bluuebunny/crossref_metadata_2025 huggingface dataset:
High Rate Interactive Energy System Through the Use of PV and EV
Authors: Mitsumoto Yuta , Kose Norihiro , Nakagawa Tsuguhiko
Published: February 2014

After the Great East Japan Earthquake disaster, it was necessary to build a new energy system that would enable us to be less dependent on nuclear power, as well as reduce carbon dioxide emissions. To accomplish this, it is necessary to consider a new method of energy supply and consumption combined with the promotion of energy conservation and the increased use of natural energy. One example, called “Smart Community”, has attracted attention. It optimizes a balance between energy supply and demand, and utilizing energy efficiently. The “Smart Community” is envisioned as different from the conventional one-way power system currently supplied by electric and fuel companies.

In this study, the authors investigate a way to efficiently use photovoltaic (PV) power in an interactive energy system. In the system, PV power is used in homes and factories as an energy source, and in electric vehicles (EV) for transportation and energy storage. The system is a two-way system, and it is important for users to determine which supply and demand method they want. For example, if you choose to include PV power in your electrical power system, there will be the problem of increased DC-AC conversion energy loss. This is due to the re-conversion of AC-DC after DC-AC conversion. In addition, the cost will increase.

In order to solve this problem, the authors propose an efficient installation location and space for PV, and an optimized battery capacity for EV with energy consumption. The authors also propose a way to cut down the DC-AC conversion loss. As a result, the system achieved a 30% reduction in carbon dioxide emissions in homes, and reduced costs. In addition, with the increased use of PV, the system also equalized electric-load. The authors also found that the new system improved PV power rate to 90%.
Improvement of Vibration Characteristics on Stator End Winding of 600MW Generator
Authors: Liu Shi , Guo Yongxiong , Li Zhi , Liu Lei , Gao Qingshui , Feng Yongxin , Zhang Chu , Yang Tao
Published: February 2014

The stator ground protection faults occurred twice in a 600MW generator. After extraction of rotor, it was found that the connection part of the stator bar with lead wire had been blown, and two fixed bolts fitting the lead wire have completely loosened. For analysis of ground-fault reasons, the generator stator end vibration analysis system was installed for on-line vibration monitoring of both sides end winding. The test results shown that the vibration of stator end winding exceeded the standard, and the main frequency component was the rotational frequency. The over-speed test and modal analysis determine that the resonance frequency of stator end wire was close to 50Hz. By increasing the stator cooling water temperature and adding sandbags, the resonance frequency of stator end wire avoid the generator operating frequency, and the end vibration was reduced to a safe level.
Numerical Simulation of Turbulent Combustion Flows for Coaxial Jet Cluster Burner
Authors: Yunoki Keita , Murota Tomoya , Miura Keisuke , Okazaki Teruyuki
Published: February 2014

We have developed a burner for the gas turbine combustor, which was high efficiency and low environmental load. This burner is named the “coaxial jet cluster burner” and, as the name indicates, it has multiple fuel nozzles and holes in a coaxial arrangement. To form lean premixed combustion, this burner mixes fuel and air in the multiple holes rapidly. The burner can change the combustion form between premixed and non-premixed combustion by controlling the mixing. However, the combustion field coexisting with premixed and non-premixed combustion is complicated. The phenomena that occur in the combustion field should be understood in detail.

Therefore, we have developed the hybrid turbulent combustion (HTC) model to calculate the form in which non-premixed flame coexists with premixed flame. Turbulent flow has been simulated using a large eddy simulation (LES) with a dynamic sub grid scale (SGS) model coupled with the HTC model. These models were programmed to a simulation tool based on the OpenFOAM library. However, there were unclear points about their applicability to an actual machine evaluation and the predictive precision of CO concentration which affects burner performance. In this study, we validate the HTC model by comparing its results with measured gas temperature and gas concentration distributions obtained with a coaxial jet cluster burner test rig under atmospheric pressure. In addition, we analyze the CO generation mechanism for the lean premixed combustion in the burner.
Analysis of High-Speed Electrical Generators for Utility Applications
Authors: Petrov Miroslav P.
Published: February 2014

High-speed alternators are believed to be well developed nowadays, following the improvement in performance and decrease of costs for electronic power converters and permanent magnet materials. Their compact design and their ability to vary the rotational speed in off-design conditions promise superior performance when compared to conventional generators. High-speed alternators are only available in limited sizes for small-scale applications, whereas improvements in efficiency and optimized part-load behavior are particularly important especially for small-scale electricity generation.

