bluuebunny/crossref_metadata_2025 huggingface dataset:
Transient Control of Combustion Phasing, Lambda in a 6-Cylinder Port-Injected Natural-Gas Engine
Authors: Kaiadi Mehrzad , Lewander Magnus , Borgqvist Patrick , Tunestal Per , Johansson Bengt
Published: August 2009

Fuel economy and emissions are the two central parameters in heavy duty engines. High EGR rates combined with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark ignition engines. With stoichiometric conditions a three way catalyst can be used which keeps the regulated emissions at very low levels. The Lambda window which results in very low emissions is very narrow. This issue is more complex with transient operation resulting in losing brake efficiency and also catalyst converting efficiency. This paper presents different control strategies to maximize the reliability for maintaining efficiency and emissions levels under transient conditions. Different controllers are developed and tested successfully on a heavy duty 6-cylinder port injected natural gas engine. Model Predictive Control (MPC) was used to control lambda which was modeled using System Identification. Furthermore, a Proportional Integral (PI) regulator combined with a feedforward map for obtaining Maximum Brake Torque (MBT) timing was applied. The results show that excellent steady-state and transient performance can be achieved.
Modeling the Effects of Steam-Fuel Reforming Products on Homogeneous Charge Compression Ignition of n-Heptane
Authors: Posada Francisco , Clark Nigel N. , Kozlov Aleksandr , Linck Martin , Boulanov Dmitri , Pratapas John
Published: August 2009

Homogeneous Charge Compression Ignition (HCCI) offers benefits of high efficiency with low emissions, but suffers load range limitations and control issues. A method to improve control of HCCI was numerically investigated based on two separate fuel streams with different autoignition characteristics to regulate timing and heat release at specific operational conditions. In this numerical study n-heptane was selected as the primary fuel, and the secondary fuel was defined as a reformed product of n-heptane (RG). The reformed fuel species composition was experimentally determined based on steam/n-heptane reforming process at a steam/carbon mole ratio of 2:1. In addition to H2 and CO, the reformed fuel stream was composed of CH4, CO2, H2O and non-reformed n-heptane. A single zone model using a detailed chemical kinetic mechanism was implemented on CHEMKIN to study the effects of base fuel and steam-fuel reforming products on the ignition timing and heat release characteristics. The study was performed considering the reformed fuel species composition at total n-heptane conversion (stoichiometric) and also at the composition corresponding to a specific set of operational reforming temperatures. The computational model confirmed that the reformed products have a strong influence on the low temperature heat release (LTHR) region, affecting the onset of the high temperature heat release (HTHR). The ignition timing was proportionally delayed with respect to the baseline fuel case when higher concentrations of reformed gas were used.
A Turbocharged, Spark-Ignition Engine: Results From an Engine Cycle Simulation Including the Second Law of Thermodynamics
Authors: Lawand Vaibhav J. , Caton Jerald A.
Published: August 2009

The use of turbocharging systems for spark-ignition engines has seen increased interest in recent years due to the importance of fuel efficiency, and in some cases, increased performance. An example of a possible strategy is to use a smaller displacement engine with turbocharging rather than a larger engine without turbocharging. To better understand the tradeoffs and the fundamental aspects of a turbocharged engine, this investigation is aimed at determining the energy and exergy quantities for a range of operating conditions for a spark-ignition engine. A 3.8 liter automotive engine with a turbocharger and intercooler was selected for this study. Various engine performance and other output parameters were determined as functions of engine speed and load. For the base case (2000 rpm and a bmep of 1200 kPa), the bsfc was about 240 g/kW-h. At these conditions, the second law analysis indicated that the original fuel exergy was distributed as follows: 34.7% was delivered as indicated work, 16.9% was moved via heat transfer to the cylinder walls, 23.0% exited with the exhaust gases, 20.6% was destroyed during the combustion process, 2.5% was destroyed due to inlet mixing processes, and 1.9% was destroyed due to the exhaust processes. The turbocharger components including the intercooler were responsible for less than 1.0% of the fuel exergy destruction or transfer.
Effect of Water Injection on Emission Characteristics of a Turbocharged Diesel Engine
Authors: Sullerey R. K. , Agarwal Ankur
Published: August 2009

The diesel engine is a very common source of small-scale power generation. While diesel engines are efficient with low carbon monoxide and hydrocarbon emissions, they have high nitrous oxide emissions. One approach to reduce the formation of nitrous oxides is by introducing water in the diesel engine system. The present paper is a study of effects on performance of direct water injection in the cylinder during the compression stroke and humidifying air prior to its entry to the engine by use of suitable models for various processes. It is observed that nitrous oxide concentrations are substantially reduced by both direct water injection as well as by use of humidified air. Use of humid air however also increases the power output of the engine with a minor loss in efficiency.
CFD Investigation of Fuel Film Formation Within a GDI Engine Under Cold Start Cranking Operation
Authors: Malaguti Simone , Fontanesi Stefano
Published: August 2009

