bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Gamma-Ray Irradiation on the Thermal Contact Conductance of Carbon Nanotube Thermal Interface Materials
Authors: Hodson Stephen L. , Sayer Robert A. , Koehler Timothy P. , Serrano Justin R. , Dalton Scott M. , Fisher Timothy S.
Published: April 2014

Thermal interface materials (TIMs) serve a critical role in the thermal management of electronic systems by enhancing the flow of heat from source to sink. Nanostructured materials, such as arrays of carbon nanotubes (CNTs) have been shown to outperform many commercially available TIMs due to their low intrinsic resistance and large compliance that enables them to conform to rough surfaces. These characteristics, combined with their low density and ability to withstand vacuum environments and extreme temperatures, make CNT-based TIMs very suitable for space applications. In space, materials are exposed to high doses of gamma radiation due to the lack of an atmosphere to serve as an absorbing medium. With typical design lifetimes of 5 to 10 years or even more, total radiation exposure can be significant and can affect the structure and performance of the TIM. In this work, the potentially adverse effects on the thermal performance of CNT TIMs of gamma-ray irradiation is reported. CNT TIMs were irradiated in a gamma cell at a rate of 250 rad/s to total doses of 50 and 100 Mrad. The thermal interface resistance was measured before and after gamma-ray irradiation using a transient photoacoustic (PA) method at room temperature and a contact pressure of 134 kPa and indicated no adverse effects of gamma-ray exposure on thermal performance.
On-Chip Power Generation: Microfluidic-Based Reactor for Catalytic Combustion of Methanol
Authors: Tian Sheng , Thundat Thomas , Bhattacharjee Subir , Cadien Kenneth C. , Mitra Sushanta K.
Published: April 2014

In this paper, a batch of microfluidic-based reactors with integrated micropillars was fabricated on silicon wafer with standard optical lithography and deep reactive-ion etching (DRIE) technique. A Bosch process of DIRE was used to obtain ∼ 85 μm etching depth and undulating sidewall profiles on the surface of those micropillars. Such structures boost surface-area-to-volume-ratio as well as enhance heat and mass transfer coefficients. Platinum (Pt) nanoparticles (NPs) stabilized by poly-acrylate sodium in a water-ethonal-based suspension were deposited on the reactor surface using a surface-selective infiltration method. By introducing methanol vapor/air gas mixture into the reactors, stable catalytic combustion of methanol over Pt NPs starting from room temperature can be achieved.
Concept Design for Sliding Boot of Submerging-Floating Moving Platform Based on Compliant Mechanism
Authors: Liu Jie , Gao Feng , Cui Meng , Xu Guoyan , Ding Nenggen
Published: April 2014

The traction force of walking device on normal pavement is determined by contact pressure and adhesion force related with road friction coefficient. Soft terrains should be sufficiently carrying-capable for walking devices to keep their trafficability and not sink into the surface. Deep soft terrains without bottom carrying layer, such as swamps, tidal flats, and paddy fields with deep layer of silt, are unable to provide sufficient load-bearing capacity for vehicles and walking devices. Aiming at solving above problem, a noval surmerging-floating moving platform is proposed. As one role of running gear, a skidding defined as “sliding boot” is designed. The sliding boot is a fixture clamped on the front wheel as a plier, when vehicle is running on invertebrate terrains. Due to dynamic characteristic of sliding boot, sliding boot is ultized as “floating” unit. In order to essure the reliability and safty of sliding boot, mechanism design is completed based on compliance of pneumatic tire. The design method is verified by test. The results show the design method of sliding boot is approved reasonable, feasible and practical.
Computational Study of Flow and Mixing Characteristics of Turbulent Opposed Jets
Authors: Abdel-Salam Tarek , Pidugu Srikanth B.
Published: April 2014

The turbulent mixing of jet flows is one of the important problems of turbulent shear flow due to its application in combustion process involving fuel-oxidizer combinations such as hydrogen-air and methane-air. Fluid dynamics of opposed jets is not completely clarified as there are questions unanswered about flow stability and structure. In the present work, three-dimensional numerical simulations were conducted to study flow and mixing characteristics of turbulent opposed-jets. The numerical simulations were carried out with a finite volume CFD code. Turbulence is treated with the two equation model, the k-ε model. Nozzle diameter (d) and nozzle separation (W) are kept constant and equals to 32mm. Also, different jet velocities (Uj) have been examined corresponding to Reynolds numbers of 4500 to 12,000. Both confined and unconfined cases were simulated.
Parametric Analysis on Hybrid System of Solid Oxide Fuel Cell and Micro Gas Turbine With CO2 Capture
Authors: Zhou Dengji , Mei Jiaojiao , Chen Jinwei , Zhang Huisheng , Weng Shilie
Published: April 2014

Three hybrid systems of solid oxide fuel cell-micro gas turbine are designed and simulated based on the IPSEPro simulation platform. The results show that Case 2 is a better one, whose system efficiency is 59% and CO2 capture rate is 99%. Case 2 is suitable to build quasi-zero carbon emission plant, and Case 3 is suitable to reformation of existing plant. Then the effect of capture rate on system performance of Case 2 and Case 3 is investigated. The suggested capture rate for Case 2 and Case 3 is given based on the result, taking both economic and carbon emission into consideration.
An Investigation Into Acoustics and Vibraton of CPAP Devices: Numerical Prediction of Centrifugal Fan Acoustics and Vibration
Authors: Vuong Xuan-Tung , Al-Jumaily A. M. , Paxton Robert
Published: April 2014

Continuous Positive Air Pressure (CPAP) devices are used to generate pressurized airflow to relieve upper airways and allow Obstructive Sleep Apnea (OSA) patients to breathe comfortably and easily. The airflow path in these devices consists of several components including but is not limited to inlet and outlet ducts, a centrifugal fan, a humidifier and a human interface. These components contribute significantly to the noise generated by the airflow.

