bluuebunny/crossref_metadata_2025 huggingface dataset:
Lubricant-Derived Ash Properties and Their Effects on Diesel Particulate Filter Pressure Drop Performance
Authors: Sappok Alexander , Wong Victor W.
Published: July 2010

Diesel particulate filters (DPF) have seen widespread use in on- and off-road applications as an effective means for meeting increasingly stringent particle emissions regulations. Over time, incombustible material or ash, primarily derived from metallic additives in the engine lubricant, accumulates in the DPF. Ash accumulation leads to increased flow restriction and an associated increase in pressure drop across the particulate filter, negatively impacting engine performance and fuel economy, and eventually requiring periodic filter service or replacement. While the adverse effects of ash accumulation on DPF performance are well known, the underlying mechanisms controlling these effects are not. The results of this work show ash accumulation and distribution in the DPF as a dynamic process with each stage of ash accumulation altering the filter’s pressure drop response. Through a combined approach employing targeted experiments and comparison with the existing knowledge base, this work further demonstrates the significant effect ash deposits have on DPF pressure drop sensitivity to soot accumulation. Ash deposits reduce the available filtration area, resulting in locally elevated soot loads and higher exhaust gas velocities through the filter, altering the conditions under which the soot is deposited and ultimately control the filter’s pressure drop characteristics. In this study, a novel accelerated ash loading system was employed to generate the ash and load the DPFs under carefully-controlled exhaust conditions. The ash loading system was coupled to the exhaust of a Cummins ISB diesel engine, allowing for accelerated ash loading and DPF performance evaluation with realistic exhaust conditions. Following DPF performance evaluation, the filters were subjected to a detailed post-mortem analysis in which key ash properties were measured and quantified. The experimental results, coupled with the ash property measurements, provide additional insight into the underlying physical mechanisms controlling ash properties, ash/soot interactions, and their effects on DPF performance.
Predicting Mixing Rates in Multiple Injection CRDI Engines
Authors: Rajkumar S. , Bakshi Shamit , Mehta Pramod S.
Published: July 2010

The possibility of multiple-injection in Common Rail Direct Injection (CRDI) engine allows achieving improved combination of oxides of nitrogen (NOx) and smoke emissions. In CRDI engines, the turbulent kinetic energy due to high pressure fuel injection is primarily responsible for fuel air mixing and hence the in-cylinder mixture formation. The air fuel mixing characteristics in the case of multiple-injection are quite different from that of single injection schedule. In this work a zero-dimensional model is proposed for mixing rate calculations with multiple-injection scheduling. The model considers generation and dissipation of in-cylinder turbulence through processes namely fuel injection, air swirl and combustion. The model constants are fine tuned with respect to the data available in existing literature. The model predictions are validated with the available data for the cylinder pressure and heat release rate histories on known single and multiple-injection schedules. These comparisons show good agreement to establish the role of mixing rate variations with multiple-injection. A single set of constants were found to match the cylinder pressure and heat release rate histories for single and multiple-injection from different sources in the literature. Further, the mixing rate and peak temperature predictions of the model are found to relate with the possible effect of specific injection scheduling on emission reductions reported in CRDI engine investigations.
Numerical Simulation of an EGR Operated C.R. Diesel Engine
Authors: Cameretti Maria Cristina , Tuccillo Raffaele
Published: July 2010

The authors discuss in this paper the combined effect of the exhaust recirculation rates and of the fuel injection laws on the performance and emission levels of a Common Rail diesel engine. As well known, such objectives often exhibit, conflicting trends specially when the NOx reduction is pursued through the EGR concept; on the other hand, the adoption of this method represents a preliminary tool for proceeding towards the ultimate HCCI goal. The study is carried out on a CFD basis, with an engine numerical simulation that includes the gas exchange periods and it aims at a comprehensive analysis of both the combustion development and the pollutant formation under different conditions induced by different choices of the above operating parameters. The most interesting results refer to the possibility of finding an effective compromise between the pollutant reduction and the engine performance preservation, through a proper combined choice of the EGR level and the injection timing.
A Comprehensive Study on Natural Gas HCCI Engine Response to Different Initial Conditions via a Thermo-Kinetic Engine Model
Authors: Jahanian Omid , Jazayeri Seyed Ali
Published: July 2010

Homogenous Charge Compression Ignition (HCCI) combustion is a promising concept to reduce engine emissions and fuel consumption. In this paper, a thermo-kinetic model is developed to study the operating characteristics of a natural gas HCCI engine. The zero-dimensional single zone model consist detail chemical kinetics of natural gas oxidation including 325 reactions with 53 chemical species, and is validated with experimental results of reference works for two different engines, Volvo TD 100 and Caterpillar 3500, in 5 operating conditions. Then, the influence of parameters such as manifold temperature/pressure and equivalence ratio on in-cylinder temperature/pressure trends and start of combustion is studied. Measurements for Volvo engine show that SOC occurs 3–5 CAD earlier with every 15K increase in initial temperature. These whole results are explained in detail to describe the engine performance thoroughly.
Exhaust-Stream and In-Cylinder Measurements and Analysis of the Soot Emissions From a Common Rail Diesel Engine Using Two Fuels
Authors: Kirchen Patrick , Boulouchos Konstantinos , Obrecht Peter , Bertola Andrea
Published: July 2010

