bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Considerations and Validation of Trailing Edge Pressure Side Bleed Cooling
Authors: Krueckels Joerg , Gritsch Michael , Schnieder Martin
Published: February 2010

One important design measure, which allows achieving a higher efficiency in heavy-duty gas turbines, is reducing the trailing edge thickness of the turbine vanes and blades. A common approach to achieve an efficient cooling of thin trailing edges is pressure side coolant ejection. As the trailing edge is one of the areas of the vanes and blades with the highest heat load, a careful design and validation approach is required. First, the most important design parameters were identified for the design of pressure side bleed. In the present investigation, focus is given to the blockage of the internal features, slot width, overhang length, pressure side lip thickness, effect of rotation and blowing rate. Flat plate test results from a low speed rig are used to choose suitable parameters, which fulfill requirements of a specific design. Previous investigations have shown that contrary to CFD using steady RaNS, unsteady detached eddy simulations can predict film effectiveness of pressure side bleed with good accuracy. Therefore, this approach is used to complete experimental data. The effect of going from low speed rig conditions to engine conditions is modeled with this approach. The final design is investigated in a high-speed cascade rig. Film effectiveness is measured using thermocromic liquid crystals. The cascade results confirm results from the low speed rig. High levels of film effectiveness allow effective cooling of the trailing edge overhang.
Improvement of Gas Turbine Combustion Reactivity Under Flue Gas Recirculation Condition With In-Situ Hydrogen Addition
Authors: Winkler Dieter , Mu¨ller Pascal , Reimer Simon , Griffin Timothy , Burdet Andre´ , Mantzaras John , Ghermay Yohannes
Published: February 2010

Carbon Capture and Storage (CCS) solutions are currently being assessed in order to address appropriately the climate change challenge. Post-combustion CO2 capture is one of the technologies proposed for both coal-fired and gas-fired power plants. In Natural Gas Combined Cycle (NGCC), the flue gas is treated after the Heat Recovery Steam Generator (HRSG) in a so-called post-combustion CO2 capture module through use of solvents. The size of systems envisaged for the capture of CO2 scales with volumetric flow to be treated together with the CO2 concentration contained in the flue gas. Flue Gas Recirculation (FGR) is proposed as a means to increase CO2 concentration in the flue gas together with a net reduction of volumetric flow to be treated by the CO2 capture module. One of the limiting factors of this technology is the vitiation of air within gas turbine combustor and the associated reduction in oxygen concentration. This paper analyses the influence of air vitiation upon combustion in a generic premix lean industrial burner. Tests are carried out under representative inlet pressure and temperature levels. Variation of inlet oxidizer composition is simulated with the addition of nitrogen and carbon dioxide to the inlet air. It is observed that CO emission increases with oxygen depletion at a fixed residence time, signaling a reduction of combustion reactivity. In addition, NOx emission is shown to be sensitive to oxygen depletion. In order to mitigate reduction of combustion reactivity, hydrogen is added to the fuel, up to 20% in volume. As another alternative, a Catalytic Partial Oxidation (CPO) reactor is used in-situ in order to reform the fuel to different syngas blends. These syngas is then used as fuel, which enables the enhancement of the combustion reactivity counter-acting the impact of FGR conditions. The hydrogen addition appears to help improving the reactivity of the flame, making this concept relevant for operation under vitiated air condition.
Model Based Control of Emissions and Pulsations in a Premixed Combustor Using Fuel Staging
Authors: Lacarelle Arnaud , Moeck Jonas P. , Paschereit Christian O. , Gelbert Gregor , King Rudibert
Published: February 2010

A mixing model of a swirl inducing premixed burner is derived from non-reacting investigation and used to control the fuel staging of the burner to ensure stability and low NOx emissions. The convective time delays, critical for the combustor stability, are obtained after identification of a step response of the outlet concentration with a one dimensional mixing model. The steady mixing is used to evaluate quantitatively the mixing quality which correlates with NOx emissions. Time delays as well as scalar unmixedness criteria derived from those measurements are used to predict the combustor stability and NOx emissions maps for different injection configurations at one operating point. The resulting model is used to extend an Extremum Seeking Controller, which adjusts the fuel repartition to reduce the pressure pulsations and NOx emissions.
Analysis of Compressor On-Line Washing to Optimize Gas Turbine Power Plant Performance
Authors: Schneider Ernst , Demircioglu Saba , Franco Susana , Therkorn Dirk
Published: February 2010

