bluuebunny/crossref_metadata_2025 huggingface dataset:
Lean-Burn Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition
Authors: Liu Jinlong , Dumitrescu Cosmin E.
Published: January 2019

Increased utilization of natural-gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduce greenhouse-gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NOx, CO, and HC emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing, engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late burn (including double-peak heat release rate) was observed for advanced spark timing. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COVIMEP < 3 %), moderate rate of pressure rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.
Shape Optimization of Microchannels Using Surrogate Modelling
Authors: Ali Muhammad Ansab , Khan Tariq S. , Salam Saqib , Al Hajri Ebrahim
Published: January 2019

To minimize the computational and optimization time, a numerical simulation of 3D microchannel heat sink was performed using surrogate model to achieve the optimum shape. Latin hypercube sampling method was used to explore the design space and to construct the model. The accuracy of the model was evaluated using statistical methods like coefficient of multiple determinations and root mean square error. Thermal resistance and pressure drop being conflicting objective functions were selected to optimize the geometric parameters of the microchannel. Multi objective shape optimization of design was conducted using genetic algorithm and the optimum design solutions are presented in the Pareto front. The application of the surrogate methods has predicted the performance of the heat sink with the sufficient accuracy employing significantly lower computational resources.
Effect of Piston Crevices on 3D Simulation of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition
Authors: Stocchi Iolanda , Liu Jinlong , Dumitrescu Cosmin E. , Battistoni Michele , Grimaldi Carlo Nazareno
Published: January 2019

3D CFD IC engine simulations that use a simplified combustion model based on the flamelets concept can provide acceptable results with minimum computational costs and reasonable running times. More, the simulation can neglect small combustion chamber details such as valve crevices, valve recesses and piston crevices volume. The missing volumes are usually compensated by changes in the squish volume (i.e., by increasing the clearance height of the model compared to the real engine). This paper documents some of the effects that such an approach would have on the simulated results of the combustion phenomena inside a conventional heavy-duty direct-injection CI engine, which was converted to port-fuel injection SI operation. 3D IC engine simulations with or without crevice volumes were run using the G-equation combustion model. A proper parameter choice ensured that the simulation results agreed well with the experimental pressure trace. The results show that including the crevice volume affected the mass of unburned mixture inside the squish region, which in turn influenced the flame behavior and heat release during late-combustion stages.
Comparison of Experimental, Thermoelastohydrodynamic (TEHD) and Thermal, Non-Deforming Computational Fluid Dynamics (CFD) Results for Thrust Bearings: Part II
Authors: Deng Xin , Watson Cori , He Minhui , Fittro Roger , Wood Houston
Published: January 2019

A thrust bearing is a particular type of rotary bearing permitting rotation between parts but designed to support a predominately axial load. Part I of this study was submitted to ASME 5th Joint US-European Fluids Engineering Summer Meeting. It compared the experimental, TEHD and CFD results for a thrust bearing. Reasonable relative errors between these three results were observed. The outlet oil film thickness at low speeds and the inlet oil film thickness at high speeds as calculated using TEHD were found to be more accurate than their counterparts. Isothermal, non-deforming CFD was found to predict outlet film thickness accurately as thermal deformation has a lower impact in the outlet region. Isothermal and non-deforming CFD was also found to produce a qualitatively accurate film thickness and pressure distribution.

Experimental data from a second paper reported by the same authors in Part I, provides temperature measurements in two different pads and showed some variation of temperature from pad to pad. A thermal CFD, different from isothermal CFD in Part I, was performed in this Part II. Different data analysis methods will be included in Part II including a comparison of leading edge, mid-plane and trailing edge temperature at two loads, two speeds. 24 different speed-load combination TEHD cases and 12 CFD cases were run in Part II in addition to the 32 TEHD cases and 8 CFD cases in Part I.

Both TEHD and CFD underpredict the slope between temperature and shaft speeds. TEHD also underpredicts the slope between temperature and bearing loads while CFD can get an accurate slope between temperature and bearing loads. An improved inlet temperature model would fix the error between temperature and bearing load in CFD, and also can enable CFD to have the same accuracy as TEHD analysis for the temperature versus shaft speed relation. The inlet film thickness from both TEHD and CFD is underestimated. TEHD is more accurate than CFD in outlet film thickness, or minimum film thickness, which is a critical performance characteristic in fluid film thrust bearings. While CFD is more accurate than TEHD in inlet film thickness and power loss.
Characterizations of Diagnostic Properties and Detection Techniques of Fentanyl and Related Synthetic Opioids
Authors: Rahman M. Shafiqur , Chakravarty Uttam K.
Published: January 2019

