bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Cavitating High Speed Liquid Flow Through a Converging-Diverging Nozzle
Authors: Asher William E. , Eckels Steven J.
Published: March 2016

Cavitation is an important and common phenomena in fluid flow in which a fluid becomes two-phase through pressure variation. In devices such as valves, orifices, and metering devices, as well as loss of coolant situations in power plants, cavitation can be of interest due to erosion, energy efficiency, safety, and other concerns.

It is possible for a cavitating flow to become sonic, accelerating and imposing additional energy losses that would not have occurred had the flow remained below the speed of sound. Models of this aspect of two-phase flow have not been fully explored and often have only been developed for the case of constant area.

In the present paper, the homogeneous equilibrium model is developed by applying the integral forms of the conservation of mass, momentum, and energy equations to a control volume of variable cross-sectional area with adiabatic walls. The developed model is then applied to experimental data with R-134a as the fluid of interest for an instrumented converging-diverging nozzle for which mass flow, pressure, and temperature are measured.

Applying the model to the experimental data yields interesting results in both the relationship between velocity and void fraction and in the predicted shear stresses down the length of the nozzle. The model predicts negative shear stresses near the nozzle’s throat an order of magnitude higher than those seen elsewhere in the nozzle. For this reason, the homogeneous model is likely not sufficient to accurately describe this variant of cavitating flow.
Feasibility Analysis of Thermal Energy Storage: Differences Using Blended Versus Actual Rate Schedules
Authors: Ramesh Vivek , Reddy T. Agami
Published: March 2016

This paper reports on the results of analyzing yearlong monitored 15 min data from the cooling plant of a large university campus consisting of multiple chillers and multiple chilled water Thermal Energy Storage (TES) tanks. The objective of the analysis was to determine whether the addition of another TES tank would be economically justified under the present electric rate structure and cooling load demand of the campus. The analysis was done: (i) using blended on-peak and off-peak energy rates (an approach commonly adopted due to its simplicity for evaluating different system alternatives and operating strategies meant to reduce cost and/or energy use), and (ii) using the actual electric rate structure which includes energy and demand charges. The latter rate structure suggests a 42 year payback, while the former rates predicted a payback period of over 100 years. If the incremental avoided cost of an additional chiller (to meet anticipated increases in cooling loads) is included in the economic analysis, the payback will be greatly reduced from the 42 year payback, and make this option a design choice meriting further investigation. The study also suggests a way of generating indifference plots which provide insights into how future changes in the electric rate structure would impact the payback period. The methodology adopted in this study would serve as a case study example to energy analysts evaluating TES systems as a design option for meeting increasing cooling demand and reducing costs in an existing building or campus facility.
Optimization of a Biomass Micro-Gasification Process for the Production of Synthesis Gas From Palm Shell
Authors: Ahumada Luz M. , Verdeza Arnaldo , Bula Antonio J.
Published: March 2016

This paper studied, through an experiment design, the significance of particle size, air speed and reactor arrangement for palm shell micro-gasification process in order to optimize the heating value of the syngas obtained. The range of variables was 8 to 13 mm for particle size, 0.8–1.4m/s for air velocity, and updraft or downdraft for the reactor type. It was found that the particle size and air velocity factors were the most significant in the optimization of the output variable, syngas heating value. A heating value of 2.69MJ / Nm3 was obtained using a fixed bed downdraft reactor, with a particle size of 13 mm and 1.4 m/s for air speed; verification of the optimum point of operation under these conditions verified that these operating conditions favor the production of a gas with a high energy value.
Active Pneumatic Road Rumble Energy Harvesting System
Authors: Coffey Melody , Dalke Raymond , Williams Ryian , Sutton Devyn , Brink Jan , Azzouz M. Salim
Published: March 2016

