Introduction: Generalities on aerofoils for fluid machines. Aerodynamic profiles for low speed applications. Aerodynamic forces: the lift and drag coefficients. Velocity triangles for rotating blades. Effect of incidence. Stall. Effect of Reynolds number. Effect of roughness. Three dimensional effects. Review of loss sources in low speed fluid machines. Operating curves.
Wind turbines: Generalities on wind as energy resource. Classification. Lift and drag driven wind turbines. Generalities on the aerodynamics of wind turbines. 1D momentum theory: power and thrust coefficients. Effects of rotation. Blade number and optimum tip speed ratio. Shrouded rotors. Operating curves and power control: passive stall, fix and variable rotational speed, blade pitch control, active stall. Similarity and model tests: blockage effects in wind tunnels.
Horizontal axis wind turbines: Basic design of HAWT: The blade element theory and the optimal design of HAWT. The Blade Element Method (BEM) for the performance analysis of HAWT. Correction for finite number of blades. Correction for high values of the induction factor. General computational scheme for HAWT performance prediction. Principles of structural analysis for.
Vertical axis wind turbines: The H-Darrieus and Troposkien geometry. The azimuthal distribution of blade load and torque. The Blade Element Method and the basic design of VAWT . The Blade Element Method (BEM) for the performance analysis of VAWT. Single and multiple stream tube methods. Double multiple stream tube (DMS). Improving DMS prediction capability: dynamic stall models, stream tubes expansion. General computational scheme for VAWT The problem of self-starting.
Wells turbine: operating principle and design criteria of Wells turbine for OWC application with and without guide vanes.
Hydraulic turbines (8 CFU): Generalities on the hydraulic energy resource including mini-hydro. Turbine classification. The models theory for hydraulic machines. Review of classical hydraulic turbines. Design procedures for single and double variable pitch axial turbines: kaplan, propeller-like and bulb turbine. Operating principles of Variable rotational speed turbines. Derivation of the hill operating diagram of hydraulic turbines. Turgo and cross-flow turbines.
The course is addressed to last year energetic and mechanical engineering master students interested in developing the necessary basic skills for the aerodynamic design of fluid machines in the frame of power production from renewable energy. Design exercises developed in team and supported by tutors, as well as seminars from industry and academic experts, integrate the lectures, and represent an essential part of the course. The object of the course is to learn and to apply the most important design methods typically used for the aerodynamic design and performance analysis of the turbines applied for the exploitation of renewable sources. The course will particularly focus on the design of wind generators, conventional and mini hydro power plants, waves, tidal and other applications based on fluid machines characterized by a design procedure very different with respect to the one of conventional turbomachinery. Three top four design exercises will be developed by each working group of 3 to 4 syudents: development of BEM for the design and the perforance analysis of HAWTs; development of a double multiple stream tube method for the performance analysis of VAWTs; conceptual design and preliminary design of Wells turbine for OWC; Design of a single regulating axial turbine for mini hydro application (8 CFU)
Course bibliografy will be communaicated during the lectures. Notes and slides from the lectures will be online available only for students.