bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of Hydraulic Design of a Ducted Azimuth Thruster
Authors: Park Jong-Hwoo , Chung Kyung-Nam , Chang Bong-Jun , Go Seok-Cheon , Chung Jae-Hoon 
Published: July 2013

In order to obtain sufficient towing force, tug boats are usually equipped with high powered engines and special thrusters such as azimuth thrusters. The hydraulic design of a ducted azimuth thruster was carried out for a 2 MW-class tug boat by using CFD. Here, the azimuth thruster consists of a fixed-pitch screw propeller, a duct, a gear casing and a strut. To design the duct propeller, the effects of design parameters of a screw propeller and a nozzle on thruster performance were evaluated. The proper section shape of the strut is also important because it can largely affect inflow velocity distribution on the propeller.
The model of the designed azimuth thruster was manufactured with a scale ratio of 10. Propeller open water and cavitation observation tests were carried out to confirm the performance of the design model.
Application of Semi-Empirical Probability Distributions in Wave-Structure Interaction Problems
Authors: Izadparast Amir H. , Niedzwecki John M. 
Published: July 2013

Ocean engineers are routinely faced with design problems for coastal and deepwater structures that must survive a wide range of environmental conditions. One of the most challenging problems in the field of ocean engineering is the accurate characterization and modeling of the interaction of ocean waves with these offshore structures. The random characteristic of ocean environment requires engineers to consider the effects of random variability of the pertinent variables in their predictive models and design processes. Thus, for ocean engineering purposes, one needs to have accurate estimates of the probability distribution of the key random variables that will be used in sensitivity studies, reliability analysis, and risk assessment in the design process.
In this study, a family of semi-empirical probability distribution is developed based on the quadratic transformation of linear random variable assuming that the linear random variable follows a Rayleigh distribution law. The estimates of model parameters are obtained from two moment based parameter estimation methods, i.e. method of moments and method of linear moments. The studied semi-empirical distribution can be applied to estimate the probability distribution of a wide range of non-linear random variables in the fields of ocean wave mechanics and wave-structure interaction. As examples, the application of the semi-empirical model in estimation of probability distribution of: a) ocean wave power, b) ocean wave crests interacting with an offshore structure is illustrated. For this purpose, numerically generated timeseries and experimentally measured data sets are utilized.
Fluid Flow Mixing of Turbulent Jets Within a Staggered Rod Bundle
Authors: Amini Noushin , Hassan Yassin A. 
Published: July 2013

In this investigation, flow mixing between turbulent jets injecting to a channel containing a rod bundle and the channel flows is studied using Particle Image Velocimetry (PIV) and Matched Index of Refraction (MIR) techniques. A specific case of a single impinging jet with a Reynolds number of 13,400 is considered for this analysis. The time-averaged vorticity fields for three different planes within the measurement volume verify the presence of coherent structures within all three fields, specifically in areas close to the jet impingement area and in the shear layer of the jet within the impingement plane. The cumulative effect of the vorticity patterns observed within all measurement planes is believed to have a significant role in the enhancement of mixing within the test section.
To further analyze the behavior of the large-scale coherent structures observed in the time-averaged vorticity fields, Proper Orthogonal Decomposition (POD) technique was applied to the PIV velocity fields. The results confirm that the jet flow is the most energetic and the dominant feature of the flow field. Therefore, to further analyze the behavior of some of the relatively smaller-scale coherent structures which could play a significant role in the mixing process, a higher number of modes or a different approach needs to be considered.
Noise Prediction in HVAC Squirrel-Cage Fans by Unsteady Reynolds Navier-Stokes Computation
Authors: Velarde-Suárez Sandra , Ballesteros-Tajadura Rafael , Fernández Oro Jesús Manuel , González José 
Published: July 2013