Transportation vehicles traveling on busy roads and highways waste an appreciable amount of their kinetic energy. The lost energy dissipation is due to many factors such as: the friction due to braking, the friction of the tires on the road, the friction of the vehicle body against the surrounding air, and the friction due to the engine’s moving parts. In an effort to save some of this lost energy, it is possible to harvest it through pneumatic and mechanical devices built into the road, especially on highly traffic highways. With over 1 billion cars in the world, there is a huge potential for tapping into the lost energy, and harvesting it for another use. This technical paper focuses on designing a pneumatic and mechanical system that collects the lost kinetic energy of multiple passing cars. A new energy harvesting system utilizing pneumatic and mechanical components has been developed. In this system, a vehicle’s tires pass over a pneumatic manifold system equipped with exciter keys. These keys are depressed and activate a pneumatic system to compress air. Each exciter key is coupled to a connecting rod and piston assembly. The compressed air generated by many exciter keys is then collected in an air tank and channeled to a pneumatic motor. The pneumatic motor transmits then a rotational motion to an electricity generator that produces electric energy. The electric energy can be stored into a series of batteries. The modular pneumatic manifold systems would be located where car drivers encounter deceleration ramps, when approaching a stop sign, or entering a toll booth plaza, etc. The pneumatic system was designed using a computer drawing CAD software. The vehicle’s kinetic energy losses are thoroughly analyzed and their distribution is comprehensively determined using the first principle of thermodynamics, and the thermodynamics theory for compressed air. Energy losses to the system keys and springs, and different friction losses are also determined. A pneumatic model of the manifold, and piping connections to the air tank has been programmed using a pneumatic software for modeling and simulation. An economic viability study of such systems has also been performed. Parameters such as the number of passing cars and the number of strokes on the exciter keys necessary to fill an air tank are determined. A physical prototype of the modular manifold has been built, and experimental measurements are expected to be performed in an upcoming second phase of the project. It is envisioned that such harvesting energy systems can be used to produce energy locally in remote road areas to power stop lights, or street lights. This type of system can also be adapted to be used with other transportation systems such as trains and buses to produce electricity for their respective stations when traffic is heavy.
Applications in Education for a Heat Conduction Database
Authors: Cole Kevin D. , de Monte Filippo , McMasters Robert L. , Woodbury Keith A. , Yeom Junghoon , Beck James V.
Published: March 2016

Applied computer solutions for conductive heat transfer are a critical component in any modern undergraduate heat transfer course. This need has been addressed in many ways through various textbook exercises and software packages. The present work involves a catalog of analytical solutions organized with a numbering system that describes the boundary conditions and initial conditions for each problem. The solutions are pre-programmed and accessible via a free web site called the Exact Analytical Conduction Toolbox, or EXACT. Students can access these solutions for use in homework and project work. In this paper examples of several types of student exercises are given, including a re-creation of the Heisler charts and a two dimensional steady-state example. Additionally, an account is given of classroom use of these tools in a graduate heat transfer course, outlining the education advantages of the EXACT web page. The concept of intrinsic verification is also discussed, focusing on the applicability of this concept to enhancing insight among undergraduate students. General support is also expressed for the need of analytical solutions to heat transfer and diffusion problems in an undergraduate setting.
Solving Military Vehicle Transient Heat Load Issues Using Phase Change Materials
Authors: Putrus Johnathon P. , Jones Stanley T. , Jawad Badih A. , Kfoury Giscard , Arslan Selin , Schihl Peter
Published: March 2016

Thermal management systems (TMS) of armored ground vehicle designs are often incapable of sustained heat rejection during high tractive effort conditions and ambient conditions. Latent heat energy storage systems that utilize Phase Change Materials (PCMs) present an effective way of storing thermal energy and offer key advantages such as high-energy storage density, high heat of fusion values, and greater stability in temperature control. Military vehicles frequently undergo high-transient thermal loads and often do not provide adequate cooling for powertrain subsystems.

This work outlines an approach to temporarily store excess heat generated by the transmission during high tractive effort situations through the use of a passive PCM retrofit thereby extending the operating time, reducing temperature transients, and limiting overheating.

A numerical heat transfer model has been developed based on a conceptual vehicle transmission TMS. The model predicts the transmission fluid temperature response with and without a PCM retrofit. The developed model captures the physics of the phase change processes to predict the transient heat absorption and rejection processes. It will be used to evaluate the effectiveness of proposed candidate implementations and provide input for TMS evaluations.

Parametric studies of the heat transfer model have been conducted to establish desirable structural morphologies and PCM thermophysical properties. Key parameters include surface structural characteristics, conduction enhancing material, surface area, and PCM properties such as melt temperature, heat of fusion, and thermal conductivity.

To demonstrate proof-of-concept, a passive PCM enclosure has been designed to be integrated between a transmission bell housing and torque converter. This PCM-augmented module will temporarily strategically absorb and release heat from the system at a controlled rate. This allows surging fluid temperatures to be clamped below the maximum effective fluid temperature rating thereby increasing component life, reliability, and performance. This work outlines cooling system boundary conditions, mobility/thermal loads, model details, enclosure design characteristics, potential PCM candidates, design considerations, performance data, cooling system impacts, conclusions, and potential future work.
Experimental Study of Combustion of Polymer Added n-Decane and n-Dodecane Droplets
Authors: Ghamari Mohsen , Ratner Albert
Published: March 2016

