bluuebunny/crossref_metadata_2025 huggingface dataset:
Mobile Robot Navigation in an Unstructured and Unknown Environment Using AI Techniques
Authors: Parasuraman S. , Ganapathy V. , Shirinzadeh Bijan
Published: November 2008

This paper shows the new approach to solve the Mobile Robot Navigation issues. The approach consists of the simple behavior design based on Situation Context of Applicability (SCA) and arbitration of the concurrent act ivies of several possible competing behaviors. This work also shows some of the reviews of the related approaches, which are attempted to resolve the robot navigational issues. In this work the design of the behavior is based on regulatory control using fuzzy logic and the coordination and behavior selection is defined by fuzzy rules, which uses the SCA for each behavior. Also, in the SCA method, the decision-making processes of a few behaviors have been developed and applied for Active Media Pioneer Robot. Fuzzy Logic Decision Mechanism (FLDM) is developed by using the Fuzzy Associate Membership process, which are used here simplifies the design of the robotic controller and reduces the number of rules to be determined. In addition, any behavior can be added or modified easily. Applying the proposed methods, experimental results are also shown for the Obstacle avoidance, Wall following and Seek-goal behaviors.
Interface in Hydroxylapatite Coated Ti6Al4V Alloys
Authors: Ergun Celalettin , Evis Zafer , Doremus Robert H.
Published: November 2008

The aim of the present study is to develop a better understanding of the interface reaction between hydroxylapatite and Ti6Al4V alloys. Hydroxylapatite coatings on Ti6Al4V, Hydroxylapatite-metallic titanium powder, hydroxylapatite-titania composites were prepared via air sintering and/or hot isostatic pressing (HIP). The reaction between components was monitored with EPMA line scanning technique, XRD, and thermal analysis. EPMA analysis on the interface between the hydroxylapatite and Ti6Al4V alloy showed interdiffusion profiles of all the hydroxylapatite and alloy elements suggesting interfacial bonding. The experiments on the composites showed no significant reaction between hydroxylapatite and metallic titanium in the vacuum environment. However, a reaction occurred between hydroxylapatite and titanium oxide, which formed CaTiO3 with a perovskite structure, Ca3(PO4)2 (tri-calcium phosphate; whitlockite) and water. Presence of air in the sintering environment promoted this reaction.
Detection of Induction Motors Faults Using Instantaneous Phase Variation
Authors: Alshandoli A. F. Saleh , Gu F. , Ball A. D.
Published: November 2008

This paper presents a new method for detecting the most common faults of squirrel cage induction motor; namely broken rotor bars, voltage imbalance and rotor misalignment. The proposed method uses Hilbert transform to determine the current instantaneous phase variation (IPV) based on only one current phase instead of the three-phase method. The number of used channels was greatly reduced to the sixth while the results are in good agreement with that obtained using the three-phase method. Experimental results show good detection capability especially at full load conditions. In addition, a comparative study has also been made between the single-phase and the three-phase method.
Path and Function Generation in Planar Mechanism Based on Gradient Determination
Authors: Sancibrian Ramon , Garcia Pablo , Viadero Fernando , Fernandez Alfonso
Published: November 2008

The basic idea of the method is to alter the link or links to bring the generated path or function close to the desired one. Planar mechanisms are modelled very easily by means of constraint equations. This approach minimizes the error between the actual path and the desired one when a large number of precision points are required. Large in this context means that only approximate synthesis is possible because the number of equations is much larger than the number of unknowns. The method proposes an objective function as a measurement of the synthesis error. The differentiated expression of the objective function is approximated by means of the Taylor’s series expansion in every increment of the input links. That means that a successive linearization of the differentiated function is used. As consequence, increments considered in the motion must be small enough to avoid errors during the optimization process. Constraints are formulated to obtain the exact gradient elements, avoiding typical problems occurring when approximate methods are used. In this way, a low computational time is necessary because the search direction is always accurate.
Injection Pressure Fluctuations Model Applied to a Multi-Dimensional Code for Diesel Engines Simulation
Authors: Ubertini Stefano
Published: November 2008

