bluuebunny/crossref_metadata_2025 huggingface dataset:
Model-Based Analysis of Transient Behavior of Large Scale CFB Boilers
Authors: Kettunen Ari , Hyppa¨nen Timo , Kirkinen Ari-Pekka , Maikkola Esa
Published: January 2009

The main objective of this study was to investigate the load change capability and effect of the individual control variables, such as fuel, primary air and secondary air flow rates, on the dynamics of large-scale CFB boilers. The dynamics of the CFB process were examined by dynamic process tests and by simulation studies. A multi-faceted set of transient process tests were performed at a commercial 235 MWe CFB unit. Fuel reactivity and interaction between gas flow rates, solid concentration profiles and heat transfer were studied by step changes of the following controllable variables: fuel feed rate, primary air flow rate, secondary air flow rate and primary to secondary air flow ratio. Load change performance was tested using two different types of tests: open and closed loop load changes. A tailored dynamic simulator for the CFB boiler was built and fine-tuned by determining the model parameters and by validating the models of each process component against measured process data of the transient test program. The know-how about the boiler dynamics obtained from the model analysis and the developed CFB simulator were utilized in designing the control systems of three new 262 MWe CFB units, which are now under construction. Further, the simulator was applied for the control system development and transient analysis of the supercritical OTU CFB boiler.
Early Agglomeration Recognition System (EARS)
Authors: Korbee R. , van Ommen J. R. , Lensselink J. , Nijenhuis J. , Kiel J. H. A. , van den Bleek C. M.
Published: January 2009

In fluidised-bed combustion and gasification of biomass and waste, agglomeration of bed/ash particles is a major problem area. This paper deals with a new method for monitoring and controlling fluidised-bed hydrodynamics, which enables the recognition of agglomeration in an early stage and provides control measures to prevent further agglomeration and defluidisation. The method, named Early Agglomeration Recognition System (EARS), is based on recognising significant differences between reference time-series of pressure fluctuations and successive time-series measured during prolonged plant operation. The early recognition provides a time interval for taking dedicated actions to counteract the agglomeration. EARS thus can be a tool helping plant operators in preventing agglomeration induced plant shutdowns and minimising bed material make-up and residue production. Results are presented of small-scale experiments showing the effectiveness and selectivity of the early agglomeration recognition. Subsequently, the development of control strategies is discussed.
A Review of Hydrogen Production Technologies
Authors: Goswami D. Yogi , Mirabal Samantha T. , Goel Nitin , Ingley H. A.
Published: January 2009

This paper describes an overview of the present status of the conventional hydrogen production technologies and some of the recent developments in the production of hydrogen using solar energy resources. It was found that conversion of fossil fuels and biomass, electrolysis of water using solar and wind energy, and direct solar conversion by thermochemical means are some of the most significant methods of H2 production. The technological status and economic analysis for commercial and near commercial technologies using renewable energy sources such as electrolysis using PV and solar thermal power, photochemical and photoelectrochemical hydrogen production, direct thermal decomposition of water, thermochemical cycles, and biological hydrogen production are outlined. Although fossil fuels are currently the least expensive and most widely used sources of hydrogen production, it is argued from an economic analysis that renewable sources of hydrogen are the most promising options for the future. Further, solar hydrogen becomes a storable fuel that is produced from this non-storable and intermittent source of energy.
Membraneless Fuel Cell Based on Laminar Flow
Authors: Choban Eric R. , Waszczuk Piotr , Markoski Larry J. , Wieckowski Andrzej , Kenis Paul J. A.
Published: January 2009

An increasing societal demand for a wide range of small, often portable devices that can operate for an extended period of time without recharging has resulted in a surge of research in micropower sources. Most efforts in this area focus on downscaling of existing fuel cell technology such as the well-known proton exchange membrane (PEM) fuel cells. Here we study a novel concept for fuel cells: the use of laminar flow instead of a physical barrier such as a PEM to separate the fuel and oxidant streams. Laminar flow, i.e. low Reynolds number flow, is a property of fluid flow at the microscale: one or more liquid streams that are brought together under low Reynolds number conditions flow in parallel and contact with each other without turbulent mixing. Mass transport transverse to the direction of flow takes place by diffusion only. In our laminar flow-based fuel cell a fuel-containing stream and an oxidant-containing stream are brought together in laminar flow conditions with the electrodes placed on opposite walls within the channel. In un-optimized fuel cell configurations, current densities as high as 10 mA/cm2 are obtained at room temperature using different fuels such as methanol or formic acid vs. oxygen saturated solvents or other oxidants.
Hydrogen Production Via the Solar Thermal Decarbonization of Fossil Fuels
Authors: v. Zedtwitz P. , Hirsch D. , Steinfeld A.
Published: January 2009