Small centrifugal and axial fans are used in automobile applications, as it is the case for HVAC systems for public transport. Typically, these fans are used to work at high speed (over 4000 rpm) and variable operation conditions, even at extreme off-design points. Flow instabilities, low efficiency and high levels of noise and vibrations appear in these machines due to these working characteristics and the need of low fabrication costs. However, lower noise levels are required today to improve the passengers comfort.
Aiming to solve these problems, it is interesting to develop a computer application to predict the generated noise level (especially at the blade passing frequency BPF), which could be used during the design phase of the fans.
In this paper, using Computational Fluid Dynamics (CFD) tools, the three-dimensional (3D) internal flow in a small squirrel-cage fan is computed unsteadily. Based upon the data acquired from the pressure fluctuations at the surfaces of 46 rotating blades and the volute tongue, the Ffowcs Williams-Hawkings analogy, which has been successfully applied in other types of turbomachines, is used to predict noise levels at the BPF.
On the other hand, in order to validate the predicted numerical results, an experimental noise characterization in a semi-anechoic chamber using capacitive microphones and a real-time frequency analyzer is performed.
Highly Subcooled Flow Boiling: A Model for Estimating Heat Transfer Behind Sliding Bubbles in a Narrow Channel
Authors: Ozer Arif B. , Hollingsworth Donald K. , Witte Larry. C. 
Published: July 2013

A quenching/diffusion analytical model has been developed for predicting the wall temperature and wall heat flux behind bubbles sliding in a confined narrow channel. The model is based on the concept of a well-mixed liquid region that enhances the heat transfer near the heated wall behind the bubble. Heat transfer in the liquid is treated as a one-dimensional transient conduction process until the flow field recovers back to its undisturbed level prior to bubble passage.
The model is compared to experimental heat transfer results obtained in a high-aspect-ratio (1.2×23mm) rectangular, horizontal channel with one wide wall forming a uniform-heat-generation boundary and the other designed for optical access to the flow field. The working fluid was Novec™ 649. A thermochromic liquid crystal coating was applied to the outside of the uniform-heat-generation boundary, so that wall temperature variations could be obtained and heat transfer coefficients and Nusselt numbers could be obtained. The experiments were focused on high inlet subcooling, typically 15–50°C.
The model is able to capture the elevated heat transfer rates measured in the channel without the need to consider nucleate boiling from the surface or microlayer evaporation from the sliding bubbles. Surface temperatures and wall heat fluxes were estimated for 17 different experimental conditions using the proposed model. Results agreed with the measured values within ±15% accuracy. The insight gathered from comparing the results of the proposed model to experimental results provides the basis for a better understanding of the physics of subcooled bubbly flow in narrow channels.
Lattice Boltzmann Simulation of Diesel Injection
Authors: Falcucci Giacomo , Jannelli Elio , Ubertini Stefano , Bella Gino , De Maio Alessandro , Palpacelli Silvia 
Published: July 2013

The evaluation and improvement of internal combustion engine performance is a challenge of major importance and it has been the object of research efforts over the last centuries. Phenomena like fuel cavitation inside diesel injector nozzles, the formation of spray and its break-up in the combustion chamber as well as the impingement of fuel droplets on engine walls are known to have a great influence on energy release during combustion and on pollutant formation and emissions, as well.
In this work, a methodology based on the Lattice Boltzmann Method (LBM) is used to directly simulate phenomena affecting diesel injection. LBM is a numerical method based on Boltzmann’s Kinetic Equation, which has been successfully employed in recent years for the simulation of phenomena of technical interest.
The results of LB simulations are displayed and compared to experimental data from literature, proving the accuracy of the proposed investigation method.
Comparing One-Dimensional and Two-Dimensional Measurement in Flash Diffusivity Experiments
Authors: McMasters Robert L. , Dinwiddie Ralph B. 
Published: July 2013

