bluuebunny/crossref_metadata_2025 huggingface dataset:
Combustion of Refinery Residues in a CFB-Combustor: Measurement of Intermediate Species Using FTIR
Authors: Barczus Christian , Henning Bjo¨rn , Scherer Viktor
Published: January 2009

Investigations have been performed to show the feasibility of burning refinery residues (calcined petroleum coke and liquid residues) in a circulating fluidized bed combustor. These experiments were done in a CFBC system with a thermal capacity of 100 kW. The unit has been equipped with an additional dosing system for liquid fuels including a newly developed fuel lance. The pollutant formation characteristics are determined using axial profile measurements at 19 different ports along the combustion chamber. To optimize the combustion process and to minimize gaseous pollutants, several operating parameters of the system are varied independently. These parameters are the primary to secondary air ratio, the global air to fuel ratio, the residence time in the primary zone, the overall temperature of the combustion chamber and the Ca/S ratio. Measurements of the flue gas components O2, CxHy, CO, CO2, H2, NOx, N2O, NH3 and SO2 are performed by standard gas analysing techniques. It is important to note that the system is equipped with a Fourier Transform Infrared Spectrometer (FTIR) to qualitatively and quantitatively determine selected gaseous species which are essential for the formation and consumption of N2O and other pollutants. The gas species measured by FTIR-Spectroscopy are CH4, C2H2, C2H4, C2H6, C3H6 and C3H8. Also the important precursors for the NOx-formation HCN and NH3 are examined with the FTIR-Spectrometer. The investigations demonstrate that (liquid) refinery residues can be burned successfully as a monofuel within the circulating fluidized bed combustor. The emissions of all pollutants detected are at a low level.
A Novel Design and Microfabrication for a Micro PEMFC
Authors: Hsieh Shou-Shing , Kuo Jenn-Kun , Hwang Ching-Fang , Tsai Hwang-Hsiu
Published: January 2009

A novel design and microfabrication were developed for a micro PEM (Proton Exchange Membrane) fuel cell with a cross section of 5cm2 and thickness (for a single cell) of about 800 μm. A new design and fabrication processes were developed for both flow field plate and MEA parts. Air flows were completed in hydrogen fuel cells with low input pressure and low velocity. Performance tests of polarization curves and power density distribution were conducted and discussed.
Fuel Cells vs. Competing Technologies
Authors: Srinivasan Supramanian , Krishnan Lakshmi , Bocarsly Andrew B. , Hsueh Kan-Lin , Lai Chiou-Chu , Peng Alex
Published: January 2009

Investments of over $1 B have been made for Fuel Cell R&D over the past five decades, for space and terrestrial applications; the latter includes military, residential power and heating, transportation and remote and portable power. The types of fuel cells investigated for these applications are PEMFCs (proton exchange membrane fuel cells), AFCs (alkaline fuel cells), DMFCs (direct methanol fuel cells), PAFCs (phosphoric acid fuel cells), MCFCs (molten carbon fuel cells), SOFCs (solid oxide fuel cells). Cell structure, operating principles, and characteristics of each type of fuel cell is briefly compared. The performances of fuel cells vs. competing technologies are analyzed. The key issues are which of these energy conversion systems are technologically advanced and economically favorable and can meet the lifetime, reliability and safety requirements. This paper reviews fuel cells vs. competing technologies in each application category from a scientific and engineering point of view.
An Analysis of Water Management for a PEM Fuel Cell System in Automotive Drive Cycles
Authors: Haraldsson Kristina , Markel Tony , Wipke Keith
Published: January 2009

Low-temperature operation of a Proton Exchange Membrane (PEM) fuel cell system requires humidification of the membrane. The amount of water produced electrochemically within the fuel cell system is directly related to the system power output. In a vehicular application where the power output may vary substantially over time, it is critical that water management be addressed in the fuel cell and vehicle system design. This paper introduces the integration of a detailed fuel cell system model within a hybrid electric vehicle system model. The newly integrated models provide the capability to better understand the impacts of a variety of fuel cell and vehicle design parameters on overall system performance. Ultimately, coupling these models leads to system optimization and increased vehicle efficiency. This paper presents the initial results of a parametric study to quantify the impacts of condenser size and cathode inlet relative humidity on system water balance under realistic drive cycles in a fuel cell hybrid electric sport utility vehicle. The vehicle simulations included operation under both hot and ambient start conditions. The study results demonstrate that ambient start or aggressive drive cycles require larger condensers or water reservoirs to maintain a neutral water balance than either hot start or less aggressive drive cycles.
Innovative Thermal Management of Fuel Cell Power Electronics
Authors: Kelly Kenneth , Vlahinos Andreas , Rodriguez Pablo , Bharathan Desikan
Published: January 2009

