bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation and Thermal Analysis on Temperature Fields During Composite Curing Process in Autoclave Technology
Authors: Xie Gongnan , Liu Jian , Zhang Weihong , Sunden Bengt
Published: October 2013

Autoclave process is a widely-used method of composite materials manufacturing. The uniformity of temperature fields during the composite curing process has an important effect on the component and then product quality. Previous simulations on composite curing temperature field had some limitations, because either in the thickness direction of thick composite component or under a rather simple external environment was only considered into the simulations, thereby leading to deviations from the actual composite curing process. In this study, taking into considerations of factors such as auxiliaries, mold and forced convection phenomenon inside autoclave, a refined simulation method has been established on composite curing temperature field in autoclave technology. On this basis, simulation and thermal analysis of the curing temperature field with regard to composite structure and material system in the aviation industry have been performed. The variables such as the time of heat preservation, heating rate are also controlled, so that the improvements of heating efficiency and uniformity of temperature field are achieved.
Effects of Film Thickness on Heat Transfer in Taylor Flows Under Constant Wall Heat Flux Boundary Condition
Authors: Talimi V. , Muzychka Y. S. , Kocabiyik S.
Published: October 2013

Numerical simulations of heat transfer in two-phase Taylor flows in microchannels have been performed for different film thicknesses. Film thickness has been changed by adjusting surface tension and consequently Capillary number to investigate effects of film thickness on heat transfer processes under constant wall flux boundary condition. As stated in the early literature, film thickness is an important factor in Taylor flow hydrodynamics and governs the ratio between the portion of liquid which is in circulation and the portion which is bypassed through the thin liquid film around gas bubbles. It has been shown that film thickness has to be considered in the heat transfer correlations for this type of flow. Something which has not been considered in previous research.
Nanoscale Characterization of Wear Particles Produced From CNF-Reinforced HDPE Composites
Authors: Akchurin Aydar , Xu Songbo , Tangpong X. W. , Liu Tian , Wood Weston , Zhong Wei-Hong
Published: October 2013

Wear debris of materials used nowadays in orthopedic replacements is known to be the major cause of failures in a long-term period. Recent studies showed that the autoimmune reaction to the foreign body is not only the consequence of the material itself, but also depends on the size and shape of the wear particles. In this paper, carbon nanofiber (CNF) reinforced high density polyethylene (HDPE) debris particles were characterized both quantitatively and morphologically. Various weight concentrations (0.5 wt.%, 1 wt.% and 3 wt.%) and silane coating thicknesses (2.8 nm and 46nm) of CNFs in the nanocomposites were investigated. Wear tests were provided by a pin-on-disk tribometer with phosphate buffered saline as the lubricant. The wear debris was collected, isolated and characterized by scanning electron microscopy (SEM) at high magnifications and also by dynamic light scattering (DLS) particle sizing. The DLS measurements were in general consistent with the SEM observations. Small sphere-shaped wear particles of various diameters (predominantly less than 100 nm) were observed on the SEM images for all materials. The particles’ diameter distributions obtained by the DLS technique also showed that the mean diameters of the majority of the particles were mostly less than 100 nm. No correlation was found between the morphology, as well as the size distributions, of the debris particles and CNF concentrations or silane coating thickness in these experiments.
Assessment of the Dynamic Behavior of a Single Person ATV in Presence of a Passenger: Outcome on the Rider and Passenger Crash Impact Kinematics Using Computational Model
Authors: Thorbole Chandrashekhar K. , Aitken Mary , Graham James , Miller Beverly , Mullins Samantha Hope
Published: October 2013

An ATV (All-terrain vehicle) is a gasoline powered, fast moving off road vehicle often used for farming and industrial activities as well as recreational activities. The popularity of this type of vehicle has increased over the last decade with more than 10 million in use today. Most ATVs are designed for only single rider even though the seat of the ATV may appear big enough to carry a passenger. The presence of an additional person on a single person ATV greatly affects its dynamic handling characteristics. This change increases the risk of a crash and subsequent injuries to both riders. ATV crashes involving climbing and descending on steep hills are common. Lateral rollover crashes are often the result of riding an ATV at a high speed on uneven terrain. The presence of passenger on a single person ATV during these conditions changes the rider impact kinematics and resulting injury outcome, as the ATV behaves differently in the presence of an additional person. The computational model of a single person, adult-sized ATV, as developed previously for the study of child injury prevention, was used for this study. The multi-body computational model of this ATV was developed using biodynamic code MADYMO. This computational model was validated against the laboratory test for its dynamic and suspension characteristics. The tilt table test and the drop test were employed to compare the computational model result. This computer model was used to simulate the crash mechanism involving climbing and descending steep hills with two people on the ATV. This model was also used to simulate the lateral rollover of ATV with two people. The rider and the additional passenger on this single rider ATV were modeled using a 50th percentile male and a 5th percentile female. The two rider simulation was compared with single rider simulation for similar terrain and ATV speed to gain insight about the influence of this additional passenger weight on the crash kinematics of the ATV and the rider. These simulations will also be used in the future to generate more visually dramatic videos for educational intervention for ATV safety programs and other injury prevention activities.
Optimizing the Topologies of Compliant Mechanisms Using the Improved Modified Quadrilateral Discretization Model
Authors: Zhou Hong , Perivilli Venkata Krishna , Chilukuri Praveen
Published: October 2013

