bluuebunny/crossref_metadata_2025 huggingface dataset:
Smart Design System for Coal-Fired Boiler Buildings in Thermal Power Plants
Authors: Kusumi Naohiro , Nagafuchi Naoyuki , Murakami Eiji , Ichinose Noriyuki , Imamura Masakatsu
Published: August 2009

To meet expanding energy requirements, supercritical sliding pressure operation has become a major trend in recent thermal power plants. The technology for this operation was developed as high efficient thermal power plants with lower emission. We have continued to develop supercritical steam plant with sliding pressure operation to meet the demand for high efficiency coal-fired power plants that has arisen due to circumstances such as high fuel prices, exacting plant site requirements, and very strict environmental requirements. Because of our accumulated expertise and practical experience, we have received orders for several coal-fired engineering, procurement, and construction (EPC) projects. We have developed a smart design system for a coal-fired boiler building using an information technology (IT) tool for a large-scale and complex system design. We call this design system the Flexible Engineering System. This system is composed of three support functions: boiler general arrangement, boiler building layout, and bill of quantity estimation. First, the boiler general arrangement support function enables us to automatically create basic engineering specifications based on the required specifications. This system generates the basic engineering required using parametric engineering practice with parameterization of several required specifications. Second, the support function of the boiler building layout planning enables us to make 3-D models of the boiler building automatically. The 3-D models of the boiler, coal silos, and air and gas ducts are generated from the boiler general arrangement. The 3-D models of the steel structures are generated from loading data. The steel structure and brace models can even reflect the results of stress analysis. The 3-D models of large components, for example, the pulverizer, forced draft fan, etc., are arranged by selecting a matching model from the data library. The 3-D piping models are generated along the optimum path routing using a search method that combines dynamic programming with a layout rule-base. The 3-D floor and head-clearance model, which means a walk space and a maintenance space, are generated taking into consideration layout rules such as those concerning installation and maintenance. This support system can check for interference between the steel structures and each component. Third, the support function of the bill of quantity estimation makes it possible to estimate the quantity of materials from the specification data and configuration data of the 3-D models. The developed system is now under operation. The results indicate that it provides high engineering accuracy and reliability.
Simulation of the Influence of Ship Voyage Profiles on Air Emissions
Authors: Shi Wei , Stapersma Douwe , Grimmelius Hugo
Published: August 2009

Simulation methodology is used to assess fuel related pollutants, CO2 and SO2, based on several reference ship voyages. Firstly, the definition of ton-mile specific emission factor is introduced. This emission factor is related to a wide range of factors extending from fuel parameters and engine operational condition to ship design and ship activity. In this case study, a simulation model is built that applies to both transient and stationary conditions. By running this model, ton-mile specific emission factors of CO2 and SO2, for both the full voyage and a single part of the voyage are achieved. The influences on exhaust emissions of ship speed fluctuation and in port operation strategy are considered, as well as the influence of loading fraction. After a series of simulations it is demonstrated that, a larger speed fluctuation and more intense variation of ship operational activities during maneuvering in port would cause higher emissions and the assumption of full load will underestimate the ton-mile specific emissions.
Numerical Investigation of the Grid, Turbulence Model and Discretization Sensitivity of an Automotive Cyclone Particle Separator
Authors: Hineiti Naser , Guessous Laila
Published: August 2009

The accuracy of Computational Fluid Dynamics (CFD) simulations of complex flows in general, and highly swirling flows in particular, depends on a number of parameters. In this paper we report on the sensitivity of CFD simulations of transient flow in an automotive reverse flow type cyclone particle separator to mesh size/type, turbulence models, and temporal discretization schemes. More specifically, this study is concerned with the effect of these modeling choices on the two main performance measures of the cyclone: overall pressure drop and particle separation efficiency.
Influence of Vehicle Model Complexity in Autonomous Emergency Manoeuvre Planning
Authors: Bortoluzzi Daniele , Biral Francesco , Bertolazzi Enrico , Bosetti Paolo , Zendri Fabrizio
Published: August 2009

In this paper the effectiveness of an optimal reference manoeuvre is analysed w.r.t. the complexity of the vehicle model used within the optimal control algorithm. The optimal reference manoeuvre is computed by means of a Nonlinear Receding Horizon planning (NRHP) strategy which is based on a simplified vehicle model. The reference manoeuvre is tracked by a controller implemented on a low level faster loop. The system is able to perform autonomously lane change and obstacle avoidance manoeuvres by tracking the computed reference one. The quality of the performed manoeuvres depends on the reference manoeuvre and consequently on the vehicle model used by the NRHP. For manoeuvres with low or mild lateral accelerations reduced order models might yield realistic and reliable reference manoeuvres. However, critical conditions (e.g. evasive manoeuvre) require a manoeuvre planner able to catch highly non-linear vehicle dynamics that characterizes such situations. On the other hand, being the NRHP computational cost generally high and related to the number of equations of the mathematical model, a trade-off between computational efficiency and model complexity is required. The work analyses the reference manoeuvres produced by two vehicle models of increasing complexity used as reference within the NRHP. Optimal planner performance evaluation on evasive manoeuvre in critical conditions will be presented with simulations results.
Theoretical and Experimental Comparison of the Heating From Shoe-Wheel and Pad-Disk Braking Systems for Railroad Freight Cars
Authors: Santos A. A. , Romano S. J. , Santos F. C.
Published: August 2009