Two hybrid solar/fossil-fuel endothermic processes, in which fossil fuels are used exclusively as the chemical source for H2 production, and solar energy as the source of high temperature process heat, are considered: 1) the solar thermal decomposition; and 2) the solar steam gasification/reforming. These processes offer viable and efficient routes for fossil fuel decarbonization and CO2 avoidance. The advantages of the solar-driven process are three-folded: a) the discharge of pollutants is avoided; b) the gaseous products are not contaminated; and c) the calorific value of the fuel is upgraded.
Tracking Systems Evaluation for the “Hybrid Lighting System”
Authors: Beshears D. L. , Capps G. J. , Earl D. D. , Jordan J. K. , Maxey L. C. , Muhs J. D. , Leonard T. M.
Published: January 2009

As part of the design and development effort for the “Hybrid Lighting System,” Oak Ridge National Laboratory (ORNL) scientists have evaluated two potential candidate-tracking systems for the solar collector. The first system, the WattSun Solar Tracker, built by Array Technologies, utilizes a patented, closed loop, optical sun sensor to sense the sun’s position and track it. The second tracking system, SolarTrak Controller, built by Enhancement Electronics, Inc., is a micro controller-based tracking system. The SolarTrak micro controller-based Tracker’s sun position is determined by computing the celestial bearing of the sun with respect to the earth using the local time, date, latitude, longitude and time zone rather than sensing the relative bearing of the sun with optical receptors. This system connects directly to the mechanical system hardware supplied by Array Technologies. Both the WattSun Solar Tracker and the SolarTrak Controller were mounted on the prototype “Hybrid Lighting” mechanical system (array) hardware. A simple switch allowed independent testing of each system. Upon completion of the evaluation of the two systems we found the WattSun Solar Tracker controller to be unacceptable for use with our prototype hybrid lighting system. The SolarTrak Controller has performed well to date and provides suitable tracking accuracy for use with our prototype “Hybrid Lighting System”. After a six-month evaluation period at ORNL, the first prototype “Hybrid Lighting System” was installed at Ohio University as part of an “Enhanced Practical Photosynthetic CO2 Mitigation.” This document will highlight the results of the tracker investigation and outline the remaining issues to be addressed, to provide a suitable tracking system for our “Hybrid Lighting” collector.
Changing Waste-to-Energy in Nashville, Tennessee
Authors: Gershman Harvey W. , Seader David L.
Published: January 2009

For almost 30 years, the Metropolitan Government of Nashville and Davidson County has been relying on one of the more innovative approaches to waste management. Since the early 1970s, the now 1,000 tons per day WTE facility has been the primary energy source for supplying steam and chilled water for a downtown district energy system serving some 39 buildings. A recent review of alternatives has resulted in Metro deciding to close the facility and replace it with a more traditional district energy supply system and at the same time re-engineer its solid waste management programs to include more efficient collection and recycling programs. This paper will present the planning process and analysis that were done; describe the key factors that led to Metro Nashville’s decisions; detail the procurement and development process that has been initiated; and outline the timetable for implementing the decided upon changes. The authors believe this case study will provide insights for other WTE projects that from time to time struggle with peaceful co-existence with other elements of integrated solid waste management. The authors have been serving as advisors to Metro throughout this process. Mr. Gershman has recently been designated by Metro as its overall Project Manager for its District Energy System.
A Waste-to-Energy Power Plant With CO2 Sequestration
Authors: Klein Alexander , Zhang Hanwei , Themelis Nickolas J.
Published: January 2009

This paper assesses the technical and economic feasibility of a novel idea: Reducing the emission of carbon dioxide, the greenhouse gas contributing to global warming, by combusting solid wastes with industrial oxygen mixed with recirculated flue gas. The process gas, consisting mostly of carbon dioxide, would be compressed and used in Enhanced Oil Recovery (EOR) projects. By using municipal and other organic wastes that are currently landfilled as a fuel and sequestering the carbon dioxide product of combustion underground, such a process would provide the maximum environmental advantages possible, by producing electricity renewably without emitting greenhouse gases. The results of this preliminary analysis indicate that this may be a good opportunity to reduce carbon emissions at a lower cost than other methods of carbon sequestration.
Development of High Strength Line Pipe for Sour Service and Full Ring Evaluation in Sour Environment
Authors: Takeuchi Izumi , Kushida Takahiro , Okaguchi Shuji , Yamamoto Akio , Miura Mitsuru
Published: January 2009

To establish mass production technology of high strength line pipe up to API-X70 grade for sour service, the HIC (Hydrogen Induced Cracking) phenomena in line pipe has been carefully examined. The micro-segregation zone originated at final solidification front, which has MnS inclusion and hard phase, was identified as the location of the initiation site of HIC. The proper procedures of Ca treatment to eliminate elongated MnS and TMCP application to reduce maximum hardness have proved to increase the HIC resistance in such segregation zone. In addition to the standard HIC test, full ring test under applied stress was conducted to assure the performance of high strength line pipe in sour service. The clean steel in mass production, which has enough HIC resistance, was attained for high strength line pipe up to API-X70.
Study of “Re-Melt” Temper Bead and Polarity Effects on Porosity in the Under Freshwater Wet Welds
Authors: Pessoa Ezequiel C. P. , Bracarense Alexandre Q. , Liu Stephen , Peres Faustino
Published: January 2009