The improved modified quadrilateral discretization model for the topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells and each quadrilateral design cell is further subdivided into 16 triangular analysis cells. All kinds of dangling full and half quadrilateral design cells and sharp-corner triangular analysis cells are removed in the improved modified quadrilateral discretization model to enhance the material utilization. Every quadrilateral design cell or triangular analysis cell is either solid or void to implement the discrete topology optimization and eradicate topology uncertainty caused by intermediate material states. The local stress constraint is directly imposed on each triangular analysis cell to make the synthesized compliant mechanism safe. The binary bit-array genetic algorithm is used to search for the optimal topology to circumvent the geometrical bias against the vertical design cells. Two topology optimization examples of compliant mechanisms are solved based on the proposed improved modified quadrilateral discretization model to verify its effectiveness.
Aerodynamic and Electromagnetic Analysis of a Variable Electromotive-Force Generator for a Wind Turbine
Authors: Goudarzi N. , Zhu W. D. , Bowers R.
Published: October 2013

A question that usually arises is whether an existing wind turbine with a specified rotor can be modified to expand its operational range and improve the power generation. There are various methods to achieve this goal and one of them can be a modified generator referred to as a variable electromotive-force generator (VEG), where the overlap between the rotor and the stator is made to be adjustable. In this work the possibility of harnessing more wind power via a VEG in areas with large changes in the wind speed from very low to high values throughout a year is investigated theoretically. Aerodynamic and mathematical techniques are used to estimate the generated power of a wind turbine in the low wind speed region, and a combination of electromagnetic and aerodynamics principles are employed to obtain the mathematical model of the VEG with an adjustable overlap between the rotor and the stator. The Neg-Micon wind turbine (NM-72) specifications for a certain site in Thailand are used for the numerical analysis. The results show the possibility of expanding the operational range and increasing the power generation of the studied wind turbine.
Identification and Quantification of Start Up Process in Oil Flooded Screw Compressors
Authors: Chukanova Ekaterina , Stosic Nikola , Kovacevic Ahmed , Rane Sham
Published: October 2013

Oil injected screw compressors, used for air compression, refrigeration and air conditioning, are usually installed in simple packages which often do not include an oil pump to supply oil to the bearings and the working chamber, since the oil is pressurised, together with the gas being compressed, in the working chamber. Consequently, normal lubrication will only start when the back pressure reaches the chamber pressure,. Due to the lack of lubrication in this start up period, the rotors will be in direct contact with insufficient or no oil film between them, while the pressure in the compression chamber will increase causing the temperature to rise. The period of un-lubricated operation then depends on the size of the oil system and the length of the discharge piping. Also, during this time, due to the lack of oil in the working chamber, the leakage flow will be higher than normal. This will increase the overall temperature in the compression chamber. It is expected that some surface damage may occur on the rotors. When the compressor operates intermittently, with frequent starts and –stops, mode, this may result in rapid wear and decrease in the compressor performance. This paper addresses such issues through experimental investigation and simulation and defines the scope of work required to understand the oil flooded compressor process in transient operation mode. This will allow prediction of wear in such compressors and give some insight to the modifications required to increase the compressor reliability.
Modeling of V-Shaped Beam-Mass Piezoelectric Energy Harvester: Impact of the Angle Between the Beams
Authors: Su Wei-Jiun , Zu Jean W.
Published: October 2013

Piezoelectric material has been widely utilized in vibration-based energy harvesters (VEH). The most common configuration of piezoelectric energy harvester is a cantilevered beam with unimorph or bimorph piezoelectric layers. In this paper, a new configuration of PEH is proposed. Two beams are assembled as V shape with tip masses attached. The first beam is a cantilevered beam with tip mass while the second beam is attached to the end of the first beam with a certain angle. Piezoelectric layers are attached to both beams in unimorph configuration for power generation. The analytical solution is derived based on Euler-Bernoulli beam theory. In this analysis, the angle varies from 0 to 135 degree to see the influence of angle on voltage and power frequency response. The V-shaped VEH is proven to have the second resonant frequency relatively close to the first resonant frequency when compared with conventional cantilevered VEH. Furthermore, the angle between the two beams will influence the ratio of the second to the first resonant frequency. By choosing a suitable angle, the V-shaped structure can effectively broaden the bandwidth.
Analytical Period-1 Motions in a Periodically Forced Oscillator With Quadratic Nonlinearity
Authors: Luo Albert C. J. , Yu Bo
Published: October 2013

