bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Conductivity Reduction in Nanostructured Semiconductor Using Broad-Band-Phonon Scattering
Authors: Kim Woochul , Reddy Pramod , Majumdar Arun , Zide Joshua , Gossard Arthur , Zeng Gehong , Bowers John , Shakouri Ali
Published: November 2008

Low thermal conductivity is essential for efficient operation of thermoelectric/thermionic power generation devices. There have been several attempts to design materials with low thermal conductivity without sacrificing electrical transport. These approaches utilized different mechanisms of phonon scattering, such as acoustic impedance mismatch of the adjacent layers in superlattices or defect scattering of phonons etc [1, 2]. However, each of these approaches scatter phonons only in a particular region of the phonon spectrum. In this paper we present experimental results of the thermal conductivity of epitaxially grown superlattices engineered to take advantage of the various scattering mechanisms to scatter phonons over the entire phonon spectrum.
Large-Scale Assembly of Carbon Nanotubes
Authors: El-Aguizy T. , Kim Sang-Gook
Published: November 2008

The scale decomposition of a multi-scale system into small-scale order domains will reduce the complexity of the system and will subsequently ensure a success in nanomanufacturing. A novel method of assembling individual carbon nanotube has been developed based on the concept of scale decomposition. Current technologies for organized growth of carbon nanotubes are limited to very small-scale order. The nanopelleting concept is to overcome this limitation by embedding carbon nanotubes into micro-scale pellets that enable large-scale assembly as required. Manufacturing processes have been developed to produce nanopellets, which are then transplanted to locations where the functionalization of carbon nanotubes are required.
Plasmonic Lithography
Authors: Srituravanich W. , Fang N. , Sun C. , Durant S. , Ambati M. , Zhang X.
Published: November 2008

As the next-generation technology moves below 100 nm mark, the need arises for a capability of manipulation and positioning of light on the scale of tens of nanometers. Plasmonic optics opens the door to operate beyond the diffraction limit by placing a sub-wavelength aperture in an opaque metal sheet. Recent experimental works [1] demonstrated that a giant transmission efficiency (>15%) can be achieved by exciting the surface plasmons with artificially displaced arrays of sub-wavelength holes. Moreover the effectively short modal wavelength of surface plasmons opens up the possibility to overcome the diffraction limit in the near-field lithography. This shows promise in a revolutionary high throughput and high density optical lithography. In this paper, we demonstrate the feasibility of near-field nanolithography by exciting surface plasmon on nanostructures perforated on metal film. Plasmonic masks of hole arrays and “bull’s eye” structures (single hole surrounded by concentric ring grating) [2] are fabricated using Focused Ion Beam (FIB). A special index matching spacer layer is then deposited onto the masks to ensure high transmissivity. Consequently, an I-line negative photoresist is spun on the top of spacer layer in order to obtain the exposure results. A FDTD simulation study has been conducted to predict the near field profile [3] of the designed plasmonic masks. Our preliminary exposure test using these hole-array masks demonstrated 170 nm period dot array patterns, well beyond the resolution limit of conventional lithography using near-UV wavelength. Furthermore, the exposure result obtained from the bull’s eye structures indicated the characteristics of periodicity and polarization dependence, which confirmed the contribution of surface plasmons.
Information Models and Virtual Prototyping in Nanomanufacturing
Authors: Cecil J. , Nathan J. Senthil , Gobinath N.
Published: November 2008

This paper discusses the use and creation of virtual reality based models and information oriented process models related to the study of Nanomanufacturing. EML, (which is an evolving language), was originally proposed [1] to enable the capture of information rich contexts at various levels of the manufacturing levels. In this paper, the use of EML models as a basis for describing and analyzing nano manufacturing processes will be described; their subsequent use in the creation of simulation models is also discussed. A framework for analysis, reasoning and simulation is proposed which includes a virtual reality based simulation module. Our experience in using VRML 2.0 (Virtual Reality Modeling Language) for the creation of such virtual reality environments will also be addressed.
Hypersonic Plasma Particle Deposition of Nanostructured Coatings and Micropatterns
Authors: Hafiz J. , Mukherjee R. , Wang X. , Mook W. , Heberlein J. V. R. , McMurry P. H. , Gerberich W. W. , Girshick S. L.
Published: November 2008

Nanostructured materials are attractive candidates for advanced friction and wear-resistant coatings due to their potentially enhanced mechanical properties. We have developed a one-step method called hypersonic plasma particle deposition [1] to produce and deposit nanoparticles using a thermal plasma reactor. Particle synthesis is achieved by dissociating vapor phase reactants in the plasma, and quenching the hot gas in a supersonic nozzle expansion. Particles are deposited on a substrate by hypersonic impaction to form a film, or are deposited as micropatterns using a process called focused particle beam deposition [2]. In-situ particle size distribution measurements are performed using a sampling probe interfaced to an extraction/dilution system for measurement by a scanning electrical mobility spectrometer.
Simulation of Thermionic Emission from Quantum Wires
Authors: Liu Yang , Fisher T. S.
Published: November 2008

