bluuebunny/crossref_metadata_2025 huggingface dataset:
Identifying the Magnitude and Location of a Load on a Slender Beam Using a Strain Gage Based Force Transducer
Authors: Bednarz Edward T. , Zhu W. D. , Smith Scott A.
Published: October 2013

A unique strain gage based method is developed to identify the magnitude and location of a load on a slender beam with non-homogeneous material, variable cross sections, and pinned, firm rest, soft rest, pinned-fixed, and fixed boundary conditions. Four uniaxial strain gages are mounted to the bottom surface of the beam, and the bending moment diagram of the beam can be constructed using measured strains on the beam. By combining individually scaled strain gage outputs, the magnitude and location of the load can be accurately identified. The strain gage based force transducer methodology is experimentally validated on prismatic beams with firm rest, soft rest, firm rest-fixed, and fixed boundary conditions, and a continuously tapered beam with rest boundary conditions. The force transducer methodology is independent of the boundary conditions of the beam and the error from strain gage drift due to uniform thermal expansion on a prismatic beam can cancel out.
An Inverse Algorithm for Resonance Inspection
Authors: Lai Kevin , Xu Wei , Sun Xin
Published: October 2013

Compared to other contemporarily used non-destructive evaluation (NDE) techniques, resonance inspection (RI), which employs the natural vibrational frequency spectra shift induced by the damage to detect defects, is advantageous in many aspects such as low cost, high testing speed, and broad applicability to complex structures. However, the inability to provide damage details, i.e. location, dimension, or types, of the flaws severely hinders its wide spread applications and further development despite its early success in the automobile industry for quality inspections of safety critical parts. In this study, an inverse RI algorithm using a maximum correlation function as the filtering function is proposed to quantify the location and size of flaws for a discrepant part. The algorithm and the numerical schemes are validated using a dog-bone shaped stainless steel sample, while the spectrum data for the original part and flawed parts were generated by a commercial FEM package. The results show that multiple flaws can be accurately identified using the proposed RI inversion method. The study further showed that the reliability of the inversion method is sensitive to the spectrum range included in the correlation function computation. It is demonstrated that the frequency range required to provide accurate predictions is inversely correlated to the defect size. Large defects can be detected using lower frequency spectrum data only, while smaller defects require a higher frequency range.
Comparative Evaluation of Fatigue Assessment Techniques on a Forged Steel Crankshaft of a Single Cylinder Diesel Engine
Authors: Metkar Rajesh M. , Sunnapwar Vivek K. , Hiwase Subhash Deo
Published: October 2013

Crankshaft is one of the critical components of an IC engine, failure of which may result in disaster and makes engine useless unless costly repair performed. It possesses intricate geometry and while operation experiences complex loading pattern. In IC engines, the transient load of cylinder gas pressure is transmitted to crankshaft through connecting rod, which is dynamic in nature with respect to magnitude and direction. However, the piston along with connecting rod and crankshaft illustrate respective reciprocating and rotating system of components. the dynamic load and rotating system exerts repeated bending and shear stress due to torsion, which are common stresses acting on crankshaft and mostly responsible for crankshaft fatigue failure. Hence, fatigue strength and life assessment plays an important role in crankshaft development considering its safety and reliable operation. The present paper is based on comparative studies of two methods of fatigue life assessment of a single cylinder diesel engine crankshaft by using fracture mechanics approach viz. linear elastic fracture mechanics (LEFM) and recently developed critical distance approach (CDA). These methods predict crack growth, time required for failure and other parameters essential in life assessment. LEFM is an analytical method based on stress intensity factor which characteristics the stress distribution in the vicinity of crack tip, where as CDA is a group of methods predicts failure using stress distance plot. The maximum stress value required for both the methods are obtained using finite element analysis. The present paper provides an insight of LEFM and CDA methods along with its benefits to the designers to correctly assess the life of crankshaft at early stage of design. This paper also gives a detailed overview of failure analysis process including theoretical methods and result integration for predicting life of components as compared to life estimation by means of software.
Numerical Study of Heat Transfer Characteristics of Liquid Flow in a Microtube With Blend of Micro Phase Change Materials
Authors: Khakpour Yasmin , Yagoobi Jamal Seyed
Published: October 2013

This numerical investigation explores the heat transfer characteristics of liquid flow with two-component (blend) micro phase change materials (MPCM) and compares them with those of a single component MPCM slurry. The numerical domain is comprised of an axisymmetric micro-tube in contact with a finite-thickness solid zone and a constant heat flux applied on the solid outer wall. The ultimate objective is to demonstrate the tunability of PCM fluid’s thermal energy properties when the phase transition temperatures of the PCMs are chosen within a range required for a specific application. This is because different pure PCM materials store latent heat at a specific range of temperatures. The MPCM slurry flow does not reach a fully developed condition as long as the MPCM particles experience phase change in the developing region. The local heat transfer coefficient strongly depends on the corresponding location of the melting zone interface.
Simulation of Fully-Developed Average Turbulent MHD Pipe Flow With Heat Transfer
Authors: Alammar K. , Vilagines R. , Shariff M. , Kaneesamkandi Z. , Abdullah S.
Published: October 2013

