bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulence Radiation Interactions in a Statistically Homogeneous Turbulence With Approximated Coal Type Particulate
Authors: Cleveland Mathew , Apte Sourabh , Palmer Todd
Published: July 2013

Turbulent radiation interaction (TRI) effects are associated with the differences in the time scales of the fluid dynamic equations and the radiative transfer equations. Solving on the fluid dynamic time step size produces large changes in the radiation field over the time step. We have modified the statistically homogeneous, non-premixed flame problem of Deshmukh et al. [1] to include coal-type particulate. The addition of low mass loadings of particulate minimally impacts the TRI effects. Observed differences in the TRI effects from variations in the packing fractions and Stokes numbers are difficult to analyze because of the significant effect of variations in problem initialization. The TRI effects are very sensitive to the initialization of the turbulence in the system. The TRI parameters are somewhat sensitive to the treatment of particulate temperature and the particulate optical thickness, and this effect is amplified by increased particulate loading.
Numerical Prediction of Particulate Flow Over a Backward-Facing Step Followed by a Filter Medium
Authors: Dange A. K. , Ravi K. C. , Chambers F. W.
Published: July 2013

Flow in air filter housings often is characterized by separation upstream of the filter. The effect of the separation on the motion of particles and their distribution at the filter is important to filter performance. The current research investigates these effects by applying CFD modeling to turbulent particulate flows over a backward-facing step followed by a porous medium representing a filter. The two-dimensional step flow was selected as it is an archetype for separated flow with many studies in the literature. The flow examined has a step expansion ratio of 1:2, with an entrance length of 30 step heights to the step followed by a length of 60 step heights. Computations were performed at step Reynolds numbers of 6550 and 10,000 for the step without a porous medium and with the medium placed 4.25 and 6.75 step heights downstream of the step. The mesh was developed in ICEM CFD and modeling was done using the Fluent commercial CFD package. The carrier phase turbulence was modeled using the RNG k-epsilon model. The particles were modeled using the discrete phase model with dispersion modeled using stochastic tracking. The boundary conditions are uniform velocity at the inlet, no-slip at the walls, porous jump at the porous medium, and outflow at the outlet. The particle boundary condition is “reflect” at the walls and “trap” at the filter. The numerical results for the no filter case matched experimental results for recirculation zone length and velocity profiles at 3.75 and 6.25 step heights well. The computed velocity profiles at 3.75 step heights do not match experimental profiles for the filter at 4.25 step heights so well, though the results show a profound effect on the recirculation zone length, matching the experiments. Differences are attributed to different velocity profiles at the step. With the medium 6.75 step heights downstream, the effect on the recirculation zone is negligible, again matching experimental results. The discrete phase model tracks injected particles and provides results which are qualitatively similar to the literature. It is observed that particles with lower Stokes number, and thus lower momentum, tend to follow the flow and enter the recirculation zone while particles with higher Stokes number tend to move directly to the porous medium. When the filter is moved downstream to 6.75 step heights, the increased length of the recirculation zone results in more particles entering the recirculation zone. Results for monodispersed and polydispersed particles agree.
CFD-Integrated in Preliminary Design of Unmanned Helicopter
Authors: Ridluan Artit , Charoenpon Attapon , Julniphitwong Achirakris , Thaworn Kasama
Published: July 2013

In helicopter performance design and optimization, aerodynamics is the primary area. Therefore to achieve the required helicopter performance to accomplish the missions, the efficient design process in preliminary design phase is crucial. In a past, the preliminary design involved the simplified equations to account for the aerodynamic behavior of a rotorcraft, resulting in the loss of aerodynamic phenomena such as turbulence and vortex flow pattern, which contribute to the nonlinear behaviors.

In order to improve overall design process, we thus propose the preliminary design process without the iteration. The proposed preliminary design applied the recent blade design theories with CFD procedure integrated in the preliminary design. The main benefit of this new methodology is to access the detailed flow physics as quick as possible, thus allowing the designer to faster analyze and improve the performance of the helicopter in early stage of design process.

Based on the design results given by the proposed preliminary design methodology, the new blade design was configurationally changed. The redesigned blade was twisted configuration with ∼9 and ∼27 degrees at the cone at the tip and cone, respectively. The computational results showed that the twisted blade increased the lift by approximately 846% relative to the fist design. In addition, the design cycle can be completed in only one cycle and the design time spent is few days.
Numerical Simulation of High-Speed Cavitating Water-Jet Issuing From a Submerged Nozzle
Authors: Peng Guoyi , Ito Hideto , Shimizu Seiji
Published: July 2013