A numerical study on the investigation of spray evolution and liquid film formation within the combustion chamber of a current production automotive Gasoline Direct Injected (GDI) engine characterised by a swirl-type side mounted injector is presented. Particularly, the paper focuses on low-temperature cranking operation of the engine, when, in view of the high injected fuel amount and the strongly reduced fuel vaporisation, wall wetting becomes a critical issue and plays a fundamental role on the early combustion stages. In fact, under such conditions, fuel deposits around the spark plug region can affect the ignition process, and even prevent engine start-up. In order to properly investigate and understand the many involved phenomena, experimental visualisation of the full injection process by means of an optically accessible engine would be a very useful tool. Nevertheless, the application of such technique, far from being feasible from an industrial point of view, appears to be very difficult even in research laboratories, due to the relevant wall wetting at cranking conditions. A numerical program was therefore carried out in order to analyze in depth and investigate the wall/spray interaction and the subsequent fuel deposit distribution on the combustion chamber walls. The CFD model describing the spray conditions at the injector nozzle was previously implemented and validated against experimental evidence. Many different injection strategies were tested and results compared in terms of both fuel film characteristics and fuel/air mixture distribution within the combustion chamber. Low-temperature cranking conditions proved to be an open challenge for the in-cylinder numerical simulations, due to the simultaneous presence of many physical sub-models (spray evolution, droplet-droplet interaction, droplet-wall interaction, liquid-film) and the very low motored engine speed. Nevertheless, the use of a properly customized and validated numerical setup led to a good understanding of the overall injection process as well as of the effects of both injection strategy and spray orientation modifications on both the air/fuel and fuel/wall interaction.
Performance and Emission Characteristics of a CRDe SUV Fueled With Neat Biodiesel (B-100) From Jatropha, Pongamea Source and Diesel Fuel
Authors: Manickam Murali , Kadambamattam Mithun , Nilesh Gajarlawar , Pundlik Ghodke , Abraham Mathew
Published: August 2009

Present investigation addresses the use of neat, indigenous biodiesel (B100) in a sports utility vehicle (SUV) with second generation common rail technology. Current research determines the effect of biodiesel (B100) on performance & emission of modern diesel engine, equipped with diesel oxidation catalyst. Biodiesel used in this study were Pongamea Methyl Ester (PME) & Jatropha Methyl Ester (JME) derived from vegetable oil. Fuel related aspects for these two raw material and its effects on engine characteristics were discussed. Both engine & vehicle level tests had been carried out with the aim of obtaining performance characteristics such as brake specific fuel consumption, brake thermal efficiency, brake power, exhaust gas temperature, & emissions such as CO, THC, NOx, smoke opacity to evaluate and compute the behaviors of diesel engine running on PME & JME. Comparative vehicle performance like drivability, gradeability and noise was also measured between biodiesel and diesel. Experimental results revealed that significant reduction in power was observed through out the operating range in both JME & PME, because of its lower heating value. Between this two biodiesel, there was a visible difference in power drop. Engine exhaust gas emission like Hydrocarbon (HC), Carbon monoxide (CO), & Smoke emission reduce significantly, when engine runs with biodiesel (JME & PME) meanwhile using of B100 causes increase in Nitrogen oxide (NOx) emission. Particulate matter was significantly lower than those of a vehicle running on fossil diesel. However loss in power, when using biodiesel has been regained by increasing the fuelling & optimizing the combustion parameters like rail pressure, injection timing & duration. Based on the study it is observed that B100 can be used as fuel in diesel engine without any hardware modification, but only by remapping the CRDe system.
Preliminary Testing of Metal-Based Thermal Barrier Coating in a Spark-Ignition Engine
Authors: Marr Michael , Wallace James S. , Pershin Larry , Chandra Sanjeev , Mostaghimi Javad
Published: August 2009

A novel metal-based thermal barrier coating was tested in a spark-ignition engine. The coating was applied to the surface of aluminum plugs and exposed to in-cylinder conditions through ports in the cylinder wall. Temperatures were measured directly behind the coating and within the plug 3 and 11 mm from the surface. In-cylinder pressures were measured and analyzed to identify and quantify knock. Test results suggest the coating does not significantly reduce overall heat transfer, but it does reduce the magnitude of temperature fluctuations at the substrate surface. It was found that heat transfer can be reduced by reducing the surface roughness of the coating. The presence of the coating did not promote knock.
Computational Investigation of HCCI Engine Performance With Fuel Reforming Effect on Lean Ethanol
Authors: Rahbari Alireza , Barari Bamdad , Shirazi Ashkan Abbasian
Published: August 2009