In this paper, period-1 motions in a quadratic nonlinear oscillator under excitation are investigated by the generalized harmonic balance method. The analytical solutions of period-1 motion for such an oscillator are presented by the Fourier series expansions. The stability and bifurcation analysis of period-1 motion is carried out via eigenvalue analysis. To verify the approximate analytical solutions, numerical simulations are performed for a better understanding of the parameter characteristics of the period-1 solutions, and the stable and unstable periodic motions are illustrated. The analytical period-1 solutions are different from the perturbation analysis.
A Study of the Mechanical Role of Enamel and Dentin in Human Teeth
Authors: Chun Keyoung Jin , Choi Hyun Ho , Lee Jong Yeop
Published: October 2013

The dental hard tissues of a tooth are combined of enamel and dentin together. The enamel protects the dentin and comes in direct contact with food during mastication. Bite force is expressed as compression force. The purpose of this study is to identify the primary roles of enamel and dentin during mastication by analyzing their mechanical properties and hardness.

Healthy human teeth (age: 19.3 ± 4.1) were used as specimens for mechanical tests. The teeth, which underwent epoxy resin molding, were machine cut to make 10 enamel specimens, 10 dentin specimens and 10 enamel–dentin composite (ED) specimens of 1.2 mm × 1.2 mm × 3.0 mm (Width × Height × Length) in size. Compression tests were conducted using a micro-load system at 0.1 mm/min test speed.

Teeth surface hardness (HV) was measured by a Vickers diamond indenter with a 300g indentation load. Data were obtained from 4 points on each enamel specimen and 4 points on each dentin specimen.

The strain (%), stress (MPa) and modulus of elasticity (E, MPa) of the specimens were obtained from compression tests. The MAX. strain of the enamel, dentin and ED specimens were 4.5 ± 0.8 %, 11.9 ± 0.1 % and 8.7 ± 2.7 %, respectively. The MAX. stress of the enamel, dentin and ED specimens were 62.2 ± 23.8 MPa, 193.7 ± 30.6 MPa and 126.1 ± 54.6 MPa, respectively. The E values of the enamel, dentin and ED specimens were 1338.2 ± 307.9 MPa, 1653.7 ± 277.9 MPa and 1628.6 ± 482.7 MPa, respectively. The E of the dentin specimens was the highest and the E of the enamel specimens was the lowest, but the E values of all specimens was not significantly different in the T-test (P > 0.1). The measured hardness value of the enamel specimens (HV = 274.8 ± 18.1) was about 4.2 times higher than that of the dentin specimens (HV = 65.6 ± 3.9).

Because of the values of MAX. stress and MAX. strain of the enamel specimens, the enamel specimens tended to fracture earlier than the dentin and ED specimens; therefore, enamel was considered to be more brittle than dentin and ED. Enamel is a harder tissue than dentin based on their measured hardness values. Therefore, enamel has a higher wear resistance, making it suitable for grinding and crushing, whereas dentin has a higher force function, making it suitable for abutment against bite force.
Wavelet Based Nano-Texture Structures for Thin Film PV Cells
Authors: Hajimirza Shima , Howell John R.
Published: October 2013

Light trapping is an important technique in increasing the efficiency of solar cells. Inverse optimization is a systematic numerical approach that allows us to find the limits of light trapping more efficiently. It is an alternative to exhaustive search simulations or experimental measurements. In this work, we use inverse optimization to study light trapping in thin film amorphous silicon cells textured by periodic patterns of metallic surface grating. We use a finite set of Haar wavelets to describe a general form of grating structure composed of multiple rectangular nano-strips. We use global simulated annealing optimization to find the coefficients of the wavelets basis for optimal absorption enhancement in thin film silicon. The motivation for choosing wavelet basis (vis-a-vis other orthonormal bases such as Fourier) is the feasibility of fabricating the resulting nano-structures. The resulting improvement in the number of absorbed photons is around 130% for wavelength range of 300–700nm, which is significantly better than the previous results using simple front surface nano-strips. In addition, we use statistical analysis to evaluate the sensitivity of the characteristics of the resulting structure to numerical uncertainties.
An Automated Stage for Scalable Imprinting of DNA Nanowires Based on a Self-Aligning Technique
Authors: Saha Sourabh K. , LaColla John J. , Culpepper Martin L.
Published: October 2013