The objective of this work was to discuss the influence of electrode polarity on bead-on-plate (BOP) welds and re-melt temper bead on the pores behavior in the weld bead section of bead-on-grove (BOG) and bead-on-bead (BOB) welds. The welds were made with E6013 electrode at 50 and 100 meters of water depth. Researchers recommend the use of direct current electrode negative DCEN for wet welding. The justifications are to prevent electrode holder electrolytic corrosion and performance improvement. On the other side, some researchers said that no significant variations should be expected while another researcher affirms that depending on the region (Mexican Golf or North Sea) where the welding will be performed, inverse polarity DCEP produces better results. In this work, a gravity feed welding system was used in a hyperbaric chamber with 200 m pressure capability to simulate the wet welds. Visual analysis, arc stability, porosity and pores location in the weld metal enable to evaluate the polarity influence. The results showed significant differences between the two polarities. DCEP produced better bead appearance and higher arc stability than DCEN. Consequently it presented less porosity and best porosity location than DCEN. Additionally, it is was observe that in multi-pass welds (BOG and BOP) the weld bead made previously is partially “re-melted” by the following bead and the pores were in this region were removed or significantly reduced. It is believed then that pores position in the weld section is important information in such welds.
The Nonlinear Interaction and Resonance of Steep Long-Crested Bichromatic Surface Waves in a Numerical Wave Tank
Authors: Baddour R. E. , Parsons W.
Published: January 2009

We are studying numerically the problem of generation and propagation of long-crested gravity waves in a tank containing an incompressible inviscid homogeneous fluid initially at rest with a horizontal free surface of finite extent and of infinite depth. A non-orthogonal curvilinear coordinate system, which follows the free surface is constructed which gives a realistic “continuity condition”, since it tracks the entire fluid domain at all times. A depth profile is assumed and employed to perform a waveform relaxation algorithm to decouple the discrete Laplacian along dimensional lines, thereby reducing its computation over this total fluid domain. In addition, the full nonlinear kinematic and dynamic free surface conditions are utilized in the algorithm. A bichromatic deterministic wave maker using a Dirichlet type boundary condition and a suitably tuned numerical beach is utilized. This paper pays special attention to satisfying the full nonlinear free surface conditions and presents the nonlinear interaction of the higher order components, especially near resonance.
Computational Fluid Dynamics Applied on an Autonomous Underwater Vehicle
Authors: Fuglestad Arnt-Lennard , Grahl-Madsen Mads
Published: January 2009

The present paper report on a comparison between experimental obtained data for the drag force acting on a model prototype of the HUGIN 3000 and data obtained from a Computer Aided Analysis of the drag force carried out by CFD (Computational Fluid Dynamics). The HUGIN 3000 was developed in the nineties, by Kongsberg Maritime and FFI (Norwegian Defence Research Establishment). The experimental results in this paper, origins from a model test carried out by Marintek. The range of Reynolds number for both the experimental data and the computational results is 2.707×106 to 1.146×107. The agreement between the experimental data and the computed results is good. Particularly for the highest Reynolds numbers, the prediction of drag force by CFD seems to be remarkable good.
Characterization of the Dynamic Loads Between Spar Top-Tensioned Riser Buoyancy Cans and Hull: Horn Mountain Field Data Measurements and Predictions
Authors: Karayaka Metin , Steen Atle , Shilling Roy , Edwards Rod
Published: January 2009

The Buoyancy Can Riser Tensioner (BCRT) systems are designed to provide tension to Top-Tensioned Risers (TTRs). BCRT systems do not transfer the riser weight to the floater and they minimize the interaction between the floating platform and the riser system. For deepwater field developments, this attractive feature allows efficient design of the floaters as well as the riser systems. Although, the vertical riser load is not transferred to the hull, the BCRT system makes lateral contact with the hull at several locations. During the past 3 years, analytical models have been developed to characterize mechanics of the contact between two large floating bodies (buoyancy can and hull) and compliant guide hardware has been developed. Placement of a compliant guide between the hull and the BCRT has become the current practice for design of Spar floaters. The initial development of the analytical models and the compliant guide hardware coincided with the Horn Mountain project. The project team placed extensive instrumentation on the hull and compliant guides with a vision to confirm robustness of the guides and to calibrate analytical models used during the design phase. This paper presents a summary of the data collected on the performance of the Spar hull, compliant guides, and the riser systems for storms up to 25 ft of significant wave height. Analytical methods and predictions are presented to characterize the dynamic interaction between the BCRT system and Spar hull.
High Holding Power Torpedo Pile: Results for the First Long Term Application
Authors: de Araujo Jairo Bastos , Machado Roge´rio Diniz , de Medeiros Junior Cipriano Jose
Published: January 2009

