bluuebunny/crossref_metadata_2025 huggingface dataset:
Twin Inclined Circular Jets Evolution Through a Cool Crossflow
Authors: Radhouane Amina , Mahjoub Sai¨d Nejla , Mhiri Hatem , Lepalec George , Bournot Philippe
Published: June 2009

The aim of this paper is to examine experimentally as well as numerically the flowfield resulting from the interaction between a twin circular inclined hot jets emerging into a cooling crossflow. The resulting flowfield is quite complex due to the presence of different vortical structures including the kidney vortex, the horse-shoe vortex, etc... The evolution of the twin inclined jets through the crossflow could be depicted by tracking the mean-flow velocity field and its associated turbulence statistics by means of the PIV technique. This evolution can be influenced by many factors. Herein, we will deal with that resulted by the injection nozzles’ inclination and the jets’ spacing. Then, we performed a three dimensional sample of the studied configuration in order to simulate the evolution of the resulting flowfield. For that, the Navier Stokes equations were simulated with an RSM second order turbulent closure model. Then a non uniform meshing was applied. A good agreement was obtained between the experimental data and the numerical modeling. After validation we could represent in addition to the available results, the temperature distribution and the effects the variation of the injection inclination and that of the jets’ spacing bring on it (on its spatial evolution).
Two-Phase Flow Characteristics in a Co-Flow Induced Microchannel With Microbubbles Generation
Authors: Yeom Sujin , Lee Seung S. , Lee Sang Yong
Published: June 2009

This paper presents a micro-fluidic device which generates micro-bubbles, ranging from 70μm to 160μm in diameter, and two-phase flow characteristics in the device were tested. The device is composed of three sub-channels: a centered gas channel (10μm×50μm) and two liquid channels (both with 85μm×50μm) on each side of the gas channel. Micro-bubbles are generated by co-flow of gas and liquid at the exit of the gas channel when the drag force becomes larger than the surface tension force as bubbles grow. Methanol and a gas mixture of CO2 and N2 were used as the working fluid. Since the flow rate of gas was very small, the gas momentum effect was considered negligible. Thus, in the present case, the controlling parameters were the liquid superficial velocity and the inlet pressure of the gas. A high speed camera was used to record two-phase flow patterns and micro-bubbles of the device. To confine the ranges of the micro-bubbles generation, two-phase flow patterns in the device is observed at first. Four different flow patterns were observed: annular, annular-slug, slug, and bubbly flow. In bubbly flows, uniform-sized micro-bubbles were generated, and the operating ranges of the liquid superficial velocity and the gas pressure were below 0.132 m/s and 0.7 bar, respectively. Diameters of the micro-bubbles appeared smaller with the higher superficial liquid velocity and/or with a lower gas pressure. Experimental results showed that, with the gas pressure lower than a certain level, the sizes of micro-bubbles were almost insensitive to the gas pressure. In such a ranges, the micro-bubble diameters could be estimated from a drag coefficient correlation, CDw = 31330/Re3, which is different from the correlations for macro-channels due to a larger wall effect with the micro-channels. In the latter part of the paper, as a potential of application of the micro-bubble generator to gas analysis, dissolution behavior of the gas components into the liquid flow was examined. The result shows that the micro-bubble generator can be adopted as a component of miniaturized gas analyzers if a proper improvement could be made in controlling the bubble sizes effectively.
A Mean-Field Lattice Boltzmann Model for Electrokinetic Slip Flow
Authors: Fu Xu , Li Baoming , Zhang Junfeng , Tian Fuzhi , Kwok Daniel Y.
Published: June 2009

Traditional computational fluid dynamics does not normally consider surface energetic effect on fluid flow in microchannels. Even if it does, the effect is usually translated into an arbitrary selected slip boundary condition in solving the Navier-Stokes equation. Moreover, this treatment has neglected another important phenomenon: electrokinetics. In this paper, we consider both effects of electrokinetics and surface energetics on fluid flow in microfluidics which are normally considered independently.
Compressibility and Rarefaction Effect on Heat Transfer in Rough Microchannels
Authors: Croce Giulio , D’Agaro Paola
Published: June 2009

High pressure drop and high length to hydraulic diameter ratios yield significant compressibility effects in microchannel flows, which compete with rarefaction phenomena at the smaller scale. In such regimes, flow field and temperature field are no longer decoupled. In presence of significant heat transfer, and combined with the effect of viscous dissipation, this yields to a quite complex thermo-fluid dynamic problem. A finite volume compressible solver, including generalized Maxwell slip flow and temperature jump boundary conditions suitable for arbitrary geometries, is adopted. Roughness geometry is modeled as a series of triangular shaped obstructions, and relative roughness from 0% to 2.65% were considered. The chosen geometry allows for direct comparison with pressure drop computations carried out, in a previous paper, under adiabatic conditions. A wide range of Mach number is considered, from nearly incompressible to chocked flow conditions. Flow conditions with Reynolds number up to around 300 were computed. The outlet Knudsen number corresponding to the chosen range of Mach and Reynolds number ranges from very low value to around 0.05, and the competing effects of rarefaction, compressibility and roughness are investigated in detail. Compressibility is found to be the most dominant effect at high Mach number, yielding even inversion of heat flux, while roughness has a strong effect in the case of rarefied flow. Furthermore, the mutual interaction between heat transfer and pressure drop is highlighted, comparing Poiseuille number values for both cooled and heated flows with previous adiabatic computations.
Gate-Controlled Microfluidic Chamber With Magnetic Bead for DNA Sequencing-by-Synthesis Technology
Authors: Esfandyarpour Hesaam , Davis Ronald W.
Published: June 2009