Fentanyl, a synthetic opioid, is an extremely fast-acting synthetic narcotic analgesic having a high potency of approximately 100 to 200 times that of Morphine. As the synthetic opioid crisis continues to sweep across the world, detection technologies are required to be enhanced to detect, categorize, and identify synthetic opioids effectively. To detect fentanyl and its analogues, immunoassay screens are commercially available for urine specimens. Simple colorimetric assays, i.e., spot tests with paper strips, offer speed, simplicity of operation, portability, and affordability. The microfluidic behavior of the paper strips along with the properties of chemical reagents play significant role in drug detection methods. Therefore, the objectives of this study are to characterize the chemical properties of fentanyl and its analogues and to conduct microfluidic analysis for design optimization and performance evaluation of the fentanyl test strips. A computational fluid dynamics model is developed to evaluate the microfluidic properties. Analytical study and Experiments with test-kit samples are also conducted to validate the results of the numerical simulation. Finally, the performance parameters based on microfluidic analysis were reported showing the room for improvements in the detection technology of fentanyl and related synthetic opioids.
Viscoelastic Characterization of Woven Dacron for Aortic Grafts by Using Direction-Dependent Quasi-Linear Viscoelasticity
Authors: Tubaldi Eleonora , Ferrari Giovanni , Balasubramanian Prabakaran , Breslavskyi Ivan , Amabili Marco
Published: January 2019

In case of direction-dependent viscoelasticity, a simplified formulation of the three-dimensional quasi-linear viscoelasticity has been obtained manipulating the original Fung equation. The experimental characterization of the static hyperelastic behaviour, the relaxation, the dynamic modulus and the loss factor of woven Dacron from a commercial aortic prosthesis has been performed. An 11 % difference of the reduced relaxation (after infinite time) between axial and circumferential directions has been observed for the woven Dacron. A very large increase in stiffness is obtained in case of harmonic loading with respect to the static loading. These findings are particularly relevant for dynamic modelling of currently used aortic grafts.
Analytical Vehicle KANO Model Development
Authors: Chen Jiaquan , Chang Yin-ping
Published: January 2019

This research proposes an analytical vehicle KANO model, called V-KANO Model, which will be able to improve vehicle technical characteristics and performance target setting more precisely at the early stage during vehicle design and development process. A vehicle needs to be designed to satisfy the wants of the customers, the key is to truthfully and accurately interpret customers’ wants into engineering specifications; in other words, to translate customers’ voices into vehicle’s technical characteristics and design targets correctly. In this research, the KANO model originally introduced by Japanese quality expert Dr. Noriaki Kano is improved and modified for vehicle’s technical characteristics and performance design targets setting. The conventional KANO model was only a qualitative-based general model lack of precision and detailed information, the new innovatively developed V-KANO Model modifies and improves it into a quantitative-based mathematical model which correlates the customers’ satisfaction degree of vehicle performance with the professional trained engineers’ evaluation index closely to successfully derive an analytical vehicle KANO model, which can be adopted to guide a new vehicle system technical characteristics and performance design targets setting and development at the early stages of vehicle design process.
Binomial Parameter Determination and Mapping for Demand Prediction: A Case Study of Bike Sharing Station Expansion Design
Authors: Watson Bryan C. , Telenko Cassandra
Published: January 2019

Quantitative approaches to estimating user demand provide a powerful tool for engineering designers. We hypothesized that estimating binomial distribution parameters n (user population size) and p (user population product affinity) from historical user data can predict demand in new situations. This approach applied to a major Bike Sharing System (BSS) expansion. BSS Operators must make key decisions when adding additional docking stations. Binomial Parameter estimation approaches are briefly discussed, followed by evidence that BSSs supply an amiable case for parameter estimation. Parameter plots reveal a continuous surface over the BSS area. These surfaces allow prediction of overall ridership levels at new station locations distinctly and more accurately from approaches currently utilized. Utilizing spearman’s Rho as a comparison benchmark, our approach yields a stronger correlation between our prediction and the observed new station utilization (rho = .830, stations = 46, p < .01) than the order implemented by the BSS operator (rho = .596, stations = 46, p < .01). Finally, this approach is mathematically straightforward, indicating potential as a mainstream BSS tool for BSS operators planning future station expansions. The results validate our approach of using current user data to determine target population characteristics, informing decisions about new design situations.
Large-Eddy Simulations of Low Pressure Turbine Endwall Flow and Heat Transfer
Authors: Lynch Stephen
Published: January 2019