Due to compressor fouling, gas turbine efficiency decreases over time, resulting in decreased power output of the plant. To counteract the effects of compressor fouling, compressor on-line and off-line washing procedures are used. The effectiveness of compressor off-line washing is enhanced if combined with the cleaning of the VIGVs and the first compressor blade row by hand. This paper presents a thorough analysis of the effects of compressor on-line washing on the gas turbine performance. The analysis is based on the measured data of six gas turbines operated at two different plants. Different washing schedules and washing fluids are analyzed and compared. Furthermore, the effects of compressor on-line washing on the load distribution within the compressor are analyzed. The performance benefit of daily compressor on-line washing compared to weekly compressor on-line washing is quantified. As expected, daily compressor on-line washing yields the lowest power degradation caused by compressor fouling. Also, the effect of washing additives is analyzed. It is shown with long term data that compressor on-line washing cleans up to the first 11 compressor stages, as can be detected well in the compressor. With a view to gas turbine performance optimization, the recommendation is to perform compressor off-line washing at regular intervals and to take advantage of occasions such as inspections, when the gas turbine is cooled down anyhow. Especially for gas turbines with a high fouling rate, a daily compressor on-line washing schedule should be considered to reduce the power loss. For gas turbines operating with high fogging, compressor on-line washing has no added benefit. To determine the optimal compressor washing schedule, compressor blade erosion also has to be considered. A reasonable balance between compressor on-line washing and off-line washing improves the gas turbine performance and optimizes the gas turbine availability.
Effects of Precooling Turbine Cooling Air on Engine Performance
Authors: Boyle R. J. , Jones S. M.
Published: February 2010

Approaches to improving gas turbine cycle efficiency by cooling the compressor discharge air used for turbine cooling are explored. From a turbine cycle standpoint, cooling the coolant air can improve cycle efficiency. A significant improvement in specific fuel consumption is achieved by raising the turbine rotor inlet temperature, and engine pressure ratio. Precooling compressor discharge air can enable rotor inlet temperature to increase up to 100 K at the same rotor cooling flow rate ratio. The efficiency gains from a 100 K rise in rotor inlet temperature translated into a fuel savings of 400 kg for a mission length of 5450 km. This fuel savings means about a 1200 kg savings in CO2 production. Compressor discharge air that passes through a heat exchanger may not have enough pressure to prevent hot gas ingestion through the cooling holes of the high pressure turbine stator. A stator analysis assuming a mixture of precooled and uncooled compressor discharge air showed only a 50 K rise in rotor inlet temperature due to precooling at the same cooling flow rate ratio.
NOx Reduction by Air-Side vs. Fuel-Side Dilution in Hydrogen Diffusion Flame Combustors
Authors: Weiland Nathan T. , Strakey Peter A.
Published: February 2010

Lean-Direct-Injection (LDI) combustion is being considered at NETL as a means to attain low NOx emissions in a high-hydrogen gas turbine combustor. Integrated Gasification Combined Cycle (IGCC) plant designs can create a high-hydrogen fuel using a water-gas shift reactor and subsequent CO2 separation. The IGCC’s air separation unit produces a volume of N2 roughly equivalent to the volume of H2 in the gasifier product stream, which can be used to help reduce peak flame temperatures and NOx in the diffusion flame combustor. Placement of this diluent in either the air or fuel streams is a matter of practical importance, and has not been studied to date for LDI combustion. The current work discusses how diluent placement affects diffusion flame temperatures, residence times, and stability limits, and their resulting effects on NOx emissions. From a peak flame temperature perspective, greater NOx reduction should be attainable with fuel dilution rather than air or independent dilution in any diffusion flame combustor with excess combustion air, due to the complete utilization of the diluent as a heat sink at the flame front, although the importance of this mechanism is shown to diminish as flow conditions approach stoichiometric proportions. For simple LDI combustor designs, residence time scaling relationships yield a lower NOx production potential for fuel-side dilution due to its smaller flame size, whereas air-dilution yields a larger air entrainment requirement and a subsequently larger flame, with longer residence times and higher thermal NOx generation. For more complex staged-air LDI combustor designs, dilution of the primary combustion air at fuel-rich conditions can result in full utilization of the diluent for reducing the peak flame temperature, while also controlling flame volume and residence time for NOx reduction purposes. However, differential diffusion of hydrogen out of a diluted hydrogen/nitrogen fuel jet can create regions of higher hydrogen content in the immediate vicinity of the fuel injection point than can be attained with dilution of the air stream, leading to increased flame stability. By this mechanism, fuel-side dilution extends the operating envelope to areas with higher velocities in the experimental configurations tested, where faster mixing rates further reduce flame residence times and NOx emissions. Strategies for accurate CFD modeling of LDI combustors’ stability characteristics are also discussed.
Improved Compressor Maps Using Approximate Solutions to the Moore-Greitzer Model
Authors: Drummond Chris , Davison Craig R.
Published: February 2010

Producing compressor maps is time consuming, costly and error prone and many data samples must be collected to give sufficient accuracy. Even then, expert input is typically required to fine tune the map to the appropriate shape. In this paper, we take some of that expertise and incorporate it in the smoothing process. The main piece of knowledge used is the cubic approximation for speed lines derived from the Moore Greitzer model. This well accepted approximation captures much of the general performance properties of compressors. But it is also widely recognized as only being very roughly true of real compressors. Nevertheless, we show that embedding this approximation, however limited, in the smoothing process results in accurate interpolation and extrapolation. The aim of this work is to substantially reduce the need for human input in the fitting process. We also anticipate a number of other benefits: less data is needed, with the commensurate time and money saved; the data collection process can be monitored for possible problems; changes in the map can be quantified and, when sufficiently small, data collection can be terminated.
Contact Steam-and-Gas Turbine Units of the “AQUARIUS” Type: The Present Status and Future Prospects
Authors: Movchan Sergey N. , Romanov Vyacheslav V. , Chobenko Volodymyr N. , Shevtsov Anatoliy P.
Published: February 2010

