Search

The Annual Energy Production (AEP) estimations are crucial to analyze the potential of wind energy projects. To calculate the AEP of a wind farm, it is necessary to accurately measure the wind speed, because small errors in these measures lead to significant deviations in the wind turbine power curve. In-field wind speed is usually measured by means of cup anemometers, which are calibrated within wind tunnels. In-field ambient conditions differ from those at the laboratory, which increases the uncertainty of the wind speed measures performed at the location of the turbine. The present work is focused on analyzing the effect of the following ambient parameters on the cup anemometer behavior: temperature, humidity and atmospheric pressure. In order to reach this target, experimental tests in a wind tunnel were performed, which allows minimizing the effect of the rest of influence parameters: turbulence, average flow inclination angle and flow direction. With this work it is determined how flow air viscous forces affect the cup anemometers, changing its rotation frequency. This explanation concludes that a variation on air temperature, humidity and/or pressure modifies moist air kinematic viscosity, which leads to change the friction between air and cups and, consequently, the cup anemometers rotational frequency. In most cases, the kinematic viscosity is inversely proportional to the air density and therefore, higher in-field densities, compared to those at the laboratory where the anemometer was calibrated, lead to underestimate the wind speed, and vice versa. The fact that this effect has been quantified during the calibration process is quite important, since it allows removing the influence of the environmental parameters studied; so that by modifying the calibration methodology, the accuracy of cup anemometers would be optimized. In order to clarify how the moist air kinematic viscosity influences the calibration curve, the calibration measurements of a real cup anemometer are mapped into a new dimensionless abacus, with the Tip Speed Ratio (TSR) and the Reynold’s number as coordinates. The key idea is that the rotation frequency of the cup anemometer is related to both wind speed and moist air kinematic viscosity. This relation is mathematically described by the equation of a hyperbolic paraboloid surface up to a value of wind speed of 15.3 m/s.

Two sugarcane biofuels and mineral diesel fuel are tested under full load conditions, under the same values of performance and under the European Transient Cycle on an engine test bench, without any modifications to the ECU. The target is to compare engine performance and emissions. At full load, engine performance varies due to the variation in LHV. Under the same values of performance, the sugarcane biodiesel-LS9 provides the lowest THC emissions. The higher CN and exhaust gas recirculation of the sugarcane biodiesel-LS9 and the higher H/C ratio of the sugarcane diesel-farnesane compared to the diesel S50 provide a NOx reduction. Neither the increment in bsfc nor the increment of %EGR for the sugarcane biodiesel-LS9 deteriorate the combustion, so its CO emissions are lower. The sugarcane biodiesel-LS9 leads to the lowest NOx and PM specific emissions under transient operation, followed by the sugarcane diesel-farnesane. The THC and CO specific emissions are higher for the biofuels in comparison to the diesel S50. The main reason for these results is the impact of the properties of the biofuels on the ECU response However, both biofuels produce less harmful emissions at idle conditions, which supports their usage to reduce exhaust emissions in urban areas.

The presented paper aims to study the influence of mineral diesel fuel and synthetic Gas-To-Liquid fuel (GTL) on the injection process, fuel flow conditions, and cavitation formation in a modern common-rail injector. First, the influence on injection characteristics was studied experimentally using an injection system test bench, and numerically using the one-dimensional computational program. Afterward, the influence of fuel properties on internal fuel flow was studied numerically using a computational program. The flow inside the injector was considered as multiphase flow and was calculated through unsteady Computational Fluid Dynamics simulations using a Eulerian–Eulerian two-fluid approach. Finally, the influence of in-cylinder back pressure on the internal nozzle flow was studied at three distinctive back pressures. The obtained numerical results for injection characteristics show good agreement with the experimental ones. The results of 3D simulations indicate that differences in fuel properties influence internal fuel flow and cavitation inception. The location of cavitation formation is the same for both fuels. The cavitation formation is triggered regardless of fuel properties. The size of the cavitation area is influenced by fuel properties and also from in-cylinder back pressure. Higher values of back pressure induce smaller areas of cavitation and vice versa. Comparing the conditions at injection hole exit, diesel fuel proved slightly higher average mass flow rate and velocities, which can be attributed to differences in fluid densities and viscosities. Overall, the obtained results indicate that when considering the injection process and internal nozzle flow, GTL fuel can be used in common-rail injection systems with solenoid injectors.