In this study, a mechanism containing ethanol reactions is employed and the effects of exhaust gas fuel reforming on operation parameters such as ignition timing, burn duration, temperature, pressure and NOx emission are studied in which a homogeneous mixture is assumed. The results show that hydrogen in the form of reformed gas helps in lowering the intake temperature required for stable HCCI operation. It is concluded that the addition of hydrogen advances the start of combustion in the cylinder. This is a result of the lowering of the minimum intake temperature required for auto-ignition to occur during the compression stroke, resulting in advanced combustion for the same intake temperatures. The obtained results from the model are compared with the experimental data published in the literature and the comparison showed a reasonable compatibility.
Combustion and Emissions Characterization of Soy Methyl Ester Biodiesel Blends in an Automotive Turbocharged Diesel Engine
Authors: Moscherosch Benjamin W. , Polonowski Christopher J. , Miers Scott A. , Naber Jeffrey D.
Published: August 2009

Recent increases in petroleum fuel costs, CAFE standards, and environmental concerns about CO2 emissions from petroleum based fuels have created an increased opportunity for diesel engines and renewable alternative fuels such as biodiesel. Additionally, the Environmental Protection Agencies Tier II heavy duty and light duty emissions regulations require significant reductions in NOx and diesel particulate matter emissions for diesel engines. As a result, the diesel engine and aftertreatment system is a highly calibrated system that is sensitive to changing fuel characteristics. This study focuses on the impact of soy methyl ester biodiesel blends on combustion performance, carbonaceous soot matter and NOX emissions. Tests were completed with an I4 1.9L, turbocharged, high speed, direct injection diesel engine using commercially available 15 ppm ultra low sulfur diesel, a soy methyl ester B20 (20% biodiesel and 80% ultra low sulfur diesel) biodiesel blend and a pure soy methyl ester biodiesel. Results show a reduction in NOx and carbonaceous soot matter emissions and an increase in brake specific fuel consumption with the use of biodiesel. Further, traditional methodology assumes that diesel fuels with a high cetane number have a reduced ignition delay. However, results from this study show the cetane number is not the only parameter effecting ignition delay.
Application of the Extended Kantorovich Method to the Static Deflection of Electrically Actuated Microplates
Authors: Ahmadian Mohammad Taghi , Moeenfard Hamid , Pirbodaghi Tohid
Published: August 2009

The aim of this paper is to present an Extended Kantorovich approach to simulate the static deflection of microplates under electrostatic voltage. The model accounts for the electric force nonlinearity of the excitation. Starting from a one term Galerkin approximation and following the Extended Kantorovich procedure, the equations governing the microplate deflection are obtained. These equations are then solved iteratively with a rapid convergence procedure to yield the desired solution. The results are validated, comparing them with other theoretical results and experimental findings, reported in the literature. It is shown that rapid convergence, high precision and independency of initial guess function makes the EKM an effective and accurate design tool for design optimization.
Optimal Synthesis of Adjustable Linkages for Precise Continuous Path Generation Using the Optimal Link Length Adjustment
Authors: Zhou Hong , Jamal Mohammed , Mohammed Arif
Published: August 2009

Conventional nonadjustable four-bar linkages can only generate the desired continuous paths approximately. With one link length adjustment, the whole desired continuous path can be generated precisely. In this paper, the length of the driven side link or coupler is adjusted to generate the desired continuous paths precisely. The linkage feasibility conditions and path generation flexibilities of the adjustable four-bar linkages are analyzed. The optimal synthesis model of adjustable four-bar linkages is established based on the required optimal link length adjustment when the desired continuous path is precisely generated. The global optimal solution is searched by a real-valued genetic algorithm in which the involved constraints are handled using the function penalty method. The effectiveness of the optimal synthesis approach proposed in the paper is verified by the demonstrated examples.
Influence of Spud-Can-Soil Interaction Modeling and Parameters on the Reliability Index of Neka Drilling Jack-Up Platform
Authors: Emami Azadi M. R.
Published: August 2009

In the present study, the influence of spud-can-soil modeling and parameters on the reliability index of jack-up platform is investigated. Neka platform is studied as a case which is a 3-leg drilling jack-up type platform located in water depth of about 91m in Caspian Sea region. Various spud-can-soil interaction models such as pinned, fixed-base, hyper-elastic and non-linear elasto-plastic spud-can models are applied. The soil type is varied from loose to dense sand and also from soft NC-clay to very stiff OC-Clay. The effects of bias and COV of the spud-can-soil interaction modeling and also the soil parameters such as effective interface soil friction angle and also un-drained shear strength of clayey soil are studied. The results showed that inclusion of spud-can-soil interaction may have a considerable effect on the reliability of the Jack-up platform. In particular, the bias and COV of soil shown to have more significant influence on the reliability of jack-up platform in loose sand and soft clayey type soils. It is also found that bias in strength modeling of jack-up itself has less profound effect on the reliability index of the jack-up-foundation-soil system. Importance factors of spud-can-soil modeling are found to be quite considerable. The key aspect is that the inclusion of jack-up-spud-can-soil interaction is more crucial with respect to the reliability of jack-up platform than the choice of interaction model itself.
Quasi-Static and Dynamic Testing as a Basis for Determining Seat Back Strength
Authors: Herbst Brian R. , Clarke Chris C. , Meyer Steven E. , Oliver Arin A. , Hock Davis A. , Hayden Joshua D. , Forrest Stephen M.
Published: August 2009

