bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Metal-Foam Filled Liquid Piston Compressor Using a Two-Energy Equation Formulation Based on Experimentally Validated Models
Authors: Zhang Chao , Wieberdink Jacob H. , Shirazi Farzad A. , Yan Bo , Simon Terrence W. , Li Perry Y. 
Published: April 2014

The present study presents CFD simulations of a liquid-piston compressor with metal foam inserts. The term “liquid-piston” implies that the compression of the gas is done with a rising liquid-gas interface created by pumping liquid into the lower section of the compression chamber. The liquid-piston compressor is an essential part of a Compressed Air Energy Storage (CAES) system. The reason for inserting metal foam in the compressor is to reduce the temperature rise of the gas during compression, since a higher temperature rise leads to more input work being converted into internal energy, which is wasted during the storage period as the compressed gas cools.
Liquid, gas, and solid coexist in the compression chamber. The two-energy equation model is used; the energy equations of the fluid mixture and the solid are coupled through an interfacial heat transfer term. The fluid mixture, which includes both the gas phase and the liquid phase, is modeled using the Volume of Fluid (VOF) method. Commercial CFD software, ANSYS FLUENT, is used, by applying its default VOF code, with user-defined functions to incorporate the two-energy equation formulation for porous media.
The CFD simulation requires modeling of a negative momentum source term (drag), and an interfacial heat transfer term. The first one is the pressure drop due to the metal foam, which is obtained from experimental measurements. To obtain the interfacial heat transfer term, a compression experiment is done, which provides instantaneous pressure and volume data. These data are compared to solutions of a zero-dimensional compression model based on different heat transfer correlations from published references. By this comparison, a heat transfer correlation which is most suitable for the present study is chosen for use in the CFD simulation.
The CFD simulations investigate two types of metal foam inserts, two different layouts of the insert (partial vs. full), and two different liquid piston speeds. The results show the influence of the metal foam inserts on secondary flows and temperature distributions.
Optimization of the Axial Porosity Distribution of Porous Inserts in a Liquid-Piston Gas Compressor Using a One-Dimensional Formulation
Authors: Zhang Chao , Simon Terrence W. , Li Perry Y. 
Published: April 2014

A One-Dimensional (One-D) numerical model to calculate transient temperature distributions in a liquid-piston compressor with porous inserts is presented. The liquid-piston compressor is used for Compressed Air Energy Storage (CAES), and the inserted porous media serve the purpose of reducing temperature rise during compression. The One-D model considers heat transfer by convection in both the fluids (gas and liquid) and convective heat exchange with the solid. The Volume of Fluid (VOF) method is used in the model to deal with the moving liquid-gas interface. Solutions of the One-D model are validated against full CFD solutions of the same problem but within a two-dimensional computation domain, and against another study given in the literature.
The model is used to optimize the porosity distribution, in the axial direction, of the porous insert. The objective is to minimize the compression work input for a given piston speed and a given overall pressure compression ratio. The model equations are discretized and solved by a finite difference method. The optimization method is based on sensitivity calculations in an iterative procedure. The sensitivity is the partial derivative of compression work with respect to the porosity value at each optimization node. In each optimization round, the One-D model is solved as many times as there are optimization nodes, and each time the porosity value at a single optimization node is changed by a small amount. From these calculations, the sensitivity of changing the porosity distribution to the total work input (objective) is obtained. Based on this, the porosity distribution is updated in the direction that favors the objective. Then, the optimization procedure marches to the next round and the same calculations are completed iteratively until an optimum solution is reached. The optimization shows that porous media with high porosity should be used in the lower part of the chamber and porous media with low porosity should be used in the upper part of the chamber. An optimal distribution of porosity over the chamber is obtained.
Non-FEA-Based Method as Means for Knowledge Based Assessment of Perceived Quality
Authors: Wagersten Ola , Wickman Casper , Söderberg Rikard 
Published: April 2014

Fit and finish of vehicle split-lines is one important contributor to the final Perceived Quality (PQ) of the product. To achieve high PQ of split-lines, effects of geometrical variation has to be considered.
In early phases of the development chain the geometry models used for simulation and visualization have low level of detail. This limits the possibility to perform certain simulations that rely on a more complete detailed design. Consequently, alternative methods have to be considered to predict and simulate possible outcome in early phases concerning PQ issues.
This paper proposes how an existing non-FEA-based deformation method can support virtual assessment of the PQ of split-lines in early phases. The method is based on mesh morphing and has been implemented in a CAT-tool (Computer-Aided Tolerancing). Its strength lies in the simplicity of generating deformed shapes. The paper specifically focuses on how available knowledge regarding issues from previous projects can be used as input to the method, to predict part deviation and part behavior. The paper further presents industrial examples where the method has been applied. The results show that the proposed technique can be used as a complement to other simulation tools in early phases, where low level of detail on geometries limits the possibility to perform FEA (Finite Element Analysis) based simulations.
Thermal and Coupled Electromagnetic-Mechanical Analyses for the Development of a Dry Type Current Limiting Reactor
Authors: Choi Jangun , Park Sungwon , Kim Yonghan , Yang Heuiweon 
Published: April 2014