Besides scientific knowledge, society requires engineers with additional skills, such as teamwork or communication competences. The latter are difficult to train due to the sequential syllabus is content-driven and the lack of methodologies to provide meaningful teamwork experiences. This paper proposes an approach to lead engineering students through a teamwork experience based on real-life projects. Concurrent engineering theory is used to provide good practices for collaborative work. Weekly and final evaluation with peer review and professors’ evaluation is used to assess the learning process. It has been found that the students’ technical and non-technical skills have been satisfactorily developed. In addition, the latter has contributed to benefit students’ understanding and knowledge of the matter. Therefore, the present methodology could be considered a valid approach to complement students’ competences and could also be easily implemented in other engineering courses.

This paper proposes a methodology for simulating engine/vehicle responses of a non-stationary test cycle by means of few steady-state operating modes, which can greatly reduce testing costs and time. The novelty of the proposed methodology is the application of a mapping from the engine working region to a square domain, which allows testing any design of experiments (DoE) regardless of the testing cycle, vehicle or engine. In this new working space (mapped region) it is easy to apply a DoE that satisfies optimality conditions. The validation of the methodology is based on experimental data obtained from the New European Driving Cycle. Firstly, the methodology consists in determining which representative responses can be instantaneously and/or cumulatively approximated via a low degree polynomial function (smooth surfaces) and, secondly, in performing a DoE analysis in the mapped working region where the points defining each DoE are placed. An approach function for each response is developed based on DoE tested points. Subsequently, this model allows simulating vehicle responses during the transient test. For the studied validation case, results show that main engine performance responses can be instantaneously and cumulatively predicted with high accuracy by means of a DoE with few runs. On the other hand, this analysis reveals a cumulative predicted response of confidence for regulated exhaust emissions, but not for the instantaneous values. These findings support future studies to determine the optimal DoE which minimizes testing time and costs with a satisfactory and accurate estimation of engine responses.

This paper presents the development of a complete simulation model for a mechanical in-line injection system feed with diesel, biodiesel, bioethanol fuel blends. The mathematical model is built by using the AVL Boost™ Hydsim software, while the required input data is carefully derived by making use of existing data as well as formulas and numerical procedures described in this work. This setup enables relatively efficient formulation and set-up of the mathematical model as well as consistent and reasonably accurate derivation of input data. The derived model is used to simulate the injection processes of various bioethanol-biodiesel and bioethanol-diesel fuel blends. The simulation results are compared to experimental data obtained on a Friedman-Maier type 12H100_h test bed at ambient temperature and several operating regimes. The results show that the compared injection pressure and needle lift histories are generally in a good agreement with the experimental ones. Consequently, the simulation model presented is fast and accurate enough to be engaged in various numerical procedures, ranging from investigations of influences of bioethanol addition to injection system optimization.

The number of mobile phones and tablets has notably been raising in last few years, which allows to extend its potential applications. In the field of education, the possibilities offered by augmented reality are yet to be explored. The experience which is proposed in this paper pretends to implement QR codes in subject teaching belonging to an industrial engineering degree. In particular, changes are shown in two subjects (electronic instrumentation and thermal engineering), with the aim to improve the learning process with the use of QR codes in the practices of both subjects. An opinion test was used to evaluate the undergraduate’s acceptance rate and satisfaction with this new technology proposed. The results of this survey were satisfactory and support the proposal to use mobile technology as part of the learning process.