Molecular combing is an established technique for aligning DNA nanowires on a surface. When performed on micro-patterned surfaces, this technique can be used to reliably align and stretch DNA nanowires across micro pillars. Imprinting of these aligned DNA nanowires is an affordable technique for fabrication of arrays of nano-scale channels across micro-scale reservoirs. In the past, DNA combing and imprinting (DCI) have been performed manually to fabricate polymer chips that are used in biomedical applications such as gene therapy and drug delivery studies. Automation of the DCI process is necessary to improve the yield and to scale-up production for these applications. However, existing automated techniques are not appropriate for DNA nanowire imprinting because these techniques cannot handle (i) fragile stamps and (ii) individual chip scale stamps of size ∼1 cm2. Herein, we present the design, fabrication and performance evaluation of an imprinting stage that enables (i) handling fragile stamps via low-cost equipment and (ii) production scale-up via simultaneous handling of multiple stamps. The stage is based on a self-aligning imprinting technique that passively aligns a stamp parallel to the substrate thereby enabling simultaneous imprinting of multiple stamps via a single stage. This self-alignment technique minimizes nanowire breakage by ensuring (i) minimal in-plane stamp motion during imprinting and (ii) that the contact forces do not exceed the weight of the stamp. Based on this technique we have designed/fabricated a stage that can simultaneously handle three stamps and is capable of further scale-up. The stage consists of a movable platform that is mounted on linear bearings and is actuated via a stepper motor. Stamps are loaded onto a holder that is mounted on the movable platform via kinematic couplings. This allows one to rapidly attach and detach the holder from the stage and also makes it possible to handle fragile stamps during loading/unloading. Imprinting of DNA nanowires with a manual stage has demonstrated the feasibility of the self-alignment scheme. Experiments that were performed to test the alignment capability of the stage verify that conformal stamp contact can be achieved across all three stamps even in the presence of an angular misalignment of 5° between the stamp and the glass slide. This ability to simultaneously align multiple stamps is a critical step in being able to scale-up and fully automate the DCI process.
A Study on Li-Ion Battery Performance Subject to Cathode Materials Using CFD
Authors: Jang Kyung-min , Choi Kwang-Woo , NamGoong John E. , Kim Kwang-Sun
Published: October 2013

As the demand of the rechargeable battery has been requested not only from operating the small devices, but also from operating the large and medium size equipment such as an electric vehicle, the research has been focused on the stability of the battery, minimization of the energy loss, and finding the new materials for effective energy storage. The Lithium-ion (Li-ion) battery consists of four main components which are cathode active material, anode active material, electrolyte, and the separator. One of current research fields of the Li-ion battery material is in the area of cathode active material. It is because the cathode active material has 30∼40% of the manufacturing cost and it vastly affects the capacity of the batteries. In this research, we conduct one-cell simulation to compare the battery performance for changing the properties of the Cathode material. It is one of the thermochemical parameters that can affect the charge/discharge rate and the life of the batteries. Although, the certain kind of active materials has been reported in previous reports, we used the new material properties and researched about the whole discharge curve for future material development. The heating behavior is also investigated with the arbitrary properties being varied.
Flow Properties of Bamboo Fiber Suspensions
Authors: Kubo Takuya , Ogata Satoshi
Published: October 2013

Reducing pipe friction by adding a drag reducing agent has attracted interest as a means to reduce energy consumption. In addition to reducing drag, drag reducing agents should also have a low environmental load and conserve natural resources. However, no drag reducing agent currently satisfies both these conditions. The present study investigates the use of bamboo fibers as a drag reducing agent that satisfies both conditions. The drag reducing effect was evaluated by measuring the pressure drop in pipe flow. Bamboo fiber suspensions reduced drag by up to 20%. In addition, bamboo fibers could be easily removed from suspensions by a filter. These results demonstrate that bamboo fibers are a drag reducing agent that both save natural resources and have a low environmental load.
Safety Management System - Workplace Activities at Toyota Motor Manufacturing, Texas, Inc.
Authors: Roussel Stephane , King Norma Jean
Published: October 2013

Implementation of a safety management system (SMS) in automotive manufacturing and assembly has been recognized as an effective way to provide a safe working environment for employees, increase employee morale, and reduce corporate costs. Toyota Motor Manufacturing, Texas, Inc. (TMMTX) has implemented a SMS in part of a regional goal initiated by Toyota Engineering & Manufacturing North America, Inc. (TEMA) to support the OSHA’s Injury & Illness Prevention Program (I2P2). This system provides a systematic way to identify hazards; eliminate or control the risk and incorporate in Toyota Production System. In addition, the established management system provides a framework to meet legal obligations under occupational health and safety regulation. The system implemented provides methods to manage injury and illness related to process safety, ergonomic, and industrial hygiene risks. The system uses joint labor and management teams to identify and evaluate jobs and develop and implement solutions. This paper summarizes the efforts of TMMTX in implementing and maintaining workplace activities that meet the requirements of this safety management system. The methodologies, strategies, and challenges are outlined to provide important links that are critical in sustaining these activities.
Particle Image Velocimetry Measurements in a Representative Gas-Cooled Prismatic Reactor Core Model: Flow in the Coolant Channels and Interstitial Bypass Gaps
Authors: Conder Thomas E. , Skifton Richard S. , Budwig Ralph S.
Published: October 2013