In the last decade, the development of automotive Diesel engines has been strongly influenced by the stringent regulations on pollutant emissions, which are directly related to the quality of the combustion process. The control of the combustion process requires primarily an understanding of its physics and chemistry as well as the capability to modify one or more of the interdependent process parameters in a given direction. Since many parameters have to be considered, numerical approaches are necessary to reduce time and costs, leaving to experimental analyses the final choice among few configurations. In this context, the research group of the University of Rome “Tor Vergata” has developed a multidimensional code for Diesel engines simulation based on the KIVA 3V code. This paper deals with the pressure supply fluctuations that occur in the fuel rail and in the injector on the immediate upstream side of the atomizer. It has been experimentally demonstrated that this has a considerable effect on the instantaneous mass flow and spray velocity thus affecting the spray hard-core structure and the atomisation process. Moreover, considering the oscillatory nature of the phenomenon, the effects on a given spray can change from one injection to the other (in modern multijet systems) and from one engine cycle to the next. The needed computing time and the uncertainty related to a detailed simulation of the injection system fluid dynamics would be unacceptable in a multidimensional computational code. Therefore a simplified model able to predict fuel pressure supply fluctuations on the upstream side of the injector has been developed and is described in this paper. The model is validated and calibrated by comparing numerical results with available experimental data. Some numerical results on a fuel spray injected in a vessel at constant pressure are finally presented, in order to quantify the impact of a given level of pressure fluctuations on fuel spray characteristics.
The Analysis of Earthquake Waves Based on Nonlinear Responses of RC Structures
Authors: Cao Hui , Yang Hong , Friswell Michael I. , Bai Shaoliang
Published: November 2008

The calculation of the nonlinear time-response of structures such as RC (reinforced concrete) frames to base excitation such as earthquake waves is vital to ensure the safety of structures. Of course the response changes significantly with the applied base excitation. The usual approaches to compare the different earthquake waves are based on non-localized spectra, such as response spectra and power spectra, which do not contain any time information. However these non-localized spectra often do not explain the large difference between structural responses, and are not able to reflect all of the characteristics of the earthquake waves. Local spectra, which can be easily obtained by the wavelet transform, calculate the energy distribution of the waves in the time-frequency domain. Using the wavelet transform it is easy to see the differences in the energy distribution via the local spectra of each wave, and therefore to understand the very different structural responses. Hence the time-frequency distribution of the wave energy should be taken into account during the selection of earthquake waves to apply to structural models to determine the nonlinear time response.
Multiple Frequency Analysis Methods for Blade Tip-Timing Data Analysis
Authors: Gallego Garrido Jon , Dimitriadis Grigorios
Published: November 2008

Blade Tip-Timing (BTT) is a method for the measurement of blade vibration in rotating bladed assemblies such as those found in turbomachinery. The system aims to replace strain gauge technology. However all current BTT analysis methods fail to recover the correct frequencies when two blade modes are excited simultaneously by a synchronous vibration. In this paper, five new methods that can recover simultaneous frequencies from BTT data are presented. The methods are based on the auto-regressive approach. The approached make use of data either from a single blade and single revolution or from multiple revolutions. Furthermore, some of the methods are designed to allow for the presence of measurement errors. The techniques are validated on three test cases in which simulated data was used. It is shown that most of the methods produce accurate estimates for the vibration frequency, even in the presence of significant noise levels, provided that a suitable amount of the response waveform is measured. The most consistent estimates are obtained from the methods that make use of data from multiple revolutions.
Control of Shaft Vibrations on Magnetic Bearings Using Neural Network and Sliding Mode Controller
Authors: Durali Mohammad , Salarieh Hassan
Published: November 2008

This article discusses a method for complete control of the dynamics of a rotating shaft on magnetic bearings under the effects of mass unbalance. The electromagnetic bearings used in this research are 2 four-pole bearing at the two ends of the rotor, which are actuated by differential currents. Full dynamic behavior of 3- dimensional rigid rotor and its effects on dynamic model are included. The effects of rotating mass unbalance are also included in the equations. The geometric couplings between electromagnetic forces of the coils are included as uncertainty. By using sliding mode controller and a neural network to estimate the system nonlinear-coupled equations, in a way suitable for sliding mode controller, a controller for this 4 input system is designed. Using a computer simulation of the real system, the difference between actual and estimated model and the effects of the controller are studied. For different operating modes the controller parameters are then determined. The present method allows the controller to apply necessary changes required by the time variant system equations.
On the Control of Dynamically Unstable Systems Using a Self Organizing Black Box Controller
Authors: Russell David W.
Published: November 2008

Many systems are difficult to control by conventional means because of the complexity of the very fabric of their being. Some systems perform very well under some conditions and then burst into wild, maybe even chaotic, oscillations for no apparent reason. Such systems exist in bioreactors, electro-plating and other application domains. In these cases a model may not exist that can be trusted to accurately replicate the dynamics of the real-world system. BOXES is a well known methodology that learns to perform control maneuvers for dynamic systems with only cursory a priori knowledge of the mathematics of the system model. A limiting factor in the BOXES algorithm has always been the assignment of appropriate boundaries to subdivide each state variable into regions. In addition to suggesting a method of alleviating this weakness, the paper shows that the accumulated statistical data in near neighboring states may be a powerful agent in accelerating learning, and may eventually provide a possible evolution to self-organization.
The Questionnaire Survey on Motion Sensation and the Evaluation of Habitability for a Floating Artificial Base
Authors: Maruyoshi Koichi , Saijo Osamu , Saito Yasutaka
Published: November 2008