Petrobras developed a new kind of anchoring device known as Torpedo. This is a steel pile of appropriate weight and shape that is launched in a free fall procedure to be used as fixed anchoring point by any type of floating unit. There are two Torpedoes, T-43 and T-98 weighing 43 and 98 metric tons respectively. On October 2002 T-43 was tested offshore Brazil in Campos Basin. The successful results approved and certified by Bureau Veritas, and the need for a feasible anchoring system for new Petrobras Units in deep water fields of Campos Basin led to the development of a Torpedo with High Holding Power. Petrobras FPSO P-50, a VLCC that is being converted with a spread-mooring configuration will be installed in Albacora Leste field in the second semester of 2004. Its mooring analysis showed that the required holding power for the mooring system would be very high. Drag embedment anchors option would require four big Anchor Handling Vessels for anchor tensioning operations at 1400 m water depth. For this purpose T-98 was designed and its field tests were completed in April 2003. This paper discusses T-98 design, building, tests and ABS certification for FPSO P-50.
BEM Modeling of Viscous Motion of Surface Water Waves
Authors: Jamali Mirmosadegh
Published: January 2009

This study is concerned with numerical modeling of viscous surface wave motion using boundary element method (BEM). The equations of motion for thin boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the surface wave motion characteristics including the decay rate. The technique is presented for a standing surface wave motion. The extension to other free surface problems is discussed.
Sensitivity of Mooring Line Pretension in the Design Cycle for Floating Caissons
Authors: Mukkamala Adinarayana , Chakrabarti Partha , Chakrabarti Subrata K.
Published: January 2009

The new parallel Tacoma Narrows Bridge being constructed by Tacoma Narrows Constructors will be mounted on two towers and these towers in turn will be supported by reinforced concrete caissons referred to as East Caisson (Tacoma side) and West Caisson (Gig Harbor side). Each Caisson is towed to the location and several stages of construction will take place at the actual site. During construction, the floating caissons will be moored in place to hold it against the flood and ebb currents in the Narrows. During the mooring system design, a desired pretension is established for the lines at each draft. However, due to practical limitations in the field some variations to this design pretension value may be expected. It is important to study the effect of this variation on the overall performance of the mooring system. In this paper, the sensitivity of the mooring line pretension on the overall performance of the mooring system for the above caisson is presented. During this study, all the variables that affect the mooring system design such as mooring system layout, mooring line makeup, anchor positions, fairlead departure angles, and fairlead locations are kept constant. The only variable changed is the pretension of the mooring lines. Two approaches for defining the variations in the pretension have been studied in this paper. In the first approach, the pretension is changed in a systematic way (predicted approach). In the second method the pretension is changed randomly. The latter is considered more likely to occur in the field for this type of complex mooring system. Both sets of results are presented for some selected drafts attained by the caisson during its construction. The difference in the results from the two methods is discussed.
Riser-Soil Interaction: Local Dynamics at TDP and a Discussion on the Eigenvalue Problem
Authors: Pesce C. P. , Martins C. A.
Published: January 2009

The eigenvalue problem of risers is of outmost importance, particularly if vortex-induced vibration (VIV) is concerned. Design procedures rely on the determination of eigenvalues and eigenmodes. Natural frequencies are not too sensitive to the proper consideration of boundary condition, within a certain extent where dynamics at the Touch down Area (TDA) may be modeled as dominated by the suspended part dynamics. Nevertheless, eigenmodes may be strongly affected in this region, as, strictly speaking, this is a nonlinear one-sided (contact type) boundary condition. Actually, we should consider a nonlinear eigenvalue problem. Locally, at TDA, riser flexural rigidity and soil interaction play important roles, affecting the dynamic curvature. Extending and jointing together former analytical solutions on TDP dynamics and on the eigenvalue problem, obtained through asymptotic and perturbation methods, the present work critically address soil and bending stiffness effects a little further.
Analysis of the Fatigue Damage on the Offshore Wind Turbines Exposed to Wind and Wave Loads Within the Typhoon Area
Authors: Yamashita Atsushi , Sekita Kinji
Published: January 2009

For the design of offshore wind turbines exposed to wind and wave loads, the method of combining the wind load and the wave load is significantly important to properly calculate the maximum stresses and deflections of the towers and the foundations1). Similarly, for the analysis of the fatigue damage critical to the structural life, the influences of combined wind and wave loads have not been clearly verified. In this paper fatigue damage at the time of typhoon passing is analyzed using actually recorded data, though intrinsically long-term data more than 10years should be used to properly evaluate the fatigue damage. This paper concludes that the fatigue damage of the tower caused by the wave load is not substantial and, thus, the fatigue damage by the combined wind and wave load is only 2–3% larger than the simple addition of the independent fatigue damages by the wind and the wave loads. The fatigue damage of the tower top, which is required to reduce the diameter in order to minimize the aerodynamic confliction with blades, is larger than that of the tower bottom. The fatigue damage at the foundation by the combined wind and wave load is 25% larger than the simple addition of the wind and wave damages, as the foundation is directly exposed to the wave load. For the foundation, the proper structural section can be designed in order to improve the structural performance against fatigue.
Calculation of Indirect Losses for the Risk Analysis of an Offshore Oil Complex in Mexico
Authors: De Leo´n David , Orgega Ce´sar
Published: January 2009