This research paper present a numerical study of a centrifugal fan performed with commercial ANSYS software package to predict the sound and vibration produced by the centrifugal fan. The methodologies are following: first, the unsteady flow field is computed using the CFD model to obtain aerodynamic quantities and sound sources. Then, the finite element method (FEM) is used to predict the flow-induced vibration using the predicted aerodynamic quantities. Finally, the Ffowcs-William and Hawkings’s (FW-H) acoustic analogy is used to predict the acoustic pressure at the far-field using the sound sources from the unsteady simulation.
A Balance Method Without Trial Mass Based on Lag Phase
Authors: Xie Dan-mei , Yang Yi , Liu Zhan-hui , Xiong Yang-heng , Zhang Heng-liang , Yu Yan-zhi
Published: April 2014

Mass unbalance is one of the most common faults found in steam turbine shafting. It was reported that about 70% of the total turbo-generator units newly put into commission needs high-speed dynamic balance in site. Because of longer shafting and relatively lower support stiffness, the vibration of multi-rotor bearing system, is much more sensitive to mass-unbalance. In most cases, trial masses and runs are required for the calculation of correction masses before balancing a turbo-generator rotor and such a procedure is time-consuming and expensive. Our experience shows that one balance for a turbo-generator rotor in China, by using traditional balance method, will take at least 3 to 5 runs, even 6 to 10 runs. That means 100∼500t oil will be consumed each time for balancing a turbo-generator unit with capacity of 200MW to 600MW. A balancing method without trial mass was proposed at the end of 1980’s. As it needs no trial runs if the magnitude and orientation of the rotor unbalance could be determined by calculating the amplitude-frequency and phase-frequency characteristics of various rotor sections, it has been adopted by highly skilled engineers. But the principle disadvantage of this method is that effective application requires a high degree of operator insight or knowledge of the support characteristics (i.e., requires data taken at previously balanced procedure, or from other units to determine the magnitude and location of the unbalance). This paper deduced empirical formula for dynamic balancing without trail mass at first. Then, based on the data of lag phase from the experience over 100 units, a balance method without trial mass was developed. Implementation of this method on a 1000MW turbo-generator rotor shows that it is an effective and economical procedure and the balancing risk is reduced.
Influence of Air Flow on the Segregation of Binary Particle Systems Under Vertical Vibrating
Authors: Wu Ping , Li Li , Huang Yuming , Tong Lige , Liu Chuanping , Wang Li
Published: April 2014

In this paper, we investigate the influences of air flow and vibration on the separation of a binary mixture, when air velocity u is less than the minimums fluidized velocity umf (0<u/umf<1). By the layered extraction method, we obtain the particle distribution both in the vertical and radial direction in a cylindrical bed. 13X molecular sieve particles with diameter 2.00 mm and 4.00 mm are used. Vibration frequency f is 30 Hz and dimensionless vibration acceleration Γ is 1.02, 2.04 and 3.06. The results indicate that as air velocity increases, the granular particles system under air flow tends to Reversed Brazilian nut BN (RBN) in vertical direction. When u/umf = 0.73 approximately, a large number of large particles begin to sink to the bottom, which is recognized as a turning point from homogeneous mixture to RBN. In the radial direction, depending on air velocity, different separation can take place. Under low air velocity, increasing u/umf leads particles from slight BN to homogeneous mixture. When air velocity is getting larger, the radial distribution is inclined to Radial Reversed BN (R-RBN), especially in the middle layers.
Investigation of an Ammonia–Water Based Power/Cooling Cogeneration System Using Sensible Waste Heat
Authors: Sun Liuli , Han Wei , Zhang Na , Lior Noam , Jin Hongguang
Published: April 2014

In this study, the problem of a parallel connected power and absorption cooling cogeneration system was analyzed and then an improved configuration based on this system was proposed. This system can make cascade utilization of the turbine exhaust heat. By varying turbine outlet pressure, different turbine exhaust vapor temperatures can be obtained, resulting in different amounts of heat that can be recovered in the refrigeration subsystem. Simulation results show that when the turbine outlet pressure in the improved system is 3 bar, 119.6 kW of heat can be recovered in the refrigeration subsystem, and the total equivalent power output of the improved system is 17.6% higher than that of the original system. The corresponding equivalent heat-to-power efficiency and thermal energy saving ratio are increased from 16.1% to 18.9% and 6.6% to 26.5%, respectively. When the turbine outlet pressure increases from 1.6 bar to 4 bar, the cooling output increases rapidly, resulting in better performance, and the ratio of power to cooling is in a wide range of 0.19 to 1. When the turbine outlet pressure is higher than 4 bar, the favorable effect on refrigeration cannot compensate for the adverse effect on power generation, leading to the performance reduction. This study provides a new method for high efficiency utilization of waste heat.
Experimental Investigation of Slug Characteristics Through a Standard Pipe Bend
Authors: Kesana N. R. , Vieira R. , Schleicher E. , McLaury B. S. , Shirazi S. A. , Hampel U.
Published: April 2014