In this paper we present a novel microfluidic platform for DNA sequencing-by-synthesis methods (e.g. pyrosequencing). The proposed platform is based on the valve-controllable PDMS channel technology with DNA-coated magnetic beads. The encapsulation of the reaction of DNA polymerization in picoliter-sized wells provides for excellent isolation and control for detection. This separation prevents cross-talk amongst neighbor reactors which is one of the most limitations for higher integration of the current technologies. Through application of an external magnetic field the beads can be allocated with better accuracy. In addition this property can help mixing for the reaction. The proposed system is useful for a number of other bio-species detection and sorting templates. This paper illustrates the design and experimental results of a primary template as well as different advantages and potential applications of the Gate-Controlled Magnetic Bead (GCMB) platform in the world of DNA sequencing and genetics.
Experimental Study on Fundamental-Microscopic Mechanism of Boiling by Using MEMS Technique: Examination From Aspect of Time Series Chaos Analysis
Authors: Sato Takato , Koizumi Yasuo , Ohtake Hiroyasu
Published: June 2009

Pool nucleate boiling heat transfer experiments were performed for water by using well-controlled and -defined heat transfer surfaces. The cavities were formed on a mirror-finished silicon plate by utilizing Micro-Electro Mechanical Systems (MEMS) technology. Those had the exactly same cylindrical shape; 10μm in diameter and 40 μm in depth, respectively. The back side of the silicon heat transfer surface was heated by applying a Laser beam. The back side surface temperature was measured with a radiation thermometer. Bubble behavior was recorded with a high speed video camera. In the single cavity case, the reconstructed return maps from the time series data of the bubble diameter exhibited strong correlation even if the delay time was increased until 0.166 ms. It was suggested that the bubble diameter from the single cavity can be predicted deterministically over long time period. In the triple cavity case, when the cavity spacing was narrow, the bubbles frequently coalesce to the bubbles generating from neighboring cavities. When the cavity spacing became wide, the bubbles coalescence was suppressed. The reconstructed return maps of the bubble diameter indicated that when the cavity spacings ≤ 3 mm, the bubble diameter after a few m seconds could not be predicted. This loss of the predictability for the bubble diameter was caused by the interaction/coalescence from the neighboring cavities. The three-dimensional reconstructed attractors of the surface temperature of the cavity position were examined. The attractors of the single cavity case and the triple cavities with S = 4 mm case were quite similar and like a ball. This suggested that when S ≥ 4 mm, the interaction between cavities disappeared and the chaotic complexity might not appear in the surface temperature variation. When S = 1 ∼ 3 mm, the attractors were conical and the chaotic complexity might exist.
Effect of Inlet Geometry on Adiabatic Gas-Liquid Two-Phase Flow in a Microchannel
Authors: Ide Hideo , Kimura Ryuji , Kawaji Masahiro
Published: June 2009

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in a circular microchannel of 100 μm diameter. By cross correlating the signals from two pairs of optical fibers and infrared photodiodes, void fraction and the lengths and velocities of gas slugs and liquid slugs were measured. The data were obtained using a T-junction with the same internal diameter as the microchannel but the lengths of the gas and liquid injection lines between the T-junction and flow control valves were quite different. The presence of a large compressible gas volume upstream of the T-junction had a significant effect on the two-phase flow characteristics in the microchannel, typified by the void fraction data. The two-phase flow characteristics in the absence of a compressible gas volume were analysed to obtain the liquid slug length and velocity data. The liquid slug velocity was found to be dependent on the slug length, since longer slugs experienced greater friction effects and moved with much slower velocities than the shorter liquid slugs.
Toward Integrated Plasmonics for Biosensing
Authors: Lin Chii-Wann , Chiu Nan-Fu , Huang Jhen-Gang , Lee Chih-Kung
Published: June 2009