The operation and emissions of a four cylinder, passenger car common-rail diesel engine operating with two different fuels was investigated on the basis of exhaust stream and in-cylinder soot measurements, as well as a thermodynamic analysis of the combustion process. The two fuels considered were a standard diesel fuel and a synthetic diesel (fuel two) with a lower aromatic content, evaporation temperature, and cetane number than the standard diesel. The exhaust stream soot emissions, measured using an FSN system, as well as a photo-acoustic soot sensor (AVL Micro Soot Sensor), were lower with the second fuel throughout the entire engine operating map. To elucidate the cause of the reduced exhaust stream soot emissions, the in-cylinder soot temperature and KL factor (proportional to concentration) were measured using miniature, three color pyrometers mounted in the glow plug bores. Using the maximum KL factor value to quantify the soot formation process, it was seen that for all operating points, less soot was formed in the combustion chamber using the second fuel. The oxidation of the soot, however, was not strongly influenced by the fuel, as the relative oxidized soot fraction was not significantly different for the two fuels. The reduced soot formation of fuel two was attributed to the lower aromatic content of the fuel. The soot cloud temperatures for operation with the two fuels were not seen differ significantly. Similar correlations between the cylinder-out soot emissions, characterized using the pyrometers, and the exhaust stream soot emissions were seen for both fuels. The combustion process itself, was only seen to differ between the two fuels to a much lesser degree than the soot formation process. The predominant differences were seen as higher maximum fuel conversion rates during premixed combustion at several operating points, when fuel two was used. This was attributed to the lower evaporation temperatures and longer ignition delays (characterized by the lower cetane number) leading to larger premixed combustion fractions.
Study of Cavitation and Wear Damages in Conrod Big End Bearing of a Heavy Duty Diesel Engine by Using Elasto-Hydrodynamic Method
Authors: Karimaei Hadiseh , Chamani Hamidreza
Published: July 2010

Wear and cavitation erosion are the common damages in engine bearing shells. In the case of cavitation damage, the generation and immediate collapse of small gas bubbles cause high pressure pulses and the bearing surface is being locally damaged. Cavitation damage is observed in heavy duty diesel engine due to highly dynamic loading, oscillation of pins, turbulence of oil flow and other factors. Wear damage induces adjustment in the bearing geometry and affects the oil film pressure and the durability of bearing shell. In this paper, wear and cavitation damages in connecting rod big end bearing have been studied. In order to compute the bearing lubrication characteristic such as minimum oil film thickness and maximum oil film pressure, Elasto-Hydrodynamic method that incorporates mass conserving algorithm has been utilized. Wear and cavitation damages in two different designs of connecting rod structure in a heavy duty diesel engine have been assessed and the results have been presented. Furthermore, the effect of connecting rod structure on wear damage has been investigated.
Modifications to Quasi-Dimensional Burning Model of Spark Ignition Engines
Authors: Modarres Razavi M. R. , Hosseini A. , Dehnavi M.
Published: July 2010

The way in which position of spark plug affects combustion in a spark ignition engine can be analyzed by using two-zone burning model. The purpose of this paper is to extract correlations to simulate the geometric interaction between the propagating flame and the general cylindrical combustion chamber. Eight different cases were recognized. Appropriate equations to calculate the flame area (Af), the burned and the unburned volume (Vb & Vu) and the heat transfer areas related to the burned and unburned regions were derived and presented for each case using Taylor expansion in order to replace numerical solution with trigonometric algebraic functions.
Combined Experimental and Numerical Analysis of Knock in Spark Ignition Engines
Authors: Forte Claudio , Corti Enrico , Bianchi Gian Marco
Published: July 2010

A detailed analysis of knocking event can help improving engine performance and diagnosis strategies. The paper aim is a better understanding of the phenomena involved in knocking combustion through the combination of CFD and signals analysis tools. CFD simulations have been used in order to reproduce knock effect on the in-cylinder pressure trace. In fact, the in-cylinder pressure signal holds information about waves propagation and heat losses: for the sake of the diagnosis it is important to relate knock severity to knock indexes values. For this purpose, a CFD model has been implemented, able to predict the combustion evolution with respect to Spark Advance, from non-knocking up to heavy knocking condition. The CFD model validation phase is crucial for a correct representation of both regular and knocking combustions: the operation has been carried out by means of an accurate statistical analysis of experimental in-cylinder pressure data. The simulation results allow relating the combustion characteristics to their effect on the in-cylinder pressure signal. It is then possible to highlight critical issues regarding typical knock detection methodologies, while disclosing novel approaches. One of the main results is the validation of knock detection strategies based on the low-frequency content of the pressure signal. These strategies can be used together with standard high-frequency based techniques in order to improve the detection robustness.
Development of an Open Loop Fuzzy Logic Urea Dosage Controller for Use With an SCR Equipped HDD Engine
Authors: Ardanese Raffaello , Ardanese Michelangelo , Besch Marc C. , Adams Theodore , Thiruvengadam Arvind , Shade Benjamin C. , Gautam Mridul , Oshinuga Adewale , Miyasato Matt
Published: July 2010

