Search

Arc flash is a constant hazard when discussing industrial safety, however, little is known about the arc flash. Current safety standards require the use of the NFPA 70E equation to establish safety limits for arc flash hazards. However, when compared to an empirically derived model, these safety limits are much too low to account for all working conditions. A comparison of these two methods will lead to the conclusion that arc flash safety distances must be increased.

Biodiesel has been a promising clean alternative fuel to fossil fuels, which cuts the emissions that are released by fossil fuels, and perhaps reduces the energy crisis induced by the exhaustion of oil resources in the near future. In this study, the effect of antioxidant additive on engine performance and emission characteristics of an engine fueled with palm biodiesel was investigated and compared with conventional diesel fuel. For this study, four fuel samples including pure diesel, diesel-biodiesel (B20), diesel-biodiesel-additive (B20+additive) and pure biodiesel (B100) were used in a multi cylinder, four stroke, water cooled, direct injection diesel engine. Engine tests were performed at various engine speed of 1000 rpm to 4000 rpm with 50% throttle opening. Engine performance and emission concentrations are investigated by determining the break specific fuel consumption (BSFC), brake thermal efficiency, CO, HC, NOx and smoke opacity using gas analyzers. The results showed that the use of baynox plus solution as additive with palm methylester gave average 3.10% higher brake power as well as 23.2% and 2.40% lower NOx and brake specific fuel consumption than the biodiesel blend without additives.

This paper proposes a new method of a high efficient charge controller used for solar PV power generation. The system explains mainly of charge controller connected to a PV and an inverter. The Maximum Power Point Tracking (MPPT) algorithm in the charge controller uses Estimate Perturb and Perturb (EPP) method which gives an estimate for every two perturb process in search of maximum output from the PV panel. A 10W prototyping PV system was executed with a boost DC-DC converter using a Micro controller to execute the proposed MPPT algorithm. Several MPPT algorithms were tested for fast changing environmental conditions, and the test results are examined and compared. It is validated that the EPP method is a promising MPPT control scheme for PV systems. This method notably improves the tracking accuracy and speed of MPPT control mechanism.

The view expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or U.S. Government. This report contains project summaries ofthe research projects in the Department ofMechanical Engineering. A list ofrecent publications is also included, which consists of conference presentations and publications, books, contributions to books, published journal papers, and technical reports. Thesis abstracts of students advised by faculty in the Department are also included.

The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or U.S. Government. This report contains project summaries of the research projects in the Department of Mechanical Engineering. A list of recent publications is also included, which consists of conference presentations and publications, books, contributions to books, published journal papers, and technical reports. Thesis abstracts of students advised by faculty in the Department are also included.

"The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U. S. Government. This report contains summaries of research projects in the Department of Mechanical Engineering. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government. This report contains summaries of research projects in the Department of Mechanical Engineering. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

International audience; For the scheme of two colour lasers in interference and holography, we uncover remarkable contribution of focusing region (spread) of the peak intensity of superposing laser beams based on the numerical studies and confirm it by mathematical calculations. The pulses having peak intensity for a wider region create better interference pattern, leading to higher modulation depth. Also, such beams having a stronger intensity gradient enhance the range of frequency detuning (difference), which would ease the experimentation in getting better holograms. A comparison of the results achieved with such beams is done with the most commonly used Gaussian beams for the better understanding of the concept for the advancement in holography.

Fish fins do not contain muscles, yet fish can change their shape with high precision and speed to produce large and complex hydrodynamic forces-a combination of high morphing efficiency and high flexural stiffness that is rare in modern morphing and robotic materials. These "flexo-morphing" capabilities are rare in modern morphing and robotic materials. The thin rays that stiffen the fins and transmit actuation include mineral segments, a prominent feature whose mechanics and function are not fully understood. Here, we use mechanical modeling and mechanical testing on 3D-printed ray models to show that the function of the segmentation is to provide combinations of high flexural stiffness and high morphing amplitude that are critical to the performance of the fins and would not be possible with rays made of a continuous material. Fish fin-inspired designs that combine very soft materials and very stiff segments can provide robotic materials with large morphing amplitudes and strong grasping forces.

Inserting obstacles such as cylindrical pins in a micromixer has the potential to significantly enhance scalar transport and improve species mixing between two co-flowing streams. However, it remains unclear how the mixing efficiency in confined microchannel flows is affected by the positioning of the fluid interface and the cylindrical pin with respect to the wall or to each other. The present work investigates the mixing induced by a single cylindrical pin placed at different gap distances from the wall of a Y-type micromixer. Two fluid interface positions are considered by mixing the fluid streams at different ratios; one located at the channel centreline and one shifted towards one of the walls. Micro particle image velocimetry (μPIV) is applied to investigate the velocity fields and streamline patterns for the different pin locations, and micro laser-induced fluorescence (μLIF) to acquire the instantaneous concentration fields and assess the mixing performance, utilising the intensity of segregation technique. Prior to the onset of vortex-shedding and when the fluid interface coincides with the channel centreline, slightly offsetting the pin from the centreline is found to yield the best mixing performance compared to centreline or near wall pin locations. However, when vortex-shedding is present, a centreline pin location exhibits the best mixing performance. The present measurements indicate that single micropins can enhance mixing, even in the absence of vortex-shedding, and when vortex-shedding occurs, they are most efficient when the pin axis and fluid interface are aligned.