The performance of a vehicle’s seat back in rear impact accidents can significantly affect occupant kinematics and the associated injury potential. Efforts to establish seat back performance requirements have generated significant debate between stiff and yielding seats [1]. While this paper will not attempt to resolve that issue, the analysis contained herein will compare various test methods for determining the strength of seat backs. This paper presents two quasi-static test methodologies that can be used to evaluate seat back performance. The first method utilizes the test procedure outlined in Federal Motor Vehicle Safety Standard (FMVSS) 207, Seating Systems, by loading the seat through its upper cross member. The second method utilizes an Anthropometric Test Dummy (ATD) and applies the load to the seat back through the ATD’s lumbar spine; this method is referred to as the Quasistatic Seat Test (QST). Four seat designs were tested utilizing these two quasistatic test methods. The observations and data obtained from these tests are then compared to dynamic test data documented in FMVSS 301, Fuel System Integrity, type rear impact and sled testing.
An Experimental Evaluation of Shock Wave Strength and Peak Pressure in a Conventional Shock Tube and a Free-Piston Compressor
Authors: Al-Falahi Amir , Yusoff M. Z. , Yusaf T.
Published: August 2009

The aim of this work is to provide a comparative experimental study on the performance of the conventional shock tube and a free-piston compressor. Experimental measurements of shock strength, peak pressure and surface temperature change of air-air as a driver/driven gas are then presented and compared with another set of experimental measurements using gas combination of He-air. The results provide very good estimates for the above mentioned parameters obtained after diaphragm rupture and also provide significant information on the role of the free piston in the facility operation conditions over the full length of the facility.
Modeling Heat Conduction Across Thermal Interface Materials With Micro-Particles
Authors: Wong C. Channy
Published: August 2009

Different types of fillers with high electrical and thermal conductivities, e.g. graphite and alumina, have been added to adhesive polymers to create composite materials with improved mechanical and electrical properties. Previous modeling efforts have found that it is relatively difficult to predict the effective thermal conductivity of a composite polymeric material when incorporated with large volume content of fillers. We have performed comprehensive computational analysis that models the thermal contacts between fillers. This unique setup can capture the critical heat conduction path to obtain the effective thermal conductivity of the composite materials. Results of these predictions and its comparison with experimental data will be presented in this paper.
An Analytical Viscoelastic Model of the Head in Blunt Impacts
Authors: Baghaei Shahab , Sadegh Ali , Rajaai Mohamad
Published: August 2009

The relative motion between the brain and skull and an increase in contact and shear stresses in the meningeal region could cause traumatic closed head injuries due to vehicular collisions, sport accidents and falls. There are many finite element studies of the brain/head models, but limited analytical models. The goal of this paper is to mathematically model subarachnoid space and the meningeal layers and to investigate the motion of the brain relative to the skull during blunt head impacts. The model consists of an elastic spherical shell representing the skull containing a visco-elastic solid material as the brain and a visco-elastic interface, which models the meningeal layers between the brain and the skull. In this study, the shell (the head) is moved toward a barrier and comes in contact with the barrier. Consequently, the skull deforms elastically and the brain is excited to come in contact with the skull. The viscoelastic characteristics of the interface (consisting of springs and dampers) are determined using experimental results of Hardy et al. [5]. Hertzian contact theory and Newtonian method are employed to acquire time dependant equations for the problem. The governing nonlinear integro-differential equations are formed and are solved using 4th order Runge Kutta method and elastic deformation of spherical shell, brain motion during the impact, and contact conditions between the brain and the skull are evaluated. Furthermore, some important mechanical parameters such as acceleration, impact force, and the impact time duration are also specified. The results of the analytical method are validated by performing an explicit finite element analysis. Acceptable agreement between these two methods is observed. The results of the analytical investigation give the contact threshold of the skull/brain, and represent the relevant velocity of this event. Furthermore, the impact analysis in different velocities is performed in order to compare the transmitted forces and the impact durations in different cases. It is concluded that the proposed mathematical model can predict head impacts in accidents and is capable in determining the relative brain motion of the skull and the brain. The mathematical model could be employed by other investigators to parametrically study the traumatic closed head injuries and hence to propose new head injury criteria.
Forming Prediction of Magnesium Alloy Sheets Using a Continuum Damage Mechanics Multistep Inverse Approach
Authors: Bapanapalli Satish K. , Nguyen Ba Nghiep
Published: August 2009

