bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of Breaking Waves Using a Level Set Method
Authors: Go´mez Pablo , Herna´ndez Julio , Lo´pez Joaqui´n , Faura Fe´lix
Published: March 2009

A numerical study of the initial stages of wave breaking processes in shallow water is presented. The waves considered are assumed to be generated by moving a piston in a two-dimensional channel, and may appear, for example, in the injection chamber of a high-pressure die casting machine under operating conditions far from the optimal. A numerical model based on a finite-difference discretization of the Navier-Stokes equations in a Cartesian grid and a second-order approximate projection method has been developed and used to carry out the simulations. The evolution of the free surface is described using a level set method, with a reinitialization procedure of the level set function which uses a local grid refinement near the free surface. The ability of different algorithms to improve mass conservation in the reinitialization step of the level set function has been tested in a time-reversed single vortex flow. The results for the breaking wave profiles show the flow characteristics after the impact of the first plunging jet onto the wave’s forward face and during the subsequent splash-up.
Jet Formation in Bubbles Bursting at a Free Surface
Authors: Duchemin Laurent , Zaleski Ste´phane
Published: March 2009

We study numerically bubbles bursting at a free surface. The Navier-Stokes equations with a free surface and surface tension are solved using a marker-chain approach. Initial conditions involve a bubble connected to the outside atmosphere by a preexisting opening in a thin liquid layer. The evolution of the bubble is studied as a function of bubble radius. The results show that the jet birth may occur with or without the formation of a tiny air bubble at the base of the jet. A series of critical radiuses exist, for which a transition from a dynamics with or without bubbles exist. This singularity is compared to the ones investigated in other contexts such Faraday waves.
Experimental Investigation of Tip Clearance Flows of an Axial Flow Fan Using PDA
Authors: Zhu Xiaocheng , Lin Wanlai , Du Zhaohui , Zhao Yan
Published: March 2009

The three-dimensional flow field in the tip region of an isolated axial flow fan rotor with two different tip clearances are investigated using a three-color, dual-beam PDA system (Particle Doppler Anemometer, DANTEC Measurement Technology). The global performance is also obtained, and is compared favorably with CFD (Computational Fluid Dynamics) modeling of this fan flow at a zero tip clearance. The detailed flow field measurements are taken at 15 axial locations upstream, inside and at the exit of the rotor. In the radial direction, 15 measurement locations are arranged from 50% of the blade span to the casing wall, mainly focusing on the tip region from 90% of the blade span location to the casing wall (about 10 measurement locations). The PDA data has provided a quantitative understanding of the flow phenomena in the tip region of the fan rotor. For both tip clearances, it has been observed that the tip leakage flow rolls up into a tip leakage vortex. Due to the rotation of the rotor, this tip leakage vortex moves away from the suction surface of the fan blade. A reverse flow is induced in the main flow passage because of the tip leakage vortex. The depth and extent of the tip leakage vortex grow noticeably with the increase of the tip clearance.
Effect of Freestream Turbulence and Flow Recovery in the Wake of a Flat Plate
Authors: Krampa-Morlu F. N. , Balachandar R.
Published: March 2009

The study of the recovery of an open channel boundary flow in the presence of increased freestream turbulence (FST) generated in the wake region of a surface mounted flat plate is presented. Detailed LDA velocity measurements were obtained upstream and downstream of the flat plate, which is 3 mm in thickness and has a thickness-to-chord ratio of 0.12. The chord is placed parallel to the flow direction. The characteristics of the mean velocity, turbulence intensity, and the velocity skewness and flatness factors were investigated. The skin friction was increased while the strength of the boundary layer wake parameter decreased in the wake region. The turbulence intensity profiles in the wake region increasingly deviated significantly from the upstream profile. Generally, the increased FST noticed in the near-wake region was observed to decay with downstream distance. As a result, the mean velocity and turbulence intensity profiles showed a general sense of recovery towards the state of the approaching flow.
Extracting Numbers From Tracer Flow Visualization: High Attack-Angle Vanes
Authors: Hoyt J. W. , Sellin R. H. J.
Published: March 2009

High attack-angle vanes have been proposed as a means of maintaining sediment in suspension in rivers and streams. Laboratory and computer studies have, up to now, been unable to describe how the flow mechanism actually works in the sediment-suspension mode. A turbulent-flow tracer has been used to study model vanes in a small water channel at the University of Bristol. The sediment-suspension capabilities of such vanes becomes evident from their highly swirling non-symmetric Ka´rma´n vortex-type wakes. The wake patterns have been analyzed using video recordings and frame-counting software. Using the video frame rate as a time base, Strouhal numbers and velocities in the vane wake can be extracted by following the movement of particular tracer strands.
PIV Experimental Analysis for the Inter Flow Characteristics in the Pump Suction Sump
Authors: Li Yong , Li Xiaoming , Zhang Botao , Wu Yulin , Okamura Tomoyoshi
Published: March 2009