Turbine airfoils are subject to strong secondary flows that produce total pressure loss and high surface heat transfer in the airfoil passage. The secondary flows arise from the high overall flow turning acting on the incoming boundary layer, as well as the generation of a horseshoe vortex at the leading edge of the airfoil. Prediction of the effects of secondary flows on endwall heat transfer using steady Reynolds-averaged Navier-Stokes (RANS) approaches has so far been somewhat unsatisfactory, but it is unclear whether this is due to unsteadiness of the secondary flow, modeling assumptions (such as the Boussinesq approximation and Reynolds analogy), strongly non-equilibrium boundary layer behavior in the highly skewed endwall flow, or some combination of all. To address some of these questions, and to determine the efficacy of higher-fidelity computational approaches to predict endwall heat transfer, a low pressure turbine cascade was modeled using a wall-modeled Large Eddy Simulation (LES) approach. The result was compared to a steady Reynolds-stress modeling (RSM) approach, and to experimental data. Results indicate that the effect of the unsteadiness of the pressure side leg of the horseshoe vortex results in a broad distribution of heat transfer in the front of the passage, and high heat transfer on the aft suction side corner, which is not predicted by steady RANS. However, the time-mean heat transfer is still not well predicted due to slight differences in the secondary flow pattern. Turbulence quantities in the blade passage agree fairly well to prior measurements and highlight the effect of the strong passage curvature on the endwall boundary layer, but the LES approach here overpredicts turbulence in the secondary flow at the cascade outlet due to a thick airfoil suction side boundary layer. Overall, more work remains to identify the specific model deficiencies in RSM or wall-modeled LES approaches.
Low Cost Optical Mechanical System for Human Robot Interaction
Authors: Weng Yulai , Specian Andrew , Yim Mark
Published: January 2019

This paper presents the design of a low cost system that can be used as a spherical humanoid robot head to display expressive animations for social robotics. The system offers a versatile canvas for Human Robot Interaction (HRI), especially for face to face communication. To maximize flexibility, both in the style and apparent motion of the robot’s head, we exploit the relatively recent availability of low-cost portable projectors in a retro-projected animated face (RAF). The optical mechanical system is comprised of a projector whose light is reflected off a hemispherical mirror and onto a 360 degree section of the spherical head with sufficient resolution and illumination. We derive the forward and inverse mapping relation between the pixel coordinates on the projection plane of the projector, and the outer spherical surface to offer fast graphic generation. Calibration of the system is achieved by controlling three parameters of image translation and scaling, resulting in a specifically devised light cone whose edges are tangential to the hemispherical mirror. Several facial expressions are tested in illuminated indoor environments to show its potential as a modular low cost robot head for HRI.
Automated Engine Calibration Optimization Using Online Extremum Seeking
Authors: Singh Ripudaman , Mansfield Andrew , Wooldridge Margaret
Published: January 2019

Emissions compliance during engine start-up conditions is a major obstacle for current automotive manufacturers across global markets. The challenges to meeting emissions targets are both due to increasingly stringent regulations and the difficulty in developing control strategies for a high degree-of-freedom and highly non-linear system. Online extremum-seeking (ES) methods offer a promising alternative to traditional optimization based on design-of-experiment based automotive calibration. With extremum-seeking methods, results from all prior experiments are used to intelligently and efficiently generate the next iteration of the control parameter(s). In this work, the applicability of the online extremum-seeking method is explored to optimize five performance variables (injection timing for two injection events, the injection fuel mass divided between the first and second injection events, air-fuel equivalence ratio and exhaust cam timing) to minimize brake specific fuel consumption while imposing different constraints on NOx emissions. The experiments were conducted using a production turbocharged four-cylinder gasoline engine with an advanced fuel injection system. The results show the utility of the ES strategy to quickly identify optimal control parameter combinations and the emissions and engine performance improvements during the calibration process. The results also demonstrate the dramatic benefit of the ES calibration strategy in terms of test time required.
Optimization of Design Process of Fused Filament Fabrication (FFF) 3D Printing
Authors: Kim Jaeyoon , Kang Bruce S.
Published: January 2019

Fused Filament Fabrication (FFF) is one of the most common Additive Manufacturing (AM) technologies for thermoplastic materials. PLA, ABS, and nylon have generally been used for prototype development. With the development of carbon fiber reinforced polymer (CFRP) filament for FFF, AM parts with improved strength and functionality can be realized. While mechanical properties of various CFRP have been well studied, design methodology for structural optimization of CFRP parts remains an active research area. In this paper, a systematic optimization of design process of FFF 3D printing methodology is proposed for CFRP. Starting with standard coupon specimen tests including tensile, bending, and creep tests to obtain mechanical properties of CFRP. Finite element analyses (FEA) are conducted to find principal directions of the AM part and computed principal directions are utilized as fiber orientations. Then, the connecting lines of principal directions are used to develop a customized tool-path in FFF 3D printing to extrude fibers aligned with principal directions. Since currently available infill-patterns in 3D printing cannot precisely draw customized lines, a specific tool-path algorithm has been developed to distribute fibers with the desired orientations. To predict/assess mechanical behavior of the AM part, 3D printing process was simulated followed by FEA to obtain the anisotropic structural behavior induced by the customized tool-path. To demonstrate the design/manufacturing methodology, spur gears of a ball milling machine were selected as a case study and carbon fiber reinforced nylon filament was chosen as the AM materials. Relevant compression tests were conducted to assess their performance compared with those printed at regular tool-path patterns.