Deep at the heart of any fuel cell system lays a crucial component, the power inverter. The design of this crucial component is a challenge for fuel cell systems due to packaging, thermal and electrical constraints. Unless the inverter is adequately and uniformly cooled it will suffer material degradation and premature failure. The search for a thermally viable inverter design is one of many challenges facing the fuel cell industry today. In this research effort several cooling techniques were considered such as pin-finned design, “cook-top” serpentine flow field, a “fish bone” fin design, high thermal conductivity graphite foam, heat pipes and aluminum extrusion with expanded metal turbulator. The pin-finned design techniques were evaluated using computational fluid dynamics. In order to enable design engineers to rapidly generate optimum designs two simplified techniques were introduced using the CFD results. 1) Formulas for computing the film coefficient based on spacing, side and configuration are provided for thermal finite element analysis that includes conduction and convection. This technique is an order of magnitude faster than the CFD analysis. 2) Behavioral modeling, an optimization technique imbedded within a feature based parametric CAD system is utilized to automatically size and build the solid model of the pin-finned design. The designer input is the heat that needs to be rejected and the available space. Behavioral modeling generates the design and plots the temperature distribution.
NASA Climatological Data for Renewable Energy Assessment
Authors: Chandler William S. , Whitlock Charles H. , Stackhouse Paul W.
Published: January 2009

This article presents the latest parameters and delivery methods that provide global solar energy and meteorological resources on the Internet. Over the past several years the number of parameters in the Surface meteorology and Solar Energy Data Set has tripled. The newest parameters include solar geometry, a suite of wind speed and wind direction data, diffuse, direct normal and tilted surface solar irradiance. Requests by users and recommendations by the renewable energy industry have prompted the growth.
Solar Energy Utilization in Externally Fired Humidified Air Turbine System
Authors: Zhao Hongbin , Jin Hongguang , Cai Ruixian
Published: January 2009

In this paper we propose a new system of solar energy power generation with an external fired humidified air turbine (EFHAT). In the EFHAT, the latent heat from the exhausts gas of gas turbine can be utilized to increase ability of humidification of air due to no limitation of dew point temperature with clean humid air. Through absorbing the solar energy, the water from the collector is brought to the saturator to enhance air humidification ability with the latent heat being more utilized in the EFHAT system. Through integration with EFHAT and latent heat utilization based on integration of the fossil and the renewable energy utilization, the performance of the new proposed solar energy utilization system might be superior to traditional solar energy power generation systems. As a result, the thermal efficiency of the solar thermal power generation will be 16∼20%, superior to conventional solar power generation system (generally about 13%); while the latent heat utilization ratio gets about 25∼35%. This will be a new way of solar energy utilization.
Net Energy Metered PV in Hawaii: Experience and Challenges
Authors: Mangelsdorf Marco A.
Published: January 2009

In June 2001, Hawaii became the 35th state in the nation to adopt a net energy metering (NEM) law to promote the installation of small (10 kW and less) renewable energy (RE) grid-connected systems across the Hawaiian Islands. What effect has the availability of this law had on the diffusion of NEM photovoltaic (PV) systems in Hawaii? Given the typical abundant sunshine here coupled with consistently high electric utility rates, NEM should be taking off, yet consumer adoption has been slow. What have been the principal impediments to homeowners and businesses going solar electric? While the relatively small number of NEM PV systems installed to date does not allow for definitive conclusions on the ability of the NEM law to achieve its purpose, this initial evaluation will identify what challenges and obstacles exist and make recommendations to overcome them.
Development and Modification of a Cassegrainian Solar Concentrator for Utilization of Solar Thermal Power
Authors: Stoynov L. A. , Yarlagadda Prasad K. D. V.
Published: January 2009

Almost all life on Earth has been using solar energy in many ways, but when high temperatures are desired, concentration of the incident solar radiation (insolation) becomes necessary. The present work is an attempt to improve and experimentally compare alternative beam delivering and focusing energy systems of a small solar concentrator. The researched solar energy concentrator (SEC) facility consists of modified two mirror Cassegrainian solar concentrator, two-speed sun-tracking manual and automatic control, concentrated insolation transmitting and continuous beam focusing systems. A number of system modifications during the development of the two stage, point focusing type solar concentrator arrangement for solar thermal power utilization have also been explored and are reported in this paper. Some of the experimental testing results obtained using single polymer fiber 14 mm in diameter, a truncated conical concentrator, and auxiliary lens system alternatives, have been compared. In addition, some details about various improvements of the sun-tracking sensor and automatics, beam transmission and continuous focusing capabilities of the SEC facility have been described.
SolTRACE: A New Optical Modeling Tool for Concentrating Solar Optics
Authors: Wendelin Tim
Published: January 2009