PIV (Particle Image Velocimetry) is a new technique of flow measurement. In this experiment PIV technique is used to measure the flow conditions in the pump sump model, which are very complicated, especially in the surrounding of the pump bell where there are very complex vortexes. These will affect the flow characteristics in the pump system broadly and result in vibration and cavitation, and decrease the efficiency of the system. And these will harm the performance of pump station, and even lead it out of order. The vortex surrounding the pump bell has the direct relationships with the structure of the pump suction sump and the pump bell. In this experiment the pump suction sump and the pump bell with particularly structure are used to research the flow situation in the surrounding of the bell. The PIV method is used in the experimental to study the flow conditions surrounding the pump bell. Using this technique the flow velocities, the streamlines and the turbulent kinetic energies in the full range can be obtained. Moreover, other important parameters can be gotten after being analyzed the base experiment data further. Here, the results of the PIV experiment on flow in pump suction sump are analyzed further, and the following parameters are obtained: circulation vector of the inlet flow of bell, three-dimensional velocity and turbulent kinetic energies. And through analyzing the experiment’s photos, the air core’s conditions in the bell also can be gotten.
Numerical Analysis of Unsteady Hydrodynamic Forces on a Diffuser Pump Impeller Due to Rotor-Stator Interaction
Authors: Zhang M. , Wang H. , Tsukamoto H.
Published: March 2009

The 2-D vortex method and the commercially available CFD software are applied to calculate unsteady hydrodynamic forces on a diffuser pump impeller and the pressure fluctuations caused by the interaction between the impeller and the diffuser vanes. Calculated pressure and fluid forces on the impeller are compared with measured ones. The numerical analysis yields fairly accurate predictions of the fluid forces and the pressure fluctuations in diffuser passages and the pipe systems. It has been demonstrated that the fluid forces caused by the interaction between the rotor and stator vanes are small when the number of vanes on impeller and diffuser is identical. In this case, however, the local pressure fluctuations are larger in diffuser passages and the pipe systems.
LES of Internal Flows in a Mixed-Flow Pump With Performance Instability
Authors: Kato Chisachi , Mukai Hiroshi , Manabe Akira
Published: March 2009

This paper describes large eddy simulation (LES) of the internal flows of a high-specific-speed mixed-flow pump at low flow-rate ratios over which measured head-flow characteristics exhibits weak instability. In order to deal with a moving boundary interface in the flow field, a form of the finite-element method in which overset grids are applied from multiple dynamic frames of reference has been developed. The method is implemented as a parallel program by applying a domain-decomposition programming model. The predicted pump heads reproduce the instability and agree quantitatively well with their measured equivalents although the predicted stall takes place at somewhat lower flow-rate ratio than in the measurements. The phase-averaged distributions of the meridional- and tangential-velocity components at the impeller’s inlet and exit cross-sections were also compared with those measured by a Laser-Doppler velocimetry (LDV). Reasonably good agreements have been obtained between the computed and measured profiles. The developed LES program thus seems to be a promising design tool for a high specific-speed mixed-flow pump particularly for off-design evaluations.
Development and Application of Fan Noise Prediction Method to Axial and Centrifugal Fan
Authors: Lee Duck-Joo , Jeon Wan-Ho , Chung Ki-Hoon
Published: March 2009

Numerical predictions of fan noise have not been studied extensively. This is due to the scattering effect of the fan casing, duct and the difficulty in obtaining aerodynamic acoustic source. New method to predict the fan noise and performance is developed and used to calculate various fan noise problems. A vortex method is used to model the fan and to calculate the flow field. Acoustic pressures are obtained from the unsteady force fluctuations of the blades using an acoustic analogy. But the acoustic analogy can be applied only in the free field in general. In order to consider the solid boundary effects of the casing, the newly developed Kirchhoff-Helmholtz BEM (Boundary Element Method) is introduced. With the above-mentioned method, the flow field and sound field of centrifugal and axial fan were calculated. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal sound. Also, in the predicted sound field, we can see the scattering effect of duct and casing.
Large Eddy Simulations of a Bubbly Mixing Layer
Authors: Smirnov A. , Celik I. , Shi S.
Published: March 2009

In this paper we present the results of the application of a Lagrangian particle dynamics (LPD) method and a random flow generation technique (RFG) developed by the authors used in conjunction with large eddy simulations (LES) applied to the case of a two-phase bubbly mixing layer. The objective is to validate the present hybrid Lagrangian-Eulerian approach within the context of LES. The dynamics of the vortices and bubble concentrations reproduced in simulations are in a good agreement with experimental data.
Effect of Turbulence on Drag Force in Gas-Particle Two-Phase Flow
Authors: You Changfu , Qi Haiying , Xu Xuchang
Published: March 2009

