PIV measurements over a double bladed Darrieus-type vertical axis wind turbine: A validation benchmark

Vertical axis wind turbines (VAWTs) are very attractive for in-home power generation since they can be adopted even at low wind speeds and highly variable wind direction. Even if significant experimental research activity has been carried out to improve VAWTs performance, the ability to accurately reproduce flow field characteristics around turbine blades by CFD (computational fluid dynamics) techniques represents a powerful approach to further enhance wind turbines performance. Thanks to CFD, in fact, it is possible to reproduce flow characteristics with a detail level impossible to achieve by experiments. Nevertheless, in order to appropriately analyze the flow structure by CFD application, an accurate validation is essential, and high-quality measurements of some main flow characteristics are required. In recent publications the authors investigated, both experimentally and numerically, the performance of an innovative double bladed Darrieus-type VAWT, with the aim to define an optimal configuration also focusing on self-starting ability of the prototype by employing CFD technique. Nevertheless, comparison between experiments and numerical results was made only in terms of power and torque coefficient. To overcome such limitation, in this paper the authors propose an experimental benchmark case for CFD results validation, describing detailed flow field in correspondence of one pair of blades of the innovative Darrieus-type VAWT in static conditions. Measurements were performed employing Particle Image Velocimetry (PIV) technique on a scaled model of the turbine blades realized by 3D printing. An uncertainty analysis was also performed which showed a high accuracy of the obtained experimental results. The measurements of the main flow characteristics (bi-dimensional velocity components) were then used for a test case CFD validation of two different turbulence model

Numerical and Experimental Investigation of the Flow over a Car Prototype for the Shell Eco Marathon

The Eco-Marathon is a challenge organized by Shell in which student teams compete in designing energy-efficient vehicles. The event spark debate about the future of mobility and inspire engineers to push the boundaries of fuel efficiency. The aim of the present work consists of the numerical and experimental investigation of the aerodynamic performance of a Shell Eco Marathon prototype designed by a group of students of the University of Cassino, Italy. The car design has been provided by means of detailed 3D CFD modelling with Comsol Multiphysics®. The numerical tool has been validated against experiments conducted at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino. In particular, a scale model of the car has been investigated in an open chamber wind tunnel by means of the Particle Image Velocimetry (PIV) technique, for different free stream velocities within the range 11 – 23 m/s. Measurements have been associated to a proper uncertainty analysis. The experimental data has been compared to numerical results obtained employing different turbulence models and the validated numerical tool has been applied to the simulation of the full-scale car model, allowing to analyse the wake flow structures, and estimate the overall drag coefficient

Numerical performance assessment of an innovative Darrieus-style vertical axis wind turbine with auxiliary straight blades

Vertical axis wind turbines (VAWTs) are receiving growing interest for small scale power generation at low wind speed condition, in particular for off-grid, home applications. VAWTs are mainly composed of two typologies: drag-based Savonius, and lift-based Darrieus turbines. Between the two, the Darrieus turbine is the most promising since it is characterized by higher efficiency, even if for applications at higher wind speeds with respect to Savonius VAWTs. A lot of research is made in order to enhance the aerodynamics of the Darrieus rotors, making them applicable for lower wind speeds without significantly affecting efficiency. One of the developments of standard Darrieus configuration is proposed in our previous paper, adopting three couples of blades for the rotor, each composed by a main and an auxiliary aerofoil. A scaled model of such rotor configuration is tested in the wind tunnel available at the Department of Civil and Mechanical Engineering (DICEM) of the University of Cassino, showing good performances in terms of power and torque coefficients, especially at the lower wind speeds. In the present paper, a Reynolds Averaged Navier-Stokes-based CFD model is used in order to investigate the performance of an innovative, real scale double-bladed wind turbine. The CFD model is validated on the basis of the wind tunnel data, and the real scale wind turbine performance is analysed by numerically evaluating the power and torque coefficients. The results of the simulations confirm the capabilities of the proposed configuration to give valuable performance even for wind speeds below 4 m·s-1

Effects of the flue gas treatment of incinerator plants on sub-micron particle concentrations at the stack

The paper is focused on the emission of sub-micron particles from incinerator plants characterized by different treatment sections. In particular, measurement of particle number concentrations and distributions in different sampling points of the flue-gas treatment sections, and/or over several years, allowed to detect, for the very first time through in-field tests, the effect of the age of the fabric filter bags and of the SCR system on the emission of sub-micron particles. In fact, tests showed that the age of the fabric filter bags can affect the particle number concentrations at the stack: indeed, for older bags higher concentrations at the stack were measured likely due to the filter cleaning process. Concerning the effect of the SCR system, the natural gas combustion performed in the SCR system leads to an increase of sub-micron particle concentrations at the stack with respect to the values measured after the filtration section