SolTRACE, a new optical modeling code developed by researchers at the National Renewable Energy Laboratory (NREL) is currently being used to model solar power optical systems and analyze their performance. Although originally intended for solar optical applications, the code can also be used to model and characterize general optical systems. The creation of the code evolved out of a need to model more complex optical systems than could be modeled with existing tools. In addition, previous codes were based on outdated operating systems that significantly limited data presentation and output capabilities. SolTRACE is written specifically for the Windows® 2000 operating environment. Ray tracing methods coupled with the memory capabilities and the speed of the Windows® 2000 operating environment provide for accurate and rapid results. Output data presentation allows scatter plots, flux maps and performance graphs to be rapidly displayed and saved. SolTRACE has enabled Department of Energy (DOE) SunLab researchers to model and predict the performance of new, complex solar optical designs that previously could not be modeled. This paper describes the code and presents a comparison of SolTRACE results with measured and earlier modeled data.
Astrophysical and Mineralogical Experiments in the DLR Solar Furnace
Authors: Sauerborn M. , Neumann A. , Seboldt W.
Published: January 2009

The DLR Solar Furnace in Cologne is a facility that concentrates direct solar radiation with a concentration factor up to 5200. The energy of such concentrated solar radiation can be used to cause thermal or photochemical effects in the irradiated materials. For astrophysical and mineralogical applications a new vacuum chamber with a specific design and instrumentation for solar experiments was developed and installed at the DLR Solar Furnace. This facility enables testing of small samples under high vacuum conditions. Within a project dealing with chondrule formation (chondrules are parts of meteorites) solid samples were melted by concentrated solar radiation. The aim was to investigate and simulate a fast heating-up (“flash heating”) of the samples and a subsequent solidification by controlled cooling. Another experiment series investigates thermal reduction of samples of metal oxide and of lunar regolith simulant. The goal of this activity is to produce oxygen and eventually also pure metals by pyrolysis. The in-situ production of oxygen and metals on the moon is a key technology for future lunar bases or manned Mars missions. The first solar furnace tests within both projects showed the performance of the new vacuum chamber and the feasibility of the different investigation paths.
Retrofit of WtE Boiler: Case Study on Bonn Plant
Authors: Pe´rilleux Mark , Eeraerts Dirk
Published: January 2009

The implementation of the European-directive requiring a residence time of at least two seconds at a temperature above 850°C (1562°F), the change in waste characteristics, and the pursuit of higher thermal efficiencies has pushed many of the existing WtE plants in Europe to their operational limits. Most existing WtE plants were not designed to operate under these conditions and may require modifications to the combustion system. Within the SEGHERS better technology (SEGHERS) company, the SEGHERS-IBB-Prism was developed to deal with the cause of these problems, which are essentially related to insufficient mixing and burnout of the flue gases in the combustion area. In the Boiler Prism the flue gas flow is divided into two parallel flows prior to entering the first radiant pass of the boiler. This division is achieved by means of a prism shaped construction, which is water-cooled and integrated with the natural circulation system of the boiler. Additional secondary air injection nozzles are fitted in the prism. This technology results in a more uniform flue gas temperature and a complete combustion of the flue gas immediately above the prism. In the Bonn Plant, these improvements in the combustion process resulted in a decrease of the fireside cleaning requirements of more than 50%.
APC Retrofits and Technologies Lower Emissions and Optimize WTE Production
Authors: Linton Robin
Published: January 2009

Air pollution control (APC) systems in waste-to-energy (WTE) plants are facing many of the same challenges that independent power facilities (IPP) have dealt with for years. The most prevalent problems being corrosion and emissions. An IPP plant in the southeastern U.S. illustrates the cause and effect that corrosion played in the plant’s operation, as well as the engineered solution designed to address the issue. The result has performed beyond expectations and lends itself well to the same issues in the WTE plants. The paper also provides information regarding the conversion of the electrostatic precipitator (ESP) to a fabric filter baghouse. By utilizing the existing housing of an ESP, a higher particulate collection efficiency can be achieved at a fraction of the capital cost. Finally, the paper discusses filter changeout to filter bags laminated with highly efficient expanded polytetrafluoroethylene (ePTFE) membrane. This media change addresses the demanding environmental regulations the industry faces, as well as providing benefits to the WTE APC system such as superior cleandown, increased airflows, and extended filter life. The ultimate results of these three technologies can help decrease maintenance time and cost and increase WTE facility production.
How Public Sector Agencies and Governments Responsible for Waste-to-Energy (WTE) Operations Maintain Cost-Effective and Environmentally Sound WTE Operations Through Active Technical, Financial, and Environmental Oversight
Authors: Lehman Andrew T. , Shabat Daniel
Published: January 2009