Nano/microtechnologies have been used to fabricate several novel surface plasmon resonant (SPR) devices for the applications in biomolecular sensing. Bioplasmonics have been used to describe the use of biomolecules as a part of the plasmon oscillating system to actively interact with nano/micro structure. We have reported a novel design of alternative dielectric layers to enhance the SPR signal quality and modulate its resonant position. Admittance loci method of thin film design has been used in the design of such a device. The revisit of Maxwell equations also leads to the development of a novel SPR device, which is based on the lateral propagation of surface plasmon wave along the metal-dielectric surface. For the realization of a hand-held SPR system, we have also developed three SPR waveguide sensors. A lateral flow microfluidic channel based on nitrocellulose membrane has been integrated with SPR waveguide sensor and achieved dynamic detection. An integrated SPR device, which couples OLED light source with nano grating structure and top sensing layer, has been tested and found anglar dependence emission. The extended applications of these fundamental principles and novel devices, especially for drug screening and disease diagnosis will be discussed during presentation.
The Aqueous Solutions With Nonlinear Surface Energy and Their Application to Flow Boiling in a Mini/Micro Tube
Authors: Ono Naoki , Yoshida Takahiro , Shoji Masahiro , Nishiguchi Shotaro
Published: June 2009

The temperature dependency of surface tension of aqueous solutions of some alcohol such as butanol and pentanol behaves in a nonlinear manner. Namely, the value of surface tension increases from some temperature when the solution is heated. Since this was discovered about 30 years ago, several experimental studies were done about the liquid motion focusing on the difference from the normal fluids. At the same time several ideas have been attempted in the application to heat pipes and so on to promote the heat transfer. The direction of thermocapillary force in liquid film of the nonlinear solution on a heated surface acts in the same direction to solute Marangoni force. This characteristic will be much marked in small scale systems such as mini/micro channels. In this talk the author surveys the research about the special aqueous solutions and their applications until now. Moreover, the author will report the new measurement results about the nonlinearity of the temperature dependency of the surface tension of the solutions. Also the author will present the result of flow boiling and the liquid motion when the nonlinear aqueous solution was used as test fluid for mini channel of 1 mm ID. The mini/micro channel was a single quartz tube with thin film heater coated on its outer surface. When the channel was mini channel of 1 mm ID, the dryout position was not much different from the case when pure water was used as test fluid. But the liquid motion was much different. The experiments when the channel was smaller micro channel (for example, 500 μm ID), are being done in the authors’ laboratory. Moreover, the author is also doing the experiments about the boiling heat transfer in regard to the increase of CHF when the nonlinear solution was used as test fluid.
The Cardiovascular Microenvironment
Authors: Reinhart-King Cynthia A. , Fujiwara Keigi , King Michael R.
Published: June 2009

Endothelial cell response to the complex hemodynamic environment of the circulatory system is critical to the pathophysiological regulation of the cardiovascular system; however the mechanism by which this mechanical signal is transduced remains poorly understood. Recent in vivo evidence suggests that cells are capable of responding locally to shear stress, on the length scale of a single cell. Because of the complexity of the in vivo environment, we have designed and characterized an in vitro microchannel chamber with well-defined rheological conditions. This system is being used to investigate endothelial cell signaling response to shear stress, thereby bridging the gap between in vivo and in vitro observations.
Numerical Study on the Formation of Taylor Bubbles in Capillary Tubes
Authors: Chen Yuming , Kulenovic Rudi , Mertz Rainer
Published: June 2009

Numerical simulations have been carried out for the transient formation of Taylor bubbles in a nozzle/tube co-flow arrangement by solving the unsteady, incompressible Navier-Stokes equations. A level set method was used to track the two-phase interface. The calculated bubble size, shape, liquid film thickness, bubble length, drift velocity, pressure drop and flow fields of Taylor flow agree well with the literature data. For a given nozzle/tube configuration, the Taylor bubble formation is found to be mainly dependent on the relative magnitude of gas and liquid superficial velocity. However, even under the same liquid and gas superficial velocities, the change of nozzle geometry alone can lead to a big change in the size of Taylor bubbles and the pressure drop behavior inside a given capillary. This indicates that the widely used flow pattern map presented in terms of liquid and gas superficial velocities is not unique.
Comparative Analysis of Microchannel Cooling Schemes Subject to a Pressure Constraint
Authors: Farnam Dylan , Sammakia Bahgat , Ackler Harold , Ghose Kanad
Published: June 2009

Leakage losses and overall increased power dissipation in the microprocessor are causing significant thermal, mechanical, and reliability problems. Aside from the issue of cooling chip hot spots in order to reduce stress-inducing thermal gradients, the traditional challenge of quelling overall operating temperatures remains. Conventional cooling methods are reaching their practical limits and new methods of lowering the operating temperature of microprocessors are being explored. Microfluidics-based cooling schemes are one approach being considered. Implementation of microchannels for forced convection at the chip level shows much promise, as the effective heat transfer surface area and attainable heat transfer coefficient are very favorable. A major design limitation to such an implementation is the pressure developed with such micro-flows, and the stresses that could result. In this study, multiple discrete microchannel configurations are analyzed computationally and compared in a cooling capability optimization sense, while total pressure drop across the flows is carefully considered. A single cooling channel over an energy source is split into two smaller channels, and so on, while total pressure drop is maintained constant, and specified such that all flows remain in the laminar regime. It is shown that for the configurations analyzed, there exists a definitive optimum cooling scheme. In addition, the effects of variation of channel height for the initially-determined optimum scheme are studied. It is shown that a slimmer design may be implemented with very little effect on cooling capability.
Synthesis and Chemical Functionalization of Ferromagnetic Nanoparticles to Manipulate Stem Cells Using External Magnetic Fields
Authors: Me´ndez-Rojas Miguel A. , Cravioto Guzman Claudia , Arias-Carrion Oscar
Published: June 2009