Slug flow is a very common flow pattern encountered during the production of petroleum fluids. Likewise, pipe bends are often used to change the direction of the fluids during transportation. This work focuses on comparing various slug characteristics before and after a pipe bend. For this investigation, a dual Wire Mesh Sensor (WMS) is utilized. Measurements are made by placing the sensor before and after the bend. In order to obtain higher spatial and temporal resolution of the signals, a sampling frequency of 10,000 Hz is used. Experiments were conducted in a 76.2 mm (3-inch) diameter pipe utilizing air and water as fluids. Effect of fluid viscosity is also studied by conducting the experiments using three different liquid viscosities: 1, 10 and 40 cP. The experiments were conducted with superficial gas velocity ranging from 9.1 m/s to 35 m/s, and superficial liquid velocity ranged from 0.45 to 0.76 m/s. The three-dimensional time series void data from the Wire-Mesh sensor before and after the bend are analyzed to obtain averaged void fractions, structure of the slugs, void in liquid slugs, bubble size distributions, and radial profiles of gas velocity. Also, this study presents the differences in the void fraction distributions in slugs and pseudo slugs. Since pseudo slugs occur between slug and annular regimes, this information can further the understanding of the effect of flow characteristics on erosion occurring from solid particles for this flow pattern. Finally, from this comprehensive analysis the influence of the bend on the gas and liquid distributions over the cross-section has been discussed.
Kinect-Based Universal Range Sensor for Laboratory Experiments
Authors: Zhang Mingshao , Zhang Zhou , Aziz El-Sayed , Esche Sven K. , Chassapis Constantin
Published: April 2014

The Microsoft Kinect is part of a wave of new sensing technologies. Its RGB-D camera is capable of providing high quality synchronized video of both color and depth data. Compared to traditional 3-D tracking techniques that use two separate RGB cameras’ images to calculate depth data, the Kinect is able to produce more robust and reliable results in object recognition and motion tracking. Also, due to its low cost, the Kinect provides more opportunities for use in many areas compared to traditional more expensive 3-D scanners. In order to use the Kinect as a range sensor, algorithms must be designed to first recognize objects of interest and then track their motions. Although a large number of algorithms for both 2-D and 3-D object detection have been published, reliable and efficient algorithms for 3-D object motion tracking are rare, especially using Kinect as a range sensor.

In this paper, algorithms for object recognition and tracking that can make use of both RGB and depth data in different scenarios are introduced. Subsequently, efficient methods for scene segmentation including background and noise filtering are discussed. Taking advantage of those two kinds of methods, a prototype system that is capable of working efficiently and stably in various applications related to educational laboratories is presented.
A Comparison of Feature Extraction Algorithms Based on Sonar Sensor Data
Authors: Ismail Hesham , Balachandran Balakumar
Published: April 2014

Simultaneous localization and mapping (SLAM) is a technique used to determine the location of a mobile vehicle in an unknown environment, while constructing a map of the unknown environment at the same time. Mobile platforms, which make use of SLAM algorithms, have industrial applications in autonomous maintenance, such as the inspection of flaws and defects in oil pipelines and storage tanks. An important component of SLAM is feature extraction, which is the process of detecting and extracting significant features such as corners, edges, and walls in an environment. Here, the use of sonars as sensors mounted on a mobile platform is examined, and a comparison of different algorithms currently in use is made and presented. This comparison is performed through a combination of experimental and numerical studies. The triangulation-based fusion algorithm is examined for point feature detection, and the standard Hough Transform and the triangulation Hough fusion (THF) are used for line detection. Comparisons are discussed and presented along with ongoing work.
Development of an Active Control System for a Variable Electromotive-Force Generator With Applications to Wind Turbines, Ships, and Hybrid Vehicles
Authors: Zhu W. D. , Goudarzi N. , Wang X. F.
Published: April 2014

An active control system is developed to adjust the overlap between the rotor and the stator of a modified generator, called a variable electromotive-force generator (VEG), based on the desired output power at different input speeds. A novel test stand for a VEG prototype, including a 700 W electric motor as the prime mover, a 12 V DC synchronous generator with an adjustable overlap between the rotor and the stator, and a stepper motor as an actuator for the active control system, is designed and fabricated. The national instrument LabVIEW platforms are used to perform the feedback control algorithm. In this paper, the performance of the VEG with an active control system to adjust the overlap between the rotor and the stator is studied theoretically and experimentally. The control algorithm can be expressed in discrete and continuous models to cover a broad range of applications of a VEG in wind turbines, ships, hybrid vehicles, and so on. The two goals of observing the increase in the generator rotor speed by decreasing the overlap between the rotor and the stator, and adjusting the overlap between the rotor and the stator based on a desired and optimum output voltage, were investigated in designing and implementing the active control system for the VEG.
Performance of Cogeneration Systems Using Waste Heat
Authors: Khennich Mohammed , Galanis Nicolas , Sorin Mikhail
Published: April 2014