Whether a given waste-to-energy (WTE) facility is publicly or privately owned and/or operated, and notwithstanding the pluses or minuses of any given Service Agreement or Operations Contract, the public sector can derive great benefit if it establishes a solid understanding of and maintains active oversight role in the technical, financial, and environmental issues associated with WTE project operations. Experience has shown that public sector clients who remain in close touch with the day-to-day operations of these capital intensive operations from the outset also retain a greater measure of influence over the inner workings, as well as the exterior/aesthetic appearances of these capital-intensive waste-processing and disposal facilities. While all parties strive for environmentally sound and safe operations, private sector operators must be concerned with profitability and/or maintaining shareholder value while the public sector entity is more typically focused on ensuring the facility provides reliable disposal services for a heterogeneous wastestream that changes over time, remains a “good corporate neighbor,” and does this at the lowest possible cost to the taxpayers and other facility users.
2nd Year Comparison of Superheater Metal Wastage Rates Utilizing Various Boiler Tube Alloys in a Waste-to-Energy Facility
Authors: Hanson Eric , Turner Mark
Published: January 2009

The SEMASS Resource Recovery Facility (SEMASS) is a processed refuse fuel (PRF) waste-to-energy plant serving Southeastern Massachusetts. The plant consists of three 1000 ton per day boilers that generate steam at 765 F and 650 psig for use in a steam turbine/generator set. Over the past several years there have been a series of plant improvements made in order to achieve compliance with the MACT emission standards. Unfortunately, metal wastage rates due to fire side corrosion of pressure containing components, have increased significantly during this same time period. In an attempt to reduce overall maintenance costs and unscheduled down time due to tube failures, a test of various alloy tube materials was undertaken in 2001 (see NAWTEC#10 paper-1021) in the primary superheater section of boiler #1. The materials tested were SA213-T22 (original spec.), SA213-T22-Heavy Wall, SA213-TP310H, SB-423 Incoloy 825, and Inconel 625 spiral weld overlay of SA213-T22 base material. This paper will summarize the results of the second year of testing including wastage rate tables and annualized costs for the various tube materials.
SafeHull Application on Conversion of Existing Tankers to FPSOs
Authors: Tam Gabriel , Huang Wei
Published: January 2009

The ABS FPI Guide and the associated SH-FPSO software system have been in use for over 3 years in the design classification of FPSO new builds and conversion from existing tankers. This paper provides information regarding the classification process of FPSO conversion in an effort to address the needs of the client. It highlights the two typical conversion processes — the basic Ordinary Conversion and the optional SH(CS) Conversion. The paper focuses on the submittal data required and the structural review process as carried out by the classification society. It also discusses some of the technical perspectives as a result of the experience gained/lessons learned from the reviews which have been performed to date.
Defect Assessments of Pipelines Using Constraint Designed SE(T) Specimens
Authors: Cravero Sebastian , Ruggieri Claudio
Published: January 2009

This work presents a numerical investigation of crack-tip constraint for SE(T) specimens and axially surface cracked pipes using plane-strain, nonlinear computations. The primary objective is to gain some understanding of the potential applicability of constraint designed fracture specimens in defect assessments of pressurized pipelines and cylindrical vessels. The present study builds upon the J-Q approach using plane-strain solutions to characterize effects of constraint on cleavage fracture behavior for fracture specimens and cracked pipes. Under increased loading, each cracked configuration follows a characteristic J-Q trajectory which enables comparison of the corresponding crack-tip driving force. The results provide a strong support to use constraint-designed SE(T) specimens in fracture assessments of pressurized pipes and cylindrical vessels.
Production Facility Choices for Moderate Water Depths
Authors: Ronalds Beverley F.
Published: January 2009

Trends are presented to assist in choosing the optimum oil and gas production system for moderate water depths (less than 500m). Databases of fixed, floating and subsea facilities employed in the North Sea are utilised to outline the distinguishing features between these systems and to demonstrate the key drivers for their selection in different circumstances. These drivers include water depth, well count, oil and gas production rates and tieback lengths.
Hull Forms for Icebreaking Tankers
Authors: Kim Hyun-Soo , Ha Mun-Keun , Ahn Dang , Molyneux David , Chun Ho Hwan
Published: January 2009

The optimum design for an icebreaking tanker will depend on the trade route and the cargo delivery requirements. For example, the hull shape of a ship that spends almost all of its time operating in heavy ice can be optimized for low speed icebreaking conditions. In contrast, a ship that spends a small portion of its time in light ice that has been previously broken and the rest of its time in open water can be optimized for different requirements. The challenge for the designer is complicated by the observation that many ship design features that enhance powering performance in ice are detrimental to open water performance. This paper presents predictions of ship resistance in pack ice, level ice and open water for four tanker designs, which include a conventional hull with no modification for ice at all and three designs proposed for operation in Arctic ice conditions. The predictions of ship performance are based on model experiments carried out in Canada and Korea. The resistance of the four hulls in open water, two concentrations of pack ice and two level ice thicknesses are compared and discussed. Information of this sort is essential for developing the optimum ship design for a particular shipping route, given known profiles of open water, pack ice and level ice.
On the Drift Forces of a Vertical Cylinder in Water of Finite Depth
Authors: Rahman Matiur , Mousavizadegan S. Hossein
Published: January 2009