In Japan, there are some floating structures on the sea. The structures take the form of pontoon and are called “floating artificial base”. Buildings are able to be constructed on it, so the floating artificial base is expected as utilization of ocean space. It is thought the structural design should be considered habitability for human living in a floating artificial base. We investigated an existing floating structure. In the concrete, vertical acceleration was measured and questionnaire survey was sent out for user of the structure in the purpose of grasping the motion and the habitability. The habitability was evaluated by Saito’s diagram. As a result of this, it is confirmed the existing floating structure shows elastic behavior and rigid motion simultaneously. It is obtained a lot of respondents felt the motion most sensitively at the dolphin mooring however they did not think uneasy or displeasingly from results of the questions. Visual is important factor in feeling the motion. The habitability became Work Level according to Saito’s diagram for evaluation. Therefore it is though activities on the structure are not difficulty.
A Web-Based Integrated Cutting Tool Management System
Authors: Vosniakos G. C. , Daskalopoulos A. , Straggas N.
Published: November 2008

Tool management functions cover tool system elements for assembly, operating conditions for process planning and NC programming, tuning operation execution on the machine, calculation of remaining tool life for planning tool changes, number of tools in stock, supplier terms for ordering and average utilization of tools over time for production planning. A database system was constructed catering for network access by being written as a web application. The system’s practical use is demonstrated by several typical scenarios of use.
Aeroelastic Stability of a Transport Aircraft With Wing Mounted Store Suspension: Part I — Analysis
Authors: Kayran Altan
Published: November 2008

The present study outlines the analysis work, backed by the relevant ground testing, performed for the verification of aeroelastic stability of a transport aircraft modified with the installation of an external store to the outer wing. The initial analysis work consisted of free vibration analysis and ground vibration testing of the modified aircraft for the identification of the natural frequencies and associated modes of vibration in still air. The beam-like half scale model of the aircraft was updated based on the results of the ground vibration test. External store wing connection stiffness was determined by means of vibration test performed for the identification of local store-wing structural interface modes. The dynamic model was updated again and flutter analyses were performed for different mass configurations of the aircraft. Mass configurations that are critical from flutter point of view were identified. Analysis results indicate that the flutter speeds of the aircraft with wing mounted store suspension, although lowered compared to the basic aircraft, stay above the values required by the flutter regulation MIL-A-8870C.
A Task Based Approach to Mechatronic Systems Education
Authors: Firth Kevin , Surgenor Brian , Wild Peter
Published: November 2008

This paper describes an elective course in mechatronic systems engineering that is project based and team-oriented with hands-on learning. Working in small teams, students add electronic components to a mobile robot base and write the programs required to make the robot perform a series of tasks. Although the application of mobile robots as an educational tool in a mechatronics course is becoming the norm at many universities, the task based organization of the Queen’s mechatronics course is believed to have a number of novel features. The paper will review the pedagogy of the course, including aspects of the student workload, the interplay between teams, and the task based approach to marking and organization of the laboratories.
Experimental Assessment of a Semi-Active Suspension With Magnetorheological Damper
Authors: Sireteanu Tudor , Stancioiu Danut , Stammers C. W.
Published: November 2008

Passive and semi-active vibration control strategies are investigated by experiments conducted on a SDOF system with magnetorheological damper. The frequency response functions and r.m.s. output to filtered white noise input, obtained in the passive case, are compared with those determined by using semi-active control strategies such as “balance logic” and “sky-hook”. It is shown that by appropriate settings of the control current supplied to the magnetorheological damper, the system vibration level can be appreciably lower than that of the passive system.
Design for X Approach to Optimise a Formula SAE Car
Authors: Capitani Renzo , Iacomelli Tommaso , Rosti Daniele G. , Tozzi Pierluigi
Published: November 2008

The Universita` degli Studi di Firenze joined the Formula Student competition (organised by SAE and IMechE) in 2002 competing in Class 3, the following year the first car was ready to compete in Class 1. In order to build this car, an integrated approach was adopted to obtain the best solution in every aspect. The purpose of the design was to optimise the car handling, fulfilling the Formula SAE rules. All the design phases were based on the Design for X approach, with the aim to optimise all the aspects of the Formula SAE project, like performance, design and cost. A Design for Manufacturing approach was added to the FEA to design all the components, like uprights and wheel spindles, in order to simplify the CNC machining. The suspensions layout was defined using a recursive method based on the Multibody Simulation and the components design. Some experimentations were conducted to verify the simulations. The experimental data were used to start the redesign, to improve the performance of the new car that will compete in the 2004 events.
Control Methods for Energy-Efficient Pneumatic Servos Employing Asymmetric Cylinders
Authors: Yang Aaimin , Pu Junsheng , Wong C. B. , Moore Philip
Published: November 2008