The recovery of exhaust gas heat in waste-heat recovery boilers (WHRBs), and the injection of superheated steam into gas turbine combustors form the basis for the development of “Aquarius” type gas turbine units. In November 2003 the first commercial “Aquarius-16” unit with 16 MW power output that was designed and built by Ukrainian specialists was put into operation at “Stavishchenskaya” gas compression station for the “Progress” gas pipeline. The efficiency of the unit is 42.1% at turbine inlet temperature (TIT) of 1358K. To date the unit has accumulated more than 9,500 hours and has saved about 13.5 million m3 of fuel gas compared to units having a similar power output operating in simple cycle configuration. The emission levels, corrected to 15% O2 (by volume) are for NOx, 40–68 mg/Nm3, and CO, 58-10 mg/Nm3. The temperature of gases discharged into atmosphere is not more than 45°C. These figures on efficiency and emission levels, although very good, still leave scope for improvement. The purpose of the paper presented here is to define the development methodology to allow the “AQUARIUS” units to achieve efficiencies of 50% and higher. It is shown that development of “AQUARIUS” units with efficiency of about 50% will require operating at maximum cycle temperature around 1673 K and pressure ratio of 25–35. Further development of the Aquarius units with water injection at the low-pressure compressor inlet, the use of more efficient cooling of the engine gas path components and additional recovery of exhaust gas heat by means of fuel will need to operate at maximum cycle temperatures around 1873 K and pressure ratio of 45–50 in order to generate efficiencies more than 50%.
Positron Defect Studies of Neutron Irradiated Iron-Based Materials
Authors: Lambrecht Marlies , Almazouzi Abderrahim
Published: February 2010

The hardening and embrittlement of reactor pressure vessel steels is of great concern in the actual nuclear power plant life assessment. The embrittlement is caused by irradiation-induced damage, like vacancies, interstitials, solutes and their clusters. But the reason for the embrittlement of the material is not yet totally known. The real nature of the irradiation damage should thus be examined as well as its evolution in time. Positron annihilation spectroscopy has been shown to be a very good method for analyzing these defects. Both vacancy type clusters and precipitates can be visualized by positrons. To be able to compare the results obtained by the positron studies, with those of other techniques (such as transmission electron microscopy, atom probe tomography and small angle neutron scattering), quantitative estimations of the size and density of the annihilation sites are needed. Using the approach proposed by A. Vehanen et al., an attempt is made to calculate the needed quantities in model alloys that were neutron irradiated to different doses. The results obtained will be discussed highlighting the difficulties in defining the annihilation centers in spite of using both lifetime and Doppler broadening measurements in the same samples, even in this simple model alloys.
Cementation of Radioactive Waste Resin by Calcium Sulfoaluminate Cement
Authors: Li Junfeng , Wang Jianlong
Published: February 2010

Spent radioactive ion-exchange resin (SIER) is a long-standing issue for radioactive waste management safety. Performance of radioactive waste form is featured with extra long-term and non-repairable. Calcium sulfoaluminate cement (SAC) was used in radioactive spent resins solidification in China. A prescription of X SAC cement + 0.5X waste resins (50%water hold) + 0.35X water was obtained first. In order to control the temperature rise caused by hydration of cement in 200L solidification matrix, various supplementary materials were tried. Based on compressive strength tests and center temperature rise, super powered zeolite was selected. In addition, more resins were added to reduce the center temperature rise. A superior combination was obtained as SAC 35wt.%, zeolite 7wt.% to mix 42wt.% of resins (50%water hold) with 16wt.% of water. The microstructures of hydrated Ordinary Portland Cement (OPC), SAC and SAC with different zeolite addition were compared by means of Scanning Electron Microscopy (SEM). From the SEM pictures, the structures of the needles or spines can be seen in SAC matrices and the needles structure of SAC change into flake structure gradually with more zeolite added. The simulated leaching tests showed that inclusion of zeolite in SAC reduced the leaching rates of radionuclides significantly. From 200L matrix test, the centre temperature curve was measured, and the highest temperature was lower than 90°C. No thermal cracks were found in the final solidified products. The effect of radiation on compressive strength and radiolysis gas generation was studied for cement solidified form of various content of ion exchange resin with Co-60 irradiator. Variation of compressive strength, as well as the compressive strength of the waste form both with and without irradiation all within the standards requirement under irradiation of 106 Gy. However, the data obtained for ion exchange resin shows that hydrogen generation under irradiation of 105 Gy reached up to 3.5% of the total gas generated. This implies that the radioactivity of spent ion exchange resin shall be limited for long term storage and disposal with High-Integrity-Container. Calculation demonstrates that cement solidification of spent radioactive ion exchange resin existing in China so far should not result in radiation stability concern. It is concluded that SAC is one of the preferential binding material for ion exchange resins, the resin loading can be up to 75 (vol%) (wet resin). It is recommended that the performance requirement for cement solidified radioactive form shall be amended and guidelines for performance characterization in certain detail should be established. Biodegradation of cement solidified resin waste would be a safety concern and shall be investigated. Modeling of leaching should be promoted.
New Non-Destructive Condition Monitoring Techniques for On-Site Assessment of Low-Voltage Cables
Authors: Guerout Fabrice M. , Cisse Ladji , Boor Richard
Published: February 2010