Enhanced energy utilization for electricity production by small utility plants or by distributed units located at private homes or commercial buildings, based on thermodynamic cycles powered by natural gas or various renewable energy sources, is possible to be achieved through a wider application of grid-integrated high-speed technology. This study presents a critical review of previous research and demonstration work on high-speed electrical machines and a summary of the technical challenges limiting their performance and their expansion into larger sizes. Conclusions are drawn for finding appropriate solutions for practical high-speed electricity generation units and their readiness for a much wider deployment.

Closer analysis is attempted on the thermal and mechanical integrity of high-speed alternators and the technical challenges that slow down their scale-up to MW-size units for utility applications. The necessary research and development work that needs to be done in the near future is outlined and discussed herein.
Optimal Upgrade of a District Heating Plant Into a Polygeneration Plant Using Biomass as Feedstock
Authors: Salomón Marianne , Gómez María F. , Martin Andrew R.
Published: February 2014

This paper aims at evaluating the possible upgrading of an existing district heating plant for production of electricity and pellets. The evaluation is carried out by optimizing the alternatives from the economic, thermodynamic and environmental point of view. In order to examine how the design can be optimized, a detailed model of the process has been elaborated using ASPEN Utilities and Matlab optimization toolbox. The parameters of the polygeneration plant have then been varied in order to examine how optimal economic benefit can be extracted from the biomass streams whilst still meeting the fundamental process demands of the industries and heat demand of the community. A multi-objective optimization has been used to investigate the Pareto-optimal trade-offs that exist between low electricity costs and investment cost. The resulting polygeneration plant designs conclude that it is feasible to produce 18 and 25 MW of power while at the same time supplying the process steam required by the nearby industries and district heating for the community. The results also shown that it is feasible to operate the plant more hours per year by producing pellets and it could be possible to generate additional district heating (up to 25 ton/h of hot water) to cover the demands of a growing community.
Lifecycle Water Consumption of Geothermal Power Systems
Authors: Clark Corrie , Harto Christopher
Published: February 2014

Previous assessments of the sustainability of geothermal energy have focused on resource management and associated environmental impacts during plant operations. Within these constraints, studies have shown that overall emissions, water consumption, and land use for geothermal electricity production have a smaller impact than traditional base-load electricity generation technologies. According to the Energy Information Administration (EIA) of the U.S. Department of Energy (DOE), geothermal energy generation in the United States is projected to increase nearly threefold, from 2.37 GW to 6.30 GW, by 2035 (EIA 2012). With this potential for significant growth in geothermal electricity production, there is a need to improve understanding of the environmental impacts across the life cycle of geothermal energy production systems.

This paper assesses the use of freshwater in construction, drilling, and production activities of various geothermal power plants. Four geothermal technologies were evaluated: air-cooled enhanced geothermal systems (EGSs), air-cooled hydrothermal binary systems, evaporative-cooled hydrothermal flash systems, and air-cooled geopressured systems that coproduce natural gas. The impacts associated with these power plant scenarios are compared to those from other electricity generating technologies as part of a larger effort to compare the lifecycle impacts of geothermal electricity generation to other power generation technologies.
Wind Energy Assessment Using a Wind Turbine With Dynamic Yaw Control
Authors: Pervez Md Nahid , Sözen Mehmet
Published: February 2014

In conducting the siting analysis of a possible on-shore or off-shore wind farm, computational tools are required to analyze the extensive wind data collected over long periods of time in order to estimate the energy that can be harnessed at that particular location. The major parameters that play a crucial role in this are the wind speed, wind direction, and presence of turbulence in the upcoming wind. However, estimation of the potential for electrical energy generation from wind at a particular site is quite complex and prone to error due to the uncertain nature of the wind. The yaw error, which is the difference between the direction of wind and the normal to the face of the rotor, can reduce the power output of a wind turbine significantly. Zero inertia assumption for the turbine rotor used by multiple assessment tools result in overestimation of the power output. For an accurate estimation of the energy that can be harnessed, the effect of directional change of the wind should be incorporated along with the other obvious parameters such as the wind speed, the effect of landscape and altitude. Most modern utility-scale wind turbines are equipped with yaw motion controller and direction measuring sensors that help change the yaw angle of the wind turbine to adjust for the wind direction. A dynamic control model and the corresponding scheme have to be incorporated in the energy estimation process. A wind energy assessment analysis for a potential off-shore wind farm in Lake Michigan is currently under way. An unmanned marine buoy, equipped with LIDAR-based data acquisition system, is deployed in Lake Michigan and data are measured at six different altitudes starting from 55 m and up to 175 m. As project participants, the authors have been working on developing a versatile, flexible and precise model and software tool to evaluate the potential for electrical energy generation. A MATLAB based program has been developed for this purpose, equipped with the capability of working with different data formats and different time averaged data sets. A dynamic model capable of considering the change in wind direction and adjusting the yaw angle has been developed as a part of the MATLAB program. The dynamic model evaluates the yaw error and implements a scheme for the adjustment of the orientation of the wind turbine in order to provide an accurate estimate of the amount of wind energy that can be converted into electrical energy. The algorithm for this dynamic model and the results obtained are discussed in this paper.
A Phenomenological Analysis of Exergy Destruction During Hydrogen Combustion With Electronically Excited Oxygen
Authors: Washington DeVon A. , Shapiro Howard N.
Published: February 2014