Preliminary results show that CFRP gear printed by customized tool-path has about 8% higher stiffness than those printed by regular patterns. Also, flow distribution of printed fibers was verified using scanning electron microscope (SEM). SEM images showed that approximately 91% of fibers were oriented as intended. In summary, assisted by FEA, a customized 3D printing tool-path for CFRP has been developed with a case study to verify the proposed AM design methodology.
Solution-Gated Ion-Sensitive Field Effect Transistor With Polymer Selective Membrane for Nitrate Detection
Authors: Kim Jungyoon , Liu Qingyuan , Cui Tianhong
Published: January 2019

In the paper, we fabricated a solution-gated ion-sensitive field effect transistor (IS-FET) and synthesized a selective membrane for the selective detection of nitrate. For sensor response, the level of Dirac point is measured to check the amount of nitrate in the water. Nitrate selective membrane is coated on graphene using a spin-coating method. The IS-FET is tested with four different ion solutions including chloride, sulfate, phosphate and nitrate at four different concentrations (0.1, 1, 10, 100 ppm). The Dirac point shift from −0.56 V to −0.36 V as increasing the concentration. The detection limit is 0.1 ppm, and the response time is less than 1 min.
Weep Hole and Interlayer Gap Flow Within Layered Pressure Vessels
Authors: Coates Cameron , Chastain Timothy
Published: January 2019

Weep hole flow rates due to interlayer gap flow generated by an external pressure source are measured experimentally for an AO Smith Layered Pressure Vessel (LPV) at the NASA Marshall Space Flight Center. A Computational Fluid Dynamics (CFD) model of the flow through the interlayer gaps is also done to provide further insight regarding flow behavior. The objectives of this project were: (i), to devise and conduct a suitable experiment that accurately measures weep hole flow rates based on pressure input at a single weep hole, and (ii), to interpret the data and provide recommendations regarding the management of potential leaks or failures of these LPVs. CFD predictions and experimental results both indicated that weep hole flow rates increase with increasing numbers of available layer gaps and increasing pressure. The highest flow rates occurred between weep holes that were longitudinally aligned, with the shortest path between them having no curvature. Flow rate results were not symmetric for weep holes located on opposite sides of any curved path. Results indicate that the proximity of weep holes to longitudinal welds appears to have a significant influence on flow symmetry, and that weep hole flow measurement may be a good indicator of localized gapping and inconsistent layer concentricity.
A Combined CFD-Solid Finite Element Model to Study the Mechanics of Sand Erosion Damage in Coated Glass Fiber Reinforced Polymer
Authors: Eraky Mohamed Tawfik , Elmelegy Tarek , Shazly Mostafa , Eltayeb N. S. M.
Published: January 2019

In desert environment, wind turbines blades undergo severe erosion process caused by air-borne sand particles. The erosion damage on blade surface is sensitive to particles velocity, mass flux and impingement angle. The objective of the present work is to get insight into the underlying mechanics of damage evolution by erodent particles in coated Glass Fiber Reinforced Polymer (GFRP) at different impingement angles within the framework of Discrete Element Method and Finite Element (DEM-FE). This paper presents a novel experimental technique to measure sand particles velocity which is then compared to Computational Fluid Dynamics (CFD) simulations based on Eulerian-Eulerian multiphase flow model. The computed sand solid phase velocity and mass flux were used into the DEM-FE analysis to investigate the erosion damage on the coated GFRP surface at multiple impingement angles. Primary findings of CFD show strong dependence between sand particles velocity and its volume fraction. DEM-FE results showed that, the evolution of eroded surface is strongly dependent on the particles impingement angle; in normal impact, the maximum material removal occurs initially, and in oblique impact there is a gradual removal of material along the erosion process.
LES and Hybrid RANS-LES Simulation of a Pulsating Channel Flow
Authors: Jamal Tausif , Wang Huiyu , Walters D. Keith
Published: January 2019

Simulation of turbulent boundary layers for flows characterized by unsteady driving conditions is important for solving complicated engineering problems such as combustion, blood flow in stenosed arteries, and flow over immersed structures. These flows are often dominated by complex vortical structures, regions of varying turbulence intensities, and fluctuating pressure fields. Pulsating channel flow is one such case that presents a unique set of challenges for newly developed and existing turbulence models used in computational fluid dynamics (CFD) solvers. In the present study, performance of the dynamic hybrid RANS-LES model (DHRL) with exponential time averaging (ETA) is evaluated against Monotonically Integrated Large Eddy Simulation (MILES) and a previously documented LES study for a fully developed channel flow with a time-periodic driving pressure gradient. Results indicate that MILES over predicts mean streamwise velocity for all forcing frequencies while the DHRL model with ETA provides a method for improved results, especially for the lower frequencies. It is concluded that a hybrid RANS-LES model with ETA is a useful alternative to simulate unsteady non-stationary flows but further work is needed to determine the appropriate filter width for ETA to significantly improve the predictive capabilities of the DHRL model.
An Experimental Setup for Multiple Air Jet Impingement Over a Surface
Authors: Barbosa Flávia V. , Silva João P. V. , Ribeiro Pedro E. A. , Teixeira Senhorinha F. C. F. , Soares Delfim F. , Santos Duarte , Cerqueira Maria F. , Teixeira José C. F.
Published: January 2019