In spite of recent attentions to renewable sources of energy, liquid hydrocarbon fuel is still the main source of energy for transportation systems. Manufactures and consumers are consistently looking for ways to optimize the efficiency of fuel combustion in terms of cost, emissions and consumer safety. Recent experimental research has shown that the addition of long chain polymers to hydrocarbon fuel imparts non-Newtonian characteristics to the fuel which results in suppressed splashing behavior upon spilling over a surface. However, the combustion characteristic of these polymer added fuel (PAF) have not been investigated yet. In this study, combustion of stationary fuel droplets of n-Decane and n-Dodecane doped with different percentages of a long chain polymer (Polybutadiene) was examined and compared with the normal hydrocarbon behavior. In contrast with hydrocarbon droplets with no polymer addition, several zones of combustion including a slow and steady burning zone, a strong swelling zone and a final fast and fairly steady combustion zone were also detected. In addition, increasing polymer percentage resulted in a more extended swelling zone and shorter slow burning zone in addition to a shorter total burning time.
Microstructure-Sensitive Fatigue Modeling of Friction Stir Welded Aluminum Alloy 6061
Authors: Cisko A. R. , Jordon Brian , Rodriguez Rogie , Rao Harish , Allison P. G.
Published: March 2016

In this work, experiments were conducted to quantify the mechanical properties and microstructure of friction stir welded (FSW) 6061 aluminum alloy butt joints. In particular, strain-control experiments were carried out to characterize the low-cycle fatigue (LCF) performance of the FSW joint and a microstructure-sensitive fatigue model was used to elucidate structure-property relationships. Under fatigue testing, two distinct modes of failure were observed. In the first case, the fatigue cracks initiated and propagated though the heat affected zone, which is due to material softening as a result of the frictional heat generated by the FSW process. The second mode of failure observed was when the fatigue crack initiated and propagated through the stir zone, as a result of inappropriate material mixing. Additionally, results of this study show a strong dependence on the tool rotational rate, where the monotonic tensile and cyclic mechanical properties increased as the tool rate increased. However, experimental results showed that the increase in the mechanical properties were observed to level off or in some case decline as the tool rotational rate continued to increase. This behavior is due to several factors including welding defects and higher frictional heat. In order to further understand the effect of microstructure and welding defects on fatigue behavior, a multi-stage fatigue (MSF) model that incorporates incubation and crack growth regimes was implemented to capture the effect of variation in tool rotational speeds. The MSF model exhibited good correlation to the experimental results, suggesting that the multi-stage approach for modeling fatigue damage in FSW joints is a reasonable approach. Furthermore, the model appears to capture the underlining mechanisms associated with damage in this type of welded joint.
Spray Cooling With HFC-134a and HFO-1234yf for Thermal Management of Automotive Power Electronics
Authors: Yaddanapudi Satvik J. , Bostanci Huseyin
Published: March 2016

This study aimed to experimentally investigate the spray cooling characteristics for active two-phase cooling of automotive power electronics. Tests were conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. Two types of refrigerants, HFC-134a (R-134a) and HFO-1234yf, were selected as the working fluids. The test section (heater), made out of oxygen-free copper, had a 1-cm2 plain, smooth surface prepared following a consistent procedure, and served as a baseline case. Matching size thick film resistors, attached onto the copper heaters, generated heat and simulated high heat flux power electronics devices. The experiments were performed with saturated working fluids at room temperature level (22°C) by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves. Performance comparisons were made based on heat transfer coefficient (HTC) and critical heat flux (CHF) values. Effects of spray characteristics and liquid flow rates on the cooling performance were determined with three types of commercially available nozzles that generate full-cone sprays with fine droplets, and with varying flow rates between 1.6 to 5.4 ml/cm2.s. The experimental data showed that HFC-134a provided better performance compared to HFO-1234yf, in terms of HTC and CHF, which is believed to be dictated by the thermophysical properties that affect both the spray characteristics and heat acquisition ability. Overall, this study provided a framework for spray cooling performance with the current and next-generation refrigerants aimed for advanced thermal management of automotive power electronics.
Thermo-Fluid Dynamic Model of Complex District Heating Networks for the Analysis of Peak Load Reductions in the Thermal Plants
Authors: Guelpa Elisa , Sciacovelli Adriano , Verda Vittorio
Published: March 2016

District heating networks are important infrastructures to provide high efficient heating and domestic hot water to buildings located in urban areas. Modern district heating networks may involve the use of waste heat, renewable sources and heat from cogeneration thermal storage systems. In addition, management is operated through advanced ICT solutions able to minimize the global primary energy consumption and to increase end user awareness.