Indirect losses result from the economical disruption after a catastrophic event destroys most of the production facilities of a certain industry, as a consequence other economic sectors may be affected. The magnitude of these losses depends on importance of the economic links between the sectors and on the elapsed time before all the economical activities of all sectors are restarted. The model is adapted after the Leontief Input-Output representation and actual figures of the Mexican economy are used to estimate the level of the economical disruption that would occur by assuming that a hurricane provokes the collapse of an oil complex in Mexico. This calculation may be used to generate redundancy measures capable to mitigate the risk exposure of the national economy regarding the potential occurrence of powerful hurricanes on the offshore oil production area of Mexico.
Tank Sloshing Interaction With Elastic Support Structure
Authors: Frandsen Jannette B.
Published: January 2009

A fully nonlinear 2-D σ-transformed finite difference solver has been developed based on inviscid flow equations in rectangular tanks. The fluid equations are coupled to an elastic support structure. Sloshing motion are simulated during structural vibration cycles at and outside resonance. The wave tank acts as a Tuned Liquid Damper (TLD). The TLD response is highly nonlinear due to the liquid sloshing. The solver is valid at any water depth except for small depth when shallow water waves and viscous effects would become important. Results of liquid sloshing induced by horizontal base excitations are presented for small to steep non-breaking waves. The effectiveness of the TLD is discussed through predictions of coupling frequencies of the tank-structural system for different tank sizes and mass ratios between fluid and structure. Good agreement is achieved between numerical model and first-order theory. It was found that the system response is extremely sensitive to small changes in forcing frequency. Furthermore, the solver removes the need for free-surface smoothing for the cases considered herein. The numerical model provides a quick and accurate way of determining system eigenfrequencies which can be hard to identify and interpret in physical experiments. Therefore the numerical solver could serve as a valuable guidance to physical experiments. The present studies can easily be expanded to include multiple wave tanks to investigate tank interaction effects, and thus cover suppression of a wider range of frequencies.
Dynamic Analysis of Long Floating Structures in Waves
Authors: Morris Eric , Allyn Norman , Isaacson Michael
Published: January 2009

This paper describes a frequency domain dynamic analysis technique for calculating the response of long floating structures in waves. Due to the large dimensions of the structure, it is necessary to account for the correlation of wave forces along the structure length to accurately calculate the response. The sea surface is therefore modeled as short-crested and is described by a directional wave spectrum. The dynamic analysis technique uses a superposition principle in which the short-crested sea is composed of numerous harmonic wave components with different frequencies and directions of propagation and amplitudes calculated from the directional wave spectrum. Hydrodynamic coefficients are calculated using a 2-dimensional diffraction program. The structure is modeled using beam elements in the ANSYS finite element program and moorings are represented using spring elements. The response of the structure to each wave component is calculated in a series of harmonic analyses. Spectral analysis is used to calculate the variance of the responses in a given storm event. The responses of interest for a given exceedence probability are then determined. The covariance of the responses is calculated and coincident response combinations are produced based on the assumption that the responses have a multi-variate normal distribution. The magnitude of coincident responses is often of interest in structural design. For example, a member subject to bi-axial bending could be designed to have excess resistance if the maximum value of the orthogonal bending moments obtained from a dynamic analysis is used rather than the coincident bending moments.
SPH Simulations of Floating Bodies in Waves
Authors: Doring Mathieu , Oger Guillaume , Alessandrini Bertrand , Ferrant Pierre
Published: January 2009

Water entry of a solid through a free surface is of interest in ship hydrodynamics applications, namely to study ships behaviour in slamming cases for instance. The study presented here deals with the introduction of a new method based on SPH, and aiming at an accurate numerical prediction of the free motion of a body in a free surface. The validation case exposed here is the water entry of a massive wedge, and comparisons with experimental data are provided. Then simulations involving a box and a pierced box in interaction with waves illustrate the flexibility of the method.
Fatigue Performance of Reeled Risers
Authors: Netto Theodoro A. , Lourenc¸o Marcelo Igor , Botto Adriana
Published: January 2009

One of the most effective installation methods of metallic risers is the reel-lay process, in which pipe segments are welded onshore and subsequently bent over a cylindrical rigid surface (reel) in a laying vessel. During installation, the line is unreeled, straightened, and then laid into the sea under tension. In this process, material properties change and eventual weld defects may increase, thus reducing the fatigue life of these joints under operational loads. Therefore, welded joints must be manufactured based on strict weld acceptance criteria. These criteria shall guarantee reliable standards regarding the fatigue life of the joints while not impairing the feasibility of weld manufacture (high cost). In this work, the reeling process is initially simulated through a nonlinear finite element model that incorporates weld defects. The results are then used as guidelines to experimentally obtain fracture mechanics parameters of typical weld and base materials under prestrained conditions. The fatigue life of as-welded and reeled joints with different defects (lack of fusion and lack of penetration) are subsequently estimated via a finite element model that accounts for the changes in the material properties due to pre-straining. The results are compared and used to suggest guidelines to the design of reeled steel catenary risers.
A Decade of Progress in Underwater Wet Welding Using the SMAW Process (1990-2003)
Authors: Liu Stephen
Published: January 2009