The number of techniques available for on-site monitoring of low-voltage cables at nuclear plants is limited because of the requirement from station personnel to use non-destructive and non-intrusive techniques. This paper summarizes the results obtained to date using two new non-destructive methods. The first technique is based on the indentation of the cable insulation or cable jacket material and the study of post-indentation parameters to characterize the visco-elastic properties of the material tested. The novelty of the technique consists of measuring the time taken by the polymeric material to recover a set portion of the initial deformation and using this duration as a material degradation indicator. The technique can be used locally on the insulation of hook-up cables, on the insulation at the termination of jacketed cables, or directly on cable jackets. The second technique is based on the measurement of electrical dissipation factors (or tan delta) in the insulating material. A broadband frequency tan delta analyser was used to measure electrical dissipation factors at various frequencies, and identify the frequency ranges showing increased sensitivity to cable degradation. Specific electrodes and measurement methods were developed for practical on-site condition monitoring work. The measurement of electrical dissipation factors can be used to assess the local degradation of cable insulation in hook-up cables and global degradation of multi-pair conductor cables. When used on multi-pair conductor cables, the technique presents the advantage of providing a global indication of the cable condition.
The Impact of Probabilistic Modelling on Predicting the Remaining Life of Pipes in Nuclear Plants
Authors: Pandey M. D. , Lu D. , Komljenovic D.
Published: February 2010

Flow accelerated corrosion (FAC) is a serious form of degradation in primary heat transport piping system (PHTS) of the nuclear reactor. Pipes transporting hot coolant from the reactor to steam generators are particularly vulnerable to FAC degradation, such as tight radius pipe bends with high flow velocity. FAC is a life limiting factor, as excessive degradation can result in the loss of structural integrity of the pipe. To prevent this, engineering codes and regulations have specified minimum wall thickness requirements to ensure fitness for service of the piping system. Nuclear utilities have implemented periodic wall thickness inspection programs and carried out replacement of pipes prior to reaching an unsafe state. To optimize the life cycle management of PHTS, accurate prediction of time of replacement or “end of life” of pipe sections is important. Since FAC is a time-dependent process of uncertain nature, the paper presents two probabilistic models for predicting the end of life. The paper illustrates that the modeling assumptions have a significant impact on the predicted number of replacements in the piping system. A practical case study is presented using wall thickness inspection data collected from Canadian nuclear plants.
Study on the Onset of Nucleate Boiling in Narrow Annular Channel by Using Wavelet and Wavelet Neural Network
Authors: Wei Huiming , Su G. H. , Qiu S. Z. , Yang Xingbo
Published: February 2010

In this study, the local modulus maxima of cubic B-spline wavelet transform are introduced to determine the location of onset of nucleate boiling (ONB). Wavelet transformation has the ability of representing a function and revealing the properties of the function in the joint local regions of the time frequency space. Based on wavelet and artificial neural network, a Wavelet Neural Network (WNN) model predicting ONB for upward flow in vertical narrow annuli with bilateral heating has been developed. The WNN mode combining the properties of the wavelet transform and the advantages of Artificial Neural Networks (ANN) has some advantages of solving non-linear problem. The methods of establishing the model and training of wavelet neural network are discussed particularly in the article. The ONB prediction is investigated by WNN with distilled water flowing upward through narrow annular channels with 0.95 mm, 1.5 mm and 2.0mm gaps, respectively. The WNN prediction results have a good agreement with experimental data. At last, the main parametric trends of the ONB are analyzed by applying WNN. The influences of system pressure, mass flow velocity and wall superheat on ONB are obtained. Simulation and analysis results show that the network model can effectually predict ONB.
A Robust Asymptotically Based Modeling Approach for Two-Phase Liquid-Liquid Flow in Pipes
Authors: Awad M. M. , Butt S. D.
Published: February 2010