Core bypass flow is one of the key issues with the prismatic Gas Turbine-Modular Helium Reactor, and it refers to the coolant that navigates through the interstitial passages between the graphite fuel blocks instead of traveling through the designated coolant channels. To determine the bypass flow, a double scale representative model was manufactured and installed in the Matched Index-of-Refraction flow facility; after which, stereo Particle Image Velocimetry (PIV) was employed to measure the flow field within. PIV images were analyzed to produce vector maps, and flow rates were calculated by numerically integrating the velocity field. It was found that the bypass flow varied between 6.9–15.8% for channel Reynolds numbers of 1,746 and 4,618 with a 6mm gap. The results were compared to computational fluid dynamic (CFD) pre-test simulations. When compared to these pretest calculations, the CFD analysis appeared to under predict the flow through the gap.
Exergy Analyses Applied to an AP-X Process for the Liquefaction of Natural Gas
Authors: Bin Omar M. N. , Morosuk T. , Tsatsaronis G.
Published: October 2013

LNG technology has been in use since the 1960s and is constantly evolving. During the last 20 years the total cost of LNG technology has decreased by approximately 30% due to improvements of the liquefaction process and shipping. One of the last developed processes for the liquefaction of the natural gas is the so-called AP-X process that is patented by Air Products and Chemicals, Inc. (US Patent No. 6308521), and is now used for industrial applications in the Middle East. The thermodynamic processes within the components of the AP-X process are complex because a mixture is used as a working fluid. This paper discusses the exergetic analysis of the AP-X process.
Evaluation of Numerical Methods Applied in the Analysis of the Transient Flow of Pipeline Systems
Authors: Flora Bruno F. , Tsukada Raphael I. , Rodrigues Vinícius M. , Mendes José R. P. , Serapião Adriane S. B.
Published: October 2013

Brazilian subsea exploration is increasing specially after the post salt petroleum field discovery. Several challenges have been imposed for the production of those fields. In this scenery, the transport of oil and gas from the production field to the continent is a problem, especially when the fields are located at a great distance from the coast. A possible solution could be the use of subsea pipeline systems, for the transportation of the fluids produced from the petroleum wells. For the pipeline system design it is highly recommended the evaluation of the transient flow, considering the water hammer phenomenon. The definition for this phenomenon is given by the pressure variation due to operation singularities in the pipe system. The disruption in the flow originated by the operation of valves or failure of a pump can be listed as some of the main causes of the water hammer. The basic equations to model the water hammer in fluid mechanics comes from two partial differential equations, the equation of continuity and momentum. The solution of those equations can be obtained by different numerical methods. In this context, this work seeks to contrast results obtained by finite difference method (FDM), the method of characteristics (MOC) and finite elements method (FEM) solutions for the water hammer problem. Those numerical methods were implemented and used to solve a simple system, which are composed of an infinite reservoir, a pipeline and a valve. In this case the valve is closed, originating the water hammer phenomenon. Although it can be considered a simple problem, it allows the evaluation of those numerical methods. Performance, convergence and accuracy were evaluated in order to support the choice of the best numerical method for the development of a numerical simulator used in complex and greater pipeline system design.
Experimental Study of Nanoengineered Molten Salts as Thermal Energy Storage in Solar Power Plants
Authors: Tiznobaik Hani , Shin Donghyun
Published: October 2013

In a concentrated solar power (CSP), high operating temperature (over 500 °C) is the key for enhancing the efficiency of the system. The operating temperature of the system mainly relies on thermal energy storage (TES) material. Existing TES materials such as mineral oil or paraffin wax cannot be applicable at high temperatures, since these materials are not thermally stable over 400 °C. However, very few materials are suitable and reliable for the high temperatures. Using molten salts (e.g., alkali nitrate, alkali carbonate, alkali chloride, etc.) as thermal energy storage material is an alternative way due to several benefits. They are cheap and environmentally safe compared with the conventional TES materials. They are thermally stable at higher temperatures (over 500 °C). However, their usage is limited due to low thermo-physical properties (e.g. Cp is less than 1.6 J/g°C). The low thermo-physical properties can be improved by dispersing nanoparticles into the salts. In this study, nanomaterials were synthesized by dispersing inorganic nanoparticles into ionic salts. Modulated differential scanning calorimeter (MDSC) was used to measure the heat capacity of the nanomaterials. Scanning electron microscopy (SEM) was used for material characteristic analysis. Hence, the application of the nanomaterials as thermal energy storage in a concentrated solar power was explored.
Evaluation of an Integrated Fuel Cell-PV Panel System as a Hybrid UAV Powerplant
Authors: Zafar Sayem , Gadalla Mohamed
Published: October 2013

