M. Dell’Isola

CFD simulations of power coefficients for an innovative Darrieus style vertical axis wind turbine with auxiliary straight blades

The increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in renewable energy sources such as wind energy. Amongst the different typologies of wind generators, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, Computational Fluid Dynamic (CFD) simulations were performed in order to investigate the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds. The micro turbine under investigation is composed of three pairs of airfoils, consisting of a main and auxiliary blades with different chord lengths. The simulations were made using the open source finite volume based CFD toolbox OpenFOAM, considering different turbulence models and adopting a moving mesh approach for the turbine rotor. The simulated data were reported in terms of dimensionless power coefficients for dynamic performance analysis. The results from the simulations were compared to the data obtained from experiments on a scaled model of the same VAWT configuration, conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). From the proposed analysis, it was observed that the most suitable model for the simulation of the performances of the micro turbine under investigation is the one-equation Spalart-Allmaras, even if under the conditions analysed in the present work and for TSR values higher than 1.1, some discrepancies between numerical and experimental data can be observed.

Analysis of Temperature and Residence Time of the Exhausts in the Combustion Chamber of an Incinerator Plant

The interest for energy recovery from waste incineration has increased over the years, in order to reduce the number of landfills and produce electricity and heat. At the same time, concern for the impact such processes have on the environment has also grown, and to reduce such an impact, new legislation is being enforced in Europe and Italy. In particular, important restrictions are imposed on the temperature of the exhausts in the combustion chamber, which must be kept above certain values for a given period of time, depending on the type of waste that is being incinerated. Such conditions can be rather difficult and certainly very expensive to monitor with acceptable accuracy. For this reason, in practical applications the temperature of the exhausts in the chamber is usually calculated through semi-empirical and approximate models that relate the temperatures in different sections of the chamber. In this work, the authors present a numerical approach for the analysis of such models that can be used to quantify the uncertainty on this type of measurement due to the common approximations used in full scale incineration plants. The analysis is based on the CFD simulation of the thermo-fluid-dynamic field in the combustion chamber of a full scale plant in Italy, whose results have verified based on a comparison with the data collected during an experimental campaign.Copyright