Brazilian freight cars use brake shoes directly applied onto the wheels. This system causes wheel heating, which in turn gives rise to thermal stresses and loss of mechanical strength. An alternate solution is a system of brake disks and pads, which would not heat the wheels. This system is not used in high load railroads. Because temperature is one of the major factors affecting braking performance, a study of the viability of replacing shoe brakes by disk brakes must evaluate and compare the heating of wheels and disks. The present work evaluates the heating of disk-pad systems when used for braking freight cars. Preliminary numerical simulations were done to check whether the expected temperatures would exceed the limits and damage friction materials and systems. Following that, real scale tests were conducted in critical braking conditions for both types of brake systems. Dynamometer tests were performed in real scale at the Railroad Laboratory of the State University of Campinas, Brazil. Results showed that, as far as system heating is concerned, there is nothing to prevent the replacement of the current system by a disk-pad system.
The Development of Active Flow Control Devices From Shape Memory Alloys for the Convective Cooling of Heated Surfaces
Authors: Aris Mohd S. , Owen Ieuan , Sutcliffe Chris J.
Published: August 2009

This paper is concerned with the convective heat transfer of heated surfaces through the use of active flow control devices. An investigation has been carried out into the use of two flow control design configurations manufactured from Shape Memory Alloys (SMAs) which are activated at specified temperatures. In this design, a high surface temperature would activate rectangular flaps to change shape and protrude at a 45° angle of attack. This protrusion would generate longitudinal vortices and at the same time allow air to flow into cooling channels underneath the flaps, cooling a heated surface downstream of the flow control device. One- and two-channel flow control configurations were explored in this work. The flow control device was made from pre-alloyed powders of SMA material in a rapid prototyping process known as Selective Laser Melting (SLM). It was tested for its heat transfer enhancement in an open test section wind tunnel supplied with low velocity air flow. Infrared thermography was used to evaluate the surface temperatures of the downstream heated surface. Promising results were obtained for the flow control design when the heated surface temperatures were varied from 20 °C to 85 °C. In the one-channel configuration, the flow control device in its activated shape increased heat transfer to a maximum of 50% compared to its deactivated shape. The activated flow control device in the two-channel configuration experienced a heat transfer enhancement of up to 90% compared to when it is deactivated.
Soft Sensor Design for Biodiesel Concentration in a Transesterification Reactor
Authors: Garci´a Jaime , Posada Jose´ , Villalba Pedro , Sanjuan Marco
Published: August 2009

Biofuels production is facing new challenges every day, related to better process control and quality monitoring. It is very important for the sustainability of these processes to implement strategies and alternatives in order to achieve a continuous production process and to control significant variables involved in the reaction. One of the most difficult variables to measure is the actual Biodiesel concentration inside the reactor. Neural networks have become a useful strategy to give solutions to complex problems; its application is growing faster at industries due to the inherent nonlinear behavior of the processes, modeled easily by this computational tool. The capacity of mapping a complex behavior trough input and output process data, without a complicated and hardly to obtain mathematical model, makes neural networks an attractive strategy to be implemented in most industries, in a soft sensor or a process model scheme. This investigation addresses the need to predict the concentrations of esters (biodiesel) when different triglycerides are reacting with alcohol. Concentration was estimated using an approach that uses a soft sensor that captures the dynamics of these variables through off line laboratory experiments. The soft sensor is actually a Random Activation Weight Neural Net (RAWN), which is a back propagation neural network with a fast training algorithm that does not need any iteration. Also, to reduce the complexity of the soft sensor an optimization procedure was carried out to determine the optimum number of neurons in the hidden layer. In this research Biodiesel was produced by transesterification of palm oil with ethanol and KOH as catalyst. During transesterification reaction the estimation of concentrations is determined by laboratory analysis at off line stages, these variables are very important to control the continuous process of a biodiesel plant.
Microstructural and Mechanical Characterization of Solder Joints Fabricated by Explosively Reacting Nanolayers
Authors: Tong Michael , Yang Jenn-Ming
Published: August 2009

The unique heat-releasing characteristics of explosively reactive nanolayers (RN) are used in this study to produce Si/solder/Si joints. The microstructure of the RN in the reacted state as well as the post-joining foil/solder interface is characterized via XRD, SEM, and TEM, which have never been done. Additionally, RN solder joints are mechanically characterized by single lap shear and nanoindentation to obtain a set of optimized processing parameters, specifically initial pressure applied (Pa) and initial temperature of the system (Ti). A maximum joint shear strength of ∼ 30MPa at Pa = 15MPa and Ti = 75°C. Furthermore, nanoindentation is used to clarify the mechanical behavior of individual layers and interfaces across the joints as a result of thermal aging.
Review of Existing Repeatable Vehicle Rollover Dynamic Physical Testing Methods
Authors: Friedman Keith , Hutchinson John
Published: August 2009