The performance of two systems using a low-temperature heat source (100 and 125 °C) and an ORC with R245fa as the working fluid for combined heat and power production has been modeled. The first system supplies the heating load with a heat exchanger in series with the ORC boiler. In the second one this function is fulfilled by the ORC condenser. The results show that the effects of the heating load on the performance of the two systems are very different. The net power output decreases monotonically with increasing heating load for the first system while it exhibits a maximum in the case of the second one. The impact of the heating load and the source temperature on the turbine size, on the total thermal conductance of the heat exchangers, on the total exergy destruction and on several other parameters is also presented and discussed.
Flow Maldistribution in Microsystems: Description and Effects
Authors: Cervantes-de Gortari J. , Torchia-Núñez J. , Hernández-Guerrero A.
Published: April 2014

Flow maldistribution is a fluid-management problem of interest in engineering. It consists in the non-uniform distribution of various flows in industrial applications like multiple accesses, manifolds, bifurcations, spreaders, etc., where the fluid currents separate, detach and reattach, break from the main body of the stream and splash within the conducts, etc. Several effects in the operation of most systems and apparatus where it occurs are common, including the interruption of fluid currents, malfunctioning, and high energy consumptions. The problem at industrial scale has been identified and treated mainly through empirical considerations, but no totally solved. It has been scarcely investigated however, in micro-technology applications with unforeseeable situations in theses very small area/volume scales, with appealing engineering tasks to solve. In any case, detailed analyses must be conducted using fluid mechanics models with experimental validation. In this paper the most relevant aspects of flow maldistribution in micro-systems where intense heat and mass transfer occur, are described. A review of their consequences and the current trends for their remediation, are presented. Examples in MEMS, fuel cells, micro-heat exchangers and micro-structured chemical reactors, are considered.
Multi-Objective Optimization of Axial Crush Performance of Square Metal–Composite Hybrid Tubes
Authors: Kalhor Roozbeh , Akbarshahi Hossein , Case Scott W.
Published: April 2014

This article deals with the multi objective optimization of square hybrid tubes (metal-composite) under axial impact load. Maximum crushing load and absorbed energy are objective functions and fiber orientation angles of the composite layers are chosen as design parameters while the maximum crush load is limited. Back-propagation artificial neural networks (ANNs) are utilized to construct the mapping between the variables and the objectives. Non-dominated sorting Genetic algorithm–II (NSGAII) is applied to obtain the optimal solutions and the finite element commercial software LS-DYNA is used to generate the training and test sets for the ANNs. Optimum results are presented as a Pareto frontier.
Investigation of Air Flow Cooling of Li-Ion Batteries
Authors: Lukhanin Alexey , Byelyayev Andrey , Fedorchenko Dmitrij , Khazhmuradov Manap , Lukhanin Oleksandr , Martynov Sergey , Rudychev Yegor , Sporov Eugene , Rohatgi Upendra S.
Published: April 2014

Lithium -ion batteries are used in electric cars, hybrid cars and Boeing 787 Dreamliner. There is an issue with heat generation in these batteries that may cause fire and reduce performance.

An experimental chamber has been setup that provides dynamic and static cooling/heating regimes for Li-ion batteries. Air flow is produced by air station with maximum output of 80 m3/h. The maximum possible pressure drop is 7000 Pa. Air station can work both in pumping and exhausting mode. This test setup will be used to study various surface topology to enhance heat transfer without increase weight.

Experimental setup contains two-stage temperature stabilization system. During the first stage we use the preliminary heating or cooling of the inlet air in the air buffer. The aim is to achieve the air temperature close to required inlet temperature. During the next stage air passes through the chamber with temperature controller where eventually the flow temperature is set. This approach provides flow temperature stabilization within −30°C to +50°C range with 0.2°C accuracy.

For our studies we have designed and manufactured simulators of Li-ion battery power cells with the same thermal properties as the original ones. Each simulator contains 40 surface temperature sensors (20 per side). The data from sensors is transferred to computer by the NI-6225 PC card for control and further processing. The design of the simulators provides information about the placement of cooling surfaces with various surface elements and its efficiency — fins, triangles, wings, etc.

In this paper, the characteristics of cooling surfaces with filleted pins will be reported. We have measured the surface temperature distributions and obtained the corresponding cooling diagrams for 10–40°C temperature range and 1 m/sec – 4 m/sec flow rates. The experimental results are compared to the computer simulation using SolidWorks Flow Simulation™ software.
Effect of Viscous Dissipation on Forced Convection Heat Transfer in Parallel Plate Channels With Asymmetric Boundary Conditions
Authors: Repaka Ramjee , Satyamurty V. V.
Published: April 2014

Effect of viscous dissipation on steady two-dimensional laminar forced convection in hydrodynamically developed and thermally developing flow between asymmetrically heated parallel plates (the plates have been kept at unequal temperatures) has been studied. The asymmetric heating is characterized by an asymmetry parameter, A, defined as the ratio of wall temperatures in excess of the fluid inlet temperature. Viscous dissipation is characterized by the Brinkman number, Br. Br <0, when the fluid is being heated and Br >0 when the fluid is being cooled. Heating and cooling have been, defined on the basis of average the wall temperatures.

