Search Results

The current quest for clean and renewable fuels has prompted the appearance of several bio-mass fuel alternatives. Ethanol is a renewable biofuel obtained from different agricultural crops. The main production process to obtain anhydrous ethanol consists of crop production, mashing and cooking, fermentation, distillation and chemical dehydration. Some attractive characteristics of ethanol as a clean energy source is the CO2 absorption through photosynthesis during the crop plantation phase and positive ethanol life cycle energy balance. Even though, ethanol production cost is still relatively high when compared to fossil fuels. Knowing that a large energy amount is spent in the distillation phase, the use of hydrous ethanol as fuel, with high water content, can be economically attractive. This paper compares the use of high water-in-ethanol volumetric content fuel, varying from 5% to 40%, in a naturally aspirated 0.668-L single-cylinder port-fuel injected spark-ignited engine.

The work investigates the effects of the time step in the modeling of the intake and in-cylinder systems of a diesel engine, under the motored condition. The engine has a bore of 79.5 mm and a stroke of 86 mm. The valves and piston movements are included. The equations are numerically solved, including a transient analysis of the intake stroke, for an engine speed of 1500 rpm, using a commercial Finite Volumes CFD code. For the purpose of examining the in-cylinder turbulence characteristics two parameters are observed: the discharge coefficient and swirl ratio. Regarding the turbulence, computations are performed with the Reynolds-Averaged Navier-Stokes, Eddy Viscosity Model k-ω SST, and also the k-ε standard cubic model (usual in the automotive industry), with standard near wall treatment. A moving hexahedral mesh independence study is presented. In the same way many convergence tests are performed, and a secure criterion established.

The work investigates the pressure waves behavior in a cavity, the way that the treatment with Finite Volumes Method can be understood, aiming future studies like pressure waves in air intake system of an internal combustion engine. Using a CFD code it is possible to analyze more complex systems, including three dimensional effects. In most of cases, the problem is solved using analytical methods or one-dimensional numerical method. In the present work, the governing equations was discretized by Finite Volumes Method with an explicit formulation, and the time integration was made using the multi-stage Runge-Kutta time stepping scheme. The solution is independent of mesh or time-step. The analysis presents a good agreement with other numerical studies.