Detailed thermo-fluid dynamic simulation tools can be of extreme importance for the optimal management of modern district heating networks. Some of the issues that simulation tools are requested to face are: peak shaving, selection of the operating temperature, operation in the case of malfunctions, storage management. An important requirement consists in the possibility to perform fast simulations, even in the case of complex networks.

This paper aims at presenting a detailed simulation approach that can be applied to large district heating networks. The entire network is represented as constituted by the main pipeline, which may be a tree shaped or a looped network, and various tree shaped subnetworks that distribute water from the main network to each single building. The main pipeline is fully modeled considering fluid flow and transient heat transfer. Subnetworks are simulated using a reduced model obtained from the full model.

This modeling approach is applied to the analysis of transient operation of the Turin district heating network. The thermal request of the users is obtained from temperature and mass flow rate measurements at the thermal substations, available each six minutes. Thermo-fluid dynamic simulation allows one obtaining the corresponding thermal load profiles at the various thermal plants. Results show that a peak request is caused by the temperature reduction in the entire system due to the small thermal request at night. Due to the advective transport of water in the network and the thermal losses, the shape and amplitude of the peak at the plant is completely different than that at the users.

A comparison between simulations and experimental results shows that the model is able to predict the network operation with good accuracy. Using this simulation approach it is therefore possible to examine the effects of variations, obtained through night attenuation or the installation local storage systems, on the thermal request profiles of some of the users on the global thermal load of the network during the start-up transient.

The proposed simulation approach is shown to represent a versatile and important tool for the implementation of advanced management to district heating systems.
Not Enough Precision to Accurately Measure the Effect of CNT Functionalization on the Thermal Conductivity of PDMS/CNT Composite Under Strain Using Stepped-Bar Apparatus
Authors: Ralphs Matthew I. , Roberts Nicholas
Published: March 2016

Carbon nanotubes (CNTs) exhibit extraordinary mechanical and thermal properties and as such have become the subject of large research interest. Furthermore, CNTs in a polymer matrix have been shown to significantly enhance the thermal conductivity of the polymer/CNT composite in some cases. A few areas of application for this work are thermal interface materials, thermally conductive composites used in aerospace applications, and polymer heat exchangers. In each of these applications the purpose of the polymer or epoxy is to take advantage of the mechanical properties or chemical inertness. The current issue with their adoption is still the poor thermal conductivity. One approach to overcoming this issue is to embed thermally conductive materials into the host material in low concentrations to enhance the effective thermal conductivity. There has been a significant amount of work in this area, but we are far from an understanding that allows us to design a nanocomposite that gives the desired thermal conductivity (specifically in the high thermal conductivity range). This work explores the role that chemical modification (functionalization) of the CNT can play in tailoring thermal transport properties of the composite under strain. It is expected that the functionalization process would have some effect on conduction between the CNT and the polymer matrix and therefore either increase or decrease the ability of the composite to transport thermal energy. This paper focuses on three different functionalizations of CNT and explores the thermal conductivity of a polymer/CNT composite that uses polydimethylsiloxane (PDMS) as the matrix. The three functionalizations of CNTs considered are that of unfunctionalized, functionalized with a carboxyl group (-COOH), and functionalized with a hydroxyl group (-OH). The CNTs used in this study are strictly multi-walled carbon nanobutes (MWCNTs) purified to 95%. The effect of these three functionalizations on the overall thermal conductivity of the composite is evaluated through experimental methods with a stepped bar apparatus at various levels of strain on the composite sample. Results show that, while functionalization of the CNT may affect the CNT/PDMS bond, the stepped bar apparatus does not provide enough precision on the level of strain placed on the sample for a comparison across functionalizations. Future work will try to elucidate both the effect of strain and functionalization using multiple thermal conductivity measurement techniques.
Effect of In-Plane Fiber Tow Waviness Upon the Tensile Strength Characteristics of Fiber Reinforced Composites of Carbon/Epoxy AS4/3501-6
Authors: Pottavathri Sai Bhargav , Nair Rajeev , Asmatulu Ramazan
Published: March 2016

