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Rojas G.,SEPI ESIME IPN | Bautista O.E.,SEPI ESIME IPN | Mendez F.,National Autonomous University of Mexico
ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2015, collocated with the ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems | Year: 2015

In this work we conduct a numerical analysis of the time periodic electroosmotic flow in a cylindrical microcapillary, whose wall is considered hydrophobic. The fluid motion is driven by the sudden imposition of a time-dependent electric field. The electrical potential is obtained by solving the nonlinear Poisson-Boltzmann equation for high zeta potential, under the assumption that the electrokinetic potential is not affected by the oscillatory external field. In addition, we neglect the channel entry and exit effects, in such manner that the flow is fully developed. The governing equations are nondimensionalized, and the solution is obtained as a function of three dimensionless parameters: the ratio of the Navier slip length to the radius of the microcapillary, δ Rω, which is the dimensionless frequency for the flow or Strouhal number and measures the competition between the diffusion time to the time scale associated to the frequency of the oscillatory electric field; and κ which represents the ratio of the radius of the microcapillary to the Debye length. The principal results show that using slippage, the bulk velocity increases for increasing values of δ For the values of the dimensionless parameters used in this analysis, by using hydrophobic walls, the bulk velocity can be increased in about 20% in comparison with the case of no-slip boundary condition. On the other hand, the dimensionless frequency for the flow or Strouhal number plays a fundamental role in determining the motion of the fluid. For Rω 〈 1, the dissipation is found in resonance with the frequency of the oscillatory electric field. For Rω 〉 1, the dissipation is not in phase with the frequency and, therefore, the velocity in the center of the microcapillary, in some cases, is almost null, and the maximum value of the velocity is near to the microcapillary wall. Copyright © 2015 by ASME.

Salmeron-Quiroz B.B.,UASLP | Guerrero Castellanos J.F.,BUAP | Rodriguez Paredes S.A.,SEPI ESIME IPN | Villegas Medina G.,SEPI ESIME IPN
Proceedings of the 2012 7th IEEE Conference on Industrial Electronics and Applications, ICIEA 2012 | Year: 2012

Generally, the attitude estimation and the measurement of the angular velocity are a requirement for the attitude control. As a result, the computational cost and the complexity of the control loop are relatively high. In the present paper, a technique for attitude stabilization is proposed; the technique proposed is designed with attitude estimation and the prediction of the movement. With this approach, only the measurements of at least two non-collinear directional sensors are needed. Since the control laws are highly simple and a model-based observer for angular velocity reconstruction is not needed, the proposed new strategy is very suitable for embedded implementations. The global convergence of the estimation and prediction techniques is proved. Simulations with some robustness tests are performed. © 2012 IEEE.

In this article a methodology to diagnose faults in rotating electrical machines is presented. The method uses spectral frequency analysis of the phase currents sidebands. Online systems to verify the magnitude of these frequencies, caused not only by mechanical faults but also electrical faults, are presented. The results of a faulty set formed by a direct current motor plus a synchronous generator of 5 kVA and two squirrel-cage induction motors of 5 HP, one with slacked bearings faults and other with broken rotor bars, are presented. Also, the results of the spectra using a conventional current sensor are compared with those of a Rogowski coil, showing that the results of both sensors are suitable to detect machine faults.

Laguna-Camacho J.R.,University of Veracruz | Cruz-Mendoza L.A.,University of Veracruz | Anzelmetti-Zaragoza J.C.,University of Veracruz | Marquina-Chavez A.,University of Veracruz | And 2 more authors.
Progress in Organic Coatings | Year: 2012

In this study, the performance of coatings that were subjected to solid particle erosion tests was evaluated. These coatings can be used to protect die casting molds. The main interest of this research project was to find possible alternatives to increase the wear resistance of these mechanical components. Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity, which is machined into two hardened tool steel or coated dies. Most die castings are made from non-ferrous metals, such as aluminium, copper, magnesium, lead, zinc, tin based alloys but also they can be protected by specific coatings that have high wear resistance. The erosive wear damage in die casting molds is caused due to the molten metal is blown into the mold by high pressure dry air. Filling the mold cavities during the blown step, molten metal and sand particles impact the internal surface producing erosive wear damage. Coatings such as chromium nitride (CrN) and titanium aluminium nitride (TiAlN) that exhibit low wear damage in these types of applications due to high abrasion and erosion resistance were tested. In addition, uncoated 4140 steel and 6061 aluminium were also tested. An erosion test rig similar to that shown in ASTM G76-95 standard was designed and built to perform the tests. The abrasive particle used was angular silicon carbide (SiC) with a particle size of 420-450 μm. Tests were carried out using different impact angles (30°, 45°, 60°and 90°) with a particle velocity of 24 ± 2 m/s and an abrasive flow rate of 0.7 ± 0.5 g/min. The particle velocity and the abrasive flow rate were low in all of the tests to reduce the interaction between the incident particles and the rebounding particles in the system. The surfaces were examined with a scanning electron microscope (SEM) to characterize the erosive damage. The wear mechanisms identified were pitting and ploughing action at low impact angles (α ≤ 45°) due to sliding component commonly observed at these incident angles whereas bigger craters, radial cracks and a more roughened surfaces were seen at angles near or at 90°.In addition, it was observed that the damaged area was extended in all of the cases at 30°and 45°reducing considerably at 60°and 90°. The wear scars were characterized by an elliptical shape at 30°and 45°, which is a characteristic feature when the specimens are impacted at low-incident angles (α ≤ 45°) whereas a roughly circular was seen at 60°and 90°. © 2011 Elsevier B.V.

Gonzalez Mendoza J.M.,SEPI ESIME IPN | Palacios Montufar C.,SEPI ESIME IPN | Flores Campos J.A.,National Polytechnic Institute of Mexico
Ingenieria e Investigacion | Year: 2013

Photovoltaic energy production systems generate electricity without emitting pollutants into the atmosphere and do so from a free, unlimited resource. The highest level of energy conversion from the photovoltaic panels can be obtained by placing them perpendicular to the sun's rays falling on their surface; this is done by installing solar tracking systems. This work proposes the use of two four-bar mechanisms as the driving force for a solar tracker; we propose the use of analytical synthesis for such mechanisms. This procedure is aimed at optimising the transmission angle, increasing mechanical advantage and decreasing driving torque. A mathematical model was used to prove synthesis results and a prototype of the solar tracker was built.

Galvan S.,Universidad Michoacana de San Nicolás de Hidalgo | De Jesus Pacheco J.,Universidad Michoacana de San Nicolás de Hidalgo | Rubio C.,Universidad Michoacana de San Nicolás de Hidalgo | Mendoza C.,Universidad Michoacana de San Nicolás de Hidalgo | Toledo M.,SEPI ESIME IPN
Revista Facultad de Ingenieria | Year: 2012

This work focuses on establishing the response of the global coefficient performance when the inlet boundary conditions are drastically changed. For this, a systematic objective and qualitative method called Fractional Factorial Design has been used, which evaluates the main and joint effects on the draft tube performance parameters. This method is applied to numerical models in the limits of the grid convergence curve. The results obtained showed that after the change of the inlet boundary conditions, even though a numerical difference exists among the global performance parameters of the numerical models, they have the same tendency and behavior. In addition, the energy loss coefficient showed an important sensitivity to the inlet boundary conditions change, compared to the average pressure coefficient which is usually used as objective function in a draft tube optimization process. Thus, a numerical model with a coarse grid density could be used when the process requires a large number of analyses, changing drastically the inlet velocity condition and knowing that the results obtained will be acceptable and computationally economical.

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