Analytical solutions for the wave-induced second-order time independent drift forces and moments due to the dynamic and the waterline pressures on a fixed vertical circular cylinder are derived. The results are displayed graphically for a number of depth to radius ratios. An analytical technique is used to determine the first-order velocity potential by considering two regions, namely, interior region and exterior region. We have also demonstrated a numerical solution by a higher order panel method in which the kernel of the integral equation is modified to make it non-singular and amenable to solutions by the Gaussian quadrature formula. The numerical results are found to comply with the analytical solutions.
Free Standing Risers for Extended Ultra Deepwater Tests
Authors: Rodrigues Roberto , Branda˜o Mansano Renato , Del Luchesse Junior Cesar , Edward Roveri Francisco , Barbosa Mauricio
Published: January 2009

Petrobras presently has a significant part of its reserves located in deep and ultra deep waters. To produce this oil economically Petrobras created the well-known research program PROCAP 3000. This paper presents one project being developed under such program, the Extended Test for Deep and Ultra Deepwater. Petrobras has been using early production system and extended test for some years. Since 1998 Petrobras has been testing wells (extended test) with the Seillean FPSO (Floating Production Storage and Offloading). One challenge in this concept is the use of a dynamically positioned (DP) tanker with a rig and a threaded pipe (drill pipe riser) to produce and test wells in deep and ultra deep water. Another challenge is the frequency of changes of location of the FPSO, since the objective of an extended test is to produce for periods of three to twelve months. Therefore the system must have enough flexibility to make the installation and recovery easier. The proposed Itinerant Production and Evaluation Pilot System concept is easy to deploy and demobilize for extended trials. Under certain circumstances, it may even work as an Early Production System. It consists of a free-standing drill pipe riser system connected directly to the Christmas tree at the sea bed and to an air can at the top, which is located around 100 metes below sea surface. A flexible jumper links the air can to an FPSO. To improve production flow rate, an electric submersible pump (ESP) is installed at either downhole or at the top of Christmas tree. The main purpose of the extended test is to collect data, enhancing knowledge of the reservoir through more reliable information. Although attempting to minimize implementation costs, it may present a negative Net Present Value for shorter periods, especially if the value of the information obtained is not included in the calculation. Most of these ideas and concepts are still under study, and some of them will certainly be reassessed, reviewed and possibly improved. Petrobras has been working with some partner companies to develop the conceptual study and assess the system feasibility. This paper presents the main issues involved in this project. The objective of this paper is to summarize a preliminary conceptual design to conduct a feasibility analysis for Petrobras’ Free Standing Drill Pipe Riser (FSDPR).
Vortex-Induced Vibration Current Tank Tests of Two Equal Diameter Cylinders Offset From Tandem
Authors: Allen Don W. , Henning Dean L. , Lee Li
Published: January 2009

Two equal diameter ABS cylinders, offset from tandem, were subjected to uniform and sheared flows in a current tank at subcritical Reynolds numbers. Both tubes were filled with a saltwater solution to produce a specific gravity of 1.38. An accelerometer in each cylinder was used to measure the vortex-induced vibration response, which primarily varied between the third and seventh transverse bending modes. The cylinders were spaced at 3 to 20 diameters in the in-line direction and at 0, 0.5, and 1.0 diameter in the offset direction. Test results indicate that a downstream cylinder, for a pure tandem (no offset) configuration, experiences less vibration than the upstream cylinder when the upstream cylinder rms displacement is larger than about 0.35D. Offsets of 0.5 and 1.0 times the outside diameter produce lower vibration of the downstream cylinder relative to that of the upstream cylinder.
Treatment of Uncertainties in Risk-Based Optimal Design of Marine Structures (Invited Lecture)
Authors: Ang Alfredo H.-S.
Published: January 2009

A systematic procedure for properly treating each of the two broad types of uncertainty, aleatory and epistemic, is proposed for the risk-based design of marine structures, and illustrated with the formulation of optimal design of a typical offshore platform in the Gulf of Mexico. Randomness in the ocean wave height at the offshore site of a platform, and the variabilities of material properties, contribute to the aleatory uncertainty; whereas the epistemic uncertainty includes the imperfections in the modeling and calculations of the structural response and damage estimation. Optimal design is then formulated on the basis of minimum life-cycle cost (LCC), in which additional epistemic uncertainties in the life-cycle cost components are also included. High percentile (90% or 75%) values of the safety index obtained for the optimal design may be appropriate for risk-aversive designs; these values are consistent with current industry standards for the design of important platforms.
Numerical and Experimental Evaluation of the Viscous Damping in a Wellbay
Authors: Maisondieu C. , Kimmoun O. , De Joue¨tte C. , Gentaz L.
Published: January 2009

