bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Elliptical Nozzle Holes on Ignition and Combustion of Transient Natural Gas Jets
Authors: Wager David , Wallace James S.
Published: August 2009

Experiments were conducted to compare the mixing and combustion properties of natural gas jets issuing from elliptical and round nozzle holes within an optically accessible combustion bomb. High speed images of combustion events were captured and analyzed along with cylinder pressure and heat release data. Hydrocarbon measurements of the combustion products were used to calculate combustion efficiencies. The elliptical nozzle holes were found to produce a more evenly distributed heat release profile, with a smoother transition from premixed to diffusion burning. The elliptical nozzle jets also produced far more luminous flames. Ignition delay and combustion efficiency were not found to vary significantly with nozzle design. The use of elliptical nozzles as a method of mixing enhancement for gaseous engine fuels remains potentially viable, although further work is necessary to fully quantify the performance and emissions impacts.
A Numerical Investigation of Transient Flow and Cavitation Within Minisac and VCO Diesel Injector Nozzles
Authors: Lee Won Geun , Reitz Rolf D.
Published: August 2009

Cavitating flow within diesel injector passages has been investigated numerically using the Homogeneous Equilibrium Model (HEM), which uses the barotropic assumption and the variable speed of sound of the mixture. To apply the HEM, the KIVA-3V code was modified to implement a generalized equation of state, and injector needle movement is simulated by the Arbitrary Lagrangian-Eulerian (ALE) approach and the snapper algorithm. It is demonstrated that the model can predict the effect of nozzle passage geometry on the flow structure and cavitation. The model is able to reproduce the transient fuel injection rate as a function of the needle lift profile. Special interest is focused on the transient behavior during the nozzle closing period, which shows that the fast decrease in flow rate can increase the cavitation in the nozzle passage. The effects of the pressure difference and environment pressure on cavitation augmentation at the end of the injection were also investigated. Flow characteristics due to different shapes of the nozzle flow passage in axisymmetric single hole nozzles and multi hole nozzle configurations (mini-sac and VCO eight-hole nozzles) were compared with emphasis on the end of injection period.
Nonlinear Dynamics in Cyclic Variations of Combustion Phasing in an HCCI Engine
Authors: Ghazimirsaied Ahmad , Shahbakhti Mahdi , Koch Charles Robert
Published: August 2009

Temporal dynamics of cyclic variation in a Homogeneous Charge Compression Ignition (HCCI) engine near misfire is analyzed using chaotic theory methods. The analysis of variation of consecutive cycles of CA50 (crank angle of 50% fuel burnt) for an n-heptane fueled engine is performed for a test point near the misfire condition. The return map of the time series of CA50 cycle values reveals the deterministic and random portions of dynamics near misfire occurring in an HCCI engine. A symbol-statistic approach is also used to find the occurrence of possible probabilities of the data points under the same operating conditions. These techniques are then used to predict CA50 one cycle-ahead. Simulated data points in phase space have similar dynamical structure to the experimental measurements.
Spark Plug Modifications for Improving Ion Sensing Capabilities in a Homogeneous Charge Compression Ignition (HCCI) Engine
Authors: Bogin Gregory , Mack J. Hunter , Dibble Robert W.
Published: August 2009

Ion sensors have shown great potential as a low-cost diagnostic tool for detecting the start of combustion (SOC) in Homogeneous Charge Compression Ignition (HCCI) engines. Ion detection in an HCCI engine depends on both the combustion event as well as the type of probe used. Optimization of the shape and size of spark plug electrodes is experimentally examined in order to improve the overall quality of the ion signal for a wide range of engine operating conditions. Idling conditions for an HCCI engine are typically lean with equivalence ratios φ ≤ 0.25, which leads to reduced peak combustion temperatures. The ion signal in HCCI engines decreases exponentially with reduced combustion temperatures. Experiments are conducted on a 1.9L 4-cylinder VW TDI diesel engine (converted to run in HCCI mode) using four modified spark plugs to understand ion detection over various equivalence ratios and operating conditions. Increasing the surface area of the positive center electrode (using a positive bias voltage) provided a significant improvement in the peak ion signal.
Characterization of Partially Premixed Combustion With Ethanol: EGR Sweeps, Low and Maximum Loads
Authors: Manente Vittorio , Johansson Bengt , Tunestal Pert
Published: August 2009