Effect of turbulence on drag force in gas-particle two-phase flow had been investigated using numerical simulation. In order to select an accurate turbulence model, some promising models, such as standard k-ε model, RNG k-ε model and Realizable k-ε model, had been examined through calculating the flow over a backward-facing step. RNG k-ε model performing better than others had been used to simulate the turbulence flow over a spherical particle. In computation, the turbulence intensity was ranged from 10% to 80%, and the turbulence length scale from 10−5m to 4m. Results show that the turbulence length scale had a small effect on the drag force, except at small length scale. Comparing with the drag on a particle in laminar flow, the turbulence intensity enhances it comparatively, especially at small particle Reynolds numbers, which differs from the previous publications.
An Adaptive Spectral Element Method for Two-Fluid Flows
Authors: Helenbrook Brian T. , Baker Timothy J.
Published: March 2009

A new mesh adaptation technique for two dimensional deforming domains has been combined with an Arbitrary-Lagrangian-Eulerian, spectral/hp finite element solver. This combination provides a powerful simulation tool for two-fluid flows; With the spectral/hp finite element method, high accuracy solutions can be obtained efficiently, but by itself this technique is limited to problems with moderate interface deformation. By combining it with a mesh adaptation strategy for deforming domains, large deformation problems can be simulated. In addition, solution-based mesh refinement can be performed which is critical for resolving multi-scale two-fluid problems. The capabilities of these techniques together are demonstrated for some preliminary examples.
Phase Distribution in Buoyancy-Driven Bubbly Flows
Authors: Esmaeeli Asghar , Ching Chan , Shoukri Mamdouh
Published: March 2009

This study aims to investigate the effect of topology change on the rise velocity of bubbly flows and the phase distribution in a channel at a moderate Reynolds number. A front tracking/finite difference method is used to solve the momentum equation inside and outside deformable bubbles. It is found that bubble/bubble coalescence enhances the average rise velocity of the bubbles dramatically and also increases the fluctuations of the liquid velocity. Examination of the pair distribution function shows that the flow becomes more non-homogeneous as a result of topology change.
A Remote Area Power Supply Using Wind Power and Cold Thermal Storage
Authors: Brown Kenneth C.
Published: March 2009

A remote area power supply using cold thermal storage and wind as the energy source is proposed. The primary objective is to provide a renewable energy remote area power supply with cheaper and more robust storage than lead-acid batteries. The proposal amalgamates a vapour compression refrigeration system with a Rankine cycle engine, both using the same working fluid. A tank of freezing brine acts as the condenser in the Rankine cycle and as the evaporator in the refrigeration cycle but also provides the “energy storage”. Analysis of the system indicates that it is practical and that its performance is comparable with existing battery based systems.
A Fundamental Study of Wake-Boundary Layer Interaction on Turbomachinery Blading
Authors: Evans R. L.
Published: March 2009

Turbulent boundary layers on turbomachine blades are three-dimensional and highly unsteady. The flow becomes periodically unsteady due to the relative motion of the rotor and stator blades in a stage. A large velocity defect within the wake of an upstream blade generates a varying incidence angle, and a fluctuating velocity at entrance to the next stage. The velocity defect, or wake, travels downstream with a finite speed and intermittently perturbs the boundary layer on downstream blades.
LES of a Three Dimensional Shock-Wave/Boundary Layer Interaction in a Channel Flow
Authors: Coquart Laure , Tenaud Christian , Ta Phuoc Loc
Published: March 2009

This study deals with the Large Eddy Simulation of a 3D unsteady shock wave/boundary layer interaction, in sight of turbomachinery applications. The simulation of a compressible flow through a 3D channel (ONERA) has been performed in LES, with a third order WENO scheme (Jiang, Shu, 1996) and the mixed scale model (Tenaud, Ta Phuoc, 1996). The flow has already been studied experimentally at ONERA (Cahen, 1995), and numerically with RANS modeling (Gerolymos, Vallet, 1997). The unsteady results obtained by LES within and downstream of the 3D interaction are presented and analyzed. The mean velocity profiles in the interaction zone, are then compared to both experiments and statistical numerical results.
Non-Steady Pressure-Exchange Ejector
Authors: Alhussan Khaled , Hong Woo Jong , Garris Charles
Published: March 2009

This paper will examine development of practical pressure-exchange ejector to useful level of performance, using our knowledge of aerodynamic design of a compressible fluid. A novel supersonic rotor-vane/pressure-exchange ejector system has been investigated both experimentally and numerically.
Wall Friction Measurements: Application in a Francis Turbine Cone
Authors: Ciocan Gabriel Dan , Avellan Franc¸ois , Berca Elena Lavinia
Published: March 2009

The boundary layers at a turbine runner outlet and their evolution with the operating points are unknown and represent an important factor for the pressure recovery of the elbow diffuser. To characterize the boundary layer, a hot film probe is used. The measurement accuracy is an important aspect of this study and the measurement procedure is exposed. An experimental campaign is realized in a turbine cone in order to characterize the wall friction evolution for 4 operating points. Both steady and transient analysis of the experimental results are presented.
A Design Methodology for Radial Turbomachinery: Application to Turbines and Compressors
Authors: Cravero Carlo
Published: March 2009