Selective Catalytic Reduction (SCR) systems have been shown to be the most promising exhaust aftertreatment system for near term in-use applications to meet the stringent US 2010 oxides of nitrogen (NOx) emissions regulations of 0.2 g/bhp-hr for on-highway heavy duty diesel engines. SCR systems use the ammonia-containing compound urea, as a reducing agent. In order to control the urea dosage during transient operation of the engine, sophisticated control strategies are needed. This study discusses the development of an open loop, non-sensor based fuzzy logic urea dosage controller. The goal of the fuzzy logic based control was to achieve maximum NOx emission reduction, while limiting the amount of ammonia slip. The open loop controller was implemented on a heavy duty diesel engine equipped with a catalyzed diesel particulate filter (DPF) and a SCR system. The control system was quantified by operating the engine over different test cycles on an engine dynamometer. This study shows that the fuzzy logic approach is a simple and effective way to control NOx, as well as ammonia slip.
An Analysis of Next Cycle Control Based on Cylinder Pressure Derived Calculations
Authors: Quillen Kristopher P. , Viele Matthew
Published: July 2010

This paper examines the detailed timing requirements necessary to implement next cycle control of an internal combustion engine based on values derived from cylinder pressure. A controller consisting of two parts is presented. The first part is found in traditional combustion analysis systems. It records crank-angle resolved cylinder pressure data and reduces it to single point values such as location of peak pressure or location of 50% mass fraction burned. The second part is an engine controller capable of controlling one or more of these analysis parameters. The focus of this paper is on the execution time and latency of the data-path from the sensor to the control value with various engine configurations and calculation methods explored. Some discussion of the data acquisition to controller interface will be included with a focus on practical engine controller latencies and safety systems. An implementation of this system using commercial off the shelf (COTS) hardware and an open software platform are presented.
Experimental Investigations of Engine Durability and Lubricating Oil Properties of Jatropha Oil Blends Fuelled DI Diesel Engine
Authors: Agarwal Avinash Kumar , Dhar Atul
Published: July 2010

Current demand of transport fuel requires exploring every possible plant resource of engine fuel which can deliver satisfactory performance, emission, combustion and engine durability. Blending smaller quantity of Jatropha oil with mineral diesel is one of the simplest alternatives which can be put into application from technical and availability perspective. High viscosity of Jatropha oil (vegetable oil) comes into acceptable range upon blending with mineral diesel upto 20% (v/v). After ensuring satisfactory performance, emission and combustion characteristics, engines were subjected to long-term endurance test of 512 hour for comparing long-term performance of J5 and J10 blends vis-a`-vis mineral diesel, in the present experimental investigation. In the long-term endurance test, the effect of use of Jatropha oil blends on wear of various engine parts and lubricating vis-a`-vis mineral diesel were evaluated. The deposits on the vital engine parts were found to be slightly higher on J10 fuelled engine while it was comparable to mineral diesel for J5 fuelled engine. The piston rating carried out on the pistons of the three engines reflected that the J5 fuelled engines demonstrated reasonable long-term performance in comparison to mineral diesel fuelled engine while performance of J10 fuelled engine was slightly inferior. J5 and J10 fuelled engine’s lubricating oil shows higher reduction in lubricating oil viscosity and flash point compared to mineral diesel, thus indicating possibly higher fuel dilution. Fe, Pb, Cr, Zn wear metal debris in the lubricating oil are lower for J5 and J10 compared to mineral diesel engine’s lubricating oil however Al content in the lubricating oil is slightly higher for J5 and J10 compared to mineral diesel engine’s lubricating oil. Physical wear measurement of vital engine parts indicate relatively higher wear of liner bore, piston rings and big end bearing for J5 and J10 fuelled engine while wear of valve mounting, piston, gudgeon pin, crank pin was found to be relatively lower than mineral diesel fuelled engine. It was found that the wear of J5 engine liners is higher compared to mineral diesel fuelled engine. However wear of J10 fuelled engine liner is found to be relatively lower compared to mineral diesel fuelled engine.
Novel Design and Analysis of a Fully Decoupled 3-DOF Spherical Parallel Robot
Authors: Zhang Dan , Zhang Fan
Published: July 2010