EGR sweeps were performed on Ethanol Partially Premixed Combustion, PPC, to show different emission and efficiency trends as compared to Diesel PPC. The sweeps showed that increasing the EGR rate the efficiency does not diminish, HC trace is flat and CO is low even with 45% of EGR. NOx exponentially decreases by increasing EGR while soot levels are nearly zero throughout the sweep. The EGR sweeps underlined that at high EGR levels, the pressure rise rate is a concern. To overcome this problem and keep high efficiency and low emissions a sweep in timing of the pilot injection and pilot-main ratio was done at ∼16.5 bar gross IMEP. It was found that with a pilot-main ratio of 50–50 and by placing the pilot at −60 with 42% of EGR, NOx and soot are below EURO VI levels, the indicated efficiency is 47% and the maximum pressure rise rate is below 10 bar/CAD. Low load conditions were examined as well. It was found that by placing the SOI at −35 TDC the efficiency is maximized on the other hand when the injection is at −25 the emissions are minimized and the efficiency is only 1.64% lower than its optimum value. The idle test also showed that a certain amount of EGR is needed in order to minimize the pressure rise rate.
Effect of Swirl Ratio and Injection Pressure on Autoignition, Combustion and Emissions in a High Speed Direct Injection Diesel Engine Fuelled With Biodiesel (B-20)
Authors: Nagaraju Vinay , Dahodwala Mufaddel , Acharya Kaushik , Bryzik Walter , Henein Naeim A.
Published: August 2009

Biodiesel has different physical and chemical properties than ultra low sulfur diesel fuel (ULSD). The low volatility of biodiesel is expected to affect the physical processes, mainly fuel evaporation and combustible mixture formation. The higher cetane number of biodiesel is expected to affect the rates of the chemical reactions. The combination of these two fuel properties has an impact on the auto ignition process, subsequently combustion and engine out emissions. Applying different swirl ratios and injection pressures affect both the physical and chemical processes. The focus of this paper is to investigate the effect of varying the swirl ratio and injection pressure in a single-cylinder research diesel engine using a blend of biodiesel and ULSD fuel. The engine is a High Speed Direct Injection (HSDI) equipped with a common rail injection system, EGR system and a swirl control mechanism. The engine is operated under simulated turbocharged conditions with 3 bar Indicated Mean Effective Pressure (IMEP) at 1500 rpm, using 100% ULSD and a blend of 20% biodiesel and 80% ULSD fuel. The biodiesel is developed from soy bean oil. A detailed analysis of the apparent rate of heat release (ARHR) is made to determine the role of the biodiesel component of B-20 in the combustible mixture formation, autoignition process, premixed, mixing controlled and diffusion controlled combustion fractions. The results explain the factors that cause an increase or a drop in NOx emissions reported in the literature when using biodiesel.
Rotorcraft Trim Analysis Using a General-Purpose Multibody Code
Authors: Federico L. , Russo A.
Published: August 2009

Rotorcraft dynamics represents a major analytical challenge to aeronautical industry and research centres. Complexities arising from large rigid motions, body elasticity, aerodynamic loads and control systems have to be taken into account in order to ensure the accuracy of a comprehensive analysis. Architected for the nonlinearities associated with large motion in three-dimensional space, the ADAMS general-purpose multibody code allows to automatically formulate and integrate the equations of motion for a wide range of mechanisms, including rotary wing systems (once provided with an aerodynamic force field description). However, the ADAMS simulation system lacks the capability to calculate periodic motions, as required in the helicopter trim analysis and stability evaluation. The prediction of the trimmed periodic motions of the rotor system implies the numerical solution of differential-algebraic boundary value problem. In this work we present a new approach to perform this task inside the ADAMS numerical environment. Thia approach is based on the perturbation of the minimal set of Ordinary Differential Equations (ODEs), being equivalent to the original system of Differential Algebraic Equations (DAEs) which defines the rotorcraft equation of motion. The transformation of DAEs to ODEs is based on the linearization of the local constraint manifold defined by the algebraic constraint equations, as suggested by Maggi in his work [1–3]. The proposed method is quite general and can be used to drive the ADAMS integration scheme within the periodic motion analysis of mechanical systems. The algotithm is adopted to simulate the wind tunnel trim test of a ECD BO105 machscaled model (EU HeliNOVI project [4]). Comparisons between numerical and experimental results are provided.
Design and Manufacture of Spiral Bevel Gears With Reduced Transmission Errors
Authors: Simon V.
Published: August 2009

A method for the determination of the optimal polynomial functions for the conduction of machine-tool setting variations in pinion teeth finishing in order to reduce the transmission errors in spiral bevel gears is presented. Polynomial functions of order up to five are applied to conduct the variation of the cradle radial setting and of the cutting ratio in the process for pinion teeth generation. Two cases were investigated: in the first case the coefficients of the polynomial functions are constant throughout the whole generation process of one pinion tooth-surface, in the second case the coefficients are different for the generation of the pinion tooth-surface on the two sides of the initial contact point. The obtained results have shown that by the use of two different fifth-order polynomial functions for the variation of the cradle radial setting for the generation of the pinion tooth-surface on the two sides of the initial contact point, the maximum transmission error can be reduced by 81%. By the use of the optimal modified roll, this reduction is 61%. The obtained results have also shown that by the optimal variation of the cradle radial setting, the influence of misalignments inherent in the spiral bevel gear pair and of the transmitted torque on the increase of transmission errors can be considerably reduced.
Detection of Fretting Damage in a Titanium Alloy by the Magnetic Sensing of Thermoelectric Currents
Authors: Carreon Hector , Ruiz Alberto
Published: August 2009

