On the influence of elasticity on propeller performance: a parametric study

Abstract

The aerodynamic performance of propellers strongly depends on their geometry and, consequently, on aeroelastic deformations. Knowledge of the extent of the impact is crucial for overall aircraft performance. An integrated simulation environment for steady aeroelastic propeller simulations is presented. The simulation environment is applied to determine the impact of elastic deformations on the aerodynamic propeller performance. The aerodynamic module includes a blade element momentum approach to calculate aerodynamic loads. The structural module is based on finite beam elements, according to Timoshenko theory, including moderate deflections. Several fixed-pitch propellers with thin-walled cross sections made of both isotropic and non-isotropic materials are investigated. The essential parameters are varied: diameter, disc loading, sweep, material, rotational, and flight velocity. The relative change of thrust between rigid and elastic blades quantifies the impact of propeller elasticity. Swept propellers of large diameters or low disc loadings can decrease the thrust significantly. High flight velocities and low material stiffness amplify this tendency. Performance calculations without consideration of propeller elasticity can lead to decreased efficiency. To avoid cost- and time-intense redesigns, propeller elasticity should be considered for swept planforms and low disc loadings.

Aeroelastic Model for Design of Composite Propellers

“…( 6), derivatives of the aerodynamic loads were computed analytically according to Eq. (7). For the derivative calculation only, it has been assumed that static aerodynamic loads are only sensitive to twist deformations because deformations in the remaining five structural degrees of freedom yield relatively small changes in aerodynamic loads and the BEM model is insensitive to changes in sweep and lean.…”

“…One design approach that has been of interest recently is the application of aeroelastic tailoring towards the improvement of performance. Indeed, it has been shown by Dwyer and Rogers [1], Yamamoto and August [2], Khan [3,4], Sandak and Rosen [5], Sodja et al [6], and Möhren et al [7], among others, that structural deformations of a propeller blade can noticeably affect aerodynamic performance at both on-and off-design conditions. In particular, coupling between bending and twisting deformations has been used to improve propeller performance through geometry modification in [5,6] and through structural modifications in [3,8,9].…”

“…Static aeroelastic analysis procedures for flexible propellers have previously been developed or applied by other researchers, including Möhren et al [7] and Gur and Rosen [10]. At the Delft University of Technology, an aeroelastic analysis framework, PROTEUS, was developed by Werter and De Breuker [11] and applied towards the conceptual design of aircraft wings in [12,13] and wind turbine blades in [9,14].…”

“…At the Delft University of Technology, an aeroelastic analysis framework, PROTEUS, was developed by Werter and De Breuker [11] and applied towards the conceptual design of aircraft wings in [12,13] and wind turbine blades in [9,14]. The structural model of PROTEUS is similar to the method applied in [7], as both models apply the finite-element method to solve deformations on a reduced-order Timoshenko finite element model, obtained from the 3D blade structure using a cross-sectional modeller. In PROTEUS, the cross-sectional modeller was developed by Ferede and Abdalla [15] and was shown to perform similarly to VABS (Variable Asymptotic Beam Section analysis), which is a commercial cross-sectional modelling program that was developed by Hodges [16].…”

“…The application of aeroelastic tailoring towards the design of dual-role propellers may enable an improvement in performance at the two opposing operating conditions. This research builds upon the work of Sodja et al [6,22], Khan et al [3,4], and Möhren et al [7] through the introduction of a computationally efficient flexible composite propeller design framework, featuring a closely coupled aeroelastic analysis that is capable of accurately assessing performance during positive-thrust and energy-harvesting conditions. The analysis framework that was developed is capable of assessing the impact on performance of composite propeller blades constructed out of symmetric laminates.…”