In this paper, we propose a unique, decoupled Three Degree-of-Freedom (DOF) parallel wrist. The condition required for synthesizing a fully isotropic parallel mechanism is obtained based on the physical meaning of the row vector in the Jacobian Matrix. Specifically, an over-constrained spherical 3-DOF parallel mechanism is presented and the modified structure, which avoids the redundant constraints, is also introduced. The proposed manipulator is capable of decoupled rotational motions around the x, y and z axes and contains an output angle that is equal to the input angle. Since this device is analyzed with the Jacobian Matrix, which is constant, the mechanism is free of singularity and maintains homogenous stiffness over the entire workspace.
Measurement of Thermodiffusion Coefficient for Binary Hydrocarbon Fluid Mixtures in Porous Medium: Experimental and Numerical Results
Authors: Jaber T. J. , Bataller H. , Saghir M. Z.
Published: July 2010

There has been a discussion that the thermodiffusion in porous medium is not identical to thermodiffusion in clear liquid. To validate this finding, a new thermodiffusion cell has been designed to measure thermal and molecular diffusion coefficients of binary mixture in porous medium under high pressure. A porous layer located between two liquid layers that cross two laser beams, is used. The difference of refractive index is obtained from the analysis of the interferograms recorded with a CCD camera. From the kinetics, the values of molecular and thermal diffusion coefficients through the porous medium were determined. The two binary systems dodecane (C12) and isobutylbenzene (IBB), and dodecane (C12) and tetrahydronaphthalene (THN) are used to validate the experimental setup at atmospheric pressure. Experimental results reveal an excellent agreement with benchmark values and a good agreement with theoretical data.
Positioning Repeatability of Robotic Systems With Synchronous Belt Drives
Authors: Hosek Martin , Krishnasamy Jay , Beale Stuart
Published: July 2010

Substrate-handling robots for pick-place operations in semiconductor manufacturing applications are subject to strict substrate placement repeatability specifications. It has been observed that the placement locations at a given workstation tend to exhibit distinct clusters, each of which can be associated with another workstation accessed by the robot in the past, resulting in an undesirable increase of the overall placement repeatability range. In the present paper, this memory-like repeatability phenomenon is studied, and attributed to multistage synchronous belt drives, which are utilized to transmit motion from centralized motors to individual links and end-effectors of the robot arms. The phenomenon is investigated experimentally, and simulated using a simplified lump-parameter model. The effects of selected belt drive design parameters are examined, and the results are utilized to improve the positioning repeatability performance of a typical substrate-handling robot.
The Research of Axial Deflection and Generatrix of Metal Belt CVT
Authors: Zhang Wu , Liu Kai , Zhou Chun-Guo , Wei Yi-Duo , Wu Ning-Qiang
Published: July 2010

To reduce the metal belt’s axial deflection of the metal belt continuously variable transmission (CVT) during the working process, the value of the axial deflection has been calculated by using numerical methods. The precision of two methods to calculate the deflection has been compared. A calculating method closer to the actual situation has been attained. According to the principle of conjugate curves, and with the involute generatrix of the metal belt as example, a solution to the generatrix of the pulley conjugated with it is obtained, and the relation between the pullys generatrix curvature and the pulleys generatrix contact strength is achieved. By changing the metal belt value of the design parameters, the state subject to force between the pulley and the metal belt can be improved. So as to ensure the whole metal belt level transmit in the process of speed changes. Theoretically, the axial deflection can be eliminated completely, and the life span of the metal belt and the reliability of the transmission, as well as the performance of the metal belt CVT can be greatly improved, so as to provide the references for the CVT design.
Efficiency and Stall Margin Enhancement in Transonic Compressor Rotors Using Synthetic Jets: A Numerical Investigation
Authors: Benini Ernesto , Biollo Roberto , Ponza Rita
Published: July 2010

Several passive and active techniques were studied and developed by compressor designers with the aim of improving the aerodynamic behavior of compressor blades by reducing, or even eliminating, flow separation. Fluidic-based methods, in particular, were investigated for a long time, including both steady and unsteady suction, blowing and oscillating jets. Recently, synthetic jets (zero mass flux) have been proposed as a promising solution to reduce low momentum fluid regions inside turbomachines. Synthetic jets, with the characteristics of zero net mass flux and non-zero momentum flux, do not require a complex system of pumps and pipes. They could be very efficient because at the suction part of the cycle the low momentum fluid is sucked into the device, whereas in the blowing part a high-momentum jet accelerates it. To the authors’ knowledge, the use of synthetic jets has never been experimented in transonic compressor rotors, where this technique could be helpful (i) to reduce the thickness and instability of blade suction side boundary layer after the interaction with the shock, and (ii) to delay the arising of the low momentum region which can take place from the shock-tip clearance vortex interaction at low flow operating conditions, a flow feature which is considered harmful to rotor stability. Therefore, synthetic jets could be helpful to improve both efficiency and stall margin in transonic compressor rotors. In this paper, an accurate and validated CFD model is used to simulate the aerodynamic behavior of a transonic compressor rotor with and without synthetic jets. Four technical solutions were evaluated, different for jet position and velocity, and one was investigated in detail.
Determining the Lewis Factor for Plastic Spur Gears With Asymmetric Teeth
Authors: Moya J. L. , Machado A. S. , Becerra A. M. , Vela´zquez J. A. , Goytisolo R.
Published: July 2010