The experimental technique used in this investigation is based on magnetic sensing of local thermoelectric currents produced by material imperfections when a temperature gradient is established in the material. These thermoelectric currents generate flux magnetic densities that are detected by a highly sensitive magnetometer. According to our preliminary results, the magnetic flux density measurements was found to be rather sensitive to changes in near-surface layers produced by the fretting damage in Ti-6Al-4V alloy specimens with the exception of the intrinsic material background magnetic signal that affected deeply the detectability of subtle material variations in noncontacting thermoelectric measurements. Hopefully, these results can help identify a non-destructive test method that can detect the level of fretting damage in metals, that is difficult to characterize by other well known NDE methods.
The Effect of Longitudinal Center of Gravity Position on the Sway Stability of a Small Cargo Trailer
Authors: Gilbert Michael G. , Godrick Daniel A. , Klein Richard H.
Published: August 2009

Small and mid-sized cargo trailers are often used to transport goods by people with limited experience in loading trailers and driving vehicles with trailers attached. This paper examines the effect of front to rear load position on the stability of a trailer by measuring its dynamic response to a variety of steer inputs at several different highway speeds. Additionally, tests with varying steers and speeds were performed with a simulated suspension malfunction to study the trailer’s dynamic response to this condition. Trailer sway has been a well-documented trailer characteristic for decades. However there are no special driver’s licensing or mandatory training requirements for even large trailers and campers. The trailer chosen for this test was a lightweight double axle cargo trailer commonly rented by people with limited to no towing experience. This consumer is likely to be unfamiliar with the best practices of trailer loading. This consumer is also likely a non-professional driver with little to no towing experience in the event of encountering unexpected trailer sway. Therefore it was the goal of the authors to determine how the stability of this type of trailer varies with different front to rear loading conditions and speeds to see if it is safe to operate on the highways by novice drivers. Trailer sway stability was determined by measuring the trailer sway (articulation) response during repeated, pulse steer tests. The trailer sway damping characteristics were measured, as a “damping ratio”, for six different hitch loads that corresponded to six different longitudinal loading conditions. These conditions, expressed as % load forward of the trailer centerline / % load aft of the trailer centerline were: 65/35, 60/40, 55/45, 50/50, 45/55, and 40/60. These loading conditions were tested per SAE J2664 [1] protocol. The resulting trailer sway characteristics for each loading condition then were compared to published trailer sway stability criteria [2, 3] to determine the suitability of this particular tow vehicle-trailer combination for use by the public in a rental market. The impact of a suspension malfunction on the trailer stability was also studied. This consisted of a detachment of one rear leaf spring hanger.
On a New Turbulent Energy Equation With Variable Thermal Conductivity
Authors: Gori Fabio , Boghi Andrea
Published: August 2009

The present work investigates the energy equation of a general fluid, Newtonian or non-Newtonian, with variable thermal conductivity in turbulent flow. The usual energy equation, without the dissipation terms, is taken into account with the fluctuating terms in the temperature as well as in the thermal conductivity. The energy equation is written for the average temperature, for the fluctuating temperature one as well as for the square of the fluctuating temperature. Besides the usual Reynolds stresses, a new term appears, which is the product of the fluctuation of the thermal conductivity and the gradient of the temperature fluctuation. This new term is interpreted and introduced in the energy equation where the variable is the square of the temperature fluctuation where new terms appear. A possible physical interpretation is given to the different terms. Assuming a polynomial relation between thermal conductivity and temperature it is then possible to write an expression for the average and the fluctuating thermal conductivity. The expressions are then simplified on the basis of physical and mathematical considerations. Specifically, the heat flux due to the fluctuating thermal conductivity is then expressed as the product of the derivative of the thermal conductivity with the mean temperature to the gradient of the square of the temperature fluctuation. Further considerations allow to write a new energy equation of the average temperature which include the new term. The solution of this energy equation is possible with the coupled solution of the equation for the square of the fluctuating temperature. The introduction of this new term in the energy equation can be of some importance in problems related to liquid metals flowing in turbulent flow and/or in very low temperature applications where the thermal conductivity becomes very high.
Analysis of the Effect of Ambient Loads on the SG-III TIL Structure Stability
Authors: Zhang Jun-wei , Zhou Hai , Lin Dong-hui , Zhou Yi , Jing Feng , Xie Na , Wang Shi-long
Published: August 2009