In the late 19th century, Edison observed electrical current flowing between hot and cold electrodes [1]. Since this discovery of thermionic emission, research has occurred with varying intensity in order to harness the simplicity and utility of the thermionic effect in power generation devices. Hatsopoulos and Gyftopoulos [2,3] provide details of the development of thermionic theory and practice. In general, thermionic power generation has not found widespread use, despite many inherent advantages over alternative power generation methods, because of material limitations that have precluded an attractive combination of power generation efficiency and capacity. This paper presents semiclassical and quantum models for the thermionic behavior of a newly developed class of materials, quantum wires, that may offer some promise in alleviating historic materials limitations of thermionic devices.
Nanoscale Heat Conduction in Data Storage Technology
Authors: Asheghi Mehdi
Published: November 2008

The magnetic data storage industry has followed a similar density (and data rate) improvement curve as the semiconductor technology (Moore’s Law) for the past decade. However, whether the storage densities will continue to increase at this rate and be able to keep up with the improvements in processor technology is under a near term threat resulting from the fundamental physics up on which the hard disk drives are based. It is expected that novel, more unconventional technological solutions become necessary to overcome limitations, however, many of these technologies rely heavily on heating and energy transport at extremely short time and length scales. It is widely believed that further advances in high-technology data storage systems will be difficult, if not impossible, without rigorous treatment of the nano-scale energy transport. The nano-scale heat transfer research effort at Data Storage System Center (DSSC) has been focused on three interwoven areas of thermal design, failure analysis, and metrology of micro/nano-devices and structures relevant to data storage technologies. In this presentation, underlying physics and fundamentals of heat transport at nanoscale will be discussed. In addition, applications of the nanoscale heat transfer to the thermal analyses of the magnetic and phase change optical data storage technologies will be presented.
Field Emission Study of Carbon Nanotubes: High Current Density From Nanotube Bundle Arrays
Authors: Bronikowski M. J. , Manohara H. M. , Siegel P. H. , Hunt B. D.
Published: November 2008

We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-μm diameter nanotube bundles spaced 5 μm apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm2 at ∼ 4 V/μm electric field, and >6 A/cm2 at 20 V/μm.
Simulation of Thermal Transport in Nanowire Composites for Macro-Electronics Applications
Authors: Kumar Satish , Murthy Jayathi Y. , Alam M. A.
Published: November 2008

Thermal transport in thin film transistors (TFTs) composed of nanowires embedded in plastic substrates is considered. Random ensembles of intersecting and contacting wires embedded in a substrate are analyzed using Fourier theory. Heat generation due to self-heating is included. A finite volume scheme is used to obtain the temperature solutions in the wires and substrate. Temperature profiles in the ensemble are investigated as a function of wire number density, wire-contact Biot number as well as the Biot number for heat transfer to the substrate.
An Integrated MEMS System for In-Situ Mechanical Testing of Nanostructures
Authors: Lu Shaoning , Chung Jaehyun , Dikin Dima , Lee Junghoon , Ruoff Rodney S.
Published: November 2008

We present a hybrid nano-electromechanical system for study of the mechanics of nanostructures. The system has a testing platform based on a deep reactive ion-etched high aspect ratio MEMS device. A new approach has been developed with top-down manufacturing of the micro-device and bottom-up post-fabrication assembly of samples (nanostructures) to be tested. A process that minimizes chemical or physical damage of the sample is used to integrate suspended nanowires/nanotubes into the system. The system provides nanoscale resolution of displacement and force. The device is used in an SEM and is being tested for in situ experiments on various nanowires or nanotubes.
Near-Field Calibration of Isolated Carbon Nanotube Field Emitters for Nanomanufacturing Applications
Authors: Hii King-Fu , Vallance R. Ryan , Kichambare Padmakar D. , Mengu¨c¸ M. Pinar
Published: November 2008

This paper reports the development of an apparatus, technique, and method for calibrating the field emission phenomena’s dependence on both the voltage applied between the anode and cathode and the electrodes gap. A precise knowledge of the electrodes gap is required for calibrating field emitters. The I-V characteristic of isolated carbon nanotube field emitter is a strong function of the electrodes gap distance. A consolidated IV curve is obtained by calculating the current density and the local electric field with the field enhancement factor taken into consideration. The field enhancement factor and emitting area are unique for each electrodes gap distance. We also found that the turn-on voltage decreases as the electrodes gap distance decreases.
Low-Dimensional Phonon Heat Capacity of Titanium Dioxide Nanotubes
Authors: Dames C. , Chen G. , Poudel B. , Wang W. , Huang J. , Ren Z. , Sun Y. , Oh J. I. , Opeil C. , Naughton M. J.
Published: November 2008