The basic weakness of plastic spur gear teeth is tooth fracture brought on by the accumulation of stress at the root of the tooth and by the geometry of the tooth. Tooth width and height play a major role in failure, as does the Lewis factor, which has a direct effect on the expression to calculate tooth strength. This study describes a theoretical analysis of a procedure to determine the Lewis factor for asymmetric teeth.
Use of Thermodynamics, Engineering Economics and Probabilistic Risk Assessment in Evaluating Climate Change Decisions
Authors: Meckler Milton , Shah Amip J.
Published: July 2010

Climate change is often considered in terms of its macroscale implications. For example, many governments and non-governmental organizations are engaged in the development of policy frameworks that could influence different societal actions and behavioral scenarios. But such macroscale policy decisions may also significantly impact the localized design of products and services in different business ecosystems. Unfortunately, products and services are generally designed only taking into account local influences. An approach that ties macroscale frameworks to localized product- or system-level design metrics is lacking. For example, the cost of upgrading the entire U.S. electrical system has been estimated to be on the order of $200 billion, and recent U.S. policy discussions in the area outline options such as “smart” grid upgrades, distributed and/or on-site renewable energy systems including solar and wind energy, infrastructural support for plug-in of electric and hybrid vehicles etc. But most existing electricity generation and thermal performance models of power generating stations or cogeneration plants fail to provide any indication of the environmental impacts associated with distributing electricity from generator to point-of-use. It is thus not intuitive how the direction of localized plant or system design should be altered given the different macro-level initiatives. This paper attempts to fill this gap by exploring a methodology that combines engineering economics, probabilistic risk assessment, and thermodynamic (2nd Law) analysis to evaluate different policy choices. Specifically, a framework that could allow quick estimation of the comparative consumption, operational power requirements, relative thermal performance and environmental footprint associated with different proposals on upgrading the grid is developed. The approach is demonstrated in the context of a representative segment of a hypothetical electrical grid distribution system located between two electric power generating stations (EPGS) facing overload as additional customer demands are projected to be integrated with renewable sources in the near-term future.
Experimental Study on Thermal Property of Alkali Treated CNT-Based Composite as Phase Change Materials
Authors: Wang Jifen , Xie Huaqing , Xin Zhong , Li Yang , Chen Lifen , Xu Na
Published: July 2010

The nanocomposites were prepared by adding the multi-walled carbon nanotubes (CNTs) to the melting palmitic acid to improve the thermal transfer property. Mechanochemical reaction was used to treat CNTs for dispersing into organic matrix easily. The treated CNTs were introduced hydoxide radical functional groups on the surfaces during ball milling with the potassium hydroxide. And they were successfully dispersed into the palmitic acid matrix without any surfactant. The resulted nanocomposites were stable and homogeneous. The thermal conductivities and latent heat capacities of these nanocomposites were measured using a transient hot wire apparatus and a differential scanning calorimetric instrument. Nanotube composites, containing a small amount of CNTs, have substantially higher thermal conductivities than the base palmitic acid matrix, with the enhancement increasing with the mass fraction of CNTs in both liquid state and solid state. While the latent heat capacities turned out a reverse with the CNT loadings.
Techniques for Teaching Communication Skills to the Millennial Generation
Authors: Bauer Candice
Published: July 2010

Techniques for teaching communication skills to engineering students of the Millennial Generation are reviewed. A detailed outline of the characteristics of the Millennial Generation are described and compared to the traits of other generations. The Millennial Generation has several distinct characteristics such as developing inclusive relationships, tolerating authority, and leading by collaboration. This contrasts with the characteristics of the Baby Boomers and Generation X (the majority of professors and the students’ parents); however, the characteristics align closely with the Traditionalist Generation (higher administration and the students’ grandparents). Strategies for working among the generations are detailed resulting in the creation of an understanding of how to teach to the Millennial Generation. In order to aid the understanding, lesson plans which focus on creating a learner-centered environment are detailed. The lesson plans include objectives, strategies, content, activities, assessment techniques, and ABET alignment. The topics include team building, effective meetings, a term project, writing skills, and speaking skills. Team building illustrates why and how a team achieves its objectives. Example activities include the development of a team charter. The effective meetings lesson plan details techniques on how to teach students project management skills. Criteria for developing term projects to match the Millennial Generation characteristics are detailed, and an example which also includes K-12 outreach activities is presented. The lesson plan for speaking and writing skills defines grading rubrics for the evaluation and assessment of technical writing and presentations. This work has been in development and implemented for nearly five years in a junior level, multidisciplinary course entitled, Engineering Communications, at the University of Nevada, Reno. The lesson plans are evaluated based on course evaluations, industry interviews, case studies, and an alumni survey.
Surface Ripple Formation Due to Solid-Liquid Slurry Erosion
Authors: Liu Juan
Published: July 2010

