A practical engineering approach to the design and manufacturing of a mini kW blade wind turbine : definition, optimisation and CFD analysis

A practical engineering approach to the design of a 60 kW wind generator with improved performances is presented. The proposed approach relies on the use of a specific, “ad hoc” developed software, OPTIWR (Optimization Software), expressly conceived to define an “optimum” rotor configuration in the framework of the blade element-momentum theory. Starting from an initial input geometric configuration (corresponding to an already existing 50 kW turbine) and for given values of the wind velocity Vwind and of the advance ratio X = Vwind/ΩR (where Ω is the blade rotational speed and R is the propeller radius), this software is used to determine iteratively the optimized distributions of chords and twists which can guarantee a constant value of the socalled axial induction factor a = 1/3 along the blade. The output configuration is then converted into a CAD model to be used, in turn, as input data for a CFD commercial software. With this tool the relative rotational motion between the fluid and the wind turbine are simulated resorting to a MRF (Moving Reference Frame) technique (for which continuity and momentum equations are solved in a rotating reference frame). The outcomes of the numerical simulations are then used to verify the improved performances of the optimized configuration and to which extent the CFD data agree with “expected” behaviours (i.e. performances predicted on the basis of the simplified model). Finally, some details about the construction technique used to turn the optimized configuration into an effective working prototype are provided, in conjunction with a critical discussion of suitable production methods for composite components

Innovative Aircraft Aeroelastic Modelling and Control

The aeroelastic design of innovative aircraft wing configurations imposes the designer to deal with specific phenomena, which are not usually considered in classical aircraft definition. The design process itself, though, gives the designer several indications on how to maintain the safety standards imposed by regulations. The investigation of the basic aeroelastic principles for unconventional wings with high aspect ratios can be extremely interesting as, once introduced in a multidisciplinary design, they can be very effective in giving an early determination of the static and dynamic behaviour of the aircraft, leading to significant improvements in the configuration weight, cost, and overall performance. The paper shows some preliminary results as part of the main objectives of the In.A.Team group (Innovative Aircraft Theoretical-Experimental Aeroelastic Modelling) at Politecnico di Torino, Italy. The In.A.Team Project has the following main objectives: 1) to develop multidisciplinary analysis methods appropriate to unconventional aircrafts (highly flexible, "morphing" vehicles); 2) to develop the capability of illustrating and understanding the effects of uncertainties on the behaviour of an aeroelastic system; 3) to apply the innovative adaptive L1 control techniques to highly flexible wings, 4) to integrate theoretical analysis with commercial structural (FEM) and aerodynamic tools (CFD). 5) to design and manufacture an aeroelastic experimental-test-model. 6) to validate theoretical/numerical results by vibration and aeroelastic wind tunnel tests

Influence of the Incomplete Diagonal Tension Field on the Nonlinear Angle of Twist of Advanced Composite Wing Boxes under Pure Torsion

AIAA JOURNAL OF AIRCRAF

Influence of the Incomplete Diagonal Tension Field on the Nonlinear Angle of Twist of Advanced Composite Wing Boxes under Pure Torsion

AIAA JOURNAL OF AIRCRAF

Scaled Size Prototype Design

NST 223, Dicembre 2003, DIASP, Politecnico di Torin

Generalized topology for resonators having N commensurate harmonics

Despite the ubiquity of both linear and nonlinear multimember resonators in MEMS and kinetic energy harvesting devices very few research efforts examine the orientation of members in the resonator on its dynamic behavior. Previous efforts to design this type of resonator constrains the members to have relative orientations that are 0° or 90° to each other, i.e., the elements are connected inline with adjoining members or are perpendicular to adjoining members. The work expands upon the existing body of research by considering the effect of the relative orientation between members on the dynamic behavior of the system. In this manuscript, we derive a generalized reduced-order model for the design of a multi-member planar resonator that has integer multiple modal frequencies. The model is based on a Rayleigh Ritz approximation where the number of degrees of freedom equals the number of structural members in the resonator. The analysis allows the generation of design curves, representing all the possible solutions for modal frequencies that are commensurate. The generalized model, valid for an N-DOF structure, is then restricted for a 2- and 3-DOF system/member resonator, where the linear dynamic behavior of the resonator is investigated in depth. Furthermore, this analysis demonstrates a rule of thumb; relaxing restrictions on the relative orientation of members in a planar structure, allows the structure to exhibit exactly N commensurable frequencies if it contains N members

EQUIVALENT PLATE MODEL OF CURVILINEAR STIFFENED PANELS

This manuscript presents the derivation of a systematic set of equations for the evaluation of equivalent plate model of curvilinear stiffened panels. The homogenized properties of the stiffened panel are derived by first imposing kinematic equivalence between the stiffener’s strains and the strains of the equivalent layer, and then equating the strain energy density among the stiffeners and the equivalent layer among the real and the equivalent structure. The derivation is based on the first-order transverse-shear deformation theory for anisotropic plates (Reissner-Mindlin type). The stiffeners are modelled consistently using the FSDT beam theory (Timoshenko). It has been demonstrated that, if the stiffener are curvilinear, the derivation can be extended in order to derive the apparent engineering constants of the stiffened layer. A comparative study has been performed to evaluate the number of sub-cells necessary to approach the asymptotic value of the stiffnesses. The effect of the stiffeners’ geometry onto the engineering constant has been investigated. To assess the validity of the proposed method, a comparative study of the buckling loads obtained with a 2D shell model and those obtained with the equivalent plate/material model is carried out

MDO/MSO of Slender Thin Walled Box Beam Model

This manuscript presents a two steps procedure, useful within preliminary design stages, to optimize High Aspect Ratio composite wing and investigate the effect of different materials on the structural performances. The selection of material is carried out based on structural performances rather than Material Selection Optimization. Notably, the effect of different material is evaluated taking advantage of the objective properties of tensor's invariants and by the application of a linear scaling law. Scaled static, dynamic and aeroelastic performances have been compared with those obtained numerically. Through the optimization of the composite wing-box of a High Altitude Long Endurance aircraft, it has been demonstrated that near optimal solutions can be identified for a wide range of composite materials with the procedure presented herein, with no additional request of time and costs