A simplified estimation for the compressibility of cavitating flow is proposed based on the bubble cavitation model and a compressible mixture flow method is developed for the numerical simulation of high-speed cavitating jet by coupling the simplified estimation of bubble cavitation to a compressible turbulent flow computation procedure. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase, which is governed by the compressibility of bubble-liquid mixture at the current status of local flow field. The method is applied to the simulation of high-speed submerged water jets issuing from an orifice nozzle. Both non-cavitating and cavitating jets are calculated under different cavitation numbers in order to clarify the cavitation property of submerged water jet. The results demonstrate that the intensity of cavitation denoted by the maximum value of gas volume fraction and the area of strong cavitation indicted by high value of gas volume fraction increase with the decrease of cavitation number. Under the effect of cavitation bubbles the discharge coefficient of orifice nozzle decreases with the cavitation number.
Investigation of Relative Importance of Some Error Sources in Particle Image Velocimetry
Authors: Harris Jeff , Smith Barton L. , Wilson Brandon
Published: July 2013

Several error sources are analyzed for 2-component PIV, including: calibration, magnification variation, perspective, resolution, and the correlation algorithm noise floor. Several of these error sources are compared with previously published estimates. New experimental data and methods for measuring the contribution of each source to velocity uncertainty are presented.

The calibration uncertainty on the velocity measurement was found to be small (so long as reasonable care is taken in the calibration) and independent of the calibration target for a 2-component PIV setup. The perspective error and magnification variation were both calculated and experimentally found to be small. The light sheet thickness only has an effect when the thickness is greater than 1% of the distance from the light sheet to the camera lens plane. The spatial resolution may be so coarse as to not capture the smaller eddies in the flow, thus attenuating the measured fluctuations. The noise floor was found to contribute significantly to the uncertainty in the velocity measurements in sub-pixel displacement.
Depth of Penetration of a Submerged Viscoplastic Non-Newtonian Jet
Authors: Hammad Khaled J.
Published: July 2013

Depth of penetration characteristics of a submerged viscoplastic non-Newtonian jet were studied by numerically solving the governing mass and momentum conservation equations along with the Bingham rheological model. Momentum and velocity based jet depths of penetration were introduced and used to analyze the obtained steady and laminar flow field information for a wide range of Reynolds and yield numbers. Depths of penetration were found to linearly increase with the Reynolds number and substantially decrease with the yield number. Penetration depths of yield stress fluids were shown to be more than an order of magnitude smaller than the ones corresponding to Newtonian fluids.
Methods of Reducing Vehicle Aerodynamic Drag
Authors: Sirenko Volodymyr , Pavlovs’ky Roman , Rohatgi Upendra S.
Published: July 2013

A small scale model (length 1710 mm) of General Motor SUV was built and tested in the wind tunnel for expected wind conditions and road clearance. Two passive devices, rear screen which is plate behind the car and rear fairing where the end of the car is aerodynamically extended, were incorporated in the model and tested in the wind tunnel for different wind conditions. The conclusion is that rear screen could reduce drag up to 6.5% and rear fairing can reduce the drag by 26%. There were additional tests for front edging and rear vortex generators. The results for drag reduction were mixed. It should be noted that there are aesthetic and practical considerations that may allow only partial implementation of these or any drag reduction options.
Experimental Test Plan and Data Analysis Based on the Design of Experiment Methodology
Authors: Esposito Angelo , Mocoteguy Philippe , Postiglione Fabio , Guida Maurizio , Pianese Cesare , Pohjoranta Antti , Wang Kun , Hissel Daniel , Péra Marie Cécile , Pofahl Stefan
Published: July 2013

The development of fault diagnostics for fuel cell (FC) stacks and systems can increase their lifetime and therefore their overall efficiency. The development of such techniques often requires a reliable computational FC stack or system model. Given the complexity of such systems, endless time and effort has to be used to test the systems and identify the related models unless an adequate trade-off between available time and desired model accuracy is found. The Design of Experiment (DoE) methodology enables determining the best compromise between the number of experiments to conduct and the obtained information. In this work, the DoE approach is used to define a test plan that is carried out on a solid oxide fuel cell stack. The methodology is then further exploited to analyse the measured data and to determine the influence of the selected parameters (i.e. input variables) on the response extracted from the monitored variables. Specifically, a Full Factorial DoE analysis is performed and the relative results are compared. The results show which parameters have a direct effect and which affect indirectly, in coupling with other parameters, on the system response.
Experimental Analysis of Flow Crossover in a Solar Thermochemical Reactor
Authors: Mayer Luke J. , James Darryl L.
Published: July 2013

As energy and fuel security continue to be of increasing importance to economies around the world, countries are looking to move away from oil dependency. Energy solutions are being sought in the area of solar fuels to meet these growing needs. Concentrated solar thermochemical technology has the potential to directly convert sunlight into a useable, carbon-neutral liquid fuel that can be easily stored and integrated into our existing forms of energy demand such as transportation and heating fuels. Ongoing research performed by several groups at Sandia National Laboratories seeks to fundamentally understand the complex physics and chemistry occurring within a solar thermochemical reactor prototype named the CR5 [counter-rotating-ring receiver/reactor/recuperator]. The CR5 utilizes a stack of counter-rotating disks with metal oxide reactive material fins which are cycled through oxidation and reduction zones. The metal oxide is thus used to reduce H2O and CO2 into H2 and CO respectively, which can be combined using known processes to form a liquid fuel.