The human brain is able to respond to several situations that promotes neural survivance, growth and neuronal cells regeneration. The potential of stem cells from the subventricular zone to be used for neuronal cell substitution has been widely studied. However, migration of endogen or transplanted cells is random, not efficient and with a very low survivance rate. The use of ferromagnetic nanoparticles may be of interest to guide the stem cells to the desired site using external fields. In this project, we have synthesized ferromagnetic nanoparticles (magnetite) with an average diameter of 10–12 nm, and functionalized with folic acid-flourosceine (with an average yield of 60–70%) in order to induce their entry into rat neuronal precursor cells in vivo and in vitro. The efficiency of cellular incorporation was low in vitro, observing clustering of the nanoparticles at the cytoplasm membrane. During the in vivo tests, no incorporation of nanoparticles was detected. Several results and perspectives are discussed in this work.
Bulk Micromachining of High Index Silicon Wafers and Possible Applications in Microchannels and Diffractive Elements
Authors: Calleja-Arriaga W. , Zu´n˜iga-Islas C. , Rosales-Quintero P. , De la Hidalga-Wade J. , Reyes-Betanzo C. , Torres-Jacome A. , Linares-Aranda M.
Published: June 2009

In this silicon bulk micromachining project we are evaluating new approaches to develop well-controlled 3-D microstructures for microfluidics and diffractive elements. Several approaches have been fabricated and reported using rectangular structures on (0 0 1) and (0 1 1) silicon wafers. In this work, n-type, 2–5 ohm-cm, two inch, 300 μ-thick, high index (1 1 3), (1 1 4), ( 5 5 12), (0 1 1) silicon wafers were used, which were produced from [1 1 2] ingots. Most micromachined structures compatible in Microsystems are fabricated on (0 0 1) and (0 1 1) wafers and rarely using high index wafers. Several sophisticated microstructures maybe fulfilled by using this kind of substrates with different crystallographic orientations. In our experimental work, the etching pattern was designed including several polygon-like structures to analyze the resulting morphology and crystallographic planes developed during a long-time etching. One of them, an array of 10 squared structures is arranged as follows: the first square is aligned parallel/perpendicular to the (0 1 1) main flat and then the next squares were slanted ranging from 5° till 45° in 5° steps. We have developed an experimental set using different KOH-H2O dilution at 60°C. All the experimental procedure was developed at the same time on (0 0 1) and (0 1 1) silicon wafers, which were used as control samples. Our etching mask containing several polygon-like structures was transferred parallel to the main (0 1 1) flat of the low and high index wafers. We are reporting the etching of several structures, watching the roughness evolution of the walls and bottom surfaces, with the main purpose of developing microstructures for microfluidics and integrated optics applications. In this way we have observed a couple of interesting structures whose very smooth walls could be used to develop a very simple fabrication procedure of blazed diffraction gratings for infrared applications.
Liquid Crystal Thermography Studies in Pool Boiling in Water at Subatmospheric Pressures
Authors: Talari Kiran , Kumar Ranganathan
Published: June 2009

An experimental nucleate pool boiling study in water is presented for a range of constant heat flux (q") operated at three different system pressures (P∞). Experiments were run at 6.2kPa, 7.0kPa and 8.0kPa with a constant heat flux varying from 1.88kW/m2 to 4.55kW/m2. The growth of vapor bubbles has been analyzed from inception to lift–off from an electrically heated 0.05 mm thick horizontal Fecralloy surface. Liquid crystal thermography, a non-intrusive technique, is used for the determination of surface temperature distributions. This technique offers some advantages, including ease of handling, reasonable accuracy, and spatial resolution of the temperature field. The color image processing is used to obtain quantitative temperature information from the TLC images captured with a reasonable accuracy and resolution. Boiling parameters like bubble size, contact and the frequency are determined. The bubble cycle with a neck formation is observed at the lowest investigated pressures 6.2kPa and 7.0kPa with a constant heat flux of 1.88kW/m2. From the corresponding TLC images it is clearly seen that a dry spot caused by evaporation of microlayer forms beneath the vapor bubble during its growth. An increase in either the heat flux or the system pressure results in a decrease in the size of the bubble and an increase in bubble frequency.
3-D Numerical Simulation of Contact Angle Hysteresis for Slug Flow in Microchannel
Authors: Fang Chen , Hidrovo Carlos , Wang Fumin , Steinbrenner Julie , Lee Eonsoo , Kim Dongrip , Goodson Kenneth
Published: June 2009