Low-dimensional nanostructures such as nanotubes, nanowires, and quantum dots are promising building blocks for electronic, optical, sensing, and energy conversion applications. For effective device design it is important to understand how the basic thermal properties of nanostructures differ from those of bulk materials. For example, the measured thermal conductivity of silicon nanowires [1] can be understood with a 3-dimensional dispersion relation [2] for diameters down to about 40 nm, although at 22 nm diameter the experiment and modeling diverge sharply.
Impact of Electron-Phonon Non-Equilibrium on Heat Dissipation of Metallic Nano-Particles Suspended in Dielectric Media
Authors: Ju Y. Sungtaek
Published: November 2008

Controlled heating of nano-particles is a key enabling technology for various nano-manufacturing and biomedical applications. They include controlled fabrication of nano-particles,1 and targeted heating of biological molecules and cells for research as well as therapeutic purposes.2 Recent studies also demonstrated improved heat transfer properties of colloids of nano-particles.3
Magnetically Assembled 3-D Mesoscopic Patterns Using Suspension of Superparamagnetic Nanoparticles
Authors: Sinha Ashok , Ganguly Ranjan , Puri Ishwar K.
Published: November 2008

A self assembly process is characterized by the spontaneous and ordered aggregation of similar components. At the nanoscale, these constituents can be colloids, or other nanoparticles that combine to form structures of meso- and macroscopic dimensions. Self assembly is most evident during the growth of biological structures. Due to its natural elegance, there is considerable interest in investigating similar methods in other fields of sciences. In principle, the process of dynamic self assembly is characterized by a competition between at least two forces — one attractive and the other repulsive — in thermodynimacally nonequilibrium systems. Several researchers have described self assembly in configurations where biological [1] or chemical [2] mediation, electrostatic [3], capillary [4] or fluid dynamic [5] forces have provided a motive potential.
A Computational Study of the Evaporation Characteristics of an Air-Blast Atomized, Kerosene Spray in Porous Media
Authors: Periasamy Chendhil , Sankara Chinthamony Sathish K. , Gollahalli S. R.
Published: November 2008

The evaporation characteristics of an air-blast atomized kerosene spray in porous media in a 2D-axisymmetric coflow environment were studied numerically. A swirling primary air stream with varying intensity was used to aid the atomization process. The effects of non-Darcy flow in porous medium were modeled using a modified form of Ergun equation. Local thermal equilibrium between the fluid mixture and porous medium was assumed. Conductive and transient heat flux terms in the energy equation were modified to include the effective thermal conductivity and thermal inertia of the solid region respectively. The effective thermal conductivity was defined as the volumetric average between solid and fluid media. First, the temperature characteristics of the porous medium, arising from different source terms, were obtained. Complete vaporization of kerosene was achieved when the maximum temperature of the porous medium was at 590 K. The effects of porous medium temperature, primary air swirl number, fuel flow rate, and secondary (coflow) air inlet temperature on vaporization were analyzed. For all cases, kerosene vapor concentration profiles at five different axial locations in the domain (0.08, 0.12, 0.13, 0.14, and 0.19m from the nozzle) were obtained. An increase in secondary air inlet temperature from 373 K to 473 K increased the completeness of evaporation from 94% to 97%. When the swirl number was increased from 0.14 to 0.34, the peak vapor concentration was reduced by 31% and more vapor spread radially. The porous medium temperature was found to be a crucial factor in obtaining the complete vaporization of the spray.
Improving Condenser Efficiency With Innovative Scale Removal System Technology
Authors: Hansen Jon T. , Saxon George E.
Published: November 2008

Identified as one of the single largest energy loss factors in power generation stations, condensers are a potential source of either savings or increased expenditure, especially as fuel prices increase. The performance of the condensers can be adversely affected by the build-up of sediment, scale, corrosion or biological growth inside the tubes. Conventional maintenance procedures to clean fouled tubes range from chemicals to off-line mechanical cleaners and brushes, to on-line systems and hydro-blasters. Sometimes, it takes an unconventional, innovative development in a cleaning system technology to combat ever-changing environmental challenges. Omaha Public Power District’s North Omaha Station had been drawing water from the Missouri River for many years with no discernable problems. Recently, they had experienced a steady rise in summertime backpressures, in the range of 3 to 3.5 in. HgAbs, resulting in poor condenser performance. Inspections revealed a build-up of calcium carbonate scale in the tubes. The station has five condenser units with a total of approximately 50,000 stainless steel condenser tubes, all displaying evidence of calcium carbonate build-up. A recently developed and patented mechanical system for the removal of calcium carbonate scale without any of the negative drawbacks of chemical alternatives was utilized at the station with excellent results, proven by subsequent observations. On completion of the process, back pressure dropped to around 2.0 in. HgAbs and overall performance improved markedly. While plant personnel strive to determine the cause of calcium carbonate buildup in the condenser, removing it from the station’s tubes is now a simple procedure and no longer a problem in search of a solution.
Theoretical Investigation and Numerical Simulation of Turbulent Combustion in an Industrial Combustor With Combustion Gases Recirculation
Authors: Zhang Kunpeng , Xue Fei , Pan Weiming
Published: November 2008