Flow viscous damping and energy dissipation around the keels in a wellbay are experimentally and numerically investigated. Experiments have been carried out using a U-shape tube. Damping coefficients are evaluated from water elevation measurements. Computations are also performed using two different numerical models under viscous fluid assumption. Comparison of results shows good agreement on both drag coefficients evaluation and velocity fields.
Damping Characteristics of Fairings for Suppressing Vortex-Induced Vibrations
Authors: Lee Li , Allen Don W. , Henning Dean L. , McMullen Doug
Published: January 2009

Vortex-induced vibration (VIV) tests have been performed on long, flexible pipes with fairings in sheared flows in a circular towing tank at prototype Reynolds numbers for production risers [1]. It is discovered that there existed strong attenuation of the vibration responses for the test configuration with fairings placed in the strong current zone, compared to the pipe configuration without any fairings. Wave attenuation is typical when waves travel in systems with dissipation. Strong attenuation is an indication of large damping. Additional pluck tests of pipes with fairings in still water were conducted to determine damping in the system in a quantitative manner. The results, though scattered, provide evidence on the level of damping that could exist in structures with fairings. Furthermore, analytical models based on a Green’s function solution and mode superposition method for a taut string were also used to complement experimental data. A range of damping values was considered to find the damping value for which the level of attenuation matched that of the experiments. It is found that this damping value is close to that from the tests.
Numerical Simulation of a Spar Interacting With a Polyester Mooring System
Authors: Kim Minsuk , Ding Yu , Zhang Jun
Published: January 2009

A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel mooring lines is extended to allow for special properties pertaining to polyester ropes, such as relatively large elongation under tension, dependence of the modulus on loads, and energy dissipation under cyclic loads. The modified CABLE3D is then integrated into a numerical package, known as COUPLE6D, for computing the interaction between a floating structure and its polyester mooring system. A classical SPAR is chosen in this study as a representative of deepwater floating structures. By considering large elongation in polyester ropes, the static offset curve of a polyester mooring system is softer than that calculated under the assumption of small elongation. The effects of the mean loads on the modulus of polyester ropes are much greater than those of the dynamic loads. The energy dissipation in polyester ropes under cyclic loading does not play a significant role in the responses of the SPAR and tensions in a polyester mooring system. The above observations though made based on a classical SPAR may still have important implications to other floating structures moored by a polyester mooring system.
Power Take Off Damping Optimisation With Regard to Wave Climate
Authors: Duclos Gaelle , Babarit Aurelien , Clement Alain H.
Published: January 2009

Considered as a source of renewable energy, wave is a resource which exhibit high variability at all time scales. Furthermore wave climate also changes significatively from place to place. Wave energy converters are very often tuned to suit the more frequent significant wave period of the project site. In this paper we show that optimizing the device necessitates to account for all possible wave conditions weighted by their occurrence frequency, as generally given by the classical wave climate scatter diagrams. Instead of a real device, a generic and very simple wave energy converter was considered here. We show how the optimal parameters can be different considering whether all wave conditions are accounted for or not, whether the device is controlled or not, whether the vertical motion is limited or not. We also show how they depend on the area where the device is to be deployed, by applying the same method to three very different sites.
Temperature Limits for Asphalt Coated Flowlines: A Design Approach
Authors: Melve Bjo̸rn
Published: January 2009

The 18” flowline from the Mikkel template in the North Sea was coated with asphalt enamel for corrosion protection and an external concrete coating for weight. The high internal temperature of 85 °C close to the template can give relative thermal movements between the outer concrete coating and the inner steel pipe. The case is considered to be similar to an adhesive joint between two tubular members. The strength approach is based on the analysis of the shear stress distribution in this “adhesive” joint. The material stiffness (shear modulus) of the asphalt was used to determine the upper temperature limit for the asphalt coating. The hotter part of the flowline had to be coated with polypropylene instead of asphalt.
Flexible Pipes In-Service Monitoring
Authors: Felix-Henry Antoine , Lembeye Philippe
Published: January 2009

Offshore flexible pipelines are designed to operate without intervention throughout the life of field, which can be 20 to 30 years long. The monitoring of these lines is more and more often considered and implemented with two main objectives: to confirm that the risers and flowlines operate within safe working limits and enable the assessment of the integrity and lifetime of these lines. The first objective can be achieved by continuous collection of the operational data, such as for example internal pressure, fluid temperature, riser top tension and vessel motions, to confirm that the pipelines continue to be operated within the design parameters. The second objective can be achieved through direct condition monitoring of the flexible pipe (for example coupons samples, temperature within the pipe structure, curvature and bending stresses). All of these techniques can contribute towards regular assessment of pipe integrity and lifetime. Flexi France is developing several monitoring and inspection technologies, some of which are already operational or ready to use. This paper will focus primarily on corrosion monitoring of flexible risers steel reinforcement layers through measurement of the annular space fluid composition and physical parameters such as temperature distribution, end-termination sealing integrity and dynamic risers curvature distribution. The state of the art monitoring technologies will be presented in this paper, and it will be explained how they can allow the field operator to optimize the inspection program, reduce the risk of potential damage in operation or enable reuse of the flexible lines at the end of field life.
Characteristics of Hydrodynamics and Generating Output of Offshore Floating Wave Energy Device “Mighty Whale”
Authors: Osawa Hiroyuki , Miyazaki Tsuyoshi , Miyajima Shogo
Published: January 2009

