The aim of our work was to study turbulent premixed flames in subatmospheric conditions. For this purpose, turbulent premixed flames of lean methane/air mixtures were stabilized in a nozzle-type Bunsen burner and analyzed using Schlieren visualization and image processing to calculate turbulent burning velocities by the mean-angle method. Moreover, hot-wire anemometer measurements were performed to characterize the turbulent aspects of the flow. The environmental conditions were 0.85 atm, 0.98 atm, and 295 ± 2 K. The turbulence–flame interaction was analyzed based on the geometric parameters combined with laminar flame properties (which were experimentally and numerically determined), integral length scale, and Kolmogorov length scale. Our results show that the effects of subatmospheric pressure on turbulent burning velocity are significant. The ratio between turbulent and laminar burning velocities increases with turbulence intensity, but this effect tends to decrease as the atmospheric pressure is reduced. We propose a general empirical correlation as a function between S T / S L and u ′/ S L based on the experimental results obtained in this study and the equivalence ratio and pressure we established.

In 2020 the COVID-19 pandemic has suddenly stopped society and changed human interaction. In this work, a thermoelectric generator wearable device for early fever detection symptoms is presented as a possible solution to avoid higher propagation of this disease. To identify a possible fever symptom, numerical and parametric simulations are developed using a highquality-refined hexahedral mesh. At first, a 2-pair-leg thermoelectric module has undergone simulations to establish temperature conditions, open-circuit voltage, and power output generation; and secondly, these previous results are extrapolated for a larger thermoelectric module containing 28 pair-leg of N-P type material. The numerical study shows that a maximum value of electrical power of 60.70 mW was reached for 28-pair-leg N-P type thermocouples under a constant temperature difference of 20 K.

Las turbinas hidrocinéticas permiten la generación de energía eléctrica a partir de una fuente renovable, utilizando la energía de las corrientes de agua, generalmente de ríos, mares y canales elaborados por el hombre, entre otros. Constituyen una tecnología que contribuye a la conservación del medio ambiente, al no requerir la construcción de represas, dado que su funcionamiento no está limitado a alturas o caídas de agua, siendo una de las principales características diferenciadoras con relación a las centrales hidroeléctricas convencionales. En este artículo se realiza una revisión sobre turbinas hidrocinéticas de eje horizontal, teniendo en cuenta una serie de aspectos de diseño, simulación computacional, materiales empleados en la fabricación y algunas mejoras implementadas para incrementar la eficiencia de este tipo de tecnología, como el uso de

In this work, we seek to predict the characteristic curve of a commercial centrifugal radial flow pump operating as a turbine, applying a novel methodology based on the state of the art. Initially, the characteristic curve in pump mode is validated through numerical simulations. The results obtained are approximate to the points awarded by the manufacturer, with an error of less than 7% at the best efficiency point. Subsequently, the characteristic curve is generated in turbine mode, obtaining an error of less than 10% respect to mathematical model. Then, velocity and pressure contours are evaluated to validate the fluid dynamic behavior. Finally, the site operating conditions for electricity generation are obtained. With this, it is proposing a methodology for the selection of these turbomachines, applying an economic technology for zones that do not have access to the electrical energy, since it was not found a method that is being applied for its correct election in the hydroelectric generation at low scale.

Water hammer problems occurs where restrictions flow suddenly change in pipelines, usually the closing or opening of valves. Presence of a high velocity pressure wave traveling though the fluid could cause damages in the pipeline structures due to the implosion of gas cavities formed by a physical phenomenon called cavitation. On this work, it is studied the water hammer physical problem considering the influence of the convective terms in the momentum and continuity equations, the cavitation problem has been evaluated by the discrete vapour cavity physical model. A MATLAB code is developed to solve the transient problem and find the hydraulic head evolution in some points along the pipeline. The method of characteristics is used to find a numerical solution of the coupled partial differential equation system. Results shows good agreement with result presented in literature reviewed, also, it is found that the influence of the convective term is small compared with a simple model where those terms are neglected, the maximum difference value of 2.4x10−4 where found, considering and neglecting the convective term on the physical model.

Las turbinas hidrocinéticas utilizan la energía contenida en el flujo de agua de mares, ríos, canales, entre otros, para generar energía eléctrica. La principal ventaja de estas turbinas es que no necesitan represas debido a que su funcionamiento es independiente de caídas o cabezas de agua, convirtiéndolas en una tecnología de bajo costo. Actualmente, los casos más exitosos de turbinas hidrocinéticas operativas se encuentran en Europa, no obstante Brasil viene marcando una gran tendencia en el estudio e implementación de las mismas. Este trabajo presenta el análisis computacional en modo transitorio de una turbina hidrocinética de eje horizontal realizado en el programa ANSYS CFX V16.2®. La turbina está constituida por tres álabes con perfil hidrodinámico NREL S822 y ángulo de ataque de 5°. También es analizado un difusor, generado a partir del mismo perfil hidrodinámico, con el fin de evaluar su efecto en el comportamiento de la turbina. Una velocidad de la corriente de agua de 1.5 m/s y una variación de la velocidad angular entre 0 y 300 RPM fueron utilizadas como condiciones de operación para la simulación. Como resultado se obtiene la potencia generada en función de la velocidad angular para ambos modelos. La mayor potencia generada por la turbina con y sin difusor fue de 879.7 W a 180 RPM y 845.9 W a 200 RPM, respectivamente, equivalente a un incremento del 3.84 %.

Surface-stabilized combustion burners or surface-radiant burners use perforated ceramic plates, ceramic foams, or metal fibers to stabilize a premixed flame. These burners are the most straightforward alternative to have both, the benefits of the reactant preheating technique and a great amount of heat transferred by radiation from the burner to the load. However, in its design, one of the greatest difficulties is to predict the flame stability limits; especially under operating conditions that lead to flashbacks and blowouts. This work presents a computational methodology based on the finite volume method with a two-dimensional domain to predict the flame curvature towards the unburned and burned gas that occurs before flashback and blowout, respectively. In the methodology, continuity, momentum, energy, and chemical species equations are solved to obtain the increase in the surface area of the flame. It was observed that this value can be used as a criterion to predict whether an operating condition is stable. When comparing the numerical results with experimental results reported in the literature, good predictions of the operating conditions that lead to flashbacks and blowouts are observed

Branch pipe T-joints are used to connect and bifurcate hydraulic channels in big hydraulic power plants size. These components are submitted to enormous strengths that must be counteracted by integrated structures to the T-joint, for this case specified arrangement type "Nun neck". The main objective in this work is about validate structurally by numerical analysis the branch pipe T-joint design with reinforcement type “Nun Neck” to the operational established conditions in hydraulic channel design. The structural T-joint design was made following AISI Buried steel Penstocks and ASME section VIII Div. 1 standards. The simulation process was made by Multiphysics Simulation Software, Ansys Workbench V 17. The branch pipe T-joint CAD model is set as 1700 mm in diameter to flow and 1200mm to derivation. The computational simulation process was executed using the mechanical structure module in ANSYS Workbench V17.0 commercial version. The boundary conditions settings were established based on internal operational pressure given as 353.14 mWC and fixed restrictions in the areas of contact with the pipe. Equivalent Von Mises stress contours were determined looking to validate the stress state in branch T-joint, findings demonstrate that the proposed design has structural failures that must had been reinforced by civil works.