Pneumatic drives or actuators are most widely used in industry, in comparison to their hydraulic and electrical counterparts. However, they are low in energy efficiency and have typically been used in performing simple actuation tasks. This paper investigates the use of pneumatic actuation for point-to-point positioning applications in the context of employing asymmetric cylinders. The focus of this research is to study appropriate control methods, aiming for improved energy efficiency in the use of pneumatic servo positioning system. Relevant mathematical models and stability analysis will be presented in this paper, with results from simulation and experimental verification. In particular, a hydraulic circuit (rapid motion circuit) is adopted in the case for pneumatic actuation. For point-to-point positioning application, in the forward moving phase, the inlet and outlet chambers will be connected via by-pass valve allowing exhausted compress air to be reused. In comparison with the conventional way in controlling the motion of an asymmetric pneumatic cylinder, a portion of the compressed can be re-used leading to an enhancement in energy-efficiency. The results show that some 15% saving in energy use can be acquired with improved stability while the settling time of the positioning system is maintained. Relevant design and applications issues will be outlined and discussed in this paper as well.
Comparing Fatigue Life Reliability of a Composite Leaf Spring With a Steel Leaf Spring
Authors: Shamsaei Nima , Rezaei Davood
Published: November 2008

In the present study, the fatigue behavior of an optimized composite leaf spring and a four leaf steel spring have been analyzed and compared. In a paper, issued by co-author, a four leaf steel spring was replaced by a composite leaf spring. The geometry of composite spring has been optimized to obtain the minimum weight under stress and displacement constraints due to the given static external forces. In this study, both above-mentioned leaf springs have been fatigue analyzed. The vehicle movement has been simulated on four different standard roads in ADAMS software and the spring supports reactions have been derived. Stress time spectrum micro-blocks in critical element of leaf springs have been obtained using ANSYS software and considering ADAMS results as loading. The stress time spectrum macro-blocks for long time from the stress time spectrum in micro-blocks have been created according to statistical and random vibration principles. After finding stress probability density functions for composite leaf spring and equivalent steel leaf spring, fatigue reliabilities have been extracted for both of them. Results showed that the fatigue life reliability in composite leaf spring is much better than steel spring.
Abrasive Wear of Piston Grooves of Highly Loaded Diesel Engines
Authors: Nayak Nagaraj , Lakshminarayanan P. A. , Gajendra Babu M. K. , Dani A. D.
Published: November 2008

The rate of wear of piston grooves on the piston is mainly a function of the peak cylinder pressure, hardness, surface roughness, depth of penetration and the number of hard particles produced by combustion or entering past the air filter. The problem of wear becomes severe as the blowby past the rings and oil consumption of the engine increases in diesel engines. In this paper, an attempt is made to estimate the wear of piston grooves quantitatively. The wear rate is correlated with the product of gaseous load, amount of hard particles past the piston lands, radius of abrasive particles, and inversely with hardness of the groove surface. Under abnormal conditions, the shear strain due to friction exceeds the plasticity limit of the material and superficial delamination occurs at the groove surface. The model was validated on a large bore engine running on heavy fuel at 22-bar bmep and the abrasive wear predicted by other earlier models are discussed [7].
Modeling of Pressure Pulsations for LDPE Reciprocating Compressors and Interaction With Mechanical System
Authors: Giacomelli Enzo , Passeri Marco , Giusti Stefano , Zagli Fabrizio , Generosi Stefano
Published: November 2008

The combination of booster-primary and hyper compressors reaches very high pressures in Low Density Polyethylene Plants. Pressure and flow pulsations due to the unsteady flow generate an acoustic energy that interacts with the mechanical system of the plant, causing mechanical vibrations. Pressure pulsation and vibration control on relatively high pressure piping is necessary to prevent failures caused by cyclic stresses due to both internal pressure fluctuations and vibrations generated by the compressor. To increase the compressor performance, safety and reliability designers require advanced methods of simulation to evaluate piping and compressor behavior during the initial stage of the project. The paper will investigate the modeling of the pulsation with the influence of fluid-dynamic aspect related to the gas and the relevant system interaction.
Numerical Evaluation of a Band-Limited Green’s Function Using the Finite Element Method for Acoustic Emission Analysis
Authors: Naber Ramez-Robert , Bahai Hamid , Jones Barry E.
Published: November 2008

The ability to model transient wave propagation in solids and determine the Green’s function plays a major role in improving the reliability of quantitative source characterization of acoustic emission. In this work, the finite element method is employed to determine a numerical solution of the Green’s function of an isotropic plate due to a point source applied normally to the surface. The advantage of using the finite element method is that it can be extended to model realistic geometries that cannot be treated analytically. The numerical results presented here are based on a two-dimensional axisymmetric transient finite element analysis. A limited bandwidth approximation of a delta function is used (Hanning function) for modeling the source. Hence the solution is called the band-limited Green’s function. The exact analytical solutions of the Green’s function of an isotropic infinite plate are used to validate the numerical solutions. Further analysis is carried out to investigate the effects of varying the spatial resolution of the finite element model on the accuracy of the solutions. Finally, it is demonstrated how the results of the band-limited Green’s function can be used to accurately convolve the response of an arbitrary source function.
Analysis of the Fixation Quality of Total Hip Replacements Using a Vibrational Technique
Authors: Jaecques Siegfried V. N. , Pastrav Cezar , Van der Perre Georges
Published: November 2008