The effectiveness of such a solar thermochemical reactor depends on its ability to efficiently integrate reduction and oxidation reactions, a solar receiver, thermal recuperation, and separation of end product gases. Efficient separation of end product gases within the reactor is of critical importance as without it, the crossover of gases occurs, which results in lower reduction rates, recombination of end product gases, and additional energy spent in downstream processes. A validation reactor model called the CR5v (v for validation) has been fabricated to validate numerical models of the reactor processes. Crossover testing is done without any chemical reactions (therefore with no O2 or H2 present), but rather by examining the flow of CO2 and Argon.

This work presents experimental crossover for the CR5v reactor as a function of ring rotation speed, internal purge gas, and sweep gas to injection gas ratio. Initial crossover experimental results from the CR5v reactor suggest that crossover levels are largely not affected by ring rotation, center purge or injection gas/sweep gas ratio. Argon flow remained on average at a crossover value of 52 %, while CO2 crossover levels were on average around 8 %. The crossover flow in the system is thought to be dominated by the flow rates of the two pumps used in the system and to a lesser degree, the geometry of the system.
The Impact of an MPL on Water Management of an Operating PEMFC Using Synchrotron X-Ray Radiography
Authors: Lee J. , Hinebaugh J. , Bazylak A.
Published: July 2013

High quality through-plane images of an operating polymer electrolyte membrane fuel cell (PEMFC) were visualized by employing synchrotron X-ray radiography to quantify liquid water in gas diffusion layers (GDL). Two types of GDLs, Toray carbon paper with and without micro-porous layers (MPLs), were employed and imaged during the operation. Performance data and x-ray images of these GDLs are compared to determine the impact of an MPL on water management. At low current density (<0.4A/cm2) under high stoichiometric ratio, the MPL has little overall effect, but may behave as a diffusion barrier for reactants. At higher current density (0.6A/cm2) and under low stoichiometric ratios, the MPL is observed to significantly affect the water management of the PEMFC and is credited for increased cell performance.
Channel Dimension Constraints for Miniature Low Humidity PEM Fuel Cells
Authors: McKahn Denise A. , Zhao Xizhu
Published: July 2013

Numerous applications exist requiring power for small loads (<5W) with minimal mass operating in extreme ambient conditions. Making progress toward reducing stack mass, we investigate the influence of flow field channel depth and endplate compression on cell performance. The best performance was found at endplate compressions of 139 psi, cathode channel depths of 0.032 in and anode channel depths of 0.032 in. The maximum power mass-density achieved with these 4.84 cm2 cells was 16.8 mW/g in a single cell stack. If deployed in a multicell stack, this same performance would translate to a power mass-density of 45.3 mW/g, nearing the performance of off-the-shelf lithium ion batteries (approximately 70 mW/g).
Three-Dimensional Numerical Simulation of Mass Transfer in Cathode Side of a Passive Direct Methanol Fuel Cell
Authors: Guo Hang , Chen Yue Ping , Xue Yan Qing , Ye Fang , Ma Chong Fang
Published: July 2013

A three-dimensional, two-phase, multiple-component, unsteady model for mass transport at the cathode side of a passive direct methanol fuel cell was developed. We assumed that the cathode was full of dry air at the beginning. The air diffuses through the cathode diffusion layer to the cathode catalyst layer where electrochemical reaction occurred. The liquid water which generated in the cathode catalyst layer is gradually moved out of the cathode catalyst layer by diffusion and gas carrying. The numerical results indicate that at the constant current density of 100 mA/cm2, the quantity of liquid water increases firstly and then keeps in a constant in both cathode diffusion layer and cathode catalyst layer while that continually rises in the air cavity. This phenomenon is caused by the gravitational effect. Under normal gravity, the liquid water flows down in the cathode catalyst layer and accumulates at the bottom. When the gravitational effect is greater than the viscous forces, the liquid water droplets escape from the cathode diffusion layer and then fall into air cavity. The distributions of species concentration and velocities along different directions are also presented.
Numerical Investigation of Heat Transfer and Pressure Loss of Double-Layer Microchannels for Chip Liquid Cooling
Authors: Xie Gongnan , Liu Yanquan , Sunden Bengt , Zhang Weihong , Zhao Jun
Published: July 2013

The problem involved in the increase of the chip output power of high-performance integrated electronic devices is the failure of reliability because of excessive thermal loads. This requires advanced cooling methods to manage the increase of the dissipated heat. The traditional air-cooling may not meet the requirements, and therefore a new generation of liquid cooling technology becomes necessary. Various microchannels are widely used to cool the electronic chips by a gas or liquid, but these microchannels are often designed to be single-layer channels. In this paper, the laminar heat transfer and pressure loss in a kind of double-layer microchannel have been investigated numerically. The layouts of parallel-flow and counter-flow for inlet/outlet flow directions are designed and then several sets of inlet flowrates are considered. The simulations show that such a double-layer microchannel can not only reduce the pressure drop effectively but also exhibits better thermal characteristics, and the parallel-flow layout is found to be better for heat dissipation when the pumping power is limited, while the counter-flow layout is better when a high pumping power is provided.
Investigations of a Reverse-Vortex Plasma Assisted Combustion System
Authors: Matveev Igor , Serbin Serhiy
Published: July 2013

