Summary of advanced methods for predicting high speed propeller performance

Abstract

Three advanced analyses for predicting aircraft propeller performance at high subsonic speeds are Aescribed. Two of these analyses use a hiring line representation for the propeller blades; and vortex filaments for the blade wakes but differ in the details of the solution. The third analysis is a finite difference solution of the unsteady, three-dimensional Euler equations for the flow between adjacent blades. Analysis results are compared to data for a high speed propeller having 8 swept blades integrally designed with the spinner and nacelle. These analyses provide tools for the propeller designer ranging from a short running program for initial design studies to a very long running program for checking final configurations.

Comparison between blade-element models of propellers

“…The direction of the trailing vortices at any point of the field coincides with the direction of the local resultant velocity (14) , thus the trailing vortices are free of forces. The free wake model is based on this condition.…”

“…The momentum model, uses an actuator disk (12) approach where the flow field is divided into concentric annuli control volumes. The liftingline is a somewhat more complex model which is based on Prandtl's lifting-line theory (13) and includes different approaches to calculating the wake geometry (9,14) . Vortex models (represented here by Theodorsen's and McCormick's models) are based on the optimal distribution of the blade's circulation and the Kutta-Joukowski theorem.…”

The NASA High-Speed Turboprop Program

“…(1) propeller structural integrity and structural dynamics at high-and low-speed when operating in the flow field generated by a swept wing, under realistic operational conditions, (2) propeller generated near-field and far-field noise, (3) propeller and flowfield induced static and dynamic loads on the nacelle and airframe, (4) passenger cabin noise and vibration levels, and effects of fuselage attenuation concepts on such noise, and (5) installed propulsive efficiency where consideration is given to aerodynamic interactions between the propeller, nacelle, pylon and wing (as a verification of predicted results from wind tunnel testing).…”