Using a zero-equation turbulence model, fully-developed average turbulent MHD pipe flow with wall heating was simulated. Uncertainty was approximated through grid-independence and model validation. Effect of Reynolds, Hartmann, and Prandtl numbers on heat transfer characteristics was investigated. With increasing Hartmann number, heat transfer was shown to increase towards the side layer. Increasing the Prandtl number was shown to enhance heat transfer. Increasing the Reynolds number decreased the effect of the Hartmann number.
Printed Circuit Board Pad Crater Test Methods and Sample Design
Authors: Embree Todd , Novita Deassy , Long Gary , Parupalli Satish
Published: October 2013

The continual drive toward smaller second level interconnect dimensions, along with the introduction of Halogen-Free circuit board materials and increased process temperatures of Lead-Free solders, have all contributed to a more frequent occurrence of Pad Crater damage in circuit board materials during manufacturing and test processes. This paper addresses the methodology and test data of some common industry methods used to evaluate Pad Crater strength in circuit board materials. Pad Crater test data is highly sensitive to sample design; as a result a discussion of sample design criteria is also included.
A Proposal for Power Quality Management Protocol in Residential Buildings With Co-Generative and Renewable Systems
Authors: Di Veroli Mario , Calabria Alfonso
Published: October 2013

The aim of this paper is to describe a management protocol for electrical and thermal loads in housing scheme equipped with co-generative unit and renewable system. In new residential buildings is very important the presence of co-generative unit and renewable system to turn from the actual electrical grid (passive) into a smart grid; in fact, nowadays “few” power plants satisfy all customer electric demands; whereas in the near future the electrical final users will became local power producers. The new management protocol allows to optimize the energy demands in according with electrical energy cost, depending on time slot, and the instant power generation from co-generative and renewable devices. This system is capable, by simplex “domotic interface”, described analyzed and design by the authors, to individuate the more convenient time for the users, to respond at their energy demands. The advantage of this system can be found on a new power quality management, with consequent cost decrease for the users.
Stress Analysis of a Rotating FGM Circular Disc With Exponentially-Varying Properties
Authors: Kurşun Ali , Topçu Muzaffer , Yücel Uğur
Published: October 2013

In this study, elastic stress analysis of a thin circular disc made of functionally graded materials (FGMs) subjected to a temperature load and an inertia force due to rotation of the disc is investigated. Based on the two dimensional thermoelastic theories, the axisymmetric problem is formulated in terms of a second order ordinary differential equation which is solved by finite difference method (FDM). The FGM disc is assumed to have exponential variation of material properties in radial direction only and Poisson’s ratio is kept constant. The result also compared with semi-analytical solution (SAS) and their consistence has been shown. Some numerical results of thermoelastic field are presented and discussed for an Al2O3/ZrO2 FGM.
A New Approach for the Derivation of the Similarity Equation of the 2-D Unsteady Boundary Layer Equations
Authors: Sattar Md. Abdus
Published: October 2013

A local similarity equation for the hydrodynamic 2-D unsteady boundary layer equations has been derived based on a time dependent length scale initially introduced by the author in solving several unsteady one-dimensional boundary layer problems. Similarity conditions for the potential flow velocity distribution are also derived. This derivation shows that local similarity solutions exist only when the potential velocity is inversely proportional to a power of the length scale mentioned above and is directly proportional to a power of the length measured along the boundary. For a particular case of a flat plate the derived similarity equation exactly corresponds to the one obtained by Ma and Hui[1]. Numerical solutions to the above similarity equation are also obtained and displayed graphically.
A Combined Cycle Power Plant With Absorption Cooling for Houses Air Conditioning
Authors: Almutairi Hamad H. , Dewsbury Jonathan , Lane-Serff Gregory F.
Published: October 2013

This study examined the viability of a single-effect water/lithium bromide absorption chiller driven by steam extracted from the steam turbine in the configuration of a combined cycle power plant (CCPP). System performance was verified based on the annual cooling load profile of 1,000 typical houses in Kuwait obtained from DesignBuilder building simulation software. Computer models that represented a CCPP with an absorption chiller and a CCPP with a Direct-Expansion (DX) air conditioning system were developed using Engineering Equation Solver software. The computer models interacted with the cooling load profiles obtained from DesignBuilder. Analysis shows that the CCPP with the absorption chiller yielded less net electrical power to the utility grid compared to similar CCPPs giving electricity both to the grid and to the Direct-Expansion air conditioning systems given the same cooling requirements. The reason for this finding is the reduction in steam turbine power output resulting from steam extraction.
Effects of Oxygenates Molecular Structure on the Sooting Tendency and PM Emissions of Ethanol-Gasoline and Biodiesel-Diesel Blends
Authors: Barrientos Eduardo J. , Boehman André L. , Neal Gary L. , Haworth Daniel C.
Published: October 2013