International audience; The majority of on-road vehicles today are powered by internal combustion engines, which are, in most cases, burning petroleum-derived liquid fuels mixed with bio-components. The power to weight ratio of internal combustion engines combined with the high energy content of conventional fuels, which can be refilled easily in matter of minutes, makes them ideal for all kinds of road transportation. Since the introduction of EURO emissions norms, the emissions from the Transport sector in the European Union have undergone significant reduction. There are several alternatives to fossil fuels with similar properties, which can replace their usage in the Transport sector. The main focus of research in recent decades has been on biofuels, which can be produced from several sources. The production of biofuels is usually energy more intensive than production of fossil fuels, but their usage can contribute to emission reduction in the Transport sector. In recent years, a lot of effort was also put into promotion of electric vehicles as zero emissions vehicles. This statement should be reconsidered, since the greenhouse impact of electrical vehicles is not negligible. Conversely, in some cases, an electrical vehicle can have an even higher emission impact than modern vehicles with sophisticated internal combustion engines. This is characteristic for countries where the majority of the electricity is produced in coal power plants. With the decrease of greenhouse gas emissions in the Electricity Production sector, and with the increase of battery capacity, the role of electric vehicles in the Transport sector will probably increase. Despite significant research and financial investments in electric vehicles development, the transport sector in near future will be mostly powered by internal combustion engines and petroleum-derived liquid fuels. The amount of pollution from transport sector will be further regulated with stricter emission norms combined with smaller amount of alternative fuel usage.

Build time is a key issue in additive manufacturing, but even nowadays, its accurate estimation is challenging. This work proposes a build time estimation method for fused filament fabrication (FFF) based on an average printing speed model. It captures the printer kinematics by fitting printing speed measurements for different interpolation segment lengths and changes of direction along the printing path. Unlike analytical approaches, printer users do not need to know the printer kinematics parameters such as maximum speed and acceleration or how the printer movement is programmed to obtain an accurate estimation. To build the proposed model, few measurements are needed. Two approaches are proposed: a fitting procedure via linear and power approximations, and a Coons patch. The procedure was applied to three desktop FFF printers, and different infill patterns and part shapes were tested. The proposed method provides a robust and accurate estimation with a maximum relative error below 8.5%.

The use of diesel-farnesane and sugarcane biodiesel is showing significant potential for reducing harmful emissions from Brazilian road transport. Both biofuels are obtained from sugarcane through synthetic biology that requires fermentation. The present work studies the effect of the sugarcane biofuels, compared to regular diesel fuel, on the performance and emissions of a modern medium-duty diesel engine following the European Steady Cycle (ESC) test procedure. Diesel-farnesane showed the lowest particulate matter (PM) specific emissions. Specific nitrogen oxides (NOx) emissions from diesel fuel were above the standard limit, while sugarcane biodiesel produced the lowest emissions. All tested fuels produced specific carbon monoxide (CO) emissions below the standard limit, but the biofuels showed higher values than the reference fuel. Sugarcane biodiesel showed an inhibition effect on the oxidation process at the Diesel Oxidation Catalyst (DOC), leading to the highest specific CO emissions after the DOC. Specific total hydrocarbons (THC) emissions were well below the standard limits for all tested fuels. Concerning the regulated emissions for diesel engines (g/h), the use of sugarcane biodiesel led to PM and NOx reductions of 32.4% and 37.3%, while diesel-farnesane led to 41.7% and 6.08% reductions, respectively. These notable reductions in harmful emissions support the application of sugarcane biofuels to road transport.

Despite of the importance of cutting time in pocket machining for manufacturing cost prediction and process planning, its estimation is usually neglected and conducted dividing the total tool path length by the programmed feed rate. Nevertheless, driving the tool with a constant feed rate is, in general, not possible. We study the cutting time dependency with the tool-path curvature, type of interpolation (linear G01 or circular G02) and the distance between interpolation points (segment length). The study, conducted in two different milling machines, shows how shorter segments increase the actual cutting time, which is lower for G01 than for G02. According to the experimental results, we define a piecewise equation that estimates the real cutting time respect to the segment length and type (G1 or G2).