Theoretical and experimental investigations of the working processes in the reverse-vortex plasma assisted combustion system have been conducted. The system operates as a multi-mode, multi-purpose reactor in a wide range of plasma feedstock gases and turn down ratios, convenient and simultaneous feeding of several reagents into the discharge zone. The selected concept of the portable plasma assisted system can provide higher performance, wider turn down ratios, more efficient propellants utilization, demonstrate potential fuel flexibility, and satisfy major gravimetric and volumetric density requirements. The results and recommendations obtained can be used for the modeling of reverse-vortex plasma assisted combustion system operation modes, geometry optimization, prospective propulsion and power generation units design and engineering.
Vortically Enhanced Heat Transfer and Mixing: State of the Art and Recent Results
Authors: Ghanem Akram , Lemenand Thierry , Della Valle Dominique , Habchi Charbel , Peerhossaini Hassan
Published: July 2013

Longitudinal and transverse pressure-driven vortices induced by shear instabilities behind vortex generators play a crucial role in convective transport phenomena. The proven influence of these turbulence promoters on heat and mass transfer enhancement has led to their incorporation in modern multifunctional heat exchangers/reactors. The purpose of this work is to demonstrate experimentally the effects of hydrodynamics on the transfer processes accompanying such flows. The high-efficiency vortex (HEV) is an innovative static mixer and a low-energy-consumption heat exchanger designed to exploit these types of vortices. Results obtained in turbulent flow with embedded vorticity in an HEV static mixer are compared with numerical results in the literature. Both numerical and experimental results confirm the high energy efficiency of the HEV static mixer flow.
Heat Transfer Performance of Lotus-Type Porous Metals
Authors: Muramatsu Kenshiro , Ide Takuya , Nakajima Hideo , Eaton John K.
Published: July 2013

Metal foams are of interest for heat transfer applications because of their high surface-to-volume ratio and high convective heat transfer coefficients. However, conventional open-cell foams have high pressure drop and low net thermal conductivity in the direction normal to a heated surface due to the fully random structure. This paper examines porous metals made by stacking thin layers of lotus metal which have many small pores aligned in the flow direction. The reduction in randomness reduces the pressure drop and increases the thermal conduction compared to conventional metal foams. Experimental results are presented for the heat transfer performance of two types of lotus metal fins, one with a deterministic pattern of machined holes and one with a random hole pattern made by a continuous casting technique. The layer spacing, the hole diameter, the porosity and the flow Reynolds number were all varied. The measurements show that spacing between fin layers and the relative alignment of pores in successive fins can have a substantial effect on the heat transfer performance.
Numerical Simulation of Single Bubble Dynamics During Pool and Flow Boiling Conditions
Authors: Becker Adam , Kapitz Marek , aus der Wiesche Stefan
Published: July 2013

Complete three-dimensional numerical simulations of single bubble dynamics under pool and flow boiling conditions are carried out using the CFD code FLOW3D© based on the volume-of-fluid (VOF) method. The analyses include a numerically robust kinetic phase change model and transient wall heat conduction. The simulation approach is calibrated by comparison with available experimental and theoretical data. It is found that the observed hydrodynamics (i.e. bubble shape, departure, and deformation) are simulated very well. The comparison with high-resolution transient temperature measurements during a heating foil experiment indicates that modeling of the spatio-temporal heat sink distribution during bubble growth requires major attention. The simulation tool is employed for single bubble dynamics during flow boiling, and the agreement is excellent with published experimental data. The numerical results indicate how bulk flow velocity and wall heat transfer influence the bubble and heat transfer characteristics.
Development of Synthetic Jet Arrays for Heat Transfer Enhancement in Air-Cooled Heat Sinks for Electronics Cooling
Authors: Zhang Min , Yeom Taiho , Yu Youmin , Huang Longzhong , Simon Terrence W. , North Mark T. , Cui Tianhong
Published: July 2013

Synthetic jet arrays driven by a piston-diaphragm structure with a translational motion were fabricated. A piezo-bow actuator generating large translational displacements at a high working frequency was used to drive the jets. Vibration analysis with a laser vibrometer shows the peak-to-peak displacement of the piston inside the jet cavity of about 0.5 mm at the second resonant vibrational frequency of 1,240 Hz. In this driving condition, the peak velocity of a 20-orifice jet array reaches 45 m/s for each orifice with a total power consumption of 1.6 W. Heat transfer performance of the jet array was tested on a 100-mm-long single channel of a 26-channel heat sink. The synthetic jet flow impinges on the tips of the fins. A cross flow through the channel enters from the two ends of the channel, and exits from the middle. Results show that the activation of jets generates a unit-average heat transfer enhancement of 9.3% when operating with a channel flow velocity of 14.7 m/s, and 23.1% when operating with a channel flow velocity of 8 m/s. The effects of various choices for orifice configuration and different dimensionless distances from the fin tips, z/d, on jet performance were evaluated. By decreasing the length of the fin channel from 100 mm to 89 mm and reducing the orifice number of the jet array from 20 to 18, jet peak velocities of about 54 m/s can be obtained with the same power consumption, and a heat transfer enhancement of 31.0% from the jets can be achieved on the 89-mm-long heat sink channel with a flow velocity of 8 m/s.
A New Model for Virtual Radiometers
Authors: Hunsaker Isaac L. , Glaze David J. , Thornock Jeremy N. , Smith Philip J.
Published: July 2013