It is well established that underwater wet welding (UWW) offers significant cost savings over other repair techniques for submerged structures such as petroleum production platforms, ships, and piers. Due to the deleterious effect of increased pressure on weld quality, innovative consumables are required for the production of quality wet welds. Manganese was added to the electrode coating to replenish its loss from the weld pool. Titanium and boron were added to control the molten metal oxygen potential and refine the as-solidified and reheated weld metal microstructure. Rare-earth metals (REM) were added to control the weld metal oxygen content. Finally, weld metal nickel content was optimized to improve impact toughness. Selected results of these approaches are presented in this work. These recent developments clearly demonstrate that it is possible to achieve significant progresses in wet welding using shielded metal arc (SMA) consumables, if these are designed following sound metallurgical principles.
Accuracy Effects of Low Frequency Wave Loads on Ships Offshore to LNG Marine Terminal Design
Authors: Holboke Monica J. , Grant Robert G.
Published: January 2009

This paper presents the results of a two-body analysis for a moored ship sheltered by a breakwater in shallow water with and without free surface forcing in the low frequency wave load calculation. The low frequency wave loads are determined by second order interactions from the first order. The free surface forcing term arises from the free surface boundary condition, which is trivial to first order but is not at second order. We demonstrate in the frequency domain the importance of this term in a two-body analysis. Additionally, we show how inaccurate calculations of the off-diagonal terms of the Quadratic Transfer Function can translate to over or under prediction of low frequency wave loads on moored ships sheltered by breakwaters in shallow water. Low frequency wave load accuracy has direct consequence for LNG marine terminal design. Generally, LNG marine terminals are sited in sheltered harbors, however increasingly they are being proposed in offshore locations where they will require protection from persistent waves and swells. Since breakwaters typically cost twice as much as the rest of the marine facilities, it is important to optimize their size, orientation and location. In a previous paper we described this optimization process [1], which identified a key step to be the transforming of waves just offshore the breakwater into wave loads on the moored ships. The ability to do this step accurately is of critical importance because if the loads are too large, the breakwater will be larger and more expensive than necessary and if the loads are too small, the terminal will experience excessive downtime and loss of revenue.
Nonlinear Dynamic Behavior of Fixed Jacket-Type Offshore Platforms Subjected to Simultaneously Acting Wave and Earthquake Loads
Authors: Etemad A. K. , Gharabaghi A. R. M. , Chenaghlou M. R.
Published: January 2009

The nonlinear dynamic response of jacket-type offshore platform (which has been installed in Persian Gulf) under simultaneously wave and earthquake loads is conducted. The interaction between soil and piles is modeled by Konagai-Nogami model. The structure is modeled by finite element method. The analyses include models with the longitudinal component of earthquake and wave in the same direction and in different directions. The results indicate that when the longitudinal component of earthquake and wave are in the same direction, wave may reduce the response of studied platform and when they are in different directions, in some cases there is an increase in the response of platform.
Collapse Testing of Thermally Treated Line Pipe for Ultra-Deepwater Applications
Authors: DeGeer Duane , Marewski Ulrich , Hillenbrand Hans-Georg , Weber Bernadette , Crawford Michael
Published: January 2009

The Mardi Gras Transportation System is an ultra deepwater pipeline system that will support a number of prospects in the Gulf of Mexico, including the Holstein, Mad Dog, Atlantis and Thunder Horse field developments. To support the design of the deepest portions of the Mardi Gras Transportation System, a full-scale collapse test program was performed, and was aimed at measuring, quantifying and documenting the increase in pipe strength and collapse resistance as a result of the thermal induction heat treatment effect (thermal aging) from the pipe coating process. This paper presents a summary of the test program and the results of all testing performed on Europipe pipe samples. Two collapse tests and five pressure + bend tests were performed on as-received and thermally treated pipe specimens. These specimens were API Grade X65 line pipe, with an outer diameter of 28 inches (711 mm) and a wall thickness of 1.5 inches (38 mm). Geometric measurements, material coupon tests, and ring expansion tests were also performed. The coupon tests also included specimens taken from the original plate samples from which the full-scale pipes were manufactured, providing data on the effect of the UOE process on circumferential compressive strength. For the thermally treated pipe specimens, thermal treatment was performed by running the specimens through a pipe coating mill, simulating a fusion bond epoxy coating operation. This process involved preheating specimens to 240°C using induction heating. Subsequent material and full-scale tests on these specimens resulted in an increase of cross-sectional residual stresses by almost threefold, an increase of the circumferential compressive yield strength of the pipe by approximately 23% and an increase of pipe collapse strength by approximately 28%. The results of these tests are also compared to the collapse and collapse + bending equations found in the DNV (DNV OSF101) and API (API RP 1111) offshore pipeline codes, as well as the collapse equations found in API Bul 5C3 for downhole casing applications. In particular, it has been shown that the thermal treatment of the UOE pipe specimens can increase the DNV fabrication factor from 0.85 to 1.0.
Ocean Wave Measurements From ENVISAT ASAR Data Using a Parametric Inversion Scheme
Authors: Schulz-Stellenfleth J. , Lehner S. , Hoja D. , Nieto-Borge J. C.
Published: January 2009