Incremental sheet forming techniques, such as Single Point Incremental Forming (SPIF), have an appealing potential in rapid prototyping and processing low volume plastic sheet products. Fitting a conventional CNC milling machine to accomplish SPIF is easy and cheap: just design and assembly a rigid frame and manufacture a semi-spherical end punch. Nevertheless, polymeric SPIF parts have a lack of dimensional accuracy and surface quality because of springback and friction effects. This experimental work shows the influence of temperature and force on final dimension and surface finishing of PVC SPIF specimens. In order to produce a temperature and force variation, the following parameters are modified: punch material, spindle rotational speed and sense.

In numerical control, pocketing is a widely extended machining operation with different industrial applications. Conventional strategies (directional and contour parallel) provide a uniform material removal rate, but they show discontinuities and undesirable stops. However, smooth spiral paths overcome discontinuities, although the removal rate is not constant, and their implementation is complex. In order to provide an in-between solution, our algorithm embeds an Archimedean spiral into a linear morphing definition of the pocket. The solution is smooth, simple, analytic, and leads to a B-spline curve. Different tests were performed to compare the proposed spiral to other conventional and spiral strategies. To study the influence of the tool-path geometry, we computed engagement angle and feed direction, and measured force and time. The results demonstrate that our spiral is a committed, analytic and easy to compute solution. We define spiral tool-paths via linear interpolation between closed curves.The algorithm is simple and provides an analytic solution in B-spline form.The tool path is smooth and maintains constant radial distances between laps.For non-convex pockets, the interpolation of its boundary and medial axis provides the spiral.Cutter engagement, feed direction, time and forces help to analyse the spiral.

This study presents a procedure to reduce the uncertainty of wind power density estimations, which is useful to improve the energy production predictions of wind farms. Power density is usually determined from the wind speed measured by a cup anemometer and the air density value (conventional procedure). An alternative procedure based on wind speed and dynamic pressure estimations provided by a cup anemometer is proposed. The dynamic pressure is obtained by means of a calibration curve that relates the anemometer rotation frequency and the dynamic pressure measured by a Pitot tube. The quadratic regression, used to define the calibration curve, and its uncertainty are both detailed. A comparison between the alternative procedure and the conventional one points out the advantage of the proposed alternative since results show a high reduction of the indirect measurement uncertainty of wind power density.

A circle packing is a set of tangent and disjoint discs. Maps between circle packings with the same tangency are discrete analogues of conformal mappings, which have application for example in mechanical, fluid, and thermal engineering. We describe an advancing front algorithm to compute the circle packing of a strip around a closed planar curve. Conformal mappings preserve local angles and shapes; our algorithm uses these properties to obtain via the fast Fourier transform the centers and radii for the circle packing of successive trigonometric Lagrange curves in a strip. To check the algorithm, different results are compared with well-known conformal mappings. Real time deformations of circle packings are possible by changing the shape of the initial closed curve.

In recent years, the presence of mobile devices is increasing significantly in society as well as its potential applications. However, in the field of education, the possibilities offered by augmented reality are still untapped. This paper aims a first approach to the integration of QR codes in teaching engineering subjects. Experience shows the restructuring of the subject “Electronic Instrumentation”, objectives and results in the application of mobile learning through QR codes implemented.

This work shows how wikis provide an adequate frame for collaborative work, and help to evaluate it. Using the wiki tools available in the educational web platform Ilias, the students of an Electronic Instrumentation course work in teams to accomplish different tasks. After the activity due date, professors use wiki tools such as contributions index, submission history, and changes list, to assess, in an objective way, group and individual progress. The experience demonstrates to motivate student participation.