Water management that ensures the effective removal of produced water in the microchannel at the cathode is critical for the performance of PEM fuel cells. The small dimension and confined space of channels leads to the importance of the surface force in determining the dynamics of inside liquid slugs. The present study focuses on the simulation of the slug detachment process in the micro-channel, using a contact angle hysteresis model within the framework of VOF approach. Based on solving the nonlinear equations accounting for the relationship among volume fraction, interface position, and contact angle, a special model is developed to replicate the hysteresis effect. In addition, a special algorithm is introduced to simulate the thin liquid/gas films. A systematic comparison between experiment and simulation has been conducted and the quantitative match in terms of slug dimensions is achieved for a wide range of flow conditions. The simulation reveals that the contact angle distribution along the slug profile could be approximated using piecewise linear function. The calculation also shows that the contact angle hysteresis might be responsible for several phenomena observed in experiment, such as slug instability.
Two Phase Boiling and Flow Instabilities in a Microchannel
Authors: Barber Jacqueline , Sefiane K. , Brutin D. , Tadrist L.
Published: June 2009

Boiling in microchannels is a very efficient mode of heat transfer. High heat and mass transfer coefficients are achieved. Evaporation of the liquid meniscus is the main contributor to the high heat fluxes achieved due to phase change at thin liquid films in a microchannel. The microscale hydrodynamic motion and the mechanisms at the immediate vicinity of the moving contact line are still not fully comprehended. There are several flow instabilities during boiling in microchannels. These instabilities need to be well understood and predicted due to their adverse effects on the heat transfer. It is hoped to understand particular flow instabilities, such as flow reversal, through experimental research at the contact line. A simultaneous visualisation and measurement experiment was carried out to investigate these flow instabilities in microchannels. Boiling has been induced in a microchannel (dh 570 μm), stabilising just one liquid-vapour interface, and observing its progression through various microchannel geometries. Images and video sequences have been achieved with both a high speed camera and an infra red camera. Analysis of these images allow the application of several existing models to be fitted to our flow instability observations, namely flow reversal and its possible mechanism of vapour recoil, at the moving contact line.
Heat Transfer Model for Condensation in Non-Circular Microchannels
Authors: Agarwal Akhil , Bandhauer Todd M. , Garimella Srinivas
Published: June 2009

A model for predicting heat transfer during condensation of refrigerant R134a in horizontal noncircular microchannels is presented. The thermal amplification technique developed and reported in earlier work by the authors is used to measure condensation heat transfer coefficients for six non-circular microchannels (0.424 < Dh < 0.839 mm) of different shapes over the mass flux range 150 < G < 750 kg/m2-s. The channels included barrel-shaped, N-shaped, rectangular, square, and triangular extruded tubes, and a channel with a W-shaped corrugated insert that yielded triangular microchannels. Results from previous work by the authors on condensation flow mechanisms in microchannel geometries were used to interpret the results based on the applicable flow regimes. The effect of tube shape was also considered in deciding the applicable flow regime. A modified version of the annular flow based heat transfer model proposed recently by the authors for circular microchannels, with the required shear stress being calculated from a noncircular microchannel pressure drop model also reported earlier was found to best correlate the present data for square, rectangular and barrel-shaped microchannels. For the other microchannel shapes with sharp acute-angle corners, a mist flow based model from the literature on larger tubes was found to suffice for the prediction of the heat transfer data. These models predict the data significantly better than the other available correlations in the literature.
Diffusion Controlled, Water-Powered Microactuator for Biomedical and Microfluidic Applications
Authors: Divetia Asheesh , Kuppermann Baruch D. , Li Guann-Pyng , Bachman Mark
Published: June 2009

Current and advanced microfluidic and implantable biomedical devices present an increasing need for controlled mechanical actuation at the micro-scale, without the use of batteries or external power. Implantable applications such as drug delivery microdevices require long term, battery free operation to perform their operation over the course of many months or years. In this paper, we present a micro-electro-mechanical systems (MEMS) microactuator which is water-powered and does not require any external power or control for its operation. Furthermore, we have demonstrated that by controlling the diffusion of water through a lithographically defined semi-permeable membrane, we can control the rate of this mechanical actuation. The microactuator uses a water-swellable polymer as the working agent and a thin membrane of PDMS (polydimethylsiloxane) as the semi-permeable membrane to allow selective diffusion of water into the actuator. The swelling of the polymer upon contact with water and the resulting pressure generated is used as the actuation mechanism. Self-powered microactuators that use this technology can be important for many microfluidic and biomedical applications such as pulsatile drug delivery.
Measurement and Analysis of Acela Express Regenerative Power Recovery
Authors: Yu J. G. , Ercolino Matthew B.
Published: June 2009