A well-established method for determining the thermal diffusivity of materials is the laser flash method. The work presented here compares two analysis methods for flash heating tests on anisotropic carbon bonded carbon fiber (CBCF). This material exhibits a higher conductivity in the direction in which the fibers are oriented than in the direction perpendicular to the fiber orientation.
The two analysis methods being compared in this experiment use different portions of the data in obtaining results. One method utilizes the temperature data from the entire surface of the sample by examining 201 temperature histories simultaneously, with each temperature history originating from an individual pixel within a line across the middle of the sample. The other analysis method utilizes only the temperature history from a single pixel in the center of the sample, similar to the data which is traditionally generated using the classical flash diffusivity method. Both analysis methods include accommodations for modeling the penetration of the laser flash into the porous surface of the CBCF material. Additionally, both models include a parameter which accounts for the non-uniform heating of the sample surface from the flash. Although the sample surface is ostensibly heated uniformly in flash diffusivity experiments, the heating has been found to be somewhat non-uniform, with more energy deposited more heavily in the center of the sample. This affects the analysis results, particularly in tests on anisotropic materials. The results in this work show very little difference between the thermal parameters arising from the two methods. The robustness of the method using the single-pixel temperature history shows that anisotropic thermal diffusivity can be measured using standard flash diffusivity instruments, avoiding the additional complexity associated with a thermal imaging camera.
A Simple Model for Prediction of Preheating and Pyrolysis Time of a Thermally Thin Charring Particle
Authors: Haseli Y. , van Oijen J. A. , de Goey L. P. H. 
Published: July 2013

The aim of this paper is to present a simple model, based on a time and space integral method, for prediction of preheating and conversion time of a charring solid particle exposed to a non-oxidative hot environment. The main assumptions are 1) thermo-physical properties remain constant throughout the process; 2) temperature profile within the particle is assumed to obey a quadratic function with respect to the space coordinate; 3) pyrolysis initiates when the surface temperature reaches a characteristic pyrolysis temperature; 4) decomposition of virgin material occurs at an infinitesimal thin layer dividing the particle into char and virgin material regions; 5) the volume of the particle remains unaltered; 6) volatiles escape through the pores immediately after formation.
Employing assumption (2) allows one to convert the energy conservation equation of the particle, which is basically described in the form of a partial differential equation (PDE), into an ordinary differential equation (ODE) by performing space integration. Next, by applying approximate time integration the ODE is transformed into an algebraic equation. Applying this approach to the preheating and pyrolysis stages of a thermally thin charring solid particle leads to a set of algebraic equations which provides reactor designers with a convenient means for computation of the heating up time, mass loss history and total conversion of particle. The accuracy of the simple model is assessed by comparing its prediction with that of a one-dimensional detailed pyrolysis model. Overall, good agreement is achieved indicating that this new model can be used for engineering and design purposes.
2-D Simulation of Hot Electron-Phonon Interactions in a Submicron Gallium Nitride Device Using Hydrodynamic Transport Approach
Authors: Fan Angie , Tarau Calin , Bonner Richard , Palacios Tomas , Kaviany Massoud 
Published: July 2013

In this study, a thermal and electrical coupled device solver is developed to simulate the energy transfer mechanism within a GaN FET with a gate length of 0.2 μm. The simulation simultaneously solves a set of hydrodynamic equations (derived from the Boltzmann Transport Equation) and the Poisson equation for electron, optical phonon and acoustic phonon energies, electron number density, electric field and electric potential. This approach has been previously established for gallium arsenide (GaAs) devices [36,37], but has not been extended to GaN due to the lack of readily available property values for GaN devices that are required. Via extensive literature study, high-fidelity properties for GaN were collected in analytical forms with respect to many dependencies, e.g. lattice temperature, electrical field, electron number density, doping rate, defects rate. These properties are then implemented into the developed code to provide a high accuracy sub-micron GaN device simulation.
Simulations show that non-equilibrium heat generation is exhibited in a typical device while the drain current is reduced due to the decrease in electron mobility. Future analysis is needed to quantify the hot-electron effect on reducing the drain current and to discover more effective ways of heat removal.
A Correlation for Critical Heat Flux in Submerged Jet Impingement
Authors: Cardenas Ruander , Narayanan Vinod 
Published: July 2013