Thermodynamic investigation was conducted to study the role of ejector system in a CGR (Combustion Gases Recirculation) combustor. Physical model was established to evaluate the intensity of CGR and the confirmed relationship between CGR and gas ejection was found. In order to validate the theory analyses, an industry combustor with CGR was modeled. The calculation results accord with the theory analyses. All the results implied that Active Control Combustion (ACC) might be implemented with control of gas ejection.
Monitoring and Improving Coal-Fired Power Plants Using the Input/Loss Method: Part IV
Authors: Lang Fred D.
Published: November 2008

The Input/Loss Method is a unique process which allows for complete thermal understanding of a power plant through explicit determinations of fuel chemistry including fuel water and mineral matter, fuel heating (calorific) value, As-Fired fuel flow, effluent flow, boiler efficiency and system heat rate. Input consists of routine plant data and any parameter which effects system stoichiometrics, including: Stack CO2, Boiler or Stack O2, and, generally, Stack H2O. It is intended for on-line monitoring of coal-fired systems; effluent flow is not measured, plant indicated fuel flow is typically used only for comparison to the computed. The base technology of the Input/Loss Method was documented in companion ASME papers: Parts I, II and III (IJPGC 1998-Pwr-33, IJPGC 1999-Pwr-34 and IJPGC 2000-15079/CD). The Input/Loss Method is protected by US and foreign patents (1994–2004). This Part IV presents details of the Method’s ability to correct any data which effects system stoichiometrics, data obtained either by direct measurements or by assumptions, using multi-dimensional minimization techniques. This is termed the Error Analysis feature of the Input/Loss Method. Addressing errors in combustion effluent measurements is of critical importance for any practical on-line monitoring of a coal-fired unit in which fuel chemistry is being computed. It is based, in part, on an “L Factor” which has been proven to be remarkably constant for a given source of coal; and, indeed, even constant for entire Ranks. The Error Analysis feature assures that every computed fuel chemistry is the most applicable for a given set of system stoichiometrics and effluents. In addition, this paper presents comparisons of computed heating values to grab samples obtained from train deliveries. Such comparisons would not be possible without the Error Analysis.
Detection of Tube Leaks and Their Location Using Input/Loss Methods
Authors: Lang Fred D. , Rodgers David A. T. , Mayer Loren E.
Published: November 2008

This paper presents an on-line method which detects steam generator tube leaks and the heat exchanger in which the leak occurs. This method (the Tube Failure Model) has been demonstrated by direct testing experience. It is based on the Input/Loss Method, a patented method (1994–2004) which computes fuel chemistry, heating value and fuel flow by integrating effluent measurements (CEMS data) with thermodynamics. This paper explains the technology supporting the detection of tube failures, the method of identifying the location of the failure, and cites direct experience of detecting tube failures at two power plants. Most importantly, this paper presents the results of direct testing at the Boardman Coal Plant in which high energy steam/water lines were routed from the drain headers of all major heat exchangers into the combustion space. When allowed flow, these lines were used to emulate tube leaks from any of the major heat exchangers. Their flow rates and locations were then compared to Tube Failure Model predications. This testing is considered significant as for the first time Δheat rate effects of tube failures will be directly determined; and, further, this testing will provide the Tube Failure Model its on-line proof-of-process.
Experimental Investigation and Numerical Simulation of Liquid Droplet Vaporization in a Compression System With Wet Compression
Authors: Zhang Kunpeng , Zou Song , Pan Weiming , Xue Fei
Published: November 2008

Experimental study of spray cooling system with wet compression has been carried out on a small hot wind tunnel. A mathematical model is established for liquid droplets evaporization and a 3D calculation bound on the model have been carried out. The results are in good accord with the experimental data. This paper will be good reference for spray system design for a wet compression system. And the detail information of the experiment and numerical computation take us further understanding of the real wet compression process.
Preoperational Cleaning Requirements for HRSG Units
Authors: Bartholomew Robert D. , Hull Emory H.
Published: November 2008

There have been no generally agreed upon practices regarding preoperational chemical cleaning of new heat recovery steam generators (HRSGs). Some have been cleaned only with warm detergent solutions while others are cleaned using alkaline detergents followed by iron oxide removal and passivation stages. Thorough inspection and monitoring of waterside surfaces from fabrication through commissioning are necessary to assess unit cleanliness. However, these activities are sometimes neglected. In some cases, there is no contingency plan should inspection reveal fouled or corroded surfaces. Poor waterside cleanliness has caused startup delays and problems during subsequent operation. This paper summarizes the recommended requirements for both companies that plan to clean and for those companies that do not expect to clean.
Underground Coal Gasification for Power Generation: High Efficiency and CO2-Emissions
Authors: Blinderman Michael S. , Anderson Bernard
Published: November 2008