Different design/analysis tools are combined in an automatic procedure for the design of radial turbomachinery. The algorithms developed have different complexity levels ranging from the meanline one-dimensional design tool to the fully three-dimensional Navier-Stokes based analysis. Each code gives complementary information to the designer. The codes have been written and developed by the author at DIMSET. The design procedure is developed for both radial compressors and turbines and it is proposed for the dimensioning of rotating machinery for microgasturbine power plants.
Computational Modeling and Experimental Characterization of Indoor Aerosol Transport
Authors: Konecni S. , Whicker J. J. , Martin R. A.
Published: March 2009

When a hazardous aerosol or gas is inadvertently or deliberately released in an occupied facility, the airborne material presents a hazard to people. Inadvertent accidents and exposures continue to occur in Los Alamos and other nuclear facilities despite state-of-art engineering and administrative controls, and heightened diligence. Despite the obvious need in occupational settings and for homeland defense, the body of research in hazardous aerosol dispersion and control in large, complex, ventilated enclosures is extremely limited. The science governing generation, transport, inhalation, and detection of airborne hazards is lacking and must be developed to where it can be used by engineers or safety professionals in the prediction of worker exposure, in the prevention of accidents, or in the mitigation of terrorist actions. In this study, a commercial computational fluid dynamics (CFD) code, CFX5.4, and experiments were used to assess flow field characteristics, and to investigate aerosol release and transport in a large, ventilated workroom in a facility at Savannah River Site. Steady state CFD results illustrating a complex, ventilation-induced, flow field with vortices, velocity gradients, and quiet zones are presented, as are time-dependent CFD and experimental aerosol dispersion results. The comparison of response times between CFD and experimental results was favorable. It is believed that future applications of CFD and experiments can have a favorable impact on the design of ventilation (HVAC) systems and worker safety with consideration to facility costs. Ultimately, statistical methods will be used in conjunction with CFD calculations to determine the optimal number and location of detectors, as well as optimal egress routes in event of a release.
A T-RANS/VLES Approach to Indoor Climate Simulations
Authors: Kenjeresˇ S. , Hanjalic´ K. , Gunarjo S. B.
Published: March 2009

For accurate prediction of flow, scalar transport and wall heat and mass transfer in complex building space we propose a time-dependent RANS (T-RANS) approach which resolves in time and space the large-scale convective motion and associated deterministic eddy structure. The residual (“subscale”) turbulence is modeled by a single-point closure. The method can be regarded as Very Large Eddy Simulations (VLES) since the deterministic and modeled contribution to the turbulence moments are of the same order of magnitude. The modeled part becomes dominant in the near-wall regions where there are no large eddies and the proper choice of the subscale model is especially important for predicting wall friction and heat transfer. We use an ensemble-averaged 〈k〉 - 〈ε〉 - 〈θ2〉 algebraic stress/flux/concentration closure as the subscale model which can provide information about the stress and heat/species flux anisotropies. The method is especially advantageous for predicting flows driven or affected by thermal buoyancy, for which the conventional eddy-viscosity/diffusivity RANS models and gradient transport hypotheses are known to fail even in simple generic configurations. The approach was validated in a series of buoyancy-driven flows for which experimental, DNS and LES data are available. Examples of full-scale application include computational simulations of real occupied and furnished residential or office space in which the furniture elements and persons are treated as passive blocking elements. The simulation showed that the T-RANS approach can be used as a reliable tool for a variety of applications such as optimization of heating and ventilation system, building space insulation, indoor quality, safety measures related to smoke and fire spreading, as well as for accurate wall heat and mass transfer predictions.
Further Studies of the Axisymmetric Disk Wake Using the “Slice POD”
Authors: Johansson Peter B. V. , George William K.
Published: March 2009

This paper presents the findings of three experiments using multi-point hot-wire arrays in the high Reynolds number axisymmetric turbulent wake behind a disk. The purpose of the multiple experiments was to validate earlier and less extensive experiments. The ‘slice POD’ was applied to all sets to examine the effects of array coverage and the disk support system. The Reynolds number based on the free stream velocity and disk diameter was kept constant at 28,000. The investigated region spanned from 10 to 60 disk diameters downstream. These results confirm the earlier findings. In particular, the eigenvalues integrated over frequency show a azimuthal mode-1 dominance at x/D = 10 which evolves to a mode-2 dominance by x/D = 50. For all downstream positions, two distinct peaks were found in the first eigenspectrum: one for azimuthal mode-2 at near zero frequency, and another for azimuthal mode-1 at a Strouhal number (fd/U∞) of 0.126. Both peaks decrease in magnitude as the flow evolves downstream, but the peak at the Strouhal number 0.126 decrease more rapidly then the one at near-zero frequency, leaving the latter to eventually dominate.
Turbulent Jet Injected Into a Cross Flow: Analysis of the Flow Structure and Wall Pressure Fluctuations
Authors: Gopalan Shridhar , Abraham Bruce , Katz Joseph
Published: March 2009