Two repeatable dynamic rollover performance testing systems have been demonstrated and reported upon. Here a review of each system is presented in which the general characteristics of each system are discussed. To assess how the results obtained from the two systems would compare, finite element models of rollover tests characterizing the two design approaches were utilized. The results from a published rollover test using one of the systems was utilized as a reference test. For each system, the vehicle rollover impacts were simulated under the same initial impact conditions. The results of the simulations were then compared. It was found that the simulations for both hardware systems produced results that were consistent with each other using state-of-the-art finite element analysis tools.
Nano-Scale Indentation Measurement of Material Properties Using an Area Function of the Tip Geometry
Authors: Ozcan S. , Farhang K. , Filip P.
Published: August 2009

A novel two-parameter area function for determination of near surface properties of Young’s modulus of elasticity and hardness has shown promise for compensating for the imperfection of the tip-end in an instrumented indentation measurement. This paper provides a comprehensive study involving a Berkovitch tip. The tip is utilized in an MTS nanoindentation measurement machine and used to establish load indentation information for fused silica samples. The geometry of the tip is then characterized independently using a highly accurate Atomic Force Microscope. Using the indentation data along with the two-parameter area function methodology, the tip-end radius of curvature is found to provide the most consistent value of modulus of elasticity. Independently, the data from the SEM measurement of the same tip is used to obtain the least squares estimation of the tip curvature. The two approaches yield favorable agreement in the estimation of tip-end radius of curvature. Therefore, the validity of the two-parameter area function method is proved. The method is shown to provide a robust, reliable and accurate measurement of modulus of elasticity and hardness in the nanoscale proximity of a surface.
Experimental and Computational Investigations of Separation and Transition on a Highly Loaded Low-Pressure Turbine Airfoil: Part 2 — High Freestream Turbulence Intensity
Authors: Volino Ralph J. , Kartuzova Olga , Ibrahim Mounir B.
Published: August 2009

Boundary layer separation, transition and reattachment have been studied on a very high lift, low-pressure turbine airfoil. Experiments were done under high (4%) freestream turbulence conditions on a linear cascade in a low speed wind tunnel. Pressure surveys on the airfoil surface and downstream total pressure loss surveys were documented. Velocity profiles were acquired in the suction side boundary layer at several streamwise locations using hot-wire anemometry. Cases were considered at Reynolds numbers (based on the suction surface length and the nominal exit velocity from the cascade) ranging from 25,000 to 300,000. At the lowest Reynolds number the boundary layer separated and did not reattach, in spite of transition in the separated shear layer. At higher Reynolds numbers the boundary layer did reattach, and the separation bubble became smaller as Re increased. High freestream turbulence increased the thickness of the separated shear layer, resulting in a thinner separation bubble. This effect resulted in reattachment at intermediate Reynolds numbers, which was not observed at the same Re under low freestream turbulence conditions. Numerical simulations were performed using an unsteady Reynolds averaged Navier-Stokes (URANS) code with both a shear stress transport k-ω model and a 4 equation shear stress transport Transition model. Both models correctly predicted separation and reattachment (if it occurred) at all Reynolds numbers. The Transition model generally provided better quantitative results, correctly predicting velocities, pressure, and separation and transition locations. The model also correctly predicted the difference between high and low freestream turbulence cases.
Evaporation Time of Gasoline and Diesel Fuel Droplets on a Hot Plate: The Influence of Fuel Deposits
Authors: Seers P. , Reguillet V. , Plamondon E. , Dufresne L. , Halle´ S.
Published: August 2009

The objective of this paper is to present experimental results of multicomponent fuel droplets impinging on a hot surface in order to quantify the influence of fuel build-up deposits on the evaporation time. The experiments were conducted with gasoline and diesel fuels to first obtain curves of evaporation time as a function of plate temperature. Based on these curves the Nukiyama and Leindenfrost temperatures were identified. In a second step, the effect of fuel deposit on the droplet evaporation time was studied. Based on the above evaporation time curves, plate temperatures were chosen as to offer a similar evaporation time but at temperatures below and above the Nukiyama and Leindenfrost temperatures respectively. This was done in order to isolate the effect of fuel deposits from the different evaporation mechanisms. The evaporation of successive impinging droplets was then measured. The results hence obtained indeed showed that the fuel deposit has a different impact on the evaporation time according the evaporating mechanism or equivalently the plate temperature. For plate temperatures lower than the Nukiyama temperature, gasoline and diesel fuel droplets showed an increase of their evaporation time as the amount of successive impinging droplets increased. The trend was reversed for plate temperatures above the Leindenfrost temperature. A hypothesis for this latter case is that the fuel deposit disrupts the vapor layer supporting the droplet and therefore provides a greater heat flux to the evaporating droplet. Finally, droplet evaporation times as a function of plate temperature were measured with an initial fuel deposit covering the plate. These results in turn showed that the global thermal diffusivity and porosity of the surface are changed by the presence of the fuel deposit. The consequence of these property changes are then shown to have a direct and global impact on the fuel evaporation time curves.
Compliant Impact Generator for Required Impact and Contact Force
Authors: Demirel Burak , Emirler Mu¨min Tolga , Yo¨ru¨kog˘lu Ahmet , Koca Nebahat , So¨nmez U¨mit
Published: August 2009