The flow of two immiscible liquids such as oil and water is very important in the petroleum industry like oil recovery processes. For example, the injection of water into the oil flowing in the pipeline reduces the resistance to flow and the pressure gradient. Thus, there is no need for large pumping units. In the present study, a simple semi-theoretical method for calculating the two-phase frictional pressure gradient for liquid-liquid flow in pipes using asymptotic analysis is presented. The two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for the more viscous liquid and the less viscous liquid flowing alone. The proposed model can be transformed into either a two-phase frictional multiplier for the more viscous liquid flowing alone (φ12) or two-phase frictional multiplier for the less viscous liquid flowing alone (φ22) as a function of the Lockhart-Martinelli parameter, X. The advantage of the new model is that it has only one fitting parameter (p). Therefore, calibration of the new model to experimental data is greatly simplified. The new model is able to model the existing multi parameters correlations by fitting the single parameter p. Comparison with experimental data for two-phase frictional multiplier versus the Lockhart-Martinelli parameter (X) is presented.
A Numerical Analysis of the Response and Air Gap Demand for Semi-Submersibles
Authors: Kurniawan Adi , Huang Zhenhua , Li Jing , Liu Chunrong , Wang Xikun , Hao Zhiyong , Tan Soon Keat , Nah Edwin
Published: February 2010

This paper examines the effects of viscous damping on the prediction of air gap demand for semi-submersibles. This is illustrated by a case study of a typical six-column, double pontoon semi-submersible in irregular waves. Linear responses of the platform and free-surface elevations at selected locations are computed using WAMIT, in which viscous damping effects are included through the use of a linear damping matrix. The spectra of the platform’s response and of the relative free-surface elevation at the selected locations, as well as the probability distributions of air gap minima obtained using different damping matrices are compared. It is demonstrated that correct modelling of viscous damping is important for an accurate prediction of air gap demand of a floating platform, especially if the peak frequency of the wave spectrum is close to the heave, roll, and pitch natural frequencies of the platform.
The Development of a Refined Assessment Procedure for the Pipeline Reeling Process Using Reliability and Finite Element Techniques
Authors: Denniel Sylvain , Tkaczyk Tomasz , Howard Brett , Levold Erik , Aamlid Olav
Published: February 2010

The reel-lay method is a fast and efficient rigid pipeline installation method for infield flowlines and smaller export lines (up to 20″). However, reeling operations induce significant bending strain in the pipeline. To avoid pipe buckling during reeling, it is a common practice to limit pipe yield strength and wall thickness variations in addition to ensuring an adequate wall thickness. Simple formulas in design standards, based on the assumption of pure bending, are often used to determine the minimum reelable wall thickness. It is, however, known that the mechanics of reeling process differs from pure moment bending. Therefore, the likelihood of pipe buckling during reeling may depend on factors that are not captured by these simple formulae. A more refined procedure for establishing the minimum reelable wall thickness and the associated probability of failure has been developed. This procedure involves the combination of finite-element and statistical analyses. It is aligned with the methodology which is regularly used by Technip to demonstrate the on-reel integrity of non-standard pipeline configurations such as thick coated pipelines with soft field joint coating or transitions between pipelines with different nominal sizes or material grades. This paper outlines the procedure, which can be used to determine the level of safety associated with the simple formulae for the minimum wall thickness in the design standards. The reeling parameter studies carried out in this work have shown that it is not only the maximum bending strain, pipe outer diameter and the statistical variations of wall thickness and yield strength that affect the reliability of the reeling process, but also the arrangement of the reeling equipment.
Using CFD to Determine Heave Added Mass and Damping of a Suction Pile
Authors: Zoontjes Richard , Siegersma Harm , Ottens Harald
Published: February 2010

This paper presents results of a research project within Heerema Marine Contractors to determine added mass and damping coefficients of suction piles using CFD. Analyses have been performed for suction piles which are fully closed and with open hatches. The results are compared with model tests presented at the OMAE by Ireland et al. (2007) and Roe et al. (2008). Two modeling approaches have been used. The first approach is simulating a forced oscillation by oscillating the flow around a fixed body. The second approach is by using a Dynamic Fluid Body Interaction (DFBI) model simulating a decay test. The DFBI model allows the (fluid induced) motion of an object to be predicted in six degrees of freedom. The oscillating flow method gives very good results for both closed and open hatch conditions. The computational costs for this method are very low. The main drawback is the inability to model oscillations close to a floor. The DFBI model gives the opportunity to quantify floor effects. At a floor clearance of h/D = 0.40 damping and added mass are accurately predicted. For a floor clearance of h/D = 0.20 added mass as well as damping is slightly overestimated. No major deviations have been noticed when comparing the results of model-scale to full-scale simulations. Apparently, Froude scaling is applicable for this particular geometry and scaling.
Design Aspects and Benefits of Sandwich Pipes for Ultra Deepwaters
Authors: Castello Xavier , Estefen Segen F. , Leon Harold R. , Chad Luis C. , Souza Juscinei
Published: February 2010