Air jet impingement technology receives considerable attention due to its high performance for heat transfer enhancement in thermal equipment, providing high heat transfer rates. Due to its inherent characteristics of high average heat transfer coefficients and uniformity of the heat transfer over the impinging surface, this technology is implemented in a variety of engineering applications and industrial processes, such as reflow soldering, drying of textile, cooling of turbojet engine blades and fusion reactors. Multiple jet impingement involves several variables such as: jets arrangement, jet diameter, nozzle-to-surface distance, nozzle shape, jet-to-jet spacing, jet velocity and Reynolds number, among others. However, the total control of all these parameters is still one of the remarkable issues of the thermal design of jet impingement systems. In some industries that have implemented this technology in their processes, such as reflow soldering, the range of values of these variables are established through empiricism and “trial and error” techniques. To improve the process and to reduce time and costs, it is fundamental to define accurately all the process parameters in order to obtain an optimized design with a high degree of control of the heat transfer over the target surface. To perform an accurate and complete study of the multiple jet impingement variables for a specific application, the development of both experimental and numerical studies is fundamental in order to obtain reliable results. In that sense, this work reports the project and construction of a purpose-built test facility which has been commissioned, using a PIV system. This experimental setup is based on the oven used in the reflow soldering process. The optimization of the multiple jets geometry which is integrated in the experimental setup is herein described and discussed both experimentally and numerically. The numerical simulation of the jet impingement inside the oven was conducted using the ANSYS software, specially designed to predict the fluid behavior. Regarding the relevance of the multiple jet impingement, this work intends to improve the knowledge in this field and to give reliable and scientifically proved answers to the industries that apply this technology in their processes.
Experimental and Simulation Studies of Corn Kernel Gasification in a Double Air Stage Downdraft Reactor
Authors: Shi Yunye , Maya Diego M. Yepes , Nascimento Regis , Sharma Tejasvi , Ratner Albert , Silva Lora Electo E.
Published: January 2019

Biomass gasification is the devolatilization and incomplete combustion of biomass resulting in the production of a combustible gas mixture including carbon monoxide (CO), hydrogen (H2) methane (CH4), and traces of other hydrocarbons (CnHm), and referred to as producer gas. Producer gas can be cleaned and then used in various engines or can be converted to various biofuels. This paper presents an experimental and simulation-based evaluation of producer gas quality resulting from corn kernel gasification in a two-stage downdraft gasifier. Test conditions were selected, based on the results of previous studies, to yield high conversion efficiency and low tar production. Experimental tests were performed with an air flow of 25 Nm3/h and with 80% of the air supplied to the first gasification stage. Simulations based on a chemical and thermal equilibrium model were carried out to examine the effect of equivalence ratio (ER) changes. Both the experimental and modelling results show that using a two-stage air supply leads to a significant reduction in the tar content of the producer gas, while maintaining a high gasification efficiency.
Computational Modeling of Blunt Impact to Head and Correlation of Biomechanical Measures With Medical Images
Authors: Tan X. Gary , D’Souza Maria M. , Khushu Subhash , Gupta Raj K. , DeGiorgi Virginia G. , Singh Ajay K. , Bagchi Amit
Published: January 2019

Mild traumatic brain injury (TBI) is a very common injury to service members in recent conflicts. Computational models can offer insights in understanding the underlying mechanism of brain injury, which can aid in the development of effective personal protective equipment. This paper attempts to correlate simulation results with clinical data from advanced techniques such as magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), functional MRI (fMRI), MR spectroscopy and susceptibility weighted imaging (SWI), to identify TBI related subtle alterations in brain morphology, function and metabolism.

High-resolution image data were obtained from the MRI scan of a young adult male, from a concussive head injury caused by a road traffic accident. The falling accident of human was modeled by combing high-resolution human head model with an articulated human body model. This mixed, multi-fidelity computational modeling approach can efficiently investigate such accident-related TBI. A high-fidelity computational head model was used to accurately reproduce the complex structures of the head. For most soft materials, the hyper-viscoelastic model was used to captures the strain rate dependence and finite strain nonlinearity. Stiffer materials, such as bony structure were simulated using an elasto-plastic material model to capture the permanent deformation. We used the enhanced linear tetrahedral elements to remove the parasitic locking problem in modeling such incompressible biological tissues. The bio-fidelity of human head model was validated from human cadaver tests.