Vibration analysis can be used as a more sensitive alternative to conventional techniques for the detection of loosening of total hip replacement (THR) components. The vibration modes of the human femur and of selected THR prosthetic stems were studied by experimental modal analysis using a CADA-X system and by finite element simulation using MARC/Mentat software. Two hypotheses were formulated: (1) the differences between the vibrational behavior of an intact femur and of the system formed by a femur and an implanted prosthesis will increase with increasing complexity of the mode shapes of the system; (2) when a prosthesis is implanted in a femur, the vibration modes of the prosthesis will be more affected by this interaction than the modes of the femur. After confirming these hypotheses, a method for per-operative assessment of the fixation quality of a THR stem was derived, based on the frequency shifts of the vibration modes of the system.
Improvement Geometrical Precision in Sheet Incremental Forming Processes
Authors: Ambrogio G. , De Napoli L. , Filice L. , Muzzupappa M.
Published: November 2008

Incremental forming is nowadays increasing its presence in industry as a new but interesting process, especially for production of small batches or unique components. Anyway, relevant efforts have to be spent in order to reduce the typical incremental forming processes drawbacks that risk to belittle the high advantages in terms of costs and simplicity. In fact, the process duration, usually equal to several minutes even if the operations are carried out on high speed numerical controlled units, and a certain tendency to produce no precise parts, can reduce industrial interest about incremental forming. A possible strategy to reduce the latter item is the design of modified trajectories able to take into account both the springback effects and the stiffness reduction due to the particular clamping equipment. In this paper the above introduced strategy is pursued integrating an on-line measuring system, based on a digital inspector, and a CNC open program. The actual geometry is acquired in some remarkable points and a compensation routine modifies the coordinates of the future punch path. The modification policy has been developed by using an effective FE code. An experimental verification shows the good potentiality of the suggested methodology.
Effect of Flow Maldistribution and Viscosity Variations on Transient Response of Plate Heat Exchangers: A Comparison With Uniform Flow and Constant Viscosity Model
Authors: Shokouhmand H. , Khareghani N.
Published: November 2008

In this paper, transient response of plate heat exchangers under flow maldistribution and viscosity variations is discussed. This transient response is compared with the response achieved from uniform flow and constant viscosity through the exchanger. Flow maldistribution (unequal flow in channels) is calculated for U and Z types of plate heat exchangers. This flow maldistribution along with viscosity variations, during the growth of the temperature profile in each channel, affect the convective heat transfer coefficient in the transient period of heat transfer, and make it to be different from that of the other channels. These conditions make the transient response of a plate heat exchanger to have some deviations from the uniform flow and constant viscosity model response, which is discussed in this paper. The governing equations of heat transfer are solved using finite difference methods. Frequency response as well as step response of the heat exchanger is implemented as a time dependent initial conditions.
Influence of Mechanical Properties of Adhesives on Stress Distributions in Lap Joints
Authors: He Xiaocong , Oyadiji S. Olutunde
Published: November 2008

This paper deals with stress analysis of a single lap-jointed cantilevered beam using the three dimensional linear elastic finite element analysis (FEA) technique. Numerical examples are provided to show the influence on the stresses of the single lap-jointed cantilevered beams using adhesives of different characteristics which encompass the entire spectrum of viscoelastic behaviour. The results indicate that the stress distributions of a single-lap jointed cantilevered beam are strongly affected by both Young’s modulus and Poisson’s ratios. The maximum stress ratio was used to determine maximum values of Young’s Modulus required in order that the static stresses of an adhesively bonded cantilevered beam will not be more than given value of that of the equivalent homogeneous structure, that is a geometrically similar beam but without a joint. The analysis results also show that by choosing suitable adhesives, the maximum stresses can be reduced and the strength can be improved.
Heat Affected Zone Induced by Laser Forming
Authors: Casamichele L. , Gisario A. , Tagliaferri V.
Published: November 2008

Laser forming induces mechanical and structural modifications around the Laser Scanning Path. Various conventional methods are currently available to estimate properties of materials like X-ray and neutron diffraction, strain/curvature measurement, hole drilling, layer removal, chemical etching, etc. but their use is severely restricted due to measurement accuracy, applicability to different materials and geometrical configurations. An application of an experimental method to estimate mechanical properties associated with laser forming of metallic sheets is proposed. This method is based on an instrumented indentation technique which offers a more flexible tool to measure mechanical properties of Heat Affected Zone. The main advantage of this technique consists of testing complex geometric forms with a cheap system able to be used for on-line implementation. The experimental validation of the method was performed calibrating the procedure by using several indentation tests in standard condition. A full map of mechanical properties was subsequently traced employing systematic investigations focused on specimens zone closer to the laser heated scanning path.
The Response of Fuel Injector Sprays to Acoustic Forcing
Authors: Greenhalgh Douglas A. , Jermy Mark C. , Doherty William G. , Hussain Mazhur
Published: November 2008