Oil&gas production on deep and ultra deepwater scenarios require very thick walled steel pipelines or heavy Pipe-in-Pipe systems, which are expensive and difficult to install. Sandwich Pipe is a new pipeline concept composed of two concentric steel pipes separated by and bonded to a polymeric annulus that provide the adequate combination of structural strength and thermal insulation. In later works, Sandwich Pipes have been analyzed regarding to the structural strength and results have indicated good relation between steel weight and external pressure resistance, mainly when compared to the Pipe-in-Pipe system. To fulfill the thermal insulation requirements, an adequate polymer for the annular layer should be selected, combining both insulation requirements and good bonding strength to steel, which are determinant for the adequate performance. Sandwich Pipes with typical inner diameters of those employed in the offshore production are analyzed numerically to evaluate the ultimate strength under external pressure. Polyurethane based materials with different mechanical and thermal properties are selected. Experimental tests are performed to evaluate adhesion strength to steel, which are used as input for the numerical models. Non-linear geometry, material and contact properties are included, as well as temperature effect on polymer stiffness. To estimate the insulation capacity for each option the global heat transfer coefficient is calculated and a maximum “U value” is considered for all systems. Also, both numerical and analytical analyses are employed to design a PIP system for a hypothetical offshore field. Similar conditions to the newly discovered sub-salt fields offshore Brazil are adopted, i.e. 2500 m water depth and 80°C produced fluid temperature. API 5L specifications table are used for thickness and diameter selection and API RP1111 is employed to design PIP inner pipe. Results indicate that Sandwich Pipes with adequate strength and insulating annular material can generate significant advantages in relation to the PIP system. In addition to the sandwich structure benefit, the initial out-of-roundness maximum diameter directions between inner and outer pipes have a secondary role that produces additional strength for the collapse pressure resistance. Lower steel weight is calculated in all cases, even when the outer pipe is larger. All cases yielded lower submerged weight, which is an important parameter for installation purposes, because less expensive lay vessels may be required.
Interrogation of Gas/Oil Flow in a Vertical Using Two Tomographic Techniques
Authors: AbdulKareem Lokman A. , Azzopardi Barry J. , Thiele Sebastian , Hunt Andrew , Da Silva Marco J.
Published: February 2010

Two tomographic techniques have been applied to the flow in a 67 mm internal diameter vertical pipe. One is Electrical Capacitance Tomography (ECT) mounted on the outside of the non-conducting pipe wall. Another technique, known as the Wire Mesh Sensor (WMS) was used. The measuring systems provide time and cross-sectionally resolved information about the spatial distribution of the phases. The information can be used to obtain space and time averaged void fractions, radial profiles of time averaged void fraction and cross-sectional averaged time series of void fraction. Simultaneous measurements were made with the two techniques for gas superficial velocities of 0.05–5.5 m/s and liquid superficial velocities of 0–0.7 m/s with air and silicone oil as the fluids. Bubble, slug and churn flows were identified from the characteristic signatures of the Probability Density Functions of the cross-sectionally averaged void fraction. In addition, the detailed shape of individual large bubbles has been extracted. The output of both instruments shows clearly that the shapes of the large bubbles in slug flow are distinctly different from the smooth bullet-shaped. In this larger diameter pipe, the interface is much more disturbed. In addition, flow can be classified according to the sizes of bubbles present. Distributions of bubble sizes are presented and the fractions of gas flowing in different bubble sizes classes quantified.
On the Numerical Modelling of the Non Linear Behaviour of a Wave Energy Converter
Authors: Babarit Aure´lien , Mouslim Hakim , Cle´ment Alain , Laporte-Weywada Pauline
Published: February 2010

Wave energy converters of the wave activated body class are designed to have large amplitudes of motion, even in moderate sea states, because their efficiency is directly related with the amplitude of their motion. Hence, classical seakeeping numerical tools based on linear potential theory, which are widely used in the design process of offshore structures, are not accurate enough in the case of wave energy conversion. So, large differences between numerical predictions and wave tank experiments are often observed. On the other hand, the use of CFD models theoretically able to provide more accurate results is still difficult for wave energy applications, mainly because this requires a huge computation time. Moreover, it is well known that viscous solver have difficulties in propagatating gravity waves accurately. In this paper, we assess the potential of two advanced hydro-dynamic numerical models in the numerical modelling of wave energy converters. These numerical models are expected to provide more accurate results than classical linear theory based numerical models and faster results than CFD models. Particularly, these tools are expected to be able to deal efficiently with large motions of wave energy converters. In the first one, the hydrostatic forces and the Froude-Krylov forces are computed on the exact wetted surface of the wave energy converter, whereas radiation and diffraction forces are computed using the standard linear potential theory. Using this model, it is shown that we were able to predict the parametric roll phenomenon in the case of the SEAREV wave energy converter. In the second one, a Navier Stokes solver, based on RANS equations, is used. Comparisons are made with experiments and it is showed that this tool is able to model quite accurately viscous effects such as slamming. However, computation time is found to be long with this last tool.
Correlation Between Hydrolysis and the Ultimate Mechanical Properties of Polyamides in Offshore Conditions
Authors: Hochstetter Gilles , Dang Patrick
Published: February 2010