In this paper, thermal and structural analyses based on numerical method have been conducted to develop a dry type current limiting reactor which can mitigate the fault current. The current limiting reactor is an effective device to reduce the breaking capacity of circuit breakers in spite of the growth of electric loads.
Temperature rise analysis of the dry type reactor is required and important to suppress the excessive temperature rise over temperature limit of an insulating material, and structural analysis for short current forces of the reactor is required to verify the structural integrity in fault current conditions. For the thermal stability of reactor, thermal-fluid analysis has been carried out to predict temperature rise of reactor winding.
Through the analyses, the optimal thickness of fiber-epoxy composite was determined to secure the structural integrity against the short current force by coupled electromagnetic-mechanical analysis. The numerical analyses results have been verified by conducting performance test for the prototype reactor.
FEM Simulation of Swelling Elastomer Seals in Downhole Applications
Authors: Akhtar Maaz , Qamar Sayyad Zahid , Pervez Tasneem , Al-Jahwari Farooq Khalfan 
Published: April 2014

Petroleum exploration and development industry is witnessing a rapid growth in the use of swelling elastomers. They are being used in new applications aimed at enhanced oil recovery through slimming of well design, zonal isolation, water shutoff, etc. Initially developed as a problem-solving strategy (for repair of damaged or deteriorating wells), swelling elastomers are now targeting major savings in cost and time through reduction in borehole diameter, reduced casing clearance, cementless completions, etc. Due to material and geometric nonlinearity, modeling and simulation of swelling elastomer applications becomes quite complex.
In this work, finite element simulation has been carried out to study swelling elastomer seal performance in downhole petroleum applications using the software ABAQUS. A hyperelastic model (that most closely resembles swelling elastomer behavior) is used for simulation of seal behavior. A series of experiments have been designed and performed to determine necessary material properties of a water-swelling elastomer as it gradually swells when exposed to saline water of two different concentrations at 50°C (to emulate field conditions of medium-depth oil wells). A large number of simulations are carried out to investigate sealing behavior against water salinity and swelling time. Sealing pressure at the contact surface between elastomer and formation (or outer casing) is studied for variations in seal length, seal thickness, compression ratio, water salinity, and swelling period. Results show that seal contact pressure increases with amount of swelling, seal length, and compression ratio; higher salinity environment results in lower sealing pressure; and more contact pressure is generated in the case of rock formation as compared to steel outer casing.
Elastomer Seal With Frictional Contact: Analytical Solution
Authors: Al-Kharusi Moosa S. M. , Qamar Sayyad Zahid , Pervez Tasneem , Akhtar Maaz 
Published: April 2014

Main motivation for this work is the need for performance evaluation of swelling (and inert) elastomer seals used in petroleum applications. Closed-form (analytical) solutions are derived for sealing pressure distribution along the elastomer seal as a function of material properties of the elastomer, seal geometry and dimensions, seal compression, and differential fluid pressure acting on the seal ends. Seal performance is also modeled and simulated numerically. Good agreement between analytical and numerical results gives confidence that the analytical solution can be used for reliable prediction of sealing behavior of the elastomer. Detailed investigation is then carried out to find out the effect of variation in seal design parameters on seal performance. For both analytical and numerical models, properties of the seal material at various stages of swelling are needed. Therefore, a series of experiments were also designed and conducted to study the effect of swelling on mechanical properties (E, G, K, and ν) of the sealing material.
One major finding is that sealing pressure distribution along the seal is not constant but varies nonlinearly depending on seal parameters and loading conditions, with maximum sealing pressure occurring at the center of the seal length. Longer seals are not necessarily better; after a certain seal length, sealing pressure reaches a steady value for a given set of field conditions. As expected, higher seal compression gives higher sealing pressure. Seal compression can be increased either by tubular expansion or by selecting an elastomer that swells more, or a combination of the two.
Experimental evaluation of swelling-elastomer seal performance can be very costly, and is not even possible in many cases. Numerical simulations, if validated, can be more convenient, but computational effort and cost can be high as simulations have to be run for each set of conditions. Analytical approach presented here not only gives an elegant closed-form solution, but can give reasonably accurate and much faster prediction of elastomer performance under various actual oil and gas field conditions.
Wear Assessment of Large Aspect Ratio Silicon Microbearing Systems
Authors: Demiri S. , Boedo S. , Holsen L. S. 
Published: April 2014