Data from an extensive experimental study of submerged jet impingement boiling performed with water at sub-atmospheric pressures and with FC-72 at atmospheric pressure are used to develop a predictive critical heat flux (CHF) correlation for use in thermal management of electronic components. The configuration was that of a circular submerged jet impinging on a high-thermal-capacity copper surface with a standoff distance of 6 nozzle diameters. Varied parameters included the Reynolds numbers (Re) from 0 (pool boiling) to 14000, surface-to-nozzle diameter ratios (by varying the nozzle diameter) from 25 to 6, system pressures (0.2, 0.3, 0.5, 1 bar), surface roughness (123 nm, 33 nm), and system subcooling. CHF is found to increase with Re, system pressure, subcooling, and roughness and decreases with increase in nozzle diameter for a fixed Re.
Comparison with correlations in literature indicated that data of sub-atmospheric jet impingement of water were poorly predicted by existing correlations while the Monde and Katto correlation [1] was found to predict the atmospheric jet impingement data with FC-72 within 10 percent at Re >4000. Data from the experiments were fitted to a submerged forced convective CHF model proposed by Haramura and Katto [2] to develop a correlation for submerged jet impingement boiling over a wide range of density ratios. Using this model, the entire CHF dataset from experiments can be predicted with a maximum error of less than 11 percent and an average error of less than 2.6 percent.
Surface Characterization Studies of Thiols as a Blocking Mechanism for Specific Adsorption for Application of Charge Selective Membrane Transport
Authors: Agonafer Damena D. , Chainani Edward , Oruc Muhammed E. , Lee Ki Sung , Shannon Mark A. 
Published: July 2013

This paper proposes the use of electrochemical impedance spectroscopy (EIS) to measure characteristics of gold (Au)-coated membranes and their inherent limitations. In this work, the fabrication of a membrane permeate flow cell is described with the aim of subsequently studying the transport of ions through conductive polycarbonate track etched membrane (PCTE) by interrogating the system using EIS and CV measurements. In particular, we would like to ascertain the voltage range that can be applied to the Au-coated membrane without getting a considerable faradaic activity; the difference between platinum and Au electrode; the effects of different electrolyte concentrations and various applied DC potentials.
We extend our previous work done [1] by studying the differences of using a hrydroxyl and methyl terminated self assembled monolayer (SAM). We also extend the quality of the monolayer with respect to the amount of time in which the monolayer is grown. Finally, finding the voltage in which a ‘defect free’ monolayer transforms from insulative to ‘leaky’ behavior extends a detailed analysis of the critical voltage of an alkane thiol.
A Parametric Study of Multi-Stage Chemical Looping Combustion for CO2 Capture Power Plant
Authors: Hassan Bilal , Shamim Tariq , Ghoniem Ahmed F. 
Published: July 2013

A thermodynamic model and parametric analysis of a natural gas fired power plant with carbon dioxide (CO2) capture using multi-stage chemical looping combustion (CLC) are presented. CLC is an innovative concept and an attractive option to capture CO2 with a significantly lower energy penalty than other carbon-capture technologies. The principal idea behind CLC is to split the combustion process into two separate steps (redox reactions) carried out in two separate reactors: an oxidation reaction and a reduction reaction, by introducing suitable metal oxide which acts as an oxygen-carrier that circulates between the two reactors.
In this study, an Aspen Plus model was developed by employing the conservation of mass and energy for all the components of the CLC system. In the analysis, equilibrium based thermodynamic reactions with no oxygen-carrier deactivation were considered. The model was employed to investigate the effect of various key operating parameters such as air, fuel and oxygen carrier (OC) mass flow rates, operating pressure, and waste heat recovery on the performance of a natural gas fired power plant with multi-stage CLC. Results of these parameters on the plant efficiency are presented. The analysis shows efficiency gain of more than 6% over that of conventional power plant with CO2 capture technologies when CLC is integrated with the power plant.
Comparative Experimental and Computational Studies for Annular Condensing and Boiling Flows in Millimeter Scale Horizontal Ducts
Authors: Narain A. , Kivisalu M. , Naik R. , Gorgitrattanagul N. , Mitra S. , Hasan M. M. 
Published: July 2013