The development of ripples and erosion on the material surfaces in a centrifugal slurry pump was investigated in laboratory tests using a sand-water slurry pot tester. The erosion of the primary material (KmTBCr26) used in the centrifugal slurry pumps was very serious. The ripple formation was influenced by the flow conditions, the impact angle of the solid particles and the particle size. Ripple formation was also observed in laboratory tests with structural steel (#40) and brittle ceramics (Al2O3, ZTA, Si3N4). The ripple profile on the structural steel surface was similar to that on the high chrome cast iron (Cr26) used in the slurry pumps. With 90° impact angles, ripples also formed on the eroded surfaces of materials tested in the sand-water slurry pot. The ripple wavelength on the ceramic surface, which was influenced by the mechanical properties and material grain size, was less than that on the metallic surfaces.
Fluid Flow and Heat Transfer Characteristics of a Centrifugal Heat Sink
Authors: Kim Juwan , Kim Sung Jin
Published: July 2010

A novel heat sink called a centrifugal heat sink is proposed. The principle of coolant pumping in the centrifugal heat sink is similar to a centrifugal fan. The blades of a fan are arranged to be placed between the fins of the heat sink. Due to the relative structure of the blades and the fins, additional space for the blades of the fan is no longer required for the centrifugal heat sink. Consequently, the centrifugal heat sink makes efficient use of its total amount of cooling space. The shape of the blades for coolant pumping is based on the design principles of centrifugal turbomachinery. Due to the design principles, it is possible to increase the volumetric flow rate of the air through the heat sink. By the rotary motion of the blades, the coolant in the heat sink passes through channels formed by the adjacent fins. In this paper, an experimental investigation is conducted to demonstrate the concept of the centrifugal heat sink. As the speed of the fan increases, the volumetric flow rate is shown to increase proportionally. Thermal performance of the centrifugal heat sink is evaluated in terms of the thermal resistance under the constant heat flux condition. As a result, the thermal resistance of the centrifugal heat sink is shown to decrease as the rotation speed of the centrifugal heat sink increases.
Fuel-Cycle Analysis of Fuel Cells for Combined Heat, Hydrogen, and Power Generation
Authors: Han Jeongwoo , Elgowainy Amgad , Wang Michael
Published: July 2010

The fuel-cycle energy use and greenhouse gas (GHG) emissions associated with the application of fuel cells to combined heat and power (CHP) generation and combined heat, hydrogen, and power (CHHP) generation are evaluated and compared with the combustion technologies of internal combustion engines and microturbines, as well as with the various technologies associated with hydrogen production and grid-electricity generation in the United States. Two types of fuel cells are considered in this analysis: a phosphoric acid fuel cell (PAFC) capable of following either heat or electric load and a molten carbonate fuel cell (MCFC) that typically follows the electric load. Three types of facilities (hospital, large office building, and warehouse) are examined in two different climatic regions (Chicago and Los Angeles) to span a wide range of electric-to-heat load ratios. Two different approaches for fuel cycle analysis of CHP and CHHP applications are considered in this analysis: a total demand approach and a displacement approach. The total demand approach provides an accurate assessment of the impact of actual demand on total energy use and GHG emissions, while the displacement approach projects the potential for more energy savings and GHG emissions benefits relative to the supply of electricity from the grid generation mix. The fuel cycle results are primarily impacted by the efficiencies of hydrogen production and electric power generation, as well as by the utility factor of the co-produced heat. The energy use and GHG emissions associated with the electric power generation represent the majority of the fuel-cycle’s total energy use and emissions for all pathways. More energy and GHG emissions benefits are realized from fuel cell technologies with increased use of available coproduced heat. In general, CHHP systems exhibit more energy and GHG emission benefits than CHP systems for any of the investigated fuel cell technologies.
Free Vibration of the Triple-Walled Carbon Nanotubes
Authors: Pentaras Demetris , Elishakoff Isaac
Published: July 2010