This study explores the preparation and mechanical behavior of free-standing polymer-dispersed liquid crystal (PDLC) film membranes. Polyurethane (PU) was used as a thermoplastic polymer matrix to form these free-standing film membranes. Cholesteryl oleyl carbonate (COC) and cholesteryl pelargonate were used as liquid crystals (LCs) with different molecular weights. PDLC membranes were produced by casting method after LCs and polymer were mixed in the tetrahydrofuran solvent at room temperature. These membranes were formed at different concentration ratios of polymer and LCs. The relationship among the phase separation, LCs and polymer contents as well as the LCs molecular weights was investigated. The morphological structures of these membranes were studied using scanning electron microscopy (SEM). SEM images exhibited that the shapes of LC droplets embedded in PU matrix were more uniform and smaller than those of the membranes which include LC with lower molecular weight. The mechanical properties of the PDLC membranes were determined by carrying out the tensile tests. It was found that the membranes which include COC LC were more flexible. Turkish Academy of Sciences (TUBA)Turkish Academy of Sciences The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This project was financially supported by the Turkish Academy of Sciences (TUBA).

Biodiesel has gained worldwide attention due to its renewable aspects. However, it needs more quality improvement. Recently, butanol has been considered as a favorable alternative fuel or additive over methanol and ethanol in compression ignition (CI) engines. In this regard, the present work deals with the evaluation of butanol–diesel–biodiesel blends as potential alternative fuels. In this work, biodiesel has been produced from Aleurites moluccanus oil followed by blending with Euro-diesel and butanol. Important characteristics such as kinematic viscosity, density and cloud point besides FT-IR, UV-vis spectra, TGA, DSC and NMR (13C and 1H) were analyzed. Some important engine and emission performance parameters, such as BP, BSFC, CO, HC, NOx and EGT were also studied in this work. Results revealed that blending butanol and Euro-diesel with biodiesel improves the properties of pure biodiesel such as kinematic viscosity (2.41–3.55 mm2/s) and density (841.8–884.6 kg/m3), while maintaining an acceptable range for cold flow properties that are analogous to Euro-diesel. In addition, reduction in BP (24.65–26.35%), HC (52.57–38.71%), and CO (39.18–30.4%) was observed for all the blends at full load compared to Euro-diesel. However, increases in both BSFC (38.17–41.14%) and NOx (24.18–8.35%) were observed. Overall, the blends appear to be good alternatives to biodiesel–diesel blends. Thus, butanol–biodiesel–diesel blends can be considered as potential sustainable fuels for fossil diesel.

An indium arsenide photovoltaic cell with gold front contacts is designed for use in a near-field thermophotovoltaic (NF-TPV) device consisting of millimeter-size surfaces separated by a nanosize vacuum gap. The device operates with a doped silicon radiator maintained at a temperature of 800 K. The architecture of the photovoltaic cell, including the emitter and base thicknesses, the doping level of the base, and the front contact grid parameters, are optimized for maximizing NF-TPV power output. This is accomplished by solving radiation and charge transport in the cell via fluctuational electrodynamics and the minority charge carrier continuity equations, in addition to accounting for the shading losses due to the front contacts and additional series resistance losses introduced by the front contacts and the substrate. The results reveal that these additional loss mechanisms negatively affect NF-TPV performance in a non-negligible manner, and that the maximum power output is a trade-off between shading losses and series resistance losses introduced by the front contacts. For instance, when the cell is optimized for a 1 x 1 mm2 device operating at a vacuum gap of 100 nm, the losses introduced by the front contacts reduce the maximum power output by a factor of ~ 2.5 compared to the idealized case when no front contact grid is present. If the optimized grid for the 1 x 1 mm2 device is scaled up for a 5 x 5 mm2 device, the maximum power output is only increased by a factor of ~ 1.08 with respect to the 1 x 1 mm2 case despite an increase of the surface area by a factor of 25. This work demonstrates that the photovoltaic cell in a NF-TPV device must be designed not only for a specific radiator temperature, but also for specific gap thickness and device surface area., 48 pages; 6 figures; 4 tables; 2 supplementary figures