The objective of this study is to characterize the velocity, vorticity, wall pressure fluctuations and resulting structural vibrations caused by injection of a round, turbulent jet into a turbulent boundary layer. The experiments are performed in a quiet water channel with back ground noise well below the local pressure fluctuations. One of the channel walls is replaced by a vibration isolated, 1m long, aluminum plate from which the 1cm-diameter jet is injected. The cross flow velocity is fixed at 2 m/s and the velocity ratio, r (ratio of mean jet velocity to the cross flow), varies from 0.5 to 2.5 and Re based on cross flow and jet diameter is 20,000. High-resolution PIV is used to measure the flow field and high sensitivity, low-noise pressure sensors are used for the wall pressure measurements. The flush-mounted transducers are installed at several locations ranging from 2–15 diameters behind the jet. Auto-spectra of the pressure signals show that the effect of the jet is in the 15–100Hz range, and increase the wall pressure levels by 25dB for r = 2.5. The fluctuations increase with velocity ratio and decrease with distance from the jet, although there is only a 6dB increase in overall levels at r = 2.5 as compared to r = 1. Hilbert-Huang “amplitude” spectrum shows the frequency content of the signal as it evolves in time, and is found to be a useful tool to characterize such unsteady phenomena. Velocity and pressure measurements have been performed simultaneously and thousands of frames have been recorded. Analysis of these frames demonstrates the relationship between the pressure fluctuations and the vortical structures. Several striking differences in the flow structure between high and low velocity ratios are described in the paper.
Droplet Temperature and Size Measurement Using Combined Two Colors Laser-Induced Fluorescence and Interference Technique: Application to the Energetic Budget of an Evaporating Monodisperse Droplet Stream
Authors: Castanet G. , Lemoine F. , Lavieille P. , Didierjean S. , Lebouche´ M. , Lavergne G. , Atthasit A. , Biscos Y.
Published: March 2009

Aerothermal properties in a fuel spray is a central problem in the field of the design of the combustion chambers of automobile engines, turbojets or rocket engines. Heat and mass transfer models are necessary in the predictive calculation schemes used by the motorists. Reliable experimental data must be obtained for both the validation and development of new physical models linked to heat transfer and evaporation in sprays, where aerodynamic interactions has a key role. This paper proposes an experimental study of the energetic budget of a monodisperse ethanol droplet stream, injected in the thermal boundary layer of an heated plate. The droplet size reduction is measured using a light scattering technique (interferential method) in order to characterize the evaporation, as the droplet mean temperature is monitored using the two colors laser-induced fluorescence technique. The convection heat transfer coefficient and the Nusselt number are inferred from the overall energetic budget, as a function of the inter-droplet distance, characterizing the interaction regime. The results are compared to physical models combined with numerical simulations available in the literature, for moving, evaporating isolated droplets and for three droplets arrangement in linear stream.
Development of Modern Electronic Control Systems for Power Distribution
Authors: Gaffney Brian D.
Published: March 2009

The power industry is increasingly affected by several trends, which require improvements in the distributed generation and control systems of on-site power. These trends include the ability to share load across generators more effectively, seamless sequencing of generators, and the ability to monitor and control power that is being produced. Electronic control systems can provide these advantages in a cost effective solution. The application of electronic controls to a power distribution system requires a thorough development program. It is imperative to assure that the controls will provide reliable, long-term performance, as well as meeting the plant’s current and future needs for power distribution. This paper describes the development and field evaluation required to apply electronic controls to existing switchgear and power distribution systems in the power generation industry. The microprocessor based electronic control system for today’s power plants replaces out-dated analog equipment and antiquated relay logic. The new systems incorporate three main functions: Paralleling generators, monitoring power requirements, and effective sequencing of generators in power plants. Integration of these functions into the microprocessor based control system provides increased reliability, reduced cost, and enhanced performance, while concurrently providing increased flexibility in the operation of the plant. Additional benefits can be realized including reduced operator requirements, reduced training costs, and reduced burden on instrumentation electricians. A primary focus of this paper is the process used to qualify the control system needed for specific types of existing distributed power systems. This process consists of current system evaluation and categorization, establishment of classification of plant (utility, merchant plant, peak shaving facility, IPP), and determining the future needs of individual plants for power distribution. Local regulatory and utility protection and interconnect requirements must also be assessed to assure that the new control system meets or exceeds them. Methods of accurately monitoring, improving performance, and providing generator sequencing are defined, including accounting for improvements in the long-term expansion of the distributed power control and monitoring system.
Feasibility of Combustion Turbine Inlet Air-Cooling in the Arabian Gulf Region
Authors: Zamzam Montaser M. , Al-Amiri Abdalla M.
Published: March 2009