The accidental fall was reconstructed using such multi-fidelity models. The localized large deformation in the head was simulated and compared with the MRI images. The shear stress and shear strain were used to correlate with the post-accident medical images with respect to the injury location and severity in the brain. The correspondence between model results and MRI findings further validates the human head models and enhances our understanding of the mechanism, extent and impact of TBI.
Mixing Enhancement in a Novel Type of “Split and Recombine” Static Mixer
Authors: Habchi Charbel , Lemenand Thierry , Azizi Fouad
Published: January 2019

Mixing in laminar flow regimes is crucial for many engineering applications in which highly viscous and fragile fluids are used. Moreover, the compactness of laminar mixers is a great challenge due to the large mixing time required to obtain the desired homogeneity. The “Split And Recombine” (SAR) static mixers are a promising solution for this challenge. This type of mixers consists of a network of separated and then recombined channels in which two fluids are introduced separately and mixed by a multi-lamination process. The SAR static mixers perform a series of baker’s transforms on the concentration profile enhancing thus the mixing process at very low Reynolds numbers. In the present study, numerical simulations are carried out to analyze the mixing process in a new topology of SAR mixer with double separation and recombination in order to increase the lateral gradients and destroy the concentration profile faster. The new geometry proposed here is compared to two SAR configurations widely studied in the open literature namely the Gray and the Chen SAR configurations. The results show a good enhancement of the mixing process in the new double SAR configuration with decrease in the power dissipation.
A Numerical Study of Solder Paste Rolling Process for PCB Printing
Authors: Oliveira Ricardo F. , Rodrigues Nelson , Teixeira José Carlos , Santos Duarte , Soares Delfim , Cerqueira Maria F. , Teixeira Senhorinha F. C. F.
Published: January 2019

The increasing demand for electronic devices associated with the increasing competitiveness between enterprises, pushes towards process automation to decrease production costs. The reflow soldering has proven to be effective in this regard. This is composed by a series of steps or processes, such as: (a) stencil printing, (b) component placement and (c) reflow oven soldering. Each process has its specific traits that contribute to the overall process efficiency.

The present study is directed towards process (a), which includes the rolling of the solder paste over the stencil surface, followed by the subsequent filling of the stencil apertures. Several parameters influence the solder paste behaviour and thus the effectiveness of the rolling process. This work focuses on the solder paste non-Newtonian viscosity properties, with the solder paste presenting a thixotropic behaviour, necessary for the filling of the stencil apertures. Although the increase in the squeegee velocity causes extra shear in the solder paste and consequently lower viscosity, the excess of velocity may cause defects in the aperture filling process. In addition, during the rolling process, air may become entrapped in the solder paste.

The complexity of this process is addressed by numerical simulation, in particular, using the work-package ANSYS to study the solder paste progress, during the rolling process, as well as the parameters influencing it. The fluid flow simulation is solved using the solver FLUENT®, a simplified 2D domain with real case dimensions, a transient prediction of the viscosity, which is a function of the solder paste solicitation, and finally by using the Volume of Fluid (VOF) method to track the solder-air interface boundary. Dynamic meshing methods are also employed to replicate the movement of the squeegee wall, in its task to push the solder paste tumble over the stencil.

This study enlightens the role played by the printing velocity in the stencil aperture filling, a logarithm correlation can be found between them. It was found that lower print velocities provide better results than higher speeds.

It was observed that the back tip of the squeegee blade causes a partial removal of the solder paste from the aperture, which is higher for faster print processes.

An analysis of the filling process over time concluded that, independently of the printing velocity, 90% of the filling occurs in the first quarter of the process.
Modeling Heat Regulation With a Structured Mesh, Finite Volume Approach in a Voxelized Domain
Authors: Amare Rohan , Bahadori Amir A. , Eckels Steven
Published: January 2019

Modeling human thermal behavior is important for applications involving medical device design, non-ionizing radiation dosimetry, and human comfort. Most thermal models use the finite element method (FEM) to represent the complicated domain structure. With the FEM, challenges in mesh and equation derivation limit rapid implementation. Finite difference (FDM) and finite volume (FVM) methods are alternatives to the FEM but have their own limitations. The FDM faces challenges in discontinuous domains at the boundaries. The FVM provides a possible solution to problems faced with FDM and FEM use.

In a computational human phantom generated from medical imaging data, the finite volume structure is readily available in the form of two-dimensional pixels and three-dimensional voxels. However, geometric characteristics of rectangular prisms prevent acceptable surface-area convergence for curved surfaces, introducing an error that substantially impacts boundaries between regions such as a convection interface.

The present work focuses on developing surface-area corrections for a domain generated from computed tomography scans. These geometric corrections are coupled with an FVM heat-transfer solution on a structured mesh. Solutions are demonstrated for thermoregulation in a domain similar to a section of the human forearm. The ultimate goal of this work is to evaluate human body temperature distributions under the influence of external stimuli and internal heat generation.
Energy and Exergy Analysis of a Biomass Based Ceramic Plant
Authors: Esteves Diogo , Vilarinho Cândida , Ferreira Manuel Eduardo , Carvalho Joana , Araújo Jorge , Teixeira José
Published: January 2019

The manufacture of relatively low commercial value ceramic products for construction is an energy intensive industry. It is important to improve and optimize the energy equation of the plant operation while simultaneously introducing renewable primary energy sources for the heat supply.