Fuel composition has a significant effect in emissions from particulate matter (PM) and soot formation in internal combustion engines. Numerous studies, both experimental and numerical, have reported that oxygenated fuels reduce particulate emissions. These studies have proved that this reduction depends not only on the oxygen content but also on the molecular structure and the different oxygen functional groups. Consequently, this paper contains an analysis of the relationship between fuel composition and soot formation and PM emissions from oxygenated fuel blends. In this study, ethanol-gasoline and biodiesel-diesel fuel blends have been tested via a smoke point lamp in order to determine the variations in the sooting tendency in relation to the oxygen content of fuel blends and the effect of oxygenated additives on the sooting propensity of the blends. Particulate matter collected from the smoke point tests has been analyzed via X-Ray Photoelectron Spectroscopy (XPS) to quantify the surface oxygen content of the soot samples and to qualitatively identify oxygen functionalities on the samples. An attempt was made to correlate these results with the oxygen concentrations and molecular structure of the fuels.
Flow Through Nanoporous Electrodes in a Microfluidic Fuel Cell
Authors: Sprague Isaac B. , Dutta Prashanta
Published: October 2013

In this paper we present how advection in the electric double layer (EDL) affects the kinetic performance of electrochemical cells. To accomplish this we use a laminar flow fuel cell model based on the Poisson-Nernst-Planck and Frumkin-Butler-Volmer equations. The model contains nonlinear physics with very disparate length scales due to the complex 3-dimensional nature of the nano-porous device. To account for these difficulties, the full mathematical model is solved numerically using a novel numerical algorithm developed based on domain decomposition method. Numerical results show that the presence of an advection flux through nano-pores on the order of the EDL width yields some novel physics that affect the structure of electrode-electrolyte interface. We also show that electrolyte advection within the EDL can be used to enhance the kinetic performance of electrodes in electrochemical cells. In the device presented the peak power density can be increased significantly with flow velocity.
Improving the Engagement Smoothness Through Multi-Variable Frictional Map in Automated Dry Clutch Control
Authors: D’Agostino V. , Cappetti N. , Pisaturo M. , Senatore A.
Published: October 2013

An Automated Manual Transmission (AMT) is directly derived from a manual one through the integration of actuators; then, development and production costs are generally lower than other automatic transmissions, while the reliability and durability are at highest level. For high class sport cars, vehicle dynamic performances and driving quality can be strongly improved with respect to automatic transmissions [1]. AMTs systems are generally constituted by a dry or wet clutch assembly and a multi-speed gearbox, both equipped with electro-mechanical or electro-hydraulic actuators, which are driven by a control unit, the transmission control unit (TCU). The operating modes of AMTs are usually two: semiautomatic or fully automatic. In both cases, after the gear shift command, the TCU manages the shifting steps according to current engine regime, driving conditions and selected program.

In this transmission type the quality of the vehicle propulsion as perceived by the driver is largely dependent on the quality of the control strategies. Furthermore, sensitivity analyses on control schemes for AMTs have shown that uncertainties in clutch torque characteristic can severely affect the performance of the clutch engagement: modeling in detail the torque transmitted by the specific clutch architecture is a crucial issue in order to design robust engagement control strategies [2, 3 and 4].

This paper aims at investigating the engagement performance of an actuated dry clutch by taking into account the inference of the pressure on the facing materials and the sliding speed. In fact, according to literature outcomes [5], the friction coefficient after a first rising behavior with the sliding speed shows an asymptotic value for a typical clutch facing; the same material exhibits a nearly linear dependence of the friction coefficient on the pressure.

The simulations consider: reduced-order dynamic system for simulation of passenger car driveline, control algorithm, experimental maps of the n-D clutch transmission characteristic, and gear shift maneuvers in different operating conditions.

The outcome of this analysis could provide valuable issues for designers of automated clutches and control engineers to overcome the well known poor engagement performances of open loop motion strategy of the throwout bearing where cost reason and complexity don’t permit the use of displacement sensor.
Encapsulating Protective Layers for Enhancing Survivability of Circuit Board Assemblies in Harsh and Extreme Environments
Authors: Chao Nien-Hua , Dispenza John A. , DeAngelis Mario E.
Published: October 2013

Potted electronics are becoming more common in precision-guided artillery-launched munitions and also missile systems due to the requirements for miniaturization and structural-robustness. In this paper we have presented a methodology for encapsulating circuit board assemblies (CBA) with a thin polymer layer. The protective polymer layer is both flexible and soft enough to protect the CBA from damage caused by CTE mismatches, and without any appreciable degradation in the structural support during the high-g forces of projectile launch.