Japan Marine Science and Technology Center (JAMSTEC) has been engaged in research and development of ocean-wave energy extraction technology for many years now. In particular, work began in 1987 an offshore floating type wave power device called “Mighty Whale”. Theoretical investigations and model tests led to an understanding of the hydrodynamic behavior of device, and provided information of constructing for the prototype of Mighty Whale. The open sea tests were started on the 10th of September 1998. Tests were conducted until March 2002. In this paper, firstly, the characteristics of hydrodynamics with “Mighty Whale” have been examined comparing with the results of experiments and calculations approving a numerical method being developed. Secondly, using developed numerical analyze method, the displacements of water level inside air chambers of “Mighty Whale” have been calculated. The generating outputs of “Mighty Whale” have been estimated using these results, the efficiency of primary conversion and the efficiency of secondary conversion of “Mighty Whale” getting through the experiments that had been carried out.
Role of Marine Warranty Surveyors and Their Requirements for Selected Items
Authors: Ghosh Susobhan , Jacobs Michael A. , Mercier John A.
Published: January 2009

For many decades, marine warranty surveyors provided services for various marine operations, such as, loadout, lifting, suitability survey of seagoing vessels, seafastening design approval, etc. But in the last few decades, the importance of marine warranty survey and their role has increased significantly because of large scale offshore activities for deep water oil exploration. In the ever changing offshore industry, installation activities have changed with the introduction of new concepts. Not only have their physical appearances changed but so have the methods of loadout, transportation, and installation. In the present environment of Spar, TLP, Semisubmersible, compliant platform, etc. the role of marine warranty surveyors have increased considerably. For example, installation of deck weighing 7000 tonnes in a single piece does not surprise the industry any more. Spars that are basically cylindrical stiffened steel structures, 750 feet long and 125 feet diameter have been dry towed for 35–40 days on heavy cargo carrying submersible ships from the fabrication yard in Finland to the Gulf of Mexico. With the changing scenario of platform loadout, transportation and installation, the companies providing marine warranty services have developed their own strategy to serve the best interest of the platform owner and the underwriters. This led to developing their own criteria based on experience and industry standard and practices. This paper has outlined primarily the role and importance of marine warranty services in the offshore industry. Since it is not possible to cover all issues specific to various methods of loadout, lifting, mooring, seafastening, installation, this paper limits its scope of presentation to key marine activities for an installation of gravity based jacket type structure. Industry standards and practices, guidelines, as well as marine warranty requirements, and “good” practices are also outlined.
Prediction of Cumulative Fatigue Damage of Mooring Dolphins
Authors: Namba Yasuhiro , Kato Shunji , Iwai Masami , Sato Hiroshi , Kokubun Kentaroh , Masanobu Sotaro
Published: January 2009

Very Large Floating Structures, so-called Mega-Floats, are the kind of social infrastructures. They are generally expected to keep their integrity for a long period, for example, more than 100 years. So, it is necessary to develop Long-Term Integrity Prediction and Diagnosis System to diagnose the soundness of Mega-Floats. In the present study, we paid our attention to dolphin-fender type mooring devices that pontoon type VLFS are equipped with. As a part of Long-Term Integrity Prediction and Diagnosis System, we developed a long-term integrity prediction code (Cumulative Fatigue Damage Prediction Code) to predict damage of these dolphins. We made an at-sea experiment with pontoon type VLFS model of 201.5 [m] length, 100 [m] breadth, and 3 [m] depth (We call this “At-Sea Experiment for Verifying Functions of Mega-Float Information Data Center”). The model had two dolphin-fender type mooring devices and we applied Cumulative Fatigue Damage Prediction Code to these devices.
Cross Flow and In-Line Damping Measurements From Forced Excitations of a Flexible Cylinder in a Uniform Flow
Authors: Venugopal Madan , Vandiver J. Kim
Published: January 2009