ICF (Inertial Confinement Fusion) drivers are large-scale precision optical facilities. Structure stability is an important design index for ICF drivers and it has a direct influence on the quality of beam shooting. The total positioning error budget designed for the SG-III Technical Integration Experiment Line (TIL) built in China is 30 micrometers (μm) at the target plane or its equivalent, among which the allocated stability budget is 27μm and the translation of a single optical element should be less than 1μm under the effect of ambient loads. Based on the previous evaluation of the TIL environment, the microvibration and thermal load are two main factors which can affect stability of the optical system. To obtain the data of the two ambient loads, acceleration seism sensors and high precision temperature sensors are used to measure the ambient vibration and temperature change for a long time. The finite element model is then built for a typical optical element and its support structure and the measured loads are exerted on the model to obtain the response of the optical system. The results show that both stability of a single optical element and stability of the laser beam can satisfy the designed index. This research is very helpful for the building of the SG-III main facility.
Piezoelectric Actuated Precise Positioning System Based on a New Hysteresis Model
Authors: Shao B. , Ru C. H. , Chen L. G. , Rong W. B. , Sun L. N.
Published: August 2009

The need for precise positioning technique draws significant attention for optical engineering, semi-conductor industry, biotechnology, and nanotechnology, etc. This paper presents a novel piezoelectric (PZT) actuated precision fast positioning system (PFPS), which consists of control module, PZT driving module, precision fast positioning mechanism (PFPM), and micro-displacement measure module. It provides fast and precise control in tilt and piston movements. The driving, mechanism and measure integrative model of the PPS is built. Due to the inherent hysteresis nonlinearity, the PZT actuator always causes positioning error in the open-loop operation and instability in the closed-loop operation. In order to improve the positioning accuracy and response speed, a control method for PZT actuator based on a PID feedback controller with a feedforward compensation is proposed. Finally, the tracking control experiments of piezoelectric actuators for a desired sinusoidal trajectory are performed according to the proposed control method. The experimental results demonstrate that the positioning precision is noticeably improved. The maximum error in tracking a sinusoidal signal is lowered about one order of magnitude in comparison with only using PID controller.
Industrial Mentors: An Often Untapped Resource in Undergraduate Research Programs
Authors: Guessous Laila , Sangeorzan Brian , Zou Qian , Wang Xia
Published: August 2009

Students taking part in a 10-week summer research experience for undergraduates (REU) program in the department of mechanical engineering at Oakland University receive three levels of mentorship: from faculty, graduate students and researchers/engineers from industry. Industrial mentors, all of whom volunteer to take part in the experience, play a variety of roles as part of the program and are viewed by the authors as an often untapped resource in undergraduate research programs. This paper focuses on the experience gained from involving industrial mentors in the REU program and on the lessons learned: what worked, what didn’t work and what improvements can be made in the following years.
A Recursive Algorithm for Solving the Generalized Velocities From the Momenta of Flexible Multibody Systems
Authors: Tong Martin M.
Published: August 2009

The computation of the generalized velocities from the generalized momenta of a multibody system is a part of the numerical solution of the dynamics equations when they are given in the Hamiltonian form. The states of these equations are the generalized coordinates and momenta, (q, p). The generalized velocity, q˙, is defined by q˙ = J−1p, where J is the system mass matrix. The effort in solving q˙ by direct methods is order(N3) where N is the number of bodies in the system. This paper presents an order(N) recursive algorithm to compute q˙ for flexible multibody systems.
An Introduction to Smart Structure and Its Application in Nanotechnology
Authors: Shih Hui-Ru , Walters Wilbur L. , Zheng Wei
Published: August 2009

The use of smart materials for the control of shape, vibration, and stability of structural systems has become more prevalent in recent years. Nanotechnology is regarded worldwide as the technology of the 21st century. As nanotechnology begins to unfold, smart materials will also play a key role in revolutionizing the productivity of emerging nano applications. To ensure the progress and success of smart-structure technology, engineering and technology educators need to make strong efforts to educate the students. At Jackson State University (JSU), two course modules have been developed and added to existing technology course that have helped undergraduate students develop hands-on experience as well as strengthen students’ foundation in smart materials and structures. The modules consist of lectures and laboratory activities. The lecture materials cover core concepts. The laboratory activities give students hands-on skills with observing, measuring and controlling the behavior of smart structures. The effectiveness of these modules has been assessed. Responses and feedback from students who have taken these modules are very positive.
A Tetralattice™ Gradient Fin: Its Creation and Testing
Authors: Kumpaty S. , Schneider A. , Benavides J. , Oware C.
Published: August 2009