A novel design of compliant slider crank mechanism is introduced and utilized as an impact force generator and contact force generator. This class of compliant slider mechanisms incorporates an elastic coupler which is an initially straight flexible beam and buckles when it hits the stopper. The elastic pin-pin coupler (a buckling beam) behaves as a rigid body prior to the impact pushing the rigid slider. At a certain crank angle the slider hits a stopper generating an impact force. Impact force can be changed by changing the angular velocity of the crank, therefore; achieving a desired velocity of the slider. Moreover, after the impact when the vibrations die out the maximum contact force can also be predetermined by designing the coupler dimensions (length, width, thickness and the amount of compression). Contact duration (crank angle) can also be changed and adjusted in this mechanism by changing the adjustable location of the impacted object.
A Heat Plate Leading Edge for Hypersonic Vehicles
Authors: Kasen Scott D. , Queheillalt Doug T. , Steeves Craig A. , Evans Anthony G. , Wadley Haydn N. G.
Published: August 2009

The intense thermal flux at the leading edges of hypersonic vehicles (traveling at Mach 5 and greater) requires creative thermal management strategies to prevent damage to leading edge components. Carbon fiber composites and/or ablative coatings have been widely utilized to mitigate the effects of the impinging heat flux. This paper focuses on an alternative, metallic leading edge heat pipe concept which combines efficient structural load support and thermal management. The passive concept is based on high thermal conductance heat pipes which redistribute the high heat flux at the leading edge stagnation point through the evaporation, vapor flow, and condensation of a working fluid to a location far from the heat source. Structural efficiency is provided by a sandwich construction using an open-cell core that also allows for vapor flow. A low temperature proof-of-concept copper–water system has been investigated by experimentation. Measuring of the axial temperature profile indicates effective spreading of thermal energy, a lowering of the maximum temperature and reduced overall thermal gradient compared to a non-heat pipe leading edge. A simple transient analytical model based on lumped thermal capacitance theory is compared with the experimental results. The low-temperature prototype shows potential for higher temperature metallic leading edges that can withstand the hypersonic thermo-mechanical environment.
Sensitivity Analyses for Viscoelastic Strength of Materials and Corresponding Continuum Mechanics Formulations
Authors: Hilton Harry H.
Published: August 2009

Comparison analyses are conducted for straight and curved viscoelastic beams based on Euler-Bernoulli strength of materials prescriptions and on rigorous formulations in terms of 3-D field equations. The concepts of elastic straight and curved beam analyses are well established. In the present paper, these geometric principles are extended to linear viscoelastic materials. The beams are considered subjected to un-symmetric bending as well as to thermal expansions. The distinct conditions leading to shear center and neutral axis motions in time, previously observed in straight beams are investigated. The applicability of the elastic-viscoelastic correspondence principle (analogy) in terms of integral transforms is demonstrated by application to several simulations. Comparison studies are based on pure bending loading configurations as these offer the least distinct geometric deformation patterns.
A Risk Based Methodology for Spare Parts Inventory Optimisation
Authors: Bharadwaj Ujjwal R. , Silberschmidt Vadim V. , Wintle John B. , Speck Julian B.
Published: August 2009

Spare parts inventories assist maintenance staff to keep equipment in operating condition. Thus the inventory level of spares has a direct bearing on machine availability, a factor that is increasingly important in capital-intensive industries. This paper presents a risk based approach for spare parts inventory optimization. At the outset, the paper highlights the unique features of maintenance inventories, such as spare parts inventories, compared to other inventories such as work-in-progress or finished product inventories. After a brief mention of the principles on which many of the current inventory management models are based and their limitations, the paper presents a risk-based methodology to spares inventory management. ‘Risk’ in the current context is the risk in monetary terms that arises when a component (spare) is not available on demand. It is the expected value of loss, i.e., the product of the likelihood of unavailability of the spare from the inventory and an estimate of the consequence(s) of that unavailability. Given a budgetary constraint and the risk profile of a number of spares, the model gives an optimal inventory of spares. By basing the inventory on the risk profile of spares, the model includes factors that are not normally considered in various other models. The ultimate aim of the methodology is to have an optimal level of spares inventory such that machine availability, to the extent it is dependent on the level of spares inventory, is maximized subject to constraints. The methodology is expected to benefit both, operational and financial managers.
Automated Weld Defects Detection Using Image Processing and CAD Methods
Authors: Nejatpour Reza , Sadabad Ali Asmari , Akbari Ali Akbar
Published: August 2009