A parametric algorithm is presented to estimate two-dimensional ocean wave spectra from ENVISAT ASAR wave mode data on a global scale. The retrieval scheme makes use of prior information taken from numerical wave models. The Partition Rescale and Shift algorithm (PARSA) is based on a partitioning technique, which splits an a priori wave spectrum into its wave system components. Integral parameters of these systems, such as mean direction, mean wavelength, waveheight, and directional spreading are then adjusted iteratively to improve the consistency with the SAR observation. The method takes into account the full nonlinear SAR imaging process and uses a maximum a posteriori approach, which is based on statistical model quantifying the errors of the SAR imaging model, the SAR measurement, and the prior wave spectra. The method is applied to a global data set of ENVISAT ASAR data acquired during the CAL/VAL phase. The benefit of cross spectra compared to conventional symmetric image spectra is demonstrated.
Remote Condition Monitoring for Railway Point Machine
Authors: Zhou F. B. , Duta M. D. , Henry M. P. , Baker S. , Burton C.
Published: January 2009

This paper presents the research work carried out at Oxford University on condition monitoring of railway point machines. The developed condition monitoring system includes a variety of sensors for acquiring trackside data related to different parameters. Key events to be logged include time stamping of points operation, opening and closing of case cover associated with a points machine, insertion and removal of a hand-crank, loss of supply current and the passage of a train. The system also has built-in Web functions. This allows a remote operator using Internet Explorer to observe the condition of the point machine at any time, while the acquired data can be downloaded automatically for offline analysis, providing more detailed information on the health condition of the monitored point machine. A short daily condition report message can also be sent to relevant staff via email. At last the experience are reported on the four trackside installed systems.
The Development of a Rail Passenger Coach Car Crush Zone
Authors: Mayville Ronald A. , Johnson Kent N. , Stringfellow Richard G. , Tyrell David C.
Published: January 2009

This paper presents information on the design of a rail vehicle crush zone for better occupant protection. The overall design requirements and characteristics are described and the configuration for the various structural subsystems is presented. The paper also includes information on full-scale component tests carried out to support the development of the design, particularly for the primary energy absorbers. Comparisons between test and finite element analysis are presented and there is a discussion of how the test results have affected the design.
Natural Convection From a Horizontal Tube Heat Exchanger Immersed in a Tilted Enclosure
Authors: Liu Wei , Davidson Jane H. , Kulacki F. A. , Mantell Susan C.
Published: January 2009

Heat transfer rates of a single horizontal tube immersed in a water-filled enclosure tilted at 30 degrees are measured. The results serve as a baseline case for a solar water heating system with a heat exchanger immersed in an integral collector storage. Experiments are conducted for isothermal and stratified enclosures with both adiabatic and uniform heat flux boundary conditions. Natural convection flow in the enclosure is interpreted from measured water temperature distributions. Formation of an appropriate temperature difference that drives natural convection is determined. Correlations for the overall heat transfer coefficient in terms of the Nusselt and Rayleigh numbers are reduced to the form NuD = 0.675RaD0.25 for 106 ≤ RaD ≤ 108.
Development of a Grid-Tied Inverter Test Protocol for Non-Stimulated Conditions
Authors: Lynn Kevin , Farhi Brian , Wilson William
Published: January 2009

The lack of consistently high performance from inverters has created numerous issues in the widespread application and confidence in grid-tied photovoltaic systems. Additionally, the lack of a metric by which inverter manufacturers can evaluate their products presents a challenge to manufacturers by not allowing them to distinguish their products from those of their competitor, and to users since there is no way of comparing seemingly-similar models. This problem is further compounded by the dearth of inverters that have high performance and reliability [1]. This document is the first draft of a test protocol under development at the Florida Solar Energy Center to assist in this area. A need for such a test protocol has been recognized nationally, and it is hoped that this document may provide a foundation for future test procedures while providing significant and reasonable findings in the interim.
The Influence of Direct Normal Irradiance Variation on the Optimal Parabolic Trough Field Size: A Problem Solved With Technical and Economical Simulations
Authors: Quaschning Volker , Kistner Rainer , Ortmanns Winfried
Published: January 2009