Rapid Prototyping (RP) has allowed prototypes with complex geometries to be possible during the past decade, such as complex geometry heat exchangers and fins. These structures are modeled after the covalent bonding between the carbon atoms of a diamond. The tetrahedron diamond lattice, or Tetralattice™, is a repeating lattice unit that lends itself to RP. Currently, fabrication of a thermal conduction module using two materials in a gradient fashion from one end to the other using intertwined Tetralattice™ pattern is being attempted at Milwaukee School of Engineering. The stainless steel (SS) portion of the gradient fin was fabricated by employing selective laser melting. The testing of this gradient fin for its performance with the base heated at a constant temperature was targeted and compared with the traditional cylindrical SS fin. Convective heat transfer was found to be enhanced due to the large surface area of the Tetralattice™ structure. A thermal imaging study was also conducted on this gradient fin. Infrared thermography captured data that would be nearly impossible to gather using thermocouples. These tests provided detailed heat transfer characteristics of this Tetralattice™ fin. This project tested the limits on fabrication of a complex geometry gradient fin; the authors project tremendous potential for use of such fins in automotive and aerospace applications.
Motion Characteristics of High Performance Rotary Tables for CNC Machines
Authors: Dassanayake K. M. Muditha , Tsutsumi Masaomi , Sato Ryuta , Ito Hisayoshi
Published: August 2009

In this paper, the characteristics of two rotary tables driven by worm gear and roller gear cam are measured and compared. The positioning accuracy and repeatability as specified in ISO 230-2 are measured together with the rotational fluctuation, backlash, friction torque, frequency response of the systems and also the influence of unbalance mass on rotational motion. Two rotary encoders which were attached to motor and output axis were used for measurements. The motor, controller, and the rotary encoders were kept the same for both tables to ignore the effects of these units on results. Furthermore, the simulations were carried out by mathematical models which were proposed by two of the authors and the results were compared with measured results. From the simulation results, the torsional stiffness and friction torque were identified and also compared. The results show that the measured and simulated data have a good agreement and therefore it can be said that the identified parameters from simulations are accurate. The result shows that the performances of the rotary table driven by roller gear cam is better than that of rotary table driven by worm gear.
On the Effect of Roller Materials on the Power Window Mechanism From a Tribological Perspective
Authors: Chee S. B. , Al Shalabi Ammar , Chin C. W. , Yousif B. F.
Published: August 2009

This study serves to delineate the effects of material on the lifespan of a polymeric roller rubbing against a steel wire. Four materials, namely nylon, polyester, borosilicate glass and epoxy are the manipulated variables in conducting a simulation with a steel wire. A block-on-ring machine was used to conduct the tribo-experiments under dry contact condition. In concurrence with average operating conditions, the machine was set to 0.15 m/s sliding velocity, at an applied load of 10 N. Worn surfaces of the polymer were subsequently studied under optical microscopy. Frictional and wear resistance results were presented versus time for a predetermined duration. There is a strong correlation between the wear resistance and material hardness but the contrary is found with elongation at break. Findings revealed better wear resistance in epoxy due to its higher hardness. The improvement attained with reference to nylon was approximately 68%. The optical images of worn surfaces which sustained scratches and grooves implied that the contact mechanism was that of abrasion.
Comparison of Plate Fin Compact Heat Exchanger Performance
Authors: Khalil Ibrahim , Abu Heiba Ahmad , Boehm Robert
Published: August 2009

Plate fin heat exchangers (PFHE) are characterized by very close temperature approaches and high thermal effectiveness, large heat transfer area per unit volume, low weight per unit transfer and possibility of heat exchange between many process streams. These advantages are only limited by operating fluid temperatures and pressures. The main target of this paper is to study the performance of plate fin compact heat exchangers and to provide full explanation of previous comparison methods of compact heat exchanger surfaces (plain, strip, louvered, wavy, pin, perforated and vortex) used in plate fin compact heat exchangers. We generalize these methods to identify the advantages and disadvantages of each type of geometry (more than sixty geometries studied) based on required size, entropy generation, pumping power, weight, and cost. The effect of using different surfaces on each side of the heat exchanger and design recommendations are also discussed.
Selection of Optimal Tool Geometry and Cutting Conditions Using a Surface Roughness Prediction Model for Hard Turning
Authors: Singh Dilbag , Rao P. Venkateswara
Published: August 2009

Due to technical and economical factors, hard turning is competing successfully with the grinding process in the industries. However, due to the large number of variables and their interactions affecting the hard turning process, the process control becomes complex. So, the selection of optimal machining conditions for good surface quality, in hard turning, is of great concern in the manufacturing industries these days. In the present work, experimental investigation has been conducted to study the effect of the tool geometry (effective rake angle and nose radius) and cutting conditions (cutting speed and feed) on the surface roughness during the hard turning of the bearing steel with mixed ceramic inserts. Central composite design was employed for experimentation. The first and the second order mathematical models were developed in terms of machining parameters by using the Response Surface Methodology (RSM) on the basis of the experimental results. Results show that all the factors and their interactions were significantly influencing the surface roughness. Analysis of Variance (ANOVA) indicated that the second order surface roughness model was significant. Further, the surface roughness prediction model has been optimized by using genetic algorithms (GA). The genetic algorithm program gives minimum values of surface roughness and their respective optimal machining conditions (cutting conditions and tool geometry).
Family-Based Project Approach to Multidisciplinary Senior Design
Authors: Walter Wayne , Hensel Edward
Published: August 2009