There exists a general need to compare radiative fluxes from experimental radiometers with fluxes computed in Thermal/Fluid simulations. Unfortunately, typical numerical simulation suites lack the ability to predict fluxes to objects with small view angles thus preventing validation of simulation results. A new model has been developed that allows users to specify arbitrary view angles, orientations, and locations of multiple radiometers, and receive as the output, high-accuracy radiative fluxes to these radiometers. This virtual radiometer model incorporates a reverse monte-carlo ray tracing algorithm adapted to meet these user specifications and runs on both unstructured and structured meshes. Verification testing of the model demonstrated the expected order of convergence. Validation testing showed good agreement between calculated fluxes from the model and measured fluxes from radiometers used in propellant fires. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DEAC0494AL85000.
Applicability of the Wright Polynomial Correction for Time-Resolved Laser-Induced Incandescence in the Transition Regime
Authors: Daun K. J. , Huberman S. C.
Published: July 2013

Sizing aerosolized nanoparticles through time-resolved laser-induced incandescence (TiRe-LII) requires an accurate model of the heat conduction from the laser-energized particle to the surrounding gas. Under transition regime conditions this is often done using Fuchs’ boundary-sphere method, which requires the analyst to specify the thickness of a collisionless layer surrounding the particle, representing the Knudsen layer. Traditionally the boundary layer thickness is set to the mean free path of the gas at the boundary temperature, but recently some TiRe-LII practitioners have adopted a more complex treatment that accounts for particle curvature and directional distribution of gas molecules. This paper presents a critical reassessment of this approach; while this modification is more representative of the true Knudsen layer thickness, it does not improve the accuracy of heat conduction rates estimated using Fuchs’ boundary sphere methods under conditions prevailing in most TiRe-LII experiments.
Experimental Investigation of Thermal and Hydrodynamic Performances of a Partial Cross-Wavy Recuperator for Microturbine Applications
Authors: Du L. X. , Yu P. Q. , Zeng M. , Wang Q. W.
Published: July 2013

In order to improve the thermal efficiency of the microturbines, the compact and high efficient primary surface heat exchangers are mandatory. Recently, the thermal and hydrodynamic performances of a cross-wavy (CW) primary surface recuperator are experimentally investigated. The recuperator tested in the experiment is only 1/3 part of the whole recuperator which is designed for a 100kW microturbine. The experimental results have shown that the comprehensive thermal and hydrodynamic performances of the CW primary surface recuperator are competitive. The overall heat transfer coefficients and the pressure drops of the recuperator are tested in the experiments. And the range of the Reynolds number is from 150 to 400. The corresponding correlations between heat transfer coefficients and Reynolds numbers and the correlations between friction factors and Reynolds numbers are obtained. The Genetic Algorithm (GA) has been used to separate the coefficients of heat transfer correlations in the hot and cold sides of the partial recuperator by separating the overall heat transfer coefficient without experimentally knowing wall temperatures. In order to improve the hydrodynamic performance, the flow arrangement is also carefully designed. Furthermore, the experimental results have also confirmed that the flow distribution in the recuperator is quite uniform.
Experimental and Numerical Investigation of Heat Transfer in Annular Channels With Flow Twisting
Authors: Tarasevich S. E. , Fedyaev V. L. , Yakovlev A. B. , Morenko I. V.
Published: July 2013

In paper the experimental and numerical modeling results of a heat transfer in annular channels with continuous twisting at one-phase water flow are presented. For a flow twisting the wire was spirally coiled on the central body of an annular channel (diameter of a wire is equal to annular gap height). The generalizing associations for heat transfer calculation on the concave and convex surfaces in a single-phase phase are presented. The analysis of features of velocity profiles and temperatures on the concave and convex surfaces are carried out. The heat transfer on a convex surface of an annular channel with a twisting considerably above than the heat transfer on a concave surface. It’s caused by increase of displacement of a maximum of a velocity profile to a concave surface under the influence of mass forces with growth of a twisting extent.
Ultra-Cooling Heat Transfer Characteristics Using Cryogenic Micro-Solid Nitrogen Spray
Authors: Oh U. , Ishimoto Jun , Harada Naoki , Tan Daisuke
Published: July 2013