Natural frequencies of the triple-walled carbon nanotubes (TWCNTs) are determined both exactly and approximately. For the case of TWCNT which is simply supported at it ends closed-form solutions are obtained. It is shown that there are three series of natural frequencies corresponding to the cubic polynomial equation for natural frequency squares. For the TWCNT that has other boundary conditions approximate Bubnov-Galerkin and Petrov-Galerkin methods are applied. Simple polynomial coordinate functions are utilized. Each of these methods yields three natural frequencies corresponding to the lower and of each frequency spectra.
Aerodynamics of a Badminton Shuttlecock
Authors: Post S. L. , McLachlan Jordan , Lonas Travis , Dancs Justin , Knobloch Daniel , Darrow Chris , Sinn Eric , Davis Sara , Neilly Dean , Funk Aaron , Golz James , Phelps Andrew , Goers Bradley
Published: July 2010

This paper presents a class project that can be performed in a junior-level fluid mechanics course. Students gain experience in design and conducting experiments, and in reviewing the relevant technical literature. Experiments were conducted to determine the drag coefficient of a badminton shuttlecock. Two types of testing were conducted: wind tunnel tests of a full-scale model, and drop tests using a high-accuracy radar gun. The drag coefficients calculated from these measurements were then compared to the limited data available in the literature. The range of drag coefficients measured was from 0.55 to 0.65.
Comparison of Pressure Drop and Endwall Heat Transfer Measurements to Flow Visualization Testing of Solid and Porous Pin Fin Arrays
Authors: Pent Jared M. , Kapat Jay S. , Ricklick Mark
Published: July 2010

This paper examines the local and averaged endwall heat transfer effects of a staggered array of porous aluminum pin fins with a channel blockage ratio (blocked channel area divided by open channel area) of 50%. Two sets of pins were used with pore densities of 0 (solid) and 10 pores per inch (PPI). The pressure drop through the channel was also determined for several flow rates using each set of pins. Local heat transfer coefficients on the endwall were measured using Thermochromatic Liquid Crystal (TLC) sheets recorded with a charge-coupled device (CCD) camera. Static and total pressure measurements were taken at the entrance and exit of the test section to determine the overall pressure drop through the channel and explain the heat transfer trends through the channel. The heat transfer and pressure data was then compared to flow visualization tests that were run using a fog generator. Results are presented for the two sets of pins with Reynolds numbers between 25000 and 130000. Local HTC (heat transfer coefficient) profiles as well as spanwise and streamwise averaged HTC plots are displayed for both pin arrays. The thermal performance was calculated for each pin set and Reynolds number. All experiments were carried out in a channel with an X/D of 1.72, a Y/D of 2.0, and a Z/D of 1.72.
Dynamics of a Cantilever Electrode Beam on a Vibrating Base
Authors: Pasic H. , Alam K. , Garg D.
Published: July 2010

Vibration of a simple uniform Bernoulli-Euler cantilever beam attached to a rigid base vibrating in a direction perpendicular to the beam is studied both analytically and experimentally. The objective is to study electrode deflection in electrostatic precipitators, with emphasis on the interaction of the vibrating electrode with the ambient fluid. The analytical solution can be used to find reliable estimates of the maximum vibration amplitude of the electrodes, which is a primary cause of detrimental sparking of the electrodes. An experimental system was built to validate the analytical results and to investigate the importance of the beam interaction with the ambient air/fluid medium — which is often overlooked in most of the existing analytical models. The results demonstrate that the drag effect of the ambient air can change the characteristics of the vibration significantly, thereby limiting the applicability of the analytical or numerical results.
Conjugate Heat Transfer Enhancement of an Internal Blade Pin-Finned Tip-Wall
Authors: Xie Gongnan , Sunde´n Bengt
Published: July 2010

To improve gas turbine performance, the operating temperature has been increased continuously. However, the heat transferred to the turbine blade is substantially increased as the turbine inlet temperature is increased. Cooling methods are therefore needed for the turbine blades to ensure a long durability and safe operation. The blade tip region is exposed to the hot gas flow and is difficult to cool. A common way to cool the tip is to use serpentine passages with 180-deg turn under the blade tip-cap taking advantage of the three-dimensional turning effect and impingement. Increasing internal convective cooling is therefore required to increase the blade tip life. In this paper, augmented heat transfer of a blade tip with internal pin-fins has been investigated numerically using a conjugate heat transfer approach. The computational model consists of a two-pass channel with 180-deg turn and an array of pin-fins mounted on the tip-cap. The computational domain includes the fluid region and the solid pins as well as the solid tip regions. Turbulent convective heat transfer between the fluid and pins, and heat conduction within pins and tip are simultaneously computed. The inlet Reynolds numbers are ranging from 100,000 to 600,000. Details of the 3D fluid flow and heat transfer over the tip surface are presented. A comparison of the overall performance of the two models is presented. It is found that due to the combination of turning impingement and pin-fin cross flow, the heat transfer coefficient of the pin-finned tip is a factor of about 3.0 higher than that of a smooth tip. This augmentation is achieved at the cost of a pressure drop penalty of about 7%. With the conjugate heat transfer method, not only the simulated model is close to the experimental model, but also the distribution of the external tip heat transfer can be relevant for thermal design of turbine blade tips.
Optofluidic Storage
Authors: Cordovez Bernardo , Erickson David
Published: July 2010