Underground Coal Gasification (UCG) is a gasification process carried out in non-mined coal seams using injection and production wells drilled from the surface, enabling the coal to be converted into product gas. The UCG process practiced by Ergo Exergy is called Exergy UCG or εUCG. εUCG was applied in the Chinchilla UCG-IGCC Project in Australia. The IGCC project in Chinchilla, Australia has been under development since July 1999. The project involves construction of the underground gasifier and demonstration of UCG technology, and installation of the power island. Since December 1999 the plant has been making gas continuously, and its maximum capacity is 80,000 Nm3/h. Approximately 32,000 tonnes of coal have been gasified, and 100% availability of gas production has been demonstrated over 30 months of operation. The UCG operation in Chinchilla is the largest and the longest to date in the Western world. The εUCG facility at Chinchilla has used air injection, and produced a low BTU gas of about 5.0 MJ/m3 at a pressure of 10 barg (145 psig) and temperature of 300° C (570° F). It included 9 process wells that have been producing gas manufactured from a 10 m thick coal seam at the depth of about 140 m. The process displayed high efficiency and consistency in providing gas of stable quality and quantity. The results of operations in Chinchilla to date have demonstrated that εUCG can consistently provide gas of stable quantity and quality for IGCC power projects at very low cost enabling the UCG-IGCC plant to compete with coal-fired power stations. This has been done in full compliance with rigorous environmental regulations. A wide range of gas turbines can be used for UCG-IGCC applications. The turbines using UCG gas will demonstrate an increase in output by up to 25% compared to natural gas. The power block efficiency reaches 55%, while the overall efficiency of the UCG-IGCC process can reach 43%. A UCG-IGCC power plant will generate electricity at a much lower cost than existing or proposed fossil fuel power plants. CO2 emissions of the plant can be reduced to a level 55% less than those of a supercritical coal-fired plant and 25% less than the emissions of NG CC.
The Bioceanic Amazon Corridors: An Opportunity for Development of Sustainable Energy System
Authors: Mendoza G. Pedro , Arroyo Ulloa Maximiliano , Naso Vincenzo
Published: November 2008

The bioceanic Amazon corridor represents a development opportunity for the Peruvian and Brazilian economy but this economic evolution is linked to the production and use of energy. Energy is a conditioning factor of economic growth and development and the application of conventional (or alternative) energy systems is strongly influenced by both quantitative and qualitative trends in energy consumption. Decentralized production of energy is necessary, and new decentralized energy technologies based on renewable sources could provide additional income opportunities, decreasing environmental risk along Amazon corridor, and providing clean fuel and electricity. It’s necessary that the bioceanic Amazon corridors call for the application of energy systems related to the renewable local resources in coast, mountain and forest. In Peru, firewood is the principal energy source for cooking and heating and this fuel is used in inefficient combustion system that increases the impact on ecosystems. Typical Peruvian biomass source are wood, agricultural residues, agro industrial waste and municipal solid waste. The most obvious it’s the availability of agricultural and agro industrial residues that could be used as a biomass fuel source in modern plant to produce electricity. Today, there is a growing interest for ethanol production from sugar cane, but it couldn’t be applied along bioceanic corridors; therefore it is necessary to integrate other renewable sources.
Practical Issues of Combustion Oxygen Measurement Specifically Related to NOx Emissions
Authors: Scott Jim , Dennis Bobby
Published: November 2008

Power plants concerned with lowering NOx emissions are making tremendous changes to accommodate EPA regulatory requirements. A substantial number of these changes include the expansion and upgrade of the plant combustion oxygen measurement equipment. There is a striking relationship between the number of NOx reductions projects and the sales quantity of insitu oxygen detectors. The reason is that power plant betterment groups, operators, boiler manufacturers and engineering firms understand the direct relationship between NOx and excess air in the combustion process. An area of daily practical importance to boiler operators and I&C teams are the common problems with insitu oxygen measurements. This paper focuses on the practical issues of combustion oxygen measurement as they relate to specifically to fuel usage and NOx emissions.
Effect of Swirl and Fuel Pulsation on Flow Dynamics, Flame Structure and Droplet Motion in Swirl-Stabilized Spray Flames
Authors: Linck Martin B. , Armani Michael D. , Gupta Ashwani K.
Published: November 2008