This paper describes experimental approaches for ensuring high heat-flux annular flow boiling and flow condensation under conditions for which shear and pressure forces dominate buoyancy effects. The paper also describes fundamental predictive tools for such flows. For annular flows, the liquid phase flows in the form of a wavy film (often micro-meter scale thin) that continuously irrigates the heat-exchange surface inside millimeter scale ducts. Controlled attainments of these annular flow configurations (which experience only second order effects of surface-tension forces) are essential to integration of functional boilers and condensers for certain space-based as well as micro-scale thermal systems. The experiments deal with flow condensation of FC-72 in a 2 mm gap horizontal channel of 1 m length and flow boiling of FC-72 in a 1.6 mm gap horizontal channel of 0.74 m length. For both boiling and condensing flow experiments, annularity of the respective flows is ensured by choice of an appropriate rate of through flow of vapor that does not actively participate in phase-change and has a flow rate which lies within a well defined range. The through flow of vapor is shown to ensure stability, annularity (by effectively suppressing nucleation in the case of flow boiling), and predictability. This fact is demonstrated by relevant flow visualization videos whose schematic and still pictures are included here. Two sets of annular condensing flow simulation results (one based on a full computational fluid dynamics based steady/unsteady simulations and another based on a quasi 1-D steady simulations) are compared against experimental heat-flux measurements obtained for annular shear driven condensing flows of FC-72 vapor. For quasi-steady annular boiling, only the quasi 1-D steady simulations approach is used for comparisons with experimental heat load measurements.
The reasonableness of the proposed 1-D predictive engineering tool, with proper understanding of its scope and limitations, enables one to generate useful results for more sophisticated simulations. Furthermore the tool readily yields results/estimates for other working fluids, channel dimensions, and flow conditions.
PR30C-LE Locomotive With DOC and Urea Based SCR: Field Trial and Emissions Testing After 1,500 and 3,000 Hours of Operation
Authors: Osborne Dustin T. , Biagini Doug , Holmes Harold , Fritz Steven G. , Jaczola Michael , Iden Michael E. 
Published: July 2013

This paper details part two of the demonstration of a 2,240 kW (3,005 HP) PR30C-LE locomotive with exhaust aftertreatment containing diesel oxidation catalysts (DOC) and urea-based selective catalytic reduction (SCR). The PR30C-LE is a remanufactured and repowered, six-axle, diesel-electric, line-haul locomotive. Program objectives were to measure emission levels of the locomotive and record locomotive and aftertreatment operations during a 12 month revenue service field trial. Phase 1 of the program involved engine baseline emissions testing as well as emissions testing with the aftertreatment at the beginning of its useful life, or the 0-hour condition. Results from Phase 1 showed engine-out emission levels were within U.S. EPA Locomotive Tier 2 limits. With aftertreatment at beginning of useful life, hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) were below Tier 4 limits, and particulate matter (PM) was below Tier 3 limits.
Phase 2 consisted of a 12 month revenue service field trial and additional emissions testing completed at the midpoint and end of the field trial. On-board GPS data, aftertreatment NOx sensor data, and various locomotive operating parameters were logged continuously during the field trial. The field trial data suggests the impact SCR technology has on locomotive NOx emissions is driven primarily by locomotive utilization and loading factor. Overall the field trial included 3,082 hours of operation and PRLX3004 generated approximately 572 MW-hours of work over the 12 month period. Emission test results at the 1,500-hour and 3,000-hour conditions showed very little change from 0-hour test results. Emission levels remained below Tier 4 limits for HC, CO, and NOx, and below the Tier 3 limit for PM. Phase 2 test results suggest there was no significant degradation in emissions performance during the field trial, and no major issues with the locomotive and aftertreatment were detected. In total there are currently five PR30C-LE locomotives in operation within California and Arizona. Together they have completed a cumulative 30,800 hours of revenue service through June 2012 without report of a major issue.