Amtrak launched the first high-speed Acela Express passenger train service in the USA in 2000 on the Northeast Corridor (NEC) between Washington, D.C, New York, and Boston. The NEC infrastructure is used by several other railroad/transit agencies that operate commuter train services under operating access agreements with Amtrak. With such an arrangement, all NEC passenger railroad/transit agencies contribute to the electrical demands of the traction power system on the southern division and in particular, between New York, and Washington, D.C. Amtrak and the other railroad/transit agencies conduct periodic reviews of the cost-sharing arrangements for the electricity bills. As part of a recent review, accurate data on the power usage by the Acela Express fleet was needed. The Acela Express power cars are equipped with modern traction drives with controls that are capable of recovering some or all of the regenerative braking power they produce. The use of regenerative braking is automatically controlled by the onboard Braking Control Computer via the internal propulsion and braking network. This feature makes the Acela Express trains efficient in energy consumption and affects the cost allocation to Amtrak. The extent of the energy recovery is dependent on how receptive the traction power system is when power is being regenerated from braking. In order to obtain realistic data, two separate Acela Express power cars were instrumented. A large amount of data was collected in normal service conditions from the onboard instrumentation. This paper describes the instrumentation and the data collection procedure, and presents the analysis results of the collected data. The analyses were focused on two parameters: the “energy recovery ratio” and the “system receptivity” of the traction power supply system. The study contributed to the successful conclusion of a new electrical cost-sharing arrangement among the NEC passenger railroad/transit agencies, which was made public in October 2006.
Radial Ultrasonic Testing of Freight Car Axles
Authors: Lonsdale Cameron P. , Tusa Brian T. , Dedmon Steven L.
Published: June 2009

North American freight car axles are one of the most robust mechanical components in railway service. Axles can be in service for many years (several decades in some cases) and undergo millions of fatigue cycles under heavy axle loads. Although for rotating bending fatigue the central axis is a zero stress location, larger internal central axis discontinuities will experience finite cyclic stress levels as the radial distance increases from the central axis. Larger internal discontinuities at the axle central axis, caused by forging bursts or unhealed pipe, are not a common occurrence; however they are irregularly shaped and represent a possible source of fatigue crack initiation. This paper describes efforts to quantify stresses at central axis discontinuities of various different sizes using finite element analysis (FEA) computer simulations. Also, the paper reviews the radial ultrasonic inspection of a large group of axles and subsequent destructive testing to examine the physical size of indications found using the ultrasonic techniques. Recommendations for radial ultrasonic testing of newly manufactured and second hand axles are provided, and changes to appropriate Association of American Railroads (AAR) axle specifications are outlined.
Rail Car Crashworthiness Design and Testing: Lessons Learned
Authors: Sarunac R.
Published: June 2009

Following National Transportation Safety Board (NTSB) recommendations and directions from early 1996, the Washington Metropolitan Transit Authority (WMATA) has worked to provide the latest crashworthiness and passenger safety requirements for its new car procurements. Taking advantage of recent developments in the field of vehicle crashworthiness, new technical requirements were developed and implemented for the 5000 and 6000 series vehicles. To date, WMATA is the first transit authority in the U.S. to require a dynamic sled test per the APTA SS-C&S-016-SS Standard, and the second (after the New York City Transit Authority) to run full-scale vehicle crash tests. Previously, the strength-based philosophy was used to ensure some level of rail vehicle crashworthiness. However, WMATA is now implementing a strength-based crashworthiness approach, augmented with “energy-based” requirements. Should a collision occur, the Authority’s ultimate goal is to reduce passenger deceleration rates during a collision, while at the same time controlling the absorption of collision energy in a manner that minimizes loss of space in the occupied volume of the vehicle. The passenger survivability measure using maximum acceleration has been supplemented by introducing the duration of the acceleration as an additional criteria following the Head Injury Criteria (HIC) and Abbreviated Injury Scale (AIS) approaches developed for the automotive industry. WMATA’s crashworthiness requirements now include sustaining a hard coupling without any damage to the body or coupler (except emergency release), and head-on collision of two eight-car trains with specified passenger loads (one train stationary with brakes applied) with no permanent deformation of the passenger compartment and with the acceleration, level and duration not to exceed the specified HIC. The implementation of an “energy-based” crashworthiness approach was divided into several logical steps/stages. During the design process, several modifications were introduced to optimize crashworthiness and to ensure structural compatibility with the existing fleet. The design was verified by implementing full-scale testing, and potential passenger injuries were assessed by using instrumented anthropomorphic test devices (ATDs), and measuring the forces and accelerations acting on these ATDs during the test.
Parameters Affecting Braking Energy Recuperation Rate in DC Rail Transit
Authors: Ac¸ikbas¸ Su¨leyman , So¨ylemez M. Turan
Published: June 2009