The purpose of this study was to investigate the strength and effectiveness when induced with ‘in-plane fiber tow waviness’ in a composite ply of carbon/epoxy AS4/3501-6. Fiber waviness is usually induced by infusion processes and inherent in fabric architectures. Composite structural details like ply drops and ply joints can cause serious fiber misalignment. These are usually dependent on parameters such as ply thickness, percentage of plies dropped, and mold geometry and pressure, and pressure of the resin which slides the dry fibers during the resin transfer molding process. Fiber disorientation due to fiber tow waviness in ‘in-plane’ direction has been the subject of recent studies on wind turbine blade materials and other aerospace laminates with reports of compression strengths and failure strains that are borderline, depending upon the reinforcement architecture, matrix resin and environment. Waviness is expected to reduce compressive strength due to two primary factors. The fibers may be oriented in such a way that the geometry that results because of the orientation may exacerbate the basic fiber, strand, or layer buckling mode of failure. The waviness could also shift the fiber orientation of the axis of the ply longitudinal direction which eventually results in matrix dominated failures for plies normally orientated in the primary load direction (0°). Both global and local stress & strain values generated by the finite element model were validated by the traditional mechanical methods using ply/local stiffness matrix and global/reduced stiffness matrix. A precise geometry of waviness on different materials was modeled with different wave severity factor and a parametric study was conducted. Three different defects were modeled where the angle of misalignment ranged from 5 to 15 degrees with wavelength ranging from 1 inch to 1.5 inches and amplitude ranging from 0.03 inches to 0.7 inches. This revealed the effect of ‘in-plane fiber tow waviness’ on the stress distribution and loss of strength in carbon/epoxy AS4/3501-6. The results clearly show that the effect of ‘in-plane fiber tow waviness’ leads to resin rich areas which causes high stress concentrations and decrease in the strength ratio, ultimately leading to delamination’s.
Development of an Instrumented Surgical Setup for Quantifying Displacement and Force in Surgical Dissection
Authors: Wang K. C. , Grant K. , Sun Q. , Gan L. S. , Zareinia K. , Lama S. , Sutherland G. R. , Maddahi Y.
Published: March 2016

Knowledge of positional and force properties of surgical dissection in neurosurgery is essential in developing simulation platforms for neurosurgical training such that realistic motion and perception can be conveyed to the trainee during practice. Most proposed models in literature utilize computational techniques to formulate required parameters. However, these models are not realistic enough compared to data obtained from experiments on real brain. Therefore, developing a setup to measure the position, orientation, and interaction forces will help researchers formulate realistic parameters. This paper presents the development of such a setup for quantification of displacements and tool-tissue interaction forces during performance of microsurgical tasks. A bipolar forceps is equipped with a set of force sensing elements to measure the tool-tissue interaction force components. The position and orientation of the forceps tips are measured by attaching a tracker to the bipolar forceps. To show proof-of-concept, an experienced surgeon and one assistant surgeon performed 35 neurosurgical tasks (320 trials) on a cadaver brain (previously-frozen) using the instrumented setup. Positional and force data of the bipolar forceps were recorded during surgical dissection of different brain structures. This paper reports results collected from two microsurgical tasks over 40 trials: dissection of sylvian cistern arachnoid (SCA) and dissection of middle cerebral artery (MCA). Results showed that the mean values of interaction forces during dissection of MCA were smaller than dissecting SCA. The maximum forces observed were 1.94 N and 1.75 N for SCA and MCA, respectively. The application of quantifying such parameters using the developed setup will be in training neurosurgery residents using surgical simulators in which the knowledge of brain tissue parameters is required to formulate the tissue model.
High-Density Computing: Efficient Versus Conventional Design
Authors: Comperchio Dan , Behere Sameer
Published: March 2016

Data centers are expensive to build and operate. Large data centers cost $9–13/W to build [1] and can consume more than forty times, and up to over two hundred times, the amount of energy and resources consumed by a typical building [2], [3]. Therefore, space and energy considerations need to be accounted for when evaluating competing designs for high-performance computing (HPC) installations.

This paper describes the results of an incremental cost and energy savings analysis conducted using data collected from a real-world case study to evaluate the impacts of efficient resource planning and implementing a total cost of ownership (TCO) model in the analysis of IT equipment and systems. The analysis presented demonstrates the advantages of using the latest technologies and IT strategies when planning the growth of new HPC installations at an enterprise level. The data also indicates an efficient design can significantly reduce the space, power, and cooling requirements of the HPC deployment while maintaining the performance and reliability criteria.
Electrochemical Model for Ionic Liquid Electrolytes in Lithium Batteries
Authors: Yoo Kisoo , Dutta Prashanta , Banerjee Soumik
Published: March 2016

A mathematical model is developed for transport of ionic components to study the performance of ionic liquid based lithium batteries. The mathematical model is based on a univalent ternary electrolyte frequently encountered in ionic liquid electrolytes used for lithium batteries. Owing to the very high concentration of components in ionic liquid, the transport of lithium ions are described by the mutual diffusion phenomena using Maxwell-Stefan diffusivity. The model is used to study a lithium ion battery where the cations and anions of ionic liquid are mppy+ and TFSI-. The electric performance results predicted by the model are in good agreement with experimental data. We also studied the effect of load current density on the performance of lithium ion battery using this model. Numerical results indicate that low rate of lithium ion transport causes lithium depleted zone in the porous cathode regions as the load current density increases. This lithium depleted region is responsible for lower specific capacity in lithium-ion cells. The model presented in this study can be used for optimum design of ionic liquid electrolytes for lithium-ion and lithium-air batteries.
A Bioinspired Active Micropump
Authors: Dutta Prashanta , Liu Jin
Published: March 2016

