Modelling and experimental framework for shaft-driven and rim-driven propellers

Abstract

This study addresses the challenge of adapting rim-driven propeller configurations to aeronautical applications, aiming to assess its feasibility and potential advantages over traditional shaft-driven systems. The scope encompasses both theoretical frameworks and practical considerations essential for this transition, focusing on a comparative analysis by examining the static thrust generated under varying rotational speeds to assess the potential viability of rim-driven systems in aeronautical applications, having already been deemed viable in maritime applications. The initial approach involved creating two distinct experimental setups to evaluate the performance of both shaft-driven and rim-driven configurations. Emphasis was placed on meticulously designing the setups to optimise convenience and effectiveness in analysing the relationship between static thrust and varying rotational speeds. To gain deeper insights into the flow dynamics within the experimental setups, Computational Fluid Dynamics (CFD) was subsequently employed by simulating the experiments using two prominent turbulence models, namely the Shear Stress Transport (SST) k-ω and the Realisable k-ε turbulence models. The simulations aimed to enhance the understanding of the experimental findings. Thus, the Realisable k-ε model demonstrated superior accuracy over the SST k-ω in replicating the behaviour observed in shaft-driven configuration, whereas the SST k-ω model provided better alignment with the experimental data for rim-driven setup. The study revealed significant differences in the effectiveness of the shaft-driven and rim-driven propeller configurations under static conditions. The shaft-driven setup excelled by producing notably higher static thrust, demonstrating much more efficient pressure differentials across its blades compared to the rim-driven setup. The rim-driven configuration exhibited less than half the thrust of the shaft-driven counterpart, and faced limitations such as enclosure constraints, restricted rotational speeds and tight air gaps. However, despite the discrepancies and inherent design challenges, the rim-driven design demonstrated promising potential advantages as it experienced only half the stresses, suggesting benefits in terms of longevity, durability and reduced wear and tear over time.