The application process described here allows for the use of a broad range of polymer materials including those that may not be formed directly against an actual CBA. Proof-of-concept experimental tests and finite-element simulations have been performed and the tests and simulation results are shared in this paper. In addition, the protective polymer layer can also be used to improve in-circuit board crosstalk and RF interference shielding, tin-whisker growth control, moisture barrier properties, and thermal management for un-potted and potted CBAs.
Failure Mechanism and Reliability Design Study of Bendable Electronic Module
Authors: Han Changwoon , Oh Chulmin , Hong Won Sik
Published: October 2013

An electronic module was designed and developed to bend easily and repeatedly for a mobile application by a low-cost roll-to-roll manufacturing process [1]. The schematic diagram of the bendable module and its numerical model are shown at Fig.1. In the module, a thin silicon electronic chip is embedded in a polymer-based encapsuling adhesive between flexible copper clad polyimide (PI) layers. The thickness of silicon chip is 50 μm. Au bump is attached to the silicon and copper lines with anisotropic conductive film (ACF).
Effect of Particle Size and Viscosity on Erosion in Annular and Slug Flow
Authors: Kesana N. R. , Throneberry J. M. , McLaury B. S. , Shirazi S. A. , Rybicki E. F.
Published: October 2013

Solid particle erosion is a mechanical process in which material is removed from a surface due to impacts of solid particles transported within a fluid. It is a common problem faced by the petroleum industry, as solid particles are also produced along with oil and gas. The erosion not only causes losses resulting from repairs and decreased production but also causes safety and environmental concerns. Therefore, the metal losses occurring in different multiphase flow patterns need to be studied and understood in order to develop protective guidelines for oil and gas production equipment. A large scale boom loop, which is capable of generating a wide variety of multiphase flow regimes was used for conducting experiments. Specifically, this work examines erosion measurements in multiphase slug and annular flow regimes. These flow regimes are selected since they produce higher metal losses than other flow regimes, and they also occur for a wide variety of operating conditions. Experiments are performed on a horizontal 0.0762 m (3-inch) diameter pipe, with superficial gas velocities ranging from 15.2 m/s (50 ft/s) to 45.7 m/s (150 ft/s) and superficial liquid velocities ranging from 0.46 m/s (1.5 ft/s) to 0.76 m/s (2.5 ft/s), for liquid viscosities of 1 cP and 10 cP. Carboxymethyl Cellulose (CMC) was used to increase the viscosity of the liquid without significantly altering the density of the liquid. Three different sand sizes (20, 150 and 300 micron sand) were used for performing tests. The shapes of the sand are also different with the 20 and 300 micron sand being sharper than the 150 micron sand. Erosion measurements are taken using Electrical Resistance (ER) probes which relate the change in electrical resistance to the change in the thickness of an exposed element resulting from erosion. Two probes are placed in a bend and another probe is placed in a straight section of pipe. The probes in the bend are flat-head probes, and they are placed flush with the outer wall in the 45 and 90 degree positions. The probe in the straight pipe is an angle-head probe which protrudes into the flow with the face placed in the center of the pipe. Under the flow conditions investigated, the angle-head probe measures the maximum erosion due to its placement. Results demonstrate a significant increase in the metal loss occurs when increasing the superficial gas velocity and decreasing the superficial liquid velocity. The effect of changing the viscosity of the liquid is not as clear. Results suggest a slight increase in metal loss by increasing the viscosity from 1cP to 10 cP in slug flow. However, for annular flow, higher erosion occurs for the lower liquid viscosity considered.
Modeling and Control of an Infinitely Variable Speed Converter With Application to Wind Turbines
Authors: Zhu W. D. , Wang X. F.
Published: October 2013

Traditional transmission in wind turbine applications has a constant output-to-input speed ratio, which needs a power converter to regulate the current frequency that can be fed into the grid. Different types of continuously variable transmission (CVT) have been developed for vehicle and wind turbine applications, which can generate constant-frequency current without using a power converter in a wind turbine. An infinitely variable speed converter (IVSC) is a specific type of CVT that can achieve a zero speed ratio and transmit a large torque at a low speed ratio. An IVSC with drivers that convert an eccentric motion of cams to a concentric motion of the output shaft through one-way bearings is introduced, and an active control system with a combined feedback and feed forward control that can automatically adjust the eccentricity of the outer cams to control the speed ratio of the transmission is developed. The kinematic model of the IVSC is derived and fitted by a polynomial function to serve as the feed forward function in the control law. The feedback control is used to reduce the system error. A dynamic model of the IVSC is derived to investigate the effect of the dynamic load on the input and output speeds. Static and dynamic tests were conducted to validate the kinematic model of the IVSC. The variation of the average output speed per revolution of the output shaft is 0.56% with respect to the desired output speed in the simulation and 0.91% in the experiments.
Analytical Dynamics of a Ball Bouncing on a Vibrating Table
Authors: Guo Yu , Luo Albert C. J.
Published: October 2013