A preliminary design concept is provided for a bioinspired active micropump. The proposed micropump uses light energy to activate the transporter proteins (bacteriorhodopsin protein and sucrose/sugar transporter proteins), which create an osmotic pressure gradient and drive the fluid flow. The purpose of the bacteriorhodopsin protein is to pump proton from the pumping section to the sucrose source for a proton gradient. This proton gradient is used by the sucrose transporter proteins to transport sugar molecules from the sucrose solution chamber to the pumping channel, which generates an osmotic pressure in the pumping section. A numerical model is used to evaluate the performance of the micropump where the concentrations of proton and sucrose molecules are calculated using the conservation of chemical species equations. The fluid flow and pressure field are calculated from momentum and mass conservation equations. Simulation results predict that the micropump is capable of generating a pressure head that is comparable to other non-mechanical pumps. The proposed bioinspired self-sustained micropump will be most effective at low flow rate.
Large Eddy Simulation of Emulsified Canola Oil Sprays in Swirl-Promoted Combustion Chamber
Authors: Li Qibo , Alvarado Jorge L.
Published: March 2016

A study has been undertaken to understand the effects of swirl-promoted turbulent flow on the spatial distribution of emulsified canola oil droplets. To fully understand the effects of swirling flow on fuel droplets, the discrete phase model (DPM) has been adopted to simulate straight vegetable oils (SVO) blend droplets. The stochastic break-up model has been used to simulate the aggregated dynamic behavior of fuel droplets in the combustion chamber. A robust and stable numerical algorithm has been selected and validated using experimental data in terms of mean flow velocity profiles and fuel droplet spray distribution using known fuel characteristics. The interaction between the swirling air flow and fuel droplets have been simulated using LES by considering two swirl numbers. The effects of swirl number on droplet spatial distributions in the combustion chamber have been considered and evaluated correspondingly. Specifically, the effects of air flow structure on fuel droplet distributions have been evaluated via numerical simulation. Results reveal that fuel droplet distribution is affected by the vortices generated by the swirler. Moreover, the results also indicate that swirl number (SN) has a distinct effect on the distribution of droplets and the evolution of vortices in the combustion chamber.
Accelerations and Jerks Associated With Shaken Baby Syndrome
Authors: Akpinar Seyda , Saboori Parisa , Walker Graham
Published: March 2016

Shaken Baby Syndrome is a collection of injuries that have been associated with the violent shaking of an infant or small child. These injuries can then lead to serious brain damage or even death. It is therefore important to identify the exact mechanism that leads from the shaking to the observed injuries, but little experimental work has been done in this area.

The first part of this study was designed to identify if a correlation exists between the physical characteristics of a person shaking a crash test dummy (CRABI) and the resulting accelerations and jerks associated with the motion of the dummy’s head. This was done by placing a three axis accelerometer in the head and two in the body (one in the chest and one in the groin) of a median twelve month old male dummy to determine the acceleration of the head and body. In particular, the relative angular acceleration and jerk of the head relative to the body was determined, since it was felt to be a better predictor of brain damage than would be the absolute linear acceleration of the head.

Similar work has been done in the past; however that study only considered the absolute acceleration of the head, and in only one direction. Since the present study allows the attitude of the head to be determined, a true relative angular acceleration of the head relative to the body was found. Consequently, it was found that no strong correlation existed between the absolute linear acceleration and any body characteristic, however a correlation (R2) of 0.6 was found to exist between the body weight of the shaker and the maximum angular jerk of the dummy’s head relative to its body, as compared to only a correlation of 0.5 when the shaker’s body weight was compared to the absolute linear acceleration of the head.

A two dimensional dynamic simulation was also developed that modelled the behavior of a child crash test dummy. The model included the legs, torso, and head of the dummy, and the elastic behavior of the neck. The model was created to allow the associated accelerations and jerks to be determined for inputs of various magnitude and temporal profiles. The model was then validated by comparing the simulation results to the test results obtained from the experimental study described above.
Application of Microscale Devices for Megawatt Scale Concentrating Solar Power Plants
Authors: Zada Kyle R. , Drost M. Kevin , Fronk Brian M.
Published: March 2016

Concentrated solar power (CSP) plants have the potential to reduce the consumption of non-renewable resources and greenhouse gas emissions in electricity production. In CSP systems, a field of heliostats focuses solar radiation on a central receiver, which is ultimately transferred to thermal electrical power plant at high temperature. However, the maximum receiver surface fluxes are low (30–100 W cm−2) with high thermal losses, which has limited the market penetration of CSP systems.