One of the simple, fast, and economical methods for controlling the condition of a weld is checking its superficial appearance. In this paper a method, based on the composition of Image Processing and CAD algorithms is presented for controlling different welding defects. The main purpose of this project is omission of the human interference in Visual Test of the weld. The main core of this system is a computer which analyses the captured images of a CCD camera and extracts the parameters of the weld such as size, position, surface smoothness and etc. By putting the results of analyses executed on the images captured from different sections of the weld next to each other, a continuous, 3D model of the weld is achieved. By comparison of this model with the standard samples, the probable defects on the weld and the type of each recognized defect is defined. Omission of human mistakes, decrease in the costs, higher speed of the control line and coincidence with the new production standards are the advantages of this method. The presented method has been implemented on the automobile rings manufactured in Mashhad Wheel Manufacturing Co.
Modeling the Propagation of Failures in Software Driven Hardware Systems to Enable Risk-Informed Design
Authors: Jensen David C. , Tumer Irem Y. , Kurtoglu Tolga
Published: August 2009

Software-driven hardware configurations account for the majority of modern complex systems. The often costly failures of such systems can be attributed to software specific, hardware specific, or software/hardware interaction failures. The understanding of the propagation of failures in a complex system is critical because, while a software component may not fail in terms of loss of function, a software operational state can cause an associated hardware failure. The least expensive phase of the product life cycle to address failures is during the design stage. This results in a need to evaluate how a combined software/hardware system behaves and how failures propagate from a design stage analysis framework. Historical approaches to modeling the reliability of these systems have analyzed the software and hardware components separately. As a result significant work has been done to model and analyze the reliability of either component individually. Research into interfacing failures between hardware and software has been largely on the software side in modeling the behavior of software operating on failed hardware. This paper proposes the use of high-level system modeling approaches to model failure propagation in combined software/hardware system. Specifically, this paper presents the use of the Function-Failure Identification and Propagation (FFIP) framework for system level analysis. This framework is applied to evaluate nonlinear failure propagation within the Reaction Control System Jet Selection of the NASA space shuttle, specifically, for the redundancy management system. The redundancy management software is a subset of the larger data processing software and is involved in jet selection, warning systems, and pilot control. The software component that monitors for leaks does so by evaluating temperature data from the fuel and oxidizer injectors and flags a jet as having a failure by leak if the temperature data is out of bounds for three or more cycles. The end goal is to identify the most likely and highest cost paths for fault propagation in a complex system as an effective way to enhance the reliability of a system. Through the defining of functional failure propagation modes and path evaluation, a complex system designer can evaluate the effectiveness of system monitors and comparing design configurations.
Enhancing Toughness of Silicon Nitrides With Nanoscale Additions
Authors: Santhanam Sridhar , Jen Kei-Peng , Wing Zachary N.
Published: August 2009

Silicon nitride ceramics for applications in demanding environments require high toughness and adequate hardness. A well known route to making tough silicon nitride compositions is to control the grain size distribution. For beta silicon nitrides, the grain shapes in the form of their acicularity is known to be very important too. In this paper, we report on the use of multiple strategies to achieve increased toughness and toughening in silicon nitrides. These strategies include the use of a blend of nano-scale and micron-scale silicon nitride powders, the use of nano-scale sintering aids, and the addition of carbon nanotubes. Microstructures and mechanical properties are determined for these hot-pressed ceramics and are compared with a baseline silicon nitride prepared with conventional micron-scale powders. Hardness and fracture toughness are determined at room temperature using hardness indents produced by a macro Vickers hardness indenter. The toughening ability of these ceramics are compared by R-curve measurements. Grain boundary debonding and crack path deviation are identified as toughening mechanisms.
An Examination of Flow Regimes Associated With Inkjet-Printed Colloidal Drops
Authors: Bromberg Vadim , Gawande Sailee , Sun Ying , Singler Timothy
Published: August 2009

An experimental study of the evaporation dynamics for an inkjet-printed drop on a solid substrate has been attempted. Using fluorescent spherical colloids, the internal flow of an evaporating drop has been observed directly. During the initial stages of the process, a novel inward radial flow carries the particles as a single group towards the center of the drop. Once the particles have converged near the center, a significantly slower outward radial flow proceeds. These flow regimes are qualitatively analyzed and their relationship to a possible thermal Marangoni flow is discussed.
Experimental and Computational Investigations of Separation and Transition on a Highly Loaded Low-Pressure Turbine Airfoil: Part 1 — Low Freestream Turbulence Intensity
Authors: Ibrahim Mounir , Kartuzova Olga , Volino Ralph J.
Published: August 2009

