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.
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