Carlos Galeano

Mezclas gasolina-etanol en motores de combustión interna en Colombia

En este trabajo se analiza el cambio sobre el desempeno y las emisiones de los motores encendidos por chispa cuando la gasolina es reemplazada por una mezcla de gasolina y etanol. Inicialmente se investiga la diferencia en las propiedades fisicoquimicas del combustible, y sus posibles efectos sobre el motor. Posteriormente se examina el efecto documentado del cambio de combustible en el desempeno y las emisiones del motor. Para llevar a cabo estos objetivos se realizo una revision bibliografica profunda de estos temas que sirve para proponer nuevas preguntas de acuerdo con el entorno colombiano. Los resultados de todos los puntos considerados indican que para que el cambio de combustible se convierta en una politica efectiva, diferentes modificaciones deben realizarse al combustible y a los motores. Las inquietudes planteadas, junto con los resultados del analisis llevado a cabo, pueden utilizarse ademas como insumo para continuar con el desarrollo de trabajos de investigacion e innovacion tendientes a aprovechar el potencial del etanol como combustible.

Numerical solution of the Falkner-Skan equation using third-order and high-order-compact finite difference schemes

We present a computational study of the solution of the Falkner-Skan equation (a third-order boundary value problem arising in boundary-layer theory) using high-order and high-order-compact finite differences schemes. There are a number of previously reported solution approaches that adopt a reduced-order system of equations, and numerical methods such as: shooting, Taylor series, Runge-Kutta and other semi-analytic methods. Interestingly, though, methods that solve the original non-reduced third-order equation directly are absent from the literature. Two high-order schemes are presented using both explicit (third-order) and implicit compact- difference (fourth-order) formulations on a semi-infinite domain; to our knowledge this is the first time that high-order finite difference schemes are presented to find numerical solutions to the non-reduced-order Falkner- Skan equation directly. This approach maintains the simplicity of Taylor-series coefficient matching methods, avoiding complicated numerical algorithms, and in turn presents valuable information about the numerical behaviour of the equation. The accuracy and effectiveness of this approach is established by comparison with published data for accelerating, constant and decelerating flows; excellent agreement is observed. In general, the numerical behaviour of formulations that seek an optimum physical domain size (for a given computational grid) is discussed. Based on new insight into such methods, an alternative optimisation procedure is proposed that should increase the range of initial seed points for which convergence can be achieved. Keywords: laminar boundary layer, similarity analysis, high-order-compact finite differences

Modelo termodinámico para el control del enfriamiento en un proceso de formación de envases de vidrio

This work shows the construction of a mathematical relation between the discharge pressure and temperature in a centrifugal blower, with the objective to fit the molds refrigeration control in a glass container manufacture cell when the enviromental conditions presents variations, which modifies the quality of the final product. The used thermodynamic model allowed to identify a linear correlation between the two studied variables, as well as to numerically calculate the value of function’s parameters. The straight line of calibration (Tracking) was implemented in the manufacture cell, allowing a reliable control of the system of molds refrigeration with a small adjustment of the parameters.