Combustion instabilities have impeded the development of lean burn low NOx gas turbine combustors. Acoustic waves in the combustor interact with the fuel/air mixing process to modulate the air-fuel ratio (AFR). The fluctuating AFR causes the heat release rate to fluctuate. If the Rayleigh criterion is obeyed the acoustic wave is amplified. The acoustic intensity may reduce the lifetime of the mechanical parts, due to vibration and increased heat transfer, or cause the operating noise levels to exceed regulatory limits. The fuel injector has an important role in the interaction of the acoustic field and the AFR. In rig tests, injectors of slightly different design can yield different noise levels in the same combustor. We have applied planer LIF and Mie imaging and Laser Sheet Dropsizing (LSD) to study the interaction of the fuel injector spray with an imposed acoustic disturbance in low cost non-combusting tests. The injector is run at pressures up to 7 bar in the Cranfield optical sprays rig. By careful scaling of the injector operating conditions the spray structure found in the rig can be made representative of that in the engine. An acoustic perturbation is imposed on the airflow. The spray field is probed with a dual LIF/Mie laser sheet imaging system. Laser Induced Fluorescence (LIF) images are calibrated to yield maps of AFR. The LIF and Mie images are ratioed and calibrated to produce maps of the Sauter Mean Diameter. Images are taken at several phases in the acoustic perturbation cycle. From these the oscillatory response of the spray to the acoustic perturbation is extracted. A transfer function describing the strength and phase of the response of AFR and SMD to the acoustic perturbation is extracted. Both AFR and SMD exhibit fluctuations which are coherent with the imposed acoustic oscillation. Comparison of the transfer functions to the results of combustion tests suggest that the spray measurements can predict which injectors are likely to encourage strong instability in the combustor.
Effect of Thickness on Deformation of Plates Subjected to Transient High Pressures
Authors: Akus Yener , Yildirim R. Orhan
Published: November 2008

Blast loading can induce a substantial amount of damage in structural elements such as, beams and plates, the shape and extent of which is quite difficult to predict. This work investigates the changes in the deformation of a square plate that undergoes a constant weight explosive detonation with changing plate thickness. As a first step, free field explosion is investigated. After the calculation of the pressures and forces acting on the plate, and the positive phase duration of the pulse, the non-dimensional impulse values are found. Plate tearing is predicted by using these non-dimensional impulse values. The same plate is modelled and solved for the numerical prediction of the midpoint deflection. Using this procedure, the effect of the plate thickness is investigated for the deformation of plates. The results of the theoretical and numerical solutions are then compared with the experimental findings.
Numerical Model of a Single Phase, Regenerative Fuel Cell
Authors: Garrard A. , Beck S. , Styring P.
Published: November 2008

A code for numerical simulating the fluid flow and electrochemistry of a single phase regenerative fuel cell is presented. Due to the potentially tiny geometries and complex multi-physical interactions, modeling presents a chance to obtain detailed quantitative data and much needed understanding about physics within the reactor. The Regenesys XL200 fuel cell has the industrial application of large scale energy storage and is the focus of this work. A two dimensional, binary reduction reaction system has been created to represent the XL200 and test the code. Commercially available CFD software Fluent was used to calculate the flow field and subroutines were used to create the dynamic calculation of electrochemistry at the reaction surface. The effect of changing the total applied potential across the domain on the potential and species concentration distribution within the domain was investigated. Results show that the code is producing qualitatively feasible results that represent the tight multi-physical coupling. The code is currently not validated against physical experimental results and this will be the focus of future work.
Technical Issues Governing the Selection and Development of Dielectric Coolants for Fuel Cell Systems
Authors: Momoda Leslie A. , Skeith Sky L. , Lee James H.
Published: November 2008

The selection of a heat transfer fluid that meets all of the requirements for fuel cell operation is daunting. There are multiple competing fluid properties needed for optimal performance: high dielectric strength, low ionic and electronic conductivity, high heat capacity, high thermal conductivity, low viscosity at low temperatures, high flash points, low toxicity and no reactivity with contacting materials. In this paper we report the results of our evaluation of numerous basic and commercial heat transfer fluids with respect to their prospective fuel cell performance. We have also examined some of the fundamental physical and chemical properties of fluids to provide guidance on engineering a fluid based temperature regulation system for a fuel cell stack.
Fuel Cell Performance Improvements Using Cell-to-Cell Flow Distribution Control
Authors: Hensel J. Peter , Gemmen Randall S. , Hetzer Brian J. , Thornton Jimmy D. , Vipperman Jeffrey S. , Clark William W. , Ayhan A. Fatih
Published: November 2008