This paper describes an experimental investigation of the role of swirl distribution in a co-annular swirl-stabilized spray combustor for passive control of flame structure using kerosene fuel. Three distinctly different flames have been examined. A low shear, a high shear, and a counter-rotating swirling flow flame have been examined. The droplet dynamics and flowfield associated with the low and high shear co-rotating swirl configurations under isothermal and combustion conditions have been examined using a phase Doppler interferometric techniques. The high-shear swirl configuration was found to decrease droplet diameter in the shear region, indicating secondary atomization of larger size droplets due to strong shear effects in the flow. Droplet mean and turbulence characteristics were obtained. In order to simulate oscillations in the flow pulsations were introduced into the fuel flow in order to excite instabilities in the burner. The role of swirl distribution was determined on the attenuation of this imposed instability. Swirl distribution was found to be effective in reducing the instability. Instabilities at the forcing and harmonic frequencies are found to be up to 5 dB more powerful in the counter-rotating flow, demonstrating the role of swirl on flame structure and the associated combustion instability in swirl-stabilized spray combustors. The airflow distribution in the burner was also found to play an important role on the alleviation of combustion instability.
Enhancing Plant Start-Up Reliability: Independent Critical Equipment Evaluations
Authors: Kinsel Calvin E. , Eckersley Richard , Stulak Stephen
Published: November 2008

This paper describes a program instituted by Reliant Energy in 2002 to enhance the reliability of certain equipment that have been designated as being critical to the successful start-up of their plants under construction. The goal of the program is to reduce the risk of failing to meet forecasted Commercial Operation dates on plants under construction due to equipment failures during commissioning and start-up.
Using Improved Remote Visual Inspection Tools to Reach Intermediate Stages in Turbomachinery
Authors: Brown Christopher P. , Smith David B.
Published: November 2008

Using conventional technology, only the outer stages (the first stage and the last one or two stages) of industrial steam turbines are generally accessible to visual inspection. Signs of problems such as erosion, or native or foreign object damage in the intermediate stages can only be detected by other diagnostic means, such as vibration monitoring. This deficiency can make turbine diagnosis difficult in some circumstances. A remote visual inspection technology that can penetrate to the intermediate stages through access from the first or last stages would provide more complete visual coverage. In a recent inspection of a large cross-compound steam turbine at Detroit Edison’s St. Clair Power Plant, new minimally invasive inspection tools were used to locate the cause of rotor imbalance in the low pressure turbine. Attempts to find the problem using conventional borescopes had failed — they could not be inserted far enough into the intermediate stages to locate the problem. Using the modified inspection tools, a missing shroud band segment was discovered on the L-3 stage of the low pressure turbine. Conventional tools had been unable to reach further than the L-1 stage. The new tools, featuring stiffness in the axial direction and flexibility in the radial direction, were maneuvered through ten stages of turbomachinery and were used to locate the problem and evaluate collateral damage to other turbine stages.
Design Considerations and Operation of Condenser Bypass Systems in Combined Cycle Power Plants: Part 1
Authors: Eaton Richard H. , Blessman Edward R. , Schoonover Kevin G.
Published: November 2008

As many Combined Cycle Power Plants have come into operation over the last 10 years, premature condenser tube failures have been experienced at several installations. This paper reviews factors and mechanisms contributing to such failures. The steam turbine condenser must operate under a demanding, wide range of conditions. Tubes within the condenser experience cyclic stresses, direct contact from admission of high-energy steam into the condenser, and the effects from a wide service range beginning with start-up and commissioning through continuous or intermittent daily operation. A number of factors go into properly designing condenser related sub-systems as required by the functional operation of the combined cycle plant. The condenser bypass system is a critical component directly affecting the operation, maintenance and control of conditions experienced by the condenser. Part 1 of this paper identifies related problems experienced, in the field, within the condenser considering operation and maintenance, and also provides design considerations to avoid occurrence of tube failures. Part 2 of this paper addresses many key points for consideration with respect to the design and implementation of the high-energy bypass system leading into the condenser.
Upgrade and Life Extension of 4 × 110 MW Units: A Case Study
Authors: Ayodhi Nynar , Radhakrishnamurthy Y.
Published: November 2008

Achieving rated capacity and economical operation of existing thermal power plants are vital issues for utilities. Plants nearing their design life are likely to show declining trend in availability as well as increasing trend in operation and maintenance costs due to ageing. Constraints in system adequacy, decreasing trend in efficiency and poor reliability are key issues to be addressed while planning life extension. 4×110 MW power plant located in southern part of India has been taken up for renovation and modernization. Pressure parts failures mainly accounted for the reduced availability of the units. The exit gas temperature in boiler was on the higher side leading to operation of the units with reduced efficiency. Change in fuel quality over the years as compared to what has been considered during design was a constraint in achieving rated capacity. The poor heat rate of turbine necessitated incorporation of the state-of-art design to achieve better heat rate. Improvements required in control and instrumentation system were also addressed in the renovation and modernization. Improvements in plant load factor, availability and unit heat rate could be achieved in the two units where renovation and modernization has been completed. The details of the renovation and modernization of these units are discussed in this paper.
Application of Neural Network in Monitoring an Industrial Plant for a Complex
Authors: Seyedan Babak , Hynes Rory
Published: November 2008