In this paper, the theory of flow switchability for discontinuous dynamical systems is applied. Domains and boundaries for such a discontinuous problem are defined and analytical conditions for motion switching are developed. The conditions explain the important role of switching phase on the motion switchability in such a system. To describe different motions, the generic mappings and mapping structures are introduced. Bifurcation scenarios for periodic and chaotic motions are presented for different motions and switchability. Numerical simulations are provided for periodic motions with impacts only and with impact chatter to stick in the system.
Investigation of Rub-Impact Setup Supported on Flexible Multi-Bearing Rotor
Authors: Falah Abdulazim H. , Khorshid Emad A. , Alhazza Khalid A.
Published: October 2013

Vibration system investigation of the chaotic response of full annular rub impact rotor system supported on two ball bearings is investigated. Modeling and experiments of nonlinear dynamics on flexible multi-bearing rotor test rig is presented in this work. The test rig has two balancers that are assembled on rotor shaft, a rub impact device at the center, and ball bearings at both ends of the shaft. A 12-degree-of-freedom (DOF) linear model was developed for this test rig. The mathematical model was developed in the beginning without considering the rub impact part in order to validate the model with the experiment results. Then, then experimentally chaotic response and bifurcation diagram of the rub impact system were investigated.
The Human Body is a Pressurized Self-Assembly Machine
Authors: Bayles Brenda K. Krkosska
Published: October 2013

The novel and self-obtained concept of this paper is that living tissues get help self-assembling by following some mechanical equations. The simple diagnostic act of checking someone’s blood pressure reminds us that the human body is a pressurized object, and blood moving throughout the pressurized body creates flows that are strikingly similar to the movements of fluids in pressurized machines. Self-assembly using two mechanical concepts and their equations is herein demonstrated for the first time to show the separation of healthy daughter cells and the nonseparation of aneuploid cells, and to show monosaccharide and disaccharide movements.
Effect of Rheology on Oil Well Plugging Process
Authors: Abdu A. , Naccache M. F. , de Souza Mendes P. R.
Published: October 2013

The process of oil well plugging is largely used in oil industry. In this process, a cement plug (higher density fluid) is placed over the drilling fluid (lower density) to seal and abandon the well. The success of the operation depends on several aspects, such as the density ratio and the rheology of the fluids. A numerical analysis of the transient flow just after the cement placement in vertical wells is performed, using Fluent software (Ansys Inc.). The conservation equations of mass and momentum are solved using the finite volume technique. The volume of fluid method is used to deal with the multiphase flow - cement / drilling fluid. Both the drilling fluid and the cement paste are viscoplastic liquids, modeled by the Herschel-Bulkley equation. The analysis of flow displacement and interface configuration between these fluids is an important tool for the process optimization. The effects of the density ratio and yield stress on the flow pattern are investigated. It is shown that the flow is highly unstable and that the above mentioned parameters strongly affect the process.
A Prediction of Total Cutting Time When Crosscutting Rounds, Pipe, and Rectangular Bar With a Portable Bandsaw
Authors: James Thomas P. , Sagar Amrit , Domblesky Joseph P.
Published: October 2013

Portable bandsaws are gaining in popularity for their use on jobsites to efficiently crosscut structural materials such as bar, pipe, angle, and channel. Some of the increased popularity is also due to the recent introduction of lithium ion batteries, which has further improved the portability of bandsaws by making them cordless. However, with cordless portable bandsaws, knowledge of cutting rates becomes more important as battery runtime limits productivity. Unlike industrial bandsaws that typically have feed rate control, portable bandsaws use operator applied pressure and gravity to control feed rate. While some research has highlighted the cutting mechanics of bandsaws and related wear processes, there is a lack of progress in the area of predicting total cutting time as a function of sawing parameters, such as applied thrust force, blade speed, workpiece material properties, and geometry of the cross section. This paper presents research that was conducted to develop and experimentally verify a mechanistic model to predict cutting rates of various cross sections with a gravity fed portable bandsaw. The model was used to predict the time required to cut steel tube for several conditions of thrust force and blade speed. Model predictions were verified by experiment to a reasonable degree of accuracy. The model serves as the algorithm for a software application to assist contractors in developing jobsite estimates of time and material.
Contact Analysis Considering Surface Stress and Surface Elasticity: Increase of Indentation Hardness and Yield Stress
Authors: Hayashi Takao , Koguchi Hideo
Published: October 2013