Balanced flow distribution to each cell in a fuel cell stack plays a significant role in the stack being able to operate at maximum capability and efficiency. This paper discusses the performance improvements in proton exchange membrane fuel cell stacks that can be obtained by using cell-to-cell flow distribution control. In a specially instrumented four-cell stack that employs needle valves to externally control the air and fuel flows to each cell, fuel to a single cell was reduced. The V-I curves collected under these conditions (unbalanced) are compared to curves collected when the fuel flow to each cell was equal (balanced). Reducing the fuel flow to a single cell by 30% decreased the V-I curve cutoff load by 8.5% — demonstrating the negative effect that unbalanced fuel flows can have on stack performance. Typical fuel cell stacks have no dynamic means to keep flows in the stack balanced between the cells, but this work indicates that flow balancing among cells can extend the V-I curve for a fuel cell to higher current values, allowing fuel cell stacks to operate reliably at higher loading and fuel utilizations. Plans to use novel, custom-built micro-valves to dynamically balance flow to individual cells in a fuel cell stack are being pursued as a result of this work, and the status of this development effort is provided.
Numerical Modeling of a Disk Shape Planar SOFC
Authors: Dang Zheng , Iwai Hiroshi , Suzuki Kenjiro
Published: November 2008

In this study, numerical modeling of air and fuel flows, electrochemical processes, heat and mass transfer and electric potential fields and related electric current has been attempted for a disk shape planar solid oxide fuel cell (SOFC). This is the extension of the previous similar works on a tubular type solid oxide fuel cell, Nishino et al. (2003) and Li and Suzuki (2004). Numerical model to be established can be used as an effective means to simulate the phenomena in the cell. Such information can be used in the optimum design and thermal management of SOFC.
A Highly Efficient Combined Cycle Fossil and Biomass Fuel Cell Power Generation and Hydrogen Production Plant With Zero CO2 Emission
Authors: Steinberg Meyer
Published: November 2008

An advanced combined cycle for fossil and biomass fuel power generation and hydrogen production is described. An electric arc hydrogen plasma black reactor (HPBR) decomposes the carbonaceous fuel (natural gas, oil, coal and biomass) to elemental carbon and hydrogen. When coal and biomass feedstocks are used, the contained oxygen converts to carbon monoxide. Any ash and sulfur present are separated and removed. The elemental carbon is fed to a molten carbonate direct carbon fuel cell (DCFC) to produce electrical power, part of which is fed back to power the hydrogen plasma. The hydrogen produced is used in a solid oxide fuel (SOFC) cell for power generation and the remaining high temperature energy in a back-end steam Rankine cycle (SRC) for additional power. Any CO formed is converted to hydrogen using a water gas shift reactor. The plasma reactor is 60% process efficient, the direct carbon fuel cell is up to 90% thermally efficient, the solid oxide fuel cell is 56% efficient and the steam Rankine cycle is 38% efficient. Depending on the feedstock, the combined cycles have efficiencies ranging from over 70% to exceeding 80% based on the higher heating value of the feedstock and are thus twice as high as conventional plants. The CO2 emissions are proportionately reduced. Since the CO2 from the direct carbon fuel cell and the water gas shift is highly concentrated, the CO2 can be sequestered to reduce emission to zero with much less energy loss than required by conventional plants. Alternatively, the combined cycle plants can produce hydrogen for the FreedomCAR program in combination with electrical power production at total thermal efficiencies greater than obtained with fossil fuel reforming and gasification plants producing hydrogen alone.
New Conceptual Gas Distributor With Mass Transfer Enhancing Function in Polymer Electrolyte Fuel Cells
Authors: Li P. W. , Chen S. P. , Chyu M. K.
Published: November 2008

A new conceptual structure of the gas distributors in polymer electrolyte fuel cells (PEFC) or proton exchange membrane (PEM) fuel cells is developed in this work. Basically, instead of partitioned channels and non-interrupted walls, the proposed new gas distributors make use of discretized elements as the current collector in the flow fields, which can help to enhance the mass transfer in the gas flow fields while maintaining the function of transmitting current out of the fuel cell. Experimental operation without external humidification of the reactant gases for single PEM fuel cells and cell stacks using conventional and the currently presented gas distributors were conducted for comparison and verification. It was found that the maximum operational cell current, beyond which there is a sharp drop of the cell voltage, could be significantly improved when using the currently proposed gas distributors and the same membrane-electrode-assembly (MEA) sheets. Correspondingly, the output electrical power can have at least 11 percent increment for the operation with free-convective airflow and around 50 percent increment for the operation with forced convective airflow.
Role of Defects on Mechanical Response of Nafion® Membranes for Fuel Cell Applications
Authors: Mian Ahsan , Newaz Golam , Vendra Lakshmi , Wu Xin , Liu Sheng
Published: November 2008