A model study was conducted to investigate the integration of a hybrid, fuel cell-PV panel power system for a small unmanned aerial vehicle (UAV). A hybrid power system is proposed as a substitute to the existing batteries to enhance the endurance of such systems. A UAV with wing area equivalent solar panel and 900Ah proton exchange membrane fuel cell, with stored pressurised hydrogen, is modeled. Maximum take-off weight of 100 N was used to make the UAV man-portable. The flight performance was simulated using available and calculated data. Aerodynamic analysis was conducted and the wing and tail geometries were determined to house the PV panels. The corresponding required power was then established from the drag and weight values. Measurements were made for the maximum required power for endurance. The results showed favorable increase in a small UAV’s flight performance when an integrated hybrid fuel cell-PV panel system is used. An endurance increment of 2384 seconds was achieved using a hybrid, fuel cell-PV panel, power system when compared to fuel cell only power system. The research proved the effectiveness of using fuel cell-PV panel hybrid system as a small UAV power plant. It also highlighted the effectiveness of using renewable sources to increase the endurance of a small UAV.
Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers
Authors: Streufert Patricia , Yan Terry X. , Baygloo Mahdi G.
Published: October 2013

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.
Numerical Study of the Free Surface Flow in a Centrifugal Gas-Liquid Separator
Authors: Stel Henrique , Ofuchi Edgar M. , Franco Admilson T. , Genaro Julio G. , Morales Rigoberto E. M.
Published: October 2013

This work presents a numerical investigation of the free surface flow in a gas-liquid separator with a cylindrical expansion chamber using Computational Fluid Dynamics. The centrifugal flow is set through a tangentially oriented nozzle at the chamber wall and is modeled using an inhomogeneous Eulerian-Eulerian multiphase flow model with the free surface approach to capture the phases interface. Fluid dynamics is examined for a range of fluid viscosities and flow rates for a single-phase liquid flow at the inlet. Liquid-gas bubbly-flow at the inlet is also considered to investigate some aspects of the phases separation inside the cylindrical chamber. Analysis of the flow field reveals that the impact of the fluid at the chamber wall combined with the centrifugal movement push part of the fluid upwards, stabilizing a liquid level above the nozzle. Near the inlet, the flow dynamics is characterized by a strong centrifugal motion, which decreases continuously below the entrance position due to gravity and viscous effects. The liquid level over the chamber wall and the centrifugal intensity increase with the flow rate, but decrease with viscosity. Viscosity also tends to enlarge the liquid layer thickness over the chamber wall and diminish the residence time of the liquid from the inlet down to the chamber’s bottom exit. Investigation of liquid-gas bubbly-flows in this equipment shows that separation occurs mainly near the chamber entrance due to the sudden expansion and the formation of a thin fluid layer over the chamber wall. In a percentage basis, phases tend to be more effectively separated for higher inlet gas volume fractions, lower liquid viscosities and bigger gas bubbles. These conclusions give technically interesting information for dimensioning hydrocyclones for gas-liquid flow separation.
Proposal of a Profile Geometry Suitable for Claw Rotor Compressors
Authors: Giuffrida Antonio
Published: October 2013

Claw rotor compressors are rotary positive displacement machines with built-in compression. They are characterized by greater performance if compared to Roots blowers and are more efficient in discharging gas at pressures substantially higher than at suction. This paper aims at proposing a rotor profile suitable for the claw-type mechanism, with thorough indication of the profile geometry. After presenting some graphical cases of rotor profiles, drawn according to the proposed geometry, comparisons with a reference profile suggest that the proposed one seems to be preferable from a filling point of view.
An Urinary Biosensor for Early Stage Ovarian Cancer Detection: Experimental Characterization
Authors: Onen Onursal , Sisman Alper , Kruk Patricia , Guldiken Rasim O.
Published: October 2013

In this study, an experimental characterization of a piezoelectric ultrasonic MEMS biosensor for detection of anti-apoptotic protein Bcl-2 in sub ng/ml scale is presented. Bcl-2 is demonstrated to be elevated at different stages of ovarian cancer in urine ranging from 0.5 to 12 ng/ml. Here, shear horizontal (SH) polarized surface acoustic waves (SAWs) were utilized by interdigital transducers (IDTs), which were micro fabricated on piezoelectric ST cut Quartz wafers. SH SAWs were generated and sensed by a pair of IDTs, separated by judiciously designed a delay path in-between with for most effective Bcl-2 capture. The Bcl-2 concentration is characterized with respect to the change in resonance frequency. The target sensitivity for diagnosis and quantifying the stage of ovarian cancer is achieved with successful detection of Bcl-2 levels as low as 0.5 ng/ml. The results are promising for the sensor system to be used in a lab-on-a-chip platform for point of care urinary ovarian cancer monitoring diagnosis.
Advantages of an LQR Controller for Stick-Slip and Bit-Bounce Mitigation in an Oilwell Drillstring
Authors: Sarker Md. Mejbahul , Rideout D. Geoff , Butt Stephen D.
Published: October 2013