The fundamental characteristics of heat transfer and cooling performance of micro-solid nitrogen particulate spray impinging on a heated substrate were numerically investigated and experimentally measured by a new type of integrated computational-experimental technique. The employed CFD based on the Euler-Lagrange model is focused on the cryogenic spray behavior of atomized particulate micro-solid nitrogen and also on its ultra-high heat flux cooling characteristics. Based on the numerically predicted performance, a new type of cryogenic spray cooling technique for application to a ultra-high heat power density device was developed. In the present integrated computation, it is clarified that the cryogenic micro-solid spray cooling characteristics are affected by several factors of the heat transfer process of micro-solid spray which impinges on heated surface as well as by atomization behavior of micro-solid particles.
Investigation of Flow Boiling Heat Transfer in Microgravity via Infrared Thermometry
Authors: Kommer Eric , Dessiatoun Serguei , Kim Jungho , Kim Tae Hoon , Solotych Valentin
Published: July 2013

Flow boiling heat transfer is an important mechanism across a wide variety of engineering disciplines. The prediction of the heat transfer rate as a function of flow conditions and temperature has been based almost exclusively on experimentally derived correlations. The quality of these correlations depends on the accuracy and resolution of the measurement technique. In addition to the complexities of flow boiling phenomenon in earth gravity, engineering design of space systems requires knowledge of the gravity dependence for heat transfer prediction.

Current research has shown significant variations in the heat transfer during pool boiling as a function of gravity magnitude. Research into flow boiling in variable gravity environments is very limited at this time, and such data is needed if multiphase systems are to be designed for space applications.

The objective of this study is to develop, validate, and use a unique infrared thermometry method to quantify the heat transfer characteristics of flow boiling over a range of gravity levels. This new method allows high spatial and temporal resolution measurements, while simultaneously allowing the flow to be visualized. Validation of this technique is demonstrated by comparison with accepted data in earth gravity environments. Measurements taken in high, earth, and zero gravity environments are used to show how the heat transfer characteristics change with gravity.
Quantifying Uncertainty in Multiscale Heat Conduction Calculations
Authors: Marepalli Prabhakar , Qiu Bo , Ruan Xiulin , Murthy Jayathi Y.
Published: July 2013

In recent years, there has been interest in employing atomistic computations to inform macroscale thermal transport analyses. In heat conduction simulations in semiconductors and dielectrics, for example, classical molecular dynamics (MD) is used to compute phonon relaxation times, from which material thermal conductivity may be inferred and used at the macroscale. A drawback of this method is the noise associated with MD simulation, which is generated due to the possibility of multiple initial configurations corresponding to the same system temperature; for phonon relaxation times, the spread may be as high as 20%. In this work we propose a method to quantify the uncertainty in thermal conductivity computations due to MD noise, and its effect on the computation of the temperature distribution in heat conduction simulations. Bayesian inference is used to construct a probabilistic surrogate model for thermal conductivity as a function of temperature, accounting for the statistical spread in MD relaxation times. The surrogate model is used in probabilistic computations of the temperature field in macroscale Fourier conduction simulations. These simulations yield probability density functions of the spatial temperature distribution. To allay the cost of probabilistic computations, a stochastic collocation technique based on generalized polynomial chaos (gPC) is used to construct a response surface for the variation of temperature (at each physical location in the domain) as a function of the random variables in the thermal conductivity model. Results are presented for the spatial variation of the probability density function of temperature as a function of spatial location in a typical heat conduction problem to establish the viability of the method.
A Methodology for Modelling Enclosure Radiation Heat Transfer Under Large Structural Deformation
Authors: Subia Samuel R. , Dempsey J. Frank , Crane Nathan K. , Thomas Jesse D.
Published: July 2013

Finite element method (FEM) numerical simulations of heat transfer for high-temperature regimes often require modeling of grey-body enclosure radiation where enclosure geometry definitions are obtained as part of the model grid generation process. Owing to the expense of solving the radiation problem, typical FEM approaches loosely couple the radiative transfer solution as boundary conditions to a standard conduction formulation. When the problem at hand is thermal-mechanical and relative motion occurs between enclosure surfaces, the simulation code is tasked with providing a means of updating the original enclosure surface geometry to reflect the deformed configuration. While this scenario is manageable for contiguously meshed discretizations, the difficulty of updating enclosure geometry is greatly increased when the model admits sliding. Here the analysis code must employ both mechanical and thermal contact, relying heavily on geometric search and contact constraints to enforce closure for the conduction formulation.

General purpose large-deformation FEM structural codes employ surface contact utilities to provide geometric search and contact constraint definitions. This paper describes an ongoing effort to leverage contact utilities for solving the enclosure radiation problem in deforming and sliding mesh scenarios while having minimal impact to a traditional modeling approach. The current effort is divided into two areas, enclosure definitions and thermal contact, but the primary focus here is on enabling use of contact to provide definition of the enclosure. The proposed methodology is demonstrated on simple enclosure radiation models using SNL Sierra Mechanics Dash contact utilities and the Chaparral enclosure radiation library with Sierra Mechanics Structural and Thermal application codes.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energys National Nuclear Security Administration under contract DE-AC04-94AL85000.
Development of a Low Emissions Upgrade Kit for EMD GP20D and GP15D Locomotives
Authors: Fritz Steven G. , Hedrick John C. , Weidemann Tom
Published: July 2013