The objective of the paper is to assess the feasibility of the neural network (NN) approach in industrial process facilities. The energy consumption of the plant can be improved by defining suitable operating levels of the various parallel components connected to the plant facility using computerized system. The concept of using a computerized procedure capable of recognizing the status of the equipment from monitoring systems and using that data to automatically optimize the plant operation could lead to significant economic and energy consumption improvements. To demonstrate this goal a “Feed Forward Neural Network” technique with a back propagation algorithm was applied to an existing facility equipped with a cogeneration system based on natural gas engines, hot water boilers, standby boilers and other heat sources. In this paper, the heat capacity of a typical installation is presented and a procedure to optimize energy utilization based on a computational model is developed, the plant existing condition is taken as a reference condition, a general block diagram of the system is presented and discussed and the installation heat load allocation is analyzed. Then the data from the physical model of the facility was used to train such a NN model. Results obtained using a conventional computing technique are compared with those of the direct method based on a NN approach. The NN simulator was capable of performing calculations in a very short computing time with a high degree of accuracy. The optimizations of neural network parameters such as the number of hidden neurons; training sample size and learning rate are discussed in the paper. Trained neural network outputs are compared with those of the computational method and discussed.
Resolution of Circulating Water Pump Problems Caused by Low River Levels at the Neal North Generating Station
Authors: Calloway Kevin , Larson Terry
Published: November 2008

Low winter water levels are causing reliability problems with once-through circulating water pump systems at several coal-fired power generating plants sited along the Missouri and Mississippi Rivers. River bottom degradation and potential COE river management changes make low river levels a likely on-going problem especially during drought years currently being experienced in the Midwest. This paper outlines circulating water pumping problems that have occurred at MidAmerican Energy’s Neal North Energy Center due to low water levels in the Missouri River, and the steps taken to resolve these problems. Remedial design solutions that were either considered or implemented, such as supplemental pumps, vacuum lift systems, suction scoops, a new river water intake, and converting to a closed-loop cooling tower system, will be discussed. An in-depth discussion will be made on the supplemental pump system installed in the fall of 2002 and currently in operation on the Unit 3 river intake. Applicable permitting requirements will also be discussed. The new supplemental pump system consists of six submersible axial flow pumps mounted on the front of the existing Unit 3 intake. The total flow capacity of the six supplemental pumps is around 220,000 gpm which is discharged into the existing intake to maintain an acceptable wet well water level for the existing circulating water pump to operate. Other system components include an overhead monorail system to facilitate annual supplemental pump installation/removal, a floating ice deflector system, and a warm-water discharge splash plate. The supplemental pumps are installed and operated during winter months when river levels are low, and removed during the river navigation season when the COE maintains higher river flows.
Using CFD to Model Coal Roping Phenomenon in Coal Transport Systems
Authors: Huang Gengxun , Bryden Kenneth M. , Vasquez Edmundo , Avancha Ravikanth
Published: November 2008

Coal roping is a well-known phenomenon occurring in pneumatic transport of pulverized coal. In coal roping the majority of the coal is concentrated in a small portion of the transport piping cross section. This region of concentrated solid flow is created by a number of factors. For example, as the two phase flow of air and coal travels through an elbow or turn in the coal transport piping the centrifugal forces exerted on the coal concentrate the coal on the outside edge of the elbow. After the coal rope is formed these particles will tend to travel together. Coal roping upstream of a coal distributor (bifuractor) can create a significant imbalance in coal loading between in the split between the two branches. This can result in unbalance coal loading between burners and ununiform coal injection in plant burners. This can significantly impact plant performance and increase NOx production. This paper examines how CFD model can be used to understand common creation and breakup mechanisms of coal roping.
Computational Modeling of Mercury Control by Sorbent Injection
Authors: Madsen Jens I. , Rogers William A. , O’Brien Thomas J.
Published: November 2008

Impending regulations of mercury emission from coal-fired utilities are driving current efforts to develop efficient control technologies. This includes a comprehensive field test program that considers full-scale use of mercury control by injection of activated carbon upstream of a particulate collection device (baghouse or ESP). The present effort aims at numerical modeling of the in-flight mercury capture by adsorption using Computational Fluid Dynamics (CFD). Such a modeling capability enables optimization of sorbent injection strategies in order to better overcome mass transfer limitations. CFD provides detailed duct-scale information on the flow of flue gases as well as the dispersion of injected sorbent. Sorbent particle trajectories are determined using Lagrangian tracking, while a convective-diffusive transport equation describes the gas-phase mercury distribution. Mercury sink terms are defined based on a particle model for mass transfer and surface adsorption on an entrained sorbent particle. We present simulation results for the sorbent dispersion of large-scale field tests carried out at the Brayton Point power station in Massachusetts.
Maximizing Plant Power Output Using Dry Cooling System
Authors: Chandran Ram
Published: November 2008