Recently, small (∼ 4 cm2), laminated micro-channel devices have shown potential to achieve concentrated surface fluxes over 100 W cm−2 using supercritical CO2 as the working fluid. The present study explores the feasibility of using these microscale devices as building blocks for a megawatt scale (250 MW thermal) open solar receiver. This allows for a modular design of the central receiver with non-standard shapes customized to the heliostat field. The results show that the microscale unit-cells have the potential to be scaled to megawatt applications while providing high heat flux and thermal efficiency. At the design incident flux and surface emissivity, a global receiver thermal efficiency of > 90% can be achieved.
The Genesis of Tool Wear in Machining
Authors: Nguyen Trung , Park Kyung-Hee , Wang Xin , Olortegui-Yume Jorge , Wong Tim , Schrock David , Kim Wonsik , Kwon Patrick , Kramer Bruce
Published: March 2016

This paper presents a series of experimental and theoretical efforts that we have made in unraveling the tool wear mechanisms under steady state conditions in machining for the last few decades. Two primary modes of steady state tool wear considered in this paper are flank and crater wear. We preface this paper by stating that flank wear is explained as abrasive wear due to the hard phases in a work material while crater wear is a combination of abrasive wear and generalized dissolution wear which encompasses both dissolution wear as well as diffusion wear. However, the flank wear was not a function of the abrasive cementite content when turning low alloy steels with pearlitic microstructures. The machined surfaces of these alloys are examined to confirm the phase transformation (ferrite to austenite), which diminishes the effect of cementite content. In particular, the cementite phase present in low alloy steels dissociates and diffuses into the transformed austenitic phase during machining. Dissolution wear is claimed to describe the behavior of crater wear at high cutting speeds. The original dissolution mechanism explains the crater wear in the machining of ferrous materials and nickel alloys at high cutting speeds, but the generalization of the dissolution wear is necessary for titanium alloys. In machining titanium alloys, the original dissolution mechanism did not show a good correlation with experimental results; generally the diffusivity of the slowest diffusing tool constituent in titanium limits the wear rate. The phase transformation from alpha (HCP) to beta (BCC) phases can also take place in machining titanium alloys, which drastically increases the crater wear due to the few orders of magnitude increase in diffusivity. The most puzzling issue is however the presence of the scoring marks even though no hard inclusion is typically present in titanium alloys. This is finally explained by the heterogeneity in the microstructure due to the anisotropic hardness of alpha (HCP) phase (the hardness in c-direction is 50% higher than the hardness in other directions) and the presence of lamellar microstructure (alternating layers of alpha and beta). The lamellar microstructure has not only the in-plane anisotropic hardness but also a greater hardness than other phases. Even though we cannot claim to fully understand the physics behind tool wear, our combined approaches have unveiled some elementary wear mechanisms.
Workers’ Eye Movements During the Manufacturing of VaRTM Preforms
Authors: Kuratani Yasunari , Hase Kentaro , Hosomi Takahiro , Kawazu Tomoe , Uozumi Tadashi , Goto Akihiko
Published: March 2016

Many companies are currently researching VaRTM molding method for practical application in the composite material industry, such as in wind-powered power generating equipment, boats and ships, and aircrafts because it can produce moldings with complicated shapes or large sizes, does not require a large amount of business investments, and can make molding cost efficient. However, it is difficult discovering the optimal conditions for molding, as VaRTM molding requires perform manufacturing process which makes the fiber base material fit into a three-dimensional shape by applying pressure and heat. It is said that the accuracy of the preform affects the mechanical properties of the molding product. In recent years, despite continued investigations into the automated manufacturing of preforms, the majority of preforms are still manufactured by the hands of workers, causing the accuracy of the preform to be dependent on the ability of the worker. In this research, we made three subjects with varying number of years’ experience create preforms and produce a VaRTM molding. Conducting an interlaminar shear strength test on the molding products revealed that they had a higher intensity in order of the most years of experience to least. In order to identify the reason why the accuracy in creating a preform is dependent on the ability of the worker, we informed all of the subjects of the work process beforehand, made them use the same tools and fiber base materials, and investigated the differences in manufacturing method and manufacturing techniques caused by the workers’ number of years of experience. Differences were observed in the expert and non-experts from an overall image of the subjects when working, such as how they handled the tools (iron), their posture when layering, how they exerted strength into layering, etc. We also measured the subjects’ eye movements, focusing on where they were looking. Rather than analyzing the amount of time and the movements of their entire bodies in each work process, instead, we focused on the movements of their line of sight when working. Thus, we compared where each of the subjects was watching and the order in which they watched them. Furthermore, as well as the movement of their line of sight, we also focused on how they moved their hands when conducting the work and investigated the coordination of all of the subjects when working. Based on the fact that there were differences in the accuracy of the preforms, it is clear that manufacturing preforms is not a general concept in which the technique is handed down. While optimizing the creation of systems, work instruction manuals and tools which produce exactly the same accuracy, regardless of the worker manufacturing the preform, we will continue to conduct research that leads to the development of automated production technology.
A Bayesian Bivariate Degradation Analysis Method for Reliability Analysis of Heavy Duty Machine Tools
Authors: Peng Weiwen , Li Yan-Feng , Mi Jinhua , Yu Le , Huang Hong-Zhong
Published: March 2016