This paper describes the development of a low emissions upgrade kit for EMD GP20D and GP15D locomotives. These locomotives were originally manufactured in 2001, and met EPA Tier 1 locomotive emission regulations. The 1,491 kW (2,000 HP) EMD GP20D locomotives are powered by Caterpillar 3516B engines, and the 1,119 kW (1,500 HP) EMD GP15D locomotives are powered by Caterpillar 3512B engines. CIT Rail owns a fleet of 50 of these locomotives that are approaching their mid-life before first overhaul. Baseline exhaust emissions testing was followed by a low emissions retrofit development focusing on fuel injection timing, crankcase ventilation filtration, and application of a diesel oxidation catalyst (DOC), and then later a diesel particulate filter (DPF). The result was a EPA Tier 0+ certification of the low emissions upgrade kit, with emission levels below EPA Line-Haul Tier 3 NOx, and Tier 4 HC, CO, and PM levels.
Diesel Particulate Filter Retrofit of a 1500 kW Multi-Engine Genset Locomotive
Authors: Hedrick John , Fritz Steve , Plunkett Kathy
Published: July 2013

This paper documents the initial test results of a locomotive diesel particulate filter (DPF) retrofit project. The locomotive used for this project was BNSF1284, a 1,566 kW National Railway Equipment Company (NREC) model 3GS21B, originally manufactured in April, 2008, and designed to be an Ultra-Low Emissions Locomotive (ULEL). This genset switcher locomotive uses three Cummins QSK19 Cummins 522 kW diesel-engine driven generator sets (Genset 1, 2, and 3) to provide the power needed to drive the traction motors.

The GT Exhaust Diesel Particulate Filter (DPF) retrofit system, installed on BNSF1284, uses catalyzed DPF elements. The DPF, and its catalyzed coating, offered significant hydrocarbons (HC), carbon monoxide (CO), and particulate (PM) emissions reduction. Additionally, the catalyzed coating should allow the diesel particulate filters to passively regenerate at moderate exhaust temperatures, thus keeping the engine back pressure within allowable limits of the manufacture.

The GT Exhaust DPF’s were installed in place of the standard mufflers on each of the three engines. The GT Exhaust DPF’s are roughly the same size as the stock muffler. The only locomotive modification needed to install the GT Exhaust DPF’s was to the muffler mounting platform, directly above the engine, where the exhaust pipe opening needed to be enlarged. There are no external modifications to the locomotive car body needed to install the GT Exhaust DPF’s.

After installation of the DPF’s, they were degreened by operating the engines at rated power for 20 hours. After degreening testing was performed according to Title 40 of the U. S. Code of Federal Regulations (CFR), Part 92, Subpart B. The addition of the DPF reduced the PM emissions to 0.016 g/kW-hr or 60 percent below the locomotive Tier 4 PM limits.

BNSF1284 was returned to revenue service in Richmond, California in March 2012, where the DPF performance will be tracked for 3,000 hours of operation as part of a California Air Resources Board (CARB) verification program.
SI Engine Piston Pin Motion Measurement as Related to Noise
Authors: Chen Yu , Deck Carol Lynn , Hall Christopher
Published: July 2013

NVH is a necessary consideration in engine component development. The piston pin joint can be a significant contributor of mechanical noise in SI engines. Although there is literature on this subject, most of it is dealing with measurement using accelerometers for vibration analysis. This however does not indicate the fundamentals of the piston pin to connecting rod pin bore interaction mechanism. Limited research was found on this matter which prompted this investigation.

A measurement system was designed to determine the connecting rod small end bore clearance in real-time from the base and side of the pin bore. In this system, we applied a high precision displacement sensor to measure the pin motion, and a linkage was designed and fabricated to transfer the signal output out of the engine. This information was then correlated with accelerometer impact measurements to create a baseline for piston pin motion. Impacts were linked to the load reversal of the piston pin to connecting rod interface.
Advanced Tribological Assessment of Ring Coatings
Authors: Maschewske Max , Karrip Kimm , Deck Carol Lynn
Published: July 2013

Friction reduction within the power cylinder assembly of internal combustion engines continues to be a one of the foremost focuses of engine manufactures. In an effort to better address this topic previously developed bench test rigs, such as the Falex, Cameron-Plint, and EMA-LS9 [1,2], have been utilized. These devices were formerly focused solely on wear mechanisms and material compatibility. Current development of new piston ring coatings has demanded significant refinements to the previously mentioned EMA-LS9 test rig for specific frictional characteristic evaluations. These developments have allowed for coefficient of friction ranking between various piston ring materials in addition to the influence and surface finish on coefficient of friction.