This paper applies a multistep inverse approach using a new method to generate the intermediate configurations to analyze the press forming of magnesium alloys. The developed approach considers a final configuration to be formed from a flat blank sheet. It accounts for a series of intermediate configurations that are estimated based on the initial and final configurations as well as tooling conditions using optimization techniques. These techniques minimize the sheet metal surface area subject to the constraints imposed on the punch and die. Due to the limited formability of magnesium alloys, it is important to realistically estimate the intermediate configurations so that a damage mechanics approach can be explored to predict damage accumulations that can cause rupture of the sheet during forming. Elastic-plastic constitutive laws are used with the modified Hill’s criterion and deformation theory of plasticity to describe the behavior of AZ31 magnesium alloys. Damage is captured by a damage variable that governs the equivalent stress. A damage-plasticity coupled approach is employed for the integration of the constitutive equations. The computed strain increment from two consecutive intermediate configurations is used to predict the resulting damage accumulations during forming. The continuum damage mechanics multistep inverse approach is applied to predict forming of AZ31 magnesium alloy sheets.
Tolerance Simulation of Compliant Sheet Metal Assemblies Using Automatic Node-Based Contact Detection
Authors: Wa¨rmefjord Kristina , Lindkvist Lars , So¨derberg Rikard
Published: August 2009

Tolerance simulation is a crucial tool for predicting the outcome in critical dimensions, and is used during early phases of product development in automotive industry. In order to increase the accuracy and the agreement with reality of the predictions even further, variation simulation software offer in some cases the possibility to perform compliant analysis, i.e. the parts are not restricted to be rigid. In compliant analysis contact modeling is an important feature. In this paper a simplified method for automatic contact detection, well suited for tolerance simulations, is suggested. Traditionally, those kinds of non-rigid simulations are very time consuming, but by using this kind of simplified contact modeling in the Monte Carlo simulations, the simulation times can be kept down. The method is tested on an industrial case study. The analyses are done with and without contact modeling and those results are compared to real inspection data. The contact modeling turns out to be an important feature; the correlation between the results with contact modeling and inspection data is much stronger than the correlation for simulations without contact modeling. When using the new contact modeling algorithm the correspondence between simulated data and inspection data is very satisfying and the algorithm seems to be faster than traditional finite element software.
Otolith-Canal Optimal Interaction for Estimating Body Angular Velocity and Orientation Based on Two Kalman Filters
Authors: Tahboub Karim A.
Published: August 2009

The human vestibular system, consisting of the otolith and semicircular canals, provides valuable information about body motion and orientation in terms of angular velocity and translational acceleration. This article discusses the dynamic characteristics of these organs and the generated signals and proposes approaches to combine these signals to infer for the body angular velocity. This is the first step towards determining the body orientation and thus the inertial acceleration. The first presented approach evolves around a complementary filter that capitalizes on the low- and high-frequency characteristics of the signals. The second approach resembles two versions of Kalman filter that allow for explicitly estimating the drift of the semicircular canal signal. The difference between the two versions is the number of states employed: the first relies on two states while the second employs innovatively four states selected to minimize the estimation error of orientation, velocity and drift.
3-D Micro-Fabrication and Separation of PDMS by Ultra-Short Pulsed Laser
Authors: Huang Huan , Guo Zhixiong
Published: August 2009

In this paper, micro-fabrication of bio-degradable polymer-PDMS via an ultra-short pulsed (USP) laser is reported for potential applications in biomaterial, biomedicine, and tissue engineering. Thin layer PDMS separation has been presented with a minimum of about 20 μm thickness and a 3-dimensional PDMS micro-channel network has also been shown. The surface condition and thickness of the separated PDMS layer are examined using SEM and surface profilometre. This work on using USP laser for separation of bio-degradable polymer is the first of its kind, and it shows great potential biomedical application for tissue microprocessing and separation.
Investigation on Force Sensor Dynamics and Their Measurement Characteristics
Authors: Klocke Fritz , Kratz Stephan , Veselovac Drazˇen , Arrazola Pedro J. , Martinez de Aramaiona Paloma
Published: August 2009

Cutting force is a common monitoring parameter reflecting the behaviour of a production process. As monitored cutting conditions are used to adjust a process’s performance to its highest feasible level, control strategies for machining operations are claimed. To ensure a control’s functionality, an accurate measurement of the cutting conditions is required. In this paper the impact of a work piece’s mass onto a sensor’s dynamic behaviour is presented. For this purpose, at different setups the measurement characteristics of piezoelectric force sensors are researched and verified. Different trials are carried out, not only taking the natural frequencies of the sensors, but also the vibration characteristics of the whole machinery into account. Based on this, methods to improve and condition a measurement system’s dynamic accuracy are approached.
Thermal Stress Measurement of Solder Joints in BGA Packages: Theoretical and Experimental
Authors: Shang H. X. , Gao J. X. , Nicholson P. I.
Published: August 2009