Knowledge of mechanical properties of polymers used in the field of very technical applications is crucial for guaranteeing the safety of those applications. This is particularly true for pressure sheaths of offshore flexible pipes. For polyamide 11 (PA-11), which has been used for 30 years in the field of oil & gas applications, the decrease of its mechanical properties due to hydrolysis can be monitored by the decrease of the molecular weight, or Corrected Inherent Viscosity (CIV). According to API 17TR2 a design limit of CIV = 1.2 has been established for the use of PA-11 in dynamic applications. This design limit includes a safety factor, related to the kinetics of the molecular weight decrease of the PA-11, between CIV = 1.2 and the end of life criteria (CIV = 1.05). We show, in this paper, that this kinetic shall be established with tests enabling to precisely determine the near-equilibrium CIV value. This supposes sufficiently long-term ageing experiments at high temperatures. As a consequence, for any new polyamide, the time to reach the CIV of 1.2 can’t be considered as a sufficient design factor. Moreover, the safety factor for a new polyamide should be carefully estimated. Therefore, the complete characterization of the mechanical behaviour should be done in relation with the ageing time and temperature. Only at this condition, one can expect to be able to establish a new and correct end of life criterion for a new polyamide based on mechanics. In a second time, this criterion could be linked to some physico-chemical parameters. We point out that the maximum elongation evolution of the material with the molecular weight couldn’t be considered as sufficiently precise to conclude about the mechanical resistance of the aged material for flexible pipe application. We thus present in this paper a new mechanical protocol.
Structural Health Monitoring System for “Uldolmok” Tidal Current Power Pilot Plant and Its Applications
Authors: Yi Jin-Hak , Lee Kwang-Soo , Park Jin-Soon , Park Woo-Sun
Published: February 2010

In this paper, the structural health monitoring system for “Uldolmok Tidal Current Power Pilot Plant (TCPP)” is briefly introduced and the measured data obtained up to now are analyzed. TCPP is basically constructed in the ocean area with high current speed, and therefore the current loading is governing the structural safety than the wave or wind loadings. Usually the soft soils are eroded due to the current and the soft and hard rocks are composing the seabed in strait which tidal current of high speed. Therefore the coring is not so easy due to rock seabed condition and also the operational time is very limited. And also the structural members should not be over designed with large size of steel pipe not to obstruct the tidal current. Due to the difficulties in coastal construction, relatively severe current loadings, and optimized slender structural members, it is very important to monitor the structural safety of the tidal current power plant in normal operation condition and also in severe storm condition. However, the sensor installation is much more difficult for TCPP structure than conventional in-land structures such as bridges and buildings since the sensors should be fully waterproof and the cables should be able to endure the corrosive condition. In this study, we installed the sensors under the sea level and are going to install the sensors above the sea level in this year after the construction is completed. Now the structure is under construction. The conventional type strain sensors and smart FBG optical sensors were installed in the lower part of the jacket legs to measure the dynamic and static strains and the MFC (Macro Fiber Composite) sensors were also installed at the same location to measure the impedance change due to loading and corrosion conditions.
FEA-Based Study of Pipeline Protection From Anchors
Authors: Wang LeQin , Chia HongKiat , Wei JianWu , Chen Qiang
Published: February 2010

This paper discusses the use of Finite Element Analysis in rock berm design for pipeline protection against anchor impact. Submarine pipelines located near harbour areas and in major shipping lanes are likely to be exposed to potential damage due to anchors and dropped object impact. To protect these pipelines, they are buried and protected with rock armour berms. The design of these rock berms has been traditionally based on model testing because there has been no analytical solution available to resolve the complex interaction between the anchor, anchor chain, seabed soil and rock armour. The authors are currently working on a Finite Element Analysis (FEA) based procedure that can be used to assess the potential anchor damage to a pipeline protected by rock backfill. The 3-D non-linear numerical analysis code ABAQUS/Explicit is used to simulate the entire process from the anchor being dropped into the seabed to the anchor being dragged out of the seabed and through the rock protection cover. The interactions between the anchor, chain, soil, rock and pipeline are all taken into consideration. From the anchor dragging trajectory within the seabed soil and protection rock cover, the clearance between the anchor fluke tip and pipeline can be obtained. This along with the pushing forces on the pipeline can be used to assess the potential damage to the pipeline. This paper presents the FEA model for an anchor dragging across a buried pipeline resting on soft clay soil and covered by rock berm. These results have been successfully validated against results obtained from physical model tests. The Finite Element Analysis procedure allows the investigation of a wide range of configurations to optimize the rock berm design, such as the effect of off-design of armour rock shape and trench profile, rock size and grading variation etc. With a better understanding of the pipeline, anchor, soil and rock berm interaction, the design of the pipeline armour rock protection against anchor damage can be carried out in a more definitive manner. This paper also presents a recent application of the FEA model to study the effectiveness of the rock berm protection due to change in seabed profile.
In Vitro
Antibacterial Activities of JNJ-Q2, a New Broad-Spectrum Fluoroquinolone
Authors: Morrow Brian J. , He Wenping , Amsler Karen M. , Foleno Barbara D. , Macielag Mark J. , Lynch A. Simon , Bush Karen
Published: February 2010