An increase in indentation hardness with decreasing indentation depth has been observed in nanoindentation studies. It is known as the indentation size effect. The indentation modulus in Molecular Dynamics (MD) contact analysis is larger than that in theoretical analysis (Hertz contact theory). In this paper, elasto-plastic contact analysis for an anisotropic elastic half-space is performed using the surface Green’s function considering surface stress and surface elasticity. A contact analysis is conducted to investigate the effect of surface stress on yield stress and indentation hardness. The discrete convolution, fast Fourier transform method and conjugate gradient method are applied to the contact analysis. The hardening model of the elasto-perfect plastic law is used in this study. The yield stress is determined so that a contact area considering surface stress is agreed with the one ignoring surface stress. Then, the yield stress ignoring surface stress and surface elasticity fixed at a constant. It is found that the yield stress considering surface stress and surface elasticity increases with decreasing the indentation depth. The indentation hardness considering surface stress and surface elasticity is calculated using the determined yield stress. The effects of surface stress and surface elasticity on the indentation hardness and the yield stress is discussed.
Analysis and Prevention of Vortex Rope Formation in the Draft Tube Cone of a Hydraulic Turbine
Authors: Foroutan Hosein , Yavuzkurt Savas
Published: October 2013

Numerical simulations and analysis of the vortex rope formation in a draft tube cone of a Francis turbine operating at part-load conditions are carried out. Steady simulations are performed using a 2-D axisymmetric computational grid and unsteady simulations are carried out using a 3-D computational grid for a simplified axisymmetric draft tube. Two part-load operating conditions with same head and different flow rates are considered. The flow rates of these two operating points correspond to 91% of the flow rate at best efficiency point (case I) and 70% of the flow rate at best efficiency point (case II). Steady, axisymmetric simulations show the formation of a central stagnant region in the draft tube which becomes larger as flow rate decreases. This region results in flow blockage and reduction of the pressure recovery coefficient. It is shown that the pressure recovery coefficient is reduced by 46% by decreasing the flow rate from 91% of the best efficiency point (case I) to 70% of the best efficiency point (case II) while loss coefficient becomes 5 times larger. Present unsteady, three-dimensional simulations correctly predict the overall shape of the vortex rope and the calculated vortex rope frequency differs only 5% from experimental data. It is shown that the vortex rope is formed due to the roll-up of the shear layer at the interface between the low-velocity inner region (results from the crown cone wake) and highly swirling outer flow. Finally a flow control technique which uses a water jet injected from the runner crown tip along the axis is investigated. The jet accelerates the flow near the centerline (stagnant region) and decreases the relative velocity and thereby the shear between low-velocity inner region and high-velocity outer flow and hence prevents the vortex rope formation. The jet discharge is optimized for minimum overall losses. The optimized jet decreases total losses by 13% for case I and the vortex rope is eliminated. The fraction of water used for the optimized jet is less than 0.5% of the turbine discharge. As shown in the present study, this control technique can suppress severe pressure fluctuations resulting from the vortex rope formation.
A Case Study for the Resonance of Marine Propulsion Shaft System Excited by Diesel Engine
Authors: Lee Don Chool , Barro Ronald D. , Kim Jun Seong
Published: October 2013

The propulsion system which applies diesel engine with reduction gear as prime mover generally installs elastic coupling between engine and intermediate shaft. This coupling can isolate the vibratory torque excited by diesel engine, or excess hydraulic variation of the propeller occurring due to external impact. Hence, diesel engine and the reduction gear can be operated safely by adapting the elastic coupling to the system. In this paper, a case is presented wherein the elastic coupling for a skimmer vessel was repeatedly damaged by unknown vibration origin during sea trial. The authors analyzed the possibilities and causes of the elastic coupling failure thru global vibration measurement and past incident investigation. Applied countermeasures are reviewed and an integrated flexible coupling design is presented.
Toward Large Scale Simulations of Emulsion Flows in Microchannels Using Fast Multipole and Graphics Processor Accelerated Boundary Element Method
Authors: Itkulova Yulia A. , Solnyshkina Olga A. , Gumerov Nail A.
Published: October 2013

Several interesting effects discovered recently, such as “dynamic blocking” and “jamming” of emulsion flows in microchannels require in depth theoretical, computational, and experimental studies. The present study is dedicated to development of efficient computational methods and tools to understand the behavior of complex two-phase Stokesian flows. Application of the conventional boundary element method is frequently limited by the computational and memory complexity. The fast multipole methods provide O(N) type algorithms, which can further be accelerated by utilization of graphics processors. We developed efficient codes, which enable direct simulation of systems of tens of thousands of deformable droplets in three dimensions or several droplets with very high discretization of the interface. Such codes can be used for detailed visualization and studies of the structure of droplet flows in channels. Example computations include droplet dynamics in shear flows and in microchannels. We discuss results of simulations and details of the algorithm. We also consider that the present work is a step towards more realistic modeling of the microchannel dispersed flows as further development of the model is required to account for properties of thin films between the droplets, processes of coalescence, etc.
Modelling Multiphase Flows in a Wellbore Using Multi-Fluid Approach
Authors: Starostin A. , Osiptsov A. , Krasnopolsky B.
Published: October 2013

We present the results of the development of a multi-fluid model for a transient multiphase flow in a wellbore. The 1D multi-fluid model governs a transient isothermal gas/oil/water flow in a deviated well.