Failure of oilwell drillstrings is very costly in terms of money and time. There are many reasons for drillstring failure, such as vibration, fatigue, and buckling. Stick-slip vibration has received considerable attention in recent years with increasing use of polycrystalline diamond compact (PDC) bits in harder formations, and has motivated extensive research on this type of drillstring vibration. This paper addresses the advantages of a linear quadratic regulator (LQR) controller, compared to a spring-damper isolator, for stick-slip and bit-bounce mitigation in an oilwell drillstring. A bond graph model of a drillstring has been used for simulation that predicts axial vibration, torsional vibration, and coupling between axial and torsional vibration due to bit-rock interaction.
Furnace Wall Temperature Investigation
Authors: Strasser Wayne , Chamoun George
Published: October 2013

It is desired to keep the outer metal walls of a heat transfer medium (HTM) furnace warm enough to prevent corrosion. A computational study was carried out in order to assess the normal and lowest possible sheet metal temperatures. Various combustion models, radiation parameters, and operating conditions were considered. Field-measured values matched CFD results closely. It was found that the walls were sufficiently warm under all reasonable modeling approaches and conceivable operating circumstances.
Development of a Teaching Laboratory for Electric Energy Storage Systems
Authors: Liao Y. Gene
Published: October 2013

Several universities and colleges recently have offered courses and certificate programs for training students and returning engineers in advanced energy storage, particularly in electric energy storage technology. However, few integrated advanced energy storage laboratories have been established for educational purposes. This paper presents the design, development and implementation of an interactive and computer-controlled test system for four different electric energy storage devices (electro-mechanical flywheel, electro-chemical batteries, supercapacitor and pumped hydroelectric) that serve as a teaching-aid. These units provide hands-on experience for students with multidisciplinary backgrounds who are enrolled in the advanced energy storage courses. The developed teaching-aid not only enhances the advanced energy storage training and education, but also inspires students’ interest in the green movement of renewable energy.
Mitigation of Milling Chatter at High-Speed
Authors: Liu Meng-Kun , Suh C. Steve
Published: October 2013

A highly interrupted machining process, milling at high speed can be dynamically unstable and chattering with aberrational tool vibrations. While its associated response is still bounded in the time domain, however, milling could become unstably broadband and chaotic in the frequency domain, inadvertently causing poor tolerance, substandard surface finish and tool damage. Instantaneous frequency along with marginal spectrum is employed to investigate the route-to-chaos process of a nonlinear, time-delayed milling model. It is shown that marginal spectra are the tool of choice over Fourier spectra in identifying milling stability boundary. A novel discrete-wavelet-based adaptive controller is explored to stabilize the nonlinear response of the milling tool in the time and frequency domains simultaneously. As a powerful feature, an adaptive controller along with an adaptive filter effective for on-line system identification is implemented in the wavelet domain. By exerting proper mitigation schemes to both the time and frequency responses, the controller is demonstrated to effectively deny milling chatter and restore milling stability as a limit cycle of extremely low tool vibrations.
Coupled-Physics Modeling of a Lithium-Ion Battery Cylindrical Cell Microstructure
Authors: Doval Peter N. , Avdeev Ilya V.
Published: October 2013

Safety of consumer vehicles is an extremely important consideration for the automotive industry. An emerging market in the automotive industry today is the electric and hybrid-electric vehicle market. As environmental concerns grow, such vehicles will become a necessity for manufacturers to remain within increasingly stringent emissions regulations. A recent problem with the high-voltage lithium-ion batteries used in many of these vehicles is that of thermal runaway following a severe collision. This paper represents our early attempt to look at one aspect of this extensive project — a coupled-physics model of battery cell microstructure. In this case, couple-physics refers only to thermal-structural coupling and the microstructure being studied here is the laminate-level structure. A 2-D finite element model of a lithium-ion cell was therefore developed. This 2-D model of the cell, also called a jellyroll, is a cross-section cut of one cell within a battery pack. Each battery cell is an assembly of alternating thin sheets of functional materials (anode, separator and cathode), which are rolled into a cylindrical shape. The cross-section then takes the form of a layered spiral. The typical cell is made of an aluminum cathode with coating, copper anode with coating, and a non-linear, viscoelastic polymer separator. Once the 2-D jellyroll FE model was created, some initial structural element simulations were run to validate the geometry setup and model integrity. Next, thermal-structural coupled-field simulations were run to investigate stress propagation resulting from thermal loads as well as the same loading cases performed with the structural-only model. Different loading conditions, including uniaxial stress-strain state, hydrostatic pressure test, and thermo-mechanical loading were simulated. The results from the simulations performed in the project set the groundwork of future models involving electrical properties and models of 3-D cells and the full battery pack.
Open Design of High Pressure Ratio Radial-Inflow Turbine for Academic Validation
Authors: Sauret Emilie
Published: October 2013