Combustion turbine inlet air-cooling systems (CTIACS) have been implemented in various regions around the globe and have displayed proven results in terms of their effectiveness and economic feasibility. Nonetheless, these systems have been rarely employed in the Arabian Gulf region with such existing installations are still undergoing continuous evaluation. The main objective of this study is to highlight the associated benefits of employing a CTIACS option in UAE. This is achieved by first exploring the weather patterns in UAE in order to propose proper weather design conditions. Moreover, the impact of a CTIACS is presented, for a prescribed inlet air temperature, on the annual gross energy increase, average heat rate reduction, cooling load requirements and net power increase. Finally, a combustion turbine unit with a relatively small mass flow rate is shown to be very much feasible economically even upon reducing inlet air temperature below the ISO rating.
Modelling and Simulation for Extra Heavy Oil Gasification on Entrained Flow Gasifier
Authors: Watanabe Hiroaki , Otaka Maromu , Hara Saburo , Ashizawa Masami , Kidoguchi Kazuhiro , Inumaru Jun
Published: March 2009

The objective of this study is to develop an evaluation tool for a design and performance of an extra heavy oil gasifier by a numerical simulation technique. The modelling and the numerical simulation for the extra heavy oil gasification on the 2.4 tons/day entrained flow gasifier of CRIEPI are described in this paper. The gas phase properties are calculated by three dimensional time-mean Eulerian conservation equations, in addition to the k-ε turbulence model. The fuel droplet behavior is modelled via a Lagrangian particle tracking approach. Four reaction processes are modelled in the present paper: atomization (micro-explosion), pyrolysis, coke gasification reaction, and gaseous phase reaction. As a result of the simulation, in a relationship between an oxygen ratio of the gasifier and the gasifier performance, such as heating value of the product gas, carbon conversion efficiency are presented. Distribution of gas temperature and gas composition in the gasifier, and the product gas composition are also presented. Comparison between the computational and the experimental results shows that the most features of the gasifier performance have been captured accurately by the computational procedure. The numerical simulation approach is very useful for the assessment of gasification performance, operation support and optimization of the gasifier design.
Thin-Wall Titanium Condenser Tubing: The Next Plateau
Authors: Schumerth Dennis J.
Published: March 2009

Commercially pure (cp.) titanium and its alloys provide excellent resistance to general and localized corrosion attack under most oxidizing, neutral and inhibited reducing conditions in aqueous environments. Titanium is also notable for its outstanding resistance to chlorides and other halides generally present in most process streams. In addition, titanium resists other malicious phenomenon including steam and particle erosion, crevice corrosion, galvanic attack and MIC. Given this general corrosion immunity, designers have increasingly applied thin-wall condenser tubing in pursuit of cost savings and performance enhancement. Typically, these thin-wall applications have, over the past several years, been limited to 25 BWG or 0.020”/0.5mm walls or heavier. The “industry” has, out of necessity, moved to address the special nuances of the 25 BWG including design, procurement, handling, fabrication and testing parameters with increasing success. It would appear however, that designers, operators and pundits alike require further education and refinement on the specific operational characteristics when integrated into the powerplant environment. Considerable work has been recently completed investigating even thinner wall titanium tubing. This paper will address the essential data elements of this expanded research focusing specifically on Grade 2 titanium in 27 BWG or 0.016”/0.4mm. Since a significant portfolio of 27 BWG installations is rapidly taking shape, it is prudent to examine key ingredients that would warrant consideration of this “next-plateau” gauge material. Indeed, work is currently underway exploring the technology required to fabricate condenser tubes as thin as 30 BWG /0.013”/0.3 mm.) In summary, the paper will present and summarize substantive evidence suitable for comparison against previously acquired empirical data and prior art.
Effect of Elliptical Burner Geometry on Stability and Global Emission Characteristics of Pre-Mixed Flames
Authors: Baird Benjamin D. , Gollahalli S. R.
Published: March 2009

An important topic in combustion research today is pollutant emission reduction. With the current demand for large amounts of economical, clean power, there is a need for research in both the increase of combustion performance and the reduction of emissions. Two methods of the so-called ‘passive’ flame controls are the use of premixing the air and fuel and the variation of the geometry of the flame. Both mechanisms offer the promise of increasing efficiency as well as reducing harmful emissions. However, the effect of these controls on the stability of the flame has not been fully studied. This paper will attempt to fill in some of this gap and will study the effects of elliptical burner geometry on premixed flames. The study will present stability results for circular and 4:1 aspect ratio elliptical burner geometry for a range of fuel mixtures of propane and hydrogen. The paper will also report the emission indices of CO and NO of the 40% by mass hydrogen in propane mixture. It was found that the 4:1 aspect ratio burner had reduced blow-out stability, produced a much shorter flame, and, in general, produced more carbon monoxide and less nitric oxide than a circular burner.
Jet Injection Into Swirling Crossflow for Improved Mixing and Combustion
Authors: Lilley David G.
Published: March 2009