Tensioned flexible cylindrical structures are important in many ocean engineering applications such as moorings for buoys and platforms, marine risers and towing cables. Modeling the vibration of these structures is complicated because these are complex three-dimensional, unsymmetrical, fluid structure interaction problems. Damping is an important, but poorly understood, component of the response prediction models developed for modeling such systems. In particular, there is a scarcity of good data on damping of flexible cylinders vibrating in uniform and non-uniform external flow. This is, in part, due to the difficulty of measuring fluid damping on a vibrating cylinder in a flow. Results are presented here which address some of these limitations. Forced vibration tests were performed on two 13 ft long tensioned flexible cylinders (an ABS tube and a steel wire) in a current tank to determine in air and still water damping as well as cross flow and in-line damping in a uniform flow. The experimental methodology is described and results are presented for a range of reduced velocities. The results show an increase in fluid damping with increased reduced velocities for small amplitudes of vibration.
Study on the Drag Characteristics for Take-Off Mode of a WIG Craft
Authors: Doss J. Vimal , Natarajan R.
Published: January 2009

Wing in ground effect (WIG) craft is one, which taps the advantage of ground effect by cruising just over the surface. Though it has the capabilities of being the most promising mode of transport in this century, many problems must be addressed before using it as future high-speed marine craft and sea liner. The greatest impediment to the overall utility of the vehicle is the high takeoff drag and the power requirement associated with it. This paper mainly deals with the drag characteristics of a typical WIG craft. The analysis has been done empirically following Savitsky’s approach.
Measuring Ocean Wave Period and Wave Height With Satellite Altimeters
Authors: Gommenginger C. P. , Srokosz M. A. , Challenor P. G. , Cotton P. D.
Published: January 2009

A novel source of ocean wave period information based on satellite altimeters measurements is examined and compared — using monthly mean climatologies — with ECMWF ERA 40 output and NDBC buoy historical records. The altimeter derived wave period appears to perform well in regions dominated by wind seas, including the Southern Ocean, but does not depict the large swell events observed in the ERA 40 output West of South America and Australia. Altimeter wave period compares well in magnitude and variability with NDBC buoy historical records in three geographical regions (Alaska, Gulf of Mexico, Central Pacific), but further validation of the altimeter model is required against in situ data in regions dominated by swell.
Self-Installed Single Column Floater
Authors: Chou Frank , Chianis John , Zhang Xinyu
Published: January 2009

This paper introduces a novel floating production platform concept for exploration and production of oil and gas in ultra deep water. The developmental effort has been supported by ABB in-house research and development budget. This novel production unit is an enhanced version of ABB Self-Installed Single Column Floater (SISCF) concept. This unit is envisioned to be completely assembled at quayside, towed to location, and be installed vertically to its target draft without the need of a major crane vessel. This enhanced feature reduces the wind load on the deck and hull significantly during wet tow as well as alleviates the uncertainty on the duration of an offshore operation, thereby widens the weather window for installation, hook-up and commissioning offshore. The enhanced SISCF (ESISCF) hull consists of four major components i.e., hard tank with center opening, soft tank with telescoping truss members and opening, permanent-stability ring, and three (3) telescoping support columns. During the installation phase, the telescoping columns are used to guide the permanent-stability ring, which provided needed stability in the installation phase. In addition, because of the way center truss being constructed, the hard tank is collapsed (or sit) right on top of the soft tank during wet tow thus reduced the wind arm (almost 100 ft) and wind forces. In its in-place position, ESISCF motion responses in waves are found to be excellent because of its deep draft. The current concept combines the advantages of a spar and a semi-submersible vessel. The paper will detail the concept, and outline the fabrication to installation scenario. The principal dimensions of a typical ESISCF for a given payload will be presented together with its stability and motion responses in waves based on the sea conditions representing a typical geographical area of Gulf of Mexico. The advantages of this concept will be explained in detail.
A Probabilistic Estimate of Extreme Value Loads on Transverse Water Tight Bulkheads
Authors: Bhattacharya Baidurya , Basu Roger , Srinivasan Sanjay
Published: January 2009

Structural integrity of watertight bulkheads (WTBs) is critical for ship survivability in the event of hull damage. Design procedures for WTBs are based on empirical and prescriptive description of loads. However, damage- causing events and damaged ship mechanics exhibit significant variabilities/ uncertainties. Hence, the design and assessment of WTBs should be performed in a probability-based format. This paper outlines the development of a physically-based probabilistic model of transverse WTB loads as an essential input to reliability analysis. For the probability modeling of the loads the hull damage events are assumed to be rare and independent. Therefore damage events are described as a Poisson process and the maximum life-time load on WTBs in damaged condition is derived. The emphasis of this paper is on the probabilistic modeling of loads; hence simple phenomenological expressions of load components are used to underline the cause and extent of randomness in WTB loads. A response surface type approach is suggested for determining ship-specific model parameters. A large Ro-Ro vessel with side shell breach below the waterline is chosen for illustrating the application of the proposed methodology; randomness is considered in ship hydrostatic properties, damage location, length of breach, occurrence and duration of damage events, the environment, curve fitting and modeling errors. Probabilistic estimates of the maximum load on any WTB in the ship are obtained through Monte Carlo simulations, these are compared with available code prescribed design values.