During academic year 2006–07, a family of four closely related multi-disciplinary senior design projects was initiated. Each project team consisted of eight undergraduate students. The family of projects has continued during the academic year 2007–08, with three additional design projects comprised of 19 students. The intent of the family of design projects is two-fold. The first objective is to introduce students to the concept of designing a product within the context of a family of closely related products, similar to the approach that a corporation may use in its strategic approach to the marketplace. The second objective is to provide an open-source, open-architecture, modular, and scalable robotic vehicle platform usable by a wide range of researchers within the Kate Gleason College of Engineering looking for a vehicle to position cameras, sensors in networks, and for other data-gathering tasks. Students were given the challenge to design and manufacture a platform based on a single design, scalable across four payload orders of magnitude from 1kg to 1,000kg. The 10kg and 100kg variants were studied in AY2006–07, and the 1kg variant was introduced in AY2007–08. The largest, 1,000kg, planned for the future, will be about the size of a Honda Civic, so safety and fail-safe engineering is important. Each project in the family is expected to build on the technology used and lessons learned from prior and concurrent projects, much like the “next model year” in the auto industry, and information sharing requirements among concurrent engineering teams. Hardware, software, and design methods are reused whenever possible, and students are expected to develop their subsystem in the context of an evolutionary platform design. In this manner, the end-product from one design group becomes the starting point for another team. Responsibilities overlap so teams must work cooperatively, which mimics the industrial environment. Starting times on various projects may be staggered, and students must deal with documentation sharing issues, and preservation of design intent across multiple-project teams and academic terms. The paper will discuss the current status of the program, the lessons learned to-date, and future plans for the program.
A Computational Study of the Thermal Performance of a 69 kV Solid State Current Limiter Submerged in FR3 Dielectric Coolant
Authors: Warzoha Ronald , Kirby Patrick , Fleischer Amy , Gandhi Mahesh , Sundaram Ashok
Published: August 2009

This paper presents the results of thermal modeling of a unique 69 kV 3000A Solid State Fault Current Limiter (SSFCL) developed by Silicon Power of Malvern, PA with support of EPRI. The development of the Solid State Fault Current Limiter is expected to modernize power distribution systems through the use of small-scale solid-state power devices. The use of this new design is expected to increase reliability and functionality while reducing footprint. However, as the footprint is reduced, the heat flux for the system is increased, leading to the significant possibility of device failure due to thermal excursions if the heat load is not properly managed. The high heat loading requires the use of aggressive thermal management in the form of liquid cooling of the electronics. This system features 288 kW of waste heat in the three phase system. The system is submerged in FR3 dielectric coolant and the desired thermal management system is liquid natural convection within the tank and shed to the ambient through an external finned array system. This project explores the feasibility of this system design.
The Potential of Using CFD in Order to Design Better Centrifugal Pumps
Authors: Yedidiah S.
Published: August 2009

Recent advances in CFD made it capable of producing fairly realistic predictions of the flow-patterns within the passages of centrifugal pumps. This raises the possibility that CFD might also be capable of assisting the pump engineer to come up with better designs. Success, however, is still very elusive. This paper discusses the reason for that state of affairs, and how to cope with it. As such, this paper can be regarded as a supplement to the discussions presented in References [1] and [2]. It has been demonstrated in Refs. [1] and [2], that the main cause for that lack of success is due to the present explosion of information. It prevents the CFD specialist from acquiring the necessary in-depth knowledge of the practical aspects of a problem, which a pump engineer has to solve. At the same time, this explosion of information makes it impossible for the pump specialist to become adequately familiar with the potentials and with the limitations of CFD. It has been demonstrated in Ref.[2] that certain problems related to centrifugal pumps can be solved easier, faster and more successfully with the aid of more conventional logical tools, than with the aid of CFD. This paper will discuss, among others, problems, which only CFD might be capable to solve.
Analysis on Cournot Oligopoly Game Models With Two Firms and More Than Two Firms
Authors: Wang Junyan
Published: August 2009

This paper reviews the standard game models and its Nash equilibrium and then analyses Cournot oligopoly game from two firms to the case with more than two firms. Due to Cournot equilibrium point, the concept of Cournot equilibrium point is the same as the concept as the non-cooperative game with pure strategy but the strategy can be chosen in Cournot game is infinity and it can not be obtained base on Nash equilibrium theorem. Finally, the existence conditions of Cournot equilibrium point are given and the theorem and its proof of the existence Cournot equilibrium point are given too.
Calibration of Hexaglide Parallel Manipulators Using Only Input Joint Variables
Authors: Abtahi Mansour , Pendar Hodjat , Alasty Aria , Vossoughi Gholamreza
Published: August 2009