One of the main problems when designing a solar thermal power plant is to find the optimal parabolic trough field size. Errors made in this context can easily lead into a financial disaster. Simulation tools that handle all aspects of a power plant (technical as well as economical) treat such economical problems as a whole and can be very helpful during the design process. However, even the smartest simulation tool depends significantly on the input parameters, such as the solar irradiance. As a result of the given considerations a new method for estimating the solar field size as a function of the solar irradiance is proposed. Additionally, this paper demonstrates a path to simulate the complexity of a parabolic trough power plant.
Deterministic Contact Model of a Rough Surface Against a Flat-Layered Surface
Authors: Pasaribu H. R. , Schipper D. J.
Published: January 2009

The effective mechanical properties of a layered surface vary as a function of indentation depth and the values of these properties range between the value of the layer itself and of the substrate. In this paper, a layered surface is modelled like a solid that has effective mechanical properties as a function of indentation depth by assuming that the layer is perfectly bounded to the substrate. The normal load as a function of indentation depth of sphere pressed against a flat layered surface is calculated using this model and is in agreement with the experimental results published by El-Sherbiney (1975), El-Shafei et al. (1983), Tang & Arnell (1999) and Michler & Blank (2001). A deterministic contact model of a rough surface against a flat layered surface is developed by representing a rough surface as an array of spherically shaped asperities with different radii and heights (not necessarily Gaussian distributed). Once the data of radius and height of every single asperity is obtained, one can calculate the number of asperities in contact, the real contact area and the load carried by the asperities as a function of the separation.
A Modified Turbulence Model for Low Reynolds Numbers: Applications to Hydrostatic Seals
Authors: Brunetie`re Noe¨l
Published: January 2009

The order of magnitude of the Reynolds number in thin lubricant films varies between 102 and 105. For Reynolds numbers higher than 103, the fluid flow becomes turbulent. It is well accepted in lubrication to use a zero equation turbulence model of the type developed by Constantinescu [1] or Elrod, Ng and Pan [2–4] or Hirs [5]. The Elrod and Ng approach is certainly the most efficient for combined pressure and shear flows where the Reynolds number is above 104. This paper proposes a modification of the Elrod and Ng model in order to ensure a good correlation with experimental data obtained with low Reynolds number turbulent flows. The present model, coupled with a scaling factor for taking into account the transition to turbulence, is therefore accurate for all the typical Reynolds number values recorded in lubrication. The model is then applied to hydrostatic noncontacting face seals, which usually operate at Reynolds numbers varying from 103 to 104. The accuracy of the model is shown for this particular application of radial rotating flow. A special study is made of the transition to turbulence. The results are compared with those obtained using the initial Elrod and Ng model. The axial stiffness coefficient and the stability threshold are significantly affected by the turbulence model.
Effect of Laser Glazing and Laser Shock Peening on Tribological Performance of 1080 Carbon Steel
Authors: Aldajah Saud , Ajayi Oyelayo O. , Fenske George R. , Reed Claude B. , Xu Zhiyue
Published: January 2009

High-power laser surface treatments in the form of glazing, shock peening, cladding, and alloying can significantly affect material tribology. In this paper, effects of laser glazing, laser shock peening, and their combination on the tribological behavior of 1080 carbon steel were investigated. Laser glazing is a process in which a high-power laser beam melts the top layer of the surface, followed by rapid cooling and resolidification. This results in a new surface layer microstructure and properties. Laser shock peening, on the other hand, is a mechanical process in which a laser generates pressure pulses on the surface of the metal, similar to shot peening. Five conditions were evaluated: untreated (baseline), laser shock peened only (PO), laser-glazed only (GO), laser-glazed then shock peened last (GFPL), and laser shock peened then glazed last (PFGL). In pin-on-disc testing, all laser-treated surfaces reduced dry friction, with the GFPL surface having maximum friction reduction of 43%. Under lubricated conditions, all laser-treated surfaces except the PO sample lowered friction. Similarly, all glazed samples reduced wear by a factor of 2–3, while the PO sample did not change wear significantly. These tribological results are associated with changes in the near-surface microstructure and properties.
Effects of Mobile and Chemically Bonded Molecules of Molecularly Thin Lubricant Film on the Vibrational Stability of a Sliding Ball
Authors: Tanaka Kentaro , Kawaguchi Masahiro , Kato Takahisa , Iwamoto Katsumi
Published: January 2009

Lubrication by an extremely thin film has become very important in micro machines, magnetic recording disks and so on. Molecularly thin perfluoropolyether (PFPE) films are considered a good lubricant for these micro devices. When the thickness of the PFPE film is thinned to several nanometers, it is possible to assume that the film consists of mobile and chemically bonded molecules. In this paper, we investigated the role of these molecules from the viewpoint of the vibrational stability of the sliding ball with the disk surface. From experiments by the ball on disk type tribotester, it is found that chemically bonded molecules prevent direct contact between the slider and the disk surface. Furthermore, when mobile molecules exist on bonded molecules, the stability is improved in wide load range.