Nafion® manufactured by Dupont is a widely used membrane material for polymer electrolyte membrane (PEM) fuel cell. Such membranes are made thin and also have to be hydrated during operation to increase proton conductivity of the cell. Since the membranes are made thin, and do not posses high mechanical properties, they are prone to any handling induced damage. In this paper, we have made an initial attempt to demonstrate the capability of thermal wave imaging nondestructive evaluation (NDE) technique in detecting various types of damage entities such as scratches, folding, and pin pricks in the membrane material. In addition, the effect of hydration and handling induced damage on the tensile behavior of Nafion® membrane is studied. It is observed that the damaged and as-received hydrated samples exhibit lower modulus and yield strength than the corresponding dry counterparts.
A Mild Hybrid Engine-Solid Oxide Fuel Cell Vehicle Configuration Using a Continuously Variable Power-Split Transmission
Authors: Gomez Miguel M. , Smith James E.
Published: November 2008

This paper focuses on a mild hybrid vehicle configuration design using a continuously variable power-split transmission (CVPST) with a solid oxide fuel cell (SOFC) as an auxiliary power unit (APU), which can provide electrical energy to an electric motor, recharge batteries and when necessary, supply energy to the vehicle’s electrical features. The advantage of this configuration design is that the IC (internal combustion) engine will use all its power capacity to only propel the vehicle and will not need to divert power for extra devices. When more power is needed, as in hills, extra load or highway acceleration pass, the electric motor can assist with an amount of power. Another advantage and interesting feature from the SOFC is that it is compatible with conventional petroleum fuels with a simple partial oxidation reforming process. It has less stringent requirements for reformate by using carbon monoxide (CO) directly as a fuel and has less sensitivity to contaminants. Mild hybrid vehicles are the probable primary candidates for near term mass market due to the low incremental costs, which is accomplished by minimizing the electrical machines and battery size. Yet, it is also considered that it improves fuel consumption and efficiency as a result of using a smaller IC engine. The mild hybrid may have the potential to provide the right cost and benefit balance in the short term, until the development of full hybrids and fuel cell vehicles can compete with standard IC engine vehicles in the market. Continuously variable transmissions (CVTs) have an infinitely variable input-output speed relationship, which allows the IC engine to operate more time in the optimum range. Continuously variable power-split transmissions were developed in order to reduce the fraction of power passing through the variator and consequently, expand its power capacity. In this paper a CVPST is used in a hybrid electric vehicle (HEV) application. This type of transmission has a planetary gear train (PGT), which can provide a branch for an electric motor that can be used in the mild hybrid electric fuel cell vehicle configuration proposed in this paper. This electric motor can either be powered by a SOFC and/or a battery.
Plasma-Catalytical Partial Oxidation of Various Carbonaceous Feeds Into Synthesis Gas
Authors: Czernichowski Albin , Czernichowski Piotr , Wesolowska Krystyna
Published: November 2008

We propose a sulfur-resistant process in which a gaseous or liquid carbonaceous matter is converted into the Synthesis Gas in a presence of high-voltage cold-plasma (“GlidArc”) that assists the exothermal Partial Oxidation. This process is performed in our 0.6 to 2-Liter reactors using atmospheric air. The reactants are mixed at the reactor entry without use of vaporizers or nozzles. Our process is initiated in the discharges’ zone in presence of active electrons, ions, and radicals generated directly in the entering mixture. Then the partially reacted steam enters a post-plasma zone of the same reactor. This zone is filled with a metallic and/or mineral material. We found several solids that present some catalytic properties enhanced by high temperatures and active species generated in the cold plasma. Atmospheric pressure reforming is presently studied. This paper recalls our earlier tests with natural gas, propane, cyclohexane, heptane, toluene, various gasolines, diesel oils (including logistic ones), and the Rapeseed oil. New experiments are then presented on the reforming of heavy naphtha and an aviation fuel. The synthesis gas issued from the last one has been successfully converted into electric energy in an on-line inserted Solid Oxide fuel Cell. All tested feeds are totally reformed into Hydrogen, Carbon Monoxide and some Methane. Other components are Steam and Carbon Dioxide. All these products are diluted in Nitrogen coming from the air. No soot, coke or tars are produced even from highly aromatic liquids. The output Synthesis Gas power issued as the result of our tests can presently reach 11 kW (accounted as the Lower Heating Value of produced H2 + CO stream). Only 0.05–0.2 kW of electric power is necessary to drive such cold-plasma-assisted reformer. Up to 45 vol.% of H2 + CO mixture (dry basis) is produced in long runs. We obtain a better than 70% thermal efficiency of the process (defined as the output combustion enthalpy of H2 + CO at 25°C concerning the Lower Heating Value of the feed). However a large part of remaining percentage of the energy leaving the reformer (the sensitive heat and CH4 at 2–3 vol.% level) can be further reused in the high-temperature Fuel Cells.