The aerodynamics benefits of lateral jet injection into swirling crossflow have long been recognized and used by combustion engineers. Studies are reported here on experimental and theoretical research on lateral jet injection into typical combustor flowfields for low-speed turbulent swirling flow conditions in the absence of combustion. The main flow is air in a round cross-sectioned plexiglass tube. The degree of swirl can be varied by varying the angles of the blades of an annular swirler, located upstream of the test section. Lateral jet injection is normal to the main airflow, from round-sectioned nozzles. Either a single lateral jet or two diametrically opposed jets are used for this secondary injection of air into the main airflow. The principal aim is to investigate the trajectory, penetration and mixing efficiency of the lateral injection. Flow visualization with helium-filled soap bubbles and multi-spark ionized path techniques, five-hole pitot probe time-mean velocity measurements, and single-wire time-mean velocity and turbulence data (normal and shear stress) have been obtained in the experimental research program. A fully three-dimensional computer code with two-equation turbulence model has been developed and used in the theoretical research program. The present paper reviews the activity and highlights key results obtained during the study.
Shared BMS Logic Systems in Boiler Applications: A Hypothetical Study
Authors: Raney Glenn A.
Published: March 2009

The National Fire Protection Association’s “NFPA 85 Boiler and Combustion Systems Hazards Code 2001 Edition” currently requires an independent logic solver for each burner management system. This requirement can result in high costs when providing burner management systems for multiple boiler applications. Current logic system technology provides dual and triplicated redundant logic solvers with the capability to reliably perform emergency shutdown functions for multiple equipment. This paper presents a hypothetical study that will quantitatively show the high level of availability and reliability that could be achieved employing a redundant logic system in multiple boiler applications. Common cause failure considerations will also be addressed.
Reducing Dissolved Oxygen Under Conditions of High Air Ingress
Authors: Harpster Joseph W.
Published: March 2009

Recent considerations of steam and air mixture dynamics in operating condensers has led to a more thorough understanding of how condenser performance is affected by air in-leakage. Results of this model-based theoretical description, which are in agreement with measurement data from operating condensers, are reviewed and used to propose beneficial design features for new and re-tubed condenser assemblies. It is anticipated from this work, that condensers can be designed which significantly reduce the amount of dissolved oxygen in condensate from locations of free air ingress above the hotwell level. This reduction also applies to other undesirable noncondensables that enter condensate driven by the same mechanism contributing to dissolved oxygen. When air in-leakage becomes sufficiently high, it contributes to excess back pressure on the turbine. In this region of high air in-leakage, the amount of dissolved oxygen can become very high. The design therefore, minimizes or eliminates the corrosive effects of air inleakage, both high and low, which is particularly important during periods of high demand when load must be maintained.
Evolution of Line-Pipe Steel and Its Implications for Transmission Pipeline Design
Authors: Leis B. N.
Published: March 2009

This paper discusses the evolution of line-pipe steel against the background of the failure incidence and the design basis for transmission pipelines, with a focus on those transporting natural gas. Working-stress design (WSD) is introduced as background for analysis of incident experience. It is shown that failure incidence does not correlate with the WSD factor of safety on pressure-induced stress, leading to the underlying causes of failure and discussion of alternative design philosophies, and consideration of safety factors other than those based on stress, or the effect of pressure. Full-scale test data are discussed to rationalize why failure frequency does not correlate with factor of safety. These results point to a very large factor of safety on pressure, with failure pressure found much in excess of the specified minimum yield stress (SMYS), the reference stress for WSD-based pipeline design. Full-scale failure at pressures much in excess of that for in-service incidents motivates discussion of causes of such failures and brings into question the utility of alternative design philosophies. The role of toughness is introduced as key to the success of WSD and alternative design philosophies. The historical evolution of both strength and toughness is then introduced along with apparent differences in toughness depending on how it is characterized. Historical trends are contrasted to those for modern steels, with diametrically opposing trends evident. The implications for design are discussed with reference to fracture control plans and methods to characterize required arrest toughness.
Investigation Into the Use of a Single Specimen for the Determination of Dynamic Steady State Propagation Resistance in High Toughness Line-Pipe Steels
Authors: Rudland David L. , Wilkowski Gery , Wang Yong-Yi , Horsley David , Rothwell Brian , Glover Alan
Published: March 2009

This paper summarizes efforts funded by TransCanada PipeLine Limited on improving the methodology for predicting a true measure of the dynamic steady-state fracture toughness of line-pipe steels using a single mill test specimen. In the past, ductile fracture methodologies generally involved using the Charpy V-notch test to empirically quantify the material dynamic ductile fracture propagation resistance. However, due to its geometry, the use of the Charpy test has proven to be unreliable for high-toughness materials, for materials that have rising-shelf energies, and for higher-grade steels (relative to those for which correlations were originally established). An improved methodology for characterizing the dynamic ductile fracture resistance is to utilize the energy from a full-thickness impact specimen, of which the Drop-Weight Tear Test (DWTT) specimen is the most frequently used type. It has been demonstrated that the total energy from a DWTT-type specimen includes; (1) the energy associated with initiation of the crack (including indentation energy and yielding of the specimen), (2) the energy for transient crack growth from initiation to reaching steady-state fracture, (3) steady-state fracture energy, and (4) a non-steady-state fracture energy region at the end of the test. During the steady-state fracture region it was observed that both the crack velocity and constant crack-tip-opening angle (CTOA) remained constant. This paper presents the results of an investigation aimed at identifying a single specimen that will capture only the steady-state fracture energy present in standard DWTT specimens. Detailed experiments and three-dimensional finite element analyses were used to verify various procedures for eliminating the initiation energy and the residual energy at the end of the tests. A non-instrumented modified specimen, the back-slotted, static-precracked DWTT (BS-SPC-DWTT) specimen, has been developed from the results of these analyses. Energy results from this specimen, for a variety of line-pipe steels, are presented. A correlation between these energies and the propagation energy from standard DWTT specimen is presented. This correlation will aid in the methodology for predicting axial crack arrest in line-pipe steels having higher toughness, a rising upper shelf, or a higher grade.
Trends in Pipeline Integrity Inspection and Rehabilitation Techniques
Authors: Mohitpour Mo , McManus Michael , Trefanenko Bill
Published: March 2009