This paper deals with the numerical analysis of the influence of bioethanol addition to diesel and biodiesel fuel on the injection process. The considered fuels are; neat mineral diesel, neat biodiesel from rapeseed oil, and bioethanol–diesel and bioethanol–biodiesel blends up to 15% bioethanol concentration (v/v) with an increment of 5%. The flow through a single assembly to one cylinder is investigated numerically by using a one-dimensional mathematical model. The fuels are experimentally investigated in a fuel injection M system at full load (FL), at several pump speeds (1100, 800 and 500 rpm), and at ambient temperature in order to verify the mathematical model. On the basis of the numerical results, the influence of bioethanol addition to diesel and to biodiesel fuel on the injection characteristics, especially on fuelling, injection timing, injection duration, mean injection rate, and maximum injection pressure, is investigated in view of harmful emission reduction. It has been shown that the determined empirical expressions for density, sound velocity and bulk modulus enable satisfactory numerical modeling of the injection process for all tested fuels. The numerically obtained characteristics were generally in good agreement with the experimental ones. The analysis of numerical results shows that for all operating regimens simulated, the addition of bioethanol to biodiesel and to diesel reduces fuelling, injection timing, injection duration, mean injection rate and maximum injection pressure.

This paper analyses the fuel injection characteristics of bioethanol–diesel fuel and bioethanol–biodiesel blends considered as fuel for diesel engines. Attention is focused on the injection characteristics which significantly influence the engine characteristics and subsequently the exhaust emissions. In this context the following injection characteristics have been investigated experimentally: fuelling, injection timing, injection delay, injection duration, mean injection rate, and injection pressure. The tested fuels were neat mineral diesel fuel, neat biodiesel made from rapeseed oil, bioethanol/diesel fuel and bioethanol/biodiesel blends up to 15% (v/v) bioethanol with an increment of 5%. The fuels blends were experimentally investigated in a fuel injection M system at rated condition (FL, 1100 rpm), peak torque (FL, 850 rpm), and maximum pump speed (1100 rpm) for different partial loads (PL 75% and PL 50%), at ambient temperature. It has been proven that for all operating regimens tested, the addition of bioethanol to biodiesel reduces fuelling, injection timing, injection duration, mean injection rate and maximum injection pressure and increases injection delay compared to pure biodiesel. Meanwhile, increasing bioethanol in diesel fuel shows no significant variations or a slightly increase in fuelling, injection timing, injection duration, and mean injection rate and a decrease in injection delay and maximum injection pressure, compared to pure diesel fuel. The influence of bioethanol in biodiesel is much more significant that in diesel fuel; it has a beneficial effect on biodiesel injection characteristics because bioethanol addition brings them nearer to the diesel fuel one and it is expected to decrease biodiesel NO x emissions.

Simulations help students to deal with complex real problems, therefore engineering instructors include these software packages in their teaching methodologies. To achieve a learning aim, different programs can be chosen. Which is the adequate choice? Based on educational criteria, we implement a well-known selection method, the analytic hierarchy process (AHP), to find a satisfactory solution. An example portrays the selection tool performance in the thermal engineering field. © 2011 Wiley Periodicals, Inc. Comput Appl Eng Educ 22:200–208, 2014; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.20546

This paper discusses the physical–chemical properties of ethanol–diesel fuel blends. The attention is focused on the properties which influence the injection and engine characteristics significantly. Main properties have been investigated experimentally. The analysis of experimentally obtained fuel properties of tested fuels and their influence on engine characteristics are presented. Physical and chemical properties of diesel fuel and ethanol–diesel fuel blends were measured according to requirements and test methods for diesel fuel (EN590, 2003). The tested fuels were neat mineral diesel fuel (D100), 5% (v/v) ethanol/diesel fuel blend (E05D95), 10% (v/v) ethanol–diesel fuel blend (E10D90) and 15% (v/v) ethanol–diesel fuel blend (E15D85). It has been proved that, for ethanol–diesel fuel blends, some additives are necessary to keep stability under low temperature conditions. Also, cold weather properties test, such as cloud point and pour point tests are negatively affected by phase separation. The rest of the properties, excepting flash point, were within diesel fuel standard specifications. Based on this study, it can be concluded that using additives to avoid phase separation and to raise flash point, blends of diesel fuel with ethanol up to 15% can be used to fuel diesel engines if engine performance tests corroborate it.