When the walls are subjected to equal wall temperature (i.e., A = 1), it may be recalled that the limiting value for the Nusselt number is 17.5 when viscous dissipation is included (Br ≠ 0), and is independent of the Brinkman number, Br. Similarly, when viscous dissipation is not included, for the case of unequal wall temperatures, (i.e., A ≠ 1), the Nusselt number in the conduction limit is 4, and is independent of the value of A, not equal to one. In the present investigation, it has been shown that the local Nusselt number values in the thermally developing region as well as in the limiting condition, do vary continuously with Brinkman number when the plates are kept at unequal temperatures. The axial location where the Nusselt number displays an unbounded swing depends on the Brinkman number for a given A, and vice versa. The axial position where the Nusselt number displays an unbounded swing depends on the combination of Br and A values and differs from the position for A = 1, Br < 0, or A > 0, Br = 0.
Fast Droplet Generation With a Printhead Manufactured With Rapid Manufacturing Techniques Mounted on a Carrier Board
Authors: Kagerer Markus , Rumschoettel Dominik , Ottnad Thomas , Lueth Tim C. , Irlinger Franz
Published: April 2014

This paper presents a piezoelectrically driven microdrop generator based on a diaphragm design. The complete microdrop generator is manufactured by rapid manufacturing techniques, such as laser micromachining. This leads to a short production time which amounts to less than 2 hours per device.

After the fabrication of the microdrop generators they have to be put into operation. This means that they have to be fluidically as well as electrically connected. Therefore, the microdrop generator is bonded onto a carrier board which includes the fluid supply, conducting paths, and soldering pads. Afterwards, the carrier board is mounted on a support plate. Here, a fluid reservoir and heating elements are integrated.

Fluidic investigations are carried out with isopropanol and distilled water for validation purposes. The dependency of the minimum excitation voltage needed for droplet ejection on the pulse width and the relation between the droplet velocity and the excitation voltage are determined. The results show that increasing the pulse width reduces the minimum excitation voltage. The reason is the prolonged energy supply. Ejecting distilled water droplets requires a lower minimum excitation voltage in comparison to isopropanol due to the lower viscosity. Furthermore, droplet velocities are determined for various excitation voltages. A linear relationship between the velocity and the excitation voltage is observed. For excitation voltages greater than 65 V droplet velocities greater than 10 m/s are achieved for isopropanol.
Fabrication of Al2O3 Nanopore Sensors for DNA Detection
Authors: Zhang Yin , Liu Lei , Sha JingJie , Si Wei , Ma Jian , Chen Yunfei
Published: April 2014

A novel and facile method on the Al2O3 nanopore fabrication is proposed for DNA molecule detection based on atomic layer deposition (ALD) technique. We prepare three Al2O3 nanopores by using the focused ion beam (FIB) for the reduction of the thick layer and formation of the nanopore. To prove its feasibility and efficiency, experimental investigation is conducted on characterization of the λ-DNA translocation. As compared with the previously made Si3N4 nanopore, blockade current and time of translocation events are similar, but the signal-to-noise ration is improved.
Investigation of the Scaling Effects in Meso-Micro EDM
Authors: Maradia Umang , Wegener Konrad , Stirnimann Josef , Knaak Reto , Boccadoro Marco
Published: April 2014

The ability to remove chip volumes in micro-nano scale has enabled implementation of electrical discharge machining (EDM) in high precision and micro-machining of difficult to machine electrically conductive materials, such as metals and ceramics. Despite of its wide spread application in tool making and precision applications, the limited process understanding limits exploitation of the EDM process capabilities. In current work, scaling effects caused due to the electrode projection area and erosion depth have been analysed for the single and multiple discharges. Material removal caused by a single discharge has been simulated using a heat conduction model and validated through the experimental results. However, the paradigm shift in the optimal pulse duration value to obtain high material removal rate observed for multiple discharge process does not correlate to the single discharge removal values, even when considering the discharge frequencies during the erosion. It has been evaluated that this shift originates from the decrease in the efficiency of material removal per spark in actual erosion conditions. Different plasma states generated due to the limited dielectric availability in micro cavities and gas bubble dynamics have been proposed to be the cause for origination of the scaling effects in meso-micro EDM.
Incorporating Research Into Capstone Design Projects
Authors: Warner Grant , O’Hern Timothy J.
Published: April 2014