Optical storage capacity in devices such as DVDs is fundamentally restricted by the diffraction limit of light. We present an optofluidic approach which exploits nanofluidic manipulation of quantum dot cocktails to achieve spectrally multiplexed data storage in a traditional planar format. Quantum dot cocktails are delivered to the vicinity of a nanowell through pressure driven flow and are subsequently trapped and stored electrokinetically. Once in the nanowells, they are excited with a blue light source and their discrete spectrographic signal is captured through a fiber spectrometer. Data erasure is performed by reversing the polarity of the applied electrical field which ejects the nanocrystals. We also extend this analysis for microwell traps which could find use in visual display applications, as well as present a method by which the fluorescent signal can be controlled and retained over various timescales.
Fluid Dynamically Driven Assembly in Three Dimensions for Programmable Matter
Authors: Kalontarov Michael , Krishnan Mekala , Erickson David
Published: July 2010

In this work we describe our development of fluidic assembly of 3D blocks as an approach to achieving programmable matter. Devices made of this matter are assembled from small building blocks, and their shape and function can be reconfigured on demand. In our implementation of such a system small building blocks are assembled in parallel to create a target structure using fluid forces in a chamber. The building blocks are centimeter-scale cubes and are attracted to sinks within an assembly chamber. In effort to investigate the behavior of these blocks with respect to the sink numerical simulations and experiments were carried out. The simulation results indicated that blocks which align with the gravity field (due to an unbalanced mass distribution) are better suited for proper alignment during assembly. Experiments have shown that blocks can be attracted to an assembly site in a robust and timely manner. Blocks with the ability to interact geometrically have been experimentally tested and the assembly and rejection of a block at a given location has been demonstrated. Finally, several methods of making block assembly more repeatable have been proposed.
Cantilever Dynamics With Attractive and Repulsive Tip Interactions
Authors: Chakraborty Ishita , Balachandran Balakumar
Published: July 2010

In tapping mode atomic force microscopy (AFM) operations, typically, a micro-scale cantilever undergoes long-range attractive and short-range repulsive forces as it approaches the surface. Due to the strong nonlinearity of the tip-sample interaction forces, a variety of nonlinear phenomena has been observed. In order to obtain a better understanding of such phenomena, in this work, a macro-scale experimental system is constructed with attractive and repulsive tip interactions. Magnetic forces are used to generate the attractive forces, and impact with a compliant surface is used to produce the repulsive forces. A reduced-order model for this system has been developed with Derjaguin-Muller-Toporov (DMT) contact mechanics. In prior work conducted in the group, period-doubling bifurcations have been observed close to near grazing conditions when AFM cantilevers are operated between first and second natural frequencies of the system. This phenomenon is further explored in this article.
Drill-String Dynamics: Reduced-Order Models
Authors: Liao Chien-Min , Balachandran Balakumar , Karkoub Mansour
Published: July 2010

Research efforts are underway to model and study the dynamics of a drill string, and preliminary results are presented in this work. The dynamics of a drill string system has non-smooth characteristics. Moreover, the drill string system dynamics exhibits qualitative changes with respect to the rotation speed of the drill string and friction coefficients associated with the contact between the drill string and the outer shell and the drill string and the well bottom. The coupling between torsion, lateral, and axial vibrations and the nonlinear interactions between them need to be investigated to better understand the dynamic behavior of the drill string system. As a preliminary step towards understanding the dynamics of the drill string, four-degree-of-freedom models are developed for the system by using two rotating sections: an inner stator that can undergo radial displacements and an outer rotor. Stickslip interactions between the drill string and the outer shell are also considered in the model development. Two sets of differential equations are obtained for the system by using displacements and momenta as system states in one model and displacements and velocities as system states in another model. For different values of friction coefficients, rotation speeds, and rotation torques, the results obtained by using the developed models are presented, discussed, and compared with experimental results.
Vibration Control of Structures Taking Power Assisted Conveyance Into Account
Authors: Hara Susumu , Yamada Yoji , Ito Koji , Morita Yoshifumi
Published: July 2010

In order to reduce physical burden of workers on conveying and mounting works in industries, power assist devices have been introduced. In many conventional power assist devices, controlled objects are assumed as rigid bodies. The vibration control technique for handling flexible structures has not been fully addressed yet. This paper presents an effective vibration control method for conveying mechanical structures with power assist. In this study, the power assist is realized by an impedance control method. If the impedance characteristics of the power assisted object are perfectly controlled by the impedance control, the impedance characteristics are known and correspond to the dynamic characteristics of the disturbance for the vibration control. Then, this study adopts the disturbance accommodated LQ optimal control method for the vibration control problem. A cart with a one-degree-of-freedom vibration system is selected as a controlled object example. The effectiveness of the proposed method is verified by simulations.