Boundary layer separation, transition and reattachment have been studied on a new, very high lift, low-pressure turbine airfoil. Experiments were done under low freestream turbulence conditions on a linear cascade in a low speed wind tunnel. Pressure surveys on the airfoil surface and downstream total pressure loss surveys were documented. Velocity profiles were acquired in the suction side boundary layer at several streamwise locations using hot-wire anemometry. Cases were considered at Reynolds numbers (based on the suction surface length and the nominal exit velocity from the cascade) ranging from 25,000 to 330,000. In all cases the boundary layer separated, but at high Reynolds number the separation bubble remained very thin and quickly reattached after transition to turbulence. In the low Reynolds number cases, the boundary layer separated and did not reattach, even when transition occurred. Three different CFD URANS (unsteady Reynolds averaged Navier-Stokes) models were utilized in this study (using Fluent CFD Code), the k-ω shear stress transport model, the ν2-fk-ε model, and the 4 equation Transition model of Menter. At Re = 25,000, the Transition model seems to perform the best. At Re = 100,000 the Transition model seems to perform the best also, although it under-predicts the pressure coefficient downstream of the suction peak. At Re = 300,000 all models perform very similar with each other. The Transition model showed a small bump in the pressure coefficient downstream from the suction peak indicating the presence of a small bubble at that location.
Experimental and Numerical Studies of Carbon Black Formation Through Thermal Decomposition of Waste Natural Gas
Authors: Moghiman M. , Hosseini N. , Raad M. H. , Javadi M.
Published: August 2009

The present study is concerned with measuring and simulating the formation process of carbon black in a natural gas furnace. Carbon black concentrations in the furnace have been measured by the gravimetric method. Fluent CFD software has been employed for numerical predictions. A chemical reaction formulation relates the production of the carbon black to the incomplete combustion and pyrolysis of natural gas as the parent fuel. The influences of feedstock flow rate and equivalence ratio on carbon black furnace output are investigated. The results show that for relatively low feedstock flow rates, most feedstock hydrocarbon burns to CO, while for higher feedstock flow rates the decomposition of feedstock and formation of solid carbon is the dominant process and has an important role in the production of carbon black. The comparison of calculated results against the experimental measurements shows good agreement.
Transient Natural Convection in Convergent Vertical Channels With Porous Media
Authors: Buonomo Bernardo , Manca Oronzio , Nardini Sergio
Published: August 2009

In this paper transient natural convection in a vertical convergent channel with or without saturated porous medium is studied numerically. The investigation is carried out in laminar, two dimensional regime and employing the Brinkman-Forchheimer-extended Darcy model. The physical domain consists of two non-parallel plates which form a convergent channel. Both plates are heated at uniform heat flux. The solutions are achieved using the commercial code FLUENT. A finite-extension computational domain is employed to simulate the free-stream condition. The results are obtained for different convergence angles, for 0° to 5°, and porosity coefficient (0.4, 0.6 and 0.9), a channel aspect ratio equal to 10, a Rayleigh number equal to 104 and a Darcy number equal to 0.01. The dimensionless results are reported in terms of average and maximum wall temperatures, average Nusselt number as a function of time and at steady state wall temperature, local Nusselt number and temperature and stream function fields. The cases with porous medium in the channel shows that in conductive regime dominant, at initial time, average and maximum wall temperatures are lower than the case without porous medium in the channel. For the convective regime dominant, the lowest average and maximum wall temperatures are attained for the case without porour medium in the channel. At steady state, in the inlet zone the cases with porous medium present wall temperature lower than the no porous case. In the other part of the channel the opposite behaviour is detected.
Numerical Investigation of Forced Convection of Nanofluids in Channels
Authors: Bianco Vincenzo , Manca Oronzio , Marzano Ferdinando , Nardini Sergio , Tamburrino Salvatore , Vitale Antonio
Published: August 2009

In this paper developing turbulent forced convection flow of a water–Al2O3 nanofluid in a square channel submitted to a constant and uniform heat flux at the wall is numerically investigated. A single model and two-phase models (discrete particles model and mixture model) are employed with constant temperature properties. The investigation is accomplished for a size particles equal to 38 nm. The CFD commercial code Fluent is employed to solve the problem by means of finite volume method. Convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement is increasing with the particle volume concentration but it is accompanied by increasing wall shear stress values. The effect of Reynolds number is great for higher concentrations. The results obtained by tree different models are presented in terms of temperatures and velocity distributions, relative increasing of heat transfer coefficient, hr, and Nusselt number profile.
Evaluation of Void Fraction Correlations for the Statistical and Numerical Analysis of Two-Phase Flows Inside Producing Geothermal Wells
Authors: A´lvarez del Castillo A. , Santoyo E. , Garci´a-Valladares O. , Sa´nchez-Upton P.
Published: August 2009