This paper examines how the test rig is utilized to characterize upper compression ring materials, surface treatments, and the impact of surface finish. The significance of these results will be examined as it applies to analytical evaluations. From these calculations a demonstration of the effect of surface finish on ring dynamics and gas flow, as well as future piston ring coating developments will be discussed.
Homogenisation of High Pressure Diesel Fuel Spray Combustion Using Porous Ceramic Media
Authors: Shahangian Navid , Honnery Damon , Ghojel Jamil
Published: July 2013

Interest is growing in the benefits of homogeneous charge compression ignition engines. In this paper we investigate a novel approach to the development of a homogenous charge like environment through the use of porous media. The primary purpose of the media is to enhance the spread of the high pressure fuel spray. In this paper we show through high speed visualizations of both cold and hot spray events, how porous media interactions can give rise to greater fuel air mixing and what role system pressure plays in further enhancing this process.
Particulate Matter Reduction From a Pilot-Ignited, Direct Injection of Natural Gas Engine
Authors: McTaggart-Cowan G. P. , Mann K. , Huang J. , Wu N. , Munshi S. R.
Published: July 2013

This paper reports an evaluation of various combustion strategies aiming to reduce engine-out particulate matter (PM) emissions from a natural-gas fuelled heavy-duty engine. The work is based on a Westport HPDI fuelling system, which provides direct injection of both natural gas and liquid diesel into the combustion chamber of an otherwise unmodified diesel engine. The diesel acts as a pilot to ignite the natural gas, which normally burns in a non-premixed fashion, leading to significant PM formation. The concepts to reduce PM evaluated in this work are: 1) adjusting the relative phasing of the natural gas and diesel injections to allow more premixing of the natural gas prior to ignition; 2) reducing the pilot quantity to increase the ignition delay of the gas jet; and 3) reducing the level of EGR at select modes to reduce PM formation. These strategies are evaluated at steady state using single- and multi-cylinder research engines, supported by CFD analysis. The results demonstrate that allowing limited premixing of the gas jet prior to ignition can significantly reduce PM emissions. Excessive premixing can lead to high rates of pressure rise; EGR can be used to moderate the combustion under these conditions, without causing increased PM emissions. Reducing pilot quantity is another effective technique to reduce PM, primarily by allowing more air to mix with the gas jet before ignition. These various techniques can be combined to form a new operating strategy that significantly reduces engine-out PM and NOx emissions compared to the baseline strategy without significantly impacting fuel consumption.
Reactivity Controlled Compression Ignition Performance With Renewable Fuels
Authors: Curran Scott J. , Szybist James P. , Wagner Robert M.
Published: July 2013

Reactivity controlled compression ignition (RCCI) combustion makes use of in-cylinder blending of two fuels with differing reactivity to tailor the reactivity of the fuel charge for improved control of the combustion process. This approach has been shown in simulations and engine experiments to have the potential for high efficiency with very low NOX and particulate matter (PM) emissions. Previous multi-cylinder RCCI experiments have been completed to understand the potential of this approach under more real-world conditions in a light-duty multi-cylinder engine (MCE) with production viable hardware. MCE experiments explored fuel injection strategy, dilution levels, piston geometry (including compression ratio), and fuel properties. Many renewable fuels have unique properties which enable expanded operation of advanced combustion methods for higher engine efficiency and lower energy requirements for emissions control devices. This study investigates the effect that renewable gasoline and diesel fuel replacements have on the load-expansion of RCCI, performance and emissions. The study focuses on ethanol blends for replacement of gasoline as the port-injected fuel (PFI) and biodiesel blends as the replacement for the direct injected (DI) fuel.
Fabrication of Micro Organs Using a Digital Micro-Mirroring Microfabrication System
Authors: Hamid Qudus , Wang Chengyang , Sun Wei
Published: July 2013

Micro-Electro-Mechanical Systems (MEMS) technologies have been very attractive and demonstrate the potential for many applications in the field of tissue engineering, regenerative medicine, and life sciences. These fields bring together the multidisciplinary field of engineering and integrated sciences to fabricate three-dimensional models that aides the exploration, generation or regeneration of organic tissues and organs. Presently, monolayer cell cultures are frequently used to investigate potential anti-cancer agents. The issues at hand are that these models give very little in terms of feedback on the effects of the microenvironment on chemotherapeutic and the heterogeneity of the tumor. Three-dimensional tumor and cancer models that mimic the actual disease are developed for in vitro investigations. These models create an environment that enables diseases to have an enhanced evaluation (compared to two dimensional) and eliminate the limitations of the traditional mainstays of cancer research. Three-dimensional Cancer models are economic, allow for biological characterizations. Cancer models are developed from investigations of the actual disease; computer tomography (CT) and magnetic resonance imaging (MRI) allow for biomodeling of the disease’s environmental conditions.

Unlike many traditional microfabrication techniques, the Digitial Micro-mirror Microfabrication (DMM) System eliminates the need for mask by incorporating a dynamic mask-less fabrication technique. The DMM is specifically designed for the developments of biologically inspired devices, whether it’s a multicellular spheroid, hollow fiber, or multicellular layer (MCL) models; the DMM has the potential to utilize its dynamic micro mirrors to build the tissue model according to its desired design and characteristics. Each model is specifically designed to mimic the in vivo conditions of the tissue of interest.