In this study, an analytical model to obtain a closed-form solution for thermomechanical behaviours of BGA (Ball Grid Array) package was derived and experimentally validated. In the theoretical analysis, the BGA package was represented by a three-layer axisymmetrical model: two layers of dissimilar materials jointed by a graded interlayer. Based on the classical bending theory, the thermal stresses induced by temperature changes were calculated accurately. 2-D FE (Finite Element) meshes of BGA packages subjected to high temperature were used to verify the theoretical solutions. Furthermore, two types of BGA samples, each with eutectic (63wt%Sn/37wt%Pb) and Pb-free SAC387 (95.5wt%Sn/3.8wt%Ag/0.7wt%Cu) solder joints respectively, were experimentally investigated by high resolution Moire´ Interferometry (MI). Thermal cycling tests were performed on each package with temperature variation from 25°C to 125°C. It was found that the thermal deformation obtained from moire´ tests matched well with those from analytical solutions and FE analyses. Based on the shear strain values, the reliability characteristics of BGA assemblies were also assessed.
Thermal Design for Probe Transformation of Phase Change Vias
Authors: Lo Hsinyi , Bain James A.
Published: August 2009

Thermal cycling of chalcogenide materials (Ge2Sb2Te5 or GeSb for example) causes switching between two electrical resistance levels in the materials. This is the basis of PC memory, and offers the possibility of use for programmable signal switching in electronic systems as well. Here we propose a design for connection topology, using dual tip AFM-type probes. The design subdivides a single phase change via into a parallel array of three-terminal sub-vias which are well-suited to addressing with probes. This sub-division reduces required power and current to acceptable levels. Experimental inputs to the model were extracted from two sources. First, current levels were limited to levels that have previously been shown possible to deliver with AFM tips. Secondly, measurements of PC resistance as a function of cooling time were used to determine required heat sinking of the sub-via structures.
S-Rail Sled Testing of Rotary Draw Bent and Hydroformed Aluminum Tubes
Authors: Mayer Robert R. , Oliveira Dino , Worswick Michael
Published: August 2009

This report provides detailed test results for the aluminum S-rail form & crash project. We considered the effect of rotary draw bending, and rotary draw bending plus hydroforming, and their effect on mean crush force, maximum crush force, and maximum bending moment for aluminum s-rails. The use of our sled test setup resulted in accurate, repeatable test results with no end plate welding. The R/D (center bend radius/tube diameter) used were 1.5, 2.0, and 2.5. Tubes were hydroformed from the circular shape into a square tube with rounded corners. Annealed tubes were used to isolate the forming effects to thickness changes alone.
A Study of Strong Shear Flow in a Narrow Gap of an Atomization Equipment
Authors: Tsutahara Michihisa , Hashimoto Kenichi , Michiwaki Akira , Masuda Yuuichi , Enomura Masakazu , Zhang Xiaofeng
Published: August 2009

The mechanism of solid particle atomization by strong shear flow inside a narrow gap between a still disk and a rapidly rotating disk of a new beadless disperser called SS5 is clarified. We show that the solid particles rotate at the same rate as fluid particles, that is the angular velocity is a half of the vorticity using a equipment consisting of a rotating cylinder inside a cylindrical vessel, instead of rotating disks. The cavitation is shown to occur inside the gap and the mechanism of atomization of solid particles is considered to be due to the cavitation collapse. The cavitation generation is also considered to be promoted by the rapid rotation of the particles due to the strong shear and also by the pressure drop due to the centrifugal force driven by the rotation of the disk.
Development of Wedge Type Impellers for Low Specific Speed Centrifugal Compressors
Authors: Tanaka M. , Kobayashi H. , Nishida H.
Published: August 2009

Low specific speed, namely low flow coefficient, Wedge type impellers with high performance are developed, which impellers are applied to high-pressure multistage compressors. Conventional low specific speed impellers because of their low volume flow rates have thin blades and their blade heights are small. Therefore, efficiency of low specific speed impellers turns out to be lower than that of high specific speed impellers, because the large wetted perimeter causes large skin friction loss. Wedge type impellers with thick blades and large blade heights are examined to reduce the skin friction loss. Blade geometry of Wedge type impellers is determined by the distribution of blade angles and thicknesses that are defined in terms of a polynomial of meridional distance. The determination of impeller geometry also takes into account the inlet and the outlet blade heights. Adiabatic efficiency of many Wedge type impellers, designed by studying various combinations of these distributions and blade heights, is estimated by the one-dimensional prediction method. This procedure leads to the determination of optimized impeller geometry with higher efficiency and wider operating flow range than available otherwise. In Wedge type impeller optimization by their design, the relative velocity ratios from impeller “inlet to throat” and from impeller “inlet to outlet”, and flow incidence at impeller inlet are restricted to certain specific values. This is done in order to ascertain wide operating flow range. Estimated efficiency of optimized Wedge type impeller with designed suction flow coefficient of 0.021 is by some percent higher than that of the conventional two-dimensional impeller with thin blades, as was determined by both the one-dimensional prediction method and by commercial CFD code. Designed Wedge type impellers were fabricated and tested for their aerodynamic performance. Results show that in case of Wedge type impeller the normalized stage efficiency increases by 6% and operating flow range expands significantly as compared with those of the conventional 2D impeller stage. The performance estimation by CFD also shows a qualitative agreement with the experimental results regarding the increase in efficiency and operating flow range. Moreover, rotating stall which often exhibits sub-synchronous low frequency shaft vibration in high-pressure centrifugal compressors was not observed in Wedge type impeller stages.
The New Approach to Analysis of Hamiltonian Systems
Authors: Magnitskii N. A.
Published: August 2009