Rail systems are well-known for their energy efficiency. Energy resources used in mass rail transit systems is predominantly electricity around the world. Energy consumption of a wide mass rail transit network operator in a city can easily be the biggest electricity consumer of the city. Therefore, it is very important that the efficiency is increased. This is also an essential requirement for sustainable development. Some trains used in mass transit systems are equipped with regenerative braking. This allows trains to brake in regenerative mode and feed the other trains on the line, if there is a demand. Researches showed that up to 40% of the total traction energy consumption could be supplied by this regenerative braking energy, if it is 100% used. This usage rate depends on many different parameters such as train operation frequency (headway), train-set auxilary power consumption rate, nominal braking acceleration rate, braking effort vs. velocity curve of trains. Power system configuration such as substation locations and distances, catenary system resistance, and nominal power feeding voltage level has also considerable effect on recuperation rate. In the paper, some of these parameters’ impacts will be examined with the help of a multi-train, multi-line DC rail system simulator. The results will be given in comparison tables and discussed. Lastly, new emerging technologies such as flywheels and super capacitors to capture the un-used braking energy will be briefly given.
Application of Parallel Three-Level Inverters to the Speed Control of Induction Motors in Traction Drives
Authors: Yeh Sheng-Nian , Hwang Jonq-Chin , Huang Han-Jung
Published: June 2009

This paper is concerned with the application of parallel operated neutral-point clamped three-level inverters to the speed control of induction motors in rapid transit system. Adopting three-level inverters can reduce total harmonic distortion and noise. It will also decrease the switching frequency of power transistors and increase efficiency. In this paper, two sets of inverters each in series with inductors are operated in parallel to drive two induction motors to propel electrical multiple unit. Voltage compensation is introduced to reduce difference current between inverters. Besides, parallel operation by inverters enhances availability, i.e., if one inverter has fault, the other inverter can provide partial power to induction motors. This paper presents analysis and design of the aforementioned system. Computer simulation shows that adopting the strategy of quadrature- and direct-axis currents as voltage compensation can not only reduce the difference current between inverters but also provide equilibrium current to induction motors. It will not be influenced by the switching frequency of inverters, switching sequence and series inductance. It is simple and can be extended to parallel operation of multi-sets of inverters.
Improving Internal Combustion Engines Efficiency by Using a Spring/Damper
Authors: Khosravi Shahriar , Gholampour Vahid
Published: June 2009

Piston engines are widely used in automobiles. Increasing engine efficiency and decreasing environmental pollution which is made by these engines, are always the most important concerns of automobile manufacturers. In this paper a new way to increase efficiency of piston engines and decrease their environmental pollution is proposed. In this method, a spring/damper is used instead of connection rod in the structure of piston in these engines.
Increasing U.S. Freight Rail Network Capacity With ECP Braking and PTC Systems
Authors: Kull Robert C.
Published: June 2009

Growth in U.S. rail freight demand, especially for intermodal and coal, is leading to capacity constraints on key corridors. The costs of building new rail lines are often prohibitive, and the industry needs to find other solutions for increasing capacity. Electronically Controlled Pneumatic (ECP) braking combined with new Positive Train Control (PTC) systems have the potential to double the traffic density on existing double-track rail corridors, as well as increase average network speeds. This has the potential to support the projected increase in rail traffic over the next 20 years, without needing significant additions to track infrastructure. Implementation of ECP and PTC is challenging, and will require close cooperation between railroads, car owners, shippers, railroad suppliers, and the Federal Railroad Administration (FRA).
Exhaust Emissions From a 2,850 kW EMD SD60M Locomotive Equipped With a Diesel Oxidation Catalyst
Authors: Osborne Dustin T. , Fritz Steven G. , Iden Mike , Newburry Don
Published: June 2009

This paper describes the test results of a program to apply an experimental diesel oxidation catalyst (DOC) to a 2,850 kW freight locomotive. Locomotive emissions and fuel consumption measurements were performed on an Electro-Motive Diesel (EMD) model SD60M locomotive, owned by Union Pacific Railroad company, that had been recently rebuilt to EPA Tier 0 exhaust emission certification levels. Emission testing was performed at the Southwest Research Institute (SwRI) Locomotive Exhaust Emissions Test Center in San Antonio, Texas. US EPA-regulated emission levels of hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), and participate (PM) were measured using U.S. EPA locomotive certification test procedures in three configurations; first a baseline with a relatively high sulfur diesel fuel (2,913 ppm sulfur) meeting EPA locomotive certification test specifications, and another baseline using ultra-low sulfur diesel fuel (ULDS), and finally a test using ULSD after the installation of a diesel oxidation catalyst designed and manufactured by MIRATECH Corporation (patent pending). The DOC was applied pre-turbine, within the exhaust manifold due to both space and exhaust temperature considerations. This paper describes the design of the DOC-equipped exhaust manifold, and reports the changes in the regulated exhaust emission levels between the baseline tests and after installation of the DOC. Also described is a locomotive on-board monitoring system used to monitor DOC performance during ongoing revenue service field testing.
Prevention of Derailments Due to Concrete Tie Rail Seat Deterioration
Authors: Choros John , Coltman Michael N. , Marquis Brian
Published: June 2009