The present paper concerns the analysis of the energy usage in a brick plant. This unit operates continuously on a 3 shift schedule. The overall annual production of five types of bricks is over 62 kton and the main energy consumption unit is the furnace. For this unit, the thermal load is supplied mainly by biomass coupled with fuel oil (80%–20% split, respectively) which yield a maximum temperature of 950 °C. The process is controlled by adjusting the air mixing in the kiln. A secondary furnace provides the heat for a rotating dryer for biomass drying which is supplied to the main furnace.

The fuel is a mixture of various sources and its characteristics were determined by means of an elemental analysis, ash content and the measurement of the heat value. Measurements of mass fluxes along with the operating temperature on critical elements of the plant and chemical composition of the flue gases were used to calculate the energy balances to the plant. Because of the diversity of the product mix the production was normalized using the mass/surface area ratio of the various types of bricks. From the results, the energy intensity is 44 kg of oil equivalent per ton.

The exergy analysis of the plant shows that most of the energy degradation occurs in the kiln. The analysis also enabled to assess the influence of the replacing fossil fuel by biomass on the increase of exergy efficiency of the plant.
Preliminary Investigation of the Effect of Dielectrophoresis on Colloidal Transport and Deposition in Evaporating Droplets
Authors: Li Xi , Maki Kara L. , Schertzer Michael J.
Published: January 2019

This work investigates the effect of negative dielectrophoresis (DEP) on polystyrene particles inside an evaporating DI water droplet on a PDMS surface. Deposition patterns of actuated droplets transitioned from a scalloped rings to a striped deposition pattern as the particle diameter increased from 20 nm to 1 μm. Increased particle size dramatically increases the negative DEP force on particles that push them toward the lower field gradient expected in fluid between active electrodes. Interestingly, deposition patterns became more uniform when particle diameter was increased to 5 μm. This uniform pattern appears to be due to interfacial trapping as the diffusion rate of the large particles was significantly slower than the velocity of the descending interface. This work suggests that DEP can be used to control deposition patterns left by evaporating colloidal droplets, but further work examining the electric field gradient inside the droplet is required to determine if this technique can be applied to a wider range of particle sizes.
Combustion Modelling of a 20 kW Pellet Boiler
Authors: Silva João , Fraga Lelis , Ferreira Manuel Eduardo , Chapela Sergio , Porteiro Jacobo , Teixeira Senhorinha F. C. F. , Teixeira José
Published: January 2019

In a domestic boiler that uses pellets as fuel, it is important to control the efficiency of the combustion process. The combustion process in the boiler is a complex process that involves several and simultaneous phenomena such as fluid flow, physical and chemical reactions and heat and mass transfer. Computational Fluid Dynamics (CFD) modeling in combination with detailed sub-models for the solid fuel conversion is a useful tool to study the combustion performance and to study, for instance, the pollutant emissions.

This paper presents the CFD simulation of the combustion in a 20 kW pellet boiler using the ANSYS Fluent software with a fully integrated packed-bed model. Furthermore, an experimental test was performed to contrast the results obtained. The CFD results were able to predict the arrangement of the particles on the grate, temperature profile of the particles and, the main gas species concentration inside of the boiler with reasonable accuracy when compared with the experimental measurements.
Preheat Limits in Practical Combustor Design: Experiments and Simulations
Authors: Fridlyand Aleksandr , Sutherland Brian , Glanville Paul
Published: January 2019

Autoignition in commercial and residential gas appliances is typically a phenomenon to be avoided. The autoignition temperature for a particular fuel, defined as the minimum temperature at which spontaneous ignition will occur without an external source of energy, is often used to characterize this phenomenon. In the design of combustion systems, it is used to demarcate conditions where autoignition may occur. In an emerging class of residential and commercial heating, cooling, and power generation appliances, preheating air and fuel can provide an effective means of boosting the overall energy efficiency by recuperating residual energy in the exhaust and reinvesting it back into the thermodynamic process. In such applications, the design question to answer is: How much can the air and fuel be preheated without autoignition? The autoignition temperature, often determined experimentally and can vary as much as 100°C for methane, may not be the most useful metric in this context. This work describes the results of a recent experimental investigation into the preheat limits for autoignition of air and natural gas with the aim of recuperating as much heat as possible in a heat pump. The experimental apparatus consisted of an air-fuel mixer supplying preheated mixture to a radiant burner. The air was first heated in excess of 750°C, cool natural gas was injected into and mixed with the hot-air stream, and all while avoiding autoignition. The current capability to predict autoignition in such applications a priori was also assessed using available chemical kinetic models and numerical simulations.
Degradation Modeling of Bioabsorbable Polymer Stent
Authors: Dong Pengfei , Wang Longzhen , Gu Linxia
Published: January 2019