It is shown in the present paper, on the basis of numerical simulations, that in some Hamiltonian systems with two degrees of freedom the transition to chaos takes place not through the destruction of two-dimensional tori of the unperturbed system in accordance with the Kolmogorov-Arnold-Moser (KAM) theory but, on the contrary, through the generation of complicated two-dimensional tori around cycles of the approximating expanded nonlinear dissipative system and through an infinite cascades of bifurcations of generation of new cycles and singular trajectories in accordance with the universal Feigenbaum-Sharkovskii-Magnitskii (FSM) theory developed initially for dissipative nonlinear systems.
Flow Dynamics Characteristics in Micro and Nano Length Scale Devices With the Lattice-Boltzmann Method: The Air Bearing Problem
Authors: Ramirez Alvaro J. , Guzman Amador M. , Escobar Rodrigo A.
Published: August 2009

The Lattice-Boltzmann Method (LBM) has been used for investigating flow behavior and characteristics in mini, micro and nano channels with the objective of describing the transition among different length scales. In particular, we have used the LBM to describe the air bearing lubrication problem at very small scales. For doing this, first we simulate and characterize the Poiseuille flow through different length scale and compare the LBM numerical results to existing experimental and numerical results. We put special attention on the application of the slip boundary condition on the channel wall for very small length scales. Our numerical results for the Poiseuille flow show an acceptable agreement with the Fukui & Kaneko numerical solution for continuous and slip-velocity regimes. For both, the rarified flow regime and the free molecular flow regime our solutions do not show an acceptable agreement with the Fukui & Kaneko Model. Then, we focus on the Couette flow characterization at very small length scales. The pressure distribution on both walls for different Knudsen numbers is obtained and compared to existing numerical results. Last, we concentrate in the air bearing problem. We have looked at the best simulation parameters for successfully describing this device flow dynamics, and particularly, for determining the pressure distribution and the net force with a good accuracy.
A Numerical and Experimental Investigation of Energy Loss Mechanisms in Tuning-Fork Gyroscopes
Authors: Xu Yang , Durgam Shiva Krishna , Hao Zhili , Williams Frances
Published: August 2009

This paper presents a comprehensive investigation of energy loss mechanisms in tuning-fork gyroscopes from both numerical and experimental perspectives. Two main energy loss mechanisms, anchor loss and thermoelastic damping (TED), are investigated through numerical models and later experimental investigation. In order to predict the qualify factor of tuning-fork gyroscopes, a separation-and-transfer method is employed to predict anchor loss and a thermal energy method is utilized to calculate thermoelastic damping. The experimental investigation is conducted to verify the developed models. It is found that HF release in fabricating these devices is a critical factor to the measured quality factor of tuning-fork gyroscopes. The calculated Quality factors are compared with the measured data, showing good agreement.
Experimental Testbed for Testing a Robotics Based Identification Method
Authors: Bruggemann Jeremy J. , Cole James R. , Gilbert Jacob , Skaggs-Ryan Gwynne , Kecman Micah , Ma Ou
Published: August 2009

As satellite on-orbit service operations become increasingly aggressive and complex (such as on-orbit refueling, rescuing, repairing, etc.), the need for identifying varied inertial properties of a satellite is becoming a critical task. The importance of this task stems from the dependence of spacecraft’s guidance, navigation and control system on these properties. In order to accurately control a spacecraft, its control system must be capable of fully identifying these properties as they change. Previous techniques use thruster firing or momentum wheels to accomplish this task. However a newly developed robotics based method requires measuring the spacecraft’s velocity changes only, which can be induced by an onboard robotic arm powered by solar energy. This paper gives a brief overview of this method and then focuses on the design of experimental verification of the method. The verification consists of a series of experiments including a simulated microgravity test onboard the NASA JSC Reduced Gravity aircraft in order to accurately simulate an environment similar to a flying satellite in orbit.
Dealing With Uncertainty of Micro Gears: Integration of Dimensional Measurement, Virtual and Physical Testing
Authors: Albers Albert , Fleischer Ju¨rgen , Bo¨rsting Peter , Enkler Hans-Georg , Leslabay Pablo , Schlipf Matthias
Published: August 2009