The DL150 CNC heavy duty lathes can fulfill multiple heavy duties with high precision, which is one type of fundament manufacturing equipment. They are now serving as indispensable equipment in the industries of energy, transportation, aerospace and defense. To achieve high availability and productivity, unit-specific condition monitoring and degradation analysis are carried out. The machining accuracy and lubrication debris are observed as performance indicators. Due to these two indicators are depended on each other and the working profile of these heavy duty lathes varied greatly from factories to factories, a method for bivariate degradation analysis under dynamic conditions is urgent. However, among traditional degradation analysis method, two types of assumptions are generally adopted for degradation analysis: single degradation indicator and constant external factors. These methods can hardly characterize the degradation of complex systems that are subjected to multiple performance indicators under dynamic conditions. Originated from reliability analysis of DL 150 heavy duty lathes, this paper introduces a bivariate degradation analysis method. It is aimed to mitigate these two general assumption by addressing two practical engineering-driven issues, including: (1) a new types of bivariate models is introduced to deal with bivariate degradation processes modeling, and (2) two types of dynamic covariates are incorporated and treated separately within the proposed model to cope with dynamic condition modeling. Finally, a numerical example drawn from a type of heavy machine tools is presented to demonstrate the application and performance of the proposed method.
Leverage Innovative Design Thinking to Design a Technology-Enhanced Interactive Learning Environment
Authors: Liu Ang , Lu Stephen C.-Y. , Morrison James , Wei Wei , Wang Chu-Yi
Published: March 2016

Through the dedicated efforts of design researchers, practitioners, and educators, the importance of design thinking has been increasingly recognized by the society in general, and by the engineering community in particular. On one hand, innovative design is commonly recognized to be a highly globalized activity that requires the effective collaboration between global stakeholders to deliver. Nevertheless, to date, there remains far from enough global design and/or innovation courses available in the current engineering education system, upon which, the global students can jointly develop, sharpen their collaborative design knowledge, skill and attitude. On the other hand, although technology is widely acknowledged to be a driven force of globalization, relatively few efforts have been devoted to leveraging the power of modern eLearning technologies in order to provide the global design learning experience right on participating student’s home campus with no more expensive international travels. Against such a background, this paper presents some of our best practices of employing innovative design thinking to systemically develop a technology-enabled global design innovation course. Not only we presented a set of domain-independent design thinking principles to guide the course design, but also we elaborated the chosen technologies and the functional requirement that each technology is meant to satisfy. The course in question has been consecutively offered for 6 years so far. An evaluation is conducted upon on the 2014 spring class in order to solicit students’ satisfaction with the course.
Bioparticle Manipulation by an Orthogonal Electrode Preconcentrator
Authors: Corral Guillermo , Islam Nazmul
Published: March 2016

Optimizing the cost and time is a major concern in bioparticle manipulation. Current bioparticle detection are multi-step processes that usually take at least several hours or even days to complete multiple reagents delivery, incubations and several washing processes. This highly labor-intensive work and lack of automation could result in reduced reliability and low efficiency. A pre-concentration or enrichment step will expand the application range to more dilute, practical samples and real-time detection. This paper reports the in-situ particle concentrators using AC electrokinetic techniques. With optimized design of channel geometry, orthogonal electrode patterns, and properly selected operation condition (ac frequency and voltage), the preconcentration system greatly reduced the reaction time to several minutes instead of several hours, and improved sensitivity of the assay. The goal of this research work is to develop an AC electrokinetic (ACEK) flow through preconcentrator for concentration of biomolecules using orthogonal electrode pattern.