This paper addresses the wear characteristics of large aspect ratio (length-to-diameter) silicon microbearing systems using an enhanced experimental test rig. The test system is comprised of a rigid rotor which has been manually assembled onto a fixed hub to form the microbearing. CMOS-based lithographic and etching processes, including deep-reactive ion etching, are employed in the construction of the rotor and hub with length to diameter ratio of approximately 0.5 and radial clearance values in the range from 3.5 to 9.2 microns. The rotor is pneumatically driven by nitrogen gas at a constant supply pressure delivered through a rectangular microchannel.
A new methodology for measuring wear was developed by digitizing optical microscope images of the rotor system, and the rotor load was calculated from CFD models of the entire rotor-hub system. It was found that the tested silicon microbearings have an adhesion wear coefficient (based on the well-known Archard relation) which falls within a relatively narrow band bounded by previously published values for polysilicon materials tested at the macroscale and microscale.
Driveline Dynamics Simulation and Analysis of the Dry Clutch Friction-Induced Vibrations in the Eek Frequency Range
Authors: Senatore Adolfo , Hochlenert Daniel , D’Agostino Vincenzo , von Wagner Utz 
Published: April 2014

Vibrations that arise during the slip phase of the clutch in the driveline of a motor vehicle yield to poor ride quality and result in discomfort and noise. The control systems in modern automated manual transmission systems couldn’t provide good improvement of vehicle longitudinal dynamics during gearshifts without a deep knowledge of the driveline model and its stiffness and damping parameters, along with the frictional conjunction between its main subparts.
In this paper an original 5-degree of freedom mathematical model of the dry clutch mechanism is presented with the intention of studying the excitation in a passenger car driveline of torsional vibration by frictional actions during the slip phase of the engagement. Furthermore, the analysis aims to deepen about the coupling between pressure plate wobbling and torsional motions in order to improve the current understanding of the excitation mechanisms in the frequency region of the so-called “eek noise”, 250–500 Hz. The results of this work substantiate that enhancing of torsional motion in the characteristic frequency range of the “eek sound” occurs even regardless of the rigid wobbling motion of the pressure plate and underline the need to include the non-linear characteristic of the clutch cushion spring in the simulation of such a phenomenon.
CO2-Filled Vertical Geothermal Boreholes: Modeling and Application
Authors: Eslami-Nejad Parham , Ouzzane Mohamed , Aidoun Zine 
Published: April 2014

In the context of extremely cold or hot climates, ground coupled heat pumps offer several environmental and energy efficiency advantages over conventional methods for heating and cooling of buildings and they are increasingly used in most near-zero and net-zero energy buildings. However, the high initial cost of the ground loop portion (geothermal boreholes) has often raised the question on the economical competitiveness of the system. In the present study, a geothermal borehole is proposed in which two-phase carbon dioxide (mixture of liquid and vapor) exchanges heat with the ground to improve the thermal performance of the borehole and thus to reduce borehole length. Carbon dioxide shows several cost and environmental advantages. Moreover, it offers superior thermophysical properties and heat transfer characteristics.
A numerical model has been developed to study the complex thermal behavior of a two-phase CO2-filled vertical geothermal borehole. The model can handle both two-phase and single-phase conditions along the borehole length. An explicit solution for fully coupled conservation equations of mass, momentum and energy as well as an equation of state are applied. The model accounts for the thermal interaction among the pipes and it predicts the fluid temperature, pressure and two-phase quality profiles. It is used to assess the thermal performance of the CO2-filled secondary loop geothermal borehole operating in heating mode. Results indicate that the proposed borehole offers superior performance due to the relatively high two-phase heat transfer characteristics of CO2.
An Adaptive-Grid Projection Method for High Density Ratio Interfacial Flows
Authors: Gómez Pablo , Zanzi Claudio , Palacios Julián , Hernández Julio , López Joaquín 
Published: April 2014

A graded-adaptive grid projection method to solve the Navier-Stokes equations for incompressible interfacial flows characterized by large density ratios is presented. The numerical model is similar to the one we proposed in [7] and extended to 3D problems in [8].
The free surface is described using a level set method. A Godunov-type method and a Crank-Nicholson temporal discretization scheme are used to solve the advection equation of the level set function and to update of the momentum equation. The reinitialization procedure of the distance function is based on solving a hyperbolic equation to steady state using third-order Runge-Kutta and fifth-order WENO schemes.
The conservation equations are discretized on a rectangular adaptive grid with an octree data structure and the pressure stored at the grid cell vertices. In order to avoid spurious pressure oscillations, the velocity components are stored at the cell edges. This new storage scheme combines the advantages of vertex-based schemes, in which the nodes where the pressure is stored are aligned, and cell center-based schemes, which avoid pressure-velocity coupling problems.
The numerical model incorporates a continuous surface tension model based on the balanced-force algorithm proposed in [6]. A special treatment of T-nodes (nodes located at vertices, edges or faces of cells belonging to two different refinement levels) is proposed that considerably improves the efficiency of the method.
Several tests in two and three dimensions have been carried out to assess the accuracy and efficiency of the proposed method. In this work we present some numerical results for a 3D kinematic test, which are compared with those obtained by other authors. We also present results for the impact of a drop of water onto a liquid surface, which are compared with experimental visualization results.
A Novel Additive Manufacturing File Format for Printed Electronics
Authors: Panhalkar Neeraj , Paul Ratnadeep , Anand Sam 
Published: April 2014