JNJ-Q2, a novel fluorinated 4-quinolone, was evaluated for its antibacterial potency by broth and agar microdilution MIC methods in studies focused on skin and respiratory tract pathogens, including strains exhibiting contemporary fluoroquinolone resistance phenotypes. Against a set of 118 recent clinical isolates of
Streptococcus pneumoniae
, including fluoroquinolone-resistant variants bearing multiple DNA topoisomerase target mutations, an MIC
90
value for JNJ-Q2 of 0.12 μg/ml was determined, indicating that it was 32-fold more potent than moxifloxacin. Against a collection of 345 recently collected methicillin-resistant
Staphylococcus aureus
(MRSA) isolates, including 256 ciprofloxacin-resistant strains, the JNJ-Q2 MIC
90
value was 0.25 μg/ml, similarly indicating that it was 32-fold more potent than moxifloxacin. The activities of JNJ-Q2 against Gram-negative pathogens were generally comparable to those of moxifloxacin. In further studies, JNJ-Q2 exhibited bactericidal activities at 2× and 4× MIC levels against clinical isolates of
S. pneumoniae
and MRSA with various fluoroquinolone susceptibilities, and its activities were enhanced over those of moxifloxacin. In these studies, the activity exhibited against strains bearing
gyrA
,
parC
, or
gyrA
plus
parC
mutations was indicative of the relatively balanced (equipotent) activity of JNJ-Q2 against the DNA topoisomerase target enzymes. Finally, determination of the relative rates or frequencies of the spontaneous development of resistance to JNJ-Q2 at 2× and 4× MICs in
S. pneumoniae
, MRSA, and
Escherichia coli
were indicative of a lower potential for resistance development than that for current fluoroquinolones. In conclusion, JNJ-Q2 exhibits a range of antibacterial activities
in vitro
that is supportive of its further evaluation as a potential new agent for the treatment of skin and respiratory tract infections.
An investigation of the pre-injury risk factors associated with children who experience traumatic brain injury
Authors: McKinlay A , Kyonka E G E , Grace R C , Horwood L J , Fergusson D M , MacFarlane M R
Published: February 2010

Background and Objective

Traumatic brain injury (TBI) is a frequently occurring event in childhood that may have significant ongoing effects. Little is known about the child and family characteristics that predispose children to these injuries. A greater understanding of the risk factors associated with childhood TBI may provide an opportunity to prevent their occurrence.

Methods

Information provided by a large birth cohort study (n=1265) was used to determine the child and family risk factors of TBI in children aged 0–15 years (n=187). All information regarding child, family, and injury events were collected prospectively and unrelated to the injury event itself. Child variables included in the analysis were sex and the level of behavioural problems. Parental variables included were family socioeconomic status, mother's age, education level, depressive symptoms, number of adverse life events experienced by the family, and parenting style.

Results

The most important risk factors were sex, adverse life events, and parenting style. The results suggest evidence of modest increases in the rate of TBI for those in the highest risk categories (male, ≥4 life events per annum, high maternal punitiveness) compared to the lowest risk categories, with hazard ratios in the region of 1.4–1.6.

Conclusions

Overall characteristics of both the family and child predicted a TBI event. An increased understanding of risks associated with TBI in childhood will provide an avenue to prevent these injuries by targeting at-risk families and aiding the development of appropriate intervention strategies.
Factors associated with worker slipping in limited-service restaurants
Authors: Courtney Theodore K , Verma Santosh K , Huang Yueng-Hsiang , Chang Wen-Ruey , Li Kai Way , Filiaggi Alfred J
Published: February 2010

Objective

Slips, trips and falls (STF) are responsible for a substantial injury burden in the global workplace. Restaurant environments are challenged by STF. This study assessed individual and work environment factors related to slipping in US limited-service restaurant workers.

Methods

Workers in 10 limited-service restaurants in Massachusetts were recruited to participate. Workers' occupational slip and/or fall history within the past 4 weeks was collected by multilingual written questionnaires. Age, gender, job tenure, work hours per week and work shift were also collected. Shoe type, condition and gross shoe contamination were visually assessed. Floor friction was measured and each restaurant's overall mean coefficient of friction (COF) was calculated. The logistic generalised estimating equations model was used to compute adjusted odds ratios (OR).

Results

Of 125 workers, 42 reported one or more slips in the past 4 weeks with two reporting a resultant fall. Results from multivariable regression showed that higher restaurant mean COF was significantly associated with a decreased risk of self-reported slipping (OR 0.59, 95% CI 0.42 to 0.82). From the highest to the lowest COF restaurant, the odds of a positive slip history increased by a factor of more than seven. Younger age, male gender, lower weekly work hours and the presence of gross contamination on worker's shoe sole were also associated with increased odds of slip history.

Conclusion

Published findings of an association between friction and slipping and falling in actual work environments are rare. The findings suggest that effective intervention strategies to reduce the risk of slips and falls in restaurant workers could include increasing COF and improving housekeeping practices.