This study investigates the effects of introducing electronically excited oxygen on trends in exergy destruction during hydrogen combustion. Electronically excited oxygen enhances many properties of combustion. By understanding how it alters the chemical kinetics, and hence the destruction of exergy, it may be possible to improve the overall exergetic efficiency of combustion thereby reducing fuel use to achieve desired energy conversion.

A numerical model was developed of an adiabatic plug flow reactor using CHEMKIN-PRO; in conjunction with a hydrogen oxidation mechanism that includes explicit reaction pathways for various electronically excited species. Exergy destruction was calculated for cases where singlet oxygen composed 0%–100% of the oxidizer while maintaining a stoichiometric oxidizer-fuel ratio; all other inlet conditions were held fixed.

Results show that an optimal range of exergetic combustion efficiency exists between 0%–20%, with the maximum occurring at approximately 10%. A detailed assessment of the total exergy destruction reveals that, for the optimal range of exergetic combustion efficiencies, as much as 60% of the total exergy destruction occurs prior to ignition. For inlet percentages of singlet oxygen greater than 20%, the majority of the total exergy destruction occurs after ignition. This paper examines the phenomenological events taking place in the reaction mechanism that give rise to the destruction of exergy during combustion. Understanding these mechanisms and the effects of introducing excited oxygen into the combustion process, sheds light on how we might use excited oxygen to increase the exergetic efficiency of combustion.
Kinetic Effects of Non-Equilibrium Plasma-Assisted Methane Steam Reforming on Heat Recovery in Chemically Recuperated Gas Turbine
Authors: Liu Qian , Zheng Hongtao , Pan Fumin , Pan Gang , Yang Ren
Published: February 2014

Plasma is proposed as a prospective tool for chemical heat recovery process without restriction from reaction temperature. The author designed DBD catalytic reactors and carried out extensive experiments to investigate methane conversion and products yield and analyze the effect laws of steam to methane ratio, resident time and reaction temperature on methane steam reforming (MSR). Based on extensive experimental studies of steam reforming, a detailed reaction mechanism for the plasma-assisted MSR was developed and evaluated by comparison of experimentally derived and numerically predicted conversion and products yield. The comparisons showed the kinetic model well predicted methane conversion and products yield in different operating conditions. By employing the kinetic model and path flux analysis module the kinetic effects of low temperature non-equilibrium plasma assisted CH4 steam reforming on the methane conversion was studied without catalyst. The results showed that CH3 recombination was the limiting reaction for CO production; meantime O was the critical species for CO production. By adding Ni catalyst can reduce methyl recombination and promote hydroxyl into oxygen, which is beneficial to heat recovery. The proposed research ensures the effect laws and characters of MSR by plasma, and contribute to improve the objective products concentration and furthermore the energy efficiency.
Get More Out of Less, Best Practices for Main Steam Measurement
Authors: Verhaagen Don , Hausman Katie , Saopraseuth Emily
Published: February 2014

The way DP flow is applied and choice of primary element often follows tried and tested methods, this can lead to higher capital expenditures (CAPEX) and operating expenditures (OPEX) costs than is necessary. The latest technology allows an alternative, better practice approach to DP flow that can result to better measurement accuracy and CAPEX and OPEX reductions.

In this study, best practices for steam flow measurement in main steam lines to allow for optimization are identified. The inherent advantages with measuring each critical point around the main steam line are discussed. There are major benefits associated with direct measurement over inferred measurement in high pressure and temperature applications. By measuring main steam line flows directly, plant and process visibility is gained. These measurements are quite accurate because changing process conditions can be captured in the flow measurement.

A technology comparison between a flow nozzle and averaging pitot tube shows the advantages of utilizing the averaging pitot tube technology for critical steam measurements. Installation and maintenance best practices are highlighted.