The model is able to predict the flow regimes with a single interface between gas and liquid mixture: stratified-smooth, stratified-wavy, and slug flow regimes. The model of a stratified flow can be modified to cover the annular flow regime. The present model is an extension of the earlier work on multi-fluid models for near-horizontal pipes [1], [2] to any inclination angle and additional phases.

The numerical algorithm is based on SIMPLE pressure-velocity coupling scheme, which is featured with the implementation of the geometry conservation based algorithm [3]. The algorithm guarantees the compliance of balance equations together with the holdup constraint within specified tolerances. The phase appearance and disappearance is treated with specific modification of governing equations.

The code is validated on the results on transitions between the regimes from hydrodynamic stability study, and particularly on the flow patterns data from open literature. We discuss the experimental and analytical flow patterns in comparison with the results by the code. The results by the model are in a reasonable agreement with earlier published work.

Finally, we focus on the initiation of the flow inside the wellbore. The wellbore considered as a long pipe starting from horizontal section and coming to surface with steep inclination. The inflow of reservoir fluids occurs in the horizontal part of the wellbore. The change of wellbore inclination induces transition between different flow regimes. The impact of realistic wellbore trajectories on the dynamics of the wellbore flow is studied.
Waste Heat Recovery for Offshore Applications
Authors: Pierobon Leonardo , Kandepu Rambabu , Haglind Fredrik
Published: October 2013

With increasing incentives for reducing the CO2 emissions offshore, optimization of energy usage on offshore platforms has become a focus area. Most of offshore oil and gas platforms use gas turbines to support the electrical demand on the platform. It is common to operate a gas turbine mostly under part-load conditions most of the time in order to accommodate any short term peak loads. Gas turbines with flexibility with respect to fuel type, resulting in low turbine inlet and exhaust gas temperatures, are often employed. The typical gas turbine efficiency for an offshore application might vary in the range 20–30%. There are several technologies available for onshore gas turbines (and low/medium heat sources) to convert the waste heat into electricity. For offshore applications it is not economical and practical to have a steam bottoming cycle to increase the efficiency of electricity production, due to low gas turbine outlet temperature, space and weight restrictions and the need for make-up water.

A more promising option for use offshore is organic Rankine cycles (ORC). Moreover, several oil and gas platforms are equipped with waste heat recovery units to recover a part of the thermal energy in the gas turbine off-gas using heat exchangers, and the recovered thermal energy acts as heat source for some of the heat loads on the platform. The amount of the recovered thermal energy depends on the heat loads and thus the full potential of waste heat recovery units may not be utilized. In present paper, a review of the technologies available for waste heat recovery offshore is made. Further, the challenges of implementing these technologies on offshore platforms are discussed from a practical point of view. Performance estimations are made for a number of combined cycles consisting of a gas turbine typically used offshore and organic Rankine cycles employing different working fluids; an optimal media is then suggested based on efficiency, weight and space considerations. The paper concludes with suggestions for further research within the field of waste heat recovery for offshore applications.
Air Flow and Heat Transfer in a Temperature-Controlled Open Top Enclosure
Authors: Barbier Charlotte , Hanson Paul J. , Todd Donald E. , Belcher Damen , Jekabson Eriks W. , Thomas Warren K. , Riggs Jeffery S.
Published: October 2013

A large 12-meter-diameter open top enclosure (OTE) equipped with two unique belowground and above ground heating systems was built and intensively tested in Oak Ridge, TN, USA. The OTE is a prototype for use within an environmental change experiment, in which replica units will be built in Minnesota to assess the response of northern peatland ecosystems to increases in temperature and elevated atmospheric CO2. For several months, temperatures, energy, wind speed and relative humidity were monitored throughout the enclosure space to assess the enclosure performance and efficiency. In parallel, Computational Fluid Dynamics (CFD) simulations were performed with ANSYS-CFX to investigate the impacts of external wind, buoyancy, and OTE design on the temperatures achieved within the enclosure. The addition of a frustum that partially reduced the top opening was also investigated experimentally and numerically. The OTE is capable of achieving a temperature differential of at least +6°C for air using a combination of 8 electrical heaters. Differential temperatures were sustained for several months. The experimental data and the numerical results showed that the addition of a frustum dramatically decreases the operating cost of the OTE and leads to better control over the differential air temperature in the enclosure. Buoyancy forces and winds heavily impacted enclosure performance. It was also found that the heating efficiency of the OTE depends mainly on the wind speed, and that there exists a critical wind speed at which the heating efficiency is the highest.
Why Engineering-Based Learning Can Revolutionize STEM Teaching in High Schools
Authors: Chin Jessica , Zeid Ibrahim , Duggan Claire , Kamarthi Sagar
Published: October 2013