Computational Fluid Dynamics (CFD) simulations are widely used in mechanical engineering. Although achieving a high level of confidence in numerical modelling is of crucial importance in the field of turbomachinery, verification and validation of CFD simulations are very tricky especially for complex flows encountered in radial turbines. Comprehensive studies of radial machines are available in the literature. Unfortunately, none of them include enough detailed geometric data to be properly reproduced and so cannot be considered for academic research and validation purposes. As a consequence, design improvements of such configurations are difficult. Moreover it seems that well-developed analyses of radial turbines are used in commercial software but are not available in the open literature especially at high pressure ratios.

It is the purpose of this paper to provide a fully open set of data to reproduce the exact geometry of the high pressure ratio single stage radial-inflow turbine used in the Sundstrand Power Systems T-100 Multipurpose Small Power Unit. First, preliminary one-dimensional meanline design and analysis are performed using the commercial software RITAL from Concepts-NREC in order to establish a complete reference test case available for turbomachinery code validation. The proposed design of the existing turbine is then carefully and successfully checked against the geometrical and experimental data partially published in the literature. Then, three-dimensional Reynolds-Averaged Navier-Stokes simulations are conducted by means of the Axcent-PushButton CFD® CFD software. The effect of the tip clearance gap is investigated in detail for a wide range of operating conditions. The results confirm that the 3D geometry is correcty reproduced. It also reveals that the turbine is shocked while designed to give a high-subsonic flow and highlight he importance of the diffuser.
A Comprehensive Model for Predicting Fatigue Life of Laser Welded Lap Joint of Galvanized High Strength Steel as a Function of Residual Stresses
Authors: Anago Joe , Kong Fanrong , Carlson Blair , Kovacevic Radovan
Published: October 2013

This paper presents a three-dimensional (3D) multi-physics finite element model (FEM) to predict the fatigue life of a laser welded lap joint of dual phase (DP) 980 steel sheets based upon the level of residual stress. A FEM-based thermal analysis is first performed to numerically predict the welding-induced temperature field combined with the corresponding experimental verification. The temperature histories are then loaded into the mechanical model as thermal loading to numerically calculate the evolution curves of thermally induced stress in order to calculate the level of residual stresses after cooling to room temperature. In order to calculate the equivalent fatigue strength in the laser-welded lap joint, the resultant multi-axial stress (including the induced residual stress (RS) result) is loaded into the equivalent uni-axial stress equation via the Sine Method (SM) in order to achieve the stress curve as a function of the loading cycles. A series of fatigue tests of lap joints are also performed in order to achieve the S-N curves, from which an empirical function between the alternating stress and loading cycle is derived in order to predict the fatigue life of the DP980 lap joint. Finally, the maximum fatigue strength can be predicted numerically through the proposed FEM instead of using experimental trials. The numerical results show that a greater temperature gradient and residual stress are mainly located within the fusion zone (FZ) and close to the heat affected zone (HAZ). The residual stress plays an important role in deciding the final fatigue strength and failure of the DP980 lap joint. An X-ray diffraction technique is used to experimentally measure the residual stress distribution within the weld, for which the numerically predicted results exhibit a good agreement. Also, the numerical simulation and experimental measurements of the fatigue life versus the applied load show a good correlation of results.
Risk Decision: Main Constraints and Approaches
Authors: Rodrigues Matilde A. , Arezes Pedro M. , Leão Celina P.
Published: October 2013

The key factor in risk management process is the risk acceptance decision. However, it is not an easy task since different approaches can be adopted. In Portugal, it is unknown how companies decide in relation to the risk acceptance of the occupational risks and on the need to implement risk reduction measures. Building on these facts, this work aims to analyze how Portuguese organizations make their decisions concerning occupational accident risk and the main constraints to the decision process, and to identify the most appropriate approach to be applied. The questionnaire Risk Decision Analysis was developed and applied on a sample of Portuguese Occupational Health & Safety Professionals. The results show that the type of OHS services was the main factor that influenced the risk analysis activities and the type of risk assessment, namely in relation to quantitative risk assessments: the in-house OHS personnel use more quantitative risk assessments than the external consultants. Both qualitative and quantitative criteria need to be considered, but quantitative criteria are preferred in relation to qualitative criteria. In relation to risk measures used, the risk matrix is the most used to evaluate the risks of particular activities and risk rates for evaluating the safety performance of organizations. The study also shows that ALARP principle is the best approach to be applied in decision-making process on occupational risk. In general, the study emphasized the need of guidelines that helps in acceptance criteria formulation.