Another case study depicts the advantages to making direct measurements around the turbine, especially with trending demand. A case study focusing on cost savings depicts how using modern flow technology can provide significant cost and energy savings.
A Dynamic Process Model of a Natural Gas Combined Cycle: Model Development With Startup and Shutdown Simulations
Authors: Liese Eric , Zitney Stephen E.
Published: February 2014

Research in dynamic process simulation for integrated gasification combined cycles (IGCC) with carbon capture has been ongoing at the National Energy Technology Laboratory (NETL), culminating in a full operator training simulator (OTS) and immersive training simulator (ITS) for use in both operator training and research. A derivative work of the IGCC dynamic simulator has been a modification of the combined cycle section to more closely represent a typical natural gas fired combined cycle (NGCC). This paper describes the NGCC dynamic process model and highlights some of the simulator’s current capabilities through a particular startup and shutdown scenario.
Measurement of Thickness and Reflectivity of Fouling Deposits on Wall Tubes in a Pulverized-Coal Firing Furnace
Authors: Menn Naftaly , Chudnovsky Boris
Published: February 2014

It is well known that fouling deposits on the wall of power generation units where solid fuels, like pulverized coal, is burnt cause significant reduction of the overall efficiency of the furnace and the boiler. In order to take fouling into account in the overall balance of the boiler it is necessary to measure two main parameters — thickness of the deposits and their reflectivity (emissivity) in the wavelength of visible and IR region.

In the present paper an electro-optical system is described which enables to perform direct on-line measurement of these two parameters of heat transfer in the course of normal operation of the power unit. The system is capable to carry out measuring procedure inside the furnace chamber at temperatures up to 1800 C. Dynamic measurement of thickness of the fouling deposits created on the wall tubes is measured with accuracy of 0.1mm. Spectral reflectivity of the wall is also continuously measured and compared with the reflectivity of the stainless steel specimen located inside the system. Experimental results are reported obtained during three months operation of the system on the power unit of Israel Electric Company (power station in Hadera).
Object-Oriented Programming of Turbine Performance Calculation With Cooling Air
Authors: Pan Fumin , Zheng Hongtao , Liu Qingzhen
Published: February 2014

In this paper, characteristics in all working conditions of some selected turbine are acquired based on the information of several given operating points and an improved ISO temperature is proposed to calculate expander power of some turbine. An object-oriented approach is used to code the turbine calculation program. Firstly, characteristics in the same rotational speeds with given variable operating points are calculated by Stodola-Flügel equation and PSO based neural networks are used to predict more characteristics. Then, the turbine thermodynamic process is divided into blending of gas and cooling air and gas expansion. The blending process is calculated by improved ISO temperature method which adopts PSO method to calculate the optimal value of recovery coefficient of gas pressure and efficiency coefficient of the cooling air enthalpy. Finally, the above calculation procedure of the turbine is coded by an object-oriented approach and it is approved to be of high accuracy. Such a calculation process proposed in this article meets the requirement of turbine performance calculation with cooling air.
Analysis of Turbulence Models in Numerical Simulation of Combustion Chamber
Authors: Yang Honglei , Zheng Hongtao , Li Zhiming , Yang Ren , Zhang Zhibo
Published: February 2014

Several turbulence models were analyzed in this paper for the chemically recuperated gas turbine (CRGT) combustor and numerical simulation of the combustor’s flow fields using these turbulence models was carried out with the aid of CFD method and finally the contrastive analysis was made. Realizable k-ε and RNG k-ε turbulence models, PDF combustion model and the SIMPLE algorithm method were adopted in the numerical simulation. Through comparison of key influencing factors of the combustor such as flame length, position of the high temperature zone, wall temperature and evenness of exit temperature field, it could be concluded that the Realizable k-ε turbulence model demonstrates better performance with high quality of convergence precision and evenly distributed parameters that meet the design requirements better.
A New Method for Numerical Prediction of Lean Blowout in Aero-Engine Combustor
Authors: Zhang Zhibo , Zheng Hongtao , Li Zhiming , Li Yajun , Pan Gang , Chen Xi
Published: February 2014

Lean blowout (LBO) is one of the most important parameters on combustor performance. A new method named Feature-Section-criterion (FSC) for predicting LBO of aero-engine annular combustor has been put forward in the present work. A CFD software FLUENT has been used to simulate the combustion flow field of an annular combustor. The prediction of LBO with FSC has been done in this paper and the effects of flow velocity, air temperature and droplet averaged-diameter on the LBO of aero-engine combustor have been discussed by using of FSC. The results show that the predictions of FSC are in agreement with corresponding experimental data. This showing that this method for predicting lean blowout is reliable and can be used for engineering applications.
Design Factors for Avoiding FAC Erosion in HRSG Low Pressure Evaporators
Authors: Moelling David , Malloy James , Graham Marc , Taylor Mark , Fabricius Andreas
Published: February 2014

Two types of flow-driven wear phenomena are a frequent source of failures in Heat Recovery Steam Generators (HRSGs): Flow-Accelerated Corrosion (FAC) and Liquid-Droplet Impingement (LDI). The two mechanisms combined are also known by an older term, erosion-corrosion. This better describes what can be viewed as a continuum of mechanisms, driven by chemistry and/or fluid velocity, which lead to wear and consequent thinning of pipe walls. One common failure location in the HRSG is in Low Pressure (LP) Evaporator circuits, both in regions with two-phase and with single-phase flow conditions.