Design and quality assurance of micro gear wheels and involute gear wheels involve multiple challenges regarding prediction of functionality and life cycle performance of complex and wear-resistant micromechanical systems. First of all, this is due to the fact that up to now no tolerance system for micro dimension has been defined. In second place, most measurement strategies for the dimensional characterization of involute micro gears cannot be brought forward from the macro world just as they are. There is few knowledge about the relevant quality characteristics for these micro systems, optical sensors’ precision is affected by fuzzy edges detection and no tactile scanning modes for relevant features smaller than 100 μm exist, which is the scale normally applied in macroscopic dimensions. Simulation methods for analyzing the influence on the whole system of different components’ geometrical deviations are very valuable to supplement the knowledge based on real tests. Furthermore, it could be also necessary to consider the material’s anisotropy caused by the not negligible grain structure to evaluate the stress field correctly. Therefore, a new approach for design and quality assurance needs to be developed, in order to assure the functionality and long-term performance of molded micro systems. This work uses a planetary gear train as a demonstrator. A validation of the entire product functionality test chain has to be conducted to come closer to an integrated robust design approach for mechanical micro systems — from simulation in the early design stages to test and to quality assurance of large series production. This paper outlines a threefold methodological approach integrating dimensional measurement, virtual tests based on real geometry and physical tests of real gears. The measurement of the micro systems components both in disassembled as in assembled state is conducted using multisensory coordinate measurement machines. Based on the measured contours of real gears, virtual gears are derived and meshed for its subsequent use in adequate FEA model. Simultaneously, the gears are mounted and tested on a micro gear test rig. Both simulation and test rig conduct a radial composite inspection adapted to the micro scale; results are then compared. Micro gears molded of zirconium oxide were selected as a demonstrator for the presented methodology. These 12 teeth gears, with a diameter of approximately 2.0 mm and a modulus of 169 μm, are produced within Collaborative Research Center (CRC) 499 “Development, Production and Quality Assurance of Primary-Shaped Micro Parts made of Metallic and Ceramic Materials” of the German Research Foundation (DFG).
The Effect of Spark Electrode Geometry on Flame Kernel of Premixed Methane-Air Mixtures
Authors: Far Kian Eisazadeh , Parsinejad Farzan , Gautreau Matt , Metghalchi Hameed
Published: August 2009

Flame kernel formation and structure is a fundamental factor of spark ignition engines’ performance. An experimental study about the effect of spark electrode geometry on premixed flame propagation has been done with methane-air premixed mixtures. The experimental system consists of a constant volume cylindrical vessel and a shadowgraph optical system. Experiments were performed at atmospheric initial pressure with various equivalence ratios and spark electrode geometries. Flame propagation pictures and movies were taken by a CMOS high speed camera at 10,000 frames per second. Flame radii were measured by MIDAS software and parameters affecting flame location and formation were investigated. Experimental results show that the spark electrode thickness and its tip impact flame location and structure propagation.
Jacket Elastic Drawstring Toggle Safety Analysis
Authors: Brickman Dennis B.
Published: August 2009

This paper addresses the eye impact hazard associated with a jacket elastic drawstring toggle which temporarily catches on an object and then releases. Approaches utilized in this safety analysis include an accident statistics survey, literature review, risk-utility analysis, and evaluation of alternative jacket drawstring technology. A variety of drawstring design alternatives are explored for accident prevention while achieving jacket function and aesthetic goals.
Thermodynamic Analysis of Electrokinetic Transport in Micro/Nanofluidics
Authors: Xuan Xiangchun , Davidson Christian , Zhu Junjie
Published: August 2009

Presented herein is an Onsager reciprocal relations-based thermodynamic analysis of the electrokinetic transport of fluids and ions in micro/nanofluidics. This analytical approach provides a straightforward understanding of electrokinetic energy conversion, streaming potential and streaming current measurements, and electrokinetic flow control in micro/nanoscale channels or networks.
A Music-Based Mechatronic System for Teaching Modeling and Control
Authors: Shilpiekandula Vijay , Song Yun Seong
Published: August 2009

Audio-based tools can enhance the learning experience in introductory modeling and control classes at the undergraduate (sophomore) level in the mechanical engineering curriculum. An example audio-based learning tool that we propose is the “FlexSynth,” a servo-actuated flexural rocker arm that sways to an electronically generated music. We have built and tested the FlexSynth as part of a project under the MIT advanced graduate subject 2.737 Mechatronics class offered in Fall 2007. The angular range of the rocking motion of the flexural arm in the FlexSynth is mapped to a set of musical notes. While the flexural rocker swayed to the generated ‘command’ music, its motion is also converted into an equivalent ‘response’ music. Two speakers are used, one to play the commanded music and the other to play the response music. The performance of control algorithms (such as proportional or proportional-integral control) can be discerned from the command and response music, and compared for better musical quality. The appeal of an electromechanical system, driven by music and controlled to see the ‘dancing’ flexural rocker, makes the overall system an interesting show-and-tell for young kids or the public at large, getting them excited about science and engineering automation. Advanced control issues such as filtering of flexural damping modes of the rocker can also be addressed with this system implementation. Advanced students in the controls area can study the design tradeoffs between robustness and speed in following the command music. While the usual debugging tools such as multimeters, oscilloscopes, and dynamic signal analyzers allow for hands-on learning about the performance of a control system, an audio-based unit such as the FlexSynth can be a valuable addition to the innovative teaching tool kit.