In this work, a computational model of PLLA (Poly L-lactic acid) stent was constructed to study the degradation behavior of the bioabsorbable stent in terms of the loss of mechanical integrity. A degradation model was improved based on experimental data from the literature, as well as a finite element (FE) model was constructed based on the model of the degradation behavior of PLLA material. The results showed that the degradation of the PLLA would switch the material property of stent from a uniform model to a heterogeneous model due to the decline of Young’s modulus locally at each location of the stent. Loss of mechanical integrity of the stent showed a bilinear behavior due to the decline of the Young’s modulus and the locale failure of the structure, respectively. The breakdown pieces of stent will stay a relative longer time in lesion after the loss of the mechanical integrity of the stent due to the nonlinear response of the degradation degree to the degradation time and strain in the material.
2-D Inverse Dynamics Knee Model: Aligning Anatomical Knee Model With Squatting Kinematic Data Using Ligament Forces
Authors: Salinas Jose Mario , Caruntu Dumitru I.
Published: January 2019

A 2-dimensional anatomical knee model was developed for aligning knee joint related bone structures with experimental kinematic data. The experimental data was collected using motion capture cameras, which recorded the position of reflective markers placed on the human subject. Velocities were calculated by numerically differentiating the marker position with respect to time. Joints, such as the hip, knee, and ankle, were represented by axes of rotation. These axes were determined by calculating the relative instantaneous center of rotation of a body segment with respect to the adjacent body segment. Body-fixed coordinate systems were set for both thigh and shin. Anatomical bone structures were obtained from an x-ray and represented mathematically as polynomials. The femoral bone surface was aligned with the experimental data by superimposing the center of rotation of the shin with respect to thigh with the geometric center of the femoral condyle. The tibial surface was aligned with the experimental data by aligning the bones at minimum flexion and then superimposing the tibia with a shared point between femur and tibia. Ligaments were modeled as non-linear elastic springs. Cruciate ligaments were divided into a posterior and anterior ligament fiber bundle. Cruciate ligament forces were calculated for the squatting exercise for five different femoral geometric centers. Geometric centers were determined using a nonlinear least squares optimization technique. Cruciate ligament forces are discussed in this paper.
Enhancing the Path Planning Generation of a Five DOF Manipulator Using Low-Cost Camera-Laser Triangulation Technique
Authors: M. Abou Elyazed Maged , AbdelHamid Ahmed Y. , E. Abo Elnor Mootaz , H. Mabrouk Mohamed
Published: January 2019

Robot path planning is considered one of the most significant tasks for industrial robotic arms, especially for those manipulators need to follow a specific path such as welding manipulators. In this work, a low cost camera-laser triangulation technique (CLTT) is implemented to facilitate the process of contact-less path acquiring. A graphical user interface (GUI) under MATLAB® is developed to receive the dominant path points locations from the proposed positioning system and sending the generated path to the robot actuators. the introduced positioning technique (CLTT) is applied practically to develop linear and circular path for a “5-DOF Mitsubishi MELFA RV-2AJ” manipulator. The results show the effectiveness of (CLTT) to achieve fast and accurate positioning system with contact-less target for real time operation.
Mechanical Performance Analysis of ULTEM 9085 in a Heated, Irradiated Environment
Authors: Ng Matthew B. , Brennan Sean N.
Published: January 2019

This paper investigates the thermal and radiation performance of 3D-printed ULTEM materials following ASTM standard D638. ULTEM is a thermoplastic in the polyetherimide (PEI) family that is regularly used as a high-grade material for 3D printing. This material has similar properties to polyether ether ketone (PEEK), which is another thermoplastic that has strong mechanical properties at elevated temperature conditions. While PEEK has stronger mechanical properties, ULTEM is significantly more cost efficient to acquire and process via 3D printing. Also, most 3D printers are unable to utilize PEEK because of the significantly higher temperature requirements this material imposes on a 3D printer.

This work is motivated by the need to rapidly deploy robotic inspection systems within a nuclear canister environment, which exposes the material to temperatures up to 170°C (340°F), and radiation levels of 270 Gy/hr (27 krad/hr), which are significantly beyond that of conventional 3D-printed parts. The design analysis was performed via an experiment consisting of three treatment groups of dogbone ULTEM test pieces. After tensile testing all of the pieces, the material properties were compared to those of the control group.

These results allow manufacturers to select a more cost-effective material to build parts to operate in such a harsh high-temperature, high-radiation environment, which could include applications in both space systems and nuclear inspection robotics. Specifically, the results were used to guide the development of a robust robotic inspection system for the Nuclear Energy University Program (NEUP) by replacing complex parts with easily-fabricated 3D-printed ULTEM pieces.