Replacement and/or redesign of the LP Evaporator system is often required. Water chemistry is known to be a key factor in determining the risk of FAC; it can be modified if required during operation to potentially affect wear rates. Another key factor, determined at the design stage, is the chrome content of the steel. The emphasis here is on evaluating other design factors, particularly local process conditions throughout the LP Evaporator circuit, that affect susceptibility to FAC and LDI. LP systems today often are designed to operate at very low pressures (< 3 barg, 45 psi) with the goal of extracting the last practical amount of thermal energy from gas turbine exhaust gas. Furthermore, many combined cycle power plants (such as those in combined power and desalinization service) have variable loads that lead to wide variations in LP operating pressures.

The overall bulk fluid circulation in natural circulation LP Evaporators of several different HRSG designs is evaluated over a range of operating conditions. These circulation calculations are sensitive to small changes in heat transfer and load conditions at low pressures, due to the high void fraction in the two-phase region. An accurate estimation of void fraction is therefore required to determine local process conditions (flow velocities and flow regimes) in this region. The limitations of some of the common methods for estimating void fractions, such as asymptotic values for high void fractions at low pressures, are considered. The evaporator process conditions determined by modeling are used as inputs to assess the potential for wear by FAC and/or LDI using several established methods (Kastner, Sanchez-Caldera). The results are compared with case studies from field investigations to assess if wall thinning encountered in actual HRSG service can be correlated with certain design factors.
Design and Evaluation of a Rooftop Wind Turbine Rotor With Untwisted Blades
Authors: Zafar Sayem , Gadalla Mohamed
Published: February 2014

A small horizontal axis wind turbine rotor was designed and tested with aerodynamically efficient, economical and easy to manufacture blades. Basic blade aerodynamic analysis was conducted using commercially available software. The blade span was constrained such that the complete wind turbine can be rooftop mountable with the envisioned wind turbine height of around 8 m. The blade was designed without any taper or twist to comply with the low cost and ease of manufacturing requirements. The aerodynamic analysis suggested laminar flow airfoils to be the most efficient airfoils for such use. Using NACA 63-418 airfoil, a rectangular blade geometry was selected with chord length of 0.27[m] and span of 1.52[m]. Glass reinforced plastic was used as the blade material for low cost and favorable strength to weight ratio with a skin thickness of 1[mm]. Because of the resultant velocity changes with respect to the blade span, while the blade is rotating, an optimal installed angle of attack was to be determined. The installed angle of attack was required to produce the highest possible rotation under usual wind speeds while start at relatively low speed. Tests were conducted at multiple wind speeds with blades mounted on free rotating shaft. The turbine was tested for three different installed angles and rotational speeds were recorded. The result showed increase in rotational speed with the increase in blade angle away from the free-stream velocity direction while the start-up speeds were found to be within close range of each other. At the optimal angle was found to be 22° from the plane of rotation. The results seem very promising for a low cost small wind turbine with no twist and taper in the blade. The tests established that non-twisted wind turbine blades, when used for rooftop small wind turbines, can generate useable electrical power for domestic consumption. It also established that, for small wind turbines, non-twisted, non-tapered blades provide an economical yet productive alternative to the existing complex wind turbine blades.
Investigation of Fluid Dynamic Properties of Liquid Field’s Metal
Authors: Lipchitz Adam , Imbert Theophile , Harvel Glenn D.
Published: February 2014

The density and viscosity Field’s metal is measured in this work and compared to traditional liquid metal coolants such as sodium and lead-bismuth eutectic. Field’s metal is a eutectic of the ternary In-Bi-Sn system. The alloy is by weight percent is 51% indium, 32.5% bismuth and 16.5% tin and possesses a melting temperature of 333 K. This work experimentally measures the density and viscosity of Field’s metal for numerical modeling and thermal hydraulic applications. The density of Field’s metal is measured using a pycnometer. The density is determined for both its solid and liquid states. In its liquid state Field’s metal is found to have a linear dependence with respect to increasing temperature. The viscosity of Field’s metal is measured using a rotational viscometer. The viscosity is measured is to be 27 mPa-s at 353 K, however further investigation is required to determine a trend at higher temperatures.
Sensitivities of Recent Electricity Generation Water Use Findings to Data Updates and Variability
Authors: Meldrum James R. , Averyt Kristen B. , Macknick Jordan E. , Newmark Robin L. , Rogers John , Madden Nadia , Fisher Jeremy I.
Published: February 2014