In an advanced heat engine course, we propose using a spreadsheet application to assist in the study of a reciprocating engine model, where the fluid composition changes and the parameters depend on the temperature. This application performs the fluid cycle analysis of different engines and also provides experience to students about computational procedures in heat engines. © 2010 Wiley Periodicals, Inc. Comput Appl Eng Educ 20: 681–691, 2012

In this paper bioethanol/diesel and bioethanol/biodiesel blends, at several concentrations and temperatures, are studied to find its possible commercial usage as a fuel to run a diesel power plant. The tested fuels were: net mineral diesel fuel (D100) , 5 % bioethanol/diesel fuel blend (v/v) (E5D95), 10 % bioethanol/diesel fuel blend (v/v) (E10D90), 15 % bioethanol/diesel fuel blend (v/v) (E15D85), neat biodiesel (B100), 5 % bioethanol/biodiesel blend (v/v) (E5B95), 10 % bioethanol/biodiesel blend (v/v) (E10B90), and 15 % bioethanol/biodiesel blend (v/v) (E15B85). The fuels were tested at: 30, 25, 8and -18 C. This paper shows the observations done in 8 samples during 5 weeks. After each week, each sample was overviewed, and changes related to stability, colour and aggregation were recorded. It has been proved that additives are not necessary to ensure stability of bioethanol/biodiesel blends under low temperature conditions, as the phase separation never happens.But in case of bioethanol/diesel blends some additives are necessary to keep stability under low temperature conditions. Based on this study, it can be concluded that blends of biodiesel fuel with bioethanol up to 15% can be used to fuel a diesel power plant if engine performance tests corroborate it. The same conclusion can be applied to blends of diesel fuel with bioethanol up to 15% blends if additives to keep stability are added.

This paper discusses the physical−chemical properties of ethanol−biodiesel blends considered as fuel for diesel engines. Attention is focused on the properties that significantly influence the injection, the engine characteristics, and subsequently, the exhaust emissions. In this context, the following properties have been investigated experimentally: fuel stability, density, viscosity, cold filter plugging point (CFPP), cloud point (CP), pour point (PP), flash point, filter plugging tendency (FPT), corrosiveness, lubricity, Fourier transformation infrared analysis, carbon−hydrogen−nitrogen (CHN) composition, and water content. Physical and chemical properties of biodiesel and ethanol−biodiesel blends have been measured according to the requirements and test methods for biodiesel (EN14214). The tested fuels were pure biodiesel (B100), 5% (v/v) ethanol−biodiesel blend (E05B95), 10% (v/v) ethanol−biodiesel blend (E10B90), and 15% (v/v) ethanol−biodiesel blend (E15B85). It has been proven that, for ethanol−b...

In the present work, we propose to design and manufacture a specific Vertical Axis Wind Turbine (VAWT) prototype in order to evaluate its performance when some geometrical parameters are modified. The key idea is to take advantage of additive manufacturing flexibility to print the main components in an easy way and at low cost. Prototype size (scale 1:250, with respect to a 2 MW wind turbine) is small enough to be tested in a 40 cm x 40 cm wind tunnel. We use a Fused Deposition Modeling (FDM) machine to print the prototype, which is previously designed via CAD software. Different tests have been performed to determine an adequate printing configuration, mainly regarding how layer height influences roughness and printing time. Main dimensions, roughness and weight of the printed pieces were measured and finally, parts of highest quality were used to assemble a working prototype. The methodology presented in this paper shows it is possible to manufacture a wind turbine prototype with the following characteristics: flexibility to modify the design throughout the course of the investigation, low cost and low time needed to obtain the components with enough quality.