Advancements in rehabilitation, maintenance, monitoring, predictive, and operational control technologies have reached the stage that long distance transmission pipelines can provide reliable and safe service without imposing safety regulations that previously were based on inaccurate assessment of pipeline systems maintainability and operation.
16 Inch Williams Gas Pipeline Inspected for SCC Using PII’s New Ultrasonic Tool
Authors: Katz David C. , Ru¨hle Udo , Wolf Thomas
Published: March 2009

The in-line-Inspection of Williams’ Gas West Pipeline in September 2001 was successfully completed using the newly developed 16” UltraScan® CD tool of GE PII Pipeline Solutions. The particular pipeline section inspected was known to be affected by Stress Corrosion Cracking (SCC). The inspection was carried out using the liquid batching technique developed by PII Pipeline Solutions. A special launcher and receiver barrel was designed to enable the handling of a series of three batching pigs in front of and two behind the inspection tool. A manifold of “kicker lines” was mounted to the barrel to launch the batching pigs and the inspection tool. The main benefits of this new design were minimizing operational downtime, ensuring complete air/natural gas displacement from the launcher, and providing for a smoother launch procedure. Due to the large elevation changes within the pipeline section, a key concern was maintaining pig velocity within 1m/s for adequate data resolution. Rather than rely on a general “rule of thumb”, a transient analysis was performed to define a range of possible batch sizes and better understand the expected pressure gradients while pumping the water slug. Based on actual data collected during this successful run, the transient model will be refined to better handle friction effects between the sealing cups and disks in future batch inspection runs. The data analysis stage for large crack features is completed and full analysis for small defects is ongoing. Analysis and excavation results are discussed in the paper. Results from this inspection are expected to considerably extend the understanding of crack formation in this pipeline and will be used to help establish an overall integrity management plan for the pipeline.
Development of 36” EmatScan® Crack Detection (CD) Tool
Authors: Yeomans Mark , Ashworth Blaine , Strohmeier Uwe , Hugger Achim , Wolf Thomas
Published: March 2009

TransCanada PipeLines has been performing periodic hydrostatic pressure tests of natural gas pipeline sections susceptible to stress corrosion cracking (SCC). In 1996, the Canadian National Energy Board (NEB) held a public inquiry into SCC and recommended that industry develop a reliable SCC In-Line Inspection (ILI) tool. This paper describes the TransCanada and PII Pipeline Solutions project to jointly develop a 36 inch (914 mm) diameter crack detection tool based on EMAT (Electro Magnetic Acoustic Transducer) technology. The EmatScan® CD tool is designed to operate in gas pipelines without a liquid couplant. The EmatScan® CD tool will detect and size longitudinally oriented external SCC features. In 2001, testing of the technology has shown that it can distinguish: • insignificant pipe wall features (stringers, laminations and inclusions) from SCC defects; • internal from external pipe wall features. Off-line tests were performed by pulling the tool through a series of pipe spools containing SCC and other pipe wall features. These pipe spools are from two sections of the TransCanada system where PII’s UltraScan® CD tool was run. This joint project to develop a new ILI tool began in early 1997, and will be completed in 2002.
Application of Data Transmission Capability on Natural Gas Transmission Pipelines
Authors: Moore Karen A. , Carrington Robert , Richardson John , Zatorski Ray A.
Published: March 2009

Third party damage is as a significant factor in natural gas pipeline failures. 75% of pipeline failures induced by a third party occur immediately following impact. Current inspection techniques are both labor intensive and expensive to implement and they represent only a point in time status. The objective is for a near real time detection and communication system that utilizes the pipe itself, i.e., a “smart pipe”. The industry is calling for an inexpensive rugged process that transmits the state of the pipe. The INEEL is developing a near real time damage detection and location system that utilizes resistive traces applied to the wall of the pipe, which detects damage by measuring the strain state of the pipeline. This data will also allow for efficient repairs and emergency response. The technique employed is a network of thermally sprayed resistive traces deposited on either the interior or exterior wall of the pipeline. The ability of a thermally sprayed resistive trace to detect damage is due to the unique manner in which a porous metal changes resistivity when placed under strain.