The modeling of heat and fluid flow inside two-phase geothermal wells is a vital task required for the study of the production performance. Gas void fraction is one of the crucial parameters required for a better prediction of pressure and temperature gradients in two-phase geothermal wells. This parameter affects the correct matching between simulated and measured data. Modeling of two-phase flow inside wells is complex because two phases exist concurrently (exhibiting various flow patterns that depend on their relative concentrations, the pipe geometry, and the mass flowrate). A reliable modeling requires the precise knowledge of the two-phase flow patterns (including their transitions and some flow parameters). In this work, ten empirical correlations were used to estimate the gas void fraction in vertical-inclined pipes, and to evaluate their effect on the prediction of two-phase flow characteristics of some Mexican geothermal wells. High quality downhole pressure/ temperature logs collected from four producing geothermal wells were studied [Los Azufres, Mich. (Az-18); Los Humeros, Pue. (H-1), and Cerro Prieto, B.C. (M-90 and M-201)]. The pressure/ temperature gradients were simulated using an improved version of the wellbore simulator GEOPOZO, and the gas void fraction correlations. The simulated results were statistically compared with measured field data.
The Effect of Vertical and Multiplanar Accelerations on Differing Production Seat Belt Sensor Designs
Authors: Meyer Steven E. , Oliver Arin A. , Hock Davis A. , Hayden Joshua D. , Forrest Stephen M. , Herbst Brian R. , Clarke Chris C.
Published: August 2009

In real world accidents, vehicles are often subjected to multiplanar crash environments such as those seen in multiple impacts or rollover collisions. These various impact environments can directly affect the accelerations experienced by the vehicle and its components. Particularly vulnerable is the vehicle sensitive (inertially activated) crash sensor that is commonly used in seat belt retractor design. Though these designs have been proven effective in the frontal crash environments, they have also been shown to be susceptible to unlocking and/or a delay in lockup by vertical and/or rotational accelerations [1–3]. Such delayed retractor response can result in belt webbing payout and significant occupant motion within the restraint system. This can increase the likelihood and severity of occupant injury within the vehicle and/or injury from partial or full ejection in rollovers. Occurrence of this phenomenon in the real world has been documented and previously published [4, 5]. Evidence of retractor sensor unlocking and resulting spoolout includes identifiable forensic markings on the restraint system components [6] as well as occupant excursion evidence including full ejection and excessive partial ejection of properly belted vehicle occupants. The subject paper will follow previously published test methodologies [1–3] and report on new testing conducted on four differing production seat belt retractor designs. The test methods include linear accelerator tests to document the effects of a vertical pulse on an inertially sensitive retractor and, secondly, rotational accelerator tests wherein the retractors were mounted on a rotating fixture and subjected to various roll rates. Two tested retractors are the ball and cup design with the retractor’s inertial sensor incorporated within the retractor mounted in the vehicle’s roof pillars. The other two tested retractor designs utilize remote mounted (near the vehicle’s center of gravity) inertial sensors. These retractors are biased to the locked position via a spring and are held unlocked only when a solenoid is energized by the vehicle’s remote inertial sensor. For the rotational acceleration tests, the retractors were mounted in similar positions to that seen in their respective production vehicles relative to the vehicle’s center of gravity. Two retractors were then tested concurrently on the same test apparatus such that they were subjected to equivalent multiplanar environments, and thus allowed for direct comparison of their retractor design sensitivities and lockup performance. Additionally, a vehicle pillar mounted retractor was tested with and without a webbing sensitive lockup feature to allow for analysis of this design feature in varying multiplanar environments. The retractors’ performance under both the linear/vertical and rollover test conditions were noticeably different and are analyzed in detail.
Effects of Microstructure Evolution on High-Temperature Mechanical Deformation of 95Sn-5Sb
Authors: Schoeller Harry , Bansal Shubhra , Knobloch Aaron , Shaddock David , Cho Junghyun
Published: August 2009

Lead-free solders have garnered much attention in recent years due to legislation banning the use of lead in electronics. As use of lead solders is phased out, there is a need for lead-free alternatives for niche applications such as high temperature environments where traditionally high lead solders are used. Electronics and sensors exposed to high-temperature environments such as those associated with deep well drilling require solder interconnects that can withstand high thermal-mechanical stresses. In an effort to characterize solder alloys for such applications, this study focuses on deformation behavior of the Sn95-Sb5 solder under high-temperature exposures (from 298°K to 473°K). As compared to conventional high-temperature Pb-based solder 90Pb–10Sn, Sn95–Sb5 exhibited very high tensile strength and modulus, as well as superior creep properties despite its lower melting temperature. Importantly, high-temperature deformation was shown to be influenced by the presence of the second phase (SnSb) distributed within the Sn-rich matrix. These second phase precipitates appeared to be dissolved into the Sn-rich phase above 453°K, which converted the solder into a single-phase alloy and resulted in a change in its deformation mechanism. Furthermore, as the service temperature is of such high homologous temperature (T > 0.5Tm), creep deformation will contribute significantly toward the life of the solder joint during thermal cycling. In order to characterize the creep behavior and to identify controlling mechanism(s), creep tests were carried out, from which the stress exponent and activation energy were determined. In this study, detailed microstructures under high-temperature are presented in conjunction with the corresponding mechanical behavior to further understand the controlling deformation mechanisms.
Sensor and Control Design Issues for Implementation of Real-Time Deposition Rate Control for Plasma Spray
Authors: Gevelber Michael , Wroblewski Donald , VanHout Michael , Ghosh Onomitra , Willoughby David , Basu Soumendra N.
Published: August 2009