Mechanical Engineering Capstone projects traditionally involve design and fabrication of a piece of hardware needed to meet the specifications of an industrial sponsor. Such projects provide an opportunity for the students to apply their classroom knowledge to a practical project and to interact and collaborate with a motivated sponsor. Howard University and Sandia National Laboratories have collaborated for the past seven years on developing research-focused projects from a national laboratory that are appropriate for Capstone design student teams. The students are exposed to a research environment and learn how to use their designs to perform experiments that can acquire high-quality data. As part of these problem-based learning projects, the students employ various Computer Aided Engineering (CAE) tools available as part of their design work, build apparatus, acquire data, and perform data analysis. The projects are focused on design, but lead to an experimental apparatus that is tested, leading to students’ experience with equipment such as data acquisition systems, high-speed cameras, image analysis, evaluation of experimental uncertainty, and comparing data with models. Two example projects will be presented in this paper, one focused on development of apparatus for testing flocculation of small particles, and another on developing a vibration test platform for experiments on bubbles under vibration.
Numerical Evaluation of Improvements in Thermal Barrier Coating Adhesion by Adoption of Plasma Treatment and Biomimicry
Authors: Hossain Naser Imran , Wahab Muhammad A. , Liang Jiandong
Published: April 2014

Thermal Barrier Coatings or TBCs for short, are an imperative part of the thermal protection system of expensive equipment and machinery in the automobile and aeronautics industries. However, the problem of adhesion has plagued the TBC field for years, leading to catastrophic failures in critical TBC systems. Efforts to chemically improve bond strength have not been entirely successful, so the other efficient way to do this would be some kind of mechanical interlocking that occurs at micro/nano scales. This work deals with the improvement of adhesion in TBC systems by numerical simulation and bench-marking of micro-geometric surface features that has been synthesized or reproduced in a laboratory environment through mechanical or electrochemical operations. For this, several geometries that benefit mechanical interlocking, and consequently improvements in mechanical ‘adhesion’ in TBCs have been compared. To simulate the mechanical and thermal loading on the micro geometries and to observe their effect, the commercial finite element software COMSOL was used. An analogy was drawn between the biological, Van der Waals dry adhesion mechanism in Gecko feet and that in the top surface of the thermally grown oxide (TGO) layer in TBC since the ‘mushroom head geometry’ in the Gecko feet provides improved adhesion (as much as 10 folds) compared to other geometries (spatular head, spherical head, or plain triangular crevices). An affordable synthesis process, termed “Electrolytic Plasma Processing (EPP)” for recreating this specific geometry, is also proposed and its utility briefly discussed.
An Experimental Study of a Single-Device Jet Impingement Cooler With Phase Change Using HFE-7100 and a Vapor Extraction Manifold
Authors: Joshi Shailesh N. , Rau Matthew J. , Dede Ercan M.
Published: April 2014

There is substantial ongoing research into jet impingement cooling with phase change for high heat flux electronics applications. Higher heat transfer coefficients can be achieved through coolant phase change, although the proper evacuation of the resulting two-phase flow is important as it can affect the overall heat transfer performance of the cooler. In prior work, the accumulation of vapor in a multi-device cooler during the two-phase heat transfer process was shown to cause a build-up of pressure inside the cooler. This increase in pressure is logically related to the position of the cooler inlet and outlet ports with respect to the internal cooling geometry. Such pressure increases lead to an increase in the saturation temperature of the coolant and additional concerns regarding fluid containment. The present study describes a novel two-phase single-device cooler with HFE-7100 as the coolant, where the design allows for efficient removal of vapor from the test-section via a sloped outlet manifold. The performance of the cooler was evaluated using smooth and finned copper heat spreaders. To assess the effectiveness of the vapor extraction manifold, a comparison is made with the performance of a related multi-device cooler. Experimental results show that the single-device design reduces pressure build-up inside the cooler by an order of magnitude from 59 kPa to 7 kPa. A 36% increase in the effective heat transfer coefficient (∼19,000 W/m2K) at 50 W/cm2) was also achieved using the new single-device design with the smooth heat spreader when compared to the multi-device cooler. Additionally, by enhancing the heat spreader surface area with fins, the effective heat transfer coefficient was further boosted to 23,000 W/m2K.
Thermal-Aware Micro-Channel Cooling of Multicore Processors: A Three-Stage Design Approach
Authors: Li Yubai , Guo Dongzhi , Yao Shi-Chune
Published: April 2014

This study goes beyond the common micro-channel cooling system composed of uniform parallel straight micro-channels. Due to the highly non-uniform power dissipation on a multicore processor, the micro-channel cooling system is designed to fit with the heat load on the multicore processor. By applying effective strategies and arranging key design parameters, stronger cooling is provided under the high power core area, and less cooling is provided under the low power cache area to save the precious pumping power. The well designed thermal-aware micro-channel cooling systems could effectively lower the hot spot temperature and temperature gradients on chip.