In the application of parallel robots, it is necessary to calibrate the geometric parameters and improve the positioning accuracy for accurate task performance. Traditionally, to perform system calibration, one needs to measure a number of robot poses using an external measuring device. However, this process is often time-consuming, expensive and difficult for robot on-line calibration. In this paper, a methodical way of self-calibrating of Hexaglide parallel robot is introduced. This method is performable only by measuring input joint variables in some sets of configurations where in each set center of the end-effector is fixed, but orientations are different. Simulations give us an idea about the number of points that must be measured, the number of orientations in each point and the effect of noise on the calibration accuracy.
Wave Guiding in Air/Silicon Phononic Crystal With Complete High Frequency Band Gap
Authors: Mohammadi Saeed , Eftekhar Ali Asghar , Hunt William D. , Adibi Ali
Published: August 2009

Phononic crystals (PC) are structures with periodic variations in their elastic properties. PC structures with complete phononic band gaps (CPBGs) are of special interest as they can be used to add new functionalities and make improvements to the conventional acoustic/elastic wave based devices. Recently, there has been a growing interest in PC structures with two-dimensional (2D) periodicity and a finite thickness in the third dimension, called PC plates (or slabs). PC slabs are interesting as the elastic waves are manipulated by the PC structure in the plane of periodicity while it is confined within the finite thickness of the slab structure in the third dimension, preventing the loss of energy out of the plane of periodicity. Although there have been a few reports on the implementation of PC plates with partial band gaps at low frequencies (below 5 MHz), the possibility of utilizing PC structures with high frequency CPBGs which can be used in wireless communication and sensing systems is still unverified. In this paper, we fist show (to the best of our knowledge) the first experimental proof for the existence of large high frequency (119MHz–150MHz) CPBGs in Si-based PC plates, and then using this CPBG, we create a waveguide by introducing a line defect in the PC structure. The structure is made by etching a hexagonal lattice of air holes in a free standing silicon plate by the use of a CMOS-compatible fabrication procedure. The transmission of elastic waves through the PC structure is measured by the use of a network analyzer and embedded interdigitated transducers. More than 30 dB attenuation in transmission through eight layers of PC structure is observed in the frequency range of the CPBG (119MHz–150MHz) with very good agreement with theoretical predictions of the CPBG. By adding a line defect to the PC structure, a PC waveguide with low loss propagation characteristics is formed and experimentally demonstrated. This result adds a new powerful functionality to micro/nano-mechanical devices that can lead to new high-performance, high-frequency devices with possible use in various wireless communication and sensing systems.
Differential Control System for Rhombus-Chassis Electric Vehicles With Independent-Powered Wheels
Authors: Li Cheng-Ho , Peng Yu-Ying , Gau Tien-Ho , Wang James H. , Chien Chin-Pin
Published: August 2009

Light electric vehicles (LEV) have been developed for the interests of green, low pollution and low noise. The development of in-wheel motors improve electric vehicles’ power efficiency and simplify the transmission system design. However, to coordinate the wheel torques and their angular velocities becomes an issue, which affects the vehicle’s dynamics and handling stability. In this paper, an electric differential system (EDS) for a rhombus-chassis EV is focused on. The relation of driving wheels’ speeds was derived particularly for rhombus configuration, and it has been carried out on a control system. Compared to the conventional control strategy for three-wheeled vehicles, the proposed method could estimate a more accurate turning center with sensing the tail wheel’s rotating angle that is beneficial to smoothen vehicle’s cornering with a more adequate differential relation. Experiments were carried out with a real concept car “ITRI LEV 1,” and tests such as straight-line test, constant-radius test, and Slalom turn test were conducted. The results show the EDS could effectively improve vehicle’s maneuverability and stability. The required steering angle became larger and trending to under steering while enabling the proposed EDS system, and wheel skidding was also effectively prevented in both constant-radius and Slalom turn tests.
A Viscoelastic Model of the Neonatal Respiratory System to Assess the Efficacy of CPAP Devices
Authors: Reddy Prasika I. , Al-Jumaily Ahmed M. , Bold Geoff T.
Published: August 2009

The objectives of this research were to; develop a validated mathematical model of the premature neonatal lung. A description of the multi-compartmental, branched airway model of the neonatal lung is presented and shown to compare well with existing in-vivo data from the literature. The model described will be used in engineering practice to assess the design of conventional and emerging forms of continuous positive airway pressure (CPAP) devices in treating respiratory distress syndrome (RDS) in premature neonates.
Transition Scenarios Due to Flow Bifurcations in Asymmetric Wavy Channel Flows With Different Spatial Periodicity on the Sinusoidal Walls
Authors: Guzman Amador M. , Donoso Fernando A. , Ortega Alfonso
Published: August 2009