Real-time control offers the potential to reduce plasma spray variations that affect yield and coating quality. Important factors for designing such controllers are discussed including sensor issues, dominant nonlinearities, and cross-coupling interactions. The performance of several alternative strategies to achieve better coating thickness control are evaluated.
A Study of AC Electrokinetic Phenomena Under DC Electroosmotic Flows
Authors: Lee Doh-Hyoung , Oh Jonghyun , Hart Robert , Farouk Bakhtier , Noh Hongseok Moses
Published: August 2009

AC electrokinetic phenomena have drawn much attention in the microfluidics and lab-on-a-chip communities since these techniques have a great potential for effective manipulation of small particles (micro- to nanoscale particles, polymer beads to biological cells and molecules) and fluids in microchannel environments. One unanswered question is how the AC electrokinetic phenomena are affected by DC electroosmotic flows that are often employed in lab-on-a-chip systems as a pumping method. This paper presents experimental and numerical studies on the interaction between AC electrokinetic phenomena and DC electroosmotic flows. The motions of polystyrene microbeads suspended in deionized water in a microchannel were studied as the main AC and DC electrokinetics parameters were varied. Numerical simulations of flow field were performed using COMSOL Multiphysics software. The forces considered in the numerical simulation include electrophoresis, DC electroosmosis, dielectrophoresis, AC electroosmosis, electrothermal effect, diffusion, Stokes drag force, and gravity. The numerical simulation results showed good agreements with experimental data. We believe that this study will contribute to the understanding of the interactions between DC and AC electrokinetic phenomena and thus enable researchers to develop powerful microdevices based on the combination of these two techniques.
Flame Synthesis of Nanostructured Transition Metal Oxides
Authors: Merchan-Merchan W. , Saveliev A. V. , Taylor Aaron
Published: August 2009

Various transition metal oxide nanostructures are synthesized using a novel probe-flame interaction method. An opposed flow flame of methane and oxygen enriched air provides a high-temperature reacting environment forming various metal oxide structures directly on the surface of pure metal probes. The unique thermal profile and chemical composition of the generated flame tends to convert almost pure bulk (99.9%) metallic materials into 1-D and 3-D structures of different chemical compositions and unique morphologies. The synthesized molybdenum, tungsten, and iron oxide structures exhibit unique morphological characteristics. The application of Mo probes results in the formation of micron size hollow and non-hollow Mo-oxide channels and elongated structures with cylindrical shapes. The use of W probes results in the synthesis of 1-D carbon-oxide nanowires, 3-D structures with rectangular shapes, and thin oxide plates with large surface areas. The formation of elongated iron-oxide nanorods is observed on iron probes. The iron nanorods’ diameters range from ten nanometers to one hundred nanometers with lengths of a few micrometers. Flame position, probe diameter, and flame exposure time tend to play an important role for material shape and selectivity.
Remotely Powered, Hermetic RF MEMS Pressure Sensor
Authors: Andarawis E. , Berkcan E. , Kashef B.
Published: August 2009

We have recently successfully developed a remote powered wireless MEMS pressure sensors for sensing pressure in remote locations without wiring or tether. The sensor is hermetically sealed, self-powered using RF energy, and has the ability to auto-compensate to remove various error sources. This constitutes a highly innovative approach to remote sensing while removing major limitations of RFID like sensors.
Noise Reduction of Three Dimensional Enclosed Sound Fields Using Nonlinear Compensation
Authors: Al-Bassyiouni M.
Published: August 2009

In this paper, the feasibility of implementing a nonlinear compensator technique in reducing noise transmitted into a three dimensional enclosure through a flexible panel is presented. A spherical wave, which is generated by a noise source located in the near field, is transmitted into a rectangular enclosure through a flexible panel. Piezoelectric patches, which are bonded symmetrically to the top and bottom surfaces of the panel, are used as actuators. The analytic model used here accounts for panel interactions with both the external and enclosed sound fields and the bonded piezoelectric patches, and this feature makes it appealing for a broad field of model-based active, passive, and hybrid noise control schemes. The nonlinear compensation scheme aims to increase the damping of the flexible panel linearly with the panel vibration amplitude and, thus, attenuates noise fields associated with structural resonance frequencies. Simulation results show that, despite the simple structure of the nonlinear compensator, high attenuation levels could be achieved. Results also show that the control input of the nonlinear compensation scheme is reduced, when compared to optimal control schemes.