Additive Manufacturing (AM) based Printed Electronics (PE) is an emerging technique where electronic components and interconnects are printed directly on substrates using a layered technique. The direct printing of the electronic components allows large scale and ultra-thin components to be printed on a wide variety of substrates including glass, silicon and plastic. These attributes make AM based Printed Electronics an invaluable manufacturing technique in the area of electronic sensors and sensor networks where thin, flexible and rugged form factors are very important. However, currently this technology is a labor intensive and manual process with the machine operator using his experience and judgment to slice the CAD file of the part to create 2D layers at different levels. This manual process increases the overall production time as well as the cost of the product and also results in inconsistent quality of parts.
A major challenge faced by existing AM based Printed Electronics users for automating this process is the lack of a standard input file format that can be used by different PE machines for producing the components in layers. To leverage the capabilities of both AM and PE processes, a new file format based on the Constructive Solid Geometry (CSG) technique is proposed in this research paper. This file format data will not only include CAD data in the form of CSG primitives and Boolean representation but will also include manufacturing information related to the AM based PE process. The manufacturing information embedded within this new format will include data about the location of the different electronic components such as interconnects, resistors, capacitors, inductors, transistors, memory and substrate, and the materials required for the different components part. Different circuit board components will be represented as primitives or a combination of primitives obtained using CSG technique. In addition to the new file format, a slicing algorithm will also be developed which can be used to create the layers automatically using user inputs. The proposed file format and the slicing algorithm will be explained with the help of a case study.
Effect of Including a Fetus in the Uterus of Pregnant Occupant Model in Crash Test Simulations
Authors: Acar B. Serpil , Moustafa M. , Acar Memis 
Published: April 2014

Motor vehicle accidents are the largest single cause of accidental death and the leading cause of traumatic injuries for the pregnant occupant and her fetus. Computational pregnant occupant modeling has a role to play in the investigation of the risk of fetal injuries and mortality in crash test simulations. Effective investigation depends on realistic representation of pregnant occupant and her fetus in a virtual environment. However, known pregnant occupant models normally do not include a fetus in the uterus. ‘Expecting’, the first computational model of a pregnant occupant with a fetus, is used in the current research. The model has a detailed multi-body representation of the fetus as well as finite element uterus and placenta.
In this paper, the effect of including the fetus in the uterus of the pregnant occupant model is investigated using ‘Expecting’ in crash test simulations. Previously, drop test simulations with and without a fetus showed that, the presence of fetus in the uterus suggests higher risks to the fetus. Using the pregnant occupant model, ‘Expecting’, with and without a fetus, provides more realistic simulations to explore the role of inclusion of fetus in the uterus. Five frontal impact speeds, 15, 20, 25 30 and 35 kph with varying levels of restraint system including ‘seatbelt and airbag’ (ie fully restrained), ‘seatbelt only’, ‘airbag only’ and ‘no restraint’ are used in the simulations. Maximum strains developed in the uteroplacental interface with and without a fetus are compared. The effect of including a fetus in the pregnant occupant model is discussed.
Definition of a Protocol for Implementing Lean Production Methodology in Textile and Clothing Case Studies
Authors: Costa Maia Laura , Carvalho Alves Anabela , Leão Celina P. 
Published: April 2014

This paper presents a protocol used in case studies with the objective to validate a Lean Production methodology in Textile and Clothing Industry (TCI) in North of Portugal. The methodology was developed under a Doctoral Program on Industrial Engineering and Systems. During the development of the methodology, the TCI contextualization was studied in parallel with the development of a survey applied to the TCI companies. The development of the methodology (structured in three phases) was followed by its validation in case studies.
Thus, this paper objective is to describe and explain the case study designed and conducted to attain feedback from companies. These case studies demanded a protocol constituted by an overview of the project, the field procedures (meetings and visits, interviews, questionnaires and checklist form), the preliminary questions of the project and the guide for the reports from the case studies. From the field procedures, the interviews was the first instrument used and it allowed the identification of the needs of change, the workers and management role in this change, the expected and achieved results. These preliminary results are presented in this paper. The questionnaire, adapted from others studies, would be used for a better context in the national framework and it would be applied in a following phase as the checklist. It will enable the data and metrics collection related with several aspects, namely work ergonomic conditions. This protocol will allow the knowledge of the work environment for a good implementation of the Lean Production.