Numerical investigations of transition scenarios due to flow bifurcations from laminar to time-dependent transitional flows in asymmetric wavy channels with different spatial periodicity on the sinusoidal wall are performed by direct numerical simulations of the mass and momentum conservation equations using a spectral element method computational program. Three aspect ratios r = a/(2L) are considered in this study: 0.125, 0.25, y 0.375. Computational meshes for both extended and periodic computational domains are used to determine first, the existence of spatial periodicity and second, the transitional flow behavior for increasing Reynolds numbers. Numerical results shows that the transition scenarios are highly dependent on the aspect ratio, r. The following scenarios develop: a) a first transition scenario with one flow bifurcation to a relatively low Reynolds numbers, Rec; b) a second scenario, with also one flow bifurcation, to a relatively high Reynolds numbers, Rec*; and, c) a third flow transition scenario with two Hopf bifurcations B1 and B2, occurring at critical Reynolds numbers Rec1 y Rec2, respectively. In this third scenario, fundamental frequencies ω1 and ω2, and sub and super harmonic combinations of the fundamental frequencies develop as the Reynolds number increases from a laminar to higher transitional flow regime. This transition scenario from a laminar flow to high transitional flow regimes is very similar to the Ruelle-Takens-Newhouse (RTN) found in another confined flow channels such as symmetric wavy, grooved and communicating channels.
Design of a 2D Electrostatic-Thermal Actuated MEMS Mirror
Authors: Braghin Francesco , Leo Elisabetta , Resta Ferruccio
Published: August 2009

MOEMS (Micro-Opto-Electro-Mechanical System) are MEMS in which the optical part plays a dominant role. MOEMS are usually used to deflect and/or focus light from/on a given spot thus acting as optical switches. Now, imagine to have a 2D array of optical switches (e.g. a CCD) and to rotate the MOEMS so that the incoming light is focused subsequently on each of these switches. What you have designed is a 2D scanner. If you reverse the process (i.e. one light source and the MOEMS projecting on a screen) you have designed a projector. The main advantage of a MOEMS projector and/or scanner are the reduced dimensions/weight with respect to traditional projectors and scanners and the fact that the necessity of optical lenses is greatly reduced thus reducing the cost of the system. In the present paper, a 2D MOEMS projector/scanner is designed. The peculiarity of the system is that the MOEMS mirror is able to rotate around two perpendicular axes having only one excitation point instead of two thus allowing to design a system that can be produced from a planar surface. This is achieved by applying the excitation to the micro-mirror indirectly through a supporting frame that is free to rotate around an eccentric vertical axis. The micro-mirror, instead, is free to rotate around an eccentric horizontal axis with respect to such supporting frame (figure 3). To be able to excite the motion of the micro-mirror along two perpendicular axes, the actuation force has to be applied in a point that is not nodal for any of the two rigid vibration modes of the system, has to be biharmonic and, to increase displacements, has to have frequencies that correspond to the two rigid eigenfrequencies of the micro-mirror.
Mathematical Model of a Full Scale Locomotive Roller Rig
Authors: Cheli Federico , Diana Giorgio , Leo Elisabetta , Mapelli Ferdinando , Sabbioni Edoardo
Published: August 2009

Experimental testing components, innovative solutions and control strategies is essential in order to increase performances, optimize efficiency and ensure a proper safety level of a railway vehicle. These tests are usually performed directly on line, thus being very expansive. In order to reduce costs and save time during the testing/analysis phase, the use of dedicated test rigs is increasing. A roller rig for testing full scale locomotives is considered in this paper. In order to investigate the influence of the roller rig dynamics on the test bench behavior in a design stage, a numerical model of the full system (including the locomotive, the roller rig and the corresponding control systems) has been developed and a parametric analysis has been carried out.
Numerical Modeling of a Turbulent Flow in Tubular Membranes Applied to the Crossflow Filtration Process
Authors: da Silva Juliana Maria , Ferreira Valdemir Garcia , Fontes Sergio Rodrigues
Published: August 2009

In this paper, a turbulent fluid flow of a non-Newtonian aqueous solution in a tubular membrane is numerically studied. The effects of several physical parameters on the concentration profile are investigated. The mathematical model, in cylindrical coordinates, comprises the mass conservation, momentum conservation and mass transport equations. The suction velocity is described by Darcy’s law (resistance-in-series model). The turbulence model utilized is the Prandtl mixing length and the equations with the associated boundary conditions are discretized by a finite-difference scheme on a staggered grid system. The convective terms are approximated by a new high-resolution upwind scheme. In order to demonstrate the capabilities of the numerical model, various test cases are presented. The numerical results compare favorably with the experimental data and the analytical solutions.
Image Processing Based on Tuning-Parameter Stochastic Resonance
Authors: Leng Yong-gang , Guo Yan , Zhang Ying
Published: August 2009

Bistable stochastic resonance (BSR) can change the image signal’s histogram distribution. In this paper, the influence of bistable system parameters on the contrast of the output image is investigated through the observation of histograms. An image-processing method of BSR via tuning parameters is proposed. The experiment on the treatment of an image plus noise has proved that it can improve the quality of the image effectively.