Aerodynamic design for a pusher propeller spinner

Abstract

The present work has placed particular importance on the spinner aerodynamic design in order to enhance the performance of a pusher propeller configuration. The research has been focused on the aerodynamic shaping of the spinner in order to provide a better understanding of the nacelle-blade-spinner interaction in cruise conditions. The set of experiments were carried out by performing a series of steady-state Reynolds-averaged Navier-Stokes (RANS) CFD simulations with k-omega STT as turbulence model. Generally speaking, the pressure drag reduction was related to large values of Cp nearby the spinner wall; however, the pressure drag of shorter spinners depended mostly on the formation of the hub vortex, while the pressure drag improvement on the longer spinner designs depended on the pressure recovery at the spinner. A tangent spinner design was introduced to reduce the peaks of the pressure distribution observed at the nacelle-spinner transition, at the same time that moved the expansion section of the spinner downstream ahead the blade root thus improving the pressure recovery. The tangent cases induced an average increment in the nacelle drag of 5.77% compared to the original value, while the torque was reduced by only 0.05%. The spinner drag was reduced by 47.82% on average and the relative propeller efficiency was improved at a maximum value of 0.88%. The tangent spinner design was tested with passive boundary layer control tools such as small baffles located close to the blade root trailing edge. The relative propeller efficiency was improved at a maximum of 1.89% and the spinner drag reduced 122.3% turning the spinner drag into a thrust component. The direction of the flow was significantly more aligned with the rotational axis (From a stationary perspective) which increased the spinner pressure recovery. The detrimental effects of the Hub vortex at the end of the spinner were completely mitigated.