A three-stage approach to design thermal-aware micro-channel cooling system for multicore processor is developed. Two micro-channel cooling systems are specifically designed for a 2 core 150W Intel Tulsa processor and an 8 core 260W (doubled power) Intel Nehalem processor, to illustrate the design approach. The working fluid is single phase HFE7100. For the Tulsa processor, a strategy named strip-and-zone approach is used. The final design leads to 30kPa pressure drop and 0.094W pumping power while maintains the hot spot temperature to be 75 °C. For the Nehalem processor, a split flow micro-channel system and a widen-inlet strategy are applied. The final design takes 15kPa pressure drop and 0.0845W pumping power while maintains the hot spot temperature to be 82.8 °C. The design approach in this study provides the basic guide for the industrial applications of effective multicore processor cooling using micro-channels.
Application of CAD/CAE, Reverse Engineering and Rapid Prototyping in New Product Development Industry
Authors: Prabaharan Muni
Published: April 2014

This paper is written based on some industrial practices. It presents some aspects about rapid prototyping which stays at the base of manufacturing design using CAD/CAE programs and its integration in industrial field. A big economical advantage is that products made by rapid prototyping express a low risk failure and the manufacturing process takes less time and lower costs than the conventional techniques. A new product design was produced by rapid prototyping techniques starting from a broken one. First, the mechanical characteristics of broken product were investigated by Finite Element Analysis (FEA). It provides a way of simulating the product design under working condition and an opportunity to understand failure modes. Therefore, problems in tooling would be minimized. After FEA simulation, a new material was chosen in order to increase the mechanical characteristics. The new product material improves all the mechanical characteristics. At the end of this paper, the case study is presented. Before that, new framework is proposed.
Analysis of Coupled Heat and Mass Transfer During Condensation of High Temperature Glide Zeotropic Mixtures in Small Channels
Authors: Fronk Brian M. , Garimella Srinivas
Published: April 2014

Condensing zeotropic mixtures have the potential to improve the thermodynamic performance of power generating, cooling, and heating systems. Further improvements can be realized by developing equipment using mini- and microchannels. However, it has been shown that the concentration gradients arising from the changing composition of the vapor and liquid phases during condensation introduce additional mass transfer resistances, degrading the overall heat transfer. Furthermore, the coupled heat and mass transfer in mixtures at this scale is not well understood. Results from experiments on condensation of ammonia/water mixtures at varying concentration (80–100% NH3), mass flux (G = 50 − 200 kg m−2 s−1), and tube diameter (D = 0.98–2.16 mm) are reported here. Other researchers have reported an apparent heat transfer coefficient for zeotropic mixtures, which fails to explicitly account for mass transfer. The present work quantifies the liquid film heat transfer coefficient by accounting for mass transfer through a film model approach, which allows the relative significance of the vapor and liquid heat and mass transfer resistances to be quantified.
Modeling of a Catalytic Flat Plate Fuel Reformer for Hydrogen-Rich Reformate Fuel
Authors: Das Susanta K. , Gadde Kranthi K.
Published: April 2014

In this study, using a two-dimensional computational fluid dynamics (CFD) model with co-current flow arrangement, steam reforming of methane coupled with methane catalytic combustion in a catalytic plate reactor is investigated. The two-dimensional approach makes the model more realistic by increasing its capability to capture the effect of design parameters such as catalyst thickness, reaction rates, inlet temperature and velocity, and channel height, and eliminates the uncertainties introduced by heat and mass transfer coefficients used in one-dimensional models. In our work, we simulate the entire flat plate reformer electro-kinetics and carry out parametric studies related to design matrices that can provide guidance for the practical implementation of such design. The operating conditions are chosen in such a way which makes possible a good comparison of the catalytic plate reactor and catalytic combustion analysis with the conventional steam reformer. The CFD results obtained in this study is very helpful to understand the optimized design parameters to build a first generation prototype.
Dynamic FE Analysis for Reducing the Flat Areas of Formed Shapes Obtained by Roll Bending Process
Authors: Tran Hoang Quan , Champliaud Henri , Feng Zhengkun , Dao Thien-My
Published: April 2014

Roll bending is a continuous forming process where plates, sheets, beams, pipes, and even rolled shapes and extrusions are bent to a desired curvature using forming rolls. Over the years, with the advantages such as reducing setting up time, the cost in tooling investment and equipment, the roll bending process was fundamental for manufacturing cylindrical shapes. However, the process always leaves a flat area along the leading and trailing edges of the workpiece. Therefore, accuracy could be a challenge when the part to be produced is large and made of high strength steel. There are several methods to minimize the flat area. Among them, for the asymmetrical configuration, moving slightly the bottom roll along the rolling direction may have the highest effect. On the other hand local adjustment of the bottom roll location is also important for providing the pressure needed for gripping and carrying the workpiece through the rolls. Then by optimizing the vertical displacement of the bottom roll one can minimize the span of flat areas.

The main objective of this research is to assess 3D dynamic Finite Element (FE) model with Ansys/LS-Dyna for the simulation and analysis of the deformation of the workpiece during the manufacturing of cylindrical parts. Various dynamic simulations based on 3D element are performed to provide better understanding of the whole deformation history and to establish the relationship between the location of the bottom roll and the end shapes of the formed cylinders. The results from FE simulations are then compared with corresponding experimental results from an industrial roll bending machine in order to improve the quality of the final shape.
Inverse Dynamic Simulation of a Hydraulic Drive With Modelica
Authors: Saad Joseph , Liermann Matthias
Published: April 2014

Inverse dynamic simulation of hydraulic drives is helpful in early design stages of hydraulic machines to answer the question whether the drive can meet dynamic load requirements and at the same time to predict the energy consumption for required load cycles. While a forward simulation of the hydraulic drive needs an implementation of the controller which generates the control input as a function of the control error, the inverse dynamic simulation can be implemented without control. This is because the required motion is simply defined as a constraint and therefore the control error is always zero.

