fluctuation method. First, by retrieving the ratio of particle concentrations at different time, the intensity of incident light is obtained. There exists narrow error between the calculated and pre-detected value of the intensity of incident light. Secondly, by combining spectrum analysis with Gregory’s theory, a multi-sub-size zone model is proposed, with which the relationship between the distribution of turbidity and the particle size distribution (PSD) can be established, and an algorithm developed to determine the distribution of turbidity. Experiments conducted in the laboratory indicate that the measured size distribution of pulverized coal conforms well with the imaging result.

Figures and Tables | References | Related Articles | Metrics
Design and operational considerations for selective catalytic reduction technologies at coal-fired boilers
Jeremy J. SCHREIFELS, Shuxiao WANG, Jiming HAO
Front Energ. 2012, 6 (1): 98-105.  
https://doi.org/10.1007/s11708-012-0171-4

Abstract   HTML   PDF (200KB)

By the end of 2010, China had approximately 650 GW of coal-fired electric generating capacity producing almost 75% of the country’s total electricity generation. As a result of the heavy reliance on coal for electricity generation, emissions of air pollutants, such as nitrogen oxides (NOx), are increasing. To address these growing emissions, the Ministry of Environmental Protection (MEP) has introduced new NOx emission control policies to encourage the installation of selective catalytic reduction (SCR) technologies on a large number of coal-fired electric power plants. There is, however, limited experience with SCR in China. It is therefore useful to explore the lessons from the use of SCR technologies in other countries. This paper provides an overview of SCR technology performance at coal-fired electric power plants demonstrating emission removal rates between 65% and 92%. It also reviews the design and operational challenges that, if not addressed, can reduce the reliability, performance, and cost-effectiveness of SCR technologies. These challenges include heterogeneous flue gas conditions, catalyst degradation, ammonia slip, sulfur trioxide (SO3) formation, and fouling and corrosion of plant equipment. As China and the rest of the world work to reduce greenhouse gas emissions, carbon dioxide (CO2) emissions from parasitic load and urea-to-ammonia conversion may also become more important. If these challenges are properly addressed, SCR can reliably and effectively remove up to 90% of NOx emissions at coal-fired power plants.

Figures and Tables | References | Related Articles | Metrics
10 articles