Electricity generating technologies require substantial amounts of water for cooling in steam cycle processes and for other operational processes [1,2]. This study expands on recent research [3,4] that uses estimates of operational water consumption and withdrawal factors for electricity generating technologies, collected from published primary literature [1,5], and power plant statistics provided by the Energy Information Administration (EIA), to calculate and understand the water use by thermoelectric power plants in the United States.
Life Cycle Water Use for Electricity Generation: Implications of the Distribution of Collected Estimates
Authors: Meldrum James R. , Macknick Jordan E. , Heath Garvin A. , Nettles-Anderson Syndi L.
Published: February 2014

Water requirements throughout the electricity generation life cycle have important implications for the electricity sector. Thermoelectric power plant operations are estimated as responsible for around 36% [1] to 41% [2] of total freshwater withdrawals in the United States and 3% of total freshwater consumption [1,3]. However, the life cycle of electricity generation consists of many stages besides power plant operation, including component manufacturing, fuel acquisition, processing, and transport, and power plant decommissioning. The water requirements associated with choices along this life cycle, such as the selection of fuel type or cooling technology, are not well understood.
Maximizing Power Generating Asset Value Through Performance Management
Authors: Sunder Raj Komandur S.
Published: February 2014

Power plant owners have been monitoring the performance of their power plant processes, equipment and instrumentation for several years. In recent years, however, they have been increasingly confronted with several challenges in maximizing the value of their generating plant assets.

The challenges include: deregulation, increased competition, aging of power plant equipment, inadequate instrumentation, aging workforce, lack of experienced/qualified personnel and tools to effectively monitor the operation, performance and condition of plant processes and equipment. These constraints have adversely impacted the capacity, availability and reliability and efficiency of the generating plant asset as well as the total cost of ownership and return on investment. On a positive note, however, technological innovations and tools such as the advent of the Internet, web-based and wireless technologies, advanced software applications and tools, automation, smart sensors and instruments with diagnostic capabilities, are all now making it possible for power plant owners to do more with less.

Using case studies, this paper discusses various initiatives and technological advances that are being utilized to maximize power generating asset value through performance management.
Numerical Study of Methane and Air Combustion Inside Heat-Recirculating Combustors
Authors: Li Yanxia , Liu Zhongliang , Wang Yan , Liu Jiaming
Published: February 2014

A numerical model on methane/air combustion inside a small Swiss-roll combustor was set up to investigate the flame position of small-scale combustion. The simulation results show that the combustion flame could be maintained in the central area of the combustor only when the speed and equivalence ratio are all within a narrow and specific range. For high inlet velocity, the combustion could be sustained stably even with a very lean fuel and the flame always stayed at the first corner of reactant channel because of the strong convection heat transfer and preheating. For low inlet velocity, small amounts of fuel could combust stably in the central area of the combustor, because heat was appropriately transferred from the gas to the inlet mixture. Whereas, for the low premixed gas flow, only in certain conditions (Φ = 0.8 ～ 1.2 when ν0 = 1.0m/s, Φ = 1.0 when ν0 = 0.5m/s) the small-scale combustion could be maintained.
Using CFD for Metrology Prediction in Flowmetering: RCS Flow Measurement in PWRs With Elbow Taps
Authors: Deneux Olivier , Favennec Jean-Mélaine , Veau José , Antunes Johan , Piedfer Olivier
Published: February 2014

The RCS flow measurement in PWRs is currently performed with a heat balance between primary and secondary systems: thus temperature heterogeneity impacts this measurement.

In case of RCS flow shutdown (incident situation), a relative measurement of the RCS flow is monitored using an existing elbow tap. The goal of the present study is to assess the feasibility of using the existing plant elbow taps to accurately measure an absolute value of the RCS flow continuously and independently of the RCS temperature measurements. RCS flow is basically proportional to the square root of the differential pressure in the pipe elbow taps. Experiments on a scale model and sensitivity analyses with CFD simulations have been carried out and show that only few parameters have an influence on the proportionality coefficient. CFD is seen as able to predict this coefficient with an adequate accuracy.

Potential applications of this method are RCS flow monitoring from start to full load after the change of primary coolant pumps or of steam generators.
Prediction of Local Entropy Generation in Turbulent Combustion Systems
Authors: Safari Mehdi , Sheikhi M. Reza H.
Published: February 2014

Analysis of local entropy generation or exergy destruction is an effective means to investigate sources of efficiency loss to optimize the performance of energy and combustion systems. The local entropy production is predicted using large eddy simulation of turbulent reacting flows. The unclosed entropy generation effects are accounted for by a novel methodology developed based on the filtered density function to embed the transport of entropy. Simulations are conducted of turbulent flames and predictions are validated via experimental data. Sources of irreversibility in turbulent combustion including viscous dissipation, heat conduction, mass diffusion and chemical reaction are predicted and analyzed. The influence of various operating parameters on local entropy generation and the exergetic efficiency of the combustion system is studied.
Analysis of Turbine Cycle Performance, Operation and Reliability Issues Using Heat Balance Techniques
Authors: Sunder Raj Komandur S.
Published: February 2014

The first law of thermodynamics is universally used in steady-state modeling and performance analysis of power plant cycles. Mass and energy balances may be effectively utilized in analyzing and evaluating turbine cycle performance issues and associated heat rate and capacity losses.