Mixed convection of carbon-nanotube/water nanofluid in a vented cavity with an inner conductive T-shaped object was examined under pulsating flow conditions under magnetic field effects with finite element method. Effects of different parameters such as Richardson number (between 0.05 and 50), Hartmann number (between 0 and 30), cavity wall inclination (between 0 ∘ and 10 ∘ ), size (between 0.1 H and 0.4 H) and orientation (between −90 ∘ and 90 ∘ ) of the T-shaped object, and amplitude (between 0.5 and 0.9) and frequency (Strouhal number between 0.25 and 5) of pulsating flow on the convective flow features were studied. It was observed that the average Nusselt number enhanced with the rise of strength of magnetic field, solid nanoparticle volume fraction, and amplitude of the pulsation, while the effect was opposite for higher values of Ri number and cavity wall inclination angle. The presence of the T-shaped object and adjusting its size and orientation had significant impact on the main flow stream from inlet to outlet and recirculations around the T-shaped object and in the vicinity of hot wall of the cavity along with the magnetic field strength. Pulsating flow resulted in heat transfer enhancement as compared to steady flow case for all configurations. However, the amount of increment was different depending on the variation of the parameters of interest. Heat transfer enhancements were 41.85% and 20.81% when the size of the T-shaped object was increased from 0.1 H to 0.4 H. The T-shaped object can be utilized in the vented cavity as an excellent tool for convective heat transfer control. As highly conductive CNT particles were used in water, significant enhancements in the average Nusselt number between 97% and 108% were obtained both in steady flow and in pulsating flow cases when magnetic field was absent or present.

International audience; There is a crucial need for effective and easily dispersible colloidal microsensors able to detect local pH changes before irreversible damages caused by demineralization, corrosion, or biofilms occur. One class of such microsensors is based on molecular dyes encapsulated or dispersed either in polymer matrices or in liquid systems exhibiting different colors upon pH variations. They are efficient but often rely on sophisticated and costly syntheses, and present significant risks of leakage and photobleaching damages, which is detrimental for mainstream applications. Another approach consists in exploiting the distance-dependent plasmonic properties of metallic nanoparticles. Still, assembling nanoparticles into dispersible colloidal pH-sensitive sensors remains a challenge. Here, we show how to combine optically active plasmonic gold nanoparticles and pH-responsive thin shells into "plasmocapsules". Upon pH change, plasmocapsules swell or 2 shrink. Concomitantly, the distance between the gold nanoparticles embedded in the polymeric matrix varies, resulting in an unambiguous color change. Billions of micron-size sensors can thus be easily fabricated. They are non-intrusive, reusable, and sense local pH changes. Each plasmocapsule is an independent reversible microsensor over a large pH range. Finally, we demonstrate their potential use for the detection of bacterial growth, thus proving that plasmocapsules are a new class of sensing materials.

Forced convection of nanofluid in a vented cavity with elastic bottom wall is studied by using an inner conductive L-shaped object and magnetic field. Simulations are performed using the finite element method when the impacts of various pertinent parameters, such as Reynolds number (between 100 and 500), Hartmann number (between 0 and 40), elastic modulus of the flexible wall (between $$10^5$$ and $$10^9$$), solid nanoparticle volume fraction (between 0 and 0.04), size (between 0.1 and 0.4H), inclination (between − 90 and 90) and location ($$x_\mathrm{c}$$ between 0.25 and 0.75 H and $$y_\mathrm{c}$$ between 0.15 and 0.65H) of the L-shaped object on the fluid flow and heat transfer features, are investigated. It was observed that wall flexibility effects are influential for the configuration with strong convection and maximum of $$11\%$$ enhancement in the average heat transfer rate for the bottom wall is achieved. Suppression of the recirculations in the vented cavity and around the L-shaped object is observed with magnetic field. It is observed that impact of magnetic field on heat transfer enhancement is different for different segments of hot wall. When the cases with the highest magnetic field and in the absence of magnetic field are compared, the average heat transfer enhancement of $$5.5\%$$ is achieved for bottom elastic wall while $$24.5\%$$ of reduction in the average heat transfer is seen for upper hot wall. The overall Nusselt number reduces slightly when the magnetic field strength is increased. Significant impacts of the size, inclination and location of the of the L-shaped conductive object on the fluid flow such as branching of the main flow stream, size of the vortex below the inlet port and heat transfer are observed. $$31.6\%$$ rise of the average heat transfer for left vertical wall and $$34.6\%$$ reduction of average heat transfer for bottom wall are achieved when the minimum and maximum of the orientation angles are compared. The location of the L-shaped object has a significant impact on the flow and thermal pattern variations. The highest variation in the contribution to the overall heat transfer is seen for right vertical hot wall segment when the Nusselt numbers at the lowest and highest values of the horizontal and vertical locations of the object are compared. L-shaped object was found to be an efficient tool to control the heat transfer features of the vented cavity. Nanofluid inclusion resulted in heat transfer enhancement in the range of 8.5–16.5% while amount of enhancement is different for different hot wall segments either in the absence or in the presence of magnetic field effects. Finally, a polynomial-type correlation for the average Nusselt number of each hot wall segments of the vented cavity is proposed for water and for nanofluid at $$\phi =0.04$$.