For many years, literature has documented the benefits of project-based learning (PBL) and its impact on student learning especially at the high school level. More often than not however, students are still losing interest in STEM (Science, Technology, Engineering, and Mathematics) education because current educational teaching pedagogies have become antiquated and are not impacting student learning, as it should. With that said, our discovery through elicitation of high school educators has cited the main reason for such disinterest is due to the inability of students to connect STEM abstract concepts and theory with STEM application to appreciate the value of learning STEM. With access to information easier than ever, students are forgetting that learning is not about getting the right answer but understanding how to solve a complex problem. In the past, PBL has benefited students in engaging them in hands-on learning however, with a more complex paradigm shift in student learning style, PBL and lecture-based learning are no longer the most effective methods of teaching. Engineering-based learning has the opportunity and potential to modify STEM education and revolutionize STEM teaching pedagogy by changing the one-size-fits-all model to an individual, student-centered learning approach where education is mass customized. This paper discusses a new teaching pedagogy dubbed Engineering-Based Learning (EBL) that is a more systematic approach to high school STEM teaching for open-ended problems. This paper presents the EBL model, the EBL tools, and its impact thus far on high school students. It also presents sample feedback from both teachers and students and how it has influenced their outlook of engineering and STEM in the real world. The purpose of this paper is also to disseminate this new teaching pedagogy to support the notion that STEM education can be successfully taught and provide students with a structured, systematic, hands-on approach, as well as the appropriate tools and resources allowing them to connect complex STEM theory and real-world application.
Integrity Study of ACSR and ACSS Two Stage Splice Connectors at High Operation Temperatures
Authors: Jiang Hao , Wang Jy-An John , Ren Fei , Lee Dominic , Chan John , Sibilant Gary
Published: October 2013

Due to material discontinuity and inherited forming mechanism, the conductor-connector system of a crimped-type splice connector is highly sensitive to aging of system components, especially during high-temperature operations. Furthermore, due to the increase in power demand and limited investment in new infrastructure, existing overhead power transmission lines often need to operate at temperatures higher than the original designed values. This has led to the accelerated aging and degradation of conductor-connector systems. The implications of connector aging are two-fold: (1) significant increase in electric resistivity of the splice connector and (2) significant reduction in the connector clamping strength. Therefore, splice connectors are one of the weakest links in the electric power transmission infrastructure. The integrity of crimped-type splice connectors is one major concern in the efficiency and reliability of power transmission system. In this paper we present results from high temperature integrity studies of two-stage splice connector systems used for both ACSR and ACSS transmission conductors. The forming process and thermal cycling degradation behaviour are simulated using finite element modeling, which shows good agreement with degradation trends obtained from experimental data. A numerical simulation protocol has been developed to provide guidance in predicting the effective lifetime of ACSR and ACSS splice connector systems.
A New Approach to Monitoring Rupture Disc Operation
Authors: Mu Xiuping
Published: October 2013

Reliable sensors for monitoring rupture disc activation (also known as burst or rupture) are needed in order to provide immediate warning of a ruptured disc resulting from abnormal process overpressure or vacuum conditions. Many rupture discs are operated in harsh and/or hazardous environments, such as high temperature, highly corrosive, or explosive atmospheres. Also for some critical applications rupture discs and accessories with non-fragmentation features are necessary. Conventional or recently emerged sensors are available for burst disc detection, such as generic pressure switches and instruments specifically designed for burst disc detection. However, many of these devices are either mechanically too fragile, economically not practical, or not suitable for critical rupture disc applications. This paper introduces a new approach of monitoring rupture disc activation using flexible membrane sensor technology. Commercially available resistive type flexible sensors were studied and those with good performance in terms of responsive to burst sensing and materials most suitable for harsh environment were prototyped for the development. An algorithm was developed to carry out the signal processing and generate status signals using microcontrollers. With the low cost membrane sensors and increased functionalities and operability of microcontrollers, the method is expected to play an increasingly important role in rupture disc monitoring as well as other dynamic flow detection.
Application of Bayesian Analysis Method in the Design Optimization of Permanent Casting Mold
Authors: Wang Yaou , Schwam David
Published: October 2013

This work is a case study of applying Bayesian analysis, a statistical data method, in the design optimization of permanent test-bar mold. The permanent test-bar mold is used in casting foundry to examine the metal quality. Since the current standard test-bar mold suffers from shrinkage porosity which detracts from best properties, a modified design is recently proposed to improve the mechanical properties. In order to validate the new design, Bayesian data analysis method is utilized to analyze the experimental data from the two designs. The effects of the mold designs and casting process operational parameters on the mechanical properties of castings are compared. Main effect to the mechanical properties is identified based on the Bayesian analysis.