This paper surveys examples of successful use of inverse dynamic simulation in engineering. We use the example of a hydraulic servo-drive to explain the procedure how to generate a state space description of the inverse problem from the given system of differential algebraic equations. Equation based modeling languages such as Modelica lend themselves naturally for inverse simulation because the definitions of which variables of the model are inputs and which are outputs is not made explicit in the model itself.
Vehicle’s New Anti-Roll System for Suspension Parasitic Stiffness Reduction and Non-Linear Roll Stiffness Characteristic
Authors: Kim Bo Min , Ko Dae Sik , Kim Jong Min
Published: April 2014

In general, vehicle uses torsional stiffness of a stabilizer bar to control the roll motion. But this stabilizer bar system has problems with degradation for ride comfort and vehicle’s NVH characteristic due to the suspension parasitic stiffness caused by deformation and wear of the stabilizer bar rubber bush. In addition, it is difficult to control the vehicle’s roll motion effectively in case of excessive vehicle roll behavior when it is designed to satisfy ride comfort simultaneously because of the stabilizer bar’s linear roll stiffness characteristic. In this paper, the new anti-roll system is suggested which consists of connecting link, push rod, laminated leaf spring, and rotational bearing. This new concept anti-roll system can minimize the suspension parasitic stiffness by using rotational bearing structure and give the vehicle non-linear roll stiffness by using the laminated leaf spring structure which are composed of main spring and auxiliary one. Reduction of suspension parasitic stiffness and realization of non-linear roll stiffness in this anti-roll system were verified with both vehicle dynamic simulation and vehicle test. Also, this study includes improvement of the system operating efficiency through material change and shape optimization of the leaf spring, and optimal configuration of the force transfer system.
Wear and Corrosion Resistance of High-Velocity Oxygen-Fuel Sprayed Iron-Based Composite Coatings
Authors: Milanti A. , Koivuluoto H. , Vuoristo P. , Bolelli G. , Bozza F. , Lusvarghi L.
Published: April 2014

Thermally sprayed iron-based coatings are being widely studied as alternative solution to conventional hardmetal (cermet) and Ni-based coatings for wear and corrosion applications in order to reduce costs, limit environmental impact and enhance the health safety. The aim of the present work is to study the cavitation erosion behaviour in distilled water and the corrosion properties in acidic solution of four high-velocity oxy-fuel (HVOF) sprayed Fe-based composite coatings. Fe-Cr-Ni-B-C powder was selected for its good sliding wear properties. In addition, a powder composition with an addition of Mo was studied in order to increase the corrosion resistance whereas additions of 20 wt. % and 40 wt. % WC-12Co as blended powder mixtures were investigated in order to increase wear resistance. Improvement of coating properties was significant with the advanced powder compositions. Dense coating structures with low porosity were detected with microstructural characterization. In addition, good cavitation wear resistance was achieved. The cavitation resistance of customized Fe-based coating with Mo addition was reported to be twice as high as that of conventional Ni-based and WC-CoCr coatings. The corrosion properties of HVOF Fe-based coatings were also evaluated by studying electrochemical behaviour in order to analyse their potential to use as corrosion barrier coatings.
Evaluation of a New Method for Customer-Orientated Rating of Clutch Systems in Conceptual Hybrid Vehicles
Authors: Brezger Friedrich , Albers Albert
Published: April 2014

Coming to hybrid vehicles regarding passenger cars there is still no final answer which hybrid topology is the best system for the market. In European countries the focus is clearly set on energy efficiency or rather on carbon dioxide emission and production costs. There are several innovative hybrids available on the market coming with different advantages for the different customers respectively driver types.

Well-known test cycles like the NEDC (Europe), the 10–15 Mode (Japan), the FTP72&FTP75 (USA) do provide an answer to the question of energy efficiency. But it is also known that this information is not necessarily valid for the special customers’ driver behavior.

For the product development process a tool is required to rate the different hybrid topologies and their components as well as their scales. One aspect is efficiency in additional consideration of the customer classes. Along the dimensioning of possible abuse maneuvers the average performance is important.

In this paper a user-friendly tool for measuring driving data is introduced in order to investigate its sufficiency to evaluate different driver behaviors. This tool uses an OBD-to-Bluetooth-device in combination with a smartphone with GPS. The advantage of this devices compared with a conventional autobox is its low cost and its simple use for all kinds of customers. This fast gained data is processed using probability density functions to create customer classes and representative reference cycles. In a second step a generic hybrid topology with an operation strategy is introduced due to include a detailed clutch system model. This clutch system model has a high fidelity regarding its drag torque behavior. The influence of little improvements at specific operating points on the drag torque will be evaluated. As a result the utility analyses show the efficiency improvement concerning the different driver classes. Thereby a sustained recommendation on further efforts for clutch optimization and its target characteristics can be proposed.