As the power industry is deregulated, the cost of power plays a major role in obtaining long-term Power Purchase agreements. More and more plants, now, are developed with Dry Cooling System for condensing steam from the steam turbine of combined cycle plants or coal-fired plants. However, Dry Cooling has become synonymous with lower plant output. This paper presents solutions to dispel that myth. 1. Options available for control of the air-cooled system, their initial cost and the impact on minimizing internal power consumption and maximizing plant power output. 2. The air-cooled condenser operates normally at high turbine exhaust pressures during high ambient temperatures. The high backpressure results in lower turbine efficiency and lower plant output. Various options available are presented to combat this deficiency to maximize power output.
A High Performance Optimized Reaction Blade for High Pressure Steam Turbines
Authors: Segawa Kiyoshi , Shikano Yoshio , Takano Tsuyoshi
Published: November 2008

A higher efficiency gain is necessary for steam turbine plants to reduce their fuel consumption rate and lessen their environmental disruption factor. Power plant manufacturers have continued to make an effort to raise steam turbine internal efficiency by developing new technologies. High pressure (HP) steam turbines should have increased efficiency owing to relatively shorter blade height compared with other turbine sections (intermediate and low pressure turbines). In order to increase efficiency, it is important to improve the steam path determined by design parameters such as degree of reaction, number of stages and rotor diameter and to develop a high performance blade applied to it. The advanced computational fluid dynamics (CFD) technique is a useful design tool, and has come to be applied generally to evaluate energy loss. A new rotating blade has been developed for small and mid-class steam turbines with a shorter blade height. The robust design method, based on the statistical theory for design of experiments, is used for the blade root profile design. It is combined with the inverse method and 2-D turbulent blade-to-blade flow analysis to evaluate the aerodynamic performance. The blade configuration is expressed by four control factors, which are turning angle, leading edge radius, pitch-chord ratio and maximum blade loading location. Linear cascade experiments are also carried out due to verify the blade performance under the optimized conditions obtained by the robust design. Consequently, the blade section has a blunt-nose, flat incidence characteristics and low energy loss, compared with the conventional one and the optimized conditions given by the robust design are aerodynamically reasonable. Finally, air turbine model tests and 3-D Reynolds-averaged Navier-Stokes analyses are performed to investigate the detailed flow pattern and stage performance of the new optimized reaction blade. An experimental investigation is still important to evaluate the performance in the real turbine stage structure, while the numerical analysis method is used based on the implicit TVD scheme with the modified k-ε turbulence model. It is found that the new optimized reaction blade has greatly improved stage efficiency of about 1.5% at the design point including the effect of leakage flow (3% improvement in stage efficiency excluding leakage flow) and realized an increase of pitch-chord ratio by about 35%. Consequently, the new optimized reaction blade is considered effective to raise the internal efficiency of the high-pressure steam turbine with improved steam path.
R&D On Micro-Gasifier for Power Generation From Solid Wastes
Authors: Yoshikawa Kunio
Published: November 2008

A small-scale power generation system including a process of producing low-BTU gas by gasification of wastes has been developed. This system is called as the Micro STAR-MEET. Because the size of this system is small, on-site waste treatment is possible. Wastes are continuously fed into the gasifier and, high temperature air and steam are introduced into the gasifier and reformer to gasify and reform wastes. A pilot plant was constructed in order to investigate the performance of the Micro STAR-MEET system, and experiments using wood chips and plastics as fuels were conducted. Sufficient amount of gas that has 4.0 MJ/m3N HHV was evolved so that the dual-fueled diesel engine could be driven. The main components of the evolved gas were CO and H2. In this study, the gas that could be used as a fuel for the engine was evolved constantly, which indicates that the Micro STAR-MEET system is technically feasible.
Mechanism of the Effect of Dilution With Different Inert Gases on Smoke Point of Propylene Diffusion Flames
Authors: Goh S. F. , Gollahalli S. R.
Published: November 2008

An experimental study to compare the smoking characteristics of diffusion flames of propylene diluted nitrogen, argon, carbon dioxide and helium was performed. The mass flow rate of propylene at smoke point condition, which was defined as the critical fuel mass flow rate (CFMFR), was first determined. Then, CFMFR was divided into ten different fractions for the study of the mechanism of inert gas dilution on smoke point. The mass flow rate of each different inert gas to achieve the smoke point condition was then determined in the same manner. Flame radiation and the visible flame height for all the diluted fuel flames were measured. The axial soot concentration profiles of nitrogen-diluted smoke point flames were also measured using the laser induced incandescence (LII) method for selective conditions. The inert gas dilution study showed two distinct regions (chemical and momentum controlled regions). The study shows the amount diluent needed to achieve smoke point was in the decreasing order of Ar, CO2, N2 and He on mass basis. The analysis of the results showed that the main reason for this phenomenon was the heat sink capability of the gas. Hence, the specific heat of the gas was an important parameter. In general, nitrogen-diluted flames had higher flame length than other inert gas diluted flames. At higher CFMFR, in helium-diluted flames radiation was higher than in other flames.