Utilizing a case study for a fleet of coal-fired power plants and different examples, this paper examines applications of heat balance techniques in evaluating and quantifying performance losses. The focus of the paper will be in analyzing, diagnosing and quantifying performance, operation and reliability issues for the turbine cycle and major equipment.
Closed Cooling Water Heat Exchanger Design for Higher Tube Inlet Water Temperature
Authors: Muldoon Thomas J. , Bruno Joseph A.
Published: February 2014

When the maximum temperature of cooling water slowly increases with temperature changes and shifting climate patterns, smaller LMTD’s (log mean temperature differences) for the CCW’s to meet the same performance heat rejection. Making the issue more critical is that the peak cooling water temperatures will usually occur at the same time as peak summer load demand.

A smaller LMTD means a larger heat exchanger and more effective tubing surface area. More surface, means more tubing or smaller diameter tubing. If the original LMTD was 12 °F, a 1 degree change may mean an increase of 9%. To maintain the same nozzle locations on a replacement exchanger means a smaller tube outside diameter and/or a larger shell. Such increases are necessary for the high summer load conditions with the highest inlet water temperatures. At lower water temperatures, the amount of excess thermal capability can become a performance and corrosion issue as the water flows are modulated to meet temperatures. To help reduce these problems, a design which allows operation with reduced surface at low temperatures is appropriate.

The temperature approach (Cooling Water Out – Service Water In) based on the higher inlet cooling water temperature can be significantly smaller than when the CCW was originally designed. This paper will address a design configuration that will work with both higher summer temperature cooling water with the flexibility of using less water for cooler winter operation. The overall affect is less pumping power during colder months, more consistent tube velocities which will help with heat transfer, and minimization of sediment settling in the tubes due to lower velocities.
Experimental Investigations on Temperature Distribution and Heat Removal Capability of Residual Heat Exchanger
Authors: Wu Jiangbo , Bi Qincheng , Zhou Chengsi
Published: February 2014

The residual heat exchanger in nuclear power plant is the key component of secondary side passive residual heat removal system, where the performance of removing decay heat by condensation and pool boiling to the secondary water storage tanks in the residual heat exchanger is crucial to the safety of the nuclear power plant. In the present paper, an experimental facility is built to evaluate the heat removal capability of the residual heat exchanger in both steady state natural circulation and forced circulation at different pressures. The high pressure steam is forced to flow and enter into heat exchanger with a slight inclined tube, which is installed in a large water pool. Experiments are carried out to study the characteristics of the steam condensation in the residual heat exchanger at different parameters. A calculation code for modeling this process and predicting the outlet temperature is also developed.

The results show that the temperature difference between inlet and outlet increases with the increase of the inlet steam pressure due to the variation of latent heat. Meanwhile, the outlet temperature also increases with increasing flow rate. The calculation results accord with the experimental data at low mass flow rate. It is also found that the two calculation models proposed by J.R. Thome predict the flow pattern well, and the Shah’s equation is more suitable to estimate the heat transfer characteristic.
Generator Stator End Winding Resonance: Problems and Solutions
Authors: Moore Bill , Maughan Clyde
Published: February 2014

Stator windings that are in resonance will have high levels of vibration, if not properly damped or braced. Windings in resonance can suffer from early conductor strand fatigue cracking, arcing and failure during operation. Evidence of high vibration can sometimes be seen through visual inspection, with observance of dusting and greasing. There are two primary methods to anticipate and detect end winding resonant vibration — the bump test and on-line monitoring. Both are important and play a key role in identifying stator winding resonance problems, as well as implementing the appropriate solution. This paper will discuss the reasons that stator end winding resonance occurs. The technology, as well as the advantages and limitations of both the bump test and vibration monitoring, will be discussed. Solution approaches to end winding vibration are included, as well as one case history.
Thermal Characteristics of Synthetic Jet Fuels in a Meso-Scale Heat Recirculating Combustor
Authors: Wierzbicki Teresa A. , Lee Ivan C. , Gupta Ashwani K.
Published: February 2014