Concrete tie rail seat abrasion/deterioration (RSA) has been an issue since the inception of concrete ties. As a result of recent derailments involving abraded concrete ties on curved track, the Federal Railroad Administration set up a task force to study abrasion/deterioration mechanisms and develop automated detection methods using existing research vehicles. A portion of this study reviews historical development of concrete abrasion due to moisture or foreign materials incorporated under the rail seat that tend to abrade concrete ties evenly across the rail seat area. This report discusses a newly identified concrete tie deterioration mechanism characterized by material loss in a triangle toward the field side of the rail seat, resulting from wheel rail interaction involving track geometry variations. The NUCARS™ model was used to evaluate the vertical and lateral loading at one of the recent derailment sites using the track geometry measured approximately one month before the derailment. Wheel loads predicted from the model, based on P-42 Amtrak Locomotive, were used to evaluate the pressure distribution at the rail concrete tie interface and were compared with allowable design bearing pressure for concrete used in the manufacture of concrete ties. The results indicate that applied stress on the field side of a concrete tie due to outward rail roll can exceed the design values. Applied pressure distribution exceeding the design strength on the field side tends to abrade concrete ties in a triangular wear pattern that produces wide gage. Charts were developed to convert measured field side abrasion/deterioration to additional gage widening under an applied vertical load for identifying critical locations with wide gage defects. Further, techniques for field inspectors to detect, measure, and evaluate rail seat abrasion/deterioration (RSA) based on commonly used inspection technology are discussed.
Implications of the Redefined Gage Widening Projection Parameter for the Deployable Split Axle Gage Restraint Measurement System
Authors: Sussmann Theodore , Lee Sung , Choros John
Published: June 2009

Recent gage restraint measurement system (GRMS) developments include the redesign of GRMS vehicles using a deployable split-axle instead of a freight truck mounted split-axle. This new test configuration results in boundary condition changes in the applied loads and split axle location, which influence test results. To ensure the equivalence of test results from these two systems, a comprehensive evaluation of the mechanistic basis for previous GRMS rulemaking was conducted and coupled with a fundamental investigation of factors influencing GRMS performance and inspection accuracy followed by field-testing to verify conclusions. Comparison tests between the original GRMS vehicle design and the redesigned vehicles identified the need to enhance the current gage widening ratio (GWR) equation to accommodate the increased range of vertical test loads represented by the different GRMS vehicles. GWR has been the leading source of test result discrepancies between the original GRMS design and redesigned vehicles over the same territory. The discrepancy between the inspections likely resulted from the increased range of vertical test loads represented by the distinct test vehicles, since GWR has treated vertical load as a constant. The Gage Widening Projection (GWP) parameter was proposed to replace GWR as a result of an ongoing investigation. GWR was originally developed as an indicator of fastener and tie performance by providing an extrapolated total gage widening deflection at a limiting load condition. Testing at the limiting load condition is not conducted because of the potential for damage to track components. A deflection at a lower load is extrapolated based on conservative track load-deflection behavior to the limit load, which represents an extreme but not unexpected gage widening event. The concept behind both GWP and GWR is similar. However, the GWP parameter includes vertical load as a variable, where GWR treated vertical load as a constant. The large variation in vertical load represented by the various test scenarios requires the consideration of variable vertical load in the extrapolation process to ensure an equivalent basis for inspection and safety. Based on analytical modeling and field-testing, the GWP parameter was found to perform more consistently between vehicles than GWR. A limiting condition based on a combination of deflection and load was selected to provide comparable inspection results and safety for both parameters. Additional testing has been conducted to further evaluate the data and indicates excellent performance of the GWP parameter, and perhaps merits further consideration regarding the limits.
Exception Criteria in Vertical Track Deflection and Modulus
Authors: Lu Sheng , Hogan Cory , Minert Brock , Arnold Richard , Farritor Shane , GeMeiner William , Clark Dwight
Published: June 2009

The network constraints of freight railroad traffic are moving the industry to heavier tonnage trains, higher axle loads and increased velocity. The dynamics of heavier axle loads and speed produce high stresses in the track infrastructure. Track integrity is strongly related to the vertical track modulus — the relationship between the rail deflection and the vertical applied load. Both low track modulus and large variations in track modulus increase dynamic loading leading to increased maintenance requirements and reduced structural integrity. Currently, there is no widely accepted method to measure vertical track deflection and modulus from a rail car traveling at speed and no criteria exist to relate variations in modulus to the track integrity. This paper presents a method to measure vertical track deflection from a moving rail car. These deflection measurements can then be used to estimate track modulus. Exception criteria are then proposed that can be used to evaluate track quality and prioritize maintenance. Revenue service test results are presented for approximately 350 miles of the Union Pacific Railroad’s heavy-haul axle freight line on the South Morrill and Powder River sub-divisions. Finally, the method is compared to other measurements of ride quality including Vehicle Track Interaction (VTI) measurements on the same sections of track.