A meso-scale heat recirculating combustor was used to examine the combustion characteristics of two specific synthetic fuels. One of the fuels was made via a Fischer-Tropsch (F-T fuel) process, while the other was produced from tallow (bio-jet fuel). The two fuels were burned in the meso-scale combustor using pure oxygen in a non-premixed injection configuration. The extinction behavior at the fuel-rich and fuel-lean combustion conditions has been investigated for each fuel. The results showed that although the two fuels showed some similarities, the F-T fuel exhibited stable, non-sooting combustion behavior at higher equivalence ratios than the bio-jet fuel. The lean stability limit for the bio-jet fuel was found to be lower (lower equivalence ratio) than that of the F-T fuel. The results were compared with conventional JP-8 jet fuel to provide a comparative analysis of combustion characteristics using the same combustor. A fuel characterization analysis was performed for each fuel, and their respective thermal efficiencies calculated. The F-T and bio-jet fuels both reached a maximum thermal efficiency of about 95% near their respective rich extinction limits.
Cyclic Operation of Supercritical High Pressure Feedwater Heater Study
Authors: Muldoon Kellen
Published: February 2014

As more renewable energy sources come on line with the inherent inconsistency of load dispatch feedwater heaters become subject to more frequent and rapid cyclic operation. In a recent project, American Exchanger Services (AM-EX) was asked to gather and analyze operating information on a high pressure feedwater heater during daily rapid load changes. This particular supercritical coal plant was designed to operate in flexible load environments, thus acquiring data during the summer months was optimal.

The heater was run from rest to full power while temperature data was acquired. All data from the study and supporting plant information was used to generate models for preparing maintenance projections, informing future designs, and repair recommendations. The primary component of focus is the desuperheating zone exhaust where tube failure tends to be greatest caused by wet wall conditions.

The result of the analysis was less conclusive than was anticipated. Actual performance of the heaters is a key issue and there were specific indications that the heaters were not performing to specifications. A more detailed thermal performance analysis using the ASME PTC12.1 should be considered to accurately determine the extent to which the heaters are meeting design performance.
Integrated Energy-Water Planning in the Western and Texas Interconnections
Authors: Tidwell Vincent , Gasper John , Goldstein Robert , Macknick Jordan , Sehlke Gerald , Webber Michael , Wigmosta Mark
Published: February 2014

While long-term regional electricity transmission planning has traditionally focused on cost, infrastructure utilization, and reliability, issues concerning the availability of water represent an emerging issue. Thermoelectric expansion must be considered in the context of competing demands from other water use sectors balanced with fresh and non-fresh water supplies subject to climate variability. An integrated Energy-Water Decision Support System (DSS) is being developed that will enable planners in the Western and Texas Interconnections to analyze the potential implications of water availability and cost for long-range transmission planning. The project brings together electric transmission planners (Western Electricity Coordinating Council and Electric Reliability Council of Texas) with western water planners (Western Governors’ Association and the Western States Water Council). This paper lays out the basic framework for this integrated Energy-Water DSS.
Strategic Plan and Roadmap for Energy and Water Utilization: Water Energy Nexus
Authors: Khalil Essam E.
Published: February 2014

All countries have realized the strategic importance of regional Energy-Water Roadmap and strategy as dictated by the world logistics and climatic changes. The purpose of the roadmap is to assess the effectiveness of existing water and energy development programs within the individual countries and among them in addressing energy and water related issues, and to assist in defining the direction of research, development, demonstration, and commercialization national and regional efforts to insure that:

1. Energy-related issues associated with providing adequate water supplies, optimal management and efficient use of water, and

2. Water-related issues associated with providing adequate supplies, optimal management and efficient use of energy are being adequately and efficiently addressed in the future.
CMOS field emission devices based on {111} silicon surfaces
Authors: Bachmann Michael , Pahlke Andreas , Axt Carolin , Hinze Bastian , Hansch Walter
Published: February 2014

A complementary metal–oxide–semiconductor process for field emission devices based on {111} silicon surfaces is presented. Structure sizes below 300 nm are produced with i-line lithography and sizes below 100 nm with an additional epitaxial layer. Dot- and line-based structures are investigated by molecular beam epitaxial growth, and {111}-apexes are formed by lateral limitation of the growth site. Qualitative agreement of the experimental observations with a simple model based on total free energy calculations is found. For widths smaller than the migration length quantitative agreement is also found. Nanometer sized silicon ridges with a {111}-apex and curvature radii below 20 nm are used as diode field emission devices. Electrical characterization by simulation and measurement are shown. Electrostatic simulations indicate emission from the ends of the ridges due to higher fields, and therefore, two emission sites per ridge are expected. Distinct linear regions in Fowler–Nordheim coordinates are observed by electrical measurements at elevated pressure levels of about 10−5 mbar. The devices show a conditioning effect, which can be explained by the creation of conducting channels in the native oxide. Immediate destruction of the devices is observed within only a few voltage sweeps. A clear lifetime improvement is obtained by reducing the distance between anode and cathode, indicating major influence of residual gas breakdown.